Chronic Intermittent Hypobaric Hypoxia Improves Cardiac Function through Inhibition of Endoplasmic Reticulum Stress.

We investigated the role of endoplasmic reticulum stress (ERS) in chronic intermittent hypobaric hypoxia (CIHH)-induced cardiac protection. Adult male Sprague-Dawley rats were exposed to CIHH treatment simulating 5000 m altitude for 28 days, 6 hours per day. The heart was isolated and perfused with Langendorff apparatus and subjected to 30-min ischemia followed by 60-min reperfusion. Cardiac function, infarct size, and lactate dehydrogenase (LDH) activity were assessed. Expression of ERS molecular chaperones (GRP78, CHOP and caspase-12) was assayed by western blot analysis. CIHH treatment improved the recovery of left ventricular function and decreased cardiac infarct size and activity of LDH after I/R compared to control rats. Furthermore, CIHH treatment inhibited over-expression of ERS-related factors including GRP78, CHOP and caspase-12. CIHH-induced cardioprotection and inhibition of ERS were eliminated by application of dithiothreitol, an ERS inducer, and chelerythrine, a protein kinase C (PKC) inhibitor. In conclusion CIHH treatment exerts cardiac protection against I/R injury through inhibition of ERS via PKC signaling pathway.

Single prolonged stress induces dysfunction of endoplasmic reticulum in a rat model of post-traumatic stress disorder.

The aim of the present study, was to investigate the involvement of the endoplasmic reticulum (ER) in post-traumatic stress disorder (PTSD) by detecting changes of ER chaperone protein 78 and ER-resident caspase 12 in the basolateral amygdala after exposure to single prolonged stress (SPS). The established rat model of PTSD was generated by exposure of the animals to SPS. The expression of glucose-regulated protein 78 (GRP78) was examined by immunofluorescence, western blot and reverse transcription-polymerase chain reaction (RT-PCR), and the expression of caspase 12 was examined by western blot and RT-PCR. The morphological changes of the ER were detected by transmission electron microscopy. The results showed that GRP78 expression significantly increased when compared to that in the control group 1 day after SPS exposure (P<0.05). The expression of caspase 12 was also significantly upregulated after SPS exposure and peaked at 7 days following SPS (P<0.05). Morphological evaluation showed that a tumescent ER, ER vacuolization and degranulation of the ER were present following SPS. In conclusion, the findings of the present study suggested that SPS induced GRP78 and caspase 12 upregulation and morphological changes of the ER in the amygdala, which may play important roles in the pathogenesis of PTSD rats.

TNF/TNFR1 pathway and endoplasmic reticulum stress are involved in ofloxacin-induced apoptosis of juvenile canine chondrocytes.

BACKGROUND AND PURPOSE: Quinolones cause obvious cartilaginous lesions in juvenile animals by chondrocyte apoptosis, which results in the restriction of their use in pediatric and adolescent patients. Studies showed that chondrocytes can be induced to produce TNFα, and the cisternae of the endoplasmic reticulum in quinolone-treated chondrocytes become dilated. We investigated whether TNF/TNFR1 pathway and endoplasmic reticulum stress (ERs) are involved in ofloxacin (a typical quinolone)-induced apoptosis of juvenile canine chondrocytes. EXPERIMENTAL APPROACH: Canine juvenile chondrocytes were treated with ofloxacin. Cell survival and apoptosis rates were determined with MTT method and flow cytometry, respectively. The gene expression levels of the related signaling molecules (TNFα, TNFR1, TRADD, FADD and caspase-8) in death receptor pathways and main apoptosis-related molecules (calpain, caspase-12, GADD153 and GRP78) in ERs were measured by qRT-PCR. The gene expression of TNFR1 was suppressed with its siRNA. The protein levels of TNFα, TNFR1 and caspase-12 were assayed using Western blotting. KEY RESULTS: The survival rates decreased while apoptosis rates increased after the chondrocytes were treated with ofloxacin. The mRNA levels of the measured apoptosis-related molecules in death receptor pathways and ERs, and the protein levels of TNFα, TNFR1 and caspase-12 increased after the chondrocytes were exposed to ofloxacin. The downregulated mRNA expressions of TNFR1, Caspase-8 and TRADD, and the decreased apoptosis rates of the ofloxacin-treated chondrocytes occurred after TNFR1-siRNA interference. CONCLUSIONS AND IMPLICATIONS: Ofloxacin-induced chondrocyte apoptosis in a time- and concentration-dependent fashion. TNF/TNFR1 pathway and ERs are involved in ofloxacin-induced apoptosis of juvenile canine chondrocytes in the early stage.

Caspase cascade pathways in apoptosis of oral lichen planus.

OBJECTIVE: Apoptosis is frequently found in oral lichen planus (OLP) lesions, but the pathways leading to apoptosis are unknown. STUDY DESIGN: This study focused on analysis of caspase expression which is essential for apoptosis. Expression of caspases 2, 3, 8, 9, and 12 was studied in 70 biopsy samples from atrophic OLP to identify which cascade pathway, extrinsic or intrinsic, is of importance in apoptosis in OLP. RESULTS: Caspase-2 expression was present in every sample, and >70% of the epithelial cells were positive in 33% of the lesions. More than 70% of the epithelial cells expressed caspase-12 in 84% of the specimens. Caspase-8 expression was shown totally in 87% of the specimens. No caspase-3 expression was found in 57% of the samples, and caspase-9 expression was absent in the entire OLP specimen. CONCLUSIONS: The high frequency of intrinsic apoptotic pathway markers caspases 2 and 12 indicates intracellular stress in atrophic OLP epithelial cells.

Mechanism of the neurotoxic effect of PBDE-47 and interaction of PBDE-47 and PCB153 in enhancing toxicity in SH-SY5Y cells.

Polybrominated diphenyl ethers (PBDEs) are used in large quantities as flame-retardant additives, especially in electrical appliances and textiles. Because of their structural similarity, PBDEs are thought to have toxicities similar to those of polychlorinated biphenyls (PCBs), which are well-known persistent compounds. Both 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) and 2,2',4,4',5, 5'-hexachlorobiphenyl (PCB153) can coexist in the environment and human tissues as dominant congeners of PBDEs and PCBs, respectively. To explore the mechanisms of the neurotoxic effect of PBDE-47 and the interaction in combination with PCB153, cell viability, lactate dehydrogenase (LDH) leakage, intracellular Ca2+ concentration ([Ca2+]i), apoptosis and expression levels of death associated protein kinase (DAPK), caspase3, caspase12 and cytochrome c mRNA and proteins were measured in SH-SY5Y cells treated with PBDE-47 (0, 1, 5, 10 micromol/L) and/or PCB153 (5 micromol/L) for 24 h. Compared to controls, the cell viabilities were clearly decreased (P<0.05), and LDH leakage, [Ca2+]i and apoptosis were significantly increased (P<0.05). Furthermore, expression levels of DAPK and caspase3 mRNA, caspase12, as well as cytochrome c mRNA and proteins were markedly increased (P<0.05), while pro-caspase3 proteins were significantly decreased (P<0.05). A positive correlation between [Ca2+]i and percentage of apoptotic cells (r=0.86, P<0.05) and an interaction between PBDE-47 and PCB153 (P<0.05) were observed. We conclude that PBDE-47 can induce SH-SY5Y cell apoptosis via three classic apoptosis pathways and interact with PCB153 to enhance neurotoxicity.

Prolonged endoplasmic reticulum stress induces apoptotic cell death in an experimental model of chronic cyclosporine nephropathy.

BACKGROUND/AIMS: Apoptosis contributes to cyclosporine (CsA)-induced renal cell death. This study tested the effects of CsA-induced endoplasmic reticulum (ER) stress on apoptotic cell death in an experimental model of chronic CsA nephropathy. METHODS: CsA (15 mg/kg per day) was given to rats for 7 or 28 days. The ER stress response was evaluated with BiP expression, and the proapoptotic response was assessed with CHOP and caspase 12 expression. ER structure was evaluated by transmission electron microscopy, and apoptotic cell death was detected with TUNEL staining. RESULTS: Short-term treatment of CsA for 7 days activated both the ER stress response (induction of BiP mRNA and protein) and the proapoptotic response (upregulation of caspase 12 and CHOP mRNAs and proteins). However, long-term treatment with CsA for 28 days decreased BiP and further increased CHOP. The imbalance between the two responses coincided with the timing of the appearance of apoptotic cell death and the disruption of the ER structure. CONCLUSION: Prolonged CsA-induced ER stress causes apoptotic cell death by depleting molecular chaperones and activating the proapoptotic pathway.

Ischemic acidosis causes apoptosis in coronary endothelial cells through activation of caspase-12.

OBJECTIVE: Myocardial ischemia has been shown to induce apoptosis of endothelial cells (EC). However, the mechanism of this endothelial injury is still poorly understood. To analyse the signaling pathway of ischemia-induced EC apoptosis was the aim of the present study. METHODS: The primary culture of rat coronary EC was exposed to simulated ischemia (glucose-free anoxia at pH(o) 6.4). Apoptosis was defined by staining of nuclei with Hoechst-33342 and TUNEL. Cytosolic Ca2+ and pH were measured with Fura-2 and BCECF, respectively. RESULTS: Apoptosis (29.2+/-1.7% of cells) induced by exposure to simulated ischemia for 2 h was accompanied by cytosolic Ca2+ overload (1090+/-52 nmol/l) and acidosis (pHi = 6.52+/-0.13). Simulated ischemia had no significant effect on caspase-8 cleavage, but induced cleavage of caspase-3 and caspase-12 and led to a slight release of cytochrome C. Prevention of cytosolic acidosis (anoxia at pH(o) 7.4) had no effect on cytochrome C release, but significantly reduced apoptosis, attenuated cytosolic Ca2+ overload, and prevented cleavage of caspase-12. A similar effect was achieved by inhibition of Ca2+ release channels in the endoplasmic reticulum with ryanodine and xestospongin C. Knock-down of caspase-12 with small interfering RNA suppressed caspase-3 activation and reduced apoptotic cell number by about 70%. CONCLUSION: Acidosis, rather than anoxia, is an important trigger of apoptosis in EC under simulated ischemia. The main pathway of the simulated ischemia-induced apoptosis consists of the Ca2+ leak from the ER followed by activation of caspase-12 and caspase-3.