Cardioprotective effect of angiotensin (1-7) in experimentally induced heart failure in rats

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic VEGA 2/0158/19, VEGA 2/0002/20; Slovak Research and Development Agency APVV-15-0119, APVV-18-0548 The extracellular matrix (ECM) is a highly dynamic structure that affects the proper functioning of various tissues. ECM is involved in cell signaling, participates in the origin and development of pathology and its positive influence can result in improved disease. The pathophysiology of ECM also affects intercellular communication, which results in various arrhythmias in the heart. In the present work, we focused on the signaling pathways involved in cardiac structural remodeling due to volume overload, and at the same time, we tested the possibilities of the cardioprotective effect of angiotensin (1-7) (Ang (1-7)). As an experimental model of volume overload, we chose the aortocaval fistula (ACF) model, where we focused on the compensatory phase of heart failure. Male, 8 weeks old rats, from the normotensive Hannover Sprague-Dawley (HSD), the hypertensive Ren-2 of transgenic rats (TGR), and transgenic rats expressing the angiotensin (1-7) producing a fusion protein (TGR(A1-7)3292), we operationally created the ACF. 5 weeks after operation, the animals were decapitated and cardiac tissue samples were taken. Right and left ventricular tissue samples were used for biometric, biochemical, and proteomic analyzes. TGR(A1-7)3292 rats had significantly less hypertrophy compared to HSD and TGR after ACF. Hydroxyproline was increased in the TGR ACF group in both ventricles and in the right ventricle it was significantly reduced by Ang (1-7) compared to TGR ACF. In our selected proteins, the group of protein kinases C (PKC) α, δ, ε, matrix metalloproteinase 2 (MMP-2), SMAD2/3, connexin 43 (Cx43) and its phosphorylated form (pCx43) there were changes in protein levels, either due to hypertension after ACF, and in several cases the cardioprotective effect of Ang (1-7) was confirmed. PKCα and PKCδ showed a decrease in the TGR ACF group compared to HSD ACF and a decrease in the TGR(A1-7)3292 ACF group compared to HSD and TGR after ACF in both chambers. MMP-2 activity in the left and right ventricles had a reduced trend in the TGR and TGR(A1-7)3292 groups after ACF compared to HSD ACF. The same change occurred in MMP-2 protein expression in the right ventricle, in contrast to the left ventricle, where no change occurred. In the right ventricle, there was a decrease in SMAD2/3 protein expression in the TGR(A1-7)3292 group of ACF compared to HSD and TGR after ACF. Cx43 and pCx43 showed a very similar trend in both chambers, with an increase in the TGR ACF group versus HSD ACF, and the TGR(A1-7)3292 ACF versus HSD and TGR after ACF. Based on the obtained results, it can be stated that the right ventricle is more significantly affected by ACF and the endogenous production of Ang (1-7) alleviated the changes of the monitored proteins and the remodeling of the ECM caused by volume overload. </jats:sec

Inhibition of RAS components attenuates progression of heart failure and its adverse consequences on myocardial remodeling in both normotensive and hypertensive rats

Abstract Rationale and purpose Prevention or attenuation of heart failure (HF) is persistent task in clinic as well as challenge for progress in research. Both, intercellular connexin-43 (Cx43) channels and extracellular matrix (ECM) exert high impact on heart function. Thus, we aimed to explore whether HF due to volume overload (VO) induces alterations in myocardial Cx43, ECM proteins MMP2, SMAD2/3, TGFβ1 and PKC signaling as well as changes that may be revealed by enzyme histochemistry. Moreover, we tested the impact of treatment suppressing RAS on examined targeted proteins. Methods VO-HF was induced in male normotensive Hannover Sprague- Dawley (HSD) and mRen-2 transgenic hypertensive (TGR) rats by creating an aorto-caval fistula (ACF) and heart response was examined 20-weeks later. Sham-rats were compared with non-treated rats with ACF and those treated for 15-weeks with ACEI (trandolapril, 6mg/l, p.o.) or ARB (losartan (200mg/l, p.o.). Left ventricular heart (LV) tissue was analyzed using western blot, zymography and enzyme histochemistry. Key results Echocardiography confirmed an increase in cardiac output and a decrease in ejection fraction in both strains of rats. BW was higher in TGR vs HSD and it was not affected by VO. HW and LVW were higher in TGR vs HSD and VO increased both parameters regardless the strain while ACEI&amp;gt;ARB attenuated it. In parallel, myocardial pro-hypertrophic PKCd expression was higher in TGR vs HSD and increased in both strains due to VO while both drugs prevent it. Glycogen phosphorylase and capillary associated 5-nucleotidase, alkaline phospatase and dipeptidyl peptidase IV activities were reduced due to VO in HSD and TGR and it was attenuated by treatment. Cx43 expression and its functional phosphorylation status were lower in TGR vs HSD and suppressed in both strains due to VO but ACEI&amp;gt;ARB prevented it. Similar trend of changes was observed in PKCe expression, which phosphorylates Cx43. Profibrotic TGFβ1-Smad2/3 pathway was suppressed along with reduced MMP2 activity in TGR comparing to HSD. VO reduced SMAD2/3 in HSD and TGFβ1 in TGR as well as MMP2 expression in both strains, whereby treatment abolished these changes. VO decreased MMP2 (63kDa) activity only in TGR and ARB prevented it. VO did not affect collagen deposition in either strain vs sham rats. Conclusions Hypertrophic and hypofibrotic phenotypes are induced by volume overload in both rat strains. Together with deterioration of Cx43 mediated intercellular coupling it may contribute to heart dysfunction. Inhibition of RAS components attenuates progression of VO and its adverse consequences. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Scientific Grant Agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic VEGA 2/0158/19, 2/0002/20 </jats:sec