Activation of KCNN3 /SK3/K Ca 2.3 channels attenuates enhanced calcium influx and inflammatory cytokine production in activated microglia

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. © 2012 Wiley Periodicals, Inc.