Lysophosphatidic acid up-regulates IL-10 production to inhibit TNF-α synthesis in Mϕs stimulated with LPS

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Bacterial lipopolysaccharide (LPS) triggers pro-inflammatory responses in macrophages (Mϕs) via CD14 and TLR4/MD-2.
• Extracellular lysophosphatidic acid (LPA) modulates Mϕ signaling, impacting conditions like atherosclerosis.
• Mechanisms of LPS-LPA signaling crosstalk and involved LPA receptors are not well understood.

Purpose of the Study:

• To investigate the molecular mechanisms of crosstalk between LPS- and LPA-induced signaling pathways in macrophages.
• To identify the specific LPA receptors involved in modulating LPS-induced inflammatory responses.
• To elucidate how LPA affects the production of pro-inflammatory (TNF-α) and anti-inflammatory (IL-10) cytokines.

Main Methods:

• Primary Mϕs and Mϕ-like J774 cells were stimulated with LPS and LPA.
• Tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) production were measured at mRNA and protein levels.
• NF-κB and p38 signaling pathways were analyzed.
• LPA5 and LPA6 receptors were depleted in J774 cells to assess their role.

Main Results:

• LPA significantly inhibited LPS-induced TNF-α production in both primary Mϕs and J774 cells.
• This inhibition was largely independent of NF-κB signaling.
• LPA stimulation enhanced IL-10 expression and secretion, preceding TNF-α reduction.
• Depletion of LPA5 and LPA6 receptors abrogated IL-10 elevation and TNF-α reduction.
• LPA-mediated p38 activation was linked to these observed effects.

Conclusions:

• LPA modulates LPS-induced inflammatory responses in macrophages.
• LPA receptors LPA5 and LPA6 are critical for this modulation.
• LPA signaling, via LPA5/LPA6 and p38 activation, up-regulates IL-10 and down-regulates TNF-α production, fine-tuning the inflammatory response.