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Paradoxical effects of rapamycin on experimental house dust mite-induced asthma.

Fredriksson K, Fielhaber JA, Lam JK, Yao X, Meyer KS, Keeran KJ, Zywicke GJ, Qu X, Yu ZX, Moss J, Kristof AS, Levine SJ - PLoS ONE (2012)

Bottom Line: Lastly, mediastinal lymph node re-stimulation experiments showed that treatment of rapamycin-naive T cells with ex vivo rapamycin decreased antigen-specific Th2 cytokine production, whereas prior exposure to in vivo rapamycin rendered T cells refractory to the suppressive effects of ex vivo rapamycin.We conclude that rapamycin had paradoxical effects on the pathogenesis of experimental HDM-induced asthma.Thus, consistent with the context-dependent effects of rapamycin on inflammation, the timing of mTOR inhibition may be an important determinant of efficacy and toxicity in HDM-induced asthma.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.

ABSTRACT
The mammalian target of rapamycin (mTOR) modulates immune responses and cellular proliferation. The objective of this study was to assess whether inhibition of mTOR with rapamycin modifies disease severity in two experimental murine models of house dust mite (HDM)-induced asthma. In an induction model, rapamycin was administered to BALB/c mice coincident with nasal HDM challenges for 3 weeks. In a treatment model, nasal HDM challenges were performed for 6 weeks and rapamycin treatment was administered during weeks 4 through 6. In the induction model, rapamycin significantly attenuated airway inflammation, airway hyperreactivity (AHR) and goblet cell hyperplasia. In contrast, treatment of established HDM-induced asthma with rapamycin exacerbated AHR and airway inflammation, whereas goblet cell hyperplasia was not modified. Phosphorylation of the S6 ribosomal protein, which is downstream of mTORC1, was increased after 3 weeks, but not 6 weeks of HDM-challenge. Rapamycin reduced S6 phosphorylation in HDM-challenged mice in both the induction and treatment models. Thus, the paradoxical effects of rapamycin on asthma severity paralleled the activation of mTOR signaling. Lastly, mediastinal lymph node re-stimulation experiments showed that treatment of rapamycin-naive T cells with ex vivo rapamycin decreased antigen-specific Th2 cytokine production, whereas prior exposure to in vivo rapamycin rendered T cells refractory to the suppressive effects of ex vivo rapamycin. We conclude that rapamycin had paradoxical effects on the pathogenesis of experimental HDM-induced asthma. Thus, consistent with the context-dependent effects of rapamycin on inflammation, the timing of mTOR inhibition may be an important determinant of efficacy and toxicity in HDM-induced asthma.

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Rapamycin attenuates mTORC1 effectors.Phosphorylation of the mTORC1 effector, S6 (phospho-S6 Ser 235/236), or the mTORC2 effector, Akt (phospho-Akt S473), was assessed by Western blot analysis. The phosphorylation of STAT6 (phospho-STAT6 Y641) was determined as a control for activation of Th2 pathways. A representative blot from 5 experiments is shown.
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pone-0033984-g009: Rapamycin attenuates mTORC1 effectors.Phosphorylation of the mTORC1 effector, S6 (phospho-S6 Ser 235/236), or the mTORC2 effector, Akt (phospho-Akt S473), was assessed by Western blot analysis. The phosphorylation of STAT6 (phospho-STAT6 Y641) was determined as a control for activation of Th2 pathways. A representative blot from 5 experiments is shown.

Mentions: Western blots of lung proteins were performed to identify the mechanism by which rapamycin mediates paradoxical effects on HDM-induced asthma. After 3 weeks in the induction model, phosphorylation of the S6 ribosomal protein was increased in the lungs of HDM-challenged mice as compared to saline-challenged mice (Figure 9). In contrast, after 6 weeks in the treatment model, S6 phosphorylation was no longer increased in HDM-challenged mice when compared to saline-challenged mice. In both the induction and treatment models, rapamycin attenuated S6 phosphorylation in HDM-challenged mice as compared to mice that received the vehicle control, which demonstrates inhibition of mTORC1 signaling. In contrast, Akt phosphorylation at serine 473 was neither increased by HDM-challenge nor inhibited by rapamycin, indicating that rapamycin did not inhibit TORC2 signaling. Lastly, although STAT6 phosphorylation was increased in HDM-challenged mice in both the induction and treatment models, it was only inhibited by rapamycin in the induction model.


Paradoxical effects of rapamycin on experimental house dust mite-induced asthma.

Fredriksson K, Fielhaber JA, Lam JK, Yao X, Meyer KS, Keeran KJ, Zywicke GJ, Qu X, Yu ZX, Moss J, Kristof AS, Levine SJ - PLoS ONE (2012)

Rapamycin attenuates mTORC1 effectors.Phosphorylation of the mTORC1 effector, S6 (phospho-S6 Ser 235/236), or the mTORC2 effector, Akt (phospho-Akt S473), was assessed by Western blot analysis. The phosphorylation of STAT6 (phospho-STAT6 Y641) was determined as a control for activation of Th2 pathways. A representative blot from 5 experiments is shown.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368343&req=5

pone-0033984-g009: Rapamycin attenuates mTORC1 effectors.Phosphorylation of the mTORC1 effector, S6 (phospho-S6 Ser 235/236), or the mTORC2 effector, Akt (phospho-Akt S473), was assessed by Western blot analysis. The phosphorylation of STAT6 (phospho-STAT6 Y641) was determined as a control for activation of Th2 pathways. A representative blot from 5 experiments is shown.
Mentions: Western blots of lung proteins were performed to identify the mechanism by which rapamycin mediates paradoxical effects on HDM-induced asthma. After 3 weeks in the induction model, phosphorylation of the S6 ribosomal protein was increased in the lungs of HDM-challenged mice as compared to saline-challenged mice (Figure 9). In contrast, after 6 weeks in the treatment model, S6 phosphorylation was no longer increased in HDM-challenged mice when compared to saline-challenged mice. In both the induction and treatment models, rapamycin attenuated S6 phosphorylation in HDM-challenged mice as compared to mice that received the vehicle control, which demonstrates inhibition of mTORC1 signaling. In contrast, Akt phosphorylation at serine 473 was neither increased by HDM-challenge nor inhibited by rapamycin, indicating that rapamycin did not inhibit TORC2 signaling. Lastly, although STAT6 phosphorylation was increased in HDM-challenged mice in both the induction and treatment models, it was only inhibited by rapamycin in the induction model.

Bottom Line: Lastly, mediastinal lymph node re-stimulation experiments showed that treatment of rapamycin-naive T cells with ex vivo rapamycin decreased antigen-specific Th2 cytokine production, whereas prior exposure to in vivo rapamycin rendered T cells refractory to the suppressive effects of ex vivo rapamycin.We conclude that rapamycin had paradoxical effects on the pathogenesis of experimental HDM-induced asthma.Thus, consistent with the context-dependent effects of rapamycin on inflammation, the timing of mTOR inhibition may be an important determinant of efficacy and toxicity in HDM-induced asthma.

View Article: PubMed Central - PubMed

Affiliation: Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.

ABSTRACT
The mammalian target of rapamycin (mTOR) modulates immune responses and cellular proliferation. The objective of this study was to assess whether inhibition of mTOR with rapamycin modifies disease severity in two experimental murine models of house dust mite (HDM)-induced asthma. In an induction model, rapamycin was administered to BALB/c mice coincident with nasal HDM challenges for 3 weeks. In a treatment model, nasal HDM challenges were performed for 6 weeks and rapamycin treatment was administered during weeks 4 through 6. In the induction model, rapamycin significantly attenuated airway inflammation, airway hyperreactivity (AHR) and goblet cell hyperplasia. In contrast, treatment of established HDM-induced asthma with rapamycin exacerbated AHR and airway inflammation, whereas goblet cell hyperplasia was not modified. Phosphorylation of the S6 ribosomal protein, which is downstream of mTORC1, was increased after 3 weeks, but not 6 weeks of HDM-challenge. Rapamycin reduced S6 phosphorylation in HDM-challenged mice in both the induction and treatment models. Thus, the paradoxical effects of rapamycin on asthma severity paralleled the activation of mTOR signaling. Lastly, mediastinal lymph node re-stimulation experiments showed that treatment of rapamycin-naive T cells with ex vivo rapamycin decreased antigen-specific Th2 cytokine production, whereas prior exposure to in vivo rapamycin rendered T cells refractory to the suppressive effects of ex vivo rapamycin. We conclude that rapamycin had paradoxical effects on the pathogenesis of experimental HDM-induced asthma. Thus, consistent with the context-dependent effects of rapamycin on inflammation, the timing of mTOR inhibition may be an important determinant of efficacy and toxicity in HDM-induced asthma.

Show MeSH
Related in: MedlinePlus