ABSTRACT
BACKGROUND AND OBJECTIVES: Cytokines such as interleukin-1beta (IL-1beta) released into cerebrospinal fluid (CSF) during bacterial meningitis play an important role in causing inflammation and tissue damage. Bacterial meningitis is often complicated by a sensorineural hearing loss. The present study is to investigate the effect of IL-1beta injected into CSF on hearing in guinea pigs. MATERIALS AND METHODS: Thirty guinea pigs (60 ears) were randomly assigned to the following three groups: 1) Control group receiving intracisternal PBS injection. 2) 10 ng group receiving intracisternal injection of 10 ng/ml of IL-1beta. 3) 100 ng group receiving intracisternal injection of 100 ng/ml of IL-1beta. Auditory brainstem response (ABR) was performed before the injection, 10, and 24 hours after the injection of PBS and IL-1beta. The concentration of IL-1beta in the perilymph was measured in each group. RESULT: The ABR threshold shift at 10 and 24 hours were respectively 3.3+/-2.6 dB, 2.8+/-2.0 dB in the control group, 21.94+/-14.46 dB, 5.83+/-9.74 dB in the 10 ng group, and 21.58+/-15.99 dB, 4.74+/-9.05 dB in the 100 ng group. The ABR thresholds were significantly increased in the 10 and 100 ng groups compared to the control group at 10 hours, but they were not significantly different at 24 hours after the injection. The concentrations of IL-1beta in the perilymph at 10 hours were 2.17+/-0.6 ng/ml in the 10 ng group and 3.58+/-1.1 ng/m in the 100 ng group. Those were 0.53+/-0.1 ng/ml in the 10 ng and 0.86+/-0.2 ng/ml in the 100 ng groups at 24 hours after the injection. CONCLUSION: The results of this study showed that IL-1beta released into CSF during meningitis may play an important role in causing hearing loss.