The Circulating GRP78/BiP Is a Marker of Metabolic Diseases and Atherosclerosis: Bringing Endoplasmic Reticulum Stress into the Clinical Scenario

The Functions of SARS-CoV-2 Receptors in Diabetes-Related Severe COVID-19

Angiotensin-converting enzyme 2 (ACE2) is considered a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor of high importance, but due to its non-ubiquitous expression, studies of other proteins that may participate in virus internalisation have been undertaken. To date, many alternative receptors have been discovered. Their functioning may provide an explanation for some of the events observed in severe COVID-19 that cannot be directly explained by the model in which ACE2 constitutes the central point of infection. Diabetes mellitus type 2 (T2D) can induce severe COVID-19 development. Although many mechanisms associated with ACE2 can lead to increased SARS-CoV-2 virulence in diabetes, proteins such as basigin (CD147), glucose-regulated protein 78 kDa (GRP78), cluster of differentiation 4 (CD4), transferrin receptor (TfR), integrins α5β1/αvβ3, or ACE2 co-receptors neuropilin 2 (NRP2), vimentin, and even syalilated gangliosides may also be responsible for worsening the COVID-19 course. On the other hand, some others may play protective roles. Understanding how diabetes-associated mechanisms can induce severe COVID-19 via modification of virus receptor functioning needs further extensive studies.

Niacin, an innovative protein kinase-C-dependent endoplasmic reticulum stress reticence in murine Parkinson's disease

AIMS

Niacin (NIA) supplementation showed effectiveness against Parkinson's disease (PD) in clinical trials. The depletion of NAD and endoplasmic reticulum stress response (ERSR) are implicated in the pathogenesis of PD, but the potential role for NAD precursors on ERSR is not yet established. This study was undertaken to decipher NIA molecular mechanisms against PD-accompanied ERSR, especially in relation to PKC.

METHODS

Alternate-day-low-dose-21 day-subcutaneous exposure to rotenone (ROT) in rats induced PD. Following the 5th ROT injection, rats received daily doses of either NIA alone or preceded by the PKC inhibitor tamoxifen (TAM). Extent of disease progression was assessed by behavioral, striatal biochemical and striatal/nigral histopathological/immunohistochemical analysis.

KEY FINDINGS

Via activating PKC/LKB1/AMPK stream, NIA post-treatment attenuated the ERSR reflected by the decline in ATF4, ATF6 and XBP1s to downregulate the apoptotic markers, CHOP/GADD153, p-JNK and active caspase-3. Such amendments congregated in motor activity/coordination improvements in open field and rotarod tasks, enhanced grid test latency and reduced overall PD scores, while boosting nigral/striatal tyrosine hydroxylase immunoreactivity and increasing intact neurons (Nissl stain) in both SNpc and striatum that showed less neurodegeneration (H&E stain). To different extents, TAM reverted all the NIA-related actions to prove PKC as a fulcrum in conveying the drug neurotherapeutic potential.

SIGNIFICANCE

PKC activation is a pioneer mechanism in the drug ERSR inhibitory anti-apoptotic modality to clarify NIA promising clinical and potent preclinical anti-PD efficacy. This kinase can be tagged as a druggable target for future add-on treatments that can assist dopaminergic neuronal aptitude against this devastating neurodegenerative disease.

Long non-coding RNA-mediated modulation of endoplasmic reticulum stress under pathological conditions

Endoplasmic reticulum (ER) stress, which ensues from an overwhelming protein folding capacity, activates the unfolded protein response (UPR) in an effort to restore cellular homeostasis. As ER stress is associated with numerous diseases, it is highly important to delineate the molecular mechanisms governing the ER stress to gain insight into the disease pathology. Long non-coding RNAs, transcripts with a length of over 200 nucleotides that do not code for proteins, interact with proteins and nucleic acids, fine-tuning the UPR to restore ER homeostasis via various modes of actions. Dysregulation of specific lncRNAs is implicated in the progression of ER stress-related diseases, presenting these molecules as promising therapeutic targets. The comprehensive analysis underscores the importance of understanding the nuanced interplay between lncRNAs and ER stress for insights into disease mechanisms. Overall, this review consolidates current knowledge, identifies research gaps and offers a roadmap for future investigations into the multifaceted roles of lncRNAs in ER stress and associated diseases to shed light on their pivotal roles in the pathogenesis of related diseases.

IRE1α: from the function to the potential therapeutic target in atherosclerosis

Inositol requiring enzyme 1 (IRE1) is generally thought to control the most conserved pathway in the unfolded protein response (UPR). Two isoforms of IRE1, IRE1α and IRE1β, have been reported in mammals. IRE1α is a ubiquitously expressed protein whose knockout shows marked lethality. In contrast, the expression of IRE1β is exclusively restricted in the epithelial cells of the respiratory and gastrointestinal tracts, and IRE1β-knockout mice are phenotypically normal. As research continues to deepen, IRE1α was showed to be tightly linked to inflammation, lipid metabolism regulation, cell death and so on. Growing evidence also suggests an important role for IRE1α in promoting atherosclerosis (AS) progression and acute cardiovascular events through disrupting lipid metabolism balance, facilitating cells apoptosis, accelerating inflammatory responses and promoting foam cell formation. In addition, IRE1α was recognized as novel potential therapeutic target in AS prevention. This review provides some clues about the relationship between IRE1α and AS, hoping to contribute to further understanding roles of IRE1α in atherogenesis and to be helpful for the design of novel efficacious therapeutics agents targeting IRE1α-related pathways.

Intestinal heat shock proteins in metabolic syndrome: Novel mediators of obesity and its comorbidities resolution after metabolic surgery

Over the past 40 years, the prevalence of obesity has risen dramatically, reaching epidemic proportions. Metabolic surgery has proven to be highly effective in treating obesity, leading to significant improvements or complete resolution of obesity-related comorbidities. Research conducted in both animals and humans suggests that the metabolic benefits achieved through metabolic surgery cannot be solely attributed to weight loss. Indeed, there has been an increasing recognition of intestinal inflammation as a novel factor influencing obesity. The gastrointestinal tract is continuously exposed to dietary components, particularly diets rich in saturated fats, which are known to contribute to obesity. It is now widely accepted that heat shock proteins can be released from various cells including intestinal epithelial cells and act as proinflammatory signals. Several studies have shown that circulating levels of glucose-regulated protein 78 (GRP78) are increased in subjects with obesity and correlate with the severity of the disease. Moreover, mice with a partial knockout of GRP78 are protected from diet-induced obesity. In this review, we discuss the role of GRP78 in the development of obesity. Several evidence suggests that GRP78 can influence adipogenesis, lipid droplets stabilization, insulin resistance, and liver steatosis. We also provide an update on GRP78 regulation following metabolic surgery, focusing on the bypass of the small intestine as a key factor for GRP78 secretion. Finally, we discuss the potential role of monoclonal antibodies against GRP78 as a treatment for obesity.

Activation of the PERK-CHOP signaling pathway during endoplasmic reticulum stress contributes to olanzapine-induced dyslipidemia

Olanzapine (OLZ) is a widely prescribed antipsychotic drug with a relatively ideal effect in the treatment of schizophrenia (SCZ). However, its severe metabolic side effects often deteriorate clinical therapeutic compliance and mental rehabilitation. The peripheral mechanism of OLZ-induced metabolic disorders remains abstruse for its muti-target activities. Endoplasmic reticulum (ER) stress is implicated in cellular energy metabolism and the progression of psychiatric disorders. In this study, we investigated the role of ER stress in the development of OLZ-induced dyslipidemia. A cohort of 146 SCZ patients receiving OLZ monotherapy was recruited, and blood samples and clinical data were collected at baseline, and in the 4th week, 12th week, and 24th week of the treatment. This case-control study revealed that OLZ treatment significantly elevated serum levels of endoplasmic reticulum (ER) stress markers GRP78, ATF4, and CHOP in SCZ patients with dyslipidemia. In HepG2 cells, treatment with OLZ (25, 50 μM) dose-dependently enhanced hepatic de novo lipogenesis accompanied by SREBPs activation, and simultaneously triggered ER stress. Inhibition of ER stress by tauroursodeoxycholate (TUDCA) and 4-phenyl butyric acid (4-PBA) attenuated OLZ-induced lipid dysregulation in vitro and in vivo. Moreover, we demonstrated that activation of PERK-CHOP signaling during ER stress was a major contributor to OLZ-triggered abnormal lipid metabolism in the liver, suggesting that PERK could be a potential target for ameliorating the development of OLZ-mediated lipid dysfunction. Taken together, ER stress inhibitors could be a potentially effective intervention against OLZ-induced dyslipidemia in SCZ.

Cholesterol-induced HRD1 reduction accelerates vascular smooth muscle cell senescence via stimulation of endoplasmic reticulum stress-induced reactive oxygen species

Senescence of vascular smooth muscle cells (VSMCs) is a key contributor to plaque vulnerability in atherosclerosis (AS), which is affected by endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) production. However, the crosstalk between ER stress and ROS production in the pathogenesis of VSMC senescence remains to be elucidated. ER-associated degradation (ERAD) is a complex process that clears unfolded or misfolded proteins to maintain ER homeostasis. HRD1 is the major E3 ligase in mammalian ERAD machineries that catalyzes ubiquitin conjugation to the unfolded or misfolded proteins for degradation. Our results showed that HRD1 protein levels were reduced in human AS plaques and aortic roots from ApoE-/- mice fed with high-fat diet (HFD), along with the increased ER stress response. Exposure to cholesterol in VSMCs activated inflammatory signaling and induced senescence, while reduced HRD1 protein expression. CRISPR Cas9-mediated HRD1 knockout (KO) exacerbated cholesterol- and thapsigargin-induced cell senescence. Inhibiting ER stress with 4-PBA (4-Phenylbutyric acid) partially reversed the ROS production and cell senescence induced by HRD1 deficiency in VSMCs, suggesting that ER stress alone could be sufficient to induce ROS production and senescence in VSMCs. Besides, HRD1 deficiency led to mitochondrial dysfunction, and reducing ROS production from impaired mitochondria partly reversed HRD1 deficiency-induced cell senescence. Finally, we showed that the overexpression of HDR1 reversed cholesterol-induced ER stress, ROS production, and cellular senescence in VSMCs. Our findings indicate that HRD1 protects against senescence by maintaining ER homeostasis and mitochondrial functionality. Thus, targeting HRD1 function may help to mitigate VSMC senescence and prevent vascular aging related diseases. TRIAL REGISTRATION: A real-world study based on the discussion of primary and secondary prevention strategies for coronary heart disease, URL:https://www.clinicaltrials.gov, the trial registration number is [2022]-02-121-01.

Intricate subcellular journey of nanoparticles to the enigmatic domains of endoplasmic reticulum

It is evident that site-specific systemic drug delivery can reduce side effects, systemic toxicity, and minimal dosage requirements predominantly by delivering drugs to particular pathological sites, cells, and even subcellular structures. The endoplasmic reticulum (ER) and associated cell organelles play a vital role in several essential cellular functions and activities, such as the synthesis of lipids, steroids, membrane-associated proteins along with intracellular transport, signaling of Ca2+, and specific response to stress. Therefore, the dysfunction of ER is correlated with numerous diseases where cancer, neurodegenerative disorders, diabetes mellitus, hepatic disorder, etc., are very common. To achieve satisfactory therapeutic results in certain diseases, it is essential to engineer delivery systems that can effectively enter the cells and target ER. Nanoparticles are highly biocompatible, contain a variety of cargos or payloads, and can be modified in a pliable manner to achieve therapeutic effectiveness at the subcellular level when delivered to specific organelles. Passive targeting drug delivery vehicles, or active targeting drug delivery systems, reduce the nonselective accumulation of drugs while reducing side effects by modifying them with small molecular compounds, antibodies, polypeptides, or isolated bio-membranes. The targeting of ER and closely associated organelles in cells using nanoparticles, however, is still unsymmetrically understood. Therefore, here we summarized the pathophysiological prospect of ER stress, involvement of ER and mitochondrial response, disease related to ER dysfunctions, essential therapeutics, and nanoenabled modulation of their delivery to optimize therapy.

Effects of 3021 meal replacement powder protect NAFLD via suppressing the ERS, oxidative stress and inflammatory responses

Objective

To explore the specific protective mechanism of 3021 meal replacement powder (MRP) against non-alcoholic fatty liver disease (NAFLD).

Materials and Methods

C57BL/6J male mice were divided into four groups: control group, 3021 MRP group, model group and test group. The lipid accumulation and endoplasmic reticulum stress (ERS)-related proteins in hepatocytes of mice were detected by hematoxylin-eosin (HE) staining, oil red O staining and Western blotting.

Results

The expressions of GRP78, GRP94, p-PERK and p-IRE1α were significantly inhibited in test group compared with those in model group. The protein expressions of p-NF-κB, p-JNK, IL-1β, IL-18 and NOX4 in test group were also significantly lower than those in model group. In vivo and in vitro experiments revealed that the body weight and lipid droplet content, and the expressions of ERS-related proteins (including BIP and XBP-1) in liver tissues all significantly declined in model group compared with those in 3021 MRP group.

Conclusion

In conclusion, 3021 MRP can greatly reduce lipid accumulation by inhibiting ERS, oxidative stress and inflammatory response in NAFLD.

Disturbed hemodynamics and oxidative stress interaction in endothelial dysfunction and AAA progression: Focus on Nrf2 pathway

Hemodynamic shear stress is one of the major factors that are involved in the pathogenesis of many cardiovascular diseases including atherosclerosis and abdominal aortic aneurysm (AAA), through its modulatory effect on the endothelial cell's redox homeostasis and mechanosensitive gene expression. Among important mechanisms, oxidative stress, endoplasmic reticulum stress activation, and the subsequent endothelial dysfunction are attributed to disturbed blood flow and low shear stress in the vascular curvature and bifurcations which are considered atheroprone regions and aneurysm occurrence spots. Many pathways were shown to be involved in AAA progression. Of particular interest from recent findings is, the (Nrf2)/Keap-1 pathway, where Nrf2 is a transcription factor that has antioxidant properties and is strongly associated with several CVDs, yet, the exact mechanism by which Nrf2 alleviates CVDs still to be elucidated. Nrf2 expression is closely affected by shear stress and was shown to participate in AAA. In the current review paper, we discussed the link between disturbed hemodynamics and its effect on Nrf2 as a mechanosensitive gene and its role in the development of endothelial dysfunction which is linked to the progression of AAA.

COVID-19, Obesity, and GRP78: Unraveling the Pathological Link

The coronavirus disease 2019 (COVID-19) pandemic, driven by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to an unprecedented global surge in infections and fatalities. Notably, obesity has emerged as an important susceptibility factor for COVID-19; however, the pathological mechanisms for this remain poorly understood. Recent studies proposed a role for glucose-regulated protein 78 (GRP78), a protein implicated in both obesity and metabolic syndrome, which may function as a binding partner and/or co-receptor for SARS-CoV-2. Given its crucial involvement in diverse biological processes, GRP78 likely plays a major role in multiple facets of the viral life cycle and the pathology of COVID-19. This perspective review discusses the potential contributions of GRP78 to the dynamics of SARS-CoV-2 infection and pathology, particularly in the context of obesity. The primary objective is to facilitate a deeper understanding of the pathogenesis of COVID-19. Through this exploration, we aim to illuminate the complex interactions underpinning the nexus of COVID-19, obesity, and GRP78, ultimately paving the way for informed therapeutic strategies and preventive measures.

Unveiling the dark side of glucose-regulated protein 78 (GRP78) in cancers and other human pathology: a systematic review

Glucose-Regulated Protein 78 (GRP78) is a chaperone protein that is predominantly expressed in the lumen of the endoplasmic reticulum. GRP78 plays a crucial role in protein folding by assisting in the assembly of misfolded proteins. Under cellular stress conditions, GRP78 can translocate to the cell surface (csGRP78) were it interacts with different ligands to initiate various intracellular pathways. The expression of csGRP78 has been associated with tumor initiation and progression of multiple cancer types. This review provides a comprehensive analysis of the existing evidence on the roles of GRP78 in various types of cancer and other human pathology. Additionally, the review discusses the current understanding of the mechanisms underlying GRP78's involvement in tumorigenesis and cancer advancement. Furthermore, we highlight recent innovative approaches employed in downregulating GRP78 expression in cancers as a potential therapeutic target.

Salvianolic acid A attenuates inflammation-mediated atherosclerosis by suppressing GRP78 secretion of endothelial cells

ETHNOPHARMACOLOGICAL RELEVANCE

Salvianolic acid A (SAA) is the main active component of the classic anti-atherosclerotic drug Salvia miltiorrhiza Bunge. Inflammation-induced infiltration of monocyte/macrophages into the vascular wall is the initiating step in atherogenesis, and targeted blocking of this step may provide a promising avenue for the precise treatment of atherosclerosis. However, the effect of salvianolic acid A on macrophages is still unknown.

AIM OF THE STUDY

To evaluate the effect of SAA on macrophage infiltration and the underlying mechanism of SAA against atherosclerosis.

MATERIALS AND METHODS

Vascular endothelial cells were stimulated with lipopolysaccharide (LPS) to simulate the inflammatory environment, and its effect on monocyte/macrophages was evaluated. Mass spectrometry was used to identify the proteins that play a key role and further validated them. LncRNA sequencing, western blot analysis, RNA immunoprecipitation, and RNA pulldown were used to elucidate the mechanism of SAA against atherosclerosis. Finally, ApoE^-/- mice were fed a high-fat diet to creat an in vivo atherosclerosis model. Secretory GRP78 content, lipid levels, plaque area, macrophage infiltration, and degree of inflammation were assessed by standard assays after 16 weeks of intragastric administration of SAA or biweekly tail vein injections of GRP78 antibody.

RESULTS

After LPS stimulation, the increased secretion of GRP78 recruits circulating monocyte/macrophages and drives monocyte/macrophage adhesion and invasion into the vascular intima to promote atherosclerosis progression. Interestingly, SAA exerts anti-atherosclerosis effects by inhibiting the secretion of GRP78. Further mechanistic studies indicated that SAA upregulates the expression of lncRNA NR2F2-AS1, which reverses the abnormal localization of the KDEL receptor (KDELR) caused by inflammation. It promotes the homing of GRP78 from the Golgi apparatus to the endoplasmic reticulum rather than secreting outside the cell.

CONCLUSION

SAA alleviates atherosclerosis by inhibiting GRP78 secretion via the lncRNA NR2F2-AS1-KDELR axis. The findings not only provide a new direction for the precise therapy of atherosclerosis based on secretory GRP78 but also elucidate the pharmacological mechanism of SAA against atherosclerosis, putting the foundation for further development and clinical application of SAA drugs.

Diallyl disulfide alleviates hypercholesterolemia induced by a western diet by suppressing endoplasmic reticulum stress in apolipoprotein E-deficient mice

BACKGROUND

The endoplasmic reticulum (ER) plays a pivotal role in maintaining cellular metabolic homeostasis. ER stress refers to the accumulation of misfolded proteins, which can trigger an unfolded protein response for survival or death in the cells. Diallyl disulfide (DADS), a major active compound in garlic, has many health benefits for patients with metabolic diseases, especially cardiovascular or fatty liver diseases. However, its role in attenuating hypercholesterolemia by suppressing ER stress remains unknown. Therefore, in this study, we determined whether DADS supplementation could reduce ER stress in apolipoprotein E-deficient (ApoE^-/-) mice fed a Western-type diet (WD).

METHODS

ApoE^-/- mice were fed either a WD alone or a WD supplemented with 0.1% DADS for 12 weeks (n = 10). Levels of plasma total cholesterol, triglyceride, leptin, and insulin were determined. Western blotting was performed to measure protein levels involved in ER stress markers. Histology and Immunostaining were performed on aortic root sections to confirm the effect of DADS on histology and expression of ER chaperone protein GRP78.

RESULTS

The metabolic parameters showed that increases in fat weight, leptin resistance, and hypercholesterolemia were reversed in DADS-supplemented mice (p < 0.05). In addition, DADS ameliorated not only the protein of ER stress markers, phospho-eukaryotic initiation factor 2 subunit alpha and C/EBP homologous protein in the liver (p < 0.05) but also glucose-related protein 78 localization in the aorta.

CONCLUSIONS

This indicates that DADS inhibits diet-induced hypercholesterolemia, at least in parts by regulating ER stress markers. DADS may be a good candidate for treating individuals with diet-induced hypercholesterolemia.

AICAR Ameliorates Non-Alcoholic Fatty Liver Disease via Modulation of the HGF/NF-κB/SNARK Signaling Pathway and Restores Mitochondrial and Endoplasmic Reticular Impairments in High-Fat Diet-Fed Rats

Non-alcoholic fatty liver disease (NAFLD) is a global health problem characterized by altered lipid and redox homeostasis, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress. The AMP-dependent kinase (AMPK) agonist 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) has been shown to improve the outcome of NAFLD in the context of AMPK activation, yet the underlying molecular mechanism remains obscure. This study investigated the potential mechanism(s) of AICAR to attenuate NAFLD by exploring AICAR's effects on the HGF/NF-κB/SNARK axis and downstream effectors as well as mitochondrial and ER derangements. High-fat diet (HFD)-fed male Wistar rats were given intraperitoneal AICAR at 0.7 mg/g body weight or left untreated for 8 weeks. In vitro steatosis was also examined. ELISA, Western blotting, immunohistochemistry and RT-PCR were used to explore AICAR's effects. NAFLD was confirmed by steatosis score, dyslipidemia, altered glycemic, and redox status. HGF/NF-κB/SNARK was downregulated in HFD-fed rats receiving AICAR with improved hepatic steatosis and reduced inflammatory cytokines and oxidative stress. Aside from AMPK dominance, AICAR improved hepatic fatty acid oxidation and alleviated the ER stress response. In addition, it restored mitochondrial homeostasis by modulating Sirtuin 2 and mitochondrial quality gene expression. Our results provide a new mechanistic insight into the prophylactic role of AICAR in the prevention of NAFLD and its complications.

Long non-coding RNAs TUG1 and MEG3 in patients with type 2 diabetes and their association with endoplasmic reticulum stress markers

BACKGROUND

Long non-coding RNAs (lncRNAs), including taurine upregulated gene 1 (TUG1), metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), and maternally expressed 3 (MEG3) play a regulatory role in endoplasmic reticulum (ER) stress. The present study aimed to investigate the expression of these lncRNAs in patients with type 2 diabetes and their association with biochemical and ER stress parameters.

MATERIALS AND METHODS

Participants included 57 patients with diabetes and 32 healthy individuals. Real-time PCR was performed to assess MALAT1, TUG1, MEG3, ATF4, and CHOP gene expression in peripheral blood mononuclear cells. Plasma GRP78, advanced glycation end products (AGEs), and insulin were measured using enzyme-linked immunosorbent assay (ELISA), and insulin resistance (IR) was calculated by the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

The expression of TUG1, MEG3, ATF4, and CHOP genes was significantly increased in the patients with diabetes compared to healthy individuals. MALAT1 gene expression was also higher in patients group; although it did not reach significant levels. TUG1 and MEG3 expression revealed significant positive correlations with the indices of glycemic control, including FBS, HbA1c, HOMA-IR, and AGEs, as well as markers of ER stress. MALAT1 expression was also positively correlated with ATF4 and AGEs.

CONCLUSION

The expression levels of TUG1 and MEG3 lncRNAs were increased in patients with diabetes and were associated with glycemic control and components of ER stress. Thus, these lncRNAs might be considered appropriate markers to identify ER stress due to hyperglycemia.

The therapeutic mavericks: Potent immunomodulating chaperones capable of treating human diseases

Two major chaperones, calreticulin (CRT) and binding immunoglobulin protein (GRP78/BiP) dependent on their location, have immunoregulatory or anti-inflammatory functions respectively. CRT induces pro-inflammatory cytokines, dendritic cell (DC) maturation and activates cytotoxic T cells against tumours. By contrast, GRP78/BiP induces anti-inflammatory cytokines, inhibits DC maturation and heightens T-regulatory cell responses. These latter functions rebalance immune homeostasis in inflammatory diseases, such as rheumatoid arthritis. Both chaperones are therapeutically relevant agents acting primarily on monocytes/DCs. Endogenous exposure of CRT on cancer cell surfaces acts as an 'eat-me' signal and facilitates improved elimination of stressed and dying tumour cells by DCs. Therefore, therapeutics that promote endogenous CRT translocation to the cell surface can improve the removal of cancer cells. However, infused recombinant CRT dampens this cancer cell eradication by binding directly to the DCs. Low levels of endogenous BiP appear as a surface biomarker of endoplasmic reticulum (ER) stress in some types of tumour cells, a reflection of cells undergoing proliferation, in which resulting hypoxia and nutrient deprivation perturb ER homeostasis triggering the unfolded protein response, leading to increased expression of GRP78/BiP and altered cellular location. Conversely, infusion of an analogue of GRP78/BiP (IRL201805) can lead to long-term immune resetting and restoration of immune homeostasis. The therapeutic potential of both chaperones relies on them being relocated from their intracellular ER environment. Ongoing clinical trials are employing therapeutic interventions to either enhance endogenous cell surface CRT or infuse IRL201805, thereby triggering several disease-relevant immune responses leading to a beneficial clinical outcome.

GRP78 Activity Moderation as a Therapeutic Treatment against Obesity

Glucose-regulated protein 78 (GRP78), a molecular chaperone, is overexpressed in patients suffering from obesity, fatty liver, hyperlipidemia and diabetes. GRP78, therefore, can be not only a biomarker to predict the progression and prognosis of obesity and metabolic diseases but also a potential therapeutic target for anti-obesity treatment. In this paper, GRP78 inhibitors targeting its ATPase domain have been reviewed. Small molecules and proteins that directly bind GRP78 have been described. Putative mechanisms of GRP78 in regulating lipid metabolism were also summarized so as to investigate the role of GRP78 in obesity and other related diseases and provide a theoretical basis for the development and design of anti-obesity drugs targeting GRP78.

Cellular stress modulates severity of the inflammatory response in lungs via cell surface BiP

Inflammation is a central pathogenic feature of the acute respiratory distress syndrome (ARDS) in COVID-19. Previous pathologies such as diabetes, autoimmune or cardiovascular diseases become risk factors for the severe hyperinflammatory syndrome. A common feature among these risk factors is the subclinical presence of cellular stress, a finding that has gained attention after the discovery that BiP (GRP78), a master regulator of stress, participates in the SARS-CoV-2 recognition. Here, we show that BiP serum levels are higher in COVID-19 patients who present certain risk factors. Moreover, early during the infection, BiP levels predict severe pneumonia, supporting the use of BiP as a prognosis biomarker. Using a mouse model of pulmonary inflammation, we observed increased levels of cell surface BiP (cs-BiP) in leukocytes during inflammation. This corresponds with a higher number of neutrophiles, which show naturally high levels of cs-BiP, whereas alveolar macrophages show a higher than usual exposure of BiP in their cell surface. The modulation of cellular stress with the use of a clinically approved drug, 4-PBA, resulted in the amelioration of the lung hyperinflammatory response, supporting the anti-stress therapy as a valid therapeutic strategy for patients developing ARDS. Finally, we identified stress-modulated proteins that shed light into the mechanism underlying the cellular stress-inflammation network in lungs.

ER-stress-induced secretion of circulating glucose-regulated protein 78kDa (GRP78) ameliorates pulmonary artery smooth muscle cell remodelling

Pulmonary arterial hypertension (PAH) is driven by vascular remodelling due to inflammation and cellular stress, including endoplasmic reticulum stress (ER stress). The main ER-stress chaperone, glucose-regulated protein 78 kDa (GRP78), is known to have protective effects in inflammatory diseases through extracellular signalling. The aim of this study is to investigate its significance in PAH. Human pulmonary arterial smooth muscle cells (PASMC) were stimulated with compounds that induce ER stress, after which the secretion of GRP78 into the cell medium was analysed by western blot. We found that when ER stress was induced in PASMC, there was also a time-dependent secretion of GRP78. Next, naïve PASMC were treated with conditioned medium (CM) from the ER-stressed donor PASMC. Incubation with CM from ER-stressed PASMC reduced the viability, oxidative stress, and expression of inflammatory and ER-stress markers in target cells. These effects were abrogated when the donor cells were co-treated with Brefeldin A to inhibit active secretion of GRP78. Direct treatment of PASMC with recombinant GRP78 modulated the expression of key inflammatory markers. Additionally, we measured GRP78 plasma levels in 19 PAH patients (Nice Group I) and correlated the levels to risk stratification according to ESC guidelines. Here, elevated plasma levels of GRP78 were associated with a favourable risk stratification. In conclusion, GRP78 is secreted by PASMC under ER stress and exhibits protective effects from the hallmarks of PAH in vitro. Circulating GRP78 may serve as biomarker for risk adjudication of patients with PAH. Proposed mechanism of ER-stress-induced GRP78 secretion by PASMC. Extracellular GRP78 can be measured as a circulating biomarker and is correlated with favourable clinical characteristics. Conditioned medium from ER-stressed PASMC reduces extensive viability, ROS formation, inflammation, and ER stress in target cells. These effects can be abolished by blocking protein secretion in donor cells by using Brefeldin A.

GRP78, a Novel Host Factor for SARS-CoV-2: The Emerging Roles in COVID-19 Related to Metabolic Risk Factors

The outbreak of coronavirus disease 19 (COVID-19), caused by the infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in an unprecedented amount of infection cases and deaths, leading to the global health crisis. Despite many research efforts, our understanding of COVID-19 remains elusive. Recent studies have suggested that cell surface glucose-regulated protein 78 (GRP78) acts as a host co-receptor for SARS-CoV-2 infection and is related to COVID-19 risks, such as older age, obesity, and diabetes. Given its significance in a wide range of biological processes, such as protein homeostasis and cellular signaling, GRP78 might also play an important role in various stages of the viral life cycle and pathology of SARS-CoV-2. In this perspective, we explore the emerging and potential roles of GRP78 in SARS-CoV-2 infection. Additionally, we discuss the association with COVID-19 risks and symptoms. We hope this review article will be helpful to understand COVID-19 pathology and promote attention and study of GRP78 from many clinical and basic research fields.

Vulnerability of The Male Reproductive System to SARS-CoV-2 Invasion: Potential Role for The Endoplasmic Reticulum Chaperone Grp78/HSPA5/BiP

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) may adversely affect male reproductive tissues and male<br />fertility. This concern is elicited by the higher susceptibility and mortality rate of men to the SARS-CoV-2 mediated coronavirus disease-19 (COVID-19), compared to the women. SARS-CoV-2 enters host cells after binding to a functional receptor named angiotensin-converting enzyme-2 (ACE2) and then replicates in the host cells and gets released into the plasma. SARS-CoVs use the endoplasmic reticulum (ER) as a site for viral protein synthesis and processing, as well as glucose-regulated protein 78 (Grp78) is a key ER chaperone involved in protein folding by preventing newly synthesized proteins from aggregation.<br />Therefore, we analyzed Grp78 expression in various human organs, particularly male reproductive organs, using Broad<br />Institute Cancer Cell Line Encyclopedia (CCLE), the Genotype-Tissue Expression (GTEx), and Human Protein Atlas online<br />datasets. Grp78 is expressed in male reproductive tissues such as the testis, epididymis, prostate, and seminal vesicle. It can facilitate the coronavirus entry into the male reproductive tract, providing an opportunity for its replication. This link between the SARS-CoV-2 and the Grp78 protein could become a therapeutic target to mitigate its harmful effects on male fertility.

Serum glucose-regulated protein 78 (GRP78) levels in COVID-19-associated mucormycosis: results of a case-control study

BACKGROUND

In experimental models, the expression of glucose-regulated protein 78 (GRP78) in endothelial cells played a role in the pathogenesis of mucormycosis. However, the role of GRP78 in COVID-19-associated mucormycosis (CAM) has not been studied. We hypothesized that serum GRP78 levels are elevated in subjects with CAM.

OBJECTIVE

To compare the serum GRP78 levels in subjects with CAM and COVID-19 controls without mucormycosis.

DESIGN AND SETTING

We performed a hospital-based, case-control study between 1 April 2021 and 31 May 2021.

PARTICIPANTS

We enrolled 24 subjects each of CAM and COVID-19 subjects without mucormycosis. We also measured serum GRP78 levels in ten healthy controls.

EXPOSURE

The primary exposure studied was serum GRP78 concentration, estimated using a commercially available ELISA kit in stored serum samples.

RESULTS

We found the mean ± standard deviation (SD) serum GRP78 levels significantly higher (p = 0.0001) among the CAM (374.3 ± 127.3 pg/mL) than the COVID-19 (246.4 ± 67.0 pg/mL) controls. The proportion of subjects with an abnormal GRP78 level (> mean [184.8 pg/mL] plus two SD [23.2 pg/mL] of GRP78 from healthy participants) was 87.5% and 45.8% in the CAM group and COVID-19 controls, respectively. Serum GRP78 level was independently associated with CAM (odds ratio 1.011; 95% confidence interval [1.002-1.019]) after adjusting for diabetes mellitus and hypoxemia during acute COVID-19.

CONCLUSION

Serum GRP78 levels were significantly higher in CAM than in COVID-19 controls. Further studies are required to the role of GRP78 in the pathogenesis of CAM.

Ziprasidone suppresses pancreatic adenocarcinoma cell proliferation by targeting GOT1 to trigger glutamine metabolism reprogramming

Pancreatic ductal adenocarcinoma (PDAC) is a fatal malignant tumor whose effective treatment has not been found. The redox state and proliferative activity of PDAC cells are maintained by the conversion of aspartic acid in the cytoplasm into oxaloacetate though aspartate aminotransferase 1 (GOT1). Therefore, GOT1 inhibitors as a potential approach for treating PDAC have attracted more attention of researchers. Ziprasidone effectively inhibited GOT1 in a non-competitive manner. The potential cytotoxicity and anti-proliferation effects of ziprasidone against PDAC cells in vitro and in vivo were evaluated. Ziprasidone can induce glutamine metabolism disorder and redox state imbalance of PDAC cells by targeting GOT1, thereby inhibiting proliferation, preventing migration, and inducing apoptosis. Ziprasidone displayed significant in vivo antitumor efficacy in SW1990 cell-derived xenografts. What's more, knockdown of GOT1 in SW1990 reduced the anti-proliferative effects of ziprasidone. As a novel GOT1 inhibitor, ziprasidone may be a lead compound for the treatment of PDAC. KEY MESSAGES: Small molecule inhibitors targeting GOT1 may provide a therapeutic target in PDAC. Ziprasidone effectively inhibited GOT1 enzyme in a non-competitive manner. Ziprasidone repressed glutamine metabolism and inhibited the growth of tumor in vivo. Knockdown of GOT1 decreased the anti-proliferative effects of ziprasidone.

Circulating TRB3 and GRP78 levels in type 2 diabetes patients: crosstalk between glucose homeostasis and endoplasmic reticulum stress

PURPOSE

Endoplasmic reticulum (ER) stress is implicated in the development of type 2 diabetes mellitus (T2DM) and insulin resistance. Tribbles homolog 3 (TRB3) is a pseudokinase upregulated by ER stress and hyperglycemia. Glucose-regulated protein 78 (GRP78) is an ER stress protein that is overexpressed under ER stress conditions. The current study aimed to investigate serum levels of TRB3 and GRP78, as an ER stress marker, in T2DM patients and their correlations with the metabolic profile.

METHODS

Fifty-seven patients with type 2 diabetes and 23 healthy control subjects were evaluated for serum concentrations of TRB3, GRP78, and AGEs by enzyme-linked immunosorbent assay (ELISA). Fasting plasma glucose (FPG), HbA1c, lipid profile, TNF-α and insulin were also measured, and insulin resistance was calculated using a homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Serum concentrations of TRB3, GRP78, AGEs, and TNF-α were significantly higher in T2DM patients compared to the healthy controls. Moreover, a statistically significant positive correlation was observed between plasma concentrations of TRB3 and FPG, HbA1c, HOMA-IR, and AGE. GRP78 levels were positively correlated with HbA1c and AGEs. There was also a positive correlation between GRP78 and TRB3. AGEs levels were positively correlated with the levels of FPG, HbA1c, HOMA-IR, and TNF-α.

CONCLUSION

The current findings suggest that TRB3 and GRP78 may contribute to the pathogenesis of T2DM and might be considered as a therapeutic targets for the treatment of this disease.

Mechanisms contributing to adverse outcomes of COVID-19 in obesity

A growing amount of epidemiological data from multiple countries indicate an increased prevalence of obesity, more importantly central obesity, among hospitalized subjects with COVID-19. This suggests that obesity is a major factor contributing to adverse outcome of the disease. As it is a metabolic disorder with dysregulated immune and endocrine function, it is logical that dysfunctional metabolism contributes to the mechanisms behind obesity being a risk factor for adverse outcome in COVID-19. Emerging data suggest that in obese subjects, (a) the molecular mechanisms of viral entry and spread mediated through ACE2 receptor, a multifunctional host cell protein which links to cellular homeostasis mechanisms, are affected. This includes perturbation of the physiological renin-angiotensin system pathway causing pro-inflammatory and pro-thrombotic challenges (b) existent metabolic overload and ER stress-induced UPR pathway make obese subjects vulnerable to severe COVID-19, (c) host cell response is altered involving reprogramming of metabolism and epigenetic mechanisms involving microRNAs in line with changes in obesity, and (d) adiposopathy with altered endocrine, adipokine, and cytokine profile contributes to altered immune cell metabolism, systemic inflammation, and vascular endothelial dysfunction, exacerbating COVID-19 pathology. In this review, we have examined the available literature on the underlying mechanisms contributing to obesity being a risk for adverse outcome in COVID-19.

PDIA4, a new endoplasmic reticulum stress protein, modulates insulin resistance and inflammation in skeletal muscle

INTRODUCTION

Endoplasmic reticulum (ER) stress has emerged as a key player in insulin resistance (IR) progression in skeletal muscle. Recent reports revealed that ER stress-induced the expression of protein disulfide isomerase family a member 4 (PDIA4), which may be involved in IR-related diseases. A previous study showed that metformin modulated ER stress-induced IR. However, it remained unclear whether metformin alleviated IR by regulating PDIA4 expression in skeletal muscle.

METHODS

Herein, we used palmitate-induced IR in C2C12 cells and a high-fat diet-induced IR mouse model to document the relations between metformin, IR, and PDIA4.

RESULTS

In C2C12 cells, palmitate-induced IR increased inflammatory cytokines and PDIA4 expression. Besides, knocking down PDIA4 decreased palmitate-induced IR and inflammation in C2C12 cells. Furthermore, metformin modulated PDIA4 expression and alleviated IR both in vitro and in vivo. In addition, serum PDIA4 concentrations are associated with IR and inflammatory cytokines levels in human subjects.

DISCUSSION

Thus, this study is the first to demonstrate that PDIA4 participates in the metformin-induced effects on skeletal muscle IR and indicates that PDIA4 is a potential novel therapeutic target for directly alleviating IR.

Relationship Between Fatty Acid Binding Protein 4 and Liver Fat in Individuals at Increased Cardiometabolic Risk

Background: Liver steatosis is considered the onset of the non-alcoholic fatty liver disease (NAFLD), a major public health challenge. Nevertheless, NAFLD detection and diagnosis remain a difficult task. Fatty acid binding protein 4 (FABP4) has been proposed as potential biomarker for the ectopic fat accumulation in non-adipose tissues, although its role reflecting liver steatosis in metabolic patients is not fully explored. The aim of this study was to assess the relationship between FABP4 and the fatty liver index (FLI) in metabolic patients and to evaluate its potential role in the fatty liver disease.

Methods: A cross-sectional study involving 389 participants at increased cardiometabolic risk was performed. FLI was calculated in order to assess liver fatty disease and a FLI ≥ 60 was considered to define liver steatosis. The serum FABP4 levels were assessed by using a sandwich enzyme-linked immunosorbent assay. Multivariable regression models were used to examine the associations of FABP4 with fatty liver after adjusting for demographic and clinical characteristics.

Results: Both, FLI and serum FABP4 levels were upregulated in diabetic, obese, and metabolic syndrome patients. Serum FABP4 levels were higher in individuals with liver steatosis. Serum FABP4 were robustly associated with FLI in metabolic patients in both linear and logistic regression analyses.

Conclusion: Our findings show that the serum FABP4 is associated to liver steatosis in metabolic patients.

Possible Involvement of Adipose Tissue in Patients With Older Age, Obesity, and Diabetes With SARS-CoV-2 Infection (COVID-19) via GRP78 (BIP/HSPA5): Significance of Hyperinsulinemia Management in COVID-19

Aging, obesity, and diabetes are major risk factors for the severe progression and outcome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (coronavirus disease 2019 [COVID-19]), but the underlying mechanism is not yet fully understood. In this study, we found that the SARS-CoV-2 spike protein physically interacts with cell surface GRP78, which promotes the binding to and accumulation in ACE2-expressing cells. GRP78 was highly expressed in adipose tissue and increased in humans and mice with older age, obesity, and diabetes. The overexpression of GRP78 was attributed to hyperinsulinemia in adipocytes, which was in part mediated by the stress-responsive transcription factor XBP-1s. Management of hyperinsulinemia by pharmacological approaches, including metformin, sodium-glucose cotransporter 2 inhibitor, or β3-adrenergic receptor agonist, decreased GRP78 gene expression in adipose tissue. Environmental interventions, including exercise, calorie restriction, fasting, or cold exposure, reduced the gene expression of GRP78 in adipose tissue. This study provides scientific evidence for the role of GRP78 as a binding partner of the SARS-CoV-2 spike protein and ACE2, which might be related to the severe progression and outcome of COVID-19 in patients with older age, obesity, and diabetes. The management of hyperinsulinemia and the related GRP78 expression could be a therapeutic or preventative target.

Connecting the Dots: Interplay of Pathogenic Mechanisms between COVID-19 Disease and Mucormycosis

Coronavirus disease (COVID-19)-associated mucormycosis (CAM) is an emerging threat globally, especially in India. More than 40,000 CAM cases have been reported in India. The emergence of CAM cases in India has been attributed to environmental, host, and iatrogenic factors. Mucorales spore burden has been reported globally; however, their presence is higher in tropical countries such as India, contributing to the emergence of CAM. Before the COVID-19 pandemic, patients with diabetes mellitus, haematological malignancies, solid organ transplants, corticosteroid therapy and neutropenia were more prone to mucormycosis, whereas in COVID-19 patients, virus-induced endothelial dysfunction, hyperglycaemia, and immune dysfunction following corticosteroid use increase the risk of acquiring mucormycosis. The interaction of Mucorales spores with the epithelial cells, followed by endothelial invasion, is a crucial step in the pathogenesis of mucormycosis. Endothelial damage and increased endothelial receptor expression induced by COVID-19 infection may predispose patients to CAM. COVID-19 infection may directly induce hyperglycaemia by damaging beta cells of the pancreas or by corticosteroid therapy, which may contribute to CAM pathogenesis. Iron acquisition from the host, especially in diabetic ketoacidosis (DKA) or deferoxamine therapy, is an important virulence trait of Mucorales. Similarly, the hyperferritinaemia caused by COVID-19 may act as a source of iron for Mucorales growth and invasion. In addition, corticosteroid treatment reduces or abolishes the innate immune functions of phagocytic cells contributing to the pathogenesis of CAM. This review aims to discuss primarily the host and iatrogenic factors shared between COVID-19 and mucormycosis that could explain the emergence of CAM.

Molecular Dysfunctions of Mitochondria-Associated Endoplasmic Reticulum Contacts in Atherosclerosis

Atherosclerosis is a chronic lipid-driven inflammatory disease that results in the formation of lipid-rich and immune cell-rich plaques in the arterial wall, which has high morbidity and mortality in the world. The mechanism of atherosclerosis is still unclear now. Potential hypotheses involved in atherosclerosis are chronic inflammation theory, lipid percolation theory, mononuclear-macrophage theory, endothelial cell (EC) injury theory, and smooth muscle cell (SMC) mutation theory. Changes of phospholipids, glucose, critical proteins, etc. on mitochondria-associated endoplasmic reticulum membrane (MAM) can cause the progress of atherosclerosis. This review describes the structural and functional interaction between mitochondria and endoplasmic reticulum (ER) and explains the role of critical molecules in the structure of MAM during atherosclerosis.

Circulating chaperones in patients with aortic valve stenosis undergoing TAVR: impact of concomitant chronic kidney disease

Chronic kidney disease (CKD) is a frequent comorbidity of aortic valve stenosis (AVS). Circulating chaperones have emerged as both effectors and prognostic markers for various diseases. We investigated the role of circulating chaperones in patients with severe AVS undergoing transcatheter aortic valve replacement (TAVR). In this observational cohort study, 159 consecutive patients undergoing TAVR were included and serum levels of Glucose-regulated protein 78 (GRP78) and heat shock protein 27 (HSP27) were measured by ELISA. The primary end point was defined as 1-year mortality. Patients with lower levels of circulating GRP78 (<1347 ng/mL) had an increased 1-year mortality rate compared to patients with higher levels of GRP78 (25.0% vs 10.3%, P = 0.026). GRP78 was associated with lower 1-year mortality in a univariate analysis (HR 0.354, P = 0.047). After adjusting for age, sex, several comorbidities and biomarkers, GRP78 (HR 0.295, P = 0.024) and CKD (HR 2.809, P = 0.044) remained independent predictors of the primary end point of 1-year mortality in a multivariate analysis. Patients with concomitant CKD had significantly higher levels of HSP27 compared to patients without CKD (1690 pg/mL vs 1076 pg/mL, P = 0.0109). In patients with CKD, elevated HSP27 was identified as a protective marker (1-year mortality: 9.6% vs 31.4%, log-rank P = 0.0166). Using cut-off values for GRP78 and HSP27 we were able to stratify patients with CKD undergoing TAVR into 4 groups with distinct mortality rates (50% vs 22.2% vs 24% vs 7.9%, log-rank P = 0.0170). GRP78 is an overall predictor of mortality after TAVR, while the combination of GRP78 and HSP27 helps to predict mortality in patients with CKD receiving TAVR.

Mechanisms linking endoplasmic reticulum (ER) stress and microRNAs to adipose tissue dysfunction in obesity

Over accumulation of lipids in adipose tissue disrupts metabolic homeostasis by affecting cellular processes. Endoplasmic reticulum (ER) stress is one such process affected by obesity. Biochemical and physiological alterations in adipose tissue due to obesity interfere with adipose ER functions causing ER stress. This is in line with increased irregularities in other cellular processes such as inflammation and autophagy, affecting overall metabolic integrity within adipocytes. Additionally, microRNAs (miRNAs), which can post-transcriptionally regulate genes, are differentially modulated in obesity. A better understanding and identification of such miRNAs could be used as novel therapeutic targets to fight against diseases. In this review, we discuss ways in which ER stress participates as a common molecular process in the pathogenesis of obesity-associated metabolic disorders. Moreover, our review discusses detailed underlying mechanisms through which ER stress and miRNAs contribute to metabolic alteration in adipose tissue in obesity. Hence, identifying mechanistic involvement of miRNAs-ER stress cross-talk in regulating adipose function during obesity could be used as a potential therapeutic approach to combat chronic diseases, including obesity.

Pathological Crosstalk Between Oxidized LDL and ER Stress in Human Diseases: A Comprehensive Review

The oxidative modification of the major cholesterol carrying lipoprotein, oxLDL, is a biomarker as well as a pathological factor in cardiovascular diseases (CVD), type 2 diabetes mellitus (T2DM), obesity and other metabolic diseases. Perturbed cellular homeostasis due to physiological, pathological and pharmacological factors hinder the proper functioning of the endoplasmic reticulum (ER), which is the major hub for protein folding and processing, lipid biosynthesis and calcium storage, thereby leading to ER stress. The cellular response to ER stress is marked by a defensive mechanism called unfolded protein response (UPR), wherein the cell adapts strategies that favor survival. Under conditions of excessive ER stress, when the survival mechanisms fail to restore balance, UPR switches to apoptosis and eliminates the defective cells. ER stress is a major hallmark in metabolic syndromes such as diabetes, non-alcoholic fatty liver disease (NAFLD), neurological and cardiovascular diseases. Though the pathological link between oxLDL and ER stress in cardiovascular diseases is well-documented, its involvement in other diseases is still largely unexplored. This review provides a deep insight into the common mechanisms in the pathogenicity of diseases involving oxLDL and ER stress as key players. In addition, the potential therapeutic intervention of the targets implicated in the pathogenic processes are also explored.

Obesity as a Risk Factor for Severe COVID-19 and Complications: A Review

Emerging data suggest that obesity is a major risk factor for the progression of major complications such as acute respiratory distress syndrome (ARDS), cytokine storm and coagulopathy in COVID-19. Understanding the mechanisms underlying the link between obesity and disease severity as a result of SARS-CoV-2 infection is crucial for the development of new therapeutic interventions and preventive measures in this high-risk group. We propose that multiple features of obesity contribute to the prevalence of severe COVID-19 and complications. First, viral entry can be facilitated by the upregulation of viral entry receptors, like angiotensin-converting enzyme 2 (ACE2), among others. Second, obesity-induced chronic inflammation and disruptions of insulin and leptin signaling can result in impaired viral clearance and a disproportionate or hyper-inflammatory response, which together with elevated ferritin levels can be a direct cause for ARDS and cytokine storm. Third, the negative consequences of obesity on blood coagulation can contribute to the progression of thrombus formation and hemorrhage. In this review we first summarize clinical findings on the relationship between obesity and COVID-19 disease severity and then further discuss potential mechanisms that could explain the risk for major complications in patients suffering from obesity.

A Weak Response to Endoplasmic Reticulum Stress Is Associated With Postoperative Organ Failure in Patients Undergoing Cardiac Surgery With Cardiopulmonary Bypass

Introduction: Endoplasmic reticulum stress (ERS) is involved in inflammatory organ failure. Our objective was to describe ERS, its unfolded protein response (UPR) expression/kinetics during cardiac surgery with cardiopulmonary bypass (CPB) and its association with postoperative organ failure (OF). Methods: Prospective study conducted on patients undergoing cardiac surgery with CPB. Blood samples were taken before (Pre-CPB), 2 h (H2-CPB) and 24 h (H24-CPB) after CPB. Plasma levels of 78 kDa Glucose- Regulated Protein (GRP78, final effector of UPR) were evaluated by ELISA. The expression of genes coding for key elements of UPR (ATF6, ATF4, sXBP1, CHOP) was evaluated by quantitative PCR performed on total blood. OF was defined as invasive mechanical ventilation and/or acute kidney injury and/or hemodynamic failure requiring catecholamines. Results: We included 46 patients, GRP78 was decreased at H2-CPB [1,328 (878-1,730) ng/ml vs. 2,348 (1,655-3,730) ng/ml Pre-CPB; p < 0.001] but returned to basal levels at H24-CPB [2,068 (1,436-3,005) ng/ml]. The genes involved in UPR had increased expression at H2 and H24. GRP78 plasma levels in patients with OF at H24-CPB (n = 10) remained below Pre-CPB levels [-27.6 (-51.5; -24.2)%] compared to patients without OF (n = 36) in whom GRP78 levels returned to basal levels [0.6 (-28.1; 26.6)%; p < 0.01]. H24-CPB ATF6 and CHOP expressions were lower in patients with OF than in patients without OF [2.3 (1.3-3.1) vs. 3.0 (2.7-3.7), p < 0.05 and 1.3 (0.9-2.0) vs. 2.2 (1.7-2.9), p < 0.05, respectively]. Conclusions: Low relative levels of GRP78 and weak UPR gene expression appeared associated with postoperative OF. Further studies are needed to understand ERS implication during acute organ failure in humans.

Obesity, Diabetes and COVID-19: An Infectious Disease Spreading From the East Collides With the Consequences of an Unhealthy Western Lifestyle

The pandemic of COVID-19, caused by the coronavirus, SARS-CoV-2, has had a global impact not seen for an infectious disease for over a century. This acute pandemic has spread from the East and has been overlaid onto a slow pandemic of metabolic diseases of obesity and diabetes consequent from the increasing adoption of a Western-lifestyle characterized by excess calorie consumption with limited physical activity. It has become clear that these conditions predispose individuals to a more severe COVID-19 with increased morbidity and mortality. There are many features of diabetes and obesity that may accentuate the clinical response to SARS-CoV-2 infection: including an impaired immune response, an atherothrombotic state, accumulation of advanced glycation end products and a chronic inflammatory state. These could prime an exaggerated cytokine response to viral infection, predisposing to the cytokine storm that triggers progression to septic shock, acute respiratory distress syndrome, and multi-organ failure. Infection leads to an inflammatory response and tissue damage resulting in increased metabolic activity and an associated increase in the mechanisms by which cells ingest and degrade tissue debris and foreign materials. It is becoming clear that viruses have acquired an ability to exploit these mechanisms to invade cells and facilitate their own life-cycle. In obesity and diabetes these mechanisms are chronically activated due to the deteriorating metabolic state and this may provide an increased opportunity for a more profound and sustained viral infection.

Induction of ER Stress by an AAV5 BDD FVIII Construct Is Dependent on the Strength of the Hepatic-Specific Promoter

Adeno-associated virus 5 (AAV5)-human factor VIII-SQ (hFVIII-SQ; valoctocogene roxaparvovec) is an AAV-mediated product under evaluation for treatment of severe hemophilia A, which contains a B-domain-deleted hFVIII (hFVIII-SQ) transgene and a hybrid liver-specific promotor (HLP). To increase FVIII-SQ expression and reduce the vector dose required, a stronger promoter may be considered. However, because FVIII-SQ is a protein known to be difficult to fold and secrete, this could potentially induce endoplasmic reticulum (ER) stress. We evaluated the effect of two AAV5-hFVIII-SQ vectors with different liver-specific promoter strength (HLP << 100ATGB) on hepatic ER stress in mice. Five weeks after receiving vehicle or vector, the percentage of transduced hepatocytes and levels of liver hFVIII-SQ DNA and RNA increased dose dependently for both vectors. At lower doses, plasma hFVIII-SQ protein levels were higher for 100ATGB. This difference was attenuated at the highest dose. For 100ATGB, liver hFVIII-SQ protein accumulated dose dependently, with increased expression of ER stress markers at the highest dose, suggesting hepatocytes reached or exceeded their capacity to fold/secrete hFVIII-SQ. These data suggest that weaker promoters may require relatively higher doses to distribute expression load across a greater number of hepatocytes, whereas relatively stronger promoters may produce comparable levels of FVIII in fewer hepatocytes, with potential for ER stress.

Preliminary Virtual Screening Studies to Identify GRP78 Inhibitors Which May Interfere with SARS-CoV-2 Infection

SARS-CoV-2 Spike protein was predicted by molecular docking to bind the host cell surface GRP78, which was suggested as a putative good molecular target to inhibit Covid-19. We aimed to confirm that GRP78 gene expression was increased in blood of SARS-CoV-2 (+) versus SARS-CoV-2 (-) pneumonia patients. In addition, we aimed to identify drugs that could be repurposed to inhibit GRP78, thus with potential anti-SARS-CoV-2 activity. Gene expression studies were performed in 10 SARS-CoV-2 (-) and 24 SARS-CoV-2 (+) pneumonia patients. A structure-based virtual screen was performed with 10,761 small molecules retrieved from DrugBank, using the GRP78 nucleotide binding domain and substrate binding domain as molecular targets. Results indicated that GRP78 mRNA levels were approximately four times higher in the blood of SARS-CoV-2 (+) versus SARS-CoV-2 (-) pneumonia patients, further suggesting that GRP78 might be a good molecular target to treat Covid-19. In addition, a total of 409 compounds were identified with potential as GRP78 inhibitors. In conclusion, we found preliminary evidence that further proposes GRP78 as a possible molecular target to treat Covid-19 and that many clinically approved drugs bind GRP78 as an off-target effect. We suggest that further work should be urgently carried out to confirm if GRP78 is indeed a good molecular target and if some of those drugs have potential to be repurposed for SARS-CoV-2 antiviral activity.