Prodigiosin 25-C and metacycloprodigiosin suppress the bone resorption by osteoclasts.

Prodigiosin 25-C and metacycloprodigiosin were found to suppress PTH-stimulated pit formation by cultured osteoclasts on bone slices. They also inhibited the acidification of vacuolar organelles in intact osteoclastic cells. Since the acidic pH in these organelles is generated by the action of proton-pumping ATPases of the organelle, these results indicate that the proton-pumping activity of V-ATPase in osteoclastic cells is essential in bone resorption and that the inhibition of the acidification of vacuolar organelles by prodigiosins results in suppression of PTH-stimulated bone resorption.