Regulation of 5-hydroxyeicosanoid dehydrogenase activity in monocytic cells
Bibliographic record
Abstract
The 5-lipoxygenase product 5-oxo-ETE (5-oxo-eicosatetraenoic acid) is a highly potent granulocyte chemoattractant that is synthesized from 5-HETE (5-hydroxyeicosatetraenoic acid) by 5-HEDH (5-hydroxyeicosanoid dehydrogenase). In the present study, we found that 5-HEDH activity is induced in U937 monocytic cells by differentiation towards macrophages with PMA and in HL-60 myeloblastic cells by 1,25-dihydroxy-vitamin D3. We used PMA-differentiated U937 cells to investigate further the regulation of 5-HEDH. This enzyme exhibits approx. 10000-fold selectivity for NADP+ over NAD+ as a cofactor for the oxidation of 5-HETE, which is maximal at pH 10.2. In contrast, the reverse reaction (5-oxo-ETE-->5-HETE) is NADPH-dependent and is maximal at pH 6. Although the K(m) for the forward reaction (670 nM) is about twice that for the reverse reaction at neutral pH, the V(max) is approx 8-fold higher. The oxidation of 5-HETE to 5-oxo-ETE is supported by very low concentrations of NADP(+) (K(m) 139 nM), inhibited by NADPH (K(i) 224 nM) and is consistent with a ping-pong mechanism. The amount of 5-oxo-ETE synthesized by 5-HEDH depends on the ratio of NADP+ to NADPH. Exposure of U937 cells to oxidative stress (t-butyl hydroperoxide) increased the ratio of NADP+ to NADPH from approx. 0.08 in resting cells to approx. 3, and this was accompanied by a dramatic increase in 5-HETE oxidation to 5-oxo-ETE. We conclude that differentiation of monocytic cells towards macrophages results in enhanced 5-oxo-ETE synthesis and that the ability of cells to synthesize 5-oxo-ETE is tightly regulated by the ratio of intracellular NADP+ to NADPH.
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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".