Abstract
Stress is an integral component of life that can sometimes cause a critical overload, depending on the qualitative and quantitative natures of the stressors. The involvement of actin, the predominant component of dendritic integrity, is a plausible candidate factor in stress-induced neuronal cytoskeletal changes. The major aim of this study was to compare the effects of three different stress conditions on the transcription and translation of actin-related cytoskeletal genes in the rat brain. Male Wistar rats were exposed to one or other of the frequently used models of physical stress, i.e. electric foot shock stress (EFSS), forced swimming stress (FSS), or psychosocial stress (PSS) for periods of 3, 7, 14, or 21 days. The relative mRNA and protein expressions of β-actin, cofilin and mitogen-activated protein kinase 1 (MAPK-1) were determined by qRT- PCR and western blotting from hippocampus and frontal cortex samples. Stressor-specific alterations in both β-actin and cofilin expression levels were seen after stress. These alterations were most pronounced in response to EFSS, and exhibited a U-shaped time course. FSS led to a significant β-actin mRNA expression elevation in the hippocampus and the frontal cortex after 3 and 7 days, respectively, without any subsequent change. PSS did not cause any change in β-actin or cofilin mRNA or protein expression in the examined brain regions. EFSS, FSS and PSS had no effect on the expression of MAPK-1 mRNA at any tested time point. These findings indicate a very delicate, stress type-dependent regulation of neuronal cytoskeletal components in the rat hippocampus and frontal cortex.
Highlights
Organisms are often exposed to periods of stress throughout their whole lives; most of these episodes can be controlled and may even be necessary for survival
The main finding of the present study was that the quantitative pattern of cytoskeletal stress response in the rat brain is unique to the stress model used to trigger it
The various stress models employed in this study affected the mRNA expression and protein levels of b-actin and cofilin differently; of the various physical and psychosocial stressors, electric foot shock stress (EFSS) induced the most pronounced changes in the investigated cytoskeletal markers
Summary
Organisms are often exposed to periods of stress throughout their whole lives; most of these episodes can be controlled and may even be necessary for survival. Filamentous actin (F-actin) is the major cytoskeletal component of the dendritic spines and plays a key role in the morphogenesis, maintenance and plasticity of these spines [6,7,9]. The actin filament dynamics are regulated by several types of proteins [10]. One of the most important is cofilin, which is regulated by the ratio of its concentration to those of actin and other actin-binding proteins [11,12]. Another regulatory factor is the mitogen-activated protein kinase 1 (MAPK-1) which contributes F-actin stabilization and arrangement [13]. MAPK-1 is responsible for the hyperphosphorylation of tau, leading to microtubule degeneration and cell death in AD [14]
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