SK-Channel Activation Alters Peripheral Metabolic Pathways in Mice, but Not Lipopolysaccharide-Induced Fever or Inflammation

Abstract

Janne Bredehöft,1 Amalia M Dolga,2 Birgit Honrath,2,3 Sybille Wache,1 Sybille Mazurek,1 Carsten Culmsee,3,4 Regien G Schoemaker,5 Rüdiger Gerstberger,1 Joachim Roth,1,4 Christoph Rummel1,4 1Institute of Veterinary Physiology and Biochemistry, Justus Liebig University Giessen, Giessen, Germany; 2Department of Molecular Pharmacology, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands; 3Institute of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, Marburg, Germany; 4Center for Mind, Brain and Behavior-CMBB, Giessen and Marburg, Germany; 5Department of Neurobiology, GELIFES, University of Groningen, Groningen, NetherlandsCorrespondence: Christoph RummelInstitute of Veterinary Physiology and Biochemistry, Justus Liebig University Giessen, Frankfurter Strasse 100, Giessen D-35392, GermanyTel [phone]Fax [phone]Email [email protected]: Previously, we have shown that CyPPA (cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine), a pharmacological small-conductance calcium-activated potassium (SK)–channel positive modulator, antagonizes lipopolysaccharide (LPS)-induced cytokine expression in microglial cells. Here, we aimed to test its therapeutic potential for brain-controlled sickness symptoms, brain inflammatory response during LPS-induced systemic inflammation, and peripheral metabolic pathways in mice.Methods: Mice were pretreated with CyPPA (15 mg/kg IP) 24 hours before and simultaneously with LPS stimulation (2.5 mg/kg IP), and the sickness response was recorded by a telemetric system for 24 hours. A second cohort of mice were euthanized 2 hours after CyPPA or solvent treatment to assess underlying CyPPA-induced mechanisms. Brain, blood, and liver samples were analyzed for inflammatory mediators or nucleotide concentrations using immunohistochemistry, real-time PCR and Western blot, or HPLC. Moreover, we investigated CyPPA-induced changes of UCP1 expression in brown adipose tissue (BAT)–explant cultures.Results: CyPPA treatment did not affect LPS-induced fever, anorexia, adipsia, or expression profiles of inflammatory mediators in the hypothalamus or plasma or microglial reactivity to LPS (CD11b staining and CD68 mRNA expression). However, CyPPA alone induced a rise in core body temperature linked to heat production via altered metabolic pathways like reduced levels of adenosine, increased protein content, and increased UCP1 expression in BAT-explant cultures, but no alteration in ATP/ADP concentrations in the liver. CyPPA treatment was accompanied by altered pathways, including NFκB signaling, in the hypothalamus and cortex, while circulating cytokines remained unaltered.Conclusion: Overall, while CyPPA has promise as a treatment strategy, in particular according to results from in vitro experiments, we did not reveal anti-inflammatory effects during severe LPS-induced systemic inflammation. Interestingly, we found that CyPPA alters metabolic pathways inducing short hyperthermia, most likely due to increased energy turnover in the liver and heat production in BAT.Keywords: neuroinflammation, fever, inflammatory markers, small-conductance calcium-activated potassium channels, locomotor activity, brown adipose tissue

Keywords

• neuroinflammation
• fever
• inflammatory markers
• small conductance calcium-activated potassium channels
• locomotor activity
• brown adipose tissue