Abstracts
1999 Digestive Disease Week

# 3484 CASPASE 2 AND 3 MODULATE GLUTAMINE-STARVATION-INDUCED APOPTOSIS IN ENTEROCYTES.
H T Papaconstantinou, D H Chung, W Zhang, N H Ansari, Mark R Hellmich, C M Townsend Jr., T C Ko, Univ of Texas Med Branch, Galveston, TX

Glutamine (Gln) regulates apoptosis in enterocytes, and is therefore important in the maintenance of gut mucosal homeostasis. However the molecular mechanisms by which Gln regulates apoptosis are not known. Caspases, a family of 13 cysteine proteases, are involved in the progression of apoptosis. Specific caspase activation depends on tissue-type and the apoptotic stimuli. The purpose of this study was (1) to determine whether inhibition of these caspases blocks apoptosis. METHODS. Cells were incubated in 5% serum ± 1 mM Gln ± 80 mM ZVAD, a general inhibitor of caspases. Cell lysates were analyzed for caspase activities by measuring cleavage of specific fluorogenic substrates (amino-trifluoromethylcoumarin [AFC]). DNA fragmentation, the hallmark of apoptosis, was quantified by ELISA assay. RESULTS. Mean±SEM, n=3. Gln starvation resulted in increased activity of caspase 2 and caspase 3 starting at 18 h and 10 h (Fig. 1), respectively, with no activation of caspase 1 or 8 by 24 h (results not shown). Furthermore, ZVAD treatment inhibited activation of caspase 2 and caspase 3 (results not shown) and completely blocked the induction of DNA fragmentation (Fig 2) in Gln-starved RIE-1 cells. CONCLUSIONS. We have shown specific activation of caspase 2 and caspase 3 which modulates the induction of apoptosis in Gln-deprived intestinal epithelial cells. Furthermore, inhibition of caspase activity blocks the induction of apoptosis, suggesting that caspase inhibitors may attenuate apoptotic responses in the gut

Copyright 1996 - 1999, SSAT, Inc.