IL-4-STAT6 axis amplifies histamine-induced vascular endothelial dysfunction and hypovolemic shock.

BACKGROUND: Mast cell (MC)-derived mediators induce vasodilatation and fluid extravasation, leading to cardiovascular failure in severe anaphylaxis. We have previously revealed a synergistic interaction between the cytokine IL-4 and the MC-derived mediator histamine in modulating vascular endothelial (VE) dysfunction and severe anaphylaxis. The mechanism by which IL-4 exacerbates histamine-induced VE dysfunction and severe anaphylaxis are unknown. OBJECTIVE: To identify the IL-4-induced molecular processes regulating the amplification of histamine-induced VE barrier dysfunction and the severity of IgE-mediated anaphylaxic reactions. METHODS: RNAseq, Western blot, Ca2+ imaging and barrier functional analyses on the vascular endothelial cell line (EA.hy926). Pharmacologic degraders (selective PROTAC (proteolysis-targeting chimera) and genetic (lentiviral shRNA) inhibitors were used to determine the roles of STAT3 and STAT6 in conjunction with in vivo model systems of histamine-induced hypovolemic shock. RESULTS: IL-4 enhancement of histamine-induced VE barrier dysfunction was associated with increased VE-Cadherin degradation, intracellular calcium flux, phospho-Src levels and required transcription and de novo protein synthesis. RNAseq analyses of IL-4 stimulated VE cells identified dysregulation of genes involved in cell proliferation, cell development, and cell growth and transcription factor motif analyses revealed a significant enrichment of differential expressed genes (DEGs) with putative STAT3 and STAT6 motif. IL-4 stimulation in EA.hy926 cells induced both STAT3Y705 and STAT3S727 phosphorylation. Genetic and pharmacologic ablation of VE STAT3 activity revealed a role for STAT3 in basal VE barrier function, however IL-4 enhancement and histamine-induced VE barrier dysfunction was predominantly STAT3-independent. In contrast, IL-4 enhancement and histamine-induced VE barrier dysfunction was STAT6-dependent. Consistent with this finding, pharmacologic knockdown of STAT6 abrogated IL-4-mediated amplification of histamine-induced hypovolemia. CONCLUSIONS: These studies unveil a novel role of the IL-4/ STAT6 signaling axis in the priming of VE cells predisposing to exacerbation of histamine-induced anaphylaxis.

The role of the glypican and syndecan families of heparan sulfate proteoglycans in cardiovascular function and disease.

Heparan sulfate proteoglycans (HSPGs) are proteoglycans formed by a core protein to which one or multiple heparan sulfate chains are covalently bound. They are ubiquitously expressed in cellular surfaces and can be found in the extracellular matrix and secretory vesicles. The cellular effects of HSPGs comprehend multiple functionalities that include 1) the interaction with other membrane surface proteins to act as a substrate for cellular migration, 2) acting as a binding site for circulating molecules, 3) to have a receptor role for proteases, 4) to act as a coreceptor that can provide finetuning of growth factor receptor activity threshold, and 5) to activate intracellular signaling pathways (Sarrazin S, Lamanna WC, Esko JD. Cold Spring Harb Perspect Biol 3: a004952, 2011). Among the different families of HSPGs, the syndecan and glypican families of HSPGs have gained increased attention in relation to their effects on cardiovascular cells and potential role in disease progression. In this review, we will summarize the effects of syndecan and glypican homologs on the different cardiovascular cell types and discuss their contribution to common processes found in cardiovascular diseases (inflammation, hypertrophy, and vascular remodeling) as well as their potential role in the development and progression of specific diseases including hypertension, heart failure, and atherosclerosis.

Oral administration of recombinant Mycobacterium smegmatis expressing a tripeptide construct derived from endogenous and microbial antigens prevents atherosclerosis in ApoE(-/-) mice.

INTRODUCTION: Immunotherapy by inducing oral tolerance to atherogenic self-antigens is gaining importance as an alternative treatment modality for atherosclerosis. The use of live bacterial vectors to express the recombinant antigen in vivo will obviate the need for large-scale purification of recombinant protein and may also augment the efficacy of oral tolerance induction. AIM: The objective of the study was to explore the use of recombinant Mycobacterium smegmatis as a live vector for oral delivery of antigens to induce immune tolerance. METHOD AND RESULTS: We developed a M. smegmatis vector to secrete a recombinant tripeptide construct (AHC; peptides from Apolipoprotein B, Heat-shock protein 60 and Chlamydia pneumoniae outer membrane protein) expressed in a dendroaspin protein scaffold in pJH154 background. Immune response and oral tolerance to the cloned peptides were studied in C57/BL6 mice. The efficacy of this live vaccine to control atherosclerosis was studied in ApoE(-/-) knockout mice in C57/BL6 background. Oral administration of M. smegmatis secreting the cloned AHC antigen was found to induce tolerance to cloned protein and reduce the development of atherosclerosis by 24.0% compared to control. Protection against atherosclerosis was associated with increase in expression of regulatory T cell-associated markers including CTLA4 (1.8-fold), Foxp3 (2.6-fold), TGF-ß (2.8-fold), IL10 (2.9-fold), and reduction in lipids, macrophage infiltration, and expression of inflammatory mediators in aorta. CONCLUSIONS: Our results suggest that M. smegmatis can be developed as an oral carrier of recombinant proteins to treat inflammatory autoimmune diseases.

Understanding the progression of atherosclerosis through gene profiling and co-expression network analysis in Apob(tm2Sgy)Ldlr(tm1Her) double knockout mice.

The objective of the study was to gain molecular insights into the progression of atherosclerosis in Apob(tm2Sgy)Ldlr(tm1Her) mice, using transcriptome profiles. Weighted gene co network analysis (WGCNA) and time course analysis using limma were used to study disease progression from 0 to 20weeks. Five co-expression modules were identified by WGCNA using the expression values of 2153 genes. Genes associated with autophagy, endoplasmic reticulum stress, inflammation and lipid metabolism were differentially expressed at early stages of atherosclerosis. Time course analysis highlighted activation of inflammatory gene signaling at 4weeks, cell proliferation and calcification at 8weeks, amyloid like structures and oxidative stress at 14weeks and enhanced production of inflammatory cytokines at 20weeks. Our results suggest that maximum gene perturbations occur during early atherosclerosis which could be the danger signals associated with subclinical disease. Understanding these genes and associated pathways can help in improvement of diagnostic and therapeutic targets for atherosclerosis.