Methods Used to Evaluate Pain Behaviors in Rodents

Probiotic supplementation mitigates sex-dependent nociceptive changes and gut dysbiosis induced by prenatal opioid exposure

The gut microbiome has emerged as a promising target for modulating adverse effects of opioid exposure due to its significant role in health and disease. Opioid use disorder (OUD) has become increasingly prevalent, specifically in women of reproductive age, contributing to an increased incidence of offspring exposed to opioids in utero. Recent studies have shown that prenatal opioid exposure (POE) is associated with notable changes to the maternal gut microbiome, with subsequent implications for the offspring's microbiome and other adverse outcomes. However, the role of the gut microbiome in mediating sex-based differences in pain sensitivity has not yet been investigated. In this study, both male and female C57BL/6 offspring were used to determine sex-based differences in nociception and gut microbial composition as a result of POE. Our data reveals significant sex-based differences in offspring prenatally exposed to opioids. The gut microbiome of opioid-exposed females showed an enrichment of commensal bacteria including Lactobacillus compared to opioid-exposed males. Additionally, POE females demonstrated decreased nociceptive sensitivity, while males demonstrated increased nociceptive sensitivity. RNA sequencing of the prefrontal cortex showed sex-based differences in several canonical pathways, including an increase in the opioid signaling pathway of opioid-exposed females, which was not observed in males. Microbiome modification via maternal probiotic supplementation attenuated sex-based differences throughout the early stages of life. Together, our study provides further insight on sex-based differences arising from POE and highlights the pivotal role of the gut microbiome as a modifiable target for mitigating its negative effects.

Effects of botulinum toxin type a on nucleotide binding oligomerization domain-like receptor 3 inflammasome in trigeminal ganglion of a rat migraine model

BACKGROUND

Botulinum toxin type A (BTX-A) has been used in the prevention and treatment of chronic migraine, but the detailed mechanism was not clear completely.

OBJECTIVE

The effects of BTX-A on nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome and interleukin-1 beta (IL-1β) were explored in the trigeminal ganglion of migraine model rats.

METHODS

Healthy adult male Sprague-Dawley (SD) rats were randomly divided into groups. Von Frey fiber filaments were used to detect the periorbital pain area of rats. The immunoblotting and Immunofluorescence were used to detect the expression of NLRP3 inflammasome and IL-1β in the trigeminal ganglia of rats.

RESULTS

The periorbital pain area of rats in the migraine model group was significantly lower than that of the Sham group, and the difference was statistically significant (p < 0.05). Compared with the Sham group, the expressions of NLRP3, pro-caspase-1, caspase-1 and mature IL-1β in the migraine model group were significantly increased, and the difference was statistically significant (p < 0.05). Compared with the IA control group, the expressions of NLRP3, pro-caspase-1, caspase-1 and mature IL-1β in 5 U/kg BTX and 10 U/kg BTX-A group were significantly reduced (p < 0.05).

CONCLUSION

BTX-A inhibits the synthesis of NLRP3 inflammasome and mature IL-1β in the trigeminal ganglion from rat migraine models. Its inhibitory effect on the inflammation of the primary nociceptive neurons of the trigeminal nerve may be one of its important mechanisms for the prevention of migraine.

Enhanced facial grimacing when laparotomy involves cutaneous and visceral tissue injury

Introduction

Laparotomy is a common surgical procedure that entails incision of the abdomen and is associated with varying degrees of postoperative pain. Laparotomies can be performed in mice and result in facial grimacing, which can be quantified using PainFace, a software platform that automates facial grimace analyses.

Objectives

We evaluated the extent to which incision of the ventral skin, peritoneum, and intestinal manipulation, all of which can occur as part of a laparotomy surgery, affects the magnitude and duration of facial grimacing in 2 strains of mice along with allodynia at the incision site in CD-1 mice.

Methods

White-coated CD-1 male and female mice and black-coated C57BL/6 male mice (8-12 weeks of age) were split into groups (n = 20 per group) that underwent laparotomies with varying manipulations.

Results

Mouse grimace scale scores were higher in both strains after surgery when the small intestine was manipulated in 2 different ways compared to groups that received a cutaneous incision alone or cutaneous and peritoneal incision.

Conclusion

These studies show that mice exhibit more pronounced facial grimacing when both cutaneous and visceral tissues are injured during laparotomy surgery. Consistent with clinical findings, our experiments suggest that postoperative pain could be reduced by minimizing visceral tissue injury during surgical procedures.

Implication of system xc- in complete Freund's adjuvant-induced peripheral inflammation and associated nociceptive sensitization

BACKGROUND

Persistent inflammation leading to neuronal sensitization in pain pathways, are key features of chronic inflammatory pain. Alike macrophages in the periphery, glial cells exacerbate hypersensitivity by releasing proalgesic mediators in the central nervous system. Expressed by peripheral and central immune cells, the cystine-glutamate antiporter system xc- plays a significant role in inflammatory responses, but its involvement in chronic inflammatory pain remains underexplored. We herein investigated the contribution of this exchanger in nociceptive hypersensitivity triggered by a peripheral inflammatory insult.

METHODS

Complete Freund's adjuvant (CFA) was injected into the left hind paw of wild-type C57Bl/6 female mice, of xCT-deficient mice (specific subunit of system xc-) and of mice receiving the system xc- inhibitor sulfasalazine. Paw edema was measured over three weeks and pain-associated behaviors were evaluated. Additionally, pro-inflammatory cytokine levels were assessed in blood samples.

RESULTS

CFA injection led to a persistent increase in paw edema and hypersensitivity to mechanical and thermal stimuli, which were less pronounced in xCT-deficient mice. This reduced sensitivity was accompanied by lower systemic pro-inflammatory cytokine levels in xCT-deficient mice. Accordingly, pharmacological inhibition of system xc- with sulfasalazine, either before or after pain induction, efficiently reduced the algesic and inflammatory responses to CFA in wild-type mice.

CONCLUSION

Our findings reveal a critical role for system xc- in the pathophysiology of inflammatory pain. xCT deficiency reduces pain behaviors and peripheral inflammation, positioning system xc- as a promising therapeutic target for alleviating chronic inflammatory pain.

Converging inputs compete at the lateral parabrachial nuclei to dictate the affective-motivational responses to cold pain

ABSTRACT

The neural mechanisms of the affective-motivational symptoms of chronic pain are poorly understood. In chronic pain, our innate coping mechanisms fail to provide relief. Hence, these behaviors are manifested at higher frequencies. In laboratory animals, such as mice and rats, licking the affected areas is a behavioral coping mechanism and it is sensitized in chronic pain. Hence, we have focused on delineating the brain circuits mediating licking in mice with chemotherapy-induced peripheral neuropathy (CIPN). Mice with CIPN develop intense cold hypersensitivity and lick their paws upon contact with cold stimuli. We studied how the lateral parabrachial nucleus (LPBN) neurons facilitate licking behavior when mice are exposed to noxious thermal stimuli. Taking advantage of transsynaptic viral, optogenetic, and chemogenetic strategies, we observed that the LPBN neurons become hypersensitive to cold in mice with CIPN and facilitate licks. Furthermore, we found that the expression of licks depends on competing excitatory and inhibitory inputs from the spinal cord and lateral hypothalamus (LHA), respectively. We anatomically traced the postsynaptic targets of the spinal cord and LHA in the LPBN and found that they synapse onto overlapping populations. Activation of this LPBN population was sufficient to promote licking due to cold allodynia. In sum, our data indicate that the nociceptive inputs from the spinal cord and information on brain states from the hypothalamus impinge on overlapping LPBN populations to modulate their activity and, in turn, regulate the elevated affective-motivational responses in CIPN.

Backbone breakthroughs: How rodent models are shaping intervertebral disc disease treatment

Intervertebral disc degeneration (IVDD) is a widespread, disabling condition that significantly contributes to the global burden of musculoskeletal disorders. To better understand its underlying mechanisms and explore potential therapeutic strategies, animal models serve as valuable tools for simulating the complicated pathophysiology of IVDD. Rodent models are extensively used due to their genetic similarities to humans, cost-effectiveness, and rapid attainment of maturity. These models enable the study of specific molecular pathways involved in IVDD, such as inflammation, matrix degradation, tissue repair, and disc microenvironment homeostasis. This review provides a comprehensive overview of the current status of rodent models used in IVDD research, highlighting their advantages, limitations, and contributions to our understanding of the disease. Specifically, we discussed various rodent models, including traumatic (such as needle puncture in the lumbar and coccygeal region, nucleotomy, and annulus fibrosus defect), non-traumatic (including compression models, lumbar spine instability, and bipedalism), chemically induced models (chymopapain, chondroitinase ABC), and genetically modified models. These models offer insights into the severity of IVDD under different conditions, such as trauma, aging, and genetics. In conclusion, rodent models remain indispensable tools for advancing our understanding of IVDD mechanisms and therapeutic interventions. Carefully selecting animal species and models can provide valuable insights that guide future clinical research and treatment approaches. Our review aims to leverage these models to identify therapeutic targets and strategies that may ultimately reduce the impact of IVDD on human health. PERSPECTIVE: This review describes the role of rodent models in IVDD, highlighting their utility in unraveling disease mechanisms and evaluating therapeutics. By replicating the complex molecular pathways and conditions of disc disease, like trauma, aging, and genetics, these models aid in identifying future advancements in managing lower back pain.

Evaluating the Preclinical Efficacy of Photobiomodulation in Alleviating Neuropathic Corneal Pain: A Behavioral Study

Purpose

Neuropathic corneal pain (NCP) is a debilitating condition characterized by persistent pain due to corneal nerve damage or dysfunction. Millions of individuals and their families endure the significant impact of chronic pain. Effective management strategies are crucial yet limited, prompting the exploration of innovative treatments such as photobiomodulation (PBM).

Design

In vivo preclinical therapeutics investigation in mice.

Subjects

Thy1-YFP mice.

Methods

This study evaluates the efficacy of PBM in treating NCP across 4 animal models: normal control, sham control, pulled nerve, and full transection (FT). Behavioral assessments, including the von Frey test (VFT) for mechanical sensitivity and the eye-wiping test (EWT) for chemical sensitivity, were employed to evaluate the therapeutic impact of PBM till day 56 (D-1, D1, D3, D5, D7, D14, D28, D42, and D56).

Main Outcome Measures

Advances in therapeutic approach for NCP through the potential of PBM.

Results

Photobiomodulation significantly reduced behavioral manifestations of pain in the pulled nerve model (VFT: no PBM [D1 = 0.043 ± 0.044, D56 = 0.05 ± 0.014] and PBM [D1 = 0.050 ± 0.008 {P value = 0.18}, D56 = 0.09 ± 0.014 {P value = 0.02}], EWT: no PBM [D1 = 11.96 ± 0.47, D56 = 12.11 ± 0.15] and PBM [D1 = 11.73 ± 0.18 {P value = 0.2}, D56 = 11.22 ± 0.31] [P value = 0.01]) and FT model (VFT: no PBM [D1 = 0.022 ± 0.0028, D56 = 0.023 ± 0.0047] and PBM [D1 = 0.024 ± 0.0028 {P value = 0.2}, D56 = 0.073 ± 0.0094] [P value = 0.02]), EWT: no PBM [D1 = 13.1 ± 0.14, D56 = 13.36 ± 0.30] and PBM [D1 = 12.86 ± 0.41, {P value = 0.2}, D56 = 12.53 ± 0.41] [P value = 0.04]}, suggesting an effective reduction of pain sensitivity and an increase in corneal nerve function. The temporal patterns also suggest that early intervention with PBM, initiated shortly after nerve injury, may be crucial for preventing the chronic progression of NCP.

Conclusions

These outcomes support PBM as a promising nonpharmacologic intervention for NCP; this not only reinforces the potential of PBM in NCP treatment but also provides a foundation for future clinical applications in managing corneal neuropathy.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Mechanistic exploration of licorice reconciling Medicine:Huangqi Guizhi Wuwu decoction and Shaoyao Gancao decoction compatibility as an example

ETHNOPHARMACOLOGICAL RELEVANCE

Glycyrrhiza uralensis Fisch. (GU) is a pivotal botanical in traditional Chinese medicine (TCM), because of its ability to reconcile various herbs, and its crucial role in numerous formulas. Huanggui Shaogan decoction (HSGD) is an empirical formula, developed by Huangqi Guizhi Wuwu decoction (HGD) and Shaoyao Gancao decoction (SGD), and prepared by adding GU to HGD. However, the mechanisms of GU reconciling medicine remain incompletely characterized.

AIM OF THE STUDY

This study aimed to explain mechanisms of GU reconciling medicine based on the differences of components, pharmacological efficacy, and the existence of the components.

METHODS

Differential components between HSGD and HGD were systematically identified using LC‒MS/MS coupled with chemometric analysis. The existence states and binding affinities of these differential components were further characterized via ultrafiltration separation. The therapeutic potential of HSGD was validated in a murine model of oxaliplatin-induced peripheral neuropathy (OIPN).

RESULTS

Twenty-two differential chemical components between HSGD and HGD were identified, including flavonoids, saponins, gingerol, and monoglycoside. The transmittance of flavonoids and gingerols increased in HSGD. However, the transmittance of astragalus saponins decreased, which may be due to micelle association and the increase in molecular clusters. HSGD could enhance the mechanical pain threshold, alleviate cold nociceptive hypersensitivity, relieve dorsal root ganglia neuron injury, and decrease the expression of nerve growth factor, 5-hydroxytryptamine, substance P, and calcitonin gene-related peptide better. The differential correlation analysis revealed the relationship between differential components and pharmacological indicators. The above results indicated that different herbs combinations had a greater impact on the dissolution and molecular state of the components of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao.

CONCLUSION

The study highlights the solubilizing effect of GU within HSGD, and it also improves the efficacy of the treatment of OIPN, which underpins its compatibility rationality. It provided an inspiration for the study of other TCM formulas.

The dorsal column nuclei scale mechanical sensitivity in naive and neuropathic pain states

During pathological conditions, tactile stimuli can aberrantly engage nociceptive pathways leading to the perception of touch as pain, known as mechanical allodynia. The brain stem dorsal column nuclei integrate tactile inputs, yet their role in mediating tactile sensitivity and allodynia remains understudied. We found that gracile nucleus (Gr) inhibitory interneurons and thalamus-projecting neurons are differentially innervated by primary afferents and spinal inputs. Functional manipulations of these distinct Gr neuronal populations bidirectionally shifted tactile sensitivity but did not affect noxious mechanical or thermal sensitivity. During neuropathic pain, Gr neurons exhibited increased sensory-evoked activity and asynchronous excitatory drive from primary afferents. Silencing Gr projection neurons or activating Gr inhibitory neurons in neuropathic mice reduced tactile hypersensitivity, and enhancing inhibition ameliorated paw-withdrawal signatures of neuropathic pain and induced conditioned place preference. These results suggest that Gr activity contributes to tactile sensitivity and affective, pain-associated phenotypes of mechanical allodynia.

LAMP2A-mediated neuronal hyperexcitability by enhancing NKAβ1 degradation underlies depression-induced allodynia

Painful physical symptoms in major depressive disorder (MDD) patients lead to poor outcomes during MDD treatment. Here, we report that decreased Na+/K+-ATPase β1 subunit (NKAβ1) expression in anterior cingulate cortex glutamatergic (ACCGlu) neurons promotes ion dyshomeostasis, leading to hyperactivity of ACCGlu-insular cortex circuits in chronic stress mice. This ultimately primes allodynia. Mechanistically, we reveal that chronic stress strengthens LAMP2A-driven chaperone-mediated autophagy (CMA) and subsequently promotes the degradation of NKAβ1. We further identify NKAβ1 as a CMA substrate. Accordingly, genetically LAMP2A loss in ACCGlu neurons reverses chronic-stress-induced neuronal hyperexcitability, subsequently ameliorating allodynia. Additionally, we develop a trans-activating transcription (TAT)-LAMP2A peptide that significantly alleviates depression-induced allodynia. Taken together, our results reveal a mechanistic connection between CMA and neuronal excitability. TAT-LAMP2A peptide intervention, by disturbing CMA-dependent NKAβ1 elimination, could be a potential pharmacological treatment for depression-induced allodynia and further facilitate the efficacy of antidepressant treatment.

Electroacupuncture Ameliorates Chronic Inflammatory Pain and Depression Comorbidity by Inhibiting Nrf2-Mediated Ferroptosis in Hippocampal Neurons

Chronic inflammatory pain and depression are highly comorbid, with nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated ferroptosis in hippocampal neurons strongly associated with the onset and progression of the comorbidity. Electroacupuncture (EA), widely used to treat pain and mood disorders, may ameliorate chronic inflammatory pain and depression comorbidity (CIPDC) by inhibiting Nrf2-mediated ferroptosis in hippocampal neurons, though its mechanism of action remains partially understood. In this study, we established the CIPDC model by administering a subcutaneous injection of complete Freund's adjuvant (CFA) into the left hind paw. Evaluations of EA's effects on pain thresholds and depressive behaviors in CIPDC rats included paw withdrawal mechanical threshold, paw withdrawal thermal latency, sucrose preference test, open field test, and forced swim test assessments. HE staining was performed to assess the pathological and morphological alterations in hippocampal neurons. FJB staining was utilized to evaluate neuronal degeneration, while transmission electron microscopy (TEM) was employed to examine ultrastructural changes in hippocampal neuronal mitochondria. Prussian blue staining was conducted to visualize ferrous ion deposition in the hippocampus, and the contents of ferrous ion (Fe2+), malondialdehyde (MDA), and glutathione (GSH) were measured using colorimetric assay kits. Western blotting (WB) was performed to determine the relative protein expression of Nrf2, FTH1, FTL, xCT, GPX4, ACSL4, LPCAT3, and LOX in the hippocampus. Additionally, the relative mRNA expression of FTH1, FTL, xCT, GPX4, ACSL4, LPCAT3, and LOX was analyzed by PCR. Flow cytometry was used to quantify ROS levels in the hippocampus, and immunofluorescence staining was applied to detect nuclear expression of Nrf2 as well as co-localization of GPX4 with the neuronal marker NeuN. Our results demonstrate that EA upregulates nuclear Nrf2 expression in hippocampal tissue, thereby alleviating iron metabolism dysregulation, enhancing antioxidant system activity, and reducing lipid peroxidation. This process inhibits ferroptosis in hippocampal neurons, promoting their repair and remodeling, and effectively treating CIPDC.

Differential modification of ascending spinal outputs in acute and chronic pain states

Pain hypersensitivity arises from the induction of plasticity in peripheral and spinal somatosensory neurons, which modifies nociceptive input to the brain, altering pain perception. We applied longitudinal calcium imaging of spinal dorsal projection neurons to determine whether and how the representation of somatosensory stimuli in the anterolateral tract, the principal pathway transmitting nociceptive signals to the brain, changes between distinct pain states. In healthy mice, we identified stable outputs selective for cooling or warming and a neuronal ensemble activated by noxious thermal and mechanical stimuli. Induction of acute peripheral sensitization by topical capsaicin transiently re-tuned nociceptive output neurons to encode low-intensity stimuli. In contrast, peripheral nerve injury resulted in a persistent suppression of innocuous spinal outputs coupled with persistent activation of a normally silent population of high-threshold neurons. These results demonstrate differential modulation of spinal outputs to the brain during nociceptive and neuropathic pain states.

Modafinil Ameliorated Fibromyalgia Syndrome in Rats by Modulating Mast Cells and Microglia Activation Through Dopamine/Substance P/MRGPRX/Histamine and PI3K/p-Akt/NF-κB Signaling Pathways

Fibromyalgia syndrome (FMS) is characterized by prolonged, widespread musculoskeletal pain accompanied by various physical and psychological disturbances. Modafinil, a wake-promoting drug, manages pain symptoms in several diseases by inhibiting dopamine reuptake and exhibiting anti-inflammatory and immunomodulatory effects, including the impairment of cytokine production, microglia, and mast cell activation. Central inflammation may involve microglial activation, which is correlated with mast cell activation. Restoring dopamine levels and modulating the communication between mast cells and microglia may represent a promising approach to managing pain symptoms in FMS. Thus, this study intended to explore the interplay between brain mast cells and microglia as an underlying mechanism in the pathophysiology of FMS and how this interaction is controlled by modafinil, with a focus on dopamine/SP/MRGPRX2/histamine and PI3K/p-Akt/NF-κB signaling pathways. Rats were arbitrarily distributed between 4 groups. Group 1 served as normal control. Reserpine (1 mg/kg/day; s.c) was injected into the remaining groups for three consecutive days. In groups 3 and 4, modafinil (100 mg/kg/day; p.o) was administered either alone or in conjunction with haloperidol (1 mg/kg/day; ip), respectively, for the following 21 days. Modafinil ameliorated reserpine-induced thermal/mechanical allodynia (1.3-fold, 2.3-fold) and hyperalgesia (0.5-fold), attenuated depression (0.5-fold), and enhanced motor coordination (1.2-fold). It mitigated the histopathological alterations and increased dopamine levels in the thalamus of rats by 88.5%. Modafinil displayed anti-inflammatory effects via inhibiting mast cells and microglia activation, manifested by reductions in SP/MRGPRX2/IL-17/histamine (52%, 58%, 56.7%, and 63.7%) and PI3K/p-Akt/t-Akt/NF-κB/TNF-α/IL-6 (31.7%, 55.5%, 41%, 47.6%, and 76.9%), respectively. Ultimately, modafinil alleviated FMS behavioral, histopathological, and biochemical abnormalities and suppressed mast cell-microglial neuroinflammation in the thalamus of rats exposed to reserpine. This study highlights the potential of repurposing modafinil to improve FMS symptoms.

The venom of Cyriopagopus schmidti spider contains a natural huwentoxin-IV analogue with unexpected improved analgesic potential

The venom of Cyriopagopus schmidti spider has been extensively investigated, thereby allowing the identification of numerous new natural peptides. Many of these peptides are active on ion channels and several of them occur from post-translational processing. In order to further identify new entities, we screened this venom against five different human voltage-gated sodium (hNav) channels. We illustrate the unusual richness of this venom in targeting this wide variety of hNav channels. We confirm the identity of previously discovered peptides active on these ion channels type (huwentoxin (HwTx)-I, HwTx-II and HwTx-IV), indicating the efficacy of the screening process by automated patch-clamp. We also identified a novel analogue of HwTx-IV that differs by the absence of amidation and the presence of an extra C-terminal Gly residue. Interestingly, this analogue is less potent than HwTx-IV itself in blocking hNav1.7 in cell lines, but turns out to be significantly more potent in TTX-sensitive dorsal root ganglia neurons. Because of this unexpected finding, this novel analogue turns out to be a more potent analgesic than HwTx-IV itself without presenting most of the Nav1.6-related toxic effects of HwTx-IV.

Morphometric Analysis of Rat and Mouse Musculoskeletal Tissues using High Field MRI

The knee is a complex articulating joint composed of bones and fibrous connective tissues with anatomy retained across species including humans, pigs, dogs, rats, and mice. Imaging developments in high field magnetic resonance imaging (MRI) has enabled non-destructive 3D structural analysis of small animal joints to further these preclinical models. The goal of this work was to apply MRI techniques for rodent knee joints using a high field MRI scanner and to characterize the morphometry of the four primary ligaments and medial and lateral menisci. Briefly, female rat and mouse knees were imaged in a 9.4T MRI scanner and the cross-sectional area (CSA) of the ligaments and the meniscal heights and widths were recorded. Tissue dependent relationships were observed in the rat and mouse ligaments. The PCL was the largest ligament in the rats with a CSA of 0.35 ± 0.08 mm 2 , while the LCL was the largest ligament in the mice, with a CSA of 0.054 ± 0.017 mm 2 . Rat and mouse meniscal width had an anatomical location dependent relationship, while meniscal height did not. This will support future work exploring morphometric effects due to aging, injury, and disease in preclinical animal models.

Sex-Specific Behavioral Features of the Prenatal Valproic Acid Rat Model of Autism Spectrum Disorder

Background/Objectives: Autism is a complex neurodevelopmental disorder characterized by restricted behaviors and impaired social and communication skills. The exact cause of autism remains unknown. One promising animal model for studying autism is the valproic acid rat model. Due to a 1 to 4 bias for males in autism occurrence, most animal model studies investigate only males and neglect females. However, female autism often appears different from that observed in males. Females are said to be less regularly diagnosed because they can "mask" their symptoms. Female autism is as necessary to investigate as male autism. Methods: Fertile adult female Sprague-Dawley rats were impregnated and injected with valproic acid on gestational day 13. Male and female offspring were subjected to behavioral tests to investigate autistic symptoms. Tests included novel object recognition, balance-beam, Y-maze, hole-board, three-chamber, marble burying, olfactory, light/dark and hot plate tests. Results: The tests revealed that VPA-exposed rats had increased anxiety-like behaviors, hyperactivity, and impaired non-verbal communication. However, they did not display repetitive behaviors or cognitive impairments. Notably, male and female rats showed different autism-like traits, with both showing hyperactivity, and males (but not females) additionally showing impaired sociability and increased anxiety. Conclusions: The findings suggest that prenatal exposure to VPA induces autism-like behaviors in both male and female Sprague-Dawley rat offspring. However, males appear more impacted by VPA exposure as evinced by their display of more autism-like symptoms relative to females. This study provides support for including both sexes in all studies modelling autism, as outcomes are seemingly impacted by the sex being observed.

Repeated activation of preoptic area recipient neurons in posterior paraventricular nucleus mediates chronic heat-induced negative emotional valence and hyperarousal states

Mental and behavioral disorders are associated with extended period of hot weather as found in heatwaves, but the underlying neural circuit mechanism remains poorly known. The posterior paraventricular thalamus (pPVT) is a hub for emotional processing and receives inputs from the hypothalamic preoptic area (POA), the well-recognized thermoregulation center. The present study was designed to explore whether chronic heat exposure leads to aberrant activities in POA recipient pPVT neurons and subsequent changes in emotional states. By devising an air heating paradigm mimicking the condition of heatwaves and utilizing emotion-related behavioral tests, viral tract tracing, in vivo calcium recordings, optogenetic manipulations, and electrophysiological recordings, we found that chronic heat exposure for 3 weeks led to negative emotional valence and hyperarousal states in mice. The pPVT neurons receive monosynaptic excitatory and inhibitory innervations from the POA. These neurons exhibited a persistent increase in neural activity following chronic heat exposure, which was essential for chronic heat-induced emotional changes. Notably, these neurons were also prone to display stronger neuronal activities associated with anxiety responses to stressful situations. Furthermore, we observed saturated neuroplasticity in the POA-pPVT excitatory pathway after chronic heat exposure that occluded further potentiation. Taken together, long-term aberration in the POA to pPVT pathway offers a neurobiological mechanism of emotional and behavioral changes seen in extended periods of hot weather like heatwaves.

Evaluating the anti-neuropathic effects of the thymol-loaded nanofibrous scaffold in a rat model of spinal cord injury

Background

Spinal cord injury (SCI) is a debilitating condition characterized by partial or complete loss of motor and sensory function caused by mechanical trauma to the spinal cord. Novel therapeutic approaches are continuously explored to enhance spinal cord regeneration and functional recovery.

Purpose

In this study, we investigated the efficacy of the poly(vinyl alcohol) and chitosan (PVA/CS) scaffold loaded with different thymol concentrations (5, 10, and 15 wt%) in a rat compression model for SCI treatment compare to other (e.g., thymol and scaffold) control groups.

Results and discussion

The thymol-loaded scaffold exhibited a smooth surface and a three-dimensional nanofibrous structure with nanoscale diameter. The conducted analyses verified the successful incorporation of thymol into the scaffold and its high water absorption, porosity, and wettability attributes. Behavioral assessment of functional recovery showed improving sensory and locomotor impairment. Furthermore, histopathological examinations indicated the regenerative potential of the thymol-loaded nanofiber scaffold, by neuronal survival.

Conclusion

Therefore, these findings suggest that the thymol-loaded nanofibrous scaffolds have promising pharmacological activities for alleviating neuropathic pain and addressing complications induced by SCI.

Dapagliflozin Ameliorate Type-2 Diabetes Associated Neuropathy via Regulation of IGF-1R Signaling

Dapagliflozin, an approved SGLT2 inhibitor, has been shown to have extra-glycemic effects like cardio-reno protection. However, the neuroprotective effects of SGLT2 inhibitors against diabetic neuropathy (DN) have not been explored. The current study aimed to determine the neuroprotective potential of Dapagliflozin against STZ-NAD-induced DN in Wistar rats via IGF-1 signaling. DN was induced by STZ-NAD in male Wistar rats. After 60 days of induction, behavioural tests were conducted to access DN, and treatment with Dapagliflozin (0.75 mg/kg & 1.50 mg/kg) was initiated for 30 days. At the end of the study, the brain and sciatic nerve were isolated and expression analysis of IGF-1R signaling molecules was carried out using western blotting, qRTPCR, and immunohistochemistry. Structural changes in the brain and sciatic nerve were ascertained by histopathology. The results showed that treatment with Dapagliflozin improved behavioural parameters in STZ-NAD-induced DN rats. The decreased expression levels of IGF1R signaling pathway molecules and increased expression of p-AKT were found to increase and decrease in the brain and sciatic nerve, respectively after the treatment. Histological studies demonstrated the restoration of normal architecture of the brain and sciatic nerve after treatment with dapagliflozin. The altered expression of IGF-1R signaling molecules established the neuroprotective potential of dapagliflozin against DN.

Validation of qMT and CEST MRI as Biomarkers of Response to Treatment After Lumbar Spinal Cord Injury in Rats

The progression and repair of a traumatically injured spinal cord (SCI) involves multifactored processes. Noninvasive, mechanism-informative objective biomarkers could greatly facilitate the translation of findings from preclinical animal models to patient applications. We aimed to develop and validate multiparametric chemical exchange saturation transfer (CEST) and quantitative magnetization transfer (qMT) magnetic resonance imaging (MRI) biomarkers for assessing SCI severity, demyelination, and neuroinflammation, as well as the response to neuroprotective drug treatment riluzole. Changes in CEST and qMT MRI metrics before and after a moderate contusion injury at the L1 level of the lumbar spinal cord were compared between two groups of rats that received either the riluzole or a vehicle treatment over 8 weeks. The specificity of these MRI biomarkers was validated by postmortem immunohistology. The functional relevance of these biomarkers was evaluated by correlation with hindlimb sensorimotor and pain behavior. The pool size ratio (PSR) maps from qMT acquisitions of the SCI region in riluzole-treated rats showed increased white matter macromolecular content compared to the HBC vehicle-treated group, suggesting increased myelin levels and possible remyelination of the injured spinal cord. CEST APT pool (3.5 ppm) amplitude decreased at the region rostral to the injury in riluzole-treated rats compared to the vehicle group, indicating potentially reduced neuroinflammatory activity. MRI metrics correlated temporally with behavioral measures of injury severity and recovery. Histological analysis spatially validated MRI-revealed myelination and neuroinflammation status and confirmed differences between the drug and vehicle treatment groups. Quantitative MRI is well suited for monitoring and quantifying the efficacy of pharmacological treatments in preclinical spinal cord injury models. Multiparametric MRI changes in white matter myelination (qMT PSR) and neuroinflammation (CEST APT) in the injured spinal cord were related to injury severity, behavioral deficits, and recovery progression over time. Both imaging metrics captured enhanced recovery from the neuroprotective drug riluzole, supporting the practical utility of these MRI biomarkers.

Mineral coated microparticles delivering Interleukin-4, Interleukin-10, and Interleukin-13 reduce inflammation and improve function after spinal cord injury in a rat

After spinal cord injury (SCI) there is excessive inflammation and extensive infiltration of immune cells that leads to additional neural damage. Interleukin (IL)-4, IL-10, and IL-13 are anti-inflammatories that have been shown to reduce several pro-inflammatory species, alter macrophage state, and provide neuroprotection. However, these anti-inflammatories have a short half-life, do not cross the blood-spinal cord barrier, and large systemic doses of ant-inflammatory cytokines can cause increased susceptibility to infections. In this study, we used mineral coated microparticles (MCMs) to bind, stabilize and deliver biologically active IL-4, IL-10, and IL-13 in a sustained manner directly to the injury site. Rats with a T10 SCI were given an intraspinal injection of cytokine-loaded MCMs 6 h post-injury. Testing of 27 cytokine/chemokine levels 24 h post-injury demonstrated that MCMs delivering IL-4, IL-10, and IL-13 significantly reduced inflammation (P < 0.0001). Rats treated with MCMs+(IL-4, IL-10, IL-13) had significantly higher Basso-Beattie-Bresnahan locomotor rating scores (P = 0.0021), Ladder Rung Test scores (P = 0.0021), and significantly longer latency threshold with the Hargreaves Test (P = 0.0123), compared to Injured Controls. Analyses of post-fixed spinal cords revealed significantly less spinal cord atrophy (P = 0.0344) in rats treated with MCMs+(IL-4, IL-10, IL-13), and diffusion tensor imaging tractography revealed significantly more tracts spanning the injury site (P = 0.0025) in rats treated with MCMs+(IL-4, IL-10, IL-13) compared to Injured Controls. In conclusion, MCMs delivering IL-4, IL-10, and IL-13 significantly reduced inflammation post-SCI, resulting in significantly less spinal cord damage and a significant improvement in hind limb function.

Baclofen modulates the immune response after spinal cord injury with locomotor benefits

BACKGROUND AND PURPOSE

Spinal cord injury (SCI) is a neurological condition that affects motor and sensory functions below the injury site. The consequences of SCI are devastating for the patients, and although significant efforts have been done in the last years, there is no effective therapy. Baclofen has emerged in the last few years as an interesting drug in the SCI field. Already used in the SCI clinical setting to control spasticity, baclofen has shown important impact on SCI recovery in animal models, such as lampreys and mice.

EXPERIMENTAL APPROACH AND KEY RESULTS

Herein, we proposed to go deeper into baclofen's mechanism of action and to study its role on the modulation of the immune response after SCI, a major process associated with the severeness of the lesion. Using a SCI compression mice model, we confirmed that baclofen leads to higher locomotor performance, but only at 1 mg·kg-1 and not in higher concentrations, as 5 mg·kg-1. Moreover, we found that baclofen at 1 mg·kg-1 can strongly modulate the immune response after SCI at local, systemic and peripheric levels. This is interesting and intriguingly at the same time, since now, additional studies should be performed to understand if the modulation of the immune response is the responsible for the locomotor outcomes observed on Baclofen treated animals.

CONCLUSION AND IMPLICATIONS

Our findings showed, for the first time, that baclofen can modulate the immune response after SCI, becoming a relevant drug in the field of the immunomodulators.

Morphine-induced hyperalgesia impacts small extracellular vesicle microRNA composition and function

Morphine and other synthetic opioids are widely prescribed to treat pain. Prolonged morphine exposure can paradoxically enhance pain sensitivity in humans and nociceptive behavior in rodents. To better understand the molecular mechanisms underlying opioid-induced hyperalgesia, we investigated changes in microRNA (miRNA) composition of small extracellular vesicles (sEVs) from the serum of mice after a morphine treatment paradigm that induces hyperalgesia. We observed significant differential expression of 18 miRNAs in sEVs from morphine-treated mice of both sexes compared with controls. Several of these miRNAs were bioinformatically predicted to regulate cyclic AMP response element binding protein (CREB), a well characterized transcription factor implicated in pain and drug addiction. We confirmed the binding and repression of Creb mRNA by miR-155 and miR-10a. We tested if serum-derived sEVs from morphine-treated mice could elicit nociceptive behavior in naïve recipient mice. Intrathecal injection of 1 μg sEVs did not significantly impact basal mechanical and thermal thresholds in naïve recipient mice. However, prophylactic 1 μg sEV administration in recipient mice resulted in faster resolution of complete Freund's adjuvant-induced mechanical and thermal inflammatory hypersensitivity. Other behaviors assayed following administration of these sEVs were not impacted, including sEV-conditioned place preference and locomotor sensitization. These results indicate that morphine regulation of serum sEV composition can contribute to analgesia and suggest a potential for sEVs to be a nonopioid therapeutic intervention strategy to treat pain. SIGNIFICANCE STATEMENT: A mouse model of opioid-induced hyperalgesia was used to show that chronic morphine treatment causes differential microRNA packaging into small extracellular vesicles (sEVs) present in the serum of mice. Two of these sEV microRNAs can downregulate CREB expression, and administration of these sEVs attenuates pain hypersensitivity in recipient mice. These studies position sEVs as a potential pain therapeutic and highlight changes underlying opioid-induced hyperalgesia, shedding light on a phenomenon with unclear pathophysiology.

Bacillus subtilis (NMCC-path-14) ameliorates acute phase of arthritis via modulating NF-κB and Nrf-2 signaling in mice model

Probiotics (PBT) have been extensively studied as an adjunct therapy for various inflammatory conditions. This is because inflammation often leads to dysbiosis, a microbial imbalance that can be corrected using PBT. Most research has focused on Lactobacillus, with limited data on Bacillus PBT for alleviating CFA-induced arthritis in animal models. While most studies focus on the chronic aspect of CFA-induced arthritis, our current research aims to evaluate the effects of pre-treatment, concurrent treatment, and post-treatment with Bacillus subtilis (NMCC-path-14) against the acute phase of arthritis induced by CFA in the mice model. Arthritis was produced by administering CFA into the subplantar region of the mouse's right hind paw. Pain-related behavioral parameters, antioxidant capacity, histological and radiological parameters, expression of essential cytokines, and DNA damage were assessed during the acute phase. B. subtilis treatment significantly reduced the paw edema and improved the arthritic index. The nocifensive threshold was also raised, and muscle coordination improved considerably after B. subtilis treatment on days 7 and 14. The antioxidant capacity and histological and radiological parameters were also enhanced. We demonstrated that B. subtilis therapy preserved the DNA during the acute phase of arthritis using the Comet assay. Comparing results to the arthritic control, a significant reduction was observed in the expression levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and nuclear factor-kappa B (NF-κB). In contrast, the level of nuclear factor erythroid 2-related factor 2 (Nrf-2) was enhanced. During the acute phase of the disease, B. subtilis displayed a potent anti-inflammatory and anti-arthritic action against CFA-induced arthritis.

Further evidence that peritraumatic 17β-estradiol levels influence chronic posttraumatic pain outcomes in women, data from both humans and animals

ABSTRACT

Chronic posttraumatic pain (CPTP) is common after traumatic stress exposure (TSE) and disproportionately burdens women. We previously showed across 3 independent longitudinal cohort studies that, in women, increased peritraumatic 17β-estradiol (E2) levels were associated with substantially lower CPTP over 1 year. Here, we assessed this relationship in a fourth longitudinal cohort and also assessed the relationship between E2 and CPTP at additional time points post-TSE. Furthermore, we used a well-validated animal model of TSE to determine whether exogenous E2 administration protects against mechanical hypersensitivity. Using nested samples and data from the Advancing Understanding of RecOvery afteR traumA study (n = 543 samples, 389 participants), an emergency department-based prospective study of TSE survivors, we assessed the relationship between circulating E2 levels and CPTP in women and men using multivariate repeated-measures mixed modeling. Male and ovariectomized female Sprague Dawley rats were exposed to TSE and administered E2 either immediately after or 3 days post-TSE. Consistent with previous results, we observed an inverse relationship between peritraumatic E2 and longitudinal CPTP in women only (β = -0.137, P = 0.033). In animals, E2 protected against mechanical hypersensitivity in female ovariectomized rats only if administered immediately post-TSE. In conclusion, peritraumatic E2 levels, but not those at post-TSE time points, predict CPTP in women TSE survivors. Administration of E2 immediately post TSE protects against mechanical hypersensitivity in female rats. Together with previous findings, these data indicate that increased peritraumatic E2 levels in women have protective effects against CPTP development and suggest that immediate post-TSE E2 administration in women could be a promising therapeutic strategy for reducing risk of CPTP.

Inhibition of SARM1 Reduces Neuropathic Pain in a Spared Nerve Injury Rodent Model

INTRODUCTION/AIMS

The function of the sterile alpha and toll/interleukin receptor motif-containing protein 1 (SARM1) in neuropathic pain development has not yet been established. This protein has a central role in regulating axon degeneration and its depletion delays this process. This study aims to demonstrate the effects of SARM1 deletion on the development of neuropathic pain.

METHODS

Thirty-two wild-type (WT) or SARM1 knockout (KO) rats underwent spared nerve injury (SNI) or sham surgery. Mechanical allodynia was assessed by electronic Von Frey and cold hyperalgesia by the acetone test. Nociception was evaluated at the baseline, Day-1, Day-2, Week-1, Week-2, Week-3, and Week-4 time points. Nerve sections were examined by immunohistochemistry (IHC).

RESULTS

WT Injury rats were more sensitive to pain than WT Sham at all postoperative time points, validating the pain model. Injured SARM1 KO rats only demonstrated a difference in mechanical or cold nociception from KO Sham at Week 3. Injured KO rats demonstrated a clear trend of decreased sensitivity compared to WT Injury nociception, reaching significance at Week 4 (p = 0.044). Injured KO rats showed attenuated sensitivity to cold allodynia relative to WT at Week 2 (p = 0.019). IHC revealed decreased macrophages in spared sural nerves of injured KO animals at 2 and 4 weeks, and the proximal portion of tibial/peroneal nerves at Week 2.

DISCUSSION

This study demonstrates that SARM1 KO rats are less sensitive to mechanical and cold nociception than WT rats in an SNI model with decreased inflammatory response. Given these results, inhibition of SARM1 should be further investigated in the treatment of neuropathic pain.

Preliminary pharmacokinetics and in vivo studies indicate analgesic and stress mitigation effects of a novel NMDA receptor modulator

N-methyl D-aspartate receptor (NMDAR) channel blockers produce analgesic and antidepressant effects by preferentially inhibiting the GluN2D subtype at lower doses. Given the distinct physiological role of GluN2 subunits, we hypothesized that compounds capable of simultaneously modulating GluN2A and GluN2D subtypes in opposite directions could serve as effective analgesics with minimal cognitive adverse effects. In this translational study, we investigated the in vivo effects of costa NMDAR stimulator 4 (CNS4), a recently discovered glutamate concentration-dependent NMDAR modulator. Pharmacokinetic data revealed that CNS4 reaches peak plasma and brain concentrations within 0.25 hours after intraperitoneal injection, with brain concentrations reaching values up to 8.4% of those in plasma (64.9 vs 5.47 μg/mL). Preliminary results showed that CNS4, a nonopioid compound, increased escape latency in mice during a hotplate assay by 1.74-fold compared with saline. In a fear conditioning experiment, CNS4 anecdotally reduced the electric shock sensation and significantly decreased stress-related defecation (fecal pellets: males, 21 vs 1; females, 19 vs 3). CNS4 also improved hyperarousal behavior (25 vs 4 jumps), without affecting fear memory parameters such as freezing episodes, duration, or latency. CNS4 caused no changes in locomotion across 8 of 9 parameters studied. Remarkably, approximately 50 hours after fear conditioning training, CNS4 prevented stress-induced excessive sucrose drinking behavior by more than 2-fold both in male and female mice. These findings suggest that CNS4 penetrates brain tissue and produces pharmacological effects such as those of NMDAR-targeting drugs but with a distinct mechanism, avoiding the undesirable side effects typical of traditional NMDAR blockers. Therefore, CNS4 holds potential as a novel nonopioid analgesic, warranting further investigation. SIGNIFICANCE STATEMENT: N-methyl D-aspartate (NMDA)-subtype glutamate receptors are an attractive target for chronic pain and posttraumatic stress disorder treatments because they play a critical role in forming emotional memories of stressful events. In this translational pharmacology work, we demonstrate the central analgesic and stress-mitigating characteristics of a novel glutamate concentration-biased NMDA receptor modulator, costa NMDA receptor stimulator 4.

Evaluation of anti-arthritic and anti-inflammatory potential of Ajugarin-I from Ajuga Bracteosa wall ex. Benth against Freund's complete adjuvant induced arthritis

Rheumatoid arthritis (RA) is a prolonged autoimmune disease that targets the lining of small joints, causing inflammation and destruction of bone and cartilage. Anti-inflammatory drugs are available but offer short-term relief with adverse side effects. The present research was planned to study the in-vivo antiarthritic potential of ajugarin-I, sequestered from the Ajuga bracteosa. In-vivo studies include anti-inflammatory, analgesic, antidepressant, hematology profile, histopathological, radiological, and antioxidant analysis. The in-vivo results revealed that a high dose (HD, 60 mg/kg) of ajugarin-I significantly decreased the inflammatory paw edema (40 ± 0.04 %). Ajugarin-I also showed excellent analgesic behavior with 89 ± 0.55 % and 85 ± 0.55 % increments in pain threshold induced by cold and hot stimuli. Whereas ajugarin-I showed 95.1 ± 0.04 % antidepressant activity. Moreover, it showed strong antioxidant potential by raising the level of catalase, glutathione-S-transferase, and reducing glutathione while decreasing MDA levels in the liver, kidney, brain, paw, and spleen. Reduced serum levels of alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) (with 67.5 ± 3.53 %, 83.5 ± 3.53 % and 85 ± 7.07 % respectively), were observed with HD of ajugarin-I. Furthermore, its 60 mg/kg dose restored hematological abnormalities by raising the Hb level (85 ± 0.7 %) RBCs (91 ± 0.5 %), MCV (83 ± 2 %), platelet count (83 ± 0.5 %) and lowered the WBC (68 ± 0.35 %) level. Abnormalities in histoarchitecture of paw, liver, and kidney were curtailed by HD of ajugarin-I demonstrating its regenerative properties. Radiological analysis of the left hind paw showed that ajugarin-I lessened the inflammation in articular areas. These findings will guide a novel area of research for exploiting ajugarin-I as novel anti-arthritic and anti-inflammatory agent.

Focal Adhesion Kinase Inhibition Ameliorates Burn Injury-Induced Chronic Pain in Rats

Burn injury-induced pain (BIP) is a significant global health concern, affecting diverse populations including children, military veterans, and accident victims. Current pharmacotherapeutics for the management of BIP are associated with severe side effects including drug addiction, respiratory depression, sedation, and constipation posing significant barrier to their clinical utility. In the present study, we have investigated the potential role of focal adhesion kinase (p-FAK) for the very first time in BIP and elucidated the associated underlying mechanisms. Defactinib (DFT), a potent p-FAK inhibitor, administered at doses of 5, 10, and 20 mg/kg via intraperitoneal injection, demonstrates significant efficacy in reducing both evoked and spontaneous pain without causing addiction or other central nervous system toxicities. Burn injury triggers p-FAK-mediated phosphorylation of Erk1/2 and NR2B signaling in the DRG, resulting in heightened hypersensitivity through microglial activation, neuropeptide release, and elevated proinflammatory cytokines. Defactinib (DFT) counteracts these effects by reducing NR2B upregulation, lowering substance P levels, inhibiting microglial activation, and restoring IL-10 levels while leaving CGRP levels unchanged. These findings provide valuable insights into the pivotal role of p-FAK in regulating BIP and highlight the potential for developing novel therapeutics for burn injury-induced pain with minimal side effects.

Low intensity trans-spinal focused ultrasound reduces mechanical sensitivity and suppresses spinal microglia activation in rats with chronic constriction injury

Low intensity, trans-spinal focused ultrasound (tsFUS) is a noninvasive neuromodulation approach that has been shown to modulate spinal circuit excitability in healthy rats. Here, we evaluated the potential of tsFUS for alleviating neuropathic pain by testing it in a chronic constriction injury (CCI) model. Male rats underwent CCI of the left sciatic nerve and then received tsFUS (2 kHz pulse repetition frequency; 40% duty cycle) or sham stimulation, targeted at spinal segment level L5 for 3 min daily over three days. As expected, CCI causes significant reduction of von Frey Threshold (vFT), a measure of mechanical sensitivity. We found that tsFUS treatment is associated with increased vFT compared to sham; this increase persists beyond the duration of treatment, through days 4 to 23 post-CCI. In spinal cords of tsFUS-treated animals, counts of spinal microglia (Iba1 + cells) and of activated, pro-inflammatory microglia (Iba1 + /CD86 + cells), are reduced compared to sham-treated animals. This reduction in microglia counts is limited to the insonified side of the spinal cord, ipsilateral to CCI. These findings suggest that tsFUS may be a promising approach for treatment of neuropathic pain at early stages, possibly by attenuating the development of microglial-driven inflammation.

Pharmacological Evaluation of Novel Hydrazide and Hydrazone Derivatives: Anti-Inflammatory and Analgesic Potential in Preclinical Models

Hydrazones, characterized by their C=N-NH functional group, are promising candidates in medicinal chemistry due to their ability to interact with biological targets. This study evaluated the anti-inflammatory and analgesic properties of N-pyrrolylcarbohydrazide (1) and four pyrrole hydrazone derivatives (1A-D) in male Wistar rats (6 weeks old). Anti-inflammatory activity was assessed using a carrageenan-induced paw edema model, while formalin, tail flick, and paw withdrawal tests evaluated analgesia. Compound 1 exhibited dose-dependent anti-inflammatory activity. At 20 mg/kg, significant edema reductions were observed at the 2nd (p = 0.035) and 3rd hours (p = 0.022), while at 40 mg/kg, reductions remained significant at the 2nd (p = 0.008) and 3rd hours (p = 0.046). Compound 1A showed pronounced effects at 20 mg/kg at the 2nd (p = 0.005), 3rd (p < 0.001), and 4th hours (p = 0.004). Other compounds demonstrated minimal or no activity. Analgesic evaluation revealed that at 40 mg/kg, compound 1 significantly reduced paw-licking time in the second phase (p = 0.038). Compounds 1B, 1C, and 1D exhibited transient effects in the first phase only (p < 0.05). Compound 1A lacked significant analgesic activity. The findings suggest that structural modifications may enhance efficacy for broader therapeutic applications.

Protocol to study neuronal membrane proteasome function in mouse peripheral sensory neurons

Neuronal membrane proteasomes (NMPs) are expressed on a subset of somatosensory dorsal root ganglion (DRG) neurons and influence mechanical and pain sensitivity. Here, we present a protocol for studying NMP function in mouse peripheral sensory neurons. We describe steps for procuring and culturing primary DRG neurons. We then detail biochemical and antibody feeding approaches to analyze NMP expression and localization. Finally, we include Ca2+ imaging techniques for investigating NMP function in DRG neurons. For complete details on the use and execution of this protocol, please refer to Villalón Landeros et al.1.

Non-invasive in vivo bidirectional magnetogenetic modulation of pain circuits

Primary nociceptors in the dorsal root ganglion (DRG) receive sensory information from discrete parts of the body and are responsible for initiating signaling events that in supraspinal regions will be interpreted as physiological or pathological pain. Genetic, pharmacologic and electric neuromodulation of nociceptor activity in freely moving non-transgenic animals has been shown to be challenging due to many factors including the immunogenicity of non-mammalian proteins, procedure invasiveness and poor temporal precision. Here, we introduce a magnetogenetic strategy that enables remote bidirectional regulation of nociceptor activity. Magnetogenetics utilizes a source of direct magnetic field (DMF) to control neuronal activity in cells that express an anti-ferritin nanobody-TRPV1 receptor fusion protein (Nb-Ft-TRPV1). In our study, AAV2retro-mediated delivery of an excitatory Nb-Ft-TRPV1 construct into the sciatic nerve of wild-type mice resulted in stable long-term transgene expression accompanied by significant reduction of mechanical withdrawal thresholds during DMF exposure, place aversion of the DMF zone and activity changes in the anterior cingulate (ACC) nucleus. Conversely, delivery of an inhibitory variant of the Nb-Ft-TRPV1 construct, engineered to gate chloride ions in response to DMF, led to reversed behavioral manifestations of mechanical allodynia and showed place preference for the DMF zone, suggestive of functional pain relief. Changes in DRG activity were confirmed by post-mortem levels, immediately following DMF exposure, of the activity-induced gene cfos, which increased with the excitatory construct in normal mice and decreased with the inhibitory construct in pain models Our study demonstrates that magnetogenetic channels can achieve long-term expression in the periphery without losing functionality, providing a stable gene therapy system for non-invasive, magnetic field regulation of pain-related neurons for research and potential clinical applications.

Elucidating interplay between myrcene and cannabinoid receptor 1 receptors to produce antinociception in mouse models of neuropathic pain

ABSTRACT

The need for nonaddictive and effective treatments for chronic pain are at an all-time high. Historical precedence, and now clinical evidence, supports the use of cannabis for alleviating chronic pain. A plethora of research on delta-9-tetrahydrocannabinol exists, yet cannabis is comprised of a multitude of constituents, some of which possess analgesic potential, that have not been systematically investigated, including the terpene myrcene. Myrcene attenuates pain hypersensitivity in preclinical models and is one of the most abundant terpenes found in cannabis. Despite these findings, it remains unclear how myrcene elicits these effects on nociceptive systems. The present study uses a male and female mouse model of neuropathic pain as well as in vitro experiments with HEK293T cells to explore these questions. We first demonstrate myrcene (1-200 mg/kg i.p.) dose-dependently increases mechanical nociceptive thresholds, where potency was greater in female compared with male pain mice. Testing canonical tetrad outcomes, mice were tested for hypolocomotion and hypothermia after myrcene administration. Myrcene did not alter locomotion or temperature, but female pain mice showed a conditioned place aversion to myrcene. A cannabinoid receptor 1 (CB1) antagonist inhibited myrcene's anti-allodynia. By contrast, in vitro cell culture experiments using a TRUPATH assay revealed myrcene does not directly activate CB1 receptors nor alter CB1 receptor activity elicited by CB1 agonist (CP 55,940) or endocannabinoids (anandamide or 2-arachidonoylglycerol). Understanding engagement of CB1 receptors in pain modulation and myrcene's mechanism of action warrants further study to understand the diversity of cannabis pharmacology and to further the frontier of pain research.

Senolytic treatment for low back pain

Senescent cells (SnCs) accumulate because of aging and external cellular stress throughout the body. They adopt a senescence-associated secretory phenotype (SASP) and release inflammatory and degenerative factors that actively contribute to age-related diseases, such as low back pain (LBP). The senolytics, o-vanillin and RG-7112, remove SnCs in human intervertebral discs (IVDs) and reduce SASP release, but it is unknown whether they can treat LBP. sparc-/- mice, with LBP, were treated orally with o-vanillin and RG-7112 as single or combination treatments. Treatment reduced LBP and SASP factor release and removed SnCs from the IVD and spinal cord. Treatment also lowered degeneration scores in the IVDs, improved vertebral bone quality, and reduced the expression of pain markers in the spinal cord. Together, our data suggest RG-7112 and o-vanillin as potential disease-modifying drugs for LBP and other painful disorders linked to cell senescence.

Using Integrated Network Pharmacology and Metabolomics to Reveal the Mechanisms of the Combined Intervention of Ligustrazine and Sinomenine in CCI-Induced Neuropathic Pain Rats

Neuropathic pain (NP) is a type of chronic pain resulting from injury or dysfunction of the nerves or spinal cord. Previous studies have shown that the combination of ligustrazine (LGZ) and sinomenine (SIN) exerts a synergistic antinociceptive effect in peripheral and central NP models. On this basis, a comprehensive analgesic evaluation was performed in a chronic constriction injury (CCI)-induced NP model in rats. Sciatic nerve histopathological changes were observed, and 22 cytokines and chemokines levels were analyzed. We also combined network pharmacology and metabolomics to explore their molecular mechanisms. Results showed that the combination of LGZ and SIN significantly alleviated the pain-like behaviors in CCI rats in a time- and dose-dependent manner, demonstrating superior therapeutic effects compared to LGZ or SIN alone. It also improved pathological damage to sciatic nerves and regulated inflammatory cytokine levels. Network pharmacology identified shared and distinct pain-related targets for LGZ and SIN, while metabolomics revealed 54 differential metabolites in plasma, and 17 differential metabolites in CSF were associated with the combined intervention of LGZ and SIN. Finally, through an integrated analysis of the core targets and differential metabolites, tyrosine metabolism, phenylalanine metabolism, and arginine and proline metabolism were identified as potential key metabolic pathways underlying the therapeutic effects of LGZ and SIN in CCI treatment. In conclusion, our study provides evidence to support the clinical application of LGZ and SIN in the treatment of NP.

Neutralization of acyl CoA binding protein (ACBP) for the experimental treatment of osteoarthritis

The plasma concentrations of acyl CoA binding protein (ACBP) encoded by the gene diazepam binding inhibitor (DBI) are increased in patients with severe osteoarthritis (OA). Here, we show that knee OA induces a surge in plasma ACBP/DBI in mice subjected to surgical destabilization of one hind limb. Knockout of the Dbi gene or intraperitoneal (i.p.) injection of a monoclonal antibody (mAb) neutralizing ACBP/DBI attenuates OA progression in this model, supporting a pathogenic role for ACBP/DBI in OA. Furthermore, anti-ACBP/DBI mAb was also effective against OA after its intraarticular (i.a.) injection, as monitored by sonography, revealing the capacity of ACBP/DBI to locally reduce knee inflammation over time. In addition, i.a. anti-ACBP/DBI mAb improved functional outcomes, as indicated by the reduced weight imbalance caused by OA. At the anatomopathological level, i.a. anti-ACBP/DBI mAb mitigated histological signs of joint destruction and synovial inflammation. Of note, i.a. anti-ACBP/DBI mAb blunted the OA-induced surge of plasma ACBP/DBI, as well as that of other inflammatory factors including interleukin-1α, interleukin-33, and tumor necrosis factor. These findings are potentially translatable to OA patients because joints from OA patients express both ACBP/DBI and its receptor GABAARγ2. Moreover, a novel mAb against ACBP/DBI recognizing an epitope conserved between human and mouse ACBP/DBI demonstrated similar efficacy in mitigating OA as an anti-mouse ACBP/DBI-only mAb. In conclusion, ACBP/DBI might constitute a promising therapeutic target for the treatment of OA.

CYP3A4 and MRP2 are predominant metabolic regulators attribute to the toxicity/efficacy of aconitine derived from Fuzi

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum carmichaelii Debx. exhibits overwhelming efficacy against heart failure, inflammation and pain, but its clinical application is limited by concomitant cardiotoxicity and neurotoxicity. Aconitine (AC), the most abundant bioactive alkaloid, has narrow therapeutic window, with well-defined toxic and therapeutic thresholds. However, the overlapping molecular targets mediating dual toxicity and efficacy of AC remain poorly characterized.

AIMS OF THE STUDY

This study aimed to evaluate dual pharmacological and toxicological roles of AC through integrative pharmacology and transgenic mouse models.

MATERIALS AND METHODS

The overlapping targets of AC-related toxicity/efficacy were identified based on integrative pharmacology. By generating Cyp3a-/- transgenic mice expressing human CYP3A4 (hCYP3A4), Ugt1, P-gp, Mrp2, BCRP, and Nrf2 knockout mice, the effects of AC on toxicity, pain, inflammation, and heart failure were assessed.

RESULTS

We identified 143 overlapping targets predominantly enriched in metabolic pathways. Symptom-based toxicity scores were strikingly elevated in AC-exposed hCYP3A4, Mrp2-/-, P-gp-/-, BCRP-/-, and Nrf2-/- mice compared to WT mice. Additionally, AC prolonged the latency of response by approximately 18s, 15s, 14s, and 5s, respectively, in hCYP3A4, Mrp2-/-, P-gp-/-, and Nrf2-/- mice by hot plate assay. Interestingly, both toxicity score and analgesic latency initially increased and subsequently decreased, peaking at 60 min. AC obviously decreased the acetic acid-induced writhing and permeability by 45.7% and 22.2% in hCYP3A4 mice, whereas these changes were amplified in Mrp2-/- mice compared to WT mice. Furthermore, AC attenuated DOX induced heart failure in hCYP3A4 mice, with an effective rate of 20.9%, with Septin4 implicated in AC-related metabolism.

CONCLUSIONS

Metabolic targets may elucidate the mechanistic overlap between the toxicity and efficacy of AC. Notably, hCYP3A4 exhibited heightened toxicity, alongside enhanced analgesic, anti-inflammatory, and cardioprotective effects. Our findings position metabolic pathways as critical nodes for AC-related dual effect, and establish Septin4 as a candidate mediator of its metabolic regulation.

Astrocyte neuronal metabolic coupling in the anterior cingulate cortex of mice with inflammatory pain

Chronic pain is a major global concern, with at least 1 in 5 people suffering from chronic pain worldwide. Mounting evidence indicates that neuroplasticity of the anterior cingulate cortex (ACC) is a critical step in the development of chronic pain. Previously, we found that chronic pain and fear learning are both associated with enhanced neuronal excitability and cause similar neuroplasticity-related gene expression changes in the ACC of male mice. However, neuroplasticity, imposes large metabolic demands. In the brain, neurons have the highest energy needs and interact with astrocytes, which extract glucose from blood, mobilize glycogen, and release lactate in response to neuronal activity. Here, we use chronic and continuous inflammatory pain models in female and male mice to investigate the involvement of astrocyte-neuronal lactate shuttling (ANLS) in the ACC of female and male mice experiencing inflammatory pain. We found that ANLS in the mouse ACC promotes the development of chronic inflammatory pain, and expresses sex specific patterns of activation. Specifically, whereas both male and female mice show similar levels of chronic pain hypersensitivity, only male mice show sustained increases in lactate levels. Accordingly, chronic pain alters the expression levels of proteins involved in lactate metabolism and shuttling in a sexually dimorphic manner. We found that disrupting astrocyte-neuronal lactate shuttling in the ACC prior to inflammatory injury prevents the development of pain hypersensitivity in female and male mice, but only reduces temporary pain in male mice. Furthermore, using a transgenic mouse model (itga1-null mice) that displays a naturally occurring form of spontaneous osteoarthritis (OA), a painful inflammatory pain condition, we found that whereas both female and male mice develop OA, only male mice show increases in mechanisms involved in astrocyte-neuronal lactate shuttling. Our findings thus indicate that there are sex differences in astrocyte-neuronal metabolic coupling in the mouse ACC during chronic pain development.

CurQ+ With Resveratrol Diminish Joint Pain in a Child With Pseudoachondroplasia: A Case Report

This case report details the successful use of over-the-counter resveratrol and CurQ+ in a five-year-old with pseudoachondroplasia (PSACH), a severe dwarfing condition caused by mutations in cartilage oligomeric matrix protein (COMP). Disproportionate short stature, abnormal joints, joint deformities, and pain starting in early childhood are characteristic findings. Adult treatments include non-steroidal anti-inflammatory drugs (NSAIDs) and joint replacement to manage joint pain. Childhood pain goes largely untreated given the concern of daily use of NSAIDs in the very young. Recently, resveratrol has been shown to reduce pain and CurQ+ improves growth in a mouse model of PSACH. The use of these over-the-counter supplements has been adopted by some families with PSACH children. One such case in this report has a daily intake of resveratrol and CurQ+ at 125 mg of trans-resveratrol and 0.66 g, respectively, in the 16.6 kg child. This resulted in a dosage of 7.6 mg/kg of resveratrol and 40 mg/kg of CurQ+ daily. To date, no side effects from CurQ+ and resveratrol were reported in the child. Pain made walking to school very difficult (600 m) prior to the use of supplements and now the child walks to school without assistance or complaint.

Discordance between preclinical and clinical testing of Na V 1.7-selective inhibitors for pain

ABSTRACT

The voltage-gated sodium channel Na V 1.7 plays an important role in pain processing according to genetic data. Those data made Na V 1.7 a popular drug target, especially since its relatively selective expression in nociceptors promised pain relief without the adverse effects associated with broader sodium channel blockade. Despite encouraging preclinical data in rodents, Na V 1.7-selective inhibitors have not yet proven effective in clinical trials. Discrepancies between preclinical and clinical results should raise alarms. We reviewed preclinical and clinical reports on the analgesic efficacy of Na V 1.7-selective inhibitors and found critical differences in several factors. Putting aside species differences, most preclinical studies tested young male rodents with limited genetic variability, inconsistent with the clinical population. Inflammatory pain was the most common preclinical chronic pain model whereas nearly all clinical trials focused on neuropathic pain despite some evidence suggesting Na V 1.7 channels are not essential for neuropathic pain. Preclinical studies almost exclusively measured evoked pain whereas most clinical trials assessed average pain intensity without distinguishing between evoked and spontaneous pain. Nearly all preclinical studies gave a single dose of drug unlike the repeat dosing used clinically, thus precluding preclinical data from demonstrating whether tolerance or other slow processes occur. In summary, preclinical testing of Na V 1.7-selective inhibitors aligned poorly with clinical testing. Beyond issues that have already garnered widespread attention in the pain literature, our results highlight the treatment regimen and choice of pain model as areas for improvement.

Synthesis and biological evaluation of new dual APN/NEP inhibitors as potent analgesics

An alternative approach for the management of acute and chronic pains involves prolonging the half-life of endogenous opiates, such as enkephalins that are released in response to nociceptive stimuli. This can be achieved through the inhibition of enzymatic pathways responsible for the hydrolysis of these peptides, particularly targeting Aminopeptidase N (APN) and Neutral Endopeptidase (NEP). In this study, we designed and synthesized a series of dual enkephalinase inhibitors (DENKIs) targeting both APN and NEP as novel analgesic treatments. Notably, SDUY812, SDUY816 and SDUY817 exhibited potent inhibition of APN activity with IC50 values of 0.38 µM, 0.68 µM and 0.29 µM, respectively, whereas their IC50 values against NEP were 6.9 µM, 6.9 µM and 7.4 µM, separately. In in-vivo antinociceptive assays, SDUY816 and SDUY817 demonstrated superior analgesic efficacy compared to Thiorphan and Bestatin in mice models of acute, inflammatory and neuropathic pains with jumping latencies exceeding 100 s and withdrawal thresholds more than 0.13 g. Moreover, the analgesic activity of these inhibitors was significantly diminished by a potent opioid antagonist, naloxone, indicating the contribution of opioid receptors to the robust analgesic properties of these newly developed DENKIs. In addition, SDUY816 and SDUY817 exerted the analgesic activity in a concentration- and time-dependent manner with SDUY816 possessing acceptable pharmacokinetic properties (t1/2 = 4.02 h and F = 27 %) and low toxicity. These findings provide alternative analgesic therapeutics that are potentially devoid of opioid-associated side effects.

Postnatal deletion of Phlpp1 in chondrocytes delays post-traumatic osteoarthritis in male mice

Objective

Osteoarthritis is a chronic, debilitating disease that causes long-term pain and immobility. Germline deletion of Phlpp1 or administration of small molecules that inhibit Phlpp1 prevents post-traumatic osteoarthritis (PTOA) in mice. However, the chondrocyte-intrinsic role of Phlpp1 in PTOA progression is unknown. The objective of this study was to determine how postnatal, chondrocyte-directed deletion of Phlpp1 affects PTOA progression in the presence or absence of Phlpp inhibitors.

Design

Phlpp1fl/fl; Agc-CreERT2 and Agc-CreERT2 mice were injected with tamoxifen at 12 weeks of age to generate Phlpp1-CKOAgcERT and control (AgcERT) groups. Male mice underwent surgery to destabilize the medial meniscus (DMM) at 17 weeks of age. A separate cohort of male Phlpp1-CKOAgcERT mice were administered an intra-articular injection of NSC117079, a Phlpp1/2 inhibitor, or saline seven weeks after DMM surgery. Activity and mechanical allodynia were monitored throughout the experiment and cartilage damage was evaluated 12 weeks post-surgery.

Results

Phlpp1-CKOAgcERT mice had less cartilage damage than AgcERT littermates 12 weeks after DMM surgery but exhibited no differences in activity. Prg4 expression was also higher in articular chondrocytes of Phlpp1-CKOAgcERT mice. Intra-articular administration of NSC117079 to Phlpp1-CKOAgcERT mice improved cartilage structure, subchondral bone sclerosis, and mechanical allodynia at 12 weeks post-DMM.

Conclusions

Postnatal deletion of Phlpp1 in chondrocytes attenuates DMM-induced cartilage damage and subchondral bone sclerosis but does not prevent pain-related behaviors. Intra-articular injection of Phlpp inhibitors delays mechanical allodynia in Phlpp1-CKOAgcERT mice. These data indicate that Phlpp1 in chondrocytes affects articular cartilage structure after injury, but pain-related behaviors are controlled by Phlpp1 or Phlpp2 in other cell types.

Increased TRPA1 functionality in the skin of rats and cancer patients following oxaliplatin treatment

Chemotherapy-induced peripheral neuropathy is a debilitating pathology affecting a majority of patients who are being treated with specific cytostatic compounds including oxaliplatin. Various in vitro, ex vivo and in vivo preclinical experiments indicate that transient receptor potential ankyrin 1 (TRPA1) plays a crucial role in the symptomatology of chemotherapy-induced peripheral neuropathy. However, it is unclear whether oxaliplatin also modulates the TRPA1 functionality in the skin of rodents or patients. Here, we quantified the vasodilation after topical application of the TRPA1 agonist cinnamaldehyde in a rodent model of chemotherapy-induced peripheral neuropathy (male Sprague Dawley rats, aged 6 weeks) as well as on fingers of patients suffering from chronic chemotherapy-induced peripheral neuropathy after oxaliplatin treatment. Compared to vehicle-treated rats, a cumulative dose of oxaliplatin 32 mg/kg enhanced the vasodilation after cinnamaldehyde application on rat abdominal skin. Likewise, also in patients with chronic chemotherapy-induced peripheral neuropathy after oxaliplatin, the response to cinnamaldehyde was significantly higher compared to sex- and age-matched healthy controls. Thereby, this study is the first to translate the evidence of increased TRPA1 functionality in vitro or ex vivo in rodents to in vivo conditions in human. The increased TRPA1 functionality in patients with chronic chemotherapy-induced peripheral neuropathy does not only confirm the potential of TRPA1 as target to hit to provide efficacious analgesia, it also paves the way for additional patient stratification on a molecular level and possible treatment response prediction. PERSPECTIVE: The cinnamaldehyde-induced, TRPA1-mediated vasodilation was enhanced in patients with oxaliplatin-induced peripheral neuropathy versus healthy controls, confirming the potential of TRPA1 as target-to-hit for this indication.

Structure-Activity Relationship of 7-Chloro-4-(Phenylselanyl) Quinoline: Novel Antinociceptive and Anti-Inflammatory Effects in Mice

The 7-chloro-4-(phenylselanyl) quinoline (4-PSQ) shows promise for its antinociceptive and anti-inflammatory properties. Here, we explored the structure-activity relationship of 4-PSQ and its analogues: 7-chloro-4-[(4-fluorophenyl) selanyl]quinoline (a), 7-chloro-4-{[3-trifluoromethyl)phenyl] selanyl} quinoline (b), 4-((3,5-Bis(trifluoromethyl)phenyl) selanyl-7-chloroquinoline (c), 7-chloro-4-[(2,4,6-trimethyl)selanyl]quinolinic acid (d) and 7-chloroquinoline-4-selenium acid (e) in models of acute inflammation and chemical, thermal and mechanical nociception in mice, alongside in silico analysis. Compounds a (-F), b (-CF3), c (-Bis-CF3), d (-CH3), e (-OOH), and 4-PSQ exhibited antinociceptive effects in chemical and thermal nociception models, except d (-CH3) and e (-OOH) in the hot plate test. None induced locomotor changes. In silico, only c (-Bis-CF3) showed low gastrointestinal absorption, and c (-Bis-CF3) and e (-OOH) lacked blood-brain barrier penetration, suggesting e (-OOH) lacked central antinociceptive effect. These compounds had higher COX-2 affinity than COX-1. Our findings suggest substituent insertion alters 4-PSQ's efficacy as an antinociceptive and anti-inflammatory agent.

Suppression of TLR4/NF-κB signaling by kaurenoic acid in a mice model of monosodium urate crystals-induced acute gout

AIM

The aim of the current study was to investigate the potential therapeutic effect of kaurenoic acid (KA) against Monosodium Urate Crystals (MSU)-induced acute gout by downregulation of NF-κB signaling pathway, mitigating inflammation and oxidative stress. KA potentially targeted NF-κB pathway activation and provided comprehensive insights through multiple approaches. This was accomplished by advanced analytical techniques. This methodology highlighted the efficacy of KA in acute gout attacks offering new approach for gout management.

METHODS

In-vivo model of acute gout was established in BALB/c mice. Anti-inflammatory and urate-lowering potential was determined through pain behavioral evaluation, biochemical analysis, histological and immunohistochemical assays, radiological assessments, Fourier Transform Infrared (FTIR) analysis, and computational analysis.

RESULTS

The paw edema, joint thickness, and the frequency and duration of acute gout flare-ups were all significantly (p < 0.001) decreased by the administration of KA. A considerable reversal of inflammation and deterioration was observed in the KA-treated groups in X-ray examination. The FTIR spectroscopy indicated the changes in the molecular makeup of tissues, and modifications of biomolecules including proteins, lipids, and carbohydrates. Histopathological changes showed marked (p < 0.001) improvements in cellular structure of the paw, and inflammatory cell infiltration in the treatment groups. Trichrome staining revealed suppressed collagen deposition, inflammation, and tissue repair in the paw. In paw tissues, the KA therapy up-regulated IκB-α expression while down-regulating toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) expression. On the other hand, KA therapy greatly increased antioxidants and decreased oxidative stress indicators significantly (p < 0.001). According to Evans's blue permeability analysis, results showed that the treatment groups' vascular permeability was intensely reduced in comparison to the diseased group. Molecular docking studies indicated that KA appeared to have a high tendency to bind to protein targets. KA was associated with the drop in the cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β).

CONCLUSION

In conclusion, this study highlighted the potential therapeutic effect of KA in alleviating MSU-induced gout by suppressing the NF-κB signaling pathway. The anti-inflammatory and antioxidant activity was demonstrated by behavioral studies and advanced biochemical evaluations including blood analysis and oxido-nitrosative stress markers. Histopathological analysis, including H&E staining, immunohistochemistry, and Masson Trichrome staining, revealed tissue preservation, while FTIR and X-ray revealed structural improvements. Molecular docking verified strong binding affinity to NF-κB-related targets, verifying its mechanistic action. These findings suggest promising applications of KA in acute gout management due to its potent NF-κB modulating activity.

Clavulanic acid prevents paclitaxel-induced neuropathic pain through a systemic and central anti-inflammatory effect in mice

Paclitaxel (PCX) based treatments, commonly used to treat breast, ovarian and lung cancers, have the highest incidence of chemotherapy-induced neuropathic pain, affecting from 38 to 94 ​% of patients. Unfortunately, analgesic treatments are not always effective for PCX-induced neuropathic pain (PINP). This study aimed to evaluate the antinociceptive effect of clavulanic acid (CLAV), a clinically used β-lactam molecule, in both therapeutic and preventive contexts in mice with PINP. A single dose of CLAV administered after the onset of PINP significantly reduced mechanical hyperalgesia. Interestingly, preventive administration of CLAV prevented PINP development. The effect of preventive CLAV on PINP was associated with increased levels of IL-10 and IFN-β in serum, and decreased levels of IL-1β and TNF-α in both the serum and CNS. Immunostaining experiments revelated that CLAV increased the levels of glutamate transporter type 1 (GLT-1) and toll-like receptor type 4 (TLR4) in the spinal cord, while reducing levels of the astrocytic marker the glial fibrillary acidic protein (GFAP). Notably, co-incubation with CLAV and PCX in triple-negative breast cancer cells did not interfere with PCX-induced cytotoxic effects. Hence, these findings suggest that CLAV could be employed as a clinical treatment aimed at preventing PINP without compromission the cytotoxic efficacy of PCX.

Elucidation of Dexmedetomidine-Induced Analgesic Tolerance Mechanisms in Neuropathic Pain With Modulation of SGK1, NR2A, and NR2B Expression via the Spinal SGK1/NF-κB Signalling Pathway

Neuropathic pain (NP), resulting from nerve damage, is difficult to manage and often requires long-term treatment. However, prolonged use of pain medications can lead to addiction and reduced effectiveness over time. Understanding drug tolerance is essential for developing improved pain management strategies. Dexmedetomidine (DEX) is effective in targeting the α2-adrenergic receptor, providing relief from pain, especially NP. However, its extended use leads to tolerance and hinders its clinical utility. Herein, we investigated tolerance mechanisms and potential applications of this drug in managing NP. Adult C57BL/6 mice (male) were distributed into DEX Dosage Groups (n = 48), DEX Tolerance Model Groups (n = 32), SGK1 Inhibitor GSK650394 Groups (n = 48), and NF-κB Inhibitor PDTC Groups (n = 32) to explore dexmedetomidine's effects on NP and tolerance mechanisms. NP was established via selective ligation of the sciatic nerve branch (SNI), followed by administration of DEX. The results revealed a dose-dependent analgesic effect of DEX, with significant increases in pain thresholds observed compared to the sham group (p < 0.05). Optimal efficacy was found at a dose of 30 μg/kg, indicating its potential as an effective treatment for NP (p < 0.05). However, continuous administration of DEX over 13 days induced analgesic tolerance, evidenced by an initial increase in pain thresholds followed by a gradual decrease (p < 0.05). Despite an initial efficacy in elevating pain thresholds, the analgesic effect of DEX diminished over time, returning to pre-dose levels after 5 days (p < 0.05). Transcriptome sequencing of spinal cord samples from mice receiving multiple DEX injections revealed differential gene expression patterns, notably upregulation of SGK1, NR2A, and NR2B subunits (p < 0.05). Inhibiting SGK1 mitigated DEX-induced tolerance, suggesting its involvement in tolerance development (p < 0.05). Moreover, NF-κB inhibition reversed DEX-induced tolerance and implicated the SGK1-NF-κB pathway in the mediation of analgesic tolerance. To sum up, these findings revealed the molecular mechanism underlying DEX-induced analgesic tolerance in the NP model and offer potential avenues for future therapeutic interventions.

Optogenetic cortical spreading depression originating from the primary visual cortex induces migraine-like pain and anxiety behaviors in freely moving C57BL/6 J mice

BACKGROUND

Migraine is the second disabling neurological disorder with a high prevalence. Aura occurs in one-third of migraineurs and visual aura accounts for over 90%. Cortical spreading depression (CSD) underlies aura and might trigger migraine headaches. Compared with CSD induction by invasive electrical, chemical, or mechanical stimulation, optogenetics avoids direct influences on meninges in the stimulation process. However, previous optogenetic CSD models mainly use Thy1-ChR2-YFP or CaMKIIα-cre transgenic mice. They are limited when the pathogenesis study requires transgenic mice to express other specific promotor, such as the dopamine or serotonin transporter promotor. In addition, reported behavioral paradigms were based on CSD induction under anesthesia. This study aimed to establish an optogenetic CSD-induced migraine model originating in the primary visual cortex (VISp) in C57BL/6 J mice and presented the behavioral paradigm when CSD induction was under awake condition.

METHODS

We performed viral transduction for the expression of light-sensitive channelrhodopsin-2 in pyramidal neurons of VISp in C57BL/6 J mice. Regional cerebral blood flow (rCBF) was measured by laser speckle flowmetry to confirm CSD induction. The von Frey, light-dark box, elevated plus maze, and open field test were conducted to verify migraine-related behaviors in freely moving mice.

RESULTS

An optogenetic stimulus induced typical spreading triphasic rCBF change with a reduction of over 20%, confirming CSD induction. A single unilateral CSD in freely moving C57BL/6 J mice triggered bilateral periorbital and hind-paw allodynia lasting for 4-24 h. Notably, the ipsilateral periorbital mechanical threshold was significantly lower than the contralateral at 1 h. It also generated photophobia and anxiety behaviors persisting for 24-48 h. Furthermore, cutaneous allodynia and anxiety behaviors were alleviated by sumatriptan.

CONCLUSIONS

This study proposes an optogenetic CSD-induced migraine model originating from VISp in awake and freely moving C57BL/6 J mice and presents the behavioral paradigm in detail. The CSD model in wild-type mice is promising to be wildly used to study the pathogenesis of MwA.

Verification of Pain-Related Neuromodulation Mechanisms of Calcitonin in Knee Osteoarthritis

Chronic pain represents the prevailing symptom among patients suffering from knee osteoarthritis (KOA). In KOA, peripheral sensitization is driven by disruptions in subchondral bone homeostasis, local inflammatory responses, and variations in neuropeptide and neurotransmitter levels. Calcitonin, a pivotal peptide involved in bone metabolism, additionally exhibits potent analgesic properties. This study aimed to elucidate the mechanisms underlying calcitonin's neuromodulatory effects related to pain in the treatment of KOA. Three experiments were conducted: (1) assessing calcitonin's therapeutic effects via histomorphology, nociceptive behavioral assessments, and Western blot analysis of proteins; (2) verification of the involvement of neurotransmitters and neuropeptides in calcitonin's action using the Signal Transduction PathwayFinder PCR Array, Bio-Plex suspension chip, and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS); and (3) exploration of calcitonin's impact on brain function through functional magnetic resonance imaging (fMRI). Experiment 1 validated calcitonin's efficacy in KOA models. Experiment 2 demonstrated the involvement of the retinoic acid signaling pathway in calcitonin treatment, confirming that its analgesic efficacy is associated with the modulation of neuropeptides and neurotransmitters. Experiment 3 revealed that calcitonin treatment could reverse regional homogeneity and amplitude of low-frequency fluctuations in the hippocampus and tegmental nucleus. The study affirmed the critical role of pain-related neuromodulation mechanisms in calcitonin treatment, demonstrating that its analgesic effects are mediated through the modulation of neurotransmitters, neuropeptides, and brain function, as observed via fMRI. These findings provide a theoretical foundation for the clinical application of calcitonin in the treatment of KOA pain.