Alternation Of Signaling Network Related To Cardiac Remodeling And Effects Of Gαq Protein Carboxyl Terminus Imitation Polypeptide HLXK In Spontaneously Hypertensive Rats

Cardiac remodeling, which tend to lead to heart failure and malignant arrhythmia, isone of the major causes of morbidity and mortality elevated in cardiovascular diseases.Accordingly, it has become one of the most important targets for the treatment ofhypertension and chronic congestive heart failure to prevent and reverse left ventricularhypertrophy and remodeling. Huilixinkang (HLXK) is a Gαq protein carboxyl terminusimitation polypeptide, which was cloned and constructed in our laboratory previously.Several studies have shown that HLXK could attenuate AngII, NE-induced cardiomyocytehypertrophy in vitro and ameliorate left ventricular remodeling efficiently in various modelsvia inhibiting Gq protein signaling pathway.However, the cardiomyocytic signal transduction system is a quite complex network,which consists of variety of components, such as neurohumoral molecules and theirreceptors, G proteins, effectors, second messengers, transcription factors, etc. Regulation ofpositive feedback and negative feedback exist between various components, whichmodulate the functional banlance within cell, tissue and whole organ. Furthermore, achange at any node may impact the entire network system. HLXK will not only affect theexpression and function of various signaling molecules downstream the Gq protein, but alsoimpact signaling molecules within other pathways via inhibiting G-protein signaling.Therefore, the present study was designed to investigate the alternation of signaltransduction network related to cardiac remodeling and the modulating effects of Gαqprotein carboxyl terminus imitation polypeptide HLXK in spontaneously hypertensive rats.It will be helpful to understand the comprehensive mechanism of cardiac remodeling, theeffects of HLXK, as well as its overall influence on myocardial function.METHODS1. Eighteen spontaneously hypertensive rats (SHR) were randomly divided into three groups, i.e. cardiac remodeling model, losartan-and HLXK-treated groups, which wereadministrated with normal saline, losartan (6mg/kg, ig, qd) and HLXK (90μg/kg, ip., bid),respectively. Another six Wistar-Kyoto rats were used as normal controls.2. The general state of all animals was observed daily during the experiment period.After8weeks’ treatment, the rats were killed for sampling, and the heart weight index andleft ventricular mass index were measured.3. The expressions of myocardial signal transduction molecules related to cardiacremodeling were assayed using RT-PCR array for rat GPCR signaling pathway.4. Expressions of some genes involved in cardiac remodeling were confirmed byreal-time PCR and Western blotting techniques, respectively.RESULTS1. The rats in model group developed into cardiac hypertrophy. HLXK couldsignificantly decrease left ventricular mass index and heart weight index, and efficientlyattenute left ventricle remodeling.2. Myocardial mRNA expressions of various signaling molecules upregulated in SHRby comparison of those in WKY controls, such as Serpine1, Jun, S1pr3, Max, Grm1, Il1r1,Cdkn1a, Crhr1, Chhr2, Ctgf, Edn1, Fgf2, Bcl2l1, AC5and Akt1. Simultaneously, themRNA expressions of Bai1, Ccnd1, Gcgr, Nos2(iNOS), Pik3cg, ptgdr, Sctr, Tnf andVcam1decreased significantly.3. The result of RT-PCR array indicated that HLXK markedly reduced the mRNAexpression level of Cdkn1a, Ctgf, Edn1, Fgf2and Rgs2, and increased that of Bail, Grm4,Grm7, Nos2and Tshr.4. Real-time PCR suggested that HLXK significantly elevated the mRNA expressionsof α-MHC, and reduced the mRNA expressions of β-MHC, CaN and Cdkn1a.5. HLXK markedly elevated the protein expression of α-MHC, and decreased theexpression of β-MHC, CaN and CDKN1A.CONCLUSION1. Myocardial remodeling and disorder of cellular signal transduction network wereinduced significantly in spontaneously hypertension rats compared with that in normalcontrols. Simultaneously, there was a distinctly expressed imbalance in various signalingmolecules including neurohumors, growth factors, receptors, effector enzymes, cell cycle regulators, oncogenes, as well as hypertrophic genes.2. The polypeptide drug HLXK ameliorated myocardial remodeling markedly.3. The mechanisms of HLXK attenuating cardiac remodeling result from downregulatingthe expressions of CDKN1A, CTGF, ET-1and CaN, upregulating the expressions of GRM4,iNOS and TSHR, as well as balancing the expressions of α-MHC and β-MHC.