Plasma fibronectin in idiopathic myelofibrosis and related chronic myeloproliferative disorders

Plasma fibronectin concentrations were measured in 49 patients with chronic myeloproliferative disorders and compared to sex- and age-matched controls. A significantly lower plasma fibronectin concentration was observed in patients with idiopathic myelofibrosis as compared with the control group (p less than 0.01). In addition, plasma fibronectin concentrations in myelofibrosis patients differed significantly, when compared with patients with polycythaemia vera (p less than 0.01), whereas no significant difference was found between myelofibrosis patients and those with a transitional myeloproliferative disorder or chronic myelogenous leukaemia (p greater than 0.05). An inverse relationship was demonstrated between plasma fibronectin and spleen size, the lowest plasma fibronectin levels being found in patients with large spleens. It is supposed that low plasma fibronectin concentrations in splenomegalic patients may be due to enhanced consumption of the opsonin in the expanded splenic mononuclear-macrophage system.     

Influence of epidural blockade on postoperative plasma fibronectin concentrations

To investigate the influence of neurogenic and hormonal stimuli during and after surgery on plasma fibronectin levels, 16 females undergoing cholecystectomy were studied. Eight patients received general anaesthesia, and eight also received a thoracic epidural block with local anaesthetic, which was maintained for 24 h postoperatively. The epidural group had significantly lower plasma levels of adrenaline and cortisol than the general anaesthesia group in the postoperative period. The previously well-documented early decrease in plasma fibronectin concentration following surgery was observed, and was essentially parallel with that of albumin, pre-albumin and thyroid hormones, with no differences between the groups. However, the restoration of the fibronectin level was slower in the epidural group, with significantly lower values as compared with controls at 48 and 72 h after surgery (p less than 0.01-0.001). It was concluded that the post-traumatic plasma fibronectin decrease is not mediated by neurogenic or adrenal stimuli. Such stimuli may, however, influence the subsequent restoration of the plasma fibronectin concentration.     

Influence of epidural blockade on postoperative plasma fibronectin concentrations

To investigate the influence of neurogenic and hormonal stimuli during and after surgery on plasma fibronectin levels, 16 females undergoing cholecystectomy were studied. Eight patients received general anaesthesia, and eight also received a thoracic epidural block with local anaesthetic, which was maintained for 24 h postoperatively. The epidural group had significantly lower plasma levels of adrenaline and Cortisol than the general anaesthesia group in the postoperative period. The previously well-documented early decrease in plasma fibronectin concentration following surgery was observed, and was essentially parallel with that of albumin, pre-albumin and thyroid hormones, with no differences between the groups. However, the restoration of the fibronectin level was slower in the epidural group, with significantly lower values as compared with controls at 48 and 72 h after surgery (p<0.01–0.001). It was concluded that the post-traumatic plasma fibronectin decrease is not mediated by neurogenic or adrenal stimuli. Such stimuli may, however, influence the subsequent restoration of the plasma fibronectin concentration.     

Lack of correlation between endotoxaemia and renal hypoperfusion in cirrhotics without overt renal failure

Abstract. Renal involvement in patients with liver cirrhosis is characterized by renal vasoconstriction, the aetiology of which remains obscure. Endotoxaemia, frequently found in patients with liver cirrhosis and renal failure, has been emphasized as a pathogenic factor.
In fifty-seven patients with liver cirrhosis without overt renal failure endotoxin plasma level (Limulus Lysate test), mean renal blood flow (MRBF) (¹³³Xe washout technique), and effective renal plasma flow (ERPF) (p-aminohippurate clearance) were determined.
MRBF was decreased in nineteen out of twenty-seven patients, averaging 1·88 ± 0·51 ml g^-1min^-1 (in fourteen controls 3·17 ± 0·51 ml g^-1ml^-1). ERPF was decreased in seventeen out of thirty patients, averaging 380±164 ml/min (in eighteen controls 624±127 ml/min). Systemic endotoxaemia was found in sixteen out of fifty-seven patients, levels ranging from 0·62 to 200 ng/ml. No significant difference in renal blood flow values was found between patients with and without endotoxaemia (MRBF = 1·78 ± 0·51 and 1·93 ± 0·52 ml g^-1min^-1 respectively; ERPF = 429±119 and 365±175 ml/min respectively). No significant difference in the frequency of endotoxaemia was found between patients with impaired and unimpaired renal blood flow. Moreover no relation was found between endotoxin plasma levels and MRBF and ERPF respectively.
In conclusion in patients with cirrhosis without overt renal failure renal vasoconstriction does not seem to be related to endotoxaemia.     

Level of plasma fibronectin in patients with peripheral vascular disease

Plasma concentration of fibronectin, a recently characterized high molecular mass glycoprotein, was determined in patients with peripheral vascular disease. The plasma fibronectin concentration was lower in patients with peripheral obstructive arterial disease as well as in patients with venous disease, than in corresponding healthy controls. Patients with venous disease had significantly lower levels of plasma fibronectin than patients with peripheral obstructive arterial disease. The patients with peripheral arterial disease were divided into two groups, one having diabetes and another not having diabetes respectively. Between these two groups there was no significant difference in plasma fibronectin concentration.     

Measurement of plasma fibronectin in patients who develop the adult respiratory distress syndrome

Depletion of plasma fibronectin has been observed in certain clinical conditions predisposing to the adult respiratory distress syndrome and has been associated with cardiopulmonary dysfunction in experimental lung injury. We evaluated prospectively the relationship between plasma fibronectin concentration and the development of the adult respiratory distress syndrome in patients known to be at high risk. Although plasma fibronectin levels in participants at study entry were lower in this population (mean 258 +/- 132 micrograms/ml) than in normal volunteers (461 +/- 127 micrograms/ml, p less than 0.0025), there was no difference between patients who subsequently developed the adult distress syndrome (mean 255 +/- 149 micrograms/ml) and those with similar illness or injury who did not develop the syndrome (260 +/- 126 micrograms/ml). Fibronectin concentration was not further depressed even after development of adult respiratory distress syndrome and did not correlate with degree of pulmonary dysfunction. These data suggest that fibronectin depletion is not an important determinant of respiratory failure in humans. Patients with sepsis syndrome had significantly lower plasma fibronectin levels than those without sepsis (187 +/- 119 micrograms/ml vs. 273 +/- 131 micrograms/ml, p less than 0.05), suggesting a possible role for fibronectin in the pathogenesis of sepsis.     

Elevated plasma levels of ED1+ ("cellular") fibronectin in patients with vascular injury

Using an enzyme-linked immunosorbent assay, we measured the concentration of fibronectin containing an extra type III domain (ED1) in the circulation of humans. Plasma levels of ED1 + fibronectin averaged 2.8 +/- 1.0 micrograms/ml in healthy individuals and did not differ substantially according to age or sex. In comparison with those from normal subjects, plasma samples obtained from patients with collagen vascular disorders contained increased average levels of ED1 + fibronectin. Among this group, levels of ED1 + fibronectin were significantly greater in samples taken from individuals with clinical evidence of vasculitis. Although levels of total (ED1 + plus ED1 -) fibronectin were also elevated in plasma samples from patients with vasculitis, only the concentration of the ED1 + variant correlated with severity of disease in two patients examined serially. Elevations in plasma content of ED1 + fibronectin, but not total fibronectin, were also noted in patients with acute vascular tissue injury associated with major trauma or sepsis syndrome. Western blot examination revealed the presence of intact dimeric ED1 + fibronectin in the circulation of all patients studied, although fragments bearing the ED1 were also detected. Human plasma normally contains small quantities of soluble ED1 + ("cellular") fibronectin, and these levels are increased in disorders involving vascular injury.     

Plasma levels of cellular fibronectin in diabetes

OBJECTIVE: Cellular fibronectin is an endothelium-derived protein involved in subendothelial matrix assembly. Elevated plasma levels of cellular fibronectin therefore reflect loss of endothelial cell polarization or injury to blood vessels. Consequently, elevated plasma levels of circulating cellular fibronectin have been described in clinical syndromes with vascular damage, although not in diabetes or atherosclerosis. RESEARCH DESIGN AND METHODS: We determined fibronectin levels in 52 patients with type 1 diabetes, 50 patients with type 2 diabetes, 54 patients with a history of ischemic stroke, 23 patients with renal artery stenosis, and 64 healthy subjects. RESULTS: Circulating cellular fibronectin was significantly elevated in patients with diabetes (4.3 +/- 2.8 microg/ml) compared with patients with ischemic stroke (2.0 +/- 0.9 microg/ml), patients with renovascular hypertension (1.7 +/- 1.1 microg/ml), and healthy subjects (1.4 +/- 0.6 microg/ml). Patients with diabetes and at least one cardiovascular risk factor had an almost 2.5-fold increase in cellular fibronectin compared with diabetic subjects without such a risk factor. In multivariate regression analysis, higher triglycerides, current or past cigarette smoking, and higher urinary albumin excretion were independently associated with an increase in circulating cellular fibronectin in diabetes. CONCLUSIONS: These results suggest that circulating cellular fibronectin may be a marker protein for endothelial cell activation, especially in diabetes. Prospective studies are needed to explore this possibility     

Kupffer cell complement receptor clearance function after surgical injury and phagocytosis of immune complexes: effect of changes in plasma fibronectin

The present study evaluated the effect of changes in plasma fibronectin levels on the degree of depression of in vivo clearance function of Kupffer cell complement receptors after injury and the phagocytosis of immune complexes. In vitro studies have suggested that fibronectin may act as an opsonin for the clearance of immune complexes from the blood by binding to C1q and may influence the expression and activation of immune receptors on macrophages. Complement receptor clearance function was assessed in rats from the hepatic uptake of rat erythrocytes coated with antierythrocyte IgM. Increasing plasma fibronectin by the injection of purified fibronectin or decreasing fibronectin by the injection of gelatin had no effect on complement receptor function in otherwise normal animals. Surgical injury depressed both plasma fibronectin levels and complement receptor function. Injection of fibronectin at the time of injury prevented the depression of receptor function; however, when fibronectin was given 1 hour after injury, receptor function remained depressed even though fibronectin levels were increased. The phagocytosis of immune complexes (IgG-coated rat erythrocytes [EIgGs]) depressed complement receptor function but did not depress plasma fibronectin levels. The depression of receptor function caused by the phagocytosis of EIgGs was prevented by administering fibronectin and was potentiated by administering gelatin, which decreased plasma fibronectin levels. Therefore, plasma fibronectin concentrations can influence in vivo Kupffer cell complement receptor function under certain conditions that lead to the depression of complement receptor function.     

The response of plasma fibronectin to acute myocardial infarction in humans

The purpose of this study was to investigate the plasma fibronectin response to complicated and uncomplicated acute myocardial infarction. All patients admitted to a Coronary Care Unit over a six-month period were prospectively assessed by measuring admission and daily plasma fibronectin levels using an electroimmunoassay. Of 166 patients admitted to the Unit, 66 were diagnosed as having an acute myocardial infarction. Plasma fibronectin levels were significantly lower 48 h after the onset of symptoms in 15 patients with a complicated acute myocardial infarction, compared to fibronectin levels in patients with an uncomplicated course; patients who had received intracoronary streptokinase had consistently higher plasma fibronectin levels than those seen in patients who did not receive this thrombolytic agent. This hepatocyte-derived plasma protein not only has diagnostic potential, but alterations in its levels may also provide insight into the systemic response to acute myocardial injury.     

The concentration of plasma fibronectin in burns patients treated with fresh frozen plasma or plasma protein fraction

A group of 10 patients with 30-70% burns were given intravenous infusions during the first 48 h following hospital admission either with fresh frozen plasma (FFP) or human plasma protein fraction ( HPPF ). FFP contained 300-400 mg/dl plasma fibronectin whereas none was detectable in HPPF . Circulating plasma fibronectin levels fell quickly in those patients receiving HPPF and levels remained low for 2-3 weeks. In those receiving FFP, plasma fibronectin remained normal during the 48-h transfusion period but fell subsequently. Fibronectin may be an important determinant in the resistance to shock and infections. Consideration should therefore be given to the use of blood products which contain fibronectin and to the monitoring of plasma levels both during the acute and recovery periods after burn injury.     

Determination of plasma fibronectin (Fn) levels. Comparison between normal subjects and patients with various pathological conditions

Fibronectin is a glycoprotein secreted by connective tissue cells into their environment and into the blood. Plasma fibronectin in circulation exhibits some important interactions with other proteins in several diseases. We have detected plasma fibronectin levels in 187 normal subjects and in 126 patients. The mean value of this glycoprotein was strongly influenced by age but not by sex. 99 cancer patients showed lightly lower fibronectin levels than in normal controls. On the contrary, 25 chronic hepatic failure patients had higher values than normal controls. The mean level of plasma fibronectin in 20 hemodialyzed patients and in 7 plasmocytoma patients did not offer from what we detected in normal controls.     

Factor XIII and its substrates, fibronectin, fibrinogen, and alpha 2-antiplasmin, in plasma and urine of patients with nephrosis

Plasma and urine concentrations of factor XIII and its circulating substrates (fibronectin, fibrinogen, and alpha 2-antiplasmin) were measured in a group of 36 patients with nephrotic syndrome. The results were compared with those obtained in a group of 32 normal volunteers (control group) and 12 patients with end-stage renal disease (ESRD). A mild but significant reduction in plasma level and an abnormal urinary excretion of alpha 2-antiplasmin was found in the nephrotic group. Plasma concentrations of factor XIII, fibronectin, and fibrinogen were significantly elevated in patients with nephrosis. In contrast, patients with ESRD showed no significant difference in the plasma concentrations of either factor XIII, fibronectin, or alpha 2-antiplasmin and only a modest elevation of fibrinogen when compared with normal controls. No significant correlation was found between serum creatinine concentration and plasma levels of factor XIII and its circulating substrates in the nephrotic group. No measurable quantities of factor XIII and only small quantities of fibronectin were found in the urine of patients with nephrosis. Elevation of plasma factor XIII, fibronectin, and fibrinogen concentrations in the nephrotic group is considered to be the result of a combination of increased synthesis and possibly contracted intravascular distribution of these macromolecular proteins in the face of their negligible urinary losses. The presence of the observed abnormalities in the nephrotic group and their absence in the non-nephrotic ESRD group tends to exclude renal failure as a cause of these abnormalities. Although the clinical significance of these abnormalities is uncertain, they can potentially contribute to the thrombophilic diathesis and platelet hyperaggregability in nephrotic syndrome.     

Demonstration of fibronectin in human cerebrospinal fluid.

Fibronectin is a glycoprotein found in plasma (cold-insoluble globulin), connective tissues, and cultures of fibroblasts and astroglial cells. This paper describes the identification of fibronectin in human CSF. Fibronectin in CSF was immunologically indistinguishable from the plasma form, as shown by double-diffusion analysis and by radioimmunoassay specific for fibronectin. Fibronectin was isolated from human CSF by affinity chromatography on Sepharose-coupled gelatin and was further analyzed by SDS-polyacrylamide gel electrophoresis. It showed a polypeptide band similar to that of plasma fibronectin. The fibronectin concentration in CSF of 17 neurological outpatients without demonstrable organic lesion in the CNS was 3.0 +/- 1.6 microgram/ml (mean +/- S.D.) which is about 0.6% of total CSF protein. In CSF of 11 MS patients, the concentration was significantly (p less than 0.005) lower (1.6 +/- 0.2 microgram/ml). Of patients with brain tumors, seven had very low levels, three were normal, and two had very high levels. The cause for the low levels in MS and tumor patients is not known.     

Plasma fibronectin in various hemopathic diseases

Plasma fibronectin was determined by laser nephelometric immunoassay in two populations: (a) healthy subjects separated into three age groups (16-29 yr, 30-50 yr and over 50 yr) and, (b) patients with various hemopathic diseases without any infection or any therapy. Results showed that fibronectin levels in a healthy population were strongly influenced by age. An increase of human plasma fibronectin was shown to occur with age. Results in hemopathic patients were expressed in terms of percentage of mean deviations as compared to normal mean values for the corresponding age range. We found that plasma fibronectin was significantly decreased in acute myeloblastic leukemia, especially in transfused patients, polycythemia vera, osteomyelofibrosis. Waldenstr?m disease, benign dysproteinemia, refractory anemia and stage IV non-Hodgkin malignant lymphoma. Plasma fibronectin-decreased levels appear to be of prognostic value in the evolution of malignant hemopathic diseases.     

Fibronectin and factor VIII-related antigen in liver cirrhosis and acute liver failure

The liver is involved in the turnover of fibronectin in two different ways: hepatic synthesis contributes substantially to the plasma fibronectin pool, while Kupffer-cells, performing an important role of the reticuloendothelial system, remove fibronectin opsonized material from the circulation. In 45 patients with histologically confirmed liver cirrhosis and six patients with acute liver failure due to intoxication we determined fibronectin concentration in plasma by electroimmunoassay and additionally measured factor VIII-related antigen, which is a large glycoprotein not synthesized in the liver. Fibronectin levels in plasma were decreased in liver cirrhosis. This decrease was correlated with the extent of porto-caval collateral circulation. Very low levels were found in patients with acute liver failure. Factor VIII-related antigen levels were greatly increased as a function of the hepatic insufficiency. Between both parameters there was a significant inverse correlation. It is concluded that the simultaneous determination of both proteins provides reliable information about the remaining liver function.     

Role of fibronectin assembly in platelet thrombus formation

Fibronectin is a component of subendothelial matrices and abundant in plasma. A role of fibronectin in thrombogenesis has been suspected for three decades. Soluble fibronectin is assembled by adherent fibroblasts and platelets and thus converted to an insoluble form that mediates cell adhesion. Recently, in vivo studies using intravital videomicroscopy revealed that plasma fibronectin is important for stabilization of platelet aggregates after vascular injury. This review goes over roles of fibronectin in platelet functions with a focus on fibronectin assembly within developing platelet thrombi.     

Differences in the carbohydrate moieties of plasma and amniotic fluid fibronectins as revealed by crossed immunoaffinity electrophoresis with concanavalin A

Human fibronectins isolated from pooled human plasma and amniotic fluid were studied as to differences in their carbohydrate moieties. The chemical analyses showed that amniotic fluid fibronectin is different from adult plasma fibronectin in carbohydrate content and composition while there seems to be no significant differences in amino acid composition. Crossed immunoaffinity electrophoresis with free concanavalin A, as well as rocket immunoelectrophoresis with immobilized concanavalin A intermediate gel, indicated that amniotic fluid fibronectin has little or no reactivity with this lectin while adult plasma fibronectin is strongly reactive. Fetal cord plasma fibronectin apparently interacted with concanavalin A, but its reactivity was weaker than that of adult plasma fibronectin. Fibronectin isolated from ascitic fluid of an ovarian cancer patient which was examined in additional experiments showed much weaker Con A-reactivity than fetal cord plasma fibronectin. These results suggest that fibronectins from various body fluids differ in their carbohydrate structures.     

Mechanism of acute depletion of plasma fibronectin following thermal injury in rats. Appearance of a gelatinlike ligand in plasma.

Plasma fibronectin was depleted within 15 min following sublethal burn, followed by partial recovery at 8 h and complete restoration by 24 h in anesthetized rats. Radiolabeled 75Se-plasma fibronectin, injected intravenously before burn, was rapidly sequestered in burn skin as well as the liver. Fibronectin levels at 2 h postburn as detected by immunoassay vs. 75Se-plasma fibronectin indicated that more fibronectin was in the plasma than detected by electroimmunoassay. Crossed immunoelectrophoretic analysis of fibronectin in early postburn plasma demonstrated a reduced electrophoretic mobility of the fibronectin antigen. Addition of heparin or fibrin, both of which have affinity for fibronectin, to normal plasma was unable to reproduce this altered fibronectin electrophoretic pattern. In contrast, addition of gelatin or native collagen to normal plasma reproduced the abnormal electrophoretic pattern of fibronectin seen in burn plasma. Extracts of burned skin, but not extracts of normal skin, when added to normal plasma, elicited a similar altered electrophoretic pattern for fibronectin. By gel filtration, fibronectin in burn plasma had an apparent molecular weight approximately 40% greater than that observed in normal plasma. These data suggest the release into the blood of a gelatinlike ligand from burned skin, which complexes with plasma fibronectin. Thus, fibronectin deficiency acutely postburn appears mediated by (a) its accumulation at the site of burn injury; (b) its removal from the circulation by the liver; and (c) its presence in the plasma in a form that is less detectable by immunoassay.     

Distribution of bronchoalveolar cells and fibronectin levels in bronchoalveolar lavage fluids from patients with lung disorders

Differential cell counts and fibronectin levels were recorded in bronchoalveolar lavage fluids (BALF) from patients with lung cancer, idiopathic pulmonary fibrosis (IPF), sarcoidosis, pneumonia, acquired immunodeficiency syndrome (AIDS), and chronic obstructive lung disease (COLD). In all groups fibronectin levels were significantly higher than in the control group; patients with sarcoidosis had a six-fold higher fibronectin level (mean values), AIDS 5.4-fold, pneumonia 4.4-fold, lung cancer, IPF and COLD 2.4-3.0-fold. In control smokers the fibronectin level was significantly higher compared to healthy nonsmokers (p less than 0.002). The increased fibronectin levels could not be explained by contamination of BALF with blood or leakage of plasma proteins. Thus, increased fibronectin levels probably reflect local (e.g. macrophage/fibroblast) synthesis.