The mechanism of long-term low-dose asymmetric dimethylarginine inducing transforming growth factor-β expression in endothelial cells

Abstract

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, accumulates in plasma during chronic kidney disease (CKD). High plasma levels of ADMA can increase transforming growth factor-β (TGF-β) expression, related to renal fibrosis, but the precise molecular mechanism is not explicit. The present study was designed to determine the mechanism through which long-term low-dose ADMA induces TGF-β expression in endothelial cells and to investigate the molecular mechanism of its action. Human umbilical vein endothelial cells (HUVECs) were exposed to low-dose ADMA (5 and 10 µmol/l) for 7 passages and TGF-β expression was determined. Human renal glomerular endothelial cells (HRGECs) were exposed to high-dose ADMA (100 µmol/l) which were used to clarify the molecular mechanism. The results showed that long-term low-dose ADMA (5 and 10 µmol/l) increases TGF-β production in both mRNA and protein levels in HUVECs in a time-dependent manner. We confirmed that exogenous ADMA (100 µmol/l) significantly enhanced stress fiber formation in HRGECs and upregulated TGF-β expression. Such effects of ADMA in HRGECs were inhibited by pre-treatment with actin depolymerizing agent, actin stabilizing agent, p38 MAPK inhibitor and NADPH oxidase inhibitor. In addition, we demonstrated that ADMA (100 µmol/l) significantly activated nuclear factor-κB (NF-κB) in HRGECs, which was markedly attenuated by actin depolymerizing agent, actin stabilizing agent, p38 MAPK inhibitor and NADPH oxidase inhibitor. In brief, the present study demonstrated that long-term low-dose ADMA induces TGF-β expression in endothelial cells at both the gene and protein levels. The actin cytoskeleton may be involved in modulation of ADMA-induced NF-κB activation and the ensuing TGF-β expression in HRGECs.

The cytoskeleton as a novel target for treatment of renal fibrosis

“…Asymmetric dimethylarginine (ADMA), which accumulates in the plasma in CKD patients (Saran et al, 2003), increases TGF- expression in human glomerular endothelial cells. It is associated with increased actin stress fibers and both depolymerization (cytochalasin D) and stabilization (jasplakinolide) of the actin cytoskeleton decreased ADMA-induced NF-B activation and TGF- expression (Feng et al, 2013). This counterintuitive finding that manipulating the actin cytoskeleton in either direction influences cell phenotype reinforces the concept that the actin cytoskeleton is highly dynamic, and this dynamic remodeling is critical to its cellular role.…”

Involvement of inflammation-related miR-155 and miR-146a in diabetic nephropathy: implications for glomerular endothelial injury

“…Increasing evidence, predominantly from animal models of diabetes, shows that several fibrosis-related miRNAs, including miR-192 [ 10 , 11 ], miR-21 [ 12 ], miR-377 [ 13 ], and miR-221 [ 14 ], are involved in hyperglycemic conditions in different intrinsic renal cell types. Specific miRNAs, such as miR-155 and miR-146a, were initially linked with the inflammatory response by virtue of their potent up-regulation in multiple immune cell lineages by Toll-like receptor ligands, inflammatory cytokines, and specific antigens [ 15 - 17 ]. However, the pathogenic role of these miRNAs in the development of DN remains unknown.…”

Role of DDAH/ADMA pathway in TGF-β1-mediated activation of hepatic stellate cells

“…After cytoskeleton actin was disrupted, the activation of NF-κB was suppressed (29). ADMA has also been reported to increase TGF-β expression (33) and to induce kidney fibrosis (29) via activation of the NF-κB signaling pathway. However, the underlying molecular mechanisms were not elucidated.…”