Biology subjects

Lopez-Juarez, A.

Publications and source records attributed to Lopez-Juarez, A..

4 recordsLinked to original sources

bioRxiv2026

Targeting Nitric Oxide Synthase 2 Reverses Learning Deficits in an Oligodendrocyte-Focused Model of Costello Syndrome

Oligodendrocyte (OL) functions greatly improve information processing in the brain; consequently, compromised OL biology negatively impacts brain function in various diseases. Young-adult Costello Syndrome (CS) patients present with learning disabilities and regression of psychomotor skills in correlation with abnormal brain white matter, delayed myelination, and dysmyelination. This suggests the involvement of OLs and myelin in abnormal brain physiology during and beyond development; however, the neuropathophysiology of CS remains poorly understood. Replacing the endogenous HRas gene with the CS-causing HRasG12V mutant gene in adult OLs (pHRasG/+ mice) induces structural myelin abnormalities; nonetheless, any functional impact is unknown. Here we show robust learning - but not memory - deficits in pHRasG/+ males and modest, delayed learning issues in females. Learning phenotypes are transient, likely involving compensatory responses from the OL lineage and microglia. Diffusion-weighted magnetic resonance imaging revealed regional time- and sex-dependent compromised myelin microstructure, coinciding with the peak of learning issues. Remarkably, transcripts associated with inflammation/immune function are upregulated and pharmacological control of nitric oxide synthase 2 restores learning in male pHRasG+/- mice. Our study supports the notion that abnormal nitric oxide signaling in mature OLs affects learning, suggests a chronic impact of glia-myelin mechanisms in CS neuropathology, and proposes molecular targets with therapeutic potential.

neuroscience↗

bioRxiv2021

L-Thyroxine improves vestibular compensation in a rat model of acute peripheral vestibulopathy

Unilateral vestibular lesions induce a vestibular syndrome, which recovers over time due to vestibular compensation. The therapeutic effect of L-Thyroxine (L-T4) on vestibular compensation was investigated by behavioral testing and immunohistochemical analysis in a rat model of unilateral vestibular neurectomy (UVN). We demonstrated that an acute L-T4 treatment reduced the vestibular syndrome and significantly promoted vestibular compensation. Thyroid hormone receptors (TR and TR{beta}) and type II iodothyronine deiodinase (DIO2) were present in the vestibular nuclei (VN), supporting a local action of L-T4. We confirmed the T4-induced metabolic effects by demonstrating an increase in the number of cytochrome oxidase-labelled neurons in the VN three days after the lesion. L-T4 treatment modulated glial reaction by decreasing both microglia and oligodendrocytes in the deafferented VN three days after UVN and increased cell proliferation. The survival of newly generated cells was not affected, but neuronal differentiation was altered by the L-T4 treatment.

neuroscience↗

bioRxiv2020

Brain-wide structural and functional disruption in mice with oligodendrocyte specific Nf1 deletion is rescued by inhibition of NOS

Neurofibromin gene (NF1) mutation causes Neurofibromatosis type 1 (NF1), a disorder in which brain white matter deficits identified by neuroimaging are common, yet of unknown cellular etiology. In mice, Nf1 loss in adult oligodendrocyte causes myelin decompaction, and increases oligodendrocyte nitric oxide (NO) levels. Nitric oxide synthase (NOS) inhibitors rescue this pathology. Whether oligodendrocyte pathology is sufficient to affect brainwide structure and account for NF1 imaging findings is unknown. Here, we show that Nf1 gene inactivation in adult oligodendrocytes (Plp-Nf1fl/+ mice) results in a motor coordination deficit. Magnetic resonance imaging in awake mice shows that fractional anisotropy is reduced in Plp-Nf1fl/+ corpus callosum and that interhemispheric functional connectivity in motor cortex is also reduced, consistent with disrupted myelin integrity. Further, NOS-specific inhibition rescued both measures. These results demonstrate that oligodendrocyte defects account for aspects of brain dysfunction in NF1, which can be identified by neuroimaging and ameliorated by NOS inhibition. Significance statementThis study assesses the effects of myelin decompaction on motor behavior and brain-wide structural and functional connectivity, and the effect of nitric oxide synthase (NOS) inhibition by N-nitro-L-arginine methyl ester (L-NAME) on these imaging measures. We report that inducible oligodendrocyte-specific inactivation of the Nf1 gene, which causes myelin decompaction, results in reduced motor coordination. Using diffusion-based MRI we show reduced myelin integrity and using functional MRI we show reduced functional connectivity in awake passive mice. L-NAME administration results in rescue of the pathology at the mesoscopic level using imaging procedures that can be directly applied to humans to study treatment efficacy in clinical trials.

neuroscience↗

bioRxiv2017

Genetic differences in the aryl hydrocarbon receptor and CYP1A2 affect susceptibility to developmental polychlorinated biphenyl exposure in mice: Relevance to studies of human neurological disorders

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that remain a human health concern with the discovery of new sources of contamination and ongoing bioaccumulation and biomagnification. Children exposed during early brain development are at highest risk of neurological deficits, but there is some evidence that high PCB exposure in adults increases the risk of Parkinsons disease. Our previous studies found allelic differences in the aryl hydrocarbon receptor and cytochrome P450 1A2 (CYP1A2) affect susceptibility to developmental PCB exposure, resulting in cognitive deficits and motor dysfunction. High-affinity AhrbCyp1a2(-/-) mice were most susceptible compared with poor-affinity AhrdCyp1a2(-/-) and wild type AhrbCyp1a2(+/+) mice. Our follow-up studies assessed biochemical, histological and gene expression changes to identify the brain regions and pathways affected. We also measured PCB and metabolite levels in multiple tissues to determine if genotype altered toxicokinetics. We found evidence of AHR-mediated immune suppression with reduced thymus and spleen weights and significantly reduced thyroxine at P14. In the brain, the greatest changes were seen in the cerebellum where a foliation defect was over-represented in Cyp1a2(-/-) mice. In contrast, we found no difference in tyrosine hydroxylase immuno-staining in the striatum. Gene expression patterns varied across the three genotypes, but there was clear evidence of AHR activation. Distribution of parent PCB congeners also varied by genotype with strikingly high levels of PCB 77 in poor-affinity AhrdCyp1a2(-/-) while AhrbCyp1a2(+/+) mice effectively sequestered coplanar PCBs in the liver. Together, our data suggest that the AHR pathway plays a role in developmental PCB neurotoxicity, but we found little evidence that developmental exposure is a risk factor for Parkinsons disease.

pharmacology and toxicology↗