Peng Duan

4-Nonylphenol induces apoptosis, autophagy and necrosis in Sertoli cells: Involvement of ROS-mediated AMPK/AKT-mTOR and JNK pathways

The xenoestrogen 4-nonylphenol (NP) induces reproductive dysfunction of male rats, but the fundamental mechanism of this phenomenon is largely unexplored. Sertoli cells (SCs) are pivotal for spermatogenesis and male fertility. The involvement of autophagy in NP-induced apoptotic and necrotic death of SCs was investigated. In this study, 24-h exposure of SCs to 20-30μM NP decreased cell viability, caused G2/M arrest, triggered ΔΨm loss, increased ROS production and induced caspase-dependent apoptosis, necrosis as well as autophagosome formation. NP-induced autophagy was confirmed by monodansylcadaverine-staining and LC3-I/LC3-II conversion. Furthermore, NP up-regulated the (Thr172)p-AMPK/AMPK and (Thr183/185)p-JNK/JNK ratios. This was followed by the down-regulation of (Ser473)p-Akt/Akt, (Thr1462)p-TSC2/TSC2, (Ser2448)p-mTOR/mTOR, (Thr389)p-p70S6K/p70S6K and (Thr37/45)p-4EBP1/4EBP1. Intriguingly, NP-induced apoptosis, autophagy and necrosis could be inhibited through blocking ROS generation by N-acetylcysteine. Autophagy inhibitor 3-MA enhanced NP-induced apoptosis and necrosis. Moreover, The activation of AMPK/mTOR/p70s6k/4EBP1 and JNK signalling pathways induced by NP could be efficiently reversed by pretreatment of N-acetylcysteine or 3-MA. Collectively, our findings provide the first evidence that NP promotes apoptosis, autophagy and necrosis simultaneously in SCs and that this process may involve ROS-dependent JNK- and Akt/AMPK/mTOR pathways. Modulation of autophagy induced by NP may serve as a survival mechanism against apoptosis and necrosis.

BPA-induced apoptosis of rat Sertoli cells through Fas/FasL and JNKs/p38 MAPK pathways

Bisphenol-A was examined for its effects on cultured Sertoli cells established from 18 to 22-day-old rat testes. Results indicated that exposure to BPA (0, 30, 50 and 70 μM) decreased the cell viability in a concentration-dependent manner and induced cell apoptosis. Apoptosis-caused cell death was observed in cells exposed to 50 and 70 μM BPA. The mRNA expressions of Fas, FasL and caspase-3 were all elevated, and the protein expressions of FasL and cleaved caspase-3 were also increased. In addition, levels of phosphorylation of JNKs/p38 MAPK were also increased and then activated JNKs/p38 MAPK up regulated target gene expressions, such as c-jun and CHOP. Translocation of NF-κB into nuclei indicated the activation of NF-κB after treatment with BPA. Taken together, observed results suggest that BPA induces apoptosis of Sertoli cells by the activation of JNKs/p38 MPAK and translocation of NF-κB, and Fas/FasL system plays a critical role in the initiation of apoptosis.

Body mass index and risk of lung cancer: Systematic review and dose-response meta-analysis

Questions remain about the significance of the dose-response relationship between body mass index (BMI) and lung cancer (LC) risk. Pertinent studies were identified through a search in EMBASE and PUBMED from July 2014 until March 2015. The summary relative risk (SRR) and confidence interval (CI) were estimated. The dose-response relationship was assessed using a restricted cubic spline. The overall meta-analysis showed evidence of a nonlinear association between BMI and LC risk (Pnonlinearity < 0.001). The SRR were 0.98 (95%CI: 0.95–1.01) for 25 kg/m2, 0.91 (95%CI: 0.85–0.98) for 30 kg/m2 and 0.81 (95% CI: 0.72–0.91) for 35 kg/m2, with mild between-study heterogeneity (I2 = 5%). The results of the stratified analysis by gender were comparable to those of the overall meta-analysis. When stratified by smoking status, linear dose-response associations were observed for current smokers, ex-smokers and non-smokers (Pnonlinearity > 0.05), whereas the effects were attenuated when restricting analysis to non-smokers, and at the point of 30 kg/m2, the SRR was 0.96 (95%CI: 0.86–1.07) for males and 0.95 (95%CI: 0.89–1.02) for females. This meta-analysis provides quantitative evidence that increasing BMI is a protective factor against LC. Keeping normal-to-moderate BMI should be prescribed as an evidence-based lifestyle tip for LC prevention in smokers.

Nonylphenol induced apoptosis and autophagy involving the Akt/mTOR pathway in prepubertal Sprague-Dawley male rats in vivo and in vitro

This research explores the detrimental effect of nonylphenol (NP) to prepubertal Sprague-Dawley male rats in vivo and in vitro. Herein, forty-two 3-week-old rats were randomly divided into six groups, which were treated with NP (0, NAC, 25, 50, 100, 100+NACmg/kg/2d for 30 consecutive days) by intraperitoneal injection. NP induced a reduction in testosterone (15.58%, 17.23%, 13.38% in 25, 50, 100mg/kg group, respectively), triggered apoptosis related to oxidative stress, and disturbed mRNA and/or protein levels of PI3K, PTEN, PDK1, p-Akt, p-mTOR, p70S6K, caspase-3, LC3B. NP induced morphological abnormality in epididymal sperm (2.00-, 3.02-fold in 50, 100mg/kg group, respectively). Pretreatment with NAC, attenuated NP-induced ROS production; recovered testosterone in serum, and ameliorated toxic effect in epididymal sperm. Sertoli cells were isolated, purified, treated with NP (0, 10, 20, and 30μM) for 12h. NP disturbed mRNA and/or protein levels of caspase-3, cleave-caspase-3, LC3B involving the PI3K/Akt/mTOR pathway. It also decreased protein levels of ABP, FSHR, N-cadherin, transferrin, vimentin; disturbed the gene levels of all, but vimentin. Pretreatment with wortmannin, alleviated an NP-induced reduction in protein levels of PI3K and PTEN. In conclusion, excess NP exposure induces apoptosis and autophagy, causes reproductive lesions involving the PI3K/AKT/mTOR pathway both in vivo and in vitro. It also triggers oxidative stress and hormonal deficiency, reduces semen quality.

Effects of 4-Nonylphenol on spermatogenesis and induction of testicular apoptosis through oxidative stress-related pathways

This study tested the hypothesis that prepubertal exposure to 4-nonylphenol (NP) affects reproductive function in male rats. Twenty-four rats at five-weeks-old were randomly divided into four groups and treated with NP at varying concentrations (0, 5, 20, and 60mg/kg/2d) for thirty days by intra-peritoneal injection. 60mg/kg NP induced spermatogenic degeneration and pronounced deficits in epididymal sperm count, motility and function, whereas potentially stimulatory effects were observed at 5 NPmg/kg. Moreover, 60mg/kg NP resulted in a significant reduction in fructose, FSH and LH; induced apoptosis related to oxidative stress; inhibited mRNA and protein levels of Bcl-2 and PCNA; as well as the additional up-regulation of p53, Bax, Apaf-1, cytochrome c, cleaved-caspase-3, Fas and FasL expression. Our data suggest potentially hormetic effects of NP on spermatogenic function. High-dose NP impairs testicular development and function by reducing cell proliferation and inducing apoptosis involving oxidative stress-related p53-Bcl-2/Bax and -Fas/FasL pathways.

4-Nonylphenol induces disruption of spermatogenesis associated with oxidative stress-related apoptosis by targeting p53-Bcl-2/Bax-Fas/FasL signaling.

4‐Nonylphenol (NP) is a ubiquitous environmental chemical with estrogenic activity. Our aim was to test the hypothesis that pubertal exposure to NP leads to testicular dysfunction. Herein, 24 7‐week‐old rats were randomly divided into four groups and treated with NP (0, 25, 50, or 100 mg/kg body weight every 2 days for 20 consecutive days) by intraperitoneal injection. Compared to untreated controls, the parameters of sperm activation rate, curvilinear velocity, average path velocity, and swimming velocity were significantly lower at doses of 100 mg/kg, while sperm morphological abnormalities were higher, indicating functional disruption and reduced fertilization potential. High exposure to NP (100 mg/kg) resulted in disordered arrangement of spermatoblasts and reduction of spermatocytes in seminiferous tubules, while tissues exhibited a marked decline in testicular fructose content and serum FSH, LH, and testosterone levels. Oxidative stress was induced by NP (50 or 100 mg/kg) as evidenced by elevated MDA, decreased SOD and GSH‐Px, and inhibited antioxidant gene expression (CAT, GPx, SOD1, and CYP1B1). In addition, NP treatment decreased proportions of Ki‐67‐positive cells and increased apoptosis in a dose‐dependent manner. Rats treated with 100 mg/kg NP exhibited significantly increased mRNA expression of caspase‐1, ‐2, ‐9, and ‐11, decreased caspase‐8 and PCNA1 mRNA expression, downregulation of Bcl‐2/Bax ratios and upregulation of Fas, FasL, and p53 at the protein and mRNA levels. Taken together, NP‐induced apoptosis, hormonal deficiencies, and depletion of fructose potentially impairs spermatogenesis and sperm function. p53‐independent Fas/FasL‐Bax/Bcl‐2 pathways may be involved in NP‐induced oxidative stress‐related apoptosis.

Bisphenol a induces autophagy and apoptosis concurrently involving the Akt/mTOR pathway in testes of pubertal SD rats

Bisphenol A (BPA), a typical endocrine disrupting chemical (EDC), has been proven to cause male reproductive toxicity. However, the precise mechanisms of this effect are still unclear. Puberty is a crucial period of reproductive development, and adolescents are more susceptible to xenobiotics. This research was designed to explore the mechanism of BPA toxicity on pubertal male reproduction. Rats were exposed to 0, 2, 10, 50 mg kg−1 bw BPA, then the levels of sex hormones, oxidative stress, and semen quality were detected. HE staining, TUNEL assay and transmission electron microscopy were used to investigate the morphological changes, apoptosis, and autophagy in testes, respectively. Expressions of relevant genes and proteins were measured by RT‐PCR, western blotting, and immunohistochemical staining. The results indicated that BPA exposure led to oxidative stress and endocrine disorders in pubertal male SD rats, caused apoptosis and autophagy in testes, and then damaged spermatogenesis ultimately. The Akt pathway was activated and the mTOR pathway was inhibited in the process. Taken together, BPA induced apoptosis and autophagy concurrently in pubertal testes, and this added a new layer to our understanding on male reproductive toxicity of BPA.

Nonlinear dose-response relationship between radon exposure and the risk of lung cancer: evidence from a meta-analysis of published observational studies

Although radon exposure (RE) has been confirmed to increase the risk of lung cancer (LC), questions remain about the shape of the dose–response relationship between RE and the risk of LC. We carried out a dose–response meta-analysis to investigate and quantify the potential dose–response association between residential and occupational exposure to radon and the risk of LC. All cohort and case–control studies published in English and Chinese on Embase, PubMed, and China National Knowledge Infrastructure (CNKI) digital databases through November 2013 were identified systematically. We extracted effect measures (relative risk, odds ratio, standardized mortality ratio, standardized incidence ratio, or standardized rate ratio) from individual studies to generate pooled results using meta-analysis approaches. We derived meta-analytic estimates using random-effects models taking into account the correlation between estimates. Restricted cubic splines and generalized least-squares regression methods were used to model a potential curvilinear relationship and to carry out a dose–response meta-analysis. Stratified analysis, sensitivity analysis, and assessment of bias were performed in our meta-analysis. Sixty publications fulfilling the inclusion criteria for this meta-analysis were finally included. Occupational RE was associated with LC [risk ratio 1.86, 95% confidence interval (CI)=1.67–2.09; I2=92.2%; 27 prospective studies], for pooled risk estimate of the: standardized mortality ratio [2.00 (95% CI=1.82–2.32)]; standardized incidence ratio [1.45 (95% CI=1.20–1.74)]; relative risk [2.10 (95% CI=1.64–2.69)]. In a subgroup analysis of uranium miners and residents exposed to occupational uranium, the summary risk was 2.23 (95% CI=1.86–2.68) and 1.23 (95% CI=1.05–1.44). The overall meta-analysis showed evidence of a nonlinear association between RE and the risk of LC (Pnonlinearity<0.014); in addition, the point value of residential radon also improved the results quantitatively, where odds ratios were 1.11 (95% CI=1.07–1.15) and 1.21 (95% CI=1.14–1.29) when the radon concentration was at the point of 100 and 200 Bq/m3 compared with the lowest. For 17 prospective studies with at least three categories of occupational cumulative radon dose, the dose–risk model estimated a risk ratio of 1.26 (95% CI=1.21–1.30) for 100 working level months and 1.51 (95% CI=1.38–1.65) for 200 working level months, respectively. The assessment of risk of bias within individual studies and across studies indicated risk that was unlikely to alter these results markedly. This meta-analysis shows a nonlinear dose–response association between environmental RE and the risk of LC. This increased risk is particularly apparent when the cumulative exposure to radon is well beyond that resulting from exposure to the recommended limit concentration for a prolonged period of time.

Prenatal bisphenol a exposure leads to reproductive hazards on male offspring via the Akt/mTOR and mitochondrial apoptosis pathways

Bisphenol A (BPA) exposure is ubiquitous, and in laboratory animals and humans, exposure has been associated with male spermatogenesis dysfunction. However, it is largely unknown if this association has a fetal origin.

Bisphenol A Induces Apoptosis in Liver Cells through Induction of ROS

Oxidative stress mechanisms are involved in hepatotoxicity. The liver is reported to be affected by bisphenol A (BPA) in animals studies and has been also reported to possess hepatic toxicity. This study aimed to examine association between liver health status and the effects of BPA on the antioxidant defense systems and liver biomarkers. BPA (0, 2, 10, and 50 mg/kg) body weight was mixed in corn oil and intraperitoneally administered every forty-eight hours for 30 days in dose-dependent manner. There was no significant difference between the body weight and weight of rat liver in BPA-treated groups and control groups. The study results show that the levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) increased after exposure to BPA. However, the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) were significantly (, , and , resp.) decreased at 50 mg/kg dosage. Liver markers activities such as lactate dehydrogenase (LDH), glutamic-oxalacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT) were significantly increased, while γ-glutamyl transferase (γ-GT) activity was decreased. BPA exposure increased activity of liver biomarkers indicating liver hyperactivity. Analysis of the liver section provided essential evidence of liver apoptosis. Moreover, BPA may lead to induced toxic response of liver oxidative system.