TNF-α Drives the CCL4 Expression in Human Monocytic Cells: Involvement of the SAPK/JNK and NF-κB Signaling Pathways

Increased circulatory levels of both TNF-α and CCL4/MIP-1β are found in metabolic diseases. However, it is unclear whether TNF-α which is a signature proinflammatory cytokine involved in metabolic inflammation, can induce/promote the expression of CCL4. THP-1 human monocytic cells and THP-1-derived macrophages were stimulated with TNF-α and LPS-treatment as a positive control. CCL4 mRNA/protein expression was measured using qRT-PCR/ELISA, respectively. Stress-activated protein kinases (SAPK)/ c-Jun N-terminal kinase (JNK) activity was determined using the assay kit. Mechanistic pathways were studied using anti-TNFR1/2 antibodies, pharmacological inhibitors, siRNAs, and NF-κB/AP-1 reporter-expressing THP-1-XBlue cells. Phosphorylation of signaling molecules was assessed by Western blotting. TNF-α induces CCL4 expression at mRNA and protein levels, in both THP-1 monocytic cells and macrophages (P