Recurrent myelin basic protein elevation in cerebrospinal fluid as a predictive marker of delayed encephalopathy after carbon monoxide poisoning

Astrocyte-derived microparticles initiate a neuroinflammatory cycle due to carbon monoxide poisoning

We hypothesized that carbon monoxide (CO) establishes an inflammatory cycle mediated by microparticles (MPs). Mice exposed to a CO protocol (1000 ​ppm for 40 ​min and then 3000 ​ppm for 20 ​min) that causes neuroinflammation exhibit NF-κB activation in astrocytes leading to generation of MPs expressing thrombospondin-1(TSP-1) that collect in deep cervical lymph nodes draining the brain glymphatic system. TSP-1 bearing MPs gain access to the blood stream where they activate neutrophils to generate a new family of MPs, and also stimulate endothelial cells as documented by leakage of intravenous 2000 ​kDa dextran. At the brain microvasculature, neutrophil and MPs sequestration, and myeloperoxidase activity result in elevations of the p65 subunit of NF-κB, serine 536 phosphorylated p65, CD36, and loss of astrocyte aquaporin-4 that persist for at least 7 days. Knock-out mice lacking the CD36 membrane receptor are resistant to all CO inflammatory changes. Events triggered by CO are recapitulated in naïve wild type mice injected with cervical node MPs from CO-exposed mice, but not control mice. All MPs-mediated events are inhibited with a NF-κB inhibitor, a myeloperoxidase inhibitor, or anti-TSP-1 antibodies. We conclude that astrocyte-derived MPs expressing TSP-1 establish a feed-forward neuroinflammatory cycle involving endothelial CD36-to-astrocyte NF-κB crosstalk. As there is currently no treatment for CO-induced neurological sequelae, these findings pose several possible sites for therapeutic interventions.

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Carbon monoxide (CO) causes neurological injuries poorly correlated to hypoxic stress.

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Astrocyte NF-κB triggers thrombospondin-1(TSP-1) microparticle (MP) production.

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TSP-1 MPs enter the blood stream, stimulating neutrophils and endothelium.

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Circulating MPs linkage to endothelial cell CD36 causes vascular damage.

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Endothelial CD36-to-astrocyte NF-κB crosstalk establishes a neuroinflammatory cycle.

Altered regional homogeneity in delayed encephalopathy after carbon monoxide poisoning: A resting-state fMRI study

OBJECTIVE

To investigate alternations in spontaneous brain activities reflected by regional homogeneity (ReHo) in patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) using resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

Twenty-one patients with DEACMP and 21 age, sex and education matched healthy controls (HCs) received rs-fMRI scanning and clinical assessment. We used the ReHo method to analyze the interregional synchronized activity of all participants. Two sample t-tests were performed to compare the ReHo maps between the two groups. Pearson correlation analysis was then used to assess the correlations between clinical measures and abnormal ReHo in DEACMP patients.

RESULTS

Compared with HCs, DEACMP patients showed significantly decreased ReHo in bilateral cerebellum posterior lobe, pons, bilateral basal ganglia, while increased in the posterior cingulate, calcarine, bilateral occipital lobe(GRF correction, voxel P value <0.001, cluster P value <0.05). Negative correlation was found between Mini-mental State Examination (MMSE) scores and the ReHo values of posterior cingulate gyrus (r = -0.672, p < 0.05) in the DEACMP group, while positively related to the time from CO poisoning to MRI scan (r = 0.428, p < 0.05).

CONCLUSION

Patients with DEACMP exhibited altered ReHo in the multiple functional brain regions, which provide evidence for local brain dysfunctions and may help to understand the neuropathologic mechanism for the disease.

Diagnosis of acute intoxications in critically ill patients: focus on biomarkers - part 2: markers for specific intoxications

In medical intensive care units, acute intoxications contribute to a large proportion of all patients. Epidemiology and a basic overview on this topic were presented in part one. The purpose of this second part regarding toxicological biomarkers in the ICU setting focuses on specific poisons and toxins. Following the introduction of anion and osmol gap in part one, it's relevance in toxic alcohols and other biomarkers for these poisonings are presented within this publication. Furthermore, the role of markers in the blood, urine and cerebrospinal fluid for several intoxications is evaluated. Specific details are presented, amongst others, for cardiovascular drug poisoning, paracetamol (acetaminophen), ethanol, pesticides, ricin and yew tree intoxications. Detailed biomarkers and therapeutic decision tools are shown for carbon monoxide (CO) and cyanide (CN^-) poisoning. Also, biomarkers in environmental toxicological situations such as mushroom poisoning and scorpion stings are presented.

Serum markers and development of delayed neuropsychological sequelae after acute carbon monoxide poisoning: anion gap, lactate, osmolarity, S100B protein, and interleukin-6

Objective

Reliable biomarkers of delayed neuropsychological sequelae (DNS) after acute carbon monoxide (CO) poisoning are lacking. This study investigated the associations between potential serum markers and the development of DNS after acute CO poisoning.

Methods

Retrospective chart reviews were conducted for patients diagnosed with acute CO poisoning during a 28-month period. The patients were divided into two groups according to the presence or absence of having developed DNS. Multivariate analysis was performed to identify predictors of DNS after CO poisoning.

Results

Of a total of 102 patients, 10 (9.8%) developed DNS. The levels of serum osmolarity, S100B protein, and serum lactate, as well as serum anion gap, were statistically significant in univariate analysis. Multiple logistic regression analysis showed that anion gap (adjusted odds ratio [AOR], 1.36; 95% confidence interval [CI], 1.11 to 1.88), serum lactate level (AOR, 1.74; 95% CI, 1.26 to 2.75), and serum S100B protein level ([AOR, 7.02×10⁵; 95% CI, 4.56×10² to 9.00×10¹⁰] in model 1, [AOR, 3.69×10⁵; 95% CI, 2.49×10² to 2.71×10¹¹] in model 2) were independently associated with DNS development.

Conclusion

Based on our preliminary results, serum lactate level, serum anion gap, and serum S100B protein level in the emergency department could be informative predictors of DNS development in patients with acute CO poisoning. These markers might have the potential to improve early recognition of DNS in patients with acute CO poisoning.

Dexamethasone therapy for preventing delayed encephalopathy after carbon monoxide poisoning

We investigated dexamethasone therapy for preventing delayed encephalopathy after carbon monoxide (CO) poisoning. Eighty healthy male rats were exposed to CO and randomly divided into four groups: hyperbaric oxygen treatment (H), treatment (D), combined hyperbaric and dexamethasone treatment (C), and a control (M) group in which the rats inhaled CO to coma in the hyperbaric oxygen chamber, then were removed without further treatment. Twelve rats were put into the hyperbaric oxygen chamber and treated with air for 60 min (N) group. An eight arm maze was used to evaluate cognitive and memory abilities of these mice. Serum myelin basic protein (MBP) levels were evaluated using ELISA, and magnetic resonance imaging was used to observe brain demyelination and morbidity associated with delayed encephalopathy. A sample of the hippocampus from each group was examined by light microscopy. Cognitive and memory functions decreased in the control group M. Three days after CO poisoning, the serum MBP level of each group increased significantly. On Day 10 after CO poisoning, the MBP levels in groups C and D decreased significantly, but returned to normal on Day 18. MBP levels in the M and H groups were elevated at all time points. Brain MRIs showed significant differences among C, D, H and control M groups. Hematoxylin & eosin staining of the hippocampus showed greater damage in the control M and H groups. Early dexamethasone treatment may be useful for preventing delayed encephalopathy after CO poisoning and may reduce serum MBP levels.

Novel clinical grading of delayed neurologic sequelae after carbon monoxide poisoning and factors associated with outcome

INTRODUCTION

Delayed neurologic sequelae (DNS) after carbon monoxide (CO) poisoning manifest as a relapse of neurologic deficits. However, the long-term outcome of DNS has not been fully clarified. Myelin basic protein (MBP) levels in the cerebrospinal fluid (CSF) have been reported to be elevated in DNS. However, the precise timing and clinical value of the CSF examination have not been fully evaluated. We aimed to clarify the long-term outcome and the factors predicting the outcome of DNS and to evaluate the utility of CSF-MBP for predicting the development and severity of DNS.

METHODS

This work was designed as a single-center, prospective, observational study. We graded DNS severity as Grade 1 (consistent independence), Grade 2 (temporary dependence), or Grade 3 (persistent dependence). We analyzed the percentage categorized in each grade and the parameters associated with outcome.

RESULTS

Of 100 patients experiencing acute CO poisoning (median age: 46 years; 69% male), 20 (20%) developed DNS, including six Grade 1 (30%), ten Grade 2 (50%), and four Grade 3 (20%) cases. The Grade 3 patients [median: 77 years; interquartile range (IQR): 76-82] were older than the Grade 1 patients [42; 30-46] (P<0.01); the DNS onset of the Grade 1 patients [median interval after poisoning: 35 days; IQR: 32-56] occurred later than that of the Grade 3 patients [10; 9-13] P<0.001) and the Grade 2 patients [25; 23-27] (P<0.05). The CSF-MBP levels of the DNS patients were higher than those of the non-DNS patients (P<0.0001). The 1-month CSF-MBP levels of the Grade 3 patients were higher than those of the Grade 1 patients (P<0.05); the MBP index, defined as [(Age)×(1-month CSF-MBP)], was higher in the Grade 3 patients than in the Grade 1 patients (P<0.01). Severe DNS were associated with advanced age (>72.5 years), earlier onset (<18 days), higher 1-month CSF-MBP (>252 pg/ml), and higher MBP index (>20.9 year × ng/ml).

CONCLUSIONS

Poor DNS outcomes were associated with advanced age and earlier onset. CSF-MBP can serve as a sensitive predictor of both the development and outcomes of DNS.

The role of MR imaging in assessment of brain damage from carbon monoxide poisoning: a review of the literature

SUMMARY

The aim of this article is to review how MR imaging and associated imaging modalities provide clinicopathologic information on brain damage after carbon monoxide poisoning. Initially, many authors documented typical findings of conventional MR imaging in the gray matter structures such as the globus pallidus and in various regions of cerebral white matter. The focus of investigation has since shifted to observation of cerebral white matter areas that are more frequently detected on MR imaging and are more responsible for chronic symptoms than the gray matter. DWI has dramatically contributed to the ability to quantitatively assess cerebral white matter damage. Subsequently, DTI has enabled more sensitive evaluation than DWI and can demonstrate progressive pathologic changes in the early stage, allowing prediction of chronic conditions. In addition, MR spectroscopy reveals changes in metabolite levels, offering quantitative clinicopathologic information on brain damage after carbon monoxide poisoning.

Fractional anisotropy in the centrum semiovale as a quantitative indicator of cerebral white matter damage in the subacute phase in patients with carbon monoxide poisoning: correlation with the concentration of myelin basic protein in cerebrospinal fluid

Carbon monoxide (CO) poisoning leads to demyelination of cerebral white matter (CWM) fibers, causing chronic neuropsychiatric symptoms. To clarify whether fractional anisotropy (FA) from diffusion tensor imaging in the centrum semiovale can depict demyelination in the CWM during the subacute phase after CO inhalation, we examined correlations between FA in the centrum semiovale and myelin basic protein (MBP) in cerebrospinal fluid. Subjects comprised 26 adult CO-poisoned patients ≤60 years old. MBP concentration was examined for all patients at 2 weeks after CO inhalation. The mean FA of the centrum semiovale bilaterally at 2 weeks was also examined for all patients and 21 age-matched healthy volunteers as controls. After these examinations, the presence of chronic symptoms was checked at 6 weeks after CO poisoning. Seven patients displayed chronic symptoms, of whom six showed abnormal MBP concentrations. The remaining 19 patients presented no chronic symptoms and no abnormal MBP concentrations, with MBP concentrations undetectable in 16 patients. The MBP concentration differed significantly between patients with and without chronic symptoms. The mean FA was significantly lower in patients displaying chronic symptoms than in either patients without chronic symptoms or controls. After excluding the 16 patients with undetectable MBP concentrations, a significant correlation was identified between MBP concentration and FA in ten patients. The present results suggest that FA in the centrum semiovale offers a quantitative indicator of the extent of demyelination in damaged CWM during the subacute phase in CO-poisoned patients.

Severe carbon monoxide poisoning complicated by hypothermia: a case report

It is proposed that the significant elevation of interleukin-6 (>400 pg/mL) in cerebrospinal fluid during the early phase of carbon monoxide poisoning may be a predictive biomarker for the development of delayed encephalopathy. A 52-year-old man presented to the emergency department with severe carbon monoxide poisoning. On arrival, the patient was comatose with decorticate rigidity (Glasgow Coma Scale, E1V1M3). His core body temperature, measured in the urinary bladder, was 32.4°C. Laboratory blood analysis revealed elevated CO-Hb (36.0%) and metabolic acidosis with elevated lactate (pH 7.081; base excess [BE], -19.2 mmol/L; HCO3, -9.8 mmol/L; lactate, 168.8 mg/dL). After treatment with hyperbaric oxygen and several different rewarming techniques, he became alert and his core body temperature increased to normal. Interleukin-6 in cerebrospinal fluid at 5.5 hours after his last exposure to carbon monoxide was significantly elevated (752 pg/mL). However, he did not develop delayed encephalopathy. In this case, hypothermia in the range of therapeutic hypothermia (32°C to 34°C) may have suppressed formation of reactive oxygen species and subsequent lipid peroxydation, preventing the development of delayed encephalopathy. Therapeutic hypothermia initiated soon after the last exposure to carbon monoxide may be an effective prophylactic method for preventing the development of delayed encephalopathy.

Assessment of damage to cerebral white matter fiber in the subacute phase after carbon monoxide poisoning using fractional anisotropy in diffusion tensor imaging

INTRODUCTION

Chronic neuropsychiatric symptoms after carbon monoxide (CO) poisoning are caused by demyelination of cerebral white matter fibers. We examined whether diffusion tensor imaging can sensitively represent damage to fibers of the centrum semiovale in the subacute phase after CO intoxication.

METHODS

Subjects comprised 13 adult patients with CO poisoning, classified into three groups according to clinical behaviors: group A, patients with transit acute symptoms only; group P, patients with persistent neurological symptoms; and group D, patients with "delayed neuropsychiatric sequelae" occurring after a lucid interval. Median fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the centrum semiovale bilaterally at 2 weeks were compared between these groups and a control group of ten healthy volunteers. Myelin basic protein (MBP) concentration in cerebrospinal fluid was examined at 2 weeks to evaluate the degree of demyelination in patients.

RESULTS

MBP concentration was abnormal or detectable for all group P and group D patients but was undetectable for all patients assigned to group A. Low FA values in groups P and D displaying chronic neurological symptoms clearly differed from those in controls and group A without chronic neurological symptoms, but ADC showed no significant differences between patient groups.

CONCLUSIONS

MBP concentration at 2 weeks after CO inhalation confirmed a certain extent of demyelination in the central nervous system of patients who would develop chronic neurological symptoms. In these patients, FA sensitively represented damage to white matter fibers in the centrum semiovale in the subacute phase after CO intoxication.