IRAK inhibitor 6

IC50: 0.16 μM for IRAK-4

IRAK inhibitor 6 is an interleukin-1 receptor associated kinase 4 (IRAK-4) inhibitor.

The interleukin-1 receptor associated kinases (IRAKs) are a family of serine/threonine kinases related with regulating cellular signalling downstream of the IL-18, IL-1 and various Toll-like receptors. IRAK-4 is reported to be essential for the activation of the intracellular signalling cascades including NFКB and MAPK pathways, which are critical for the production of inflammatory cytokines.

In vitro: A quantitative structure–activity relationship (QSAR) study of IRAK inhibitor 6 and its analogs were conducted by using the genetic algorithm and multiple linear regression (GA-MLR) method [1]. In vitro study showed that compared with its unsubstituted phenyl amide analog, the ortho-substitution with chloro, methoxy and difluoromethoxy analogs of IRAK inhibitor 6 improved potency against IRAK-4 significantly. These potency effects were additive, with the most active example in the set being IRAK inhibitor 6, in which the presence of nitrogen-linked substituents at the para position had a beneficial effect on the rate of turnover by human microsomes (20 μL/min/mg protein) [2].

Clinical trial: N/A

References:
[1] Pourbasheer E, Riahi S, Ganjali MR, Norouzi P.  Quantitative structure-activity relationship (QSAR) study of interleukin-1 receptor associated kinase 4 (IRAK-4) inhibitor activity by the genetic algorithm and multiple linear regression (GA-MLR) method. J Enzyme Inhib Med Chem. 2010 Dec;25(6):844-53.
[2] Buckley GM, Gowers L, Higueruelo AP, Jenkins K, Mack SR, Morgan T, Parry DM, Pitt WR, Rausch O, Richard MD, Sabin V, Fraser JL.  IRAK-4 inhibitors. Part 1: a series of amides. Bioorg Med Chem Lett. 2008 Jun 1;18(11):3211-4.

Immunomodulatory Molecule IRAK-M Balances Macrophage Polarization and Determines Macrophage Responses during Renal Fibrosis.[Pubmed:28701510]

J Immunol. 2017 Aug 15;199(4):1440-1452.

Activation of various innate immune receptors results in IL-1 receptor-associated kinase (IRAK)-1/IRAK-4-mediated signaling and secretion of proinflammatory cytokines such as IL-12, IL-6, or TNF-alpha, all of which are implicated in tissue injury and elevated during tissue remodeling processes. IRAK-M, also known as IRAK-3, is an inhibitor of proinflammatory cytokine and chemokine expression in intrarenal macrophages. Innate immune activation contributes to both acute kidney injury and tissue remodeling that is associated with chronic kidney disease (CKD). Our study assessed the contribution of macrophages in CKD and the role of IRAK-M in modulating disease progression. To evaluate the effect of IRAK-M in chronic renal injury in vivo, a mouse model of unilateral ureteral obstruction (UUO) was employed. The expression of IRAK-M increased within 2 d after UUO in obstructed compared with unobstructed kidneys. Mice deficient in IRAK-M were protected from fibrosis and displayed a diminished number of alternatively activated macrophages. Compared to wild-type mice, IRAK-M-deficient mice showed reduced tubular injury, leukocyte infiltration, and inflammation following renal injury as determined by light microscopy, immunohistochemistry, and intrarenal mRNA expression of proinflammatory and profibrotic mediators. Taken together, these results strongly support a role for IRAK-M in renal injury and identify IRAK-M as a possible modulator in driving an alternatively activated profibrotic macrophage phenotype in UUO-induced CKD.

Lactobacillus paracasei modulates LPS-induced inflammatory cytokine release by monocyte-macrophages via the up-regulation of negative regulators of NF-kappaB signaling in a TLR2-dependent manner.[Pubmed:28088611]

Cytokine. 2017 Apr;92:1-11.

The application of the probiotic lactobacillus is suggested in the treatment of some inflammatory diseases of intestines due to its potential ability to attenuate inflammation. However, the mechanism is not completely understood. In PBMCs, Lactobacillus paracasei (L. Paracasei) down-regulated the LPS-induced production of TNF-alpha and IL-6. Using a macrophage-like differentiated THP-1 cell line induced by PMA, we investigated the effect of L. paracasei on the production of pro-inflammatory cytokines by monocyte-macrophages. Treatment of the differentiated THP-1 cells with L. paracasei either concurrently with or before LPS challenge attenuated the LPS-induced secretion of TNF-alpha and IL-1beta. This effect was due to a decrease in IkappaB phosphorylation and NF-kappaB nuclear translocation. Furthermore, treatment of the differentiated THP-1 cells with L. paracasei induced the expression of negative regulators of the NF-kappaB signaling pathway, including the deubiquitinating enzyme A20, suppressor of cytokine signaling (SOCS) 1, SOCS3, and IL-1 receptor-associated kinase (IRAK) 3. Pretreatment with an IRAK4 inhibitor suppressed the L. paracasei-induced expression of these negative regulators and further increased the LPS-mediated expressions of TNF-alpha and IL-1beta. Moreover, treatment with an antibody against Toll-like receptor (TLR) 2 reversed the effect of L. paracasei on inducing negative regulators and inhibiting TNF-alpha and IL-1beta productions. Our findings suggest that L. paracasei inhibits the production of pro-inflammatory cytokines by monocyte-macrophages via the induction of negative regulators of the NF-kappaB signaling pathway in a TLR2-IRAK4-dependent manner.

Dual Inhibition of Rip2 and IRAK1/4 Regulates IL-1beta and IL-6 in Sarcoidosis Alveolar Macrophages and Peripheral Blood Mononuclear Cells.[Pubmed:27402699]

J Immunol. 2016 Aug 15;197(4):1368-78.

Sarcoidosis is a multisystem granulomatous disease of unknown etiology that primarily affects the lungs. Our previous work indicates that activation of p38 plays a pivotal role in sarcoidosis inflammatory response. Therefore, we investigated the upstream kinase responsible for activation of p38 in sarcoidosis alveolar macrophages (AMs) and PBMCs. We identified that sustained p38 phosphorylation in sarcoidosis AMs and PBMCs is associated with active MAPK kinase 4 but not with MAPK kinase 3/6. Additionally, we found that sarcoidosis AMs exhibit a higher expression of IRAK1, IRAK-M, and receptor interacting protein 2 (Rip2). Surprisingly, ex vivo treatment of sarcoidosis AMs or PBMCs with IRAK1/4 inhibitor led to a significant increase in IL-1beta mRNA expression both spontaneously and in response to TLR2 ligand. However, a combination of Rip2 and IRAK-1/4 inhibitors significantly decreased both IL-1beta and IL-6 production in sarcoidosis PBMCs and moderately in AMs. Importantly, a combination of Rip2 and IRAK-1/4 inhibitors led to decreased IFN-gamma and IL-6 and decreased percentage of activated CD4(+)CD25(+) cells in PBMCs. These data suggest that in sarcoidosis, both pathways, namely IRAK and Rip2, are deregulated. Targeted modulation of Rip2 and IRAK pathways may prove to be a novel treatment for sarcoidosis.

Thymoquinone: An IRAK1 inhibitor with in vivo and in vitro anti-inflammatory activities.[Pubmed:28216638]

Sci Rep. 2017 Feb 20;7:42995.

Thymoquinone (TQ) is a bioactive component of black seed (Nigella sativa) volatile oil and has been shown to have anti-oxidative, anti-inflammatory, and anti-cancer properties. In the present study, we explored the molecular mechanisms that underlie the anti-inflammatory effect of TQ and its target proteins using lipopolysaccharide (LPS)-stimulated murine macrophage-like RAW264.7 and human monocyte-like U937 cells, together with LPS/D-galactosamine (GalN)-induced acute hepatitis and HCl/EtOH-induced gastritis mouse models. TQ strongly inhibited the production of nitric oxide (NO) and repressed NO synthase (iNOS), tumor necrosis factor (TNF)-alpha, cyclooxygenase (COX)-2, interleukin (IL)-6, and IL-1beta expression in LPS-activated RAW264.7 cells. Treatment of LPS/D-GalN-induced hepatitis and EtOH/HCl-induced gastritis mouse models with TQ significantly ameliorated disease symptoms. Using luciferase reporter gene assays, we also showed that the nuclear levels of transcription factors and phosphorylation patterns of signaling proteins, activator protein (AP)-1, and nuclear factor (NF)-kappaB pathways were all affected by TQ treatment. Finally, we used additional kinase and luciferase validation assays with interleukin-1 receptor-associated kinase 1 (IRAK1) to show that IRAK1 is directly suppressed by TQ treatment. Together, these findings strongly suggest that the anti-inflammatory actions of TQ are caused by suppression of IRAK-linked AP-1/NF-kappaB pathways.

Middle east respiratory syndrome corona virus spike glycoprotein suppresses macrophage responses via DPP4-mediated induction of IRAK-M and PPARgamma.[Pubmed:28118607]

Oncotarget. 2017 Feb 7;8(6):9053-9066.

Middle East Respiratory Syndrome Corona Virus (MERS-CoV) is transmitted via the respiratory tract and causes severe Acute Respiratory Distress Syndrome by infecting lung epithelial cells and macrophages. Macrophages can readily recognize the virus and eliminate it. MERS-CoV infects cells via its Spike (S) glycoprotein that binds on Dipeptidyl-Peptidase 4 (DPP4) receptor present on macrophages. Whether this Spike/DPP4 association affects macrophage responses remains unknown. Herein we demonstrated that infection of macrophages with lentiviral particles pseudotyped with MERS-CoV S glycoprotein results in suppression of macrophage responses since it reduced the capacity of macrophages to produce TNFalpha and IL-6 in naive and LPS-activated THP-1 macrophages and augmented LPS-induced production of the immunosuppressive cytokine IL-10. MERS-CoV S glycoprotein induced the expression of the negative regulator of TLR signaling IRAK-M as well as of the transcriptional repressor PPARgamma. Inhibition of DPP4 by its inhibitor sitagliptin or siRNA abrogated the effects of MERS-CoV S glycoprotein on IRAK-M, PPARgamma and IL-10, confirming that its immunosuppressive effects were mediated by DPP4 receptor. The effect was observed both in THP-1 macrophages and human primary peripheral blood monocytes. These findings support a DPP4-mediated suppressive action of MERS-CoV in macrophages and suggest a potential target for effective elimination of its pathogenicity.