Blomster, Linda V
Strobaek, Dorte
Hougaard, Charlotte
Klein, Jessica
Pinborg, Lars H
Mikkelsen, Jens D
Christophersen, Palle
2016-07-29
<p>The K<sub>Ca</sub> 3.1 channel (KCNN4) is an important modulator of microglia responses in rodents, but no information exists on functional expression on microglia from human adults. We isolated and cultured microglia (max 1% astrocytes, no neurons or oligodendrocytes) from neocortex surgically removed from epilepsy patients and employed electrophysiological whole-cell measurements and selective pharmacological tools to elucidate functional expression of K<sub>Ca</sub> 3.1. The channel expression was demonstrated as a significant increase in the voltage-independent current by NS309, a K<sub>Ca</sub> 3.1/K<sub>Ca</sub> 2 activator, followed by full inhibition upon co-application with NS6180, a highly selective K<sub>Ca</sub> 3.1 inhibitor. A major fraction (79%) of unstimulated human microglia expressed K<sub>Ca</sub> 3.1, and the difference in current between full activation and inhibition (ΔK<sub>Ca</sub> 3.1) was estimated at 292 ± 48 pA at -40 mV (n = 75), which equals at least 585 channels per cell. Serial K<sub>Ca</sub> 3.1 activation/inhibition significantly hyperpolarized/depolarized the membrane potential. The isolated human microglia were potently activated by lipopolysaccharide (LPS) shown as a prominent increase in TNF-α production. However, incubation with LPS neither changed the K<sub>Ca</sub> 3.1 current nor the fraction of K<sub>Ca</sub> 3.1 expressing cells. In contrast, the anti-inflammatory cytokine IL-4 slightly increased the K<sub>Ca</sub> 3.1 current per cell, but as the membrane area also increased, there was no significant change in channel density. A large fraction of the microglia also expressed a voltage-dependent current sensitive to the K<sub>Ca</sub> 1.1 modulators NS1619 and Paxilline and an inward-rectifying current with the characteristics of a K<sub>ir</sub> channel. The high functional expression of K<sub>Ca</sub> 3.1 in microglia from epilepsy patients accentuates the need for further investigations of its role in neuropathological processes.</p>
https://doi.org/10.1002/glia.23040
oai:zenodo.org:59250
Zenodo
https://zenodo.org/communities/inmind
https://zenodo.org/communities/eu
info:eu-repo/semantics/openAccess
Creative Commons Attribution 4.0 International
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Glia, 64(12), 2065-2078, (2016-07-29)
neuroinflammation
potassium channel
patch clamp
glial cell
IK channel
BK channel
Quantification of the functional expression of the Ca2+ -activated K+ channel KCa 3.1 on microglia from adult human neocortical tissue.
info:eu-repo/semantics/article