Vasorelaxant and Antioxidant Effects of Aframomum pruinosum Gagnep. (Zingiberaceae) Seed Extracts May Mediate Their Cardioprotective Activity against Isoproterenol-Induced Myocardial Infarction

Aframomum pruinosum seeds are traditionally used in Cameroon to treat cardiac palpitations. The present work evaluates the cardioprotective effects of the aqueous (AE) and ethanolic (EE) extracts from A. pruinosum seeds against isoproterenol-induced myocardial infarction. Male Wistar rats were pretreated for 14 days with AE or EE at doses of 75 and 150 mg/kg/day or propranolol (10 mg/kg/day). On days 15 and 16, they were injected subcutaneously with isoproterenol (85 mg/kg/day). Blood pressure and heart rate were weekly recorded by tail-cuff plethysmography during pretreatment and 24 hours after the second dose of isoproterenol. At the end of the treatment period, serum Lactate Dehydrogenase (LDH), Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), cardiac nitric oxide (NO), myeloperoxidase (MPO), and oxidative stress parameters (SOD, catalase, MDA, and GSH) were assayed. Sections of left ventricle tissue were subjected to histological analysis. The vasorelaxant effects of cumulative concentrations of AE or EE (3–300 µg/mL) were evaluated on intact or endothelium-denuded isolated aorta rings precontracted with noradrenaline (1 µM). The vasorelaxant effects of the plant extracts were also tested in the presence of N^ω-nitro-L-arginine methyl ester (L-NAME; 100 µM). AE and EE significantly prevented blood pressure decrease and heart rate increase elicited by isoproterenol. Both plant extracts inhibited the increase in ALT, AST, NO, and MPO but did not prevent LDH surge. Oxidative stress parameters were improved following A. pruinosum pretreatment. AE and EE highly reduced cardiomyocyte necrosis and fibrosis but did not prevent leukocyte infiltration. Both extracts induced a concentration-dependent vasorelaxation that was significantly inhibited by the destruction of the endothelium and by L-NAME. Extracts of A. pruinosum exhibited cardioprotective effects, and EE was the most active. The cardioprotective effects of A. pruinosum extracts could be ascribed to their antioxidant, antinecrotic, and endothelium-dependent vasorelaxant effects.

SUR2B/Kir6.1 channel openers correct endothelial dysfunction in chronic heart failure via the miR-1-3p/ET-1 pathway

The SUR2B/Kir6.1 channel openers iptakalim and natakalim reverse cardiac remodeling and ameliorate endothelial dysfunction by re-establishing the balance between the nitric oxide and endothelin systems. In this study, we investigated the microRNAs (miRs) involved in the molecular mechanisms of SUR2B/Kir6.1 channel opening in chronic heart failure. Both iptakalim and natakalim significantly upregulated the expression of miR-1-3p, suggesting that this miR is closely associated with the therapeutic effects against chronic heart failure. Bioinformatic analysis showed that many of the 183 target genes of miR-1-3p are involved in cardiovascular diseases, suggesting that miR-1-3p plays a vital role in such diseases and vascular remodeling. Target gene prediction showed that miR-1-3p combines with the 3' untranslated region (UTR) of endothelin-1 (ET-1) mRNA. Iptakalim and natakalim upregulated miR-1-3p expression and downregulated ET-1 mRNA expression in vitro. The dual luciferase assay confirmed that there is a complementary binding sequence between miR-1-3p and the 3' UTR 158-165 sequence of ET-1 mRNA. To verify the effect of miR-1-3p on ET-1, lentiviral vectors overexpressing or inhibiting miR-1-3p were constructed for the transduction of rat primary cardiac microvascular endothelial cells. The results showed that natakalim enhanced the miR-1-3p level. miR-1-3p overexpression downregulated the expression of ET-1, whereas miR-1-3p inhibition had the opposite effect. Therefore, we verified that SUR2B/Kir6.1 channel openers could correct endothelial imbalance and ameliorate chronic heart failure through the miR-1-3p/ET-1 pathway in endothelial cells. Our study provides comprehensive insights into the molecular mechanisms behind the SUR2B/Kir6.1 channel's activity against chronic heart failure.

Cardioprotective effects of ulinastatin against isoproterenol-induced chronic heart failure through the PI3K‑Akt, p38 MAPK and NF-κB pathways

The purpose of the present study was to evaluate the cardioprotective effect of ulinastatin against isoproterenol‑induced chronic heart failure (CHF). Compared with the control group, treatment with ulinastatin decreased interventricular septal thickness and left ventricular posterior wall thickness, and improved the left ventricular ejection fraction, left ventricular fractional shortening and peak E and peak A ratio in the isoproterenol‑induced CHF rat. In addition, ulinastatin suppressed inflammation, oxidative stress and apoptosis in heart tissue from isoproterenol‑induced CHF rats. Ulinastatin induced the activation of the phosphatidylinositol 3‑kinase (PI3K)/RAC‑α serine/threonine protein kinase (Akt) signaling pathway and downregulated the p38 mitogen‑activated protein kinase (MAPK) and nuclear factor (NF)‑κB pathway in isoproterenol‑induced CHF rats. These data demonstrated the cardioprotective effect of ulinastatin against isoproterenol‑induced chronic heart failure through the PI3K‑Akt, p38 MAPK and NF‑κB pathways.

Pharmacological evidence: a new therapeutic approach to the treatment of chronic heart failure through SUR2B/Kir6.1 channel in endothelial cells

Both iptakalim (Ipt) and natakalim (Nat) activate the SUR2B/Kir6.1 channel, an ATP-sensitive potassium channel (KATP) subtype, with high selectivity. In this study we investigated the therapeutic effects of Ipt and Nat against isoproterenol-induced chronic heart failure (ISO-CHF) in rats, and demonstrated a new therapeutic approach to the treatment of CHF through activation of the SUR2B/Kir6.1 channel in endothelial cells. In ISO-CHF rats, oral administration of Nat (1, 3, 9 mg·kg-1·d-1) or Ipt (3 mg·kg-1·d-1) for 60 days significantly improved cardiac dysfunction, reversed cardiac remodeling, significantly attenuated the pathological increases in BNP levels, and improved endothelial dysfunction by adjusting the balance between endothelin and NO systems. The therapeutic effects of Nat were prevented by the selective KATP blocker glibenclamine (Gli, 50 mg·kg-1·d-1), confirming that these effects were mediated through activation of the SUR2B/Kir6.1 channel in endothelial cells. The molecular mechanisms underlying the therapeutic effects of Nat were further addressed using proteomic methods. We identified 724 proteins in the plasma of ISO-CHF rats; 55 proteins were related to Nat. These differentially expressed proteins were mainly involved in single-organism processes and the regulation of biological quality relative to CHF, including proteasome (Psm) and ATP protein clusters. We screened out PRKAR2β, GAS6/eNOS/NO and NO/PKG/VASP pathways involved in the amelioration of CHF among the 24 enriched pathways. We further confirmed 6 protein candidates, including PRKAR2β, GAS6 and VASP, which were involved in the endothelial mechanisms, and ATP, TIMP3 and AGT, which contributed to its cardiovascular actions. This study demonstrates a new pharmacological approach to the treatment of CHF through activation of the SUR2B/Kir6.1 channel in endothelial cells, and that the eNOS/VASP pathways are involved in its signaling mechanisms.