Upregulation of HIV-1 expression in cocultures of chronically infected promonocytes and human brain cells by dynorphin

Using cocultures of human fetal brain cells and a chronically human immunodeficiency virus-1 (HIV-1)-infected promonocytic line U1, we investigated the effect of dynorphin, an endogenous opioid peptide found in the CNS, on upregulation of HIV-1 expression. Dynorphin and the synthetic κ receptor agonist U50,488 promoted HIV-1 expression with a bell-shaped concentration-response relationship in which maximal effects were observed at 10^-13 and 10^-11 M, respectively. Pretreatment for 30 min with the κ receptor antagonist nor-binaltorphimine completely blocked the stimulatory effect of dynorphin and U50,488. The involvement of cytokines on HIV-1 expression was tested. Dynorphininduced upregulation of HIV-1 in the cocultures was largely blocked by antibodies to tumor necrosis factor (TNF)-α and interleukin (IL)-6 but not by antibodies to IL-10. Also, dynorphin stimulated TNF-α and IL-6 in the brain cell cultures at both mRNA and protein levels, suggesting the involvement of these cytokines in opioid-induced HIV-1 expression. These findings suggest that endogenous opioid peptides such as dynorphin may have an immunomodulatory function in the CNS and could act as a cofactor in the neuropathogenesis of HIV-1.