Alcohol consumption induces murine osteoporosis by downregulation of natural killer T-like cell activity.

INTRODUCTION: Chronic alcohol consumption (CAC) can induce several deleterious effects on the body, including the promotion of osteoporosis; however, the immunological mechanism underlying alcohol-induced osteoporosis is still unclear. METHODS: We administered alcohol to mice for 4 weeks as the experimental CAC model and analyzed the bone and immune cells that are located in the vicinity of a bone. RESULTS: IL-4 is known to be a suppressive factor for osteoclastogenesis, and we found that natural killer T (NKT)-like cells, which showed NK1.1-positive, CD3-positive, and α-galactosylceramide-loaded CD1d tetramer-negative, produced IL-4 more effectively than CD4+ T and natural killer (NK) cells. The alcohol consumption facilitated a significant decrease of bone mineral density with the upregulation of nuclear factor of activated T cells 1 and receptor activator of NF-κB ligand expression. Meanwhile, we confirmed that alcohol consumption suppressed the activity of antigen-presenting cells (APCs) and NKT-like cells, leading to decreased IL-4 secretion. Moreover, these harmful effects of alcohol consumption were reduced by simultaneous treatment with a glycolipid antigen OCH. CONCLUSIONS: Our results indicate that the inactivation of innate immune cells, APCs, and NKT-like cells are likely to be crucial for alcohol-induced osteoporosis and provide a new therapeutic approach for preventing osteoporosis.

The Contribution of Alcohol Dehydrogenase 3 to the Development of Alcoholic Osteoporosis in Mice.

BACKGROUND: Alcohol dehydrogenase 3 (ADH3) plays major roles not only in alcohol metabolism but also in nitric oxide metabolism as S-nitrosoglutathione reductase (GSNOR). ADH3/GSNOR regulates both adipogenesis and osteogenesis through the denitrosylation of peroxisome proliferator-activated receptor γ. The current study investigated the contribution of ADH3 to the development of alcoholic osteoporosis in chronic alcohol consumption (CAC). METHODS: Nine-week-old male mice of different ADH genotypes [wild-type (WT) and Adh3-/-] were administered a 10% ethanol solution for 12 months. The femurs were evaluated by histochemical staining and computed tomography-based bone densitometry. The mRNA levels of ADH3 were evaluated in the WT mice by reverse transcription-quantitative polymerase chain reaction. RESULTS: The Adh3-/- control mice exhibited increased activities of both osteoblasts and osteoclasts and lower bone masses than the WT control mice. CAC exhibited no remarkable change in osteoblastic and osteoclastic activities, but decreased bone masses were observed in WT mice despite an increase in the mRNA levels of ADH3. Conversely, bone masses in the Adh3-/- control mice were not reduced after CAC. CONCLUSIONS: The Adh3-/- control mice exhibited a high turnover of osteoporosis since osteoclastogenesis dominated osteoblastogenesis; however, bone resorption was not enhanced after CAC. In comparison, CAC lead to alcoholic osteoporosis in WT mice, accompanied by increased mRNA levels of ADH3. Hence, ADH3 can prevent osteoporosis development in normal ADH genotypes with no alcohol ingestion. However, ADH3 contributes to the development of alcoholic osteoporosis under CAC by participating in alcohol metabolism, increasing metabolic toxicity, and lowering GSNO reducing activity.