Salubrinal attenuates β-amyloid-induced neuronal death and microglial activation by inhibition of the NF-κB pathway

"Investigation of the potential cellular changes induced by magnesium sulfate and salubrinal in a lipopolysaccharide-induced chorioamnionitis model"

Chorioamnionitis is closely associated with preterm labor and poses a significant public health concern. In this pathological process where inflammation plays a key role, intracellular mechanisms such as endoplasmic reticulum stress are crucial. In this study, we aimed to explore the potential positive outcomes of the combined use of salubrinal (SLB) with magnesium (Mg) treatment in chorioamnionitis. Thirty pregnant rats were divided into 5 groups as: Control, LPS (1 mg/kg), LPS + SLB (1 mg/kg), LPS + Mg (Dhaka protocol), LPS + SLB + Mg. Rats were sacrificed 4 h after LPS administration, then placental and fetal brain tissues were collected. LPS administration enhanced the levels of tumor necrosis factor-alpha, vascular endothelial growth factor, caspase-3 immunoexpressions, BAX, eukaryotic initiation factor 2-alpha, s100, and glial fibrillary acidic protein expressions and lowered BCL2 expressions in the placenta or fetal brains. SLB and Mg treatments were observed to reverse all these findings, and the most significant positive effect was in the LPS + SLB + Mg group. The known anti-inflammatory activity of Mg, when used with SLB, preventing the transition to apoptosis and increasing antioxidant enzyme activity, as identified in this study, can contribute significantly to the literature. However, these results need to be supported by additional molecular studies.

Mammalian integrated stress responses in stressed organelles and their functions

The integrated stress response (ISR) triggered in response to various cellular stress enables mammalian cells to effectively cope with diverse stressful conditions while maintaining their normal functions. Four kinases (PERK, PKR, GCN2, and HRI) of ISR regulate ISR signaling and intracellular protein translation via mediating the phosphorylation of eukaryotic translation initiation factor 2 α (eIF2α) at Ser51. Early ISR creates an opportunity for cells to repair themselves and restore homeostasis. This effect, however, is reversed in the late stages of ISR. Currently, some studies have shown the non-negligible impact of ISR on diseases such as ischemic diseases, cognitive impairment, metabolic syndrome, cancer, vanishing white matter, etc. Hence, artificial regulation of ISR and its signaling with ISR modulators becomes a promising therapeutic strategy for relieving disease symptoms and improving clinical outcomes. Here, we provide an overview of the essential mechanisms of ISR and describe the ISR-related pathways in organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Meanwhile, the regulatory effects of ISR modulators and their potential application in various diseases are also enumerated.

Targeting unfolded protein response reverts ER stress and ER Ca2+ homeostasis in cardiomyocytes expressing the pathogenic variant of Lamin A/C R321X

BACKGROUND

We previously demonstrated that an Italian family affected by a severe dilated cardiomyopathy (DCM) with history of sudden deaths at young age, carried a mutation in the Lmna gene encoding for a truncated variant of the Lamin A/C protein (LMNA), R321X. When expressed in heterologous systems, such variant accumulates into the endoplasmic reticulum (ER), inducing the activation of the PERK-CHOP pathway of the unfolded protein response (UPR), ER dysfunction and increased rate of apoptosis. The aim of this work was to analyze whether targeting the UPR can be used to revert the ER dysfunction associated with LMNA R321X expression in HL-1 cardiac cells.

METHODS

HL-1 cardiomyocytes stably expressing LMNA R321X were used to assess the ability of 3 different drugs targeting the UPR, salubrinal, guanabenz and empagliflozin to rescue ER stress and dysfunction. In these cells, the state of activation of both the UPR and the pro-apoptotic pathway were analyzed monitoring the expression levels of phospho-PERK, phospho-eIF2α, ATF4, CHOP and PARP-CL. In addition, we measured ER-dependent intracellular Ca²⁺ dynamics as indicator of proper ER functionality.

RESULTS

We found that salubrinal and guanabenz increased the expression levels of phospho-eIF2α and downregulated the apoptosis markers CHOP and PARP-CL in LMNA R321X-cardiomyocytes, maintaining the so-called adaptive UPR. These drugs also restored ER ability to handle Ca²⁺ in these cardiomyocytes. Interestingly, we found that empagliflozin downregulated the apoptosis markers CHOP and PARP-CL shutting down the UPR itself through the inhibition of PERK phosphorylation in LMNA R321X-cardiomyocytes. Furthermore, upon empagliflozin treatment, ER homeostasis, in terms of ER ability to store and release intracellular Ca²⁺ was also restored in these cardiomyocytes.

CONCLUSIONS

We provided evidence that the different drugs, although interfering with different steps of the UPR, were able to counteract pro-apoptotic processes and to preserve the ER homeostasis in R321X LMNA-cardiomyocytes. Of note, two of the tested drugs, guanabenz and empagliflozin, are already used in the clinical practice, thus providing preclinical evidence for ready-to-use therapies in patients affected by the LMNA R321X associated cardiomyocytes.

An Antioxidant and Anti-ER Stress Combo Therapy Decreases Inflammation, Secondary Brain Damage and Promotes Neurological Recovery following Traumatic Brain Injury in Mice

The complex pathophysiology of post-traumatic brain damage might need a polypharmacological strategy with a combination of drugs that target multiple, synergistic mechanisms. We currently tested a combination of apocynin (curtails formation of reactive oxygen species), tert-butylhydroquinone (promotes disposal of reactive oxygen species), and salubrinal (prevents endoplasmic reticulum stress) following a moderate traumatic brain injury (TBI) induced by controlled cortical impact in adult mice. Adult mice of both sexes treated with the above tri-combo showed alleviated motor and cognitive deficits, attenuated secondary lesion volume, and decreased oxidative DNA damage. Concomitantly, tri-combo treatment regulated post-TBI inflammatory response by decreasing the infiltration of T cells and neutrophils and activation of microglia in both sexes. Interestingly, sexual dimorphism was seen in the case of TBI-induced microgliosis and infiltration of macrophages in the tri-combo-treated mice. Moreover, the tri-combo treatment prevented TBI-induced white matter volume loss in both sexes. The beneficial effects of tri-combo treatment were long-lasting and were also seen in aged mice. Thus, the present study supports the tri-combo treatment to curtail oxidative stress and endoplasmic reticulum stress concomitantly as a therapeutic strategy to improve TBI outcomes.SIGNIFICANCE STATEMENT Of the several mechanisms that contribute to TBI pathophysiology, oxidative stress, endoplasmic reticulum stress, and inflammation play a major role. The present study shows the therapeutic potential of a combination of apocynin, tert-butylhydroquinone, and salubrinal to prevent oxidative stress and endoplasmic reticulum stress and the interrelated inflammatory response in mice subjected to TBI. The beneficial effects of the tri-combo include alleviation of TBI-induced motor and cognitive deficits and lesion volume. The neuroprotective effects of the tri-combo are also linked to its ability to prevent TBI-induced white matter damage. Importantly, neuroprotection by the tri-combo treatment was observed to be not dependent on sex or age. Our data demonstrate that a polypharmacological strategy is efficacious after TBI.

Activation of autophagy reverses progressive and deleterious protein aggregation in PRPF31 patient-induced pluripotent stem cell-derived retinal pigment epithelium cells

INTRODUCTION

Mutations in pre-mRNA processing factor 31 (PRPF31), a core protein of the spliceosomal tri-snRNP complex, cause autosomal-dominant retinitis pigmentosa (adRP). It has remained an enigma why mutations in ubiquitously expressed tri-snRNP proteins result in retina-specific disorders, and so far, the underlying mechanism of splicing factors-related RP is poorly understood.

METHODS

We used the induced pluripotent stem cell (iPSC) technology to generate retinal organoids and RPE models from four patients with severe and very severe PRPF31-adRP, unaffected individuals and a CRISPR/Cas9 isogenic control.

RESULTS

To fully assess the impacts of PRPF31 mutations, quantitative proteomics analyses of retinal organoids and RPE cells were carried out showing RNA splicing, autophagy and lysosome, unfolded protein response (UPR) and visual cycle-related pathways to be significantly affected. Strikingly, the patient-derived RPE and retinal cells were characterised by the presence of large amounts of cytoplasmic aggregates containing the mutant PRPF31 and misfolded, ubiquitin-conjugated proteins including key visual cycle and other RP-linked tri-snRNP proteins, which accumulated progressively with time. The mutant PRPF31 variant was not incorporated into splicing complexes, but reduction of PRPF31 wild-type levels led to tri-snRNP assembly defects in Cajal bodies of PRPF31 patient retinal cells, altered morphology of nuclear speckles and reduced formation of active spliceosomes giving rise to global splicing dysregulation. Moreover, the impaired waste disposal mechanisms further exacerbated aggregate formation, and targeting these by activating the autophagy pathway using Rapamycin reduced cytoplasmic aggregates, leading to improved cell survival.

CONCLUSIONS

Our data demonstrate that it is the progressive aggregate accumulation that overburdens the waste disposal machinery rather than direct PRPF31-initiated mis-splicing, and thus relieving the RPE cells from insoluble cytoplasmic aggregates presents a novel therapeutic strategy that can be combined with gene therapy studies to fully restore RPE and retinal cell function in PRPF31-adRP patients.

E3 ubiquitin ligase Nedd4-2 exerts neuroprotective effects during endoplasmic reticulum stress

The neural precursor cell expressed developmentally down-regulated protein 4-like (Nedd4-2) is an E3 ubiquitin ligase critical for neurodevelopment and homeostasis of neural circuit excitability. While dysregulation of Nedd4-2 has been linked to elevated seizure susceptibility through impaired ubiquitination of multiple direct substrates, it remains largely unclear whether Nedd4-2 interconnects other cellular pathways that affect neuronal activity and seizure susceptibility. Here, we first showed that Nedd4-2 associates with the endoplasmic reticulum (ER) and regulates the expression of multiple ER-resident proteins. Furthermore, utilizing Nedd4-2 conditional knockout mice, we showed that Nedd4-2 is required for the maintenance of spontaneous neural activity and excitatory synapses following the induction of ER stress. When analyzing activation of the canonical pathways of ER stress response, we found that Nedd4-2 is required for phosphorylation of eIF2α. While phosphorylation of eIF2α has been shown to reduce seizure susceptibility, attempts to facilitate phosphorylation of eIF2α in Nedd4-2 conditional knockout mice failed to produce such a beneficial function, suggesting a role for Nedd4-2 in integrating the ER stress response to modulate seizure susceptibility. Altogether, our study demonstrates neuroprotective functions of Nedd4-2 during ER stress in neurons and could provide insight into neurological diseases in which the expression or activity of Nedd4-2 is impaired.

PKC Delta Activation Promotes Endoplasmic Reticulum Stress (ERS) and NLR Family Pyrin Domain-Containing 3 (NLRP3) Inflammasome Activation Subsequent to Asynuclein-Induced Microglial Activation: Involvement of Thioredoxin-Interacting Protein (TXNIP)/Thioredoxin (Trx) Redoxisome Pathway

A classical hallmark of Parkinson's disease (PD) pathogenesis is the accumulation of misfolded alpha-synuclein (αSyn) within Lewy bodies and Lewy neurites, although its role in microglial dysfunction and resultant dopaminergic (DAergic) neurotoxicity is still elusive. Previously, we identified that protein kinase C delta (PKCδ) is activated in post mortem PD brains and experimental Parkinsonism and that it participates in reactive microgliosis; however, the relationship between PKCδ activation, endoplasmic reticulum stress (ERS) and the reactive microglial activation state in the context of α-synucleinopathy is largely unknown. Herein, we show that oxidative stress, mitochondrial dysfunction, NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, and PKCδ activation increased concomitantly with ERS markers, including the activating transcription factor 4 (ATF-4), serine/threonine-protein kinase/endoribonuclease inositol-requiring enzyme 1α (p-IRE1α), p-eukaryotic initiation factor 2 (eIF2α) as well as increased generation of neurotoxic cytokines, including IL-1β in aggregated αSyn_agg-stimulated primary microglia. Importantly, in mouse primary microglia-treated with αSyn_agg we observed increased expression of Thioredoxin-interacting protein (TXNIP), an endogenous inhibitor of the thioredoxin (Trx) pathway, a major antioxidant protein system. Additionally, αSyn_agg promoted interaction between NLRP3 and TXNIP in these cells. In vitro knockdown of PKCδ using siRNA reduced ERS and led to reduced expression of TXNIP and the NLRP3 activation response in αSyn_agg-stimulated mouse microglial cells (MMCs). Additionally, attenuation of mitochondrial reactive oxygen species (mitoROS) via mito-apocynin and amelioration of ERS via the eIF2α inhibitor salubrinal (SAL) reduced the induction of the ERS/TXNIP/NLRP3 signaling axis, suggesting that mitochondrial dysfunction and ERS may act in concert to promote the αSyn_agg-induced microglial activation response. Likewise, knockdown of TXNIP by siRNA attenuated the αSyn_agg-induced NLRP3 inflammasome activation response. Finally, unilateral injection of αSyn preformed fibrils (αSyn_PFF) into the striatum of wild-type mice induced a significant increase in the expression of nigral p-PKCδ, ERS markers, and upregulation of the TXNIP/NLRP3 inflammasome signaling axis prior to delayed loss of TH⁺ neurons. Together, our results suggest that inhibition of ERS and its downstream signaling mediators TXNIP and NLRP3 might represent novel therapeutic avenues for ameliorating microglia-mediated neuroinflammation in PD and other synucleinopathies.

Hereditary Spastic Paraplegia and Future Therapeutic Directions: Beneficial Effects of Small Compounds Acting on Cellular Stress

Hereditary spastic paraplegia (HSP) is a group of inherited neurodegenerative conditions that share a characteristic feature of degeneration of the longest axons within the corticospinal tract, which leads to progressive spasticity and weakness of the lower limbs. Mutations of over 70 genes produce defects in various biological pathways: axonal transport, lipid metabolism, endoplasmic reticulum (ER) shaping, mitochondrial function, and endosomal trafficking. HSPs suffer from an adequate therapeutic plan. Currently the treatments foreseen for patients affected by this pathology are physiotherapy, to maintain the outgoing tone, and muscle relaxant therapies for spasticity. Very few clinical studies have been conducted, and it's urgent to implement preclinical animal studies devoted to pharmacological test and screening, to expand the rose of compounds potentially attractive for clinical trials. Small animal models, such as Drosophila melanogaster and zebrafish, have been generated, analyzed, and used as preclinical model for screening of compounds and their effects. In this work, we briefly described the role of HSP-linked proteins in the organization of ER endomembrane system and in the regulation of ER homeostasis and stress as a common pathological mechanism for these HSP forms. We then focused our attention on the pharmacodynamic and pharmacokinetic features of some recently identified molecules with antioxidant property, such as salubrinal, guanabenz, N-acetyl cysteine, methylene blue, rapamycin, and naringenin, and on their potential use in future clinical studies. Expanding the models and the pharmacological screening for HSP disease is necessary to give an opportunity to patients and clinicians to test new molecules.

Homeostasis of the ER redox state subsequent to proteasome inhibition

Endoplasmic reticulum (ER) maintains within, an oxidative redox state suitable for disulfide bond formation. We monitored the ER redox dynamics subsequent to proteasome inhibition using an ER redox probe ERroGFP S4. Proteasomal inhibition initially led to oxidation of the ER, but gradually the normal redox state was recovered that further led to a reductive state. These events were found to be concomitant with the increase in the both oxidized and reduced glutathione in the microsomal fraction, with a decrease of total intracellular glutathione. The ER reduction was suppressed by pretreatment of a glutathione synthesis inhibitor or by knockdown of ATF4, which induces glutathione-related genes. These results suggested cellular adaptation of ER redox homeostasis: (1) inhibition of proteasome led to accumulation of misfolded proteins and oxidative state in the ER, and (2) the oxidative ER was then reduced by ATF4 activation, followed by influx of glutathione into the ER.

Molecular Dysfunctions of Mitochondria-Associated Membranes (MAMs) in Alzheimer's Disease

Alzheimer’s disease (AD) is a multifactorial neurodegenerative pathology characterized by a progressive decline of cognitive functions. Alteration of various signaling cascades affecting distinct subcellular compartment functions and their communication likely contribute to AD progression. Among others, the alteration of the physical association between the endoplasmic reticulum (ER) and mitochondria, also referred as mitochondria-associated membranes (MAMs), impacts various cellular housekeeping functions such as phospholipids-, glucose-, cholesterol-, and fatty-acid-metabolism, as well as calcium signaling, which are all altered in AD. Our review describes the physical and functional proteome crosstalk between the ER and mitochondria and highlights the contribution of distinct molecular components of MAMs to mitochondrial and ER dysfunctions in AD progression. We also discuss potential strategies targeting MAMs to improve mitochondria and ER functions in AD.

The Integrated Stress Response and Phosphorylated Eukaryotic Initiation Factor 2α in Neurodegeneration

The proposed molecular mechanisms underlying neurodegenerative pathogenesis are varied, precluding the development of effective therapies for these increasingly prevalent disorders. One of the most consistent observations across neurodegenerative diseases is the phosphorylation of eukaryotic initiation factor 2α (eIF2α). eIF2α is a translation initiation factor, involved in cap-dependent protein translation, which when phosphorylated causes global translation attenuation. eIF2α phosphorylation is mediated by 4 kinases, which, together with their downstream signaling cascades, constitute the integrated stress response (ISR). While the ISR is activated by stresses commonly observed in neurodegeneration, such as oxidative stress, endoplasmic reticulum stress, and inflammation, it is a canonically adaptive signaling cascade. However, chronic activation of the ISR can contribute to neurodegenerative phenotypes such as neuronal death, memory impairments, and protein aggregation via apoptotic induction and other maladaptive outcomes downstream of phospho-eIF2α-mediated translation inhibition, including neuroinflammation and altered amyloidogenic processing, plausibly in a feed-forward manner. This review examines evidence that dysregulated eIF2a phosphorylation acts as a driver of neurodegeneration, including a survey of observations of ISR signaling in human disease, inspection of the overlap between ISR signaling and neurodegenerative phenomenon, and assessment of recent encouraging findings ameliorating neurodegeneration using developing pharmacological agents which target the ISR. In doing so, gaps in the field, including crosstalk of the ISR kinases and consideration of ISR signaling in nonneuronal central nervous system cell types, are highlighted.

Inhibition of the PERK-Dependent Unfolded Protein Response Signaling Pathway Involved in the Pathogenesis of Alzheimer's Disease

OBJECTIVES

There is a body of evidence that neurodegenerative disease entities are directly correlated with the perturbations on the molecular level. Hence, the ER stress-mediated Unfolded Protein Response (UPR) is activated resulting in PERK-dependent phosphorylation of the Eukaryotic initiation factor 2 (eIF2α). Thus, the levels of ATF4 and CHOP proteins are significantly increased, which subsequently switches the pro-adaptive branch of the UPR into the pro-apoptotic directly leading to neuronal loss and initiation of the neurodegenerative process. The aim of the presented study was the evaluation of the biological activity of highly specific, small-molecule inhibitors of the PERKdependent UPR signaling pathway.

METHODS

The study was conducted on rat astrocytic DI TNC1 cell line. The level of p-eIF2α was measured by Western blot technique, the cytotoxicity of the investigated compound was assessed by the MTT assay and using the FITC-conjugated Annexin V (Annexin V-FITC) to indicate apoptosis and propidium iodide (PI) to indicate necrosis. The effect of tested compound on cell cycle progression was measured by flow cytometry, where the PI-labelled nuclei were analysed for DNA content.

RESULTS

As a result one of the investigated compound LDN-0060609 triggers a significant inhibition of the eIF2α phosphorylation in DI TNC1 cell line. Moreover, we showed that compound LDN-0060609 is non-cytotoxic and has no effect on cell cycle progression.

CONCLUSION

In conclusion, LDN-0060609 may constitute a novel, targeted treatment approach against neurodegenerative diseases, including Alzheimer's disease (AD), where pathogenesis and progression are closely associated with the overactivation of the PERK-dependent UPR signaling pathway.

The PERK-Dependent Molecular Mechanisms as a Novel Therapeutic Target for Neurodegenerative Diseases

Higher prevalence of neurodegenerative diseases is strictly connected with progressive aging of the world population. Interestingly, a broad range of age-related, neurodegenerative diseases is characterized by a common pathological mechanism-accumulation of misfolded and unfolded proteins within the cells. Under certain circumstances, such protein aggregates may evoke endoplasmic reticulum (ER) stress conditions and subsequent activation of the unfolded protein response (UPR) signaling pathways via the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dependent manner. Under mild to moderate ER stress, UPR has a pro-adaptive role. However, severe or long-termed ER stress conditions directly evoke shift of the UPR toward its pro-apoptotic branch, which is considered to be a possible cause of neurodegeneration. To this day, there is no effective cure for Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), or prion disease. Currently available treatment approaches for these diseases are only symptomatic and cannot affect the disease progression. Treatment strategies, currently under detailed research, include inhibition of the PERK-dependent UPR signaling branches. The newest data have reported that the use of small-molecule inhibitors of the PERK-mediated signaling branches may contribute to the development of a novel, ground-breaking therapeutic approach for neurodegeneration. In this review, we critically describe all the aspects associated with such targeted therapy against neurodegenerative proteopathies.

Exposure to CuO Nanoparticles Mediates NFκB Activation and Enhances Amyloid Precursor Protein Expression

Amyloid precursor protein (APP) is directly related to Aβ amyloidosis—a hallmark of Alzheimer’s disease (AD). However, the impact of environmental factors upon APP biology and Aβ amyloid pathology have not been well studied. The increased use of nanoparticles (NPs) or engineered nanomaterials (ENMs) has led to a growing body of evidence suggesting that exposure to metal/metal oxide NPs, such as Fe₂O₃, CuO, and ZnO, may contribute to the pathophysiology of neurodegenerative diseases such as AD through neuroinflammation. Our previous studies indicated that exposure to CuO nanoparticles (CuONPs) induce potent in vitro neurotoxicity. Herein, we investigated the effects on APP expression in neuronal cells exposed to different metal oxide NPs. We found a low dose of CuONPs effectively activated the NFκB signaling pathway and increased APP expression. Moreover, the inhibition of p65 expression using siRNA abolished CuONP-mediated APP expression, suggesting that NFκB-regulated APP expression in response to CuONP exposure may be associated with AD pathology.

Endoplasmic reticulum stress signaling in cancer and neurodegenerative disorders: Tools and strategies to understand its complexity

The endoplasmic reticulum (ER) comprises a network of tubules and vesicles that constitutes the largest organelle of the eukaryotic cell. Being the location where most proteins are synthesized and folded, it is crucial for the upkeep of cellular homeostasis. Disturbed ER homeostasis triggers the activation of a conserved molecular machinery, termed the unfolded protein response (UPR), that comprises three major signaling branches, initiated by the protein kinase RNA-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and the activating transcription factor 6 (ATF6). Given the impact of this intricate signaling network upon an extensive list of cellular processes, including protein turnover and autophagy, ER stress is involved in the onset and progression of multiple diseases, including cancer and neurodegenerative disorders. There is, for this reason, an increasing number of publications focused on characterizing and/or modulating ER stress, which have resulted in a wide array of techniques employed to study ER-related molecular events. This review aims to sum up the essentials on the current knowledge of the molecular biology of endoplasmic reticulum stress, while highlighting the available tools used in studies of this nature.

Transient upregulation of translational efficiency in prodromal and early symptomatic Tg2576 mice contributes to Aβ pathology

TG2576 mice show highest levels of the full length mutant Swedish Human Amyloid Precursor Protein (APPKM670/671LN) during prodromal and early sympotomatic stages. Interestingly, this occurs in association with the unbalanced expression of two of its RNA Binding proteins (RBPs) opposite regulators, the Fragile-X Mental Retardation Protein (FMRP) and the heteronuclear Ribonucleoprotein C (hnRNP C). Whether an augmentation in overall translational efficiency also contributes to the elevation of APP levels at those early developmental stages is currently unknown. We investigated this possibility by performing a longitudinal polyribosome profiling analysis of APP mRNA and protein in total hippocampal extracts from Tg2576 mice. Results showed that protein polysomal signals were exclusively detected in pre-symptomatic (1 months) and early symptomatic (3 months) mutant mice. Differently, hAPP mRNA polysomal signals were detected at any age, but a peak of expression was found when mice were 3-month old. Consistent with an early but transient rise of translational efficiency, the phosphorylated form of the initial translation factor eIF2α (p-eIF2α) was reduced at pre-symptomatic and early symptomatic stages, whereas it was increased at the fully symptomatic stage. Pharmacological downregulation of overall translation in early symptomatic mutants was then found to reduce hippocampal levels of full length APP, Aβspecies, BACE1 and Caspase-3, to rescue predominant LTD at hippocampal synapses, to revert dendritic spine loss and memory alterations, and to reinstate memory-induced c-fosactivation. Altogether, our findings demonstrate that overall translation is upregulated in prodromal and early symptomatic Tg2576 mice, and that restoring proper translational control at the onset of AD-like symptoms blocks the emergence of the AD-like phenotype.

A positive allosteric modulator of mGluR5 promotes neuroprotective effects in mouse models of Alzheimer's disease

Alzheimer's Disease (AD) is the most prevalent neurodegenerative disorder. Despite advances in the understanding of its pathophysiology, none of the available therapies prevents disease progression. Excess glutamate plays an important role in excitotoxicity by activating ionotropic receptors. However, the mechanisms modulating neuronal cell survival/death via metabotropic glutamate receptors (mGluRs) are not completely understood. Recent data indicates that CDPPB, a positive allosteric modulator of mGluR5, has neuroprotective effects. Thus, this work aimed to investigate CDPPB treatment effects on amyloid-β (Aβ) induced pathological alterations in vitro and in vivo and in a transgenic mouse model of AD (T41 mice). Aβ induced cell death in primary cultures of hippocampal neurons, which was prevented by CDPPB. Male C57BL/6 mice underwent stereotaxic surgery for unilateral intra-hippocampal Aβ injection, which induced memory deficits, neurodegeneration, neuronal viability reduction and decrease of doublecortin-positive cells, a marker of immature neurons and neuronal proliferation. Treatment with CDPPB for 8 days reversed neurodegeneration and doublecortin-positive cells loss and recovered memory function. Fourteen months old T41 mice presented cognitive deficits, neuronal viability reduction, gliosis and Aβ accumulation. Treatment with CDPPB for 28 days increased neuronal viability (32.2% increase in NeuN⁺ cells) and reduced gliosis in CA1 region (Iba-1⁺ area by 31.3% and GFAP⁺ area by 37.5%) in transgenic animals, without inducing hepatotoxicity. However, it did not reverse cognitive deficit. Despite a four-week treatment did not prevent memory loss in aged transgenic mice, CDPPB is protective against Aβ stimulus. Therefore, this drug represents a potential candidate for further investigations as AD treatment.

Lychee Seed Fraction Inhibits Aβ(1-42)-Induced Neuroinflammation in BV-2 Cells via NF-κB Signaling Pathway

In our previous studies, an active fraction derived from lychee seed could inhibit β-amyloid-induced apoptosis of PC12 cells and neurons. The primarily microglia cells are recognized as the brain’s resident macrophages and thought to remodel of the brain by removing presumably redundant, apoptotic neurons. In the current study, we aimed to investigate the anti-neuroinflammation effect of lychee seed fraction (LSF) in Aβ(1-42)-induced BV-2 cells and the underlying mechanism. The morphology results displayed that LSF could improve the status of Aβ(1-42)-induced BV-2 cells. The enzyme-linked immunosorbent assay, real-time PCR, and Western blotting results showed that LSF could significantly reduce the release, mRNA levels, and protein expressions of the pro-inflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) in Aβ(1-42)-induced BV-2 cells, which were downregulated through suppressing the NF-κB signaling pathway. Furthermore, LSF could upregulate Bcl-2 and downregulate Bax, Caspase-3, and cleaved-PARP protein expressions. Taken together, our results first demonstrated that LSF could suppress the inflammatory response via inhibiting NF-κB signaling pathway, and inhibit apoptosis in Aβ(1-42)-induced BV-2 cells. Our findings further prove that LSF as a potential drug may be used for treating AD in the future.

Translating protein phosphatase research into treatments for neurodegenerative diseases

Many of the major neurodegenerative disorders are characterized by the accumulation of intracellular protein aggregates in neurons and other cells in brain, suggesting that errors in protein quality control mechanisms associated with the aging process play a critical role in the onset and progression of disease. The increased understanding of the unfolded protein response (UPR) signaling network and, more specifically, the structure and function of eIF2α phosphatases has enabled the development or discovery of small molecule inhibitors that show great promise in restoring protein homeostasis and ameliorating neuronal damage and death. While this review focuses attention on one or more eIF2α phosphatases, the wide range of UPR proteins that are currently being explored as potential drug targets bodes well for the successful future development of therapies to preserve neuronal function and treat neurodegenerative disease.

Integrated Stress Response as a Therapeutic Target for CNS Injuries

Central nervous system (CNS) injuries, caused by cerebrovascular pathologies or mechanical contusions (e.g., traumatic brain injury, TBI) comprise a diverse group of disorders that share the activation of the integrated stress response (ISR). This pathway is an innate protective mechanism, with encouraging potential as therapeutic target for CNS injury repair. In this review, we will focus on the progress in understanding the role of the ISR and we will discuss the effects of various small molecules that target the ISR on different animal models of CNS injury.

Rosuvastatin Attenuates High-Salt and Cholesterol Diet Induced Neuroinflammation and Cognitive Impairment via Preventing Nuclear Factor KappaB Pathway

Recent attention is focused on the impact of diet on health and mental well-being. High-salt and cholesterol diet (HSCD) is known to be associated with neuroinflammation which is the predominant factor for neurodegenerative disease like Alzheimer disease (AD). In the present study, we examined the neuroprotective potential of rosuvastatin, an HMG-CoA reductase inhibitor against HSCD induced neuroinflammation and cognitive impairment. Our results demonstrated that HSCD-induced cognitive impairment as determined by Morris water maze (MWM) task. HSCD also activated nuclear factor kappaB (NF-kB) signaling pathway. The cytokine response was measured using a cytometric bead-based assay quantified by flow cytometry. Treatment with rosuvastatin decreased the production of nitric oxide (NO), tumor necrosis factor alpha (TNF-α) and increased interleukin-10 (IL-10) in a dose-dependent manner. Our results also demonstrated that the rosuvastatin modulates neuronal cell death by inhibiting the overexpression of NF-kB in the CA1 region of hippocampus. In addition, molecular docking study of rosuvastatin indicated high affinity and tighter binding capacity for the active site of the NF-kB. These results suggest that HSCD-triggered inflammatory response and cognitive impairment may be associated with NF-κB signaling pathway. Therefore, treatment with rosuvastatin could be a potential new therapeutic strategy for sporadic dementia of AD.

Activation of liver X receptor α protects amyloid β1-40 induced inflammatory and senescent responses in human retinal pigment epithelial cells

OBJECTIVE

To investigate whether activation of the liver X receptors (LXRs) inhibits amyloid β_1-40 (Aβ_1-40) induced inflammatory and senescent responses in human retinal pigment epithelial (RPE) cells.

MATERIALS AND METHODS

Confluent cultures of human primary RPE and ARPE-19 cells pretreated with 5 μΜ of TO901317 (TO90), a synthetic agonist of LXR, or vehicle were incubated with 1 μΜ of Aβ_1-40 or Aβ_40-1. The optimum concentrations of Aβ_1-40 and TO90 were determined by cell viability assay. Pro-inflammatory cytokines IL-6, IL-8, MCP-1 were detected by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Expression and localization of an aging protein p16INK4a (p16) were analyzed by western blotting and immunofluorescence. Expressions of LXRs and one of their target genes ATP-binding cassette transporter A1 (ABCA1) were examined by real-time PCR and western blotting. Phosphorylated transcription inhibition factor-κB-α (p-IκB-α) was assessed by western blotting.

RESULTS

A negative linear relationship between the Aβ_1-40 concentration and the cell viability was evident, indicating Aβ_1-40 decreased ARPE-19 cell viability in a dose-dependent manner. Aβ_1-40 enhanced the expression of IL-6, IL-8, MCP-1 as well as p16 in both RPE cell lines at both mRNA and protein levels, whereas TO90 counteracted the detrimental effects. TO90 upregulated the expression of LXRα and its target gene ABCA1, but it did not affect the expression of LXRβ. Meanwhile, TO90 inhibited the phosphorylation of IκB-α mediated by Aβ_1-40 stimulation.

CONCLUSION

Activation of the LXRα-ABCA1 axis may alleviate Aβ_1-40 induced inflammatory and senescent responses in RPE cells. The beneficial effect appears associated with the inhibition of the NF-κB signaling pathway.

Salubrinal protects against Clostridium difficile toxin B-induced CT26 cell death

Clostridium difficile (C. difficile) is considered to be the major cause of the antibiotic-associated diarrhea and pseudomembranous colitis in animals and humans. The prevalence of C. difficile infections (CDI) has been increasing since 2000. Two exotoxins of C. difficile, Toxin A (TcdA) and Toxin B (TcdB), are the main virulence factors of CDI, which can induce glucosylation of Rho GTPases in host cytosol, leading to cell morphological changes, cell apoptosis, and cell death. The mechanism of TcdB-induced cell death has been investigated for decades, but it is still not completely understood. It has been reported that TcdB induces endoplasmic reticulum stress via PERK-eIF2α signaling pathway in CT26 cell line (BALB/C mouse colon tumor cells). In this study, we found that salubrinal, a selective inhibitor of eIF2α dephosphorylation, efficiently protects CT26 cell line against TcdB-induced cell death and tried to explore the mechanism underlying in this protective effect. Our results demonstrated that salubrinal protects CT26 cells from TcdB-mediated cytotoxic and cytopathic effect, inhibits apoptosis and death of the toxin-exposed cells via caspase-9-dependent pathway, eIF2α signaling pathway, and autophagy. These findings will be helpful for the development of CDI therapies.

Salubrinal reduces oxidative stress, neuroinflammation and impulsive-like behavior in a rodent model of traumatic brain injury

Traumatic brain injury (TBI) is the leading cause of trauma related morbidity in the developed world. TBI has been shown to trigger secondary injury cascades including endoplasmic reticulum (ER) stress, oxidative stress, and neuroinflammation. The link between secondary injury cascades and behavioral outcome following TBI is poorly understood warranting further investigation. Using our validated rodent blast TBI model, we examined the interaction of secondary injury cascades following single injury and how these interactions may contribute to impulsive-like behavior after a clinically relevant repetitive TBI paradigm. We targeted these secondary pathways acutely following single injury with the cellular stress modulator, salubrinal (SAL). We examined the neuroprotective effects of SAL administration on significantly reducing ER stress: janus-N-terminal kinase (JNK) phosphorylation and C/EBP homology protein (CHOP), oxidative stress: superoxide and carbonyls, and neuroinflammation: nuclear factor kappa beta (NFκB) activity, inducible nitric oxide synthase (iNOS) protein expression, and pro-inflammatory cytokines at 24h post-TBI. We then used the more clinically relevant repeat injury paradigm and observed elevated NFκB and iNOS activity. These injury cascades were associated with impulsive-like behavior measured on the elevated plus maze. SAL administration attenuated secondary iNOS activity at 72h following repetitive TBI, and most importantly prevented impulsive-like behavior. Overall, these results suggest a link between secondary injury cascades and impulsive-like behavior that can be modulated by SAL administration.

eIF2α-Independent Inhibition of TNF-α-Triggered NF-κB Activation by Salubrinal

Salubrinal is a selective inhibitor of cellular complexes that dephosphorylate eukaryotic translation initiation factor 2α (eIF2α). In previous reports, salubrinal was shown to have the potential to inhibit the activation of nuclear factor-κB (NF-κB) by several stimuli. However, the effects of salubrinal on NF-κB signaling are largely unknown. In this study, we investigated whether and how salubrinal affects NF-κB activation induced by tumor necrosis factor (TNF)-α and interleukin (IL)-1β. We found that salubrinal selectively blocked TNF-α- but not IL-1β-induced activation of NF-κB. This inhibitory effect occurred upstream of transforming growth factor (TGF)-β-activated kinase 1 (TAK1). Further experiments revealed that salubrinal blocked TNF-α-triggered NF-κB activation independent of its action on eIF2α because knockdown of eIF2α by small interfering RNA (siRNA) did not reverse the inhibitory effect of salubrinal on NF-κB. Moreover, guanabenz, a selective inhibitor of the regulatory subunit of protein phosphatase (PP) 1, also preferentially inhibited TNF-α-triggered activation of NF-κB. These findings raise the possibility that salubrinal may selectively block TNF-α-triggered activation of the NF-κB pathway through inhibition of the PP1 complex.

Dominant and recessive mutations in rhodopsin activate different cell death pathways

Mutations in rhodopsin (RHO) are a common cause of retinal dystrophy and can be transmitted by dominant or recessive inheritance. Clinical symptoms caused by dominant and recessive mutations in patients and animal models are very similar but the molecular mechanisms leading to retinal degeneration may differ. We characterized three murine models of retina degeneration caused by either Rho loss of function or expression of the P23H dominant mutation in Rho. Rho loss of function is characterized by activation of calpains and apoptosis-inducing factor (Aif) in dying photoreceptors. Retinas bearing the P23H dominant mutations activate both the calpain-Aif cell death pathway and ER-stress responses that together contribute to photoreceptor cell demise. In vivo treatment with the calpastatin peptide, a calpain inhibitor, was strongly neuroprotective in mice lacking Rho while photoreceptor survival in retinas expressing the P23H dominant mutation was more affected by treatment with salubrinal, an inhibitor of the ER-stress pathway. The further reduction of photoreceptor cell demise by co-treatment with calpastatin and salubrinal suggests co-activation of the calpain and ER-stress death pathways in mice bearing dominant mutations in the Rho gene.

Experimental Evidence Shows Salubrinal, an eIF2α Dephosphorylation Inhibitor, Reduces Xenotoxicant-Induced Cellular Damage

Accumulating evidence indicates that endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) are involved in the pathogenesis of not only the protein misfolding disorders such as certain neurodegenerative and metabolic diseases, but also in the cytotoxicity of environmental pollutants, industrial chemicals, and drugs. Thus, the modulation of ER stress signaling pathways is an important issue for protection against cellular damage induced by xenotoxicants. The substance salubrinal has been shown to prevent dephosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α). The phosphorylation of eIF2α appears to be cytoprotective during ER stress, because inhibition of the translation initiation activity of eIF2α reduces global protein synthesis. In addition, the expression of activating transcription factor 4 (ATF4), a transcription factor that induces the expression of UPR target genes, is up-regulated through alternative translation. This review shows that salubrinal can protect cells from the damage induced by a wide range of xenotoxicants, including environmental pollutants and drugs. The canonical and other possible mechanisms of cytoprotection by salubrinal from xenotoxicant-induced ER stress are also discussed.

Bee venom ameliorates lipopolysaccharide-induced memory loss by preventing NF-kappaB pathway

Background

Accumulation of beta-amyloid and neuroinflammation trigger Alzheimer’s disease. We previously found that lipopolysaccharide (LPS) caused neuroinflammation with concomitant accumulation of beta-amyloid peptides leading to memory loss. A variety of anti-inflammatory compounds inhibiting nuclear factor kappaB (NF-κB) activation have showed efficacy to hinder neuroinflammation and amyloidogenesis. We also found that bee venom (BV) inhibits NF-κB.

Methods

A mouse model of LPS-induced memory loss used administration of BV (0.8 and 1.6 μg/kg/day, i.p.) to ICR mice for 7 days before injection of LPS (2.5 mg/kg/day, i.p.). Memory loss was assessed using a Morris water maze test and passive avoidance test. For in vitro study, we treated BV (0.5, 1, and 2 μg/mL) to astrocytes and microglial BV-2 cells with LPS (1 μg/mL).

Results

We found that BV inhibited LPS-induced memory loss determined by behavioral tests as well as cell death. BV also inhibited LPS-induced increases in the level of beta-amyloid (Aβ), β-and γ-secretases activities, NF-κB and its DNA-binding activity and expression of APP, and BACE1 and neuroinflammation proteins (COX-2, iNOS, GFAP and IBA-1) in the brain and cultured cells. In addition, pull-down assay and molecular modeling showed that BV binds to NF-κB.

Conclusions

BV attenuates LPS-induced amyloidogenesis, neuroinflammation, and therefore memory loss via inhibiting NF-κB signaling pathway. Thus, BV could be useful for treatment of Alzheimer’s disease.

Chondroprotective effects of Salubrinal in a mouse model of osteoarthritis

OBJECTIVES

Salubrinal is a synthetic agent that elevates phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α) and alleviates stress to the endoplasmic reticulum. Previously, we reported that in chondrocytes, Salubrinal attenuates expression and activity of matrix metalloproteinase 13 (MMP13) through downregulating nuclear factor kappa B (NFκB) signalling. We herein examine whether Salubrinal prevents the degradation of articular cartilage in a mouse model of osteoarthritis (OA).

METHODS

OA was surgically induced in the left knee of female mice. Animal groups included age-matched sham control, OA placebo, and OA treated with Salubrinal or Guanabenz. Three weeks after the induction of OA, immunoblotting was performed for NFκB p65 and p-NFκB p65. At three and six weeks, the femora and tibiae were isolated and the sagittal sections were stained with Safranin O.

RESULTS

Salubrinal suppressed the progression of OA by downregulating p-NFκB p65 and MMP13. Although Guanabenz elevates the phosphorylation level of eIF2α, it did not suppress the progression of OA.

CONCLUSIONS

Administration of Salubrinal has chondroprotective effects in arthritic joints. Salubrinal can be considered as a potential therapeutic agent for alleviating symptoms of OA. Cite this article: Bone Joint Res 2015;4:84-92.

3,3'-Diindolylmethane (DIM) and its ring-substituted halogenated analogs (ring-DIMs) induce differential mechanisms of survival and death in androgen-dependent and -independent prostate cancer cells

We recently reported that novel ring-substituted analogs of 3,3'-diindolylmethane (ring-DIMs) induce apoptosis and necrosis in androgen-dependent and -independent prostate cancer cells. In this paper, we have focused on the mechanism(s) associated with ring-DIM-mediated cell death, and on identifying the specific intracellular target(s) of these compounds. The 4,4'- and 7,7'-dichloroDIMs and 4,4'- and 7,7'-dibromoDIMs induced the death of LNCaP, C42B and DU145 prostate cancer cells, but not that of immortalized normal human prostate epithelial (RWPE-1) cells. Ring-DIMs caused the early loss of mitochondrial membrane potential (MMP) and decreased mitochondrial ATP generation in prostate cancer cells. Cyclosporin A, an inhibitor of the mitochondrial permeability transition pore, inhibited ring-DIM-mediated cell death, and salubrinal, an inhibitor of ER stress, inhibited cell death mediated only by 4,4'-dihaloDIMs. We found that although salubrinal did not inhibit the onset of ER stress, it prevented 4,4'-dibromoDIM mediated loss of MMP. Salubrinal potentiated cell death in response to 7,7'-dihaloDIMs and DIM, and this effect concurred with increased loss of MMP. Using in silico 3-D docking affinity analysis, we identified Ca2+/calmodulin-dependent kinase II (CaMKII) as a potential direct target for the most toxic ring-DIM, 4,4'-dibromoDIM. An inhibitor of CaMKII, KN93, but not its inactive analog KN92, abrogated cell death mediated by 4,4'-dibromoDIM. The ring-DIMs induced ER stress and autophagy, but these processes were not necessary for ring-DIM-mediated cell death. Inhibition of autophagy with bafilomycin A1, 3-methyladenine or by LC3B gene silencing sensitized LNCaP and C42B, but not ATG5-deficient DU145 cells to ring-DIM- and DIM-mediated cell death. We propose that autophagy induced by the ring-DIMs and DIM has a cytoprotective function in prostate cancer cells.

Significance of NF-κB as a pivotal therapeutic target in the neurodegenerative pathologies of Alzheimer's disease and multiple sclerosis

INTRODUCTION

Advances in molecular pathogenesis suggest that the chronic inflammation is a shared mechanism in the initiation and progression of multiple neurodegenerative diseases with diverse clinical manifestations such as Alzheimer's disease (AD) and Multiple sclerosis (MS). Restricted cell renewal and regenerative capacity make the neural tissues extremely vulnerable to the uncontrolled inflammatory process leading to irreversible tissue damage.

AREAS COVERED

A predominant consequence of increased inflammatory signaling is the upregulation of the transcription factor, NF-κB with subsequent neuroprotective or deleterious effects depending on the strength of the signal and the type of NF-κB dimers activated. We discuss the interplay between neuroinflammation and neurodegeneration keeping in focus NF-κB signaling as the point of convergence of multiple pathways associated with the development of the neurodegenerative pathologies, AD and MS.

EXPERT OPINION

Considerable interest exists in developing efficient NF-κB inhibitors for neurodegenerative diseases. The review includes an overview of natural compounds and rationally designed agents that inhibit NF-κB and mediate neuroprotection in AD and MS. The key chemical moieties of the natural and the synthetic compounds provide efficient leads for the development of effective small molecule inhibitors that selectively target NF-κB activation; this would result in the desired benefit to risk therapeutic effects.

Quetiapine attenuates glial activation and proinflammatory cytokines in APP/PS1 transgenic mice via inhibition of nuclear factor-κB pathway

BACKGROUND

In Alzheimer's disease, growing evidence has shown that uncontrolled glial activation and neuroinflammation may contribute independently to neurodegeneration. Antiinflammatory strategies might provide benefits for this devastating disease. The aims of the present study are to address the issue of whether glial activation and proinflammatory cytokine increases could be modulated by quetiapine in vivo and in vitro and to explore the underlying mechanism.

METHODS

Four-month-old amyloid precursor protein (APP) and presenilin 1 (PS1) transgenic and nontransgenic mice were treated with quetiapine (5mg/kg/d) in drinking water for 8 months. Animal behaviors, total Aβ levels, and glial activation were evaluated by behavioral tests, enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot accordingly. Inflammatory cytokines and the nuclear factor kappa B pathway were analyzed in vivo and in vitro.

RESULTS

Quetiapine improves behavioral performance, marginally affects total Aβ40 and Aβ42 levels, attenuates glial activation, and reduces proinflammatory cytokines in APP/PS1 mice. Quetiapine suppresses Aβ1-42-induced activation of primary microglia by decresing proinflammatory cytokines. Quetiapine inhibits the activation of nuclear factor kappa B p65 pathway in both transgenic mice and primary microglia stimulated by Aβ1-42.

CONCLUSIONS

The antiinflammatory effects of quetiapine in Alzheimer's disease may be involved in the nuclear factor kappa B pathway. Quetiapine may be an efficacious and promising treatment for Alzheimer's disease targeting on neuroinflammation.

Early activation of microglia and astrocytes in mouse models of spinocerebellar ataxia type 1

Spinocerebellar ataxia type 1 (SCA1) is an incurable, dominantly inherited neurodegenerative disease of the cerebellum caused by a polyglutamine-repeat expansion in the protein ataxin-1 (ATXN1). While analysis of human autopsy material indicates significant glial pathology in SCA1, previous research has focused on characterizing neuronal dysfunction. In this study, we characterized astrocytic and microglial response in SCA1 using a comprehensive array of mouse models. We have discovered that astrocytes and microglia are activated very early in SCA1 pathogenesis even when mutant ATXN1 expression was limited to Purkinje neurons. Glial activation occurred in the absence of neuronal death, suggesting that glial activation results from signals emanating from dysfunctional neurons. Finally, in all different models examined glial activation closely correlated with disease progression, supporting the development of glial-based biomarkers to follow disease progression.

Network pharmacology-based prediction and verification of the molecular targets and pathways for schisandrin against cerebrovascular disease

AIM

To illuminate the molecular targets for schisandrin against cerebrovascular disease based on the combined methods of network pharmacology prediction and experimental verification.

METHOD

A protein database was established through constructing the drug-protein network from literature mining data. The protein-protein network was built through an in-depth exploration of the relationships between the proteins. The computational platform was implemented to predict and extract the sensitive sub-network with significant P-values from the protein-protein network. Then the key targets and pathways were identified from the sensitive sub-network. The most related targets and pathways were also confirmed in hydrogen peroxide (H2O2)-induced PC12 cells by Western blotting.

RESULTS

Twelve differentially expressed proteins (gene names: NFKB1, RELA, TNFSF10, MAPK1, CHUK, CASP8, PIGS2, MAPK14, CREB1, IFNG, APP, and BCL2) were confirmed as the central nodes of the interaction network (45 nodes, 93 edges). The NF-κB signaling pathway was suggested as the most related pathway of schisandrin for cerebrovascular disease. Furthermore, schisandrin was found to suppress the expression and phosphorylation of IKKα, as well as p50 and p65 induced by H2O2 in PC12 cells by Western blotting.

CONCLUSION

The computational platform that integrates literature mining data, protein-protein interactions, sensitive sub-network, and pathway results in identification of the NF-κB signaling pathway as the key targets and pathways for schisandrin.

Chronic inflammation and cancer: potential chemoprevention through nuclear factor kappa B and p53 mutual antagonism

Activation of nuclear factor-kappa B (NF- κB) as a mechanism of host defense against infection and stress is the central mediator of inflammatory responses. A normal (acute) inflammatory response is activated on urgent basis and is auto-regulated. Chronic inflammation that results due to failure in the regulatory mechanism, however, is largely considered as a critical determinant in the initiation and progression of various forms of cancer. Mechanistically, NF- κB favors this process by inducing various genes responsible for cell survival, proliferation, migration, invasion while at the same time antagonizing growth regulators including tumor suppressor p53. It has been shown by various independent investigations that a down regulation of NF- κB activity directly, or indirectly through the activation of the p53 pathway reduces tumor growth substantially. Therefore, there is a huge effort driven by many laboratories to understand the NF- κB signaling pathways to intervene the function of this crucial player in inflammation and tumorigenesis in order to find an effective inhibitor directly, or through the p53 tumor suppressor. We discuss here on the role of NF- κB in chronic inflammation and cancer, highlighting mutual antagonism between NF- κB and p53 pathways in the process. We also discuss prospective pharmacological modulators of these two pathways, including those that were already tested to affect this mutual antagonism.

Salubrinal protects against rotenone-induced SH-SY5Y cell death via ATF4-parkin pathway

Parkinson's disease (PD) is a progressive neurodegenerative disorder, for which there are no effective disease-modifying therapies. Growing evidence from studies in human PD brain, in addition to genetic and toxicological models, indicates that endoplasmic reticulum (ER) stress is a common feature of the disease and contributes to neurodegeneration. We examine whether salubrinal, a ER stress inhibitor, can protect the rotenone-induced SH-SY5Y cell death and explore the mechanisms underlying this protection. Our results demonstrated that rotenone induced a significant ER stress response and caused cell apoptosis, which was inhibited by salubrinal. Activating transcription factor 4 (ATF4), a member of the ATF/CREB family of basic leucine zipper transcription factors, has been implicated in the pathogenesis of neurodegeneration. We showed that salubrinal increased the up-regulation of ATF4 expression. An ATF4 siRNA significantly increased the rotenone cytotoxicity and decreased the salubrinal's protection. Further, we showed that ATF4 siRNA inhibited the expression of parkin, and parkin knockdown similarly aggravated the rotenone cytotoxicity and reduced the salubrinal's protection. Additionally, the protein level of parkin was declined after treatment with rotenone, whereas this reduction was rescued by salubrinal. These findings indicate ATF4-parkin pathway plays an important role in the salubrinal-mediated neuroprotection of rotenone-induced dopaminergic cell death.

Effects of salubrinal on development of osteoclasts and osteoblasts from bone marrow-derived cells

Background

Osteoporosis is a skeletal disease leading to an increased risk of bone fracture. Using a mouse osteoporosis model induced by administration of a receptor activator of nuclear factor kappa-B ligand (RANKL), salubrinal was recently reported as a potential therapeutic agent. To evaluate the role of salubrinal in cellular fates as well as migratory and adhesive functions of osteoclast/osteoblast precursors, we examined the development of primary bone marrow-derived cells in the presence and absence of salubrinal. We addressed a question: are salubrinal’s actions more potent to the cells isolated from the osteoporotic mice than those isolated from the control mice?

Methods

Using the RANKL-injected and control mice, bone marrow-derived cells were harvested. Osteoclastogenesis was induced by macrophage-colony stimulating factor and RANKL, while osteoblastogenesis was driven by dexamethasone, ascorbic acid, and β-glycerophosphate.

Results

The results revealed that salubrinal suppressed the numbers of colony forming-unit (CFU)-granulocyte/macrophages and CFU-macrophages, as well as formation of mature osteoclasts in a dosage-dependent manner. Salubrinal also suppressed migration and adhesion of pre-osteoclasts and increased the number of CFU-osteoblasts. Salubrinal was more effective in exerting its effects in the cells isolated from the RANKL-injected mice than the control. Consistent with cellular fates and functions, salubrinal reduced the expression of nuclear factor of activated T cells c1 (NFATc1) as well as tartrate-resistant acid phosphatase.

Conclusions

The results support the notion that salubrinal exhibits significant inhibition of osteoclastogenesis as well as stimulation of osteoblastogenesis in bone marrow-derived cells, and its efficacy is enhanced in the cells harvested from the osteoporotic bone samples.

Restoring endoplasmic reticulum homeostasis improves functional recovery after spinal cord injury

The endoplasmic reticulum (ER) stress response (ERSR) is activated to maintain protein homeostasis or induce apoptosis in the ER in response to distinct cellular insults including hypoxia, inflammation, and oxidative damage. Recently, we showed ERSR activation in a mouse model of a contusive spinal cord injury (SCI) and an improved hindlimb locomotor function following SCI when the pro-apoptotic arm of ERSR was genetically inhibited. The objective of the current study was to explore if the pharmacological enhancement of the homeostatic arm of the ERSR pathway can improve the functional outcome after SCI. Salubrinal enhances the homeostatic arm of the ERSR by increasing phosphorylation of eIF2α. Salubrinal significantly enhanced the levels of phosphorylated eIF2α protein and modulated the downstream ERSR effectors assessed at the lesion epicenter 6h post-SCI. Hindlimb locomotion showed significant improvement in animals treated with salubrinal. Treadmill-based-gait assessment showed a significant increase in maximum speed of coordinated walking and a decrease in rear stance time and stride length in salubrinal-treated animals. This improved functional recovery corresponded with increased white matter sparing and decreased oligodendrocyte apoptosis. In addition, salubrinal protected cultured mouse oligodendrocyte progenitor cells against the ER stress-inducing toxin tunicamycin. These data suggest that boosting the homeostatic arm of the ERSR reduces oligodendrocyte loss after traumatic SCI and support the contention that pharmacological targeting of the ERSR after CNS trauma is a therapeutically viable approach.

Salubrinal reduces expression and activity of MMP13 in chondrocytes

OBJECTIVE

Stress to the endoplasmic reticulum (ER) and inflammatory cytokines induce expression and activity of matrix metalloproteinase 13 (MMP13). Since a synthetic agent, salubrinal, is known to alleviate ER stress and attenuate nuclear factor kappa B (NFκB) signaling, we addressed a question whether upregulation of MMP13 by ER stress and cytokines is suppressed by administration of salubrinal.

METHODS

Using C28/I2 human chondrocytes, we applied ER stress with tunicamycin and inflammatory distress with tumor necrosis factor α (TNFα) and interleukin 1β (IL1β). RNA interference with siRNA specific to NFκB p65 (RelA) was employed to examine a potential involvement of NFκB signaling in salubrinal's action in regulation of MMP13. We also employed primary human chondrocytes and evaluated MMP13 activity.

RESULTS

The result showed that tunicamycin activated p38 mitogen-activated protein kinase (MAPK), while inflammatory cytokines activated p38 MAPK and NFκB. In both cases, salubrinal significantly reduced expression and activity of MMP13. Silencing NFκB reduced inflammatory cytokine-driven upregulation of MMP13 activity.

CONCLUSIONS

The results demonstrate that salubrinal downregulates expression and activity MMP13 through p38 and NFκB signaling, suggesting its potential usage to treat degenerative diseases such as osteoarthritis.

BACE1 is at the crossroad of a toxic vicious cycle involving cellular stress and β-amyloid production in Alzheimer's disease

Alzheimer’s disease (AD) is a complex age-related pathology, the etiology of which has not been firmly delineated. Among various histological stigmata, AD-affected brains display several cellular dysfunctions reflecting enhanced oxidative stress, inflammation process and calcium homeostasis disturbance. Most of these alterations are directly or indirectly linked to amyloid β-peptides (Aβ), the production, molecular nature and biophysical properties of which likely conditions the degenerative process. It is particularly noticeable that, in a reverse control process, the above-described cellular dysfunctions alter Aβ peptides levels. β-secretase βAPP-cleaving enzyme 1 (BACE1) is a key molecular contributor of this cross-talk. This enzyme is responsible for the primary cleavage generating the N-terminus of “full length” Aβ peptides and is also transcriptionally induced by several cellular stresses. This review summarizes data linking brain insults to AD-like pathology and documents the key role of BACE1 at the cross-road of a vicious cycle contributing to Aβ production.

Eukaryotic initiation factor 2 (eIF2) signaling regulates proinflammatory cytokine expression and bacterial invasion

In eukaryotic cells, there are two well characterized pathways that regulate translation initiation in response to stress, and each have been shown to be targeted by various viruses. We recently showed in a yeast-based model that the bacterial virulence factor YopJ disrupts one of these pathways, which is centered on the α-subunit of the translation factor eIF2. Here, we show in mammalian cells that induction of the eIF2 signaling pathway occurs following infection with bacterial pathogens and that, consistent with our yeast-based findings, YopJ reduces eIF2 signaling in response to endoplasmic reticulum stress, heavy metal toxicity, dsRNA, and bacterial infection. We demonstrate that the well documented activities of YopJ, inhibition of NF-κB activation and proinflammatory cytokine expression, are both dependent on an intact eIF2 signaling pathway. Unexpectedly, we found that cells with defective eIF2 signaling were more susceptible to bacterial invasion. This was true for pathogenic Yersinia, a facultative intracellular pathogen, as well as for the intracellular pathogens Listeria monocytogenes and Chlamydia trachomatis. Collectively, our data indicate that the highly conserved eIF2 signaling pathway, which is vitally important for antiviral responses, plays a variety of heretofore unrecognized roles in antibacterial responses.