Sun-Young Oh

Activation of Vanilloid Receptor 1 (VR1) by Eugenol

The structural similarity of eugenol with capsaicin suggests that these two agents may share molecular mechanisms to produce their effects. We investigated the effects of eugenol in comparison with those of capsaicin using whole-cell patch clamp and Fura-2-based calcium-imaging techniques in a heterologous expression system and with sensory neurons. In vanilloid receptor 1 (VR1)-expressing human embryonic kidney (HEK) 293 cells and trigeminal ganglion (TG) neurons, eugenol activated inward currents, whereas capsazepine, a competitive VR antagonist, and ruthenium red (RR), a functional VR antagonist, completely blocked eugenol-induced inward currents. Moreover, eugenol caused elevation of [Ca2+]i, and this was completely abolished by both capsazepine and ruthenium red in VR1-expressing HEK 293 cells and TG neurons. Our results provide strong evidence that eugenol produces its effects, at least in part, via VR1 expressed by the sensory nerve endings in the teeth.

Eugenol inhibits calcium currents in dental afferent neurons.

Eugenol is a topical analgesic agent widely used in the dental clinic. To elucidate the molecular mechanism underlying its analgesic action, we investigated the effect of eugenol on high-voltage-activated calcium channel (HVACC) currents in dental primary afferent neurons, and with a heterologous expression system. Dental primary afferent neurons were identified by retrograde labeling with a fluorescent dye, DiI. Eugenol inhibited HVACC currents in both capsaicin-sensitive and capsaicin-insensitive dental primary afferent neurons. The HVACC inhibition by eugenol was not blocked by capsazepine, a competitive transient receptor potential vanilloid 1 (TRPV1) antagonist. Eugenol inhibited N-type calcium currents in the cell line C2D7, stably expressing the human N-type calcium channels, where TRPV1 was not endogenously expressed. Our results suggest that the HVACC inhibition by eugenol in dental primary afferent neurons, which is not mediated by TRPV1 activation, might contribute to eugenol’s analgesic effect. Abbreviations: high-voltage-activated calcium channel, HVACC; transient receptor potential vanilloid 1, TRPV1; trigeminal ganglion, TG; dorsal root ganglion, DRG; capsazepine, CZP.

Isolated Nodular Infarction

Background and Purpose— Isolated nodular infarction has rarely been described in human. The purpose of this study is to report clinical and laboratory findings of isolated nodular infarction. Methods— Eight patients with isolated nodular infarction were recruited from 6 hospitals in Korea. All patients underwent a complete and standardized neurotological evaluation including ocular torsion, bithermal caloric tests, and rotatory chair test in addition to MRI and MR angiography. Results— All patients presented with isolated vertigo and moderate to severe imbalance. The most common manifestation was unilateral nystagmus and falling in the opposite direction, which mimicked peripheral vestibulopathy. Six patients had unilateral lesion, and 2 showed bilateral lesions. The direction of the spontaneous nystagmus was all ipsilesional in the unilateral lesion. However, head impulse and bithermal caloric tests were normal. Other findings include periodic alternating nystagmus, perverted head shaking nystagmus, paroxysmal positional nystagmus, and impaired tilt suppression of the postrotatory nystagmus. Hypoplasia of the ipsilesional vertebral artery was the only abnormal finding on MR angiography in 3 patients. The prognosis was excellent. Conclusions— Isolated nodular infarction mostly presents with isolated vertigo mimicking acute peripheral vestibulopathy. However, severe imbalance and a negative head impulse test are important clinical discriminants between nodular infarcts and peripheral vestibular dysfunction. The findings of isolated nodular infarctions are consistent with impaired gravito-inertial processing of the vestibular signals and disrupted nodular inhibition on the vestibular secondary neurons and the velocity storage mechanism.

IL-13 Receptor α2 Selectively Inhibits IL-13-Induced Responses in the Murine Lung

IL-13 is a critical cytokine at sites of Th2 inflammation. In these locations it mediates its effects via a receptor complex, which contains IL-4Rα and IL-13Rα1. A third, high-affinity IL-13 receptor, IL-13Rα2, also exists. Although it was initially felt to be a decoy receptor, this has not been formally demonstrated and the role(s) of this receptor has recently become controversial. To define the role(s) of IL-13Rα2 in IL-13-induced pulmonary inflammation and remodeling, we compared the effects of lung-targeted transgenic IL-13 in mice with wild-type and null IL-13Rα2 loci. We also investigated the effect of IL-13Rα2 deficiency on the OVA-induced inflammatory response. In this study, we show that in the absence of IL-13Rα2, IL-13-induced pulmonary inflammation, mucus metaplasia, subepithelial fibrosis, and airway remodeling are significantly augmented. These changes were accompanied by increased expression and production of chemokines, proteases, mucin genes, and TGF-β1. Similarly, an enhanced inflammatory response was observed in an OVA-induced phenotype. In contrast, disruption of IL-13Rα2 had no effect on the tissue effects of lung-targeted transgenic IL-4. Thus, IL-13Rα2 is a selective and powerful inhibitor of IL-13-induced inflammatory, remodeling, and physiologic responses in the murine lung.

Vascular endothelial growth factor is a key mediator in the development of T cell priming and its polarization to type 1 and type 17 T helper cells in the airways.

Chronic inflammatory airway diseases including asthma are characterized by immune dysfunction to inhaled allergens. Our previous studies demonstrated that T cell priming to inhaled allergens requires LPS, which is ubiquitously present in household dust allergens. In this study, we evaluated the role of vascular endothelial growth factor (VEGF) in the development of T cell priming and its polarization to Th1 or Th17 cells when exposed to LPS-contaminated allergens. An asthma mouse model was induced by airway sensitization with LPS-contaminated allergens and then challenged with allergens alone. Therapeutic intervention was performed during allergen sensitization. The present study showed that lung inflammation induced by sensitization with LPS-contaminated allergens was decreased in mice with homozygous disruption of the IL-17 gene; in addition, allergen-specific Th17 immune response was abolished in IL-6 knockout mice. Meanwhile, in vivo production of VEGF was up-regulated by airway exposure of LPS. In addition, airway sensitization of allergen plus recombinant VEGF induced both type 1 and type 17 Th cell (Th1 and Th17) responses. Th1 and Th17 responses induced by airway sensitization with LPS-contaminated allergens were blocked by treatment with a pan-VEGF receptor (VEGFR; VEGFR-1 plus VEGFR-2) inhibitor during sensitization. These effects were accompanied by inhibition of the production of Th1 and Th17 polarizing cytokines, IL-12p70 and IL-6, respectively. These findings indicate that VEGF produced by LPS plays a key role in activation of naive T cells and subsequent polarization to Th1 and Th17 cells.

Functional epitope of muscarinic type 3 receptor which interacts with autoantibodies from Sjögren's syndrome patients

OBJECTIVES Recently, autoantibodies directed against muscarinic type 3 receptor (M3R) have been reported in patients with primary SS. However, the precise epitope(s) of the M3R that interacts with SS autoantibodies remains unclear. The aim of this study was to identify the functional epitope of M3R which interacts with SS immunoglobulin G (IgG). METHODS Purified IgGs were obtained from the sera of seven SS patients (six primary and one secondary SS) and two normal persons. We examined whether SS IgG inhibits M3R function and identified the epitope using six synthetic peptides covering all the extracellular domains of M3R by microspectrofluorimetry and surface plasmon resonance-based optical biosensor system (BIAcore system). RESULTS A volume of 0.5 mg/ml SS IgG inhibited carbachol (CCh)-induced [Ca(2+)](i) transient (CICT) in human submandibular gland (HSG) cells. However, co-incubation of SS IgG with the 6th peptide (514-527 amino acid region) corresponding to the third extracellular loop of M3R, recovered CICT. The result was further confirmed by BIAcore analysis. We found that the 6th peptide interacts with IgGs from three primary SS patients in a concentration-dependent manner. The synthetic peptide which consists of amino acids 228-237 corresponding to the COOH-terminus of the second extracellular loop of M3R also bound to SS IgG. However, normal IgGs did not interact with the 6th peptide. CONCLUSIONS The results suggest that the third extracellular loop of M3R represents a functional epitope bound by SS IgG, and thereby partly inhibits M3R function.

Randomized clinical trial for geotropic horizontal canal benign paroxysmal positional vertigo

Objectives: To determine the immediate and long-term therapeutic efficacies of barbecue rotation and Gufoni maneuvers, a randomized, prospective, and sham-controlled study was conducted in patients with the geotropic type of benign paroxysmal positional vertigo involving the horizontal semicircular canal (HC-BPPV). Methods: In 10 nationwide dizziness clinics in Korea, 170 consecutive patients (107 women, age range 11−97 years, mean age ± SD 61 ± 15 years, median = 61 years) with geotropic HC-BPPV were randomly assigned to barbecue rotation (n = 56), Gufoni (n = 64), or sham maneuver (n = 50). An immediate response was determined within 1 hour after a maximum of 2 trials of each maneuver on the visit day. We also assessed the cumulative results of each maneuver by following up the patients for 1 month. Results: After a maximum of 2 maneuvers on the initial visit day, barbecue rotation (38 of 55 [69.1%]) and Gufoni (39 of 64 [60.9%]) maneuvers showed better responses than the sham maneuver (17 of 48 [35.4%]). The cumulative therapeutic effects were also better with barbecue rotation (p = 0.006) and Gufoni (p = 0.031) maneuvers than with the sham maneuver. However, therapeutic efficacies did not differ between the barbecue rotation and Gufoni groups in terms of both immediate (p = 0.46) and long-term (p = 0.10) outcomes. Conclusion: Using a prospective randomized trial, we demonstrated that barbecue rotation and Gufoni maneuvers are effective in treating geotropic HC-BPPV. Classification of evidence: This study provides Class I evidence that barbecue rotation and Gufoni maneuvers are effective in the treatment of geotropic HC-BPPV.

The vestibulo-ocular reflexes during head impulse in Wernicke's encephalopathy

Ocular motor findings in Wernicke’s encephalopathy (WE) include gaze evoked nystagmus (GEN), central positional nystagmus, weakness of abduction, internuclear ophthalmoplegia and horizontal or vertical gaze palsy to total ophthalmoplegia. Another feature of WE is vestibular paresis.1 2 Previous studies documented hypoactive vestibular responses to both caloric and rotational stimuli, and a short vestibulo-ocular reflex (VOR) time constant. To address differential susceptibility of individual semicircular canals (SCC) according to stimulation frequency, we measured high acceleration VOR of the individual SCC using head impulse manoeuvres, and the low frequency VOR using bithermal caloric and rotatory chair tests in two patients with WE. Figure 1 (A) T2 weighted MRIs of patient No 1. Symmetrical hyperintense lesions are shown at dorsal portions of both the medulla, periaqueductal gray matter and medial portions of both thalami. (B) Bithermal caloric tests in patient No 1 show minimal responses in both ears initially (B-1), which markedly improved 6 months after thiamine replacement (B-2)

Cellular and Molecular Mechanisms of Dental Nociception

Due, in part, to the unique structure of the tooth, dental pain is initiated via distinct mechanisms. Here we review recent advances in our understanding of inflammatory tooth pain and discuss 3 hypotheses proposed to explain dentinal hypersensitivity: The first hypothesis, supported by functional expression of temperature-sensitive transient receptor potential channels, emphasizes the direct transduction of noxious temperatures by dental primary afferent neurons. The second hypothesis, known as hydrodynamic theory, attributes dental pain to fluid movement within dentinal tubules, and we discuss several candidate cellular mechanical transducers for the detection of fluid movement. The third hypothesis focuses on the potential sensory function of odontoblasts in the detection of thermal or mechanical stimuli, and we discuss the accumulating evidence that supports their excitability. We also briefly update on a novel strategy for local nociceptive anesthesia via nociceptive transducer molecules in dental primary afferents with the potential to specifically silence pain fibers during dental treatment. Further understanding of the molecular mechanisms of dental pain would greatly enhance the development of therapeutics that target dental pain.

Characterization of Dental Nociceptive Neurons

Selective blockade of nociceptive neurons can be achieved by the delivery of permanently charged sodium channel blockers through the pores of nociceptive ion channels. To assess the feasibility of this application in the dental area, we investigated the electrophysiological and neurochemical characteristics of nociceptive dental primary afferent (DPA) neurons. DPA neurons were identified within trigeminal ganglia labeling with a retrograde fluorescent dye applied to the upper molars of adult rats. Electrophysiological studies revealed that the majority of dental primary afferent neurons showed characteristics of nociceptive neurons, such as sensitivity to capsaicin and the presence of a hump in action potential. Immunohistochemical analysis revealed a large proportion of DPA neurons to be IB4-positive and to express TRPV1 and P2X3. Single-cell RT-PCR revealed mRNA expression of various nociceptive channels, including the temperature-sensitive TRPV1, TRPA1, TRPM8 channels, the extracellular ATP receptor channels P2X2 and P2X3, as well as the nociceptor-specific sodium channel, NaV1.8. In conclusion, DPA neurons have the electrophysiological characteristics of nociceptors and express several nociceptor-specific ion channels. Analysis of these data may assist in the search for a new route of entry for the delivery of membrane-impermeant local anesthetics. Abbreviations: AP, action potential; DiI, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate; DPA, dental primary afferent; FITC, fluorescein 5(6)-isothiocyanate; IB4, isolectin-B4; RT-PCR, reverse-transcription polymerase chain-reaction; TRP, transient receptor potential.