The compatible solute ectoine reduces the exacerbating effect of environmental model particles on the immune response of the airways

Abstract

Exposure of humans to particulate air pollution has been correlated with the incidence and aggravation of allergic airway diseases. In predisposed individuals, inhalation of environmental particles can lead to an exacerbation of immune responses. Previous studies demonstrated a beneficial effect of the compatible solute ectoine on lung inflammation in rats exposed to carbon nanoparticles (CNP) as a model of environmental particle exposure. In the current study we investigated the effect of such a treatment on airway inflammation in a mouse allergy model. Ectoine in nonsensitized animals significantly reduced the neutrophilic lung inflammation after CNP exposure. This effect was accompanied by a reduction of inflammatory factors in the bronchoalveolar lavage. Reduced IL-6 levels in the serum also indicate the effects of ectoine on systemic inflammation. In sensitized animals, an aggravation of the immune response was observed when animals were exposed to CNP prior to antigen provocation. The coadministration of ectoine together with the particles significantly reduced this exacerbation. The data indicate the role of neutrophilic lung inflammation in the exacerbation of allergic airway responses. Moreover, the data suggest to use ectoine as a preventive treatment to avoid the exacerbation of allergic airway responses induced by environmental air pollution.

Figure 1

Lung inflammation induced by increasing doses of CNP. Female C57/Bl6 mice (8 weeks old) were exposed once to the indicated dose of CNP suspended in PBS. Animal numbers were 0 mg/kg n = 4, 2.5 mg/kg n = 5, 5 mg/kg n = 4, and 10 mg/kg n = 5. Inflammation parameters were determined 24 h after exposure. (a) Total number of cells per mL BAL; (b) total number of neutrophilic granulocytes per mL BAL; (c) total number of macrophages and monocytes per mL BAL; (d) pg/mL of KC in BAL. r, correlation coefficient of Pearson correlation; P, two sided significance; nd, not detectable.

Figure 2

Time course of lung inflammation after single application of 5 mg/kg CNP in the presence or absence of ectoine (1 mM). Animals (n = 5) were analysed after the indicated time points. (a) Total number of cells per mL BAL; (b) total number of neutrophilic granulocytes per mL BAL; (c) total number of macrophages and monocytes per mL BAL; (d) pg/mL of KC in BAL. *, significantly different to the respective control (PBS or ectoine) after Tukey's HSD post hoc testing considering multiple testing; E, ectoine; nd, not detectable.

Figure 3

Effect of ectoine treatment on inflammatory mediators 12 h after exposure. (a) BAL analyses of two animals from each group. Given error bars are based on duplicates from both measurements. Significant values cannot be calculated. (b) IL-6 in BAL of 5 animals; (c) IL-6 in serum of 5 animals. CNP, 5 mg/kg carbon nanoparticles; E, 1 mM ectoine. Significant values (two sided) in (b) and (c) were calculated by Mann-Whitney U-test.

Figure 4

Effect of CNP and ectoine on OVA provocation-induced lung inflammation in sensitized animals (control groups n = 3 and exposure groups n = 5). (a) Experimental design. Animals were sensitized by repetitive intraperitoneal OVA application. At day 0, 5 mg/kg CNP in the presence or absence of 1 mM ectoine was applied to the animals. OVA provocation by inhalation (1%, 30 min) was performed 12 h after treatment. Measurements were made 24 h after challenge. (b) Total number of cells per mL BAL; (c) total number of neutrophilic granulocytes per mL BAL; (d) total number of macrophages and monocytes per mL BAL; (e) total number of other cells including lymphocytes and eosinophilic granulocytes.