preproenkephalin and Chronic-Pain

Joint pain is a major clinical problem mainly associated to osteoarthritis, and characterized by articular cartilage degradation resulting in a complex chronic pain state that includes nociceptive, emotional and cognitive manifestations. Memory impairment, depressive- and anxiety-like symptoms have been reported to be associated with chronic pain, leading to a decrease of life quality. In this study, we evaluated the involvement of the endogenous dynorphin/kappa opioid receptor (KOR) system on the nociceptive, emotional, cognitive, neurochemical and epigenetic manifestations of joint pain. The murine model of monosodium iodoacetate (MIA) was used to induce joint pain in knockout mice for KOR (KOR-KO), prodynorphin (PDYN-KO) and their wild-type (WT) littermates. KOR-KO and PDYN-KO mice developed mechanical allodynia after intra-articular injection of MIA. This allodynia was significantly increased in both KOR-KO and PDYN-KO when compared to WT mice. Accordingly, both mutants showed increased microglial activation on the lumbar section of the spinal cord after MIA. The emotional responses were evaluated by measuring anxiety-like behaviour in the elevated plus maze and anhedonia as depressive-like behaviour, and cognitive alterations in the object recognition paradigm. Emotional and cognitive impairments after joint pain were differently modified in KOR-KO and PDYN-KO mice. Alterations of corticotropin-releasing factor (CRF) on the amygdala and hippocampus and down regulation of histone 3 acetylation on the amygdala suggest a possible mechanism to explain these emotional and cognitive manifestations. Our results reveal a specific involvement of the dynorphin/KOR system on joint pain manifestations that are usually associated to osteoarthritis.

Topics: Acetylation; Amygdala; Animals; Arthralgia; Chronic Pain; Cognition; Corticotropin-Releasing Hormone; Disease Models, Animal; Emotions; Enkephalins; Epigenesis, Genetic; Hippocampus; Histones; Hyperalgesia; Mice, Inbred C57BL; Mice, Knockout; Microglia; Osteoarthritis; Protein Precursors; Receptors, Opioid, kappa; Spinal Cord

To determine whether herpes simplex virus-based vectors can efficiently transduce mouse trigeminal ganglion (TG) neurons and attenuate preexisting nerve injury-induced whisker pad mechanical hypersensitivity in a trigeminal inflammatory compression (TIC) neuropathic pain model.. Tissue transduction efficiencies of replication-conditional and replication-defective vectors to mouse whisker pads after topical administration and subcutaneous injection were assessed using quantitative real-time PCR (qPCR). Tissue tropism and transgene expression were assessed using qPCR and reverse-transcriptase qPCR following topical application of the vectors. Whisker pad mechanical sensitivities of TIC-injured mice were determined using graduated von Frey fibers before and after application of human preproenkephalin expressing replication-conditional vector (KHPE). Data were analyzed using one-way analysis of variance (ANOVA) and post hoc tests.. Transduction of target TGs was 8- to 50-fold greater after topical application than subcutaneous injection and ≥ 100-fold greater for replication-conditional than replication-defective vectors. Mean KHPE loads remained constant in TGs (4.5-9.8 × 10(4) copies/TG) over 3 weeks but were below quantifiable levels (10 copies/tissue) within 2 weeks of application in other nontarget cephalic tissues examined. Transgene expression in TGs was maximal during 2 weeks after topical application (100-200 cDNA copies/mL) and was below quantifiable levels (1 cDNA copy/mL) in all nontarget tissues. Topical KHPE administration reduced TIC-related mechanical hypersensitivity on whisker pads 4-fold (P < .05) for at least 1 week.. Topically administered KHPE produced a significant antinociceptive effect in the TIC mouse model of chronic facial neuropathic pain. This is the first report in which a gene therapeutic approach reduced trigeminal pain-related behaviors in an established pain state in mice.

Topics: Administration, Topical; Animals; Chronic Pain; Disease Models, Animal; Enkephalins; Facial Pain; Genetic Therapy; Genetic Vectors; Humans; Injections, Subcutaneous; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Protein Precursors; Simplexvirus; Touch; Transduction, Genetic; Transfection; Transgenes; Trigeminal Ganglion; Trigeminal Neuralgia

To observe the analgesic effect of intrathecal transplant of immortalized rat astrocyte genetically modified by human preproenkephalin gene (IAST/hPPE) on chronic neuropathic pain.. 40 adult male Sprague-Dawley rats were randomly divided into four groups, 10 rats for each group. Naive group, SNI group, SNI + IAST group and SNI + IAST/hPPE group. The immortalized rat astrocyte (IAST) or IAST/hPPE co-incubated with bromodeoxyuridine (BrdU) in vitro were transplanted in the lumbar 4 to 6 subarachnoid space near the spinal cord 1 week after right side spared nerve injury (SNI). All animals were tested for bilateral 50% hindpaw withdrawal threshold (PWT) to a graded series of Von Frey hairs stimulation once a week from one week before SNI to six weeks after transplant, the difference value for right 50% PWT minus left 50% PWT was calculated and the effect of intraperitoneal naloxone on the analgesic efficacies was also observed. The content of L-EK in the spinal cord of L4 - 6 and was determined using immunohistochemistry and radioimmunoassay, and the expression of BrdU in grafts was determined using immunohistochemistry.. Allodynia-like behaviour after 1 week following SNI was observed. As compared with Naive group, the difference value for the right 50% PWT minus left 50% PWT in the other three groups was higher significantly (P < 0.01). The tactile allodynia induced by SNI was significantly alleviated during the 1 to 6 week period after transplantation of IAST/hPPE cells, but transplants of IAST cells had no effect on the allodynia-like behaviour. The difference value for the right 50% PWT minus left 50% PWT in SNI + IAST/hPPE group was lower significantly than that in the SNI and SNI +I AST group (P < 0.01), but there was no significant difference between SNI and SNI + IAST group (P > 0.05). The efficacies were reversed by intraperitoneal naloxone in SNI + IAST/hPPE group. The content of L-EK in the lumbar spinal cord in IAST/hPPE group (108.1 pg/mg +/- 12.5 pg/mg) was significantly higher than that in other three groups (P < 0.01), but there was no significant difference between SNI and SNI + IAST group (25.4 pg/mg +/- 1.9 pg/mg vs 28.0 pg/mg +/- 2.1 pg/mg, P > 0.05). Furthermore, The grafts in the surface of dorsal horn were still stained positively for BrdU, they survived greater than 6 weeks on the pia mater around the spinal cord.. Intrathecal transplant of IAST/hPPE cells could alleviate the allodynia-like behaviour after chronic neuropathic pain, which is associated with enkephalin secreted continuously from the grafts and conducted via opiate receptors.

Topics: Animals; Astrocytes; Cells, Cultured; Chronic Pain; Disease Models, Animal; Enkephalins; Genetic Therapy; Humans; Male; Neuralgia; Protein Precursors; Rats; Rats, Sprague-Dawley