DNA damage to human genetic disorders with neurodevelopmental defects

Although some mutations are beneficial and are the driving force behind evolution, it is important to maintain DNA integrity and stability because it contains genetic information. However, in the oxygen-rich environment we live in, the DNA molecule is under constant threat from endogenous or exogenous insults. DNA damage could trigger the DNA damage response (DDR), which involves DNA repair, the regulation of cell cycle checkpoints, and the induction of programmed cell death or senescence. Dysregulation of these physiological responses to DNA damage causes developmental defects, neurological defects, premature aging, infertility, immune system defects, and tumors in humans. Some human syndromes are characterized by unique neurological phenotypes including microcephaly, mental retardation, ataxia, neurodegeneration, and neuropathy, suggesting a direct link between genomic instability resulting from defective DDR and neuropathology. In this review, rare human genetic disorders related to abnormal DDR and damage repair with neural defects will be discussed.

Type of sperm DNA strand breaks in infertile men and its clinical implication / 中华男科学杂志

<p><b>OBJECTIVE</b>To observe the characteristics of sperm single-stranded DNA breaks (SSB) and double-stranded DNA breaks (DSB) in infertile men, explore the association of DSB with male infertility, and provide a new observation index and idea for the diagnosis and treatment of the disease.</p><p><b>METHODS</b>This study involved 60 infertile men (infertility group) and 30 normal healthy males with infertile wives (control group). We comparatively analyzed the seminal parameters of the two groups, determined sperm concentration and viability using the computer aided sperm analysis system, measured the sperm survival rate by hypoosmotic swelling (HOS) test, examined sperm morphology by Diff-Quick staining, and detected sperm DNA damage by two-tail comet assay.</p><p><b>RESULTS</b>Nine two-tail comet models were established for detecting sperm DNA integrity. Comparisons between the fertility and control groups showed that the sperm DNA fragmentation index (DFI) was (33.8 ± 13.1) vs (16.3 ± 7.9)% (P < 0.01), the SSB-DFI was (19.2 ± 11.4) vs (14.9 ± 7.6)% (P > 0.05), the SSB-DFI/DFI was (56.8 ± 32.4) vs (91.4 ± 27.8)% (P < 0.01), the DSB-DFI was (23.9 +13.4) vs (6.1 ± 2.7)% (P < 0.01), and the DSB-DFI/DFI was (70.8 ± 19.5) vs (37.4 ± 11.3)% (P < 0.01). The optimal cut-off value of DSB-DFI/DFI in the diagnosis of male infertility was 39.5%, with the AUG, sensitivity, and specificity of 0.969, 98.3%, and 90%; that of DSB-DFI was 15.85%, with the AUC, sensitivity, and specificity of 0.912, 86.7%, and 80%; and that of DFI was 18.65%; with the AUC, sensitivity, and specificity of 0.861, 90%, 70%, respectively. In the infertile men, neither SSB-DFI nor SSB-DFI/DFI exhibited any correlation with semen parameters (P > 0.05); DFI was correlated negatively with the percentage of progressively motile sperm, sperm survival rate, and the percentage of morphologically normal sperm (P < 0.05 or P < 0.01), but not correlated with sperm concentration (P > 0.05); both DSB-DFI and DSB-DFI/DFI showed a negative correlation with sperm concentration, sperm survival rate, and the percentages of progressively motile sperm and morphologically normal sperm (P < 0.05 or P < 0.01).</p><p><b>CONCLUSION</b>Double-stranded, rather than single-stranded DNA breaks, may be a factor inducing male infertility. The type of sperm DNA strand damage is of much reference value for the assessment of male fertility.</p>

Apple pectin, a dietary fiber, ameliorates myocardial injury by inhibiting apoptosis in a rat model of ischemia/reperfusion

BACKGROUND/OBJECTIVE: Myocardial cell death due to occlusion of the coronary arteries leads to myocardial infarction, a subset of coronary heart disease (CHD). Dietary fiber is known to be associated with a reduced risk of CHD, the underlying mechanisms of which were suggested to delay the onset of occlusion by ameliorating risk factors. In this study, we tested a hypothesis that a beneficial role of dietary fiber could arise from protection of myocardial cells against ischemic injury, manifested after occlusion of the arteries. MATERIALS/METHODS: Three days after rats were fed apple pectin (AP) (with 10, 40, 100, and 400 mg/kg/day), myocardial ischemic injury was induced by 30 min-ligation of the left anterior descending coronary artery, followed by 3 hr-reperfusion. The area at risk and infarct area were evaluated using Evans blue dye and 2,3,5-triphenyltetrazolium chloride (TTC) staining, respectively. DNA nicks reflecting the extent of myocardial apoptosis were assessed by TUNEL assay. Levels of cleaved caspase-3, Bcl-2, and Bax were assessed by immunohistochemistry. RESULTS: Supplementation of AP (with 100 and 400 mg/kg/day) resulted in significantly attenuated infarct size (IS) (ratio of infarct area to area at risk) by 21.9 and 22.4%, respectively, in the AP-treated group, compared with that in the control group. This attenuation in IS showed correlation with improvement in biomarkers involved in the apoptotic cascades: reduction of apoptotic cells, inhibition of conversion of procaspase-3 to caspase-3, and increase of Bcl-2/Bax ratio, a determinant of cell fate. CONCLUSIONS: The findings indicate that supplementation of AP results in amelioration of myocardial infarction by inhibition of apoptosis. Thus, the current study suggests that intake of dietary fiber reduces the risk of CHD, not only by blocking steps leading to occlusion, but also by protecting against ischemic injury caused by occlusion of the arteries.

Apple pectin, a dietary fiber, ameliorates myocardial injury by inhibiting apoptosis in a rat model of ischemia/reperfusion

BACKGROUND/OBJECTIVE: Myocardial cell death due to occlusion of the coronary arteries leads to myocardial infarction, a subset of coronary heart disease (CHD). Dietary fiber is known to be associated with a reduced risk of CHD, the underlying mechanisms of which were suggested to delay the onset of occlusion by ameliorating risk factors. In this study, we tested a hypothesis that a beneficial role of dietary fiber could arise from protection of myocardial cells against ischemic injury, manifested after occlusion of the arteries. MATERIALS/METHODS: Three days after rats were fed apple pectin (AP) (with 10, 40, 100, and 400 mg/kg/day), myocardial ischemic injury was induced by 30 min-ligation of the left anterior descending coronary artery, followed by 3 hr-reperfusion. The area at risk and infarct area were evaluated using Evans blue dye and 2,3,5-triphenyltetrazolium chloride (TTC) staining, respectively. DNA nicks reflecting the extent of myocardial apoptosis were assessed by TUNEL assay. Levels of cleaved caspase-3, Bcl-2, and Bax were assessed by immunohistochemistry. RESULTS: Supplementation of AP (with 100 and 400 mg/kg/day) resulted in significantly attenuated infarct size (IS) (ratio of infarct area to area at risk) by 21.9 and 22.4%, respectively, in the AP-treated group, compared with that in the control group. This attenuation in IS showed correlation with improvement in biomarkers involved in the apoptotic cascades: reduction of apoptotic cells, inhibition of conversion of procaspase-3 to caspase-3, and increase of Bcl-2/Bax ratio, a determinant of cell fate. CONCLUSIONS: The findings indicate that supplementation of AP results in amelioration of myocardial infarction by inhibition of apoptosis. Thus, the current study suggests that intake of dietary fiber reduces the risk of CHD, not only by blocking steps leading to occlusion, but also by protecting against ischemic injury caused by occlusion of the arteries.

[Biomonitoring of genotoxicity and antioxidant enzymatic changes in workers occupationally exposed to asphalt fumes]

Asphalt fumes consist of the gases and vapor emitted from the heated asphalt as well as the aerosols and mists resulting from their condensation after volatilization .Moreover, asphalate workers are exposed to variety of asphalted fumes and dusts, which can exert their toxic effects via production of reactive oxygen species. The spectrum of oxidative DMA damage includes strand breaks. Information on genotoxic risk for bitumen workers is limited. The aim of the present study was biomonitoring of genotoxicity and different antioxidant enzymes activity of workers occupationally exposed to asphalted fumes. Method It was conducted on fifty male workers employed in asphalted and proofing materials manufacturing. Fifty subjects were recruited as a control group matched for age, sex and socio-economic status. revealed that high significant association in the levels of genotoxicity [DMA single strand breaks and urinary thioethers] and slightly significant reduction in the levels of antioxidant enzymes [SOD and CAT] and significant increase in GSH levels in exposed workers in comparison with control group. Moreover, level of Sulphur dioxide and Nitrogen dioxide did not exceed the standards Particulate matter which is exceeded the standard limits of indoor air quality. Present data indicate that asphalted fumes exposed workers exhibit an increase in GSH levels and oxidative stress induced by fumes may partly be attributed to the inhibited activities of SOD and CAT as well as increase in the potentials genotoxic risks by increasing the percentage of DNASSB and increase excretion of urinary thioethers

PARP inhibitors: its role in treatment of cancer / 癌症

PARP is an important protein in DNA repair pathways especially the base excision repair (BER). BER is involved in DNA repair of single strand breaks (SSBs). If BER is impaired, inhibiting poly(ADP-ribose) polymerase (PARP), SSBs accumulate and become double stand breaks (DSBs). The cells with increasing number of DSBs become more dependent on other repair pathways, mainly the homologous recombination (HR) and the nonhomologous end joining. Patients with defective HR, like BRCA-deficient cell lines, are even more susceptible to impairment of the BER pathway. Inhibitors of PARP preferentially kill cancer cells in BRCA-mutation cancer cell lines over normal cells. Also, PARP inhibitors increase cytotoxicity by inhibiting repair in the presence of chemotherapies that induces SSBs. These two principles have been tested clinically. Over the last few years, excitement over this class of agents has escalated due to reported activity as single agent in BRCA1- or BRCA2-associated ovarian or breast cancers, and in combination with chemotherapy in triple negative breast cancer. This review covers the current results of clinical trials testing those two principles. It also evaluates future directions for the field of PARP inhibitor development.

The Effects of Mild Hypothermia on the Expression of the Apoptosis-related Proteins following Transient Global Ischemia in Gerbil Hippocampus / 대한구급학회지

BACKGROUND: The neuroprotective mechanisms of hypothermia remain unclear. Recently, attenuation of apoptosis by hypothermia has been suggested as one of the responsible mechanisms. The aim of this study is to investigate the effects of post-ischemic hypothermia on apoptotic neuronal death as well as expression of some apoptosis-related proteins in a gerbil transient global ischemia model. METHODS: Following 5 minutes of ischemia, normothermia (NT, 37+/-0.5degrees C) or mild hypothermia (HT, 33+/-0.5degrees C) was immediately induced and maintained for 3 hours. The hippocampal CA1 neurons were examined on day 2, 3, 4, and 7 after ischemia for the survived neuronal densities, DNA nick end labeling and immunohistochemical expressions of Bcl-2, Bax, and caspase 3 in each group. Additionally, DNA gel electrophoresis and western blot analysis for each protein in hippocampus were performed. RESULTS: The neuronal death in CA1 area on day 3, 4, and 7 was significantly reduced in HT group compared to NT group. The number of TUNEL positive cells in HT group was also significantly reduced than NT group on day 3, 4, and 7. DNA laddering of hippocampus on day 4 and 7 also reduced in HT group. Expressions of Bax on days 2, 3 and activated caspase 3 on days 3, 4 were reduced in HT group. Western blots also disclosed a decrease in the intensity of the Bax on day 2 and 3 in HT group compared to NT group. CONCLUSIONS: These results suggest that mild post-ischemic hypothermia attenuates the apoptotic neuronal death through the inhibition of the intrinsic pathway of caspase activation following transient global ischemia and these effects may be related to a reduction of pro-apoptotic events.

Effect of low-intensity microwave of on mitomycin C-induced genotoxicity in vitro / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study that low-intensity microwave whether or not enhances the genotoxic effects of mitomycin C(MMC) on human lymphocytes.</p><p><b>METHODS</b>Single strand DNA breaks and chromosomal aberrations were measured by comet assay and cytokinesis-blocked micronucleus(CBMN) test in vitro when human lymphocytes were exposed to 2,450-MHz microwave (5.0 mW/cm2) alone and in combination with mitomycin C.</p><p><b>RESULTS</b>In the comet assay, the average comet lengths of microwave group[(29.1 +/- 8.1) micron in male and (25.9 +/- 7.5) micron in female] were not significantly different from those of control groups [(26.3 +/- 6.6) and (24.1 +/- 4.3) micron respectively] (P > 0.05). The average comet lengths of MMC group(0.0125, 0.0250, 0.0500, 0.1000 microgram/ml) were significantly longer than those of control groups (P < 0.01) and were increased with the dose of MMC. The average comet lengths of microwave combined with MMC (MW + MMC) also were increased with the doses of MMC and were significantly longer than those of control groups (P < 0.01). When MMC was > or = 0.0250 microgram/ml, microwave and MMC synergistically increased the single strand DNA breaks. In the micronucleus test, the average micronucleus rates of microwave groups were not higher than those of control groups (P > 0.05). The average micronucleus rates of MMC groups and MW + MMC groups were significantly higher than those of control groups (P < 0.01) when MMC was > or = 0.0500 microgram/ml. The average micronucleus rates of MW + MMC groups seemed higher than those of corresponding MMC groups, however the difference was not significant (P > 0.05).</p><p><b>CONCLUSION</b>Low-intensity(2,450-MHz) microwave did not induce DNA and chromosome damages on human lymphocytes, but enhanced the effects of DNA breaks induced by MMC.</p>

The Expression of Apoptosis in Lupus Nephritis / 대한내과학회지

BACKGROUND: A few researches on apoptosis in proliferative glomerulonephritis including lupus nephritis, have been reported on the basis of animal experimental models and human renal biopsy tissues. Systemic lupus erythematosus has been reported as a disease with an apoptosis defect of lymphocyte, so that it leads to the decreased immunologic tolerance and activated autoimmunity. The lupus nephritis is frequently accompanied with a interstitial fibrosis and tubuloepithelial change, as compared to other nephitis. In addition to that, the pathologic evolution from one class to other class is also feasible and these things make us to think that the lupus nephritis is tightly linked to the apoptosis. METHOD: We evaluated the relationship between the apoptosis and pathologic characteristics, which was focused on class IV, in 22 patients with clinically and biopsy proven lupus nephritis by comparing with control specimens. The study on the apoptosis was observed through in situ DNA nick end-labeling method and the review on the medical history. RESULTS: 1) An apoptosis in glomerulus was observed in only five patients (zero in Class II, 50% in Class IV) of proliferative glomerulonephritis. But 14 patients (50% in Class II, 75% in Class IV) were detected on the site of tubulo-interstitium. 2) The apoptosis detected in tubulo-interstitial area was significantly correlated with nephrotic syndrome (P<0.025), but correlations with the complement serum level, renal function and the used amount of steroid was not determined. CONCLUSION: The apoptosis of glomerulus in the lupus nephritis was observed in 50% of proliferative cases (especially, in class IV), but in the area of tubulointerstitium, the higher rate (more than 50%) of apoptotic expressions were observed in class II and class IV. The observation on apoptosis in renal tissue could be another prognostic factor.