Role of endothelin in cyclosporine-induced glomerular dysfunction

Since recent studies indicate that cyclosporine (CsA) disrupts endothelial integrity and that injured endothelial cells release excess endothelin, we examined endothelin's role in acute cyclosporine nephrotoxicity. Following CsA (20 mg/kg i.v.), rabbit anti-porcine endothelin (aE) serum was continuously infused into a first order branch of the main renal artery in Munich-Wistar rats whereupon the hemodynamics of glomeruli not infused with aE as well as those infused with aE within the same kidney were simultaneously assessed by micropuncture techniques. In CsA treated kidneys, in glomeruli not infused with aE, single nephron GFR (SNGFR) and glomerular plasma flow rate (QA) fell profoundly (on average by 42 and 48%, respectively) below the baseline values in association with lower glomerular capillary pressure and elevated afferent arteriolar resistance. By contrast, in glomeruli infused with aE within the same CsA treated kidneys, this vasoconstrictive pattern was markedly attenuated: SNGFR was, on average, only 19% lower than baseline and values for QA as well as other parameters determining glomerular filtration were at or near the levels observed before administration of CsA. In another group of rats (N = 6) an identical dose of CsA was given to measure the circulating level of endothelin. In these CsA treated rats, endothelin level (measured by radioimmunoassay) was elevated at 41.7 +/- 14.7 pg/ml, contrasting the value of less than 2 pg/ml uniformly observed in identically instrumented normal rats not given CsA (N = 5). Thus, cyclosporine is a potential inducer for endothelin release and endothelin appears to have a pivotal role in pathophysiology of cyclosporine-induced acute renal vasoconstriction and glomerular dysfunction.

Activated human monocytes exhibit receptor-mediated adhesion to a non-enzymatically glycosylated protein substrate

Non-enzymatic glycosylation of proteins is thought to play an important role in the development of diabetic vascular disease. Advanced glycosylation end products have been shown to accumulate on basement membranes and collagen in diabetes, and receptors for such adducts have recently been found on murine macrophages. We have observed that human monocytes activated by endotoxin express receptors for advanced glycosylation end products of similar affinity and number as has been previously reported for murine macrophages. In addition, there is an increased adherence of activated human monocytes to a non-enzymatically glycosylated albumin substrate, and such adhesion can be competitively inhibited up to 50% by soluble, non-enzymatically glycosylated albumin. We suggest that increased adherence of activated monocytes to non-enzymatically glycosylated proteins in the vessel wall may result in monocyte stimulation and/or local monocyte accumulation and thereby contribute to vascular disease in diabetes.

Bartonella bacilliformis stimulates endothelial cells in vitro and is angiogenic in vivo

Bartonellosis, a biphasic disease caused by motile intracellular bacteria, produces in its tissue phase a characteristic dermal eruption (Verruga peruana) resulting from a pronounced endothelial cell proliferation. Bacteria are found in the interstitium and within the cytoplasm of endothelial cells (Rocha-Lima inclusion). The aim of this study was to determine if Bartonella bacilliformis produce a substance(s) that might be responsible for the vascular proliferation seen in the Verruga. This was assessed in an in vitro system using human endothelial cells and measuring proliferation as well as production of tissue type plasminogen activator after exposure to the endothelial cultures to B. bacilliformis extracts. Our results indicate that B. bacilliformis possess an activity that stimulates endothelial cell proliferation up to three times that of control. The factor(s) is specific for endothelial cells, heat sensitive, larger than 12 to 14 kd, not enhanced by heparin, has no affinity for heparin, and is precipitated by 45% ammonium sulfate. In addition, the B. bacilliformis extracts stimulate production of t-PA antigen in a concentration-dependent fashion. This activity is also heat sensitive and not lost after dialysis (12 to 14 kd). B. bacilliformis extracts, however, do not increase the production of plasminogen activator inhibitor. It was also determined that B. bacilliformis extracts stimulate the formation of new blood vessels in an in vivo model for angiogenesis. These results describe a bacterial factor(s) that stimulates two important steps in the development of new blood vessels in vitro, as well as the formation of new blood vessels in vivo. Determining the mechanism of action, combined with a complete characterization of this factor(s), may help in understanding the pathogenesis not only of the Verruga and angiogenesis in general but also the recently described Cat-Scratch-associated epithelioid hemangiomas in patients with AIDS and Kaposi sarcoma.

Loop diuretic-sensitive potassium flux pathways of rat glomerular mesangial cells

Glomerular mesangial cells are smooth muscle-like contractile cells that mediate hormonal regulation of glomerular filtration. To gain better understanding of ionic events that accompany contraction/relaxation of these cells, flux pathways of K+ and their regulation by vasoactive agents were investigated in cultured rat mesangial cells using 86Rb+ as a tracer. Of total 86Rb+ influx (16.6 +/- 0.6 nmol x mg protein -1 x min-1), 46% was inhibited by 2 mM ouabain. Loop diuretics inhibited 43% of ouabain-insensitive 86Rb+ influx (3.9 +/- 0.2 nmol x mg protein-1 x min-1). Half-maximum inhibition was observed at 2 and 0.4 microM for furosemide and bumetanide, respectively. Loop diuretic-sensitive 86Rb+ influx was dependent on extracellular Na+ and Cl-; a hyperbolic dependency on extracellular Na+ was noted with apparent Michaels constant of 39 mM while a sigmoidal dependency on extracellular Cl- was present, which, assuming 1:1:2 stoichiometry for Na(+)-K(+)-Cl-, produced an apparent mean affinity constant of 64 mM. Moreover, a fraction of amiloride-insensitive 22Na+ influx was found to be sensitive to furosemide and dependent on extracellular K+ and Cl-, further indicating the presence of Na(+)-K(+)-Cl- cotransport. Efflux of 86Rb+ followed first-order kinetics, of which 60% was inhibitable by furosemide. Manipulations of extracellular osmolarity revealed that these furosemide-sensitive 86Rb+ flux pathways were coordinately regulated in response to osmotic stress. Concentration-dependent stimulation of Na(+)-K(+)-Cl- cotransport-mediated 86Rb+ influx was induced by two vasoconstrictors, angiotensin II (ANG II) and arginine vasopressin (AVP), and by a vasodilator, atrial natriuretic peptide (ANP).(ABSTRACT TRUNCATED AT 250 WORDS)

Ceruloplasmin reduces the adhesion and scavenges superoxide during the interaction of activated polymorphonuclear leukocytes with endothelial cells

The plasma protein, ceruloplasmin, has been implicated as an anti-inflammatory agent, although this property has not been demonstrated unequivocally in vivo. The role of this protein in an in vitro system of cultured endothelial cells and polymorphonuclear leukocytes (PMNs) was investigated. One of the initial steps in an inflammatory response is increased adhesion between PMNs and the endothelial lining of the blood vessels. The results showed that ceruloplasmin interferes with this process and reduces the number of phorbol myristate acetate-activated leukocytes that adhere to endothelium. Preincubation of either the activated PMNs or the endothelium with ceruloplasmin did not produce the same results, suggesting that the continuous presence of ceruloplasmin is required. During attachment PMNs become activated and release a variety of substances, including toxic oxygen species such as superoxide and hydrogen peroxide. In the in vitro system used in this study no injury occurred to the endothelial cells, as measured by 51Cr release, when activated PMNs were added with ceruloplasmin. The data show that ceruloplasmin reduced, in a dose dependent manner, the levels of superoxide produced by the activated PMNs, further supporting ceruloplasmin's previously reported role as a scavenger of superoxide. Ceruloplasmin also reduced the levels of superoxide when activated PMNs were in contact with endothelial cells. Although ceruloplasmin interfered with the copper-dependent scavenger enzyme, superoxide dismutase (SOD), in a cell-free system, ceruloplasmin had no effect on SOD in intact endothelial cells. These results suggest that ceruloplasmin may act as an anti-inflammatory agent by reducing the number of PMNs attaching to endothelium and by acting as an extracellular scavenger of superoxide.

Leukotriene D4 binding and signal transduction in rat glomerular mesangial cells

We examined the characteristics of [3H]leukotriene D4 (LTD4) binding to mesangial cells in culture. Binding is stereoselective, specific, saturable, and rapidly reversible. Two binding sites are recognized with dissociation constants and binding site densities at equilibrium of 2.2 and 16.8 nM and 1.1 x 10(4) and 3 x 10(4) binding sites per cell. LTD4, LTE4, (5R,6S)LTD4, LTB4, and the LTD4-receptor antagonist, SKF 104353, competitively inhibit radioligand binding in the following rank order of potency: LTD4 greater than LTE4 = SKF 104353 greater than (5R,6S)LTD4 greater than LTB4. LTD4 also induces time- and concentration-dependent phosphoinositide hydrolysis in mesangial cells. Formation of inositol 1,4,5-trisphosphate (IP3) is maximal at 5 s, followed by a time-dependent increase in inositol monophosphate generation, and inhibited by 100-fold excess concentration of SKF 104353. Addition of LTD4 to mesangial cells is associated with an increase in intracellular pH and dose-dependent stimulation of [3H]thymidine incorporation and mitogenesis. Thus rat mesangial cells possess specific binding sites for LTD4, the activation of which stimulates IP3 formation and induces cellular alkalinization and mitogenic responses. These studies provide insight into the cellular basis for LTD4-mesangial cell interactions, which are of potential pathophysiological relevance during acute glomerular inflammatory injury.

Cholesterol-fed heterozygous Watanabe heritable hyperlipidemic rabbits: a new model for atherosclerosis

Homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits are used widely to study atherosclerosis, but the WHHL heterozygous rabbit has received little attention. To study their potential as a model for atherosclerosis, heterozygous WHHL and New Zealand white (NZW) rabbits were fed diets containing 0%, 0.5% and 1.0% cholesterol. Plasma lipids were analyzed at 0, 4, 8, 12, 16 and 24 weeks, and animals were killed at 12 and 24 weeks. Plasma cholesterol levels were significantly higher in cholesterol-fed WHHL heterozygotes at 8 weeks compared with NZW rabbits, but no differences were apparent at other times. Atherosclerotic plaques in the aortas of cholesterol-fed WHHL heterozygous rabbits differed from those in NZW rabbits, in that the WHHL had complicated lesions with necrosis, cholesterol clefts, fibrous caps and calcification, similar to that found in humans and homozygous WHHL rabbits. In contrast, NZW rabbits had predominantly foam cell lesions. Heterozygous WHHL rabbits also had less extensive extravascular foam cell deposits. Our results suggest that the cholesterol-fed heterozygous WHHL rabbit may provide a promising model for studying the pathogenesis of atherosclerosis.

Evaluation of fibrinolytic capacity in plasma during thrombolytic therapy with single (scu-PA) or two-chain urokinase type plasminogen activator (tcu-PA) by a combined assay system for urokinase type plasminogen activator antigen and function

A combined assay for urokinase type plasminogen activator (u-PA) activity and antigen determination in plasma samples is described. This assay is based on binding of u-PA to an antibody immobilized on a microtiter plate followed by determination of the enzymatic activity of the bound u-PA. Thereafter bound u-PA antigen can be quantified by means of a specific peroxidase labelled monoclonal antibody against u-PA. By use of this assay system u-PA activity and antigen can be determined with lower detection limits of 0.08 IU/ml and 1.0 ng/ml, respectively, and intraassay as well as interassay coefficients of variation of 10% and 12% for activity and 5% and 7% for antigen determinations, respectively. Normal plasma levels of u-PA antigen could be determined to be 1.88 ng/ml +/- 0.61. Furthermore, this assay system allows specific quantification of u-PA antigen and activity during thrombolytic therapy.

Vascular origin determines plasminogen activator expression in human endothelial cells. Renal endothelial cells produce large amounts of single chain urokinase type plasminogen activator

Positioned at the boundary between intra- and extravascular compartments, endothelial cells may influence many processes through their production of plasminogen activators (PA). Available data have shown that tissue-type plasminogen activator (t-PA) is the major form produced by human endothelial cells. We have compared the molecular forms of PA produced by human endothelial cells from different microvascular and large vessel sources including two different sites within the circulation of the kidney. Using combined immunoactivity assays specific for u-PA and t-PA activity and antigen, we found that both human renal microvascular and renal artery endothelial cells produced high levels of u-PA antigen (60.48 ng/10(5) cells/24 h and 50.42 ng/10(5) cells/24 h, respectively) and corresponding levels of u-PA activity after activation with plasmin. Activity was not evident before plasmin activation, showing that the u-PA produced is almost exclusively as single chain form U-PA. In contrast, human omental microvascular endothelial cells and human umbilical vein endothelial cells produced exclusively t-PA (8.80 ng/10(5) cells/24 h and 2.17 ng/10(5) cells/24 h, respectively). Neither endothelial cell type from human kidney produced plasminogen activator inhibitor, as determined by reverse fibrin autography and titration assays. Agents including phorbol ester, thrombin, and dexamethasone were shown to regulate the renal endothelial cell production and mRNA expression of both u-PA and t-PA. Among the macro- and microvascular endothelial cells tested, only those from the renal circulation produced high levels of single chain form U-PA, suggesting the vascular bed of origin determines the expression of plasminogen activators.

Evidence for glomerular actions of epidermal growth factor in the rat

Epidermal growth factor (EGF), an endogenous mitogenic peptide, has recently been shown to be a potent vasoconstrictor of vascular smooth muscle. In view of its potential role in proliferative and inflammatory renal glomerular diseases, we examined the effects of EGF both on cultured rat mesangial cells and on in vivo glomerular hemodynamics. Mesangial cells possess specific, saturable EGF receptors of differing affinities, with Kd's of 0.1 and 1.7 nM, respectively. EGF produced a rapid increase in intracellular pH of 0.12 +/- 0.01 pH U, which was sodium dependent and amiloride inhibitable. The addition of EGF to mesangial cells cultured on either glass or dimethylpolysiloxane substratum induced reproducible cell contraction. Intrarenal EGF infusion did not affect systemic blood pressure or hematocrit but reversibly decreased GFR and renal blood flow from 4.19 +/- 0.33 to 3.33 +/- 0.26 and from 1.17 +/- 0.09 to 0.69 +/- 0.07 ml/min, respectively. Glomerular micropuncture confirmed decreases in single nephron plasma flow and in single nephron GFR (from 142 +/- 9 to 98 +/- 8 and from 51.6 +/- 11.7 to 28.5 +/- 3.5 nl/min, respectively) which were due to significant increases in both pre- and postglomerular arteriolar resistances (from 1.97 +/- 0.31 to 2.65 +/- 0.36 and from 1.19 +/- 0.11 to 2.00 +/- 0.15 10(10) dyn.s.cm-5 respectively) and to a significant decrease in the ultrafiltration coefficient, Kf, which fell from 0.100 +/- 0.019 to 0.031 +/- 0.007 nl/(s.mmHg). These studies demonstrate that mesangial cells possess specific receptors for EGF, and exposure of these cells to physiologic concentrations of EGF results in an in vitro functional response characterized by activation of Na+/H+ exchange and by resultant intracellular alkalinization, as well as by cell contraction. EGF administration in vivo significantly reduces the glomerular capillary ultrafiltration coefficient, Kf, which, in combination with EGF-induced constriction of both preglomerular and postglomerular arterioles, results in acute major reductions in the rates of glomerular filtration and perfusion.

Reduction in pO2 decreases the fibrinolytic potential of cultured bovine endothelial cells derived from pulmonary arteries and lung microvasculature

The effect of anoxia on the fibrinolytic potential of cultured endothelial cells derived from bovine pulmonary artery and bovine lung microvasculature was studied. Both cell types reacted with an increase in plasminogen activator inhibitor (PAI) activity and a decrease in the plasminogen activator (PA) activity in the media after incubation under anoxic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by fibrin autography and reverse fibrin autography indicated that the change in fibrinolytic potential was due to an impaired release of PA and not an increase in the production of PAI. Although anoxia did not affect the viability of the cells as judged by 51Cr release, their metabolism was influenced, which is reflected by increases in the levels of lactate in cell lysates and media. Furthermore, the effect of short-term anoxia on PA and PAI could not be reversed by reoxygenation for 24 hours. The results are discussed in terms of helping to explain the tendency of reocclusion after successful thrombolytic therapy, the development of pulmonary hypertension, and the thrombotic tendency of areas with an impaired circulatory supply.

Effects of hyperthermia on cell survival and patterns of protein synthesis in endothelial cells from different origins

Thermotolerance, transient resistance to heat induced by heat itself, is generally thought to be linked to the accumulation of heat-shock proteins in eukaryotic cells. The induction of thermotolerance and the synthesis of heat-shock proteins in primary and passage cultures of bovine aortic endothelium, passage cultures of bovine brain capillaries, and passage cultures of rat epididymal capillaries were examined. Primary and passage cultures of bovine aortic endothelial cells readily acquired thermotolerance; however, passage cultures of rat epididymal capillary cells and bovine brain capillary cells were very heat sensitive. In all endothelial cell types examined except rat epididymal capillary cells, the levels of HSP71, the most inducible of the HSP70 family, correlated well with thermotolerance. With prolonged passage, rat epididymal capillary cells and bovine brain capillary cells lost their ability to acquire heat resistance. Endothelial cells from different origins (aortic endothelium versus capillary endothelium) but from the same species and about the same passage number had a notably different response in terms of thermotolerance and synthesis of proteins after exposure to hyperthermia. The results of this study suggest that, while the expression of HSP71 may be a good indicator of heat resistance, the reverse is not necessarily true. Furthermore, the data show that endothelial cells from different origins are dissimilar in their response to hyperthermia.

Effects of heat shock on the expression of thrombospondin by endothelial cells in culture

Heat-shock proteins from confluent primary cultures of bovine aortic endothelial cells were analyzed by SDS-polyacrylamide gels. In addition to the increased synthesis of the classical heat-shock proteins, there is an increase of a 180,000-mol wt polypeptide in the growth media of heat-shocked cells. Immunoprecipitation with specific antiserum indicates that the 180,000-mol wt polypeptide is thrombospondin. Assay of mRNA levels coding for thrombospondin after brief hyperthermic treatment (45 degrees C, 10 min), followed by a recovery of 2 h at 37 degrees C, results in a twofold increase in mRNA abundance. In contrast, the activation level of the 71,000-mol wt heat-shock protein mRNA occurs at an earlier time than for thrombospondin mRNA. Immunofluorescence microscopy was used to study the intracellular and extracellular distribution of thrombospondin. Thrombospondin is localized to a prominent pattern of granules of intracellular fluorescence in a perinuclear distribution in cells not exposed to heat. Upon heat treatment, the pattern of granules of intracellular fluorescence appears more pronounced, and the fluorescence appears to be clustered more about the nucleus. There are at least three pools of extracellular forms of thrombospondin: (a) the fine fibrillar extracellular matrix thrombospondin; (b) the punctate granular thrombospondin; and (c) the thrombospondin found in the conditioned medium not associated with the extracellular matrix. When bovine aortic endothelial cells are exposed to heat, the extracellular matrix staining of a fibrillar nature is noticeably decreased, with an increase in the number and degree of fluorescence of focal areas where the punctate granule thrombospondin structures are highly localized. No gross morphological changes in extracellular matrix staining of fibronectin was noted. However, the intermediate filament network was very sensitive and collapsed around the nucleus after heat shock. We conclude that the expression of thrombospondin is heat-shock stimulated.

Electrical resistance and macromolecular permeability of brain endothelial monolayer cultures

Electrophysiological measurements were made on endothelial cells initially isolated as individual clones from bovine brain microvessels, and then grown as monolayers on a permeable support of glutaraldehyde-treated collagen gel. When transendothelial cell resistance (R) of the clones was measured, there was a range of values from a low of 157.4 +/- 4.5 omega.cm2 (n = 6) to a high of 783.2 +/- 7.0 omega.cm2 (n = 34). With the high-resistance cells, there was also a small potential difference of -0.46 +/- 0.03 mV luminal-side negative (n = 34). In comparison, endothelial cells from bovine aortas and rat epididymal fat pads cultured on the collagen gels had transendothelial R values of 13.5 +/- 0.2 (n = 62) and 0.45 +/- 0.03 (n = 10) omega.cm2, respectively. Exposure of the high-resistance brain endothelial cell monolayers to a Ca2+-free medium for 10 min decreased the R to 75% of the control values. Addition of Ca2+ back to the medium caused a return of the transendothelial R to control values within 1 h. Endothelial cells were also grown to confluency on microcarrier beads for permeability measurements to Evans blue dye-bovine serum albumin. Microcarriers with no cells (control) and microcarriers with bovine and epididymal endothelial cell monolayers showed no difference in the amount of adsorbed dye. Microcarriers with brain endothelial monolayers excluded up to 80% of the dye. This mammalian brain endothelial culture system will be a useful model for studies of the electrophysiological and permeability properties of the blood-brain barrier.

Collagen polymorphism in cultured rat kidney mesangial cells

Studies have been performed to evaluate both the relative amounts and the molecular forms of the collagens synthesized by cultured rat kidney mesangial (RKM) cells. The collagens secreted into the culture medium and extracted from the cell layers of cultured RKM cells were isolated after limited pepsin digestion and differential salt fractionation. Polyacrylamide gel electrophoresis under denaturing conditions of the RKM cell collagens indicated the presence of components corresponding to the chains present in types I, III, IV, and V collagen. Analysis of each fraction by carboxymethyl-trisacryl chromatography revealed that approximately 95% of the total collagen synthesized by the cultured mesangial cells was type I and that approximately one-half of this genetic type of collagen was present as type I trimers. The type IV molecules synthesized by RKM cells exhibited the molecular structure [alpha 1(IV)]3, whereas the type V molecules had the molecular composition [alpha 1(V)]2 alpha 2(V). Furthermore, in contrast to the type I and V collagens which were identified in both the secreted and cell-associated fractions, no type III or type IV components were detected among the collagens retained by the cells. These data establish the relative proportions of the collagens synthesized by cultured mesangial cells and suggest that the process of cell culture may induce a wound-healing or sclerosing phenotype in the glomerular mesangial cell.

Effects of dietary supplementation with marine fish oil on leukocyte lipid mediator generation and function in rheumatoid arthritis

Twelve patients with active rheumatoid arthritis supplemented their usual diet with 20 gm of Max-EPA fish oil, daily, for 6 weeks. Following this supplementation, the ratio of arachidonic acid to eicosapentaenoic acid in the patients' neutrophil cellular lipids decreased from 81:1 to 2.7:1, and the mean generation of leukotriene B4 (with calcium ionophore stimulation) significantly declined by 33%. The mean neutrophil chemotaxis to both leukotriene B4 and FMLP significantly increased toward the normal range at week 6. The generation of 5-lipoxygenase products by calcium ionophore-stimulated monocytes was not significantly suppressed, but a significant decline (37%) in platelet-activating factor generation was noted at week 6. The modulation of these measures of leukocyte inflammatory potential suggests that fish oil supplementation may have an antiinflammatory effect.

Adhesion of polymorphonuclear leukocytes to endothelium enhances the efficiency of detoxification of oxygen-free radicals

Polymorphonuclear leukocytes can produce active oxygen species such as hydrogen peroxide and superoxide under various conditions. Because these substances can be toxic to cells, it is possible that the interaction between the circulating leukocytes and the blood vessel wall, either in normal circulation or during the acute inflammatory response, could damage the endothelial lining. Using an in vitro system of cultured endothelial cells and isolated polymorphonuclear leukocytes, we have measured the levels of detectable superoxide when neutrophils are attached to either endothelial monolayers or to plastic. Our results show that the levels of superoxide, on a per-cell basis, are lower when the neutrophils are attached to endothelium than when attached to plastic, even if the neutrophils are stimulated with phorbol myristate acetate. This is also reflected in data showing that no injury occurs to the endothelial cells, as measured by 51Cr release, under these same conditions. When endothelial cells are pretreated with an inhibitor of superoxide dismutase, diethyldithiocarbamate, the levels of superoxide detected are the same for neutrophils stimulated on plastic and those on the endothelial monolayer, suggesting that endothelial superoxide dismutase may remove a portion of the neutrophil-generated superoxide from the detection system. Further evidence for the role of endothelium in destroying superoxide is suggested by results that show that the level of detectable superoxide released from neutrophils attached to formalin-fixed endothelial monolayers is the same as that for neutrophils attached to plastic. It is important to note that with the inhibitor of superoxide dismutase present, the endothelial monolayers do not display enhanced 51Cr release under the conditions employed. When both endothelial catalase and glutathione reductase are inhibited, we detect increased 51Cr release from endothelial cells in response to stimulated neutrophils. Our results show that the endothelial cells are important in affecting the apparent reduction of toxic oxygen products derived from polymorphonuclear leukocytes attached to their surface.

Selenium pretreatment enhances the radioprotective effect and reduces the lethal toxicity of WR-2721

Although WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, is an effective radioprotector, its use is limited by its toxicity. Combining WR-2721 with other agents might decrease its toxicity and/or increase its effectiveness. The effect of selenium (Se) pretreatment on the acute toxicity and radioprotective effect of WR-2721 was studied in male CD2F1 mice. Injection of 1.6 mg/kg Se 24 hr before WR-2721 (800-1200 mg/kg, IP) decreased the lethality of WR-2721 significantly. Lower doses of Se were also effective, but simultaneous administration was not effective. Se injection alone (1.6 mg/kg) 24 hr before cobalt-60 irradiation increased the survival (dose reduction factor, DRF = 1.1) significantly. A synergistic effect on post-irradiation survival was observed when Se was injected 24 hr before WR-2721 (200-600 mg/kg IP 1/2 before irradiation). For example, after exposure to 22 Gy (1 Gy/min), 30-day survival was 100% when mice were treated with both Se and 600 mg/kg WR-2721, and was 13% with WR-2721 alone. The DRF after 400 mg/kg WR-2721 was 2.6 with Se compared to 2.2 without Se pretreatment. Alkaline phosphatase activity in bone marrow cells and serum was significantly depressed after treatment with 1.6 mg/kg Se, suggesting that a retardation of conversion of WR-2721 to its active free sulfhydryl form through the action of alkaline phosphatase might be partly responsible for the effects of Se. Other possible mechanisms related to the antioxidant properties of Se are under investigation.

Glomerular endothelial cells secrete a heparinlike inhibitor and a peptide stimulator of mesangial cell proliferation

The regulation of cell growth in the kidney glomerulus plays a key role in many physiologic and pathologic processes. In this communication the authors have examined the possible role of glomerular endothelial cells as potential regulators of mesangial cell proliferation. Conditioned medium was collected from confluent cultures of glomerular endothelial cells and tested for its effects on glomerular mesangial cell and vascular smooth muscle cell growth. When glomerular endothelial cell-conditioned medium was mixed 1:1 with normal growth medium, the growth of these two closely related cell types was inhibited by 60-70%. If the conditioned medium was diluted to 1:9, a stimulation of mesangial and smooth muscle cells growth was seen. Approximately 70% of the antiproliferative activity was destroyed by a highly purified heparinase; the other 30% was sensitive to trypsin. Approximately 90% of the mitogenic activity was protease-sensitive. These results suggest that glomerular endothelial cells may participate in part in mesangial cell growth regulation via a heparin-mediated mechanism.

Dietary cholesterol-induced changes in macrophage characteristics. Relationship to atherosclerosis

In diet-induced hypercholesterolemia, circulating monocytes adhere to the endothelium of the vessel wall and emigrate into the intima. Atherosclerotic lesions may develop, characterized by the presence of lipid-laden macrophages and proliferating smooth muscle cells recruited from the media. Using rat peritoneal macrophages, the authors examined the influence of diet-induced hypercholesterolemia on several variables of macrophage function that may contribute to lesion formation, including adhesion to bovine aortic endothelial cells (BAECs) and vascular smooth muscle cells (VSMCs), the production of chemoattractants and mitogens for VSMCs, and the release of the reactive oxygen species, superoxide. In general, a hypercholesterolemia-induced augmentation of macrophage function was observed. In comparison with macrophages from normal animals (N M phi s), macrophages from hypercholesterolemic animals (H M phi s) were 50-80% more adhesive to BAECs and VSMCs. H M phi-secreted products increased VSMC migration 6 to 7-fold, whereas N M0s only stimulated motility 2.5-fold. In addition, H M phi-conditioned media produced increased VSMC growth 5-fold, compared with a 2.5-fold increase produced by N M phi-conditioned media. Although the production of superoxide was found to be the same for both N M phi s and H M phi s, the release of superoxide by macrophages found in the intima of hypercholesterolemic animals may contribute to the necrosis of cells in the developing lesion. These results suggest that dietary cholesterol may accelerate atherosclerotic lesion formation by inducing specific changes in the properties of circulating monocytes and intimal macrophages.

Subcellular distribution of leukotriene C4 binding units in cultured bovine aortic endothelial cells

The subcellular distribution of specific binding sites for [3H]leukotriene C4 ([3H]LTC4) was analyzed after sedimentation of organelles from disrupted bovine aortic endothelial cells on sucrose density gradients and was shown to be in membrane fractions I (20% sucrose) and IV (35% sucrose). Saturation binding studies of [3H]LTC4 on endothelial cell monolayers at 4 degrees C demonstrated high-affinity binding sites with a dissociation constant (Kd) of 6.8 +/- 2.2 nM (mean +/- SD) and a density of 0.12 +/- 0.02 pmol/10(6) cells. At 4 degrees C, the specific binding of [3H]LTC4 by each of the subcellular fractions reached equilibrium at 30 min and remained stable for an additional 60 min. After 30 min of incubation with [3H]LTC4, the addition of excess unlabeled LTC4 to each subcellular fraction reversed more than 70% of [3H]LTC4 binding in 10 min. The [3H]LTC4 binding activities of subcellular fractions were enhanced approximately twofold to fourfold in the presence of Ca2+, Mg2+, and Mn2+, whereas Na+, K+, and Li+ were without effect. As measured by saturation experiments, the Kd and density of LTC4 binding sites in fraction I were 4.8 +/- 1.6 nM and 16.5 +/- 1.9 pmol/mg of protein, respectively, and in fraction IV were 4.7 +/- 1.5 nM and 81.4 +/- 19 pmol/mg of protein, respectively. Inhibition of [3H]LTC4 binding in membrane-enriched subcellular fractions I and IV by LTC4 occurred with molar inhibition constant (Ki) values of 4.5 +/- 0.1 nM and 4.7 +/- 1.2 nM, respectively, whereas Ki values for LTD4 were 570 +/- 330 nM and 62.5 +/- 32.8 nM, respectively, and for LTE4 were greater than 1000 nM for each fraction; LTB4 and reduced glutathione were even less active. FPL55712, a putative antagonist of the sulfidopeptide LT components of slow reacting substance of anaphylaxis, had Ki values of 1520 +/- 800 nM and 1180 +/- 720 nM for [3H]LTC4 binding sites on membrane-enriched subcellular fractions I and IV, respectively. Thus as defined by Kd, Ki, and specificity, the LTC4 binding units that are distributed to the plasma membrane and the binding units in the subcellular fraction of greater density were similar to each other. Pretreatment of the isolated subcellular membrane fractions with trypsin abolished [3H]LTC4 binding by fraction I, enriched for the plasma membrane marker 5' nucleotidase, and that by fraction IV, enriched for the mitochondrial membrane marker succinate-cytochrome C reductase.(ABSTRACT TRUNCATED AT 400 WORDS)

Subcellular distribution of leukotriene C4 binding units in cultured bovine aortic endothelial cells

The subcellular distribution of specific binding sites for [3H]leukotriene C4 ([3H]LTC4) was analyzed after sedimentation of organelles from disrupted bovine aortic endothelial cells on sucrose density gradients and was shown to be in membrane fractions I (20% sucrose) and IV (35% sucrose). Saturation binding studies of [3H]LTC4 on endothelial cell monolayers at 4 degrees C demonstrated high-affinity binding sites with a dissociation constant (Kd) of 6.8 +/- 2.2 nM (mean +/- SD) and a density of 0.12 +/- 0.02 pmol/10(6) cells. At 4 degrees C, the specific binding of [3H]LTC4 by each of the subcellular fractions reached equilibrium at 30 min and remained stable for an additional 60 min. After 30 min of incubation with [3H]LTC4, the addition of excess unlabeled LTC4 to each subcellular fraction reversed more than 70% of [3H]LTC4 binding in 10 min. The [3H]LTC4 binding activities of subcellular fractions were enhanced approximately twofold to fourfold in the presence of Ca2+, Mg2+, and Mn2+, whereas Na+, K+, and Li+ were without effect. As measured by saturation experiments, the Kd and density of LTC4 binding sites in fraction I were 4.8 +/- 1.6 nM and 16.5 +/- 1.9 pmol/mg of protein, respectively, and in fraction IV were 4.7 +/- 1.5 nM and 81.4 +/- 19 pmol/mg of protein, respectively. Inhibition of [3H]LTC4 binding in membrane-enriched subcellular fractions I and IV by LTC4 occurred with molar inhibition constant (Ki) values of 4.5 +/- 0.1 nM and 4.7 +/- 1.2 nM, respectively, whereas Ki values for LTD4 were 570 +/- 330 nM and 62.5 +/- 32.8 nM, respectively, and for LTE4 were greater than 1000 nM for each fraction; LTB4 and reduced glutathione were even less active. FPL55712, a putative antagonist of the sulfidopeptide LT components of slow reacting substance of anaphylaxis, had Ki values of 1520 +/- 800 nM and 1180 +/- 720 nM for [3H]LTC4 binding sites on membrane-enriched subcellular fractions I and IV, respectively. Thus as defined by Kd, Ki, and specificity, the LTC4 binding units that are distributed to the plasma membrane and the binding units in the subcellular fraction of greater density were similar to each other. Pretreatment of the isolated subcellular membrane fractions with trypsin abolished [3H]LTC4 binding by fraction I, enriched for the plasma membrane marker 5' nucleotidase, and that by fraction IV, enriched for the mitochondrial membrane marker succinate-cytochrome C reductase.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation of bovine aortic endothelial cell plasma membranes: identification of membrane-associated cytoskeletal proteins

The plasma membrane of bovine aortic endothelium was isolated, characterized, and found to contain at least four membrane-associated cytoskeletal proteins. Exposure of the plasma membranes to salt media (up to 1M KCl) resulted in the release of 30% of the total plasma membrane-associated proteins and extraction with 1% Triton X-100, 60%. At least four heavily glycosylated bands (185-, 165-, 150-, and 130,000 mol-wt) were evident. The Triton-insoluble pellet fraction contained several major polypeptides (30-, 43-, 58-, and 240,000 mol-wt), two of which were identified by immunoblotting as cytoplasmic actin (43,000 mol-st) and vimentin (58,000 mol-wt). Strikingly, vimentin and a 240,000 mol-wt polypeptide were routinely present in approximately a mole ratio of 4:1 in more than 60% of the plasma membrane preparations. We also report the presence of a 2.1-like and a 4.1-like protein associated with plasma membranes. The 2.1-like protein demonstrated similar solubilities and apparent molecular weight (210,000) as erythroid protein 2.1. Likewise, the endothelial 4.1-like protein exhibited similar solubilities and apparent molecular weight as erythroid protein 4.1. Immunofluorescence staining of fixed and permeabilized cultures with anti-2.1 antibodies showed a fibrillar pattern. In contrast, cells stained with anti-protein 4.1 were brightly fluorescent, bearing both a diffuse and punctate pattern. This paper presents several novel observations pertaining to the composition of bovine aortic endothelial cell plasma membranes, namely: the presence of two erythroid-like cytoskeletal polypeptides; the presence of vimentin and a 240,000 mol-wt polypeptide in a 4:1 mole ratio in more than 60% of the plasma membrane preparations and the co-elution in a 4:1 mol ratio with a protein perturbant; and the inability to release actin from the plasma membrane preparations, suggesting the association of actin with other molecules in the plasma membrane preparation.