Inhibition of the potassium channel Kv1.3 reduces infarction and inflammation in ischemic stroke

Abstract

ObjectiveInhibitors of the voltage‐gated K+ channel Kv1.3 are currently in development as immunomodulators for the treatment of autoimmune diseases. As Kv1.3 is also expressed on microglia and has been shown to be specifically up‐regulated on “M1‐like” microglia, we here tested the therapeutic hypothesis that the brain‐penetrant small‐molecule Kv1.3‐inhibitor PAP‐1 reduces secondary inflammatory damage after ischemia/reperfusion.MethodsWe studied microglial Kv1.3 expression using electrophysiology and immunohistochemistry, and evaluated PAP‐1 in hypoxia‐exposed organotypic hippocampal slices and in middle cerebral artery occlusion (MCAO) with 8 days of reperfusion in both adult male C57BL/6J mice (60 min MCAO) and adult male Wistar rats (90 min MCAO). In both models, PAP‐1 administration was started 12 h after reperfusion.ResultsWe observed Kv1.3 staining on activated microglia in ischemic infarcts in mice, rats, and humans and found higher Kv1.3 current densities in acutely isolated microglia from the infarcted hemisphere than in microglia isolated from the contralateral hemisphere of MCAO mice. PAP‐1 reduced microglia activation and increased neuronal survival in hypoxia‐exposed hippocampal slices as effectively as minocycline. In mouse MCAO, PAP‐1 dose‐dependently reduced infarct area, improved neurological deficit score, and reduced brain levels of IL‐1β and IFN‐γ without affecting IL‐10 and brain‐derived nerve growth factor (BDNF) levels or inhibiting ongoing phagocytosis. The beneficial effects on infarct area and neurological deficit score were reproduced in rats providing confirmation in a second species.InterpretationOur findings suggest that Kv1.3 constitutes a promising therapeutic target for preferentially inhibiting “M1‐like” inflammatory microglia/macrophage functions in ischemic stroke.

Biophysical basis for Kv1.3 regulation of membrane potential changes induced by P2X4‐mediated calcium entry in microglia

“…Microglial Kv1.3, Kir2.1 and P2X4 expression was studied in brains of 16 week-old male or female CX 3 CR1 +/GFP mice subjected to transient MCAO surgery (60 min occlusion) with 8 days of reperfusion as described previously (Chen et al, 2018).…”

“…Similarly, in vivo Kv1.3 expression is upregulated in microglia from intracerebroventricular (ICV)-LPS injected brains (Di Lucente, Nguyen, Wulff, Jin, & Maezawa, 2018). Elevated Kv1.3 expression is also observed in activated microglia from rodents and humans with AD (Maezawa et al, 2018;Rangaraju, Gearing, Jin, & Levey, 2015) and following ischemic stroke (Chen et al, 2016;Chen, Nguyen, Maezawa, Jin, & Wulff, 2018), making Kv1.3 an attractive target for immunomodulatory therapy. Accordingly, our group showed that both genetic deletion and pharmacological blockade of Kv1.3 diminished microglial activation and concomitant inflammatory responses, leading to improved pathological and neurological outcomes in multiple animal models of neuroinflammation (Chen et al, 2018;Di Lucente et al, 2018;Maezawa et al, 2018).…”

Kv1.3 Channel as a Key Therapeutic Target for Neuroinflammatory Diseases: State of the Art and Beyond

“…Therefore, it is most likely to inhibit the proliferation of TEM cells by effectively blocking the Kv1.3 channel. ChTX might be a potential drug for MS. BmKTX-D33H inhibits cytokine production and proliferation in human T cells in vitro and significantly improves delayed hypersensitivity (DTH) response (Chen et al, 2018), highlighting its advantages as a potential drug for autoimmune diseases. Moreover, oligodendrocyte (OLG) causes axonal myelination of the CNS (Trapp et al, 1997) and the complement complex (C5b-9, composed of C5b, C6, C7, C8, and C9 proteins) is capable of inducing cell cycle activation in OLGs .…”

“…Similarly, microglia are highly malleable and can exhibit different phenotypes depending on different microenvironmental signals. Lipopolysaccharide (LPS) and IFN-γ promote the differentiation of microglia into classical activated M1 type, along with producing high levels of pro-inflammatory cytokines, nitric oxide, and continuously impairing the CNS parenchyma , which contribute to the secondary expansion of the infarct (Chen et al, 2018).…”

“…The most effective and specific small molecule, PAP-1 can inhibit Kv1.3 at an IC 50 of 2 nmol/L (Schmitz et al, 2005), is orally available, brain penetrant, and does not have any long-term toxicity in rodents or primates (Azam et al, 2007;Pereira et al, 2007). It is worth noting that PAP-1 significantly reduces the levels of pro-inflammatory cytokines and infarct volume after ischemic injury and improves neurological deficits (Chen et al, 2018).…”