TLR4 and hearing loss disorder: S100A8 is the endogenous ligand for Toll like receptor 4 (TLR4) which activates NF-ĸB [44], whereas LCN2 is an NF-ĸB target gene and pro-inflammatory cytokine, that can itself activate the NF-ĸB pathway and is implicated in inflammation [54], neurodegeneration [55] and noise-induced hearing loss [56].