RESUMEN
BACKGROUND: Probiotics have been shown to prevent various allergic diseases by producing extracellular vesicles (EVs). However, the role of EVs in allergic asthma has not yet been completely determined. METHODS: Gut microbial composition, mainly genera related to probiotics, was investigated in allergic asthmatic mice. Moreover, EVs were isolated from Lactococcus lactis (L. lactis, a selected bacterium) and EV proteins were identified by peptide mass fingerprinting. EV functions in immune responses were evaluated in vivo or ex vivo. Furthermore, the levels of specific IgG antibodies (an alternative marker for EV quantification) to L. lactis-EVs were measured by ELISA in the sera of 27 asthmatic patients and 26 healthy controls. RESULTS: Allergic asthmatic mice showed a lower proportion of Lactococcus compared to healthy mice. L. lactis was cultured and its EVs abundantly contained pyruvate kinase. When allergic asthmatic mice were intranasally treated with EVs, airway hyperresponsiveness, eosinophil number, cytokine secretion, and mucus production were significantly decreased. Moreover, L. lactis-EV treatment shifted immune responses from Th2 to Th1 by stimulating dendritic cells to produce IL-12. In addition, significantly lower levels of serum specific IgG4 (but not IgG1) to L. lactis-EVs were noted in asthmatic patients than in healthy controls. A positive correlation between the levels of EV-specific IgG4 and FEV1 (%), but a negative correlation between the levels of EV-specific IgG4 and IL-13 were observed. CONCLUSION: These findings suggest that L. lactis-EVs may have immune-regulating effects on airway inflammation mediated by dendritic cell activation, providing a potential benefit for allergic asthma.
RESUMEN
PURPOSE: Neutrophils are considered key effector cells in the pathogenic mechanisms of airway inflammation in asthma. This study assessed the activation status of neutrophils in adult asthmatics, and the therapeutic potential of FTY720, a synthetic sphingosine-1-phosphate analog, on activated neutrophils using an in vitro stimulation model. METHODS: We isolated peripheral blood neutrophils (PBNs) from 59 asthmatic patients (including 20 aspirin-exacerbated respiratory disease [AERD] and 39 aspirin-tolerant asthma [ATA] groups). PBNs were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) or lipopolysaccharide (LPS) and their activation status was determined based on reactive oxygen species (ROS) production, cell surface expression of CD11b, interleukin (IL)-8 and matrix metallopeptidase (MMP)-9 release. PBNs were primed with FTY720 to evaluate its anti-inflammatory action. RESULTS: In vitro PBN stimulation with fMLP or LPS induced a significant increase in ROS/CD11b/IL-8/MMP-9 levels (P < 0.05 for all). In asthmatics, fMLP-induced ROS level was significantly correlated with values of forced expiratory volume in 1 second/forced vital capacity (r = -0.278; P = 0.036), maximal mid-expiratory flow (r = -0.309; P = 0.019) and PC20 methacholine (r = -0.302; P = 0.029). In addition, ROS levels were significantly higher in patients with AERD and in those with severe asthma than in those with ATA or non-severe asthma (P < 0.05 for all). FTY720 treatment could suppress ROS/CD11b levels, and LPS-induced IL-8 and MMP-9 levels (P < 0.05 for all). Responders to FTY720 treatment had significantly higher neutrophil counts in sputum (P = 0.004). CONCLUSIONS: Our findings suggest a useful in vitro PBN stimulation model for evaluating the neutrophil functional status and the therapeutic potentials of neutrophil-targeting candidates in asthmatics.