Treatment of NZB/W ("lupus") mice with 15(S)-15 methyl PGE1

Suppression of acute inflammation with liposome associated prostaglandin E1

Prostaglandin E1 (PGE1) suppresses leucocyte effector function and reduces inflammation in several animal models of acute and chronic inflammation. A drawback to its use as a therapeutic agent is the relatively high doses needed to suppress inflammation. We present evidence in this report that liposome associated PGE1 (LAP) reduces markedly acute inflammation induced in a subcutaneous air pouch by monosodium urate crystals, and by the polypeptide mediators, interleukin 1-beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). A single dose of 12 micrograms/kg LAP given intravenously 2 hr after inflammation was induced, reduced accumulation of cells and exudate by 31-49%.

Improvement of gingival and alveolar bone status in periodontitis-affected hamsters treated with 15-methyl prostaglandin E1

Exogenous PGE1 at pharmacological doses suppresses acute and chronic inflammation manifestations. As periodontitis possesses features of both acute and chronic inflammation, attenuation of periodontal destruction in hamsters was attempted by using 15-M-PGE1, a stable PGE1 analog. The agent was tested at 2 different doses (100 and 150 micrograms/kg/d) and its effects were matched against disease-free and periodontitis-affected animals. No effect was found with the 100 micrograms regimen. In contrast, in the 150 micrograms group, in the gingiva around the first right mandibular molar the pocket epithelium and infiltrated connective tissue (ICT) areas, the mean vascular lumen, the number of PMNLs adherent to blood vessels and infiltrating the ICT were significantly reduced. The number of osteoclasts was markedly diminished as well, but their intrinsic activity was enhanced. Bone formation was totally inhibited in this treatment group. These results indicated that 15-M-PGE1 effectively improved gingival inflammation mostly by reducing edema and PMNL recruitment and controlled alveolar bone destruction by reducing the osteoclast recruitment. From a therapeutic point of view the complete inhibition of formation seems to contraindicate its use.

Cyclophosphamide and 15(S)-15 methyl PGE1 correct the T/B lymphocyte ratios of NZB/NZW mice

The lupus of NZB/NZW F1 female mice is associated with immune complex glomerulonephritis and premature death. Cyclophosphamide and 15(S)-15 methyl PGE1 therapy halt disease progression. Fluorescein conjugated antibodies were utilized to label specific leukocytes and the subsets were quantitated using a Fluorescence Activated Cell Sorter. Normal outbred CD-1 female mice showed a decrease in absolute T and B cell numbers with age, but the ratio of T and B cells remained essentially constant through 9 months of age. By contrast the NZB/W female mice showed decreased numbers of total lymphocytes relative to CD-1 controls at all ages. Moreover relative to CD-1s, there was a far greater decrease in T cell numbers (7 x for NZB/W versus 2 x for CD-1) and B cell numbers failed to decrease with age. The characteristic decline in T lymphocyte numbers and relative increase in B cell numbers in NZB/W mice were corrected with cyclophosphamide and PGE1 therapy. However, there was no selective modification of T cell subsets (L3T4+ or Ly2+) with therapy. Our investigation suggests correction of the abnormal T/B cell ratio may be a useful marker of therapeutic activity in NZB/W mice.

Effect of misoprostol on immune function in elderly subjects

The immunologic effects of misoprostol, an oral prostaglandin E1 (PGE1) analog, were tested in 25 individuals over age 65, compared to 25 individuals given placebo. Elderly subjects were chosen because previous in vitro studies had found an increased sensitivity to PGE of lymphocytes in older subjects. After two weeks of ingestion of misoprostol or placebo, there was a small but statistically significant decrease in IgM-rheumatoid factor in the misoprostol group when compared to control and a significant decrease in the in vitro sensitivity of lymphocytes from the misoprostol group to inhibition by PGE. There were no differences in total lymphocyte count, T cell or T cell subset count, delayed hypersensitivity skin test reactivity, serum immunoglobulins, or response to mitogens between the two groups. Therefore, the short term administration of an oral PGE analogue to normal elderly individuals is not associated with any detrimental effects on immunologic function after two weeks.

The role of arachidonic acid metabolites in mononuclear phagocytic cell interactions

Numerous investigations support the theory that arachidonic acid metabolites play a critical role in dictating the progression of chronic immune reactions. With regard to macrophage-mediated inflammatory responses, enzymatic oxygenation of arachidonic acid via the lipoxygenase or cyclooxygenase pathway can result in the production of compounds that may potentiate or suppress the inflammatory lesion. We recently have presented data demonstrating that lipoxygenase derived leukotriene B4 and C4 can induce the release of IL-1 by macrophages, while PGE2 and PGI2 can suppress the production of IL-1. Macrophages are central to the induction of immune responses and the progression of chronic inflammatory reactions. Therefore, an understanding of the role that macrophage-derived arachidonic acid metabolites play in the initiation, maintenance, and resolution of chronic immune responses is essential. As shown in Figure 3, there are a number of chemical signals that occur between macrophages and lymphocytes that are critical for immune cell communication. The investigations described above have demonstrated that the macrophage may regulate the production and expression of any or all of these signals, such that the inflammatory response is potentiated, sustained, suppressed, or resolved. A better comprehension of the activity of these potent arachidonate derivates will undoubtedly aid in the therapeutic manipulation of inflammatory disease.

Effect of chronic ingestion of a prostaglandin E analogue on immunologic function in healthy elderly subjects

The immunologic effects of an oral prostaglandin E1 (PGE1) analogue were tested in 25 individuals over age 65, compared to 25 individuals given placebo. Elderly subjects were chosen because previous in vitro studies had found an increased sensitivity to PGE of lymphocytes in older subjects. After 2 weeks of ingestion of PGE analogue or placebo, there was a small but statistically significant decrease in IgM-rheumatoid factor in the PGE analogue group compared to control and a significant decrease in the in vitro sensitivity of lymphocytes from the PGE analogue group to inhibition by PGE. There were no differences in total lymphocyte count, T cell or T cell subset count, delayed hypersensitivity skin test reactivity, serum immunoglobulins, or response to mitogens between the two groups. Administration of an oral PGE analogue to normal elderly individuals is not associated with any detrimental effects on immunologic function after 2 weeks.

Membrane fluidity and cholesterol in thymus and spleen cells from mice treated with immunomodulatory drugs

We have used spin labeling, fluorescence polarization, and chemical analysis to characterize membrane properties of thymocytes from mice treated with immunomodulatory drugs. The number of thymocytes was reduced 90-95% by treatment of 6-9 week old mice with hydrocortisone acetate (HCA) or methylprednisolone (both 125 mg/kg) or with cyclophosphamide (250 mg/kg). Electron spin resonance (esr) examination of thymocytes labeled with 5-nitroxyl stearic acid indicated that the membranes of cells remaining after treatment with any of these drugs were more rigid than those from saline-treated controls. The total cholesterol/phospholipid (C/PL) molar ratio of the HCA-resistant thymocytes was twice that of the control mice. Treatment of mice with other immunomodulatory drugs, cyclophosphamide, cytosine arabinoside (Ara-C), 2-amino-5-bromo-6-phenyl-4-(3H)-pyrimidinone (ABPP) and 15(S)-methyl prostaglandin E1 (15(S)-methyl PGE1), also altered the C/PL ratio in thymocytes and, in some cases, in spleen cells. Fluorescence polarization measurements of thymocytes labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH) did not reveal the differences between cells from HCA-and saline-treated mice that were detected by spin labeling and chemical analysis. Our results indicate that the greater rigidity detected by spin labeling of hydrocortisone-resistant thymocytes may be due, at least in part, to greater membrane cholesterol content. Of the methods employed, chemical analysis was the most sensitive in revealing drug-induced alterations in thymocyte populations.

Abrogation of suppressor cell function by inhibitors of prostaglandin synthesis

The weekly intraperitoneal injection of rat erythrocytes into mice induces both a stable autoimmune state, as judged by the appearance of anti-mouse erythrocyte autoantibody and suppressor T cells capable of regulating this response; the latter being demonstrable only in a subsequent transfer system. This autoimmune response and the parallel anti-rat erythrocyte response were both insensitive to exogenous prostaglandin E2 (PGE2). The administration of prostaglandin synthetase inhibitors (indomethacin or aspirin) to mice undergoing immunization with rat erythrocytes had no effect on the anti-rat response, yet mildly exacerbated the onset of the autoimmune state and potently inhibited the generation of suppressor cells. Furthermore the administration of these drugs to recipients of suppressor cells virtually abrogated suppressor cell activity. These observations imply that both the generation and effector function of these suppressor cells may be modulated by prostaglandin synthetase inhibitors while at the same time T helper and B cell functions remain unimpaired.

Suppression of acute and chronic inflammation by orally administered prostaglandins

Oral administration of a stable analog of prostaglandin E1 (PGE1) 15-(S)-15-methyl-prostaglandin E1, can suppress both chronic adjuvant-induced polyarthritis and acute immune complex-induced vasculitis in a dose dependent manner. Histopathologic studies of tibiotarsal joints from rats with adjuvant disease showed suppression of arthritis in animals treated with the PGE1 analog from time of adjuvant challenge. This study represents the first demonstration of suppressed experimental polyarthritis by an orally administered prostaglandin. Suppression of the acute immune complex-induced vasculitis was demonstrated using 15- methyl-PGE1 administered orally 12 hours prior to antigen-antibody challenge. Diminution of tissue injury resulting from immune complex-induced vasculitis is reflected by a decrease in vaso-permeability, indicating suppressed vascular damage in animals treated with prostaglandin. These studies demonstrate the potential use of orally active prostaglandins as an antiinflammatory agent.