Oleate rescues INS-1E ß-cells from palmitate-induced apoptosis by preventing activation of the unfolded protein response.
Biochem Biophys Res Commun
; 441(4): 770-6, 2013 Nov 29.
Article
em En
| MEDLINE
| ID: mdl-24189472
ABSTRACT
BACKGROUND:
Saturated free fatty acids (FFAs), such as palmitate, cause ß-cell apoptosis whereas unsaturated FFAs, e.g. oleate, are not harmful. The toxicity of palmitate could be mediated through endoplasmic reticulum (ER) stress which triggers the activation of a signal responding cascade also called unfolded protein response (UPR). We investigated whether or not palmitate induced ß-cell apoptosis through UPR activation and whether or not oleate as a monounsaturated fatty acid could counteract these effects.METHODS:
INS-1E ß-cells were incubated with palmitate [0.5mM], oleate [1mM] or the combination [0.5/1mM] for 1, 6 and 24h. Viability and induction of apoptosis were measured by WST-1 assay and FITC-Annexin/PI-staining, respectively. Western blot analyses were performed for UPR specific proteins and mRNA expression of target molecules was determined by qPCR.RESULTS:
Palmitate significantly decreased viability (29±8.8%) of INS-1E ß-cells compared to controls after 24h. Stimulation with oleate showed no effect on viability but the combination of oleate and palmitate improved viability compared to palmitate treated cells (55±9.3%) or controls (26±5.3%). The number of apoptotic cells was increased 2-fold after 24h incubation with palmitate compared to controls. Again, oleate showed no effect but in combination ameliorated the effect of palmitate to control level. Phosphorylation of eIF2α was increased after 6 and 24h incubation with palmitate. In contrast, oleate had no effect and in combination prevented phosphorylation of eIF2α. Increased Xbp1 splicing was visible already 6h after palmitate treatment and remained elevated at 24h. The combination with oleate abolished Xbp1 splicing. Interestingly, mRNA expression of the chaperones Bip, Pdi, Calnexin and Grp94 was not altered by FFA treatment. Only the proapoptotic transcription factor Chop was significantly enhanced by palmitate incubation. In accordance with sustained cell survival the combination as well as oleate alone, did not result in increased Chop levels compared to controls. In summary, we showed that oleate protects INS-1E ß-cells from palmitate-induced apoptosis by the suppression of ER stress which was independent of chaperone activation.Palavras-chave
ATF6; Apoptosis; Beta cell; Bip/Grp78; C/EBP homologous protein; Chop; ER; ER stress; FFA; Grp94; IRE1; MUFA; Oleate; PERK; Palmitate; Pdi; SCD1; SFA; UPR; X-box-binding protein 1; Xbp1; activating-transcription-factor 6; eIF2α; endoplasmic reticulum; eukaryotic initiation factor 2α; free fatty acid; glucose-regulated protein 94kDa; immunoglobulin heavy-chain binding protein; inositol-requiring-enzyme1; monounsaturated fatty acid; protein disulfide isomerase; protein-kinase-regulated-by-RNA-like-ER-associated-kinase; saturated fatty acid; stearoyl-CoA desaturase 1; unfolded protein response
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Palmitatos
/
Apoptose
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Ácido Oleico
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Citoproteção
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Células Secretoras de Insulina
/
Resposta a Proteínas não Dobradas
Limite:
Animals
Idioma:
En
Revista:
Biochem Biophys Res Commun
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Alemanha