Electroacupuncture Pretreatment Mitigates Myocardial Ischemia/Reperfusion Injury via XBP1/GRP78/Akt Pathway

ER Stress Decreases Gene Expression Of Transmembrane Protein 117 Via Activation of PKR-like ER Kinase

Stress response is an inherent mechanism in the endoplasmic reticulum (ER). The inducers of ER cause a specific cascade of reactions, leading to gene expression. Transmembrane protein 117 (TMEM117) is in the ER and plasma membrane. In our previous study, TMEM117 protein expression was found to be decreased by an ER stress inducer. However, the mechanism underlying this decrease in TMEM117 protein expression remains unclear. This study aimed to elucidate the mechanism underlying the decrease in TMEM117 protein expression during ER stress and identify the unfolded protein response (UPR) pathway related to decreased TMEM117 protein expression. We showed that the gene expression levels of TMEM117 were decreased by ER stress inducers and were regulated by PKR-like ER kinase (PERK), indicating that TMEM117 protein expression was regulated by the signaling pathway. Surprisingly, gene knockdown of activating transcription factor 4 (ATF4) downstream of PERK did not affect the gene expression of TMEM117. These results suggest that TMEM117 protein expression during ER stress is transcriptionally regulated by PERK but not by ATF4. TMEM117 has a potential to be a new therapeutic target against ER stress-related diseases.

ADSCs-exo attenuates hepatic ischemia-reperfusion injury after hepatectomy by inhibiting endoplasmic reticulum stress and inflammation

Hepatic ischemia-reperfusion (I/R) injury commonly occurs during liver surgery. Exosomes from adipose-derived stem cells (ADSCs-exo) induce a hepatoprotective effect during hepatic I/R injury. This study aimed to investigate the possible mechanism by which ADSCs-exo attenuates hepatic I/R injury in rats. Rats were randomly divided into four groups: Sham, I30R + PH, ADSCs, and ADSCs-exo groups. Liver tissues were collected immediately after 24 h of reperfusion for further analyses. The content of inflammatory factors in liver tissue was detected using enzyme-linked immunosorbent assay. The pathological changes in liver tissue were analyzed using HE staining. Transmission electron microscopy was used to visualize the ultrastructural changes of hepatocytes. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were used to detect the expression of endoplasmic reticulum stress (ERS)-related genes and proteins. Liver histomorphology and hepatocyte ultrastructure changes improved after ADSCs-exo treatment. Moreover, ADSCs-exo treatment significantly downregulated tumor necrosis factor-α, interleukin-1β (IL-1β), and IL-6 levels while upregulating IL-10 levels. Western blot analysis suggested that the protein expressions of GRP78, p-PERK, p-eIF2α, p-IRE1α, XBP1s, ATF-6, ATF-4, CHOP, p-JNK, cleaved-Caspase-3, cleaved Caspase-9, and cleaved Caspase-12 significantly decreased after ADSCs-exo treatment. RT-qPCR results demonstrated that mRNA expression of GRP78, IRE1α, XBP1, ATF-6, ATF-4, CHOP, JNK, Caspase-3, Caspase-9, and Caspase-12 markedly reduced after ADSCs-exo treatment. In conclusion, ADSCs-exo protects against hepatic I/R injury after hepatectomy by inhibiting ERS and inflammation. Therefore, ADSCs-exo can be considered as a viable option for the treatment of hepatic I/R injury.

Molecular Mechanism Underlying Role of the XBP1s in Cardiovascular Diseases

Spliced X-box binding protein-1 (XBP1s) is a protein that belongs to the cAMP-response element-binding (CREB)/activating transcription factor (ATF) b-ZIP family with a basic-region leucine zipper (bZIP). There is mounting evidence to suggest that XBP1s performs a critical function in a range of different cardiovascular diseases (CVDs), indicating that it is necessary to gain a comprehensive knowledge of the processes involved in XBP1s in various disorders to make progress in research and clinical therapy. In this research, we provide a summary of the functions that XBP1s performs in the onset and advancement of CVDs such as atherosclerosis, hypertension, cardiac hypertrophy, and heart failure. Furthermore, we discuss XBP1s as a novel therapeutic target for CVDs.

Repair effect of the poly (D,L-lactic acid) nanoparticle containing tauroursodeoxycholic acid-eluting stents on endothelial injury after stent implantation

Background

Chronic endoplasmic reticulum stress (ERS) plays a crucial role in cardiovascular diseases. Thus, it can be considered a therapeutic target for these diseases. In this study, poly (D,L-lactic acid) (PDLLA) nanoparticle-eluting stents loaded with tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, was fabricated to assess their ability to reduce endothelial cell apoptosis and promote re-endothelialization after stent implantation.

Materials and methods

PDLLA nanoparticles loaded with TUDCA were prepared via the emulsification-solvent evaporation method. The cumulative release rates of TUDCA were measured in vitro via high-performance liquid chromatography. The carotid arteries of rabbits were subsequently implanted with stents in vivo. The rabbits were then sacrificed after 4 weeks for scanning electron microscopy. Meanwhile, TUDCA concentration in the homogenate of the peripheral blood and distal vascular tissue after stent implantation was measured. The effect of TUDCA on ERS, apoptosis, and human umbilical vein endothelial cell (HUVEC) function was investigated in vitro by performing cell migration assay, wound healing assay, cell proliferation assays, endoplasmic reticulum (ER)-specific fluorescence staining, immunofluorescence, and western blotting.

Results

TUDCA nanoparticles were released slowly over 28 days. In addition, TUDCA-eluting stents enhanced re-endothelialization and accelerated the recovery of endotheliocytes in vivo. ERS and apoptosis significantly increased in H₂O₂-treated HUVECs in vitro. Meanwhile, TUDCA reduced apoptosis and improved function by inhibiting ERS in H₂O₂-treated HUVECs. Decreased rates of apoptosis and ERS were observed after silencing XBP-1s in H₂O₂-treated HUVECs.

Conclusion

TUDCA can inhibit apoptosis and promote re-endothelialization after stent implantation by inhibiting IRE/XBP1s-related ERS. These results indicate the potential therapeutic application of TUDCA as a drug-coated stent.

Interaction between COX-2 and ER stress is involved in the apoptosis-induced myocardial ischemia/reperfusion injury

PURPOSE

Apoptosis induced by excessive endoplasmic reticulum (ER) stress is accompanied by the occurrence and progression of myocardial ischemia/reperfusion (I/R) injury. COX-2 is also known to affect the development of I/R damage in myocardium. However, the interaction between COX-2 and ER stress in aggravating myocardial I/R lesion is not well characterized. Therefore, the purpose of our research was to explore the interaction between COX-2 and ER stress on myocardial apoptosis.

METHODS

The left anterior descending (LAD) coronary artery was ligatured with a 6-0# suture for 0.5 hours and subsequently subjected to reperfusion for 3 hours to simulate myocardial I/R in mice. Oxygen glucose deprivation/reoxygenation (OGD/R) was performed on H9c2 cells to construct an in vitro model of this experiment. NS398 (COX-2 specific inhibitor) and Salubrinal (Sal, ER stress inhibitor) were administered to assess the function of COX-2 and ER stress in myocardial I/R impairment. CCK-8 assay was used to evaluate the viability of H9c2 cells under different treatment conditions. TUNEL and Hoechst staining were used to detect the occurrence of apoptosis. Infarct area/area at risk and Hematoxylin-eosin stained sections were assessed after I/R. Protein expressions of glucose-regulated protein 78 (GRP78), COX-2, phosphorylation of eukaryotic translation initiation factor 2 alpha (p-eIF2α), CCAAT/enhancer-binding protein homologous protein (CHOP), and Cleaved caspase 3 in the myocardium were examined using Western blotting. Changes in Cleaved caspase 3 expression in myocardial slices were measured by immunohistochemistry.

RESULTS

Sal or NS398 partly reduced I/R-induced damage as testified by the apparent decrease in infarct size after I/R and reduced cell viability following OGD/R. Sal distinctly increased p-eIF2α, but caused decreased expression of COX-2, Cleaved caspase 3, and ER stress-associated proteins after I/R, suggesting that Sal effectively inhibited ER stress, apoptosis, and COX-2. Pretreatment with NS398 blocked I/R or OGD/R-induced upregulation of COX-2, Cleaved caspase 3, and ER stress-related marker proteins.

CONCLUSIONS

Interaction of COX-2 and ER stress regulates apoptosis and contributes to Myocardial lesion induced by I/R.