Immunomodulation by Bifidobacterium animalis subsp. lactis Bb12: Integrative Analysis of miRNA Expression and TLR2 Pathway-Related Target Proteins in Swine Monocytes

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.

Hypoxia drives apoptosis independently of p53 and metallothionein transcript levels in hemocytes of the whiteleg shrimp Litopenaeus vannamei

The cellular mechanisms used by the shrimp Litopenaeus vannamei to respond to hypoxia have been studied from the energetic metabolism and antioxidant angles. We herein investigated the participation of p53 and metallothionein (MT) in the apoptotic process in response to hypoxia in shrimp hemocytes. The Lvp53 or LvMT genes were efficiently silenced by injection of double stranded RNA for p53 or MT. The effects of silencing on apoptosis were measured as caspase-3 activity and flow cytometry in hemocytes after 24 and 48 h of hypoxia (1.5 mg DO L(-1)). Hemocytes from unsilenced animals had significantly higher apoptosis levels upon both times of hypoxia. The apoptotic levels were diminished but not suppressed in dsp53-silenced but not dsMT-silenced hemocytes after 24 h of hypoxia, indicating a contribution of Lvp53 to apoptosis. Apoptosis in normoxia was significantly higher in dsp53-and dsMT-silenced animals compared to the unsilenced controls, pointing to a possible cytoprotective role of LvMT and Lvp53 during the basal apoptotic program in normoxia. Overall, these results indicate that hypoxia augments apoptosis in shrimp hemocytes and high mRNA levels of Lvp53 and LvMT are not necessary for this response.