Exploring the ameliorative effects of blueberry extract on atopic dermatitis (AD) and elucidating its mechanisms of action through changes in skin microbiota, restoration of barrier function, and improvement of Th2-type inflammation.

The AD mouse model was induced by topical application of the vitamin D3 analog calcipotriol (MC903). Ear thickness was measured in a double-blind manner on days 1, 3, 5, 7, 10, 12, and 14, and scratching episodes within 30 minutes were recorded on day 14. Ear tissue samples were collected for hematoxylin-eosin (HE) staining and epidermal thickness measurement. The mRNA expression of inflammatory cytokines (IL-33, IL-22, TSLP, TNF-α, IL-6, and IL-1β) was detected by RT-qPCR. 16S rRNA sequencing was used to analyze the effect of blueberry extract on the microbial community in AD mice. A cellular model was established by stimulating human keratinocytes (HaCaT) with lipopolysaccharide (LPS, 20 μg/mL). The effect of different concentrations of blueberry extract on cell viability was assessed using the CCK-8 assay. Expression of IL-33, TSLP, and IL-4Rα proteins were detected by Western blot. The composition of blueberry extract was identified by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Comparisons between two groups were performed using the independent samples t-test. Comparisons among multiple groups were conducted using either one-way ANOVA or repeated-measures ANOVA, as appropriate. Post hoc pairwise comparisons were carried out with Tukey's test.

Compared with the model group, blueberry extract significantly alleviated ear swelling in AD mice, reduced scratching frequency [ (9.00 ± 0.89) vs (14.67 ± 2.06) times] and epidermal thickness [ (37.78 ± 2.68) vs (54.90 ± 10.09) μm] (all P < 0.05). Blueberry extract downregulated the expression of Th2 inflammatory cytokines and pro-inflammatory factors mRNA. Compared with the model group, the expression levels of IL-33 (0.95 ± 0.18 vs 1.36 ± 0.23), TSLP (27.12 ± 4.73 vs 39.09 ± 4.61), IL-22 (1.98 ± 0.45 vs 3.43 ± 0.36), and IL-1β (4.47 ± 1.44 vs 20.26 ± 3.30) mRNA were decreased in treatment group (P < 0.05). 16S rRNA analysis revealed that blueberry extract mitigated microbial community dysbiosis and loss of diversity, inhibiting the proliferation of pathogenic bacteria such as Streptococcus, Staphylococcus, and Enterobacter. In the cellular experiments, compared with the LPS-induced model group, treatment with 80 μmol/L blueberry extract significantly reduced the protein expression of IL-4Rα (1.64 ± 0.31 vs 5.90 ± 0.24), IL-33 (0.90 ± 0.15 vs 4.27 ± 0.41), and TSLP (0.15 ± 0.07 vs 5.61 ± 0.40), as well as the mRNA expression of IL-4Rα (2.57 ± 0.54 vs 13.20 ± 3.43), IL-33 (2.00 ± 0.44 vs 5.40 ± 1.24), and TSLP (1.47 ± 0.06 vs 4.04 ± 0.21) (all P < 0.05). Further mass spectrometry identification indicated that delphinidin might be the core active component in blueberry extract.

Blueberry extract significantly alleviated symptoms in the AD mouse model by modulating the skin microbiota, restoring barrier function, suppressing Th2-type inflammatory responses, and reducing inflammatory cytokine expression in HaCaT cells, with delphinidin identified as its potential core active constituent.