Effects of Estrogen on the Expression of Caspase-3 in Guinea Pigs Inner Ear under the Compound Factors of Simulated Weightlessness and Noise in Spaceship / 听力学及言语疾病杂志

ABSTRACT

Objective To study the effects of compound factors of simulated weightlessness and noise in spaceship on auditory function ,and the expression of apoptotic marker Caspase -3 in inner ear in guinea pigs ,and study the influence of compound factor above on its hearing loss and apoptosis of inner ear .Methods Thirty -six guinea pigs were randomly divided into four groups ,6 in control group ,10 in simulated weightlessness with noise group (Group A) ,treatment estrogen group (Group B) and prevention estrogen (Group C) ,respectively .All the experiment groups were suspended posterior limb ,with the exposure of the simulated noise circumstance in space-ship .Estrogen prevention group received intramuscular injection of estradiol benzoate for 3 days before the experiment ,while estrogen treatment group was treated in the same way for 8 days from the beginning of experiment to 3 days after the experiment .Bilateral auditory brainstem response thresholds (ABR) were tested in pre- exposure ,post-exposure and 3 -day recovery respectively .Cochleae were obtoined for immunohistochemistry staining to observe the expression of the apoptotic marker Caspase -3 in inner ear .Results At the time point of post -exposure ,ABR threshold in Group B was lower than those in Group A by 14 .5 dB and Group C by 9 dB .For the ABR change of pre ,and post-exposure ,Group B was lower 12 .75 dB than those of in Group A and 7 .75 dB than in Group C .For the ABR change between pre ,and post-recovery ,ABR threshold of Group C was higher than those of in Group A by 14 .5 dB and in Group B by 7 dB .These differences were significant (P<0 .05) .The expression of Caspase-3 was positive in the hair cell ,spiral ganglion cells and stria vascularis of three groups in both post exposure and 3-day recovery .The expression of Caspase-3 in hair cell and stria vascularis was strongly positive in spiral ganglion cells in Group C in post -exposure ,while it was slightly positive in Group B .After 3 -day recovery ,Group A turned to negative ,while Group B and Group C were still in positive expression with an increase of that in post -ex-posure .Conclusion Estrogen treatment could effectively reduce the hearing loss and the apoptosis of inner ear in-duced by the compound factor of weightlessness and noise .Preventive use of estrogen could not produce an instant protection on the hearing loss induced by exposure ,and the apoptosis was enhanced .However ,it speeded up the procedure of recovery and reduced the apoptosis of inner ear .