Relationship between functional Nrf2 gene promoter polymorphism and sperm DNA damage 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.

IGF-1 outperforms vitamin E and crocin in improving semen quality, antioxidant profile and fertility gene expression in cryopreserved goat (Capra hircus) semen

Semen cryopreservation combined with artificial insemination (AI) benefits germplasm conservation, production, and breeding. Sperm cells are vulnerable to oxidative and other stressors during cryopreservation, necessitating the use of additives/antioxidants to mitigate this damage. This study aimed to evaluate the effects of vitamin E, IGF-1, and crocin supplementation on the quality of cryopreserved goat semen. A total of 48 pooled ejaculates from six goat bucks were diluted in Tris-Citrate-Fructose-Egg Yolk-Glycerol (TCFEYG) extender and divided into four groups: a control group (no antioxidant addition) and groups supplemented with 2 mM vitamin E, 125 ng/mL IGF-1 and 1 mM crocin. The semen samples were cryopreserved in liquid nitrogen (LN2) and analyzed post-thaw for sperm quality attributes, antioxidant enzyme activities and mRNA expression levels. IGF-1 supplementation significantly (P < 0.05) enhanced in vitro sperm quality, and antioxidant enzyme viz., catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione S transferase (GST) and superoxide dismutase (SOD) compared to other treatments. Lipid peroxidation (LPO) levels were significantly (P < 0.05) lower, and fertility-related mRNA transcripts (NFE2L2, GPx4, CAT, and SOD2) were significantly (P < 0.05) upregulated in the IGF-1 group. No significant (P > 0.05) differences in pregnancy rates were observed among treatments after AI. In conclusion, IGF-1 supplementation significantly improved the post-thaw quality of cryopreserved goat semen, enhancing antioxidant activity and fertility-related mRNA expression compared to vitamin E and crocin treatments.

Exploring Endocannabinoid System: Unveiling New Roles in Modulating ER Stress

The endoplasmic reticulum (ER) is the organelle mainly involved in maintaining cellular homeostasis and driving correct protein folding. ER-dependent defects or dysfunctions are associated with the genesis/progression of several pathological conditions, including cancer, inflammation, and neurodegenerative disorders, that are directly or indirectly correlated to a wide set of events collectively named under the term "ER stress". Despite the recent increase in interest concerning ER activity, further research studies are needed to highlight all the mechanisms responsible for ER failure. In this field, recent discoveries paved the way for the comprehension of the strong interaction between ER stress development and the endocannabinoid system. The activity of the endocannabinoid system is mediated by the activation of cannabinoid receptors (CB), G protein-coupled receptors that induce a decrease in cAMP levels, with downstream anti-inflammatory effects. CB activation drives, in most cases, the recovery of ER homeostasis through the regulation of ER stress hallmarks PERK, ATF6, and IRE1. In this review, we focus on the CB role in modulating ER stress, with particular attention to the cellular processes leading to UPR activation and oxidative stress response extinguishment, and to the mechanisms underlying natural cannabinoids' modulation of this complex cellular machine.

Multiple omics integration analysis reveals the regulatory effect of chitosan oligosaccharide on testicular development

Infertility is a global health problem affecting millions of people of reproductive age worldwide, with approximately half caused by males. Chitosan oligosaccharide (COS) has strong antioxidant capacity, but its impact on the male reproductive system has not been effectively evaluated. To address this, we integrated RNA-seq, serum metabolomics and intestinal 16 S rDNA analysis to conduct a comprehensive investigation on the male reproductive system. The results showed that COS has potential targets for the treatment of oligospermia, which can promote the expression of meiotic proteins DDX4, DAZL and SYCP1, benefit germ cell proliferation and testicular development, enhance antioxidant capacity, and increase the expression of testicular steroid proteins STAR and CYP11A1. At the same time, COS can activate PI3K-Akt signaling pathway in testis and TM3 cells. Microbiome and metabolomics analysis suggested that COS alters gut microbial community composition and cooperates with serum metabolites to regulate spermatogenesis. Therefore, COS promotes male reproduction by regulating intestinal microorganisms and serum metabolism, activating PI3K-Akt signaling pathway, improving testicular antioxidant capacity and steroid regulation.

Oral administration of proniosomal glibenclamide formulation protects testicular tissue from hyperglycemia fluctuations and ROS via Nrf2/HO-1 pathway

Type 2 diabetes causes high blood sugar due to insulin malfunction and is linked to male infertility. Using proniosomes can enhance the effectiveness of Glibenclamide, a medication that stimulates insulin secretion. In our study, male rats with diabetes were treated with GLB with or without proniosomal for 14 days. Proniosomal formulations maintained glucose levels prevented weight loss and showed normal testicular tissue. GLB-proniosomal reduces ROS caused by T2DM through Nrf2, HO-1 pathway and increases CAT, SOD, and GSH production in response to insulin and glucose uptake. The reference and proniosomal treatments showed CAT and SOD significant enzymatic elevation compared to the positive and negative control. CAT significantly correlated with Gpx4 expression with P = 0.0169 and r = 0.98; similarly, the enzymatic activity of SOD also showed a positive correlation between the average glucose levels (r = 0.99 and P = 0.0037). Intestinally, GSH analysis revealed that only proniosomal-GLB samples are significantly elevated from the positive control, with a P value of 0.0210. The data showed proniosomal-GLB was more effective than pure GLB, confirmed by higher Nrf2 (2.050 folds), HO-1 (2.148 folds), and GPx4 (1.9 folds) transcript levels relative to the control with less sample diversity compared to the reference samples, indicating proniosomal stabilized GLB in the blood. Administering GLB and proniosomes formulation has effectively restored testicular function and sperm production in diabetic rats by regulating ROS levels and upregulating anti-ROS in response to glucose uptake. These findings may lead to better treatments for diabetic patients who have infertility issues.

Role of nuclear factor erythroid 2-related factor 2 (Nrf2) in female and male fertility

Oxidative stress refers to a condition where there is an imbalance between the production of reactive oxygen species and their removal by antioxidants. While the function of reactive oxygen species as specific second messengers under physiological conditions is necessary, their overproduction can lead to numerous instances of cell and tissue damage. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of many cytoprotective genes that respond to redox stresses. Nrf2 is regularly degraded by kelch-like ECH-associated protein 1 through the ubiquitin-proteasome pathway. The kelch-like ECH-associated protein 1 and Nrf2 complex have attracted attention in both basic and clinical infertility research fields. Oxidative stress is implicated in the pathogenesis of female infertility, including primary ovarian insufficiency, polycystic ovarian syndrome, and endometriosis, as well as male infertility, namely varicocele, cryptorchidism, spermatic cord torsion, and orchitis. Most scientists believe that Nrf2 is a potential therapeutic method in female and male infertility disorders due to its antioxidant effect. Here, the potential roles of oxidative stress and Nrf2 in female and male infertility disorders are reviewed. Moreover, the key role of Nrf2 in the inhibition or induction of these diseases is discussed.

Redox Homeostasis and Nrf2-Regulated Mechanisms Are Relevant to Male Infertility

Infertility represents a significant global health challenge, affecting more than 12% of couples worldwide, and most cases of infertility are caused by male factors. Several pathological pathways are implicated in male infertility. The main mechanisms involved are driven by the loss of reduction-oxidation (redox) homeostasis and the resulting oxidative damage as well as the chronic inflammatory process. Increased or severe oxidative stress leads to sperm plasma membrane and DNA oxidative damage, dysregulated RNA processing, and telomere destruction. The signaling pathways of these molecular events are also regulated by Nuclear factor-E2-related factor 2 (Nrf2). The causes of male infertility, the role of oxidative stress in male infertility and the Keap1-Nrf2 antioxidant pathway are reviewed. This review highlights the regulatory role of Nrf2 in the balance between oxidants and antioxidants as relevant mechanisms to male fertility. Nrf2 is involved in the regulation of spermatogenesis and sperm quality. Establishing a link between Nrf2 signaling pathways and the regulation of male fertility provides the basis for molecular modulation of inflammatory processes, reactive oxygen species generation, and the antioxidant molecular network, including the Nrf2-regulated antioxidant response, to improve male reproductive outcomes.

KEAP1-NRF2 system regulates age-related spermatogenesis dysfunction

Purpose

The average fatherhood age has been consistently increasing in developed countries. Aging has been identified as a risk factor for male infertility. However, its impact on various mechanisms remains unclear. This study focused on the KEAP1-NRF2 oxidative stress response system, by investigating the relationship between the KEAP1-NRF2 system and age-related changes in spermatogenesis.

Methods

For examination of age-related changes, we used 10-, 30-, 60-, and 90-week-old mice to compare sperm count, sperm motility, and protein expression. For assessment of Keap1 inhibition, 85-week-old C57BL/6J mice were randomly assigned to the following groups: control and bardoxolone methyl (KEAP1 inhibitor). Whole-exome sequencing of a Japanese cohort of patients with non-obstructive azoospermia was performed for evaluating.

Results

Sperm count decreased significantly with aging. Oxidative stress and KEAP1 expression in the testes were elevated. Inhibition of KEAP1 in aging mice significantly increased sperm count compared with that in the control group. In the human study, the frequency of a missense-type SNP (rs181294188) causing changes in NFE2L2 (NRF2) activity was significantly higher in patients with non-obstructive azoospermia than in healthy control group.

Conclusions

The KEAP1-NRF2 system, an oxidative stress response system, is associated with age-related spermatogenesis dysfunction.

Sericin and melatonin mitigate diethylnitrosamine-instigated testicular impairment in mice: Implications of oxidative stress, spermatogenesis, steroidogenesis, and modulation of Nrf2/WT1/SF-1 signaling pathways

AIMS

This study aimed to investigate the therapeutic influence of combination therapy with sericin and melatonin on attenuating diethylnitrosamine (DEN)-instigated testicular dysfunction in mice and defining the molecular mechanisms involved in orchestrating redox signaling pathways and restoring spermatogenesis and steroidogenesis.

MATERIALS AND METHODS

Different groups of male Swiss albino mice were established and injected with respective drugs intraperitoneally. Semen analysis, hormonal assays, and oxidative stress biomarkers were evaluated. Additionally, melatonin and its receptors, WT1, SF-1, vimentin, Nrf2, and ANXA1 expressions were assessed. Histopathological and ultrastructural features of the testes were investigated by semithin, SEM, and TEM analyses.

KEY FINDINGS

Exposure to DEN exhibited pathophysiological consequences, including a remarkable increase in lipid peroxidation associated with substantial diminutions in SOD, CAT, GPx, GSH, GSH:GSSG, and GST. Furthermore, it disrupted spermatozoa integrity, testosterone, FSH, LH, melatonin, and its receptors (MT1 and MT2) levels, implying spermatogenesis dysfunction. By contrast, treatment with sericin and melatonin significantly restored these disturbances. Interestingly, the combination therapy of sericin and melatonin noticeably augmented the Nrf2, WT1, and SF-1 expressions compared to DEN-treated mice, deciphering the amelioration perceived in antioxidant defense and spermatogenesis inside cells. Furthermore, immunohistochemical detection of ANXA1 alongside histopathological and ultrastructural analyses revealed evident maintenance of testicular structures without discernible inflammation or anomalies in mice administered with sericin and melatonin compared to the DEN-treated group.

SIGNIFICANCE

Our findings highlighted that treatment with sericin and melatonin alleviated the testicular tissues in mice from oxidative stress and dysregulated spermatogenesis and steroidogenesis engendered by DEN.

The Regulatory Effects of JAK2/STAT3 on Spermatogenesis and the Redox Keap1/Nrf2 Axis in an Animal Model of Testicular Ischemia Reperfusion Injury

The male reproductive system requires the pleiotropic activity of JAK/STAT to maintain its function, especially spermatogenesis. The study aims to investigate the effect of JAK2 signaling on the expression of the Keap1/Nrf2 axis, spermatogenesis, and the Sertoli cells (Sc) junctions in an animal model of testicular ischemia reperfusion injury (tIRI). Testes subjected to tIRI exhibited increased JAK2/STAT3 activity associated with spermatogenic arrest and reduced expression of the Sc junctions. In addition, there was an increased protein expression of Keap1 and decreased Nrf2., which was coupled with the downregulation of gene expression of antioxidant enzymes. Reduced SOD and CAT activities were accompanied by increased lipid peroxidation and protein carbonylation during tIRI. Increased caspase 9 activity and Bax/Bcl2 ratio indicated initiation of apoptosis. Inhibition of JAK2 activity by AG490 maintained the integrity of spermatogenesis and SC junctions, normalized the expression of the Keap1/Nrf2 axis and its downstream antioxidant enzymes, and prevented germ cell apoptosis. The results further emphasized the regulatory role of JAK2/STAT3 on spermatogenesis, Keap1/Nrf2 signaling, and maintenance of the testicular redox balance to combat testicular dysfunction and male infertility.

L-Carnitine and Male Fertility: Is Supplementation Beneficial?

L-Carnitine, a natural antioxidant found in mammals, plays a crucial role in the transport of long-chain fatty acids across the inner mitochondrial membrane. It is used as a nutritional supplement by professional athletes, improving performance and post-exercise recovery. Additionally, its therapeutic applications, including those in male infertility, have been investigated, as it may act as a defense mechanism against the excessive production of reactive oxygen species (ROS) in the testis, a process that can lead to sperm damage. This effect is achieved by enhancing the expression and activity of enzymes with antioxidant properties. Nevertheless, the mechanisms underlying the benefits of L-Carnitine remain unknown. This review aims to consolidate the current knowledge about the potential benefits of L-Carnitine and its role in male (in)fertility. Considering in vitro studies with Sertoli cells, pre-clinical studies, and investigations involving infertile men, a comprehensive understanding of the effects of L-Carnitine has been established. In vitro studies suggest that L-Carnitine has a direct influence on somatic Sertoli cells, improving the development of germ cells. Overall, evidence supports that L-Carnitine can positively impact male fertility, even at a relatively low dose of 2 g/day. This supplementation enhances sperm parameters, regulates hormone levels, reduces ROS levels, and subsequently improves fertility rates. However, further research is needed to elucidate the underlying mechanisms and establish optimal doses. In conclusion, the role of L-Carnitine in the field of male reproductive health is highlighted, with the potential to improve sperm quality and fertility.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: The protection of mammalian spermatozoa against oxidative stress

In brief

This review focuses on the enzymatic antioxidant mechanisms to fight oxidative stress by spermatozoa, highlighting the differences among mammalian species. We discuss recent evidence about players that promote and fight oxidative stress and the need for novel strategies to diagnose and treat cases of male infertility associated with oxidative damage of the spermatozoon.

Abstract

The spermatozoon is very sensitive to high reactive oxygen species (ROS) levels due to its limited antioxidant system. A consortium of antioxidant enzymes, including superoxide dismutase (SOD), glutathione peroxidases (GPXs), peroxiredoxins (PRDXs), thioredoxins, and glutathione-S-transferases, is necessary to produce healthy spermatozoa and to maintain sperm quality to ensure motility, capacitation, and DNA integrity. A delicate balance between ROS production and antioxidant enzymes is needed to ensure ROS-dependent sperm capacitation. GPX4 is an essential component of the mitochondrial sheath in mammalian spermatozoa, and GPX5 is a crucial antioxidant defence in the mouse epididymis to protect the sperm genome during the maturation of the spermatozoon. The mitochondrial superoxide (O2·–) production is controlled by SOD2, and the hydrogen peroxide (H2O2) generated by SOD2 activity and peroxynitrite (ONOO–) are scavenged mainly by PRDXs in human spermatozoa. PRDXs regulate the redox signalling necessary for sperm motility and capacitation, particularly by PRDX6. This enzyme is the first line of defence against oxidative stress to prevent lipid peroxidation and DNA oxidation by scavenging H2O2 and ONOO– through its peroxidase activity and repairing oxidized membranes by its calcium-independent phospholipase A2 activity. The success of antioxidant therapy in treating infertility resides in the proper diagnosis of the presence of oxidative stress and which type of ROS are produced. Thus, more research on the molecular mechanisms affected by oxidative stress, the development of novel diagnostic tools to identify infertile patients with oxidative stress, and randomized controlled trials are of paramount importance to generate personalized antioxidant therapy to restore male fertility.