Experimental study on blood-inner ear barrier function in MRP1 and p-glycoprotein gene knockout mice

本研究利用mdr1a p-gp基因敲除小鼠[mdr1a（-/-）小鼠]和野生型mdr1a（+/+）小鼠研究了p-糖蛋白（p-gp）在内耳中的功能。药代动力学分析表明，与mdr1a（+/+）小鼠相比，mdr1a（-/-）小鼠对p-gp转运药物如阿霉素和长春花碱表现出超敏反应，并且这些药物在内耳的积累增加。然而，使用耳毒性药物顺铂后未检测到p-gp积累增加，表明p-gp对挤压药物具有选择性。使用听觉脑干反应的电生理学研究显示，仅在mdr1a（-/-）小鼠中，单独给予阿霉素或长春花碱后，波I和波I至V峰间潜伏期的阈值升高和延长。此外，在mdr1a（+/+）小鼠中，与环孢素A共同给药对p-gp功能的抑制导致阿霉素和长春花碱在内耳的积累增加。在环孢素A预处理后，单独使用阿霉素或长春花碱治疗的mdr1a（+/+）小鼠检测到听力障碍。由此可见，mdr1a p-gp作为外排泵，可抑制阿霉素、长春花碱等p-gp底物引起的野生型小鼠耳毒性。免疫组化法检测了多药耐药蛋白1 （MRP1）在大鼠耳蜗、豚鼠前庭迷路和内淋巴囊的表达。MRP1在血管纹外侧壁、螺旋韧带、螺旋突起和摩尺蠖的耳蜗神经纤维中检测到。此外，MRP1在壶腹嵴、胞室、囊泡和内淋巴囊上皮细胞的上皮细胞中被发现。由于p-gp和MRP1具有挤压泵的作用，它们可能参与特定药物穿过血内耳屏障的双极渗透屏障，导致耳蜗、前庭器官和内淋巴囊内的毒性物质和治疗药物浓度较低，在血内耳屏障中起重要作用。少

The present study investigated the p-glycoprotein (p-gp) function in the inner ear using mdr1a p-gp gene knock-out mice [mdr1a(-/-) mice] and wild-type mdr1a(+/+) mice. Pharmacokinetic analyses indicated that mdr1a(-/-) mice displayed hypersensitivity to p-gp transported drugs such as doxorubicin (adriamycin) and vinblastine, and increased accumulation of these drugs in the inner ear compared with that in mdr1a(+/+) mice. However, increased accumulation was not detected after administering with ototoxic drug cisplatin, indicating that p-gp had a selectivity for extruding drugs. Electrophysiological studies using auditory brainstem response showed elevated thresholds and prolongations of wave I and wave I to V interpeak latencies only in mdr1a(-/-) mice after administering with doxorubicin or vinblastine alone. Furthermore, inhibition of p-gp function by co-administration with cyclosporin A in mdr1a(+/+) mice resulted in increased accumulation of doxorubicin and vinblastine in the inner … More ear. After pretreatment with cyclosporin A, hearing impairment was detected in mdr1a(+/+) mice treated with doxorubicin or vinblastine alone. From these results, it was suggested that mdr1a p-gp, which acts as an efflux pump, prevented ototoxicity induced by p-gp substrate drugs such as doxorubicin and vinblastine in wild-type mice.Expression of multidrug resistance protein 1 (MRP1) was detected in the rat cochlea and in the vestibular labyrinth and endolymphatic sac of the guinea pig by immunohistochemical analyses. MRP1 was detected in the lateral wall of the stria vascularis, spiral ligament, spiral prominence and in the cochlear nerve fibers of the modiolus. Furthermore, MRP1 was found in the epithelial lining of the crista ampullaris, utricle, saccule, and epithelial cells of the endolymphatic sac. Since p-gp and MRP1 act as extrusion pumps, they may participate in a bipolar permeation barrier for selected drugs crossing the blood-inner ear barrier resulting in a low concentration of toxic substances and therapeutic drugs in the cochlea, vestibular organs and endolymphatic sac and play an important role in the blood-inner ear barrier. Less