Dimethylarginine Dimethylaminohydrolase - 1 expression is increased under tBHP-induced oxidative stress regulates nitric oxide production in PCa cells attenuates mitochondrial ROS-mediated apoptosis

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) expression is frequently elevated in different cancers including prostate cancer (PCa) and enhances nitric oxide (NO) production in tumor cells by metabolising endogenous nitric oxide synthase (NOS) inhibitors. DDAH1 protects the PCa cells from cell death and promotes survival. In this study, we have investigated the cytoprotective role of DDAH1 and determined the mechanism of DDAH1 in protecting the cells in tumor microenvironment. Proteomic analysis of PCa cells with stable overexpression of DDAH1 has identified that oxidative stress-related activity is altered. Oxidative stress promotes cancer cell proliferation, survival and causes chemoresistance. A known inducer of oxidative stress, tert-Butyl Hydroperoxide (tBHP) treatment to PCa cells led to elevated DDAH1 level that is actively involved in protecting the PCa cells from oxidative stress induced cell damage. In PC3-DDAH1- cells, tBHP treatment led to higher mROS levels indicating that the loss of DDAH1 increases the oxidative stress and eventually leads to cell death. Under oxidative stress, nuclear Nrf2 controlled by SIRT1 positively regulates DDAH1 expression in PC3 cells. In PC3-DDAH1+ cells, tBHP induced DNA damage is well tolerated compared to wild-type cells while PC3-DDAH1- became sensitive to tBHP. In PC3 cells, tBHPexposure has increased the production of NO and GSH which may be acting as an antioxidant defence to overcome oxidative stress. Furthermore, in tBHP treated PCa cells, DDAH1 is controlling the expression of Bcl2, active PARP and caspase 3. Taken together, these results confirm that DDAH1 is involved in the antioxidant defence system and promotes cell survival.

HIF-1α and Nrf2 regulates hypoxia induced overexpression of DDAH1 through promoter activation in prostate cancer

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is overexpressed in prostate cancer (PCa) and promotes PCa progression in in vivo through the ADMA-NO pathway by degrading nitric oxide synthase (NOS) inhibitors such as asymmetric dimethylarginine (ADMA) and monomethylamine arginine (L-NMMA). In this study, we investigated the molecular mechanism involved in the overexpression of DDAH1 in PCa and examined its potential role as a therapeutic target. We observed that DDAH1expression is elevated in PCa (PC3, LNCaP, and DU145) cell lines under hypoxia. ChIP and reporter assay results confirmed that DDAH1 expression is positively regulated by HIF-1α through directly binding to the hypoxia response elements (HRE) located within the promoter region between - 1242/- 1238 upstream of its transcription start site (TSS). Under hypoxia, HIF-1α is translocated into the nucleus and activates its target gene expression in PC3 cells. Interestingly, in the event of HIF-1α inhibition or siRNA-mediated knockdown, an alternative transcription factor Nrf2 promotes DDAH1 expression through antioxidant response elements (AREs) on its promoter. ChIP assay results showed that Nrf2 binds to AREs located between -1016 / -1008 bp from the TSS of DDAH1. Furthermore, knockdown of PCa therapeutic target HSP90, an essential co-factor for both HIF-1α and Nrf2 causes attenuation of hypoxia induced DDAH1 overexpression in PCa cells. These results demonstrate that hypoxia induced upregulation of DDAH1 expression is positively regulated by HIF-1α and Nrf2 in association with HSP90. Therefore, targeting tumor angiogenesis promoting DDAH1 along with standard androgen receptor (AR) targeted therapy may offer an effective strategy to prevent PCa progression.

Asymmetric dimethylarginine (ADMA) as an important risk factor for the increased cardiovascular diseases and heart failure in chronic kidney disease

Patients with chronic kidney disease have an increased cardiovascular morbidity and mortality. It has been recognized that the traditional cardiovascular risk factors could only partially explain the increased cardiovascular morbidity and mortality in patients with chronic kidney disease. Asymmetric dimethylarginine (ADMA) and N-monomethy l-arginine (L-NMMA) are endogenous inhibitors of nitric oxide synthases that attenuate nitric oxide production and enhance reactive oxidative specie generation. Increased plasma ADMA and/or L-NMMA are strong and independent risk factor for chronic kidney disease, and various cardiovascular diseases such as hypertension, coronary artery disease, atherosclerosis, diabetes, and heart failure. Both ADMA and L-NMMA are also eliminated from the body through either degradation by dimethylarginine dimethylaminohydrolase-1 (DDAH1) or urine excretion. This short review will exam the literature of ADMA and L-NMMA degradation and urine excretion, and the role of chronic kidney diseases in ADMA and L-NMMA accumulation and the increased cardiovascular disease risk. Based on all available data, it appears that the increased cardiovascular morbidity in chronic kidney disease may relate to the dramatic increase of systemic ADMA and L-NMMA after kidney failure.

Effect of asymmetric dimethylarginine (ADMA) on heart failure development

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthases that limits nitric oxide bioavailability and can increase production of NOS derived reactive oxidative species. Increased plasma ADMA is a one of the strongest predictors of mortality in patients who have had a myocardial infarction or suffer from chronic left heart failure, and is also an independent risk factor for several other conditions that contribute to heart failure development, including hypertension, coronary artery disease/atherosclerosis, diabetes, and renal dysfunction. The enzyme responsible for ADMA degradation is dimethylarginine dimethylaminohydrolase-1 (DDAH1). DDAH1 plays an important role in maintaining nitric oxide bioavailability and preserving cardiovascular function in the failing heart. Here, we examine mechanisms of abnormal NO production in heart failure, with particular focus on the role of ADMA and DDAH1.