Rosiglitazone reduces a wide range of proinflammatory profiles in synovial fibroblast SW982 under spheroid culture

Effects of Cellular 11β-hydroxysteroid Dehydrogenase 1 on LPS-induced Inflammatory Responses in Synovial Cell Line, SW982

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyzes the conversion of inactive cortisone into active cortisol, which has pleiotropic roles in various biological conditions, such as immunological and metabolic homeostasis. Cortisol is mainly produced in the adrenal gland, but can be locally regenerated in the liver, fat, and muscle. Its diverse actions are primarily mediated by binding to the glucocorticoid receptor. SW982, a human synovial cell line, expresses 11β-HSD type 1, but not type 2, that catalyzes the conversion of cortisone to cortisol. In this study, therefore, we investigated the control of lipopolysaccharide (LPS)-induced inflammatory responses by prereceptor regulation-mediated maintenance of cortisol levels. Preliminarily, cell seeding density and incubation period were optimized for analyzing the catalytic activity of SW982. Additionally, cellular 11β-HSD1 still remained active irrespective of monolayer or spheroid culture conditions. Inflammatory stimulants, such as interleukin (IL)-1β, tumor necrosis factor (TNF)α, and LPS, did not affect the catalytic activity of 11β-HSD1, although a high dose of LPS significantly decreased its activity. Additionally, autocrine effects of cortisol on inflammatory responses were investigated in LPS-stimulated SW982 cells. LPS upregulated pro-inflammatory cytokines, including IL-6 and IL-1β, in SW982 cells, while cortisol production, catalyzed by cellular 11β-HSD1, downregulated LPS-stimulated cytokines. Furthermore, suppression of NFκB activation-mediated pro-inflammatory responses by cortisol was revealed. In conclusion, the activity of cellular 11β-HSD1 was closely correlated with suppression of LPS-induced inflammation. Therefore, these results partly support the notion that prereceptor regulation of locally regenerated cortisol could be taken into consideration for treatment of inflammation-associated diseases, including arthritis.

Acidic environments enhance the inhibitory effect of statins on proliferation of synovial cells

Many previous studies in animal models and clinical investigations have suggested that statins are useful chemotherapeutics against rheumatoid arthritis, whereas in vitro experiments using synovial cell lines showed no significant effect of statins on cell proliferation until now. Since synovial fluid in rheumatoid joint knee was found to be acidic, we examined the effect of statins on human synovial sarcoma cell line SW982 cells in acidic medium. Statins suppressed the proliferation of SW982 cells at pH6.7, while the suppression was very weak in pH7.5 medium. It was shown that the suppression was caused by the decrease in geranylgeranyl diphosphate, suggesting that a geranylgeranylated protein(s) has an essential role in cell proliferation of SW982 cells under acidic conditions. Our present data clearly implied that statins had high efficacy against SW982 cells in acidic medium whose pH is close to that of rheumatoid arthritis loci in patients. These results lead us to anticipate that screening of chemicals having high therapeutic efficacy in acidic medium promotes the development of new microenvironment-dependent medicines for chemotherapies against rheumatoid arthritis.

The role of the circadian clock in rheumatoid arthritis

Rheumatoid arthritis exhibits diurnal variation in symptoms, with patients suffering with increased painful joint stiffness in the early morning. This correlates with an early morning rise in circulating levels of pro-inflammatory cytokines, such as interleukin-6. This temporal variation in disease pathology is directed by the circadian clock, both at a systemic level, through signalling pathways derived in the central clock, and at a local level by autonomous clocks found within inflammatory organs and cells. Indeed, many cellular components of the immune system, which are involved in the pathogenesis of rheumatoid arthritis, possess independent clocks that facilitate temporal gating of their functions. Furthermore, the circadian clock regulates the expression and activity of several genes and proteins that have demonstrated roles in progression of this autoimmune disease. These include a number of nuclear receptors and also fat-derived adipokines. Employing the knowledge we have about how the inflammatory response is regulated by the clock will facilitate the development of chronotherapy regimens to improve the efficacy of current treatment strategies. Furthermore, a full understanding of the mechanisms by which the clock couples to the immune system may provide novel therapeutic targets for the treatment of this debilitating disease.

Rosiglitazone negatively regulates c-Jun N-terminal kinase and toll-like receptor 4 proinflammatory signalling during initiation of experimental aortic aneurysms

OBJECTIVE

Development and rupture of aortic aneurysms (AA) is a complex process involving inflammation, cell death, tissue and matrix remodelling. The thiazolidinediones (TZDs) including Rosiglitazone (RGZ) are a family of drugs which act as agonists of the nuclear peroxisome proliferator-activated receptors and have a broad spectrum of effects on a number of biological processes in the cardiovascular system. In our previous study we have demonstrated that RGZ has a marked effect on both aneurysm rupture and development, however, the precise mechanism of this is unknown.

METHODS AND RESULTS

In the present study, we examined possible targets of RGZ action in the early stages of Angiotensin II-induced AA in apolipoprotein E-deficient mice. For this purpose we employed immunoblotting, ELISA and antibody array approaches. We found that RGZ significantly inhibited c-Jun N-terminal kinase (JNK) phosphorylation and down-regulated toll-like receptor 4 (TLR4) expression at the site of lesion formation in response to Angiotensin II infusion in the initiation stage (6-72 h) of experimental AA development. Importantly, this effect was also associated with a decrease of CD4 antigen and reduction in production of TLR4/JNK-dependant proinflammatory chemokines MCP-1 and MIP-1α.

CONCLUSION

These data suggest that RGZ can modulate inflammatory processes by blocking TLR4/JNK signalling in initiation stages of AA development.