T lymphocytes are critical cells involved in allergy. Here, we report that the natural tetranortriterpenoid gedunin impaired allergic responses primarily by modulating T lymphocyte functions. The intraperitoneal (i.p.) administration of gedunin inhibited pleural leukocyte accumulation triggered by intra-pleural (i.pl.) challenge with ovalbumin (OVA) in previously sensitized C57BL/6 mice; this inhibition was primarily due to the impairment of eosinophil and T lymphocyte influx. Likewise, i.pl. pre-treatment with gedunin inhibited eosinophil and T lymphocyte migration into mouse lungs 24 h after OVA intra-nasal (i.n.) instillation. Pre-treatment with gedunin diminished the levels of CCL2, CCL3, CCL5, CCL11, Interleukin-5 and leukotriene B(4) at the allergic site. In vitro pre-treatment with gedunin failed to inhibit T lymphocyte adhesion and chemotaxis towards pleural washes recovered from OVA-challenged mice, suggesting that gedunin inhibits T lymphocyte migration in vivo via the inhibition of chemotactic mediators in situ. In vivo pre-treatment with gedunin reduced the numbers of CD69(+) and CD25(+) T lymphocytes in the pleura and CD25(+) cells in the thoracic lymph nodes 24 h after OVA i.pl. challenge. In accordance, in vitro treatment of T lymphocytes with gedunin inhibited α-CD3 mAb-induced expression of CD69 and CD25, proliferation, Interleukin-2 production and nuclear translocation of NFκB and NFAT. Notably, post-treatment of mice with gedunin reverted OVA-induced lung allergic inflammation by decreasing the T lymphocyte and eosinophil counts and the levels of eosinophilotactic mediators in bronchoalveolar lavage fluid. Our results demonstrate a remarkable anti-allergic effect of gedunin due to its capability to modulate T cell activation and trafficking into the airways.
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