Novel non-specific lipid-Transfer Protein (TdLTP4) isolated from Durum wheat: Antimicrobial activities to control pathogen and spoilage bacteria and Anti-Inflammatory properties in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages

Abstract

Background: Lipid transfer proteins (LTP) are members of the family of pathogenesis-related proteins (PR-14) that play a key role in plant defense mechanisms.Methods: In this study, a novel gene TdLTP4 encoding an antifungal protein from wheat (cv. Om Rabiaa) was subcloned, overexpressed in Escherichia coli BL-21 (DE3) and enriched using ammonium sulfate fractionation. The TdLTP4 fusion protein was then tested against a panel of pathogens, food-borne and spoilage bacteria and fungi in order to evaluate the antimicrobial properties. Our protein was applied to 0.5 µg/mL LPS-induced RAW 264.7 macrophages in vitro at different concentrations (5, 10, 20, 50 and 100 µg/ml). Levels of nitric oxide (NO), pro-inflammatory cytokines interleukin (IL)-1β (IL-1 β), interleukin (IL)-6 (IL-6), tumor necrosis factor (TNF-α) and anti-inflammatory cytokine IL-10 in the supernatant fraction were measured using enzyme-linked immunosorbent assay (ELISA). Expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were detected via Western blot. Results: The inhibition zones and minimal inhibitory concentration (MIC) values of bacterial strains were in the range of 14-26 mm and 62.5-250 µg/mL, respectively. Moreover, a remarkable activity against several fungal strains was revealed. TdLTP4 (5–100 µg/mL) decreased the production of NO (IC50= 4.32 µg/mL), IL-6 (IC50= 11.52 µg/mL), IL-1β (IC50= 7.87 µg/mL) and TNF-α (IC50 =8.66 µg/mL) by lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Our protein could modulate the macrophages inflammatory mode by causing reduction in iNOS and COX2.Conclusion: According to these findings, LTP fusion protein could be used as natural anti-inflammatory and antimicrobial agent in food preservation and human health.