Inhibition of serum- and glucocorticoid-inducible kinase 1 enhances TLR-mediated inflammation and promotes endotoxin-driven organ failure

Effect of IL-9 neutralising antibody on pyroptosis via SGK1/NF-κB/NLRP3/GSDMD in allergic rhinitis mice

Allergic rhinitis is a common non-infectious inflammatory disease that affects approximately 15 % of people worldwide and has a complex and unclear aetiology. In recent years, pyroptosis has been found to play a role in the development of allergic rhinitis. IL-9, pyroptosis, serum and glucocorticoid-induced protein kinase 1 (SGK1), NOD-like receptor 3 (NLRP3), and nuclear factor kappa B (NF-κB) have been shown to influence each other. Herein, we aimed to explore the role of IL-9 neutralising antibody in pyroptosis involving IL-9, SGK1, NF-κB, and NLRP3 in allergic rhinitis. We observed a decrease in cytokines involved in pyroptosis and gasdermin D (GSDMD) compared with those in mice with allergic rhinitis. Further, phosphorylation of NF-κB/p65 decreased compared with that in mice with allergic rhinitis; NLRP3 and ASC also decreased, although the levels were higher than those in controls. SGK1 levels decreased compared with that in mice with allergic rhinitis and increased after using IL-9 neutralising antibodies, thus demonstrating its negative regulatory effects. The IL-9 neutralising antibody reduced the inflammatory and pyroptosis responses via SGK1 and NF-κB/NLRP3/GSDMD pathway. Our research results indicate that IL-9 regulates allergic rhinitis via the influence of SGK1 and NF-κB/NLRP3/GSDMD signalling pathway, providing new insights for developing novel drugs to treat allergic rhinitis.

Inhibition the ubiquitination of ENaC and Na,K-ATPase with erythropoietin promotes alveolar fluid clearance in sepsis-induced acute respiratory distress syndrome

Sepsis-induced acute respiratory distress syndrome (ARDS) causes significant fatalities worldwide and lacks pharmacological intervention. Alveolar fluid clearance (AFC) plays a pivotal role in the remission of ARDS and is markedly impaired in the pathogenesis of ARDS. Here, we demonstrated that erythropoietin could effectively ameliorate lung injury manifestations and lethality, restore lung function and promote AFC in a rat model of lipopolysaccharide (LPS)-induced ARDS. Moreover, it was proven that EPO-induced restoration of AFC occurs through triggering the total protein expression of ENaC and Na,K-ATPase channels, enhancing their protein abundance in the membrane, and suppressing their ubiquitination for degeneration. Mechanistically, the data indicated the possible involvement of EPOR/JAK2/STAT3/SGK1/Nedd4-2 signaling in this process, and the pharmacological inhibition of the pathway markedly eliminated the stimulating effects of EPO on ENaC and Na,K-ATPase, and subsequently reversed the augmentation of AFC by EPO. Consistently, in vitro studies of alveolar epithelial cells paralleled with that EPO upregulated the expression of ENaC and Na,K-ATPase, and patch-clamp studies further demonstrated that EPO substantially strengthened sodium ion currents. Collectively, EPO could effectively promote AFC by improving ENaC and Na,K-ATPase protein expression and abundance in the membrane, dependent on inhibition of ENaC and Na,K-ATPase ubiquitination, and resulting in diminishing LPS-associated lung injuries.

The role of the SGK3/TOPK signaling pathway in the transition from acute kidney injury to chronic kidney disease

Introduction: Profibrotic phenotype of renal tubular epithelial cells (TECs) featured with epithelial to mesenchymal transition (EMT) and profibrotic factors secretion, and aberrant accumulation of CD206⁺ M2 macrophages are the key points in the transition from acute kidney injury (AKI) to chronic kidney disease (CKD). Nevertheless, the underlying mechanisms involved remain incompletely understood. Serum and glucocorticoid-inducible kinase (SGK) is a serine/threonine protein kinase, required for intestinal nutrient transport and ion channels modulation. T-LAK-cell-originated protein kinase (TOPK) is a member of the mitogen activated protein kinase family, linked to cell cycle regulation. However, little is known about their roles in AKI-CKD transition. Methods: In this study, three models were constructed in C57BL/6 mice: low dose and multiple intraperitoneal injection of cisplatin, 5/6 nephrectomy and unilateral ureteral obstruction model. Rat renal tubular epithelial cells (NRK-52E) were dealt with cisplatin to induce profibrotic phenotype, while a mouse monocytic cell line (RAW264.7) were cultured with cisplatin or TGF-β1 to induce M1 or M2 macrophage polarization respectively. And co-cultured NRK-52E and RAW264.7 through transwell plate to explore the interaction between them. The expression of SGK3 and TOPK phosphorylation were detected by immunohistochemistry, immunofluorescence and western blot analysis. Results: In vivo, the expression of SGK3 and p-TOPK were gradually inhibited in TECs, but enhanced in CD206⁺ M2 macrophages. In vitro, SGK3 inhibition aggravated epithelial to mesenchymal transition through reducing the phosphorylation state of TOPK, and controlling TGF-β1 synthesis and secretion in TECs. However, SGK3/TOPK axis activation promoted CD206⁺ M2 macrophage polarization, which caused kidney fibrosis by mediating macrophage to myofibroblast transition (MMT). When co-cultured, the TGF-β1 from profibrotic TECs evoked CD206⁺ M2 macrophage polarization and MMT, which could be attenuated by SGK3/TOPK axis inhibition in macrophages. Conversely, SGK3/TOPK signaling pathway activation in TECs could reverse CD206⁺ M2 macrophages aggravated EMT. Discussion: We revealed for the first time that SGK3 regulated TOPK phosphorylation to mediate TECs profibrotic phenotype, macrophage plasticity and the crosstalk between TECs and macrophages during AKI-CKD transition. Our results demonstrated the inverse effect of SGK3/TOPK signaling pathway in profibrotic TECs and CD206⁺ M2 macrophages polarization during the AKI-CKD transition.

Estrogen-sensitive activation of SGK1 induces M2 macrophages with anti-inflammatory properties and a Th2 response at the maternal-fetal interface

BACKGROUND

Decidual macrophages participate in immune regulation at the maternal-fetal interface. Abnormal M1/M2 polarization of decidual macrophages might predispose immune maladaptation in recurrent pregnancy loss (RPL). However, the mechanism of decidual macrophage polarization is unclear. We explored the role of Estradiol (E₂)-sensitive serum-glucocorticoid regulated kinase (SGK) 1 in promoting macrophage polarization and suppressing inflammation at the maternal-fetal interface.

METHODS

We assessed serum levels of E₂ and progesterone during first trimester of pregnancy in women with or without threatened miscarriages (ended in live birth, n = 448; or early miscarriages, n = 68). For detection of SGK1 in decidual macrophages, we performed immunofluorescence labeling and western blot analysis applying decidual samples from RPL (n = 93) and early normal pregnancy (n = 66). Human monocytic THP-1 cells were differentiated into macrophages and treated with Toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS), E₂, inhibitors or siRNA for in vitro analysis. Flow cytometry analysis were conducted to detect macrophages polarization. We also applied ovariectomized (OVX) mice with hormones exploring the mechanisms underlying the regulation of SGK1 activation by E₂ in the decidual macrophages in vivo.

RESULTS

SGK1 expression down regulation in the decidual macrophages of RPL was consistent with the lower concentration and slower increment of serum E₂ from 4 to 12 weeks of gestation seen in these compromised pregnancies. LPS reduced SGK1 activities, but induced the pro-inflammatory M1 phenotype of THP-1 monocyte-derived macrophages and T helper (Th) 1 cytokines that favored pregnancy loss. E₂ pretreatment promoted SGK1 activation in the decidual macrophages of OVX mice in vivo. E₂ pretreatment amplified SGK1 activation in TLR4-stimulated THP-1 macrophages in vitro through the estrogen receptor beta (ERβ) and PI3K pathway. E₂-sensitive activation of SGK1 increased M2 macrophages and Th2 immune responses, which were beneficial to successful pregnancy, by inducing ARG1 and IRF4 transcription, which are implicated in normal pregnancy. The experiments on OVX mice have shown that pharmacological inhibition of E₂ promoted nuclear translocation of NF-κB in the decidual macrophages. Further more, pharmacological inhibition or knockdown of SGK1 in TLR4-stimulated THP-1 macrophages activated NF-κB by promoting its nuclear translocation, leading to increased secretion of pro-inflammatory cytokines involved in pregnancy loss.

CONCLUSION

Our findings highlighted the immunomodulatory roles of E₂-activated SGK1 in Th2 immune responses by priming anti-inflammatory M2 macrophages at the maternal-fetal interface, resulting in a balanced immune microenvironment during pregnancy. Our results suggest new perspectives on future preventative strategies for RPL.

Serum/glucocorticoid-inducible kinase 1 deficiency induces NLRP3 inflammasome activation and autoinflammation of macrophages in a murine endolymphatic hydrops model

Ménière's disease, a multifactorial disorder of the inner ear, is characterized by severe vertigo episodes and hearing loss. Although the role of immune responses in Ménière's disease has been proposed, the precise mechanisms remain undefined. Here, we show that downregulation of serum/glucocorticoid-inducible kinase 1 is associated with activation of NLRP3 inflammasome in vestibular-resident macrophage-like cells from Ménière's disease patients. Serum/glucocorticoid-inducible kinase 1 depletion markedly enhances IL-1β production which leads to the damage of inner ear hair cells and vestibular nerve. Mechanistically, serum/glucocorticoid-inducible kinase 1 binds to the PYD domain of NLRP3 and phosphorylates it at Serine 5, thereby interfering inflammasome assembly. Sgk^-/- mice show aggravated audiovestibular symptoms and enhanced inflammasome activation in lipopolysaccharide-induced endolymphatic hydrops model, which is ameliorated by blocking NLRP3. Pharmacological inhibition of serum/glucocorticoid-inducible kinase 1 increases the disease severity in vivo. Our studies demonstrate that serum/glucocorticoid-inducible kinase 1 functions as a physiologic inhibitor of NLRP3 inflammasome activation and maintains inner ear immune homeostasis, reciprocally participating in models of Ménière's disease pathogenesis.

High extracellular sodium chloride concentrations induce resistance to LPS signal in human dendritic cells

Recent evidence showed that in response to elevated sodium dietary intakes, many body tissues retain Na⁺ ions for long periods of time and can reach concentrations up to 200 mM. This could modulate the immune system and be responsible for several diseases. However, studies brought contrasted results and the effects of external sodium on human dendritic cell (DC) responses to danger signals remain largely unknown. Considering their central role in triggering T cell response, we tested how NaCl-enriched medium influences human DCs properties. We found that DCs submitted to high extracellular Na⁺ concentrations up to 200 mM remain viable and maintain the expression of specific DC markers, however, their maturation, chemotaxis toward CCL19, production of pro-inflammatory cytokines and ROS in response to LPS were also partially inhibited. In line with these results, the T-cell allostimulatory capacity of DCs was also inhibited. Finally, our data indicate that high NaCl concentrations triggered the phosphorylation of SGK1 and ERK1/2 kinases. These results raised the possibility that the previously reported pro-inflammatory effects of high NaCl concentrations on T cells might be counterbalanced by a downregulation of DC activation.

Inhibition of Serum- and Glucocorticoid-Regulated Protein Kinase-1 Aggravates Imiquimod-Induced Psoriatic Dermatitis and Enhances Proinflammatory Cytokine Expression through the NF-kB Pathway

Although the anti-inflammatory effect of serum- and glucocorticoid-regulated protein kinase 1 (SGK1) has been established in other diseases, the possible regulatory role of SGK1 in psoriasis and the underlying molecular mechanisms remain largely unknown. In this study, we found that SGK1 expression was decreased in macrophages from patients with psoriasis. Moreover, a specific pharmacological SGK1 inhibitor, EMD638683, significantly enhanced imiquimod-mediated toll-like receptor 7/8 activity and proinflammatory cytokine production in RAW264.7 cells, and this result was confirmed by Sgk1 small interfering RNA. Further mechanistic data showed that SGK1 inhibition increased the phosphorylation of Bruton's agammaglobulinemia tyrosine kinase; moreover, Bruton's agammaglobulinemia tyrosine kinase inhibition abrogated the proinflammatory effects of the SGK1 inhibitor on toll-like receptor 7/8 activation, thereby validating that SGK1 inhibition enhances the toll-like receptor 7/8 pathway by increasing Bruton's agammaglobulinemia tyrosine kinase phosphorylation. In addition, our in vivo results showed that SGK1 inhibition significantly increased the secretion of proinflammatory cytokines, including IL-1β, IL-6, and TNF-α, and the infiltration of T helper 17 cells in an imiquimod-induced psoriasis mouse model. Altogether, these results show that SGK1 plays a critical role in the pathogenesis of psoriasis by modulating inflammatory responses in skin lesions, indicating that SGK1‒Bruton's agammaglobulinemia tyrosine kinase signaling could be a novel therapeutic target for the control of psoriasis.

SGK1 negatively regulates inflammatory immune responses and protects against alveolar bone loss through modulation of TRAF3 activity

Serum- and glucocorticoid-regulated kinase 1 (SGK1) is a serine/threonine kinase that plays important roles in the cellular stress response. While SGK1 has been reported to restrain inflammatory immune responses, the molecular mechanisms involved remain elusive, especially in oral bacteria-induced inflammatory milieu. Here, we found that SGK1 curtails Porphyromonas gingivalis-induced inflammatory responses through maintaining levels of tumor necrosis factor receptor-associated factor (TRAF) 3, thereby suppressing NF-κB signaling. Specifically, SGK1 inhibition significantly enhances production of proinflammatory cytokines, including tumor necrosis factor α, interleukin (IL)-6, IL-1β, and IL-8 in P. gingivalis-stimulated innate immune cells. The results were confirmed with siRNA and LysM-Cre-mediated SGK1 KO mice. Moreover, SGK1 deletion robustly increased NF-κB activity and c-Jun expression but failed to alter the activation of mitogen-activated protein kinase signaling pathways. Further mechanistic data revealed that SGK1 deletion elevates TRAF2 phosphorylation, leading to TRAF3 degradation in a proteasome-dependent manner. Importantly, siRNA-mediated traf3 silencing or c-Jun overexpression mimics the effect of SGK1 inhibition on P. gingivalis-induced inflammatory cytokines and NF-κB activation. In addition, using a P. gingivalis infection-induced periodontal bone loss model, we found that SGK1 inhibition modulates TRAF3 and c-Jun expression, aggravates inflammatory responses in gingival tissues, and exacerbates alveolar bone loss. Altogether, we demonstrated for the first time that SGK1 acts as a rheostat to limit P. gingivalis-induced inflammatory immune responses and mapped out a novel SGK1-TRAF2/3-c-Jun-NF-κB signaling axis. These findings provide novel insights into the anti-inflammatory molecular mechanisms of SGK1 and suggest novel interventional targets to inflammatory diseases relevant beyond the oral cavity.

Mechanistic insights into the role of serum-glucocorticoid kinase 1 in diabetic nephropathy: A systematic review

Aberrant expression of serum-glucocorticoid kinase 1 (SGK1) contributes to the pathogenesis of multiple disorders, including diabetes, hypertension, obesity, fibrosis, and metabolic syndrome. SGK1 variant is expressed in the presence of insulin and several growth factors, eventually modulating various ion channels, carrier proteins, and transcription factors. SGK1 also regulates the enzymatic activity of Na⁺ K⁺ ATPase, glycogen synthase kinase-3, ubiquitin ligase Nedd4-2, and phosphomannose mutase impacting cell cycle regulation, neuroexcitation, and apoptosis. Ample evidence supports the crucial role of aberrant SGK1 expression in hyperglycemia-mediated secondary organ damage. Diabetic nephropathy (DN), a dreadful microvascular complication of diabetes, is the leading cause of end-stage renal failures with high morbidity and mortality rate. The complex pathogenesis of DN encompasses several influencing factors, including transcriptional factors, inflammatory markers, cytokines, epigenetic modulators, and abnormal enzymatic activities. SGK1 plays a pivotal role by controlling various physiological functions associated with the occurrence and progression of DN; therefore, targeting SGK1 may favorably influence the clinical outcome in patients with DN. This review aimed to provide mechanistic insights into SGK1 regulated DN pathogenesis and summarize the evidence supporting the therapeutic potential of SGK1 inhibition and its consequences on human health.

Cross-regulation of notch/AKT and serum/glucocorticoid regulated kinase 1 (SGK1) in IL-4-stimulated human macrophages

Notch signaling regulates the responses of macrophages to different stimuli in a context-dependent manner. The roles of Notch signaling in proinflammatory macrophages are well characterized, whereas its involvement, if any, in IL-4-stimulated macrophages (M(IL-4)) is still unclear. We observed that Notch signaling is functional in human M(IL-4). We performed transcriptome analysis of the Notch1 intracellular domain (NIC1)-overexpressing human monocytic cell line THP-1 with or without IL-4 stimulation to understand the global impact of Notch signaling in M(IL-4). The results revealed that NIC1-overexpressing THP-1 upregulated proinflammatory-associated genes and target genes of IL-4 signaling. We identified serum/glucocorticoid regulated kinase 1 (SGK1) as one of the genes increased by NIC1 overexpression in M(IL-4). To dissect the signaling pathway leading to SGK1 upregulation, we pretreated THP-1-derived macrophages with specific inhibitors of Notch (DAPT), AKT (LY294002) or ERK (U0126). Among these inhibitors, only LY294002 decreased the SGK1 mRNA levels in M(IL-4), indicating that the AKT pathway plays a key role in SGK1 transcription in M(IL-4). Furthermore, treatment of THP-1-derived macrophages with the SGK1 inhibitor (GSK650394) suppressed AKT phosphorylation, but not STAT6, in response to IL-4, indicating that SGK1 positively regulates AKT pathway in M(IL-4). Finally, GSK650394 treatment of human M(IL-4) increased the levels of PPARG mRNA and its protein, indicating a negative role of SGK1 in M(IL-4) function. Overall, we report that the Notch signaling and AKT pathways cooperatively regulate SGK1 expression in M(IL-4) where SGK1, in turn, plays an important role in suppressing IL-4-induced PPAR_γ expression.

Interaction Between Serum/Glucocorticoid-Regulated Kinase 1 and Interleukin-6 in Chronic Rhinosinusitis

PURPOSE

Serum/glucocorticoid-regulated kinase 1 (SGK1) has recently emerged as a critical regulator of inflammatory diseases. In this study, we examined SGK1 expression and its possible pathogenic roles in chronic rhinosinusitis (CRS).

METHODS

Immunohistochemistry, western blotting, Bio-Plex assay, enzyme-linked immunosorbent assays, and quantitative real-time polymerase chain reaction were performed to assess protein and gene expression levels. The mRNA expression levels of SGK1 and interleukin-6 (IL-6) were extracted from a CRS database to perform correlation analysis. Stable cell lines with SGK1 overexpression (16HBE) and knockdown (A549) were constructed to investigate the interaction between SGK1 and IL-6 in vitro.

RESULTS

SGK1 exhibited strong cytoplasmic and nuclear staining in the epithelial layers and the lamina propria of nasal polyps (NPs) and in the mucosal tissues of CRS without nasal polyps (CRSsNP). The mRNA and protein expression levels of SGK1 and IL-6 were significantly increased in NPs and CRSsNP tissues, compared to control tissues. SGK1 phosphorylation was significantly greater in NPs than in CRSsNP tissues (P < 0.01). The mRNA levels of SGK1 and IL-6 were significantly correlated (P < 0.001, r = 0.649). Exposure to IL-6 significantly increased SGK1 expression in cultured dispersed NP cells, 16HBE cells, and A549 cells. IL-6 expression was significantly down-regulated in SGK1-overexpressing 16HBE cells (P < 0.01) and significantly up-regulated in SGK1-knockdown A549 cells (P < 0.05). Administration of GSK650394, a SGK1 inhibitor, significantly increased IL-6 self-induced mRNA expression in cultured dispersed NP cells and 16HBE cells.

CONCLUSIONS

The interaction between SGK1 and IL-6 may play an anti-inflammatory role in IL-6-induced inflammation in the pathogenesis of CRS.

NLR family pyrin domain containing 3 (NLRP3) and caspase 1 (CASP1) modulation by intracellular Cl- concentration

The impairment of the cystic fibrosis transmembrane conductance regulator (CFTR) activity induces intracellular chloride (Cl- ) accumulation. The anion Cl- , acting as a second messenger, stimulates the secretion of interleukin-1β (IL-1β), which starts an autocrine positive feedback loop. Here, we show that NLR family pyrin domain containing 3 (NLRP3) and caspase 1 (CASP1) are indirectly modulated by the intracellular Cl- concentration, showing maximal expression and activity at 75 mM Cl- , in the presence of the ionophores nigericin and tributyltin. The expression of PYD and CARD domain containing (PYCARD/ASC) remained constant from 0 to 125 mM Cl- . The CASP1 inhibitor VX-765 and the NLRP3 inflammasome inhibitor MCC950 completely blocked the Cl- -stimulated IL-1β mRNA expression and partially the IL-1β secretion. DCF fluorescence (cellular reactive oxygen species, cROS) and MitoSOX fluorescence (mitochondrial ROS, mtROS) also showed maximal ROS levels at 75 mM Cl- , a response strongly inhibited by the ROS scavenger N-acetyl-L-cysteine (NAC) or the NADPH oxidase (NOX) inhibitor GKT137831. These inhibitors also affected CASP1 and NLRP3 mRNA and protein expression. More importantly, the serum/glucocorticoid regulated kinase 1 (SGK1) inhibitor GSK650394, or its shRNAs, completely abrogated the IL-1β mRNA response to Cl- and the IL-1β secretion, interrupting the autocrine IL-1β loop. The results suggest that Cl- effects are mediated by SGK1, in which under Cl- modulation stimulates the secretion of mature IL-1β, in turn, responsible for the upregulation of ROS, CASP1, NLRP3 and IL-1β itself, through autocrine signalling.

Serum- and Glucocorticoid-Inducible Kinase 1 Promotes Alternative Macrophage Polarization and Restrains Inflammation through FoxO1 and STAT3 Signaling

Expression and activity of serum- and glucocorticoid-inducible kinase 1 (SGK1) are associated with many metabolic and inflammatory diseases. In this study, we report that SGK1 promotes alternative macrophage polarization and restrains inflammation in the infectious milieu of the gingiva. Inhibition of SGK1 expression or activity enhances characteristics of classically activated (M1) macrophages by directly activating the transcription of genes encoding iNOS, IL-12P40, TNF-α, and IL-6 and repressing IL-10 at message and protein levels. Moreover, SGK1 inhibition robustly reduces the expression of alternatively activated (M2) macrophage molecular markers, including arginase-1, Ym-1, Fizz1, and Mgl-1. These results were confirmed by multiple gain- and loss-of-function approaches, including small interfering RNA, a plasmid encoding SGK1, and LysM-Cre-mediated sgk1 gene knockout. Further mechanistic analysis showed that SGK1 deficiency decreases STAT3 but increases FoxO1 expression in macrophages under M2 or M1 macrophage-priming conditions, respectively. Combined with decreased FoxO1 phosphorylation and the subsequent suppressed cytoplasmic translocation observed, SGK1 deficiency robustly enhances FoxO1 activity and drives macrophage to preferential M1 phenotypes. Furthermore, FoxO1 inhibition abrogates M1 phenotypes, and STAT3 overexpression results in a significant increase of M2 phenotypes, indicating that both FoxO1 and STAT3 are involved in SGK1-mediated macrophage polarization. Additionally, SGK1 differentially regulates the expression of M1 and M2 molecular markers, including CD68 and F4/F80 and CD163 and CD206, respectively, and protects against Porphyromonas gingivalis-induced alveolar bone loss in a mouse model. Taken together, these results have demonstrated that SGK1 is critical for macrophage polarization and periodontal bone loss, and for the first time, to our knowledge, we elucidated a bifurcated signaling circuit by which SGK1 promotes alternative, while suppressing inflammatory, macrophage polarization.

Modulation of microglial activity by salt load and SGK1

Microglial cells are derived from myelogenous cells and their chronic activation elicits brain inflammation, which influences neurological activity. Comprehensive understanding of the regulation of microglial activation could therefore contribute to overcoming neuropsychiatric disorders. Recently, the importance of serum- and glucocorticoid-inducible kinases (SGKs) has been explored in immune cells such as T cells, dendritic cells and macrophages. We have already shown that SGK1 and SGK3 are expressed in microglial cells and associated with the regulation of lipopolysaccharide (LPS)-induced inflammatory molecules. Here we investigate whether salt load influences expression of SGK1 and inflammatory responses in murine primary microglia and an immortalized microglial cell line, BV-2. Additional amounts of NaCl were administrated and immunoblotting was carried out, and SGK1 was induced in dose- and time-dependent manners. Next, the dynamics of inflammatory mediators iNOS and TNFα were investigated by administration of LPS. iNOS mRNA was induced by LPS application and enhanced by NaCl preload. In support of these results, nitric oxide was produced by LPS and accelerated by NaCl preload. In contrast, however, NaCl preload reduced the release of TNFα, suggesting the modulation of immune responses by salt load. The effects of salt load on both cases were attenuated in SGK1-deleted cells. Taken together, these results indicate that salt load modulates inflammatory responses and that SGK1 assists salt load-induced inflammatory responses.

Systems Approach to Pathogenic Mechanism of Type 2 Diabetes and Drug Discovery Design Based on Deep Learning and Drug Design Specifications

In this study, we proposed a systems biology approach to investigate the pathogenic mechanism for identifying significant biomarkers as drug targets and a systematic drug discovery strategy to design a potential multiple-molecule targeting drug for type 2 diabetes (T2D) treatment. We first integrated databases to construct the genome-wide genetic and epigenetic networks (GWGENs), which consist of protein–protein interaction networks (PPINs) and gene regulatory networks (GRNs) for T2D and non-T2D (health), respectively. Second, the relevant “real GWGENs” are identified by system identification and system order detection methods performed on the T2D and non-T2D RNA-seq data. To simplify network analysis, principal network projection (PNP) was thereby exploited to extract core GWGENs from real GWGENs. Then, with the help of KEGG pathway annotation, core signaling pathways were constructed to identify significant biomarkers. Furthermore, in order to discover potential drugs for the selected pathogenic biomarkers (i.e., drug targets) from the core signaling pathways, not only did we train a deep neural network (DNN)-based drug–target interaction (DTI) model to predict candidate drug’s binding with the identified biomarkers but also considered a set of design specifications, including drug regulation ability, toxicity, sensitivity, and side effects to sieve out promising drugs suitable for T2D.

Neuroprotection of SAK3 on scopolamine-induced cholinergic dysfunction in human neuroblastoma SH-SY5Y cells

Alzheimer's disease (AD) is the most common type of senile dementia. A number of factors have been proposed regarding pathology of AD, such as presence of β-amyloid, and cholinergic and oxidative stress. SAK3 (ethyl 8'-methyl-2',5-dioxo-2-piperidin-1-ylspiro[cyclopentene-3,3'-imidazo[1,2-a]pyridine]-1-carboxylate) reduces β-amyloid deposition and improves cognitive functions in amyloid precursor protein knock-in mice. Scopolamine is used to induce in cell lines a cholinergic deficit that mimics AD. In order to evaluate the possible neuroprotective properties of SAK3, human neuroblastoma SH-SY5Y cells were pretreated with the compound (25-100 nM) and further incubated in the presence of scopolamine (2 mM). SAK3 inhibited scopolamine-induced cellular apoptosis (morphologically and by determination of pro- and anti-apoptotic factor levels), increase in ROS levels, decrease in choline acetyltransferase level, phosphorylation of NF-κB, activation of Akt, JNK and p38 intracellular signaling pathways, and elevation of proinflammatory cytokines IL-1β and IL-6, but not enhanced level of β-site amyloid precursor protein cleaving enzyme 1 (BACE1). These results indicate SAK3 possessed protective properties against cholinergic deficit associated with anti-oxidant, anti-apoptotic and anti-inflammatory activities, suggesting that SAK3 might be a potential agent in the development of AD drug therapeutics.

TLR4 induced Wnt3a-Dvl3 restrains the intensity of inflammation and protects against endotoxin-driven organ failure through GSK3β/β-catenin signaling

BACKGROUND

Accumulating evidence suggests a regulatory role of Wnt proteins in innate immune responses. However, the effects of Wnt3a signaling on TLR4-mediated inflammatory responses are controversial and the signaling crosstalk between TLR4 and Wnt3a remains uncertain.

METHODS

Gain- and Loss- of function approaches were utilized to determine the function of Wnt3a signaling in TLR4-mediated inflammatory responses. Cytokine production at protein and mRNA levels and phosphorylation of signaling molecules were measured by ELISA, qRT-PCR, and Western Blot, respectively. Endotoxemia mouse model was employed to assess the effect of Wnt3a on systemic inflammatory cytokine levels and neutrophil infiltration.

RESULTS

LPS stimulation leads to an increase of Wnt3a expression and its downstream molecule, Dvl3, in primary monocytes. Inhibition or silence of Wnt3a or Dvl3 significantly increases the production of pro-inflammatory cytokines (IL-12, IL-6, TNFα), robustly reduces β-catenin accumulation, and enhances the phosphorylation of NF-κB P65 and its DNA binding activity. These results were confirmed by multiple gain- and loss- of function approaches including specific siRNA and ectopic expression of Dvl3, GSK3β, and β-catenin in monocytes. Moreover, in vivo relevance was established in a murine endotoxin model, in which Wnt3a inhibition enhances the inflammatory responses by augmenting the systemic pro-inflammatory cytokine levels and neutrophil infiltration.

CONCLUSIONS

TLR4 activation promotes Wnt3a-Dvl3 signaling, which acts as rheostats to restrain the intensity of inflammation through regulating GSK3β-β-catenin signaling and NF-κB activity.

GENERAL SIGNIFICANCE

Wnt3a-Dvl3-β-catenin signaling axis could be a potential interventional target for manipulating the direction and intensity of inflammatory responses.

Design and screening of SGK1, Src dual inhibitors using pharmacophore models, molecular docking, and molecular dynamics simulation

Serum and glucocorticoid-regulated protein kinase 1 that can promote the growth of tumor cells is highly expressed in many tumors. Sarcoma gene plays an important role in the pathogenesis of cancer and is an important kinase in tumor cell expression pathways.

Rosiglitazone promotes ENaC-mediated alveolar fluid clearance in acute lung injury through the PPARγ/SGK1 signaling pathway

Background

Pulmonary edema is one of the pathological characteristics of acute respiratory distress syndrome (ARDS). The epithelial sodium channel (ENaC) is thought to be the rate-limiting factor for alveolar fluid clearance (AFC) during pulmonary edema. The peroxisome proliferator-activated receptor γ (PPARγ) agonist rosiglitazone was shown to stimulate ENaC-mediated salt absorption in the kidney. However, its role in the lung remains unclear. Here, we investigated the role of the PPARγ agonist in the lung to find out whether it can regulate AFC during acute lung injury (ALI). We also attempted to elucidate the mechanism for this.

Methods

Our ALI model was established through intratracheal instillation of lipopolysaccharide (LPS) in C57BL/6 J mice. The mice were randomly divided into 4 groups of 10. The control group underwent a sham operation and received an equal quantity of saline. The three experimental groups underwent intratracheal instillation of 5 mg/kg LPS, followed by intraperitoneal injection of 4 mg/kg rosiglitazone, 4 mg/kg rosiglitazone plus 1 mg/kg GW9662, or only equal quantity of saline. The histological morphology of the lung, the levels of TNF-α and IL-1β in the bronchoalveolar lavage fluid (BALF), the level of AFC, and the expressions of αENaC and serum and glucocorticoid-induced kinase-1 (SGK1) were determined. Type 2 alveolar (AT II) cells were incubated with rosiglitazone (15 μM) with or without GW9662 (10 μM). The expressions of αENaC and SGK1 were determined 24 h later.

Results

A mouse model of ALI was successfully established. Rosiglitazone significantly ameliorated the lung injury, decreasing the TNF-α and IL-1β levels in the BALF, enhancing AFC, and promoting the expressions of αENaC and SGK1 in ALI mice, which were abolished by the specific PPARγ blocker GW9662. In vitro, rosiglitazone increased the expressions of αENaC and SGK1. This increase was prevented by GW9662.

Conclusions

Rosiglitazone ameliorated the lung injury and promoted ENaC-mediated AFC via a PPARγ/SGK1-dependent signaling pathway, alleviating pulmonary edema in a mouse model of ALI.

Glucocorticoid-Induced Leucine Zipper: A Novel Anti-inflammatory Molecule

Glucocorticoids (GCs) are the most commonly used drugs for treatment of autoimmune and inflammatory diseases. Their efficacy is due to their ability to bind cytoplasmic receptors (glucocorticoid receptors, GR) and other cytoplasmic proteins, thus regulating gene expression. Although GCs are potent life-saving drugs, their therapeutic effects are transitory and chronic use of GCs is accompanied by serious side effects. Therefore, new drugs are needed to replace GCs. We have identified a gene, glucocorticoid-induced leucine zipper (GILZ or tsc22d3), that is rapidly and invariably induced by GCs. Human GILZ is a 135-amino acid protein that mediates many GC effects, including inhibition of the NF-κB and MAPK pathways. Similar to GCs, GILZ exerts anti-inflammatory activity in experimental disease models, including inflammatory bowel diseases and arthritis. While transgenic mice that overexpress GILZ are more resistant, GILZ knockout mice develop worse inflammatory diseases. Moreover, the anti-inflammatory effect of GCs is attenuated in GILZ-deficient mice. Importantly, in vivo delivery of recombinant GILZ protein cured colitis and facilitated resolution of lipopolysaccharide-induced inflammation without apparent toxic effects. A synthetic GILZ-derived peptide, corresponding to the GILZ region that interacts with NF-κB, was able to suppress experimental autoimmune encephalomyelitis. Collectively, these findings indicate that GILZ is an anti-inflammatory molecule that may serve as the basis for designing new therapeutic approaches to inflammatory diseases.

Nuclear PTEN enhances the maturation of a microRNA regulon to limit MyD88-dependent susceptibility to sepsis

Sepsis-induced organ damage is caused by systemic inflammatory response syndrome (SIRS), which results in substantial comorbidities. Therefore, it is of medical importance to identify molecular brakes that can be exploited to dampen inflammation and prevent the development of SIRS. We investigated the role of phosphatase and tensin homolog (PTEN) in suppressing SIRS, increasing microbial clearance, and preventing lung damage. Septic patients and mice with sepsis exhibited increased PTEN expression in leukocytes. Myeloid-specific Pten deletion in an animal model of sepsis increased bacterial loads and cytokine production, which depended on enhanced myeloid differentiation primary response gene 88 (MyD88) abundance and resulted in mortality. PTEN-mediated induction of the microRNAs (miRNAs) miR125b and miR203b reduced the abundance of MyD88. Loss- and gain-of-function assays demonstrated that PTEN induced miRNA production by associating with and facilitating the nuclear localization of Drosha-Dgcr8, part of the miRNA-processing complex. Reconstitution of PTEN-deficient mouse embryonic fibroblasts with a mutant form of PTEN that does not localize to the nucleus resulted in retention of Drosha-Dgcr8 in the cytoplasm and impaired production of mature miRNAs. Thus, we identified a regulatory pathway involving nuclear PTEN-mediated miRNA generation that limits the production of MyD88 and thereby limits sepsis-associated mortality.

Glucocorticoid-induced phosphorylation by CDK9 modulates the coactivator functions of transcriptional cofactor GRIP1 in macrophages

The glucocorticoid (GC) receptor (GR) suppresses inflammation by activating anti-inflammatory and repressing pro-inflammatory genes. GR-interacting protein-1 (GRIP1) is a GR corepressor in macrophages, however, whether GRIP1 mediates GR-activated transcription, and what dictates its coactivator versus corepressor properties is unknown. Here we report that GRIP1 loss in macrophages attenuates glucocorticoid induction of several anti-inflammatory targets, and that GC treatment of quiescent macrophages globally directs GRIP1 toward GR binding sites dominated by palindromic GC response elements (GRE), suggesting a non-redundant GRIP1 function as a GR coactivator. Interestingly, GRIP1 is phosphorylated at an N-terminal serine cluster by cyclin-dependent kinase-9 (CDK9), which is recruited into GC-induced GR:GRIP1:CDK9 hetero-complexes, producing distinct GRE-specific GRIP1 phospho-isoforms. Phosphorylation potentiates GRIP1 coactivator but, remarkably, not its corepressor properties. Consistently, phospho-GRIP1 and CDK9 are not detected at GR transrepression sites near pro-inflammatory genes. Thus, GR restricts actions of its own coregulator via CDK9-mediated phosphorylation to a subset of anti-inflammatory genes.

Glucocorticoid reduces inflammation by both inducing anti-inflammatory genes and suppressing pro-inflammatory genes, but how these two functions are dictated is unclear. Here the authors show that phosphorylated glucocorticoid receptor-interacting protein 1 (GRIP1) serves as a coactivator for this response in macrophage.

Expression of serum- and glucocorticoid-regulated kinase 1 and its association with clinicopathological factors and the survival of patients with adenocarcinoma of the esophagogastric junction

While the aberrant expression and the controversial results of serum- and glucocorticoid-regulated kinase (SGK1) have been reported in a number of malignancies, the expression of SGK1 and its possible association with the progression of adenocarcinoma in the esophagogastric junction (AEG) remain to be elucidated. To the best of our knowledge, the expression and localization of SGK1 was examined for the first time in the present study in cancerous and adjacent tissue from 60 patients with AEG, and compared with 20 healthy mucosa control tissue samples. Furthermore, the association between SGK1 expression and the clinicopathological characteristics, and prognosis of patients with AEG was statistically analyzed. The expression level of SGK1 was identified to be significantly higher (P<0.0001) in the cancerous AEG tissue samples (65%) compared with that of the adjacent tissue (31.7%) and healthy control (10%) samples. Enhanced SGK1 was primarily localized in the cytoplasm and the expression level of SGK1 was associated with the differentiation (P=0.045) and lymph node metastasis (P=0.006) of AEG. Notably, increased expression of SGK1 was demonstrated to be significantly correlated with poor overall survival (P=0.027). The results of the present study revealed the expression profile of SGK1 in AEG and demonstrated that SGK1 expression in cancerous tissue is an indicator for the progression of AEG. Thus, SGK1 may be a potential molecular marker for the diagnosis, interference therapy and prognosis of AEG.

Estradiol Suppresses TLR4-triggered Apoptosis of Decidual Stromal Cells and Drives an Anti-inflammatory TH2 Shift by Activating SGK1

A pro-inflammatory cytokine profile at the feto-maternal interface may predispose immune maladaptation notably in early miscarriages. We investigated the involvement of estradiol (E2)-activated serum-glucocorticoid regulated kinase 1 (SGK1) in preserving the tolerogenic and pro-survival intrauterine microenvironment beneficial to gestation maintenance. Decidual SGK1 was down-regulated in early miscarriage, consistent with the lower serum E2 concentration seen in pregnancy loss. Lipopolysaccharide (LPS)/Toll-like receptors 4 (TLR4) signaling induced apoptosis and the pro-inflammatory T helper type (TH) 1 response of decidual stromal cells (DSCs) were associated with miscarriage. SGK1 activation was suppressed by LPS/TLR4 signaling and would be rescued by E2 administration via the PI3K signaling pathway in DSCs. SGK1 activation attenuated TLR4-mediated cell apoptosis, while promoting cell viability of DSCs by up-regulating the pro-survival genes BCL2 and XIAP, and enhancing the phosphorylation of FOXO1. Furthermore, E2-induced SGK1 activation reduced the secretion of pro-inflammatory TH1 cytokines, and promoted the generation of TH2 cytokines and elevated IRF4 mRNA and protein levels in LPS-incubated DSCs. Pharmacologic inhibition of SGK1 or suppression by small interfering (si) RNA increased the phosphorylation and nuclear translocation of NF-κB to reverse the pro-TH2 and anti-inflammatory effects of E2 pretreatment, leading to compromised pregnancy. These findings suggest that the E2-mediated SGK1 activation suppressed LPS-mediated apoptosis and promoted the anti-inflammatory TH2 responses in DSCs, ultimately contributing to a successful pregnancy.

Serum- and glucocorticoid-inducible kinases in microglia

Microglia are derived from myelogenous cells and contribute to immunological and inflammatory responses in central nervous system. They play important roles not only in infectious diseases and inflammation after stroke, but also in psychiatric diseases such as schizophrenia. While recent studies suggest the significances of serum- and glucocorticoid-inducible kinases (SGKs) in other immune cells such as macrophages, T cells and dendritic cells, their role in microglia remains unknown. Here we, for the first time, report that SGK1 and SGK3 are expressed in multiple microglial cell lines. An SGK inhibitor, gsk650394, inhibits cell viability. In addition, lipopolysaccharide-induced expression of inflammatory regulators iNOS and TNFα was enhanced by gsk650394. Furthermore, translocation of NF-κB was enhanced by gsk650394. Taken together, these findings suggest that SGKs may play an important role in regulating microglial viability and inflammatory responses.

Resolvin D1, resolvin D2 and maresin 1 activate the GSK3β anti-inflammatory axis in TLR4-engaged human monocytes

Pro-resolving, docosahexaenoic acid-derived mediators have recently emerged as important potential therapeutic agents for the amelioration of complications arising from inflammation, such as vascular disease, asthma, acute lung injury and colitis. While resolvin D1 (RVD1), resolvin D2 (RVD2) and maresin 1 (MaR1) are established pro-resolvins, their mechanisms of action remain unclear. Here we show that, in LPS-stimulated primary human monocytes, RVD1, RVD2 and MaR1 each suppress the release of pro-inflammatory cytokines (TNF, IL-1β, IL-8) and the innate/adaptive bridging cytokine, IL-12 p40, while simultaneously augmenting the production of the anti-inflammatory cytokine, IL-10. Such resolving activity is accompanied by the increased phosphorylation (enhanced anti-inflammatory state) of glycogen synthase kinase 3β (GSK3β) along with increased phosphorylation (activation) of Akt, SGK1 and CREB but not MAPK-related molecules. Gain and loss of function experiments confirm a key role for GSK3β and CREB in the anti-inflammatory actions of resolvins. These results suggest that induction of the GSK3β anti-inflammatory axis is a common mechanism of action for RVD1, RVD2 and MaR1.

2-Amino-4-(3,4-(methylenedioxy)benzylamino)-6-(3-methoxyphenyl)pyrimidine is an anti-inflammatory TLR-2, -4 and -5 response mediator in human monocytes

OBJECTIVE AND DESIGN

To elucidate the influence of 2-amino-4-(3,4-(methylenedioxy)benzylamino)-6-(3-methoxyphenyl)pyrimidine (AMBMP), a canonical Wnt/β-catenin pathway activator, on the inflammatory response of TLR-engaged innate cells in vitro.

MATERIAL OR SUBJECT

Primary human monocytes.

TREATMENT

AMPMB (0-10 μM), LPS (0-1.0 μg/ml), Pam3CSK4, FSL-1, or S. typhimurium flagellin (0-0.25 μg/ml).

METHODS

TLR-induced cytokine release (TNF, IL-6, IL-12 p40) was monitored by ELISA while Wnt-related signals (GSK3β, p65, IκB, β-catenin) were assessed by Western blot, pharmaceutical inhibition and gene silencing.

RESULTS

AMBMP induced the rapid phosphorylation of NFκB p65 at Ser(536) and abrogated total IκB, accompanied by a subsequent increase in pro-inflammatory cytokine production (TNF, IL-6, IL-12 p40) in otherwise naive monocytes. However, in TLR2, -4 and -5-engaged monocytes, AMBMP-suppressed cytokine production. In the context of LPS stimulation, this occurred concomitant with the phosphorylative inactivation of GSK3β at Ser(9), β-catenin accumulation and abrogation of NFκB p65 phosphorylation. AMBMP-mediated suppression of the TLR4 -induced inflammatory response was reversed by two pharmaceutical Wnt/β-catenin pathway inhibitors, IWP-2 and PNU-74654 and by Wnt3a silencing.

CONCLUSIONS

Herein, we show that AMBMP induces canonical Wnt signaling events and acts as a suppressor of inflammation in surface TLR-engaged primary human monocytes.