Comparative cardioprotective effects of carvedilol versus atenolol in a rat model of cardiorenal syndrome type 4

Cardiomyopathy in chronic kidney disease: clinical features, biomarkers and the contribution of murine models in understanding pathophysiology

The cardiorenal syndrome (CRS) is described as a multi-organ disease encompassing bidirectionally heart and kidney. In CRS type 4, chronic kidney disease (CKD) leads to cardiac injury. Different pathological mechanisms have been identified to contribute to the establishment of CKD-induced cardiomyopathy, including a neurohormonal dysregulation, disturbances in the mineral metabolism and an accumulation of uremic toxins, playing an important role in the development of inflammation and oxidative stress. Combined, this leads to cardiac dysfunction and cardiac pathophysiological and morphological changes, like left ventricular hypertrophy, myocardial fibrosis and cardiac electrical changes. Given that around 80% of dialysis patients suffer from uremic cardiomyopathy, the study of cardiac outcomes in CKD is clinically highly relevant. The present review summarizes clinical features and biomarkers of CKD-induced cardiomyopathy and discusses underlying pathophysiological mechanisms recently uncovered in the literature. It discloses how animal models have contributed to the understanding of pathological kidney-heart crosstalk, but also provides insights into the variability in observed effects of CKD on the heart in different CKD mouse models, covering both "single hit" as well as "multifactorial hit" models. Overall, this review aims to support research progress in the field of CKD-induced cardiomyopathy.

Dapagliflozin protects heart function against type-4 cardiorenal syndrome through activation of PKM2/PP1/FUNDC1-dependent mitophagy

Dapagliflozin (DAPA) confers significant protection against heart and kidney diseases. However, whether DAPA can alleviate type 4 cardiorenal syndrome (CRS-4)-related cardiomyopathy remains unclear. We tested the hypothesis that DAPA attenuates CRS-4-related myocardial damage through pyruvate kinase isozyme M2 (PKM2) induction and FUN14 domain containing 1 (FUNDC1)-related mitophagy. Cardiomyocyte-specific PKM2 knockout (PKM2CKO) and FUNDC1 knockout (FUNDC1CKO) mice were subjected to subtotal (5/6) nephrectomy to establish a CRS-4 model in vivo. DAPA enhanced PKM2 expression and improved myocardial function and structure in vivo, and this effect was abrogated by PKM2 knockdown. A significant improvement in mitochondrial function was observed in HL-1 cells exposed to sera from DAPA-treated mice, as featured by increased ATP production, decreased mtROS production, improved mitochondrial membrane potential, preserved mitochondrial complex activity, and reduced mitochondrial apoptosis. DAPA restored FUNDC1-dependent mitophagy through post-transcriptional dephosphorylation in a manner dependent on PKM2 whereas ablation of FUNDC1 abolished the defensive actions of DAPA on myocardium and mitochondria under CRS-4. Co-IP and molecular docking assays indicated that PKM2 directly interacted with protein phosphatase 1 (PP1) and FUNDC1, leading to PP1-mediated FUNDC1 dephosphorylation. These results suggest that DAPA attenuates CRS-4-related cardiomyopathy through activating the PKM2/PP1/FUNDC1-mitophagy pathway.

Atenolol Ameliorates Skeletal Muscle Atrophy and Oxidative Stress Induced by Cast Immobilization in Rats

(1) Background: Skeletal muscle atrophy is a common and debilitating condition associated with disease, bed rest, and inactivity. We aimed to investigate the effect of atenolol (ATN) on cast immobilization (IM)-induced skeletal muscle loss. (2) Methods: Eighteen male albino Wistar rats were divided into three groups: a control group, an IM group (14 days), and an IM+ATN group (10 mg/kg, orally for 14 days). After the last dose of atenolol, forced swimming test, rotarod test, and footprint analysis were performed, and skeletal muscle loss was determined. Animals were then sacrificed. Serum and gastrocnemius (GN) muscles were then collected, serum creatinine, GN muscle antioxidant, and oxidative stress levels were determined, and histopathology and 1H NMR profiling of serum metabolites were performed. (3) Results: Atenolol significantly prevented immobilization-induced changes in creatinine, antioxidant, and oxidative stress levels. Furthermore, GN muscle histology results showed that atenolol significantly increased cross-sectional muscle area and Feret's diameter. Metabolomics profiling showed that glutamine-to-glucose ratio and pyruvate, succinate, valine, citrate, leucine, isoleucine, phenylalanine, acetone, serine, and 3-hydroxybutyrate levels were significantly higher, that alanine and proline levels were significantly lower in the IM group than in the control group, and that atenolol administration suppressed these metabolite changes. (4) Conclusions: Atenolol reduced immobilization-induced skeletal muscle wasting and might protect against the deleterious effects of prolonged bed rest.

Carvedilol ameliorates dexamethasone-induced myocardial injury in rats independent of its action on the α1-adrenergic receptor

The current study aimed to investigate the cardiotoxic effect of dexamethasone-high-dose in rats, the therapeutic effect of carvedilol and the role of α1-adrenergic receptor (α1AR). The experiment involved 6 groups: control, dexamethasone (10 mg/kg), carvedilol (10 mg/kg), phenylephrine (1 mg/kg), phenylephrine plus carvedilol and propranolol (30 mg/kg). Drugs and vehicles were given for 7 days. Dexamethasone was given with the drugs in the last 4 groups. On the 8th-day and after overnight fasting, serum and cardiac samples were collected. Serum levels of cardiac troponin I and creatine kinase-myoglobin as well as cardiac levels of diacylglycerol, malondialdehyde, kinase activity of Akt, transforming growth factor-β, Smad3 and alpha smooth muscle actin were measured. Cardiac samples were also used for histopathological examination using hematoxylin-eosin and Sirius red stains, in addition to immunohistochemical examination using β-arrestin2 antibody. Dexamethasone induced cardiac injury via increasing oxidative stress, apoptosis and profibrotic signals. Carvedilol significantly reduced the dexamethasone-induced cardiotoxicity. Using phenylephrine, a competitive α1-agonist, with carvedilol potentiated the cardioprotective actions of carvedilol. Propranolol, a β-blocker without activity on α1ARs, showed higher cardiac protection than carvedilol. Dexamethasone-high-dose upregulates cardiac oxidative stress, apoptotic and profibrotic signals and induces cardiac injury. Blocking the α1-adrenergic receptor by carvedilol attenuates its cardioprotective effects against dexamethasone-induced cardiotoxicity.

NPCdc, a synthetic natriuretic peptide, is a substrate to neprilysin and enhances blood pressure-lowering induced by enalapril in 5/6 nephrectomized rats

NPCdc is a natriuretic peptide synthesized from the amino acid sequence of the Crotalus durissus cascavella snake venom peptide, NP2Casca. NPCdc presents hypotensive and antioxidants effects. This study aimed to investigate in vivo whether angiotensin I-converting enzyme (ACE) inhibition would influence the impact of NPCdc in arterial pressure of rats submitted to 5/6 nephrectomy (Nx). Adult male Wistar rats following a 5/6 Nx were treated with enalapril (NxE group, 10 mg/kg/day, n = 9) or vehicle (Nx group, n = 8) for two weeks. On the 15th day after Nx, rats were anaesthetized and submitted to mean arterial pressure (MAP) determination before and after receiving two intravenous injections of saline (vehicle, n = 9) or NPCdc (0.3 μg/kg dissolved in saline, n = 18) separated by a 20-min interval. The kidneys were submitted to oxidative stress analysis. The basal MAP of the NxE group was nearly 20% lower (P < 0.05) than non-treated rats. NPCdc administration decreased the MAP in both groups; however, in the NxE group, the effects were observed only in the second injection. The peptide also decreased the NADPH oxidase activity in the renal cortex. Additionally, the hydrolysis of NPCdc by recombinant neprilysin (NEP) was monitored by mass spectrometry. NPCdc was cleaved by NEP at different peptides with an inhibition constant (Ki) of 1.5 μM, determined by a competitive assay using the NEP fluorescence resonance energy transfer (FRET) peptide substrate Abz-(d)Arg-Gly-Leu-EDDnp. Docking experiments confirmed the high affinity of NPCdc toward NEP. These findings provide new insights into the antihypertensive and antioxidant mechanism of action of NPCdc. Altogether, the results presented here suggest that NPCdc must be further studied as a potential therapy for cardiorenal syndromes.