We previously showed that H2 acts as a novel antioxidant to protect cells against oxidative stress. Subsequently, numerous studies have indicated the potential applications of H2 in therapeutic and preventive medicine. Moreover, H2 regulates various signal transduction pathways and the expression of many genes. However, the primary targets of H2 in the signal transduction pathways are unknown. Here, we attempted to determine how H2 regulates gene expression. In a pure chemical system, H2 gas (approximately 1%, v/v) suppressed the autoxidation of linoleic acid that proceeds by a free radical chain reaction, and pure 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine (PAPC), one of the major phospholipids, was autoxidized in the presence or absence of H2. H2 modified the chemical production of the autoxidized phospholipid species in the cell-free system. Exposure of cultured cells to the H2-dependently autoxidized phospholipid species reduced Ca2+ signal transduction and mediated the expression of various genes as revealed by comprehensive microarray analysis. In the cultured cells, H2 suppressed free radical chain reaction-dependent peroxidation and recovered the increased cellular Ca2+, resulting in the regulation of Ca2+-dependent gene expression. Thus, H2 might regulate gene expression via the Ca2+ signal transduction pathway by modifying the free radical-dependent generation of oxidized phospholipid mediators.
We previously reported that molecular hydrogen (H2) acts as a novel antioxidant to exhibit multiple functions. Moreover, long-term drinking of H2-water (water infused with H2) enhanced energy expenditure to improve obesity and diabetes in db/db mice accompanied by the increased expression of fibroblast growth factor 21 (FGF21) by an unknown mechanism. H2 was ingested by drinking of H2-water or by oral administration of an H2-producing material, MgH2. The comprehensive gene expression profile in the liver of db/db mice was analyzed by DNA microarray. The molecular mechanisms underlying the gene expression profile was investigated using cultured HepG2 cells. Moreover, the effects on lifespan of drinking H2-water were examined using wild-type mice that were fed a fatty diet. Pathway analyses based on comprehensive gene expression revealed the increased expression of various genes involved in fatty acid and steroid metabolism. As a transcription pathway, the PPARα signaling pathway was identified to upregulate their genes by ingesting H2. As an early event, the gene expression of PGC-1α was transiently increased, followed by increased expression of FGF21. The expression of PGC-1α might be regulated indirectly through sequential regulation by H2, 4-hydroxy-2-nonenal, and Akt/FoxO1 signaling, as suggested in cultured cell experiments. In wild-type mice fed the fatty diet, H2-water improved the level of plasma triglycerides and extended their average of lifespan. H2 induces expression of the PGC-1α gene, followed by stimulation of the PPARα pathway that regulates FGF21, and the fatty acid and steroid metabolism.
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