Mechanical stretch induces the apoptosis regulator PUMA in vascular smooth muscle cells.
OBJECTIVE
The expression of PUMA (p53-up-regulated modulator of apoptosis), an apoptosis-regulating gene, increases during endoplasmic reticulum stress. The mechanisms by which cyclic stretch influences the regulation of PUMA in vascular smooth muscle cells (VSMCs) during apoptosis remain unclear. We hypothesized that cyclic stretch enhances PUMA expression in VSMCs undergoing apoptosis.


RESULTS
Human VSMCs grown on a Flexcell I flexible membrane base were stretched via vacuum to 20% of elongation at a frequency of 1 Hz. An in vivo model of volume overload with aorta-caval shunt and pressure overload with aortic banding in adult rats was used to study PUMA expression. Cyclic stretch markedly enhanced PUMA protein and gene expression after stretch. Addition of c-jun N-terminal kinase (JNK) inhibitor SP600125 and interferon-γ (IFN-γ) antibody 30 min before stretch inhibited PUMA expression. Gel shift assay demonstrated that stretch increased the DNA binding activity of interferon regulatory factor-1 (IRF-1). SP600125, JNK small interfering RNA, and IFN-γ antibody attenuated the DNA binding activity induced by stretch. PUMA-Mut plasmid, SP600125, and IRF-1 antibody attenuated the promoter activity. Stretch increased secretion of IFN-γ from VSMCs, and conditioned media from stretched VSMCs increased PUMA protein expression. The in vivo model of aorta-caval shunt and aortic banding also showed increased PUMA protein expression in the aorta.


CONCLUSIONS
Cyclic mechanical stretch increases PUMA expression in cultured human VSMCs. The PUMA expression induced by stretch is mediated by IFN-γ, JNK, and IRF-1 pathways. These findings suggest that PUMA is an important mediator in VSMC apoptosis induced by stretch.
Division of Cardiology, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
Wen-Pin
WP
Cheng
Bao-Wei
BW
Wang
Shih-Chung
SC
Chen
Hang
H
Chang
Kou-Gi
KG
Shyu
D000818:Animals; D001011:Aorta / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000235:genetics; D001483:Base Sequence; D002478:Cells, Cultured; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism; D007371:Interferon-gamma / Q000096:biosynthesis / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013314:Stress, Mechanical; D015854:Up-Regulation
D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; C533952:Bbc3 protein, rat; D050856:Interferon Regulatory Factor-1; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D007371:Interferon-gamma; D048031:JNK Mitogen-Activated Protein Kinases