Effects of Long-term Endogenous Acetylcholine Deficiency in Lung Inflammation in a Model of Asthma-copd Overlap in Mice

Abstract ID 128092 Poster Board 005 Cholinergic anti-inflammatory system, especially by activation of nicotinic receptors, has been shown to modulate lung inflammation in several models of lung diseases. ACO is a syndrome that involves asthma and COPD features, such as eosinophilic inflammation and non-reversible airway obstruction, in the same patients. This syndrome remains a challenge to the medicine since these patients did not respond adequately to the treatments commercially available. Aims: We investigated the effects of long-term endogenous acetylcholine deficiency by a reduction in the levels of vesicular acetylcholine transporter (VAChT) in a model of asthma-COPD overlap (ACO). Material and Methods: Male and female mutant (KD) and wild-type (WT) mice, the latter with reduced cholinergic signaling by genetic modification in the levels of VAChT, were sensitized with ovalbumin (OVA) on days 1 and 14. Afterward, animals received an intratracheal instillation of porcine pancreatic elastase (PPE) on day 21 and were then submitted to inhalations with ovalbumin on days 21, 23, 25 and 27. Control WT and KD mice received saline. On day 28, animals were anesthetized and mechanically ventilated. We also used treatment with PNU282987 (2mg/Kg each dose), an agonist of α7 nicotinic receptor (α7nAChR) on days 21, 23, 25, 27 and 28 until the end of the protocol. After that, they were euthanized, and bronchoalveolar lavage fluid was collected to evaluate lung inflammation. Data were analyzed with a t-test (Wire hang test) and two-way analysis of variance (ANOVA). A p < 0.05 was considered significant. Results: Mutant KD mice showed a reduction in the wire hang test compared to WT mice (P < 0.001). ACO increased total cells, neutrophils, and lymphocytes in BALF independently of the genotyping (P < 0.05). In mutant mice, ACO also increased the number of eosinophils in BALF compared to mutant KD mice submitted to saline treatments (P < 0.05). Considering lung mechanics, there was an interaction between genotyping and ACO in respiratory system resistance, where mutant mice with ACO seem to have a higher respiratory system resistance (P = 0.05) than the other groups. PNU treatment reduced the number of eosinophils in the BALF by 50%. Conclusion: In this model of ACO, endogenous ACh seems to protect against eosinophil inflammation, which could influence airway obstruction. This anti-inflammatory effect of ACh could be due to the activation of α7nAChR. Financial Support: Fapesp 2022/02510-5.