Elsevier

Free Radical Biology and Medicine

Volume 49, Issue 12, 15 December 2010, Pages 2068-2077
Free Radical Biology and Medicine

Original Contribution
Cardiac-specific overexpression of catalase attenuates paraquat-induced myocardial geometric and contractile alteration: Role of ER stress

https://doi.org/10.1016/j.freeradbiomed.2010.10.686Get rights and content

Abstract

Paraquat, a quaternary nitrogen herbicide, is a highly toxic pro-oxidant that causes multiorgan failure including that of the heart via generation of reactive oxygen species, although the underlying mechanism has not been well elucidated. This study examined the influence of cardiac-specific overexpression of catalase, an antioxidant detoxifying H2O2, on paraquat-induced myocardial geometric and functional alterations, with a focus on ER stress. FVB and catalase transgenic mice were administered paraquat for 48 h. Myocardial geometry, contractile function, apoptosis, and ER stress were evaluated using echocardiography, edge detection, caspase-3 activity, and immunoblotting. Our results revealed that paraquat treatment significantly enlarged left ventricular (LV) end diastolic and systolic diameters; increased LV mass and resting myocyte length; reduced fractional shortening, cardiomyocyte peak shortening, and maximal velocity of shortening/relengthening; and prolonged relengthening duration in the FVB group. Whereas the catalase transgene itself did not alter myocardial geometry and function, it mitigated or significantly attenuated paraquat-elicited myocardial geometric and functional changes. Paraquat promoted overt apoptosis and ER stress as evidenced by increased caspase-3 activity, apoptosis, and ER stress markers including Bax, Bcl-2, GADD153, calregulin, and phosphorylated JNK, IRE1α, and eIF2α; all were ablated by the catalase transgene. Paraquat-induced cardiomyocyte dysfunction was mitigated by the ER stress inhibitor tauroursodeoxycholic acid. Moreover, the JNK inhibitor SP600125 reversed paraquat-induced ER stress as evidenced by enhanced GADD153 and IRE1α phosphorylation. Taken together, these data revealed that catalase may rescue paraquat-induced myocardial geometric and functional alteration possibly by alleviating JNK-mediated ER stress.

Section snippets

Experimental animals and paraquat treatment

The experimental protocol described in this study was approved by the Animal Use and Care Committees at the University of Wyoming (Laramie, WY, USA). Cardiac-specific overexpression catalase mice were used as described [20], [21]. FVB littermates were used as wild type. A primer pair derived from the MHC promoter and rat catalase cDNA was used for identification of the catalase transgene, with the reverse sequence of 5′-AATATCGTGGGTGACCTCAA-3′ and the forward sequence of

Echocardiographic properties of FVB and catalase mice with or without paraquat treatment

Measurement of catalase activity revealed significantly elevated enzymatic activity only in hearts and not in brain, liver, kidney, or skeletal muscles (gastrocnemius) (Fig. 1), validating the cardiac specificity of the transgene overexpression. Heart rate and LV wall thickness were not significantly affected by the catalase transgene or paraquat treatment. Paraquat significantly increased EDD, ESD, and calculated LV mass as well as suppressing fractional shortening in FVB mice. Catalase

Discussion

Data from this study revealed that the antioxidant catalase mitigated the herbicide pro-oxidant paraquat-induced cardiac geometric alteration, myocardial contractile dysfunction, apoptosis, and ER stress. In addition, paraquat-induced cardiomyocyte dysfunction was mitigated by the ER stress inhibitor tauroursodeoxycholic acid, whereas the JNK inhibitor SP600125 reversed paraquat-induced ER stress. These findings support the previous observation that paraquat exerts devastating cardiac anomalies

Acknowledgments

This work was presented in part in abstract form during Experimental Biology 2010 in Anaheim, California, USA. The founder mice of the catalase transgenic line were kindly provided by Professor Paul N. Epstein from the University of Louisville (Louisville, KY, USA). This work was supported in part by NIH 1R01 AA013412 and 5P20 RR016474 (J.R.).

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