Kundu S, Pushpakumar SB, Tyagi A, Coley D, Sen U. Hydrogen sulfide deficiency and diabetic renal remodeling: role of matrix metalloproteinase-9. Am J Physiol Endocrinol Metab 304: E1365-E1378, 2013. First published April 30, 2013 doi:10.1152/ajpendo.00604.2012.-Matrix metalloproteinase-9 (MMP-9) causes adverse remodeling, whereas hydrogen sulfide (H2S) rescues organs in vascular diseases. The involvement of MMP-9 and H2S in diabetic renovascular remodeling is, however, not well characterized. We determined whether MMP-9 regulates H2S generation and whether H2S modulates con-Ϫ/Ϫ mice and in vitro cell culture were used in our study. Hyperglycemic Akita mice exhibited increased level of MMP-9 and decreased production of H2S. H2S-synthesizing enzymes cystathionine-␤-synthase and cystathionine-␥-lyase were also diminished. In addition, increased expressions of NMDA-R1 and connexin-40 and -43 were observed in diabetic kidney. As expected, MMP-9 mRNA was not detected in M9KO kidneys. However, very thin protein expression and activity were detected. No other changes were noticed in M9KO kidney. In DKO mice, all the above molecules showed a trend toward baseline despite hyperglycemia. In vitro, glomerular endothelial cells treated with high glucose showed induction of MMP-9, attenuated H2S production, NMDA-R1 induction, and dysregulated conexin-40 and -43 expressions. Silencing MMP-9 by siRNA or inhibition of NMDA-R1 by MK801 or H2S treatment preserved connexin-40 and -43. We conclude that in diabetic renovascular remodeling MMP-9 plays a major role and that H2S has therapeutic potential to prevent adverse diabetic renal remodeling.

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More than 29 million adults in the United States have been diagnosed with hearing loss. Interestingly, elevated homocysteine (Hcy) levels, known as hyperhomocysteinemia (HHcy) is also associated with impaired hearing. However, the associated mechanism remains obscure. The collagen receptor such as discoidin domain receptor 1 and matrix metalloproteinase (MMP) play a significant role in inner ear structure and function. We hypothesize that HHcy increases hearing thresholds by compromise in inner ear vasculature resulted from impaired Hcy metabolism, increased oxidative stress, collagen IVa and collagen la turnover. The treatment with folic acid (FA) protects elevated hearing thresholds and prevents reduction in vessel density by lowering abundant collagen deposition and oxidative stress in inner ear. To test this hypothesis we employed 8 weeks old male wild type (WT), cystathionine-beta-synthase heterozygote knockout (CBS+/−) mice, WT+FA (0.0057 μg/g/day, equivalent to a 400 μg/70 kg/day human dose in drinking water); and CBS(+/−)+FA. The mice were treated for four weeks. The hearing thresholds were determined by recording the auditory brainstem responses. Integrity of vessels was analyzed by perfusion of horseradish peroxidase (HRP) tracer. Endothelial permeability was assessed, which indicated restoration of HRP leakage by FA treatment. A total Hcy level was increased in stria vascularis (SV) and spiral ligament (SL) of CBS+/− mice which was lowered by FA. Interestingly, FA treatment lowered Col IVa Immunostaining by affecting its turnover. The levels of MMP-2, -9, methylenetetrahydrofolate reductase (MTHFR) and cystathione gamma lyase (CSE) were measured by Western blot analysis. The oxidative stress was high in SV and SL of CBS+/− compared to WT however the treatment with FA lowered oxidative stress in CBS+/− mice. These data suggested that hearing loss in CBS+/− mice was primarily due to leakage in inner ear circulation, also partly by induced collagen imbalance, increase in Hey and oxidative stress in inner ear.

Diabetic nephropathy is a leading cause of vascular morbidity and mortality. Recently, the involvement of N‐methyl‐D‐aspartate receptor (NMDAR) and hydrogen sulfide (H2S) in diabetes associated complications has been implicated. Our aim in this study was to determine whether H2S mitigates diabetic nephropathy by modulating gap junction and matrix proteins by antagonizing NMDAR. We used a diabetic model (Akita, C57BL/6J‐Ins1Akita), matrix metalloproteinase‐9 knockout (KO) [(MMP‐9−/−)] and double KO of Akita/MMP‐9−/− mice and in vitro cell culture.ResultsDiabetic kidneys showed decreased levels of H2S and its enzymes CBS and CSE in both mRNA and protein level and increased expression of NMDA‐R1, connexin‐40, ‐43 (Cx‐40,‐43) and MMP‐9. Treatment with H2S reversed these effects. In double KO mice, NMDA‐R1 was high but Cx‐40, ‐43 was normal. Additionally, treatment with NMDA‐R1 blocker dizicilpine (MK801) failed to disrupt connexin. Glomerular endothelial cells treated with high glucose indicated dysregulated Cx‐40, ‐43. Inhibition of NMDA‐R1 by MK801, silencing MMP‐9 by siRNA or H2S treatment preserved gap junction proteins. We conclude that in diabetic nephropathy, remodeling is mediated by NMDA‐R1 associated MMP‐9 activation and H2S plays a significant role in mitigating nephropathy.

This case describes an anticoagulation strategy in a postpartum patient on venoarterial extracorporeal membrane oxygenation (VA ECMO) for a pulmonary embolism (PE) with a concurrent ischemic stroke. After receiving systemic lysis, the patient had impending cardiovascular collapse, right heart strain, worsening clinical picture, prompting VA ECMO cannulation and subsequent cautious management of the patient’s anticoagulation. There have been no similar cases published describing an ECMO anticoagulation strategy and management for this complex clinical situation. By withholding a heparin bolus and delaying initiation of a heparin drip for 24 hours, thromboelastogram (TEG) R-time and partial thromboplastin time (PTT) could be closely monitored while the patient began to recover.