Visceral Adipose Tissue Drives Cardiac Aging Through Modulation of Fibroblast Senescence by Osteopontin Production.

BACKGROUND: Aging induces cardiac structural and functional changes linked to the increased deposition of extracellular matrix proteins, including OPN (osteopontin), conducing to progressive interstitial fibrosis. Although OPN is involved in various pathological conditions, its role in myocardial aging remains unknown. METHODS: OPN deficient mice (OPN-/-) with their wild-type (WT) littermates were evaluated at 2 and 14 months of age in terms of cardiac structure, function, histology and key molecular markers. OPN expression was determined by reverse-transcription polymerase chain reaction, immunoblot and immunofluorescence. Luminex assays were performed to screen plasma samples for various cytokines/adipokines in addition to OPN. Similar explorations were conducted in aged WT mice after surgical removal of visceral adipose tissue (VAT) or treatment with a small-molecule OPN inhibitor agelastatin A. Primary WT fibroblasts were incubated with plasma from aged WT and OPN-/- mice, and evaluated for senescence (senescence-associated ß-galactosidase and p16), as well as fibroblast activation markers (Acta2 and Fn1). RESULTS: Plasma OPN levels increased in WT mice during aging, with VAT showing the strongest OPN induction contrasting with myocardium that did not express OPN. VAT removal in aged WT mice restored cardiac function and decreased myocardial fibrosis in addition to a substantial reduction of circulating OPN and transforming growth factor ß levels. OPN deficiency provided a comparable protection against age-related cardiac fibrosis and dysfunction. Intriguingly, a strong induction of senescence in cardiac fibroblasts was observed in both VAT removal and OPN-/- mice. The addition of plasma from aged OPN-/- mice to cultures of primary cardiac fibroblasts induced senescence and reduced their activation (compared to aged WT plasma). Finally, Agelastatin A treatment of aged WT mice fully reversed age-related myocardial fibrosis and dysfunction. CONCLUSIONS: During aging, VAT represents the main source of OPN and alters heart structure and function via its profibrotic secretome. As a proof-of-concept, interventions targeting OPN, such as VAT removal and OPN deficiency, rescued the heart and induced a selective modulation of fibroblast senescence. Our work uncovers OPN's role in the context of myocardial aging and proposes OPN as a potential new therapeutic target for a healthy cardiac aging.

Total synthesis of (-)-agelastatin A: an SH2' radical azidation strategy.

A reagent generated from TMSN3/KMnO4/BnEt3NCl was found to promote an SH2' radical azidation of a bromo silyl enol ether to furnish an azido silyl enol ether via olefin transposition. With the present azidation protocol, a new synthetic approach to agelastatin A, a potent antitumor marine alkaloid, has been established.

2-aminoethoxydiphenyl borate provides an anti-oxidative effect and mediates cardioprotection during ischemia reperfusion in mice.

Excessive levels of reactive oxygen species (ROS) and impaired Ca2+ homeostasis play central roles in the development of multiple cardiac pathologies, including cell death during ischemia-reperfusion (I/R) injury. In several organs, treatment with 2-aminoethoxydiphenyl borate (2-APB) was shown to have protective effects, generally believed to be due to Ca2+ channel inhibition. However, the mechanism of 2-APB-induced cardioprotection has not been fully investigated. Herein we investigated the protective effects of 2-APB treatment against cardiac pathogenesis and deciphered the underlying mechanisms. In neonatal rat cardiomyocytes, treatment with 2-APB was shown to prevent hydrogen peroxide (H2O2) -induced cell death by inhibiting the increase in intracellular Ca2+ levels. However, no 2-APB-sensitive channel blocker inhibited H2O2-induced cell death and a direct reaction between 2-APB and H2O2 was detected by 1H-NMR, suggesting that 2-APB chemically scavenges extracellular ROS and provides cytoprotection. In a mouse I/R model, treatment with 2-APB led to a considerable reduction in the infarct size after I/R, which was accompanied by the reduction in ROS levels and neutrophil infiltration, indicating that the anti-oxidative properties of 2-APB plays an important role in the prevention of I/R injury in vivo as well. Taken together, present results indicate that 2-APB treatment induces cardioprotection and prevents ROS-induced cardiomyocyte death, at least partially, by the direct scavenging of extracellular ROS. Therefore, administration of 2-APB may represent a promising therapeutic strategy for the treatment of ROS-related cardiac pathology including I/R injury.