Lipid emulsion treatment for local anesthetic systemic toxicity in pediatric patients: A systematic review.

BACKGROUND: Local anesthetic systemic toxicity (LAST) is rare, but fatal; the current widely used treatment is lipid emulsion (LE). The goal of this study was to analyze and review case reports on LE treatment for LAST in pediatric patients. METHODS: We performed a systematic review using case reports on LE treatment for LAST in pediatric patients, searching PubMed and Scopus databases to March 2023 using the following keywords: ("local anesthetic toxicity" OR "local anesthetic systemic toxicity" OR LAST") AND ("newborn" OR "infant" OR "child" OR "children" OR "adolescent" OR "pediatric") AND ("lipid emulsion" OR "Intralipid"). RESULTS: Our search yielded 21 cases, revealing that nearly 43% patients with LAST were less than 1 year old, and most cases were caused by bupivacaine (approximately 67% cases). "Inadvertent intravascular injection" by anesthesiologists and "overdose of local anesthetics" mainly by surgeons were responsible for 52% and 24% cases of LAST, respectively. LAST occurred in the awake state (52%) and under general anesthesia (48%), mainly causing seizures and arrhythmia, respectively. Approximately 55% of patients received LE treatment in <10 minutes after LAST, mainly improving cardiovascular symptoms. A 20% LE (1.5 mL/kg) dose followed by 0.25 mL/kg/minutes dose was frequently used. LE and anticonvulsants were mainly used in the awake state, whereas LE with or without vasopressors was mainly used under general anesthesia. LE treatment led to full recovery from LAST in 20 cases; however, 1 patient died due to underlying disease. CONCLUSION: Consequently, our findings reveal that LE is effective in treating pediatric LAST.

Epidermal growth factor receptor phosphorylation contributes to levobupivacaine-induced contraction in isolated rat aorta.

Vasoconstriction induced by levobupivacaine, a local anesthetic, is mediated by increased levels of calcium, tyrosine kinase, c-Jun NH2-terminal kinase (JNK), and phospholipase D, which are associated with prolonged local anesthesia. Epidermal growth factor receptor (EGFR) phosphorylation is associated with vasoconstriction. However, its role in levobupivacaine-induced contractions remains unknown. We determined whether EGFR phosphorylation is associated with levobupivacaine-induced contractions in isolated rat thoracic aortas and identified the underlying cellular signaling pathways. The effects of various inhibitors and a calcium-free solution alone or in combination on levobupivacaine-induced contractions were then assessed. Furthermore, we examined the effects of various inhibitors on levobupivacaine-induced EGFR and JNK phosphorylation and calcium levels in vascular smooth muscle cells (VSMCs) of rat aortas. The EGFR tyrosine kinase inhibitor AG1478, matrix metalloproteinase (MMP) inhibitor GM6001, Src kinase inhibitors PP1 and PP2, and JNK inhibitor SP600125 attenuated levobupivacaine-induced contractions. Moreover, although the calcium-free solution abolished levobupivacaine-induced contractions, calcium reversed this inhibitory effect. The magnitude of the calcium-mediated reversal of abolished levobupivacaine-induced contractions was lower in the combination treatment with calcium-free solution and AG1478 than in the treatment with calcium-free solution alone. Levobupivacaine induced EGFR and JNK phosphorylation. However, AG1478, GM6001, and PP2 attenuated levobupivacaine-induced EGFR and JNK phosphorylation. Moreover, although levobupivacaine induced JNK phosphorylation in control siRNA-transfected VSMCs, EGFR siRNA inhibited levobupivacaine-induced JNK phosphorylation. Furthermore, AG1478 inhibited levobupivacaine-induced calcium increases in VSMCs. Collectively, these findings suggest that levobupivacaine-induced EGFR phosphorylation, which may occur via the Src kinase-MMP pathway, contributes to vasoconstriction via JNK phosphorylation and increased calcium levels.

Correction: Chloroquine inhibits vasodilation induced by ATP-sensitive potassium channels in isolated rat aorta.

Another affiliation: 2 Department of Anesthesiology and Pain Medicine, Gyeongsang National University College of Medicine, Jinju-si, Gyeongsangnam-do, Republic of Korea was added for the author Kyeong-Eon Park at his own request.

Lipid Emulsion Inhibits Amlodipine-Induced Nitric Oxide-Mediated Vasodilation in Isolated Rat Aorta.

This study aimed to examine the effect of lipid emulsion on the vasodilation induced by a toxic dose of amlodipine in isolated rat aorta and elucidate its mechanism, with a particular focus on nitric oxide. The effects of endothelial denudation, NW-nitro-L-arginvine methyl ester (L-NAME), methylene blue, lipid emulsion, and linolenic acid on the amlodipine-induced vasodilation and amlodipine-induced cyclic guanosine monophosphate (cGMP) production were examined. Furthermore, the effects of lipid emulsion, amlodipine, and PP2, either alone or combined, on endothelial nitric oxide synthase (eNOS), caveolin-1, and Src-kinase phosphorylation were examined. Amlodipine-induced vasodilation was higher in endothelium-intact aorta than in endothelium-denuded aorta. L-NAME, methylene blue, lipid emulsion, and linolenic acid inhibited amlodipine-induced vasodilation and amlodipine-induced cGMP production in the endothelium-intact aorta. Lipid emulsion reversed the increased stimulatory eNOS (Ser1177) phosphorylation and decreased inhibitory eNOS (Thr495) phosphorylation induced via amlodipine. PP2 inhibited stimulatory eNOS, caveolin-1, and Src-kinase phosphorylation induced via amlodipine. Lipid emulsion inhibited amlodipine-induced endothelial intracellular calcium increase. These results suggest that lipid emulsion attenuated the vasodilation induced via amlodipine through inhibiting nitric oxide release in isolated rat aorta, which seems to be mediated via reversal of stimulatory eNOS (Ser1177) phosphorylation and inhibitory eNOS (Thr495) dephosphorylation, which are also induced via amlodipine.

Chloroquine inhibits vasodilation induced by ATP-sensitive potassium channels in isolated rat aorta.

This study examined the effect of chloroquine on vasodilation induced by levcromakalim in isolated endothelium-denuded rat aortas and clarified the underlying mechanisms. We examined the effects of chloroquine, hydroxychloroquine, lipid emulsion, reactive oxygen species (ROS) scavenger N-acetyl-ʟ-cysteine (NAC), and KATP channel inhibitor glibenclamide on levcromakaliminduced vasodilation. The effects of chloroquine, hydroxychloroquine, NAC, and levcromakalim on membrane hyperpolarization and ROS production were examined in aortic vascular smooth muscle cells (VSMCs). Chloroquine inhibited levcromakalim-induced vasodilation more than hydroxychloroquine. NAC attenuated chloroquine-mediated inhibition of levcromakalim-induced vasodilation, while lipid emulsion had no effect. Glibenclamide eliminated levcromakalim-induced vasodilation in aortas pretreated with chloroquine. Chloroquine and hydroxychloroquine inhibited levcromakalim-induced membrane hyperpolarization in VSMCs. Chloroquine and hydroxychloroquine both produced ROS, but chloroquine produced more. NAC inhibited chloroquine-induced ROS production in VSMCs. Collectively, these results suggest that, partially through ROS production, chloroquine inhibits levcromakalim-induced vasodilation. In addition, chloroquine-induced KATP channel-induced vasodilation impairment was not restored by lipid emulsion.

Lipid emulsion-induced recovery from unconsciousness caused by lidocaine toxicity: A case report.

Lipid emulsion is used to treat systemic toxicity caused by local anesthetics. In addition, lipid emulsion was reported to be effective in ameliorating cardiovascular depression evoked by non-local anesthetic drug toxicity with high lipid solubility. A 47-year-old woman underwent local anesthetic infiltration with 40 mL of 2% lidocaine (20 and 20 mL) to remove a mass in the upper back. After operation, she experienced convulsions and loss of consciousness due to lidocaine toxicity. Midazolam followed by lipid emulsion was administered to treat central nervous system symptoms including unconsciousness and decreased Glasgow Coma Scale. The patient recovered from unconsciousness and presented improved Glasgow Coma Scale after lipid emulsion administration, and then fully recovered from local anesthetic systemic toxicity. This case suggests that early lipid emulsion treatment, before further progression of local anesthetic systemic toxicity, provides an enhanced recovery from unconsciousness and decreased Glasgow Coma Scale due to lidocaine toxicity.

Mechanisms underlying lipid emulsion resuscitation for drug toxicity: a narrative review.

Currently, lipid emulsion (LE) is widely used to treat local anesthetic systemic toxicity (LAST). LE also ameliorates intractable cardiovascular collapse caused by lipid-soluble non-local anesthetic drug toxicity. This review aims to provide the underlying mechanism of LE resuscitation in drug toxicity (including LAST) and a detailed description of LE treatment and to discuss further research directions. We searched for relevant articles using the following keywords: "local anesthetic systemic toxicity or LAST or toxicity or intoxication or poisoning" and "Intralipid or lipid emulsion". The underlying mechanisms of LE treatment can be classified into indirect and direct effects. One indirect effect known as the lipid shuttle is a commonly accepted mechanism of LE treatment. The lipid shuttle involves the absorption of highly lipid-soluble drugs (e.g., bupivacaine) from the heart and brain through the lipid phase, which are then delivered to the muscle, adipose tissue, and liver for storage and detoxification. The direct effects include inotropic effects, fatty acid supply, attenuation of mitochondrial dysfunction, glycogen synthase kinase-3ß phosphorylation, and inhibition of nitric oxide. These mechanisms appear to act synergistically to treat drug toxicity. The recommended protocol for LE treatment of LAST is as follows: a bolus administration of 20% LE at 1.5 ml/kg over 2-3 min followed by 20% LE at 0.25 ml/kg/min. LAST most commonly occurs after intravenous administration of local anesthetics. However, non-local anesthetic drugs that cause drug toxicity are orally administered. Further studies are needed to determine the optimal dosing schedule of LE treatment for non-local anesthetic drug toxicity.

Lipid Emulsion Treatment for Drug Toxicity Caused by Nonlocal Anesthetic Drugs in Pediatric Patients: A Narrative Review.

OBJECTIVE: Lipid emulsion (LE) has been used to treat children with cardiovascular collapse induced by toxic doses of nonlocal anesthetics with high lipid solubility. We aimed to analyze case reports on LE administration for resuscitation of toxicity induced by these drugs in pediatric patients. METHODS: Case reports involving pediatric patients undergoing LE treatment for toxicity caused by nonlocal anesthetic drugs until December 31, 2021, were searched through PubMed and Scopus using the following terms: "toxicity, or intoxication, or poisoning, or overdose" and "LE or intralipid." RESULTS: Twenty-eight cases on LE treatment for toxicity induced by nonlocal anesthetic drugs in pediatric patients (younger than 19 years) were retrieved. The total number of patients was 31. Lipid emulsion treatment was carried out during toxicity caused by amitriptyline, flecainide, bupropion, propranolol, and lamotrigine, which was unresponsive to supportive treatment. These drugs are highly lipid-soluble and inhibit cardiac sodium channels, which is similar to pharmacological properties of the local anesthetic bupivacaine. The most frequent method of delivery involved bolus administration followed by continuous infusion; 1.5 mL/kg LE administration followed by 0.25 mL/kg/min LE was most frequently used. Lipid emulsion improved various symptoms of drug toxicity in 29 patients (29/31, 93.54%), and symptoms were improved in 14 patients (14/31, 45.16%) within an h after LE administration. The trend in frequency of improved symptoms after LE treatment was as follows: the cardiovascular symptom alone > symptoms of the central nervous system alone > symptoms of the cardiovascular and central nervous systems. The adverse effects of LE treatment in the reported cases were hypertriglyceridemia, mild pancreatitis, and elevated levels of aspartate and alanine aminotransaminases. CONCLUSIONS: Lipid emulsion treatment may be effective in ameliorating intractable cardiovascular depression when systemic toxicity caused by drugs, including cardiac sodium channel blockers, is unresponsive to supportive treatments.

Lipid emulsion inhibits the cardiac toxicity caused by chloroquine via inhibition of reactive oxygen species production.

BACKGROUND: Lipid emulsion (LE) is effective in treating intractable cardiac depression induced by the toxicity of highly lipid-soluble drugs including local anesthetics. However, the effect of LE on chloroquine (CQ)-evoked cardiac toxicity remains unclear. This study aimed to examine the effect of Lipofundin MCT/LCT, an LE, on the cardiotoxicity caused by CQ in H9c2 rat cardiomyoblasts and elucidate the underlying cellular mechanism. METHODS: The effects of CQ (1 × 10-4 M), LE, and the reactive oxygen species (ROS) scavengers mitotempo and N-acetyl-L-cysteine (NAC), alone or combined, on cell viability and migration, apoptosis, ROS production, calcium levels, mitochondrial membrane potential, and adenosine triphosphate (ATP) were examined. Additionally, the effects of LE on the activities of catalase (CAT), malondialdehyde (MDA), and superoxide dismutase (SOD) induced by CQ were assessed. RESULTS: Pretreatment with LE, mitotempo, or NAC reversed the reduction in cell migration and viability, mitochondrial membrane potential, and ATP levels evoked by CQ, and inhibited the increase in cleaved caspase-3, ROS, and calcium concentration induced by CQ. LE inhibited the increase in Bax expression, terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells, MDA activity, and late apoptosis, and reversed the reduction in SOD and CAT activity induced by CQ. CQ did not significantly affect cleaved caspase-8 expression, and LE did not significantly affect CQ concentration. CONCLUSIONS: Collectively, these results suggest that LE (Lipofundin MCT/LCT) inhibits the cardiotoxicity and late apoptosis induced by CQ toxicity via the intrinsic mitochondrial apoptotic pathway that is associated with direct inhibition of ROS production.

Novel Chitosan Dermal Filler with Enhanced Moldability and Elasticity.

Currently, dermal fillers are largely based on commercialized cross-linked hyaluronic acid (HA) injections, which require a large injection force. Additionally, HA can be easily decomposed by enzymes, and HA-treated tissues present a risk of developing granuloma. In this study, a chitosan-based dermal filler is presented that operates on a liquid-to-gel transition and allows the injection force to be kept ≈4.7 times lower than that required for HA injections. Evaluation of the physical properties of the chitosan filler indicates high viscoelasticity and recovery rate after gelation at 37 °C. Furthermore, in an in vivo evaluation, the liquid injection-type chitosan filler transitions to a gel state within 5 min after injection into the body, and exhibits a compressive strength that is ≈2.4 times higher than that of cross-linked HA. The filler also exhibits higher moldability and maintains a constant volume in the skin for a longer time than the commercial HA filler. Therefore, it is expected that the chitosan filler will be clinically applicable as a novel material for dermal tissue restoration and supplementation.

Lipid emulsion attenuates propranolol-induced early apoptosis in rat cardiomyoblasts.

OBJECTIVE: Propranolol is used to treat several cardiovascular diseases; however, toxic doses of propranolol cause severe myocardial depression and cardiac arrest. The aim of this study was to examine the effects of lipid emulsion (LE) on cardiotoxicity induced by toxic doses of propranolol in H9C2 rat cardiomyoblast cell line and to elucidate the underlying mechanism. METHODS: The experimental groups comprised control, propranolol alone, esmolol alone, or LE followed by propranolol or esmolol treatment, and reactive oxygen species (ROS) inhibitor N-acetyl-L-cysteine (NAC) followed by propranolol treatment. The effects of propranolol, esmolol, NAC, and LE, alone or in combination, on cell viability, apoptosis, and ROS production were examined. Additionally, we investigated the effect of LE on propranolol concentration. RESULTS: LE and NAC reversed the inhibition of cell viability induced by propranolol (p < .001). However, LE had no effect on the inhibition of cell viability caused by esmolol. The LE inhibited propranolol-induced expressions of cleaved caspase-3 (p < .001), caspase-9 (p < .001), and Bax (p < .01), but not caspase-8. NAC inhibited the propranolol-induced expression of cleaved caspase-3. LE inhibited propranolol-induced early apoptosis, but had no effect on late apoptosis. Additionally, LE inhibited the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells generated by propranolol. It attenuated propranolol-induced ROS production. However, it had no effect on propranolol concentration. CONCLUSION: LE inhibits early apoptosis caused by a toxic dose of propranolol by suppressing the intrinsic apoptotic pathway, via direct inhibition of ROS production.

Early Use of ECMO for Refractory Kounis Syndrome Concealed by General Anesthesia-A Case Report.

A 46-year-old woman demonstrated refractory Kounis syndrome (KS) after induction of anesthesia. Despite conventional management of anaphylaxis and advanced cardiac life support, her cardiovascular function continued to deteriorate until she had a cardiac arrest, and after extracorporeal membrane oxygenation (ECMO) therapy, electrical cardiac activity reappeared. A large number of patients with KS-"allergic angina syndrome"-has been known to recover well with vasodilators; however, this patient showed antibiotics-induced refractory KS during general anesthesia. Severe bronchospasms with desaturation appeared as initial anaphylactic features; however, these did not respond to conventional treatment for anaphylaxis. Patient's hemodynamic signs eventually worsened, leading to cardiac arrest despite ephedrine administration and chest compressions. During cardiopulmonary cerebral resuscitation, the central line was secured, and epinephrine, atropine, as well as sodium bicarbonate were administered repeatedly; nevertheless, cardiac arrest was sustained. After initiation of veno-arterial ECMO, atrial fibrillation was observed, which was later converted to sinus tachycardia by electrical cardioversions and amiodarone. Coronary angiography was performed before the patient was admitted to the intensive care unit; there were no indications of an impending cardiac arrest. The patient was discharged uneventfully owing to early use of ECMO despite the emergence of KS symptoms that were initially masked by anesthesia but later worsened abruptly.

Dexmedetomidine-Induced Aortic Contraction Involves Transactivation of the Epidermal Growth Factor Receptor in Rats.

In this study, we examined whether aortic contraction, induced by the alpha-2 adrenoceptor agonist dexmedetomidine, is involved in the transactivation of the epidermal growth factor receptor (EGFR) in isolated endothelium-denuded rat aortas. Additionally, we aimed to elucidate the associated underlying cellular mechanisms. The effects of the alpha-2 adrenoceptor inhibitor rauwolscine, EGFR tyrosine kinase inhibitor AG1478, Src kinase inhibitors PP1 and PP2, and matrix metalloproteinase inhibitor GM6001 on EGFR tyrosine phosphorylation and c-Jun NH2-terminal kinase (JNK) phosphorylation induced by dexmedetomidine in rat aortic smooth muscles were examined. In addition, the effects of these inhibitors on dexmedetomidine-induced contraction in isolated endothelium-denuded rat aorta were examined. Dexmedetomidine-induced contraction was inhibited by the alpha-1 adrenoceptor inhibitor prazosin, rauwolscine, AG1478, PP1, PP2, and GM6001 alone or by a combined treatment with prazosin and AG1478. AG1478 (3 × 10-6 M) inhibited dexmedetomidine-induced contraction in isolated endothelium-denuded rat aortas pretreated with rauwolscine. Dexmedetomidine-induced EGFR tyrosine and JNK phosphorylation were inhibited by rauwolscine, PP1, PP2, GM6001, and AG1478. Furthermore, dexmedetomidine-induced JNK phosphorylation reduced upon EGFR siRNA treatment. Therefore, these results suggested that the transactivation of EGFR associated with dexmedetomidine-induced contraction, mediated by the alpha-2 adrenoceptor, Src kinase, and matrix metalloproteinase, caused JNK phosphorylation and increased calcium levels.

Fulminant Giant Cell Myocarditis following Heterologous Vaccination of ChAdOx1 nCoV-19 and Pfizer-BioNTech COVID-19.

A 48-year-old female patient underwent a heart transplantation for acute fulminant myocarditis, following heterologous vaccination with the ChAdOx1 nCoV-19 and Pfizer-BioNTech COVID-19. She had no history of severe acute respiratory syndrome coronavirus-2 infection. She did not exhibit clinical signs or have laboratory findings of concomitant infection before or after vaccination. Heart transplantation was performed because her heart failed to recover with venoarterial extracorporeal oxygenation support. Organ autopsy revealed giant cell myocarditis, possibly related to the vaccines. Clinicians may have to consider the possibility of the development of giant cell myocarditis, especially in patients with rapidly deteriorating cardiac function and myocarditis symptoms after COVID-19 vaccination.

Lipid emulsions attenuate the inhibition of carnitine acylcarnitine translocase induced by toxic doses of local anesthetics in rat cardiomyoblasts.

The aim of this study was to examine the effects of lipid emulsions on carnitine palmitoyltransferase I (CPT-I), carnitine acylcarnitine translocase (CACT), carnitine palmitoyltransferase II (CPT-II), and the mitochondrial dysfunctions induced by toxic doses of local anesthetics in H9c2 rat cardiomyoblasts. The effects of local anesthetics and lipid emulsions on the activities of CPT-I, CACT, and CPT-II, and concentrations of local anesthetics were examined. The effects of lipid emulsions, N-acetyl-L-cysteine (NAC), and mitotempo on the bupivacaine-induced changes in cell viability, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), and intracellular calcium levels were examined. CACT, without significantly altering CPT-I and CPT-II, was inhibited by toxic concentration of local anesthetics. The levobupivacaine- and bupivacaine-induced inhibition of CACT was attenuated by all concentrations of lipid emulsion, whereas the ropivacaine-induced inhibition of CACT was attenuated by medium and high concentrations of lipid emulsion. The concentration of levobupivacaine was slightly attenuated by lipid emulsion. The bupivacaine-induced increase of ROS and calcium and the bupivacaine-induced decrease of MMP were attenuated by ROS scavengers NAC and mitotempo, and the lipid emulsion. Collectively, these results suggested that the lipid emulsion attenuated the levobupivacaine-induced inhibition of CACT, probably through the lipid emulsion-mediated sequestration of levobupivacaine.

Ultrasound-guided central venous catheterization via internal jugular vein in a patient with subcutaneous neck emphysema: A case report.

In patients with subcutaneous neck emphysema, ultrasound images of the internal jugular vein are unclear due to air bubbles. Central venous catheterization can be safely achieved by pushing the accumulated air laterally using an ultrasound probe.

The Emergence of Creative Leaders Within Social Networks: The Case of Andy Warhol in the Art World of New York.

The creative leadership literature has identified personality traits, skills, states, and behaviours which are effective within creative contexts and organisations, but it is yet to address how creative leaders emerge from social networks. This conceptual paper delineates the processes of creative leader emergence within the context of contemporary visual arts. Using a relational view of creative leader emergence, this paper incorporates the leader emergence processes of achievement and ascription, and then adjusts them to the context of the art world. We argue that both competence and identity contribute to the status construction of creative leaders by enabling their emergence within social networks. In addition to the processes of leader prototypicality through which leaders emerge within groups, we also identify processes of leader atypicality through which creative leaders emerge within network structures. Finally, our conceptual analysis is illustrated by the case of Pop artist Andy Warhol, focusing on his emergence as a creative leader within the art world of New York and his art studio, the factory.

Nitric oxide-dependent vasodilation induced by minoxidil in isolated rat aorta.

We examined the effect of endothelium and lipid emulsion on vasodilation induced by minoxidil at a toxic dose and determined the underlying mechanism. The effects of endothelial denudation, NW-nitro-L-arginine methyl ester (L-NAME), methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one (ODQ), and glibenclamide, alone or in combination, on minoxidil-induced vasodilation in endothelium-intact rat aorta were examined. Additionally, the effects of lipid emulsion on minoxidil-induced membrane hyperpolarization and minoxidil concentration were examined. The vasodilatory effects of minoxidil at the toxic dose were higher in endothelium-intact aorta than in endothelium-denuded aorta. L-NAME, methylene blue, ODQ, and glibenclamide attenuated minoxidil-induced vasodilation of endothelium-intact rat aorta. Combined treatment with L-NAME and glibenclamide almost eliminated minoxidil-induced vasodilation. However, lipid emulsion pretreatment did not significantly alter minoxidil-induced vasodilation. Lipid emulsion did not significantly alter minoxidil-induced membrane hyperpolarization and minoxidil concentration. Overall, minoxidil-induced vasodilation is mediated by ATP-sensitive potassium channels and pathways involving nitric oxide and guanylate cyclase.

Lipid Emulsion Enhances Vasoconstriction Induced by Dexmedetomidine in the Isolated Endothelium-Intact Aorta.

This study aimed to examine the effect of lipid emulsion (LE) on the vasoconstriction induced by dexmedetomidine (DMT) in the isolated rat aorta and elucidate the associated cellular mechanism. The effect of LE, NW-nitro-L-arginine methyl ester (L-NAME), and methyl-ß-cyclodextrin (MßCD) on the DMT-induced contraction was examined. We investigated the effect of LE on the DMT-induced cyclic guanosine monophosphate (cGMP) formation and DMT concentration. The effect of DMT, LE, 4-Amino-3-(4-chlorophenyl)-1-(t-butyl)-1H-pyrazolo[3,4-d]pyrimidine,4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2), and rauwolscine on the phosphorylation of endothelial nitric oxide synthase (eNOS), caveolin-1, and Src kinase was examined in the human umbilical vein endothelial cells. L-NAME, MßCD, and LE (1%, standardized mean difference (SMD): 2.517) increased the DMT-induced contraction in the endothelium-intact rat aorta. LE (1%) decreased the DMT (10-6 M) concentration (SMD: -6.795) and DMT-induced cGMP formation (SMD: -2.132). LE (1%) reversed the DMT-induced eNOS (Ser1177 and Thr496) phosphorylation. PP2 inhibited caveolin-1 and eNOS phosphorylation induced by DMT. DMT increased the Src kinase phosphorylation. Thus, LE (1%) enhanced the DMT-induced contraction by inhibition of NO synthesis, which may be caused by the decreased DMT concentration. DMT-induced NO synthesis may be caused by the increased eNOS (Ser1177) phosphorylation and decreased eNOS (Thr495) phosphorylation potentially mediated by Src kinase-induced caveolin-1 phosphorylation.