MAPK3 and endothelial dysfunction: Compared to control, morphine upregulated gene signature shows enrichment of GOs and pathways associated with defense responses such as interleukin signaling pathways, innate and adaptive immune cell activation, response to bacteria and LPS etc. Notably, other upregulated GOs such as MAPK and ERK1/2 signaling cascade, vascular inflammation, endothelial dysfunction, and O-linked glycosylation, were also emphasized in morphine group.