Shu Meng

Blockade of NOX2 and STIM1 signaling limits lipopolysaccharide-induced vascular inflammation

During sepsis, acute lung injury (ALI) results from activation of innate immune cells and endothelial cells by endotoxins, leading to systemic inflammation through proinflammatory cytokine overproduction, oxidative stress, and intracellular Ca2+ overload. Despite considerable investigation, the underlying molecular mechanism(s) leading to LPS-induced ALI remain elusive. To determine whether stromal interaction molecule 1-dependent (STIM1-dependent) signaling drives endothelial dysfunction in response to LPS, we investigated oxidative and STIM1 signaling of EC-specific Stim1-knockout mice. Here we report that LPS-mediated Ca2+ oscillations are ablated in ECs deficient in Nox2, Stim1, and type II inositol triphosphate receptor (Itpr2). LPS-induced nuclear factor of activated T cells (NFAT) nuclear accumulation was abrogated by either antioxidant supplementation or Ca2+ chelation. Moreover, ECs lacking either Nox2 or Stim1 failed to trigger store-operated Ca2+ entry (SOCe) and NFAT nuclear accumulation. LPS-induced vascular permeability changes were reduced in EC-specific Stim1-/- mice, despite elevation of systemic cytokine levels. Additionally, inhibition of STIM1 signaling prevented receptor-interacting protein 3-dependent (RIP3-dependent) EC death. Remarkably, BTP2, a small-molecule calcium release-activated calcium (CRAC) channel blocker administered after insult, halted LPS-induced vascular leakage and pulmonary edema. These results indicate that ROS-driven Ca2+ signaling promotes vascular barrier dysfunction and that the SOCe machinery may provide crucial therapeutic targets to limit sepsis-induced ALI.

Early Hyperlipidemia Promotes Endothelial Activation via a Caspase-1-Sirtuin 1 Pathway

Objective— The role of receptors for endogenous metabolic danger signals–associated molecular patterns has been characterized recently as bridging innate immune sensory systems for danger signals–associated molecular patterns to initiation of inflammation in bone marrow–derived cells, such as macrophages. However, it remains unknown whether endothelial cells (ECs), the cell type with the largest numbers and the first vessel cell type exposed to circulating danger signals–associated molecular patterns in the blood, can sense hyperlipidemia. This report determined whether caspase-1 plays a role in ECs in sensing hyperlipidemia and promoting EC activation. Approach and Results— Using biochemical, immunologic, pathological, and bone marrow transplantation methods together with the generation of new apoplipoprotein E (ApoE)−/−/caspase-1−/− double knockout mice, we made the following observations: (1) early hyperlipidemia induced caspase-1 activation in ApoE−/− mouse aorta; (2) caspase-1−/−/ApoE−/− mice attenuated early atherosclerosis; (3) caspase-1−/−/ApoE−/− mice had decreased aortic expression of proinflammatory cytokines and attenuated aortic monocyte recruitment; and (4) caspase-1−/−/ApoE−/− mice had decreased EC activation, including reduced adhesion molecule expression and cytokine secretion. Mechanistically, oxidized lipids activated caspase-1 and promoted pyroptosis in ECs by a reactive oxygen species mechanism. Caspase-1 inhibition resulted in accumulation of sirtuin 1 in the ApoE−/− aorta, and sirtuin 1 inhibited caspase-1 upregulated genes via activator protein-1 pathway. Conclusions— Our results demonstrate for the first time that early hyperlipidemia promotes EC activation before monocyte recruitment via a caspase-1–sirtuin 1–activator protein-1 pathway, which provides an important insight into the development of novel therapeutics for blocking caspase-1 activation as early intervention of metabolic cardiovascular diseases and inflammations.

Homocysteine induces inflammatory transcriptional signaling in monocytes.

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease. Here, we studied transcriptional regulation in homocysteine (Hcy)-induced gene expression in monocytes (MC). We identified 11 Hcy-induced genes, 17 anti-inflammatory cytokine interleukin 10-induced, 8 pro-inflammatory cytokine interferon gamma (IFN gamma)-induced and 8 pro-inflammatory cytokine tumor necrosis factor alpha (TNF alpha)-induced genes through literature search. Binding frequency of 36 transcription factors (TFs) implicated in inflammation and MC differentiation were analyzed within core promoter regions of identified genes, and classified into 3 classes based on the significant binding frequency to the promoter of Hcy-induced genes. Class 1 TFs exert high significant binding frequency in Hcy-induced genes. Class 2 and 3 TFs have low and no significant binding frequency, respectively. Class 1 TF binding occurrence in Hcy-induced genes is similar to that in IFN gamma -induced genes, but not that in TNF alpha -induced. We conclude that Hcy is a pro-inflammatory amino acid and induces inflammatory transcriptional signal pathways mediated by class 1 TF. We term class 1 TF as putative Hcy-responsive TFs.

Inflammatory and Autoimmune Reactions in Atherosclerosis and Vaccine Design Informatics

Atherosclerosis is the leading pathological contributor to cardiovascular morbidity and mortality worldwide. As its complex pathogenesis has been gradually unwoven, the regime of treatments and therapies has increased with still much ground to cover. Active research in the past decade has attempted to develop antiatherosclerosis vaccines with some positive results. Nevertheless, it remains to develop a vaccine against atherosclerosis with high affinity, specificity, efficiency, and minimal undesirable pathology. In this review, we explore vaccine development against atherosclerosis by interpolating a number of novel findings in the fields of vascular biology, immunology, and bioinformatics. With recent technological breakthroughs, vaccine development affords precision in specifying the nature of the desired immune response—useful when addressing a disease as complex as atherosclerosis with a manifold of inflammatory and autoimmune components. Moreover, our exploration of available bioinformatic tools for epitope-based vaccine design provides a method to avoid expenditure of excess time or resources.