Katsuhisa Ikeda

Novel mutations in the connexin 26 gene (GJB2) responsible for childhood deafness in the Japanese population

Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein and is expressed in the inner ear, have been shown to be responsible for a major part of nonsyndromic hereditary prelingual (early-childhood) deafness in Caucasians. We have sequenced the GJB2 gene in 39 Japanese patients with prelingual deafness (group 1), 39 Japanese patients with postlingual progressive sensorineural hearing loss (group 2), and 63 Japanese individuals with normal hearing (group 3). Three novel mutations were identified in group 1: a single nucleotide deletion (235delC), a 16-bp deletion (176-191 del (16)), and a nonsense mutation (Y136X) in five unrelated patients. The 235delC mutation was most frequently observed, accounting for seven alleles in 10 mutant alleles. Screening of 203 unrelated normal individuals for the three mutations indicated that the carrier frequency of the 235delC mutation was 2/203 in the Japanese population. No mutation was found in group-2 patients. We also identified two novel polymorphisms (E114G and I203T) as well as two previously reported polymorphisms (V27I andV37I). Genotyping with these four polymorphisms allowed normal Japanese alleles to be classified into seven haplotypes. All 235delC mutant alleles identified in four patients resided only on haplotype type 1. These findings indicate that GJB2 mutations are also responsible for prelingual deafness in Japan.

Cisplatin-induced apoptotic cell death in Mongolian gerbil cochlea

Cisplatin is well known to cause cochleotoxicity. In order to determine the underlying mechanisms of cisplatin-induced cell death in the cochlea, we investigated the apoptotic changes and the expression of bcl-2 family proteins controlling apoptosis. Mongolian gerbils were administered 4 mg/kg/day cisplatin consecutively for 5 days. The cisplatin-treated animals showed a significant deterioration in the responses of both distortion product otoacoustic emissions and the endocochlear potential as compared with those of the age-matched controls, suggesting outer hair cell and stria vascularis dysfunction. The presence of DNA fragmentation revealed by a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling method was recognized in the organ of Corti, the spiral ganglion, and the stria vascularis in the cisplatin-treated animals whereas almost negative results were obtained in the control animals. The nuclear morphology obtained by Hoechst 33342 staining revealed pyknotic and condensed nuclei, confirming the presence of the characteristic features of apoptosis. A significant increase and reduction in the number of bax- and bcl-2-positive cells, respectively, following cisplatin treatment was observed in the cells of the organ of Corti, the spiral ganglion, and the lateral wall. These findings suggest a critical role for bcl-2 family proteins in the regulation of apoptotic cell death induced by cisplatin. The underlying mechanisms of the cisplatin-induced cell death are discussed.

Novel scoring system and algorithm for classifying chronic rhinosinusitis: the JESREC Study.

Chronic rhinosinusitis (CRS) can be classified into CRS with nasal polyps (CRSwNP) and CRS without nasal polyps (CRSsNP). CRSwNP displays more intense eosinophilic infiltration and the presence of Th2 cytokines. Mucosal eosinophilia is associated with more severe symptoms and often requires multiple surgeries because of recurrence; however, even in eosinophilic CRS (ECRS), clinical course is variable. In this study, we wanted to set objective clinical criteria for the diagnosis of refractory CRS.

Endoscopic Sinus Surgery Improves Pulmonary Function in Patients with Asthma Associated with Chronic Sinusitis

We evaluated the clinical efficacy of endonasal endoscopic sinus surgery (ESS) in patients with asthma associated with chronic sinusitis. Twenty-one patients (13 men and 8 women) from 27 to 72 years old were enrolled in this study. All patients had had sinus-related symptoms for more than 3 months and had computed tomographic evidence of paranasal sinus opacification. Fifteen patients underwent bilateral endonasal ESS under local anesthesia, and 6 other patients without surgery were controls. The sinus-related symptoms of the preoperative and postoperative periods were assessed via a questionnaire. The period 6 months prior to surgery was compared with that 6 months postoperatively with regard to peak expiratory flow and total dosage of systemic glucocorticoids. Sinus-related symptoms in the ESS group were significantly improved 6 months postoperatively. The average peak expiratory flow 6 months following surgery was improved in the ESS patients, ranging from 40 to 190 L/min. Seven patients showed a reduction in the need for corticosteroids, whereas 2 patients were unchanged and 2 patients required larger dosages. The remaining 4 patients needed no corticosteroids before or after ESS. No significant changes in sinus-related symptoms or peak expiratory flow were obtained for the control group. Improvement of paranasal sinus disease by successful ESS can alleviate pulmonary dysfunction in asthma associated with chronic sinusitis. We believe that adequate and positive treatment for chronic sinusitis would reduce not only the nasal and sinus-related symptoms evoked by chronic sinusitis, but also some of the signs induced by asthma.

Electrochemical profiles for monovalent ions in the stria vascularis: Cellular model of ion transport mechanisms

The electrochemical profiles for K+, Na+, and Cl- ions in tissues of the lateral wall of the cochlea in the chinchilla were measured using an ion-selective microelectrode. Based upon the changes of the d.c. resting potential and ion composition, five distinct compartments were identified in the lateral wall. The first compartment, corresponding to the spiral ligament, showed an ionic composition similar to perilymph. The second, corresponding to the basal cell layer of the stria vascularis, showed a characteristic recording of the ion-sensitive barrel: a spike-like change of the ion concentration (K+: 100.1 +/- 16.8 mM, Na+: 33.9 +/- 20.2 mM, Cl-: 70.2 +/- 9.4 mM). The third compartment, corresponding to the extracellular space of the stria vascularis, showed a higher d.c. potential (60.4 +/- 9.5 mV) than that of the second region, with a low K+ concentration (22.1 +/- 14.9 mM) and a high Na+ (78.3 +/- 5.7 mV) than the fifth compartment, corresponding to the scala media (78.1 +/- 4.1 mV), and K+ and Na+ concentrations similar to those of endolymph, while the Cl- concentration in the fourth compartment (117.6 +/- 21.5 mM) was lower than that of endolymph (143.3 +/- 13.9 mM). A thermodynamic study of electrochemical potential gradients suggests the possibility that the Na-K pump and Na-K-2Cl cotransport exist at the basolateral membrane of the marginal cells.

Expression of connexin 31 in the developing mouse cochlea.

Connexin 31 (C×31) mutations cause an autosomal dominant form of high-frequency hearing loss. The immunohistochemical localization of C×31 in mouse cochlea was studied at different ages between 0 and 60 days after birth (DAB). C×31-like immunoreactivity was detected in fibrocytes of spiral ligament and spiral limbus at 12 DAB, gradually enhanced with the increase of age and reached the adult pattern on 60 DAB. Immunoreactivity decreased gradually from the basal to apical turn in all developmental stages. The mRNA of C×31 was also identified by RT-PCR. The distribution of C×31 and connexin 26 were obviously different in the developing mouse cochlea. The expression and distribution of C×31 in the development may explain the progressive hearing loss in human C×31 mutations.

Mechanism of neutrophil recruitment induced by IL-8 in chronic sinusitis

BACKGROUND The mechanism of neutrophil recruitment in patients with chronic sinusitis is unclear. OBJECTIVE This study aims to elucidate the role of IL-8 in inducing neutrophil accumulation in the nasal discharge of patients with chronic sinusitis. METHODS Nasal discharge and mucosal specimens were obtained from two groups of patients, those with chronic sinusitis and those with allergic rhinitis. The samples were subjected to immunohistochemical examination and in situ hybridization. The IL-8 level in the nasal discharge was measured by enzyme immunoassay. RESULTS Immunoreactivity to IL-8 was observed in polymorphonuclear cells of nasal smear, in nasal gland duct cells, and in epithelial cells of the chronic sinusitis group; whereas those of the allergic rhinitis group mostly showed little or no reaction. Similar patterns of localization were shown by in situ hybridization for IL-8 messenger RNA. The IL-8 level in nasal discharge was significantly higher in the chronic sinusitis group than in the allergic rhinitis group. CONCLUSION These results suggest that chemotactic factors in sinus effusion, including IL-8 derived from nasal gland duct cells and epithelial cells, attract neutrophils out of mucosa, and the neutrophils that have emigrated into the sinus effusion secrete IL-8. This induces further neutrophil accumulation in the sinus effusion of patients with chronic sinusitis.

Inhibitory Effect of Macrolides on Interleukin-8 Secretion From Cultured Human Nasal Epithelial Cells

The mechanism of macrolide therapy in chronic sinusitis patients is unclear. The authors studied the effect of macrolides on interleukin (IL)‐8 secretion from cultured human nasal epithelial cells. Epithelial cells harvested from the nasal polyps of patients with chronic sinusitis were primary‐cultured, and secreted IL‐8 in culture media was measured by enzyme immunoassay. The cells secreted considerable amounts of IL‐8 constitutively and in response to lipopolysaccharide. The secretion was significantly inhibited by 10−5 M of erythromycin, clarithromycin, roxithromycin, and josamycin. 10−6 M erythromycin still showed the inhibitory effect, whereas the same concentration of josamycin did not. These results indicate that macrolide antibiotics may act as an immunomodulator to reduce IL‐8 in inflammatory sites and, at least partially, account for the clinically discrepant effects between 14‐ and 16‐membered ring macrolides in long‐term low‐dose therapy for chronic sinusitis.

Eotaxin-1, -2, and -3 immunoreactivity and protein concentration in the nasal polyps of eosinophilic chronic rhinosinusitis patients.

Eosinophilic chronic rhinosinusitis (CRS) is characterized by the accumulation of numerous eosinophils in the sinus mucosa and nasal polyps, which are frequently difficult to control, even with surgery. The present study was designed to evaluate the expression and localization of eotaxins, which are well known to be potent and selective chemoattractants for eosinophils in CRS.

Subclassification of chronic rhinosinusitis with nasal polyp based on eosinophil and neutrophil.

Japanese patients with chronic rhinosinusitis with nasal polyps (CRSwNP), differing from European and U.S. patients, are suggested to show two distinct phenotypes: Th2‐polarized and Th1‐shifted immunity. The purpose of this study was to conduct clinical subgrouping of CRSwNP based on inflammatory cell infiltration, which was evaluated and supported by clinical backgrounds and immunological characteristics.