Opposing Effects of Valproic Acid Treatment Mediated by Histone Deacetylase Inhibitor Activity in Four Transgenic<i>X. laevis</i>Models of Retinitis Pigmentosa
Bibliographic record
Abstract
Retinitis pigmentosa (RP) is an inherited retinal degeneration (RD) that leads to blindness for which no treatment is available. RP is frequently caused by mutations in Rhodopsin ; in some animal models, RD is exacerbated by light. Valproic acid (VPA) is a proposed treatment for RP and other neurodegenerative disorders, with a phase II trial for RP under way. However, the therapeutic mechanism is unclear, with minimal research supporting its use in RP. We investigated the effects of VPA on Xenopus laevis models of RP expressing human P23H, T17M, T4K, and Q344ter rhodopsins, which are associated with RP in humans. VPA ameliorated RD associated with P23H rhodopsin and promoted clearing of mutant rhodopsin from photoreceptors. The effect was equal to that of dark rearing, with no additive effect observed. Rescue of visual function was confirmed by electroretinography. In contrast, VPA exacerbated RD caused by T17M rhodopsin in light, but had no effect in darkness. Effects in T4K and Q344ter rhodopsin models were also negative. These effects of VPA were paralleled by treatment with three additional histone deacetylase (HDAC) inhibitors, but not other antipsychotics, chemical chaperones, or VPA structural analogues. In WT retinas, VPA treatment increased histone H3 acetylation. In addition, electron microscopy showed increased autophagosomes in rod inner segments with HDAC inhibitor (HDACi) treatment, potentially linking the therapeutic effects in P23H rhodopsin animals and negative effects in other models with autophagy. Our results suggest that the success or failure of VPA treatment is dependent on genotype and that HDACi treatment is contraindicated for some RP cases. SIGNIFICANCE STATEMENT Retinitis pigmentosa (RP) is an inherited, degenerative retinal disease that leads to blindness for which no therapy is available. We determined that valproic acid (VPA), currently undergoing a phase II trial for RP, has both beneficial and detrimental effects in animal models of RP depending on the underlying disease mechanism and that both effects are due to histone deacetylase (HDAC) inhibition possibly linked to autophagy regulation. Off-label use of VPA and other HDAC inhibitors for the treatment of RP should be limited to the research setting until this effect is understood and can be predicted. Our study suggests that, unless genotype is accounted for, clinical trials for RP treatments may give negative results due to multiple disease mechanisms with differential responses to therapeutic interventions.
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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".