Immunotherapy targeting cytokines in neuropathic pain

Surgical management of nervus intermedius neuralgia: A report of 4 cases and literature review

BACKGROUND

Nervus intermedius neuralgia (NIN) is characterized by paroxysmal episodes of sharp, lancinating pain in the deep ear. Unfortunately, only a few studies exist in the literature on this pain syndrome, its pathology and postoperative outcomes.

METHOD

We conducted a retrospective review of four cases diagnosed with NIN who underwent a neurosurgical intervention at our center from January 2015 to January 2023. Detailed information on their MRI examinations, intraoperative findings and other clinical presentations were obtained, and the glossopharyngeal and vagus nerves were isolated for immunohistochemistry examination.

RESULTS

A total of 4 NIN patients who underwent a microsurgical intervention at our institution were included in this report. The NI was sectioned in all patients and 3 of them underwent a microvascular decompression. Of these 4 patients, 1 had a concomitant trigeminal neuralgia (TN), and 1 a concomitant glossopharyngeal neuralgia (GPN). Three patients underwent treatment for TN and 2 for GPN. Follow-up assessments ranged from 8 to 99 months. Three patients reported complete pain relief immediately after the surgery until last follow-up, while in the remaining patient the preoperative pain gradually resolved over the 3 month period. Immunohistochemistry revealed that a greater amount of CD4+ and CD8+ T cells had infiltrated the glossopharyngeal versus vagus nerve.

CONCLUSIONS

NIN is an extremely rare condition showing a high degree of overlap with TN/GPN. An in depth neurosurgical intervention is effective to completely relieve NIN pain, without any serious complications. It appears that T cells may play regulatory role in the pathophysiology of CN neuralgia.

Neuroinflammation: Breaking barriers and bridging gaps

Neurons are the cells of the nervous system and are responsible for every thought, movement and perception. Immune cells are the cells of the immune system, constantly protecting from foreign pathogens. Understanding the interaction between the two systems is especially important in disease states such as autoimmune or neurodegenerative disease. Unfortunately, this interaction is typically detrimental to the host. However, recent efforts have focused on how neurons and immune cells interact, either directly or indirectly, following traumatic injury to the nervous system. The outcome of this interaction can be beneficial - leading to successful neural repair, or detrimental - leading to functional deficits, depending on where the injury occurs. This review will discuss our understanding of neuron-immune cell interactions after traumatic injury to both the peripheral and central nervous system.

Diagnosis and Management of Neuropathic Pain in Spine Diseases

Neuropathic pain is generally defined as a non-physiological pain experience caused by damage to the nervous system. It can occur spontaneously, as a reaction to a given stimulus, or independently of its action, leading to unusual pain sensations usually referred to as firing, burning or throbbing. In the course of spine disorders, pain symptoms commonly occur. According to available epidemiological studies, a neuropathic component of pain is often present in patients with spinal diseases, with a frequency ranging from 36% to 55% of patients. Distinguishing between chronic nociceptive pain and neuropathic pain very often remains a challenge. Consequently, neuropathic pain is often underdiagnosed in patients with spinal diseases. In reference to current guidelines for the treatment of neuropathic pain, gabapentin, serotonin and norepinephrine reuptake inhibitors and tricyclic antidepressants constitute first-line therapeutic agents. However, long-term pharmacologic treatment often leads to developing tolerance and resistance to used medications. Therefore, in recent years, a plethora of therapeutic methods for neuropathic pain have been developed and investigated to improve clinical outcomes. In this review, we briefly summarized current knowledge about the pathophysiology and diagnosis of neuropathic pain. Moreover, we described the most effective treatment approaches for neuropathic pain and discussed their relevance in the treatment of spinal pain.

Sciatic nerve stimulation alleviates acute neuropathic pain via modulation of neuroinflammation and descending pain inhibition in a rodent model

Background

Neuropathic pain (NP) is characterized by abnormal activation of pain conducting pathways and manifests as mechanical allodynia and thermal hypersensitivity. Peripheral nerve stimulation is used for treatment of medically refractory chronic NP and has been shown to reduce neuroinflammation. However, whether sciatic nerve stimulation (SNS) is of therapeutic benefit to NP remains unclear. Moreover, the optimal frequency for SNS is unknown. To address this research gap, we investigated the effect of SNS in an acute NP rodent model.

Methods

Rats with right L5 nerve root ligation (NRL) or Sham surgery were used. Ipsilateral SNS was performed at 2 Hz, 20 Hz, and 60 Hz frequencies. Behavioral tests were performed to assess pain and thermal hypersensitivity before and after NRL and SNS. Expression of inflammatory proteins in the L5 spinal cord and the immunohistochemical alterations of spinal cord astrocytes and microglia were examined on post-injury day 7 (PID7) following NRL and SNS. The involvement of the descending pain modulatory pathway was also investigated.

Results

Following NRL, the rats showed a decreased pain threshold and latency on the von Frey and Hargreaves tests. The immunofluorescence results indicated hyperactivation of superficial spinal cord dorsal horn (SCDH) neurons. Both 2-Hz and 20-Hz SNS alleviated pain behavior and hyperactivation of SCDH neurons. On PID7, NRL resulted in elevated expression of spinal cord inflammatory proteins including NF-κB, TNF-α, IL-1β, and IL-6, which was mitigated by 2-Hz and 20-Hz SNS. Furthermore, 2-Hz and 20-Hz SNS suppressed the activation of spinal cord astrocytes and microglia following NRL on PID7. Activity of the descending serotoninergic pain modulation pathway showed an increase early on PID1 following 2-Hz and 20-Hz SNS.

Conclusions

Our results support that both 2-Hz and 20-Hz SNS can alleviate NP behaviors and hyperactivation of pain conducting pathways. We showed that SNS regulates neuroinflammation and reduces inflammatory protein expression, astrocytic gliosis, and microglia activation. During the early post-injury period, SNS also facilitates the descending pain modulatory pathway. Taken together, these findings support the therapeutic potential of SNS for acute NP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02513-y.

The 7-Hydroxyflavone attenuates chemotherapy-induced neuropathic pain by targeting inflammatory pathway

Vincristine and paclitaxel are widely used chemotherapeutic drugs for the treatment of brain tumors, breast cancer, leukemia, lymphomas, and malignant solid tumors. Though, these drugs are associated with some severe adverse effects including peripheral neuropathic pain. The anti-nociceptive and anti-inflammatory properties of the 7-Hydroxyflavone (7HF) were evaluated in the mice using thermally- and chemically-induced nociception, naloxone antagonistic test, and carrageenan-induced paw edema models. Initially, the in-vitro cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) inhibitory assays were carried out. Peripheral neuropathic pain was induced in the Sprague Dawley (SD) rats by administration of paclitaxel (4 mg/kg) and vincristine (200 µg/kg) on days 1, 3, 5, 7, and 9, respectively. The protective effect of 7HF was assessed against the chemotherapy-induced peripheral neuropathy in the rats. Moreover, the expression of the inflammatory mediators in the spinal cord was investigated through RT-PCR. In addition, a computational study was performed to find the potential therapeutic targets and the binding mechanism of 7HF. The 7HF caused concentration-dependent inhibition of COX-2 and 5-LOX, it attenuated the nociceptive pain, carrageenan-induced paw edema, and the development of mechanical and cold allodynia, and hyperalgesia dose-dependently without causing motor coordination deficit. Likewise, the 7HF decreased the vincristine-induced increased expression of different inflammatory mediators including COX-2, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and nuclear factor-kappa B (NF-κB). The computational study showed the effective interactions of 7HF with the binding sites of NF-κB, COX-2, and 5-LOX, exert its inhibitory activities. These findings reveal that the 7HF has anti-nociceptive, anti-inflammatory, and anti-neuropathic potentials.

Tmem160 contributes to the establishment of discrete nerve injury-induced pain behaviors in male mice

Chronic pain is a prevalent medical problem, and its molecular basis remains poorly understood. Here, we demonstrate the significance of the transmembrane protein (Tmem) 160 for nerve injury-induced neuropathic pain. An extensive behavioral assessment suggests a pain modality- and entity-specific phenotype in male Tmem160 global knockout (KO) mice: delayed establishment of tactile hypersensitivity and alterations in self-grooming after nerve injury. In contrast, Tmem160 seems to be dispensable for other nerve injury-induced pain modalities, such as non-evoked and movement-evoked pain, and for other pain entities. Mechanistically, we show that global KO males exhibit dampened neuroimmune signaling and diminished TRPA1-mediated activity in cultured dorsal root ganglia. Neither these changes nor altered pain-related behaviors are observed in global KO female and male peripheral sensory neuron-specific KO mice. Our findings reveal Tmem160 as a sexually dimorphic factor contributing to the establishment, but not maintenance, of discrete nerve injury-induced pain behaviors in male mice.

The Short-Term Kinetics of sICAM-1 after Induction of Acute Experimental Pain in Healthy Volunteers

Intercellular adhesion molecule-1 (ICAM-1) mediates extravasation of leukocytes, releasing proinflammatory cytokines or endogenous opioids in the inflamed tissue. Thus, ICAM-1 is a crucial component of peripheral antinociception. Previously, we demonstrated a significant correlation between the soluble form of ICAM (sICAM-1) in serum and pain intensity reported by chronic pain patients. The present study examines the role and kinetics of sICAM-1 in experimentally induced acute pain. Three groups of 10 subjects were exposed to 10 min of high (capsaicin-enhanced) or low-intensity heat pain or cold pain, respectively. Thermal stimuli were induced using a device for quantitative sensory testing. Topical capsaicin significantly increased heat pain intensity without the risk of thermal tissue damage. Pain intensity was recorded every minute during testing. sICAM-1 concentrations in serum were determined by ELISA before, immediately after, and 60 min after test termination. Among all experimental groups, sICAM-1 significantly decreased immediately after pain induction. After 60 min, sICAM-1 concentrations returned towards initial values. Interestingly, a linear correlation was found between the extent of sICAM-1 changes and the initial concentrations. Whereas high initial values led to a distinct decrease of sICAM-1, low concentrations tended to increase. There was no statistically significant correlation between levels or alterations of serum sICAM-1 and pain intensity reported by the test subjects. In contrast to our previous findings in chronic pain patients, the present results show that sICAM-1 values do not correlate with the intensity of acute experimental pain. However, we were able to detect short-term changes of sICAM-1 after induction of nociceptive thermal stimuli, suggesting that this marker is part of a demand-oriented homeostatically controlled system.

Attenuation of nociceptive and paclitaxel-induced neuropathic pain by targeting inflammatory, CGRP and substance P signaling using 3-Hydroxyflavone

Paclitaxel is an anti-microtubule agent, most widely used chemotherapeutic agent for the treatment of malignant solid tumors. However, it is associated with some severe side effects including painful neurotoxicity with reporting of neuropathic pain and sensory abnormalities by patients during and after paclitaxel therapy. Peripheral neuropathy was induced by the administration of paclitaxel (4 mg/kg on days 1, 3, 5, and 7). In this study, the anti-nociceptive and anti-inflammatory propensity of 3-Hydroxyflavone (3HF) in mice and the preventive effect of 3HF against paclitaxel-induced peripheral neuropathy in Sprague Dawley (SD) rats were investigated. Moreover, tactile and cold allodynia, thermal and tail immersion hyperalgesia, and effects on motor-coordination were also evaluated. Furthermore, the expression of proinflammatory cytokines i.e. Calcitonin gene-related peptide (CGRP), and Substance P from the spinal cord was examined through RT-PCR. Additionally, a computational structural biology approach was applied to search the potential therapeutic targets and to predict the binding mechanism of 3HF. Treatment of 3HF alleviated the nociceptive pain, paw edema, development of tactile and cold allodynia, and hyperalgesia. Similarly, treatment with 3HF suppressed the paclitaxel-induced increase in mRNA expression of several inflammatory cytokines including tumor necrosis factor -α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), CGRP, and Substance P. However, the daily treatment of 3HF did not affect the motor behaviors of rats. The inhibitory mechanism of 3HF in neuropathic pain is predicted with extensive computational bioinformatics approach which indicates that the 3HF effectively interacts with the binding domains of Nuclear factor-kappa B (NF-κB), CGRP receptor and the receptor of Substance P to exert its inhibitory activities. However, the computationally predicted binding affinities revealed that the potential of binding of the compound with Substance P receptor (Neurokinin 1 receptor) is higher than the other receptors; there NK1R could be the most possible binding target of 3HF. These findings indicate that 3HF has anti-nociceptive, anti-inflammatory, and anti-neuropathic pain effects against paclitaxel-induced neuropathic pain.

αvβ3 Integrin Antagonists Enhance Chemotherapy Response in an Orthotopic Pancreatic Cancer Model

Pancreatic cancer decreases survival time and quality of life because of drug resistance and peripheral neuropathy during conventional treatment. This study was undertaken to investigate whether αvβ3 integrin receptor antagonist compounds NDAT and XT199 can suppress the development of cisplatin resistance and cisplatin-induced peripheral neuropathy in an orthotopic pancreatic SUIT2-luc cancer cell mouse model. Anticancer effects of these compounds and their combination with cisplatin were assessed in this tumor mouse model with bioluminescent signaling and histopathology, and a cytokine assay was used to examine expression of inflammatory cytokines IL-1β, IL-6, IL-10, and TNF-α from plasma samples. To determine the neuroprotective effects of the compounds on cisplatin-induced peripheral neuropathy, behavioral hind-limb posture of the mice was evaluated. The combination therapy of NDAT or XT199 with cisplatin elicited greater inhibition of tumor growth and increased tumor necrosis compared to cisplatin alone. NDAT and XT199 in combination with cisplatin significantly decreased expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α and significantly increased expression of anti-inflammatory cytokine IL-10 in comparison to cisplatin alone. Cisplatin-treated groups showed stocking-glove hind-limb posture, whereas NDAT and XT199 with cisplatin-treated groups displayed normal hind-limb posture. Results clearly suggest that NDAT and XT199 treatment with cisplatin that inactivates NF-κB may contribute to increased antitumor and anti-inflammatory efficacy as well as alleviate cisplatin-mediated loss of motor function in this pancreatic tumor mouse model.

Impact of IL-2 on Treatment Tolerance in Patients With High-Risk Neuroblastoma Treated With Dinutuximab Beta-Based Immunotherapy

Patients with high-risk neuroblastoma treated with continuous long-term infusion of anti-GD2 antibody dinutuximab beta (DB) in combination with IL-2 show an acceptable safety profile. Here, we compared treatment tolerance with and without IL-2. Ninety-nine patients with high-risk neuroblastoma received up to five cycles of DB given as long-term infusion (10 mg/m²/d, 100 mg/m²; per cycle) with IL-2 (53 patients; regimen A; 6 × 10⁶ IU/m²/d; 60 × 10⁶ IU/m²/cycle) and without IL-2 (46 patients; regimen B) in a single-center compassionate use program. Clinical parameters (body temperature, vital signs, Lansky performance score), laboratory values [C-reactive protein, IFN-γ, IL-6, and IL-18 (cycle 1)], and requirement of i.v. co-medication (e.g., morphine, metamizole) were systematically assessed. Patients with stable clinical parameters and that did not require co-medication were defined as potential "outpatient candidates." Patients showed higher levels of body temperature and CRP in regimen A compared to B. However, IL-6 serum concentrations were similar in pts of both cohorts in the first cycle. Patients receiving regimen B showed a shorter time to achieve normal vital parameters and required less co-medication compared to patients in regimen A that resulted in a shorter median time period to discharge and to achieve a potential outpatient status (6d regimen A and 3-5d regimen B after start of antibody infusion, respectively). This study shows that omitting IL-2 from immunotherapy with DB allows reduced co-medication and hospitalization time and therefore results in improved quality of life in patients with high-risk neuroblastoma.

Ameliorative Effect of Berberine on Neonatally Induced Type 2 Diabetic Neuropathy via Modulation of BDNF, IGF-1, PPAR-γ, and AMPK Expressions

Neonatal-streptozotocin (n-STZ)-induced diabetes mimics most of the clinicopathological symptoms of type 2 diabetes mellitus (T2DM) peripheral neuropathy. Berberine, a plant alkaloid, is reported to have antidiabetic, antioxidant, anti-inflammatory, and neuroprotective potential. The aim of the present study was to investigate the potential of berberine against n-STZ-induced painful diabetic peripheral polyneuropathy by assessing various biochemical, electrophysiological, morphological, and ultrastructural studies. Type 2 diabetes mellitus was produced neonatal at the age of 2 days (10-12 g) by STZ (90 mg/kg intraperitoneal). After confirmation of neuropathy at 6 weeks, rats were treated with berberine (10, 20, and 40 mg/kg). Administration of n-STZ resulted in T2DM-induced neuropathic pain reflected by a significant alterations (P < .05) in hyperalgesia, allodynia, and motor as well as sensory nerve conduction velocities whereas berberine (20 and 40 mg/kg) treatment significantly attenuated (P < .05) these alterations. Berberine treatment significantly inhibited (P < .05) STZ-induced alterations in aldose reductase, glycated hemoglobin, serum insulin, hepatic cholesterol, and triglyceride levels. The elevated oxido-nitrosative stress and decreased Na-K-ATPase and pulse Ox levels were significantly attenuated (P < .05) by berberine. It also significantly downregulated (P < .05) neural tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 messenger RNA (mRNA), and protein expressions both. Streptozotocin-induced downregulated mRNA expressions of brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF-1), and peroxisome proliferator-activated receptors-γ (PPAR-γ) in sciatic nerve were significantly upregulated (P < .05) by berberine. Western blot analysis revealed that STZ-induced alterations in adenosine monophosphate protein kinase (AMPK; Thr-172) and protein phosphatase 2C-α protein expressions in dorsal root ganglia were inhibited by berberine. It also attenuated histological and ultrastructural alterations induced in sciatic nerve by STZ. In conclusion, berberine exerts its neuroprotective effect against n-STZ-induced diabetic peripheral neuropathy via modulation of pro-inflammatory cytokines (TNF α, IL-1β, and IL-6), oxido-nitrosative stress, BDNF, IGF-1, PPAR-γ, and AMPK expression to ameliorate impaired allodynia, hyperalgesia, and nerve conduction velocity during T2DM.

Preliminary Effectiveness of Auricular Point Acupressure on Chemotherapy-Induced Neuropathy: Part 2 Laboratory-Assessed and Objective Outcomes

PURPOSE

To manage chemotherapy-induced neuropathy (CIN), this paper explores reliable and valid objectives measures to evaluate the treatment effects of auricular point acupressure (APA).

DESIGN/METHOD

This study was a repeated-measures one-group design. Participants received four weeks of APA to manage their CIN. The laboratory-assessed and objective outcomes included quantitative sensory testing, grip and pinch strength, and inflammatory biomarkers. Wilcoxon matched pairs signed-rank tests were conducted to determine change scores of outcomes at pre- vs. post- and pre- vs. 1-month follow-up. Spearman's rho correlation coefficient was used to examine the linear association of score changes of all objective study outcomes.

RESULTS

Comparing pre-and-post APA, (1) the mean score of the monofilament for all lower extremity sites tested decreased after APA, indicating sensory improvement; (2) the suprathreshold pinprick stimuli mean scores on the upper extremities increased, except the scores from the index finger and thumb; (3) the pain tolerance of thumb and trapezius areas increased; (4) decreasing IL1β (p = .05), IFNγ (p = .02), IL-2 (p = .03), IL-6 (p = .05), IL-10 (p = .05), and IP10/CXCL10 (p = .04) were observed pre-post APA. Conditional pain modulation was significantly (p< .05) associated with pain intensity (r = 0.55), tingling (r = 0.59); and IL1β concentration (r = 0.53) pre-post APA. The sustained effects of 4-week APA were observed at the 1-month follow-up.

CONCLUSIONS

Our study findings demonstrated the promising effectiveness of APA in the management of CIN, and these treatment effects can be assessed using reliable and valid objective measures.

CLINICAL IMPLICATIONS

If the efficacy of APA to manage CIN is confirmed in a larger sample, APA has the potential to be a scalable treatment for CIN because it is a reproducible, standardized, and easy-to-perform intervention.

Antagonism of Transient Receptor Potential Ankyrin Type-1 Channels as a Potential Target for the Treatment of Trigeminal Neuropathic Pain: Study in an Animal Model

Transient receptor potential ankyrin type-1 (TRPA1) channels are known to actively participate in different pain conditions, including trigeminal neuropathic pain, whose clinical treatment is still unsatisfactory. The aim of this study was to evaluate the involvement of TRPA1 channels by means of the antagonist ADM_12 in trigeminal neuropathic pain, in order to identify possible therapeutic targets. A single treatment of ADM_12 in rats 4 weeks after the chronic constriction injury of the infraorbital nerve (IoN-CCI) significantly reduced the mechanical allodynia induced in the IoN-CCI rats. Additionally, ADM_12 was able to abolish the increased levels of TRPA1, calcitonin gene-related peptide (CGRP), substance P (SP), and cytokines gene expression in trigeminal ganglia, cervical spinal cord, and medulla induced in the IoN-CCI rats. By contrast, no significant differences between groups were seen as regards CGRP and SP protein expression in the pars caudalis of the spinal nucleus of the trigeminal nerve. ADM_12 also reduced TRP vanilloid type-1 (TRPV1) gene expression in the same areas after IoN-CCI. Our findings show the involvement of both TRPA1 and TRPV1 channels in trigeminal neuropathic pain, and in particular, in trigeminal mechanical allodynia. Furthermore, they provide grounds for the use of ADM_12 in the treatment of trigeminal neuropathic pain.

Impact of HACA on Immunomodulation and Treatment Toxicity Following ch14.18/CHO Long-Term Infusion with Interleukin-2: Results from a SIOPEN Phase 2 Trial

GD₂-directed immunotherapies improve survival of high-risk neuroblastoma (NB) patients (pts). Treatment with chimeric anti-GD₂ antibodies (Ab), such as ch14.18, can induce development of human anti-chimeric Ab (HACA). Here, we report HACA effects on ch14.18/CHO pharmacokinetics, pharmacodynamics and pain intensity in pts treated by long-term infusion (LTI) of ch14.18/CHO combined with IL-2. 124 pts received up to 5 cycles of ch14.18/CHO 10 days (d) infusion (10 mg/m²/d; d8–18) combined with s.c. IL-2 (6 × 10⁶ IU/m²/d; d1–5, d8–12). HACA, treatment toxicity, ch14.18/CHO levels, Ab-dependent cellular- (ADCC) and complement-dependent cytotoxicity (CDC) were assessed using respective validated assays. HACA-negative pts showed a steadily decreased pain in cycle 1 (74% pts without morphine by d5 of LTI) with further decrease in subsequent cycles. Ch14.18/CHO peak concentrations of 11.26 ± 0.50 µg/mL found in cycle 1 were further elevated in subsequent cycles and resulted in robust GD₂-specific CDC and ADCC. Development of HACA (21% of pts) resulted in strong reduction of ch14.18/CHO levels, abrogated CDC and ADCC. Surprisingly, no difference in pain toxicity between HACA-positive and -negative pts was found. In conclusion, ch14.18/CHO LTI combined with IL-2 results in strong activation of Ab effector functions. Importantly, HACA response abrogated CDC but did not affect pain intensity indicating CDC-independent pain induction.

Antiallodynic and antihyperalgesic activities of zerumbone via the suppression of IL-1β, IL-6, and TNF-α in a mouse model of neuropathic pain

Background

Neuropathic pain is a debilitating condition that severely affects the quality of life for those with this pain condition, and treatment for pain relief is greatly sought-after. Zerumbone (Zer), a sesquiterpene compound isolated from the rhizomes of a Southeast Asian ginger plant, Zingiber zerumbet (L.) Roscoe ex Smith. (Zingiberaceae), showed antinociceptive and antiinflammatory properties when previously tested on models of nociception and inflammation.

Objective

This study investigated the effects of prophylactic administration of zerumbone on allodynia and hyperalgesia in a mouse model of chronic constriction injury (CCI)-induced neuropathic pain.

Methods

Intraperitoneal administration of Zer (5–50 mg/kg) from day 1 post-surgery was carried out to identify the onset and progression of the pain condition. Responses toward mechanical and cold allodynia, and mechanical and thermal hyperalgesia were assessed on days 3, 5, 7, 9, 11, and 14 post-surgery. Blood plasma and spinal cord levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and IL-10 were screened using enzyme-linked immunosorbent assay on day 15.

Results

Zer (10 and 50 mg/kg) attenuated pain symptoms on all days of behavioral testing without any signs of sedation in the rotarod test. ED₅₀ values for mechanical allodynia, cold allodynia, thermal hyperalgesia, and mechanical hyperalgesia were 9.25, 9.507, 8.289, and 9.801 mg/kg, respectively. Blood plasma and spinal levels of IL-1β, IL-6, and tumor necrosis factor-α but not IL-10 were significantly (p<0.05) suppressed by zer treatment.

Discussion and conclusion

Zer exhibits its antiallodynic and antihyperalgesic properties via reduced sensitization at nociceptor neurons possibly through the suppression of inflammatory mediators. Zer may prove to be a novel and beneficial alternative for the management of neuropathic pain.

Bioactive Fraction of Annona reticulata Bark (or) Ziziphus jujuba Root Bark along with Insulin Attenuates Painful Diabetic Neuropathy through Inhibiting NF-κB Inflammatory Cascade

The present study explains the neuroprotective ability of bioactive fractions of Annona reticulata bark (ARB) and Ziziphus jujuba root bark (ZJ) along with insulin against diabetic neuropathy. By using different solvents of increasing polarity ARB and ZJ were undergone for bioactive guided fractionation. The neuroprotective ability of the all the plant fractions were tested against H₂O₂ induced toxicity in SHSY5Y neuroblastoma cell lines and DRG neuronal cells. Among all the fractions tested, the methanol extract of ARB and ZJ (ARBME and ZJME) and its water fractions (ARBWF and ZJWF) exhibited significant neuroprotection against H₂O₂ induced toxicity in SHSY5Y cells and DRG neuronal cells. Further both the active fractions were tested against streptozotocin (55 mg/kg i.p.) induced diabetic neuropathy in male Wistar rats. Body weight changes, blood glucose levels and pain threshold through hot plate, tail immersion, cold plate and Randall-Sillitto methods were measured throughout the study at weekly interval. After completion of the drug treatment period, all the animals were sacrificed to measure the sciatic nerve lipid peroxidation, antioxidative enzyme levels (SOD, catalase, and GSH) and cytokine levels (IL-1β, IL-6, IL-10, TNF-α, iNOS, and NFκB) through ELISA and western blotting analysis. Results of this study explain that ARBME, ZJME, ARBWF, and ZJWF along with insulin potentially attenuate the thermal, mechanical hyperalgesia and cold allodynia in diabetic neuropathic rats, where insulin treatment alone failed to diminish the same. Reduction of sciatic nerve oxidative stress, NF-κB and iNOS mediated inflammatory cascade and normalization of abnormal cytokine release confirms the possible mechanism of action. The present study confirms the neuroprotective ability of ARB and ZJ against painful diabetic neuropathy through inhibiting oxidative stress and NF-κB inflammatory cascade.

Soluble intercellular adhesion molecule-1: a potential biomarker for pain intensity in chronic pain patients

AIM

Pain therapy is strongly guided by patients' self-reporting. However, when self-reporting is not an option, pain assessment becomes a challenge and may lead to undertreatment of painful conditions. Pain is a complex and multifactorial phenomenon. Recent work has connected pain pathophysiology also with the inflammatory system. We therefore hypothesized that pain intensity could be predicted by cytokine-levels.

PATIENTS & METHODS

In this observational, single-center study, we investigated 30 serum cytokines to predict pain intensity in a screening/follow-up set of 95 chronic pain patients and controls. We then prospectively validated soluble intercellular adhesion molecule-1 (sICAM-1)'s discriminatory capability (n = 21).

RESULTS & CONCLUSION

sICAM-1 was significantly associated with patient-reported pain intensity and yielded differential serum levels in patients of varying degrees of pain intensity. Changes in pain ratings over time correlated with changes in sICAM-1 levels. Our findings suggest the possibility of a clinical use of sICAM-1 as a potential biomarker for pain intensity.

Anti-nociceptive and anti-inflammatory actions of sulforaphane in chronic constriction injury-induced neuropathic pain mice

Neuropathic pain is still considered as incurable disease as current therapies are not ideal in terms of efficacy and tolerability. It is imperative to search for novel drugs to obtain better treatments. Sulforaphane (SFN), a derivative of glucoraphanin present in cruciferous vegetables, exhibits therapeutic effects on inflammation-related diseases. Since inflammation plays an important role in regulating chronic pain, in the present study, we investigated anti-nociceptive effects of SFN and its underlying mechanisms in a neuropathic pain mouse model, sciatic nerve chronic constriction injury (CCI). SFN (0.1-100 mg/kg) was injected intraperitoneally for 7 days when pain behaviors, including mechanical allodynia and thermal hyperalgesia, reached to the maximum in CCI mice. We observed that SFN dose-dependently attenuated CCI-induced pain behavioral hypersensitivity, accompanied by reduction in pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and upregulation of an anti-inflammatory cytokine (IL-10). Moreover, SFN counteracted CCI enhancement of COX2 and iNOS in injured nerves, two key enzymes implicated in inflammation and neuropathic pain. Furthermore, pretreatment of naloxone, an antagonist of opioid receptors, significantly blocked SFN attenuation of behavioral hypersensitivity without affecting SFN modulation of inflammatory cytokines in CCI mice. Interestingly, CCI-induced increase in µ-opioid receptors in injured sciatic nerves was further increased by SFN treatment. Taken together, SFN has both anti-nociceptive and anti-inflammatory actions.

Red LED photobiomodulation reduces pain hypersensitivity and improves sensorimotor function following mild T10 hemicontusion spinal cord injury

Background

The development of hypersensitivity following spinal cord injury can result in incurable persistent neuropathic pain. Our objective was to examine the effect of red light therapy on the development of hypersensitivity and sensorimotor function, as well as on microglia/macrophage subpopulations following spinal cord injury.

Methods

Wistar rats were treated (or sham treated) daily for 30 min with an LED red (670 nm) light source (35 mW/cm²), transcutaneously applied to the dorsal surface, following a mild T10 hemicontusion injury (or sham injury). The development of hypersensitivity was assessed and sensorimotor function established using locomotor recovery and electrophysiology of dorsal column pathways. Immunohistochemistry and TUNEL were performed to examine cellular changes in the spinal cord.

Results

We demonstrate that red light penetrates through the entire rat spinal cord and significantly reduces signs of hypersensitivity following a mild T10 hemicontusion spinal cord injury. This is accompanied with improved dorsal column pathway functional integrity and locomotor recovery. The functional improvements were preceded by a significant reduction of dying (TUNEL⁺) cells and activated microglia/macrophages (ED1⁺) in the spinal cord. The remaining activated microglia/macrophages were predominantly of the anti-inflammatory/wound-healing subpopulation (Arginase1⁺ED1⁺) which were expressed early, and up to sevenfold greater than that found in sham-treated animals.

Conclusions

These findings demonstrate that a simple yet inexpensive treatment regime of red light reduces the development of hypersensitivity along with sensorimotor improvements following spinal cord injury and may therefore offer new hope for a currently treatment-resistant pain condition.

Virus Infections Incite Pain Hypersensitivity by Inducing Indoleamine 2,3 Dioxygenase

Increased pain sensitivity is a comorbidity associated with many clinical diseases, though the underlying causes are poorly understood. Recently, chronic pain hypersensitivity in rodents treated to induce chronic inflammation in peripheral tissues was linked to enhanced tryptophan catabolism in brain mediated by indoleamine 2,3 dioxygenase (IDO). Here we show that acute influenza A virus (IAV) and chronic murine leukemia retrovirus (MuLV) infections, which stimulate robust IDO expression in lungs and lymphoid tissues, induced acute or chronic pain hypersensitivity, respectively. In contrast, virus-induced pain hypersensitivity did not manifest in mice lacking intact IDO1 genes. Spleen IDO activity increased markedly as MuLV infections progressed, while IDO1 expression was not elevated significantly in brain or spinal cord (CNS) tissues. Moreover, kynurenine (Kyn), a tryptophan catabolite made by cells expressing IDO, incited pain hypersensitivity in uninfected IDO1-deficient mice and Kyn potentiated pain hypersensitivity due to MuLV infection. MuLV infection stimulated selective IDO expression by a discreet population of spleen cells expressing both B cell (CD19) and dendritic cell (CD11c) markers (CD19⁺ DCs). CD19⁺ DCs were more susceptible to MuLV infection than B cells or conventional (CD19^neg) DCs, proliferated faster than B cells from early stages of MuLV infection and exhibited mature antigen presenting cell (APC) phenotypes, unlike conventional (CD19^neg) DCs. Moreover, interactions with CD4 T cells were necessary to sustain functional IDO expression by CD19⁺ DCs in vitro and in vivo. Splenocytes from MuLV-infected IDO1-sufficient mice induced pain hypersensitivity in uninfected IDO1-deficient recipient mice, while selective in vivo depletion of DCs alleviated pain hypersensitivity in MuLV-infected IDO1-sufficient mice and led to rapid reduction in splenomegaly, a hallmark of MuLV immune pathogenesis. These findings reveal critical roles for CD19⁺ DCs expressing IDO in host responses to MuLV infection that enhance pain hypersensitivity and cause immune pathology. Collectively, our findings support the hypothesis elevated IDO activity in non-CNS due to virus infections causes pain hypersensitivity mediated by Kyn. Previously unappreciated links between host immune responses to virus infections and pain sensitivity suggest that IDO inhibitors may alleviate heightened pain sensitivity during infections.

Chronic pain is a factor in diseases that afflict many people, yet the underlying causes of pain are poorly understood. Here we assess the effects of virus infections on pain sensitivity in mice. Infecting mice with two different viruses, influenza and mouse leukemia virus (MuLV) increased pain sensitivity. Influenza infection caused transient increase in pain sensitivity, which returned to normal levels after infections were cleared. However persistent MuLV infections caused sustained increase in pain sensitivity. Virus-induced pain sensitivity was reduced substantially in mice lacking the enzyme indoleamine 2,3 dioxygenase (IDO), which degrades the amino acid tryptophan. Moreover a natural compound produced by cells expressing IDO enhanced pain sensitivity when administered to mice lacking IDO genes. Thus cells expressing IDO caused increased pain sensitivity in infected mice. A distinctive cell type expressed IDO selectively and accumulated in spleens of MuLV-infected mice. Transfer of spleen cells from MuLV-infected mice caused increased pain sensitivity in uninfected mice while eliminating specific cells in MuLV-infected mice abolished enhanced pain sensitivity. Our findings show that host immune responses to virus infections cause increased pain sensitivity and suggest novel ways to alleviate pain during infections.

Pain in an era of armed conflicts: Prevention and treatment for warfighters and civilian casualties

Chronic pain is a common squealae of military- and terror-related injuries. While its pathophysiology has not yet been fully elucidated, it may be potentially related to premorbid neuropsychobiological status, as well as to the type of injury and to the neural alterations that it may evoke. Accordingly, optimized approaches for wounded individuals should integrate primary, secondary and tertiary prevention in the form of thorough evaluation of risk factors along with specific interventions to contravene and mitigate the ensuing chronicity. Thus, Premorbid Events phase may encompass assessments of psychological and neurobiological vulnerability factors in conjunction with fostering preparedness and resilience in both military and civilian populations at risk. Injuries per se phase calls for immediate treatment of acute pain in the field by pharmacological agents that spare and even enhance coping and adaptive capabilities. The key objective of the Post Injury Events is to prevent and/or reverse maladaptive peripheral- and central neural system's processes that mediate transformation of acute to chronic pain and to incorporate timely interventions for concomitant mental health problems including post-traumatic stress disorder and addiction We suggest that the proposed continuum of care may avert more disability and suffering than the currently employed less integrated strategies. While the requirements of the armed forces present a pressing need for this integrated continuum and a framework in which it can be most readily implemented, this approach may be also instrumental for the care of civilian casualties.

Toll-like receptor 4 signaling in neurons of trigeminal ganglion contributes to nociception induced by acute pulpitis in rats

Pain caused by acute pulpitis (AP) is a common symptom in clinical settings. However, its underlying mechanisms have largely remained unknown. Using AP model, we demonstrated that dental injury caused severe pulp inflammation with up-regulated serum IL-1β. Assessment from head-withdrawal reflex thresholds (HWTs) and open-field test demonstrated nociceptive response at 1 day post injury. A consistent up-regulation of Toll-like receptor 4 (TLR4) in the trigeminal ganglion (TG) ipsilateral to the injured pulp was found; and downstream signaling components of TLR4, including MyD88, TRIF and NF-κB, and cytokines such as TNF-α and IL-1β, were also increased. Retrograde labeling indicated that most TLR4 positve neuron in the TG innnervated the pulp and TLR4 immunoreactivity was mainly in the medium and small neurons. Double labeling showed that the TLR4 expressing neurons in the ipsilateral TG were TRPV1 and CGRP positive, but IB4 negative. Furthermore, blocking TLR4 by eritoran (TLR4 antagonist) in TGs of the AP model significantly down-regulated MyD88, TRIF, NF-κB, TNF-α and IL-1β production and behavior of nociceptive response. Our findings suggest that TLR4 signaling in TG cells, particularly the peptidergic TRPV1 neurons, plays a key role in AP-induced nociception, and indicate that TLR4 signaling could be a potential therapeutic target for orofacial pain.