IL-4 mediated by HSV vector suppresses morphine withdrawal response and decreases TNFα, NR2B, and pC/EBPβ in the periaqueductal gray in rats

Chronic opiates induce the development of physical dependence. Opioid physical dependence characterized by withdrawal symptoms, may have very long-lasting effects on the motivation for reward, including the incubation of cue-induced drug-seeking behavior. Elucidation of the mechanisms involved in physical dependence is crucial to developing more effective treatment strategies for opioid dependence. Chronic morphine induces production of proinflammatory cytokines in regional-specific sites of the brain. Interleukin-4 (IL-4) is a prototypical anti-inflammatory cytokine that globally suppresses proinflammatory cytokines. Here, we used recombinant herpes simplex virus vector S4IL4 that encode mouse il4 gene to evaluate the therapeutic potential of IL-4 in naloxone-precipitation morphine withdrawal (MW). One week after microinjection of the vector S4IL4 into the PAG LacZ or mouse IL-4 immunoreactivity in the vlPAG was visualized. ELISA assay showed that vector S4IL4 into the PAG induced the expression of IL-4. S4IL4 blunted the morphine withdrawal syndrome. S4IL4 suppressed the upregulated TNFα, NR2B and pC/EBPβ in the PAG induced by MW. These results show that inhibition of proinflammatory factor in the PAG suppressed MW. This study may provide a novel therapeutic approach to morphine physical withdrawal symptoms.