A Study On Protection Of Ligustrazine Against Cisplatin-Induced Ototoxicity

Objective:Study the protection of ligustrazine against cisplatin-induced ototoxicity and the protective effect of ligustrazine against cisplatin-induced ototoxicity to provide theoretical evidence for the protection of ligustrazine against ototoxicity in clinic.Materials and methods:Fifty white guinea pigs with normal hearing were divided into three groups randomly,including a control group,an experimental group and an inhibited group.Physiological saline(4ml/kg/d) was injected to the abdominal cavities of the ten guinea pigs in control group for 4 days.The experimental group(the cisplatin group) comprised 20 guinea pigs received cisplatin (4mg/kg/d) for 4 consecutive days.And the inhibited group(ligustrazine group) including 20 guinea pigs received ligustrazine 140mg/kg/d and cisplatin 4mg/kg/d. Ligustrazine was injected in the first and second day solely.From the third day to the eighth day cisplatin was used just after ligustrazine was injected half an hour later. The alternation of hearing function were evaluated by the examination of auditory brainstem response and the latency of wave.Then all the guinea pigs were killed by broken neck after the final examination of auditory brainstem response was completed.The cochleas were removed and divided into three parts.One part was perfused by AgNO₃ in cochear duct to observe the impaired condition of cochlear hair cells.One part of the specimens was sent for immunohistochemistry to detect the expression of iNOS and Caspase-3.The rest part was taken for transmission electron microscope observation. Results:1.General health status of the three groups was different.The Cisplatin group was worst,and the inhibited group was better.2.Auricle reflex in the experimental group was decreased dramatically and high-frequent auditory acuity was affected principally.3.The auditory brainstem response thresholds were elevated and the latency of wave was significantly delayed in cisplatin group.But in the inhibited group,the threshold of ABR and the latency of the wave were reduced.The threshold of ABR and latency of wave was normal in control group.Compared with control group,the threshold of ABR and latency of wave in group CDDP and TMP were significant different.There was a significant difference between the experimental group and the inhibited group(t-test).4.Same results also were detected by morphology.The outer hair cell and spiral ganglion cell were damaged more seriously in the cisplatin group than in the inhibited group.The degree of damaged cell was gradually increased from the cupula to the base of cochlea and from the third to the first hair cell in the same turn.5.Under immunohistochemistry staining,there was no expression of iNOS and Caspase-3 in Cortis',spiral ganglion cell and stria vascularis in normal cochlear.In cisplatin group,the expression became stronger in spiral ganglion cell,stria vascularis,spiral ligament and Cortis'. Ligustrazine reduced the expression of iNOS and Caspase-3 induced by cisplatin. There was statistically significant difference between the experimental and the inhibited group.6.The results under transmission electron microscope showed that the bioblast in spiral ganglion cell of experimental group was decreased.The fracture of construction was more serious in experimental group than in inhibited group.Conclusions:1.Cisplatin damaged cochlea hair cells,spiral ganglion cell and stria vascularis.Cisplatin resulted in the damage of hearing function,especially high-frequency hearing loss.2.The high expression of iNOS in experimental group was related to the oxidative stress damage of Cisplatin.The high expression of Caspase-3 indicated that Cisplatin led to apoptosis.3.Ligustrazine reduced the cisplatin-induced ototoxicity through removing free radical and lessening apoptosis. Ligustrazine could be used to treat the cisplatin-induced ototoxicity and prevent the chemotherapy complication..