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J Neuroinflammation. 2019 Jun 1;16(1):116. doi: 10.1186/s12974-019-1510-8.

Temporal profiling of Kv1.3 channel expression in brain mononuclear phagocytes following ischemic stroke.

Author information

1
Department of Neurology, Emory University, Atlanta, GA, USA.
2
Xiangya Hospital, Central South University, Changsha, Hunan, 410008, China.
3
Division of Neuropharmacology and Neurologic Diseases, Yerkes National Primate Research Center, Atlanta, GA, USA.
4
Department of Neurology, Veterans Affairs Medical Center, Atlanta, GA, USA.
5
Department of Neurology, Emory University, Atlanta, GA, USA. srikant.rangaraju@emory.edu.

Abstract

BACKGROUND:

Microglia and CNS-infiltrating monocytes/macrophages (CNS-MPs) perform pro-inflammatory and protective anti-inflammatory functions following ischemic stroke. Selective inhibition of pro-inflammatory responses can be achieved by Kv1.3 channel blockade, resulting in a lower infarct size in the transient middle cerebral artery occlusion (tMCAO) model. Whether beneficial effects of Kv1.3 blockers are mediated by targeting microglia or CNS-infiltrating monocytes/macrophages remains unclear.

METHODS:

In the 30-min tMCAO mouse model, we profiled functional cell-surface Kv1.3 channels and phagocytic properties of acutely isolated CNS-MPs at various timepoints post-reperfusion. Kv1.3 channels were flow cytometrically detected using fluorescein-conjugated Kv1.3-binding peptide ShK-F6CA as well as by immunohistochemistry. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was performed to measure Kv1.3 (Kcna3) and Kir2.1 (Kcnj2) gene expression. Phagocytosis of 1-μm microspheres by acutely isolated CNS-MPs was measured by flow cytometry.

RESULTS:

In flow cytometric assays, Kv1.3 channel expression by CD11b+ CNS-MPs was increased between 24 and 72 h post-tMCAO and decreased by 7 days post-tMCAO. Increased Kv1.3 expression was restricted to CD11b+CD45lowLy6clow (microglia) and CD11b+CD45highLy6Clow CNS-MPs but not CD11b+CD45highLy6chigh inflammatory monocytes/macrophages. In immunohistochemical studies, Kv1.3 protein expression was increased in Iba1+ microglia at 24-48 h post-tMCAO. No change in Kv1.3 mRNA in CNS-MPs was observed following tMCAO.

CONCLUSIONS:

We conclude that resident microglia and a subset of CD45highLy6clow CNS-MPs are the likely cellular targets of Kv1.3 blockers and the delayed phase of neuroinflammation is the optimal therapeutic window for Kv1.3 blockade in ischemic stroke.

KEYWORDS:

Ischemic stroke; Kv1.3; Macrophage; Microglia; Middle cerebral artery occlusion; Neuroinflammation

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