Protein Kinase RNA-like Endoplasmic Reticulum Research Articles

Tyrosine Kinase Inhibitor Lenvatinib Causes Cardiotoxicity by Inducing Endoplasmic Reticulum Stress and Apoptosis through Activating ATF6, IRE1α and PERK Signaling Pathways.

Lenvatinib is a tyrosine kinase inhibitor that can improve progression-free survival in patients with thyroid cancer and hepatocellular carcinoma. However, it is limited by adverse cardiovascular events, including hypertension and cardiac dysfunction. Activation of endoplasmic reticulum stress is involved in cardiomyocyte apoptosis. This study aimed to confirm whether the cardiotoxicity of lenvatinib is associated with endoplasmic reticulum stress by targeting the activating transcription factor 6 (ATF6), inositol- requiring enzyme 1α (IRE1α) and protein kinase RNA-like ER kinase (PERK) signaling pathways. Male C57/BL6 mice were intragastric administration with 30 mg/kg/day lenvatinib. Electrocardiography (ECG) and echocardiography were used to detect arrhythmias and cardiac function. Neonatal rat cardiomyocytes were treated with lenvatinib for 48h. Cell counting kit (CCK8), 2´,7´-dichlorodihydrofluoresceine diacetate (H2DCFHDA), Hoechst 33258 and dihydrorhodamine 123 were respectively used for evaluating cell viability, the level of reactive oxygen species (ROS), nuclear morphological changes and mitochondrial membrane potential (MMP) level. Lenvatinib remarkably decreased the posterior wall thickness of left ventricle during diastole and systole but caused little decrease to the left ventricular ejection fraction (LVEF, %). Furthermore, lenvatinib greatly prolonged the corrected QT interval (QTc) and altered the morphology of cardiomyocytes. No dramatic difference in fibrosis was found in mouse cardiac slices. Lenvatinib upregulates apoptosis-related protein expression. In addition, lenvatinib increased ERS-related protein expression (GRP78, CHOP, and ATF6) and enhanced PERK phosphorylation. In neonatal rat cardiac myocytes, lenvatinib markedly decreased the viability of cardiomyocytes and induced apoptosis. Furthermore, ROS production increased and MMP decreased. Similar to the mice experiment, lenvatinib caused upregulation of apoptosis-related and ERS-related proteins and increased the phosphorylation levels of PERK and IRE1α. Lenvatinib-induced cardiotoxicity is associated with ERS-induced apoptosis by targeting the ATF6, IRE1α, and PERK signaling pathways.

Proteome profiling of cutaneous leishmaniasis lesions due to dermotropic Leishmania donovani in Sri Lanka

BackgroundCharacterization of the host response in cutaneous leishmaniasis (CL) through proteome profiling has gained limited insights into leishmaniasis research compared to that of the parasite. The primary objective of this study was to comprehensively analyze the proteomic profile of the skin lesions tissues in patients with CL, by mass spectrometry, and subsequent validation of these findings through immunohistochemical methods.MethodsEight lesion specimens from leishmaniasis-confirmed patients and eight control skin biopsies were processed for proteomic profiling by mass spectrometry. Formalin-fixed paraffin-embedded lesion specimens from thirty patients and six control skin specimens were used for Immunohistochemistry (IHC) staining. Statistical analyses were carried out using SPSS software. The chi-square test was used to assess the association between the degree of staining for each marker and the clinical and pathological features.ResultsSixty-seven proteins exhibited significant differential expression between tissues of CL lesions and healthy controls (p < 0.01), representing numerous enriched biological processes within the lesion tissue, as evident by both the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Reactome databases. Among these, the integrated endoplasmic reticulum stress response (IERSR) emerges as a pathway characterized by the up-regulated proteins in CL tissues compared to healthy skin. Expression of endoplasmic reticulum (ER) stress sensors, inositol-requiring enzyme-1 (IRE1), protein kinase RNA-like ER kinase (PERK) and activating transcription factor 6 (ATF6) in lesion tissue was validated by immunohistochemistry.ConclusionsIn conclusion, proteomic profiling of skin lesions carried out as a discovery phase study revealed a multitude of probable immunological and pathological mechanisms operating in patients with CL in Sri Lanka, which needs to be further elaborated using more in-depth and targeted investigations. Further research exploring the intricate interplay between ER stress and CL pathophysiology may offer promising avenues for the development of novel diagnostic tools and therapeutic strategies in combating this disease.

Bombyx mori UFL1 facilitates BmNPV proliferation by regulating host cell apoptosis through PERK.

Ubiquitin-fold modifier 1 (UFM1) is attached to protein substrates through the sequential activity of an E1 (UBA5)-E2 (UFC1)-E3 (UFL1) cascade. UFL1 is the E3 ligase for UFMylation in vertebrates. However, there have been no studies on UFL1 in silkworm to date. In this study, we identified a UFL1 ortholog in Bombyx mori genome. Spatio-temporal expression profiles showed that BmUFL1 expression was high in the midgut, epidermis, and testis and in the pupa-adult stage. BmUFL1 knockdown inhibited B. mori nucleopolyhedrovirus (BmNPV)proliferation, while BmUFL1 overexpression promoted BmNPV proliferation. Mechanically, protein kinase RNA-like endoplasmic reticulum kinase (PERK) signaling and cell apoptosis are involved in BmUFL1-regulatedBmNPV proliferation. Overall, these results suggest that BmUFL1 facilitates BmNPV proliferation in silkworm.

Beta-adrenergic stimulation promotes an endoplasmic reticulum stress-dependent inflammatory program in salivary gland epithelial cells.

The effect of beta-adrenergic stimulation on human labial minor salivary gland epithelial cells (LMSGEC) on IL-6 production, and its dependency to endoplasmic reticulum (ER) stress were investigated. Primary LMSGEC from Sjögren's syndrome (SS) patients and controls in culture were stimulated with epinephrine and IL-6 expression was evaluated by qPCR and ELISA. The expression of β-ARs in cultured LMSGEC was tested by qPCR, while adrenoceptors and cAMP levels were examined in LMSGs by immunofluorescence. ER evaluation was performed by Transmission electron microscopy (TEM) and ER stress by Western blot. Adrenergic induced IL-6 production by cultured LMSGEC was evaluated after alleviation of the ER stress by applying Tauroursodeoxycholic acid (TUDCA) and silencing of PKR-like ER kinase (PERK) and activating transcription factor 4 (ATF4) RNAs. Expression of IL-6 by LMSGEC was upregulated after β-adrenergic stimulation, while the silencing of adrenoreceptors downregulated IL-6. The amelioration of ER stress, as well as the silencing of PERK/ATF4, prevented epinephrine-induced upregulation of IL-6. Adrenergic stimulation led to higher and sustained IL-6 levels secreted by LMSGEC of SS patients compared to controls. Adrenergic signaling was endogenously enhanced in LMSGEC of SS patients (expression of β-ARs in situ, intracellular cAMP in cultured LMSGEC). In parallel, SS-LMSGEC expressed dilated ER (TEM) and higher levels of GRP78/BiP. PERK/ATF4 pathway of the ER stress emerged a considerable mediator of adrenergic stimulation for IL-6 production by the LMSGEC. An enhanced endogenous adrenergic activation and a stressed ER observed in SS-LMSGEC may contribute to a sustained IL-6 production by these cells after adrenergic stimulation.

Hepatoprotective effects of zingerone on sodium arsenite-induced hepatotoxicity in rats: Modulating the levels of caspase-3/Bax/Bcl-2, NLRP3/NF-κB/TNF-α and ATF6/IRE1/PERK/GRP78 signaling pathways

ObjectiveLong-term exposure to arsenic has been linked to several illnesses, including hypertension, diabetes, hepatic and renal diseases and cardiovascular malfunction. The aim of the current investigation was to determine whether zingerone (ZN) could shield rats against the hepatotoxicity that sodium arsenite (SA) causes. MethodsThe following five groups of thirty-five male Sprague Dawley rats were created: I) Control; received normal saline, II) ZN; received ZN, III) SA; received SA, IV) SA + ZN 25; received 10 mg/kg body weight SA + 25 mg/kg body weight ZN, and V) SA + ZN 50; received 10 mg/kg body weight SA + 50 mg/kg body weight ZN. The experiment lasted 14 days, and the rats were sacrificed on the 15th day. While oxidative stress parameters were studied by spectrophotometric method, apoptosis, inflammation and endoplasmic reticulum stress parameters were measured by RT-PCR method. ResultsThe SA disrupted the histological architecture and integrity of the liver and enhanced oxidative damage by lowering antioxidant enzyme activity, such as those of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH) level and increasing malondialdehyde (MDA) level in the liver tissue. Additionally, SA increased the mRNA transcript levels of Bcl2 associated x (Bax), caspases (−3, −6, −9), apoptotic protease-activating factor 1 (Apaf-1), p53, tumor necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB), interleukin-1β (IL-1β), interleukin-6 (IL-6), c-Jun NH2-terminal kinase (JNK), mitogen-activated protein kinase 14 (MAPK14), MAPK15, receptor for advanced glycation endproducts (RAGE) and nod-like receptor family pyrin domain-containing 3 (NLRP3) in the liver tissue. Also produced endoplasmic reticulum stress by raising the mRNA transcript levels of activating transcription factor 6 (ATF-6), protein kinase RNA-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and glucose-regulated protein 78 (GRP-78). These factors together led to inflammation, apoptosis, and endoplasmic reticulum stress. On the other hand, liver tissue treated with ZN at doses of 25 and 50 mg/kg showed significant improvement in oxidative stress, inflammation, apoptosis and endoplasmic reticulum stress. ConclusionsOverall, the study's data suggest that administering ZN may be able to lessen the liver damage caused by SA toxicity.

A multicenter, open-label, phase 1a study of HC-5404 in patients with advanced solid tumors.

e15118 Background: Tumor cells have been shown to adapt to the endoplasmic reticulum (ER) stress resulting from activated oncogenes, nutrient stress, and hypoxia by activating one of the kinases in the Unfolded Protein Response (UPR) pathway, Protein kinase RNA-like Endoplasmic Reticulum Kinase (PERK). This adaptation enables them to survive these stresses and develop resistance to standard of care. Targeting PERK in cancer cells could disrupt their ability to thrive under adverse conditions, potentially leading to apoptosis. HC-5404 is a novel, highly selective and potent PERK inhibitor that demonstrates bioavailability and target engagement at efficacious doses across preclinical tumor models. Herein, we report clinical data from the Ph1a study evaluating HC-5404 in patients with advanced solid tumors. Methods: In this first-in-human trial, HC-5404 was administered orally in 21-day cycles to patients ≥18 years old with advanced solid tumors. A Bayesian Optimal Interval (BOIN) design was employed to escalate through 7 dose levels (25 mg to 600 mg BID). Dose Limiting Toxicity (DLT) was assessed during the first cycle. The primary objectives were to establish the Maximum Tolerated Dose (MTD) and evaluate the safety and tolerability of HC-5404. The secondary objectives included evaluating PK/PD and antitumor activity (response rate and survival outcomes). Results: 23 patients received HC-5404 across various dose levels. Of these, 47.8% were ≥ 65 years old, 52.2% were male, and 82.6% had received ≥3 prior therapies. Overall, 1 partial response (PR) with a duration of 130 weeks was observed in a renal cell carcinoma (RCC) patient who started at the 25 mg dose and was escalated to 50 mg, while 8 patients had stable disease (SD) as best overall response. Three DLTs were observed, including hyperglycemia (300 mg), increased AST, ALP, GGT (200 mg) and decreased ejection fraction (EF) (100 mg). Hyperglycemia was observed only at higher doses (≥300 mg) above clinically relevant exposures of 25-100 mg. The MTD was not established. Treatment-related adverse events (TRAEs) of any grade occurred in 69.6% of patients with common events (≥ 20%) including nausea, fatigue, diarrhea, and dry mouth. Grade ≥3 TRAEs occurred in 17.4% of patients and included hyperglycemia, acute myocardial infarction, decreased EF, increased troponin, AST, GGT, ALP, and lipase. HC-5404 PK analysis showed rough dose-proportionality across 25-600mg doses and PK/PD analyses demonstrated the human dose range of 25-100 to be functionally equivalent to the pre-clinical efficacious doses. Final analysis of safety and clinical response are ongoing. Conclusions: HC-5404 showed a favorable safety profile and encouraging preliminary efficacy in heavily pretreated patients with advanced solid tumors. Safety and exposure-response analyses support further exploration of the 25-100 mg dose level of HC-5404, as monotherapy and in novel combinations. Clinical trial information: NCT04834778 .

Effect and mechanism of Gusong Qianggu Decoction on reducing bone loss in ovariectomized mice by targeting endoplasmic reticulum stress-induced apoptosis of osteocytes

This study aims to investigate the role and mechanism of Gusong Qianggu Decoction(GSQG) in attenuating bone loss in ovariectomized mice by targeting the endoplasmic reticulum stress(ERS)-induced apoptosis of osteocytes. After the modeling of osteoporosis in mice with bilateral ovary removal(OVX), 60 mice were randomized by the random number method into six groups: sham,model, low-, medium-, and high-dose GSQG(GSQG-L, GSQG-M, and GSQG-H, respectively), and estradiol(E_2), with 10 mice in each group. The mice in each group were administrated with corresponding drugs by gavage one month after surgery and the administration lasted for 3 months. Enzyme-linked immunosorbent assay(ELISA) was employed to determine the serum levels of osteocalcin(OCN), procollagen type Ⅰ N-terminal propeptide(PINP), carboxy-terminal cross-linked telopeptide of type Ⅰ collagen(CTX),and anti-tartarte acid phosphatase 5b(TRAcP-5b). Micro-CT was employed to observe the changes in bone microstructure of the distal femur. Hematoxylin-eosin(HE) staining was employed to observe the morphology of the bone tissue. RT-qPCR was conducted to determine the m RNA levels of tibial stem osteogenesis-associated genes [type Ⅰ collagen(Col-Ⅰ), alkaline phosphatase(ALP), Runtrelated transcription factor-2(Runx2), bone sialoprotein(BSP), and OCN] and bone-breaking related genes [tartrate-resistant acid phosphatase(TRAP), nuclear factor-activated T cell 1(NFATc1), and cathepsin K(CATK)]. TUNEL staining and immunohistochemistry were employed to detect the apoptosis of osteoblasts. Western blot was employed to measure the expression of ERS-related proteins glucose-regulated protein 78( Grp78), protein kinase RNA-like endoplasmic reticulum kinase( PERK), phosphorylated PERK(p-PERK),eukaryotic translation initiation factor 2 alpha(eIF2α), phosphorylated e IF2α(p-eIF2α), inositol-requiring enzyme 1 alpha(IRE1α), phosphorylated IRE1α(p-IRE1α), and activating transcription factor 6(ATF6) in the proximal tibial bone tissue. The results showed that GSQG significantly recovered the levels of OCN, PINP, TRAc P-5b, and CTX in the serum of ovariectomized mice, and Micro-CT showed that GSQG improved the bone microstructure of distal femur in a dose-dependent manner. Compared with the model group, GSQG widened and increased the bone trabeculae, restored the reticular structure with neat arrangement and enlarged interstitial gaps, and reduced the number of TUNEL-positive cells(P&lt;0. 05, P&lt;0. 01). Furthermore, GSQG down-regulated the expression levels of cysteine aspartate protease-3( caspase-3) and factor Bcl-2-associated X protein( Bax)(P&lt; 0. 05,P&lt;0. 01) and up-regulated the expression level of Bcl-2(P&lt;0. 05, P&lt;0. 01). The GSQG groups showed up-regulated m RNA levels of Col-Ⅰ, ALP, Runx2, BSP, and OCN(P&lt; 0. 01) and down-regulated m RNA levels of TRAP, NFATc1, and CATK(P&lt; 0. 05,P&lt;0. 01). In addition, GSQG, especially GSQG-H, down-regulated the protein levels of Grp78, p-PERK, p-eIF2, p-IRE1α, and ATF6(P&lt; 0. 05, P&lt; 0. 01). In conclusion, GSQG can inhibit the apoptosis of osteocytes by inhibiting the Grp78/PERK/e IF2α/IRE1α/ATF6 signaling pathway in the proximal tibia tissue, thus reducing bone loss in ovariectomized mice.

Mild endoplasmic reticulum stress alleviates FB1-triggered intestinal pyroptosis via the Sec62-PERK pathway

Fumonisin B1 (FB1), a water-soluble mycotoxin released by Fusarium moniliforme Sheld, is widely present in corn and its derivative products, and seriously endangers human life and health. Recent studies have reported that FB1 can lead to pyroptosis, however, the mechanisms by which FB1-induced pyroptosis remain indistinct. In the present study, we aim to investigate the mechanisms of pyroptosis in intestinal porcine epithelial cells (IPEC-J2) and the relationship between FB1-induced endoplasmic reticulum stress (ERS) and pyroptosis. Our experimental results showed that the pyroptosis protein indicators in IPEC-J2 were significantly increased after exposure to FB1. The ERS markers, including glucose-regulated Protein 78 (GRP78), PKR-like ER kinase protein (PERK), and preprotein translocation factor (Sec62) were also significantly increased. Using small interfering RNA silencing of PERK or Sec62, the results demonstrated that upregulation of Sec62 activates the PERK pathway, and activation of the PERK signaling pathway is upstream of FB1-induced pyroptosis. After using the ERS inhibitor 4-PBA reduced the FB1-triggered intestinal injury by the Sec62-PERK pathway. In conclusion, we found that FB1 induced pyroptosis by upregulating Sec62 to activate the PERK pathway, and mild ERS alleviates FB1-triggered damage. It all boils down to one fact, the study provides a new perspective for further, and improving the toxicological mechanism of FB1.Graphical

Treponema pallidum recombinant protein Tp0768 enhances the ability of HUVECs to promote neutrophil chemotaxis through TLR2/ER stress signaling pathway.

Neutrophils are essential cells involved in inflammation. However, the specific mechanism of neutrophil chemotaxis induced by Treponema Pallidum (T. pallidum) remains unknow. In this study, human umbilical vein endothelial cells (HUVECs) were utilized as target cells to investigate the expression levels of chemokines when stimulated with different concentrations of Tp0768(also known as TpN44.5 or TmpA, a T. pallidum infection dependent antigen). The results indicated that Tp0768 treatment enhanced neutrophil chemotaxis in HUVECs, which was closely associated with the expression levels of CXCL1(C-X-C Motif Chemokine Ligand 1), CXCL2(C-X-C Motif Chemokine Ligand 2), and CXCL8(C-X-C Motif Chemokine Ligand 8, also known as interleukin-8). At the same time, the results show that Toll Like Receptor 2 (TLR2) signaling pathway is activated and endoplasmic reticulum stress (ER stress) occurs. Furthermore, the findings revealed that the use of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and Immunoglobulin-Regulated Enhancer 1 (IRE1) inhibitors reduced the expression levels of CXCL1, CXCL2, and CXCL8. Additionally, inhibiting TLR2 significantly decreased the expression levels of ER stress-related proteins (PERK and IRE1), CXCL1, CXCL2, and CXCL8. Consequently, neutrophil chemotaxis was significantly inhibited after treatment with TLR2, PERK, and IRE1 inhibitors. These findings shed light on the role of Tp0768 in enhancing neutrophil chemotaxis in endothelial cells, providing a foundation for further exploration of syphilis pathogenesis and offering a new direction for the diagnosis and treatment of T. pallidum infection.

A new G3BP1-GFP reporter system for assessing skin toxicity by real-time monitoring of stress granules in vitro

The skin, the organ with the largest surface area in the body, is the most susceptible to chemical exposure from the external environment. In this study, we aimed to establish an in vitro skin toxicity monitoring system that utilizes the mechanism of stress granule (SG) formation induced by various cellular stresses. In HaCaT cells, a keratinocyte cell line that comprises the human skin, a green fluorescent protein (GFP) was knocked in at the C-terminal genomic locus of Ras GTPase-activating protein-binding protein 1 (G3BP1), a representative component of SGs. The G3BP1-GFP knock-in HaCaT cells and wild-type (WT) HaCaT cells formed SGs containing G3BP1-GFP upon exposure to arsenite and household chemicals, such as bisphenol A (BPA) and benzalkonium chloride (BAC), in real-time. In addition, the exposure of G3BP1-GFP knock-in HaCaT cells to BPA and BAC promoted the phosphorylation of eukaryotic initiation factor 2 alpha and protein kinase R-like endoplasmic reticulum kinase, which are cell signaling factors involved in SG formation, similar to WT HaCaT cells. In conclusion, this novel G3BP1-GFP knock-in human skin cell system can monitor SG formation in real-time and be utilized to assess skin toxicity to various substances.

Box-Behnken Design-Based Optimization of Phytochemical Extraction from Diplazium esculentum (Retz.) Sw. Associated with Its Antioxidant and Anti-Alzheimer's Properties.

A previous study reported that the ethanolic extract of the edible fern, Diplazium esculentum (Retz.) Sw. (DE), obtained from a non-optimized extraction condition exhibited anti-Alzheimer's disease (AD) properties through the inhibition of a rate-limiting enzyme in amyloid peptide formation, β-secretase-1 (BACE-1). Nevertheless, a non-optimized or suboptimal extraction may lead to several issues, such as a reduction in extraction efficiency and increased time and plant materials. In this study, extraction of the DE was optimized to obtain appropriate BACE-1 inhibition using a Box-Behnken design (BBD) and response surface methodology (RSM). Data revealed that the optimal extraction condition was 70% (v/v) aqueous ethanol, 50 min extraction time, 30 °C extraction temperature, and 1:30 g/mL solid/liquid ratio, giving BACE-1 inhibition at 56.33%. In addition, the extract also exhibited significant antioxidant activities compared to the non-optimized extraction. Metabolomic phytochemical profiles and targeted phytochemical analyses showed that kaempferol, quercetin, and their derivatives as well as rosmarinic acid were abundant in the extract. The optimized DE extract also acted synergistically with donepezil, an AD drug suppressing BACE-1 activities. Data received from Drosophila-expressing human amyloid precursor proteins (APPs) and BACE-1, representing the amyloid hypothesis, showed that the optimized DE extract penetrated the fly brains, suppressed BACE-1 activities, and improved locomotor functions. The extract quenched the expression of glutathione S transferase D1 (GSTD1), inositol-requiring enzyme (IRE-1), and molecular chaperone-binding immunoglobulin (Bip), while donepezil suppressed these genes and other genes involved in antioxidant and endoplasmic reticulum (ER) stress response, including superoxide dismutase type 1 (SOD1), activating transcription factor 6 (ATF-6), and protein kinase R-like endoplasmic reticulum kinase (PERK). To sum up, the optimized extraction condition reduced extraction time while resulting in higher phytochemicals, antioxidants, and BACE-1 inhibitors.

Phenformin activates ER stress to promote autophagic cell death via NIBAN1 and DDIT4 in oral squamous cell carcinoma independent of AMPK

The efficient clinical treatment of oral squamous cell carcinoma (OSCC) is still a challenge that demands the development of effective new drugs. Phenformin has been shown to produce more potent anti-tumor activities than metformin on different tumors, however, not much is known about the influence of phenformin on OSCC cells. We found that phenformin suppresses OSCC cell proliferation, and promotes OSCC cell autophagy and apoptosis to significantly inhibit OSCC cell growth both in vivo and in vitro. RNA-seq analysis revealed that autophagy pathways were the main targets of phenformin and identified two new targets DDIT4 (DNA damage inducible transcript 4) and NIBAN1 (niban apoptosis regulator 1). We found that phenformin significantly induces the expression of both DDIT4 and NIBAN1 to promote OSCC autophagy. Further, the enhanced expression of DDIT4 and NIBAN1 elicited by phenformin was not blocked by the knockdown of AMPK but was suppressed by the knockdown of transcription factor ATF4 (activation transcription factor 4), which was induced by phenformin treatment in OSCC cells. Mechanistically, these results revealed that phenformin triggers endoplasmic reticulum (ER) stress to activate PERK (protein kinase R-like ER kinase), which phosphorylates the transitional initial factor eIF2, and the increased phosphorylation of eIF2 leads to the increased translation of ATF4. In summary, we discovered that phenformin induces its new targets DDIT4 and especially NIBAN1 to promote autophagic and apoptotic cell death to suppress OSCC cell growth. Our study supports the potential clinical utility of phenformin for OSCC treatment in the future.

PERK specific inhibitor AMG-44 protects against Trimethylamine N-oxide (TMAO)-induced Endoplasmic Reticular Stress and Endothelial Dysfunction

The gut microbiota is known to release metabolites detrimental to the endothelial cell lining of the vascular wall leading to endothelial dysfunction. We have earlier reported that Trimethylamine N-oxide (TMAO), an intestinal microbe derived metabolite, caused endothelial dysfunction. In the present study we hypothesized that protein kinase R-like endoplasmic reticulum kinase (PERK)/eIF2α/ATF4 signaling is involved in TMAO-induced endoplasmic reticular (ER) stress and that treatment with PERK inhibitor AMG-44 protects against TMAO-induced ER stress. The endothelial cells were treated with a range of increasing doses of TMAO (0-300 μM) to induce ER stress. PERK inhibitor AMG-44 (20 – 200nM) was used to treat the TMAO treated and control cells. TAMO showed a dose-dependent upregulation of ER stress marker proteins involved in the PERK/eIF2α/ATF4 ER-stress signaling pathway. Western blot analysis showed significant increase in p-PERK/PERK, p-eIF2α/eIF2α, and IRE1α, AFT-4 protein expression which was further confirmed by immunofluorescent analysis in endothelial cells. Treatment with AMG-44 significantly attenuated the PERK/eIF2α/ATF4 axis also protected against increased endothelial cell permeability induced by TMAO (n=6/group; p&lt;0.05). Our results demonstrate that TMAO-induced endothelial dysfunction via the ER stress-mediated PERK- eIF2 α -ATF4 signaling pathway and that treatment with PERK specific inhibitor AMG-44 could be a novel therapeutic strategy in protection against TMAO-induced ER stress and endothelial dysfunction. NIH R01HL148711 to Dr. Sai Sudha Koka. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Activating Transcription Factor 6 (ATF6) Acts as a Rheostat To Balance UPR Signaling and The Proteostatic Response To Mutant SFTPC Substrates By The Alveolar Epithelium

The alveolar type II (AT2) epithelial cell is a metabolically active, biosynthetically robust component of the distal lung responsible for the synthesis of pulmonary surfactant. Disruption of AT2 cell quality control provides a molecular signature found in Idiopathic Pulmonary Fibrosis (IPF), a progressive interstitial lung disease. Mutations in the surfactant protein C (SP-C) gene ( SFTPC) are a high effect size etiological cause of PF in a subset of these patients. Prior in vitro studies from our lab showed that mutations located within the SFTPC BRICHOS domain of the SP-C proprotein result in production of ER retained and aggregation prone conformers. Two critical aspects of the proteostasis network are ER Associated Degradation (ERAD) and the unfolded protein response (UPR). Misfolded conformers activate the UPR via one or more of 3 ER transmembrane sensing proteins (Protein kinase R-like ER kinase (PERK), the Inositol-Requiring kinase 1 alpha (IRE1α) and Activating Transcription Factor 6 (ATF6). We have shown in vitro and in mouse models that clinical IPF associated BRICHOS SFTPC conformers produce unbalanced, exuberant UPR signaling and AT2 dysfunction. The goal of this study was to probe AT2 proteostatic repertoires using BRICHOS SFTPC mutants as substrates. For this, we generated stable doxycycline-inducible Mouse Lung Epithelial (MLE-12) cell lines expressing either Wild Type (SP-CWT) or an aggregating mutant (SP-CC121G) which were interrogated using cycloheximide chase and / or treatments with activators or inhibitors of ATF6, IRE1, and PERK as well as ERAD (VCP/p97), the proteasome, or macroautophagy. Readouts included fluorescence microscopy, qPCR, luciferase reporters, and immunoblotting to assess SFPTC aggregate formation, UPR signaling, and downstream ER stress related events. Using this model system, we found that SP-CC121G was ER retained and activated the UPR within 8 hours of Dox induction (as BIP expression). Commensurate with this, IRE1α (as p-IREα and spliced XBP1 (sXBP1)), ATF6 (by luciferase assay), and PERK (as p-Eif2α, ATF4, CHOP) signals were activated by SP-CC121G. The clearance of mutant SP-CC121G as well as a portion of proSP-CWT was dependent on ERAD and the Ubiquitin-Proteasome System (UPS) as their disruption using either inhibitors of p97 (EEY) or the proteasome (MG132) induced formation of higher molecular weight aggregates. Bafilomycin failed to induce SP-CC121G aggregates or block their clearance. The ATF6 agonist AA147 administered during ERAD inhibition accelerated aggregate protein degradation. When SP-CC121G MLE12 cells were treated with an ATF6 inhibitor (CEAPIN7), we observed marked increases in IRE1α kinase activity with downstream activation of JNK accompanied by commensurate activation of PERK signals and initiation of caspase-3 cleavage. Collectively, these data demonstrate a primary role for ERAD in the AT2 proteostatic response to mutant SFTPC substrates and identify ATF6 as a critical UPR rheostat to provide protection from SFTPC mutant expression both by limiting SP-C aggregate formation and balancing exuberant UPR signals from IRE1α and PERK. NIH R01 HL145408 (MFB), VA Merit Review 2I01BX001176-09 (MFB), Pulmonary Fibrosis Foundation (LRR), NIH 2T32 HL007586-36 (SB), NIH K08 HL150226 (JBK). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Berberine alleviates ovarian tissue damage in mice with hepatolenticular degeneration by suppressing ferroptosis and endoplasmic reticulum stress

ObjectiveHepatolenticular degeneration (HLD) is an autosomal recessive disorder that manifests as multiorgan damage due to impaired copper (Cu) metabolism. Female patients with HLD often experience reproductive impairments. This study investigated the protective effect of berberine against ovarian damage in toxic-milk (TX) mice, a murine model for HLD. MethodsMice were categorized into control group, HLD TX group (HLD group), penicillamine (Cu chelator)-treated TX group and berberine-treated TX group. Body weight, ovary weight and the number of ovulated eggs were recorded. Follicular morphology and cellular ultrastructure were examined. Total iron, ferrous iron (Fe2+) and trivalent iron (Fe3+) levels, as well as malondialdehyde (MDA), glutathione (GSH) and oxidized glutathione (GSSG), were measured in the ovaries. Western blot analysis was used to analyze the expression of proteins related to ferroptosis and endoplasmic reticulum (ER) stress. ResultsOvarian tissue damage was evident in the HLD group, with a significant increase in ferroptosis and ER stress compared to the control group. This damage was inhibited by treatment with penicillamine, a Cu chelator. Compared with the HLD group, berberine increased the number of ovulations, and improved ovarian morphology and ultrastructure. Further, we found that berberine reduced total iron, Fe2+, MDA and GSSG levels, elevated GSH levels, decreased the expression of the ferroptosis marker protein prostaglandin-endoperoxide synthase 2 (PTGS2), and increased glutathione peroxidase 4 (GPX4) expression. Furthermore, berberine inhibited the expression of ER stress-associated proteins mediated by the protein kinase RNA-like ER kinase (PERK) pathway. ConclusionFerroptosis and ER stress are involved in Cu-induced ovarian damage in TX mice. Berberine ameliorates ovarian damage in HLD TX mice by inhibiting ferroptosis and ER stress.Please cite this article as: Liu QZ, Han H, Fang XR, Wang LY, Zhao D, Yin MZ, Zhang N, Jiang PY, Ji ZH, Wu LM. Berberine alleviates ovarian tissue damage in mice with hepatolenticular degeneration by suppressing ferroptosis and endoplasmic reticulum stress. J Integr Med. 2024; Epub ahead of print.

The modulation of autophagy and unfolded protein response by ent-kaurenoid derivative CPUK02 in human colorectal cancer cells.

CPUK02 (15-Oxosteviol benzyl ester) is a semi-synthetic derivative of stevioside known for its anticancer effects. It has been reported that the natural compound of stevioside and its associated derivatives enhances the sensitivity of cancer cells to conventional anti-cancer agents by inducing endoplasmic reticulum (ER) stress. In response to ER stress, autophagy and unfolded protein responses (UPR) are activated to restore cellular homeostasis. Consequently, the primary aim of this study is to investigate the impact of CPUK02 treatment on UPR and autophagy markers in two colorectal cancer cell lines. HCT116 and SW480 cell lines were treated with various concentrations of CPUK02 for 72h. The expression levels of several proteins and enzymes were evaluated to investigate the influence of CPUK02 on autophagy and UPR pathways. These include glucose-regulated protein 78 (GRP78), Inositol-requiring enzyme 1-α (IRE1-α),spliced X-box binding protein 1 (XBP-1s), protein kinase R-like ER kinase (PERK), C/EBP homologous protein (CHOP), Beclin-1, P62 and Microtubule-associated protein1 light chain 3 alpha (LC3βII). The evaluation was conducted using western blotting and quantitative real-time PCR techniques. The results obtained indicate that the treatment with CPUK02 reduced the expression of UPR markers, including GRP78 and IRE1-α at protein levels and XBP-1s, PERK, and CHOP at mRNA levels in both HCT116 and SW480 cell lines. Furthermore, CPUK02 also influenced autophagy by decreasing Beclin-1 and increasing P62 and LC3βII at mRNA levels in both HCT116 and SW480 treated cells. The study findings suggest CPUK02 may exert its cytotoxic effects by inhibiting UPR and autophagy flux in colorectal cancer cells.

SIRT1 exerts protective effects by inhibiting endoplasmic reticulum stress and NF-κB signaling pathways.

Silent information regulator two homolog 1 (SIRT1), an NAD + -dependent histone deacetylase, plays a pivotal regulatory role in a myriad of physiological processes. A growing body of evidence suggests that SIRT1 can exert protective effects in metabolic disorders and neurodegenerative diseases by inhibiting endoplasmic reticulum (ER) stress and the nuclear factor-κB (NF-κB) inflammatory signaling pathway. This review systematically elucidates the molecular mechanisms and biological significance of SIRT1 in regulating ER stress and the NF-κB pathway. On one hand, SIRT1 can deacetylate key molecules in the ER stress pathway, such as glucose-regulated protein 78 (GRP78), X-box binding protein 1 (XBP1), PKR-like ER kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6), thereby alleviating ER stress. On the other hand, SIRT1 can directly or indirectly remove the acetylation modification of the NF-κB p65 subunit, inhibiting its transcriptional activity and thus attenuating inflammatory responses. Through these mechanisms, SIRT1 can ameliorate insulin resistance in metabolic diseases, exert cardioprotective effects in ischemia-reperfusion injury, and reduce neuronal damage in neurodegenerative diseases. However, it is important to note that while these findings are promising, the complex nature of the biological systems involved warrants further investigation to fully unravel the intricacies of SIRT1's regulatory mechanisms. Nevertheless, understanding the regulatory mechanisms of SIRT1 on ER stress and the NF-κB pathway is of great significance for expanding our knowledge of the pathogenesis of related diseases and exploring new preventive and therapeutic strategies targeting SIRT1.

The Role of Endoplasmic Reticulum Stress in Metabolic Diseases.

The endoplasmic reticulum (ER), the center of protein folding, also controls the cell's life-and-death signaling mechanisms. ER stress caused by unfolded or misfolded proteins leads to the activation of the unfolded protein response (UPR) in the cell. The UPR utilizes three main signaling pathways to restore disrupted ER homeostasis. These signaling pathways are protein kinase R-like endoplasmic reticulum kinase, inositol-requiring enzyme 1, and activating transcription factor 6. Studies have reported that ER stress (ERS) plays a role in the pathogenesis of metabolic disorders such as diabetes, obesity, atherosclerosis, and nonalcoholic liver disease. This review will briefly discuss the ERS response in these metabolic diseases.

Effects of electroacupuncture of different intensities and durations on PERK/ATF4/CHOP signaling pathway in liver of non-alcoholic fatty liver disease rats.

To analyze the effects of electroacupuncture (EA) at "Fenglong" (ST40) and "Zusanli" (ST36) of different intensities and durations on rats with non-alcoholic fatty liver disease (NAFLD) based on the protein kinase R-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP) signaling pathway, so as to explore its mechanism underlying improvement of NAFLD. SD rats were randomly divided into normal diet group, high-fat model group, sham EA group, strong stimulation EA (SEA) group, and weak stimulation EA (WEA) group, with 15 rats in each group. Each group was further divided into 2, 3, and 4-week subgroups. NAFLD rat model was established by feeding a high-fat diet. After successful modeling, rats in the SEA and WEA groups received EA at bilateral ST40 and ST36 with dense and sparse waves (4 Hz/20 Hz) at current intensities of 4 mA (SEA group) and 2 mA (WEA group), lasting for 20 minutes, once a day, 5 days a week with 2 days of rest. The sham EA group only had the EA apparatus connected without electricity. Different duration subgroups were intervened for 2, 3, and 4 weeks. After the intervention, the contents of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in rats were detected by an automatic biochemical analyzer；liver morphological changes were observed by Oil Red O staining；real-time fluorescence quantitative PCR and Western blot were used to detect the expression of PERK, ATF4, and CHOP mRNAs and proteins in the rat liver tissue. In the high-fat model group, there was a significant accumulation of red lipid droplets in the liver cells, which was reduced significantly in the SEA group at the 4th week. Compared with the normal diet group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and proteins in the liver tissue were elevated (P<0.01) in the high-fat model group . Compared with the high-fat model group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, CHOP mRNAs and proteins in the liver tissue were decreased (P<0.01, P<0.05) in the SEA and WEA groups. Compared with the sham EA group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs were decreased (P<0.01, P<0.05) in the SEA and WEA groups, the expression of PERK, ATF4, and CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA group at the 2nd, 3rd, and 4th week, the expression of PERK and CHOP proteins at the 2nd, 3rd, 4th week and ATF4 protein at 2nd week in the liver tissue were decreased (P<0.01, P<0.05) in the WEA group. Compared with the SEA group with the same treatment duration, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and proteins in the liver tissue were elevated (P<0.05, P<0.01) in the WEA group. Compared with the 2-week time point within the groups, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs and PERK proteins in the liver tissue were decreased (P<0.01, P<0.05) in the SEA and WEA groups at 3rd and 4th week, the expression of ATF4 proteins in the liver tissue was decreased (P<0.01) in the SEA group at 3rd and 4th week, and the expression of CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA group at 4th week and in the WEA group at 3rd and 4th week. Compared with the 3-week time point within the groups, the contents of serum ALT, AST, and the expression of PERK, ATF4, and CHOP mRNAs were significantly decreased (P<0.05, P<0.01) in the SEA and WEA groups at 4th week, the expression of PERK and CHOP proteins in the liver tissue was decreased (P<0.01) in the SEA and WEA groups at 4th week, and the expression of ATF4 protein in the liver tissue was decreased (P<0.05) in the SEA group at 4th week. EA at ST40 and ST36 can significantly improve liver function in NAFLD rats, and its mechanism of action may involve inhibiting PERK expression thereby targeting the downstream ATF4/CHOP signaling pathway to suppress endoplasmic reticulum stress, exerting a liver protective effect；the optimal effect was observed with EA intensity of 4 mA for 4 weeks.

Loss of TRIM29 mitigates viral myocarditis by attenuating PERK-driven ER stress response in male mice

Viral myocarditis, an inflammatory disease of the myocardium, is a significant cause of sudden death in children and young adults. The current coronavirus disease 19 pandemic emphasizes the need to understand the pathogenesis mechanisms and potential treatment strategies for viral myocarditis. Here, we found that TRIM29 was highly induced by cardiotropic viruses and promoted protein kinase RNA-like endoplasmic reticulum kinase (PERK)-mediated endoplasmic reticulum (ER) stress, apoptosis, and reactive oxygen species (ROS) responses that promote viral replication in cardiomyocytes in vitro. TRIM29 deficiency protected mice from viral myocarditis by promoting cardiac antiviral functions and reducing PERK-mediated inflammation and immunosuppressive monocytic myeloid-derived suppressor cells (mMDSC) in vivo. Mechanistically, TRIM29 interacted with PERK to promote SUMOylation of PERK to maintain its stability, thereby promoting PERK-mediated signaling pathways. Finally, we demonstrated that the PERK inhibitor GSK2656157 mitigated viral myocarditis by disrupting the TRIM29-PERK connection, thereby bolstering cardiac function, enhancing cardiac antiviral responses, and curbing inflammation and immunosuppressive mMDSC in vivo. Our findings offer insight into how cardiotropic viruses exploit TRIM29-regulated PERK signaling pathways to instigate viral myocarditis, suggesting that targeting the TRIM29-PERK axis could mitigate disease severity.