The differential effects of PGE on the immune response in normal and immunosuppressed mice

Prostaglandin E1 enhances tumoricidal activity of 5-fluoro-2'-deoxyuridine in rats

Addition of prostaglandin E1 (PGE1) to 5-fluoro-2'-deoxyuridine (FUDR) infused via the portal vein has been shown to diminish both the regional and the systemic toxicity of this chemotherapeutic agent. The effect of concomitant PGE1 infusion on tumor growth has not yet been determined. This study was designed to assess the effect of PGE1 in combination with FUDR on an established adenocarcinoma in the rat model. Fifty-gram Fischer rats underwent placement of a 3-mm3 fragment of colon carcinoma 4047 in the left thigh pad. After 6 weeks to allow for tumor growth, the animals were randomly assigned to receive a 7-day intravenous infusion of (1) saline, (2) PGE1 (0.1 microgram/kg/min), (3) FUDR (3 mg/kg/day), or (4) PGE1 + FUDR. At 10 days animals receiving PGE1 + FUDR had a significant decrease in tumor volume (mm3, log 10) (3.39 +/- 0.24 vs 3.85 +/- 0.12, P less than 0.05) compared with animals receiving FUDR alone. We conclude that PGE1 may be useful as an adjunctive cytotoxic agent.

Postburn suppression of murine lymphocyte and neutrophil functions is not reversed by prostaglandin blockade

Certain arachidonic acid metabolites, including prostaglandins (PGs) E1 and E2, have been shown to exert marked immunosuppressive effects on T-cell and macrophage functions. Cyclooxygenase blockade with indomethacin or ibuprofen may ameloriate these effects. In the current study we measured lymphocyte proliferation by thymidine incorporation, the presence of T-cell activation antigens with monoclonal antibodies and two-color flow cytometry, and neutrophil (PMN) oxidative burst using a fluorescent marker, in control mice and in burned mice treated with indomethacin for 10 days after injury. One-half of the cell cultures were treated with indomethacin in vitro to ensure its continued presence during stimulation. Separate groups of mice were fed a fish oil-based diet which leads to the production of PGE3 rather than PGE2, versus standard mouse chow, a soy-bean oil-based diet which leads to PGE2 production. Lymphocyte proliferation, expression of T-cell activation antigens, and PMN oxidative burst remained depressed in burned mice treated with indomethacin in vivo (plus in vitro) and in those which received the fish oil-based diet, compared to control. Blockade of PG synthesis after murine burn injury by cyclooxygenase inhibition or alterations in the diet failed to restore T-lymphocyte activation or proliferation or to improve PMN oxidative burst. These data suggest that PGE2 alone does not explain the immunosuppression noted after burn injury.

Effect of in vivo administration of prostaglandins and interferon on natural killer activity and on B-16 melanoma growth in mice

We investigated the effect on in vivo administration of 16,16-dimethyl-prostaglandin E2 (di-M-PGE2) alone and in combined treatment with alpha-beta interferon (IFN) on NK activity in normal, cyclophosphamide (CY)-treated, tumor bearing or irradiated and bone marrow reconstituted mice and on B-16 melanoma growth. Normal mice inoculated with IFN (30,000 U/mouse, 24 hr before testing) showed a significant increase in NK activity, while those treated with di-M-PGE2 (10 micrograms/mouse daily X 4 days) showed a suppressed NK response. No difference was observed between mice treated with di-M-PGE2 alone and those treated with di-M-PGE2 associated with IFN. In immunosuppressed animals single treatments were slightly (di-M-PGE2) or not (IFN) effective, while the combined administration of di-M-PGE2 and IFN caused a marked increase in NK activity. Moreover, di-M-PGE2 was able to accelerate the recovery rate of NK activity in bone marrow-reconstituted murine chimeras, suggesting that the synergistic effect of prostaglandins and IFN could derive from the action of di-M-PGE2 on progenitor pre-NK cells and of IFN on effector cells. Finally, we observed a good correlation between the enhancement of the NK activity and the tumor growth inhibition.

Altered immune response during cadmium administration in mice

C57BL/6 mice were administered 50 or 200 ppm of Cd as CdCl2 in the drinking water for either 3 to 4 (short term) or 9 to 11 (long term) weeks. In other experimental designs, mice were exposed orally to 300 ppm of Cd or injected with 2.5 mg/kg of Cd ip. The proliferative response to the T cell mitogens Con A and PHA was increased in cultures of spleen cells from orally treated mice in most of the experiments performed. After primary immunization with sheep red blood cells, the number of IgM antibody forming cells per 10(7) spleen cells was also moderately higher in mice exposed to 50 or 200 ppm of Cd for short or long term. In contrast, long-term exposure to 300 ppm of Cd depressed the antibody response to SRBC. Administration of ZnCl2 prevented the enhancement of the PFC response in mice orally administered 50 ppm of Cd. The capacity to suppress the antibody response of spleen cells preincubated with sodium periodate was decreased after short-term oral or ip. Cd administration but was completely or partially recovered after long-term exposure to either 50 or 200 ppm of Cd.