Peroxisome Proliferator-Activated Receptor-Gamma Reduces ER Stress and Inflammation via Targeting NGBR Expression

Increased Nogo-B receptor (NGBR) expression in the liver improves insulin sensitivity by reducing endoplasmic reticulum stress (ER stress) and activating the AMPK pathway, although it remains elusive the mechanisms by which NGBR is induced. In this study, we found that PPARγ ligands (rosiglitazone or pioglitazone) increased NGBR expression in hepatic cells and HUVECs. Furthermore, promoter analysis defined two PPREs (PPARγ-responsive elements) in the promoter region of NGBR, which was further confirmed by the ChIP assay. In vivo, using liver-specific PPARγ deficient (PPARγLKO) mice, we identified the key role of PPARγ expression in pioglitazone-induced NGBR expression. Meanwhile, the basal level of ER stress and inflammation was slightly increased by NGBR knockdown. However, the inhibitory effect of rosiglitazone on inflammation was abolished while rosiglitazone-inhibited ER stress was weakened by NGBR knockdown. Taken together, these findings show that NGBR is a previously unrecognized target of PPARγ activation and plays an essential role in PPARγ-reduced ER stress and inflammation.

Intestinal Disorder in Zebrafish Larvae (Danio rerio): The Protective Action of N-Palmitoylethanolamide-oxazoline

IBD (Inflammatory Bowel Disease) is an inflammatory disease affecting the gastrointestinal tract that is common in both humans and veterinarians. Several studies have revealed the pharmacological properties of the oxazoline of palmitoylethanolamide (PEAOXA). Zebrafish larvae were exposed to sodium dextran sulphate (DSS) to induce enterocolitis and study the protective action of PEAOXA. After repetitive exposure with 0.25% DSS, larvae presented gut alteration with an increase in mucus production. Furthermore, DSS exposure induced an increase in the inflammatory pathway in the intestine, related to an increase in the Endoplasmic-reticulum (ER) stress genes. PEAOXA exposure at a concentration of 10 mg/L decreased the DSS-induced gut damage and mucus production, as well as being able to reduce the inflammatory and ER stress-related genes expression. In conclusion, our results demonstrate that the alterations induced by repeated exposure to DSS were counteracted by PEAOXA action that was able to inhibit the increase in inflammation and ER stress involved in the progression of enterocolitis.

GDF11 alleviates neointimal hyperplasia in a rat model of artery injury by regulating endothelial NLRP3 inflammasome activation and rapid re-endothelialization

Background Neointimal hyperplasia induced by interventional surgery can lead to progressive obliteration of the vascular lumen, which has become a major factor affecting prognosis. The rate of re-endothelialization is known to be inversely related to neointima formation. Growth differentiation factor 11 (GDF11) is a secreted protein with anti-inflammatory, antioxidant, and antiaging properties. Recent reports have indicated that GDF11 can improve vascular remodeling by maintaining the differentiated phenotypes of vascular smooth muscle cells. However, it is not known whether and how GDF11 promotes re-endothelialization in vascular injury. The present study was performed to clarify the influence of GDF11 on re-endothelialization after vascular injury. Methods An adult Sprague–Dawley rat model of common carotid artery balloon dilatation injury was surgically established. A recombinant adenovirus carrying GDF11 was delivered into the common carotid artery to overexpress GDF11. Vascular re-endothelialization and neointima formation were assessed in harvested carotid arteries through histomolecular analysis. CCK-8 analysis, LDH release and Western blotting were performed to investigate the effects of GDF11 on endothelial NLRP3 inflammasome activation and relevant signaling pathways in vitro. Results GDF11 significantly enhanced re-endothelialization and reduced neointima formation in rats with balloon-dilatation injury by suppressing the activation of the NLRP3 inflammasome. Administration of an endoplasmic reticulum stress (ER stress) inhibitor, 4PBA, attenuated endothelial NLRP3 inflammasome activation induced by lysophosphatidylcholine. In addition, upregulation of LOX-1 expression involved elevated ER stress and could result in endothelial NLRP3 inflammasome activation. Moreover, GDF11 significantly inhibited NLRP3 inflammasome-mediated endothelial cell pyroptosis by negatively regulating LOX-1-dependent ER stress. Conclusions We conclude that GDF11 improves re-endothelialization and can attenuate vascular remodeling by reducing endothelial NLRP3 inflammasome activation. These findings shed light on new treatment strategies to promote re-endothelialization based on GDF11 as a future target.

MFG-E8 Maintains Cellular Homeostasis by Suppressing Endoplasmic Reticulum Stress in Pancreatic Exocrine Acinar Cells

Excessive endoplasmic reticulum (ER) stress contributes significantly to the pathogenesis of exocrine acinar damage in acute pancreatitis. Our previous study found that milk fat globule EGF factor 8 (MFG-E8), a lipophilic glycoprotein, alleviates acinar cell damage during AP via binding to αvβ3/5 integrins. Ligand-dependent integrin-FAK activation of STAT3 was reported to be of great importance for maintaining cellular homeostasis. However, MFG-E8’s role in ER stress in pancreatic exocrine acinar cells has not been evaluated. To study this, thapsigargin, brefeldin A, tunicamycin and cerulein + LPS were used to induce ER stress in rat pancreatic acinar cells in vitro. L-arginine- and cerulein + LPS-induced acute pancreatitis in mice were used to study ER stress in vivo. The results showed that MFG-E8 dose-dependently inhibited ER stress under both in vitro and in vivo conditions. MFG-E8 knockout mice suffered more severe ER stress and greater inflammatory response after L-arginine administration. Mechanistically, MFG-E8 increased phosphorylation of FAK and STAT3 in cerulein + LPS-treated pancreatic acinar cells. The presence of specific inhibitors of αvβ3/5 integrin, FAK or STAT3 abolished MFG-E8’s effect on cerulein + LPS-induced ER stress in pancreatic acinar cells. In conclusion, MFG-E8 maintains cellular homeostasis by alleviating ER stress in pancreatic exocrine acinar cells.

Caffeine and MDMA (ecstasy) exacerbate ER stress triggered by hyperthermia

Drugs of abuse can cause local and systemic hyperthermia, a known trigger of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). Another trigger of ER stress and UPR is ER calcium depletion which causes ER exodosis, the secretion of ER resident proteins. Club drugs such as 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) can create hyperthermic conditions in the brain and cause toxicity that is affected by the environmental temperature and the presence of other drugs, such as caffeine. Here we examine the secretion of ER resident proteins and activation of the UPR under combined exposure to MDMA and caffeine in a cellular model of hyperthermia. We show that hyperthermia triggers the secretion of normally ER resident proteins and that this aberrant protein secretion is potentiated by the presence of MDMA, caffeine, or a combination of the two drugs. Hyperthermia activates the UPR but the addition of MDMA or caffeine does not alter canonical UPR gene expression despite the drug effects on ER exodosis of UPR-related proteins. One exception was increased BiP/Grp78 mRNA levels in MDMA-treated cells exposed to hyperthermia. These findings suggest that club drug use under hyperthermic conditions exacerbates disruption of ER proteostasis contributing to cellular toxicity.

Endoplasmic Reticulum-Shaping Atlastin Proteins Facilitate KSHV Replication

Kaposi’s sarcoma-associated herpesvirus (KSHV) has two life cycle modes: the latent and lytic phases. The endoplasmic reticulum (ER) is the site for KSHV production. Furthermore, ER stress can trigger reactivation of KSHV. Little is known about the nature of the ER factors that regulate KSHV replication. Atlastin proteins (ATLs which include ATL1, ATL2, and ATL3) are large dynamin-related GTPases that control the structure and the dynamics of the ER membrane. Here, we show that ATLs can regulate KSHV lytic activation and infection. Overexpression of ATLs enhances KSHV lytic activation, whereas ATLs silence inhibits it. Intriguingly, we find that silencing of ATLs impairs the response of cells to ER stress, and ER stress can promote the lytic activation of KSHV. Our study establishes that ATLs plays a critically regulatory role in KSHV infection, thus expanding the known scope of biological processes controlled by ATLs to include KSHV infection.

Endoplasmic Reticulum Stress and Unfolded Protein Response Signaling in Plants

Plants are sensitive to a variety of stresses that cause various diseases throughout their life cycle. However, they have the ability to cope with these stresses using different defense mechanisms. The endoplasmic reticulum (ER) is an important subcellular organelle, primarily recognized as a checkpoint for protein folding. It plays an essential role in ensuring the proper folding and maturation of newly secreted and transmembrane proteins. Different processes are activated when around one-third of newly synthesized proteins enter the ER in the eukaryote cells, such as glycosylation, folding, and/or the assembling of these proteins into protein complexes. However, protein folding in the ER is an error-prone process whereby various stresses easily interfere, leading to the accumulation of unfolded/misfolded proteins and causing ER stress. The unfolded protein response (UPR) is a process that involves sensing ER stress. Many strategies have been developed to reduce ER stress, such as UPR, ER-associated degradation (ERAD), and autophagy. Here, we discuss the ER, ER stress, UPR signaling and various strategies for reducing ER stress in plants. In addition, the UPR signaling in plant development and different stresses have been discussed.

Zinc Supplementation Enhances the Pro-Death Function of UPR in Lymphoma Cells Exposed to Radiation

We have previously shown that Zinc supplementation triggered ER stress/UPR in cancer cells undergoing treatment by genotoxic agents, reactivated wtp53 in cancer cells harboring mutant p53 (mutp53) and potentiated the activity of wtp53 in those carrying wtp53. In this study, we used Zinc chloride alone or in combination with 2 Gy radiation to treat Primary Effusion Lymphoma (PEL) cells, an aggressive B-cell lymphoma associated with KSHV that harbors wt or partially functioning p53. We found that Zinc triggered a mild ER stress/UPR in these lymphoma cells and activated ERK1/2, molecule known to sustain cell survival in the course of UPR activation. In combination with radiations, Zinc triggered a stronger p53 activation that counteracted its mediated ERK1/2 phosphorylation, further upregulating the UPR molecule CHOP and promoting cell death. These data suggest that Zinc supplementation could be a promising strategy to reduce the doses of radiation and possibly of other DNA-damaging agents to obtain an efficient capacity to induce lymphoma cell death.