Biphasic effect of protein kinase C activators on spontaneous and glucocorticoid-induced apoptosis in primary mouse thymocytes.

Spontaneous and glucocorticoid (fluocinolone acetonide, FA)-induced apoptosis of primary mouse thymocytes was inhibited by protein kinase C (PKC) activators such as bryostatin-1 and phorbol ester 12-O-tetradecanoyl-phorbol-13 acetate (TPA) within the first 2-4 h of incubation but was enhanced upon prolonged treatment. Only the anti-apoptotic but not the pro-apoptotic effect of TPA was completely suppressed by the PKC inhibitor Goe 6983 and moderately inhibited by Goe 6976. Immunoblot analysis revealed distinct PKC alpha, beta, delta, eta, theta, mu and zeta signals, a very faint PKCepsilon and no PKCgamma signal. Upon prolonged TPA treatment all PKC isoenzymes became downregulated, albeit at different rates (PKCdelta>alpha>mu>beta,theta>>eta,zeta). No significant generation of caspase-derived catalytic PKC fragments, as found to be produced upon induction of apoptosis and to be pro-apoptotic in other systems, was observed in FA- or TPA-treated thymocytes. It is concluded that the early anti-apoptotic effect of TPA depends on the activation of n-type PKC isoenzymes, whereas stimulation of spontaneous and FA-induced apoptosis by TPA ensues, at least partially, from a downregulation (or inactivation) of anti-apoptotic PKC species, i.e. in primary thymocytes PKC activation is primarily involved in a negative regulation of apoptosis.

Topical betamethasone 17-valerate is an anticorticosteroid in the rat. 2. Anti-inflammatory and anti-lymphocyte activities.

In the oxazolone-induced delayed hypersensitivity inflammation in the rat ear, betamethasone 17-valerate, in contrast to other topical corticosteroids, is incapable of suppressing oedema. When given in combination with triamcinolone acetonide, betamethasone 17-valerate competitively antagonizes the anti-inflammatory action of the active steroid. When tested in the mouse, betamethasone 17-valerate behaved as an anti-inflammatory agent 15 and 80 times as potent as betamethasone and hydrocortisone respectively. In an in vivo lymphocyte culture system in which preincubation with corticosteroids prevents subsequent phytohaemagglutinin induced DNA synthesis, betamethasone 17-valerate was less active than even hydrocortisone when rat lymph node cells were used, but with human cell preparations it was more potent than either hydrocortisone or betamethasone. Betamethasone 17-valerate behaves uniquely in the rat as an anticorticosteroid; in mouse and in man the compound behaves as a normal corticosteroid.