The use of gene-based techniques to produce antinociceptive molecules has been actively investigated for treatment of neuropathic pain and trauma of central nervous system. Among the endogenous opioids, b-endorphin (b-EP) is the most potent one, which is derived from pro-opiomelanocortin (POMC). In addition to b-endorphin, POMC is also the precursor of many neuropeptides such as adrenocorticotropin hormone (ACTH), melanocyte-stimulating hormone (a-MSH), ¡Ketc. Appropriate administration of POMC gene is essential for the success of its clinical application. Thus, gene transfer approach seems to be suitable for continuous supply of b-endorphin to alleviate intractable pain. Recombinant adenovirus was used as gene delivery system for POMC because of its high titer, wide host range, and transduction efficiency. In the present study, we have generated and characterized the recombinant adenovirus encoding POMC (Ad-POMC) by PCR and western blot analysis, and detect the presence of opioid peptides including ACTH, a-MSH and b-EP by RIA and chemilluminiscent assay. GH3 cells infected with Ad-POMC showed significantly higher levels of ACTH, b-endorphin, and a¡VMSH comparing with cells of control groups. By using Ad-GFP, the optimal MOI for adenovirus vector to infect neuronal GH3 cells, glial C6 cells, hepatoma Hep3B cells, smooth muscle G8 cells, fibroblast CCD-965K cells, and endothelial EA.hy926 cells was determined at 50, 500, 50, 500, 500, and 200, respectively. The results of determining the efficiency of POMC processing in different types of cells after in vitro cell cultures gene delivery indicated that peripheral cells, though at a lower extent, are capable of cleaving POMC and releasing opioid peptides after POMC gene delivery like neuronal cells of central nervous system. In formalin test, the intrathecal POMC gene delivery significantly decreased the magnitude of the formalin-evoked flinching response phase 1 (P < 0.05) and phase 2 (P < 0.001) when compared with rats receiving saline or Ad-GFP. In conclusion, the intrathecal POMC gene delivery can produce effectively attenuation on the inflammatory pain response. So far, there have been various gene delivery studies confirming the potential role of POMC in antinociception. In the future, more experiments will be needed to characterize the effects of POMC expression on cellular lipid metabolism. This will enable us to evaluate the therapeutic potential of POMC on treatment of obesity.

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