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

Asymmetric dimethylarginine: An crucial regulator in tissue fibrosis

Fibrosis is a reparative process with very few therapeutic options to prevent its progression to organ dysfunction. Chronic fibrotic diseases contribute to an estimated 45% of all death in the industrialized world. Asymmetric dimethylarginine (ADMA), an endothelial nitric oxide synthase inhibitor, plays a crucial role in the pathogenesis of various cardiovascular diseases associated with endothelial dysfunction. Recent reports have focused on ADMA in the pathogenesis of tissue fibrosis. This review discusses the current knowledge about ADMA biology, its association with risk factors of established fibrotic diseases and the potential pathophysiological mechanisms implicating ADMA in the process of tissue fibrosis.

MicroRNA-326-3p ameliorates high glucose and ox-LDL-IC- induced fibrotic injury in renal mesangial cells by targeting FcγRIII

AIM

The aim of the present study was to identify the regulatory relationship between miR-326-3p and FcγRIII, and to explore the involvement of miR-326-3p/FcγRIII/TGF-β/Smad signalling pathway in fibrotic injury, which was induced by the high glucose (HG) and oxidized low density lipoprotein immune complex (ox-LDL-IC) in mouse glomerular mesangial cells (GMCs).

METHODS

Dual-luciferase reporter system and real time PCR (RT-PCR) were used to identify FcγRIII as a target gene of miR-326-3p. Lentiviral transduction was used to construct different expression of miR-326-3p in GMCs, which were divided into three groups: miR-326-3p mimics group (miR-326-3p group), miR-326-3p inhibitor group (miR-326-3p-inhibit group) and scramble control group (control group). Then, each group was stimulated by normal glucose (NG), HG, ox-LDL-IC and HG + ox-LDL-IC, respectively. RT-PCR and western blot were used to measure the expressions of Col-I, CTGF, α-SMA, TGF-β, Smad2/3 and pSmad2/3.

RESULTS

FcγRIII was regulated negatively by miR-326-3p in GMCs under the condition of HG and ox-LDL-IC, which implied FcγRIII as a target gene of miR-326-3p. Furthermore, compared with normal glucose group, the expressions of Col-I, CTGF, α-SMA, TGF-β and pSmad2/3 were higher under the condition of HG, ox-LDL-IC and HG + ox-LDL-IC (P < 0.05). In particular, miR-326-3p-inhibit groups exhibited the most significant increase (P < 0.05), while miR-326-3p could attenuate the increase (P < 0.05).

CONCLUSION

FcγRIII was identified as a target gene of miR-326-3p. MiR-326-3p/FcγRIII/TGF-β/Smad signaling pathway was investigated to be involved in the pathophysiology of renal fibrosis of DKD.

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

Asymmetric dimethylarginine (ADMA) is catalyzed by the enzyme dimethylarginine dimethylaminohydrolase (DDAH) in humans, and the role for ADMA has been associated with hepatic fibrogenesis. Transforming growth factor‑β (TGF‑β) has been shown to mediate the myofibroblastic transformation of quiescent hepatic stellate cells (HSCs), a pivotal step in liver fibrogenesis. However, the underlying molecular mechanisms are not well understood. Accumulation of ADMA due to low activity of DDAH has been reported to be associated with liver damage and hepatic fibrosis. In this study, the role of the DDAH/ADMA pathway in the TGF‑β1‑induced HSC activation was assessed. Freshly harvested primary HSCs from rat liver were used in this study. It was demonstrated that TGF‑β1 treatment significantly suppressed the DDAH protein expression and activity, and increased levels of ADMA in the culture medium of rat primary HSCs. Notably, the TGF‑β1‑mediated effects on DDAH/ADMA were significantly abrogated by the p38 mitogen activated protein kinase specific inhibitor, SB203580. Furthermore, it was demonstrated that excessive ADMA led to an increase in the number of TGF‑β1‑positive HSCs and induced the expression of α‑smooth muscle actin and collagen type I in rat primary HSCs. In addition, rat primary HSCs exposed to excessive ADMA showed a significant increase in the expressions of α‑SMA and collagen type I. Finally, it was revealed that ADMA treatment promoted the proliferation of rat primary HSCs. In conclusion, the results obtained from the study suggest a potentially novel role for the ADMA/DDAH1 signaling pathway in TGF‑β1‑induced HSC activation, and along with the studies of others, suppression of the ADMA/DDAH1 pathway may be an alterative approach for the treatment of liver fibrosis.

The cytoskeleton as a novel target for treatment of renal fibrosis

The incidence of chronic kidney disease (CKD) is increasing, with an estimated prevalence of 12% in the United States (Synder et al., 2009). While CKD may progress to end-stage renal disease (ESRD), which necessitates renal replacement therapy, i.e. dialysis or transplantation, most CKD patients never reach ESRD due to the increased risk of death from cardiovascular disease. It is well-established that regardless of the initiating insult - most often diabetes or hypertension - fibrosis is the common pathogenic pathway that leads to progressive injury and organ dysfunction (Eddy, 2014; Duffield, 2014). As such, there has been extensive research into the molecular and cellular mechanisms of renal fibrosis; however, translation to effective therapeutic strategies has been limited. While a role for the disruption of the cytoskeleton, most notably the actin network, has been established in acute kidney injury over the past two decades, a role in regulating renal fibrosis and CKD is only recently emerging. This review will focus on the role of the cytoskeleton in regulating pro-fibrotic pathways in the kidney, as well as data suggesting that these pathways represent novel therapeutic targets to manage fibrosis and ultimately CKD.

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

BACKGROUND

MicroRNAs have been demonstrated to play an important role in the pathogenesis of diabetic nephropathy (DN). In this study, we investigated both the repertoire of miRNAs in the kidneys of patients with DN and their potential regulatory role in inflammation-mediated glomerular endothelial injury.

METHODS

The miRNA expression profiling of the renal biopsy samples was performed by a microarray analysis; then, in situ hybridization and real-time polymerase chain reaction (PCR) were used to determine the localization and expression of two of the miRNAs significantly up-regulated in human DN kidney samples, miR-155 and miR-146a, in the kidney tissues from type 1 and type 2 DN rat models. Human renal glomerular endothelial cells (HRGECs) cultured under high-glucose conditions were transfected with miR-155 and miR-146a mimics, and the transforming growth factor (TGF)-β1, tumor necrosis factor (TNF)-α, and nuclear factor (NF)-κB expressions were examined by western blot, real-time PCR, and an electrophoresis mobility shift assay.

RESULTS

The expression of both miR-155 and miR-146a was increased more than fivefold in the kidney samples of the DN patients compared with the controls, and the miR-155 expression was closely correlated with the serum creatinine levels (R = 0.95, P = 0.004). During the induction and progression of the disease in type 1 and type 2 DN rat models, miR-155 and miR-146a were demonstrated to increase gradually. In vitro, high glucose induced the over-expression of miR-155 and miR-146a in the HRGECs, which, in turn, increased the TNF-α, TGF-β1, and NF-κB expression.

CONCLUSIONS

Taken together, these findings indicate that the increased expression of miR-155 and miR-146a in the DN patients and in the experimental DN animal models was found to contribute to inflammation-mediated glomerular endothelial injury.

Role of kidney biomarkers of chronic kidney disease: An update

Chronic kidney disease (CKD) is a progressive pathological condition marked by deteriorating renal function over time. Diagnostic of kidney disease depend on serum creatinine level and glomerular filtration rate which is detectable when kidney function become half. The detection of kidney damage in an early stage needs robust biomarkers. Biomarkers allow monitoring the disease progression at initial stages of disease. On the onset of impairment in cellular organization there is perturbation in signaling molecules which are either up-regulated or down-regulated and act as an indicator or biomarker of diseased stage. This review compiled the cell signaling of different kidney biomarkers associated with the onset of chronic kidney diseases. Delay in diagnosis of CKD will cause deterioration of nephron function which leads to End stage renal disease and at that point patients require dialysis or kidney transplant. Detailed information on the complex network in signaling pathway leading to a coordinated pattern of gene expression and regulation in CKD will undoubtedly provide important clues to develop novel prognostic and therapeutic strategies for CKD.