Bifidobacterium longum-Derived Extracellular Vesicles Prevent Hepatocellular Carcinoma by Modulating the TGF-β1/Smad Signaling in Mice.

BACKGROUND

The involvement of gut microbiota in carcinogenesis has gradually been highlighted in past decades. Bacteria could play its role by the secretion of extracellular vesicles (EVs); however, interrelationship between bacterial EVs and hepatocellular carcinoma (HCC) development has not been investigated much.

METHODS

Diethylnitrosamine (DEN) was utilized to produce HCC model in mice, of which fecal was collected for detecting Bifidobacterium longum (B.longum) with real-time polymerase chain reaction (PCR). EV isolated from B.longum (B.longum-EV) with ultracentrifugation were stained with PKH26 to investigate the cellular uptake of murine hepatocytes (AML12). After treatment with B.longum-EV, TGF-β1-induced AML12 cells were subjected to morphological observation, fibrosis- and apoptosis-related marker detection with western blot, apoptotic ratio and reactive oxygen species (ROS) level analysis with flow cytometry, and oxidative stress biomarker assessment with enzyme-linked immunosorbent assay (ELISA); meanwhile, animal studies including liver function, tumor formation rate, and histological analysis, were also performed to investigate the role of B.longum-EV in the fibrosis, apoptosis, oxidative stress, and carcinogenesis of the liver in vivo.

RESULTS

The levels of B.longum were significantly reduced in HCC model mice. B.longum-EV could enter AML12 cells and effectively attenuate TGF-β1-induced fibrosis, apoptosis, and oxidative stress in AML12 cells. In vivo studies showed that B.longum-EV administration alleviated DEN-induced liver fibrosis, apoptosis, and oxidative stress at the early stage. Moreover, B.longum-EV administration also effectively reduced the tumor formation rate and liver function injury in DEN-induced mice and down-regulated TGF-β1 expression and Smad3 phosphorylation of mouse liver.

CONCLUSIONS

B.longum-EVs protect hepatocytes against fibrosis, apoptosis, and oxidative damage, which exert a potential of preventing HCC development.