ATP-citrate lyase controls endothelial gluco-lipogenic metabolism and vascular inflammation in sepsis-associated organ injury.

Sepsis involves endothelial cell (EC) dysfunction, which contributes to multiple organ failure. To improve therapeutic prospects, elucidating molecular mechanisms of vascular dysfunction is of the essence. ATP-citrate lyase (ACLY) directs glucose metabolic fluxes to de novo lipogenesis by generating acetyl-Co-enzyme A (acetyl-CoA), which facilitates transcriptional priming via protein acetylation. It is well illustrated that ACLY participates in promoting cancer metastasis and fatty liver diseases. Its biological functions in ECs during sepsis remain unclear. We found that plasma levels of ACLY were increased in septic patients and were positively correlated with interleukin (IL)-6, soluble E-selectin (sE-selectin), soluble vascular cell adhesion molecule 1 (sVCAM-1), and lactate levels. ACLY inhibition significantly ameliorated lipopolysaccharide challenge-induced EC proinflammatory response in vitro and organ injury in vivo. The metabolomic analysis revealed that ACLY blockade fostered ECs a quiescent status by reducing the levels of glycolytic and lipogenic metabolites. Mechanistically, ACLY promoted forkhead box O1 (FoxO1) and histone H3 acetylation, thereby increasing the transcription of c-Myc (MYC) to facilitate the expression of proinflammatory and gluco-lipogenic genes. Our findings revealed that ACLY promoted EC gluco-lipogenic metabolism and proinflammatory response through acetylation-mediated MYC transcription, suggesting ACLY as the potential therapeutic target for treating sepsis-associated EC dysfunction and organ injury.

Transferability and interpretability of the sepsis prediction models in the intensive care unit.

BACKGROUND: We aimed to develop an early warning system for real-time sepsis prediction in the ICU by machine learning methods, with tools for interpretative analysis of the predictions. In particular, we focus on the deployment of the system in a target medical center with small historical samples. METHODS: Light Gradient Boosting Machine (LightGBM) and multilayer perceptron (MLP) were trained on Medical Information Mart for Intensive Care (MIMIC-III) dataset and then finetuned on the private Historical Database of local Ruijin Hospital (HDRJH) using transfer learning technique. The Shapley Additive Explanations (SHAP) analysis was employed to characterize the feature importance in the prediction inference. Ultimately, the performance of the sepsis prediction system was further evaluated in the real-world study in the ICU of the target Ruijin Hospital. RESULTS: The datasets comprised 6891 patients from MIMIC-III, 453 from HDRJH, and 67 from Ruijin real-world data. The area under the receiver operating characteristic curves (AUCs) for LightGBM and MLP models derived from MIMIC-III were 0.98 - 0.98 and 0.95 - 0.96 respectively on MIMIC-III dataset, and, in comparison, 0.82 - 0.86 and 0.84 - 0.87 respectively on HDRJH, from 1 to 5 h preceding. After transfer learning and ensemble learning, the AUCs of the final ensemble model were enhanced to 0.94 - 0.94 on HDRJH and to 0.86 - 0.9 in the real-world study in the ICU of the target Ruijin Hospital. In addition, the SHAP analysis illustrated the importance of age, antibiotics, net balance, and ventilation for sepsis prediction, making the model interpretable. CONCLUSIONS: Our machine learning model allows accurate real-time prediction of sepsis within 5-h preceding. Transfer learning can effectively improve the feasibility to deploy the prediction model in the target cohort, and ameliorate the model performance for external validation. SHAP analysis indicates that the role of antibiotic usage and fluid management needs further investigation. We argue that our system and methodology have the potential to improve ICU management by helping medical practitioners identify at-sepsis-risk patients and prepare for timely diagnosis and intervention. TRIAL REGISTRATION: NCT05088850 (retrospectively registered).

Time of dissociation between microcirculation, macrocirculation, and lactate levels in a rabbit model of early endotoxemic shock.

BACKGROUND: The relationship between macrocirculation and microcirculation remains controversial. The loss of coherence between microcirculation and macrocirculation has already been found in late-stage sepsis shock. The objective of this study was to determine the earliest possible time of detecting the loss of coherence between microcirculation and macrocirculation in early-stage endotoxemic shock. METHODS: We randomized 24 female New Zealand white rabbits into two groups: endotoxemic shock group (n = 14) and control group (n = 10). Rabbits in the endotoxemic shock group were equipped with arterial and venous catheters and received an intravenous infusion of Escherichia coli lipopolysaccharide (LPS, 2 mg/kg over 10 min). Rabbits in the control group received the same dose of saline infusion. Microcirculatory perfusion parameters were assessed in the sublingual mucosa using sidestream dark-field video microscopy. Systemic hemodynamics and blood lactate levels were measured at baseline and over a 120-min period. RESULTS: Ninety minutes after completing LPS infusion, all animals in the endotoxemic shock group developed a hypodynamic septic condition, characterized by low cardiac output and increased systemic vascular resistance; 120 min after completing LPS infusion, the mean arterial pressure decreased by 25% (P = 0.01), confirming ongoing endotoxemic shock. However, significant decreases in sublingual microcirculatory parameters of small vessels (microvascular flow index, perfused vessel density, and proportion of small perfused vessels) were observed 30 min after completing LPS infusion (P = 0.01, for all), and threshold decreases of 30% were found 60 min after completing LPS infusion (P = 0.001, for all) in the endotoxemic shock group. Lactate levels significantly increased to more than 2 mm/L at 90 min and more than 4 mm/L at 120 min in the endotoxemic shock group (P = 0.02 and P = 0.01, respectively). CONCLUSIONS: Changes in microcirculatory perfusion precede changes in macrocirculation and lactate levels in a rabbit model of endotoxemia shock. Microcirculation, macrocirculation, and oxygen metabolism are distinct in early-stage endotoxic shock.

[Clinical study on the early predictive value of renal resistive index in acute kidney injury associated with severe acute pancreatitis].

OBJECTIVE: To investigate the value of renal resistive index (RRI) in early predictor and discriminator of severe acute pancreatitis (SAP)-related acute kidney injury (AKI). METHODS: A retrospective observational study was conducted. SAP patients complicated with AKI (within 1 week of onset) and admitted to intensive care unit (ICU) of Ruijin Hospital Shanghai Jiaotong University School of Medicine from January 2016 to June 2019 were enrolled. The RRI within 24 hours admission was measured. Clinical data such as acute physiology and chronic health evaluation II (APACHE II), heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), intra-abdominal pressure (IAP), arterial blood lactate (Lac), oxygenation index (PaO2/FiO2), base excess (BE), serum creatinine (SCr), urine output, norepinephrine (NE) and RRI were collected. Within 24 hours and 7 days after ICU admission, patients were grouped according to AKI classification criteria of Kidney Disease: Improving Global Outcomes (KDIGO), and the differences of relevant parameters were statistically analyzed. Influence factors of AKI grading were screened by Logistic regression analysis. Pearson correlation analysis was used to analyze the correlation between RRI and other parameters. The predictive value of RRI for AKI classification was analyzed by receiver operating characteristic (ROC) curve. RESULTS: A total 57 patients were included, with an average age of (54.6±13.5) years old, and APACHE II score of 21.8±5.6. Within 24 hours, the number of patients suffered from stage 1-3 AKI were 19 (33.3%), 18 (31.6%) and 20 (35.1%), respectively. On day 7, the number of patients suffered from stage 0-3 AKI were 21 (36.9%), 8 (14.0%), 9 (15.8%) and 19 (33.3%), respectively. The higher APACHE II score, CVP, IAP, Lac, NE dosage and RRI were found in the group with higher AKI grades, especially in the group with stage 3 AKI on day 7. RRI of patients with stage 3 AKI was significantly higher than that of patients with stage 1 and 2 AKI within 24 hours (0.74±0.04 vs. 0.65±0.05, 0.68±0.05, both P < 0.05). Similarly, RRI of patients with stage 2 and 3 AKI were significantly higher than that of patients with stage 0 and 1 AKI on day 7 (0.70±0.04, 0.74±0.04 vs. 0.65±0.05, 0.66±0.05, all P < 0.05). Multivariate Logistic regression analysis showed that RRI was an independent factor of AKI classification [odds ratio (OR) = 3.15, 95% confidence interval (95%CI) = 1.09-9.04, P < 0.05], and IAP and CVP also had significant impacts on AKI grading [OR value was 2.11 (95%CI = 1.16-4.22), 3.78 (95%CI = 1.21-12.90), both P < 0.05]. ROC curve analysis showed that the area under curve (AUC) of RRI for predicting AKI ≥2 stage was 0.87 (P < 0.05); the cut-off > 0.71, sensitivity was 71% and specificity was 83%. The correlation analysis showed that RRI was positively correlated to a certain extent with IAP and lactic acid (r1 = 0.49, r2 = 0.39, both P < 0.05). CONCLUSIONS: High RRI on ICU admission was a significant predictor for development of severe AKI during the first week, and RRI can help predict the tendency of AKI in SAP.

p120 inhibits LPS/TNFα-induced endothelial Ang2 synthesis and release in an NF-κB independent fashion.

Adherens junction protein p120 is thought to be crucial for maintaining vascular integrity, which is important in many pathologies and diseases including atherosclerosis, vascular malformations, hemorrhagic stroke, sepsis and others. However, the mechanisms responsible for this is not completely understood. In this study, using an unbiased proteomics approach, followed by other experimental techniques, we identified that in HUVECs p120 overexpression inhibits LPS/TNFα-induced angiopoietin-2 (Ang2) expression, a key switch of endothelial destabilization. Interestingly, p120 overexpression did not inhibit LPS/TNFα-induced expression of adhesion molecules/cytokines including VCAM-1, ICAM-1, E-selectin, MCP-1, IL-8 and IL-6 in our experimental system. Furthermore, this p120-mediated repression of Ang2 is in an NF-κB independent manner, possibly via transcription factor Ets1. Our results demonstrate that p120 influences vascular integrity by secreted signals, providing new insights into the mechanisms of p120-mediated vascular stability.

VE-cadherin regulates migration inhibitory factor synthesis and release.

OBJECTIVE: Vascular endothelial (VE)-cadherin-mediated adherens junction is critical to maintain endothelial integrity. Besides its role of homophilic intercellular adhesion, VE-cadherin also has a role of outside-in signaling with functional consequences for vascular physiology. However, the nature of these signals remains not completely understood. MATERIALS AND METHODS: Human umbilical vein endothelial cells (HUVECs) were used in cell culture experiments. Confluent HUVECs were treated with VE-cadherin function-blocking antibodies BV9 (50 µg/ml) or IgG control. Antibody array was used to screen for cytokine/chemokine in supernatant. For VE-cadherin knockdown, siRNA transfection was used. ELISA, Western blot, and qRT-PCR were used to confirm the expression of screened cytokine/chemokine. To explore the possible mechanisms, Scr phosphorylation was detected and Scr inhibitor PP2 (1 µM) was used. To investigate in vivo relevance of the findings, BV9 and the indicated neutralizing antibodies were injected into mice and then lung vascular leak and inflammation were examined by Evans blue assay and lung tissue H&E, respectively. RESULTS: Using a non-biased, high-throughout human cytokine/chemokine antibody array, we first found that disruption of VE-cadherin-mediated adhesion by function-blocking antibody BV9 triggered the release of migration inhibitory factor (MIF). This VE-cadherin-mediated release of MIF further confirmed by ELISA with both VE-cadherin blocking antibody and siRNA technique was due to enhanced expression of MIF mRNA, which was mediated by Src kinase activation. In addition, in vivo lung vascular leak induced by VE-cadherin function-blocking antibody was partly alleviated by neutralizing MIF. CONCLUSIONS: VE-cadherin regulates MIF synthesis and release via Src kinase. Our data provide additional evidence to the concept that VE-cadherin transfers intracellular signals to coordinate the state of cell-cell adhesion with gene expression.

Metformin ameliorates endotoxemia-induced endothelial pro-inflammatory responses via AMPK-dependent mediation of HDAC5 and KLF2.

Exaggerated endothelial pro-inflammatory response is a hallmark in the early stage of sepsis and contributes to the subsequent tissue injury and organ failure. The anti-inflammatory effects of AMP-activated protein kinase (AMPK) activator metformin in sepsis has been revealed. However, the underlying mechanisms remain not fully understood. In the present study, the potential roles of histone deacetylase 5 (HDAC5) and kruppel-like factor 2 (KLF2) in the effects of metformin on endothelial pro-inflammatory responses were investigated. The results showed that metformin pretreatment increased the phosphorylation of HDAC5 at serine 498, leading to the upregulation of KLF2, and eliminated lipopolysaccharide (LPS) and tumor necrosis factor ⍺ (TNF⍺)-induced upregulation of vascular cell adhesion molecule 1 (VCAM1). Furthermore, the adhesion of HL60 leukocytes to endothelial monolayer was effectively inhibited by metformin. In addition, the in vivo data confirmed that AMPK activation attenuated local and systemic inflammation in endotoxic mice induced by LPS via mediating phosphorylating HDAC5 and restoring KLF2 expression. Our findings revealed that AMPK activation-mediated HDAC5 phosphorylation and KLF2 restoration is, at least partially, responsible to the anti-inflammatory effects of metformin in endotoxemia-induced endothelial cells, which has important implications for the future development of interfering therapies of sepsis.

The Glycolytic Enzyme PFKFB3 Controls TNF-α-Induced Endothelial Proinflammatory Responses.

Endothelial cells play an important role in health and a variety of diseases. Recent evidences show that endothelial cells rely on glycolysis rather than on oxidative phosphorylation to generate energy to support cellular functions such as angiogenesis. However, the effect of endothelial glycolysis on vascular inflammation remains little known. Here, we investigate the role of key glycolytic enzyme PFKFB3 in tumor necrosis factor-α (TNF-α)-induced endothelial proinflammatory responses. siRNAs were used to knockdown the expression of PFKFB3. In some experiments, PFKFB3 inhibitors were also used. TNF-α at 20 ng/ml was added to confluent endothelial cells for different time period of stimulation. PFKFB3 expression was examined by RT-PCR and western blotting. Cytokine antibody panel membranes were employed to detect different cytokines/chemokines in culture supernatant of endothelial cells. The determination of monocyte adhesion to endothelial cells after TNF-α treatment was conducted using THP-1 cells. The monocyte attraction was performed using Transwell filters. For further mechanisms, NF-κB-p65 localization was examined by immunofluorescence. Expression of total IκB, phospho-IκB, phospho-NF-κB-p65, and Ikkß was detected by western blotting. DNA-binding activity of NF-κB was assessed using electrophoretic mobility shift assay. We found that TNF-α increased endothelial PFKFB3 expression. Knockdown of PFKFB3 almost blocked all TNF-α-induced release of the proinflammatory cytokines/chemokines (MCP-1, IL-8, CXCL1, GMCSF, RANTES, TNF-α) and ICAM-1. PFKFB3 knockdown also significantly inhibited TNF-α-induced monocyte adhesion and transmigration. Furthermore, inhibition of PFKFB3 inhibited TNF-α-induced Ikkß phosphorylation, IκBα phosphorylation and degradation, NF-κB-p65 phosphorylation, nuclear translocation, and DNA-binding activity. Thus, our results demonstrate that glycolytic enzyme PFKFB3 plays a critical role in TNF-α-induced endothelial inflammation.

The Current Epidemiological Landscape of Ventilator-associated Pneumonia in the Intensive Care Unit: A Multicenter Prospective Observational Study in China.

Background: Ventilator-associated pneumonia (VAP) is among the most important hospital-acquired infections in the intensive-care unit setting. However, clinical data regarding the epidemiology of VAP in China are limited. Methods: A multicenter, longitudinal, observational study was performed from March 2013 to December 2015 to prospectively collect data on patients diagnosed with VAP. Specifically, patients supported by invasive mechanical ventilation for longer than 48 hours were included. Clinical data were recorded for each VAP patient. The exact pathogen distribution and the incidence of VAP were calculated. Risk factors associated with mortality were analyzed using univariate and multivariate regression analyses. Results: A total of 2492 patients received mechanical ventilation for longer than 48 hours and were enrolled in the study. A total of 129 (5.0%) patients fulfilled the VAP criteria, and 38 (29.5%) patients were diagnosed with early-onset VAP. The incidence of VAP was 4.5 per 1000 ventilation days, with a 28-day mortality rate of 45%. Individual pathogens, including 115 bacteria and 2 fungi, were identified in 117 (90.7%) enrollees, and 87 (75.7%) bacteria were multidrug-resistant organisms. Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa were the most commonly detected pathogens causing VAP. No difference in the distribution of pathogens was observed between early- and late-onset VAP or between surviving and non-surviving patients. Multivariate regression revealed that older ages and Sequential Organ Failure Assessment Scores were correlated with increased 28-day mortality rates. Conclusions: High pathogen resistance and mortality were found in both early- and late-onset VAP. Clinical Trials Registration: NCT01943331.

Endothelial microparticles activate endothelial cells to facilitate the inflammatory response.

Endothelial microparticles (EMPs) and endothelial cells (ECs) are involved in the pathophysiological mechanisms of sepsis and septic shock. EMPs are small vesicles released by ECs and are considered biomarkers for endothelial cell function and mediators for intercellular information exchange. However, the effect of EMPs on their parental ECs remains unknown. The present study collected tumor necrosis factor­α­derived EMPs and detected the proinflammatory cytokines released from unstimulated and EMP­stimulated ECs by proteome profiler array. This revealed that EMPs induce an inflammatory response in ECs. Within this response, interferon γ­induced protein 10 was revealed by ELISA to be associated with the activity of EMPs in a time­ and dose­dependent manner. It was hypothesized that the possible mechanism underlying this phenomenon was nuclear factor­κB. This was demonstrated to be crucial for the expression of IP­10 in EMP­stimulated ECs and the function of EMPs by immunofluorescence and western blot analysis. The present study enhances understanding of the involvement of EMPs and ECs in sepsis and will assist with the early diagnosis and treatment of sepsis.

Consensus development of core competencies in intensive and critical care medicine training in China.

BACKGROUND: The aim of this study is to develop consensus on core competencies required for postgraduate training in intensive care medicine. METHODS: We used a combination of a modified Delphi method and a nominal group technique to create and modify the list of core competencies to ensure maximum consensus. Ideas were generated modified from Competency Based Training in Intensive Care Medicine in Europe collaboration (CoBaTrICE) core competencies. An online survey invited healthcare professionals, educators, and trainees to rate and comment on these competencies. The output from the online survey was edited and then reviewed by a nominal group of 13 intensive care professionals to identify each competence for importance. The resulting list was then recirculated in the nominal group for iterative rating. RESULTS: The online survey yielded a list of 199 competencies for nominal group reviewing. After five rounds of rating, 129 competencies entered the final set defined as core competencies. CONCLUSIONS: We have generated a set of core competencies using a consensus technique which can serve as an indicator for training program development.

Sox9 activation is essential for the recovery of lung function after acute lung injury.

BACKGROUND/AIMS: Acute lung injury (ALI) often predisposes acute respiratory distress syndrome (ARDS) in humans, and is featured with neutrophilic alveolitis, injury of the alveolar epithelium and endothelium, hyaline membrane formation, and microvascular thrombi. Although the pathogenesis of ALI is relatively well studied, the knowledge on the molecular regulation of the post-ALI lung recovery are poorly understood. METHODS: Here, we used a widely applied bleomycin-induced ALI model to study the molecular mechanisms that underlie the post-ALI lung recovery in mice. We analyzed Sox9 expression in mouse lung by RT-qPCR, Western blot and immunohistochemistry. We analyzed miR-101 levels in mouse lung by RT-qPCR. We inhibited Sox9 in mouse lung by expressing either shRNA for Sox9 or miR-101, and analyzed the effects of Sox9 suppression on lung recovery. RESULTS: We detected a significant increase in Sox9 protein but not mRNA, and a signifcant decrease in miR-101 levels in the mouse lung after ALI. MiR-101 was found to target 3'-UTR of Sox9 mRNA to inhibit its expression. Sox9 inhibition by either shRNA for Sox9 or by miR-101 further impaired the functional recovery of the lung after ALI. CONCLUSION: Our data suggest that Sox9 activation is essential for the recovery of lung function after ALI, which highlights a previously unappreciated mechanism that controls the post-ALI lung recovery.

Sources of multidrug-resistant Acinetobacter baumannii and its role in respiratory tract colonization and nosocomial pneumonia in intensive care unit patients.

BACKGROUND: Multidrug-resistant Acinetobacter baumannii (MDRAB) is an important and emerging hospital-acquired pathogen worldwide. This study was conducted to identify the sources of MDRAB and its role in respiratory tract colonization and nosocomial pneumonia in intensive care unit (ICU) patients. METHODS: We conducted a prospective active surveillance study of MDRAB in three ICUs at a Chinese Hospital from April to August 2011, to identify the sources of MDRAB and its role in respiratory tract colonization and nosocomial pneumonia. RESULTS: One hundred and fourteen (13.0%) MDRAB isolates were detected from 876 specimens, with a sensitivity of 11.6% (55/474) in screening of the pharyngeal and tracheal swabs, and 14.7% (59/402) of the sputum/endotracheal aspirates. MDRAB colonization/infection was found in 34 (26.8%) of 127 patients, including 16 (12.6%) cases of pure colonization and 18 (14.2%) cases of pneumonia (two pre-ICU-acquired cases of pneumonia and 16 ICU-acquired cases of pneumonia). Previous respiratory tract MDRAB colonization was found in 22 (17.3%) patients: eight (6.3%) were pre-ICU-acquired colonization and 14 (11.0%) ICU-acquired colonization. Of eight pre-ICU-colonized patients, five were transferred from other wards or hospitals with hospitalization > 72 hours, and three came from the community with no previous hospitalization. Overall, 6/22 colonized patients presented with secondary pneumonia; only two (9.1%) colonized MDRAB strains were associated with secondary infections. Respiratory tract MDRAB colonization had no significant relationship with nosocomial pneumonia (P = 0.725). In addition, acute respiratory failure, mechanical ventilation, renal failure, and prior carbapenem use were risk factors for MDRAB colonization/infection. CONCLUSIONS: A high proportion of cases of MDRAB colonization/infection in ICU patients were detected through screening cultures. About one-third were acquired from general wards and the community before ICU admission. The low incidence of MDRAB colonization-related pneumonia questions the appropriateness of targeted antibiotic therapy.

Invasive candidiasis in intensive care units in China: a multicentre prospective observational study.

OBJECTIVES: To describe the epidemiology, microbiology and management of invasive Candida infection (ICI) in intensive care units (ICUs) in China. METHODS: A multicentre, prospective, observational study in 67 hospital ICUs across China. Patients were ≥18 years old with clinical signs of infection and at least one of the following diagnostic criteria: (i) histopathological, cytopathological or microscopic confirmation of yeast cells from a normally sterile site; (ii) at least one peripheral blood culture positive for Candida; and (iii) positive Candida culture from a normally sterile site. The China-SCAN study is registered with ClinicalTrials.gov (NCT T01253954). RESULTS: ICI incidence was 0.32% (306 patients/96,060 ICU admissions) and median time between ICU admission and diagnosis was 10.0 days. Candida albicans was the most prevalent single isolate (41.8% of patients), although non-albicans species accounted for the majority of infections. Diagnostic confirmation was based solely on at least one positive blood culture in 290 (94.8%) cases. Treatment was initiated after diagnostic confirmation in 166/268 (61.9%) patients. Triazoles (62.7%) and echinocandins (34.2%) were the most commonly used antifungal agents; first-line therapy was typically fluconazole (37.7%). The median duration of antifungal therapy was 14 days. The mortality rate was 36.6% (112/306); the median time between diagnosis and death was 14.5 days. Mortality was higher in older individuals, those with solid tumours, those with recent invasive mechanical ventilation and those with a higher sequential organ failure assessment score at diagnostic confirmation. Susceptibility to first-line antifungals was associated with lower mortality than dose-dependent susceptibility or complete resistance (P=0.008). CONCLUSIONS: More infections were caused by non-albicans than Candida albicans strains. The majority of patients were treated only after diagnostic confirmation, rather than empirically. First-line antifungal susceptibility was associated with lower mortality.

Effect of serum from patients with severe acute pancreatitis on vascular endothelial permeability.

OBJECTIVE: This study aimed to investigate the effect of serum taken from patients with severe acute pancreatitis (SAP) on vascular endothelial permeability. METHODS: The monolayer permeability of endothelial cells (ECs) was assessed. Morphological changes in ECs, induced by serum from patients with SAP were assessed. Expressions of RhoA, myosin light chain (MLC) phosphorylation, and VE-cadherin protein were detected by Western blot. RESULTS: Compared with the control group, 20% SAP serum significantly increased endothelial monolayer permeability (P < 0.01), markedly induced transcellular F-actin redistribution with stress fiber formation and VE-cadherin derangement with fragmentations located at the cell borders, and increased gaps between ECs. Furthermore, Western blotting showed that SAP serum induced rapid activation of Rho protein, and markedly increased the level of phosphorylated MLC. However, pretreatment with Y-27632 (an inhibitor for Rho kinase) significantly inhibited endothelial hyperpermeability and the morphological changes of F-actin rearrangement and VE-cadherin redistribution. This was associated with a down-regulation of Rho protein expression and a reduction in the level of MLC phosphorylation. CONCLUSIONS: The SAP serum induces the loss of vascular endothelial monolayer integrity, with endothelial F-actin stress fiber formation and VE-cadherin redistribution. One of the mechanisms for this process involves the activation of the Rho/Rho kinase signaling pathway.