Lactobacillus paracasei is a major probiotic and is well known for its anti-inflammatory properties. Thus, we investigated the effects of L. paracasei-derived extracellular vesicles (LpEVs) on LPS-induced inflammation in HT29 human colorectal cancer cells and dextran sulfate sodium (DSS)-induced colitis in C57BL/6 mice. ER stress inhibitors (salubrinal or 4-PBA) or CHOP siRNA were utilized to investigate the relationship between LpEV-induced endoplasmic reticulum (ER) stress and the inhibitory effect of LpEVs against LPS-induced inflammation. DSS (2%) was administered to male C57BL/6 mice to induce inflammatory bowel disease, and disease activity was measured by determining colon length, disease activity index, and survival ratio. In in vitro experiments, LpEVs reduced the expression of the LPS-induced pro-inflammatory cytokines IL-1α, IL-1β, IL-2, and TNFα and increased the expression of the anti-inflammatory cytokines IL-10 and TGFβ. LpEVs reduced LPS-induced inflammation in HT29 cells and decreased the activation of inflammation-associated proteins, such as COX-2, iNOS and NFκB, as well as nitric oxide. In in vivo mouse experiments, the oral administration of LpEVs also protected against DSS-induced colitis by reducing weight loss, maintaining colon length, and decreasing the disease activity index (DAI). In addition, LpEVs induced the expression of endoplasmic reticulum (ER) stress-associated proteins, while the inhibition of these proteins blocked the anti-inflammatory effects of LpEVs in LPS-treated HT29 cells, restoring the pro-inflammatory effects of LPS. This study found that LpEVs attenuate LPS-induced inflammation in the intestine through ER stress activation. Our results suggest that LpEVs have a significant effect in maintaining colorectal homeostasis in inflammation-mediated pathogenesis.
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While links between microbiota composition and IBD have been established, the specific underlying molecular mechanisms of action remain unclear. An often overlooked bacterial function is the release of extracellular vesicles (EVs), nanometer-sized vesicles composed of lipid bilayer membranes designed to transport diverse biomolecules. Due to their ability to transverse epithelial cells, bacterial EVs can be found in both the extracellular space and various biological fluids and have a crucial role in the transport of microRNAs (miRNAs), messenger RNAs (mRNAs), and proteins from parental cells to recipient cells11,12. EVs play an important role in cell-to-cell communication and, consequently, the regulation of cellular physiology and pathophysiology. Indeed, EVs in biological fluids have been found to play a role in the body’s immunological mechanisms13–16. These findings imply that circulating microbial EVs may directly influence the health-promoting functions of probiotics and represent a primary molecular mechanism of the immunomodulatory effects of probiotics. This is supported by previous reports that Lactobacillus-derived EVs alleviate inflammatory responses by regulating cytokine production17,18.
© 2020, The Author(s).