Effect of prostaglandin E1 treatment on murine acute immune complex glomerulonephritis

Activated T-lymphocytes induce growth inhibition and prostaglandin E2 release from syngeneic glomerular mesangial cells

The concept of an active role of T lymphocytes in the initiation and development of autoimmune glomerulonephritis has gradually evolved from recent investigations. In the present study we started in a murine coculture system to directly examine cellular interactions of intrinsic glomerular mesangial cells (MC) and syngeneic T lymphocytes. Lymph node lymphocytes and, moreover, cloned T helper cells specifically affected syngeneic proliferating MC, causing growth inhibition and prostaglandin E2 (PGE2) release. The T cell specificity of mesangial cell responses was confirmed by demonstrating (i) that MC cocultured with other cell types showed no reaction and (ii) that additional activation of T lymphocytes by IL-2 or concanavalin A significantly enhanced the MC responses. Subsequently, we confirmed the presence of T cell factors in the supernatants responsible for the observed effects: interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF). Experiments with combinations of recombinant mouse IFN-gamma and human lymphotoxin or TNF-alpha showed that these lymphokines could substitute for the direct T lymphocyte effects causing a synergistic growth inhibition and PGE2 release from mouse MC. The observed lymphokine activities were not due to mesangiolysis as shown by neutral red uptake of MC. Pointing to the essential role of T helper cell-specific products, IFN-gamma antibodies abolished both the IFN-gamma and the combined IFN-gamma/TNF-alpha effect. Thus, our investigations with syngeneic MC-lymphocyte cocultures demonstrated that cultured MC specifically responded to T lymphocytes and their products.

Eicosanoids: role in experimental renal disease

Because of their vasodilator and vasoconstrictor properties, vasoactive prostaglandins and thromboxane A2 have been proposed as modulators of the hemodynamic changes that occur in experimental models of renal disease. Increased synthesis of vasodilatory prostaglandins (PGE2) and perhaps prostaglandin I2 (PGI2) play a role in the maintenance of renal blood flow and GFR during states of impaired perfusion. In contrast, thromboxane A2 has been implicated as the vasoconstrictor responsible for the reduction of renal blood flow and GFR in certain animal models of experimental renal disease. These products and other metabolites of arachidonic acid may also participate in the immunological events underlying the onset and/or progression of experimental renal disease. It is evident that the pathophysiologic role of eicosanoids in experimental renal disease is not fully understood. Additional studies and further understanding of the many other potential roles of eicosanoids on immunological events, hemodynamic states, mesangial cell physiology, etc. are needed to comprehend more fully the extent of the participation of eicosanoids in the pathogenesis and pathophysiology of renal disease.

Effects of a specific thromboxane synthetase inhibitor on development of experimental Dirofilaria immitis immune complex glomerulonephritis in the dog

Twelve Beagle dogs were immunized with aqueous-soluble Dirofilaria immitis antigens, and subsequent to at least fivefold increases in serum antibody titer, 6 mg of homologous antigen was infused into the left renal artery. Six dogs were treated once daily starting the day of infusion with 0.75 mg/kg of 1-benzylimidazole (1-BIM) in saline. Six control dogs were given saline only. Light, immunofluorescent, and transmission electron microscopic examinations of renal tissue from control dogs, 10 days after antigen infusion, showed a mesangioproliferative glomerulonephritis in the left kidney with polymorphonuclear leukocyte (PMNL) infiltration and fibrin deposition. Immunoglobulin (Ig) G, M, C3, and Dirofilaria antigen deposits were observed in a segmental granular pattern. Mesangial, subendothelial, and intramembranous electron dense deposits were observed, and anti-Dirofilaria antibodies were demonstrated in kidney eluates from each dog. Administration of 1-BIM had no significant effect on IgG, IgM, C3, or antigen deposits, electron dense deposits, or concentration of antibody in kidney eluates. However, 1-BIM-treated dogs had less glomerular cell proliferation, periodic acid-Schiff (PAS) positive glomerular staining, PMNL infiltration, and fibrin deposition. These data suggest that thromboxane is an important mediator in the development of immune complex glomerulonephritis, and that in certain circumstances, inhibition of thromboxane synthesis may be an effective therapy for immune complex glomerulonephritis in the dog.

Mechanism of prostaglandin E2 inhibition of acute changes in vascular permeability

In order to determine the mechanism of antiinflammatory activity, prostaglandin E2 (PGE2) or diluent was administered to rats 2 h prior to intradermal injections of various mediators of inflammatory vascular permeability changes. Vascular permeability was measured as the accumulation of [125I]rat serum albumin at the site of mediator injunction. PGE2 at 500 micrograms significantly inhibited protein leakage produced by histamine, platelet activating factor, zymosan, and zymosan-activated plasma. Pretreatment with PGE2 had no effect on protein leakage induced by injection of lysosomal enzymes, glucose oxidase, or xanthine oxidase. The accumulation of polymorphonuclear leukocytes (PMNs) at the site of injection of zymosan or zymosan-activated plasma was not altered by PGE2 administration. In separate experiments, the ability of PGE2 to alter phagocytosis and oxygen radical production by PMN was examined. PGE2 significantly inhibited phagocytosis at 2 h, but this returned to normal by 6 h. Production of hydrogen peroxide by PMN was not affected by PGE2. These results suggest that PGE2 prevents acute changes in vascular protein leakage by preventing endothelial cell contraction and by inhibiting specific PMN functions.

Alteration of mercuric chloride-induced autoimmune glomerulonephritis in brown-Norway rats by herring oil, evening primrose oil and OKY-046 a selective TXA-synthetase inhibitor

Repeated subcutaneous (SC) injections of mercuric chloride (MC) in Brown Norway (BN) rats induce an autoimmune glomerulonephritis (GN) due to antiglomerular basement membrane (BM) antibody deposition in the glomeruli. The aim of this study was to investigate the effects on MC-induced autoimmune GN of OKY-046, a selective TXA-synthetase inhibitor herring oil (HO), which is rich in eicosapentaenoic acid (EPA) (5.6%) precursor of the three series of prostaglandins (PGs) and of (inactive) thromboxane (TXA3), and evening primrose oil (EPO), which is rich in linoleic acid (LA) (72%) and gamma-linolenic acid (GLNA) (9%), precursors of the one series of PGs, mainly PGE1, and of (inactive) TXA1. The administration of OKY-046 significantly inhibited proteinuria, partially prevented fibrin thrombi (FT) formation in the glomeruli, decreased urinary TXB, enhanced 6ketoPGF excretion and, increased survival rate of the animals from 60% (group receiving only MC) to 86%. However, OKY-046 did not prevent body weight (BW) loss or the development and deposition of IgG in the glomeruli. Increased intake of HO (80 days prior and throughout the experiment) and avoidance of arachidonic acid (AA) intake produced an effect comparable to that of OKY-046 in the rats. Furthermore, HO significantly inhibited the deposition of IgG in the glomeruli, increased the survival rate of the animals to 100% and further enhanced the increased urinary PGE excretion induced by MC. However, HO did not prevent BW loss in the animals. Increased intake of EPO and avoidance of AA intake produced an effect comparable to that of HO. Additionally, EPO completely prevented BW loss induced by MC in these animals. These findings suggest that the metabolites of AA, EPA and GLNA play an important role either in the development or in the modulation of this model of MC induced GN.

Protective effect of polyunsaturated fatty acid supplementation in apoferritin induced murine glomerulonephritis

The effects of increasing two dietary polyunsaturated fatty acids, eicosapentaenoic and linoleic, on the glomerulonephritis induced by repeated injections of apoferritin in the mouse were studied. Urinary protein excretion was measured serially; serum creatinine, aortic and renal production of eicosanoids and kidney histology were measured at sacrifice at 8 weeks. Both high EPA and LA feedings were associated with lesser proteinuria, normalization of renal function and profound changes in the tissue production of prostaglandin and thromboxane, which may explain their protective effect in this model of renal disease.

Renal gallium accumulation in mice with acute immune complex glomerulonephritis

67Ga uptake and heparan sulfate (HS) content were investigated during the recovery of mouse kidney from acute immune complex glomerulonephritis induced by daily injections of bovine serum, and the binding of 67Ga to glomerular basement membrane (GBM) was studied in vitro. The results were as follows. 67Ga uptake in the kidney increased after the start of bovine serum injection, and peaked on the 20th day. The uronic acid content in 1.2 M NaCl-soluble fraction (which contained predominantly HS) and the hydroxyproline content (an index of collagen) were increased at the 10th day, reaching a maximum at the 20th day. This pattern of HS content was essentially the same as that of 67Ga accumulation in the kidney. Urinary protein and gamma-GTP activity peaked at the 5th day, and these patterns were different from that of 67Ga uptake. 67Ga binding to GBM was significantly inhibited by treatments with HS-degrading enzyme (heparitinase), nitrous acid, trypsin or papain. However, the binding to GBM was unaffected by treatment with chondroitinase ABC. These results provide further evidence that the 67Ga-binding substance in tumor tissues and inflammatory lesions is probably HS.

Effect of platelet-activating factor and serum-treated zymosan on prostaglandin E2 synthesis, arachidonic acid release, and contraction of cultured rat mesangial cells

The interaction of inflammatory cells and glomerular prostaglandins (PG) may be important during glomerulonephritis. We therefore examined the influence of platelet-activating factor (PAF), (a mediator of inflammation released from leukocytes) and of phagocytosis of zymosan on arachidonic acid metabolism and on cell contractility in rat glomerular mesangial cells in culture. PAF increased PGE2 synthesis (determined by radioimmunoassay) within minutes (threshold: 10(-10)M; maximal effect: 10(-7)M). Serum-treated zymosan also stimulated PGE2, but with a slower onset. In cells prelabeled with [14C]arachidonic acid both PAF and serum-treated zymosan released 14C from phospholipids and increased free [14C]arachidonate. The ratio of 14C-release to PGE2 was, however, different with PAF and serum-treated zymosan, indicating different phospholipid pools. Under phase-contrast microscopy, PAF caused contraction of mesangial cells with a dose-response and time-course parallel to that for PGE2 synthesis. Serum-treated zymosan caused no contraction. The PAF-induced contraction was enhanced by PG synthesis inhibition and was attenuated by addition of PGE2, indicating a feedback mechanism. The mesangial contraction by PAF may be important in favoring deposition of immune complexes, while the PGE2 synthesis stimulated by PAF and by phagocytosis of zymosan may counteract the deleterious effects of PAF during induction of glomerulonephritis.

Treatment of murine immune complex glomerulonephritis with prostaglandin E2: dose--response of immune complex deposition, antibody synthesis, and glomerular damage

A model of immune complex glomerulonephritis (ICGN) produced in mice by the daily injection of apoferritin was employed to study the effect of treatment with various doses of prostaglandin E2 (PGE2) on glomerular damage, immune complex deposition, proteinuria, and serum anti-apoferritin antibody. Administration of PGE2, 200 micrograms twice daily, resulted in a significant decrease in glomerular damage and immune complex deposition, prevented the development of proteinuria, and significantly reduced serum levels of anti-apoferritin antibody. PGE2, 100 micrograms twice daily, resulted in a decrease in immune complex deposition as assessed by immunofluorescence microscopy, but this dosage did not significantly alter glomerular damage, proteinuria, or antibody levels. PGE2 dosages of 50 and 25 micrograms twice daily had no effect on any of these parameters. The protective effect of PGE2 on the development of ICGN occurred only at dosages that were associated with decreased anti-apoferritin antibody.

Mesangial IgA nephritis

Current data suggest that mesangial IgA nephritis is mediated by the mesangial deposition of soluble antigen-IgA class antibody complexes from the circulation. It is likely that common infectious gut flora and dietary antigens contribute to the immune complex load. Defects in antigen exclusion at the mucosa, in the control of IgA production, and in immune complex clearance are postulated to account for each of the recognized clinical syndromes. As yet no effective treatment is available, and a detailed analysis of the mediation pathways will be required before prevention or therapy can be attempted.

Alteration in immune complex glomerulonephritis by arachidonic acid

We employed a model of immune complex glomerulonephritis produced in mice by the daily injection of apoferritin to study the effect of treatment with arachidonic acid (AA). Apoferritin injections produced demonstrable glomerular damage by light microscopy associated with deposition of immunoglobulin along peripheral capillary loops. Treatment with AA 100 micrograms daily resulted in significantly less glomerular damage and a shift inthe location of immune complex deposition to the mesangium. The amount of anti-apoferritin antibody was determined by hemagglutination and found to be significantly decreased in mice treated with AA. Separate studies employing this dose of AA revealed that the number of IgM antibody producing cells to SRBC was not altered by AA.