Selective activation of cannabinoid receptor-2 reduces white matter injury via PERK signaling in a rat model of traumatic brain injury.

BACKGROUND AND PURPOSE: Traumatic brain injury (TBI) destroys white matter, and this destruction is aggravated by secondary neuroinflammatory reactions. Although white matter injury (WMI) is strongly correlated with poor neurological function, understanding of white matter integrity maintenance is limited, and no available therapies can effectively protect white matter. One candidate approach that may fulfill this goal is cannabinoid receptor 2 (CB2) agonist treatment. Here, we confirmed that a selective CB2 agonist, JWH133, protected white matter after TBI. METHODS: The motor evoked potentials (MEPs), open field test, and Morris water maze test were used to assess neurobehavioral outcomes. Brain tissue loss, WM damage, Endoplasmic reticulum stress (ER stress), microglia responses were evaluated after TBI. The functional integrity of WM was measured by diffusion tensor imaging (DTI) and transmission electron microscopy (TEM). Primary microglia and oligodendrocyte cocultures were used for additional mechanistic studies. RESULTS: JWH133 increased myelin basic protein (MBP) and neurofilament heavy chain (NF200) levels and anatomic preservation of myelinated axons revealed by DTI and TEM. JWH133 also increased the numbers of oligodendrocyte precursor cells and mature oligodendrocytes. Furthermore, JWH133 drove microglial polarization toward the protective M2 phenotype and modulated the redistribution of microglia in the striatum. Further investigation of the underlying mechanism revealed that JWH133 downregulated phosphorylation of the protein kinase R (PKR)-like endoplasmic reticulum (ER) kinase (PERK) signaling pathway and its downstream signals eukaryotic translation initiation factor 2 α (eIF2α), activating transcription factor 4 (ATF4) and Growth arrest and DNA damage-inducible protein (GADD34); this downregulation was followed by p-Protein kinase B(p-Akt) upregulation. In primary cocultures of microglia and oligodendrocytes, JWH133 decreased phosphorylated PERK expression in microglia stimulated with tunicamycin and facilitated oligodendrocyte survival. These data reveal that JWH133 ultimately alleviates WMI and improves neurological behavior following TBI. However, these effects were prevented by SR144528, a selective CB2 antagonist. CONCLUSIONS: This work illustrates the PERK-mediated interaction between microglia and oligodendrocytes. In addition, the results are consistent with recent findings that microglial polarization switching accelerates WMI, highlighting a previously unexplored role for CB2 agonists. Thus, CB2 agonists are potential therapeutic agents for TBI and other neurological conditions involving white matter destruction.

Endoplasmic reticulum stress potentiates the autophagy of alveolar macrophage to attenuate acute lung injury and airway inflammation.

Endoplasmic reticulum (ER) stress has been reported to play a role in acute lung injury (ALI), yet the in-depth mechanism remains elusive. This study aims to investigate the effect of ER stress-induced autophagy of alveolar macrophage (AM) on acute lung injury (ALI) and airway inflammation using mouse models. ALI models were induced by intranasal instillation of lipopolysaccharide (LPS). The lung weight/body weight (LW/BW) ratio and excised lung gas volume (ELGV) in each group were measured. Mouse bronchoalveolar lavage fluid (BALF) was collected for cell sorting and protein concentration determination. Expression of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) in lung tissues and BALF was also detected. Mouse AMs were isolated to observe the autophagy. Expression of GRP78, PERK, LC3I, LC3II and Beclin1 was further determined. The results indicated that tunicamycin (TM) elevated GRP78 and PERK expression of AMs in ALI mice in a dose-dependent manner. Low dosage of TM abated LC3I expression, increased LC3II and Beclin1 expression, triggered ER stress and AM autophagy, and alleviated pathological changes of AMs in ALI mice. Also, in ALI mice, low dosage of TM attenuated goblet cell proliferation of tracheal wall, and declined LW/BW ratio, ELGV, total cells and neutrophils, protein concentrations in BALF, and IL-6 and TNF-α expression in lung tissues and BALF. Collectively, this study suggests that a low dosage of TM-induced ER stress can enhance the autophagy of AM in ALI mice models, thus attenuating the progression of ALI and airway inflammation.

The complement receptor C5aR2 promotes protein kinase R expression and contributes to NLRP3 inflammasome activation and HMGB1 release from macrophages.

The NLR family pyrin domain-containing 3 (NLRP3) inflammasome is a multimeric protein complex that mediates maturation of the cytokines IL-1ß and IL-18 as well as release of the proinflammatory protein high-mobility group box 1 (HMGB1) and contributes to several inflammatory diseases, including sepsis, gout, and type 2 diabetes. In this context, the well-studied active complement fragment C5a and its receptor C5aR1 or C5aR2 orchestrate the inflammatory responses in many diseases. Although a C5a-C5aR interaction in NLRP3-associated diseases has been suggested, little is known about the details of C5a-C5aR cross-talk with the NLRP3 inflammasome in macrophages. In this study, using mice and murine macrophages and cytokines, immunoblotting, siRNA, and quantitative real-time PCR assays, we demonstrate that C5aR2 deficiency restricts activation of the NLRP3 inflammasome and release of HMGB1 both in vitro and in vivo Mechanistically, we found that C5aR2 promotes NLRP3 activation by amplifying dsRNA-dependent PKR expression, which is an important NLRP3-activating factor. We also observed that elevation of PKR expression because of the C5a-C5aR2 interaction depends on the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase pathway and type I IFN signaling. In conclusion, these findings reveal that C5aR2 contributes to NLRP3 inflammasome activation and HMGB1 release from macrophages.

Innate immune response in astrocytes infected with herpes simplex virus 1.

Herpes simplex virus 1 (HSV-1), a double-stranded DNA virus, infects epithelial surfaces and establishes latency in the central nervous system, where astrocytes are a major immune cell type. Here, we report changes that occur in the expression of pathogen recognition receptors, such as Toll-like receptors, DNA and RNA sensors, interferons, and interferon-stimulated genes, when astrocytes are infected with HSV-1 strain F. We observed upregulation of Toll-like receptors 2, 6 and 9, MDA5, and DAI along with an increase in the expression of type I interferons and interferon-stimulated genes such as IFIT1, IFIT3 and RNase L. These genes encode proteins that mediate the antiviral immune response.

Increased PKR level in human CADASIL brains.

Cerebral autosomal dominant arteriolopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is the most common form of hereditary small vessel disease (SVD) of the brain. Neuronal apoptosis has been demonstrated in the cortex of patients. Whether it is associated with an activation of the pro-apoptotic protein PKR pathway is unknown. Similarly, activation of autophagy in CADASIL has never been explored. Immunostaining of four CADASIL brains previously analyzed for cortical neuronal apoptosis and five control brains for PKR (phosphoPKR) and autophagy (ATG5, LC3II) activation markers. Significant nuclear pPKR staining was observed in CADASIL neurons comparatively to controls (p = 0.001). No difference was observed between patients and controls with autophagy markers. We demonstrated the activation of PKR pathway in CADASIL. This was not associated with a detectable modulation of autophagy. These results open a new field to explore in order to better understand the mechanisms underlying cortical neurons apoptosis.

Interaction of IRF9 and STAT2 synergistically up-regulates IFN and PKR transcription in Ctenopharyngodon idella.

IRF9 is a key factor in the JAK-STAT pathway. Under the stimulation of type I IFN, IRF9 interacts with STAT1 and STAT2 to form the IFN-I-stimulated gene factor 3 (ISGF3) which activates the transcription of ISG. However, many studies also showed that the dimmer IRF9/STAT2 rather than the tripolymer IRF9/STAT1/STAT2 acts as the ISGF3 in cells in response to IFN signals. In the present study, the full-length cDNA sequence of IRF9 (termed CiIRF9, KT601055) and STAT2 (term CiSTAT2, KT781914) from grass carp were cloned and identified. A low level of constitutive expression of CiIRF9 was detected by RT-PCR in grass carp tissues, but it was significantly up-regulated by LPS and poly I:C stimulation. In vitro, a high-affinity interaction between CiIRF9 and the promoter of CiIFN or CiPKR was demonstrated by gel mobility shift assay. In vivo, the promoter activities of CiIFN and CiPKR were not only increased by transient transfection of CiIRF9, but also prominently increased by co-transfection of CiIRF9 and CiSTAT2. Moreover, the interaction of CiIRF9 and CiSTAT2 was further investigated by in vivo and in vitro protein interaction assays. Recombinant CiIRF9 and CiSTAT2, both tagged with FLAG (or HA), were expressed in HEK 293T cells by transient transfection experiment. Co-immunoprecipitation assays showed that CiIRF9 can interact with CiSTAT2 in vivo. Soluble GST-ST2-936 (containing the N-terminal and coiled-coil domain of CiSTAT2) was expressed and purified from E. coli. A GST pull-down assay suggested that GST-tagged ST2-936 efficiently bound to FLAG-tagged IRF9. The data indicated that interaction of IRF9 and STAT2 synergistically up-regulated the transcriptional level of IFN and ISG genes.

PERK Is a Haploinsufficient Tumor Suppressor: Gene Dose Determines Tumor-Suppressive Versus Tumor Promoting Properties of PERK in Melanoma.

The unfolded protein response (UPR) regulates cell fate following exposure of cells to endoplasmic reticulum stresses. PERK, a UPR protein kinase, regulates protein synthesis and while linked with cell survival, exhibits activities associated with both tumor progression and tumor suppression. For example, while cells lacking PERK are sensitive to UPR-dependent cell death, acute activation of PERK triggers both apoptosis and cell cycle arrest, which would be expected to contribute tumor suppressive activity. We have evaluated these activities in the BRAF-dependent melanoma and provide evidence revealing a complex role for PERK in melanoma where a 50% reduction is permissive for BrafV600E-dependent transformation, while complete inhibition is tumor suppressive. Consistently, PERK mutants identified in human melanoma are hypomorphic with dominant inhibitory function. Strikingly, we demonstrate that small molecule PERK inhibitors exhibit single agent efficacy against BrafV600E-dependent tumors highlighting the clinical value of targeting PERK.

Non-thermal gas plasma-induced endoplasmic reticulum stress mediates apoptosis in human colon cancer cells.

Colorectal cancer is a common type of tumor among both men and women worldwide. Conventional remedies such as chemotherapies pose the risk of side­effects, and in many cases cancer cells develop chemoresistance to these treatments. Non­thermal gas plasma (NTGP) was recently identified as a potential tool for cancer treatment. In this study, we investigated the potential use of NTGP to control SNUC5 human colon carcinoma cells. We hypothesized that NTGP would generate reactive oxygen species (ROS) in these cells, resulting in induction of endoplasmic reticulum (ER) stress. ROS generation, expression of ER stress­related proteins and mitochondrial calcium levels were analyzed. Our results confirmed that plasma­generated ROS induce apoptosis in SNUC5 cells. Furthermore, we found that plasma exposure resulted in mitochondrial calcium accumulation and expression of unfolded protein response (UPR) proteins such as glucose­related protein 78 (GRP78), protein kinase R (PKR)­like ER kinase (PERK), and inositol­requiring enzyme 1 (IRE1). Elevated expression of spliced X­box binding protein 1 (XBP1) and CCAAT/enhancer­binding protein homologous protein (CHOP) further confirmed that ROS generated by NTGP induces apoptosis through the ER stress signaling pathway.

Accumulation of RNA-dependent protein kinase (PKR) in the nuclei of lung cancer cells mediates radiation resistance.

We have previously demonstrated that radiation induced cell death in PKR (-/-) deficient mouse embryo fibroblasts (MEFs) but not in PKR (+/+) wild type MEFs. Our study indicated that PKR can also be involved in survival pathways following radiation therapy through activation of the AKT survival pathways in these MEFs is mediated in part through PKR. The role of PKR on radiation sensitivity in cancer cells has not been evaluated. In this study, we demonstrated that radiation treatment causes nuclear translocation of PKR in human lung cancer cells. The transduction of lung cancer cells with a dominant negative adenoviral PKR vector blocks nuclear translocation of PKR and leads to the reversal of radiation resistance. Plasmid transduction of lung cancer cells with nuclear targeted wild type PKR vectors also increased radiation resistance. This effect is selectively abrogated by plasmid transduction of dominant negative PKR vectors which restore radiation sensitivity. These findings suggest a novel role for PKR in lung cancer cells as a mediator of radiation resistance possibly through translocation of the protein product to the nucleus.

Placental growth factor inhibition modulates the interplay between hypoxia and unfolded protein response in hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality. We previously showed that the inhibition of placental growth factor (PlGF) exerts antitumour effects and induces vessel normalisation, possibly reducing hypoxia. However, the exact mechanism underlying these effects remains unclear. Because hypoxia and endoplasmic reticulum stress, which activates the unfolded protein response (UPR), have been implicated in HCC progression, we assessed the interactions between PlGF and these microenvironmental stresses. METHODS: PlGF knockout mice and validated monoclonal anti-PlGF antibodies were used in a diethylnitrosamine-induced mouse model for HCC. We examined the interactions among hypoxia, UPR activation and PlGF induction in HCC cells. RESULTS: Both the genetic and pharmacological inhibitions of PlGF reduced the chaperone levels and the activation of the PKR-like endoplasmic reticulum kinase (PERK) pathway of the UPR in diethylnitrosamine-induced HCC. Furthermore, we identified that tumour hypoxia was attenuated, as shown by reduced pimonidazole binding. Interestingly, hypoxic exposure markedly activated the PERK pathway in HCC cells in vitro, suggesting that PlGF inhibition may diminish PERK activation by improving oxygen delivery. We also found that PlGF expression is upregulated by different chemical UPR inducers via activation of the inositol-requiring enzyme 1 pathway in HCC cells. CONCLUSIONS: PlGF inhibition attenuates PERK activation, likely by tempering hypoxia in HCC via vessel normalisation. The UPR, in turn, is able to regulate PlGF expression, suggesting the existence of a feedback mechanism for hypoxia-mediated UPR that promotes the expression of the angiogenic factor PlGF. These findings have important implications for our understanding of the effect of therapies normalising tumour vasculature.

ELANE mutant-specific activation of different UPR pathways in congenital neutropenia.

A number of studies have demonstrated induction of the unfolded protein response (UPR) in patients with severe congenital neutropenia (CN) harbouring mutations of ELANE, encoding neutrophil elastase. Why UPR is not activated in patients with cyclic neutropenia (CyN) carrying the same ELANE mutations is unclear. We evaluated the effects of ELANE mutants on UPR induction in myeloid cells from CN and CyN patients, and analysed whether additional CN-specific defects contribute to the differences in UPR induction between CN and CyN patients harbouring identical ELANE mutations. We investigated CN-specific p.C71R and p.V174_C181del (NP_001963.1) and CN/CyN-shared p.S126L (NP_001963.1) ELANE mutants. We found that transduction of haematopoietic cells with p.C71R, but not with p.V174_C181del or p.S126L ELANE mutants induced expression of ATF6, and the ATF6 target genes PPP1R15A, DDIT3 and HSPA5. Recently, we found that levels of secretory leucocyte protease inhibitor (SLPI), a natural ELANE inhibitor, are diminished in myeloid cells from CN patients, but not CyN patients. Combined knockdown of SLPI by shRNA and transduction of ELANE p.S126L in myeloid cells led to elevated levels of ATF6, PPP1R15A and HSPA5 RNA, suggesting that normal levels of SLPI in CyN patients might protect them from the UPR induced by mutant ELANE. In summary, different ELANE mutants have different effects on UPR activation, and SLPI regulates the extent of ELANE-triggered UPR.

Interferon induction by avian reovirus.

We have previously shown that the replication of avian reovirus (ARV) in chicken embryo fibroblasts (CEF) is more resistant to the antiviral action of interferon (IFN) than the replication of vesicular stomatitis virus (VSV) or vaccinia virus (VV). In this study we examined the capacity of these three viruses to induce the expression of IFN when infecting avian cells. Efficient expression of both type-α and type-ß IFNs, as well as of the double-stranded RNA (dsRNA)-activated protein kinase (PKR), takes place in ARV-infected CEF, but not in cells infected with VSV or VV. PKR expression is not directly induced by ARV infection, but by the IFN secreted by ARV-infected cells. IFN induction in ARV-infected cells requires viral uncoating, but not viral gene expression, a situation similar to that reported for apoptosis induction by ARV-infected cells. However, our results demonstrate that IFN induction by ARV-infected CEF occurs by a caspase-independent mechanism.

Lloviu virus VP24 and VP35 proteins function as innate immune antagonists in human and bat cells.

Lloviu virus (LLOV) is a new member of the filovirus family that also includes Ebola virus (EBOV) and Marburg virus (MARV). LLOV has not been cultured; however, its genomic RNA sequence indicates the coding capacity to produce homologs of the EBOV and MARV VP24, VP35, and VP40 proteins. EBOV and MARV VP35 proteins inhibit interferon (IFN)-alpha/beta production and EBOV VP35 blocks activation of the antiviral kinase PKR. The EBOV VP24 and MARV VP40 proteins inhibit IFN signaling, albeit by different mechanisms. Here we demonstrate that LLOV VP35 suppresses Sendai virus induced IFN regulatory factor 3 (IRF3) phosphorylation, IFN-α/ß production, and PKR phosphorylation. Additionally, LLOV VP24 blocks tyrosine phosphorylated STAT1 binding to karyopherin alpha 5 (KPNA5), STAT1 nuclear accumulation, and IFN-induced gene expression. LLOV VP40 lacks detectable IFN antagonist function. These activities parallel EBOV IFN inhibitory functions. EBOV and LLOV VP35 and VP24 proteins also inhibit IFN responses in bat cells. These data suggest that LLOV infection will block innate immune responses in a manner similar to EBOV.

miR-195 plays a role in steroid resistance of ulcerative colitis by targeting Smad7.

An imbalance in pro- and anti-inflammation is an important mechanism of steroid resistance in UC (ulcerative colitis), and miRNAs may participate in this process. The present study aimed to explore whether miRNAs play a role in the steroid resistance of UC by regulating gene expression of the inflammation signal pathway. SS (steroid-sensitive) patients, SR (steroid-resistant) patients and healthy individuals were recruited. In vivo miRNA profiles of serum samples showed that miR-195 was decreased significantly in the SR group compared with the SS group (P<0.05). This result was confirmed by qPCR (quantitative real-time PCR) and miRNA ISH (in situ hybridization) in serum and colon tissue samples. Online software was used to identify Smad7 mRNA as a potential target of miR-195. The direct interaction of miR-195 and Smad7 mRNA was investigated using a biotinylated miR-195 pull-down assay. Overexpression of a miR-195 precursor lowered cellular levels of Smad7 protein; conversely, antagonism of miR-195 enhanced Smad7 translation without disturbing Smad7 mRNA levels. A luciferase reporter assay revealed a repressive effect of miR-195 via a single Smad7 3'-UTR target site, and point mutation of this site prevented miR-195-induced repression of Smad7 translation. Furthermore, increased levels of miR-195 led to a decrease in c-Jun and p65 expression. In contrast, transfection with anti-miR-195 led to increased levels of c-Jun and p65 protein. The decrease in miR-195 led to an increase in Smad7 expression and corresponding up-regulation of p65 and the AP-1 (activator protein 1) pathway, which might explain the mechanism of steroid resistance in UC patients.

Resveratrol induces AMPK-dependent MDR1 inhibition in colorectal cancer HCT116/L-OHP cells by preventing activation of NF-κB signaling and suppressing cAMP-responsive element transcriptional activity.

Resveratrol, a natural polyphenolic compound found in foods and beverages, has attracted increasing attention in recent years because of its potent chemopreventive and anti-tumor effects. In this study, the effects of resveratrol on the expression of P-glycoprotein/multi-drug resistance protein 1 (P-gp/MDR1), and the underlying molecular mechanisms, were investigated in oxaliplatin (L-OHP)-resistant colorectal cancer cells (HCT116/L-OHP). Resveratrol downregulated MDR1 protein and mRNA expression levels and reduced MDR1 promoter activity. It also enhanced the intracellular accumulation of rhodamine 123, suggesting that resveratrol can reverse multi-drug resistance by downregulating MDR1 expression and reducing drug efflux. Resveratrol treatment also reduced nuclear factor-κB (NF-κB) activity, reduced phosphorylation levels of IκBα, and reduced nuclear translocation of the NF-κB subunit p65. Moreover, downregulation of MDR1 expression and promoter activity was mediated by resveratrol-induced AMP-activated protein kinase (AMPK) phosphorylation. The inhibitory effects of resveratrol on MDR1 expression and cAMP-responsive element-binding protein (CREB) phosphorylation were reversed by AMPKα siRNA transfection. We found that the transcriptional activity of cAMP-responsive element (CRE) was inhibited by resveratrol. These results demonstrated that the inhibitory effects of resveratrol on MDR1 expression in HCT116/L-OHP cells were closely associated with the inhibition of NF-κB signaling and CREB activation in an AMPK-dependent manner.

Serum Amyloid A Stimulates PKR Expression and HMGB1 Release Possibly through TLR4/RAGE Receptors.

Serum amyloid A (SAA) proteins are known to be surrogate markers of sepsis, but their pathogenic roles remain poorly elucidated. Here we provide evidence to support a possible role of SAA as a pathogenic mediator of lethal sepsis. In a subset of septic patients for which serum high mobility group box 1 (HMGB1) levels paralleled the clinical scores, some anti-HMGB1 antibodies detected a 12-kDa protein belonging to the SAA family. In contrast to the most abundant SAA1, human SAA induced double-stranded RNA-activated protein kinase R (PKR) expression and HMGB1 release in the wild-type, but not toll-like receptor 4/receptor for advanced glycation end products (TLR4/RAGE)-deficient, macrophages. Pharmacological inhibition of PKR phosphorylation blocked SAA-induced HMGB1 release, suggesting an important role of PKR in SAA-induced HMGB1 release. In animal models of lethal endotoxemia and sepsis, recombinant SAA exacerbated endotoxemic lethality, whereas SAA-neutralizing immunoglobulins G (IgGs) significantly improved animal survival. Collectively, these findings have suggested SAA as an important mediator of inflammatory diseases. Highlights of this study include: human SAA is possibly only expressed in a subset of septic patients; SAA induces HMGB1 release via TLR4 and RAGE receptors; SAA supplementation worsens the outcome of lethal endotoxemia; whereas SAA-neutralizing antibodies confer protection against lethal endotoxemia and sepsis.

Expression of markers of endoplasmic reticulum stress-induced apoptosis in the placenta of women with early and late onset severe pre-eclampsia.

OBJECTIVES: Endoplasmic reticulum (ER) stress-induced apoptosis has been implicated in severe pre-eclampsia (SPE) and is characterized by the activation of three signaling pathways: PKR-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring 1 (Ire1). This study was designed to investigate the role of ER stress in the pathogenesis of SPE. MATERIALS AND METHODS: Placental tissues were collected from 32 women with normal pregnancies and two cohorts of women with early (n = 32) or late onset (n = 32) SPE. The expression of glucose-regulated protein 78 (GRP78), PERK, eukaryotic initiation factor 2 subunit a (eIF2α), activating transcription factor 6 (ATF4), ATF6, Ire1, CHOP (ClEBP homologus protein), and caspase 12 mRNA and protein in the placentas was analyzed using real-time reverse transcription-polymerase chain reaction and Western blotting, respectively. RESULTS: The levels of GRP78, PERK, eIF2α, CHOP, ATF6, and caspase 12 mRNA and protein expression were significantly higher in the placentas of women with early and late SPE than in the control women, whereas there were no differences in ATF6 and Ire1 mRNA and protein. CONCLUSION: ER stress-induced apoptosis was important in the development of SPE, especially in early onset SPE and was probably due to the activation of the PERK signaling pathway.

The IFNγ-PKR pathway in the prefrontal cortex reactions to chronic excessive alcohol use.

BACKGROUND: Brain cell death is a major pathological consequence of alcohol neurotoxicity. However, the molecular cascades in alcohol-induced brain tissue injury are unclear. METHODS: Using Western blot and double immunofluorescence, we examined the expression of interferon (IFN)-induced protein kinase R (PKR), phosphorylated-PKR (p-PKR), and IFN gamma (IFNγ) in the prefrontal cortex (PFC) of postmortem brains from subjects with alcohol use disorders (AUD). RESULTS: The protein levels of PKR, p-PKR, and IFNγ were significantly increased in subjects with AUD compared with control subjects without AUD, and a younger age of onset of AUD was significantly correlated with higher protein levels of p-PKR. In addition, elevated PKR- and p-PKR-IR were observed in both neurons and astrocytes in the PFC of subjects with AUD compared to subjects without AUD. CONCLUSIONS: The activation of the IFNγ-PKR pathway in PFC of humans is associated with chronic excessive ethanol use with an age of onset dependent manner, and activation of this pathway may play a pivotal role in AUD-related brain tissue injury. This study provides insight into neurodegenerative key factors related to AUD and identifies potential targets for the treatment of alcohol-induced neurotoxicity.

Andes virus nucleocapsid protein interrupts protein kinase R dimerization to counteract host interference in viral protein synthesis.

UNLABELLED: Pathogenic hantaviruses delay the type I interferon response during early stages of viral infection. However, the robust interferon response and induction of interferon-stimulated genes observed during later stages of hantavirus infection fail to combat the virus replication in infected cells. Protein kinase R (PKR), a classical interferon-stimulated gene product, phosphorylates the eukaryotic translation initiation factor eIF2α and causes translational shutdown to create roadblocks for the synthesis of viral proteins. The PKR-induced translational shutdown helps host cells to establish an antiviral state to interrupt virus replication. However, hantavirus-infected cells do not undergo translational shutdown and fail to establish an antiviral state during the course of viral infection. In this study, we showed for the first time that Andes virus infection induced PKR overexpression. However, the overexpressed PKR was not active due to a significant inhibition of autophosphorylation. Further studies revealed that Andes virus nucleocapsid protein inhibited PKR dimerization, a critical step required for PKR autophosphorylation to attain activity. The studies reported here establish a hantavirus nucleocapsid protein as a new PKR inhibitor. These studies provide mechanistic insights into hantavirus resistance to the host interferon response and solve the puzzle of the lack of translational shutdown observed in hantavirus-infected cells. The sensitivity of hantavirus replication to PKR has likely imposed a selective evolutionary pressure on hantaviruses to evade the PKR antiviral response for survival. We envision that evasion of the PKR antiviral response by NP has likely helped hantaviruses to exist during evolution and to survive in infected hosts with a multifaceted antiviral defense. IMPORTANCE: Protein kinase R (PKR), a versatile antiviral host factor, shuts down the translation machinery upon activation in virus-infected cells to create hurdles for the manufacture of viral proteins. The studies reported here reveal that the hantavirus nucleocapsid protein counteracts the PKR antiviral response by inhibiting PKR dimerization, which is required for its activation. We report the discovery of a new PKR inhibitor whose expression in hantavirus-infected cells prevents the PKR-induced host translational shutdown to ensure the continuous synthesis of viral proteins required for efficient virus replication.

PKR and HMGB1 expression and function in rheumatoid arthritis.

The pathogenesis of rheumatoid arthritis (RA) is characterized by inflammation. We aimed to examine the roles of double-stranded RNA-activated protein kinase (PKR) and high-mobility group box chromosomal protein 1 (HMGB1) in a rat model of RA. Male SD rats were divided into three groups: control, RA model, and intervention (RA model plus treatment). The model of RA was made by injecting Freund's adjuvant into the posterior right limb of the rat and the intervention group received a PKR-specific inhibitor C16 after RA modeling. The degree of limb swelling was measured following RA modeling and intervention. In addition, plasma levels of HMGB1 were determined using ELISA. The mRNA and protein levels of PKR and HMGB1 were detected in rat synovium using quantitative PCR and western blot, respectively. The degree of limb swelling in the RA model was increased compared to control, while it was decreased in the intervention model compared to the RA model. Plasma HMGB1 levels in the model group were significantly higher compared to the control group but were lower in the intervention group compared to the model group. PKR and HMGB1 protein and mRNA levels in the rat synovium were elevated in the model group and markedly reduced in the intervention group. Increased levels of PKR and HMGB1 in synovium or blood appear to be involved in the occurrence and development of RA in a rat model. Selective inhibition of PKR improves the symptoms of RA, perhaps by inhibiting the release of HMGB1.