BackgroundWe investigated a potential link between genetic polymorphisms in genes XRCC1 (Arg399Gln), OGG1 (Ser326Cys), XRCC3 (Thr241Met), and XRCC4 (Ile401Thr) with the level of DNA damage and repair, accessed by comet and micronucleus test, in 51 COPD patients and 51 controls.MethodsPeripheral blood was used to perform the alkaline and neutral comet assay; and genetic polymorphisms by PCR/RFLP. To assess the susceptibility to exogenous DNA damage, the cells were treated with methyl methanesulphonate for 1-h or 3-h. After 3-h treatment the % residual damage was calculated assuming the value of 1-h treatment as 100%. The cytogenetic damage was evaluated by buccal micronucleus cytome assay (BMCyt).ResultsCOPD patients with the risk allele XRCC1 (Arg399Gln) and XRCC3 (Thr241Met) showed higher DNA damage by comet assay. The residual damage was higher for COPD with risk allele in the four genes. In COPD patients was showed negative correlation between BMCyt (binucleated, nuclear bud, condensed chromatin and karyorrhexic cells) with pulmonary function and some variant genotypes.ConclusionOur results suggest a possible association between variant genotypes in XRCC1 (Arg399Gln), OGG1 (Ser326Cys), XRCC3 (Thr241Met), and XRCC4 (Ile401Thr), DNA damage and progression of COPD.

DNA alkylation damage is repaired by base excision repair (BER) initiated by alkyladenine DNA glycosylase (AAG). Despite its role in DNA repair, AAG-initiated BER promotes cytotoxicity in a process dependent on poly (ADP-ribose) polymerase-1 (PARP-1); a NAD + -consuming enzyme activated by strand break intermediates of the AAG-initiated repair process. Importantly, PARP-1 activation has been previously linked to impaired glycolysis and mitochondrial dysfunction. However, whether alkylation affects cellular metabolism in the absence of AAG-mediated BER initiation is unclear. To address this question, we temporally profiled repair and metabolism in wild-type and Aag −/− cells treated with the alkylating agent methyl methanesulfonate (MMS). We show that, although Aag −/− cells display similar levels of alkylation-induced DNA breaks as wild type, PARP-1 activation is undetectable in AAG-deficient cells. Accordingly, Aag −/− cells are protected from MMS-induced nAD + depletion and glycolysis inhibition. MMS-induced mitochondrial dysfunction, however, is AAGindependent. Furthermore, treatment with FK866, a selective inhibitor of the NAD + salvage pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT), synergizes with MMS to induce cytotoxicity and Aag −/− cells are resistant to this combination FK866 and MMS treatment. Thus, AAG plays an important role in the metabolic response to alkylation that could be exploited in the treatment of conditions associated with NAD + dysregulation.DNA base damage is unavoidable and abundant, arising from hydrolysis, oxidation, deamination and alkylation reactions 1 . Base damage arises both as a by-product of cellular metabolism and by exposure to environmental agents and has been associated with several pathologies such as cancer, chronic inflammation and neurodegeneration 2,3 . Chiefly dealing with endogenous DNA base lesions is the base excision repair (BER) pathway. Initiation of the BER pathway occurs via the removal of a damaged base by one of many glycosylases displaying substrate specificities. Base excision leads to the formation of abasic sites and strand breaks that are subsequently processed by downstream enzymes so that DNA synthesis and ligation can take place 4 (Fig. 1A). Since many of the

This study assessed the chronic effects of physical exercise on the level of DNA damage and the susceptibility to exogenous mutagens in peripheral blood cells of chronic obstructive pulmonary disease (COPD) patients. The case-control study enrolled COPD patients separated into two groups (group of physical exercise (PE-COPD; n=15); group of nonphysical exercise (COPD; n=36)) and 51 controls. Peripheral blood was used to evaluate DNA damage by comet assay and lipid peroxidation by measurement of thiobarbituric acid reactive species (TBARS). The cytogenetic damage was evaluated by the buccal micronucleus cytome assay. The results showed that the TBARS values were significantly lower in PE-COPD than in COPD group. The residual DNA damage (induced by methyl methanesulphonate alkylating agent) in PE-COPD was similar to the controls group, in contrast to COPD group where it was significantly elevated. COPD group showed elevated frequency of nuclear buds (BUD) and condensed chromatin (CC) in relation to PE-COPD and control groups, which could indicate a deficiency in DNA repair and early apoptosis of the damaged cells. We concluded that the physical exercise for COPD patients leads to significant decrease of lipid peroxidation in blood plasma, decrease of susceptibility to exogenous mutagenic, and better efficiency in DNA repair.

Seckel syndrome is a type of microcephalic primordial dwarfism (MPD) that is characterized by growth retardation and neurodevelopmental defects, including reports of retinopathy. Mutations in key mediators of the replication stress response, the mutually dependent partners ATR or ATRIP, are among the known causes of Seckel syndrome. However, it remains unclear how their deficiency disrupts the development and function of the central nervous system (CNS). Here, we investigate the cellular and molecular consequences of ATRIP deficiency in different cell populations of the developing neural retina. We discovered that conditional inactivation of Atrip in photoreceptor neurons does not affect their survival or function. In contrast, Atrip deficiency in retinal progenitor cells (RPCs) leads to severe lamination defects followed by secondary photoreceptor degeneration and loss of vision. Furthermore, we show that RPCs lacking functional ATRIP exhibit higher levels of replicative stress and accumulate endogenous DNA damage, that is accompanied by stabilization of TRP53. Notably, inactivation of Trp53 prevents apoptosis of Atrip-deficient progenitor cells and is sufficient to rescue retinal dysplasia, neurodegeneration and vision loss. Together, these results reveal an essential role of ATRIP-mediated replication stress response in CNS development and suggest that the TRP53-mediated apoptosis of progenitor cells may contribute to retinal malformations in Seckel syndrome and other MPD disorders.

The precise replication of DNA and the successful segregation of chromosomes are essential for the faithful transmission of genetic information during the cell cycle. Alterations in the dynamics of genome replication, also referred to as DNA replication stress, may lead to DNA damage and, consequently, mutations and chromosomal rearrangements. Extensive research has revealed that DNA replication stress drives genome instability during tumorigenesis. Over decades, genetic studies of inherited syndromes have established a connection between the mutations in genes required for proper DNA repair/DNA damage responses and neurological diseases. It is becoming clear that both the prevention and the responses to replication stress are particularly important for nervous system development and function. The accurate regulation of cell proliferation is key for the expansion of progenitor pools during central nervous system (CNS) development, adult neurogenesis, and regeneration. Moreover, DNA replication stress in glial cells regulates CNS tumorigenesis and plays a role in neurodegenerative diseases such as ataxia telangiectasia (A-T). Here, we review how replication stress generation and replication stress response (RSR) contribute to the CNS development, homeostasis, and disease. Both cell-autonomous mechanisms, as well as the evidence of RSR-mediated alterations of the cellular microenvironment in the nervous system, were discussed.