Inhibition of VCAM-1 expression by CORM-3: the role of the ubiquitin proteasome system, p38 and mitochondrial respiration

Carbon monoxide (CO) abrogates TNF-alpha mediated inflammatory responses in endothelial cells, yet, the underlying mechanism hereof is still elusive. We sought to explore potential mechanisms by which CO down-regulates VCAM-1 expression on TNF-alpha stimulated human umbilical vein endothelial cells (HUVEC). By genome-wide gene expression profiling and pathway analysis we studied the relevance of particular pathways for the anti-inflammatory effect of CO. In CO-releasing molecules-3 (CORM-3) stimulated HUVEC, significant changes in gene expression were found for genes implicated in the proteasome and porphyrine pathways. Although proteasome activities were increased by CORM-3, proteasome inhibitors did not abolish CORM-3s effect. Likewise, HO-1 inhibitors did not abrogate the ability of CORM-3 to down-regulate VCAM-1 expression. MAPK p38 was inhibited by CORM-3. Accordingly, VCAM-1 expression was down-regulated by the p38 inhibitor SB203580. Down-regulation of VCAM-1 by CORM-3 only occurred at concentrations that partly inhibit ATP production. Sodium azide and oligomycin paralleled the effect of CORM-3 in this regard. In conclusion, down-regulation of VCAM-1 by CORM-3 seems to be mediated via inhibition of p38 and mitochondrial respiration. Although CORM-3 up-regulates several genes in the ubiquitin proteasome sytem (UPS) or porphyrin pathway, there is no evidence that these changes are involved in the anti-inflammatory properties of CORM-3.

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