Endoplasmic Reticulum Stress-induced Apoptosis Pathway Research Articles

The Antihypertensive Effects and Mechanisms of Huotan Jiedu Tongluo Decoction in Rats with H-Type Hypertension.

H-type hypertension, which is a specific form of hypertension characterized by elevated plasma homocysteine (Hcy) levels, has become a major public health challenge worldwide. This study investigated the hypotensive effects and underlying mechanisms of Huotan Jiedu Tongluo decoction (HTJDTLD), a highly effective traditional Chinese medicine formula commonly used to treat vascular stenosis. Methionine was used to induce H-type hypertension in rats, and HTJDTLD was administered intragastrically. Then, the systolic and diastolic blood pressures of the caudal artery of rats were measured by noninvasive rat caudal manometry. Histological assessment of the aorta was performed by hematoxylin-eosin (HE) staining. Enzyme-linked immunosorbent assay (ELISA) was used to measure Hcy levels, and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blotting were used to determine the mRNA and protein levels of Glucose regulatory protein 78 (GRP78), Tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2), c-Jun N-terminalkinases (JNK), and caspase-3. The results showed that HTJDTLD significantly lowered blood pressure, alleviated histopathological lesions, and decreased Hcy levels after methionine treatment. Moreover, HTJDTLD significantly inhibited the gene and protein expression of GRP78, JNK, TRAF2, and caspase 3, which are involved mainly in the endoplasmic reticulum (ER) stress-induced apoptosis pathway. Overall, the results indicated that HTJDTLD had effective antihypertensive effects in rats with H-type hypertension and revealed the antihypertensive mechanisms associated with inhibition of ER stress-induced apoptosis pathway activation.

Ulinastatin improves myocardial ischemia-reperfusion injury in rats through endoplasmic reticulum stress-induced apoptosis pathway.

To investigate the protective role of ulinastatin (UTI) on myocardial ischemia-reperfusion (I/R) injury in rats via endoplasmic reticulum stress (ERS)-induced apoptosis pathway. A total of 60 rats were randomly divided into normal group (n=20), myocardial I/R model group (model group, n=20), and myocardial I/R model+UTI treatment group (treatment group, n=20). The myocardial function indicators [creatinine (Scr) and creatine kinase (CK)] were detected. Enzyme-linked immunosorbent assay (ELISA) was performed to measure serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and matrix metalloproteinase-9 (MMP-9). Meanwhile, the contents of reactive oxygen species (ROS), superoxide dismutase (SOD), and malondialdehyde (MDA) in rat left ventricular tissues were determined by ELISA as well. The cardiac function indexes were determined via magnetic resonance imaging (MRI) and echocardiography (ECG). Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) staining assay was carried out to detect the apoptosis of myocardial tissues. Additionally, the expression levels of endoplasmic reticulum stress and apoptosis genes were measured through quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) assay and Western blotting analysis, respectively. Serum levels of alanine aminotransferase (ALT), CK, and Scr in model group were significantly higher than those in normal group (p<0.05). Besides, rats in model group had significantly lowered SOD, ejection fraction (EF, %), and fractional shortening (FS, %) than those in normal group (p<0.05). In addition, remarkably increased contents of TNF-α, IL-6, MMP-9, MDA, and ROS, as well as higher left ventricular end-diastolic diameter (LVEDd) and left ventricular end-systolic diameter (LVESd) were observed in model group in comparison with normal group (p<0.05). TUNEL staining results revealed that there were more apoptotic cells in model group than that in the other two groups (p<0.05). Expression levels of cysteine aspartic acid-specific protease 12 (Caspase-12) and glucose-regulated protein 78 (GRP78) were evidently higher in model group than those in normal group (p<0.05), while the expression level of B-cell lymphoma 2 (Bcl-2) was clearly lower in model group than that in normal group (p<0.05). UTI treatment partially reversed the above expression changes (p<0.05). UTI has a protective effect against myocardial I/R injury in rats by repressing the occurrence of ERS-induced apoptosis.

Hydrogen-rich saline protects intestinal epithelial tight junction barrier in rats with intestinal ischemia–reperfusion injury by inhibiting endoplasmic reticulum stress-induced apoptosis pathway

AimTo investigate the effects of hydrogen-rich saline (HRS) on intestinal epithelial tight junction (TJ) barrier in rats with intestinal ischemia–reperfusion injury (IIRI). Materials and methodsThirty-two healthy male Sprague–Dawley (SD) rats were randomly divided into four groups (n = 8 each): Sham group, I/R group, HRS group and 4-PBA group. After 45 min of ischemia and 6 h of reperfusion, the rats were sacrificed to collect serum and ileum for detection. Hematoxylin and eosin (H&E) staining was used to observe the morphology of small intestine. The serum expression levels of intestinal fatty acid binding protein (IFABP), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were determined by enzyme linked immunosorbent assay (ELISA). Imunohistochemistry, immunofluorescence and Western blot were used to detect key proteins in intestinal epithelial TJs, ERS, and ERS-induced apoptosis, including occludin, zonula occludens-1 (ZO-1), glucose-regulated protein 78 (GRP78), X-box binding protein-1 (XBP1), C/EBP-homologous protein (CHOP) and caspase-3. Data was presented as mean ± SEM and compared using one-way ANOVA. A p-value <0.05 was considered significant. ResultsCompared with rats in the I/R group, the Chiu score of ileum damage in the HRS group and 4-PBA group were lower. The levels of serum IFABP, TNF-α, and IL-1β were statistically significant among the groups. Increased expression of TJ proteins occludin and ZO-1 by reducing various parameters of ERS and ERS-induced apoptosis evidenced by down-regulation of the protein levels of GRP78, XBP1, CHOP and caspase-3 were shown in the HRS and 4-PBA groups. ConclusionHRS had potential protective effects on intestinal barrier in IIRI rats. This study suggested that inhibition of excessive ERS and ERS-induced apoptosis by HRS may reduce intestinal epithelial cells damage and maintain the integrity of intestinal epithelial TJ barrier in rats with IIRI.

High expression of active ATF6 aggravates endoplasmic reticulum stress‑induced vascular endothelial cell apoptosis through the mitochondrial apoptotic pathway.

Activating transcription factor 6 (ATF6), one of three sensor proteins in the endoplasmic reticulum (ER), is an important regulatory factor in the ER stress-induced apoptosis pathway. Although recent studies have made some progress in elucidating the regulation mechanism of ATF6, the specific regulatory mechanism of ER stress-induced vascular endothelial cell (VEC) apoptosis is still unclear. The present study was designed to investigate the role of ATF6 in VECs under thapsigargin (TG)-induced ER stress. ATF6 (1–366aa; ATF6 high-expressed plasmid) and ATF6 (151-366aa; plasmid without transcriptional activity) were transfected into VECs to yield an ATF6 high-expression model and a positive control model, respectively. High expression of ATF6 decreased viability and aggravated ER stress-induced apoptosis in VECs. Increased expression of apoptosis-related genes, including those encoding caspase-3, caspase-9, C/EBP homologous protein (CHOP), cytochrome c and B-cell lymphoma-associated protein X (Bax)/B-cell lymphoma (Bcl-)2, was detected by polymerase chain reaction and western blotting in the ATF6 (1-366aa) + TG group. No significant effect of TG treatment and high ATF6 expression was indicated on the expression of death receptor-related genes, including those encoding caspase-8 and Fas. The results demonstrated that high expression of activated ATF6 aggravates ER stress-induced VEC apoptosis through the mitochondrial apoptotic pathway. Furthermore, in response to ER stress, ATF6 upregulates the expression of caspase-3, caspase-9, CHOP, cytochrome c and Bax/Bcl-2.

Activation of γ-aminobutyric Acid (A) Receptor Protects Hippocampus from Intense Exercise-induced Synapses Damage and Apoptosis in Rats.

Background:Our previous study has confirmed that one bout of exhaustion (Ex) can cause hippocampus neurocyte damage, excessive apoptosis, and dysfunction. Its initial reason is intracellular calcium overload in hippocampus triggered by N-methyl-D-aspartic acid receptor (NMDAR) over-activation. NMDAR activation can be suppressed by γ-aminobutyric acid (A) receptor (GABAAR). Whether GABAAR can prevent intense exercise-induced hippocampus apoptosis, damage, or dysfunction will be studied in this study.Methods:According to dose test, rats were randomly divided into control (Con), Ex, muscimol (MUS, 0.1 mg/kg) and bicuculline (BIC, 0.5 mg/kg) groups, then all rats underwent once swimming Ex except ones in Con group only underwent training. Intracellular free calcium concentration ([Ca2+]i) was measured by Fura-2-acetoxymethyl ester; glial fibrillary acidic protein (GFAP) and synaptophysin (SYP) immunofluorescence were also performed; apoptosis were displayed by dUTP nick end labeling (TUNEL) stain; endoplasmic reticulum stress-induced apoptosis pathway was detected by Western blotting analysis; Morris water maze was used to detect learning ability and spatial memory.Results:The appropriate dose was 0.1 mg/kg for MUS and 0.5 mg/kg for BIC. Ex group showed significantly increased [Ca2+]i and astrogliosis; TUNEL positive cells and levels of GFAP, B cell lymphoma-2 (Bcl-2) associated X protein (Bax), caspase-3, caspase-12 cleavage, CCAAT/enhancer binding protein homologous protein (CHOP), and p-Jun amino-terminal kinase (p-JNK) in Ex group also raised significantly compared to Con group, while SYP, synapse plasticity, and Bcl-2 levels in Ex group were significantly lower than those in Con group. These indexes were back to normal in MUS group. BIC group had the highest levels of [Ca2+]i, astrogliosis, TUNEL positive cell, GFAP, Bax, caspase-3, caspase-12 cleavage, CHOP, and p-JNK, it also gained the lowest SYP, synapse plasticity, and Bcl-2 levels among all groups. Water maze test showed that Ex group had longer escape latency (EL) and less quadrant dwell time than Con group; all indexes between MUS and Con groups had no significant differences; BIC had the longest EL and least quadrant dwell time among all groups.Conclusions:Activation of GABAA R could prevent intense exercise-induced synapses damage, excessive apoptosis, and dysfunction of hippocampus.

Intense exercise can cause excessive apoptosis and synapse plasticity damage in rat hippocampus through Ca2+ overload and endoplasmic reticulum stress-induced apoptosis pathway

Intense exercise can cause injury and apoptosis, but few studies have reported its effect on the central nervous system (CNS). The initial reason for hippocampus injury is the excitotoxicity of glutamate and calcium overload. Intracellular free Ca(2+) ([Ca(2+)]i) overload may trigger the apoptosis pathway and neuron damage. The aim of this study was to investigate whether intense exercise could cause hippocampus apoptosis and neuron damage and then to determine which pathway was activated by this apoptosis. We used one bout of swimming exhaustion rats as models. Intracellular [Ca(2+)]i was measured to estimate the calcium overload by Fura-2/AM immediately after exhaustion; glial fibrillary acidic protein (GFAP) and synaptophysin (SYP) immunofluorescence were performed for estimating astrocyte activation and synapse plasticity 24 hours after exhaustion. Apoptosis cells were displayed using dUTP nick end labelling (TUNEL) stain; endoplasmic reticulum (ER) stress-induced apoptosis pathway and mitochondrial apoptosis pathway were synchronously detected by Western blotting. An increasing level of intracellular [Ca(2+)]i (P < 0.01) was found in the hippocampus immediately after exhaustion. GFAP and SYP immunofluorescence showed that the astrocytes are activated, and the synapse plasticity collapsed significantly 24 hours after exhaustion. TUNEL stain showed that the number of apoptosis cells were notably raised (P < 0.01); Western blotting of the apoptosis pathway showed increasing levels of caspase-3 cleavage (P < 0.01), Bax (P < 0.01), caspase-12 cleavage (P < 0.01), C/EBP-homologous protein (CHOP) (P < 0.01), and phospho-Junaminoterminal kinases (p-JNK; P < 0.01) and decreasing level of Bcl-2 (P < 0.01). Our results proved that exhaustion can induce hippocampus injury and apoptosis by [Ca(2+)]i overload, with collapsed synaptic plasticity as the injury pattern and ER stress-induced apoptosis as the activated pathway. Intense exercise can cause excessive apoptosis and synapse plasticity damage in the hippocampus with [Ca(2+)]i overload as the initial reason, and thus provides leads for therapeutic interventions in the brain health of athletes.

ApoG2 induces ER stress-dependent apoptosis in gastric cancer cells in vitro and its real-time evaluation by bioluminescence imaging in vivo

Apogossypolone (ApoG2), a potent small molecular inhibitor of Bcl-2 family proteins, is reported to have a significant anti-cancer effect in several types of cancers, but it has not been investigated in gastric cancer. In this study, we demonstrate in vitro and in vivo that ApoG2 inhibits human gastric cancer. Gastric carcinoma cell growth and proliferation was significantly hampered in vitro, as measured by MTT and colony formation assays. Real-time bioluminescence imaging indicated that ApoG2 causes tumor growth delay in a murine xenograft model. Further studies revealed that the ApoG2 induced apoptosis in gastric cancer cells was associated with the endoplasmic reticulum stress-induced apoptosis pathway. Conclusively, our results indicate that ApoG2 may be a promising agent for gastric cancer therapy.

Albumin Overload Induces Apoptosis in Renal Tubular Epithelial Cells through a CHOP-Dependent Pathway

The proteinuria-induced apoptosis of proximal tubular cells (PTCs) plays a crucial role in renal tubulointerstitial injury in chronic kidney disease. Recent studies have shown that endoplasmic reticulum (ER) stress is involved in proteinuria-induced apoptosis of PTCs. Our study showed that albumin overload led to ER stress, CCAAT/enhancer-binding protein-homologous protein (CHOP), and PKR-like kinase (PERK) activation and to apoptosis of PTCs in proteinuria patients. The apoptotic index of proximal renal tubular cells in the nephrotic kidneys was about 13-fold higher than that in control kidneys. The increased tubular expression of GRP78, ORP150, and CHOP and nuclear localization of CHOP in nephrotic kidneys were also detected. The expression of GRP78, CHOP, PERK, and phosphorylated PERK increased proportionately with HSA overload in a dose- and time-dependent manner. Knockdown of CHOP by siRNA significantly reduced the HSA-induced apoptosis of HKC. The expression of PERK did not significantly change, but the phosphorylation of PERK increased. Furthermore, knockdown of PERK significantly inhibited HSA-induced CHOP expression, suppressing apoptosis in HKCs by 2.48-fold compared to controls. Overexpression of CHOP enhanced the apoptosis of HKC induced by albumin, no significant difference was observed in the expression of PERK, whereas the phosphorylation of PERK decreased. Our data indicated that proteinuria induces ER stress in renal tubular cells, which may subsequently lead to tubular damage through a PERK-CHOP-dependent pathway. This ER stress-induced apoptosis pathway may contribute to renal tubulointerstitial injury by proteinuria in chronic kidney disease.

The Calpain, Caspase 12, Caspase 3 Cascade Leading to Apoptosis Is Altered in F508del-CFTR Expressing Cells

In cystic fibrosis (CF), the most frequent mutant variant of the cystic fibrosis transmembrane conductance regulator (CFTR), F508del-CFTR protein, is misfolded and retained in the endoplasmic reticulum (ER). We previously showed that the unfolded protein response (UPR) may be triggered in CF. Since prolonged UPR activation leads to apoptosis via the calcium-calpain-caspase-12-caspase-3 cascade and because apoptosis is altered in CF, our aim was to compare the ER stress-induced apoptosis pathway between wild type (Wt) and F508del-CFTR expressing cells. Here we show that the calcium-calpain-caspase-12-caspase-3 cascade is altered in F508del-CFTR expressing cells. We propose that this alteration is involved in the altered apoptosis triggering observed in CF.

Albumin induces endoplasmic reticulum stress and apoptosis in renal proximal tubular cells

Chronic proteinuria appears to be a key factor in tubulointerstitial damage. Recent studies have emphasized a pathogenic role of endoplasmic reticulum (ER) stress which is induced by the accumulation of misfolded proteins in ER, extracellular stress, etc. In the present study, we investigated ER stress and ER stress-induced apoptosis in proximal tubular cells (PTCs). Immortalized rat PTCs (IRPTCs) were cultured with bovine serum albumin (BSA). The viability of IRPTCs decreased proportionately with BSA overload in a time-dependent manner. Quantitative real-time polymerase chain reaction analysis revealed that 40 mg/ml BSA increases mRNA of ER stress markers by 7.7- and 4.6-fold (glucose-regulated protein 78 (GRP78) and oxygen-regulated protein 150 (ORP150), respectively) as compared to control. The increased expression of ORP150 and GRP78 in IRPTCs with albumin overload was detected by Western blot and immunofluorescence study. These in vitro observations were supported by in vivo studies, which demonstrated that ER stress proteins were upregulated at PTCs in experimental proteinuric rats. Furthermore, increased ER stress-induced apoptosis and activation of caspase-12 were observed in IRPTCs with albumin overload and kidneys of experimental proteinuric rats. We confirmed that apoptotic cell death was attenuated by co-incubation with caspase-3 inhibitor or calpain inhibitors. These results indicate that the ER stress-induced apoptosis pathway contributed to the insult of tubular cells by proteinuria. In conclusion, renal tubular cells exposed to high protein load suffer from ER stress. ER stress may subsequently lead to tubular damage by activation of caspase-12.