Abstract 164: Hypoxia-Induced Cardiomyocyte Mitophagy and Mitochondrial Permeability Transition are Inhibited by Bnip3 Phosphorylation
Bibliographic record
Abstract
Bnip3 is a hypoxia-inducible initiator of cardiomyocyte cell death and has also been implicated as a mitochondrial receptor for the cellular mitophagy machinery. Previous work from our group demonstrates that the prostaglandin E1 analogue, misoprostol, prevents hypoxia-induced mitochondrial dysfunction and is a potent activator of PKA. We hypothesize that misoprostol alters the phosphorylation status of Bnip3, inhibiting its ability to induce cardiomyocyte mitophagy, mitochondrial dysfunction and cell death. Using a rodent model of neonatal hypoxia, in combination with rat primary ventricular neonatal cardiomyocytes (PVNC’s) and H9c2 cells, we assessed the effect of hypoxia and misoprostol drug treatments on mitochondrial function, mitophagy, and cell viability. In postnatal day 5 rats, hypoxia caused a 30% increase in the concentration of serum cardiac troponin-I, a clinically relevant marker for cardiomyocyte cell death, which was absent with the addition of misoprostol drug treatments (n=3). Using PVNC’s we further demonstrated that hypoxia reduced measures of mitochondrial function including membrane potential (47%) and maximal respiration (46%), which were restored back to control levels with the addition of misoprostol (p<0.01). Furthermore, hypoxia induced a 36% increase in mitophagy, concurrent with a 210% increase in mitochondrial permeability transition, both of which were reversed with misoprostol drug treatment (p<0.01). Using a combination of mass spectrometry and mutagenesis, we also show that PKA directly phosphorylates the transmembrane domain of Bnip3 to inhibit its function. Mechanistically, when the PKA phosphorylation site on Bnip3 was neutralized, the protective effect of misoprostol on mitochondrial membrane potential, mitophagy and permeability transition was lost. Taken together, these results demonstrate a foundational role for Bnip3 phosphorylation in the molecular regulation of cardiomyocyte mitochondrial dysfunction. These findings further identify a pharmacological mechanism, through PKA, which may ultimately be able to prevent hypoxia-induced myocardial injury.
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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 | 0.001 | 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".