Intestinal Permeability and IgA Provoke Immune Vasculitis Linked to Cardiovascular Inflammation.

Recent experimental data and clinical, genetic, and transcriptome evidence from patients converge to suggest a key role of interleukin-1ß (IL-1ß) in the pathogenesis of Kawasaki disease (KD). However, the molecular mechanisms involved in the development of cardiovascular lesions during KD vasculitis are still unknown. Here, we investigated intestinal barrier function in KD vasculitis and observed evidence of intestinal permeability and elevated circulating secretory immunoglobulin A (sIgA) in KD patients, as well as elevated sIgA and IgA deposition in vascular tissues in a mouse model of KD vasculitis. Targeting intestinal permeability corrected gut permeability, prevented IgA deposition and ameliorated cardiovascular pathology in the mouse model. Using genetic and pharmacologic inhibition of IL-1ß signaling, we demonstrate that IL-1ß lies upstream of disrupted intestinal barrier function, subsequent IgA vasculitis development, and cardiac inflammation. Targeting mucosal barrier dysfunction and the IL-1ß pathway may also be applicable to other IgA-related diseases, including IgA vasculitis and IgA nephropathy.

NLRP3 Inflammasome Mediates Immune-Stromal Interactions in Vasculitis.

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Hesperidin Methyl Chalcone Reduces the Arthritis Caused by TiO2 in Mice: Targeting Inflammation, Oxidative Stress, Cytokine Production, and Nociceptor Sensory Neuron Activation.

Arthroplasty is an orthopedic surgical procedure that replaces a dysfunctional joint by an orthopedic prosthesis, thereby restoring joint function. Upon the use of the joint prosthesis, a wearing process begins, which releases components such as titanium dioxide (TiO2) that trigger an immune response in the periprosthetic tissue, leading to arthritis, arthroplasty failure, and the need for revision. Flavonoids belong to a class of natural polyphenolic compounds that possess antioxidant and anti-inflammatory activities. Hesperidin methyl chalcone's (HMC) analgesic, anti-inflammatory, and antioxidant effects have been investigated in some models, but its activity against the arthritis caused by prosthesis-wearing molecules, such as TiO2, has not been investigated. Mice were treated with HMC (100 mg/kg, intraperitoneally (i.p.)) 24 h after intra-articular injection of 3 mg/joint of TiO2, which was used to induce chronic arthritis. HMC inhibited mechanical hyperalgesia, thermal hyperalgesia, joint edema, leukocyte recruitment, and oxidative stress in the knee joint (alterations in gp91phox, GSH, superoxide anion, and lipid peroxidation) and in recruited leukocytes (total reactive oxygen species and GSH); reduced patellar proteoglycan degradation; and decreased pro-inflammatory cytokine production. HMC also reduced the activation of nociceptor-sensory TRPV1+ and TRPA1+ neurons. These effects occurred without renal, hepatic, or gastric damage. Thus, HMC reduces arthritis triggered by TiO2, a component released upon wearing of prosthesis.

Therapeutic Potential of Flavonoids in Pain and Inflammation: Mechanisms of Action, Pre-Clinical and Clinical Data, and Pharmaceutical Development.

Pathological pain can be initiated after inflammation and/or peripheral nerve injury. It is a consequence of the pathological functioning of the nervous system rather than only a symptom. In fact, pain is a significant social, health, and economic burden worldwide. Flavonoids are plant derivative compounds easily found in several fruits and vegetables and consumed in the daily food intake. Flavonoids vary in terms of classes, and while structurally unique, they share a basic structure formed by three rings, known as the flavan nucleus. Structural differences can be found in the pattern of substitution in one of these rings. The hydroxyl group (-OH) position in one of the rings determines the mechanisms of action of the flavonoids and reveals a complex multifunctional activity. Flavonoids have been widely used for their antioxidant, analgesic, and anti-inflammatory effects along with safe preclinical and clinical profiles. In this review, we discuss the preclinical and clinical evidence on the analgesic and anti-inflammatory proprieties of flavonoids. We also focus on how the development of formulations containing flavonoids, along with the understanding of their structure-activity relationship, can be harnessed to identify novel flavonoid-based therapies to treat pathological pain and inflammation.

The granulopoietic cytokine granulocyte colony-stimulating factor (G-CSF) induces pain: analgesia by rutin.

Rutin is a glycone form of the flavonol quercetin and it reduces inflammatory pain in animal models. Therapy with granulocyte colony-stimulating factor (G-CSF) is known by the pain caused as its main side effect. The effect of rutin and its mechanisms of action were evaluated in a model of hyperalgesia induced by G-CSF in mice. The mechanical hyperalgesia induced by G-CSF was reduced by treatment with rutin in a dose-dependent manner. Treatment with both rutin + morphine or rutin + indomethacin, at doses that are ineffectual per se, significantly reduced the pain caused by G-CSF. The nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-ATP-sensitive potassium channel (KATP) signaling pathway activation is one of the analgesic mechanisms of rutin. Rutin also reduced the pro-hyperalgesic and increased anti-hyperalgesic cytokine production induced by G-CSF. Furthermore, rutin inhibited the activation of the nuclear factor kappa-light-chain enhancer of activated B cells (NFκB), which might explain the inhibition of the cytokine production. Treatment with rutin upregulated the decreased mRNA expression of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) combined with enhancement of the mRNA expression of the Nrf2 downstream target heme oxygenase (HO-1). Intraperitoneal (i.p.) treatment with rutin did not alter the mobilization of neutrophils induced by G-CSF. The analgesia by rutin can be explained by: NO-cGMP-PKG-KATP channel signaling activation, inhibition of NFκB and triggering the Nrf2/HO-1 pathway. The present study demonstrates rutin as a promising pharmacological approach to treat the pain induced by G-CSF without impairing its primary therapeutic benefit of mobilizing hematopoietic progenitor cells into the blood.

Spinal cord oligodendrocyte-derived alarmin IL-33 mediates neuropathic pain.

Neuropathic pain from injury to the peripheral and CNS represents a major health care issue. We have investigated the role of IL-33/IL-33 receptor (ST2) signaling in experimental models of neuropathic pain in mice. Chronic constriction injury (CCI) of the sciatic nerve induced IL-33 production in the spinal cord. IL-33/citrine reporter mice revealed that oligodendrocytes are the main cells expressing IL-33 within the spinal cord together with a minor expression by neurons, microglia. and astrocytes. CCI-induced mechanical hyperalgesia was reduced in IL-33R (ST2)(-/ -) mice compared with wild-type (WT) mice. Intrathecal treatment of WT mice with soluble IL-33 receptor (IL-33 decoy receptor) markedly reduced CCI-induced hyperalgesia. Consistent with these observations, intrathecal injection of IL-33 enhanced CCI hyperalgesia and induced hyperalgesia in naive mice. IL-33-mediated hyperalgesia during CCI was dependent on a reciprocal relationship with TNF-α and IL-1ß. IL-33-induced hyperalgesia was markedly attenuated by inhibitors of PI3K, mammalian target of rapamycin, MAPKs (p38, ERK, and JNK), NF-κB, and also by the inhibitors of glial cells (microglia and astrocytes). Furthermore, targeting these signaling pathways and cells inhibited IL-33-induced TNF-α and IL-1ß production in the spinal cord. Our study, therefore, reveals an important role of oligodendrocyte-derived IL-33 in neuropathic pain.

Pyrrolidine dithiocarbamate inhibits superoxide anion-induced pain and inflammation in the paw skin and spinal cord by targeting NF-κB and oxidative stress.

We evaluated the effect of pyrrolidine dithiocarbamate (PDTC) in superoxide anion-induced inflammatory pain. Male Swiss mice were treated with PDTC and stimulated with an intraplantar or intraperitoneal injection of potassium superoxide, a superoxide anion donor. Subcutaneous PDTC treatment attenuated mechanical hyperalgesia, thermal hyperalgesia, paw oedema and leukocyte recruitment (neutrophils and macrophages). Intraplantar injection of superoxide anion activated NF-κB and increased cytokine production (IL-1ß, TNF-α and IL-10) and oxidative stress (nitrite and lipid peroxidation levels) at the primary inflammatory foci and in the spinal cord (L4-L6). PDTC treatment inhibited superoxide anion-induced NF-κB activation, cytokine production and oxidative stress in the paw and spinal cord. Furthermore, intrathecal administration of PDTC successfully inhibited superoxide anion-induced mechanical hyperalgesia, thermal hyperalgesia and inflammatory response in peripheral foci (paw). These results suggest that peripheral stimulus with superoxide anion activates the local and spinal cord oxidative- and NF-κB-dependent inflammatory nociceptive mechanisms. PDTC targets these events, therefore, inhibiting superoxide anion-induced inflammatory pain in mice.

Vanillic Acid Inhibits Inflammatory Pain by Inhibiting Neutrophil Recruitment, Oxidative Stress, Cytokine Production, and NFκB Activation in Mice.

Vanillic acid (1) is a flavoring agent found in edible plants and fruits. It is an oxidized form of vanillin. Phenolic compounds form a substantial part of plant foods used as antioxidants with beneficial biological activities. These compounds have received considerable attention because of their role in preventing human diseases. Especially, 1 presents antibacterial, antimicrobial, and chemopreventive effects. However, the mechanisms by which 1 exerts its anti-inflammatory effects in vivo are incompletely understood. Thus, the effect of 1 was evaluated in murine models of inflammatory pain. Treatment with 1 inhibited the overt pain-like behavior induced by acetic acid, phenyl-p-benzoquinone, the second phase of the formalin test, and complete Freund's adjuvant (CFA). Treatment with 1 also inhibited carrageenan- and CFA-induced mechanical hyperalgesia, paw edema, myeloperoxidase activity, and N-acetyl-ß-D-glucosaminidase activity. The anti-inflammatory mechanisms of 1 involved the inhibition of oxidative stress, pro-inflammatory cytokine production, and NFκB activation in the carrageenan model. The present study demonstrated 1 presents analgesic and anti-inflammatory effects in a wide range of murine inflammation models, and its mechanisms of action involves antioxidant effects and NFκB-related inhibition of pro-inflammatory cytokine production.

Pimaradienoic acid inhibits inflammatory pain: inhibition of NF-κB activation and cytokine production and activation of the NO-cyclic GMP-protein kinase G-ATP-sensitive potassium channel signaling pathway.

Pimaradienoic acid (1) is a pimarane diterpene (ent-pimara-8(14),15-dien-19-oic acid) extracted at high amounts from various plants including Vigueira arenaria Baker. Compound 1 inhibited carrageenan-induced paw edema and acetic acid-induced abdominal writhing, which are its only known anti-inflammatory activities. Therefore, it is important to further investigate the analgesic effects of 1. Oral administration of 1 (1, 3, and 10 mg/kg) inhibited the acetic acid-induced writhing. This was also observed at 10 mg/kg via sc and ip routes. Both phases of the formalin- and complete Freund's adjuvant (CFA)-induced paw flinch and time spent licking the paw were inhibited by 1. Compound 1 inhibited carrageenan-, CFA-, and PGE2-induced mechanical hyperalgesia. Treatment with 1 inhibited carrageenan-induced production of TNF-α, IL-1ß, IL-33, and IL-10 and nuclear factor κB activation. Pharmacological inhibitors also demonstrated that the analgesic effects of 1 depend on activation of the NO-cyclic GMP-protein kinase G-ATP-sensitive potassium channel signaling pathway. Compound 1 did not alter plasma levels of AST, ALT, or myeloperoxidase activity in the stomach. These results demonstrate that 1 causes analgesic effects associated with the inhibition of NF-κB activation, reduction of cytokine production, and activation of the NO-cyclic GMP-protein kinase G-ATP-sensitive potassium channel signaling pathway.

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.

Long-term cardiovascular inflammation and fibrosis in a murine model of vasculitis induced by Lactobacillus casei cell wall extract.

Background: Kawasaki disease (KD), an acute febrile illness and systemic vasculitis, is the leading cause of acquired heart disease in children in industrialized countries. KD leads to the development of coronary artery aneurysms (CAA) in affected children, which may persist for months and even years after the acute phase of the disease. There is an unmet need to characterize the immune and pathological mechanisms of the long-term complications of KD. Methods: We examined cardiovascular complications in the Lactobacillus casei cell wall extract (LCWE) mouse model of KD-like vasculitis over 4 months. The long-term immune, pathological, and functional changes occurring in cardiovascular lesions were characterized by histological examination, flow cytometric analysis, immunofluorescent staining of cardiovascular tissues, and transthoracic echocardiogram. Results: CAA and abdominal aorta dilations were detected up to 16 weeks following LCWE injection and initiation of acute vasculitis. We observed alterations in the composition of circulating immune cell profiles, such as increased monocyte frequencies in the acute phase of the disease and higher counts of neutrophils. We determined a positive correlation between circulating neutrophil and inflammatory monocyte counts and the severity of cardiovascular lesions early after LCWE injection. LCWE-induced KD-like vasculitis was associated with myocarditis and myocardial dysfunction, characterized by diminished ejection fraction and left ventricular remodeling, which worsened over time. We observed extensive fibrosis within the inflamed cardiac tissue early in the disease and myocardial fibrosis in later stages. Conclusion: Our findings indicate that increased circulating neutrophil counts in the acute phase are a reliable predictor of cardiovascular inflammation severity in LCWE-injected mice. Furthermore, long-term cardiac complications stemming from inflammatory cell infiltrations in the aortic root and coronary arteries, myocardial dysfunction, and myocardial fibrosis persist over long periods and are still detected up to 16 weeks after LCWE injection.

The intestinal microbiota contributes to the development of immune-mediated cardiovascular inflammation and vasculitis in mice.

Alterations in the intestinal microbiota contribute to the pathogenesis of various cardiovascular disorders, but how they affect the development of Kawasaki disease (KD), an acute pediatric vasculitis, remains unclear. We report that depleting the gut microbiota reduces the development of cardiovascular inflammation in a murine model mimicking KD vasculitis. The development of cardiovascular lesions was associated with alterations in the intestinal microbiota composition and, notably, a decreased abundance of Akkermansia muciniphila and Faecalibacterium prausnitzii. Oral supplementation with either of these live or pasteurized individual bacteria, or with short-chain fatty acids (SCFAs) produced by them, attenuated cardiovascular inflammation. Treatment with Amuc_1100, the TLR-2 signaling outer membrane protein from A. muciniphila , also decreased the severity of vascular inflammation. This study reveals an underappreciated gut microbiota-cardiovascular inflammation axis in KD vasculitis pathogenesis and identifies specific intestinal commensals that regulate vasculitis in mice by producing metabolites or via extracellular proteins acting on gut barrier function. IN BRIEF: It remains unclear whether changes in the intestinal microbiota composition are involved in the development of cardiovascular lesions associated with Kawasaki disease (KD), an immune-mediated vasculitis. Jena et al. observe alterations in the intestinal microbiota composition of mice developing vasculitis, characterized by reduced A. muciniphila and F. prausnitzii . Oral supplementation with either of these bacteria, live or pasteurized, or with bacteria-produced short-chain fatty acids (SCFAs) or Amuc_1100, the TLR-2 signaling outer membrane protein of A. muciniphila , was sufficient to alleviate the development of cardiovascular lesions in mice by promoting intestinal barrier function. HIGHLIGHTS: Absence or depletion of the microbiota decreases the severity of vasculitis in a murine model mimicking KD vasculitis. Supplementation of B. wadsworthia and B. fragilis promotes murine KD vasculitis. Decreased abundances of F. prausnitzii and A. muciniphila are associated with the development of cardiovascular lesions in mice. Supplementation with either live or pasteurized A. muciniphila and F. prausnitzii, or the TLR-2 signaling Amuc_1100, reduces the severity of vasculitis by promoting gut barrier function.

Vitexin inhibits inflammatory pain in mice by targeting TRPV1, oxidative stress, and cytokines.

The flavonoid vitexin (1) is a flavone C-glycoside (apigenin-8-C-ß-D-glucopyranoside) present in several medicinal and other plants. Plant extracts containing 1 are reported to possess antinociceptive, anti-inflammatory, and antioxidant activities. However, the only evidence that 1 exhibits antinociceptive activity was demonstrated in the acetic acid-induced writhing model. Therefore, the analgesic effects and mechanisms of 1 were evaluated. In the present investigation, intraperitoneal treatment with 1 dose-dependently inhibited acetic acid-induced writhing. Furthermore, treatment with 1 also inhibited pain-like behavior induced by phenyl-p-benzoquinone, complete Freund's adjuvant (CFA), capsaicin (an agonist of transient receptor potential vanilloid 1, TRPV1), and both phases of the formalin test. It was also observed that inhibition of carrageenan-, capsaicin-, and chronic CFA-induced mechanical and thermal hyperalgesia occurred. Regarding the antinociceptive mechanisms of 1, it prevented the decrease of reduced glutathione levels, ferric-reducing ability potential, and free-radical scavenger ability, inhibited the production of hyperalgesic cytokines such as TNF-α, IL-1ß, IL-6, and IL-33, and up-regulated the levels of the anti-hyperalgesic cytokine IL-10. These results demonstrate that 1 exhibits an analgesic effect in a variety of inflammatory pain models by targeting TRPV1 and oxidative stress and by modulating cytokine production.

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.

Intense Acute Swimming Induces Delayed-Onset Muscle Soreness Dependent on Spinal Cord Neuroinflammation.

Unaccustomed exercise involving eccentric contractions, high intensity, or long duration are recognized to induce delayed-onset muscle soreness (DOMS). Myocyte damage and inflammation in affected peripheral tissues contribute to sensitize muscle nociceptors leading to muscle pain. However, despite the essential role of the spinal cord in the regulation of pain, spinal cord neuroinflammatory mechanisms in intense swimming-induced DOMS remain to be investigated. We hypothesized that spinal cord neuroinflammation contributes to DOMS. C57BL/6 mice swam for 2 h to induce DOMS, and nociceptive spinal cord mechanisms were evaluated. DOMS triggered the activation of astrocytes and microglia in the spinal cord 24 h after exercise compared to the sham group. DOMS and DOMS-induced spinal cord nuclear factor κB (NFκB) activation were reduced by intrathecal treatments with glial inhibitors (fluorocitrate, α-aminoadipate, and minocycline) and NFκB inhibitor [pyrrolidine dithiocarbamate (PDTC)]. Moreover, DOMS was also reduced by intrathecal treatments targeting C-X3-C motif chemokine ligand 1 (CX3CL1), tumor necrosis factor (TNF)-α, and interleukin (IL)-1ß or with recombinant IL-10. In agreement, DOMS induced the mRNA and protein expressions of CX3CR1, TNF-α, IL-1ß, IL-10, c-Fos, and oxidative stress in the spinal cord. All these immune and cellular alterations triggered by DOMS were amenable by intrathecal treatments with glial and NFκB inhibitors. These results support a role for spinal cord glial cells, via NFκB, cytokines/chemokines, and oxidative stress, in DOMS. Thus, unveiling neuroinflammatory mechanisms by which unaccustomed exercise induces central sensitization and consequently DOMS.

The diterpene from Sphagneticola trilobata (L.) Pruski, kaurenoic acid, reduces lipopolysaccharide-induced peritonitis and pain in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Sphagneticola trilobata (L.) Pruski is a plant species belonging to the Asteraceae family. Kaurenoid acid (KA) is a diterpene metabolite and one of the active ingredients of Sphagneticola trilobata (L.) Pruski. Extracts containing KA are used in traditional medicine to treat pain, inflammation, and infection. AIM: The goal of the present study was to investigate the in vivo effects of KA (1-10 mg/kg, per oral gavage) upon LPS inoculation in mice by intraperitoneal (i.p.) or intraplantar (i.pl.; subcutaneous plantar injection) routes at the dose of 200 ng (200 µL or 25 µL, respectively). METHODS: In LPS paw inflammation, mechanical and thermal hyperalgesia MPO activity and oxidative imbalance (TBARS, GSH, ABTS and FRAP assays) were evaluated. In LPS peritonitis we evaluated leukocyte migration, cytokine production, oxidative stress, and NF-κB activation. RESULTS: KA inhibited LPS-induced mechanical and thermal hyperalgesia, MPO activity and modulated redox status in the mice paw. Pre- and post-treatment with KA inhibited migration of neutrophils and monocytes in LPS peritonitis. KA inhibited the pro-inflammatory/hyperalgesic cytokine (e.g., TNF-α, IL-1ß and IL-33) production while enhanced anti-inflammatory/analgesic cytokine IL-10 in peritoneal cavity. In agreement with the effect of KA over pro-inflammatory cytokines it inhibited oxidative stress (total ROS, superoxide production and superoxide positive cells) and NF-κB activation during peritonitis. CONCLUSION: KA efficiently dampens LPS-induced peritonitis and hyperalgesia in vivo, suggesting it as a suitable candidate to control excessive inflammation and pain during gram-negative bacterial infections and bringing mechanistic explanation to the ethnopharmacological application of Sphagneticola trilobata (L.) Pruski in inflammation and infection.

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.

Experimental Trypanosoma cruzi Infection Induces Pain in Mice Dependent on Early Spinal Cord Glial Cells and NFκB Activation and Cytokine Production.

The neglected tropical infirmity Chagas disease (CD) presents high mortality. Its etiological agent T. cruzi is transmitted by infected hematophagous insects. Symptoms of the acute phase of the infection include fever, fatigue, body aches, and headache, making diagnosis difficult as they are present in other illnesses as well. Thus, in endemic areas, individuals with undetermined pain may be considered for CD. Although pain is a characteristic symptom of CD, its cellular and molecular mechanisms are unknown except for demonstration of a role for peripheral TNF-α in CD pain. In this study, we evaluate the role of spinal cord glial cells in experimental T. cruzi infection in the context of pain using C57BL/6 mice. Pain, parasitemia, survival, and glial and neuronal function as well as NFκB activation and cytokine/chemokine production were assessed. T. cruzi infection induced chronic mechanical and thermal hyperalgesia. Systemic TNF-α and IL-1ß peaked 14 days postinfection (p.i.). Infected mice presented increased spinal gliosis and NFκB activation compared to uninfected mice at 7 days p.i. Glial and NFκB inhibitors limited T. cruzi-induced pain. Nuclear phosphorylated NFκB was detected surrounded by glia markers, and glial inhibitors reduced its detection. T. cruzi-induced spinal cord production of cytokines/chemokines was also diminished by glial inhibitors. Dorsal root ganglia (DRG) neurons presented increased activity in infected mice, and the production of inflammatory mediators was counteracted by glial/NFκB inhibitors. The present study unveils the contribution of DRG and spinal cord cellular and molecular events leading to pain in T. cruzi infection, contributing to a better understanding of CD pathology.

[Ru(bpy)2(NO)SO3](PF6), a Nitric Oxide Donating Ruthenium Complex, Reduces Gout Arthritis in Mice.

Monosodium urate crystals (MSU) deposition induces articular inflammation known as gout. This disease is characterized by intense articular inflammation and pain by mechanisms involving the activation of the transcription factor NFκB and inflammasome resulting in the production of cytokines and oxidative stress. Despite evidence that MSU induces iNOS expression, there is no evidence on the effect of nitric oxide (NO) donors in gout. Thus, the present study evaluated the effect of the ruthenium complex donor of NO {[Ru(bpy)2(NO)SO3](PF6)} (complex I) in gout arthritis. Complex I inhibited in a dose-dependent manner MSU-induced hypersensitivity to mechanical stimulation, edema and leukocyte recruitment. These effects were corroborated by a decrease of histological inflammation score and recruitment of Lysm-eGFP+ cells. Mechanistically, complex I inhibited MSU-induced mechanical hypersensitivity and joint edema by triggering the cGMP/PKG/ATP-sensitive K (+) channels signaling pathway. Complex I inhibited MSU-induced oxidative stress and pro-inflammatory cytokine production in the knee joint. These data were supported by the observation that complex I inhibited MSU-induced NFκB activation, and IL-1ß expression and production. Complex I also inhibited MSU-induced activation of pro-IL-1ß processing. Concluding, the present data, to our knowledge, is the first evidence that a NO donating ruthenium complex inhibits MSU-induced articular inflammation and pain. Further, complex I targets the main physiopathological mechanisms of gout arthritis. Therefore, it is envisaged that complex I and other NO donors have therapeutic potential that deserves further investigation.