RESUMO
The endoplasmic reticulum (ER) is related to the various signal routes that are activated in unfolded protein response (UPR). The Grp78, Grp94, CHOP, MTJ1 and HMOX1 genes expressions demonstrate UPR activity. In this study, we investigated the UPR gene expressions in larynx epidermoid carcinoma (HEp2) to which dexamethasone (dex) was applied. HEp2 cells were administered for 48 h with different combinations using 0.1 μM and 1 μM dex, 1 mM phenyl butyric acid (PBA) and 100 ng/ml lipopolysaccharide (LPS). The Grp78, Grp94, CHOP, MTJ1 and HMOX1 genes expression was determined using quantitative RT-PCR. The Grp78, MTJ1 and HMOX1 gene expression increased with the administration of 1 µM dex. CHOP expression, on the other hand, decreased with 0.1 µM dex. When dex was combined with LPS, nearly all gene expressions decreased. The increase in Grp78, Grp94, HMOX1 and MTJ1 gene expression was greater in groups in which dex was administered in combination with PBA than in groups in which dex was administered alone. Dex in low dose (0.1 μM) caused a decrease in CHOP expression in HEp2 cells and an increase in Grp78 expression, in particular. The changes in UPR genes expressions may lead to the extended survival of the cells.
Assuntos
Apoptose/efeitos dos fármacos , Ácido Butírico/farmacologia , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Dexametasona/farmacologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Proteínas de Choque Térmico HSP40/genética , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico/genética , Heme Oxigenase-1/genética , Humanos , Lipopolissacarídeos/farmacologia , Proteínas de Membrana/genética , Fator de Transcrição CHOP/genética , Resposta a Proteínas não Dobradas/efeitos dos fármacos , Resposta a Proteínas não Dobradas/genéticaRESUMO
Baicalein is one of the major flavonoids in Scutellaria baicalensis Georgi and possesses various effects, including cytoprotection and anti-inflammation. Because endoplasmic reticulum (ER) stress has been implicated in neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and cerebral ischemia, we investigated the effects of baicalein on apoptotic death of HT22 mouse hippocampal neuronal cells induced by thapsigargin (TG) and brefeldin A (BFA), two representative ER stress inducers. Apoptosis, reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) were measured by flow cytometry. Expression level and phosphorylation status of ER stress-associated proteins and activation and cleavage of apoptosis-associated proteins were analyzed by Western blot. Baicalein reduced TG- and BFA-induced apoptosis of HT22 cells and activation and cleavage of apoptosis-associated proteins, such as caspase-12 and -3 and poly(ADP-ribose) polymerase. Baicalein also reduced the TG- and BFA-induced expression of ER stress-associated proteins, including C/EBP homologous protein (CHOP) and glucose-regulated protein 78, the cleavage of X-box binding protein-1 and activating transcription factor 6alpha, and the phosphorylation of eukaryotic initiation factor-2alpha and mitogen-activated protein kinases, such as p38, JNK, and ERK. Knock-down of CHOP expression by siRNA transfection and specific inhibitors of p38 (SB203580), JNK (SP600125), and ERK (PD98059) as well as anti-oxidant (N-acetylcysteine) reduced TG- or BFA-induced cell death. Baicalein also reduced TG- and BFA-induced ROS accumulation and MMP reduction. Taken together, these results suggest that baicalein could protect HT22 neuronal cells against ER stress-induced apoptosis by reducing CHOP induction as well as ROS accumulation and mitochondrial damage.