Modification of postischemic increase of leukocyte adhesion and vascular permeability in the hamster by Iloprost

Guideline for in vivo assessment of adherent and rolling leukocytes in human skin microvasculature via reflectance confocal videomicroscopy

OBJECTIVE

To develop a guideline that reliably identifies cutaneous adherent and rolling leukocytes from mimicking scenarios via in vivo reflectance confocal videomicroscopy.

METHODS

We used a clinical reflectance confocal microscope, the VivaScope 1500, to acquire 1522 videos of the upper dermal microcirculation from 12 healthy subjects and 60 patients after allogeneic hematopoietic cell transplantation. Blinded to clinical information, two trained raters independently counted the number of adherent and rolling leukocytes in 88 videos. Based on discrepancies in the initial assessments, we developed a guideline to identify both types of leukocyte-endothelial interactions via a modified Delphi method (without anonymity). To test the guideline's ability to improve the inter-rater reliability, the two raters assessed the remaining 1434 videos by using the guideline.

RESULTS

We demonstrate a guideline that consists of definitions, a step-by-step flowchart, and corresponding visuals of adherent and rolling leukocytes and mimicking scenarios. The guideline improved the inter-rater reliability of the manual assessment of both interactions. The intraclass correlation coefficient (ICC) of adherent leukocyte counts increased from 0.056 (95% confidence interval: 0-0.236, n = 88 videos, N = 10 subjects) to 0.791 (0.770-0.809, n = 1434, N = 67). The ICC of rolling leukocyte counts increased from 0.385 (0.191-0.550, n = 88, N = 10) to 0.626 (0.593-0.657, n = 1434, N = 67). Intra-rater ICC post-guideline was 0.953 (0.886-0.981, n = 20, N = 12) and 0.956 (0.894-0.983, n = 20, N = 12) for adherent and rolling, respectively.

CONCLUSION

The guideline aids in the manual identification of adherent and rolling leukocytes via in vivo reflectance confocal videomicroscopy.

Babassu (Attalea glassmanii Zona) Nut Oil Is More Effective than Olive Oil for Treating Ischemia-Reperfusion Injury

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death in Western civilizations. The type of fatty acid which makes up the diet is related to the cardiovascular morbimortality and the formation of atheromas. Populations with high consumption of oils and fats have a higher number of deaths from CVD.

PURPOSE

In the present study, the objective was to comparatively analyze the microcirculatory effects of unrefined babassu oil with olive oil in microcirculation and liver of male hamsters of the species Mesocricetus auratus, checking the permeability to macromolecules after ischemia-reperfusion (I/R) without and with topical application of histamine 5 × 10-6 M. This is an experimental study, using as model the hamster's cheek pouch, which was prepared for intravital microscopy. The hamsters were divided into seven groups and orally treated for 14 days, twice a day (at 8 AM and 4 PM), orally received treatments in the following doses: unrefined babassu oil (BO) 0.02 mL/dose (group BO-2), 0.06 mL/dose (group BO-6), and 0.18 mL/dose (BO-18 group); extra virgin olive oil (OI) 0.02 mL/dose (group OI-2), 0.06 mL/dose (group OI-6), and 0.18 mL/dose (OI-18 group); and mineral oil (MO) 0.18 mL/dose (MO-18 group). The observations were made on the 15th day on the hamsters' cheek pouch; the increase of vascular permeability induced by I/R with and without histamine application was evaluated, and in the liver the biological material was collected aseptically then fixed in 10% buffered formalin.

RESULTS

Microcirculatory analyses showed a significant reduction in the number of leaks after I/R with and without the topical use of histamine in animals treated with unrefined BO 0.06 mL/dose (BO-6) and 0.18 mL/dose (BO-18) compared to animals treated with OI. The BO group (p < 0.001) presented a dose-response relationship for decreasing leaks after I/R with and without topical use of histamine. Histological liver analyses showed no fat deposition changes in any of the treatment groups. Phytochemical analyses evidenced a chemical compound (C31H60NO8) in unrefined BO but not in OI.

CONCLUSIONS

This experiment demonstrates the protective effect of unrefined BO on the microcirculatory system and its greater dose effect than that of OI. Finding a chemical compound (C31H60NO8) that is present in BO but not in OI opens the possibility of investigating whether this chemical compound was responsible for the protective effect on membrane permeability.

Bone marrow lesions and subchondral bone pathology of the knee

Bone marrow lesions (BMLs) around the knee are a common magnetic resonance imaging (MRI) finding. However, despite the growing interest on BMLs in multiple pathological conditions, they remain controversial not only for the still unknown role in the etiopathological processes, but also in terms of clinical impact and treatment. The differential diagnosis includes a wide range of conditions: traumatic contusion and fractures, cyst formation and erosions, hematopoietic and infiltrated marrow, developmental chondroses, disuse and overuse, transient bone marrow oedema syndrome and, lastly, subchondral insufficiency fractures and true osteonecrosis. Regardless the heterogeneous spectrum of these pathologies, a key factor for patient management is the distinction between reversible and irreversible conditions. To this regard, MRI plays a major role, leading to the correct diagnosis based on recognizable typical patterns that have to be considered together with coexistent abnormalities, age, and clinical history. Several treatment options have been proposed, from conservative to surgical approaches. In this manuscript the main lesion patterns and their management have been analysed to provide the most updated evidence for the differential diagnosis and the most effective treatment.

Effects of babassu nut oil on ischemia/reperfusion-induced leukocyte adhesion and macromolecular leakage in the microcirculation: observation in the hamster cheek pouch

Background

The babassu palm tree is native to Brazil and is most densely distributed in the Cocais region of the state of Maranhão, in northeastern Brazil. In addition to the industrial use of refined babassu oil, the milk, the unrefined oil and the nuts in natura are used by families from several communities of African descendants as one of the principal sources of food energy. The objective of this study was to evaluate the effects of babassu oil on microvascular permeability and leukocyte-endothelial interactions induced by ischemia/reperfusion using the hamster cheek pouch microcirculation as experimental model.

Methods

Twice a day for 14 days, male hamsters received unrefined babassu oil (0.02 ml/dose [BO-2 group], 0.06 ml/dose [BO-6 group], 0.18 ml/dose [BO-18 group]) or mineral oil (0.18 ml/dose [MO group]). Observations were made in the cheek pouch and macromolecular permeability increase induced by ischemia/reperfusion (I/R) or topical application of histamine, as well as leukocyte-endothelial interaction after I/R were evaluated.

Results

The mean value of I/R-induced microvascular leakage, determined during reperfusion, was significantly lower in the BO-6 and BO-18 groups than in the MO one (P < 0.001). In addition, histamine-induced increase of microvascular permeability was significantly less pronounced in BO groups compared to MO one. No significant differences among groups in terms of leukocyte adhesion, concentrations of tumor necrosis factor alpha, interleukin 1, and interleukin 6 were found.

Conclusions

Our findings suggest that unrefined babassu oil reduced microvascular leakage and protected against histamine-induced effects in postcapillary venules and highlights that these almost unexploited nut and its oil might be secure sources of food energy.

Prostacyclin treatment in severe traumatic brain injury: a microdialysis and outcome study

Prostacyclin (PGI(2)) is a potent vasodilator, inhibitor of leukocyte adhesion, and platelet aggregation. In trauma the balance between PGI(2) and thromboxane A(2) (TXA(2)) is shifted towards TXA(2). Externally provided PGI(2) would, from a theoretical and experimental point of view, improve the microcirculation in injured brain tissue. This study is a prospective consecutive double-blinded randomized study on the effect of PGI(2) versus placebo in severe traumatic brain injury (sTBI). All patients with sTBI were eligible.

INCLUSION CRITERIA

verified sTBI, Glasgow Coma Score (GCS) at intubation and sedation of <or=8, age 15-70 years, a first-recorded cerebral perfusion pressure (CPP) of >or=10 mm Hg, and arrival within 24 h of trauma. All subjects received an intracranial pressure (ICP) measuring device, bilateral intracerebral microdialysis catheters, and a microdialysis catheter in the abdominal subcutaneous adipose tissue. Subjects were treated according to an ICP-targeted therapy based on the Lund concept. 48 patients (mean age of 35.5 years and a median GCS of 6 [3-8]) were included. We found no significant effect of prostacyclin (epoprostenol, Flolan) on either the lactate-pyruvate ratio (L/P) at 24 h or the brain glucose levels. There was no significant difference in clinical outcome between the two groups. The median Glasgow Outcome Score (GOS) at 3 months was 4, and mortality was 12.5%. The favorable outcome (GOS 4-5) was 52%. The initial L/P did not prognosticate for outcome. Thus our results indicate that there is no effect of PGI(2) at a dose of 0.5 ng/kg/min on brain L/P, brain glucose levels, or outcome at 3 months.

Endothelin 1 and prostacyclin attenuate increases in hydraulic permeability caused by platelet-activating factor in rats

We have previously documented that endothelin 1 (ET-1) and prostacyclin (PGI2) decrease basal state hydraulic permeability (Lp). The aim of this study was to investigate the ability of ET-1 and PGI2 to modulate transendothelial fluid flux during situations in which Lp was artificially elevated with platelet-activating factor (PAF). We hypothesized that ET-1 and PGI2 administration before PAF exposure would prevent the increase in Lp secondary to PAF. In addition, in a potentially more clinically relevant situation, we also hypothesized that ET-1 and PGI2 administration after PAF exposure would attenuate the increase in Lp secondary to PAF. Microvascular Lp was measured in rat mesenteric postcapillary venules. Exposure to 10 nM PAF increased Lp 4-fold (P < 0.001). If the administration of 80 pM ET-1 or 10 microM PGI2 was completed before PAF exposure, no PAF-associated increase in Lp was observed (P < 0.001). The administration of ET-1 or PGI2 after PAF exposure attenuated the peak increase in Lp caused by PAF alone by 55% and 57%, respectively (P < 0.001). We conclude that ET-1 and PGI2 administration before PAF exposure prevents PAF-induced elevations in Lp, and in a more clinically relevant situation, ET-1 and PGI2 administered after PAF exposure attenuate the PAF-induced increase in Lp. Endothelin 1 and PGI2 receptors may provide important therapeutic targets for decreasing the microvascular fluid leak-associated morbidity resulting from shock and sepsis.

Prostacyclin reduces elevation of intracranial pressure and plasma volume loss in lipopolysaccharide-induced meningitis in the cat

BACKGROUND

Severe meningitis may compromise cerebral perfusion through increases in intracranial pressure (ICP) and through hypovolemia caused by a general inflammation with systemic plasma leakage. From its antiaggregative/antiadhesive and permeability-reducing properties, prostacyclin (PGI2) is a potential adjuvant treatment in meningitis, but previously published data have been ambiguous. The objective of this study was to evaluate the effects of PGI2 on meningitis on ICP, plasma volume, blood pressure, and cerebral oxidative metabolism.

METHODS

Meningitis was induced by intrathecal injection of lipopolysaccharide (LPS, 0.8 x 10 units/kg) in cats. Four hours after the injection, the animals were randomized to intravenous treatment with either low-dose PGI2 (1 ng/kg/min) or the vehicle for 6 hours (n = 7 in each group). No LPS and no PGI2 or vehicle was given to three cats (sham group). Effects of treatment on ICP, mean arterial pressure, plasma volume (I-albumin technique), and brain tissue lactate/pyruvate ratio (microdialysis technique) were evaluated.

RESULTS

ICP increased from 10.0 mm Hg +/- 1.3 mm Hg and 10.8 mm Hg +/- 1.7 mm Hg to 19.9 mm Hg +/- 1.7 mm Hg and 19.6 mm Hg +/- 3.3 mm Hg in the PGI2 and the vehicle group, respectively, 4 hours after the LPS injection (not significant). ICP increased further to 21.8 mm Hg +/- 4.5 mm Hg and to 25.8 mm Hg +/- 6.0 mm Hg after treatment for 6 hours with PGI2 or vehicle, respectively (p < 0.05). There was no significant difference in arterial pressure between groups. Plasma volume loss was less in the PGI2 group than in the vehicle group at the end of the experiment and urine production and arterial oxygenation was higher in the PGI2 group. Lactate/pyruvate ratio was within the normal range in all groups.

CONCLUSION

Low-dose PGI2 may be a beneficial adjuvant therapy for meningitis by reducing elevation of ICP and plasma volume loss.

Rationale for prostaglandin I2 in bone marrow oedema--from theory to application

Introduction

Bone marrow oedema (BME) and avascular osteonecrosis (AVN) are disorders of unclear origin. Although there are numerous operative and non-operative treatments for AVN, pain management in patients with AVN remains challenging. Prostaglandins play an important role in inflammatory responses and cell differentiation. It is thought that prostaglandin I₂ ([PGI₂] or synonoma prostacyclin) and its analogues promote bone regeneration on a cellular or systemic level. The purpose of this study was to assess the curative and symptomatic efficacy of the prostacyclin analogue iloprost in BME and AVN patients.

Method

We are reporting on 50 patients (117 bones) affected by BME/AVN who were treated with iloprost. Pain levels before, during and 3 and 6 months after iloprost application were evaluated by a visual analogue scale (VAS). The short form(SF)-36 health survey served to judge general health status before and after treatment. Harris Hip Score (HHS) and Knee Society Score (KSS) were performed as functional scores and MRI and X-rays before and 3 and 6 months after iloprost application served as objective parameters for morphological changes of the affected bones.

Results

We found a significant improvement in pain, functional and radiological outcome in BME and early AVN stages after iloprost application, whereas patients with advanced AVN stages did not benefit from iloprost infusions. Mean pain level decreased from 5.26 (day 0) to 1.63 (6 months) and both HHS and KSS increased during follow-up. Moreover, the SF-36 increased from 353.2 (day 0) to 560.5 points (6 months). We found a significant decrease in BME on MRI scans after iloprost application.

Conclusions

In addition to other drugs, iloprost may be an alternative substance which should be considered in the treatment of BME/AVN-associated pain.

Increased cortical cell loss and prolonged hemodynamic depression after traumatic brain injury in mice lacking the IP receptor for prostacyclin

Prostacyclin is the major arachidonic acid metabolite of the vascular endothelium and is produced mainly via the cyclooxygenase-2 pathway. By acting on the prostacyclin (IP) receptor on platelets and vascular smooth muscle cells, prostacyclin exerts vasodilatory and antiaggregative/antiadhesive effects. Previous studies have shown that prostacyclin production increases after brain trauma, but the importance of prostacyclin for posttraumatic hemodynamic alterations and neuron survival has not been investigated. This study evaluated if endogenous prostacyclin plays a role in the pathophysiologic process in the brain after brain trauma. This was performed by comparing prostacyclin (IP) receptor-deficient (IP(-/-)) mice and mice with functional IP receptor (IP(+/+)) after a controlled cortical injury regarding contusion volume, cerebral blood flow ([(14)C]iodoantipyrine autoradiography), number of perfused capillaries (fluorescein isothiocyanate-dextran fluorescence technique), the transfer constant (K(i)) for [(51)Cr]EDTA, and brain water content (wet vs dry weight) in the injured and contralateral cortex. Contusion volume was increased in IP(-/-) mice compared with IP(+/+) mice. Three hours after trauma, cortical blood flow was decreased in the injured cortex of both groups and the reduction in blood flow in the cortex of the IP(-/-) mice persisted from 3 to 24 h, whereas blood flow approached normal values in the IP(+/+) mice after 24 h. No differences could be detected between the two genotypes regarding other hemodynamic parameters. We conclude that the prostacyclin IP receptor is beneficial for neuron survival after brain trauma in mice, an effect that may be mediated by improved cortical perfusion.

Interplay between parasite cysteine proteases and the host kinin system modulates microvascular leakage and macrophage infection by promastigotes of the Leishmania donovani complex

Kinins, the vasoactive peptides proteolytically liberated from kininogens, were recently recognized as signals alerting the innate immune system. Here we demonstrate that Leishmania donovani and Leishmania chagasi, two etiological agents of visceral leishmaniasis (VL), activate the kinin system. Intravital microscopy in the hamster cheek pouch showed that topically applied promastigotes induced macromolecular leakage (FITC-dextran) through postcapillary venules. Peaking at 15 min, the parasite-induced leakage was drastically enhanced by captopril (Cap), an inhibitor of angiotensin-converting enzyme (ACE), a kinin-degrading metallopeptidase. The enhanced microvascular responses were cancelled by HOE-140, an antagonist of the B2 bradykinin receptor (B2R), or by pre-treatment of promastigotes with the irreversible cysteine proteinase inhibitor N-methylpiperazine-urea-Phe-homoPhe-vinylsulfone-benzene (N-Pip-hF-VSPh). In agreement with the above-mentioned data, the promastigotes vigorously induced edema in the paw of Cap-treated J129 mice, but not Cap-B2R-/- mice. Analysis of parasite-induced breakdown of high molecular weight kininogens (HK), combined with active site-affinity-labeling with biotin-N-Pip-hF-VSPh, identified 35-40 kDa proteins as kinin-releasing cysteine peptidases. We then checked if macrophage infectivity was influenced by interplay between these kinin-releasing parasite proteases, kininogens, and kinin-degrading peptidases (i.e. ACE). Our studies revealed that full-fledged B2R engagement resulted in vigorous increase of L. chagasi uptake by resident macrophages. Evidence that inflammatory macrophages treated with HOE-140 became highly susceptible to amastigote outgrowth, assessed 72 h after initial macrophage interaction, further suggests that the kinin/B2R activation pathway may critically modulate inflammation and innate immunity in visceral leishmaniasis.

Endothelin-1 decreases postcapillary fluid efflux via prostacyclin release

BACKGROUND

Endothelin-1 (ET-1) decreases water efflux across the endothelial barrier (Lp). ET-1 may exert this permeability-decreasing effect by stimulating prostacyclin (PGI2) release. The purposes of this study were to (1) examine the effect of PGI2 on Lp, (2) measure Lp after inhibition of PGI(2) synthesis, and (3) determine the effect of ET-1 on Lp during inhibition of PGI2 production.

METHODS

After microscopic cannulation of mesenteric venules, Lp was measured during PGI2 infusion (0.1 micromol/L, 1 micromol/L, and 10 micromol/L; n = 6 in each group). Lp was also measured after 100 micromol/L of the PGI2 synthase inhibitor, tranylcypromine (TCPN) (n = 6). Finally, the influence of ET-1 on Lp during PGI2 synthase inhibition was assessed (n = 6).

RESULTS

Compared to baseline Lp of 1.05 +/- 0.06, PGI2 decreased Lp at 1 micromol/L (Lp = 0.63 +/- 0.03, P < .003) and 10 micromol/L (Lp = 0.52 +/- 0.04, P < .0001). TCPN increased Lp compared to baseline (P < .0001). Compared to ET-1 alone, venules perfused with TCPN + ET-1 increased Lp (P < .005). Units for Lp ) are 10(-7) cm x sec(-1) x cmH2O(-1).

CONCLUSIONS

We found that (1) PGI2 decreases Lp, (2) inhibition of PGI2 synthesis increases Lp, and (3) permeability-decreasing effects of ET-1 can be blocked by inhibiting PGI2 synthesis. These data suggest that constitutive production of PGI2 modulates basal microvessel permeability and that ET-1 may exert its permeability-decreasing effect via the stimulation of PGI2 release.

Microvascular in vivo assessment of reperfusion injury: significance of prostaglandin E1 and I2 in postischemic “no-reflow” and “reflow-paradox”

BACKGROUND

Microvascular ischemia-reperfusion (I/R) injury is characterized by failure of capillary perfusion ("no-reflow") and reoxygenation-associated phenomena ("reflow-paradox"), including activation of leukocyte-endothelium interaction with cytotoxic mediator-induced loss of endothelial integrity. The objectives of this study were to elucidate the impact of both prostaglandins E(1) (PGE(1)) and I(2) (PGI(2)) in microvascular reperfusion injury, with special focus on the distinct pathophysiology of no-reflow- and reflow-paradox phenomena.

MATERIALS AND METHODS

By use of the hamster dorsal skinfold preparation and in vivo fluorescence microscopy, the microcirculation of a striated skin muscle was assessed before 4 h of pressure-induced ischemia and 0.5, 2, and 24 h after onset of reperfusion.

RESULTS

I/R was characterized by enhanced leukocyte-endothelium interaction in postcapillary venules, increase of macromolecular leakage, and reduction of functional capillary perfusion (P < 0.05). Intravenous 2-h infusion of PGE(1), starting with onset of reperfusion, reduced leukocyte adhesion and macromolecular leakage in postcapillary venules during early reperfusion (P < 0.05), while 6-h infusion, given during ischemia and early reperfusion, showed no significant effects. PGI(2) infusion also attenuated postischemic leukocyte adhesion, which was significant by a 6-h prolonged administration (P < 0.05), but did not influence the increase of microvascular permeability. Both prostaglandins were unable to prevent the postischemic failure of capillary perfusion (no-reflow).

CONCLUSIONS

Both prostaglandins did not significantly influence postischemic no-reflow phenomena, but appeared as potent inhibitors of reflow-paradox under the experimental circumstances of this study.

Low-Dose Prostacyclin Restores an Increased Protein Permeability after Trauma in Cat Skeletal Muscle

BACKGROUND

Increased microvascular permeability inducing leakage of plasma from the intravascular to the extravascular space after trauma is a pathophysiologic event of great clinical significance. A substance reducing an increased microvascular permeability, and especially an increased protein permeability, therefore could be of value to maintain normovolemia and to reduce the need for plasma substitution. Prostacyclin is suggested to have permeability-reducing properties as shown for fluid permeability, but its effects on protein permeability, which may be controlled by partly different mechanisms, are unclear. The present study evaluates whether prostacyclin at a low, clinically relevant, nonvasodilating dose can reestablish an increased protein permeability after trauma.

METHODS

The study was randomized, blinded, and performed on surgically traumatized, autoperfused, and denervated cat calf muscle. Relative changes in the osmotic reflection coefficient for albumin after 1.5 hours of prostacyclin (1 ng/min/kg) (n = 7) or vehicle (n = 7) treatment were used as a measure of altered protein permeability from a state of increased permeability after trauma.

RESULTS

We found that the osmotic reflection coefficient for albumin was increased by about 35% in the prostacyclin group compared with the vehicle-treated group (p < 0.001).

CONCLUSION

If applicable to humans, prostacyclin is a potential therapy for reducing plasma leakage in the critically ill trauma patient by restoring permeability from an increased level.

Reperfusion of ischemic corporal tissue: physiologic and biochemical changes in an animal model of ischemic priapism

OBJECTIVES

To assess the physiologic and biochemical changes resulting from ischemia and reperfusion. Effective therapy for ischemic priapism reestablishes corporal venous outflow and arterial inflow and results in increased corporal partial pressure of oxygen. Data are limited concerning reperfusion injury of ischemic erectile tissue associated with reactive oxygen species (ROS) and the potential role of ROS scavengers in the clinical therapy of ischemic priapism.

METHODS

Anesthetized adult New Zealand white male rabbits (n = 7) were exposed to a low oxygen tension breathing gas to achieve hypoxia within the corpora cavernosa. This resulted in a mean systemic oxygen saturation of 60%. The pelvic nerve was electrically stimulated to induce penile erection, and the base of the erect penis was clamped. After varying durations of ischemia, the clamp was removed to allow reperfusion. We determined the intracavernosal oxygen tension, histologic changes, myeloperoxidase activity, and lipid peroxidation.

RESULTS

Corporal partial pressure of oxygen progressively decreased as the duration of priapism increased. A statistically significant increase was noted in myeloperoxidase activity and lipid peroxidation with corporal reperfusion. Polymorphonuclear leukocyte infiltration was documented in the ischemic reperfused tissue.

CONCLUSIONS

In the management of ischemic priapism, reperfusion causes erectile tissue injury owing to the presence of ROS. There is a need to investigate the utility of ROS scavengers and antioxidants in the management of ischemic priapism.

Low-dose prostacyclin improves cortical perfusion following experimental brain injury in the rat

It was recently shown that prostacyclin at a low dose reduces cortical cell death following brain trauma in the rat. Conceivably, prostacyclin with its vasodilatory, anti-aggregatory, anti-adhesive and permeability-reducing properties improved a compromised perfusion caused by post-traumatic vasoconstriction, microthrombosis and increased microvascular permeability. The objective of the present study was therefore to investigate the hemodynamic effects of low-dose prostacyclin in the traumatized rat cortex. Following a fluid percussion brain injury or a sham procedure, animals were treated with a continuous intravenous infusion of prostacyclin of 1 or 2 ng x kg(-1) x min(-1), or vehicle. Blood flow ([(14)C]-iodoantipyrine), the permeability-surface area product (PS) for [(51)Cr]-EDTA, and brain water content were measured after 3 or 48 h of treatment. Blood flow values in the injured cortex were transiently reduced to 0.42 +/- 0.2 mL x min(-1) in the vehicle group 3 h following trauma from a corresponding value of about 1.6 mL x min(-1) in the sham group, with recovery of blood flow after 48 h. Prostacyclin treatment caused a dose-dependent increase in blood flow which reached statistical significance 48 h following trauma. Brain water content and PS increased in the injured cortex post trauma and the higher dose of prostacyclin increased these parameters further at 48 h compared to the vehicle group (p < 0.05). The latter effects of prostacyclin cannot be attributed to an increase in permeability, as prostacyclin did not influence PS or brain water content following sham trauma. In fact prostacyclin has been shown to have permeability-decreasing properties. We conclude that prostacyclin improves cortical perfusion following brain trauma. The simultaneous aggravation of brain edema can be explained by an increased surface area, perhaps in combination with increased capillary hydrostatic pressure.

Endothelin-1 reduces microvascular fluid permeability through secondary release of prostacyclin in cat Skeletal muscle

The aim of the study was to analyze effects of various plasma concentrations of the vasoconstrictor endothelin-1 on microvascular fluid permeability and on transcapillary fluid exchange. We also analyzed whether the permeability-reducing substance prostacyclin is involved in the permeability effects of endothelin-1, as prostacylin is suggested to be released via ET(B) receptor stimulation. The study was performed on an autoperfused cat calf muscle preparation, and a capillary filtration coefficient (CFC) technique was used to estimate variations in microvascular fluid permeability (conductivity). Intraarterial infusion of endothelin-1 in low doses (5 and 10 ng/min/100 g muscle) caused transcapillary absorption, whereas higher doses (20-40 ng/min/100 g) induced filtration despite further vasoconstriction. Low-dose endothelin-1 had no significant effect on CFC, while CFC was reduced to at most 55% of baseline at higher doses (P < 0.01). Simultaneous local intraarterial infusion of the prostacyclin synthesis inhibitor tranylcypromine restored CFC to 114% of baseline (P < 0.01) and further increased vascular resistance. A low, non-vasodilator dose of prostacyclin given intravenously counteracted the tranylcypromine effect on CFC. The decreased CFC induced by a high dose of endothelin-1 was counteracted by the ET(B) receptor antagonist BQ-788 with no change in vascular resistance (P < 0.05). We conclude that the decreased CFC following high doses of endothelin-1 can be attributed to a decrease in microvascular hydraulic conductivity, mediated by secondary release of prostacylin via stimulation of the ET(B) receptor. Endothelin-1 may induce edema through postcapillary vasoconstriction.

Effects of L-NA and sodium nitroprusside on ischemia/reperfusion-induced leukocyte adhesion and macromolecular leakage in hamster cheek pouch venules

Our objective was to study how the topical application of a nitric oxide synthase inhibitor (l-NA, Nomega-nitro-L-arginine) and a nitric oxide donor, sodium nitroprusside (SNP), could modulate leukocyte adhesion (sticking) and microvascular permeability as altered by ischemia/reperfusion (I/R) and topically applied histamine after I/R. Golden hamsters were prepared for intravital microscopy. Ischemia was induced by an inflatable silicon rubber cuff mounted around the neck of the cheek pouch prepared for intravital microscopy. Saline, L-NA, sodium nitroprusside, and histamine were applied in the superfusion solution. FITC-dextran was injected iv 30 min before initiation of ischemia as a marker of microvascular permeability. L-NA 10(-5) M inhibited both the increase in number of sticking leukocytes and the increase in vascular permeability after I/R compared with the untreated control group of hamsters. SNP neutralized this effect of L-NA on leukocytes and vascular permeability and caused arteriolar dilation at the concentration used, 10(-6) M. Both SNP and L-NA + SNP enhanced the I/R-induced macromolecular leakage. The topical application of SNP and SNP + L-NA did not modify the response to histamine after I/R compared with the untreated control group. In hamsters not subjected to I/R, histamine-induced macromolecular leakage was inhibited by L-NA and L-NA + SNP but was unchanged by SNP. It is concluded that inhibition of nitric oxide formation by L-NA reduced both leukocyte adhesion in postcapillary venules and the increase in macromolecular leakage and that a NO donor such as SNP could enhance the macromolecular leakage response to I/R.

Infusion of prostacyclin following experimental brain injury in the rat reduces cortical lesion volume

Endothelial-derived prostacyclin is an important regulator of microvascular function, and its main actions are inhibition of platelet/leukocyte aggregation and adhesion, and vasodilation. Disturbances in endothelial integrity following traumatic brain injury (TBI) may result in insufficient prostacyclin production and participate in the pathophysiological sequelae of brain injury. The objective of this study was to evaluate the potential therapeutic effects of a low-dose prostacyclin infusion on cortical lesion volume, CA3 neuron survival and functional outcome following TBI in the rat. Anesthetized animals (sodium pentobarbital, 60 mg/kg, i.p.) were subjected to a lateral fluid percussion brain injury (2.5 atm) or sham injury. Following TBI, animals were randomized to receive a constant infusion of either prostacyclin (1 ng/kg x min(-1) i.v.) or vehicle over 48 h. All sham animals received vehicle (n = 6). Evaluation of neuromotor function, lesion volume, and CA3 neuronal loss was performed blindly. By 7 days postinjury, cortical lesion volume was significantly reduced by 43% in the prostacyclin-treated group as compared to the vehicle treated group (p < 0.01; n = 12 prostacyclin, n = 12 vehicle). No differences were observed in neuromotor function (48 h and 7 days following TBI), or in hippocampal cell loss (7 days following TBI) between the prostacyclin- and vehicle-treated groups. We conclude that prostacyclin in a low dose reduces loss of neocortical neurons following TBI and may be a potential clinical therapeutic agent to reduce neuronal cell death associated with brain trauma.

Prostacyclin reduces microvascular fluid conductivity in cat skeletal muscle through opening of ATP-dependent potassium channels

Prostacyclin is suggested to reduce microvascular permeability, but the cellular mechanisms mediating this response in the microvascular endothelial cells are still unknown. Considering that prostacyclin relaxes vascular smooth muscle cells via opening of ATP-dependent potassium channels, and opening of ATP-dependent potassium channels in the endothelial cells is suggested to influence microvascular permeability, this study was designed to test (1) if ATP-dependent potassium channels are involved in the regulation of microvascular hydraulic permeability, (2) if the permeability-reducing effect of prostacyclin is mediated through opening of ATP-dependent potassium channels, and (3) if cAMP is involved in this process. An autoperfused cat calf hindlimb was used as experimental model, and microvascular hydraulic permeability (conductivity) was estimated by a capillary filtration coefficient (CFC) technique. The potassium channel opener PCO-400 (0.5 microg x min(-1) per 100 g muscle, intra-arterially), prostacyclin (1 ng x min(-1) per kg body weight, intravenously) and the cAMP analogue dibutyryl-cAMP (24 microg x min(-1) per 100 g muscle, intra-arterially), decreased CFC to 77, 72 and 69% compared to control, respectively (p < 0.01). The decrease in CFC obtained by these substances was completely restituted after the start of a simultaneous infusion of the ATP-dependent potassium channel blocker glibenclamide (6 microg x min(-1) per 100 g muscle, intra-arterially; p < 0.01). Infusion of glibenclamide alone increased CFC to 107% of control (p < 0.05). In conclusion, the ATP-dependent potassium channels contribute to the regulation of microvascular hydraulic conductivity, and the prostacyclin permeability-reducing effect may act through this mechanism via increase in intracellular cAMP.

Antioxidative properties of organotellurium compounds in cell systems

The protective/antioxidative properties of diaryl tellurides were demonstrated in cellular systems of increasing complexity. In the presence of glutathione, bis(4-hydroxyphenyl) telluride (1a), bis(4-aminophenyl) telluride (1d) and bis(2-carboxyphenyl) telluride (1h) reduced by more than 50% t-butyl hydroperoxide-induced cell death in lung fibroblast cultures at concentrations below 2 microM. Bis(2,6-dimethyl-4-hydroxyphenyl) telluride (2b) reduced by more than 50% leukocyte-mediated and phorbol-12-myristate-13-acetate-stimulated damage to Caco-2 cells at 0.1 microM concentration. As judged by their abilities to reduce formation of thiobarbituric acid reactive substances at concentrations close to 1 microM, diaryl tellurides 1a, 1d and 2b protected rat kidney tissue against oxidative damage caused by anoxia and reoxygenation. The organotellurium compounds also offered protection after systemic administration. In the presence of diaryl telluride 2b (0.1-1 microM), the ischemia/reperfusion-induced vascular permeability increase in the hamster cheek pouch was significantly reduced as compared with the control. Some of the most active organotellurium cell protectants were evaluated for their ability to inhibit formation of the inflammatory mediators leukotriene B4 and interleukin-1beta. An inhibitory effect on the secretion of these species was seen for compounds 1a and 2b at or above 10 microM concentrations. The protective effects of diaryl tellurides against t-butyl hydroperoxide-induced cell injury can be ascribed mainly to the peroxide-decomposing, glutathione peroxidase-like capacity of the compounds. The chain-breaking, electron- or hydrogen atom-donating ability of diaryl tellurides seems to be the main reason for their protection against leukocyte-mediated cell damage in Caco-2 cells and in the oxidatively challenged rat kidney and hamster cheek pouch.

Soluble selectins and ICAM-1 modulate neutrophil-endothelial adhesion and diapedesis in vitro

We observed that normal plasma dramatically reduces neutrophil-endothelial adhesion. Therefore, we identified factors in plasma which might limit PMN adhesion in vitro. We found that the anti-adhesive effect was not mediated by vasoactive lipids present in plasma. Immunoprecipitation of soluble adhesion molecules, P and E-selectins and ICAM-1 restored PMN adhesion to control values. We further examined whether soluble adhesion molecules in plasma might also regulate PMN endothelial migration in response to fMLP (10(-6) M). Plasma significantly reduced PMN migration, and this effect was prevented only by the simultaneous removal of soluble P and E selectins and ICAM-1 together, but not individually. These data show that soluble selectins and ICAM-1 may regulate PMN adhesion and diapedesis, and that alterations in the levels of these molecules may regulate PMN-endothelial interactions in vivo.

Effects of oral administration of purified micronized flavonoid fraction on increased microvascular permeability induced by various agents and on ischemia/reperfusion in the hamster cheek pouch

The effects of a clinically used purified micronized flavonoid fraction (S 5682) containing 90% diosmin and 10% hesperidin on increased microvascular permeability induced by histamine, bradykinin, and leukotriene B4 (LTB4) were investigated by intravital microscopy in the hamster cheek pouch preparation. The authors also investigated the effects of S 5682 on macromolecular permeability increase and leukocyte adhesion during ischemia-reperfusion by using the same preparation. S 5682, suspended in 10% lactose solution, or vehicle (10% lactose) was administered orally to male hamsters for ten days at 20 mg/kg/day (10 mg/kg twice a day). Fluorescein isothiocyanate (FITC)-labeled dextran (mol wt 150,000) was given intravenously, thirty minutes after completion of the cheek pouch preparation. The leukocytes were stained by continuous IV infusion of acridine orange (0.5 mg/kg/minute). Histamine (2 microM), bradykinin (1 microM), and LTB4 (0.01 microM), applied topically for five minutes, increased the number of fluorescent vascular leakage sites in postcapillary venules. A temporary ischemia with total circulatory arrest of the cheek pouch was obtained by clamping the neck of the everted pouch. The maximum number of leaky sites (per cm2 in the prepared area) that occurred either at five minutes after the beginning of each topical application or ten minutes after the onset of reperfusion was quantified in ultraviolet light microscopy. The results from 60 animals divided into 10 groups of 6 animals each are presented as means +/- SEM. In comparison with vehicle, S 5682 significantly inhibited the macromolecular permeability increasing effect of histamine (343.5 +/- 22.3 versus 207.5 +/- 32.0 leaks/cm2; P < 0.01), bradykinin (345.2 +/- 19.0 versus 206.2 +/- 21.6 leaks/cm2; P < 0.01), and LTB4 (353.3 +/- 27.5 versus 242.7 +/- 33.6 leaks/cm2; P < 0.05). At reperfusion, after thirty minutes of ischemia, S 5682 significantly decreased the observed macromolecular permeability (103.6 +/- 15.4 versus 42.6 +/- 9.3 leaks/cm2; P < 0.01). Flavonoid-treated animals also displayed a statistically significant lower number of adhering leukocytes to the venular endothelium (83.5 +/- 9.5 versus 48.4 +/- 12.3 per 6 mm2; P < 0.05). These results demonstrate that oral administration of S 5682 for ten days at 20 mg/kg body weight/day had a protective effect against leakage of macromolecules after application of permeability-increasing substances and during ischemia-reperfusion in the cheek pouch microvasculature. Since firm leukocyte attachment to the endothelial wall and subsequent emigration of leukocytes into the interstitium is a mechanism for tissue damage during inflammation, attenuation of this phenomenon during conditions of ischemia-reperfusion can in part explain previous observations that this purified micronized flavonoid fraction decreases edema formation. The present data illustrating the inhibitory effect of a clinically relevant dose of S 5682 on the inflammatory processes induced in this in vivo model of microcirculation may serve as a rational basis to explain its clinical efficacy.

Microvascular reactivity after ischemia/reperfusion in the hamster cheek pouch: beneficial effects of different oral doses of S-5682 (Daflon 500 mg)

Daflon 500 mg (S-5682) is a purified, micronized flavonoid fraction containing 90% diosmin and 10% hesperidin that is currently used to treat chronic venous insufficiency and hemorrhoidal disease. Thus, it seemed of interest to evaluate the effects of S-5682 on ischemia/reperfusion, ie, the changes in mean internal diameter and blood flow of arterioles and venules and the functional capillary density (FCD) during reperfusion after ninety minutes of total ischemia in the hamster cheek pouch microvasculature. Different doses of S-5682 (5, 20, 80, and 160 mg/kg body weight/day), suspended in 10% lactose solution or vehicle (10% lactose) were administered orally to male hamsters for ten days twice a day. The cheek pouch preparation was placed under an intravital microscope coupled to a closed-circuit TV system. A ninety-minute local ischemia was obtained by a cuff mounted around the neck of the everted pouch where it left the mouth of the hamster. Mean arteriolar and venular internal diameters were determined by means of an image-shearing device, IPM model 907; red blood cell (RBC) velocity was measured by the dual-slit photometric technique; microvessel volume flow was calculated from diameters and RBC velocities; and FCD was defined as the number of red-cell-perfused capillaries per observation field. During reperfusion, placebo-treated animals showed significant vasodilatation concomitant with a decrease in blood flow and FCD compared with preischemic values and an impairment of the myogenic response. In S-5682-treated animals, there was a significant dose-dependent improvement in all these parameters including the myogenic tonus. These results clearly demonstrated that oral administration of different doses of S-5682 for ten days improved the microvascular reactivity and FCD after ischemia/reperfusion in a dose-dependent fashion in the hamster cheek pouch microvasculature.

Effects of hypoxia/reoxygenation on aortic vasoconstrictor responsiveness

The purpose of the present study was to assess the effects of hypoxia/reoxygenation (H/R) on vasoconstrictor effectiveness, in vitro. Aortic rings were obtained from rats and placed on isometric force transducers in oxygenated Krebs buffer (95% O2/5% CO2, PO2 > 500 torr). Cumulative concentration/effect relationships to norepinephrine, G-protein activation by AlICl3/NaF, depolarization by KCl or BayK-8644, mobilization of intracellular calcium by caffeine, and protein kinase C activation by l-indolactam were evaluated. Hypoxia (PO2 < 5 torr) was induced by rapidly bubbling the Krebs buffer with 95% N2/5% CO2 for 15 min. Vessel rings were reoxygenated for 30 min and concentration/effect relationships reevaluated. The dissociation constant (KA) for norepinephrine was also determined. The pD2 for maximal norepinephrine responsiveness decreased from 7.7 to 7.3 following H/R. Maximal tension generation was significantly decreased following H/R. Endothelium denudation or nitric oxide synthesis inhibition did not prevent the right shift in norepinephrine concentration/effect relationship caused by H/R. The combination of superoxide dismutase and catalase prevented the dextral shift in the concentration/effect curve. The dissociation constant for norepinephrine increased from 0.16 to 0.32 microM following H/R, suggesting decreased affinity of adrenergic receptor. H/R did not alter AlCl3/NaF, KCl, BayK-8644 or l-indolactam-induced vasoconstriction. Caffeine-induced vasoconstriction was significantly impaired following H/R, suggesting that release of calcium from the sarcoplasmic reticulum is compromised. These results suggest that H/R leads to an endothelium independent, oxidant-mediated decrease in vascular norepinephrine responsiveness that may be related to defects in the mobilization of intracellular calcium from the sarcoplasmic reticulum pool.

Pyocyanin from Pseudomonas aeruginosa inhibits prostacyclin release from endothelial cells

Pseudomonas aeruginosa pneumonia causes a vasculitis of small pulmonary arteries. While the fully developed lesion demonstrates vessel wall necrosis, the early lesion is remarkable for preservation of viable endothelium despite vessel wall invasion by bacteria. Pyocyanin, an exoproduct of P. aeruginosa, markedly inhibited prostacyclin production by pulmonary artery endothelial cells without causing cell lysis. Pyocyanin might after vascular homeostasis in the absence of cytolysis.

In vivo effects of prostacyclin on segmental vascular resistances, on myogenic reactivity, and on capillary fluid exchange in cat skeletal muscle

OBJECTIVE

To analyze the local circulatory effects of prostacyclin in skeletal muscle.

DESIGN

A prospective experimental study.

SETTING

A university laboratory.

SUBJECTS

Twelve adult cats.

INTERVENTIONS

The study was performed on autoperfused, sympathectomized gastrocnemius muscle.

MEASUREMENTS AND MAIN RESULTS

Arterial blood flow, total and segmental vascular resistances (arterial vessels of > 25 microns, arterioles of < 25 microns, and veins), hydrostatic capillary pressure, tissue volume, myogenic reactivity, and the capillary filtration coefficient were followed. The capillary filtration coefficient reflects the functional capillary fluid exchange area. Myogenic reactivity was evaluated as the arteriolar resistance increase after a standardized decrease in extravascular pressure. Arterial infusion of prostacyclin decreased vascular resistance by approximately 50% at the highest dose given (500 ng/kg/min). This effect was more pronounced on the arterial side, especially in arterial vessels of > 25 microns. Hydrostatic capillary pressure increased by 1.9 +/- 0.3 mm Hg, causing fluid filtration. The relative fluid filtration was less than that value shown for some other vasodilator drugs (isoprenaline, calcium-channel blockers, thiopental) in this muscle preparation. Capillary filtration coefficient decreased by 25%. Myogenic reactivity was depressed but to a lesser extent than previously observed for other vasodilator mechanisms (muscle exercise, beta-adrenergic receptor stimulation, thiopental infusion, nifedipine infusion).

CONCLUSIONS

Prostacyclin is a vasodilator, both on the arterial and venous side, that restricts the increase in hydrostatic capillary pressure. The decrease in capillary filtration coefficient most likely reflects a decrease in capillary permeability, explaining the smaller relative filtration rate. The relatively well-preserved myogenic reactivity may imply a better preserved microvascular flow distribution and peripheral oxygen uptake.

Iloprost reduces leukocyte adhesion in skeletal muscle venules following ischaemia in a rat model of femorodistal bypass

Intraarterial bolus treatment with the prostacyclin analogue iloprost appears to have a prolonged beneficial effect on femorodistal bypass graft flow which extends beyond the duration of its vasodilator properties. The effect of iloprost on the microcirculation rendered ischaemic over the time course of a distal bypass operation was investigated in this study without the use of fluorescent light.

METHODS

A rat model was designed to allow prolonged direct observation of leukocyte-venular endothelial adhesion in a femorodistal bypass simulation. The extensor digitorum longus (EDL) muscle of 10 rats was subjected to two 30 minute periods of ischaemia by a non-venous occluding tourniquet and to simulate some of the changes of chronic ischaemia the adverse effect of ischaemia was accentuated by indirect electrical stimulation via the lateral popliteal nerve.

RESULTS

Intraarterial bolus treatment with iloprost significantly reduced the total numbers of leukocytes observed in EDL venules, and the numbers exhibiting evidence of adhesion by rolling or sticking to venule endothelium compared with saline controls at one hour post ischaemia. Ischaemia induced vasodilatation and reduced shear stress by a similar and significant amount in both groups.

CONCLUSION

Two periods of ischaemia and reperfusion similar to those which occur during bypass grafting resulted in changes in the distal microcirculation consistent with reperfusion injury. Intraarterial bolus treatment with iloprost prevented these leucocyte-endothelial changes. It appears iloprost may have a role in reducing leukocyte-induced reperfusion injury in femorodistal bypass surgery.

Role of the leucocyte in the pathogenesis of vascular disease

The leucocyte plays a key role in the local and systemic tissue injury that results from peripheral arterial disease and chronic venous insufficiency. Despite the apparent dissimilarities between limb ischaemia and chronic venous ulceration, in both diseases macrovascular abnormalities lead to microvascular leucocyte trapping and activation. Activated leucocytes adhere to and damage adjacent endothelium by expressing adhesion molecules and releasing harmful moieties such as proteases and free radicals. Subsequent loss of endothelial integrity and the migration of activated leucocytes outwith the circulation leads to destruction of surrounding tissue. Leucocytes and their products are also involved in the systemic manifestations of ischaemia such as multiple organ failure and coagulopathy. An overview of leucocyte biology as it pertains to peripheral arterial and venous disease is presented. The opportunities for novel therapeutic interventions based on a better understanding of this biology are also discussed.

Role of prostanoids in the inflammatory reaction and their therapeutic potential in the skin

Vasodilatory prostaglandins (PG), contributing to the inflammatory reaction, have gained considerable attention. It is becoming apparent that PG have pharmacological effects traceable to biological activities distinct from smooth muscle relaxation. The data from pharmacological experiments presented here indicate the diverse action of vasodilatory PG analogues in the skin of laboratory animals. Nocloprost, a stable PGE2 analogue, induced erythema in intact skin of rats when applied topically and inhibited in the same dose range an irritant-induced inflammatory reaction in the ears of mice. Iloprost, a stable PGI2 analogue, showed proinflammatory activity after local application by enhancing the leukotriene B4 induced cell infiltration in the skin of mice. The attenuation of the spreading of ear necrosis in mice, on the other hand, indicates an anti-ischemic therapeutic potential of iloprost. Research in the past has elucidated the influence of PG on the vascular component of inflammation, but the role of PG on the cellular component of inflammation is less clear. The diverse effects of PG in skin indicate the need for a better understanding of their local actions.