DHA protects against monosodium urate-induced inflammation through modulation of oxidative stress

Fatty acid traits mediate the effects of uric acid on cancers: a Mendelian randomization study

Introduction

Previous findings on the association between uric acid (UA) levels and cancer risk are conflicting. Moreover, the mechanisms underlying the interactions between UA levels, fatty acid traits, and cancer outcomes remain complex; it is still unclear whether elevated UA levels influence fatty acid traits and, thereby, contribute to an increased cancer risk. Therefore, we aimed to investigate the association between UA levels and cancer risk, with a specific focus on the potential mediating role of fatty acid traits.

Methods

We employed a Mendelian randomization (MR) analysis utilizing genetic data from large-scale genome-wide association studies to assess the causal relationships among UA levels, fatty acid traits, and cancer risk. The primary method used was the inverse variance-weighted approach alongside Bayesian-weighted Mendelian randomization. Other MR models were also applied for comparison. Sensitivity analyses, based on various statistical assumptions, were also performed to evaluate the robustness of the findings. A two-step MR analysis was conducted to explore the mediating effects of fatty acid traits on the relationship between UA levels and cancer risk.

Results and Discussion

Elevated UA levels were associated with an increased risk of in situ neoplasms, cervical cancer, and invasive mucinous ovarian cancer, while they were linked to a decreased risk of cancers of the eye and adnexa, small cell lung cancer, bronchus and lung cancer, respiratory system and intrathoracic organ cancers, as well as lung cancer. Mediation analysis revealed that fatty acid traits, particularly the docosahexaenoic acid/trans fatty acid ratio, mediated the relationship between UA levels and lung cancer risk. These findings underscore the potential of fatty acid traits to mediate the association between UA levels and cancer risk, offering new insights for targeted interventions and potentially improving clinical outcomes.

Docosahexaenoic acid (DHA) alleviates inflammation and damage induced by experimental colitis

PURPOSE

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic gastrointestinal disorders associated with significant morbidity and complications. This study investigates the therapeutic potential of docosahexaenoic acid (DHA) in a trinitrobenzene sulfonic acid (TNBS) induced colitis model, focusing on inflammation, oxidative stress, and intestinal membrane permeability.

METHODS

Wistar albino rats were divided into Control, Colitis, and Colitis + DHA groups (n = 8-10/group). The Colitis and Colitis + DHA groups received TNBS intrarectally, while the Control group received saline. DHA (600 mg/kg/day) or saline was administered via gavage for six weeks. Macroscopic and microscopic evaluations of colon tissues were conducted. Parameters including occludin and ZO-1 expressions, myeloperoxidase (MPO) activity, malondialdehyde (MDA), glutathione (GSH), total antioxidant status (TAS), total oxidant status (TOS), Interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) levels were measured in colon tissues.

RESULTS

Colitis induction led to significantly higher macroscopic and microscopic damage scores, elevated TOS levels, reduced occludin and ZO-1 intensity, decreased mucosal thickness, and TAS levels compared to the Control group (p < 0.001). DHA administration significantly ameliorated these parameters (p < 0.001). MPO, MDA, TNF-α, and IL-6 levels were elevated in the Colitis group but significantly reduced in the DHA-treated group (p < 0.001 for MPO, MDA; p < 0.05 for TNF-α and IL-6).

CONCLUSION

DHA demonstrated antioxidant and anti-inflammatory effects by reducing reactive oxygen species production, enhancing TAS capacity, preserving GSH content, decreasing proinflammatory cytokine levels, preventing neutrophil infiltration, reducing shedding in colon epithelium, and improving gland structure and mucosal membrane integrity. DHA also upregulated the expressions of occludin and ZO-1, critical for barrier function. Thus, DHA administration may offer a therapeutic strategy or supplement to mitigate colitis-induced adverse effects.

Dietary polyunsaturated fatty acids intake is negatively associated with hyperuricemia: The National Health and Nutrition Examination Survey 2003-2015

BACKGROUND AND AIMS

The objective of this research was to explore the associations between dietary PUFAs intake and hyperuricemia risk.

METHODS AND RESULTS

Based on the National Health and Nutrition Examination Survey (NHANES) 2003-2015, all eligible individuals were divided into hyperuricemia and non-hyperuricemia groups based on diagnostic criteria for hyperuricemia (serum uric acid >420 μmol/L for men and >360 μmol/L for women). Multivariate-adjusted logistic regression was employed to explore the relationship between dietary PUFAs intake and hyperuricemia risk. Total PUFAs and their subtypes were modeled to isocalorically replace saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs). Higher intake of n-3 PUFAs, n-6 PUFAs, linoleic acid (LA), alpha-linoleic acid (ALA), and non-marine PUFAs intake correlated with decreased hyperuricemia risk, with adjusted odds ratio (OR) and 95% confidence interval (95%CIs) were 0.77 (0.63, 0.93), 0.75 (0.61, 0.92), 0.75 (0.61, 0.91), 0.69 (0.55, 0.87), and 0.73 (0.59, 0.91), respectively. Replacing 5% of total energy intake from SFAs with isocaloric PUFAs was associated with decreased odds of hyperuricemia in men (0.69 (0.57, 0.84)) and in individuals (0.81 (0.71, 0.92)). Similar trends were observed in the substitution of SFAs with non-marine PUFAs in men (0.87 (0.80, 0.94)) and in all individuals (0.92 (0.88, 0.98)). Sensitivity analyses exhibited consistent results with primary analyses.

CONCLUSION

Higher dietary intake of n-3 PUFAs, n-6 PUFAs, LA, ALA, and non-marine PUFAs was associated with decreased hyperuricemia risk. These results support the recommendation to substitute SFAs with PUFAs in diet.

Mechanism of Reactive Oxygen Species-Guided Immune Responses in Gouty Arthritis and Potential Therapeutic Targets

Gouty arthritis (GA) is an inflammatory disease caused by monosodium urate (MSU) crystals deposited in the joint tissues causing severe pain. The disease can recur frequently and tends to form tophus in the joints. Current therapeutic drugs for the acute phase of GA have many side effects and limitations, are unable to prevent recurrent GA attacks and tophus formation, and overall efficacy is unsatisfactory. Therefore, we need to advance research on the microscopic mechanism of GA and seek safer and more effective drugs through relevant targets to block the GA disease process. Current research shows that the pathogenesis of GA is closely related to NLRP3 inflammation, oxidative stress, MAPK, NET, autophagy, and Ferroptosis. However, after synthesizing and sorting out the above mechanisms, it is found that the presence of ROS is throughout almost the entire spectrum of micro-mechanisms of the gout disease process, which combines multiple immune responses to form a large network diagram of complex and tight connections involved in the GA disease process. Current studies have shown that inflammation, oxidative stress, cell necrosis, and pathological signs of GA in GA joint tissues can be effectively suppressed by modulating ROS network-related targets. In this article, on the one hand, we investigated the generative mechanism of ROS network generation and its association with GA. On the other hand, we explored the potential of related targets for the treatment of gout and the prevention of tophus formation, which can provide effective reference ideas for the development of highly effective drugs for the treatment of GA.

Mild hyperthermia enhanced synergistic uric acid degradation and multiple ROS elimination for an effective acute gout therapy

BACKGROUND

Acute gouty is caused by the excessive accumulation of Monosodium Urate (MSU) crystals within various parts of the body, which leads to a deterioration of the local microenvironment. This degradation is marked by elevated levels of uric acid (UA), increased reactive oxygen species (ROS) production, hypoxic conditions, an upsurge in pro-inflammatory mediators, and mitochondrial dysfunction.

RESULTS

In this study, we developed a multifunctional nanoparticle of polydopamine-platinum (PDA@Pt) to combat acute gout by leveraging mild hyperthermia to synergistically enhance UA degradation and anti-inflammatory effect. Herein, PDA acts as a foundational template that facilitates the growth of a Pt shell on the surface of its nanospheres, leading to the formation of the PDA@Pt nanomedicine. Within this therapeutic agent, the Pt nanoparticle catalyzes the decomposition of UA and actively breaks down endogenous hydrogen peroxide (H2O2) to produce O2, which helps to alleviate hypoxic conditions. Concurrently, the PDA component possesses exceptional capacity for ROS scavenging. Most significantly, Both PDA and Pt shell exhibit absorption in the Near-Infrared-II (NIR-II) region, which not only endow PDA@Pt with superior photothermal conversion efficiency for effective photothermal therapy (PTT) but also substantially enhances the nanomedicine's capacity for UA degradation, O2 production and ROS scavenging enzymatic activities. This photothermally-enhanced approach effectively facilitates the repair of mitochondrial damage and downregulates the NF-κB signaling pathway to inhibit the expression of pro-inflammatory cytokines.

CONCLUSIONS

The multifunctional nanomedicine PDA@Pt exhibits exceptional efficacy in UA reduction and anti-inflammatory effects, presenting a promising potential therapeutic strategy for the management of acute gout.

Manganese-doped albumin-gelatin composite nanogel loaded with berberine applied to the treatment of gouty arthritis in rats via a SPARC-dependent mechanism

In this study, manganese-doped albumin-gelatin composite nanogels (MAGN) were prepared and used to load berberine (Ber) for the treatment of gouty arthritis (GA). The nanodrug delivery system (Ber-MAGN) can target inflammatory joints due to the intrinsic high affinity of albumin for SPARC, which is overexpressed at the inflammatory site of GA. Characterization of the pharmaceutical properties in vitro showed that Ber-MAGN had good dispersion, and the particle size was 121 ± 10.7 nm. The sustained release effect significantly improved the bioavailability of berberine. In vitro and in vivo experimental results showed that Ber-MAGN has better therapeutic effects in relieving oxidative stress and suppressing inflammation. Therefore, Ber-MAGN, as a potential pharmaceutical preparation for GA, provides a new reference for the clinical treatment plan of GA.

Docosahexaenoic Acid as Master Regulator of Cellular Antioxidant Defenses: A Systematic Review

Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid that benefits the prevention of chronic diseases. Due to its high unsaturation, DHA is vulnerable to free radical oxidation, resulting in several unfavorable effects, including producing hazardous metabolites. However, in vitro and in vivo investigations suggest that the relationship between the chemical structure of DHA and its susceptibility to oxidation may not be as clear-cut as previously thought. Organisms have developed a balanced system of antioxidants to counteract the overproduction of oxidants, and the nuclear factor erythroid 2-related factor 2 (Nrf2) is the key transcription factor identified for transmitting the inducer signal to the antioxidant response element. Thus, DHA might preserve the cellular redox status promoting the transcriptional regulation of cellular antioxidants through Nrf2 activation. Here, we systematically summarize the research on the possible role of DHA in controlling cellular antioxidant enzymes. After the screening process, 43 records were selected and included in this review. Specifically, 29 studies related to the effects of DHA in cell cultures and 15 studies concerned the effects of consumption or treatment with DHA in animal. Despite DHA's promising and encouraging effects at modulating the cellular antioxidant response in vitro/in vivo, some differences observed among the reviewed studies may be accounted for by the different experimental conditions adopted, including the time of supplementation/treatment, DHA concentration, and cell culture/tissue model. Moreover, this review offers potential molecular explanations for how DHA controls cellular antioxidant defenses, including involvement of transcription factors and the redox signaling pathway.

Docosahexaenoic acid protects against lipopolysaccharide-induced fetal growth restriction via inducing the ubiquitination and degradation of NF-κB p65 in placental trophoblasts

Lipopolysaccharide (LPS) could induce adverse birth outcomes by evoking inflammation. We investigated the effect and mechanism of docosahexaenoic acid (DHA) on LPS-induced placental inflammation and fetal growth restriction (FGR). In vivo, pregnant CD-1 mice were divided into four groups: Ctrl, DHA, LPS and DHA+LPS group. We found that DHA pretreatment reduced the incidence of FGR induced by LPS and activated the expression of peroxisome proliferators-activated receptor gamma (PPARγ) in placental tissue. Moreover, the LPS-induced increase of mRNA levels of Tnf-α, Il-6, Il-1β, Mip-2 and Kc in placental tissue was significantly attenuated by DHA pretreatment. A similar effect of DHA was observed in serum of pregnant mice and amniotic fluid. In contrast, the levels of the IL-10 were significantly increased after DHA pretreatment. In vitro, we clarified that DHA antagonized the activation of the NF-κB signaling pathway induced by LPS, which was dependent on PPARγ. Subsequently, CHX (translation inhibitor) was used to indicated that PPARγ significantly increased the degradation rate of p65, an effect that was inhibited by MG132 (proteasome inhibitor) treatment. Finally, it was confirmed that the activation of PPARγ could significantly promote the ubiquitination and degradation of p65. Our results suggested that DHA alleviated LPS-induced inflammatory responses and FGR by activating PPARγ expression, leading to p65 ubiquitination and degradation.

The function of omega-3 polyunsaturated fatty acids in response to cadmium exposure

Throughout history, pollution has become a part of our daily life with the improvement of life quality and the advancement of industry and heavy industry. In recent years, the adverse effects of heavy metals, such as cadmium (Cd), on human health have been widely discussed, particularly on the immune system. Here, this review summarizes the available evidence on how Cd exposure may affect health. By analyzing the general manifestations of inflammation caused by Cd exposure, we find that the role of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) in vivo can counteract Cd-induced harm. Additionally, we elucidate the effects of n-3 PUFAs on the immune system, and analyze their prophylactic and therapeutic effects on Cd exposure. Overall, this review highlights the role of n-3 PUFAs in the pathological changes induced by Cd exposure. Although n-3 PUFAs remain to be verified whether they can be used as therapeutic agents, as rehabilitation therapy, supplementation with n-3 PUFAs is reliable and effective.

Protective effects of di-caffeoylquinic acids from Artemisia selengensis Turcz leaves against monosodium urate-induced inflammation via the modulation of NLRP3 inflammasome and Nrf2 signaling pathway in THP-1 macrophages

Artemisia selengensis Turcz (AST) as a common vegetable is rich in di-caffeoylquinic acids (di-CQAs) and has been reported to possess multiple health benefits. However, whether di-CQAs from AST leaf extracts (ASTE) could alleviate gout inflammation is still unknown. Herein, this study explored the inhibitory mechanism of ASTE on gout inflammation in THP-1 macrophages. Results suggested that ASTE suppressed the secretion and mRNA levels of inflammatory cytokines including interleukin-18, interleukin-1β, interleukin-6, and tumor necrosis factor-α. Pretreatment with ASTE inhibited lipopolysaccharide-induced of IκBα degradation, p65 phosphorylation and up-regulation of Nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome proteins. Moreover, ASTE inhibited monosodium urate-induced the up-regulation of active caspase-1 and interleukin-1β, promoted nuclear factor E2-related factor2 (Nrf2) to translocate into the nucleus, reducing the generation of MSU-induced reactive oxygen species. These results suggested that ASTE alleviated gout inflammation via inhibiting NLRP3 inflammasome activation and activating Nrf2 signaling pathway. PRACTICAL APPLICATIONS: Artemisia selengensis Turcz (AST) as a common vegetable in China belongs to genus Artemisia, which are rich in di-caffeoylquinic acids. This study aimed to investigate the effect of ASTE on alleviating gout inflammation and whether NLRP3 inflammasome and Nrf2 signaling pathways are involved in the protection of ASTE against gout inflammation. Our findings are significant for developing di-CQAs from AST by-products as an effective functional food for preventing gout.

Reactive oxygen species induced by uric acid promote NRK‑52E cell apoptosis through the NEK7‑NLRP3 signaling pathway

Increasing uric acid (UA) could induce renal tubular epithelial cell (NRK-52E) injury. However, the specific mechanism by which UA induces renal tubular epithelial cell injury remains unknown. It was hypothesized that UA induces renal tubular epithelial cell injury through reactive oxygen species (ROS) and the Never in mitosis gene A (NIMA)-related kinase 7 (NEK7)/NLR family pyrin domain containing 3 (NLRP3) signaling pathway. TUNEL assay and flow cytometry were applied to measure apoptosis, and the results of the present study showed that UA treatment induced apoptosis of NRK-52E cells in a concentration-dependent manner. Western blotting was performed to determine the expression levels of cleaved caspase-3, Bax and Bcl-xl, it was found that levels were significantly increased after UA treatment in NRK-52E cells. ROS and apoptosis were predominantly induced in NRK-52E cells and there was an association between ROS and apoptosis. Enhanced expression of NEK7, NLRP3, apoptosis-associated speck-like and caspase-1 were observed in NRK-52E cells treated with UA. The ROS inhibitor, N-acetyl-l-cysteine, exerted a protective effect on the UA-induced apoptosis of tubular epithelial cells by reducing excess ROS production, which significantly inhibited NEK7 and NLRP3 inflammasome activation. These results indicated that UA activates ROS and induces apoptosis of NRK-52E cells. The mechanism might be related to the regulation of the NEK7/NLRP3 signaling pathway.

Decoy Receptor 3 Inhibits Monosodium Urate-Induced NLRP3 Inflammasome Activation via Reduction of Reactive Oxygen Species Production and Lysosomal Rupture

Gout is a common inflammatory arthritis caused by the deposition of monosodium urate (MSU) crystals in the joints. This activates the macrophages into a proinflammatory state by inducing NLRP3-dependent interleukin-1β (IL-1β) secretion, resulting in neutrophil recruitment. Soluble decoy receptor 3 (DcR3) is an immune modulator and can exert biological functions via decoy and non-decoy actions. Previously, we showed that DcR3 suppresses lipopolysaccharides (LPS)- and virus-induced inflammatory responses in the macrophages and promotes the macrophages into the M2 phenotype. In this study, we clarified the actions of DcR3 and its non-decoy action motif heparin sulfate proteoglycan (HSPG) binding domain (HBD) in the MSU crystal-induced NLRP3 inflammasome activation in the macrophages and in mice. In bone marrow-derived macrophages, THP-1 and U937 cells, we found that the MSU crystal-induced secretion of IL-1β and activation of NLRP3 were suppressed by both DcR3.Fc and HBD.Fc. The suppression of the MSU-induced NLRP3 inflammasome activation is accompanied by the inhibition of lysosomal rupture, mitochondrial production of the reactive oxygen species (ROS), expression of cathepsins, and activity of cathepsin B, without affecting the crystal uptake and the expression of NLRP3 or pro-IL-1β. In the air pouch mice model of gout, MSU induced less amounts of IL-1β and chemokines secretion, an increased M2/M1 macrophage ratio, and a reduction of neutrophil recruitment in DcR3-transgenic mice, which expresses DcR3 in myeloid cells. Similarly, the mice intravenously treated with DcR3.Fc or HBD.Fc displayed less inflammation response. These findings indicate that HBD of DcR3 can reduce MSU crystal-induced NLRP3 inflammasome activation via modulation of mitochondrial and lysosomal functions. Therefore, we, for the first time, demonstrate a new therapeutic potential of DcR3 for the treatment of gout.

Antioxidant Activity of Docosahexaenoic Acid (DHA) and Its Regulatory Roles in Mitochondria

Reactive oxygen species (ROS) are single-electron-bearing oxidation-reduction products that are mainly produced in mitochondria. Excessive ROS accumulation may lead to oxidative damage. Docosahexaenoic acid (DHA) is an essential component of brain phospholipids and is mainly derived from the diet. Its antioxidant activities have been extensively studied. However, its regulatory roles in mitochondria and the underlying mechanism remain to be elucidated. In this study, the DHA's effect on cellular antioxidant capacity and mitochondrial functions was examined in HepG2 cells. The results showed that 100 μM DHA decreased cellular and mitochondrial ROS levels to 75.2 ± 9.4% (P < 0.05) and 55.1 ± 1.4% (P < 0.01), respectively. It also increased the total antioxidant capacity by 55.6 ± 0.1 and 49.2 ± 1.1% (P < 0.05), based on ABTS and FRAP assay results, respectively. Consistently, it increased the activities and gene expression of major antioxidant enzymes by at least 35 and 40% (P < 0.05), respectively. Furthermore, DHA promoted mitochondrial functions and biogenesis. These data suggested that DHA's antioxidant activity can be attributed to its enhancement of mitochondrial functions and biogenesis. This study may shed light on the molecular mechanisms underlying DHA's function in improving resistance to and relieving the symptoms of chronic disease.

Ethnopharmacology of Fruit Plants: A Literature Review on the Toxicological, Phytochemical, Cultural Aspects, and a Mechanistic Approach to the Pharmacological Effects of Four Widely Used Species

Fruit plants have been widely used by the population as a source of food, income and in the treatment of various diseases due to their nutritional and pharmacological properties. The aim of this study was to review information from the most current research about the phytochemical composition, biological and toxicological properties of four fruit species widely used by the world population in order to support the safe medicinal use of these species and encourage further studies on their therapeutic properties. The reviewed species are: Talisia esculenta, Brosimum gaudichaudii, Genipa americana, and Bromelia antiacantha. The review presents the botanical description of these species, their geographical distribution, forms of use in popular medicine, phytochemical studies and molecules isolated from different plant organs. The description of the pharmacological mechanism of action of secondary metabolites isolated from these species was detailed and toxicity studies related to them were reviewed. The present study demonstrates the significant concentration of phenolic compounds in these species and their anti-inflammatory, anti-tumor, photosensitizing properties, among others. Such species provide important molecules with pharmacological activity that serve as raw materials for the development of new drugs, making further studies necessary to elucidate mechanisms of action not yet understood and prove the safety for use in humans.

Study on the Multitarget Mechanism of Sanmiao Pill on Gouty Arthritis Based on Network Pharmacology

Sanmiao pill (SMP), a Chinese traditional formula, had been used to treat gouty arthritis (GA). However, the active compounds and underlying mechanism remained unclear. Hence, network pharmacology and molecular docking were utilized to explore bioactive compounds and potential mechanism of action of SMP in treating GA. In the study, the compounds of SMP, corresponding targets, and GA-related targets were mined from various pharmacological databases. Then, herb-compound-target, compound-target, PPI, and target-pathway networks were constructed. Ultimately, molecular docking was carried out to verify the predicted results. The results indicated that 47 active compounds, 338 targets, and 144 disease targets were collected. Network analysis implied that Phellodendron chinense Schneid. played a vital role in the whole formula. Moreover, 7 compounds (quercetin, kaempferol, wogonin, rutaecarpine, baicalein, beta-sitosterol, and stigmasterol) and 4 targets (NFKB1, RELA, MAPK1, and TNF) might be the kernel compounds and targets of SMP against GA. According to GOBP and KEGG pathway enrichment analysis and target-pathway network, SMP might exert a therapeutic role in GA by regulating numerous biological processes and pathways, including lipopolysaccharide-mediated signaling pathway, positive regulation of transcription, Toll-like receptor signaling pathway, JAK-STAT signaling pathway, NOD-like receptor signaling pathway, and MAPK signaling pathway. The results of molecular docking showcased that 11 pairs of compound with targets had tight binding strength. Thereinto, 4 compounds of MAPK1 and 5 compounds of NFKB1 possessed a better combination, suggesting that MAPK1 and NFKB1 might be considered as therapeutic targets in treatment of GA. This study verified that SMP had synergistic effect on GA by multicomponents, multitargets, and multipathways.

Mitochondrial superoxide/hydrogen peroxide: An emerging therapeutic target for metabolic diseases

Mitochondria are well known for their roles as energy and metabolic factory. Mitochondrial reactive oxygen species (mtROS) refer to superoxide anion radical (^•O₂^-) and hydrogen peroxide (H₂O₂). They are byproducts of electron transport in mitochondrial respiratory chain and are implicated in the regulation of physiological and pathological signal transduction. Especially when mitochondrial ^•O₂^-/H₂O₂ production is disturbed, this disturbance is closely related to the occurrence and development of metabolic diseases. In this review, the sources of mitochondrial ^•O₂^-/H₂O₂ as well as mitochondrial antioxidant mechanisms are summarized. Furthermore, we particularly emphasize the essential role of mitochondrial ^•O₂^-/H₂O₂ in metabolic diseases. Specifically, perturbed mitochondrial ^•O₂^-/H₂O₂ regulation aggravates the progression of metabolic diseases, including diabetes, gout and nonalcoholic fatty liver disease (NAFLD). Given the deleterious effect of mitochondrial ^•O₂^-/H₂O₂ in the development of metabolic diseases, antioxidants targeting mitochondrial ^•O₂^-/H₂O₂ might be an attractive therapeutic approach for the prevention and treatment of metabolic diseases.

Eucalyptol alleviates inflammation and pain responses in a mouse model of gout arthritis

BACKGROUND AND PURPOSE

Gout arthritis, which is provoked by monosodium urate (MSU) crystal accumulation in the joint and periarticular tissues, induces severe pain and affects quality of life of the patients. Eucalyptol (1,8-cineol), the principal component in the essential oils of eucalyptus leaves, is known to possess anti-inflammatory and analgesic properties. We aimed to examine the therapeutic effects of eucalyptol on gout arthritis and related mechanisms.

EXPERIMENTAL APPROACH

A mouse model of gout arthritis was established via MSU injection into the ankle joint. Ankle oedema, mechanical allodynia, neutrophil infiltration, oxidative stress, NLRP3 inflammasome, and TRPV1 expression were examined.

KEY RESULTS

Eucalyptol attenuated MSU-induced mechanical allodynia and ankle oedema in dose-dependently, with effectiveness similar to indomethacin. Eucalyptol reduced inflammatory cell infiltrations in ankle tissues. Eucalyptol inhibited NLRP3 inflammasome activation and pro-inflammatory cytokine production induced by MSU in ankle tissues in vivo. Eucalyptol reduced oxidative stress induced by MSU in RAW264.7 cells in vitro as well as in ankle tissues in vivo, indicated by an increase in activities of antioxidant enzymes and reduction of ROS. Eucalyptol attenuated MSU-induced up-regulation of TRPV1 expression in ankle tissues and dorsal root ganglion neurons innervating the ankle. The in vivo effects of eucalyptol on ankle oedema, mechanical allodynia, NLRP3 inflammasome, IL-1β, and TRPV1 expression were mimicked by treating MSU-injected mice with antioxidants.

CONCLUSION AND IMPLICATIONS

Eucalyptol alleviates MSU-induced pain and inflammation via mechanisms possibly involving anti-oxidative effect. Eucalyptol and other antioxidants may represent promising therapeutic options for gout arthritis.