IRAK1 Phosphorylation Research Articles

Selective targeting of IRAK1 attenuates low molecular weight hyaluronic acid-induced stemness and non-canonical STAT3 activation in epithelial ovarian cancer

Advanced epithelial ovarian cancer (EOC) survival rates are dishearteningly low, with ~25% surviving beyond 5 years. Evidence suggests that cancer stem cells contribute to acquired chemoresistance and tumor recurrence. Here, we show that IRAK1 is upregulated in EOC tissues, and enhanced expression correlates with poorer overall survival. Moreover, low molecular weight hyaluronic acid, which is abundant in malignant ascites from patients with advanced EOC, induced IRAK1 phosphorylation leading to STAT3 activation and enhanced spheroid formation. Knockdown of IRAK1 impaired tumor growth in peritoneal disease models, and impaired HA-induced spheroid growth and STAT3 phosphorylation. Finally, we determined that TCS2210, a known inducer of neuronal differentiation in mesenchymal stem cells, is a selective inhibitor of IRAK1. TCS2210 significantly inhibited EOC growth in vitro and in vivo both as monotherapy, and in combination with cisplatin. Collectively, these data demonstrate IRAK1 as a druggable target for EOC.

Gooderoside A from Anoectochilus elatus attenuates acute and chronic pains by inhibiting NO/cGMP and IRAK4/IRAK1/TAK1 signaling pathways

Ethnopharmacological relevanceAnoectochilus elatus Lindl. was traditionally used for pain treatment and Gooderoside A (GA) was regarded as its principal constituent. Aim of the studyTo investigate whether GA can be responsible for the antinociceptive activity of A. elatus and explore its underlying mechanism. Materials and methodsAcetic acid-induced abdominal writhing and tail flick tests were employed to evaluate the antinociceptive activity of ethanolic extract of A. elatus (EEA) and GA. Formalin test was used to ascertain the antinociceptive pattern of GA. Entobarbital sodium induced sleep test was adopted to exclude its hypnotic effect, while open-field test was performed to rule out its motor impairment effect. Chronic constriction injury (CCI)-induced neuropathic pain in rats was developed to evaluate its efficacy on neuropathic pain, and BV-2 cells were used to explore the underlying mechanism. ResultsEEA and GA, significantly inhibited chemical and thermal nociception. GA suppressed nociception in formalin test in both phase I and II, whereas methylene blue and L-NAME partially reversed its efficacy. GA located inner and slightly blocked sodium channel current, and did not show any hypnotic effect or motor impairment effect. Crucially, GA markedly attenuated chronic neuropathic pain in rats, inhibited the phosphorylation of IRAK4, IRAK1 and TAK1, and suppressed MAPKs pathway in BV-2 cells. ConclusionGA relieved acute and chronic pains in vivo. The mechanism of action involves the blocking of NO/cGMP and IRAK4/IRAK1/TAK1 pathways. These results suggested GA may be a promising candidate for antinociceptive drug development.

The oncogenic human B-cell lymphoma MYD88 L265P mutation genocopies activation by phosphorylation at the Toll/interleukin-1 receptor (TIR) domain

MYD88 is the key signaling adaptor-protein for Toll-like and interleukin-1 receptors. A somatic L265P mutation within the Toll/interleukin-1 receptor (TIR) domain of MYD88 is found in 90% of Waldenström macroglobulinemia cases and in a significant subset of diffuse large B-cell lymphomas. MYD88-L265P strongly promotes NF-κB pathway activation, JAK-STAT signaling and lymphoma cell survival. Previous studies have identified other residues of the TIR-domain crucially involved in NF-κB activation, including serine 257 (S257), indicating a potentially important physiological role in the regulation of MYD88 activation. Here, we demonstrate that MYD88 S257 is phosphorylated in B-cell lymphoma cells and that this phosphorylation is required for optimal TLR-induced NF-κB activation. Furthermore, we demonstrate that a phosphomimetic MYD88-S257D mutant promotes MYD88 aggregation, IRAK1 phosphorylation, NF-κB activation and cell growth to a similar extent as the oncogenic L265P mutant. Lastly, we show that expression of MYD88-S257D can rescue cell growth upon silencing of endogenous MYD88-L265P expression in lymphoma cells addicted to oncogenic MYD88 signaling. Our data suggest that the L265P mutation promotes TIR domain homodimerization and NF-κB activation by copying the effect of MY88 phosphorylation at S257, thus providing novel insights into the molecular mechanism underlying the oncogenic activity of MYD88-L265P in B-cell malignancies.

IRAK1 inhibition blocks the HIV-1 RNA mediated pro-inflammatory cytokine response from microglia.

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) are a common source of morbidity in people living with HIV (PLWH). Although antiretroviral therapy (ART) has lessened the severity of neurocognitive disorders, cognitive impairment still occurs in PLWH receiving ART. The pathogenesis of HAND is likely multifaceted, but common factors include the persistence of HIV transcription within the central nervous system, higher levels of pro-inflammatory cytokines in the cerebrospinal fluid, and the presence of activated microglia. Toll-like receptor (TLR) 7 and TLR8 are innate pathogen recognition receptors located in microglia and other immune and non-immune cells that can recognise HIV RNA and trigger pro-inflammatory responses. IL-1 receptor-associated kinase (IRAK) 1 is key to these signalling pathways. Here, we show that IRAK1 inhibition inhibits the TLR7 and TLR8-dependent pro-inflammatory response to HIV RNA. Using genetic and pharmacological inhibition, we demonstrate that inhibition of IRAK1 prevents IRAK1 phosphorylation and ubiquitination, and the subsequent recruitment of TRAF6 and the TAK1 complex to IRAK1, resulting in the inhibition of downstream signalling and the suppression of pro-inflammatory cytokine and chemokine release.

IRAK-M suppresses the activation of microglial NLRP3 inflammasome and GSDMD-mediated pyroptosis through inhibiting IRAK1 phosphorylation during experimental autoimmune encephalomyelitis

The activation of the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome triggers pyroptosis proinflammatory cell death in experimental autoimmune encephalomyelitis (EAE). However, the underlying mechanisms of the inflammatory processes of microglia in EAE remain unclear. Our previous studies suggested that interleukin-1 receptor-associated kinase (IRAK)-M down-regulates the toll-like receptor 4/interleukin-1 receptor signaling pathway. Here, we used IRAK-M knockout (IRAK-M−/−) mice and their microglia to dissect the role of IRAK-M in EAE. We found that deletion of IRAK-M increased the incidence rate and exacerbated the clinical symptoms in EAE mice. We then found that IRAK-M deficiency promoted the activation of microglia, activated NLRP3 inflammasomes, and enhanced GSDMD-mediated pyroptosis in the microglia of EAE. In contrast, over-expression of IRAK-M exerted inhibitory effects on neuroinflammation, NLRP3 activation, and pyroptosis. Moreover, IRAK-M deficiency enhanced the phosphorylation of IRAK1, while IRAK-M over-expression downregulated the level of phosphorylated IRAK1. Finally, we found upregulated binding of IRAK1 and TNF receptor-associated factor 6 (TRAF6) in IRAK-M−/− EAE mice compared to WT mice, which was blocked in AAVIRAK-M EAE mice. Our study reveals a complex signaling network of IRAK-M, which negatively regulates microglial NLRP3 inflammasomes and pyroptosis by inhibiting IRAK1 phosphorylation during EAE. These findings suggest a potential target for the novel therapeutic approaches of multiple sclerosis (MS)/EAE and NLRP3-related inflammatory diseases.

Inhibitory Mechanism of IL-6 Production by Orento in Oral Squamous Cell Carcinoma Cell Line CAL27 Stimulated by Pathogen-Associated Molecular Patterns from Periodontopathogenic Porphyromonas gingivalis.

Orento is a traditional Japanese medicinal kampo preparation that is also prescribed in oral care. In oral squamous cell carcinoma cell line CAL27, orento significantly inhibited periodontopathogenic bacterium Porphyromonas gingivalis lipopolysaccharide (LPS) and lipoproteins (PAMP)-stimulated production of interleukin (IL)-6. This suggests that orento negatively regulates PAMP-mediated toll-like receptor (TLR) signaling. Orento significantly suppressed PAMP-stimulated activation of the IL-6 promoter, indicating that orento may suppress the production of IL-6 by PAMP at the transcriptional level. Orento also suppressed TLR-mediated activation of transcription factor nuclear factor-kappa B (NF-kB) that was stimulated by PAMP. This finding indicates that orento may suppress the function and activation of factors involved in TLR signaling, thereby suppressing NF-kB-dependent expression of various genes. Orento suppressed IL-1 receptor-associated kinase (IRAK4), IRAK1, and c-Jun N-terminal kinase (JNK) phosphorylation in PAMP-stimulated CAL27 cells. This result indicates that orento is involved in the initiation of TLR signaling by PAMP and suppresses the downstream signaling pathways of myeloid differentiation primary response gene 88 (MyD88) such as mitogen-activated protein kinase (MAPK) and NF-kB cascades. These findings suggest that orento has an inhibitory effect on the production of inflammatory cytokines.

Suppression of TLR signaling by IRAK-1 and -4 dual inhibitor decreases TPF-resistance-induced pro-oncogenic effects in HNSCC.

Combination of docetaxel, cisplatin and 5-FU, known as TPF, is an FDA-approved treatment for head and neck squamous cell carcinoma (HNSCC). Acquired chemo-resistance to TPF, a primary reason for non-responsiveness to the treatment and relapse of tumor is a major concern for treatment failure, especially in elder patients. In this study, we investigated the role of Interleukin-1 receptor-associated kinases (IRAK) mediated Toll-like receptor (TLR)-signaling in chemo-resistance using a cell line-based in-vitro TPF-resistant HNSCC model of laryngeal origin. TPF chemo-resistant state showed over-expression and phosphorylation of the active downstream kinases IRAK-1 and IRAK-4 along with enhanced proliferative potential, survival, stemness and metastatic capability as compared to the parent cell line. Pharmacological inhibition of IRAK-1 and -4 had a cytostatic effect on chemo-resistant cells and re-sensitized them to chemotherapy. The treatment also decreased the pro-oncogenic effects of the chemo-resistant cells. Our study provides insights into the pro-oncogenic role of amplified IRAK-1 and-4 mediated TLR signaling in TPF-resistant HNSCC. Pharmacological inhibition of IRAK-1 and-4 signaling is a promising therapeutic strategy for TPF-resistant HNSCC. It can also be used as a combination therapy or a chemo-drug sparing regimen in HNSCC.

IRAK1 Duplication in MECP2 Duplication Syndrome Does Not Increase Canonical NF-κB–Induced Inflammation

PurposeBesides their developmental and neurological phenotype, most patients with MECP2/IRAK1 duplication syndrome present with recurrent and severe infections, accompanied by strong inflammation. Respiratory infections are the most common cause of death. Standardized pneumological diagnostics, targeted anti-infectious treatment, and knowledge of the underlying pathomechanism that triggers strong inflammation are unmet clinical needs. We investigated the influence of IRAK1 overexpression on the canonical NF-κB signaling as a possible cause for excessive inflammation in these patients.MethodsNF-κB signaling was examined by measuring the production of proinflammatory cytokines and evaluating the IRAK1 phosphorylation and degradation as well as the IκBα degradation upon stimulation with IL-1β and TLR agonists in SV40-immortalized fibroblasts, PBMCs, and whole blood of 9 patients with MECP2/IRAK1 duplication syndrome, respectively.ResultsBoth, MECP2/IRAK1-duplicated patients and healthy controls, showed similar production of IL-6 and IL-8 upon activation with IL-1β and TLR2/6 agonists in immortalized fibroblasts. In PBMCs and whole blood, both patients and controls had a similar response of cytokine production after stimulation with IL-1β and TLR4/2/6 agonists. Patients and controls had equivalent patterns of IRAK1 phosphorylation and degradation as well as IκBα degradation upon stimulation with IL-1β.ConclusionPatients with MECP2/IRAK1 duplication syndrome do not show increased canonical NF-κB signaling in immortalized fibroblasts, PBMCs, and whole blood. Therefore, we assume that these patients do not benefit from a therapeutic suppression of this pathway.

Pacritinib Inhibition of IRAK1 Blocks Aberrant TLR8 Signalling by SARS-CoV-2 and HIV-1-Derived RNA

Macrophages promote an early host response to infection by releasing pro-inflammatory cytokines such as interleukin (IL) 1β (IL-1β), tumour necrosis factor (TNF), and IL-6. One of the mechanisms through which cells sense pathogenic microorganisms is through Toll-like receptors (TLRs). IL-1 receptor-associated kinase (IRAK) 1, IRAK2, IRAK3, and IRAK4 are integral to TLR and IL-1 receptor signalling pathways. Recent studies suggest a role for aberrant TLR8 and NLRP3 inflammasome activation during both COVID-19 and HIV-1 infection. Here, we show that pacritinib inhibits the TLR8-dependent pro-inflammatory cytokine response elicited by GU-rich single-stranded RNA derived from SARS-CoV-2 and HIV-1. Using genetic and pharmacologic inhibition, we demonstrate that pacritinib inhibits IRAK1 phosphorylation and ubiquitination which then inhibits the recruitment of the TAK1 complex to IRAK1, thus inhibiting the activation of downstream signalling and the production of pro-inflammatory cytokines.

Innate Immune Signal Pathway Activation Induced By Combined Loss of Del(5q) MDS Genes, Tifab and Mir-146a, Accelerates Hematopoietic Stem Cell Exhaustion Driven By Chronic Exposure to a TLR Ligands

Deletion of the long arm of chromosome 5 (del(5q)) is the most frequently observed chromosomal abnormality in patients with myelodysplastic syndrome (MDS). We previously reported that deletion of TRAF-interacting protein with forkhead-associated domain B (TIFAB) and miR-146a, two haploinsufficient genes in del(5q) MDS, activates the Toll-like receptor (TLR) signaling cascade in hematopoietic stem/progenitor cells (HSPC) by increasing TRAF6 protein stability and mRNA translation, respectively (Varney et al., JEM 2015 and Varney et al., Leukemia 2017). To investigate the epistasis of TIFAB and miR-146a, we generated a mouse model in which Tifab and miR-146a were simultaneously deleted (Tifab-/-; miR-146a-/-, herein dKO). Consistent with increased TRAF6 expression, dKO mice exhibit phosphorylation of IRAK1 and IRAK4 kinases, indicating activation of the TLR/innate immune pathway in bone marrow (BM) HSPC of dKO mice. To determine whether combined deletion of Tifab and miR-146a exaggerates the hematopoietic-specific defects observed in either Tifab- or miR-146a-deficient mice in vivo, BM cells from WT, Tifab-/-, miR-146a-/-, and dKO mice were transplanted into lethally-irradiated syngeneic recipient mice. As previously reported, a minor subset of Tifab-/- and ~ 50% of miR-146a-/- mice succumbed to a bone marrow failure (BMF)-like disease. For dKO mice, 80% of mice developed a more rapid and penetrant BMF-like disease as compared to loss of Tifab or miR-146a alone. Moribund dKO mice presented with leukopenia, severe anemia, and thrombocytopenia. Since TLR activation is a common feature of MDS due to overexpression and secretion of damage-associated molecular patterns (DAMPs) within the BM microenvironment (Monlish et al., Front Immunol 2016), we explored the biological effect of systemic TLR activation on hematopoietic stem cell (HSC) function of dKO mice following exposure to chronic low dose lipopolysaccharide (LPS), a TLR4 agonist. After 4 weeks, the proportion of myeloid cells in peripheral blood (PB) of LPS-treated dKO mice was significantly increased as compared to WT mice exposed to LPS. BM cellularity of dKO mice was dramatically decreased by LPS exposure while that of WT mice was only slightly affected by LPS. The proportion of CD48-CD150+Lineage-Sca1+c-Kit+ (LSK) of dKO mice was significantly reduced by exposure to LPS as compared to WT mice, which correlated with loss of HSC quiescence. We next performed competitive repopulation assays using WT and dKO BM cells exposed to LPS. As expected, the chimerism of donor-derived PB cells from LPS-treated WT mice was significantly lower than that from WT control mice. Intriguingly, LPS-treated dKO mice showed significantly reduced chimerism of donor-derived PB and CD48-CD150+ LSK BM cells as compared to vehicle-treated dKO mice or WT mice exposed to LPS. Importantly, the impaired hematopoietic reconstitution was more pronounced following serial BM transplantation. These results indicate that deletion of Tifab and miR-146a diminishes the long-term repopulating potential of HSC driven by in vivo TLR stimulation. To uncover the molecular consequences that explain the functional HSC defect of dKO mice exposed to TLR activation, RNA-sequencing was performed on LSK from dKO and WT mice treated with LPS. Following TLR activation, we observed differential expression of distinct genes in dKO LSK as compared to WT LSK. Pathway network analyses revealed changes in chromatin organization, epigenetic regulations, and cellular senescence in WT LSK exposed to LPS as compared to control WT cells. In contrast, dKO LSK exposed to LPS exhibited enrichment in pathways associated with axon guidance, carbohydrate metabolism, and megakaryocyte development and platelet production as compared to control dKO cells. These results suggest the differential impact of TLR stimulation on hematopoiesis in Tifab;miR-146a-deficient mice. Collectively, our findings indicate that innate immune signal pathway activation induced by combined loss of Tifab and miR-146a accelerates HSC exhaustion driven by chronic exposure to TLR ligands via the activation of distinct signal pathways. These findings have important implications in the role of TLR stimulation in the cellular consequence of MDS HSC. DisclosuresNo relevant conflicts of interest to declare.

Erythorbyl laurate suppresses TNF-α-induced adhesion of monocytes to the vascular endothelium

Abstract Erythorbyl laurate (EL) can be produced via lipase-catalyzed esterification between erythorbic acid and lauric acid. In this study, we evaluate the anti-inflammatory effect of EL in the early stage of atherosclerosis. EL suppressed tumor necrosis factor (TNF)-α-induced monocyte adhesion to vascular endothelial cells and expression of vascular cell adhesion molecule (VCAM)-1 in human umbilical vein endothelial cells (HUVECs). Additionally, EL suppressed TNF-α-induced p65/IκB kinase (IKK)/IκB phosphorylation in HUVECs. Western blot analysis of cytosolic and nuclear cell fractions and immunofluorescence showed that EL suppressed TNF-α-induced translocation of p65 from the cytoplasm to the nucleus. EL also inhibited phosphorylation of extracellular-signal-regulated kinase (ERK) 1/2, p38, and c-Jun N-terminal kinases (JNK) 1/2 in HUVECs. EL suppressed TNF-α-induced phosphorylation of Akt, IRAK1, and TAK1 in HUVECs. Quantitative RT-PCR analysis showed that EL significantly suppressed TNF-α-induced interleukin (IL)1B, IL6, TNFA, and CCL2 mRNA expression in HUVECs. Additionally, oral administration of EL suppressed TNF-α-induced IL6 and TNFA expression in the mouse aorta. EL could represent a promising functional nutrient that can be ingested for the prevention of vascular inflammation via decreased monocyte infiltration to the vascular endothelium and suppression of inflammatory nuclear factor (NF)-κB and mitogen-activated protein kinases (MAPKs) signaling pathways.

Targeting the IRAK1-S100A9 Axis Overcomes Resistance to Paclitaxel in Nasopharyngeal Carcinoma.

Novel strategies to treat late-stage nasopharyngeal carcinoma that often develop resistance to chemotherapy remains an unmet clinical demand. In this study, we identify the multi-kinase inhibitor pacritinib as capable of resensitizing the response to paclitaxel in an acquired resistance model. Transcriptome analysis of paclitaxel-sensitive and -resistant cell lines, as well as chemorefractory clinical samples, identified S100A9 as the top candidate gene suppressed by pacritinib and whose overexpression was significantly associated with paclitaxel resistance and poor clinical outcome. Moreover, both paclitaxel-resistant nasopharyngeal carcinoma cells and relapsed/metastatic clinical samples exhibited increased IRAK1 phosphorylation and demonstrated that pacritinib could abolish the IRAK1 phosphorylation to suppress S100A9 expression. Functional studies in both in vitro and in vivo models showed that genetic or pharmacologic blockade of IRAK1 overcame the resistance to paclitaxel, and combined treatment of pacritinib with paclitaxel exhibited superior antitumor effect. Together, these findings demonstrate an important role for the IRAK1-S100A9 axis in mediating resistance to paclitaxel. Furthermore, targeting of IRAK1 by pacritinib may provide a novel therapeutic strategy to overcome chemoresistance in nasopharyngeal carcinoma. SIGNIFICANCE: Deregulation of the IRAK1-S100A9 axis correlates with poor prognosis, contributes to chemoresistance in nasopharyngeal carcinoma, and can be targeted by pacritinib to overcome chemoresistance in nasopharyngeal carcinoma.

Selective inhibition of interleukin-1 receptor-associated kinase 1 ameliorates lipopolysaccharide-induced sepsis in mice

Interleukin-1 receptor-associated kinases (IRAKs), particularly IRAK1 and IRAK4, are important in transducing signal from Toll-like receptor 4. We interrogated if a selective inhibition of IRAK1 could alleviate lipopolysaccharide (LPS)-induced sepsis. In this study, we tested the impact of a novel selective IRAK1 inhibitor Jh-X-119-01 on LPS-induced sepsis in mice. Survival at day 5 was 13.3% in control group where septic mice were treated by vehicle, while the values were 37.5% (p = 0.046, vs. control) and 56.3% (p = 0.003, vs. control) for 5 mg/kg and 10 mg/kg Jh-X-119-01-treated mice. Jh-X-119-01 alleviated lung injury and reduced production of TNFα and IFNγ in peritoneal macrophages. Jh-X-119-01 decreased phosphorylation of NF-κB and mRNA levels of IL-6 and TNFα in LPS-treated macrophages in vitro. Jh-X-119-01 selectively inhibited IRAK1 phosphorylation comparing with a non-selective IRAK1/4 inhibitor which simultaneously inhibited phosphorylation of IRAK1 and IRAK4. Both Jh-X-119-01 and IRAK1/4 inhibitor increased survival of septic mice, but Jh-X-119-01-treated mice had higher blood CD11b+ cell counts than IRAK1/4 inhibitor-treated ones [24 h: (1.18 ± 0.26) × 106/ml vs. (0.79 ± 0.20) × 106/ml, p = 0.001; 48 h: (1.00 ± 0.30) × 106/ml vs. (0.67 ± 0.23) × 106/ml, p = 0.042]. IRAK1/4 inhibitor induced more apoptosis of macrophages than Jh-X-119-01 did in vitro. IRAK1/4 inhibitor decreased protein levels of anti-apoptotic BCL-2 and MCL-1 in RAW 264.7 and THP-1 cells, an effect not seen in Jh-X-119-01-treated cells. In conclusion, Jh-X-119-01 selectively inhibited activation of IRAK1 and protected mice from LPS-induced sepsis. Jh-X-119-01 showed less toxicity on macrophages comparing with a non-selective IRAK1/4 inhibitor.

IRAK-M Down-regulates the Activation of Microglial NLRP3 Inflammasome and GSDMD-Mediated Pyroptosis in Microglial through Inhibiting IRAK1/TRAF6 Combination During Experimental Autoimmune Encephalomyelitis

Abstract The NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) is a protein complex which mediates pro-inflammatory response and pyroptosis. The activation of NLRP3 inflammasome triggers pyroptosis via cleavage of the pore-forming protein gasdermin D. Previous studies have demonstrated that NLRP3 inflammasome activation in microglial contributes to the pathogenesis of EAE, while Inhibition of microglial NLRP3 inflammasome and the subsequent pyroptosis attenuates the severity of EAE. In addition, Interleukin-1 receptor-associated kinase (IRAK)-M, mainly expressed in microglial in the central nervous system, negatively regulates the TLR4/IL-1R signaling pathway through inhibiting the phosphorylation of IRAK1 and dissociation of IRAK1 from MyD88/IRAK-4/IRAK-1 complex as well as the formation of IRAK-1 and TRAF6 complex. Our recent study suggests the protective effect of microglial IRAK-M in EAE mice. Therefore, we hypothesize that IRAK-M may alleviate IRAK1-induced NLRP3 inflammasome activation and pyroptosis through inhibiting dissociation of IRAK1 from MyD88/IRAK-4/IRAK-1 complex and the following association of IRAK1 and TRAF6. Here, we used IRAK-M knockout mice and their microglia to clarify the role of IRAK-M in EAE. We demonstrated that IRAK-M decreased the incidence rate and improved the clinical symptoms accompanied by mild demyelination in EAE mice, and which was parallel to the inhibition of microglial NLRP3 inflammasome activation, pyroptosis, and IRAK1/TRAF6 formation in EAE. Our findings fill the gap in knowledge of IRAK-M on activation of NLRP3 inflammasome and pyroptosis and provide a potential novel target for the therapeutic strategy of multiple sclerosis and NLRP3-related diseases.

Jieduquyuziyin Prescription-Treated Rat Serum Suppresses Activation of Peritoneal Macrophages in MRL/Lpr Lupus Mice by Inhibiting IRAK1 Signaling Pathway.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease, and Jieduquyuziyin prescription (JP) is a traditional Chinese medicine (TCM) formula that has been testified to be effective for SLE treatment as an approved hospital prescription for many years in China. However, its mechanism of action in the treatment of this disease is largely unknown. The purpose of this study was to determine whether JP-treated rat serum can inhibit the activation of peritoneal macrophages in MRL/lpr mice by downregulating the IRAK1 signaling pathway, thereby achieving the effect of improving SLE. The JP-treated rat serum was prepared, and the peritoneal macrophages of MRL/lpr lupus mice were isolated in vitro, and the effect of JP on cell viability was detected by the CCK8 method. After LPS induction and shRNA lentiviral transfection, the effect of JP on the expression of IRAK1 in cells was detected by immunofluorescence staining. The content of TNF-α and IL-6 in the cell supernatant was determined by ELISA. The expression of IRAK1, NF-κB, TNF-α, and IL-6 mRNA was detected by RT-PCR, and the expression levels of IRAK1, p-IRAK1, TRAF6, IKBα, p-IKBα, IKK + IKK, NF-κB, and p-NF-κB proteins was detected by western blot method. We investigated the role of JP in peritoneal macrophages of the MRL/lpr mouse and identified the possible mechanisms of action. The results showed that JP could reduce the phosphorylation of IRAK1 and its downstream proteins induced by LPS and inhibit the expression of inflammatory cytokines, including TNF-α and IL-6. In addition, after the transfection of cells with shRNA lentiviral, the results of JP tended to be consistent. In conclusion, JP may inhibit the activation of peritoneal macrophages in MRL/lpr mice by downregulating the IRAK1-NF-κB signaling pathway, and IRAK1 may be a potential target for JP treatment of SLE.

Glycyrrhetinic acid pretreatment attenuates liver ischemia/reperfusion injury via inhibiting TLR4 signaling cascade in mice

Glycyrrhetinic acid (GA), the main bioactive substances of glycyrrhiza uralensis Fisch, has been reported to exhibit hepatoprotective and anti-inflammatory properties. However, the effects and underlying mechanisms of GA in liver ischemia/reperfusion (I/R) injury remain elusive. In this study, mice were pretreated with GA (100 mg/kg) three times a day by gavage prior to I/R injury, and then hepatic histopathological damages, biochemical parameters and inflammatory molecules were evaluated. We found that mice performed with liver I/R showed a significantly increase in plasma aminotransferase (ALT), aspartate aminotransferase (AST), liver cell apoptosis and infiltration of neutrophils compared with the control group. GA pretreatment notably improved liver function, histopathology of liver tissues, and lowered liver cell apoptosis and infiltration of neutrophils. Besides, further analysis indicated that GA pretreatment reduced I/R-induced expression of extracellular HMGB1, inhibited activation of TLR4 and following phosphorylation of IRAK1, ERK, P38 and NF-κB, and attenuated TNF-α and IL-1β production. These data suggested that GA protected against liver I/R injury through a HMGB1-TLR4 signaling pathway and it might be a promising drug for future clinical use in liver transplantation.

Kakkalide and irisolidone alleviate 2,4,6-trinitrobenzenesulfonic acid-induced colitis in mice by inhibiting lipopolysaccharide binding to toll-like receptor-4 and proteobacteria population

The flower of Pueraria lobata (family Fabaceae) has been clinically used in traditional Chinese medicine to counteract symptoms associated with drinking alcohol and liver injury and to alleviate inflammatory diseases. Its major constituent kakkalide is metabolized to irisolidone by gut microbiota. This research study was undertaken to understand the anti-colitis mechanism of kakkalide and irisolidone in vitro and in vivo. Kakkalide and its metabolite irisolidone inhibited lipopolysaccharide (LPS)-stimulated NF-κB activation and TNF-α expression in macrophages. They also inhibited LPS-induced phosphorylation of IRAK1 and TAK1 and activation of NF-κB by inhibiting the binding of Alexa Fluor 488-conjugated LPS in vitro. Orally administered irisolidone or kakkalide alleviated colon shortening and myeloperoxidase activity in mice with 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. Their treatments also protected epithelial cell disruption and infiltration of CD11b+/CD11c+ cells in the colon. Furthermore, they suppressed TNBS-induced expression of M1 macrophage markers TNF-α, CD80, CD86, and Arg2 expression while the expression of M2 macrophage markers Arg1, CD163, CD206, and IL-10 was induced. They also suppressed the fecal Proteobacteria population. Overall, the anti-colitic effects of irisolidone were superior to those of kakkalide. Kakkalide and its metabolite irisolidone inhibited inflammation in vitro and in vivo by inhibiting LPS binding to toll-like receptor 4 and gut proteobacteria population.

The Role of interleukin‐1 receptor‐associated kinase 4 in drug addiction

Drug addiction remains an unmanageable and costly disease. Apart from neuronal adaptation, growing recognition arises that glial proinflammatory activation importantly contributes to the rewarding effects of multiple drugs of abuse. Recent studies suggest the central importance of Toll‐like receptor 4 (TLR4), a candidate neuroimmune therapeutic target for drug addiction. While Interleukin‐1 receptor associated kinase 4 (IRAK4) plays a crucial role in TLR4 mediated innate immunity, there is no further studies support its functioning in drug addiction. We hypothesized that drug‐taking activates IRAK4 and induces reinforcing effects, and disruption of IRAK4 signaling attenuates the addictive behaviors. In the present study, IRAK4 and IRAK1 phosphorylation after morphine and cocaine self‐administration was evaluated using western blotting. The role of IRAK4 in morphine self‐administration and cue‐induced reinstatement was examined with its inhibitor, PF06650833. Moreover, local pharmacological manipulation was conducted to determine the role of IRAK4 in the nucleus accumbens (NAc) core in the cue‐induced reinstatement of morphine seeking. We found that morphine self‐administration significantly increased the phosphorylation of IRAK4, but not IRAK1, both in NAc and VTA. However, neither cocaine short access nor long access self‐administration had any effect on the phosphorylation of IRAK4. Systemic administration of PF06650833 significantly attenuated cue‐induced reinstatement of morphine seeking without affecting the spontaneous locomotion in rats, and microinjection of PF06650833 into NAc core sufficiently decreased cue‐induced morphine reinstatement. These results demonstrated that modulation of IRAK4 activity regulates the cue‐induced morphine reinstatement, and suggested it as a novel candidate target in treating drug addiction.Support or Funding InformationThis work was supported by NIDA [Grant R21DA040777].This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

IRAK-M Deficiency Exacerbates Ischemic Neurovascular Injuries in Experimental Stroke Mice.

Background: Innate immune response to neuronal death is one of the key events of the pathogenesis of ischemic brain injury. Interleukin-1 receptor-associated kinase (IRAK)-M, encoded by gene Irak3, negatively regulates toll-like receptor signaling by interacting with the MyD88–IRAK-4–IRAK-1 complex and blocking the phosphorylation and dissociation of IRAK-1. Its function in the ischemic stroke is unknown.Objective: This study aims to investigate whether IRAK-M deficiency could exacerbate neuroinflammation and neurovascular injuries during cerebral ischemia and reperfusion.Methods: Male C57BL/6 mice and Irak3 knockout mice were subjected to 45 min of middle cerebral artery occlusion and 4 or 24 h of reperfusion. Transcription of Irak3 gene was evaluated by quantitative real-time PCR (qRT-PCR). Then, infarct volume, neurological score, brain water content, and Evans blue leakage were compared between knock-out and wild-type mice after reperfusion. Through the observation of gross brain specimen after cerebral ischemia, the incidence of hemorrhage transformation was compared between KO and WT mice. To explore underlying signaling pathways involved in IRAK-M deficiency, major proinflammatory cytokines and NF-κB signaling were measured by qRT-PCR and Western blot.Results: The expression of IRAK-M peaked at 1 h after reperfusion, and then gradually decreased within the first 24 h, which was abolished by blocking the expression of hypoxia induced factor 1α. IRAK-M deficiency increased infarct volume, brain edema, the incidence of hemorrhage transformation, and the permeability of blood–brain barrier. In addition, the NF-κB-mediated expressions of proinflammatory cytokines and the activation of microglia in the ipsilateral brain from knock-out mice were much higher than those in wild-type littermates.Conclusion: IRAK-M deletion exacerbates neurovascular damages which are related to the pronounced activation of NF-κB signaling and neuroinflammatory responses during cerebral ischemia-reperfusion in mice. Our study indicates that IRAK-M has neuroprotective effect and has potential to facilitate the development of new pharmaceuticals that reduce neurovascular complications.

IL-1β-induced ICAM-1 and IL-8 expression/secretion of dental pulp cells is differentially regulated by IRAK and p38

Interleukin 1 beta (IL-1β) is a pro-inflammatory cytokine involved in the acute and chronic inflammatory processes of dental pulp. Intercellular adhesion molecule-1 (ICAM-1) and IL-8 are two major inflammatory mediators. However, the role of interleukin-1 receptor-associated kinases (IRAKs) signaling pathways in responsible for the inflammatory effects of IL-1β on dental pulp cells is not clear. Cultured human dental pulp cells were exposed to IL-1β with/without pretreatment and co-incubation with IRAK1/4 inhibitor or SB203580 (p38 inhibitor). IRAK-1 phosphorylation was evaluated by immunno fluorescent staining. The protein expression of ICAM-1 and IL-8 were tested by western blotting. The secretion of soluble ICAM-1 (sICAM-1) and IL-8 was measured by enzyme-linked immunosorbant assay (ELISA). IL-1β stimulated IRAK-1 phosphorylation of pulp cells within 120min of exposure. IRAK1/4 inhibitor attenuated the IL-1β-induced ICAM-1, but not IL-8 protein expression. IRAK1/4 inhibitor also prevented the IL-1β-induced sICAM-1, but not IL-8 secretion. SB203580 showed little effect on IL-1β-induced sICAM-1 secretion, but effectively inhibited its induction of IL-8 secretion in pulp cells. The Results reveal the important role of IL-1β in pulpal inflammatory responses via stimulation of IL-8 and ICAM-1 expression and secretion. Moreover, IL-1β-induced effects on IL-8 and ICAM-1 are differentially regulated by IRAK1/4 and p38 signaling in dental pulp cells. Blocking of IRAKs and p38 signaling may have potential to control inflammation of dental pulp in the future.