Epidermal Adenylate Cyclase Response Research Articles

Epidermal adenylate cyclase system is regulated by diacylglycerol-protein kinase C signal, but not by calcium signal

The breakdown of inositol phospholipids is an important transmembrane signalling system that is composed of two kinds of signals: the diacylglycerol-protein kinase C signal, and the inositol trisphosphate-Ca2+ signal. Using membrane-permeable diacylglycerol, I-oleoyl-2-acetylglycerol (OAG), and calcium ionophore, A-23187, the effects of these chemicals on the epidermal adenylate cyclase system were investigated. OAG increased forskolin- and cholera toxin-induced cyclic AMP accumulations, but receptor adenylate cyclase responses were markedly decreased by treatment with OAG. The effects of OAG were inhibited by the protein kinase C inhibitor, H-7. Calcium ionophore, A-23187, had no effect on the epidermal adenylate cyclase responses. Combinations of OAG and A-23187 (as well as the calcium chelator, EGTA), showed that the action of OAG was mostly unaffected by the modulation of intracellular and extracellular Ca2+ concentrations. The results suggest that among the signals triggered by the breakdown of inositol phospholipids, only diacylglycerol-protein kinase C signal is involved in the regulation of the epidermal adenylate cyclase system.

Effects of the tumor promoter, phorbol 12-myristate, 13-acetate, on the epidermal adenylate cyclase system: Evidence for adenylate cyclase-regulation by protein kinase C

Exposure of pig epidermal sheets to the protein kinase C (PKC) activator, phorbol 12-myristate, 13-acetate (PMA) resulted in an increase in forskolin-induced cyclic AMP accumulation in the epidermis. Cholera toxin-induced cyclic AMP accumulation was moderately increased by PMA treatment, but this was not statistically significant. On the other hand, receptor-mediated adenylate cyclase responses (beta-adrenergic-, prostaglandin E-, adenosine-, and histamine (H2)-adenylate cyclase responses) were significantly decreased. These PMA-induced effects on the epidermal adenylate cyclase system were mimicked by 1-oleoyl-2-acetylglycerol, a membrane-permeable synthetic diacylglycerol, and by the non-phorbol PKC activator, mezerein. 4-O- methyl PMA, a very weak PKC activator, had no effect on adenylate cyclase responses of the epidermis. The addition of the PKC inhibitor, H-7 (1-(5-isoquinoline-sulfonyl)-2-methyl piperazine dihydrochloride), to the incubation medium significantly inhibited the effect of PMA on forskolin induced cyclic AMP accumulation. Furthermore, following H-7 treatment, the epidermal receptor-adenylate cyclase responses were significantly increased. These results indicate that PKC modulates epidermal adenylate cyclase responses resulting in an increase in forskolin-induced cyclic AMP accumulation and a decrease in receptor-adenylate cyclase responses of the epidermis.

Effects of UVB irradiation on epidermal adenylate cyclase responses in vitro: its relation to sunburn cell formation

UVB irradiation augmented the beta-adrenergic adenylate cyclase response of pig skin epidermis in vitro. The effect was observed 2-4 h following the irradiation and lasted at least for 48 h. There was no significant difference in cyclic AMP phosphodiesterase activity between control and UVB-irradiated epidermis at lower irradiation dose (150 mJ/cm2), which is the dose of the most marked beta-adrenergic augmentation effect. The augmentation effect was specific to the beta-adrenergic system; adenosine and histamine adenylate cyclase responses were unchanged or decreased depending on the irradiation dose. Histologically, marked sunburn-cell formation was observed following the UVB irradiation. It has been suggested that oxygen intermediates generated by ultraviolet radiation participate in sunburn-cell formation. The addition of superoxide dismutase (SOD) in the incubation medium significantly inhibited sunburn-cell formation. On the other hand, the beta-adrenergic augmentation effect was not affected by the addition of SOD. Other scavengers of oxygen intermediates (catalase, catalase + SOD, xanthine, or mannitol) did not inhibit the UVB-induced beta-adrenergic augmentation effect. Further, superoxide-anion generating systems (hypoxanthine-xanthine oxidase system and acetaldehyde-xanthine oxidase system) revealed no stimulatory effect on the beta-adrenergic response of epidermis. These results indicate that (a) the UVB-induced beta-adrenergic augmentation effect is inherent to skin and does not depend on systemic factors such as inflammatory infiltrates following UVB irradiation; (b) in contrast to sunburn-cell formation, induction of the beta-adrenergic adenylate cyclase response is not directly associated with oxygen intermediates generated by UVB irradiation.

Melittin-induced alteration of epidermal adenylate cyclase responses

Using an in vitro pig skin-slice incubation system, we investigated the effect of melittin, a phospholipase A2 (PLA2) stimulator, on the adenylate cyclase-cyclic AMP (cAMP) system. Significant decreases of various epidermal (beta-adrenergic, adenosine, and histamine) adenylate cyclase responses were observed as early as 1 h following the melittin treatment (50 micrograms/ml). The effect of melittin was concentration-dependent and the minimal concentration of melittin was 10 micrograms/ml for the inhibition of the beta-adrenergic adenylate cyclase response, whereas more than 50 micrograms/ml concentration was required for the inhibition of the adenosine and histamine adenylate cyclase responses. There was no significant difference in either low or high Km cAMP phosphodiesterase activity between control and melittin-treated skin. The beta-adrenergic augmentation effect by various chemicals (colchicine and Ro10-1670, an active form of Ro10-9359) were suppressed by the simultaneous addition of melittin in the incubation medium. Our data indicate that melittin affects not only on the beta-adrenergic adenylate cyclase system but also on the adenosine and histamine adenylate cyclase systems. However, the beta-adrenergic system was shown to be more sensitive to melittin than the other receptor adenylate cyclase systems.

Effects of In vitro PUVA Treatment on Adenylate Cyclase Responses of Epidermis

AbstractWe investigated the effect of 8‐methoxypsoralen (8‐MOP) plus long wave ultraviolet irradiation (PUVA) on the pig skin epidermal cyclic AMP (cAMP) system. Following PUVA treatment in vitro, pig skin squares were incubated in RPMI 1640 medium, and the cAMP accumulation by various adenylate cyclase stimulators was determined. A significant increase of the beta‐adrenergic adenylate cyclase response was observed as early as 6‐h following PUVA treatment; the maximal effect was reached at 24‐h and lasted at least for 72‐h. This augmentation effect of PUVA treatment was potentiated by increasing the 8‐MOP concentration (0.5–160 μg/ml) and UVA irradiation dose (0.05–1.4 J/cm2). At higher irradiation doses (2.1–2.8 J/cm2), the beta‐adrenergic augmentation effect was less marked. There were no significant differences in the adenosine‐and histamine‐adenylate cyclase response up to 1.4 J/cm2 irradiation; however, the latter was decreased at a higher irradiation dose (2.8 J/cm2). Although UVA irradiation alone had no effect on the beta‐adrenergic response, 8‐MOP treatment alone increased this receptor response at higher concentrations; this effect was much weaker than that induced by PUVA treatment. Cyclic AMP phosphodiesterase activities were not affected by PUVA treatment. These results indicate that epidermal adenylate cyclase response is affected by in vitro PUVA treatment.

A new synthetic retinoid, E-5166, augments epidermal beta-adrenergic adenylate cyclase response

Effects of a new synthetic retinoid, 3, 7, 11, 15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid (E-5166), on the cyclic AMP system of pig skin epidermis was investigated. When pig skin slices were incubated in vitro for 24 h, the beta-adrenergic adenylate cyclase response (epinephrine-induced cyclic AMP accumulation) was decreased. The addition of E-5166 in the incubation medium resulted in an increase of this receptor response of epidermis. On the other hand, histamine-induced cyclic AMP accumulations were decreased by the E-5166 treatment. The effect of E-5166 was concentration-dependent; the maximal effect was observed at 50-100 microM. Ro 10-1670 (an active derivative of Ro 10-9359 (etretinate)) is known to have similar beta-adrenergic augmentation effect. The simultaneous addition of E-5166 and Ro 10-1670 at their optimal concentrations resulted in neither additive nor synergistic effect on the epinephrine-induced cyclic AMP accumulations. There was no significant difference in cyclic AMP phosphodiesterase activity between control and E-5166-treated epidermis. These data indicate that pig skin epidermal adenylate cyclase responses are modulated by E-5166 probably through the same mechanism induced by other retinoids.

Ultraviolet Radiation Augments Epidermal Beta-Adrenergic Adenylate Cyclase Response

Pig skin was irradiated in vivo with fluorescent sunlamp tubes (peak emission at 305 nm). A significant increase in epidermal beta-adrenergic adenylate cyclase response was observed as early as 12 h following 1-2 minimum erythema doses (MEDs) UVB exposure, which lasted at least 48 h. The augmentation of adenylate cyclase response was relatively specific to the beta-adrenergic system and there was no significant difference in either adenosine- or histamine-adenylate cyclase response of epidermis. The increased beta-adrenergic adenylate cyclase response was less marked at higher doses of UVB exposure (5 MEDs); in the latter condition, a significant reduction in adenosine- or histamine-adenylate cyclase response was observed. There was no significant difference in either low- or high-Km cyclic AMP phosphodiesterase activity between control and UVB-treated skin at 1-2 MEDs. Our data indicate that the epidermal adenylate cyclase responses are affected in vivo by UVB irradiation, which might be a significant regulatory mechanism of epidermal cyclic AMP systems.