Authors: J Nylandsted M Jäättelä E K Hoffmann S F Pedersen
Publish Date: 2004/08/31
Volume: 449, Issue: 2, Pages: 175-185
Abstract
Cell shrinkage is a ubiquitous feature of programmed cell death PCD but whether it is an obligatory signalling event in PCD is unclear Heat shock protein 70 Hsp70 potently counteracts PCD in many cells by mechanisms that are incompletely understood In the present investigation we found that severe hypertonic stress greatly diminished the viability of murine fibrosarcoma cells WEHI902 and immortalized murine embryonic fibroblasts iMEFs This effect was attenuated markedly by Hsp70 overexpression To determine whether the protective effect of Hsp70 was mediated via an effect on volume regulatory ion transport we compared regulatory volume decrease RVD and increase RVI in control WEHI902 cells and after increasing Hsp70 levels by heat shock or overexpression WEHI912 Hsp70 levels affected neither RVD RVI nor the relative contributions of the Na+/H+exchanger NHE1 and Na+K+2Cl−cotransporter NKCC1 to RVI Hypertonic stress induced caspase3 activity in WEHI cells and iMEFs an effect potentiated by Hsp70 in WEHI cells but inhibited by Hsp70 in iMEFs Osmotic shrinkageinduced PCD was associated with Hsp70inhibitable cysteine cathepsin release in iMEFs and attenuated by caspase and cathepsin inhibitors in WEHI cells Treatment with TNFα or the NHE1 inhibitor 5’NethylNisopropylamiloride EIPA reduced the viability of WEHI cells further under isotonic and mildly but not severely hypertonic conditions Thus it is concluded that shrinkageinduced PCD involves both caspase and cathepsindependent death mechanisms and is potently counteracted by Hsp70The work presented above was supported by the Carlsberg Foundation SFP grant No 990209/20840 the Danish National Research Council EKH grant No 21010507 the Danish Medical Research Council MJ the Danish Cancer Research Foundation JN and the Danish Cancer Society MJ and JN The authors are grateful to Birgit Poulsen for excellent technical assistance
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