Cyclic AMP in skin: effects of acute ischaemia

A dose-response study of adrenaline combined with lignocaine 2%: effect on acute postoperative pain after oral soft tissue surgery

AIMS

The combination of lignocaine and adrenaline may cause more postoperative pain than other types of local anaesthetic agents with comparable clinical efficacy. This study investigates the dose-response effect of adrenaline added to lignocaine on postoperative pain, when used as local anaesthetic for oral soft tissue surgery.

METHODS

A controlled, randomized, double-blind, parallel group study included 195 patients (108 females/87 males) with mean age 49 years (range 26-75 years). The patients were allocated to one of three treatment groups receiving lignocaine 2% (n = 66), lignocaine 2% with adrenaline 1 : 160 000 (n = 63) or lignocaine 2% with adrenaline 1 : 80 000 (n = 66).

RESULTS

Lignocaine 2% with adrenaline 1 : 80 000 gave significantly more pain intensity than lignocaine 2% or lignocaine 2% with adrenaline 1 : 160 000. The postoperative pain intensity courses after lignocaine 2% and lignocaine 2% with adrenaline 1 : 160 000 showed a similar pattern except for the time period just after completion of surgery when lignocaine 2% with adrenaline 1 : 80 000 caused less pain.

CONCLUSIONS

High adrenaline concentrations (1 : 80 000) combined with lignocaine local anaesthetic solution offers no advantage with respect to pain alleviation during the immediate postoperative pain period. High exogenous adrenaline concentrations may play a significant role in enhancing acute postoperative intensity.

Increase in volume of lignocaine/adrenaline-containing local anaesthetic solution causes increase in acute postoperative pain after gingivectomy

A randomized, single-blind, within-patient, crossover study was done in 44 patients (27 women and 17 men mean age 47 years, range 29-63) who had bilateral 'identical' gingivectomies. On one occasion a standard volume of local anaesthetic containing lignocaine 2% and adrenaline (1/80 000) was infiltrated into the mucosal tissue before operation. On the other occasion double the standard volume was infiltrated. The intensity of pain postoperatively was recorded by the patients on 100 mm visual analogue scale every hour for an 11-hour observation period. The intensity of pain when double volume had been given was significantly higher than that after the standard volume from 2 to 8 hours postoperatively (P < 0.04), the median (range) being 52.0 mm (0.0-434.0) compared with 30.5 mm (0.0-359.0) after the standard volume (P < 0.005). Doubling the volume of local anaesthetic containing adrenaline that was infiltrated increased the intensity of acute pain after gingivectomy.

Beta-adrenergic stimulation of cyclic AMP is defective in cultured dermal fibroblasts of psoriatic subjects

Epidermal cells from psoriatic lesions demonstrate a very low cAMP response to beta-adrenergic stimuli. We have shown that a similar abnormality occurs in dermal fibroblasts from affected areas of skin. The cells, after 5-12 passages in tissue culture, had a much reduced response to 10(-8) M and 10(-6) M isoproterenol when compared with fibroblasts from control subjects. The abnormality was not abolished by the addition of the phosphodiesterase inhibitor, 3-isobutyl-I-methylxanthine. Other putative agonists tested were vasoactive intestinal peptide and peptide histidine methionine. Neither of these had an effect on dermal fibroblasts from either normal controls or from lesions of psoriasis.

Cyclosporin A induced augmentation of the beta-adrenergic adenylate cyclase response of pig epidermis

It has been known that beta-adrenergic adenylate cyclase response is decreased in psoriatic-involved epidermis. Since the immunosuppressive agent, cyclosporin A, is reported to be effective on psoriasis clinically, the effect of cyclosporin A on beta-adrenergic adenylate cyclase response in pig skin was examined in vitro. Therapeutic serum levels of cyclosporin A (100-400 ng/ml) augmented the beta-adrenergic adenylate cyclase response of the epidermis. Highest levels of cyclosporin A (2-20 micrograms/ml) did not have any effect on its response. Both low Km and high Km cyclic AMP phosphodiesterases were not affected by cyclosporin A. Therefore, it is suggested that the clinical efficacy of cyclosporin A on psoriasis can be explained partially by its direct effect on the keratinocyte itself.

Dimethyl sulfoxide-induced augmentation of adenosine-adenylate cyclase response of pig skin epidermis

Adenosine-adenylate cyclase response in pig skin epidermis showed a specific increase after long-term (24 h) incubation in the presence of 0.5%-1% dimethyl sulfoxide (DMSO). There was no significant difference between control and DMSO-treated epidermis with regard to cyclic AMP (cAMP) phosphodiesterase activity. DMSO had no effect on the basal cAMP levels of epidermis; beta-adrenergic and histamine-adenylate cyclase responses were not affected. The direct addition of DMSO at the time of incubation with various adenylate cyclase stimulators (adenosine, epinephrine, and histamine) had no effect on agonist-induced cAMP accumulation effects. It was concluded that DMSO affected epidermal keratinocytes during long-term incubation, resulting in a specific increase in the adenosine-adenylate cyclase response. Although the biological significance of this DMSO effect remains to be determined, it should be kept in mind when using DMSO as a solvent for various chemicals in the experiments dealing with epidermal keratinocytes in vitro.

Ionophore A23187 stimulates arachidonic acid release and cyclic GMP accumulation in pig epidermis

We studied the effect of Ionophore A23187 (A23187) on phospholipid degradation and the accumulation of cyclic GMP in pig epidermis. A23187 stimulated the release of AA, probably partially through the activation of phospholipase A2. A23187 also stimulated the accumulation of epidermal cyclic GMP, but the activity of cyclic GMP-dependent phosphodiesterases was not altered. Mepacrine, an inhibitor of phospholipase A2, inhibited the A23187-stimulated accumulation of cyclic GMP. The results suggest that A23187 stimulates the accumulation of epidermal cyclic GMP by a calcium-dependent process which also requires products of phospholipid degradation.

Topical PUVA treatment increases epidermal beta-adrenergic adenylate cyclase responsiveness

The effects of topical PUVA treatment on the epidermal cyclic AMP system were investigated. 8-methoxypsoralen (8-MOP), 0.3% in ethanol was applied to the backs of pigs which were then irradiated with UVA. A significant increase in the epidermal beta-adrenergic adenylate cyclase response was observed 24 h after low (1.1 J/cm2) and moderate (2.1 J/cm2) dose irradiation. There was no significant change in the adenosine- or histamine-mediated adenylate cyclase responses. 8-MOP application or UVA irradiation alone had no effect on the beta-adrenergic adenylate cyclase response. PUVA treatment with a higher irradiation dose (4.2 J/cm2) produced no increase in the beta-adrenergic response and adenosine- and histamine-mediated adenylate cyclase responses were decreased. Cyclic AMP phosphodiesterase activity was decreased by PUVA treatments using UVA doses of 1.1 and 2.1 J/cm2; however, the change was not statistically significant. The increased beta-adrenergic response was also observed in the presence of the cyclic AMP phosphodiesterase inhibitor, isobutylmethylxanthine. These results indicate that epidermal adenylate cyclase responsiveness is affected by topical PUVA treatment in vivo.

"Ischemic" rise of epidermal cyclic AMP is a beta-adrenergic adenylate cyclase-dependent process

The endogenous level of epidermal cyclic AMP does not remain constant but increases rapidly and transiently after removal of the tissue; this is known as the "ischemia" effect. UVB-irradiated epidermis which shows increased beta-adrenergic response revealed an increased ischemia effect, while psoriatic involved epidermis which shows decreased beta-adrenergic response revealed a decreased ischemia effect. Because of the similar rise-and-fall pattern between the ischemia effect and the beta-adrenergic response, the mechanism of the ischemia effect was investigated, especially in terms of the beta-adrenergic relationship. The ischemic rise of epidermal cyclic AMP was well preserved after 6 h pretreatment at 4 degrees C, and, following the pretreatment, the skin markedly increased its cyclic AMP level by the 37 degrees C treatment with 1 mM isobutylmethyl xanthine. The addition of propranolol or cimetidine at the time of 37 degrees C treatment (following the 4 degrees C pretreatment) had no effect on the ischemia effect; both skin groups markedly increased their cyclic AMP levels to an extent similar to that of the control skin. However, the addition of propranolol at the time of both preincubation (at 4 degrees C) and incubation (at 37 degrees C) markedly decreased the ischemic rise of cyclic AMP. Similar treatment by cimetidine had no effect on the ischemia effect. There was no significant difference in cyclic AMP phosphodiesterase activities among skin groups by propranolol or cimetidine pretreatment. These results indicate that the so-called ischemic rise of epidermal cyclic AMP is actually the beta-adrenergic adenylate cyclase-dependent process. Our results also indicate that the magnitude of the "ischemic" rise of cyclic AMP is generally parallel to the beta-adrenergic responsiveness of epidermis.

Effects of retinoids on the cyclic AMP system of pig skin epidermis

Although retinoids reveal various biologic and biochemical activities on epidermal keratinocytes, their effects on the epidermal cyclic AMP (cAMP) system has been less well characterized. In order to elucidate the relation between them, an in vitro pig skin-slice incubation system was employed. After a long-term (up to 24 h) incubation in vitro, control skin responded to epinephrine only slightly. The addition of Ro 10-1670, an active derivative of Ro 10-9359 (etretinate) in the incubation medium, resulted in an increase of the beta-adrenergic adenylate cyclase response of epidermis. On the other hand, histamine-induced cAMP accumulation was decreased by the retinoid treatment after long-term incubation. The augmentation of the beta-adrenergic response was observed at 1 microM concentration and the maximal effect was observed at 10 microM. There was no significant difference in cAMP phosphodiesterase activities between the control and retinoid-treated skin. The effect was also observed by the addition of all-trans-retinoic acid, retinol, and Ro 10-9359; the latter two compounds revealed much lesser effects. The addition of combinations of various drugs (Ro 10-1670 and hydrocortisone; Ro 10-1670 and colchicine) resulted in more marked (additive or synergistic) effects than the single addition of each chemical. On the other hand, the addition of Ro 10-1670 and all-trans-retinoic acid resulted in neither additive nor synergistic effect, suggesting that they probably work on the same site. Our data indicate that the epidermal beta-adrenergic adenylate cyclase response is modulated by retinoids probably as an independent mechanism stimulated by glucocorticoids or colchicine.

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.

Effects of adenosine and 2'-deoxyadenosine on epidermal keratinocyte proliferation: its relation to cyclic AMP formation

Although it has been reported that adenosine has an inhibitory effect on keratinocyte proliferation at both G2 and S phases of the cell cycle, its relation to cyclic AMP formation through the adenylate cyclase system has been less well characterized. In order to determine the precise mechanism of the adenosine effect, another physiologic adenine nucleoside, 2'-deoxyadenosine was employed. 2'-Deoxyadenosine was shown to be remarkably different from adenosine in its ability to stimulate the epidermal adenylate cyclase; whereas adenosine markedly increased cyclic AMP levels of pig epidermis, deoxyadenosine had a much weaker effect on the cyclic AMP levels of the skin. Using several parameters of cell proliferation, comparison was made between the effects of these two compounds. Pig keratinocyte explant culture system was employed for the measurement of outgrowth and mitosis. Mitosis was determined after 72-h incubation (to monitor the overall cell proliferation inhibition) and 4-h incubation (to monitor G2 phase inhibition) with the chemicals. Pig skin keratome slice system was employed for [3H]thymidine uptake measurement. Both adenosine and deoxyadenosine were shown to have marked inhibitory effects on keratinocyte out-growth, [3H]thymidine uptake, and keratinocyte mitosis. The effects of deoxyadenosine on outgrowth and [3H]thymidine uptake were greater than that of adenosine. The inhibitory effect of adenosine and deoxyadenosine on mitosis were about the same in both 4-h and 72-h incubation systems. Thus deoxyadenosine, which is a much weaker stimulator of epidermal adenylate cyclase, was also shown to be as potent an inhibitor of keratinocyte proliferation as adenosine. These results further substantiate the view that cyclic AMP elevating agents (such as adenosine and deoxyadenosine) might not necessarily reveal their inhibitory effects on keratinocyte proliferation through their effects of cyclic AMP formation.

Colchicine-induced alteration of hormone-stimulated cyclic AMP synthesis in pig skin (epidermis)

Effects of colchicine on the epidermal adenylate cyclase systems were investigated. When pig skin (epidermis) was incubated in RPMI 1640 medium without the addition of serum, the beta-adrenergic adenylate cyclase response (epinephrine-induced cyclic AMP accumulations) gradually decreased, whereas adenosine and histamine responses remained high or increased during the long-term (up to 48 h) incubation period. The addition of colchicine (1 mumol/liter) in the incubation medium resulted in an increase in the beta-adrenergic responsiveness and a decrease in adenosine and histamine responsivenesses. The effects of colchicine were both time- and concentration-dependent; they could be observed after 9-12 h incubation, and the maximal effect was obtained at a concentration of 0.1 mumol/liter. Similar effects were observed by the addition of another microtubule-disruptive agent, vinblastine. On the other hand, cytochalasin B, which affects the microfilament system, apparently decreased the beta-adrenergic response and increased adenosine and histamine responses during the long-term incubation period. The addition of serum in the incubation medium resulted in essentially the same effect as that of colchicine; in the presence of serum, colchicine-treated skin responded much more markedly to epinephrine (and much less to adenosine and histamine) than the control skin after 24- and 48-h incubation. Previously we reported that hydrocortisone has similar potentiating effects on the beta-adrenergic system of epidermis. The comparison of the effects of both compounds revealed that colchicine had a stronger effect than hydrocortisone, and furthermore, the simultaneous addition of both compounds (colchicine and hydrocortisone) in the incubation medium resulted in the more marked increase of beta-adrenergic response than the single addition of each chemical. Our overall results, coupled with the finding that hydrocortisone has no toxic effects on the adenosine- or histamine-adenylate cyclase system of epidermis, suggest that colchicine affects epidermal adenylate cyclase systems probably through a mechanism that is independent of glucocorticoid (hydrocortisone) effect.

Regulation of beta-adrenergic adenylate cyclase responsiveness of pig skin epidermis by suboptimal concentrations of epinephrine

Although receptor-specific refractoriness has been suggested to be one of the regulatory mechanisms of epidermal adenylate cyclase systems, its physiologic significance has been a subject of controversy because of the requirement of unusually high concentrations of agonists to induce refractoriness. In order to determine whether the epidermal adenylate cyclase system is regulated through a refractoriness mechanism by suboptimal concentrations of receptor agonists, this study was undertaken using pig skin epidermal adenylate cyclase systems. Pretreatment of pig skin with 0.1-1 microM epinephrine in vitro resulted in the reduction of the maximal epinephrine response (epinephrine-induced cyclic AMP accumulations) to various degrees without alterations in either low or high Km cyclic AMP phosphodiesterase activities. Repeated pretreatments were shown to be more effective in inducing refractoriness than a single pretreatment. Apparently there was no change in the Km value for epinephrine, suggesting that the decrease in epinephrine response represents a reduction in the number but not in the affinity of functional beta-adrenergic adenylate cyclase receptor sites. This refractoriness by low concentrations of catecholamine pretreatment was specific to the beta-adrenergic system, since there was no reduction in histamine response after the epinephrine pretreatment. These results indicate that the epidermal beta-adrenergic adenylate cyclase system is regulated by much lower concentrations of catecholamine than were previously described. It was suggested that physiologic fluctuations of plasma catecholamine levels might have a profound effect on epidermal beta-adrenergic adenylate cyclase responsiveness, resulting in the alteration of the minimal catecholamine level required for the successive activation of cyclic AMP-dependent protein kinase, which is the predominant target of cyclic AMP in epidermis.

Phospholipase A2 activity modulates "ischemic effect" in pig skin

The level of cyclic AMP in the epidermis rapidly increase within 15 min after separation from the in vivo condition. This phenomenon is the so-called "ischemic effect." In order to elucidate the possible mechanism of the ischemic effect, the effects of melittin and mepacrine on the ischemic condition of the skin were studied. Melittin, a stimulator of phospholipase A2, lessened the increase of cyclic AMP, while mepacrine, an inhibitor of phospholipase A2, potentiated the increase of cyclic AMP during the ischemic condition. The overall results suggest that phospholipase A2 may play an important role in the induction of the ischemic condition through membrane alteration.

Cyclic AMP-dependent protein kinase isozymes of pig skin and human skin from normal and psoriatic subjects

Cyclic AMP-dependent protein kinase isozymes of pig and human skin (epidermis) were separated by DEAE-cellulose column chromatography after micromodification for small biopsy samples. Clear-cut separations of type I and type II isozymes, which were of about equal amounts, could be obtained only when the ischemia effect was avoided by in vivo freezing of skin and homogenization for less than 10 s. Intradermal injections of epinephrine caused dose-dependent activation of type I isozyme, but not of type II. Injections of other skin adenylate cyclase stimulators such as histamine, adenosine, and prostaglandin E2 elevated the local cyclic AMP levels to not more than 5 pmol/mg protein and also stimulated only the type I isozyme. Incubation of keratome-sliced pig skin under various conditions caused both activation by dissociation and inactivation by reassociation of the subunits, which appeared to be dependent on the cyclic AMP content. Epinephrine added to the incubation medium led to complete activation of both type I and type II isozymes (the intraepidermal cyclic AMP contents ranged from 20-50 pmol/mg protein). The isozymes of normal skin and involved skin of psoriatics showed identical peaks of type I and type II isozymes of equal amounts. The data indicate that protein kinase in the involved skin is not in an activated (by cyclic AMP) state.

Epidermal surface receptors which link pharmacological mediators to the adenylate cyclase system

The major purpose of our studies has been to investigate various stimulators of the epidermal adenylate cyclase system. We have recognized the occurrence of four distinct adenylate cyclase systems which respond respectively to catecholamine, histamine, prostaglandin and adenosine. The exposure of floating skin slices in vitro to a stimulator causes a rapid intracellular accumulation of cyclic AMP, which is always transient. Further addition of the same stimulator will not stimulate the same receptor system against the state of 'refractoriness'. The addition of any of the other stimulators can increase the cyclic AMP level. Furthermore, the fact that each stimulator can yield an 'additive' stimulatory effects leads to the conclusion that the epidermis has four distinctly specific and independent adenylate cyclase systems. Our recent investigations have been directed to the analyses of subunits of these skin surface receptor-adenylate cyclase systems. We used two experimental systems, i.e. one being a 'leaky' cell system in which its subunits such as receptor, GTP-regulatory protein and the catalytic unit (adenylate cyclase) are still linked together, and the other being independent preparations of the receptor and catalytic units (with GTP-regulatory protein). These systems allowed us to probe the cell membrane from the inside as well as from the outside. Some of the preliminary kinetic data are herein introduced.

Measurement of adenosine 3',5'-monophosphate-dependent protein kinase and phosphorylase activities in in vivo conditions

Microassay procedures for cAMP-dependent protein kinase and phosphorylase were developed which detected these activities in less than 25 micrograms of frozen-dried epidermis from a punch biopsy of skin without homogenization. Using these procedures, the activation of cAMP-dependent protein kinase and phosphorylase by beta-adrenergic stimulation in mouse skin was studied in vivo. Cyclic AMP-dependent protein kinase was stimulated by isoproterenol and inhibited by propranolol. Isoproterenol stimulation also activated phosphorylase a in mouse skin. In normal epidermis and uninvolved and involved epidermis from psoriatic patients no significant differences were found in the activities of cAMP-dependent kinase and phosphorylase a. In all experiments we observed that the unstimulated activity ratios of phosphorylase a/total phosphorylase were around 20-30%; these values were much lower than those hitherto reported and show a preponderance of phosphorylase b rather than a. We suggest that in previous reports where phosphorylase a domination was found, phosphorylase b to a activation occurred during homogenization. The data also suggest that in the steady state no obvious defect in basic activities of cAMP-dependent protein kinase and phosphorylase is observed in psoriatic skin.

Decreased accumulation of cyclic adenosine 3',5'-monophosphate in "ischemic" skin after 12-0-tetradecanoyl-phorbol-13-acetate treatment

The effect of 12-0-tetradecanoyl-phorbol-13-acetate (TPA) on cyclic adenosine 3',5'-monophosphate (cyclic AMP) level in adult mouse skin in response to ischemia was examined. The incubation of skin pieces in a buffered salts medium at 37 degrees C resulted in a rapid accumulation of cyclic AMP. In mouse skin pieces maximum accumulation (about 6 times the basal level) occurred after 2 min incubation and was followed by a rapid decline in the cyclic AMP level. This "ischemic" rise in epidermal cyclic AMP was greatly reduced if skin was used 16 hr after a single application of 17 nmoles of TPA. The effect of TPA on cyclic AMP accumulation in response to ischemia was first observed at 1 hr after TPA treatment and was maximal at 4 hr. The lack of "ischemic" response in TPA-treated skin was not related to an increase in the activity of cyclic AMP phosphodiesterase after TPA application. In addition, the accumulation of cyclic AMP in skin in response to both ischemia and exposure to isoproterenol, adenosine, histamine, or prostaglandin E2 (PGE2) was not observed in skin treated with the tumor promoter TPA.

The effect of ischemia on cyclic adenosine 3',5'monophosphate accumulation in mouse skin

The incubation of adult mouse skin pieces in a buffered salts medium at 37 degrees C led to a rapid accumulation of cyclic adenosine 3'5-monophosphate (cyclic AMP) in the tissue. In mouse skin maximum accumulation occurred after 2 min incubation; levels reverted to near control levels after a further 7 min incubation. the increase in cyclic AMP contents of the skin pieces was probably not due to the release of materials which activate adenylate cyclase after binding to cellular receptors. Thus, cyclic AMP accumulation was unaffected by the inclusion of alpha- or beta-adrenergic antagonists, or by the pretreatment of adult mouse skin with indomethacin (an inhibitor of prostaglandin synthetase). Furthermore, adenosine, a known activator of epidermal adenylate cyclase, could not be detected in the incubation medium. The functional integrity of epidermal adenylate cyclase was maintained during the cyclic AMP accumulation in response to ischemia. Thus, adenosine, histamine, isoproterenol and prostaglandin E2 (PGE2) augmented the cyclic AMP response. Cyclic AMP accumulation at 37 degrees C was not observed in newborn mouse skin; this lack of cyclic AMP accumulation was probably not due to increased activity of low affinity cyclic AMP phosphodiesterase in newborn mouse skin.

Activation of cAMP-dependent protein kinase in epidermis by the compounds which increase epidermal cAMP

Pig epidermal slices were incubated with various compounds which increased epidermal cAMP (adenosine 3',5'-monophosphate), and the change in cAMP-dependent protein kinase activity ratio was studied by the method of Cherrington et al (J Biol Chem 251:5209-5218, 1976) with modification. Epinephrine (5 x 10(-5) M), histamine (10(-4) M) and adenosine (10(-3) M), potent agonists of epidermal adenyl cyclase, fully activated the protein kinase (PK) during an incubation of 30 to 45 seconds, that was much shorter than that required for maximal cAMP accumulation under the same conditions (5 min). With such a brief stimulus, the epidermal cAMP-PK system did not become refractory and responded to repeated stimuli. Prostaglandin E2 (PGE2) and isobuthylmethylxanthine (IBMX) and ethanol only partially activated the enzyme. Prostaglandin F2 alpha (PGF2 alpha) and theophylline which were much less effective in increasing epidermal cAMP, activated the enzyme to the same extent as PGE2 and IBMX respectively. These results suggest that protein kinase activation takes place in response to a cAMP increase in small locus of the cell. Such an increase in cAMP can be very small or even not measurable when measured as total cAMP in the tissue homogenate. Also, increases above this level may not be physiologic. It is concluded that measurement of cAMP-dependent protein kinase activity ratio is a more direct and more sensitive way to study the effect of compounds which act through cAMP mediated mechanisms.

Effects of trypsin on the cyclic AMP system of the pig skin

Trypsin increased cyclic AMP levels of the pig skin. This effect was markedly potentiated by the cyclic nucleotide phosphodiesterase inhibitor theophylline. Without theophylline this trypsin-induced cyclic AMP accumulation was transient and the maximal accumulation was noted by 5 min. Soybean trypsin inhibitor inhibited this trypsin-induced cyclic AMP accumulation. After the trypsin treatment, marked acantholysis was noted histologically and the decreased responsiveness to other adenylate cyclase stimulators was seen. The decrease of the epinephrine response was most marked and that of histamine response was much less. Both low and high Km cyclic nucleotide phosphodiesterase activities were decreased by the trypsin treatment. However, at 5 min incubation time, when the increase in cyclic AMp level was most marked, the decrease in the phosphodiesterase activities was minimal. Trypsin seems to reveal its action through the proteolytic activation of adenylate cyclase system of the skin.

Inhibition of epidermal adenyl cyclase by lithium carbonate

An in vitro floating system was used to investigate the effect of lithium carbonate (Li2CO3) on the activity of adenyl cyclase in normal pig epidermis. Li2CO3 decreased the responsiveness of adenyl cyclase to stimulation by histamine, adenosine monophosphate (AMP) and epinephrine. This abnormality is similar but not identical to the previously described impaired responsiveness of adenyl cyclase to epinephrine and PGE2 in psoriatic plaques compared to normal adjacent skin. Involved and uninvolved skin from a psoriatic on lithium therapy demonstrated decreased responsiveness to in vitro stimulation by epinephrine, histamine and adenosine when compared to skin from psoriatics who were not on lithium therapy. These results are consistent with the observation that lithium therapy worsens psoriatic lesions.

Cyclic AMP accumulation in the beta adrenergic mechanism of eccrine sweat secretion

Tissue cyclic 3'5'-AMP (cAMP) concentrations were measured after stimulation of isolated monkey palm eccrine sweat glands with various stimulants of sweat secretion. The cellular cAMP levels increased curvilinearly with time of incubation to reach a steady state after 5 min of incubation with isoproterenol. Theophylline more than doubled the isoproterenol-induced cAMP accumulation, whereas theophylline alone increased the basal cAMP level to a minor extent. Phenylephrine failed to stimulate cAMP accumulation. There was no increase in the cAMP level after stimulation with methacholine. A calcium ionophore, A23187, also failed to stimulate cAMP accumulation. Since isoproterenol, theophylline (or isobutylmethylxanthine), and dibutyryl cAMP all induced eccrine sweat secretion in isolated, cannulated sweat glands to varying degrees in vitro, cAMP is probably involved in the beta adrenergic mechanism of sweat induction. The isoproterenol-induced cAMP accumulation was not inhibited by removal of Ca2+ from the incubation medium for as long as 30 min. The striking similarity between the eccrine sweat gland and the salivary glands in the roles that Ca2+ and cAMP play in stimulus secretion coupling indicates that the eccrine sweat gland will serve as another useful model system for the study of the mechanisms of exocrine secretion.

Epidermal cyclic GMP is increased in psoriasis lesions

Cyclic GMP levels in epidermis of normal subjects and of psoriatic patients were measured with a highly sensitive radioimmunoassay method. Technical improvements for the assay are 2-fold: (1) skin samples were frozen in vivo before biopsy and local injection of any anesthetic was avoided to overcome ischemia effect which could lower cyclic GMP artificially; (2) epidermis was microdissected to avoid contamination of dermis and keratin layers. The results show that on a per mg tissue dry weight basis the cyclic GMP levels are about 200 fmol in the involved lesional epidermis and 70 fmol in the uninvolved or normal epidermis. Similarly increases in the cyclic GMP levels in the lesional epidermis are observed when the data are expressed either on a DNA or protein basis. The cyclic GMP level in normal epidermis from nonpsoriatic subjects is the same as that in the uninvolved epidermis of psoriasis patients.

Immunohistochemical localization of cyclic nucleotides in guinea pig lip

The cellular localization of cAMP and cGMP in the guinea pig lip was investigated with an indirect immunofluorescence technique. cAMP was distributed both in cell membranes and cytoplasmic elements with coarse and granular intranuclear fluorescence, while cGMP was localized in nuclear sites including nuclear membranes as well as cell membranes and cytoplasm. In the basal portion, both cAMP and cGMP fluorescence was weaker in cytoplasm and cell membranes than seen in the upper portion.

Effects of hydrocortisone on the adrenaline-adenylate cyclase system of the skin

Using pig skin slices, we investigated the effects of hydrocortisone on the adenylate cyclase system of the skin. In short-term experiments, hydrocortisone, when added singly or in combination with other stimulators of adenylate cyclase in the skin (adrenaline or histamine), had no effect on cyclic AMP accumulation. However, when skin slices were incubated with hydrocortisone for more than 6 h, the response to adrenaline differed, with a greater accumulation of cyclic AMP in the hydrocortisone-treated skin. This effect was seen at a concentration of more than I micrometer hydrocortisone and was most marked 48 h later, while responses to adrenaline in control skin gradually decreased and remained low. Histamine, which is another stimulator of adenylate cyclase of the skin, did not cause a greater cyclic AMP accumulation in response to this hydrocortisone treatment. There was no significant difference in either low Km or high Km cyclic AMP phosphodiesterase activities as a result of this hydrocortisone treatment. Hydrocortisone seems to act by protecting the adrenaline-adenylate cyclase system of the skin.

The effect of steroid and dithranol therapy on cyclic nucleotides in psoriatic epidermis

Absolute values of both cAMP and cGMP leves were measured in the involved and uninvolved skin of psoriatic patients, and also the effect of topical therapy on these levels in the involved skin was studied. The mean cGMP level in the untreated psoriatic plaque was increased by 300% compared to the non-involved skin (which did not differ from normal skin), but no significant difference in cAMP levels was found. Epidermal stripping of uninvolved skin, which stimulates cell proliferation, did not change the cGMP level. Treatment of the psoriasis with dithranol caused the cGMP levels to return to normal, but a potent topical glucocorticoid, in contrast, produced no such decrease. This may imply that the two drugs act at different levels in suppressing cell replication, and dithranol may be a useful tool for the further investigation of cyclic nucleotide metabolism.

Diurnal variation in cyclic nucleotide levels in normal and phorbol myristate acetate treated mouse epidermis

The diurnal variations in cyclic AMP, cyclic GMP and cyclic GMP/cyclic AMP were determined in mouse epidermis. Slight (60%) diurnal fluctuations were observed in the levels of cyclic AMP and cyclic GMP/cyclic AMP while cyclic GMP showed a more substantial (250%) variation. All 3 parameters showed peaks between 10 AM and 2 PM. The tumor promoter phorbol myristate acetate had no effect on the variation in either cyclic AMP or cyclic GMP, but did appear to reduce the extent of diurnal variation in cyclic GMP/cyclic AMP ratios. The diurnal variation in epidermal mitosis in these mice showed a maximum at 2 PM and a minimum at 10 PM to 2 AM.

Studies on the plasma membrane of normal and psoriatic keratinocytes. 2. Cyclic AMP and its response to hormonal stimulation

Cyclic AMP levels have been determined for the first time in isolated keratinocytes. Values were more reproducible than those reported using epidermal slices. Evidence is presented to show that damage to hormone receptors is minimal. Other observations include the following: (1) Keratinocytes from psoriatic lesions showed reduced 'resting' levels of cyclic AMP as well as a diminished response to adrenaline. (2) Cyclic AMP levels were maximal in the basal cells, falling dramatically in fully differentiated keratinocytes. (3) The topical application of a corticosteroid (fluocinolone acetonide) did not modulate the response of adenyl cyclase to hormonal stimulation.

Cyclic GMP System in epidermis: I. Effect of ischemia

When keratome-sliced pig epidermis was floated on Hank's balanced salt solution, we observed a rapid decrease in the intracellular level of cyclic GMP. A portion of the lost cyclic GMP was detected in the incubation medium. When the epidermis was kept in air at room temperature, the cyclic GMP level also decreased rapidly but to a lesser degree. Incubating the epidermal slice at 37 degrees C in Hank's balanced salt solution with the addition of 3-isobutyl-1-methyl xanthine (IBMX) prevented the decrease. Also, after the cyclic GMP level had fallen, it could be raised to be the in vitro level by the addition of IBMX. Increased amounts of cyclic GMP were detectable in the medium in this case. These data indicate that the decrease in cyclic GMP in ischemic epidermis is due to sudden activation of epidermal cyclic GMP-phosphodiesterase and also in part due to leakage of cyclic GMP extracellularly. In contrast to the rapid decline in the cyclic GMP level, ischemia caused a rapid and transient increase in epidermal cyclic AMP. This confirms previous data by ourselves and by others (Br J Dermatol 92: 249-254, 1975; J Invest Dermatol 68:125-127, 1977). These "ischemic effects" must be avoided in order to measure the "in vivo level" of cyclic nucleotides in epidermis.

Effect of in vitro cultivation and Mycoplasma pneumoniae infection on intracellular cyclic AMP levels in hamster tracheal organ cultures

Exogenous cyclic AMP and dibutyryl cyclic AMP decreased the relative ciliary activity values of tracheal organ cultures. In contrast, theophylline and cholera toxin were not ciliostatic. The use of a radioimmunoassay for cyclic AMP indicated that all of the tested substances increased intracellular cyclic AMP levels to some extent (from 3-fold for cholera toxin to almost 40-fold for dibutyryl cyclic AMP). Physical inactivation of explants by either freeze-thaw or heat destroyed all ciliary activity and greatly decreased intracellular cyclic AMP levels. Cyclic AMP levels of explants remained relatively constant during in vitro cultivation. Three strains of Mycoplasma pneumoniae were found to contain extremely low amounts of cyclic AMP. Infection of tracheal explants produced a significant decrease in relative ciliary activity, but only a slight decline in organ-culture cyclic AMP levels.

Effects of local anesthesia on gingival cAMP levels

The basal levels of cAMP in the attached gingiva of Rhesus monkeys and the changes in tissue cAMP levels produced by infiltration anesthesia with lidocaine and lidocaine containing 1:100,000 epinephrine were studied. The basal level of cAMP in uninjected monkey gingiva ranged from 12 to 20 picomoles of cAMP per mg of gingival protein. This level was 75 times greater than the cAMP content of monkey blood plasma. Infiltration of the attached gingiva with saline or plain lidocaine for 5 minutes did not produce any significant changes in tissue cAMP levels. Infiltration of the gingiva with lidocaine containing 1:100,000 epinephrine, on the other hand, caused a very marked increase in tissue cAMP levels. Thirty seconds after infiltration with lidocaine with 1:100,000 epinephrine there was a 250% increase in cAMP content of the anesthetized tissue versus the uninjected control tissues. The maximal increase in tissue cAMP levels was observed 5 minutes after infiltration when the cAMP content of the gingiva was 1000 to 1100% above the control level. It is proposed that regulation of tissue cAMP levels by epinephrine or other agents may prove of therapeutic usefulness in regulating inflammation and healing of tissues after surgery or other trauma.

Cyclic AMP accumulation in psoriatic skin: differential responses to histamine, AMP, and einephrine by the uninvolved and involved epidermis

Using the uninvolved and involved skin from psoriatic patients, we investigated the effects of histamine and AMP (or adenosine) in vitro on the intracellular cyclic AMP levels. Both agents activated adenylate cyclase of the uninvolved and involved resulting in the accumulation of cyclic AMP. Without a cyclic nucleotide phosphodiesterase (PDE) inhibitor, these responses were biphasic and the maximal accumulation was observed in 5 min. With the PDE inhibitor both responses were markedly potentiated and high levels of cyclic AMP were observed for more than 20 min. The response to histamine by the involved skin was much greater than that by the uninvolved. The degree of the response to adenosine was approximately equal. In accordance with our previous work, the response to epinephrine by the involved skin was much less than that by the uninvolved. Thus adenylate cyclases of involved skin from psoriatic patients exhibit a markedly diminished response to epinephrine while at the same time exhibiting a markedly enhanced response to histamine. This precludes the possibility that the unresponsiveness to epinephrine can be due to a generalized inability of the epidermal psoriatic plaque cell to make a functioning cell membrane.

Epinephrine activation of pig skin adenylate cyclase in vivo and subsequent refractoriness to activation

Epinephrine injected intradermally activated pig skin adenylate cyclase and increased the epidermal cyclic AMP level in vivo. This biphasic response reached a maximum in 5 min and gradually decreased thereafter. The simultaneous injection of a cyclic AMP phosphodiesterase inhibitor, isobutyl methyl xanthin (IBMX) potentiated the increase. The simultaneous injection of a specific beta-adrenergic receptor inhibitor, propranolol, inhibited this accumulation of cyclic AMP. After the first activation by epinephrine in vivo, there was a marked refractoriness of the skin (epidermal) adenylate cyclase to subsequent epinephrine stimulation vivo and in vitro. This refractoriness was specific for catecholamine stimulation as responses to histamine were normal. Recovery from refractoriness started at 48 hr and was completed at 1 week after the injection of epinephrine.

Microwave irradiation: a new rapid technique for separating epidermal tissue from mouse skin preserving RNA, DNA, protein and phorbol ester-induced ornithine decarboxylase levels

Exposure of mouse skin to microwave radiation for 10 sec allows the epidermis to be separated from the dermis by gentle scraping of the skin with a scapel. At the end of the irrradiation period the subcutaneous temperature was 55 degrees C. Histologically, the microwave irradiated skin resembled skin exposed to an established heat separation procedure (i.e., immersion in 55 degrees C water followed by immersion in 0-4 degrees C water). The recoveries of DNA, RNA, and protein on a per area basis were the same for the microwave and conventional heat separation procedures, and the TPA-induced ornithine decarboxylase levels were comparable.

Epidermal adenylate cyclase: stimulation of the histamine (H2) receptor by tolazoline

Tolazoline (2-benzyl-2-imidazoline) activated adenylate cyclase in pig epidermal slices resulting in the accumulation of cyclic AMP. This effect was highly potentiated by the addition of the cyclic AMP-phosphodiesterase inhibitor, theophylline. Specific histamine (H2) receptor inhibitors (metiamide and cimetidine) completely blocked the tolazoline activation of adenylate cylase. At low concentrations (10-100 micrometer), a histamine (H1) receptor inhibitor (diphenhydramine) and a beta-adrenergic blocker (propranolol) did not inhibit this effect. The stimulation of cyclic AMP formation by the combination of tolazoline and histamine was about the same as the stimulation by histamine alone (nonadditive), whereas the stimulatory effects by tolazoline and epinephrine were additive. These data suggest that tolazoline, an alpha-adrenergic blocker, also activates adenylate cyclase at the histamine (H2) receptor site which is distinct from the beta-adrenergic receptor site. Another alpha-adrenergic blocker, phentolamine, did not have this effect.

Epidermal adenylate cyclase systems: the retention of hormone responsiveness after enzymatic separation of pure epidermis

Although it has been shown that keratome-sliced skin contains active adenylate cyclase systems which respond to various hormones and drugs, unequivocal proof that the epidermis contains these hormone-responsive systems is still lacking. We demonstrate in this study that "pure" epidermis obtained after either collagenase or trypsin treatment does contain the hormone-sensitive adenylate cyclase systems.

Specific refractoriness of adenylate cyclase in skin to epinephrine, prostaglandin E, histamine and AMP

The cyclic AMP level in pig skin (epidermis) increases markedly after incubation with epinephrine, prostaglandin E, histamine or adenosine 5'-monophosphate. This increase is transient and "spiking" is the consistent response to these four stimulators. The "spiking" is due to a non-responsiveness or refractoriness which develops within minutes and is specific to any one stimulating hormone but not to the others. The addition of inhibitors of protein syntheses did not prevent the development of the refractoriness. Adenylate cyclase and phosphodiesterase activities measured in skin homogenates prepared from skin samples taken before, during and after the "spiking" did not change significantly. The hormone-induced refractoriness in this skin system appears to be due to a specific, localized loss of function of the adenylate cyclase system.

Accumulation of cyclic adenosine 3',5'-monophosphate in adult and newborn mouse skin: responses to ischemia and isoproterenol

Levels of cyclic adenosine 3',5'-monophosphate in adult mouse skin pieces were rapidly increased on incubation at 37 degrees C, or on exposure to isoproterenol. Accumulation of the cyclic nucleotide under both conditions was greatly decreased in newborn mouse skin, or in adult skin treated with the tumor promotor 12-0-tetradecanoyl-phorbol-13-acetate.

Phosphodiesterase inhibitors: their comparative effectiveness in vitro in various organs

The inhibitor constants of several inhibitors for cyclic AMP- and cyclic GMP-phosphodiesterase from various organs are compared. The inhibitors were classical theophyline, papaverine, and some of newly developed inhibitors: an imidazolidinone compound, RO20-1724, and two phthalazinol compounds, EG 467 and EG 626. Among the inhibitors tested, papaverine and EG 626 were found to be the most potent. Both compounds were extremely inhibitory to platelet and arterial phosphodiesterases. EG 626 was much more inhibitory to cyclic AMP phosphodiesterase than to cyclic GMP phosphodiesterase in platelet- and brain-extract and RO20-1724 was inhibitory to cyclic AMP- but not cyclic GMP-phosphodiesterase in brain-extract. When the skin adenyl cyclase was activated by AMP, the addition of theophylline blocked this activation, but EG 626 or EG 467 further potentiated the activation. These in vitro studies may serve as basic screening tests for the effectiveness of the specific phosphodiesterase inhibitors.