Air freshener could be one of the multiple sources that release volatile organic compounds (VOCs) into the indoor environment. The use of these products may be associated with an increase in the measured level of terpene, such as xylene and other volatile air freshener components, including aldehydes, and esters. Air freshener is usually used indoors, and thus some compounds emitted from air freshener may have potentially harmful health impacts, including sensory irritation, respiratory symptoms, and dysfunction of the lungs. The constituents of air fresheners can react with ozone to produce secondary pollutants such as formaldehyde, secondary organic aerosol (SOA), oxidative product, and ultrafine particles. These pollutants then adversely affect human health, in many ways such as damage to the central nervous system, alteration of hormone levels, etc. In particular, the ultrafine particles may induce severe adverse effects on diverse organs, including the pulmonary and cardiovascular systems. Although the indoor use of air freshener is increasing, deleterious effects do not manifest for many years, making it difficult to identify air freshener-associated symptoms. In addition, risk assessment recognizes the association between air fresheners and adverse health effects, but the distinct causal relationship remains unclear. In this review, the emitted components of air freshener, including benzene, phthalate, and limonene, were described. Moreover, we focused on the health effects of these chemicals and secondary pollutants formed by the reaction with ozone. In conclusion, scientific guidelines on emission and exposure as well as risk characterization of air freshener need to be established.
Nicardipine hydrochloride (NIC) injection has been widely used for emergency treatment of abnormally high blood pressure. However, NIC injection often causes severe peripheral vascular injury. The purpose of the present study was to reduce the NIC-induced cell injury in human vascular endothelial cells by use of clinical agents. The mechanism of NIC-induced cell injury was evaluated by time-lapse microscopic imaging, autophagosome staining with monodansylcadaverine, immunostaining of light chain 3 isoform B (LC-3B) and assessment of cell viability after exposure to NIC with or without an inhibitor of autophagosome formation (3-methyladenine, 3-MA). Results from autophagosome labeling and immunostaining of LC-3B revealed an increase of autophagosomes and LC-3B in NIC-treated cells. NIC-mediated reduction of cell viability was inhibited by 3-methyladenine. Moreover, we found that N-acetylcysteine (NAC) reduced NIC-induced cell injury in human vascular endothelial cells. These findings suggest that NIC causes severe peripheral venous irritation via induction of autophagic cell death and that inhibition of autophagy with NAC could contribute to the reduction of NIC-induced vascular injury.
Environmental biological and chemical agents can modulate innate and acquired immunity in the lung via the stimulation of Toll-like receptors (TLRs). To investigate the effect of environmental chemical agents on the activation of NF-κB and activator protein (AP)-1 subunits and the role of TLR4 signaling in the lung, C3H/HeN and C3H/HeJ (TLR4-defective) mice were exposed to 0 or 50 ppm of toluene for 6 hr/day, 5 days/week for 6 weeks. Some groups of mice were also stimulated with OVA or LPS as a biological agent. The DNA-binding activities of the NF-κB subunits (p50, p52, p65 and RelB) and AP-1 family members (FosB, c-Fos, +c-Jun, JunD) were compared using TransAMTM ELISA kits. Exposure to toluene alone produced no significant changes in both mice. Although stimulation with OVA or LPS alone significantly increased the DNA binding activities of p50 and p52 in C3H/HeN mice, there were no interactions between biological factors and toluene. In the C3H/HeJ mice, stimulation with OVA or LPS increased p65 and p52 binding activity and the combination of exposure to toluene and OVA significantly increased the DNA binding activities of the p65 and p52 in the lung. During AP-1 activation, co-exposure to toluene and OVA increased JunD binding activity in C3H/HeJ mice, while co-exposure to toluene and LPS influenced c-Fos binding activity in C3H/HeN mice. These results indicate that TLR4 may play an important role in activation of NF-κB or AP-1 family following exposure to environmental biological and chemical agents.
Bisphenol A (BPA) is an environmental endocrine disrupter (EED). Previous studies by our group showed that pre- and postnatal administration of low-level BPA induced depression-like behavior in rats. In this study, we evaluated the effects of prenatal BPA on behavioral responses to a predator odor by using a novel cross-form apparatus consisting of 4 plastic chambers. On the first day, nothing was placed into the chambers (Session 1). On the second day, a predator odor (fox odor) was located in separate chambers at 2 opposite corners of the apparatus (Session 2). Pregnant Wistar rats were exposed to low-dose BPA (less than the reference dose) during the 7 days just before birth, and the offspring of the treated rats were evaluated as adults. The locomotor activity and avoidance response of each rat on both test days were compared. The control and BPA groups showed reduced locomotor activity in the presence of the predator odor, but the odor-avoidance response was significant only in the BPA rats. The BPA-exposed rats were obviously sensitive to the predator odor. These results suggest that prenatal BPA exposure has an amplifying effect on avoidance responses to predator odor stress.
In this study, we investigated the in vivo effects of exogenous glutathione and buthionine sulfoximine on arsenic methylation and antioxidant capacity in mice exposed to arsenic via drinking water. Thirty-six female albino mice were randomly divided into six groups. All groups were given free access to drinking water that contained arsenic continuously except the control group. After ten days, mice were treated with different levels of glutathione or buthionine sulfoximine. The levels of the metabolites of arsenic were determined in the liver and urine. The levels of glutathione and total antioxidant capacity were determined in the whole blood and liver. Our results showed that the increase of arsenic species in the liver as well as the decrease of blood and hepatic glutathione and total antioxidant capacity, were all relieved by exogenous glutathione consistently. We also observed the involvement of glutathione in promoting arsenic methylation and urinary elimination in vivo. Increase of total arsenic in the urine was mainly due to the increase of dimethylated arsenic. Furthermore, administration of glutathione increased the first methylation ratio and secondary methylation ratio in the liver and urine, which resulted in the consequent increase of dimethylated arsenic percent and decrease of inorganic arsenic percent in the urine. Opposite effects appeared with the administration of buthionine sulfoximine, a scavenger of glutathione. Our study indicated that exogenous glutathione not only accelerated the methylation and the excretion of arsenic, but also relieve the arsenic-induced oxidative stress. This provides a potential useful chemopreventive dietary component for human populations being at risk of arsenic exposure.
Insulin-like growth factor-1 (IGF-1), with an age-related decline, regulates the proliferation and survival of multiple cell types, particularly stimulates cartilage matrix synthesis, and inhibits matrix degradation. The present study was to investigate the regulatory role of IGF-1 against hydrogen peroxide(H2O2)-induced mitochondrial dysfunction and apoptosis in murine chondrocytic ATDC5 cells. We firstly determined mitochondrial dysfunction and apoptosis in ATDC5 cells which were exposed to H2O2. We then constructed an IGF-1-overexpressed adenovirus (IGF-1-Ad) harboring the IGF-1 coding sequence, and investigated the regulatory role of the overexpressed IGF-1 against the H2O2-induced mitochondrial dysfunction and apoptosis in ATDC5 cells. It was demonstrated that H2O2 treatment promoted the mitochondrial dysfunction, and further reduced the viability and induced apoptosis of ATDC5 cells. However, the IGF-1 overexpression by adenovirus inhibited the H2O2-induced mitochondrial dysfunction and further inhibited the H2O2-promoted apoptosis in ATDC5 cells. In conclusion, the present study found that oxidative stress promoted mitochondrial dysfunction and induced apoptosis in the murine chondrocytic ATDC5 cells, and the adenoviral vector-expressed IGF-1 protected the murine chondrocytic ATDC5 cells against such mitochondrial dysfunction and apoptosis. This study implies the protective role of IGF-1 against the oxidative stress in murine chondrocytic ATDC5 cells and demonstrates the promising anti-oxidative stress effect of the recombinant IGF-1-Ad against oxidative stress in chondrocytic cells.
Exposure to 2,4,6-trinitrotoluene (TNT) causes methemoglobin (metHb) formation, hemolysis and negative heme balance in vivo, but the mechanistic details are poorly understood. In the present study, we examined the participation of metabolic activation in TNT-mediated hematotoxicity. Exposure of rats with TNT (300 mg/kg, i.p.) for 4 days resulted in a decrease of hematocrit value coupled to an increase in metHb formation. The red blood cells treated with 4-hydroxylamino-2,6-dinitrotoluene (HADNT), a metabolite of TNT, underwent readily hemolysis in vitro, whereas such a phenomenon was not seen with TNT. Consistent with this, HADNT is active toward metHb formation and the decrease in thiol content of the globin moiety compared with TNT and its metabolites 4-amino-2,6-dinitrotoluene (ADNT) and 4-acetylamino-2,6-dinitrotoluene (AADNT). Furthermore, interaction of purified rat oxyhemoglobin (oxyHb) with HADNT, but not TNT, ADNT, and AADNT, caused a concentration-dependent production of H2O2 and ferrylhemoglobin (ferrylHb) which is a highly oxidizing state formed by reaction of oxyHb with H2O2. Notably, hemin was released during interaction of oxyHb with HADNT. Taken together, these findings suggest that HADNT is an active metabolite that mediates TNT-induced hematotoxicity via formation of prooxidants such as H2O2 and ferrylHb.
Vascular endothelium is a target of cadmium (Cd) toxicity. Cd exposure has been reported to be associated with vascular disorders. In this study, we aimed to investigate the effects of Cd exposure on markers of endothelial function in human subjects chronically exposed to Cd. Based on blood Cd levels, seventy-five women were categorized into non-exposed, Cd-exposed and severely Cd-exposed groups. Nitrite, L-arginine, asymmetric dimethylarginine (ADMA), and soluble thrombomodulin levels in blood were measured. Nitrite levels were lower in Cd-exposed subjects than non-exposed subjects. Plasma L-arginine decreased while ADMA, an endogenous endothelial nitric oxide synthase (eNOS) inhibitor, increased in Cd-exposed subjects. Soluble thrombomodulin also increased in Cd-exposed subjects. In Cd-exposed subjects, plasma malondialdehyde and protein carbonyl groups increased while the erythrocytic glutathione decreased. Multiple linear regression analysis revealed a negative association between urinary Cd and nitrite levels in erythrocytes. Our research suggests that subjects with chronic Cd exposure have endothelial dysfunction.
Advanced glycation end products (AGEs) by nonenzymatic glycation reactions are extremely accumulated in the diabetic vascular cells, neurons, and glia, and are confirmed to play important role in the pathogenesis of diabetes mellitus -induced cardiovascular complications. Sirt 1, known as mammalian sirtuin, has been recognized to regulate insulin secretion and protect cells against oxidative stress, which is promoted by the accumulated AGEs in cardiovascular cells. In the present study, we treated human endothelial Eahy926 cells with AGEs, and determined the apoptosis induction, caspase activation, the Sirt 1 activity, the expression and acetylation of p53. Then we manipulated Sirt 1 activity with a Sirt 1 activator, Resveratrol (RSV), and a Sirt 1 inhibitor, sirtinol, in the AGE-BSA-treated Eahy926 cells, and then re-evaluated the apoptosis induction, caspase activation, the expression and acetylation of p53. Results demonstrated that AGEs induced apoptosis in the human endothelial Eahy926 cells, by promoting the cytochrome c release, activation of caspase 9/3. Also, the AGE-BSA treatment promoted the total p53 level and acetylated (Ac) p53, but reduced the Sirt 1 level and activity. On the other hand, the Sirt 1 inhibitor/activator not only deteriorated/ameliorated the promotion to p53 level and Ac p53, but also aggravated/inhibited the AGE-induced apoptosis and the promotion to apoptosis-associated signaling molecules. In conclusion, the present study confirmed the apoptosis promotion by AGEs in endothelial Eahy926 cells, by regulating the Sirt 1 activity and p53 signaling, it also implies the protective role of Sirt 1 activator against the AGE-induced apoptosis.
Contradictory results have been reported for in vitro evaluations of whether zinc oxide nanoparticles (ZnO NPs) are cytotoxic. Though there have been reports of ZnO NPs cytotoxicity due to Zn ions released from the nanoparticles, there have also been reports concluding that Zn ions are not cytotoxic. This inconsistency is mostly attributed to the types of cells used. In this research, we investigated the difference in the level of ZnO NPs cytotoxicity due to culturing conditions. The sensitivity of human lung epithelial cells to ZnO NPs cytotoxicity differed depending on the dispersing medium, physiological state of the cells resulting from their growth stage, and composition of the medium. Further, with regard to the toxicity of ZnO NPs, NPs internalized into cells had a greater cytotoxic effect than Zn ions released from ZnO NPs. Instead of inducing cell death, ZnO NPs internalized into cells slowed the rate of cell proliferation. Furthermore, the cytotoxicity of ZnO NPs depended greatly on the concentration of calcium ions (Ca2+) in the medium. When the concentration of Ca2+ was low, the cytotoxicity of ZnO NPs increased markedly. However, the toxicity of ZnO NPs was mitigated by the addition of CaCl2 to the medium. Global gene expression analysis revealed that Ca2+-induced upregulation of cell cycle functionscould be attributable to the mitigation of ZnO NP toxicity by Ca2+.
Mechanisms underlining oxidative stress-induced injury to cardiomyocytes during myocardial infarction (MI) or acute ischemia/reperfusion (I/R) are not well recognized. Forkhead box O (FOXO) transcription factors have been defined as critical mediators of oxidative stress resistance in multiple cell types, but their cardioprotective functions have not been reported previously. In the present study, we investigated the promotion to FOXO1 by the treatment with hydrogen peroxide (H2O2) during the H2O2-induced apoptosis in cardiomyocyte H9c2 cells. We then silenced FOXO1 with FOXO1-specific siRNA, and re-evaluated the H2O2-induced apoptosis. In addition, we also examined the H2O2-induced autophagy and the autophagy induction post FOXO1 silence. Results demonstrated that H2O2 induced a significantly high level of apoptosis in H9c2 cells. Interestingly, the FOXO1 in both mRNA and protein levels were not significantly regulated, however, the phosphorylated form of FOXO1 was significantly promoted in the H2O2-treated H9c2 cells. On the other hand, post the significant knockout of FOXO1 with the transfection with FOXO1-specific siRNA, the apoptosis induction was more significant in H9c2 cells subjected to H2O2. In addition, we found a significantly higher level of autophagy induction in the H2O2-treated H9c2 cells. However, the autophagy was markedly reduced by the knockout of FOXO1. In summary, these data support the critical role for FOXO1 in promoting cardiomyocytes against oxidative stress probably through inducing autophagy.
Based on the findings of epidemiological studies in Japan that occupational exposure to 1,2-dichloropropane (1,2-DCP) was associated with increased cholangiocarcinomas, 1,2-DCP has recently been classified as being carcinogenic to humans (Group 1). However, the cholangiocarcinogenicity of 1,2-DCP has not been demonstrated experimentally, and it was negative for cholangiocarcinogenicity in rats and mice. The present study determined the effects of 1,2-DCP on N-nitrosobis(2-oxopropyl)amine (BOP)-induced cholangiocarcinogenesis in male hamsters. We found that 1,2-DCP did not enhance the development of BOP-induced atypical biliary hyperplasia and did not induce any lesions in liver bile duct when administered alone. Notably, 1,2-DCP had no effect on the proliferative activity of bile duct epithelial cells regardless of BOP-initiation. These results demonstrate that 1,2-DCP lacks promoting effects on BOP-induced cholangiocarcinogenesis and suggest the possibility that 1,2-DCP is not cholangiocarcinogenic to the hamster in the present model. In addition, 1,2-DCP also lacks promoting effects on pancreatic, lung, and renal carcinogenesis. As the occurrence of occupational cholangiocarcinomas in Japan might be attributed to exposure to multiple chemicals, the results of the present study indicate that it will be necessary to determine the cholangiocarcinogenic effects of concurrent exposure of 1,2-DCP and the other halogen solvents to which workers with cholangiocarcinomas were exposed.
Ochratoxin A (OTA), a toxin produced by several species of Aspergillus and Penicillium, is one of the most abundant food-contaminating mycotoxins. The International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen. Our previous study showed that there were high levels of OTA contaminations in wheat in the areas with high incidence of esophageal cancer in north China. This finding suggests that exposure to low levels of OTA may be a critical etiological factor for esophageal cancer in these areas. However, up to now, the potential biological effects of OTA on human esophageal epithelial cells have not been fully elucidated. In the present study, we explored the cytotoxicity of OTA in human esophageal epithelium immortalized cells (Het-1A). We found that OTA could induce DNA strand breaks and chromosome aberrations in Het-1A cells. OTA-induced DNA damage was followed by G2 cell cycle arrest, and down-regulation of Cdc2 and cyclinB1 contributed to the OTA-induced G2 arrest in Het-1A cells. Additionally, OTA induced apoptosis in Het-1A cells by activating caspase-3. In conclusion, our results indicated that OTA could induce DNA damage, G2 arrest and apoptosis in Het-1A cells, which may be involved in the esophageal toxicity of OTA.
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