Application of the comet assay for the evaluation of DNA damage in mature sperm

5-Aminolevulinate acid improves boar semen quality by enhancing the sperm mitochondrial function

5-Aminolevulinic acid (5-ALA) is a crucial metabolic intermediate that affect mitochondrial function in somatic cells. However, the mechanisms by which 5-ALA regulates boar reproductive performance remain unclear. The effect of dietary supplementation of 5-ALA on boar semen quality and reproductive performance were investigated in this study. Forty-five boars were randomly assigned to a control group and four 5-ALA-treatment groups (125, 250, 500, and 1000 mg/kg/d). After nine weeks of treatment, serum and semen samples were collected from the boars for analysis. Results showed that the supplementation of 5-ALA to boar diet significantly (p < 0.05) increased semen volume, total sperm count, and sperm motility while reducing the proportion of abnormality (p < 0.05). Specifically, 250 mg/kg/d 5-ALA treatment significantly (p < 0.05) reduced sperm DNA oxidative damage and elevated serum testosterone levels. Metabolomic analysis revealed that 250 mg/kg/d 5-ALA supplementation significantly increased (p < 0.05) the levels of tricarboxylic acid (TCA) cycle intermediates such as malate and isocitrate, while significantly (p < 0.05) reducing harmful metabolites such as N-acetyl phenylalanine that negatively impact sperm quality and fertility. Notably, 250 mg/kg/d 5-ALA supplementation upregulated the protein levels of mitochondrial oxidative phosphorylation (OXPHOS) complex subunits (NDUFB8, SDHB, UQCRC2, MTCO2, and ATP5A1) and improved sperm mitochondrial membrane potential, adenosine triphosphate (ATP) levels, and complex IV activity (p < 0.05). Regarding reproductive performance, compared to the control, the percentage of piglets born alive increased by 2.97 %, the farrowing rate improved by 10.59 %, and the occurrence of mummified fetuses decreased by 1.07 % in the 5-ALA-treated groups (p < 0.05). Additionally, 250 mg/kg/d 5-ALA had a long-term beneficial advantage on boar semen quality parameters. Accordingly, dietary supplementation of 5-ALA, specifically, 250 mg/kg/d 5-ALA improved boar semen quality by enhancing seminal plasma metabolome, sperm mitochondrial function and overall reproductive performance.

Pesticide stress induces spermatozoa DNA damage and morphological abnormalities in Apis mellifera populations

The rising losses of honey bee colonies are causing public concern regarding the species' long-term sustainability. Therefore, this study aimed to assess how pesticide exposure affects DNA damage and morphological traits of drone spermatozoa across different Apis mellifera populations, categorized by varying colony loss rates. Chromatographic analysis identified 24 pesticide residues in bee samples and colony food stocks. Significant differences were found in comet assay parameters (tail intensity and Olive tail moment), frequency of morphological abnormalities, and morphometric variations in spermatozoa between apiaries experiencing high versus low mortality rates. The findings indicate that DNA damage and morphological abnormalities in spermatozoa, potentially caused by pesticide stress, compromise the reproductive ability of honey bee drones, contributing to the complex phenomenon of colony loss. The comet assay parameters and morphological aberrations of honey bee spermatozoa may serve as effective biomarkers for evaluating the fitness of drone spermatozoa and assessing environmental hazards to bee populations.

Perspective in the Mechanisms for Repairing Sperm DNA Damage

DNA damage in spermatozoa is a major cause of male infertility. It is also associated with adverse reproductive outcomes (including reduced fertilization rates, embryo quality and pregnancy rates, and higher rates of spontaneous miscarriage). The damage to sperm DNA occurs during the production and maturation of spermatozoa, as well as during their transit through the male reproductive tract. DNA damage repair typically occurs during spermatogenesis, oocytes after fertilization, and early embryonic development stages. The known mechanisms of sperm DNA repair mainly include nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), and double-strand break repair (DSBR). The most severe type of sperm DNA damage is double-strand break, and it will be repaired by DSBR, including homologous recombination (HR), classical non-homologous end joining (cNHEJ), alternative end joining (aEJ), and single-strand annealing (SSA). However, the precise mechanisms of DNA repair in spermatozoa remain incompletely understood. DNA repair-associated proteins are of great value in the repair of sperm DNA. Several repair-related proteins have been identified as playing critical roles in condensing chromatin, regulating transcription, repairing DNA damage, and regulating the cell cycle. It is noteworthy that XRCC4-like factor (XLF) and paralog of XRCC4 and XLF (PAXX) -mediated dimerization promote the processing of populated ends for cNHEJ repair, which suggests that XLF and PAXX have potential value in the mechanism of sperm DNA repair. This review summarizes the classic and potential repair mechanisms of sperm DNA damage, aiming to provide a perspective for further research on DNA damage repair mechanisms.

Sperm DNA Fragmentation and Fertility

Elevated levels of sperm deoxyribonucleic acid (DNA) fragmentation (SDF) have been associated with several adverse reproductive outcomes, including: lower natural and assisted reproductive technology (ART) pregnancy rates, abnormal embryo development, and recurrent pregnancy loss. However, due to conflicting study results, limited high-level evidence, multiple clinically available assays, and variable standard reference ranges, precisely how SDF testing should be applied to the evaluation and treatment of infertile men remains controversial. To better understand SDF and its role in clinical practice, this chapter aims to: (1) review the literature that has made SDF such a controversial topic, (2) discuss newly published evidence contributing to this complex discussion, and (3) outline the most recent practice guidelines currently available.

Evaluation of Oxidative Stress in Mammalian Spermatozoa

Oxidative stress, characterized by an imbalance between prooxidants and antioxidants in favor of the former, can lead to cellular damage due to the accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In spermatozoa, oxidative stress plays a crucial role in signaling pathways associated with capacitation, a process essential for fertilization. However, the limited capacity of spermatozoa to buffer ROS makes them susceptible to oxidative stress. Measurement of oxidative stress in spermatozoa is important as it precedes or directly causes the loss of basic sperm functions-such as motility and the membrane changes required for zona binding and gamete fusion-associated with fertility. This chapter aims to describe protocols for assessing oxidative damage in spermatozoa, encompassing the generation of ROS in mitochondria to the manifestation of oxidative damage in DNA, proteins, and lipids. In addition to the detailed instructions provided within this chapter, we have sought to provide background information on the development and significance of the assays which we most commonly utilize in our laboratory.

Optimization of concentrations and exposure durations of commonly used positive controls in the in vitro alkaline comet assay

Endogenous and exogenous factors cause DNA damage through chemical changes in the genomic DNA structure. The comet assay is a versatile, rapid, and sensitive method for evaluating DNA integrity at the individual cell level. It is used in human biomonitoring studies, the identification of DNA lesions, and the measurement of DNA repair capacity. Despite its widespread application, variations between studies remain problematic, often due to the lack of a common protocol and appropriate test controls. Using positive controls is essential to assess inter-experimental variability and ensure reliable results. Hydrogen peroxide (H2O2) is the most commonly used positive control, while potassium bromate (KBrO₃), methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), N-ethyl-N-nitrosourea (ENU), and etoposide are used less frequently. However, differences in concentrations and exposure durations prevent the confirmation of test method efficacy. This study investigates the dose-response relationship for H2O2, KBrO3, MMS, EMS, ENU and etoposide in the comet assay for 30 and 60-minute exposure durations in 3T3 cell lines. Accordingly recommended concentrations and exposure durations were found to be 50 μM 30 minutes (H2O2); 500 μM 60 min. (MMS); 10 μM 30 min. (Etoposide); 0.2 mM 30 min. and 2 mM 60 min. (EMS); 2 mM 30 min. (ENU); 500 μM 30 min. and 50 μM 60 min. (KBrO3). Our findings will contribute to reducing inter-laboratory variability by offering guidance on selecting doses and exposure durations for positive controls in the in vitro alkaline comet assay.

Designing and applying a methodology to assess sperm cell viability and DNA damage in a model amphipod

Sperm quality is defined as the sperm cell ability to successfully fertilize eggs and allow normal embryo development⁠. Few studies explore sperm quality using aquatic invertebrates. Parhyale hawaiensis is a marine amphipod with a circumtropical distribution and considered a model for evolution, development, and ecotoxicological studies. We aimed to develop a methodology to collect sperm cells of P. hawaiensis and evaluate their viability and DNA damage (comet assay). We directly exposed the sperm cells to different mutagenic agents to optimize/develop the protocols. Then, as a proof of concept, we exposed the males to mutagenic compounds (EMS, benzo[a]pyrene (BaP), azo and anthraquinone dyes) at non-lethal concentrations verified by the proposed viability test and analyzed their sperm cells for DNA damage (comet assay). Organisms exposed to EMS presented a clear concentration response in the DNA damage response. We also showed that BaP was able to induce a statistically significant increase in DNA damage of the sperm cells. For the two dyes, although DNA damage increased, statistically differences were not observed. We believe we successfully developed a test to detect genotoxicity of chemicals in sperm cells using an invertebrate model. The protocol for sperm cell viability needs to be further explored with different chemicals to verify its utility as a toxicity endpoint. The developed genotoxicity test has the advantages to employ organisms that are easily cultivated in reduced space, use simple laboratory resources and reduced amount of material and reagents. Positive responses with this model could be used to disclose new germ cell mutagen candidates which could be further confirmed in vertebrates' systems.

Comparison of DNA damage in fresh and frozen blood samples: implications for the comet assay in human biomonitoring studies

The use of the comet assay in large biomonitoring studies may present logistical and technical challenges because of the processing of numerous samples. Proper sample preservation becomes imperative to prevent spurious DNA breakage. Previous research has shown the feasibility of conducting the comet assay on frozen blood samples, highlighting the potential of freezing at - 80 °C in preserving DNA integrity. Nonetheless, this approach presents challenges, including potential DNA damage during freezing and thawing, variability in processing, and the need for standardized protocols. Our objective was to evaluate whether there are comparable results in DNA migration assessed by the comet assay between fresh and frozen blood samples on a larger scale (N = 373). In our findings, elevated DNA migration was evident in frozen samples relative to fresh ones. Additionally, smoking, alcohol consumption, and season were linked to increased DNA damage levels in whole blood cells. Based on our results and available literature, conducting the comet assay on frozen blood samples emerges as a practical and efficient approach for biomonitoring and epidemiological research. This method enables the assessment of DNA damage in large populations over time, with samples, if properly cryopreserved, that may be used for years, possibly even decades. These observations hold significant implications for large-scale human biomonitoring and long-term epidemiological studies, particularly when samples are collected during fieldwork or obtained from biobanks. Continued method optimization and validation efforts are essential to enhance the utility of this approach in environmental and occupational health studies, emphasizing caution when comparing data obtained between fresh and frozen blood samples.

GL-V9 synergizes with oxaliplatin of colorectal cancer via Wee1 degradation mediated by HSP90 inhibition

OBJECTIVES

GL-V9 exhibited anti-tumour effects on various types of tumours. This study aimed to verify if GL-V9 synergized with oxaliplatin in suppressing colorectal cancer (CRC) and to explore the synergistic mechanism.

METHODS

The synergy effect was tested by MTT assays and the mechanism was examined by comet assay, western blotting and immunohistochemistry (IHC). Xenograft model was constructed to substantiated the synergy effect and its mechanism in vivo.

RESULTS

GL-V9 was verified to enhance the DNA damage effect of oxaliplatin, so as to synergistically suppress colon cancer cells in vitro and in vivo. In HCT-116 cells, GL-V9 accelerated the degradation of Wee1 and induced the abrogation of cell cycle arrest and mis-entry into mitosis, bypassing the DNA damage response caused by oxaliplatin. Our findings suggested that GL-V9 binding to HSP90 was responsible for the degradation of Wee1 and the vulnerability of colon cancer cells to oxaliplatin. Functionally, overexpression of either HSP90 or WEE1 annulled the synergistic effect of GL-V9 and oxaliplatin.

CONCLUSIONS

Collectively, our findings revealed that GL-V9 synergized with oxaliplatin to suppress CRC and displayed a promising strategy to improve the efficacy of oxaliplatin.

In vitro exposure to environmentally relevant concentrations of norgestrel affects sperm physiology and reproductive success of the Pacific oyster Crassostrea gigas

Progestins in aquatic environments are of increasing concern, as shown by the results of toxicological studies on adult invertebrates with external fertilization. However, their potential effects on the gametes and reproductive success of such animals remain largely unknown. Thus, the current study assessed the effect of in vitro exposure of environmentally relevant concentrations (10 ng/L and 1000 ng/L) of norgestrel (NGT) on the sperm of Pacific oyster Crassostrea gigas, analyzing sperm motility, ultrastructure, mitochondrial function, ATP status, characteristic enzyme activities, and DNA integrity underlying fertilization and hatching success. The results showed that NGT increased the percentage of motile sperm by elevating intracellular Ca²⁺ levels, Ca²⁺-ATPase activity, creatine kinase activity, and ATP content. Although superoxide dismutase activity was enhanced to eliminate reactive oxygen species generated by NGT, oxidative stress occurred, as indicated by the increase in malonaldehyde content and damage to plasma membranes and DNA. As a consequence, fertilization rates decreased. However, hatching rates did not alter significantly, possibly as a result of DNA repair processes. This study demonstrates oyster sperm as a useful, sensitive tool for toxicological research of progestins and provides ecologically relevant information on reproductive disturbance in oysters resulting from exposure to NGT.

Measuring DNA modifications with the comet assay: a compendium of protocols

The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.

Nanoparticles for cancer therapy: a review of influencing factors and evaluation methods for biosafety

Nanoparticles are widely used in the biomedical field for diagnostic and therapeutic purposes due to their small size, high carrier capacity, and ease of modification, which enable selective targeting and as contrast agents. Over the past decades, more and more nanoparticles have received regulatory approval to enter the clinic, more nanoparticles have shown potential for clinical translation, and humans have increasing access to them. However, nanoparticles have a high potential to cause unpredictable adverse effects on human organs, tissues, and cells due to their unique physicochemical properties and interactions with DNA, lipids, cells, tissues, proteins, and biological fluids. Currently, issues, such as nanoparticle side effects and toxicity, remain controversial, and these pitfalls must be fully considered prior to their application to body systems. Therefore, it is particularly urgent and important to assess the safety of nanoparticles acting in living organisms. In this paper, we review the important factors influencing the biosafety of nanoparticles in terms of their properties, and introduce common methods to summarize the biosafety evaluation of nanoparticles through in vitro and in body systems.

Genotoxic Risks to Male Reproductive Health from Radiofrequency Radiation

During modern era, mobile phones, televisions, microwaves, radio, and wireless devices, etc., have become an integral part of our daily lifestyle. All these technologies employ radiofrequency (RF) waves and everyone is exposed to them, since they are widespread in the environment. The increasing risk of male infertility is a growing concern to the human population. Excessive and long-term exposure to non-ionizing radiation may cause genetic health effects on the male reproductive system which could be a primitive factor to induce cancer risk. With respect to the concerned aspect, many possible RFR induced genotoxic studies have been reported; however, reports are very contradictory and showed the possible effect on humans and animals. Thus, the present review is focusing on the genomic impact of the radiofrequency electromagnetic field (RF-EMF) underlying the male infertility issue. In this review, both in vitro and in vivo studies have been incorporated explaining the role of RFR on the male reproductive system. It includes RFR induced-DNA damage, micronuclei formation, chromosomal aberrations, SCE generation, etc. In addition, attention has also been paid to the ROS generation after radiofrequency radiation exposure showing a rise in oxidative stress, base adduct formation, sperm head DNA damage, or cross-linking problems between DNA & protein.

Sperm DNA Damage and Its Relevance in Fertility Treatment: A Review of Recent Literature and Current Practice Guidelines

Sperm deoxyribonucleic acid (DNA) damage has recently emerged as one of the most controversial topics in male reproductive medicine. While level I evidence indicates that abnormal sperm DNA damage has substantial adverse effects on reproductive outcomes (including chance of pregnancy and risk of miscarriage), there is limited consensus on how sperm DNA fragmentation (SDF) testing should be performed and/or interpreted in clinical practice. In this article, we review: (1) how SDF is assessed, (2) cumulative evidence regarding its impact on reproductive outcomes, (3) methods for mitigating high SDF, and (4) the most recent practice guidelines available for clinicians regarding the use and interpretation of SDF testing.

An evaluation of aging measures: from biomarkers to clocks

With the increasing number of aged population and growing burden of healthy aging demands, a rational standard for evaluation aging is in urgent need. The advancement of medical testing technology and the prospering of artificial intelligence make it possible to evaluate the biological status of aging from a more comprehensive view. In this review, we introduced common aging biomarkers and concluded several famous aging clocks. Aging biomarkers reflect changes in the organism at a molecular or cellular level over time while aging clocks tend to be more of a generalization of the overall state of the organism. We expect to construct a framework for aging evaluation measurement from both micro and macro perspectives. Especially, population-specific aging clocks and multi-omics aging clocks may better fit the demands to evaluate aging in a comprehensive and multidimensional manner and make a detailed classification to represent different aging rates at tissue/organ levels. This framework will promisingly provide a crucial basis for disease diagnosis and intervention assessment in geroscience.

Evaluating the relationship between the respiratory exposure to the benzene with the primary damages of deoxyribonucleic acid and total antioxidant capacity in one of the oil companies in Iran

Benzene is a carcinogenic chemical substance which causes the injuries and damages through producing the free radicals in DNA (deoxyribonucleic acid) and the antioxidants are the agents which reduce the impacts of DNA damages by inhibiting the free radicals. This study was conducted aiming at determination of primary damages of DNA and level of plasma oxidative stress markers resulting from the respiratory exposure to the benzene found in petroleum compounds among the workers at loading platforms of a petroleum products distribution center. This study was an analytical (case control) research conducted among the workers in a working shift serving at the loading platforms of petroleum products. The exposure group included the workers with a history of contact with benzene and the control group was composed of the persons with no history of exposure to benzene. To investigate the level of the personnel's exposure to benzene, NIOSH-1501 method was utilized; to analyze the samples taken from the air, GC mass (gas chromatography-mass spectrometry) was applied; and to determine the average of DNA primary damages, comet assay was used. Total antioxidant capacity was determined by a photometric method. Results indicated that tail length (TL), tail density (TD), tail momentum (TM), percentage of tail in the DNA (%DNA), and %TAC in control group were 78.59, 8.35, 1.20, 10.05, and 25.58 and in the exposure group were 59.21, 75.74, 57.74, 3.5, and 16.58, respectively. The previously mentioned results showed a decrease in the TL, %DNA, and %TAC values among the workers already exposed to benzene while an increase in the TD and TM values of the same group compared to the control non-exposed group. In comparing the averages between two studied groups, all study variables had statistically meaningful difference (p < 0.05). More studies are recommended to be conducted on using the methods which identify the special places of breakage and damage in DNA chain due to the exposure to benzene and consequently prevent the complications and consequences.