CHRONIC 1,25-DIHYDROXYVITAMIN D-3-MEDIATED INDUCTION OF NERVE GROWTH-FACTOR MESSENGER-RNA AND PROTEIN IN L929 FIBROBLASTS AND IN ADULT-RAT BRAIN

We have proposed that elevating levels of nerve growth factor (NGF) in the CNS is a rational strategy for treating certain neurodegenerative disorders. The present studies were conducted to determine: (1) if pharmacologically induced levels of NGF could be sustained for an extended time, and (2) if correlations exist between increases in NGF mRNA and NGF protein in L929 cells and in vivo. Short-term treatment of L929 cells with 1,25-dihydroxyvitamin D, resulted in a two-fold increase in both NGF mRNA and NGF protein. These increases were sustained for up to 48 h with continuous exposure to 1,25-dihydroxyvitamin D-3. In rats, 1,25-dihydroxyvitamin D-3 (2:5 nmol; i.c.v.) induced NGF mRNA transiently, with peak two-fold increases observed 4 h post-injection. In contrast to L929 cells, 1,25-dihydroxyvitamin D-3 did not elicit an increase in NGF protein after a single adminstration in vivo. However, consistent with long-term exposure in L929 cells, chronic 6 day infusion of 1,25-dihydroxyvitamin D-3 resulted in induction of both NGF mRNA and NGF protein in the brain. These results indicate that 1,25-dihydroxyvitamin D-3-mediated NGF induction in cultured L929 cells may predict of NGF induction in vivo, suggesting that L929 cells may have utility in studying underlying mechanisms of NGF induction by 1,25-dihydroxyvitamin D-3. On the basis of NGF's ability to increase cholinergic function in animal models of cholinergic degeneration, these results are supportive of a role for NGF inducers as potential drugs for neurodegenerative disorders.