Intracardiac Thrombosis Secondary to the Silent Killer: A Case Report about Monoxide Carbon Poisoning in a Child

Carbon monoxide (CO) poisoning is a frequent cause of emergency room admissions, especially during winter days, the symptoms are varied ranging from a simple headache to a serious cardiac and neurological impairment that can be deadly. Diagnosis is based on the circumstances of occurrence as well as the dosage of carboxyhemoglobin in the blood. Exposure to CO has serious consequences, neurological and cardiac manifestations are not negligible and vary from repolarization disorders to heart attack. Treatment is urgent with normobaric or hyperbaric oxygen therapy. We report a case of a 2-year male child admitted to the emergency room for CO intoxication with an intracardiac thrombus subsequently complicated by an ischemic stroke with a fatal outcome in order to highlight this complication rarely described in literature.

Absolute partial and total ionization cross sections of carbon monoxide with electron collision from 350 eV to 8000 eV

The absolute partial and total cross sections for electron impact ionization of carbon monoxide are reported for electron energies from 350 eV to 8000 eV.The product ions(CO^(+),C^(+),O^(+),CO^(2+),C^(2+),and O^(2+))are measured by employing an ion imaging mass spectrometer and two ion-pair dissociation channels(C^(+)+O^(+)and C^(2+)+O^(+))are identified.The absolute cross sections for producing individual ions and their total,as well as for the ion-pair dissociation channels are obtained by normalizing the data of CO^(+)to that of Ar^(+)from CO-Ar mixture target with a fixed 1:1 ratio.The overall errors are evaluated by considering various kinds of uncertainties.A comprehensive comparison is made with the available data,which shows a good agreement with each other over the energy ranges that are overlapped.This work presents new cross-section data with electron energies above 1000 eV.

Carbon Monoxide Modulates Auxin Transport and Nitric Oxide Signaling in Plants under Iron Deficiency Stress

Carbon monoxide(CO)and nitric oxide(NO)are signal molecules that enhance plant adaptation to environmental stimuli.Auxin is an essential phytohormone for plant growth and development.CO and NO play crucial roles in modulating the plant’s response to iron deficiency.Iron deficiency leads to an increase in the activity of heme oxygenase(HO)and the subsequent generation of CO.Additionally,it alters the polar subcellular distribution of Pin-Formed 1(PIN1)proteins,resulting in enhanced auxin transport.This alteration,in turn,leads to an increase in NO accumulation.Furthermore,iron deficiency enhances the activity of ferric chelate reductase(FCR),as well as the expression of the Fer-like iron deficiency-induced transcription factor 1(FIT)and the ferric reduction oxidase 2(FRO2)genes in plant roots.Overexpression of the long hypocotyl 1(HY1)gene,which encodes heme oxygenase,or the CO donor treatment resulted in enhanced basipetal auxin transport,higher FCR activity,and the expression of FIT and FRO2 genes under Fe deficiency.Here,a potential mechanism is proposed:CO and NO interact with auxin to address iron deficiency stress.CO alters auxin transport,enhancing its accumulation in roots and up-regulating key iron-related genes like FRO2 and IRT1.Elevated auxin levels affect NO signaling,leading to greater sensitivity in root development.This interplay promotes FCR activity,which is crucial for iron absorption.Together,these molecules enhance iron uptake and root growth,revealing a novel aspect of plant physiology in adapting to environmental stress.

Sub-2 nm mixed metal oxide for electrochemical reduction of carbon dioxide to carbon monoxide

Mixed metal oxide(MMO) represents a critical class of materials that can allow for obtaining a dynamic interface between its components:reduced metal and its metal oxide counterpart during an electrocatalytic reaction.Here,a synthetic method utilizing a MOF-derived micro/mesoporous carbon as a template to prepare sub-2 nm MMO catalysts for CO_(2) electro reduction is reported.Starting from the zeolite imidazolate framework(ZIF-8),the pyrolyzed derivatives were used to synthesize sub-2 nm Pd-Ni MMO with different compositions.The Ni-rich(Pd_(20)-Ni_(80)/ZC) catalyst exhibits unexpectedly superior performance for CO production with an improved Faradaic efficiency(FE) of 95.3% at the current density of 200 mA cm^(-2) at-0.56 V vs.reversible hydrogen electrode(RHE) compared to other Pd-Ni compositions.X-ray photoelectron spectroscopy(XPS) analysis confirms the presence of Ni^(2+) and Pd^(2+) in all compositions,demonstrating the presence of MMO.Density functional theory(DFT) calculation reveals that the lower CO binding energy on the surface of the Pd_(20)-Ni_(80) cluster eases CO desorption,thus increasing its production.This work provides a general synthetic strategy for MMO electrocatalysts and can pave a new way for screening multimetallic catalysts with a dynamic electrochemical interface.

Carbon Monoxide and Respiratory Disorders in Professional Female Fish Smokers at 2 Artisanal Sites in Benin

Introduction: The use of biomass for cooking is a very common practice in Africa and Benin, and is associated with exposure to organic pollutants. The aim of this study was to assess carbon monoxide exposure and respiratory disorders in women at artisanal fish-smoking sites. Methods: This was a cross-sectional study of women fish smokers at two artisanal fish-smoking sites in Benin. Recruitment was exhaustive. An interview using a respiratory questionnaire inspired by the Union questionnaire, spirometry and carbon monoxide (CO) measurement were carried out. Descriptive analysis and comparison of means using Student’s t-test with a threshold of p = 0.05 were performed. Results: The median age of the 81 people surveyed was 40, with an interquartile range (IQT) of [25 to 75]. The median duration of daily exposure to smoke was 6 h IQT [4, 7]. Of those surveyed, 64 (79.01%) were illiterate and 39 (48.24%) had been working for 20 years. CO levels at the start of activity varied from 89 to 145 ppm in one case and from 40 to 89 ppm in the other. Respiratory symptoms were present in 19 (23.46%);18 (22.22%) had mild airway impairment on spirometry. There was a statistically significant decrease between the mean values of peak expiratory flow (PEF), mean expiratory volume in seconds (FEV1) and forced vital capacity (FVC) before and after exposure to smoke. Conclusion: CO levels are high on fish smoking sites and respiratory problems are common. Improved working conditions are important for these women.

Association of carbon monoxide poisonings and carboxyhemoglobin levels with COVID-19 and clinical severity

BACKGROUND Coronavirus disease 2019(COVID-19),which recently spread throughout the entire world,is still a significant health issue.Additionally,the most common cause of risky poisoning in emergency services is carbon monoxide(CO)poisoning.Both disorders seem to merit more research as they have an impact on all bodily systems via the lungs.AIM To determine how arterial blood gas and carboxyhemoglobin(COHb)levels affect the clinical and prognostic results of individuals requiring emergency treatment who have both COVID-19 and CO poisoning.METHODS Between January 2018 and December 2021,479 CO-poisoning patients participated in this single-center,retrospective study.Patients were primarily divided into two groups for analysis:Pre-pandemic and pandemic periods.Additionally,the pandemic era was divided into categories based on the presence of COVID-19 and,if present,the clinical severity of the infection.The hospital information system was used to extract patient demographic,clinical,arterial blood gas,COVID-19 polymerase chain reaction,and other laboratory data.RESULTS The mean age of the 479 patients was 54.93±11.51 years,and 187(39%)were female.226(47%)patients were in the pandemic group and 143(30%)of them had a history of COVID-19.While the mean potential of hydrogen(pH)in arterial blood gas of all patients was 7.28±0.15,it was 7.35±0.10 in the pre-pandemic group and 7.05±0.16 in the severe group during the pandemic period(P<0.001).COHb was 23.98±4.19%in the outpatients and 45.26%±3.19%in the mortality group(P<0.001).Partial arterial oxygen pressure(PaO2)was 89.63±7.62 mmHg in the pre-pandemic group,and 79.50±7.18 mmHg in the severe group during the pandemic period(P<0.001).Despite the fact that mortality occurred in 35(7%)of all cases,pandemic cases accounted for 30 of these deaths(85.7%)(P<0.001).The association between COHb,troponin,lactate,partial arterial pressure of carbon dioxide,HCO3,calcium,glucose,age,pH,PaO2,potassium,sodium,and base excess levels in the pre-pandemic and pandemic groups was statistically significant in univariate linear analysis.CONCLUSION Air exchange barrier disruption caused by COVID-19 may have pulmonary consequences.In patients with a history of pandemic COVID-19,clinical results and survival are considerably unfavorable in cases of CO poisoning.

Nitrogen Dioxide, Carbon Monoxide, Natural and Anthropomorphic Effects, and Earth’s Changing Climate

This study will both compare and contrast the characteristics and roles of two pollutants: nitrogen dioxide and carbon monoxide. It will begin by tracing each gas’ negative contributions to the Earth’s spheres, as well as relate any negative links that each plays concerning human activity, health, and interaction with the environment. It will include an in-depth analysis of what the proliferation of such toxic gases indicates about human production and causality, plus reflect on any current attempts being made to improve the effects of these pollutants on the environment. This examination will also inspect three NASA missions, i.e., MOPITT/Terra, AIRS/Aqua, and OMI/Aura, the aim of which, among many other tasks, is to detect pollutants within the Earth’s various spheres, as well as analyze weather anomalies, improve prediction methodology, and chronicle meteorological patterns for future study. It will also cover some of the goals, engineering breakthroughs, and in one case, the limitations, of these three satellite missions. Finally, it should be noted that in all stages of this discussion, the author’s main aim will be to focus on the positives that need to be implemented in order to improve the current situations that both anthropogenic and natural disasters have created for the planet.

Unintentional Carbon Monoxide Poisoning Outbreak from 2 to 9 October 2019 in Ulaanbaatar, Mongolia

Carbon monoxide poisoning (COP) from 2 to 9 October 2019 was a major public health concern in Ulaanbaatar, Mongolia, after a transition from consumption of raw coal to upgraded briquette fuel. During the period, a total of 186 residents, which is 16 times more than the previous years, were exposed to COP and 6 persons died at home. We conduct a cross-sectional study by using registration data and medical history of all hospitalized patients with a diagnosis of COP from 2 to 9 October 2019 and had an in-depth interview. 144 (77.4%) people from 85 households registered as potential cases and 124 (86.1%) people were diagnosed with COP. All households used upgraded briquettes, and 41 households (48.2%) used them for the first time. In 50% of cases, the stove was broken, the chimney was short, not heated, and the clay joint connecting the wall stove was broken. The majority of interviewees were unaware of COP and improperly used briquettes, and the safety of chimneys and stoves was insufficient which caused unintentional COP. It is necessary to provide information to the local population about the potential risks of COP, install CO alarms in households, and educate the population. In further, a well-established poisoning surveillance system is an important aspect of public health emergency preparedness in Mongolia.

Prevalence of Acute Myocardial and Brain Toxicity in Emergency Department Patients Exposed to Carbon Monoxide

Introduction: Due to its severe toxicity, carbon monoxide poisoning is an emergency that leads to cardiac and brain involvement, and emergency physicians should aim to master this diagnosis. This study is intended to describe the expected prevalence of these severe toxicities in the emergency department. Materials and Methods: A retrospective cohort of consecutive patients over 16 years of age presenting with carbon monoxide poisoning to the emergency department of the Hospital Universitario Austral, Argentina, during the period from January 2018 to June 2022. The prevalence of myocardial and brain toxicity was assessed regarding percentage, continuous variables with mean and standard deviation, categorical variables with percentage and absolute frequency. Positive findings of acute neurological toxicity included seizures, syncope and coma, while cardiovascular toxicity encompassed acute myocardial infarction (MI) diagnosed by electrocardiogram or elevated troponin levels, arrhythmias, and the development of pulmonary edema/ congestive heart failure (CHF) confirmed by chest X-ray with suggestive signs or clinically compatible symptoms. Patients were followed-up for 90 days to estimate hospitalization and mortality. Results: A total of 67 patients were evaluated;44.77% of them were males with a mean age of 38.5 ± 14.97 years. The prevalence of acute myocardial toxicity was 7.46% (n: 5). Among these patients, 3 had overweight as a risk factor, and 3 showed ECG abnormalities with negative T-waves. The prevalence of acute brain toxicity was 8.9% (n: 6). In total, 37% (n: 25) of patients met the criteria for hyperbaric oxygen therapy, of which 32% (n: 8) underwent more than one session. A total of 7.46% of patients (n: 5) required hospitalization. Mortality at 90 days was 0%. Conclusion: Among the patients who presented to the emergency department, the prevalence of acute myocardial toxicity was 7.46% (n: 5), which is lower than the prevalence reported in other studies to date. The prevalence of acute brain toxicity was 8.9% (n: 6), and there are no studies describing the prevalence of acute brain toxicity in the emergency department to date. There were no fatalities in our series.

Kinetic analysis of iron ore powder reaction with hydrogen-carbon monoxide

Iron ore powder was isothermally reduced at 1023-1373 Kwith hydrogen/carbon monoxide gas mixture(from 0vol%H_(2)/100vol%CO to 100vol%H_(2)/0vol%CO).Results indicated that the whole reduction process could be divided into two parts that proceed in series.The first part represents a double-step reduction(Fe_(2)O_(3)→Fe_(3)O_(4)→FeO),in which the kinetic condition is more feasible compared with that in the second part representing a single-step reduction(FeO→Fe).The influence of hydrogen partial pressure on the reduction rate gradually increases as the reaction proceeds.The average reduction rate of hematite ore with pure hydrogen is about three and four times higher than that with pure carbon monoxide at 1173 and 1373 K,respectively.In addition,the logarithm of the average rate is linear to the composition of the gas mixture.Hydrogen can prominently promote carbon deposition to about 30%at 1023 K.The apparent activation energy of the reduction stage increases from about 35.0 to 45.4 kJ/mol with the increase in hydrogen content from 20vol%to 100vol%.This finding reveals that the possible rate-controlling step at this stage is the combined gas diffusion and interfacial chemical reaction.

Acute carbon monoxide poisoning and delayed neurological sequelae: a potential neuroprotection bundle therapy

Currently, there is no known optimal therapy for carbon monoxide （CO） poisoning and CO-associated delayed neu- rological sequelae. Hyperbaric oxygen therapy （HBOT） is a well-known treatment method, but its use for CO poison- ing patients is controversial to use due to lack of evidences regarding its efficacy. Thus, it is unlikely that HBOT alone will be accepted as the standard treatment method. In this article, current and potential treatment methods of CO poi- soning are presented as well as the tentative multi-factorial pathophysiology. A series of treatments are suggested for use as a bundle therapy, with targeted temperature management as the base treatment method. Such a therapy holds a great potential, especially for the cases where HBOT is not readily available. We suggest further investigations for elucidating the effects of these suggested treatments and their roles in terms of the complex pathophysiology of CO poisoning. Future ac- ceptance of this therapy based on the improved scientific and clinical knowledge may result in injury prevention and mini- mization of the signs and the symptoms in CO poisoning.

Catalytic reduction of nitric oxide with carbon monoxide on copper-cobalt oxides supported on nano-titanium dioxide

A series of copper-cobalt oxides supported on nano-titanium dioxide were prepared for the reduction of nitric oxide with carbon monoxide and characterized using techniques such as XRD, BET and TPR. Catalyst CuCoOx/TiO2 with Cu/Co molar ratio of 1/2, CuCo total loading of 30% at the calcination temperature of 350℃ formed CuCo204 spinel and had the highest activity. NO conversion reached 98.9% at 200℃. Mechanism of the reduction was also investigated, N20 was mainly yielded below 100℃, while N2 was produced instead at higher temperature. O2 was supposed to accelerate the reaction between NOx and CO for its oxidation of NO to give more easily reduced NO2, but the oxidation of CO by O2 to CO2 decreased the speed of the reaction greatly. Either SO2 or H20 had no adverse impact on the activity of NO reduction; however, in the presence of both SO2 and H20, the catalyst deactivated quickly.

Early Biomarkers in 1H Nuclear Magnetic Resonance Spectroscopy of Striatal Pathological Mechanisms after Acute Carbon Monoxide Poisoning in Rats

Objective In vivo Proton Magnetic Resonance Spectroscopy （1H-MRS） can be used to evaluate the levels of specific neurochemical biomarkers of pathological mechanisms in the brain. Methods We conducted T2-Weighted Magnetic Resonance Imaging （MRI） and 1H-MRS with a 3.0-Tesla animal MRI system to investigate the early microstructural and metabolic profiles in vivo in the striatum of rats following carbon monoxide （CO） poisoning. Results Compared to baseline, we found significant cortical surface deformation, cerebral edema changes, which were indicated by the unclear gray/white matter border, and lateral ventricular volume changes in the brain. A significant reduction in the metabolite to total creatine （Cr） ratios of N-acetylaspartate （NAA） was observed as early as 1 h after the last CO administration, while the lactate （Lac） levels increased marginally. Both the Lac/Cr and NAA/Cr ratios leveled off at 6 h and showed no subsequent significant changes. In addition, compared to the control, the choline （Cho）/Cr ratio was slightly reduced in the early stages and significantly increased after 6 h. In addition, a pathological examination revealed mild cerebral edema on cessation of the insult and more severe cerebral injury after additional CO poisoning. Conclusion The present study demonstrated that 1H-MRS of the brain identified early metabolic changes after CO poisoning. Notably, the relationship between the increased Cho/Cr ratio in the striatum and delayed neuropsychologic sequelae requires further research.

On the Variability and Correlation of Surface Ozone and Carbon Monoxide Observed in Hong Kong Using Trajectory and Regression Analyses

This paper investigates, the variability and correlation of surface ozone (Os) and carbon monoxide (CO) observed at Cape D'Aguilar in Hong Kong from 1 January 1994 to 31 December 1995. Statistical analysis shows that the average O3 and CO mixing ratios during the two years are 32±17ppbv and 305±191 ppbv, respectively. The O3/CO ratio ranges from 0.05 to 0.6 ppbv/ppbv with its frequency peaking at 0.15. The raw dataset is divided into six groups using backward trajectory and cluster analyses. For data assigned to the same trajectory type, three groups are further sorted out based on CO and NOX mixing ratios. The correlation coefficients and slopes of O3/CO for the 18 groups are calculated using linear regression analysis. Finally, five kinds of air masses with different chemical features are identified: continental background (CB), marine background (MB), regional polluted continental (RPC), perturbed marine (P*M), and local polluted (LP) air masses. Further studies indicate that O3 and CO in the continental and marine background air masses (CB and MB) are positively correlated for the reason that they are well mixed over the long range transport before arriving at the site. The negative correlation between O3 and CO in air mass LP is believed to be associated with heavy anthropogenic influence, which results from the enhancement by local sources as indicated by high CO and NOx and depletion of O3 when mixed with fresh emissions. The positive correlation in the perturbed marine air mass P*M favors the low photochemical production of O3. The negative correlation found in the regional polluted continental air mass RPC is different from the observations at Oki Island in Japan due to the more complex O3 chemistry at Cape D'Aguilar.

Catalytic methanol decomposition to carbon monoxide and hydrogen over Pd/CeO_2-ZrO_2-La_2O_3 with different Ce/Zr molar ratios

Hairong Wang, Yaoqiang Chen, Qiulin Zhang, Qingchao Zhu, Maochu Gong, Ming Zhao（ Key Laboratory of Green Chemistry ＆ Technology of Ministry Education, College of Chemistry, Sichuan University, Chengdu 610064, Sichuan, China

Carbon Monoxide Inhibits the Nuclear-cytoplasmic Translocation of HMGB1 in an In Vitro Oxidative Stress Injury Model of Mouse Renal Tubular Epithelial Cells

Carbon monoxide（CO）,as a vital small molecule in signaling pathways,is found to be involved in ischemia-reperfusion injury（IRI） in renal transplantation.CO-releasing molecule-2（CORM-2）,a CO-releasing molecule,is a type of metal carbonyl complexes which can quickly release CO in vivo.In this study,an in vitro oxidative stress injury model was established to examine the effect of CORM-2 pretreatment on the nuclear-cytoplasmic translocation of high mobility group box 1 protein（HMGB1） in mouse primary renal proximal tubular epithelial cells（RPTECs）.Immunofluorescence staining showed that HMGB1 in the medium-and CORM-2-treated groups was predominantly localized in the nucleus of the cells,whereas higher amounts of HMGB1 translocated to the cytoplasm in the H2O2-and inactive CORM-2（i CORM-2）-treated groups.Western blotting of HMGB1 showed that the total amounts of cytoplasmic HMGB1 in the H2O2-treated（0.59±0.27） and i CORM-2-treated（0.57±0.22） groups were markedly higher than those in the medium-treated（0.19±0.05） and CORM-2-treated（0.21±0.10） groups（P〈0.05）.Co-immunoprecipitation showed that the levels of acetylated HMGB1 in the H2O2-treated（642.98±57.25） and i CORM-2-treated（342.11±131.25） groups were markedly increased as compared with the medium-treated（78.72±74.17） and CORM-2-treated（71.42±53.35） groups（P〈0.05）,and no significant difference was observed between the medium-treated and CORM-2-treated groups（P〉0.05）.In conclusion,our study demonstrated that in the in vitro oxidative stress injury model of primary RPTECs,CORM-2 can significantly inhibit the nuclear-cytoplasmic translocation of HMGB1,which is probably associated with the prevention of HMGB1 acetylation.

Preparation of Palladium Supported on Ferric Oxide Nano-catalysts for Carbon Monoxide Oxidation in Low Temperature

Catalytic property of Pd/Fe2O3 catalysts on carbon monoxide(CO) oxidation at low temperature were investigated in this paper. Both the as-prepared and H2-pretreated Pd/Fe2O3 catalysts show catalytic performances on CO oxidation. The CO was completely converted at 333 K for the as-prepared sample,whereas at 313 K for H2-pretreated Pd/Fe2O3-573 catalyst. The catalytic performance of the Pd/Fe2O3 catalyst decreases with increased calcination temperature. This may be due to the increased crystallinity of the support and decreased metal-support interaction. Progressive deactivation of the catalysts during long-time reaction was associated with the formation of carbonates on the catalyst surface that inhibits CO activation or intermediate transformation.

Carbon Monoxide Signal Breaks Primary Seed Dormancy by Transcriptional Silence of DOG1 in Arabidopsis thaliana

Primary seed dormancy is an adaptive strategy that prevents germination for viable seeds in harsh environment,ensuring seeds germination under favorable condition.Accurately inducing seeds germination in a controllable manner is important for crop production.Thus searching the chemicals that efficiently breaks seed dormancy is valuable.DOG1 protein abundance in the freshly harvested seed is high,and its level is correlated to seed dormancy intensity,thus DOG1 is regarded as the timer to evaluate the seed dormancy degree.In this study,we found the carbon monoxide(CO)donor treatment,the transgenic line with high CO content,showed lower seed dormancy,while scavenging CO,or the mutant with lower CO level,presented strong primary seed dormancy,genetic analysis showed that DOG1 was targeted by CO signal and was prerequisite for CO-dependent seed dormancy release.Furthermore,we found CO signal activated the expression of ERF/AP2 transcriptional factor ERF12,as well as enhanced the binding of ERF12 to the promoter of DOG1,ultimately transcriptional silence of DOG1 expression to break primary seed dormancy.Meanwhile CO signal reduced the histone acetylation level at the chromatin of DOG1 locus to suppress its expression.Together,our results revealed that CO acts as the novel regulator to suppress DOG1 expression and efficiently break primary seed dormancy through activating the negative factor ERF12.

Catalytic performance of iron carbide for carbon monoxide hydrogenation

Novel iron carbide and potassium-promoted iron carbide catalysts were prepared and investigated for CO hydrogenation. The iron carbide showed high activity for CO hydrogenation under high pressures; with the addition of potassium, activity and selectivity to C5＋ hydrocarbons were greatly enhanced, and the selectivity to methane was suppressed under high pressure.

Existence of Heme Oxygenase-carbon Monoxide-cyclic Guanosine Monophosphate Pathway in Human Trabecular Meshwork Cells In Vitro

To confirm the existence of heme oxygenase (HO)-carbon monoxide (CO)- cyclic guanosine monophosphate (cGMP) pathway in the cultured human trabecular meshwork cells (HTMCs) in vitro, and to evaluate the inductive role of hemin on this pathway, HTMCs of the third to fourth generation were cultured in vitro. Reverse transcripase-polymerase chain reaction (RT-PCR) was employed for detection of HO-1 and HO-2 mRNA. Immunohistochemical staining was used to detect HO-1 and HO-2 proteins. Hemin was added into the culture solution. The HO-1 mRNA levels were quantified by RT-PCR. The relative amount of carbon monoxide released into the media was measured with the quantifying carbon monoxide hemoglobin (HbCO) by spectrophotometry. Radioimmunoassay was used to determine changes of cGMP in HTMCs. The results showed that cultured cells had the specific characteristics of HTMCs. Both HO-1 and HO-2 genes were expressed in HTMCs, as well as HO-1 and HO-2 proteins in HTMCs. Hemin induced HO-1 mRNA, HbCO and cGMP in a dose-dependent manner. In conclusion, HO-CO-cGMP pathway exists in the cultured HTMCs and can be induced by hemin. Pharmacological stimulation of HO-CO-cGMP pathway may constitute a novel therapeutic approach to rescuing glaucoma.