Nuclear Envelope Protein-LaminA/C Modulates Apoptosis Of Vascular Smooth Muscle Cells During Cyclic Stretch

Vascular remodeling is one of the basic pathological processes of hypertension and other cardiovascular diseases.During hypertension,the cyclic stretch is abnormally increased which plays an important role in the pathogenesis of vascular remodeling.Vascular smooth muscle cells(VSMCs)locating in the media of vascular wall are exposed to the cyclic stretch in vivo.Therefore,it will be valuable to study the effect of different amplitude of cyclic stretch on the function of VSMCs,which may contribute to better understanding the pathogenesis of vascular remodeling.Our previous vascular proteomics study revealed that LaminA/C is mechano-sensitive molecule.When VSMCs are subjected to cyclic stretch,the expression of LaminA/C is significantly changed which participates dysfunctions of VSMCs during hypertension.However,the molecular mechanism involved in regulation of LaminA/C expression and the role of LaminA/C in the VSMC apoptosis during cyclic stretch application are still unclear.In the present study,VSMCs were subjected to different amplitudes of cyclic steetch in vitro: 0%(static control),5% cyclic stretch(physiological strain)or 15% cyclic stretch(pathological strain).The expression of 2 different selective cleavage isomers of LaminA/C,i.e.LaminA and LaminC,and the apoptosis of VSMCs were detected.The results showed that compared with 5% group,15% cyclic stretch significantly decreased the expression of LaminA and LaminC,and promoted the apoptosis of VSMCs.Using specific small interfering RNA(siRNA)transfection which targets on LMNA the encoding gene of LaminA/C,the expression of LaminA and LaminC in VSMCs was significantly decreased,and the apoptosis was significantly increased.In order to study the molecular mechanism involved in cyclic stretch regulating the expression of LaminA/C,we focused on the microRNA(miR).Bioinformatics analysis showed that the 3’ untranslated region(3’UTR)of LMNA has two potential binding sites to miR-124-3p.Double luciferase reported system revealed that both sites have binding abilities to miR-124-3p.Under static condition,miR-124-3p inhibitor significantly up-regulated the expression levels of LaminA and LaminC,while the miR-124-3p mimics significantly down-regulated them.RT-PCR results showed that 15% cyclic stretch significantly up-regulated the expression of miR-124-3p compared with 5% cyclic stretch.Furthermore in order to study the role of changeed LaminA/C in VSMC apoptosis,LMNA-specific siRNA was transfected to repress the expression of LaminA/C in VSMCs,and Protein/DNA microarray was used to detecte the activity of transcription factors.The transcription factors whose activity were changed significantly(increase or decrease more than 2 times)were analyzed by cluster analysis and ingenurity pathway analysis(IPA).Six transcription factors associated with apoptosis were screened,in which TP53 was activated by the specific siRNA transfection and the other 5 were inavtived,including EP300,NKX2.5,STAT1,MYC and WT1.In summary,the present study suggest that abnormally increased cyclic stretch(15%)up-regulates the expression of miR-124-3p in VSMCs,which subsequently targets on the 3’UTR of LMNA and decreases the expression of nuclear envelope protein LaminA/C;the repressed LaminA/C may play an important role in the apoptosis of VSMCs by regulating the activity of virious transcription factors,such as TP53,EP300,NKX2.5,STAT1,MYC and WT1.The present study may provide a new insight into understanding the molecular mechanisms of vascular remodeling.