mezerein and Hyperplasia

Chemically induced epidermal carcinogenesis is often divided into two stages: initiation, which involves the conversion of some epidermal cells into latent neoplastic cells, and promotion, which allows the evolution of this neoplastic change into the formation of a neoplasm. The hallmark of epidermal tumor promotion is the transformation of the normal epidermis into a hyperplastic epidermis. A major unanswered question about epidermal tumor promotion is whether the epidermal hyperplasia that characterizes promoted skin is a regenerative epidermal hyperplasia resulting from damage produced by the promoter. The opinion currently held is that the epidermal hyperplasia produced by tumor promoters is not simply a regenerative epidermal hyperplasia and possesses characteristics which a regenerative hyperplasia does not have, enabling it to evolve into an epidermal neoplasm. The purpose of this review is to present recent evidence which strongly suggests that promoter-induced epidermal hyperplasia is a regenerative hyperplasia. Three principal lines of evidence are reviewed. The first demonstrates that an epidermal regenerative hyperplasia repeatedly produced by wounding or abrasion can promote epidermal carcinogenesis in the initiated skin of mice. The second line of evidence demonstrates that the epidermal hyperplasia produced by the application of 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the most powerful and widely used promoter of skin carcinogenesis, is preceded by damage to the epidermis. This strongly suggests that the epidermal hyperplasia which ensues is a regenerative hyperplasia. Thirdly, evidence is presented which demonstrates that hyperplasia-producing agents which do not promote, produce an epidermal hyperplasia which is different from that produced by tumor promoters. Finally, the review discusses the evidence which suggests that the production of a hyperplasia may be the mechanism for tumor promotion in other organs, such as the liver, bladder, and intestine.

Topics: Acetates; Acetic Acid; Animals; Carcinogens; Cell Differentiation; Connective Tissue Cells; Diterpenes; Epidermal Cells; Humans; Hyperplasia; Inflammation; Models, Biological; Regeneration; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate; Time Factors

The mechanisms by which lipoxin A(4) (LXA(4)) inhibit skin inflammation remain unclear. In the present studies, the ear inflammatory model was induced by topical application of mezerein. Treatment of the mouse ear with LXA(4) exhibited the inhibitory effects on oedema, neutrophil infiltration, vascular permeability, expressions of interleukin (IL)-1, IL-6 and IL-8 mRNA, DNA-binding activity of nuclear factor-kappaB (NF-kappaB), and on dermal hyperplasia. NF-kappaB reporter activities and nuclear translocations of NF-kappaB p65 in cultured keratinocytes stimulated by mezerein were inhibited by pretreatment of the cells with LXA(4). LXA(4) reduced degradation, but not phosphorylation of IkappaBalpha in cultured keratinocytes stimulated by mezerein, suggesting that LXA(4)-attenuated IkappaBalpha degradation may restore the mezerein-blocked inhibitory effects of IkappaB on nuclear translocation and DNA-binding activity of NF-kappaB. Our results demonstrated that LXA(4) displays the anti-inflammatory and anti-proliferative role on ear inflammatory model induced by mezerein and these effects were related with downregulation of DNA-binding activity of NF-kappaB.

Topics: Administration, Topical; Animals; Anti-Inflammatory Agents, Non-Steroidal; Carcinogens; Cell Line; Cytokines; Dermis; Disease Models, Animal; Diterpenes; Female; Humans; Hyperplasia; Inflammation; Keratinocytes; Lipoxins; Mice; Mice, Inbred Strains; NF-kappa B

E6201 [(3S,4R,5Z,8S,9S,11E)-14-(ethylamino)-8,9,16-trihydroxy-3,4-dimethyl-3,4,9,10-tetrahydro-1H-2-benzoxacyclotetradecine-1,7(8H)-dione)] is a novel anti-inflammatory agent that has potent inhibitory effects on the production of proinflammatory cytokines from leukocytes and antiproliferative activity on keratinocytes. To characterize the in vivo pharmacological activity of E6201, topically administered E6201 was evaluated in several different animal models of dermatitis. E6201 formulated as an ointment or cream showed dose-dependent inhibition of croton oil-induced acute edema formation and neutrophil infiltration into mouse skin. In addition, E6201 cream inhibited the 1-fluoro-2,4-dinitrobenzene-induced contact hypersensitivity reaction mediated by T cells in mice. In this model, E6201 cream also suppressed the migration of neutrophils and lymphocytes into the inflammatory site. Pretreatment with E6201 cream attenuated phorbol-12 myristate 13-acetate-induced ornithine decarboxylase activity, a marker of proliferation in epidermis. Furthermore, E6201 ointment showed inhibitory effects on both mezerein-induced and interleukin (IL)-23-induced epidermal hyperplasia. E6201 also suppressed T cell receptor-stimulated IL-17 production from human T cells. These results indicate that topically administered E6201 may be a useful agent for the prevention and treatment of cutaneous inflammatory and hyperproliferative diseases such as psoriasis.

Topics: Administration, Topical; Animals; Antineoplastic Agents, Phytogenic; Croton Oil; Dinitrofluorobenzene; Diterpenes; Drug Eruptions; Hyperplasia; Indicators and Reagents; Interleukin-17; Interleukin-23; Lactones; Male; MAP Kinase Kinase Kinase 1; Mice; Mice, Inbred BALB C; Mitogen-Activated Protein Kinase 1; Ornithine Decarboxylase; Peroxidase; Protein Kinase Inhibitors; Psoriasis; Skin; T-Lymphocytes; Tetradecanoylphorbol Acetate

Although mezerein resembles 12-O-tetradecanoylphorbol-13-acetate (TPA) in being a potent ligand for protein kinase C in vitro, its properties as a tumor promoter on mouse skin differ from those of TPA. Mezerein is a good second-stage promoter of papillomas, an inefficient complete promoter of papillomas, and an effective promoter of carcinomas. The mechanism and structural features responsible for the anomalous tumor promoting activity of mezerein are unknown. We have examined here the in vitro and in vivo activities of octahydromezerein (OHM) and compared them to those of TPA and mezerein. OHM was of interest because if it acted like mezerein it would afford a convenient route for radioactive labeling. Alternatively, if it functioned as a complete tumor promoter, it would implicate unsaturation as the critical structural feature of mezerein responsible for its altered promoting activity. Consistent with this latter possibility, we find that OHM was an effective complete tumor promoter for SENCAR mice. Moreover, the pattern and magnitude of papilloma induction, yielding a peak at 16-20 weeks followed by a decline by 30-32 weeks, resembled that for TPA; mezerein, in contrast, induced a gradual but steady increase in the number of papillomas which did not reach the OHM level by 32 weeks. The dosage of OHM for inducing a comparable degree of acute and chronic hyperplasia to that induced by mezerein was 3- to 10-fold higher. This difference agrees with the relative binding affinities to protein kinase C; the Ki for OHM was 2.7 nM, compared to 0.58 nM for mezerein.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Diterpenes; Enzyme Activation; Female; Hyperplasia; Mice; Mice, Inbred Strains; Papilloma; Protein Kinase C; Skin; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

Tumor-promoting phorbol esters are potent inflammatory agents for mouse skin, and the potential mechanistic role of inflammation in tumor promotion is under active investigation. We have shown previously that resiniferatoxin, a uniquely irritant phorbol-related diterpene, acts as a capsaicin analogue to induce and then to block neurogenic inflammation. We report here that pretreatment of CD-1 mice with resiniferatoxin blocked the early (3 h) erythema and edema (6 h) in response to phorbol 12-myristate 13-acetate (PMA), whereas the edema at later times (12-24 h) was only partially blocked. Since the efficiency of resiniferatoxin pretreatment decreased as a function of time if PMA was applied 24, 48, or 96 h after resiniferatoxin administration, the late edema response to PMA may be a combination of increasing edema of nonneurogenic origin and the recovering neurogenic response due to the decreasing desensitization. For other phorbol esters, 12-deoxyphorbol mono- and diesters, and mezerein, differing kinetics of edema and differing degrees of blockade of edema following resiniferatoxin pretreatment were observed, as expected from the discrepancies between their inflammatory and tumor-promoting activities. PMA-induced skin hyperplasia, unlike edema, was not inhibited by resiniferatoxin pretreatment, suggesting that the early component of neurogenic inflammation was not essential for hyperplasia under our conditions. Distinction between inflammatory mechanisms may help to clarify the role of inflammation in tumor promotion.

Topics: Administration, Topical; Animals; Diterpenes; Dose-Response Relationship, Drug; Erythema; Female; Hyperplasia; Inflammation; Mice; Mice, Inbred Strains; Phorbol Esters; Skin; Terpenes; Tetradecanoylphorbol Acetate

Using an 18 week two-stage protocol we have compared the tumour-promoting properties of a range of phorbol and daphnane esters on female CD-1 mice. The induction of epidermal hyperplasia in this mouse strain by these compounds has also been assessed by comparison with the standard phorbol ester, 12-O-tetradecanoylphorbol-13-O-acetate (TPA). Two compounds, sapintoxin D (SAP D) and thymeleatoxin A (TA) (a daphnane structurally related to the second-stage promoter mezerein) were shown to be second-stage promoters using 5 nmol TPA as a first-stage promoter and 0.2 mumol 7,12-dimethylbenz[a]anthracene (DMBA) as initiator. Both compounds at a dose of 17 nmol were hyperplasiogenic. Two further derivatives, sapintoxin C (SAP C) and 4 alpha-sapinine (alpha-SAP) were inactive as promoters and hyperplastic agents. 4 alpha-sapinine, which prevents in vitro stimulation of protein kinase C (PKC), by 12-O-tetradecanoylphorbol-13-O-acetate (TPA) failed to inhibit significantly TPA-induced promotion and hyperplasia at a dose of 20 nmol and 100 nmol respectively. Sapintoxin A (SAP A), a potent activator of PKC, was neither a complete nor second-stage promoter at doses of up to 20 nmol. A series of in vivo and in vitro experiments which were carried out to determine the metabolic fate of this compound under experimental conditions showed that SAP A was not metabolized to any significant extent up to 48 h. When SAP A was co-administered with sub-hyperplastic doses of the calcium ionophore A23187 (5 micrograms and 10 micrograms) tumours appeared in a dose-dependent manner. This combination was also hyperplasiogenic in mouse skin. SAP A may be a useful probe for studying the involvement of PKC isozymes in tumour promotion and cell proliferation.

Topics: Animals; Carcinogens; Chemical Phenomena; Chemistry; Diterpenes; Female; Hyperplasia; Phorbol Esters; Rats; Skin; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

The effects of promoter treatments prior to initiation on subsequent promotion by mezerein were examined in SENCAR mice. Groups of mice received two applications of various complete as well as first and second stage promoters given at various time intervals prior to initiation ranging from 3 days to 10 weeks. The mice were then initiated with 2 micrograms of 7,12-dimethylbenz[a]anthracene (DMBA) followed 2 weeks later by twice-weekly treatments with 2 micrograms of mezerein. The papilloma response in mice, receiving pretreatments with 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate (TPA) either 3 days, 1, 2, 3 or 5 weeks before initiation, was similar to that seen when TPA was given after initiation during stage I of promotion followed by stage II of promotion with mezerein (4-5 papillomas per mouse in all groups). Surprisingly, pretreatment with the stage II promoter, mezerein (2 micrograms), either 2 or 5 weeks prior to initiation, also gave papilloma responses similar to that induced with the standard two-stage promotion protocol (4.7 and 6.4 papillomas per mouse, respectively). The papilloma response was less than that in the standard two-stage promotion protocol when pretreatments with the stage I promoter A23187 (80 micrograms/mouse) were given either 2 or 5 weeks before initiation (2.6 and 2.3 papillomas per mouse, respectively). However, a repeat experiment (currently in progress) with a higher dose of A23187 (160 micrograms/mouse) given 2 weeks prior to initiation indicates that it is more effective than the 80 micrograms dose. When the time interval between pretreatment and initiation was increased to 10 weeks, the papilloma response with TPA and A23187 pretreatment was reduced to below two papillomas per mouse and with mezerein pretreatment to below three papillomas per mouse, indicating the effect was reversible. Histological changes in epidermis of mice which received two applications of these compounds correlated with the tumor response. In this regard, treatment with two applications of TPA and mezerein resulted in an epidermal hyperplasia of similar magnitude (epidermal thickness of 53.5 +/- 1.5 and 50.0 +/- 1.1 microns, respectively). The hyperplasia produced by treatment with two applications of 80 micrograms A23187 (39.4 +/- 1.8 microns) was significantly less. The ability of pretreatments with benzoyl peroxide (20 mg) and chrysarobin (50 micrograms) to affect the subsequent promoting activity of mezerein was also examined.(ABSTRAC

Topics: Animals; Calcimycin; Diterpenes; Drug Synergism; Female; Hyperplasia; Mice; Papilloma; Skin; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

Intracutaneous injection of cholera toxin into mice induced epidermal hyperplasia to a greater extent than 12-O-tetradecanoylphorbol-13-acetate. It also induced adenylate cyclase and though weakly, ornithine decarboxylase of the epidermis. Cholera toxin, however, showed no tumor promoting activity in mouse skin carcinogenesis. In the single stage promotion, cholera toxin (50 ng) was injected once a week for 10 weeks into the skin of SENCAR mice initiated with 25 micrograms 7,12-dimethylbenz[a]anthracene, but no tumors developed. In the two-stage promotion test, cholera toxin (10-100 ng) was injected for one or two weeks into the initiated skin and then mezerein (4 micrograms) was applied twice a week for 18 weeks, but the toxin did not increase incidence or numbers of papillomas.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Cholera Toxin; Cocarcinogenesis; Cyclic AMP; Diterpenes; Enzyme Induction; Epidermis; Hyperplasia; Mice; Ornithine Decarboxylase; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

The ability of the non-promoter phorbol diacetate (PDA) to modulate superoxide anion radical production by the complete tumor promoter phorbol myristate acetate (PMA) or the second stage promoter mezerein was assessed. Superoxide anion radical production was measured by the superoxide dismutase inhibitable reduction of nitroblue tetrazolium (NBT) to a blue intracellular formazan precipitate. These studies demonstrated that superoxide anion radical production by murine peritoneal exudate cells (PEC) stimulated by i.p. injection with mezerein (100 ng) is inhibited in a dose-dependent manner by co-administration with PDA (1-1000 ng). There was no effect on the number of formazan-positive PEC when PDA was co-administered with PMA. In a two-stage tumor promotion bioassay in female SENCAR mice initiated with 25.6 micrograms dimethylbenz[a]anthracene (DMBA) followed by first stage promotion with PMA (4X, 2 micrograms), co-administration of mezerein (2 micrograms) with 2 micrograms or 20 micrograms PDA reduced the number of papillomas after 14 weeks by 38% and 44%, respectively, compared with mezerein treatment alone. PDA (20 micrograms) when co-administered with mezerein (2 micrograms) does not inhibit mezerein induced hyperplasia in mouse skin. These results suggest a correlation between the ability of PDA to inhibit both superoxide anion radical production and tumor promotion by mezerein.

Topics: Animals; Carcinogens; Diterpenes; Female; Free Radicals; Hyperplasia; Macrophages; Mice; Phorbol Esters; Skin; Skin Neoplasms; Superoxides; Terpenes; Tetradecanoylphorbol Acetate

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Diterpenes; Female; Hyperplasia; Mice; Neoplasms, Experimental; Phorbol Esters; Phorbols; Skin; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

Topics: Alkynes; Anthralin; Calcimycin; Carcinogens; Diterpenes; Epidermal Cells; Epidermis; Hyperplasia; Keratins; Phorbol Esters; Terpenes; Tetradecanoylphorbol Acetate

Topics: Animals; Diterpenes; Electrophoresis, Polyacrylamide Gel; Epidermis; Fluocinolone Acetonide; Hyperplasia; Keratins; Mice; Molecular Weight; Phorbol Esters; Phorbols; Protein Biosynthesis; Proteins; Terpenes; Tetradecanoylphorbol Acetate