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Effects of non-ionic polymers of surfactant additives on stress induced apoptosis in type II pneumocytes.

The present study was initiated to evaluate the effect of nonionic polymers or surfactant additives on stress induced apoptosis in tumorigenic human lung epithelial cell line A549. The cell line procured from National Centre for Cell Sciences, Pune was maintained in the prescribed culture medium supplemented with 5% FCS/antibodies and under specific culture conditions (37[degrees]C, 5% [O.sub.2]/95% air incubator.. Cell populations with 70-80% confluency, exhibiting 100% viability and excellent morphology were used for the study. Cells incubated in the absence of apoptotic inducers e.g etoposide, U.V. light or hyperoxic exposure served as control group and those incubated in the presence of apoptotic inducers served as test group.

The exposure of the cells to hyperoxia/etoposide/ UV could result in increased apoptosis. Presence of surfactant resulted in a decrease in the percentage of apoptotic cell death in all the cases. Further, the extent of apoptosis was reduced in the cells exposed to hyperoxia/UV in presence of PEG/dextran alone or along with surfactant. However, an increase in the percentage of apoptotic cell death was noticed in case of cells exposed to etoposide in presence of PEG/dextran alone. These results were further substantiated by cell death detection ELISA. Formation of the nucleosomal DNA ladder is the hallmark of apoptosis so analysis of the pattern of DNA isolated from the cells exposed to different stress inducers was done. The ladder like appearance of the fragmented DNA was quite prominent in cells exposed to [O.sub.2] for 8h. No such ladder was observed in the control cells. Very faint ladder was detected in the cells exposed to hyperoxia in presence of surfactant/nonionic polymers like PEG/dextran. Exposure of cells to etoposide/UV also resulted in formation of ladder which was not very prominent in these cells in presence of surfactant/ nonionic polymer. Further, the oxygen exposed cells and the cells exposed to etoposide/UV showed maximum FITC-dUTP end labeling which pointed to the higher percentage of apoptosis in these cells as compared to the control cells and also the cells cotreated with the modulators.

Western blotting was performed to assess the expression level of Bcl-XI (antiapoptotic protein. and Bax (proapoptotic protein., which revealed a decreased expression of Bcl-XI in the stress (hyperoxic, etoposide/ UV. exposed cells. Bcl-XI expression was comparably same in the control cells and also the cells exposed to stress in the presence of modulators like surfactant or nonionic polymer. Expression of proapoptotic protein Bax was found to increase in the cells exposed to hyperoxia or other stress inducers as compared to the control cells.

S. Majumdar

Professor & Head

Department of Experimental

Medicine & Biotechnology


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Title Annotation:ABSTRACTS: Some Research Projects Completed Recently
Author:Majumdar, S.
Publication:ICMR Bulletin
Date:Oct 1, 2007
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