Immunomodulatory Potential of Quinoline Q3, a Selective Inhibitor of the Canonical NF-κB Pathway in Macrophages

The NF-κB transcription factor pathway is a major driver of inflammation, regulating proinflammatory cytokine synthesis in innate immune cells. Its dysregulation is linked to chronic inflammatory diseases, as well as autoimmune conditions. We investigated the inhibitory effect of a novel quinoline Q3 on NF-κB activation in murine and human macrophages. Without little/no effect on cell survival or proliferation of J774A.1 macrophages, lipopolysaccharide (LPS)-induced NF-κB-regulated luciferase signal in lentivirally transduced macrophages was significantly reduced in the presence of 5 µM Q3. Q3 also inhibited LPS-induced transcription of proinflammatory genes Tnf, Il6, and Il12b as shown by qPCR. Q3 was also seen to significantly reduce intracellular levels of pre-TNF; however, Q3 could not diminish the released cytokines, in both mouse and human macrophages. NF-κB ELISA further revealed that Q3 inhibited p65 DNA-binding activity, while it enhanced p50 DNA-binding, a combination that could lead to inhibition of target gene transcription, since in silico analysis revealed interaction between Q3 and the p50 homodimer/DNA complex. Q3 also inhibited p65/NF-κB DNA-binding in LPS-stimulated human macrophages, but there was no impact of Q3 on c-Rel DNA-binding activity. Therefore, Q3 differentially interferes with the DNA-binding of specific NF-κB dimers, and this could be exploited to target NF-κB-regulated inflammation.