Nrf2 activators modulate oxidative stress responses and bioenergetic profiles of human retinal epithelial cells cultured in normal or high glucose conditions

Retinal pigment epithelial cells exert an important supporting role in the eye and develop adaptive responses to oxidative stress or high glucose levels, as observed during diabetes. Endogenous antioxidant defences are mainly regulated by Nrf2, a transcription factor that is activated by naturally-derived and electrophilic compounds. Here we investigated the effect of the Nrf2 activators dimethylfumarate (DMF) and carnosol on antioxidant pathways, oxygen consumption rate and wound healing in human retinal pigment epithelial cells (ARPE-19) cultured in medium containing normal (NG, 5mM) or high (HG, 25 mM) glucose levels. We also assessed wound healing using an in vivo corneal epithelial injury model. We found that Nrf2 nuclear translocation and heme oxygenase activity increased in ARPE cells treated with 10 μM DMF or carnosol irrespective of glucose culture conditions. However, HG rendered retinal cells more sensitive to regulators of glutathione synthesis or inhibition and caused a decrease of both cellular and mitochondrial reactive oxygen species. Culture in HG also reduced ATP production and mitochondrial function as measured with the Seahorse XF analyzer and electron microscopy analysis revealed morphologically damaged mitochondria. Acute treatment with DMF or carnosol did not restore mitochondrial function in HG cells; conversely, the compounds reduced cellular maximal respiratory and reserve capacity, which were completely prevented by N-acetylcysteine thus suggesting the involvement of thiols in this effect. Interestingly, the scratch assay showed that wound closure was faster in cells cultured in HG than NG and was accelerated by carnosol. This effect was reversed by an inhibitor of heme oxygenase activity. Moreover, topical application of carnosol to the cornea of diabetic rats significantly accelerated wound healing. In summary, these data indicate that culture of retinal epithelial cells in HG does not affect the activation of the Nrf2/heme oxygenase axis but influences other crucial oxidative and mitochondrial-dependent cellular functions. The additional effect on wound closure suggests that results obtained in in vitro experimental settings need to be carefully evaluated in the context of the glucose concentrations used in cell culture.

N-acetylcysteine protects against liver injure induced by carbon tetrachloride via activation of the Nrf2/HO-1 pathway

Chronic liver injury is an important clinical problem which eventually leads to cirrhosis, hepatocellular carcinoma and end-stage liver failure. It is well known that cell damage induced by reactive oxygen species (ROS) is an important mechanism of hepatocyte injure. N-acetylcysteine (NAC), a precursor of glutathione (GSH), is well-known role as the antidote to acetaminophen toxicity in clinic. NAC is now being utilized more widely in the clinical setting for non-acetaminophen (APAP) related causes of liver injure. However, the mechanisms underlying its beneficial effects are poorly defined. Thus, Aim of the present study was to investigate potential hepatic protective role of NAC and to delineate its mechanism of action against carbon tetrachloride (CCl4)-induced liver injury in models of rat. Our results showed that the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities as well as malondialdehyde (MDA) contents decreased significantly in CCl4-induced rats with NAC treatment. GSH content and superoxide dismutase (SOD) activities remarkably increased in the NAC groups compared with those in CCl4-induced group. Treatment with NAC had been shown to an increase in nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) mRNA levels. In conclusion, these results suggested that NAC upregulated HO-1 through the activation of Nrf2 pathway and protected rat against CCl4-induced liver injure. The results of this study provided pharmacological evidence to support the clinical application of NAC.

[A experiment research of beryllium oxide induced oxidative lung injury and the protective effects of LBP in rats]

OBJECTIVE

To explore beryllium oxide induced oxidative lung injury and the protective effects of LBP.

METHODS

Intoxication of animals were induced by once intratracheal injection and LBP intervention by intragastric administration. The content of HIF-1, VEGF and HO-1 of lung tissues were measured by kits. The pathological changes of lung tissue were showed by pathological section. The changes of lung ultrastructure were observed by electron microscope.

RESULTS

Pathological changes of the lung tissue in beryllium oxide exposure group rats were in line with the characteristics of beryllium disease in human. Compared with the control group, HO-1 was increased in beryllium oxide exposure 40 d group and low doses of LBP group, compared with the control group, HO-1 was increased in beryllium oxide exposure 80d group and LBP treatment groups (P < 0.05 or P < 0.01). Compared with the control group, HIF-1 was increased in beryllium oxide exposure 40 d group, LBP treatment groups, beryllium oxide exposure 60 d and 80 d groups (P < 0.05 or P < 0.01). Compared with the control group, VEGF was increased of all phases, especially in beryllium oxide exposure 40d and 80 groups, LBP treatment groups and beryllium oxide exposure 60 d (P < 0.05 or P < 0.01). The content of HO-1 of beryllium oxide exposure group was higher than the LBP treatment for 40d group but below LBP treatment for 80 d group (P < 0.05). The content of HIF1 of beryllium oxide exposure group was higher than high dose of LBP treatment for 60d group and LBP treatment for 80 d group (P < 0.01). The content of VEGF of beryllium oxide exposure group was higher than LBP treatment for 40 d group and high dose of LBP treatment for 60 d (P < 0.05 or P < 0.01).

CONCLUSIONS

BeO can cause abnormal expression of related genes of lung tissue in rats, LBP has protective effects on BeO caused lung injury.

Glutamine ameliorates intestinal ischemia-reperfusion Injury in rats by activating the Nrf2/Are signaling pathway

Ischemia-reperfusion (I/R)-mediated intestinal mucosal injury is usually induced by oxygen-derived toxic free radicals from the xanthine oxidase system after reperfusion, but the detailed molecular mechanisms underlying glutamine protection is still unclear. This study aims to elucidate whether glutamine prevents damage to the intestinal mucosa after I/R in rats and to investigate signaling by the Nrf2/ARE pathway induced by GLN in a rat model. Our results revealed that Glutamine pretreatment reduced jejunum injury and microvascular hyper-permeability induced by I/R. MDA level significantly increased while the SOD and GSH-Px levels decreased in the I/R group compared to the sham group and the GLN-I/R group. Both the mRNA and protein levels of the Nrf2 and HO-1 were significantly elevated by GLN pretreatment when compared to the I/R group. GLN treatment also elevated Bcl-2 levels, and accordingly suppressed apoptotic damage in the jejunum cells shown by decreased cleaved caspase-3 level. Mechanistic investigation revealed that GLN treatment augmented binding of Nrf2 onto Bcl2 gene promoter. These results indicate that glutamine has protective effects on I/R in vivo by activating the Nrf2/ARE signaling pathway to inhibit ROS production and reduce intestinal apoptosis.

Induction of a Proinflammatory Response in Cortical Astrocytes by the Major Metabolites Accumulating in HMG-CoA Lyase Deficiency: the Role of ERK Signaling Pathway in Cytokine Release

3-Hydroxy-3-methylglutaric aciduria (HMGA) is an inherited metabolic disorder caused by 3-hydroxy-3-methylglutaryl-CoA lyase deficiency. It is biochemically characterized by predominant tissue accumulation and high urinary excretion of 3-hydroxy-3-methylglutarate (HMG) and 3-methylglutarate (MGA). Affected patients commonly present acute symptoms during metabolic decompensation, including vomiting, seizures, and lethargy/coma accompanied by metabolic acidosis and hypoketotic hypoglycemia. Although neurological manifestations are common, the pathogenesis of brain injury in this disease is poorly known. Astrocytes are important for neuronal protection and are susceptible to damage by neurotoxins. In the present study, we investigated the effects of HMG and MGA on important parameters of redox homeostasis and cytokine production in cortical cultured astrocytes. The role of the metabolites on astrocyte mitochondrial function (thiazolyl blue tetrazolium bromide (MTT) reduction) and viability (propidium iodide incorporation) was also studied. Both organic acids decreased astrocytic mitochondrial function and the concentrations of reduced glutathione without altering cell viability. In contrast, they increased reactive species formation (2'-7'-dichlorofluorescein diacetate (DCFHDA) oxidation), as well as IL-1β, IL-6, and TNF α release through the ERK signaling pathway. Taken together, the data indicate that the principal compounds accumulating in HMGA induce a proinflammatory response in cultured astrocytes that may possibly be involved in the neuropathology of this disease.

Lipoic acid and N-acetylcysteine prevent ammonia-induced inflammatory response in C6 astroglial cells: The putative role of ERK and HO1 signaling pathways

Hyperammonemia induces significant changes in the central nervous system (CNS) in direct association with astroglial functions, such as oxidative damage, glutamatergic excitotoxicity, and impaired glutamine synthetase (GS) activity and pro-inflammatory cytokine release. Classically, lipoic acid (LA) and N-acetylcysteine (NAC) exhibit antioxidant and anti-inflammatory activities by increasing glutathione (GSH) biosynthesis and decreasing pro-inflammatory mediator levels in glial cells. Thus, we evaluated the protective effects of LA and NAC against ammonia cytotoxicity in C6 astroglial cells. Ammonia decreased GSH levels and increased cytokine release and NFκB transcriptional activation. LA and NAC prevented these effects by the modulation of ERK and HO1 pathways. Taken together, these observations show that LA and NAC prevent the ammonia-induced inflammatory response.

Di-(2-ethylhexyl)-phthalate induces oxidative stress in human endometrial stromal cells in vitro

Di-(2-ethylhexyl)-phthalate (DEHP) accumulates in the environment, and its exposure is possibly associated with endocrine-related disease in women of reproductive age. The effects of DEHP on human endometrial cells are unknown. We treated human endometrial stromal cells with 10, 100, and 1000 pmol of DEHP and measured reactive oxygen species (ROS) generation, expression levels of antioxidant enzymes, alteration of MAPK/NF-κB signaling and hormonal receptors. DEHP increased reactive oxygen species (ROS) generation and decreased expression of superoxide dismutase (SOD), glutathione peroxidase (GPX), heme oxygenase (HO), and catalase (CAT). By DEHP exposure, p-ERK/p-p38 and NF-κB mediated transcription was increased. Additionally, DEHP induced estrogen receptor-α (ER-α) expression in a dose-dependent manner. This study shows the need for future mechanistic studies of oxidative stress, MAPK/NF-κB signaling, and ER-α as molecular mediators of DEHP-associated endometrial stromal cell alterations, which may be associated with the development of endocrine-related disease such as endometriosis.

Spectroscopic studies reveal that the heme regulatory motifs of heme oxygenase-2 are dynamically disordered and exhibit redox-dependent interaction with heme

Heme oxygenase (HO) catalyzes a key step in heme homeostasis: the O2- and NADPH-cytochrome P450 reductase-dependent conversion of heme to biliverdin, Fe, and CO through a process in which the heme participates both as a prosthetic group and as a substrate. Mammals contain two isoforms of this enzyme, HO2 and HO1, which share the same α-helical fold forming the catalytic core and heme binding site, as well as a membrane spanning helix at their C-termini. However, unlike HO1, HO2 has an additional 30-residue N-terminus as well as two cysteine-proline sequences near the C-terminus that reside in heme regulatory motifs (HRMs). While the role of the additional N-terminal residues of HO2 is not yet understood, the HRMs have been proposed to reversibly form a thiol/disulfide redox switch that modulates the affinity of HO2 for ferric heme as a function of cellular redox poise. To further define the roles of the N- and C-terminal regions unique to HO2, we used multiple spectroscopic techniques to characterize these regions of the human HO2. Nuclear magnetic resonance spectroscopic experiments with HO2 demonstrate that, when the HRMs are in the oxidized state (HO2(O)), both the extra N-terminal and the C-terminal HRM-containing regions are disordered. However, protein NMR experiments illustrate that, under reducing conditions, the C-terminal region gains some structure as the Cys residues in the HRMs undergo reduction (HO2(R)) and, in experiments employing a diamagnetic protoporphyrin, suggest a redox-dependent interaction between the core and the HRM domains. Further, electron nuclear double resonance and X-ray absorption spectroscopic studies demonstrate that, upon reduction of the HRMs to the sulfhydryl form, a cysteine residue from the HRM region ligates to a ferric heme. Taken together with EPR measurements, which show the appearance of a new low-spin heme signal in reduced HO2, it appears that a cysteine residue(s) in the HRMs directly interacts with a second bound heme.

[Peculiarities of the Structural-Functional State of the Cytochrome Part of Liver Mitochondrial Respiratory Chain under Conditions of Acetaminophen-induced Hepatitis against the Background of Alimentary Deprivation of Protein]

Activity of the key enzyme of the cytochrome part of the respiratory chain--cytochrome oxidase, quantitative redistribution of mitochondrial cytochromes b, c1, c and aa3, activity of the key enzymes of cytochromes' heme metabolism--delta-aminolevulinate synthase and heme oxygenase under conditions of acetaminophen-induced hepatitis against the background of alimentary deprivation of protein were studied. It was found out, that under conditions of acetaminophen-induced hepatitis against the background of alimentary deprivation of protein, an inhibition of cytochrome oxidase activity and a decrease in the quantitative content of mitochondrial cytochromes against the background of the increase in the delta-aminolevulinate synthase and heme oxygenase activity are observed. In animals with toxic liver injury, maintained under conditions of alimentary deprivation of protein, a progressive decrease in the quantitative content of mitochondrial cytochromes b, c1, c and aa3 against the background. of the increase in heme oxygenase activity and preservation of delta-aminolevulinate synthase activity on the control level is identified. The conclusion was made, that alimentary deprivation of protein is a critical factor for the development of the disturbances of structural-functional integrity of the cytochromic part of the respiratory chain. The identified changes may be considered as one of the possible mechanisms of energy biotransformation system disturbances under conditions of alimentary deprivation of protein.

17α-Ethinylestradiol can disrupt hemoglobin catabolism in amphibians

Different chemical substances, which enter the environment due to anthropogenic influences, can affect the endocrine system and influence development and physiology of aquatic animals. One of these endocrine disrupting chemicals is the synthetic estrogen, 17α-ethinylestradiol (EE2), which is a main component of various oral contraceptives and demonstrably affects many different aquatic vertebrates at extremely low concentrations by feminization phenomena. The aim of the present study was to investigate whether a four week exposure to three different concentrations of EE2 (0.3 ng/L, 29.6 ng/L and 2960 ng/L) affects the catabolism of hemoglobin of the amphibian Xenopus laevis. The results of this study demonstrate for the first time that beside an increase of the hepatic vitellogenin gene expression, exposure to EE2 also decreases the gene expression of the hepatic heme oxygenase 1 and 2 (HO1, HO2), degrading heme of different heme proteins to biliverdin, as well as of the biliverdin reductase A (BLVRA), which converts biliverdin to bilirubin. The results further suggest that EE2 already at the environmentally relevant concentration of (29.6 ng/L) can disrupt hemoglobin catabolism, indicated by decreased gene expression of HO2, which becomes evident at the highest EE2 concentration that led to a severe increase of biliverdin in plasma.

Hydrogen sulfide accelerates wound healing in diabetic rats

AIM

The aim of this study was to explore the role of hydrogen sulfide on wound healing in diabetic rats.

METHODS

Experimental diabetes in rats was induced by intraperitoneal injection of streptozotocin (STZ) (in 0.1 mol/L citrate buffer, Ph 4.5) at dose of 70 mg/kg. Diabetic and age-matched non-diabetic rats were randomly assigned to three groups: untreated diabetic controls (UDC), treated diabetic administrations (TDA), and non-diabetic controls (NDC). Wound Healing Model was prepared by making a round incision (2.0 cm in diameter) in full thickness. Rats from TDA receive 2% sodium bisulfide ointment on wound, and animals from UDC and NDC receive control cream. After treatment of 21 days with sodium bisulfide, blood samples were collected for determination of vascular endothelial growth factor (VEGF), intercellular cell adhesion molecule-1 (ICAM-1), antioxidant effects. Granulation tissues from the wound were processed for histological examination and analysis of western blot.

RESULTS

The study indicated a significant increase in levels of VEGF and ICAM-1 and a decline in activity of coagulation in diabetic rats treated with sodium bisulfide. Sodium bisulfide treatment raised the activity of superoxide dismutase (SOD) and heme oxygenase-1 (HO-1) protein expression, and decreased tumor necrosis factor α (TNF-α) protein expression in diabetic rats.

CONCLUSIONS

The findings in present study suggested that hydrogen sulfide accelerates the wound healing in rats with diabetes. The beneficial effect of H2S may be associated with formation of granulation, anti-inflammation, antioxidant, and the increased level of vascular endothelial growth factor (VEGF).

Heme Degradation by Heme Oxygenase Protects Mitochondria but Induces ER Stress via Formed Bilirubin

Heme oxygenase (HO), in conjunction with biliverdin reductase, degrades heme to carbon monoxide, ferrous iron and bilirubin (BR); the latter is a potent antioxidant. The induced isoform HO-1 has evoked intense research interest, especially because it manifests anti-inflammatory and anti-apoptotic effects relieving acute cell stress. The mechanisms by which HO mediates the described effects are not completely clear. However, the degradation of heme, a strong pro-oxidant, and the generation of BR are considered to play key roles. The aim of this study was to determine the effects of BR on vital functions of hepatocytes focusing on mitochondria and the endoplasmic reticulum (ER). The affinity of BR to proteins is a known challenge for its exact quantification. We consider two major consequences of this affinity, namely possible analytical errors in the determination of HO activity, and biological effects of BR due to direct interaction with protein function. In order to overcome analytical bias we applied a polynomial correction accounting for the loss of BR due to its adsorption to proteins. To identify potential intracellular targets of BR we used an in vitro approach involving hepatocytes and isolated mitochondria. After verification that the hepatocytes possess HO activity at a similar level as liver tissue by using our improved post-extraction spectroscopic assay, we elucidated the effects of increased HO activity and the formed BR on mitochondrial function and the ER stress response. Our data show that BR may compromise cellular metabolism and proliferation via induction of ER stress. ER and mitochondria respond differently to elevated levels of BR and HO-activity. Mitochondria are susceptible to hemin, but active HO protects them against hemin-induced toxicity. BR at slightly elevated levels induces a stress response at the ER, resulting in a decreased proliferative and metabolic activity of hepatocytes. However, the proteins that are targeted by BR still have to be identified.

Comparative proteomic analysis of the molecular responses of mouse macrophages to titanium dioxide and copper oxide nanoparticles unravels some toxic mechanisms for copper oxide nanoparticles in macrophages

Titanium dioxide and copper oxide nanoparticles are more and more widely used because of their catalytic properties, of their light absorbing properties (titanium dioxide) or of their biocidal properties (copper oxide), increasing the risk of adverse health effects. In this frame, the responses of mouse macrophages were studied. Both proteomic and targeted analyses were performed to investigate several parameters, such as phagocytic capacity, cytokine release, copper release, and response at sub toxic doses. Besides titanium dioxide and copper oxide nanoparticles, copper ions were used as controls. We also showed that the overall copper release in the cell does not explain per se the toxicity observed with copper oxide nanoparticles. In addition, both copper ion and copper oxide nanoparticles, but not titanium oxide, induced DNA strands breaks in macrophages. As to functional responses, the phagocytic capacity was not hampered by any of the treatments at non-toxic doses, while copper ion decreased the lipopolysaccharide-induced cytokine and nitric oxide productions. The proteomic analyses highlighted very few changes induced by titanium dioxide nanoparticles, but an induction of heme oxygenase, an increase of glutathione synthesis and a decrease of tetrahydrobiopterin in response to copper oxide nanoparticles. Subsequent targeted analyses demonstrated that the increase in glutathione biosynthesis and the induction of heme oxygenase (e.g. by lovastatin/monacolin K) are critical for macrophages to survive a copper challenge, and that the intermediates of the catecholamine pathway induce a strong cross toxicity with copper oxide nanoparticles and copper ions.

Heme oxygenase-1 protects rat liver against warm ischemia/reperfusion injury via TLR2/TLR4-triggered signaling pathways

AIM: To investigate the efficacy and molecular mechanisms of induced heme oxygenase (HO)-1 in protecting liver from warm ischemia/reperfusion (I/R) injury.

METHODS: Partial warm ischemia was produced in the left and middle hepatic lobes of SD rats for 75 min, followed by 6 h of reperfusion. Rats were treated with saline, cobalt protoporphyrin (CoPP) or zinc protoporphyrin (ZnPP) at 24 h prior to the ischemia insult. Blood and samples of ischemic lobes subjected to ischemia were collected at 6 h after reperfusion. Serum transaminases level, plasma lactate dehydrogenase and myeloperoxidase activity in liver were measured. Liver histological injury and inflammatory cell infiltration were evaluated by tissue section and liver immunohistochemical analysis. We used quantitative reverse transcription polymerase chain reaction to analyze liver expression of inflammatory cytokines and chemokines. The cell lysates were subjected to immunoprecipitation with anti-Toll-IL-1R-containing adaptor inducing interferon-β (TRIF) and anti-myeloid differentiation factor 88 (MyD88), and then the immunoprecipitates were analyzed by SDS-PAGE and immunoblotted with the indicated antibodies.

RESULTS: HO-1 protected livers from I/R injury, as evidenced by diminished liver enzymes and well-preserved tissue architecture. In comparison with ZnPP livers 6 h after surgery, CoPP treatment livers showed a significant increase inflammatory cell infiltration of lymphocytes, plasma cells, neutrophils and macrophages. The Toll-like receptor (TLR)-4 and TANK binding kinase 1 protein levels of rats treated with CoPP significantly reduced in TRIF-immunoprecipitated complex, as compared with ZnPP treatment. In addition, pretreatment with CoPP reduced the expression levels of TLR2, TLR4, IL-1R-associated kinase (IRAK)-1 and tumor necrosis factor receptor-associated factor 6 in MyD88-immunoprecipitated complex. The inflammatory cytokines and chemokines mRNA expression rapidly decreased in CoPP-pretreated liver, compared with the ZnPP-treated group. However, the expression of negative regulators Toll-interacting protein, suppressor of cytokine signaling-1, IRAK-M and Src homology 2 domain-containing inositol-5-phosphatase-1 in CoPP treatment rats were markedly up-regulated as compared with ZnPP-treated rats.

CONCLUSION: HO-1 protects liver against I/R injury by inhibiting TLR2/TLR4-triggered MyD88- and TRIF-dependent signaling pathways and increasing expression of negative regulators of TLR signaling in rats.

Novel lead structures and activation mechanisms for CO-releasing molecules (CORMs)

Carbon monoxide (CO) is an endogenous small signalling molecule in the human body, produced by the action of haem oxygenase on haem. Since it is very difficult to apply safely as a gas, solid storage and delivery forms for CO are now explored. Most of these CO-releasing molecules (CORMs) are based on the inactivation of the CO by coordinating it to a transition metal centre in a prodrug approach. After a brief look at the potential cellular target structures of CO, an overview of the design principles and activation mechanisms for CO release from a metal coordination sphere is given. Endogenous and exogenous triggers discussed include ligand exchange reactions with medium, enzymatically-induced CO release and photoactivated liberation of CO. Furthermore, the attachment of CORMs to hard and soft nanomaterials to confer additional target specificity to such systems is critically assessed. A survey of analytical methods for the study of the stoichiometry and kinetics of CO release, as well as the tracking of CO in living systems by using fluorescent probes, concludes this review. CORMs are very valuable tools for studying CO bioactivity and might lead to new drug candidates; however, in the design of future generations of CORMs, particular attention has to be paid to their drug-likeness and the tuning of the peripheral 'drug sphere' for specific biomedical applications. Further progress in this field will thus critically depend on a close interaction between synthetic chemists and researchers exploring the physiological effects and therapeutic applications of CO.

Role of hematin and sodium nitroprusside in regulating Brassica nigra seed germination under nanosilver and silver nitrate stresses

Silver nanoparticles (AgNPs) are one of the most widely used nanomaterials, although the mechanisms of AgNP toxicity in terrestrial plants is still unclear. We compared the toxic effects of AgNPs and AgNO3 on Brassica nigra seed germination at physiological and molecular levels. Both AgNPs and AgNO3 inhibited seed germination, lipase activity, soluble and reducing sugar contents in germinating seeds and seedlings. These reductions were more pronounced in AgNP treatments than AgNO3 treatments. Application of 200-400mg/L both AgNPs and AgNO3 increased transcription of heme oxygenase-1. However, at 800, 1600 mg/L, AgNPs or AgNO3 suppressed HO-1 expression. At 400mg/L, AgNPs or AgNO3-induced inhibitory effects on seed germination and were ameliorated by the HO-1 inducer, hematin, or NO donor, sodium nitroprusside (SNP). Additionally, 4 μM hematin and 400 μM SNP were able to markedly boost the HO/NO system. However, the addition of the HO-1 inhibitor (ZnPPIX) or the specific scavenger of NO (cPTIO) not only reversed the protective effects conferred by hematin, but also blocked the up-regulation of HO activity. In addition, hematin-drived NO production in B. niger seeds under AgNPs was confirmed. Our results at physiological and molecular levels suggested that AgNPs were more toxic than AgNO3. Based on these results, for the first time, we suggest that endogenous HO is needed to alleviate AgNPs-induced germination inhibition, which might have a possible interaction with NO.

Carbon monoxide and the CNS: challenges and achievements

Haem oxygenase (HO) and its product carbon monoxide (CO) are associated with cytoprotection and maintenance of homeostasis in several different organs and tissues. This review focuses upon the role of exogenous and endogenous CO (via HO activity and expression) in various CNS pathologies, based upon data from experimental models, as well as from some clinical data on human patients. The pathophysiological conditions reviewed are cerebral ischaemia, chronic neurodegenerative diseases (Alzheimer's and Parkinson's diseases), multiple sclerosis and pain. Among these pathophysiological conditions, a variety of cellular mechanisms and processes are considered, namely cytoprotection, cell death, inflammation, cell metabolism, cellular redox responses and vasomodulation, as well as the different targeted neural cells. Finally, novel potential methods and strategies for delivering exogenous CO as a drug are discussed, particularly approaches based upon CO-releasing molecules, their limitations and challenges. The diagnostic and prognostic value of HO expression in clinical use for brain pathologies is also addressed.

Carbon monoxide and nitric oxide interactions in magnocellular neurosecretory neurones during water deprivation

Nitric oxide (NO) and carbon monoxide (CO) are diffusible gas messengers in the brain. Previously, we have shown their independent involvement in central fluid/electrolyte homeostasis control. In the present study, we investigated a possible functional interaction between NO/CO in the regulation of vasopressin (VP) and oxytocin (OT) magnocellular neurosecretory cells (MNCs) activity in euhydrated (EU) and dehydrated [48-h water-deprived (48WD)] rats. Using brain slices from EU and 48WD rats, we measured, by immunohistochemistry, the expression of neuronal NO synthase (nNOS, which synthesises NO) and haeme-oxygenase (HO-1, which synthesises CO) in the hypothalamic supraoptic nucleus (SON). In addition, we used patch-clamp electrophysiology to investigate whether regulation of SON MNC firing activity by endogenous CO was dependent on NO bioavailability and GABAergic inhibitory synaptic function. We found a proportion of OT and VP SON MNCs in EU rats to co-express both of HO-1 and nNOS (33.2 ± 2.9% and 15.3 ± 1.4%, respectively), which was increased in 48WD rats (55.5 ± 0.9% and 21.0 ± 1.7%, respectively, P < 0.05 for both). Inhibition of endogenous HO activity [chromium mesoporphyrin IX chloride (CrMP) 20 μm] induced MNC membrane hyperpolarisation and decreased firing activity, and these effects were blunted by previous blockade of endogenous NOS activity (l-NAME, 2 mm) or blockade of inhibitory GABA function [Picrotoxin (Sigma-Aldrich, St Louis, MO, USA), 50 μm]. No significant changes in SON NO bioavailability (4,5 diaminofluorescein diacetate fluorescence) were observed after CrMP treatment. Taken together, our results support a state-dependent functional inter-relationship between NO and CO in MNCs, in which CO acts as an excitatory gas molecule, whose effects are largely dependent on interactions with the inhibitory SON signals NO and GABA.

Curcumin enhances recovery of pancreatic islets from cellular stress induced inflammation and apoptosis in diabetic rats

The phytochemical, curcumin, has been reported to play many beneficial roles. However, under diabetic conditions, the detail mechanism of its beneficial action in the glucose homeostasis regulatory organ, pancreas, is poorly understood. The present study has been designed and carried out to explore the role of curcumin in the pancreatic tissue of STZ induced and cellular stress mediated diabetes in eight weeks old male Wistar rats. Diabetes was induced with a single intraperitoneal dose of STZ (65 mg/kg body weight). Post to diabetes induction, animals were treated with curcumin at a dose of 100 mg/kg body weight for eight weeks. Underlying molecular and cellular mechanism was determined using various biochemical assays, DNA fragmentation, FACS, histology, immunoblotting and ELISA. Treatment with curcumin reduced blood glucose level, increased plasma insulin and mitigated oxidative stress related markers. In vivo and in vitro experimental results revealed increased levels of proinflammatory cytokines (TNF-α, IL1-β and IFN-γ), reduced level of cellular defense proteins (Nrf-2 and HO-1) and glucose transporter (GLUT-2) along with enhanced levels of signaling molecules of ER stress dependent and independent apoptosis (cleaved Caspase-12/9/8/3) in STZ administered group. Treatment with curcumin ameliorated all the adverse changes and helps the organ back to its normal physiology. Results suggest that curcumin protects pancreatic beta-cells by attenuating inflammatory responses, and inhibiting ER/mitochondrial dependent and independent pathways of apoptosis and crosstalk between them. This uniqueness and absence of any detectable adverse effect proposes the possibility of using this molecule as an effective protector in the cellular stress mediated diabetes mellitus.

The heme oxygenase/biliverdin reductase system in skin cancers

The heme oxygenase/biliverdin reductase (HO/BVR) pathway enhances cell stress response by degrading excess heme or producing antioxidant and cytoprotective molecules. Recently, members of the HO/BVR system have been proposed as biomarkers for the early diagnosis of free radical-related diseases. In this study, the presence of both the inducible and constitutive HO isoforms (HO-1 and HO-2, respectively) and BVR was evaluated by immunohistochemistry in human skin cancer samples. Moderate/strong immunoreactivities against HO-1, HO-2 and BVR were detected in 100% of the nodular malignant melanoma samples, whereas in basal cell carcinoma specimens these figures were 62%, 88% and 60%, respectively, with a faint/moderate degree of expression. Faint/moderate HO-1, HO-2 and BVR immunoreactivities were detected in 33%, 66% and 100% of melanocytic nevi samples, respectively. In conclusion, HO-1 and HO-2 and BVR were expressed in the cytosols of skin cancer cells, whereas perilesional normal epidermis showed only faint staining, thus leading to the hypothesis that the HO/BVR system is activated in skin cancers.

[ERKl/2 signaling pathway mediates heme oxygenase-1 up-regulation by minocycline in PC12 cells exposed to oxygen glucose deprivation]

OBJECTIVE

To investigate the effects of minocycline in promoting the survival of pheochromocytoma (PCI2) cells exposed to oxygen glucose deprivation (OGD) and explore the underlying mechanisms.

METHODS

An in vitro cell model of cerebral ischemia was established by OGD for 6 h in PCI2 cells with pretreatment with minocycline or an ERK1/2 inhibitor. At 24 h after OGD injury, the cells were evaluated for cell viability by MTT assay and expressions of heme oxygenase-I (HO-I) and phospholylated extracellular signal-regulated protein kinase 1/2 (ERK1/2) by Western blotting.

RESULTS

The cell viability decreased dramatically following OGD. Pretreatment with minocycline (O.I-IO JJ.mol/L) induced a significant increase in the cell viability after OGD and caused up-regulation of HO-I protein and enhanced ERK1/2 phospholylation, and the effects were especially obvious with 1 JJ.mol/L minocycline and were abolished by inhibition of ERK1/2 activity with UOI26 (IO JJ.mol/L).

CONCLUSION

Minocycline can protect PCI2 cells against OGD-induced toxicity by up-regulating HO-I protein expression through ERKl/2 signaling pathways.

Ethyl 3,4-dihydroxy benzoate, a unique preconditioning agent for alleviating hypoxia-mediated oxidative damage in L6 myoblasts cells

The importance of hypoxia inducible factor (HIF) as the master regulator of hypoxic responses is well established. Oxygen-dependent prolyl hydroxylase domain enzymes (PHDs) negatively regulate HIF directing it to the path of degradation under normoxia and are, consequently, attractive therapeutic targets. Inhibition of PHDs might upregulate beneficial HIF-mediated processes. In this study, we have examined the efficacy of PHD inhibitor ethyl 3,4-dihydroxy benzoate (EDHB) in affording protection against hypoxia-induced oxidative damage in L6 myoblast cells. L6 cells were exposed to hypoxia (0.5 % O2) after preconditioning with EDHB for different times. Levels of HIF-1α, oxidative stress and antioxidant status were measured after hypoxia exposure. Preconditioning with EDHB significantly improved cellular viability, and the diminished levels of protein oxidation and malondialdehyde indicated a decrease in oxidative stress when exposed to hypoxia. EDHB treatment also conferred enhanced anti-oxidant status, as there was an increase in the levels of glutathione and antioxidant enzymes like superoxide dismutase and glutathione peroxidase. Further, augmentation of the levels of HIF-1α boosted protein expression of antioxidative enzyme heme-oxygenase I. There was enhanced expression of metallothioneins which also have antioxidant, anti-inflammatory properties. These results thus accentuate the potential cytoprotective efficacy of EDHB against hypoxia-induced oxidative damage.

Heatstroke Effect on Brain Heme Oxygenase-1 in Rats

Exposure to high environmental temperature leading to increased core body temperature above 40°C and central nervous system abnormalities such as convulsions, delirium, or coma is defined as heat stroke. Studies in humans and animals indicate that the heat shock responses of the host contribute to multiple organ injury and death during heat stroke. Heme oxygenase-1 (HO-1)-a stress-responsive enzyme that catabolizes heme into iron, carbon monoxide, and biliverdin-has an important role in the neuroprotective mechanism against ischemic stroke. Here, we investigated the role of endogenous HO-1 in heat-induced brain damage in rats. RT-PCR results revealed that levels of HO-1 mRNA peaked at 0 h after heat exposure and immunoblot analysis revealed that the maximal protein expression occurred at 1 h post-heat exposure. Subsequently, we detected the HO-1 expression in the cortical brain cells and revealed the neuronal cell morphology. In conclusion, HO-1 is a potent protective molecule against heat-induced brain damage. Manipulation of HO-1 may provide a potential therapeutic approach for heat-related diseases.

Acute stress-induced antinociception is cGMP-dependent but heme oxygenase-independent

Endogenous carbon monoxide (CO), which is produced by the enzyme heme oxygenase (HO), participates as a neuromodulator in physiological processes such as thermoregulation and nociception by stimulating the formation of 3',5'-cyclic guanosine monophosphate (cGMP). In particular, the acute physical restraint-induced fever of rats can be blocked by inhibiting the enzyme HO. A previous study reported that the HO-CO-cGMP pathway plays a key phasic antinociceptive role in modulating noninflammatory acute pain. Thus, this study evaluated the involvement of the HO-CO-cGMP pathway in antinociception induced by acute stress in male Wistar rats (250-300 g; n=8/group) using the analgesia index (AI) in the tail flick test. The results showed that antinociception induced by acute stress was not dependent on the HO-CO-cGMP pathway, as neither treatment with the HO inhibitor ZnDBPG nor heme-lysinate altered the AI. However, antinociception was dependent on cGMP activity because pretreatment with the guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) blocked the increase in the AI induced by acute stress.

Alleviated mucosal and neuronal damage in a rat model of Crohn’s disease

AIM: To establish a rat model suitable to investigate the repetitive relapsing inflammations (RRI) characteristic to Crohn’s disease.

METHODS: Colitis was induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). RRI were mimicked by repeating administrations of TNBS. Tissue samples were taken from control, once, twice and three times treated rats from the inflamed and adjacent non-inflamed colonic segments at different timepoints during the acute intestinal inflammation. The means of the ulcerated area were measured to evaluate the macroscopic mucosal damage. The density of myenteric neurons was determined on whole mounts by HuC/HuD immunohistochemistry. Heme oxygenase-1 (HO-1) expression was evaluated by molecular biological techniques.

RESULTS: TNBS-treated rats displayed severe colitis, but the mortality was negligible, and an increase of body weight was characteristic throughout the experimental period. The widespread loss of myenteric neurons, and marked but transient HO-1 up-regulation were demonstrated after the first TNBS administration. After repeated doses the length of the recovery time and extent of the ulcerous colonic segments were markedly decreased, and the neuronal loss was on a smaller scale and was limited to the inflamed area. HO-1 mRNA level was notably greater than after a single dose and overexpression was sustained throughout the timepoints examined. Nevertheless, the HO-1 protein up-regulation after the second TNBS treatment proved to be transient. Following the third treatment HO-1 protein expression could not be detected.

CONCLUSION: Experimentally provoked RRI may exert a protective preconditioning effect against the mucosal and neuronal damage. The persistent up-regulation of HO-1 mRNA expression may correlate with this.

Localization of heat shock proteins in cerebral cortical cultures following induction by celastrol

Hsp70, Hsp32, and Hsp27 were induced by celastrol in rat cerebral cortical cultures at dosages that did not affect cell viability. Pronounced differences were observed in the cellular localization of these heat shock proteins in cell types of cerebral cortical cultures. Celastrol-induced Hsp70 localized to the cell body and cellular processes of neurons that were identified by neuron-specific βIII-tubulin. Hsp70 was not detected in adjacent GFAP-positive glial cells that demonstrated a strong signal for Hsp27 and Hsp32 in both glial cell bodies and cellular processes. Cells in the cerebral cortex region of the brain are selectively impacted during the progression of Alzheimer's disease which is a "protein misfolding disorder." Heat shock proteins provide a line of defense against misfolded, aggregation-prone proteins. Celastrol is a potential agent to counter this neurodegenerative disorder as recent evidence indicates that in vivo administration of celastrol in a transgenic model of Alzheimer's reduces an important neuropathological hallmark of this disease, namely, amyloid beta pathology that involves protein aggregation.

Indole acetic acid is responsible for protection against oxidative stress caused by drought in soybean plants: the role of heme oxygenase induction

Objectives This study was focused on the role of indole acetic acid (IAA) in the defense against oxidative stress damage caused by drought in soybean plants and to elucidate whether heme oxygenase-1 (HO-1) and nitric oxide (NO) are involved in this mechanism. IAA is an auxin that participates in many plant processes including oxidative stress defense, but to the best of our knowledge no information is yet available about its possible action in drought stress. Methods To this end, soybean plants were treated with 8% polyethylene glycol (PEG) or 100 µM IAA. To evaluate the behavior of IAA, plants were pretreated with this compound previous to PEG addition. Lipid peroxidation levels (thiobarbituric acid reactive substances (TBARS)), glutathione (GSH) and ascorbate (AS) contents, catalase (CAT), superoxide dismutase (SOD), and guaiacol peroxidase (POD) activities were determined to evaluate oxidative damage. Results Drought treatment (8% PEG) caused a significant increase in TBARS levels as well as a marked decrease in the non-enzymatic (GSH and AS) and enzymatic (CAT, SOD, and POD) antioxidant defense systems. Pre-treatment with IAA prevented the alterations of stress parameters caused by drought, while treatment with IAA alone did not produce changes in TBARS levels, or GSH and AS contents. Moreover, the activities of the classical enzymes involved in the enzymatic defense system (SOD, CAT, and POD) remained similar to control values. Furthermore, this hormone could enhance HO-1 activity (75% with respect to controls), and this increase was positively correlated with protein content as well as gene expression. The direct participation of HO-1 as an antioxidant enzyme was established by performing experiments in the presence of Zn-protoporphyrin IX, a well-known irreversible inhibitor of this enzyme. It was also demonstrated that HO-1 is modulated by NO, as shown by experiments performed in the presence of an NO donor (sodium nitroprusside), an NO scavenger (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), or an NO synthesis inhibitor (N-nitro-l-arginine methyl ester, NAME). Discussion It is concluded that IAA is responsible, at least in part, for the protection against oxidative stress caused by drought in soybean plants through the modulation of NO levels which, in turn, enhances HO-1 synthesis and activity.

Curcumin-induced heme oxygenase-1 expression prevents H2O2-induced cell death in wild type and heme oxygenase-2 knockout adipose-derived mesenchymal stem cells

Mesenchymal stem cell (MSC) administration is a promising adjuvant therapy to treat tissue injury. However, MSC survival after administration is often hampered by oxidative stress at the site of injury. Heme oxygenase (HO) generates the cytoprotective effector molecules biliverdin/bilirubin, carbon monoxide (CO) and iron/ferritin by breaking down heme. Since HO-activity mediates anti-apoptotic, anti-inflammatory, and anti-oxidative effects, we hypothesized that modulation of the HO-system affects MSC survival. Adipose-derived MSCs (ASCs) from wild type (WT) and HO-2 knockout (KO) mice were isolated and characterized with respect to ASC marker expression. In order to analyze potential modulatory effects of the HO-system on ASC survival, WT and HO-2 KO ASCs were pre-treated with HO-activity modulators, or downstream effector molecules biliverdin, bilirubin, and CO before co-exposure of ASCs to a toxic dose of H₂O₂. Surprisingly, sensitivity to H₂O₂-mediated cell death was similar in WT and HO-2 KO ASCs. However, pre-induction of HO-1 expression using curcumin increased ASC survival after H₂O₂ exposure in both WT and HO-2 KO ASCs. Simultaneous inhibition of HO-activity resulted in loss of curcumin-mediated protection. Co-treatment with glutathione precursor N-Acetylcysteine promoted ASC survival. However, co-incubation with HO-effector molecules bilirubin and biliverdin did not rescue from H₂O₂-mediated cell death, whereas co-exposure to CO-releasing molecules-2 (CORM-2) significantly increased cell survival, independently from HO-2 expression. Summarizing, our results show that curcumin protects via an HO-1 dependent mechanism against H₂O₂-mediated apoptosis, and likely through the generation of CO. HO-1 pre-induction or administration of CORMs may thus form an attractive strategy to improve MSC therapy.

Young Leaf Chlorosis 2 encodes the stroma-localized heme oxygenase 2 which is required for normal tetrapyrrole biosynthesis in rice

Rice heme oxygenase 2 (OsHO2) mutants are chlorophyll deficient with distinct tetrapyrrole metabolite and transcript profiles, suggesting a potential regulatory role of the stromal-localized OsHO2 in tetrapyrrole biosynthesis. In plants, heme oxygenases (HOs) are classified into the subfamilies HO1 and HO2. HO1 are highly conserved plastid enzymes required for synthesizing the chromophore in phytochromes which mediate a number of light-regulated responses. However, the physiological and biochemical functions of HO2, which are distantly related to HO1, are not well understood, especially in crop plants. From a population of (60)Coγ-irradiated rice mutants, we identified the ylc2 (young leaf chlorosis 2) mutant which displays a chlorosis phenotype in seedlings with substantially reduced chlorophyll content. Normal leaf pigmentation is gradually restored in older plants while newly emerged leaves remain yellow. Transmission electron microscopy further revealed defective chloroplast structures in the ylc2 seedlings. Map-based cloning located the OsYLC2 gene on chromosome 3 and it encodes the OsHO2 protein. The gene identification was confirmed by complementation and T-DNA mutant analyses. Subcellular localization and chloroplast fractionation experiments indicated that OsHO2 resides in the stroma. However, recombinant enzyme assay demonstrated that OsHO2 is not a functional HO enzyme. Analysis of tetrapyrrole metabolites revealed the reduced levels of most chlorophyll and phytochromobilin precursors in the ylc2 mutant. On the other hand, elevated accumulation of 5-aminolevulinic acid and Mg-protoporphyrin IX was observed. These unique metabolite changes are accompanied by consistent changes in the expression levels of the corresponding tetrapyrrole biosynthesis genes. Taken together, our work suggests that OsHO2 has a potential regulatory role for tetrapyrrole biosynthesis in rice.

[Effect of astaxanthin on preeclampsia rat model]

The effect of astaxanthin on N(Ω)-nitro-L-arginine methyl ester (L-NAME) induced preeclampsia disease rats was investigated. Thirty pregnant Sprague-Dawley rats were randomly divided into three groups (n = 10): blank group, L-NAME group and astaxanthin group. From day 5 to 20, astaxanthin group rats were treated with astaxanthin (25 mg x kg(-1) x d(-1) x bw(-1)) from pregnancy (day 5). To establish the preeclamptic rat model, L-NAME group and astaxanthin group rats were injected with L-NAME (125 mg x kg(-1) x d(-1) x bw(-1)) from days 10-20 of pregnancy. The blood pressure and urine protein were recorded. Serum of each group was collected and malondialdehyde (MDA), superoxide dismutase (SOD) and nitric oxide synthase (NOS) activities were analyzed. Pathological changes were observed with HE stain. The expression of NF-κB (nuclear factor kappa B), ROCK II (Rho-associated protein kinase II), HO-1 (heme oxygenase-1) and Caspase 3 were analyzed with immunohistochemistry. L-NAME induced typical preeclampsia symptoms, such as the increased blood pressure, urinary protein, the content of MDA, etc. Astaxanthin significantly reduced the blood pressure (P < 0.01), the content of MDA (P < 0.05), and increased the activity of SOD (P < 0.05) of preeclampsia rats. The urinary protein, NO, and NOS were also decreased. HE stain revealed that after treated with astaxanthin, the thickness of basilal membrane was improved and the content of trophoblast cells and spiral arteries was reduced. Immunohistochemistry results revealed that the expressions of NF-κB, ROCK II and Caspase 3 in placenta tissue were effectively decreased, and HO-1 was increased. Results indicated that astaxanthin can improve the preeclampsia symptoms by effectively reducing the oxidative stress and inflammatory damages of preeclampsia. It revealed that astaxanthin may be benefit for prevention and treatment of preeclampsia disease.

Heme oxygenase-1 upregulation modulates tone and fibroelastic properties of internal anal sphincter

A compromise in the internal anal sphincter (IAS) tone and fibroelastic properties (FEP) plays an important role in rectoanal incontinence. Herein, we examined the effects of heme oxygenase (HO)-1 upregulation on these IAS characteristics in young rats. We determined the effect of HO-1 upregulator hemin on HO-1 mRNA and protein expressions and on basal IAS tone and its FEP before and after HO-1 inhibitor tin protoporphyrin IX. For FEP, we determined the kinetics of the IAS smooth muscle responses, by the velocities of relaxation, and recovery of the IAS tone following 0 Ca(2+) and electrical field stimulation. To characterize the underlying signal transduction for these changes, we determined the effects of hemin on RhoA-associated kinase (RhoA)/Rho kinase (ROCK) II, myosin-binding subunit of myosin light chain phosphatase 1, fibronectin, and elastin expression levels. Hemin increased HO-1 mRNA and protein similar to the increases in the basal tone, and in the FEP of the IAS. Underlying mechanisms in the IAS characteristics are associated with increases in the genetic and translational expressions of RhoA/ROCKII, and elastin. Fibronectin expression levels on the other hand were found to be decreased following HO-1 upregulation. The results of our study show that the hemin/HO-1 system regulates the tone and FEP of IAS. The hemin/HO-1 system thus provides a potential target for the development of new interventions aimed at treatment of gastrointestinal motility disorders, specifically the age-related IAS dysfunction.

Heme oxygenase in neuroprotection: from mechanisms to therapeutic implications

Heme oxygenase (HO) was regarded as an enzyme to degrade heme in aging red blood cells; recent studies suggested HO might have other functions such as neuroprotection. HO degrades heme to produce carbon monoxide (CO), iron (Fe²⁺) and biliverdin, which is rapidly converted to bilirubin (BR). Three isoforms of HO were identified in the brain: inducible form (HO-1) and constitutive forms (HO-2 and HO-3). HO-1 and HO-2 may have different mechanisms to protect neurons from oxidative stress. HO-1 is normally barely detectable in the brain. HO-1 can be induced mainly in microglia and astrocytes by oxidative stimulus rapidly. HO-1 might function as an emerging molecule to protect neurons against acute insults mediated by facilitating iron efflux from cells under stress conditions. Up-regulation of HO-1 was also found in brain glial cells in the aging and neurodegenerative diseases. This may lead to iron deposition and oxidative mitochondrial injury. HO-1 may confer neuroprotection or neurotoxic effect because of the balance between beneficial and toxic effects of heme and heme products. Pharmacological modulation of HO-1 induction represents a therapeutic strategy for several nervous system disorders. HO-2 predominantly expressed in neurons. Bilirubin has been demonstrated to protect neurons from oxidative stress in vivo and in vitro. Bilirubin can be oxidized to biliverdin by scavenging peroxyl radicals. HO-2 could protect neurons through bilirubin pathway. HO-2 might also promote neuronal survival through the CO-cGMP-MAPK pathway. Biliverdin/bilirubin may be possible therapeutic candidates to treat nervous system disease related with oxidative damage.

[Effect of Nrf2 and related factors on the progression of nonalcoholic steatohepatitis]

OBJECTIVE

To explore the role of NF-E2-related factor 2(Nrf2) and its related factors in the progression of nonalcoholi steatohepatitis (NASH) by investigating the alterations of lipid metabolism and liver histopathology as well as the changes of mRNA and protein expression levels of Nrf2 and its related factors in rats during NASH progression.

METHODS

Male SD rats were randomly divided into normal group and model group, which were administrated with high fat diet to establish nonalcoholic steatohepatitis model. The rats from both groups were randomly killed at the end of 4, 12 weeks respectively. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) were detected in the serum and liver tissue; Changes in fat deposition in liver tissue were determined by oil red O staining. HE staining were used to observe the pathological changes of liver tissue and to calculate nonalcoholic fatty liver disease (NAFLD) activity score (hepatic steatosis, inflammation and ballooning degeneration of liver cells). The expression of Nrf2 in liver was detected by immunohistochemical staining. The mRNA and protein levels of Nrf2 and related factors in liver were determined by Realtime PCR and Western blot, respectively.

RESULTS

After 4 weeks of high fat diet, the levels of ALT, AST, TC in rat serum and TC, TG, LDL-C in liver were significantly increased compared with that of the normal group (P < 0.01, P < 0.05). After 4 weeks of high fat diet, the levels of ALT, AST, TC, TG in serum and TC, TG, LDL- C in liver increased further (P < 0.01, P < 0.05). Until the 12th week, the content of HDL-C in liver was significantly lower than that of the normal group (P < 0.05). At the end of the 4th or the 12th week, lipid droplets in the model rat liver cells were heavily dyed red and hepatic steatosis increased severely, with ballooning degeneration of liver cells. With the extension of high fat diet feeding time, fat deposition in the liver tissue, hepatic steatosis, NAFLD score, Nrl2 expression were significantly increased (P < 0.01). Expression levels of mRNA and protein of Nrf2, heme oxyenase 1(HO1), NADPH quinone oxidoreductase 1(NQO1), γ-glutamylcysteine synthethase (γ-GCS), glutathione S-transferase (GST) in the model rats increased or decreased at the end of the 4th or the 12th week differentially, (P < 0.01, P < 0.05) with the more significant changes at the end of the 4th week than the 12th week.

CONCLUSION

Nrf2 and its related factors may be involved in the occurrence and development of nonalcoholic fatty liver disease, which may play an important role in the process of NASH formation.

Upregulation of heat shock protein 32 with hemin alleviates acute heat-induced hepatic injury in mice

Heat shock protein 32 (HSP32) is a stress response protein that can be induced by heat stress in the liver, and its induction can act as an important cellular defence mechanism against heat-induced liver injury. To investigate the functional role of HSP32 in protecting liver tissue against heat stress in mice and the mechanism by which it achieves this protective effect, HSP32 expression and carbon monoxide (CO) contents in a model of mice subjected to acute, transient heat exposure were examined. Furthermore, functional and histological parameters of liver damage and the possible involvement of oxidative stress to induce oxidative deterioration of liver functions and caspase-3 expression were also investigated in this study. We found that heat treatment of mice produced severe hepatic injury, whereas upregulation of HSP32 with hemin pretreatment prevented mice from liver damage. In contrast, addition of Sn-protoporphyrin (SnPP) to inhibit HSP32 expression completely reversed its hepatoprotective effect. It is concluded that upregulation of HSP32 by hemin could alleviate acute heat-induced hepatocellular damage in mice, and its by-product CO seems to play a more important role in hepatoprotective mechanism.

[Long-term effects of heme oxygenase 1 overexpression on post-infarction heart function in diabetic rats]

OBJECTIVE

To clarify the impact of increased heme oxygenase-1 (HO-1) expression on cardiac function of diabetic rats with myocardial infarction and its mechanism.

METHODS

Sixty adult male Wistar rats were randomly divided into five groups (n = 12): sham operation group (sham), diabetes + sham operation group (DM + sham), diabetes + MI group (DM + MI) , diabetes + myocardial infarction + cobalt original porphyrin (CoPP) group (DM + MI + CoPP), diabetes + myocardial infarction + CoPP+ tin porphyrin (SnMP) group (DM + MI + CoPP + SnMP). CoPP 4.5 mg/kg or SnMP 15 mg/kg were administered at the day next to MI operation, for six weeks, once a week. At the 28th week post operation, the echocardiography, left heart via the carotid artery indoor intubation were used to observe the long-term influence of HO-1 inducer (cobalt protoporphyrin, CoPP) and activity of HO inhibitor (tin porphyrin, SnMP) on the indices of left ventricular remodeling and cardiac function after the intervention. Blood glucose (GLU), total cholesterol (TC), C-reactive protein (CRP), serum creatinine (Cr), aminotransferase (ALT) and other indicators were measured. ELISA was used to test interleukin-6 (IL-6), tumor necrosis factor (TNF), nitric oxide (NO), prostacyclin (PGI2), adiponectin, and ultra sensitive CRP (HsCRP) level.

RESULTS

HO-1 inducer, CoPP, could ameliorate ± dp/dtmax, left ventricular ejection fraction and left ventricular shortening fraction in diabetic myocardial infarction rats. It could also decrease left ventricular end-diastolic diameter. The serum bilirubin, NO and PGI2 levels, myocardial phosphorylated endothelial nitric oxide synthasee(peNOS), phosphorylated activated protein kinase (pAkt), phosphorylated adenosine monophosphate-activated protein kinase (pAMPK) expression were also significantly elevated, and the serum hs-CRP and TNF levels were significantly inhibited. Compared to inducer group, cardiac function were worse in the inhibitor group.

CONCLUSION

Upregulated HO-1 level can improve the endothelial function, inhibite of the inflammatory response and enhance the antioxidant substances in serum bilirubin via peNOS-pAMPK pathway, which effectively inhibit ventricular remodeling and improve the long-term cardiac function after infarction in diabetic rats.

Activation of the phase II enzymes for neuroprotection by ginger active constituent 6-dehydrogingerdione in PC12 cells

The cellular endogenous antioxidant system plays pivotal roles in counteracting or retarding the pathogenesis of many neurodegenerative diseases. Molecules with the ability to enhance the antioxidant defense thus are promising candidates for neuroprotective drugs. 6-Dehydrogingerdione (6-DG), one of the major components of dietary ginger, has received increasing attention due to its multiple pharmacological activities. However, how this pleiotropic molecule works on the neuronal system has not been studied. This paper reports that 6-DG efficiently scavenges various free radicals in vitro and displays remarkable cytoprotection against oxidative stress-induced neuronal cell damage in the neuron-like rat pheochromocytoma cell line, PC12 cells. Pretreatment of PC12 cells with 6-DG significantly up-regulates a panel of phase II genes as well as the corresponding gene products, such as glutathione, heme oxygenase,

NAD(P)H

quinone oxidoreductase, and thioredoxin reductase. Mechanistic study indicates that activation of the Keap1-Nrf2-ARE pathway is the molecular basis for the cytoprotection of 6-DG. This is the first revelation of this novel mechanism of 6-DG as an Nrf2 activator against oxidative injury, providing the potential therapeutic use of 6-DG as neuroprotective agent.

Diffusible gas transmitter signaling in the copepod crustacean Calanus finmarchicus: identification of the biosynthetic enzymes of nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) using a de novo assembled transcriptome

Neurochemical signaling is a major component of physiological/behavioral control throughout the animal kingdom. Gas transmitters are perhaps the most ancient class of molecules used by nervous systems for chemical communication. Three gases are generally recognized as being produced by neurons: nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S). As part of an ongoing effort to identify and characterize the neurochemical signaling systems of the copepod Calanus finmarchicus, the biomass dominant zooplankton in much of the North Atlantic Ocean, we have mined a de novo assembled transcriptome for sequences encoding the neuronal biosynthetic enzymes of these gases, i.e. nitric oxide synthase (NOS), heme oxygenase (HO) and cystathionine β-synthase (CBS), respectively. Using Drosophila proteins as queries, two NOS-, one HO-, and one CBS-encoding transcripts were identified. Reverse BLAST and structural analyses of the deduced proteins suggest that each is a true member of its respective enzyme family. RNA-Seq data collected from embryos, early nauplii, late nauplii, early copepodites, late copepodites and adults revealed the expression of each transcript to be stage specific: one NOS restricted primarily to the embryo and the other was absent in the embryo but expressed in all other stages, no CBS expression in the embryo, but present in all other stages, and HO expressed across all developmental stages. Given the importance of gas transmitters in the regulatory control of a number of physiological processes, these data open opportunities for investigating the roles these proteins play under different life-stage and environmental conditions in this ecologically important species.

[Hereditary porphyrias and heme related disorders]

Hereditary porphyrias comprise a group of eight metabolic disorders of the haem biosynthesis pathway, characterised by acute neurovisceral symptoms and/or skin lesions. Each porphyria is caused by abnormal functioning of a particular enzymatic step, resulting in specific accumulation of heme precursors. Seven porphyrias are due to a partial enzyme deficiency, while a gain-of-function mechanism has recently been identify in a novel porphyria. Acute porphyrias present with severe abdominal pain, nausea, constipation and confusion, and are sometimes complicated by seizures and severe neurological disorders, which may be life-threatening. Cutaneous porphyrias can also be present, with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe chronic neurological symptoms or chronic haemolysis and severe cutaneous photosensitivity. Porphyrias are still under-diagnosed, but recent advances in the pathogenesis and genetics of human porphyrias are leading to better care of these patients and their families.

Impairment of nitric oxide synthase but not heme oxygenase accounts for baroreflex dysfunction caused by chronic nicotine in female rats

We recently reported that chronic nicotine impairs reflex chronotropic activity in female rats. Here, we sought evidence to implicate nitric oxide synthase (NOS) and/or heme oxygenase (HO) in the nicotine-baroreflex interaction. Baroreflex curves relating changes in heart rate to increases (phenylephrine) or decreases (sodium nitroprusside) in blood pressure were generated in conscious female rats treated with nicotine or saline in absence and presence of pharmacological modulators of NOS or HO activity. Compared with saline-treated rats, nicotine (2 mg/kg/day i.p., for 14 days) significantly reduced the slopes of baroreflex curves, a measure of baroreflex sensitivity (BRS). Findings that favor the involvement of NOS inhibition in the nicotine effect were (i) NOS inhibition (Nω-Nitro-L-arginine methyl ester, L-NAME) reduced BRS in control rats but failed to do so in nicotine-treated rats, (ii) L-arginine, NO donor, reversed the BRS inhibitory effect of nicotine. Alternatively, HO inhibition (zinc protoporphyrin IX, ZnPP) had no effect on BRS in nicotine- or control rats and failed to reverse the beneficial effect of L-arginine on nicotine-BRS interaction. Similar to female rats, BRS was reduced by L-NAME, but not ZnPP, in male rats and the L-NAME effect was not accentuated after concomitant administration of nicotine. Baroreflex dysfunction caused by nicotine in female rats was blunted after supplementation with hemin (HO inducer) but not tricarbonyldichlororuthenium(II) dimer (CORM-2), a carbon monoxide (CO) releasing molecule, or bilirubin, the breakdown product of heme catabolism. The facilitatory effect of hemin was abolished upon simultaneous treatment with L-NAME or 1H-[1], [2], [4] oxadiazolo[4,3-a] quinoxalin-1-one (inhibitor of soluble guanylate cyclase, sGC). The activities of HO and NOS in brainstem tissues were also significantly increased by hemin. Thus, the inhibition of NOS, but not HO, accounts for the baroreflex depressant of chronic nicotine. Further, hemin alleviates the nicotine effect through a mechanism that is NOS/sGC but not CO or bilirubin-dependent.

An improved monomeric infrared fluorescent protein for neuronal and tumour brain imaging

Infrared fluorescent proteins (IFPs) are ideal for in vivo imaging, and monomeric versions of these proteins can be advantageous as protein tags or for sensor development. In contrast to GFP, which requires only molecular oxygen for chromophore maturation, phytochrome-derived IFPs incorporate biliverdin (BV) as the chromophore. However, BV varies in concentration in different cells and organisms. Here we engineered cells to express the haeme oxygenase responsible for BV biosynthesis and a brighter monomeric IFP mutant (IFP2.0). Together, these tools improve the imaging capabilities of IFP2.0 compared with monomeric IFP1.4 and dimeric iRFP. By targeting IFP2.0 to the plasma membrane, we demonstrate robust labelling of neuronal processes in Drosophila larvae. We also show that this strategy improves the sensitivity when imaging brain tumours in whole mice. Our work shows promise in the application of IFPs for protein labelling and in vivo imaging.

Cardioprotective effects of rhamnetin in H9c2 cardiomyoblast cells under H₂O₂-induced apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Many studies have emphasized that flavonoids, found in various fruits, vegetables, and seeds, as well as tea and red wine, have potential health-promoting and disease-preventing effects. Rhamnetin is a flavonoid that exhibits antioxidant capabilities. However, little is known about its effect on cardiac myocytes under oxidative stress and the underlying mechanisms.

MATERIALS AND METHODS

H9c2 cardiomyoblast cells were subjected to H2O2, to study the protective effect of rhamnetin on cell viability, apoptosis, and ROS production. Signaling proteins related to apoptosis, survival, and redox were analyzed by Western blot. Furthermore, the mRNA expressions of SIRTs were tested by real time-polymerase chain reaction (PCR).

RESULTS

We investigated the protective effects of rhamnetin against H₂O₂-induced apoptosis in H9c2 cardiomyoblasts. Rhamnetin protected cells against H₂O₂-induced cell death without any cytotoxicity, as determined by the XTT assay, LDH assay, TUNEL assay, Hoechst 33342 assay, and Western blot analysis of apoptosis-related proteins. Rhamnetin also enhanced the expression of catalase and Mn-SOD, thereby inhibiting production of intracellular ROS. Furthermore, rhamnetin recovered the H₂O₂-induced decrease in phosphorylation of Akt/GSK-3β and MAPKs (ERK1/2, p38 MAPK, and JNK) and pretreatment with their inhibitors, attenuating the rhamnetin-induced cytoprotective effect. Further studies with real time-PCR and a sirtuin inhibitor showed that cardioprotection by rhamnetin occurred through induction of SIRT3 and SIRT4.

CONCLUSIONS

Taken together, these results suggest that rhamnetin may have novel therapeutic potential to protect the heart from ischemia-related injury.

[Curcumin alleviated liver oxidative stress injury of rat induced by paraquat]

OBJECTIVE

To investigate the effect of curcumin on liver injury in rats induced by paraquat-mediated oxidative stress and the mechanism underlying its effect.

METHODS

Sixty rats were randomly divided into 4 groups: control group, curcumin control group (curcumin 50 mg/kg), paraquat group (2% paraquat solution 100 mg/kg), and curcumin intervention group (curcumin 50 mg/kg at 15 min, 24 h, or 48 h after paraquat exposure). On days 1, 3, or 7 after paraquat administration, and liver tissue was collected thereafter. The content of malonaldehyde (MDA) and the activities of superoxide dismutase activity (SOD) and catalase (CAT) in the liver tissue were determined by chemical colorimetry. The activities of heme oxygenase 1 (HO-1) and quinone oxidoreductase 1 (NQO-1) in the liver tissue were determined by ELISA. The mRNA and protein levels of NF-E2-related factor 2 (Nrf2) were determined by RT-PCR and Western blot, respectively. The pathological changes of liver tissue were examined by optical microscopy.

RESULTS

No significant change was observed between the control group and the curcumin control group in any examination of this study (P > 0.05). Both paraquat group and curcumin intervention group showed increase in MDA content, decreases in SOD and CAT activities, increases in HO-1 and NQO-1 activities, and increases in the protein and mRNA levels of Nrf2, in comparison with the control group (P < 0.05 for all except HO-1 activity in paraquat group on day 7). In comparison with the parquet group on the same day, the curcumin intervention group showed decrease in MDA content, increases in the activities of SOD, CAT, HO-1, and NQO-1, and increases in the mRNA and protein levels of Nrf2 on days 1, 3, and 7 (P < 0.05). The pathological examination revealed that the damage of liver tissue in the paraquat group was the most serious on the 3rd day after paraquat exposure, and the damage was consistently alleviated by curcumin intervention on days 1, 3, and 7, as compared with the paraquat group.

CONCLUSION

Oxidative stress plays an important role in paraquat-induced acute liver damage in rats, and curcumin can exert a hepatoprotective effect against oxidative stress by increasing the expression of Nrf2 and the activities of HO-1, NQO-1, SOD, and CAT and reducing the content of MDA.

Interaction between HY1 and H2O2 in auxin-induced lateral root formation in Arabidopsis

Haem oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are two key downstream signals of auxin, a well-known phytohormone regulating plant growth and development. However, the inter-relationship between HO-1 and H2O2 in auxin-mediated lateral root (LR) formation is poorly understood. Herein, we revealed that exogenous auxin, 1-naphthylacetic acid (NAA), could simultaneously stimulate Arabidopsis HO-1 (HY1) gene expression and H2O2 generation. Subsequently, LR formation was induced. NAA-induced HY1 expression is dependent on H2O2. This conclusion was supported by analyzing the removal of H2O2 with ascorbic acid (AsA) and dimethylthiourea (DMTU), both of which could block NAA-induced HY1 expression and LR formation. H2O2-induced LR formation was inhibited by an HO-1 inhibitor zinc protoporphyrin IX (Znpp) in wild-type and severely impaired in HY1 mutant hy1-100. Simultaneously, HY1 is required for NAA-mediated H2O2 generation, since Znpp inhibition of HY1 blocked the NAA-induced H2O2 production and LR formation. Genetic data demonstrated that hy1-100 was significantly impaired in H2O2 production and LR formation in response to NAA, compared with wild-type plants. The addition of carbon monoxide-releasing molecule-2 (CORM-2), the carbon monoxide (CO) donor, induced H2O2 production and LR formation, both of which were decreased by DMTU. Moreover, H2O2 and CORM-2 mimicked the NAA responses in the regulation of cell cycle genes expression, all of which were blocked by Znpp or DMTU, respectively, confirming that both H2O2 and CO were important in the early LR initiation. In summary, our pharmacological, genetic and molecular evidence demonstrated a close inter-relationship between HY1 and H2O2 existing in auxin-induced LR formation in Arabidopsis.

Amyloid-beta transporter expression at the choroid plexus in normal aging: the possibility of reduced resistance to oxidative stress insults

Accumulation of amyloid-beta peptides (Aβ) results in amyloid burden in normal aging brain. Clearance of this peptide from the brain occurs via active transport at the interfaces separating the central nervous system (CNS) from the peripheral circulation. The present study was to investigate the change of Aβ transporters expression at the choroid plexus (CP) in normal aging. Morphological modifications of CP were observed by transmission electron microscope. Real-time RT-PCR was used to measure mRNA expressions of Aβ(42) and its transporters, which include low density lipoprotein receptor-related protein-1 and 2 (LRP-1 and -2), P-glycoprotein (P-gp) and the receptor for advanced glycation end-products (RAGE), at the CP epithelium in rats at ages of 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33 and 36 months. At the same time, the mRNA expressions of oxidative stress-related proteins were also measured. The results showed that a striking deterioration of the CP epithelial cells and increased Aβ(42) mRNA expression were observed in aged rats, and there was a decrease in the transcription of the Aβ efflux transporters, LRP-1 and P-gp, no change in RAGE mRNA expression and an increase in LRP-2, the CP epithelium Aβ influx transporter. Heme oxygenase-1 (HO-1) and caspase-3 expressions at the CP epithelium increased with age at the mRNA level. These results suggest the efficacy of the CP in clearing of Aβ deceases in normal aging, which results in the increase of brain Aβ accumulation. And excess Aβ interferes with oxidative phosphorylation, leads to oxidative stress and morphological structural changes. This in turn induces further pathological cascades of toxicity, inflammation and neurodegeneration process.

PI3K/Akt-independent NOS/HO activation accounts for the facilitatory effect of nicotine on acetylcholine renal vasodilations: modulation by ovarian hormones

We investigated the effect of chronic nicotine on cholinergically-mediated renal vasodilations in female rats and its modulation by the nitric oxide synthase (NOS)/heme oxygenase (HO) pathways. Dose-vasodilatory response curves of acetylcholine (0.01–2.43 nmol) were established in isolated phenylephrine-preconstricted perfused kidneys obtained from rats treated with or without nicotine (0.5–4.0 mg/kg/day, 2 weeks). Acetylcholine vasodilations were potentiated by low nicotine doses (0.5 and 1 mg/kg/day) in contrast to no effect for higher doses (2 and 4 mg/kg/day). The facilitatory effect of nicotine was acetylcholine specific because it was not observed with other vasodilators such as 5′-N-ethylcarboxamidoadenosine (NECA, adenosine receptor agonist) or papaverine. Increases in NOS and HO-1 activities appear to mediate the nicotine-evoked enhancement of acetylcholine vasodilation because the latter was compromised after pharmacologic inhibition of NOS (L-NAME) or HO-1 (zinc protoporphyrin, ZnPP). The renal protein expression of phosphorylated Akt was not affected by nicotine. We also show that the presence of the two ovarian hormones is necessary for the nicotine augmentation of acetylcholine vasodilations to manifest because nicotine facilitation was lost in kidneys of ovariectomized (OVX) and restored after combined, but not individual, supplementation with medroxyprogesterone acetate (MPA) and estrogen (E2). Together, the data suggests that chronic nicotine potentiates acetylcholine renal vasodilation in female rats via, at least partly, Akt-independent HO-1 upregulation. The facilitatory effect of nicotine is dose dependent and requires the presence of the two ovarian hormones.

Inhibitory effects of palm tocotrienol-rich fraction supplementation on bilirubin-metabolizing enzymes in hyperbilirubinemic adult rats

BACKGROUND

Phenylhydrazine, a hemolytic agent, is widely used as a model of experimental hyperbilirubinemia. Palm tocotrienol-rich fraction (TRF) was shown to exert beneficial effects in hyperbilirubinemic rat neonates.

AIM

To investigate the effects of palm TRF supplementation on hepatic bilirubin-metabolizing enzymes and oxidative stress status in rats administered phenylhydrazine.

METHODS

Twenty-four male Wistar rats were divided into two groups; one group was intraperitoneally injected with palm TRF at the dose of 30 mg/kg/day, while another group was only given vehicle (control) (vitamin E-free palm oil) for 14 days. Twenty-four hours after the last dose, each group was further subdivided into another two groups. One group was administered phenylhydrazine (100 mg/kg, intraperitoneally) and another group was administered normal saline. Twenty-four hours later, blood and liver were collected for biochemical parameter measurements.

RESULTS

Phenylhydrazine increased plasma total bilirubin level and oxidative stress in the erythrocytes as well as in the liver, which were reduced by the pretreatment of palm TRF. Palm TRF also prevented the increases in hepatic heme oxygenase, biliverdin reductase and UDP-glucuronyltransferase activities induced by phenylhydrazine.

CONCLUSION

Palm tocotrienol-rich fraction was able to afford protection against phenylhydrazine-induced hyperbilirubinemia, possibly by reducing oxidative stress and inhibiting bilirubin-metabolizing enzymes in the liver.

MauG, a diheme enzyme that catalyzes tryptophan tryptophylquinone biosynthesis by remote catalysis

MauG contains two c-type hemes with atypical physical and catalytic properties. While most c-type cytochromes function simply as electron transfer mediators, MauG catalyzes the completion of tryptophan tryptophylquinone (TTQ)(1) biosynthesis within a precursor protein of methylamine dehydrogenase. This posttranslational modification is a six-electron oxidation that requires crosslinking of two Trp residues, oxygenation of a Trp residue and oxidation of the resulting quinol to TTQ. These reactions proceed via a bis-Fe(IV) state in which one heme is present as Fe(IV)O and the other is Fe(IV) with axial heme ligands provided by His and Tyr side chains. Catalysis does not involve direct contact between the protein substrate and either heme of MauG. Instead it is accomplished by remote catalysis using a hole hopping mechanism of electron transfer in which Trp residues of MauG are reversibly oxidized. In this process, long range electron transfer is coupled to the radical mediated chemical reactions that are required for TTQ biosynthesis.