Effects of Nerve Growth Factor shRNA Inhibition on Asthma Phenotypes in a Mouse Model of Asthma

Nerve growth factor (NGF) plays an important role in airway hyper-responsiveness (AHR). In this study, we aimed at investigating the effect of NGF inhibition on AHR and other asthma phenotypes in a mouse model of asthma. 12 mice in each group were injected with lentiviral vectors expressing non-targeting shRNA (sham shRNA), targeting NGF (shRNA-1 and shRNA-2), or normal saline for control before the asthma models were established. Peak inspiratory pressure (PIP), NGF levels in bronchoalveolar lavage fluid (BALF), and bronchoconstriction in response to acetylcholine (ACh) were measured. Immunohistochemistry semi-quantitative analysis of muscarinic acetylcholine receptor M3 (mAChR M3) and alpha-smooth muscle actin (a-SMA) were measured by Image Pro Plus (IPP), and qRT-PCR analysis of mRNAs of cholinergic receptors, muscarinic 3 (Chrm3), Ngf and Tropomyosin receptor kinase A (TrkA) were performed. Immunohistochemistry showed mAChR M3 was overexpressed and a-SMA was hyperplasia in control and sham shRNA, semi-quantitative analysis revealed optical density (OD) values were significantly higher than shRNA-1 and shRNA-2, (p<0.001). BALF NGF levels were significantly higher in control and sham shRNA (457.16±45.32, 676.43±111.64) compared with shRNA-1 and shRNA-2 (261.56±25.81, 129.12±15.96 pg/mL) (p<0.001). PIP was significantly higher in control, compared with shRNA-1, shRNA-2, (p=0.045, 0.003), bronchoconstriction response to ACh was significantly higher in sham shRNA, compared with shRNA-1, shRNA-2, (p=0.02, 0.006). Expression of mRNAs of Chrm3, Ngf and TrkA genes in sham shRNA group were higher than shRNA-1 and shRNA-2. Inhibiting NGF via NGF-targeting shRNAs appears to lessen the severity of asthma phenotypes in this mouse model of asthma.