Pharmacology

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease (CVD). We previously demonstrated that homocysteine (Hcy) suppresses endothelial cell (EC) proliferation, migration, and post-injury EC repair, but the molecular mechanism underlying Hcy-induced EC injury is unclear. In this study, we identified a novel gene, Carom, which mediates Hcy-induced suppression of EC migration and angiogenesis. We identified FCH and double SH3 domains 2 (FCHSD2), a novel gene, as an Hcy-responsive gene through Differential Display in Hcy (50µM)-treated human umbilical vein endothelial cells (HUVEC). FCHSD2 was initially named as Carom, based on the identification of this molecule as an interacting protein of calcium/calmodulin-dependent serine protein kinase (CASK) and membrane associated guanylate kinase, WW and PDZ domain containing 1 (MAGI1). In this thesis, we describe this gene as Carom. Carom belongs to the Fes/CIP4 homology and Bin/amphiphysin/Rvs (F-BAR) protein family, which is a group of multivalent adaptors linking plasma membrane and cytoskeleton, involved in endocytosis and cell migration. However, Carom's function is poorly characterized. Based on the findings that CASK and MAGI1 inhibit cell migration and growth, and the role of F-BAR proteins in cell migration, we hypothesize that Hcy up-regulates Carom to inhibit EC growth and/or migration, finally leading to CVD. We confirmed the significant induction of Carom mRNA expression in Hcy-treated HUVECs or human aortic endothelial cells (HAEC) by Northern blot and Real-time PCR. In addition, we found that Carom protein expressions were significantly increased both in Hcy-treated HAECs and lung ECs isolated from HHcy mice by Western blot using our homemade rabbit antibody against Carom. These data indicate that Hcy increases endothelial expression of Carom both in vitro and in vivo. Furthermore, in order to characterize Carom function in EC, we generated recombinant adenovirus Adv-Carom to transduce Carom for gain-of-function study and Adv-Carom-shRNA to express Carom shRNA for loss-of-function study. We found that neither adenovirus-transduced Carom expression nor adenoviral Carom shRNA had any impact on HUVEC proliferation by using [3H]-thymidine incorporation. Interestingly, we demonstrated that Adv-Carom inhibited HAEC migration, while Hcy-induced HEAC migration inhibition could be rescued by Adv-Carom-shRNA. These data suggest that Carom may inhibit angiogenesis via a cell proliferation-independent mechanism. Furthermore, we found that Hcy significantly increased the intracellular level of S-adenosyl homocysteine (SAH) but not S-adenosyl methionine (SAM), and decreased the SAM/SAH ratio, an indicator of cellular methylation, in HAECs, by using High-performance liquid chromatography/electrospray tandem mass spectrometry (HPLC-MS) to measure SAH and SAM levels. Meanwhile, Carom protein expression was significantly induced by azacytidine (AZC), a DNA methyltransferse inhibitor, in a dose-dependent manner in HAECs. Based on these…

Microbiology and Immunology

Conventional Dendritic cells (cDCs), a specialized group of immunological sentinels with tree-like or dendritic shapes, are critical for recognition of danger signals, presentation of antigens and control of a spectrum of innate and adaptive immune responses. Type I interferons (IFNs), as important danger signals, activate cDCs through the canonical type I IFN receptor signaling. Type I IFNs are the first line of host defense against viral infection by up-regulating IFN-stimulated genes (ISGs). However, there are circumstances in which the silencing of excessive type I IFNs could be beneficial to the host, such as IFN-dependent autoimmune diseases, gene therapy that uses viral vectors and transplantation. The role of type I IFNs in DC development, activation and antigen presentation function remains to be completely investigated. In this dissertation, we studied the regulation of Type I IFNs in murine DCs, both cDCs and plasmacytoid DCs (pDCs), and specifically we investigated the role of two molecules, Signal Transducer and Activator of Transcription 2 (STAT2) and Three prime Repair EXonuclease 1 (Trex1), in DC biology. Our research furthers our understanding of DC development, activation and function, and provides important data for the therapeutic application of modified DCs to induce immunological tolerance in gene therapy, IFN-dependent autoimmune diseases and transplantation. STAT2 is a nuclear transcription factor downstream of type I IFN receptor-mediated signaling, the role of which has been mostly explored in antiviral responses mediated by type I IFNs. However, the involvement of STAT2 in cDC activation and function such as cross-presentation remains hitherto unclear. We report that STAT2 is essential for murine cDC activation upon TLR3, -4, -7 and -9 stimulation. In the absence of STAT2, cDCs displayed impaired up-regulation of type I IFN response (costimulatory molecules and type I IFN-stimulated genes), and reduced inflammatory cytokine production when stimulated with TLR ligands. STAT2 was required in all of the DC responses to exogenous IFNα, suggesting that the canonical STAT1-STAT2 heterodimers are the major signaling transducers downstream of type I IFNs in DCs. Of interest, LPS-induced TNFα and IL6 production were reduced in STAT2-/- DCs but not in IFNAR1-/- DCs, suggesting a novel STAT2-dependent pathway mediated by LPS, bypassing type I IFN-receptor signaling. STAT2-deficient cDCs showed impaired cross-presentation leading to decreased CD8+ T cell response both in vitro and CTL killing in vivo, indicating that STAT2 is essential for TLR-induced cross-presentation. These results demonstrate that STAT2 is critical in the regulation of TLR-induced DC activation and cross-presentation, suggesting an essential role for STAT2 in anti-viral and anti-tumor immune responses. We also propose a novel regulatory function of STAT2 in the LPS response independent of type I IFN receptor signaling. Trex1 mutations are associated with a spectrum of type I IFN-dependent…

Microbiology and Immunology

The Adeno-Associated Virus(AAV) is a small, single stranded DNA virus that has been developed as a gene transfer vector. Early clinical trials using recombinant AAV vectors (rAAV) have identified the following concerns that need to be addressed in order to increase efficiency of these vectors. It has since been determined that AAV vector efficiency decreases due to the following mechanisms: ineffective endocytosis, endosomal degradation, inefficient trafficking, and the need to convert from a single-stranded AAV genome to a transcriptional active double-stranded form. The purpose of this study is to elucidate mechanisms that help stabilize the AAV genome in order to make it a more efficient vector for gene therapy. Previously, there have been studies using fluorescent labeling to track the movement of AAV into the nucleus. An integral part of AAV genomic stability may be the obstacles it encounters in the cytoplasm prior to entering the nucleus. Previous studies on improving AAV transduction have focused primarily on the nucleus. The study will hopefully shed light on the hurdles AAV encounters as it moves through the cytoplasm. Thus, this project has designed and utilized a new system for specifically tracking the status of AAV genomes in the cytoplasm as well as in the nucleus. This project utilizes a novel dual luciferase reporter system to track the movement of AAV particles from the cytoplasm into the nucleus to elucidate mechanisms that could contribute to the stabilization of the AAV genome. The novel dual reporter system is comprised of a single-stranded vector containing two different types of secreted luciferases: Cypridina Luciferase and Gaussia Luciferase. Cypridina Luciferase is placed under the control of a nuclear promoter and therefore it is expressed only in the nucleus. The second, Gaussia Luciferase, is under the control of a cytoplasmic promoter that will only be expressed in the cytoplasm upon the presence of T7 RNA polymerase. Using this dual reporter luciferase system along with RT qPCR quantification in a Hek293 cell line expressing the T7 RNA polymerase, demonstrated that genomes are present in the cytoplasm at 18 and 24 hours post infection. The second part of this study is using the dual reporter system to understand the trafficking patterns of rAAV and looking at ways to enhance transduction. One method could be administering rAAV vectors in conjunction with a drug; this approach may help overcome some of these cellular barriers encountered during infection as well as help stabilize the genome. Cidofovir (CDV) is a monophosphate nucleotide analogue that competitively inhibits the incorporation of deoxycytidine triphosphate into viral DNA via viral DNA polymerase. In vitro, CDV actively inhibits a number of DNA viruses including herpes viruses, adenovirus, polyomavirus, papillomavirus, and poxviruses. Cidofovir has already been approved by the Food and Drug Administration (FDA) for the treatment of cytomegalovirus (CMV) retinitis in patients with acquired…

Microbiology and Immunology

Chronic inflammation follows defined phases of induction, inflammation, and resolution. The resolution phase requires cycloxygenase-2 (COX-2) activity. This study aims to address what other molecules are required for a functional resolution phase. We demonstrated that in murine collagen-induced arthritis the transcription factor, PPARgamma plays a role in the resolution phase. Inhibition of COX-2 activity results in fewer PPARgamma positive cells in the arthritic synovium. Treatment with a PPARgamma antagonist, SR202, alone, also disrupts the process of resolution. PPARgamma antagonist treatment results in a decrease in eNOS phosphorylation within the arthritic synovium. These observations indicate that PPARgamma may function to regulate eNOS activity. The source of pro-resolving nitric oxide is eNOS but not, iNOS. The effect of COX-2 inhibition on the resolution phase is ameliorated by injection of a PGE2 analog. Restoration of PGE2 levels results in an increase in PPARgamma positive cells in the arthritic synovium which correlates with this restoration of resolution. Thus, this study provides in vivo evidence for the pro-resolving role of PPARgamma and its relationship with PGE2 and eNOS.

Temple University – Theses

Pharmacology

Homocysteine (Hcy) is a thiol amino acid formed upon methionine de - methylation. A number of studies have revealed an association between hyperhomocysteinemia (HHcy), in which plasma Hcy levels exceed 15 µM, and diabetic atherosclerosis [1]. Despite these associations, the mechanisms underlying HHcy - associated diabetic atherosclerosis have not been clearly defined. This study assessed the effect of HHcy on diabetic atherosclerosis and its underlying mechanisms. We established a mouse model with a combination of three metabolic disorders, including HHcy (to mimic human HHcy), hyperglycemic (to mimic type 1 diabetes) and dyslipidemia (to exacerbate ApoE-/- mouse's susceptibility to atherosclerosis). In this mouse model, severe HHcy was developed due to mouse Cbs deficiency (mean plasma Hcy 182 µM) in a noval HHcy mouse model (Tg-hCBS Cbs ApoE-/-) generated by our collaborator [2]. Hyperglycemia was developed by 50 mg/kg streptozotocin (STZ) consecutive injection for 5 days (mean blood glucose 397 mg / dL). Dyslipedimia was introduced by high fat (HF, 21.0 % by weight) diet to accelerate aortic lesion formation in the Tg-hCBS Cbs ApoE-/- mice. An inducible human CBS (hCBS) transgene (Tg) was introduced to circumvent the neonatal lethality due to the mouse Cbs deficiency (Tg-hCBS Cbs-/- ApoE-/- mice). A zinc supplement in water could induce hCBS transgene expression and reverse Hcy level (reduced plasma Hcy from 182 µM to 5 µM, p < 0.001). Severe HHcy aggravated metabolic abnormalities, including increased urine secretion (from 8.35 ± 6.81 g/d/mouse in hyperglycemia only mice to 21.14 ± 5.95 g / d / mouse in hyperglycemic HHcy mice, p=0.042), increased water consumption (from 27.28 ± 9.46 g / d / mouse to 44.20 ± 4.66 g / d / mouse, p = 0.026), increased blood glucose level (from 443.20 ± 107.82 mg / dL to 614.27 ± 199.36 mg/dL, p = 0.031), increased heart weight (from 0.08 ± 0.02 g / cm to 0.11 ± 0.03 g / cm, p = 0.031) (data not shown) and decreased body weight (from -0.05 ± 0.92 g / 2 weeks / mouse to -1.78 ± 2.38 g / 2 weeks / mouse, p = 0.017). Hcy-lowering by zinc water reversed HHcy - induced hyperglycemia (from 614.27 ± 199.36 mg / dL to 440.20 ± 134.37 mg / dL, p = 0.032), increased urine secretion (from 21.14 ± 5.95 g / d / mouse to 0.90 ± 1.24 g / d / mouse, p = 0.042), and increased water consumption (from 44.20 ± 4.66 g / d / mouse to 6.08 ± 1.84 g / d / mouse, p = 0.008) in hyperglycemic mice. Increased atherosclerotic lesions were also found in the aortic roots of hyperglycemic HHcy mice (from 30.38 ± 14.34 % of the lumen area to 48.18 ± 12.07 %, p = 0.040). Increased accumulation of monocytes (MCs) and inflammatory MCs were found in atherosclerotic lesions of hyperglycemic HHcy mice. By sequential double immune - fluorescence staining with monoclonal antibodies (mAbs) anti MOMA - 2 (MC / macrophage [MØ] marker) and anti - Ly6C (inflammatory MC marker), we found that hyperglycemic HHcy mice had the largest area and percentage of MC / MØ (MOMA - 2+), and the largest area and percentage…

Pharmacology

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease (CVD). Both HHcy and insulin resistance (IR) are associated with atherosclerotic CVD. Recent studies have confirmed that insulin is not only a principle regulator of glucose homeostasis but also an important vasoactive hormone involved in the modulation of vascular tone. Epidemiological studies and animal studies have demonstrated the positive correlation of HHcy with IR and diabetes. Nevertheless, the effect and mechanism of HHcy on endothelial insulin signaling and insulin resistance has not been studied. In this study, we investigated the role and mechanism of HHcy on endothelial IR in vivo using transgenic mouse model of HHcy (Tg-hCBS Cbs -/- mice, plasma Hcy levels of 102.6 ± 9.1µmol/L) and in vitro using human aortic endothelial cells (HAEC). Using bioinformatics approach, we found tissue differential expression of Insulin/PI3K pathway genes in human and mouse. Furthermore, we measured tissue Hcy, S-adenosyl methionine (SAM), S-adenosyl homocysteine (SAH) levels in Tg-hCBS Cbs +/+ mice and examined correlation of insulin signaling genes with tissue Hcy, SAH levels and SAM/SAH ratio. We found negative correlation of Insulin/PI3K signaling genes with Hcy and SAH levels and positive correlation of Insulin/PI3K signaling genes with SAM/SAH ratio. These results led us to hypothesize that HHcy might negatively regulate insulin signaling and further contributes to IR. We found that HHcy impaired glucose metabolism (p<0.01 vs controls [CT]) and insulin sensitivity (p<0.05 vs CT) in Tg-hCBS Cbs -/- mice compared to their littermate controls (Tg-hCBS Cbs -/+ or +/+ mice). Furthermore, HHcy impaired insulin-induced vasorelaxation (31% vs CT, p<0.05) and endothelium-dependent relaxation (26% vs CT, p<0.05) in Tg-hCBS Cbs -/- mouse mesenteric arterioles. HHcy did not affect endothelium-independent relaxation and potassium chloride (KCl) & phenylephrine (PE)-induced contraction responses. Moreover, we found that HHcy significantly inhibited insulin-stimulated Akt and eNOS phosphorylation and activation in HAEC, mesenteric arterial tree, and in aorta. Pre-treatment of mesenteric arterioles with Wortmanin (PI3K inhibitor) and L-NAME (Nitric oxide synthase inhibitor) significantly inhibited insulin-induced vasorelaxation in controls (p<0.05 vs vehicle pre-treatment) but not in Tg-hCBS Cbs -/- mice, suggesting that HHcy impairs insulin-induced PI3K/Akt/eNOS signaling pathway. Moreover, we found that HHcy augmented insulin-induced MAPK pathway in HAEC, mesenteric arteries, and in aorta. In addition, pre-treatment of mesenteric arterioles with MEK inhibitor (PD98059) and endothelin-1A receptor blocker (BQ123) significantly improved (p<0.05 vs vehicle pre-treatment) insulin-induced vasorelaxation in Tg-hCBS Cbs -/- mice. Further analysis of upstream insulin signaling genes show that HHcy downregulated insulin receptor substrates (IRS) 1/2 mRNAs and protein expression but did not affect insulin receptor mRNA…

Pharmacology

Atherosclerosis, considered a chronic inflammatory disease, is the underlying mechanism for several cardiovascular diseases. Hyperlipidemia is the number one risk factor for atherogenesis. Caspase-1 is an inflammatory caspase, which can be activated by the metabolic stresses through pathogen associated molecular patterns (PAMPs)-recognition receptors, (PRR) recognition and inflammasome assembly. Activated caspase-1 can initiate inflammation in multiple ways. Thus, regulating inflammasome components expression is essential to control caspase-1 activation and its subsequent inflammatory processes. I hypothesized that the readiness of inflammasome component expression for caspase-1 activation in tissues is an index for inflammation privilege. Endothelial cells (EC) which are the innermost layer of the vessel and are the critical gatekeeper for monocyte migration. The first step of atherogenesis is activation of ECs, which allows monocyte adhesion and migration into the sub-endothelial layer. I also hypothesized that caspase-1 can sense hyperlipidemia and regulate EC activation and inflammation during early atherogenesis. I first determined the expression profiles of inflammasome components, pro-inflammatory caspases and PRRs is different among tissues, and cardiovascular tissues express relative less PRRs via a database-mining method. According to the readiness of inflammasome components, tissues could be classified into three tiers. The first tier consists of tissues with constitutively expressed inflammasomes. The second tier of tissues includes potentially inducible expression of one inflammasome component. The third tier of tissues has inducible expression of at least two inflammasome components. This three-tier model can be applied to determine the inflammation privilege of tissues in response to pro-inflammatory stimuli. I also demonstrated that hyperlipidemia induced caspase-1 expression and activation in aorta along with the atherogenesis in apolipoprotein E (ApoE)-/- mice with high fat (HF) diet, experimentally. We then generated the ApoE-/-/Casp-1-/- double knockout mice, and found that the ApoE-/-/Casp-1-/- mice contained significantly less atherosclerotic lesion in aortic sinus and less cytokine and chemokine expression in aortic tissues compared with ApoE-/- mice. ApoE-/-/Casp-1-/- mice also had less CD11b+/F4/80- neutrophil and CD11b+/F4/80+ monocyte recruitments into aorta compared with ApoE-/- mice. However, the percentage of monocyte subsets in peryphery blood remained at the same level in between ApoE-/- mice and ApoE-/-/Casp-1-/- mice. I then proposed that perhaps the caspase-1 activation in vascular cells, in ECs played the essential role of controling monocyte migraion. My in vitro data demonstrated that oxidized low density lipoprotein (ox-LDL) and its componnents could induced caspase-1 activation in human aortic ECs (HAECs) through ROS pathway which then led to EC activation and pyroptotic cell death. Deficiency of caspase-1 in aortic EC attenuated hyperlipidemia induced EC…

Pharmacology

Cardiovascular disease (CVD) is the leading cause of death worldwide, and is projected to remain so for at least the next decade. Ever since its discovery in the urine and blood of children with inborn errors of metabolism, homocysteine (Hcy) at elevated plasma concentrations has been associated with CVD clinically and epidemiologically. Observational studies and meta-analyses have noted that changes in plasma Hcy by 5μM increase the odds ratio of developing coronary artery disease by 1.6-1.8 among other CVD. Clinical trials aimed at reducing plasma Hcy for benefit against development of subsequent cardiovascular events have had unconvincing results, but have moreover failed to address the mechanisms by which Hcy contributes to CVD. Recommendations from national agencies like the American Heart Association and the United States Preventive Services Task Force emphasize primordial prevention as a way to combat CVD. Reducing plasma Hcy as secondary and primary interventions does not fulfill this recommendation. In order to best understand the role of Hcy in CVD, an investigation into its mechanisms of action must be undertaken before measures of primordial prevention can be devised. Numerous experimental studies in the literature identify vascular endothelium as a target for the pathological effects of Hcy. Endothelial injury and impairment are contributory processes to atherosclerosis, and Hcy has been demonstrated to inhibit endothelial cell (EC) growth and proliferation through mechanisms involving cell cycle arrest, oxidative stress, and programmed cell death in vitro. Animal models have also confirmed that high levels of Hcy accelerate atherosclerotic plaque development and lead to impairment of vascular reendothelialization following injury. Hcy has been shown to have the opposite effect in vascular smooth muscle cells (SMC), causing their proliferation and again contributing to atherosclerosis. The cell-type specificity of Hcy remains to be understood, and among the aims of this research was to further characterize the effects of Hcy in EC. The overarching goal was discovery in order to direct future investigations of Hcy-mediated pathology. To begin, the first investigation considered the transcriptional and regulatory milieu in EC following exposure to Hcy. High-throughput screening using microarrays determined the effect of Hcy on 26,890 mRNA and 1,801 miRNA. Two different in vitro models of hyperhomocysteinemia (HHcy) were considered in this analysis. The first used a high dose of 500µ Hcy to mimic plasma concentrations of patients wherein the transsulfuration pathway of Hcy metabolism is impaired as in inborn cystathionine-ß-synthase deficiency. The other set of conditions used 50µ Hcy in the presence of adenosine to approximate impairment of the remethylation pathway of Hcy metabolism wherein s-adenosylhomocysteine accumulates, thus inhibiting s-adenosylmethionine formation and methylation reactions. These distinctions are important because most clinical trials do not distinguish between…

Pharmacology

Endothelial cell (EC) activation is a change of the endothelium from a quiescent state to one that is involved in immune reactions. Activation of ECs is associated with the inception of atherosclerosis. Atherosclerosis is a chronic inflammatory disease that involves adaptive and innate immunity. There are many pro-inflammatory stimuli which activate the endothelium. The pro-inflammatory cytokine interleukin-17 (IL-17) has been shown to activate lung microvascular ECs. Enhanced expression of the IL-17 receptor by synovial ECs is associated with rheumatoid arthritis. These studies suggest that IL-17 plays an important role in EC biology. Nevertheless, the role of IL-17 in EC activation and endothelial dysfunction in the context of hyperlipidemia-induced atherosclerosis has not been studied. In the current study, we investigated the role of IL-17 in EC activation in vitro with mouse aortic ECs and human aortic ECs. In addition, we used the IL-17/ApoE double knock-out mouse to determine the role of IL-17 in vessel function and atherosclerosis development. First, we found that hyperlipidemia increased the number of IL-17-producing cells in the spleens from wild type mice and ApoE-/- mice that were fed a Western diet when compared to their respective normal chow diet controls. We also found that after treatment with the pro-atherogenic factor, oxidized LDL, there was an increase in the expression of IL-17 receptor by ECs. Using an EC specific array, we found that IL-17 induced significant up-regulation of four genes that are associated with EC activation in mouse aortic ECs. The four genes induced in IL-17-treated mouse aortic ECs were Cxcl1, Cxcl2, Il6, and Csf2. Moreover, we also found that IL-17 induced these four genes in human aortic ECs, and we showed that enhanced monocyte adhesion to ECs was dependent on these four genes. It was previously observed that a Western diet induced vessel dysfunction in the aortas of ApoE-/- mice. Thus, we sought to determine whether IL-17-deficiency rescues impaired endothelium-dependent relaxation in ApoE-/- mice that were fed a Western diet with the Wire Myograph System. We found that ApoE-/- mice on a 3-week Western diet had impaired endothelium-dependent relaxation when compared to IL-17-/-ApoE-/- mice. Endothelium-independent relaxation in response to sodium nitroprusside (SNP) and contraction responses induced by potassium chloride (KCl) and phenylephrine (PE) were not different in ApoE-/- mice and IL-17-/-ApoE-/- mice. Since our in vitro studies and vessel function assay pointed to a pro-atherogenic role for IL-17, we investigated lesion formation in ApoE-/- mice and IL-17-/-ApoE-/- mice. Lesion formation was assessed with Sudan IV staining of the whole aorta and Oil red O staining of aortic sinus cross sections. IL-17 deficiency in ApoE-/- mice did not affect atherosclerotic lesion formation in our study. Hyperlipidemia is a well-established risk factor for atherosclerosis so we investigated whether the pro-atherogenic role of IL-17 may have been compromised by…

Pharmacology

The global incidence of overweight and obese individuals has skyrocketed in the past few decades resulting in a new health epidemic. In 1980, 5% of males and 8% of females were categorized as obese; by 2008 these values doubled equating to half a billion adults worldwide. This surge of overweight and obese individuals has driven a dramatic increase in people afflicted with metabolic disorders. As such, the term "metabolic syndrome" (MetS) has been coined to describe several interrelated metabolic risk factors which often present in concert. Specifically, metabolic syndrome refers to the presence of at least three of the following five conditions: central obesity, elevated triglycerides, diminished high density lipoprotein (HDL) cholesterol, hypertension, and insulin resistance (IR). MetS is a major health concern due to its ability to increase the likelihood of cardiovascular disease (CVD), diabetes, and other life-threatening ailments. In light of this growing medical epidemic, we have concentrated our efforts in evaluating the role of microRNA-155 (miR-155) in MetS development. MicroRNAs are a newly defined class of small, non-coding RNA which contain the unique ability to regulate gene expression through RNA interference. As a result of this ability, microRNAs can mediate a wide variety of cellular processes. In order to evaluate the function of miR-155 in MetS, we established a novel miR-155-/-/ApoE-/- (DKO) mouse model. Coupling this model with the use of normal rodent or high fat diets allowed us to investigate how states of caloric balance and surplus affected the manifestation of the individual MetS components. We found that male and female DKO mice fed a high fat diet had significantly augmented body masses of 18% and 10% respectively, when compared to ApoE-/- counterparts on the same diet. Evaluation of this phenotype with body composition analysis revealed an 18% and 46% increase in body fat percentage among the male DKO mice on normal and high fat diets, respectively. This trend was also observed in female DKO mice, albeit to a lesser extent. This phenotype was further substantiated by the observation of augmented gonadal white adipose tissue pad mass within male and female DKO mice fed either chow. This equated to a 43% and 112% increase in male mice and a 45% and 57% augmentation in female mice for normal and high fat chow diets, respectively. In light of our findings, we also evaluated how miR-155 impacted glucose and insulin sensitivity. We found levels of insulin to be augmented by 181% and 148% in male DKO mice on normal and high fat diets, respectively. Furthermore, we found these mice to be euglycemic. These observations suggest that DKO mice are IR but capable of compensating for their insensitivity with elevated insulin production. Due to the tight association between MetS and the development of non-alcoholic fatty liver disease (NAFLD) as well as CVD, we felt it prudent to investigate the manifestation of these conditions. We found elevated hepatic mass of 40% and 13%…

Pharmacology

Lysophosphatidylcholines (LPCs) are a class of pro-inflammatory lipids that play important roles in atherogenesis. LPC activates endothelial cells (ECs) to upregulate adhesion molecules, cytokines and chemokines, which is the initiation step of atherogenesis. However, the mechanisms underlying LPC-triggered EC activation are not fully understood. Previously considered as the toxic by-products of cellular metabolism, mitochondrial reactive oxygen species (mtROS) are recently found to directly contribute to both the innate and adaptive immune responses. Here we tested a novel hypothesis that mtROS serve as signaling mediators for LPC-induced EC activation. Using electron spin resonance and flow cytometry with mtROS-specific fluorescence probe MitoSOX, we found that several LPC species including LPC 16:0, 18:0, and 18:1 induced mtROS in human primary aortic ECs (HAECs). Mechanistically, our analysis using confocal microscopy and Seahorse XF96 mitochondrial function analyzer showed that LPC induced mtROS via increasing mitochondrial calcium-mediated increase of mitochondrial respiration. In addition, we found that mtROS scavenger MitoTEMPO abolished LPC-induced EC activation by downregulating Intercellular adhesion molecule 1 (ICAM-1) in HAECs. Moreover, our analysis with mass spectrometer analysis of histone H3 lysine acetylation and electrophoretic mobility shift assay (EMSA) showed that MitoTEMPO acts by blocking LPC-induced histone H3 lysine 14 acetylation (H3K14ac) and nuclear translocation of pro-inflammatory transcription factor activator protein-1 (AP-1). Remarkably, all the above effects can be inhibited by anti-inflammatory cytokines interleukin (IL-35) and IL-10. Our results indicate that mtROS are responsible for LPC-induced EC activation, which can be inhibited by anti-inflammatory cytokines. MtROS targeting therapies and anti-inflammatory cytokines such as IL-35 may serve as novel therapeutic targets for vascular inflammation and cardiovascular diseases. The studies in this dissertation were supported by grants from the National Institutes of Health (NIH) funded to Dr. Xiao-Feng Yang.

Temple University – Theses

Physiology

Our lab has recently shown that IL-19 is expressed in angiogenic ECs, opening the possibility for its use as a medicine to increase perfusion in patients with PAD. The first aim of the current study is to show IL-19’s ability to increase perfusion in vivo using C57BL/6 wild type and IL-19 KO mice in the hindlimb ischemia (HLI) model. Wild-type mice injected with 10ng/g/day of rmIL-19 after being subject to hindlimb ischemia showed significantly greater levels of perfusion than PBS injected littermates. Immunohistochemistry of harvested gastrocnemius muscle showed a greater level of capillary density in IL-19 injected mice as well. IL-19-/- mice also showed a slower recovery of perfusion in a ligated limb in addition to less CD31 positive cells in gastrocnemius muscle when compared to C57BL/6 wild type mice. IL-19 -/- mice also showed increased perfusion when injected with rmIL-19. The second aim of the study is to show more precisely if IL-19 increases angiogenesis by increasing angiogenic cytokine production, polarizing macrophage phenotype, or by influencing angiogenic and anti-angiogenic factors. Spleen, serum, and bone marrow derived macrophage (BMDM) from mouse models used in Aim 1 showed increased levels of angiogenic cytokines, decreased anti-angiogenic cytokines, and markers of M2 macrophage polarization when IL-19 was injected i.p. or present genetically. The third aim of the study examines whether or not IL-19 can increase perfusion within an atherosclerotic background. It also addresses whether IL-19 can both simultaneously reduce atherosclerosis and increase perfusion. This aim also uses mice lacking LDLR-/- genes to further evaluate these questions. LDLR-/- mice fed a high fat diet for 12 weeks underwent HLI and had perfusion levels measured using Doppler imaging in addition to four weeks of 10ng/g/day of IL-19 or PBS injections. Upon sacrifice mice also had their aortas harvested and stained for plaque measurement. This experiment seeks to demonstrate if IL-19 can increase perfusion on an atherosclerotic background. Additionally, a second set of experiments addresses if LDLR-/- mice injected with recombinant mouse IL-19 (rmIL-19) or PBS for 16 weeks on a HFD in addition to HLI being performed at week 12 showed decreased levels of plaque and increased levels of hindlimb perfusion. These experiments seek to demonstrate if IL-19 can simultaneously reduce atherosclerosis while increasing perfusion. A third set of experiments attempts to evaluate the hypothesis that double knock out mice (DKO) lacking both LDLR and IL-19 genes will have increased plaque after being fed a HFD for 16 weeks. These aims all support the overall hypothesis that IL-19 can increase angiogenesis while additionally proving to be anti-inflammatory and anti-atherogenic in vivo

Temple University – Theses

Pharmacology

Patients with chronic kidney disease (CKD) develop hyperhomocysteinemia (HHcy), have increased inflammatory monocytes (MC) and 10-times higher cardiovascular mortality than the general population. Here, we investigated HHcy-related MC differentiation in CKD. Twenty seven CKD and CVD, and 14 healthy subjects were recruited. CD40 was selected as a CKD-induced MC activation marker by mining for CKD-MC-mRNA screen database. We found that CD14++CD16+ MC, often denoted as inflammatory subset, soluble CD40 ligand (sCD40L), and TNFα/IL-6 levels were augmented in CVD and CKD subjects. CD40hiCD14++CD16+ MC, plasma homocysteine (Hcy) and S-adenosylhomocysteine (SAH) levels were increased in CVD and further elevated in CKD subjects. In cultured human peripheral blood mononuclear cells, CKD patient serum, Hcy, CD40L and TNFα/IL-6 induced CD40hiCD14++CD16+ MC differentiation, which was prevented by Hcy-lowering folic acid and neutralizing antibodies against TNFα and IL-6. Interestingly, CD14++CD16+ and CD40hiCD14++CD16+ MCs were negatively correlated with plasma S-adenosylmethionine/SAH (SAM/SAH) ratios, an indicator of methylation status, in CKD and CVD subjects. In white blood cells (WBC) isolated from CKD and CVD subjects with lower SAM/SAH ratios, hypomethylation was identified on the CG pair of NFκB consensus element in the core promoter located at the CpG island of CD40 gene by DNA methylation mapping using bisulfite converting pyrosequencing. Moreover, Hcy inhibited DNA methyltransferase-1 activity in cultured human blood MC. In conclusion, HHcy induces CD14++CD16+ and CD40hiCD14++CD16+ MC differentiation, at least in part, via sCD40L induction and CD40 DNA hypomethylation in CKD and CVD subjects. To study the role of CD40 in the development of kidney pathology and vascular disease, we then established mouse model of CKD-induced CVD (5/6 nephrectomy CKD model plus left carotid artery ligation) in CD40-/- mice. Bone marrow (BM)-derived cells were traced by the transplantation of BM cells from enhanced green fluorescent protein (EGFP) transgenic CD40+/+ mice after sublethal irradiation of the recipient CD40-/- mice. We demonstrated here that CKD accelerated carotid artery atherosclerosis, exacerbated metabolism, increased spleen weight and circulating CD40+ inflammatory MC, and further increased differentiation of mononuclear phagocytic cells (MPC); CD11b+F4/80- MC, CD11b+F4/80+ macrophage (Mϕ) and CD11c+CD11b+F4/80+ bone marrow-derived dendritic cell in the kidney and aorta, which were abolished by CD40-/- mice. We also found that CKD kidney elevated CD40 expression and induced MC chemotactic signals; CCL2, CCL12, and CCL5 chemokines, which were abolished in CD40-/- mice. In conclusion, our results suggest that CD40 induction in the chronic kidney disease mediates kidney chemokine production, which in turn contributes to acceleration of myeloid cell infiltration, MPC differentiation, and carotid artery atherosclerosis.

Temple University – Theses

Microbiology and Immunology

Interleukin-27 (p28/EBI3) is an immunomodulatory cytokine expressed by activated antigen presenting cells. Although first discovered to be involved in Th1 cell differentiation, further studies demonstrated the immunosuppressive functions of IL-27 including inhibition of Th2 and Th17 differentiation, development of a tolerogenic phenotype in dendritic cells (DC), and promoting type 1 regulatory T cells (Tr1). The anti-inflammatory effects of IL-27 have been demonstrated in vivo in murine models of parasitic infections and autoimmune diseases. Despite the prevalence of studies detailing the induction of IL-27 expression and the role of IL-27 in Tr1 differentiation, little is known about factors that negatively regulate IL-27 expression and Tr1 differentiation. Prostaglandin E2 (PGE2), a lipid mediator abundant at inflammatory sites, was shown to act as a proinflammatory agent in models of inflammatory/autoimmune diseases primarily by promoting CD4 Th1/Th17 differentiation. Here we describe a novel proinflammatory mechanism for PGE2 through the inhibition of IL-27 production in conventional dendritic cells (cDC) and the inhibition of Tr1 differentiation. PGE2 inhibits IL-27 production in bone marrow-derived DC and macrophages, as well as in splenic cDC, through EP2/EP4 receptors, induction of cAMP, and downregulation of IRF1 expression and binding to the p28 IL-27 ISRE site. The inhibitory effect of PGE2 on p28 and irf1 expression does not involve endogenous IFN-β, STAT1 or STAT2, and inhibition of IL-27 does not appear to be mediated through PKA, EPAC, PI3K, or MAPKs. We observed similar inhibition of p28 expression in vivo in splenic DC following administration of dimethyl PGE2 in conjunction with LPS. In addition to the inhibition of IL-27 production in APCs, PGE2 also directly affects Tr1 differentiation by reducing IL-27-induced CD4+CD49b+LAG-3+Foxp3- Tr1 cells and IL-10 production. The inhibitory effect is mediated by EP4 and induction of cAMP in differentiating CD4 T cells. IL-27-induced Tr1 differentiation and function depends primarily on the sustained expression of c-Maf in addition to AhR and Blimp-1. PGE2 significantly reduced expression of c-Maf without affecting AhR and only marginally reducing Egr-2/Blimp-1 expression. The effects of PGE2 on Tr1 cells are independent of STAT1/STAT3 signaling and of IL-21 signaling. In addition, the effect of PGE2 on CD4+CD49b+LAG-3+ Tr1 differentiation was not associated with either induction of Foxp3 or IL-17 production, suggesting a lack of transdifferentiation into Foxp3+ Treg or effector Th17 cells. The effects of PGE2 on both IL-27 production and IL-27-induced Tr1 differentiation represent novel proinflammatory mechanisms of PGE2.

Temple University – Theses

Pharmacology

Background: Epidemiology, clinical trials and meta-analysis studies have established that Hyperhomocysteinemia (HHcy) is an independent risk factor for stroke. However, the exact molecular mechanism underlying the HHcy-induced risk of stroke is unclear. Our study aims to investigate the role of HHcy in stroke. Methods and results: We established a mice mode of focal ischemic stroke, termed transient Middle Cerebral Artery Occlusion (tMCAO) and conducted surgery on a mice model of HHcy (plasma homocysteine level ~150μM), in which a Zn2+ inducible human cystathionine β-synthase (CBS) transgene was introduced to circumvent the neonatal lethality of the CBS gene deficiency (Tg-hCBS Cbs-/- mice). Fourteen-week-old male mice were used in the experiment. A student’s t-test was used for the evaluation of the statistical significance between the two groups. For the comparison across multiple groups, one-way ANOVA was used. We found that HHcy 1) increased the infarction volume from 42.3 ± 4.9 mm

Temple University – Theses

Pharmacology

Background: Hyperhomocysteinemia (HHcy) is an established risk factor for thrombotic diseases yet the underlying mechanism remain unclear. In this study we investigated the effect of HHcy on endothelial cell-platelet interaction and its role in thrombosis. Methods and Results: We used a novel mouse model of HHcy (plasma homocysteine, Hcy 80 micromolar) in which a Zn2+ inducible human cystathionine beta-synthase (CBS) transgene was introduced to circumvent the neonatal lethality of the Cbs gene deficiency (Tg-hCBS Cbs-/- mice). Hcy-lowering therapy was performed by giving ZnSO4 water to induce human CBS transgene expression in adult mice. Thrombus formation was examined by photo dye-induced cremaster microvasculature thrombosis using intravital microscopy, in which endothelium was preserved, and by FeCl3-induced carotid artery thrombosis, which denudated the endothelium. HHcy accelerated cremaster arteriolar thrombosis and decreased blood flow cessation time from 41.8 min in control mice to 30.5 min in TghCBS Cbs-/- mice. Venular blood flow cessation time was slightly decreased from 5.6 to 5.0 min. Hcy-lowering therapy reduced Hcy level from 80 micromolar to 6.8 micromolar after 2 weeks of ZnSO4 water and prolonged arteriolar blood cessation time from 30.5 to 37.8 min. Interestingly, FeCl3-induced carotid artery thrombosis did not change the occlusion time. Hcy did not potentiate the aggregation and secretion function in washed human platelets from healthy donor treated with Hcy (50, 100 micromolar) or from Tg-hCBS Cbs-/- mice. However, inter-cellular adhesion molecule 1 (ICAM-1) levels, but not vascular adhesion molecule 1 (VCAM-1), were increased in cremaster tissues from Tg-hCBS Cbs-/- mice by western blot. In cultured human umbilical vein ECs (HUVEC), Hcy (100 micromolar, 24h) promoted human platelet adhesion by 200% in static adhesion assay. Using western blot, FACS and RT-PCR, we found that Hcy increased protein and mRNA levels of ICAM-1, but not that of VCAM-1, in HUVEC. ICAM-1 blocking antibody partially reversed Hcy increased platelets adhesion to HUVEC. Hcy induced ICAM-1 expression and reduced DNA methylation on ICAM-1 promoter, which were mimicked by DNA methyltransferase inhibitor azacytidine, and histone deacetylase inhibitors sodium butyrate and trichostatin A. Hcy treatment also increased intracellular Hcy, Sadenosylhomocysteine (SAH) accumulation and decreased SAM/SAH ratio in HUVECs. Hcy decreased methyl CpG binding protein 2 (MeCP2) binding and increased acetylated histone H3 (AcH3) binding to ICAM-1 core promoter region using chromatin immunoprecipitation. Pyrosequencing of ICAM-1 core promoter and adjacent region shows a decreased DNA methylation by Hcy treatment. In high methionine diet-induce HHcy in WT and Icam-/- mice, Icam-/- mice fed with HM diet only show moderately accelerated venular and barely accelerated arteriolar occlusion time compared with WT mice with CT diet using photo dye-induced thrombosis model. Conclusion: HHcy accelerates arteriolar thrombosis and increases…