Use of molecular imaging to quantify response to IKK‐2 inhibitor treatment in murine arthritis

Abstract

Objective. The NF-B signaling pathway promotes the immune response in rheumatoid arthritis (RA) and in rodent models of RA. NF-B activity is regulated by the IKK-2 kinase during inflammatory responses. To elucidate how IKK-2 inhibition suppresses disease development, we used a combination of in vivo imaging, transcription profiling, and histopathology technologies to study mice with antibodyinduced arthritis.Methods. ML120B, a potent, small molecule inhibitor of IKK-2, was administered to arthritic animals, and disease activity was monitored. NF-B activity in diseased joints was quantified by in vivo imaging. Quantitative reverse transcriptase-polymerase chain reaction was used to evaluate gene expression in joints. Protease-activated near-infrared fluorescence (NIRF) in vivo imaging was applied to assess the amounts of active proteases in the joints.Results. Oral administration of ML120B suppressed both clinical and histopathologic manifestations of disease. In vivo imaging demonstrated that NF-B activity in inflamed arthritic paws was inhibited by ML120B, resulting in significant suppression of multiple genes in the NF-B pathway, i.e., KC, epithelial neutrophil-activating peptide 78, JE, intercellular adhesion molecule 1, CD3, CD68, tumor necrosis factor ␣, interleukin-1␤, interleukin-6, inducible nitric oxide synthase, cyclooxygenase 2, matrix metalloproteinase 3, cathepsin B, and cathepsin K. NIRF in vivo imaging demonstrated that ML120B treatment dramatically reduced the amount of active proteases in the joints.Conclusion. Our data demonstrate that IKK-2 inhibition in the murine model of antibody-induced arthritis suppresses both inflammation and joint destruction. In addition, this study highlights how gene expression profiling can facilitate the identification of surrogate biomarkers of disease activity and treatment response in an experimental model of arthritis.

Near-infrared fluorescence imaging of experimentally collagen-induced arthritis in rats using the nonspecific dye tetrasulfocyanine in comparison with gadolinium-based contrast-enhanced magnetic resonance imaging, histology, and clinical score

“…23 They found fluorescence intensity to be highest 10 to 20 min after TSC injection with a subsequent decrease. 23 High correlation between near-infrared SI and clinical arthritis scores was also found by Izmailova et al 45 using specific probes in an animal model. Dyes with molecular specificity used for arthritis detection and monitoring of therapy by other study groups such as protease-activated dyes, 18,45,46 fluorescence-labeled folate probes, 16 and dyes coupled to antibodies 17 result in higher contrast in inflammatory areas compared to normal controls.…”

A Novel, Highly Selective, Tight Binding IκB Kinase-2 (IKK-2) Inhibitor: A Tool to Correlate IKK-2 Activity to the Fate and Functions of the Components of the Nuclear Factor-κB Pathway in Arthritis-Relevant Cells and Animal Models

“…This property of PHA-408 allowed us to correlate IKK-2 activity and efficacy endpoints in disease relevant cells and in acute and chronic models of inflammation. These findings are novel because in the previous reports utilizing rapidly reversible inhibitors McIntyre et al, 2003;Podolin et al, 2005;Ziegelbauer et al, 2005;Schopf et al, 2006;Wen et al, 2006;Izmailova et al, 2007), the assessment of the inhibition of endogenous IKK-2 activity was an indirect readout, relying on the inhibition of efficacy endpoints such as p65 or IB phosphorylation, IB␣ stabilization, gene expression, and/or imaging and histopathological analyses. The ability of PHA-408 to bind tightly to both the inactive and active forms of IKK-2 may explain why, in addition to its excellent pharmaceutical properties, PHA-408 was equally potent against IKK-2 in cell-free and living cell systems.…”

Role of IκB Kinase-β in the Growth-Promoting Effects of Angiotensin II In Vitro and In Vivo

“…28,29 ML120B was also shown to inhibit lipopolysaccharide-induced tumor necrosis factor α production in vivo and reduce inflammation and bone destruction in a rodent model of arthritis. 30,31 In our hands, this inhibitor was potent in inhibiting NF-κB activation because it antagonized tumor necrosis factor α-induced IκBα degradation, with maximal efficacy occurring at 30 µmol/L in human aortic VSMC ( Figure IA …”