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Sensitization by pulmonary reactive oxygen species of rat vagal lung C-fibers: the roles of the TRPV1, TRPA1, and P2X receptors.

Ruan T, Lin YJ, Hsu TH, Lu SH, Jow GM, Kou YR - PLoS ONE (2014)

Bottom Line: The potentiating effect of H2O2 on the apneic responses to α,β-methylene-ATP was reduced by capsazepine (a TRPV1 receptor antagonist), and by HC-030031.The potentiating effect of H2O2 on the VLCF responses to phenylbiguanide was totally prevented when all antagonists were combined.Inhalation of 0.05% H2O2 indeed increased the level of ROS in the lungs.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Department of Physiology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan.

ABSTRACT
Sensitization of vagal lung C-fibers (VLCFs) induced by mediators contributes to the pathogenesis of airway hypersensitivity, which is characterized by exaggerated sensory and reflex responses to stimulants. Reactive oxygen species (ROS) are mediators produced during airway inflammation. However, the role of ROS in VLCF-mediated airway hypersensitivity has remained elusive. Here, we report that inhalation of aerosolized 0.05% H2O2 for 90 s potentiated apneic responses to intravenous capsaicin (a TRPV1 receptor agonist), α,β-methylene-ATP (a P2X receptor agonist), and phenylbiguanide (a 5-HT3 receptor agonist) in anesthetized rats. The apneic responses to these three stimulants were abolished by vagatomy or by perivagal capsaicin treatment, a procedure that blocks the neural conduction of VLCFs. The potentiating effect of H2O2 on the apneic responses to these VLCF stimulants was prevented by catalase (an enzyme that degrades H2O2) and by dimethylthiourea (a hydroxyl radical scavenger). The potentiating effect of H2O2 on the apneic responses to capsaicin was attenuated by HC-030031 (a TRPA1 receptor antagonist) and by iso-pyridoxalphosphate-6-azophenyl-2',5'-disulphonate (a P2X receptor antagonist). The potentiating effect of H2O2 on the apneic responses to α,β-methylene-ATP was reduced by capsazepine (a TRPV1 receptor antagonist), and by HC-030031. The potentiating effect of H2O2 on the apneic responses to phenylbiguanide was totally abolished when all three antagonists were combined. Consistently, our electrophysiological studies revealed that airway delivery of aerosolized 0.05% H2O2 for 90 s potentiated the VLCF responses to intravenous capsaicin, α,β-methylene-ATP, and phenylbiguanide. The potentiating effect of H2O2 on the VLCF responses to phenylbiguanide was totally prevented when all antagonists were combined. Inhalation of 0.05% H2O2 indeed increased the level of ROS in the lungs. These results suggest that 1) increased lung ROS sensitizes VLCFs, which leads to exaggerated reflex responses in rats and 2) the TRPV1, TRPA1, and P2X receptors are all involved in the development of this airway hypersensitivity.

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Role of ROS in the sensitizing effect of H2O2 on the apneic responses to intravenous agonists.Data in each panel were obtained from one individual group of rats. Each rat received three consecutive inhalations. Catalase (CAT) is an enzyme that is able to degrade H2O2, while heat-inactivated catalase (HICAT) serves as the control treatment. Dimethylthiourea (DMTU) is a ·OH scavenger, while its vehicle serves as the control treatment. Intravenous agonist injection of capsaicin (A), α,β-meATP (B) or phenylbiguanide (C) was performed at 1 min after inhalation of H2O2 (0.05%) or PBS. Pretreatment was made 10 min prior to the second H2O2 sensitization by delivery of aerosolized CAT (13500 IU/ml) or HICAT (13500 IU/ml) into lower airways for 5 min, or by slow infusion of DMTU (1 g/kg) or its vehicle into the jugular vein over a 10-min duration. An elapsed time of 90 min was allowed between any two inhalations. ap<0.05 vs. response before H2O2 sensitization; bp<0.05 vs. response before CAT or DMTU pretreatment. Data in each group are the mean ± SE of eight rats. Note that the sensitizing effect of H2O2 was totally abolished by CAT and was partly reduced by DMTU, while HICAT or vehicle of DMTU had no such effect. See legends of figures 1 and 2 for further explanations of H2O2 sensitization, function of agonist, and calculation of the apneic ratio.
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pone-0091763-g004: Role of ROS in the sensitizing effect of H2O2 on the apneic responses to intravenous agonists.Data in each panel were obtained from one individual group of rats. Each rat received three consecutive inhalations. Catalase (CAT) is an enzyme that is able to degrade H2O2, while heat-inactivated catalase (HICAT) serves as the control treatment. Dimethylthiourea (DMTU) is a ·OH scavenger, while its vehicle serves as the control treatment. Intravenous agonist injection of capsaicin (A), α,β-meATP (B) or phenylbiguanide (C) was performed at 1 min after inhalation of H2O2 (0.05%) or PBS. Pretreatment was made 10 min prior to the second H2O2 sensitization by delivery of aerosolized CAT (13500 IU/ml) or HICAT (13500 IU/ml) into lower airways for 5 min, or by slow infusion of DMTU (1 g/kg) or its vehicle into the jugular vein over a 10-min duration. An elapsed time of 90 min was allowed between any two inhalations. ap<0.05 vs. response before H2O2 sensitization; bp<0.05 vs. response before CAT or DMTU pretreatment. Data in each group are the mean ± SE of eight rats. Note that the sensitizing effect of H2O2 was totally abolished by CAT and was partly reduced by DMTU, while HICAT or vehicle of DMTU had no such effect. See legends of figures 1 and 2 for further explanations of H2O2 sensitization, function of agonist, and calculation of the apneic ratio.

Mentions: We pretreated the animals with catalase (an enzyme to degrade H2O2), heat-inactivated catalase, dimethylthiourea (a •OH scavenger), or the vehicle of dimethylthiourea in order to investigate whether the potentiating effect was specific to the action of H2O2. As shown in figure 4, the potentiating effect of 0.05% H2O2 on the apneic responses to capsaicin (Figure 4A), α,β-meATP (Figure 4B) or phenylbiguanide (Figure 4C) was completely prevented by pretreatment with catalase (panels in 1st column) and was partially reduced by dimethylthiourea (panels in 3rd column), but was unaltered by pretreatment with heat-inactivated catalase (panels in 2nd column) or when the vehicle of dimethylthiourea was used (panels in 4th column).


Sensitization by pulmonary reactive oxygen species of rat vagal lung C-fibers: the roles of the TRPV1, TRPA1, and P2X receptors.

Ruan T, Lin YJ, Hsu TH, Lu SH, Jow GM, Kou YR - PLoS ONE (2014)

Role of ROS in the sensitizing effect of H2O2 on the apneic responses to intravenous agonists.Data in each panel were obtained from one individual group of rats. Each rat received three consecutive inhalations. Catalase (CAT) is an enzyme that is able to degrade H2O2, while heat-inactivated catalase (HICAT) serves as the control treatment. Dimethylthiourea (DMTU) is a ·OH scavenger, while its vehicle serves as the control treatment. Intravenous agonist injection of capsaicin (A), α,β-meATP (B) or phenylbiguanide (C) was performed at 1 min after inhalation of H2O2 (0.05%) or PBS. Pretreatment was made 10 min prior to the second H2O2 sensitization by delivery of aerosolized CAT (13500 IU/ml) or HICAT (13500 IU/ml) into lower airways for 5 min, or by slow infusion of DMTU (1 g/kg) or its vehicle into the jugular vein over a 10-min duration. An elapsed time of 90 min was allowed between any two inhalations. ap<0.05 vs. response before H2O2 sensitization; bp<0.05 vs. response before CAT or DMTU pretreatment. Data in each group are the mean ± SE of eight rats. Note that the sensitizing effect of H2O2 was totally abolished by CAT and was partly reduced by DMTU, while HICAT or vehicle of DMTU had no such effect. See legends of figures 1 and 2 for further explanations of H2O2 sensitization, function of agonist, and calculation of the apneic ratio.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3974698&req=5

pone-0091763-g004: Role of ROS in the sensitizing effect of H2O2 on the apneic responses to intravenous agonists.Data in each panel were obtained from one individual group of rats. Each rat received three consecutive inhalations. Catalase (CAT) is an enzyme that is able to degrade H2O2, while heat-inactivated catalase (HICAT) serves as the control treatment. Dimethylthiourea (DMTU) is a ·OH scavenger, while its vehicle serves as the control treatment. Intravenous agonist injection of capsaicin (A), α,β-meATP (B) or phenylbiguanide (C) was performed at 1 min after inhalation of H2O2 (0.05%) or PBS. Pretreatment was made 10 min prior to the second H2O2 sensitization by delivery of aerosolized CAT (13500 IU/ml) or HICAT (13500 IU/ml) into lower airways for 5 min, or by slow infusion of DMTU (1 g/kg) or its vehicle into the jugular vein over a 10-min duration. An elapsed time of 90 min was allowed between any two inhalations. ap<0.05 vs. response before H2O2 sensitization; bp<0.05 vs. response before CAT or DMTU pretreatment. Data in each group are the mean ± SE of eight rats. Note that the sensitizing effect of H2O2 was totally abolished by CAT and was partly reduced by DMTU, while HICAT or vehicle of DMTU had no such effect. See legends of figures 1 and 2 for further explanations of H2O2 sensitization, function of agonist, and calculation of the apneic ratio.
Mentions: We pretreated the animals with catalase (an enzyme to degrade H2O2), heat-inactivated catalase, dimethylthiourea (a •OH scavenger), or the vehicle of dimethylthiourea in order to investigate whether the potentiating effect was specific to the action of H2O2. As shown in figure 4, the potentiating effect of 0.05% H2O2 on the apneic responses to capsaicin (Figure 4A), α,β-meATP (Figure 4B) or phenylbiguanide (Figure 4C) was completely prevented by pretreatment with catalase (panels in 1st column) and was partially reduced by dimethylthiourea (panels in 3rd column), but was unaltered by pretreatment with heat-inactivated catalase (panels in 2nd column) or when the vehicle of dimethylthiourea was used (panels in 4th column).

Bottom Line: The potentiating effect of H2O2 on the apneic responses to α,β-methylene-ATP was reduced by capsazepine (a TRPV1 receptor antagonist), and by HC-030031.The potentiating effect of H2O2 on the VLCF responses to phenylbiguanide was totally prevented when all antagonists were combined.Inhalation of 0.05% H2O2 indeed increased the level of ROS in the lungs.

View Article: PubMed Central - PubMed

Affiliation: School of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan; Department of Physiology, School of Medicine, Chung Shan Medical University, Taichung, Taiwan.

ABSTRACT
Sensitization of vagal lung C-fibers (VLCFs) induced by mediators contributes to the pathogenesis of airway hypersensitivity, which is characterized by exaggerated sensory and reflex responses to stimulants. Reactive oxygen species (ROS) are mediators produced during airway inflammation. However, the role of ROS in VLCF-mediated airway hypersensitivity has remained elusive. Here, we report that inhalation of aerosolized 0.05% H2O2 for 90 s potentiated apneic responses to intravenous capsaicin (a TRPV1 receptor agonist), α,β-methylene-ATP (a P2X receptor agonist), and phenylbiguanide (a 5-HT3 receptor agonist) in anesthetized rats. The apneic responses to these three stimulants were abolished by vagatomy or by perivagal capsaicin treatment, a procedure that blocks the neural conduction of VLCFs. The potentiating effect of H2O2 on the apneic responses to these VLCF stimulants was prevented by catalase (an enzyme that degrades H2O2) and by dimethylthiourea (a hydroxyl radical scavenger). The potentiating effect of H2O2 on the apneic responses to capsaicin was attenuated by HC-030031 (a TRPA1 receptor antagonist) and by iso-pyridoxalphosphate-6-azophenyl-2',5'-disulphonate (a P2X receptor antagonist). The potentiating effect of H2O2 on the apneic responses to α,β-methylene-ATP was reduced by capsazepine (a TRPV1 receptor antagonist), and by HC-030031. The potentiating effect of H2O2 on the apneic responses to phenylbiguanide was totally abolished when all three antagonists were combined. Consistently, our electrophysiological studies revealed that airway delivery of aerosolized 0.05% H2O2 for 90 s potentiated the VLCF responses to intravenous capsaicin, α,β-methylene-ATP, and phenylbiguanide. The potentiating effect of H2O2 on the VLCF responses to phenylbiguanide was totally prevented when all antagonists were combined. Inhalation of 0.05% H2O2 indeed increased the level of ROS in the lungs. These results suggest that 1) increased lung ROS sensitizes VLCFs, which leads to exaggerated reflex responses in rats and 2) the TRPV1, TRPA1, and P2X receptors are all involved in the development of this airway hypersensitivity.

Show MeSH
Related in: MedlinePlus