Gap junction inhibitors modulate S100B secretion in astrocyte cultures and acute hippocampal slices.
Astrocytes sense, integrate, and respond to stimuli generated by neurons or neural injury; this response involves gap junction (GJ) communication. Neuronal vulnerability to injury increased when cocultures of astrocytes and neurons were exposed to GJ inhibitors. However, GJ uncoupling could limit the extension of a lesion. We investigated a possible link between GJ communication and S100B secretion. S100B is a calcium-binding protein of 21 kDa that is predominantly expressed and secreted by astrocytes, which has trophic paracrine activity on neurite growth, glial proliferation, and neuronal survival. GJ inhibitors were analyzed in isolated astrocytes in primary cultures from hippocampus, acute hippocampal slices, and C6 glioma cells, which were used as a negative control. Our data indicate that GJ blocking stimulates S100B secretion in astrocyte cultures and acute hippocampal slices. Different assays were used to confirm cell integrity during exposure to GJ inhibitors. S100B secretion was observed with different types of GJ inhibitors; the resulting event was dependent on time, the nature of the inhibitor, its putative molecular target of GJ blocking, and/or the cell preparation used. Only carbenoxolone induced a fast and persistent increase in S100B secretion in both preparations. Endothelin-1 increased S100B secretion in astrocyte cultures at 1 hr, but a decrease was observed at 6 hr or in acute hippocampal slices. Physiologically, a local GJ closure associated with release of S100B in injury conditions favors the idea of a common mechanism available to limit the extension of lesion and increase the chances of cell survival.
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
Marina Concli
MC
Leite
Fabiana
F
Galland
Daniela F
DF
de Souza
Maria Cristina
MC
Guerra
Larissa
L
Bobermin
Regina
R
Biasibetti
Carmem
C
Gottfried
Carlos-Alberto
CA
Gonçalves
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D002229:Carbenoxolone / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D002491:Central Nervous System Agents / Q000494:pharmacology; D019332:Endothelin-1 / Q000378:metabolism; D005439:Flufenamic Acid / Q000494:pharmacology; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism*; D019695:Glycyrrhizic Acid / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D009414:Nerve Growth Factors / Q000378:metabolism*; D000442:Octanols / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism*; D013997:Time Factors
D002491:Central Nervous System Agents; D019332:Endothelin-1; D009414:Nerve Growth Factors; D000442:Octanols; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579160:S100B protein, human; C579158:S100b protein, rat; D005439:Flufenamic Acid; D019695:Glycyrrhizic Acid; D002229:Carbenoxolone; D006221:Halothane