Hirotada Ikeda

Effects of Ozone Exposure on Experimental Asthma in Guinea Pigs Sensitized with Ovalbumin through the Airway

As ozone (O3) is known to cause airway inflammation and hyperresponsiveness, we examined the effects of O3 exposure (1, 3, or 5 ppm, 2 h) on sensitization and provocation in guinea pigs sensitized with ovalbumin (OA) through the airway. In groups exposed to O3 before sensitization, 5 ppm increased the production of IgG1 antibodies and decreased the OA sensitization threshold from 0.01 to 0.002%. In those exposed before provocation, 1, 3, or 5 ppm of O3 decreased the OA provocation threshold from 0.5 to 0.02%, and this enhancement appeared to depend on airway hyperresponsiveness. We conclude that O3 exposure may play an important role in causing asthmatic attacks rather than enhancing allergic sensitization.

Tachykinins via tachykinin NK2 receptor activation mediate ozone-induced increase in the permeability of the tracheal mucosa in guinea-pigs

Acute exposure to ozone is known to cause airway hyperresponsiveness, which, at least in part, seems to result from an increase in the permeability of the airway mucosa. Recently, we demonstrated that depletion of sensory neuropeptides inhibits the ozone‐induced increase in the permeability of the tracheal mucosa in guinea‐pigs. The aim of this study was to determine whether tachykinins mediate ozone‐induced increase in the permeability of the tracheal mucosa in guinea‐pigs. Anaesthetized guinea‐pigs were exposed to either 3 p.p.m. ozone or filtered air for 30 min. Immediately after exposure, a tracheal segment was isolated in vivo and administered with horseradish peroxidase (HRP). The permeability was assessed by monitoring the appearance of HRP in the blood. A low dose of NKA increased the permeability of the tracheal mucosa, whereas a low dose of SP was without effect. Low and high doses of the selective NK3 receptor agonist, senktide, were also without effect. The effect of a low dose of NKA was abolished by the NK2 receptor antagonist, SR‐48,968. A high dose of SP increased the permeability in a manner reversible by the NK1 receptor antagonist, CP‐96,345. Pretreatment with SR‐48,968 completely inhibited the ozone‐induced increase in the permeability, whereas CP‐96,345 had no effect. It is thus concluded that endogenous tachykinins mediate the ozone‐induced increase in the permeability of the tracheal mucosa in guinea‐pigs mainly via NK2 receptor activation.

Enhanced neural regeneration from transected vagus nerve terminal in diabetic mice in vitro.

This study examined the effect of diabetes on neural regeneration in vitro. Nodose ganglia (NG) with vagal nerve fibers, dissected from streptozotocin-induced diabetic and normal C57BL/6J mice were embedded in collagen gel. After 3 and 7 days in culture, the numbers of regenerating neurites from transected nerve terminals of NG in diabetic mice were significantly greater than those in controls. Although many studies have revealed diabetes-associated impairment in neural regeneration, the results in the present study suggest that experimental diabetes could induce the potential to enhance regenerative capability of vagal sensory nerves after axotomy.

Dose‐response relationship of ozone‐induced airway hyperresponsiveness in unanesthetized guinea pigs

The effect of ozone dose (the product of ozone concentration and exposure time) on airway responsiveness was examined in unanesthetized, spontaneously breathing guinea pigs. Airway responsiveness was assessed by measuring specific airway resistance (sRaw) as a function of increasing concentration of inhaled methacholine (Mch) aerosol (the concentration of Mch required in order to double the baseline sRaw: PC200Mch). The airway responsiveness was measured before and at 5 min, 5 h, and 24 h after exposure. A 30-min exposure to 1 ppm ozone (dose 30 ppm.min) did not change PC200Mch at any time after exposure. Both a 90-min exposure to 1 ppm ozone and a 30-min exposure to 3 ppm ozone, which are identical in terms of ozone dose (90 ppm.min), decreased PC200Mch to a similar degree. A 120-min exposure to 3 ppm ozone (360 ppm.min) produced a much greater decrease of PC200Mch at 5 min and 5 h after exposure, compared with low-dose exposure. There was a significant correlation between ozone dose and the change in airway responsiveness. In all groups, the baseline sRaw was increased by approximately 50% at 5 min after exposure, but there was no correlation between the changes in PC200Mch and the baseline sRaw. This study suggests that ozone-induced airway hyperresponsiveness in guinea pigs is closely related to ozone dose.

Role of superoxide anions in airway hyperresponsiveness induced by cigarette smoke in conscious guinea pigs

To investigate the involvement of superoxide in airway hyperresponsiveness and bronchoconstriction induced by cigarette smoke (CS), we evaluated the effects of superoxide dismutase (SOD), a scavenger of superoxide anion, and apocynin, an inhibitor of superoxide anion-generating NADPH oxidase in phagocytes, on the airway responses induced by CS in conscious guinea pigs. Airway responsiveness was assessed by PC2OOMch, the concentration required to produce a doubling in the baseline specific airway resistance (sRaw) to an inhaled methacholine aerosol, in nonanesthetized spontaneously breathing animals. Before being exposed to ten puffs of CS, animals inhaled either SOD (5,000 units/ml or 25,000 units/ml) or vehicle. Although SOD did not affect PC2OOMch, in the air control group, this agent significantly reduced the CS-induced airway hyperresponsiveness. Repeated administration of apocynin (12 mg/kg for 4 days) did not affect PC2OOMch, after exposure to CS. These data suggest that the superoxide from CS was involved in the airway hyperresponsiveness induced by CS, whereas phagocytic reactive oxygen species were not. The data also suggest a potential therapeutic role for antioxidants in airway hyperresponsiveness.

Combined effects of ozone and cigarette smoke on airway responsiveness and vascular permeability in guinea pigs.

The effects of combined exposure to ozone and cigarette smoke on airway responsiveness and tracheal vascular permeability, compared with those of single exposure were examined in guinea pigs. Airway responsiveness was assessed by measuring the specific airway resistance (sRaw) as a function of increasing concentration of inhaled methacholine aerosol immediately, 5 hr, and 24 hr after exposure. In a parallel study, tracheal vascular permeability was quantified by measuring the tracheal extravasation of intravenously administered Evans blue dye. Neither exposure to 1 ppm ozone for 30 min nor 5 puffs of cigarette smoke increased airway responsiveness or vascular permeability at any time after exposure. Combined exposure to 1 ppm ozone for 30 min and 5 puffs of cigarette smoke caused airway hyperresponsiveness and increased vascular permeability immediately after exposure. Exposure to 1 ppm ozone for 90 min increased both airway responsiveness and vascular permeability immediately after exposure. Exposure to 10 puffs of cigarette smoke increased airway responsiveness but not vascular permeability immediately after exposure. Combined exposure to 1 ppm ozone for 90 min and 10 puffs of cigarette smoke increased both airway responsiveness and vascular permeability immediately after exposure. The combined exposure to ozone and cigarette smoke thus increased both airway responsiveness and tracheal vascular permeability to a greater extent than did exposure to a single agent, suggesting that a combination of air pollutants has a more deleterious effect both on airway responsiveness and on tracheal vascular permeability than does either agent alone in guinea pigs.

Involvement of superoxide anions in ozone-induced airway hyperresponsiveness in unanesthetized guinea pigs.

To evaluate the involvement of superoxide in ozone (O(3))-induced airway hyperresponsiveness, we studied the effects of superoxide dismutase (SOD), a scavenger of superoxide anion, and apocynin, an inhibitor of superoxide anion-generating NADPH oxidase in phagocytes, on the airway responses induced by O(3) in unanesthetized guinea pigs. Airway responsiveness was measured by PC(200)Mch, the concentration required to produce a doubling in the baseline specific airway resistance to an inhaled methacholine aerosol, in spontaneously breathing animals. Before exposure to 3 ppm O(3) for 30 min, animals inhaled either SOD (5000 U/ml) or vehicle for 5 min. Although SOD did not affect PC(200)Mch in the air control group, this agent reduced the O(3)-induced airway hyperresponsiveness. Repeated administration of apocynin (12 mg/kg for 4 days) also attenuated the O(3)-induced airway hyperresponsiveness. These data suggest that superoxide may be involved in the pathogenesis of O(3)-induced airway hyperresponsiveness, possibly through the stimulation of superoxide anions release from bronchoalveolar phagocytes. The data also suggest a potential therapeutic role for antioxidants in oxidant injury by air pollutants.

Neuropeptides mediate the ozone-induced increase in the permeability of the tracheal mucosa in guinea pigs

We examined the effects of acute exposure to ozone on the permeability of the tracheal mucosa and the contribution of neural pathways to the effects of ozone using horseradish peroxidase (HRP; mol wt 40,000) as a marker of lumen-to-blood transfer of a macromolecule in guinea pigs in vivo. Each guinea pig was anesthetized and exposed for 30 min to either ozone [0.5 or 3 parts/million (ppm)] or air. Immediately after exposure, a tracheal segment was isolated between two polyethylene cannulas in vivo and filled with HRP solution (50 mg/ml). Blood samples were drawn before and 10, 20, 30, and 40 min after the intratracheal instillation of HRP. The plasma levels of HRP in guinea pigs exposed for 30 min to 3 ppm of ozone, but not to 0.5 ppm of ozone, were significantly greater than those in guinea pigs exposed to air. Although the increased plasma HRP levels after exposure to 3 ppm of ozone were unaffected by propranolol or atropine, they were completely inhibited by pretreatment with capsaicin (50 mg/kg sc, injected in two doses). These results suggest that endogenous neuropeptides mediate the ozone-induced increase in the permeability of the tracheal mucosa in guinea pigs in vivo, but neither an adrenergic nor a cholinergic pathway appears to be involved.We examined the effects of acute exposure to ozone on the permeability of the tracheal mucosa and the contribution of neural pathways to the effects of ozone using horseradish peroxidase (HRP; mol wt 40,000) as a marker of lumen-to-blood transfer of a macromolecule in guinea pigs in vivo. Each guinea pig was anesthetized and exposed for 30 min to either ozone [0.5 or 3 parts/million (ppm)] or air. Immediately after exposure, a tracheal segment was isolated between two polyethylene cannulas in vivo and filled with HRP solution (50 mg/ml). Blood samples were drawn before and 10, 20, 30, and 40 min after the intratracheal instillation of HRP. The plasma levels of HRP in guinea pigs exposed for 30 min to 3 ppm of ozone, but not to 0.5 ppm of ozone, were significantly greater than those in guinea pigs exposed to air. Although the increased plasma HRP levels after exposure to 3 ppm of ozone were unaffected by propranolol or atropine, they were completely inhibited by pretreatment with capsaicin (50 mg/kg sc, injected in two doses). These results suggest that endogenous neuropeptides mediate the ozone-induced increase in the permeability of the tracheal mucosa in guinea pigs in vivo, but neither an adrenergic nor a cholinergic pathway appears to be involved.

Trachea enhances neurite regeneration from adult rat nodose ganglia in vitro

Trachea is intensely innervated with vagal afferent nerve fibers, and may play an important role in vagus nerve regeneration after axonal injury caused by trauma and surgical operation. We investigated the effects of tracheal tissue on neuronal cell survival and neurite regeneration in adult rat nodose ganglia (NG) in vitro. Co-culture with trachea significantly increased the average number of neurites regenerated from transected nerve terminals of NG explants, from 73.7 to 154.2 after 3 days, from 68 to 186.7 after 5 days, and from 31 to 101.5 after 7 days in culture. Dissociated NG neurons could continue to survive and extend neurites only in the co-existence with satellite cells in collagen gel. Co-cultured trachea improved the ratios of survival and neurite-bearing cells of NG neurons, from 56.7% and 11.1% to 72.3% and 37.6% after 4 days, and from 41.1% and 20.3% to 56.4% and 47.2% after 7 days in culture, respectively. These results imply that tracheal tissue secretes a factor, which could enhance neuronal cell survival and neurite regeneration in NG in the presence of satellite cells in vitro.

Large cell carcinoma of the lung metastatic to nuchal muscle

Abstract Clinically apparent hematogenous skeletal muscle metastases from lung cancer are extremely rare. We present a 72‐year‐old man with a large cell lung carcinoma metastatic to nuchal muscle. Cervical computed tomography (CT) and magnetic resonance imaging (MRI) revealed the presence of a well‐defined mass in the left splenius capitis muscle. A percutaneous needle biopsy was performed to establish a diagnosis. Localized skeletal muscle swelling may rarely prove to be metastases in patients with lung cancer, but should be investigated in the case of muscle swelling.