Smoking-induced preconditioning: acute, but not chronic, smoking paradoxically protects the endothelium from ischemia and reperfusion
Bibliographic record
Abstract
Purpose: We set out to investigate whether the oxidative stress associated with acute, short-term exposure to cigarette smoking could induce a paradoxical protection similar to the phenomenon known as ischemic preconditioning. Background: Cigarette smoking is a well-accepted risk factor for myocardial infarction, stroke, and mortality. Paradoxically, however, several large epidemiological studies reported that, among patients who experience a myocardial infarction, those who smoke have lower mortality and morbidity. Methods and results: Radial artery endothelium-dependent Flow-Mediated Dilation (FMD) was measured in 10 healthy non-smoker subjects (7 males, 25-28 years old) before and after local ischemia/reperfusion (15 minutes ischemia followed by 15' reperfusion). Subjects underwent, in randomized order, two protocols: in the first, they smoked two cigarettes 15' after receiving 2 grams of intravenous vitamin C. In the second, they smoked two cigarettes 15' after receiving an intravenous placebo. A separate group of 10 light smokers (7 males, age 24-28 years, 3-10 cigarettes/day) underwent the same protocol after a 24-hour non-smoking interval. There were no differences among groups in resting arterial diameter, blood pressure, heart rate, blood flow before each FMD measurement (P>0.5 for both). After smoking + normal saline, FMD was not impaired by ischemia/reperfusion (P=0.3). In contrast, in those who smoked two cigarettes and received 2gr. i.v. vitamin C, this paradoxical protective effect of smoking was lost, and FMD after ischemia/reperfusion was significantly blunted as compared to the baseline FMD (P=0.008). Smoking did not induce any preconditioning-like effect in those who smoked 2-4 cigarettes per day for a week, and ischemia/reperfusion was associated with a significant blunting in FMD (P=0.005). Discussion: Beyond their role in the pathophysiology of atherosclerosis and endothelial dysfunction, reactive oxygen species are also important agents of cellular signal transduction, and their importance in the phenomenon called ischemic preconditioning has been demonstrated in animal and human studies. In certain situations, short oxidative bursts might paradoxically be associated with protective phenomena. Importantly, this protection appears to be lost in the setting of chronic (light) smoking.
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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 | 0.000 | 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) | 0.001 | 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 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".