Cardiac-specific overexpression of metallothionein attenuates myocardial remodeling and contractile dysfunction in l-NAME-induced experimental hypertension: Role of autophagy regulation.

Abstract

Hypertension is an independent risk factor for heart disease and is responsible for the increased cardiac morbidity and mortality. Oxidative stress plays a key role in hypertensive heart diseases although the precise mechanism remains unclear. This study was designed to examine the effect of cardiac-specific overexpression of metallothionein, a cysteine-rich antioxidant, on myocardial contractile and intracellular Ca(2+) anomalies in N(G)-nitro-l-arginine methyl ester (l-NAME)-induced experimental hypertension and the mechanism involved with a focus on autophagy. Our results revealed that l-NAME treatment (14 days) led to hypertension and myocardial anomalies evidenced by interstitial fibrosis, cardiomyocyte hypertrophy, increased LV end systolic and diastolic diameters (LVESD and LVEDD) along with suppressed fractional shortening. l-NAME compromised cardiomyocyte contractile and intracellular Ca(2+) properties manifested as depressed peak shortening, maximal velocity of shortening/relengthening, electrically-stimulated rise in intracellular Ca(2+), elevated baseline and peak intracellular Ca(2+). These l-NAME-induced histological and mechanical changes were attenuated or reconciled by metallothionein. Protein levels of autophagy markers LC3B and p62 were decreased and increased, respectively. Autophagy signaling molecules AMPK, TSC2 and ULK1 were inactivated while those of mTOR and p70s6K were activated by l-NAME, the effects of which were ablated by metallothionein. Autophagy induction mimicked whereas autophagy inhibition nullified the beneficial effect of metallothionein against l-NAME. These findings suggested that metallothionein protects against l-NAME-induced myocardial anomalies possibly through restoration of autophagy.

• Authors: Lifang Yang, Jian-Yuan Gao, Jipeng Ma, Xihui Xu, Qiurong Wang, Lize Xiong, Jian Yang, Jun Ren
• Journal: Toxicology letters (Toxicol Lett) Vol. 237 Issue 2 Pg. 121-32 (Sep 02 2015) ISSN: 1879-3169 [Electronic] Netherlands
• PMID: 26068063 (Publication Type: Journal Article)
• Copyright: Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Reactive Oxygen Species
• Metallothionein
• Calcium
• NG-Nitroarginine Methyl Ester
• Sirolimus

Topics

• Animals
• Autophagy (physiology)
• Calcium (metabolism)
• Hypertension (chemically induced, physiopathology)
• Male
• Metallothionein (physiology)
• Mice
• Myocardial Contraction
• Myocardium (pathology)
• NG-Nitroarginine Methyl Ester (toxicity)
• Oxidative Stress
• Reactive Oxygen Species (metabolism)
• Sirolimus (pharmacology)