Effects Of Antisense Inhibition Of β₁-Adrenergic Receptor MRNA On Cardiac Extracelluar Matrix And Left Ventricular Function In Spontaneously Hypertensive Rat

Essential hypertension (EH) is a multi-factor caused disease and increased sympathetic activity plays a key role in the pathogenesis of EH. Essential hypertensive patients display systemic and regional (heart, brain and kidney) norepinephrine (NE) values greater than those of normotensive individuals. Long term of high level of blood pressure (BP), catecholamine and angiotensin â…¡ can induce cardiac hypertrophy and hyperplasia, eventually can cause left ventricular hypertrophy (LVH) and myocardial fibrosis (MF). LVH, an independent risk factor for cardiovascular morbidity and mortality in hypertensive subjects, has been suggested to contribute to systolic and diastolic dysfunction of left ventricle. It indicates that the hyperactivity of β₁ adrenergic receptor (β₁-AR) plays a important role in the progression LVH, knowing the fact that periodical injection of high dose of isoprenaline in rats or overexpression of the human β₁^AR in transgenic mice could cause LVH and MF. It was confirmed by certain experiment that through antisense inhibition of β₁-AR mRNA, treatment with antisense oligonucleotides against rats' β₁-AR mRNA (β₁-AS-ODNs) could effectively reduce blood pressure in spontaneously hypertensive rats (SHRs). However, whether it can reverse LVH and MF on the basis of the BP reduction is still unknown. Reorganization of the extracellular matrix through protein synthesis and degradation is a key characteristic of hypertensive left ventricular remodeling. The MMPs constitute a family of 20 zinc- dependent peptidases categorized on the basis of substrate specificity and structure. Balanced collagen turnover is controlled by specific MMPs and their inhibitors TIMPs under normal hemodynamic conditions. In the process of left ventricular remodeling in SHRs, the activity of MMP-1 and MMP-2 was significantlyelevated suggesting an altered balance between collagen deposition and collagen degradation in this model of left ventricular hypertrophy and hypertension12'31. With the treatment of 3 ,-AS-ODNs in SHRs, our research aims at finding whether it can reverse left ventricular remodeling and rescue left ventricular function as well as reduce blood pressure.Objective: To investigate whether antisense oligonucleotides against rat 0 ,-adrenergic receptor O ,-AR) mRNA (|3 rAS-ODNs) delivered in cationic liposomes can reverse cardiac fibrosis and rescue impaired left ventricular function in spontaneously hypertensive rats (SHRs).Methods: This study was performed in 20 19-week-old male SHRs and 6 age-matched male Wistar Kyoto Rats (WKY). Two groups of SHRs were treated via tail vein injection with P ,-AS-ODNs (n=7, 1. Omg ? kg"1 ? 20d"') or inverted oligonucleotides against rat ï¿¡,-AR mRNA (0 ,-IN-ODN) (n-7, l.Omg ? kg"1 ? 20d"') for 3 times. 6 untreated SHRs and 6 WKY rats served as positive and normal controls respectively. Blood pressure, left ventricular mass index (LVMI) and cardiac haemodynamics were measured; The distribution of FITC labled oligonucleotides was detected by microfluorescent technology; Left ventricular collagen volume fraction (CVF) was examined by Van Gieson method; Left ventricular CVFs of type I , type III collagen and the expression of MMP-2 were examined by immunohis-tochemistry; The expression of P ,-AR mRNA in left ventricle was measured with RT-PCR.Results: (1) 3 days after transfection, oligonucleotides were effectively uptaken by cardiac myocytes; (2) Compared with WKY rats, SHRs exhibited significantly increased BP, LVMI, CVF and impaired left ventricular function; (3) With the significantly decreased expression of left ventricular ï¿¡ ,^AR mRNA and MMP-2, 0 ,-AS-ODNs treated SHRs exhibited significantly decreased BP, LVMI and CVF, while left ventricular function was significantly improved as well.Conclusions: Through antisense inhibition of 3 i^AR mRNA at transcriptional level in SHR, treatment with 3 i-AS-ODN can effectively reverse left ventricular fibrosis and rescue left ventricular function as well as reduce blood pressure.