SIRT3-dependent mitochondrial redox homeostasis mitigates CHK1 inhibition combined with gemcitabine treatment induced cardiotoxicity in hiPSC-CMs and mice.

Administration of CHK1-targeted anticancer therapies is associated with an increased cumulative risk of cardiac complications, which is further amplified when combined with gemcitabine. However, the underlying mechanisms remain elusive. In this study, we generated hiPSC-CMs and murine models to elucidate the mechanisms underlying CHK1 inhibition combined with gemcitabine-induced cardiotoxicity and identify potential targets for cardioprotection. Mice were intraperitoneally injected with 25 mg/kg CHK1 inhibitor AZD7762 and 20 mg/kg gemcitabine for 3 weeks. hiPSC-CMs and NMCMs were incubated with 0.5 uM AZD7762 and 0.1 uM gemcitabine for 24 h. Both pharmacological inhibition or genetic deletion of CHK1 and administration of gemcitabine induced mtROS overproduction and pyroptosis in cardiomyocytes by disrupting mitochondrial respiration, ultimately causing heart atrophy and cardiac dysfunction in mice. These toxic effects were further exacerbated with combination administration. Using mitochondria-targeting sequence-directed vectors to overexpress CHK1 in cardiomyocyte (CM) mitochondria, we identified the localization of CHK1 in CM mitochondria and its crucial role in maintaining mitochondrial redox homeostasis for the first time. Mitochondrial CHK1 function loss mediated the cardiotoxicity induced by AZD7762 and CHK1-knockout. Mechanistically, mitochondrial CHK1 directly phosphorylates SIRT3 and promotes its expression within mitochondria. On the contrary, both AZD7762 or CHK1-knockout and gemcitabine decreased mitochondrial SIRT3 abundance, thus resulting in respiration dysfunction. Further hiPSC-CMs and mice experiments demonstrated that SIRT3 overexpression maintained mitochondrial function while alleviating CM pyroptosis, and thereby improving mice cardiac function. In summary, our results suggest that targeting SIRT3 could represent a novel therapeutic approach for clinical prevention and treatment of cardiotoxicity induced by CHK1 inhibition and gemcitabine.

Evaluating the Utility of Colchicine in Acute Coronary Syndrome: A Systematic Review and Meta-Analysis.

ABSTRACT: Colchicine has demonstrated promising effects in inhibiting local and systemic inflammation during acute coronary syndrome (ACS). However, the efficacy of colchicine in ACS is controversial. We performed a meta-analysis to assess the utility of colchicine in ACS by systematically searching randomized controlled trials. Recurrent myocardial infarction, coronary revascularization, and stroke were included as efficacy endpoint parameters whereas safety endpoints chosen were all-cause mortality, cardiovascular mortality, infectious events, and gastrointestinal (GI) adverse events. Nine identified studies were included (n = 7207 participants). Colchicine may reduce the risk of coronary revascularization by 54% [relative risk (RR) 0.46, 95% confidence interval (CI) 0.29-0.73; P < 0.01] and stroke by 61% (RR 0.39, 95%CI 0.18-0.81; P = 0.01). We observed no significant difference in all-cause mortality (RR 1.25, 95%CI 0.70-2.24; P = 0.46), cardiovascular mortality (RR 0.99, 95%CI 0.58-1.69; P = 0.98), recurrent myocardial infarction (RR 0.75, 95%CI 0.49-1.14; P = 0.18), and infectious events (RR 0.67, 95%CI 0.08-5.52; P = 0.71). Colchicine increased the risk of GI adverse reactions (RR 1.89, 95%CI 1.25-2.84; P < 0.01). Subgroup analysis of loading doses did not reveal significant differences in all endpoints (all P > 0.05), whereas subgroup analysis of follow-up periods showed a lower risk of GI adverse reactions with longer follow-up ( P < 0.01), which may be related to establishing tolerability. Trial sequential analysis suggested that further data are needed before definitive conclusions can be drawn. Colchicine may decrease the occurrence of stroke and revascularization in ACS, whereas slightly increasing the risk of GI reactions. The loading doses probably did not significantly improve the prognosis of patients.

PEX3 promotes regenerative repair after myocardial injury in mice through facilitating plasma membrane localization of ITGB3.

The peroxisome is a versatile organelle that performs diverse metabolic functions. PEX3, a critical regulator of the peroxisome, participates in various biological processes associated with the peroxisome. Whether PEX3 is involved in peroxisome-related redox homeostasis and myocardial regenerative repair remains elusive. We investigate that cardiomyocyte-specific PEX3 knockout (Pex3-KO) results in an imbalance of redox homeostasis and disrupts the endogenous proliferation/development at different times and spatial locations. Using Pex3-KO mice and myocardium-targeted intervention approaches, the effects of PEX3 on myocardial regenerative repair during both physiological and pathological stages are explored. Mechanistically, lipid metabolomics reveals that PEX3 promotes myocardial regenerative repair by affecting plasmalogen metabolism. Further, we find that PEX3-regulated plasmalogen activates the AKT/GSK3ß signaling pathway via the plasma membrane localization of ITGB3. Our study indicates that PEX3 may represent a novel therapeutic target for myocardial regenerative repair following injury.

Circular RNA IGF1R Promotes Cardiac Repair via Activating ß-Catenin Signaling by Interacting with DDX5 in Mice after Ischemic Insults.

The potential of circular RNAs (circRNAs) as biomarkers and therapeutic targets is becoming increasingly evident, yet their roles in cardiac regeneration and myocardial renewal remain largely unexplored. Here, we investigated the function of circIGF1R and related mechanisms in cardiac regeneration. Through analysis of circRNA sequencing data from neonatal and adult cardiomyocytes, circRNAs associated with regeneration were identified. Our data showed that circIGF1R expression was high in neonatal hearts, decreased with postnatal maturation, and up-regulated after cardiac injury. The elevation was validated in patients diagnosed with acute myocardial infarction (MI) within 1 week. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and myocardial tissue from mice after apical resection and MI, we observed that circIGF1R overexpression enhanced cardiomyocyte proliferation, reduced apoptosis, and mitigated cardiac dysfunction and fibrosis, while circIGF1R knockdown impeded endogenous cardiac renewal. Mechanistically, we identified circIGF1R binding proteins through circRNA precipitation followed by mass spectrometry. RNA pull-down Western blot and RNA immunoprecipitation demonstrated that circIGF1R directly interacted with DDX5 and augmented its protein level by suppressing ubiquitin-dependent degradation. This subsequently triggered the ß-catenin signaling pathway, leading to the transcriptional activation of cyclin D1 and c-Myc. The roles of circIGF1R and DDX5 in cardiac regeneration were further substantiated through site-directed mutagenesis and rescue experiments. In conclusion, our study highlights the pivotal role of circIGF1R in facilitating heart regeneration and repair after ischemic insults. The circIGF1R/DDX5/ß-catenin axis emerges as a novel therapeutic target for enhancing myocardial repair after MI, offering promising avenues for the development of regenerative therapies.