Ryuichi Hirota

Capsaicin receptor expression in rat laryngeal innervation.

Capsaicin elicits a sensation of burning pain by selectively activating sensory neurons that convey information about noxious stimuli to the central nervous system. Vanilloid receptor subtype 1 (VR1) and the vanilloid receptor-like protein 1 (VRL-1) are activated, not only by capsaicin, but also by noxious heat and protons, and it has been suggested that they are polymodal nociceptors. We investigated the expression of VR1 and VRL-1 in the rat larynx and nodose ganglion using VR1 and VRL-1 immunohistochemical analysis with visualization by diaminobenzidine reaction. Fibers positive for VRL-1 were detected in the laryngeal epithelium and lamina propria. Cells positive for VRL-1 were distributed in the intralaryngeal ganglia. Half of the neurons in the nodose ganglion had VR-1 immunoreactivity, and almost 10% of the nodose ganglion neurons were positive for VRL-1. These findings suggest that these capsaicin receptors play an important role in the nociception of the laryngeal innervation.

K+-Cl-Cotransporter 1 (KCC1) Negatively Regulates NGF-induced Neurite Outgrowth in PC12 Cells

Potassium chloride cotransporters (KCCs) mediate electroneutrally-coupled transport of K+ and Cl-, and play crucial roles in various cell functions including regulation of cell volume and homeostasis of cellular Cl-content. Four isoforms of KCCs (KCC1, 2, 3, and 4) have been identified. KCC1 is ubiquitously expressed, whereas KCC2 is mainly expressed in neuronal cells of central nervous system. KCC3 is highly expressed in heart, skeletal muscle, kidney, lung and placenta. KCC4 is mainly expressed in epithelial cells. In this study, we investigated roles of KCCs in NGF-induced neurite outgrowth of rat pheochromocytoma PC12 cells. The most abundantly expressed isoform in PC12 cells was KCC1. Inhibition of KCCs using [(dihydronindenyl)oxy] alkanoic acid (DIOA), an inhibitor of KCCs, enhanced the NGF-induced neurite outgrowth of PC12 cells in a dose-dependent manner. Treatment of PC12 cells with NGF significantly decreased mRNA expression of KCC1, whereas other isoforms, KCC2-4, showed no changes in their mRNA expression in response to NGF treatment. Knockdown of KCC1 using small interfering RNA (siRNA) enhanced the NGF-induced neurite outgrowth. These results suggest that KCC1 negatively regulates the NGF-induced neurite outgrowth of PC12 cells.

Differential Responses to Steroid Hormones in Fibroblasts From the Vocal Fold, Trachea, and Esophagus

There is accumulating evidence that fibroblasts are target cells for steroids such as sex hormones and corticoids. The characteristics of fibroblasts vary among tissues and organs. Our aim in this study is to examine differences in responses to steroid hormones among fibroblasts from different cervicothoracic regions. We compared the actions of steroid hormones on cultured fibroblasts from the vocal folds, which are considered to be the primary target of steroid hormones, and the trachea and esophagus in adult male rats. Expression of steroid hormone receptors (androgen receptor, estrogen receptor α, and glucocorticoid receptor) was identified by immunofluorescence histochemistry. Androgen receptor was much more frequently expressed in fibroblasts from the vocal fold than in those from the trachea and esophagus. Cell proliferation analysis showed that administration of testosterone, estradiol, or corticosterone suppressed growth of all 3 types of fibroblasts. However, mRNA expression for extracellular matrix-associated genes, including procollagen I and III and elastin, and hyaluronic acid synthase I was elevated only by addition of testosterone to fibroblasts from the vocal fold. These results indicate that each steroid hormone exerts region-specific effects on cervicothoracic fibroblasts with different properties through binding to specific receptors.

Localization and regulation of aquaporins in the murine larynx

Abstract Conclusion: Expression of aquaporins (AQPs) in the vocal folds and the parasympathetic regulation of AQPs in the laryngeal glands may be important for controlling laryngeal secretion and vocal fold hydration. These findings are thought to be an initial step towards understanding potential mechanisms of water flow through the vocal fold surface. Objectives: Lubrication of the vocal folds is important for phonation and laryngeal defense. However, the system of water transport in the laryngeal epithelium has not yet been clarified. We investigated the expression of AQP water channnels (AQP1–9) in the murine larynx and examined the neural regulating mechanisms of these subtypes. Methods: The distribution of AQPs (AQP1–9) in the murine larynx was examined by immunohistochemistry. Next, the neural mechanism regulating AQPs in the larynx was investigated using unilaterally vagotomized mice. Results: AQP1, 4, and 5 were expressed in the laryngeal epithelium including the vocal folds. Vocal fold AQP expression was minimal at the vocal process. AQP2, 3, 5, 6, 7, and 8 were localized to the submucosal glands. Expression of AQPs in the vagotomized region was significantly decreased compared with the contralateral intact side. The expression in the laryngeal glands was also decreased in the aged mice.

Motor Nerve Endings

The activity of the intralaryngeal muscles is controlled by complex sensory and motor neuron systems. The motor endplates on the intralaryngeal muscles, which require fine control of muscle activity, are smaller than the motor endplates on other skeletal muscles, and approximately 20,000–30,000 of them are believed to exist on the thyroarytenoid muscle. In addition, skeletal muscle motor endplates are usually present in the center of each muscle fiber and are commonly observed in a belt shape that covers the center of the belly of the whole muscle. By contrast, in the intralaryngeal muscle, the motor endplates are not necessarily located in the center of each muscle, and various distribution patterns are observed. We revealed the presence of either NADPHd-positive or CGRP-positive motor nerve endings in the thyroarytenoid muscle. We believe that NO and CGRP participate in the complex motor control of the larynx.

Laryngeal stenosis in a patient with severe congenital neutropenia

We report the first case of laryngeal stenosis with granuloma in a patient with severe congenital neutropenia (SCN).

A Case Report of Cervical Thymic Cyst.

A case of cervical thymic cyst is reported, and the Japanese literature is reviewed in this paper. A 12-year-old-boy presented with a painless left neck mass (5 x 4 cm). The preoperative diagnosis was cystic disease of the neck, based on ultrasound examination, CT and MRI study. At surgery, a cyst adhering to the vagus nerve was extirpated from both the carotid artery and the jugular vein, which were connected to the mediastinum. The pathological diagnosis was multilocular thymic cyst, which showed normal thymic tissue, in addition to granulation with areas of chronic inflammation and fibrosis with cholesterol clefts and Hassalls corpuscles in the cystic wall.Twenty-eight cases of cervical thymic cyst in the Japanese literature are reviewed and discussed briefly. The mean age of the patients was 31 years. Sixteen cervical thymic cysts (57%) occurred on the left side of the neck. Painless neck swelling was noticed in all except 3 patients. Seven cervical thymic cysts (32%) had mediastinal connections. Some cysts included foci of thyroid tissue (one patient) and parathyroid tissue (3 patients). Due to their rare occurrence, cervical thymic cysts can be misdiagnosed as other cystic lesions of the neck. Cervical thymic cysts should be taken into account in the differential diagnosis of neck masses.

Localization of Heme Oxygenase-2 in the Canine Larynx

The localization of heme oxygenase-2 (HO-2) in the larynx of the dog was investigated using immunohistochemistry. HO-2-positive cells were seen among neurons in intralaryngeal ganglia. Nerve fibers positive to HO-2 immunohistochemistry were seen surrounding laryngeal glands and arterioles and also in the adventitia of arterioles. HO-2-positive fibers were also seen running parallel to the mucosa in the lamina propria but no positive fibers were seen in the epithelium. Some of the intramuscular neurons found in the intrinsic laryngeal muscles were HO-2-positive, although no positive motor fibers were seen, and the neuromuscular junctions were also HO-2-negative. The results implicate the participation of HO-2-in the parasympathetic innervation of the larynx.The localization of heme oxygenase-2 (HO-2) in the larynx of the dog was investigated using immunohistochemistry. HO-2-positive cells were seen among neurons in intralaryngeal ganglia. Nerve fibers positive to HO-2 immunohistochemistry were seen surrounding laryngeal glands and arterioles and also in the adventitia of arterioles. HO-2-positive fibers were also seen running parallel to the mucosa in the lamina propria but no positive fibers were seen in the epithelium. Some of the intramuscular neurons found in the intrinsic laryngeal muscles were HO-2-positive, although no positive motor fibers were seen, and the neuromuscular junctions were also HO-2-negative. The results implicate the participation of HO-2-in the parasympathetic innervation of the larynx.