Discovery of imidazo[1,2-b]pyridazines as IKKβ inhibitors. Part 2: improvement of potency in vitro and in vivo

We have increased the potency of imidazo[1,2-b]pyridazine derivatives as IKKβ inhibitors with two strategies. One is to enhance the activity in cell-based assay by adjusting the polarity of molecules to improve permeability. Another is to increase the affinity for IKKβ by the introduction of additional substituents based on the hypothesis derived from an interaction model study. These improved compounds showed inhibitory activity of TNFα production in mice.     

Hyaluronan-binding protein 1 (HABP1/p32/gC1qR) induces melanoma cell migration and tumor growth by NF-kappa B dependent MMP-2 activation through integrin α(v)β(3) interaction

Cell migration is the hallmark of cancer regulating anchorage independent growth and invasiveness of tumor cells. Hyaluronan (HA), an ECM polysaccharide is shown to regulate this process. In the present report, we demonstrated, supplementation of purified recombinant hyaluronan binding protein 1(HABP1/p32/gC1qR) from human fibroblast cDNA enhanced migration potential of highly invasive melanoma (B16F10) cells. Exogenous HABP1 adhered to the cell surface transiently and was shown to interact and colocalize with α_vβ₃ integrin, a regulatory molecule of cell migration. In HABP1 treated cells, the phosphorylation of nuclear factor inducing kinase (NIK) and IκBα was observed, followed by nuclear translocation of p65 subunit of NFκB, along with its DNA-binding and transactivation, resulting in upregulation of MT1-MMP expression and finally MMP-2 activation. To substantiate our findings, prior to HABP1 treatment, the expression of NIK was reduced by small interfering RNA mediated knockdown and confirmed the inhibition of nuclear translocation of p65 subunit of NFκB and upregulation of MT1-MMP expression. In addition, the use of curcumin, an anti-cancer drug, or GRGDSP, the blocking peptide along with exogenous HABP1, inhibited such NFκB-dependent pathway, confirming that HABP1-induced cell migration is α_vβ₃ integrin-mediated and downstream signaling by NFκB. Finally, we translated the in vitro data in mice model and observed enhanced tumor growth with higher MT1-MMP expression and MMP-2 activation in the tumors upon injection of HABP1 treated melanoma cells. The treatment of curcumin, the anticancer drug along with HABP1, inhibited the migration, expression of MT1-MMP and activation of MMP-2 and finally tumor growth supports the involvement of HABP1 in tumor formation.     

ROS/Epac1-mediated Rap1/NF-kappaB activation is required for the expression of BAFF in Raw264.7 murine macrophages

B-cell activating factor (BAFF) plays a role for the maturation and the maintenance of B cells. Lipopolysaccharide (LPS) activates toll-like receptor 4 (TLR4)-dependent signal transduction, which resulted in BAFF expression through nuclear factor kappa B (NF-κB) activation. Here, we investigated whether BAFF expression could be regulated by p65 phosphorylation through the production of reactive oxygen species (ROS) or cyclic AMP (cAMP) in Raw264.7 murine macrophages. mBAFF expression was reduced by ROS scavengers and it was increased by dibutyl-cAMP, a cAMP analogue. mBAFF expression and mBAFF promoter activity were increased by co-transfection of p65 but they were reduced by p65-small interference (si) RNA. Serine (Ser) 276 phosphorylation of p65 was increased by LPS-mediated PKA activation or by the treatment with forskolin, adenylate cyclase activator and dibutyl-cAMP. In contrast, p65 phosphorylation at Ser276 was decreased by ROS scavengers. H₂O₂ increased intracellular cAMP concentration, significantly. While no increase in p65 phosphorylation at Ser276 was detected by the treatment with H₂O₂, CREB and p65 phosphorylation at Ser133 and Ser536 was observed, respectively. It implicates that p65 phosphorylation at Ser276 is independent of ROS-induced cAMP production. As another cAMP effector protein was cAMP-responsive guanine nucleotide exchange factor (Epac), a Rap GDP exchange factor, NF-κB was activated by the treatment with 8-(4-chloro-phenylthio)-2′-O-methyladenosine-3′,5′-cyclic monophosphate (CPT) that is an activator to Epac. Epac1-mediated Rap1 was activated by the treatment with H₂O₂ but it was inhibited by ROS scavengers. CPT induced p65 phosphorylation at both Ser276 and Ser536. CPT also increased not only mBAFF expression but mBAFF promoter activity. Data demonstrate that TLR4-mediated mBAFF expression was resulted from the crosstalk of p65 phosphorylation at Ser536 and Ser276 through ROS- and/or cAMP-mediated signal transduction. It suggests for the first time that ROS/Epac1-mediated Rap1/NF-κB pathway could be required for BAFF expression.     

Epigallocatechin-3-gallate prevents lupus nephritis development in mice via enhancing the Nrf2 antioxidant pathway and inhibiting NLRP3 inflammasome activation

Patients with lupus nephritis show an impaired oxidative status and increased levels of interleukin (IL)-1β and IL-18, which are closely linked to inflammation and correlated with disease activity. Although epigallocatechin-3-gallate (EGCG), the major bioactive polyphenol present in green tea with antioxidant and free radical scavenging activities, has been reported to have anti-inflammatory effects by inhibiting nuclear factor-kappa B (NF-κB)-mediated inflammatory responses in vivo, its effectiveness for the treatment of lupus nephritis is still unknown. In the present study, 12-week-old New Zealand black/white (NZB/W) F1 lupus-prone mice were treated daily with EGCG by gavage until sacrificed at 34 weeks old for clinical, pathological, and mechanistic evaluation. We found that the administration (1) prevented proteinuria, renal function impairment, and severe renal lesions; (2) increased renal nuclear factor E2-related factor 2 (Nrf2) and glutathione peroxidase activity; (3) reduced renal oxidative stress, NF-κB activation, and NLRP3 mRNA/protein expression and protein levels of mature caspase-1, IL-1β, and IL-18; and (4) enhanced splenic regulatory T (Treg) cell activity. Our data clearly demonstrate that EGCG has prophylactic effects on lupus nephritis in these mice that are highly associated with its effects of enhancing the Nrf2 antioxidant signaling pathway, decreasing renal NLRP3 inflammasome activation, and increasing systemic Treg cell activity.     

Reactive oxygen species alter autocrine and paracrine signaling

Cytochrome P450 (P450) 3A4 (CYP3A4) is the most abundant P450 protein in human liver and intestine and is highly inducible by a variety of drugs and other compounds. The P450 catalytic cycle is known to uncouple and release reactive oxygen species (ROS), but the effects of ROS from P450 and other enzymes in the endoplasmic reticulum have been poorly studied from the perspective of effects on cell biology. In this study, we expressed low levels of CYP3A4 in HepG2 cells, a human hepatocarcinoma cell line, and examined effects on intracellular levels of ROS and on the secretion of a variety of growth factors that are important in extracellular communication. Using the redox-sensitive dye RedoxSensor red, we demonstrate that CYP3A4 expression increases levels of ROS in viable cells. A custom ELISA microarray platform was employed to demonstrate that expression of CYP3A4 increased secretion of amphiregulin, intracellular adhesion molecule 1, matrix metalloprotease 2, platelet-derived growth factor (PDGF), and vascular endothelial growth factor, but suppressed secretion of CD14. The antioxidant N-acetylcysteine suppressed all P450-dependent changes in protein secretion except for CD14. Quantitative RT-PCR demonstrated that changes in protein secretion were consistently associated with corresponding changes in gene expression. Inhibition of the NF-κB pathway blocked P450 effects on PDGF secretion. CYP3A4 expression also altered protein secretion in human mammary epithelial cells and C10 mouse lung cells. Overall, these results suggest that increased ROS production in the endoplasmic reticulum alters the secretion of proteins that have key roles in paracrine and autocrine signaling.     

Redox regulation of human protease-activated receptor-2 by activated factor X

Activated factor X (FXa) exerts coagulation-independent actions such as proliferation of vascular smooth muscle cells (SMCs) through the protease-activated receptors PAR-1 and PAR-2. Both receptors are upregulated upon vascular injury but the underlying mechanisms have not been defined. We examined if FXa regulates PAR-1 and PAR-2 in human vascular SMCs. FXa increased PAR-2 mRNA, protein, and cell-surface expression and augmented PAR-2-mediated mitogenesis. PAR-1 was not influenced. The regulatory action of FXa on PAR-2 was concentration-dependent and mimicked by a PAR-2-selective activating peptide. PAR-2 regulation was not influenced by the thrombin inhibitor argatroban or PAR-1 siRNA. FXa increased dichlorofluorescein diacetate fluorescence and 8-isoprostane formation and induced expression of the NADPH oxidase subunit NOX-1. NOX-1 siRNA prevented FXa-stimulated PAR-2 regulation, as did ebselen and cell-permeative and impermeative forms of catalase. Exogenous H₂O₂ increased PAR-2 expression and mitogenic activity. FXa promoted nuclear translocation and PAR-2/DNA binding of nuclear factor κB (NF-κB); NF-κB inhibition prevented PAR-2 regulation by FXa. FXa also promoted PAR-2 mRNA stabilization through increased human antigen R (HuR)/PAR-2 mRNA binding and cytoplasmic shuttling. HuR siRNA abolished FXa-stimulated PAR-2 expression. Thus FXa induces functional expression of PAR-2 but not of PAR-1 in human SMCs, independent of thrombin formation, via a mechanism involving NOX-1-containing NADPH oxidase, H₂O₂, NF-κB, and HuR.