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Investigation of Chondroprotective Mechanisms of Selenium

dc.contributor.advisor Kraus, Virginia B.
dc.contributor.author Cheng, Wai Ming
dc.date.accessioned 2011-01-06T16:01:21Z
dc.date.available 2012-12-12T05:30:14Z
dc.date.issued 2010
dc.identifier.uri https://hdl.handle.net/10161/3097
dc.description.abstract <p>Selenium (Se) is an essential trace element and metalloid involved in several key metabolic activities: protection against oxidative damage, regulation of immune and thyroid function, and fertility. Several recent lines of evidence from epidemiology, genetic, and transgenic animal studies suggest that Se may play a protective role in Osteoarthritis (OA). However, the exact protective mechanism of Se is still unclear. </p><p>In this study, we hypothesized that Se exerts its chondroprotective benefit via an anti-oxidative and anti-inflammatory effect mediated by specific selenoproteins that neutralize cytokine-induced inflammatory responses in chondrocytes. We established an in vitro system for studying the effect of Se in the chondrosarcoma cell line SW-1353 and in human primary chondrocytes. Selenomethionine (SeMet) induced gene expression and enzyme activity of both antioxidative enzymes glutathione peroxidase (GPX) and thioredoxin reductase (TR) in SW-1353 cells. Our data suggest that Se may be protective against oxidative stress through regulation of the activity of these antioxidative enzymes.</p><p>As IL-1&beta; is one of the primary pro-inflammatory cytokines contributing to the progression in OA, we next investigated the effect of Se on the gene expression induced by physiological doses of IL-1&beta;. SeMet inhibited IL-1&beta; induced catabolic gene expression of matrix metalloproteinase 1 (MMP1) and MMP13 as well as total MMP activity in chondrocytes. Similarly, SeMet inhibited chondrocyte gene expression of IL-1&beta; induced nitric oxide synthase (iNOS) and cyclooxygenase (COX2) with corresponding reductions in nitric oxide (NO) and prostaglandin E2 (PGE2) production. In addition, SeMet pretreatment attenuated the IL-1&beta; induced activation of p38 MAPK but not the ERK, JNK or NFkB pathways. Taken together, our results suggest that Se inhibits IL-1&beta; induced expression of inflammatory and catabolic genes, partly through inhibition of IL-1&beta; cell signaling. </p><p>Since Se may function through selenoproteins, we evaluated the role of three specific major selenoproteins, GPX1, TR1 and DIO2, in modifying the inflammatory response stimulated by IL-1&beta; in chondrocytes by RNA interference. Based on RNA interference results, DIO2 and TR1 mediated the inhibitory effect of SeMet on IL-1&beta; induced COX2 gene expression, while GPX1 did not show a significant inhibitory effect on Se. Depletion of DIO2 increased the IL-1&beta; induced COX2 gene expression. This suggests that DIO2 may negatively modulate the IL-1&beta; response. Our data also suggest that part of this inhibitory effect of DIO2 could be through regulation of IL-1&beta; gene expression itself. These results highlight a potential new role of DIO2 in modulating the inflammatory response in chondrocytes </p><p>In summary, the result of this study suggests that Se may exert its chondroprotective effect through specific selenoproteins which neutralize oxidative stress and modify the inflammatory response in chondrocytes.</p>
dc.subject Pathology
dc.subject Cellular Biology
dc.subject Molecular Biology
dc.subject chondrocyte
dc.subject COX2
dc.subject IL-1&beta
dc.subject inflammation
dc.subject iNOS
dc.subject selenium
dc.title Investigation of Chondroprotective Mechanisms of Selenium
dc.type Dissertation
dc.department Pathology
duke.embargo.months 24


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