Biology subjects

Tribble, J. R.

Publications and source records attributed to Tribble, J. R..

5 recordsLinked to original sources

bioRxiv2026

Supplementation via DAF-16 and pnk-1 driven pantothenate-coenzyme A flux improves disease related stress resistance in C. elegans

Metabolic pathways are increasingly recognized as tractable targets in aging and disease. Building on prior work demonstrating that supplementation with low-molecular weight metabolites (amino acids, vitamins, and their intermediates) can extend lifespan in Caenorhabditis elegans, we focused on pantothenate (vitamin B5), which is dysregulated in sarcopenic muscle and in several neurodegenerative and metabolic disorders. Pantothenate is the obligate precursor of coenzyme A through a short, highly conserved biosynthetic pathway in which loss-of-function mutations can cause neurodegeneration with brain iron accumulation. In C. elegans, the longevity curtailing transcription factor DAF-16/FOXO has a conserved binding element in the promoter region of pnk-1, encoding the first enzyme (PNK-1) in the coenzyme A pathway, and pnk-1 is markedly upregulated in long-lived daf-2 (insulin/-like receptor) mutants, implicating coenzyme A metabolism in longevity. Here, we demonstrate that CoA levels naturally increase during early life and decrease towards older age in C. elegans. Dietary pantothenate supplementation increases coenzyme A levels with minimal effects on lifespan but systemic effects on lipid metabolism, mitochondrial dynamics, and muscle structure under basal conditions. Under DAF-16-associated stress conditions, including heat and oxidative stress, pnk-1 expression is upregulated and pantothenate supplementation robustly extends lifespan and improves mobility. Finally, we demonstrate dysregulation of daf-16 and pnk-1 expression in amyotrophic lateral sclerosis (ALS) models, in which pantothenate supplementation confers both lifespan extension and cholinergic neuroprotection.

neuroscience↗

bioRxiv2020

Nicotinamide provides neuroprotection in glaucoma by protecting against mitochondrial and metabolic dysfunction

Nicotinamide adenine dinucleotide (NAD) is a REDOX cofactor and metabolite essential for neuronal survival. Glaucoma is a common neurodegenerative disease in which neuronal levels of NAD decline. Repleting NAD via dietary supplementation of nicotinamide (a precursor to NAD) is effective in preventing retinal ganglion cell neurodegeneration in mouse models. Supporting this, short-term oral nicotinamide treatment in human glaucoma patients provides a recovery of retinal ganglion cell function implying a protection of visual function. Despite this, the mechanism of neuroprotection and full effects of nicotinamide on retinal ganglion cells is unclear. Glaucoma is a complex neurodegenerative disease in which a mix of healthy, stressed, and degenerating retinal ganglion cells co-exist, and in which retinal ganglion cells display compartmentalized degeneration across their visual trajectory. Therefore, we assess the effects of nicotinamide on retinal ganglion cells in normal physiological conditions and across a range of glaucoma relevant insults. We confirm neuroprotection afforded by nicotinamide in rodent models which represent isolated ocular hypertensive, axon degenerative, and mitochondrial degenerative insults. We define a small molecular weight metabolome for the retina, optic nerve, and superior colliculus which demonstrates that ocular hypertension induces widespread metabolic disruption that can be prevented by nicotinamide. Nicotinamide provides these neuroprotective effects by increasing oxidative phosphorylation, buffering and preventing metabolic stress, and increasing mitochondrial size and motility whilst simultaneously dampening action potential firing frequency. These data support continued determination of the utility of long-term NAM treatment as a neuroprotective therapy for human glaucoma. One Sentence SummaryThe NAD precursor nicotinamide has a potent neuroprotective effect in the retina and optic nerve, targeting neuronal function, metabolism, and mitochondrial function.

neuroscience↗

bioRxiv2020

Protrudin functions as a scaffold in the endoplasmic reticulum to support axon regeneration in the adult central nervous system

Adult mammalian central nervous system axons have intrinsically poor regenerative capacity, so axonal injury has permanent consequences. One approach to enhancing regeneration is to increase the axonal supply of growth molecules and organelles. We achieved this by expressing the adaptor molecule Protrudin which is normally found at low levels in non-regenerative neurons. Elevated Protrudin expression enabled robust central nervous system regeneration both in vitro in primary cortical neurons and in vivo in the injured adult optic nerve. Protrudin overexpression facilitated the accumulation of endoplasmic reticulum, integrins and Rab11 endosomes in the distal axon, whilst removing Protrudins endoplasmic reticulum localization, kinesin-binding or phosphoinositide-binding properties abrogated the regenerative effects. These results demonstrate that Protrudin promotes regeneration by functioning as a scaffold to link axonal organelles, motors and membranes, establishing important roles for these cellular components in mediating regeneration in the adult central nervous system.

neuroscience↗

bioRxiv2019

Suppression of homeostatic gene expression and increased expression of metabolism-related genes are early features of glaucoma in optic nerve head microglia

Glaucoma is the leading cause of irreversible vision loss. Ocular hypertension is a major risk factor for glaucoma and recent work has demonstrated critical early neuroinflammatory insults occur in the optic nerve head following ocular hypertension. Microglia and infiltrating monocytes are likely candidates to drive these neuroinflammatory insults. However, the exact molecular identity / transcriptomic profile of microglia early following ocular hypertensive insults is unknown. To elucidate the molecular identity of microglia during early glaucoma pathogenesis, we performed RNA-sequencing of microglia mRNA from the optic nerve head of a genetic mouse model of glaucoma (DBA/2J) at a time point following ocular hypertensive insults, but preceding detectable neurodegeneration (with microglia identified as being CD45lo/CD11b+/CD11c-). Furthermore, RNA-sequencing was performed on optic nerve head microglia from mice treated with radiation therapy, a potent therapy preventing neuroinflammatory insults. Transcriptomic profiling of optic nerve head microglia mRNA identifies early metabolic priming with marked changes in mitochondrial gene expression, and changes to phagocytosis, inflammatory, and sensome pathways. The data predict that many functions of microglia that help maintain tissue homeostasis are affected. Comparative analysis of these data with data from previously published whole optic nerve head tissue or monocyte-only samples from DBA/2J mice demonstrate that many of the neuroinflammatory signatures in these data sets arise from infiltrating monocytes and not reactive microglia. Finally, our data demonstrate that radiation therapy of DBA/2J mice potently abolishes these microglia metabolic transcriptomic changes at the same time points. Together, our data provide a unique resource for the community to help drive further hypothesis generation and testing in glaucoma.

neuroscience↗

bioRxiv2019

When is a control not a control? Reactive microglia occur throughout the control contralateral visual pathway in experimental glaucoma

PurposeAnimal models show retinal ganglion cell injuries that replicate features of glaucoma and the contralateral eye is commonly used as an internal control. There is significant cross-over of retinal ganglion cell axons from the ipsilateral to the contralateral side at the level of the optic chiasm which may confound findings when damage is restricted to one eye. The effect of unilateral glaucoma on neuroinflammatory damage to the contralateral visual pathway has largely been unexplored. MethodsOcular hypertensive glaucoma was induced unilaterally or bilaterally in the rat and retinal ganglion cell neurodegenerative events were assessed. Neuroinflammation was quantified in the retina, optic nerve head, optic nerve, lateral geniculate nucleus, and superior colliculus by high resolution imaging, and in the retina by flow cytometry and protein arrays. ResultsFollowing ocular hypertensive stress, peripheral monocytes enter the retina, and microglia become reactive. This effect is more marked in animals with bilateral ocular hypertensive glaucoma. In rats where glaucoma was induced unilaterally there was significant microglia activation in the contralateral (control) eye. Microglial activation extended into the optic nerve and terminal visual thalami, where it was similar across hemispheres irrespective of whether ocular hypertension was unilateral or bilateral. ConclusionsThese data suggest that caution is warranted when using the contralateral eye as control in unilateral models of glaucoma. Translational RelevanceUse of a contralateral eye as a control may confound discovery of human relevant mechanism and treatments in animal models. We also identify neuroinflammatory protein responses that warrant further investigation as potential disease modifiable targets.

neuroscience↗