Identification of novel bone-specific molecular targets of binge alcohol and ibandronate by transcriptome analysis

Background: Our laboratory established that binge alcohol-related bone damage is prevented by aminobisphosphonates, suggesting bone resorption increases following binge exposure. We examined the effects of binge alcohol and antiresorptive therapy on the relationship between bone damage and modulation of the vertebral transcriptome, in an attempt to determine how alcohol-induced bone damage and its prevention modulate bone-related biological pathways. Methods: Male Sprague-Dawley rats were assigned to 1 of 6 treatment groups (n = 12/group). (C1) saline ip 3 d/wk for 1 week, (A1) binge alcohol, 3 g/kg, ip 3 d/wk for 1 week, (C4) saline ip, 3 d/wk for 4 weeks, (A4) binge alcohol, ip, 3 g/kg 3 d/wk for 4 weeks, (I4) ibandronate, saline ip 3 d/wk for 4 weeks, plus a single ip injection of ibandronate at 120 mu g/animal, and (AI4) binge alcohol plus ibandronate as above. After 1 or 4 weeks, adjacent lumbar vertebrae were assayed for bone damage or transcriptional changes. Results: Bone loss was not observed after 1 week of binge alcohol treatment. After 4 weeks, binge alcohol decreased vertebral BMD by 23% (p < 0.05) and compressive strength by 18% compared to saline controls (p < 0.05). Concurrent ibandronate prevented bone loss, increasing these parameters by 145 and 134% respectively compared to binge alcohol. (p < 0.05). Analysis of the vertebral transcriptome identified gene clusters specific for acute and chronic binge alcohol-related bone damage. Acute binge alcohol modulated the expression of integrin signaling-specific genes, while chronic binge alcohol modulated canonical Wnt signaling gene expression. Ibandronate normalized the expression of approximately 20% of the genes affected by chronic binge alcohol, allowing the identification of a unique subset of alcohol-sensitive, ibandronate-responsive genes. Conclusions: Identification of bone-specific gene expression clusters associated with acute and chronic binge alcohol treatment allowed for the identification of cellular pathways affected by binge treatment with known involvement in bone remodeling (Integrin, Canonical Wnt signaling) not previously identified as alcohol-sensitive. This data provides a basis for a plausible mechanistic explanation for the known detrimental effects of alcohol on bone formation and resorption.