Expression of toll-like receptor genes in leukocytes of patients with sudden sensorineural hearing loss

Objectives/Hypothesis Sudden sensorineural hearing loss (SNNHL) is a disease entity that could be caused by multiple etiologies in which the innate immunity status of the patients might be involved. The aim of this study is to investigate the expression of Toll-like receptor (TLR) genes in peripheral blood leukocytes of SNNHL patients. Study Design Basic research. Methods We examined the expression of six TLR genes in the peripheral blood leukocytes of SNNHL patients and normal controls using real-time quantitative reverse transcriptase-polymerase chain reaction. Results We found significantly higher expression of TLR2, TLR3, TLR4, TLR7, TLR8, and TLR9 genes in SNNHL patients as compared with normal controls (P < 0.05). Higher expression of the TLR2 gene was found in patients with profound hearing loss compared with those with less severe hearing loss (P < 0.05). The result was validated by the positively stained leukocytes for TLR2 protein in SNNHL patients using the immunocytochemical study. In addition, the percentage of CD14⁺ monocytes expressing TLR2 in SNNHL patients was higher than in normal controls assessed by flow cytometry and significantly correlated with the hearing thresholds of the affected ear (P < 0.05). Conclusion Our study implies a role for TLRs in SNNHL. The expression of TLR2 in particular correlates with the severity of the disease. Level of Evidence N/A.