MMP-2 INHIBITION ATTENUATES HYPERTENSIVE ECCENTRIC CARDIAC HYPERTROPHY AND DYSFUNCTION BY PRESERVING TROPONIN I AND DYSTROPHIN

Abstract

Objective: To verify wether increased matrix metalloproteinase (MMP)-2 activity contributes to the proteolysis of troponin I and dystrophin in the left ventricle (LV) of two kidney-one clip (2K1C) rats thus favoring the transition from concentric (C-LVH) to eccentric hypertrophy (E-LVH) and cardiac dysfunction. Design and method: Male 7-week old Wistar rats were sham or 2K1C operated and treated with water or doxycycline (MMP inhibitor, 15 mg/kg/day) by gavage from the tenth to the sixteenth week post-surgery. To establish this aim, tail-cuff plethysmography, echocardiogram, morphological analysis (collagen deposition and cardio myocyte hypertrophy assay), gelatin and in situ zymography, confocal microscopy of MMP-2 and troponin I, troponin I western blotting and mass spectrometry, and dystrophin in silico analysis and immunofluorescence were performed. Results were analyzed by two-way ANOVA or unpaired t test (Ethics Committee approval number: 023/2015-1). Results: All 2K1C rats had increased systolic blood pressure when compared to controls (p < 0.05) and doxycycline did not decrease it (p > 0.05). About 25% of 2K1C rats had E-LVH followed by reduced ejection fraction and fractional shortening (p < 0.05). The remaining had C-LVH with preserved cardiac function (p < 0.05). Doxycycline prevented the transition from C-LVH to E-LVH. Both C-LVH and E-LVH rats had cardio myocyte hypertrophy (p < 0.05) and doxycycline reverted it (p < 0.05). E-LVH was the only group who had more collagen deposition in the LV (p < 0.05). MMP-2 activity increased in C- and E-LVH hearts when compared to controls (p < 0.05) and doxycycline inhibited it (p < 0.05). MMP-2 and troponin I co-localize in the LV of control rats (p < 0.05). This was associated with an increase in troponin I cleavage products in E-LVH when compared to C-LVH (p < 0.05) confirmed by western blotting and mass spectrometry. Moreover, about ten putative MMP-2 cleavage sites in rat dystrophin were found and, in fact, a decline in dystrophin levels was observed in E-LVH when compared to controls (p < 0.05) which was prevented by doxycycline (p < 0.05). Conclusions: Hypertension causes increased cardiac MMP-2 activity which reduces both troponin I and dystrophin levels and contributes to the transition from C-LVH to E-LVH.