Improvement of intestinal drug absorption based on structural changes of tight junction and functional changes of P-glycoprotein

我们研究了吸收增强剂改善细胞旁和细胞间药物运输的作用机制。酒石酸（tataric acid， TA）在较低的pH值下降低了细胞内ATP水平和细胞内pH值。由此可以认为，TA的作用机制之一是细胞内酸中毒通过降低ATP水平使钙水平升高，进而打开紧结（tight junction， TJ）。TA和吡洛替德康（PTD）也通过生理ph值下p -糖蛋白（P-gp）的功能改变和TJ的开放增加了跨细胞转运，特别是TA增加了罗丹明123 （Rho123）和柔红霉素在回肠的吸收，但TJ没有开放，P-gp的表达水平也没有改变。另一方面，TA显著抑制Rho123从血液向管腔的排泄。这些结果表明，TA增加了肠道对P-gp底物的吸收，可能是通过抑制P-gp的功能而不影响P-gp在大鼠肠道中的表达。基于P-gp的功能改变，PTD对Rho123的鼻腔和肠道吸收有增强作用。因此，我们发现TJ的增加和P-gp的抑制增加了肠道对亲水性化合物和P-gp底物的吸收。多药耐药（mdr）基因编码的P-gp在淋巴细胞和肠上皮细胞表面表达。本实验测定了糖多糖诱导感染性疾病、缺血/再灌注（I/R）、炎症性肠病（IBD）和正常情况下外周血淋巴细胞（PBL）和mdr的变化，探讨外周血淋巴细胞（PBL）、粘膜上皮内淋巴细胞（IEL）和粘膜上皮细胞（EC） mdr表达的关系。与对照组相比，在I/R和IBD等疾病条件下，PBL mdr显著降低。PBL和粘膜mdr表达均与疾病活度相关，PBL mdr表达与肠道P-gp底物吸收、IEL表达与EC表达均有显著相关性。在糖皮质激素治疗的情况下，PBL和粘膜mdr表达可能在确定各种疾病对P-gp底物的反应中发挥重要作用。少

We investigated the action mechanisms of absorption enhancers that improve paracellular and transcellular drug transport. Tartaric acid (TA) decreased the intracellular ATP level and the intracellular pH at the lower pH. From this results, it was considered that one of the action mechanism of TA is that the intracellular acidosis increases the calcium level through decrease in ATP levels, followed by opening the tight junction (TJ). TA and Pirotiodecan (PTD) also increased the transcellular transport based on the functional changes of P-glycoprotein (P-gp) in addition to TJ opening at the physiological pH. In particular, TA increased the absorption of rhodamine123 (Rho123) and daunorubicin in the ileum without TJ opening and change of expression level of P-gp. On the other hand, TA significantly inhibited the excretion of Rho123 from blood to lumen. These results suggest that TA increases the intestinal absorption of P-gp substrates, possibly by inhibiting the P-gp function without cha … More nge the expression level of P-gp in the rat intestine. PTD had enhancing effects on nasal and intestinal absorption of Rho123 based on functional changes of P-gp. Consequently, we showed the expansion of TJ and inhibition of P-gp increase intestinal absorption of hydrophilic compounds and P-gp substrates.The multidrug resistance (mdr) gene codes for P-gp expressed on the surface of lymphocytes and intestinal epithelial cells. We measured peripheral lymphocyte (PBL) and mdr in infective diseases condition induced by lypopolysaccharide, ischemia/reperfusion (I/R), inflammation bowel diseases (IBD) and normal condition, to assess the relationship among PBL, mucosal intraepithelial lymphocyte (IEL) and mucosal epithelial cells (EC) mdr expression. Compared with controls, PBL mdr was significantly decreased in the diseases condition such as I/R and IBD. Both PBL and mucosal mdr expression appeared dependent of diseases activity, and there was a significant correlation both between PBL mdr expression and P-gp substrate absorption from intestine, and between IEL expression and EC expression. PBL and mucosal mdr expression may possibly play an important role in determination of the response of various diseases to P-gp substrate in the case such as glucocorticiod therapy. Less