BDNF specifically expressed in hippocampal neurons is involved in methylmercury neurotoxicity resistance

Methylmercury (MeHg) causes selective neuronal damage to cerebrocortical neurons (CCNs) in the central nervous system, but not to hippocampal neurons (HiNs), which are highly vulnerable to neurodegenerative diseases. In our previous study using cultured rat neurons, we performed a comprehensive gene expression analysis and found that the brain-derived neurotrophic factor (BDNF), a neurotrophin (NT), was specifically expressed in HiNs. Therefore, to elucidate the causal factors of MeHg toxicity resistance in HiNs, we conducted a comparative study of the protein expression and function of several NTs, including BDNF, using CCNs showing vulnerability to MeHg toxicity and HiNs showing resistance. BDNF was specifically expressed in HiNs, whereas nerve growth factor was barely detectable in either neuron type. In addition, other NTs, NT3 and NT4/5, were expressed in small but nearly equal amounts in both neuron types. Furthermore, among the various pathways involved in MeHg neurotoxicity, the p44/42 MAPK pathway was specifically activated in HiNs, even without MeHg treatment. siRNAs were used to reduce NTs in both neuron types. Only a specific reduction in BDNF attenuated the resistance to MeHg toxicity and p44/42 MAPK activation in HiNs. In addition, the external addition of BDNF and NT4/5, which act on the same tyrosine receptor kinase (Trk), TrkB, suppressed MeHg neurotoxicity in both neuron types. These results suggest that BDNF, expressed specifically in HiNs, is involved in the resistance to MeHg neurotoxicity via TrkB. Additionally, the activation of the p44/42 MAPK pathway may contribute to the inhibitory effect of BDNF on MeHg neurotoxicity.

Cystine-dependent antiporters buffer against excess intracellular reactive sulfur species-induced stress

Reactive sulfur species (RSS) play a role in redox homeostasis; however, adaptive cell responses to excessive intracellular RSS are not well understood. Therefore, in this study, we generated transgenic (Tg) mice overexpressing cystathionine gamma-lyase (CSE) to produce excessive RSS. Contrary to expectations, tissue concentrations of RSS, such as cysteine persulfide (CysSSH), were comparable in both wild-type and CSE Tg mice, but the plasma concentrations of CysSSH were significantly higher in CSE Tg mice than in wild-type mice. This export of surplus intracellular RSS was also observed in primary hepatocytes of CSE Tg mice. Exposure of primary hepatocytes to the RSS generator sodium tetrasulfide (Na2S4) resulted in an initial increase in the intracellular concentration of RSS, which later returned to basal levels after export into the extracellular space. Interestingly, among all amino acids, cystine (CysSSCys) was found to be essential for CysSSH export from primary mouse hepatocytes, HepG2 cells, and HEK293 cells during Na2S4 exposure, suggesting that the cystine/glutamate transporter (SLC7A11) contributes, at least partially, to CysSSH export. We established HepG2 cell lines with knockout and overexpression of SLC7A11 and used them to confirm SLC7A11 as the predominant antiporter of CysSSCys and CysSSH. We observed that the poor efflux of excess CysSSH from the cell enhanced cellular stresses induced by Na2S4 exposure, such as polysulfidation of intracellular proteins, mitochondrial damage, and cytotoxicity. These results suggest the presence of a cellular response to excess intracellular RSS that involves the extracellular efflux of excess CysSSH by a cystine-dependent transporter to maintain intracellular redox homeostasis.

Preliminary evaluation of the mechanism underlying vulnerability/resistance to methylmercury toxicity by comparative gene expression profiling of rat primary cultured cerebrocortical and hippocampal neurons

Methylmercury (MeHg), an environmentally toxic substance, causes site-specific neuronal cell death; while MeHg exposure causes death in cerebrocortical neurons, interestingly, it does not in hippocampal neurons, which are generally considered to be vulnerable to toxic substances. This phenomenon of site-specific neuronal cell death can be reproduced in animal experiments; however, the mechanism underlying the resistance of hippocampal neurons to MeHg toxicity has not been clarified. In this study, we comparatively analyzed the response to MeHg exposure in terms of viability and the expression characteristics of primary cultured cerebrocortical neurons and hippocampal neurons derived from fetal rat brain. Neuronal differentiated hippocampal neurons were more resistant to MeHg toxicity than cerebrocortical neurons, as indicated by a 2‒3 fold higher half-maximal inhibitory concentration (IC₅₀; 3.3 μM vs. 1.2 μM), despite similar intracellular mercury concentrations in both neuronal cell types. Comprehensive RNA sequencing-based gene expression analysis of non-MeHg-exposed cells revealed that 80 out of 15,208 genes showed at least 10-fold higher expression in hippocampal neurons than in cerebrocortical neurons, whereas six genes showed at least 10-fold higher expression in cerebrocortical neurons than in hippocampal neurons. In particular, genes related to neuronal function, including those encoding transthyretin and brain-derived neurotrophic factor, showed approximately 50-fold higher expression in hippocampal neurons than in cerebrocortical neurons. In conclusion, the resistance of hippocampal neurons to MeHg toxicity may be related to the high expression of neuronal function-related proteins.

Concentrations of nucleophilic sulfur species in small Indian mongoose (Herpestes auropunctatus) in Okinawa, Japan

Reactive sulfur species (RSS), such as hydrogen per (poly)sulfide, cysteine per (poly)sulfide, glutathione per (poly)sulfide, and protein-bound per (poly)sulfides, can easily react with environmental electrophiles such as methylmercury (MeHg), because of their high nucleophilicity. These RSS are produced by enzymes such as cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) and are found in mammalian organs. Organs of wildlife have not been analyzed for hydrogen sulfide, cysteine, glutathione, and RSS. In this study, low molecular weight nucleophilic sulfur substances, including RSS, were quantified by stable isotope dilution assay-based liquid chromatography-mass spectrometry using β-(4-hydroxyphenyl)ethyl iodoacetamide to capture the target chemicals in the small Indian mongoose which species possesses high mercury content as same as some marine mammals. Western blotting revealed that the mongoose organs (liver, kidney, cerebrum, and cerebellum) contained proteins that cross-reacted with anti-CBS and CSE antibodies. The expression patterns of these enzymes were similar to those in mice, indicating that mongoose organs contain CBS and CSE. Moreover, bis-methylmercury sulfide (MeHg)₂S, which is a low toxic compound in comparison to MeHg, was found in the liver of this species. These results suggest that the small Indian mongoose produces RSS and monothiols associated with detoxification of electrophilic organomercury. The animals which have high mercury content in their bodies may have function of mercury detoxification involved not only Se but also RSS interactions.

Spatio-temporal distribution of reactive sulfur species during methylmercury exposure in the rat brain

Brain susceptibility to methylmercury (MeHg) is developmentally and regionally specific in both humans and rodents, but the mechanism is not well clarified. Reactive sulfur species (RSS) with high nucleophilicity can react with MeHg, leading to the formation of a less toxic metabolite bismethylmercury sulfide, thus exerting cytoprotection. In this study, we assessed the variation of RSS content in the rat brain and evaluated its relevance in sensitivity to MeHg. Analyses of fetal/juvenile rat brains showed low RSS levels in early developmental stages. Site-specific analysis of adult rat brains revealed that cerebellar RSS levels were lower than those of the hippocampus. Microscopically, RSS levels of the granular cell layer were lower than those of the molecular layer in the cerebellum. Thus, low RSS levels corresponded with age and site of the brain that is vulnerable to MeHg. Taken together with the finding that brain RSS were consumed during MeHg exposure, these results indicate that RSS is a factor that defines the specificity of MeHg vulnerability in the brain.

Percutaneous coronary intervention on combined VA-ECMO and IMPELLA (ECPELLA) support may reduce myocardial damage in cardiogenic shock patients with STEMI who required mechanical circulatory support

Background

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is an effective therapeutic modality for patients with cardiogenic shock (CS) including STEMI. The VA-ECMO maintains end-organ perfusion, however, it significantly increases damaged left ventricular (LV) afterload. Combined treatment of VA-ECMO and a micro-axial Impella pump, ECPELLA, simultaneously provides systemic circulatory support and LV loading reduction (LV unloading). Studies in ischemic animal models displayed that LV unloading reduced myocardial size. However, it remains unknown whether LV unloading effect by ECPELLA during percutaneous coronary intervention (PCI) can reduce myocardial damage in human STEMI patients with severe cardiogenic shock.

Purpose

This study was to assess whether PCI on ECPELLA support can reduce myocardial damage in STEMI patients with severe cardiogenic shock.

Methods

Sixteen consecutive patients with STEMI and lethal CS (SCAI stage E) were enrolled. All patients suffered from cardiac arrest. Fifteen patients (94%) underwent extracorporeal cardiopulmonary resuscitation using VA-ECMO. From October 2018 to November 2019, PCI was carried out on VA-ECMO support and the mechanical circulatory support (MCS) modality during PCI was switched to ECPELLA since December 2019. There were 8 patients who underwent PCI on ECPELLA support (ECPELLA-PCI) and 8 patients who underwent PCI on single VA-ECMO support (ECMO-PCI). All patients in ECMO-PCI group were escalated to ECPELLA after PCI. Therefore, the difference between groups was timing of LV unloading, i.e., pre-PCI or post-PCI condition. We assessed total MCS flow during PCI, and peak and time course changes in CK-MB levels from days 0 to 3.

Results

There were no significant differences in age, rate of male sex, body surface area, shockable rhythm, serum lactate levels, and door to MCS time. Patients in ECPELLA-PCI had significantly longer door to recanalization time (73min in ECPELLA vs. 49min in VA-ECMO, p<0.05), and higher total MCS flow during PCI (3.1 L/min/sqM vs. 2.0 L/min/sqM, p<0.05). Peak and the area under the curves (AUC) from day 0 to day 3 of CK-MB in ECPELLA-PCI were significantly lower than ECMO-PCI group (peak CK-MB 120 vs. 524 IU/L and CK-MB AUC 143 vs. 464 IU/L*Day, respectively, p<0.05). While all patients received red blood cell (RBC) and plasma (PL) transfusions, ECPELLA-PCI required larger amount of RBC and PL transfusions (p<0.05).

Conclusion

The ECPELLA-PCI appeared to reduce myocardial damage shown by peak and AUC of CK-MB levels. Lager amount of blood transfusion is a major drawback of this treatment modality. Further studies are necessary whether ECPELLA-PCI is an effective revascularization approach for myocardial damage reduction with favorable mid- and long-term outcome in patients with STEMI with severe cardiogenic shock.

Funding Acknowledgement

Type of funding sources: None. Total MCS FLow and Ttoal MCS flow indexPeak CK-MB and CK-MB AUC

Combined use of VA-ECMO and IMPELLA (ECPELLA) as a possible strategy to improve outcomes in patients who underwent E-CPR

Background

Extracorporeal Cardio-Pulmonary Resuscitation (E-CPR) is an effective tool for patients with refractory cardiac arrest (CA). Since VA-ECMO provides strong afterload, IABP is often used to increase left ventricular load. Recently, in Japan, the effectiveness of VA-ECMO in combination with IMPELLA, a forward flow mechanical circulatory support device (ECPELLA) is gaining attention.

Purpose

We investigated usefulness of ECPELLA in patients with refractory CA.

Method

We reviewed 133 patients that had E-CPR from January 2012 through January 2020 {mean age: 67±15 years, male 65%, Out of hospital Cardiac Arrest (OHCA) 35%, Acute coronary Syndrome (ACS) 54%}. We divided these patients into ECMO with IMPELLA (ECPELLA group), ECMO with IABP (IABP group) and ECMO alone (ECMO alone group). The primary endpoint is 30-day survival and good neurological prognosis defined as CPC (cerebral performance categories) 1 or 2.

Result

During the study period, of the 133 patients, there were 20 in the ECPELLA group, 78 in the IABP group, 35 in the ECMO alone group. There were no significant differences in age in all three groups. There were more males, shockable rhythm, OHCA and ACS in the ECPELLA and IABP groups compared to the ECMO alone group. But there was no significant difference between the ECPELLA and IABP groups. Compared with other groups, ECPELLA had the shortest time from cardiac arrest to ECMO placement. Regarding endpoints, the rate of 30-day survival and favorable neurological prognosis were higher in the ECPELLA group, followed by the IABP group and then the ECMO alone group. (ECPELLA: 55% vs. IABP: 23% vs. ECMO alone: 9%; P=0.0009, ECPELLA: 35% vs. IABP: 13% vs. ECMO alone: 9%; P=0.04) Next, Kaplan Meier analysis was performed to analyze 30-day all-cause mortality. The ECPELLA group had a significantly higher survival rate (P=0.01 by log-rank test). Multivariate cox proportional hazard analysis including the age, OHCA, shockable rhythm, ACS, Collapse-to-ECMO under 60 min revealed that the age (hazard ratio [HR], 1.28 (10 years increase), 95% confidence interval [CI], 1.08–1.53, P=0.004) and Collapse-to-ECMO under 60 min (HR, 0.37, 95% CI, 0.21–0.68, P=0.001) or ECPELLA (HR, 0.46, 95% CI, 0.20–0.694, P=0.03) were significantly associated with mortality.

Conclusion

ECPELLA used with E-CPR is an effective tool to improve mortality and neurologic status.

Funding Acknowledgement

Type of funding source: None

Impact of glucose tolerance status on the relationship between vascular endothelial growth factor D and mortality in patients with suspected coronary artery disease: a subanalysis of the ANOX study

Background

Vascular endothelial growth factor D (VEGF-D) is a secreted glycoprotein that can act as lymphangiogenic and angiogenic growth factors through binding to its specific receptors, VEGFR-3 and VEGFR-2. VEGF-D signaling via VEGFR-3 plays an important role in lipoprotein metabolisms which may contribute to coronary artery disease (CAD). We recently reported that serum levels of VEGF-D are independently associated with mortality in patients with suspected or known CAD. However, the impact of glucose tolerance status on the relationship between VEGF-D and mortality in patients with suspected CAD is unclear.

Methods

Serum VEGF-D levels were measured in 1,717 patients with suspected CAD undergoing elective coronary angiography, enrolled in the development of novel biomarkers related to angiogenesis or oxidative stress to predict CV events (ANOX) study, and followed up for 3 years. After excluding 67 patients with no HbA1c data, 1,650 patients were divided into 3 groups according to the glucose tolerance status: diabetes (DM, n=693), prediabetes (preDM, n=541) defined as an HbA1c of 5.7 to 6.4%, and normal glucose tolerance (NGT, n=416) defined as an HbA1c of 5.6% or less. The outcomes were total death, CV death, and major adverse CV events (MACE) defined as a composite of CV death, nonfatal myocardial infarction, and nonfatal stroke.

Results

During the follow-up, 80 DM, 45 preDM, and 30 NGT patients died from any cause, 24 DM, 13 preDM, and 12 NGT died from CV disease, and 54 DM, 30 preDM, and 19 NGT developed MACE. After adjustment for established risk factors, VEGF-D levels were significantly associated with total death (hazard ratio [HR] for 1-SD increase, 1.28; 95% confidence interval [CI], 1.12–1.47), but not with CV death (HR, 1.20; 95% CI, 0.93–1.52) or MACE (HR, 1.23; 95% CI, 0.997–1.48) in DM; VEGF-D levels were not significantly associated with total death (HR, 0.97; 95% CI, 0.70–1.34), CV death (HR, 1.39; 95% CI, 0.92–2.11), or MACE (HR, 1.09; 95% CI, 0.74–1.50) in preDM; VEGF-D levels were not significantly associated with total death (HR, 1.34; 95% CI, 0.98–1.84), CV death (HR, 1.32; 95% CI, 0.78–2.13), or MACE (HR, 1.01; 95% CI, 0.66–1.46) in NGT. Even after incorporation of N-terminal pro-brain natriuretic peptide, contemporary sensitive cardiac troponin I, and high-sensitivity C-reactive protein into a model with established risk factors, the addition of VEGF-D levels further improved the prediction of total death (P=0.040 for continuous net reclassification improvement [NRI], P=0.007 for integrated discrimination improvement [IDI]), but not that of CV death or MACE in DM, while it did not significantly improved the prediction of total death, CV death, or MACE either in preDM or in NGT.

Conclusions

The VEGF-D level was independently associated with total death in DM, but not in preDM or in NGT. The relationship between VEGF-D and total mortality may depend on the presence of DM in patients with suspected CAD.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): The ANOX study is supported by a Grant-in-Aid for Clinical Research from the National Hospital Organization.

Decreased plasma thiol antioxidant capacity precedes neurological signs in a rat methylmercury intoxication model

The main target organ for MeHg is the nervous system, and its neurological dysfunction remains irreversible. Therefore, predictive biomarkers associated with individual susceptibility to MeHg and future clinical severity are needed to protect against the progression of MeHg toxicity. In this study, we demonstrated that plasma thiol antioxidant capacity (-SHp) is a useful predictive biomarker associated with future clinical severity using MeHg-intoxicated rats administered 1 mg/kg/day for 4 weeks. Blood samples were collected from the subclavian vein of each rat once a week to examine total blood mercury concentrations and the levels of plasma oxidative stress markers. Time course analyses of the correlation between these weekly blood examination values and hind limb crossing signs score after 4 weeks of MeHg exposure were performed, and plasma -SHp levels after 2 weeks of MeHg exposure showed strong correlations with future hind limb crossing sign scores. Neuropathological changes also developed in parallel with hind limb crossing sign scores. Quantitative analysis of vacuolar areas in the spinal cord showed a strong correlation with hind limb crossing sign scores. In conclusion, evaluation of plasma -SHp levels allowed us to detect individuals at risk for health damage and could protect the sensitive population against MeHg toxicity.

Repression of mercury accumulation and adverse effects of methylmercury exposure is mediated by cystathionine γ-lyase to produce reactive sulfur species in mouse brain

Reactive sulfur species (RSS), such as hydropersulfides and hydropolysulfides with high nucleophilicity, contain mobilized sulfur that readily captures xenobiotic electrophiles, leading to their sulfur adducts. We have previously reported that RSS produced by cystathionine γ-lyase (CSE) captures the electrophilic metal methylmercury (MeHg) to form inert sulfur adducts, which in turn play a critical role in the protection against MeHg-induced motor impairment in mice. However, the mechanism underlying this neuroprotective effect is not fully understood. Here, we addressed this using CSE-knockout mice. The cerebellum of CSE-knockout mice was more susceptible to MeHg than that of wild type mice. Moreover, these CSE-deficient mice exhibited a higher level of mercury accumulation in the brain. However, co-treatment with sodium tetrasulfide, an RSS able to capture MeHg, leading to the formation of its sulfur adducts, blocked the increased accumulation of mercury, motor dysfunction and mortality caused by CSE deficiency. Our findings suggest that capturing MeHg by RSS in association with its sulfur adduct formation is involved in the repression of the brain distribution and deleterious effects of MeHg.

Adaptive Responses to Electrophilic Stress and Reactive Sulfur Species as their Regulator Molecules

We are exposed to numerous xenobiotic electrophiles on a daily basis through the environment, lifestyle, and dietary habits. Although such reactive species have been associated with detrimental effects, recent accumulated evidence indicates that xenobiotic electrophiles appear to act as signaling molecules. In this review, we introduce our findings on 1) activation of various redox signaling pathways involved in cell proliferation, detoxification/excretion of electrophiles, quality control of cellular proteins, and cell survival during exposure to xenobiotic electrophiles at low concentrations through covalent modification of thiol groups in sensor proteins, and 2) negative regulation of reactive sulfur species (RSS) in the modulation of redox signaling and toxicity caused by xenobiotic electrophiles.

P3639Vascular endothelial growth factor-C and mortality in patients with suspected but no history of coronary heart disease: a subanalysis of the ANOX study

Background

The lymphatic system has been suggested to play an important role in cholesterol metabolism and cardiovascular disease. Recently, we demonstrated that serum levels of vascular endothelial growth factor-C (VEGF-C), a central player of lymphangiogenesis, are inversely and independently associated with the risk of all-cause mortality in patients with suspected or known coronary heart disease (CHD). However, the prognostic value of VEGF-C in patients with suspected but no history of CHD is still unclear.

Methods

Serum VEGF-C levels were measured in 1,717 patients with suspected but no history of CHD undergoing elective coronary angiography, enrolled in the development of novel biomarkers related to angiogenesis or oxidative stress to predict cardiovascular events (ANOX) study, and followed up for 3 years. The primary outcome was all-cause death. The secondary outcomes were cardiovascular death, and major adverse cardiovascular events (MACE) defined as a composite of cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke.

Results

During the follow-up, 161 patients died from any cause, 50 died from cardiovascular disease, and 104 developed MACE. After adjustment for established risk factors, VEGF-C levels were significantly and inversely associated with all-cause death (hazard ratio [HR] for 1-SD increase, 0.69; 95% confidence interval [CI], 0.58–0.83) and cardiovascular death (HR, 0.72; 95% CI, 0.52–0.998), but not with MACE (HR, 0.91; 95% CI, 0.74–1.13). Even after incorporation of N-terminal pro-brain natriuretic peptide, contemporary sensitive cardiac troponin-I, and high-sensitivity C-reactive protein into a model with established risk factors, the addition of VEGF-C levels further improved the prediction of all-cause death (continuous net reclassification improvement [NRI], 0.282; 95% CI, 0.121–0.443; P<0.001; integrated discrimination improvement [IDI], 0.009; 95% CI, 0.003–0.016; P=0.005), but not that of cardiovascular death (NRI, 0.178; 95% CI, r=−0.103–0.458; P=0.214; IDI, 0.004; 95% CI, r=−0.002–0.009; P=0.194) or MACE (NRI, 0.037; 95% CI, r=−0.162–0.235; P=0.717; IDI, 0.000; 95% CI, r=−0.0004–0.0005; P=0.872).

Conclusions

In patients with suspected but no history of CHD undergoing elective coronary angiography, a low VEGF-C value may predict all-cause mortality independent of established risk factors and cardiovascular biomarkers.

Acknowledgement/Funding

The ANOX study is supported by a Grant-in-Aid for Clinical Research from the National Hospital Organization

5195Growth differentiation factor-15 and mortality in suspected or known coronary heart disease patients with diabetes: a subanalysis of the ANOX study

Background

Diabetes is a risk factor for coronary heart disease (CHD), but further risk stratification in patients with diabetes is necessary to improve the prediction and prevention of cardiovascular events and deaths. Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine, which plays an important role in the regulation of the inflammatory response, growth and cell differentiation. Elevated GDF-15 was found in various diseases including diabetes and stable CHD, and was reported to predict mortality and cardiovascular events in general or established CHD population. However, the prognostic value of GDF-15 in suspected or known CHD patients with diabetes is unknown.

Methods

Serum GDF-15 levels were measured in 1,087 suspected or known CHD patients with diabetes undergoing elective coronary angiography, enrolled in the development of novel biomarkers related to angiogenesis or oxidative stress to predict cardiovascular events (ANOX) study, and followed up for 3 years. The primary outcome was all-cause death. The secondary outcomes were cardiovascular death, and major adverse cardiovascular events (MACE) defined as a composite of cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke.

Results

During the follow-up, 147 patients died from any cause, 47 died from cardiovascular disease, and 94 developed MACE. After adjustment for established risk factors, GDF-15 levels were significantly associated with all-cause death (hazard ratio [HR] for 1-SD increase, 1.66; 95% confidence interval [CI], 1.48–1.86), cardiovascular death (HR, 1.63; 95% CI, 1.34–1.99), and MACE (HR, 1.41; 95% CI, 1.20–1.65). Even after incorporation of N-terminal pro-brain natriuretic peptide, contemporary sensitive cardiac troponin-I, and high-sensitivity C-reactive protein into a model with established risk factors, the addition of GDF-15 levels further improved the prediction of all-cause death (continuous net reclassification improvement [NRI], 0.344; 95% CI, 0.172–0.517; P<0.001; integrated discrimination improvement [IDI], 0.049; 95% CI, 0.026–0.072; P<0.001), but not that of cardiovascular death (NRI, −0.013; 95% CI, −0.300–0.274; P=0.931; IDI, 0.023; 95% CI, 0.003–0.043; P=0.026) or MACE (NRI, 0.059; 95% CI, −0.151–0.268; P=0.583; IDI, 0.005; 95% CI, −0.004–0.015; P=0.244).

Conclusions

In suspected or known CHD patients with diabetes undergoing elective coronary angiography, elevated GDF-15 levels may predict all-cause mortality independent of established risk factors and cardiovascular biomarkers.

Acknowledgement/Funding

The ANOX study is supported by a Grant-in-Aid for Clinical Research from the National Hospital Organization.

Environmental Electrophile-Mediated Toxicity in Mice Lacking Nrf2, CSE, or Both

BACKGROUND

Transcription factor Nrf2 (nuclear factor-erythroid 2-related factor 2) plays a key role in detoxification of electrophiles via formation of glutathione (GSH) adducts and subsequent excretion into extracellular spaces. We found that reactive sulfur species (RSS), such as cysteine persulfides produced by cystathionine [Formula: see text] (CSE), capture environmental electrophiles through formation of sulfur adducts. However, contributions of Nrf2 and CSE to the blockage of environmental electrophile-mediated toxicity remain to be evaluated.

OBJECTIVES

The aim of this study was to clarify roles that CSE and Nrf2 play in the protection against various environmental electrophiles. We also wished to clarify the molecular basis of the developmental window of toxicity through investigating expression levels of Nrf2, RSS-producing enzymes, and sulfur nucleophiles during developmental stages of mice.

METHODS

Wild-type (WT), CSE knockout (KO), Nrf2 KO, Nrf2/CSE double KO (DKO) mice, and their primary hepatocytes were analyzed in this study. Cadmium (Cd), methylmercury (MeHg), 1,4-naphthoquinone, crotonaldehyde, and acrylamide were used. We conducted Western blotting, real-time polymerase chain reaction (PCR), 3-(4,5-dimethylthiazol-2-yl)-2,5-triphenyl tetrazolium bromide (MTT) assays, liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis, alanine transaminase (ALT) activity, histopathological analysis, and rotarod test.

RESULTS

Primary hepatocytes from DKO mice were significantly more sensitive to the environmental electrophiles than each single KO counterpart. Both Nrf2 and CSE single KO mice were highly susceptible to Cd and MeHg, and such sensitivity was further exacerbated in the DKO mice. Lower-level expressions of CSE and sulfur nucleophiles than those in adult mice were observed in a window of developmental stage.

CONCLUSIONS

Our mouse model provided new insights into the response to environmental electrophiles; while Nrf2 is recognized as a key transcription factor for detoxification of environmental electrophiles, CSE is crucial factor to repress their toxicity in a parallel mode. In addition, the sensitivity of fetuses to MeHg appears to be, at least in part, associated with the restricted production of RSS due to low-level expression of CSE. https://doi.org/10.1289/EHP4949.

Molecular Pathways Associated With Methylmercury-Induced Nrf2 Modulation

Methylmercury (MeHg) is a potent neurotoxin that affects particularly the developing brain. Since MeHg is a potent electrophilic agent, a wide range of intracellular effects occur in response to its exposure. Yet, the molecular mechanisms associated with MeHg-induced cell toxicity have yet to be fully understood. Activation of cell defense mechanisms in response to metal exposure, including the up-regulation of Nrf2- (nuclear factor erythroid 2-related factor 2)-related genes has been previously shown. Nrf2 is a key regulator of cellular defenses against oxidative, electrophilic and environmental stress, regulating the expression of antioxidant proteins, phase-II xenobiotic detoxifying enzymes as well phase-III xenobiotic transporters. Analogous to other electrophiles, MeHg activates Nrf2 through modification of its repressor Keap1 (Kelch-like ECH-associated protein 1). However, recent findings have also revealed that Keap1-independent signal pathways might contribute to MeHg-induced Nrf2 activation and cytoprotective responses against MeHg exposure. These include, Akt phosphorylation (Akt/GSK-3β/Fyn-mediated Nrf2 activation pathway), activation of the PTEN/Akt/CREB pathway and MAPK-induced autophagy and p62 expression. In this review, we summarize the state-of-the-art knowledge regarding Nrf2 up-regulation in response to MeHg exposure, highlighting the modulation of signaling pathways related to Nrf2 activation. The study of these mechanisms is important in evaluating MeHg toxicity in humans, and can contribute to the identification of the molecular mechanisms associated with MeHg exposure.

1,4-Naphthoquinone activates the HSP90/HSF1 pathway through the S-arylation of HSP90 in A431 cells: Negative regulation of the redox signal transduction pathway by persulfides/polysulfides

The current consensus is that environmental electrophiles activate redox signal transduction pathways through covalent modification of sensor proteins with reactive thiol groups at low concentrations, while they cause cell damage at higher concentrations. We previously exposed human carcinoma A431 cells to the atmospheric electrophile 1,4-naphthoquinone (1,4-NQ) and found that heat shock protein 90 (HSP90), a negative regulator of heat shock factor 1 (HSF1), was a target of 1,4-NQ. In the study presented here, we determined whether 1,4-NQ activates HSF1. We also examined whether such redox signaling could be regulated by nucleophilic sulfur species. Exposure of A431 cells to 1,4-NQ covalently modified cellular HSP90, resulting in repression of the association between HSF1 with HSP90, thereby enhancing HSF1 translocation into the nuclei. Liquid chromatography-tandem mass spectrometry analysis with recombinant HSP90 revealed that the modifications site were Cys412 and Cys564. We found that HSF1 activation mediated by 1,4-NQ upregulated downstream genes, such as HSPA6. HSF1 knockdown accelerated 1,4-NQ-mediated cytotoxicity in the cells. While simultaneous treatment with reactive persulfide and polysulfide, Na₂S₂ and Na₂S₄, blocked 1,4-NQ-dependent protein modification and HSF1 activation in A431 cells, the knockdown of Cys persulfide producing enzymes cystathionine β-synthase (CBS) and/or cystathionine γ-lyase (CSE) enhanced these phenomena. 1,4-NQ-thiol adduct and 1,4-NQ-S-1,4-NQ adduct were produced during the enzymatic reaction of recombinant CSE in the presence of 1,4-NQ. The results suggest that activation of the HSP90-HSF1 signal transduction pathway mediated by 1,4-NQ protects cells against 1,4-NQ and that per/polysulfides can diminish the reactivity of 1,4-NQ by forming sulfur adducts.

Serum lipid and lipoprotein abnormalities in major clinical entities of renal disease

More than half of the patients with glomerulonephritis, nephrotic syndrome and renovascular hypertension showed obviously abnormal profiles of serum lipoproteins (Lps). The abnormal profiles returned to normal or near-normal when the disease was ameliorated or corrected surgically. A unique Lp profile (broad midband pattern, BMP) was observed in approximately 89% of uremic patients on hemodialysis therapy. The results of the current investigations indicated that the BMP could probably be formed by the accumulation of catabolic remnants of VLDL.

Role of activation of PIP5Kgamma661 by AP-2 complex in synaptic vesicle endocytosis

Synaptic vesicles (SVs) are retrieved by clathrin-mediated endocytosis at the nerve terminals. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] drives this event by recruiting the components of the endocytic machinery. However, the molecular mechanisms that result in local generation of PI(4,5)P2 remain unclear. We demonstrate here that AP-2 complex directly interacts with phosphatidylinositol 4-phosphate 5-kinase gamma661 (PIP5Kgamma661), the major PI(4,5)P2-producing enzyme in the brain. The beta2 subunit of AP-2 was found to bind to the C-terminal tail of PIP5Kgamma661 and cause PIP5Kgamma661 activation. The interaction is regulated by PIP5Kgamma661 dephosphorylation, which is triggered by depolarization in mouse hippocampal neurons. Finally, overexpression of the PIP5Kgamma661 C-terminal region in hippocampal neurons suppresses depolarization-dependent SV endocytosis. These findings provide evidence for the molecular mechanism through which PIP5Kgamma661 locally generates PI(4,5)P2 in hippocampal neurons and suggest a model in which the interaction trigger SV endocytosis.

Changes in respiratory physiological dead space and compliance during non-abdominal, upper abdominal and lower abdominal surgery under general anaesthesia

BACKGROUND AND OBJECTIVE

To evaluate the temporal changes in respiratory physiological dead space and dynamic compliance of the respiratory system during non-abdominal, upper abdominal and lower abdominal surgery under general anaesthesia with intermittent positive pressure ventilation.

METHODS

Thirty-four adult patients were studied (non-abdominal surgery, n = 8; upper abdominal surgery, n = 13 and lower abdominal surgery in lithotomy position, n = 13). Physiological dead space was measured using the single breath carbon dioxide test. The physiological dead space to tidal volume ratio (VD/VT), dynamic compliance of respiratory system, expiratory tidal volume and respiratory rate were measured 10 min after tracheal intubation, and 30, 60 and 120 min later.

RESULTS

In lower abdominal surgery group, VD/VT was significantly increased at 120 min compared with 0 min (P = 0.005) and 30 min (P = 0.009). There were no significant differences in VD/VT between the three groups at any time point. Compliance decreased significantly in patients with upper abdominal (120 min) and lower abdominal surgery (60 and 120 min), but there were no significant changes during non-abdominal surgery.

CONCLUSIONS

We found that the VD/VT increased in patients undergoing lower abdominal surgery in lithotomy and head down tilt, and compliance decreased in those undergoing upper abdominal and lower abdominal surgery over time.

Clinical manifestations of influenza a myocarditis during the influenza epidemic of winter 1998-1999

OBJECTIVES

The clinical features of myocarditis that developed during the influenza epidemic of winter 1998-1999 were investigated to emphasize the need for medical attention to this disease.

METHODS

Nine patients were treated under diagnoses of acute myocarditis during the winter of 1998-1999. Five (two males and three females, mean age 52 +/- 18 years) were examined with myocarditis associated with influenza A. The diagnosis of influenza A myocarditis was based on electrocardiographic and echocardiographic abnormalities, increased creatine kinase levels and at least a four-fold increase in influenza A virus titers using paired sera.

RESULTS

All patients had preceding flu-like symptoms and fever. Cardiac involvement developed between 4 and 7 days after the onset of influenza symptoms. Dyspnea progressively worsened in three patients, one went into shock and one had persistent fever, cough and mild dyspnea without apparent cardiac symptoms. Three patients had ST elevation associated with Q waves and one had complete left bundle branch block. The creatine kinase levels were abnormally increased and global wall motion of the left ventricle on echocardiography was decreased in all patients. Two patients had diagnoses of fulminant myocarditis. One patient died of pneumonia following cerebral infarction, but the left ventricular dysfunction normalized in the remaining four patients.

CONCLUSIONS

Cardiac involvement occurred between 4 and 7 days after the onset of influenza symptoms, and worsening dyspnea was the most common symptom. Electrocardiography, echocardiography and creatine kinase levels should be checked to determine the potential for cardiac involvement when patients present with suspected influenza associated with worsening dyspnea or prolonged weakness. Increasing the awareness of influenza myocarditis may help in the earlier identification and treatment of this disease during influenza epidemics.

[Recurrent pulmonary embolism from left subclavian thrombosis: a case report]

A 38-year-old woman was admitted to our hospital because of pulmonary thromboembolism. Thrombolysis therapy resulted in initial improvement in symptoms and laboratory data. However, 4 months later, pulmonary thromboembolism recurred despite antiplatelet and anticoagulation therapy. Contrast venography and venous ultrasonography of both upper and lower extremities revealed subtotal occlusion and venous thrombosis of the left subclavian vein with collateral vessels, but no evidence of lower extremity venous thrombosis. She had no history of subclavian venous catheterization, neoplasm, hypercoagulability or other predisposing cause of thrombus formation. Operative ligation of the left subclavian vein was performed at the junction with the internal jugular vein. White thrombus was identified within the venous lumen. She was well without recurrent pulmonary thromboembolism or venous insufficiency for 10 months after the operation. Surgical interruption of the subclavian vein may be effective to prevent recurrent pulmonary thromboembolism in patients with recurrent pulmonary thromboembolism due to venous thrombosis of the upper extremity despite therapeutic anticoagulation.

[One-hour protocol stress myocardial scintigraphy: prospective study of diagnostic accuracy for the detection of coronary artery stenosis]

A one-hour protocol for stress myocardial scintigraphy using technetium-99m-tetrofosmin (Tc-tetrofosmin) was compared with coronary arteriography for the detection of coronary artery stenosis in 90 consecutive patients without prior myocardial infarction, revascularization procedure or vasospastic angina. Tc-tetrofosmin stress myocardial scintigraphy acquired a rest image 20 min after intravenous administration of Tc-tetrofosmin (185 MBq, 1/5 vial) using a three-head gamma camera collecting 20-sec views over 360 degrees. The stress test using bicycle ergometer was performed and administration of Tc-tetrofosmin (740 MBq, 4/5 vial) was repeated at the peak stress point. The stress image was acquired 15 min after the second injection with 5-sec views over 360 degrees. Coronary arteriography revealed the presence of significant coronary artery stenosis (> 75%) in 56 vessels of 45 patients, including 35 patients with single-vessel disease, 5 with two-vessel disease, 2 with three-vessel disease, and 3 with left main trunk disease. The overall sensitivity and specificity for the detection of coronary artery disease by visual analysis were 91.1% and 77.8%, respectively, and by quantitative analyses (using bull's-eye method) were 95.6% and 91.1%, respectively. The individual stenotic vessel sensitivities in the right coronary artery, left anterior descending artery, and left circumflex artery were 84.6%, 90.9%, and 78.6%, respectively. The specificities were 97.3%, 95.9%, and 100.0%, respectively. These results suggest that stress myocardial scintigraphy using the present new protocol is a promising approach for the detection of coronary artery stenosis.

Effect of pacing rate in pacing therapy in hypertrophic obstructive cardiomyopathy

The effects of dual-chamber pacing therapy in patients with hypertrophic obstructive cardiomyopathy (HOCM) have been reported in short- and long-term studies. Almost all of these studies have reported that the key factor in pacing therapy is the setting of the atrioventricular (AV) interval. However, studies focusing on the effects of pacing rate on the hemodynamic state are rare. In this study, cardiac catheterization was performed in 2 patients during temporary pacing at various rates and AV intervals. When the pacing rate was increased slightly (to 70-90/min), AV sequential pacing decreased peak subaortic pressure gradient and increased systolic aortic pressure without increase in pulmonary capillary wedge pressure, left ventricular end-diastolic pressure, and the time constant of isovolumetric relaxation. In another case, of a patient who became refractory to AV sequential pacing therapy at an optimum AV interval, pacing at a slightly higher rate relieved syncope. Thus, AV sequential pacing therapy performed at a slightly higher rate than normal in a patient with HOCM may lead to a decreased subaortic pressure gradient and relief of symptoms without noticeable deterioration in cardiac function.

Rapidly-growing ectopic pituitary adenoma within the sphenoid sinus--case report

A 75-year-old male with left abducens nerve paresis presented with an ectopic pituitary adenoma invading the posterior wall of the sphenoid sinus. The sphenoidal mass grew rapidly for 6 months with left ophthalmoplegia and was partially removed via the transsphenoidal approach. The histological examination showed a benign pituitary adenoma, but the MIB-1 proliferating cell index was 6.8%, reflecting the clinically malignant behavior. The symptom gradually improved without tumor regrowth over 1.5 years after conventional irradiation.

An autopsy case of diffuse malignant mesothelioma of the pericardium

A report is presented of an autopsy case of a 71-year-old Japanese man with a diffuse malignant epithelial mesothelioma of the pericardium with massive pericardial effusion and a thickened pericardium. He had no history of exposure to asbestos. He suffered severe heart failure and later died. Autopsy revealed that the tumor had developed over the pericardium. Microscopically, the tumor cells were arranged in an epithelial form, and histochemically, the cytoplasm of these cells contained glycogen and hyaluronic acid. The tumor tissue showed immunohistochemical positivity for cytokeratin, epithelial membrane antigen, vimentin, cancer antigen 125, thrombomodulin, mesothelial antigen, muscle actin and human milk fat globule. In contrast, all the tumor cells were negative for human carcinoembryonic antigen and epithelial antigen. Ultrastructurally, the tumor cells had long, thin microvilli, abundant intermediate filaments, intracytoplasmic lumina and long desmosomes. It is considered that the patient had a typical malignant epithelial mesothelioma of the pericardium.

Total capsular calcification in a prolactinoma--case report

A 42-year-old male presented with a prolactin-producing pituitary adenoma with an atypical radiological appearance. The tumor was incidentally found by magnetic resonance imaging, which demonstrated a cystic tumor in the enlarged and partially empty sella turcica. Computed tomography revealed the tumor was surrounded by calcification with an egg-shell appearance. The serum prolactin level was 37 ng/ml. The operative finding was a calcified shell-containing cystic tumor. Immunohistochemical staining revealed prolactin-positive cells. The combination of the unusual calcification, and enlarged and partially empty sella was considered to be a sequela of spontaneous degeneration of the tumor.

[A technique for removal of entrapped intra-aortic balloon catheter through the left axillary artery]

A case of intra-aortic balloon pumping (IABP) entrapment in which the ruptured catheter could be removed through the left axillary artery was reported. A 68-year-old man was admitted with persistent chest pain, and because of his poor cardiac condition, an IAB catheter was inserted by the Seldinger technique. During attempted extraction of the IAB catheter resistance was encountered and it turned out to be entrapped. Then a guide-wire was passed through the IAB lumen to the left axillary artery, the artery was exposed, and the tip of the guide-wire and IAB catheter were led to the arteriotomy site. After the balloon was dissected, the IAB catheter could be removed through the axillary artery. Finally, left femoro-left branchial artery bypass was performed with e-PTFE graft because of the arterial injury and ischemia of the involved arm. The patient recovered from this episode.

Illumination of mastoid air cell for suboccipital craniotomy: technical note

The mastoid air cell was illuminated to estimate the location of the sigmoid sinus in 12 cases of a retrosigmoid suboccipital craniotomy for cerebellopontine angle tumors. A special illuminator system was designed, and the tip of the illuminator was placed inside the external auditory canal. The posterior margin of the illuminated air cell was delineated on the outer surface of the skull after the skin flap was turned and the position of the sigmoid sinus was estimated with reference to the preoperative computed tomographic scan. The posterior margin of the mastoid air cell in an axial slice, including the internal auditory canal, usually exists within the breadth of the sigmoid sinus. A gap between the posterior margin of the mastoid air cell and the position of the sigmoid sinus was easily corrected by the computed tomographic finding. This method was found to be simple and reliable in performing the suboccipital craniotomy with safety and exactness.

[The experiences of a large amount of steroid therapy for symptomatic vasospasm after subarachnoid hemorrhage: clinical analysis of 21 cases]

Among 48 cases of subarachnoid hemorrhage, 21 cases (43.8%) showed symptomatic vasospasm. We attempted treatment, using a large amount of steroid therapy for them in accord with our own protocol. In the 21 cases who received steroid therapy for symptomatic vasospasm, 18 cases (85.7%) showed improvement of their symptoms. This was especially evident in about 8 cases where the steroid effect was remarkable. There was a serious side effect, GI--tract bleeding, in one case. Although the effect of the steroid therapy was evident for slight or moderate spasm cases, 5 severe spasm cases responded poorly. We concluded that a large amount of steroid therapy was effective for slight or moderate symptomatic vasospasm cases, and that in severe ones possibly another therapy combined with steroid therapy would be necessary.

[Generalized choreic movement associated with subarachnoid hemorrhage]

A case of generalized choreic movement associated with subarachnoid hemorrhage is reported. A 71 year-old hypertensive woman suddenly developed severe headache 14 days before admission. Consciousness disturbance and involuntary movement involving the face and upper extremities appeared about 8 days after onset. The involuntary motion was diagnosed as generalized choreic movement. CT scans showed subarachnoid hemorrhage with ventricular dilatation and periventricular lucency involving bilateral caudate nuclei. On admission the patient was stuporous with Hunt & Kosnik Grade 4. She showed involuntary choreic movement in both arms, trunk and face; hemiparenis and hyperreflexia were absent. An angiography revealed a right internal carotid-anterior choroidal artery aneurysm with vasospasm. After clipping the aneurysm in the following day, the consciousness disturbance and choreic movement gradually improved. By eight days after operation, the choreic movement completely disappeared. An MRI showed lacunar infarcts in the bilateral basal ganglia, predominantly in the caudate nuclei. In our case, the choreic movement is supposed to have been caused by impaired circulation in the bilateral corpora striata due to vasospasm and hydrocephalus after subarachnoid hemorrhage, in addition to the preexisting lacunar infarcts in the basal ganglia. This is claimed to be the first reported case of generalized choreic movement in associated with subarachnoid hemorrhage, which improved after surgery.

Diurnal change of plasma atrial natriuretic peptide concentrations in patients with congestive heart failure

Diurnal change of plasma atrial natriuretic peptide (ANP) concentration was observed in 14 patients with congestive heart failure (CHF) and in eight healthy control subjects. Blood pressure, heart rate, and plasma concentration of ANP were obtained at intervals of 4 hours beginning immediately after midnight. In the CHF group, plasma ANP concentrations at the time of blood sampling were all higher than those in the control group. Patients with severe CHF had higher plasma ANP concentrations than those in patients with less severe CHF. Plasma ANP concentration in the control group was highest at 4:00 AM and was lowest at 4:00 PM. The percent change of ANP secretion (% delta ANP): [(ANP at 4:00 AM-ANP at 4:00 PM)/ANP at 4:00 PM] x 100%, increased in the control group, while it decreased in the CHF group. Moreover, % delta ANP was much lower in patients with severe CHF than it was in patients with less severe CHF. There was a possible relation between the severity of CHF and the increase of ANP secretion associated with the relative diminution of nocturnal ANP secretion. Thus the present data imply that the diurnal change in ANP was lost in patients with CHF.

[Successful chemotherapy in undescended testicular and extragonadal germ cell tumors: report of 2 cases]

Two patients with advanced germ cell tumor who entered complete remission following intensive combination chemotherapy, radiation therapy and surgical intervention are reported. A 28-year-old businessman presented with abdominal pain and masses associated with an elevated HCG level for which he underwent exploratory laparotomy. Large retroperitoneal masses were found and microscopical examination of the masses were revealed seminoma. Three courses of combination chemotherapy consisting of CDDP, VLB and PEP were given to the patient followed by radiation therapy to the parailiac, paraaortic, mediastinal and supraclavicular lymph nodes with boost irradiation to the paraaortic lymph nodes where the large masses were located. The other patient was a 21-year-old student who developed sharp precordial chest pain which proved to be due to a large mediastinal mass accompanied by an elevated AFP level. He was treated with radiation therapy to the mediastinum, surgical resection and combination chemotherapy. However, he showed recurrence in the lungs associated with rising AFP levels, and was given a salvage chemotherapy consisting of 3 courses of CDDP, ADR, PEP and Etoposide. Both patients were successfully treated with combined modalities of treatment including intensive chemotherapy and have been off therapy without recurrence for over 12 and 4 months, respectively.