•Vanadium(IV) complex with 4-chlorodipicolinic acid (VOdipic-Cl) inhibits lipid storage.•VOdipic-Cl regulates the transcriptional factors and their downstream lipogenic proteins.•VOdipic-Cl activates liver kinase B1 AMP-activated protein kinase signaling pathway.Our previous studies demonstrated that vanadium(IV) complex with 4-chlorodipicolinic acid (VOdipic-Cl) alleviates lipid abnormalities in streptozotocin (STZ)-induced diabetic rats. However, the molecular mechanisms are not fully understood. In the present study, the effect of VOdipic-Cl on adipogenesis and mechanisms of action in 3T3-L1 preadipocytes were investigated. The 3T3-L1 preadipocytes were induced to differentiate in the presence or absence of VOdipic-Cl for 8 days. The cells were determined for proliferation, differentiation, lipid accumulation as well as the protein expressions of molecular targets that are involved in fatty acid synthesis. The results demonstrated that VOdipic-Cl at concentrations ranging from 2.5 μM to 10 μM reduced the intracellular lipid content by 10%, 22% and 30% compared to control. VOdipic-Cl down-regulated the expression of peroxisome proliferator-activated receptor (PPARγ), CCAAT element binding protein a (C/EBPα), sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase (FAS) and fatty acid-binding protein 4 (FABP4) and activated the phosphorylation of acetyl coenzyme A carboxylase (ACC), adenosine monophosphate-activated protein kinase (AMPK) and liver kinase B1 (LKB1) in a dose-dependent manner. Further studies showed that AMPK small interfering RNA (siRNA) markedly up-regulated PPARγ, C/EBPα, FAS and FABP4 expression in the presence of VOdipic-Cl, respectively. When LKB1 was silenced with siRNA, the effect of VOdipic-Cl on AMPK phosphorylation was diminished. Taken together, these results suggested that VOdipic-Cl can inhibit 3T3-L1 preadipocyte differentiation and adipogenesis through activating the LKB1/AMPK-dependent signaling pathway. These findings raise the possibility that VOdipic-Cl may be a promising therapy in treatment of obesity.Vanadium(IV) complex with 4-chlorodipicolinic acid (VOdipic-Cl) inhibits 3T3-L1 preadipocyte differentiation and adipogenesis by regulating the transcriptional factors and their downstream lipogenic targets via the activation of liver kinase B1 (LKB1)/adenosine monophosphate-activated protein kinase (AMPK) signaling pathway.

•VOSO4 enhances glucose uptake in HepG2 cells.•VOSO4 increases IR and Akt phosphorylation in HepG2 cells.•VOSO4 triggers increase in intracellular reactive oxygen species (ROS) generation.•·OH may be involved in activation of IR/Akt signaling pathway for glucose uptake caused by VOSO4.The insulin-mimetic and anti-diabetic properties of vanadium and related compounds have been well documented both in vitro and in vivo. However, the molecular basis of the link between vanadium and the insulin signaling pathway in diabetes mellitus is not fully described. We investigated the effects of reactive oxygen species (ROS) induced by oxidovanadium(IV) sulfate (VOSO4) on glucose uptake and the insulin signaling pathway in human hepatoma cell line HepG2. Exposure of cells to VOSO4 (5–50 μM) resulted in an increase in glucose uptake, insulin receptor (IR) and protein kinase B (Akt) phosphorylation and intracellular ROS generation. Using Western blot, we found that catalase and sodium formate, but not superoxide dismutase, prevented the increase of hydroxyl radical (·OH) generation and significantly decreased VOSO4-induced IR and Akt phosphorylation. These results suggest that VOSO4-induced ·OH radical, which is a signaling species, promotes glucose uptake via the IR/Akt signaling pathway.Vanadium compounds with various oxidation states have different anti-diabetic effects due to vanadium-mediated generation of ROS as signaling molecules to activate cellular stress-sensitive signaling pathways.

Vanadium compounds exert various insulin-mimetic and anti-diabetic effects both in vitro and in vivo. Vanadium(III, IV, V)-chlorodipicolinate (Vdipic-Cl) compounds, including H[VIII(dipic-Cl)2] · 5H2O (V3dipic-Cl), VIVO(dipic-Cl)(H2O)2 (V4dipic-Cl) and K[VVO2(dipic-Cl)] (V5dipic-Cl), were synthesized with the indicated oxidation states. The present study was conducted to investigate if chemical valence and anti-oxidation effects of vanadium compounds are involved in the anti-diabetic effects observed in streptozotocin (STZ)-induced diabetic rats treated with these vanadium compounds. V3dipic-Cl, V4dipic-Cl, V5dipic-Cl, inorganic vanadium salts vanadyl sulfate (VOSO4) or sodium metavanadate (NaVO3) were orally administered in drinking water (50 μgV/ml) to STZ-induced diabetic rats for 28 days. The results showed that Vdipic-Cl treatment significantly improved hyperglycemia and glucose intolerance, as well as increased hepatic glycogen synthesis in diabetic rats. The mRNA levels of key glycolytic enzymes in liver, phosphoenolpyruvate carboxykinase (PEPCK), glucokinase (GK), and L-pyruvate kinase (L-PK) altered in diabetic animals were significantly restored towards normal values by treatment with some of the vanadium compounds. Moreover, the diabetes elevated activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in serum were significantly decreased after treatment with Vdipic-Cl complexes. Furthermore, treatment of diabetic rats with V4dipic-Cl and V5dipic-Cl compounds significantly reduced malondialdehyde (MDA) production and increased glutathione peroxidase (GSH-Px) and catalase (CAT) activities. These data suggest that vanadium compounds with the indicated chemical valence promote glycogen synthesis and recover suppressed glycolysis in the liver of diabetic rats due to their capacity to reduce oxidative stress by stimulating antioxidant enzymes.Vanadium compounds with varying oxidation states may have different therapeutic benefits in the treatment of diabetes due to the differing capacity to reduce oxidative stress by stimulating antioxidant enzymes.

Our group was the first one reporting that autophagy could be triggered by airborne fine particulate matter (PM) with a mean diameter of less than 2.5 μm (PM2.5) in human lung epithelial A549 cells, which could potentially lead to cell death. In the present study, we further explored the potential interactions between autophagy and apoptosis because it was well documented that PM2.5 could induce apoptosis in A549 cells. Much to our surprise, we found that PM2.5-exposure caused oxidative stress, resulting in activation of multiple cell death pathways in A549 cells, that is, the tumor necrosis factor-alpha (TNF-α)-induced pathway as evidenced by TNF-α secretion and activation of caspase-8 and -3, the intrinsic apoptosis pathway as evidenced by increased expression of pro-apoptotic protein Bax, decreased expression of anti-apoptotic protein Bcl-2, disruption of mitochondrial membrane potential, and activation of caspase-9 and -3, and autophagy as evidenced by an increased number of double-membrane vesicles, accompanied by increases of conversion and punctuation of microtubule-associated proteins light chain 3 (LC3) and expression of Beclin 1. It appears that reactive oxygen species (ROS) function as signaling molecules for all the three pathways because pretreatment with N-acetylcysteine, a scavenger of ROS, almost completely abolished TNF-α secretion and significantly reduced the number of apoptotic and autophagic cells. In another aspect, inhibiting autophagy with 3-methyladenine, a specific autophagy inhibitor, enhanced PM2.5-induced apoptosis and cytotoxicity. Intriguingly, neutralization of TNF-α with an anti-TNF-α special antibody not only abolished activation of caspase-8, but also drastically reduced LC3-II conversion. Thus, the present study has provided novel insights into the mechanism of cytotoxicity and even pathogenesis of diseases associated with PM2.5 exposure.

It has been well documented in in vitro studies that ambient airborne particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM2.5) is capable of inducing oxidative stress, which plays a key role in PM2.5-mediated cytotoxicity. Although nuclear factor erythroid-2-related factor 2 (Nrf2) has been shown to regulate the intracellular defense mechanisms against oxidative stress, a potential of the Nrf2-mediated cellular defense against oxidative stress induced by PM2.5 remains to be determined. This study was aimed to explore the potential signaling pathway of Nrf2-mediated defense mechanisms against PM2.5-induced oxidative stress in human type II alveolar epithelial A549 cells. We exposed A549 cells to PM2.5 particles collected from Beijing at a concentration of 16 μg/cm2. We observed that PM2.5 triggered an increase of intracellular reactive oxygen species (ROS) in a time-dependent manner during a period of 2 h exposure. We also found that Nrf2 overexpression suppressed and Nrf2 knockdown increased PM2.5-induced ROS generation. Using Western blot and confocal microscopy, we found that PM2.5 exposure triggered significant translocation of Nrf2 into nucleus, resulting in AKT phosphorylation and significant transcription of ARE-driven phases II enzyme genes, such as NAD(P)H:quinone oxidoreductase (NQO-1), heme oxygenase-1 (HO-1), and glutamate-cysteine ligase catalytic subunit (GCLC) in A549 cells. Evaluation of signaling pathways showed that a phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002), but not an ERK 1/2 inhibitor (PD98059) or a p38 MAPK (SB203580), significantly down-regulated PM2.5-induced Nrf2 nuclear translocation and HO-1 mRNA expression, indicating PI3K/AKT is involved in the signaling pathway leads to the PM2.5-induced nuclear translocation of Nrf2 and subsequent Nrf2-mediated HO-1 transcription. Taken together, our results suggest that PM2.5-induced ROS may function as signaling molecules to activate Nrf2-mediated defenses, such as HO-1 expression, against oxidative stress induced by PM2.5 through the PI3K/AKT signaling pathway.

•PM2.5 exposure increases ROS production, which up-regulates a lncRNA named loc146880.•Loc146880 increases the autophagy of A549 cells.•PM2.5-induced ROS and loc146880 promote cell migration, invasion and EMT.BackgroundEvidence shows that individuals who are under long-term exposure to environmental PM2.5 are at increased risk of lung cancer. Various laboratory experiments also suggest several mechanistic links between PM2.5 exposure and lung carcinogenesis. However, a long non-coding RNA (lncRNA) mediated pathogenic change after PM2.5 exposure and its potential roles in tumorigenesis and disease progression have not been reported.MethodsCytotoxicity induced by PM2.5 was assessed by using scanning electron microscopy and transmission electron microscopy. ROS generation, autophagy, and metastasis induced by PM2.5 were detected by using comprehensive approaches. Expression of lncRNA-loc146880 and lc3b (autophagy marker) in A549 cells, lung tissue and serum were determined by RT-PCR and Western blotting.ResultsPM2.5 could be internalized into lung cancer cells, resulting in marked increases in ROS levels and autophagy. ROS may be responsible for increased expression of loc146880 which further up-regulates autophagy. Both loc146880 and autophagy could promote lung tumor cell migration, invasion and EMT. In addition, a positive correlation was observed between loc146880 expression and lc3b levels in tumor tissues and serum of lung cancer patients.ConclusionTaken together, our data suggest that PM2.5 exposure induces ROS, which activates loc146880 expression. The lncRNA, in turn, up-regulates autophagy and promotes the malignant behaviors of lung cancer cells.General significanceThe results show the toxicological effects of PM2.5 in lung tumor progression and metastasis.Download high-res image (48KB)Download full-size image

•PM1 with high concentrations of transition metals induces oxidative stress.•Transition metals are responsible for the higher toxicity of sPM1 compared to uPM1.•Metal-containing sPM1 significantly induces autophagy as compared to uPM1.•sPM1 is more potent in inhibiting surfactant protein B and C expressions than uPM1.BackgroundThere is a strong link between smaller air pollution particles and a range of serious health conditions. Thus, there is a need for understanding the impacts of airborne fine particulate matter (PM) with an aerodynamic diameter of < 1 μm (PM1) on lung alveolar epithelial cells. In the present study, mouse lung epithelial type II cell MLE-12 cells were used to examine the intracellular oxidative responses and the surfactant protein expressions after exposure to various concentrations of PM1 collected from an urban site and a steel-factory site (referred as uPM1 and sPM1 hereafter, respectively).MethodsPhysicochemical characterization of PM1 was performed by using scanning electron microscopy and transmission electron microscopy. Cytotoxicity and autophagy induced by PM1 were assessed by using comprehensive approaches after MLE-12 cells were exposed to different concentrations of PM1 for various times. Expression of surfactant proteins B and C in MLE-12 cells was determined by Western blotting.ResultsAll of the tested PM1 induced cytotoxicity evidenced by significant decrease of cell viability and increase of lactate dehydrogenase (LDH) release in a time- and concentration-dependent manner in the exposed cells compared with the unexposed cells. A similar pattern of increase of intercellular reactive oxygen species (ROS) generation and decrease of superoxide dismutase (SOD) and catalase (CAT) activities was also observed. PM1-induced autophagy was evidenced by an increase in microtubule-associated protein light chain-3 (LC3) puncta, accumulation of LC3II, and increased levels of beclin1. Data from Western blotting showed significant decrease of surfactant protein B and C expressions. Relatively high concentrations of transition metals, including Fe, Cu and Mn, may be responsible for the higher toxicity of sPM1 compared with uPM1. Moreover, pretreatment with N-acetylcysteine (NAC) or Chelex (a metal chelating agent, which removes a large suite of metals from PM1) prevented the increase of PM1-inudced ROS generation and autophagy, and down-regulated the expression of surfactant proteins B and C.ConclusionPM1, particularly PM1 with high concentrations of transition metals, such as Fe, Cu and Mn, induces oxidative damage and autophagy, as well as inhibits surfactant protein B and C expressions in lung alveolar type II epithelial cells.General significanceThis study will help to understand the mechanism underlying the toxicological effects of PM1 in lung alveolar type II epithelial cells. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

•Short-term exposure of PM2.5 directly affected macrophage polarization.•PM2.5 treatment increased M1 polarization by ROS pathway.•PM2.5 exposure inhibited M2 polarization partially by mTOR-dependent pathway.BackgroundExposure of atmospheric particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) is epidemiologically associated with illnesses. Potential effects of air pollutants on innate immunity have raised concerns. As the first defense line, macrophages are able to induce inflammatory response. However, whether PM2.5 exposure affects macrophage polarizations remains unclear.MethodsWe used freshly isolated macrophages as a model system to demonstrate effects of PM2.5 on macrophage polarizations. The expressions of cytokines and key molecular markers were detected by real-time PCR, and flow cytometry. The specific inhibitors and gene deletion technologies were used to address the molecular mechanisms.ResultsPM2.5 increased the expression of pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor alpha (TNFα). PM2.5 also enhanced the lipopolysaccharide (LPS)-induced M1 polarization even though there was no evidence in the change of cell viability. However, PM2.5 significantly decreased the number of mitochondria in a dose dependent manner. Pre-treatment with NAC, a scavenger of reactive oxygen species (ROS), prevented the increase of ROS and rescued the PM2.5-impacted M1 but not M2 response. However, mTOR deletion partially rescued the effects of PM2.5 to reduce M2 polarization.ConclusionsPM2.5 exposure significantly enhanced inflammatory M1 polarization through ROS pathway, whereas PM2.5 exposure inhibited anti-inflammatory M2 polarization through mTOR-dependent pathway.General significanceThe present studies suggested that short-term exposure of PM2.5 acts on the balance of inflammatory M1 and anti-inflammatory M2 macrophage polarizations, which may be involved in air pollution-induced immune disorders and diseases. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.Download high-res image (181KB)Download full-size image

•PFOS is capable to cause hepatotoxicity.•PFOS triggers ROS generation and induces apoptosis both in vivo and in vitro assays.•PFOS-induced ROS inhibits Nrf2 expression and its transactivation function.•PFOS promotes miR155 expression in liver and HepG2 cells.•miR-155 is involved in PFOS-induced hepatotoxicity by disrupting Nrf2/ARE pathway.Studies demonstrated that perfluorooctane sulfonate (PFOS) tends to accumulate in the liver and is capable to cause hepatomegaly. In the present study, we investigated the roles of miR-155 in PFOS-induced hepatotoxicity in SD rats and HepG2 cells. Male SD rats were orally administrated with PFOS at 1 or 10 mg/kg/day for 28 days while HepG2 cells were treated with 0–50 μM of PFOS for 24 h or 50 μM of PFOS for 1, 3, 6, 12 or 24 h, respectively. We found that PFOS significantly increased the liver weight and serum alanine transaminase (ALT) and aspartate amino transferase (AST) levels in rats. Morphologically, PFOS caused actin filament remodeling and endothelial permeability changes in the liver. Moreover, PFOS triggered reactive oxygen species (ROS) generation and induced apoptosis in both in vivo and in vitro assays. Immunoblotting data showed that NF-E2-related factor-2 (Nrf2) expression and activation and its target genes were all suppressed by PFOS in the liver and HepG2 cells. However, PFOS significantly increased miR-155 expression. Further studies showed that pretreatment of HepG2 cells with catalase significantly decreased miR-155 expression and substantially increased Nrf2 expression and activation, resulting in reduction of PFOS-induced cytotoxicity and oxidative stress. Taken together, these results indicated that miR-155 plays an important role in the PFOS-induced hepatotoxicity by disrupting Nrf2/ARE signaling pathway.Download high-res image (62KB)Download full-size image