Early CALP2 expression and microglial activation are potential inducers of spinal IL-6 up-regulation and bilateral pain following motor nerve injury.

Previous work from our laboratory showed that motor nerve injury by lumbar 5 ventral root transection (L5-VRT) led to interleukin-6 (IL-6) over-expression in bilateral spinal cord, and that intrathecal administration of IL-6 neutralizing antibody delayed the induction of mechanical allodynia in bilateral hind paws. However, early events and upstream mechanisms underlying spinal IL-6 expression following L5-VRT require elucidation. The model of L5-VRT was used to induce neuropathic pain, which was assessed with von Frey hairs and the plantar tester in adult male Sprague-Dawley rats. Calpain-2 (CALP2, a calcium-dependent protease) knockdown or over-expression and microglia depletion were conducted intrathecally. Western blots and immunohistochemistry were performed to explore the possible mechanisms. Here, we provide the first evidence that both IL-6 and CALP2 levels are increased in lumbar spinal cord within 30 min following L5-VRT. IL-6 and CALP2 co-localized in both spinal dorsal horn (SDH) and spinal ventral horn. Post-operative (PO) increase in CALP2 in ipsilateral SDH was evident at 10 min PO, preceding increased IL-6 at 20 min PO. Knockdown of spinal CALP2 by intrathecal CALP2-shRNA administration prevented VRT-induced IL-6 overproduction in ipsilateral spinal cord and alleviated bilateral mechanical allodynia. Spinal microglia activation also played a role in early IL-6 up-regulation. Macrophage/microglia markers ED1/Iba1 were increased at 30 min PO, while glial fibrillary acidic protein (astrocyte) and CNPase (oligodendrocyte) markers were not. Increased Iba1 was detected as early as 20 min PO and peaked at 3 days. Morphology changed from a small soma with fine processes in resting cells to an activated ameboid shape. Depletion of microglia using Mac-1-saporin partially prevented IL-6 up-regulation and attenuated VRT-induced bilateral mechanical allodynia. Taken together, our findings provide evidence that increased spinal cord CALP2 and microglia cell activation may have early causative roles in IL-6 over-expression following motor nerve injury. Agents that inhibit CALP2 and/or microglia activation may therefore prove valuable for treating neuropathic pain.

Calpain-2 contributes to neuropathic pain following motor nerve injury via up-regulating interleukin-6 in DRG neurons.

Motor nerve injury by L5 ventral root transection (L5-VRT) initiates interleukin-6 (IL-6) up-regulation in primary afferent system contributing to neuropathic pain. However, the early upstream regulatory mechanisms of IL-6 after L5-VRT are still unknown. Here, we monitored both the activity of calpain, a calcium-dependent protease suggested as one of the earliest mediators for cytokine regulation, and the expression of IL-6 in bilateral L4-L6 dorsal root ganglias (DRGs) soon after L5-VRT. We found that the protein level of calpain-2 in DRGs, but not calpain-1 was increased transiently in the first 10 min(-1)h ipsilaterally and 20 min(-1)h contralaterally after L5-VRT, long before mechanical allodynia was initiated (5-15 h ipsilaterally and 15 h(-1)d contralaterally). The early activation of calpain evaluated by the generation of spectrin breakdown products (SBDP) correlated well with IL-6 up-regulation in bilateral DRGs. Double immunofluorescence staining revealed that almost all the calpain-2 positive neurons expressed IL-6, indicating an association between calpain-2 and IL-6. Inhibition of calpain by pre-treatment with MDL28170 (25mg/kg, i.p.) attenuated the rat mechanical allodynia and prevented the early up-regulation of IL-6 following L5-VRT. Addition of exogenous calpain-2 onto the surface of left L5 DRG triggered a temporal allodynia and increased IL-6 in bilateral DRGs simultaneously. Taken together, the early increase of calpain-2 in L5-VRT rats might be responsible for the induction of allodynia via up-regulating IL-6 in DRG neurons.

Calpain-2 Regulates TNF-α Expression Associated with Neuropathic Pain Following Motor Nerve Injury.

Both calpain-2 (CALP2) and tumor necrosis factor-α (TNF-α) contribute to persistent bilateral hypersensitivity in animals subjected to L5 ventral root transection (L5-VRT), a model of selective motor fiber injury without sensory nerve damage. However, specific upstream mechanisms regulating TNF-α overexpression and possible relationships linking CALP2 and TNF-α have not yet been investigated in this model. We examined changes in CALP2 and TNF-α protein levels and alterations in bilateral mechanical threshold within 24 h following L5-VRT model injury. We observed robust elevation of CALP2 and TNF-α in bilateral dorsal root ganglias (DRGs) and bilateral spinal cord neurons. CALP2 and TNF-α protein induction by L5-VRT were significantly inhibited by pretreatment using the calpain inhibitor MDL28170. Administration of CALP2 to rats without nerve injury further supported a role of CALP2 in the regulation of TNF-α expression. Although clinical trials of calpain inhibition therapy for alleviation of neuropathic pain induced by motor nerve injury have not yet shown success, our observations linking CALP2 and TNF-α provide a framework of a systems' approach based perspective for treating neuropathic pain.

CD8+CD28+/CD8+CD28- T cell equilibrium can predict the active stage for patients with inflammatory bowel disease.

BACKGROUND/AIM: The balance of blood CD8+CD28+/CD8+CD28- T cells has been verified to be vital for patients with ulcerative colitis (UC), but their role in inflammatory bowel disease (IBD) remains unknown. This investigation aimed to evaluate the efficiency of the balance in predicting the active stage in IBD patients. METHODS: Fifty-three IBD subjects, including 31 UC and 22 Crohn's disease (CD) patients, were enrolled, and their peripheral blood CD8+CD28+ and CD8+CD28- T cell levels were tested using flow cytometry. The risk factors related to prognosis were compared between UC and CD patients. A 1-year follow-up was performed for all the IBD patients, and the CD8+ T cells and their ratio were compared at the 3rd, 6th, 9th, and 12th months during follow-up. The sensitivity and specificity of the CD8+ T cell level and balance were analyzed through receiver operator characteristic (ROC) curves. The cumulative remission lasting rates (CRLRs) under the different factors were analyzed using the Kaplan-Meier method. RESULTS: Higher prescription rates of immunosuppressants, steroids, probiotics, and biological agents (BAs) were found in CD subjects in comparison to UC subjects (P=0.005, 0.024, 0.034, and 0.001), as was a higher active rate during follow-up (95.5% of CD patients vs 67.7% of UC patients, P=0.035). The CD8+CD28+ T cell level and the CD8+CD28+/CD8+CD28- T cell ratio were significantly higher in UC patients than in CD patients, but the reverse was true for CD8+CD28- T cells during follow-up at the 9th and 12th month (all P<0.05). The diagnostic models of the initial CD8+CD28+ and CD8+CD28- T cell numbers and the CD8+CD28+/CD8+CD28- T cell ratio in predicting the active stage were found to be significant, with areas under the curves (AUCs) of 0.883, 0.098, and 0.913 for UC subjects (with 95% CI: 0.709-0.940, 0.009-0.188, and 0.842-1.003; P=0.001, 0.00, and 0.000) and 0.812, 0.078, and 0.898 for CD subjects (with 95% CI: 0.683-0.957, 0.003-0.158, and 0.837-0.998; P=0.003, 0.00, and 0.000). The cut-off values showed that when the ratios were 1.30 for UC and 1.22 for CD patients, the best sensitivity and specificity were observed, with 91.6% and 89.0% for UC and 88.5% and 85.1% for CD, respectively. The CRLRs were significantly higher in female, non-BA-treated, non-surgical IBD subjects when compared to male, BA-treated, surgical subjects (P=0.031, 0.000, and 0.000). The number of CD8+CD28+ and CD8+CD28- T cells and the CD8+CD28+/CD8+CD28- T cell ratio were correlated with BA treatment and surgery (all P<0.05). CONCLUSION: The CD8+CD28+/CD8+CD28- T cell balance, expected to be a novel immunologic marker, presented a satisfactory efficiency with high sensitivity and specificity in predicting the active stage in UC and CD patients, and the balance was closely related to the use of BAs and surgery.

[Immunological balance of CD8+CD28+/CD8+CD28- T lymphocytes can predict gastrointestinal hemorrhage in patients with inflammatory bowel disease].

OBJECTIVE: To evaluate the sensitivity and specificity of CD8+CD28+/CD8+CD28- T lymphocyte balance in predicting the gastrointestinal hemorrhage (GH) in patients with inflammatory bowel disease (IBD). METHODS: Forty-nine IBD patients, including 30 with ulcerous colitis (UC) and 19 with Crohn's disease (CD), were enrolled to test peripheral blood CD8+CD28+ and CD8+CD28- T cells using flow cytometry. All the patients were followed up for one year. The receiver-operating characteristic (ROC) curves were used to test the efficiency of CD8+CD28+/CD8+CD28- T lymphocyte balance to predict GH. The differences in lasting time of remission (LTR) under different factors were compared using Kaplan-Meier survival analysis, and the correlation between CD8+ T lymphocytes and the factors were analyzed. RESULTS: The utilization rates of immunosuppressant, steroids, and biological agent (BA) were significantly higher in CD patients than in UC patients (P=0.003, 0.043 and 0.002, respectively). The frequencies of CD8+CD28+T cells were obviously higher in UC patients than those in CD patients (t=3.022, P=0.004). CD8+CD28+T cells, CD8+CD28- T cells, and especially CD8+CD28+/CD8+CD28- ratio (area under curve of 0.977, P=0.000; cut-off value of 1.14 [13.95%/12.24%] with a sensitivity of 93.3% and a specificity of 91.2%) showed good efficiencies in predicting GH (P<0.01). The mean and median of LTR of IBD patients who did not receive BA or surgical treatment were significantly longer (Χ2=9.730, P=0.002; Χ2=15.981, P=0.000). CD8+CD28+/CD8+CD28- ratio was significantly related to both BA (P=0.009) and surgery (P=0.038). CONCLUSION: Both decreased CD8+CD28+T cells and elevated CD8+CD28-T cells are closely correlated with GH, and their ratio can predict the occurrence of GH with a high sensitivity and specificity and is correlated with BA and surgery at the cut-off value of 1.14.

The up-regulation of IL-6 in DRG and spinal dorsal horn contributes to neuropathic pain following L5 ventral root transection.

Our previous works have shown that pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) plays an important role in neuropathic pain produced by lumber 5 ventral root transection (L5-VRT). In the present work we evaluate the role of interleukin-6 (IL-6), another key inflammatory cytokine, in the L5-VRT model. We found that IL-6 was up-regulated in the ipsilateral L4 and L5 dorsal root ganglian (DRG) neurons and in bilateral lumbar spinal cord following L5-VRT. Double immunofluorescence stainings revealed that in DRGs the increased immunoreactivity (IR) of IL-6 was almost restricted in neuronal cells, while in the spinal dorsal horn IL-6-IR up-regulated in both glial cells (astrocyte and microglia) and neurons. Intrathecal administration of IL-6 neutralizing antibody significantly delayed the induction of mechanical allodynia in bilateral hindpaws after L5-VRT. Furthermore, inhibition of TNF-α synthesis by intraperitoneal thalidomide prevented both mechanical allodynia and the up-regulation of IL-6 in DRGs following L5-VRT. These data suggested that the increased IL-6 in afferent neurons and spinal cord contribute to the development of neuropathic pain following motor fiber injury, and that TNF-α is responsible for the up-regulation of IL-6.