Obesogenic polystyrene microplastic exposures disrupt the gut-liver-adipose axis

Microplastics (MP) derived from the weathering of polymers, or synthesized in this size range, have become widespread environmental contaminants and have found their way into water supplies and the food chain. Despite this awareness, little is known about the health consequences of MP ingestion. We have previously shown that the consumption of polystyrene (PS) beads was associated with intestinal dysbiosis and diabetes and obesity in mice. To further evaluate the systemic metabolic effects of PS on the gut-liver-adipose tissue axis, we supplied C57BL/6J mice with normal water or that containing 2 sizes of PS beads (0.5 and 5 µm) at a concentration of 1 µg/ml. After 13 weeks, we evaluated indices of metabolism and liver function. As observed previously, mice drinking the PS-containing water had a potentiated weight gain and adipose expansion. Here we found that this was associated with an increased abundance of adipose F4/80+ macrophages. These exposures did not cause nonalcoholic fatty liver disease but were associated with decreased liver:body weight ratios and an enrichment in hepatic farnesoid X receptor and liver X receptor signaling. PS also increased hepatic cholesterol and altered both hepatic and cecal bile acids. Mice consuming PS beads and treated with the berry anthocyanin, delphinidin, demonstrated an attenuated weight gain compared with those mice receiving a control intervention and also exhibited a downregulation of cyclic adenosine monophosphate (cAMP) and peroxisome proliferator-activated receptor (PPAR) signaling pathways. This study highlights the obesogenic role of PS in perturbing the gut-liver-adipose axis and altering nuclear receptor signaling and intermediary metabolism. Dietary interventions may limit the adverse metabolic effects of PS consumption.

Sex-specific effects of acute chlordane exposure in the context of steatotic liver disease, energy metabolism and endocrine disruption

Chlordane is an organochlorine pesticide (OCP) that is environmentally persistent. Although exposures to OCPs including chlordane have been associated with elevated liver enzymes, current knowledge on OCPs' contribution to toxicant-associated steatotic liver disease (TASLD) and underlying sex-specific metabolic/endocrine disruption are still widely limited. Therefore, the objective of this study was to investigate the sex-dependent effects of chlordane in the context of TASLD. Age-matched male and female C57BL/6 mice were exposed to chlordane (20 mg/kg, one-time oral gavage) for two weeks. Female mice generally exhibited lower bodyfat content but more steatosis and hepatic lipid levels, consistent with increased hepatic mRNA levels of genes involved in lipid synthesis and uptake. Surprisingly, chlordane-exposed females demonstrated lower hepatic cholesterol levels. With regards to metabolic disruption, chlordane exposure decreased expression of genes involved in glycogen and glucose metabolism (Pklr, Gck), while chlordane-exposed females also exhibited decreased gene expression of HNF4A, an important regulator of liver identity and function. In terms of endocrine endpoints, chlordane augmented plasma testosterone levels in males. Furthermore, chlordane activated hepatic xenobiotic receptors, including the constitutive androstane receptor, in a sex-dependent manner. Overall, chlordane exposure led to altered hepatic energy metabolism, and potential chlordane-sex interactions regulated metabolic/endocrine disruption and receptor activation outcomes.

Rapid-dissolving electrospun nanofibers for intra-vaginal antibiotic or probiotic delivery

The emergence of probiotics as an alternative and adjunct to antibiotic treatment for microbiological disturbances of the female genitourinary system requires innovative delivery platforms for vaginal applications. This study developed a new, rapid-dissolving form using electrospun polyethylene oxide (PEO) fibers for delivery of antibiotic metronidazole or probiotic Lactobacillus acidophilus, and performed evaluation in vitro and in vivo. Fibers did not generate overt pathophysiology or encourage Gardnerella growth in a mouse vaginal colonization model, inducing no alterations in vaginal mucosa at 24 hr post-administration. PEO-fibers incorporating metronidazole (100 µg MET/mg polymer) effectively prevented and treated Gardnerella infections (∼3- and 2.5-log reduction, respectively, 24 hr post treatment) when administered vaginally. Incorporation of live Lactobacillus acidophilus (107 CFU/mL) demonstrated viable probiotic delivery in vitro by PEO and polyvinyl alcohol (PVA) fibers to inhibit Gardnerella (108 CFU/mL) in bacterial co-cultures (9.9- and 7.0-log reduction, respectively, 24 hr post-inoculation), and in the presence of vaginal epithelial cells (6.9- and 8.0-log reduction, respectively, 16 hr post-inoculation). Administration of Lactobacillus acidophilus in PEO-fibers achieved vaginal colonization in mice similar to colonization observed with free Lactobacillus. acidophilus. These experiments provide proof-of-concept for rapid-dissolving electrospun fibers as a successful platform for intra-vaginal antibiotic or probiotic delivery.

Investigating the Acute Metabolic Effects of the N-Methyl Carbamate Insecticide, Methomyl, on Mouse Liver

Many pesticides have been identified as endocrine and metabolism-disrupting chemicals with hepatotoxic effects. However, data are limited for insecticides in the n-methyl carbamate class, including methomyl. Here, we investigate the liver and systemic metabolic effects of methomyl in a mouse model. We hypothesize that methomyl exposure will disrupt xenobiotic and intermediary metabolism and promote hepatic steatosis in mice. Male C57BL/6 mice were exposed daily to 0-5 mg/kg methomyl for 18 days. Mice were fed water and regular chow diet ad libitum. Metabolic phenotyping was performed, and tissue samples were collected. Effects were generally greatest at the highest methomyl dose, which induced Cyp1a2. Methomyl decreased whole body weight while the liver:body weight and testes:body weight ratios were increased. Hepatic steatosis increased while plasma LDL decreased. Fasting blood glucose and the glucose tolerance test area under the curve decreased along with hepatic glycogen stores. Methomyl, however, did not increase liver oxidative stress or injury. Collectively, these data demonstrate that methomyl disrupts hepatic xenobiotic and intermediary metabolism while increasing the testes:body weight ratio, suggesting that it may be an endocrine disrupting chemical. Besides methomyl's known action in cholinesterase inhibition, it may be involved in aryl hydrocarbon receptor activation. The potential impact of n-methyl carbamate insecticides on metabolic health and diseases, including toxicant-associated steatotic liver disease (TASLD), warrants further investigation.

Can Zinc Supplementation Attenuate High Fat Diet-Induced Non-Alcoholic Fatty Liver Disease?

The pathogenesis of non-alcoholic fatty liver disease (NAFLD), the most prevalent chronic liver disease, is associated with zinc deficiency. Previous studies show zinc supplementation improves steatosis and glucose metabolism, but its therapeutic effects in patients with established NAFLD remain unclear. We developed an in vivo model to characterize the effects of zinc supplementation on high-fat diet (HFD) induced NAFLD and hypothesized that the established NAFLD would be attenuated by zinc supplementation. Male C57BL/6J mice were fed a control diet or HFD for 12 weeks. Mice were then further grouped into normal and zinc-supplemented diets for 8 additional weeks. Body composition and glucose tolerance were determined before and after zinc supplementation. At euthanasia, plasma and liver tissue were collected for characterization and downstream analysis. As expected, 12 weeks of HFD resulted in reduced glucose clearance and altered body composition. Eight weeks of subsequent zinc supplementation did not alter glucose handling, plasma transaminases, steatosis, or hepatic gene expression. Results from our model suggest 8-week zinc supplementation cannot reverse established NAFLD. The HFD may have caused NAFLD disease progression beyond rescue by an 8-week period of zinc supplementation. Future studies will address these limitations and provide insights into zinc as a therapeutic agent for established NAFLD.

Mice lacking α4 nicotinic acetylcholine receptors are protected against alcohol-associated liver injury

BACKGROUND

Chronic heavy alcohol consumption is a major risk factor for the development of liver steatosis, fibrosis, and cirrhosis, but the mechanisms by which alcohol causes liver damage remain incompletely elucidated. This group has reported that α4 nicotinic acetylcholine receptors (α4 nAChRs) act as sensors for alcohol in lung cells. This study tested the hypothesis that α4 nAChRs mediate the effects of alcohol in the liver.

METHODS

Expression of acetylcholine receptor subunits in mouse liver was determined by RNA sequencing (RNA-seq). α4 nAChR knockout (α4 KO) mice were generated in C57BL/6J mice by introducing a mutation encoding an early stop codon in exon 4 of Chrna4, the gene encoding the α4 subunit of the nAChR. The presence of the inactivating mutation was established by polymerase chain reaction and genomic sequencing, and the lack of α4 nAChR function was confirmed in primary fibroblasts isolated from the α4 KO mice. Wild-type (WT) and α4 KO mice were fed the Lieber-DeCarli diet (with 36% of calories from alcohol) or pair fed an isocaloric maltose-dextrin control diet for a 6-week period that included a ramping up phase of increasing dietary alcohol.

RESULTS

Chrna4 was the most abundantly expressed nAChR subunit gene in mouse livers. After 6 weeks of alcohol exposure, WT mice had elevated serum transaminases and their livers showed increased fat accumulation, decreased Sirt1 protein levels, and accumulation of markers of oxidative stress and inflammation including Cyp2E1, Nos2, Sod1, Slc7a11, TNFα, and PAI1. All these responses to alcohol were either absent or significantly attenuated in α4 KO animals.

CONCLUSION

Together, these observations support the conclusion that activation of α4 nAChRs by alcohol or one of its metabolites is one of the initial events promoting the accumulation of excess fat and expression of inflammatory mediators. Thus, α4 nAChRs may represent viable targets for intervention in chronic alcohol-related liver disease.

The profibrotic and senescence phenotype of old lung fibroblasts is reversed or ameliorated by genetic and pharmacological manipulation of Slc7a11 expression

Increased senescence and expression of profibrotic genes in old lung fibroblasts contribute to disrepair responses. We reported that primary lung fibroblasts from old mice have lower expression and activity of the cystine transporter Slc7a11/xCT than cells from young mice, resulting in changes in both the intracellular and extracellular redox environments. This study examines the hypothesis that low Slc7a11 expression in old lung fibroblasts promotes senescence and profibrotic gene expression. The levels of mRNA and protein of Slc7a11, senescence markers, and profibrotic genes were measured in primary fibroblasts from the lungs of old (24 mo) and young (3 mo) mice. In addition, the effects of genetic and pharmacological manipulation of Slc7a11 were investigated. We found that decreased expression of Slc7a11 in old cells was associated with elevated markers of senescence (p21, p16, p53, and β-galactosidase) and increased expression of profibrotic genes (Tgfb1, Smad3, Acta2, Fn1, Col1a1, and Col5a1). Silencing of Slc7a11 in young cells replicated the aging phenotype, whereas overexpression of Slc7a11 in old cells decreased expression of senescence and profibrotic genes. Young cells were induced to express the senescence and profibrotic phenotype by sulfasalazine, a Slc7a11 inhibitor, whereas treatment of old cells with sulforaphane, a Slc7a11 inducer, decreased senescence without affecting profibrotic genes. Like aging cells, idiopathic pulmonary fibrosis fibroblasts show decreased Slc7a11 expression and increased profibrotic markers. In short, old lung fibroblasts manifest a profibrotic and senescence phenotype that is modulated by genetic or pharmacological manipulation of Slc7a11.

Effect of vinyl chloride exposure on cardiometabolic toxicity

Vinyl chloride (VC) is an organochlorine mainly used to manufacture its polymer polyvinyl chloride, which is extensively used in the manufacturing of consumer products. Recent studies suggest that chronic low dose VC exposure affects glucose homeostasis in high fat diet-fed mice. Our data suggest that even in the absence of high fat diet, exposure to VC (0.8 ppm, 6 h/day, 5 day/week, for 12 weeks) induces glucose intolerance (1.0 g/kg, i.p.) in male C57BL/6 mice. This was accompanied with the depletion of hepatic glutathione and a modest increase in lung interstitial macrophages. VC exposure did not affect the levels of circulating immune cells, endothelial progenitor cells, platelet-immune cell aggregates, and cytokines and chemokines. The acute challenge of VC-exposed mice with LPS did not affect lung immune cell composition or plasma IL-6. To examine the effect of VC exposure on vascular inflammation and atherosclerosis, LDL receptor-KO mice on C57BL/6 background maintained on western diet were exposed to VC for 12 weeks (0.8 ppm, 6 h/day, 5 day/week). Unlike the WT C57BL/6 mice, VC exposure did not affect glucose tolerance in the LDL receptor-KO mice. Plasma cytokines, lesion area in the aortic valve, and markers of lesional inflammation in VC-exposed LDL receptor-KO mice were comparable with the air-exposed controls. Collectively, despite impaired glucose tolerance and modest pulmonary inflammation, chronic low dose VC exposure does not affect surrogate markers of cardiovascular injury, LPS-induced acute inflammation in C57BL/6 mice, and chronic inflammation and atherosclerosis in the LDL receptor-KO mice.

Na/H Exchange Regulatory Factor 1 Deficient Mice Show Evidence of Oxidative Stress and Altered Cisplatin Pharmacokinetics

(1) Background: One third of patients who receive cisplatin develop an acute kidney injury. We previously demonstrated the Na/H Exchange Regulatory Factor 1 (NHERF1) loss resulted in increased kidney enzyme activity of the pentose phosphate pathway and was associated with more severe cisplatin nephrotoxicity. We hypothesized that changes in proximal tubule biochemical pathways associated with NHERF1 loss alters renal metabolism of cisplatin or response to cisplatin, resulting in exacerbated nephrotoxicity. (2) Methods: 2-4 month-old male wild-type and NHERF1 knock out littermate mice were treated with either vehicle or cisplatin (20 mg/kg dose IP), with samples taken at either 4, 24, or 72 h. Kidney injury was determined by urinary neutrophil gelatinase-associated lipocalin and histology. Glutathione metabolites were measured by HPLC and genes involved in glutathione synthesis were measured by qPCR. Kidney handling of cisplatin was assessed by a kidney cortex measurement of γ-glutamyl transferase activity, Western blot for γ-glutamyl transferase and cysteine S-conjugate beta lyase, and ICP-MS for platinum content. (3) Results: At 24 h knock out kidneys show evidence of greater tubular injury after cisplatin and exhibit a decreased reduced/oxidized glutathione ratio under baseline conditions in comparison to wild-type. KO kidneys fail to show an increase in γ-glutamyl transferase activity and experience a more rapid decline in tissue platinum when compared to wild-type. (4) Conclusions: Knock out kidneys show evidence of greater oxidative stress than wild-type accompanied by a greater degree of early injury in response to cisplatin. NHERF1 loss has no effect on the initial accumulation of cisplatin in the kidney cortex but is associated with an altered redox status which may alter the activity of enzymes involved in cisplatin metabolism.

The Digestive Diverticula in the Carnivorous Nudibranch, Melibe leonina, Do Not Contain Photosynthetic Symbionts

A number of nudibranchs, including Melibe engeli and Melibe pilosa, harbor symbiotic photosynthetic zooxanthellae. Melibe leonina spends most of its adult life on seagrass or kelp, capturing planktonic organisms in the water column with a large, tentacle-lined oral hood that brings food to its mouth. M. leonina also has an extensive network of digestive diverticula, located just beneath its translucent integument, that are typically filled with pigmented material likely derived from ingested food. Therefore, the focus of this project was to test the hypothesis that M. leonina accumulates symbiotic photosynthetic dinoflagellates in these diverticula. First, we conducted experiments to determine if M. leonina exhibits a preference for light, which would allow chloroplasts that it might be harboring to carry out photosynthesis. We found that most M. leonina preferred shaded areas and spent less time in direct sunlight. Second, we examined the small green circular structures in cells lining the digestive diverticula. Like chlorophyll, they exhibited autofluorescence when illuminated at 480 nm, and they were also about the same size as chloroplasts and symbiotic zooxanthellae. However, subsequent electron microscopy found no evidence of chloroplasts in the digestive diverticula of M. leonina; the structures exhibiting autofluorescence at 480 nm were most likely heterolysosomes, consistent with normal molluscan digestion. Third, we did not find evidence of altered oxygen consumption or production in M. leonina housed in different light conditions, suggesting the lack of any significant photosynthetic activity in sunlight. Fourth, we examined the contents of the diverticula, using HPLC, thin layer chromatography, and spectroscopy. The results of these studies indicate that the diverticula did not contain any chlorophyll, but rather harbored other pigments, such as astaxanthin, which likely came from crustaceans in their diet. Together, all of these data suggest that M. leonina does sequester pigments from its diet, but not for the purpose of symbiosis with photosynthetic zooxanthellae. Considering the translucent skin of M. leonina, the pigmented diverticula may instead provide camouflage.

Effects of cadmium and high-fat diet on essential metal concentration in the mouse testis

The effects of exposure to the environmental toxicant cadmium, in combination with obesity, on the metal content in mouse testis were evaluated. Starting in utero and continuing through to 10 or 24 weeks post-weaning, male mice were exposed to cadmium (0, 0.5 or 5 ppm), and fed either a low (LFD) or high fat diet (HFD) post-weaning. Testicular levels of cadmium and essential metals were determined 10 and 24 weeks post-weaning by ICP-MS. Similar to what has been previously observed in the liver, kidney, heart and brain, significant levels of cadmium accumulated in the testis under all exposure conditions. Additionally, HFD-fed animals accumulated more cadmium than did their LFD-treated counterparts. Both treatments affected essential metal homeostasis in the testis. These findings suggest that cadmium and obesity may compromise the reproductive potential in the male mouse by disrupting essential metal levels.

The Distribution and Possible Roles of Small Cardioactive Peptide in the Nudibranch Melibe leonina

The neuropeptide small cardioactive peptide (SCP) plays an integrative role in exciting various motor programs involved in feeding and locomotion in a number of gastropod species. In this study, immunohistochemistry, using monoclonal antibodies against SCPB, was used to localize SCPB-like-immunoreactive neurons in the central nervous system, and map their connections to various tissues, in the nudibranch, Melibe leonina. Approximately 28-36 SCPB-like-immunoreactive neurons were identified in the M. leonina brain, as well as one large neuron in each of the buccal ganglia. The neuropil of the pedal ganglia contained the most SCPB-like-immunoreactive varicosities, although only a small portion of these were due to SCPB-like-immunoreactive neurons in the same ganglion. This suggests that much of the SCPB-like immunoreactivity in the neuropil of the pedal ganglia was from neurons in other ganglia that projected through the pedal-pedal connectives or the connectives from the cerebral and pleural ganglia. We also observed extensive SCPB innervation along the length of the esophagus. Therefore, we investigated the impact of SCPB on locomotion in intact animals, as well as peristaltic contractions of the isolated esophagus. Injection of intact animals with SCPB at night led to a significant increase in crawling and swimming, compared to control animals injected with saline. Furthermore, perfusion of isolated brains with SCPB initiated expression of the swim motor program. Application of SCPB to the isolated quiescent esophagus initiated rhythmic peristaltic contractions, and this occurred in preparations both with and without the buccal ganglia being attached. All these data, taken together, suggest that SCPB could be released at night to arouse animals and enhance the expression of both feeding and swimming motor programs in M. leonina.

Impact of sex, age and diet on the cysteine/cystine and glutathione/glutathione disulfide plasma redox couples in mice

Age, sex and diet are well-established risk factors for several diseases. In humans, each of these variables has been linked to differences in plasma redox potentials (E_h) of the glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS) redox couples. Mice have been very useful for modeling human disease processes, but it is unknown if age, sex and diet affect redox couples in mice as they do in humans. The purpose of the present study was to examine the effects of these factors on plasma redox potentials in C57BL/6J mice. We found that age had no effect on either redox couple in either sex. Plasma E_h Cys/CySS and E_h GSH/GSSG were both more oxidized (more positive) in females than in males. A 24-hour fast negated the sex differences in both redox potentials by oxidizing both redox couples in male mice, while having no effect on E_h Cys/CySS and a smaller effect on E_h GSH/GSSG in female mice. A diet with excess sulfur amino acids reduced the plasma E_h Cys/CySS in females to a level comparable to that seen in male mice. Thus, sex-specific differences in plasma E_h Cys/CySS could be normalized by two different dietary interventions. Some of these findings are consistent with reported human studies, while others are not. Most strikingly, mice do not exhibit age-dependent oxidation of plasma redox potentials. Care must be taken when designing and interpreting mouse studies to investigate redox regulation in humans.

Arsenite Exposure Displaces Zinc from ZRANB2 Leading to Altered Splicing

Exposure to arsenic, a class I carcinogen, affects 200 million people globally. Skin is the major target organ, but the molecular etiology of arsenic-induced skin carcinogenesis remains unclear. Arsenite (As³⁺)-induced disruption of alternative splicing could be involved, but the mechanism is unknown. Zinc finger proteins play key roles in alternative splicing. As³⁺ can displace zinc (Zn²⁺) from C3H1 and C4 zinc finger motifs (zfm's), affecting protein function. ZRANB2, an alternative splicing regulator with two C4 zfm's integral to its structure and splicing function, was chosen as a candidate for this study. We hypothesized that As³⁺ could displace Zn²⁺ from ZRANB2, altering its structure, expression, and splicing function. As³⁺/Zn²⁺ binding and mutual displacement experiments were performed with synthetic apo-peptides corresponding to each ZRANB2 zfm, employing a combination of intrinsic fluorescence, ultraviolet spectrophotometry, zinc colorimetric assay, and liquid chromatography-tandem mass spectrometry. ZRANB2 expression in HaCaT cells acutely exposed to As³⁺ (0 or 5 μM, 0-72 h; or 0-5 μM, 6 h) was examined by RT-qPCR and immunoblotting. ZRANB2-dependent splicing of TRA2B mRNA, a known ZRANB2 target, was monitored by reverse transcription-polymerase chain reaction. As³⁺ bound to, as well as displaced Zn²⁺ from, each zfm. Also, Zn²⁺ displaced As³⁺ from As³⁺-bound zfm's acutely, albeit transiently. As³⁺ exposure induced ZRANB2 protein expression between 3 and 24 h and at all exposures tested but not ZRANB2 mRNA expression. ZRANB2-directed TRA2B splicing was impaired between 3 and 24 h post-exposure. Furthermore, ZRANB2 splicing function was also compromised at all As³⁺ exposures, starting at 100 nm. We conclude that As³⁺ exposure displaces Zn²⁺ from ZRANB2 zfm's, changing its structure and compromising splicing of its targets, and increases ZRANB2 protein expression as a homeostatic response both at environmental/toxicological exposures and therapeutically relevant doses.

Plasma cysteine/cystine and glutathione/glutathione disulfide redox potentials in HIV and COPD patients

Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (E_h) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma E_h Cys/CySS than patients with normal lung function, but plasma E_h GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma E_h Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma E_h Cys/CySS, but plasma E_h Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma E_h Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.

Cadmium and High-Fat Diet Disrupt Renal, Cardiac and Hepatic Essential Metals

Exposure to the environmental toxicant cadmium (Cd) contributes to the development of obesity-associated diseases. Obesity is a risk factor for a spectrum of unhealthy conditions including systemic metabolic dyshomeostasis. In the present study, the effects of whole-life exposure to environmentally-relevant concentrations of Cd on systemic essential metal distribution in adult mice fed a high-fat diet (HFD) were examined. For these studies, male and female mice were exposed to Cd-containing drinking water for >2 weeks before breeding. Pregnant mice and dams with offspring were exposed to Cd-containing drinking water. After weaning, offspring were continuously exposed to the same Cd concentration as their parents, and divided into HFD and normal (low) fat diet (LFD) groups. At 10 and 24 weeks, mice were sacrificed and blood, liver, kidney and heart harvested for metal analyses. There were significant concentration dependent increases in Cd levels in offspring with kidney > liver > heart. Sex significantly affected Cd levels in kidney and liver, with female animals accumulating more metal than males. Mice fed the HFD showed > 2-fold increase in Cd levels in the three organs compared to similarly treated LFD mice. Cadmium significantly affected essential metals levels in blood, kidney and liver. Additionally, HFD affected essential metal levels in these three organs. These findings suggest that Cd interacts with HFD to affect essential metal homeostasis, a phenomenon that may contribute to the underlying mechanism responsible for the development of obesity-associated pathologies.

Age-dependent oxidation of extracellular cysteine/cystine redox state (Eh(Cys/CySS)) in mouse lung fibroblasts is mediated by a decline in Slc7a11 expression

Aging is associated with progressive oxidation of the extracellular environment. The redox state of human plasma, defined by the concentrations of cysteine (Cys) and cystine (CySS), becomes more oxidized as we age. Recently, we showed that fibroblasts isolated from the lungs of young and old mice retain this differential phenotype; old cells produce and maintain a more oxidizing extracellular redox potential (E_h(Cys/CySS)) than young cells. Microarray analysis identified down-regulation of Slc7a11, the light subunit of the CySS/glutamate transporter, as a potential mediator of age-related oxidation in these cells. The purpose of the present study was to investigate the mechanistic link between Slc7a11 expression and extracellular E_h(Cys/CySS). Sulforaphane treatment or overexpression of Slc7a11 was used to increase Slc7a11 in lung fibroblasts from old mice, and sulfasalazine treatment or siRNA-mediated knock down was used to decrease Slc7a11 in young fibroblasts. Slc7a11 mRNA levels were measured by real-time PCR, Slc7a11 activity was determined by measuring the rate of glutamate release, Cys, CySS, glutathione (GSH) and its disulfide (GSSG) were measured by HPLC, and E_h(Cys/CySS) was calculated from the Nernst equation. The results showed that both E_h(Cys/CySS) and E_h(GSH/GSSG) were more oxidized in the conditioned media of old cells than in young cells. Up-regulation of Slc7a11 via overexpression or sulforaphane treatment restored extracellular E_h(Cys/CySS) in cultures of old cells, whereas down-regulation reproduced the oxidizing E_h(Cys/CySS) in young cells. Only sulforaphane treatment was able to increase total GSH and restore E_h(GSH/GSSG), whereas overexpression, knock down and sulfasalazine had no effect on these parameters. In addition, inhibition of GSH synthesis with buthionine sulfoximine had no effect on the ability of cells to restore their extracellular redox potential in response to an oxidative challenge. In conclusion, our study reveals Slc7a11 is the key regulator of age-dependent changes in extracellular E_h(Cys/CySS) in primary mouse lung fibroblasts, and its effects are not dependent on GSH synthesis.

Multipurpose tenofovir disoproxil fumarate electrospun fibers for the prevention of HIV-1 and HSV-2 infections in vitro

Sexually transmitted infections affect hundreds of millions of people worldwide. Both human immunodeficiency virus (HIV-1 and -2) and herpes simplex virus-2 (HSV-2) remain incurable, urging the development of new prevention strategies. While current prophylactic technologies are dependent on strict user adherence to achieve efficacy, there is a dearth of delivery vehicles that provide discreet and convenient administration, combined with prolonged-delivery of active agents. To address these needs, we created electrospun fibers (EFs) comprised of FDA-approved polymers, poly(lactic-co-glycolic acid) (PLGA) and poly(DL-lactide-co-ε-caprolactone) (PLCL), to provide sustained-release and in vitro protection against HIV-1 and HSV-2. PLGA and PLCL EFs, incorporating the antiretroviral, tenofovir disoproxil fumarate (TDF), exhibited sustained-release for up to 4 weeks, and provided complete in vitro protection against HSV-2 and HIV-1 for 24h and 1 wk, respectively, based on the doses tested. In vitro cell culture and EpiVaginal tissue tests confirmed the safety of fibers in vaginal and cervical cells, highlighting the potential of PLGA and PLCL EFs as multipurpose next-generation drug delivery vehicles.

Development, Prevention, and Treatment of Alcohol-Induced Organ Injury: The Role of Nutrition

Alcohol and nutrition have the potential to interact at multiple levels. For example, heavy alcohol consumption can interfere with normal nutrition, resulting in overall malnutrition or in deficiencies of important micronutrients, such as zinc, by reducing their absorption or increasing their loss. Interactions between alcohol consumption and nutrition also can affect epigenetic regulation of gene expression by influencing multiple regulatory mechanisms, including methylation and acetylation of histone proteins and DNA. These effects may contribute to alcohol-related organ or tissue injury. The impact of alcohol-nutrition interactions has been assessed for several organs and tissues, including the intestine, where heavy alcohol use can increase intestinal permeability, and the liver, where the degree of malnutrition can be associated with the severity of liver injury and liver disease. Alcohol-nutrition interactions also play a role in alcohol-related lung injury, brain injury, and immune dysfunction. Therefore, treatment involving nutrient supplementation (e.g., with zinc or S-adenosylmethionine) may help prevent or attenuate some types of alcohol-induced organ damage.

Metabolomic analysis of the effects of chronic arsenic exposure in a mouse model of diet-induced Fatty liver disease

Arsenic is a widely distributed environmental component that is associated with a variety of cancer and non-cancer adverse health effects. Additional lifestyle factors, such as diet, contribute to the manifestation of disease. Recently, arsenic was found to increase inflammation and liver injury in a dietary model of fatty liver disease. The purpose of the present study was to investigate potential mechanisms of this diet-environment interaction via a high-throughput metabolomics approach. GC×GC-TOF MS was used to identify metabolites that were significantly increased or decreased in the livers of mice fed a Western diet (a diet high in fat and cholesterol) and co-exposed to arsenic-contaminated drinking water. The results showed that there are distinct hepatic metabolomic profiles associated with eating a high fat diet, drinking arsenic-contaminated water, and the combination of the two. Among the metabolites that were decreased when arsenic exposure was combined with a high fat diet were short-chain and medium-chain fatty acid metabolites and the anti-inflammatory amino acid, glycine. These results are consistent with the observed increase in inflammation and cell death in the livers of these mice and point to potentially novel mechanisms by which these metabolic pathways could be altered by arsenic in the context of diet-induced fatty liver disease.

An interactive video-computer tracking system for quantification of locomotor behavior

We have developed a flexible, moderately priced, behavioral analysis system which has been used to determine the response of salmonids to certain olfactory stimulants. The system, which we call ITS for interactive computer-video tracking system, consists of a 128K Apple IIe computer with software, a video camera and videocassette recorder, and a special-effects generator. Experiments are video taped and then, during playback, the special effects generator is used to simultaneously display the video image and the graphics output of the computer on a monitor. The user tracks the animal of interest using an electronic pen, and the position of that animal in the test chamber, in the form ofx-y coordinates, is determined by the computer at user-defined time intervals. When tracking is complete, a plot of the track of the animal is printed within the outline of the test chamber. The following data can also be calculated: swimming velocity, distance from a predetermined point in the chamber (for example, olfactory stimulant source), and time spent in a given area. These variables can be calculated over any chosen time periods and/or for the entire experiment. ITS has numerous advantages over commercially available devices that perform similar tasks. First, it is relatively inexpensive, especially if one already owns video equipment and a computer. Second, it can analyze many types of experiments that can be stored on video tape, including field observations or manipulations. Third, because it is not automated, it is easy to track multiple objects, even if their tracks cross or are not easily located against a low-contrast background. Finally, because whole images do not have to be digitized, and data collection intervals can be adjusted by the user, it is possible to analyze very long experiments with a microcomputer. In this paper we describe ITS and then we demonstrate how we have used it to demonstrate that changes in ambient pH alter the behavioral response of juvenile Atlantic salmon to olfactory stimuli.

S-adenosylhomocysteine inhibits NF-κB-mediated gene expression in hepatocytes and confers sensitivity to TNF cytotoxicity

BACKGROUND

Chronic alcohol exposure results in liver injury that is driven in part by inflammatory cytokines such as tumor necrosis factor-α (TNF). Hepatocytes are normally resistant to the cytotoxic effects of TNF, but they become sensitized to TNF by chronic alcohol exposure. Recently, we reported that the decrease in the ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH) that occurs with alcoholic liver injury renders hepatocytes sensitive to TNF cytotoxicity. The purpose of this study was to determine whether inhibition of the transcription factor nuclear factor-kappaB (NF-κB) contributed to TNF-induced cell death in hepatocytes with high levels of SAH.

METHODS

Primary human hepatocytes or HepG2 cells were pre-incubated with a combination of adenosine plus homocysteine to increase SAH levels. Following exposure to TNF, viability was determined by the MTT assay, and activation of the NF-κB pathway was assessed by measuring degradation of cytosolic IκB-α, phosphorylation and translocation of NF-κB to the nucleus, and expression of NF-κB-dependent genes. TNF-induced apoptotic signaling pathways were assessed by monitoring levels of the anti-apoptotic protein, A20, and cleavage products of the caspase-8 substrate, RIP1.

RESULTS

NF-κB-mediated gene expression was inhibited in cells with high SAH, despite the fact that TNF-induced degradation of the cytoplasmic inhibitor IκB-α and accumulation of NF-κB in the nucleus persisted for much longer. In contrast to control cells, the NF-κB that accumulated in the nucleus of cells with high SAH levels was not phosphorylated at serine 536, a modification associated with activation of the transactivation potential of this transcription factor. The inhibition of transactivation by NF-κB resulted in lower mRNA and protein levels of the anti-apoptotic protein A20 and increased cleavage of RIP1.

CONCLUSIONS

High SAH levels inhibited NF-κB-mediated gene expression and sensitized primary hepatocytes and HepG2 cells to the cytotoxic effects of TNF. It is likely that crosstalk with other transcription factors is perturbed under these conditions, resulting in still other changes in gene expression.

MetPP: a computational platform for comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry-based metabolomics

MOTIVATION

Due to the high complexity of metabolome, the comprehensive 2D gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS) is considered as a powerful analytical platform for metabolomics study. However, the applications of GC×GC-TOF MS in metabolomics are not popular owing to the lack of bioinformatics system for data analysis.

RESULTS

We developed a computational platform entitled metabolomics profiling pipeline (MetPP) for analysis of metabolomics data acquired on a GC×GC-TOF MS system. MetPP can process peak filtering and merging, retention index matching, peak list alignment, normalization, statistical significance tests and pattern recognition, using the peak lists deconvoluted from the instrument data as its input. The performance of MetPP software was tested with two sets of experimental data acquired in a spike-in experiment and a biomarker discovery experiment, respectively. MetPP not only correctly aligned the spiked-in metabolite standards from the experimental data, but also correctly recognized their concentration difference between sample groups. For analysis of the biomarker discovery data, 15 metabolites were recognized with significant concentration difference between the sample groups and these results agree with the literature results of histological analysis, demonstrating the effectiveness of applying MetPP software for disease biomarker discovery.

AVAILABILITY

The source code of MetPP is available at http://metaopen.sourceforge.net

CONTACT

xiang.zhang@louisville.edu

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

GSH or palmitate preserves mitochondrial energetic/redox balance, preventing mechanical dysfunction in metabolically challenged myocytes/hearts from type 2 diabetic mice

In type 2 diabetes, hyperglycemia and increased sympathetic drive may alter mitochondria energetic/redox properties, decreasing the organelle's functionality. These perturbations may prompt or sustain basal low-cardiac performance and limited exercise capacity. Yet the precise steps involved in this mitochondrial failure remain elusive. Here, we have identified dysfunctional mitochondrial respiration with substrates of complex I, II, and IV and lowered thioredoxin-2/glutathione (GSH) pools as the main processes accounting for impaired state 4→3 energetic transition shown by mitochondria from hearts of type 2 diabetic db/db mice upon challenge with high glucose (HG) and the β-agonist isoproterenol (ISO). By mimicking clinically relevant conditions in type 2 diabetic patients, this regimen triggers a major overflow of reactive oxygen species (ROS) from mitochondria that directly perturbs cardiac electro-contraction coupling, ultimately leading to heart dysfunction. Exogenous GSH or, even more so, the fatty acid palmitate rescues basal and β-stimulated function in db/db myocyte/heart preparations exposed to HG/ISO. This occurs because both interventions provide the reducing equivalents necessary to counter mitochondrial ROS outburst and energetic failure. Thus, in the presence of poor glycemic control, the diabetic patient's inability to cope with increased cardiac work demand largely stems from mitochondrial redox/energetic disarrangements that mutually influence each other, leading to myocyte or whole-heart mechanical dysfunction.

Simultaneous inhibition of glutathione- and thioredoxin-dependent metabolism is necessary to potentiate 17AAG-induced cancer cell killing via oxidative stress

17-Allylamino-17-demethoxygeldanamycin (17AAG) is an experimental chemotherapeutic agent believed to form free radicals in vivo, and cancer cell resistance to 17AAG is believed to be a thiol-dependent process. Inhibitors of thiol-dependent hydroperoxide metabolism [L-buthionine-S,R-sulfoximine (BSO) and auranofin] were combined with the glucose metabolism inhibitor 2-deoxy-d-glucose (2DG) to determine if 17AAG-mediated cancer cell killing could be enhanced. When 2DG (20mM, 24h), BSO (1mM, 24h), and auranofin (500nM, 3h) were combined with 17AAG, cell killing was significantly enhanced in three human cancer cell lines (PC-3, SUM159, MDA-MB-231). Furthermore, the toxicity of this drug combination was significantly greater in SUM159 human breast cancer cells, relative to HMEC normal human breast epithelial cells. Increases in toxicity seen with this drug combination also correlated with increased glutathione (GSH) and thioredoxin (Trx) oxidation and depletion. Furthermore, treatment with the thiol antioxidant NAC (15mM, 24h) was able to significantly protect from drug-induced toxicity and ameliorate GSH oxidation, Trx oxidation, and Trx depletion. These data strongly support the hypothesis that simultaneous inhibition of GSH- and Trx-dependent metabolism is necessary to sensitize human breast and prostate cancer cells to 2DG+17AAG-mediated killing via enhancement of thiol-dependent oxidative stress. These results suggest that simultaneous targeting of both GSH and Trx metabolism could represent an effective strategy for chemosensitization in human cancer cells.

Transactivation of gene expression by NF-κB is dependent on thioredoxin reductase activity

The redox-sensitive transcription factor NF-κB mediates the expression of genes involved in inflammation and cell survival. Thioredoxin reductase-1 (TR1) and its substrate thioredoxin-1 act together to reduce oxidized cysteine residues within the DNA-binding domain of NF-κB and promote maximal DNA-binding activity in vitro. It is not clear, however, if NF-κB is regulated via this mechanism within living cells. The purpose of this study was to determine the mechanism of NF-κB modulation by TR1 in cells stimulated with the inflammatory cytokine tumor necrosis factor-α (TNF). In both control cells and cells depleted of TR1 activity through chemical inhibition or siRNA knockdown, TNF stimulation resulted in degradation of the cytoplasmic NF-κB inhibitor IκB-α and translocation of NF-κB to the nucleus. Similarly, the DNA-binding activity and redox state of NF-κB were unaffected by TR1 depletion. In contrast, NF-κB-mediated gene expression was markedly inhibited in cells lacking TR1 activity, suggesting that the transactivation potential of NF-κB is sensitive to changes in TR1 activity. Consistent with this concept, phosphorylation of the transactivation domain of NF-κB was inhibited in the presence of curcumin. Surprisingly, another TR1 inhibitor, 1-chloro-2,4-dinitrobenzene, had no effect, and siRNA knockdown of TR1 actually increased phosphorylation at this site. These results demonstrate that TR1 activity controls the transactivation potential of NF-κB and that more than one mechanism may mediate this effect.

Dietary selenium as a modulator of PCB 126-induced hepatotoxicity in male Sprague-Dawley rats

Homeostasis of selenium (Se), a critical antioxidant incorporated into amino acids and enzymes, is disrupted by exposure to aryl hydrocarbon receptor (AhR) agonists. Here we examined the importance of dietary Se in preventing the toxicity of the most toxic polychlorinated biphenyl congener, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), a potent AhR agonist. Male Sprague-Dawley rats were fed a modified AIN-93 diet with differing dietary Se levels (0.02, 0.2, and 2 ppm). Following 3 weeks of acclimatization, rats from each dietary group were given a single ip injection of corn oil (vehicle), 0.2, 1, or 5 μmol/kg body weight PCB 126, followed 2 weeks later by euthanasia. PCB exposure caused dose-dependent increases in liver weight and at the highest PCB 126 dose decreases in whole body weight gains. Hepatic cytochrome P-450 (CYP1A1) activity was significantly increased even at the lowest dose of PCB 126, indicating potent AhR activation. PCB exposure diminished hepatic Se levels in a dose-dependent manner, and this was accompanied by diminished Se-dependent glutathione peroxidase activity. Both these effects were partially mitigated by Se supplementation. Conversely, thioredoxin (Trx) reductase activity and Trx oxidation state, although significantly diminished in the lowest dietary Se groups, were not affected by PCB exposure. In addition, PCB 126-induced changes in hepatic copper, iron, manganese, and zinc were observed. These results demonstrate that supplemental dietary Se was not able to completely prevent the toxicity caused by PCB 126 but was able to increase moderately the levels of several key antioxidants, thereby maintaining them roughly at normal levels.

Thioredoxin reductase-2 is essential for keeping low levels of H(2)O(2) emission from isolated heart mitochondria

Respiring mitochondria produce H(2)O(2) continuously. When production exceeds scavenging, H(2)O(2) emission occurs, endangering cell functions. The mitochondrial peroxidase peroxiredoxin-3 reduces H(2)O(2) to water using reducing equivalents from NADPH supplied by thioredoxin-2 (Trx2) and, ultimately, thioredoxin reductase-2 (TrxR2). Here, the contribution of this mitochondrial thioredoxin system to the control of H(2)O(2) emission was studied in isolated mitochondria and cardiomyocytes from mouse or guinea pig heart. Energization of mitochondria by the addition of glutamate/malate resulted in a 10-fold decrease in the ratio of oxidized to reduced Trx2. This shift in redox state was accompanied by an increase in NAD(P)H and was dependent on TrxR2 activity. Inhibition of TrxR2 in isolated mitochondria by auranofin resulted in increased H(2)O(2) emission, an effect that was seen under both forward and reverse electron transport. This effect was independent of changes in NAD(P)H or membrane potential. The effects of auranofin were reproduced in cardiomyocytes; superoxide and H(2)O(2) levels increased, but similarly, there was no effect on NAD(P)H or membrane potential. These data show that energization of mitochondria increases the antioxidant potential of the TrxR2/Trx2 system and that inhibition of TrxR2 results in increased H(2)O(2) emission through a mechanism that is independent of changes in other redox couples.

Nrf2-dependent sulfiredoxin-1 expression protects against cigarette smoke-induced oxidative stress in lungs

Oxidative stress results in protein oxidation and is involved in the pathogenesis of lung diseases such as chronic obstructive pulmonary disorder (COPD). Sulfiredoxin-1 (Srx1) catalyzes the reduction of cysteine sulfinic acid to sulfenic acid in oxidized proteins and protects them from inactivation. This study examined the mechanism of transcriptional regulation of Srx1 and its possible protective role during oxidative stress associated with COPD. Nrf2, a transcription factor known to influence susceptibility to pulmonary diseases, upregulates Srx1 expression during oxidative stress caused by cigarette smoke exposure in the lungs of mice. Disruption of Nrf2 signaling by genetic knockout in mice or RNAi in cells downregulated the expression of Srx1. In silico analysis of the 5'-promoter-flanking region of Srx1 identified multiple antioxidant-response elements (AREs) that are highly conserved. Reporter and chromatin-immunoprecipitation assays demonstrated that ARE1 at -228 is critical for the Nrf2-mediated response. Attenuation of Srx1 expression with RNAi potentiated the toxicity of hydrogen peroxide (H2O2), whereas overexpression of Srx1 protected against H2O2-mediated cell death in vitro. Immunoblot analysis revealed dramatic decreases in Srx1 expression in lungs from patients with COPD relative to nonemphysematous lungs together with a decline in Nrf2 protein. Thus, Srx1, a key Nrf2-regulated gene, contributes to protection against oxidative injury in the lung.

RNAi-mediated silencing of nuclear factor erythroid-2-related factor 2 gene expression in non-small cell lung cancer inhibits tumor growth and increases efficacy of chemotherapy

Nuclear factor erythroid-2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that regulates the expression of electrophile and xenobiotic detoxification enzymes and efflux proteins, which confer cytoprotection against oxidative stress and apoptosis in normal cells. Loss of function mutations in the Nrf2 inhibitor, Kelch-like ECH-associated protein (Keap1), results in constitutive activation of Nrf2 function in non-small cell lung cancer. In this study, we show that constitutive activation of Nrf2 in lung cancer cells promotes tumorigenicity and contributes to chemoresistance by up-regulation of glutathione, thioredoxin, and the drug efflux pathways involved in detoxification of electrophiles and broad spectrum of drugs. RNAi-mediated reduction of Nrf2 expression in lung cancer cells induces generation of reactive oxygen species, suppresses tumor growth, and results in increased sensitivity to chemotherapeutic drug-induced cell death in vitro and in vivo. Inhibiting Nrf2 expression using naked siRNA duplexes in combination with carboplatin significantly inhibits tumor growth in a subcutaneous model of lung cancer. Thus, targeting Nrf2 activity in lung cancers, particularly those with Keap1 mutations, could be a promising strategy to inhibit tumor growth and circumvent chemoresistance.

Oxidation and nuclear localization of thioredoxin-1 in sparse cell cultures

Reactive oxygen species (ROS) were once viewed only as mediators of toxicity, but it is now recognized that they also contribute to redox signaling through oxidation of specific cysteine thiols on regulatory proteins. Cells in sparse cultures have increased ROS relative to confluent cultures, but it is not known whether protein redox states are affected under these conditions. The purpose of the present study was to determine whether culture conditions affect the redox state of thioredoxin-1 (Trx1), the protein responsible for reducing most oxidized proteins in the cytoplasm and nucleus. The results showed that Trx1 was more oxidized in sparse HeLa cell cultures than in confluent cells. The glutathione pool was also more oxidized, demonstrating that both of the major cellular redox regulating systems were affected by culture density. In addition, the total amount of Trx1 protein was lower and the subcellular distribution of Trx1 was different in sparse cells. Trx1 in sparse cultures was predominantly nuclear whereas it was predominantly cytoplasmic in confluent cultures. This localization pattern was not unique to HeLa cells as it was also observed in A549, Cos-1 and HEK293 cells. These findings demonstrate that Trx1 is subject to changes in expression, redox state and subcellular localization with changing culture density, indicating that the redox environments of the cytoplasm and the nucleus are distinct and have different requirements under different culture conditions.

Redox-regulation of Erk1/2-directed phosphatase by reactive oxygen species: role in signaling TPA-induced growth arrest in ML-1 cells

Extracellular signal-regulated kinase (Erk)1/2 activity signals myeloid cell differentiation induced by 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Previously, we reported that Erk1/2 activation (phosphorylation) induced by TPA required reactive oxygen species (ROS) as a second messenger. Here, we hypothesized that ROS generated in response to TPA inhibit Erk1/2-directed phosphatase activity, which leads to an increase phosphorylation of Erk1/2 to signal p21(WAF1/Cip1)-mediated growth arrest in ML-1 cells. Incubation of ML-1 cells with TPA resulted in a marked accumulation of phosphorylated Erk1/2, and is subsequent to H2O2 generation. Interestingly, post-TPA-treatment with N-acetylcysteine (NAC) stimulated a marked and a rapid dephosphorylation of Erk1/2, suggesting a regeneration of Erk1/2-directed phospahatase activity by NAC. ROS generation in ML-1 cells induced by TPA was suggested to occur in the mitochondrial electron transport chain (METC) based on the following observations: (i) undifferentiated ML-1 cells not only lack p67-phox and but also express a low level of p47-phox key components required for NADPH oxidase enzymatic activity, (ii) pretreatment with DPI, an inhibitor of NADH- and NADPH-dependent enzymes, or rhein, an inhibitor of complex I, blocked the ROS generation, and (iii) examination of the microarray analysis data and Western blot analysis data revealed an induction of MnSOD expression at both mRNA and protein levels in response to TPA. MnSOD is a key member of the mitochondrial defense system against mitochondrial-derived superoxide. Together, this study suggested that TPA stimulated ROS generation as a second messenger to activate Erk1/2 via a redox-mediated inhibition of Erk1/2-directed phosphatase in ML-1 cells.

Thioredoxin reductase-1 knock down does not result in thioredoxin-1 oxidation

The active site of thioredoxin-1 (Trx1) is oxidized in cells with increased reactive oxygen species (ROS) and is reduced by thioredoxin reductase-1 (TrxR1). The purpose of the present study was to determine the extent to which the redox state of Trx1 is sensitive to changes in these opposing reactions. Trx1 redox state and ROS generation were measured in cells exposed to the TrxR1 inhibitors aurothioglucose (ATG) and monomethylarsonous acid (MMA(III)) and in cells depleted of TrxR1 activity by siRNA knock down. The results showed that all three treatments inhibited TrxR1 activity to similar extents (90% inhibition), but that only MMA(III) exposure resulted in oxidation of Trx1. Similarly, ROS levels were elevated in response to MMA(III), but not in response to ATG or TrxR1 siRNA. Therefore, TrxR1 inhibition alone was not sufficient to oxidize Trx1, suggesting that Trx1-independent pathways should be considered when evaluating pharmacological and toxicological mechanisms involving TrxR1 inhibition.

The effects of glutaredoxin and copper activation pathways on the disulfide and stability of Cu,Zn superoxide dismutase

Mutations in Cu,Zn superoxide dismutase (SOD1) can cause amyotrophic lateral sclerosis (ALS) through mechanisms proposed to involve SOD1 misfolding, but the intracellular factors that modulate folding and stability of SOD1 are largely unknown. By using yeast and mammalian expression systems, we demonstrate here that SOD1 stability is governed by post-translational modification factors that target the SOD1 disulfide. Oxidation of the human SOD1 disulfide in vivo was found to involve both the copper chaperone for SOD1 (CCS) and the CCS-independent pathway for copper activation. When both copper pathways were blocked, wild type SOD1 stably accumulated in yeast cells with a reduced disulfide, whereas ALS SOD1 mutants A4V, G93A, and G37R were degraded. We describe here an unprecedented role for the thiol oxidoreductase glutaredoxin in reducing the SOD1 disulfide and destabilizing ALS mutants. Specifically, the major cytosolic glutaredoxin of yeast was seen to reduce the intramolecular disulfide of ALS SOD1 mutant A4V SOD1 in vivo and in vitro. By comparison, glutaredoxin was less reactive toward the disulfide of wild type SOD1. The apo-form of A4V SOD1 was highly reactive with glutaredoxin but not SOD1 containing both copper and zinc. Glutaredoxin therefore preferentially targets the immature form of ALS mutant SOD1 lacking metal co-factors. Overall, these studies implicate a critical balance between cellular reductants such as glutaredoxin and copper activation pathways in controlling the disulfide and stability of SOD1 in vivo.

Compartmentation of Nrf-2 redox control: regulation of cytoplasmic activation by glutathione and DNA binding by thioredoxin-1

Nrf-2 is a redox-sensitive transcription factor that is activated by an oxidative signal in the cytoplasm but has a critical cysteine that must be reduced to bind to DNA in the nucleus. The glutathione (GSH) and thioredoxin (TRX) systems have overlapping functions in thiol/disulfide redox control in both the cytoplasm and the nucleus, and it is unclear whether these are redundant or have unique functions in control of Nrf-2-dependent signaling. To test whether GSH and Trx-1 have distinct functions in Nrf-2 signaling, we selectively modified GSH by metabolic manipulation and selectively modified Trx-1 expression by transient transfection. Cytoplasmic activation of Nrf-2 was measured by its nuclear translocation and nuclear activity of Nrf-2 was measured by expression of a luciferase reporter construct containing an ARE4 from glutamate cysteine ligase. Results showed that tert-butylhydroquinone (TBHQ), a transcriptional activator that functions through Nrf-2/ARE, promoted Nrf-2 nuclear translocation by a type I (thiylation) redox switch which was regulated by GSH not by Trx-1. In contrast, the ARE reporter was principally controlled by nuclear-targeted Trx-1 and not by GSH. The data show that the GSH and TRX systems have unique, compartmented functions in the control of transcriptional regulation by Nrf-2/ARE.

Thioredoxin and Its Role in Toxicology

Thioredoxins (Trx) are members of an evolutionarily conserved family of redox-active proteins containing a conserved active site dithiol motif. Trx supports diverse reduction reactions, including several of direct toxicologic interest, but relatively little information is available concerning the roles of Trx under specific toxicologic conditions. Accumulating evidence suggests that Trx serves a partially overlapping and highly complementary role to the glutathione (GSH) system in protecting against toxicity. GSH and Trx both function in the reduction of peroxides through the action of multiple GSH peroxidases and Trx peroxidases (peroxiredoxins), respectively. However, GSH is a small molecule that is present at millimolar concentrations, thereby providing a potential mechanism for elimination of alkylating electrophiles. In contrast, even though Trx is only present at micromolar or submicromolar concentrations, its dithiol motif makes it suited to reverse oxidative changes to proteins, including reduction of protein disulfides, methioninyl sulfoxides, and cysteinyl sulfenic acids. Moreover, Trx functions in redox-sensitive signal transduction, transcriptional activation of stress response genes, ribonucleotide reduction in synthesis of deoxyribonucleotides for DNA repair, and post-injury cell proliferation. Molecular studies show that the predominant cytoplasmic/nuclear form, Trx-1, and the mitochondrial form, Trx-2, both protect against oxidative stress, that both are essential for embryonic development, and that Trx-1 is inducible in response to oxidative stress. Because of the differences between GSH and Trx in distribution, catalytic activities and reactivities with electrophiles, particularly with the important role to be played by glutathione S-transferases, considerable research is needed to clarify their respective roles in protection against specific toxicologic conditions.

Redox potential of human thioredoxin 1 and identification of a second dithiol/disulfide motif

Thioredoxin (Trx1) is a redox-active protein containing two active site cysteines (Cys-32 and Cys-35) that cycle between the dithiol and disulfide forms as Trx1 reduces target proteins. Examination of the redox characteristics of this active site dithiol/disulfide couple is complicated by the presence of three additional non-active site cysteines. Using the redox Western blot technique and matrix assisted laser desorption ionization time-of-flight mass spectrometry mass spectrometry, we determined the midpoint potential (E0) of the Trx1 active site (-230 mV) and identified a second redox-active dithiol/disulfide (Cys-62 and Cys-69) in an alpha helix proximal to the active site, which formed under oxidizing conditions. This non-active site disulfide was not a substrate for reduction by thioredoxin reductase and delayed the reduction of the active site disulfide by thioredoxin reductase. Within actively growing THP1 cells, most of the active site of Trx1 was in the dithiol form, whereas the non-active site was totally in the dithiol form. The addition of increasing concentrations of diamide to these cells resulted in oxidation of the active site at fairly low concentrations and oxidation of the non-active site at higher concentrations. Taken together these results suggest that the Cys-62-Cys-69 disulfide could provide a means to transiently inhibit Trx1 activity under conditions of redox signaling or oxidative stress, allowing more time for the sensing and transmission of oxidative signals.

Oxidation of nuclear thioredoxin during oxidative stress

Thioredoxin 1 (Trx1) is a key redox control system within the nucleus, yet little is known about the sensitivity of nuclear Trx1 to oxidative stress. The present study compared oxidant-induced changes in the redox states of nuclear Trx1, cytoplasmic Trx1, and cellular glutathione (GSH). Nuclear Trx1 was more reducing than cytoplasmic Trx1 and cellular GSH in proliferating cells. tert-Butylhydroperoxide caused an increase in the total amount of nuclear Trx1, but this was accompanied by a 60 mV oxidation. Thus, the increase in nuclear Trx1 levels did not correspond to an increase in the overall reducing capacity of Trx1 in the nucleus.

Glutathione and thioredoxin redox during differentiation in human colon epithelial (Caco-2) cells

Cellular redox, maintained by the glutathione (GSH)- and thioredoxin (Trx)-dependent systems, has been implicated in the regulation of a variety of biological processes. The redox state of the GSH system becomes oxidized when cells are induced to differentiate by chemical agents. The aim of this study was to determine the redox state of cellular GSH/glutathione disulfide (GSH/GSSG) and Trx as a consequence of progression from proliferation to contact inhibition and spontaneous differentiation in colon carcinoma (Caco-2) cells. Results showed a significant decrease in GSH concentration, accompanied by a 40-mV oxidation of the cellular GSH/GSSG redox state and a 28-mV oxidation of the extracellular cysteine/cystine redox state in association with confluency and increase in differentiation markers. The redox state of Trx did not change. Thus the two central cellular antioxidant and redox-regulating systems (GSH and Trx) were independently controlled. According to the Nernst equation, a 30-mV oxidation is associated with a 10-fold change in the reduced/oxidized ratio of a redox-sensitive dithiol motif. Therefore, the measured 40-mV oxidation of the cellular GSH/GSSG couple or the 28-mV oxidation of the extracellular cysteine/cystine couple should be sufficient to function in signaling or regulation of differentiation in Caco-2 cells.

Swimming behavior of the nudibranch Melibe leonina

Swimming in the nudibranch Melibe leonina consists of five types of movements that occur in the following sequence: (1) withdrawal, (2) lateral flattening, (3) a series of lateral flexions, (4) unrolling and swinging, and (5) termination. Melibe swims spontaneously, as well as in response to different types of aversive stimuli. In this study, swimming was elicited by contact with the tube feet of the predatory sea star Pycnopodia helianthoides, pinching with forceps, or application of a 1 M KCl solution. During an episode of swimming, the duration of swim cycles (2.7 +/- 0.2 s [mean +/- SEM], n = 29) and the amplitude of lateral flexions remained relatively constant. However, the latency between the application of a stimulus and initiation of swimming was more variable, as was the duration of an episode of swimming. For example, when touched with a single tube foot from a sea star (n = 32), the latency to swim was 7.0 +/- 2.4 s, and swimming continued for 53.7 +/- 9.4 s, whereas application of KCl resulted in a longer latency to swim (22.3 +/- 4.5 s) and more prolonged swimming episodes (174.9 +/- 32.1 s). Swimming individuals tended to move in a direction perpendicular to the long axis of the foot, which propelled them laterally when they were oriented with the oral hood toward the surface of the water. The results of this study indicate that swimming in Melibe, like that in several other molluscs, is a stereotyped fixed action pattern that can be reliably elicited in the laboratory. These characteristics, along with the large identifiable neurons typical of many molluscs, make swimming in this nudibranch amenable to neuroethological analyses.

Oxidation of the glutathione/glutathione disulfide redox state is induced by cysteine deficiency in human colon carcinoma HT29 cells

Glutathione (GSH) has a central role in the maintenance of the thiol-disulfide redox state in mammalian cells. GSH synthesis can be physiologically limited by the availability of cysteine (Cys), and Cys and its precursors are variable in the human diet. The purpose of this study was to determine the effect of severe Cys deficiency and readdition of Cys on the redox state of the GSH/glutathione disulfide (GSSG) pool in human colon carcinoma HT29 cells. Cells were cultured in Cys- (and cystine-)limiting medium for 48 h followed by culture in medium containing either Cys or cystine for 24 h. GSH and GSSG were measured by HPLC. Cys limitation decreased cellular GSH and GSSG concentrations with an associated >80 mV oxidation of the GSH/GSSG redox state. Upon addition of either Cys or its disulfide cystine (CySS), redox of GSH/GSSG recovered in 4 h, whereas GSH concentration continued to increase over 12 h. Maximal GSH concentrations attained were 200% of control cell values. These results show that severe Cys deficiency can have marked effects on cellular redox state but that redox recovers rapidly upon resupply. The magnitude of oxidation during Cys limitation in this cell model is sufficient to result in a >100-fold change in the reduced/oxidized ratio of redox-sensitive dithiol/disulfide motifs in proteins. If redox changes occur in vivo in association with variations in dietary Cys and its precursors, these changes could have important physiologic effects through altered redox signaling and control of cell proliferation and apoptosis.

S-Adenosylmethionine, cytokines, and alcoholic liver disease

Hepatic deficiency of S-adenosylmethionine (AdoMet) is a critical acquired metabolic abnormality in alcoholic liver disease (ALD) and in many experimental models of hepatotoxicity. Subnormal AdoMet, elevated serum tumor necrosis factor (TNF), and endotoxemia (LPS) are hallmarks of ALD and experimental liver injury. AdoMet deficiency is attributed to its subnormal synthesis, but mechanisms for increased TNF are not known. AdoMet deficiency may affect the critical balance of proinflammatory (e.g., TNF) and antiinflammatory [e.g., interleukin (IL)-10] cytokines. Rats maintained on a choline-deficient diet with limited amounts of methionine (MCD diet) developed AdoMet deficiency. When challenged with LPS, rats fed MCD diet had significantly increased serum TNF levels and worse liver injury compared with findings for controls. Exogenous AdoMet attenuated liver injury and serum TNF levels. Results of in vitro studies with the use of RAW 264.7 cells demonstrated that exogenous AdoMet supplementation lowered LPS-induced TNF formation in a dose-dependent manner, and AdoMet deficiency enhanced TNF secretion and TNF gene expression. AdoMet also dose-dependently decreased LPS-stimulated TNF production from monocytes obtained from patients with alcoholic hepatitis. Finally, AdoMet supplementation stimulated production of the antiinflammatory cytokine IL-10. Interleukin-10 plays a critical role in the modulation of TNF production, and IL-10 may inhibit hepatic fibrosis. This article will review (1) the role of AdoMet in ALD/liver injury, (2) the role of TNF/proinflammatory cytokines in ALD, (3) potential roles of AdoMet in TNF/proinflammatory cytokine regulation in ALD, and (4) conclusions and future directions.

Detection of salinity by the lobster, Homarus americanus

Changes in the heart rates of lobsters (Homarus americanus) were used as an indicator that the animals were capable of sensing a reduction in the salinity of the ambient seawater. The typical response to a gradual (1 to 2 ppt/min) reduction in salinity consisted of a rapid increase in heart rate at a mean threshold of 26.6 +/- 0.7 ppt, followed by a reduction in heart rate when the salinity reached 22.1 +/- 0.5 ppt. Animals with lesioned cardioregulatory nerves did not exhibit a cardiac response to changes in salinity. A cardiac response was elicited from lobsters exposed to isotonic chloride-free salines but not to isotonic sodium-, magnesium- or calcium-free salines. There was little change in the blood osmolarity of lobsters when bradycardia occurred, suggesting that the receptors involved are external. Furthermore, lobsters without antennae, antennules, or legs showed typical cardiac responses to low salinity, indicating the receptors are not located in these areas. Lobsters exposed to reductions in the salinity of the ambient seawater while both branchial chambers were perfused with full-strength seawater did not display a cardiac response until the external salinity reached 21.6 +/- 1.8 ppt. In contrast, when their branchial chambers were exposed to reductions in salinity while the external salinity was maintained at normal levels, changes in heart rate were rapidly elicited in response to very small reductions in salinity (down to 29.5 +/- 0.9 ppt in the branchial chamber and 31.5 +/- 0.3 ppt externally). We conclude that the primary receptors responsible for detecting reductions in salinity in H. americanus are located within or near the branchial chambers and are primarily sensitive to chloride ions.

Identifiable nitrergic neurons in the central nervous system of the nudibranch Melibe leonina localized with NADPH-diaphorase histochemistry and nitric oxide synthase immunoreactivity

Nitric oxide (NO) is a gaseous intercellular messenger produced by the enzyme nitric oxide synthase (NOS). In this study, we used two different techniques-nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and NOS immunocytochemistry-to demonstrate that NOS is present in a pair of identifiable cells in the central nervous system of the nudibranch Melibe leonina. In the Melibe brain, NADPH-d histochemistry revealed only a single pair of bilaterally symmetrical cells in the cerebropleural ganglia. NOS activity also was found in the neuropil of the cerebral, pedal, and buccal ganglia; in the tentacles of the oral hood; in the sensory end of the rhinophores; and in the epithelial tissue of the mouth, preputium, and glans penis. Immunocytochemistry using NOS antisera corroborated the results of the NADPH-d histochemistry by staining the same two cells in the cerebropleural ganglia. Each of these identifiable nitrergic neurons projects into the ipsilateral pedal ganglion. Because the pedal ganglia play a critical role in the control of locomotion, our results provide morphological evidence suggesting that NO may influence swimming or crawling in Melibe leonina.

Reversal of nonarteritic anterior ischemic optic neuropathy associated with coexisting primary antiphospholipid syndrome and Factor V Leiden mutation

PURPOSE

To report nonarteric anterior ischemic optic neuropathy (NAION) as an ocular manifestation in a woman with combined primary antiphospholipid syndrome and Factor V Leiden (FVL) mutation.

METHODS

Case report of a middle-aged woman with hematological investigations confirming the diagnosis of both primary antiphospholipid syndrome and Factor V Leiden mutation, who presented with visual disturbance in her left eye.

RESULTS

NAION was noted in her left eye. The patient was promptly treated with low molecular weight heparin, followed by warfarin, which resulted in the reversal of the ischemic optic neuropathy.

CONCLUSIONS

Primary antiphospholipid syndrome and coexisting Factor V Leiden mutation should be considered in the differential diagnosis of NAION. Prompt treatment with anticoagulants can result in the reversal of the ischemic process.

Diet and apoptosis

A range of compounds in or derived from the diet modulates apoptosis in cell cultures in vitro. These observations have important implications concerning the mechanisms whereby dietary components affect health. Proapoptotic compounds could protect against cancer by enhancing elimination of initiated, precancerous cells, and antiapoptotic compounds could promote tumor formation by inhibiting apoptosis in genetically damaged cells. Proapoptotic compounds could also contribute to age-related degenerative diseases by activating cell death in postmitotic cells or shifting the normal balance of mitosis and apoptosis in tissues with regenerative capacity. Many age-related diseases, for example macular degeneration and Parkinson's disease, appear to have oxidative stress as an underlying component that interacts with genetic, dietary, and environmental factors to determine relative risk in an individual. Oxidative stress activates apoptosis, and antioxidants protect against apoptosis in vitro; thus, a central role of dietary antioxidants may be to protect against apoptosis. However, little in vivo data are available to directly link diet with altered apoptosis as an underlying determinant of disease. Moreover, the possible antagonistic effects of different dietary components and the uncertainty about whether proapoptotic compounds that may protect against cancer could contribute to degenerative diseases and vice versa indicate that there is a great need for better in vivo assessment of apoptosis and that caution should be exercised when extrapolating in vitro data on apoptosis to in vivo dietary recommendations.