Involvement of monocyte-derived extracellular vesicle-associated tissue factor activity in convallatoxin-induced hypercoagulability

OBJECTIVES

Convallatoxin (CNT) is a natural cardiac glycoside extracted from lily of the valley ( Convallaria majalis ). Although it is empirically known to cause blood coagulation disorders, the underlying mechanism remains unclear. CNT exerts cytotoxicity and increases tissue factor (TF) expression in endothelial cells. However, the direct action of CNT on blood coagulation remains unclear. Therefore, herein, we investigated the effects of CNT on whole blood coagulation system and TF expression in monocytes.

METHODS

Blood samples were collected from healthy volunteers to measure plasma thrombin-antithrombin complex (TAT) concentration using ELISA and to perform rotational thromboelastometry (ROTEM) and whole-blood extracellular vesicle (EV)-associated TF (EV-TF) analysis. The effects of CNT were also investigated using the monocytic human cell line THP-1. Quantitative real-time PCR and western blotting were performed, and PD98059, a mitogen-activated protein kinase (MAPK) inhibitor, was used to elucidate the action mechanism of CNT-mediated TF production.

RESULTS

CNT treatment increased EV-TF activity, shortened the whole blood clotting time in rotational thromboelastometry analysis, and increased TAT levels, which is an index of thrombin generation. Furthermore, CNT increased TF mRNA expression in THP-1 cells and EV-TF activity in the cell culture supernatant. Therefore, CNT may induce a hypercoagulable state with thrombin generation, in which elevated EV-TF activity derived from monocytes might be involved. These procoagulant effects of CNT were reversed by PD98059, suggesting that CNT-induced TF production in monocytes might be mediated by the MAPK pathway.

CONCLUSIONS

The findings of the present study have further clarified the procoagulant properties of CNT.

Arterial thromboxane A2-induced transient contraction after IL-1β exposure

The involvement of thromboxane A2 (TXA2) in systemic inflammation and infection is well recognized. However, there are few reports on the involvement of prostanoids in warm shock (the initial pathology of sepsis). Previous studies showed that interleukin (IL)-1β causes a rapid inducible nitric oxide synthase/nitric oxide (iNOS/NO)-mediated relaxation in peripheral blood vessels during warm shock. Furthermore, a transient contraction was seen before this relaxation occurred. The present study aimed to elucidate the mechanism of this transient contraction. We measured isometric tension changes in the superior mesenteric arteries from normal male Wistar rats by adding IL-1β at the point of maximum contraction by phenylephrine (Ph). The same study was performed for each vessel pretreated with various inhibitors, including SQ29548, a TXA2 receptor antagonist, 30 min before Ph contraction. In addition, the concentration of thromboxane B2 (TXB2) in SMA was measured by probe electrospray ionization. Treatment of endothelial vessels with cyclooxygenase 1 (COX1)/2 inhibitors SC560/NS398 and TXA2 receptor antagonist SQ29548 suppressed IL-1β–induced transient contractions. This transient contraction reaction was derived from TXA2. Additionally, gene expression of COX2/TXA2 synthetase and the concentration of TXB2 were significantly increased in IL-1β-exposed vessels. It was demonstrated for the first time in inflamed blood vessels that endothelial cell-derived COX2/TXA2 is induced before iNOS and causes transient contractions. TXA2 may be considered an early sign of warm shock or as a biological defense mechanism in the early stages of septic shock.

Endothelium-Independent Relaxation of Vascular Smooth Muscle Induced by Persimmon-Derived Polyphenol Phytocomplex in Rats

The vasorelaxant effect of polyphenols is well known, and the mortality rate due to coronary artery disease is low in people who consume polyphenol-containing foods. We aimed to elucidate the mechanism by which polyphenols derived from persimmon juice (PJ) and persimmon leaves (PLs) induce vasorelaxation and suppress vasocontraction in the superior mesenteric arteries isolated from male Sprague Dawley rats. Vasocontraction was induced with 1 µM phenylephrine, and polyphenol-induced vasorelaxation was expressed as a percentage of the previous tone induced by phenylephrine. PJ powder (100 mg/L) induced higher levels of vasorelaxation (mean ± standard error of the mean, 88.6% ± 4.4%) than PLs powder (1 g/L; 72.0% ± 10.8%). Nitric oxide pathway inhibitors (NG-nitro-L-arginine methyl ester + carboxy-PTIO) did not affect persimmon-derived polyphenol-induced vasorelaxation, whereas potassium chloride, tetraethylammonium, and potassium-channel inhibitors did. Vasorelaxation was endothelium independent with both extracts. Phenylephrine-induced vasocontraction was suppressed by pretreatment with PJ and PLs powder, even when inositol triphosphate-mediated Ca²⁺ release and extracellular Ca²⁺ influx were inhibited. These results suggest that persimmon-derived polyphenol phytocomplex cause vasorelaxation and inhibit vasocontraction through hyperpolarization of smooth muscle cells. Persimmon-derived polyphenols may be able to prevent cardiovascular diseases caused by abnormal contraction of blood vessels.

Convallatoxin, the primary cardiac glycoside in lily of the valley (Convallaria majalis), induces tissue factor expression in endothelial cells

BACKGROUND

Convallotoxin (CNT), present in lily of the valley (Convallaria majalis), is a toxin that causes food poisoning among humans and companion animals. Although various symptoms of CNT poisoning have been well described, hypercoagulability owing to CNT is only empirically known among some veterinarians, and the underlying mechanism remains to be elucidated. CNT exerts cytotoxic effects on endothelial cells.

OBJECTIVES

This study aimed to determine whether CNT induces the expression of tissue factor (TF), a potent initiator of the extrinsic coagulation cascade, in endothelial cells and leads to a hypercoagulable state.

METHODS

Human umbilical vein endothelial cells (HUVECs) were used for in vitro experiments. HUVECs were treated with or without CNT (50 and 100 nM) for 4 h. Phosphate-buffered saline was used as a control. Cell viability was determined using the WST-8 assay. Quantitative real-time polymerase chain reaction was performed to determine TF mRNA expression. TF protein expression was observed using a laser scanning confocal microscope.

RESULTS

The viability of HUVECs significantly reduced after CNT treatment compared with that of non-treated cells (p < 0.05). Moreover, a significant increase in TF mRNA and protein expression was observed after 4 h of CNT treatment. CNT elicited these effects in a dose-dependent manner.

CONCLUSIONS

TF expression induced by CNT in endothelial cells can contribute to the development of a hypercoagulable state. The present study partially revealed the mechanisms underlying the CNT-induced hypercoagulable state. The findings can contribute to the development of a novel therapy for lily of the valley poisoning.

Cardiac sudden death in a young cannabis user

We report a case of sudden death due to acute coronary syndrome (ACS) in a young cannabis user. A man in his late thirties died at home, and marijuana was found. The autopsy revealed severe occlusion by an atherosclerotic plaque in the left anterior descending artery. The histopathological examination revealed ischemic changes, likely caused by cannabis-induced sympathetic β-adrenergic stimulation. Both cannabinoid receptors (CB1 and CB2) were expressed in the atherosclerotic lesions. The CB2 expression was higher than CB1 expression in the atherosclerotic plaque, corresponding to macrophage infiltration. Since cannabis is regarded as a casual drug due to its lower levels of dependency, some individuals have supported legalized marijuana use. However, this case report will provide cautions on the casual use of cannabis.

Induced Pluripotent Stem Cell-Derived Hematopoietic Embryoid Bodies Improve Mouse Status in Septic Peritonitis

We examined the efficacy of embryoid bodies from 6-day induced pluripotent stem cells an in vivo sepsis model. Injection of embryoid bodies to septic mice improved the condition of their lungs and significantly increased their survival rate. Although embryoid bodies secretedsphingosine-1-phosphate in vitro, its serum levels in mouse plasma were significantly reduced compared to that in the control (untreated mice receiving PBS). Low concentrations of sphingosine-1-phosphate protected endothelial cells, while high concentrations disrupted endothelial barrier integrity. Therefore, exogenous sphingosine-1-phosphate secreted by embryoid bodies during early stage of sepsis might down regulate endogenous production of sphingosine-1-phosphate. Inhibition of excessive sphingosine-1-phosphate release protects against endothelial injury and suppresses a vicious cycle of inflammatory reactions. The obtained results open new prospects in induced pluripotent stem cells-based therapy for sepsis.

Enhancement of Tissue Factor Expression in Monocyte-Derived Dendritic Cells by Pentraxin 3 and Its Modulation by C1 Esterase Inhibitor

BACKGROUND

We have previously shown that human monocyte-derived dendritic cells (moDCs) may participate in immune system-mediated hypercoagulable state through enhanced tissue factor (TF) expression and that the complement system may be involved in this process.

OBJECTIVES

The aim of this study was to explore the role of pentraxin 3 (PTX3) and the complement system in enhanced TF expression in moDCs.

METHODS

moDCs were generated from isolated human monocytes. PTX3 levels in whole human blood supplemented with moDCs were determined after lipopolysaccharide (LPS) stimulation. PTX3 release by the generated moDCs upon LPS stimulation was also assessed. The effect of PTX3 on whole blood coagulation was investigated using thromboelastometric analysis. TF expression in stationary moDCs treated with LPS and/or PTX3 was determined by measuring TF activity. The effect of complement inhibitors on TF activity in moDCs treated with LPS and/or PTX3 under low-shear conditions was evaluated.

RESULTS

PTX3 levels were higher in whole blood supplemented with moDCs than in the presence of monocytes and were further elevated by LPS stimulation. PTX3 release from generated moDCs was also increased by LPS stimulation. PTX3 reduced whole blood coagulation time in a dose-dependent manner. However, PTX3 did not increase TF expression in stationary moDCs. Under low-shear conditions, PTX3 increased TF expression in moDCs. C1 esterase inhibitor (C1-inh) suppressed this effect.

CONCLUSIONS

PTX3 might have a thrombophilic activity and enhance TF expression in moDCs under low-shear conditions. Furthermore, suppression of moDC-associated hypercoagulability by C1-inh might be partly ascribed to its inhibitory effect on PTX3.

Acute ethanol intoxication suppresses pentraxin 3 expression in a mouse sepsis model involving cecal ligation and puncture

Acute ethanol intoxication impairs immunological reactions and increases the risk of sepsis; however, the underlying mechanism remains unclear. Pentraxin (PTX) 3 is a humoral pattern recognition receptor whose levels rapidly increase in response to inflammation. PTX3 production is triggered by tumor necrosis factor (TNF)-α and is mediated by c-Jun N-terminal kinase (JNK). As PTX3 exerts protective effects against sepsis as well as acute lung injury, we investigated whether acute ethanol exposure exacerbates sepsis by altering PTX3 expression. Sepsis was induced in C57/BL6 mice by cecal ligation and puncture (CLP) after ethanol/saline administration. Survival rates were significantly lower in ethanol-treated than in saline-treated mice. Increased vascular permeability and attenuation of PTX3 expression were observed in the lungs of ethanol-treated mice 4 h after CLP. Concomitant with a delayed increase of plasma TNF-α in ethanol-treated mice, plasma PTX3 was also suppressed in the early phase of sepsis. Although TNF-α level in ethanol-treated mice exceeded that in saline-treated mice 16 h after CLP, PTX3 levels were still suppressed in the former group. JNK phosphorylation in lung tissue was suppressed in both groups 4 and 16 h after CLP. Furthermore, JNK phosphorylation in ethanol-treated human umbilical vein endothelial cells was suppressed even in the presence of exogenous TNF-α, resulting in inhibition of PTX3 mRNA and protein expression. Our results suggest that ethanol suppresses de novo PTX3 synthesis via two mechanisms - i.e., suppression of TNF-α production and inhibition of JNK phosphorylation. PTX3 suppression may therefore contribute to exacerbation of sepsis in acute ethanol intoxication.

Relevance of hemolysis-induced tissue factor expression on monocytes in soft clot formation in alcohol-containing blood

The fluidity of cadaveric blood is an important characteristic in the post-mortem examination of cases of asphyxial death. Although it is empirically known that soft blood clots are present in cadaveric blood containing alcohol, the relationship between such clots and blood alcohol is unclear. We addressed this issue through in vitro studies using blood collected from healthy volunteers. Assessment of global hemostasis by rotational thromboelastometry revealed that ethanol treatment enhanced the procoagulant activity of whole blood. However, ethanol inhibited epinephrine-induced platelet aggregation, whereas plasma levels of von Willebrand factor and the activity of coagulation factors VIII and IX were unaffected. In contrast, tissue factor (TF) activity was higher in plasma obtained from ethanol-treated whole blood than that in plasma from untreated blood. Ethanol induced hemolysis of red blood cells, and the consequent hemoglobin (Hb) release promoted de novo synthesis of TF in isolated monocytes, as determined by real-time reverse transcription PCR, western blotting, and flow cytometry. However, ethanol itself did not induce TF expression in monocytes. Given that TF activates the extrinsic coagulation pathway and amplifies hemostatic reactions, Hb-induced TF expression in monocytes might contribute to soft blood clot formation.

[Two autopsy cases in which previous surgery facilitated the positive identification of decomposed bodies]

The positive identification of decomposed corpses is often difficult. We describe two autopsy cases in which medical materials, which had been implanted during previous surgical treatments, facilitated positive identification. The discovery of decomposed corpses is increasingly common in Japan, due to the increasing number of lonely deaths. Implanted medical materials and devices may be a useful tool for personal identification in the near future.

Ethanol attenuates vasorelaxation via inhibition of inducible nitric oxide synthase in rat artery exposed to interleukin-1β

Nitric oxide produced by inducible nitric oxide synthase (iNOS) regulates sepsis-induced hypotension. During septic shock, interleukin (IL)-1β is synthesized in endothelial cells and smooth muscle cells by endotoxin. Ethanol (EtOH) suppresses endotoxin-induced hypotension. The present study aimed to elucidate the effect of EtOH on gradual relaxation and iNOS expression induced by IL-1β in isolated rat superior mesenteric arteries (SMAs). Exposure to IL-1β-induced contraction in SMA rings, followed by a gradual relaxation of phenylephrine precontracted tone. Contraction was abolished by indomethacin (IM), cycloheximide (Chx), and endothelium denudation. In contrast, the gradual relaxation was abolished by NOS inhibitors, Chx, endothelium denudation, and inhibited by EtOH (50 and 100 mM). However, IM had no effect on relaxation. Western blot analysis demonstrated that iNOS expression was induced by IL-1β and was inhibited by EtOH and endothelium denudation. Furthermore, messenger RNA expression of iNOS, but not endothelial NOS, was inhibited by EtOH. These data suggest that IL-1β-induced contraction is mediated by thromboxane A2, whereas IL-1β-induced relaxation occurs via NO derived from iNOS. The endothelium plays an important role in vasorelaxation. Taken together, EtOH inhibits IL-1β-mediated vasorelaxation by suppressing endothelium iNOS expression. This study provides the first evidence of EtOH -induced inhibition of IL-1β-mediated vasorelaxation.

sHLA-G and sHLA-I levels in follicular fluid are not associated with successful implantation

In the field of in vitro fertilization (IVF), useful markers for the prediction of successful implantation for oocyte or embryo selection are essential. It has been reported that sHLA-G (sHLA-G1/HLA-G5) could be detected in the supernatant of the fertilized embryo and in follicular fluid samples (FFs), and that the presence of sHLA-G was related to successful implantation. If sHLA-G could be used as a marker of oocyte selection from multiple FFs, oocytes could be selected without physical contact, thus reducing the likelihood of damage. To investigate the potential for sHLA-G as a marker of oocyte selection from multiple FFs in one patient, protein levels of total protein, sHLA-G, and sHLA-I (sHLA-A, B, and C) were examined in FFs. The variation among multiple FFs in total protein level and sHLA-G level was not related to successful pregnancy. The average sHLA-I levels did not differ in the successful implantation and unsuccessful implantation groups, indicating that sHLA-I levels were not related to successful pregnancy. Furthermore, sHLA-G in FFs was not detected by western blotting, despite being detected by ELISA, while sHLA-I was detected by both ELISA and western blot. These data suggest that sHLA-G in FF might not be a useful marker for oocyte selection as measurements of sHLA-G were inconsistent and there was no association with successful pregnancy. Further, more rigorously tested ELISA systems for detecting sHLA-G in body fluids are necessary before the utility of sHLA-G for diagnosis can be established.

[Effect of alcohol on vascular function]

Vascular function is regulated by a balance of vasoconstriction and vasorelaxation. Disorder in this balance due to alcohol consumption causes various clinical conditions. In this review, we discuss the effects of acute and chronic ethanol consumption on vascular responses, including vasoconstriction, endothelium-dependent vasorelaxation, and nerve-mediated vasorelaxation. Acute ethanol administration induces vasoconstriction in ethanol-naive animals in vitro. Furthermore, ethanol can both potentiate and suppress agonist-induced Ca(2+)-dependent vasoconstriction. Moreover, ethanol augments Ca(2+)-independent vasoconstriction by increasing Ca2+ sensitivity. Endothelium-dependent relaxation is mediated by the nitric oxide (NO) pathway and the endothelium-derived hyperpolarizing factor (EDHF) pathway. Acute ethanol treatment inhibits both NO- and EDHF-mediated relaxation. Furthermore, acute ethanol ingestion can also potentiate and suppress calcitonin gene-related peptide (CGRP)-induced nerve-mediated relaxation. These opposing effects may be due to differences in species or vascular beds. Thus, acute ethanol treatment decreases vasorelaxation, thereby shifting the contraction-relaxation balance towards contraction. Combined, these effects are one mechanism by which acute heavy alcohol consumption causes circulatory disturbances such as vasospasms or ischemic heart disease. In contrast, chronic low-dose ethanol has no effect on vasoconstriction, whereas chronic high-dose ethanol increases vasoconstriction. Additionally, chronic ethanol intake has diminished, unchanged, and even increased effects on nerve-mediated relaxation; therefore, conclusions on these effects are not possible at present. Interestingly, chronic low-dose ethanol administration enhanced endothelium-dependent relaxation; however, higher doses inhibited these responses. Therefore, regular or light-to-moderate alcohol intake increases vasorelaxation and may suppress elevated blood pressure, whereas chronic heavy alcohol consumption may raise blood pressure, causing various clinical conditions.

The Inhibitory Effect of Ethanol on Interleukin-1 β-Induced Suppression of Contractile Response in the Rat Superior Mesenteric Artery

Interleukin (IL)-1 β is a cytokine that is upregulated by the pro-inflammatory bacterial endotoxin lipopolysaccharide. This study examined the effect of ethanol on IL-1 β-mediated suppression of phenylephrine-induced contractility and inducible nitric oxide synthase (iNOS) expression in the rat superior mesenteric artery (SMA). IL-1 β suppressed the phenylephrine-induced contractile response, and this effect was inhibited by ethanol. The IL-1 β-mediated effects were also blocked by cycloheximide, an inhibitor of protein synthesis, as well as AMT and 1400W, which are iNOS inhibitors, and PTIO, an NO scavenger. However, indomethacin, a cyclooxygenase (COX) inhibitor that promotes NO-independent vasodilation, did not affect IL-1 β-mediated suppression of the contractile response. Western blot analysis revealed that iNOS levels in SMA were upregulated by IL-1 β and inhibited by ethanol (50 and 100 mM). These results indicate that the suppression of the SMA contractile response by IL-1 β requires iNOS activity, but not COX-2. Furthermore, these data suggest that ethanol inhibits the effects of IL-1 β on the contractile response via inhibition of iNOS, rather than COX-2.

Asphyxial death related to postextraction hematoma in an elderly man

We here report an autopsy case of a man in his seventies who died from asphyxia due to compression of the trachea caused by postextraction bleeding after extraction of his left mandibular third molar by a dentist in private practice. On the morning after the tooth extraction, he had complained of dyspnea and became unconscious at home. Although he was brought to the emergency room by ambulance, he died 7 days later without regaining consciousness. Autopsy examination revealed that the lingual side of the alveolar bone was fractured at the extraction socket. Moreover, subcutaneous bleeding that extended from the extraction socket to the thyrohyoid ligament in the cervical region and deviation of the epiglottis due to the bleeding were observed. Histological findings revealed liver cirrhosis; there were no significant findings in other organs. On the basis of these findings, we concluded that alveolar bone fracture occurred during the extraction and that the bleeding spread to the cervical region. Thus, the patient had died from asphyxia resulting from airway obstruction caused by cervical subcutaneous bleeding derived from postextraction bleeding. We emphasize that tooth extraction may cause fatal complications in patients with bleeding tendencies, particularly in the elderly.