Influence of polysaccharide fractions isolated from Caltha palustris L. on the cellular immune response in collagen-induced arthritis (CIA) in mice. A comparison with methotrexate.

ETHNOPHARMACOLOGICAL RELEVANCE: The extracts from Caltha palustris have been used in traditional Canadian and Asian medicine to treat arthritis and rheumatism.

AIMS: The aim of the study was to investigate the anti-arthritis and immunomodulatory activity of the polysaccharide fractions B and C of Caltha palustris L. herbal extracts in collagen-induced arthritis (CIA) mice, an animal model of rheumathoid arthritis. The results were compared with those of methotrexate (MTX) treatment.

MATERIALS AND METHODS: CIA was induced in male and female DBA/1J mice by intradermal injection of chicken type II collagen in Freund's complete adjuvant (cFA). Booster injection of collagen (in incomplete Freund's adjuvant) was given on day 21 of the experiment. Mice were treated daily for 21 consecutive days with investigated fractions B or C at a dose of 10mg/kg (the first dose was given 24h after the booster) or phosphate buffered saline (PBS) (negative and positive control group). MTX was administered in parallel, intraperitoneally at three weekly cycles-every 48 h for 3 weeks at a dose of 6.6 mg/kg, the first dose was given on day 22 of the experiment. The severity of arthritis was evaluated by arthritic scores. Flow cytometry was used to investigate subsets of T lymphocytes in the thymus, and T and B lymphocytes in the spleen, and in mesenteric lymph nodes. T regulatory lymphocytes in the spleen were also quantified by means of flow cytometry. The levels of IL-2, IL-6, IL-10, IFN-γ and TNF-α in serum were also measured.

RESULTS: The results revealed that fraction B significantly reduced the severity of joint swelling and erythema to a similar degree as MTX. It was also found that B fraction and MTX inhibited leucocytosis in peripheral blood caused by CIA, however the inhibitory effect of MTX persisted longer than that of fraction B. The analysis of lymphocyte T subsets demonstrated that both investigated fractions and MTX caused a partial or complete normalization in the percentage and the absolute number of CD4(-)CD8(-) thymocytes (immature, double-negative cells), and increased the percentage of CD8(+) T cells in peripheral lymphoid organs of mice with CIA. Moreover, an increase in the percentage of CD4(+) thymic cells was observed after treatment with fraction B or MTX. Fraction C showed the weakest effect in normalization of the percentage and the absolute number of CD4(-)CD8(-) thymus lymphocytes in mice with CIA. The potency of fraction B was comparable to MTX. A significant decrease in the percentage and the absolute count of splenic T-regulatory cells (CD4(+)CD25(+)FOXP3(+)) was observed after treatment with both Caltha palustris fractions. The inhibiting influence of investigated fractions on TNF-α serum concentration was significant and lasted longer in the case of fraction C. Production of other cytokines was modulated slightly (increase in IFN-γ) or markedly (decrease in IL-2).

CONCLUSION: The results of the experiment suggested that the administration of polysaccharide B fraction from Caltha palustris extract significantly suppressed the progression of CIA. These results are similar to those obtained in the case of MTX treatment. This indicates that fraction B may be a potent candidate for botanical anti-arthritic agent.