Role of Glutathione-S-Transferase Family Genes in Male Infertility

S, Dolma S, Kaur R, Kapoor HS, Goyal LD, Khetarpal P. Xenobiotic metabolizing gene variants and the risk of male infertility - A systematic review, meta-analysis and in silico analysis

Many studies have been performed to explore the role of xenobiotic metabolizing gene variants and male infertility risk. However, the results remain inconclusive and contradictory. Therefore, the objective of the present study was to investigate the association among 16 genes and its 24 variants (CAT rs1001179, rs7943316, SOD2 rs4880, GPX1 rs1050450, CYP1A1 rs1048943, rs4646903, GSTP1 rs1695, MTHFR rs1801133, rs1801131, rs2274976, rs2066472, MTHFD1 rs2236225, MTRR rs1801394, CYP2D6 rs3892097, PON1 rs854560, rs662, PON2 rs7493, NAT2 rs1799930, NRF2 rs6721961, AHR rs2066853, rs1476080, rs6960165, null GSTM1, null GSTT1) involved in xenobiotic metabolism and their correlation with male infertility. A literature search was done using PubMed, Google Scholar, and Science Direct. Meta-analysis was conducted using Review Manager 5.3 software. Genotype-tissue expression (GTEx) portal and RegulomDB were used to determine genotype and tissue expression. Pathogenicity of significant gene variants was determined using I-Mutant 2.0, PolyPhen 2, SNP & GO, SIFT, and CADD tools. A total of 106 studies were selected for the present study to analyze 16 genes and their variants. SOD2 rs4880, CYP1A1 rs4646903, MTHFR rs1801133, rs1801131, rs2274976, PON1 rs854560, NRF2 rs6721961, and null GSTM1 gene variants are associated with increased risk of male infertility. SOD2 rs4880 and MTHFR rs1801133, rs1801131, rs2274976 are found to decrease the stability of the protein. However, no significant association was observed between CAT rs1001179, rs7943316, GPX1 rs1050450, CYP1A1 rs1048943,GSTP1 rs1695,MTHFR rs2066472, MTHFD1 rs2236225, MTRR rs1801394, CYP2D6 rs3892097, PON1 rs662, PON2 rs7493, NAT2 rs1799930, AHR rs2066853, rs1476080, rs6960165, null GSTT1 gene polymorphisms and the risk of male infertility.

Genome-wide identification of glutathione S-transferase (GST) gene family and its regulating characteristics responding to sperm capacitation in Eriocheir sinensis

Sperm capacitation is regarded to be a process of redox regulation. Within the oxidative regulatory system, glutathione S-transferases (GSTs) are important in the maintenance of the redox balance of reactive oxygen species (ROS). We identify 56 GST genes in the Chinese mitten crab Eriocheir sinensis genome, and categorize them into 13 classes, of which the largest is Mu. Chromosomal localization reveals an uneven distribution of EsGSTs across the E. sinensis genome, yet similar structures and conserved motifs occur within a class. Proteome analysis reveals EsGSTz2, EsGSTm2, and EsGSTd/e5 to be significantly up-regulated and EsGSTt to be down-regulated considerably after incubation with egg water. Capacitation also triggered the acetylation alteration in EsGSTs. Notably, six acetylation sites are identified in EsGSTm2, with notable deacetylation in K43, K132, and K123. Activity analysis reveals that deacetylation in both K43 and K123 can improve GST activity, whereas double-site mutations of K43R and K132R reduce enzyme activity. At pH 8.2, K123R has higher activity compared with other arginine mutants. Blocking of EsGSTm2 induces an imbalance in sperm oxidation levels and intracellular calcium homeostasis, and inhibits sperm acrosome reaction. This work extends our understanding of the GST regulation mechanisms during crustacean sperm capacitation.

Effects and possible mechanisms of combined exposure to noise and carbon monoxide on male reproductive system in rats

Environmental hazards are an increasing concern due to the rapid pace of industrialization. Among these hazards, noise and carbon monoxide (CO) are common risk factors and have been shown to cause serious health problems. However, existing studies focused on the individual effects of noise and CO exposure and the combined effects of these two factors remain poorly understood. Our study aimed to examine the combined effects of noise and CO exposure on testicular function by constructing individual and combined exposure models. Our findings indicated that combined exposure to noise and CO was associated with a higher risk of testicular damage and male reproductive damage when compared to exposure alone. This was evidenced by poorer semen quality and more severe pathological damage to the testis. This combined exposure led to higher levels of oxidative stress and apoptosis in the testes, with bioinformatics analyses suggesting the signaling pathways involved in these responses. Specifically, activation of the P53 signaling pathway was found to contribute to the testicular damage caused by the combined exposure. Encouragingly, pterostilbene (PTE), a novel phytochemical, alleviated combined exposure-induced testicular damage by reducing oxidative stress and germ cell apoptosis. Overall, we identified joint reproductive toxicity resulting from the exposure to noise and CO, and found that PTE is a promising potential treatment for injuries caused by these factors. The cover image is based on the Research Article Effects and possible mechanisms of combined exposure to noise and carbon monoxide on male reproductive system in rats by Yingqing Li et al., https://doi.org/10.1002/tox.23927.

Oxidative Stress, Telomere Length and Telomerase Activity in Spermatogenesis Disorders (Review of Scientific Activity)

The paper systematizes the available data on the study of oxidative stress, the relative length of telomeres, and telomerase activity in male infertility and disorders of spermatogenesis. The study of telomeres, the structures that protect chromosome ends and genome integrity, is of interest for researchers in various fields, from cell biology and epidemiology to ecology and evolutionary biology. The review includes our own data on the study of the relative length of telomeres, oxidative stress, and telomerase activity and reflects modern ideas about the importance of these structures both in the maintenance of genome stability during cell division and in gametogenesis and reproduction. Many studies indicate the role of oxidative stress in the pathogenesis of various diseases, including male infertility. In turn, studies of telomeres as a biomarker of male infertility are insufficient, and the results obtained are extremely controversial and require deeper knowledge about the mechanisms underlying the dynamics of telomere length.

Differential Sperm Proteomics Reveals the Significance of Fatty Acid Synthase and Clusterin in Idiopathic Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is a pervasive health issue affecting a large number of couples globally, which leads to increased emotional and financial strain on the affected families. While female factors have been extensively studied and are well known, the contribution of male factors to RPL remains largely unknown. As high as 40% of RPL cases are unexplained, which are termed as idiopathic RPL (iRPL), necessitating the investigation of male factors. The role of spermatozoa in early embryonic development is now well established, and recent research studies have shown that oxidative stress and DNA fragmentation in sperm cells are linked to RPL. The aim of this study was to identify proteomic markers of iRPL in human spermatozoa using tandem mass spectrometry. A label-free method quantified a total of 1820 proteins, and statistical analysis identified 359 differentially expressed proteins, the majority of which were downregulated in iRPL samples (344). Bioinformatics analysis revealed that proteomic alterations were mainly associated with biological processes such as response to stress, protein folding, chromatin organization, DNA conformation change, oxidative phosphorylation, and electron transport chain. In coherence with past studies, we determined fatty acid synthase (FASN) and clusterin (CLU) to be the most potential sperm markers for iRPL and confirmed their expression changes in iRPL by western blotting. Conclusively, we believe that FASN and CLU might serve as potential markers of iRPL and suggest exploratory functional studies to identify their specific role in pregnancy loss.

Association of GSTM1 Polymorphism and Redox Potential with Idiopathic Male Infertility

BACKGROUND

The aim of this case-control study is to investigate possible associations between GSTM1 polymorphism and redox potential with sperm parameters.

METHODS

The study group consisted of sperm samples from 51 infertile men according to the WHO guidelines. The control group included 39 samples from men with normal seminal parameters. DNA was extracted and genotyped for the detection of the GSTM1 polymorphism. An evaluation of the static redox potential (sORP) using the MiOXSYSTM system was conducted.

RESULTS

The frequency of the GSTM1-null genotype was higher in infertile male individuals (60.78%) than in the controls (41.03%) and was associated with a 2.228-fold increased risk for male infertility. Fertile controls carrying the GSTM1-null genotype presented a lower percentage of typical sperm morphology and lower slow progressive motility. An excess of redox potential was observed in infertile males compared to fertile ones. In the control group higher sORP values had a positive correlation with immotility percentage and a negative correlation regarding total motility. In the study group sORP values had a negative correlation with total count, concentration, and slow progressive motility.

CONCLUSIONS

The present study highlights that GSTM1 polymorphism and redox potential affect both fertile and in fertile males. Moreover, redox potential levels could be used as an additional indicator along with the routine semen analysis for a comprehensive screening between infertile and fertile men.

Integration of transcriptomic and metabolomic reveals metabolic pathway alteration in earthworms (Eisenia fetida) under copper exposure

Copper is a trace element that necessary for plant growth in the soil. However, in recent years, due to human activities, the content of copper in soil exceeds the standard seriously, which is threatening the safety of soil animals, plants and even human beings. In this study, we investigated the effects and molecular mechanisms of 60 days long-term copper exposure on earthworms (Eisenia fetida) at 67.58 mg/kg, 168.96 mg/kg and 337.92 mg/kg concentration by using transcriptome and metabolomics. Transcriptome analysis showed that the expression of energy metabolism related genes (LDH, GYS, ATP6N, GAPDH, COX17), immune system related genes (E3.2.1.14) and detoxification related genes (UGT, CYP2U1, CYP1A1) were down-regulated, the expression of antioxidant system related genes (GCLC, HPGDS) were up-regulated in copper exposure experiment of earthworms. Similarly, metabolomics analysis revealed that the expression of energy metabolism related metabolites (Glucose-1-phosphate, Glucose-6-phosphate), TCA cycle related metabolites (fumaric acid, allantoic acid, malate, malic acid) were down-regulated, digestion and immune system related metabolites (Trehalose-6-phosphate) were up-regulated. Integrating transcriptome and metabolomics data, it was found that higher antioxidant capacity and accelerated TCA cycle metabolism may be an adaptive strategy for earthworms to adapt to long-term copper stress. Collectively, the results of this study will greatly contribute to incrementally understand the stress responses on copper exposure to earthworms and supply molecular level support for evaluating the environmental effects of copper on soil organisms.

Antioxidant Paradox in Male Infertility: 'A Blind Eye' on Inflammation

The pathophysiology of male infertility involves various interlinked endogenous pathways. About 50% of the cases of infertility in men are idiopathic, and oxidative stress (OS) reportedly serves as a central mechanism in impairing male fertility parameters. The endogenous antioxidant system operates to conserve the seminal redox homeostasis required for normal male reproduction. OS strikes when a generation of seminal reactive oxygen species (ROS) overwhelms endogenous antioxidant capacity. Thus, antioxidant treatment finds remarkable relevance in the case of idiopathic male infertility or subfertility. However, due to lack of proper detection of OS in male infertility, use of antioxidant(s) in some cases may be arbitrary or lead to overuse and induction of 'reductive stress'. Moreover, inflammation is closely linked to OS and may establish a vicious loop that is capable of disruption to male reproductive tissues. The result is exaggeration of cellular damage and disruption of male reproductive tissues. Therefore, limitations of antioxidant therapy in treating male infertility are the failure in the selection of specific treatments targeting inflammation and OS simultaneously, two of the core mechanisms of male infertility. The present review aims to elucidate the antioxidant paradox in male infertility treatment, from the viewpoints of both induction of reductive stress as well as overlooking the inflammatory consequences.

Glutathione S-transferase kappa 1 is positively related with sperm quality of porcine sperm

The glutathione S-transferase (GST) superfamily members play an important role in the male reproductive tract and sperm physiology. However, the expression profiles of some members of this protein family and their effect on sperm quality remain unclear. In this study, we found that GST kappa 1 (GSTK1) encoded protein is abundant in the testes and capacitated sperm acrosome. Western blot analysis revealed that the decreased abundance of GSTK1 was observed in low motile spermatozoa; moreover, GSTK1 expression decreased in sperm stored at 17°C under a long preservation time. In vitro analyses revealed that GSTK1 had no significant effect on sperm motility, capacitation, or acrosome reaction. Notably, after capacitated sperm were incubated with 4 and 8 μg/ml anti-GSTK1 antibodies, the fertilization rate significantly decreased in vitro fertilization assay. The current study demonstrates that GSTK1 is correlated with sperm quality and is a promising marker for the assessment of sperm quality and provides a basis for understanding the potential molecular mechanism for targeting pathogenic factors in male infertility.

Indicators of the Lipid Peroxidation-Antioxidant Protection System as Important Metabolic Markers of Reproductive Potential in Men

We analyze results of recent studies demonstrating unfavorable state of the reproductive health in the male population that manifested not only in spermatogenesis deterioration, but also in oxidative stress (both systemic and in seminal fluid). The data on the effect of ROS and components of the antioxidant defense system on gamete quality in men with infertility associated with obesity and diabetes mellitus are presented. Some features of oxidative stress in men of reproductive age of various ethnic groups are shown. Evaluation of the parameters of oxidative stress provides new insight into the molecular mechanisms of functional activity of the semen and may become a promising direction for the development of new methodological recommendations for personalized diagnosis, prevention, and correction of reproductive disorders in men.

Sperm DNA integrity status is associated with DNA methylation signatures of imprinted genes and non-imprinted genes

PURPOSE

To evaluate the association between the DNA methylation of specific genes and sperm DNA integrity status in human sperm samples.

METHODS

A total of 166 semen samples were evaluated (86 controls and 80 cases with impaired sperm DNA integrity). We detected the methylation status of 257 CpG sites among two imprinted genes (H19 and SNRPN) and four non-imprinted genes related to male infertility (MTHFR, GSTM1, DAZL, and CREM) by using a targeted next-generation sequencing method.

RESULTS

Differential methylation was found in 43 CpG sites of the promoters of the six candidate genes. H19, SNRPN, MTHFR, DAZL, GSTM1, and CREM contained 22, 12, 1, 4, 0, and 4 differentially methylated CpG sites (P<0.05), respectively. The imprinting genes were associated with relatively higher rates of differentially methylated CpG sites (28.21% in H19 and 41.38% in SNRPN) than the non-imprinting genes. One CpG site in H19 remained significant after performing strict Bonferroni correction.

CONCLUSION

In this study, we found that different site-specific DNA methylation signatures were correlated with sperm DNA integrity status. Further studies are needed to investigate the specific mechanisms leading to the epigenetic modifications.

Deactivation of the JNK Pathway by GSTP1 Is Essential to Maintain Sperm Functionality

Fifty percent of male subfertility diagnosis is idiopathic and is usually associated with genetic abnormalities or protein dysfunction, which are not detectable through the conventional spermiogram. Glutathione S-transferases (GSTs) are antioxidant enzymes essential for preserving sperm function and maintaining fertilizing ability. However, while the role of GSTP1 in cell signaling regulation via the inhibition of c-Jun N-terminal kinases (JNK) has been enlightened in somatic cells, it has never been investigated in mammalian spermatozoa. In this regard, a comprehensive approach through immunoblotting, immunofluorescence, computer-assisted sperm assessment (CASA), and flow cytometry analysis was used to characterize the molecular role of the GSTP1–JNK heterocomplex in sperm physiology, using the pig as a model. Immunological assessments confirmed the presence and localization of GSTP1 in sperm cells. The pharmacological dissociation of the GSTP1–JNK heterocomplex resulted in the activation of JNK, which led to a significant decrease in sperm viability, motility, mitochondrial activity, and plasma membrane stability, as well as to an increase of intracellular superoxides. No effects in intracellular calcium levels and acrosome membrane integrity were observed. In conclusion, the present work has demonstrated, for the first time, the essential role of GSTP1 in deactivating JNK, which is crucial to maintain sperm function and has also set the grounds to understand the relevance of the GSTP1–JNK heterocomplex for the regulation of mammalian sperm physiology.

Exploring Seminal Plasma GSTM3 as a Quality and In Vivo Fertility Biomarker in Pigs-Relationship with Sperm Morphology

Glutathione S-transferases Mu 3 (GSTM3) is an essential antioxidant enzyme whose presence in sperm has recently been related to sperm cryotolerance, quality and fertility. However, its role in seminal plasma (SP) as a predictor of the same sperm parameters has never been investigated. Herein, cell biology and proteomic approaches were performed to explore the presence, origin and role of SP-GSTM3 as a sperm quality and in vivo fertility biomarker. GSTM3 in SP was quantified using a commercial Enzyme-Linked Immunosorbent Assay (ELISA) kit specific for Sus scrofa, whereas the presence of GSTM3 in testis, epididymis and accessory sex glands was assessed through immunoblotting analysis. Sperm quality and functionality parameters were evaluated in semen samples at 0 and 72 h of liquid-storage, whereas fertility parameters were recorded over a 12-months as farrowing rate and litter size. The presence and concentration of GSTM3 in SP was established for the first time in mammalian species, predominantly synthesized in the epididymis. The present study also evidenced a relationship between SP-GSTM3 and sperm morphology and suggested it is involved in epididymal maturation rather than in ejaculated sperm physiology. Finally, the data reported herein ruled out the role of this antioxidant enzyme as a quality and in vivo fertility biomarker of pig sperm.

The triple role of glutathione S-transferases in mammalian male fertility

Male idiopathic infertility accounts for 15-25% of reproductive failure. One of the factors that has been linked to this condition is oxidative stress (OS), defined as the imbalance between antioxidants and reactive oxygen species. Amongst the different factors that protect the cell against OS, the members of the glutathione S-transferase (GST) superfamily play an important role. Interestingly, reduction or lack of some GSTs has been associated to infertility in men. Therefore, and to clarify the relationship between GSTs and male fertility, the aim of this work is to describe the role that GSTs play in the male reproductive tract and in sperm physiology. To that end, the present review provides a novel perspective on the triple role of GSTs (detoxification, regulation of cell signalling and fertilisation), and reports their localisation in sperm, seminal plasma and the male reproductive tract. Furthermore, we also tackle the existing correlation between some GST classes and male fertility. Due to the considerable impact of GSTs in human pathology and their tight relationship with fertility, future research should address the specific role of these proteins in male fertility, which could result in new approaches for the diagnosis and/or treatment of male infertility.

SNP's in xenobiotic metabolism and male infertility

1. Glutathione S-transferases (GST) and cytochrome P450s (CYPs) are xenobiotic metabolizing enzymes participating in the protection of cell. The present study aimed to investigate the relationship between polymorphisms of glutathione S-transferase M1 (GSTM1) null, glutathione S-transferase T1 (GSTT1) null, glutathione S-transferase P1 (GSTP1) Ile105Val, cytochrome P450 1A2 (CYP1A2) 734 C→A, cytochrome P450 2D6 (CYP2D6) 1934 G→A and male infertility.2. A total of 306 azoospermic or oligozoospermic infertile men and 129 normozoospermic or fertile controls were enrolled in the study. Multiplex polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism methods were used for genotyping. There was a significant relationship between male infertility and CYP2D6 GG genotype (p < 0.001). CYP1A2 AA genotype was slightly higher in the infertile group (p = 0.056).3. There was no association between GSTT1 null polymorphisms and male infertility (p = 0.068), GSTM1 null (p = 0.843) and GSTP1 Ile105Val (p = 0.192) genes. GSTM1 null genotype frequency was higher in azoospermic men (p = 0.009). Men carrying CYP1A2 AA genotype had higher risk of infertility risk (OR = 3.14; %95 CI = 1.16-8.54) in the smoker group.4. Our results demonstrated that polymorphisms of CYP2D6 and CYP1A2 may play a role in idiopathic male infertility in our sample population.