Melatonin relieves heat-induced spermatocyte apoptosis in mouse testes by inhibition of ATF6 and PERK signaling pathways

Sestrin2 and Sestrin3 protect spermatogenesis against heat-induced meiotic defects†

Heat stress induces testicular oxidative stress, impairs spermatogenesis, and increases the risk of male infertility. Recent studies have highlighted the antioxidative properties of the Sestrins family in reducing cellular oxidative damage. However, the role of Sestrins (Sestrin1, 2, and 3) in the testicular response to heat stress remains unclear. Here, we found that Sestrin2 and 3 were highly expressed in the testis relative to Sestrin1. Then, the Sestrin2-/- and Sestrin3-/- mice were generated by CRISPR/Cas9 to investigate the role of them on spermatogenesis after heat stress. Our data showed that Sestrin2-/- and Sestrin3-/- mice testes exhibited more severe damage manifested by exacerbated loss of germ cells and higher levels of oxidative stress as compared to wild-type counterparts after heat stress. Notably, Sestrin2-/- and Sestrin3-/- mice underwent a remarkable increase in heat-induced spermatocyte apoptosis than that of controls. Furthermore, the transcriptome landscape of spermatocytes and chromosome spreading showed that loss of Sestrin2 and Sestrin3 exacerbated meiotic failure by compromising DNA double-strand breaks repair after heat stress. Taken together, our work demonstrated a critical protective function of Sestrin2 and Sestrin3 in mitigating the impairments of spermatogenesis against heat stress.

Heat stress induces calcium dyshomeostasis to subsequent cognitive impairment through ERS-mediated apoptosis via SERCA/PERK/eIF2α pathway

Heat exposure is an environmental stressor that has been associated with cognitive impairment. However, the neural mechanisms that underlie this phenomenon have yet to be extensively investigated. The Morris water maze test was utilized to assess cognitive performance. RNA sequencing was employed to discover the primary regulators and pathological pathways involved in cognitive impairment caused by heat. Before heat exposure in vivo and in vitro, activation of the sarco/endoplasmic reticulum (SR/ER) calcium (Ca2+)-ATPase (SERCA) was achieved by CDN1163. Hematoxylin-Eosin, Nissl staining, calcium imaging, transmission electron microscopy, western blot, and immunofluorescence were utilized to visualize histological changes, intracellular calcium levels, endoplasmic reticulum stress (ERS) markers, apoptosis, and synaptic proteins alterations. Heat stress (HS) significantly induced cognitive decline and neuronal damage in mice. By the transcriptome sequencing between control (n = 5) and heat stress (n = 5) mice in hippocampal tissues, we identified a reduction in the expression of the atp2a gene encoding SERCA, accompanied by a corresponding decrease in its protein level. Consequently, this dysregulation resulted in an excessive accumulation of intracellular calcium ions. Furthermore, HS exposure also activated ERS and apoptosis, as evidenced by the upregulation of p-PERK, p-eIF2α, CHOP, and caspase-3. Consistently, a reduction in postsynaptic density protein 95 (PSD95) and synaptophysin (SYN) expressions indicated modifications in synaptic function. Notably, the impacts on neurons caused by HS were found to be mitigated by CDN1163 treatment both in vivo and in vitro. Additionally, SERCA-mediated ERS-induced apoptosis was attenuated by GSK2606414 treatment via inhibiting PERK-eIF2α-CHOP axis that not only curtailed the level of caspase-3 but also elevated the levels of PSD95 and SYN. These findings highlight the significant impact of heat stress on cognitive impairment, and further elucidate the underlying mechanism involving SERCA/PERK/eIF2α pathway.

Deactivation of the Unfolded Protein Response Aggravated Renal AA Amyloidosis in HSF1 Deficiency Mice

Systemic amyloid A (AA) amyloidosis, which is considered the second most common form of systemic amyloidosis usually takes place several years prior to the occurrence of chronic inflammation, generally involving the kidney. Activated HSF1, which alleviated unfolded protein response (UPR) or enhanced HSR, is the potential therapeutic target of many diseases. However, the effect of HSF1 on AA amyloidosis remains unclear. This study focused on evaluating effect of HSF1 on AA amyloidosis based on HSF1 knockout mice. As a result, aggravated amyloid deposits and renal dysfunction have been found in HSF1 knockout mice. In progressive AA amyloidosis, HSF1 deficiency enhances serum amyloid A production might to lead to severe AA amyloid deposition in mice, which may be related to deactivated unfolded protein response as well as enhanced inflammation. Thus, HSF1 plays a significant role on UPR related pathway impacting AA amyloid deposition, which can mitigate amyloidogenic proteins from aggregation pathologically and is the possible way for intervening with the pathology of systemic amyloid disorder. In conclusion, HSF1 could not only serve as a new target for AA amyloidosis treatment in the future, but HSF1 knockout mice also can be considered as a valuable novel animal model for renal AA amyloidosis.

The advancement of polysaccharides in disease modulation: Multifaceted regulation of programmed cell death

Programmed cell death (PCD), also known as regulatory cell death (RCD), is a process that occurs in all organisms and is closely linked to both normal physiological processes and disease states. Various signaling pathways, such as TP53, KRAS, NOTCH, hypoxia, and metabolic reprogramming, have been found to regulate RCD. Polysaccharides, which are essential natural products, have been the subject of extensive research in the fields of food, nutrition, and medicine due to their wide range of pharmacological effects. Studies have shown that polysaccharides have biological activities and the potential to target signal transduction pathways for the treatment of diseases. This paper provides a review of the mechanisms through which polysaccharides exert their therapeutic effects at different levels and explores the relationship between different types of RCD and human diseases. The aim of this review is to provide a theoretical basis for the further clinical use and application of polysaccharide bioactivities.

α-Synuclein reduces acetylserotonin O-methyltransferase mediated melatonin biosynthesis by microtubule-associated protein 1 light chain 3 beta-related degradation pathway

Previous studies have demonstrated that α-synuclein (α-SYN) is closely associated with rapid eye movement sleep behavior disorder (RBD) related to several neurodegenerative disorders. However, the exact molecular mechanisms are still rarely investigated. In the present study, we found that in the α-SYNA53T induced RBD-like behavior mouse model, the melatonin level in the plasma and pineal gland were significantly decreased. To elucidate the underlying mechanism of α-SYN-induced melatonin reduction, we investigated the effect of α-SYN in melatonin biosynthesis. Our findings showed that α-SYN reduced the level and activity of melatonin synthesis enzyme acetylserotonin O-methyltransferase (ASMT) in the pineal gland and in the cell cultures. In addition, we found that microtubule-associated protein 1 light chain 3 beta (LC3B) as an important autophagy adapter is involved in the degradation of ASMT. Immunoprecipitation assays revealed that α-SYN increases the binding between LC3B and ASMT, leading to ASMT degradation and a consequent reduction in melatonin biosynthesis. Collectively, our results demonstrate the molecular mechanisms of α-SYN in melatonin biosynthesis, indicating that melatonin is an important molecule involved in the α-SYN-associated RBD-like behaviors, which may provide a potential therapeutic target for RBD of Parkinson's disease.

The Role of Melatonin to Ameliorate Oxidative Stress in Sperm Cells

It is widely accepted that oxidative stress (OS) coming from a wide variety of causes has detrimental effects on male fertility. Antioxidants could have a significant role in the treatment of male infertility, and the current systematic review on the role of melatonin to ameliorate OS clearly shows that improvement of semen parameters follows melatonin supplementation. Although melatonin has considerable promise, further studies are needed to clarify its ability to preserve or restore semen quality under stress conditions in varied species. The present review examines the actions of melatonin via receptor subtypes and its function in the context of OS across male vertebrates.

ATF6 aggravates apoptosis in early porcine embryonic development by regulating organelle homeostasis under high-temperature conditions

Activating transcription factor 6 (ATF6), one of the three sensor proteins in the endoplasmic reticulum (ER), is an important regulator of ER stress-induced apoptosis. ATF6 resides in the ER and, upon activation, is translocated to the Golgi apparatus, where it is cleaved by site-1 protease (S1P) to generate an amino-terminal cytoplasmic fragment. Although recent studies have made progress in elucidating the regulatory mechanisms of ATF6, its function during early porcine embryonic development under high-temperature (HT) stress remains unclear. In this study, zygotes were divided into four groups: control, HT, HT+ATF6 knockdown, and HT+PF (S1P inhibitor). Results showed that HT exposure induced ER stress, which increased ATF6 protein expression and led to a decrease in the blastocyst rate. Next, ATF6 expression was knocked down in HT embryos under microinjection of ATF6 double-stranded RNA (dsRNA). Results revealed that ATF6 knockdown (ATF6-KD) attenuated the increased expression of CHOP, an ER stress marker, and Ca 2+ release induced by HT. In addition, ATF6-KD alleviated homeostasis dysregulation among organelles caused by HT-induced ER stress, and further reduced Golgi apparatus and mitochondrial dysfunction in HT embryos. AIFM2 is an important downstream effector of ATF6. Results showed that ATF6-KD reduced the occurrence of AIFM2-mediated embryonic apoptosis at HT. Taken together, our findings suggest that ATF6 is a crucial mediator of apoptosis during early porcine embryonic development, resulting from HT-induced ER stress and disruption of organelle homeostasis.

Application of Matrigel in the 3-dimension culture of female germline stem cells

Female germline stem cells (FGSCs) are a group of rare undifferentiated cells found in ovarian cortex, which have the unique ability to self-renew and differentiate. Stable maintenance and proliferation of FGSCs in culture are pivotal for clinic research. However, conventional 2-D (dimension) culture systems are limited in their ability to mimic the ovarian microenvironment during in vitro studies. To establish a suitable in vitro microenvironment for FGSCs, we conducted experiments using a Matrigel-based 3-D culture system. This involves testing different dilution ratios, medium compositions, and co-culture cells to find the optimal conditions for FGSCs maintenance and proliferation. Our results demonstrated the feasibility of using Matrigel as a FGSCs 3-D culture media. Moreover, co-culturing FGSCs with some types of cells in the Matrigel-based 3-D culture system had the potential to form ovarian organoids. Meanwhile, the safety of Matrigel was confirmed in vivo through transplantation experiment, which suggests the potential for clinic research.

Remodeling of Gut Microbiota by Probiotics Alleviated Heat Stroke-Induced Necroptosis in Male Germ Cells

SCOPE

Systemic heat stress (or heatstroke; HS) induces germ cell death and spermatogenesis disorders in men and male mammals. Also, it affects the immune environment of the circulatory system promoting gut inflammation and intestinal permeability, leading to pathogenic infection. In this study, the crosstalk between the gut and testis (gut-testis axis) under HS is explored, by examining the effects of intestinal immune status on the health of the male reproductive system in mice.

METHODS AND RESULTS

A mouse model of systemic heat stress is established to investigate the effect of probiotics on testis health. The results reveal that pro-inflammatory factor receptor activation pathway and pathogen infection response pathway are significantly upregulated in HS testes, leading to necroptosis, while pro-inflammatory factor and endotoxin are detected locally in the intestine and then entered the blood. The study then uses probiotics to intervene in gut microbiota, which results in milder gut microbial changes, lower inflammatory responses in the HS gut, and less necroptosis in the HS testes.

CONCLUSION

Probiotics-based remodeling of gut microbiota (GM) reduces the proliferation of abnormal bacteria and decreases the spread of gut-derived inflammatory mediators into the blood circulation under long-term systemic heat stress, which relieves inflammation on germ cells.

Melatonin Supplementation during In Vitro Maturation of Porcine Oocytes Alleviates Oxidative Stress and Endoplasmic Reticulum Stress Induced by Imidacloprid Exposure

Imidacloprid (IMI) is an endogenous neonicotinoid insecticide widely used in agriculture and has attracted researchers' attention because of its risks to the environment and human health. Melatonin (MT) is an antioxidant hormone produced by the pineal gland of the brain. Studies have shown that it has a variety of physiological functions and plays a crucial role in the development of animal germ cells and embryos. The potential protective effects of MT against oocyte damage caused by neonicotinoid pesticide toxicity remain unclear. In this study, we report the toxicity of IMI against, and its effects on the quality of, porcine oocytes and the protective effect of MT on IMI-exposed oocytes. The results show that IMI exposure adversely affected oocyte maturation, while MT supplementation ameliorated its toxic effects. Specifically, IMI exposure increased oxidative stress (OS), endoplasmic reticulum stress (ERS), and apoptosis, which may affect polar body expulsion rates and blastocyst formation. Also, IMI exposure reduced oocyte cleavage rates and the number of cells in blastocysts. However, all of these toxic effects can be restored after a melatonin supplementation treatment. In conclusion, these results suggest that melatonin has a protective effect on IMI-induced defects during porcine oocyte maturation.

Melatonin: Facts, Extrapolations and Clinical Trials

Melatonin is a fascinating molecule that has captured the imagination of many scientists since its discovery in 1958. In recent times, the focus has changed from investigating its natural role as a transducer of biological time for physiological systems to hypothesized roles in virtually all clinical conditions. This goes along with the appearance of extensive literature claiming the (generally) positive benefits of high doses of melatonin in animal models and various clinical situations that would not be receptor-mediated. Based on the assumption that melatonin is safe, high doses have been administered to patients, including the elderly and children, in clinical trials. In this review, we critically review the corresponding literature, including the hypotheses that melatonin acts as a scavenger molecule, in particular in mitochondria, by trying not only to contextualize these interests but also by attempting to separate the wheat from the chaff (or the wishful thinking from the facts). We conclude that most claims remain hypotheses and that the experimental evidence used to promote them is limited and sometimes flawed. Our review will hopefully encourage clinical researchers to reflect on what melatonin can and cannot do and help move the field forward on a solid basis.

Effects of Cooling Interventions with Different Target Temperatures on Heat Stroke Rats

Purpose

To investigate the optimal target temperature of cooling intervention in heat stroke (HS) rats and explore the potential mechanisms of cooling intervention in alleviating heat stroke-induced damage.

Materials and Methods

A total of 32 Sprague-Dawley rats were randomly divided into 4 groups (n=8/group), including control, HS[core body temperature (Tc)], HS(Tc-1°C) and HS(Tc+1°C) group. Heat stroke model was established in rats of HS(Tc), HS(Tc-1°C) and HS(Tc+1°C) group. Rats in HS(Tc) group were cooled to baseline core body temperature after establishing heat stroke model, HS(Tc-1°C) group to baseline core body temperature minus 1°C and HS(Tc+1°C) group to baseline core body temperature plus 1°C. We compared the histopathological changes of lung, liver and renal tissue, as well as cell apoptosis and expression of critical proteins in phosphatidylinositol 3´-kinase (PI3K)/Akt signaling pathway.

Results

Heat stroke caused the histopathological damage and cell apoptosis of lung, liver and renal tissue, which could be alleviated by cooling intervention to a certain extent. Notably, HS(Tc+1°C) group demonstrated a better effect on alleviating cell apoptosis although the differences were not significant. Heat stroke lead to the elevated expression of p-Akt, which subsequently induced the elevated expression of Caspase-3 and Bax, as well as the decreased expression of Bcl-2. Cooling intervention could reverse this trend. Notably, the expression level of Bax in lung tissue of HS(Tc+1°C) group was significantly lower than that of HS(Tc) and HS(Tc-1°C) group.

Conclusion

The mechanisms of cooling intervention in alleviating heat stroke-induced damage were associated with the expression changes of p-Akt, Caspase-3, Bax and Bcl-2. The better effect of Tc+1°C might be associated with low expression of Bax.

Transcription factor Dmrt1 triggers the SPRY1-NF-κB pathway to maintain testicular immune homeostasis and male fertility

Bacterial or viral infections, such as Brucella, mumps virus, herpes simplex virus, and Zika virus, destroy immune homeostasis of the testes, leading to spermatogenesis disorder and infertility. Of note, recent research shows that SARS-CoV-2 can infect male gonads and destroy Sertoli and Leydig cells, leading to male reproductive dysfunction. Due to the many side effects associated with antibiotic therapy, finding alternative treatments for inflammatory injury remains critical. Here, we found that Dmrt1 plays an important role in regulating testicular immune homeostasis. Knockdown of Dmrt1 in male mice inhibited spermatogenesis with a broad inflammatory response in seminiferous tubules and led to the loss of spermatogenic epithelial cells. Chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq) revealed that Dmrt1 positively regulated the expression of Spry1, an inhibitory protein of the receptor tyrosine kinase (RTK) signaling pathway. Furthermore, immunoprecipitation-mass spectrometry (IP-MS) and co-immunoprecipitation (Co-IP) analysis indicated that SPRY1 binds to nuclear factor kappa B1 (NF-κB1) to prevent nuclear translocation of p65, inhibit activation of NF-κB signaling, prevent excessive inflammatory reaction in the testis, and protect the integrity of the blood-testis barrier. In view of this newly identified Dmrt1- Spry1-NF-κB axis mechanism in the regulation of testicular immune homeostasis, our study opens new avenues for the prevention and treatment of male reproductive diseases in humans and livestock.

Heat Stress-Induced Intestinal Barrier Impairment: Current Insights into the Aspects of Oxidative Stress and Endoplasmic Reticulum Stress

Heat stress (HS) occurs when the sensible temperature of animals exceeds their thermoregulatory capacity, a condition that exerts a detrimental impact on health and growth. The intestinal tract, as a highly sensitive organ, has been shown to respond to HS by exhibiting mucosal injury, intestinal leakage, and disturbances in the gut microbiota. Oxidative stress and endoplasmic reticulum stress (ERS) are both potential outcomes of long-term exposure to high temperatures and have been linked to apoptosis, autophagy, and ferroptosis. In addition, HS alters the composition of the gut microbiota accompanied by changed levels of bacterial components and metabolites, rendering the gut more vulnerable to stress-related injury. In this review, we present recent advances in mechanisms of oxidative stress-associated ERS in response to HS, which is destructive to intestinal barrier integrity. The involvement of autophagy and ferroptosis in ERS was highlighted. Further, we summarize the relevant findings regarding the engagement of gut microbiota-derived components and metabolites in modulation of intestinal mucosal injury induced by HS.

The protective role of melatonin in citalopram-induced reproductive toxicity via modulating nitro-oxidative stress and apoptosis in male mice

Citalopram is the most potent selective serotonin reuptake inhibitor, commonly prescribed as an antidepressant, which can cause sexual dysfunction. Melatonin is a natural, highly effective antioxidant playing a pivotal role in the male reproductive system. The present study aimed to explore the ameliorating potential of melatonin on citalopram-evoked testicular toxicity and injury in mice. In this regard, mice were randomly divided into six groups: control, citalopram, melatonin 10 mg/kg, melatonin 20 mg/kg, melatonin 10 mg/kg plus citalopram, and melatonin 20 mg/kg plus citalopram. Adult male mice were intraperitoneally (i.p.) injected with 10 mg/kg of citalopram for 35 days with or without melatonin. At the end of the study, sperm parameters, testosterone level, testicular levels of malondialdehyde (MDA), nitric oxide (NO), total antioxidant capacity (TAC), and apoptosis (Tunel essay) were evaluated. Our findings revealed that melatonin restored spermatogenesis by improving sperm count, motility, viability, morphology, and chromatin integrity. Testosterone levels and the histopathology of the testes were markedly improved in the melatonin-administrated groups. Furthermore, citalopram administration significantly increased oxidative stress; however, melatonin restored antioxidant status by enhancing TAC levels and decreasing NO and MAD levels. More notably, citalopram therapy induced a significant increase in the number of Tunel-positive cells, while melatonin administration significantly mitigated the apoptotic impacts of citalopram. Together, melatonin therapy provides protection against citalopram-induced testicular damage via modulating nitro-oxidative stress and apoptosis, which provides evidence for melatonin as a promising treatment against antidepressant drug-associated reproductive toxicity and male sub/infertility.

Cyanidin-3-O-glucoside and protocatechuic acid alleviate heat stress-induced testicular damage

Testicular hyperthermia induced by unhealthy living habits and pathological or occupational factors can cause spermatogenic dysfunction with an outcome of sub-fertility or even infertility. Cyanidin-3-O-glucoside (C3G) is the most typical anthocyanin in foods that has been recognized as an antioxidant with promising protection for male reproduction. However, its specific effect against testicular hyperthermia and the mechanisms involving its primary gastrointestinal metabolite protocatechuic acid (PCA) are still unexplored. In the present study, testicular hyperthermia in mice was established by employing a single hot water bath at 43 °C for 30 min. C3G and PCA were intragastrically given to investigate their prevention ability against heat stress-induced testicular damage. It was found that C3G and PCA restored the external diameter and thickness, and alleviated atrophy and vacuolation of seminiferous tubules. Simultaneously, C3G and PCA enhanced testicular heat stress tolerance through reducing superfluous eIF2α phosphorylation and stress granule formation. C3G and PCA effectively improved the testicular antioxidant system and regulated the IRE1α-XBP1 pathway, contributing to mitigatory spermatogenesis dysfunction and testicular damage. This finding revealed that anthocyanins were the novel compounds for alleviating testicular damage, and provided a reliable theoretical basis for improving male fertility disturbed by heat stress.

Endoplasmic Reticulum Stress in Elderly Patients with COVID-19: Potential of Melatonin Treatment

Aging processes, including immunosenescence, inflammation, inflammasome formation, genomic instability, telomeric attrition, and altered autophagy, are involved in viral infections and they may contribute to increased pathophysiological responses to the SARS-CoV-2 infection in the elderly; this poses additional risks of accelerated aging, which could be found even after recovery. Aging is associated with oxidative damage. Moreover, SARS-CoV-2 infections may increase the production of reactive oxygen species and such infections will disturb the Ca++ balance via an endoplasmic reticulum (ER) stress-mediated unfolded protein response. Although vaccine development and anti-inflammation therapy lower the severity of COVID-19, the prevalence and mortality rates are still alarming in some countries worldwide. In this review, we describe the involvement of viral proteins in activating ER stress transducers and their downstream signals and in inducing inflammation and inflammasome formation. Furthermore, we propose the potential of melatonin as an ER stress modulator, owing to its antioxidant, anti-inflammatory, and immunoregulatory effects in viral infections. Considering its strong safety profile, we suggest that additive melatonin supplementation in the elderly could be beneficial in treating COVID-19.

The endoplasmic reticulum stress and B cell lymphoma-2 related ovarian killer participate in docosahexaenoic acid-induced adipocyte apoptosis in grass carp (Ctenopharyngodon idellus)

Docosahexaenoic acid (DHA) lessens adipose tissue lipid deposition partly by inducing adipocyte apoptosis in grass carp, but the underlying mechanism remains unclear. Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) is the novel pathway for inducing apoptosis. This study aimed to explore the potential role of ER stress in DHA-induced apoptosis in grass carp (Ctenopharyngodon idellus) adipocytes. DHA induced apoptosis by deforming the nuclear envelope, condensing the chromatin, and increasing the expression of apoptosis-related proteins and genes in vivo and in vitro (P < 0.05). However, the ER stress inhibitor, 4-phenylbutyric acid (4-PBA), effectively suppressed DHA-induced apoptosis (P < 0.05), indicating that ER stress mediates DHA-induced adipocyte apoptosis. Furthermore, we observed that 200 μM DHA significantly up-regulates the transcripts of B cell lymphoma-2 (BCL-2) related ovarian killer (BOK) in vitro (P < 0.05). BOK is a pro-apoptotic protein in the BCL-2 family, which governs the mitochondria apoptosis pathway. Hence, we hypothesized that BOK might be an important linker between ER stress and apoptosis. We cloned and identified two grass carp BOK genes, BOKa and BOKb, which encode peptides of 213 and 216 amino acids, respectively. BOKa primarily localizes in ER and mitochondria in the cytoplasm, while BOKb localizes in the nucleus and cytoplasm of grass carp adipocytes. Moreover, 200 μM DHA treatment up-regulated the mRNA expression of BOKa and BOKb, whereas 4-PBA suppressed the DHA-induced expressions. These results raised the possibility that BOK participates in DHA-induced adipocyte apoptosis through ER stress signaling, in line with its localization in ER and mitochondria. Two UPR branches, the inositol-requiring enzyme 1 (IRE1α) and activating transcription factor 6 (ATF6) signaling pathways, are possibly important in DHA-induced adipocyte apoptosis, unlike protein kinase RNA-activated-like ER kinase. The study also emphasized the roles of BOKa and BOKb in IRE1α- and ATF6-mediated apoptosis. This work is the first to elucidate the importance of the ER stress-BOK pathway during adipocyte apoptosis in teleost.

Protective effects of melatonin against physical injuries to testicular tissue: A systematic review and meta-analysis of animal models

BACKGROUND

Modern societies face infertility as a global challenge. There are certain environmental conditions and disorders that damage testicular tissue and may cause male infertility. Melatonin, as a potential antioxidant, may protect testicular tissue. Therefore, we conducted this systematic review and meta-analysis to evaluate the effects of melatonin in animal models against physical, heat, and ischemic damage to the testicular tissue.

METHODS

PubMed, Scopus, and Web of Science were systematically searched to identify animal trials evaluating the protective effect of melatonin therapy on rodent testicular tissue when it is exposed to physical, thermal, ischemic, or hypobaric oxygen stress. Random-effect modeling was used to estimate the standardized mean difference and 95% confidence intervals based on the pooled data. Additionally, the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool was used to assess the risk of bias. The study protocol was prospectively registered in PROSPERO (CRD42022354599).

RESULTS

A total of 41 studies were eligible for review out of 10039 records. Studies employed direct heat, cryptorchidism, varicocele, torsion-detorsion, testicular vascular occlusion, hypobaric hypoxia, ischemia-reperfusion, stress by excessive or restraint activity, spinal cord injury, and trauma to induce stress in the subjects. The histopathological characteristics of testicular tissue were generally improved in rodents by melatonin therapy. Based on the pooled data, sperm count, morphology, forward motility, viability, Johnsen's biopsy score, testicular tissue glutathione peroxidase, and superoxide dismutase levels were higher in the melatonin treatment rodent arms. In contrast, the malondialdehyde level in testicular tissue was lower in the treatment rodent arms. The included studies suffered from a high risk of bias in most of the SYRCLE domains.

CONCLUSION

This study concludes that melatonin therapy was associated with improved testicular histopathological characteristics, reproductive hormonal panel, and tissue markers of oxidative stress in male rodents with physical, ischemic, and thermal testicular injuries. In this regard, melatonin deserves scientific investigations as a potential protective drug against rodent male infertility.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022354599.

Overview of biological effects of melatonin on testis: A review

Infertility is a major global health issue and male factors account for half of all infertility cases. One of the causes of male infertility is the loss of spermatogonial stem cells, which may occur because of chemotherapy, radiotherapy or genetic defects. In numerous animal species, the evidence suggests the pineal gland and melatonin secretion in their reproductive activities are involved. Recently, considerable attention has pointed to the usage of melatonin in the treatment of diseases. Melatonin is associated with the regulation of circadian and seasonal rhythmic functions, immune system functions, retinal physiology, spermatogenesis and inhibition of tumour growth in different species. Several studies demonstrated that melatonin acts as an anti-apoptotic, anti-inflammatory, anticancer and antioxidant agent. Melatonin can also protect testicles and spermatogonia against oxidative damage, chemotherapy drugs, environmental radiation, toxic substances, hyperthermia, ischemia/reperfusion, diabetes-induced testicular damage, metal-induced testicular toxicity, improve sperm quality and it affects the testosterone secretion pathway by affecting Leydig cells. Therefore, the objective of this study is to investigate the biological effects of melatonin as a natural antioxidant on testicles and their disorders.

Probing the Potential Mechanism of Quercetin and Kaempferol against Heat Stress-Induced Sertoli Cell Injury: Through Integrating Network Pharmacology and Experimental Validation

Quercetin and kaempferol are flavonoids widely present in fruits, vegetables, and medicinal plants. They have attracted much attention due to their antioxidant, anti-inflammatory, anticancer, antibacterial, and neuroprotective properties. As the guarantee cells in direct contact with germ cells, Sertoli cells exert the role of support, nutrition, and protection in spermatogenesis. In the current study, network pharmacology was used to explore the targets and signaling pathways of quercetin and kaempferol in treating spermatogenic disorders. In vitro experiments were integrated to verify the results of quercetin and kaempferol against heat stress-induced Sertoli cell injury. The online platform was used to analyze the GO biological pathway and KEGG pathway. The results of the network pharmacology showed that quercetin and kaempferol intervention in spermatogenesis disorders were mostly targeting the oxidative response to oxidative stress, the ROS metabolic process and the NFκB pathway. The results of the cell experiment showed that Quercetin and kaempferol can prevent the decline of cell viability induced by heat stress, reduce the expression levels of HSP70 and ROS in Sertoli cells, reduce p-NF-κB-p65 and p-IκB levels, up-regulate the expression of occludin, vimentin and F-actin in Sertoli cells, and protect cell structure. Our research is the first to demonstrate that quercetin and kaempferol may exert effects in resisting the injury of cell viability and structure under heat stress.

Gut microbiota supports male reproduction via nutrition, immunity, and signaling

Gut microbiota (GM) is a major component of the gastrointestinal tract. Growing evidence suggests that it has various effects on many distal organs including the male reproductive system in mammals. GM and testis form the gut-testis axis involving the production of key molecules through microbial metabolism or de novo synthesis. These molecules have nutrition, immunity, and hormone-related functions and promote the male reproductive system via the circulatory system. GM helps maintain the integral structure of testes and regulates testicular immunity to protect the spermatogenic environment. Factors damaging GM negatively impact male reproductive function, however, the related mechanism is unknown. Also, the correlation between GM and testis remains to be yet investigated. This review discusses the complex influence of GM on the male reproductive system highlighting the impact on male fertility.

Melatonin promotes sirtuin 1 expression and inhibits IRE1α–XBP1S–CHOP to reduce endoplasmic reticulum stress–mediated apoptosis in chondrocytes

Osteoarthritis (OA) is the most common chronic disease characterized by a loss of chondrocytes and the degeneration of cartilage. Inflammation plays an important role in the pathogenesis and progression of OA via the activation of the endoplasmic reticulum (ER) stress signaling pathway. In this study, we stimulated human primary chondrocytes with lipopolysaccharide (LPS) to reduce cell viability and induce chondrocyte apoptosis. LPS–stimulated human primary chondrocytes induced ER stress and significantly upregulated the ER chaperone glucose–regulated protein 78 (GRP78) and increased the expression level of C/EBP–homologous protein (CHOP), a key mediator of ER stress––induced apoptosis. Interestingly, melatonin treatment attenuated ER stress–mediated chondrocyte apoptosis. Melatonin inhibited the expression of cleaved caspase-3, cleaved caspase-10, Bax, CHOP, GRP78, cleaved caspase-4, phospho–inositol–requiring enzyme 1α (P-IRE1α), and spliced X-box-binding protein 1 (XBP1S). In an anterior cruciate ligament transection mouse model of OA, melatonin (50 and 150 mg/kg) dose–dependently relieved joint cartilage degeneration and inhibitied of chondrocyte apoptosis. Immunohistochemical analysis indicated that melatonin could promote SIRT1 the expression and inhibit CHOP and cleaved caspase-3 expression in OA mice. In conclusion, our findings demonstrate for the first time that melatonin inhibits the IRE1α-XBP1S-CHOP signaling pathway by promoting the expression of SIRT1 in LPS-treated human chondrocytes and delaying OA progression in vivo.

Astragalus polysaccharide alleviates transport stress-induced heart injury in newly hatched chicks via ERS-UPR-Autophagy dependent pathway

Transport stress (TS) not only affects animal welfare but also eventually leads to higher morbidity and mortality. Moreover, TS could induce heart injury in animals, but the possible mechanism has yet to be fully explored. Astragalus polysaccharide (APS) is a main active component of Radix Astragali, which has an extensive anti-stress effect. However, the effect of APS on TS-induced heart injury has not yet been elucidated. In this study, a chick model of simulated TS was used. 240 newly hatched chicks were arranged into 4 groups: Control (Con), Transport group (T), Transport + water group (TW), and Transport + APS group (TA). Before transport, the chicks of the TW and TA groups were treated with deionized water and APS (0.25 mg/mL, 100 µL) by oral drops respectively. The histopathological analysis of myocardial tissue was assessed by hematoxylin and eosin staining. qRT-PCR and Western Blotting assays were employed to measure the expression of genes and proteins. Semiquantitative PCR was performed for the X box-binding protein-1 (XBP-1) mRNA splicing assay. The results indicated that APS significantly reduced TS-induced myocardial histopathological changes. Meanwhile, TS induced endoplasmic reticulum stress (ERS), evidenced by an activation of the unfolded protein response (UPR) signaling pathway and up-regulation of ERS-markers (P < 0.05). Moreover, TS markedly triggered autophagy induction by activating AMP-activated protein kinase (AMPK), reflected by augmented LC3-II/LC3-I, AMPK phosphorylation and autophagy-related genes (ATGs) expression (P < 0.05). Importantly, our study manifested that treatment of APS could reduce TS-induced ERS and AMPK-activated autophagy, accordingly alleviating heart injury of transported chicks. In summary, these findings indicate that TS induces heart injury in chicks via an ERS-UPR-autophagy-dependent pathway, and APS as an effective therapeutic method to alleviate it.

Temperature is not a major factor in the differentiation of gonocytes into ad spermatogonia and fertility outcome in congenitally cryptorchid boys

Spermatogenesis in mammals is a heat-sensitive developmental pathway incompatible with the typical mammalian body temperature of 37 °C. It is thought that this is the reason why the testicles of most mammalian males are outside of the body cavity, in the scrotum, where they function at approximately 33 °C. It has been suggested that the abnormally high temperature environment of cryptorchid testes may lead to impaired testicular development and adult infertility. Here, I summarize the clinical, genetic, and histological evidence that argues against temperature stress and in favor of hypogonadotropic hypogonadism as the underlying cause of adult infertility in cryptorchidism.

Patient summary: Infertility and an increased risk of testicular cancer in patients diagnosed with undescended testes are the consequence of a hormonal deficiency rather than temperature-induced cellular damage. Cryptorchidism therefore requires both surgical and hormonal treatment.