Increased intracellular Ca2+ selectively suppresses IL-1-induced NO production by reducing iNOS mRNA stability.
This study addresses the role of intracellular calcium (Ca2+) in the expression of iNOS, an IL-1 inducible gene in human articular chondrocytes. The calcium ionophore A23187 and ionomycin did not induce NO release or iNOS expression but inhibited dose dependently IL-1-induced NO release with IC50 of 200 nM and 100 nM, respectively. Increased intracellular Ca2+ induced by thapsigargin or cyclopiazonic acid, inhibitors of the endoplasmic reticulum Ca2+ ATPase, had similar inhibitory effects with IC50 of 1 nM and 3 microM, respectively. LPS and TNF alpha induced NO production were also suppressed by these Ca2+ elevating drugs. Levels of IL-1-induced iNOS protein were reduced by A23187, thapsigargin, and cyclopiazonic acid. These drugs as well as Bay K 8644 and KCl inhibited IL-1-induced iNOS mRNA expression. To analyze the role of Ca2+ in the expression of other IL-1 responsive genes in chondrocytes, these Ca2+ modulating drugs were tested for effects on COXII. In contrast to the inhibitory effects on iNOS mRNA, these drugs induced COXII mRNA expression and in combination with IL-1, enhanced COXII mRNA levels. Ca2+ mediated increases in COXII mRNA expression were associated with an increase in COXII protein. The kinetics of Ca2+ effects on IL-1-induced iNOS mRNA levels suggested a posttranscriptional mechanism. Analysis of iNOS mRNA half life showed that it was 6-7 h in IL-1-stimulated cells and decreased by A23187 to 2-3 h. In conclusion, these results show that Ca2+ inhibits IL-1-induced NO release, iNOS protein, and mRNA expression in human articular chondrocytes by reducing iNOS mRNA stability. Under identical conditions increased Ca2+ enhances IL-1-induced COXII gene and protein expression.
Geng
Y
Y
Sam and Rose Stein Institute for Research on Aging, University of California, San Diego, La Jolla 92093-0663, USA.
Lotz
M
M
D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002358:Cartilage, Articular / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000201:enzymology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007527:Isoenzymes / Q000096:biosynthesis; D007700:Kinetics; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase; D011189:Potassium Chloride / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors
D007211:Indoles; D007375:Interleukin-1; D007527:Isoenzymes; D012333:RNA, Messenger; D013729:Terpenes; D009569:Nitric Oxide; D000001:Calcimycin; D011189:Potassium Chloride; D019284:Thapsigargin; D019001:Nitric Oxide Synthase; D011451:Prostaglandin-Endoperoxide Synthases; D000594:Amino Acid Oxidoreductases; D000252:Calcium-Transporting ATPases; D002118:Calcium; C000543:cyclopiazonic acid