The possible role of prostaglandins in mediating immune suppression by nonspecific T suppressor cells

Alterations in target cell membrane phospholipids alter T cell but not NK cell killing

The ability of tumor cells to grow progressively in vivo despite the host immune response remains a major conundrum in tumor immunology. Various mechanisms have been proposed to explain how tumors evade immune destruction. The work presented herein shows that simple alterations in plasma membrane phospholipid composition can alter susceptibility to immune lysis. The phospholipid composition of target cells was specifically altered by growth in medium containing choline analogs. Manipulation of membrane phospholipids was observed to alter cell susceptibility to murine CTL but not NK cell lysis. The effects of such changes in phospholipid composition on CTL-mediated lysis appeared to occur during the recognition phase of lysis. This mechanism could be a means by which tumor cells, as well as other pathogenic organisms, escape immune detection and destruction.

Cyclo-oxygenase-2 and its inhibition in cancer: is there a role?

Despite recent improvements in chemotherapy and radiation therapy in cancer management with the addition of biological agents, novel treatment approaches are needed to further benefit patients. Cyclo-oxygenase (COX)-2 inhibition represents one such possibility. COX-2 is an enzyme induced in pathological states such as inflammatory disorders and cancer, where it mediates production of prostanoids. The enzyme is commonly expressed in both premalignant lesions and malignant tumours of different types. A growing body of evidence suggests an association of COX-2 with tumour development, aggressive biological tumour behaviour, resistance to standard cancer treatment, and adverse patient outcome. COX-2 may be related to cancer development and propagation through multiple mechanisms, including stimulation of growth, migration, invasiveness, resistance to apoptosis, suppression of the immunosurveillance system, and enhancement of angiogenesis. Epidemiological data suggest that NSAIDs and selective COX-2 inhibitors might prevent the development of cancers, including colorectal, oesophageal and lung cancer. Preclinical investigations have demonstrated that inhibition of this enzyme with selective COX-2 inhibitors enhances tumour response to radiation and chemotherapeutic agents. These preclinical findings have been rapidly advanced to clinical oncology. Clinical trials of the combination of selective COX-2 inhibitors with radiotherapy, chemotherapy or both in patients with a number of cancers have been initiated, and preliminary results are encouraging. This review discusses the role of COX-2, its products (prostaglandins) and its inhibitors in tumour growth and treatment.

COX-2 and its inhibition as a molecular target in the prevention and treatment of lung cancer

Lung cancer is the leading cause of cancer death in the USA. Conventional therapy using chemotherapy, radiation therapy, and a combination of the two, has yielded modest improvement in patient outcome. Dysfunction and dysregulation of many molecular processes and signaling pathways are involved in the development and growth of malignant lung tumors, and in conferring resistance to standard cancer treatments. Cyclooxygenase (COX)-2, an enzyme involved in prostaglandin production in pathologic states, is often overexpressed in premalignant and malignant lesions. Overexpression of COX-2 in lung cancer is associated with more aggressive biologic tumor behavior and adverse patient outcome. In preclinical studies, inhibition of this enzyme with selective COX-2 inhibitors enhances tumor response to radiation and chemotherapeutic agents. These findings quickly led to clinical studies. Phase I and II clinical trials of the combination of selective COX-2 inhibitors with radiotherapy, chemotherapy, or both in patients with lung cancer have been initiated and some preliminary results are available. In this review, the relationship between overexpression of COX-2 and lung cancer, the antitumor effect of selective COX-2 inhibitors, and the rationale for using selective COX-2 inhibitors combined with radiotherapy and chemotherapy, will be described. Current clinical protocols and preliminary findings will also be summarized.

Improvement strategies for molecular targeting: cyclooxygenase-2 inhibitors as radiosensitizers for non-small cell lung cancer

Cyclooxygenase-2 (COX-2) is an enzyme involved in prostaglandin production in pathologic states such as inflammatory processes and cancer. The enzyme is often overexpressed in premalignant lesions and various cancers, including cancer of the lung. Inhibition of this enzyme with selective COX-2 inhibitors was found to enhance tumor response to radiation in preclinical studies, suggesting that these agents can improve the response of various cancers to radiotherapy. On the basis of these preclinical findings, we initiated clinical trials of the combination of celecoxib, a selective COX-2 inhibitor, with radiotherapy in patients with lung cancer. Here we discuss the rationale for using selective COX-2 inhibitors and describe current clinical protocols and the initial findings.

Role of Cyclooxygenase-2 Inhibitors in Combination with Radiation Therapy in Lung Cancer

Cyclooxygenase-2 (COX-2) is an enzyme involved in prostaglandin production in pathologic states such as inflammatory disorders and cancer. The enzyme is often overexpressed in premalignant lesions and cancer of the lung. Overexpression of COX-2 in lung cancer is associated with more aggressive biological tumor behavior and adverse patient outcome. In preclinical studies, inhibition of this enzyme with selective COX-2 inhibitors enhances tumor response to radiation and chemotherapeutic agents. These findings have been rapidly advanced to clinical oncology. Clinical trials of the combination of selective COX-2 inhibitors with radiation therapy, chemotherapy, or both in patients with lung cancer have been initiated and some preliminary results are available. In this review, we describe the relationship between overexpression of COX-2 and lung cancer, the antitumor effect of selective COX-2 inhibitors, discuss the rationale for using selective COX-2 inhibitors combined with radiation therapy and chemotherapy, and summarize current clinical protocols and initial findings.

Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3

The essentiality of n-6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20:4n-6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (1 8:2n-6, LA) for membrane phospholipids. Low n-6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n-6 PUFA produced by gamma-linolenic acid (18:3n-6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n-6 PUFA, GLA, dihomo-gamma-linolenic acid (20:3n-6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (TGF)-beta-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha production. Low intakes of long-chain n-3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and Th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n-3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n-3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n-3 PUFA augment disease, whereas n-6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n-6 and n-3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n-6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Lithium and antidepressants: inhibiting eicosanoids, stimulating immunity, and defeating microorganisms

Infection-emerging, reemerging, antibiotic-resistant, and bioengineered-increasingly threatens mankind. It is widely assumed that immunostimulating agents, were they to exist, would be ideal in battling microorganisms. Various investigators have established lithium and antidepressants as immunostimulants and antimicrobials and they have identified the mechanisms involved. Eicosanoids both depress immunity and activate microorganisms and lithium and antidepressants oppose eicosanoids. Such philosophers of science as Paul Feyerabend have argued that special interests invariably oppose revolutionary paradigms.

Cyclooxygenase-2 (COX-2) enzyme inhibitors as potential enhancers of tumor radioresponse

Cyclooxygenase-2 (COX-2) is an enzyme induced by a variety of factors including tumor promoters, cytokines, growth factors and hypoxia. It is involved in the metabolic conversion of arachidonic acid to prostanoids, primarily in inflammatory states and tumors. In normal tissues, prostanoids are synthesized by COX-1, and they exert numerous homeostatic physiologic functions. COX-2 overexpression is linked to carcinogenesis, maintenance of progressive tumor growth and facilitation of metastatic spread. COX-2 and its products may act as protectors against cell damage by ionizing radiation. I describe findings showing that inhibition of COX-2 or prostanoids by selective COX-2 inhibitors or commonly used nonsteroidal antiinflammatory drugs (NSAIDs) has antitumor activity and may improve tumor response to radiation without significantly affecting normal tissue radioresponse. COX-2 inhibitors and radiation interact in multiple complex ways, with the enzyme inhibitor directly or indirectly augmenting tumor cell destruction by radiation. COX-2 represents a potential molecular target for improvement of cancer radiotherapy.

The preoperative administration of lentinan ameliorated the impairment of natural killer activity after cardiopulmonary bypass

The aim of this study was to determine whether the preoperative administration of lentinan, which is used clinically to activate T cell function in cancer patients, prevents the impairment of lymphocyte function after cardiopulmonary bypass (CPB). A total of 25 adults undergoing coronary artery bypass grafting were enrolled in this study. Lentinan (2 mg) was given to 10 randomly selected patients 7 d before surgery, while the other 15 patients were considered as a control. The white blood cell count, percentage of lymphocytes, subsets of lymphocytes, and natural killer cell activity were measured preoperatively, immediately after CPB and 1, 3, and 6 d after surgery. The white blood cell counts and the percentage of lymphocytes were not significantly different between the two groups; however, the percentage of CD4-positive cells in the lentinan group recovered to normal more rapidly than in the control group. Although natural killer cell activity was impaired in the control group after CPB, it maintained a nearly normal level in the lentinan group. The preoperative administration of lentinan for patients undergoing CPB ameliorated the impairment of natural killer activity and promoted the rapid recovery of CD4-positive cells.

Ibuprofen-induced inhibition of cyclooxygenase isoform gene expression and regression of rat mammary carcinomas

A single dose of 75 mg/kg 7,12 dimethylbenz[a]anthracene was administered to 50-day-old virgin female Sprague-Dawley rats and 100 days later, animals were randomized and provided with Teklad rodent chow mixed with a dose of 25 mg/rat/day ibuprofen for 35 days. Ibuprofen treatment reduced tumor volume (P < 0.05) and significantly inhibited gene expression of both cyclooxygenase- and cyclooxygenase-2 (P < 0.02). These results indicate that ibuprofen induced significant regression of established mammary carcinomas which was associated with inhibition of expression of isoforms of the gene responsible for prostaglandin production.

Antitumor effect of DT-5461, a lipid A derivative, against human tumor xenografts is mediated by intratumoral production of tumor necrosis factor and affected by host immunosuppressive factors in nude mice

We previously reported that DT-5461, a synthetic low-toxic lipid A analog, inhibits growth of various murine tumors through activation of host immune systems. In the present study, DT-5461 also exhibited significant antitumor effects against 5 out of 6 human tumor xenografts in nude mice. The antitumor activity was similar to or greater than those of chemotherapeutics. Antitumor effects of DT-5461 significantly correlated with intratumoral levels of tumor necrosis factor (TNF) induced by the compound (r = 0.701, p < 0.05). In vitro TNF production by DT-5461-stimulated macrophages was augmented by tumor cells, and the augmentative effect correlated with TNF activity detected in these tumor tissues. Meanwhile, a weaker therapeutic efficacy of DT-5461 was observed against certain tumors that caused a significant increase in the level of immunosuppressive factors in host blood. These findings support the idea that intratumoral TNF plays a crucial role in the antitumor mechanisms of DT-5461 and suggest that its antitumor action is influenced by an augmentative effect of tumor cells on TNF production and by blood levels of immunosuppressive factors.

Effect of combined administration of a synthetic low-toxicity lipid A derivative, DT-5461a, and indomethacin in various experimental tumor models of colon 26 carcinoma in mice

We investigated the antitumor effects of a synthetic lipid A derivative, DT-5461a, in combination with indomethacin in three experimental tumor models (peritoneal carcinomatosis, liver tumor, and lung tumor models) of transplanted colon 26 carcinoma in mice. This carcinoma produces the immunosuppressive prostaglandin E2 (PGE2). Intravenous administration of DT-5461a alone resulted in little or no prolongation of survival time [increase in life span (ILS): -2%-22%]. When indomethacin was given in drinking water a slight or moderate increase in survival time was seen (ILS: 4%-45%). In contrast, the combination of DT-5461a and indomethacin induced an additive increase in life span (ILS: 16% to more than 193%). The strongest antitumor effect of this combined therapy was seen in the peritoneal carcinomatosis model; in this model, plasma PGE2 concentrations were considerably higher than in normal mice, and concentrations were further but transiently increased by DT-5461a administration. Following oral indomethacin administration, these elevated PGE2 concentrations were reduced to the level in untreated normal mice. Furthermore, intratumoral tumor necrosis factor (TNF) activity in the group receiving the combined therapy was significantly higher than that in the DT-5461a-treated group. No TNF production was induced by the administration of indomethacin alone. These results suggest that the antitumor effect of DT-5461a can be enhanced by combination with indomethacin, and that the inhibition of PGE2 production may have a role in this antitumor effect.

Inhibitory effects of inhibitors of arachidonic acid metabolism on the evolution of rat liver preneoplastic foci into nodules and hepatocellular carcinomas with or without phenobarbital exposure

Effects of inhibitors of arachidonic acid (AA) metabolism on the evolution of preneoplastic foci into nodules and of nodules into hepatocellular carcinomas were examined in F344 male rat livers with or without phenobarbital (PB) exposure. p-Bromophenacyl bromide (BPB), acetylsalicylic acid (ASA), and quercetin (QU) were used as inhibitors of phospholipase A2, cyclooxygenase and lipoxygenase, respectively. Preneoplastic liver foci were induced by initiation with N-nitrosodiethylamine (200 mg/kg, i.p.) followed by selection using the procedure of Cayama et al. For the nodule experiment, starting 1 week after completion of the selection procedure, animals bearing foci were given diets containing 0.05% PB plus 0.75, 1, or 1.5% of one of the inhibitors, 0.05% PB alone, or 0.75, 1 or 1.5% of inhibitor alone, or basal diet for 9 weeks. For the carcinoma experiment, 3 weeks after completion of the selection procedure, animals bearing nodules were given the same diets mentioned above for 29 weeks. BPB, ASA and QU either with or without PB accelerated the remodeling of preneoplastic foci, significantly decreasing the numbers of persistent nodules and hyperplastic nodules. ASA either with or without PB significantly decreased the number of hepatocellular carcinomas per rat. BPB and QU, however, significantly decreased the numbers of hepatocellular carcinomas with but not without PB. The results suggested an involvement of AA metabolism in the process of evolution of preneoplastic foci into nodules and hepatocellular carcinomas in rat liver with or without PB exposure.

Evidence for prostaglandin-producing suppressor cells in drug-induced liver injury and implications in the diagnosis of drug sensitization

Lymphocyte reactivity to drugs is present in a minority [corrected] of cases of drug-induced liver injury when in vitro proliferation assays to the suspected drugs are used. One possible explanation to this could be that adherent suppressor cells mediating their action through the production of prostaglandin E2 would suppress the lymphocyte proliferation to drugs in vitro. We studied 42 patients with a clinical diagnosis of drug-induced liver injury by comparing lymphocyte proliferation observed in cultures with five different concentrations of the suspected drug with the lymphocyte proliferation observed in cultures with drug and a prostaglandin inhibitor (indomethacin). Forty-four healthy subjects and 15 individuals with a recent exposure to the suspected drug without development of adverse drug reactions were also studied as controls. In nine (21%) out of 42 patients with drug-induced liver injury a significant lymphocyte reactivity to drugs was detected. When a prostaglandin inhibitor was added to the cultures, the detection of lymphocyte reactivity increased from 21% to 57%. No cases of lymphocyte reactivity to drugs or drugs with prostaglandin inhibitor were found in the control groups. The phenomenon of increase of lymphocyte proliferation with the addition of a prostaglandin inhibitor was more frequent in patients whose hepatitis was cured in less than 2 months, was more frequently found in certain pharmacological groups and was significantly associated to a latency period to development of hepatitis of less than 8 days. In conclusion, the in vitro phenomenon described here may be used to improve the ability to demonstrate lymphocyte sensitization in drug-induced liver injury and the clinical correlations found are consistent with the possibility of its relevance in vivo.

Effect of prostaglandin E in multiple experimental models. VIII. Effect on host response to metastatic tumor

Prostaglandin E (PGE) is produced by certain tumors and is reported to decrease primary tumor growth. We evaluated its effect in multiple tumor models utilizing a 1 week course of the long acting PGE derivative dimethyl-PGE (dPGE) at a dosage of 100 micrograms/kg/day vs. a lactated Ringers control. For all tumor models, a suspension of 1 x 10(6) colon carcinoma cells were injected into Wistar-Furth rats. When the suspension was injected subcutaneously and the drug was begun at the time of tumor challenge, there was no effect on survival. When the tumor was injected intraperitoneally or intravenously and the drug begun at the time of tumor challenge, dPGE decreased survival time. When the tumor was administered intravenously but dPGE was delayed for 5 days, there was no effect on survival time. When rats were given a 1 week course of dPGE or saline, dPGE was found not to alter natural killer (NK) cell cytotoxicity, macrophage cytotoxicity, spontaneous lymphocyte blastogenesis, or mitogen stimulated blastogenesis. dPGE failed to alter lymphocyte metabolism of glucose in nonstimulated lymphocytes, but decreased the rate of glucose metabolism and adenosine deaminase activity in mitogen stimulated lymphocytes. In conclusion, PGE appears to enhance metastatic growth of tumor lines where it does not alter primary tumor growth. This effect does not appear immunologically mediated.

Effect of low dose recombinant interleukin 2 plus indomethacin on mortality after sepsis in a murine burn model

Under anaesthesia, 129 8-week-old male A/J mice were subjected to a 25 per cent scald or sham burn and then resuscitated. They were divided at random into two groups. Mice from the first group were allocated into two groups. Mice from the first group were allocated into four subgroups to receive 6 days intraperitoneal (I.P.) injections as follows: (i) recombinant human interleukin 2 (rhIL-2) (250 units day-1); (ii) saline; (iii) indomethacin (5 micrograms-1 day-1); or (iv) rhIL-2 (250 units) + indomethacin (5 micrograms). Sham burned mice served as no treatment controls. All animals were subjected to peritonitis induced by caecal ligation and puncture 10 days after the burn and mortality was assessed. Mice from the second group were allocated to two subgroups to receive 6 days intraperitoneal injections of: (i) rhIL-2 + indomethacin; or (ii) saline. Animals in this group did not undergo septic challenge. They were randomly killed on days 7, 9 or 10 after the burn. Their splenocytes were harvested and assayed for response to the mitogens phytohaemagglutinin (PHA) and concanavalin A (Con A), and for production of interleukin 2. Mortality rate in animals subjected to burn and septic challenge without treatment was 75 per cent; in mice receiving rhIL-2 alone it was 68 per cent, in mice receiving indomethacin alone it was 62 per cent (no significance) and in mice receiving rhIL-2 + indomethacin it was reduced to 38 per cent (P less than 0.02). Splenocytes from animals receiving combination therapy had markedly improved responses to PHA on days 7 (P = 0.01), 9 (P = 0.02), and 10 (P = 0.008), and to Con A on days 7 (P = 0.001), 9 (P = 0.002) and 10 (P = 0.001), after burn injury. Interleukin 2 production was also significantly (P = 0.004) improved by therapy with rhIL-2 + indomethacin. These data suggest that low dose rhIL-2 in combination with indomethacin may have potential use in the therapy of burn victims.

Splenic natural cytotoxic activity is enhanced during growth of a murine fibrosarcoma

We have shown previously that the natural killer (NK) cell activity of DBA/2J mice bearing M-1 fibrosarcomas is consistently depressed at the later stages of tumor growth. The apparent mechanisms of inhibition are suppressor cell activation and prostaglandin E (PGE) production by tumor and lymphoid cells. In contrast, we show here that the natural cytotoxic (NC) activity of cells from the spleen, blood, and lymph nodes of mice bearing M-1 tumors is enhanced when compared to that of age- and sex-matched control mice. This enhanced NC activity does not appear to be due to increased cytolytic activity of macrophages but, rather, to enhanced cytolytic activity of multiple populations of non-adherent cells including B and T cells. Correlated with this is the finding that the NC activity of normal spleen cells is not inhibited in vitro by either PGE1 or PGE2 at levels which are inhibitory to NK cells. NC activity, although independent of PGE, is in fact enhanced by PGE1 in a dose-related fashion. These data indicate that NK and NC cells are regulated differently by PGE and during tumor growth. Utilizing a Winn assay, we also demonstrate that a cloned cell line with NC activity is capable of slowing tumor growth in vivo and that this action is improved if mice are treated with indomethacin concomitantly.

Chronic thromboxane inhibition preserves function of rejecting rat renal allografts

Increased production of thromboxane (TX) by rejecting renal allografts results in significant and partially reversible renal vasoconstriction. In this study, we evaluated the potential benefit of chronically administering the TX synthetase inhibitor OKY-046 from the time of transplantation in a rat model of acute renal allograft rejection. In animals which received 75 mg/kg/day of OKY-046 by intermittent i.p. injection, allograft function was not improved, but renal thromboxane production was not significantly inhibited. However, animals which received an equivalent dose of OKY-046 by continuous intra-arterial infusion for four days maintained clearances of inulin (4.46 +/- 0.79 ml/min/kg) and PAH (23.86 +/- 1.81 ml/min/kg) at normal levels not different from non-rejecting isografts (4.83 +/- 0.93 and 18.33 +/- 2.55 ml/min/kg, respectively). In contrast, animals which received continuous infusion of saline vehicle alone developed a significant reduction in renal function (CIn: 1.58 +/- 0.27 ml/min/kg; CPAH: 9.12 +/- 1.51 ml/min/kg) by the fourth day after transplantation. Intra-arterial infusion of OKY-046 significantly reduced four-day allograft TXB2 production, as well as urinary TXB2 excretion, but had no effect on allograft production of PGE2 or 6-keto-PGF1 alpha. Despite the beneficial effects on allograft function, OKY-046 neither altered the morphologic appearance of the cellular infiltrate nor the systemic proliferative and cytotoxic anti-donor cellular immune responses. Six days following transplantation, renal TXB2 production was only partially inhibited in animals given continuous infusions of OKY-046, and remained markedly elevated. This partial inhibition of TX production resulted in a slight but insignificant functional improvement.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of indomethacin on burn-induced immunosuppression

Recent interest in the role of prostaglandin inhibitors as immunomodulators following major injury prompted us to study the effect of indomethacin on burn-induced immunosuppression in rats as measured by the delayed-type hypersensitivity (DTH) skin test response, ability to contain an intradermal bacterial challenge (10(8) Staphylococcus aureus 502A injected intradermally), and overall survival from spontaneous burn wound sepsis. Fifty male Sprague-Dawley rats sensitized to keyhole limpet hemocyanin (KLH) were subjected to a 30% full-thickness scald burn. Group 1 (n = 24) received indomethacin at 0.5 mg/kg intraperitoneally once daily with the first dose given immediately following the burn. Group 2 (n = 24) received vehicle only. Prostaglandin E2 measured by radioimmunoassay on day 17 was 2553 +/- 832 pcg/ml serum (+/- SEM) in the vehicle group and 1042 +/- 231 pcg/ml in the indomethacin group (P = 0.058, unpaired t test). Burn injury induced a decrease in the DTH response to KLH and an increase in the Staph lesion size (P less than 0.05) which was not corrected by indomethacin treatment. All animals developed spontaneous burn wound sepsis by day 14. Survival after 17 days in the indomethacin group was 100% compared to that of the vehicle group, 79%, P less than 0.05 (Fisher exact test). We conclude that despite unmeasurable corrections of the burn-induced suppression of the DTH response and local nonspecific bacterial defenses, low-dose indomethacin improves survival following burn sepsis.

Prostaglandin E2 of the upper aerodigestive tract

Mucosal specimens obtained from the upper aerodigestive tract of 101 patients were assayed for prostaglandin E2 (PGE2). Prostaglandin was detected in all specimens evaluated. Children and nonsmoking adults demonstrated lower concentrations of PGE2 than smoking adults. Tumor specimens from patients with squamous cell carcinoma of the upper aerodigestive tract demonstrated significantly increased levels of PGE2 (p less than .05). Normal mucosa obtained from patients with squamous carcinoma elsewhere in their upper aerodigestive tract was found to contain significantly more PGE2 than that from adults without tumors (p less than .05). The amount of PGE2 released from a tissue biopsy was not related to the amount of mononuclear cell infiltrate. No age-related trends in PGE2 levels were noted. Prostaglandin levels were higher in patients with advanced tumors in comparison to smaller tumors. The possible impact of elevated levels of PGE2 upon the immune system, the subsequent development of second primary carcinomas, and the relationship between PGE2 and the use of tobacco products is discussed.

Neck node immunoreactivity in head and neck carcinoma

T-lymphocyte subpopulations were quantitated in lymph nodes that contained metastatic tumor--or no metastasis--from patients who had squamous cell carcinoma of the upper aerodigestive tract. In addition, the lymphocyte subpopulations in peripheral blood were quantitated. The content of prostaglandin E2 within each node that was evaluated was also determined. Lymph nodes containing metastatic tumor had significantly higher helper/suppressor ratio than lymph nodes that were not involved. Quantification of the T-lymphocyte subpopulations in peripheral blood did not indicate the presence of metastatic disease. Significantly more prostaglandin E2 was present in lymph nodes containing metastatic disease, in comparison to lymph nodes without metastatic disease. Thus, both the lymphocyte subpopulations and prostaglandin levels were found to differentiate lymph nodes with metastasis from those without.

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.

Prevention of alterations in postoperative lymphocyte subpopulations by cimetidine and ibuprofen

Surgical procedures probably result in a temporary state of immunosuppression. Identification of functional lymphocyte subclasses using appropriate monoclonal antibodies appears to serve as a sensitive, accurate, and reproducible measure of immune status in patients in many disease states. Using monoclonal antibodies specific for lymphocyte surface markers and immunofluorescent assay, we quantitated lymphocyte subpopulations in patients undergoing surgical procedures. Cholecystectomy, colon surgery, and coronary bypass procedures all resulted in postoperative decreases in helper and inducer populations and increases in cytotoxic suppressor populations, with resultant depressions in the helper to suppressor lymphocyte ratio. Studies in an additional group of patients who underwent cholecystectomy demonstrated that these changes could be prevented by perioperative administration of ibuprofen and cimetidine. These results suggest that prostaglandins and histamines are involved in immunoregulatory events after major operation. The ability of specific pharmacologic therapy to prevent alterations in lymphocyte populations suggest that postoperative immunity may be preserved, hopefully leading to greater host resistance against infection and tumor dissemination.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

Activation of suppressor T cells by low-molecular-weight factors secreted by spleen cells from tumor-bearing mice

The spleens of mice bearing large M-1 fibrosarcomas have been shown to contain several populations of cells which nonspecifically suppress antibody synthesis by cocultured normal spleen cells. It has now been shown that the spleens of tumor-bearing mice also contain inducer cells which secrete soluble factors capable of activating suppressor T cells from unprimed precursor cells. The activated suppressor cells are Thy 1+, Lyt 1+2+ and secrete a soluble suppressive factor. They inhibit the in vitro generation of antibody-forming cells by cocultured normal spleen cells stimulated by T-cell-dependent antigens. They do not, however, suppress the antibody response to T-cell-independent antigens and do not inhibit antibody synthesis by cocultured nude mouse spleen cells cultured with T-cell-dependent antigens and exogenous helper factors. In addition, suppression is blocked if conditioned medium containing T-cell growth factors is added to the suppressor cell assays. These data suggest that cells in the spleens of tumor-bearing mice secrete inducing factors which activate suppressor cells. These activated suppressor cells in turn secrete soluble suppressor factors which inhibit antibody synthesis, possibly by interfering with the synthesis or release of T-cell growth factors.

The immunomodulating effect of TP5 and indomethacin in burn-induced hypoimmunity

Hypoimmunity after major trauma and thermal injury appears to predispose to septicemia. An increase of immune suppressive T cells and the inhibitory monocytes product PGE2 has been demonstrated postburn and are suggested as contributing to postburn hypoimmunity. TP5, the biologically active part of thymopoientin, has an immunomodulating effect on T cells. Indomethacin, an irreversible blocker of the prostaglandin synthesis has been suggested to reduce the inhibitory monocytes-mediated immunosuppression. In this study strains 2 and 13 guinea pigs received 20-30% TBSA scald burn and were subsequently injected with either TP5 or indomethacin or a combination of both on the 3 following days postburn. The ability of splenocytes to produce a secondary immune response to SRBC was measured in the in vitro AFC assay. The animals who had received TP5 and indomethacin showed significant improvement in their ability to mount an immune response in the AFC assay.

Relationship of natural killer cytotoxicity to clinical and biochemical parameters of primary human breast cancer

We have determined the natural killer (NK) activity of peripheral blood lymphocytes obtained from 121 women undergoing surgery for primary breast cancer. NK activity was measured using 51Cr-labeled K562 target cells and effector: target ratios of 100:1, 50:1 and 10:1. The patients' lymphocytes gave a wide range of values with a mean (+/- S.E.) cytotoxicity of 22.6% +/- 1.3, and a median of 20.9% at the 50:1 effector:target ratio. These results did not differ significantly from the mean and median NK levels obtained with the peripheral blood lymphocytes of normal blood donors (mean = 23.1% +/- 1.9, median = 18.8%). Mean NK activity determined at the first postsurgical examination (less than or equal to 6 months postoperative) was significantly lower than the mean NK activity at surgery. The most significant decreases were seen in patients undergoing chemotherapy prior to the first follow-up examination. Subsequent tests (greater than 6 mo, less than or equal to 12 mo) show a recovery of NK activity to preoperative levels. A negative correlation was seen between NK level and maximum tumor diameter. NK levels also varied with tumor histiotype. No association was seen between NK levels and either the number of involved lymph nodes, pathologic tumor grade, the presence of estrogen or progesterone receptor, or the age, menopausal status or smoking history of the patients. A positive correlation was seen, however, between NK levels and number of pregnancies and live births.

Macrophage-derived prostaglandin E modulation of the mixed-lymphocyte reaction: an anomaly of increased production and decreased T-cell susceptibility during tumor growth

One-way mixed-lymphocyte reactions (MLR) were used to assess macrophage (M phi)-derived factor-mediated modulation of normal and tumor-bearing host (TBH) T-cell immune responsiveness. Normal and TBH M psi culture supernatants contained the inhibitory substance prostaglandin E (PGE) in concentrations of 10(-8) to 10(-9) M, with TBH M phi supernatant containing approximately twice the amount of PGE as its normal counterpart. Normal and TBH MLR reactivity were both suppressed by the addition of normal host M phi supernatant. However, TBH T cells were less inhibited by TBH M phi supernatant (55%) as compared to normal host T cells (73%). Although dialyzed M phi supernatants were less inhibitory (17-19%) on normal host T-cell MLR reactivity, TBH T-cell responses were enhanced (20-46%). Indomethacin or eicosatetraynoic acid treatment of M phi reduced PGE levels in the supernatants and in general enhanced MLR reactivity. When PGE1 and PGE2 were titrated in the MLR, normal host T lymphocytes were more susceptible to inhibition than were TBH. Concentrations of PGE1 and PGE2 comparable to that found in normal host M phi supernatants caused approximately 38% inhibition whereas whole M phi supernatants decreased MLR reactivity by greater than 70%, suggesting that another factor(s) was necessary to account for the additional M phi-mediated suppression of lymphocyte function. Isoelectric focusing was used to fractionate normal host M phi supernatant. Two factors with isoelectric points in the pH ranges 7.0-8.5 and 4.5-5.0 were inhibitory in the MLR. An enhancing factor was also identified with an pI in the range of pH 6.0-7.0. These data suggest that TBH M phi-derived PGE production was increased over its normal counterpart, but that TBH T cells were less susceptible to its effect and an additional factor(s) was working in concert with PGE.

Suppression of polyclonal, tumor cell and alloantigen-induced proliferation: identification of cyclooxygenase pathway dependent and independent mechanisms

Polyclonal T cell activation, syngeneic tumor cell and alloantigen-induced proliferative responses were studied to determine if the regulation of these responses in normal and tumor-bearing NBR rats is mediated through products of the cyclooxygenase pathway and prostaglandin E2 (PGE2) in particular. Young rats and tumor-bearing rats have previously been shown to produce poor proliferative responses to PHA, Con A and syngeneic methylcholanthrene (MCA)-induced fibrosarcoma cells. The poor responses to PHA and Con A are mediated by PGE2 in unfractionated ( UNF ) and nylon wool adherent (ADH) cells. The same relationship was also established in the mixed leukocyte tumor cell (MLTC) response to MCA tumor cells although it appears to be of only minor significance as the enhancement following indomethacin (IND) treatment is still a relatively poor response. Indomethacin generally had no effect on the proliferative responses of tumor-bearing animals indicating that the suppression was not mediated through the cyclooxygenase pathway. We have also extended a previous observation in which UNF cells were found to be unresponsive to alloantigen stimulation. This suppression does not appear to be mediated through cyclooxygenase products as IND treatment does not enhance the UNF response although it does enhance the ADH response. These data indicate that a complex network of cyclooxygenase dependent and independent regulation exists in normal and tumor-bearing NBR rats.

Pharmacological modulation of suppressor cell activity in mice with disseminated histoplasmosis

Indomethacin and cyclophosphamide (CY) were used in an attempt to modify the suppressive effects of spleen cell populations from mice with disseminated histoplasmosis at 1 week of infection. In vitro addition of indomethacin did not alter the depressed plaque-forming cell response to sheep erythrocytes of normal spleen cells cocultured with unfractionated or nylon wool-fractionated spleen cells from infected mice. Likewise, indomethacin given intraperitoneally did not enhance the subnormal in vivo plaque-forming cell response of spleen cells from infected mice. Conversely, 20 mg of CY per kg given intraperitoneally 2 days before or 6 h after the inoculation with Histoplasma capsulatum partially reversed the suppression effected by splenic T cells (nylon wool passed) in vitro, whereas 50 mg of CY per kg given intraperitoneally 6 h after the injection of H. capsulatum ablated suppressor T cell activity in vitro; neither dosage of CY altered the suppression mediated by unseparated or nylon wool-adherent spleen cells. Furthermore, the administration of 50 mg of CY per kg failed to improve the depressed footpad responses of mice infected for 1 week to sheep erythrocytes in sheep erythrocyte-sensitized mice or to histoplasmin. These findings indicate that in experimental disseminated histoplasmosis, suppression effected by splenic T cells can be alleviated by CY; however, there is a persistent immunosuppressor mechanism(s) that cannot be counteracted by either indomethacin or CY.

Effects of dietary enrichment with eicosapentaenoic acid upon autoimmune nephritis in female NZB X NZW/F1 mice

A menhaden oil diet, rich in eicosapentaenoic acid, protected female NZB X NZW/F1 mice from autoimmune nephritis. Only 15% of mice treated with the diet from weaning had died with severe renal disease at 19 months, versus 98% of controls on a beef tallow diet. The menhaden oil also protected these mice from renal disease when instituted at 4 and 5 months of age and, under these conditions, levels of anti-native DNA antibodies were similar in both dietary groups. Our data suggest that the menhaden oil diet may act primarily to reduce inflammation via the ability of eicosapentaenoic acid to alter the production of prostaglandins and leukotrienes.

Excessive prostaglandin E2 production by suppressor monocytes in head and neck cancer patients

The proliferative response of peripheral blood mononuclear cells (PBMC) to the mitogens PHA and Con A significantly depressed in 86% of 45 head and neck cancer patients compared with 44 normal controls. This depression of immune competence was greatest in older patients and in those with more advanced disease stages. The abnormal mitogen responses could be restored toward normal (especially with Con A stimulation) by incubating the cells with either of two prostaglandin synthetase inhibitors (indomethacin or RO-205720). This augmentation of immune response was independent of other factors, including the primary tumor site, disease stage, treatment (surgery, radiation therapy, or chemotherapy) or the patients's age or race. The most likely explanation for this depressed level of immunocompetence was an excessive production of PGE2 by suppressor cells. This was confirmed by the finding that PBMC from patients produced more PGE2 than PBMC from normal individuals (8.4 ng/ml vs. 5.2 ng/ml, p=0.002). This difference was greatest among patients less than 60 years of age whose cultured PBMC produced 91% more PGE2 than controls (p less than 0.0007). Virtually all of the PGE2 was produced by a population of monocytes defined by a monoclonal antibody and purified with a fluorescence-activated cell sorter. Patients with epidermoid cancer of the head and neck thus have an abnormality of immunoregulatory monocytes that can contribute significantly to their depression of cellular immunity by elaborating prostaglandin E2. This abnormality could be partially corrected in vitro by incubating their PMBC with a prostaglandin synthetase inhibitor.

Augmentation of concanavalin A-induced immunosuppression by indomethacin

These studies show that, in BALB/C mice, when antibody synthesis against sheep red blood cells is suppressed by concanavalin A, treatment with indomethacin (4-8 mg/kg per os) will augment this suppression. Two other nonsteroidal anti-inflammatory drugs, flufenamic acid and meclofenamic acid (50 mg/kg), also have this effect, whereas phenylbutazone was inactive at this dose. The augmentation of concanavalin A-induced immunosuppression by indomethacin could not be demonstrated on the response to the T-independent antigen polyvinypyrrolidone. In contrast to indomethacin, which inhibits cyclooxygenase, neither nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway, nor eicosa-5,8,11,14-tetraynoic acid, an inhibitor of both the cyclooxygenase and the lipoxygenase pathways, had this augmenting effect. Therefore, we do not have strong evidence that the absence of a prostaglandin is responsible for the effect of indomethacin. However, inhibition of the pathway leading to prostaglandin synthesis causes an increase in arachidonic acid metabolism via the lipoxygenase pathway. A product of this pathway, such as a leukotriene, may have immunosuppressive effects in this model. Evidence for the enhancement of a suppressor cell population is provided by an in vitro coculture assay. Cells treated with concanavalin A and indomethacin had more suppressive activity than cells treated with concanavalin A or indomethacin alone.

Effect of protein aggregation on murine splenic prostaglandin F2 alpha levels

Intravenous injection of deaggregated human gamma globulin and deaggregated keyhole limpet hemocyanin into C57Bl/6 mice does not result in an increase in splenic prostaglandin F2 alpha. However, when aggregated human gamma globulin or aggregated keyhole limpet hemocyanin were injected, significant increases in splenic PGF2 alpha were observed. Mice which had been rendered immunologically tolerant to human gamma globulin (HGG) also demonstrated increases in splenic PGF2 alpha and PGE2 5 min after boosting with aggregated HGG with no increases in antibody against HGG. These results imply that the property of protein aggregation will engender increases in splenic prostaglandin levels and that these increases don't appear to affect the tolerant state.

The effect of prostaglandin metabolism on immunoglobulin and antibody production in naive and educated whole spleen cells

Addition of prostaglandin E2 or inhibitors of prostaglandin biosynthesis to Mishell-Dutton cultures results in changes of immunoglobulin levels, particularly IgM, secreted into the culture supernatant. These changes in the quantity of immunoglobulin found in the supernatant are minimal in cultures containing naive cells. When BSA educated cells from C57B1/6 immunized mice were cultured, PGE2 was very effective in amplifying the biosynthesis of immunoglobulin when placed in culture in the presence of BSA. Whole spleen cell cultures from C57B1/6 mice immunized with sRBC also had increased immunoglobulin concentrations in culture supernatants upon exposure to PGE2 at culture initiation. However, the addition of sRBC to these cultures did not further increase immunoglobulin production. In all cases indomethacin inhibited the appearance of immunoglobulin into the supernatant by antigen educated cells. This inhibition which may be a result of inhibited immunoglobulin synthesis and not an impairment of transport, could be overcome by the inclusion of PGE2 in the cultures. PGE2 added to cultures containing cells educated against human gamma globulin caused an increase in the quantity of human gamma globulin-specific antibody in the culture supernatant while it had no effect on naive cells. These results indicate that prostaglandin metabolism may exert a greater influence on educated lymphocytes than naive lymphocytes in terms of immunoglobulin secretion and specific antibody production.

Inhibition of murine tumor growth and prostaglandin synthesis by indomethacin

Inhibition of the growth of a transplantable methylcholanthrene-induced tumor was achieved in mice by administering indomethacin or aspirin in the drinking water, these drugs having in common the ability to inhibit prostaglandin synthesis. Indomethacin was able to reduce the levels of prostaglandin E (PGE) in the tumor tissue. When tumors from these animals were cultured in vitro, the culture supernatant fluid from drug-treated animals showed lower levels of PGE released into the media, but after several days in culture, tumor cells from indomethacin-treated animals fully recovered their ability to produce PGE. The relative size of tumors in untreated animals was directly related to the amount of PGE activity present in these tumors.