Mechanistic insights into the hepatic metabolism of lentinan: A TLR2-ROS-lysosome axis

Lentinan (LNT), a β-glucan polysaccharide extracted from Lentinus edodes, exhibits potent immunomodulatory and antitumor activities and exhibits extensive hepatic disposition following intravenous or oral administration. However, several key issues related to LNT fate in the liver, including LNT hepatic disposition and the mechanisms underlying its recognition, uptake, and metabolism, remain poorly understood. Recently, pattern recognition receptor (PRR)-mediated polysaccharide metabolism has emerged as a process that may help researchers understand the hepatic disposition of natural polysaccharides. Toll-like receptors (TLRs), key mediators of innate immune responses, have not been thoroughly explored in the context of LNT hepatic disposition. Here, we aimed to investigate the roles of TLRs in LNT hepatic recognition, uptake, and metabolism. Transcriptomic profiling of LNT-treated Kupffer cells (KCs) suggested that Toll-like receptor 2 (TLR2) is a potential recognition receptor. Functional assays demonstrated that siRNA-mediated Tlr2 knockdown reduced LNT uptake by approximately 41%, confirming the essential role of TLR2 in LNT recognition and internalization. In parallel, pharmacological inhibitors targeting the TLR2/MyD88/NF-κB pathway decreased LNT uptake, further verifying that KCs internalized LNT via the TLR2/MyD88/NF-κB signaling pathway. Moreover, this pathway increased reactive oxygen species (ROS) production by 4-fold and promoted lysosomal maturation, facilitating efficient LNT degradation. Our findings expand the conceptual framework of PRR-mediated polysaccharide metabolism by highlighting a broader role for TLR signaling pathways in linking pathogen-associated molecular pattern recognition with macrophage metabolic functions, thus establishing a mechanistic bridge between LNT pharmacokinetics and pharmacodynamics.