Silica nanoparticles induce abnormal mitosis and apoptosis via PKC-δ mediated negative signaling pathway in GC-2 cells of mice

Silica nanoparticles induce male reproductive toxicity via Crem hypermethylation mediated spermatocyte apoptosis and sperm flagella damage

Exposure to silica nanoparticles (SiNPs) could causally contribute to malfunctioning of the spermatogenesis, but the underlying mechanism is rarely known. This study was designed to explore the mechanism of Crem hypermethylation in SiNP-induced reproductive toxicity. The male mice were exposure to SiNPs (0 and 20 mg/kg·bw) once every 5 days via intratracheal instillation for 35 days. After exposure stopped, half of each group was killed, and the rest were sacrificed after another 15-day feeding. GC-2 cells were treated with 0 and 20 μg/mL SiNPs. The results showed that SiNPs led to structure damage of spermatocyte and sperm, caused spermatocyte apoptosis, and decreased sperm quantity and quality. After 15 days of the withdrawal, the testicular tissue damage gradually recovered. Mechanistic study showed that SiNPs induced hypermethylation of the gene of cAMP responsive element modulator (Crem) in the promoter region. Downregulation of Crem inhibited the expression of outer dense fiber 1 (Odf1), resulting in abnormal sperm flagella structure; at the same time, Crem inhibited the expression of Bcl-xl, causing upregulation of cytochrome-C, cleaved-caspase-9/caspase-9, cleaved-caspase-3/caspase-3, resulting in mitochondrial dependent apoptotic pathway. However, 5-aza, DNA methylation inhibitor, could reverse the SiNP-induced downregulation of Crem and reverse the Crem/Bcl-xl-mediated mitochondrial dependent apoptotic pathway. These results suggested SiNPs could disrupt spermatogenesis by causing Crem hypermethylation to regulate the Odf1 and Bcl-xl in spermatocytes resulting in the sperm flagella structure and spermatocyte apoptosis. Our study provided new insights into the male reproductive toxicity mechanism of SiNPs; Crem demethylation may be a potential way to prevent reproductive dysfunction from SiNP exposure.

Silica Nanoparticles Shed Light on Intriguing Cellular Pathways in Human Tracheal Smooth Muscle Cells: Revealing COX-2/PGE2 Production through the EGFR/Pyk2 Signaling Axis

The use of manufactured silica nanoparticles (SiNPs) has become widespread in everyday life, household products, and various industrial applications. While the harmful effects of crystalline silica on the lungs, known as silicosis or chronic pulmonary diseases, are well understood, the impact of SiNPs on the airway is not fully explored. This study aimed to investigate the potential effects of SiNPs on human tracheal smooth muscle cells (HTSMCs). Our findings revealed that SiNPs induced the expression of cyclooxygenase-2 (COX-2) mRNA/protein and the production of prostaglandin E2 (PGE2) without causing cytotoxicity. This induction was transcription-dependent, as confirmed by cell viability assays and COX-2 luciferase reporter assays. Further analysis, including Western blot with pharmacological inhibitors and siRNA interference, showed the involvement of receptor tyrosine kinase (RTK) EGF receptor (EGFR), non-RTK Pyk2, protein kinase Cα (PKCα), and p42/p44 MAPK in the induction process. Notably, EGFR activation initiated cellular signaling that led to NF-κB p65 phosphorylation and translocation into the cell nucleus, where it bound and stimulated COX-2 gene transcription. The resulting COX-2 protein triggered PGE2 production and secretion into the extracellular space. Our study demonstrated that SiNPs mediate COX-2 up-regulation and PGE2 secretion in HTSMCs through the sequential activation of the EGFR/Pyk2/PKCα/p42/p44MAPKs-dependent NF-κB signaling pathway. Since PGE2 can have both physiological bronchodilatory and anti-inflammatory effects, as well as pathological pro-inflammatory effects, the increased PGE2 production in the airway might act as a protective compensatory mechanism and/or a contributing factor during airway exposure to SiNPs.

Prospects and hazards of silica nanoparticles: Biological impacts and implicated mechanisms

With the thrive of nanotechnology, silica nanoparticles (SiNPs) have been extensively adopted in the agriculture, food, cosmetic, and even biomedical industries. Due to the mass production and use, SiNPs inevitably entered the environment, resulting in ecological toxicity and even posing a threat to human health. Although considerable investigations have been conducted to assess the toxicity of SiNPs, the correlation between SiNPs exposure and consequent health risks remains ambiguous. Since the biological impacts of SiNPs can differ from their design and application, the toxicity assessment for SiNPs may be extremely difficult. This review discussed the application of SiNPs in different fields, especially their biomedical use, and documented their potential release pathways into the environment. Meanwhile, the current process of assessing SiNPs-related toxicity on various model organisms and cell lines was also detailed, thus estimating the health threats posed by SiNPs exposure. Finally, the potential toxic mechanisms of SiNPs were also elaborated based on results obtained from both in vivo and in vitro trials. This review generally summarizes the biological effects of SiNPs, which will build up a comprehensive perspective of the application and toxicity of SiNPs.

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

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

Silica nanoparticles suppressed the spermatogenesis via downregulation of miR-450b-3p by targeting Layilin in spermatocyte of mouse

Silica nanoparticles (SiNPs) suppressed spermatogenesis leading to male reproductive toxicity, while the precise mechanism remains uncertain. Here, this study explored the role of miR-450b-3p in male reproductive toxicity induced by SiNPs. In vivo study, we found that SiNPs caused apoptosis of spermatocytes, decreased quantity and quality of sperms, up-regulated the cytoskeleton proteins (Layilin, Talin, and Vinculin), activated the Hippo pathway (Rho A, Yap, and p73), downregulated the expression of miR-450b-3p, damaged the compactness and density of desmosomes between spermatocytes and the basal of the testis. Moreover, in vitro study, we confirmed that SiNPs increased the expressions of cytoskeleton proteins, activated the Hippo pathway, and suppressed miR-450b-3p expressions. Meanwhile, miR-450b-3p mimic inhibited the up-regulation of cytoskeleton proteins, suppressed the activation of the Hippo pathway, and relieved the adhesion and traction stress. Eventually, atomic force microscopy (AFM) was performed to validate the traction stress and adhesion between GC-2spd cells enhanced by deregulation of miR-450b-3p. Taken together, we concluded that SiNPs suppressed spermatogenesis via inhibiting miR-450b-3p, in turn up-regulating the expression of cytoskeleton proteins, then inducing apoptosis via activating the Hippo pathway and enhancing the traction force and adhesion between GC-2spd cells. This work provides novel evidence for the study of reproductive toxicity and risk assessment of SiNPs.

Impact of Nanoparticles on Male Fertility: What Do We Really Know? A Systematic Review

The real impact of nanoparticles on male fertility is evaluated after a careful analysis of the available literature. The first part reviews animal models to understand the testicular biodistribution and biopersistence of nanoparticles, while the second part evaluates their in vitro and in vivo biotoxicity. Our main findings suggest that nanoparticles are generally able to reach the testicle in small quantities where they persist for several months, regardless of the route of exposure. However, there is not enough evidence that they can cross the blood-testis barrier. Of note, the majority of nanoparticles have low direct toxicity to the testis, but there are indications that some might act as endocrine disruptors. Overall, the impact on spermatogenesis in adults is generally weak and reversible, but exceptions exist and merit increased attention. Finally, we comment on several methodological or analytical biases which have led some studies to exaggerate the reprotoxicity of nanoparticles. In the future, rigorous clinical studies in tandem with mechanistic studies are needed to elucidate the real risk posed by nanoparticles on male fertility.

Kinesin-5 Eg5 mediates centrosome separation to control spindle assembly in spermatocytes

Timely and accurate centrosome separation is critical for bipolar spindle organization and faithful chromosome segregation during cell division. Kinesin-5 Eg5 is essential for centrosome separation and spindle organization in somatic cells; however, the detailed functions and mechanisms of Eg5 in spermatocytes remain unclear. In this study, we show that Eg5 proteins are located at spindle microtubules and centrosomes in spermatocytes both in vivo and in vitro. We reveal that the spermatocytes are arrested at metaphase I in seminiferous tubules after Eg5 inhibition. Eg5 ablation results in cell cycle arrest, the formation of monopolar spindle, and chromosome misalignment in cultured GC-2 spd cells. Importantly, we find that the long-term inhibition of Eg5 results in an increased number of centrosomes and chromosomal instability in spermatocytes. Our findings indicate that Eg5 mediates centrosome separation to control spindle assembly and chromosome alignment in spermatocytes, which finally contribute to chromosome stability and faithful cell division of the spermatocytes.

Silica nanoparticles inhibiting the differentiation of round spermatid and chromatin remodeling of haploid period via MIWI in mice

Researches have shown that silica nanoparticles (SiNPs) could reduce both the quantity and quality of sperm. However, the mechanism of toxicity induced by SiNPs in the male reproductive system is still unclear. In this study, male mice were randomly divided into a control group, and SiNPs treated group (20 mg/kg dose; n = 30 per group). Half of the mice per group were sacrificed on 35 days and the remaining on 50 days of the SiNPs exposure. SiNPs were found to decrease sperm count and mobility, increase the sperm abnormality rate, and damage the testes' structure. Furthermore, SiNPs decreased the protein levels of Protamine 1(PRM1) and elevated the histones' levels and suppressed the chromatin condensation of sperm. There was a significant reduction of the ubiquitinated H2A (ubH2A)/H2B (ubH2B) and RING finger protein 8 (RNF8) levels in the spermatid nucleus, while the RNF8 level in the spermatid cytoplasm increased evidently. The protein expression levels of PIWI-like protein 1(MIWI) in the late spermatids significantly increased on day 35 of SiNPs exposure. After 15 days of the withdrawal, the sperm parameters and protamine levels, and histones in the epididymal sperm were unrecovered; however, the changes in testis induced by SiNPs were recovered. Our results suggested that SiNPs could decrease the RNF8 level in the nucleus of spermatid either by upregulating of the expression of MIWI or by inhibiting its degradation. This resulted in the detention of RNF8 in the cytoplasm that maybe inhibited the RNF8-mediated ubiquitination of ubH2A and ubH2B. These events culminated in creating obstacles during the H2A and H2B removal and chromatin condensation, thereby suppressing the differentiation of round spermatids and chromatin remodeling, which compromised the sperm quality and quantity.

The effect of SiNPs on DNA methylation of genome in mouse spermatocytes

Silica nanoparticles (SiNPs), which are the main inorganic components of atmospheric particulate matter, have been proved to have certain male reproductive toxicity in previous studies. Spermatogenesis involves complex epigenetic regulation, but it is still unclear if SiNPs exposure will interfere with the DNA methylation patterns in mouse spermatocytes. The present study was designed to investigate the effects of SiNPs on DNA methylation in the mouse spermatocyte GC-2spd(ts). GC-2 cells were treated with 0 and 20 μg/mL SiNPs for 24 h. MeDIP-seq assay was then performed to analyze the differentially methylated genes related to spermatogenesis. The results showed that SiNPs induced extensive methylation changes in the genome of GC-2 cells, and 24a total of 428 hyper-methylated genes and 398 hypo-methylated genes were identified. Gene Ontology and pathway analysis showed that differential DNA methylation induced by SiNPs was probably involved with abnormal transcription and translation, mitochondrial damage, and cell apoptosis. Results from qRT-PCR verification showed that the expression of spermatogenesis-related genes Akap1, Crem, Spz1, and Tex11 were dysregulated by SiNPs exposure, which was consistent with the MeDIP-seq assay. In general, this study suggested that SiNPs caused genome-wide DNA methylation changes in GC-2 cells, providing valuable reference for the future epigenetic studies in SiNPs-induced male reproductive toxicity.

Activation of Nrf2/HO-1 signaling pathway attenuates ROS-mediated autophagy induced by silica nanoparticles in H9c2 cells

Silica nanoparticles (SiNPs) as one of the most productive nano-powder, has been extensively applied in various fields. There has been increasing concern about the adverse effects of SiNPs on the health of ecological organisms and human. The potential cardiovascular toxicity of SiNPs and involved mechanisms remain elusive. Hence, in this study, we investigated the cardiovascular toxicity of SiNPs (60 nm) and explored the underlying mechanisms using H9c2 cardiomyocytes. Results showed that SiNPs induced oxidative stress and activated the Nrf2/HO-1 antioxidant pathway. Autophagy was also activated by SiNPs. Interestingly, N-acetyl-L-cysteine (NAC）attenuated autophagy after inhibiting reactive oxygen species (ROS). Meanwhile, down-regulation of Nrf2 enhanced autophagy. In summary, these data indicated that SiNPs induce autophagy in H9c2 cardiomyocytes through oxidative stress, and the Nrf2/HO-1 pathway has a negative regulatory effect on autophagy. This study provides new evidence for the cardiovascular toxicity of SiNPs and provides a reference for the safe use of nanomaterials in the future.

The alterations of miRNA and mRNA expression profile and their integration analysis induced by silica nanoparticles in spermatocyte cells

Air pollution and the application of Silica nanoparticles (SiNPs) have increased the risk of human exposure to SiNPs. SiNPs are known to induce cytotoxicity in spermatocyte cells (GC-2spd cells) of mice and male reproductive system damage. However, the expression profiles of miRNA and mRNA and the molecular mechanism of miRNA-mRNA integration in reproductive toxicity induced by SiNPs in GC-2spd cells are still unclear. Therefore, GC-2spd cells were divided into 0 μg/mL and 5 μg/mL SiNPs groups, and the cells were collected and analyzed after passaging for 30 generations using miRNA microarray and Illumina high-throughput sequencing (Illumina HiSeq) for the integrated analysis of miRNA and mRNA expression. Both miRNA Microarray and Illumina Hiseq identified 15 significant differentially expressed miRNAs and 1648 significant differentially expressed mRNAs. Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and miRNA-gene-pathway-network analysis revealed 15 significant differentially expressed miRNAs that could regulate the DNA replication and the fatty acid metabolism, respectively. Furthermore, the mRNA-mRNA regulatory network analysis revealed that Pkfl (phosphofructokinase, liver, B-type) and DHCR24 (24-dehydrocholesterol reductase) were highly expressed, but also affected DNA replication and fatty acid metabolism in SiNPs-treated GC-2spd cells. Additionally, miRNA-mRNA integration analysis revealed that miRNA-138-1-3p might have a regulatory relationship with fatty acid metabolism and DNA replication. It is confirmed that SiNPs could decrease the expression of 10 miRNAs and increase the expression of 5 miRNAs. These findings suggest that the cytotoxicity of GC-2spd cells induced by SiNPs depends on the deregulation of multiple miRNAs, which regulate the DNA replication and fatty acid metabolism. Our results are the first to establish an integrated analysis of miRNA-mRNA interactions and mRNA-mRNA and defines multiple pathways involved in SiNPs-treated GC-2spd cells.

Uterine pyruvate metabolic disorder induced by silica nanoparticles act through the pentose phosphate pathway

Silica nanoparticles (SiNPs) have drawn considerable attention due to their environmental health effects, while enhanced understanding of metabolic disorders has provided insight into related diseases. To investigate the impacts of SiNPs exposure on reproduction and reveal their pathogenic mechanisms, this study was designed and conducted from a metabolic perspective. First, fluorescein isothiocyanate (FITC)-SiNPs were chemically synthesized and applied to track SiNPs in vitro and in vivo. Next, 30 pregnant mice were intratracheally instilled with 1.25 mg of SiNPs/mouse, then sacrificed 24 h post-treatment. We found that SiNPs penetrated the trophoblast membrane, triggering apoptosis and inhibiting cell proliferation, invasion, and tube formation in a dose-dependent manner. Mechanistically, SiNPs dysregulated phosphofructokinase (Pfkl) and fructose-bisphosphatase 2 (Fbp2) and induced glucose depletion and pyruvate accumulation via the pentose phosphate pathway. Besides, the downregulation of caspase-3 suggested a causal relationship between pyruvate accumulation, pentose phosphate pathway activation, and cell apoptosis. Pfkl and Fbp2 was also dysregulated in vivo, and the uterine inflammation aggravated in a time-dependent manner. In conclusion, SiNPs triggered acute cytotoxicity and uterine inflammation by inducing glucose depletion and pyruvate overload in trophoblasts, which were mediated in part by Pfkl and Fbp2 via the pentose phosphate pathway.

Silica nanoparticles inducing the apoptosis via microRNA-450b-3p targeting MTCH2 in mice and spermatocyte cell

Silica nanoparticles (SiNPs) could cause reproductive toxicity. The role of miRNAs in reproductive toxicity induced by SiNPs is still ambiguous. The present study was designed to investigate the role of miRNA-450 b-3p. In vivo, 40 male mice were randomly divided into control, and 20 mg/kg SiNPs groups. The mice were administrated by tracheal perfusion for 35 days. In vitro, spermatocyte cells (GC-2spd cells) were divided into 6 groups: 0 μg/mL SiNPs groups, 5 μg/mL SiNPs groups, 5 μg/mL SiNPs + miRNA-450 b-3p mimic transfection group, 5 μg/mL SiNPs + miRNA-450 b-3p mimic negative control group, 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor transfection group, and 5 μg/mL SiNPs + miRNA-450 b-3p inhibitor negative control group. The results showed that SiNPs induced the apoptosis of spermatogenic cells, decreased the quantity and quality of the sperm, reduced the expressions of miR-450 b-3p, and increased the protein expressions of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, and Caspase-3 in the testis. In vitro, the mimic of miRNA-450 b-3p reversed the decrease of viability and the increase of apoptosis rate and significantly antagonized the expression enhancements of the MTCH2, BID, BAX, Cytochrome C, Caspase-9, Caspase-3 induced by SiNPs, while inhibitor of miRNA-450 b-3p further promoted the effects induced by SiNPs. The result suggested that SiNPs could inhibit the miR-450 b-3p expression resulting in activation of the mitochondrial apoptosis signaling pathways by regulating the MTCH2 in the spermatocyte cells and, thus, induce the reproductive toxicity.

Can nanomaterials induce reproductive toxicity in male mammals? A historical and critical review

The nanotechnology enabled the development of nanomaterials (NMs) with a variety of industrial, biomedical, and consumer applications. However, the mechanism of action (MoA) and toxicity of NMs remain unclear, especially in the male reproductive system. Thus, this study aimed to perform a bibliometric and systematic review of the literature on the toxic effects of different types of NMs on the male reproductive system and function in mammalian models. A series of 236 articles related to the in vitro and in vivo reproductive toxicity of NMs in mammalian models were analyzed. The data concerning the bioaccumulation, experimental conditions (types of NMs, species, cell lines, exposure period, and routes of exposure), and the MoA and toxicity of NMs were summarized and discussed. Results showed that this field of research began in 2005 and has experienced an exponential increase since 2012. Revised data confirmed that the NMs have the ability to cross the blood-testis barrier and bioaccumulate in several organs of the male reproductive system, such as testis, prostate, epididymis, and seminal vesicle. A similar MoA and toxicity were observed after in vitro and in vivo exposure to NMs. The NM reproductive toxicity was mainly related to ROS production, oxidative stress, DNA damage and apoptosis. In conclusion, the NM exposure induces bioaccumulation and toxic effects on male reproductive system of mammal models, confirming its potential risk to human and environmental health. The knowledge concerning the NM reproductive toxicity contributes to safety and sustainable use of nanotechnology.

Silica nanoparticles induce spermatogenesis disorders via L3MBTL2-DNA damage-p53 apoptosis and RNF8-ubH2A/ubH2B pathway in mice

Silica nanoparticles (SiNPs) can reduce both quality and quantity of sperm via inhibiting the progress of meiosis and mitosis and inducing apoptosis of spermatogenic cells, however, their specific mechanism and effects on the later stage of spermatogenesis are still unclear. To investigate the effects of SiNPs on the reproductive system, male mice were treated with SiNPs (0, 1.25, 5 and 20 mg/kg.bw) via intratracheal instillation once every 3 days and for a total of 15 days. Results revealed that exposure to SiNPs induced reduction in the rate of sperm activity, histological abnormalities in seminiferous epithelium as well as apoptosis of spermatogenic cells, which are associated with decreased level of Lethal (3) malignant brain tumor like 2 (L3MBTL2) and activation of DNA damage-p53-mitochondrial apoptosis pathways. Moreover, reduction in L3MBTL2 level caused by SiNPs also led to the lower expression of RNF8-ubH2A/ubH2B pathway, thus resulting in incomplete histone-to-protamine exchange. These results suggest that the inhibition of L3MBTL2 expression caused by SiNPs not only activates DNA damage-p53-mitochondrial apoptosis pathway leading to the apoptosis of spermatogenic cells, but also inhibits RNF8-ubH2A/ubH2B pathway resulting in incomplete histone-to-protamine exchange, thereby affected spermatogenesis. This indicates that L3MBTL2 plays an important role in reproductive toxicity of males caused by SiNPs.

Silica nanoparticles induce spermatocyte cell autophagy through microRNA-494 targeting AKT in GC-2spd cells

Researches had shown that silica nanoparticles (SiNPs) could reduce the quantity and quality of sperms. However, chronic effects of SiNPs have not been well addressed. In this study, mice spermatocyte cells (GC-2spd cells) were continuously exposed to SiNPs (5 μg/mL) for 30 passages and then the changes of microRNA (miRNA) profile and mRNA profile were detected. The function of miRNAs was verified by inhibitors to explore the regulation role of miRNAs in reproductive toxicity induced by SiNPs. The results showed that SiNPs induced cytotoxicity, and activated autophagy in GC-2spd cells. SiNPs led to a total of 1604 mRNAs (697 up-regulated and 907 down-regulated) and 15 miRNAs (6 up-regulated such as miRNA-138 and miRNA-494 and 9 down-regulated) with different expression in GC-2spd cells. The combined miRNA profile and mRNA profile showed that 415 mRNAs with different expression in 5 μg/mL SiNPs group were regulated by miRNA. Furthermore, our study demonstrated that SiNPs decreased the expressions of AKT mRNAs. Moreover, SiNPs had an activation effect on the AMPK/TSC/mTOR pathway. However, inhibitor of miRNA-494 could attenuate the expression levels of AMPK, TSC, LC3Ⅱ and alleviate the decreased of AKT, mTOR, p-mTOR induced by SiNPs. The above results suggested that the low-dose SiNPs exposure could promote autophagy by miRNA-494 targeting AKT, thereby activating AMPK/TSC/mTOR pathway in GC-2spd cells. MiRNA-494 is an important regulator of autophagy by targeting AKT, which provides new evidence for the male reproductive toxicity mechanism of SiNPs.

Increasing ERK phosphorylation by inhibition of p38 activity protects against cadmium-induced apoptotic cell death through ERK/Drp1/p38 signaling axis in spermatocyte-derived GC-2spd cells

Many studies report that cadmium chloride (CdCl₂)-induces oxidative stress is associated with male reproductive damage in the testes. CdCl₂ also induces mitochondrial fission by increasing dynamin-related protein 1 (Drp1) expression as well as the mitochondria-dependent apoptosis pathway by extracellular signal-regulated kinase (ERK) activation. However, it remains unclear whether mechanisms linked to the mitochondrial damage signal via CdCl₂-induced mitogen-activated protein kinases (MAPK) cause damage to spermatocytes. In this study, increased intracellular and mitochondrial reactive oxygen species (ROS) levels, mitochondrial membrane potential (∆Ψm) depolarization, and mitochondrial fragmentation and swelling were observed at 5 μM of CdCl₂ exposure, resulting in increased apoptotic cell death. Moreover, CdCl₂-induced cell death is closely associated with the ERK/Drp1/p38 signaling axis. Interestingly, SB203580, a p38 inhibitor, effectively prevented CdCl₂-induced apoptotic cell death by reducing ∆Ψm depolarization and intracellular and mitochondrial ROS levels. Knockdown of Drp1 expression diminished CdCl₂-induced mitochondrial deformation and ROS generation and protected GC-2spd cells from apoptotic cell death. In addition, electron microscopy showed that p38 inhibition reduced CdCl2-induced mitochondrial interior damage more effectively than N-acetyl-L-cysteine (NAC), an ROS scavenger; ERK inhibition; or Drp1 knockdown. Therefore, these results demonstrate that inhibition of p38 activity prevents CdCl₂-induced apoptotic GC-2spd cell death by reducing depolarization of mitochondrial membrane potential and mitochondrial ROS levels via ERK phosphorylation in a signal pathway different from the CdCl₂-induced ERK/Drp1/p38 axis and suggest a therapeutic strategy for CdCl₂-induced male infertility.

Fine particulate matters induce apoptosis via the ATM/P53/CDK2 and mitochondria apoptosis pathway triggered by oxidative stress in rat and GC-2spd cell

Fine particulate matters (PM_2.5) have been associated with male reproductive toxicity because it can penetrate into the lung's gas-exchange region, and spread to the whole body via circulatory system. Previous studies have shown that PM_2.5 could induce DNA damage and apoptosis by reactive oxygen species (ROS). The aim of the present study is to determine the exact mechanism and role of apoptosis induced by PM_2.5 in spermatocyte cells. Male Sprague-Dawley (SD) rats were treated with normal saline (control group) or PM_2.5 with the doses of 1.8, 5.4 and 16.2 mg/kg bw. via intratracheal instillation every 3 days for 30 days. Mouse spermatocyte-derived cells (GC-2spd cells) were treated with various concentrations (0, 50, 100, 200 μg/mL) of PM_2.5 for 24 h. The results showed that exposure to PM_2.5 resulted in injury of testicular tissue and impaired mitochondria integrity in GC-2spd cells. Moreover, PM_2.5 induced DNA damage and apoptosis in GC-2spad cells via ROS generation, and the ATM/P53/CDK2 and mitochondria apoptosis pathway autophagy signal pathway were activated. N-Acetyl-L-cysteine (NAC), a well-known antioxidant, ameliorated DNA damage, and inhibited apoptosis. These findings demonstrated PM_2.5 might induce apoptosis via the mitochondrial apoptosis pathway through causing DNA damage resulting from oxidative stress, and finally caused spermatogenesis disorder.

Mel1c Mediated Monochromatic Light-Stimulated IGF-I Synthesis through the Intracellular Gαq/PKC/ERK Signaling Pathway

Previous studies have demonstrated that monochromatic light affects plasma melatonin (MEL) levels, which in turn regulates hepatic insulin-like growth factor I (IGF-I) secretion via the Mel1c receptor. However, the intracellular signaling pathway initiated by Mel1c remains unclear. In this study, newly hatched broilers, including intact, sham operation, and pinealectomy groups, were exposed to either white (WL), red (RL), green (GL), or blue (BL) light for 14 days. Experiments in vivo showed that GL significantly promoted plasma MEL formation, which was accompanied by an increase in the MEL receptor, Mel1c, as well as phosphorylated extracellular regulated protein kinases (p-ERK1/2), and IGF-I expression in the liver, compared to the other light-treated groups. In contrast, this GL stimulation was attenuated by pinealectomy. Exogenous MEL elevated the hepatocellular IGF-I level, which is consistent with increases in cyclic adenosine monophosphate (cAMP), G_αq, phosphorylated protein kinase C (p-PKC), and p-ERK1/2 expression. However, the Mel1c selective antagonist prazosin suppressed the MEL-induced expression of IGF-I, G_αq, p-PKC, and p-ERK1/2, while the cAMP concentration was barely affected. In addition, pretreatment with Ym254890 (a G_αq inhibitor), Go9863 (a PKC inhibitor), and PD98059 (an ERK1/2 inhibitor) markedly attenuated MEL-stimulated IGF-I expression and p-ERK1/2 activity. These results indicate that Mel1c mediates monochromatic GL-stimulated IGF-I synthesis through intracellular G_αq/PKC/ERK signaling.