Activation of Cannabinoid Receptor Type II by AM1241 Ameliorates Myocardial Fibrosis via Nrf2-Mediated Inhibition of TGF-β1/Smad3 Pathway in Myocardial Infarction Mice.
OBJECTIVE
Myocardial interstitial fibrosis is a major histologic landmark resulting in cardiac dysfunction after myocardial infarction (MI). Activation of cannabinoid receptor type II (CB2 receptor) have been demonstrated to reduce fibrosis in hepatic cirrhotic rat. However, the anti-fibrotic effect of CB2 receptor activation in infarcted hearts was still unclear. In this study, we aimed to investigate the effects of a CB2 receptor selective agonist AM1241 on myocardial fibrosis post MI in mice.


METHODS
Echocardiograph was conducted to assess cardiac function. Fibrosis markers such as type I and type III collagen, fibronectin, Plasminogen activator inhibitor(PAI)-1 and tissue inhibitor of metalloprotease(TIMP)-1 were examined by Western blot, while collagens were directly observed by Sirius-red staining. Primary cultured cardiac fibroblasts(CFs) were subjected to hypoxia/serum deprivation (H/SD) injury to simulate ischemic conditions in vivo. Nrf2 siRNA were applied to explore the role of Nrf2 and TGF-β1/Smad3 pathway in this process.


RESULTS
Echocardiography showed that AM1241 significantly improved cardiac function, suppressed the expression of fibrosis markers such as collagen I and collagen III, fibronectin, PAI-1 and TIMP-1 in mice with MI. In cardiac fibroblasts subjected to H/SD injury, AM1241 reduced the elevated levels of α-SMA, collagen I and collagen III, which were partially abrogated by the Nrf2 siRNA transfection. Furthermore, AM1241 not only activated and accelerated the translocation of Nrf2 to nucleus, but also inhibited TGF-β1/ Smad3 pathway in an Nrf2 dependent manner.


CONCLUSIONS
CB2 receptor agonist AM1241 alleviated myocardial interstitial fibrosis via Nrf2 -mediated down-regulation of TGF-β1/Smad3 pathway, which suggested that CB2 receptor activation might represent a promising target for retarding cardiac fibrosis after MI.
Department of Cardiology, Xijing Hospital, Fourth Military Medical University, Xi'an, China.
Xiang
X
Li
Dong
D
Han
Zuhong
Z
Tian
Beilei
B
Gao
Miaomiao
M
Fan
Congye
C
Li
Xiujuan
X
Li
Yabin
Y
Wang
Sai
S
Ma
Feng
F
Cao
D000818:Animals; D002186:Cannabinoids / Q000494:pharmacology; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024061:Collagen Type III / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D005355:Fibrosis; D005786:Gene Expression Regulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D058258:Serpin E2 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051900:Smad3 Protein / Q000235:genetics* / Q000378:metabolism; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics* / Q000378:metabolism
C439263:AM 1241; D002186:Cannabinoids; D024042:Collagen Type I; D024061:Collagen Type III; D005353:Fibronectins; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D034741:RNA, Small Interfering; D043885:Receptor, Cannabinoid, CB2; D058258:Serpin E2; C511869:Serpine2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C508961:Tgfb1 protein, mouse; C560825:Timp1 protein, mouse; D019715:Tissue Inhibitor of Metalloproteinase-1; D053773:Transforming Growth Factor beta1