Dose-Dependent Targeted Suppression of P-glycoprotein Expression and Function in Caco-2 Cells
Bibliographic record
Abstract
The efflux transporter P-glycoprotein (Pgp), encoded by the ABCB1 gene, decreases the bioavailability of a wide range of orally administered drugs. Drug permeability studies using the in vitro Caco-2 cell model commonly rely on small molecule modulators to estimate the contribution of Pgp to drug efflux. The use of such modulators may be limited by their interactions with other membrane transporters. RNA interference, a tool allowing for the specific degradation of a target gene's mRNA, has emerged as a technique to study gene expression and function. This manuscript describes the use of chemically modified small interfering RNA (siRNA) for a dose-dependent suppression of ABCB1 in Caco-2 cells and the subsequent drug permeability assay. We transfected Caco-2 cells while in suspension with chemically modified synthetic siRNA-lipid complexes and then seeded the cells on polycarbonate semipermeable supports. Once the monolayer of Caco-2 cells formed tight junctions and expressed brush border enzymes, we determined the dose-dependent suppression of the ABCB1 gene using RT-qPCR. We measured the duration of silencing at the optimal siRNA dose by Western blot for Pgp protein. The utility of this in vitro model was determined by performing bidirectional transport studies using a well-established substrate for Pgp, rhodamine 123. A single 4 h transfection of the Caco-2 cells with ≥100 nM siRNA reduced the expression of ABCB1 mRNA by >85% at day five in culture. The time-course study revealed that the single transfection reduces Pgp protein levels for 9 days in culture. This magnitude of silencing was sufficient to reduce the efflux of rhodamine 123 as measured by the apparent permeability coefficient and intracellular accumulation. In this study, we demonstrate the dose-dependent, targeted degradation of Pgp in Caco-2 cells as a new model for assessing drug efflux from enterocytes. The dose-dependent nature of the Pgp silencing in this study offers significant improvements over other approaches to creating a Caco-2 model with suppressed ABCB1 expression. We envision that this technique, in conjunction with better small molecule inhibitors, will provide a useful tool for future drug permeability studies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".