Neuroprotective effect of targeted regulatory Nrf2 gene on rats with acute brain injury induced by carbon monoxide poisoning.

Oxidative stress has been considered as an important cause of neurocyte damage induced by carbon monoxide (CO) poisoning; however, the precise mechanisms are not fully understood. The study aimed to elucidate the molecular mechanism and the neuroprotective effect of targeted regulatory nuclear factor erythroid2-related factor 2 (Nrf2) gene on acute brain injury in CO poisoning rats. An acute CO poisoning rat model was established by CO inhalation in hyperbaric oxygen chamber and followed by the administration of Nrf2 gene-loaded lentivirus. Mitochondrial membrane potential (ΔΨM), the levels of Nrf2, glutamate-cysteine ligase catalytic subunit (GCLC), catalase (CAT) and glutathione peroxidase (GSH-Px), and cell apoptosis were determined in brain tissue in rats. We found that CO poisoning could decrease ΔΨm of cells, slightly increase the expressions of Nrf2 and GCLC at mRNA and protein levels, reduce CAT and GSH-Px, and thus initiate apoptosis process. The Nrf2 gene treatment could obviously enhance the expressions of Nrf2 at mRNA and protein levels, and increase the concentrations of CAT and GSH-Px, maintain the ΔΨm of cells in brain tissue, significantly inhibit cell apoptosis as compared with the CO poisoning group (p < .05). These findings suggest that CO poisoning could induce oxidative stress and impair mitochondrial function of cells in brain tissue. The administration of Nrf2 gene could notably strengthen the antioxidant capacity of cells through regulating the downstream genes of Nrf2/antioxidant responsive element signal pathway, and positively protect cells against brain injury induced by acute severe CO poisoning.

Carbon monoxide increases utero-placental angiogenesis without impacting pregnancy specific adaptations in mice.

BACKGROUND: Cigarette smokers have a reduced risk of developing preeclampsia, possibly attributed to an increase in carbon monoxide (CO) levels. Carbon monoxide is a gasotransmitter that has been implicated in maintaining vascular tone, increasing angiogenesis, and reducing inflammation and apoptosis at physiological concentrations. Moderately increasing CO concentrations may have therapeutic potential to prevent or treat preeclampsia; however, the effects of CO on pregnancy are under studied. Our objective was to investigate the effect of CO on major angiogenic and inflammatory markers in pregnancy, and to evaluate the effect of CO on indicators of placental health. FINDINGS: Pregnant CD-1 mice were constantly exposed to either ambient air or 250 ppm CO from conception until gestation day (GD)10.5 or GD16.5. Using a qRT-PCR array, we identified that CO increased expression of major angiogenic genes at the implantation site on GD10.5, but not GD16.5. Pro-inflammatory cytokines in the plasma and tissue lysates from implantation sites in treated mice were not significantly different compared to controls. Additionally, CO did not alter the implantation site phenotype, in terms of proliferative capacity, invasiveness of trophoblasts, or abundance of uterine natural killer cells. CONCLUSIONS: This study suggests that CO exposure is pro-angiogenic at the maternal-fetal interface, and is not associated with demonstrable concerns during murine pregnancy. Future studies are required to validate safety and efficacy of CO as a potential therapeutic for vascular insufficiency diseases such as preeclampsia and intrauterine growth restriction.

RNA sequencing analysis reveals new findings of hyperbaric oxygen treatment on rats with acute carbon monoxide poisoning.

OBJECTIVE: To elucidate the altered gene network in the brains of carbon monoxide (CO) poisoned rats after treatment with hyperbaric oxygen (HBO2). METHODS: RNA sequencing (RNA-seq) analysis was performed to examine differentially expressed genes (DEGs) in brain tissue samples from nine male rats: a normal control group; a CO poisoning group; and an HBO2 treatment group (three rats/group). Reverse transcription polymerase chain reaction (RT-PCR) and real-time quantitative PCR were used for validation of the DEGs in another 18 male rats (six rats/group). RESULTS: RNA-seq revealed that two genes were upregulated (4.18 and 8.76 log to the base 2 fold change) (p⟨0.05) in the CO-poisoned rats relative to the control rats; two genes were upregulated (3.88 and 7.69 log to the base 2 fold change); and 23 genes were downregulated (3.49-15.12 log to the base 2 fold change) (p⟨0.05) in the brains of the HBO2-treated rats relative to the CO-poisoned rats. Target prediction of DEGs by gene network analysis and analysis of pathways affected suggested that regulation of gene expressions of dopamine metabolism and nitric oxide (NO) synthesis were significantly affected by CO poisoning and HBO2 treatment. Results of RT-PCR and real-time quantitative PCR indicated that four genes (Pomc, GH-1, Pr1 and Fshß) associated with hormone secretion in the hypothalamic-pituitary system have potential as markers for prognosis of CO. CONCLUSION: This study is the first RNA-seq analysis profile of HBO2 treatment on rats with acute CO poisoning. It concludes that changes of hormone secretion in the hypothalamic-pituitary system, dopamine metabolism and NO synthesis involved in brain damage and behavior abnormalities after CO poisoning and HBO2 therapy may regulate these changes.

Relationship between carbon monoxide intoxication and sister chromatid exchange in lymphocytes.

AIM: Carbon monoxide (CO) intoxication can be serious and is reported to be the cause of more than half of all fatal intoxications. In this study, we aimed to identify its genotoxic effects based on sister chromatid exchange (SCE). MATERIALS AND METHODS: CO-poisoned patients presented to the emergency services department were identified. Their demographic characteristics, vital findings, laboratory markers, source of CO gas, risk factors, and smoking habits were recorded. The genotoxic effect was assessed using the SCE method. RESULTS: A total of 38 patients were recruited. Their ages ranged from 16-64 years (mean: 29.79 ± 10.92 years). In all the cases, the source of CO gas was a flash heater. The mean carboxyhemoglobin (COHb) level was 25.05 ± 7.15%. Of all the patients, 12 (31.6%) had a the Glasgow Coma Scale (GCS) scores of less than 15, and an important negative correlation was found between the GCS and COHb level (r = -0.825; p < 0.001). Genotoxicity investigations revealed a significantly higher SCE frequency among patients with high COHb levels compared with that of control subjects with physiological COHb levels (p < 0.001). However, no correlation between increased SCE frequency and COHb level was found (r = 0.16; p = 0.34). CONCLUSION: CO poisoning was shown to result in genotoxicity via an increase in the frequency of SCE. This study is the first to demonstrate a genotoxic effect of CO independent of other chemicals.

The effect of acute carbon monoxide poisoning on micronuclei frequency and proliferation in human peripheral blood lymphocytes (case-control study).

OBJECTIVE: Carbon monoxide (CO) exposure is still one of the leading causes of unintentional poisonings. Although its neurological sequels have been extensively studied, the knowledge about cytogenetic conse- quences still remains very limited. The aim of this study was to estimate the genotoxic potential of carbon monoxide in the course of acute poisoning. METHODS: The examined group consisted of 73 patients treated because of accidental acute CO poisoning, and 22 healthy control individuals. Poisoning severity was estimated on the basis of neurological symptoms at admission, age, duration of exposure, carboxyhemoglobin (COHb) level and blood lactate concentration. The cytochalasine-B (cytokinesis blocker) micronucleus assay (CBMN) was used to analyze the cytogenetic alterations in lymphocytes from peripheral blood of the patients. RESULTS: Intoxicated patients displayed higher numbers of micronuclei (MN) than controls. The frequency of MN depended on the age of patients, loss of consciousness, neurological symptoms at admission, and the level of carboxyhemoglobin, but did not correlate with lactate level. We also observed differences in cell responses depending on the gender. CONCLUSION: Our results confirm the presence of cytogenetic changes after carbon monoxide poisoning. Based on these data we conclude, that CO might have genotoxic potential.

Investigation of the relationship between MBP gene polymorphisms and delayed encephalopathy after acute carbon monoxide poisoning.

Increasing evidence reveals that delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) results from the combined effects of environmental and genetic factors. The main pathological feature of DEACMP was generalized demyelination of cerebral white matter. Myelin basic protein (MBP) levels in cerebrospinal fluid (CSF) and serum samples from DEACMP patients were elevated. This study investigated the association of MBP single nucleotide polymorphisms(SNPs) (rs470555, rs470724, rs4890785, rs595997, rs76452994, and rs921336) with DEACMP. We genotyped 416 DEACMP patients and 785 age, educational level, and sex-matched ACMP patients for rs470555, rs470724, rs4890785, rs595997, rs76452994, and rs921336 SNPs using the Agena MassArray. There were no significant differences in the allele frequency distribution, four genetic models, and genotype distributions between the DEACMP and ACMP groups for rs470555, rs470724, rs4890785, and rs595997. However, significant differences were observed for rs76452994 and rs921336. This study revealed that the MBP polymorphisms, rs470555, rs470724, rs4890785, and rs595997, were not associated with DEACMP. Based on the codominant, dominant, and overdominant genetic inheritability patterns, the MBP rs76452994 and rs921366 polymorphisms were associated with DEACMP. Furthermore, the G allele of rs76452994 and T allele of rs921336 could lead to higher DEACMP risk.

Association of the genes for tumor necrosis factor-α and myelin basic protein with delayed encephalopathy after acute carbon monoxide poisoning.

There is structural damage to myelin and secondary immune injury in the development of delayed encephalopathy after acute carbon monoxide (CO) poisoning (DEACMP). In order to assess the role of genetic factors in this mechanism, we studied the association between tumor necrosis factor-α308 (TNF-α308) and myelin basic protein (MBP) 5'-side tetranucleotide repetitive sequence (TGGA) n gene polymorphism and DEACMP. We selected 109 DEACMP patients from the Han population in the Northern Henan Province as the case group, and 115 patients without delayed encephalopathy (called the acute CO poisoning group or the control group). There were no significant differences in TNF-α308 and MBP 5'-side TGGA n genotype distribution and allele frequency between the DEACMP group and the acute CO poisoning group (all P > 0.05). When the population was stratified by gender, only the MBP 5'-side TGGA n allele frequency was significantly different, and the frequency of allele L in the DEACMP group was significantly higher than that of the acute CO poisoning group in males (χ(2) = 4.089, P = 0.043, odds ratio = 2.103, 95% confidence interval = 1.014-4.363). The results showed that there was association between MBP 5'-side TGGA n gene polymorphism and DEACMP, and that allele L could increase the risk of occurrence in male patients with DEACMP. DEACMP may be the result of interaction of environmental and genetic factors.

The Relationship between Cadherin Polymorphisms and the Risk of Delayed Encephalopathy after Acute Carbon Monoxide Poisoning in the Chinese Han Population.

OBJECTIVE: The purpose of this study was to analyze the relationship between cadherin gene single-nucleotide polymorphisms (SNPs) and the risk of delayed encephalopathy after acute carbon monoxide poisoning (DEACMP). MATERIALS AND METHODS: A total of 416 patients with DEACMP and 754 patients with acute carbon monoxide poisoning (ACMP) were recruited. We used the Sequenom MassARRAY® system to detect cadherin gene SNPs related to DEACMP. Using different genetic analysis models, we evaluated the relationship between the cadherin gene polymorphisms and risk of DEACMP. RESULTS: We found that rs1944294 in the N-cadherin (CDH2) gene showed significant differences in genotype frequencies between the two groups under codominant and dominant inheritance models. Similarly, rs2513796 in the cadherin-17 (CDH17) gene showed significant differences under the codominant, dominant, and overdominant genetic models. And the T allele frequency of rs1944294 in the DEACMP group was significantly higher than that in the ACMP group (P = 0.023). CONCLUSIONS: Cadherin gene SNPs (rs1944294, rs2513796) are associated with an increased risk of DEACMP in the Chinese population.

Association between Neuron-Specific Enolase Gene Polymorphism and Delayed Encephalopathy after Acute Carbon Monoxide Poisoning.

OBJECTIVE: The aim of this study is to explore the relationship between neuron-specific enolase (NSE) gene polymorphism and delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) and provide a theoretical basis for DEACMP pathogenesis, diagnosis, and prognosis. METHODS: To investigate this relationship, we screened 6 NSE single nucleotide polymorphisms (SNPs), based on the results of the previous genome-wide association studies (GWAS). A total of 1,201 patients, including 416 in the DEACMP group and 785 in the acute carbon monoxide poisoning (ACMP) group, were detected by the Sequenom MassARRAY® method. The genotype frequencies and alleles of the 6 NSE SNPs (rs2071074, rs2071417, rs2071419, rs11064464, rs11064465, and rs3213434) were compared using different genetic models. RESULTS: In the SNPs rs2071419 and rs3213434, we found that the genotypes and allele frequencies in the two groups significantly correlated with the grouping of patients (χ 2 = 6.596, p = 0.037; χ 2 = 8.769, p = 0.012). The haplotypes GGTTTC and CCTTTC of ACMP and DEACMP were different (χ 2 = 6.563, p = 0.010; χ 2 = 4.151, p = 0.042). We also observed that rs2071419 and rs3213434 significantly correlated with DEACMP-increased risk in the dominant, codominant, and overdominant genetic models. In addition, we speculated that the C allele of the rs2071419 polymorphism and the T allele of the rs3213434 polymorphism in NSE may increase the DEACMP risk (p = 0.011, p = 0.006). CONCLUSIONS: The results show that rs2071419 and rs3213434 are susceptible sites of DEACMP. The NSE C allele of rs2071419 and T allele of rs3213434 and the haplotypes GGTTTC and CCTTTC may be risk factors for DEACMP.

Bench-to-bedside review: Carbon monoxide--from mitochondrial poisoning to therapeutic use.

Carbon monoxide (CO) is generated during incomplete combustion of carbon-containing compounds and leads to acute and chronic toxicity in animals and humans depending on the concentration and exposure time. In addition to exogenous sources, CO is also produced endogenously by the activity of heme oxygenases (HOs) and the physiological significance of HO-derived CO has only recently emerged. CO exerts vasoactive, anti-proliferative, anti-oxidant, anti-inflammatory and anti-apoptotic effects and contributes substantially to the important role of the inducible isoform HO-1 as a mediator of tissue protection and host defense. Exogenous application of low doses of gaseous CO might provide a powerful tool to protect organs and tissues under various stress conditions. Experimental evidence strongly suggests a beneficial effect under pathophysiological conditions such as organ transplantation, ischemia/reperfusion, inflammation, sepsis, or shock states. The cellular and molecular mechanisms mediating CO effects are only partially characterized. So far, only a few studies in humans are available, which, however, do not support the promising results observed in experimental studies. The protective effects of exogenous CO may strongly depend on the pathological condition, the mode, time point and duration of application, the administered concentration, and on the target tissue and cell. Differences in bioavailability of endogenous CO production and exogenous CO supplementation might also provide an explanation for the lack of protective effects observed in some experimental and clinical studies. Further randomized, controlled clinical studies are needed to clarify whether exogenous application of CO may turn into a safe and effective preventive and therapeutic strategy to treat pathophysiological conditions associated with inflammatory or oxidative stress.

Magnesium sulfate ameliorates carbon monoxide­induced cerebral injury in male rats.

Carbon monoxide (CO) has been shown to induce several cardiovascular abnormalities, as well as necrosis, apoptosis and oxidative stress in the brain. Magnesium sulfate (MS) has been shown to have beneficial activities against hypoxia in the brain. In the present study, the possible protective effects of MS against CO­induced cerebral ischemia were investigated. For this purpose, 25 male Wistar rats were exposed to 3,000 ppm CO for 1 h. The animals were divided into 5 groups (n=5 in each group) as follows: The negative control group (not exposed to CO), the positive control group (CO exposed and treated with normal saline), and 3 groups of CO­exposed rats treated with MS (75, 150 and 300 mg/kg/day) administered intraperitoneally for 5 consecutive days. On the 5th day, the animals were sacrificed and the brains were harvested for the evaluation of necrosis, apoptosis and oxidative stress. Histopathological evaluation revealed that MS reduced the number and intensity of necrotic insults. The Bax/Bcl2 ratio and malondialdehyde (MDA) levels were significantly decreased in a dose­dependent manner in the MS­treated rats compared to the positive control group, while a significant dose­dependent increase in Akt expression, a pro­survival protein, was observed. In addition, MS administration reduced pro­apoptotic indice levels, ameliorated histological insults, favorably modulated oxidative status and increased Akt expression levels, indicating a possible neuroprotective effect in the case of CO poisoning. On the whole, the findings of this study indicate that MS may prove to be useful in protecting against CO­induced cerebral injury.

Apolipoprotein E genotype and response of carbon monoxide poisoning to hyperbaric oxygen treatment.

RATIONALE: Hyperbaric oxygen (HBO2) reduced the incidence of cognitive sequelae 6 weeks after carbon monoxide (CO) poisoning compared with normobaric oxygen (NBO2). The apolipoprotein (APOE) epsilon4 allele predicts unfavorable neurologic outcome after brain injury and stroke. OBJECTIVES: To assess the effects of the epsilon4 allele on 6-week cognitive sequelae after CO poisoning. METHODS: We tested APOE genotypes in 86 of 152 CO-poisoned patients from our randomized trial. Logistic regression was used to control for risk factors while testing for effects with the epsilon4 allele or interactions with epsilon4 and treatment on 6-week and 6- and 12-month cognitive sequelae. MEASUREMENTS AND MAIN RESULTS: We enrolled 86 patients: 44 received HBO2 and 42 NBO2 therapy. A total of 31 (36%) patients had at least one epsilon4 allele. Six-week cognitive sequelae rates for patients treated with HBO2 and NBO2, respectively: epsilon4 allele absent, 11% (3/27) and 43% (12/28); epsilon4 allele present, 35% (6/17) and 29% (4/14). The epsilon4 allele was not associated with 6-week cognitive sequelae, 27% (15/55) without and 32% (10/31) with the epsilon4 allele (P = 0.323). The interaction between the epsilon4 allele and treatment was significantly associated with 6-week cognitive sequelae (P = 0.048). The interaction between the epsilon4 allele and treatment was not associated with 6- and 12-month cognitive sequelae. CONCLUSIONS: HBO2 therapy reduces cognitive sequelae after CO poisoning in the absence of the epsilon4 allele. Because apolipoprotein genotype is unknown at the time of poisoning, we recommend that patients with acute CO poisoning receive HBO2.

Hydroxyl radical production via NADPH oxidase in rat striatum due to carbon monoxide poisoning.

Severe poisoning induced by carbon monoxide (CO) at 3000 ppm, but not 1000 ppm, enhances hydroxyl radical (OH) production in rat striatum, which is greatly susceptible to inhibitors of NADPH oxidase (NOX), including diphenyleneiodonium (DPI), but not xanthine oxidase. The quantitative real-time PCR confirmed the previous microarray finding that CO at 3000 ppm, but not 1000 ppm, enhanced mRNA expression of dual oxidase 2 (DUOX2), but not DUOX1, in rat striatum, both of which are NOX family members producing reactive oxygen species. However, the protein levels of DUOX2 and DUOX1 were decreased by 3000 ppm CO. The CO-induced OH production was resistant to chelerythrine and SB230580, inhibitors of protein kinase C and p38MAPK, respectively, which are reported to mediate activation of DUOX1 and DUOX2, respectively. Deprivation of Ca2+, which is required for activation of both DUOXs, failed to suppress the CO-induced OH production. The CO-induced OH production was strongly suppressed by EHT1864, an inhibitor of Rac (Ras-related C3 botulinum toxin substrate), which is a factor for activation of NOX1, NOX2 and NOX3 (the role of Rac on Nox3 activation is controversial) as much as that was suppressed by DPI. In addition, EHT1864 in combination with DPI further suppressed the CO-induced OH production. There were no significant changes in the protein levels of NOX1 through NOX4 and Rac1. It is likely that the CO-induced OH production is mediated through the activation of Rac-dependent NOX enzymes, such as Nox1, Nox2, and Nox3.

Apoptosis and delayed neuronal damage after carbon monoxide poisoning in the rat.

Delayed neurological damage after CO hypoxia was studied in rats to determine whether programmed cell death (PCD), in addition to necrosis, is involved in neuronal death. In rats exposed to either air or CO (2500 ppm), microdialysis in brain cortex and hippocampus was performed to determine the extent of glutamate release and hydroxyl radical generation during the exposures. Groups of control and CO-exposed rats also were tested in a radial maze to assess the effects of the CO exposures on learning and memory. At 3, 7, and 21 days after CO exposure brains were perfusion-fixed and hematoxylin-eosin (H&E) was used to assess injury and to select regions for further examination. DNA fragmentation was sought by examining cryosections with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) reaction. We found significant increases in glutamate release and .OH generation during and immediately after CO hypoxia. CO-exposed rats showed learning and memory deficits after exposure associated with heterogeneous cell loss in cortex, globus pallidus, and cerebellum. The frontal cortex was affected most seriously; the damage was slight at Day 3, increased at Day 7, and persistent at Day 21 after CO exposure. TUNEL staining was positive at all three time points, and TUNEL-labeled cells were distributed similarly to eosinophilic cells. The number of cells stained by TUNEL was less than by H&E and amounted to 2 to 5% of all cell nuclei in regions of injury. Ultrastructural features of both neuronal necrosis and apoptosis also were observed readily by electron microscopy. These findings indicate that both necrosis and apoptosis (PCD) contribute to CO poisoning-induced brain cell death.