Publications by authors named "Seung-Hyun Ahn"

Article Synopsis
  • Lipid emulsions are explored for their potential to counteract cardiovascular issues caused by excessive labetalol, indicating their role as therapeutic agents against drug toxicity.
  • The study found that the presence of intact endothelial cells enhances labetalol-induced vasodilation, while lipid emulsions significantly decrease this effect, regardless of endothelial presence.
  • The mechanisms behind this inhibition include reducing cyclic guanosine monophosphate (cGMP) levels, modulating endothelial nitric oxide synthase (eNOS) activity, and lowering the concentration of labetalol itself.
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Dexmedetomidine is widely used to induce sedation in the perioperative period. This study examined the effect of hypothermia (33 and 25 °C) on dexmedetomidine-induced contraction in an endothelium-intact aorta with or without the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME). In addition, the effect of hypothermia on the contraction induced by dexmedetomidine in an endothelium-denuded aorta with or without a calcium-free Krebs solution was examined.

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Vasoconstriction induced by levobupivacaine, a local anesthetic, is mediated by increased levels of calcium, tyrosine kinase, c-Jun NH-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.

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This study aimed to examine the endothelial dependence of vasodilation induced by the phosphodiesterase inhibitor theophylline in isolated rat thoracic aortas and elucidate the underlying mechanism, with emphasis on endothelial nitric oxide (NO). The effects of various inhibitors and endothelial denudation on theophylline-induced vasodilation, and the effect of theophylline on vasodilation induced by NO donor sodium nitroprusside, cyclic guanosine monophosphate (cGMP) analog bromo-cGMP, and β-agonist isoproterenol in endothelium-denuded aorta were examined. The effects of theophylline and sodium nitroprusside on cGMP formation were also examined.

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Oxidative stress contributes to tumourigenesis by altering gene expression. One accompanying modification, 8-oxoguanine (oG) can change RNA-RNA interactions via oG•A base pairing, but its regulatory roles remain elusive. Here, on the basis of oG-induced guanine-to-thymine (oG > T) variations featured in sequencing, we discovered widespread position-specific oGs in tumour microRNAs, preferentially oxidized towards 5' end seed regions (positions 2-8) with clustered sequence patterns and clinically associated with patients in lower-grade gliomas and liver hepatocellular carcinoma.

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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.

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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, N-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.

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Article Synopsis
  • - This study explores how chloroquine affects the widening of blood vessels (vasodilation) caused by levcromakalim in rat aortas without endothelial cells, focusing on the underlying mechanisms.
  • - Chloroquine was found to be more effective than hydroxychloroquine in inhibiting vasodilation, and this effect was partially reversed by N-acetyl-ʟ-cysteine (NAC), a reactive oxygen species (ROS) scavenger.
  • - The research indicates that chloroquine not only inhibits vasodilation through the production of ROS but also impairs the function of KATP channels, with lipid emulsion showing no impact on this impairment.
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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.

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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.

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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 NH-terminal kinase (JNK) phosphorylation induced by dexmedetomidine in rat aortic smooth muscles were examined.

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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.

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Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is associated with fatal pulmonary fibrosis. Small interfering RNAs (siRNAs) can be developed to induce RNA interference against SARS-CoV-2, and their susceptible target sites can be inferred by Argonaute crosslinking immunoprecipitation sequencing (AGO CLIP). Here, by reanalysing AGO CLIP data in RNA viruses, we delineated putative AGO binding in the conserved non-structural protein 12 (nsp12) region encoding RNA-dependent RNA polymerase (RdRP) in SARS-CoV-2.

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Article Synopsis
  • The study investigated how the endothelium and lipid emulsion affect vasodilation (widening of blood vessels) caused by minoxidil at a toxic dose in rat aorta.
  • Results showed that minoxidil caused more vasodilation in aorta with an intact endothelium, and several inhibitors (like L-NAME and glibenclamide) significantly reduced this effect.
  • Lipid emulsion did not impact the vasodilation, membrane hyperpolarization, or minoxidil concentration, indicating that minoxidil's effects rely on ATP-sensitive potassium channels and nitric oxide pathways.
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Protein arginine methyltransferase (PRMT) 1 is involved in the regulation of various metabolic pathways such as glucose metabolism in liver and atrophy in the skeletal muscle. However, the role of PRMT1 in the fat tissues under the disease state has not been elucidated to date. In this study, we delineate the function of this protein in adipocytes in vivo.

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Article Synopsis
  • - The study explored how lipid emulsion (LE) affects the vasoconstriction caused by dexmedetomidine (DMT) in rat aorta, focusing on cellular mechanisms involved in nitric oxide (NO) synthesis and phosphorylation of specific proteins.
  • - Results showed that LE increased DMT-induced contractions and reduced both DMT concentration and cyclic guanosine monophosphate (cGMP) formation, indicating that LE may inhibit NO production.
  • - The findings suggested that the effects of DMT on NO synthesis and protein phosphorylation were influenced by LE through mechanisms involving Src kinase and caveolin-1, ultimately enhancing the vasoconstrictive response.
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Small interfering RNAs (siRNAs) therapeutically induce RNA interference (RNAi) of disease-causing genes, but they also silence hundreds of seed-matched off-targets as behaving similar to microRNAs (miRNAs). miRNAs control the pathophysiology of tumors, wherein their accessible binding sites can be sequenced by Argonaute crosslinking immunoprecipitation (AGO CLIP). Herein, based on AGO CLIP, we develop potent anticancer siRNAs utilizing miRNA-like activity (mi/siRNAs).

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Article Synopsis
  • The study investigated how linolenic acid affects the contraction of rat aorta induced by phenylephrine, focusing on both endothelium-intact and -denuded conditions, and exploring various inhibitors like L-NAME and ODQ.
  • Linolenic acid increased contraction in endothelium-intact aorta but decreased it in endothelium-denuded aorta, influencing calcium sensitivity and intracellular calcium levels differently in these conditions.
  • The findings indicate that linolenic acid enhances contraction mainly by inhibiting the release of nitric oxide from the endothelium, rather than by reducing calcium levels in smooth muscle cells.
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Amlodipine-induced toxicity has detrimental effects on cardiac cells. The aim of this study was to examine the effect of lipid emulsion on decreased H9c2 rat cardiomyoblast viability induced by amlodipine toxicity. The effects of amlodipine, lipid emulsion, LY 294002, and glibenclamide, either alone or in combination, on cell viability and count, apoptosis, and expression of cleaved caspase-3 and -8, and Bax were examined.

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In pathophysiology, reactive oxygen species oxidize biomolecules that contribute to disease phenotypes. One such modification, 8-oxoguanine (oG), is abundant in RNA but its epitranscriptional role has not been investigated for microRNAs (miRNAs). Here we specifically sequence oxidized miRNAs in a rat model of the redox-associated condition cardiac hypertrophy.

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Axon regeneration is regulated by a neuron-intrinsic transcriptional program that is suppressed during development but that can be reactivated following peripheral nerve injury. Here we identify , which encodes the stem cell marker prominin-1, as a regulator of the axon regeneration program. expression is developmentally down-regulated, and the genetic deletion of in mice inhibits axon regeneration in dorsal root ganglion (DRG) cultures and in the sciatic nerve, revealing the neuronal role of in injury-induced regeneration.

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Percutaneous aspiration with sclerotherapy (PAS) and laparoscopic marsupialization (LM) are minimally invasive treatment modalities for renal cysts. We aimed to compare the efficacy and cost/effectiveness of LM and PAS for the treatment of simple symptomatic renal cysts. Data were prospectively collected from three health care institutions in which 80 patients with symptomatic simple renal cysts underwent a single session of PAS with 95% ethanol (PAS group,  = 40) or underwent LM under general anesthesia (LM group,  = 40) between March 2012 and May 2016.

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The goals of this study were to examine the cellular signaling pathways associated with the phosphorylation of caldesmon, the phosphorylation-dependent inhibitory protein of myosin phosphatase (CPI-17), and the 20-kDa regulatory light chain of myosin (MLC) induced by levobupivacaine in isolated rat aortas. The effects of genistein, tyrphostin 23, GF109203X, PD98059, Y-27632, 1-butanol, and ML-7 HCl on levobupivacaine-induced contraction were assessed. The effect of genistein on the simultaneous calcium-tension curves induced by levobupivacaine was examined.

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High-throughput sequencing of RNAs isolated by crosslinking immunoprecipitation (HITS-CLIP, also called CLIP-Seq) has been used to map global RNA-protein interactions. However, a critical caveat of HITS-CLIP results is that they contain non-linear background noise-different extent of non-specific interactions caused by individual transcript abundance-that has been inconsiderately normalized, resulting in sacrifice of sensitivity. To properly deconvolute RNA-protein interactions, we have implemented CLIPick, a flexible peak calling pipeline for analyzing HITS-CLIP data, which statistically determines the signal-to-noise ratio for each transcript based on the expression-dependent background simulation.

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