Biology subjects

O'Day, P.

Publications and source records attributed to O'Day, P..

3 recordsLinked to original sources

bioRxiv2025

Target validation uncouples TSPO from 19-Atriol-mediated inhibition of steroidogenesis and reveals true enzymatic targets

The mitochondrial translocator protein (TSPO) was once proposed to mediate mitochondrial cholesterol import for steroid hormone biosynthesis, but genetic deletion studies in multiple models have refuted this role. Nevertheless, the idea that pharmacological ligands of TSPO can modulate steroid output continues to be invoked. One such compound, 19-Atriol (androst-5-ene-3{beta},17{beta},19-triol), was reported to inhibit progesterone synthesis via TSPO binding in MA-10 Leydig cells. To evaluate this proposed mechanism, we used CRISPR/Cas9-generated Tspo-deleted MA-10 cells to study 19-Atriol activity. We found that 19-Atriol inhibited Bt2-cAMP-stimulated steroid output independent of TSPO expression; it acted as a competitive inhibitor of 3{beta}-hydroxysteroid dehydrogenase (3{beta}-HSD), blocking the conversion of pregnenolone to progesterone. Mass spectrometry revealed that 19-Atriol is also a substrate for 3{beta}-HSD, yielding 19-hydroxytestosterone (19-OHT), which itself inhibits 3{beta}-HSD activity. In addition to this effect, both 19-Atriol and 19-OHT decreased cholesterol-to-pregnenolone conversion during stimulation. Partial inhibition of 22R-hydroxycholesterol metabolism by CYP11A1 was observed with 19-Atriol, but not 19-OHT, suggesting direct or indirect effects on this upstream step, potentially involving the steroidogenic acute regulatory protein (STAR). These findings decisively exclude TSPO as a functional mediator of 19-Atriol activity and instead identify direct enzymatic targets within the de novo steroidogenic pathway. By resolving a key mechanistic misattribution, this study underscores the importance of rigorous target validation, particularly for compounds previously assumed to act via TSPO.

pharmacology and toxicology↗

bioRxiv2025

Down syndrome with Alzheimers disease brains have increased iron and associated lipid peroxidation consistent with ferroptosis

INTRODUCTIONCerebral microbleeds (MB) are associated with sporadic Alzheimers Disease (AD) and Down Syndrome with AD (DSAD). Higher MB iron may cause iron mediated lipid peroxidation. We hypothesize that amyloid deposition is linked to MB iron and that amyloid precursor protein (APP) triplication increases iron load and lipid peroxidation. METHODSPrefrontal cortex and cerebellum of cognitively normal (CTL), AD and DSAD ApoE3,3 carriers were examined for proteins that mediated iron metabolism, antioxidant response, and amyloid processing in lipid rafts. RESULTSIron was 2-fold higher in DSAD than CTL and AD. Iron storage proteins and lipid peroxidation were increased in prefrontal cortex, but not in the cerebellum. The glutathione synthesis protein GCLM was decreased by 50% in both AD and DSAD. Activity of lipid raft GPx4, responsible for membrane repair, was decreased by at least 30% in AD and DSAD. DISCUSSIONDSAD shows greater lipid peroxidation than AD consistent with greater MBs and iron load. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=189 HEIGHT=200 SRC="FIGDIR/small/636731v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@fd0d2aorg.highwire.dtl.DTLVardef@16b65d5org.highwire.dtl.DTLVardef@1eab2ddorg.highwire.dtl.DTLVardef@184e6d2_HPS_FORMAT_FIGEXP M_FIG C_FIG Cerebral microbleeds result in increased brain iron and lipid peroxidation in DSAD consistent with ferroptosis as reported for Alzheimers disease. A{beta}; beta-amyloid peptides, APP; amyloid precursor protein, GCLC; glutathione cysteine ligase catalytic subunit, GCLM; glutathione cysteine modifier subunit, GPx4; glutathione peroxidase 4, HNE; 4-hydroxynonenal. RESEARCH IN CONTEXTO_LISystematic Review: DS is associated with increased microbleeds and brain iron that may be mediated by increased APP from Trisomy 21. To assess potential links between amyloid and iron levels, we examined sporadic and DS with AD brains for amyloid processing and antioxidant enzyme defense in lipid rafts. We further compared DSAD with rare variants of DS: partial and mosaic T21. C_LIO_LIInterpretation: DSAD brains showed greater oxidation of lipid rafts where APP is processed than sporadic AD. Corresponding decreases in lipid raft antioxidant enzymes, despite increased total levels of these antioxidant enzymes, present a new mechanism for aberrant amyloid processing during AD. C_LIO_LIFuture Directions: Iron chelation therapies in combination with amyloid monoclonals may benefit DSAD. C_LI

neuroscience↗

bioRxiv2024

Iron chelation by oral deferoxamine treatment decreased brain iron and iron signaling proteins

BackgroundDeferoxamine (DFO) and other iron chelators are clinically used for cancer and stroke. They may also be useful for Alzheimers disease (AD) to diminish iron from microbleeds. DFO may also stimulate antioxidant membrane repair which is impaired during AD. DFO, and other chelators do enter the brain despite some contrary reports. ObjectiveLow dose, oral DFO was given in lab chow to wildtype (WT) C57BL/6 mice to evaluate potential impact on iron levels, iron-signaling and storage proteins, and amyloid precursor protein (APP) and processing enzymes. Young WT mice do not have microbleeds or disrupted blood-brain barrier of AD mice. MethodsIron was measured by MRI and chemically after two weeks of dietary DFO. Cerebral cortex was examined for changes in iron metabolism, antioxidant signaling, and APP processing by Western blot. ResultsDFO decreased brain iron by 18% (MRI) and decreased seven major proteins that mediate iron metabolism by at least 25%. The iron storage proteins ferritin light and heavy chain decreased by at least 30%. APP and secretase enzymes also decreased by 30%. ConclusionsWT mice respond to DFO with decreased APP, amyloid processing enzymes, and antioxidant repair. Potential DFO treatment for early-stage AD by DFO should consider the benefits of lowered APP and secretase enzymes.

neuroscience↗