Interleukin-12 increases interleukin 8 production and release by human polymorphonuclear neutrophils

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Interleukin-12 (IL-12) is a cytokine produced by phagocytes and antigen-presenting cells.
• IL-8 is a key chemokine for polymorphonuclear neutrophils (PMNs).
• The interaction between IL-12 and PMN IL-8 production was previously unclear.

Purpose of the Study:

• To investigate the effect of IL-12 on IL-8 production by PMNs.
• To elucidate the molecular mechanisms underlying IL-12's influence on IL-8 expression.
• To explore the role of IL-12 in inflammatory responses.

Main Methods:

• Stimulation of human PMNs with IL-12, lipopolysaccharide (LPS), and other reagents.
• Measurement of IL-8 protein and mRNA levels.
• Use of Actinomycin D to assess gene transcription and mRNA stability.
• Inhibition studies using parthenolide and tyrphostin AG490.
• Investigation of the roles of Tumor Necrosis Factor-alpha (TNF-alpha) and Interferon-gamma (IFN-gamma).

Main Results:

• IL-12 alone did not significantly affect IL-8 production, but it was additive with LPS at both protein and mRNA levels.
• Gene transcription, involving nuclear factor-kappaB and STAT4, plays a crucial role in IL-8 induction.
• The additive effect of IL-12 was specific to IL-8 release and occurred after 18 hours.
• TNF-alpha and IFN-gamma were found to have intermediate roles, with their inhibition reducing IL-12's effect.
• IL-12's mechanism appears to involve autocrine amplification of IL-8 release by PMNs in the presence of LPS.

Conclusions:

• IL-12, in conjunction with LPS, significantly enhances IL-8 production by PMNs.
• This effect is mediated by transcriptional regulation and involves key signaling pathways and inflammatory mediators like TNF-alpha and IFN-gamma.
• IL-12 plays a novel role in inflammation by amplifying IL-8 release through an autocrine loop.