The novel antibody fusion protein rhNRG1-HER3i promotes heart regeneration by enhancing NRG1-ERBB4 signaling pathway.

Stimulating cardiomyocyte proliferation in the adult heart has emerged as a promising strategy for cardiac regeneration following myocardial infarction (MI). The NRG1-ERBB4 signaling pathway has been implicated in the regulation of cardiomyocyte proliferation. However, the therapeutic potential of recombinant human NRG1 (rhNRG1) has been limited due to the low expression of ERBB4 in adult cardiomyocytes. Here, we investigated whether a fusion protein of rhNRG1 and an ERBB3 inhibitor (rhNRG1-HER3i) could enhance the affinity of NRG1 for ERBB4 and promote adult cardiomyocyte proliferation. In vitro and in vivo experiments were conducted using postnatal day 1 (P1), P7, and adult cardiomyocytes. Western blot analysis was performed to assess the expression and activity of ERBB4. Cardiomyocyte proliferation was evaluated using Ki67 and pH 3 immunostaining, while fibrosis was assessed using Masson staining. Our results indicate that rhNRG1-HER3i, but not rhNRG1, promoted P7 and adult cardiomyocyte proliferation. Furthermore, rhNRG1-HER3i improved cardiac function and reduced cardiac fibrosis in post-MI hearts. Administration of rhNRG1-HER3i inhibited ERBB3 phosphorylation while increasing ERBB4 phosphorylation in adult mouse hearts. Additionally, rhNRG1-HER3i enhanced angiogenesis following MI compared to rhNRG1. In conclusion, our findings suggest that rhNRG1-HER3i is a viable therapeutic approach for promoting adult cardiomyocyte proliferation and treating MI by enhancing NRG1-ERBB4 signaling pathway.

Porcupine inhibitor CGX1321 alleviates heart failure with preserved ejection fraction in mice by blocking WNT signaling.

Heart failure with preserved ejection fraction (HFpEF) is highly prevalent, and lacks effective treatment. The aberration of WNT pathway underlies many pathological processes including cardiac fibrosis and hypertrophy, while porcupine is an acyltransferase essential for the secretion of WNT ligands. In this study we investigated the role of WNT signaling pathway in HFpEF as well as whether blocking WNT signaling by a novel porcupine inhibitor CGX1321 alleviated HFpEF. We established two experimental HFpEF mouse models, namely the UNX/DOCA model and high fat diet/L-NAME ("two-hit") model. The UNX/DOCA and "two-hit" mice were treated with CGX1321 (3 mg·kg-1·d-1) for 4 and 10 weeks, respectively. We showed that CGX1321 treatment significantly alleviated cardiac hypertrophy and fibrosis, thereby improving cardiac diastolic function and exercise performance in both models. Furthermore, both canonical and non-canonical WNT signaling pathways were activated, and most WNT proteins, especially WNT3a and WNT5a, were upregulated during the development of HEpEF in mice. CGX1321 treatment inhibited the secretion of WNT ligands and repressed both canonical and non-canonical WNT pathways, evidenced by the reduced phosphorylation of c-Jun and the nuclear translocation of ß-catenin and NFATc3. In an in vitro HFpEF model, MCM and ISO-treated cardiomyocytes, knockdown of porcupine by siRNA leads to a similar inhibitory effect on WNT pathways, cardiomyocyte hypertrophy and cardiac fibroblast activation as CGX1321 did, whereas supplementation of WNT3a and WNT5a reversed the anti-hypertrophy and anti-fibrosis effect of CGX1321. We conclude that WNT signaling activation plays an essential role in the pathogenesis of HFpEF, and porcupine inhibitor CGX1321 exerts a therapeutic effect on HFpEF in mice by attenuating cardiac hypertrophy, alleviating cardiac fibrosis and improving cardiac diastolic function.

Canagliflozin ameliorates hypobaric hypoxia-induced pulmonary arterial hypertension by inhibiting pulmonary arterial smooth muscle cell proliferation.

Pulmonary arterial hypertension (PAH) is a disease with a high mortality and few treatment options to prevent the development of pulmonary vessel remodeling, pulmonary vascular resistance, and right ventricular failure. Canagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, is originally used in diabetes patients which could assist the glucose excretion and decrease blood glucose. Recently, a few studies have reported the protective effect of SGLT2 inhibitor on monocrotaline-induced PAH. However, the effects of canagliflozin on hypobaric hypoxia-induced PAH as well as its mechanism still unclear. In this study, we used hypobaric hypoxia-induced PAH mice model to demonstrate if canagliflozin could alleviate PAH and prevent pulmonary vessel remodeling. We found that daily canagliflozin administration significantly improved survival in mice with hypobaric hypoxia-induced PAH compared to vehicle control. Canagliflozin treatment significantly reduced right ventricular systolic pressure and increased pulmonary acceleration time determined by hemodynamic assessments. Canagliflozin significantly reduced medial wall thickening and decreased muscularization of pulmonary arterioles compared to vehicle treated mice. In addition, canagliflozin inhibited the proliferation and migration of pulmonary arterial smooth muscle cells through suppressing glycolysis and reactivating AMP-activated protein kinase signaling pathway under hypoxia condition. In summary, our findings suggest that canagliflozin is sufficient to inhibit pulmonary arterial remodeling which is a potential therapeutic strategy for PAH treatment.

The role of G protein-coupled receptor kinase 4 in cardiomyocyte injury after myocardial infarction.

AIMS: G protein-coupled receptor kinase 4 (GRK4) has been reported to play an important role in hypertension, but little is known about its role in cardiomyocytes and myocardial infarction (MI). The goal of present study is to explore the role of GRK4 in the pathogenesis and progression of MI. METHODS AND RESULTS: We studied the expression and distribution pattern of GRK4 in mouse heart after MI. GRK4 A486V transgenic mice, inducible cardiomyocyte-specific GRK4 knockout mice, were generated and subjected to MI with their control mice. Cardiac infarction, cardiac function, cardiomyocyte apoptosis, autophagic activity, and HDAC4 phosphorylation were assessed. The mRNA and protein levels of GRK4 in the heart were increased after MI. Transgenic mice with the overexpression of human GRK4 wild type (WT) or human GRK4 A486V variant had increased cardiac infarction, exaggerated cardiac dysfunction and remodelling. In contrast, the MI-induced cardiac dysfunction and remodelling were ameliorated in cardiomyocyte-specific GRK4 knockout mice. GRK4 overexpression in cardiomyocytes aggravated apoptosis, repressed autophagy, and decreased beclin-1 expression, which were partially rescued by the autophagy agonist rapamycin. MI also induced the nuclear translocation of GRK4, which inhibited autophagy by increasing HDAC4 phosphorylation and decreasing its binding to the beclin-1 promoter. HDAC4 S632A mutation partially restored the GRK4-induced inhibition of autophagy. MI caused greater impairment of cardiac function in patients carrying the GRK4 A486V variant than in WT carriers. CONCLUSION: GRK4 increases cardiomyocyte injury during MI by inhibiting autophagy and promoting cardiomyocyte apoptosis. These effects are mediated by the phosphorylation of HDAC4 and a decrease in beclin-1 expression.

Irisin exerts a therapeutic effect against myocardial infarction via promoting angiogenesis.

Irisin, a myokine, is cleaved from the extracellular portion of fibronectin domain-containing 5 protein in skeletal muscle and myocardium and secreted into circulation as a hormone during exercise. Irisin has been found to exert protective effects against lung and heart injuries. However, whether irisin influences myocardial infarction (MI) remains unclear. In this study we investigated the therapeutic effects of irisin in an acute MI model and its underlying mechanisms. Adult C57BL/6 mice were subjected to ligation of the left anterior descending coronary artery and treated with irisin for 2 weeks after MI. Cardiac function was assessed using echocardiography. We found that irisin administration significantly alleviated MI-induced cardiac dysfunction and ventricular dilation at 4 weeks post-MI. Irisin significantly reduced infarct size and fibrosis in post-MI hearts. Irisin administration significantly increased angiogenesis in the infarct border zone and decreased cardiomyocyte apoptosis, but did not influence cardiomyocyte proliferation. In human umbilical vein endothelial cells (HUVEC), irisin significantly increased the phosphorylation of ERK, and promoted the migration of HUVEC detected in wound-healing and transwell chamber migration assay. The effects of irisin were blocked by the ERK inhibitor U0126. In conclusion, irisin improves cardiac function and reduces infarct size in post-MI mouse heart. The therapeutic effect is associated with its pro-angiogenic function through activating ERK signaling pathway.

Activation of angiotensin II type 1 receptors increases D4 dopamine receptor expression in rat renal proximal tubule cells.

Both the dopaminergic and renin-angiotensin systems play important roles in the regulation of blood pressure. Our previous study showed that the stimulation of dopaminergic D4 receptors reduced angiotensin II type 1 (AT1) receptor expression in renal proximal tubule (RPT) cells. In this study, we tested whether AT1 receptors, in return, would regulate D4 receptor expression and function in RPT cells. Expression of the D4 receptor from Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHRs) RPT cells and renal cortex tissues were determined by western blot, and Na+-K+ ATPase activity was determined using an enzyme assay. Urine volume and urine sodium of WKY rats and SHRs treated with or without D4 receptor stimulation were measured. Thus, activation of AT1 receptors with angiotensin II (Ang II) increased D4 receptor protein expression in RPT cells, and this increase was blocked by nicardipine, a calcium influx blocker. The D4 receptor agonist PD168077 inhibited Na+-K+ ATPase activity in WKY RPT cells but not in SHR RPT cells. Ang II pre-treatment promoted D4 receptor-mediated inhibition of Na+-K+ ATPase in RPT cells in WKY rats but not in SHRs. Meanwhile, Ang II pre-treatment augmented the natriuretic effect of PD168077 in WKY rats but not in SHRs. In conclusion, AT1 stimulation can regulate the expression and natriuretic function of dopaminergic D4 receptors in RPT cells and might be involved in the pathogenesis of essential hypertension.