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Regulation of ceramide synthase-mediated crypt epithelium apoptosis by DNA damage repair enzymes.

ABSTRACT: Acute endothelial cell apoptosis and microvascular compromise couple gastrointestinal tract irradiation to reproductive death of intestinal crypt stem cell clonogens (SCCs) following high-dose radiation. Genetic or pharmacologic inhibition of endothelial apoptosis prevents intestinal damage, but as the radiation dose is escalated, SCCs become directly susceptible to an alternate cell death mechanism, mediated via ceramide synthase (CS)-stimulated de novo synthesis of the proapoptotic sphingolipid ceramide, and p53-independent apoptosis of crypt SCCs. We previously reported that ataxia-telangiectasia mutated deficiency resets the primary radiation lethal pathway, allowing CS-mediated apoptosis at the low-dose range of radiation. The mechanism for this event, termed target reordering, remains unknown. Here, we show that inactivation of DNA damage repair pathways signals CS-mediated apoptosis in crypt SCCs, presumably via persistent unrepaired DNA double-strand breaks (DSBs). Genetic loss of function of sensors and transducers of DNA DSB repair confers the CS-mediated lethal pathway in intestines of sv129/B6Mre11(ATLD1/ATLD1) and C57BL/6(Prkdc/SCID) (severe combined immunodeficient) mice exposed to low-dose radiation. In contrast, CS-mediated SCC lethality was mitigated in irradiated gain-of-function Rad50(s/s) mice, and epistasis studies order Rad50 upstream of Mre11. These studies suggest unrepaired DNA DSBs as causative in target reordering in intestinal SCCs. As such, we provide an in vivo model of DNA damage repair that is standardized, can be exploited to understand allele-specific regulation in intact tissue, and is pharmacologically tractable.

SUBMITTER: Rotolo JA

PROVIDER: S-EPMC4440583 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Regulation of ceramide synthase-mediated crypt epithelium apoptosis by DNA damage repair enzymes.

Rotolo Jimmy A JA Mesicek Judith J Maj Jerzy J Truman Jean-Philip JP Haimovitz-Friedman Adriana A Kolesnick Richard R Fuks Zvi Z

Cancer research 20100119 3

Acute endothelial cell apoptosis and microvascular compromise couple gastrointestinal tract irradiation to reproductive death of intestinal crypt stem cell clonogens (SCCs) following high-dose radiation. Genetic or pharmacologic inhibition of endothelial apoptosis prevents intestinal damage, but as the radiation dose is escalated, SCCs become directly susceptible to an alternate cell death mechanism, mediated via ceramide synthase (CS)-stimulated de novo synthesis of the proapoptotic sphingolipi ...[more]

PMID: 20086180

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Project description:We have used human umbilical vein endothelial cell line (HUVEC) as a model to investigate the effect of ultrasound (US) activated micro-bubbles on sensitizing the tumour response to radiation and to check the implication of this approach on gene expression. The use of micro-bubbles in cancer therapy is a novel approach that is being recently investigated, and patterns of gene expressions were not yet characterized. Gene analysis has identified about 19,264 genes; where, 239 – 517 genes have shown more than two folds up-regulation in response to the different treatments. This included a number of genes that are known to be involved in apoptosis and ceramide-induced apoptosis pathways, such as Sphingomyelin phosphodiesterase 2, neutral sphingomyelinase (SMPD2), sphingomyelin phosphodiesterase 1, acid lysosomal (ASM; SMPD1), UDP-galactose ceramide galactosyltransferase (UGT8), cytochrome c oxidase (COX6B1), Caspase-9 and mitogen-activated protein kinase kinase 1 (MAP2K1). To verify these results, we have performed Real time RT-PCR, which indicated an up-regulation that ranged from 2 to 200 folds, specifically in the combined treatment of US, 3.3% micro-bubbles and 8 Gy. The observed higher levels of expression of UGT8, SMPD2 and Caspase 9-alpha when compared to the control or to radiation only indicated the involvement of ceramide, which possibly induces apoptosis . These results support the hypothesis that micro-bubbles play a role in increasing sensitization to radiation, and can prove to be an effective cancer therapeutic approach. Gene analysis has identified about 19,264 genes; where, 239 – 517 genes have shown more than two folds up-regulation in response to the different treatments. This included a number of genes that are known to be involved in apoptosis and ceramide-induced apoptosis pathways, such as Sphingomyelin phosphodiesterase 2, neutral sphingomyelinase (SMPD2), sphingomyelin phosphodiesterase 1, acid lysosomal (ASM; SMPD1), UDP-galactose ceramide galactosyltransferase (UGT8), cytochrome c oxidase (COX6B1), Caspase-9 and mitogen-activated protein kinase kinase 1 (MAP2K1). To verify these results, we have performed Real time RT-PCR, which indicated an up-regulation that ranged from 2 to 200 folds, specifically in the combined treatment of US, 3.3% micro-bubbles and 8 Gy. The observed higher levels of expression of UGT8, SMPD2 and Caspase 9-alpha when compared to the control or to radiation only indicated the involvement of ceramide, which possibly induces apoptosis . These results support the hypothesis that micro-bubbles play a role in increasing sensitization to radiation, and can prove to be an effective cancer therapeutic approach.

Dataset Information

Regulation of ceramide synthase-mediated crypt epithelium apoptosis by DNA damage repair enzymes.

Publications

Regulation of ceramide synthase-mediated crypt epithelium apoptosis by DNA damage repair enzymes.

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