title: Mechanical stress-evoked but angiotensin II-independent activation of angiotensin II type 1 receptor induces cardiac hypertrophy through calcineurin pathway.
abstract: Mechanical stress can induce cardiac hypertrophy through angiotensin II (AngII) type 1 (AT(1)) receptor independently of AngII, however, the intracellular mechanisms remain largely indeterminate. Since calcineurin, a Ca(2+)-dependent phosphatase, plays a critical role in pressure overload-induced cardiac hypertrophy, we therefore, asked whether calcineurin is involved in the AT(1) receptor-mediated but AngII-independent cardiac hypertrophy. Mechanical stretch failed to elicit hypertrophic responses in COS7 cells co-transfected with plasmid of AT(1) receptor and siRNA of calcineurin. Mechanical stresses for 2weeks in vivo and for 24h in vitro significantly induced upregulation of calcineurin expression and hypertrophic responses, such as the increases in cardiomyocytes size and specific gene expressions, in cardiomyocytes of angiotensinogen gene knockout (ATG(-/-)) mice, both of which were significantly suppressed by a specific calcineurin inhibitor FK506, suggesting a critical role of calcineurin in mechanical stress-induced cardiac hypertrophy in the ATG(-/-) mice. Furthermore, an AT(1) receptor blocker Losartan not only attenuated cardiac hypertrophy but also abrogated upregulation of cardiac calcineurin expression induced by mechanical stresses in the AngII-lacking mice, indicating that calcineurin expression is regulated by AT(1) receptor without the involvement of AngII after mechanical stress. These findings collectively suggest that mechanical stress-evoked but AngII-independent activation of AT(1) receptor induces cardiac hypertrophy through calcineurin pathway.
authors.affiliation: Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, 180 Feng Lin Road, Shanghai 200032, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhou
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Gong
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Niu
authors.forename: Aijun
authors.initials: A
authors.lastname: Sun
authors.forename: Junbo
authors.initials: J
authors.lastname: Ge
authors.forename: Yunzeng
authors.initials: Y
authors.lastname: Zou
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D006332:Cardiomegaly / Q000378:metabolism / Q000503:physiopathology* / Q000517:prevention & control; D002522:Chlorocebus aethiops; D019808:Losartan / Q000494:pharmacology; D051379:Mice; D008817:Mice, Mutant Strains; D044140:Receptor, Angiotensin, Type 1 / Q000819:agonists / Q000378:metabolism*; D013314:Stress, Mechanical; D016559:Tacrolimus / Q000494:pharmacology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D065095:Calcineurin Inhibitors; D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D019703:Calcineurin; D019808:Losartan; D016559:Tacrolimus