| Background and aims:Pancreatic fibrosis is a major pathological feature of chronic pancreatitis(CP),pancreatic stellate cells(PSC)play a key role in the occurrence and development of pancreatic fibrosis in CP.In healthy pancreas,PSC is quiescent,which contains vitamin A containing lipid droplets(LD)in cytoplasm upon injuring of pancreas,PSC can be activated which losts LD in its cytoplasm,showing myofibroblast-like phenotypic changes and expressing of activation marker α-smooth muscle actin(α-SMA).Retinol and its active metabolites have been confirmed to induce the transformation of PSC from activated to quiescent,inhibiting the synthesis of extracellular matrix and playing an anti-fibrosis effect.However,the role of all-trans retinoic acid(ATRA)in lipid metabolism of PSC is unknown.The aim of this study was to determine the effects of ATRA on lipid metabolism and lipid particles of PSC.Methods: The rat activated pancreatic stellate cell line(RP-2 cells)was used in this study.After treatment of RP-2 cells with ATRA,the formation of cytoplasmic lipid particles in PSC induced by ATRA was detected by Bodipy fluorescence staining,PSC proteome was detected by liquid chromatography-mass spectrometry(LC-MS/MS).The expression of ɑ-SMA m RNA and protein in PSC were detected by q RT-PCR and ELISA respectively.Results:(1)Bodipy fluorescence staining showed that ATRA could significantly promote the formation of lipid particles in RP-2 cells.(2)The proteomic changes of PSC in ATRA versus control group(Ctrl)were detected by LC-MS/MS,and the differential proteins related to lipid metabolism were analyzed and classified:A.ATRA could up-regulate retinol binding protein 1(RBP1),short chain dehydrogenase/reductase(SDR),acyl-Co A: diacylglycerol acyltransferase 1(DGAT1)and retinol dehydrogenase 11(RDH11)in RP-2 cells,and down-regulate lysosomal acid lipase(LAL)which promotes retinyl ester hydrolysis,indirectly suggesting that ATRA may promote retinyl ester synthesis in PSC;B.ATRA could up-regulate CREB-regulated transcription coactivator 2(CRTC2),ATP-binding cassette subfamily A member 1(ABCA1),oxysterol-binding protein(OSBPL3),OSBPL6 and PAS domain containing serine(PASK),but down-regulate tubby-like protein(TULP3)in PSC,which indirectly suggests that ATRA may promote the synthesis of triglycerides and cholesterol esters of PSC;C.ATRA could up-regulate acyl-Co A desaturase 1(SCD1),MORC family CW-type zinc finger 2(MORC2),acetyl-Co A carboxylase 1(ACACA)and fatty acid synthase(FASN),and down-regulate serine palmitoyltransferase 2(SPTLC2),long-chain-fatty-acid--Co A ligase 5(ACSL5),protein S100-A4(S100A4)and AF4/FMR2 family,member 1(AFF1)in RP-2 cells,suggesting indirectly that ATRA can accelerate the turnover of fatty acid the remodeling of phospholipid to promote the formation of LD.(3)ATRA could inhibit the expression of α-SMA in rat PSC and induce the transition from activated to quiescent.Conclusions: The results of this study indicate that ATRA can induce PSC to have multiple effects in retinyl ester and neutral lipid(triglycerides and cholesterol esters)synthesis and bilaterally regulations in the protein related to metabolism of fatty acids and that ATRA can inhibit the expression of α-SMA and induce the formation of LD in the PSC.These results indirectly suggest that ATRA may lead to the formation of LD by promoting the synthesis of retinyl ester,triglyceride and cholesteryl ester and by accelerating the turnover of fatty acid and the remodeling of phospholipid in the PSC,leading to the conversion of activated PSC to quiescence.This study provides an experimental basis for ATRA targeting PSC to inhibit pancreatic fibrosis. |
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