The effect of endurance training and testosterone supplementation on the expression of blood spinal cord barrier proteins in rats.

The present study aimed to estimate the effect of endurance training, two doses of testosterone, and the combination of these stimuli on the level of the endothelial proteins claudin, occludin, JAM-1, VE-cadherin, ZO-1, ZO-2, and P-glycoprotein in rat spinal cords. Adult male Wistar rats were trained using a motor-driven treadmill for 6 weeks (40-60 min, 5 times per week) and/or were treated for 6 weeks with two doses of testosterone (i.m.; 8 mg/kg or 80 mg/kg body weight). Spinal cords were collected 48 hours after the last training cycle and stored at -80°C. The levels of selected proteins in whole tissue lysates of the spinal cord were measured by western blot. Testosterone-treated trained rats had significantly lower claudin levels than vehicle-treated trained rats. High doses of testosterone resulted in a significant decrease in claudin-5 in untrained rats compared to the control group. Both doses of testosterone significantly reduced occludin levels compared to those in vehicle-treated untrained rats. The JAM-1 level in the spinal cords of both trained and untrained animals receiving testosterone was decreased in a dose-dependent manner. The JAM-1 level in the trained group treated with high doses of testosterone was significantly higher than that in the untrained rats treated with 80 mg/kg of testosterone. VE-cadherin levels were decreased in all groups receiving testosterone regardless of endurance training and were also diminished in the vehicle-treated group compared to the control group. Testosterone treatment did not exert a significant effect on ZO-1 protein levels. Testosterone and/or training had no significant effects on ZO-2 protein levels in the rat spinal cords. Endurance training increased P-glycoprotein levels in the rat spinal cords. The results suggest that an excessive supply of testosterone may adversely impact the expression of endothelial proteins in the central nervous system, which, in turn, may affect the blood-brain barrier function.

Immunosuppressant cytoprotection correlates with HMGB1 suppression in primary astrocyte cultures exposed to combined oxygen-glucose deprivation.

The protective potential of immunosuppressants has been reported in many experimental models of ischemia both in vivo and in vitro, suggesting a novel therapeutic application of these drugs. Because high-mobility group box 1 (HMGB1) protein has recently been reported to be involved in ischemic brain injury, the purpose of the present study was to determine whether treatment with immunosuppressants could decrease the expression and release of HMGB1 in astrocytes exposed to simulated ischemic conditions (combined oxygen-glucose deprivation, OGD). We also investigated whether immunosuppressive drugs could attenuate necrosis in astrocyte cultures exposed to OGD. Finally, we studied the influence of immunosuppressants on the expression of NFκB, inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). Cells were treated with cyclosporine A, FK506 and rapamycin (all drugs at concentrations of 0.1, 1 and 10 µM). Our study provides evidence that immunosuppressants decrease the expression and release of HMGB1 in ischemic astrocytes. Our data suggest that HMGB1 release may be partly an active process triggered by oxidative stress because the antioxidant N-acetylcysteine (NAC) clearly attenuated HMGB1 expression and release. Furthermore, we show that the immunosuppressants, at the same concentrations that significantly suppressed HMGB1 expression and release, were also able to prevent the necrosis of ischemic astrocytes and inhibit the expression of inflammatory mediators (NFκ, iNOS and COX-2). These results provide further information about the cytoprotective mechanisms of immunosuppressants on ischemic astrocytes, especially in relation to the pathophysiology of ischemic brain injury. It appears that the protective effects of immunosuppressants can be mediated in part by the suppressing the expression and release of HMGB1 in astrocytes, which leads to the attenuation of ischemia-induced necrosis and neuroinflammation.

Cytosolic phospholipase A2 inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation.

The protective potential of nortriptyline has been reported in a few experimental models of brain ischemia, both in vivo and in vitro. However, the detailed molecular mechanisms of the protective action of the drug are still unresolved. The aim of the present study was to determine whether treatment with low or medium concentrations of nortriptyline (0.1-10 µM) might have an effect on cPLA2 protein and/or mRNA expression in ischemic astrocytes, and whether this influence might be related to its potential positive influence on cell viability. On the 21(st) day in vitro, primary cultures of rat cortical astrocytes were subjected to ischemia-simulating conditions (combined oxygen glucose deprivation, OGD) for 24 h and exposed to nortriptyline. The drug at concentrations of 0.1 and 1 µM attenuated the expression of cPLA2 (both the phosphorylated and unphosphorylated forms) together with a significant decrease in the cPLA2 mRNA level in ischemic astrocytes. We have demonstrated that nortriptyline influences a decrease in cPLA2-mediated arachidonic acid (AA) release through a mechanism that appears to involve the attenuation of both PKC and Erk1/2 kinase expression. Nortriptyline also significantly prevented mitochondrial depolarization in ischemic astrocytes. Moreover, the antidepressant protected glial cells against OGD-induced apoptosis and necrosis. Our findings document a role for cPLA2 expression attenuation and AA release inhibition in the protective effect of nortriptyline in ischemic astrocytes.

Effect of FK506 and cyclosporine A on the expression of BDNF, tyrosine kinase B and p75 neurotrophin receptors in astrocytes exposed to simulated ischemia in vitro.

We investigated whether the immunosuppressive drugs, FK506 and cyclosporine A, increase BDNF protein and/or mRNA expression in ischemic astrocytes and if an increase could be related to changes in the nuclear expression of p-CREB, p-Erk1/2 and p-Akt. The influence of these immunosuppressants on protein and mRNA levels of TrkB and p75(NTR) receptors was also examined. On day 21, cultures of rat astrocytes were subjected to ischemic conditions simulated in vitro (combined oxygen glucose deprivation, OGD) for 8h and exposed to FK506 (10-1000nM) and cyclosporine A (0.25-10microM). FK506 and cyclosporine A (at 1000nM and 0.25microM, respectively) stimulated the expression and release of BDNF in cultured rat cerebral cortical astrocytes exposed to OGD. The immunosuppressants at these doses simultaneously increased p-CREB and p-Erk1/2 expression in the nuclear fraction of astrocytes. The results RT-PCR and Western blot analysis provided further evidence of a modulating influence of the drugs on the expression of trkB and p75(NTR) genes and their protein products in ischemic astrocytes.

Physiology and pharmacological role of the blood-brain barrier.

The central nervous system (CNS) is a perfectly regulated environment with conditions far different from those in the rest of the organism. Even slight changes in this machinery affect its functioning. The blood-brain barrier (BBB) is the frontier that isolates brain tissues from the substances circulating in the blood vascular system. It is also a diffusion barrier that allows only water and small lipophilic molecules to freely access the brain in accordance with their concentration gradients. Moreover, animal studies have revealed differences in the barrier tightening time-course during development. The BBB becomes resistant to larger molecules before it stops smaller ones. Thus, its maturation has a progressive scheme. A similar scheme is true for BBB transporters. Due to all of these facts, the BBB is the most significant element responsible for the preservation of CNS homeostasis. As a functional system, the BBB can be investigated as a frontier composed of pericytes, astrocytic end feet, and brain endothelial cells (ECs). Special emphasis is placed on the tight junctions (TJs) existing between them. An alternative point of view considers the BBB to be a functional complex consisting not only of bricks of cells but also of structures between those cells and their cofunctioning elements.