Several recent works indicates that obesity is an important risk factor for the development of asthma. Obese animals exhibit bronchial hyperresponsiveness, which could take place independently on the local inflammation. Our preliminary data suggests that isolated bronchial rings from obese mice exhibit increased contractile response to muscarinic agonist carbachol, which is normalized by the chronic treatment with the insulin sensitizing agent metformin. Moreover, recent work showed that insulin inhibits brainstem situated pre-ganglionic cholinergic neurons that irrigate gastrointestinal system, regulating gastric motility. The aim of the present study is to investigate whether central insulin regulates the bronchus responsiveness through an inhibitory action in the pre-ganglionic cholinergic neurons. Moreover we also aim to access the involvement of central insulin resistance on the bronchial hyperresponsiveness in obese mice fed with high fat diet. We will perform in vitro (concentration-response curves in isolated tissues) and in vivo (airway flow resistance studies). For the second one, the animals will undergo intracerebroventricular (ICV) cannulation and after an acclimation period of one week will be submitted to plethysmography and Forced Oscilatory Technique (FOT) studies, where dose-response curves to methacoline will be performed in the absence and in the presence of the PI3K/AKT or MAPK inhibitors drugs. Western blot analysis to detect the content of the proteins involved in the PI3K/AKT or MAPK pathways and measurements of cytosolic Ca2+ levels by fluorescence will be performed in primary culture of cholinergic neuron cells from nucleus ambiguus in order to characterize the signaling pathway triggered by insulin in these cells. Metformin treated and Toll Like Receptor 4 (TLR4) loss-of-function mutant (C3H/HeJ) obese and lean mice will be also studied in order to evaluate the effect of insulin sensitization on the bronchial hyperresponsiveness and also to determine the role of TLR4 in the physiopathology of this dysfunction.
News published in Agência FAPESP Newsletter about the scholarship: