Is the Conjunctiva a Potential Target for Advanced Therapy Medicinal Products?

The conjunctiva is a complex ocular tissue that provides mechanical, sensory, and immune protection for the ocular surface. It is affected by many diseases through different pathological mechanisms. If a disease is not treated and conjunctival function is not fully restored, the whole ocular surface and, therefore, sight is at risk. Different therapeutic approaches have been proposed, but there are still unsolved conjunctival alterations that require more sophisticated therapeutic options. Advanced therapy medicinal products (ATMPs) comprise a wide range of products that includes cell therapy, tissue engineering, and gene therapy. To the best of our knowledge, there is no commercialized ATMP specifically for conjunctival treatment yet. However, the conjunctiva can be a potential target for ATMPs for different reasons. In this review, we provide an overview of the advances in experimental phases of potential ATMPs that primarily target the conjunctiva. Important advances have been achieved through the techniques of cell therapy and tissue engineering, whereas the use of gene therapy in the conjunctiva is still marginal. Undoubtedly, future research in this field will lead to achieving commercially available ATMPs for the conjunctiva, which may provide better treatments for patients.

Dark and Photoinduced Cytotoxic Activity of the New Chlorophyll-a Derivatives with Oligoethylene Glycol Substituents on the Periphery of Their Macrocycles

In the present work, we investigated the dark and photoinduced cytotoxic activity of the new chlorophyll-a derivatives which contain the substituents of oligoethylene glycol on the periphery of their macrocycles. These compounds were tested using human cell lines to estimate their potential as photosensitizers for photodynamic therapy of cancer. It was shown that all the tested compounds have expressed photoinduced cytotoxic activity in vitro. Detailed study of the biological activity of one of the most perspective compound in this series—pyropheophorbide-a 17-diethylene glycol ester (Compound 21) was performed. This new compound is characterized by lower dark cytotoxicity and higher photoinduced cytotoxicity than previously described in a similar compound (DH-I-180-3) and clinically used Photolon^TM. Using fluorescent microscopy, it was shown that Compound 21 quickly penetrates the cells. Analysis of caspase-3 activity indicated an apoptosis induction 40 min after exposure to red light (λ = 660 nm). The induction of DNA damages and apoptosis was shown using Comet assay. The results of expression analysis of the stress-response genes indicate an activation of the genes which control the cell cycle and detoxification of the free radicals after an exposure of HeLa cells to Compound 21 and to red light. High photodynamic activity of this compound and the ability to oxidize biomolecules was demonstrated on nuclear-free mice erythrocytes. In addition, it was shown that Compound 21 is effectively activated with low energy 700 nm light, which can penetrate deep into the tissue. Thus, Compound 21 is a prospective substance for development of the new drugs for photodynamic therapy of cancer.

Differential Molecular Stress Responses to Low Compared to High Doses of Ionizing Radiation in Normal Human Fibroblasts

Understanding the mechanisms producing low dose ionizing radiation specific biological effects represents one of the major challenges of radiation biology. Although experimental evidence does suggest that various molecular stress response pathways may be involved in the production of low dose effects, much of the detail of those mechanisms remains elusive. We hypothesized that the regulation of various stress response pathways upon irradiation may differ from one another in complex dose-response manners, causing the specific and subtle low dose radiation effects. In the present study, the transcription level of 22 genes involved in stress responses were analyzed using RT-qPCR in normal human fibroblasts exposed to a range of gamma-doses from 1 to 200 cGy. Using the alkali comet assay, we also measured the level of DNA damages in dose-response and time-course experiments. We found non-linear dose responses for the repair of DNA damage after exposure to gamma-radiation. Alterations in gene expression were also not linear with dose for several of the genes examined and did not follow a single pattern. Rather, several patterns could be seen. Our results suggest a complex interplay of various stress response pathways triggered by low radiation doses, with various low dose thresholds for different genes.

Cigarette smoking is associated with human semen quality in synergy with functional NRF2 polymorphisms

Although cigarette smoking is considered a major risk factor for several human diseases, the effects of smoking on male fertility are controversial. Studies on the consequences of smoking, which also take into account genetic background, may facilitate understanding of the interactions between genes and smoking and their effects on male fertility. In this study, genetic variants of two functional polymorphisms of erythroid 2-related factor 2 (NRF2), mRNA expression levels of the antioxidant gene NRF2, catalase (CAT), superoxide dismutase isoenzyme-2 (SOD2), glutathione S-transferase-M1 (GSTM1), and seminal SOD activities were compared in 314 heavy smokers and 314 matched nonsmokers. The NRF2 rs6721961 TT genotype was found to be associated with low semen quality in heavy smokers (OR [95% CI] = 2.370 [1.106-5.081]). This variant genotype was found more frequently in heavy smokers with low semen quality than in those with high semen quality (P = 0.011). Heavy smokers with this genotype had significantly lower sperm concentrations and sperm counts (P < 0.05) when compared with those without this genotype. Smoking was also significantly associated with decreased seminal SOD activity (P < 0.05) and reduced NRF2 and SOD2 mRNA expression in heavy smokers with this variant genotype. These results were specific to heavy smokers with the NRF2 rs6721961 TT genotypes, but did not apply to nonsmokers or heavy smokers that did not carry this genotype. This study suggests an association between cigarette smoking in heavy smokers with NRF2 rs6721961 TT genotype and a decrease in semen quality.

Low NRF2 mRNA expression in spermatozoa from men with low sperm motility

Antioxidant genes and enzymes play important roles in human spermatogenesis. Although low levels of antioxidant enzyme expression are associated with poor sperm quality, it is not clear whether mRNA expression of antioxidant genes is lower in these men than in normozoospermic men. In this study, 55 asthenozoospermic and oligoasthenozoospermic patients and 65 controls were recruited. Quantitative real-time reverse transcription PCR was performed and the abundance of mRNA of four antioxidant genes known to be important to spermatogenesis were evaluated. These genes were nuclear factor erythroid 2-related factor 2 (NRF2), catalase (CAT), glutathione S-transferase Mu 1 (GSTM1), and superoxide dismutase isoenzyme 2 (SOD2). Results showed the level of NRF2 mRNA expression to be significantly lower in patients than in controls (P < 0.001), but no statistically significant difference in the level of SOD2, CAT, or GSTM1 gene expression was observed between the two groups. A significant correlation was observed between the level of NRF2 mRNA expression and specific sperm function parameters, including concentration, progressive motility, immotility, vitality, and morphology (all P < 0.01). NRF2 expression was also found to be associated with seminal SOD activity and mRNA levels of the CAT and SOD2 genes (all P < 0.05). Therefore, our data demonstrated that the level of NRF2 mRNA expression is significantly lower in human males with low sperm motility and correlated with specific sperm function parameters. This suggests that NRF2 is important to spermatogenesis and may serve as a useful biomarker in the prediction of male infertility.

2-Deoxy-D-glucose and 6-aminonicotinamide-mediated Nrf2 down regulation leads to radiosensitization of malignant cells via abrogation of GSH-mediated defense

Enhanced level of nuclear erythroid-related factor-2 (Nrf2) has been associated with cancer chemo/radioresistance. Therefore, the role of Nrf2 in radiosensitization of malignant cells induced by a combination of 2-deoxy-D-Glucose (2-DG) and 6-aminonicotinamide (6-AN) was investigated. Two established human malignant cells lines namely KB (head and neck squamous carcinoma) and BMG-1 (cerebral glioma) were used. Following treatment with a combination of 2-DG (5 mM) and 6-AN (5 μM), irradiated (2Gy) KB and BMG-1 cells were assessed for protein level of Nrf2, Keap1 and γ-glutamylcysteine synthetase (γ-GCS) by western blotting and mRNA expression of γ-GCS, glutathione reductase (GR) and glutathione peroxidase (GPx1) by RT-PCR at 24 hours post treatment. A significant decrease in the level of Nrf2 with a concomitant increase in Keap1 was observed in both the irradiated malignant cells at 24 hours following treatment with combination (2-DG + 6-AN). Down regulation of γ-GCS, GR and GPx1 at 24 hours following treatment with combination (2-DG + 6-AN) resulted in abrogation of glutathione (GSH)-mediated defense in both the irradiated malignant cells. Eventual accumulation of ROS led to radiosensitization of both the malignant cells. These results indicate that deregulated Nrf2-Keap1 signalling leads to the radiosensitization of malignant cells due to abrogated glutathione defense. Metabolic modification-mediated down regulation of Nfr2 and its downstream signalling may have a potential of improving tumour radiotherapy.

Genetic variation in the Nrf2 promoter associates with defective spermatogenesis in humans

Defective spermatogenesis, which severely impairs male fertility, can be caused by excessive reactive oxygen species (ROS). Nuclear factor erythroid 2-related factor 2 (Nrf2) regulates transcription of genes encoding enzymes important for protection against ROS. In human seminal plasma and spermatozoa, superoxide dismutase isoenzymes (SOD) and glutathione S-transferases (GST) are key antioxidant enzymes. We hypothesized that decreased function of the Nrf2-antioxidant response element (ARE) pathway might predispose individuals to male infertility. In this study, we identified three functional single nucleotide polymorphisms (SNPs) in the Nrf2 promoter regions of 196 idiopathic asthenozoospermic patients, 140 idiopathic oligoasthenozoospermic patients, and 295 controls. We found that two of the Nrf2 SNPs (-617 G > T and -653 T > C) were associated with oligoasthenozoospermia (p = 0.001) and individuals with 617 TT and 653 TT genotypes had higher risk of oligoasthenozoospermia (p = 0.006 and p = 0.002). Four haplotypes of Nrf2 promoters were identified, and two of them (GCC and TCT) had different frequencies in oligoasthenozoospermic patients than in controls (p = 0.019 and p = 0.011). In vitro reporter assay indicated that oligoasthenozoospermia associated genotypes of Nrf2 had significantly decreased transcriptional capabilities. The GCC and TCT haplotypes both showed lower Nrf2 mRNA expression in spermatozoa than GCT. TCT also showed decreased levels of antioxidant gene GSTM1 and SOD2 mRNA. Analysis of total seminal SOD activity elucidated that oligoasthenozoospermic patients had less SOD activity than controls. This study is the first to demonstrate a strong association between functional polymorphisms in Nrf2 promoters with defective spermatogenesis in humans.

Do toxic heavy metals affect antioxidant defense mechanisms in humans?

The aim of this study was to prove whether anthropogenic pollution affects antioxidant defense mechanisms such as superoxide dismutase (SOD) and catalase (CAT) activity, ferritin (FRT) concentration and total antioxidant status (TAS) in human serum. The study area involves polluted and salted environment (Kujawy region; northern-middle Poland) and Tuchola Forestry (unpolluted control area). We investigated 79 blood samples of volunteers from polluted area and 82 from the control in 2008 and 2009. Lead, cadmium and iron concentrations were measured in whole blood by the ICP-MS method. SOD and CAT activities were measured in serum using SOD and CAT Assay Kits by the standardized colorimetric method. Serum TAS was measured spectrophotometrically by the modified Benzie and Strain (1996) method and FRT concentration-by the immunonefelometric method. Pb and Cd levels and SOD activity were higher in volunteers from polluted area as compared with those from the control (0.0236 mg l(-1) vs. 0.014 mg l(-1); 0.0008 mg l(-1) vs. 0.0005 mg l(-1); 0.137 Um l(-1) vs. 0.055 Um l(-1), respectively). Fe level, CAT activity and TAS were lower in serum of volunteers from polluted area (0.442 g l(-1) vs. 0.476 gl(-1); 3.336 nmol min(-1)ml(-1) vs. 6.017 nmol min(-1)ml(-1); 0.731 Trolox-equivalents vs. 0.936 Trolox-equivalents, respectively), whilst differences in FRT concentration were not significant (66.109 μg l(-1) vs. 37.667 μg l(-1), p=0.3972). Positive correlations between Pb (r=0.206), Cd (r=0.602) and SOD in the inhabitants of polluted area, and between Cd and SOD in the control (r=0.639) were shown. In volunteers from both studied environments TAS-FRT (polluted: r=0.625 vs. control: r=0.837) and Fe-FRT (polluted area: r=0.831 vs. control: r=0.407) correlations, and Pb-FRT (r=0.360) and Pb-TAS (r=0.283) in the control were stated. The higher lead and cadmium concentrations in blood cause an increase of SOD activity. It suggests that this is one of the defense mechanisms of an organism against oxidative stress caused by environmental factors, whilst non-enzymatic mechanisms marked by TAS are the main antioxidant defense system in relation with Pb concentration in humans from unpolluted area. Simultaneously, the higher CAT activity and TAS can indicate that these mechanisms play a key role in the antioxidant protection in non-stressed environments.