Endothelins are extracellular signals modulating cytoskeletal actin organization in rat cultured astrocytes.
Effects of endothelin-3 on rapid morphological changes and cytoskeletal actin organization of rat cortical cultured astrocytes were examined. In serum-free medium, treatments with 1 mM dibutyryl cAMP and 5 microM cytochalasin B, an inhibitor of actin polymerization, caused astrocytic morphological changes with cytoplasmic retraction (stellation). Concurrent addition of 1 nM endothelin-3 prevented astrocytic stellation by dibutyryl cAMP and cytochalasin B. The inhibition of endothelin-3 on the astrocytic stellation was dose-dependent, where IC50 and maximal effective dose were about 50 pM and 0.1 nM, respectively. Endothelin-1 and sarafotoxin S6b prevented the cytochalasin B-induced stellation with similar potencies to endothelin-3. Endothelin-3 reversed the stellate morphology of cytochalasin B-treated cells. Sixty minutes after addition of endothelin-3, most cytochalasin B-treated astrocytes lost their apparent distinction between cell body and processes. Treatment with dibutyryl cAMP and cytochalasin B decreased actin content in a 0.5% Triton X-100-insoluble fraction (cytoskeletal fraction) of cultured astrocytes. Subsequent treatments with endothelin-3 for 2 h restored the decreased cytoskeletal actin to that of non-treated cells. Rhodamine-phalloidin staining showed that a prominent structure of organized filamentous actin in protoplasmic astrocytes is stress fibers. The astrocytic stress fibers disappeared after treatment with dibutyryl cAMP and cytochalasin B. Endothelin-3 stimulated reorganization of stress fibers both in the dibutyryl cAMP- and the cytochalasin B-treated astrocytes. These results suggest that endothelins are extracellular signals to regulate cytoskeletal actin organization of astrocytes.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Suita, Japan.
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Koyama
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Baba
D000199:Actins / Q000378:metabolism; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D003994:Bucladesine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002478:Cells, Cultured; D003571:Cytochalasin B / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D016232:Endothelins / Q000494:pharmacology*; D005110:Extracellular Space / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D000199:Actins; D003598:Cytoskeletal Proteins; D016232:Endothelins; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; D003571:Cytochalasin B; D003994:Bucladesine