Mononuclear Phagocyte-Derived Microparticulate Caspase-1 Induces Pulmonary Vascular Endothelial Cell Injury

Lung endothelial cell apoptosis and injury occurs throughout all stages of acute lung injury (ALI/ARDS) and impacts disease progression. Lung endothelial injury has traditionally been focused on the role of neutrophil trafficking to lung vascular integrin receptors induced by proinflammatory cytokine expression. Although much is known about the pathogenesis of cell injury and death in ALI/ARDS, gaps remain in our knowledge; as a result of which there is currently no effective pharmacologic therapy. Enzymes known as caspases are essential for completion of the apoptotic program and secretion of pro-inflammatory cytokines. We hypothesized that caspase-1 may serve as a key regulator of human pulmonary microvascular endothelial cell (HPMVEC) apoptosis in ALI/ARDS. Our recent experiments confirm that microparticles released from stimulated monocytic cells (THP1) induce lung endothelial cell apoptosis. Microparticles pretreated with the caspase-1 inhibitor, YVAD, or pan-caspase inhibitor, ZVAD, were unable to induce cell death of HPMVEC, suggesting the role of caspase-1 or its substrate in the induction of HPMVEC cell death. Neither un-induced microparticles (control) nor direct treatment with LPS induced apoptosis of HPMVEC. Further experiments showed that caspase-1 uptake into HPMVEC and the induction of HPMVEC apoptosis was facilitated by caspase-1 interactions with microparticulate vesicles. Altering vesicle integrity completely abrogated apoptosis of HPMVEC suggesting an encapsulation requirement for target cell uptake of active caspase-1. Taken together, we confirm that microparticle centered caspase-1 can play a regulator role in endothelial cell injury.     

Autophagy in hypothalamic AgRP neurons regulates food intake and energy balance

Macroautophagy is a lysosomal degradative pathway that maintains cellular homeostasis by turning over cellular components. Here we demonstrate a role for autophagy in hypothalamic agouti-related peptide (AgRP) neurons in the regulation of food intake and energy balance. We show that starvation-induced hypothalamic autophagy mobilizes neuron-intrinsic lipids to generate endogenous free fatty acids, which in turn regulate AgRP levels. The functional consequences of inhibiting autophagy are the failure to upregulate AgRP in response to starvation, and constitutive increases in hypothalamic levels of pro-opiomelanocortin and its cleavage product α-melanocyte-stimulating hormone that typically contribute to a lean phenotype. We propose a conceptual framework for considering how autophagy-regulated lipid metabolism within hypothalamic neurons may modulate neuropeptide levels to have immediate effects on food intake, as well as long-term effects on energy homeostasis. Regulation of hypothalamic autophagy could become an effective intervention in conditions such as obesity and the metabolic syndrome.     

Aberrant expression of imprinted genes in post-implantation rat embryos

AimImprinted genes are known regulators of embryo growth. Studies from our laboratory have demonstrated that treatment of adult male rats with tamoxifen increased post-implantation loss at around midgestation. Expression of insulin like growth factor 2 (Igf2), a paternally expressed imprinted gene was down-regulated in the resorbing embryos obtained at embryonic day 13. Hypomethylation of Igf2-H19 imprint control region was observed in the resorbing embryo sires and spermatozoa obtained from tamoxifen-treated rats thereby suggesting that errors in imprint acquisition during spermatogenesis can result in embryo loss. The present study aims at studying the expression of other imprinted genes, besides Igf2 in the embryos sired by tamoxifen-treated males.Main methodsGene expression profiles of resorbing versus normal embryos were assessed by microarrays. Real time quantitative RT-PCR for six imprinted genes and four genes involved in cell cycle was done to validate gene expression data. The affected pathways and functions were identified in the resorbing embryos and effect on cell cycle was confirmed by flow cytometry.Key findingsAberrant expression of a number of imprinted genes was observed in the resorbing embryos when compared to the normal embryos at embryonic days 11 and 13. Down-regulation of Notch signaling, Wnt signaling and cell cycle pathway was observed in the resorbing embryos.SignificanceThe study suggests that exposure of male germ cells to tamoxifen during adulthood results in aberrant expression of imprinted genes and down-regulation of development associated pathways in the F₁ progeny thereby causing embryo loss.     

Microparticulate P2X7 and GSDM-D mediated regulation of functional IL-1β release

Purinergic Signalling - The pro-inflammatory cytokine IL-1β is a secreted protein that is cleaved by caspase-1 during inflammasome activation upon recognition of internal and external insults...