Neurovascular dysfunction arising from endothelial cell damage is an early pathogenic event that contributes to the neurodegenerative process occurring in Alzheimer's disease (AD). Since the mechanisms underlying endothelial dysfunction are not fully elucidated, this study was aimed to explore the hypothesis that brain endothelial cell death is induced upon the sustained activation of the endoplasmic reticulum (ER) stress response by amyloid-beta (Aβ) peptide, which deposits in the cerebral vessels in many AD patients and transgenic mice. Incubation of rat brain endothelial cells (RBE4 cell line) with Aβ1-40 increased the levels of several markers of ER stress-induced unfolded protein response (UPR), in a time-dependent manner, and affected the Ca(2+) homeostasis due to the release of Ca(2+) from this intracellular store. Finally, Aβ1-40 was shown to activate both mitochondria-dependent and -independent apoptotic cell death pathways. Enhanced release of cytochrome c from mitochondria and activation of the downstream caspase-9 were observed in cells treated with Aβ1-40 concomitantly with caspase-12 activation. Furthermore, Aβ1-40 activated the apoptosis effectors' caspase-3 and promoted the translocation of apoptosis-inducing factor (AIF) to the nucleus demonstrating the involvement of caspase-dependent and -independent mechanisms during Aβ-induced endothelial cell death. In conclusion, our data demonstrate that ER stress plays a significant role in Aβ1-40-induced apoptotic cell death in brain endothelial cells suggesting that ER stress-targeted therapeutic strategies might be useful in AD to counteract vascular defects and ultimately neurodegeneration.
Keywords: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; AD; AIF; AM; APP; ATF; Alzheimer's disease; Amyloid-beta peptide; Apoptosis; Aβ; BBB; CAAT/enhancer binding protein homologous protein; CHOP; Calcium homeostasis; DMSO; ECF; ECs; ER; Endoplasmic reticulum stress; Endothelial cells; GAPDH; GRP78; IRE1; JNK; LDH; LRP; MTT; NAD+; NADH; PARP1; PERK; PI; PS; PVDF; RAGE; RBE4; RT; Ry; RyR; SDS-PAGE; SDS-polyacrylamide gel; SERCA; TATA-binding protein; TBP; TBS-T; TBS-Tween; TUNEL; ThS; UPR; WB; Western blot; X-box binding protein-1; XBP-1; acetoxymethyl ester; activating transcription factor; amyloid precursor protein; amyloid-beta; apoptosis-inducing factor; bFGF; basic fibroblast growth factor; blood–brain barrier; c-jun N-terminal kinase; dimethyl sulfoxide; eIF2α; endoplasmic reticulum; endothelial cells; enhanced chemifluorescence; glucose-regulated protein of 78kDa; glyceraldehyde-3-phosphate dehydrogenase; inositol-requiring protein-1; lactate dehydrogenase; low-density lipoprotein receptor-related protein; mitochondrial membrane potential; nicotinamide adenine dinucleotide; oxidized nicotinamide adenine dinucleotide; poly(ADP-ribose) polymerase 1; polyvinylidene difluoride; presenilinM; propidium iodide; protein kinase RNA-like ER kinase; rat brain endothelial cell line; receptor for advanced glycation end products; room temperature; ryanodine; ryanodine receptor; sarco/ER Ca(2+) ATPase; terminal deoxynucleotidyl transferase dUTP nick-end labeling; thioflavine S; unfolded protein response; Δψmit; α subunit of eukaryotic translation initiation factor 2.
© 2013.