Additive anti-hyperalgesia of electroacupuncture and intrathecal antisense oligodeoxynucleotide to interleukin-1 receptor type I on carrageenan-induced inflammatory pain in rats.

Accumulating evidence shows that spinal interleukin-1beta (IL-1beta) plays a critical role in inflammatory pain. Electroacupuncture (EA) can effectively attenuate inflammatory hyperalgesia both in clinical practices and experimental studies. However, little is known about the relationship between spinal IL-1beta and EA analgesia. The present study was designed to evaluate the effects of EA and antisense oligodeoxynucleotide (ODN) to IL-1 receptor type I (IL-1RI) on carrageenan-induced thermal hyperalgesia and the expression of IL-1beta as well as IL-1RI. It was demonstrated that carrageenan induced marked thermal hyperalgesia in the injected paw, hence making paw withdrawal latency (PWL) decrease to 3.47+/-0.31 s at 180 min post-injection. Nevertheless, when EA was administered for 30 min at 180 min post-carrageenan injection, the PWLs were significantly increased between 10 and 90 min following the beginning of EA treatment and peaked at 30 min to 5.91+/-0.61 s. And also EA partly reversed the elevation of IL-1beta and IL-1RI expression induced by carrageenan. Down-regulation of IL-1RI expression by repeated intrathecal antisense ODN (50 microg/10 microl) significantly increased the mean PWL up to 5.75+/-0.15 s in 180-300 min post-carrageenan injection. Additionally, when the combination of EA with antisense ODN was used, thermal hyperalgesia was further alleviated than EA or antisense ODN alone, with a maximum PWL of 7.66+/-0.50 s at 30 min post the beginning of EA treatment. The results suggested an involvement of the spinal IL-1beta/IL-1RI system in EA-induced anti-hyperalgesia in inflammatory pain.

Lipopolysaccharide-induced protein kinase D activation mediated by interleukin-1beta and protein kinase C.

Protein kinase D (PKD), a newly described serine/threonine kinase, has been implicated in many signal transduction pathways. The present study was designed to determine whether and how PKD is activated in inflammation. The results demonstrated that lipopolysaccharide (LPS, 30 microg/ml) stimulated PKD and protein kinase C (PKC) phosphorylation in spinal neurons within 0.5 h, and the activation reached a maximum at 3 or 8 h and declined at 12 h. The phosphorylation could be inhibited by the selective inhibitors for PKC (100 nM), mainly for PKCalpha and PKCbeta, suggesting the involvement of the PKC pathway. Particularly, PKCalpha might be critical for LPS-induced PKD activation since the PKCbeta inhibitor (100 nM) observed no effect on the phosphorylation of PKD. Furthermore, the expression of interleukin-1beta (IL-1beta) was significantly induced by LPS within 0.5 h, and reached a maximum at 8 h. IL-1 receptor antagonist inhibited PKD and PKCs activation induced by LPS at a concentration of 50 nM and achieved maximum at 1000 nM. These results demonstrated for the first time that PKD could be activated by LPS in spinal neurons, might via the IL-1beta/PKCalpha pathway. Additionally, immunostaining showed an increase in number of phosphorylated PKD-immunoreactive cells of adult spinal dorsal horn induced by intraplantar injected carrageenan (2 microg/100 microl), and antisense oligodeoxynucleotide to IL-1 receptor type I (50 microg/10 microl, intrathecal injected) inhibited the PKD activation, suggesting an involvement of IL-1beta/PKD pathway in inflammation in adult spinal cord.