Luteolin Alleviated Neutrophilic Asthma By Inhibiting IL-36γ Secretion-mediated MAPK Pathways

BackgroundBronchial asthma is a common,chronic,inflammatory disease of the airways.The internationally recognized system of classification for asthma is into two types:T2-high asthma and T2-low asthma.T2-low asthma is usually characterized by neutrophils or fewer granulocytes.T2-low asthma especially neutrophilic asthma is often associated with severe disease and poor response to treatment.Luteolin is a typical flavonoid that plays an important role in many processes such as anti-inflammatory,antioxidant and immune enhancement processes.And luteolin can relieve T2-high asthma through many ways,especially alleviate the inflammation of asthma.However,the anti-inflammatory effects of luteolin in neutrophilic asthma and specific pathways have rarely been studied and need to be further explored.Interleukin(IL)-36γ belongs to the IL-1 cytokine family,and this molecule activates target cells via the mitogen-activated protein kinase(MAPK)and nuclear factor-κ B(NF-κB)pathways via the receptor IL-36R.A previous study found that IL-36 played an important role in lung diseases,especially those diseases characterized by the accumulation of neutrophils,including severe T2-low asthma.And IL-36y is the upstream inflammatory driver of human neutrophils and small airway epithelial cells.This research explored the specific mechanism of luteolin and the role of IL-36γ in improving neutrophilic asthma by constructing an animal model of OVA-LPS neutrophilic asthma.ObjectivesWe aim to determine the effect of luteolin on IL-36y secretion-mediated MAPK pathway signaling in neutrophilic asthma.MethodsThis research was conducted through animal experiments and in vitro experiments.C57BL/6 mice were selected for animal experiments which were conducted with ovalbumin(OVA)and lipopolysaccharide(LPS),and the role of luteolin in the neutrophilic asthma and the relationship of luteolin,IL-36γ and MAPK pathway in the animal models was detected by experimental methods such as HE staining,PAS staining,immunohistochemistry and Western blot.In vitro experiments,the bronchial airway epithelial cell Beas-2B cells are chosen.And ELISA and Western blot are used to study the effect of luteolin on IL-36γ secretion-mediated MAPK pathway signaling in Beas-2B cells.Results1.The results revealed that IL-36γ secretion and MAPK/IL-1β signaling significantly increased in the neutrophilic asthma compared with control.However,the level of IL-36y secretion and MAPK/IL-1β signaling were reduced by luteolin.2.In vitro experiments,luteolin also inhibited IL-36γ and MAPK/IL-1β levels after LPS stimulating Beas-2B cells.We also found that luteolin inhibited activation of the MAPK pathway and IL-1β expression following stimulation with IL-36y in Beas-2B cells.Finally,IL-1β and phosphorylated MAPK levels were found to be lower in IL-36y siRNA+LPS group than the NC siRNA+LPS group.ConclusionsLuteolin alleviated neutrophilic asthma by inhibiting IL-36γ secretion-mediated MAPK pathways.