Kir4.1 potassium channel regulation via microRNA-205 in astrocytes exposed to hyperglycemic conditions

Kir4.1 is specifically expressed and active in non-myelinating Schwann cells

Non-myelinating Schwann cells (NMSC) play important roles in peripheral nervous system formation and function. However, the molecular identity of these cells remains poorly defined. We provide evidence that Kir4.1, an inward-rectifying K+ channel encoded by the KCNJ10 gene, is specifically expressed and active in NMSC. Immunostaining revealed that Kir4.1 is present in terminal/perisynaptic SCs (TPSC), synaptic glia at neuromuscular junctions (NMJ), but not in myelinating SCs (MSC) of adult mice. To further examine the expression pattern of Kir4.1, we generated BAC transgenic Kir4.1-CreERT2 mice and crossed them to the tdTomato reporter line. Activation of CreERT2 with tamoxifen after the completion of myelination onset led to robust expression of tdTomato in NMSC, including Remak Schwann cells (RSC) along peripheral nerves and TPSC, but not in MSC. In contrast, activating CreERT2 before and during the onset of myelination led to tdTomato expression in NMSC and MSC. These observations suggest that immature SC express Kir4.1, and its expression is then downregulated selectively in myelin-forming SC. In support, we found that while activating CreERT2 induces tdTomato expression in immature SC, it fails to induce tdTomato in MSC associated with sensory axons in culture. NMSC derived from neonatal sciatic nerve were shown to express Kir4.1 and exhibit barium-sensitive inwardly rectifying macroscopic K+ currents. Thus, this study identified Kir4.1 as a potential modulator of immature SC and NMSC function. Additionally, it established a novel transgenic mouse line to introduce or delete genes in NMSC.

β-HB inhibits the apoptosis of high glucose-treated astrocytes via activation of CREB/BDNF axis

OBJECTIVE

Nerve damage can cause severe limb dysfunction and even leave a lifelong disability. The apoptosis of astrocytes may contribute to the nerve damage. In this research, we sought to investigate the effect of β-HB on nerve damage in vitro.

DESIGN

Astrocytes were treated with high glucose (HG) to mimic in vitro model of nerve damage. RT-qPCR and western blot were used to detect expressions of CREB, BDNF, Ki-67, PCNA, Bax, Bcl-2 and cleaved caspase 3 in astrocytes, respectively. MTT was used to measure the cell viability. In addition, flow cytometry was used to detect the cell apoptosis.

RESULTS

β-HB significantly promoted the proliferation and inhibited apoptosis in HG-treated astrocytes. Results showed that of PCNA and Bcl-2 were upregulated, and Bax and cleaved caspase 3 were downregulated after β-HB stimulated in HG-treated astrocytes. In addition, HG-induced inhibition on BDNF expression in astrocytes was notably reversed by β-HB. Furthermore, β-HB promoted the growth and inhibited apoptosis of high glucose-treated astrocytes via activation of CREB/BDNF axis.

CONCLUSION

β-HB promotes the growth and inhibits the apoptosis of high glucose-treated astrocytes via activation of CREB/BDNF axis, which may serve as a new target for treatment of nerve damage.

Activation of Glutamate Transporter-1 (GLT-1) Confers Sex-Dependent Neuroprotection in Brain Ischemia

Stroke is one of the leading causes of long-term disability. During ischemic stroke, glutamate is released, reuptake processes are impaired, and glutamate promotes excitotoxic neuronal death. Astrocytic glutamate transporter 1 (GLT-1) is the major transporter responsible for removing excess glutamate from the extracellular space. A translational activator of GLT-1, LDN/OSU 0212320 (LDN) has been previously developed with beneficial outcomes in epileptic animal models but has never been tested as a potential therapeutic for ischemic strokes. The present study evaluated the effects of LDN on stroke-associated brain injury. Male and female mice received LDN or vehicle 24 h before or 2 h after focal ischemia was induced in the sensorimotor cortex. Sensorimotor performance was determined using the Rung Ladder Walk and infarct area was assessed using triphenyltetrazolium chloride staining. Males treated with LDN exhibited upregulated GLT-1 protein levels, significantly smaller infarct size, and displayed better sensorimotor performance in comparison to those treated with vehicle only. In contrast, there was no upregulation of GLT-1 protein levels and no difference in infarct size or sensorimotor performance between vehicle- and LDN-treated females. Taken together, our results indicate that the GLT-1 translational activator LDN improved stroke outcomes in young adult male, but not female mice.