Interleukin-1 beta-induced up-regulation of opioid receptors in the untreated and morphine-desensitized U87 MG human astrocytoma cells.

Journal of Neuroinflammation (Impact Factor: 4.9). 11/2012; 9(1):252. DOI: 10.1186/1742-2094-9-252
Source: PubMed

ABSTRACT BACKGROUND: Interleukin-1beta (IL-1beta) is a pro-inflammatory cytokine that can be produced in the central nervous system during inflammatory conditions. We have previously shown that IL-1beta expression is altered in the rat brain during a morphine tolerant state, indicating that this cytokine may serve as a convergent point between the immune challenge and opiate mediated biological pathways. We hypothesized that IL-1beta up-regulates opioid receptors in human astrocytes in both untreated and morphine-desensitized states. METHODS: To test this hypothesis, we compared the basal expression of the mu (MOR), delta (DOR), and kappa (KOR) opioid receptors in the human U87 MG astrocytic cell line to SH-SY5Y neuronal and HL-60 immune cells using absolute quantitative real time RT-PCR (AQ-rt-RT-PCR). To demonstrate that IL-1beta induced up-regulation of the MOR, DOR and KOR, U87 MG cells (2 x 105 cells/well) were treated with IL-1beta (20 ng/mL or 40 ng/mL), followed by co-treatment with interleukin-1 receptor antagonist protein (IL-1RAP) (400 ng/mL or 400 ng/mL). The above experiment was repeated in the cells desensitized with morphine, where U87 MG cells were pre-treated with 100 nM morphine. The functionality of the MOR in U87 MG cells was then demonstrated using morphine inhibition of forksolin-induced intracellular cAMP, as determined by radioimmunoassay. RESULTS: U87 MG cells treated with IL-1beta for 12 h showed a significant up-regulation of MOR and KOR. DOR expression was also elevated, although not significantly. Treatment with IL-1beta also showed a significant up-regulation of the MOR in U87 MG cells desensitized with morphine. Co-treatment with IL-1beta and interleukin-1 receptor antagonist protein (IL-1RAP) resulted in a significant decrease in IL-1beta-mediated MOR up-regulation. CONCLUSION: Our results indicate that the pro-inflammatory cytokine, IL-1beta, affects opiate-dependent pathways by up-regulating the expression of the MOR in both untreated and morphine-desensitized U87 MG.

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