Chemical carcinogens stimulate canine kidney (MDCK) cells to produce prostaglandins

Effect of gamma-linolenic acid and prostaglandins E1 on gamma-radiation and chemical-induced genetic damage to the bone marrow cells of mice

The effect of gamma-linolenic acid (GLA) and prostaglandin E1 (PGE1) on gamma-radiation, diphenylhydantoin (DPH), benzo(a)pyrene (BP), and 4-alpha-phorbol-induced genetic damage to the bone marrow cells of mice, using the sensitive micronucleus (MN) test was investigated. PGE1 and its precursor GLA prevented gamma-radiation, DPH, BP, and 4-alpha-phorbol-induced genetic damage.

Prostaglandins, their inhibitors and cancer

Prostaglandins (PGs) and their analogs endoperoxides are a large series of compounds which mainly enhanced cancer development and progression, acting as cocarcinogens or tumor promoters, and having profound effects on carcinogenesis. Although PGs are ubiquitous tissue hormones exerting pleiotropic effects on cancer cells, their mechanism(s) of action at molecular and cellular levels are not yet elucidated. Autoradiographic, ultrastructural, antigenic, and cell surface studies revealed that PGs act namely by their specific receptors and by interfering with DNA, RNA and protein synthesis, cell membranes and cell communications. PGs also play a role in tumor immunology and transplantation, acting as immunomodulators. Prostaglandins exert their effects by autocrine and paracrine mechanisms similar to hormone-like substances, and hypophysectomy reduces some of their tumor-promoting effects. PGs may act synergistically with hormones, growth factors (GFs), and vitamins. Several drugs called PG-synthesis inhibitors or PG-antagonists are found to markedly inhibit the cyclooxygenase activity. Most of these PG-inhibitors (aspirin, ibuprofen, indomethacin, piroxicam, sulindac) or commonly called NSAIDs (nonsteroidal antiinflammatory drugs) also significantly inhibit cancer development and cancer progression, and are recently used in epidemiological studies for cancer prevention and treatment. Developing more active and less toxic NSAIDs, which can also more selectively inhibit PG synthesis, is a promising field in prostaglandin research.

Prostaglandin endoperoxide synthase gene structure: identification of the transcriptional start site and 5'-flanking regulatory sequences

The gene for the murine prostaglandin endoperoxide (PGH) synthase (8, 11, 14-eicosatrienoate, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.1) has been cloned. The gene was isolated from a mouse NIH 3T3 cell genomic library and is contained in four overlapping lambda FIXII bacteriophage clones. The gene spans approximately 22 kb and consists of 11 exons. Primer extension and RNAse protection assays indicate that transcription of the gene begins at an initiation site 63 nucleotides 5' to the ATG translation initiation codon. Neither TATA or CAAT boxes are present immediately upstream of the transcriptional start site, but SP1 binding sites are present at positions -47 to -42 and -30 to -25, relative to the transcription initiation site. Examination of the 5'-end and 2400 bp of the 5'-flanking sequence of the gene revealed sequences with homology to several transcriptional regulatory sequences. Three putative AP-1 binding sites were found, two within the first exon and intron and another at position -2097 to -2090. The AP-1 site at position -2097 is adjacent to a sequence with similarity to a negative glucocorticoid regulatory element (nGRE) (position -2123 to -2009). The presence of AP sites by themselves, or in conjunction with an nGRE sequence, suggests a possible interplay between jun/fos regulatory proteins and the glucocorticoid receptor for positive and negative regulation of the PGH synthase gene. An unexpected finding was the presence at position -403 to -385 of a putative dioxin responsive element, a sequence found to be responsible for the induction of transcription of the cytochrome P450IA1 gene (CYPIA1) and other genes involved in detoxification/activation of polycyclic aromatic hydrocarbons.

Changes in tissue fatty acid composition in murine malignancy and following anticancer therapy

We studied the mouse NC tumour, a subcutaneously transplanted adenocarcinoma originally of mammary origin. Measurements per g tissue were made of 17 fatty acids (FAs), the combined amounts of n-3, n-6, saturated, unsaturated, and total FAs, and of various FA ratios in the tumour, mammary tissue, spleen, liver and plasma. Compared with mammary tissue from normal mice, tumours of vehicle-treated controls had less of seven of the FAs and more of two FAs. Mice bearing the NC tumour often had changed (usually decreased) amounts of FAs in the 'normal' spleen, liver and plasma, but not in mammary tissue. Treatment with methotrexate (MTX) was studied alone and with indomethacin which can potentiate MTX cytotoxicity. Indomethacin 1.25 mg kg-1 (INDO) increased the amounts of 3/17 tumours FAs and the unsaturated FAs, but reduced 9/17 FAs, the saturated and the unsaturated FAs in 'normal' mammary tissue, and usually had no effect on the FAs of other tissues. MTX 2 or 4 mg kg-1 (MTX 2 or 4 mg) +/- INDO in general partly restored (increased) the amounts of tumour FAs, and reduced the saturated/unsaturated FA ratio. In the 'normal' spleen and plasma also, but not in the liver, MTX 2 mg generally somewhat restored the FA composition. However, as in the liver, the spleen 20:4 and 22:6 (which form prostaglandins and lipid peroxides) did not increase in the presence of INDO. With MTX 4 mg, some of the plasma and liver FAs decreased, in contrast to the tumour. There was generally no evidence of MTX potentiation by INDO. These results are discussed in relation to carcinogenesis, cachexia, and the response to treatment.

Cellular mechanism of synergistic stimulation of PGE2 production by phorbol diester and Ca2+ ionophore A23187 in cultured Madin-Darby canine kidney cells

The synergistic stimulation of arachidonic acid release and prostaglandin (PG) E2 production was observed when quiescent Madin-Darby canine kidney (MDCK) cells were exposed to phorbol 12-myristate 13-acetate (PMA) and Ca2+ ionophore, A23187. Addition of PMA or A23187 by itself was not effective. When cells were treated with 50 nM PMA and 0.1 microM A23187 at a suboptimal concentration, there was a marked increase in the production of PGE2. In the presence of higher concentrations of A23187 (5-10 microM), 50 nM PMA was only synergistic in potentiating the liberation of free arachidonic acid, but failed to stimulate the PGE2 production. The amount of free arachidonic acid liberated by 50 nM PMA and 10 microM A23187 reached a maximum level within several hours, whereas PGE2 synthesis induced by 50 nM PMA and 0.1 microM A23187 proceeded with a slower process requiring more than 24 h to reach a maximum. The stimulated PGE2 synthesis was blocked by transcription and translation inhibitors. The addition of 50 nM PMA alone or the mixture of 50 nM PMA and 0.1 microM A23187 was found similarly to increase the cellular PG endoperoxide synthase activity, suggesting that PMA was responsible for the increased enzyme activity. However, these agents failed to enhance the activities of phospholipases and PGE2 synthase from PGH2. Northern blot analysis confirmed the increased level of PG endoperoxide synthase mRNA in the cells treated with PMA. The effect of PMA was mimicked by other protein kinase C activators. The pretreatment with PMA caused a down-regulation in the PGE2 production. The stimulated PGE2 production was abolished in the presence of selective protein kinase C inhibitors such as staurosporine and H-7. In addition, sphingosine, dihyrosphingosine, and psychosine, recently found to be protein kinase C inhibitors, blocked the effect of PMA in intact MDCK cells. Thus, the results indicate that the synergistically stimulated PGE2 production with phorbol diesters and 0.1 microM A23187 occurred principally through the de novo synthesis of PG endoperoxide synthase, also implying a role for protein kinase C.

Indomethacin inhibits the chemical carcinogen benzo(a)pyrene but not dimethylbenz(a)anthracene from altering Langerhans cell distribution and morphology

Treatment of murine skin with the polyaromatic hydrocarbon carcinogens benzo(a)pyrene (BP) or dimethylbenz(a)anthracene (DMBA) for 3 weeks resulted in an increase and a decrease in epidermal Langerhans cell (LC) numbers, respectively, compared with solvent-treated skin. Implantation of subcutaneous indomethacin pellets prior to carcinogen treatment prevented the changes in LC numbers and morphology in BP, but not DMBA-treated skin. Indomethacin treatment was also found to reduce elevated prostaglandin E2 (PGE)2 levels in the skin of BP-treated mice, whereas PGE2 levels were not significantly raised in DMBA-treated mice. There thus appears to be a link between altered prostaglandin levels and LC numbers in murine skin treated with BP, but not DMBA. In the latter, LC numbers were reduced by mechanisms not reversed by indomethacin. It is concluded that increased prostaglandin levels may contribute to the impairment of cutaneous immunity previously observed in BP-treated mice by altering LC density and morphology within the epidermis.

Modulation by indomethacin or prostaglandin E2 of the incidence of diethylnitrosamine-induced gamma-glutamyltranspeptidase-positive foci in rat liver

We investigated the effect of a pretreatment with indomethacin (IMC, ip 3.6 mg/kg body weight (bw)) or dimethylprostaglandin E2 (PGE2, ip 10 micrograms/kg bw) on the incidence and development of gamma-glutamyltranspeptidase (GGT)-positive foci of altered hepatocytes, scored 8 or 14 weeks after ip injection of diethylnitrosamine (DENA, 50 mg/kg bw) to rats submitted to two-thirds hepatectomy (PH) or sham operation (Sh). IMC reduced by about 4 times the incidence of DENA-induced GGT-positive foci per cm3 of liver tissue in sham-operated as well as in two-thirds hepatectomized rats, compared to the respective unpretreated controls. In contrast, PGE2 pretreatment increased the incidence of DENA-induced foci in both groups, this effect, in terms of absolute numbers of foci, being additive to that of PH alone. IMC pretreatment resulted in foci with lower average size in the Sh but not in the PH animals, whereas with PGE2 pretreatment the mean volume of the foci was increased in the two groups of rats. At the dose used, IMC did not modify the proliferative response of hepatocytes to PH, and PGE2 did not stimulate proliferation in the sham-operated animals. Altogether, these results indicate that: 1, the incidence of DENA-induced foci can be negatively modulated by interfering with the prostaglandins pathway through a mechanism that does not involve an action either on proliferative activity or on any other process that would be specific to the post-hepatectomy regenerative state; 2, positive modulation of the incidence of DENA-induced foci does not necessarily require stimulation of proliferation.

Prostaglandins can modify gamma-radiation and chemical induced cytotoxicity and genetic damage in vitro and in vivo

The effect of prostaglandin E1, E2, and F2 alpha on gamma-radiation, benzo(a)pyrene and diphenylhydantoin-induced cytotoxicity in vivo and genotoxicity in vitro was investigated. Prostaglandin E1 prevented both cytotoxic and genotoxic actions of all the three agents, where as both PGE2 and PGF2 alpha were ineffective. In fact, it was seen that both PGE2 and PGF2 alpha are genotoxic by themselves. Gamma-linolenic acid and dihomogamma-linolenic acid, the precursor of PGE1 were also as protective as that of PGE1, where as arachidonic acid, the precursor of 2 series PGs, has genotoxic actions to human lymphocytes in vitro. These results suggest that prostaglandins and their precursors can determine the susceptibility of cells to cytotoxic and genotoxic actions of chemicals and radiation. This study is particularly interesting since, it is known that some tumor cells contain excess of PGE2 and PGF2 alpha and many carcinogens can augment the synthesis of 2 series of PGs.

Renal cell culture

Methods for the establishment and growth of renal cell types in culture are reviewed, with emphasis on current trends. General techniques available for the isolation and culture of glomerular cells have progressed from explant to enzyme dissociation and cloning techniques. The growth characteristics and properties of cultured glomerular endothelial, epithelial, mesangial, and bone-marrow-derived cells are discussed. Studies are described in which cultures of contractile mesangial cells have led to an elucidation of their role both in normally functioning glomeruli and in disease states. Renal tubule culture techniques also have progressed from mixed tissue explants and cell isolates to fractionation of enriched tubule populations and growth of specific, individually microdissected proximal convoluted, proximal straight, thick ascending limb of Henle's loop, and collecting tubules. The differentiated tubule epithelial-specific properties of such primary cultures are discussed in relation to those of permanently growing cell lines such as MDCK and LLC-PK1. Renal tubule cultures will be invaluable for the study of the role of hormones and extracellular matrix in epithelial growth and polarity of normal structure and function. In addition, in vitro models of cultured renal tubules have been established to study the effects of age, nephrotoxins, and anoxic injury.

Metabolism of arachidonic acid by hamster trachea lack of stimulation by A23187

The metabolism of arachidonic acid has been studied using hamster trachea in short-term organ culture. To study endogenous substrate utilization, tissue lipids were labeled with [3H]-arachidonic acid, whereas exogenous substrate turnover was assessed by the addition of 100 microM [14C]-arachidonic acid to the medium. Both exogenous and endogenous arachidonate were converted primarily to 6-keto-PGF1 alpha and PGE2, with varying amounts of an unidentified non-polar product noted. Production of the prostanoids increased steadily with time up to 24 hours. No significant generation of lipoxygenase products was found. Release of incorporated labeled arachidonic acid was nearly linear with time, resulting in the transfer of about 10% of the total label into the medium after 24 hours. About 3% of the total label was converted to prostaglandins. In the presence of 10 microM A23187, release of label was increased by only 25 to 60% relative to the control. Analysis of labeled compounds in the medium showed that this increase resulted from increased release of unchanged arachidonic acid, and that the yield of oxygenated products was the same as from the control incubations.

Prostaglandins and their precursors can modify genetic damage-induced by gamma-radiation and benzo(a)pyrene

Experiments were performed to study the effect of various prostaglandins (PGs) and their precursors, gamma-linolenic acid (GLA) and arachidonic acid (AA) on gamma-radiation and benzo (a) pyrene (BP)-induced genetic damage to the bone marrow cells of mice, using the sensitive micronucleus (MN) test. Thromboxane B2 prostaglandin E1 and GLA completely prevented BP-induced and reduced to a great degree radiation-induced genetic damage, where as PGE2, PGF2 alpha and AA were without any effect. Since GLA and AA are widely distributed in the cell membranes, and as PGs can be formed virtually in response to any type of stimulus, it is likely that GLA and PGE1 may function as endogenous anti-mutagenic chemicals.

Phospholipase A2 dependent release of fatty acids from peroxidized membranes

Unilamellar vesicles (liposomes) consisting of liver phosphatidylcholine and phosphatidylethanolamine were used as model membranes and subjected to lipid peroxidation. Following peroxidation samples were treated with phospholipase A2 from snake venom and subsequently analyzed for products of lipid peroxidation and of phospholipase A2 action. A significantly increased susceptibility to phospholipase A2 was noted for liposomes subjected to peroxidation, as compared to controls, which correlated with the extent of lipid peroxidation measured by the formation of thiobarbituric acid reacting products and conjugated dienes. Low levels of peroxides were detected in control liposomes and these peroxidases were rapidly cleaved by phospholipase A2, such that nearly 40% of the total peroxide content was associated with free fatty acids after l5 min incubation. Oxidized liposomes contained over seven fold the level of lipid peroxidation products, and the were also rapidly cleaved by phospholipase A2 where over 50% were recovered as free fatty acids following l5 min of exposure to phospholipase A2. Along with this high order of removal of oxidized fatty acids, a marked hydrolysis of intact fatty acids was also observed. The extent of fatty acid release was roughly correlated with the degree of fatty acid unsaturation. A substantial increase in the release of arachidonic acid was found when peroxidized membranes were analyzed.

2,3,7,8-Tetrachlorodibenzo-p-dioxin: examination of biochemical effects involved in the proliferation and differentiation of XB cells

XB, a cell line derived from a mouse teratoma, differentiates into stratified squamous epithelium when incubated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). To examine the possible biochemical mediators of this response, we compared the effects produced by TCDD to those elicited by other compounds which stimulate epidermal proliferation and/or differentiation in mice. XB/3T3 cultures keratinize when incubated with cholera toxin, epidermal growth factor (EGF), or TCDD, but not 12-0-tetradecanoylphorbol-13-acetate (TPA). Incubation of XB cells with TCDD (10(-9)M) for 48 hours produces a 20% increase in thymidine incorporation, a response which is neither as large nor as rapid as that produced by cholera toxin, TPA, or EGF. Although both cholera toxin and TCDD stimulate differentiation and thymidine incorporation in XB/3T3 cultures, cholera toxin increases cAMP 30-fold in these cells, while TCDD does not affect cAMP accumulation at any of the times studies (15 min to 120 hours). Inhibitors of arachidonic acid metabolism, which block epidermal proliferative responses to TPA in vivo, do not prevent the differentiation of XB cells in response to TCDD. In XB/3T3 cultures, TPA stimulates arachidonic acid release at all times tested (1,6, and 24 hours) and increases the incorporation of 32Pi into total phospholipids and phosphatidylcholine after 3 hours. In contrast, TCDD affects neither arachidonic acid release nor the turnover of phosphatidylinositol or phosphatidylcholine at any of the times tested. Although we examined biochemical effects which have been suggested as part of the mechanism of TCDD and which are produced by other epidermal proliferative compounds in XB cells, no mediator of the TCDD-produced differentiation of XB/3T3 cultures was observed.

Eicosapentaenoic acid: its effects on arachidonic acid metabolism by cells in culture

Some eukaryotic cells in culture synthesize a variety of lipoxygenase and/or cyclooxygenase products when stimulated by appropriate agonists. Under normal nutritional conditions, these products are derived from the polyunsaturated fatty acid (PUFA) 5,8,11,14-eicosatetraenoic acid (ETA), arachidonic acid, which before metabolism must be liberated from cellular lipids by deesterification. If the cellular lipids are preloaded with 5,8,11,14,17-eicosapentaenoic acid (EPA) and cells are then stimulated to metabolize the PUFAs, levels of cyclooxygenase and lipoxygenase products synthesized are altered. Cyclooxygenase products decrease, while lipoxygenase products are not significantly affected and may even increase. The decrease in the production of cyclooxygenase products results from reduced utilization of the substrate (ETA). Decreased prostaglandin production by rat basophil leukemia-1 cells preloaded with EPA and radiolabeled with [3H]ETA and [14C]EPA can also be demonstrated by high-performance liquid chromatographic analyses of [3H]- and [14C] radiolabeled metabolites in culture fluids of cells stimulated to metabolize PUFA by the Ca2+ ionophore A23187.

Identification of a purine (P2) receptor linked to ion transport in a cultured renal (MDCK) epithelium

1 Exogenous adenosine triphosphate (ATP) stimulates the short circuit current (SCC) in a cultured renal-derived epithelium (MDCK). Half-maximal stimulation is achieved at 1.91 X 10(-5) M ATP. 2 It is suggested that ATP interacts with a P2 purine receptor upon the basis of (a) agonist potency (ATP greater than adenosine diphosphate much greater than adenosine monophosphate, adenosine; ATP greater than uridine triphosphate greater than inosine triphosphate much greater than cytosine triphosphate, guanosine triphosphate); (b) the inhibition of the ATP response by quinidine (1 X 10(-3) M) but not by theophylline (1 X 10(-3) M). 3 Indomethacin (1 X 10(-5) M) inhibits the response of the cultured epithelium to ATP. 4 Prostaglandin E1 (PGE1) stimulates SCC but potentiates the effect of ATP on SCC. The divalent cationic ionophore A23187 (1 X 10(-6) M) transiently stimulates SCC itself and abolishes ATP-induced stimulation of the SCC.

Plasma prostaglandins in mucositis due to radiotherapy and chemotherapy for head and neck cancer

Patients with head and neck cancer were treated with synchronous radiotherapy and chemotherapy (vincristine, bleomycin and methotrexate). Before treatment, mucositis was absent and low amounts of prostaglandin-like material were extracted from peripheral plasma. As treatment proceeded mucositis occurred, and its degree correlated with the amount of prostaglandin-like material extracted from the plasma. Some patients were given moderate doses of drugs which inhibit prostaglandin synthesis, but mucositis still occurred.

Decrease in aspirin-induced gastric mucosal damage in rats by oral administration of the cytotoxic drugs melphalan and methotrexate

Gastric mucosal damage by aspirin and chemotherapeutic drugs was studied in Wistar rats. Aspirin 60 mg given by stomach tube caused substantial gastric mucosal damage as judged by visual examination of the stomachs removed four hours later. Melphalan and methotrexate given daily for four days had no significant macroscopic effect on the gastric mucosa, but reduced the damage caused by aspirin. This protective effect my involve a stimulation of prostaglandin synthesis by the stomach, increased mucus secretion, and/or inhibition of acid secretion.

alpha-Tocopherol inhibits 12-O-tetradecanoyl-phorbol-13-acetate-stimulated deacylation of cellular lipids, prostaglandin production, and changes in cell morphology of Madin-Darby canine kidney cells

Incubation of the tumor-promoting phorbol diester, 12-O-tetradecanoyl-phorbol-13-acetate with Madin-Darby canine kidney cells (MDCK) stimulated deacylation of phospholipids, prostaglandin production and altered cell morphology. alpha-Tocopherol, if present during the incubation, inhibited these effects. For inhibition, alpha-tocopherol had to be present during incubation of 12-O-tetradecanoyl-phorbol-13-acetate and cells; pretreatment or posttreatment of the cells with alpha-tocopherol was not effective. Inhibition of the 12-O-tetradecanoyl-phorbol-13-acetate effects was specific for the tumor promoter extracted from the Croton tiglium L. plant of the family Euphorbiaceae. Stimulated prostaglandin production by another tumor promotor (phorbol-12, 13-didecanoate), a semisynthetic product of that plant, was also inhibited by alpha-tocopherol. But that of structurally related diterpenoid esters isolated from plants of the family Thymelaeaceae, such as mezerein, gnidimacrin, gnilatimacrin, and gnilatimacrin-20-palmitate, were not. Stimulation of prostaglandin production in MDCK cells by compounds such as benzo(a)pyrene, adriamycin and 17 beta-estradiol or even the basal synthetic activity of MDCK cells was not affected by alpha-tocopherol.

Review: prostaglandins and cancer

This paper reviews work on the role of prostaglandins in cancer. A substantial body of evidence demonstrates elevated amounts of E series of prostaglandins in human and experimental tumors. Blockade of prostaglandin synthesis in vitro or in vivo results in inhibition of tumor growth. Involvement of prostaglandins is implicated in the actions of tumor promoters like phorbol and polycyclic aromatic hydrocarbon carcinogens. Symptoms like hypercalcemia, osteolysis and tumor metastasis are discussed where disordered synthesis and/or action of prostaglandins and related substances might have a role in the altered metabolism associated with neoplasia.

Epidermal prostaglandins after topical application of a tumor promotor

The topical application of the promoter, 12-O-tetradecanoyl-13-acetate, on the shaved backs of mice was attended by a striking increase in the PGE concentration within epidermis as early as 1 h later. This increase peaked at 24 h but the prostaglandin value remained elevated for at least 48 h. PGF, on the other hand, showed only a modest increase in epidermis with a maximum at 12 h. By 48 h, the PGF concentration returned to normal.

Tumor promoting phorbol diesters stimulate release of radioactivity from [3H]-arachidonic acid labeled- but not [14C]linoleic acid labeled-cells. Indomethacin inhibits the stimulated release from [3H] arachidonate labeled cells

The tumor promoting phorbol diester, 12-O-tetradecanoyl-phorbol-13-acetate, stimulates MDCK cells to deacylate cellular phospholipids and to produce prostaglandins when measured as the release of arachidonic acid and its metabolites into the culture fluid. Indomethacin, at levels of 2.8 x 10(-8) to 2.8 x 10(-6) M, inhibits the release of radioactivity from [3H]arachidonate labeled cells stimulated by 12-O-tetradecanoyl-phorbol-13-acetate treatment in a concentration dependent manner. At these concentrations, the conversion of released [3H]arachidonic acid into prostaglandins E2 and F2alpha and the production of PGE2 measured serologically also is suppressed in a concentration dependent manner. Indomethacin, at these levels, has no effect on the acylation of [3H]arachidonic acid into cellular lipids. The tumor promoting phorbol diester does not stimulate the release of radioactive materials from MDCK cells labeled with [14C]linoleic acid, although prostaglandin production by these cells is stimulated.

Adriamycin stimulates canine kidney (MDCK) cells to deacylate cellular lipids and to produce prostaglandins

Dog kidney (MDCK) cells treated with adriamycin (0.5 micrograms/ml) for 1 hr, produced from 2 to 7 times more prostaglandins E2 and F2alpha when measured in culture media 24, 48 and 72 hrs after the treatment. Indomethacin (ID50 less than 2 x 10(-8) M) and cycloheximide (0.5 micrograms/ml) inhibited this adriamycin-stimulated prostaglandin production. The aglycone of adriamycin (0.5 to 5.0 micrograms/ml) had little stimulating effect. Treatment of [3H]arachidonic acid-labeled MDCK cells with adriamycin (0.5 micrograms/ml) for 1 hr also stimulated deacylation of cellular lipids during subsequent incubation. Altered morphology of MDCK cells resulted from such treatment with adriamycin; indomethacin did not inhibit this change, but cycloheximide did.

Inflammatory, tumor initiating and promoting activities of polycyclic aromatic hydrocarbons and diterpene esters in mouse skin as compared with their prostaglandin releasing potency in vitro

Release of prostaglandin E2 (PGE2) in cultured peritoneal macrophages of NMRI mice by skin irritant tumor initiators and promoters was investigated. Initiators of the polycyclic aromatic hydrocarbon type, e.g., DMBA, caused slight irritation on the mouse ear but even relatively high doses did not stimulate PGE2-release to any measurable extent within 4 h after administration in vitro. Apparently there is no correlation between irritation and initiating activity in mouse skin and PGE2-release in macrophages. On the other hand, promoters of the diterpene ester type, e.g., TPA, were strong irritants on the mouse ear. Even low doses of these compounds stimulated PGE2-release from macrophages dramatically within 1 h after administration in vitro. Moreover, a good correlation was established between irritant and promoting activity in mouse skin and PGE2-release in macrophages of a series of tigliane, ingenane and daphnane type diterpene derivatives. These results suggest that also in mouse skin PGE2-release may occur following exposure of the target cells to promoters of the diterpene ester type resembling one of the most early molecular events of promotion. This event could initiate both skin irritation and cell proliferation.