title: Activation of KCNN3/SK3/K(Ca)2.3 channels attenuates enhanced calcium influx and inflammatory cytokine production in activated microglia.
abstract: In neurons, small-conductance calcium-activated potassium (KCNN/SK/K(Ca)2) channels maintain calcium homeostasis after N-methyl-D-aspartate (NMDA) receptor activation, thereby preventing excitotoxic neuronal death. So far, little is known about the function of KCNN/SK/K(Ca)2 channels in non-neuronal cells, such as microglial cells. In this study, we addressed the question whether KCNN/SK/K(Ca)2 channels activation affected inflammatory responses of primary mouse microglial cells upon lipopolysaccharide (LPS) stimulation. We found that N-cyclohexyl-N-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-4-pyrimidinamine (CyPPA), a positive pharmacological activator of KCNN/SK/K(Ca)2 channels, significantly reduced LPS-stimulated activation of microglia in a concentration-dependent manner. The general KCNN/SK/K(Ca)2 channel blocker apamin reverted these effects of CyPPA on microglial proliferation. Since calcium plays a central role in microglial activation, we further addressed whether KCNN/SK/K(Ca)2 channel activation affected the changes of intracellular calcium levels, [Ca(2+)](i), in microglial cells. Our data show that LPS-induced elevation of [Ca(2+)](i) was attenuated following activation of KCNN2/3/K(Ca)2.2/K(Ca)2.3 channels by CyPPA. Furthermore, CyPPA reduced downstream events including tumor necrosis factor alpha and interleukin 6 cytokine production and nitric oxide release in activated microglia. Further, we applied specific peptide inhibitors of the KCNN/SK/K(Ca)2 channel subtypes to identify which particular channel subtype mediated the observed anti-inflammatory effects. Only inhibitory peptides targeting KCNN3/SK3/K(Ca)2.3 channels, but not KCNN2/SK2/K(Ca)2.2 channel inhibition, reversed the CyPPA-effects on LPS-induced microglial proliferation. These findings revealed that KCNN3/SK3/K(Ca)2.3 channels can modulate the LPS-induced inflammatory responses in microglial cells. Thus, KCNN3/SK3/K(Ca)2.3 channels may serve as a therapeutic target for reducing microglial activity and related inflammatory responses in the central nervous system.
authors.affiliation: Institute of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, 35032, Marburg, Germany. dolga@staff.uni-marburg.de
authors.forename: Amalia M
authors.initials: AM
authors.lastname: Dolga
authors.forename: Till
authors.initials: T
authors.lastname: Letsche
authors.forename: Maike
authors.initials: M
authors.lastname: Gold
authors.forename: Nunzianna
authors.initials: N
authors.lastname: Doti
authors.forename: Michael
authors.initials: M
authors.lastname: Bacher
authors.forename: Nipavan
authors.initials: N
authors.lastname: Chiamvimonvat
authors.forename: Richard
authors.initials: R
authors.lastname: Dodel
authors.forename: Carsten
authors.initials: C
authors.lastname: Culmsee
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001030:Apamin / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology*; D002478:Cells, Cultured; D016207:Cytokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000502:physiology; D015536:Down-Regulation / Q000187:drug effects; D018836:Inflammation Mediators / Q000037:antagonists & inhibitors / Q000502:physiology* / Q000633:toxicity; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000633:toxicity; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D011720:Pyrazoles / Q000037:antagonists & inhibitors / Q000633:toxicity; D011743:Pyrimidines / Q000037:antagonists & inhibitors / Q000633:toxicity; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism / Q000502:physiology*
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; C496900:Kcnn3 protein, mouse; D008070:Lipopolysaccharides; D011720:Pyrazoles; D011743:Pyrimidines; D051640:Small-Conductance Calcium-Activated Potassium Channels; C552889:cyclohexyl-(2-(3,5-dimethylpyrazol-1-yl)-6-methylpyrimidin-4-yl)amine; D001030:Apamin