Two Saponins From Liquorice Reverse Secondary Structure Modifications of Lysozyme and Mitigate Cytotoxicity and Inflammatory Responses in Vascular Smooth Muscle Cells

Natural lysozyme (N-Lyso) is an important natural preservative widely used in the food industry and biomedical fields. However, the specific properties and safety of lysozyme after secondary structure modification (M-Lyso) are still poorly understood. Compared to N-Lyso, M-Lyso at the same concentration exhibits increased protease sensitivity, reduced enzymatic activity, but no significant change in antibacterial activity. Multispectral analysis combined with cell experiments revealed that M-Lyso, characterized by a decreased α-helix content and increased β-sheet structure, induced an increase in PDE4D expression in vascular smooth muscle cells (VSMCs) and elevated levels of PDE4D and IL-6 in the cell culture supernatants, accompanied by a decrease in cell viability. However, treating M-Lyso with glycyrrhizic acid (GL) or glycyrrhetinic acid (GA) from liquorice reversed the above phenomena. Molecular docking results indicated GL and GA formed supramolecular complexes with lysozyme. The understanding of specific properties of N-Lyso and M-Lyso not only provides valuable insights into the safety profile of lysozyme but also offers for the prevention and treating diseases related to alterations in the protein secondary structure.