Signal transduction of beta2m-induced expression of VCAM-1 and COX-2 in synovial fibroblasts.
BACKGROUND
beta2 microglobulin (beta2m) amyloidosis is a destructive articular disease affecting dialysis patients. We have demonstrated that beta2m increases the expression of vascular cell adhesion molecule (VCAM-1) and cyclooxygenase-2 (COX-2) in human osteoarthritic synovial fibroblasts (SFLs).


METHODS
To determine the cell signaling pathways, SFLs were incubated with beta2m in the presence or absence of various inhibitors for 24 hours. Intracellular calcium ([Ca2+]i) was measured by fluorometric techniques and vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2) expression was determined by immunohistochemistry and Western blotting.


RESULTS
beta2m increased [Ca2+]i levels in a dose dependent manner (P < 0.05) in SFLs. BAPTA-AM, a [Ca2+]i chelator, completely inhibited beta2m-induced expression of VCAM-1 and COX-2. U73122 [phospholipase C (PLC) inhibitor] or 2-APB [specific inhibitor of inositol 1,4,5-trisphosphate (IP3)-induced [Ca2+]i release] completely blocked the beta2m-induced increase in [Ca2+]i and the up-regulation of VCAM-1 and COX-2. However, pretreatment with staurosporin, a protein kinase C inhibitor, had no effect. Disruption of the actin cytoskeleton by treatment with cytochalasin D or latrunculin A blocked beta2m up-regulation of VCAM-1 and COX-2. Finally, cells treated with phosphatidylinositol-3 kinase (PI-3 kinase) inhibitors wortmannin or LY294002 also failed to express VCAM-1 and COX-2.


CONCLUSIONS
These results demonstrate that IP3-mediated [Ca2+]i release, PI-3 kinase, and actin cytoskeleton reorganization are involved in beta2m-induced expression of VCAM-1 and COX-2 in human SFLs. Understanding the potential pathways by which beta2m exerts its inflammatory-like effects may lead to the development of future therapies.
Chen
Neal X
NX
Indiana University School of Medicine and Richard L. Roudebush VAMC, Indianapolis, Indiana, USA. xuechen@iupui.edu
O'Neill
Kalisha D
KD
Niwa
Toshimitsu
T
Moe
Sharon M
SM
D000199:Actins / Q000378:metabolism; D000686:Amyloidosis / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D003599:Cytoskeleton / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000032:analysis / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis / Q000096:biosynthesis*; D013583:Synovial Membrane / Q000473:pathology; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis / Q000096:biosynthesis*; D001613:beta 2-Microglobulin / Q000494:pharmacology*
D000199:Actins; D002118:Calcium; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors; D015544:Inositol 1,4,5-Trisphosphate; D007527:Isoenzymes; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011451:Prostaglandin-Endoperoxide Synthases; D019010:Vascular Cell Adhesion Molecule-1; D001613:beta 2-Microglobulin; C496540:PTGS2 protein, human