Dual modulation of the T-cell receptor-activated signal transduction pathway by morphine in human T lymphocytes

In this study, we aimed to investigate the effect of morphine on the activation of extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB), both of which play crucial roles in T-cell activation.

Human CD3+ T cells and Jurkat T cells were stimulated by anti-CD3 antibody or phorbol 12-myristate 13-acetate plus ionomycin with or without 24-h pretreatment with morphine. Activation of ERK was assessed by immunoblot analysis of phosphorylated ERK. Activation of the NF-κB signaling pathway was examined by analyzing nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) phosphorylation using immunoblotting, and interleukin-2 (IL-2) gene expression using quantitative real-time reverse-transcriptase polymerase chain reaction.

Morphine pretreatment enhanced ERK phosphorylation, but inhibited IκBα phosphorylation and IL-2 gene expression in activated T cells. The effects of morphine on ERK phosphorylation and IL-2 gene expression were not antagonized by naloxone. We detected κ-opioid receptor transcript in T cells, but U50,488, a κ-receptor-selective agonist, did not enhance ERK phosphorylation.

Morphine enhances ERK signaling, whereas it inhibits NF-κB signaling in activated human T cells. These effects of morphine are unlikely to be mediated by known opioid receptors.