Acute Effects of Citrulline Malate Supplementation on Nocturnal Blood Pressure Dipping After Exercise in Hypertensive Patients: A Randomized, Placebo-Controlled Trial.

BACKGROUND: Citrulline malate (CM), especially when used in conjunction with physical exercise, has demonstrated potential as a non-pharmacological adjunct in the management of hypertension. Nevertheless, its impact on nocturnal blood pressure dipping remains unexplored. OBJECTIVE: Evaluate the impact of a single dose of CM on nocturnal blood pressure dipping after exercise in hypertensive individuals. METHODS: In a double-blind, placebo-controlled, parallel-group clinical trial, twenty hypertensive adults (55 ± 16 years) were randomly assigned to either a CM (6 g) or placebo (6 g of corn starch) group (PLA). Resting blood pressure was measured after a 20-min period of comfortable seating in a calm environment. Both groups underwent 40 min of treadmill running/walking at an intensity of 60-70% of their reserve heart rate, 120 min after ingesting the substances. Ambulatory blood pressure monitoring was employed to measure blood pressure over 24 h. RESULTS: No significant differences in systolic blood pressure values were observed between the CM and PLA groups at rest, during wakefulness, sleep, or over a 24-h period. However, CM exhibited a significant reduction in diastolic blood pressure in several metrics: delta 24 h (-14 mmHg vs -6 mmHg, p = 0.047), delta wakefulness (-12 mmHg vs -4 mmHg, p = 0.024), percent delta 24 h (-16% vs -6%, p = 0.024), and percent delta wakefulness (-14% vs -4%, p = 0.013). No significant differences were found between CM and PLA in terms of systolic and diastolic nocturnal absolute reductions (-13 mmHg vs -12 mmHg, p = 0.808, and -13 mmHg vs -8 mmHg, p = 0.273, respectively) or nocturnal percentage decrease (-9.9% vs -9.4%, p = 0.844, and -15.3% vs -11.7%, p = 0.399, respectively). CONCLUSIONS: The study found no significant changes in the post-exercise nocturnal blood pressure dip following a single dose of CM supplementation. However, a notable reduction in diastolic blood pressure was observed during the waking period and over the average 24-h monitoring period. CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE: ClinicalTrials.gov platform (NCT03378596).

A Narrative Review of the Dorsal Root Ganglia and Spinal Cord Mechanisms of Action of Neuromodulation Therapies in Neuropathic Pain.

Neuropathic pain arises from injuries to the nervous system in diseases such as diabetes, infections, toxicity, and traumas. The underlying mechanism of neuropathic pain involves peripheral and central pathological modifications. Peripheral mechanisms entail nerve damage, leading to neuronal hypersensitivity and ectopic action potentials. Central sensitization involves a neuropathological process with increased responsiveness of the nociceptive neurons in the central nervous system (CNS) to their normal or subthreshold input due to persistent stimuli, leading to sustained electrical discharge, synaptic plasticity, and aberrant processing in the CNS. Current treatments, both pharmacological and non-pharmacological, aim to alleviate symptoms but often face challenges due to the complexity of neuropathic pain. Neuromodulation is emerging as an important therapeutic approach for the treatment of neuropathic pain in patients unresponsive to common therapies, by promoting the normalization of neuronal and/or glial activity and by targeting cerebral cortical regions, spinal cord, dorsal root ganglia, and nerve endings. Having a better understanding of the efficacy, adverse events and applicability of neuromodulation through pre-clinical studies is of great importance. Unveiling the mechanisms and characteristics of neuromodulation to manage neuropathic pain is essential to understand how to use it. In the present article, we review the current understanding supporting dorsal root ganglia and spinal cord neuromodulation as a therapeutic approach for neuropathic pain.

Leishmania spp. amastigotes surrounding sensory nerve fibers in human painless skin ulcers: Evidence of pathogen-neuron proximity and absence of neuronal apoptosis.

In this present study, carried out between November 2020 and July 2023 at Londrina's University Hospital, patients with active lesions of cutaneous leishmaniasis (CL) were analyzed regarding pain perception and anatomopathological aspects of the ulcers. Pain was assessed using a numerical rating scale (NRS) to compare five patients diagnosed with CL with four control patients diagnosed with vascular skin ulcers. Histopathological evaluations were used to investigate the nociceptor neuron-Leishmania interface. Patients with CL ulcers reported less pain compared to patients with vascular ulcers (2.60 ± 2.30 and 7.25 ± 0.95, respectively, p = 0.0072). Histopathology evidenced Leishmania spp. amastigote forms nearby sensory nerve fibers in profound dermis. Schwann cells marker (S100 protein) was detected, and caspase-3 activation was not evidenced in the in the nerve fibers of CL patients' samples, suggesting absence of apoptotic activity in nerve endings. Additionally, samples taken from the active edge of the lesion were negative for bacilli acid-alcohol resistant (BAAR), which excludes concomitant leprosy, in which painless lesions are also observed. Thus, the present data unveil for the first time anatomopathological and microbiological details of painless ulcers in CL patients, which has important clinical implications for a better understanding on the intriguing painless clinical characteristic of CL.

New drug targets for the treatment of gout arthritis: what's new?

INTRODUCTION: Gout arthritis (GA) is an intermittent inflammatory disease affecting approximately 10% of the worldwide population. Symptomatic phases (acute flares) are timely spaced by asymptomatic periods. During an acute attack, redness, joint swelling, limited movement, and excruciating pain are common symptoms. However, the current available therapies are not fully effective in reducing symptoms and offer numerous side effects. Therefore, unveiling new drug targets and effector molecules are required in developing novel GA therapeutics. AREAS COVERED: This review discusses the pathophysiological mechanisms of GA and explores potential pharmacological targets to ameliorate disease outcome. In addition, we listed promising pre-clinical studies demonstrating effector molecules with therapeutical potential. Among those, we emphasized the importance of natural products, including traditional Chinese medicine formulas and their multitarget mechanisms of action. EXPERT OPINION: In our search, we observed that there is a massive gap between pre-clinical and clinical knowledge. Only a minority (4.4%) of clinical trials aimed to intervene by applying natural products or current hot targets described herein. In this sense, we envisage four possibilities for GA therapeutics, which include the repurposing of existing therapies, ALX/FPR2 agonism for improvement in disease outcome, the use of multitarget drugs (e.g. natural products), and targeting the neuroinflammatory component of GA.

Therapeutic activity of lipoxin A4 in TiO2-induced arthritis in mice: NF-κB and Nrf2 in synovial fluid leukocytes and neuronal TRPV1 mechanisms.

Background: Lipoxin A4 (LXA4) has anti-inflammatory and pro-resolutive roles in inflammation. We evaluated the effects and mechanisms of action of LXA4 in titanium dioxide (TiO2) arthritis, a model of prosthesis-induced joint inflammation and pain. Methods: Mice were stimulated with TiO2 (3mg) in the knee joint followed by LXA4 (0.1, 1, or 10ng/animal) or vehicle (ethanol 3.2% in saline) administration. Pain-like behavior, inflammation, and dosages were performed to assess the effects of LXA4 in vivo. Results: LXA4 reduced mechanical and thermal hyperalgesia, histopathological damage, edema, and recruitment of leukocytes without liver, kidney, or stomach toxicity. LXA4 reduced leukocyte migration and modulated cytokine production. These effects were explained by reduced nuclear factor kappa B (NFκB) activation in recruited macrophages. LXA4 improved antioxidant parameters [reduced glutathione (GSH) and 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonate (ABTS) levels, nuclear factor erythroid 2-related factor 2 (Nrf2) mRNA and Nrf2 protein expression], reducing reactive oxygen species (ROS) fluorescent detection induced by TiO2 in synovial fluid leukocytes. We observed an increase of lipoxin receptor (ALX/FPR2) in transient receptor potential cation channel subfamily V member 1 (TRPV1)+ DRG nociceptive neurons upon TiO2 inflammation. LXA4 reduced TiO2-induced TRPV1 mRNA expression and protein detection, as well TRPV1 co-staining with p-NFκB, indicating reduction of neuronal activation. LXA4 down-modulated neuronal activation and response to capsaicin (a TRPV1 agonist) and AITC [a transient receptor potential ankyrin 1 (TRPA1) agonist] of DRG neurons. Conclusion: LXA4 might target recruited leukocytes and primary afferent nociceptive neurons to exert analgesic and anti-inflammatory activities in a model resembling what is observed in patients with prosthesis inflammation.

Evaluation of a preemptive intervention regimen with hesperidin methyl chalcone in delayed-onset muscle soreness in young adults: a randomized, double-blinded, and placebo-controlled trial study.

PURPOSE: Delayed-onset muscle soreness (DOMS) describes an entity characterized by ultrastructural muscle damage. Hesperidin methyl chalcone (HMC) is a synthetic flavonoid presenting analgesic, anti-inflammatory, and antioxidant properties. We evaluated the effects of HMC upon DOMS. METHOD: In a preventive paradigm, 31 sedentary young men were submitted to a randomized, double-blinded parallel trial and received HMC 500 mg or one placebo capsule × 3 days before an intense dynamic exercise protocol (concentric/eccentric actions) applied for lower limbs for inducing muscle damage. Assessments were conducted at baseline, and 24 and 48 h after, comprising physical performance, and post-muscle soreness and damage, inflammation, recovery of muscle strength, and postural balance associated with DOMS. HMC safety was also evaluated. Thirty participants completed the study. RESULTS: HMC improved the performance of participants during exercise (40.3 vs 51.3 repetitions to failure, p = 0.0187) and inhibited CPK levels (90.5 vs 57.9 U/L, p = 0.0391) and muscle soreness during passive quadriceps palpation (2.6 vs 1.4 VAS cm, p = 0.0439), but not during active actions, nor did it inhibit IL-1ß or IL-10 levels. HMC improved muscle strength recovery, and satisfactorily refined postural balance, without inducing injury to kidneys or liver. CONCLUSIONS: Preemptive HMC supplementation may be beneficial for boosting physical performance and for the amelioration of clinical parameters related to DOMS, including pain on muscle palpation, increased blood CPK levels, and muscle strength and proprioceptive deficits, without causing adverse effects. These data advance the understanding of the benefits provided by HMC for DOMS treatment, which supports its usefulness for such purpose.

Kaurenoic Acid Reduces Ongoing Chronic Constriction Injury-Induced Neuropathic Pain: Nitric Oxide Silencing of Dorsal Root Ganglia Neurons.

Kaurenoic acid (KA) is a diterpene extracted from Sphagneticola trilobata (L.) Pruski. KA presents analgesic properties. However, the analgesic activity and mechanisms of action of KA in neuropathic pain have not been investigated so far; thus, we addressed these points in the present study. A mouse model of neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve. Acute (at the 7th-day post-CCI surgery) and prolonged (from 7-14th days post-CCI surgery) KA post-treatment inhibited CCI-induced mechanical hyperalgesia at all evaluated time points, as per the electronic version of von Frey filaments. The underlying mechanism of KA was dependent on activating the NO/cGMP/PKG/ATP-sensitive potassium channel signaling pathway since L-NAME, ODQ, KT5823, and glibenclamide abolished KA analgesia. KA reduced the activation of primary afferent sensory neurons, as observed by a reduction in CCI-triggered colocalization of pNF-κB and NeuN in DRG neurons. KA treatment also increased the expression of neuronal nitric oxide synthase (nNOS) at the protein level as well as the intracellular levels of NO in DRG neurons. Therefore, our results provide evidence that KA inhibits CCI neuropathic pain by activating a neuronal analgesic mechanism that depends on nNOS production of NO to silence the nociceptive signaling that generates analgesia.

Chikungunya Virus and Its Envelope Protein E2 Induce Hyperalgesia in Mice: Inhibition by Anti-E2 Monoclonal Antibodies and by Targeting TRPV1.

Chikungunya virus is an arthropod-borne infectious agent that causes Chikungunya fever disease. About 90% of the infected patients experience intense polyarthralgia, affecting mainly the extremities but also the large joints such as the knees. Chronic disease symptoms persist for months, even after clearance of the virus from the blood. Envelope proteins stimulate the immune response against the Chikungunya virus, becoming an important therapeutic target. We inactivated the Chikungunya virus (iCHIKV) and produced recombinant E2 (rE2) protein and three different types of anti-rE2 monoclonal antibodies. Using these tools, we observed that iCHIKV and rE2 protein induced mechanical hyperalgesia (electronic aesthesiometer test) and thermal hyperalgesia (Hargreaves test) in mice. These behavioral results were accompanied by the activation of dorsal root ganglia (DRG) neurons in mice, as observed by calcium influx. Treatment with three different types of anti-rE2 monoclonal antibodies and absence or blockade (AMG-9810 treatment) of transient receptor potential vanilloid 1 (TRPV1) channel diminished mechanical and thermal hyperalgesia in mice. iCHIKV and rE2 activated TRPV1+ mouse DRG neurons in vitro, demonstrating their ability to activate nociceptor sensory neurons directly. Therefore, our mouse data demonstrate that targeting E2 CHIKV protein with monoclonal antibodies and inhibiting TRPV1 channels are reasonable strategies to control CHIKV pain.

Ehrlich Tumor Induces TRPV1-Dependent Evoked and Non-Evoked Pain-like Behavior in Mice.

We standardized a model by injecting Ehrlich tumor cells into the paw to evaluate cancer pain mechanisms and pharmacological treatments. Opioid treatment, but not cyclooxygenase inhibitor or tricyclic antidepressant treatments reduces Ehrlich tumor pain. To best use this model for drug screening it is essential to understand its pathophysiological mechanisms. Herein, we investigated the contribution of the transient receptor potential cation channel subfamily V member 1 (TRPV1) in the Ehrlich tumor-induced pain model. Dorsal root ganglia (DRG) neurons from the Ehrlich tumor mice presented higher activity (calcium levels using fluo-4 fluorescent probe) and an increased response to capsaicin (TRPV1 agonist) than the saline-injected animals (p < 0.05). We also observed diminished mechanical (electronic von Frey) and thermal (hot plate) hyperalgesia, paw flinching, and normalization of weight distribution imbalance in TRPV1 deficient mice (p < 0.05). On the other hand, TRPV1 deficiency did not alter paw volume or weight, indicating no significant alteration in tumor growth. Intrathecal injection of AMG9810 (TRPV1 antagonist) reduced ongoing Ehrlich tumor-triggered mechanical and thermal hyperalgesia (p < 0.05). Therefore, the contribution of TRPV1 to Ehrlich tumor pain behavior was revealed by genetic and pharmacological approaches, thus, supporting the use of this model to investigate TRPV1-targeting therapies for the treatment of cancer pain.

The Flavonoid Hesperidin Methyl Chalcone Targets Cytokines and Oxidative Stress to Reduce Diclofenac-Induced Acute Renal Injury: Contribution of the Nrf2 Redox-Sensitive Pathway.

Hesperidin is derived from citrus fruits among other plants. Hesperidin was methylated to increase its solubility, generating hesperidin methyl chalcone (HMC), an emerging flavonoid that possess anti-inflammatory and antioxidant properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a powerful regulator of cellular resistance to oxidant products. Previous data evidenced HMC can activate Nrf2 signaling, providing antioxidant protection against diverse pathological conditions. However, its effects on kidney damage caused by non-steroidal anti-inflammatory drugs (NSAIDs) have not been evaluated so far. Mice received a nephrotoxic dose of diclofenac (200 mg/kg) orally followed by intra-peritoneal (i.p.) administration of HMC (0.03-3 mg/kg) or vehicle. Plasmatic levels of urea, creatinine, oxidative stress, and cytokines were assessed. Regarding the kidneys, oxidative parameters, cytokine production, kidney swelling, urine NGAL, histopathology, and Nrf2 mRNA expression and downstream targets were evaluated. HMC dose-dependently targeted diclofenac systemic alterations by decreasing urea and creatinine levels, and lipid peroxidation, as well as IL-6, IFN-γ, and IL-33 production, and restored antioxidant properties in plasma samples. In kidney samples, HMC re-established antioxidant defenses, inhibited lipid peroxidation and pro-inflammatory cytokines and upregulated IL-10, reduced kidney swelling, urine NGAL, and histopathological alterations. Additionally, HMC induced mRNA expression of Nrf2 and its downstream effectors HO-1 and Nqo1, as well as reduced the levels of Keap1 protein detected in renal tissue. The present data demonstrate HMC is a potential compound for the treatment of acute renal damage caused by diclofenac, a routinely prescribed non-steroidal anti-inflammatory drug.

RvD1 disrupts nociceptor neuron and macrophage activation and neuroimmune communication, reducing pain and inflammation in gouty arthritis in mice.

BACKGROUND AND PURPOSE: Gouty arthritis is characterized by an intense inflammatory response to monosodium urate crystals (MSU), which induces severe pain. Current therapies are often ineffective in reducing gout-related pain. Resolvin D1 (RvD1) is a specialized pro-resolving lipid mediator with anti-inflammatory and analgesic proprieties. In this study, we evaluated the effects and mechanisms of action of RvD1 in an experimental mouse model of gouty arthritis, an aim that was not pursued previously in the literature. EXPERIMENTAL APPROACH: Male mice were treated with RvD1 (intrathecally or intraperitoneally) before or after intraarticular stimulation with MSU. Mechanical hyperalgesia was assessed using an electronic von Frey aesthesiometer. Leukocyte recruitment was determined by knee joint wash cell counting and immunofluorescence. IL-1ß production was measured by ELISA. Phosphorylated NF-kB and apoptosis-associated speck-like protein containing CARD (ASC) were detected by immunofluorescence, and mRNA expression was determined by RT-qPCR. CGRP release was determined by EIA and immunofluorescence. MSU crystal phagocytosis was evaluated by confocal microscopy. KEY RESULTS: RvD1 inhibited MSU-induced mechanical hyperalgesia in a dose- and time-dependent manner by reducing leukocyte recruitment and IL-1ß production in the knee joint. Intrathecal RvD1 reduced the activation of peptidergic neurons and macrophages as well as silenced nociceptor to macrophage communication and macrophage function. CGRP stimulated MSU phagocytosis and IL-1ß production by macrophages. RvD1 downmodulated this phenomenon directly by acting on macrophages, and indirectly by inhibiting CGRP release and CGRP-dependent activation of macrophages. CONCLUSIONS AND IMPLICATIONS: This study reveals a hitherto unknown neuro-immune axis in gouty arthritis that is targeted by RvD1.

Pimenta pseudocaryophyllus (Gomes) Landrum extract inhibits inflammatory pain in mice: targeting neutrophil recruitment, oxidative stress, and cytokine production.

Pimenta pseudocaryophyllus (Gomes) Landrum is a Brazilian native plant. The mechanisms by which it promotes analgesia are unknown. We demonstrated the analgesic effect of P. pseudocaryophyllus dried extract (3 mg/kg; i.p.) in the following models of inflammatory pain (maximal inhibition): phenyl-p-benzoquinone (89%), formalin (72% - 1st phase and 96% - 2nd phase for flinches, and 50% - 1st phase and 71% - 2nd phase for licking behavior), complete Freund's adjuvant (95% - flinches and 33% - licking behavior), and carrageenin (56% - mechanical and 85% - thermal hyperalgesia) without motor impairment. Its analgesic effect depends on inhibiting neutrophil recruitment (95% - histopathology, 83% - myeloperoxidase activity, and 80% - LysM-eGFP mice), oxidative stress (86% - GSH and 98% - superoxide anion), and cytokine production (35% - IL-33, 80% - TNF-α, and 95% - IL-1ß). The present study advances in understanding the analgesic mechanisms of P. pseudocaryophyllus.

Effect of running exercise on titanium dioxide (TiO2)-induced chronic arthritis and sarcopenia in mice. A titanium prosthesis loosening injury model study.

AIMS: This study aimed to investigate if titanium dioxide (TiO2) joint administration is a useful pre-clinical model to study sarcopenia-related chronic arthritis, and if exercise is a useful therapeutic approach against the pathogenesis of TiO2-induced arthritis and sarcopenia in mice. MAIN METHODS: Two experiments were conducted. Firstly, 36 female Swiss mice were randomly divided into a control group (n = 12) and two groups who received intra-articular TiO2 injections of 0.3-mg (n = 12) and 3-mg (n = 12), respectively. Mice were euthanized 4 and 8 weeks after TiO2 injections. Based on data of the first experiment, mice were exposed to four groups: control (C, n = 10), exercised (Ex, n = 10), injected with 3-mg of TiO2 (TiO2, n = 10), and injected with 3-mg of TiO2 and exercised (TiO2 + Ex, n = 10) for a total of 8-weeks. KEY FINDINGS: Eight-week of 3 mg of TiO2 joint administration promoted characteristics of chronic inflammation such as elevated histopathological score, inflammation, edema and pain. Hallmarks of sarcopenia were also observed such as muscle atrophy and loss of strength. Furthermore, voluntary exercise running reduced TiO2-induced chronic inflammation and pain, attenuating chronic arthritis-related muscle atrophy, strength loss and impairment of locomotion capacity. In addition, exercise was also able to prevent TiO2-induced collagen degradation, an important marker of functional and structural integrity loss of cartilage and chronic arthritis disease progression. SIGNIFICANCE: TiO2 joint administration mimed titanium prosthesis release-induced joint chronic arthritis and sarcopenia-related chronic arthritis, disturbances that were attenuated by voluntary exercise.

Association between IL-10 systemic low level and highest pain score in patients during symptomatic SARS-CoV-2 infection.

BACKGROUND: Despite the wide variety of Covid-19 symptoms, pain and the related mechanisms underlying unsettled nociceptive status are still under-prioritized. Understanding the complex network of Covid-19-related pain may result in new lines of study. It is unknown whether patient's immunological background influences pain in the acute phase of Covid-19, including musculoskeletal pain. Thus, we evaluated the blood levels of selected molecules that are upregulated in SARS-CoV-2 infection and analyzed a possible correlation with pain during Covid-19. METHODS: A cohort of 20 hospitalized patients with confirmed diagnoses for Covid-19 were evaluated in the context of pain. Visual analogic scale (VAS) was applied to quantitate pain level. Blood tests were used to determine the systemic levels of cytokines (IL-10 and IL-1ß), substance P, and leptin. The data were correlated when appropriate to determine the association between pain-related markers and assessed pain intensity. RESULTS: Our findings show that systemic levels of IL-10 have strong negative correlation with pain intensity on Covid-19 patients. Additionally, we also show that leptin systemic levels were increased in Covid-19 patients with pain, however, with moderate positive correlation between these events. IL-1ß and SP levels did not differ between Covid-19 patients with or without pain. Men reported less pain compared to women. No differences were found between genders in the levels of the molecules evaluated in patients with pain. CONCLUSION: IL-10 has been described over the years as an anti-inflammatory and analgesic cytokine. The present data support that low IL-10 levels might contribute to Covid-19-associated pain.

Therapeutic Potential of Controlled Delivery Systems in Asthma: Preclinical Development of Flavonoid-Based Treatments.

Asthma is a chronic disease with increasing prevalence and incidence, manifested by allergic inflammatory reactions, and is life-threatening for patients with severe disease. Repetitive challenges with the allergens and limitation of treatment efficacy greatly dampens successful management of asthma. The adverse events related to several drugs currently used, such as corticosteroids and ß-agonists, and the low rigorous adherence to preconized protocols likely compromises a more assertive therapy. Flavonoids represent a class of natural compounds with extraordinary antioxidant and anti-inflammatory properties, with their potential benefits already demonstrated for several diseases, including asthma. Advanced technology has been used in the pharmaceutical field to improve the efficacy and safety of drugs. Notably, there is also an increasing interest for the application of these techniques using natural products as active molecules. Flavones, flavonols, flavanones, and chalcones are examples of flavonoid compounds that were tested in controlled delivery systems for asthma treatment, and which achieved better treatment results in comparison to their free forms. This review aims to provide a comprehensive understanding of the development of novel controlled delivery systems to enhance the therapeutic potential of flavonoids as active molecules for asthma treatment.

Resolvin D5 (RvD5) Reduces Renal Damage Caused by LPS Endotoxemia in Female Mice.

In self-revolving gram-negative Escherichia coli infection, Resolvin D5 (RvD5) was found to enhance bacteria phagocytosis and reduce the production of inflammatory mediators, contributing to the resolution of infection. LPS (lipopolysaccharide) is a gram-negative bacterial structure product which activates the immune system and, at high doses, leads to endotoxemia. To our knowledge, the effect of RvD5 against LPS endotoxemia has not been investigated to date. Female Swiss mice received an i.p. treatment with RvD5 (0.1, 1 or 10 ng/animal). After 1 h, they were stimulated with LPS (10 mg/kg, i.v.), and samples were collected after additional 6 h. The resulting data demonstrated that RvD5 protected the kidneys (urea and creatinine serum levels) from tissue injury. These effects were related to an improvement in histopathological parameters and a reduction of enzymatic markers of leukocyte infiltration, pro-inflammatory cytokine (IL-1ß, TNF-α, and IL-6) production, and oxidative stress. Antioxidant markers were also increased by RvD5, but IL-10 (an anti-inflammatory cytokine) levels were unaltered. We also observed that RvD5 reduced the infiltration of CD45+ hematopoietic cells into the kidneys, reduced the activation of NFκB and promoted the Nrf2 pathway by reducing Keap-1 levels. Our data indicate that RvD5 may be a therapeutic possibility to reduce kidney lesions in LPS endotoxemia.

Brief research report: Repurposing pentoxifylline to treat intense acute swimming-Induced delayed-onset muscle soreness in mice: Targeting peripheral and spinal cord nociceptive mechanisms.

In this study, we pursue determining the effect of pentoxifylline (Ptx) in delayed-onset muscle soreness (DOMS) triggered by exposing untrained mice to intense acute swimming exercise (120 min), which, to our knowledge, has not been investigated. Ptx treatment (1.5, 4.5, and 13.5 mg/kg; i.p., 30 min before and 12 h after the session) reduced intense acute swimming-induced mechanical hyperalgesia in a dose-dependent manner. The selected dose of Ptx (4.5 mg/kg) inhibited recruitment of neutrophils to the muscle tissue, oxidative stress, and both pro- and anti-inflammatory cytokine production in the soleus muscle and spinal cord. Furthermore, Ptx treatment also reduced spinal cord glial cell activation. In conclusion, Ptx reduces pain by targeting peripheral and spinal cord mechanisms of DOMS.

Redox interactions of immune cells and muscle in the regulation of exercise-induced pain and analgesia: implications on the modulation of muscle nociceptor sensory neurons.

The mechanistic interactions among redox status of leukocytes, muscle, and exercise in pain regulation are still poorly understood and limit targeted treatment. Exercise benefits are numerous, including the treatment of chronic pain. However, unaccustomed exercise may be reported as undesirable as it may contribute to pain. The aim of the present review is to evaluate the relationship between oxidative metabolism and acute exercise-induced pain, and as to whether improved antioxidant capacity underpins the analgesic effects of regular exercise. Preclinical and clinical studies addressing relevant topics on mechanisms by which exercise modulates the nociceptive activity and how redox status can outline pain and analgesia are discussed, in sense of translating into refined outcomes. Emerging evidence points to the role of oxidative stress-induced signaling in sensitizing nociceptor sensory neurons. In response to acute exercise, there is an increase in oxidative metabolism, and consequently, pain. Instead, regular exercise can modulate redox status in favor of antioxidant capacity and repair mechanisms, which have consequently increased resistance to oxidative stress, damage, and pain. Data indicate that acute sessions of unaccustomed prolonged and/or intense exercise increase oxidative metabolism and regulate exercise-induced pain in the post-exercise recovery period. Further, evidence demonstrates regular exercise improves antioxidant status, indicating its therapeutic utility for chronic pain disorders. An improved comprehension of the role of redox status in exercise can provide helpful insights into immune-muscle communication during pain modulatory effects of exercise and support new therapeutic efforts and rationale for the promotion of exercise.

Peripheral mechanisms involved in Tityus bahiensis venom-induced pain.

Scorpionism is a public health burden in Brazil. Tityus bahiensis is responsible for most accidents in the Southeastern region of Brazil. Here, the hyperalgesic mechanisms of Tityus bahiensis venom were investigated, focusing on the role of pro-inflammatory cytokines (tumor necrosis factor alpha [TNF-α] and interleukin 1 beta [IL-1ß]) and activation of the transcription factor NFκB. Intraplantar (i.pl.) administration of Tityus bahiensis venom (0.2, 0.6, 1.2 and 2.4 µg/20 µL i.pl.) induced mechanical hyperalgesia and thermal hyperalgesia. The 2.4 µg dose of Tityus bahiensis venom induced overt pain-like behavior and increased myeloperoxidase (MPO) and N-acetyl-beta-D-glucosaminidase (NAG) activities, TNF-α and IL-1ß levels in the paw tissue. Systemic pre-treatment with etanercept (soluble TNF-α receptor; 10 mg/kg), IL-1ra (IL-1 receptor antagonist; 30 mg/kg) and pyrrolidine dithiocarbamate (PDTC, nuclear factor kappa B [NFκB] inhibitor; 100 mg/kg) inhibited Tityus bahiensis venom-induced mechanical and thermal hyperalgesia, MPO and NAG activity and overt pain-like behavior. These data demonstrate the involvement of TNF-α and IL-1ß signaling as well as NFκB activation in Tityus bahiensis venom-induced mechanical and thermal hyperalgesia, overt pain-like behavior, and MPO activity and NAG activity, indicating thus, that targeting these mechanisms might contribute to reducing the pain in this scorpionism.

Jararhagin, a snake venom metalloproteinase, induces mechanical hyperalgesia in mice with the neuroinflammatory contribution of spinal cord microglia and astrocytes.

Jararhagin is a hyperalgesic metalloproteinase from Bothrops jararaca venom. In rodents, jararhagin induces nociceptive behaviors that correlate with an increase in peripheral cytokine levels. However, the role of the spinal cord glia in pain processing after peripheral stimulus of jararhagin has not been investigated. Aiming to explore this proposal, mice received intraplantar (i.pl.) injection of jararhagin and the following parameters were evaluated: hyperalgesia, spinal cord TNF-α, IL-1ß levels, and CX3CR1, GFAP and p-NFκB activation. The effects of intrathecal (i.t.) injection of TNF-α soluble receptor (etanercept), IL-1 receptor antagonist (IL-1Ra), and inhibitors of NFκB (PDTC), microglia (minocycline) and astrocytes (α-aminoadipate) were investigated. Jararhagin inoculation induced cytokine production (TNF-α and IL-1ß) in the spinal cord, which was reduced by treatment with PDTC (40% and 50%, respectively). Jararhagin mechanical hyperalgesia and cytokine production were inhibited by treatment with etanercept (67%), IL-1Ra (60%), PDTC (70%), minocycline (60%) and α-aminoadipate (45%). Furthermore, jararhagin induced an increase in p-NFκB, CX3CR1 and GFAP detection in the spinal cord indicating activation of NFκB, microglia and astrocytes. These results demonstrate for the first time that jararhagin-induced mechanical hyperalgesia is dependent on spinal cord activation of glial cells, consequent NFκB activation, and cytokine production in mice.