Pretreatment with cilnidipine attenuates hypoxia/reoxygenation injury in HL-1 cardiomyocytes through enhanced NO production and action potential shortening

Azelnidipine protects HL-1 cardiomyocytes from hypoxia/reoxygenation injury by enhancement of NO production independently of effects on gene expression

It remains to be elucidated whether Ca2+ antagonists induce pharmacological preconditioning to protect the heart against ischemia/reperfusion injury. The aim of this study was to determine whether and how pretreatment with a Ca2+ antagonist, azelnidipine, could protect cardiomyocytes against hypoxia/reoxygenation (H/R) injury in vitro. Using HL-1 cardiomyocytes, we studied effects of azelnidipine on NO synthase (NOS) expression, NO production, cell death and apoptosis during H/R. Action potential durations (APDs) were determined by the whole-cell patch-clamp technique. Azelnidipine enhanced endothelial NOS phosphorylation and NO production in HL-1 cells under normoxia, which was abolished by a heat shock protein 90 inhibitor, geldanamycin, and an antioxidant, N-acetylcysteine. Pretreatment with azelnidipine reduced cell death and shortened APDs during H/R. These effects of azelnidipine were diminished by a NOS inhibitor, L-NAME, but were influenced by neither a T-type Ca2+ channel inhibitor, NiCl2, nor a N-type Ca2+ channel inhibitor, ω-conotoxin. The azelnidipine-induced reduction in cell death was not significantly enhanced by either additional azelnidipine treatment during H/R or increasing extracellular Ca2+ concentrations. RNA sequence (RNA-seq) data indicated that azelnidipine-induced attenuation of cell death, which depended on enhanced NO production, did not involve any significant modifications of gene expression responsible for the NO/cGMP/PKG pathway. We conclude that pretreatment with azelnidipine protects HL-1 cardiomyocytes against H/R injury via NO-dependent APD shortening and L-type Ca2+ channel blockade independently of effects on gene expression.

Effects of Neonatal Administration of Non-Opiate Analogues of Leu-Enkephalin to Heart Tissue Homeostasis of Prepubertal Albino Rats Exposed to Hypoxia

Hypobaric hypoxia (pO2 65 mm Hg, duration 4 h) induced a significant increase in the number of cardiomyocytes expressing р53, beclin-1, endothelial NO synthase and accumulation and degranulation of mast cells in the epicardium in hearts of prepubertal female rats (age 45-47 days); the number of cardiomyocytes with nucleoli decreased, while the number of single-nucleolar cardiomyocytes increased after this exposure. Five-fold administration of non-opiate analogue of leu-enkephalin (NALE peptide: Phe-D-Ala-Gly-Phe-Leu-Arg; 100 μg/kg) during the neonatal period reduced the severity of the post-hypoxic changes in the heart. Neonatal administration of NALE (100 μg/kg) against the background of NO synthase blockade with L-NAME (50 mg/kg) did not abolish the cardioprotective effects of the peptide. A similar correction of posthypoxic changes in the heart was observed after neonatal administration of original peptide G (Phe-D-Ala-Gly-Phe-Leu-Gly; 100 μg/kg). Thus, NO synthase-NO system and C-terminal amino acid Arg in the molecule of non-opiate analogue of leu-enkephalin are not required for the cardioprotective effects of peptides. Non-opiate leu-enkephalin analogs, peptides NALE and G, can be considered as promising substances for increasing heart resistance to hypoxia during later age periods.

Current Updates on Potential Role of Flavonoids in Hypoxia/Reoxygenation Cardiac Injury Model

Clinically, timely reperfusion strategies to re-establish oxygenated blood flow in ischemic heart diseases seem to salvage viable myocardium effectively. Despite the remarkable improvement in cardiac function, reperfusion therapy could paradoxically trigger hypoxic cellular injury and dysfunction. Experimental laboratory models have been developed over the years to explain better the pathophysiology of cardiac ischemia-reperfusion injury, including the in vitro hypoxia-reoxygenation cardiac injury model. Furthermore, the use of nutritional myocardial conditioning techniques have been successful. The cardioprotective potential of flavonoids have been greatly linked to its anti-oxidant, anti-apoptotic and anti-inflammatory properties. While several studies have reviewed the cardioprotective properties of flavonoids, there is a scarce evidence of their function in the hypoxia-reoxygenation injury cell culture model. Hence, the aim of this review was to lay out and summarize our current understanding of flavonoids' function in mitigating hypoxia-reoxygenation cardiac injury based on evidence from the last five years. We also discussed the possible mechanisms of flavonoids in modulating the cardioprotective effects as such information would provide invaluable insight on future therapeutic application of flavonoids.

Visualizing the Underlying Signaling Pathway Related to Nitric Oxide and Glutathione in Cardiovascular Disease Therapy by a Sequentially Activated Fluorescent Probe

Clarifying the signaling pathway associated with nitric oxide (NO) and glutathione (GSH) in cardiovascular disease therapy is important for understanding its physiological and pathological processes but is challenging due to the lack of efficient analytical techniques. Herein, we report a BODIPY-based fluorescent probe for recognition of NO and GSH in sequence with high sensitivity and selectivity. The probe exhibits turn-on fluorescence triggered by NO, followed by red-shifted emission in the presence of GSH. The sequentially activated mechanism allows the visualization of NO-induced GSH upregulation in drug-treated endothelial cells and zebrafish for the first time, revealing a signal pathway during the therapy. We hope that it can be used as a convenient and efficient tool for the study of the interplay between NO and GSH and for the screening of effective drugs for cardiovascular disease therapy.