Fig. 4

Opposite effects of JUUL-exposed WT and MMP12 KO mice on allergen-induced BALF pulmonary inflammation. Sub-chronic (60 days) exposures to JUUL menthol-flavored aerosol. a, e resulted in no significant increase in BALF total cell count in WT mice, whereas total cell count was significantly increased in JUUL + HDM MMP12 KO mice compared to JUUL PBS KO controls; b, f caused significant neutrophilic inflammation in Air + HDM WT mice, with JUUL + HDM exposure suppressing neutrophilic inflammation, whereas it caused a significant influx in eosinophilic inflammation in Air + HDM MMP12 KO mice, with JUUL + HDM exposure increasing cellular inflammation; c, g significantly increased total protein concentration in Air + HDM WT mice compared to Air control group, while no significant effect on lung permeability were seen in MMP12 KO mice; d, h significantly increased serum IgE levels in Air + HDM WT mice compared to the Air control group, whereas serum IgE levels were significantly augmented in Air + HDM, JUUL + PBS and JUUL + HDM MMP12 KO mice compared to Air + PBS MMP12 KO controls. Data represent the mean ± SEM for n = 4–8 animals per group. One-way ANOVA followed by the Tukey’s test post-hoc test. *p < 0.05 and **p < 0.01 statistically different from Air control