Gabapentin improves neuropathic pain in Minamata disease model rats.

BACKGROUND: Methylmercury (MeHg), the causative agent of Minamata disease, damages the cranial nervous system and causes specific sensory disturbances, especially hypoesthesia, in the extremities. However, recent reports demonstrate that patients with chronic Minamata disease conversely develop neuropathic pain in the lower extremities. Studies on our established Minamata disease model rats showed that MeHg-mediated neurodegeneration might induce neuropathic pain by over time through inducing rewiring with neuronal activation in the somatosensory cortex via microglial activation in the spinal dorsal horn. METHODS: In this study, the effects of gabapentin, a potentially effective treatment for neuropathic pain, was evaluated using this Minamata disease model rats. To further elucidate the mechanism of its medicinal effects, histochemical and biochemical analyses of the nervous system of Minamata disease model rats were conducted. RESULTS: Gabapentin treatment restored the reduction in the pain threshold caused by MeHg exposure in rats. Histochemical and biochemical analyses revealed that gabapentin showed no effect on MeHg-induced neurodegeneration in entire nervous system and microglial activation in the spinal dorsal horn. However, it was shown that gabapentin may reduce excessive synaptogenesis through its antagonist action on the alpha2-delta-1 subunit of calcium channels in the somatosensory cortex. CONCLUSIONS: These results indicate that gabapentin may alleviated neuropathic pain in MeHg poisoning, as typified by Minamata disease, by reversibly modulation synaptic rewiring in the somatosensory cortex.

Pyrazoles as Anti-inflammatory and Analgesic Agents: In-vivo and In-silico Studies.

BACKGROUND: Pyrazole is a well-known nucleus in the pharmacy field with a wide range of other activities in addition to anti-inflammatory and analgesic, i.e., anticonvulsant, antiviral, and anticancer activities. There are well-known marketed drugs having pyrazole moiety as celecoxib, and lonazolac as COX-II inhibitors. AIMS: We aim to synthesize better anti-inflammatory than existing ones. Thiophene is also known for its analgesic and anti-inflammatory action. Thus, the fusion of both gives better anti-inflammatory agents. In the present studies, derivatives from two series of pyrazole were prepared by reacting substituted chalcone (3a-3f) derivatives prepared from 2-acetyl thiophene. They substituted aromatic aldehydes with phenyl hydrazine to form (5a-5f) and with 2, 4-dinitro phenyl hydrazine giving compounds (6a-6f) separately. METHODS: Purified and characterized pyrazoles have been analyzed for in-vivo analgesic and anti-inflammatory activities by using standard methods. Compounds 5e, 5f, and 6d were proved to be potent analgesics and series (5a-5f) was found to have anti-inflammatory action, which was further validated using docking and ADME studies. RESULTS: The ADME profile of synthesized compounds was found to be satisfactory. CONCLUSION: The synthesized compounds can serve as lead for further drug designing.

Linalyl acetate exerts analgesic effects by inhibiting nociceptive TRPA1 in mice.

Clary sage essential oil (CSEO) is utilized in perfumery, aromatherapy, and skincare. Linalyl acetate (LA), a primary component of CSEO, possesses sedative, anxiolytic, and analgesic properties. However, the mechanism of its analgesic action is not clearly understood. Transient receptor potential ankyrin 1 (TRPA1) channel, a non-selective cation channel, is mainly expressed in sensory neurons and serves as a sensor of various irritants. In this study, we investigated the effects of LA on TRPA1 channel using heterologous expression system and isolated sensory neurons. To detect channel activity, we employed Ca2+ imaging and the whole-cell patch-clamp technique. The analgesic action of LA was measured in a pain-related behavioral mouse model. In cells that heterologously expressed TRPA1, LA diminished [Ca2+]i and current responses to allylisothiocyanate (AITC) and carvacrol: exogenous TRPA1 agonists, and the inhibitory effects were more pronounced for the former than for the latter. Moreover, LA suppressed [Ca2+] i and current responses to PGJ2: an endogenous TRPA1 agonist. Similar inhibitory actions were observed in native TRPA1 channels expressed in mouse sensory neurons. Furthermore, LA diminished PGJ2-induced nociceptive behaviors in mice. These findings suggest that analgesic effects of LA exert through inhibition of nociceptive TRPA1, making it a potential candidate for novel analgesic development.

Turning down the body heat: A novel mechanism for TRPV1 antagonist-induced hyperthermia.

While effective analgesics, TRPV1 antagonists can dangerously alter thermoregulation. In this issue of Neuron, Huang et al.1 demonstrate that interaction with the S4-S5 linker of TRPV1 determines whether an antagonist affects core body temperature, with promising implications for analgesic development.

The Analgesic Potential of Litsea Species: A Systematic Review.

Various plant species from the Litsea genus have been claimed to be beneficial for pain relief. The PRISMA approach was adopted to identify studies that reported analgesic properties of plants from the Litsea genus. Out of 450 records returned, 19 primary studies revealed the analgesic potential of nine Litsea species including (1) Litsea cubeba, (2) Litsea elliptibacea, (3) Litsea japonica, (4) Litsea glutinosa, (5) Litsea glaucescens, (6) Litsea guatemalensis, (7) Litsea lancifolia, (8) Litsea liyuyingi and (9) Litsea monopetala. Six of the species, 1, 3, 4, 7, 8 and 9, demonstrated peripheral antinociceptive properties as they inhibited acetic-acid-induced writhing in animal models. Species 1, 3, 4, 8 and 9 further showed effects via the central analgesic route at the spinal level by increasing the latencies of heat stimulated-nocifensive responses in the tail flick assay. The hot plate assay also revealed the efficacies of 4 and 9 at the supraspinal level. Species 6 was reported to ameliorate hyperalgesia induced via partial sciatic nerve ligation (PSNL). The antinociceptive effects of 1 and 3 were attributed to the regulatory effects of their bioactive compounds on inflammatory mediators. As for 2 and 5, their analgesic effect may be a result of their activity with the 5-hydroxytryptamine 1A receptor (5-HT1AR) which disrupted the pain-stimulating actions of 5-HT. Antinociceptive activities were documented for various major compounds of the Litsea plants. Overall, the findings suggested Litsea species as good sources of antinociceptive compounds that can be further developed to complement or substitute prescription drugs for pain management.

Analgesic and Psychotropic Effects of a New Bradykinin Antagonist.

A bradykinin B1 receptors antagonist PAV-0056, an 1,4-benzodiazepin-2-one derivative, intragastrically administrated to mice at doses of 0.1 and 1 mg/kg causes analgesia in the "formalin test" not inferior to that of diclofenac sodium (10 mg/kg) and tramadol (20 mg/kg). PAV-0056 at doses of 0.1 and 10 mg/kg has no anxiolytic and central muscle relaxant effects in mice and does not damage the gastric mucosa in rats. Based on the results of the conditioned place preference test, PAV-0056 also does not induce addiction in mice.

Mechanisms and Preventative Strategies for Persistent Pain following Knee and Hip Joint Replacement Surgery: A Narrative Review.

Chronic postsurgical pain (CPSP) following total knee arthroplasty (TKA) and total hip arthroplasty (THA) is a prevalent complication of joint replacement surgery which has the potential to decrease patient satisfaction, increase financial burden, and lead to long-term disability. The identification of risk factors for CPSP following TKA and THA is challenging but essential for targeted preventative therapy. Recent meta-analyses and individual studies highlight associations between elevated state anxiety, depression scores, preoperative pain, diabetes, sleep disturbances, and various other factors with an increased risk of CPSP, with differences observed in prevalence between TKA and THA. While the etiology of CPSP is not fully understood, several factors such as chronic inflammation and preoperative central sensitization have been identified. Other potential mechanisms include genetic factors (e.g., catechol-O-methyltransferase (COMT) and potassium inwardly rectifying channel subfamily J member 6 (KCNJ6) genes), lipid markers, and psychological risk factors (anxiety and depression). With regards to therapeutics and prevention, multimodal pharmacological analgesia, emphasizing nonopioid analgesics like acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs), has gained prominence over epidural analgesia. Nerve blocks and local infiltrative anesthesia have shown mixed results in preventing CPSP. Ketamine, an N-methyl-D-aspartate (NMDA)-receptor antagonist, exhibits antihyperalgesic properties, but its efficacy in reducing CPSP is inconclusive. Lidocaine, an amide-type local anesthetic, shows tentative positive effects on CPSP. Selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs) have mixed results, while gabapentinoids, like gabapentin and pregabalin, present hopeful data but require further research, especially in the context of TKA and THA, to justify their use for CPSP prevention.

The Effect of Melatonin on Reducing the Frequency and Severity of Migraine Attacks: A Double-Blind, Randomized Clinical Trial.

Background: There is no definite recommendation for melatonin supplementation in episodic migraine. This study aimed to evaluate the effect of melatonin on reducing the frequency and severity of migraine attacks. Methods: This randomized, double-blind clinical trial was conducted at Golestan Hospital of Ahvaz, Iran, in 2021. A total of 60 patients with episodic migraine were randomly assigned into 2 groups of receiving 3 mg melatonin (intervention group; n=30) or the same dose of placebo (control group; n=30) along with baseline therapy (propranolol 20 mg, BID) for two months. The attack frequency, attack duration, attack severity (based on VAS), the number of analgesic intakes, drug complications, Migraine Disability Assessment score (MIDAS), and Pittsburgh sleep quality index (PSQI) were evaluated at baseline and in the first, second, third, and fourth months of follow-up. The independent t test, chi-square, and analysis of variance (ANOVA) with repeated measures were used to compare variables between the two groups. Results: In both groups, the frequency, duration, and severity of attacks, taking analgesics, MIDAS, and PSQI scores during follow-up decreased significantly (P<0.001). After treatment, the mean frequency (P=0.032) and duration of attacks (P=0.001), taking analgesic (P<0.001), and MIDAS (P<0.001) and PSQI scores (P<0.001) in the melatonin group were lower than placebo. Only the attack severity was not significantly different between the two groups (P=0.126). Side effects were observed in two patients (6.7%) in the melatonin group and one patient (3.3%) in the placebo group (P>0.999). Conclusion: Our study shows that melatonin was more efficacious than the placebo in the reduction of frequency and duration of migraine attacks. It was equally safe as the placebo and might be effective in the preventive treatment of episodic migraine in adults.Trial Registration Number: IRCT20190107042264N5.

Transient receptor potential vanilloid 1 involved in the analgesic effects of total flavonoids extracted from Longxuejie ().

OBJECTIVE: To evaluate the analgesic effects of total flavonoids of Longxuejie (Resina Dracaenae Cochinchinensis) (TFDB) and explore the possible analgesic mechanism associated with transient receptor potential vanilloid 1 (TRPV1). METHODS: Whole-cell patch clamp technique was used to observe the effects of TFDB on capsaicin-induced TRPV1 currents. Rat experiments in vivo were used to observe the analgesic effects of TFDB. Western blot and immunofluorescence experiments were used to test the change of TRPV1 expression in DRG neurons induced by TFDB. RESULTS: Results showed that TFDB inhibited capsaicin-induced TRPV1 receptor currents in acutely isolated dorsal root ganglion (DRG) neurons of rats and the half inhibitory concentration was (16.7 ± 1.6) mg/L. TFDB (2-20 mg/kg) showed analgesic activity in the phase Ⅱ of formalin test and (0.02-2 mg per paw) reduced capsaicin-induced licking times of rats. TFDB (20 mg/kg) was fully efficacious on complete Freund's adjuvant (CFA)-induced inflammatory thermal hyperalgesia and capsaicin could weaken the analgesic effects. The level of TRPV1 expressions of DRG neurons was also decreased in TFDB-treated CFA-inflammatory pain rats. CONCLUSION: All these results indicated that the analgesic effect of TFDB may contribute to their modulations on both function and expression of TRPV1 channels in DRG neurons.

Analgesic effects of oral Yokukansan on acute postoperative pain and involvement of the serotonin nervous system: a mouse model study.

BACKGROUND: Yokukansan, a traditional Japanese medicine (Kampo), has been widely used to treat neurosis, dementia, and chronic pain. Previous in vitro studies have suggested that Yokukansan acts as a partial agonist of the 5-HT1A receptor, resulting in amelioration of chronic pain through inhibition of nociceptive neuronal activity. However, its effectiveness for treating postoperative pain remains unknown, although its analgesic mechanism of action has been suggested to involve serotonin and glutamatergic neurotransmission. This study aimed to investigate the effect of Yokukansan on postoperative pain in an animal model. METHODS: A mouse model of postoperative pain was created by plantar incision, and Yokukansan was administered orally the day after paw incision. Pain thresholds for mechanical and heat stimuli were examined in a behavioral experiment. In addition, to clarify the involvement of the serotonergic nervous system, we examined the analgesic effects of Yokukansan in mice that were serotonin-depleted by para-chlorophenylalanine (PCPA) treatment and intrathecal administration of NAN-190, 5-HT1A receptor antagonist. RESULTS: Orally administered Yokukansan increased the pain threshold dose-dependent in postoperative pain model mice. Pretreatment of para-chlorophenylalanine dramatically suppressed serotonin immunoreactivity in the spinal dorsal horn without changing the pain threshold after the paw incision. The analgesic effect of Yokukansan tended to be attenuated by para-chlorophenylalanine pretreatment and significantly attenuated by intrathecal administration of 2.5 µg of NAN-190 compared to that in postoperative pain model mice without para-chlorophenylalanine treatment and NAN-190 administration. CONCLUSION: This study demonstrated that oral administration of Yokukansan has acute analgesic effects in postoperative pain model mice. Behavioral experiments using serotonin-depleted mice and mice intrathecally administered with a 5-HT1A receptor antagonist suggested that Yokukansan acts as an agonist at the 5-HT1A receptor, one of the serotonin receptors, to produce analgesia.

Efficacy assessment of novel methanimine derivatives in chronic constriction injury-induced neuropathic model: An in-vivo, ex-vivo and In-Silico approach.

The multicomponent etiology, complex clinical implications, dose-based side effect and degree of pain mitigation associated with the current pharmacological therapy is incapable in complete resolution of chronic neuropathic pain patients which necessitates the perpetual requirement of novel medication therapy. Therefore, this study explored the ameliorative aptitude of two novel methanimine imitative like (E)-N-(4-nitrobenzylidene)-4­chloro-2-iodobenzamine (KB 09) and (E)-N-(4-methylbenzylidene)-4­chloro-2-iodobenzamine (KB 10) in chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain in rat model. Standard behavioral tests like dynamic and static allodynia, cold, thermal and mechanical hyperalgesia along with rotarod activity were performed at various experimental days like 0, 3, 7, 14 and 21. Enzyme linked immunosorbent assay (ELISA) on spinal tissue and antioxidant assays on sciatic nerve were executed accompanied by molecular docking and simulation studies. Prolonged ligation of sciatic nerve expressively induced hyperalgesia as well as allodynia in rats. KB 09 and KB 10 substantially attenuated the CCI elicited hyperalgesia and allodynia. They significantly reduced the biomarkers of pain and inflammation like Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in ELISA and while enhanced the GSH, SOD and CAT and diminished the MDA levels during antioxidant assays. KB 09 displayed -9.62 kcal/mol with TNF-α and -7.68 kcal/mol binding energy with IL-6 whereas KB 10 exhibited binding energy of -8.20 kcal/mol with IL-6 while -11.68 kcal/mol with TNF-α and hence both trial compounds ensured stable interaction with IL-6 and TNF-α during computational analysis. The results advocated that both methanimine derivatives might be novel candidates for attenuation of CCI-induced neuropathic pain prospects via anti-nociceptive, anti-inflammatory and antioxidant mechanisms.

Anti-Nociceptive Effects of Sphingomyelinase and Methyl-Beta-Cyclodextrin in the Icilin-Induced Mouse Pain Model.

The thermo- and pain-sensitive Transient Receptor Potential Melastatin 3 and 8 (TRPM3 and TRPM8) ion channels are functionally associated in the lipid rafts of the plasma membrane. We have already described that cholesterol and sphingomyelin depletion, or inhibition of sphingolipid biosynthesis decreased the TRPM8 but not the TRPM3 channel opening on cultured sensory neurons. We aimed to test the effects of lipid raft disruptors on channel activation on TRPM3- and TRPM8-expressing HEK293T cells in vitro, as well as their potential analgesic actions in TRPM3 and TRPM8 channel activation involving acute pain models in mice. CHO cell viability was examined after lipid raft disruptor treatments and their effects on channel activation on channel expressing HEK293T cells by measurement of cytoplasmic Ca2+ concentration were monitored. The effects of treatments were investigated in Pregnenolone-Sulphate-CIM-0216-evoked and icilin-induced acute nocifensive pain models in mice. Cholesterol depletion decreased CHO cell viability. Sphingomyelinase and methyl-beta-cyclodextrin reduced the duration of icilin-evoked nocifensive behavior, while lipid raft disruptors did not inhibit the activity of recombinant TRPM3 and TRPM8. We conclude that depletion of sphingomyelin or cholesterol from rafts can modulate the function of native TRPM8 receptors. Furthermore, sphingolipid cleavage provided superiority over cholesterol depletion, and this method can open novel possibilities in the management of different pain conditions.

LMD and LC-MS-based chemical constituents and pharmacological effects assessment for two different processing methods of the root of Paeonia lactiflora Pall.

The plant of Paeonia lactiflora Pall. belongs to Ranunculaceae, and its root can be divided into two categories according to different processing methods, which included that one was directly dried without peeling the root of the P. lactiflora (PR), and the other was peeled the root of the P. lactiflora (PPR) after boiled and dried. To evaluate the difference of chemical components, UPLC-ESI-Q-Exactive Focus-MS/MS and UPLC-QQQ-MS were applied. The distribution of chemical components in different tissues was located by laser microdissection (LMD), especially the different ingredients. A total of 86 compounds were identified from PR and PPR. Four kind of tissues were isolated from the fresh root of the P. lactiflora (FPR), and 54 compounds were identified. Especially the content of gallic acid, albiflorin, and paeoniflorin with high biological activities were the highest in the cork, but they were lower in PR than that in PPR, which probably related to the process. To illustrate the difference in pharmacological effects of PR and PPR, the tonifying blood and analgesic effects on mice were investigated, and it was found that the tonifying blood and analgesic effects of PPR was superior to that of PR, even though PR had more constituents. The material basis for tonifying blood and analgesic effect of the root of P. lactiflora is likely to be associated with an increase in constituents such as paeoniflorin and paeoniflorin lactone after boiled and peeled. The study was likely to provide some theoretical support for the standard and clinical application.

The Effect of Pregabalin on Microglia Differentiation in Rat with Neuropathic pain: A Preliminary Study.

This study investigated the effects of pregabalin on microglial differentiation in rats with neuropathic pain (NP) induced by sciatic nerve ligation and transection. After confirming NP, the rats were randomly allocated to either a pregabalin or control group. The pregabalin group received intraperitoneal injections of 10 mg/kg pregabalin, while the control group received an equivalent volume of normal saline following surgery. On postoperative day 28, neuronal damage, microglial activity, and microglial differentiation were assessed. The pregabalin group exhibited significantly less neuronal damage compared to the control group, along with a significant decrease in activated microglial expression in both the brain and spinal cord. Pregabalin treatment also significantly altered the microglial phenotype expression, with a decrease in the M1 phenotype percentage and an increase in the M2 phenotype percentage in both the brain (M1 phenotype: 43.52 ± 12.16% and 18.00 ± 8.57% in the control and pregabalin groups, respectively; difference: 27.26 [15.18-42.10], p = 0.002; M2 phenotype: 16.88 ± 6.47% and 39.63 ± 5.82% in the control and pregabalin groups, respectively; difference 22.04 [17.17-32.70], p < 0.001) and the spinal cord ipsilateral to nerve injury (M1 phenotype: 44.35 ± 12.12% and 13.78 ± 5.39% in the control and pregabalin groups, respectively; difference 30.46 [21.73-44.45], p < 0.001; M2 phenotype: 7.64 ± 3.91% and 33.66 ± 7.95% in the control and pregabalin groups, respectively; difference 27.41 [21.21-36.30], p < 0.001). Overall, pregabalin treatment significantly decreased the microglial M1 phenotype while increasing the microglial M2 phenotype in NP rats.

Selective inhibition of A-fiber-mediated excitatory transmission underlies the analgesic effects of KCNQ channel opening in the spinal dorsal horn.

Neuronal voltage-gated KCNQ (Kv7) channels, expressed centrally and peripherally, mediate low-threshold and non-inactivating M-currents responsible for the control of tonic excitability of mammalian neurons. Pharmacological opening of KCNQ channels has been reported to generate analgesic effects in animal models of neuropathic pain. Here, we examined the possible involvement of central KCNQ channels in the analgesic effects of retigabine, a KCNQ channel opener. Behaviorally, intraperitoneally applied retigabine exerted analgesic effects on thermal and mechanical hypersensitivity in male mice developing neuropathic pain after partial sciatic nerve ligation, which was antagonized by the KCNQ channel blocker XE991 preadministered intraperitoneally and intrathecally. Intrathecally applied retigabine also exerted analgesic effects that were inhibited by intrathecally injected XE991. We then explored the synaptic mechanisms underlying the analgesic effects of retigabine in the spinal dorsal horn. Whole-cell recordings were made from dorsal horn neurons in spinal slices with attached dorsal roots from adult male mice developing neuropathic pain, and the effects of retigabine on miniature and afferent-evoked postsynaptic currents were examined. Retigabine reduced the amplitude of A-fiber-mediated EPSCs without affecting C-fiber-mediated excitatory synaptic transmission. A-fiber-mediated EPSCs remained unaltered by retigabine in the presence of XE991, consistently with the behavioral findings. The frequency and amplitude of mEPSCs were not affected by retigabine. Thus, opening of KCNQ channels in the central terminals of primary afferent A-fibers inhibits excitatory synaptic transmission in the spinal dorsal horn, most likely contributing to the analgesic effect of retigabine.

Multiple drug-delivery strategies to enhance the pharmacological and toxicological properties of Mefenamic acid.

OBJECTIVE: To improve the biological and toxicological properties of Mefenamic acid (MA), the galactosylated prodrug of MA named MefeGAL was included in polymeric solid dispersions (PSs) composed of poly(glycerol adipate) (PGA) and Pluronic® F68 (MefeGAL-PS). MefeGAL-PS was compared with polymeric solid formulations of MA (MA-PS) or a mixture of equal ratio of MefeGAL/MA (Mix-PS). METHODS: The in vitro and in vivo pharmacological and toxicological profiles of PSs have been investigated. In detail, we evaluated the anti-inflammatory (carrageenan-induced paw edema test), analgesic (acetic acid-induced writhing test) and ulcerogenic activity in mice after oral treatment. Additionally, the antiproliferative activity of PSs was assessed on in vitro models of colorectal and non-small cell lung cancer. RESULTS: When the PSs were resuspended in water, MefeGAL's, MA's and their mixture's apparent solubilities improved due to the interaction with the polymeric formulation. By comparing the in-vivo biological performance of MefeGAL-PS with that of MA, MefeGAL and MA-PS, it was seen that MefeGAL-PS exhibited the same sustained and delayed analgesic and anti-inflammatory profile as MefeGAL but did not cause gastrointestinal irritation. The pharmacological effect of Mix-PS was present from the first hours after administration, lasting about 44 hours with only slight gastric mucosa irritation. In-vitro evaluation indicated that Mix-PS had statistically significant higher cytotoxicity than MA-PS and MefeGAL-PS. CONCLUSIONS: These preliminary data are promising evidence that the galactosylated prodrug approach in tandem with a polymer-drug solid dispersion formulation strategy could represent a new drug delivery route to improve the solubility and biological activity of NSAIDs.

Bioassay-guided isolation of anti-inflammatory and antinociceptive metabolites among three Moroccan Juniperus leaves extract supported with in vitro enzyme inhibitory assays.

ETHNOPHARMACOLOGICAL RELEVANCE: Herbs of the genus Juniperus (family Cupressaceae) have been commonly used in ancestral folk medicine known as "Al'Araar" for treatment of rheumatism, diabetes, inflammation, pain, and fever. Bioassay-guided isolation of bioactives from medicinal plants is recognized as a potential approach for the discovery of novel drug candidates. In particular, non-addictive painkillers are of special interest among herbal phytochemicals. AIM OF THE STUDY: The current study aimed to assess the safety of J. thurifera, J. phoenicea, and J. oxycedrus aqueous extracts in oral treatments; validating the traditionally reported anti-inflammatory and analgesic effects. Further phytochemical investigations, especially for the most bioactive species, may lead to isolation of bioactive metabolites responsible for such bioactivities supported with in vitro enzyme inhibition assays. MATERIALS AND METHODS: Firstly, the acute toxicity study was investigated following the OECD Guidelines. Then, the antinociceptive, and anti-inflammatory bioactivities were evaluated based on chemical and mechanical trauma assays and investigated their underlying mechanisms. The most active J. thurifera n-butanol fraction was subjected to chromatographic studies for isolating the major anti-inflammatory metabolites. Moreover, several enzymatic inhibition assays (e.g., 5-lipoxygenase, protease, elastase, collagenase, and tyrosinase) were assessed for the crude extracts and isolated compounds. RESULTS: The results showed that acute oral administration of the extracts (300-500 mg/kg, p. o.) inhibited both mechanically and chemically triggered inflammatory edema in mice (up to 70% in case of J. thurifera) with a dose-dependent antinociceptive (tail flick) and anti-inflammatory pain (formalin assay) activities. This effect was partially mediated by naloxone inhibition of the opioid receptor (2 mg/kg, i. p.). In addition, 3-methoxy gallic acid (1), quercetin (2), kaempferol (3), and ellagic acid (4) were successfully identified being involved most likely in J. thurifera extract bioactivities. Nevertheless, quercetin was found to be the most potent against 5-LOX, tyrosinase, and protease with IC50 of 1.52 ± 0.01, 192.90 ± 6.20, and 399 ± 9.05 µM, respectively. CONCLUSION: J. thurifera extract with its major metabolites are prospective drug candidates for inflammatory pain supported with inhibition of inflammatory enzymes. Interestingly, antagonism of opioid and non-opioid receptors is potentially involved.

Exploration on pharmacological mechanisms of YZP against neuropathic pain via inhibiting spinal inflammation and the rationality of its compatibility.

ETHNOPHARMACOLOGICAL RELEVANCE: Yuanhu Zhitong Prescription (YZP) is a well-known traditional Chinese medicine (TCM) formula for neuropathic pain (NP) therapy with a satisfying clinical efficacy. However, the underlying pharmacological mechanism and its compatibility principle remain unclear. AIM OF THE STUDY: This study aims to investigate the analgesic and compatibility mechanisms of YZP on neuropathic pain (NP) at the gene and biological process levels. MATERIALS AND METHODS: The chronic constriction injury (CCI) rats were intragastrically administrated with extracts of YZP, YH and BZ separately, and then mechanical hypersensitivity were measured to evaluate the analgesic effects between YH and BZ before and after compatibility. Then, RNA-seq and bioinformatics analyses were performed to elucidate the potential mechanisms underlying YZP's analgesia and compatibility. Finally, the expression levels and significant differences of key genes were analyzed. RESULTS: Behaviorally, both YZP and YH effectively alleviated mechanical allodynia in CCI rats, with YZP being superior to YH. In contrast, we did not observe an analgesic effect of BZ. Genetically, YZP, YH, and BZ reversed the expression levels of 52, 34, and 42 aberrant genes in the spinal cord of CCI rats, respectively. Mechanically, YZP was revealed to alleviate NP mainly by modulating the inflammatory response and neuropeptide signaling pathway, which are the dominant effective processes of YH. Interestingly, the effective targets of YZP were especially enriched in leukocyte activation and cytokine-mediated signaling pathways. Moreover, BZ was found to exert an adjunctive effect in enhancing the analgesic effect of YH by promoting skeletal muscle tissue regeneration and modulating calcium ion transport. CONCLUSIONS: YH, as the monarch drug, plays a dominant role in the analgesic effect of YZP that effectively relieves NP by inhibiting the spinal inflammation and neuropeptide signaling pathway. BZ, as the minister drug, not only synergistically enhances analgesic processes of YH but also helps to alleviate the accompanying symptoms of NP. Consequently, YZP exerted a more potent analgesic effect than YH and BZ alone. In conclusion, our findings offer new insights into understanding the pharmacological mechanism and compatibility principle of YZP, which may support its clinical application in NP therapy.

Almond fixed oil from Syagrus coronata (Mart.) Becc. has antinociceptive and anti-inflammatory potential, without showing oral toxicity in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Syagrus coronata, a palm tree found in northeastern Brazil, popularly known as licuri, has socioeconomic importance for the production of vegetable oil rich in fatty acids with nutritional and pharmacological effects. Licuri oil is used in traditional medicine to treat inflammation, wound healing, mycosis, back discomfort, eye irritation, and other conditions. AIM OF THE STUDY: The study aimed to evaluate the antinociceptive, anti-inflammatory, and antipyretic effects of treatment with Syagrus coronata fixed oil (ScFO), as well as to determine the safety of use in mice. MATERIALS AND METHODS: Initially, the chemical characterization was performed by gas chromatography-mass spectrometry. Acute single-dose oral toxicity was evaluated in mice at a dose of 2000 mg/kg. Antinociceptive activity was evaluated through abdominal writhing, formalin, and tail dipping tests, and the anti-inflammatory potential was evaluated through the model of acute inflammation of ear edema, peritonitis, and fever at concentrations of 25, 50, and 100 mg/kg from ScFO. RESULTS: In the chemical analysis of ScFO, lauric (43.64%), caprylic (11.7%), and capric (7.2%) acids were detected as major. No mortality or behavioral abnormalities in the mice were evidenced over the 14 days of observation in the acute toxicity test. ScFO treatment decreased abdominal writhing by 27.07, 28.23, and 51.78% at 25, 50, and 100 mg/kg. ScFO demonstrated central and peripheral action in the formalin test, possibly via opioidergic and muscarinic systems. In the tail dipping test, ScFO showed action from the first hour after treatment at all concentrations. ScFO (100 mg/kg) reduced ear edema by 63.76% and leukocyte and neutrophil migration and IL-1ß and TNF-α production in the peritonitis test. CONCLUSION: Mice treated with ScFO had a reduction in fever after 60 min at all concentrations regardless of dose. Therefore, the fixed oil of S. coronata has the potential for the development of new pharmaceutical formulations for the treatment of pain, inflammation, and fever.

Transcriptomic signature, bioactivity and safety of a non-hepatotoxic analgesic generating AM404 in the midbrain PAG region.

Safe and effective pain management is a critical healthcare and societal need. The potential for acute liver injury from paracetamol (ApAP) overdose; nephrotoxicity and gastrointestinal damage from chronic non-steroidal anti-inflammatory drug (NSAID) use; and opioids' addiction are unresolved challenges. We developed SRP-001, a non-opioid and non-hepatotoxic small molecule that, unlike ApAP, does not produce the hepatotoxic metabolite N-acetyl-p-benzoquinone-imine (NAPQI) and preserves hepatic tight junction integrity at high doses. CD-1 mice exposed to SRP-001 showed no mortality, unlike a 70% mortality observed with increasing equimolar doses of ApAP within 72 h. SRP-001 and ApAP have comparable antinociceptive effects, including the complete Freund's adjuvant-induced inflammatory von Frey model. Both induce analgesia via N-arachidonoylphenolamine (AM404) formation in the midbrain periaqueductal grey (PAG) nociception region, with SRP-001 generating higher amounts of AM404 than ApAP. Single-cell transcriptomics of PAG uncovered that SRP-001 and ApAP also share modulation of pain-related gene expression and cell signaling pathways/networks, including endocannabinoid signaling, genes pertaining to mechanical nociception, and fatty acid amide hydrolase (FAAH). Both regulate the expression of key genes encoding FAAH, 2-arachidonoylglycerol (2-AG), cannabinoid receptor 1 (CNR1), CNR2, transient receptor potential vanilloid type 4 (TRPV4), and voltage-gated Ca2+ channel. Phase 1 trial (NCT05484414) (02/08/2022) demonstrates SRP-001's safety, tolerability, and favorable pharmacokinetics, including a half-life from 4.9 to 9.8 h. Given its non-hepatotoxicity and clinically validated analgesic mechanisms, SRP-001 offers a promising alternative to ApAP, NSAIDs, and opioids for safer pain treatment.