[Effects of Rho/ROCK signal pathway on AGEs-induced morphological and functional changes in human dermal microvascular endothelial cells.].

The present study aimed to determine the role of Rho/Rho kinase (Rho/ROCK) phosphorylation on advanced glycation end products (AGEs)-induced morphological and functional changes in human dermal microvascular endothelial cells (HMVECs). HMVECs were respectively incubated with different concentrations of AGEs-modified human serum albumin (AGEs-HSA) for different time. In some other cases, HMVECs were pretreated with ROCK inhibitors (H-1152 or Y-27632). The morphological changes of F-actin cytoskeleton were visualized by rhodamine-phalloidin staining and the phosphorylation of Rho and ROCK were determined by Western blot. Endothelial monolayer permeability was assessed by measuring the flux of FITC-albumin across the endothelial cells. The results showed that the distribution of F-actin was significantly altered by AGEs-HSA in time and dose-dependent patterns. These effects were inhibited by ROCK inhibitors. The phosphorylation of Rho and RCOK was remarkably increased by AGEs-HSA treatment while total Rho and ROCK protein levels were not affected. The permeability of endothelial monolayer was dramatically increased by AGEs-HSA, and both ROCK inhibitors (H-1152 or Y-27632) attenuated these hyperpermeability responses. The results obtained suggest that the phosphorylation of Rho/ROCK plays an important role in AGEs-induced morphological and functional alterations in HMVECs.

Calcium mobilization is required for peroxynitrite-mediated enhancement of spontaneous transient outward currents in arteriolar smooth muscle cells.

Transiently local release of Ca(2+) from the sarcoplasmic reticulum (SR) activates nearby Ca(2+)-activated K(+) channels to produce spontaneous transient outward currents (STOCs) in smooth muscle cells. The purpose of the present study was to investigate the possible effect of peroxynitrite (ONOO(-)) on STOCs in mesenteric arteriolar smooth muscle cells (ASMCs) and decide whether Ca(2+) mobilization was involved in STOCs alteration by ONOO(-). STOCs were recorded and characterized using the perforated whole-cell patch-clamp configuration. The results demonstrated that STOCs activity was greatly suppressed by removal of extracellular Ca(2+); by addition of nifedipine, a specific inhibitor of L-type voltage-gated Ca(2+) channels (VGCCs); or by addition of ryanodine, a SR ryanodine receptors (RyRs) blocker. In contrast, both caffeine, a RyR activator, and 2-aminoethoxydiphenylborate (2-APB), a membrane-permeable inositol 1,4,5-trisphosphate receptors, (IP3R) antagonist, increased STOCs activity. 3-morpholinosydnonimine (SIN-1), an ONOO(-) donor, at concentrations of 20-200 microM, induced a dose-dependent enhancement of STOCs in ASMCs and led to conspicuous increases in STOCs frequency and amplitude, which were prevented by prior exposure to low external Ca(2+) (200 nM), ryanodine (10 microM), or nifedipine (10 microM). In contrast, caffeine (0.5 mM) did not further stimulate STOCs in ASMCs preincubated with SIN-1, and pretreatment with 2-APB (50 microM) had little effect on ONOO(-) -induced STOCs activation. These findings suggest that complex Ca(2+)-mobilizing pathways, including external Ca2+ influx through VGCCs activation and subsequent internal Ca(2+) release through RyRs but not IP3Rs, are involved in ONOO(-)mediated STOCs enhancement in ASMCs.

Effects of lipopolysaccharide on actin reorganization and actin pools in endothelial cells.

OBJECTIVE: To investigate the dose and time-dependent effects of lipopolysaccharide (LPS) on cytoskeletal F-acitn and G-actin reorganizations by visualizing their distribution and measuring their contents in human umbilical vein endothelial cell line ECV-304. METHODS: F-actin was labeled with rhodamine-phalloidin and G-actin with deoxyribonuclease I (DNase I)conjugated with fluorescein isothiocyanate (FITC). Contents of cytoskeletal proteins were obtained by flow cytometry. RESULTS: F-actin was mainly distributed peripherally in endothelial cells under normal conditions. LPS stimulation caused the formation of stress fibers and filopodia. G-actin was normally seen in perinuclear and nuclear areas in control ECV-304 cells. Under LPS stimulation, G-actin dots appeared in the cytoplasmic region. The actin disorganization was accompanied by the time- and dose- dependent decrease in F-actin pool and increase in G-actin pool. CONCLUSIONS: LPS can induce characteristic morphological alterations of actin cytoskeleton and formation of intercellular gap in endothelial cells, accompanied by changes in F-actin and G-actin pools.

Myosin light-chain kinase contributes to short-term endothelial cell cytoskeletal alteration induced by serum from burned rats.

OBJECTIVES: To investigate the time-dependent effects of serum from burned rats on cytoskeletal filamentous actin (F-actin) reorganization by visualizing their distribution in human umbilical vein endothelial cell line ECV-304 and evaluate the role of myosin light-chain kinase (MLCK) in this process. METHODS: The serum-starved ECV-304 cells were incubated with the serum from burned rats for 30 min, 1, 2, 4, and 6 h, respectively, and 30 min before or after the incubation, the cells were treated with 5 micromol/L ML-7 for 30 min. F-actin was stained with rhodamine-phalloidin and observed under fluorescence microscope. RESULTS: Under normal condition, F-actin was distributed mainly in the cortical area of the endothelial cells. After stimulation with the burn serum, stress fiber formation could be clearly seen in the endothelial cells, exhibiting a time-dependent enhancement in a time course ranging from 30 min to 6 h. Such an effect could be significantly inhibited by a 30-min pretreatment of the cells with MLCK-specific inhibitor ML-7. Inhibition of MLCK also reversed actin reorganization in the endothelial cells pretreated with the burn serum. CONCLUSION: Serum from burned rats induces characteristic morphological changes in the endothelial cell actin cytoskeleton mainly due to the MLCK activation, an effect that can be reversed by the inhibition of MLCK.

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

The present study was designed to investigate the possible effects of peroxynitrite (ONOO(-)) on the intracellular calcium concentration ([Ca(2+)](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 [Ca(2+)](i). Bolus administration with a low concentration of ONOO(-) (25 microM) decreased [Ca(2+)](i), whereas higher concentrations (50 or 100 microM) increased [Ca(2+)](i) persistently. Further experiments demonstrated that pretreatment of ASMCs with calcium-free medium completely abolished [Ca(2+)](i) increase by 100 microM ONOO(-). Additionally, nifedipine, an antagonist of selective L-type voltage-gated calcium channels (VGCCs), delayed the [Ca(2+)](i) response to ONOO(-), and ryanodine, an inhibitor of intracellular calcium release from the sarcoplasmic reticulum, effectively antagonized [Ca(2+)](i) increase during the late stage of ONOO(-) exposure. Furthermore, [Ca(2+)](i) alteration by ONOO(-) appeared to be intimately associated with the subsequent membrane potential changes. Although the mechanisms by which ONOO(-) alters [Ca(2+)](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 [Ca(2+)](i) in ASMCs by a low concentration of ONOO(-) may participate in the pathogenesis of low vasoreactivity in shock, and the increase of [Ca(2+)](i) by high concentrations of ONOO(-) may lead to calcium overload with cellular injury.

Effect of SOD and NaHCO3 on the vascular hyporeactivity of rats after severe hemorrhagic shock.

OBJECTIVE: To investigate the effect of SOD and NaHCO3 on the vascular hyporeactivity after severe hemorrhagic shock in rats. METHODS: Twenty eight Sprague-Dawley rats were divided randomly into 4 groups of 7 each: SOD-treated group, NaHCO3-treated group, SOD+NaHCO3-treated group and normal saline-treated control group. The responses of arterioles to norepinephrine (NE), the effects of dopamine on blood pressure, blood flow velocity in arterioles, the mean arterial pressure (MAP), and the survival time within 24 h were measured. RESULTS: Two hours after shock, the arteriolar vasoreactivity was significantly reduced and threshold concentration of NE was increased by 24 to 27 folds. After beting treated separately with SOD, NaHCO3 and SOD+NaHCO3, arteriolar vasoreactivity was restored to some extent, among which the SOD+NaHCO3 group obtained a most significant effect with decreased threshold concentration of NE to 21% of its normal level. In SOD+NaHCO3-treated group, injection of dopamine indicated a most significant effect on MAP with 1.9 times more than that in control group, and the enhanced MAP was maintained at a level of more than 13.33 kPa after reinfusion of shed blood. The blood flow in arteriole was 2.54-fold higher than that in control group after 2 h resuscitation. The average survival time in SOD+NaHCO3- treated group was 2.9 times longer than that in control group. CONCLUSIONS: SOD and NaHCO3 could both recover the lower vasoreactivity and increase the enhancing effect of dopamine on blood pressure of rats in severe hemorrhagic shock, suggesting that coadministration of SOD and NaHCO3 could be a new approach to the treatment of severe hemorrhagic shock.

[Influence of inhibitors of nitric oxide synthase and L-arginine on the survival rate in a rat model of traumatic shock].

OBJECTIVE: To investigate the influence of inhibitors of nitric oxide synthase (NOS) and L-arginine on the survival rate in a rat model of traumatic shock. METHODS: A rat model of traumatic shock was established by fracturing the posterior limb of the rat. Nomega-nitro-L-arginine-methyl ester (L-NAME, non-selective NOS inhibitor, 10 mg/kg), amino- guanidine (AG, selective inducible nitric oxide synthase (iNOS) inhibitor, 100 mg/kg) and L-arginine (L-Arg, the precursor of nitric oxide (NO) synthesis 100 mg/kg) were injected intravenously during resuscitation,survival time and survival rate were observed. RESULTS: There were no significant changes in survival time and 24-hour survival rate between L-NAME ((23.80+/-9.09) hours and 40 percent) and control group (18.78+/-4.64)hours and 10 percent, both P>0.05); the survival time of AG group (28.72+/-6.25) hours and L-Arg group (30.64+/-8.77) hours prolonged apparently (both P<0.01), and 24-hour survival rate was also increased (both 80 percent, both P<0.01). CONCLUSION: Selective iNOS inhibitor AG and L-Arg exert beneficial effects on after traumatic shock rats.

Peroxynitrite induces arteriolar smooth muscle cells membrane hyperpolarization with arteriolar hyporeactivity in rats.

Peroxynitrite (ONOO-) has been recently known to act as a potent cytotoxin during pathogenesis of various diseases. This study aimed to investigate the possible effect of ONOO- on the cremaster muscle arteriolar reactivity in response to noradrenaline and subsequently determined whether membrane hyperpolarization and potassium channel activation were involved in ONOO(-)-induced alteration of arteriolar reactivity. The results demonstrated that 1) ONOO- could decrease arteriolar reactivity in a time- and concentration-dependent manner with no significant alteration of arteriolar diameter; 2) Superfusion with 20 microM ONOO- over 40 minutes showed slight but not significant influence on the resting potential (Em) of arteriolar smooth muscle cells (ASMCs). However, ASMCs subjected to 50 or 100 microM ONOO- administration were significantly hyperpolarized. As control, treatment with 50 microM decomposed ONOO- or Kreb's solution had little effect on the Em of ASMCs; 3) ONOO(-)-induced arteriolar hyporeactivity could be greatly reversed by co-administration of KCl and partially by TEA. The above results indicated that membrane hyperpolarization and potassium channel activation were preferentially responsible for the reduction of cremaster muscle arteriolar reactivity after exposure to ONOO-.

[Properties of large-conductance calcium-activated potassium channel in rat mesenteric arteriole smooth muscle cells].

OBJECTIVE: To investigate the electrophysiological properties of large-conductance calcium-activated potassium channel (BKCa) in mesenteric arteriole smooth muscle cells of rat. METHOD: Mesenteric arteriolar smooth muscle cells from rats were isolated and inside-out patch clamp technique was used to study BKCa. RESULTS: The single channel conductance of BKCa recorded was 221+/-6 pS and the reversal potential was -0.12 mV in the presence of high potassium in the bathing and pipette solutions. The open probability (NPo) of the channel was both voltage- and intracellular calcium dependent, whereas the amplitude of the channel was not calcium-dependent. Prolonged closed state could be observed at intracellular calcium concentrations of 1 micromol/L or above, known as calcium-dependent inactivation. CONCLUSION: BKCa in rat mesenteric arterial smooth muscle cells has the properties of large conductance, high potassium selectivity, steep voltage dependence and high calcium sensitivity. The high sensitivity to calcium of BKCa may be related to the compensatory regulation of the smooth muscles in pathophysiological conditions.

[Effect of protein kinase on endothelial cytoskeleton induced by septic shock].

OBJECTIVE: To study the effect of cGMP-dependent protein kinase (PKG) on the pathogenesis of septic shock. METHODS: Confluent endothelial cells were disintegrated and centrifugated to obtain cell lysates after being treated with LPS or PKG activator 8-Br-cGMP. PKG activity of lysates was measured with radioactive isotope label method in a reaction system of phosphorylation of specific substrate H2B by PKG, and the shape and the distribution of intracellular filamentous actin were detected by specific fluorescence staining. For the control study, the PKG specific inhibitor KT5823 was used to pretreat the endothelial cells before the administration of LPS or PKG activator 8-Br-cGMP. RESULTS: Exposure to LPS for 5, 10, 30 and 60 minutes led to a rapid time-dependent increase in endothelial PKG activity (P < 0.01 compared to the blank) and the polar distribution of intracellular filamentous actin and preincubation with KT5823 abolished these effects. 8-Br-cGMP was similar to LPS. CONCLUSIONS: The results suggested that LPS can mediate PKG activation and the stress variety of filamentous actin in the vascular endothelial cells, which probably induce the endothelial hyperpermeability after septic shock.

[Effects of aging and hypoxia on the proliferation of cultured rat pulmonary arterial smooth muscle cells].

OBJECTIVE: To study the effects of aging and hypoxia on the proliferative behavior of cultured pulmonary arterial smooth muscle cells (PASMCs). METHODS: PASMCs isolated from aged (18-24 months) and young (3-4 months) rats were divided, according to the different treatments the cells were subjected to, into young and aged normoxic groups (groups A and B) and young and aged hypoxic groups (groups C and D) respectively. MTT cell proliferation assay, 3H-TdR incorporation assay, flow cytometriy and immunocytochemical analysis were respectively employed to observe the proliferative behavior. RESULTS: Compared with the cells from young rats, PASMCs from aged rats had a higher proliferation rate, more 3H-TdR incorporation, increased mitotic cell ratio, reduced amount of the total protein, and elevated content of proliferating cell nuclear antigen (PCNA). In comparison with normoxic condition, hypoxia elicited higher proliferation rate of the cells with inhibition of 3H-TdR incorporation that was subsequently increased. Higher percentage of mitotic cells, less total protein amount and increased PCNA were also observed in response to hypoxia. CONCLUSIONS: Aging and hypoxia may directly induce PASMC proliferation, and in aging PASMCs, the proliferation is the most obvious in response to hypoxic stimulation.

Dynamic changes in serum level of nitric oxide and its mechanisms in rats with traumatic shock.

OBJECTIVE: To investigate the dynamic changes of serum nitric oxide (NO) level and its mechanisms in rats in traumatic shock. METHODS: Rat models of traumatic shock were established by fracturing the posterior limb of the rats. Serum levels of nitrate/nitrite were measured with the method described by Griess. RESULTS: No significant changes in serum NO level took place during traumatic shock. One hour after resuscitation, however, serum NO level first underwent marked decline and then increased to the peak level at 6 h after resuscitation, retaining a high level till 24 h after resuscitation. No obvious changes of serum NO levels were observed in rats without resuscitation. CONCLUSION: Serum NO level does not significantly alter during traumatic shock, while after resuscitation, NO level increases after transient decrease, possibly due to reperfusion injury.