Dysfunction in immune surveillance during anticancer
chemotherapy of patients often causes weakness of the host defense system and a subsequent increase in microbial
infections. However, the deterioration of organ-specific function related to microbial challenges in
cisplatin-treated patients has not yet been elucidated. In this study, we investigated
cisplatin-induced TLR4 expression and its binding to LPS in mouse cochlear tissues and the effect of this interaction on hearing function.
Cisplatin increased the transcriptional and translational expression of TLR4 in the cochlear tissues, organ of Corti explants, and HEI-OC1 cells. Furthermore,
cisplatin increased the interaction between TLR4 and its microbial
ligand LPS, thereby upregulating the production of proinflammatory
cytokines, such as TNF-α, IL-1β, and
IL-6, via NF-κB activation. In C57BL/6 mice, the combined injection of
cisplatin and LPS caused severe
hearing impairment compared with that in the control,
cisplatin-alone, or LPS-alone groups, whereas this hearing dysfunction was completely suppressed in both TLR4 mutant and knockout mice. These results suggest that hearing function can be easily damaged by increased TLR expression and microbial
infections due to the weakened host defense systems of
cancer patients receiving
therapy comprising three to six cycles of
cisplatin alone or
cisplatin combined with other chemotherapeutic agents. Moreover, such damage can occur even though patients may not experience ototoxic levels of cumulative
cisplatin concentration.