Shun Wang1, Mian Cheng2, Zhengqing Hu3, Shan Hu1, Qiang Zou1, Xin Lai1, Beilei Liu1, Hong Jiang1, Congxin Huang1, Gang Wu1,3. 1. Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China. 2. Department of Geriatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China. 3. Department of Cardiology, Ezhou Hospital, Renmin Hospital of Wuhan University, Ezhou, China.
Abstract
BACKGROUND/AIMS: Angiotensin II (Ang II) has been shown to promote cardiac remodeling during the process of hypertrophy. Myosin light chain kinase (MLCK), a specific kinase for the phosphorylation of myosin light chain 2 (MLC2), plays an important role in regulating cardiac muscle contraction and hypertrophy. However, whether Ang II could facilitate cardiac hypertrophy by altering the expression of MLCK remains unclear. This study aimed to investigate this effect and the underlying mechanisms. METHODS: Cardiac hypertrophy was induced via pressure overload in rats, which were then evaluated via histological and biochemical measurements and echocardiography. Angiotensin-converting enzyme inhibitor (ACEI) was used to inhibit Ang II. Neonatal rat cardiomyocytes were stimulated with Ang II to induce hypertrophy and were treated with a matrix metalloproteinase 9 (MMP9) inhibitor. Myocyte hypertrophy was evaluated using immunofluorescence and qRT-PCR. Degradation of recombinant human MLCK by recombinant human MMP9 was tested using a cleavage assay. The expression levels of MLCK, MLC2, phospho-myosin light chain 2 (p-MLC2), myosin phosphatase 2 (MYPT2), and calmodulin (CaM) were measured using western blotting. RESULTS: ACEI improved cardiac function and remodeling and increased the levels of MLCK and p-MLC2 as well as reduced the expression of MMP9 in pressure overload-induced cardiac hypertrophy. Moreover, the MMP9 inhibitor alleviated myocyte hypertrophy and upregulated the levels of MLCK and p-MLC2 in Ang II-induced cardiomyocyte hypertrophy. Recombinant human MLCK was concentration- and time-dependently degraded by recombinant human MMP9 in vitro, and this process was prevented by the MMP9 inhibitor. CONCLUSION: Our results suggest that Ang II is involved in the degradation of MLCK in pressure overload-induced cardiac hypertrophy and that this process was mediated by MMP9.
BACKGROUND/AIMS: Angiotensin II (Ang II) has been shown to promote cardiac remodeling during the process of hypertrophy. Myosin light chain kinase (MLCK), a specific kinase for the phosphorylation of myosin light chain 2 (MLC2), plays an important role in regulating cardiac muscle contraction and hypertrophy. However, whether Ang II could facilitate cardiac hypertrophy by altering the expression of MLCK remains unclear. This study aimed to investigate this effect and the underlying mechanisms. METHODS:Cardiac hypertrophy was induced via pressure overload in rats, which were then evaluated via histological and biochemical measurements and echocardiography. Angiotensin-converting enzyme inhibitor (ACEI) was used to inhibit Ang II. Neonatal rat cardiomyocytes were stimulated with Ang II to induce hypertrophy and were treated with a matrix metalloproteinase 9 (MMP9) inhibitor. Myocyte hypertrophy was evaluated using immunofluorescence and qRT-PCR. Degradation of recombinant humanMLCK by recombinant humanMMP9 was tested using a cleavage assay. The expression levels of MLCK, MLC2, phospho-myosin light chain 2 (p-MLC2), myosin phosphatase 2 (MYPT2), and calmodulin (CaM) were measured using western blotting. RESULTS: ACEI improved cardiac function and remodeling and increased the levels of MLCK and p-MLC2 as well as reduced the expression of MMP9 in pressure overload-induced cardiac hypertrophy. Moreover, the MMP9 inhibitor alleviated myocyte hypertrophy and upregulated the levels of MLCK and p-MLC2 in Ang II-induced cardiomyocyte hypertrophy. Recombinant humanMLCK was concentration- and time-dependently degraded by recombinant humanMMP9 in vitro, and this process was prevented by the MMP9 inhibitor. CONCLUSION: Our results suggest that Ang II is involved in the degradation of MLCK in pressure overload-induced cardiac hypertrophy and that this process was mediated by MMP9.