Regulation of Immune Cell Function by Nicotinamide Nucleotide Transhydrogenase

Contribution of MLKL to the development of doxorubicin-induced cardiomyopathy and its amelioration by rapamycin

Necroptosis, necrosis characterized by RIPK3-MLKL activation, has been proposed as a mechanism of doxorubicin (DOX)-induced cardiomyopathy. We showed that rapamycin, an mTORC1 inhibitor, attenuates cardiomyocyte necroptosis. Here we examined role of MLKL in DOX-induced myocardial damage and protective effects of rapamycin. Cardiomyopathy was induced in mice by intraperitoneal injections of DOX (10 mg/kg, every other day) and followed for 7 days. DOX-treated mice showed a significant decline in LVEF assessed by cardiac MRI (45.5 ± 5.1% vs. 65.4 ± 4.2%), reduction in overall survival rates, and increases in myocardial RIPK3 and MLKL expression compared with those in vehicle-treated mice, and those changes were prevented by administration of rapamycin (0.25 mg/kg) before DOX injection. In immunohistochemical analyses, p-MLKL signals were detected in the cardiomyocytes of DOX-treated mice, and the signals were reduced by rapamycin. Mlkl+/- and Mlkl-/- mice were similarly resistant to DOX-induced cardiac dysfunction, indicating that a modest reduction in MLKL level is sufficient to prevent the development of DOX-induced cardiomyopathy. However, evidence of cardiomyocyte necrosis assessed by C9 immunostaining, presence of replacement fibrosis, and electron microscopic analyses was negligible in the myocardium of DOX-treated mice. Thus, MLKL-mediated signaling contributes to DOX-induced cardiac dysfunction primarily by a necrosis-independent mechanism, which is inhibitable by rapamycin.

Genomics of aging: Reactive oxidation and inefficient mitochondria

ABSTRACT

Many things are associated with decreased health and lifespan, including cancer, diabetes, atherosclerosis, high blood pressure, and chronic inflammatory conditions. Clinicians may not be familiar with the role that mitochondrial mutations and associated mitochondrial dysfunction play in a shortened lifespan. This article, the fifth in the JAANP Genomics of Aging series, describes the role that mitochondrial dysfunction plays in the development of age-related diseases such as Alzheimer disease, Parkinson disease, cancer, heart disease, and stroke.

Vitamin C protects the spleen against PFOA-induced immunotoxicity

Perfluorooctanoic acid (PFOA) is widely used in industrial and consumer products of our daily life. It is well-documented that PFOA is closely associated with fatty liver disease. Recently, cumulating studies demonstrated the immunotoxicity of PFOA, but its harmful effect on the largest immune organ, spleen is still largely unknown. In the present study, we used PFOA-exposed mouse model together with comparative transcriptomic analysis to understand the molecular mechanisms underlying the immunotoxicity of PFOA. Furthermore, we investigated the possible use of vitamin C to reverse the PFOA-induced immunotoxicity in spleen. Our result showed that the PFOA exposure could reduce the spleen weight and plasma lymphocytes, and the splenic comparative transcriptomic analysis highlighted the alteration of cell proliferation, metabolism and immune response through the regulation of gene clusters including nicotinamide nucleotide transhydrogenases (NNT) and lymphocyte antigen 6 family member D and K (LY6D and LY6K). More importantly, the supplementation of vitamin C would relieve the PFOA-reduced spleen index and white blood cells. The bioinformatic analysis of transcriptome suggested its involvement in the spleen cell proliferation and immune response. For the first time, our study delineated the molecular mechanisms underlying the PFOA-induced immunotoxicity in the spleen. Furthermore, our results suggested that the supplementation of vitamin C had beneficial effect on the PFOA-altered spleen functions.