Etanercept improves endothelial function via pleiotropic effects in rat adjuvant-induced arthritis

Nitric Oxide Synthases in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by severe joint damage and disability. However, the specific mechanism of RA has not been thoroughly clarified over the past decade. Nitric oxide (NO), a kind of gas messenger molecule with many molecular targets, is demonstrated to have significant roles in histopathology and homeostasis. Three nitric oxide synthases (NOS) are related to producing NO and regulating the generation of NO. Based on the latest studies, NOS/NO signaling pathways play a key role in the pathogenesis of RA. Overproduction of NO can induce the generation and release of inflammatory cytokines and act as free radical gas to accumulate and trigger oxidative stress, which can involve in the pathogenesis of RA. Therefore, targeting NOS and its upstream and downstream signaling pathways may be an effective approach to managing RA. This review clearly summarizes the NOS/NO signaling pathway, the pathological changes of RA, the involvement of NOS/NO in RA pathogenesis and the conventional and novel drugs based on NOS/NO signaling pathways that are still in clinical trials and have good therapeutic potential in recent years, with an aim to provide a theoretical basis for further exploration of the role of NOS/NO in the pathogenesis, prevention and treatment of RA.

Orchiectomy but not adjuvant-induced arthritis induces structural modifications in rat aortas

Purpose: This study aimed to verify whether Adjuvant-Induced Arthritis (AIA) and/or Orchiectomy (ORX) modify the expression of the Nox1, Nox2 and Nox4 isoforms, the endothelial function or the structure of rat aortas. Methods: Sixty-three Wistar rats were distributed into four groups: 1) Control; 2) ORX; 3) AIA; 4) Orchiectomy plus to Arthritis-induction (ORX/AIA). Thus, 21 days after the onset of AIA (by intradermal injection of Mycobacterium tuberculosis), the presence of Nox1, Nox2 and Nox4, the acetylcholine (ACh)-induced relaxation and the media layer thickness were assessed in the aorta taken from these animals. Results: The Nox1, Nox2 and Nox4 were immunostained in intima, media and adventitia layers of aortas taken from all studied groups and AIA apparently increased this immunostaining. These modifications of Nox1, Nox2 or Nox4 expression, however, were not confirmed by Western blotting. In addition, neither AIA nor ORX changed the endothelial function, but ORX increased the media layer thickness in the studied aortas. Conclusion: The present study showed weak clues of increased expression of Nox1, Nox2 and Nox4 as a result of AIA, as well as of Nox1 reduction caused by ORX. In addition, the endothelial function was not modified in the aortas of these animals by both AIA and/or ORX. On the other hand, ORX increased significantly the aorta media layer thickness in the studied animals, which was apparently mitigated by AIA.

Etanercept Mitigates Cadmium Chloride-induced Testicular Damage in Rats "An Insight into Autophagy, Apoptosis, Oxidative Stress and Inflammation"

RATIONALE

Cadmium (Cd) is an environmental and occupational toxin that represents a serious health hazard to humans and other animals. One of the negative consequences of cadmium exposure is testicular injury.

OBJECTIVE

This study aimed to investigate the therapeutic effect of etanercept against cadmium chloride-induced testicular damage and the probable underlying mechanisms of its action.

METHODS

A total of sixty rats were divided into six groups: control, cadmium chloride (CdCl₂) (7 mg/ kg i.p.), and CdCl₂ treated with etanercept (5,10 and 15 mg/kg s.c.) and etanercept only (15 mg/kg s.c.). CdCl₂ was administrated as a single dose, while etanercept was administered every 3 days for 3 weeks.

RESULTS

CdCl₂ reduced serum testosterone, testicular glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). However, it elevated the levels of malondialdehyde (MDA) and microtubule-associated protein light chain 3B (LC3B) in the testes. Cadmium caused pathogenic alterations as well as increased levels of inflammatory biomarkers such as tumor necrosis factor-alpha (TNF-α) and nuclear factor-kappa B (NF-κB). Besides, the gene expressions of caspase-3 and inducible nitric oxide synthase (i-NOS) and Beclin-1 protein increased with CdCl₂ exposure. Interestingly, etanercept relieved the previous toxic effects induced by CdCl₂ in a dose-dependent manner as evidenced by inhibition of oxidative stress, inflammatory markers, Beclin-1, LC3B, and caspase-3 accompanied by improvement in histopathological changes.

CONCLUSION

Etanercept provides a potential therapeutic approach to treat testicular tissue against the damaging effects of Cd by reducing oxidative stress, inflammation, apoptosis, and autophagy.

Elevated serum extracellular vesicle arginase 1 in type 2 diabetes mellitus: a cross-sectional study in middle-aged and elderly population

BACKGROUND

Serum extracellular vesicle (EV)-derived arginase 1 (ARG 1) plays a critical role in diabetes-associated endothelial dysfunction. This study was performed to determine the levels of serum EV-derived ARG 1 in T2DM and non-T2DM participants and to examine the association of serum EV-derived ARG 1 with T2DM incidence.

METHODS

We performed a cross-sectional study in 103 Chinese, including 73 T2DM patients and 30 non-T2DM. Serum EVs were prepared via ultracentrifugation. Serum EV-derived ARG 1 levels were measured by enzyme-linked immunosorbent assay. The correlations between serum EV-derived ARG 1 and clinical variables were analyzed. The association of serum EV-derived ARG 1 levels with T2DM was determined by multivariate logistic regression analysis. Interaction subgroup analysis was used to evaluate the interaction of the relevant baselines on the association between serum EV-derived ARG 1 levels and T2DM.

RESULTS

Serum EV-derived ARG 1 levels were significantly higher in T2DM patients compared with non-T2DM patients (p < 0.001). Correlation analysis revealed that serum EV-derived ARG 1 levels were positively associated with fasting plasma glucose (FPG) (r = 0.316, p = 0.001) and glycated hemoglobin (HbA1c) (r = 0.322, p = 0.001). Serum EV-derived ARG 1 levels were significantly associated with T2DM, especially in the subgroup of T2DM for more than 10 years (OR 1.651, 95% CI = 1.066-2.557; P value, 0.025), after adjusting for confounding factors.

CONCLUSIONS

Elevated concentration of serum EV-derived ARG 1 is closely associated with T2DM.

The effect of TNF-α inhibitor treatment on microRNAs and endothelial function in collagen induced arthritis

Chronic inflammation causes dysregulated expression of microRNAs. Aberrant microRNA expression is associated with endothelial dysfunction. In this study we determined whether TNF-α inhibition impacted the expression of miRNA-146a-5p and miRNA-155-5p, and whether changes in the expression of these miRNAs were related to inflammation-induced changes in endothelial function in collagen-induced arthritis (CIA). Sixty-four Sprague-Dawley rats were divided into control (n = 24), CIA (n = 24) and CIA+etanercept (n = 16) groups. CIA and CIA+etanercept groups were immunized with bovine type-II collagen, emulsified in incomplete Freund’s adjuvant. Upon signs of arthritis, the CIA+etanercept group received 10mg/kg of etanercept intraperitoneally, every three days. After six weeks of treatment, mesenteric artery vascular reactivity was assessed using wire-myography. Serum concentrations of TNF-α, C-reactive protein, interleukin-6, vascular adhesion molecule-1 (VCAM-1) and pentraxin-3 (PTX-3) were measured by ELISA. Relative expression of circulating miRNA-146a-5p and miRNA-155-5p were determined using RT-qPCR. Compared to controls, circulating miRNA-155-5p, VCAM-1 and PTX-3 concentrations were increased, and vessel relaxation was impaired in the CIA (all p<0.05), but not in the CIA+etanercept (all p<0.05) groups. The CIA group had greater miRNA-146a-5p expression compared to the CIA+etanercept group (p = 0.005). Independent of blood pressure, miRNA-146a-5p expression was associated with increased PTX-3 concentrations (p = 0.03), while miRNA-155-5p expression was associated with impaired vessel relaxation (p = 0.01). In conclusion, blocking circulating TNF-α impacted systemic inflammation-induced increased expression of miRNA-146a-5p and miRNA-155-5p, which were associated with endothelial inflammation and impaired endothelial dependent vasorelaxation, respectively.

Tofacitinib improved peripheral endothelial dysfunction and brain-derived neurotrophic factor levels in the rat adjuvant-induced arthritis model

This study aimed to explore the effect of Tofacitinib on endothelial dysfunction and cerebral levels of brain-derived neurotrophic factor (BDNF) in the adjuvant-induced arthritis (AIA) rat model. Tofacitinib (10 mg/kg twice a day) or vehicle was administered from the first signs of inflammation. Arthritis scores were daily monitored while other parameters including endothelial function assessed from aortic rings, radiographic scores, blood pressure, heart rate, circulating levels of triglycerides, cholesterol, and interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), IL-17A, and cerebral BDNF levels were determined after 3 weeks of treatment. A group of non-AIA rats served as controls. In AIA rats, as compared with vehicle, Tofacitinib significantly reduced arthritis and radiographic scores, decreased total cholesterol and low-density lipoprotein cholesterol (LDL-C), but changed neither blood pressure nor heart rate and proinflammatory cytokines levels. It also fully restored acetylcholine (Ach)-induced relaxation (p < 0.05) through increased nitric oxide (NO) synthase activity, reduced BH₄ deficiency and O₂ ^-° production, decreased cyclo-oxygenase-2 (COX-2)/arginase activities, and enhanced endothelium-derived hyperpolarizing factor (EDHF) production. These effects translated into a decrease in atherogenic index and an elevation of BDNF levels in the prefrontal cortex (p < 0.05) and hippocampus (p < 0.001). The present study identified Tofacitinib as an efficient therapeutic option to reduce cardiovascular risk and improve BDNF-dependent cognition in arthritis.

Mammalian Arginase Inhibitory Activity of Methanolic Extracts and Isolated Compounds from Cyperus Species

Polyphenolic enriched extracts from two species of Cyperus, Cyperus glomeratus and Cyperus thunbergii, possess mammalian arginase inhibitory capacities, with the percentage inhibition ranging from 80% to 95% at 100 µg/mL and 40% to 64% at 10 µg/mL. Phytochemical investigation of these species led to the isolation and identification of two new natural stilbene oligomers named thunbergin A-B (1–2), together with three other stilbenes, trans-resveratrol (3), trans-scirpusin A (4), trans-cyperusphenol A (6), and two flavonoids, aureusidin (5) and luteolin (7), which were isolated for the first time from C.thunbergii and C. glomeratus. Structures were established on the basis of the spectroscopic data from MS and NMR experiments. The arginase inhibitory activity of compounds 1–7 was evaluated through an in vitro arginase inhibitory assay using purified liver bovine arginase. As a result, five compounds (1, 4–7) showed significant inhibition of arginase, with IC₅₀ values between 17.6 and 60.6 µM, in the range of those of the natural arginase inhibitor piceatannol (12.6 µM). In addition, methanolic extract from Cyperus thunbergii exhibited an endothelium and NO-dependent vasorelaxant effect on thoracic aortic rings from rats and improved endothelial dysfunction in an adjuvant-induced arthritis rat model.

Atherosclerosis in Rheumatoid Arthritis: Promoters and Opponents

Substantial epidemiological data identified cardiovascular (CV) diseases as a main cause of mortality in patients with rheumatoid arthritis (RA). In light of this, RA patients may benefit from additional CV risk screening and more intensive prevention strategies. Nevertheless, current algorithms for CV risk stratification still remain tailored on general population and are burdened by a significant underestimation of CV risk in RA patients. Acute CV events in patients with RA are largely related to an accelerated atherosclerosis. As pathophysiological features of atherosclerosis overlap those occurring in the inflamed RA synovium, the understanding of those common pathways represents an urgent need and a leading challenge for CV prevention in patients with RA. Genetic background, metabolic status, gut microbiome, and systemic inflammation have been also suggested as additional key pro-atherosclerotic factors. The aim of this narrative review is to update the current knowledge about pathophysiology of atherogenesis in RA patients and potential anti-atherosclerotic effects of disease-modifying anti-rheumatic drugs.

Arginase inhibitory properties of flavonoid compounds from the leaves of Mulberry (Morus alba, Moraceae)

OBJECTIVES

We aimed to isolate and identify bioactive molecules from Morus alba (Moraceae) leaves having arginase inhibitory activity towards the combat of clinical outcomes related to endothelial dysfunction.

METHOD

Extraction and isolation were carried out by successive macerations, prepurification by using a Solid Phase Extraction (SPE) and separation using preparative PLC. The structures of the isolated components were established and confirmed by spectroscopic analyses, including the ESI-HRMS and NMR spectroscopic investigations. Biological evaluation was performed by using an in vitro assay with liver bovine purified arginase and by an ex vivo aortic ring study.

KEY FINDINGS

We demonstrated that a phenolic extract from the leaves of M. alba possesses mammalian arginase inhibitory capacities. Investigation of the chemical constituents of its leaves results in the isolation and identification of ten compounds investigated in vitro for their arginase inhibitory capacities. Four compounds showed significant inhibition of arginase, with percentage inhibition ranging from 54% to 83% at 100 µm. In isolated rat aortic rings incubated with NO synthase inhibitor, Luteolin-7-diglucoside compound (2) was able to increase acetylcholine-induced relaxation.

CONCLUSIONS

These results demonstrated the attractive ability of M. alba to be a potential source for the discovery of new active products on vascular system.

Role of the eNOS Uncoupling and the Nitric Oxide Metabolic Pathway in the Pathogenesis of Autoimmune Rheumatic Diseases

Atherosclerosis and its clinical complications constitute the major healthcare problems of the world population. Due to the central role of endothelium throughout the atherosclerotic disease process, endothelial dysfunction is regarded as a common mechanism for various cardiovascular (CV) disorders. It is well established that patients with rheumatic autoimmune diseases are characterized by significantly increased prevalence of cardiovascular morbidity and mortality compared with the general population. The current European guidelines on cardiovascular disease (CVD) prevention in clinical practice recommend to use a 1,5-factor multiplier for CV risk in rheumatoid arthritis as well as in other autoimmune inflammatory diseases. However, mechanisms of accelerated atherosclerosis in these diseases, especially in the absence of traditional risk factors, still remain unclear. Oxidative stress plays the major role in the endothelial dysfunction and recently is strongly attributed to endothelial NO synthase dysfunction (eNOS uncoupling). Converted to a superoxide-producing enzyme, uncoupled eNOS not only leads to reduction of the nitric oxide (NO) generation but also potentiates the preexisting oxidative stress, which contributes significantly to atherogenesis. However, to date, there are no systemic analyses on the role of eNOS uncoupling in the excess CV mortality linked with autoimmune rheumatic diseases. The current review paper addresses this issue.

Evaluation of the antirheumatic effects of isoflavone-free soy protein isolate and etanercept in rats with adjuvant-induced arthritis

IMPACT STATEMENT

In view of the partial clinical benefit and significant toxicity of traditional rheumatoid arthritis (RA) treatments, there is a growing trend to use complementary therapy. The antiarthritic activity of soy is related to the effect of soy isoflavones. However, little is known about the antiarthritic activity of soy protein itself. This study demonstrates that soy protein isolate (SPI) and etanercept (ETN), a tumor necrosis factor-α (TNF-α) inhibitor, protect rats against the effects of adjuvant-induced arthritis (AIA) by reducing inflammation (TNF-α and matrix metalloproteinase-3), autoantibody production (anticyclic citrullinated peptide), and lipid peroxidation (malondialdehyde). Only SPI improved dyslipidemia accompanied by RA, giving it the advantage of reducing cardiovascular risk. Additionally, the severity of arthritis-induced pathology, including inflammatory infiltrates, synovial hyperplasia, pannus formation, synovial vascularity, and cartilage erosions, was reduced by both SPI and ETN. This research ascertains the possible antiarthritic effect of SPI, making it a recommended alternative therapy for RA.

Acupuncture decreased the risk of coronary heart disease in patients with rheumatoid arthritis in Taiwan: a Nationwide propensity score-matched study

Background

Patients with rheumatoid arthritis (RA) have a higher risk of coronary heart disease (CHD). Acupuncture, a commonly used treatment for patients with RA, has not been reported to prevent CHD in patients with RA. We aimed to assess the risk of developing CHD in acupuncture users and non-users of patients with RA.

Methods

We identified 29,741 patients with newly diagnosed RA from January 1997 to December 2010 from the Registry of Catastrophic Illness Patients Database from the Taiwanese National Health Insurance Research Database. Among them, 10,199 patients received acupuncture (acupuncture users), and 19,542 patients did not receive acupuncture (no-acupuncture users). After performing 1:1 propensity score matching by sex, age, baseline comorbidity, conventional treatment, initial diagnostic year, and index year, there were 9932 patients in both the acupuncture and no-acupuncture cohorts. The main outcome was the diagnosis of CHD in patients with RA in the acupuncture and no-acupuncture cohorts.

Results

Acupuncture users had a lower incidence of CHD than non-users (adjusted HR = 0.60, 95% CI = 0.55–0.65). The estimated cumulative incidence of CHD was significantly lower in the acupuncture cohort (log-rank test, p < .001). Subgroup analysis showed that patients receiving manual acupuncture of traditional Chinese medicine style, electroacupuncture, or combination of both all had a lower incidence of CHD than patients never receiving acupuncture treatment. The beneficial effect of acupuncture on preventing CHD was independent of age, sex, diabetes mellitus, hypertension, hyperlipidemia, and statins use.

Conclusions

This is the first large-scale study to reveal that acupuncture might have beneficial effect on reducing the risk of CHD in patients with RA. This study may provide useful information for clinical utilization and future studies.

Hypertension: Focus on autoimmunity and oxidative stress

Understanding the causal role of the immune and inflammatory responses in hypertension has led to questions regarding the links between hypertension and autoimmunity. Immune pathology in primary hypertension mimics several autoimmune mechanisms observed in the pathogenesis of systemic lupus erythematosus, psoriasis, systemic sclerosis, rheumatoid arthritis and periodontitis. More importantly, the prevalence of hypertension in patients with these autoimmune diseases is significantly increased, when compared to control populations. Clinical and epidemiological evidence is reviewed along with possible mechanisms linking hypertension and autoimmunity. Inflammation and oxidative stress are linked in a self-perpetuating cycle that significantly contributes to the vascular dysfunction and renal damage associated with hypertension. T cell, B cell, macrophage and NK cell infiltration into these organs is essential for this pathology. Effector cytokines such as IFN-γ, TNF-α and IL-17 affect Na⁺/H⁺ exchangers in the kidney. In blood vessels, they lead to endothelial dysfunction and loss of nitric oxide bioavailability and cause vasoconstriction. Both renal and vascular effects are, in part, mediated through induction of reactive oxygen species-producing enzymes such as superoxide anion generating NADPH oxidases and dysfunction of anti-oxidant systems. These mechanisms have recently become important therapeutic targets of novel therapies focused on scavenging oxidative (isolevuglandin) modification of neo-antigenic peptides. Effects of classical immune targeted therapies focused on immunosuppression and anti-cytokine treatments are also reviewed.

Vascular brain-derived neurotrophic factor pathway in rats with adjuvant-induced arthritis: Effect of anti-rheumatic drugs

BACKGROUND AND AIMS

In rheumatoid arthritis, the control of both disease activity and standard cardiovascular (CV) risk factors is expected to attenuate the increased CV risk. Evidence that brain-derived neurotrophic factor (BDNF) plays a role in vascular biology led us to investigate the vascular BDNF pathway in arthritis rats as well as the interaction between endothelial nitric oxide (NO) and BDNF production.

METHODS

The aortic BDNF pathway was studied in rats with adjuvant-induced arthritis, (AIA) using Western blot and immunohistochemical analysis. Control of arthritis score was achieved by administration (for 3 weeks) of an equipotent dosage of etanercept, prednisolone, methotrexate, celecoxib or diclofenac. Aortas were exposed to an NO donor or an NO synthase inhibitor and vasoreactivity experiments were performed using LM22A-4 as a TrkB agonist.

RESULTS

Vascular BDNF and full length tropomyosin-related kinase B receptor (TrkB-FL) were higher in AIA than in control rats. These changes coincided with decreased endothelial immunoreactivity in BDNF and pTrkB^tyr816 and were disconnected from arthritis score. Among anti-rheumatic drugs, only prednisolone and methotrexate prevented AIA-induced vascular BDNF loss. The effect of AIA on aortic BDNF levels was reversed by an NO donor and reproduced by an NOS inhibitor. Finally, LM22A-4 induced both NO-dependent vasodilation and phosphorylation of endothelial NO synthase at serine 1177.

CONCLUSIONS

Our study identified changes in the BDNF/TrkB pathway as a disease activity-independent component of AIA-associated changes in endothelial phenotype. It provides new perspectives in the understanding and management of the high CV risk reported in rheumatoid arthritis.

Diclofenac but not celecoxib improves endothelial function in rheumatoid arthritis: A study in adjuvant-induced arthritis

BACKGROUND AND AIMS

We aimed at investigating the effect of celecoxib (COX-2 selective inhibitor) and diclofenac (non-selective COX inhibitor) on endothelial function, and at identifying the underlying mechanisms in adjuvant-induced arthritis (AIA).

METHODS

At the first signs of AIA, diclofenac (5 mg/kg twice a day, i.p), celecoxib (3 mg/kg/day, i.p) or saline (Vehicle) was administered for 3 weeks. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of NOS, arginase, EDHF and superoxide anions (O₂^-°) production. Aortic expression of eNOS, Ser1177-phospho-eNOS, COX-2, arginase-2, p22^phox and p47^phox was evaluated by Western blotting analysis. Arthritis scores, blood pressure, glycaemia and serum ADMA levels were measured.

RESULTS

Diclofenac and celecoxib significantly reduced arthritis score to the same extent (p<0.05). As compared to vehicle-treated AIA, celecoxib did not change whereas diclofenac improved endothelial function (p<0.05) through increased EDHF production, decreased arginase activity and expression, decreased superoxide anions production and expression of p22^phox and p47^phox. Diclofenac but not celecoxib significantly enhanced blood pressure and serum ADMA levels. Glycaemia was unchanged by both treatments.

CONCLUSIONS

Our study reveals that the effect of NSAIDs on endothelial function cannot be extrapolated from their impact on arthritis severity and suggest that changes in blood pressure and plasma ADMA levels may not be useful to predict CV risk of NSAIDs in RA.

Innate Immune Activation Can Trigger Experimental Spondyloarthritis in HLA-B27/Huβ2m Transgenic Rats

Spondyloarthritis (SpA) does not display the typical features of auto-immune disease. Despite the strong association with MHC class I, CD8⁺ T cells are not required for disease induction in the HLA-B27/Huβ2m transgenic rats. We used Lewis HLA-B27/Huβ2m transgenic rats [21-3 × 283-2]F1, HLA-B7/Huβ2m transgenic rats [120-4 × 283-2]F1, and wild-type rats to test our hypothesis that SpA may be primarily driven by the innate immune response. In vitro, splenocytes were stimulated with heat-inactivated Mycobacterium tuberculosis and cytokine expression and production was measured. In vivo, male and female rats were immunized with 30, 60, or 90 µg of heat-inactivated M. tuberculosis and clinically monitored for spondylitis and arthritis development. After validation of the model, we tested whether prophylactic and therapeutic TNF targeting affected spondylitis and arthritis. In vitro stimulation with heat-inactivated M. tuberculosis strongly induced gene expression of pro-inflammatory cytokines such as TNF, IL-6, IL-1α, and IL-1β, in the HLA-B27 transgenic rats compared with controls. In vivo immunization induced an increased spondylitis and arthritis incidence and an accelerated and synchronized onset of spondylitis and arthritis in HLA-B27 transgenic males and females. Moreover, immunization overcame the protective effect of orchiectomy. Prophylactic TNF targeting resulted in delayed spondylitis and arthritis development and reduced arthritis severity, whereas therapeutic TNF blockade did not affect spondylitis and arthritis severity. Collectively, these data indicate that innate immune activation plays a role in the initiation of HLA-B27-associated disease and allowed to establish a useful in vivo model to study the cellular and molecular mechanisms of disease initiation and progression.

Glucocorticoids improve endothelial function in rheumatoid arthritis: a study in rats with adjuvant-induced arthritis

To determine the effect of glucocorticoids (GCs) on endothelial dysfunction (ED) and on traditional cardiovascular (CV) risk factors in the adjuvant-induced arthritis (AIA) rat model. At the first signs of AIA, a high dose (HD) [10 mg/kg/day, intraperitoneally (i.p.), GC-HD] or low dose (LD) (1 mg/kg/day, i.p., GC-LD) of prednisolone was administered for 3 weeks. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of nitric oxide synthase (NOS), cyclooxygenase 2 (COX-2), arginase, endothelium derived hyperpolarizing factor (EDHF) and superoxide anions ( O2-°) production. Aortic expression of endothelial NOS (eNOS), Ser1177-phospho-eNOS, COX-2, arginase-2, p22^phox and p47^phox was evaluated by Western blotting analysis. Arthritis scores, blood pressure, heart rate and blood levels of cytokines, triglycerides, cholesterol and glucose were measured. GC-HD but not GC-LD reduced arthritis score significantly and improved Ach-induced relaxation (P < 0·05). The positive effect of GC-HD resulted from increased NOS activity and EDHF production and decreased COX-2/arginase activities and O2-° production. These functional effects relied upon increased phospho-eNOS expression and decreased COX-2, arginase-2 and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase expression. Despite the lack of effect of GC-LD on ED, it increased NOS and EDHF and down-regulated O2-° pathways but did not change arginase and COX-2 pathways. GC-HD increased triglycerides levels and blood pressure significantly (P < 0·05). Both doses of GCs decreased to the same extent as plasma interleukin (IL)-1β and tumour necrosis factor (TNF)-α levels (P < 0·05). Our data demonstrated that subchronic treatment with prednisolone improved endothelial function in AIA via pleiotropic effects on endothelial pathways. These effects occurred independently of the deleterious cardiometabolic effects and the impact of prednisolone on systemic inflammation.