Cardiac protective effects of irbesartan via the PPAR-gamma signaling pathway in angiotensin-converting enzyme 2-deficient mice.
BACKGROUND
Angiotensin-converting enzyme 2 (ACE2), a monocarboxypeptidase which metabolizes angiotensin II (Ang II) to generate Ang-(1-7), has been shown to prevent cardiac hypertrophy and injury but the mechanism remains elusive. Irbesartan has the dual actions of angiotensin receptor blockade and peroxisome proliferator-activated receptor-γ (PPARγ) activation. We hypothesized that irbesartan would exert its protective effects on ACE2 deficiency-mediated myocardial fibrosis and cardiac injury via the PPARγ signaling.


METHODS
10-week-old ACE2 knockout (ACE2KO; Ace2(-/y)) mice received daily with irbesartan (50 mg/kg) or saline for 2 weeks. The wild-type mice (Ace2(+/y)) were used to the normal controls. We examined changes in myocardial ultrastructure, fibrosis-related genes and pathological signaling by real-time PCR gene array, Western blotting, Masson trichrome staining and transmission electron microscope analyses, respectively.


RESULTS
Compared with the Ace2(+/y) mice, cardiac expression of PPARα and PPARγ were reduced in Ace2(-/y) mice and the myocardial collagen volume fraction (CVF) and expression of fibrosis-related genes were increased, including transforming growth factor-β1 (TGFβ1), connective tissue growth factor (CTGF), collagen I and collagen III. Moreover, ACE2 deficiency triggered cardiac hypertrophy, increased myocardial fibrosis and adverse ultrastructure injury in ACE2KO hearts with higher levels of atrial natriuretic factor (ANF) and phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), without affecting cardiac systolic function. Intriguingly, treatment with irbesartan significantly reversed ACE2 deficiency-mediated pathological hypertrophy and myocardial fibrosis in Ace2(-/y) mice linked with enhancement of plasma Ang-(1-7) level and downregulation of AT1 receptor in heart. Consistent with attenuation of myocardial fibrosis and ultrastructure injury, the myocardial CVF and levels of ANF, TGFβ1, CTGF, collagen I, collagen III and phosphorylated ERK1/2 were lower, and expression of PPARγ was higher in ACE2KO mice in response to irbesartan treatment, without affecting cardiac expression of PPARα, PPARδ, β-myosin heavy chain, TGFβ2 and fibronectin.


CONCLUSIONS
We conclude that irbesartan prevents ACE2 deficiency-mediated pathological hypertrophy and myocardial fibrosis in ACE2 mutant mice via activation of the PPARγ signaling and suppression of the TGFβ-CTGF-ERK signaling, resulting in attenuation of myocardial injury. Drugs targeting ACE2 and PPARγ represent potential candidates to prevent and treat myocardial injury and related cardiac disorders.
State Key Laboratory of Medical Genomics, Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai Institute of Hypertension, 197 Ruijin 2nd Road, Shanghai, 200025, China. gaopingjin@sibs.ac.cn.
Zhen-Zhou
ZZ
Zhang
Qian-Hui
QH
Shang
Hai-Yan
HY
Jin
Bei
B
Song
Gavin Y
GY
Oudit
Lin
L
Lu
Tong
T
Zhou
Ying-Le
YL
Xu
Ping-Jin
PJ
Gao
Ding-Liang
DL
Zhu
Josef M
JM
Penninger
Jiu-Chang
JC
Zhong
D000803:Angiotensin I / Q000378:metabolism; D000804:Angiotensin II / Q000378:metabolism; D000085962:Angiotensin-Converting Enzyme 2; D000818:Animals; D001713:Biphenyl Compounds; D006332:Cardiomegaly / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D002316:Cardiotonic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D003094:Collagen / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005355:Fibrosis; D005786:Gene Expression Regulation / Q000187:drug effects; D000077405:Irbesartan; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009206:Myocardium / Q000201:enzymology / Q000473:pathology / Q000648:ultrastructure; D047493:PPAR alpha / Q000235:genetics / Q000378:metabolism; D047494:PPAR delta / Q000235:genetics / Q000378:metabolism; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D007703:Peptidyl-Dipeptidase A / Q000172:deficiency* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013777:Tetrazoles; D016212:Transforming Growth Factor beta / Q000378:metabolism
D001713:Biphenyl Compounds; C526318:CCN2 protein, mouse; D002316:Cardiotonic Agents; D047493:PPAR alpha; D047494:PPAR delta; D047495:PPAR gamma; D010446:Peptide Fragments; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D016212:Transforming Growth Factor beta; D000804:Angiotensin II; D055513:Connective Tissue Growth Factor; D003094:Collagen; D000803:Angiotensin I; D048049:Extracellular Signal-Regulated MAP Kinases; D007703:Peptidyl-Dipeptidase A; C000705328:Ace2 protein, mouse; D000085962:Angiotensin-Converting Enzyme 2; C118790:angiotensin I (1-7); D000077405:Irbesartan