title: Forced treadmill exercise can induce stress and increase neuronal damage in a mouse model of global cerebral ischemia.
abstract: Physical exercise is known to be a beneficial factor by increasing the cellular stress tolerance. In ischemic stroke, physical exercise is suggested to both limit the brain injury and facilitate behavioral recovery. In this study we investigated the effect of physical exercise on brain damage following global cerebral ischemia in mice. We aimed to study the effects of 4.5 weeks of forced treadmill running prior to ischemia on neuronal damage, neuroinflammation and its effect on general stress by measuring corticosterone in feces. We subjected C57bl/6 mice (n = 63) to either treadmill running or a sedentary program prior to induction of global ischemia. Anxious, depressive, and cognitive behaviors were analyzed. Stress levels were analyzed using a corticosterone ELISA. Inflammatory and neurological outcomes were analyzed using immunohistochemistry, multiplex electrochemoluminescence ELISA and Western blot. To our surprise, we found that forced treadmill running induced a stress response, with increased anxiety in the Open Field test and increased levels of corticosterone. In accordance, mice subjected to forced exercise prior to ischemia developed larger neuronal damage in the hippocampus and showed higher cytokine levels in the brain and blood compared to non-exercised mice. The extent of neuronal damage correlated with increased corticosterone levels. To compare forced treadmill with voluntary wheel running, we used a different set of mice that exercised freely on running wheels. These mice did not show any anxiety or increased corticosterone levels. Altogether, our results indicate that exercise pre-conditioning may not be beneficial if the animals are forced to run as it can induce a detrimental stress response.
authors.affiliation: Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
authors.forename: Martina
authors.initials: M
authors.lastname: Svensson
authors.affiliation: Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
authors.forename: Philip
authors.initials: P
authors.lastname: Rosvall
authors.affiliation: Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
authors.forename: Antonio
authors.initials: A
authors.lastname: Boza-Serrano
authors.affiliation: Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
authors.forename: Emelie
authors.initials: E
authors.lastname: Andersson
authors.affiliation: Department of Health Sciences, Lund University, 221 00 Lund, Sweden; Department of Neurology and Rehabilitation, Skane University Hospital, 221 85 Lund, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Lexell
authors.affiliation: Experimental Neuroinflammation Laboratory, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Deierborg
keywords: Corticosterone; Cytokines; Forced exercise; Microglia; Neuroinflammation; Stress