Gilibili Ravindranath Reddy, Kurawattimath Vishwanath, Murali Bokka Venkata, Lai Yurong, Mariappan T Thanga, Shen Hong, Chatterjee Sagnik
Pharmaceutical Candidate Optimization, Biocon Bristol-Myers Squibb R&D Center (BBRC), Syngene International Ltd., Bangalore 560100, India.
Department of drug metabolism, Gilead Sciences Inc., Foster City, CA 94404, USA.
Pharmaceutics. 2018 Aug 8;10(3):125. doi: 10.3390/pharmaceutics10030125.
Previously we reported that coproporphyrin-I (CP-I) is an optimal probe substrate for multidrug resistance-associated protein 2 (MRP2), and stimulation of MRP2-mediated transport is probe substrate-dependent. In the present investigation, we assessed if the in vitro stimulation is physiologically relevant. Similar to human MRP2 transport, CP-I was transported by rat Mrp2 in a typical Michaelis-Menten kinetics with apparent K and V values of 15 ± 6 µM and 161 ± 20 pmol/min/mg protein, respectively. In vivo Mrp2 functions were monitored by biliary and renal secretion of CP-I and its isomer CP-III, in bile-duct cannulated rats before and after treatment with mitoxantrone, progesterone, and verapamil. These compounds stimulated Mrp2-mediated CP-I transport in vitro. No significant increase in biliary or renal clearances, as well as in the cumulative amount of CP-I or CP-III eliminated in bile, were detected following treatment with the in vitro stimulators, indicating an in vitro to in vivo disconnect. In presence of 10 µM bilirubin, the in vitro stimulation was suppressed. We concluded that the in vitro stimulation of CP-I transport mediated by Mrp2 is not translatable in vivo, and proposed that the presence of endogenous compounds such as bilirubin in the liver may contribute to the in vitro to in vivo disconnect.
此前我们报道过，粪卟啉-I（CP-I）是多药耐药相关蛋白2（MRP2）的最佳探针底物，且MRP2介导的转运刺激是探针底物依赖性的。在本研究中，我们评估了体外刺激是否具有生理相关性。与人类MRP2转运相似，CP-I由大鼠Mrp2以典型的米氏动力学进行转运，其表观K值和V值分别为15±6μM和161±20 pmol/分钟/毫克蛋白。在胆管插管大鼠中，用米托蒽醌、孕酮和维拉帕米治疗前后，通过CP-I及其异构体CP-III的胆汁和肾脏分泌来监测体内Mrp2的功能。这些化合物在体外刺激了Mrp2介导的CP-I转运。在用体外刺激剂治疗后，未检测到胆汁或肾脏清除率以及胆汁中消除的CP-I或CP-III累积量有显著增加，表明存在体外与体内的脱节现象。在存在10μM胆红素的情况下，体外刺激受到抑制。我们得出结论，Mrp2介导的CP-I转运的体外刺激在体内无法转化，并提出肝脏中胆红素等内源性化合物的存在可能导致了体外与体内的脱节。
