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Exogenous hydrogen sulfide (H 2 S) protects kidneys from diabetic injuries in animal models. In order to explore the role of endogenous H 2 S in diabetic nephropathy, we determined the renal H2S producing enzymes in vivo and in vitro. In diabetic mice, H 2 S levels in blood and kidney were decreased while cystathionine β-synthase (CBS), mainly located in mouse renal proximal convoluted tubules (PCT), was reduced selectively. In cultured mouse PCT cells treated with high glucose, CBS protein and activity was reduced while ubiquitinated CBS was increased, which was abolished by a proteasome inhibitor MG132 at 1 hour; high glucose drove CBS colocalized with proteasome 26S subunit ATPase6, indicating an involvement of ubiquitination proteasome degradation. At 48 hours, high glucose also selectively decreased CBS protein, concentration-dependently, but increased the ubiquitination of CBS; silence of CBS by siRNA increased nitrotyrosine, a marker for protein oxidative injury. Nitrotyrosine was also increased by high glucose treatments. The increases of nitrotyrosine either by cbs-siRNA or by glucose were restored by GYY4137, indicating that the H 2 S donor may protect kidney from oxidative injury induced by CBS deficiency. In diabetic kidneys, ubiquitinated CBS and nitrotyrosine were increased but restored by GYY4137. The treatment also ameliorated albuminuria and renal morphologic changes in diabetic mice. Our findings suggest that high glucose induces reduction of renal CBS protein and activity in vivo and in vitro that is critical to the pathogenesis of diabetic kidney disease.

Background Docetaxel resistance affects prognosis in advanced prostate cancer (PCa). The precise mechanisms remain unclear. Transcription factor Forkhead box M1 (FOXM1), which participates in cell proliferation and cell cycle progression, has been reported to affect the sensitivity of chemotherapy. This study explores the role of FOXM1 in PCa docetaxel resistance and its association with kinesin family member 20 A (KIF20A), which is known to promote therapeutic resistance in some cancers. Methods We monitored cell growth using MTT and colony formation assays, and cell apoptosis and cell cycle progression using flow cytometry. Wound-healing and transwell assays were used to detect cell invasion and migration. mRNA and protein expression were analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blotting. We monitored FOXM1 binding to the KIF20A promoter using a ChIP assay. Tumorigenicity in nude mice was used to assess in vivo tumorigenicity. Results FOXM1 knockdown induced cell apoptosis and G2/M cell cycle arrest, suppressing cell migration and invasion in docetaxel-resistant PCa cell lines (DU145-DR and VCaP-DR). Exogenous FOXM1 overexpression was found in their parental cells. Specific FOXM1 inhibitor thiostrepton significantly weakened docetaxel resistance in vitro and in vivo. We also found that FOXM1 and KIF20A exhibited consistent and highly correlated overexpression in PCa cells and tissues. FOXM1 also regulated KIF20A expression at the transcriptional level by acting directly on a Forkhead response element (FHRE) in its promoter. KIF20A overexpression could partially reverse the effect on cell proliferation, cell cycle proteins (cyclinA2, cyclinD1 and cyclinE1) and apoptosis protein (bcl-2 and PARP) of FOXM1 depletion. Conclusions Our findings indicate that highly expressed FOXM1 may help promote docetaxel resistance by inducing KIF20A expression, providing insight into novel chemotherapeutic strategies for combatting PCa docetaxel resistance.

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