(R)-α-Lipoic acid treatment restores ceramide balance in aging rat cardiac mitochondria

Abstract

Inflammation results in heightened mitochondrial ceramide levels, which cause electron transport chain dysfunction, elevates reactive oxygen species, and increases apoptosis. As mitochondria in aged hearts also display many of these characteristics, we hypothesized that mitochondrial decay stems partly from an age-related ceramidosis that heretofore has not been recognized for the heart. Intact mitochondria or their purified inner membranes (IMM) were isolated from young (4-6 mo) and old (26-28 mo) rats and analyzed for ceramides by LC-MS/MS. Results showed that ceramide levels increased by 32% with age and three ceramide isoforms, found primarily in the IMM (e.g. C16-, C18-, and C24:1-ceramide), caused this increase. The ceramidosis may stem from enhanced hydrolysis of sphingomyelin, as neutral sphingomyelinase (nSMase) activity doubled with age but with no attendant change in ceramidase activity. Because (R)-α-lipoic acid (LA) improves many parameters of cardiac mitochondrial decay in aging and lowers ceramide levels in vascular endothelial cells, we hypothesized that LA may limit cardiac ceramidosis and thereby improve mitochondrial function. Feeding LA [0.2% wt/wt] to old rats for two weeks prior to mitochondrial isolation reversed the age-associated decline in glutathione levels and concomitantly improved Complex IV activity. This improvement was associated with lower nSMase activity and a remediation in mitochondrial ceramide levels. In summary, LA treatment lowers ceramide levels to that seen in young rat heart mitochondria and restores Complex IV activity which otherwise declines with age.

Age-related decline in mitochondrial bioenergetics: Does supercomplex destabilization determine lower oxidative capacity and higher superoxide production?

“…In addition, several alterations of the complex III holo-protein result in its lower activity, particularly in post-mitotic tissues of aging rodents [2, 4, 69, 71] and primates [72]. These results agree with other studies showing that defects of complex IV correlate with lower mitochondrial oxidative capacity in post-mitotic tissues of elder humans [73, 74], primates [72, 75], and rodents [3, 43, 76-79]. …”

“…Cholesterol accumulates in the IMM, alters membrane fluidity, and may promote greater H + leakage [7, 91]. In a similar vein, using LC-MS/MS analysis, we recently demonstrated that aged cardiac mitochondria accumulate ceramide, a pro-apoptotic sphingolipid, which results in inhibition of complex IV activity [79]. Furthermore, three ceramide isoforms in the IMM (e.g.…”

Effect of Procysteine on aging-associated changes in hepatic GSH and SMase: evidence for transcriptional regulation of smpd3

“…It seems that ceramides with various chain lengths can be generated in a specifi c manner and have distinct bioactivities ( 50 ). The effects of aging on the FA composition of ceramide have been investigated in several models including mouse CD4+ T-cells ( 51 ), cardiomyocytes ( 52 ), and skeletal muscle ( 53 ). Our mass spectrometry-based analysis of ceramide species in the livers of aged and young mice reveals that aging leads to the accumulation of C16:0 and C24:1 ceramides and has no effect on the less abundant C18:0, C18:1, and C24:0 ceramides, while the level of C20:0 ceramide is modestly suppressed.…”

Lactosylceramide contributes to mitochondrial dysfunction in diabetes

“…There is a diverse localization of alkaline ceramidases: ACER1 is localized to the ER and is mainly expressed in the skin, ACER2 is localized to the Golgi, and ACER3 is localized to both the Golgi and ER. Although NCDase was thought to preferentially localize to the plasma membrane, accumulating evidence demonstrates the presence of NCDase activity, or the enzyme itself (depending on the tissue/cell studied), in endosomal/lysosomal compartments ( 57 ) and mitochondria (9)(10)(11)58 ). In our previous studies, we have shown that mitochondria-resident NCDase modulates the ceramide profi le of liver mitochondria ( 9 ).…”