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 μM 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

Glycogen Synthetase [Udp Glucose: α-1, 4-Glucan α-4-Glucosyl Transferase (Ec 2.4.1.11)] of Human Epidermis

Normal human epidermis contains glycogen synthetase in activities which are approximately 10% of that found in brain and muscle. The enzyme is activated by glucose-6-phosphate (Glc-6-P) and seems to have characteristics which are similar to those reported for the same enzyme in other tissues. About 50% of the enzyme is normally in the I form which presumably correlates with the very low levels of glycogen (0.35 µg/mg) normally present in human epidermis

Defective IL-10 signaling in hyper-IgE syndrome results in impaired generation of tolerogenic dendritic cells and induced regulatory T cells

Dendritic cells from patients with hyper-IgE syndrome less efficiently generate induced regulatory T cells

Ultraviolet B Radiation Upregulates the Production of Macrophage Migration Inhibitory Factor (MIF) in Human Epidermal Keratinocytes

Human epidermal cells are capable of secreting various cytokines with immunologic, inflammatory, and proliferative properties. In a previous study, by reverse transcription–polymerase chain reaction and immunohistochemical analysis, we have shown that human epidermal keratinocytes express macrophage migration inhibitory factor and identified its presence in the cytoplasm. In this study, we detected an increased serum macrophage migration inhibitory factor level by enzyme-linked immunosorbent assay after a single total-body ultraviolet B exposure in vivo, indicating that human keratinocytes respond and release this cytokine in response to ultraviolet B irradiation. Moreover, we evaluated the effect of ultraviolet B on migration inhibitory factor production in cultured human epidermal keratinocytes and epidermal sheets. The results of enzyme-linked immunosorbent assay and northern blot analyses showed that migration inhibitory factor production of cultured keratinocytes was increased by ultraviolet B exposure. During the past few years, migration inhibitory factor was found to have a variety of biologic functions, such as being essential for T cell activation and induction of inflammatory cytokines. In this context, these results should encourage further investigation on the pathophysiologic role of migration inhibitory factor in cutaneous inflammatory reactions and immune responses

Damage Evaluation Using Magnetic Properties in Stainless Steels under Biaxial Stress

Various stainless steels were investigated to examine the new NDE technique. The new NDE technique did not depend on either magnetization or demagnetization of materials. The magnetic flux caused by stress concentration in stainless steels was examined with the ultra sensitive magnetic flux density meter. Tensile and biaxial fatigue tests were conducted to observe the magnetic flux leakage. Results from biaxial fatigue tests indicated that the measured magnetic flux curves had local periodical cycles with global increasing tendencies. The defect evaluation would be possible by comparing the flux density value at the stress concentration regions with that of other areas

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 out- growth 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 outgrowth, [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

Differentiation-Associated Localization of nPKCμ, a Ca++-Independent Protein Kinase C, in Normal Human Skin and Skin Diseases

The expression of nPKCμ, a Ca++-independent isoform of protein kinase C in normal human skin, and skin from patients with psoriasis, squamous cell carcinoma, basal cell epithelioma, nevus pigmentosus, and seborrheic keratosis, were examined by immunohistochemical staining using a polyclonal antibody raised against a synthetic peptide at a diverse region of the nPKCμ molecule. In normal epidermis, the strongest staining was observed in the uppermost granular layer with no staining of the spinous or basal layers. The inner layer of the intra-epidermal eccrine duct was also strongly stained. Weak staining was observed in several layers of the outer root sheath of the follicular infundibulum. No staining was detected in the inner root sheath of the hair follicles, hair matrix, sebaceous gland, eccrine gland, intradermal eccrine duct, arrectores pilorum, melanocytes, Langerhans cells, fibroblasts, or blood vessels. In psoriatic skin, stained keratinocytes were distributed in the suprabasal layers with the most being observed in the uppermost layer and the least in layers closed to the basal layer. In squamous cell carcinoma, weak staining was observed in the keratotic cells around horny pearls. In the basal cell epithelioma and nevus pigmentosus, the cells were not stained, whereas in seborrheic keratosis, cells that stained were located in the granular layer. We conclude from the evidence presented above that nPKCμ is expressed in close association with epidermal differentiation in normal skin and skin diseases