Collagen receptor- and metalloproteinase-dependent hypertensive stress response in mesangial and glomerular endothelial cells.

Progressive alteration of the extracellular matrix (ECM) is the characteristic of hypertensive nephropathy (HN). Both mesangial and endothelial cells have the ability to synthesize and degrade ECM components, including collagens through the activation of matrix metalloproteinases (MMPs) in stress conditions, such as in hypertension. On the other hand, hydrogen sulfide (H2S) has been shown to mitigate hypertensive renal matrix remodeling. Surprisingly, whether H2S ameliorates receptor-mediated (urokinase plasminogen activator receptor-associated protein, uPARAP/Endo180) collagen dysregulation in Ang-II hypertension is not clear. The purpose of this study was to determine whether Ang-II alters the expression of Endo180, tissue plasminogen activator (tPA), MMPs, and their tissue inhibitors (TIMPs) leading to the dysregulation of cellular collagen homeostasis and whether H2S mitigates the collagen turnover. Mouse mesangial cells (MCs) and glomerular endothelial cells (MGECs) were treated without or with Ang-II and H2S donor GYY (GYY4137) for 48 h. Cell lysates were analyzed by Western blot and RT-PCR, and cells were analyzed by immunocytochemistry. The results indicated that, while Ang-II differentially expressed MMP-13 and TIMP-1 in MCs and in MGECs, it predominantly decreased tPA, Endo 180, and increased plasminogen activator inhibitor-1 (PAI-1), MMP-14, and collagen IIIA and IV in both the cell types. Interestingly, H2S donor GYY treatment normalized the above changes in both the cell types. We conclude that Ang-II treatment causes ECM remodeling in MCs and MGECs through PAI-1/tPA/Endo180 and MMP/TIMP-dependent collagen remodeling, and H2S treatment mitigates remodeling, in part, by modulating these pathways.

Hydrogen sulfide inhibits Ca2+-induced mitochondrial permeability transition pore opening in type-1 diabetes.

Hydrogen sulfide (H2S) attenuates N-methyl-d-aspartate receptor-R1 (NMDA-R1) and mitigates diabetic renal damage; however, the molecular mechanism is not well known. Whereas NMDA-R1 facilitates Ca2+ permeability, H2S is known to inhibit L-type Ca2+ channel. High Ca2+ activates cyclophilin D (CypD), a gatekeeper protein of mitochondrial permeability transition pore (MPTP), thus facilitating molecular exchange between matrix and cytoplasm causing oxidative outburst and cell death. We tested the hypothesis of whether NMDA-R1 mediates Ca2+ influx causing CypD activation and MPTP opening leading to oxidative stress and renal injury in diabetes. We also tested whether H2S treatment blocks Ca2+ channel and thus inhibits CypD and MPTP opening to prevent renal damage. C57BL/6J and Akita (C57BL/6J-Ins2Akita) mice were treated without or with H2S donor GYY4137 (0.25 mg·kg-1·day-1 ip) for 8 wk. In vitro studies were performed using mouse glomerular endothelial cells. Results indicated that low levels of H2S and increased expression of NMDA-R1 in diabetes induced Ca2+ permeability, which was ameliorated by H2S treatment. We observed cytosolic Ca2+ influx in hyperglycemic (HG) condition along with mitochondrial-CypD activation, increased MPTP opening, and oxidative outburst, which were mitigated with H2S treatment. Renal injury biomarker KIM-1 was upregulated in HG conditions and normalized following H2S treatment. Inhibition of NMDA-R1 by pharmacological blocker MK-801 revealed similar results. We conclude that NMDA-R1-mediated Ca2+ influx in diabetes induces MPTP opening via CypD activation leading to increased oxidative stress and renal injury, and H2S protects diabetic kidney from injury by blocking mitochondrial Ca2+ permeability through NMDA-R1 pathway.

Regulation and involvement of matrix metalloproteinases in vascular diseases.

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

Homocysteine in renovascular complications: hydrogen sulfide is a modulator and plausible anaerobic ATP generator.

Homocysteine (Hcy) is a non-protein amino acid derived from dietary methionine. High levels of Hcy, known as hyperhomocysteinemia (HHcy) is known to cause vascular complications. In the mammalian tissue, Hcy is metabolized by transsulfuration enzymes to produce hydrogen sulfide (H2S). H2S, a pungent smelling gas was previously known for its toxic effects in the central nervous system, recent studies however has revealed protective effects in a variety of diseases including hypertension, diabetes, inflammation, atherosclerosis, and renal disease progression and failure. Interestingly, under stress conditions including hypoxia, H2S can reduce metabolic demand and also act as a substrate for ATP production. This review highlights some of the recent advances in H2S research as a potential therapeutic agent targeting renovascular diseases associated with HHcy.