Michał Kowalski

Genetic polymorphisms in DNA base excision repair gene XRCC1 and the risk of squamous cell carcinoma of the head and neck

BackgroundThe genes of base excision repair (BER) pathway have been extensively studied in the association with various human cancers. We performed a case-control study to test the association between two common single nucleotide polymorphisms (SNPs) of XRCC1 gene with human head and neck squamous cell carcinoma (HNSCC).MethodsThe genotype analysis of Arg194Trp and Arg399Gln gene polymorphisms for 92 HNSCC patients and 124 controls of cancer free subjects, in Polish population were performed using the PCR-based restriction fragment length polymorphism (PCR-RFLP) with endonuclease Msp I.ResultsNo altered risk has been found individually for these SNPs, however haplotypes analysis showed high association with head and neck cancer. The highest frequency, according to wild-type of Arg194Arg and Arg399Arg genotypes, was identified for Arg194Trp-Arg399Arg haplotype (OR, 2.96; 95% CI, 1.01–8.80).ConclusionFinally, we identified the combined Arg194Trp-Arg399Arg genotype of base excision repair gene XRCC1 that was associated with HNSCC and may have an impact on identification of a high-risk cancer population.

Evaluation of oxidative stress markers in pathogenesis of primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is the leading cause of blindness in the industrial countries. It is reported that oxidative stress might be an important risk factor in the pathogenesis of POAG. Forty subjects including 20 patients with open-angle glaucoma (9 men and 12 women, mean age 61.8±12.1yr) and 20 controls without glaucoma symptoms (9 men and 12 women, mean age 58.1±17.7yr) were enrolled in our study. The main aim of the work was to evaluate oxidative stress markers in the pathogenesis of open-angle glaucoma. In our work the activity of antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) as well as the total antioxidant status (TAS) was estimated. An alkaline comet assay was used to measure DNA damage of strand breaks (SB), oxidized purines as glicosylo-formamido-glicosylase (Fpg) sites, and oxidized pirmidines as endonuclease III (Nth) sites. We measured endogenous as well as exogenous DNA damage after 10μM hydrogen peroxide treatment (H(2)O(2)). We did not observe any statistical changes of DNA strand break lesion in examined POAG patients according to healthy subjects (P>0.05). However, either endogenous (P<0.01) or exogenous (P<0.001) levels of oxidative DNA damage in POAG patients were found to be statistically higher than controls. A significant decrease of antioxidant enzymes: CAT (P<0.001), SOD (P<0.05), and GPX (P<0.001) and a non-statistical decrease of TAS status (P>0.05) in glaucoma patients according to controls were also indicated. In conclusion our data revealed that oxidative stress had a pathogenic role in primary open-angle glaucoma. Therefore, we suggested that the modulation of a pro-oxidant/antioxidant status might be a relevant target for glaucoma prevention and therapy.

Serum MicroRNAs as Potential Biomarkers of AMD

Background Age-related macular degeneration (AMD) is a major cause of blindness worldwide. Circulating microRNAs (miRNAs) in serum have emerged as novel candidate biomarkers for many diseases. The aim of the present study was to identify a serum microRNA (miRNA) expression profile specific for dry and wet forms of AMD. Material/Methods Serum miRNA expression was first screened using TaqMan® Human MicroRNA Array A (Applied Biosystems). An extensive, self-validated, individual, quantitative RT-PCR (qRT-PCR) study was then performed on a cohort of 300 AMD patients (150 wet form and 150 dry form) and 200 controls. The Mann-Whitney U test and nonparametric Spearman’s rank correlation coefficient were used for statistical analysis. Results miRNA expression analysis revealed increased expression of miR661 and miR3121 in serum of patients with dry AMD and miR4258, miR889, and Let7 in patients with wet form. Expression of analyzed miRNA was not observed or remained at low level in controls. Conclusions Differences in miRNA serum profile exist between patients with wet and dry form of AMD, which indicates miRNAs as potential biomarkers of AMD. Further studies should be performed to confirm its significance in clinical practice.

Role of base-excision repair in the treatment of childhood acute lymphoblastic leukaemia with 6-mercaptopurine and high doses of methotrexate

Methotrexate (MTX) and 6-mercaptopurine (6MP) are the most commonly used drugs in the therapy of childhood acute lymphoblastic leukaemia (ALL). The main genotoxic effect of MTX resulting from inhibition of thymidylate synthase is mis-incorporation of uracil into DNA, which is considered essential for the effectiveness of the Protocol M in ALL IC BFM 2002/EURO LB 2002 regimens. In this study, we investigated the level of basal and induced DNA damage as well as the effectiveness of DNA repair in lymphocytes of children with ALL at four time-points during therapy with MTX and 6MP. To assess DNA damage and the efficacy of DNA repair we used the modified alkaline comet assay with uracil DNA glycosylase (Udg) and endonuclease III (EndoIII). In addition, we examined the induction of apoptosis in the lymphocytes of the patients during treatment. Finally, we compared the activity of base-excision repair (BER), involved in removal of both uracil and oxidized bases from DNA in lymphocytes of children with ALL and lymphocytes of healthy children. BER efficiency was estimated in an in vitro assay with cellular extracts and plasmid substrates of heteroduplex DNA with an AP-site. Our results indicate that there is a significant decrease in the efficacy of DNA repair associated with an increased level of uracil in DNA and induction of apoptosis during therapy. Moreover, it was found that the BER capacity was decreased in the lymphocytes of ALL patients in contrast to that in lymphocytes of healthy children. Thus, we suggest that an impairment of the BER pathway may play a role in the pathogenesis and therapy of childhood ALL.

Ferric Reducing Ability of Tears in Healthy Subjects—Diurnal Variation and Dependence on Defined Demographic Data

Purpose: The assay of the ferric reducing ability of tears (FRAT) can be useful for monitoring ocular antioxidant capacity in clinical settings. FRAT diurnal variation was evaluated in healthy subjects and its relation with age, sex, body mass index, and ferric reducing ability of plasma (FRAP) were studied. Material and Methods: FRAT of 10-μ l tear samples collected with capillary tubes from 68 healthy subjects (age 10 to 92 yrs, 46 women, 22 men) were measured after 0, 3, 5, and 10 min of incubation with Fe3 +. FRAT diurnal variation was estimated in 11 subjects, with tear samples collected every 4 hr during the day. Comparison of FRAT versus FRAP was determined in 20 subjects. Results: Mean FRAT after 10-min incubation reached 207.7 ± 136.8 μ mol/l. No differences were found between FRAT of men and women. Only donor age correlated with FRAT (ρ = 0.40, p < 0.01). Subjects ≤ 59 years had lower FRAT levels than those age > 59 yrs (179.4 ± 95.4 versus 237.2 ± 151.7 μ mol/l, p < 0.01). For all investigated times of incubation, FRAT was approximately two times lower than FRAP (p < 0.01). FRAT revealed diurnal variation, with the highest value at 08:00 hours, upon awakening. Conclusion: The significance of age-matched controls and the specific time of the day for tears collection should be considered in the trial design and investigations with FRAT as a marker of the ocular antioxidant defense system.

The role of Cat -262C/T, GPX1 Pro198Leu and Sod1+35A/C gene polymorphisms in a development of primary open-angle glaucoma in a Polish population

The development of glaucoma may be connected with a long-term exposure to oxidative stress caused by free radical (ROS). The main aim of this work was an analysis of associations of Cat-262C/T, GPX1 Pro198Leu and SOD1 35 A/C gene polymorphisms of antioxidant enzymes with a risk of open-angle glaucoma (POAG) in a Polish population. DNA samples collected from 209 patients with POAG and 191 healthy controls were used in this study. Polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). We found that the +35A/C polymorphisms of SOD1 were not associated with a risk of POAG. We found that C/T genotype (1-GPX1Pro198Leu, 2-Cat C262T) is associated with increased risk of open angle glaucoma (1-OR = 2.24; 95% CI: 1.46-3.44; p = 0.0001, 2-OR = 2.16; 95% CI: 1.35-3.34; p = 0.001). We also found that T/T genotype is a risk factor for progression of POAG (1-OR = 3.86; 95% Cl: 1.36-10.96; p = 0.007, 2-OR = 6.37; 95% CI: 1.39-29.28; p = 0.007). Finally our data suggest that gene polymorphisms of GPX1 Pro198Leu and CAT C262T may have a protective role in the development of primary open-angle glaucoma in a Polish population.

Ethylene glycol dimethacrylate and diethylene glycol dimethacrylate exhibits cytotoxic and genotoxic effect on human gingival fibroblasts via induction of reactive oxygen species

Although methacrylic acid derivatives in their polymeric form are considered to be safe, insufficient polymerization and the release of monomers due to either mechanical or enzymatical factors can lead to their reaching millimolar concentrations in local tissue. The present study evaluates the effect of two methacrylate monomers - ethylene glycol dimethacrylate (EGDMA) and diethylene glycol dimethacrylate (DEGDMA) - on human gingival fibroblasts (HGFs). Both monomers were found to reduce cells viability in MTT assay, increase apoptosis and cause cell cycle arrest in G1/G0 phase. They also increased intracellular reactive oxygen species (ROS) production as measured by DCFH-DA and DHE probes and increased expression of GPx4 and SOD2. Both monomers increased DNA damage in comet assay. Moreover, HGFs were not able to repair those lesions within 120min of repair incubation. However, the monomers were not found to have any effect on the integrity of isolated plasmids. We postulate that EGDMA and DEGDMA exhibit their cytotoxic and genotoxic properties via increased production of ROS, which cause DNA damage, affect apoptosis, viability and cell cycle. Further studies are needed to better understand the properties of methacrylic acid monomers and to evaluate the risk that they cause for patients, dentists and dental technicians.