| Summary: | Asthma, a global health issues with steadily rising prevalence worldwide, is characterised by airway inflammation. While commercial drugs have proven effective in managing asthma symptoms, they are not without limitations, including the risk of side effects from steroid-based medication, over-reliance, non-responsiveness, and tolerance development. Therefore, there is growing interest in exploring natural medicinal mushroom therapy as an alternative for asthma management and prevention. One such mushroom, scientifically known as Lignosus rhinocerotis (LR), has attracted attention due to its potential medicinal properties. However, limited scientific studies have been conducted to elucidate the effect of this fungus, particularly in the context of allergic asthma. This study was designed to isolate polysaccharide from the LR’s sclerotia, with a focus on their anti-asthmatic properties in a murine model of asthma. LR polysaccharide (LRP) was extracted via hot-water extraction using a Soxhlet apparatus and fractionated with DEAE cellulose and Sephadex G-100. Comprehensive understanding of the LRP structure was pursued using High-performance Liquid Chromatography (HPLC), Fourier Transform Infrared (FTIR) spectroscopy, Nuclear magnetic Resonance (NMR), X-ray Crystallography (XRD). Cytotoxicity of LRP was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium (MTS) assay on Vero cell lines across different concentrations (15.6-4000 µg/ml) and time points (24, 48, and 72 hours). The effectiveness of LRP in addressing airway inflammation was evaluated in a subacute
murine model of asthma. Female BALB/c mice were sensitised with ovalbumin (OVA) and aluminium hydroxide at day 0 and day 14, followed by OVA challenges from day 21 to day 27. LRP (1, 10 and 100 mg/kg) and dexamethasone (DEX) (0.25 mg/kg) were administered intranasally following each challenge, with a normal group receiving only PBS treatment. Bronchoalveolar lavage fluid (BALF) was collected for cytokine analysis and differential blood count, serum for immunoglobulin E (IgE), lungs for histopathological, immunohistopathological and gene expression. The findings revealed that LRP exhibited a semi-crystalline structure primarily composed of glucose, with the predicted structural elements of →4)-α-D-Glcp-(1→ and →3)-β-D-Glcp-(1→. Cell viability studies demonstrated that LRP had no cytotoxic effects on Vero cell lines over 24-48 hours of treatment, with cell viability remaining above 80 %. LRP treatments significantly reduced Th2 cytokines production and IgE levels (p<0.05). Histological assessment revealed a decrease in inflammatory cell infiltration, mucus production, and TGF-β1 expression in the lungs of LRP treatment groups. Furthermore, gene expression analysis exhibited reduced COX-2, iNOS and Muc5ac expression in LRP treatment groups, with iNOS exhibiting a significant reduction. In conclusion, LRP has the potential to mitigate allergic inflammation in an OVA-challenged murine model, offering potential as an alternative approach for managing allergic asthma.
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