Influence Of Mevalonate To Human Mesangial Cell And Its Mechanisms

Background Mesangial proliferative glomerulonephritis is the most common form of primary glomerular disease in China, which is characterized by mesangial cell(MC) proliferation and extracellular matrix (ECM) deposition resulting in golmerular sclerosis and end-stage renal disease. MC participate in various forms of glomerular injury by proliferation and secretion of cytokines such as transforming growth factor beta (TGF-β₁), which regulates cell proliferation and differentiation thus promotes ECM, including normally existed component such as collagen typeâ…£(Col-â…£) and interstitial collagen such as collagen typeâ… (Col-â… ), expansion. Dysregulation cell apoptosis also contribute to ECM expansion. Bcl-2 family members, such as Bcl-2 (an anti-apoptotic protein) and Bax (a pro-apoptotic protein) are important regulators of cell apoptosis, and the ratio of Bcl-2 to Bax determines survival or apoptosis of mesangial cell. Mechanisms of mesangial cell proliferation and ECM deposition is not clearly understood yet. Hyperlipemia is responsible for many renal diseases, and the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors exert modulatory effects on a number of cell signaling cascades, including cell proliferation, signal transduction and cell apoptosis, by preventing the synthesis of various isoprenoids derived from the mevalonate (MVA) pathway. Mitogen- activated protein kinases (MAPKs), including extracellular signal.regulated kinase (ERK), c-Jun NH2-teminal Kinase (JNK)/stress-activated protein kinase, (SAPK), P38MAPK and ERK5/BMK1 (Extracellular Signal-related Protein K), are key regulators of mesangial cell proliferation and ECM deposition, thus closely related with the development of mesangial proliferative glomerulonephritis. But the influence of MVA to mesangial cell and its mechanisms as well as the influence of MVA to the MAPKs and downstream transcription factors are currently unknown. The relationship of the MAPKs in MC is not clear yet.Objective To investigate the effects of MVA on human mesangial cell (HMC) proliferation, apoptosis, cell cycle and extracellular matrix deposition, as well as the role of TGF-β₁ and the MAPKs in the processes in order to explore the mechanism of MVA in the development of mesangial proliferative glomerulonephritis.Methods 1. Cultured HMC were divided into 8 groups according to the concentration of MVA(0nmol/l, 1×10^-9mol/L, 1×10^-8mol/L,1×10^-7mol/L,1×10^-6mol/L,1×10^-5mol/L,1×10^-4 mol/L,1×10^-3 mol/L). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra- zolium bromide (MTT) reduction assay was used to measure the proliferation of HMC and flow cytometry was explored to assess the proliferative index (PI). 2. HMC were divided into the following 2 groups, control group and MVA group, and were cultured for 12 h, 24 h and 48 h. Cell proliferation was measured by MTT. PI and cell apoptosis were assessed by flow cytometry. The secretion of transforming growth factor beta 1 (TGF-β₁), Col-â…£and Col-â… were measured by enzyme linked immunosorbent assay (ELISA). Expressions of Bcl-2 and Bax were assessed by Western blot analysis. 3. HMC were divided into the following 8 groups, control group, PD98059 (ERK inhibitor) group, SP600125 (JNK inhibitor) group, SB203580 (P38 MAPK inhibitor) group, MVA group, MVA+ PD98059 group, MVA+SP600125 group and MVA+SB203580 group. Cell proliferation, PI, cell apoptosis, TGF-β₁, Col-â…£, Col-â… , Bcl-2 and Bax expressions as well as p-ERK1/2,p-JNK,p-p38 were measured. 4. Inhibitors of each MAPK were used separately to assess the role of ERK, JNK and P38 MAPK.Results 1. MVA promoted HMC proliferation and increase PI in a concentration-dependent manner ranging from 1×10^-9mol/L to 1×10^-7mol/L and a time-dependent manner ranging from 12 h to 48 h. 2. MVA of 1×10^-7mol/L promoted HMC proliferation, increased PI, TGF-α₁,Col-â…£, Col-â… secretions and up-regulated Bcl-2 and Bax expressions. These effects could be partly reversed by ERK or JNK inhibitor, while P38 MAPK inhibitor had no influence.Conclusion MVA promoted HMC proliferation and ECM deposition by proliferation effects of TGF-β₁ and by cell apoptosis inhibitory effects, which were mediated, at lease partly, by JNK and ERK MAPK pathways.