Influence of altered life conditions on the regulation of AMP-activated kinase (AMPK) in inflammatory pain
Final Report Abstract
Pharmacological activation of the AMP dependent kinase (AMPK) is associated with anti-nociceptive effects. However, it is well known that life style changes such as exercise, restriction diet or age can also induce AMPK activation. In our project, we assessed the impact of these interventions on AMPK activation in the nervous system and on the nociceptive response in inflammatory models in mice. We investigated exercise-induced effects after a single bout of treadmill running in the model of formalin-induced inflammatory nociception. Our results showed that wild type mice displayed a reduced nociceptive response in the formalin test after treadmill running, while exercise had no effect on inflammatory nociception in AMPK alpha 2 knockout mice. Levels of the endocannabinoid anandamide (AEA) were increased after physical activity in both wild type and AMPK alpha 2 knockout mice, in association with decreased expression of the AEA-hydrolyzing enzyme FAAH and an increased level of the cannabinoid receptor 1 (CB1). Accordingly, treatment of wild type mice with the CB1 inverse agonist AM251 prior to the treadmill running reversed exercise-induced anti-nociception. However, if mice received AM251 in combination with the AMPK activator 5-amino-1-ß-D-ribofuranosyl-imidazole-4-carboxamide (AICAR), the positive effect of treadmill running on inflammatory nociception was restored, indicating that AMPK affects exercise-induced anti-nociception downstream of endocannabinoids. This assumption was further supported by cell culture experiments showing AMPK activation after stimulation of neuronal cells with AEA. In a second model, we assessed the impact of caloric restriction (CR) on inflammatory nociception in mice, which were either fed ad libitum or subjected to CR with 80% of the daily average for two weeks. The behavioral tests revealed that zymosan-induced inflammatory nociception was significantly decreased when wild-type mice underwent CR. In contrast, AMPK alpha 2 knock-out mice lacked the anti-nociceptive effects after CR. Endocannabinoid levels of anandamide (AEA) and 2-arachidonyl glycerol (2-AG) determined in serum by LC-MS/MS were not affected by either CR alone or in combination with zymosan treatment. However, cannabinoid receptor type 1 (CB1 receptor) expression in the spinal cord, which was not altered by CR in control mice, was significantly increased after CR in zymosan-induced paw inflammation. From these results and the significant activation of AMPK in cell culture, we concluded that CB1 signaling influences AMPK activity also after CR. In the third part of the project, we analyzed the effect of increased age on AMPK activation and nociception (12-months-old versus 6-8-weeks-old mice). Our data showed that AMPK is not involved in age-dependent inhibition of nociception in our model. The reduced nociceptive response might rather be due to a higher level of cortisol in the spinal cord of aged mice. Among potential cortisol targets, the NF-KB inhibitor protein alpha (IKB alpha) was increased, which might contribute to inhibition of NF-κB and a decreased expression and activity of the inducible nitric oxide synthase (iNOS). In conclusion, our results revealed that exercise- and diet-induced anti-nociceptive effects are associated with changes in AMPK activation and the endocannabinoid system. On the other hand, a reduced nociceptive response in aged mice is independent of AMPK, but might be at least partially mediated by an augmented inflammation-induced increase in the hormonal inhibitory system involving cortisol.
Publications
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LPS inhibits caspase 3-dependent apoptosis in RAW264.7 macrophages induced by the AMPK activator AICAR. Biochemical and Biophysical Research Communications, Vol. 447. 2014, Issue 3, pp. 520-525.
Russe OQ, Möser CV, Kynast KL, King TS, Olbrich K, Grösch S, Geisslinger G, Niederberger E.
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Age-Dependent Changes in the Inflammatory Nociceptive Behavior of Mice. International Journal of Molecular Sciences, Vol. 16. 2015, Issue 11, pp. 27508-27519.
King-Himmelreich T.S., Möser C.V., Wolters M.C., Olbrich K., Geisslinger G., Niederberger E.
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AMP-activated protein kinase is activated by non-steroidal anti-inflammatory drugs. European Journal of Pharmacology, Vol. 762. 2015, pp. 299-305.
King TS, Russe OQ, Möser CV, Ferreirós N, Kynast KL, Knothe C, Olbrich K, Geisslinger G, Niederberger E
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The impact of endurance exercise on global and AMPK gene-specific DNA methylation. Biochem Biophys Res Commun. 2016, 474(2):284-90
King-Himmelreich TS, Schramm S, Wolters MC, Schmetzer J, Möser CV, Knothe C, Resch E, Peil J, Geisslinger G, Niederberger E
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AMP- activated kinase and the endogenous endocannabinoid system might contribute to antinociceptive effects of prolonged moderate caloric restriction in mice, Molecular Pain, Vol. 13. 2017, 12 p.
King-Himmelreich T.S., Möser C.V., Wolters M.C., Schmetzer J., Geisslinger G., Niederberger E.
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AMPK contributes to aerobic exercise-induced antinociception downstream of endocannabinoids. Neuropharmacology, Vol. 124. 2017, pp. 134-142.
King-Himmelreich TS, Möser CV, Wolters MC, Schmetzer J, Schreiber Y, Ferreirós N, Russe OQ, Geisslinger G, Niederberger E
