Immunomodulation Properties of a Novel β-Glucan Extract from the Mushroom Lentinus Edodes in an In-Vitro Lung Injury Model

Rationale: Acute Respiratory Distress Syndrome (ARDS) is characterized by an acute lung inflammatory process. This results in lung parenchyma injury and promotes activation of the immune system with the up-regulation of pro-inflammatory cytokines. β-glucans - a diverse group of polysaccharides - have been reported to have immune-modulating properties which could have the potential to regulate the cytokine cascade during ARDS. A pure β-glucan compound is required. However, mass produced commercial products contain various contaminants including α-glucans, that might affect the active immune-modulating component. We performed a novel extraction process to achieve a pure β-glucan compound, determined by megazyme analysis kit. We hypothesized that the purer sample would have an increased immunomodulatory activity in different cell lines, including pulmonary type II alveolar cell line (A549), compared to a commercial source β-glucan. Methods: Lentinan is a β-glucan extracted from the mushroom Lentinus edodes. Commercial Lentinan (CL) was purchased as a sterile powder from Carbosynth Ltd, UK. In-house Lentinan (IHL) was extracted from crude mushroom using a proprietary process. Cells exposed to both extracts comprised of pulmonary type II alveolar cell line (A549), human monocytic cells (THP-1) and human mesenchymal stem cells derived from bone marrow (BM-MSCs). Assays carried out included cytotoxicity, phagocytosis and luciferase to determine inflammation via NF-kB pathway and analysis of cytokine release profile using Enzyme Linked Immuno Sorbent Assay. Test series were carried out to determine potential preliminary in-vitro activity of the novel IHL extract. Results: IHL extract contained a higher percentage of β-glucans and lower levels of α-glucans compared to CL. Both extracts demonstrated low to minimal toxicity in all cell lines. Both extracts significantly reduced percentage phagocytic index in lipopolysaccharide injured and non-injured phorbol-12-myristate-13-acetate activated THP-1 cells. A reduction in inflammation was observed with both IHL and CL in IL-1β injured A549 cells determined with IL-8 expression and luciferase assay. IHL and CL had no effect on the expression of IL-8 and IL-6 in BM-MSCs and THP-1. IHL increased levels of IL-1 and TNF-α in THP-1. Both β-glucans extracts increased release of VEGF in BM-MSCs. Conclusions: We reported that the novel IHL is a purer β-glucan extract from Lentinan edodes compared to CL, with no contaminating α-glucans. We observed that IHL and CL had both inflammatory and antiinflammatory properties, with IHL showing a greater immune-modulating profile compared to CL. Further investigations about immunomodulation potential of this novel extract are required in future in-vivo studies.