The protein kinase 2 inhibitor tetrabromobenzotriazole protects against renal ischemia reperfusion injury

Pharmacological inhibition of CK2 by silmitasertib mitigates sepsis-induced circulatory collapse, thus improving septic outcomes in mice

Casein kinase II (CK2) has recently emerged as a pivotal mediator in the propagation of inflammation across various diseases. Nevertheless, its role in the pathogenesis of sepsis remains unexplored. Here, we investigated the involvement of CK2 in sepsis progression and the potential beneficial effects of silmitasertib, a selective and potent CK2α inhibitor, currently under clinical trials for COVID-19 and cancer. Sepsis was induced by caecal ligation and puncture (CLP) in four-month-old C57BL/6OlaHsd mice. One hour after the CLP/Sham procedure, animals were assigned to receive silmitasertib (50 mg/kg/i.v.) or vehicle. Plasma/organs were collected at 24 h for analysis. A second set of experiments was performed for survival rate over 120 h. Septic mice developed multiorgan failure, including renal dysfunction due to hypoperfusion (reduced renal blood flow) and increased plasma levels of creatinine. Renal derangements were associated with local overactivation of CK2, and downstream activation of the NF-ĸB-iNOS-NO axis, paralleled by a systemic cytokine storm. Interestingly, all markers of injury/inflammation were mitigated following silmitasertib administration. Additionally, when compared to sham-operated mice, sepsis led to vascular hyporesponsiveness due to an aberrant systemic and local release of NO. Silmitasertib restored sepsis-induced vascular abnormalities. Overall, these pharmacological effects of silmitasertib significantly reduced sepsis mortality. Our findings reveal, for the first time, the potential benefits of a selective and potent CK2 inhibitor to counteract sepsis-induced hyperinflammatory storm, vasoplegia, and ultimately prolonging the survival of septic mice, thus suggesting a pivotal role of CK2 in sepsis and silmitasertib as a novel powerful pharmacological tool for drug repurposing in sepsis.

HIF-1α participates in the regulation of S100A16-HRD1-GSK3β/CK1α pathway in renal hypoxia injury

S100 calcium-binding protein 16 (S100A16) is implicated in both chronic kidney disease (CKD) and acute kidney injury (AKI). Previous research has shown that S100A16 contributes to AKI by facilitating the ubiquitylation and degradation of glycogen synthase kinase 3β (GSK3β) and casein kinase 1α (CK1α) through the activation of HMG-CoA reductase degradation protein 1 (HRD1). However, the mechanisms governing S100A16-induced HRD1 activation and the upregulation of S100A16 expression in renal injury are not fully understood. In this study, we observed elevated expression of Hypoxia-inducible Factor 1-alpha (HIF-1α) in the kidneys of mice subjected to ischemia-reperfusion injury (IRI). S100A16 deletion attenuated the increased HIF-1α expression induced by IRI. Using a S100A16 knockout rat renal tubular epithelial cell line (NRK-52E cells), we found that S100A16 knockout effectively mitigated apoptosis during hypoxic reoxygenation (H/R) and cell injury induced by TGF-β1. Our results revealed that H/R injuries increased both protein and mRNA levels of HIF-1α and HRD1 in renal tubular cells. S100A16 knockout reversed the expressions of HIF-1α and HRD1 under H/R conditions. Conversely, S100A16 overexpression in NRK-52E cells elevated HIF-1α and HRD1 levels. HIF-1α overexpression increased HRD1 and β-catenin while decreasing GSK-3β. HIF-1α inhibition restored HRD1 and β-catenin upregulation and GSK-3β downregulation by cellular H/R injury. Notably, Chromatin immunoprecipitation (ChIP) and luciferase reporter assays demonstrated HIF-1α binding signals on the HRD1 promoter, and luciferase reporter gene assays confirmed HIF-1α's transcriptional regulation of HRD1. Additionally, we identified Transcription Factor AP-2 Beta (TFAP2B) as the upregulator of S100A16. ChIP and luciferase reporter assays confirmed TFAP2B as a transcription factor for S100A16. In summary, this study identifies TFAP2B as the transcription factor for S100A16 and demonstrates HIF-1α regulation of HRD1 transcription within the S100A16-HRD1-GSK3β/CK1α pathway during renal hypoxia injury. These findings provide crucial insights into the molecular mechanisms of kidney injury, offering potential avenues for therapeutic intervention.

Cardiomyocyte intercellular signalling increases oxidative stress and reprograms the global- and phospho-proteome of cardiac fibroblasts

Pathological reprogramming of cardiomyocyte and fibroblast proteome landscapes drive the initiation and progression of cardiac fibrosis. Although the secretome of dysfunctional cardiomyocytes is emerging as an important driver of pathological fibroblast reprogramming, our understanding of the downstream molecular players remains limited. Here, we show that cardiac fibroblast activation (αSMA+) and oxidative stress mediated by the secretome of TGFβ-stimulated cardiomyocytes is associated with a profound reprogramming of their proteome and phosphoproteome landscape. Within the fibroblast global proteome there was a striking dysregulation of proteins implicated in extracellular matrix, protein localisation/metabolism, KEAP1-NFE2L2 pathway, lysosomes, carbohydrate metabolism, and transcriptional regulation. Kinase substrate enrichment analysis of phosphopeptides revealed potential role of kinases (CK2, CDK2, PKC, GSK3B) during this remodelling. We verified upregulated activity of casein kinase 2 (CK2) in secretome-treated fibroblasts, and pharmacological CK2 inhibitor TBB (4,5,6,7-Tetrabromobenzotriazole) significantly abrogated fibroblast activation and oxidative stress. Our data provides molecular insights into cardiomyocyte to cardiac fibroblast crosstalk, and the potential role of CK2 in regulating cardiac fibroblast activation and oxidative stress.

Formulation and Investigation of CK2 Inhibitor-Loaded Alginate Microbeads with Different Excipients

The aim of this study was to formulate and characterize CK2 inhibitor-loaded alginate microbeads via the polymerization method. Different excipients were used in the formulation to improve the penetration of an active agent and to stabilize our preparations. Transcutol® HP was added to the drug-sodium alginate mixture and polyvinylpyrrolidone (PVP) was added to the hardening solution, alone and in combination. To characterize the formulations, mean particle size, scanning electron microscopy analysis, encapsulation efficiency, swelling behavior, an enzymatic stability test and an in vitro dissolution study were performed. The cell viability assay and permeability test were also carried out on the Caco-2 cell line. The anti-oxidant and anti-inflammatory effects of the formulations were finally evaluated. The combination of Transcutol® HP and PVP in the formulation of sodium alginate microbeads could improve the stability, in vitro permeability, anti-oxidant and anti-inflammatory effects of the CK2 inhibitor.

Casein Kinase 2 Alpha Inhibition Protects against Sepsis-Induced Acute Kidney Injury

Sepsis-induced acute kidney injury (AKI) is a common complication in critically ill patients, often resulting in high rates of morbidity and mortality. Previous studies have demonstrated the effectiveness of casein kinase 2 alpha (CK2α) inhibition in ameliorating ischemia-reperfusion-induced AKI. In this study, our aim was to investigate the potential of the selective CK2α inhibitor, 4,5,6,7-tetrabromobenzotriazole (TBBt), in the context of sepsis-induced AKI. To assess this, we initially confirmed an upregulation of CK2α expression following a cecum ligation and puncture (CLP) procedure in mice. Subsequently, TBBt was administered to a group of mice prior to CLP, and their outcomes were compared to those of sham mice. The results revealed that, following CLP, the mice exhibited typical sepsis-associated patterns of AKI, characterized by reduced renal function (evidenced by elevated blood urea nitrogen and creatinine levels), renal damage, and inflammation (indicated by increased tubular injury score, pro-inflammatory cytokine levels, and apoptosis index). However, mice treated with TBBt demonstrated fewer of these changes, and their renal function and architecture remained comparable to that of the sham mice. The anti-inflammatory and anti-apoptotic properties of TBBt are believed to be associated with the inactivation of the mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) signaling pathways. In conclusion, these findings suggest that inhibiting CK2α could be a promising therapeutic strategy for treating sepsis-induced AKI.

Casein Kinase 2 Signaling in White Matter Stroke

The growth of the aging population, together with improved stroke care, has resulted in an increase in stroke survivors and a rise in recurrent events. Axonal injury and white matter (WM) dysfunction are responsible for much of the disability observed after stroke. The mechanisms of WM injury are distinct compared to gray matter and change with age. Therefore, an ideal stroke therapeutic must restore neuronal and axonal function when applied before or after a stroke, and it must also protect across age groups. Casein kinase 2 (CK2), is expressed in the brain, including WM, and is regulated during the development and numerous disease conditions such as cancer and ischemia. CK2 activation in WM mediates ischemic injury by activating the Cdk5 and AKT/GSK3β signaling pathways. Consequently, CK2 inhibition using the small molecule inhibitor CX-4945 (Silmitasertib) correlates with preservation of oligodendrocytes, conservation of axon structure, and axonal mitochondria, leading to improved functional recovery. Remarkably, CK2 inhibition promotes WM function when applied after ischemic injury by specifically regulating the AKT/GSK3β pathways. The blockade of the active conformation of AKT confers post-ischemic protection to young and old WM by preserving mitochondria, implying AKT as a common therapeutic target across age groups. Using a NanoString nCounter miRNA expression profiling, comparative analyses of ischemic WM with or without CX-4945 treatment reveal that miRNAs are expressed at high levels in WM after ischemia, and CX-4945 differentially regulates some of these miRNAs. Therefore, we propose that miRNA regulation may be one of the protective actions of CX-4945 against WM ischemic injury. Silmitasertib is FDA approved and currently in use for cancer and Covid patients; therefore, it is plausible to repurpose CK2 inhibitors for stroke patients.

Lipopolysaccharide from Rhodobacter spheroids modulate toll-like receptors expression and tissue damage in an animal model of bilateral renal ischemic reperfusion injury

Ischemic reperfusion injury (IRI) of the kidneys is a direct sequela of surgical procedures associated with the interruption of blood supply. The pathophysiology of IRI is complicated, and several inflammatories, apoptosis, and oxidative stress pathways are implicated. Among the major receptors directly involved in renal IRI are the toll-like receptors (TLRs), specifically TLR2 and TLR4. In this study, we investigated the effects of Lipopolysaccharide from Rhodobacter Sphaeroides (TLR2 and TLR4 antagonist, LPS-RS) and the ultrapure form (pure TLR4 antagonist, ULPS-RS) on the histopathological changes and TLRs expression in an animal model of bilateral renal IRI. Forty-eight adult male rats were allocated into six groups (N=8) as follows: sham group (negative control without IRI), control group (rats underwent bilateral renal ischemia for 30 minutes and 2 hours of reperfusion), vehicle group (IRI+ vehicle), LPS-RS group (IRI+ 0.5 mg/kg of LPS-RS), ULPS-RS group (IRI+ 0.1 mg/kg of ULPS-RS), ULPS-RSH group (IRI+ 0.2 mg/kg of ULPS-RS). Significant improvement in the histopathological damages induced by renal IRI was found in the ULPS-RS treated groups at both doses compared with the control group. The protective effect of ULPS-RS was associated with significantly reduced TLR4 expression without affecting TLR2. Regarding LPS-RS, the tested dose adversely affected the renal tissues as manifested by the histopathological findings, although it similarly affected TLRs expression as ULPS-RS. Our results demonstrated that ULPS-RS was renoprotective while LPS-RS had no protective effect against the tissue damages induced by renal IRI.

Advances in the study of emodin: an update on pharmacological properties and mechanistic basis

Rhei Radix et Rhizoma, also known as rhubarb or Da Huang, has been widely used as a spice and as traditional herbal medicine for centuries, and is currently marketed in China as the principal herbs in various prescriptions, such as Da-Huang-Zhe-Chong pills and Da-Huang-Qing-Wei pills. Emodin, a major bioactive anthraquinone derivative extracted from rhubarb, represents multiple health benefits in the treatment of a host of diseases, such as immune-inflammatory abnormality, tumor progression, bacterial or viral infections, and metabolic syndrome. Emerging evidence has made great strides in clarifying the multi-targeting therapeutic mechanisms underlying the efficacious therapeutic potential of emodin, including anti-inflammatory, immunomodulatory, anti-fibrosis, anti-tumor, anti-viral, anti-bacterial, and anti-diabetic properties. This comprehensive review aims to provide an updated summary of recent developments on these pharmacological efficacies and molecular mechanisms of emodin, with a focus on the underlying molecular targets and signaling networks. We also reviewed recent attempts to improve the pharmacokinetic properties and biological activities of emodin by structural modification and novel material-based targeted delivery. In conclusion, emodin still has great potential to become promising therapeutic options to immune and inflammation abnormality, organ fibrosis, common malignancy, pathogenic bacteria or virus infections, and endocrine disease or disorder. Scientifically addressing concerns regarding the poor bioavailability and vague molecular targets would significantly contribute to the widespread acceptance of rhubarb not only as a dietary supplement in food flavorings and colorings but also as a health-promoting TCM in the coming years.

How can a traffic light properly work if it is always green? The paradox of CK2 signaling

CK2 is a constitutively active protein kinase that assuring a constant level of phosphorylation to its numerous substrates supports many of the most important biological functions. Nevertheless, its activity has to be controlled and adjusted in order to cope with the varying needs of a cell, and several examples of a fine-tune regulation of its activity have been described. More importantly, aberrant regulation of this enzyme may have pathological consequences, e.g. in cancer, chronic inflammation, neurodegeneration, and viral infection. Our review aims at summarizing our current knowledge about CK2 regulation. In the first part, we have considered the most important stimuli shown to affect protein kinase CK2 activity/expression. In the second part, we focus on the molecular mechanisms by which CK2 can be regulated, discussing controversial aspects and future perspectives.

Making endo-cyclizations favorable again: a conceptually new synthetic approach to benzotriazoles via azide group directed lithiation/cyclization of 2-azidoaryl bromides

Although benzotriazoles are important and ubiquitous, currently there is only one conceptual approach to their synthesis: bridging the two ortho-amino groups with an electrophilic nitrogen atom. Herein, we disclose a new practical alternative - the endo-cyclization of 2-azidoaryl lithiums obtained in situ from 2-azido-aryl bromides. The scope of the reaction is illustrated using twenty-four examples with a variety of alkyl, alkoxy, perfluoroalkyl, and halogen substituents. We found that the directing effect of the azide group allows selective metal-halogen exchange in aryl azides containing several bromine atoms. Furthermore, (2-bromophenyl)diazomethane undergoes similar cyclization to give an indazole. Thus, cyclizations of aryl lithiums containing an ortho-X = Y = Z group emerge as a new general approach for the synthesis of aromatic heterocycles. DFT computations suggested that the observed endo-selectivity applies to the anionic cyclizations of other functionalities that undergo "1,1-additions" (i.e., azides, diazo compounds, and isonitriles). In contrast, cyclizations with the heteroatomic functionalities that follow the "1,2-addition" pattern (cyanates, thiocyanates, isocyanates, isothiocyanates, and nitriles) prefer the exo-cyclization path. Hence, such reactions expand the current understanding of stereoelectronic factors in anionic cyclizations.

Pyrogallol-Phloroglucinol-6,6-Bieckol from Ecklonia cava Attenuates Tubular Epithelial Cell (TCMK-1) Death in Hypoxia/Reoxygenation Injury

The hypoxia/reoxygenation (H/R) injury causes serious complications after the blood supply to the kidney is stopped during surgery. The main mechanism of I/R injury is the release of high-mobility group protein B1 (HMGB1) from injured tubular epithelial cells (TEC, TCMK-1 cell), which triggers TLR4 or RAGE signaling, leading to cell death. We evaluated whether the extracts of Ecklonia cava (E. cava) would attenuate TEC death induced by H/R injury. We also evaluated which phlorotannin-dieckol (DK), phlorofucofuroeckol A (PFFA), pyrogallol phloroglucinol-6,6-bieckol (PPB), or 2,7-phloroglucinol-6,6-bieckol (PHB)-would have the most potent effect in the context of H/R injury. We used for pre-hypoxia treatment, in which the phlorotannins from E. cava extracts were added before the onset of hypoxia, and a post- hypoxia treatment, in which the phlorotannins were added before the start of reperfusion. PPB most effectively reduced HMGB1 release and the expression of TLR4 and RAGE induced by H/R injury in both pre- and post-hypoxia treatment. PPB also most effectively inhibited the expression of NF-kB and release of the inflammatory cytokines TNF-α and IL-6 in both models. PPB most effectively inhibited cell death and expression of cell death signaling molecules such as Erk/pErk, JNK/pJNK, and p38/pp38. These results suggest that PPB blocks the HGMB1-TLR4/RAGE signaling pathway and decreases TEC death induced by H/R and that PPB can be a novel target for renal H/R injury therapy.

Inhibition of Casein Kinase 2 Protects Oligodendrocytes From Excitotoxicity by Attenuating JNK/p53 Signaling Cascade

Oligodendrocytes are highly vulnerable to glutamate excitotoxicity, a central mechanism involved in tissue damage in Multiple Sclerosis (MS). Sustained activation of AMPA receptors in rat oligodendrocytes induces cytosolic calcium overload, mitochondrial depolarization, increase of reactive oxygen species, and activation of intracelular pathways resulting in apoptotic cell death. Although many signals driven by excitotoxicity have been identified, some of the key players are still under investigation. Casein kinase 2 (CK2) is a serine/threonine kinase, constitutively expressed in all eukaryotic tissues, involved in cell proliferation, malignant transformation and apoptosis. In this study, we identify CK2 as a critical regulator of oligodendrocytic death pathways and elucidate its role as a signal inductor following excitotoxic insults. We provide evidence that CK2 activity is up-regulated in AMPA-treated oligodendrocytes and CK2 inhibition significantly diminished AMPA receptor-induced oligodendroglial death. In addition, we analyzed mitogen-activated protein kinase (MAPK) signaling after excitotoxic insult. We observed that AMPA receptor activation induced a rapid increase in c-Jun N-terminal kinase (JNK) and p38 phosphorylation that was reduced after CK2 inhibition. Moreover, blocking their phosphorylation, we enhanced oligodendrocyte survival after excitotoxic insult. Finally, we observed that the tumor suppressor p53 is activated during AMPA receptor-induced cell death and, interestingly, down-regulated by JNK or CK2 inhibition. Together, these data indicate that the increase in CK2 activity induced by excitotoxic insults regulates MAPKs, triggers p53 activation and mediates subsequent oligodendroglial loss. Therefore, targeting CK2 may be a useful strategy to prevent oligodendrocyte death in MS and other diseases involving central nervous system (CNS) white matter.

CK2 inhibition confers functional protection to young and aging axons against ischemia by differentially regulating the CDK5 and AKT signaling pathways

White matter (WM) is injured in most strokes, which contributes to functional deficits during recovery. Casein kinase 2 (CK2) is a protein kinase that is expressed in brain, including WM. To assess the impact of CK2 inhibition on axon recovery following oxygen glucose deprivation (OGD), mouse optic nerves (MONs), which are pure WM tracts, were subjected to OGD with or without the selective CK2 inhibitor CX-4945. CX-4945 application preserved axon function during OGD and promoted axon function recovery when applied before or after OGD. This protective effect of CK2 inhibition correlated with preservation of oligodendrocytes and conservation of axon structure and axonal mitochondria. To investigate the pertinent downstream signaling pathways, siRNA targeting the CK2α subunit identified CDK5 and AKT as downstream molecules. Consequently, MK-2206 and roscovitine, which are selective AKT and CDK5 inhibitors, respectively, protected young and aging WM function only when applied before OGD. However, a novel pan-AKT allosteric inhibitor, ARQ-092, which targets both the inactive and active conformations of AKT, conferred protection to young and aging axons when applied before or after OGD. These results suggest that AKT and CDK5 signaling contribute to the WM functional protection conferred by CK2 inhibition during ischemia, while inhibition of activated AKT signaling plays the primary role in post-ischemic protection conferred by CK2 inhibition in WM independent of age. CK2 inhibitors are currently being used in clinical trials for cancer patients; therefore, our results will provide rationale for repurposing these drugs as therapeutic options for stroke patients by adding novel targets.

ERK and p38 Upregulation versus Bcl-6 Downregulation in Rat Kidney Epithelial Cells Exposed to Prolonged Hypoxia

Hypoxia is a common cause of kidney injury and a major issue in kidney transplantation. Mitogen-activated protein kinases (MAPKs) are involved in the cellular response to hypoxia, but the precise roles of MAPKs in renal cell reactions to hypoxic stress are not well known yet. This work was conducted to investigate the regulation of extracellular signal-regulated kinase-1 and -2 (ERK1/2) and p38 and their signaling-relevant molecules in kidney epithelial cells exposed to prolonged hypoxia. Rat kidney epithelial cells Normal Rat Kidney (NRK)-52E were exposed to hypoxic conditions (1% O₂) for 24 to 72 h. Cell morphology was examined by light microscopy, and cell viability was checked by 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxypheny]-2-[4-sulfophenyl]-2H-tetrazolium (MTS). The expression of ERK1/2 and p38 MAPK, as well as their signaling-related molecules, was measured by Western blot and real-time polymerase chain (RT-PCR) reaction. At the 1% oxygen level, cell morphology had no appreciable changes compared to the control up to 72 h of exposure under light microscopy, whereas the results of MTS showed a slight but significant reduction in cell viability after 72 h of hypoxia. On the other hand, ERK1/2 and p38 phosphorylation remarkably increased in these cells after 24 to 72 h of hypoxia. In sharp contrast, the expression of transcription factor B-cell lymphoma 6 (Bcl-6) was significantly downregulated in response to hypoxic stress. Other intracellular molecules relevant to the ERK1/2 and p38 signaling pathway, such as protein kinase A, protein kinase C, Bcl-2, nuclear factor erythroid 2-related factor 2, tristetraprolin, and interleukin-10(IL-10), had no significant alterations after 24 to 72 h of hypoxic exposure. We conclude that hypoxic stress increases the phosphorylation of both ERK1/2 and p38 but decreases the level of Bcl-6 in rat kidney epithelial cells.

The importance of negative determinants as modulators of CK2 targeting. The lesson of Akt2 S131

CK2 is a pleiotropic S/T protein kinase (formerly known as casein kinase 2) which is attracting increasing interest as therapeutic target, and the identification of its substrates is a crucial step in determining its involvement in different pathological conditions. We recently found that S131 of Akt2 (homologous to the well established CK2 target S129 of Akt1) is not phosphorylated by CK2 either in vitro or in vivo, although the consensus sequence recognized by CK2 (S/T-x-x-E/D/pS/pT) is conserved in it. Here, by exploiting synthetic peptides, in cell transfection experiments, and computational analysis, we show that a single sequence element, a T at position n+1, hampers phosphorylation, causing an α-helix structure organization which prevents the recognition of its own consensus by CK2. Our results highlight the role of negative determinants as crucial modulators of CK2 targeting and corroborate the concept that Akt1 and Akt2 display isoform specific features. Experiments with synthetic peptides suggest that Akt2 S131 could be phosphorylated by kinases of the Plk (Polo-like kinase) family, which are insensitive to the presence of the n+1 T. The low phylogenetic conservation of the Akt2 sequence around S131, as opposed to the extremely well-conserved Akt1 homologous sequence, would indicate a dominant positive role in the selective pressure only for the Akt1 phosphoacceptor site committed to undergo phosphorylation by CK2. By contrast, Akt2 S131 may mediate the response to specific physio/pathological conditions, being consequently shielded against basal CK2 targeting.

Nrf2-mediated neuroprotection against oxygen-glucose deprivation/reperfusion injury by emodin via AMPK-dependent inhibition of GSK-3β

Objectives

Our study verified the neuroprotective properties of emodin against oxygen-glucose deprivation/reoxygenation (OGD/R) and demonstrated its mechanism.

Methods

Human neuronal SH-SY5Y cells were investigated by analysing cell viability, lactate dehydrogenase levels, expression of molecules related to apoptotic cell death, and using biochemical techniques, flow cytometry and Western blot assays.

Key findings

Emodin reduced OGD/R-lead to neurotoxicity in SH-SY5Y cells. OGD/R significantly increased levels of cleaved poly ADP ribose polymerase, cleaved caspase-3, cleaved caspase-9, p53, p21 and Bax protein. However, emodin treatment effectively inhibited these OGD/R-induced changes. Emodin treatment also increased HO-1 and NQO1 expression in a concentration- and time-dependent manner and caused antioxidant response element (ARE) transcription activity and nuclear Nrf2 accumulation. Emodin phosphorylated AMPK and GSK3β, and pretreatment of cells with an AMPK inhibitor suppressed emodin-induced nuclear Nrf2 accumulation and HO-1 and NQO1 expression. AMPK inhibitor treatment decreased GSK3β phosphorylation, suggesting that AMPK is upstream of GSK3β, Nrf2, HO-1 and NQO1. Emodin's neuroprotective effect was completely blocked by HO-1, NQO1 and Nrf2 knock-down and an AMPK inhibitor, indicating the action of AMPK/GSK3β/Nrf2/ARE in the neuroprotective effect of emodin subjected to OGD/R.

Conclusions

Emodin treatment protected against OGD/R-lead to neurotoxicity by potentiating Nrf2/ARE-regulated neuroprotection through the AMPK/GSK3β pathway, indicating that emodin may be useful for treating neurodegenerative disorders.

Emodin, A Chinese Herbal Medicine, Inhibits Reoxygenation-Induced Injury in Cultured Human Aortic Endothelial Cells by Regulating the Peroxisome Proliferator-Activated Receptor-γ (PPAR-γ) and Endothelial Nitric Oxide Synthase (eNOS) Signaling Pathway

Background

Ischemia-reperfusion injury is associated with vascular dysfunction. The aim of this study was to investigate the role of emodin, a Chinese herbal medicine, in hypoxia-reoxygenation injury in cultured human aortic endothelial cells (HAECs) and its effects on the expression of the peroxisome proliferator-activated receptor-γ (PPAR-γ) and endothelial nitric oxide synthase (eNOS) signaling pathway.

Material/Methods

An in vitro hypoxia-reoxygenation model used cultured human aortic endothelial cells (HAECs). A colorimetric method evaluated the activity of peroxisome proliferator-activated receptor-γ (PPAR-γ). Phosphorylation of PPAR-γ and endothelial nitric oxide synthase (eNOS) were measured by Western blotting. Expression of inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8 were evaluated by enzyme-linked immunosorbent assay (ELISA) and Western blotting. Nitric oxide (NO) production was detected by diaminofluorescein-FM diacetate (DAF-FM DA) fluorescence. Immunoprecipitation was used to evaluate the molecular coupling of heat shock protein (HSP)90 and eNOS.

Results

Hypoxia-reoxygenation injury of HAECs reduced the activity and phosphorylation of PPAR-γ, and eNOS, NO production, and HSP90/eNOS molecular coupling in a time-dependent manner. Hypoxia-reoxygenation increased the levels of inflammatory cytokines TNF-α, IL-6, and IL-8 in a time-dependent manner. Emodin treatment recovered PPAR-γ activity and phosphorylation, eNOS phosphorylation, and HSP90/eNOS coupling in HAECS in a concentration-dependent manner, which was reversed by the PPAR-γ inhibitor GW9662, and the eNOS inhibitor, L-NAME. The recovery of HSP90/eNOS coupling by emodin was impaired by GW9662 treatment.

Conclusions

An in vitro hypoxia-reoxygenation (ischemia-reperfusion injury) model of induction of endothelial cell inflammatory mediators showed that emodin recovered the PPAR-γ and eNOS pathway activity.

Amelioration of lung ischemia‑reperfusion injury by JNK and p38 small interfering RNAs in rat pulmonary microvascular endothelial cells in an ischemia‑reperfusion injury lung transplantation model

The inhibition of mitogen‑activated protein kinases (MAPKs), including c‑Jun NH2‑terminal protein kinase (JNK), p38 MAPK (p38) and extracellular signal‑regulated protein kinase 1/2 (ERK1/2), have an important effect on lung ischemia‑reperfusion injury (IRI) during lung transplantation (LT). However, the way in which combined MAPK inhibition exerts optimal protective effects on lung IRI remains to be elucidated. Therefore, the present study evaluated the therapeutic efficacy of the inhibition of MAPKs in rat pulmonary microvascular endothelial cells (PMVECs) in an IRI model of LT. The rat PMVECs were transfected with small interfering RNAs (siRNAs) against JNK, p38 or ERK1/2. Cotransfection was performed with siRNAs against JNK and p38 in the J+p group, JNK and ERK1/2 in the J+E group, p38 and ERK1/2 in the p+E group, or all three in the J+p+E group. Non‑targeting (NT) siRNA was used as a control. The PMVECs were then treated to induce IRI, and the levels of inflammation, apoptosis and oxidative stress were detected. Differences between compared groups were determined using Tukey's honest significant difference test. In all groups, silencing of the MAPKs was shown to attenuate inflammation, apoptosis and oxidative stress to differing extents, compared with the NT group. The J+p and J+p+E groups showed lower levels of interleukin (IL)‑1β, IL‑6 and malondialdehyde, a lower percentage of early‑apoptotic cells, and higher superoxide dismutase (SOD) activity, compared with the other groups. No significant differences were observed in the inflammatory response, SOD activity or early apoptosis between the J+p and J+p+E groups. These findings suggested that the dual inhibition of JNK and p38 led to maximal amelioration of lung IRI in the PMVECs of the IRI model of LT, which occurred through anti‑inflammatory, anti‑oxidative and anti‑apoptotic mechanisms.

PGC-1α attenuates hydrogen peroxide-induced apoptotic cell death by upregulating Nrf-2 via GSK3β inactivation mediated by activated p38 in HK-2 Cells

Ischemia/reperfusion injury triggers acute kidney injury (AKI) by aggravating oxidative stress mediated mitochondria dysfunction. The peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) is a master player that regulates mitochondrial biogenesis and the antioxidant response. We postulated that PGC-1α functions as cytoprotective effector in renal cells and that its regulation mechanism is coordinated by nuclear factor erythroid 2-related factor 2 (Nrf-2). In this study, to understand the effect and molecular mechanisms of PGC-1α, we developed an empty vector or PGC-1α-overexpressing stable cell lines in HK-2 cells (Mock or PGC-1α stable cells). PGC-1α overexpression increased the viability of cells affected by H₂O₂ mediated injury, protected against H₂O₂-mediated apoptotic events and inhibited reactive oxygen species accumulation in the cytosol and mitochondria as compared to that in Mock cells. The cytoprotective effect of PGC-1α was related to Nrf-2 upregulation, which was counteracted by Nrf-2-specific knockdown. Using inhibitor of p38, we found that regulation of the p38/glycogen synthase kinase 3β (GSK3β)/Nrf-2 axis was involved in the protective effects of PGC-1α. Taken together, we suggest that PGC-1α protects human renal tubule cells from H₂O₂-mediated apoptotic injury by upregulating Nrf-2 via GSK3β inactivation mediated by activated p38.

Diosmetin protects against ischemia/reperfusion-induced acute kidney injury in mice

BACKGROUND

Renal ischemia/reperfusion (I/R)-induced acute kidney injury remains to be a troublesome condition in clinical practice. Although the exact molecular mechanisms underlying renal I/R injury are incompletely understood, the deleterious progress of renal I/R injury involves inflammation, apoptosis, and oxidative stress. Diosmetin is a member of the flavonoid glycosides family, which suppresses the inflammatory response and cellular apoptosis and enhances antioxidant activity. The purpose of this study was to investigate the protective effect of diosmetin on I/R-induced renal injury in mice.

METHODS

Thirty BALB/c mice were randomly divided into five groups. Four groups of mice received diosmetin (0.25, 0.5, and 1 mg/kg) or vehicle (I/R group) before ischemia. Another group received vehicle without ischemia to serve as a negative control (sham-operated group). Twenty-four hours after reperfusion, serum and renal tissues were harvested to evaluate renal function and histopathologic features. In addition, the expression of inflammation-related proteins, apoptotic molecules, and antioxidant enzymes was analyzed.

RESULTS

Compared with sham mice, the I/R group significantly exacerbated renal function and renal tube architecture and increased the inflammatory response and renal tubule apoptosis. Nevertheless, pretreatment with diosmetin reversed these changes. In addition, diosmetin treatment resulted in a marked increase in antioxidant protein expression compared with I/R mice.

CONCLUSIONS

The renoprotective effects of diosmetin involved suppression of the nuclear factor-κB and mitochondrial apoptosis pathways, as well as activation of the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Diosmetin has significant potential as a therapeutic intervention to ameliorate renal injury after renal I/R.

Exploring the CK2 Paradox: Restless, Dangerous, Dispensable

The history of protein kinase CK2 is crowded with paradoxes and unanticipated findings. Named after a protein (casein) that is not among its physiological substrates, CK2 remained in search of its targets for more than two decades after its discovery in 1954, but it later came to be one of the most pleiotropic protein kinases. Being active in the absence of phosphorylation and/or specific stimuli, it looks unsuitable to participate in signaling cascades, but its “lateral” implication in a variety of signaling pathways is now soundly documented. At variance with many “onco-kinases”, CK2 is constitutively active, and no oncogenic CK2 mutant is known; still high CK2 activity correlates to neoplasia. Its pleiotropy and essential role may cast doubts on the actual “druggability” of CK2; however, a CK2 inhibitor is now in Phase II clinical trials for the treatment of cancer, and cell clones viable in the absence of CK2 are providing information about the mechanism by which cancer becomes addicted to high CK2 levels. A phosphoproteomics analysis of these CK2 null cells suggests that CK2 pleiotropy may be less pronounced than expected and supports the idea that the phosphoproteome generated by this kinase is flexible and not rigidly pre-determined.

Sirtuin 2 aggravates postischemic liver injury by deacetylating mitogen-activated protein kinase phosphatase-1

Sirtuin 2 (Sirt2) is known to negatively regulate anoxia-reoxygenation injury in myoblasts. Because protein levels of Sirt2 are increased in ischemia-reperfusion (I/R)-injured liver tissues, we examined whether Sirt2 is protective or detrimental against hepatic I/R injury. We overexpressed Sirt2 in the liver of C57BL/6 mice using a Sirt2 adenovirus. Wild-type and Sirt2 knockout mice were subjected to a partial (70%) hepatic ischemia for 45 minutes, followed by various periods of reperfusion. In another set of experiments, wild-type mice were pretreated intraperitoneally with AGK2, a Sirt2 inhibitor. Isolated hepatocytes and Kupffer cells from wild-type and Sirt2 knockout mice were subjected to hypoxia-reoxygenation injury to determine the in vitro effects of Sirt2. Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Prior injection with Sirt2 adenovirus aggravated liver injury, as demonstrated by increases in serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration relative to control virus-injected mice. Pretreatment with AGK2 resulted in significant improvements in serum aminotransferase levels and histopathologic findings. Similarly, experiments with Sirt2 knockout mice also revealed reduced hepatocellular injury. The molecular mechanism of Sirt2's involvement in this aggravation of hepatic I/R injury includes the deacetylation and inhibition of mitogen-activated protein kinase phosphatase-1 and consequent activation of mitogen-activated protein kinases.

CONCLUSION

Sirt2 is an aggravating factor during hepatic I/R injury. (Hepatology 2017;65:225-236).

Protein Kinase CK2 Regulates Leukocyte-Endothelial Cell Interactions during Ischemia and Reperfusion in Striated Skin Muscle

BACKGROUND

Ischemia and reperfusion (I/R) causes tissue injury by inflammatory processes. This involves the upregulation of endothelial surface proteins by phospho-regulated signaling pathways, resulting in enhanced interactions of leukocytes with endothelial cells. Recently, we found that protein kinase CK2 is a crucial regulator of leukocyte-mediated inflammation. Therefore, in this study we investigated the involvement of CK2 in leukocyte-endothelial cell interactions during I/R injury.

METHODS

We first analyzed the inhibitory action of (E)-3-(2,3,4,5-tetrabromophenyl)acrylic acid (TBCA) and CX-4945 on CK2 kinase activity and the viability of human dermal microvascular endothelial cells (HDMEC). To mimic I/R conditions in vitro, HDMEC were exposed to hypoxia and reoxygenation and the expression of adhesion molecules was analyzed by flow cytometry. Moreover, we analyzed in vivo the effect of CK2 inhibition on leukocyte-endothelial cell interactions in the dorsal skinfold chamber model of I/R injury by means of repetitive intravital fluorescence microscopy and immunohistochemistry.

RESULTS

We found that TBCA and CX-4945 suppressed the activity of CK2 in HDMEC without affecting cell viability. This was associated with a significant downregulation of E-selectin and intercellular adhesion molecule (ICAM)-1 after in vitro hypoxia and reoxygenation. In vivo, CX-4945 treatment significantly decreased the numbers of adherent and transmigrated leukocytes in striated muscle tissue exposed to I/R.

CONCLUSION

Our findings indicate that CK2 is involved in the regulation of leukocyte-endothelial cell interactions during I/R by mediating the expression of E-selectin and ICAM-1.