Oxidative Stress: A Comprehensive Review of Biochemical, Molecular, and Genetic Aspects in the Pathogenesis and Management of Varicocele

Cancer risk and male Infertility: Unravelling predictive biomarkers and prognostic indicators

In recent years, there has been a global increase in cases of male infertility. There are about 30 million cases of male infertility worldwide and male reproductive health is showing rapid decline in last few decades. It is now recognized as a potential risk factor for developing certain types of cancer, particularly genitourinary malignancies like testicular and prostate cancer. Male infertility is considered a potential indicator of overall health and an early biomarker for cancer. Cases of unexplained male factor infertility have high levels of oxidative stress and oxidative DNA damage and this induces both denovo germ line mutations and epimutations due to build up of 8-hydroxy 2 deoxygunaosine abase which is highly mutagenic and also induces hypomethylation and genomic instability. Consequently, there is growing evidence to explore the various factors contributing to an increased cancer risk. Currently, the available prognostic and predictive biomarkers associated with semen characteristics and cancer risk are limited but gaining significant attention in clinical research for the diagnosis and treatment of elevated cancer risk in the individual and in offspring. The male germ cell being transcriptionally and translationally inert has a highly truncated repair mechanism and has minimal antioxidants and thus most vulnerable to oxidative injury due to environmental factors and unhealthy lifestyle and social habits. Therefore, advancing our understanding requires a thorough evaluation of the pathophysiologic mechanisms at the DNA, RNA, protein, and metabolite levels to identify key biomarkers that may underlie the pathogenesis of male infertility and associated cancer. Advanced methodologies such as genomics, epigenetics, proteomics, transcriptomics, and metabolomics stand at the forefront of cutting-edge approaches for discovering novel biomarkers, spanning from infertility to associated cancer types. Henceforth, in this review, we aim to assess the role and potential of recently identified predictive and prognostic biomarkers, offering insights into the success of assisted reproductive technologies, causes of azoospermia and idiopathic infertility, the impact of integrated holistic approach and lifestyle modifications, and the monitoring of cancer susceptibility, initiation and progression. Comprehending these biomarkers is crucial for providing comprehensive counselling to infertile men and cancer patients, along with their families.

The Male Reproductive Toxicity Caused by 2-Naphthylamine Was Related to Testicular Immunity Disorders

2-naphthylamine (NAP) was classified as a group I carcinogen associated with bladder cancer. The daily exposure is mostly from cigarette and E-cigarette smoke. NAP can lead to testicular atrophy and interstitial tissue hyperplasia; however, the outcomes of NAP treatment on spermatogenesis and the associated mechanisms have not been reported. The study aimed to investigate the effect of NAP on spermatogenesis and sperm physiologic functions after being persistently exposed to NAP at 5, 20, and 40 mg/kg for 35 days. We found that sperm motility, progressive motility, sperm average path velocity, and straight-line velocity declined remarkably in the NAP (40 mg/kg) treated group, and the sperm deformation rate rose upon NAP administration. The testis immunity- and lipid metabolism-associated processes were enriched from RNA-sequence profiling. Plvap, Ccr7, Foxn1, Trim29, Sirpb1c, Cfd, and Lpar4 involved in testis immunity and Pnliprp1 that inhibit triglyceride and cholesterol absorption were confirmed to rise dramatically in the NAP-exposed group. The increased total cholesterol and CD68 levels were observed in the testis from the NAP-exposed group. Gpx5, serving as an antioxidant in sperm plasma, and Semg1, which contributes to sperm progressive motility, were both down-regulated. We concluded that the short-term exposure to NAP caused reproductive toxicity, primarily due to the inflammatory abnormality in the testis.

Impact of Varicocele on Testicular Oxidative Stress and Sperm Parameters in Experimental Animals: A Systematic Review and Meta-Analysis

PURPOSE

Varicocele has been associated with high seminal oxidative stress (OS), impaired semen quality, and reduced male fertility potential. However, the exact mechanism(s) underlying the development of varicocele-mediated infertility and the cause-effect relationship between varicocele and testicular dysfunction are not fully understood. The aim of this systematic review and meta-analysis (SRMA) is to investigate the impact of varicocele on testicular OS markers and sperm parameters in experimental animals with varicocele as compared to animals without varicocele.

MATERIALS AND METHODS

A literature search was performed using the Scopus and PubMed databases on studies that investigated testicular OS markers and sperm parameters in animals with varicocele. The primary outcomes included malondialdehyde (MDA) (nmol/mg) levels whereas the secondary outcomes included total sperm count (×106), sperm vitality (%), total sperm motility (%), and sperm DNA fragmentation (SDF) (%). Standardized mean difference (SMD) (95% confidence interval [CI]) was chosen to express the effect size. The quality of the included studies was evaluated using the Cambridge Quality Checklist.

RESULTS

Out of 76 identified articles, 6 studies on rats were included in the meta-analysis. The analysis showed a significant increase of MDA (SMD: 15.61 [1.93, 29.29]; p=0.03) in rats with varicocele vs. controls. We also observed a significant decrease in total sperm count (SMD: -17.45 [-28.97, -5.93]; p<0.01), sperm vitality (SMD: -16.41 [-26.30, -6.52]; p<0.01), total sperm motility (SMD: -17.67 [-24.90, -10.44]; p<0.01), and a significant increase of SDF (SMD: 7.41 [1.23, 13.59]; p=0.02), in rats with varicocele vs. controls. The quality of the included studies was ranked as high.

CONCLUSIONS

This SRMA indicates a significant increase in levels of testicular MDA and SDF and a reduction of sperm quality in experimental animals with varicocele. These findings support the potential role of testicular OS in the development of varicocele-induced testicular damage.

Effect of varicocele and varicocelectomy on sperm deoxyribonucleic acid fragmentation rates in infertile men with clinical varicocele

Varicocele is the leading cause of male infertility. It can affect sperm quantity and quality through various non-mutually exclusive pathophysiological mechanisms, mainly oxidative stress. Excessive production of reactive oxygen species may overwhelm the sperm's defenses against oxidative stress and harm the sperm's DNA. Excessive sperm DNA breaks, so-called sperm DNA fragmentation, result from the oxidative stress cascade and are commonly found in the ejaculates of men with varicocele and fertility-related issues. Measuring sperm DNA fragmentation can provide valuable information on the extent of harm and might help select candidates for surgical treatment. Varicocelectomy is beneficial for alleviating oxidative stress-associated infertility and improving sperm DNA integrity. However, reproductive outcomes of infertile men with elevated sperm DNA fragmentation rates and surgically treated varicoceles remain poorly studied, and there is a need for well-designed trials to determine the impact of sperm DNA fragmentation reduction on natural and medically assisted reproduction.

Effect of N-acetyl-L-cysteine on Testicular Tissue in Busulfan-Induced Dysfunction in the Male Reproductive System

PURPOSE

This study aimed to evaluate the protective effect of N-acetyl-L-cysteine (NAC) as an antioxidant on busulfan-induced testicular dysfunction in mice and elucidate its possible mechanism of action.

MATERIALS AND METHODS

Thirty-two C57BL/6 male mice were randomly divided into four groups (n=8/group) as follows: (1) control group (oral administration of saline [0.1 mL daily] for 35 days); (2) NAC group (oral administration of NAC [10 mg/kg daily] for 35 days); (3) busulfan group (double intraperitoneal injections of 20 mg/kg; total dose of 40 mg/kg); and (4) busulfan+NAC group (after double intraperitoneal injections of 20 mg/kg; total dose of 40 mg/kg, NAC administration [10 mg/kg daily] for 35 days). The testes were removed, weighed, and subjected to sperm parameter analysis and morphology assessment. Reproductive hormone, serum/testicular reactive oxygen species (ROS) level, oxidative stress and antioxidant markers were evaluated. The testicular expression of Nrf2 and HO-1 was examined using RT-qPCR.

RESULTS

Busulfan treatment significantly decreased testicular weight, sperm count, and serum testosterone levels. Atrophy and degeneration of germinal epithelium were observed in the busulfan group. NAC administration after busulfan treatment partially attenuated the deterioration of testis weight, sperm quality, serum hormones, histomorphometric changes, and oxidative and antioxidative status. NAC treatment resulted in a considerable improvement in Nrf2 and HO-1 mRNA expression levels.

CONCLUSIONS

This study provides compelling evidence that NAC as a potent antioxidant has significant protective effects against busulfan-induced male reproductive impairment possibly through modification of the Nrf2/HO-1 signaling pathway.

Ni/Mn-Complex-Tethered Tetranuclear Polyoxovanadates: Crystal Structure and Inhibitory Activity on Human Hepatocellular Carcinoma (HepG-2)

Polyoxometalates (POMs) exhibit unique structural characteristics and excellent physical and chemical properties, which have attracted significant attention from scholars in the fields of anticancer research and chemotherapy. Herein, we successfully synthesized and structurally characterized two novel polyoxovanadates (POVs), denoted as POVs-1 and POVs-2, where [M(1-vIM)4]2[VV4O12]·H2O (M: NiII and MnII, 1-vinylimidazole abbreviated as 1-vIM) serve as ligands. The two POVs are isomeric and consist of fundamental structural units, each comprising one [V4O12]4- cluster, two [M(1-vIM)4]2+ cations, and one water molecule. Subsequently, we evaluated the cell viability of human hepatocellular carcinoma (HepG-2) cells treated with the synthesized POVs using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide) assay. And the changes in cell nucleus morphology, mitochondrial membrane potential (Δψm), and reactive oxygen species levels in HepG-2 exposed to POVs were monitored using specific fluorescent staining techniques. Both hybrid POVs showed potent inhibitory activities, induing apoptosis in HepG-2 cells along with significant mitochondria dysfunction and a burst of reactive oxygen species. Notably, the inhibitory effects of POVs-2 were more pronounced than those of POVs-1, which is primarily attributed to the different transition metal ions present. These findings underscore the intricate relationship between the metal components, structural characteristics, and the observed antitumor activities in HepG-2 cells.

The time course of nod-like receptor family pyrin domain containing 3 inflammasome complex expressions in the testis tissue of an experimental varicocele rat model: An experimental study

Background

Varicocele is characterized by abnormal dilation of the testicular vein, which results in hypoxia, the accumulation of reactive oxygen species, and the production of proinflammatory cytokines. It seems that a group of cytosolic receptors named nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, is activated and involved in the pathogenesis of varicocele.

Objective

We aim to determine the time course of NLRP3 inflammasome expression in the testis tissue following varicocele induction.

Materials and Methods

In this experimental study, 36 adult Wistar rats (8 wk, 200-250 gr) were used. For the varicocele induction, the left renal vein was partially ligated. The mRNA levels of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 were evaluated by real-time polymerase chain reaction at 1, 2, 4, 8, and 12 wk after varicocele induction.

Results

Results showed that the gene expression of NLRP3 inflammasome component including NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase-1 did not alter during week 1, 2, 4, and 8 after operation (p = 0.09). 12 wk after varicocele induction, gene expression levels were significantly up-regulated (p = 0.02).

Conclusion

Our data provides clear evidence that varicocele stimulates inflammasome activation in the testis tissue 12 wk after the operation, and this time is required for investigating NLRP3 activity in the varicocele rat model.

Investigation on the mechanisms of human sperm DNA damage based on the proteomics analysis by SWATH-MS

BACKGROUND

Spermatozoa have the task of delivering an intact paternal genome to the oocyte and supporting successful embryo development. The detection of sperm DNA fragmentation (SDF) has been emerging as a complementary test to conventional semen analysis for male infertility evaluation, but the mechanism leading to SDF and its impact on assisted reproduction remain unclear. Therefore, the study identified and analyzed the differentially expressed proteins of sperm with high and low SDF.

METHODS

Semen samples from men attended the infertility clinic during June 2020 and August 2020 were analyzed, and sperm DNA fragmentation index (DFI) was detected by the sperm chromatin structure assay. Semen samples with low DFI (< 30%, control group) and high DFI (≥ 30%, experimental group) were optimized by density gradient centrifugation (DGC), and the differentially expressed proteins of obtained sperm were identified by the Sequential Window Acquisition of All Theoretical Mass Spectra Mass Spectrometry (SWATH-MS) and performed GO and KEGG analysis.

RESULTS

A total of 2186 proteins were identified and 1591 proteins were quantified, of which 252 proteins were identified as differentially expressed proteins, including 124 upregulated and 128 downregulated. These differentially expressed proteins were involved in metabolic pathways, replication/recombination/repair, acrosomal vesicles, kinase regulators, fertilization, tyrosine metabolism, etc. Western blotting results showed that the expression levels of RAD23B and DFFA proteins and the levels of posttranslational ubiquitination and acetylation modifications in the experimental group were significantly higher than those in the control group, which was consistent with the results of proteomics analysis.

CONCLUSIONS

Proteomic markers of sperm with high DNA fragmentation can be identified by the SWATH-MS and bioinformatic analysis, and new protein markers and posttranslational modifications related to sperm DNA damage are expected to be intensively explored. Our findings may improve our understanding of the basic molecular mechanism of sperm DNA damage.

Varicoceles: Overview of Treatment from a Radiologic and Surgical Perspective

A testicular varicocele is the result of the expansion of the venous pampiniform plexus of the scrotum. Often painless, a significant number of patients experience orchialgia, swelling, testicular atrophy, and abnormalities in spermatic parameters. Treatment of symptomatic varicocele involves a radiologic or surgical intervention to obstruct the reflux of venous drainage. Testicular anatomy, diagnostic evaluation and imaging, options for surgical intervention, and a step-by-step description of retrograde embolization and antegrade scrotal sclerotherapy are discussed. Furthermore, included is an overview of postprocedural management and patient outcomes for radiological interventions, and the most up-to-date evidence on the efficacy of varicocele treatments as well as how they compare to each other.

Cryopreservation of rabbit semen: impacts of permeable and non-permeable mixture of cryoprotectant, male group individuality, freezing rate, semen package size and antioxidant bovine serum albumin on rabbit semen freezability

In the present study, three experiments were designed to identify the most appropriate technique for freezing rabbit semen. Experiment 1 aimed to determine the optimal levels of dimethyl sulfoxide (DMSO) contents in freezing medium and their effects on individual bucks. Semen ejaculates for each buck (n=15 bucks) were mixed and split into three portions for extension with a freezing medium containing varying concentrations of DMSO (0.75, 1.0, and 1.4 M). Diluted semen samples were packaged in 0.25 mL straws and suspended above liquid nitrogen (LN) for 10 min, then dipped in LN. A few days after freezing, post-thaw semen evaluation was assessed, and according to the results, six bucks and an extender containing 0.75 M of DMSO were used for experiments 2 and 3. In experiment 2, the pooled semen from 6 bucks was divided into two portions for packaging in two straw sizes (0.25 and 0.50 mL). Each straw size was divided into five groups and suspended at different heights above LN (2, 4, 6, 8, and 10 cm) for 10 minutes before being preserved in LN. In experiment 3, the pooled semen was divided into four portions for dilution with freezing medium containing different concentrations of bovine serum albumin (BSA; 0, 2.5, 5.0, and 7.5 mg/mL). Semen samples were packaged in a 0.50 mL straw and suspended 10 min, 4 cm above LN for freezing. Pre-freezing and post-thawing, semen samples were evaluated for semen quality. Results showed that the extender containing 0.75 M DMSO had higher significant values for post-thaw sperm motility, longevity, acrosome integrity and sperm plasma membrane permeability. Bucks’ individuality had significant effects on post-thaw motility, acrosome and sperm plasma membrane integrity. A significant interaction was recorded between DMSO concentrations and bucks’ individuality on sperm longevity. Semen package sizes had no significant effects on the evaluated parameters. Semen was frozen at 2 and 4 cm above LN had significantly better post-thaw quality. BSA at concentrations 5 and 7.5 mg/mL improved recovery rates of acrosome integrity and sperm membrane permeability. DMSO 0.75 M and freezing 4 cm above LN seem to be more adequate for rabbit semen cryopreservation. The appropriate level of DMSO differs between bucks, as the post-thaw sperm longevity is affected. BSA enhanced acrosome and sperm membrane integrity. Results obtained will need further investigation to be confirmed in the field.

The Role of NLRP3 Inflammasome Activation and Oxidative Stress in Varicocele-Mediated Male Hypofertility

Varicocele (VC) is the most common abnormality identified in men evaluated for hypofertility. Increased levels of reactive oxygen species (ROS) and reduced antioxidants concentrations are key contributors in varicocele-mediated hypofertility. Moreover, inflammation and alterations in testicular immunity negatively impact male fertility. In particular, NLRP3 inflammasome activation was hypothesized to lead to seminal inflammation, in which the levels of specific cytokines, such as IL-1β and IL-18, are overexpressed. In this review, we described the role played by oxidative stress (OS), inflammation, and NLRP3 inflammasome activation in VC disease. The consequences of ROS overproduction in testis, including inflammation, lipid peroxidation, mitochondrial dysfunction, chromatin damage, and sperm DNA fragmentation, leading to abnormal testicular function and failed spermatogenesis, were highlighted. Finally, we described some therapeutic antioxidant strategies, with recognized beneficial effects in counteracting OS and inflammation in testes, as possible therapeutic drugs against varicocele-mediated hypofertility.

Oxidative Stress and Male Infertility: Evidence From a Research Perspective

Male fertility potential can be influenced by a variety of conditions that frequently coincide. Spermatozoa are particularly susceptible to oxidative damage due to their limited antioxidant capacity and cell membrane rich in polyunsaturated fatty acids (PUFAs). The role of oxidative stress (OS) in the etiology of male infertility has been the primary focus of our Stellenbosch University Reproductive Research Group (SURRG) over the last 10 years. This review aims to provide a novel insight into the impact of OS on spermatozoa and male reproductive function by reviewing the OS-related findings from a wide variety of studies conducted in our laboratory, along with those emerging from other investigators. We will provide a concise overview of the production of reactive oxygen species (ROS) and the development of OS in the male reproductive tract along with the physiological and pathological effects thereof on male reproductive functions. Recent advances in methods and techniques used for the assessment of OS will also be highlighted. We will furthermore consider the current evidence regarding the association between OS and ejaculatory abstinence period, as well as the potential mechanisms involved in the pathophysiology of various systemic diseases such as obesity, insulin resistance, hypertension, and certain mental health disorders which have been shown to cause OS induced male infertility. Finally, special emphasis will be placed on the potential for transferring and incorporating research findings emanating from different experimental studies into clinical practice.