The role of proteasome in muscle wasting of experimental arthritis

Abstract Background Rheumatoid arthritis is an autoimmune inflammatory disease that often leads patients to muscle impairment and physical disability. This study aimed to evaluate changes in the activity of proteasome system in skeletal muscles of mice with collagen-induced arthritis (CIA) and treated with etanercept or methotrexate. Methods Male DBA1/J mice were divided into four groups (n = 8 each): CIA-Vehicle (treated with saline), CIA-ETN (treated with etanercept, 5.5 mg/kg), CIA-MTX (treated with methotrexate, 35 mg/kg) and CO (healthy control group). Mice were treated two times a week for 6 weeks. Clinical score and hind paw edema were measured. Muscles were weighted after euthanasia and used to quantify proteasome activity, gene (MuRF-1, PMSα4, PSMβ5, PMSβ6, PSMβ7, PSMβ8, PSMβ9, and PSMβ10), and protein (PSMβ1, PSMβ5, PSMβ1i, PSMβ5i) expression of proteasome subunits. Results Both treatments slowed disease development, but only CIA-ETN maintained muscle weight compared to CIA-MTX and CIA-Vehicle groups. Etanercept treatment showed caspase-like activity of 26S proteasome similar to CO group, while CIA-Vehicle and CIA-MTX had higher activity compared to CO group (p: 0.0057). MuRF-1 mRNA expression was decreased after etanercept administration compared to CIA-Vehicle and CO groups (p: 0.002, p: 0.007, respectively). PSMβ8 and PSMβ9 mRNA levels were increased in CIA-Vehicle and CIA-MTX compared to CO group, while CIA-ETN presented no difference from CO. PMSβ6 mRNA expression was higher in CIA-Vehicle and CIA-MTX groups than in CO group. Protein levels of the PSMβ5 subunit were increased in CO group compared to CIA-Vehicle; after both etanercept and methotrexate treatments, PSMβ5 expression was higher than in CIA-Vehicle group and did not differ from CO group expression (p: 0.0025, p: 0.001, respectively). The inflammation-induced subunit β1 (LMP2) was enhanced after methotrexate treatment compared to CO group (p: 0.043). Conclusions The results of CIA-Vehicle show that arthritis increases muscle proteasome activation by enhanced caspase-like activity of 26S proteasome and increased PSMβ8 and PSMβ9 mRNA levels. Etanercept treatment was able to maintain the muscle weight and to modulate proteasome so that its activity and gene expression were compared to CO after TNF inhibition. The protein expression of inflammation-induced proteasome subunit was increased in muscle of CIA-MTX group but not following etanercept treatment. Thus, anti-TNF treatment may be an interesting approach to attenuate the arthritis-related muscle wasting.

Efeito do exercício aeróbico em modelo experimental de artrite / Effect of aerobic exercise on an experimental model of arthritis

INTRODUÇÃO: A artrite reumatoide é uma doença inflamatória sistêmica autoimune que acomete preferencialmente as articulações, mas também outros tecidos, como o músculo esquelético. A perda de massa muscular determina uma grande repercussão na funcionalidade e qualidade de vida desses pacientes e o exercício físico surge como uma alternativa terapêutica para esse acometimento. OBJETIVO: Avaliar o efeito do exercício físico aeróbico moderado sobre a perda muscular em artrite induzida por colágeno (CIA). MÉTODOS: Esse é um estudo-piloto em que CIA foi induzida em camundongos machos DBA1/J divididos em dois grupos: (i) animais com exercício (EXE, n=5), (ii) animais sem exercício (semEXE, n=4). Foram avaliados o escore clínico, o edema da pata traseira, o peso do animal e a locomoção espontânea periodicamente. Após a morte, a histopatologia da articulação tibiotarsal e a área da miofibra dos músculos gastrocnêmio e tibial anterior foram avaliados. Significância foi considerada se p<0,05.RESULTADOS: Não foi observada diferença significativa entre os grupos nos parâmetros de atividade da doença, peso e locomoção espontânea. Entretanto, a histopatologia da articulação demonstrou redução da erosão cartilaginosa no grupo EXE. Também se observou aumento significativo na área seccional da miofibra do grupo EXE, representando uma diferença média de 24%. CONCLUSÃO: Este é o primeiro estudo com exercício aeróbico moderado em esteira em modelo experimental de artrite. O protocolo de exercício testado não parece impactar no desenvolvimento clínico da doença, mas demonstrou benefício sobre a perda muscular consequente da artrite, reduzindo a atrofia da miofibra.

BACKGROUND: Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease that affects primarily the joints, but also other tissues such as skeletal muscle. Muscle wasting significantly impairs the functionality and quality of life of patients with RA and physical exercise is an alternative therapy for this outcome. AIM: To evaluate the effect of moderate aerobic physical exercise on muscle loss caused by collagen-induced arthritis (CIA). METHODS: This is a pilot study in which CIA was induced in DBA/1J mice divided into two groups: (i) animals which exercised (EXE, n=5), (ii) animals which did not exercise (semEXE, n=4). Clinical score, hind paw swelling, weight, and spontaneous locomotion were evaluated periodically. After death, the histopathological score of the ankle and the myofiber area of the gastrocnemius and tibialis anterior muscles were evaluated. Significance was considered when p<0.05. RESULTS: No significant difference was observed between groups regarding clinical parameters of disease activity, animal weight, and spontaneous locomotion. However, joint histopathology demonstrated a decrease in cartilage erosion in the EXE group. There was also significant difference in the myofiber sectional area, with a 24% increase in the EXE group. CONCLUSION: This is the first interventional study with moderate aerobic exercise on a treadmill in an arthritis experimental model. The tested exercise program does not seem to have a clinical impact on the process of arthritis. However, it has a positive effect on muscle wasting caused by arthritis, demonstrated mainly by the reduction of myofiber atrophy.

Glutathione levels in and total antioxidant capacity of Candida sp. cells exposed to oxidative stress caused by hydrogen peroxide / Níveis de glutationa e capacidade antioxidante total em células de Candida sp. expostas a estresse oxidativo causado por peróxido de hidrogênio

INTRODUCTION: The capacity to overcome the oxidative stress imposed by phagocytes seems to be critical for Candida species to cause invasive candidiasis. METHODS: To better characterize the oxidative stress response (OSR) of 8 clinically relevant Candida sp., glutathione, a vital component of the intracellular redox balance, was measured using the 5,5'-dithiobis-(2-nitrobenzoic acid (DTNB)-glutathione disulfide (GSSG) reductase reconversion method; the total antioxidant capacity (TAC) was measured using a modified method based on the decolorization of the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic) acid radical cation (ABTS*+). Both methods were used with cellular Candida sp. extracts treated or not with hydrogen peroxide (0.5 mM). RESULTS: Oxidative stress induced by hydrogen peroxide clearly reduced intracellular glutathione levels. This depletion was stronger in Candida albicans and the levels of glutathione in untreated cells were also higher in this species. The TAC demonstrated intra-specific variation. CONCLUSIONS: Glutathione levels did not correlate with the measured TAC values, despite this being the most important non-enzymatic intracellular antioxidant molecule. The results indicate that the isolated measurement of TAC does not give a clear picture of the ability of a given Candida sp. to respond to oxidative stress.

INTRODUÇÃO: A capacidade de suportar o estresse oxidativo imposto por fagócitos parece ser crítica para que espécies de Candida causem candidíase invasiva. MÉTODOS: Para melhor caracterizar a resposta ao estresse oxidativo (REO) de oito Candida sp. clinicamente relevantes, um componente vital do balanço redox intracelular, a glutationa, foi mensurada pelo método de reconversão DTNB-GSSG redutase e a capacidade antioxidante total (CAT) foi mensurada por um método modificado baseado na descoloração do ABTS*+. Ambos os métodos foram utilizados em extratos celulares das espécies de Candida tratadas ou não com peróxido de hidrogênio (0,5mM). RESULTADOS: O estresse oxidativo induzido pelo peróxido de hidrogênio claramente reduziu os níveis intracelulares de glutationa. Esta diminuição foi mais intensa em C. albicans e os níveis de glutationa em células não tratadas foram também maiores nesta espécie. A capacidade antioxidante total demonstrou variação intraespecífica na capacidade antioxidante. CONCLUSÕES: Os níveis de glutationa não se correlacionaram com a capacidade antioxidante total mensurada, apesar desta ser a defesa antioxidante intracelular não-enzimática mais importante. Os resultados indicam que a medição isolada da CAT não fornece um quadro claro da habilidade de certa espécie de Candida responder ao estresse oxidativo.