Hypothermic preconditioning in human cortical neurons: coupling neuroprotection to ontogenic reversal of tau

Hypothermia is potently neuroprotective, but the molecular basis of this effect remains obscure and the practical challenges of cooling have restricted its clinical use. This thesis was borne on the premise that considerable therapeutic potential may lie in a deeper understanding of the neuronal physiology of cooling. Rodent studies indicate that hypothermia can elicit preconditioning wherein a subtoxic stress confers resistance to an otherwise lethal injury. This cooling-induced tolerance requires de novo protein synthesis – a fundamental arm of the cold-shock response, for which data in human neurons is lacking. Since cooling protects the human neonatal brain, experiments herein address the molecular effects of clinicallyrelevant cooling using functional, maturationally-comparable cortical neurons differentiated from human pluripotent stem cells (hCNs). Several core hypothermic phenomena are explored, with particular scrutiny of neuronal tau, since this protein is modified extensively in brains that are resistant to injury. Mild-to-moderate hypothermia produces an archetypal cold-shock response in hCNs and protects them from oxidative and excitotoxic stress. Principal features of human cortical tau development are recapitulated during hCN differentiation, and subsequently reversed by cooling, returning tau transcriptionally and post-translationally to an earlier foetallike state. These findings provide the first evidence of cold-stress-mediated ontogenic reversal in human neurons. Furthermore, neuroprotective hypothermia induces mild endoplasmic reticulum (ER) stress in hCNs, with subsequent activation of the unfolded protein response (UPR). Reciprocal modulation of both tau phosphorylation and the ER-UPR cascade suggests that cold-induced hyperphosphorylation of tau and ER-hormesis (preconditioning) represent significant components of hypothermic neuroprotection. Cooling thus modifies proteostatic pathways in a manner that supports neuronal viability. Historically, hypothermic preconditioning has been limited to the acute injury setting, and tau hyperphosphorylation is an established hallmark of chronic neural demise. More recently however, preconditioning has been proposed as a target for neurodegenerative disease and neuroprotective roles of phospho-tau have emerged. To date, hypothermia has protected hCNs against oxidative, excitotoxic and ER stress, all of which have been implicated in traumatic as well as degenerative processes. This ‘cross-tolerance’ effect places exponential value on the molecular neurobiology of cooling, with the potential to extract multiple therapeutic targets for an unmet need

Restored vision in a young dog following corticosteroid treatment of presumptive hypophysitis

Background: Hypophysitis is an umbrella term for a group of disorders involving inflammation of the pituitary gland. A rare occurrence in humans, hypophysitis can produce a range of clinical signs including (but not limited to) visual deficits and diabetes insipidus. Only five cases of canine hypophysitis exist in the literature, all presenting in mature dogs with no visual deficits and a grave outcome. This case report describes the clinical and advanced imaging features of blindness-inducing presumptive hypophysitis in a dog, which rapidly resolved with medical management. Case presentation: A 1-year-and-seven-month-old neutered male Standard Poodle presented with subacute blindness, ataxia, and polyuria/polydipsia (PUPD). Magnetic resonance imaging (MRI) detected a contrast-enhancing pituitary mass with perilesional oedema compromising the optic chiasm. Suspecting neoplasia, anti-inflammatory corticosteroid was commenced prior to radiation therapy planning. Complete resolution of neurological and visual deficits occurred within 12 days of starting steroid treatment. Repeated advanced imaging indicated macroscopic resolution of the lesion. An extended thyroid panel with insulin-like growth factor-1 analysis supported a diagnosis of hypophysitis. Resolution of PUPD was achieved with tapering courses of prednisolone and desmopressin; the dog has since been clinically normal for 14 months and treatment-free for 11 months. Conclusions: To the authors’ knowledge, this is the first instance in which a canine pituitary mass has demonstrated long-term resolution with palliative medical treatment alone, alongside reversal of associated blindness and presumptive diabetes insipidus. We suspect this lesion to be a form of hypophysitis, which should be included among differential diagnoses for pituitary masses, and for subacute blindness in dogs. Where possible, we advocate biopsy-confirmation of hypophysitis prior to timely intervention with anti-inflammatory treatment

Maturation of AMPAR Composition and the GABAAR Reversal Potential in hPSC-Derived Cortical Neurons

Rodent-based studies have shown that neurons undergo major developmental changes to ion channel expression and ionic gradients that determine their excitation-inhibition balance. Neurons derived from human pluripotent stem cells theoretically offer the potential to study classical developmental processes in a human-relevant system, although this is currently not well explored. Here, we show that excitatory cortical-patterned neurons derived from multiple human pluripotent stem cell lines exhibit native-like maturation changes in AMPAR composition such that there is an increase in the expression of GluA2(R) subunits. Moreover, we observe a dynamic shift in intracellular Cl(−) levels, which determines the reversal potential of GABA(A)R-mediated currents and is influenced by neurotrophic factors. The shift is concomitant with changes in KCC2 and NKCC1 expression. Because some human diseases are thought to involve perturbations to AMPAR GluA2 content and others in the chloride reversal potential, human stem-cell-derived neurons represent a valuable tool for studying these fundamental properties

Expression of microRNAs in cerebrospinal fluid of dogs with central nervous system disease

Abstract In this pilot study we investigated the expression of 14 microRNAs in the cerebrospinal fluid (CSF) of dogs with neoplastic, inflammatory and degenerative disorders affecting the central nervous system (CNS). CSF microRNA (miRNA) expression profiles were compared to those from dogs with neurological signs but no evidence of structural or inflammatory CNS disease. Seven miRNAs were easily detected in all samples: miR-10b-5p, miR-19b, miR-21-5p, miR-30b-5p, miR-103a-3p, miR-124, and miR-128-3p. Expression of miR-10b-5p was significantly higher in the neoplastic group compared to other groups. There was no relation between miRNA expression and either CSF nucleated cell count or CSF protein content. Higher expression of miR-10b-5p in the neoplastic group is consistent with previous reports in human medicine where aberrant expression of miR-10b is associated with various neoplastic diseases of the CNS