Kim Song-Ja, Hwang Sang-Gu, Kim Il-Chul, Chun Jang-Soo
Department of Biological Science, Kongju National University, Gongju, Chungnam 314-701, Korea.
J Biol Chem. 2003 Oct 24;278(43):42448-56. doi: 10.1074/jbc.M304887200. Epub 2003 Aug 7.
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
关节软骨细胞中的一氧化氮（NO）通过调节细胞外信号调节激酶1和2（ERK-1和-2）、p38激酶以及蛋白激酶C（PKC）α和ζ来调控细胞分化、存活及炎症反应。在本研究中，我们调查了肌动蛋白细胞骨架结构对NO诱导的关节软骨细胞去分化、凋亡、环氧合酶（COX）-2表达及前列腺素E2生成的影响，重点关注ERK-1/-2、p38激酶和PKC信号通路。用细胞松弛素D（CD）破坏肌动蛋白细胞骨架，可抑制在塑料培养皿上培养的软骨细胞或软骨外植体培养过程中NO诱导的凋亡、去分化、COX-2表达及前列腺素E2生成。CD处理不影响ERK-1/-2的激活，但阻断了NO诱导的去分化、凋亡及COX-2表达所需的信号事件，如p38激酶的激活以及PKCα和ζ的抑制。CD还抑制了p38激酶和PKC下游信号的激活，如NF-κB激活、p53积累及caspase-3激活，这些都是NO诱导凋亡所必需的。关节软骨细胞中NO的产生导致磷脂酰肌醇（PI）3激酶和Akt活性下调。CD处理可阻断PI 3激酶和Akt的下调，用LY294002抑制PI 3激酶可消除CD对凋亡、p38激酶以及PKCα和ζ的影响。我们的结果共同表明，肌动蛋白细胞骨架通过调节PI 3激酶和Akt的下调、p38激酶的激活以及PKCα和ζ的抑制，介导NO对软骨细胞的调节作用。
