Bifidobacterium animalis subsp. lactis Bb12 is a widely used probiotic that provides numerous health benefits to its host, many due to its immunomodulatory properties. Although the precise mechanism of modulation is still under investigation, several reports associate the interaction of TLR2 with components of the bacterial cell wall inducing a signaling cascade that culminates with the production of cytokines and co-stimulatory molecules. MicroRNAs (miRNAs) have emerged as important post-transcriptional regulators of immune responses, including those toward probiotics. In this study, we analyzed the miRNA expression profile in swine monocytes exposed to Bb12 by using an anti-TLR2 blocking strategy and Bb12 involvement in the regulation of the TLR2 pathway. As a result, the expression of 40 miRNAs was influenced by the treatments (p < 0.01), and 15 differentially expressed miRNAs with validated miRNA–mRNA interactions with around 26 proteins related to the TLR2 pathway were identified. The miRNAs upregulated in response to Bb12 included miR-15a-5p, miR-16-5p, miR-26a-5p, miR-29b-3p, and miR-30d-5p, and the following showed downregulation: miR-181a-5p, miR-19b-3p, miR-21-5p, miR-23a-5p, and miR-221-3p. The expression of let-7c-5p, let-7f-5p, miR-146b-5p, miR-150-5p, and miR-155-5p was increased by Bb12 only when TLR2 was blocked. The identified miRNA common targets were downstream proteins from bacterial recognition via TLR2, such as MyD88, TRAF6, and MAPK members; transcription factors such as NF-κB and AP-1; and cytokines such as IL-6, IL-10, and TNF-α. TLR2 participation was abrogated by anti-TLR2 antibody and suggests that bacterial recognition is complemented by other receptors since there were still changes in the microtranscriptome.

动物双歧杆菌亚种。乳酸菌Bb12 是一种广泛使用的益生菌，可为宿主提供许多健康益处，其中许多是由于其免疫调节特性。尽管调节的精确机制仍在研究中，但一些报告将 TLR2 与细菌细胞壁成分的相互作用联系起来，诱导信号级联，最终产生细胞因子和共刺激分子。MicroRNAs (miRNAs) 已成为免疫反应的重要转录后调节因子，包括针对益生菌的免疫反应。在本研究中，我们通过使用抗 TLR2 阻断策略和 Bb12 参与 TLR2 通路的调节分析了暴露于 Bb12 的猪单核细胞中的 miRNA 表达谱。结果，40 种 miRNA 的表达受到处理的影响（p < 0.01），鉴定了 15 个差异表达的 miRNA，它们与约 26 种与 TLR2 通路相关的蛋白质具有经验证的 miRNA-mRNA 相互作用。响应 Bb12 上调的 miRNA 包括 miR-15a-5p、miR-16-5p、miR-26a-5p、miR-29b-3p 和 miR-30d-5p，以下显示下调：miR-181a-5p 、miR-19b-3p、miR-21-5p、miR-23a-5p 和 miR-221-3p。仅当 TLR2 被阻断时，Bb12 才会增加 let-7c-5p、let-7f-5p、miR-146b-5p、miR-150-5p 和 miR-155-5p 的表达。鉴定出的 miRNA 共同靶点是通过 TLR2 识别细菌的下游蛋白，如 MyD88、TRAF6 和 MAPK 成员；转录因子，如 NF-κB 和 AP-1；和细胞因子，如 IL-6、IL-10 和 TNF-α。