Upregulation and nuclear translocation of testicular ghrelin protects differentiating spermatogonia from ionizing radiation injury

Nicotinamide mononucleotide ameliorates ionizing radiation-induced spermatogenic dysfunction in mice by modulating the glycolytic pathway

Radiotherapy, a common cancer treatment, leads to infertility in male cancer survivors, particularly young and middle-aged patients. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD +), plays crucial roles in energy metabolism, DNA repair, and gene expression. The purpose of this study is to investigate the protective effects and underlying mechanisms of NMN against ionizing radiation (IR)-induced testicular injury and spermatogenic dysfunction in an adult male mouse model. To assess the effects of NMN, single whole-body γ-ray irradiation is used to induce testicular injury and spermatogenic dysfunction in adult male mice. NMN is orally administered at 500 mg/kg before and after IR exposure. The structural and cellular damage to the testes caused by 5 Gy γ-ray irradiation, as well as the protective effect of NMN on testicular spermatogenic dysfunction, are evaluated. The serum hormone testosterone, LH, and FSH levels, as well as testicular NAD +, lactate, and pyruvate levels, are detected. Furthermore, the expressions of the apoptosis-related genes Bcl-2, Bax, and Caspase-3 and the rate-limiting enzymes HK2, PKM2, and LDHA, which are potentially associated with the mechanism of injury, are examined. The results demonstrate that 5 Gy γ-ray irradiation exposure causes a decrease in the serum testosterone, LH, and FSH levels in adult male mice, as well as in the testicular NAD +, lactate, and pyruvate levels, and causes damage to the testicular structure and cells. Morphometric analysis reveal a decrease in the testis mass, seminiferous tubule diameter, and height of the germinal epithelium. The sperm quantity, motility, and testicular volume are reduced in the 5 Gy group but are restored by NMN supplementation. NMN intervention downregulates the expressions of proapoptotic genes ( Bax and Caspase-3) and upregulates the expression of an antiapoptotic gene ( Bcl- 2). Sertoli cells marker genes ( WT-1, GATA-4, SOX9, and vimentin) and glycolysis rate-limiting enzyme-encoding genes ( HK2, PKM2, LDHA) are significantly upregulated. In summary, NMN has a positive regulatory effect on testicular spermatogenic dysfunction in male mice induced by ionizing radiation. This positive effect is likely achieved by promoting the proliferation of spermatogenic cells and activating glycolytic pathways. These findings suggest that NMN supplementation may be a potential protective strategy to prevent reproductive damage to male subjects from ionizing radiation.

Combined exposure of PS-MPs with NaF induces Sertoli cell death and dysfunction via ferroptosis and apoptosis

The individual toxicity of sodium fluoride (NaF) and microplastics (MPs) has been extensively documented. Owing to their high specific surface area, widespread presence and durability, MPs can adsorb a broad spectrum of environmental contaminants into the organism. However, the combined toxicity of NaF and MPs has not been investigated. This study aimed to assess the effects of combined exposure to NaF and MPs on the function of testicular Sertoli cells (SCs) in male mice, and to investigate the underlying molecular mechanisms. The study revealed that combined exposure to NaF and MPs resulted in a decrease in the negative surface charge of MPs, along with an increase in the number of MPs entering the SCs. Through in vivo observation of the testicular pathological structure, spermatogenesis, and cell apoptosis in 180-day-old male mice, we discovered that combined exposure to NaF (80 mg/L) and MPs (10 mg/L) heightened reproductive toxicity compared to the individual exposure groups. This was evidenced by testicular structural defects, impaired spermatogenesis, and increased testicular cell apoptosis. Our in vitro studies showed that NaF (21 μg/mL) and MPs (100 μg/mL) synergistically induced SCs apoptosis and ferroptosis, leading to a reduction in SCs number and dysfunction. This ultimately resulted in structural and functional damage to the testes. Our findings demonstrate, for the first time, the synergistic effects of NaF and MPs on reproductive toxicity in mammals. These insights may provide valuable contributions to co-toxicity studies involving MPs and other environmental pollutants.

Ultrastructural Analysis of Large Japanese Field Mouse (Apodemus speciosus) Testes Exposed to Low-Dose-Rate (LDR) Radiation after the Fukushima Nuclear Power Plant Accident

Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, great attention has been paid to the impact of chronic low-dose-rate (LDR) radiation exposure on biological systems. The reproductive system is sensitive to radiation, with implications connected to infertility. We investigated the testis ultrastructure of the wild large Japanese field mouse (Apodemus speciosus) from three areas contaminated after the FDNPP accident, with different levels of LDR radiation (0.29 µSv/h, 5.11 µSv/h, and 11.80 µSv/h). Results showed good preservation of the seminiferous tubules, comparable to the unexposed animals (controls), except for some ultrastructural modifications. Increases in the numerical density of lipid droplet clusters in spermatogenic cells were found at high levels of LDR radiation, indicating an antioxidant activity rising due to radiation recovery. In all groups, wide intercellular spaces were found between spermatogenic cells, and cytoplasmic vacuolization increased at intermediate and high levels and vacuolated mitochondria at the high-level. However, these findings were also related to the physiological dynamics of spermatogenesis. In conclusion, the testes of A. speciosus exposed to LDR radiation associated with the FDNPP accident showed a normal spermatogenesis, with some ultrastructural changes. These outcomes may add information on the reproductive potential of mammals chronically exposed to LDR radiation.

Fecal Microbiota Transplantation-Mediated Ghrelin Restoration Improves Neurological Functions After Traumatic Brain Injury: Evidence from 16S rRNA Sequencing and In Vivo Studies

This study aimed to investigate how gut microbiota dysbiosis impacts the repair of the blood-brain barrier and neurological deficits following traumatic brain injury (TBI). Through 16S rRNA sequencing analysis, we compared the gut microbiota of TBI rats and normal controls, discovering significant differences in abundance, species composition, and ecological function, potentially linked to Ghrelin-mediated brain-gut axis functionality. Further, in vivo experiments showed that fecal microbiota transplantation or Ghrelin injection could block the intracerebral TNF signaling pathway, enhance GLP-1 expression, significantly reduce brain edema post-TBI, promote the repair of the blood-brain barrier, and improve neurological deficits. However, the TNF signaling pathway activation could reverse these beneficial effects. In summary, our research suggests that by restoring the balance of gut microbiota, the levels of Ghrelin can be elevated, leading to the blockade of intracerebral TNF signaling pathway and enhanced GLP-1 expression, thereby mitigating post-TBI blood-brain barrier disruption and neurological injuries.

TUNEL-n-DIFL Method for Detection and Estimation of Apoptosis Specifically in Neurons and Glial Cells in Mixed Culture and Animal Models of Central Nervous System Diseases and Injuries

Detection of merely apoptosis does not reveal the type of central nervous system (CNS) cells that are dying in the CNS diseases and injuries. In situ detection and estimation of amount of apoptosis specifically in neurons or glial cells (astrocytes, oligodendrocytes, and microglia) can unveil valuable information for designing therapeutics for protection of the CNS cells and functional recovery. A method was first developed and reported from our laboratory for in situ detection and estimation of amount of apoptosis precisely in neurons and glial cells using in vitro and in vivo models of CNS diseases and injuries. This is a combination of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and double immunofluorescent labeling (DIFL) or simply TUNEL-n-DIFL method for in situ detection and estimation of amount of apoptosis in a specific CNS cell type. An anti-digoxigenin (DIG) IgG antibody conjugated with 7-amino-4-methylcoumarin-3-acetic acid (AMCA) for blue fluorescence, fluorescein isothiocyanate (FITC) for green fluorescence, or Texas Red (TR) for red fluorescence can be used for in situ detection of apoptotic cell DNA, which is earlier labeled with TUNEL using alkali-stable DIG-11-dUTP. A primary anti-NeuN (neurons), anti-GFAP (astrocytes), anti-MBP (oligodendrocytes), or anti-OX-42 (microglia) IgG antibody and a secondary IgG antibody conjugated with one of the above fluorophores (other than that of ani-DIG antibody) are used for in situ detection of apoptosis in a specific CNS cell type in the mixed culture and animal models of the CNS diseases and injuries.

Acylated ghrelin suppresses doxorubicin-induced testicular damage and improves sperm parameters in rats via activation of Nrf2 and mammalian target of rapamycin

Background

Exogenous administration of acylated ghrelin (AG) afforded reproductive protective effect in several animal models but not in those treated with doxorubicin (DOX). This study evaluated the protective effect of AG against DOX-induced testicular damage and impairment in sperm parameters in rats and examined the potential mechanisms of action.

Materials and Methods

Adult male rats were divided into five groups (n = 8/each) as control, control + AG (40 nmol/kg/day; subcutaneous), DOX (10 mg/kg/day 1; intraperitoneal [i.p.]), DOX + AG, and DOX + AG + brusatol (an Nrf2 inhibitor) (2 mg/kg/every 3 days; i.p.). The treatment regimen continued for 65 days.

Results

AG prevented testicular damage and apoptosis; increased sperm count, motility, and viability; and reduced the number of abnormal sperms. It also increased their circulatory levels of AG, des-acylated ghrelin (DAG), and AG/DAG ratio and the testicular mRNA levels of ghrelin and growth hormone secretagogue receptor 1a Concomitantly, AG increased serum and testicular testosterone levels, reduced serum levels of the follicle-stimulating hormone and luteinizing hormone, and upregulated the testicular protein levels of the steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase in DOX-treated rats. In the testes of the control and DOX-treated rats, AG increased the phosphorylation of mammalian target of rapamycin and stimulated the levels of glutathione and superoxide dismutase, as well as the nuclear activation of Nrf2. All these effects were completely prevented by co-treatment with brusatol.

Conclusion

AG replacement therapy could be a novel strategy to prevent reproductive toxicity in cancer patients.

TNF-α/ENO1 signaling facilitates testicular phagocytosis by directly activating Elmo1 gene expression in mouse Sertoli cells

Phagocytic clearance of apoptotic germ cells (GCs), as well as residual bodies (RBs) released from developing spermatids, is critical for Sertoli cells (SCs) to maintain inner environment homeostasis within testis. However, the molecular mechanisms controlling the phagocytosis are ill defined. Here, we identify a new role for alpha-enolase (ENO1), a key enzyme during glycolysis, as a molecule that facilitates testicular phagocytosis via transactivation of the engulfment and cell motility 1 (Elmo1) gene. Using immunohistochesmitry and double-labeling immunofluorescence, ENO1 was observed to be expressed exclusively in the nuclei of SCs and its expression correlated with the completion of Sertoli cell differentiation. By incubating TM4 cells with different pharmacological inhibitors and establishing TM4^Tnfr1-/- cells, we demonstrated that Sertoli cell-specific expression of ENO1 was under a delicate paracrine control from apoptotic GCs. In turn, persistent blockade of ENO1 expression by a validated siRNA protocol resulted in the disturbance of spermatogenesis and impairment of male fertility. Furthermore, using chromatin immunoprecipitation, electrophoretic mobility shift assay and luciferase reporter assay, we showed that in the presence of apoptotic GCs, ENO1 binds to the distal region of the Elmo1 promoter and facilitates transactivation of the Elmo1 gene. In agreement, overexpression of ELMO1 ameliorated ENO1 deficiency-induced impairment of phagocytosis in TM4 cells. These data reveal a novel role for Sertoli cell-specific expression of ENO1 in regulating phagocytosis in testis, identify TNF-α and ELMO1 as critical upstream and downstream factors in mediating ENO1 action, and have important implications for understanding paracrine control of Sertoli cell function by adjacent GCs.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus-pituitary-gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

The Role of the Gastric Hormones Ghrelin and Nesfatin-1 in Reproduction

Ghrelin and nesfatin-1 are enteroendocrine peptide hormones expressed in rat X/A-like and human P/D1cells of the gastric mucosa. Besides their effect on food intake, both peptides are also implicated in various other physiological systems. One of these is the reproductive system. This present review illustrates the distribution of ghrelin and nesfatin-1 along the hypothalamus–pituitary–gonadal (HPG) axis, their modulation by reproductive hormones, and effects on reproductive functions as well as highlighting gaps in current knowledge to foster further research.

Environmentally relevant perinatal exposure to DBP disturbs testicular development and puberty onset in male mice

Di-n-butyl phthalate (DBP) is considered as a potential modifier of puberty. However, different results indicate that DBP plays an accelerated, delayed, or neutral role in the initiation of puberty. Furthermore, whether the effect of DBP on puberty will disrupt the function of reproductive system in the adults is still ambiguous. Therefore, we aimed to investigate the effect of maternal exposure to DBP on the onset of puberty in male offspring mice and the subsequent changes in the development of reproductive system. Here, pregnant mice were treated with 0 (control), 50, 250, or 500 mg/kg/day DBP in 1 mL/kg corn oil administered daily by oral gavage from gestation day (GD) 12.5 to parturition. Compared with the control group, the 50 mg/kg/day DBP group accelerated puberty onset and testicular development were quite remarkable in male offspring mice during early puberty. Furthermore, in 22-day male offspring mice, 50 mg/kg/day DBP induced increased levels of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone in serum, and promoted the expression of steroidogenesis-related genes in the testes. Testicular Leydig cells (LCs) were isolated from the testes of 3-week-old mice and treated with 0 (control), 0.1, 1 mM monobutyl phthalate (MBP, the active metabolite of DBP) for 24 h. Consistent with the in vivo results, the expression of steroidogenesis-related genes and testosterone production were increased in LCs following exposure to 0.1 mM MBP. In adulthood, testes of the male offspring mice exposed to all doses of DBP exhibited adverse morphology compared with the control group. These results demonstrated that maternal exposure to 50 mg/kg/day DBP induced earlier puberty and precocious development of the testis, and eventually damaged the reproductive system in the later life.

Testicular STAC3 regulates Leydig cell steroidogenesis through potentiating mitochondrial membrane potential and StAR processing

SH3 and cysteine-rich protein 3 (STAC3), a small adapter protein originally identified as a core component of excitation–contraction coupling machinery, regulates the voltage-induced Ca²⁺ release in skeletal muscle. However, the possibility of additional, as yet unknown, non-muscle effects of STAC3 cannot be ruled out. Herein, we provide the evidence for the expression and functional involvement of STAC3 in spermatogenesis. STAC3 expression was localized in the testicular interstitium of rodent and human testes. By using the cytotoxic drug ethylene dimethane sulfonate (EDS), STAC3 expression was observed to be decreased sharply in rat testis after selective withdrawal of Leydig cells (LCs), and reappeared immediately after LCs repopulation, indicating that testicular expression of STAC3 mainly stems from LCs. From a functional standpoint, in vivo lentiviral vector–mediated suppression of STAC3 resulted in a significant decrease in testosterone production, and thereafter caused impairment of male fertility by inducing oligozoospermia and asthenospermia. The indispensible involvement of STAC3 in testicular steroidogenesis was validated using the in vivo knockdown model with isolated primary LCs as well as in vitro experiments with primary LCs. By generating the TM3^Stac3−/− cells, we further revealed that STAC3 depletion attenuated mitochondrial membrane potential and StAR processing in db-cAMP-stimulated LCs. Thus, the inhibitory effect of STAC3 deficiency on testicular steroidogenesis may be ascribed to a disturbed mitochondrial homeostasis. Collectively, the present results strongly suggest that STAC3 may function as a novel regulator linking mitochondrial homeostasis and testicular steroidogenesis in LCs. Our data underscore an unexpected reproductive facet of this muscle-derived factor.

Monophosphoryl lipid A alleviated radiation-induced testicular injury through TLR4-dependent exosomes

Radiation protection on male testis is an important task for ionizing radiation-related workers or people who receive radiotherapy for tumours near the testicle. In recent years, Toll-like receptors (TLRs), especially TLR4, have been widely studied as a radiation protection target. In this study, we detected that a low-toxicity TLR4 agonist monophosphoryl lipid A (MPLA) produced obvious radiation protection effects on mice testis. We found that MPLA effectively alleviated testis structure damage and cell apoptosis induced by ionizing radiation (IR). However, as the expression abundance differs a lot in distinct cells and tissues, MPLA seemed not to directly activate TLR4 singling pathway in mice testis. Here, we demonstrated a brand new mechanism for MPLA producing radiation protection effects on testis. We observed a significant activation of TLR4 pathway in macrophages after MPLA stimulation and identified significant changes in macrophage-derived exosomes protein expression. We proved that after MPLA treatment, macrophage-derived exosomes played an important role in testis radiation protection, and specially, G-CSF and MIP-2 in exosomes are the core molecules in this protection effect.

Low-dose ionizing irradiation triggers apoptosis of undifferentiated spermatogonia in vivo and in vitro

Background

The present study aimed to investigate the mechanism of low-dose ionizing radiation (IR) induced apoptosis of undifferentiated spermatogonia in vivo and in vitro.

Methods

Following 50 mGy IR, testicular tissues were collected from the adult DBA/2 mice at 1, 2 and 24 h; mice in the control group received pseudo-irradiation. Immunofluorescence (IF) staining and TUNEL were performed to assess DNA damage and apoptosis, respectively, in the irradiated testicular tissues. Furthermore, the spermatogonia were also irradiated in vitro, and the expression of apoptosis-related proteins was detected by Western blotting. TUNEL and flow cytometry were applied to assess cell apoptosis.

Results

γH2AX (a marker of DNA damage) was up-regulated in the seminiferous tubules at 1 and 2 h after IR, but it was reduced following the DNA repair. This was consistent with the finding that apoptosis of germline cells was present in the seminiferous tubules after IR, especially at 1 h (IF and TUNEL). Apoptosis was also present in the PLZF(+) spermatogonia, particularly at 1 h after IR. Apoptotic cells decreased with the increase in DNA repair time after IR. Moreover, the caspase-3 protein was expressed in the undifferentiated spermatogonia following IR. The expression of caspase-3, P53, Ku70 and DNA-PKcs in the cultured spermatogonia was also up-regulated following IR in vitro, but their expression decreased gradually over time after IR, which was supported by the findings from flow cytometry, and the apoptosis of spermatogonia peaked at 24 h post IR.

Conclusions

IR may induce the apoptosis of spermatogonia at early stage in vivo, but the apoptosis of spermatogonia secondary to IR occurs at a relatively later time point (24 h) in vitro mainly. The apoptosis of spermatogonia is improved over time after IR.

Coenzyme Q10 mitigates ionizing radiation-induced testicular damage in rats through inhibition of oxidative stress and mitochondria-mediated apoptotic cell death

Radiotherapy is a common treatment modality for cancer patients; however, its use is limited by decreasing the probability of fertility in male cancer survivors. Therefore, this study aimed to define the capability of coenzyme Q10 (CoQ10), a potent stimulator of mitochondrial function, in attenuating ionizing radiation (IR)-induced spermatogenesis impairments. Male Sprague Dawley rats were exposed to a single dose of ϒ-rays (10 Gy) and/or treated with CoQ10 (10 mg/kg, orally, for 2 consecutive weeks). IR mediated irregular seminiferous tubules, which were emerged with typical morphological characteristics of apoptosis, and nuclear condensation, while CoQ10 significantly preserved the testicular structure and maintained spermatogenesis, which was displayed by higher levels of serum estradiol and testosterone. CoQ10 remarkably augmented sperm count, motility, and viability while diminished the rate of sperm-defects relatively to their counterparts after IR exposure. CoQ10 modulations in reproductive parameters were underpinned by attenuating IR-induced oxidative stress as evidenced by decreasing lipid peroxidation and increasing the antioxidant enzymes glutathione peroxidase and glutathione-s-transferase activities, and glutathione level. Supporting the involvement of CoQ10 in the anti-apoptotic response, the reduced mRNA expression levels of p53, Puma, and Bax accompanied by the increased Bcl-2 mRNA expression were observed. Subsequently, CoQ10 ameliorated the mitochondria dependent apoptotic pathway through diminishing Bax/Bcl-2 ratio, caspase-3 protein expression, and DNA fragmentation in testes of irradiated rats. Taken together, our findings showed that CoQ10 conserved against IR-induced steroidogenesis disruption through subsiding mitochondria-mediated oxidative stress injury in germinal cells.

Ghrelin alleviates endoplasmic reticulum stress and inflammation-mediated reproductive dysfunction induced by stress

PURPOSE

Psychological stress exists widely in modern society and results in the disruption of testicular tight junctions, germ cell apoptosis, and the disorder of fertility hormones and even causes infertility. Ghrelin (GHRL), a 28-amino acid peptide secreted mainly by the stomach and pancreas, has been reported to alleviate male reproductive injury through inhibiting apoptosis. However, whether GHRL has a beneficial effect on psychological stress-induced testicular injury and the possible mechanisms remain poorly understood.

METHODS

Male mice were immobilized in Decapicone bags for 3 h daily for 14 days treated with or without GHRL (i.p. 100 mg/kg body weight). Body weight and testicular weight were measured. Histological alterations and apoptosis were examined by H.E. staining and TUNEL staining, respectively. The expression of endoplasmic reticulum (ER) stress markers, inflammatory cytokines, Toll-like receptor 4 (TLR4), and nuclear factor-κB (NF-κB) in the testes was investigated.

RESULTS

Exposure to stress caused testicular histological alterations, an elevation of the Johnsen score, and germ cell apoptosis, while GHRL partially alleviated the adverse effects. The expression of ER stress marker proteins, including GRP78, CHOP, ATF6, p-JNK, and XBP-1, was upregulated in the stress group; however, GHRL treatment significantly suppressed the activation of ER stress in the testes. GHRL also inhibited the expression of TNF-α, IL-1β, IL-6, IL-10, TLR4, and NF-κB.

CONCLUSIONS

GHRL alleviated testicular injury induced by ER stress and inflammation which is associated with the TLR4/NF-κB signaling pathway, and these findings may provide a novel strategy for preventing and treating reproductive dysfunction.

Relationships between Ghrelin and Obestatin with MDA, Proinflammatory Cytokines, GSH/GSSG Ratio, Catalase Activity, and Semen Parameters in Infertile Patients with Leukocytospermia and Varicocele

Ghrelin and obestatin are involved in many biological functions including reproduction. Growing evidences suggest that both peptides could exert protective and antioxidant activities. In this study, the relationships between ghrelin/obestatin, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), expressed as the GSH/GSSG ratio, catalase (CAT), and semen parameters in infertile patients with varicocele or leukocytospermia and controls were investigated. Fifty-six infertile patients (32 with leukocytospermia and 24 with varicocele) and 14 controls participated in this study. Semen analysis was performed following the WHO guidelines. Apoptotic and necrotic sperm were scored by annexin V/propidium iodide assay. Seminal plasma samples were used for the following determinations: ghrelin, obestatin, IL-6, and TNF-α were measured by an immunological method, GSH/GSSG by an enzymatic method, and CAT by spectrophotometric determination. With respect to controls, both the leukocytospermia and varicocele groups showed altered sperm parameters, significantly increased sperm apoptosis (P = 0.009 and P = 0.011, respectively), IL-6 (P = 0.0001 and P = 0.004, respectively), and TNF-α levels (P = 0.0001 and P = 0.002, respectively); both groups had significantly decreased levels of ghrelin (P = 0.0001), obestatin (P = 0.0001 and P = 0.006, respectively), and GSH/GSSG ratio (P = 0.003 and P = 0.0001, respectively). The MDA concentration was significantly increased in the leukocytospermia group vs. controls (P = 0.0001), in the varicocele group vs. controls (P = 0.011), and in the leukocytospermia group vs. the varicocele group (P = 0.008). CAT activity was augmented in both the leukocytospermia and varicocele groups (P = 0.0001)vs. controls. The results indicate that both ghrelin and obestatin may play a protective role in human semen and this effect is probably due to their antioxidant properties.

KLF14 potentiates oxidative adaptation via modulating HO-1 signaling in castrate-resistant prostate cancer

Insights into the mechanisms by which key factors stimulate cell growth under androgen-depleted conditions is a premise to the development of effective treatments with clinically significant activity in patients with castration-resistant prostate cancer (CRPC). Herein, we report that, the expression of Krüppel-like factor 14 (KLF14), a master transcription factor in the regulation of lipid metabolism, was significantly induced in castration-insensitive PCa cells and tumor tissues from a mouse xenograft model of CRPC. KLF14 upregulation in PCa cells, which was stimulated upstream by oxidative stress, was dependent on multiple pathways including PI3K/AKT, p42/p44 MAPK, AMPK and PKC pathways. By means of ectopic overexpression and genetic inactivation, we further show that KLF14 promoted cell growth via positive regulation of the antioxidant response under androgen-depleted conditions. Mechanistically, KLF14 coupled to p300 and CBP to enhance the transcriptional activation of HMOX1, the gene encoding the antioxidative enzyme heme oxygenase-1 (HO-1) that is one of the most important mechanisms of cell adaptation to stress. Transient knockdown of HMOX1 is sufficient to overcome KLF14 overexpression-potentiated PCa cell growth under androgen-depleted conditions. From a pharmacological standpoint, in vivo administration of ZnPPIX (a specific inhibitor of HO-1) effectively attenuates castration-resistant progression in the mouse xenograft model, without changing KLF14 level. Together, these results provide comprehensive insight into the KLF14-dependent regulation of antioxidant response and subsequent pathogenesis of castration resistance and indicate that interventions targeting the KLF14/HO-1 adaptive mechanism should be further explored for CRPC treatment.

Effects of Ghrelin on the Apoptosis of Rheumatoid Arthritis Fibroblast-Like Synoviocyte MH7A Cells

Ghrelin is a circulating peptide hormone, which involved in promoting feeding and regulating energy metabolism in human and rodents. Abnormal synovial hyperplasia is the most important pathologic hallmark of rheumatoid arthritis (RA), which is characterised by tumor-like expansion. Existing studies indicated that there may exist some relation between the decreased ghrelin and the abnormally proliferating synovial cells in RA. Therefore, the aim of this study is to explore the apoptotic effects of ghrelin on MH7A synovial cells in vitro. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the effects of ghrelin on the viability of MH7A cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) and flow cytometry were used to test the apoptotic effects of ghrelin. At last, Western blot and real-time PCR were performed to explore the expression of caspases-8, -9, and -3 after the treatment of ghrelin. MTT experiments showed that ghrelin could inhibit viability of MH7A cells. The results of flow cytometry and TUNEL showed that ghrelin could induce apoptosis of MH7A synovial cells. Western blot showed that expression of cleaved-caspases-8, -9, and -3 were increased in ghrelin stimulation group compared with the control group, while expression of pro-caspases-8, -9, and -3 had no significant difference. In mRNA levels, ghrelin can decrease pro-caspases-8, -9, and -3 mRNA expression, which confirmed the results of protein levels. Then these apoptotic effects were significantly reversed by [D-Lys₃] GHRP-6 (ghrelin receptor antagonist). This study found that ghrelin can induce apoptosis of MH7A cells through caspase signaling pathways.

Interference with lactate metabolism by mmu-miR-320-3p via negatively regulating GLUT3 signaling in mouse Sertoli cells

Disruption of the nursery function in Sertoli cells (SCs) by reducing lactate production, a preferred energy substrate for developed germ cells (spermatocytes and spermatids), is tightly associated with spermatogenic failure such as SC-only syndrome (SCOS). However, whether this complicated pathogenesis is regulated by certain miRNAs at the post-transcriptional level remain fascinating but largely unknown. Here we show for the first time that mmu-miR-320-3p was exclusively expressed in murine SCs and this expression was significantly induced in busulphan-treated murine testis. The most efficient stimulatory germ cell types for the induction of apoptosis-elicited mmu-miR-320-3p expression were meiotic spermatocytes and haploid spermatids. Functionally, forced expression of the exogenous mmu-miR-320-3p in SCs compromises male fertility by causing oligozoospermia and defection of sperm mobility. Mechanistically, mmu-miR-320-3p negatively regulates lactate production of SCs by directly inhibiting glucose transporter 3 (GLUT3) expression. Thus, dysregulation of mmu-miR-320-3p/GLUT3 cascade and consequently of lactate deficiency may be a key molecular event contributing the germ cell loss by SC dysfunction. Future endeavor in the continuous investigation of this important circulating miRNA may shed novel insights into epigenetic regulation of SCs nursery function and the etiology of azoospermia, and offers novel therapeutic and prognostic targets for SCOS.

miR-1271 inhibits ERα expression and confers letrozole resistance in breast cancer

Attenuation of estrogen receptor α (ERα) expression via unknown mechanism(s) is a hallmark of endocrine-resistant breast cancer (BCa) progression. Here, we report that miR-1271 was significantly down-regulated in letrozole-resistant BCa tissues and in letrozole-resistant BCa cells. miR-1271 directly targeted the chromatin of DNA damage-inducible transcript 3 (DDIT3) gene. miR-1271 expression level was inversely correlated to DDIT3 mRNA level in BCa biopsies. Form a mechanistic standpoint, reintroduction of exogenous miR-1271 could effectively restore ERα level via inhibiting DDIT3 expression, thereby potentiating letrozole sensitivity in BCa cells. Moreover, DDIT3 deregulation promoted letrozole-resistance by acting as a potent corepressor of ESR1 transcription. Taken together, we have identified that disruption of the miR-1271/DDIT3/ERα cascade plays a causative role in the pathogenesis of letrozole resistance in BCa.

Linking Stress and Infertility: A Novel Role for Ghrelin

Infertility affects a remarkable one in four couples in developing countries. Psychological stress is a ubiquitous facet of life, and although stress affects us all at some point, prolonged or unmanageable stress may become harmful for some individuals, negatively impacting on their health, including fertility. For instance, women who struggle to conceive are twice as likely to suffer from emotional distress than fertile women. Assisted reproductive technology treatments place an additional physical, emotional, and financial burden of stress, particularly on women, who are often exposed to invasive techniques associated with treatment. Stress-reduction interventions can reduce negative affect and in some cases to improve in vitro fertilization outcomes. Although it has been well-established that stress negatively affects fertility in animal models, human research remains inconsistent due to individual differences and methodological flaws. Attempts to isolate single causal links between stress and infertility have not yet been successful due to their multifaceted etiologies. In this review, we will discuss the current literature in the field of stress-induced reproductive dysfunction based on animal and human models, and introduce a recently unexplored link between stress and infertility, the gut-derived hormone, ghrelin. We also present evidence from recent seminal studies demonstrating that ghrelin has a principal role in the stress response and reward processing, as well as in regulating reproductive function, and that these roles are tightly interlinked. Collectively, these data support the hypothesis that stress may negatively impact upon fertility at least in part by stimulating a dysregulation in ghrelin signaling.

Regulation of Docetaxel Sensitivity in Prostate Cancer Cells by hsa-miR-125a-3p via Modulation of Metastasis-Associated Protein 1 Signaling

OBJECTIVE

To identify the potential downstream targets of hsa-miR-125a-3p, a mature form of miR-125a, during the pathogenesis of chemoresistance in prostate cancer (PCa).

MATERIALS AND METHODS

The expression levels of hsa-miR-125a-3p were assessed in chemoresistant PCa tissues and experimentally established chemoresistant cells using quantitative reverse transcription-polymerase chain reaction. The effect of hsa-miR-125a-3p knockdown or hsa-miR-125a-3p overexpression on the Dox-induced cell death was evaluated using apoptosis ELISA in chemosensitive PC-3 cells or in chemoresistant PC-3 cells (PC-3R). Finally, using multiple assays, the regulation of metastasis-associated protein 1 (MTA1), an essential component of the Mi-2-nucleosome remodeling deacetylation complex, by hsa-miR-125a-3p was studied at both molecular and functional levels.

RESULTS

The expression of hsa-miR-125a-3p was significantly downregulated in chemoresistant PCa tissues and cells. Inhibition of hsa-miR-125a-3p significantly increased docetaxel (Dox) resistance in PC-3 cells, whereas upregulation of hsa-miR-125a-3p effectively reduced Dox resistance in PC-3R, suggesting that this microRNA (miRNA) may act as a tumor suppressor along the pathogenesis of drug resistance. Mechanistically, hsa-miR-125a-3p induced apoptosis and Dox sensitivity in PCa cells through regulating MTA1.

CONCLUSION

Our results collectively indicate that miRNA-MTA1 can form a delicate regulatory loop to maintain a bistable state in the Dox chemosensitivity, and future endeavor in this filed should provide important clues to develop miRNA-based therapies that benefit advanced PCa patients through modulating the functional status of MTA1.

Regulation of cancerous progression and epithelial-mesenchymal transition by miR-34c-3p via modulation of MAP3K2 signaling in triple-negative breast cancer cells

Emerging but limited data have evidenced an essential involvement of microRNAs (miRNAs) in the development and progression of triple negative breast cancer (TNBC), which empowers these small regulators as an innovative therapeutic approach, especially for this unique tumor subgroup still lacking an efficient and specific therapeutic target. Herein, we reported the down-regulation of miR-34c-3p level in TNBC tissues, and its expression was closely associated with estrogen receptor alpha (ERα), but not other receptors, in well-characterized breast cancer (BCa) cells. Functionally, ectopic expression of miR-34c-3p inhibited migration, invasion and epithelial-mesenchymal transition (EMT) in TNBC cells. From a mechanistic standpoint, bioinformatics coupled with luciferase and gain-of-function, loss-of-function assays showed that miR-34c-3p may regulate TNBC progression by directly targeting the 3'-untranslated region (UTR) of mitogen-activated protein kinase kinase kinase 2 (MAP3K2). Consistently, MAP3K2 overexpression could effectively rescue miR-34c-3p mimics-induced suppression of cell invasion and EMT. In light of these findings, miR-34c-3p may function as a tumor suppressor in regulating of TNBC invasiveness and EMT through negatively modulating MAP3K2 pathway. Future endeavor in this field may help to identify a novel biomarker to predict prognosis and response to therapy in TNBC.

Repression of neuronal nitric oxide (nNOS) synthesis by MTA1 is involved in oxidative stress-induced neuronal damage

The Metastasis-associated protein 1 (MTA1) coregulator, an essential component of the nucleosome remodeling and deacetylase (NuRD) complex, potentiates neuroprotective effects against ischemia/reperfusion (I/R) injury. But the underlying mechanism(s) remain largely unknown. Here, we discovered that neuronal MTA1 was a target of oxidative stress, and stimulation of neurons with oxygen glucose deprivation (OGD) treatment significantly inhibited MTA1 expression. Additionally, MTA1 depletion augmented ischemic oxidative stress and thus promoted oxidative stress-induced neuronal cell death by OGD. While studying the impact of MTA1 status on global neuronal gene expression, we unexpectedly discovered that MTA1 may modulate OGD-induced neuronal damage via regulation of distinct nitric oxide synthase (NOS) (namely neuronal NOS, nNOS) signaling. We provided in vitro evidence that NOS1 is a chromatin target of MTA1 in OGD-insulted neurons. Mechanistically, neuronal ischemia-mediated repression of NOS1 expression is accompanied by the enhanced recruitment of MTA1 along with histone deacetylases (HDACs) to the NOS1 promoter, which could be effectively blocked by a pharmacological inhibitor of the HDACs. These findings collectively reveal a previously unrecognized, critical homeostatic role of MTA1, both as a target and as a component of the neuronal oxidative stress, in the regulation of acute neuronal responses against brain I/R damage. Our study also provides a molecular mechanistic explanation for the previously reported neurovascular protection by selective nNOS inhibitors.

Enforced expression of hsa-miR-125a-3p in breast cancer cells potentiates docetaxel sensitivity via modulation of BRCA1 signaling

Epigenetic gene inactivation by microRNAs (miRNAs) plays a key role in malignant transformation, prevention of apoptosis, drug resistance and metastasis. It has been shown that miR-125a is down-regulated in HER2-amplified and HER2-overexpressing breast cancers (BCa), and this miRNA is believed to serve as an important tumor suppressor. miR-125a has two mature forms: hsa-miR-125a-3p and hsa-miR-125a-5p. However, the functional details of these miRNAs in BCa, particularly during pathogenesis of drug resistance, remain largely unexplored. Herein, we reported that hsa-miR-125a-3p expression was significantly reduced in chemoresistant BCa tissues and in experimentally established chemoresistant BCa cells. hsa-miR-125a-3p knockdown promoted cell proliferation and compromised docetaxel (Dox)-induced cell death, whereas overexpression of hsa-miR-125a-3p attenuated Dox chemoresistance in BCa cells. From a mechanistic standpoint, hsa-miR-125a-3p directly targeted 3'-untranslated regions (3'-UTRs) of breast cancer early onset gene 1 (BRCA1) and inhibits its protein expression via translational repression mechanism. In addition, suppression of BRCA1 expression by siRNA treatment effectively improved hsa-miR-125a-3p deficiency-triggered chemoresistance in BCa cells. Collectively, these findings suggest that hsa-miR-125a-3p may function as a tumor suppressor by regulating the BRCA1 signaling, and reintroduction of hsa-miR-125a-3p analogs could be a potential adjunct therapy for advanced/chemoresistant BCa.

The protective effect of regucalcin against radiation-induced damage in testicular cells

AIMS

Regucalcin (RGN), a protein broadly expressed in the male reproductive tract, has shown to have beneficial effects on spermatogenesis suppressing chemical-induced apoptosis. This study aimed to evaluate whether RGN overexpression ameliorates the spermatogenic phenotype after radiation treatment.

MAIN METHODS

Transgenic rats overexpressing RGN (Tg-RGN) and their wild-type (Wt) counterparts were exposed to a single dose of X-rays (6Gy), and at ten weeks after irradiation, the testicular status and the epididymal sperm parameters were evaluated. The expression of RGN and several cell cycle and apoptosis regulators, the enzymatic activity of caspase-3, and RGN immunostaining were also assessed.

KEY FINDINGS

Tg-RGN animals displayed higher gonadosomatic index, and augmented sperm viability and motility relatively to their Wt counterparts after irradiation, as well as higher frequency of normal sperm morphology and a diminished incidence of head-defects. The differences in reproductive parameters were underpinned by a lower rate of apoptosis, as evidenced by the reduced activity of caspase-3, lower levels of caspase-8, and increased Bcl-2/Bax ratio in the testis of Tg-RGN animals. Supporting the involvement of RGN in the anti-apoptotic response, an enhanced expression of RGN was observed in irradiated rats.

SIGNIFICANCE

Transgenic-overexpression of RGN protected against radiation-induced testicular damage, which strengthens the role of this protein protecting cells from the damage of external agents. These findings also indicated that the modulation of RGN testicular levels would be a mechanism for fertility preservation in men undergoing oncological treatment.

Unexpected requirement for a binding partner of the syntaxin family in phagocytosis by murine testicular Sertoli cells

Testicular phagocytosis by Sertoli cells (SCs) plays an essential role in the efficient clearance of apoptotic spermatogenic cells under both physiological and pathological conditions. However, the molecular mechanism underlying this unique process is poorly understood. Herein, we report for the first time that α-taxilin protein (TXLNA), a binding partner of the syntaxin family that functions as a central player in the intracellular vesicle traffic, was dominantly expressed in SCs. Induction of apoptosis in murine meiotic spermatocytes and haploid spermatids by busulfan treatment stimulated a significant increase of TXLNA in SCs at day (d) 14 and d 24 after busulfan treatment, respectively. Consistently, TXLNA expression was steadily upregulated when SCs were co-cultured with apoptotic germ cells (GCs). Moreover, using siRNA treatment, we found that ablation of endogenous TXLNA significantly impaired the phagocytotic capacity of SCs and thereby resulted in defective spermiogenesis and reduced fertility during the late recovery after testicular heat stress. Mechanistically, upregulation of TXLNA expression by apoptotic GCs was associated with the stabilization of ATP-binding cassette transporter 1 (ABCA1), a transporter-mediated lipid efflux from SCs and influencing male fertility. TXLNA acted as an upstream suppressor of ABCA1 ubiquitination and thus promoted ABCA1 stability and accumulation following GC apoptosis. We further provide in vitro evidence that epidermal growth factor receptor (EGFR)-mediated phosphorylation regulated ABCA1 ubiquitination and was enhanced by TXLNA deficiency during testicular phagocytosis. Taken together, the TXLNA/ABCA1 cascade may serve as an important feedback mechanism to modulate the magnitude of subsequent phagocytotic process of SCs in response to testicular injury.

Abnormal Accumulation of Collagen Type I Due to the Loss of Discoidin Domain Receptor 2 (Ddr2) Promotes Testicular Interstitial Dysfunction

Background

Loss of functional allele for discoidin domain receptor 2 (Ddr2) results in impaired Leydig cell response to luteinizing hormone (LH), low testosterone production and arrested spermatogenesis in older male Ddr2^slie/slie mice. However, the underlying mechanism responsible for this phenotype remains unknown. Herein, we reported for the first time that the deregulated expression of Ddr2 cognate ligand, namely collagen type I (COL1), may account for the disruption of the testicular steroidogenesis in Ddr2^slie/slie mutant testes.

Methodology/Principal Findings

Expression of Ddr2 increased gradually along postnatal development, whereas COL1 expression became negligible from adulthood onwards. In Ddr2^slie/slie mutant testis, however, in contrast to the undetectable staining of Ddr2, COL1 expression was constantly detected, with the highest values detected during adulthood. In the experimental vasectomy model, Ddr2^slie/slie mutant mice exhibited an early androgen deficiency than wild-type mice, along with the accumulation of fibrotic tissue in the interstitium. Functionally, ablation of endogenous Ddr2 resulted in a significant decrease of testosterone (T) level in TM3 cells in the presence of higher concentration of COL1 treatment. Conversely, overexpression of Ddr2 could help TM3 cells to maintain a normal testicular steroidogenesis even in the presence of high concentration of COL1. Additionally, attenuated expression of Ddr2 correlates to the deregulated level of serum T levels in human pathological testes.

Conclusions

Abnormal accumulation of interstitial COL1 may be responsible for the steroidogenic dysfunction in Ddr2^slie/slie mutant testes.

Ghrelin Prevents Cisplatin-Induced Testicular Damage by Facilitating Repair of DNA Double Strand Breaks Through Activation of p53 in Mice

Cisplatin administration induces DNA damage resulting in germ cell apoptosis and subsequent testicular atrophy. Although 50 percent of male cancer patients receiving cisplatin-based chemotherapy develop long-term secondary infertility, medical treatment to prevent spermatogenic failure after chemotherapy is not available. Under normal conditions, testicular p53 promotes cell cycle arrest, which allows time for DNA repair and reshuffling during meiosis. However, its role in the setting of cisplatin-induced infertility has not been studied. Ghrelin administration ameliorates the spermatogenic failure that follows cisplatin administration in mice, but the mechanisms mediating these effects have not been well established. The aim of the current study was to characterize the mechanisms of ghrelin and p53 action in the testis after cisplatin-induced testicular damage. Here we show that cisplatin induces germ cell damage through inhibition of p53-dependent DNA repair mechanisms involving gamma-H2AX and ataxia telangiectasia mutated protein kinase. As a result, testicular weight and sperm count and motility were decreased with an associated increase in sperm DNA damage. Ghrelin administration prevented these sequelae by restoring the normal expression of gamma-H2AX, ataxia telangiectasia mutated, and p53, which in turn allows repair of DNA double stranded breaks. In conclusion, these findings indicate that ghrelin has the potential to prevent or diminish infertility caused by cisplatin and other chemotherapeutic agents by restoring p53-dependent DNA repair mechanisms.

The proteasome inhibitor bortezomib induces testicular toxicity by upregulation of oxidative stress, AMP-activated protein kinase (AMPK) activation and deregulation of germ cell development in adult murine testis

Understanding how chemotherapeutic agents mediate testicular toxicity is crucial in light of compelling evidence that male infertility, one of the severe late side effects of intensive cancer treatment, occurs more often than they are expected to. Previous study demonstrated that bortezomib (BTZ), a 26S proteasome inhibitor used to treat refractory multiple myeloma (MM), exerts deleterious impacts on spermatogenesis in pubertal mice via unknown mechanisms. Here, we showed that intermittent treatment with BTZ resulted in fertility impairment in adult mice, evidenced by testicular atrophy, desquamation of immature germ cells and reduced caudal sperm storage. These deleterious effects may originate from the elevated apoptosis in distinct germ cells during the acute phase and the subsequent disruption of Sertoli-germ cell anchoring junctions (AJs) during the late recovery. Mechanistically, balance between AMP-activated protein kinase (AMPK) activation and Akt/ERK pathway appeared to be indispensable for AJ integrity during the late testicular recovery. Of particular interest, the upregulated testicular apoptosis and the following disturbance of Sertoli-germ cell interaction may both stem from the excessive oxidative stress elicited by BTZ exposure. We also provided the in vitro evidence that AMPK-dependent mechanisms counteract follicle-stimulating hormone (FSH) proliferative effects in BTZ-exposed Sertoli cells. Collectively, BTZ appeared to efficiently prevent germ cells from normal development via multiple mechanisms in adult mice. Employment of antioxidants and/or AMPK inhibitor may represent an attractive strategy of fertility preservation in male MM patients exposed to conventional BTZ therapy and warrants further investigation.

Ghrelin partially protects against cisplatin-induced male murine gonadal toxicity in a GHSR-1a-dependent manner

The chemotherapeutic drug cisplatin causes a number of dose-dependent side effects, including cachexia and testicular damage. Patients receiving a high cumulative dose of cisplatin may develop permanent azoospermia and subsequent infertility. Thus, the development of chemotherapeutic regimens with the optimal postsurvival quality of life (fertility) is of high importance. This study tested the hypothesis that ghrelin administration can prevent or minimize cisplatin-induced testicular damage and cachexia. Ghrelin and its receptor, the growth hormone secretagogue receptor (GHSR-1a), are expressed and function in the testis. Targeted deletion of ghrelin, or its receptor, significantly increases the rate of cell death in the testis, suggesting a protective role. Intraperitoneal administration of vehicle, ghrelin, or cisplatin alone or in combination with ghrelin, in cycles of 9 or 18 days, to adult male C57Bl/6 mice was performed. Body weight was measured daily and testicular and epididymal weight, sperm density and motility, testicular histology, and testicular cell death were analyzed at the time of euthanization. Ghrelin coadministration decreased the severity of cisplatin-induced cachexia and gonadal toxicity. Body, testicular, and epididymal weights significantly increased as testicular cell death decreased with ghrelin coadministration. The widespread damage to the seminiferous epithelium induced by cisplatin administration was less severe in mice simultaneously treated with ghrelin. Furthermore, ghrelin diminished the deleterious effects of cisplatin on testis and body weight homeostasis in wild-type but not Ghsr(-/-) mice, showing that ghrelin's actions are mediated via GHSR. Ghrelin or more stable GHSR agonists potentially offer a novel therapeutic approach to minimize the testicular damage that occurs after gonadotoxin exposure.

Protection of murine spermatogenesis against ionizing radiation-induced testicular injury by a green tea polyphenol

Epigallocatechin-3-gallate (EGCG), a bioactive polyphenol in green tea, exerts antiapoptotic activity and prevents tissue damage against different stimuli. Herein, we investigated the effects of EGCG treatment to simultaneously improve spermatogenesis following ionizing radiation (IR) (at a dose of 2 Gy). Mice were intraperitoneally injected with 50 mg/kg EGCG or vehicle control 3 days prior to the irradiation, and the treatment lasted intermittently for 24 days. Supplement with exogenous EGCG protected against short-term germ cell loss and attenuated IR-elicited testicular oxidative stress. Mechanistically, prosurvival effects of EGCG treatment upon IR stress were regulated, at least in part, via the mitogen-activated protein kinase/BCL2 family/caspase 3 pathway. Consistently, at post-IR Day 21, histological analyses revealed tubule damage, desquamation of germ cells, and impairment of caudal parameters in irradiated testis, which could be significantly improved by intermittent EGCG treatment. In addition, long-term EGCG application ameliorated the IR-induced blood-testicular barrier permeability and suppressed testicular steroidogenesis, thus exerting a stimulatory effect on the spermatogenic recovery. Collectively, EGCG appeared to efficiently prevent germ cells from radiation-induced cell death via multiple mechanisms. Employment of this bioactive polyphenol should be an attractive strategy to preserve fertility in males exposed to conventional radiation therapy and warrants further investigation.