Static Magnetic Field Stimulation Enhances Shunting Inhibition via a SLC26 Family Cl- Channel, Inducing Intrinsic Plasticity

Magnetic fields are being used for detailed anatomical and functional examination of the human brain. In addition, evidence for their efficacy in treatment of brain dysfunctions is accumulating. Transcranial static magnetic field stimulation (tSMS) is a recently developed technique for noninvasively modifying brain functions. In tSMS, a strong and small magnet when placed over the skull can temporarily suppress brain functions. Its modulatory effects persist beyond the time of stimulation. However, the neurophysiological mechanisms underlying tSMS-induced plasticity remain unclear. Here, using acute motor cortical slice preparation obtained from male C57BL/6N mice, we show that tSMS alters the intrinsic electrical properties of neurons by altering the activity of chloride (Cl-) channels in neurons. Exposure of mouse pyramidal neurons to a static magnetic field (SMF) at a strength similar to human tSMS temporarily decreased their excitability and induced transient neuronal swelling. The effects of SMF were blocked by DIDS and GlyH-101, but not by NPPB, consistent with the pharmacological profile of SLC26A11, a transporter protein with Cl- channel activity. Whole-cell voltage-clamp recordings of the GlyH-101-sensitive Cl- current component showed significant enhancement of the component at both subthreshold and depolarized membrane potentials after SMF application, resulting in shunting inhibition and reduced repetitive action potential (AP) firing at the respective potentials. Thus, this study provides the first neurophysiological evidence for the inhibitory effect of tSMS on neuronal activity and advances our mechanistic understanding of noninvasive human neuromodulation.

SLC26A11 Inhibition Reduces Oncotic Neuronal Death and Attenuates Stroke Reperfusion Injury

Neuronal swelling is a pathological feature of stroke which contributes to the formation of cytotoxic edema. Under hypoxic condition, aberrant accumulation of sodium and chloride ions inside neurons increases osmotic pressure, leading to cell volume increase. Sodium entry pathway in neurons has been studied extensively. Here, we determine whether SLC26A11 is the major chloride entry pathway under hypoxia and could be the target for protection against ischemic stroke. In this study, electrophysiological properties of chloride current in primary cultured neurons were characterized using low chloride solution, 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid, and SLC26A11-specific siRNA under physiological conditions or ATP-depleted conditions. In vivo effect of SLC26A11 was evaluated on a rat stroke reperfusion model. We found that SLC26A11 mRNA in primary cultured neurons was upregulated as early as 6 h after oxygen glucose deprivation, and later, the protein level was elevated accordingly. Blockade of SLC26A11 activity could reduce chloride entry and attenuate hypoxia-induced neuronal swelling. In the animal stroke model, SLC26A11 upregulation was mainly located in surviving neurons close to the infarct core. SLC26A11 inhibition ameliorates infarct formation and improves functional recovery. These findings demonstrate that SLC26A11 is a major pathway for chloride entry in stroke, contributing to neuronal swelling. Inhibition of SLC26A11 could be a novel therapeutic strategy for stroke.