Figure 5.

Trans-tympanic administration of SB22500 reduced inflammatory cell markers in the cochlea induced by cisplatin. (A) Wistar rats were administered vehicle or SB225002 in both ears, followed by cisplatin (11 mg/kg) 30 min later. Rats were sacrificed 72 h later and cochleae were processed for mid-modiolar sectioning. The level of CXCL1, CD68, CD45 and IBA1 was detected by diaminobenzidine tetrahydrochloride (DAB) staining while cell nuclei were stained with hematoxylin stain. DAB staining revealed in high levels of CXCL1 (dark-brown labeling) in OC, SG, SLi and in cisplatin-treated rat cochleae over that obtained in vehicle-treated controls. Blockade of CXCR2 by SB225002 attenuated the increases in CXCL1 immunoreactivity compared to the rats treated with vehicle plus cisplatin. (B) Immunolabeling for CD68 showed increased number of dark brown stained cells in the different region of SVA, SL and in areas surrounding the SG neurons. Inhibition of CXCR2 by SB225002 reduced the number of cells in the SVA. Dark brown staining in the intermediate layer likely represent staining of perivascular macrophage. (C, D), CD45 and IBA1 immunolabeling were increased in SVA, SL and SLi following cisplatin treatment. Lower levels of immunolabeling were observed in the animals pretreated with SB225002, followed by cisplatin. Figures shown are a representative of similar obtained in six independent animals per treatment group. Open arrows in (A) indicate hair cells while solid arrows represent labeling of SG neurons and SV. Solid arrows in panels b-d represent labeling of immune cells in the SG, SV and SL regions of the cochlea. Increased labeling of immune cells in the SV and SL was observed following cisplatin administration. Scale bars – black = 50 µm, red = 20 µm.