Induction of interleukin-1 and tumor necrosis factor by 12-O-tetradecanoylphorbol-13-acetate in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

12-O-tetradecanoylphorbol-13-acetate (TPA), the most potent skin tumor promoter known, evokes significant inflammatory responses in mouse skin after topical application. Infiltrating inflammatory cells have been hypothesized to contribute to genetic damage in epidermal cells through the generation of reactive oxygen intermediates (ROIs), thus facilitating the development of tumors. Interleukin-1 (IL-1) and tumor necrosis factor (TNF), small mol. wt cytokines produced by macrophages (MPs), are known to have important roles in the inflammatory process. Lipopolysaccharide (LPS)-triggered release of IL-1 and TNF was determined in culture supernatants of splenic MPs from phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice following topical application of 8 micrograms of TPA twice in one week. The findings reported herein indicated that topical application of TPA primed splenic MPs from both SENCAR and B6C3F1 mice in a quantitatively similar manner for the production of IL-1 and TNF; in addition, the release of IL-1 and TNF by splenic MPs from control (naive or acetone-dosed) SENCAR and B6C3F1 mice in response to LPS-triggering in vitro was not significantly different. Therefore, the production and release of these cytokines by activated MPs does not correlate with the reported strain-dependent susceptibilities to TPA-induced inflammation and/or tumor promotion.

Induction of suppressor macrophages by 12-O-tetradecanoylphorbol-13-acetate in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

Following topical application of 8 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA) twice in one week, the ability of splenic macrophages (M phi s) isolated from phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice to suppress the phytohemagglutinin (PHA)-induced lymphocyte blastogenesis and NK activity mediated by spleen cells from naive animals was determined. In B6C3F1 mice, suppression of lectin-induced lymphocyte blastogenesis was mediated by M phi s from TPA-dosed animals. Alternatively, in TPA-dosed SENCAR mice, induction of M phi s suppressive to lectin responses was not apparent. In addition, suppressor M phi s did not mediate the decreased splenic natural killer (NK) activity that is characteristically observed in TPA-dosed SENCAR mice. Therefore, it is proposed that the decreased PHA responsiveness and NK activity observed in vivo in TPA-dosed SENCAR mice may be the result of a decreased proportion of lectin-responding T cells and NK cells in the spleen as a result of proliferation of inflammatory cell precursors.

Modulation of natural killer activity by 12-O-tetradecanoylphorbol-13-acetate and benzoyl peroxide in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice.

Following two weeks of topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) at 2, 4 and 8 micrograms/mouse on alternate days (7X total) or benzoyl peroxide (BZP) at 10, 20 and 40 mg/mouse, natural killer (NK) activity was determined in local (lymph nodes draining the lower dorsal region) and systemic (spleen) lymphoid tissue in phorbol ester-sensitive (SENCAR) and resistant (B6C3F1) mice. SENCAR mice, sensitive to tumor induction by TPA in two-stage chemical-induced carcinogenesis protocols, demonstrated suppression of NK activity in the spleen (no significant change in lymph nodes) and substantial dose-dependent increases in cell numbers in these organs after topical exposure to TPA. B6C3F1 (C57BL/6 X C3H F1) mice, reported to be resistant to TPA-induced promotion, demonstrated significant increases in NK activity in lymph nodes/spleen with an increase in cell numbers in the draining nodes only. Unlike the C57BL/6 parental strain, B6C3F1 mice are also reported to be resistant to promotion with BZP. Significantly, studies in this laboratory indicated that B6C3F1 mice dosed with BZP demonstrated increased NK activity in the spleen as was observed after dosing with TPA. These data suggest that alterations in NK activity as a result of exposure to tumor promoters may, in part, account for the resistance of particular strains of mice to tumor development. In both SENCAR and B6C3F1 mice, the blastogenic response of spleen cell suspensions isolated from TPA-dosed animals to phytohemagglutinin (PHA), a T cell lectin, was suppressed in a dose-dependent manner; BZP had no effect on spleen cell responses in either strain. Blastogenic responses of lymph node cells to PHA were enhanced in both strains of mice after topical application of TPA and BZP. Therefore, alterations in lymphoid cell responsiveness to PHA appeared unrelated to the reported sensitivities of SENCAR and B6C3F1 mice to tumor promotion.

Effect of hydrocortisone on terbutaline stimulated insulin release from isolated pancreatic islets.

Subchronic treatment with hydrocortisone (HC; 125 mg/kg, ip) in the rat for seven days significantly increased plasma insulin levels without affecting plasma glucose concentrations or insulinogenic indices. The role of the beta-adrenergic activity of the pancreatic beta cells in HC-induced hyperinsulinemia was assessed by determining if HC treatment would potentiate beta-adrenergic agonist-stimulated insulin release from isolated rat islets. Terbutaline (TB; 10(-3)M) and isolated islets from fasted rats were used to test this hypothesis since TB significantly increased insulin release in 300 mg/dl glucose-containing medium (HGM) from the islets of fasted but not of fed rats. Pancreatic islets from overnight-fasted control and HC-pretreated rats were incubated in HGM or HGM containing either 10(-3)TB, 10(-6)M HC, or both TB and HC. It was found that glucose-stimulated and TB-induced insulin release from HC-pretreated rat islets were not different from those of control rat islets. HC (10(-6)M) added in vitro did not affect glucose-stimulated or TB-induced insulin release from the islets of either control or HC-treated rats. In summary, it was found that the insulinotropic effect of TB depends on medium glucose concentration and the nutritional state of animals. However, the results do not support the hypothesis that the hyperinsulinemia caused by subchronic treatment with HC involves enhancement of the beta-adrenergic activity of the pancreatic beta cells.