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Impact of ozone exposure on the response to glucocorticoid in a mouse model of asthma: involvements of p38 MAPK and MKP-1.

Bao A, Li F, Zhang M, Chen Y, Zhang P, Zhou X - Respir. Res. (2014)

Bottom Line: Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17.Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone.Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory Medicine, Shanghai First People's Hospital, Shanghai Jiao tong University, 100 Haining Road, Shanghai 200080China. xzhou53@163.com.

ABSTRACT

Background: Molecular mechanisms involved in the oxidative stress induced glucocorticoids insensitivity remain elusive. The mitogen-activated protein kinase phosphatase (MKP) 1 mediates a part of glucocorticoids action and can be modified by exogenous oxidants. Whether oxidant ozone (O3) can affect the function of MKP-1 and hence blunt the response to corticotherapy is not clear.

Methods: Here we employed a murine model of asthma established with ovalbumin (OVA) sensitization and challenge to evaluate the influence of O3 on the inhibitory effect of dexamethasone on AHR and airway inflammation, and by administration of SB239063, a selective p38 MAPK inhibitor, to explore the underlying involvements of the activation of p38 MAPK and the expression of MKP-1.

Results: Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17. Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone. Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

Conclusions: The glucocorticoids insensitivity elicited by ozone exposure on current asthma model may involve the enhanced phosphorylation of p38 MAPK and disturbed expression of MKP-1.

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Related in: MedlinePlus

Schematic diagram of experimental protocol. Mice were sensitized at day 1 and 14, and challenged at day 24, 25, 26 with OVA or saline. Dexamethasone or saline was administrated intraperitoneally 1 hr before each challenge. Equal number of mice were selected to expose to 1.0 ppm O3 or filtered air for 3 consecutive hrs on day 23, 25 and 27. In p38 MAPK inhibition experiment, same amount of animals were injected through tail vein with SB239063 or DMSO. On day 28, measurements were performed including enhanced pause (Penh), BAL cells and cytokines, lung tissues for pathological staining and biological testing.
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Fig1: Schematic diagram of experimental protocol. Mice were sensitized at day 1 and 14, and challenged at day 24, 25, 26 with OVA or saline. Dexamethasone or saline was administrated intraperitoneally 1 hr before each challenge. Equal number of mice were selected to expose to 1.0 ppm O3 or filtered air for 3 consecutive hrs on day 23, 25 and 27. In p38 MAPK inhibition experiment, same amount of animals were injected through tail vein with SB239063 or DMSO. On day 28, measurements were performed including enhanced pause (Penh), BAL cells and cytokines, lung tissues for pathological staining and biological testing.

Mentions: On days 23, 25 and 27, conscious mice were exposed to ozone [1.0 parts/million (ppm) for 3 h] or filtered air. Ozone was generated by directing an air stream with a micro air pump (SC3601PM, Shenzhen, China) into a AQUA MEDIC O3 generator (model 300, AB Aqua Medic GmbH, Bissendorf, Germany). Ozone concentration in the chamber was monitored continuously by an Ozone Switch (OS-4, Newark, USA), which also controlled the operation of the ozone generator in response to the instantaneous value. The target O3 concentration range was set as 0.77 ppm ~ 1.32 ppm, which has been proved by our preliminary experiment to be able to maintain a comparatively stable O3 concentration averaged as 1.01 ± 0.02 ppm (data not shown). This methodology of O3 exposure has been adapted by previous study which had documented that, such level of ozone inhalation can induced the airway inflammation but not influence the body weight of mice [17], which means less toxic effect. One hour before and 4 hrs after the O3 exposure, mice were injected through tail vein SB239063 (Sigma Aldrich, St. Louis, MO) dissolved in 3% DMSO (0.1 ml, Sigma Aldrich, St. Louis, MO) or DMSO only, respectively. The dosages of SB239063 were titrated in a preliminary experiment, where the final dosage of 4.0 mg/kg was selected. The present experimental protocol was outlined in Figure 1.Figure 1


Impact of ozone exposure on the response to glucocorticoid in a mouse model of asthma: involvements of p38 MAPK and MKP-1.

Bao A, Li F, Zhang M, Chen Y, Zhang P, Zhou X - Respir. Res. (2014)

Schematic diagram of experimental protocol. Mice were sensitized at day 1 and 14, and challenged at day 24, 25, 26 with OVA or saline. Dexamethasone or saline was administrated intraperitoneally 1 hr before each challenge. Equal number of mice were selected to expose to 1.0 ppm O3 or filtered air for 3 consecutive hrs on day 23, 25 and 27. In p38 MAPK inhibition experiment, same amount of animals were injected through tail vein with SB239063 or DMSO. On day 28, measurements were performed including enhanced pause (Penh), BAL cells and cytokines, lung tissues for pathological staining and biological testing.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4196074&req=5

Fig1: Schematic diagram of experimental protocol. Mice were sensitized at day 1 and 14, and challenged at day 24, 25, 26 with OVA or saline. Dexamethasone or saline was administrated intraperitoneally 1 hr before each challenge. Equal number of mice were selected to expose to 1.0 ppm O3 or filtered air for 3 consecutive hrs on day 23, 25 and 27. In p38 MAPK inhibition experiment, same amount of animals were injected through tail vein with SB239063 or DMSO. On day 28, measurements were performed including enhanced pause (Penh), BAL cells and cytokines, lung tissues for pathological staining and biological testing.
Mentions: On days 23, 25 and 27, conscious mice were exposed to ozone [1.0 parts/million (ppm) for 3 h] or filtered air. Ozone was generated by directing an air stream with a micro air pump (SC3601PM, Shenzhen, China) into a AQUA MEDIC O3 generator (model 300, AB Aqua Medic GmbH, Bissendorf, Germany). Ozone concentration in the chamber was monitored continuously by an Ozone Switch (OS-4, Newark, USA), which also controlled the operation of the ozone generator in response to the instantaneous value. The target O3 concentration range was set as 0.77 ppm ~ 1.32 ppm, which has been proved by our preliminary experiment to be able to maintain a comparatively stable O3 concentration averaged as 1.01 ± 0.02 ppm (data not shown). This methodology of O3 exposure has been adapted by previous study which had documented that, such level of ozone inhalation can induced the airway inflammation but not influence the body weight of mice [17], which means less toxic effect. One hour before and 4 hrs after the O3 exposure, mice were injected through tail vein SB239063 (Sigma Aldrich, St. Louis, MO) dissolved in 3% DMSO (0.1 ml, Sigma Aldrich, St. Louis, MO) or DMSO only, respectively. The dosages of SB239063 were titrated in a preliminary experiment, where the final dosage of 4.0 mg/kg was selected. The present experimental protocol was outlined in Figure 1.Figure 1

Bottom Line: Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17.Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone.Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

View Article: PubMed Central - PubMed

Affiliation: Department of Respiratory Medicine, Shanghai First People's Hospital, Shanghai Jiao tong University, 100 Haining Road, Shanghai 200080China. xzhou53@163.com.

ABSTRACT

Background: Molecular mechanisms involved in the oxidative stress induced glucocorticoids insensitivity remain elusive. The mitogen-activated protein kinase phosphatase (MKP) 1 mediates a part of glucocorticoids action and can be modified by exogenous oxidants. Whether oxidant ozone (O3) can affect the function of MKP-1 and hence blunt the response to corticotherapy is not clear.

Methods: Here we employed a murine model of asthma established with ovalbumin (OVA) sensitization and challenge to evaluate the influence of O3 on the inhibitory effect of dexamethasone on AHR and airway inflammation, and by administration of SB239063, a selective p38 MAPK inhibitor, to explore the underlying involvements of the activation of p38 MAPK and the expression of MKP-1.

Results: Ozone exposure not only aggravated the pulmonary inflammation and AHR, but also decreased the inhibitory effects of dexamethasone, accompanied by the elevated oxidative stress, airway neutrophilia, enhanced phosphorylation of p38 MAPK, and upregulated expression of IL-17. Administration of SB239063 caused significant inhibition of the p38 MAPK phosphorylation, alleviation of the airway neutrophilia, and decrement of the ozone-induced IL-17 expression, and partly restored the ozone-impaired effects of dexamethasone. Ozone exposure not only decreased the protein expression of MKP-1, but also diminished the dexamethasone-mediated induction process of MKP-1 mRNA and protein expression.

Conclusions: The glucocorticoids insensitivity elicited by ozone exposure on current asthma model may involve the enhanced phosphorylation of p38 MAPK and disturbed expression of MKP-1.

Show MeSH
Related in: MedlinePlus