Activation of caspases in intestinal villus epithelial cells of normal and nematode infected rats.

Background: Small intestinal epithelial cells (IEC) show apoptosis in physiological turnover of cells and in certain inflammatory diseases. Aims: To investigate the role of caspases in the progression of IEC apoptosis in vivo. Methods: IEC were separated along the villus-crypt axis from the jejunum of normal and Nippostrongylus brasiliensis infected rats at 4 degreesC. Caspases were examined by a fluorometric assay method, histochemistry, and immunoblotting. Results: Villus cell rich IEC from normal rats exhibited a high level of caspase-3-like activity whereas activities of caspase-1, -8, and -9 were negligible. Immunoblotting analysis of villus cell rich IEC revealed partial cleavage of procaspose-3 into a 17 kDa molecule as well as cleavage of a caspase-3 substrate, poly(ADP-ribose) polymerase (PARP), whereas in crypt cell rich IEC, caspase-3 cleavage was less significant. Caspase-3 activity was also observed histochemically in villus epithelium on frozen sections of the normal small intestine. IEC prepared at 4 degreesC did not reveal nuclear degradation whereas subsequent incubation in a suspension at 37 degreesC induced intense nuclear degradation within one hour in accordance with increases in active caspase-3. This apoptosis was partially suppressed by the caspase inhibitor Z-VAD-fmk. Nematode infected animals showed villus atrophy together with significant increases in levels of caspase-3 in IEC but not of caspose-1, -8, or -9. Conclusion: Caspase-3 may have an important role in the physiological replacement of IEC as well as in progression of IEC apoptosis induced by nematode infection.