Toxic effects of cobalt in primary cultures of mouse astrocytes. Similarities with hypoxia and role of HIF-1alpha.
Cobalt is suspected to cause memory deficit in humans and was reported to induce neurotoxicity in animal models. We have studied the effects of cobalt in primary cultures of mouse astrocytes. CoCl(2) (0.2-0.8mM) caused dose-dependent ATP depletion, apoptosis (cell shrinkage, phosphatidylserine externalization and chromatin rearrangements) and secondary necrosis. The mitochondria appeared to be a main target of cobalt toxicity, as shown by the loss of mitochondrial membrane potential (DeltaPsi(m)) and release from the mitochondria of apoptogenic factors, e.g. apoptosis inducing factor (AIF). Pre-treatment with bongkrekic acid reduced ATP depletion, implicating the involvement of the mitochondrial permeability transition (MPT) pore. Cobalt increased the generation of oxygen radicals, but antioxidants did not prevent toxicity. There was also an impaired response to ATP stimulation, evaluated as a lower raise in intracellular calcium. Similarly to hypoxia and dymethyloxallyl glycine (DMOG), cobalt triggered stabilization of the alpha-subunit of hypoxia-inducible factor HIF-1 (HIF-1alpha). This early event was followed by an increased expression of HIF-1 regulated genes, e.g. stress protein HO-1, pro-apoptotic factor Nip3 and iNOS. Although all of the three stimuli activated the HIF-1alpha pathway and decreased ATP levels, the downstream effects were different. DMOG only inhibited cell proliferation, whereas the other two conditions caused cell death by apoptosis and necrosis. This points to cobalt and hypoxia not only inducing HIF-1alpha regulated genes but also affecting similarly other cellular functions, including metabolism.
Karovic
Olga
O
Department of Physiology and Pharmacology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Tonazzini
Ilaria
I
Rebola
Nelson
N
Edström
Erik
E
Lövdahl
Cecilia
C
Fredholm
Bertil B
BB
Daré
Elisabetta
E
D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects*; D020013:Calcium Signaling; D015687:Cell Hypoxia; D002478:Cells, Cultured; D003035:Cobalt / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D051379:Mice; D010100:Oxygen / Q000378:metabolism*; D017382:Reactive Oxygen Species
D000600:Amino Acids, Dicarboxylic; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017382:Reactive Oxygen Species; D003035:Cobalt; C018021:cobaltous chloride; D010100:Oxygen; C040947:oxalylglycine