Rabbits with elevated serum C-reactive protein exhibit diminished neutrophil infiltration and vascular permeability in C5a-induced alveolitis

In previous studies, we have shown that C-reactive protein (CRP) inhibits chemotaxis of neutrophils to complement fragments in vitro. To evaluate the effect of CRP on C5a-induced inflammation in vivo, a rabbit model of alveolitis was used. Rabbits pretreated with subcutaneous injections of croton oil had serum CRP increase from undetectable levels to 270 +/- 70 micrograms/ml 48 hours later. Rabbits were intubated and C5a des arg (10 micrograms/ml) instilled directly into the lungs via an endotracheal tube. Four to six hours later, the animals were killed and bronchoalveolar lavage performed. Rabbits pretreated with croton oil had significantly (P < 0.01) reduced C5a des arg-stimulated neutrophil infiltration (30 +/- 5%) into alveolar air spaces compared to untreated rabbits (64 +/- 9%). Increased numbers of total leukocytes in the alveolar washes coincided with increased neutrophil numbers whereas alveolar macrophages remained unchanged in all groups. Rabbits pretreated with croton oil also had a significant decrease (P < 0.05) in total protein (320 +/- 50 micrograms/ml) in lavage fluid after C5a instillation compared with untreated animals (850 +/- 140 micrograms/ml). In vitro, rabbit CRP (50 micrograms/ml) added to normal rabbit serum significantly (P < 0.05) inhibited chemotaxis of human neutrophils by 41%. Finally, direct intravenous pretreatment of rabbits with purified CRP also significantly reduced C5a-induced alveolitis. The CRP-C5a group had 33 +/- 10% neutrophil infiltration, a significant (P < 0.01) reduction from the C5a group (71 +/- 6%). The total protein content of the CRP-C5a rabbits was 986 +/- 165 micrograms/ml in the lavage fluid, which was significantly (P < 0.05) lower than the C5a group (1645 +/- 363 micrograms/ml). Therefore, CRP inhibits the development of neutrophil alveolitis and protein leakage in vivo and inhibits neutrophil chemotaxis in vitro. These data indicate that CRP offers a protective effect in neutrophil-mediated lung injury by reducing neutrophil influx and protein leak.

Effects of Topical Retinoids on Cytoskeletal Proteins: Implications for Retinoid Effects on Epidermal Differentiation

In vivo effects of retinoids on epidermal differentiation were investigated by analyzing cytoskeletal proteins in rhino mice treated topically with all-trans-retinoic acid (RA) and other retinoids (13-cis-retinoic acid, etretinate, TTNPB). Non-disulfide-linked cytoskeletal proteins, including keratins from the epidermal "living layers," were first selectively extracted using 9.5 M urea; subsequently, keratins of the stratum corneum were isolated using 9.5 M urea plus a reducing agent. Gel electrophoresis and immunoblot analysis showed that urea extracts of epidermis from vehicle-treated skin were composed predominantly of four major keratins (analogous to human epidermal keratins K1, K5, K10, and K14), and the keratin filament-associated protein filaggrin. In contrast, extracts of epidermis from retinoid-treated skin contained additional keratins (K6, K16, and K17) and almost no detectable filaggrin. Furthermore, similar analysis of stratum corneum keratins demonstrated that extracts from RA-treated skin did not contain the partially proteolyzed keratins typically observed in stratum corneum extracts of control animals. Hyperplasia-inducing agents (salicylic acid, croton oil) caused an increase in keratins K6, K16, and K17, but they did not effect filaggrin or alter proteolysis of stratum corneum keratins. The result that RA induced expression of keratins K6, K16, and K17, as commonly expressed in hyperproliferative epidermis, is consistent with the notion that retinoids increase epidermal cell proliferation in the basal and/or lower spinous layers. The findings that topical RA decreased filaggrin expression and reduced proteolysis of stratum corneum keratins, despite increased size and number of granular cells and the presence of an anucleate stratum corneum, suggest that topical RA may also modulate a later stage of epidermal differentiation involved in stratum corneum formation.

Decreased number and function of antigen-presenting cells in the skin following application of irritant agents: relevance for skin cancer?

The mechanism of irritant dermatitis and the immunologic consequences of such reactions are unclear. We evaluated the number and function of epidermal antigen-presenting cells contained in epidermal cell suspensions obtained from normal and irritant patch test reaction sites. Application of sodium lauryl sulfate or croton oil to human skin in vivo resulted in a progressive depletion in the number of epidermal OKT6+HLA-DR+ (T6+DR+) Langerhans cells (LC) from 3.1 +/- 0.2% of total epidermal cells (EC) to 1.2 +/- 0.1% after 8 d (mean values +/- SEM, N = 9). Between 1-4 d irritant patch test sites demonstrated an influx of non-Langerhans cell T6-DR+ cells. These cells were not DR+ keratinocytes but appeared to be of bone marrow derivation because they expressed the marker, HLe1. Among bone marrow derived cells, the T6-DR+EC appeared to be of monocyte, macrophage lineage, because they expressed the determinant recognized by the OKM5 (M5) antibody. Despite the induction of M5+DR+EC the total number of DR+EC showed progressively decreasing percentages over an 8-d period. Partial recovery to 73 +/- 12% of control value was observed at 2 weeks, with full recovery by 4 weeks after challenge. Concomitantly with the depletion of DR+EC, the capacity of EC to present alloantigens to T cells decreased. This reduction in antigen-presenting cell activity was strongly correlated to the reduction in total DR+ EC (r = 0.94, p less than 0.05). Thus, the capacity of irritants such as croton oil to abrogate the function of epidermal antigen-presenting cells may be related to the tumor promoting potential of these agents.

Hypotheses on a possible role of some mediators in various inflammatory reactions on mouse ear

Thanks to local application of various compounds that inhibit the effects or the synthesis of histamine, serotonin, prostaglandins, thromboxanes and leukotrienes, hypotheses are proposed about the possible role of these mediators in various experimental inflammations induced on mouse ear: reactions to arachidonic acid, croton oil and cantharidin (6-h and 24-h phases); primary irritation and delayed hypersensitivity reaction to picryl chloride; and semi-delayed (6-h) and delayed (24-h) hypersensitivity to oxazolone. Histamine seems to play a major role in the acute phase (6-h) of the reaction to cantharidin and in the primary irritation due to picryl chloride. Serotonin seems to be more involved in edema due to arachidonic acid and to croton oil and in the semi-delayed phase of hypersensitivity to oxazolone. Leukotrienes seem to have a more pronounced role in arachidonic-acid-induced inflammation and in the primary irritation and delayed hypersensitivity reactions to picryl chloride. Prostaglandins and/or thromboxanes might have some influence in edema due to arachidonic acid and to croton oil, and in the primary irritation reaction to picryl chloride.

Suppressing effect of croton oil on intestinal carcinogenesis induced by methylazoxymethanol acetate in rats

The effect of croton oil on intestinal carcinogenesis by methylazoxymethanol acetate (MAM) was examined in ACI/N rats. Twenty seven male and 28 female ACI/N rats were given a single intragastric intubation of MAM at a dose of 25 mg/kg body weight, followed by croton oil at 0.25 ml/kg body weight, 3 times a week, by gastric intubation until the termination of this experiment (365 days). The animals had diarrhea with administration of the croton oil, but the diarrhea had no effect on their gain in weight. Rats from all groups surviving more than 216 days were counted as effective animals. Seventeen out of 54 effective rats which were treated with MAM and croton oil developed intestinal tumors and the incidence of the intestinal tumors was significantly less than that of the group treated with MAM alone (30 out of 50 rats, P less than 0.01). The average number of tumors per rat in the experimental group which was treated with MAM and croton oil (0.6 +/- 1.1) was also smaller than that in the group which was treated with MAM alone (1.0 +/- 1.8), although the difference was not significant. These results suggest that croton oil may suppress some tumor growth at the proper dose in intestinal carcinogenesis which is initiated by MAM.

Croton macrostachys, a plant used in traditional medicine: purgative and inflammatory activity

Croton macrostachys seeds are widely used in Somalia as a purgative. In the present study, pharmacologic and chemical investigations confirm the laxative effect of the seeds and indicate the presence of phorbolesters. There appears to be no direct correlation between phorbolester content and laxative effect.

Calcium-independent induction of cytocidal activity of polymorphonuclear leukocytes by phorbol myristate acetate-like tumor promoters

Tumor promoters were tested for the ability to induce cytocidal activity of polymorphonuclear leukocytes (PMNs), and the extracellular calcium-dependency of their PMN cytotoxicities were examined in comparison with that by some immunomodulators. Immunomodulators such as linear beta-1, 3-D-glucan (TAK) induced potent cytocidal activity of PMNs. The induction was dependent on extracellular Ca2+. Tumor promoters such as phorbol 12-myristate 13-acetate (PMA) and its derivatives, teleocidin which is structurally unrelated to PMA, and croton oil as an example of mixture also induced potent PMN cytotoxicities. In the latter cases, however, the induction was not dependent on extracellular Ca2+. The ability of these tumor promoters to induce PMN cytotoxicity correlated well with their skin-tumor promoting activities. These results indicate that inductions by PMA-like tumor promoters are distinguishable from those by TAK-like immunomodulators in not being Ca2+-dependent. The application of Ca2+-independent PMN cytotoxicity to detect PMA-like tumor promoters is discussed.

Effect of immunosuppressive agents and sunscreens on UV carcinogenesis in the hairless mouse

The effect of two immunosuppressive agents, azathioprine and cyclophosphamide, with and without UVB sunscreen protection on UV-induced skin carcinogenesis was studied in the albino hairless mouse. In a daily treatment regime spanning 9 weeks, groups of mice were immunosuppressed with either drug, and were exposed to minimally erythemal doses of a light source simulating the UV portion of the solar spectrum. The accumulated UV exposure alone induced skin tumours in 77% of mice. Azathioprine, but not cyclophosphamide, significantly enhanced the incidence of UV tumorigenesis. Photoprotection by topical application of one of two commonly used UVB sunscreens, 2-ethyl-hexyl-p-methoxycinnamate (2-EHMC) or octyl-N-dimethyl-p-aminobenzoate (o-PABA), reduced the UV tumour incidence to zero in immunologically normal mice and to 8-15% in immunosuppressed mice. Unexpressed latent tumour initiations were revealed in all sunscreen-protected groups by the subsequent application of a tumour promoter, croton oil. In immunologically normal mice 2-EHMC had allowed initiations in 39% of UV-irradiated mice, and o-PABA in 16.5%. However, in UV-irradiated mice immunosuppressed with azathioprine there had been initiations in 78% of mice protected with 2-EHMC and 65% of mice protected with o-PABA. Photoprotected mice immunosuppressed with cyclophosphamide did not show the same increase in UV-initiations (22% with 2-EHMC, 23% with o-PABA). These results provide evidence that azathioprine increases the susceptibility of the skin to UV carcinogenesis. However, UVB sunscreens afford effective protection from overt tumour expression in the absence of a tumour promoter.

Test of catechol, tannic acid, Bidens pilosa, croton oil, and phorbol for cocarcinogenesis of esophageal tumors induced in rats by methyl-n-amylnitrosamine

Catechol (CAS: 120-80-9), given in drinking water to rats, was the most effective of 5 phenols in enhancing [3H]thymidine incorporation [( 3H]dThd-l) into esophageal DNA. To test for esophageal cocarcinogenesis, groups of 30 male MRC-Wistar rats received 3 weekly ip injections of 25 mg methyl-n-amylnitrosamine [(MNAN) CAS: 13256-07-0]/kg. From the time of the first MNAN injection, each group also received catechol, tannic acid (CAS: 1401-55-4), dried leaves of Bidens pilosa L., or croton oil (CAS: 8001-28-3) (respectively, 2, 10, 50, and 2 g/kg semipurified diet), or were given 20 ip injections of 6 mg phorbol (CAS: 17673-25-5)/rat. The rats were killed after 20-45, 46-52, or 53-72 weeks (subgroups A, B, and C). In the group given MNAN alone, most esophageal papillomas developed during the first 45 weeks. Both catechol and B. pilosa significantly increased the esophageal papilloma multiplicity (No. of papillomas/rat) induced by MNAN, with a maximum tumor yield of 2.2 times that in the corresponding subgroup treated with MNAN alone. Papilloma multiplicity increased from subgroup A to subgroup C in the MNAN plus B. pilosa group but not in the MNAN plus catechol group. No tumors were induced by the test cocarcinogens given without MNAN. We concluded that a) an increased esophageal [3H]dThd-I indicates potential cocarcinogenicity and b) catechol and B. pilosa were weak esophageal cocarcinogens. These results support the view that catechol in cigarette smoke and B. pilosa as eaten in South Africa contribute to the etiology of human esophageal cancer.

Nuclear enlargement--an early change produced in mouse epidermis by carcinogenic chemicals applied topically in the presence of a promoter

A series of 27 compounds, including 11 polycyclic hydrocarbons, 8 proximate carcinogens and 8 other compounds, were tested for their ability to induce epidermal nuclear enlargement in mouse skin. The materials were applied topically in methyl ethyl ketone containing 0.1% croton oil, repetitively for 3 days. Nuclear enlargement present on the fourth day was determined with the aid of a Quantiment image-analysing computer. The results obtained indicated a close correlation between the topical carcinogenicity of the test compounds and their ability to induce epidermal nuclear enlargement in the presence of croton oil.

The influence on the dermal cellular infiltrate of topical steroid applications and vehicles in guinea pig skin: normal skin, allergic and toxic reactions

The mechanisms of the anti-inflammatory effects of corticosteroids are uncertain but could be explained by an influence on infiltrating leukocytes. Our method for the qualitative and quantitative investigation of the dermal cellular infiltrate makes it possible to study the effects of topically applied corticosteroid preparations and vehicles on the infiltrating leukocytes of normal skin, allergic and toxic reactions in guinea pig skin. Ointment and cream vehicles as well as corticosteroid cream and ointment preparations often caused erythema and increased mononuclear infiltrate after only short periods of application (24-72 h). The strongest steroid ointment gave the most marked macroscopic response and propylene glycol preparations the most marked cellular response. In both toxic and allergic reactions, application of steroid preparations after the provocation gave no beneficial result either macroscopically or microscopically. Macroscopic scores were worsened by cream and ointment preparations. Although steroid solutions had no beneficial effect, they caused no detrimental effect. The guinea pig seems to be extremely sensitive to irritants and has not proved to be a suitable model for this approach to the study of the efficacy of topically applied steroids.

Carcinogenicity of some pyrrolic pyrrolizidine alkaloid metabolites and analogues

Repeated topical doses of dehydromonocrotaline, a putative primary toxic metabolite of the pyrrolizidine alkaloid monocrotaline, followed by repeated treatments with croton oil, produced malignant tumours of the skin in LACA mice. A chemically similar alkylating agent, 2,3-bistrimethylace-toxymethyl-1-methylpyrrole, was carcinogenic without use of a promoter, confirming a preliminary report. Its high activity was due to the intact ester, not to its hydrolysis products. Dehydroretronecine (DHR), a less reactive secondary metabolite of monocrotaline, was also carcinogenic to LACA mouse skin, but it was less active than previously reported in experiments with another strain. Similar carcinogenicity was shown by the synthetic 2,3-bishydroxymethyl-1-methylpyrrole, but not by 2,3-bis-hydroxymethyl-5-methyl-1-phenylpyrrole, which has a high level of antimitotic activity.

Expression of Ia antigen on epidermal keratinocytes is a consequence of cellular immunity

Ia antigen is seen in the normal epidermis only in Langerhans cells. However, when there is damage to the epidermis induced by cellular immunity Ia is expressed in the keratinocytes. This phenomenon is not seen in trauma or chemical inflammation. It is suggested that the expression of Ia in keratinocytes is due to cellular immunity possibly due to a lymphokine.

Enhancement of spontaneous VCA and EA induction in B95-8 cells and EA induction in Raji cells treated with human leukocyte interferon

The purpose of this study was to determine the antiviral effect of human leukocyte interferon on Epstein-Barr virus (EBV) viral capsid antigen (VCA) and early antigen (EA) induction in B95-8 and Raji cells. Interferon made at the Institute of Virology, Beijing, and that provided by Dr. Cantell gave unexpected results. Both interferon preparations markedly enhanced spontaneous VCA and EA induction in B95-8 cells and EA induction in Raji cells simultaneously treated with croton oil and n-butyrate. Interferon treatment alone had no effect on EA induction in Raji cells. Thus, the effect of interferon on EA and VCA induction was related to the type of EBV infection, i.e., productive or latent. The enhancing activity of interferon could only be partially inhibited by retinoid 7901. It is suggested that the mechanism for enhancement of EA induction by interferon is different from that of EA induction in Raji cells by croton oil and n-butyrate.

Skin carcinogenesis and promoter binding characteristics in different mouse strains

The sensitivity of various mouse strains to skin carcinogenesis has been investigated in two ways; (i) by comparing carcinogenesis induced by treatments involving both the application of tumour promoters and the application of single or multiple doses of a carcinogen, and (ii) by comparing the binding characteristics of the tumour promoter [3H]phorbol-12,13-dibutyrate to particulate skin preparations. The mouse strains tested were Swiss albino, Balb/c, C3H, LACA and AKR/J. Although some differences were apparent, Swiss albino, LACA and C3H mice were generally sensitive to skin carcinogenesis by both benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene, either with or without promotion with croton oil. AKR/J mice were sensitive to both carcinogens with promotion but relatively insensitive in the absence of promotion. Balb/c mice had low sensitivity except when exposed to repeated low doses of benzo[a]pyrene. The [3H]phorbol-12,13-dibutyrate binding characteristics of particulate skin preparations from all strains were indistinguishable.

Combined effect of the extracts from Croton tiglium, Euphorbia lathyris or Euphorbia tirucalli and n-butyrate on Epstein-Barr virus expression in human lymphoblastoid P3HR-1 and Raji cells

The combined usage of n-butyrate and 12-O-tetradecanoylphorbol-13-acetate (TPA) or the oily extracts from Croton tiglium, Euphorbia lathyris or Euphorbia tirucalli exerted a marked effect on induction of Epstein-Barr virus (EBV)-associated early (EA) and viral capsid (VCA) antigens in EBV genome-carrying human lymphoblastoid cell lines. In producer P3HR-1 cells, the enhancing effect of the 2 components was additive both for EA and VCA, while in non-producer Raji cells, a synergistic increase of EA was observed. The possible implication of these findings relating to the cause of EBV-associated diseases is discussed.

Correlation between in vitro DNA synthesis, DNA strand separation and in vivo multiplication of cancer cells

The chemicals 9, 10-dimethylbenzanthracene (DMBA), ethionine, daunorubicin, actinomycin D, 1-(2-chloroethyl-1)-nitrosourea (CCNU), steroids, croton oil and dimethyl-sulfoxide (DMSO) were used in order to correlate their effect on the in vitro synthesis of normal and cancer DNA, on DNA strand separation and on accelerated in vivo multiplication of cancer cells. All of the compounds tested strongly stimulate the synthesis of cancer DNA in vitro catalyzed by DNA-dependent DNA polymerase I and measured as an acid-precipitable labeled product. Under the same conditions, the synthesis of DNA originating from healthy tissues is only slightly enhanced, except in the case of croton oil and DMSO. These substances are almost equally active on cancer and normal DNA. Although both cancer and normal DNA contain a large amount of double-stranded regions, the extent of DNA strand separation measured by the increase in UV absorbance (hyperchromicity) in the presence of each compound tested is much higher for all cancer DNA than for corresponding normal DNA. In contrast, DMSO and croton oil do not appear to distinguish cancer DNA from normal DNA. Additive and differential effects of various compounds on cancer DNA strand separation can be observed. Small doses of DMBA and CCNU stimulate the multiplication of Ehrlich ascites tumor cells in vivo in mice. There is thus a possible correlation between DNA strand separation, DNA synthesis, multiplication and differentiation of cancer cells in the presence of the above compounds, which is different from the response of normal cells to these compounds.

The in vivo glucocorticoid and antiglucocorticoid actions of medroxyprogesterone acetate

The in vivo glucocorticoid actions of medroxyprogesterone acetate [6 alpha-methyl-17-acetoxy-pregn-4-ene-3,20-dione (MPA)] were assessed in intact prepubertal female Wistar rats using five simultaneous assays: plasma glucose, plasma corticosterone, hepatic glycogen content, hepatic tyrosine aminotransferase activity, and croton oil-induced ear inflammation. Antiglucocorticoid acitivity was measured through interference by MPA with the glucocorticoid effect of a standard 5-microgram dose of dexamethasone in these same assays. The glucocorticoid activity of MPA was evident from suppression of corticosterone and ear inflammation and stimulation of tyrosine aminotransferase activity. The antiglucocorticoid activity of MPA was detected through inhibition of basal and dexamethasone-stimulated hepatic glycogen and partial reversal of the suppression of ear inflammation by dexamethasone. The progestational steroid MPA was thus found to have assay-specific glucocorticoid and antiglucocorticoid actions and may have a potential use in the treatment of some states of glucocorticoid excess.