Effects of thromboxane synthetase inhibition on immune complex glomerulonephritis.

To determine the role of thromboxane A2 in the pathogenesis of experimentally induced immune complex glomerulonephritis, 12 concanavalin A-immunized Beagles were infused with 1 mg of concanavalin A via each renal artery and treated twice daily for 8 days with either 30 mg of CGS 12970/kg, PO, a specific thromboxane synthetase inhibitor, or placebo. The effect of treatment was assessed by measuring endogenous creatinine clearance and urine protein and eicosanoid excretion, and by evaluating changes in glomerular morphometric characteristics. On postinfusion day 8, urine protein, thromboxane B2, and 11-dehydro-thromboxane B2 excretion, glomerular epithelial crescent formation, and glomerular cell proliferation in the CGS 12970-treated dogs were significantly decreased when compared with values in the placebo-treated group. Differences were not observed in endogenous creatinine clearance, urine prostaglandin E2 and 6-keto-prostaglandin F1 alpha excretion, or glomerular polymorphonuclear leukocyte infiltration between groups in this study. These findings suggest thromboxane A2 has a role in the development of immune complex glomerulonephritis and that thromboxane synthetase inhibition may be beneficial in attenuating some of the functional and histological changes associated with immune complex glomerulonephritis.

Effects of a specific thromboxane synthetase inhibitor on thromboxane generation and excretion in healthy dogs.

A specific thromboxane synthetase inhibitor, 3-methyl-2 (3-pyridyl)-1-indoleoctanoic acid (CGS 12970) was administered orally to 6 healthy adult Beagles at a dosage of 30 mg/kg of body weight. Blood generation of thromboxane B2 and urinary excretion of thromboxane B2 were measured before and after administration of CGS 12970. Although 97 +/- 0.4% inhibition of thromboxane B2 generation was observed within 2 hours after a single dose of CGS 12970 was administered orally, an effect on urinary excretion of thromboxane B2 was not observed. Additionally, oral administration of 30 mg/kg every 12 hours resulted in 80 +/- 14% inhibition of thromboxane B2 generation but had no effect on urinary thromboxane B2 excretion.

Experimental Dirofilaria immitis-associated glomerulonephritis induced in part by in situ formation of immune complexes in the glomerular capillary wall.

Eight dogs were immunized with an aqueous-soluble extract of adult Dirofilaria immitis. Subsequent to at least 7-fold increases in antibody titer, the left renal artery of each dog was infused with 6 mg of D. immitis antigen. Fourteen days after infusion, the left kidney was compared to the right kidney and preinfusion biopsies. All dogs developed glomerular lesions in the left kidney characterized by 1 or more of the following: mesangial cell proliferation, neutrophil infiltration, increased periodic acid-Schiff-positive staining of the mesangium and glomerular basement membrane (GBM), fibrin deposition, and thickening of the GBM. Left kidney glomerular immunofluorescence was positive in 7 of the 8 dogs using polyclonal antisera for canine IgG and C3 in a linear or fine granular pattern. Ultrastructural lesions were present in the left kidney of all dogs and consisted of irregular GBM thickening, intramembranous and mesangial electron-dense deposits, and mesangial and endothelial cell proliferation. Antibodies directed against D. immitis antigen were demonstrated in all kidney eluates from the left kidney. The right kidneys of 3 of the dogs developed lesions; however, in comparison to the left kidney, the lesions in the right kidneys were inconsistent, mild, and focal. The histologic findings in the left kidney were similar to those observed in dogs with naturally occurring D. immitis infections. In sham-immunized control dogs, renal arterial infusion of D. immitis antigen did not cause consistent immune complex glomerulonephritis; however, antigen adherence to glomerular capillary walls was observed by immunofluorescent microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Parasite excretory-secretory antigen and antibody to excretory-secretory antigen in body fluids and kidney tissue of Dirofilaria immitis infected dogs.

Excretory-secretory (ES) antigens of adult Dirofilaria immitis were detected by enzyme-linked immunosorbent assay (ELISA) in serum and urine from each of 12 experimentally infected dogs. Excretory-secretory antigens in serum were first detected 154 days postinfection. Serum antibodies directed against parasite ES antigens were detected by ELISA in all dogs. Kidney tissue elution studies were performed in 10 dogs, and antibody and parasite ES antigens were demonstrated in each case. Antibody or parasite antigen was not detected in serum, urine, or kidney eluates from uninfected dogs. At peak concentrations of the ES antigens in serum, there were correlations with the number of adult D. immitis present in the dogs (r2 = 23.8, P less than 0.05) and with the antigen concentration in kidney eluates (r2 = 73.5, P less than 0.001). Peak serum antibody concentrations were not correlated with either the number of adult worms or the antibody concentrations in kidney eluates. This study suggests that detection of parasite antigens in urine may be an important diagnostic aid. In addition, the correlation between the concentration of D. immitis ES antigens in kidney tissue and in serum without a similar correlation between serum and kidney antibody concentrations suggests that D. immitis ES antigens adhere to kidney tissue.

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.

Clinicopathologic and histologic evaluation of Dirofilaria immitis-induced nephropathy in dogs.

Twelve beagles were infected with 200 Dirofilaria immitis infective larvae to study glomerular lesions associated with filariasis. All developed high serum levels of antibodies to dirofilarial antigens and became persistently microfilaremic. The dogs were killed at various times between 398 and 562 days post-infection and renal lesions were examined by light, electron, and immunofluorescent microscopy and antibody elution techniques. A membranoproliferative glomerulonephritis was observed in all dogs. Immunofluorescence was positive in all; predominantly in a fine granular pattern along the glomerular capillary wall. Ultrastructural examination showed intramembranous globular electron-dense deposits and a linear band of fine electron-dense particles in all dogs. Antibody elution studies demonstrated antibody reactive to dirofilarial antigens. In a subsequent experiment, an aqueous-soluble antigen prepared from adult female D. immitis was infused into the renal arteries of 5 heartworm-naive dogs. Immunofluorescent examination of the infused kidneys showed dirofilarial antigen present on the glomerular capillary wall in a fine granular pattern indicating there was adherence of the antigen to the capillary wall. These observations support the hypothesis of in situ immune complex formation as part of the pathogenesis of glomerulonephritis associated with dirofilariasis.

Phase I trial of tiazofurin administered by i.v. bolus daily for 5 days, with pharmacokinetic evaluation.

Tiazofurin is a novel C-nucleoside with significant antitumor activity in murine tumor models. In a phase I clinical trial, patients received tiazofurin by bolus iv infusion daily for 5 days. Six doses ranging from 550 to 4100 mg/m2/day were evaluated. Thirty-one treatment courses were initiated in 21 patients. Tiazofurin induced multiple, transient toxic effects at all but the lowest dose level, and treatment interruption was a common result. Nine of 28 treatment courses initiated at doses greater than or equal to 1100 mg/m2/day were interrupted at less than 5 days; only five of eight courses initiated at 1100 mg/m2/day were completed. Symptoms leading to treatment interruption included headache, nausea and emesis, and lethargy and malaise. Other significant, transient toxic effects included skeletal muscle injury manifest as pain, weakness, or serum biochemical abnormalities; mucocutaneous effects; and mental or mood changes. One case each of transient pericarditis and fatal cardiomyopathy occurred at the highest dose. Myelosuppression was observed but was transient and not dose limiting. In addition to leukopenia and thrombocytopenia, unexpected declines in serum hemoglobin were observed, although these were of uncertain significance. Tiazofurin induced significant increases in uric acid production which could be reversed with coadministration of allopurinol. Pharmacokinetic analysis revealed tiazofurin plasma elimination to be at least biphasic, with a beta-half-time of 4.2 hours; most of an injected dose could be recovered from the urine as unaltered compound within 24 hours. From this study we conclude that an appropriate dose for phase II trials with this schedule is less than or equal to 1000 mg/m2/day. The schedule may be a difficult one for clinical evaluation of antitumor activity, however, because of the possibility of frequent treatment interruption due to multiple systemic toxic effects.