Flow cytometry analysis of inflammatory cells isolated from the sciatic nerve and DRG after chronic constriction injury in mice.

BACKGROUND: Cellular responses to nerve injury play a central role in the pathogenesis of neuropathic pain. However, the analysis of site specific cellular responses to nerve injury and neuropathic pain is limited to immunohistochemistry staining with numerous limitations. NEW METHODS: We proposed to apply flow cytometry to overcome some of the limitations and developed two protocols for isolation of cells from small specimens of the sciatic nerve and dorsal root ganglion (DRG) in mice. RESULTS AND COMPARASION WITH EXISTING: methods We found that both the non-enzymatic and enzymatic approaches were highly effective in harvesting a sufficient number of cells for flow cytometry analysis in normal and pathological conditions. The total number of cells in the injury site of the sciatic and its DRGs increased significantly 14days after chronic constriction injury (CCI) of the sciatic nerve, compared to sham surgery control or the contralateral control. The enzymatic approach yielded a significantly higher total number of cells and CD45 negative cells, suggesting that this approach allows for harvest of more resident cells, compared to the non-enzymatic method. The percentage of CD45+/CD11b+ cells was significantly increased in the sciatic nerve but not in the DRG. These results were consistent with both protocols. CONCLUSIONS: We thus offer two simple and effective protocols that allow for application of flow cytometry to the investigation of cellular and molecular mechanisms of neuropathic pain.

In vivo and systems biology studies implicate IL-18 as a central mediator in chronic pain.

Inflammation is associated with peripheral neuropathy, however the interplay among cytokines, chemokines, and neurons is still unclear. We hypothesized that this neuroinflammatory interaction can be defined by computational modeling based on the dynamics of protein expression in the sciatic nerve of rats subjected to chronic constriction injury. Using Dynamic Bayesian Network inference, we identified interleukin (IL)-18 as a central node associated with neuropathic pain in this animal model. Immunofluorescence supported a role for inflammasome activation and induction of IL-18 at the site of injury. Combined in vivo and in silico approaches may thus highlight novel targets in peripheral neuropathy.

[Expression of Wnt5a in dorsal root ganglia in rat model of chronic compression of dorsal root ganglia].

OBJECTIVE: To investigate the role of Wnt5a in the mechanism of radiculopathy and the relation between Wnt5a and tumor necrosis factor α (TNF-α) by observing the change of the expression of Wnt5a in the rat model of chronic compression of dorsal root ganglia (CCD). METHODS: A total of 192 adult male Sprague Dawley rats were allocated into 4 groups: shame group (group A, n = 48), CCD group (group B, n = 48), CCD + saline group (group C, n = 48), and CCD + etanercept group (group D, n = 48). An L-shaped needle (about 3.5 mm in length, 0.6 mm in diameter) was inserted into the L5 intervertebral foramen, and the dorsal root ganglia (DRG) was compressed by the needle to prepare the CCD model in groups B, C, and D, and then normal saline (5.5 mg/kg) or etanercept was injected intraperitoneally in groups C and D. The intervertebral foramen was exposed in group A. The mechanical pain threshold of the posterior paw was tested by the von Frey filaments at 1, 3, 5, and 7 days after operation; the expressions of Wnt5a protein and mRNA were detected at 3 and 7 days after operation by immunohistochemical staining and RT-PCR, respectively. RESULTS: The mechanical pain threshold of groups B and C was significantly lower than that of groups A and D, and in group D than in group A (P < 0.05), but no significant difference was found between groups B and C (P > 0.05). The Wnt5a positive cells and the mRNA expression of Wnt5a at 7 days were significantly more than those at 3 days in groups B, C, and D (P < 0.05). The Wnt5a positive cells and the mRNA expression of Wnt5a in groups B and C were significantly more than in groups A and D, and in group D than in group A (P < 0.05), but no significant difference was shown between groups B and C (P > 0.05). CONCLUSION: The expression of Wnt5a in the DRG is increased after CCD. The expression of Wnt5a in the DRG is decreased after the administration of the inhibitor of TNF-α.

Chemical and mechanical nerve root insults induce differential behavioral sensitivity and glial activation that are enhanced in combination.

Both chemical irritation and mechanical compression affect radicular pain from disc herniation. However, relative effects of these insults on pain symptoms are unclear. This study investigated chemical and mechanical contributions for painful cervical nerve root injury. Accordingly, the C7 nerve root separately underwent chromic gut exposure, 10gf compression, or their combination. Mechanical allodynia was assessed, and glial reactivity in the C7 spinal cord tissue was assayed at days 1 and 7 by immunohistochemistry using GFAP and OX-42 as markers of astrocytes and microglia, respectively. Both chromic gut irritation and 10gf compression produced ipsilateral increases in allodynia over sham (p<0.048); combining the two insults significantly (p<0.027) increased ipsilateral allodynia compared to either insult alone. Behavioral hypersensitivity was also produced in the contralateral forepaw for all injuries, but only the combined insult was significantly increased over sham (p<0.031). Astrocytic activation was significantly increased over normal (p<0.001) in the ipsilateral dorsal horn at 1 day after either compression or the combined injury. By day 7, GFAP-reactivity was further increased for the combined injury compared to day 1 (p<0.001). In contrast, spinal OX-42 staining was generally variable, with only mild activation at day 1. By day 7 after the combined injury, there were significant (p<0.003) bilateral increases in OX-42 staining over normal. Spinal astrocytic and microglial reactivity follow different patterns after chemical root irritation, compression, and a combined insult. The combination of transient compression and chemical irritation produces sustained bilateral hypersensitivity, sustained ipsilateral spinal astrocytic activation and late onset bilateral spinal microglial activation.

Localization and changes of intraneural inflammatory cytokines and inducible-nitric oxide induced by mechanical compression.

STUDY DESIGN: Investigation of intraneural inflammation induced by mechanical compression. OBJECTIVES: In order to investigate the mechanism of neuropathy, this study used a median nerve compression model in dogs. Immunohistochemistry was used to examine the localization and changes of inflammatory cytokines and nitric oxide (NO). SUMMARY OF BACKGROUND DATA: The manifestation of pain at sites of inflammation has a close relationship with the release of mediators from macrophages such as interleulin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha), as well as with NO. However, the mediators involved in inflammation of nerve due to mechanical compression remain almost unknown. METHODS: In this study, the median nerve of dogs was compressed with a clip for three weeks to observe the changes caused by compression. Immunohistochemistry was done by the avidin-biotin-peroxidase complex method to observe the changes of T cells (CD45) and macrophages (Mac-1) after compression. Antibodies against IL-1beta, TNF-alpha, and inducible nitric oxide synthesis (i-NOS) were used to examine the localization and changes of these mediators caused by nerve compression. RESULTS: In control animals, resident T cells were detected, but there were no macrophages. IL-1beta was positive in the Schwann cells and vascular endothelial cells. However, no cells showed TNF-alpha or i-NOS positively. After nerve compression, numerous T cells and macrophages appeared among the demyelinized nerve fibers. The macrophages were positive for IL-1beta, TNF-alpha and i-NOS. CONCLUSION: Inflammatory cytokines and NO may be involved in intraneural inflammatory changes arising from mechanical compression. Such mediators may be of importance in the manifestation of neuropathy.

A comparison of chronic pain behavior following local application of tumor necrosis factor alpha to the normal and mechanically compressed lumbar ganglia in the rat.

To study the role of inflammatory cytokines in the initiation and persistence of radiculopathy as seen in humans, tumor necrosis factor alpha (TNF-alpha) was administered either to normal, uninjured L5 dorsal root ganglia (DRG) of rats via a hole drilled through the transverse process, or to chronically compressed L5 DRG via a hollow stainless steel rod inserted into the intervertebral foramen. In other experiments, a mixture of soluble TNF receptors (sTNF-Rs: sTNF-RIplus minussTNF-RII) was locally delivered to the chronically or acutely compressed DRG to neutralize the activity of endogenous TNF-alpha. Behavioral tests of mechanical allodynia were performed before and after TNF-alpha administration. Infusion of the normal DRG with TNF-alpha at a rate of 1 microl/h for 7 days induced ipsilateral mechanical allodynia (i.e. decreased mechanical withdrawal threshold) that lasted about 2 weeks. Infusion of the compressed DRG did not alter compression-induced allodynia within the first operative week but substantially enhanced the ipsilateral allodynia after the first postoperative week. Neutralizing the activity of endogenous TNF-alpha of the compressed DRG with sTNF-Rs reduced allodynia for 3 days, but was subsequently without effect. Similar results were obtained when sTNF-Rs were chronically administrated at the acutely compressed ganglion. Results demonstrated that exogenous TNF-alpha causes pain and mechanical allodynia when deposited at the normal DRG, and further enhances the ongoing allodynia when administrated at the compressed DRG. Results also suggest that endogenous TNF-alpha contributes to the early development of mechanical allodynia in rats with chronic DRG compression.

Axonal transport of TNF-alpha in painful neuropathy: distribution of ligand tracer and TNF receptors.

Tumor necrosis factor-alpha (TNF-alpha) is a key player in peripheral nerve injury. In the inflammatory chronic constriction injury (CCI) model of sciatic neuropathy, upregulation of TNF-alpha mRNA and protein at the site of nerve injury has been associated with pain. We now report the distribution of endogenous TNF-alpha protein and its receptors along normal and CCI-injured sciatic nerves, and within the corresponding lumbar dorsal root ganglia (DRG). Using Western blotting, TNF-alpha was found to be distinctly increased at the injury site, as well as in the axons just distal to the corresponding DRG. The TNF-alpha signal between the injury site and DRG (midaxonal) was induced between 2 and 5 days post-CCI, suggesting activation of TNF-alpha axonal transport. Endogenous TNF-alpha was localized in small-diameter, presumably nociceptive, and large-diameter, presumably mechanoceptive, DRG sensory neurons in both normal and CCI animals. Intraneural microinjection of biotin-labeled TNF-alpha showed specific axonal uptake at the injection site, as detected by avidin-biotin-peroxidase histochemistry, and confirmed by co-localization with neurobiotin tracer. In control animals, fast retrograde transport of biotinylated TNF-alpha to both L4 and L5 DRG neurons was apparent 6 h following injection. TNF receptors TNFRI and TNFRII co-localized with biotinylated TNF-alpha tracer along the nerve trunk, suggesting that TNF-alpha transport may be receptor-mediated. In animals with CCI neuropathy, uptake of biotinylated TNF-alpha by neuronal soma was inhibited. Instead, there was signal accumulation in the axons immediately distal to the DRG, and TNFRI and RII were increased at this same anatomic location. These findings highlight a dynamic process of TNF-alpha protein and receptor regulation throughout the peripheral neural axis that bears on both the normal function of DRG neurons and the pathogenesis of painful neuropathies.

[Autoimmune component of inflammatory reactions in the radicular syndromes of lumbar osteochondrosis]. / Ob autoimmunnom komponente vospalitel'nykh reaktsii pri koreshkovykh sindromakh poiasnichnogo osteokhondroza.

Experimental and clinical studies of the autoimmune component of the reactive inflammatory process in tissues of the vertebral canal, caused by the presence of elements of an intervertebral disk, have allowed the authors to investigate the immune reaction of a delayed type and prove that it is immunocomplex in nature and manifests 3 weeks after the elements of the intervertebral disk have found their way into the immunocompetent system. The presence of immunoglobulins around the vessels and in the spinal membranes sheds some light on the autoimmune origin of cicatricial changes in these anatomical structures.