Kir4.1 channel activation in NG2 glia contributes to remyelination in ischemic stroke

Cav3.2 channel regulates cerebral ischemia/reperfusion injury: a promising target for intervention

JOURNAL/nrgr/04.03/01300535-202419110-00028/figure1/v/2024-03-08T184507Z/r/image-tiff Calcium influx into neurons triggers neuronal death during cerebral ischemia/reperfusion injury. Various calcium channels are involved in cerebral ischemia/reperfusion injury. Cav3.2 channel is a main subtype of T-type calcium channels. T-type calcium channel blockers, such as pimozide and mibefradil, have been shown to prevent cerebral ischemia/reperfusion injury-induced brain injury. However, the role of Cav3.2 channels in cerebral ischemia/reperfusion injury remains unclear. Here, in vitro and in vivo models of cerebral ischemia/reperfusion injury were established using middle cerebral artery occlusion in mice and high glucose hypoxia/reoxygenation exposure in primary hippocampal neurons. The results showed that Cav3.2 expression was significantly upregulated in injured hippocampal tissue and primary hippocampal neurons. We further established a Cav3.2 gene-knockout mouse model of cerebral ischemia/reperfusion injury. Cav3.2 knockout markedly reduced infarct volume and brain water content, and alleviated neurological dysfunction after cerebral ischemia/reperfusion injury. Additionally, Cav3.2 knockout attenuated cerebral ischemia/reperfusion injury-induced oxidative stress, inflammatory response, and neuronal apoptosis. In the hippocampus of Cav3.2-knockout mice, calcineurin overexpression offset the beneficial effect of Cav3.2 knockout after cerebral ischemia/reperfusion injury. These findings suggest that the neuroprotective function of Cav3.2 knockout is mediated by calcineurin/nuclear factor of activated T cells 3 signaling. Findings from this study suggest that Cav3.2 could be a promising target for treatment of cerebral ischemia/reperfusion injury.

Early intensive rehabilitation reverses locomotor disruption, decrease brain inflammation and induces neuroplasticity following experimental Cerebral Palsy

BACKGROUND

Cerebral Palsy (CP) is a major cause of motor and cognitive disability in children due to injury to the developing brain. Early intensive sensorimotor rehabilitation has been shown to change brain structure and reduce CP symptoms severity. We combined environmental enrichment (EE) and treadmill training (TT) to observe the effects of a one-week program of sensorimotor stimulation (EETT) in animals exposed to a CP model and explored possible mechanisms involved in the functional recovery.

METHODS

Pregnant Wistar rats were injected with Lipopolysaccharide (LPS - 200 µg/kg) intraperitoneally at embryonic days 18 and 19. At P0, pups of both sexes were exposed to 20' anoxia at 37 °C. From P2 to P21, hindlimbs were restricted for 16 h/day during the dark cycle. EETT lasted from P21 to P27. TT - 15 min/day at 7 cm/s. EE - 7 days in enriched cages with sensorimotor stimulus. Functional 3D kinematic gait analysis and locomotion were analyzed. At P28, brains were collected for ex-vivo MRI and histological assessment. Neurotrophins and key proteins involved in CNS function were assessed by western blotting.

RESULTS

CP model caused gross and skilled locomotor disruption and altered CNS neurochemistry. EETT reversed locomotor dysfunction with minor effects over gait kinematics. EETT also decreased brain inflammation and glial activation, preserved myelination, upregulated BDNF signaling and modulated the expression of proteins involved in excitatory synaptic function in the brain and spinal cord.

CONCLUSIONS

Using this translational approach based on intensive sensorimotor rehabilitation, we highlight pathways engaged in the early developmental processes improving neurological recovery observed in CP.

Mild hypothermia promotes neuronal differentiation of human neural stem cells via RBM3-SOX11 signaling pathway

Both therapeutic hypothermia and neural stem cells (NSCs) transplantation have shown promise in neuroprotection and neural repair after brain injury. However, the effects of therapeutic hypothermia on neuronal differentiation of NSCs are not elucidated. In this study, we aimed to investigate whether mild hypothermia promoted neuronal differentiation in cultured and transplanted human NSCs (hNSCs). A significant increase in neuronal differentiation rate of hNSCs was found when exposed to 35°C, from 33% to 45% in vitro and from 7% to 15% in vivo. Additionally, single-cell RNA sequencing identified upregulation of RNA-binding motif protein 3 (RBM3) in neuroblast at 35°C, which stabilized the SRY-box transcription factor 11 (SOX11) mRNA and increased its protein expression, leading to an increase in neuronal differentiation of hNSCs. In conclusion, our study highlights that mild hypothermia at 35°C enhances hNSCs-induced neurogenesis through the novel RBM3-SOX11 signaling pathway, and provides a potential treatment strategy in brain disorders.

Protective effects of METRNL overexpression against pathological cardiac remodeling

At present, meteorin-like protein (METRNL) has been proven to be widely expressed in the myocardium and participates in the pathogenic process of various cardiovascular diseases. However, the effects of METRNL on pathological cardiac hypertrophy is still unknown. In the present study, we used a mouse model of transverse aortic constriction (TAC) surgery to mimic pathological cardiac hypertrophy and gene delivery system to overexpress METRNL in vivo. The results showed that METRNL overexpression improved TAC-induced pathological cardiac hypertrophy in mice and neonatal cardiomyocytes. In addition, METRNL overexpression diminished TAC-induced cardiac oxidative damage, inflammation and cardiomyocyte apoptosis. Moreover, the cardioprotective effect of METRNL overexpression was directly related to the activation of AMP-activated protein kinase (AMPK) and sirtuin1 (SIRT1). In summary, our data identified that METRNL may be a promising therapeutic target to mitigate pathological cardiac hypertrophy in the future.

Astrocyte-like subpopulation of NG2 glia in the adult mouse cortex exhibits characteristics of neural progenitor cells

Glial cells expressing neuron-glial antigen 2 (NG2), also known as oligodendrocyte progenitor cells (OPCs), play a critical role in maintaining brain health. However, their ability to differentiate after ischemic injury is poorly understood. The aim of this study was to investigate the properties and functions of NG2 glia in the ischemic brain. Using transgenic mice, we selectively labeled NG2-expressing cells and their progeny in both healthy brain and after focal cerebral ischemia (FCI). Using single-cell RNA sequencing, we classified the labeled glial cells into five distinct subpopulations based on their gene expression patterns. Additionally, we examined the membrane properties of these cells using the patch-clamp technique. Of the identified subpopulations, three were identified as OPCs, whereas the fourth subpopulation had characteristics indicative of cells likely to develop into oligodendrocytes. The fifth subpopulation of NG2 glia showed astrocytic markers and had similarities to neural progenitor cells. Interestingly, this subpopulation was present in both healthy and post-ischemic tissue; however, its gene expression profile changed after ischemia, with increased numbers of genes related to neurogenesis. Immunohistochemical analysis confirmed the temporal expression of neurogenic genes and showed an increased presence of NG2 cells positive for Purkinje cell protein-4 at the periphery of the ischemic lesion 12 days after FCI, as well as NeuN-positive NG2 cells 28 and 60 days after injury. These results suggest the potential development of neuron-like cells arising from NG2 glia in the ischemic tissue. Our study provides insights into the plasticity of NG2 glia and their capacity for neurogenesis after stroke.

Omaveloxolone ameliorates isoproterenol-induced pathological cardiac hypertrophy in mice

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcriptional regulator that plays a protective role against various cardiovascular diseases. Omaveloxolone is a newly discovered potent activator of Nrf2 that has a variety of cytoprotective functions. However, the potential role of omaveloxolone in the process of pathological cardiac hypertrophy and heart failure are still unknown. In this study, an isoproterenol (ISO)-induced pathological cardiac hypertrophy model was established to investigate the protective effect of omaveloxolone in vivo and in vitro. Our study first confirmed that omaveloxolone administration improved ISO-induced pathological cardiac hypertrophy in mice and neonatal cardiomyocytes. Omaveloxolone administration also diminished ISO-induced cardiac oxidative stress, inflammation and cardiomyocyte apoptosis. In addition, omaveloxolone administration activated the Nrf2 signaling pathway, and Nrf2 knockdown almost completely abolished the cardioprotective effect of omaveloxolone, indicated that the cardioprotective effect of omaveloxolone was directly related to the activation of the Nrf2 signaling. In summary, our study identified that omaveloxolone may be a promising therapeutic agent to mitigate pathological cardiac hypertrophy.

Inward rectifying Kir4.1 channels regulate oligodendrocyte precursor cell differentiation and CNS myelination in vivo

The functions of K_ir4.1 in oligodendrocyte development have been in controversial. We recently reported that inhibiting K_ir4.1 impeded oligodendrocyte precursor cell (OPC) differentiation and oligodendrocyte (OL) maturation, due to K_ir4.1 altering intracellular pH of OPCs through Na⁺/H⁺ exchangers. However, our conclusion was limited by in vitro observation, thereby it becomes necessary to seek in vivo evidence to determine the roles of K_ir4.1 on OPC development and CNS myelination. Here, we used Olig1-Cre to knockout K_ir4.1 in OPCs from the early developmental stage. We found that the cell-specific deletion of K_ir4.1 significantly impeded OPC differentiation and reduced the number of mature OLs in the cerebral cortex and the corpus callosum. Hence, our in vivo evidence supports that K_ir4.1 can regulate OPC differentiation and is essential to CNS myelination.