Troponin I and Dystrophin Proteolysis by Matrix Metalloproteinase 2 Contribute to Chronic Cardiac Remodeling and Dysfunction in Renovascular Hypertension

Aim: Increased MMP-2 activity contributes to hypertension-induced chronic cardiac morphological and functional changes by proteolyzing troponin I and dystrophin. Methods: Male Wistar rats were sham or two kidney-one clip (2K1C) operated and treated with water or doxycycline (15 mg/kg/day) by gavage for six weeks, starting from the tenth week. To establish this aim tail-cuff plethysmography, echocardiogram, in situ zymography, troponin I western blotting and dystrophin immunofluorescence were performed. Results were analyzed by Two-way ANOVA (Ethics Committee approval number: 023/2015-1). Results: Systolic blood pressure (SBP) of 2K1C rats was higher than sham after sixteen weeks of hypertension (215.7 ± 4.8 vs. 120.9 ± 4.4, p<0.05) and doxycycline did not decrease it (216.1 ± 6.1, p>0.05). After four months of hypertension, 25% (6 of 24) of 2K1C rats had left ventricular eccentric hypertrophic remodeling (LVEHR (2K1C-D)) while others remained at left ventricular concentric hypertrophic remodeling (LVCHR (2K1C-H)). Interestingly, 17.6% (3 of 17) of 2K1C rats treated with doxycycline had LVEHR while others 2K1C had LVCHR. Furthermore, 2K1C-D rats had reduced ejection fraction (EF: 39.8 ± 2.9 vs. 66.7 ± 1.7 and 66.2 ± 1.6, p<0.05) and shortening fraction (SF: 20.4 ± 1.6 vs. 38.7 ± 1.4 and 38.4 ± 1.3, p<0.05) when compared to 2K1C-H and Sham. Doxycycline preserved both EF and SF (66.4 ± 2.3 and 38.6 ± 1.8, p<0.05). MMP-2 activity was increased in both 2K1C rats (2K1C-H: 7.2 ± 0.5 and 2K1C-D: 6.5 ± 0.4 vs. 5.3 ± 0.3 Sham, p<0.05) and treatment with doxycycline decreased it (5.5 ± 0.3, p<0.05). Higher amounts of degradation products of troponin I were observed in 2K1C-D when compared to 2K1C-H and Sham (3.6x10 -8 ± 7.9x10 -9 vs. 2.0x10 -8 ± 2.3x10 -9 and 2.0x10 -8 ± 3.4x10 -9 , p=0.06) and doxycycline prevented it (1.9x10 -8 ± 3.0x10 -9 , p<0.05). The levels of dystrophin also decreased in 2K1C-H and -D when compared to Sham (13.5 ± 1.4 and 10.7 ± 2.1 vs. 15.6 ± 1.7) and doxycycline reversed it (16.9 ± 0.6, p<0.05). Conclusion: Increased MMP-2 activity contributes to diminish troponin I and dystrophin levels in 2K1C and this effect may lead to chronic cardiac remodeling and dysfunction.