Biphasic regulation of P-glycoprotein function and expression by NO donors in Caco-2 cells

Abstract

Aim: To investigate the effects of nitric oxide (NO) donors on the function and expression of P-glycoprotein (P-gp) in Caco-2 cells. Methods: Caco-2 cells were exposed to NO donors for designated times. P-gp function and expression were assessed using Rhodamine123 uptake assay and Western blotting, respectively. Intracellular reactive oxygen species (iROS) and intracellular reactive nitrogen species (iRNS) levels were measured using ROS and RNS assay kits, respectively. Results: Exposure of Caco-2 cells to 0.1 or 2 mmol/L of sodium nitroprusside (SNP) affected the function and expression of P-gp in concentration-and time-dependent manners. A short-term (4 h) exposure reduced P-gp function and expression accompanied with significantly increased levels of iROS and iRNS. In contrast, a long-term (24 h) exposure stimulated the P-gp function and expression. The stimulatory effects of 2 mmol/L SNP was less profound as compared to those caused by 0.1 mmol/L SNP. The other NO donors SIN-1 and SNAP showed similar effects. Neither the NO scavenger PTIO (2 mmol/L) nor soluble guanylate cyclase inhibitor ODQ (50 µmol/L) reversed the SNP-induced alteration of P-gp function. On the other hand, free radical scavengers ascorbate, glutathione and uric acid (2 mmol/L for each), PKC inhibitor chelerythrine (5 µmol/L), PI3K/Akt inhibitor wortmannin (1 µmol/L) and p38 MAPK inhibitor SB203580 (10 µmol/L) reversed the upregulation of P-gp function by the long-term exposure to SNP, but these agents had no effect on the impaired P-gp function following the short-term exposure to SNP. Conclusion: NO donors time-dependently regulate P-gp function and expression in Caco-2 cells: short-term exposure impairs P-gp function and expression, whereas long-term exposure stimulates P-gp function and expression. The regulation occurs via a NO-independent mechanism.

Synthesis of novel natural product-like diaryl acetylenes as hypoxia inducible factor-1 inhibitors and antiproliferative agents

“…The pharmacological investigations of the genus Selaginella have revealed that it has anticancer, antivirus, antioxidant and anti-inammatory activities. 2 The phytochemical investigations of the genus Selaginella have led to the identication of more than forty natural alkynyl phenols hitherto, including selaginellin, 3 selaginellins A-W, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] selariscinins A-D, 14,17 and selaginpulvilins A-L. [20][21][22][23][24][25] All these natural products possess unique skeletons characterized by biphenyl-containing diaryl acetylene, as shown in Fig. 1.…”

The down-regulation of SLC7A11 enhances ROS induced P-gp over-expression and drug resistance in MCF-7 breast cancer cells

“…Based on our previous results 20 , we fully investigated the role of SLC7A11 and cystine in the over-expression of P-gp in the current study. Moreover, to exclude the possible direct activity of ADR on P-gp, the effect of the direct addition of ROS agents and the direct modulation on SLC7A11 or cystine, alone or in combination, were evaluated, although a potential correlation between ROS and P-gp has been reported 25 – 27 . Our goal was to examine the specific role of elevated ROS coupled with a decreased anti-oxidative capacity in the ADR-induced over-expression of P-gp.…”

Uremic Toxins Induce ET-1 Release by Human Proximal Tubule Cells, which Regulates Organic Cation Uptake Time-Dependently

“…The mechanisms behind this long-term (24 h) regulation could not be explained by the known NO, PKC or cGMP mediated pathways. These observations are reminiscent of both the biphasic and NO-independent pathways that were described for the efflux transporter P-gp [ 70 , 71 ], for which a second pathway, next to NO mediated regulation, was identified involving activation of Toll Like Receptor 4 and translocation of NF-κB. Further research would be warranted to investigate this pathway in the regulation of proximal tubular organic cation uptake.…”