Wenyi Qian

Perinatal bisphenol A exposure and adult glucose homeostasis: identifying critical windows of exposure.

Bisphenol A (BPA) is a widespread endocrine-disrupting chemical used as the building block for polycarbonate plastics. Epidemiological evidence has correlated BPA exposure with higher risk of heart disease and type 2 diabetes. However, it remains unknown whether there are critical windows of susceptibility to BPA exposure on the development of dysglycemia. This study was an attempt to investigate the critical windows and the long-term consequences of perinatal exposure to BPA on glucose homeostasis. Pregnant mice were given either vehicle or BPA (100 µg/kg/day) at different time of perinatal stage: 1) on days 1–6 of pregnancy (P1–P6, preimplantation exposure); 2) from day 6 of pregnancy until postnatal day (PND) 0 (P6–PND0, fetal exposure); 3) from lactation until weaning (PND0–PND21, neonatal exposure); and 4) from day 6 of gestation until weaning (P6–PND21, fetal and neonatal exposure). At 3, 6 and 8 months of age, offspring in each group were challenged with glucose and insulin tolerance tests. Then islet morphometry and β-cell function were measured. The glucose homeostasis was impaired in P6-PND0 mice from 3 to 6 months of age, and this continued to 8 months in males, but not females. While in PND0-PND21 and P6-PND21 BPA-treated groups, only the 3-month-old male offspring developed glucose intolerance. Moreover, at the age of 3 months, perinatal exposure to BPA resulted in the increase of β-cell mass mainly due to the coordinate changes in cell replication, neogenesis, and apoptosis. The alterations of insulin secretion and insulin sensitivity, rather than β-cell mass, were consistent with the development of glucose intolerance. Our findings suggest that BPA may contribute to metabolic disorders relevant to glucose homeostasis and the effects of BPA were dose, sex, and time-dependent. Fetal development stage may be the critical window of susceptibility to BPA exposure.

MAPK and NF-κB Pathways Are Involved in Bisphenol A-Induced TNF-α and IL-6 Production in BV2 Microglial Cells

Microglial activation has been reported to play an important role in neurodegenerative diseases by producing pro-inflammatory cytokines. Bisphenol A (BPA, 2,2-bis (4-hydroxyphenyl) propane), known as a ubiquitous endocrine-disrupting chemical, is reported to perform both mimic- and anti-estrogen properties; however, whether it affects cytokine production or immune response in central nervous system remains unclear. The present study was aimed to explore whether BPA was involved in inflammatory action and to investigate the potential mechanisms in microglial cells. BV2, the murine microglial cell line, was used in the present work as the cell model. BPA-associated morphologic changes, cytokine responses, and signaling events were examined using immunofluorescence analysis, real-time PCR, enzyme-linked immunosorbent assay, and western blot. Our results indicated that BPA increased BV2 cells activation and simultaneously elevated tumor necrosis factor-α and interleukin 6 expression, which could be partially reversed by estrogen receptor antagonist, ICI182780. In addition, the c-Jun N-terminal protein kinase (JNK) inhibitor (SP600125), rather than ERK1/2 blocker (PD98059), displayed anti-inflammatory properties on BPA-elicited cytokine responses. Moreover, the inflammatory transcription factor NF-κB was specifically activated by BPA as well. These results, taken together, suggested that BPA may have functional effects on the response of microglial cell activation via, in part, the estrogen receptor, JNK, ERK mitogen-activated protein kinase, and NF-κB signaling pathways with its subsequent influence on pro-inflammatory action.

Dexmedetomidine Inhibits Tumor Necrosis Factor-Alpha and Interleukin 6 in Lipopolysaccharide-Stimulated Astrocytes by Suppression of c-Jun N-Terminal Kinases

Astrocytes play an important role in immune regulation in the central nervous system (CNS). Dexmedetomidine (DEX) has been reported to exert anti-inflammatory effects on astrocytes stimulated by lipopolysaccharide (LPS) both in vitro and in vivo studies. However, the underlying molecular mechanisms remain poorly understood. This study was designed to evaluate the effects of DEX on tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6) gene expressions in LPS-challenged astrocytes. Moreover, c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinase (MAPK) pathways in LPS-challenged astrocytes were also investigated. In the present study, astrocytes were stimulated with LPS in the absence and presence of various concentrations of DEX. With real-time PCR assay, we found that LPS significantly increased expressions of TNF-α and IL-6 in mRNA level; however, these effects could be attenuated by DEX. Furthermore, JNK pathway might be involved in LPS-induced astrocyte activation because JNK phosphorylation was significantly increased, and the inhibition of this pathway mediated by DEX as well as SP600125 (JNK inhibitor) decreased TNF-α and IL-6 expressions. Moreover, p38 MAPK was also activated by LPS; however, this pathway seemed to have not participated in DEX-mediated LPS-induced inflammation. These results, taken together, suggest that JNK rather than p38 MAPK signal pathway, provides the potential target for the therapeutic effects of DEX for neuronal inflammatory reactions.

Involvement of CaM-CaMKII-ERK in bisphenol A-induced Sertoli cell apoptosis.

Bisphenol A (BPA), one of the most prevalent chemicals for daily use, has been reported as a xenoestrogen to induce reproductive toxicity, but its mechanism is poorly understood. In the present study, we aimed to explore whether CaM-CaMKII-ERK1/2 signaling pathway was involved in BPA-induced Sertoli cells injury via the mitochondrial apoptotic pathway. TM4 cells were cultured with 0, 0.02, 0.2, 2.0, 20μM BPA, and cell viability, mitochondrial function and CaM-CaMKII-ERK1/2 signal pathway were examined. With the MTT assay, BPA was found to suppress cell viability in a dose- and time-dependent manner. Moreover, mitochondrial mass loss, membrane potential decrease, cytochrome c release, Bcl-2 family members down-regulation and caspases-3 up-regulation were obviously observed when the TM4 cells were exposed to BPA. Additionally, the expression of calmodulin (CaM) and phosphorylation of calcium/calmodulin dependent kinase II (CaMKII) significantly increased, and pretreatment with 10μM antagonist of CaM (W-7) or CaMKII (KN62) prevented cell damage through mitochondrial apoptotic pathway. In parallel, ERK1/2 pathway was proved to participate in BPA-induced cell damage, since W-7 and KN62 partially suppressed ERK1/2 activation, and PD98059, the ERK1/2 antagonist, significantly attenuated BPA-induced cell damage. These data, taken together, indicated that CaM-CaMKII-ERK axis might transmit apoptotic signals to the mitochondria during BPA-induced cell apoptosis. By exploring the mechanisms of the Ca(2+) homeostasis and the corresponding proteins, our study provides new insight into BPA-induced reproductive toxicity.

Integrated long non-coding RNA analyses identify novel regulators of epithelial-mesenchymal transition in the mouse model of pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease characterized by aberrant accumulation of fibroblast population and deposition of extra cellular matrix. Increasing evidence support that epithelial‐mesenchymal transition (EMT) of alveolar epithelial cells is a critical process in the pathogenesis of IPF. Although delivery of bleomycin to induce acute lung injury is the most well‐studied animal model of pulmonary fibrosis, there is considerable interest to pursue other models to understand the common and/or specific pathological mechanisms. In this study, we established a mouse model of pulmonary injury and progressive interstitial fibrosis via intraperitoneal injection of paraquat, a widely used herbicide known to cause pulmonary fibrosis in human. Using transcriptome sequencing and microarray analysis, we profiled expression of long non‐coding RNAs (lncRNAs) and identified 513 up‐regulated and 204 down‐regulated lncRNAs in paraquat‐induced fibrotic lung tissues. Gene ontology analysis revealed that the differentially expressed lncRNAs are implicated in cell differentiation, epithelium morphogenesis and wound healing, pathways closely associated with EMT. Furthermore, we identified the evolutionally conserved target genes of two up‐regulated lncRNAs, uc.77 and 2700086A05Rik, as Zeb2 and Hoxa3, respectively, both of which are important modulators of EMT. Consistently, overexpression of uc.77 or 2700086A05Rik in human lung epithelial cells induced EMT as demonstrated by changes in gene and protein expression of various EMT markers and cell morphology. Collectively, our results uncovered a crucial role of lncRNA in the regulation of EMT during lung fibrosis and provide potential avenues for the discovery of novel molecular markers and therapeutic targets for IPF.

The toxic effects of Bisphenol A on the mouse spermatocyte GC-2 cell line: the role of the Ca2+-calmodulin-Ca2+/calmodulin-dependent protein kinase II axis.

Bisphenol A (BPA), an endocrine‐disrupting chemical (EDC), is known to induce male reproductive toxicity in rodents. However, its toxic effects on the germ cells are still poorly understood. It has been proposed that Ca2+ homeostasis and Ca2+ sensors, including calmodulin (CaM) and calmodulin‐dependent protein kinase II (CaMKII), play critical roles in spermatogenesis. Therefore, in the present study, we aimed to investigate whether a perturbation in Ca2+‐CaM‐CaMKII signaling was involved in the BPA‐induced injury to mouse spermatocyte GC‐2spd (ts) (GC‐2) cells. Our results showed that BPA (range from 0.2 to 20 μM) induced obvious GC‐2 cell injury, including decreased cell viability, the release of mitochondrial cytochrome c and the activation of caspase‐3. However, these processes could be partially abrogated by pretreatment with a Ca2+ chelator (BAPTA/AM), a CaM antagonist (W7) or a CaMKII inhibitor (KN93). These results, taken together, indicate that BPA exposure contributes to male germ cell injury, which may be partially mediated through a perturbation in Ca2+/CaM/CaMKII signaling and the mitochondrial apoptotic process. Copyright

Effects of Bisphenol A on glucose homeostasis and brain insulin signaling pathways in male mice.

The potential effects of Bisphenol A (BPA) on peripheral insulin resistance have recently gained more attention, however, its functions on brain insulin resistance are still unknown. The aim of the present study was to investigate the effects of BPA on insulin signaling and glucose transport in mouse brain. The male mice were administrated of 100 μg/kg/day BPA or vehicle for 15 days then challenged with glucose and insulin tolerance tests. The insulin levels were detected with radioimmunoassay (RIA), and the insulin signaling pathways were investigated by Western blot. Our results revealed that BPA significantly increased peripheral plasma insulin levels, and decreased the insulin signals including phosphorylated insulin receptor (p-IR), phosphorylated insulin receptor substrate 1 (p-IRS1), phosphorylated protein kinase B (p-AKT), phosphorylated glycogen synthase kinase 3β (p-GSK3β) and phosphorylated extracellular regulated protein kinases (p-ERK1/2) in the brain, though insulin expression in both hippocampus and profrontal cortex was increased. In parallel, BPA exposure might contribute to glucose transport disturbance in the brain since the expression of glucose transporters were markedly decreased. In conclusion, BPA exposure perturbs the insulin signaling and glucose transport in the brain, therefore, it might be a risk factor for brain insulin resistance.

Dexmedetomidine inhibits inducible nitric oxide synthase in lipopolysaccharide-stimulated microglia by suppression of extracellular signal-regulated kinase.

Abstract Objective: Dexmedetomidine (DEX) has been implicated in modulating the inflammatory response in central nervous system (CNS). However, the mechanism is still poorly understood. In this study, we evaluate the effects of DEX on lipopolysaccharide (LPS)-induced microglia activation and elucidate its possible signaling pathway involved in its anti-inflammatory effects. Methods: BV2 and primary microglia were pretreated with various concentrations of DEX (0·01, 0·1, 1, and 10 μM) and/or PD98059 for 1 hour, then microglia were incubated with LPS (1 μg/ml) for 24 hours. Nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression were measured by Griess reagent and real-time polymerase chain reaction. Furthermore, two intracellular signaling cascades including extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK) were investigated by western blot analysis. Results: Dexmedetomidine significantly attenuated LPS-induced NO production and iNOS expression in both BV2 cells and primary microglial cells. Lipopolysaccharide activated both ERK1/2 and JNK signal pathways; however, DEX exerted a specific inhibitory effect on ERK1/2 rather than JNK. Intriguingly, treatment of primary microglia and BV2 cells with DEX in combination with ERK1/2 inhibitor (PD98059) enhanced attenuation of LPS-induced NO production and iNOS expression. Discussion: Dexmedetomidine attenuates NO and iNOS accumulation by inhibiting extracellular signal-regulated kinase (ERK) activation in both BV2 cells and primary microglial cells.

α-ENaC, a therapeutic target of dexamethasone on hydrogen sulfide induced acute pulmonary edema

Acute pulmonary edema (APE) is one of the fatal outcomes after exposure to high levels of hydrogen sulfide (H2S), available evidence suggest that dexamethasone (DXM), a potent anti-inflammatory agent, has been widely used or proposed as a therapeutic approach for H2S-induced APE in clinical practice, however, the underlying mechanism remains poorly understood. Ample evidence suggest that epithelial Na(+) channel, especially for the subunit α-epithelial Na(+) channel (α-ENaC) plays a critical role in alveolar fluid clearance. Therefore, the present study is undertaken to investigate the effects of DXM on α-ENaC following H2S exposure. The Sprague Dawley rats were exposed to H2S to establish APE model, in parallel, A549 cells were treated with NaHS to establish cell model. In vivo study, we found that DXM significantly attenuated H2S-induced lung histopathological changes and alveolar fluid clearance decrement, however, these preventive effects of DXM can be obviously counteracted by the mifepristone (MIF), the glucocorticoid receptor (GR) blocker. Moreover, DXM markedly attenuated H2S-mediated α-ENaC down-regulation, and similarly, the process can be partially retarded by MIF. Furthermore, DXM obviously prevented H2S-mediated ERK1/2 activation both in vitro and in vivo study. These results, taken together, suggested that DXM exerted protective effects on H2S-induced APE, and α-ENaC might be a potential therapeutic target for APE induced by H2S.

17β-Estradiol regulates the gene expression of voltage-gated sodium channels: role of estrogen receptor α and estrogen receptor β.

Estradiol (E2) plays a key role in pain modulation, and the biological effects of E2 are transduced by binding estrogen receptors (ERs). Voltage-gated sodium (Nav) channels are responsible for the generation and propagation of action potentials in the membranes of most neurons and excitable cells. Adult dorsal root ganglion (DRG) neurons can express the ERs (ERα and ERβ), and Nav channels (TTX-S: Nav1.1, Nav1.6, and Nav1.7; and TTX-R: Nav1.8, and Nav1.9). Although E2 modulates Nav channel currents, little is known about the molecular mechanisms involved. In this study, we investigate the mRNA expressions of Nav channel subtypes mediated differentially by the ERs in the DRGs of wild-type (WT) and estrogen receptor knockout (αERKO and βERKO) mice. By means of quantitative real-time PCR, we found that the expressions of Nav1.1, Nav1.7, Nav1.8, and Nav1.9 subtypes were elevated in αERKO and βERKO mice, whereas Nav1.6 mRNA decreased in αERKO, but not in βERKO mice. The mRNA expressions of Nav subtypes were increased in E2-treated WT ovariectomized animals. We also found that E2-regulation of Nav1.1 and Nav1.9 mRNA expressions is dependent on ERα, ERβ, and another ER, whereas E2-regulation of Nav1.8 appears to be in an ERβ-dependent manner.