Abstract 11607: Novel Assay for Detection of LDL Transcytosis Across Coronary Endothelium Reveals an Unexpected Role for SR-B1
Bibliographic record
Abstract
Introduction: Retention of LDL beneath the arterial endothelium initiates an inflammatory response culminating in atherosclerosis. How LDL crosses the endothelium to enter the arterial wall remains unknown. While LDL could conceivably pass between endothelial cells (paracellularly) or through them (transcytosis), electron microscopy studies in animals revealed LDL in intracellular vesicles and none at intercellular junctions. This, combined with the absence of endothelial injury or intercellular gaps in early atherosclerosis, suggests that transcytosis is the major route. However, technical challenges with studying transcytosis have made confirming and extending these findings difficult. We developed and validated a novel assay for measuring the transcytosis of native LDL across live human coronary artery endothelium in vitro. Using this assay, we propose to elucidate the regulation of LDL transcytosis and have identified a novel role for SR-B1. Methods and Results: Experiments were performed using primary human coronary artery endothelial monolayers. Transcytosis was quantified in single live cells in real time using total internal reflectance fluorescence microscopy. Transcytosis of LDL was saturable and inhibited by excess unlabeled LDL. By fluorescence microscopy we found that DiI-LDL colocalized significantly with scavenger receptor, class B, type 1 (SR-B1). Unexpectedly, overexpression of SR-BI resulted in increased LDL transcytosis, while knockdown of SR-BI by siRNA inhibited transcytosis. Excess HDL, the canonical SR-B1 ligand, also decreased LDL transcytosis. To confirm the occurrence of transcytosis in an intact vessel, we perfused murine aortas ex vivo with both LDL and dextran of a smaller molecular radius. We observed the accumulation of subendothelial LDL without dextran, indicating that transcytosis of LDL occurs in intact vessels. Conclusions: The accumulation of LDL in the subendothelial intima is the first step of atherosclerosis yet little is known about how it occurs. Our data suggests that transcytosis of LDL is an important contributor, particularly in the early stages of the disease. By identifying the mechanisms of transcytosis, our work could have important implications for its pathogenesis and therapy.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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 source (direct Gemma or distilled Codex), 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".