Lack of association between polymorphisms of the DNA base excision repair genes MUTYH and hOGG1 and keratoconus in a Polish subpopulation

INTRODUCTION

Keratoconus (KC) is a non-inflammatory thinning of the cornea and a leading indication for corneal transplantation. Oxidative stress plays a role in the pathogenesis of this disease. The products of the hOGG1 and MUTYH genes play an important role in the repair of oxidatively modified DNA in the base excision repair pathway. We hypothesized that variability in these genes may change susceptibility to oxidative stress and predispose individuals to the development of KC. We investigated the possible association between the c.977C>G polymorphism of the hOGG1 gene (rs1052133) and the c.972G>C polymorphism of the MUTYH gene (rs3219489) and KC occurrence as well as the modulation of this association by some KC risk factors.

MATERIAL AND METHODS

A total of 205 patients with KC and 220 controls were included in this study. The polymorphisms were genotyped with polymerase chain reaction (PCR) restriction fragment length polymorphism and PCR-confronting two-pair primer techniques. Differences in genotype and allele frequency distributions were evaluated using the χ(2) test, and KC risk was estimated with an unconditional multiple logistic regression with and without adjustment for co-occurrence of visual impairment, allergies, sex and family history for KC.

RESULTS

We did not find any association between the genotypes and combined genotypes of the c.977C>G polymorphism of the hOGG1 gene and the c.972G>C polymorphism of the MUTYH gene and the occurrence of KC.

CONCLUSIONS

Our findings suggest that the c.977C>G-hOGG1 polymorphism and the c.972G>C-MUTYH polymorphism may not be linked with KC occurrence in this Polish subpopulation.

First Report of Cabbage Head Rot Caused by Fusarium avenaceum in Poland

Cabbage (Brassica oleracea L. var. capitata L.) is an important crop in Poland. Symptoms of a disease affecting cabbage were observed in 2012 and 2013 both in mid-August during the growing season and during storage in January and February. The disease affected about 30 to 40% of crops grown on ~9,000 ha over three locations: Charsznica in south Poland and Bedlno and Skierniewice in central Poland. Circular, watery lesions ranging from 10 to 60 mm in diameter on the surface of affected cabbage heads included whitish aerial mycelium that developed orange sporodochia in the center of each lesion. After 2 to 3 weeks, infection covered each entire cabbage head. A fungal pathogen was isolated from the orange lesions and from infected internal tissue. After sterilization of the excised tissue in 70% ethanol, the sections were each rinsed twice with sterilized water, dried on sterilized filter paper, and plated onto potato dextrose agar (PDA). Isolations consistently yielded morphologically homogeneous fungal colonies with abundant aerial mycelium that ranged from yellow to brownish yellow. The fungus produced pigmentation that changed the agar medium from dark yellow to brownish-burgundy. The mean colony growth was 66 mm after 7 days at 25°C. The fungus formed macroconidia, but microconidia and chlamydospores were not observed. Macroconidia were slender, slightly falcate, usually 3- to 5-septate, 44.7 to 60.7 × 3.7 to 5.5 μm, and formed in abundant orange sporodochia. On PDA, the isolates lost the ability to form sporodochia. Morphological and cultural features were typical of those of F. avenaceum (Fries) Saccardo (2). Koch's postulates were conducted to establish pathogenicity of each of four of the isolates on cabbage heads of the cv. Jaguar F1 (Bejo Seeds, Poland). The outer leaf of each head was inoculated with an 8-mm-diameter PDA plug colonized by the appropriate isolate (four cabbage heads/isolate), and the heads stored in a growth chamber at 25°C. After 5 to 7 days, lesions similar to those observed on naturally infested cabbage were observed on all the inoculated cabbage leaves. Four cabbage heads treated similarly with water as a control treatment remained symptomless. The experiment was repeated. DNA extracted from two of the four isolates was subjected to a PCR assay with primers ITS5 and ITS4 (4) for species identification based on the ITS1 and ITS2 sequences of ribosomal DNA (rDNA). The two sequences differed by 1 bp in the ITS2 region and had 100% identity with ITS sequences of F. avenaceum Accession Nos. AY147283 and AY147285 in GenBank. The sequences were deposited in GenBank as KM189440 and KM189441. Descriptions of fusarium head rot of cabbage in the United States (1) and Canada (3) were consistent with these observations in Poland. To our knowledge, this is the first report of F. avenaceum causing head rot of cabbage in Poland and in Europe. References: (1) H. R. Dillard and A. C. Cobb. Phytopathology 96:30. 2006. (2) J. F. Leslie and B. A. Summerell. Page 132 in: The Fusarium Laboratory Manual, Blackwell Publishing, Hoboken, NJ, 2006. (3) R. D. Peters et al. HortSci. 42:737. 2007. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

Helicobacter pylori infection and antioxidants can modulate the genotoxic effects of heterocyclic amines in gastric mucosa cells

Helicobacter pylori (H. pylori) infection plays an important role in gastric carcinogenesis. This bacterium may induce cancer transformation and change the susceptibility of gastric mucosa cells to various exogenous dietary irritants. The aim of the study was to evaluate the influence of H. pylori infection on the reaction of the stomach cells to a genotoxic effect of heterocyclic amines (HCAs). These well-known mutagens are formed during cooking of protein-rich foods, primarily meat. Taking into account that persons consuming a mixed-western diet are exposed to these compound nearly an entire lifetime and more than half of human population is infected with H. pylori, it is important to assess the combined effect of H. pylori infection and HCAs in the context of DNA damage in gastric mucosa cells, which is a prerequisite to cancer transformation. We employed 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) because these substances are present in a great amount in cooked and fried meat. Using alkaline comet assay, we showed that the extent of the DNA damage induced by HCAs was significantly higher in H. pylori infected gastric mucosa cells than in non-infected counterparts. We did not observed any difference in the efficiency of repair of DNA lesions induced by HCAs in both type of cells. Vitamin C reduced the genotoxic effects of HCAs in H. pylori infected and non-infected gastric mucosa cells. Melatonin more effectively decreased DNA damage caused by HCAs in H. pylori infected gastric mucosa cells as compared with control. Our results suggest that H. pylori infection may influence the susceptibility of gastric mucosa cells to HCAs and dietary antioxidative substances, including vitamin C and melatonin may inhibit the genotoxic effects of HCAs on gastric mucosa cells and may reduce the risk of carcinogenesis caused by food borne mutagens and H. pylori infection.