Endothelial cAMP deactivates ischemia-reperfusion-induced microvascular hyperpermeability via Rap1-mediated mechanisms.

Approaches to reduce excessive edema due to the microvascular hyperpermeability that occurs during ischemia-reperfusion (I/R) are needed to prevent muscle compartment syndrome. We tested the hypothesis that cAMP-activated mechanisms actively restore barrier integrity in postischemic striated muscle. We found, using I/R in intact muscles and hypoxia-reoxygenation (H/R, an I/R mimic) in human microvascular endothelial cells (HMVECs), that hyperpermeability can be deactivated by increasing cAMP levels through application of forskolin. This effect was seen whether or not the hyperpermeability was accompanied by increased mRNA expression of VEGF, which occurred only after 4 h of ischemia. We found that cAMP increases in HMVECs after H/R, suggesting that cAMP-mediated restoration of barrier function is a physiological mechanism. We explored the mechanisms underlying this effect of cAMP. We found that exchange protein activated by cAMP 1 (Epac1), a downstream effector of cAMP that stimulates Rap1 to enhance cell adhesion, was activated only at or after reoxygenation. Thus, when Rap1 was depleted by small interfering RNA, H/R-induced hyperpermeability persisted even when forskolin was applied. We demonstrate that 1) VEGF mRNA expression is not involved in hyperpermeability after brief ischemia, 2) elevation of cAMP concentration at reperfusion deactivates hyperpermeability, and 3) cAMP activates the Epac1-Rap1 pathway to restore normal microvascular permeability. Our data support the novel concepts that 1) different hyperpermeability mechanisms operate after brief and prolonged ischemia and 2) cAMP concentration elevation during reperfusion contributes to deactivation of I/R-induced hyperpermeability through the Epac-Rap1 pathway. Endothelial cAMP management at reperfusion may be therapeutic in I/R injury.NEW & NOTEWORTHY Here, we demonstrate that 1) stimulation of cAMP production deactivates ischemia-reperfusion-induced hyperpermeability in muscle and endothelial cells; 2) VEGF mRNA expression is not enhanced by brief ischemia, suggesting that VEGF mechanisms do not activate immediate postischemic hyperpermeability; and 3) deactivation mechanisms operate via cAMP-exchange protein activated by cAMP 1-Rap1 to restore integrity of the endothelial barrier.

Impact of Acute Kidney Injury on Early to Long-Term Outcomes in Patients Who Underwent Surgery for Type A Acute Aortic Dissection.

Acute kidney injury (AKI) is relatively common after cardiothoracic surgery for type A acute aortic dissection (TA-AAD) and increases mortality. We investigated the incidence and risk factors for AKI in patients with TA-AAD and its impact on their outcomes. The records of 375 consecutive patients who underwent surgical treatment for TA-AAD from October 2007 to March 2013 were analyzed retrospectively. We defined AKI using the Kidney Disease Improving Global Outcomes criteria, which are based on serum creatinine concentration or glomerular filtration rate. We used Kaplan-Meier methods and multivariate Cox proportional hazards regression to assess the impact of AKI on both mortality and major adverse cardiovascular and cerebrovascular events. We also examined the association between risk factors and AKI using logistic regression modeling. Postoperative AKI was observed in 165 patients (44.0%). The overall 30-day and mid- to long-term mortality was 1.6% and 8.8%, respectively. Mortality and major adverse cardiovascular and cerebrovascular events correlated significantly with the severity of AKI, and multivariate analysis showed that AKI stage 3 (the most sever stage) was an independent risk factor for mortality (hazard ratio 6.83, 95% confidence interval 2.52 to 18.52) after adjustment for important confounding factors. Extracorporeal circulation time, body mass index, perioperative peak serum C-reactive protein concentration, renal malperfusion, and perioperative sepsis were found to be risk factors for AKI. In conclusion, AKI was common in patients who underwent surgery for type A acute aortic dissection. The severity of AKI strongly influences patient outcomes, so it should be recognized promptly and treated aggressively when possible.

Surgical repair for popliteal venous aneurysm causing severe or recurrent pulmonary thromboembolism: three case reports.

Poplitealvenous aneurysms (PVA) are associated with deep venous thrombosis and recurrentpulmonary thromboembolism (PE). We report three cases of PVA. In all three patients the first sign of PVA was acute PE; in one case, the PE was recurrent. Computed tomography and duplex ultrasonography revealed not only PE but also popliteal venous dilatation with thrombus. Surgical reconstruction was performed in each case after treatment for PE. No postoperative complications occurred, including recurrent PE. Surgical repair of PVA is safe and is a recommended treatment.

Prior cardiac and thoracic aortic surgery as a complication risk factor for abdominal aortic aneurysm repair.

BACKGROUND: Patients with both cardiothoracic lesions and abdominal aortic aneurysm (AAA) are increasing in Japan. The objective of this study was to clarify the effect of 2-staged surgery on complication rates. METHODS AND RESULTS: Three hundred and forty-six patients who underwent elective surgery for infrarenal AAA were entered. History of cardiac and thoracic aortic surgery within 1 year before AAA repair was recorded. A retrospective study regarding perioperative complications was performed. Operative mortality and complication rates were 0.6% and 10.7%, respectively. Seventy patients (20.2%) underwent prior cardiac and thoracic aortic surgery before AAA repair. There was no significant difference in preoperative characteristics between the group with prior cardiac and thoracic aortic surgery and the group without prior surgery. Significant risk factors for postoperative morbidity were: (1) prior cardiac and thoracic aortic surgery (odds ratio [OR] 2.5; 95%CI 1.1-5.1); (2) open aneurysm repair (OAR) (OR 2.7; 95%CI 1.3-5.1); and (3) VSG-CRI score ≥6 (OR 2.9; 95%CI 1.2-6.8). Subanalysis revealed that, although prior cardiac and thoracic aortic surgery was still a risk within patients undergoing OAR, it was not a risk factor for patients undergoing endovascular aneurysm repair (EVAR). CONCLUSIONS: Prior cardiac and thoracic aortic surgery carries high risk for AAA repair. To lower complication rates, we propose to perform EVAR on these patients if they are anatomically suitable.

Mitogen-activated protein kinases regulate platelet-activating factor-induced hyperpermeability.

OBJECTIVE: The authors tested the hypothesis that p42/44- (ERK-1/2) and/or p38-mitogen-activated protein kinases (MAPK) are in vivo regulatory elements in the platelet-activating factor (PAF) activated signaling cascade that stimulates microvascular hyperpermeability. METHODS: FITC-dextran 70 was used as the macromolecular tracer for microvascular permeability in the mouse mesenteric fat tissue. Interstitial integrated optical intensity (IOI) was used as an index of permeability. RESULTS: An application of 10(-7) M PAF increased IOI from 23.1 +/- 3.6 to 70.8 +/- 7.4 (mean +/- SEM). Inhibition of ERK-1/2 with 3 microM and 30 microM AG126 reduced IOI to 32.3 +/- 2.5. Similarly, inhibition of p38-MAPK with 6 nM, 60 nM and 600 nM SB203580 lowered IOI to 29.1 +/- 2.4. CONCLUSIONS: The results demonstrate that ERK-1/2 and p38MAPK participate in the signaling cascade that regulates PAF-induced microvascular hyperpermeability in vivo.

Clinical implication of plasma level of soluble fibrin monomer-fibrinogen complex in patients with abdominal aortic aneurysm.

OBJECTIVE: We prospectively studied the clinical implication of plasma level of soluble fibrin monomer (FM)-fibrinogen complex, a recently established molecular marker reflecting thrombin activity, in patients with abdominal aortic aneurysm (AAA) undergoing elective aortic repair. METHODS: The study included 49 patients who underwent elective aneurysm repair using a gelatin-sealed or nonimpregnated Dacron prosthesis. Plasma level of soluble FM-fibrinogen complex was measured before surgery and on days 1, 3, 5, 7, and 10 postoperatively by latex agglutination assay utilizing monoclonal antibody IF-43. Plasma levels of thrombin-antithrombin complex (TAT), D-dimer, alpha2-plasmin inhibitor-plasmin complex (PIC), and fibrinogen were also evaluated. RESULTS: The preoperative level of soluble FM-fibrinogen complex showed variation in the degree of hemostatic activation, with fair correlations with TAT (r = 0.509, P < .001), D-dimer (r = 0.521, P < .001), and PIC (r = 0.579, P < .001). The patients with greater intraoperative blood loss (> or = 800 mL) showed a significantly elevated plasma level of soluble FM-fibrinogen complex preoperatively compared with those with less intraoperative blood loss (P = .009). Its postoperative fluctuation showed a similar pattern to that of TAT, reflecting the time course of coagulation activity. Gelatin impregnation of the Dacron vascular graft did not seem to influence the postoperative systemic coagulation mechanism. CONCLUSIONS: The results indicated that soluble FM-fibrinogen complex appears to be a useful diagnostic molecular marker to assess the activity of the coagulation system, and that its preoperative level may serve as a potential risk factor for intraoperative hemorrhagic diathesis in patients undergoing elective AAA repair.

Ischemic preconditioning improves oxygenation of exercising muscle in vivo.

BACKGROUND: Ischemic preconditioning (IP) improves tissue tolerance to prolonged ischemia. In this study, we investigated the functional effect of IP on skeletal muscle of rat hind limb by means of near-infrared spectroscopy (NIRS) and by measuring myeloperoxidase (MPO) activity. MATERIALS AND METHODS: Adult male Sprague Dawley rats were divided into four separate protocol groups according to different preparations prior to 2 h of global ischemia: a group of ischemic reperfusion without any preparation (I/R), ischemic reperfusion with ischemic preconditioning (IP+IR), ischemic reperfusion with adenosine infusion (ADO+I/R), and sham operation. Ischemia and ischemic preconditioning were induced by clamping infrarenal abdominal aorta and left common iliac artery. For each rat, an exercise test of gastrocnemius muscles was performed by stimulating sciatic nerve before and after global ischemia while performing NIRS. MPO activity of ischemic muscles was also measured. RESULTS: Half-resaturation time after exercise and MPO activity were significantly improved in IP+IR and ADO+I/R groups. Difference of oxyhemoglobin during exercise was also improved in the IP+IR group. CONCLUSION: This study has demonstrated that IP provides the protective effect on in vivo skeletal muscle oxygenation during exercise.

Vascular endothelial growth factor stimulates differential signaling pathways in in vivo microcirculation.

Vascular endothelial growth factor (VEGF) induces mild vasodilation and strong increases in microvascular permeability. Using intravital microscopy and digital integrated optical intensity image analysis, we tested, in the hamster cheek pouch microcirculation, the hypothesis that differential signaling pathways in arterioles and venules represent an in vivo regulatory mechanism in the control of vascular diameter and permeability. The experimental design involved blocking specific signaling molecules and simultaneously assessing VEGF-induced changes in arteriolar diameter and microvascular transport of FITC-Dextran 150. Inhibition of Akt [indirectly via phosphatidylinositol 3-kinase with LY-294002 or wortmannin] or PKC (with bisindolylmaleimide) reduced VEGF-induced hyperpermeability. However, phosphatidylinositol 3-kinase/Akt inhibition enhanced the early phase and attenuated the late phase of VEGF-induced vasodilation, whereas blocking PKC had no effect. Inhibition of extracellular signal-regulated kinase (ERK)-1/2 (with PD-98059 or AG-126) also reduced VEGF-induced hyperpermeability but did not block VEGF-induced vasodilation. Blockade of endothelial nitric oxide synthase (with N(omega)-monomethyl-l-arginine) inhibited VEGF-induced changes in both permeability and diameter. Furthermore, immunofluorescence studies with human umbilical vein endothelial cells revealed that bisindolylmaleimide, PD-98059, and l-NMMA attenuate VEGF-induced reorganization of vascular endothelial cadherin. Our data demonstrate that 1) endothelial nitric oxide synthase is a common convergence pathway for VEGF-induced changes in arteriolar diameter and microvascular permeability; 2) PKC and ERK-1/2 do not play a major role in VEGF-induced vasodilation in the hamster cheek pouch microcirculation; and 3) Akt, PKC, and ERK-1/2 are elements of the signaling cascade that regulates VEGF-stimulated microvascular hyperpermeability. Our data provide evidence for differential signaling as a regulatory step in VEGF-stimulated microvascular dynamics.