Figure 8.

CXCR2 knockdown attenuated cisplatin-induced hearing loss. (A) A diagram represents experimental procedure that describes the dosage and route of administration for CXCR2 siRNA (siCXCR2) and cisplatin (11mg/kg). (B) Pretreatment ABR thresholds were recorded in rats, which were then injected by the trans-tympanic route with vehicle or siCXCR2 (0.9 µg) in both ears. Rats were then administered cisplatin 48 h later by intraperitoneal injections. Post-treatment ABRs were recorded 72 h following cisplatin administration. Cisplatin increased ABR thresholds for all frequencies while knockdown of CXCR2 attenuated this response (P<0.0001 between vehicle cisplatin and siCXCR2+cisplatin, F(10,132)=24.29 and DF=132). (C) Cochleae were collected and prepared, as described in Methods, and whole-mount sections were dissection to isolate the three different turns of the cochlea. Sections were stained for myosin VIIa (magenta). Representative whole-mount images show significant OHCs damage (white arrow) by cisplatin, while trans-tympanic siRNA (0.9 µg) protects OHCs damaging caused by cisplatin. Scale bar represent 20 µm. (D) Percentage of missing OHCs in basal, middle and apex turns of cochlea which was significantly attenuated by siCXCR2 (P<0.0001 between vehicle cisplatin and siCXCR2+cisplatin, F(3,42)=103.5 and DF=45) Data are presented as the mean ± SEM. Asterisks (*) indicates significant difference from vehicle group, while (**) indicate significant difference form cisplatin. (#) Indicate statistically significant difference from the cisplatin-treated group and from vehicle group (n=4). Statistical analyses among groups were tested using one-way analysis of variance (ANOVA).