Structural analysis and immunomodulatory activity of a homopolysaccharide isolated from Parabacteroides distasonis

A homopolysaccharide fraction (PEP-1A) with desired immunomodulatory activity was isolated from culture broth of Parabacteroides distasonis. Structural characterization uncovered that PEP-1A had a molecular weight of 3.40 x 10(6) Da and possessed mannose merely. Comprehensive analysis of FT-IR, GC-MS and 1D/2D NMR confirmed that the structure of PEP-1A was expected as follows: [->[6)-alpha-D-Manp-(1](5)->[6)-alpha-Manp(3 up arrow & nbsp;alpha-D-Manp-1)(1]](3)->[6)-alpha-D-Manp(2 up arrow alpha-D-Manp-1)(4 <- 1-alpha-D-Manp)-(1](1)->[2)-alpha-Manp(1](7)->[3)-alpha-D-Manp-(1]-(6)->[2)-alpha-Manp(4 up arrow & nbsp;alpha-D-Manp-1)(1]](8)->](n)& nbsp;Finally, the activity assays on RAW 264.7 macrophages showed that PEP-1A could promote proliferation, increase the production of reactive oxygen species (ROS), enhance the phagocytosis, and promote the secretion of nitric oxide (NO) and inflammatory cytokines including IL-1 beta, IL-6 and TNF-alpha. Furthermore, PEP-1A could give play to immunoregulation effect through NF-kappa B, MAPK and Akt signaling pathways. Collectively, the study of PEP-1A offers a molecular underpinning for the future application of PEP-1A as a potential immunostimulant. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University.

Automated summary

In this study, a homopolysaccharide fraction (PEP-1A) with desired immunomodulatory activity was isolated from the culture broth of Parabacteroides distasonis. Structural characterization revealed that PEP-1A had a molecular weight of 3.40 x 10(6) Da and consisted solely of mannose. Functional assays demonstrated that PEP-1A could promote macrophage proliferation, increase reactive oxygen species (ROS) production, enhance phagocytosis, and stimulate the secretion of nitric oxide (NO) and inflammatory cytokines. Furthermore, PEP-1A exerted its immunoregulatory effects through NF-kappa B, MAPK, and Akt signaling pathways. These findings provide a molecular basis for the future application of PEP-1A as a potential immunostimulant.