Induction of heme oxygenase-1 with hemin attenuates hippocampal injury in rats after acute carbon monoxide poisoning

The effect of preconditioning agents on cardiotoxicity and neurotoxicity of carbon monoxide poisoning in animal studies: a systematic review

BACKGROUND

Carbon monoxide (CO) poisoning is a common intoxication and many people die yearly due to CO poisoning and preconditioning agents attenuate brain and cardiac injury caused by intoxication. It is critical to fully understand the efficacy of new methods to directly target the toxic effect of CO, such as conditioning agents, which are currently under development. This study aims to systematically investigate current evidence from animal experiments and the effects of administration preconditions in acute and late phases after CO poisoning on cardiotoxicity and neurotoxicity.

METHODS

Four databases (PubMed, Embase, Scopus, and Web of Science) were systematically searched without language restrictions, and hand searching was conducted until November 2021. We included studies that compare preconditioning agents with the control group after CO poisoning in animals. The SYRCLE RoB tool was used for risk of bias assessments.

RESULTS

Thirty-seven studies were included in the study. Erythropoietin, granulocyte colony-stimulating factor (GCSF), hydrogen-rich saline, and N-butylphthalide (NBP) were found to have positive effects on reducing neurotoxicity and cardiotoxicity. As other preconditions have fewer studies, no valuable results can be deduced. Most of the studies were unclear for sources of bias.

DISCUSSION

Administration of the examined preconditioning agents including NBP, hydrogen-rich saline, and GCSF in acute and late phases could attenuate neurotoxicity and cardiotoxicity of CO poisoned animals. For a better understanding of mechanisms and activities, and finding new and effective preconditioning agents, further preclinical and clinical studies should be performed to analyze the effects of preconditioning agents.

A pilot study of neuroprotective effect of granulocyte colony-stimulating factor (G-CSF) in patients with carbon monoxide poisoning: a double-blind, randomized, placebo-controlled trial

Although neuroprotective effects of granulocyte colony-stimulating factor (G-CSF) have been shown in rats exposed to carbon monoxide (CO), this pilot clinical trial was performed to assess the feasibility of treatment with G-CSF in patients with acute CO poisoning. A double-blind, randomized, placebo-controlled pilot clinical trial was conducted on twenty-six patients with acute CO poisoning. G-CSF (90 μg/kg) was administered intravenously for 72 h. Demographic data, routine laboratory tests, differential blood counts, venous blood gas, and adverse reactions were recorded. The primary endpoint was brain ischemia improvement based on CT findings and the secondary endpoints examined improvements in the modified Rankin Scale (mRS), National Institutes of Health Stroke Scale (NIHSS), and Barthel Index as well as S-100β concentrations. Fourteen patients received G-CSF, and 12 received a placebo. Twenty-six were followed for 30 days and no one in both groups died during follow-up. Neurological complications, brain ischemic changes, Barthel, and mRS were compared between the two groups on determined days after the onset of therapeutic intervention, and no significant differences were observed between the two groups. Favorable results were achieved for treated patients by different measures; NIHSS was decreased 72 h after treatment (p = 0.046), and S-100β levels were significantly higher in the G-CSF group than in the control group, 12 h and 72 h after the treatment. G-CSF appears to have potential effects on several clinical parameters in patients with acute CO poisoning. The trial was registered at the Iranian Registry of Clinical Trials with the ID: (IRCT201607232083N7).

Hemin Ameliorates the Inflammatory Activity in the Inflammatory Bowel Disease: A Non-Clinical Study in Rodents

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract. Currently, there is no cure, and pharmacological treatment aims to induce and maintain remission in patients, so it is essential to investigate new possible treatments. Hemin is a heme-oxygenase inducer which can confer anti-inflammatory, cytoprotective, and antiapoptotic effects; therefore, it can be considered an asset for different gastrointestinal pathologies, namely for IBD.

AIM

This experiment aims to evaluate the efficacy and safety of hemin, in a chronic 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis model in rodents.

METHODS

The induction of chronic colitis consisted of five weekly intrarectal administrations of 1% TNBS. Then, the mice were treated daily with 5 mg/kg/day or 10 mg/kg/day of hemin, through intraperitoneal injections, for 14 days.

RESULTS

Hemin demonstrated an anti-inflammatory effect through the reduction in tumor necrosis factor (TNF)-α levels, fecal calprotectin, and fecal hemoglobin. It was also found to be safe in terms of extraintestinal manifestations, since hemin did not promote renal and/or hepatic changes.

CONCLUSIONS

Hemin could become an interesting tool for new possible pharmacological approaches in the management of IBD.

Dynamic cerebral blood flow changes with FOXOs stimulation are involved in neuronal damage associated with high-altitude cerebral edema in mice

Acute hypobaric hypoxia (AHH) exposure causes altitude mountain sickness (AMS) and life-threatening high altitude cerebral edema (HACE). Despite decades of research, the role of cerebral blood flow (CBF) changes in the pathophysiology of severe AMS remains unclear. The current study evaluated spatiotemporal responses of CBF associated with HACE in mice during the early stages of ascent to high altitudes. First, mice were exposed to AHH to test their tolerance to increasing altitudes (3000-8000 m). Because of its significant influence on both locomotor activity and rotarod behavior tests in mice, further observations were initiated at an altitude of 6000 m to investigate the specific pathophysiology of AMS. Compared with controls, laser speckle contrast imaging (LSCI) revealed a significant decrease in CBF during the early stage (0.5-24 h) at an altitude of 6000 m that was accompanied by a significant increase in brain water content (BWC). Moreover, observations of brain lipid oxidative damage and oxidative stress during the early stage of AHH exposure revealed DNA and cellular damage in cortical and hippocampal regions. Transcriptome profiling of the hippocampus revealed upregulation of forkhead box transcription factors. Similarly, western blot assays revealed upregulation of FOXO1a, FOXO3a, caspase-3 and Bax, and downregulation of Bcl-2, indicating a temporal influence of AHH on mitochondrial function and neuronal apoptosis. Thus, we found that the pathophysiology of HACE occurred with dynamic CBF changes, which triggered oxidative stress and neuronal damage in the mouse brain after AHH exposure. Our findings provide potential strategies for treatment of AHH in the future.

Acute carbon monoxide poisoning with low saturation of carboxyhaemoglobin: a forensic retrospective study in Shanghai, China

Carbon monoxide (CO) poisoning is a common cause of death, leading to morbidity and mortality worldwide. Features of the CO poisoning with low carboxyhemoglobin (COHb) levels remain to be characterized. This study collected a total of 307 CO poisoning cases from Shanghai Public Security Bureau, an official organization that handles the most complicated and life-threatening cases across Shanghai municipality in China, and regrouped these cases into three categories: group 1, 10% < COHb% < 30% (n = 58); group 2, 30% ≤ COHb% < 50% (n = 79); group 3, COHb% ≥ 50% (n = 170). Epidemiological, demographic, and forensic aspects of the CO poisoning cases, particularly those with low COHb levels, were analyzed. Our results showed that group 2 and 3 were mostly observed in younger victims (≤ 30 years), while group 1 equally distributed to all age groups (p = 0.03). All the CO poisoning from group 2 and 3 occurred in enclosed spaces, whereas cases from group 1 died additionally in outdoor spaces (p = 0.01). 81.03% of group 1 cases died in fire circumstances, while only 45.57% from group 2 and 30.59% from group 3 were fire-related (p = 0.00). Accordingly, group 1 was mostly related with fire burns, while group 2 or 3 were largely associated with gas leakage (p = 0.00). A combination with alcohol, but not other psychotropic drugs, associated with significant higher levels of blood COHb% in fire-unrelated (p = 0.021) but not fire-related cases (p = 0.23). Five extremely low COHb% (< 30%)-related poisoning deaths were negative of any cardiopulmonary pathology and psychoactive substances. In conclusion, CO poisoning with low COHb% significantly associates with fire circumstances and outdoor spaces and has no age preference. Further diagnostic markers mandates to be identified in order to avoid disputes in cases of extremely low COHb%-related poisoning.

Hemin-decreased cadmium uptake in pak choi (Brassica chinensis L.) seedlings is heme oxygenase-1 dependent and relies on its by-products ferrous iron and carbon monoxide

Cadmium (Cd) is a major pollutant in farmland, which not only greatly restricts crop production, but also brings a serious threat to human health through entering the food chain. Our previous study showed that hemin treatment could reduce the accumulation of Cd in pak choi seedlings. However, the underlying mechanism remains unclear. In this study, we used non-invasive micro-test technology (NMT) to detect the real-time Cd²⁺ flux from pak choi roots and demonstrated that hemin treatment decreased Cd uptake rather than its translocation within plants. Moreover, through comparing the responses of different chemical treatments in pak choi seedlings and Arabidopsis wild-type and heme oxygenase-1 (HO-1) mutant, we provided evidence that hemin-decreased Cd uptake was HO-1 dependent. Furthermore, analyses of hemin degradation products suggested that the hemin-derived suppression of Cd uptake suppression was probably relying on its degradation by-products, ferrous iron (Fe²⁺) and carbon monoxide (CO), via repressing the expression of a Fe²⁺/Cd²⁺ transporter BcIRT1 in pak choi roots.

Carbon monoxide-triggered health effects: the important role of the inflammasome and its possible crosstalk with autophagy and exosomes

Carbon monoxide (CO) has long been known as a "silent killer" because of its ability to bind hemoglobin (Hb), leading to reduced oxygen carrying capacity of Hb, which is the main cause of CO poisoning (COP) in humans. Emerging studies suggest that mitochondria is a key target of CO action that can impact key biological processes, including apoptosis, cellular proliferation, inflammation, and autophagy. Despite its toxicity at high concentrations, CO also exhibits cyto- and tissue-protective effects at low concentrations in animal models of organ injury and disease. Specifically, CO modulates the production of pro- or anti-inflammatory cytokines and mediators by regulating the NLRP3 inflammasome. Given that human diseases are strongly associated with inflammation, a deep understanding of the exact mechanism is helpful for treatment. Autophagic factors and inflammasomes interact in various situations, including inflammatory disease, and exosomes might function as the bridge between the inflammasome and autophagy activation. Thus, the interplay among autophagy, mitochondrial dysfunction, exosomes, and the inflammasome may play pivotal roles in the health effects of CO. In this review, we summarize the latest research on the beneficial and toxic effects of CO and their underlying mechanisms, focusing on the important role of the inflammasome and its possible crosstalk with autophagy and exosomes. This knowledge may lead to the development of new therapies for inflammation-related diseases and is essential for the development of new therapeutic strategies and biomarkers of COP.

Current and research therapies for the prevention and treatment of delayed neurological syndrome associated with carbon monoxide poisoning: A narrative review

Severe carbon monoxide (CO) poisoning causes fulminant deaths in common environment as well as neurological sequelae to survivors. Prevention of delayed neurological syndrome (DNS) after exposure to CO, the most important sequela, is based up to date on hyperbaric oxygen administration. Nevertheless, its use remains controversial due to the lack of evidence regarding its efficacy. The aim of this review is to report therapies under investigation for preventing or improving DNS, some of them with promising results in humans.

Unraveling the Role of Heme in Neurodegeneration

Heme (iron-protoporphyrin IX) is an essential co-factor involved in several biological processes, including neuronal survival and differentiation. Nevertheless, an excess of free-heme promotes oxidative stress and lipid peroxidation, thus leading to cell death. The toxic properties of heme in the brain have been extensively studied during intracerebral or subarachnoid hemorrhages. Recently, a growing number of neurodegenerative disorders have been associated to alterations of heme metabolism. Hence, the etiology of such diseases remains undefined. The aim of this review is to highlight the neuropathological role of heme and to discuss the major heme-regulated pathways that might be crucial for the survival of neuronal cells. The understanding of the molecular mechanisms linking heme to neurodegeneration will be important for therapeutic purposes.

Hemin reduces inflammation associated with TNBS-induced colitis

Purpose

Hemin is a heme-oxygenase inducer, which can confer anti-inflammatory, cytoprotective, and antiapoptotic effects. These properties are beneficial therapeutical effects to inflammatory bowel disease (IBD). IBD is a worldwide health problem characterized by chronic inflammation of intestinal epithelium, which promotes intestinal and extraintestinal symptomatology. Current treatment only induces and maintains the patient in remission and results in many side effects. The research of other pharmacologic approaches is crucial to the treatment of IBD. The aim of this study is to evaluate the effect of hemin in the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis model.

Materials and methods

Male CD-1 mice with TNBS-induced colitis were treated with a daily dose of hemin 5 mg/kg body weight/day and 10 mg/kg body weight/day intraperitoneal, during 4 days. The evaluated parameters were fecal hemoglobin, alkaline phosphatase (ALP), myeloperoxidase, tumor necrosis factor-α, interleukin (IL)-1β, IL-10, histopathologic analysis, urea, creatinine, and alanine aminotransferase.

Results

The hemin-treated mice presented a decrease in fecal hemoglobin, ALP, and proinflammatory cytokine concentrations compared to the TNBS group. Histopathology analysis confirmed the decrease in lesion extension produced by hemin.

Conclusion

These findings suggest that hemin treatment reduces hemorrhagic focus, intestinal damage, tissue inflammation, and lesion extension associated with experimental colitis.

Hemin provides protection against lead neurotoxicity through heme oxygenase 1/carbon monoxide activation

The neurotoxicity of lead (Pb) is well established, and oxidative stress is strongly associated with Pb-induced neurotoxicity. Heme oxygenase 1 (HO-1) is an important antioxidative enzyme for protection against oxidative stress in many disease models. In this study, we applied hemin, the substrate and a well-known inducer of HO-1, to investigate the possible role of HO-1 in protecting against Pb neurotoxicity. Hemin can significantly attenuate Pb acetate-induced cell death and oxidative stress in the hippocampus and frontal cortex of developmental rats. Consistent with in vivo results, the protective effects of hemin were also observed in SH-SY5Y cells after inducing cell survival and maintaining redox balance. However, knocking down HO-1 could significantly abolish the cytoprotective action of hemin against Pb toxicity, confirming HO-1 contributed to the protection. Finally, the HO-1-derived production of carbon monoxide, but not of bilirubin or Fe²⁺ , mediated the protective effects of HO-1 activation induced by hemin treatment against Pb-induced cell death and oxidative stress in SHSY5Y cells. Overall, this study showed that hemin provided protection against Pb neurotoxicity by HO-1/carbon monoxide activation.

A novel effective chemical hemin for the treatment of acute carbon monoxide poisoning in mice

There is no effective drug for the therapy of acute carbon monoxide (CO) poisoning. The purpose of the present study was to investigate the potential preventive and therapeutic effects of hemin on an animal model of acute CO poisoning and to provide a potential therapeutic candidate drug. A total of 80 Kunming mice were randomly divided into four groups, namely the air control, acute CO poisoning, hemin-treatment + CO and hemin-pretreatment + CO groups (n=20 each). Furthermore, the mortality rate of mice, blood carboxyhaemoglobin (HbCO) concentration and serum malondialdehyde (MDA) concentration were measured, and pathological changes of the hippocampal area were determined using histochemical staining. The mice with acute CO poisoning had a 50% mortality rate at 1 h, with an increase in blood HbCO, serum MDA levels and pathological impairments of the hippocampus. Furthermore, the mortality rate, blood HbCO and serum MDA levels of mice with pretreatment and treatment of hemin were decreased. Additionally, the pathological changes of the hippocampal area were improved in the hemin-treatment and hemin-pretreatment groups compared with the mice treated with CO. These results suggest that hemin is a novel effective chemical for the prevention and treatment of acute CO poisoning in mice. Therefore, the present study provides a novel method and experimental basis for the application of hemin in treating patients with acute CO poisoning.

Neuro-Protective Effects of Resveratrol on Carbon Monoxide-Induced Toxicity in Male Rats

Acute carbon monoxide (CO) poisoning causes neurotoxicity through induction of necrosis, apoptosis, lipid peroxidation and oxidative stress. Resveratrol (RES) is a natural polyphenolic phytoalexin that exhibits neuroprotective effects in ischemia/reperfusion due to its anti-apoptotic, anti-necrotic and strong anti-oxidant properties as well as its ability to activate pro-survival pathways. In this study, rats were exposed to CO 3000 ppm for 1 h. Immediately after poisoning and on the next four consecutive days, RES (1, 5 and 10 mg/kg) was administered intraperitoneally. On the fifth day, animals' brains were excised, and necrosis, lipid peroxidation level and the level of Akt, BAX and BCL2 expression were evaluated. The results showed that RES 10 mg/kg significantly reduced lipid peroxidation, but RES 1 and 5 mg/kg had no significant effect on this parameter. Furthermore, RES 5 and 10 mg/kg significantly increased Akt expression level, while BAX/BCL2 ratio was reduced by RES 1, 5 and 10 mg/kg. Moreover, RES reduced necrotic foci in the brain, but the best results were seen following treatment with RES 10 mg/kg. In summary, RES showed neuroprotective effect in CO-poisoned rats as it decreased necrosis and BAX/BCL2 ratio and increased Akt expression levels. Copyright © 2017 John Wiley & Sons, Ltd.

Hemin protects against oxygen-glucose deprivation-induced apoptosis activation via neuroglobin in SH-SY5Y cells

This study aimed to investigate the mechanism underlying the neuroprotective effect of hemin in oxygen-glucose deprivation (OGD)-treated neurons. OGD-treated SH-SY5Y cells (human neuroblastoma cells) were used in the study. The cellular viability of SH-SY5Y cells was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the cell apoptosis rate was determined by flow cytometry analysis with Annexin V-fluorescein isothiocyanate and propidium iodide staining with or without hemin pretreatment. Cell viability and apoptotic activation were detected after hemin administration combined with neuroglobin (Nqb), thioredoxin-1, peroxiredoxin-2, or heme oxygenase-1 siRNA transient transfection. The release of cytochrome c from mitochondria and the interaction between Ngb and cytochrome c were examined with hemin pretreatment. Hemin had a neuroprotective effect in OGD-treated SH-SY5Y cells, which was mainly mediated by the upregulation of Ngb. Moreover, the release of cytochrome c from mitochondria was inhibited by hemin-induced Ngb expression through facilitating the interaction of Ngb with cytochrome c in mitochondria. The present findings provided new insights into the neuroprotective mechanisms of hemin. It was concluded that low-dose hemin pretreatment had a neuroprotective effect in OGD-treated SH-SY5Y cells, through inhibiting cell apoptosis. The neuroprotective effects of hemin following hypoxic-ischemic neuronal damage were mainly mediated by Ngb. One underlying mechanism was hemin-induced overexpression of mitochondrial Ngb, which inhibited endogenous apoptosis via the association with cytochrome c.

G-CSF administration attenuates brain injury in rats following carbon monoxide poisoning via different mechanisms

Acute severe carbon monoxide (CO) poisoning induces hypoxia that leads to cardiovascular and nervous systems disturbances. Different complex mechanisms lead to CO neurotoxicity including lipid peroxidation, inflammatory and immune-mediated reactions, myelin degeneration and finally neuronal apoptosis and necrosis. Granulocyte colony-stimulating factor (G-CSF) is considered to be a novel neuroprotective agent. In this study, we evaluated the efficacy of G-CSF therapy on CO neurotoxicity in rats with acute CO poisoning. Rats were exposed to 3000 ppm CO in air (0.3%) for 1 h, and then different doses (50,100, and 150 µg/kg) of G-CSF or normal saline were administrated intraperitoneally. Water content of brain as an indicator for total edema and blood brain barrier integrity (Evans blue extravasation) were evaluated. Malondialydehyde was determined in order to evaluate the effect of G-CSF on CO-induced lipid peroxidation in brain tissues. Also, the effect of G-CSF on myeloperoxidase activity in the brain tissue was evaluated. The effect of G-CSF administration on induced apoptosis in the brain was measured using TUNEL method. To evaluate the level of MBP, STAT3 and pSTAT3 and HO-1 proteins and the effect of G-CSF on these proteins Western blotting was carried out. G-CSF reduced water content of the edematous poisoned brains (100 µg/kg) and BBB permeability (100 and 150 µg/kg) (P < 0.05). G-CSF (150 µg/kg) reduced the MDA level in the brain tissues (P < 0.05 as compared to CO poisoned animals). G-CSF did not decrease the MPO activity after CO poisoning in any doses. G-CSF significantly reduced the number of apoptotic neurons and Caspase 3 protein levels in the brain. Western blotting results showed that G-CSF treatment enhanced expression of HO-1 and MBP, STAT3 and pSTAT3 proteins in the brain tissues. Based on our results, a single dose of G-CSF immediately after CO poisoning significantly attenuates CO neurotoxicity via different mechanisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 37-47, 2017.

Diverse mechanisms underlying the regulation of ion channels by carbon monoxide

Carbon monoxide (CO) is firmly established as an important, physiological signalling molecule as well as a potent toxin. Through its ability to bind metal-containing proteins, it is known to interfere with a number of intracellular signalling pathways, and such actions can account for its physiological and pathological effects. In particular, CO can modulate the intracellular production of reactive oxygen species, NO and cGMP levels, as well as regulate MAPK signalling. In this review, we consider ion channels as more recently discovered effectors of CO signalling. CO is now known to regulate a growing number of different ion channel types, and detailed studies of the underlying mechanisms of action are revealing unexpected findings. For example, there are clear areas of contention surrounding its ability to increase the activity of high conductance, Ca(2+) -sensitive K(+) channels. More recent studies have revealed the ability of CO to inhibit T-type Ca(2+) channels and have unveiled a novel signalling pathway underlying tonic regulation of this channel. It is clear that the investigation of ion channels as effectors of CO signalling is in its infancy, and much more work is required to fully understand both the physiological and the toxic actions of this gas. Only then can its emerging use as a therapeutic tool be fully and safely exploited.

Salvianolic acids attenuate rat hippocampal injury after acute CO poisoning by improving blood flow properties

Carbon monoxide (CO) poisoning causes the major injury and death due to poisoning worldwide. The most severe damage via CO poisoning is brain injury and mortality. Delayed encephalopathy after acute CO poisoning (DEACMP) occurs in forty percent of the survivors of acute CO exposure. But the pathological cause for DEACMP is not well understood. And the corresponding therapy is not well developed. In order to investigate the effects of salvianolic acid (SA) on brain injury caused by CO exposure from the view point of hemorheology, we employed a rat model and studied the dynamic of blood changes in the hemorheological and coagulative properties over acute CO exposure. Compared with the groups of CO and 20% mannitol + CO treatments, the severe hippocampal injury caused by acute CO exposure was prevented by SA treatment. These protective effects were associated with the retaining level of hematocrit (Hct), plasma viscosity, fibrinogen, whole blood viscosities and malondialdehyde (MDA) levels in red blood cells (RBCs). These results indicated that SA treatment could significantly improve the deformation of erythrocytes and prevent the damage caused by CO poisoning. Meanwhile, hemorheological indexes are good indicators for monitoring the pathological dynamic after acute CO poisoning.

Neuroprotective effect of hemeoxygenase-1/glycogen synthase kinase-3β modulators in 3-nitropropionic acid-induced neurotoxicity in rats

The present study has been designed to explore the possible interaction between hemeoxygenase-1 (HO-1) and glycogen synthase kinase-3β (GSK-3β) pathway in 3-nitropropionic acid (3-NP)-induced neurotoxicity in rats. 3-NP produces neurotoxicity by inhibition of the mitochondrial complex II (enzyme succinate dehydrogenase) and by sensitizing the N-methyl-D-aspartate receptor. Recent studies have reported the therapeutic potential of HO-1/GSK-3β modulators in different neurodegenerative disorders. However, their exact role is yet to be explored. The present study is an attempt to investigate the effect of pharmacological modulation of HO-1/GSK-3β pathway against 3-NP-induced behavioral, biochemical and molecular alterations in rat. Behavioral observation, oxidative stress, pro-inflammatory [tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)], HO-1 and GSK-3β activity were evaluated post 3-NP treatment. Findings of the present study demonstrate a significant alteration in the locomotor activity, motor coordination, oxidative burden (increased lipid peroxidation, nitrite concentration and decreased endogenous antioxidants), pro-inflammatory mediators [TNF-α, IL-1β], HO-1 and GSK-3β activity in 3-NP-treated animals. Further, administration of hemin (10- and 30-mg/kg; i.p.) and lithium chloride (LiCl) (25- and 50-mg/kg; i.p.) prevented the alteration in body weight, motor impairments, oxidative stress and cellular markers. In addition, combined administration of hemin (10-mg/kg) and LiCl (25-mg/kg) showed synergistic effect on 3-NP-treated rats. Pretreatment with Tin (IV) protoporphyrin (40 μM/kg), HO-1 inhibitor reversed the beneficial effect of LiCl and hemin. Outcomes of the present study suggest that HO-1 and GSK-3β enzymes are involved in the pathophysiology of HD. The modulators of both the pathways might be used as adjuvants or prophylactic therapy for the treatment of HD-like symptoms.

Hemin and Zinc Protoporphyrin IX Affect Granisetron Constipating Effects In Vitro and In Vivo

Granisetron is a 5-HT3 receptors antagonist used in the management of emesis associated with anticancer chemotherapy. It affects intestinal motility with constipating effect. Since the pathway heme oxygenase/carbon monoxide (HO/CO) is involved in gastrointestinal motility, we evaluated the possible interplay between granisetron and agents affecting HO/CO pathways such as zinc protoporphyrin IX (ZnPPIX), an HO inhibitor, or hemin, an HO-1 inducer. ZnPPIX (10 µM) or hemin (10 µM), but not granisetron (0.1, 0.3, 1 µM), affected spontaneous basal activity recorded in rat duodenal strips, in noncholinergic nonadrenergic conditions. Granisetron restored spontaneous basal activity after ZnPPIX, but not after hemin. ZnPPIX decreased and hemin increased the inhibition of activity after electrical field stimulation (EFS), but they did not affect the contraction that follows the relaxation induced by EFS called off contraction. Granisetron did not alter the response to EFS per se but abolished both ZnPPIX and hemin effect when coadministered. In vivo study showed constipating effect of granisetron (25, 50, 75 µg/kg/sc) but no effect of either ZnPPIX (50 µg/kg/i.p.) or hemin (50 µM/kg/i.p.). When coadministered, granisetron effect was abolished by ZnPPIX and increased by hemin. Specimens from rats treated in vivo with hemin (50 µM/kg/i.p.) showed increased HO-1 protein levels. In conclusion, granisetron seems to interact with agents affecting HO/CO pathway both in vitro and in vivo.

Hemin ameliorates indomethacin-induced small intestinal injury in mice through the induction of heme oxygenase-1

BACKGROUND AND AIM

Although non-steroidal anti-inflammatory drugs can induce intestinal injury, the mechanisms are not fully understood, and treatment has yet to be established. Heme oxygenase-1 (HO-1) has recently gained attention for anti-inflammatory and cytoprotective effects. This study aimed to investigate the effects of hemin, an HO-1 inducer, on indomethacin-induced enteritis in mice.

METHODS

Enteritis was induced by single subcutaneous administration of indomethacin (10 mg/kg) in male C57BL/6 mice. Hemin (30 mg/kg) was administered by intraperitoneal administration 6 h before indomethacin administration. Mice were randomly divided into four groups: (i) sham + vehicle; (ii) sham + hemin; (iii) indomethacin + vehicle; or (iv) indomethacin + hemin. Enteritis was evaluated by measuring ulcerative lesions. Myeloperoxidase activity was measured as an index of neutrophil accumulation. The mRNA expression of inflammatory cytokines and chemokines, such as tumor necrosis factor-α, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α, and keratinocyte chemoattractant, were analyzed by real-time polymerase chain reaction.

RESULTS

The area of ulcerative lesions, myeloperoxidase activity, and mRNA expression of inflammatory cytokines and chemokines were significantly increased in mice administrated with indomethacin compared with vehicle-treated sham mice. Development of intestinal lesions, increased levels of myeloperoxidase activities, and mRNA expressions of inflammatory cytokines and chemokines were significantly suppressed in mice treated with hemin compared with vehicle-treated mice. Protective effects of hemin were reversed by co-administration of tin protoporphyrin, an HO-1 inhibitor.

CONCLUSIONS

Induction of HO-1 by hemin inhibits indomethacin-induced intestinal injury through upregulation of HO-1. Pharmacological induction of HO-1 may offer a novel therapeutic strategy to prevent indomethacin-induced small intestinal injury.

Low dose of carbon monoxide intraperitoneal injection provides potent protection against GalN/LPS-induced acute liver injury in mice

Carbon monoxide (CO) is an important effector-signaling molecule involved in various pathophysiological processes. Here we investigated the protective effects of exogenous CO in a murine model of acute liver damage induced by d-galactosamine (GalN) and lipopolysaccharide (LPS). Exogenous CO gas was administered to mice via intraperitoneal injection (first at a dose of 15 ml kg(-1) and then, 6 h later, 8 ml kg(-1)), which caused a significant elevation of blood carboxyhemoglobin levels of up to 12-14% for more than 12 h. GalN/LPS were given to induce acute liver damage in mice 30 min prior to CO exposure. This showed that GalN/LPS induced severe liver injury in mice, whereas CO injection remarkably improved the survival rate of mice and led to attenuated hepatocellular damage. CO exhibited anti-oxidative capabilities by inhibiting hepatic malondialdehyde contents and restoring superoxide dismutase and glutathione, as well as by reducing inducible NOS/NO production. The anti-apoptotic and anti-inflammatory effects of CO were substantial, characterized by a notable inhibition of hepatocyte apoptosis and a reduction of pro-inflammatory cytokines in mice. Our findings thus supported the hypothesis that exogenous CO provides protective effects against acute liver damage in mice, mainly dependent on its anti-oxidative, anti-inflammatory and anti-apoptotic properties.

Peroxynitrite mediates disruption of Ca2+ homeostasis by carbon monoxide via Ca2+ ATPase degradation

AIM

Sublethal carbon monoxide poisoning causes prolonged neurological damage involving oxidative stress. Given the central role of Ca(2+) homeostasis and its vulnerability to stress, we investigated whether CO disrupts neuronal Ca(2+) homeostasis.

RESULTS

Cytosolic Ca(2+) transients evoked by muscarine in SH-SY5Y cells were prolonged by CO (applied via the donor CORM-2), and capacitative Ca(2+) entry (CCE) was dramatically enhanced. Ca(2+) store mobilization by cyclopiazonic acid was similarly augmented, as was the subsequent CCE, and that evoked by thapsigargin. Ca(2+) rises evoked by depolarization were also enhanced by CO, and Ca(2+) levels often did not recover in its presence. CO increased intracellular nitric oxide (NO) and all effects of CO were prevented by inhibiting NO formation. However, NO donors did not mimic the effects of CO. The antioxidant ascorbic acid inhibited effects of CO on Ca(2+) signaling, as did the peroxynitrite scavenger, FeTPPS, and CO increased peroxynitrite formation. Finally, CO caused significant loss of plasma membrane Ca(2+)ATPase (PMCA) protein, detected by Western blot, and this was also observed in brain tissue of rats exposed to CO in vivo.

INNOVATION

The cellular basis of CO-induced neurotoxicity is currently unknown. Our findings provide the first data to suggest signaling pathways through which CO causes neurological damage, thereby opening up potential targets for therapeutic intervention.

CONCLUSION

CO stimulates formation of NO and reactive oxygen species which, via peroxynitrite formation, inhibit Ca(2+) extrusion via PMCA, leading to disruption of Ca(2+) signaling. We propose this contributes to the neurological damage associated with CO toxicity.

Blood-brain barrier disruption and oxidative stress in guinea pig after systemic exposure to modified cell-free hemoglobin

Systemic exposure to cell-free hemoglobin (Hb) or its breakdown products after hemolysis or with the use of Hb-based oxygen therapeutics may alter the function and integrity of the blood-brain barrier. Using a guinea pig exchange transfusion model, we investigated the effect of a polymerized cell-free Hb (HbG) on the expression of endothelial tight junction proteins (zonula occludens 1, claudin-5, and occludin), astrocyte activation, IgG extravasation, heme oxygenase (HO), iron deposition, oxidative end products (4-hydroxynonenal adducts and 8-hydroxydeoxyguanosine), and apoptosis (cleaved caspase 3). Reduced zonula occludens 1 expression was observed after HbG transfusion as evidenced by Western blot and confocal microscopy. Claudin-5 distribution was altered in small- to medium-sized vessels. However, total expression of claudin-5 and occludin remained unchanged except for a notable increase in occludin 72 hours after HbG transfusion. HbG-transfused animals also showed increased astrocytic glial fibrillary acidic protein expression and IgG extravasation after 72 hours. Increased HO activity and HO-1 expression with prominent enhancement of HO-1 immunoreactivity in CD163-expressing perivascular cells and infiltrating monocytes/macrophages were also observed. Consistent with oxidative stress, HbG increased iron deposition, 4-hydroxynonenal and 8-hydroxydeoxyguanosine immunoreactivity, and cleaved caspase-3 expression. Systemic exposure to an extracellular Hb triggers blood-brain barrier disruption and oxidative stress, which may have important implications for the use of Hb-based therapeutics and may provide indirect insight on the central nervous system vasculopathies associated with excessive hemolysis.

Erythropoietin attenuates hyperoxia-induced oxidative stress in the developing rat brain

Oxygen toxicity contributes to the pathogenesis of adverse neurological outcome in survivors of preterm birth in clinical studies. In infant rodent brains, hyperoxia triggers widespread apoptotic neurodegeneration, induces pro-inflammatory cytokines and inhibits growth factor signaling cascades. Since a tissue-protective effect has been observed for recombinant erythropoietin (rEpo), we hypothesized that rEpo would influence hyperoxia-induced oxidative stress in the developing rat brain. The aim of this study was to investigate the level of glutathione (reduced and oxidized), lipid peroxidation and the expression of heme oxygenase-1 (HO-1) and acetylcholinesterase (AChE) after hyperoxia and rEpo treatment. Six-day-old Wistar rats were exposed to 80% oxygen for 2-48 h and received 20,000 IU/kg rEpo intraperitoneally (i.p.). Sex-matched littermates kept under room air and injected with normal saline or rEpo served as controls. Treatment with rEpo significantly reduced hyperoxia-induced upregulation of oxidized glutathione (GSSG) and malondialdehyde, a product of lipid breakdown, whereas reduced glutathione (GSH) was upregulated by rEpo. In parallel, hyperoxia-treated immature rat brains revealed rEpo-suppressible upregulation of synaptic AChE-S as well as of the stress-inducible AChE-R variant, together predicting rEpo-protected cholinergic signaling and restrained inflammatory reactions. Furthermore, treatment with rEpo induced upregulation of HO-1 on mRNA, protein and activity level in the developing rat brain. Our results suggest that rEpo generates its protective effect against oxygen toxicity by a reduction of diverse oxidative stress parameters and by limiting the stressor-inducible changes in both HO-1 and cholinergic functions.