EFFECTS OF ETHANOL ON GENE-EXPRESSION IN RAT BONE - TRANSIENT DOSE-DEPENDENT CHANGES IN MESSENGER-RNA LEVELS FOR MATRIX PROTEINS, SKELETAL GROWTH-FACTORS, AND CYTOKINES ARE FOLLOWED BY REDUCTIONS IN BONE-FORMATION

Several studies were performed in female rats to determine dose and ti me course changes in mRNA levels for matrix proteins in bone after a s ingle administration of ethanol. As expected, dose-dependent transient increases in blood ethanol were measured. Additionally, there was mil d hypocalcemia with no change in immunoreactive parathyroid hormone. C oordinated dose-dependent increases in mRNA for type 1 collagen, osteo nectin, and osteocalcin were noted in the proximal tibial metaphysis 6 hr after ethanol was given, with the peak values occurring at a dose of 1.2 g/kg (0.4 mi). Similar increases in mRNA levels for matrix prot eins were noted in lumbar vertebrae after ethanol treatment. The chang es were specific for bone; ethanol had no effect on mRNA levels for ma trix proteins in the uterus or liver, although the mRNA concentrations tended to be reduced in uterus. Message levels for several cytokines implicated in the regulation of bone turnover were also assayed; mRNA levels for transforming growth factor-beta(1), transforming growth fac tor-beta(2), interferon-gamma and interleukin-6 were unchanged at dose s ranging from 0.14 to 1.7 g/kg. At the highest dose of ethanol, the m RNA level for tumor necrosis factor-alpha was elevated while the level for insulin-like growth factor-1 was reduced. The time course effects of ethanol (0.4 ml dose) were determined in a separate experiment. Et hanol resulted in a transient increase in mRNA levels for the three bo ne matrix proteins assayed. However, matrix protein synthesis, as dete rmined by incorporation of H-3-proline into the proximal tibial metaph ysis, was not changed after 6 hr. The changes in mRNA levels for the m atrix proteins were preceded by brief, transient decreases in mRNA lev els for interleukin-lp, interferon-gamma, and migration inhibitory fac tor, and followed by a more prolonged decrease in the mRNA level for i nsulin-like growth factor-1. A subsequent study was performed to deter mine the effects of repetitive daily treatment with ethanol on rat bon e. After 7 days, there were highly significant decreases in the mRNA l evel for type 1 collagen, as well as decreased bone formation. These r esults suggest that ethanol may alter bone metabolism by disturbing si gnal transduction pathways that regulate the expression of genes for b one matrix proteins, skeletal growth factors, and cytokines.