The objectives of this work were to evaluate the direct effects of diallysulfide (DAS) and diallyldisulfide (DADS), two major organosulfur compounds of garlic oil, on mitochondrial function and integrity, by using isolated mouse liver mitochondria in a cell-free system. DADS produced concentration-dependent mitochondrial swelling over the range 125–1000 μM, while DAS was ineffective. Swelling experiments performed with de-energized or energized mitochondria showed similar maximal swelling amplitudes. Cyclosporin A (1 μM), or ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA, 1 mM) were ineffective in inhibiting DADS-induced mitochondrial swelling. DADS produced a minor (12%) decrease in mitochondrial membrane protein thiols, but did not induce clustering of mitochondrial membrane proteins. Incubation of mitochondria with DADS (but not DAS) produced an increase in the oxidation rate of 2′,7′ dichlorofluorescein diacetate (DCFH-DA), together with depletion of reduced glutathione (GSH) and increased lipid peroxidation. DADS (but not DAS) produced a concentration-dependent dissipation of the mitochondrial membrane potential, but did not induce cytochrome c release. DADS-dependent effects, including mitochondrial swelling, DCFH-DA oxidation, lipid peroxidation and loss of mitochondrial membrane potential, were inhibited by antioxidants and iron chelators. These results suggest that DADS causes direct impairment of mitochondrial function as the result of oxidation of the membrane lipid phase initiated by the GSH- and iron-dependent generation of oxidants.
Diallyl disulfide; Diallyl sulfide; Garlic; Mitochondria; Oxidative stress
Lumen-to-cell transport, cellular accumulation, and toxicity of L-cysteine (Cys), glutathione (GSH) and N-acetylcysteine (NAC) S-conjugates of methylmercury (CH3Hg+) were evaluated in isolated, perfused rabbit proximal tubular segments. When these conjugates were perfused individually through the lumen of S2 segments of the proximal tubule it was found that Cys-S-CH3Hg and GSH-S-CH3Hg were transported avidly, while NAC-S-CH3Hg was transported minimally. In addition, 95% of the 203Hg taken up by the tubular cells was associated with precipitable proteins of the tubular extract, while very little was found in the acid-soluble cytosol extract. No visual cellular pathological changes were observed during 30 min of study. Luminal uptake of Cys-S-CH3Hg was temperature-dependent and inhibited significantly by the amino acids L-methionine and L-cystine. Rates of luminal uptake of GSH-S-CH3Hg were twice as great as that of Cys-S-CH3Hg and uptake was inhibited significantly (74%) by the presence of acivicin. When 2,3-bis(sulfanyl)propane-1-sulfonate (DMPS) was added to the bathing or luminal fluid, luminal uptake of Cys-S-CH3Hg was diminished significantly. Overall, our data indicate that Cys-S-CH3Hg is likely a transportable substrate of one or more amino acid transporters (such as system B0,+ and system b0,+) involved in luminal absorption of L-methionine and L-cystine along the renal proximal tubule. In addition, GSH-S-CH3Hg appears to be degraded enzymatically to Cys-S-CH3Hg, which can then be taken up at the luminal membrane. By contrast NAC-S-CH3Hg and Cys-S-CH3Hg (in the presence of DMPS) are not taken up avidly at the luminal membrane of proximal tubular cells, thus promoting the excretion of CH3Hg+ into the urine.
Thiol S-conjugates; Methylmercury; Membrane Transport; Renal Proximal Tubular Segments; Rabbit; Cystine; Cysteine; Methionine; 2, 3-bis(sulfanyl)propane-1-sulfonate (DMPS); amino acid transporters; molecular mimicry
Previous studies in humans and animals have suggested a possible association between lead (Pb) exposure and the etiology of Alzheimer’s disease (AD). Animals acutely exposed to Pb display an over-expressed amyloid precursor protein (APP) and the ensuing accumulation of beta-amyloid (Aβ) in brain extracellular spaces. This study was designed to examine whether in vivo Pb exposure increased brain concentrations of Aβ, resulting in amyloid plaque deposition in brain tissues. Human Tg-SWDI APP transgenic mice, which genetically over-express amyloid plaques at age of 2-3 months, received oral gavages of 50 mg/kg Pb acetate once daily for 6 wk; a control group of the same mouse strain received the same molar concentration of Na acetate. ELISA results revealed a significant increase of Aβ in the CSF, brain cortex and hippocampus. Immunohistochemistry displayed a detectable increase of amyloid plaques in brains of Pb-exposed animals. Neurobehavioral test using Morris water maze showed an impaired spatial learning ability in Pb-treated mice, but not in C57BL/6 wild type mice with the same age. In vitro studies further uncovered that Pb facilitated Aβ fibril formation. Moreover, the synchrotron X-ray fluorescent studies demonstrated a high level of Pb present in amyloid plaques in mice exposed to Pb in vivo. Taken together, these data indicate that Pb exposure with ensuing elevated Aβ level in mouse brains appears to be associated with the amyloid plaques formation. Pb apparently facilitates Aβ fibril formation and participates in deposition of amyloid plaques.
Lead or Pb; beta-amyloid or Aβ; amyloid plaques; Tg-SWDI mouse; fibril formation; X-ray fluorescence or XRF; hippocampus
B(a)P; Signaling Pathway; Cell cycle; c-Jun; Akt; p53
Acetaminophen (APAP) overdose leads to severe hepatotoxicity, increased oxidative stress and mitochondrial dysfunction. S-adenosyl-L-methionine (SAMe) protects against APAP toxicity at a mmol/kg equivalent dose to N-acetylcysteine (NAC). SAMe acts as a principle biological methyl donor and participates in polyamine synthesis which increase cell growth and has a role in mitochondrial protection. The purpose of the current study tested the hypothesis that SAMe protects against APAP toxicity by maintaining critical antioxidant enzymes and markers of oxidative stress. Male C57Bl/6 mice were treated with vehicle (Veh; water 15 ml/kg, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg, ip), and SAMe + APAP (SAMe given 1 h following APAP). Liver was collected 2 and 4 h following APAP administration; mitochondrial swelling as well as hepatic catalase, glutathione peroxidase (GPx), glutathione reductase, and both Mn- and Cu/Zn-superoxide dismutase (SOD) enzyme activity were evaluated. Mitochondrial protein carbonyl, 3-nitrotyrosine cytochrome c leakage were analyzed by Western blot. SAMe significantly increased SOD, GPx, and glutathione reductase activity at 4 h following APAP overdose. SAMe greatly reduced markers of oxidative stress and cytochrome C leakage following APAP overdose. Our studies also demonstrate that a 1.25 mmol/kg dose of SAMe does not inhibit CYP 2E1 enzyme activity. The current study identifies a plausible mechanism for the decreased oxidative stress observed when SAMe is given following APAP.
S-adenosyl-L-methionine; Acetaminophen; Hepatotoxicity; Oxidative stress; Antioxidant; Nitrotyrosine
Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5 μm, PM2.5) air pollution to increased morbidity and mortality of cardiovascular diseases in the general population, but the biologic mechanisms of these associations are yet to be elucidated. In this study, we aimed to evaluate the relationship between daily variations in exposure to PM2.5 and inflammatory responses in mice during and for 2 months after the Beijing Olympic Games. Male C57BL/6 mice were exposed to Beijing PM2.5 or filtered air (FA) in 2008 during the 2 months of Beijing Olympic and Paralympic Games, and for 2 months after the end of the Games. During the Games, circulating monocyte chemoattractant protein 1 and interleukin 6 were increased significantly in the PM2.5 exposure group, when compared with the FA control group, although there were no significant inter-group differences in tumor necrosis factor α or interferon γ, or in macrophages, neutrophils or lymphocytes in the spleen or thymus between these 2 groups. However, macrophages were significantly increased in the lung and visceral fat with increasing PM2.5. After the Olympic Games, there were no significant PM2.5-associated differences for macrophages, neutrophils or lymphocytes in the thymus, but macrophages were significantly elevated in the lung, spleen, subcutaneous and visceral fat with increasing PM2.5, and the numbers of macrophages were even higher after than those during the Games. Moreover, the number of neutrophils was markedly higher in the spleen for the PM2.5-exposed- than the FA-group. These data suggest that short-term increases in exposure to ambient PM2.5 leads to increased systemic inflammatory responses, primarily macrophages and neutrophils in the lung, spleen, and visceral adipose tissue. Short-term air quality improvements were significantly associated with reduced overall inflammatory responses.
air pollution; inflammation; PM2.5
Microsomal cytochrome P450 (P450) enzymes, which are important in the metabolism of carcinogens, are expressed in both epithelial and stromal cells in the mammary gland. The aim of this study was to investigate the roles of mammary epithelial P450 enzymes in the bioactivation and disposition of 7,12-dimethylbenz(a)anthracene (DMBA), a breast carcinogen, in the mammary gland. A new mouse model (named MEpi-Cpr-null) was produced, wherein P450 activities in the mammary epithelial cells are suppressed through tissue-specific deletion of the gene for P450 reductase (Cpr), an enzyme required for the activities of all microsomal P450 enzymes. Comparisons between wild-type and MEpi-Cpr-null mice showed that the tissue-specific deletion of Cpr in the mammary epithelial cells was accompanied by significant increases in the levels of DMBA and DMBA-DNA adduct in the mammary gland following a single intraperitoneal injection of DMBA at 50 mg/kg. Immunohistochemical and immunoblot analysis further revealed greater induction of CYP1B1 expression by the DMBA treatment in the mammary stroma of the MEpi-Cpr-null mice than in that of the WT mice. These findings not only demonstrate that the epithelial P450 enzymes play important roles in the clearance of DMBA, but also suggest that P450 enzymes in both mammary epithelial and stromal cells contribute to carcinogen-mediated DNA damage.
Cytochrome P450; cytochrome P450 reductase; gene knockout; mammary gland; 7,12-dimethylbenz[a]anthracene; DNA adduct; mice
Neuron specific enolase (ENO2, γ-enolase) is a biomarker used to help identify neuroendocrine differentiation in tumors. This laboratory has shown that ENO2 might be a biomarker for exposure to cadmium and arsenite. In this study these observations are extended to the urothelial cell, where environmental exposures are strongly linked to urothelial cancer. The UROtsa urothelial cell line and its Cd+2- and As+3-transformed counterparts were used as the model. Acute exposure of the UROtsa cells to both As+3- and Cd+2-caused significant increases in ENO2 expression. Treatment with the histone deacetlyase inhibitor was also shown to significantly increase the expression of ENO2 mRNA. The expression of ENO2 was significantly elevated in the Cd+2- and As+3-transformed UROtsa cells and tumor transplants. In contrast, ENO1, was unaffected by exposure to As+3 or Cd+2. Immunofluorescence showed ENO2 associated with both the nucleus and cytoplasm and cytoplasmic ENO2 co-localized with ENO1. The findings extend the evidence suggesting a link between As+3 and Cd+2 exposure and neuroendocrine differentiation in tumors. The results suggest that ENO2 might be a biomarker of human exposure to Cd+2 and As+3 that operates through histone modification.
arsenic; cadmium; urothelial cancer; UROtsa; enolase; biomarker
Carbonyl reductase 1 (CBR1) reduces various xenobiotic carbonyl substrates to corresponding alcohol metabolites. Here we demonstrated that benzo[a]pyrene (B[a]P), a potent pro-carcinogen and predominant polycyclic aromatic hydrocarbon (PAH) compound in cigarette smoke and air pollutants, upregulates CBR1 gene expression in vitro and in vivo, and that a proximal xenobiotic response elements (XRE) motif (−122XRE) mediates the induction effect of B[a]P. First, we observed 46% and 50% increases in CBR1 mRNA and CBR1 protein levels, respectively, in human lung tissue samples from smokers compared to never-smokers. Second, we detected 3.0-fold (p < 0.0001) induction of CBR1 mRNA and 1.5-fold (p < 0.01) induction of CBR1 protein levels in cells of the human lung cancer cell line A549 incubated with 2.5µM B[a]P for 24 hours. Third, results from experiments with CBR1 promoter constructs indicated that a proximal XRE motif (−122XRE) mediates induction of reporter activity in response to B[a]P. Furthermore, we detected enhanced nuclear translocation of aryl hydrocarbon receptor (AhR) following B[a]P exposure in A549 cells. Finally, we demonstrated increased binding of specific protein complexes to −122XRE in nuclear extracts from B[a]P-treated cells and the presence of the AhR/Arnt complex in the specific nuclear protein−122XRE complexes.
Human Carbonyl Reductase 1 (CBR1); benzo[a]pyrene; cigarette smoke metabolism
Prior research suggests that sex hormones and metabolic changes, such as obesity and hyperglycemia, can alter renal transporter expression in rodents. The purpose of this study was to characterize the expression of kidney efflux transporters and regulatory transcription factors in response to Type I diabetes and pregnancy. Female C57BL/6 mice were treated with multiple low doses of streptozotocin (STZ) to induce hyperglycemia and then mated with normoglycemic male mice. Transporter mRNA and protein expression were quantified in kidneys from vehicle- and STZ-treated non-pregnant and pregnant mice on gestation day 14. Pregnancy decreased the expression of Mdr1b, Mrp4, and 5 proteins and increased the mRNA and protein expression of Mrp3 by 50 to 60%. STZ treatment elevated Mrp1, 2, 4, and 5 and reduced Mrp3, 6, and Mdr1b mRNA and/or protein in non-pregnant mice. Pregnancy had little effect on STZ-mediated changes in renal efflux transporter expression. Transcriptional profiles of Hnf1α, PXR, AhR, and Nrf2 were altered in patterns similar to some efflux transporters suggesting potential involvement in their regulation. Taken together, these results suggest that renal drug efflux transporters and regulatory signaling pathways are altered by endocrine and metabolic changes that occur during pregnancy and Type I diabetes.
Diabetes; Mrp; renal transporters; kidney; pregnancy
While waterpipe tobacco smoking has become a global phenomenon, its potential health consequences are poorly understood. In this manuscript, we report the in-vitro mutagenicity of waterpipe smoke condensate (WSC), the alteration in cellular parameters of lung alveolar cells in response to WSC exposure and discuss the implication of cellular responses in the pathophysiology of chronic obstructive pulmonary disease (COPD).
The mainstream WSC was generated using a standard laboratory machine protocol. We assessed its mutagenicity using Ames test. In addition, we studied the effect of WSC on the proliferation and cell cycle of alveolar type II cells and vascular endothelial cells. We also assessed the effect of WSC on the expression of genes involved in cell cycle arrest and inflammation.
Within the range of tested doses, WSC did not elicit sufficient response to be considered mutagenic in any of the strains tested (TA98, TA100, TA102, and TA97a) but were found to be toxic for strains TA97a and TA102 at the highest tested doses. However, WSC induced cell cycle arrest and cellular senescence mediated by the p53-p21 pathway. Also our study indicated that WSC induced an increase in the transcriptional expression of matrix metalloproteinases, MMP-2 and MMP-9 and an immune response regulator, Toll Like Receptor-4.
The data reported here represent the first in vitro demonstration of the effect of waterpipe smoke on cellular parameters providing evidence of the potential involvement of WPS in the pathogenesis of COPD through impairing cellular growth and inducing inflammation.
waterpipe smoke; mutagenicity; cytotoxicity; inflammation; alveolar lung cells; COPD
Endoplasmic reticulum (ER) stress refers to a condition of accumulation of unfolded or misfolded proteins in the ER lumen, which is known to activate an intracellular stress signaling termed Unfolded Protein Response (UPR). A number of pharmacologic reagents or pathophysiologic stimuli can induce ER stress and activation of the UPR signaling, leading to alteration of cell physiology that is associated with the initiation and progression of a variety of diseases. Non-alcoholic steatohepatitis (NASH), characterized by hepatic steatosis and inflammation, has been considered the precursor or the hepatic manifestation of metabolic disease. In this study, we delineated the toxic effect and molecular basis by which pharmacologic ER stress, induced by a bacterial nucleoside antibiotic tunicamycin (TM), promotes NASH in an animal model. Mice of C57BL/6J strain background were challenged with pharmacologic ER stress by intraperitoneal injection of TM. Upon TM injection, mice exhibited a quick NASH state characterized by hepatic steatosis and inflammation. An increase in hepatic triglycerides (TG) and a decrease in plasma lipids, including plasma TG, plasma cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL), were observed in the TM-treated mice. In response to TM challenge, cleavage of sterol responsive binding protein (SREBP)-1a and SREBP-1c, the key trans-activators for lipid and sterol biosynthesis, was dramatically increased in the liver. Consistent with the hepatic steatosis phenotype, expression of some key regulators and enzymes in de novo lipogenesis and lipid droplet formation was up-regulated, while expression of those involved in lipolysis and fatty acid oxidation was down-regulated in the liver of mice challenged with TM. Moreover, TM treatment significantly increased phosphorylation of NF-κB inhibitors (IκB), leading to the activation of NF-κB-mediated inflammatory pathway in the liver. Our study not only confirmed that pharmacologic ER stress is a strong “hit” that triggers NASH, but also demonstrated crucial molecular links between ER stress, lipid metabolism, and inflammation in the liver in vivo.
ER Stress; Non-alcoholic Steatohepatitis; Tunicamycin; Lipid Metabolism; Hepatic Inflammation
Arsenic is associated with bladder cancer risk even at low exposure levels. Genetic variation in enzymes involved in xenobiotic and arsenic metabolism may modulate individual susceptibility to arsenic-related bladder cancer. Through a population-based case-control study in NH (832 cases and 1191 controls), we investigated gene-environment interactions between arsenic metabolic gene polymorphisms and arsenic exposure in relation to bladder cancer risk. Toenail arsenic concentrations were used to classify subjects into low and high exposure groups. Single nucleotide polymorphisms (SNPs) in GSTP1, GSTO2, GSTZ1, AQP3, AS3MT and the deletion status of GSTM1 and GSTT1 were determined. We found evidence of genotype-arsenic interactions in the high exposure group; GSTP1 Ile105Val homozygous individuals had an odds ratio (OR) of 5.4 [95% confidence interval (CI): 1.5-20.2; P for interaction = 0.03] and AQP3 Phe130Phe carriers had an OR=2.2 (95% CI: 0.8-6.1; P for interaction = 0.10). Bladder cancer risk overall was associated with GSTO2 Asn142Asp (homozygous; OR=1.4; 95% CI: 1.0-1.9; P for trend=0.06) and GSTZ1 Glu32Lys (homozygous; OR=1.3; 95%CI: 0.9-1.8; P for trend=0.06). Our findings suggest that susceptibility to bladder cancer may relate to variation in genes involved in arsenic metabolism and oxidative stress response and potential gene-environment interactions requiring confirmation in other populations.
arsenic; genetic polymorphisms; bladder cancer; case-control study; gene-environment interaction
3,3′,4,4′,5-Pentachlorobiphenyl (PCB 126), an aryl hydrocarbon receptor (AhR) agonist and most potent dioxin-like PCB congener, significantly alters gene expression, lipid metabolism, and oxidative stress in the liver. PON1, an antioxidant and anti-atherogenic enzyme, is produced in the liver and secreted into the blood where it is incorporated into high density lipoprotein (HDL) and protects LDL and cellular membranes against lipid peroxidation. To explore the regulation of PON1, male Sprague-Dawley rats were treated with ip injections of 0, 1 or 5 μmol/kg PCB 126 and euthanized up to two weeks afterwards. Serum total and HDL-cholesterol were increased by low dose and decreased by high dose exposure, while LDL-cholesterol was unchanged. PCB 126 significantly increased hepatic PON1 gene expression and liver and serum PON1 activities. Liver and serum thiobarbituric acid reactive substances levels were not elevated except for high dose and long exposure times. Serum antioxidant capacity was unchanged across all exposure doses and time points. This study, the first describing the regulation of gene expression of PON1 by a PCB congener, raises interesting questions whether elevated PON1 is able to ameliorate PCB 126-induced lipid peroxidation and whether serum PON1 levels may serve as a new biomarker of exposure to dioxin-like compounds.
Paraoxonase 1; PCB 126; TBARS; rat; liver; AhR; plasma lipids
Alcohol and MDMA (ecstasy) are frequently co-abused, but recent findings indicate a harmful drug interaction between these two agents. In our previous study, we showed that MDMA exposure inhibits the activity of the acetaldehyde (ACH) metabolizing enzyme, aldehyde dehydrogenase2 (ALDH2). Based on this finding, we hypothesized that the co-administration of MDMA and ethanol would reduce the metabolism of ACH and result in increased accumulation of ACH. Rats were treated with MDMA or vehicle and then administered a single dose of ethanol. Liver ALDH2 activity decreased by 35% in the MDMA-treated rats compared to control rats. The peak concentration and the area under the concentration versus time curve of plasma ACH was 31% and 59% higher, respectively, in the MDMA-ethanol group compared to the ethanol-only group. In addition, the MDMA-ethanol group had 80% higher plasma transaminase levels than the ethanol-only group, indicating greater hepatocellular damage. Our results not only support a drug interaction between MDMA and ethanol but a novel underlying mechanism for the interaction.
alcohol; ethanol; 3,4-methylenedioxymethamphetamine (MDMA); ecstasy; metabolism; acetaldehyde; aldehyde dehydrogenase; drug interaction; liver toxicity; transaminase
Inorganic arsenic, an early life carcinogen in humans and mice, can initiate lesions promotable by other agents in later life. The biomethylation product of arsenic, dimethylarsinic acid (DMA), is a multi-site tumor promoter. Thus, pregnant CD1 mice were given drinking water (0 or 85 ppm arsenic) from gestation day 8 to 18 and after weaning male offspring received DMA (0 or 200 ppm; drinking water) for up to 2 years. No renal tumors occurred in controls or DMA alone treated mice while gestational arsenic exposure plus later DMA induced a significant renal tumor incidence of 17% (primarily renal cell carcinoma). Arsenic plus DMA or arsenic alone also increased renal hyperplasia over control but DMA alone did not. Arsenic alone, DMA alone and arsenic plus DMA all induced urinary bladder hyperplasia (33–35%) versus control (2%). Compared to control (6%), arsenic alone tripled hepatocellular carcinoma (20%), and arsenic plus DMA doubled this rate again (43%), but DMA alone had no effect. DMA alone, arsenic alone, and arsenic plus DMA increased lung adenocarcinomas and adrenal adenomas versus control. Overall, DMA in adulthood promoted tumors/lesions initiated by prenatal arsenic in the kidney and liver, but acted independently in the urinary bladder, lung and adrenal.
arsenic; mouse; cancer; kidney; liver; early life; lung; DMA
Multi-drug resistance protein (MRP) 4, an ATP-binding cassette (ABC) transporter, has broad substrate specificity. It facilitates the transport of bile salt conjugates, conjugated steroids, nucleoside analogs, eicosanoids, and cardiovascular drugs. Recent studies in liver carcinoma cells and hepatocytes showed that MRP4 expression is regulated by the aryl hydrocarbon receptor (AhR) and nuclear factor E2-related factor 2 (Nrf2). The AhR has particular importance in the lung and is most commonly associated with the up-regulation of cytochrome P-450 (CYP)-mediated metabolism of benzo[a]pyrene (B[a]P) to reactive intermediates. Treatment of H358, human bronchoalveolar, cells with 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) or (−)-benzo[a]pyrene-7,8-dihydro-7,8-diol (B[a]P-7,8-dihydrodiol), the proximate carcinogen of B[a]P, revealed that MRP4 expression was increased compared to control. This suggested that MRP4 expression might contribute to the paradoxical decrease in (+)-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene-2′-deoxyguanosine ((+)-anti-trans-B[a]PDE-dGuo) DNA-adducts observed in TCDD-treated H358 cells. We have now found that decreased MRP4 expression induced by a short hairpin RNA (shRNA), or chemical inhibition with probenecid, increased (+)-anti-trans-B[a]PDE-dGuo formation in cells treated with (−)-B[a]P-7,8-dihydrodiol, but not the ultimate carcinogen (+)-anti-trans-B[a]PDE. Thus, up-regulation of MRP4 increased cellular efflux of (−)-B[a]P-7,8-dihydrodiol, which attenuated DNA-adduct formation. This is the first report identifying a specific MRP efflux transporter that decreases DNA damage arising from an environmental carcinogen.
benzopyrene; environmental carcinogen; LC-MS; aryl hydrocarbon receptor
Human exposure to particulate matter (PM) elicits a variety of responses on the cardiovascular system through both direct and indirect pathways. Indirect effects of PM on the cardiovascular system are mediated through the autonomic nervous system, which controls heart rate variability, and inflammatory responses, which augment acute cardiovascular events and atherosclerosis. Recent research demonstrates that PM also affects the cardiovascular system directly by entry into the systemic circulation. This process causes myocardial dysfunction through mechanisms of reactive oxygen species production, calcium ion interference, and vascular dysfunction. In this review, we will present key evidence in both the direct and indirect pathways, suggest clinical applications of the current literature, and recommend directions for future research.
particulate matter; cardiovascular dysfunction; air pollution; inflammation; reactive oxygen species
Despite data linking amphibole asbestos exposure with production of autoantibodies, the role of autoantibodies in subsequent disease is unknown. Residents of Libby, Montana have experienced significant exposure to amphibole asbestos due to the mining of asbestos-contaminated vermiculite near the community over several decades. This population predominantly exhibits pleural disease, and an autoimmune-like disorder that has yet to be well defined. This study sought to determine whether autoantibodies from asbestos-exposed subjects were associated with pleural lesions. Serum samples of subjects from Libby were evaluated for anti-nuclear antibodies (ANA) and mesothelial cell autoantibodies (MCAA) using cell based ELISA. The presence of radiographic abnormalities detected during the time frame of serum collection was determined from screening records. In accord with previous studies, 61.3% (76/124) of the Libby samples were ANA positive, a frequency much higher than expected for a healthy population. The odds of having pleural or interstitial abnormalities in Libby was nearly 3.55 times greater for individuals that tested positive for ANA compared with individuals negative for ANA (p =0.004). MCAA were also detected at a strikingly high frequency (18.5%; 23/124) in samples from Libby. Individuals with MCAA had 4.9 times the risk of having pleural abnormalities compared to MCAA-negative subjects (p=0.044). In conclusion, ANA and MCAA were elevated in a study population that was known to have chronic exposure to asbestos, and these autoantibodies were associated with pleural abnormalities, the predominant finding in the asbestos-exposed population of Libby. Additional research is needed to determine the role these autoantibodies may play in pulmonary disease.
Libby MT; amphibole; Autoimmune disease; pleural
Dioxins are widespread environmental contaminants that induce the carcinogen-activating enzyme, cytochrome P450 1A1 (CYP1A1) through an aryl hydrocarbon receptor (AhR)-dependent mechanism. We previously demonstrated that harmine inhibits the dioxin-mediated induction of Cyp1a1 activity in murine hepatoma cells. Therefore, the aim of this study is to determine the effect of harmine and its main metabolite, harmol, on the dioxin-mediated induction of CYP1A1 in human HepG2 and murine Hepa 1c1c7 hepatoma cells. Our results showed that harmine and harmol significantly inhibited the dioxin-mediated induction of CYP1A1 at mRNA, protein, and activity levels in a concentration-dependent manner in human and murine hepatoma cells. Moreover, harmine and harmol inhibited the AhR-dependent luciferase activity and the activation and transformation of AhR using the electrophoretic mobility shift assay. In addition, harmine and harmol displaced [3H]TCDD in the competitive ligand binding assay. At posttranslational level, both harmine and harmol decreased the protein stability of CYP1A1, suggesting that posttranslational mechanism is involved. Furthermore, we demonstrated that the underlying mechanisms of the posttranslational modifications of both compounds involve ubiquitin-proteasomal pathway and direct inhibitory effects of CYP1A1 enzyme. We concluded that harmine and its metabolite, harmol, are new inhibitors of dioxin-mediated effects.
Aryl hydrocarbon receptor; Carcinogenesis; CYP 1A1; Harmine; Harmol
Increased levels of inducible nitric oxide synthase (iNOS) during cardiac stress such as ischemia-reperfusion, sepsis and hypertension may display both beneficial and detrimental roles in cardiac contractile performance. However, the precise role of iNOS in the maintenance of cardiac contractile function remains elusive. This study was designed to determine the impact of chronic iNOS inhibition on cardiac contractile function and the underlying mechanism involved with a special focus on the NO downstream signaling molecule Akt. Male C57 or Akt2 knockout [Akt2(−/−)] mice were injected with the specific iNOS inhibitor 1400W (2 mg/kg/d) or saline for 7 days. Both 1400W and Akt2 knockout dampened glucose and insulin tolerance without additive effects. Treatment of 1400W decreased heart and liver weights as well as cardiomyocyte cross-sectional area in C57 but not Akt2 knockout mice. 1400W but not Akt2 knockout compromised cardiomyocyte mechanical properties including decreased peak shortening and maximal velocity of shortening/relengthening, prolonged relengthening duration, reduced intracellular Ca2+ release and decay rate, the effects of which were ablated or attenuated by Akt2 knockout. Akt2 knockout but not 1400W increased the levels of intracellular Ca2+ regulatory proteins including SERCA2a and phospholamban phosphorylation. 1400W reduced the level of anti-apoptotic protein Bcl-2, the effect of which was unaffected by Akt2 knockout. Neither 1400W nor Akt2 knockout significantly affected ER stress, autophagy, the post-insulin receptor signaling Akt, GSK3β and AMPK, as well as the stress signaling IΚB, JNK, ERK and p38 with the exception of elevated IΚB phosphorylation with jointed effect of 1400W and Akt2 knockout. Taken together, these data indicated that an essential role of iNOS in the maintenance of cardiac morphology and function possibly through an Akt2-dependent mechanism.
Akt; nitric oxide; myocardial contractile function; intracellular Ca2+
Esophageal cancer has been associated with tobacco and alcohol consumption, gastric reflux, exposure to nitrosamines from food or other environmental sources, and diets lacking folate. Susceptibility to esophageal cancer may be modified by functional polymorphisms in genes along the folate metabolic pathway, such as methylenetetrahydrofolate reductase (MTHFR). The C677T polymorphism is the most common functional variant, leading to a reduction in enzyme activity. We report a pooled analysis of 5 studies on the association of MTHFR C677T polymorphism and esophageal cancer, including 725 cases and 1531 controls. A significant association between the MTHFR 677 TT genotype and esophageal cancer was observed (OR = 2.63, 95% CI: 1.75–3.94), although there was significant heterogeneity between studies. A sensitivity analysis excluded one study; the association between TT genotype and esophageal cancer was still present, although of reduced magnitude (OR = 1.57, 95% CI: 0.96–2.56). A significant interaction between smoking and TT genotype on esophageal cancer risk was observed, while no interaction was observed between alcohol consumption and genotype.
Methylenetetrahydrofolate reductase; Esophagus; Genetic epidemiology; case control studies
Although BRCA1 is the most prevalent genetic factor in breast cancer, the pathologic mechanism of tumorigenesis caused by its deficiency has not been elucidated. We have previously demonstrated that BRCA1 can modulate responses to xenobiotic stress by regulating expression of genes involved in metabolic activation, detoxification and antioxidant reactions. In this study, we examined whether BRCA1 deficiency is more vulnerable to xenobiotic stress by employing an in vitro cell model system. Benzo[a]pyrene (B[a]P), used as a xenobiotic insult, increased intracellular reactive oxygen species (ROS) levels in breast epithelial cells. Accumulation of ROS upon B[a]P exposure was significantly augmented by abrogation of BRCA1 compared to the control. Overexpression of Nrf2 in BRCA1 deficient cells reduced elevated ROS to the control levels. Bioactive food components such as sulforaphane (SFN) and resveratrol (RSV) significantly reduced B[a]P-induced ROS accumulation regardless of BRCA1 presence. In addition, these bioactive food components increased Nrf2 levels and Nrf2 transcriptional activity, which led to attenuation of B[a]P-induced DNA damages. Likewise, incubation with bioactive food components reduced B[a]P-mediated DNA damage in BRCA1 deficient cells. In conclusion, we demonstrated that the lack of BRCA1 renders cells more susceptible to ROS-induced DNA damage, which may eventually result in tumorigenesis, and that administration of Nrf2-activating bioactive food components can reduce those risks.
BRCA1; Nrf2; oxidative stress; bioactive food components; carcinogenesis; chemoprevention