Low-density lipoprotein promotes epithelial-mesenchymal transition and extracellular matrix accumulation in human peritoneal mesothelial cells / 中华肾脏病杂志

ABSTRACT

Objective To investingate the effect of low-density lipoprotein (LDL) on epithelial -mesenchymal transition and extracellular matrix (ECM) accumulation in human peritoneal mesothelial cells (HPMCs).Methods (1)HPMCs were randomly divided into control group,LDL group (100 mg/L) and LDL (100 mg/L) + lactoferrin (100 mg/L,LDL receptor blocking agent) group.After co-cultured for 24 h,the expression of LDL receptor in HPMCs was examined by immunofluorescence staining,and the LDL uptake by HPMCs was observed with oil red O staining.(2)HPMCs were cultured with different concentrations of LDL (0,25,50,100 mg/L).After co-cultured for 24 h,the change of cell morphology was observed by inverted phase contrast microscope,and the expression of α-smooth muscle actin (α-SMA) was examined by immunofluorescence.(3) HPMCs were randomly divided into control group (5.6 mmol/L glucose),mannitol group (M,2.18％ mannitol),low glucose group (LG,30 mmol/L),high glucose group (HG,120 mmol/L) and HG + LDL group (120 mmol/L glucose + 100 mg/L LDL).Cocultured for 48 h,the mRNA expression of α-SMA,E-cadherin and type 1 plasminogen activator inhibitor (PAI-1) was detected by real-time quantitative PCR,the protein expression of α-SMA was detected by Western blotting,the content of type I collagen (Col I) and PAI-1 in supernatant was detected by ELISA.Results (1) After co-cultured with LDL for 24 h,the expressin of LDL receptor was found on the cell membrane of HPMCs.Oil red staining showed that LDL could be uptaken into the cells and abolished by LDL receptor blocker.(2) HPMCs tended to be loosely intercellular connected to each ofher,and prsesnted significant formation of fibroblast-like spindle morphology.The cytoplasm immunofluorescence intensity of α-SMA gradually increased with the increase of LDL concentration.Compared to the control group,the expressions of α-SMA mRNA and protein were significantly increased,and the expression of E-cadherin mRNA was decreased in HG + LDL group(all P ＜ 0.05).But the expressions of the parameters above-mentioned were not significant different between HG group and HG + LDL group or between HG group and control group.(3) Compared with HG group or control group,the concentrations of Col Ⅰ [(19.27±0.17) μg/L vs (14.09±0.30) μg/L or (14.81±0.91) μg/L,all P ＜ 0.05] and PAI-1 [(498.24±76.91) ng/L vs (342.19±30.43) ng/L or (220.39±33.82) ng/L,all P ＜ 0.05] in supernatant of HPMCs were significantly up-regulated in HG + LDL group,meanwhile the expression of PAI-1 mRNA was significantly higer than that in control group (P =0.022).Conclusions HPMCs uptake LDL into cells via LDL receptors.LDL can induce HPMCs transdifferentiation in the condition of high glucose,increase the secretion of Col Ⅰ,inhibit the degradation of ECM through up-regulating the expression of PAI-1,and lead to ECM accumulation.