Keigo Suzukawa

Epithelial cell-derived IL-25, but not Th17 cell-derived IL-17 or IL-17F, is crucial for murine asthma.

IL-17A, IL-17F, and IL-25 are ligands for IL-17RA. In the current study, we demonstrated that IL-25–deficient mice—but not IL-17A–, IL-17F–, IL-17A/F–, IL-23p19–, or retinoic acid-related orphan receptor (ROR)-γt–deficient mice—showed significant suppression of 1) the number of eosinophils and the levels of proinflammatory mediators in bronchoalveolar lavage fluids, 2) airway hyperresponsiveness to methacholine, and 3) OVA-specific IgG1 and IgE levels in the serum during OVA-induced Th2-type/eosinophilic airway inflammation. The IL-25 deficiency did not affect lung dendritic cell migration or Ag-specific memory–Th2 cell expansion during Ag sensitization. Adoptive transfer of T cells, mast cells, or bone marrow cells from IL-25–deficient mice revealed that induction of Th2-type/eosinophilic airway inflammation was dependent on activation of lung epithelial cells and eosinophils by IL-25 produced by airway structural cells such as epithelial cells but not by such hematopoietic stem-cell-origin immune cells as T cells and mast cells. Therefore, airway structural cell-derived IL-25—rather than Th17 cell-derived IL-17A and IL-17F—is responsible for induction of local inflammation by promoting activation of lung epithelial cells and eosinophils in the elicitation phase of Th2-type/eosinophilic airway inflammation. It is not required for Ag-specific Th2 cell differentiation in the sensitization phase.

Age-related changes in cell dynamics of the postnatal mouse olfactory neuroepithelium: Cell proliferation, neuronal differentiation, and cell death

Age‐related changes in cell proliferation, neuronal differentiation, and cell death in mouse olfactory neuroepithelium were investigated. Mice at the age of 10 days through 16 months were given a single injection of bromodeoxyuridine (BrdU). The olfactory mucosae were fixed at 9 timepoints ranging from 2 hours to 3 months after the injection and examined using double immunostaining for BrdU and olfactory marker protein (OMP), and double staining with terminal deoxynucleotidyl transferase‐mediated biotinylated dUTP nick end labeling (TUNEL) and immunostaining for OMP. The number of BrdU‐labeled cells/mm epithelial length initially increased, peaked at 2–3 days after the BrdU injection, then declined at each age. The number of BrdU‐ and TUNEL‐labeled neuronal cells both decreased with increasing age, suggesting that the rates of both cell proliferation and cell death in the olfactory neuroepithelium decrease with increasing age. Double‐labeled cells for BrdU and OMP appeared at 7 days after injection in all age groups, suggesting that the time required for neuronal differentiation is broadly similar irrespective of age. In older age groups, smaller amounts of the newly produced cohort are integrated into the OMP‐positive ORN population, and even once it is integrated it is eliminated from the population more rapidly compared to the younger age groups. Furthermore, TUNEL assay showed that the fraction of apoptotic cells distributed in the OMP‐positive layer/total apoptotic cells decreased with age. This observation suggests that the turnover of mature ORNs is slower in the older neuroepithelium compared to the younger neuroepithelium. J. Comp. Neurol. 518:1962–1975, 2010.

Expression of IL‐33 and its receptor ST2 in chronic rhinosinusitis with nasal polyps

Interleukin (IL)−33 is a novel member of the IL‐1 cytokine family and a ligand for the orphan IL‐1 family receptor ST2. IL‐33 induces T helper 2‐type inflammatory responses and is considered to play a crucial role in allergic inflammatory reactions such as asthma and atopic dermatitis. However, the role of IL‐33 and its receptor ST2 in chronic rhinosinusitis remains unclear.

Methimazole-induced cell death in rat olfactory receptor neurons occurs via apoptosis triggered through mitochondrial cytochrome c-mediated caspase-3 activation pathway.

The administration of methimazole is known to induce cell death in rat olfactory receptor neurons (ORNs). We investigated whether this injury occurs via apoptosis or through necrosis and whether it involves the extrinsic or intrinsic pathway. Rats were intraperitoneally injected with vehicle (control) or 300 mg/kg methimazole. The experimental animals were also administered vehicle or a caspase‐3 or caspase‐9 inhibitor 30 min earlier. The administration of methimazole induced cell death predominantly in the mature ORNs and partially reduced olfactory sensitivity in the rats; the injured cells were TUNEL‐positive and showed a nuclear staining pattern. This insult induced cytochrome c release from the mitochondria and a significant increase in the immunoreactivity of activated caspase‐3 and caspase‐9 as well as that of cleaved poly‐ADP‐ribose‐polymerase; in addition, it caused a significant increase in the fluorogenic activity of caspase‐3 and caspase‐9. However, it did not affect the immunoreactivity of activated caspase‐8 or the fluorogenic activity of caspase‐8. Pretreatment with a caspase‐3 or caspase‐9 inhibitor nearly completely prevented the morphologic, biochemical, and functional changes induced by methimazole. These findings suggest strongly that methimazole‐induced cell death in rat ORNs is predominantly apoptosis; moreover, the majority of this apoptotic cell death is triggered through mitochondrial cytochrome c‐mediated caspase‐3 activation pathway, and both caspase‐3 and caspase‐9 inhibitors can prevent methimazole‐induced cell death in the ORNs.

A protein derived from the fusion of TAT peptide and FNK, a Bcl-xL derivative, prevents cochlear hair cell death from aminoglycoside ototoxicity in vivo

We constructed a powerful artificial cytoprotective protein, FNK, from an antiapoptotic member of the BCL‐2 family, Bcl‐xL. To test the efficacy of FNK in protecting cochlear hair cells (HCs) from aminoglycoside‐induced cell death in vivo, we fused FNK with protein transduction domain, TAT, of the HIV/Tat protein to construct a fusion protein of TAT‐FNK. We demonstrated that, after an intraperitoneal administration to guinea pigs, TAT‐myc‐FNK protein was diffusely distributed in the cochlea, most prominently in the HCs and supporting cells, followed by the spiral ganglion cells, 3 hr after the injection. We next demonstrated that TAT‐FNK attenuated cochlear damage induced by an ototoxic combination of kanamycin sulfate (KM) and ethacrynic acid (EA) administered at 2 different dosages: 400 mg/kg KM + 50 mg/kg EA and 200 mg/kg KM + 40 mg/kg EA. TAT‐FNK or vehicle was intraperitoneally injected from 3 hr before through 5 hr after inducing the ototoxic insults, 14 days after which auditory brainstem response (ABR) and HC loss were evaluated. In comparison with vehicle‐administered controls, the TAT‐FNK protein significantly attenuated ototoxic drug‐induced ABR threshold shifts and the extent of HC death at either dosage. The TAT‐FNK protein also significantly reduced the amount of cleaved poly‐(ADP‐ribose) polymerase‐positive HCs 8 hr after the ototoxic insults compared with that in the vehicle‐administered controls. These findings indicate that systemically administered TAT‐FNK was successfully delivered to the guinea pig cochlea and effectively prevented apoptotic cell death of the cochlear HCs induced by KM and EA.

Age‐related changes of the regeneration mode in the mouse peripheral olfactory system following olfactotoxic drug methimazole‐induced damage

We investigated age‐related changes in the mode of regeneration in the mouse peripheral olfactory system after olfactotoxic drug‐induced damage. Mice at postnatal ages of 10 days, 3 months, and 16 months were given an intraperitoneal injection of methimazole to produce damage in the olfactory neuroepithelium. The olfactory neuroepithelia were harvested and analyzed immunohistochemically at various postlesion timepoints, from 1 day through to 94 days, to investigate neuroepithelial cell proliferation, the time course of neuronal differentiation, the reconstitution of neuroepithelium, and the innervation of the olfactory bulb. Functional recovery was assessed using the vanillin avoidance behavioral test. The chronological pattern in the expression of Ki67, beta III tubulin, and olfactory marker protein, molecular markers for neuronal cell proliferation and differentiation, changed similarly among the different age groups. In contrast, the extent of neuroepithelial cell proliferation after injury decreased with age, and the final histological recovery of the olfactory neuroepithelium and the innervation of the olfactory bulb were significantly smaller in the 16‐month‐old group compared to the younger age groups. These results suggest that the age‐related decline in the capacity of olfactory neuroepithelium to reconstitute neuroepithelium is associated with its age‐related decrease in proliferative activity after the neuroepithelial injury rather than changes in the process of neuronal differentiation. In spite of these incomplete anatomical recoveries, 16‐month‐old mice regained the ability to avoid vanillin solution by 1 month postlesion, suggesting that the extent of anatomical epithelial damage is not necessarily proportional to the threshold of olfactory perception. J. Comp. Neurol. 519:2154–2174, 2011.

Influence of chronic middle ear diseases on gustatory function: an electrogustometric study.

Objective: We aimed to quantitatively determine whether middle ear inflammation associated with unilateral chronic otitis media (COM), cholesteatoma, or otosclerosis affects gustatory function. Study Design: Prospective study. Setting: University Hospital, Department of Otolaryngology. Patients: Forty-two patients had unilateral COM (22 men, 20 women; mean age, 54.2 yr), 57 had unilateral cholesteatoma (35 men, 22 women; mean age, 42.1 yr), and 19 had unilateral otosclerosis (10 men, 9 women; mean age, 49.3 yr). Main Outcome Measures: Patients underwent taste testing using electrogustometry (EGM) and sensation thresholds were compared in the affected and unaffected ears among groups and between affected and unaffected ears in each group. Results: Patients with COM and cholesteatoma exhibited an increase in taste threshold in the affected ears compared to the unaffected ears (p < 0.05), whereas otosclerosis patients did not. The extent of the increase of the sensation thresholds in the affected ears was very similar between patients with COM and those with cholesteatoma (p = 0.548). Conclusion: Our EGM study showed that cholesteatoma and chronic middle ear inflammation affected gustatory function to a similar degree.

Hydrogen in drinking water attenuates noise-induced hearing loss in guinea pigs

It has been shown that molecular hydrogen acts as a therapeutic and preventive antioxidant by selectively reducing the hydroxyl radical, the most cytotoxic of the reactive oxygen species. In the present study, we tested the hypothesis that acoustic damage in guinea pigs can be attenuated by the consumption of molecular hydrogen. Guinea pigs received normal water or hydrogen-rich water for 14 days before they were exposed to 115 dB SPL 4-kHz octave band noise for 3h. Animals in each group underwent measurements for auditory brainstem response (ABR) or distortion-product otoacoustic emissions (DPOAEs) before the treatment (baseline) and immediately, 1, 3, 7, and 14 days after noise exposure. The ABR thresholds at 2 and 4 kHz were significantly better on post-noise days 1, 3, and 14 in hydrogen-treated animals when compared to the normal water-treated controls. Compared to the controls, the hydrogen-treated animals showed greater amplitude of DPOAE input/output growth functions during the recovery process, with statistical significance detected on post-noise days 3 and 7. These findings suggest that hydrogen can facilitate the recovery of hair cell function and attenuate noise-induced temporary hearing loss.

Recovery of facial movement and facial synkinesis in Bell's palsy patients.

Objective: We examined the relationship between the time course of development of facial synkinesis in patients with Bells palsy and the severity of facial nerve damage. Study Design: Retrospective study. Setting: Tertiary referral center. Patients: Thirty-nine consecutive patients with Bells palsy who developed synkinesis. Intervention: Diagnostic. Main Outcome Measures: Subjects were divided into groups A (electroneurographic [ENoG] value, <10%; n = 31) and B (ENoG value, ≥10%; n = 8). Development of facial synkinesis was assessed based on the appearance of synkinetic potentials from the orbicularis oris muscle on the blink reflex test. Times to appearance of facial synkinesis in groups A and B were compared. The proportion of patients who developed facial synkinesis after complete recovery of facial movement was also assessed in 14 patients whose facial movement recovered completely. Results: The mean time to maximal recovery of facial movement was significantly longer in group A than in group B (p < 0.001), whereas the duration between the appearance of facial synkinesis and the onset of facial paralysis did not differ significantly between the 2 groups (p = 0.72). The proportion of patients who developed facial synkinesis after complete recovery of facial movement was significantly greater in group B than in group A (p = 0.015). Conclusion: During the course of recovery from Bells palsy, the patients with an ENoG value of 10% or greater have a higher risk of developing facial synkinesis after complete recovery of facial movement.

Local increase in IgE and class switch recombination to IgE in nasal polyps in chronic rhinosinusitis

Chronic rhinosinusitis with nasal polyps is generally characterized by local Th2 inflammation and is categorized into two subtypes in Japan: eosinophilic chronic rhinosinusitis (similar to chronic rhinosinusitis with nasal polyps in western countries) and non‐eosinophilic chronic rhinosinusitis (characterized by Th1‐dominant inflammation).