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To investigate the role of TRPA1 in the development of pathological cardiac hypertrophy.
The C57/B6J mice were randomly assigned to either transverse aortic constriction (TAC) or a sham operation. The mice were received oral daily treatment with vehicle or HC-030031 (HC, 10 mg/kg), a selective TRPA1 antagonist, by gastric gavage and started one week after surgery and maintained for a further 3 weeks. The four groups were named as sham + vehicle, sham + HC, TAC +vehicle and TAC +HC respectively. Neonatal rat cardiomyocytes (NRCMs) was also treated with angiotensin II (Ang II 1 μmol/L) with or without HC (100μmol/L) for 24 hours to induce hypertrophy. Cardiac hypertrophy was evaluated through morphological assessments, echocardiographic parameters and histological analyses. The RT-PCR, Western blot and Immunofluorescence analysis were also applied.
The results indicated that TRPA1 expression was upregulated in the hearts of patients with hypertrophic cardiomyopathy (HCM) and in mice models of pressure overload-induced cardiac hypertrophy. Consistently, high TRPA1 protein levels were also found in NRCMs that were stimulated with Ang II for 24 or 48 h compared with PBS-treated controls. Next, the hypertrophic response was significantly suppressed in HC-treated mice after 4 weeks of TAC, as demonstrated by direct examination of the gross heart, the myocyte cross sectional area (CSA), heart weight/body weight (HW/BW), heart weight/tibia length (HW/TL), lung weight/body weight (LW/BW), and lung weight/tibia length (LW/TL) compared to the sham group. Meanwhile, echocardiographic was used to determine cardiac function of mice in each group. Mice exhibited increased left ventricular end-diastolic diameter (LVEDD) and left ventricular end-systolic diameter (LVESD), and decreased ejection fraction (EF) and fractional shortening (FS), in response to TAC. However, HC treatment significantly attenuated the chamber dilation and dysfunction of the left ventricle (LV) exposed to pressure overload. Similarly, the mRNA expression levels of several hypertrophic markers, including ANP, BNP, and β-MHC after TAC surgery were also significantly blunted in HC-treated mice compared with TAC-treated group. Dramatic interstitial fibrosis was observed in mice subjected to TAC surgery, but HC administration attenuated interstitial fibrosis obviously compared with mice after subjected to TAC. Finally, the mRNA levels of the fibrotic markers CTGF, collagen I, collagen III, and TGFβ1 were markedly decreased in the hearts of HC-treated mice instead of vehicle administration mice after subjected to TAC. Interestingly, there were no differences between HC and vehicle in sham group. We subsequently performed the functional contribution of TRPA1 in vitro studies using cultured NRCMs. Obviously, Ang II-induced cell hypertrophy was abolished in HC-treated cardiomyocytes, as detected by CSA. In accordance with these results, the mRNA expression levels of cardiac hypertrophic markers, including ANP, BNP, and β-MHC, were remarkably a suppressed in HC administration cardiomyocytes in response to Ang II. Consequently, our data indicated that CaMKII was significantly activated in TAC mice. Also, HC reduced the activation of CaMKII after TAC.
The loss of function of the TRPA1 protected against cardiac hypertrophy and fibrosis with pressure overload or Ang II challenge, which involve in Ca2+/ CaMKII pathway.