In vitro H2O2 stress and patterns of mitochondrial damage in the NCTC 2544 continuous cell line--a morphologic and morphometric study.

The morpho-functional and energy condition of NCTC 2544 cells exposed for 1 hr to a high concentration of H 2 O 2 (500 μM) was studied at 4 and 24 hr to investigate the short- and medium-term biomolecular mechanisms affecting energetic mitochondrial capability. Morphometric data obtained from ultrastructural investigations clearly showed significant modifications of the different mitochondrial parameters - numerical density (N v ), volume density (V v ) and V v /N v ratio, in interkinetic, apoptotic and mitotic cells after H 2 O 2 exposure (from 4 to 24 hr). These results were confirmed by the detection at 24 hr of mitochondrial cytochrome c release in the cytosol, indicating impairment in mitochondrial membrane permeability. Data supporting these observations were obtained from the MTT test which showed reduced cell viability in H 2 O 2 treated cultures at 4 hr and an even greater decrement at 24 hr. In conclusion our data imply that significant cause-effect relationships exist between the toxicity of reactive oxygen species (i.e. 500 μM H 2 O 2 ) and morpho-structural mitochondrial damage in interkinetic, apoptotic and mitotic cells, respectively. They support previous results present both in the literature and also in one of our earlier papers which show that early nuclear DNA damage could initiate mitochondrial or intrinsic apoptotic pathway after H 2 O 2 exposure.