Endoplasmic Reticulum Stress Is Implicated In Phenotype Transformation Of Cultured Human Glomerular Mesangial Cell Induced By High Glucose

Nowadays, the incidence rate of diabetic nephropathy(DN) increases rapidly all overthe world and it has become one of the most common cause of end-stage renal disease.Although volumes of very compelling studies have been published, exact mechanism of DNhas not been clarifiedand and successful therapeutics have not been developed. The mainpathological features of DN are proliferation of glomeruler mesangial cells andaccumulation of ECM. Transformation of HGMCs’ phenotype including hypertrophy ofHGMCs, increased secretion of α-SMA and ECM induced by hyperglycosemia is crucial inthe pathological process of DN. To date, it is considered that the pleiotropism of cellmetabolic stress induced by high glucose is a typical disbalance of signal net in cytoplasm,and the pathogenesy of DN is very complex which closely correlate with hemodynamicschanges in renal glomerulus, disordered metabolic pathway of polyatomic alcohol,abnormal expression of cytokines and so on. However, recent research suggest that ERS isprobably the key trigger of this signal net disbalance. As one of the biggest organelle, ERhas not only manage protein synthesis but also the integration place of signal pathways incytoplasm with a lot of signaling moleculars located on it. A lot of research has proved thatthe high glucose environment can induce cellular ERS in kinds of target cells includingHGMCs. So it is reasonable to believe that regulation of ERS could ameliorate the cellphenotype transformation induced by DN and may offer a new way to clinic therapeutics ofDN. ObjectiveTo study the role of endoplasmic reticulum stress in cultured human glomerularmesangial cells phenotype transformation induced by high glucose. And investigate theeffect of molecular chaperone4-PBA on glomerular mesangial cells by regulating ERS inhigh glucose environment.Methods1.Cultrued human glomerular mesangial cells were divided into three groups: controlgroup，high glucose group and high glucose+4-PBA group.2. CCK-8kit was used to assess cell number of proliferation.3. Cell cycle was measured by flow cytometric analysis.4. Expression of α-SMA was assessed by immunohistochemistry and observed throughlaser scanning confocal microscope.5. Involved mRNA and protein expression were measured by real-time RT-PCR andWestern blot analysis.Results1. Effects of high glucose and4-PBA on HGMCs cultured with high glucoseCompared with NC group, cell number of proliferation and S transitional proportionwere significantly increased in DN group HGMCs for indicated time, the expression ofα-SMA was significantly increased in HG group HGMCs for indicated time.4-PBA couldsignificantly inhibit the proliferation of cultural human glomerular mesangial cells andeffectively reduce the expression of α-SMA induced by high glucoseand. These resultsindicated that as an effective means of intervention,4-PBA remarkably inhibited theHGMCs transformate to the active phenotype.2. Expressions of ERS indicators in high glucose-cultured HGMCs and thetherapeuticrole of4-PBACompared with NC group, the expression of Grp78mRNA and protein weresignificantly increased in HG group HGMCs for indicated time. All the indices werepeaked at12h. Compared with HG group, the levels of Grp78mRNA and protein inHG+4-PBA group HGMCs were significantly decreased for indicated time. These results indicated that Endoplasmic Reticulum Stress was markedly elevated by high glucose invitro, and4-PBA could effectively attenuate it.3. Expression of key cytokines in HGMCs cultured with high glucose and thetherapeuticrole of4-PBACompared with NC group, the mRNA and protein expression of TGFβ1and FN weresignificantly increased in HG group HGMCs for indicated time. All the indices werepeaked at24h. Compared with HG group, the levels of mRNA and protein expression ofTGFβ1and FN in HG+4-PBA group HGMCs were significantly decreased for indicatedtime. At the same time, high glucose could mediate HGMCs to express more mRNA andprotein of NOX4and NF-kb,4-PBA could restrain this trend significantly. These resultsindicated that the expression of key cytokines of fibrosis, oxidative stress and inflammationof HGMCs in high glucose condition were significantly increased, and could also beobviously inhibited by4-PBA.Conclusions1. High glucose could induce typical cellular ERS in HGMCs.2. ERS is involved in the phenotype transformation of HGMCs induced by highglucose.