title: Bacterial fucose-rich polysaccharide stabilizes MAPK-mediated Nrf2/Keap1 signaling by directly scavenging reactive oxygen species during hydrogen peroxide-induced apoptosis of human lung fibroblast cells.
abstract: Continuous free radical assault upsets cellular homeostasis and dysregulates associated signaling pathways to promote stress-induced cell death. In spite of the continuous development and implementation of effective therapeutic strategies, limitations in treatments for stress-induced toxicities remain. The purpose of the present study was to determine the potential therapeutic efficacy of bacterial fucose polysaccharides against hydrogen peroxide (H2O2)-induced stress in human lung fibroblast (WI38) cells and to understand the associated molecular mechanisms. In two different fermentation processes, Bacillus megaterium RB-05 biosynthesized two non-identical fucose polysaccharides; of these, the polysaccharide having a high-fucose content (∼ 42%) conferred the maximum free radical scavenging efficiency in vitro. Structural characterizations of the purified polysaccharides were performed using HPLC, GC-MS, and (1)H/(13)C/2D-COSY NMR. H2O2 (300 µM) insult to WI38 cells showed anti-proliferative effects by inducing intracellular reactive oxygen species (ROS) and by disrupting mitochondrial membrane permeability, followed by apoptosis. The polysaccharide (250 µg/mL) attenuated the cell death process by directly scavenging intracellular ROS rather than activating endogenous antioxidant enzymes. This process encompasses inhibition of caspase-9/3/7, a decrease in the ratio of Bax/Bcl2, relocalization of translocated Bax and cytochrome c, upregulation of anti-apoptotic members of the Bcl2 family and a decrease in the phosphorylation of MAPKs (mitogen activated protein kinases). Furthermore, cellular homeostasis was re-established via stabilization of MAPK-mediated Nrf2/Keap1 signaling and transcription of downstream cytoprotective genes. This molecular study uniquely introduces a fucose-rich bacterial polysaccharide as a potential inhibitor of H2O2-induced stress and toxicities.
authors.affiliation: Materials Science Centre, Indian Institute of Technology Kharagpur, West Bengal, India; Immunology lab, Department of Zoology, University of Calcutta, West Bengal, India.
authors.forename: Sougata
authors.initials: S
authors.lastname: Roy Chowdhury
authors.affiliation: Immunology lab, Department of Zoology, University of Calcutta, West Bengal, India.
authors.forename: Suman
authors.initials: S
authors.lastname: Sengupta
authors.affiliation: Immunology lab, Department of Zoology, University of Calcutta, West Bengal, India.
authors.forename: Subir
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Materials Science Centre, Indian Institute of Technology Kharagpur, West Bengal, India.
authors.forename: Tridib Kumar
authors.initials: TK
authors.lastname: Sinha
authors.affiliation: Department of Biotechnology, Indian Institute of Technology Kharagpur, West Bengal, India.
authors.forename: Ramkrishna
authors.initials: R
authors.lastname: Sen
authors.affiliation: Materials Science Centre, Indian Institute of Technology Kharagpur, West Bengal, India.
authors.forename: Ratan Kumar
authors.initials: RK
authors.lastname: Basak
authors.affiliation: Materials Science Centre, Indian Institute of Technology Kharagpur, West Bengal, India.
authors.forename: Basudam
authors.initials: B
authors.lastname: Adhikari
authors.affiliation: Immunology lab, Department of Zoology, University of Calcutta, West Bengal, India.
authors.forename: Arindam
authors.initials: A
authors.lastname: Bhattacharyya
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001410:Bacillus megaterium / Q000378:metabolism; D002240:Carbohydrate Sequence; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016166:Free Radical Scavengers / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D005643:Fucose / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D000072019:Kelch-Like ECH-Associated Protein 1; D008168:Lung / Q000166:cytology; D008928:Mitochondria / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D016166:Free Radical Scavengers; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D011135:Polysaccharides, Bacterial; D017382:Reactive Oxygen Species; C085953:exopolysaccharide, Bacillus; D005643:Fucose; D045304:Cytochromes c; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases