Ionizing radiation-induced gene modulations, cytokine content changes and telomere shortening in mouse fetuses exhibiting forelimb defects

Abstract

Several lines of evidence have linked limb teratogenesis to radiation-induced apoptosis and to the p53 status in murine fetuses. In previous reports, we studied the occurrence of various malformations after intrauterine irradiation and showed that these malformations were modulated by p53-deficiency as well as by the developmental stage at which embryos were irradiated. In this new study, we focused onto one particular phenotype namely forelimb defects to further unravel the cellular and molecular mechanisms underlying this malformation. We measured various parameters expected to be directly or indirectly influenced by irradiation damage. The mouse fetuses were irradiated at day 12 p.c. (post conception) and examined for forelimb defects on gestational days 15, 16, 17 and 19 of development. The release of inflammatory cytokines was determined in the amniotic fluid on day 16 p.c. and the mean telomere lengths assessed at days 12, 13 and 19 p.c. Differential gene expression within the forelimb bud tissues was determined using Real Time quantitative PCR (RTqPCR) 24 h following irradiation. Apoptosis was investigated in the normal and malformed fetuses using the TUNEL assay and RTqPCR. First, we found that irradiated fetuses with forelimb defects displayed excessive apoptosis in the predigital regions. Besides, overexpression of the pro-apoptotic Bax gene indicates a mitochondrial-mediated cell death. Secondly, our results showed overexpression of MKK3 and MKK7 (members of the stress-activated MAP kinase family) within the malformed fetuses. The latter could be involved in radiation-induced apoptosis through activation of the p38 and JNK pathways. Thirdly, we found that irradiated fetuses exhibiting forelimb defects showed a marked telomere shortening. Interestingly, telomere shortening was observed as the malformations became apparent. Fourthly, we measured cytokine levels in the amniotic fluid and detected a considerable inflammatory reaction among the irradiated fetuses as evidenced by the increase in pro-inflammatory cytokine levels. Altogether, our data suggest that transcriptional modulations of apoptotic, inflammation, stress, and DNA damage players are early events in radiation-induced forelimb defects. These changes resulted in harsh developmental conditions as indicated by a marked increase in cytokine levels in the amniotic fluid and telomere shortening, two features concomitant with the onset of the forelimb defect phenotype in our study.

Hypothesising that salts of iodine, strontium and caesium reverse ageing induced by nuclear radiation

“…If these sequences become shortened to the point beyond repair, then cell replicating error and death can occur. The actual shortening of the telomeres due to ionising radiation has been conclusively found in mouse foetuses by Derradji et al (2008), along with gene modulations and cytokine content changes. Short telomeres are associated with diseases such as cardiovascular disease, cancer, degenerative disc disease, Down syndrome, muscular dystrophy, Alzheimer's disease, osteoarthritis and rheumatoid arthritis (Cohen et al, 2007).…”

“…As we discussed earlier, radiation in general accelerates ageing via a number of important well-characterised cellular disruptive mechanisms (Soler et al, 2009;Richardson, 2009;Mayo Clinic, 2011;Hoel, 2006;Derradji et al, 2008;Cohen et al, 2007;Telomerase Anti-Ageing, 2010;Eisenberg, 2011;Wang et al, 2011;Kiang et al, 2010;Portess et al, 2007;Yamaoka et al, 2004). More specifically, it was found that an oral dose of caesium of 50 mg maintains elevated blood caesium levels for 80 days (Braverman et al, 1988).…”

Telomeres And Early Life Stress: A Review

“…12,13 Several genes and proteins that regulate telomere length have been identified 14 , and telomere shortening is also induced by physiologic stressors such as exposure to radiation and toxins 15 , oxidative stress. 16 Of particular relevance to psychiatric disorders are recent findings in humans of an association between psychological stress and shortened leukocyte telomere length.…”

Radiation treatment and cancer stem cells

“…In response of irradiation, many inflammatory cytokines or soluble factors are known to be secreted in tumor microenvironment (Siva et al 2014;Muller and Meineke 2007;Derradji et al 2008). Possibly, these radiation-induced secretory factors could contribute to the increase in cancer stem cell population (Fig.…”