Actin cytoskeletal architecture regulates nitric oxide-induced apoptosis, dedifferentiation, and cyclooxygenase-2 expression in articular chondrocytes via mitogen-activated protein kinase and protein kinase C pathways.
Nitric oxide (NO) in articular chondrocytes regulates differentiation, survival, and inflammatory responses by modulating ERK-1 and -2, p38 kinase, and protein kinase C (PKC) alpha and zeta. In this study, we investigated the effects of the actin cytoskeletal architecture on NO-induced dedifferentiation, apoptosis, cyclooxygenase (COX)-2 expression, and prostaglandin E2 production in articular chondrocytes, with a focus on ERK-1/-2, p38 kinase, and PKC signaling. Disruption of the actin cytoskeleton by cytochalasin D (CD) inhibited NO-induced apoptosis, dedifferentiation, COX-2 expression, and prostaglandin E2 production in chondrocytes cultured on plastic or during cartilage explants culture. CD treatment did not affect ERK-1/-2 activation but blocked the signaling events necessary for NO-induced dedifferentiation, apoptosis, and COX-2 expression such as activation of p38 kinase and inhibition of PKCalpha and -zeta. CD also suppressed activation of downstream signaling of p38 kinase and PKC, such as NF-kappaB activation, p53 accumulation, and caspase-3 activation, which are necessary for NO-induced apoptosis. NO production in articular chondrocytes caused down-regulation of phosphatidylinositol (PI) 3-kinase and Akt activities. The down-regulation of PI 3-kinase and Akt was blocked by CD treatment, and the CD effects on apoptosis, p38 kinase, and PKCalpha and -zeta were abolished by the inhibition of PI 3-kinase with LY294002. Our results collectively indicate that the actin cytoskeleton mediates NO-induced regulatory effects in chondrocytes by modulating down-regulation of PI 3-kinase and Akt, activation of p38 kinase, and inhibition of PKCalpha and -zeta
Kim
Song-Ja
SJ
Department of Biological Science, Kongju National University, Gongju, Chungnam 314-701, Korea.
Hwang
Sang-Gu
SG
Kim
Il-Chul
IC
Chun
Jang-Soo
JS
D000199:Actins / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology* / Q000378:metabolism*; D051546:Cyclooxygenase 2; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000502:physiology*; D015232:Dinoprostone / Q000096:biosynthesis; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000187:drug effects*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000187:drug effects*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051571:Protein Kinase C-alpha; D011817:Rabbits; D015398:Signal Transduction; D000099293:Protein Kinase C-lambda
D000199:Actins; D051546:Cyclooxygenase 2; D015638:Cytochalasin D; D015232:Dinoprostone; D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D009569:Nitric Oxide; D011451:Prostaglandin-Endoperoxide Synthases; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D000099293:Protein Kinase C-lambda