A non-calcemic analog of 1 alpha,25 dihydroxy vitamin D-3 (JKF) upregulates the induction of creatine kinase B by 17 beta estradiol in osteoblast-like ROS 17/2.8 cells and in rat diaphysis

We have reported that multiple treatments with so-called 'non-hypercalcemic ',analogs of 1 alpha ,25(OH)(2) vitamin D-3 (1,25(OH)(2)D-3) stimulate the specific activity of creatine kinase BB (CK) in ROS 17/2.8 osteoblast-like cells, and that pretreatment with these analogs upregulates responsiveness and sensitivity to 17 beta estradiol (E-2) for the induction of CK. However , since the analogs showed toxicity in vivo, we have now studied the action of a demonstrably non-calcemic, hybrid analog of vitamin D in ROS 17/2.8 c ells, and prepubertal rats. The analog JKF was designed to separate its cal cemic activity from other biological activities by combining a calcemic-low ering 1-hydroxymethyl group with a potentiating C, D-ring side chain modifi cation including 24 difluoronation. Treatment with 1 pM JKF alone significa ntly stimulated CK specific activity at 4 h by 30 +/- 10%. However after th ree daily pretreatments, JKF upregulated the extent of induction by 30 nM E -2 by 33% at 1 pM and by 97% at 1 nM; the E-2 dose needed for a significant stimulation of CK activity was lowered to 30 pM. The action of the SERMS t amoxifen, tamoxifen methiodide and raloxifene, at 3 muM, was also upregulat ed by three daily pretreatments with 1 nM JKF; unexpectedly, this pretreatm ent prevented the inhibition of E-2 stimulation by the SERMS. Upregulation of E-2 action by 1 nM JKF was inhibited by 1 nM ZK159222, an inhibitor of t he nuclear action of 1,25(OH)(2)D-3. In vivo, three daily injections of 0.0 5 ng/g body weight of JKF augmented the response of prepubertal female rat diaphysis and epiphysis to E-2. Therefore, demonstrably non-calcemic analog s of 1,25(OH)(2)D-3 may have potential for use in combination with estrogen s or SERMS in the prevention and/or treatment of metabolic bone diseases su ch as postmenopausal osteoporosis. (C) 2001 Elsevier Science Ltd. All right s reserved.