Biomedical subjects

K Douwes

Publications and source records attributed to K Douwes.

3 recordsLinked to original sources

PubMed1999

UVB increases urokinase-type plasminogen activator receptor (uPAR) expression.

Keratinocytes synthesize and secrete urokinase-type plasminogen activator, which binds to its specific receptor on keratinocytes. When bound to urokinase-type plasminogen activator receptor, urokinase-type plasminogen activator proteolytically converts surface bound plasminogen to plasmin, which in turn cleaves many extracellular components leading to pericellular proteolysis. The activation of the urokinase system has been observed during re-epithelialization of skin wounds and in lesions of the autoimmune blistering skin disease pemphigus. As pemphigus is photoinducible, we investigated the effect of ultraviolet B on urokinase-type plasminogen activator and urokinase-type plasminogen activator receptor expression in the epidermal keratinocyte cell line A431. Ultraviolet B increased cellular and secreted urokinase-type plasminogen activator protein (enzyme-linked immunosorbent assay) and urokinase-type plasminogen activator receptor cell surface expression (flow cytometry) 24 h postirradiation. Northern blot analysis indicated that ultraviolet B increased urokinase-type plasminogen activator receptor mRNA. Compared with a more rapid mRNA induction by epidermal growth factor (maximal after 4 h) the ultraviolet B response was maximal after 24 h and prolonged up to 36 h. The mRNA induction was not dependent on protein synthesis as judged by cycloheximide incubation. Ultraviolet B did not influence urokinase-type plasminogen activator receptor mRNA stability (actinomycin D incubation). A transiently transfected chloramphenicol acetyltransferase-reporter construct containing a -398/+51 urokinase-type plasminogen activator receptor promoter fragment was activated when cells were exposed to ultraviolet B. This induction was almost completely abolished by mutating a -182/-176 AP-1 binding sequence. Ultraviolet B increased the binding capacity at this AP-1 motif in electrophoretic mobility shift assays. These data identify a distinct transcriptional mechanism by which ultraviolet B induces urokinase-type plasminogen activator receptor. The epidermal induction of components of the proteolytic urokinase system by ultraviolet B may help explain the photoinducibility of pemphigus lesions.

Binding Sites↗

PubMed1998

Vascular activation of adhesion molecule mRNA and cell surface expression by ionizing radiation.

During cutaneous inflammatory reactions the recruitment of circulating leukocytes into the tissue critically depends on the regulated expression of endothelial cell adhesion molecules (CAMs). Various proinflammatory stimuli upregulate endothelial CAMs, including cytokines and UV irradiation. We have investigated the effects of ionizing radiation (IR) on endothelial CAM expression. Organ cultures of normal human skin as well as cultured human dermal microvascular endothelial cells (HDMEC) were exposed to IR. Expression of three major endothelial CAMs was studied in skin organ cultures by immunohistochemistry and in cell culture by Northern blot analysis and flow cytometry. In skin organ cultures vascular immunoreactivity for ICAM-1, E-selectin, and VCAM-1 was strongly induced 24 h after exposure to 5 or 10 Gy of IR, while immunoreactivity for CD31/PECAM-1, a constitutively expressed endothelial cell adhesion molecule, remained unchanged. In cultured HDMEC IR upregulated ICAM-1, VCAM-1, and E-selectin mRNAs and cell surface expression in a time- and dose-dependent fashion. Cellular morphology and viability remained unaltered by IR up to 24 h postirradiation. This study characterizes microvascular activation of adhesion molecule expression in response to ionizing radiation in a clinically relevant IR dose range. The findings also underscore the ability of endothelial cells to integrate environmental electromagnetic stimuli.

Antigens, CD↗

PubMed1995

Rapid effects of aldosterone on sodium transport in vascular smooth muscle cells.

Increasing evidence has accumulated for rapid nongenomic steroid actions in various cell systems and, more recently, for rapid aldosterone effects on the Na(+)-H+ antiport in human mononuclear leukocytes. The aim of the present study was to demonstrate a rapid, nongenomic aldosterone action in rat vascular smooth muscle cells as a key effector cell in cardiovascular regulation. Basal 22Na+ influx in quiescent vascular smooth muscle cells was 22.1 +/- 1.9 nmol/mg protein per minute (mean +/- SEM, n = 9). Aldosterone (1 nmol/L) stimulated influx to 28.6 +/- 1.5 nmol/mg protein per minute after 4 minutes (n = 9, P < .05), with a half-maximal effect between 0.1 and 0.5 nmol/L; the effects were inhibited by ethylisopropylamiloride, the specific inhibitor of the Na(+)-H+ exchanger, demonstrating the involvement of this transport system in rapid effects of aldosterone. Hydrocortisone (1 mumol/L) was ineffective, and fludrocortisone and deoxycorticosterone increased influx with half-maximal effects at approximately 0.5 nmol/L. Canrenone, a classic antagonist of aldosterone action, did not inhibit stimulation by aldosterone at a 1000-fold excess concentration. Aldosterone significantly stimulated intracellular inositol 1,4,5-trisphosphate levels (P < .05) after 30 seconds; the inhibitors of phospholipase C, neomycin and U-73122, inhibited aldosterone-stimulated Na+ influx and increase of intracellular inositol 1,4,5-trisphosphate. The rapid stimulation of sodium transport in vascular smooth muscle cells and the pharmacological characteristics of this effect are clearly incompatible with the classic, genomic pathway of steroid action and represent further evidence for nongenomic effects of aldosterone.

Aldosterone↗