Probiotic Bacillus amyloliquefaciens SC06 Induces Autophagy to Protect against Pathogens in Macrophages

Abstract

Probiotics are increasingly applied in popularity in both humans and animals. Decades of research has revealed their beneficial effects, including the immune modulation in intestinal pathogens inhibition. Autophagy—a cellular process that involves the delivery of cytoplasmic proteins and organelles to the lysosome for degradation and recirculation—is essential to protect cells against bacterial pathogens. However, the mechanism of probiotics-mediated autophagy and its role in the elimination of pathogens are still unknown. Here, we evaluated Bacillus amyloliquefaciens SC06 (Ba)-induced autophagy and its antibacterial activity against Escherichia coli (E. coli) in murine macrophage cell line RAW264.7 cells. Western blotting and confocal laser scanning analysis showed that Ba activated autophagy in a dose- and time-dependent manner. Ba-induced autophagy was found to play a role in the elimination of intracellular bacteria when RAW264.7 cells were challenged with E. coli. Ba induced autophagy by increasing the expression of Beclin1 and Atg5-Atg12-Atg16 complex, but not the AKT/mTOR signaling pathway. Moreover, Ba pretreatment attenuated the activation of JNK in RAW264.7 cells during E. coli infection, further indicating a protective role for probiotics via modulating macrophage immunity. The above findings highlight a novel mechanism underlying the antibacterial activity of probiotics. This study enriches the current knowledge on probiotics-mediated autophagy, and provides a new perspective on the prevention of bacterial infection in intestine, which further the application of probiotics in food products.

Bacillus amyloliquefaciens Ameliorates H2O2-Induced Oxidative Damage by Regulating Transporters, Tight Junctions, and Apoptosis Gene Expression in Cell Line IPEC-1

“…In previous studies, our team has shown that Ba (1 × 10 8 cfu/mL) facilitated polarization of M1 macrophages and enhanced its phagocytic capacity in vitro [14]. Moreover, this probiotic strain could induce autophagy-related signaling pathway and improve growth performance of piglets [15,16]. Different strains of Bacillus amyloliquefaciens have been shown to not only improve growth performance, increase the ratio of villus height to crypt depth, and ameliorate cecal microflora in broilers [17,18], but also regulate cytokine and strengthen host immune status in fish [19].…”

Lactobacillus plantarum BSGP201683 Isolated from Giant Panda Feces Attenuated Inflammation and Improved Gut Microflora in Mice Challenged with Enterotoxigenic Escherichia coli

“…The relationship between probiotics and improved gut health has received considerable scientific interest for more than a century. To protect animal guts, scientists have shown that probiotics, such as Lactobacillus, Bifidobacterium , and Bacillus , prevent gut bacterial disease (Barba-Vidal et al, 2017 ; Nishida et al, 2017 ; Wu et al, 2017 ). In the present study, L. plantarum G83 was isolated from the feces of healthy giant panda and confirmed beneficial in vitro .…”

Macrophage Autophagy and Bacterial Infections

“…Specific T cells can also stimulate autophagic activity in M. tuberculosis -infected human macrophages ( 44 ). Finally, microbiota may influence autophagy response too, as recently, probiotic Bacillus amyloliquefaciens has been shown to upregulate autophagy genes in macrophages, which lead to enhanced Escherichia coli killing ( 45 ).…”