Zhao Ks

ROLE OF p38 MAPK IN ICAM-1 EXPRESSION OF VASCULAR ENDOTHELIAL CELLS INDUCED BY LIPOPOLYSACCHARIDE

Lipopolysaccharide (LPS) stimulation of endothelial cells induces the expression of intercellular adhesion molecule-1 (ICAM-1), a critical adhesion molecule involved in the adhesive interaction between leukocytes and endothelial cells in shock and inflammation. Although there is little literature about role of p38 mitogen-activated protein kinase (MAPK) in ICAM-1 protein expression of LPS-induced endothelial cells, it is still not defined whether gene transcription is regulated by p38 MAPK in ICAM-1 expression of LPS-induced endothelial cells. In this study, the potential role of p38 MAPK in ICAM-1 expression of LPS-induced endothelial cells was studied in vitro and in vivo. In vitro studies, the results showed that compared with basic expression of ICAM-1 protein on cultured human umbilical vein endothelial cells (HUVECs), the ICAM-1 expression was increased initially at 2 h after LPS stimulation, reached peak value at 24 h, and descended at 36 h obviously. A dose-dependent relationship existed between LPS concentration and ICAM-1 expression. The abundance of ICAM-1 mRNA in cytoplasma of endothelial cells was upregulated significantly by LPS stimulation at 2 h and was maintained at a high level from 4 to 36 h. The upregulation of ICAM-1 protein and mRNA expression of LPS-induced HUVECs was markedly inhibited by SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole], a highly specific inhibitor of p38 MAPK. Activity of p38 MAPK in HUVECs was increased at 15 min after LPS stimulation and reached the maximum at 60 min, then descended significantly. Activity of p38 MAPK was inhibited significantly by SB203580 in vitro. In vivo studies, administration of SB203580 (12.5 or 25 mg/kg, per ora) markedly reduced LPS-induced expression of ICAM-1 protein and mRNA of lung tissues of male BALB/c mice. These data highlight that the upregulation of ICAM-1 expression of LPS-induced endothelial cells in vitro and in vivo is mediated by p38 MAPK pathway at the level of gene transcription. The ICAM-1 expression of LPS-induced endothelial cells is characteristic of time dependence and dose dependence, and tolerates to chronic LPS stimulation. Inhibition of the p38 MAPK signal pathway may be used as an approach to attenuate ICAM-1 production in the treatment of septic shock.

Lung, spleen, and kidney are the major places for inducible nitric oxide synthase expression in endotoxic shock: Role of p38 mitogen-activated protein kinase in signal transduction of inducible nitric oxide synthase expression

Bacterial lipopolysaccharide (LPS) is known to induce endotoxic shock with inducible nitric oxide (NO) synthase (iNOS) expression and NO production. However, the major place for NO production in shock remains unclear. Although there is some literature about p38 mitogen-activated protein kinase (MAPK) in regulating LPS-induced iNOS expression, the results are contradictory. To interpret the precise cell mechanism and the role of p38 MAPK in the expression of iNOS during endotoxic shock, we carried out the following investigations. A severe endotoxic shock model was reproduced in mice 6 h after LPS injection. The plasma NO level was increased in a dose- and time-dependent manner after LPS stimulation and was suppressed by administration of SB203580 [4-(4-fluorophenyl)-2-4-methylsulfonylphenyl-5-(4-pyridyl) imidazole], a highly specific inhibitor of p38 MAPK. The iNOS expression was increased in many organs, including heart, liver, spleen, lung, gut, and kidney in endotoxic shock. Among them, the highest expression of iNOS mRNA and protein was in the lung, moderate expression was in the spleen and kidney, and the lowest expression was in the heart, gut, and liver. The level of expression in lung was 5.5 times that of iNOS mRNA and was 3.1 times that of iNOS protein than in heart, and 1.6 and 1.8 times that of iNOS mRNA and 1.7 and 1.4 times that of iNOS protein than in spleen and kidney, respectively. The p38 MAPK activity increased after LPS injection, and SB203580 markedly reduced LPS-induced expressions of iNOS protein and mRNA in the lung. The results indicates that lung, spleen, and kidney are the major places for iNOS expression in endotoxic shock and are important therapeutic target organs for attenuating NO production in shock treatment.

Hypersensitivity of BKCa to Ca2+ Sparks Underlies Hyporeactivity of Arterial Smooth Muscle in Shock

Large conductance Ca2+-activated K+ channels (BKCa) play a critical role in blood pressure regulation by tuning the vascular smooth muscle tone, and hyposensitivity of BKCa to Ca2+ sparks resulting from its altered &bgr;1 subunit stoichiometry underlies vasoconstriction in animal models of hypertension. Here we demonstrate hypersensitivity of BKCa to Ca2+ sparks that contributes to hypotension and blunted vasoreactivity in acute hemorrhagic shock. In arterial smooth muscle cells under voltage-clamp conditions (0 mV), the amplitude and duration, but not the frequency, of spontaneous transient outward currents of BKCa origin were markedly enhanced in hemorrhagic shock, resulting in a 265% greater hyperpolarizing current. Concomitantly, subsurface Ca2+ spark frequency was either unaltered (at 0 mV) or decreased in hyperpolarized resting cells. Examining the relationship between spark and spontaneous transient outward current amplitudes revealed a hypersensitive BKCa activity to Ca2+ spark in hemorrhagic shock, whereas the spark–spontaneous transient outward current coupling fidelity was near unity in both groups. Importantly, we found an acute upregulation of the &bgr;1 subunit of the channel, and single-channel recording substantiated BKCa hypersensitivity at micromolar Ca2+, which promotes the &agr; and &bgr;1 subunit interaction. Treatment of shock animals with the BKCa inhibitors iberiotoxin and charybdotoxin partially restored vascular membrane potential and vasoreactivity to norepinephrine and blood reinfusion. Thus, the results underscore a dynamic regulation of the BKCa–Ca2+ spark coupling and its therapeutic potential in hemorrhagic shock–associated vascular disorders.

New approach to treatment of shock--restitution of vasoreactivity.

Our objective was to observe the therapeutic effect of restituting vasoreactivity agent in severe shock. A hemorrhagic shock (HS) model was reproduced in rat and the response of arterioles of spinotrapezius muscle to norepinephrine (NE) in HS was tested. The diameter, blood velocity, and volumetric flow in arteriole, and the mean arterial pressure (MAP) were measured. The therapeutic effect was observed after the treatment of restituting vasoreactivity agent (glybenclamide—an inhibitor of ATP sensitive potassium channel, and tiron—an oxygen free radical scavenger). The arteriolar vasoreactivity was significantly reduced with 15 fold increase of NE threshold 2 h post HS. After treated with restituting agent(RA), the vascular hyporeactivity of rat was apparently recovered, and the increased level of MAP following injection of dopamine was 1.8 times and 1.9 times more than that in NS-treated and DMSO-treated group respectively. After reinfusion of shed blood, the value of systemic blood pressure maintained more than 100mmHg and volumetric flow in arterioles in RA group were 2 times more than those in NS treated group within the 2h observation periods. The average survival time in RA treated group was also 1.8 times and 1.6 times longer than that in NS-treated and DMSO-treated group respectively. The restituting vasoreactivity agent is able to recover the lower vasoreactivity with excellent anti-shock effect in severe hemorrhagic shock.

Effect of sphingosine 1-phosphate on morphological and functional responses in endothelia and venules after scalding injury.

OBJECTIVE The uncontrolled increase of vascular permeability is the major obstacle in treatment of severe burns. Sphingosine 1-phosphate (S1P) has emerged as an important modulator of EC barrier function. This study was designed to explore the effect of S1P on morphological alteration in cultured endothelial cells (ECs) after burned plasma stimulation, and second to investigate the hyper-permeability response in intact vessels after scalding injury. METHODS The distribution of VE-cadherin and F-actin was observed by double staining in primary cultured human umbilical vein endothelial cells (HUVECs) with immunofluorescence and fluorescent probes; respectively. Permeability changes were measured by a fluorescence ratio technique in isolated venules from rat skin. Burned plasma was obtained from a third-degree scald covering 30% of the total body surface area. RESULTS The intervention with burned plasma on injured rats cultured HUVECs caused a significant disruption of intercellular adherens junction labeled by VE-cadherin staining, accompanied by the formation of F-actin stress fibers in the cells. S1P prevented or reversed these burned plasma-induced morphological alterations in cultured endothelial cells. The inhibition of S1P synthesis with N,N-dimethylsphingosine (DMS) mimicked the burned plasma-evoked redistribution of VE-cadherin and reorganization of F-actin. Venules isolated from burned rats demonstrated similar endothelial cytoskeleton changes with cultured cells under the influence of S1P or DMS. Both pre- and post-burn application of S1P attenuated increased permeability in isolated and perfused skin venules after burned plasma stimulation. CONCLUSION Our results indicate that S1P plays a role in maintaining basal vascular barrier function and could be protective in burn injury by enhancing the endothelial barrier function.

Mobilization of intracellular calcium by peroxynitrite in arteriolar smooth muscle cells from rats

Abstract The present study was designed to investigate the possible effects of peroxynitrite (ONOO-) on the intracellular calcium concentration ([Ca2+]i) of mesenteric arteriolar smooth muscle cells (ASMCs), and to reveal the underlying mechanisms by using fluorescence imaging analysis. The results showed that ONOO- could exert a concentration- and time-dependent but also a dual effect on [Ca2+]i. Bolus administration with a low concentration of ONOO- (25 μM) decreased [Ca2+]i, whereas higher concentrations (50 or 100 μM) increased [Ca2+]i persistently. Further experiments demonstrated that pretreatment of ASMCs with calcium-free medium completely abolished [Ca2+]i increase by 100 μM ONOO-. Additionally, nifedipine, an antagonist of selective L-type voltage-gated calcium channels (VGCCs), delayed the [Ca2+]i response to ONOO-, and ryanodine, an inhibitor of intracellular calcium release from the sarcoplasmic reticulum, effectively antagonized [Ca2+]i increase during the late stage of ONOO- exposure. Furthermore, [Ca2+]i alteration by ONOO- appeared to be intimately associated with the subsequent membrane potential changes. Although the mechanisms by which ONOO- alters [Ca2+]i are complex, we conclude that a series of variables such as external calcium influx, activation of VGCCs, intracellular calcium release, and membrane potential changes are involved. The decrease of [Ca2+]i in ASMCs by a low concentration of ONOO- may participate in the pathogenesis of low vasoreactivity in shock, and the increase of [Ca2+]i by high concentrations of ONOO- may lead to calcium overload with cellular injury.

Effect of salvianolic acid B on TNF-α induced cerebral microcirculatory changes in a micro-invasive mouse model.

Purpose To investigate the effects of salvianolic acid B (SAB) on tumor necrosis factor α (TNF-α) induced alterations of cerebral microcirculation with a bone-abrading model. Methods The influences of craniotomy model and bone-abrading model on cerebral microcirculation were compared. The bone-abrading method was used to detect the effects of intracerebroventricular application of 40 μg/kg·bw TNF-α on cerebral venular leakage of fluorescein isothiocyanate (FITC)-albulmin and the rolling and adhesion of leukocytes on venules with fluorescence tracer rhodamine 6G. The therapeutical effects of SAB on TNF-α induced microcirculatory alteration were observed, with continuous intravenous injection of 5 mg/kg·h SAB starting at 20 min before or 20 min after TNF-α administration, respectively. The expressions of CD11b/CD18 and CD62L in leukocytes were measured with flow cytometry. Immunohistochemical staining was also used to detect E-selectin and ICAM-1 expression in endothelial cells. Results Compared with craniotomy method, the bone-abrading method preserved a higher erythrocyte velocity in cerebral venules and more opening capillaries. TNF-α intervention only caused responses of vascular hyperpermeability and leukocyte rolling on venular walls, without leukocyte adhesion and other hemodynamic changes. Pre- or post-SAB treatment attenuated those responses and suppressed the enhanced expressions of CD11b/CD18 and CD62L in leukocytes and E-selectin and ICAM-1 in endothelial cells induced by TNF-α. Conclusions The pre- and post-applications of SAB during TNF-α stimulation could suppress adhesive molecular expression and subsequently attenuate the increase of cerebral vascular permeability and leukocyte rolling.