Effects of PGE1 in murine models of SLE: changes in circulating immune complexes

Prostaglandin E1 inhibits collagen expression in anti-thymocyte antibody-induced glomerulonephritis: possible role of TGF beta

To test whether or not prostaglandins mediate extracellular matrix formation in immune-mediated glomerular disease, rats with anti-thymocyte antibody-induced glomerulonephritis were treated with prostaglandin E1 (PGE1) (250 micrograms/twice daily/s.c.). Glomerular expression of collagen types III and IV was assessed by Northern blotting, immunohistology and Western blotting. Proliferation of glomerular cells was evaluated by staining for the proliferating cell nuclear antigen (PCNA) and consecutive cell counting. At day five after induction of the disease, glomerular mRNA levels of collagen types III and IV were three- to fivefold higher compared with non-nephritic controls. Similarly glomerular deposition of these collagens was markedly increased when assessed by immunohistology. The treatment of nephritic rats with PGE1 reduced the increased glomerular mRNA levels as well as the protein concentration and the deposition of extracellular collagens. The number of PCNA positive cells which was significantly higher in nephritic rats when compared with control animals (24 hr, nephritis 2.53 +/- 0.33 and Control 0.26 +/- 0.06, P = 0.011; 5 days, nephritis 5.10 +/- 1.13 and Control 0.75 +/- 0.08, cells per glomerular cross section, P = 0.03) was reduced by PGE1 (24 hr, nephritis+PGE1 0.44 +/- 0.30, P = 0.0001; 5 days, nephritis +/- PGE1 1.91 +/- 1.84 cells per glomerular cross section, P = 0.001). Prostaglandin E1 also ameliorated the glomerular infiltration of monocytes at 24 hours (nephritis 4.36 +/- 2.82, nephritis + PGE1 2.20 +/- 1.82, cells per glomerular cross section) and five days (nephritis 1.51 +/- 0.58, nephritis+PGE1 1.12 +/- 0.61, cells per glomerular cross section). To further characterize possible mechanisms by which PGE1 reduces extracellular matrix deposition, the glomerular expression of transforming growth factor (TGF-beta), and interleukin 1 beta (IL-1 beta) was assessed by Northern blotting. Nephritic glomeruli showed increased mRNA levels of TGF-beta at day 5 and IL-1 beta at 24 hours when compared with control kidneys. Treatment of the animals with PGE1 inhibited the mRNA expression of TGF-beta and IL-1 beta. These data demonstrate that PGE1 reduces the glomerular expression of extracellular matrix proteins in anti-thymocyte antibody-induced glomerulonephritis, suggesting a beneficial role of prostaglandins in this proliferative glomerular immune injury. The effects of PGE1 might be mediated by inhibition of TGF-beta and IL-1 beta production.

Environmental influences on fatty acid composition of membranes from autoimmune MRL lpr/lpr mice

We analyzed fatty acid make up of cells and organs from autoimmune and immunologically normal mice to determine whether intrinsic differences in composition might be associated with an inflammatory phenotype. Macrophages (MO) isolated from 4-6-week-old MRL lpr/lpr mice were cultured with phorbol ester (PMA), fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2) and medium control to determine whether these cell signals might induce membrane fatty acid changes. Individual phospholipid analysis showed 8.4- and 5.1-fold increases in phosphatidylcholine arachidonate (20:4) mole % over baseline values following culture with FGF-1 and FGF-2, respectively. Unfractionated analysis on kidney and liver extracts from 4-6 week MRL lpr/lpr, 16-20 week lpr and 12-20 week MRL +/-/+/- mice demonstrated no significant intrastrain fatty acid differences. Higher levels of 20:4 in 4-6 week lpr mice were noted compared to 16-20 week lpr or +/+ mice in kidney, and liver samples (P < 0.05). It is possible that membrane changes precipitated by microenvironmental cytokine concentrations may contribute to the expression of autoimmune disease in this model.

Composition of peritoneal macrophage membranes in autoimmune MRL lpr/lpr mice

Adult MRL lpr/lpr mice display phenotypic features that are consistent with both rheumatoid arthritis and systemic lupus erythematosus. Previous studies have reported that peritoneal macrophages harvested from this model have an increased propensity for both spontaneous and elicited release of prostaglandins and leukotrienes relative to immunologically normal control mice. To investigate whether one aspect of the differences in secretory potential between autoimmune and normal mice was at the level of increased substrate availability, gas chromatographic analysis of peritoneal macrophage membranes from autoimmune MRL lpr/lpr, young lpr, wild type +/+, and immunologically normal mice was done. The results demonstrate enrichment of arachidonate in adult lpr macrophage membranes in all major phospholipid classes relative to young lpr, +/+ and immunologically normal C3H/HeN mice. Similarly, there was an increased mole % of arachidonic acid in lpr mice relative to controls. Elevated membrane arachidonate may contribute to the increased propensity of autoimmune strains to participate in the inflammatory process.

Altered blood rheology in the pathogenesis of diabetic and other neuropathies

Although a substantial literature confirms the abnormal flow properties of diabetic blood, only in a few papers has the vasculitis of diabetic neuropathy been considered to have a hemorheological cause. It is proposed that the pathogenesis of nerve lesions involves an interaction between the specialized nerve vascular system and focal ischemic lesions resulting from rheologically induced stasis. The proposition is extended into other conditions with abnormal blood rheology such as hypothyroidism, uremia, dysglobulinemia, polyarteritis nodosa, and lepromatous leprosy. It is concluded that the treatment of such polyneuropathies should include an agent which would improve the flow properties of the blood.

Eicosanoids in experimental and human renal disease

The renal prostaglandins and thromboxanes are powerful autacoids with potential effects on renal hemodynamics, salt and water metabolism, and the immune system. The possibility of adverse effects on renal function in certain patients with renal disease due to cyclooxygenase inhibition with nonsteroidal anti-inflammatory drugs has long been appreciated. Experimental evidence indicates that renal prostaglandin and thromboxane production is increased in several models of renal disease and that similar decrements in renal function occur with cyclooxygenase inhibition and may be due to inhibition of vasodilator prostaglandins. Additionally, several investigators have shown that administration of prostaglandins may be therapeutic in some forms of renal disease, particularly immunologically mediated diseases. Dietary modification to affect prostaglandin production has also been promising in certain experimental models. In contrast to vasodilator prostaglandins, thromboxane is a potent vasoconstrictor and would be expected to have adverse effects on renal function. Despite demonstration of elevated glomerular thromboxane, studies using inhibitors of thromboxane synthesis in immunologically mediated glomerular disease have been disappointing. There is some evidence, however, that these drugs may be of benefit in ureteric obstruction and renal transplant rejection.

Prostaglandin synthesis inhibitors and primary antibody response in experimental nephrotic syndrome

The effect of prostaglandin (PG) synthesis inhibitors on the primary antibody response to sheep red blood cells (SRBC) in rats with aminonucleoside-of-puromycin (AP) nephrosis was studied. The response to SRBC was determined 5 days after intraperitoneal administration of SRBC by measuring IgM antibody-forming spleen cells (AFC). In nephrotic rats, SRBC were injected when animals were fully nephrotic. A significant decrease in the number of AFC (P less than 0.05) and a significant increase in the plasma concentration of 6-keto-PGF1 alpha (P less than 0.02) were observed in 22 nephrotic rats compared to 24 normal rats. Treatment of nephrotic rats with indomethacin (5 mg/kg per day, 8 rats) and aspirin (200 mg/kg per day, 7 rats) initiated before the development of nephrosis returned the antibody response and the plasma level of 6-keto-PGF1 alpha to normal, while the same treatment in control rats did not alter the antibody response. These data suggest that in AP nephrosis the observed decrease in antibody response to SRBC is likely due to an increase in PG production at the time of immunization.