The RalGAPα1-RalA signal module protects cardiac function through regulating calcium homeostasis

Jin-Xin-Kang alleviates heart failure by mitigating mitochondrial dysfunction through the Calcineurin/Dynamin-Related Protein 1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic heart failure (CHF) is a severe consequence of cardiovascular disease, marked by cardiac dysfunction. Jin-Xin-Kang (JXK) is a traditional Chinese herbal formula used for the treatment of CHF. This formula consists of seven medicinal herbs, including Ginseng (Ginseng quinquefolium (L.) Alph.Wood), Astragali Radix (Astragalus membranaceus (Fisch.) Bunge), Salvia miltiorrhiza (Salvia miltiorrhiza Bunge), Descurainiae Semen Lepidii Semen (Descurainia sophia (L.) Webb ex Prantl), Leonuri Herba (Leonurus japonicus Houtt.), Cinnamomi Ramulus (Cinnamomum cassia (L.) J.Presl), and Ilex pubescens (Ilex pubescens Hook. & Arn.). Its clinical efficacy has been validated through prospective randomized controlled studies. However, the specific mechanisms of action for this formula have yet to be elucidated.

AIM OF THE STUDY

This study aimed to investigate the effect of JXK on mitochondrial function and its mechanism in the treatment of CHF.

METHODS

JXK components were qualitatively analyzed using UPLC-Q-Orbitrap-MS. HF was induced in mice via transverse aortic constriction (TAC). After successful model establishment, lyophilized JXK-L (4.38 g/kg) and JXK-H (13.14 g/kg) were administered for 8 weeks. In vitro, hypertrophic myocardium was induced using angiotensin II (Ang II) for 48 h, followed by JXK-L and JXK-H treatment. Network pharmacology and molecular docking techniques were used to predict the relevant targets of JXK. Cardiac function, serum markers, and histopathological changes were evaluated to assess cardiac function. Immunofluorescence of Tomm20, mitochondrial membrane potential, and ROS were measured to assess mitochondrial dysfunction. Protein expression of calcineurin (CaN) and Drp1 in the myocardium was assessed by Western blot analysis.

RESULTS

We detected that the active components of JXK include terpenes, glycosides, flavonoids, amino acids, and alkaloids, among others. In mice with CHF, JXK improved cardiac function and reversed ventricular remodeling. Network pharmacology indicated that JXK can inhibit the calcium signaling pathway. The molecular docking results demonstrated that the active components of JXK effectively bind with CaN. Both in vitro and in vivo experiments confirmed that JXK regulated the CaN/Drp1 pathway and alleviated mitochondrial dysfunction.

CONCLUSION

JXK can inhibit the CaN/Drp1 pathway to improve mitochondrial function, and consequently treat CHF.

FGF13 deficiency ameliorates calcium signaling abnormality in heart failure by regulating microtubule stability

Calcium signaling abnormality in cardiomyocytes, as a key mechanism, is closely associated with developing heart failure. Fibroblast growth factor 13 (FGF13) demonstrates important regulatory roles in the heart, but its association with cardiac calcium signaling in heart failure remains unknown. This study aimed to investigate the role and mechanism of FGF13 on calcium mishandling in heart failure. Mice underwent transaortic constriction to establish a heart failure model, which showed decreased ejection fraction, fractional shortening, and contractility. FGF13 deficiency alleviated cardiac dysfunction. Heart failure reduces calcium transients in cardiomyocytes, which were alleviated by FGF13 deficiency. Meanwhile, FGF13 deficiency restored decreased Cav1.2 and Serca2α expression and activity in heart failure. Furthermore, FGF13 interacted with microtubules in the heart, and FGF13 deficiency inhibited the increase of microtubule stability during heart failure. Finally, in isoproterenol-stimulated FGF13 knockdown neonatal rat ventricular myocytes (NRVMs), wildtype FGF13 overexpression, but not FGF13 mutant, which lost the binding site of microtubules, promoted calcium transient abnormality aggravation and Cav1.2 downregulation compared with FGF13 knockdown group. Generally, FGF13 deficiency improves abnormal calcium signaling by inhibiting the increased microtubule stability in heart failure, indicating the important role of FGF13 in cardiac calcium homeostasis and providing new avenues for heart failure prevention and treatment.

SUMMIT-FA: a new resource for improved transcriptome imputation using functional annotations

Transcriptome-wide association studies (TWAS) integrate gene expression prediction models and genome-wide association studies (GWAS) to identify gene-trait associations. The power of TWAS is determined by the sample size of GWAS and the accuracy of the expression prediction model. Here, we present a new method, the Summary-level Unified Method for Modeling Integrated Transcriptome using Functional Annotations (SUMMIT-FA), which improves gene expression prediction accuracy by leveraging functional annotation resources and a large expression quantitative trait loci (eQTL) summary-level dataset. We build gene expression prediction models in whole blood using SUMMIT-FA with the comprehensive functional database MACIE and eQTL summary-level data from the eQTLGen consortium. We apply these models to GWAS for 24 complex traits and show that SUMMIT-FA identifies significantly more gene-trait associations and improves predictive power for identifying "silver standard" genes compared to several benchmark methods. We further conduct a simulation study to demonstrate the effectiveness of SUMMIT-FA.

Rab8a as a mitochondrial receptor for lipid droplets in skeletal muscle

Dynamic interaction between lipid droplets (LDs) and mitochondria controls the mobilization of long-chain fatty acids (LCFAs) from LDs for mitochondrial β-oxidation in skeletal muscle in response to energy stress. However, little is known about the composition and regulation of the tethering complex mediating LD-mitochondrion interaction. Here, we identify Rab8a as a mitochondrial receptor for LDs forming the tethering complex with the LD-associated PLIN5 in skeletal muscle. In rat L6 skeletal muscle cells, the energy sensor AMPK increases the GTP-bound active Rab8a that promotes LD-mitochondrion interaction through binding to PLIN5 upon starvation. The assembly of the Rab8a-PLIN5 tethering complex also recruits the adipose triglyceride lipase (ATGL), which couples LCFA mobilization from LDs with its transfer into mitochondria for β-oxidation. Rab8a deficiency impairs fatty acid utilization and decreases endurance during exercise in a mouse model. These findings may help to elucidate the regulatory mechanisms underlying the beneficial effects of exercise on lipid homeostasis control.

1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic Acid Acetoxymethyl Ester Loaded Reactive Oxygen Species Responsive Hyaluronic Acid-Bilirubin Nanoparticles for Acute Kidney Injury Therapy via Alleviating Calcium Overload Mediated Endoplasmic Reticulum Stress

Calcium overload is one of the early determinants of the core cellular events that contribute to the pathogenesis of acute kidney injury (AKI), which include oxidative stress, ATP depletion, calcium overload, and inflammatory response with self-amplifying and interactive feedback loops that ultimately lead to cellular injury and renal failure. Excluding adjuvant therapy, there are currently no approved pharmacotherapies for the treatment of AKI. Using an adipic dihydride linker, we modified the hyaluronic acid polymer chain with a potent antioxidant, bilirubin, to produce an amphiphilic conjugate. Subsequently, we developed a kidney-targeted and reactive oxygen species (ROS)-responsive drug delivery system based on the flash nanocomplexation method to deliver a well-known intracellular calcium chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM, BA), with the goal of rescuing renal cell damage via rapidly scavenging of intracellularly overloaded Ca²⁺. In the ischemia-reperfusion (I/R) induced AKI rat model, a single dose of as-prepared formulation (BA 100 μg·kg^-1) 6 h post-reperfusion significantly reduced renal function indicators by more than 60% within 12 h, significantly alleviated tissular pathological changes, ameliorated tissular oxidative damage, significantly inhibited apoptosis of renal tubular cells and the expression of renal tubular marker kidney injury molecule 1, etc., thus greatly reducing the risk of kidney failure. Mechanistically, the treatment with BA-loaded NPs significantly inhibited the activation of the ER stress cascade response (IRE1-TRAF2-JNK, ATF4-CHOP, and ATF6 axis) and regulated the downstream apoptosis-related pathway while also reducing the inflammatory response. The BA-loaded NPs hold great promise as a potential therapy for I/R injury-related diseases.