Effects of different doses of complete Freund's adjuvant on nociceptive behaviour and inflammatory parameters in polyarthritic rat model mimicking rheumatoid arthritis

A Novel Diabetic Arthritic Model in Rats Induced by Streptozotocin, High-Fat Diet, and Complete Freund's Adjuvant

Introduction

Ankle arthrodesis is one of the treatments of choice, particularly in late-stage and unstable diabetic Charcot arthropathy. Unfortunately, poor healing capacity might play a role in the high nonunion rate (10-40%). The advancement in regenerative medicine opens a new horizon for enhancing fusion after ankle arthrodesis in patients with poor healing capacity. However, a suitable small animal model is warranted to study the effectivity of these regenerative medicine approaches. Streptozotocin (STZ)-induced diabetes models and adjuvant-induced arthritis models with complete Freund's adjuvant are two established models. However, no study has combined those two models to make a diabetic arthritic model that more closely resembles the condition in Charcot arthropathy.

Methods

Twenty male Sprague-Dawley rats were assigned into five groups, consisting of one control group, and four diabetic groups which were induced by STZ injection and a high-fat diet. Among these diabetic rats, two groups received complete Freund's adjuvant (CFA) injections to the left ankle of the hind limb. The control group, one of the diabetic-only groups, and one of the arthritic-diabetic-induced groups were euthanized at 4 weeks after STZ induction, and the remainder were euthanized 6 weeks after STZ induction. Clinical, radiological, and histological examinations were then compared in all five groups.

Results

Diabetic status was successfully achieved in the model, which was maintained until the completion of the study. The CFA-induced ankles were significantly larger than the contralateral ankles in all groups (p<0.05). Histopathological evaluation confirmed arthritic changes in the CFA-induced group with less variability after 4 weeks of arthritis induction.

Conclusion

This rat model of arthritic diabetic mimics the progressive and chronic nature of Charcot arthropathy in humans. This model can be further use to study treatments that might enhance the fusion rate in ankle arthrodesis in healing-defective patients such as those with diabetes.

Level of Clinical Evidence

5.

Trans-Chalcone (1-3-diphenyl-2-propen-1-one) as a Therapeutic Candidate in Joint Inflammation via Reduction of TNF-α, IL-1β, IL-6, and IL-17 in Rodents: An In Vivo Study by RT-PCR and ELISA analysis

Autoimmune disorders include vast and distinct illnesses and are characterized by an immune system-mediated attack on the body's own tissues. Because of their ability to impact any portion of the body, their clinical symptoms are incredibly varied. The variations in symptoms are normally linked with the release and activation of vasoactive, chemotactic substances and cytokines. Cytokines perform a multitude of vital biological tasks, such as immune response control, inflammation, proliferation, and tissue repair. The reversal of inflammatory cytokines and leukocyte infiltration into the inflamed tissue by natural compounds provides an effective remedy for autoimmune diseases. Here, the oral administration of trans-chalcone (TC) for 28 days was tested with gradually increasing doses (30, 60, and 120 mg/kg) in complete Freund's adjuvant (CFA)-provoked joint tissue stiffness in rats. Paw edema, arthritic index, joint stiffness, thermal and flexion pain, C-reactive protein, and rheumatoid factor (RF) levels were determined to check the tested drug effectiveness in a chronic inflammatory model. Molecular docking studies revealed strong binding affinity with inflammatory cytokines and mediators such as TNF-α, IL-17, COX-2, and iNOS; further, they were quantified at the mRNA level by RT-PCR and ELISA analysis. Oral administration of TC significantly ameliorated paw edema, thymus and spleen indices, joint stiffness, thermal and flexion pain, C-reactive protein, RF, mobility, and stance of the treated animals. This therapeutic effectiveness was linked with a reduction in the mRNA expression of proinflammatory cytokines such as IL-1β, IL-6, and IL-17. The findings of the reported research confirmed the effectiveness of TC in ameliorating joint stiffness and flexion pain by prominently lowering the inflammatory cytokines.

Exploring Localized Provoked Vulvodynia: Insights from Animal Model Research

Provoked vulvodynia represents a challenging chronic pain condition, characterized by its multifactorial origins. The inherent complexities of human-based studies have necessitated the use of animal models to enrich our understanding of vulvodynia's pathophysiology. This review aims to provide an exhaustive examination of the various animal models employed in this research domain. A comprehensive search was conducted on PubMed, utilizing keywords such as "vulvodynia", "chronic vulvar pain", "vulvodynia induction", and "animal models of vulvodynia" to identify pertinent studies. The search yielded three primary animal models for vulvodynia: inflammation-induced, allergy-induced, and hormone-induced. Additionally, six agents capable of triggering the condition through diverse pathways were identified, including factors contributing to hyperinnervation, mast cell proliferation, involvement of other immune cells, inflammatory cytokines, and neurotransmitters. This review systematically outlines the various animal models developed to study the pathogenesis of provoked vulvodynia. Understanding these models is crucial for the exploration of preventative measures, the development of novel treatments, and the overall advancement of research within the field.

Complex alterations in inflammatory pain and analgesic sensitivity in young and ageing female rats: involvement of ASIC3 and Nav1.8 in primary sensory neurons

OBJECTIVE AND DESIGN

Our aim was to determine an age-dependent role of Nav1.8 and ASIC3 in dorsal root ganglion (DRG) neurons in a rat pre-clinical model of long-term inflammatory pain.

METHODS

We compared 6 and 24 months-old female Wistar rats after cutaneous inflammation. We used behavioral pain assessments over time, qPCR, quantitative immunohistochemistry, selective pharmacological manipulation, ELISA and in vitro treatment with cytokines.

RESULTS

Older rats exhibited delayed recovery from mechanical allodynia and earlier onset of spontaneous pain than younger rats after inflammation. Moreover, the expression patterns of Nav1.8 and ASIC3 were time and age-dependent and ASIC3 levels remained elevated only in aged rats. In vivo, selective blockade of Nav1.8 with A803467 or of ASIC3 with APETx2 alleviated mechanical and cold allodynia and also spontaneous pain in both age groups with slightly different potency. Furthermore, in vitro IL-1β up-regulated Nav1.8 expression in DRG neurons cultured from young but not old rats. We also found that while TNF-α up-regulated ASIC3 expression in both age groups, IL-6 and IL-1β had this effect only on young and aged neurons, respectively.

CONCLUSION

Inflammation-associated mechanical allodynia and spontaneous pain in the elderly can be more effectively treated by inhibiting ASIC3 than Nav1.8.

A New 4-Thiazolidinone Derivative (Les-6490) as a Gut Microbiota Modulator: Antimicrobial and Prebiotic Perspectives

A novel 4-thiazolidinone derivative Les-6490 (pyrazol-4-thiazolidinone hybrid) was designed, synthesized, and characterized by spectral data. The compound was screened for its antimicrobial activity against some pathogenic bacteria and fungi and showed activity against Staphylococcus and Saccharomyces cerevisiae (the Minimum Inhibitory Concentration (MIC) 820 μM). The compound was studied in the rat adjuvant arthritis model (Freund's Adjuvant) in vivo. Parietal and fecal microbial composition using 16S rRNA metagenome sequences was checked. We employed a range of analytical techniques, including Taxonomic Profiling (Taxa Analysis), Diversity Metrics (Alpha and Beta Diversity Analysis), Multivariate Statistical Methods (Principal Coordinates Analysis, Principal Component Analysis, Non-Metric Multidimensional Scaling), Clustering Analysis (Unweighted Pair-group Method with Arithmetic Mean), and Comparative Statistical Approaches (Community Differences Analysis, Between Group Variation Analysis, Metastat Analysis). The compound significantly impacted an increasing level of anti-inflammatory microorganisms (Blautia, Faecalibacterium prausnitzii, Succivibrionaceae, and Coriobacteriales) relative recovery of fecal microbiota composition. Anti-Treponemal activity in vivo was also noted. The tested compound Les-6490 has potential prebiotic activity with an indirect anti-inflammatory effect.

An update of murine models and their methodologies in immune-mediated joint damage and pain research

Murine models have played an indispensable role in the understanding of rheumatic and musculoskeletal disorders (RMD), elucidating the genetic, endocrine and biomechanical pathways involved in joint pathology and associated pain. To date, the available models in RMD can be classified as induced or spontaneous, both incorporating transgenic alternatives that improve specific insights. It is worth noting that the selection of the most appropriate model together with the evaluation of their specific characteristics and technical capabilities are crucial when designing the experiments. Furthermore, it is also imperative to consistently adhere to the ethical standards concerning animal experimentation. Recognizing the inherent limitation that any model can entirely encapsulates the complexity of the pathophysiology of these conditions, the aim of this review is to provide an updated overview on the methodology of current murine models in major arthropathies and their immune-mediated pathways, addressing to basic, translational and pharmacological research in joint damage and pain.

When inflammatory stressors dramatically change, disease phenotypes may transform between autoimmune hematopoietic failure and myeloid neoplasms

Aplastic anemia (AA) and hypoplastic myelodysplastic syndrome are paradigms of autoimmune hematopoietic failure (AHF). Myelodysplastic syndrome and acute myeloid leukemia are unequivocal myeloid neoplasms (MNs). Currently, AA is also known to be a clonal hematological disease. Genetic aberrations typically observed in MNs are detected in approximately one-third of AA patients. In AA patients harboring MN-related genetic aberrations, a poor response to immunosuppressive therapy (IST) and an increased risk of transformation to MNs occurring either naturally or after IST are predicted. Approximately 10%-15% of patients with severe AA transform the disease phenotype to MNs following IST, and in some patients, leukemic transformation emerges during or shortly after IST. Phenotypic transformations between AHF and MNs can occur reciprocally. A fraction of advanced MN patients experience an aplastic crisis during which leukemic blasts are repressed. The switch that shapes the disease phenotype is a change in the strength of extramedullary inflammation. Both AHF and MNs have an immune-active bone marrow (BM) environment (BME). In AHF patients, an inflamed BME can be evoked by infiltrated immune cells targeting neoplastic molecules, which contributes to the BM-specific autoimmune impairment. Autoimmune responses in AHF may represent an antileukemic mechanism, and inflammatory stressors strengthen antileukemic immunity, at least in a significant proportion of patients who have MN-related genetic aberrations. During active inflammatory episodes, normal and leukemic hematopoieses are suppressed, which leads to the occurrence of aplastic cytopenia and leukemic cell regression. The successful treatment of underlying infections mitigates inflammatory stress-related antileukemic activities and promotes the penetration of leukemic hematopoiesis. The effect of IST is similar to that of treating underlying infections. Investigating inflammatory stress-powered antileukemic immunity is highly important in theoretical studies and clinical practice, especially given the wide application of immune-activating agents and immune checkpoint inhibitors in the treatment of hematological neoplasms.

Ondansetron or beta-sitosterol antagonizes inflammatory responses in liver, kidney, lung and heart tissues of irradiated arthritic rats model

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disorder mainly affecting joints, yet the systemic inflammation can influence other organs and tissues. The objective of this study was to unravel the ameliorative capability of Ondansetron (O) or β-sitosterol (BS) against inflammatory reactions and oxidative stress that complicates Extra-articular manifestations (EAM) in liver, kidney, lung, and heart of arthritic and arthritic irradiated rats.

METHODS

This was accomplished by exposing adjuvant-induced arthritis (AIA) rats to successive weekly fractions of total body γ-irradiation (2 Gray (Gy)/fraction once per week for four weeks, up to a total dose of 8 Gy). Arthritic and/or arthritic irradiated rats were either treated with BS (40 mg/kg b.wt. /day, orally) or O (2 mg/kg) was given ip) or were kept untreated as model groups.

RESULTS

Body weight changes, paw circumference, oxidative stress indices, inflammatory response biomarkers, expression of Janus kinase-2 (JAK-2), Signal transducer and activator of transcription 3 (STAT3), high mobility group box1 (HMGB1), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), as well as pro- and anti-inflammatory mediators in the target organs, besides histopathological examination of ankle joints and extra-articular tissues. Treatment of arthritic and/or arthritic irradiated rats with BS or O powerfully alleviated changes in body weight gain, paw swelling, oxidative stress, inflammatory reactions, and histopathological degenerative alterations in articular and non-articular tissues.

CONCLUSION

The obtained data imply that BS or O improved the articular and EAM by regulating oxidative and inflammatory indices in arthritic and arthritic irradiated rats.

Clinical Evaluation of Collagen-Induced Arthritis in Female Lewis Rats: A Comprehensive Analysis of Disease Progression and Severity

OBJECTIVE

The collagen-induced arthritis (CIA) model is the most commonly studied autoimmune model of rheumatoid arthritis (RA). In this study, we investigated the usefulness of collagen type II emulsified in Freund's incomplete adjuvant (CII/IFA) as a suitable method for establishing RA in Lewis rats. The aim of the present study was to present a straightforward and effective method for inducing CIA in rats.

MATERIALS AND METHODS

In this experimental study, animals were divided into two equal groups (n=5); control and CIA. Five rats were injected intradermally at the base of the tail with a 0.2 ml CII/IFA emulsion. On the seventh day, a 0.1 ml CII/IFA emulsion booster was injected. Arthritis symptoms that arose were evaluated at clinical, histological, radiological, and at protein expression levels to find out if the disease had been induced successfully.

RESULTS

Our finding showed a decreasing trend in the body weight during the RA induction period, while the arthritis score and paw thickness were increased during this period. The results of the enzyme-linked immunosorbent assay (ELISA) for serum samples revealed that the levels of proinflammatory cytokines, interleukin (IL)-1β, IL-6, IL-17, and tumor necrosis factor (TNF)-α and anti-CII IgG were significantly increased in CIA rats compared to the control group. After CIA induction, the level of anti-inflammatory protein IL-10 was decreased significantly. Radiographic examination of the hind paws showed soft tissue swelling, bone erosion, and osteophyte formation in CIA rats. Additionally, based on histological evaluations, the hind paws of the CIA group showed pannus formation, synovial hyperplasia, and bone and cartilage destruction.

CONCLUSION

It seems that CII/IFA treatment can be an appropriate and effective method to induce RA disease in Lewis rats. This well-established and well-characterized CIA model in female Lewis rats could be considered to study aspects of RA and develop novel anti-arthritic agents.

Comprehensive phytochemical characterization of Persea americana Mill. fruit via UPLC/HR-ESI-MS/MS and anti-arthritic evaluation using adjuvant-induced arthritis model

Persea americana Mill. (avocado fruit) has many health benefits when added to our diet due to various pharmacological activities, such as preventing bone loss and inflammation, modulating immune response and acting as an antioxidant. In the current study, the total ethanol extract (TEE) of the fruit was investigated for in vitro antioxidant and anti-inflammatory activity via DPPH and cyclooxygenase enzyme inhibition. Biological evaluation of the antiarthritic effect of the fruit extract was further investigated in vivo using Complete Freund's Adjuvant (CFA) arthritis model, where the average percentages of body weight change, inhibition of paw edema, basal paw diameter/weight and spleen index were estimated for all animal groups. Inflammatory mediators such as serum IL-6 and TNF-α were also determined, in addition to histopathological examination of the dissected limbs isolated from all experimental animals. Eighty-one metabolites belonging to different chemical classes were detected in the TEE of P. americana fruit via UPLC/HR-ESI-MS/MS. Two classes of lyso-glycerophospholipids; lyso-glycerophosphoethanolamines and lysoglycerophosphocholines were detected for the first time in avocado fruit in the positive mode. The TEE of fruit exhibited significant antioxidant and anti-inflammatory activity in vitro. In vivo anti-arthritic activity of the fruit TEE improved paw parameters, inflammatory mediators and spleen index. Histopathological findings showed marked improvements in the arthritic condition of the excised limbs. Therefore, avocado fruit could be proposed to be a powerful antioxidant and antiarthritic natural product.

In vitro-in vivo assessments of apocynin-hybrid nanoparticle-based gel as an effective nanophytomedicine for treatment of rheumatoid arthritis

Apocynin (APO), a well-known bioactive plant-based phenolic phytochemical with renowned anti-inflammatory and antioxidant pharmacological activities, has recently emerged as a specific nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase inhibitor. As far as we know, no information has been issued yet regarding its topical application as a nanostructured-based delivery system. Herein, APO-loaded Compritol® 888 ATO (lipid)/chitosan (polymer) hybrid nanoparticles (APO-loaded CPT/CS hybrid NPs) were successfully developed, characterized, and optimized, adopting a fully randomized design (32) with two independent active parameters (IAPs), namely, CPT amount (XA) and Pluronic® F-68 (PF-68) concentration (XB), at three levels. Further in vitro-ex vivo investigation of the optimized formulation was performed before its incorporation into a gel base matrix to prolong its residence time with consequent therapeutic efficacy enhancement. Subsequently, scrupulous ex vivo-in vivo evaluations of APO-hybrid NPs-based gel (containing the optimized formulation) to scout out its momentous activity as a topical nanostructured system for beneficial remedy of rheumatoid arthritis (RA) were performed. Imperatively, the results support an anticipated effectual therapeutic activity of the APO-hybrid NPs-based gel formulation against Complete Freund's Adjuvant-induced rheumatoid arthritis (CFA-induced RA) in rats. In conclusion, APO-hybrid NPs-based gel could be considered a promising topical nanostructured system to break new ground for phytopharmaceutical medical involvement in inflammatory-dependent ailments.

Enalapril attenuated CFA provoked arthritic manifestation by modulating proinflammatory and anti-inflammatory cytokine network

Enalapril with documented anti-inflammatory potential was evaluated in current investigation to explore its anti-arthritic efficacy. For anti-arthritic evaluation of enalapril, CFA-instigated arthritic model was employed after which various parameters comprising paw volume, body weight, arthritic index, hematological and biochemical parameters, radiographic analysis and level of various cytokines were estimated. Enalapril demonstrated significant (p˂0.001) anti-arthritic activity by suppressing paw volume, arthritic index while preserved CFA instigated weight loss. Likewise, enalapril also normalized the hematological and biochemical alterations, suppressed the level of proinflammatory cytokines with elevation of anti-inflammatory cytokines. Radiographic and histopathological analysis also further validates the anti-arthritic attribute of enalapril where enalapril preserved the normal architecture of arthritis induced joints. Outcomes of the study pointed out a notable anti-arthritic activity of enalapril. However detailed mechanistic studies are still required to point out the exact mechanism of action.

Electrical Stimulation of the Auricular Branch Vagus Nerve Using Random and Alternating Frequencies Triggers a Rapid Onset and Pronounced Antihyperalgesia via Peripheral Annexin A1-Formyl Peptide Receptor 2/ALX Pathway in a Mouse Model of Persistent Inflammatory Pain

This study evaluated the antihyperalgesic and anti-inflammatory effects of percutaneous vagus nerve electrical stimulation (pVNS) by comparing the effects of alternating and random frequencies in an animal model of persistent inflammatory hyperalgesia. The model was induced by Freund's complete adjuvant (CFA) intraplantar (i.pl.) injection. Mice were treated with different protocols of time (10, 20, or 30 min), ear laterality (right, left or both), and frequency (alternating or random). Mechanical hyperalgesia was evaluated, and some groups received i.pl. WRW4 (FPR2/ALX antagonist) to determine the involvement. Edema, paw surface temperature, and spontaneous locomotor activity were evaluated. Interleukin-1β, IL-6, IL-10, and IL4 levels were verified by enzyme-linked immunosorbent assay. AnxA1, FPR2/ALX, neutrophil, M1 and M2 phenotype macrophage, and apoptotic cells markers were identified using western blotting. The antihyperalgesic effect pVNS with alternating and random frequency effect is depending on the type of frequency, time, and ear treated. The pVNS random frequency in the left ear for 10 min had a longer lasting antihyperalgesic effect, superior to classical stimulation using alternating frequency and the FPR2/ALX receptor was involved in this effect. There was a reduction in the levels of pro-inflammatory cytokines and an increase in the immunocontent of AnxA1 and CD86 in mice paw. pVNS with a random frequency in the left ear for 10 min showed to be optimal for inducing an antihyperalgesic effect. Thus, the random frequency was more effective than the alternating frequency. Therefore, pVNS may be an important adjunctive treatment for persistent inflammatory pain.

Evidence for Endogenous Opioid Dependence Related to Latent Sensitization in a Rat Model of Chronic Inflammatory Pain

Studies performed in a mouse model of chronic inflammatory pain induced by intraplantar injection of complete Freund's adjuvant (CFA) have shown that constitutive activation of the endogenous opioid signaling, besides serving as a mechanism of endogenous analgesia that tonically represses pain sensitization, also generates a state of endogenous opioid dependence. Since species-related differences concerning pain biology and addictive behaviors occur between mice and rats, the present study explored whether the coexistence of endogenous opioid analgesia and endogenous opioid dependence also characterizes a homologous rat model. To this aim, CFA-injured Wistar rats were treated with either 3 mg/kg or 10 mg/kg of the opioid receptor inverse agonist naltrexone (NTX) during the pain remission phase and monitored for 60 min for possible withdrawal behaviors. At 3 mg/kg, NTX, besides inducing the reinstatement of mechanical allodynia, also caused a distinct appearance of ptosis, with slight but nonsignificant changes to the occurrence of teeth chatters and rearing. On the other hand, 10 mg/kg of NTX failed to unmask pain sensitization and induced significantly lower levels of ptosis than 3 mg/kg. Such an NTX-related response pattern observed in the rat CFA model seems to differ substantially from the pattern previously described in the mouse CFA model. This supports the knowledge that mice and rats are not identical in terms of pharmacological response and stresses the importance of choosing the appropriate species for preclinical pain research purposes depending on the scientific question being asked.

Novel mannich-based derivative of 2-mercaptobenzimidazole (AK7): a new candidate for the treatment of inflammatory arthritis owing to its NF-κB1 inhibitory potential

This study investigated the anti-arthritic potential of novel mannich-based derivatives of 2-mercaptobenzimidazole (AK7 and AK9) in rats. The compounds were characterized by NMR and FTIR spectroscopies and their acute anti-inflammatory effects were measured by carrageenan (CRG)-induced paw edema model. The most potent doses of AK7 and AK9 were subsequently evaluated in the complete Freund's adjuvant (CFA)-induced inflammatory arthritis model. AK7 and AK9 inhibited CRG-induced inflammation in a dose-dependent fashion and a similar reduction in CFA-induced paw inflammation was observed. Moreover, X-ray and histopathological analyses of AK7-treated animals displayed normal joint structure whereas AK9, despite of its anti-inflammatory effects, failed to protect against cartilage destruction. Interestingly, biochemical analysis revealed a better safety profile for AK7 than for AK9 and methotrexate. Both compounds suppressed mRNA levels of pro-inflammatory mediators (IRAK1, NF-κB1, TNF-α, IL1B) while only AK7 reduced the transcript levels of interstitial collagenase (MMP1). Molecular docking analysis of AK7 and AK9 with TNF-α and MMP1 also supported the experimental data. These findings clearly highlight the beneficial effects of AK7 in the prevention and/or treatment of inflammatory arthritis.

Improving safety of oil adjuvant-based vaccines

High adjuvant reactogenicity is the main limitation for increasing the effectiveness of vaccine therapy. The aim was to reduce the immunotoxicity effects of complete Freunds adjuvant (CFA) in warm-blooded animals. Materials and methods. The study examined Wistar rats by dividing animals into negative control (solvents); positive control (single subcutaneous CFA injection of 0.1 ml/200 g body weight (b.w.)); the minimum and maximum (per os administration of 1:4 citric and succinic acids in ratio of 17 and 88 mg/kg b.w. during 4 weeks after immunization of CFA) experiment. Body weight, hematological (complete blood count) and biochemical (hydroperoxides, malondialdehyde, catalase activity, mitochondrial dehydrogenase activity) parameters were dynamically investigated. At the end of the experiment, necropsy was performed and the relative internal organ mass coefficients were calculated. The spleen and connective tissue (knee joint) were examined histologically. The median, C25C75 quartiles, MannWhitney U-test were calculated. Results and discussion. it was found that parameters examined were within normal range in animals of negative control group. Immunization of warm-blooded animals with CFA was accompanied by transition of acute-to- chronic inflammatory reaction (week 3 and week 7, respectively). The total leukocyte count increased from 12.5 109 (negative control) up to 26.6 109/L (P = 0.01) on week 3 followed by its decline down to 19.2 109/L (P = 0.01) by week 7. Platelet count also increased significantly: from 506 109 (negative control) up to 656 109/L (P = 0.01, week 3) followed by decrease down to 610 109/L by week 7 (P = 0.01). Activation of lipid peroxidation was manifested by malondialdehyde (MDA) level elevated by 55.861.8% (P = 0.01); the general CFA-related toxic effect resulted in 11.7% weight loss (P = 0.01), spleen swelling and thymus reduction. Administration of antioxidant acids led to a dose-dependent decline in inflammation (leukocyte count at the minimum dosage 19.6 10920.9 109/L; at the maximum 16.6 10916.0 109/L), as well as normalized the platelet/leukocyte index up to 29.536.3 (positive control 24.6, negative control 40.5). The acid-related protective effect was also manifested as maintained body weight, activated catalase and inhibited lipid peroxidation. The therapeutic effect in alleviated degenerative changes in the spleen and connective tissue were revealed: reduced hemorrhagic focuses and swelling as well as preserved histoarchitectonics. Conclusion. The use of citric and succinic acids contributes to profoundly lowered CFA toxicity due to increased total antioxidant status, inhibited lipid peroxidation, improved mitochondrial metabolic activity, which ultimately lead to a decline in general systemic inflammation and allows to recommend such acids as immunoprotectors from oil adjuvant-coupled effects.

Dexmedetomidine alleviates hyperalgesia in arthritis rats through inhibition of the p38MAPK signaling pathway

BACKGROUND

Dexmedetomidine (DEX) has showed significant analgesic effects in neuropathic pain, but the underlying mechanism has remained elusive. Our present study aimed to explore the effect of DEX on hyperalgesia with the involvement of p38MAPK signaling pathway a rat model of monoarthritis (MA).

METHODS

MA rat model was induced by injection of Complete Freund's Adjuvant (CFA). Pathological changes of ma rats were observed by HE staining and Safranin-O/Fast Green staining. Ankle circumference, paw withdrawal latency (PWL) and paw withdrawal threshold (PWT) was measured to judge the degree of hyperalgesia in MA rats. Immunohistochemistry and ELISA were applied to observe the degree of inflammation in rats. Western blot analysis was conducted to detect expression of p38MAPK signaling pathway-related factors. The mechanism of p38MAPK signaling pathway in MA rats was observed via treatment of Anisomycin or SB203580 combined with DEX.

RESULTS

After 8 h of CFA induction, joint swelling and hyperalgesia occurred in rats. There were obvious pathological changes in the joint cavity, the joint cavity space became narrow and synovial bursa became rough. A large number of inflammatory cell infiltration was observed under microscope. After injection of DEX and SB203580, PWT and PWL was prolonged, the expression of serum inflammatory factors was decreased, and the expression of p38MAPK signaling pathway-related factors was decreased; while all the detected indexes were recovered in MA rats after treated with DEX and Anisomycin.

CONCLUSIONS

Our study provided evidence that DEX could alleviate hyperalgesia in arthritis rats through inhibition of the p38MAPK signaling pathway.