Cold Plate Test Research Articles

Discovery of novel oxindole derivatives as TRPA1 antagonists with potent analgesic activity for pain treatment.

Transient Receptor Potential Ankyrin 1 (TRPA1) is a non-selective cation channel involved in detecting harmful stimuli and endogenous ligands, primarily expressed in sensory neurons. Due to its role in pain and itch, TRPA1 is a potential drug target. We identified an oxindole core structure via high-throughput screening, modified it, and tested the modified compounds in vitro and in vivo. Calcium influx assays in primary dorsal root ganglion (DRG) cells and TRPA1-overexpressing HEK-293T cells identified best compound ZQMT-10. ZQMT-10 demonstrated strong interaction with TRPA1 in the CETSA and MST assays. Oral administration of ZQMT-10 in C57BL/6J mice significantly reduced abnormal responses in the cold plate test. ZQMT-10 alleviated pain induced by AITC application on the mouse paw or by intracolonic administration, while also increasing the pain threshold and relieving persistent inflammatory pain. These results suggest ZQMT-10 as a promising TRPA1-targeted therapeutic agent.

The challenge to identify sensitive safety biomarkers of peripheral neurotoxicity in the rat: A collaborative effort across industry and academia (IMI NeuroDeRisk project)

Peripheral nervous system (PNS) toxicity assessment in non-clinical safety studies is challenging and relies mostly on histopathological assessment. The present work aims to identify blood-based biomarkers that could detect peripheral neuropathy in rats upon exposure to neurotoxic compounds. Three anticancer agents (oxaliplatin, cisplatin, paclitaxel) and a developmental compound (NVS-1) were assessed in male rats (Wistar Han). Clinical and/or functional endpoints (i.e., electronic Von Frey, Cold Plate, and Paw Pressure tests) and blood biomarkers (i.e., neurofilament light chain (NfL), neurofilament heavy chain (NF-H), microtubule-associated protein Tau (Tau), neuron specific enolase (NSE), vascular endothelial growth factor A (VEGFA), and glial fibrillary acidic protein (GFAP)) were assessed. Drug exposure and histopathological evaluations were conducted on selected nervous tissues. Oxaliplatin, cisplatin and paclitaxel treatment resulted in a significant decrease of nociceptive thresholds. Clinical signs suggestive of PNS toxicity were observed with NVS-1. NfL was consistently increased in the NVS-1 study and correlated with moderate microscopic findings in dorsal root ganglia (DRG). Only minimal microscopic findings were observed in oxaliplatin-treated animals, whereas no treatment-related microscopic findings were observed in animals treated with cisplatin and paclitaxel. For all compounds, exposure was confirmed in the PNS tissues. Clinical and functional changes were observed with all the compounds evaluated. NfL levels in plasma proved to be the most sensitive indicator of PNS toxicities, capturing moderate nervous degeneration in DRG. A combined approach that includes both functional assessments and biomarker measurements offers a more comprehensive evaluation than histopathological analysis alone when monitoring drug-induced neurotoxicity in rat models.

Astaxanthin has a beneficial influence on pain-related symptoms and opioid-induced hyperalgesia in mice with diabetic neuropathy-evidence from behavioral studies

BackgroundThe treatment of painful diabetic neuropathy is still a clinical problem. The aim of this study was to determine whether astaxanthin, a substance that inhibits mitogen-activated protein kinases, activates nuclear factor erythroid 2-related factor 2 and influences N-methyl-D-aspartate receptor, affects nociceptive transmission in mice with diabetic neuropathy.MethodsThe studies were performed on streptozotocin-induced mouse diabetic neuropathic pain model. Single intrathecal and intraperitoneal administrations of astaxanthin at various doses were conducted in both males and females. Additionally, repeated twice-daily treatment with astaxanthin (25 mg/kg) and morphine (30 mg/kg) were performed. Hypersensitivity was evaluated with von Frey and cold plate tests.ResultsThis behavioral study provides the first evidence that in a mouse model of diabetic neuropathy, single injections of astaxanthin similarly reduce tactile and thermal hypersensitivity in both male and female mice, regardless of the route of administration. Moreover, repeated administration of astaxanthin slightly delays the development of morphine tolerance and significantly suppresses the occurrence of opioid-induced hyperalgesia, although it does not affect blood glucose levels, body weight, or motor coordination. Surprisingly, astaxanthin administered repeatedly produces a better analgesic effect when administered alone than in combination with morphine, and its potency becomes even more pronounced over time.ConclusionsThese behavioral results provide a basis for further evaluation of the potential use of astaxanthin in the clinical treatment of diabetic neuropathy and suggest that the multidirectional action of this substance may have positive effects on relieving neuropathic pain in diabetes.

Humanin attenuates metabolic, toxic, and traumatic neuropathic pain in mice by protecting against oxidative stress and increasing inflammatory cytokine

Neuropathic pain is associated with diverse etiologies, including sciatica, diabetes, and the use of chemotherapeutic agents. Despite the varied origins, mitochondrial dysfunction, oxidative stress, and inflammatory cytokines are recognized as key contributing factors in both the initiation and maintenance of neuropathic pain. The effects of the mitochondrial-derived peptide humanin on neuropathic pain, however, remain unclear, despite its demonstrated influence on these mechanisms in numerous disease models. This study aimed to evaluate the effects of humanin on pain behavior in murine models of metabolic (streptozotocin/STZ), toxic (oxaliplatin/OXA), traumatic (sciatic nerve cuffing/cuff), and neuropathic pain. A secondary objective was to assess whether humanin modulates oxidative damage and inflammatory cytokine levels in these neuropathic pain models.Humanin (4 mg/kg) was administered intraperitoneally (i.p.) to BALB/c male mice with induced neuropathic pain over a period of 15 days, with pain thresholds assessed using hot plate, cold plate, and Von Frey tests. Serum levels of antioxidant enzymes, oxidative stress markers, and inflammatory/anti-inflammatory cytokines were measured via enzyme-linked immunosorbent assay (ELISA).In neuropathic pain-induced mice, humanin administration resulted in a statistically significant increase in pain threshold values in the STZ + Humanin, OXA + Humanin, and cuff + Humanin groups compared to their respective control groups (P < 0.05) over 15 days. Furthermore, humanin treatment significantly elevated antioxidant enzyme levels and anti-inflammatory cytokine concentrations, while reducing oxidative stress markers and pro-inflammatory cytokine levels compared to control groups (P < 0.01).These findings suggest that humanin exhibits therapeutic potential in the treatment of neuropathic pain induced by STZ, OXA, and cuff models. The ability of humanin to mitigate neuropathic pain through the suppression of oxidative stress and inflammatory cytokines indicates its promise as a novel therapeutic strategy.

Harmaline attenuates chemotherapy-induced peripheral neuropathy: Modulation of Nrf-2 pathway and NK-1 receptor signaling

Peripheral neuropathy, resulting from damage to peripheral nerves, manifests as weakness, numbness, and pain, primarily affecting extremities and significantly impairing quality of life, especially in the elderly. Current treatments often entail severe side effects, necessitating the exploration of alternative therapies. Harmaline, a β-carboline alkaloid derived from Peganum harmala, exhibits promising antioxidant and anti-inflammatory properties. This study aimed to assess the efficacy of harmaline in a vincristine-induced mouse model of peripheral neuropathy. Swiss albino mice received vincristine (0.1 mg/kg, i.p.) for 10 days to induce neuropathy. Harmaline (5 and 10 mg/kg, i.p.) was administered 30 min before vincristine and continued until day 14 to evaluate its protective effects. Behavioral assessments were conducted on days 7 and 14. Vincristine treatment significantly heightened sensitivity to cold, measured by cold plate and acetone drop tests, and to heat, assessed via the hot plate test, while also impairing motor coordination. Biochemical analyses revealed decreased levels of GSH and Nrf-2, alongside elevated TBARS and IL-1β levels in sciatic nerve tissue. Harmaline administration markedly alleviated both behavioral and biochemical alterations induced by vincristine, with the 10 mg/kg dose exhibiting the most pronounced effects. Notably, harmaline treatment elevated GSH and Nrf-2 levels while reducing TBARS and IL-1β. Furthermore, substance-P treatment reversed the protective effects of harmaline, implicating the NK-1 receptor in its mechanism of action. In conclusion, harmaline demonstrates significant potential in mitigating vincristine-induced peripheral neuropathy by reducing oxidative stress through Nrf-2 activation and lowering IL-1β levels, likely via NK-1 receptor inhibition.

Preventing social defeat stress-induced behavioural and neurochemical alterations by repeated treatment with a mix of Centella asiatica, Echinacea purpurea and Zingiber officinale standardized extracts.

Background: Prolonged exposure to stress is a risk factor for the onset of several disorders. Modern life is burdened by a pervasive prevalence of stress, which represents a major societal challenge requiring new therapeutic strategies. In this context, botanical drug-based therapies can have a paramount importance. Methods: Here we studied the preventive effects of a repeated treatment (p.o. daily, 3weeks) with a combination of Centella asiatica (200mg/kg), Echinacea purpurea (20mg/kg) and Zingiber officinale (150mg/kg) standardized extracts, on the chronic social defeat stress (CSDS) deleterious outcomes. After 10days of CSDS exposure, male mice' performances were evaluated in paradigms relevant for social (social interaction test), emotional (tail suspension test), cognitive (novel object recognition) domains as well as for pain perception (cold plate and von Frey tests) and motor skills (rotarod). Mice were then sacrificed, the spinal cords, hippocampi and frontal cortices dissected and processed for RT-PCR analysis. Results: Extracts mix treatment prevented stress-induced social aversion, memory impairment, mechanical and thermal allodynia and reduced behavioural despair independently of stress exposure. The treatment stimulated hippocampal and cortical BDNF and TrkB mRNA levels and counteracted stress-induced alterations in pro- (TNF-α, IL-1β and IL-6) and anti-inflammatory (IL4, IL10) cytokines expression in the same areas. It also modulated expression of pain related genes (GFAP and Slc1a3) in the spinal cord. Conclusion: The treatment with the extracts mix obtained from C. asiatica, E. purpurea and Z. officinale may represent a promising strategy to promote resilience and prevent the deleterious effects induced by extended exposure to psychosocial stress.

Evaluating the Antihyperalgesic Potential of Sildenafil-Metformin Combination and Its Impact on Biochemical Markers in Alloxan-Induced Diabetic Neuropathy in Rats.

(1) Background: Globally, about 600 million people are afflicted with diabetes, and one of its most prevalent complications is neuropathy, a debilitating condition. At the present time, the exploration of novel therapies for alleviating diabetic-neuropathy-associated pain is genuinely captivating, considering that current therapeutic options are characterized by poor efficacy and significant risk of side effects. In the current research, we evaluated the antihyperalgesic effect the sildenafil (phosphodiesterase-5 inhibitor)-metformin (antihyperglycemic agent) combination and its impact on biochemical markers in alloxan-induced diabetic neuropathy in rats. (2) Methods: This study involved a cohort of 70 diabetic rats and 10 non-diabetic rats. Diabetic neuropathy was induced by a single dose of 130 mg/kg alloxan. The rats were submitted to thermal stimulus test using a hot-cold plate and to tactile stimulus test using von Frey filaments. Moreover, at the end of the experiment, the animals were sacrificed and their brains and livers were collected to investigate the impact of this combination on TNF-α, IL-6, nitrites and thiols levels. (3) Results: The results demonstrated that all sildenafil-metformin combinations decreased the pain sensitivity in the von Frey test, hot plate test and cold plate test. Furthermore, alterations in nitrites and thiols concentrations and pro-inflammatory cytokines (specifically TNF-α and IL-6) were noted following a 15-day regimen of various sildenafil-metformin combinations. (4) Conclusions: The combination of sildenafil and metformin has a synergistic effect on alleviating pain in alloxan-induced diabetic neuropathy rats. Additionally, the combination effectively decreased inflammation, inhibited the rise in NOS activity, and provided protection against glutathione depletion.

Gadolinium-based contrast agents aggravate mechanical and thermal hyperalgesia in a nitroglycerine-induced migraine model in male mice

In the diagnosis of migraine, which is a neurovascular disease, gadolinium-based contrast agents (GBCAs) are used to rule out more serious conditions. On the other hand, it remains unclear as a scientific gap whether GBCAs may trigger migraine-related pain. The aim of this study was to investigate the effect of GBCAs on mechanical and thermal pain behaviour in a nitroglycerin (NTG)-induced migraine model in mice.NTG (10 mg/kg) was administered intraperitoneally to adult (6–8weeks old) BALB/c mice 2 h before behavioral tests 5 times every other day on days 1st, 3rd, 5th and 9th to induce migraine model (N = 50). As GBCAs, gadobenate dimeglumine (linear-ionic), Gadodiamide (linear-nonionic), and gadobutrol (macrocyclic-nonionic) were delivered intravenously through the tail vein of mice for 5 days on test days. Mechanical pain threshold (plantar and facial withdrawal threshold) was evaluated by plantar von Frey and periorbital von Frey tests on days 1st, 5th, and 9th, and thermal pain threshold (latency) was evaluated by hot plate and cold plate tests on days 3rd and 7th. There was a statistically significant increase in mechanical and thermal hyperalgesia in NTG administered groups compared to the control group. Gadodiamide, gadobutrol and gadobenate dimeglumine administration significantly decreased latency, paw and facial withdrawal threshold (0.18 ± 0.05, 0.17 ± 0.07, 0.16 ± 0.09; 9th day values respectively) compared to NTG group (0.27 ± 0.05). The results of this in vivo study show that GBCAs produce effects that may trigger migraine attacks in migraine. It is recommended that these effects be further investigated and supported by further clinical studies.

Evaluation of the Modulatory Effects of Capsicum Chinensis Methanol Extract in Streptozotocin-Induced Diabetic Neuropathic Pain in Mice

Diabetes is one of the common causes of neuropathic pain. The first-line treatment drugs used in alleviating neuropathic pain can cause adverse effects. Therefore, the aim of this study is to evaluate the analgesic property of Capsicum chinensis, since the plant was reported to be used against chronic pain in traditional medicine. Streptozotocin-induced diabetes was adopted to model neuropathy in mice and the antihyperalgesic effect of the extract was evaluated using a hot plate test, cold allodynia test, and Randall- Selitto paw pressure test. The plasma level of pain-associated inflammatory biomarkers like interleukin-6 (IL-6) and tissue necrotic factor-α (TNF-α) was also measured. Treatment with varying doses of extract (1, 2.5, and 5 mg/kg) significantly (p &lt; 0.05) increased the mean reaction time to thermal pain during hot and cold plate tests. During the Paw pressure test, reaction time was significantly prolonged in the treatment groups and the plasma level of TNF-α and IL-6 were reduced (p &lt; 0.05). The extract showed a better antihyperalgesic effect than the positive control drug (gabapentin). The result obtained showed that Capsicum chinensis extract can alleviate diabetes neuropathic pain in mice models with a better analgesic effect thanthe control drug (gabapentin).

Effectiveness of Low-Level Laser Therapy and Low Intensity Pulsed Ultrasound in Sensory Recovery in Experimentally Induced Peripheral Nerve Injury Rat Model

Background: Peripheral nerve injuries are known to cause significant functional impairment and diminishedsensory recovery, necessitating the exploration of effective therapeutic interventions.Purpose: The purpose of this research is to find the effectiveness of low-level laser therapy (LLLT) and low intensitypulsed ultrasound (LIPUS) sensory recovery in an experimentally induced peripheral nerve injury rat model.Materials and Methods: In this study, 18 adult male wistar rats which are divided into LLLT (n = 6), LIPUS (n = 6),and control (n = 6) groups. All rats underwent a standardized procedure to induce peripheral nerve injury, whilethe control group received sham procedures. Hot-Plate test and Cold-Plate Tests were conducted for pre- andpost-operative evaluation of sensory recovery at POD 7, 14, 21 days.Results: The study’s findings revealed that LLLT exhibited significantly improved sensory recovery compared toLIPUS and control groups on POD 14 and 21, indicating its potential as a promising non-invasive intervention formanaging peripheral nerve injuries (P &lt;0.001).Conclusion: The study recommends that LLLT is more effective when compared with LIPUS in promoting sensoryrecovery and enhancing in a rat model of peripheral nerve injury. Positive outcomes indicate LLLT’s potential asa promising intervention for managing peripheral nerve injuries.

Lidocaine-Liposomes-A Promising Frontier for Transdermal Pain Management.

(1) Background: We aim to develop novel gel formulations for transdermal drug delivery systems in acute and inflammatory pain therapy. (2) Methods: We induced inflammation by the injection of λ-carrageenan on the hind paw of 80 Wistar male rats. The animals were randomized into eight groups of 10 rats each: C (placebo gel), E (EMLATM), L (lidocaine 2%), L-CD (lidocaine + cyclodextrin 2.5%), L-LP (lidocaine + liposomes 1.7%), L-CS (lidocaine + chitosan 4%), L-CSh (lidocaine + chitosan hydrochloride), and L-CS-LP (lidocaine + chitosan + liposomes). The behavior response was determined with a hot plate, cold plate, and algesimeter, each being performed at 30, 60, 120, 180, and 240 min after pain induction. At the end of the experiment, tissue samples were collected for histological assessment. (3) Results: L-LP had the greatest anesthetic effects, which was proven on the cold plate test compared to placebo and EMLATM (all p ≤ 0.001). L-CS-LP had a significant effect on cold plate evaluation compared to placebo (p ≤ 0.001) and on hot plate evaluation compared to EMLATM (p = 0.018). (4) Conclusions: L-LP is a new substance with a substantial analgesic effect demonstrated by the cold plate in the first 120 min. Further studies with more animals are needed to determine the maximum doses that can be applied for a better analgesia with minimum side effects.

Cold nociception as a measure of hyperalgesia during spontaneous heroin withdrawal in mice

Opioids are powerful analgesic drugs that are used clinically to treat pain. However, chronic opioid use causes compensatory neuroadaptations that result in greater pain sensitivity during withdrawal, known as opioid withdrawal-induced hyperalgesia (OWIH). Cold nociception tests are commonly used in humans, but preclinical studies often use mechanical and heat stimuli to measure OWIH. Thus, further characterization of cold nociception stimuli is needed in preclinical models. We assessed three cold nociception tests—thermal gradient ring (5–30 °C, 5–50 °C, 15–40 °C, and 25–50 °C), dynamic cold plate (4 °C to −1 °C at −1 °C/min, −1 °C to 4 °C at +1 °C/min), and stable cold plate (10 °C, 6 °C, and 2 °C)—to measure hyperalgesia in a mouse protocol of heroin dependence. On the thermal gradient ring, mice in the heroin withdrawal group preferred warmer temperatures, and the results depended on the ring's temperature range. On the dynamic cold plate, heroin withdrawal increased the number of nociceptive responses, with a temperature ramp from 4 °C to −1 °C yielding the largest response. On the stable cold plate, heroin withdrawal increased the number of nociceptive responses, and a plate temperature of 2 °C yielded the most significant increase in responses. Among the three tests, the stable cold plate elicited the most robust change in behavior between heroin-dependent and nondependent mice and had the highest throughput. To pharmacologically characterize the stable cold plate test, we used μ-opioid and non-opioid receptor-targeting drugs that have been previously shown to reverse OWIH in mechanical and heat nociception assays. The full μ-opioid receptor agonist methadone and μ-opioid receptor partial agonist buprenorphine decreased OWIH, whereas the preferential μ-opioid receptor antagonist naltrexone increased OWIH. Two N-methyl-d-aspartate receptor antagonists (ketamine, MK-801), a corticotropin-releasing factor 1 receptor antagonist (R121919), a β2-adrenergic receptor antagonist (butoxamine), an α2-adrenergic receptor agonist (lofexidine), and a 5-hydroxytryptamine-3 receptor antagonist (ondansetron) had no effect on OWIH. These data demonstrate that the stable cold plate at 2 °C yields a robust, reliable, and concise measure of OWIH that is sensitive to opioid agonists.

Cleomin Exerts Acute Antinociceptive Effects in Mice via GABAB and Muscarinic Receptors.

Cleomin, a 1,3-oxazolidine-2-thione, was recently isolated from Neocalyptrocalyx longifolium, a species traditionally used for treating painful conditions. Reports about the pharmacological activities of cleomin are lacking. Here, the antinociceptive effects of cleomin were investigated using mice models of pain, namely the formalin, the cold plate, and the tail flick tests. Motor integrity was assessed in the rota-rod test. Antagonism assays and in silico docking analyses were performed to investigate the putative mechanisms of action. Cleomin (12.5-25 mg/kg), at doses that did not induce motor impairment, induced dose-dependent antinociception in both early and late phases of the formalin test and reduced nociceptive behaviors in both the cold plate and tail flick tests. Pretreatments with phaclofen and atropine attenuated the antinociceptive effects of cleomin, implicating the involvement of GABAB and muscarinic receptors. In silico docking studies suggested satisfactory coupling between cleomin and GABAB and M2 receptors, hence corroborating their role in cleomin's activity. Pretreatments with naloxone, yohimbine, bicuculline, and methysergide did not affect the antinociception of cleomin. In silico pharmacokinetics prediction showed a good drug ability profile of cleomin. In conclusion, cleomin promoted antinociception mediated by GABAB and muscarinic receptors. These findings support further investigation of the analgesic potential of cleomin.

Neurofilament light chain in plasma as a sensitive diagnostic biomarker of peripheral neurotoxicity: In Vivo mouse studies with oxaliplatin and paclitaxel - NeuroDeRisk project

Identifying compounds that are neurotoxic either toward the central or the peripheral nervous systems (CNS or PNS) would greatly benefit early stages of drug development by derisking liabilities and selecting safe compounds. Unfortunately, so far assays mostly rely on histopathology findings often identified after repeated-dose toxicity studies in animals. The European NeuroDeRisk project aimed to provide comprehensive tools to identify compounds likely inducing neurotoxicity. As part of this project, the present work aimed to identify diagnostic non-invasive biomarkers of PNS toxicity in mice. We used two neurotoxic drugs in vivo to correlate functional, histopathological and biological findings. CD1 male mice received repeated injections of oxaliplatin or paclitaxel followed by an assessment of drug exposure in CNS/PNS tissues. Functional signs of PNS toxicity were assessed using electronic von Frey and cold paw immersion tests (oxaliplatin), and functional observational battery, rotarod and cold plate tests (paclitaxel). Plasma concentrations of neurofilament light chain (NF-L) and vascular endothelial growth factor A (VEGF-A) were measured, and histopathological evaluations were performed on a comprehensive list of CNS and PNS tissues. Functional PNS toxicity was observed only in oxaliplatin-treated mice. Histopathological findings were observed dose-dependently only in paclitaxel groups. While no changes of VEGF-A concentrations was recorded, NF-L concentrations were increased only in paclitaxel-treated animals as early as 7 days after the onset of drug administration. These results show that plasma NF-L changes correlated with microscopic changes in the PNS, thus strongly suggesting that NF-L could be a sensitive and specific biomarker of PNS toxicity in mice.

Hypericum perforatum ekstresinin siyatik sinir hasarı ile indüklenen periferik nöropati üzerindeki düzenleyici etkisi: fareler üzerinde deneysel bir çalışma

Purpose: The effect of Hypericum perforatum (HP), which is a medicinal plant, on sciatic nerve injury-induced peripheral neuropathy has been less studied so far. The current experimental study aimed to investigate the neuroprotective and antinociceptive effects of Hypericum perforatum (HP) extract on sciatic nerve injury-induced peripheral neuropathy in mice.&#x0D; Materials and Methods: In the present study, 18 Balb/C albino mice were allocated equally into three groups. The first group was determined as controls, and no procedure was performed on these mice. Neuropathy was generated by the partial sciatic nerve ligation method on mice allocated to the second and third groups. Mice in the third group received HP extract at a dose of 70 mg/kg per day for fourteen days. Nociception (cold allodynia) was evaluated using the cold plate test at the end of the experimental period. Tumor necrosis factor –αlpha (TNF-α) and interleukin-6 (IL-6) in plasma; inducible nitric oxide synthase (iNOS), phospholipase A2, cyclooxygenase-2 (COX-2), nuclear factor-kappa B (NF-κB), caspase-3, Bcl-2, and Bax levels in sciatic nerve were measured by enzyme-linked immunosorbent assay test. &#x0D; Results: Cold plate latencies (sec) of the neuropathy + HP, neuropathy, and control groups were 8.33 ± 0.67, 5.17 ± 0.60, and 13 ± 0.73, respectively. Plasma TNF-α, IL-6 levels, and sciatic nerve iNOS, COX-2, NF-κB, caspase-3, and Bax levels were significantly decreased after HP supplementation. Bcl-2 levels of the neuropathy + HP, neuropathy, and control groups were 9.92 ± 0.71, 5.37 ± 0.53, and 13.65 ± 0.68, respectively.&#x0D; Conclusion: HP has improved oxidative, inflammatory, and apoptotic responses, as well as cytokine levels in plasma and sciatic nerves of mice. It has been concluded that HP provided neuroprotective, anti-inflammatory, and antinociceptive effects in experimental mice with sciatic nerve injury models, which is suggested to guide future studies on neuropathic pain management.

Analgesic Effects of Fisetin, Peimine, Astaxanthin, Artemisinin, Bardoxolone Methyl and 740 Y-P and Their Influence on Opioid Analgesia in a Mouse Model of Neuropathic Pain.

Treatment of neuropathic pain remains a challenge for modern medicine due to the insufficiently understood molecular mechanisms of its development and maintenance. One of the most important cascades that modulate the nociceptive response is the family of mitogen-activated protein (MAP) kinases and phosphatidylinositol-3-kinase (PI3K), as well as nuclear factor erythroid 2-related factor 2 (Nrf2). The aim of this study was to determine the effect of nonselective modulators of MAP kinases-fisetin (ERK1/2 and NFκB inhibitor, PI3K activator), peimine (MAPK inhibitor), astaxanthin (MAPK inhibitor, Nrf2 activator) and artemisinin (MAPK inhibitor, NFκB activator), as well as bardoxolone methyl (selective activator of Nrf2) and 740 Y-P (selective activator of PI3K)-in mice with peripheral neuropathy and to compare their antinociceptive potency and examine their effect on analgesia induced by opioids. The study was performed using albino Swiss male mice that were exposed to chronic constriction injury of the sciatic nerve (CCI model). Tactile and thermal hypersensitivity was measured using von Frey and cold plate tests, respectively. Single doses of substances were administered intrathecally on day 7 after CCI. Among the tested substances, fisetin, peimine, and astaxanthin effectively diminished tactile and thermal hypersensitivity in mice after CCI, while artemisinin did not exhibit analgesic potency in this model of neuropathic pain. Additionally, both of the activators tested, bardoxolone methyl and 740 Y-P, also showed analgesic effects after intrathecal administration in mice exposed to CCI. In the case of astaxanthin and bardoxolone methyl, an increase in analgesia after combined administration with morphine, buprenorphine, and/or oxycodone was observed. Fisetin and peimine induced a similar effect on tactile hypersensitivity, where analgesia was enhanced after administration of morphine or oxycodone. In the case of 740 Y-P, the effects of combined administration with each opioid were observed only in the case of thermal hypersensitivity. The results of our research clearly indicate that substances that inhibit all three MAPKs provide pain relief and improve opioid effectiveness, especially if they additionally block NF-κB, such as peimine, inhibit NF-κB and activate PI3K, such as fisetin, or activate Nrf2, such as astaxanthin. In light of our research, Nrf2 activation appears to be particularly beneficial. The abovementioned substances bring promising results, and further research on them will broaden our knowledge regarding the mechanisms of neuropathy and perhaps contribute to the development of more effective therapy in the future.

The Antinociceptive Activity of (E)-3-(thiophen-2-yl)- N -(p-tolyl)acrylamide in Mice Is Reduced by (E)-3-(furan-2-yl)- N -methyl- N -(p-tolyl)acrylamide Through Opposing Modulatory Mechanisms at the α7 Nicotinic Acetylcholine Receptor.

The primary objective of this study was to characterize the pharmacological and behavioral activity of 2 novel compounds, DM497 [(E)-3-(thiophen-2-yl)- N -(p-tolyl)acrylamide] and DM490 [(E)-3-(furan-2-yl)- N -methyl- N -(p-tolyl)acrylamide], structural derivatives of PAM-2, a positive allosteric modulator of the α7 nicotinic acetylcholine receptor (nAChR). A mouse model of oxaliplatin-induced neuropathic pain (2.4 mg/kg, 10 injections) was used to test the pain-relieving properties of DM497 and DM490. To assess possible mechanisms of action, the activity of these compounds was determined at heterologously expressed α7 and α9α10 nAChRs, and voltage-gated N-type calcium channel (Ca V 2.2) using electrophysiological techniques. Cold plate tests indicated that 10 mg/kg DM497 was able to decrease neuropathic pain in mice induced by the chemotherapeutic agent oxaliplatin. In contrast, DM490 induced neither pro- nor antinociceptive activity but inhibited DM497's effect at equivalent dose (30 mg/kg). These effects are not a product of changes in motor coordination or locomotor activity. At α7 nAChRs, DM497 potentiated whereas DM490 inhibited its activity. In addition, DM490 antagonized the α9α10 nAChR with >8-fold higher potency than that for DM497. In contrast, DM497 and DM490 had minimal inhibitory activity at the Ca V 2.2 channel. Considering that DM497 did not increase the mouse exploratory activity, an indirect anxiolytic mechanism was not responsible for the observed antineuropathic effect. The antinociceptive activity of DM497 and the concomitant inhibitory effect of DM490 are mediated by opposing modulatory mechanisms on the α7 nAChR, whereas the involvement of other possible nociception targets such as the α9α10 nAChR and Ca V 2.2 channel can be ruled out.

Pharmacological Modulation of the MIP-1 Family and Their Receptors Reduces Neuropathic Pain Symptoms and Influences Morphine Analgesia: Evidence from a Mouse Model

Neuropathic pain pathophysiology is not fully understood, but it was recently shown that MIP-1 family members (CCL3, CCL4, and CCL9) have strong pronociceptive properties. Our goal was to examine how pharmacological modulation of these chemokines and their receptors (CCR1 and CCR5) influence hypersensitivity after nerve injury in Albino Swiss male mice. The spinal changes in the mRNA/protein levels of the abovementioned chemokines and their receptors were measured using RT-qPCR and ELISA/Western blot techniques in a mouse model of chronic constriction injury of the sciatic nerve. Behavioral studies were performed using the von Frey and cold plate tests after pharmacological treatment with neutralizing antibodies (nAbs) against chemokines or antagonists (CCR1-J113863, CCR5-TAK-220/AZD-5672) alone and in coadministration with morphine on Day 7, when the hypersensitivity was fully developed. Our results showed enhanced protein levels of CCL3 and CCL9 1 and 7 days after nerve injury. The single intrathecal administration of CCL3 or CCL9 nAb, J113863, TAK-220, or AZD-5672 diminished neuropathic pain symptoms and enhanced morphine analgesia. These findings highlight the important roles of CCL3 and CCL9 in neuropathic pain and additionally indicate that these chemokines play essential roles in opioid analgesia. The obtained results suggest CCR1 and CCR5 as new, interesting targets in neuropathy treatment.

Exercise combined with administration of adipose-derived stem cells ameliorates neuropathic pain after spinal cord injury.

Experimental studies have shown that exercise and human adipose-derived stem cells (ADSCs) play positive roles in spinal cord injury (SCI). However, whether ADSCs and/or exercise have a positive effect on SCI-induced neuropathic pain is still unclear. Thus, there is a need to explore the effects of exercise combined with administration of ADSCs on neuropathic pain after SCI. In this study, a thoracic 11 (T11) SCI contusion model was established in adult C57BL/6 mice. Exercise was initiated from 7 days post-injury and continued to 28 days post-injury, and approximately 1 × 105 ADSCs were transplanted into the T11 spinal cord lesion site immediately after SCI. Motor function and neuropathic pain-related behaviors were assessed weekly using the Basso Mouse Scale, von Frey filament test, Hargreaves method, and cold plate test. Histological studies (Eriochrome cyanine staining and immunohistochemistry) were performed at the end of the experiment (28 days post-injury). Exercise combined with administration of ADSCs partially improved early motor function (7, 14, and 21 days post-injury), mechanical allodynia, mechanical hypoalgesia, thermal hyperalgesia, and thermal hypoalgesia. Administration of ADSCs reduced white and gray matter loss at the lesion site. In addition, fewer microglia and astrocytes (as identified by expression of ionized calcium-binding adapter molecule 1 and glial fibrillary acidic protein, respectively) were present in the lumbar dorsal horn in the SCI + ADSCs and SCI + exercise + ADSCs groups compared with the sham group. Our findings suggest that exercise combined with administration of ADSCs is beneficial for the early recovery of motor function and could partially ameliorate SCI-induced neuropathic pain.

Echinacea purpurea against neuropathic pain: Alkamides versus polyphenols efficacy.

Chemotherapy-induced neuropathy represents the main dose-limiting toxicity of several anticancer drugs, such as oxaliplatin, leading to chronic pain and an impairment of the quality of life. Echinacea purpurea n-hexane extract (EP4 -RE ; rich in alkamides) and butanolic extract (EP4 -RBU ; rich in polyphenols) have been characterized and tested in an in vivo model of oxaliplatin-induced neuropathic pain, addressing the endocannabinoid system with alkamides and counteracting the redox imbalance with polyphenols. Thermal hypersensitivity was evaluated by the Cold Plate test. EP4 -RE showed a dose-dependent anti-hyperalgesic profile. The extract was more effective than its main constituent, dodeca-2 E,4 E,8Z,10 E/Z-tetraenoic acid isobutylamide (18 mg kg-1 , twofold to equimolar EP4 -RE 30 mg kg-1 ), suggesting a synergy with other extract constituents. Administration of cannabinoid type 2 (CB2) receptor-selective antagonist completely blocked the anti-allodynic effect of EP4 -RE , differently from the antagonism of CB1 receptors. EP4 -RBU (30 mg kg-1 ) exhibited anti-neuropathic properties too. The effect was mainly exerted by chicoric acid, which administered alone (123 μg kg-1 , equimolar to EP4 -RBU 30 mg kg-1 ) completely reverted oxaliplatin-induced allodynia. A synergy between different polyphenols in the extract had not been highlighted. Echinacea extracts have therapeutic potential in the treatment of neuropathic pain, through both alkamides CB2-selective activity and polyphenols protective properties.