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Aim: Myocardial ischaemia/reperfusion (I/R) produces structural and functional alterations depending on the duration of ischaemia. Brief ischaemia followed by reperfusion causes reversible contractile dysfunction (stunned heart) but long-lasting ischaemia followed by reperfusion can result in irreversible injury with cell death. Events during I/R can alter endoplasmic reticulum (ER) function leading to the accumulation of unfolded/misfolded proteins. The resulting ER stress induces activation of several signal transduction pathways, known as unfolded protein response (UPR). Experimental evidence shows that UPR contributes to cell death in irreversible I/R injury; however, there is still uncertainty for its occurrence in the stunned myocardium. This study investigated the ER stress response and its functional impact on the post-ischaemic cardiac performance of the stunned heart., Methods: Perfused rat hearts were subjected to 20 minutes of ischaemia followed by 30 minutes of reperfusion. UPR markers were evaluated by qRT-PCR and western blot. Post-ischaemic mechanical recovery was measured in absence and presence of two chemical chaperones: tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA)., Results: Analysis of mRNA and protein levels of various ER stress effectors demonstrated that different UPR signalling cascades, involving both pro-survival and pro-apoptotic pathways, are activated. Inhibition of the UPR with chemical chaperones improved the post-ischaemic recovery of cardiac mechanical function without affecting the I/R-induced increase in oxidative stress., Conclusion: Our results suggest that prevention of ER stress by chemical chaperones could be a therapeutic tool to limit deterioration of the contractile function in clinical settings in which the phenomenon of myocardial stunning is present., (© 2019 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.)

Endoplasmic reticulum-thioflavin T (ER-ThT ), a thioflavin T-based fluorescent chemosensor, was developed to detect protein aggregates in the endoplasmic reticulum (ER) and was applied to live cells under various forms of ER stress. Upon dithiothreitol (DTT)-induced reductive denaturation of lysozyme and albumin, the intensity was increased in a protein concentration-dependent way, following a nonfluorescent lag phase. ER-ThT detects protein aggregates rather than unfolded proteins in solution, and the protein aggregation can be visualized in the presence of lipid membranes or native proteins. Within live HeLa cells, ER-ThT is localized in the ER and its fluorescence was dramatically increased upon ER stress induction by DTT, Thapsigargin, or Brefeldin A. Moreover, in the presence of ER stress modulators (tauroursodeoxycholic acid, trimethylamine N -oxide, or 4-phenylbutyric acid), also known as chemical chaperones, the fluorescence under Thapsigargin treatment was suppressed to the level of the control group. Thus, ER-ThT is capable of detecting the accumulation of protein aggregates under ER stress in living cells and acts as an in vitro screening tool for ER stress modulators, putative prodrugs against ER-related proteopathy. Overall, the results strongly suggest that protein aggregation is intricately involved in the activation of the unfolded protein response following ER stress.

Protein misfolding may be the result of a variety of different processes that disrupt the ability of a protein to form a thermodynamically stable tertiary structure that allows it to perform its proper function. In this chapter, we explore the nature of a protein's form that allows it to have a stable tertiary structure, and examine specific mutation that are known to occur in the coding regions of DNA that disrupt a protein's ability to be folded into a thermodynamically stable tertiary structure. We examine the consequences of these protein misfoldings in terms of the endoplasmic reticulum stress response and resulting unfolded protein response. These conditions are specifically related to renal diseases. Further, we explore novel therapeutics, pharmacological chaperones, that are being developed to alleviate the disease burden associated with protein misfolding caused by mutations. These interventions aim to stabilize protein folding intermediates and allow proper folding to occur as well as prevent protein aggregation and the resulting pathophysiological consequences., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Sedentary lifestyle coupled with excessive consumption of high caloric food has been related to the epidemic increase of non-alcoholic fatty liver disease, which can progress from simple steatosis to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis and, eventually, may culminate in hepatocellular carcinoma. Although the precise mechanisms underlying the progression of NASH are not completely understood, endoplasmic reticulum (ER) dysfunction seems to play a key role in the process. Hepatic ER stress has been associated to hepatic steatosis, insulin resistance, inflammation, oxidative stress and hepatocyte death, contributing to liver dysfunction. Physical exercise seems to be the most effective preventive and therapeutic non-pharmacological strategy to mitigate several features related to NASH, possibly targeting most of the referred mechanisms associated with the pathophysiology of ER-related NASH. Nevertheless, little is known about the impact of physical exercise on NASH-related ER stress. In this review, we will discuss the ER stress associated to NASH conditions and highlight the possible benefits of physical exercise in the attenuation and/or reversion of NASH-related ER stress., (Copyright © 2015. Published by Elsevier Inc.)

Genome-wide association studies (GWASs) have identified many disease-associated variant alleles, but understanding whether and how different genes/loci interact requires a platform for probing how the variant alleles act mechanistically. Isogenic mutant human embryonic stem cells (hESCs) provide an unlimited resource to derive and study human disease-relevant cells. Here, we focused on CDKAL1, linked by GWASs to diabetes. Through transcript profiling, we find that expression of the metallothionein (MT) gene family, also linked by GWASs to diabetes, is significantly downregulated in CDKAL1−/− cells that have been differentiated to insulin-expressing pancreatic beta-like cells. Forced MT1E expression rescues both hypersensitivity of CDKAL1 mutant cells to glycolipotoxicity and pancreatic beta-cell dysfunction in vitro and in vivo. MT1E functions at least in part through relief of ER stress. This study establishes an isogenic hESC-based platform to study the interaction of GWAS-identified diabetes gene variants and illuminate the molecular network impacting disease progression.

Summary Genome-wide association studies (GWASs) have identified many disease-associated variant alleles, but understanding whether and how different genes/loci interact requires a platform for probing how the variant alleles act mechanistically. Isogenic mutant human embryonic stem cells (hESCs) provide an unlimited resource to derive and study human disease-relevant cells. Here, we focused on CDKAL1 , linked by GWASs to diabetes. Through transcript profiling, we find that expression of the metallothionein ( MT ) gene family, also linked by GWASs to diabetes, is significantly downregulated in CDKAL1 −/− cells that have been differentiated to insulin-expressing pancreatic beta-like cells. Forced MT1E expression rescues both hypersensitivity of CDKAL1 mutant cells to glycolipotoxicity and pancreatic beta-cell dysfunction in vitro and in vivo. MT1E functions at least in part through relief of ER stress. This study establishes an isogenic hESC-based platform to study the interaction of GWAS-identified diabetes gene variants and illuminate the molecular network impacting disease progression. [ABSTRACT FROM AUTHOR]