Effects of calcitonin gene-related peptide on bone resorption mediated by interleukin-1

We examined the effects of calcitonin gene-related peptide CGRP on the bone resorption stimulated by IL-1 alpha after neonatal mouse calvaria were cultured in vitro and bone resorption was determined by measuring the release of calcium into the medium after alpha 48-hour incubation. CGRP (10(-9)-10(-8) M) blocked completely the IL1 alpha-mediated increase in bone resorption and inhibited the basal bone resorption. In accordance with the effects of calcitonin on osteoclasts, CGRP caused cessation of lamellipodia activity and gradual retraction of lamellipodia when added into the culture medium. Quantitative analysis showed that CGRP (10(-6) M) caused a gradual reduction of osteoclastic surface area and convex perineum. These data show that CGRP inhibits IL1 alpha mediated bone resorption because of its direct regulation of osteoclast activity.