Increased Plasma Protein Extravasation Research Articles

Adenoviral VEGF-DΔN ΔC gene therapy for myocardial ischemia.

Background: Cardiovascular diseases are the leading cause of death globally. In spite of the availability of improved treatments, there is still a large group of chronic ischemia patients who suffer from significant symptoms and disability. Thus, there is a clear need to develop new treatment strategies for these patients. Therapeutic angiogenesis is a novel therapy method which has shown promising results in preclinical studies. In this study, we evaluated safety and efficacy of adenoviral (Ad) VEGF-DΔNΔC gene transfer for the treatment of myocardial ischemia in a pig model. Methods: Adenoviral VEGF-DΔNΔC gene transfer was given to pigs (n = 26) via intramyocardial injections using an electromechanical injection catheter. Angiogenic effects were evaluated in an acute myocardial infarction model (n = 18) and functionality of the lymphatic vessels were tested in healthy porcine myocardium (n = 8). AdLacZ was used as a control. Results: AdVEGF-DΔNΔC induced safe and effective myocardial angiogenesis by inducing a four-fold increase in mean capillary area at the edge of the myocardial infarct six days after the gene transfer relative to the control AdLacZ group. The effect was sustained over 21 days after the gene transfer, and there were no signs of vessels regression. AdVEGF-DΔNΔC also increased perfusion 3.4-fold near the infarct border zone relative to the control as measured by fluorescent microspheres. Ejection fraction was 8.7% higher in the AdVEGF-DΔNΔC treated group 21days after the gene transfer relative to the AdLacZ control group. Modified Miles assay detected a transient increase in plasma protein extravasation after the AdVEGF-DΔNΔC treatment and a mild accumulation of pericardial effusate was observed at d6. However, AdVEGF-DΔNΔC also induced the growth of functional lymphatic vasculature, and the amount of pericardial fluid and level of vascular permeability had returned to normal by d21. Conclusion: Endovascular intramyocardial AdVEGF-DΔNΔC gene therapy proved to be safe and effective in the acute porcine myocardial infarction model and provides a new potential treatment option for patients with severe coronary heart disease.

Association of Intranasal and Neurogenic Dural Inflammation in Experimental Acute Rhinosinusitis.

BackgroundNasal cavity and sinus disorders, such as allergic rhinitis, rhinosinusitis, or certain anatomical defects, are often associated with transient or ongoing headaches. On the other hand, migraine headache patients often exhibit pain referral over the area of nasal sinuses and typical nasal autonomic symptoms involving congestion and rhinorrhea. Mechanism for convergence of nasal or sinus disorders and headaches is unknown. Herein, we examined the association of sino-nasal inflammatory pain with common preclinical indicators of trigeminovascular system activation such as dural neurogenic inflammation (DNI) and neuronal activation in brainstem nociceptive nuclei.MethodsNasal and paranasal cavity inflammation and pain was induced by formalin (2.5%/10 μl) or capsaicin (0.1%/10 μl) instillation at the border of maxillary sinus and nasal cavity in rats. Quantification of inflammation of nasal mucosa and DNI was performed by spectrophotometric measurement of Evans blue - plasma protein complex extravasation. Pain behavior was quantified by rat grimace scale (RGS). Nociceptive neuronal activation in caudal part of spinal trigeminal nucleus (TNC) was assessed by c-Fos protein immunohistochemistry.ResultsCapsaicin and formalin administered into rat nasal cavity increased plasma protein extravasation in the nasal mucosa and dura mater. Intensity of plasma protein extravasation in nasal mucosa correlated with extravasation in dura. Similarly, facial pain intensity correlated with nociceptive neuronal c-Fos activation in the TNC.ConclusionPresent data show that inflammatory stimuli in deep nasal and paranasal structures provoke distant intracranial changes related to trigeminovascular system activation. We hypothesize that this phenomenon could explain overlapping symptoms and comorbidity of nasal/paranasal inflammatory disorders with migraine.

Understanding migraine: Potential role of neurogenic inflammation.

Neurogenic inflammation, a well-defined pathophysiologial process is characterized by the release of potent vasoactive neuropeptides, predominantly calcitonin gene-related peptide (CGRP), substance P (SP), and neurokinin A from activated peripheral nociceptive sensory nerve terminals (usually C and A delta-fibers). These peptides lead to a cascade of inflammatory tissue responses including arteriolar vasodilation, plasma protein extravasation, and degranulation of mast cells in their peripheral target tissue. Neurogenic inflammatory processes have long been implicated as a possible mechanism involved in the pathophysiology of various human diseases of the nervous system, respiratory system, gastrointestinal tract, urogenital tract, and skin. The recent development of several innovative experimental migraine models has provided evidence suggestive of the involvement of neuropeptides (SP, neurokinin A, and CGRP) in migraine headache. Antidromic stimulation of nociceptive fibers of the trigeminal nerve resulted in a neurogenic inflammatory response with marked increase in plasma protein extravasation from dural blood vessels by the release of various sensory neuropeptides. Several clinically effective abortive antimigraine medications, such as ergots and triptans, have been shown to attenuate the release of neuropeptide and neurogenic plasma protein extravasation. These findings provide support for the validity of using animal models to investigate mechanisms of neurogenic inflammation in migraine. These also further strengthen the notion of migraine being a neuroinflammatory disease. In the clinical context, there is a paucity of knowledge and awareness among physicians regarding the role of neurogenic inflammation in migraine. Improved understanding of the molecular biology, pharmacology, and pathophysiology of neurogenic inflammation may provide the practitioner the context-specific feedback to identify the novel and most effective therapeutic approach to treatment. With this objective, the present review summarizes the evidence supporting the involvement of neurogenic inflammation and neuropeptides in the pathophysiology and pharmacology of migraine headache as well as its potential significance in better tailoring therapeutic interventions in migraine or other neurological disorders. In addition, we have briefly highlighted the pathophysiological role of neurogenic inflammation in various other neurological disorders.

The Influence of Alpha1-Adrenoreceptors on Neuropeptide Release from Primary Sensory Neurons of the Lower Urinary Tract

ObjectivesAdrenergic α1-receptors agonists and antagonists have been reported to increase and reduce, respectively, neurogenic inflammatory responses mediated by capsaicin-sensitive sensory neurons. However, the precise role and localization of the α1-adrenoceptors involved in these effects are not known. MethodsWe have studied in the rat whether functional α1-adrenoreceptors are expressed in primary sensory neurons, and whether they regulate neurogenic inflammation and nociceptive responses in the urinary bladder. ResultsThe α1-adrenoreceptor agonist phenylephrine (1μmol/l) (1) mobilized intracellular Ca2+ in cultured lumbar and sacral dorsal root ganglia neurons, (2) caused the release of substance P (SP) from terminals of capsaicin-sensitive sensory neurons from the lumbar enlargement of the dorsal spinal cord and urinary bladder, and (3) increased plasma protein extravasation in the urinary bladder. All these effects were abolished by the α1-adrenoceptor antagonist alfuzosin (10μmol/l). Furthermore, alfuzosin (30μg/kg, iv) partially, but significantly, inhibited cyclophosphamide-induced plasma protein extravasation in the rat urinary bladder. Phenylephrine-induced Ca2+ mobilization in cultured dorsal root ganglia neurons was exaggerated by pretreating the rats in vivo with cyclophosphamide. Finally, cyclophosphamide increased c-fos expression in the rat lumbar spinal cord. Also these in vitro and in vivo effects were inhibited by pretreatment with alfuzosin. Conclusionsα1-Adrenoceptors are functionally expressed by capsaicin-sensitive, nociceptive, primary sensory neurons of the rat urinary tract, and their activation may contribute to signal irritative and nociceptive responses arising from the urinary tract. It is possible that, at least, part of the beneficial effects of α1-adrenoceptor antagonists in the amelioration of storage symptoms in the lower urinary tract derives from their inhibitory effect on neurogenic inflammatory responses.

15-Deoxy-Δ 12,14-prostaglandin J 2 attenuates development of cyclophosphamide-induced cystitis in rats

Objectives To investigate whether an endogenous prostaglandin (PG) D 2 metabolite, 15-deoxy-Δ 12,14-PGJ 2 (15d-PGJ 2), can attenuate cyclophosphamide (CYP)-induced cystitis in the rat. Methods Male Sprague-Dawley rats received a single intraperitoneal injection of CYP (200 mg/kg). In a separate group of animals, 15d-PGJ 2 (10 and 100 μg/kg intraperitoneal bolus 10 minutes before and 24 hours after CYP injection) or a selective inducible nitric oxide synthase (iNOS) inhibitor, N-(3-(aminomethyl)benzyl)acetamidine ([1400W] 10 mg/kg intraperitoneal bolus 10 minutes before and 12 and 24 hours after CYP injection), was administered. At 48 hours after CYP injection, the rats were killed, and tissues were removed for evaluation of cystitis. Results CYP injection resulted in severe cystitis. 15d-PGJ 2, as well as 1400W, significantly reduced the increase in plasma protein extravasation (Evans blue dye method), iNOS enzymatic activity, urinary excretion of nitric oxide metabolites, and myeloperoxidase activity in the bladder caused by CYP. Moreover, 15d-PGJ 2 significantly decreased the cytokine interleukin-1β in the bladder. In addition, 15d-PGJ 2 significantly reduced the degree of CYP-induced bladder tissue damage and increase in immunohistochemical staining for iNOS in the bladder. Conclusions These results indicate that 15d-PGJ 2 can attenuate the development of CYP-induced cystitis by suppression of cytokine production and iNOS induction. Thus, treatment with cyclopentenone prostaglandins such as 15d-PGJ 2 may be effective against CYP-induced cystitis.

Neurogenic inflammation in mice deficient in heparin-synthesizing enzyme.

Mast cell activation, or neurogenic inflammation, is known to induce lowering of interstitial fluid pressure (P(if)) and plasma protein extravasation (PPE) in several tissues from both rats and mice. To examine a possible role of connective tissue mast cells (CTMCs) in these inflammatory responses, we used mice with dysfunctional CTMCs due to lack of the N-deacetylase/N-sulfotransferase-2 enzyme (NDST-2(-/-)). P(if) and PPE were measured after challenge with compound 48/80 (C48/80), and P(if) alone was measured after treatment either with capsaicin, substance P (SP), or calcitonin gene-related peptide (CGRP). Measurements of P(if) in anesthetized (fentanyl/fluanison and midazolam, 1:1) mice were performed in paw skin with glass capillaries connected to a servo-controlled counterpressure system. PPE was measured with microdialysis by using hollow plasmapheresis fibers (cutoff at 3,000 kDa) placed subcutaneously on the back. Intravenous administration of C48/80 lowered P(if) significantly (P < 0.05) in NDST-2(-/-) mice (-1.67 +/- 0.42 mmHg) compared with vehicle (-0.57 +/- 0.17 mmHg) but the lowering was significantly (P < 0.05) less compared with that of the NDST-2(+/+) mice (-2.31 +/- 0.47 mmHg). PPE was increased 300% after treatment with C48/80 in NDST-2(+/+) mice, whereas there was no increase in PPE in NDST-2(-/-) mice. Capsaicin, SP, and CGRP lowered P(if) significantly (P < 0.05) compared with vehicle and to the same extent in both NDST-2(+/+) and NDST-2(-/-) mice. We can conclude that although NDST-2(-/-) mice demonstrate an altered response in P(if) after mast cell activation, there was no similar alteration after neurogenic inflammation. Therefore, we suggest that neurogenic inflammation in mouse skin is not exclusively dependent on intact CTMCs.

Continuous measurements of plasma protein extravasation with microdialysis after various inflammatory challenges in rat and mouse skin.

This study describes the use of microdialysis technique for continuous measurement of plasma protein extravasation (PPE) in rat and mouse skin with drug application either intravenously or via the microdialysis fiber. Hollow plasmapheresis fibers (3-cm length, 0.4-mm diameter, cutoff 3,000 kDa) were placed subcutaneously on the back of anesthetized mice and rats. Intravenous injection of dextran (Macrodex, 60 mg/ml) increased PPE by 355% from baseline within 30 min in rats with ligated kidneys (n = 6; P < 0.05) but not in animals with intact kidneys. Phalloidin (500 microg/kg iv 40 min before dextran, n = 6; P < 0.05) did not change the response to dextran in either group. Animals receiving PGE1, compound 48/80 (mice), paclitaxel, docetaxel, and cremophor EL via the microdialysis fiber were also provided with a control fiber receiving vehicle. Both rats and mice had constant PPE in the control fiber, and there was no change in PPE in the NaCl-treated groups (rats, n = 4; mice, n = 6). Application via the fiber of PGE1 (20 microg/ml), compound 48/80 (mice; 4 mg/ml), and docetaxel (0.5 mg/ml) increased PPE compared with baseline within 60 min by 139% (n = 6; P < 0.05), 273% (n = 6; P < 0.05), and 325% (n = 5; P < 0.05), respectively. Phalloidin alone did not increase PPE (n = 5; P < 0.05). Pretreatment with phalloidin did not inhibit the increase after PGE1 or compound 48/80 but inhibited that after docetaxel (n = 6). Paclitaxel (0.6 mg/ml, n = 5) or vehicle (Cremophor) (n = 5) gave no increase in PPE. The results demonstrate that microdialysis can be used to continuously measure changes in PPE after inflammatory challenges in skin of rats and mice.

Protective effect of the tachykinin NK2receptor antagonist nepadutant in acute rectocolitis induced by diluted acetic acid in guinea-pigs

We have evaluated the potential protective activity of nepadutant, a selective tachykinin NK2receptor antagonist, in a model of acute rectocolitis induced by an enema with 7.5% acetic acid in guinea-pigs. The injury was quantified visually by using a macroscopic injury score, and histologically by using a necrosis score. In addition, changes in myeloperoxidase activity, a marker for neutrophil infiltration, and plasma protein extravasation were evaluated. The injury caused by 7.5% acetic acid was mild, affecting the superficial layers and producing a strong edema of the submucosa. A single administration of nepadutant (0.3–10mg/kg s.c., 1h before acetic acid) markedly reduced the macroscopic damage and necrosis score and the increase in plasma protein extravasation induced by 7.5% acetic acid in the early phase of the injury. Single administration of nepadutant (3mg/kg s.c.) reduced the macroscopic score and myeloperoxidase activity at the top (24h) of inflammation. Repeated administration (3mg/kg s.c. three times during 24h) or co-administration of the tachykinin NK1receptor antagonist MEN 11467 (3mg/kg s.c.) did not enhance the antiulcer effect obtained with the single treatment with nepadutant. These data suggest the involvement of tachykinin NK2receptors in the first phases of inflammation induced by acetic acid.

Sensory nerve-mediated immediate nasal responses to inspired acrolein.

To investigate the role of sensory C-fiber stimulation and tachykinin release in the immediate nasal responses to the sensory irritant acrolein, the upper respiratory tract of the urethan-anesthetized male Fischer 344 rat was isolated via insertion of an endotracheal tube, and acrolein-laden air [2, 5, 10, or 20 parts/million (ppm)] was drawn continuously through that site at a flow rate of 100 ml/min for 50 min. Uptake of the inert vapor acetone was measured throughout the exposure to assess nasal vascular function. Plasma protein extravasation into nasal tissue and nasal lavage fluid was also assessed via injection of Evans blue dye. At 20 ppm, acrolein induced 1) a twofold increase in acetone uptake, indicative of vasodilation, followed by a progressive decline toward basal levels and 2) increased plasma protein extravasation, as indicated by dye leakage into nasal tissue and nasal lavage. These responses were inhibited by capsaicin pretreatment and the neurokinin type 1 antagonist N-acetyltrifluoromethyl tryptophan benzyl ester and were potentiated by the peptidase inhibitors phosphoramidon and captopril, suggesting that these responses were mediated by tachykinin. At lower exposure concentrations, acrolein was without effect on dye leakage but produced vasodilation, as indicated by increased acetone uptake. The responses at the lower concentrations were inhibited by capsaicin pretreatment, implicating nasal sensory C-fiber involvement, but were not influenced by N-acetyltrifluoromethyl tryptophan benzyl ester, phosphoramidon, or captopril, suggesting the involvement of a mediator other than the tachykinins substance P and neurokinin A.

Inhibitory modulation of cutaneous vascular responses by endogenous galanin in the pigeon

The possible role of endogenous galanin in modulation of cutaneous vascular responses was studied in pigeons. Chemically induced plasma extravasation and regional skin blood flow changes were measured simultaneously with a capillary perfusion technique and a laser Doppler imager, respectively. Perfusion with both histamine and bradykinin increased plasma protein extravasation which was dose-dependently and significantly augmented by co-administration of M35, a specific galanin antagonist. This effect of M35 was abolished after chronic cutaneous denervation. In intact but not denervated skin, M35 increased the vasodilatatory effect of histamine, too. It is suggested that galanin-containing nerves may play an inhibitory efferent role in the modulation of cutaneous inflammatory responses.

Effect of MEN 11467, a new tachykinin NK 1 receptor antagonist, in acute rectocolitis induced by acetic acid in guinea-pigs

The aim of this study was to evaluate the effect of MEN 11467 (1 R,2 S)-2- N[1( H)indol-3-yl-carbonyl]-1- N{ N-( p-tolylacetyl)- N-(methyl)- d-3(2-Naphthyl)alanyl}diaminocyclohexane), a new potent tachykinin NK 1 receptor antagonist, in an experimental model of acute rectocolitis induced by an enema with 7.5% acetic acid in guinea-pigs. This effect was compared to that of mesalazine (5-amino-2-hydroxybenzoic acid). The injury was quantified visually by using a macroscopic injury score and histologically by using a necrosis score. In addition, changes in myeloperoxidase activity, a marker for neutrophil infiltration, and plasma protein extravasation were evaluated. The injury caused by 7.5% acetic acid was mild, affecting the superficial layers and producing a strong edema of the submucosa. A single administration of MEN 11467 (0.3–10 mg/kg s.c., 1 h before acetic acid) reduced the macroscopic damage and necrosis score and the increase in plasma protein extravasation induced by 7.5% acetic acid in the early acute phase of the injury (death at 2.5 h). Mesalazine (100 mg/kg p.o., 1 h before) reduced the macroscopic score but not the plasma protein extravasation. Repeated administration of MEN 11467 (1–3 mg/kg s.c., −1, +6 and +23 h after 7.5% acetic acid) reduced the macroscopic score and myeloperoxidase activity but not the plasma protein extravasation induced in the late phase of acute injury (death at 24 h). At this time mesalazine markedly reduced the macroscopic score, myeloperoxidase activity and plasma protein extravasation induced by 7.5% acetic acid. These results suggest a greater involvement of tachykinin NK 1 receptors in the early phase than in the late phase of colonic inflammation in response to chemical injury.

The role of tachykinin receptor antagonists in the prevention of bronchial hyperresponsiveness, airway inflammation and cough.

Several recent observations suggest that tachykinins, such as substance P and neurokinin A, might be involved in the pathogenesis of bronchopulmonary alterations. Progress in investigations on the physiological and pathological roles of tachykinins has been greatly facilitated by the availability of a number of highly selective nonpeptide antagonists for tachykinin neurokinin 1, 2 and 3 (NK1, NK2 and NK3) receptors. The use of selective tachykinin NK2 receptor antagonists suggests that tachykinin NK2 receptor stimulation plays an important role in the development of airway hyperresponsiveness in the guinea-pig. Others studies have also indicated that tachykinin NK1-receptors are involved in immediate or delayed neurogenic inflammation including microvascular leakage and the subsequent increase in plasma protein extravasation. A role for the sensory neuropeptide system has also been proposed in cough, as shown by the observation that the antitussive effect of tachykinin NK2 receptor antagonists has clearly been demonstrated in several experimental conditions, but the effect of tachykinin NK1 receptor antagonists is still debated. Taken together, the results obtained with the various selective receptor antagonists provide pharmacological evidence that tachykinins play a role in delayed bronchopulmonary alterations and suggest that tachykinin receptor antagonists may be useful for investigating mechanisms and possibly reducing airway functional alterations in asthmatic patients.

Role of the 5-HT receptor in neurogenic inflammation in Fisher 344 rat airways

The increased plasma protein extravasation in the airways of Fisher 344 rats upon stimulation of sensory nerves is in part due to the degranulation of mast cells. In this study, we examined the role of 5-HT and histamine receptors in the capsaicin-induced increase in plasma protein extravasation in Fisher 344 rat airways, using Evans blue as an intravascular marker. We found that only 5-HT 2 receptor agonists increased baseline plasma protein extravasation. Furthermore, the 5-HT 2 receptor antagonist ketanserin reduced the capsaicin-induced increase in plasma protein extravasation. Combining ketanserin with the tachykinin NK 1 receptor antagonist (±)-RP 67,580 ((3 aR,7 aR)-(7,7-diphenyl-2(1-imino-2-(2-methoxyphenylethyl)-perhydraisoinositol-4-one))) abolished the neurogenic increase in plasma protein extravasation. Finally, using selective receptor agonists and antagonists, we demonstrated that there was no modulation of the capsaicin-induced rise in plasma protein extravasation by stimulation of either histamine receptors or 5-HT 1, 5-HT 3 and 5-HT 4 receptors. We conclude that, in the airways of Fisher 344 rats, the neurogenic increase in plasma protein extravasation is caused by activation of both tachykinin NK 1 receptors and 5-HT 2 receptors. © 1997 Elsevier Science B.V. All rights reserved.

Involvement of tachykinin NK1 receptors in plasma protein extravasation induced by tachykinins in the guinea pig upper airways.

Plasma protein extravasation in the upper airways of anesthetized guinea pigs was measured with the FITC (Fluorescein isothiocyanate)-dextran technique. The effect of selective tachykinin (NK1 and NK2) receptor agonists and antagonists, capsaicin or antigen was studied. The tachykinin NK1 receptor agonist, [Sar9]substance P sulfone, induced an increase in FITC-dextran extravasation which was blocked by the nasal application (30-100 nmol/kg) of the tachykinin NK1 receptor antagonist FK888, but not by 1 micromol/kg of the tachykinin NK2 receptor antagonist, MEN10,627. The tachykinin NK2 receptor agonist, [betaAla8]neurokinin A-(4-10), had no effect on dye leakage. FK888 (30 nmol/kg intranasal) abolished the increase in the tracer recovery induced both by antigen and capsaicin. Conversely, the intranasal administration of MEN10,627 (0.1-1.0 micromol/kg) significantly reduced capsaicin-induced and only marginally inhibited antigen-induced increase in plasma protein extravasation. Pretreatment with the neutral endopeptidase inhibitor, phosphoramidon, increased the effect of all inflammatory agents. These findings show that the plasma extravasation of the upper airways induced by exogenous or endogenous tachykinins is primarily mediated by tachykinin NK1 receptors. This inflammatory response could be controlled by locally applied tachykinin NK1 receptor antagonist.

Plasma volume expansion with colloids increases blood-tissue albumin transport.

Extravasation of plasma proteins is increased after volume expansion with whole blood or plasma. To investigate the mechanisms responsible for this phenomenon, we measured extravascular accumulation of exogenous 131I-labeled bovine serum albumin in several tissues and organs of anesthetized rats. Plasma volume was increased acutely by infusion of isoncotic albumin or polyvinylpyrrolidone, with or without subsequent infusion of a 1:10 dilution of the colloid to induce blood-to-tissue fluid movement. Controls were given only a slow sustaining infusion of saline. The amounts of fluid and plasma protein lost from the circulation were followed simultaneously by two methods: 1) material balance in the whole animal, and 2) changes in 131I-labeled albumin uptake (VA) and water content (VW) in the individual tissues. Plasma volume expansion of 80-90% increased plasma protein extravasation in the whole rat by an average of 2.7-fold over a 30-min period. Of the protein extravasated, 42% entered the abdominal cavity. The rest was distributed in the interstitial compartment of various tissues and organs. Tracer albumin accumulation (averaged over 30 min) was increased 38-82% in skin and paw, 40-59% in skeletal muscles, 131% in hearts, and 167-230% in different parts of the intestine. Increased convective transport does not appear to be a major factor. There was little or no relation of albumin transport increase to the magnitude or direction of net fluid transfer. Coupling of albumin transport to volume flow was not greater than previously reported for saline infusion or venous congestion. Convective redistribution (convective transport without net fluid transfer, "volume recirculation") is estimated to increase albumin transport no more than 10% under the conditions of our experiments. The greater part of the increase is thus dissipative, i.e., attributable to increased diffusion or increased vesicular exchange. Control of dissipative transport of albumin may play an important role in regulating plasma volume.

Neurogenic inflammation in the airways. I. Neurogenic stimulation induces plasma protein extravasation into the rat airway lumen.

Activation of sensory nerves in rodent airways results in microvascular permeability and edema formation, presumably due to release of vasoactive neuropeptides from the nerve endings. We examined the possibility that neurogenic stimulation may also induce movement of plasma proteins into the airway lumen. Neurogenic plasma protein extravasation (PPE) was induced in Sprague-Dawley rats by electrical stimulation of both vagal nerves (EVS) at 10 V, 5 ms, 20 Hz. After 90 s of EVS, histologic examination showed Monastral blue B, a macromolecular tracer, extravasated within the endothelium of vessels in the subepithelial layer of the tracheobronchial mucosa. In animals given 125I-labeled albumin intravenously, PPE was quantitated as microliters of plasma deposited into the airways, lung, and tracheobronchial (TB) and bronchoalveolar (BA) lavages. One minute of EVS induced an immediate increase in PPE in the tracheal (+117%) and bronchial wall (+125%) but not in the peripheral lung. There was a concomitant increase in the 125I-labeled albumin recovered from both TB fluid (net increase, 1.29 microliter of plasma = +259%) and BA fluid (net increase, 2.79 microliters of plasma = +107%). In addition, both total protein and endogenous albumin concentrations in TB fluid also increased after EVS. The albumin/total protein ratio (the albumin percentage) in TB lavages was also significantly increased (1.4 x, 1.7 x, and 2.5 x in three separate experiments, respectively), indicating the vascular origin of the increased luminal proteins. Neither cholinergic (atropine) nor adrenergic blockade (phentolamine + propranolol) influenced EVS-induced PPE into the airway walls or movement of radiolabeled albumin into the airway lumen.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-2-adrenoceptor agonists as inhibitors of lung vascular permeability to radiolabelled transferrin in the adult respiratory distress syndrome in man.

Increased lung vascular permeability leading to increased plasma protein extravasation and accumulation (PPA) is a characteristic feature of acute lung injury. Using a previously described technique, PPA was monitored in the lungs of patients with the adult respiratory distress syndrome (ARDS)--an extreme example of acute lung injury in man. An external radiation probe detector was used to monitor the pulmonary accumulation of the plasma protein transferrin radiolabelled in-vivo with 113mIn. Ten patients with ARDS exhibiting increased PPA indices (greater than 1.0 x 10(-3)/min) were given an intravenous infusion of terbutaline (7 micrograms/kg) over 30 min. Of the four patients in whom the post-drug PPA indices remained within the ARDS range, none survived, whilst five of the six patients in whom the post-drug PPA indices were reduced to below 1.0 x 10(-3)/min survived. PPA indices prior to the administration of terbutaline were not significantly different between the survivor (n = 5) and non-survivor (n = 5) groups. There was a significant decrease in the PPA indices following terbutaline in survivors (p less than 0.01) but not in non-survivors. Thus beta-2-agonists in therapeutic doses can inhibit increased lung vascular permeability in man. These findings may have prognostic and therapeutic implications for beta-2-agonists in ARDS.

A noninvasive technique for monitoring lung vascular permeability in man.

Increased microvascular permeability resulting in increased plasma protein extravasation is the hallmark of acute inflammatory oedema and hence radiolabelled proteins can be used to monitor this process. The adult respiratory distress syndrome (ARDS) is characterized by acute inflammatory oedema and thus provides an ideal model for studying this type of oedema in the human lung. A noninvasive technique applicable to the intensive care unit has been developed for monitoring the pulmonary accumulation of the plasma protein transferrin. Transferrin was radiolabelled in vivo with indium-113m and its accumulation was monitored using a portable probe radiation detector. After correcting for changes in intrathoracic blood distribution, by simultaneously monitoring the accumulation of technetium-99m-labelled red blood cells, an index of plasma protein accumulation was calculated. In all patients with established ARDS (n = 10) the index values were greater than 1.0 X 10(-3) min-1 and these were clearly separate from the values of less than 0.5 X 10(-3) min-1 in all healthy volunteers (n = 5; P less than 0.001). The technique can clearly detect raised plasma protein accumulation indices in the lungs of patients with established inflammatory oedema of ARDS and hence may provide a pharmacological tool for the rapid evaluation in these conditions of the effects of drugs (like corticosteroids) which are known to modulate inflammatory oedema.

Synergistic interaction between prostaglandins and paf-acether in experimental animals and man

Platelet activating factor (PAF-acether) is released from a variety of inflammatory cell types and has properties appropriate to a mediator of allergy and inflammation. Here, we have examined the interaction between PAF-acether and the prostaglandins, PGE2 and ZK 36374 (a stable analogue of prostacyclin, PGI2) in the skin of guinea-pigs and human volunteers. PGE2 and ZK36374 significantly potentiated increased plasma protein extravasation induced by PAF-acether in guinea-pigs, assessed by extravasation of I-125-HSA. In addition, PGE2 significantly potentiated the ability of PAF-acether to elicit acute wheal (volume) and flare responses in human skin. The inflammatory properties of PAF-acether should not be considered in isolation since this phospholipid interacts synergistically with prostaglandins which are recognised as modulators of inflammation.

Inflammatory actions of platelet activating factor (Pafacether) in guinea-pig skin.

Cutaneous responses to synthetic platelet activating factor (Paf-acether) have been studied in guinea-pigs by means of radioisotopic marker techniques. Intradermal injection of Paf-acether elicited increased plasma protein extravasation (IPPE) (0.2-200 pmol/site), platelet accumulation (PA) (20-200 pmol/site) and red blood cell accumulation (RBCA) (200 pmol/site), whereas lyso-Paf (up to 2 nmol/site) was inactive in all these respects. Following intradermal injection, the IPPE responses to Paf-acether (2 and 20 pmol/site) were complete within 15 and 30 min respectively, although in response to 200 pmol/site, IPPE was detectable up to 1.5 h. The PA and RBCA responses to Paf-acether (200 pmol/site) were complete within 1 h. IPPE induced by Paf-acether (3 pmol/site) was potentiated by concomitant intradermal injection of a cutaneous vasodilator prostaglandin E2 (PGE2, 1 nmol/site) and inhibited by the beta-adrenoceptor agonist, isoprenaline (4.5 nmol/site) or the alpha-adrenoceptor agonist, phenylephrine (6 nmol/site). Such observations are consistent with Paf-acether effecting increased vessel wall permeability. Intradermal injection of PGE1 (3 nmol/site) significantly reduced PA in response to Paf-acether (200 pmol/site), whilst significantly enhancing IPPE. This dissociation of increased vascular permeability from PA is consistent with Paf-acether eliciting IPPE via a platelet-independent mechanism. These results indicate that a direct effect on vessel wall permeability contributes to the inflammatory response to Paf-acether in guinea-pig skin. It is suggested that Paf-acether is a potential mediator of allergy and inflammation.