Neutrophil function in an experimental model of hemolytic uremic syndrome.

To understand the role of neutrophil leukocytosis in hemolytic uremic syndrome, we studied the changes in neutrophil function in the modified generalized Shwartzman reaction in rabbits. This model resembles hemolytic uremic syndrome associated with endotoxemia. At the end of an endotoxin infusion, we observed leukopenia, thrombocytopenia, and a decrease in hematocrit associated with schistocytosis. Plasma B-glucuronidase levels increased and this was associated with a decrease in neutrophil content of the enzyme. The chemotactic index and neutrophil aggregation to zymosan-activated serum were impaired compared to controls. The neutrophil procoagulant content increased after endotoxin infusion. The serum creatinine concentration and proteinuria increased in the endotoxin-treated animals. The changes returned to normal by 48 h. Renal cortical malondialdehyde, a reflection of lipid peroxidation, was higher in the endotoxin-treated animals than in the controls. We have shown enzyme release by neutrophils, impairment of chemotaxis and aggregation, increased procoagulant content in neutrophils, and evidence of lipid peroxidation in renal cortical tissue in this model. These observations raise the possibility that leukocytes may have a role in the pathogenesis of the hemolytic uremic syndrome.

Colchicine reduces proteinuria in passive Heymann nephritis.

Colchicine was given to rats in the heterologous phase of passive Heymann nephritis to see whether this drug could reduce proteinuria. Treatment with 0.06 mg/day for 14 days caused significant reductions in proteinuria and albuminuria. Administration of dimethyl sulfoxide (DMSO) alone or in combination with colchicine also reduced protein and albumin excretion. In a long-term experiment, rats treated with colchicine had significantly less proteinuria. After stopping therapy, urine protein excretion was similar to controls. No differences in glomerular C3 and IgG deposition were found between treated and control rats 24 h, 3,7 and 14 days after immunization. Depressed serum C3 levels were measured at 24 h in colchicine-treated rats. No difference in serum-circulating immune complexes was detected between the two groups. Concurrent administration of indomethacin and colchicine to rats with passive Heymann nephritis (PHN) partially reversed the reduction in proteinuria and albuminuria seen in rats treated with colchicine alone. The G.F.R, however, was significantly reduced in colchicine-treated rats as well as in rats treated with colchicine and indomethacin. Serum cholesterol and triglyceride levels were significantly lower in colchicine-treated rats than in controls. Serum cholesterol concentrations in rats given both colchicine and indomethacin were similar to control values. These findings suggest that colchicine reduces urine protein and albumin excretion, and hyperlipidemia in PHN. The finding that indomethacin partially blocks the effects of colchicine suggests that renal prostaglandin stimulation by colchicine may have been involved in the reduction in proteinuria.

Interactions of dimethyl sulfoxide and nonsteroidal anti-inflammatory agents in passive Heymann's nephritis.

The effect of treatment with indomethacin on the ability of dimethyl sulfoxide (DMSO) to reduce proteinuria in rats with passive Heymann's nephritis (PHN) was studied. PHN rats treated with DMSO alone excreted significantly less protein by day 14 than PHN rats treated with buffer or with indomethacin alone. Rats treated with DMSO excreted 19 +/- 6.0 mg protein/24 hr, and those treated with DMSO and indomethacin excreted 161 +/- 27.4 mg protein/24 hr (P less than 0.001). Rats treated with DMSO alone had significantly higher serum albumin and significantly lower serum cholesterol and triglyceride concentrations than those given the two drugs together. Glomerular deposits of C3 were reduced in DMSO-treated rats, but serum C3 concentrations and rat antirabbit serum antibody titers were similar in the two groups. When a higher dose of indomethacin (5 mg/kg) plus DMSO was used, protein excretion was significantly reduced. Rats treated with DMSO and acetylsalicylic acid (ASA) (37 mg/kg/day) or DMSO and meclofenamate (5 mg/kg/day) did not have a significant reduction in protein excretion compared with untreated controls. High-dosage indomethacin alone did not reduce proteinuria. Low doses of nonsteroidal anti-inflammatory agents therefore appear to block the effect of DMSO on proteinuria. This was in marked contrast to the finding of reduction of proteinuria induced by larger doses of indomethacin (5 mg/kg) plus DMSO. DMSO did not reduce proteinuria in rats with nephrosis induced by puromycin of aminonucleoside.

Reduction of protein excretion by dimethyl sulfoxide in rats with passive Heymann nephritis.

Passive Heymann nephritis, a model of immune complex nephritis, was produced in rats by injection of rabbit antibrush border membrane vesicle antibodies to examine the effect of treatment of epimembranous glomerulonephritis with dimethyl sulfoxide. Administration of DMSO twice a day, 5 days a week for 4 weeks significantly reduced protein excretion in the autologous phase of the model. This beneficial effect occurred in animals in which treatment was started a day after administration of the antibody and persisted for 4 weeks after treatment was discontinued. Serum triglyceride concentrations were significantly decreased, whereas, BUN, serum cholesterol, and globulin levels were significantly, but not reproducibly, reduced. That DMSO did not reduce proteinuria to normal values in rats treated after proteinuria was well established, but was able to reduce proteinuria significantly. Treatment of normal rats and those with nephrotoxic serum nephritis did not reduce protein excretion. Glomeruli of rats with passive Heymann nephritis treated with DMSO studied by immunofluorescent microscopy appeared to have less fluorescence for IgG than control rats, but these differences were not significant. However, C3 deposits were significantly decreased in treated rats, but only during the first week of the disease and in vitro C3 fixation was also significantly reduced in glomeruli of rats that had been treated with DMSO. There was very little effect on serum complement activity: CH50 was reduced only on day 1 of treatment, whereas the alternate pathway activity and serum C3 concentration were unaffected. DMSO may therefore reduce protein excretion, in part, by inhibiting C3-dependent proteinuria. These studies indicate that DMSO is capable of significantly reducing protein excretion in rats with passive Heymann nephritis and that its action may involve reduction of complement deposition within the glomeruli during the heterologous phase. Toxic effects included a 2.5% mortality and decreased weight gain while being treated with larger doses of DMSO. Treatment with a much smaller dose succeeded in reducing proteinuria significantly without affecting weight gain. There was no evidence of drug-induced liver or renal damage.

Impaired and exhausted platelets in modified generalized Shwartzman reaction: an analogue of hemolytic uremic syndrome associated with endotoxemia.

Thrombocytopenia is characteristically associated with septicemia and hemolytic uremic syndrome (HUS), a subset of which has been shown to be associated with endotoxemia and shigellosis. An experimental model that closely resembles these clinical conditions is the generalized Shwartzman reaction modified with a continuous intravenous infusion of endotoxin for 5 hr in rabbits. In addition to exhibiting the triad of HUS (thrombocytopenia, hemolytic anemia, and azotemia), these animals also had circulating platelet aggregates, leukocytosis, lipidemia, hemoglobinemia, hyperfibrinogenemia, and prolonged partial thromboplastin time. Platelets that remained in circulation were chemically exhausted in serotonin content and functionally impaired in aggregation activities. Plasma from animals during thrombocytopenia and platelet functional deficiency had no effect of the aggregation responses of normal platelets. Although the single triggering event of endotoxin infusion was stopped at hour 5, recovery from abnormalities was only partial on day 2 and within normal limits by day 3. In vitro studies supported platelet exhaustion as a mechanism for decreased platelet function after endotoxin infusion. The presence of circulating platelet aggregates and exhausted platelets suggested that the process of platelet activation took place at as long as 24 hr after the cessation of LPS infusion. Endotoxin and other mechanism(s) are likely to be operative in the pathogenesis leading to platelet activation. Further studies to reveal the mechanism of platelet exhaustion in the experimental model may help our understanding of corresponding events in clinical endotoxic injury and HUS associated with endotoxemia.

Impairment of platelet aggregation in hemolytic uremic syndrome: evidence for platelet "exhaustion".

Thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure are the hallmarks of hemolytic-uremic syndrome (HUS). This report presents the results on platelet studies from 10 consecutive HUS patients in childhood. During their acute illness, they all displayed a characteristic pattern of impaired platelet function: no aggregating responses to epinephrine, some to ADP, and moderate to collagen. In addition, platelet contents of beta-thromboglobulin (beta TG) were markedly reduced. As these patients improved clinically, their platelet-aggregating responses also normalized despite their uremic state. Incubation of platelets with uremic plasma or guanidino-succinic acid, a uremic toxin, had minor effects on platelet-aggregating activity. Since low levels of platelet beta TG suggest that these platelets were in an exhausted state, in vitro experiments were performed to exhaust normal platelets by incubation at 37 degrees C. A proportional impairment of platelet-aggregating responses and decreasing levels of platelet beta TG were noted. Furthermore, the pattern of impairment was similar to that found in the platelet-aggregating activities of HUS patients. Thus, "exhaustion," in addition to azotemia and thrombocytopenia, are factors that contribute to the functional impairment of platelets in these patients. Further studies to reveal mechanisms that lead to platelet exhaustion in HUS are of fundamental importance in the understanding of this illness.

Turner's syndrome, 46X, del (X) (p 11), persistent complement activation and membranoproliferative glomerulonephritis.

An adolescent girl with short stature and learning disability was found to have an unusual variant of Turner's syndrome, 46X, del (X) (p 11) and an abnormal urinary sediment. Further studies demonstrated persistent depression of C3 and histologic evidence of membranoproliferative glomerulonephritis (MPGN). The occurrence of MPGN in this case may have been a manifestation of the known tendency for Turner patients to develop immunologic disease.

Muscle extract infusion in rabbits. A new experimental model of the crush syndrome.

Previous studies provide inconclusive data concerning the nephrotoxicity of myoglobin following muscle injury. We investigated the possibility that released muscle constituents other than myoglobin may be associated with renal damage, and studied accompanying hematological and coagulation changes. An extract of homologous or autologous muscle was infused intravenously in rabbits in a dose of 100 mg of muscle extract protein/kg; equine myoglobin was given to control animals. Experimental animals developed proteinuria, cylindruria, and a 50% reduction in glomerular filtration rate. Leukopenia, thrombocytopenia and evidence of intravascular coagulation also were seen. The muscle extract was shown to have thromboplastic activity; however inhibition of this by phospholipase C did not prevent the changes induced by muscle extract infusion possibly because the intrinsic changes coagulation pathway still was activated. Although moderate hypotension and ECG changes developed in some rabbits, these were not consistent and the renal functional changes appeared to be independent of these factors. Pulmonary and glomerular microthrombi were seen in experimental animals and there was vacuolation of the renal proximal tubular cells. The studies indicate that a number of biological systems are activated following muscle extract infusion and that these may be more important than the nephrotoxicity of myoglobin in the pathogenesis of the renal injury.

Reduced platelet aggregation in hemolytic-uremic syndrome.

Platelet aggregation was studied in three patients during the course of the hemolytic-uremic syndrome (HUS) when the platelet count was below 100,000/mm3 and after the platelet count had normalized. Platelet aggregation was examined in response to epinephrine, adenosine diphosphate (ADP) and collagen. Aggregation did not occur in response to epinephrine when the patients were thrombocytopenic but normal tracings were obtained when the platelet counts had returned to normal. In contrast, platelet-rich plasma from normal subjects diluted with platelet-poor plasma from patients to comparable platelet counts, showed normal aggregation responses. This study demonstrates that platelet aggregation is reduced in the early phase of the HUS.

Renal injury after muscle extract infusion in rats: absence of toxicity with myoglobin.

A crude muscle extract infused into rats produced oliguria, a precipitous drop in total hemolytic complement, and in circulating white cell and platelets counts. A mild vaso-depressor effects was noted. These changes were not produced by myoglobin or saline infusion. Muscle constituents other than myoglobin are responsible for the systemic and renal nephrotoxic effects observed.

Polymyxin B sulfate modification of bacterial endotoxin: effects on the development of endotoxin shock in dogs.

The effects of endotoxin (lipopolysaccharide [LPS]) on the pathogenesis of canine endotoxin shock were compared with those of LPS which had interacted with polymyxin B sulfate prior to administration. Both LPS and polymyxin B-modified LPS caused comparable early decreases in aortic blood pressure, leukocyte and platelet numbers, and serum complement levels. However, in dogs receiving polymyxin B-modified LPS the late hypotensive phase was significantly ameliorated and lethality was significantly decreased. These data indicate that polymyxin B-modified LPS, though significantly less lethal than unmodified LPS, was capable of major interactions with several components of the humoral defense system, and support the concept that such interactions are not determinative in the pathogenesis of canine endotoxin shock.

Lipid peroxidation in the hemolytic uremic syndrome.

Based on recent evidence of a genetic influence on prognosis (1) and the existence of red cell membrane phospholipid depletion with low or absent serum alpha-tocopherol (2) levels in three children with the Hemolytic Uremic Syndrome (H.U.S.), we wish to suggest the existence of an inborn error of antioxident capacity as the basic pathogenetic mechanism in the development of the hemolytic uremic syndrome (H.U.S.).

A hemolytic plate method for alternative-pathway complement activity assay.

A new hemolytic plate method for the functional assessment of alternative-pathway complement activity is described. The plates are easy to prepare and the method simple to perform. Analysis of 23 normal serum samples showed a mean lysis diameter of 4.1 +/- 0.2 mm (1 standard deviation).

Treponemal antigens in congenital and acquired syphilitic nephritis: demonstration by immunofluorescence studies.

Two patients, a 4-month-old infant girl with congenital syphilis and a 45-year-old man with secondary syphilis, had the nephrotic syndrome with glomerulonephritis. Immunoglobulins and treponemal antigenic material were seen in the glomeruli of both patients by immunofluorescence microscopic studies of renal tissue. Electron micrographs showed subepithelial electron dense deposits along the glomerular basement membrane. This confirms earlier suggestions that the renal injury is of an immune-complex type.

Role of platelets in the pathogenesis of canine endotoxin shock.

Endotoxin-platelet interactions are thought to be of major importance in the response of dogs and other species to bacterial endotoxin; the mechanisms postulated are: (i) the release of vasoactive substances, (ii) the formation of occlusive platelet aggregates, and (iii) induction of intravascular coagulation. The role of platelets in canine endotoxin shock was examined in animals with thrombocytopenia induced by estrogen pretreatment (less than 10,000 platelets/mm3) and in controls. After intravenously administered endotoxin, the hemodynamic responses, mortality, and gross necropsy findings were similar in both groups. These data indicate that endotoxin-platelet interactions are not determinative in the pathogenesis of canine endotoxin shock.