Different anti-allergic mechanism of 2 green tea extracts in murine rhinitis model

RATIONALE: To evaluate the anti-allergic effects of green tea extract (GTE) containing different ingredients such as epigallocatechin-3-gallate (EGCG) and/or O-methylated form of EGCG (EGCG”Me) and elucidate the underlying mechanism, we conducted the study using murine allergic rhinitis model.

METHODS: BALB/c mice were sensitized and challenged with ovalbumin (OVA) to induce allergic rhinitis. In the process of making the allergic rhinitis mice model, the GTE A (containing EGCG) and GTE B (containing EGCG and EGCG”Me) were dissolved in water and administered orally four times a week respectively. We measured multiple parameters of allergic responses to determine the effects of the GTE A and GTE B on allergic rhinitis.

RESULTS: In GTE A or GTE B fed group showed inhibitory effects on both symptoms and eosinophil infiltration in nasal tissue, respectively. GTE A treatment induced IFN-γ protein expression and downregulated IL-4, 5 and 10 protein levels in the splenocyte culture as well as increased IgG2a levels and decreased IgG1 level in serum compared with positive allergic rhinitis group significantly. In addition, GTE A suppressed IL-4 and IL-10 expression in both nasal tissue and cervical lymph node significantly. In GTE B fed group, significantly decreased antigen-specific IgE formation as well as suppressed both systemic and local inflammation.

CONCLUSIONS: The GTE A could induce anti-allergic effects by regulating the Th1/Th2 response, while GTE B could improve anti-allergic effects by suppressing the pro-inflammatory cytokines production and antigen-specific IgE formation. Therefore, the two type of GTE might be having an additional adjunctive role to control allergic rhinitis.