Rheumatoid arthritis (RA) is a common severe joint disease that involves all age groups. This is one of the conditions in which oxidative stress (OS) has been shown to play a role by regulating the progression of the inflammatory response. Adjuvant arthritis (AA) is a rat model of autoimmune erosive arthritis widely used to evaluate etiopathogenetic mechanisms in RA as well as for testing anti-inflammatory drugs. Pinosylvin (PIN), 3,5-dihydroxy-trans-stilbene, is an analogue of resveratrol mainly found in the heartwood of Pinus sylvestris. The aim of the present study was to examine the eventual antioxidant and anti-inflammatory effect of PIN on the progression of AA in rats in monotherapy and in combination with methotrexate (MTX).
AA was induced by a single intradermal injection of heat-inactivated Mycobacterium butyricum in incomplete Freund’s adjuvant. The experiments included healthy animals, arthritic animals not treated, arthritic animals treated with MTX, with PIN, and with a combination of PIN and MTX. The two latter groups received a daily oral dose of 50 mg/kg b.w. of PIN, either alone or with MTX in an oral dose of 0.4 mg/kg b.w. twice a week during 28 experimental days.
Our data demonstrated that PIN potentiated both the anti-arthritic (decrease of hind paw volume) and the antioxidant effect of MTX (TBARS in plasma). The level of inflammatory protein CRP in plasma and activity of GGT in spleen were not improved by addition of PIN to MTX due to the prominent effect of MTX alone on these parameters. Arthritic animals showed increased OS, also evaluated as plasma levels of isoprostanes. PIN alone or in combination with MTX strongly reduced isoprostane levels (about 50%). Anti-inflammatory and antioxidant functions have been attributed to heme oxygenase (HO-1). Our data show a significant decline in HO-1 (about 40%) in the lung from AA rats. In these animals, PIN alone increased the levels of HO-1 by about 30% more than MTX. Moreover, the combination therapy was the most effective in increasing the levels of HO-1 (3-fold in respect to AA values). Finally, activated NF-B plays an important role in the expression of pro-inflammatory genes. In our model, we observed a marked increase in NF-B in the lung and liver from AA animals. This increase was strongly reduced by PIN alone as well as in combination with MTX. These results suggest that the anti-inflammatory activity of PIN can be mediated by suppression of NF-B activation.
In conclusion, PIN is able to reduce OS in AA rat model. In fact, the combined administration of PIN and MTX suppressed arthritic progression more effectively than did MTX alone. This natural compound may then be useful in the treatment of rheumatoid arthritis.
Acknowledgement: VEGA 2/0045/11, APVV-052-10, CNR/SAV bilateral project 2010-2012: In vitro and in vivo models of arthritic processes for studying the mechanisms of inflammation and oxidative stress link-up. New perspectives for arthritis therapy. Pinosylvin used in this study was prepared by Prof. Jan Šmidrkal (Institute of Chemical Technology, Prague, Czech Republic) and Ing. Juraj Harmatha, PhD (Institute of Organic Chemistry and Biochemistry, Academy of Sciences of Czech Republic)
