Nuclear apoptosis induced by isolated mitochondria

HSP70 and EndoG modulate cell death by heat in human skin keratinocytes in vitro

We examined how young and old keratinocytes died from heat stress in vitro. We found that keratinocyte cell death was not due to oxidative stress as neither Mn-SOD nor Cu-Zn-SOD was produced in either young or old heated keratinocytes. Instead, analysis of the anti-apoptotic factors, Bcl2 and HSP70, and the pro-apoptotic factors, caspase 3, caspase 8, Apaf-1, cytochrome c, AIF, and EndoG, indicated that keratinocyte cell death occurred via the caspase-independent EndoG apoptotic pathway. We found that both young and old keratinocytes died via the same pathway, and that we could specifically reduce both young and old keratinocyte death by addition of the EndoG inhibitor NEM. Further analysis suggested that the difference between young and old keratinocyte death was due to the synthesis of HSP70 protein, with the increase in response to heat more pronounced in young keratinocytes than in old keratinocytes. When we inhibited HSP70 by adding quercetin, death was increased in both young and old keratinocytes, but more so in old keratinocytes. These data suggest that old keratinocytes may die more readily than young keratinocytes when heated because they synthesize HSP70 at a lower efficiency. Such findings suggest that HSP70 production may be age-dependent.

Mitochondrial aggregation patterns and activity in porcine oocytes and apoptosis in surrounding cumulus cells depends on the stage of pre-ovulatory maturation

In this study, we evaluated the distribution and oxidative activity of mitochondria in ex vivo pre-ovulatory porcine oocytes using the fluorescence probe MitoTracker CMTM Ros Orange. Cumulus-oocyte complexes (COCs) were classified according to cumulus morphology and time from hCG administration. The meiotic configuration of the oocytes and the degree of apoptosis in the surrounding cumulus cells were also evaluated. Estrus was synchronized in 45 crossbred Landrace gilts by feeding altrenogest for 15 days and administering 1000 IU PMSG on Day 16. The LH peak was simulated by treatment with 500 IU hCG, given 80 h after PMSG. Endoscopic oocyte recovery was carried out 2 h before or 10, 22, or 34 h after hCG administration. Altogether 454 COCs were aspirated from follicles with a diameter of more than 5 mm. Cumulus morphology in the majority of COCs recovered 2 h before and 10 h after hCG was compact (60.4 and 52.7%, respectively; P<0.05). At 22 h after hCG, COC morphology changed significantly from 10 h dramatically: 74% of COCs had an expanded cumulus (P<0.01). At 34 h after hCG, 100% of recovered COCs had an expanded cumulus. The percentage of oocytes with a mature meiotic configuration differed among COC morphologies and increased as the interval after hCG administration increased (P<0.05). The type of mitochondrial distribution in the oocytes (n=336) changed from homogeneous to heterogeneous as the interval after hCG administration increased (P<0.01) and was associated with the cumulus morphology. Representative mitochondrial distributions were found as follows: -2 h: fine homogeneous in compact and dispersed COCs; 10 h: granulated homogeneous in compact and dispersed COCs; 22 h: granulated homogeneous in expanded COCs; and 34 h: granulated heterogeneous and clustered heterogeneous in expanded COCs (P<0.01). The oxidative activity of mitochondria measured by fluorescence intensity (Em: 570 nm) per oocyte after Mitotracker CMTM Ros Orange labeling increased in the oocyte as the post-hCG interval increased (P<0.01) and depended on the type of mitochondrial distribution. Lowest oxidative activity of mitochondria was found in oocytes with fine homogeneous distribution (253.1+/-9.4 microA). The oxidative activity increased (334.4+/-10.3 microA) in oocytes with granulated homogeneous distribution of mitochondria, and reached highest level in oocytes with granulated heterogeneous (400.9+/-13.0 microA) and clustered heterogeneous distributions (492.8+/-13.9 microA) (P<0.01). Mitochondrial activity in oocytes coincided with apoptosis in surrounding cumulus cells which increased in a time-dependent manner during pre-ovulatory maturation in vivo (P<0.01). These results indicate that there is a relationship between meiotic progression, cumulus expansion and mitochondrial redistribution and their oxidative activity during final pre-ovulatory maturation in pig oocytes. It appears that increased levels of mitochondrial activities in oocytes are correlated to increased levels of apoptosis in surrounding cumulus cells, in which mitochondria may play a role.

Changes of NF-κB, p53, Bcl-2 and caspase in apoptosis induced by JTE-522 in human gastric adenocarcinoma cell line AGS cells: role of reactive oxygen species

AIM: To identify whether JTE-522 can induce apoptosis in AGS cells and ROS also involved in the process, and to investigate the changes in NF-κB, p53, bcl-2 and caspase in the apoptosis process.

METHODS: Cell culture, MTT, Electromicroscopy, agarose gel electrophoresis, lucigenin, Western blot and electrophoretic mobility shift assay (EMSA) analysis were employed to investigate the effect of JTE-522 on cell proliferation and apoptosis in AGS cells and related molecular mechanisms.

RESULTS: JTE-522 inhibited the growth of AGS cells and induced the apoptosis. Lucigenin assay showed the generation of ROS in cells under incubation with JTE-522. The increased ROS generation might contribute to the induction of AGS cells to apoptosis. EMSA and Western blot revealed that NF-κB activity was almost completely inhibited by preventing the degradation of IkBα. Additionally, by using Western blot we confirmed that the level of bcl-2 was decreased, whereas p53 showed a great increase following JTE-522 treatment. Their changes were in a dose-dependent manner.

CONCLUSION: These findings suggest that reactive oxygen species, NF-κB, p53, bcl-2 and caspase-3 may play an important role in the induction of apoptosis in AGS cells after treatment with JTE-522.

Effects of phosphocreatine on apoptosis in a cell-free system

The characteristic morphological and biochemical changes during caspase-mediated apoptosis can be reproduced to a large extent in a Xenopus laevis egg extract cell-free system by addition of mouse liver nuclei and exogenous cytochrome c. We show that in this system phosphocreatine accelerated the apoptotic morphological changes of the nuclei, but selectively inhibited DNA fragmentation. Western blot showed that the degradation of lamins A and C is accelerated, which is possibly responsible for the nuclear changes during cell apoptosis. However, the degradation of ICAD/DFF45-like protein in the egg extracts is inhibited in a time-dependent manner. Exogenous creatine, ATP, and several organic acids have no effect on DNA fragmentation, excluding the possibility that creatine, ATP, or acidic conditions resulting from phosphocreatine are responsible for inhibiting DNA fragmentation. Lithium chloride, a kinase inhibitor, can overcome the phosphocreatine effects and can restore DNA fragmentation. Our results indicate that phosphocreatine protects ICAD/DFF45-like protein from proteolysis, probably through kinase actions, resulting in its resistance to caspase cleavage and leading to an inhibition of DNA fragmentation.