Potential of Inducible Nitric Oxide Synthase as a Therapeutic Target for Allergen-Induced Airway Hyperresponsiveness: A Critical Connection to Nitric Oxide Levels and PARP Activity

Figure 4

Effects of PARP inhibition on iNOS expression in LPS/IFN-γ-treated MEFs and of iNOS inhibition on the protection conferred by the PARP inhibitor olaparib against AHR in chronically HDM-exposed mice. (a) MEFs derived from WT or PARP-1^−/− mice were treated with a combination of 1 μg/mL LPS and 10 ng/mL IFN-γ. RNA was isolated after 6 hours of treatment and reverse-transcribed to generate cDNA, which was subjected to quantitative PCR with primers specific to mouse iNOS or β-actin. The data is expressed as fold change normalized to levels of β-actin. and , difference from nonstimulated cells with and , respectively; , difference from LPS/IFN-γ-treated WT cells with . (b) WT mice were subjected to HDM sensitization followed by a chronic i.n. challenge with HDM or left unchallenged. Challenged mice were administered i.p. 5 mg/kg olaparib with or without 5 mg/kg of L-NIL 30 min after each HDM challenge. Penh was recorded 24 h after the last challenge in response to increasing doses of MeCh. Results are plotted as maximal fold increase of Penh relative to baseline and expressed as mean ± SEM, where mice per group. , difference from HDM challenged mice; , difference from the group that received 5 mg/kg olaparib; . RNA isolated from the lungs of the different experimental groups was reverse-transcribed and the resulting cDNA was subjected to real time PCR with primer sets specific to mouse IL-5 or β-actin. Data is expressed as fold change of values detected in lungs of control mice. , difference from control unchallenged mice; , difference from HDM-exposed mice receiving olaparib; ns, no significant difference. Note that values of control and HDM-exposed mice are the same as those described for Figure 3(c).

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