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

Janne Bredehöft; Amalia M Dolga; Birgit Honrath; Sybille Wache; Sybille Mazurek; Carsten Culmsee; Regien G Schoemaker; Rüdiger Gerstberger; Joachim Roth; Christoph Rummel

doi:10.2147/JIR.S338812

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

J Inflamm Res. 2022 Jan 23:15:509-531. doi: 10.2147/JIR.S338812. eCollection 2022.

Authors

Janne Bredehöft¹, Amalia M Dolga², Birgit Honrath^{2

3}, Sybille Wache¹, Sybille Mazurek¹, Carsten Culmsee^{3

4}, Regien G Schoemaker⁵, Rüdiger Gerstberger¹, Joachim Roth^{1

4}, Christoph Rummel^{1

4}

Affiliations

¹ Institute of Veterinary Physiology and Biochemistry, Justus Liebig University Giessen, Giessen, Germany.
² Department of Molecular Pharmacology, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, Netherlands.
³ Institute of Pharmacology and Clinical Pharmacy, Philipps University of Marburg, Marburg, Germany.
⁴ Center for Mind, Brain and Behavior-CMBB, Giessen and Marburg, Germany.
⁵ Department of Neurobiology, GELIFES, University of Groningen, Groningen, Netherlands.

Abstract

Purpose: 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: brown adipose tissue; fever; inflammatory markers; locomotor activity; neuroinflammation; small-conductance calcium-activated potassium channels.

Grants and funding

Part of this work was supported by Deutsche Forschungsgemeinschaft (DFG FOR2107/CU 43/9-1 to CC, DO 1525/3-1 to AMD) and by funding of the “Lung-brain axis in health and disease” initiative by the Research Campus Mid-Hessen (FCMH) to CC and CR. AMD is the recipient of a Rosalind Franklin Fellowship cofunded by European Union and University of Groningen.