Influência da estimulação colinérgica na modulação da resposta inflamatória em modelo experimental da síndrome do desconforto respiratório agudo (SDRA) induzida por lipopolissacarideo

Abstract

Acute respiratory distress syndrome (ARDS), characterized by acute lung inflammation involving both the recruitment and activation inflammatory cells as well as the release of inflammatory factors that cause lung injury and contributes to systemic inflammation. These cytokines cause alveolocapillary damage, high permeability and pulmonary edema, with a high mortality rate. Despite significant advances in understanding the underlying pathogenic mechanisms of ARDS, no effective therapeutic approach has emerged. The anti-inflammatory cholinergic reflex has been postulated as an important mechanism that modulates the immune system in both aseptic and septic experimental models. Strategies to increase cholinergic activity include direct vagal nerve stimulation and administration of drugs that act on components of cholinergic reflex. Pyridostigmine bromide (PB) is a reversible anticholinesterase agent that causes increased availability of acetylcholine and parasympathetic activity is routinely used in the treatment of myasthenia gravis. The aim of this study was to investigate the effect of cholinergic stimulation through the PB treatment on the pulmonary and systemic inflammatory response in an experimental model of LPS-induced ARDS. Methods: C57Bl/6 male mice (n=57) were distributed into four groups Control (Control), pyridostigmine-treated (PB), LPS installation (LPS), LPS installation and pyridostigmine treatment (PB+LPS) Animals were monitored for 24 or 72 hours. Acute respiratory distress syndrome (ARDS) model: Mice were anesthetized (ketamine 100 mg/kg and xylazine 10 mg/kg) and given one intratracheal instillation of 10 μg LPS/ per mice, during 24 hours e 3 days. Cholinergic stimulation: Pyridostigmine bromide (PB) 3 mg/kg/day was administered twice a day by oral gavage at 1h post-LPS to achieve around 85-90% cholinergic inhibition as previously reported. We analyzed, total and differential cell count, the levels of cytokine (TNF-α, IL-1β, IL-6, IFN-γ and IL-10) in bronchoalveolar lavage fluid (BALF) and plasma, were also quantified the neutrophil density in lung tissue. Results: 24 hours treatment with pyridostigmine after the bacterial endotoxin significantly reduced the number of both total cells and neutrophils in BAL fluid (p<0.001). Reduced the levels of the inflammatory cytokines TNF-α (p<0,001), IL-1β (p<0,05) and IL-6 (p<0,01) but not IL-10 levels in BALF when compared with LPS group. Reduced the levels of all of the inflammatory cytokines TNF-α (p<0,01), IL-1β (p<0,05), IL-6 (p<0,001) and IFN-γ (p<0,01) but not the levels IL-10 in plasma when compared with LPS group. At 72 hours treatment with pyridostigmine after the bacterial endotoxin significantly reduced the number of total cells, neutrophils, macrophages (P<0.001) and lymphocytes (p<0.01), the levels of all of the inflammatory cytokines TNF-α, IL-6 (p<0.001), IL-1β and INF-γ (p<0.05) but not the levels IL-10 in the BAL when compared with LPS group. Reduced the levels of all of the inflammatory cytokines TNF-α (p<0.001), IL-1β (p<0.05), IL-6 and INF-γ (p<0.01) in the plasma, lower density of neutrophils in the lung parenchyma (p<0.001) when compared with LPS group. In conclusion, our results show that the anti-inflammatory cholinergic system can control lung inflammation and that treatment with BP can activate the cholinergic system to reduce pulmonary and systemic inflammatory in an experimental model of LPS-induced ARDS. These results support the cholinergic system as an important pharmacological target for ARDS treatment.