Cellular stress response is a universal mechanism of extraordinary pathophysiological and pharmacological significance [1]. Dysregulation of the stress protein expression is known to play a determining role in the pathology of different human diseases and aging [2]. Identification of the primary sensors that perceive various stress stimuli and of the transducers that carry, amplify and integrate the signals culminating in the expression of a particular heat shock protein (HSP) is therefore of key importance [3,4].HSP expression in mammalian cells is primarily regulated at the level of transcription and, although not exclusively, is mainly mediated by heat shock factors (HSF), especially HSF1 [5]. The conversion of HSFs to their active, DNA-binding form involves oligomerization to a trimeric state and reversible hyperphosphorylation at multiple sites [6]. The exact mechanism of HSF1 hyperphosphorylation is currently unknown, and the regulation of the mammalian heat shock response appears to be more complex The concentrations of two structurally distinct membrane fluidizers, the local anesthetic benzyl alcohol (BA) and heptanol (HE), were used at concentrations so that their addition to K562 cells caused identical increases in the level of plasma membrane fluidity as tested by 1,6-diphenyl-1,3,5-hexatriene (DPH) anisotropy. The level of membrane fluidization induced by the chemical agents on isolated membranes at such concentrations corresponded to the membrane fluidity increase seen during a thermal shift up to 42°C. The formation of isofluid membrane states in response to the administration of BA or HE resulted in almost identical downshifts in the temperature thresholds of the heat shock response, accompanied by increases in the expression of genes for stress proteins such as heat shock protein (HSP)-70 at the physiological temperature. Similarly to thermal stress, the exposure of the cells to these membrane fluidizers elicited nearly identical increases of cytosolic Ca 2+ concentration in both Ca 2+ -containing and Ca 2+ -free media and also closely similar extents of increase in mitochondrial hyperpolarization. We obtained no evidence that the activation of heat shock protein expression by membrane fluidizers is induced by a proteinunfolding signal. We suggest, that the increase of fluidity in specific membrane domains, together with subsequent alterations in key cellular events are converted into signal(s) leading to activation of heat shock genes.Abbreviations BA, benzyl alcohol; DPH, 1,6-diphenyl-1,3,5-hexatriene; ERK, extracellular signal-regulated kinase; HE, heptanol; HSF, heat shock factor; HSP, heat shock protein; TMA-DPH, 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene; DW m , mitochondrial membrane potential.

Stress is well-known to contribute to the development of both neurological and psychiatric diseases. While the role of the blood-brain barrier is increasingly recognized in the development of neurodegenerative disorders, such as Alzheimer's disease, dysfunction of the blood-brain barrier has been linked to stress-related psychiatric diseases only recently. In the present study the effects of restraint stress with different duration (1, 3, and 21 days) were investigated on the morphology of the blood-brain barrier in male adult Wistar rats. Frontal cortex and hippocampus sections were immunostained for markers of brain endothelial cells (claudin-5, occluding, and glucose transporter-1) and astroglia (GFAP). Staining pattern and intensity were visualized by confocal microscopy and evaluated by several types of image analysis. The ultrastructure of brain capillaries was investigated by electron microscopy. Morphological changes and intensity alterations in brain endothelial tight junction proteins claudin-5 and occludin were induced by stress. Following restraint stress significant increases in the fluorescence intensity of glucose transporter-1 were detected in brain endothelial cells in the frontal cortex and hippocampus. Significant reductions in GFAP fluorescence intensity were observed in the frontal cortex in all stress groups. As observed by electron microscopy, 1-day acute stress induced morphological changes indicating damage in capillary endothelial cells in both brain regions. After 21 days of stress thicker and irregular capillary basal membranes in the hippocampus and edema in astrocytes in both regions were seen. These findings indicate that stress exerts time-dependent changes in the staining pattern of tight junction proteins occludin, claudin-5, and glucose transporter-1 at the level of brain capillaries and in the ultrastructure of brain endothelial cells and astroglial endfeet, which may contribute to neurodegenerative processes, cognitive and behavioral dysfunctions.