Expression of heat shock protein 70 in cochlea of guinea pigs with gentamicin-toxic deafness and protection of ligustrazine

Yueqiu NI; Hao TANG; Wenshuang FU; Lijuan SHI

ABSTRACT

BACKGROUND:

Ligustrazine possesses the effect to reduce ototoxicity of gentamicin, whether does it antagonize the ototoxicity of gentamicin through influencing the expression of heat shock protein (HSP) 70 in cochlea of guinea pigs with gentamicin induced ototoxicity? BJECTIVE To investigate the effect of ligustrazine on the expression of HSP70 in cochlea of guinea pigs with gentamicin induced ototoxicity through immunohistochemistry and image analysis technique in combination with the measurement of auditory brainstem response (ABR).

DESIGN:

A randomized controlled study, and linear correlation analysis. ETTING Physiological Department of Shenyang Medical College and Audiological Laboratory of China Medical University.MATERIALS Totally 40 white and red-eye healthy guinea pigs of lean grade and with keen auricle reflect, weighing 200 - 250 g, of either gender, were at random divided as gentamicin group, ligustrazine + gentamicin group, ligustrazine group, and normal control group, with 10 in each group.

METHODS:

Ligustrazine injection 140 mg/kg was intraperitoneally at the left side given for animals in ligustrazine + gentamicin group, and at the same time gentamicin sulfate injection 100 mg/kg was given intraperitoneally at the right side. The same dosage of gentamicin sulfate injection was intraperitoneally given for animals in gentamicin group. The same dosage of ligustrazine was intraperitoneally give for animals in ligustrazine group. The normal saline 2.5 mL/kg was intraperitoneally given for animals in normal control group. Administration was consecutively given for 10 days for each group, once a day. The body mass was measured every day for regulating the dosage. Before starting and after finishing the administration, the thresholds of ABR of all animals in each group were measured respectively. After finishing administration, all animals in each group were put to death, and the conditions of expressions of HSP70 in cochlea of guinea pigs were investigated by SABC immunohistochemistry and image analysis technology.MAIN OUTCOME

MEASURES:

① the thresholds of ABR of all animals in each group; ② expressions of HSP70 in cochlea of guinea pigs in each group.

RESULTS:

① The thresholds of ABR of guinea pigs The thresholds in ligustrazine + gentamicin group and gentamicin group were obviously higher than that in normal control group [(21.09±4.50) dBnHL, (36.55±6.13)dBnHL, (2.50±2.75) dBnHL, t=15.764-22.665, P ＜ 0.001]. The threshold in ligustrazine + gentamicin group was obviously lower than that in gentamicin group (t=9.092, P ＜ 0.001). ② The expressions of HSP70 in each part of cochlea of guinea pigs The mean gray values of cellular HSP70 positive reaction products in Corti's organ, vascular stria and spiral ligament, spiral limbus and spiral ganglion in gentamicin group were lower than those in normal control group (88.24±4.34, 96.85±1.05; 121.24±0.92,128.76±1.59; 96.15±1.10, 98.78±0.54; 117.73±1.18, 120.51±0.80, t=6.097-18.307, P ＜ 0.001). The mean gray values of cellular HSP70 positive reaction products in ligustrazine + gentamicin group were lower than those in gentamicin group (92.53±2.25, 88.24±4.34; 125.20±1.43, 121.24±0.92;98.71±0.91, 96.15±1.10, 118.91±0.46, 117.73±1.18, t=3.925-10.415, P＜ 0.001).③ The mean gray value of cellular HSP70 positive reaction products in each part of cochlea of guinea pigs was highly correlated with the threshold of ABR (r=-0.814 1 to -0.984 1, P ＜ 0.001).

CONCLUSION:

Ligustrazine could reduce the threshold of ABR and the expression of HSP70 in cochlea with gentamicin toxicosis so as to relieve gentamicin ototoxic injury, hence improving auditory function.