ABSTRACT
Hypothermia is potently neuroprotective but poor mechanistic understanding has restricted its clinical use. Rodent studies indicate that hypothermia can elicit preconditioning, wherein a subtoxic cellular stress confers resistance to an otherwise lethal injury. The molecular basis of this preconditioning remains obscure. Here we explore molecular effects of cooling using functional cortical neurons differentiated from human pluripotent stem cells (hCNs). Mild-to-moderate hypothermia (28-32 °C) induces cold-shock protein expression and mild endoplasmic reticulum (ER) stress in hCNs, with full activation of the unfolded protein response (UPR). Chemical block of a principal UPR pathway mitigates the protective effect of cooling against oxidative stress, whilst pre-cooling neurons abrogates the toxic injury produced by the ER stressor tunicamycin. Cold-stress thus preconditions neurons by upregulating adaptive chaperone-driven pathways of the UPR in a manner that precipitates ER-hormesis. Our findings establish a novel arm of neurocryobiology that could reveal multiple therapeutic targets for acute and chronic neuronal injury.
Subject(s)
Cerebral Cortex/cytology , Cold-Shock Response/physiology , Endoplasmic Reticulum Stress/physiology , Hypothermia, Induced/methods , Neurons/cytology , Cells, Cultured , DNA-Binding Proteins/genetics , Endoplasmic Reticulum/pathology , Humans , Neurons/metabolism , Neuroprotection/physiology , Oxidative Stress/physiology , Pluripotent Stem Cells/cytology , Regulatory Factor X Transcription Factors , Transcription Factors/genetics , Tunicamycin/pharmacology , Unfolded Protein Response/physiologySubject(s)
Axons/metabolism , Ciliary Neurotrophic Factor/metabolism , Nerve Degeneration/metabolism , Neurodegenerative Diseases/metabolism , STAT3 Transcription Factor/metabolism , Animals , Axons/pathology , Ciliary Neurotrophic Factor/pharmacology , Humans , Nerve Degeneration/drug therapy , Nerve Degeneration/physiopathology , Neurodegenerative Diseases/drug therapy , Neurodegenerative Diseases/physiopathology , STAT3 Transcription Factor/pharmacologyABSTRACT
Axonal maintenance, plasticity, and regeneration are influenced by signals from neighboring cells, in particular Schwann cells of the peripheral nervous system. Schwann cells produce neurotrophic factors, but the mechanisms by which ciliary neurotrophic factor (CNTF) and other neurotrophic molecules modify the axonal cytoskeleton are not well understood. In this paper, we show that activated signal transducer and activator of transcription-3 (STAT3), an intracellular mediator of the effects of CNTF and other neurotrophic cytokines, acts locally in axons of motoneurons to modify the tubulin cytoskeleton. Specifically, we show that activated STAT3 interacted with stathmin and inhibited its microtubule-destabilizing activity. Thus, ectopic CNTF-mediated activation of STAT3 restored axon elongation and maintenance in motoneurons from progressive motor neuronopathy mutant mice, a mouse model of motoneuron disease. This mechanism could also be relevant for other neurodegenerative diseases and provide a target for new therapies for axonal degeneration.
