A novel stroke rehabilitation strategy and underlying stress granule regulations through inhibition of NLRP3 inflammasome activation

Abstract

ObjectiveDynamic changes in ischemic pathology after stroke suggested a “critical window” of enhanced neuroplasticity immediately after stroke onset. Although physical exercise has long been considered a promising strategy of stroke rehabilitation, very early physical exercise may exacerbate brain injury. Since remote ischemic conditioning (RIC) promotes neuroprotection and neuroplasticity, the present study combined RIC with sequential exercise to establish a new rehabilitation strategy for a better rehabilitative outcome.MethodsA total of 120 adult male Sprague‐Dawley rats were used and divided into five groups: (1) sham, (2) stroke, (3) stroke with exercise, (4) stroke with RIC, and (5) stroke with RIC followed by exercise. Brain damage was evaluated by infarct volume, neurological deficit, cell death, and lactate dehydrogenase (LDH) activity. Long‐term functional outcomes were determined by grid walk tests, rotarod tests, beam balance tests, forelimb placing tests, and the Morris water maze. Neuroplasticity was evaluated through measurements of both mRNA and protein levels of synaptogenesis (synaptophysin [SYN], post‐synaptic density protein‐95 [PSD‐95], and brain‐derived neurotrophic factor [BDNF]) and angiogenesis (vascular endothelial growth factor [VEGF], angiopoietin‐1 [Ang‐1], and angiopoietin‐2 [Ang‐2]). Inflammasome activation was measured by concentrations of interleukin‐18 (IL‐18) and IL‐1β detected by enzyme‐linked immunosorbent assay (ELISA) kits, mRNA expressions of NLR pyrin domain containing 3 (NLRP3), apoptosis‐associated speck‐like protein containing a C‐terminal caspase recruitment domain (ASC), IL‐18 and IL‐1β, and protein quantities of NLRP3, ASC, cleaved‐caspase‐1, gasdermin D‐N (GSDMD‐N), and IL‐18 and IL‐1β. Stress granules (SGs), including GTPase‐activating protein‐binding protein 1 (G3BP1), T cell‐restricted intracellular antigen‐1 (TIA1), and DEAD‐box RNA helicase 3X (DDX3X) were evaluated at mRNA and protein levels. The interactions between DDX3X with NLRP3 or G3BP1 were determined by immunofluorescence and co‐immunoprecipitation.ResultsEarly RIC decreased infarct volumes, neurological deficits, cell death, and LDH activity at post‐stroke Day 3 (p < 0.05). All treatment groups showed significant improvement in functional outcomes, including sensory, motor, and cognitive functions. RIC and exercise, as compared to RIC or physical exercise alone, had improved functional outcomes after stroke (p < 0.05), as well as synaptogenesis and angiogenesis (p < 0.05). RIC significantly reduced mRNA and protein expressions of NLRP3 (p < 0.05). SGs formation peaked at 0 h after ischemia, then progressively decreased until 24 h postreperfusion, which was reversed by RIC (p < 0.05). The assembly of SGs consumed DDX3X and then inhibited NLRP3 inflammasome activation.ConclusionsRIC followed by exercise induced a better rehabilitation in ischemic rats, while early RIC alleviated ischemia‐reperfusion injury via stress‐granule‐mediated inhibition of NLRP3 inflammasome.

Constraint-Induced Movement Therapy Modulates Neuron Recruitment and Neurotransmission Homeostasis of the Contralesional Cortex to Enhance Function Recovery after Ischemic Stroke

“…Neural plasticity plays an essential role in neural development and recovery following brain ischemic injury, involving axonal sprouting, alterations in synaptic strength, formation of new synapses, compensation by the contralateral cortex, and so on. , Rehabilitative training can subserve synaptogenesis and increase the stability of those newborn synapses, such as physical exercise training and CIMT. − It has been reported that the exercise-induced paralysis recovery of brain ischemic rats may be related to the upregulation of both GAP-43 phosphorylated at serine 41 (pSer41-GAP-43) and GAP-43. The possible mechanisms, which include neurite formation, synaptic connections and remodeling, might be related to the interaction between GAP-43 and calmodulin, PKC, and nerve growth factor (NGF) .…”