Minocycline modulates cytokine and chemokine production in lipopolysaccharide-stimulated THP-1 monocytic cells by inhibiting IκB kinase α/β phosphorylation

Minocycline, which is a member of the broad-spectrum bacteriostatic tetracycline antibiotics group, has also recently been shown to have additional effects that are separate from their antimicrobial function; however, the detailed mechanisms involved remain unknown. We examined the effects of minocycline on cytokine and chemokine production and the expression levels of intracellular phosphorylated proteins in a lipopolysaccharide (LPS)-induced cytokine response model in vitro. In the present study, 3 cytokines (tumor necrosis factor [TNF]-α, interleukin [IL]-6, and interferon [IFN]-γ) and 7 chemokines (IL-8, interferon inducible protein [IP]-10, monocyte chemoattractant protein [MCP]-1, macrophage inflammatory protein [MIP]-1α, MIP-1β, regulated upon activation normal T-cell expressed secreted [RANTES], and eotaxin) were suppressed by minocycline in a dose-dependent manner. Moreover, the phosphorylation of inhibitor of nuclear factor-κB alpha (IκBα) and IκB kinase (IKK)α/β, which is located upstream from IκBα, was significantly suppressed by minocycline, whereas the phosphorylation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK), p38, and TGF-β-activated kinase (TAK)1 were not affected. Thus, minocycline appears to inhibit the signaling pathway at the level of IKKα/β phosphorylation. In conclusion, minocycline was found to reduce the production of multiple cytokines and chemokines by inhibiting LPS-induced IKKα/β phosphorylation. That is, minocycline appears to be a potent inhibitor of IKKα/β phosphorylation. From a clinical and translational significance point-of view, these findings suggest that the use of minocycline offers the advantage of providing both antimicrobial and anti-inflammatory effects, which may be key in treating certain types of infectious diseases, particularly those that lead to hypercytokinemia and chronic inflammatory disorders.