Chondrocyte cell death mediated by reactive oxygen species-dependent activation of PKC-βI

Abstract

DelCarlo, Marcello, and Richard F. Loeser. Chondrocyte cell death mediated by reactive oxygen species-dependent activation of PKC-␤I. Am J Physiol Cell Physiol 290: C802-C811, 2006. First published October 19, 2005 doi:10.1152/ajpcell.00214.2005.-Signals generated by the extracellular matrix (ECM) promote cell survival. We have shown that chondrocytes detached from their native ECM and plated without serum at low density on poly-L-lysine undergo significant cell death that is associated with the production of reactive oxygen species (ROS). No cell death or ROS production was observed when cells were plated on fibronectin under the same conditions. Cell death on poly-L-lysine could be completely inhibited with the addition of either antioxidants or inhibitors of specific protein kinase C (PKC) isoforms including PKC-␤I. PKC-␤I was noted to translocate from the cytosol to the particulate membrane after plating on poly-L-lysine, and this translocation was inhibited by the addition of an antioxidant. Time-course analyses implicated endogenous ROS production as a secondary messenger leading to PKC-␤I activation and subsequent chondrocyte cell death. Cell survival on poly-L-lysine was significantly improved in the presence of oligomycin or DIDS, suggesting that ROS production occurred via complex V of the electron transport chain of the mitochondria and that ROS were released to the cytosol via voltage-dependent anion channels. Together, these results represent a novel mechanism by which ROS can initiate cell death through the activation of PKC-␤I. articular cartilage; osteoarthritis; cell signaling; fibronectin CELL CONTACT with the extracellular matrix (ECM) promotes survival in many cell types, but the exact mechanism is not completely understood. Studies have shown apoptotic cell death in epithelial (9) and endothelial

Hsp90 mediates insulin‐like growth factor 1 and interleukin‐1β signaling in an age‐dependent manner in equine articular chondrocytes

“…The relationship of diminished levels of Hsp90 protein in chondrocyte metabolism during OA has not been determined, but in another study, Hsp90 mRNA was diminished in OA compared with normal cartilage samples (9). Taken together, these findings suggest that decreased Hsp90 levels might play a role in ageassociated alterations in chondrocyte responses to external cues such as oxidative stress, which is an increasingly apparent contributor to older age-onset OA (38)(39)(40)(41)(42)(43)(44). Decreased levels of Hsp90 during aging may also contribute to altered growth factor responses and increased cellular senescence and therefore increased risk of older age-onset OA.…”

Specifying protein kinase C functions in melanoma

“…Ectopic expression of PKCb in melanoma cells inhibited tyrosine phosphorylation of Gab1 and the hepatocyte growth factor-induced activation of PI3K, and these effects were associated with reduced melanoma cell invasion (Voris et al, 2010). PKCb can also phosphorylate the adaptor protein p66Shc involved in increasing mitochondrial permeability and inducing apoptosis (DelCarlo and Loeser, 2006;Pinton et al, 2007). Consistent with pro-differentiation and pro-apoptotic functions of PKCb, re-expression of PKCb in melanoma cells suppresses growth in soft agar (Voris et al, 2010).…”

“…PKCb is activated in response to oxidative stress, which is produced by UV radiation and is elevated in melanoma because of oncogene activation (e.g., BRAF) (de Souza et al, 2006;Fried and Arbiser, 2008;Govindarajan et al, 2007;Meyskens et al, 2001;Zaidi et al, 2008). Elevated reactive oxygen species (ROS) are also produced in response to PKCb activation because of the phosphorylation of p66Shc and activation of the mitochondrial permeability pore, resulting in a positive feedback involving PKCb activation and ROS generation (DelCarlo and Loeser, 2006;Giorgio et al, 2005;Pinton et al, 2007;Voris et al, 2010). PRKCB gene expression is in part regulated by the microphthalmia-associated transcription factor, MITF, a master melanocyte developmental transcription factor, consistent with the role of PKCb in melanin biosynthesis (Park et al, 2006).…”

N-Acetylcysteine Inhibits Post-Impact Chondrocyte Death in Osteochondral Explants

“…Rotenone blocked mitogen-activated kinase activation and catabolic gene induction in chondrocytes stimulated with fibronectin fragments 27 . Moreover, production of oligomycin-sensitive reactive oxygen species in chondrocytes plated on polylysine is suppressed by intact fibronectin 28 . These two related studies suggest that disruption of integrin-matrix interactions induces production of mitochondrial reactive oxygen species.…”