Effect Of Non-Selective MMPs Inhibitor Doxycycline On Hypertension-Induced Left Ventricular Remodeling

Objective:Left ventricular (LV) remodeling induced by hypertension is an early cardiac compensatory response to pressure-overload,which characterized by presentation of enhanced myocardial contractility and increased cardiac output. However,chronic pressure-overload will lead to ventricular hypertrophy and extracellular matrix (ECM) abnormalities of heart, then left ventricular dilation and cardiac dysfunction,and ultimately to heart failure.ECM plays a vital role in maintaining structural and functional integrity of the myocardium.At the same time, Matrix metalloproteinases (MMPs) have the predominant role in the metabolism of ECM proteins, and have been proposed to mediate collagen degradation.Thus, Abnormal protein concentration and activities of cardiac MMPs may impact on balance of ECM systhesis and degradation. Inhibition of protein expression and activities of MMPs can depress expansion of abdominal aortic aneurysm,eventually delay the development of aneurysm.However,in the setting of hypertension propagation and without the influence of anti-hypertensive drugs,the role of MMPs inhibition in the process of LV remodeling remains controversial.Therefore,in the present study,we hypothesized that doxycycline,a nonselective MMPs inhibitor,may be of beneficial effects on hypertension induced LV remodeling.Methods:7-week-old male stroke-prone spontaneously hypertensive rats (SHR-SPs,n=80) of were randomly divided into 2 groups (control group and doxycycline-treat group),age-matched male Wistar-Kyoto (WKY) rats (n=10) were used as negtive control.Subsequently, SHR-SPs received doxycyctine (30mg.Kg- 1.day_-1 in drinking water) or vehicle since 8th week,respectively.Throughout the intervention,body weight and indirect tail-cuff systolic blood pressure measurement were continuously preformed every 2 weeks.The follow-up was terminated when mortality of the control group reached 50%.At 33 weeks,survival SHR-SPs and WKY rats were anesthetized for invasive hemodynamic measurement by Millar pressure-volume (P-V) conductance catheter.The rats were sacrificed after the hemodnamic analysis,then hearts were dissected and quickly frozen by liquid nitrogen and stored in—80℃for further study.Some heart were embedded in araffin and sectioned for morphological study. Picrosirius red staining plus microscopy was carried out to evaluate ECM deposition on cardiac interstitium and perivascular area. The activities and protein espression of MMP-2 in cardiac tissue of the left ventricle was detected by gelatin zymography and western blot.Subsequently, semi-quantitative analysis was performed by Image Pro Plus software.Results:1 Compared with control group,collagen volume fraction (CVF) [(10.05±8.13)ï¼…vs.(5.474-4.94)ï¼…,P<0.05],ratio of perivascular collagen area to luminal area(PVCA/LA) [(181.2±24.1)ï¼…vs.(134.0+92.9)ï¼…, P<0.05],myocardial cross-sectional area [458.754±146.43 vs.348.04±121.57μm₂,P<0.05] and the medial area to luminal area ratio (MA/LA) [1.054±0.76 vs.0.54+0.17,P<0.05] of the doxycycline-treat group were all markly increased at 33 weeks. Compared to WKY rats,LV weight to body weight ratio,CVF,PVCA/LA,myocardial cross-sectional area and MA/LA were increased in control group and doxycycline-treat group (P<0.05).Our results show that doxycycline could increase depositon of cardiac ECM.2 Compared with control group,gelatin zymography and western blot analysis of MMPs in LV indicated that MMP-2 activities (2.46±0.18 vs.2.00±0.16,P<0.05) and protein level markly reduced in doxycycline-treat group (9.15±1.68 vs.2.794±0.99,P<0.05).These results indicate that doxycycline could inhibit activities and protein expression of cardiac MMP-2.3 Compared with WKY rats,significantly increased hemodynamic parametersin control group were left ventricular end-systolic pressure (LVESP) (183.9±26.2 vs.105.8±12.6mmHg,P<0.05),left ventricular end-systolic volume (LVESV) (134.3±61.9 vs.68.3±19.μL,P<0.05),+dp/dt_max (9804±2047 vs.8261±1802mmHg/s,P<0.05) and—dp/dt_max (—7291±1912 vs.—5671±1206mmHg/s,P<0.05),and significantly decreased hemodynamic parameters were ejection fraction (EF) (48.17±14.51 vs.71.28+3.91,P<0.05),stroke volume (SV) (111.3±31.2 vs.134.7±12.8μL,P<0.05),cardiac output (CO) (32616±10469 vs.50818±5801μL/min,P<0.05) and+dV/dt_max (4134±1182 vs.5478±939μL/s,P<0.05).However,EF (63.89±13.10 vs.48.17±14.51,P<0.05),SV (134.0±23.8 vs.111.3±31.2μL,P<0.05),stroke work (SW) (17490±3604 vs.12528+3169mmHg·μL,P<0.05),CO (43653±7202 vs.32616±10469μL/min,P<0.05),+dp/dt_max (14110±2652 vs.9803±2046mmHg/s,P<0.05) and—dp/dt_max (—8896±2194 vs.—7291±1912mmHg/s,P<0.05) in doxycycline-treat group notablely higher than control group.In brief,chronic overload-pressure induced LV dysfunction,but doxycycline could partially preserve systolic function of left ventricle.4 Compared with WKY rats,control group increased in LVEDP (15.17±5.75 vs.8.11±3.06mmHg,P<0.05),LVEDV (238.57±60.15 vs.182.07±29.06μL,P<0.05) and c(Glantz) (19.51±3.86 vs.13.46±1.50ms,P<0.05).Tau,a parameter to reflex active diastolic properties in LV,was of no statistical difference between control group and doxycycline-treat group (P>0.05).Values for c(Glantz) showed statistical significance in doxycycline-treat group compared with that of WKY rats (18.77±6.57 vs.13.46±1.50ms,P<0.05).These data indicate that LV diastolic function were impaired in control group and doxycycline-treat group.Conclusion:Taken together, pressure-overload can mediate cardiac interstitial fibrosis,increase MMPs activity of LV myocardium and contribute to cardiac dysfunction.The dose of doxycycline used in the experiment was efficient to suppress cardiac MMP-2 protein expression,which results in increased ECM deposition in cardiac interstitium.However,increased ECM in the setting of uncontrolled hypertension, does not impair cardiac pump function as previously thought.Instead of accelerate heart failure,excessive ECM may delay the transition from compensated concentric hypertrophy to eccentric dilation of left ventricle, and partially preserve systolic properties.