Hiromasa Ogawa

In vivo release of glutamate in nucleus tractus solitarii of the rat during hypoxia.

1. An attempt has been made to test the hypothesis that, in the caudal part of nucleus tractus solitarii (NTS) where carotid sinus nerve (CSN) afferents project, L‐glutamate (Glut) modulates the hypoxic ventilatory response. 2. Unanaesthetized, peripherally chemodenervated (carotid body denervated; CBD) and sham‐operated, freely moving rats were used. During peripheral chemoreceptor stimulation by hypoxia (10% O2 for 30 min) or doxapram (Dox) infusion (2 mg kg‐1 (30 min)‐1), ventilation was recorded and successively, under the same conditions, the extracellular Glut concentration ([Glut]o) in the caudal NTS was measured by in vivo microdialysis. [Glut]o was also measured during hyperoxic hypercapnia (10% CO2‐30% O2 for 30 min). 3. Furthermore, the effects on ventilation of exogenous Glut, the NMDA (N‐methyl‐D‐aspartate) receptor antagonist MK‐801 or the ionotropic receptor antagonist kynurenate microinjected into the caudal NTS were investigated in sham‐operated rats. 4. In sham‐operated rats, both ventilation and [Glut]o in NTS were increased during peripheral chemoreceptor stimulation. On the other hand, no increases in either ventilation or Glut release were observed in CBD rats. In spite of ventilatory augmentation during hypercapnia, no response of [Glut]o to hypercapnia was observed in either group. 5. Local Glut application into NTS increased ventilation. Pretreatment with MK‐801 or kynurenate reduced the hypoxic ventilatory response. This reduction in ventilation was mainly due to the decrease in tidal volume. 6. These results suggest that hypoxia induced the release of Glut in NTS and that this effect was mediated by arterial chemosensory input.

Nitric oxide as a retrograde messenger in the nucleus tractus solitarii of rats during hypoxia.

1. We examined the role of nitric oxide (NO) in respiratory regulation in the nucleus tractus solitarii (NTS), where L‐glutamate release associated with peripheral chemoreceptor activation modulates the hypoxic ventilatory response. 2. Experiments were performed in unanaesthetized freely moving rats. First, the effects on the hypoxic ventilatory response of sodium nitroprusside (SNP, a NO donor) or NG‐monomethyl‐L‐arginine (L‐NMMA, a NO synthase inhibitor), microinjected into the NTS, were investigated. Second, using in vivo microdialysis, changes in extracellular L‐glutamate during hypoxia were examined in the presence of L‐NMMA. Third, the effect of L‐NMMA on ventilatory augmentation by exogenous L‐glutamate was examined. Furthermore, we measured extracellular L‐citrulline concentration changes during hypoxia in the NTS to assess NO formation indirectly and also examined the effect of MK‐801 (an NMDA receptor antagonist) on L‐citrulline levels during hypoxia. 3. SNP increased ventilation during both normoxia and hypoxia. L‐NMMA did not alter ventilation or L‐glutamate levels during normoxia but significantly attenuated the hypoxic ventilatory response and the increase in L‐glutamate during hypoxia. The inhibition by L‐NMMA was blocked by L‐arginine. The ventilatory augmentation by exogenous L‐glutamate was attenuated by L‐NMMA. L‐Citrulline increased during hypoxia, and this increase was inhibited by MK‐801. 4. We provide the first in vivo evidence that, in the NTS, NO works as a retrograde messenger in an L‐glutamate‐releasing positive feedback system contributing to the augmentation of ventilation during hypoxia.

Narcolepsy as an initial manifestation of neuromyelitis optica with antiaquaporin-4 antibody

JO N 3139 brospinal fluid (CSF) hypocretin level is useful for a diagnosis of narcolepsy [3]. The symptoms of narcolepsy are also known to occur secondary to hypothalamic lesions of various neurological conditions, such as brain tumors [6] and multiple sclerosis (MS) [2, 9]. Neuromyelitis optica (NMO) is a demyelinating disease typically manifesting transverse myelitis and bilateral optic neuritis. Anti-aquaporin-4 (AQP4) antibody was discovered as a disease-specific autoantibody in NMO patients [5]. Recently, brain lesions of NMO have been identified by many investigators and it has been reported that the lesions are generally observed in the hypothalamic region [7, 10]. In this paper, we report a case of NMO with anti-AQP4 antibody, whose initial manifestation was narcolepsy and marked decrease of CSF hypocretin level. A 35-year-old woman was referred for evaluation of excessive daytime sleepiness. On examination, apart from excessive daytime sleepiness, no neurological deficit was detected. She had no episode of cataplexy. A MRI scan showed a nonenhancing T2 lesion in the hypothalamus (Fig. 1 A). CSF study showed a slight degree of pleocytosis (12/mm3) and a normal protein level (23 mg/dl). The CSF hypocretin-1 level was markedly decreased (91 pg/ml; normal 200–350 pg/ml). She had narcolepsy-associated HLA haplotypes such as DR2 [3], but the DNA haplotypes were not typical for this disease (DRB1*1502, DQB1*0301, and DQB1*0601). Her sleep pattern was evaluated by nocturnal polysomnography (PSG) and multiple sleep latency test (MSLT). Her sleep latency was less than 10 min with SOREMP and total sleep time was 9.5 hours in PSG. The mean sleep latency by MSLT (4 naps) was 6 min with 4 SOREMPs. She was diagnosed as having narcolepsy due to Toru Baba Ichiro Nakashima Takashi Kanbayashi Masatoshi Konno Toshiyuki Takahashi Kazuo Fujihara Tatsuro Misu Atsushi Takeda Yusei Shiga Hiromasa Ogawa Yasuto Itoyama

Role of the parabrachial nucleus in ventilatory responses of awake rats.

1. The parabrachial nucleus (PBN) is thought to play an important role in cardiorespiratory control. However, the circumstances under which it affects ventilation are still not known. The purpose of the present study was to investigate how the PBN modulates the ventilatory responses to hypercapnia, hypoxia or a resistive load in awake rats with chemical lesions of the PBN. 2. In three groups of rats (with lateral PBN lesion, with Kölliker‐Fuse nucleus lesion and control), ventilation was measured under various conditions. 3. There was no difference in the breathing of normal room air in any of the groups. However, the lesioned groups showed a reduced ventilatory response to hyperoxic hypercapnia (inspired CO2 fractions (FI,CO2) of 3, 5, 8 and 10%) and to graded hypoxia (inspired O2 fractions (FI,O2) of 16, 12, 10 and 8%) compared with the control group. The control group showed a biphasic response to sustained hypoxia (FI,O2 at 10% for 30 min), known as ‘hypoxic depression’, while the lesioned groups showed moderate ventilatory exaggeration throughout hypoxia. In response to a resistive load, the lateral PBN lesion group showed no change in ventilatory compensation. 4. The PBN appeared to have a considerable influence on ventilation stimulated in various ways during wakefulness.

Xanthine oxidase inhibition reduces reactive nitrogen species production in COPD airways

Reactive nitrogen species (RNS) have been reported to be involved in the inflammatory process in chronic obstructive pulmonary disease (COPD). However, there are no studies on the modulation of RNS in COPD. It was hypothesised that inhibition of xanthine oxidase (XO) might decrease RNS production in COPD airways through the suppression of superoxide anion production. Ten COPD and six healthy subjects participated in the study. The XO inhibitor allopurinol (300 mg·day−1 p.o. for 4 weeks) was administered to COPD patients. RNS production in the airway was assessed by 3‐nitrotyrosine immunoreactivity and enzymic activity of XO in induced sputum as well as by exhaled nitric oxide (eNO) concentration. XO activity in the airway was significantly elevated in COPD compared with healthy subjects. Allopurinol administration to COPD subjects significantly decreased XO activity and nitrotyrosine formation. In contrast, eNO concentration was significantly increased by allopurinol administration. These results suggest that oral administration of the xanthine oxidase inhibitor allopurinol reduces airway reactive nitrogen species production in chronic obstructive pulmonary disease subjects. This intervention may be useful in the future management of chronic obstructive pulmonary disease.

Quantitative assessment of protein-bound tyrosine nitration in airway secretions from patients with inflammatory airway disease.

Because reactive nitrogen species (RNS) have potent inflammatory activity, they may be involved in the inflammatory process in pulmonary diseases. We recently reported increased numbers of 3-nitrotyrosine immunopositive cells, which are evidences of RNS production, in the sputum of patients with chronic obstructive pulmonary disease (COPD) and patients with asthma compared with healthy subjects. In the present study, we attempted to quantify this protein nitration in the airways by means of high-performance liquid chromatography (HPLC) used together with an electrochemical detection system that we developed. Sputum samples were obtained from 15 stable COPD patients, 9 asthmatic patients and 7 healthy subjects by using hypertonic saline inhalation. The values for the molar ratio of protein-bound 3-nitrotyrosine/tyrosine in patients with asthma (4.31±1.13 × 10-6, p<0.05) and patients with COPD (3.04±0.36 × 10-6, p<0.01) were significantly higher than those in healthy subjects (1.37±0.19 × 10-6). The levels of protein-bound 3-nitrotyrosine in the airways were not significantly different in asthmatic patients and COPD patients. A significant negative correlation was found between values for protein-bound 3-nitrotyrosine/tyrosine and % FEV1 values in patients with COPD (r=-0.53, p<0.05) but not in patients with asthma. These results suggest that our HPLC-electrochemical method is useful for quantifying RNS production in human airways. More importantly, they show that increased RNS production in the airways seems to contribute in a critical way to the pathogenesis of COPD, and that the effects of RNS in airways may differ in asthma and COPD.

Application of impulse oscillometry for within-breath analysis in patients with chronic obstructive pulmonary disease: pilot study

Background The impulse oscillometry is increasingly used for assessing the oscillatory mechanics of the respiratory system. The within-breath behaviour of the oscillatory mechanics in chronic obstructive pulmonary disease (COPD) is a well-known physiological feature. The purpose of this study was to develop a new approach for assessing this feature using impulse oscillometry. Methods The oscillatory mechanics were assessed by a commercially available impulse oscillometry device. The respiratory system resistance (Rrs) and reactance (Xrs) were measured during tidal breathing in patients with COPD (n=39) and healthy subjects (n=5). Selected data, the Rrs at 5 Hz (R5), Rrs at 20 Hz (R20), Xrs at 5 Hz (X5), and resonant frequency of Xrs (Fres) every 0.2 s, were extracted from the device. These data were divided into eight time fractions during the respiratory cycle to form averaged respiratory phases. Results The time courses of the R5 and X5 were notably dependent on the respiratory cycles in patients with COPD, while there was little such dependency in healthy subjects. Irrespective of respiratory phase, R5 and Fres increased, and X5 fell to a more negative level in patients with COPD in a severity-dependent fashion. The increase in the R5 and negative level in the X5 were more prominent in the middle of the expiratory phase. The severity dependence in the R20 was relatively small compared with that in the R5. Conclusions The results of this study suggest that impulse oscillometry can assess the within-breath behaviour of the oscillatory mechanics with high temporal resolution, which may be helpful for evaluating the severity of COPD. Further studies are needed to reveal which biomarkers obtained with this approach would be suitable for evaluating the airway obstruction.

Mesenchymal Stem Cells Correct Inappropriate Epithelial–mesenchyme Relation in Pulmonary Fibrosis Using Stanniocalcin-1

Current hypotheses suggest that aberrant wound healing has a critical role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). In these hypotheses, continuous TGF-β1 secretion by alveolar epithelial cells (AECs) in abnormal wound healing has a critical role in promoting fibroblast differentiation into myofibroblasts. Mesenchymal stem cells (MSCs) home to the injury site and reduce fibrosis by secreting multifunctional antifibrotic humoral factors in IPF. In this study, we show that MSCs can correct the inadequate-communication between epithelial and mesenchymal cells through STC1 (Stanniocalcin-1) secretion in a bleomycin-induced IPF model. Inhalation of recombinant STC1 shows the same effects as the injection of MSCs. Using STC1 plasmid, it was possible to enhance the ability of MSCs to ameliorate the fibrosis. MSCs secrete large amounts of STC1 in response to TGF-β1 in comparison to AECs and fibroblasts. The antifibrotic effects of STC1 include reducing oxidative stress, endoplasmic reticulum (ER) stress, and TGF-β1 production in AECs. The STC1 effects can be controlled by blocking uncoupling protein 2 (UCP2) and the secretion is affected by the PI3/AKT/mTORC1 inhibitors. Our findings suggest that STC1 tends to correct the inappropriate epithelial-mesenchymal relationships and that STC1 plasmid transfected to MSCs or STC1 inhalation could become promising treatments for IPF.

Lack of ventilatory threshold in patients with chronic obstructive pulmonary disease.

We investigated whether the ventilatory threshold (VET) could be detected in 25 patients with severe chronic obstructive pulmonary disease (COPD). Exercise on a treadmill was performed until symptom-limited maximum oxygen uptake (VO2SL) was obtained. VET was absent in 14 patients (56%, VET(-) group) and present in the others (44%, VET(+) group). Basal pulmonary functions and dyspnea index (VE,SL/MVV) were not different between the two groups. Endurance time and exercise tolerance (VO2SL/bw) were significantly less in VET(-) than in VET(+). In the former group, PaO2 and pH at maximal exercise decreased and PaCO2 increased significantly, but HCO3- did not change compared with the corresponding values before exercise. In the latter group, PaCO2 at maximal exercise increased significantly, and pH and HCO3- decreased significantly compared with the values before exercise, but PaO2 did not. The changes in PaO2 and PaCO2 were not different between the two groups, but changes in pH and HCO3- in VET(+) were greater than those in VET(-). These results suggest that the absence of VET in some COPD patients indicates a lower exercise capacity without producing metabolic acidosis. This may be caused by rapidly developing dyspnea.

The effect of upper airway structural changes on central chemosensitivity in obstructive sleep apnea-hypopnea.

We examined the efficiency of upper airway structural changes in uvulopalatopharyngoplasty and/or tonsillectomy on central chemosensitivity, and whether the outcome of such surgeries can be predicted by the central chemosensitivity in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients. In 11 patients with OSAHS group, the average of the hypercapnic ventilatory response (HCVR) slope was 1.93 ± 0.20 L/min/mm Hg preoperatively and 1.78 ± 0.22 L/min/mm Hg postoperatively. The average of the mouth occlusion pressure at 0.1 second after the onset of inspiration (P0.1) slope was 0.47 ± 0.06 cm H2O/mm Hg and 0.44 ± 0.08 cm H2O/mm Hg, before and after surgery, respectively. There were no significant differences before and after treatment, although OSAHS was improved by these surgeries. In control group with 5 patients, the HCVR slope and P0.1slope also showed no significant difference before and after the procedure. When we divided the 11 OSAHS patients into 7 responders (apnea-hypopnea index < 20 events/h and > 50% reduction) and 4 poor responders, there was a significant difference between the average HCVR slope of responders (1.59 ± 0.21 L/min/mm Hg) and that of poor responders (2.52 ± 0.20 L/min/mm Hg). We saw no significant difference in physiologic (age, body mass index, one-piece tonsil weight), blood gas values, cephalometric, spirometric, or sleep parameters.