Melatonin daily oral supplementation attenuates inflammation and oxidative stress in testes of men with altered spermatogenesis of unknown aetiology

Effects of acute hypothyroidism on plasma melatonin and Aanat and Asmt expression in the pineal gland and gonads of rats

Introduction

The reproductive system is tightly regulated by environmental and physiological signals. Melatonin, known as the hormone of darkness, plays a crucial role in regulating both the circadian and reproductive systems in mammals. Hypothyroidism is a key endocrine disorder that harms the reproductive system. Despite many studies on melatonin's effects on the reproductive system, there is conflicting information regarding melatonin synthesis modulation in hypothyroidism. The objective of this study was to investigate the modulation of plasma melatonin levels and gene expression of Aanat and Asmt in the pineal gland and gonads of rats with hypothyroidism at different times of the day.

Methods

Female and male Wistar rats were divided into control and hypothyroid groups. Hypothyroidism was induced using propylthiouracil (PTU) for 15 days, rats were euthanized six hours after lights on (ZT6), before lights off (ZT11.5), and six hours after lights off (ZT18). Free thyroxine (FT4) and melatonin were quantified in plasma, and gene expressions of melatonin synthesizing enzymes (Aanat and Asmt) were measured in pineal and sexual organs (testis and ovary). Also, morphological analysis was performed in sexual organs.

Results

The results reveal some disparities between the sexes. Hypothyroidism reduced antral and primary follicles in the ovary, and reduced the weight of testis, epididymis, and prostate. In relation to gene expression, we observed a reduction in Aanat expression in the pineal gland during the light phase (ZT6), and in males, this reduction occurred during the dark phase (ZT18). Regarding Asmt expression, there was a decrease in females also during the dark phase (ZT18). In the gonads, there was an increase in expression in both sexes at ZT11.5. Additionally, it was interesting to observe the association between FT4 levels and Asmt expression in the gonads.

Conclusions

This study showed that acute hypothyroidism can affect components of the melatonergic system in gonads, particularly gene expression of melatonin synthesis enzymes (Aanat and Asmt) contributing to changes in reproduction organs during disease progression. These findings enhance our understanding of melatonin synthesis in the reproductive system during hypothyroidism, showing distinct responses in male and female rats, and suggest that hypothyroidism affects the circadian rhythmicity of melatonin synthesis in a sex-dependent manner.

Biogenic amines in the testis: sources, receptors and actions

Biogenic amines are signaling molecules with multiple roles in the central nervous system and in peripheral organs, including the gonads. A series of studies indicated that these molecules, their biosynthetic enzymes and their receptors are present in the testis and that they are involved in the regulation of male reproductive physiology and/or pathology. This mini-review aims to summarize the current knowledge in this field and to pinpoint existing research gaps. We suggest that the widespread clinical use of pharmacological agonists/antagonists of these signaling molecules, calls for new investigations in this area. They are necessary to evaluate the relevance of biogenic amines for human male fertility and infertility, as well as the potential value of at least one of them as an anti-aging compound in the testis.

Melatonin improves oxidative state and lactate metabolism in rodent Sertoli cells

Antioxidant actions of melatonin and its impact on testicular function and fertility have already been described. Considering that Sertoli cells contribute to provide structural support and nutrition to germ cells, we evaluated the effect of melatonin on oxidative state and lactate metabolism in the immature murine TM4 cell line and in immature hamster Sertoli cells. A prooxidant stimulus applied to rodent Sertoli cells expressing MT1/MT2 receptors, increased lipid peroxidation whereas decreased antioxidant enzymes (superoxide dismutase 1, catalase, peroxiredoxin 1) expression and catalase activity. These changes were prevented by melatonin. Furthermore, melatonin stimulated lactate dehydrogenase (LDH) expression/activity via melatonin receptors, and increased intracellular lactate production in rodent Sertoli cells. Interestingly, oral melatonin supplementation in infertile men positively regulated LDHA testicular mRNA expression. Overall, our work provides insights into the potential benefits of melatonin on Sertoli cells contributing to testicular development and the future establishment of a sustainable spermatogenesis.

Probiotics improve polystyrene microplastics-induced male reproductive toxicity in mice by alleviating inflammatory response

As a new type of environmental pollutant, microplastics have been garnered increasing attention, especially in regard to their effects on the reproductive system. However, researchers have yet to report whether prevention and treatment measures exist for reproductive injury caused by microplastics. The aim of this study was therefore to explore the mechanism of spermatogenic injury induced by polystyrene microplastics (PS-MPs) and the intervention effect of probiotics based on the gut microbiota-testis axis. Mice were orally exposed for 35 days to 5 µm of PS-MPs with a gavage dose was 0.1 mg/day, and the intervention group was given probiotics (Lactobacillus, Bifidobacterium longum, and Enterococcus) orally. Fecal samples were then subjected to 16 S rRNA sequencing analysis, and sperm motion was analyzed by a Hamilton-Thorne Sperm analyzer. The results showed that PS-MPs exposed mice had significant spermatogenic dysfunction and testicular inflammation. In addition, the intestinal microbial structure of exposed mice changed significantly; the abundance of Lactobacillus decreased, and the abundance of Prevotella increased. Furthermore, with fecal microbiota transplantation, the recipient mice showed a significant decrease in sperm quality. However, probiotics supplementation helped inhibit the activation of IL-17A signaling driven by gut microbes, thereby alleviating the inflammatory response and improving sperm quality decline caused by PS-MPs. These results may provide a scientific basis for further understanding of the mechanism of male reproductive damage caused by environmental pollutants such as microplastics and for novel reproductive damage intervention measures.

Protective effects of exogenous melatonin therapy against oxidative stress to male reproductive tissue caused by anti-cancer chemical and radiation therapy: a systematic review and meta-analysis of animal studies

Background

Male testicular dysfunction is a considerable complication of anti-cancer therapies, including chemotherapy and radiotherapy, partly due to the increased oxidative stress caused by these treatments. Melatonin is an effective antioxidant agent that protects testicles against physical and toxic chemical stressors in animal models. This study aims to systematically review the melatonin's protective effects against anti-cancer stressors on rodential testicular tissue.

Materials and Method

An extensive search was conducted in Web of Science, Scopus, and PubMed for animal studies investigating exogenous melatonin's protective effects on rodent testicles exposed to anti-cancer chemicals and radiotherapeutic agents. Using the DerSimonian and Laird random-effect model, standardized mean differences and 95% confidence intervals were estimated from the pooled data. The protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42022355293).

Results

The meta-analysis included 38 studies from 43 studies that were eligible for the review. Rats and mice were exposed to radiotherapy (ionizing radiations such as gamma- and roentgen radiation and radioactive iodine) or chemotherapy (methotrexate, paclitaxel, busulfan, cisplatin, doxorubicin, vinblastine, bleomycin, cyclophosphamide, etoposide, Taxol, procarbazine, docetaxel, and chlorambucil). According to our meta-analysis, all outcomes were significantly improved by melatonin therapy, including sperm quantity and quality (count, motility, viability, normal morphology, number of spermatogonia, Johnsen's testicular biopsy score, seminiferous tubular diameter, and seminiferous epithelial height), serum level of reproductive hormones (Follicle-Stimulating Hormone and testosterone), tissue markers of oxidative stress (testicular tissue malondialdehyde, superoxide dismutase, glutathione peroxidase, catalase, glutathione, caspase-3, and total antioxidant capacity), and weight-related characteristics (absolute body, epididymis, testis, and relative testis to body weights). Most SYRCLE domains exhibited a high risk of bias in the included studies. Also, significant heterogeneity and small-study effects were detected.

Conclusion

In male rodents, melatonin therapy was related to improved testicular histopathology, reproductive hormones, testis and body weights, and reduced levels of oxidative markers in testicular tissues of male rodents. Future meticulous studies are recommended to provide a robust scientific backbone for human applications.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022355293, identifier CRD42022355293.

Mitigation of triptolide-induced testicular Sertoli cell damage by melatonin via regulating the crosstalk between SIRT1 and NRF2

BACKGROUND

Triptolide (TP) is an important active compound from Tripterygium wilfordii Hook F (TwHF), however, it is greatly limited in clinical practice due to its severe toxicity, especially testicular injury. Melatonin is an endogenous hormone and has beneficial effects on the reproductive system. However, whether triptolide-induced testicular injury can be alleviated by melatonin and the underlying mechanism are not clear.

PURPOSE

In this study, we aimed to explore whether triptolide-induced testicular Sertoli cells toxicity can be mitigated by melatonin and the underlying mechanisms involved.

METHODS

Cell apoptosis was assessed by flow cytometry, western blot, immunofluorescence and immunohistochemistry. Fluorescent probe Mito-Tracker Red CMXRos was used to observe the mitochondria morphology. Mitochondrial membrane potential and Ca²⁺ levels were used to investigate mitochondrial function by confocal microscope and flow cytometry. The expression levels of SIRT1/Nrf2 pathway were detected by western blot, immunofluorescence and immunohistochemistry. Small interfering RNA of NRF2 and SIRT1 inhibitor EX527 was used to confirm the role of SIRT1/NRF2 pathway in the mitigation of triptolide-induced Sertoli cell damage by melatonin. Co-Immunoprecipitation assay was used to determine the interaction between SIRT1 and NRF2.

RESULTS

Triptolide-induced dysfunction of testicular Sertoli cells was significantly improved by melatonin treatment. Specifically, triptolide-induced oxidative stress damage and changes of mitochondrial morphology, mitochondrial membrane potential, and BTB integrity were alleviated by melatonin. Mechanistically, triptolide inhibited SIRT1 and then reduced the activation of NRF2 pathway via regulating the interaction between SIRT1 and NRF2, thereby downregulating the downstream antioxidant genes, which was reversed by melatonin. Nevertheless, knockdown of NRF2 or inhibition of SIRT1 abolished the protective effect of melatonin.

CONCLUSION

Triptolide-induced testicular Sertoli cell damage could be alleviated by melatonin via regulating the crosstalk between SIRT1 and NRF2, which is helpful for developing a new strategy to alleviate triptolide-induced toxicity.

The role of N6-methyladenosine modification in benzene-induced testicular damage and the protective effect of melatonin

Benzene is a universal ambient pollutant. Population-based studies have shown that benzene exposure affects male fertility. However, the mechanism of benzene-induced reproductive toxicity is unknown. Here, we established a dynamic inhalation model and exposed C57BL/6J mice to 0, 10, and 50 ppm benzene (6 h/day, 6 days/week, 7 weeks). Our study revealed that benzene exposure caused testicular injury, including structural damage to spermatogenic tubules, reduced semen quality, and decreased testosterone levels. In addition, the decrease in the global level of N⁶-Methyladenosine (m⁶A) and the change of m⁶A important regulatory enzymes in mice testes suggested that m⁶A was involved in the benzene-induced testicular injury. Further genome-wide m⁶A methylation analysis showed that 1469 differential m⁶A peaks were present in the testes of control and benzene groups, indicating that benzene exposure modulated m⁶A methylation in testes. Furthermore, the comprehensive analysis of m⁶A-sequencing and transcriptome revealed that hypermethylated Rara and its consequent reduced expression impaired the sperm production process. In particular, melatonin alleviated benzene-induced testicular injury by modulating m⁶A-related genes. Overall, our research provides a new idea and fundamental knowledge into the possible mechanisms of m⁶A modifications in benzene-induced testicular impairment, as well as a new experimental basis for benzene-induced male fertility therapy.

Melatonin enhances spermatogonia activity through promoting KIAA1429-mediated m6A deposition to activate the PI3K/AKT signaling

Melatonin is a key neuroendocrine hormone that promotes spermatogenesis and sperm motility, but the underlying mechanisms remains poorly understood. In this study, we aimed to investigate the possible roles of m⁶A (N⁶--methyl-adenosine) in mediating melatonin-regulated spermatogonia activity alterations. In this study, mouse-derived GC-1 spermatogonia (spg) cell line was used as the in vitro cellular model. The viability, proliferation rates and apoptosis of spermatogonia were detected via CCK-8, Edu staining and flow cytometry respectively. Total m⁶A level was quantitated by dot blot, while mRNA and proteins contents in spermatogonia were measured by qRT-PCR and western blot respectively. Differentially expressed mRNAs were characterized by deep RNA sequencing method. Results showed that melatonin significantly promoted viability and proliferation rate while inhibited apoptosis in the GC-1 spg cells. The total m⁶A levels in GC-1 spg cells were also greatly increased by melatonin treatment, accompanied by remarkable expressional elevation of the m⁶A writer KIAA1429. Moreover, the regulation of GC-1 spg cell viability, proliferation and apoptosis by melatonin were greatly abrogated by KIAA1429 silencing but effectively strengthened by KIAA1429 overexpression. In addition, KIAA1429 overexpression regulates multiple biological process and signaling pathways in spermatogonia such as the PI3K/AKT signaling. The PI3K inhibitor LY294002 effectively mitigated the regulation of spermatogonia activity by KIAA1429 overexpression under melatonin treatment. Taken together, melatonin promotes spermatogonia activity via enhancing KIAA1429 expression and m⁶A RNA methylation to activate the downstream PI3K/AKT signaling pathway.

The effects and molecular mechanism of heat stress on spermatogenesis and the mitigation measures

Under normal conditions, to achieve optimal spermatogenesis, the temperature of the testes should be 2-6 °C lower than body temperature. Cryptorchidism is one of the common pathogenic factors of male infertility. The increase of testicular temperature in male cryptorchidism patients leads to the disorder of body regulation and balance, induces the oxidative stress response of germ cells, destroys the integrity of sperm DNA, yields morphologically abnormal sperm, and leads to excessive apoptosis of germ cells. These physiological changes in the body can reduce sperm fertility and lead to male infertility. This paper describes the factors causing testicular heat stress, including lifestyle and behavioral factors, occupational and environmental factors (external factors), and clinical factors caused by pathological conditions (internal factors). Studies have shown that wearing tight pants or an inappropriate posture when sitting for a long time in daily life, and an increase in ambient temperature caused by different seasons or in different areas, can cause an increase in testicular temperature, induces testicular oxidative stress response, and reduce male fertility. The occurrence of cryptorchidism causes pathological changes within the testis and sperm, such as increased germ cell apoptosis, DNA damage in sperm cells, changes in gene expression, increase in chromosome aneuploidy, and changes in Na⁺/K⁺-ATPase activity, etc. At the end of the article, we list some substances that can relieve oxidative stress in tissues, such as trigonelline, melatonin, R. apetalus, and angelica powder. These substances can protect testicular tissue and relieve the damage caused by excessive oxidative stress.

Pleiotropic actions of melatonin in testicular peritubular myoid cells of immature Syrian hamsters

BACKGROUND

Peritubular myoid cells are emerging as key regulators of testicular function in adulthood. However, little is known about the role of testicular peritubular myoid cells (TPMCs) in the development of the male gonad. We found that, compared to testes of young adult hamsters, gonads of 21 day-old animals show increased melatonin concentration, seminiferous tubular wall thickening and a heterogeneous packaging of its collagen fibers thus raising the question whether melatonin may be involved in the regulation of TPMCs.

METHODS

We established primary cultures of TPMCs from immature hamsters (ihaTPMCs), which we found express melatonergic receptors.

RESULTS

Exogeneous melatonin decreased the levels of inflammatory markers (NLRP3 inflammasome, IL1β) but increased the expression of cyclooxygenase 2 (COX2, key enzyme mediating prostaglandin synthesis) and of the glial cell line-derived neurotrophic factor (GDNF) in ihaTPMCs. Melatonin also stimulated ihaTPMCs proliferation and the expression of extracellular matrix proteins such as collagen type I and IV. Furthermore, collagen gel contraction assays revealed an enhanced ability of ihaTPMCs to contract in the presence of melatonin.

CONCLUSION

Melatonin regulates immune and inflammatory functions as well as contractile phenotype of the peritubular wall in the hamster testis.

GENERAL SIGNIFICANCE

If transferable to the in vivo situation, melatonin-dependent induction of ihaTPMCs to produce factors known to exert paracrine effects in other somatic cell populations of the gonad suggests that the influence of melatonin may go beyond the peritubular wall and indicates its contribution to testicular development and the establishment of a normal and sustainable spermatogenesis.

COVID-19, Oxidative Stress and Male Reproduction: Possible Role of Antioxidants

Coronavirus disease 2019 (COVID-19) involves a complex pathogenesis and with the evolving novel variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the long-term impacts of the unceasing COVID-19 pandemic are mostly uncertain. Evidence indicates deleterious impact of this disease upon male reproductive health. It is concerning that COVID-19 may contribute to the already global declining trend of male fertility. The adverse impacts of COVID-19 on male reproduction may primarily be attributed to the induction of systemic inflammatory responses and oxidative stress (OS), which operate as a vicious loop. Bringing the systemic inflammation to a halt is critical for ‘putting out’ the ‘cytokine storm’ induced by excessive reactive oxygen species (ROS) generation. The possibility of OS playing a prime role in COVID-19-mediated male reproductive dysfunctions has led to the advocacy of antioxidant therapy. An array of antioxidant defense medications has shown to be effective in experimental and clinical studies of COVID-19. The present review thus discusses the possibilities as to whether antioxidant drugs would contribute to combating the SARS-CoV-2 infection-induced male reproductive disruptions, thereby aiming at kindling research ideas that are needed for identification and treatment of COVID-19-mediated male reproductive impairments.

Non-coding RNA-based regulation of inflammation

Inflammation is a multifactorial process and various biological mechanisms and pathways participate in its development. The presence of inflammation is involved in pathogenesis of different diseases such as diabetes mellitus, cardiovascular diseases and even, cancer. Non-coding RNAs (ncRNAs) comprise large part of transcribed genome and their critical function in physiological and pathological conditions has been confirmed. The present review focuses on miRNAs, lncRNAs and circRNAs as ncRNAs and their potential functions in inflammation regulation and resolution. Pro-inflammatory and anti-inflammatory factors are regulated by miRNAs via binding to 3'-UTR or indirectly via affecting other pathways such as SIRT1 and NF-κB. LncRNAs display a similar function and they can also affect miRNAs via sponging in regulating levels of cytokines. CircRNAs mainly affect miRNAs and reduce their expression in regulating cytokine levels. Notably, exosomal ncRNAs have shown capacity in inflammation resolution. In addition to pre-clinical studies, clinical trials have examined role of ncRNAs in inflammation-mediated disease pathogenesis and cytokine regulation. The therapeutic targeting of ncRNAs using drugs and nucleic acids have been analyzed to reduce inflammation in disease therapy. Therefore, ncRNAs can serve as diagnostic, prognostic and therapeutic targets in inflammation-related diseases in pre-clinical and clinical backgrounds.

Melatonin ameliorates endocrine dysfunction and defective sperm integrity associated with high-fat diet-induced obesity in male Wistar rats

Obesity (OBS) has been established as a link to male hypogonadism with consequent infertility. Previous studies have shown that melatonin (MEL) modulates hypothalamic-pituitary-gonadal function. The present study therefore investigated the hypothesis that MEL supplementation would attenuate spermatogenic and steroidogenic dysfunctions associated with obesity induced by high-fat diet (HFD). Twenty-four adult male Wistar rats (n = 6/group) were used: control group received vehicle (normal saline), obese group received 40% high-fat diet and distilled water, MEL-treated group received MEL (4 mg/kg), and OBS + MEL group received MEL and 40% HFD and the treatment lasted for 12 weeks. HFD caused increased body weight, glucose intolerance, plasma triglyceride and low-density lipoprotein cholesterol/ very low-density lipoprotein cholesterol and malondialdehyde, as well as decreased antioxidant capacity, high-density lipoprotein cholesterol, gonadotrophin-releasing hormone, follicle-stimulating hormone and testosterone and altered sperm parameters. However, all these alterations were attenuated when supplemented with MEL. Taken together, these results indicate that HFD exposure causes endocrine dysfunction and disrupted sperm parameters in obese animals, which are accompanied by lipid peroxidation/defective antioxidant capacity. In addition, the present results suggest that melatonin supplementation restores endocrine function and sperm integrity in obese rat model by suppression of oxidative stress-dependent mechanism.

Male and female gonadal ageing: its impact on health span and life span

Ageing is linked to changes in the hypothalamic-pituitary-gonadal axis and a progressive decline in gonadal function. While women become infertile when they enter menopause, fertility decline in ageing men does not necessarily involve a complete cessation of spermatogenesis. Gonadal dysfunction in elderly people is characterized by morphological, endocrine and metabolic alterations affecting the reproductive function and quality of life. With advancing age, sexuality turns into a critical emotional and physical factor actually defining the number of years that ageing people live a healthy life. Gonadal ageing correlates with comorbidities and an increased risk of age-related diseases including diabetes, kidney problems, cardiovascular failures and cancer. This article briefly summarizes the current state of knowledge on ovarian and testicular senescence, explores the experimental models used in the study of gonadal ageing, and describes the local pro-inflammatory, oxidative and apoptotic events and the associated signalling pathways that take place in the gonads while people get older. Overall, literature reports that ageing exacerbates a mutual crosstalk among oxidative stress, apoptosis and the inflammatory response in the gonads leading to detrimental effects on fertility. Data also highlight the clinical implications of novel therapeutic interventions using antioxidant, anti-apoptotic and anti-inflammatory drugs on health span and life span.

Is Melatonin the Cornucopia of the 21st Century?

Melatonin, an indoleamine hormone produced and secreted at night by pinealocytes and extra-pineal cells, plays an important role in timing circadian rhythms (24-h internal clock) and regulating the sleep/wake cycle in humans. However, in recent years melatonin has gained much attention mainly because of its demonstrated powerful lipophilic antioxidant and free radical scavenging action. Melatonin has been proven to be twice as active as vitamin E, believed to be the most effective lipophilic antioxidant. Melatonin-induced signal transduction through melatonin receptors promotes the expression of antioxidant enzymes as well as inflammation-related genes. Melatonin also exerts an immunomodulatory action through the stimulation of high-affinity receptors expressed in immunocompetent cells. Here, we reviewed the efficacy, safety and side effects of melatonin supplementation in treating oxidative stress- and/or inflammation-related disorders, such as obesity, cardiovascular diseases, immune disorders, infectious diseases, cancer, neurodegenerative diseases, as well as osteoporosis and infertility.