IinQ attenuates systemic inflammatory responses via selectively impairing the Myddosome complex formation upon TLR4 ligation.

A specific small-molecule inhibitor of the TLR4 signaling complex upstream of the IKK would likely provide therapeutic benefit for NF-κB-mediated inflammatory disease. We previously identified brazilin as a selective upstream IKK inhibitor targeting the Myddosome complex. In this study, using a cell-based ubiquitination assay for IRAK1 and a chemical library comprising a series of structural analogues of brazilin, a novel small molecule, 2-hydroxy-5,6-dihydroisoindolo[1,2-a]isoquinoline-3,8-dione (IinQ), was identified as a selective and potent inhibitor of IRAK1-dependent NF-κB activation upon TLR4 ligation. In RAW264.7 macrophages, IinQ drastically suppressed activation of upstream IKK signaling events including membrane-bound IRAK1 ubiquitination and IKK phosphorylation by the TLR4 ligand, resulting in reduced expression of proinflammatory mediators including IL-6, TNF-α, and nitric oxide. Interestingly, IinQ did not suppress NF-κB activation via the TLR3 ligand, DNA damaging agents, or a protein kinase C activator, indicating IinQ is specific for TLR4 signaling. Analysis of upstream signaling events further confirmed that IinQ disrupts the MyD88-IRAK1-TRAF6 complex formation induced by LPS treatment, without affecting TLR4 oligomerization. Moreover, intravenous administration of IinQ significantly reduced lethality and attenuated systemic inflammatory responses in an in vivo mouse model of endotoxin shock following LPS challenge. Thus, IinQ represents a novel class of brazilin analogues with improved potency and specificity toward disruption of Myddosome complex formation in TLR4 signaling, indicating that IinQ may be a promising therapeutic candidate for the treatment of systemic inflammatory diseases.

Synthesis and anti-tubercular activity of 2-nitroimidazooxazines with modification at the C-7 position as PA-824 analogs.

Tuberculosis (TB) is a major global health problem, and new drug targets and scaffolds need to be identified to combat the emergence of drug resistant TB. The nitroimidazooxazine PA-824 represents a new class of bio-reductive drug to treat TB. In this study we report a 2-nitroimidazooxazine derivative with modification at the C-7 position that exhibited better activity than PA-824 against Mycobacterium tuberculosis (Mtb) H37Rv strain in vitro. From 7a as a key intermediate, we functionalized with benzyl ether (8), phenyl ether (9), benzyl carbonate (10) and benzyl carbamate (11). Among the 23 compounds produced, 8a-R (MIC=0.078 µM) with trifluoromethoxy benzyl group was 5-fold more potent than PA-824 (MIC=0.390 µM) in the in vitro assays against the wild-type Mtb, and the phenyl ether compound 9g-R (MIC=0.050 µM) exhibited the most potent antimycobacterial activity.