Endoplasmic Reticulum Stress Aggravates Viral Myocarditis by Raising Inflammation Through the IRE1-Associated NF-κB Pathway

Novel insight on IRE1 in the regulation of chondrocyte dedifferentiation through ER stress independent pathway

Inositol-requiring enzyme-1 (IRE1) is the master regulator of the unfolded protein response pathway, associated with the endoplasmic reticulum (ER) in sensing and regulating cell stress. The activity of IRE1 is highly explored and well-characterized in cancer and other cells. However, the IRE1 molecular mechanism in chondrocytes is poorly understood. The present study explored the effect of IRE1 on chondrocytes regarding its chondrogenic gene expression and its correlation with different cellular pathways and cell behavior. Chondrocytes transfected with the cDNA of IRE1 reduced the expression of type II collagen, disrupting chondrocyte differentiation as confirmed by western blotting and immunofluorescence. Upon siRNA treatment, the influence of IRE1 on chondrocyte differentiation is restored by reviving the normal expression of type II collagen. Different molecular pathways were explored to investigate the role of IRE1 in causing chondrocyte dedifferentiation. However, we found no significant correlation, as IRE1 induces dedifferentiation through independent pathways. In response to various endoplasmic reticulum (ER) agonists (2-deoxy-D-glucose), and ER stress antagonists (tauroursodeoxycholic acid and salubrinal), IRE1 overexpression did not affect GRP78/94, as implicated in the pathogenesis of ER stress. Moreover, when IRE1 overexpression was correlated with the inflammation pathway, nuclear factor-kappa B (NFκB), IRE1 substantially increased the expression of p50 while decreasing the expression of nuclear factor kappa light polypeptide alpha (IκBα). These results suggest that IRE1 induces dedifferentiation in chondrocytes by modulating inflammatory pathways that cause dedifferentiation by disrupting type II collagen expression.

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.

Ganoderic acid A slows osteoarthritis progression by attenuating endoplasmic reticulum stress and blocking NF-Κb pathway

Osteoarthritis (OA) is a prevalent degenerative pathology, however, there exists a lack of cost-effective pharmacological interventions that efficaciously inhibit its progression. ganoderic acid A (GAA), a triterpenoid derived from Ganoderma lucidum, possesses antiapoptotic and -inflammatory effects. Our objective was to better understand the therapeutic effects of GAA on OA as well as to elucidate the underlying mechanisms of its action. To establish an OA cell model in vitro, chondrocytes (CHONs) were treated with interleukin (IL)-1β. Subsequently, the investigation was conducted afterward according to the following indicators: cell viability, apoptosis, inflammation, and extracellular matrix (ECM) degradation. Western blotting analysis (WB) was employed to assess both endoplasmic reticulum (ER) stress and proteins associated with the nuclear factor-kappa B (NF-κB) signaling pathway. Furthermore, based on molecular docking studies, GAA exhibits a significant binding competence to p65. OA mouse models were constructed by performing a destabilization medial meniscus (DMM) operation. Moreover, histopathology and immunohistochemistry were used to determine the GAA therapeutic effect in reducing OA in vivo. Our findings revealed that GAA has antiapoptotic, anti-inflammatory, and anti-ECM degradation effects by inhibiting the ER stress and NF-κB axis in CHONs in vitro. Furthermore, our findings suggest that GAA may attenuate the progression of osteoarthritis in vivo. GAA can protect CHONs by regulating apoptosis, ECM changes, and inflammation thereby preventing OA progression. These promising results indicate that GAA may be a therapeutic agent for OA treatment.

XBP1 Modulates the Aging Cardiorenal System by Regulating Oxidative Stress

X-box binding protein 1 (XBP1) is a unique basic-region leucine zipper (bZIP) transcription factor. Over recent years, the powerful biological functions of XBP1 in oxidative stress have been gradually revealed. When the redox balance remains undisturbed, oxidative stress plays a role in physiological adaptations and signal transduction. However, during the aging process, increased cellular senescence and reduced levels of endogenous antioxidants cause an oxidative imbalance in the cardiorenal system. Recent studies from our laboratory and others have indicated that these age-related cardiorenal diseases caused by oxidative stress are guided and controlled by a versatile network composed of diversified XBP1 pathways. In this review, we describe the mechanisms that link XBP1 and oxidative stress in a range of cardiorenal disorders, including mitochondrial instability, inflammation, and alterations in neurohumoral drive. Furthermore, we propose that differing degrees of XBP1 activation may cause beneficial or harmful effects in the cardiorenal system. Gaining a comprehensive understanding of how XBP1 exerts influence on the aging cardiorenal system by regulating oxidative stress will enhance our ability to provide new directions and strategies for cardiovascular and renal safety outcomes.

Involvement of IGF1 in endoplasmic reticulum stress contributes to cataract formation through regulating Nrf2/NF-κB signaling

Endoplasmic reticulum (ER) stress is reportedly involved in the development of ophthalmic diseases. This study aimed to investigate the role and potential mechanism of insulin-like growth factor 1 (IGF1) in ER stress. A mouse cataract model was constructed by subcutaneous injection of sodium selenite, and sh-IGF1 was used to evaluate the effect of silencing IGF1 on cataract progression. Slit-lamp and histological examination of the lens were performed to examine lens damage. The regulatory effects of IGF1 on inflammatory responses, oxidative stress, and ER stress were evaluated using ELISA, reverse transcription-quantitative PCR (RT-qPCR), and immunoblotting analysis. Tunicamycin was used to induce ER stress in the lens of epithelial cells. The NF-E2 related factor-2 (Nrf2) inhibitor ML385 and nuclear factor-κB (NF-κB) agonist diprovocim were used to confirm whether IGF1 regulates inflammation and ER stress through Nrf2/NF-κB signaling. Silencing IGF1 alleviated lens damage and reduced lens turbidity in the cataract mice. Silencing IGF1 inhibited inflammatory response, oxidative stress and ER stress response. Meanwhile, IGF1 was highly expressed in sodium selenite-treated lens epithelial cells. The ER stress agonist tunicamycin suppressed cell viability as well as induced ER stress, oxidative stress and inflammation. Silencing IGF1 increased cell viability, EdU-positive rate and migration. Also, silencing of IGF1 reduced inflammation and ER stress via regulating Nrf2/NF-κB pathway. This study reveals silencing IGF1 attenuated cataract through regulating Nrf2/NF-κB signaling, which shares novel insights into the underlying mechanism of cataract and provides potential therapeutic target for cataract.

Thioredoxin interacting protein protects mice from fasting induced liver steatosis by activating ER stress and its downstream signaling pathways

Under normal conditions, fasting results in decreased protein disulfide isomerase (PDI) activity and accumulation of unfolded proteins, leading to the subsequent activation of the unfolded protein response (UPR)/autophagy signaling pathway to eliminate damaged mitochondria. Fasting also induces upregulation of thioredoxin-interacting protein (TXNIP) expression and mice deficient of this protein (TXNIP-KO mice) was shown to develop severe hypoglycemia, hyperlipidemia and liver steatosis (LS). In the present study, we aimed to determine the role of TXNIP in fasting-induced LS by using male TXNIP-KO mice that developed LS without severe hypoglycemia. In TXNIP-KO mice, fasting induced severe microvesicular LS. Examinations by transmission electron microscopy revealed mitochondria with smaller size and deformities and the presence of few autophagosomes. The expression of β-oxidation-associated genes remained at the same level and the level of LC3-II was low. PDI activity level stayed at the original level and the levels of p-IRE1 and X-box binding protein 1 spliced form (sXBP1) were lower. Interestingly, treatment of TXNIP-KO mice with bacitracin, a PDI inhibitor, restored the level of LC3-II after fasting. These results suggest that TXNIP regulates PDI activity and subsequent activation of the UPR/autophagy pathway and plays a protective role in fasting-induced LS.

The role of endoplasmic reticulum stress in astrocytes

Astrocytes are glial cells that support neurological function in the central nervous system (CNS), in part, by providing structural support for neuronal synapses and blood vessels, participating in electrical and chemical transmission, and providing trophic support via soluble factors. Dysregulation of astrocyte function contributes to neurological decline in CNS diseases. Neurological diseases are highly heterogeneous but share common features of cellular stress including the accumulation of misfolded proteins. Endoplasmic reticulum (ER) stress has been reported in nearly all neurological and neurodegenerative diseases. ER stress occurs when there is an accumulation of misfolded proteins in the ER lumen and the protein folding demand of the ER is overwhelmed. ER stress initiates the unfolded protein response (UPR) to restore homeostasis by abating protein translation and, if the cell is irreparably damaged, initiating apoptosis. Although protein aggregation and misfolding in neurological disease has been well described, cell-specific contributions of ER stress and the UPR in physiological and disease states are poorly understood. Recent work has revealed a role for active UPR signaling that may drive astrocytes toward a maladaptive phenotype in various model systems. In response to ER stress, astrocytes produce inflammatory mediators, have reduced trophic support, and can transmit ER stress to other cells. This review will discuss the current known contributions and consequences of activated UPR signaling in astrocytes.

The expression of STAT3 inhibited the NF-ΚB signalling pathway and reduced inflammatory responses in mice with viral myocarditis

BACKGROUND

The aim of this study was to investigate the mechanism of STAT3 in reducing the inflammatory responses in mice with viral myocarditis (VMC).

METHODS

Induce and generate viral myocarditis by using coxsackievirus B3 (CVB3) infected cardiomyocyte-specific STAT3 conditional knockout (STAT3cKO) mice and BALB/c mice. Use RT-PCR and western blot techniques to detect the expression of related cytokines in the uninfected wild-type mice group (Control group), myocarditis wild-type mice group (Model group) and STAT3cKO group, as well as the differentiation of spleen T cells in each group. Eukaryotic expression plasmid pcDNA3-STAT3 can reduce the expression of inflammatory factors the in vitro cultured cardiomyocytes of the STAT3cKO group.

RESULTS

RT-PCR showed that compared with the Control group, the expression levels of VMC-related genes (NF-κB, TNF‑α, IL-1β and IL-1) and anti-inflammation-related cytokines (IL-10 and TGF-β) in the Model group went up (*p < 0.05, **p < 0.01, ***p < 0.001); and also compared with the Control group, the rise in the expression levels of the above VMC-related genes in the STAT3cKO group was particularly significant (***p < 0.001, ****p < 0.0001) but there was no significant difference in the expression of IL-10 and TGF-β. After 4 weeks, a second RT-PCR showed that the expression of inflammation-related genes in the STAT3cKO group continued to be activated (***p < 0.001, ****p < 0.0001). Western blotting was performed to detect the expression of p65, a key protein of the NF-κB signalling pathway. The results showed that the p65 protein content was increased and the IL-10 protein content was decreased in the STAT3cKO group; the results of the T cell differentiation test showed that the T cell differentiation rate increased in the STAT3cKO group (**p < 0.01). Eukaryotic expression plasmid pcDNA3-STAT3 could reduce the expression of NF-κB, TNF-α, IL-1β and IL-17 (**p < 0.01).

CONCLUSION

The expression of STAT3 gene in VMC could to a certain extent inhibit the NF-κB signalling pathway and reduce the inflammatory responses of VMC.

Thioredoxin-1 Is a Target to Attenuate Alzheimer-Like Pathology in Diabetic Encephalopathy by Alleviating Endoplasmic Reticulum Stress and Oxidative Stress

Varying degrees of central nervous system neuropathy induced by diabetes mellitus (DM) contribute to a cognitive disorder known as diabetic encephalopathy (DE), which is also one of the independent risk factors for Alzheimer's disease (AD). Endoplasmic reticulum stress (ERS) plays a critical role in the occurrence and development of DE and AD. However, its molecular mechanism remains largely unknown. This study aims to investigate whether thioredoxin-1 (Trx-1) could alleviate DE and AD through ERS, oxidative stress (OS) and apoptosis signaling pathways. Mice were randomly divided into a wild-type group (WT-NC), a streptozotocin (STZ)-treated DM group (WT-DM), a Trx-1-TG group (TG-NC) and a Trx-1-TG DM group (TG-DM). Diabetic animals showed an increase in the time spent in the target quadrant and the number of platform crossings as well as AD-like behavior in the water maze experiment. The immunocontent of the AD-related protein Tau and the levels of cell apoptosis, β-amyloid (Aβ) plaque formation and neuronal degeneration in the hippocampus of the diabetic group were increased. Some key factors associated with ERS, such as protein disulfide isomerase (PDI), glucose-regulated protein 78 (GRP78), inositol-requiring enzyme 1α (IRE1α), tumor necrosis factor receptor-associated factor 2 (TRAF2), apoptosis signal-regulating kinase-1 (ASK1), c-Jun N-terminal kinase (JNK), protein kinase RNA (PKR)-like ER kinase (PERK), and C/EBP homologous protein (CHOP), were upregulated, and other factors related to anti-oxidant stress, such as nuclear factor erythroid 2-related factor (Nrf2), were downregulated in the DM group. Moreover, DM caused an increase in the immunocontents of caspase-3 and caspase-12. However, these changes were reversed in the Trx-1-tg DM group. Therefore, we conclude that Trx-1 might be a key factor in alleviating DE and AD by regulating ERS and oxidative stress response, thus preventing apoptosis.

Curcumin Reduces Cognitive Deficits by Inhibiting Neuroinflammation through the Endoplasmic Reticulum Stress Pathway in Apolipoprotein E4 Transgenic Mice

Apolipoprotein E4 (ApoE4) is the main genetic risk factor for Alzheimer's disease (AD), but the exact way in which it causes AD remains unclear. Curcumin is considered to have good therapeutic potential for AD, but its mechanism has not been clarified. This study aims to observe the effect of curcumin on ApoE4 transgenic mice and explore its possible molecular mechanism. Eight-month-old ApoE4 transgenic mice were intraperitoneally injected with curcumin for 3 weeks, and the Morris water maze test was used to evaluate the cognitive ability of the mice. Immunofluorescence staining, immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay (ELISA) were used to examine the brain tissues of the mice. Curcumin reduced the high expression of ApoE4 and the excessive release of inflammatory factors in ApoE4 mice. In particular, the expression of marker proteins of endoplasmic reticulum (ER) stress was significantly increased in ApoE4 mice, while curcumin significantly reduced the increase in the expression of these proteins. Collectively, curcumin alleviates neuroinflammation in the brains of ApoE4 mice by inhibiting ER stress, thus improving the learning and cognitive ability of transgenic mice.

Allicin alleviated acrylamide-induced NLRP3 inflammasome activation via oxidative stress and endoplasmic reticulum stress in Kupffer cells and SD rats liver

Acrylamide (AA) in heat-processed food leads to widespread concerns due to its hepatotoxicity. Allicin, a plant-derived antioxidant, possesses a significant protective effect on AA-induced hepatotoxicity, but the mechanism is still unclear. Herein, we investigated the mechanism in Kupffer cells and SD rats liver. Molecular docking, molecular dynamics simulation and LigPlus software speculated that allicin inhibited the activity of CYP2E1 expression by binding to its amino acid residues Phe116, Phe207, Leu210, Phe298, Ala299, Thr303, Val364 and Phe478 through hydrophobic interactions. Allicin decreased the reactive oxygen species (ROS) release and CYP2E1 protein expression and then alleviated the appearance of OS. Meanwhile, allicin significantly reduced ERS characteristic proteins GRP78, CHOP and UPR branch IRE1α pathway key proteins p-IRE, p-ASK, TRAF2 and XBP-1s expression. Simultaneously, allicin ameliorated OS and ERS activation, which inhibited the activation of the MAPK and NF-κB pathways, and down-regulated JNK, ERK, p38, p65 and IκBα phosphorylation. Allicin pre-treatment inhibited AA-induced inflammation as evidenced by reducing NLRP3 inflammasome activation, decreasing Cleaved-Caspase-1 expression as well as IL-1β, IL-18, IL-6 and TNF-α secretion. Taken together, our data provide new insights into possible signaling pathways involved in allicin attenuating AA-induced hepatotoxicity in vivo and in vitro.

MicroRNA-425-3p inhibits myocardial inflammation and cardiomyocyte apoptosis in mice with viral myocarditis through targeting TGF-β1

Objective

Emerging articles have profiled the relations between microRNAs and viral myocarditis. This research was unearthed to explore the capacity of miR‐425‐3p on cardiomyocyte apoptosis in mice with viral myocarditis and its mechanism.

Methods

A total of 120 mice were classified into 4 groups in a random fashion (n = 30). The mice were intraperitoneally injected with coxsackievirus type B3 (CVB3) to induce myocarditis. On the 7th day after CVB3 infection, 10 mice in each group were euthanized to assess the heart function indices of mice, observe the pathological conditions, detect myocardial tissue apoptosis, and measure the inflammatory factor levels in myocardial tissues. Expression of miR‐425‐3p, transforming growth factor (TGF‐β1), and apoptosis‐associated proteins in myocardial tissues was determined. The remaining 20 mice in each group were used for survival observation. The luciferase activity assay was implemented to validate the relationship between miR‐425‐3p and TGF‐β1. miR‐425‐3p mimic was transfected into mouse cardiomyocytes HL‐1 and then infected with CVB3 to further verify the regulatory effect of miR‐425‐3p on the cardiomyocyte apoptosis in viral myocarditis.

Results

miR‐425‐3p was lowly expressed in myocardial tissues of mice with viral myocarditis. Overexpressed miR‐425‐3p improved the cardiac function, alleviated pathological conditions, reduced cardiomyocyte apoptosis, decreased Bax and cleaved Caspase‐3 expression, elevated Bcl‐2 expression, decreased levels of inflammatory factors and improved survival rate of mice with viral myocarditis. Luciferase activity assay verified that miR‐425‐3p could bind to TGF‐β1, and overexpressed miR‐425‐3p suppressed TGF‐β1, p‐smad2/smad2 and p‐smad3/smad3 expression. In vitro experiments further verified that overexpression of miR‐425‐3p inhibited the apoptosis of CVB3‐HL‐1 cells, and the addition of TGF‐β1 would reverse this effect.

Conclusion

Our research indicates that miR‐425‐3p is poorly expressed in myocardial tissues of mice with viral myocarditis. Overexpressed miR‐425‐3p inhibits cardiomyocyte apoptosis and myocardial inflammation in mice with viral myocarditis as well as improves their survival rates through suppressing the TGF‐β1/smad axis.

The Roles of Endoplasmic Reticulum in NLRP3 Inflammasome Activation

The NLRP3 (nucleotide-binding domain, leucine-rich-repeat-containing family, pyrin domain-containing 3) inflammasome senses pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), and activates caspase-1, which provokes release of proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18 as well as pyroptosis to engage in innate immune defense. The endoplasmic reticulum (ER) is a large and dynamic endomembrane compartment, critical to cellular function of organelle networks. Recent studies have unveiled the pivotal roles of the ER in NLRP3 inflammasome activation. ER–mitochondria contact sites provide a location for NLRP3 activation, its association with ligands released from or residing in mitochondria, and rapid Ca²⁺ mobilization from ER stores to mitochondria. ER-stress signaling plays a critical role in NLRP3 inflammasome activation. Lipid perturbation and cholesterol trafficking to the ER activate the NLRP3 inflammasome. These findings emphasize the importance of the ER in initiation and regulation of the NLRP3 inflammasome.

Roles and Mechanisms of Interleukin-12 Family Members in Cardiovascular Diseases: Opportunities and Challenges

Cardiovascular diseases represent a complex group of clinical syndromes caused by a variety of interacting pathological factors. They include the most extensive disease population and rank first in all-cause mortality worldwide. Accumulating evidence demonstrates that cytokines play critical roles in the presence and development of cardiovascular diseases. Interleukin-12 family members, including IL-12, IL-23, IL-27 and IL-35, are a class of cytokines that regulate a variety of biological effects; they are closely related to the progression of various cardiovascular diseases, including atherosclerosis, hypertension, aortic dissection, cardiac hypertrophy, myocardial infarction, and acute cardiac injury. This paper mainly discusses the role of IL-12 family members in cardiovascular diseases, and the molecular and cellular mechanisms potentially involved in their action in order to identify possible intervention targets for the prevention and clinical treatment of cardiovascular diseases.

Activation of CaMKII via ER-stress mediates coxsackievirus B3-induced cardiomyocyte apoptosis

Cardiomyocyte apoptosis contributes to the development of coxsackievirus B3 (CVB3)-induced myocarditis, but the mechanism for the apoptosis by CVB3 infection remains unclear. Here, we showed that CVB3-induced endoplasmic reticulum (ER) stress response and apoptosis in cultured H9c2 cardiomyocytes. We found that Ca²⁺ -calmodulin-dependent kinase II (CaMKII) was activated by ER stress-dependent intracellular Ca²⁺ overload in the CVB3-infected H9c2 cardiomyocytes. Treatment with an inhibitor of ER stress, 4-phenylbutyric acid (4-PBA), attenuated intracellular Ca²⁺ accumulation indirectly and reduced CaMKII activity. Inhibition of CaMKII with pharmacological inhibitor (KN-93) or short hairpin RNA reduced CVB3-induced H9c2 apoptosis and repressed cytochrome c release from mitochondria to cytoplasm; whereas overexpression of the activated mutant of CaMKII (CaMKII-T287D) enhanced CVB3-induced H9c2 apoptosis and mitochondrial cytochrome c release, which could be alleviated by blocking of mitochondrial Ca²⁺ uniporter or mitochondrial permeability transition pore. Further in vivo investigation revealed that blocking of CaMKII with KN-93 prevented cardiomyocytes apoptosis and improved cardiac contractile function in CVB3-infected mouse heart. Collectively, these findings provide a novel evidence that CaMKII plays a vital role in the promotion of CVB3-induced cardiomyocyte apoptosis, which links ER stress and mitochondrial Ca²⁺ uptake.

Protective effects of curcumin against chronic alcohol-induced liver injury in mice through modulating mitochondrial dysfunction and inhibiting endoplasmic reticulum stress

Background

Curcumin is a major active ingredient extracted from powdered dry rhizome of Curcuma longa. In Ayurveda and traditional Chinese medicine, it has been used as a hepatoprotective agent for centuries. However, the underlying mechanisms are not clear.

Objective

The present study is to investigate the hepatoprotective effects of curcumin in chronic alcohol-induced liver injury and explore its mechanism.

Design

Alcohol-exposed Balb/c mice were treated with curcumin (75 and 150 mg/kg) once per day for 8 weeks. Tissue from individual was fixed with formaldehyde for pathological examination. The activities of mitochondrial antioxidant enzymes, Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase, were determined. The level of mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (MPTP) opening was also determined. The expression of PGC-1α, NRF1, Mn-SOD, GRP78, PERK, IRE1α, nuclear NF-κB, and phosphorylated IκBα was quantified by western blot. The contents of TNF-α, IL-1β, and IL-6 in the liver were measured using the ELISA method.

Results

Curcumin significantly promoted hepatic mitochondrial function by reducing the opening of MPTP, thus increasing the MMP, promoting the activity of Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺/Mg²⁺-ATPase, and attenuating oxidative stress. Curcumin upregulated the expression of PGC-1α, NRF1, and Mn-SOD, and downregulated the expression of GRP78, PERK, and IRE1α in hepatic tissue. Curcumin also attenuated inflammation by inhibiting the IκBα–NF-κB pathway, which reduced the production of TNF, IL-1β, and IL-6.

Conclusion

Curcumin attenuates alcohol-induced liver injury via improving mitochondrial function and attenuating endoplasmic reticulum stress and inflammation. This study provides strong evidence for the beneficial effects of curcumin in the treatment of chronic alcohol-induced liver injury.

Regulation of P300 and HDAC1 on endoplasmic reticulum stress in isoniazid-induced HL-7702 hepatocyte injury

P300 and HDAC1 can be involved in the development of various liver diseases by regulating gene transcription. Endoplasmic reticulum stress (ERS) is one of the main pathways of apoptosis and is activated during inflammatory responses, but the roles of P300 and HDAC1 in ERS in antituberculosis drug-induced liver injury (ADLI) are not clear. This study confirms that isoniazid can change the states of P300 and HDAC1 in HL-7702 hepatocyte metabolism and induce ERS, causing hepatocyte injury and apoptosis. When combined with C646, however, P300 can be reduced. HL-7702 cells were flattened, and the cytoplasm became crinkled. To a certain extent, ERS was relieved, but hepatocytes suffered worse damage, and the rate of cell apoptosis markedly increased. When MS-275 was applied, HDAC1 level was increased, cell fusion appeared, and fluorescence intensity of endoplasmic reticulum was weakened. In addition, ERS was aggravated, but liver injury was relieved, and the apoptosis rate significantly decreased. Therefore, alteration of P300 and HDAC1 status and ERS are involved in ADLI, and changes in P300 and HDAC1 can regulate ERS and then affect cell damage.

Psoralen induces hepatic toxicity through PERK and ATF6 related ER stress pathways in HepG2 cells

Psoralen has potential hepatotoxicity and has a certain promoting effect on the clinical liver injury of Psoralea corylifolia L (Fructus Psoraleae). This study investigated the underlying mechanisms of psoralen-induced hepatotoxicity in vitro. HepG2 cells were treated with psoralen for 6, 12, 24, or 48 h, and an endoplasmic reticulum (ER) stress-specific inhibitor, 4-PBA, was employed to investigate the mechanism of psoralen on ER stress and unfolded protein response (UPR). Cell viability was tested by MTT assay, ATP assay, and cell death by LDH. The apoptosis was reflected by the flow cytometry, caspase-8, and caspase-3 activates. The expression of ER stress-related markers was determined by RT-PCR and western blot. We found that psoralen significantly decreased cell viability, increased activities of caspase-8 and caspase-3, and upregulated expression of CHOP and BAX in a time- and dose-dependent manner. Moreover, psoralen significantly increased the expression and transcription levels of ER stress-related markers, including Grp78, PERK, eIF2α, ATF4, and ATF6, while IRE1α was not significantly affected. And 4-PBA could effectively inhibit psoralen-induced cell death and apoptosis along with the inhibition of ER stress responses. These results suggested that psoralen causes liver injury due to the induction of the ER stress-mediated apoptosis via PERK-eIF2α-ATF4-CHOP and ATF6-CHOP related pathways.

Macrophage NLRP3 inflammasome activated by CVB3 capsid proteins contributes to the development of viral myocarditis

Viral myocarditis, mainly caused by enteroviruses specially coxsackievirus B3 (CVB3) infection, is a common clinical cardiovascular disease and characterized by cardiac massive inflammation. Our previous study showed that CVB3-induced myocardial NLRP3 contributed to the development of viral myocarditis. In this study, we found that beside of being up-regulated in myocardiocytes, NLPR3 was also obviously increased in the cardiac infiltrating macrophages. While whether this accumulated NLRP3 influences, macrophage inflammatory responses remains unknown. By adoptive transfer assays, we found that mice receiving NLRP3 up-regulated macrophages showed much more abundant cardiac IL-1β production and more severe myocardial inflammation, while those receiving NLRP3 down-regulated macrophages showed much less IL-1β production and milder myocarditis, indicating that NLRP3 up-regulated macrophages played a pathological role in CVB3-induced myocarditis. In addition, we further found that it was CVB3 capsid proteins VP1 (predominant) and VP2, but not viral RNAs, robustly triggered macrophage NLRP3 up-regulation and activation. Our study demonstrated macrophage NLRP3 inflammasome could be efficiently be activated by CVB3 capsid proteins, and contributed to the pathogenesis of viral myocarditis. It might provide some clues to the development of new therapeutic strategies based on macrophage NLRP3 modulation.

Inhibitory effect of melatonin on Mst1 ameliorates myocarditis through attenuating ER stress and mitochondrial dysfunction

Viral myocarditis has been found to be one of the leading causes of sudden death in young adults. However, no effective drugs have been developed to intervene the progression of myocarditis. Accordingly, the present study is carried out to explore the protective role played by melatonin in the setting of viral myocarditis with a focus on Mst1-Hippo pathway, mitochondrial dysfunction and ER stress. Cardiac function was determined via echocardiographic examination. Mitochondrial function and ER stress were detected via ELISA, western blots, and immunofluorescence. Our data demonstrated that virus injection induced cardiac dysfunction as evidenced by reduced contractile function in myocardium. Besides, LDH release assay and western blotting analysis demonstrated that cardiomyocyte death was activated by virus injection. Interestingly, melatonin treatment improved cardiac function and repressed virus-mediated cardiomyocyte apoptosis. At the molecular levels, mitochondrial dysfunction was induced by virus infection, as indicated by mitochondrial membrane potential reduction, mPTP opening rate elevation and caspase-9-related apoptosis activation. Besides, ER stress parameters were also elevated in virus-treated cardiomyocytes. Interestingly, melatonin treatment maintained mitochondrial dysfunction and repressed ER stress. To the end, we found that Mst1 was upregulated by virus infection; this effect was attenuated through supplementation with melatonin. However, Mst1 overexpression reduced the beneficial impact exerted by melatonin on cardiomyocyte viability, mitochondrial function and ER homeostasis. Our study illustrated that melatonin treatment attenuated viral myocarditis via sustaining cardiomyocyte viability, repressing mitochondrial dysfunction and inhibiting ER stress in a manner dependent on Mst1 inhibition.

Vildagliptin Reduces Stenosis of Injured Carotid Artery in Diabetic Mouse Through Inhibiting Vascular Smooth Muscle Cell Proliferation via ER Stress/NF-κB Pathway

Dipeptidyl peptidase-4 (DPP-4) inhibitors are novel anti-hyperglycemic drugs for type 2 diabetes. It has been reported that DDP-4 inhibitor could exert pleiotropic effects on cardiovascular system. This study was to explore the effect and mechanism of vildagliptin on the stenosis of injured carotid artery in diabetic mouse. Twenty six-week-old male db/db mice (BKS) were randomized into vildagliptin treated and vehicle control groups. Ligation injury was first performed in left carotid arteries of all diabetic mice, then oral vildagliptin or equal amount of PBS was correspondingly administered to the mice from the next day to ligation injury for 4 weeks. Effects on proliferation were detected via histological and morphometric analysis. Endoplasmic reticulum (ER) stress and nuclear factor kappa B (NF-κB) markers were determined by immunoblot analysis. After 4 weeks of vildagliptin delivery, it was observed that the intimal area and neointimal thickness of the ligated carotid arteries were significantly reduced as compared to the control group. In vivo, vildagliptin suppressed the expressions of PCNA and α-SMA, phospho-p65, phospho-IKKα/β, GRP78 and CHOP, as well as IRE-1 in vascular smooth muscle cells (VSMCs). In vitro, the proliferation and hypertrophy of VSMCs were significantly inhibited by blocking the IRE-1 pathway, and the inhibition of phospho-IRE-1 expression down-regulated the expression of phospho-IKKα/β in VSMCs. Vildagliptin reduced the stenosis of injured carotid arteries in diabetic mice, and this effect was achieved via inhibiting the activation of ER stress/NF-κB pathway.

Icariin and icaritin ameliorated hippocampus neuroinflammation via inhibiting HMGB1-related pro-inflammatory signals in lipopolysaccharide-induced inflammation model in C57BL/6 J mice

Inflammation is a defensive response of the body and is at the center of many diseases' process like depression. High mobility group protein box 1 (HMGB1), has been proved to function as a pro-inflammatory cytokine. We aim to explore the role of HMGB1 played in the neuroinflammation here. In this study, we used LPS to induce an acute inflammatory response, and to measure the anti-neuroinflammation effect of icariin (ICA) and icaritin (ICT). We found that LPS could increase the expression of HMGB1 in serum and hippocampus, along with a high expression of HMGB1 in the cytoplasm and a high expression of RAGE, which could be rescued by ICA and ICT, and ethyl pyruvate (EP) pretreatment showed similar effects here. We speculated that the translocation of HMGB1 from the nucleus to the cytoplasm played an important role in neuroinflammatory process, and HMGB1-RAGE signal was involved in this process. Furthermore, we found that ICA and ICT treatment activated TLR4-XBP1s related NF-κB signal, which we thought was relevant with the neuroprotective effect of ICA and ICT. However, EP pretreatment suppressed TLR4-XBP1s- endoplasmic reticulum stress related NF-κB signal to anti-inflammatory response, which was almost absolutely opposite with ICA and ICT treatment. We speculated that it might be caused by the duration of inflammation. We supposed that ICA and ICT could ameliorate neuroinflammation in hippocampus via suppressing HMGB1-RAGE signaling and might show a neuroprotective effect via activating TLR4-XBP1s related NF-κB signal at the same time, making it possible to act as an anti-neuroinflammatory drugs.

Nuclear factor-kappa B-dependent X-box binding protein 1 signalling promotes the proliferation of nucleus pulposus cells under tumour necrosis factor alpha stimulation

OBJECTIVES

Tumour necrosis factor alpha (TNF-α) expressed by nucleus pulposus cells (NPCs) plays a critical role in intervertebral disc (IVD) degeneration. A key unfolded protein response (UPR) component, X-box binding protein 1 (XBP1) and nuclear factor-kappa B (NF-κB) are essential for cell survival and proliferation. The aim of our study was to elucidate the roles of XBP1 and NF-κB in IVD degeneration (IDD).

MATERIALS AND METHODS

Rat NPCs were cultured with TNF-α in the presence or absence of XBP1 and NF-κB-p65 small interfering RNA. The associated genes and proteins were evaluated through quantitative real-time PCR, Western blot analyses and immunofluorescence staining to monitor UPR and NF-κB signalling and identify the regulatory mechanism of p65 by XBP1. Cell counting kit-8 assay, cell cycle analysis and related gene and protein expression were performed to examine the proliferation of NPCs.

RESULTS

The acute exposure of TNF-α accelerated the proliferation of rat NPCs by activating the UPR/XBP1 pathway. XBP1 signalling favoured the phosphorylation and nuclear translocation of p65 subunit of NF-κB. The activation of NF-κB in the later phase also enhanced NPC proliferation.

CONCLUSIONS

Unfolded protein response reinforces the survival and proliferation of NPCs under TNF-α stimulation by activating the XBP1 pathway, and NF-κB serves as a vital mediator in these events. The XBP1 signalling of UPR can be a novel therapeutic target in IDD.

Paeoniflorin prevents endoplasmic reticulum stress-associated inflammation in lipopolysaccharide-stimulated human umbilical vein endothelial cells via the IRE1α/NF-κB signaling pathway

Endoplasmic reticulum (ER) stress-associated inflammation is a critical molecular mechanism involved in the pathogenesis of endothelial dysfunction (ED). Hence, strategies for alleviating ER stress-induced inflammation may be essential for the prevention of cardiovascular diseases. Paeoniflorin (PF), a bioactive compound from Paeonia lactiflora Pallas is known for its functional properties against vascular inflammation. However, to date, PF-mediated protection against ER stress-dependent inflammation has not been identified. Herein, we investigate the protective effect of PF on lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cell (HUVEC) injury and explore its underlying mechanism. The result of the cell viability assay indicates that PF promotes the cell survival rate in LPS-stimulated HUVECs. In addition, the LPS-induced over-production of inflammatory cytokines (interleukin-6 (IL-6) and monocyte chemotactic protein 1 (MCP-1)) and ER stress markers (78 kDa glucose regulated protein (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP)) are significantly decreased by PF and the ER stress inhibitor 4-phenylbutric acid (4-PBA). The transmission electron microscopy (TEM) assay implies that the ultrastructural abnormalities in ER are reversed by PF treatment, which is similar to the protective effect of 4-PBA. Impressively, we find that the inositol-requiring enzyme 1α (IRE1α)/nuclear factor-kappa B (NF-κB) pathway is significantly activated and contributes to the progress of LPS-induced HUVEC injury by promoting inflammatory cytokine production. IRE1α siRNA, AEBSF (ATF6 inhibitor), GSK2656157 (PERK inhibitor), PDTC (NF-κB inhibitor) and thapsigargin (TG, IRE1 activator) are used to confirm the role of the IRE1α/NF-κB pathway in PF-mediated protection against LPS-induced HUVEC injury. Our findings indicate that PF has an inhibitory effect on endothelial injury. To summarize, PF might be a potential therapeutic agent to inhibit ER stress-associated vascular inflammation.

STF-083010, an inhibitor of XBP1 splicing, attenuates acute renal failure in rats by suppressing endoplasmic reticulum stress-induced apoptosis and inflammation

Endoplasmic reticulum (ER) stress is one of the driving forces of ischemia/reperfusion (IR)-induced acute renal failure (ARF). STF-083010, an inhibitor of the endonuclease activity of inositol-requiring enzyme-1 (IRE1), has the potential to block the initiation of a prolonged unfolded protein response (UPR) that is stimulated by ER stress and alleviates the impairments due to ER stress. In the current study, it was hypothesized that STF-083010 was capable of ameliorating ER stress-related damages in IR-induced ARF. Rats were administrated with STF-083010 and were subjected to induction of ARF using a ligation method. Then the effect of STF-083010 administration on the renal structure and function, oxidative stress, and inflammation in model rats was assessed. Furthermore, the levels of expression of UPR members and downstream effectors regulating apoptosis were detected as well. The results showed that establishment of the ARF model induced ER stress and impaired the renal structure and function. Administration of STF-083010 ameliorated impairments in the structure and function of the kidneys and the effect was associated with the suppressed oxidative stress and inflammation. At the molecular level, STF-083010 inhibited the prolonged UPR by downregulating the expressions of GRP78, p-IRE1, XBP1s, CHOP, and caspase 3, partially explaining the decreased apoptotic rate. The current study evaluated the potential of STF-083010 in treating ER stress-induced symptoms in ARF for the first time, and the findings demonstrated that STF-083010 resulted in effective treatment outcomes of ARF.

Endoplasmic reticulum stress in perivascular adipose tissue promotes destabilization of atherosclerotic plaque by regulating GM-CSF paracrine

Background

Perivascular adipose tissue (PVAT) accelerates plaque progression and increases cardiovascular risk. We tested the hypothesis that PVAT contributed to plaque vulnerability and investigated whether endoplasmic reticulum stress (ER stress) in PVAT played an important role in vulnerable plaque.

Methods

We transplanted thoracic aortic PVAT or subcutaneous adipose tissue as a control, from donor mice to carotid arteries of recipient apolipoprotein E deficient (apoE^−/−) mice after removing carotid artery collar placed for 6 weeks. Two weeks after transplantation, ER stress inhibitor 4-phenyl butyric acid (4-PBA) was locally administrated to the transplanted PVAT and then animals were euthanized after 4 weeks. Immunohistochemistry was performed to quantify plaque composition and neovascularization. Mouse angiogenesis antibody array kit was used to test the angiogenic factors produced by transplanted adipose tissue. In vitro tube formation assay, scratch wound migration assay and mouse aortic ring assay were used to assess the angiogenic capacity of supernatant of transplanted PVAT.

Results

Ultrastructural detection by transmission electron microscopy showed transplanted PVAT was a mixed population of white and brown adipocytes with abundant mitochondria. Transplanted PVAT increased the intraplaque macrophage infiltration, lipid core, intimal and vasa vasorum neovascularization and MMP2/9 expression in plaque while decreased smooth muscle cells and collagen in atherosclerotic plaque, which were restored by local 4-PBA-treatment. Antibody array analysis showed that 4-PBA reduced several angiogenic factors [Granulocyte Macrophage Colony Stimulating Factor (GM-CSF), MCP-1, IL-6] secreted by PVAT. Besides, conditioned medium from 4-PBA treated-PVAT inhibited tube formation and migration capacity of endothelial cells and ex vivo mouse aortic ring angiogenesis compared to conditioned medium from transplanted PVAT. mRNA expression and protein levels of GM-CSF were markedly elevated in adipocytes under ER stress which would be suppressed by 4-PBA. In addition, ER stress enhanced NF-κB binding to the promoter of the mouse GM-CSF gene in adipocytes confirmed by Chromatin immunoprecipitation analyses.

Conclusions

Our findings demonstrate that ER stress in PVAT destabilizes atherosclerotic plaque, in part through increasing GM-CSF paracrine via transcription factor NF-κB.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1481-z) contains supplementary material, which is available to authorized users.

Tauroursodeoxycholic Acid Protects against the Effects of P-Cresol-Induced Reactive Oxygen Species via the Expression of Cellular Prion Protein

Mesenchymal stem cells (MSCs) could be a promising solution in the treatment of various diseases including chronic kidney disease (CKD). However, endoplasmic reticulum (ER) stress induced by ischemia in the area of application limits the integration and survival of MSCs in patients. In our study, we generated ER stress-induced conditions in MSCs using P-cresol. As P-cresol is a toxic compound accumulated in the body of CKD patients and induces apoptosis and inflammation through reactive oxygen species (ROS), we observed ER stress-induced MSC apoptosis activated by oxidative stress, which in turn resulted from ROS generation. To overcome stress-induced apoptosis, we investigated the protective effects of tauroursodeoxycholic acid (TUDCA), a bile acid, on ER stress in MSCs. In ER stress, TUDCA treatment of MSCs reduced ER stress-associated protein activation, including GRP78, PERK, eIF2α, ATF4, IRE1α, and CHOP. Next, to explore the protective mechanism adopted by TUDCA, TUDCA-mediated cellular prion protein (PrP^C) activation was assessed. We confirmed that PrP^C expression significantly increased ROS, which was eliminated by superoxide dismutase and catalase in MSCs. These findings suggest that TUDCA protects from inflammation and apoptosis in ER stress via PrP^C expression. Our study demonstrates that TUDCA protects MSCs against inflammation and apoptosis in ER stress by PrP^C expression in response to P-cresol exposure.

The PI3K/Akt/mTOR pathway is involved in CVB3-induced autophagy of HeLa cells

Recent studies have found that viral myocarditis (VMC) associated with coxsackievirus B3 (CVB3) causes autophagy activation after infection, but the specific mechanism is not clear. The present study demonstrated that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB)/mammalian target of rapamycin (mTOR) signaling pathway participates in CVB3-induced autophagy. We found that the light chain 3 (LC3)-II/LC3-I ratio was increased and p62 and p-mTOR were altered at different times during CVB3 infection. To further assess the effects of this signaling pathway on CVB3 infection and viral replication, we selected 24 h post-inoculation (h.p.i.) as our research time point to conduct our next study. We inhibited the function of PI3K, Akt1 and mTOR. The outcome showed that inhibition of PI3K with ZSTK474 alleviated autophagy and decreased CVB3 mRNA replication and VP1 expression. Inhibition of mTOR with rapamycin promoted autophagy and viral mRNA replication but did not impact VP1 expression. Inhibition of Akt with MK2206 aggravated autophagy induced by viral infection. In our research, p62 exhibited a decrease at the beginning of infection but then increased as infection time increased. This finding may serve as a clue to elucidate the function of autophagy at different times of infection. However, the details merit further study. In conclusion, our findings suggest that the PI3K/Akt/mTOR signaling pathway participates in the process of autophagy induced by CVB3 infection. This finding may provide a new perspective of CVB3-induced autophagy.

Transmissible endoplasmic reticulum stress from myocardiocytes to macrophages is pivotal for the pathogenesis of CVB3-induced viral myocarditis

Infiltrating macrophages have been proven as a pivotal pathological inflammatory cell subset in coxsackievirus B3 (CVB3) induced viral myocarditis. However, the mechanisms underlying the initiation and promotion of macrophage pro-inflammatory responses are still blur. We previously reported that cardiac ER stress contributed to CVB3-induced myocarditis by augmenting inflammation. In this study, we focused on the influence of ER stress on the macrophage inflammatory responses in the viral myocarditis. We found that ER stress was robustly induced in the cardiac infiltrating macrophages from CVB3-infected mice, and robustly facilitated the production of pro-inflammatory cytokines (IL-6, IL-12, MCP-1 and IP-10). Consistently, adoptive transfer of ER stressed macrophages significantly worsened the viral myocarditis; while transfer of ER stress-inhibited macrophages obviously alleviated the myocarditis. To our surprise, this significantly activated ER stress was not directly caused by the virus stimulation, but was transferred from the CVB3-infected, ER stressed myocardiocytes via soluble molecules in a TLR2, 4-independent way. In the present study, we reported that the transmissible ER stress from the infected myocardiocytes to macrophages could augment the pro-inflammatory responses and promoted the pathogenesis of viral myocarditis. Blocking ER stress transmission, instead of inhibiting its initiation, may represent novel therapeutic strategies against viral myocarditis.

Role of endoplasmic reticulum stress signalling in diabetic endothelial dysfunction and atherosclerosis

It is well established that diabetes mellitus accelerates atherosclerotic vascular disease. Endothelial injury has been proposed to be the initial event in the pathogenesis of atherosclerosis. Endothelium not only acts as a semi-selective barrier but also serves physiological and metabolic functions. Diabetes or high glucose in circulation triggers a series of intracellular responses and organ damage such as endothelial dysfunction and apoptosis. One such response is high glucose-induced chronic endoplasmic reticulum stress in the endothelium. The unfolded protein response is an acute reaction that enables cells to overcome endoplasmic reticulum stress. However, when chronically persistent, endoplasmic reticulum stress response could ultimately lead to endothelial dysfunction and atherosclerosis. Herein, we discuss the scientific advances in understanding endoplasmic reticulum stress-induced endothelial dysfunction, the pathogenesis of diabetes-accelerated atherosclerosis and endoplasmic reticulum stress as a potential target in therapies for diabetic atherosclerosis.

Chemical Chaperone 4-Phenylbutyric Acid Reduces Cardiac Ischemia/Reperfusion Injury by Alleviating Endoplasmic Reticulum Stress and Oxidative Stress

Background

Cardiovascular diseases are the leading cause of death in many countries and myocardial ischemia-reperfusion (I/R) injury is the cause of many serious heart diseases. Recent reports suggested that endoplasmic reticulum (ER) stress is associated with the progress of ischemia/reperfusion (I/R) injury. In a previous study, we illustrated that 4-phenylbutyric acid (4-PBA) reduces I/R-induced cell death in vitro through inhibiting the ER stress-initiated cell apoptosis. In the present study we investigated whether 4-PBA improves heart function in isolated rat hearts subjected to I/R and elucidated the potential mechanisms involved in 4-PBA-induced cardioprotective effects.

Material/Methods

The isolated rat hearts were subjected to global ischemia and reperfusion in the absence or presence of 4-PBA. Hemodynamic parameters (LVSP, LVEDP, ±dP/dt_max, and HR) were monitored and histopathological examination was applied. The biomarkers related to oxidative stress were detected by LDH, ROS, MDA, CK, SOD, and GSH-Px kits. A TUNEL apoptosis assay kit was used to detect apoptosis. The expression levels of ER stress and apoptosis proteins were evaluated by Western blotting.

Results

We found that 4-PBA (5 mM, 10 mM) pretreatment significantly attenuated cardiac dysfunction and depressed oxidative stress induced by I/R. Moreover, I/R activated the ER stress proteins Grp78 and PERK, which are all decreased by 4-PBA. 4-PBA pretreatment also inhibited the expression of CHOP, Caspase-12, and Bax, reduced the phosphorylation of JNK, and enhanced the expression of anti-apoptotic protein Bcl-2.

Conclusions

We elucidated the significant protective effects of 4-PBA against I/R injuries by inhibition of ER stress, oxidative stress, and their associated apoptosis.

Melittin ameliorates CVB3-induced myocarditis via activation of the HDAC2-mediated GSK-3β/Nrf2/ARE signaling pathway

Viral myocarditis (VMC) is characterized as an inflammatory process of the myocardium and can be fatal in infants and children. Melittin is a major polypeptide in honey bee venom that has been traditionally used against inflammation. However, its effect on VMC and the underlying molecular mechanism has not been reported. In this study, BALB/c mice were intraperitoneally injected with CVB3 to build a VMC model and treated with melittin. The results showed that melittin increased the mice's body weight and inhibited CVB3 replication. HE staining also showed that melittin alleviated myocardial injury in the VMC model. Flow cytometry showed that melittin inhibited myocardial cell apoptosis; in addition, real-time PCR showed that melittin decreased the expression of bax and caspase-3, and increased the expression of bcl-2. The results of echocardiographic examination showed that melittin improved cardiac function. Moreover, melittin decreased the activity of AST, CK, HBDH and LDH, and decreased the production of IL-1β, IL-6, TNF-α and MCP-1 in CVB3-induced myocardial tissues. Finally, we also found that melittin increased the expression of HDAC2 and activated the GSK-3β/Nrf2/ARE signaling pathway, whereas these changes were reversed by inhibition of HDAC2 in VMC model mice. In conclusion, our results suggested that melittin ameliorates CVB3-induced myocarditis via activation of the HDAC2-mediated GSK-3β/Nrf2/ARE signaling pathway.

Protein 2B of Coxsackievirus B3 Induces Autophagy Relying on Its Transmembrane Hydrophobic Sequences

Coxsackievirus B (CVB) belongs to Enterovirus genus within the Picornaviridae family, and it is one of the most common causative pathogens of viral myocarditis in young adults. The pathogenesis of myocarditis caused by CVB has not been completely elucidated. In CVB infection, autophagy is manipulated to facilitate viral replication. Here we report that protein 2B, one of the non-structural proteins of CVB3, possesses autophagy-inducing capability. The autophagy-inducing motif of protein 2B was identified by the generation of truncated 2B and site-directed mutagenesis. The expression of 2B alone was sufficient to induce the formation of autophagosomes in HeLa cells, while truncated 2B containing the two hydrophobic regions of the protein also induced autophagy. In addition, we demonstrated that a single amino acid substitution (56V→A) in the stem loop in between the two hydrophobic regions of protein 2B abolished the formation of autophagosomes. Moreover, we found that 2B and truncated 2B with autophagy-inducting capability were co-localized with LC3-II. This study indicates that protein 2B relies on its transmembrane hydrophobic regions to induce the formation of autophagosomes, while 56 valine residue in the stem loop of protein 2B might exert critical structural influence on its two hydrophobic regions. These results may provide new insight for understanding the molecular mechanism of autophagy triggered by CVB infection.

Halofuginone alleviates acute viral myocarditis in suckling BALB/c mice by inhibiting TGF-β1

Viral myocarditis (VMC) is an inflammation of heart muscle in infants and young adolescents. This study explored the function of halofuginone (HF) in Coxsackievirus B3 (CVB3) -treated suckling mice. HF-treated animal exhibited higher survival rate, lower heart/body weight, and more decreased blood sugar concentration than CVB3 group. HF also reduced the expressions of interleukin(IL)-17 and IL-23 and the numbers of Th17 cells. Moreover, HF downregulated pro-inflammatory cytokine levels and increased anti-inflammatory cytokine levels. The expressions of transforming growth factor(TGF-β1) and nuclear factor kappa-light-chain-enhancer of activated B (NF-κB) p65/ tumor necrosis factor-α (TNF-α) proteins were decreased by HF as well. Finally, the overexpression of TGF-β1 counteracted the protection effect of HF in CVB3-treated suckling mice. In summary, our study suggests HF increases the survival of CVB3 suckling mice, reduces the Th17 cells and pro-inflammatory cytokine levels, and may through downregulation of the TGF-β1-mediated expression of NF-κB p65/TNF-α pathway proteins. These results offer a potential therapeutic strategy for the treatment of VMC.

Endoplasmic Reticulum Stress Interacts With Inflammation in Human Diseases

The endoplasmic reticulum (ER) is a critical organelle for normal cell function and homeostasis. Disturbance in the protein folding process in the ER, termed ER stress, leads to the activation of unfolded protein response (UPR) that encompasses a complex network of intracellular signaling pathways. The UPR can either restore ER homeostasis or activate pro-apoptotic pathways depending on the type of insults, intensity and duration of the stress, and cell types. ER stress and the UPR have recently been linked to inflammation in a variety of human pathologies including autoimmune, infectious, neurodegenerative, and metabolic disorders. In the cell, ER stress and inflammatory signaling share extensive regulators and effectors in a broad spectrum of biological processes. In spite of different etiologies, the two signaling pathways have been shown to form a vicious cycle in exacerbating cellular dysfunction and causing apoptosis in many cells and tissues. However, the interaction between ER stress and inflammation in many of these diseases remains poorly understood. Further understanding of the biochemistry, cell biology, and physiology may enable the development of novel therapies that spontaneously target these pathogenic pathways.

4-Phenylbutyric Acid Attenuates Pancreatic Beta-Cell Injury in Rats with Experimental Severe Acute Pancreatitis

Endoplasmic reticulum (ER) stress is a particular process with an imbalance of homeostasis, which plays an important role in pancreatitis, but little is known about how ER stress is implicated in severe acute pancreatitis (SAP) induced pancreatic beta-cell injury. To investigate the effect of 4-phenylbutyric acid (4-PBA) on the beta-cell injury following SAP and the underlying mechanism, twenty-four Sprague-Dawley rats were randomly divided into sham-operation (SO) group, SAP model group, and 4-PBA treatment group. SAP model was induced by infusion of 5% sodium taurocholate into the biliopancreatic duct. 4-PBA or normal saline was injected intraperitoneally for 3 days in respective group before successful modeling. Results showed that 4-PBA attenuated the following: (1) pancreas and islet pathological injuries, (2) serum TNF-α and IL-1β, (3) serum insulin and glucose, (4) beta-cell ultrastructural changes, (5) ER stress markers (BiP, ORP150, and CHOP), Caspase-3, and insulin expression in islet. These results suggested that 4-PBA mitigates pancreatic beta-cell injury and endocrine disorder in SAP, presumably because of its role in inhibiting excessive endoplasmic reticulum stress. This may serve as a new therapeutic target for reducing pancreatic beta-cell injury and endocrine disorder in SAP upon 4-PBA treatment.