Basic calcium phosphate crystal-induced collagenase production: role of intracellular crystal dissolution.
OBJECTIVE
To investigate the potential therapeutic effects of inhibiting intracellular dissolution of basic calcium phosphate (BCP) crystals in tissue culture by raising lysosomal pH using bafilomycin A1, a specific vacuolar pump inhibitor.


METHODS
45Ca-labeled crystals were used to demonstrate intracellular crystal dissolution in human foreskin fibroblasts (HF). Mitogenesis was evaluated using [3H]thymidine incorporation assays and cell counts. Northern blot and Western blot were used to study collagenase [matrix metalloproteinase-1 (MMP1)] mRNA accumulation and protein secretion, respectively.


RESULTS
Bafilomycin A1 inhibited intracellular dissolution of BCP crystals and caused a concentration-dependent inhibition of BCP crystal-induced mitogenesis. Doses of bafilomycin A1 which inhibited intracellular crystal dissolution and mitogenesis had no effect on BCP crystal-induced MMP1 mRNA accumulation or protein secretion.


CONCLUSIONS
Raising lysosomal pH to inhibit intracellular BCP crystal dissolution attenuates the proliferative response to BCP crystals in HF but does not prevent metalloprotease synthesis and secretion. The therapeutic potential of lysosomotropic agents for preventing joint destruction in BCP crystal deposition disease is limited.
McCarthy
G M
GM
Department of Medicine, Medical College of Wisconsin, Milwaukee, USA. gmcc@post.its.mcw.edu
Cheung
H S
HS
Abel
S M
SM
Ryan
L M
LM
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015152:Blotting, Northern; D002130:Calcium Phosphates / Q000378:metabolism*; D002478:Cells, Cultured; D017364:Collagenases / Q000096:biosynthesis*; D003460:Crystallization; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes; D018942:Macrolides; D008666:Metalloendopeptidases / Q000096:biosynthesis; D008938:Mitosis
D000900:Anti-Bacterial Agents; D002130:Calcium Phosphates; D018942:Macrolides; C057620:bafilomycin A; D017364:Collagenases; D008666:Metalloendopeptidases