| Previous studies from our laboratory have confirmed that mast cells are activated significantly by H5N1virus (A/chicken/Henan/1/2004) infection and can possibly intensify the tissue phathologic injuries that result from H5N1infection by releasing proinflammatory mediators. Mice’ lung lesions and mortality induced by H5N1infection are reduced dramatically by treatment with ketotifen, which is a mast cell degranulation inhibitor. To further investigate cellular responses to influenza A viruses (IAVs) infection, apoptosis has been studied in mouse mastocytoma cell line P815in this research.TUNEL assay and transmission electron microscopy were used in the study to determine whether IAVs could induce mast cells apoptosis. The results demonstrated that all the three different subtypes of IAVs, H1N1(A/WSN/33), H5N1(A/Chicken/Henan/1/04), and H7N2(A/Chicken/Hebei/2/02), had the ability to induce mast cell apoptosis. Phosphatidylserine staining and the following flow cytometric analysis were used to compare the mast cells apoptosis rates induced by the three different IAVs and the result shown that H5N1could induce the most dramatic apoptosis of mast cells, while H7N2cuold induce the least dramatic apoptosis comparatively.We have also investigated the signal pathway of mast cells apoptosis induced by IAVs infection by using Western Blot assay, apoptosis inhibition assay, and phosphatidylserine staining and the following flow cytometric analysis. Mast cells apoptosis induced by IAVs infection was found to do this mainly through the mitochondria/cytochrome c-mediated intrinsic pathway, while the activation of caspase8-mediated extrinsic pathway was here found to be weak. Bcl-2family members have been confirmed to be the important proteins to regulate apoptosis. In our study, two pro-apoptotic members of the Bcl-2family, Puma and Bim, appeared to regulate the mast cell apoptosis induced by IAVs infection with their increasing expression. |
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