Platelets are a previously unrecognised source of MIF.

Area of Science:

• Immunology
• Cell Biology
• Cardiovascular Research

Background:

• Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine involved in atherogenesis.
• Platelets are implicated in atherogenesis and release chemokines.
• The role of platelets in MIF production and secretion was previously uninvestigated.

Purpose of the Study:

• To determine if platelets express and secrete MIF.
• To investigate the subcellular localization and mRNA presence of MIF in platelets.
• To assess the functional role of platelet-derived MIF in inflammatory cell recruitment.

Main Methods:

• Western blot and ELISA were used to detect and quantify MIF protein in human and mouse platelets.
• Confocal microscopy examined MIF localization within platelets.
• Quantitative PCR (qPCR) assessed MIF mRNA levels.
• Transwell assays evaluated monocyte chemotaxis using platelet supernatants, with and without MIF-neutralizing antibodies.

Main Results:

• MIF protein was detected and quantified in human and mouse platelets.
• MIF localized to granular structures within platelets but did not co-localize with known platelet cytokines.
• Platelets contain low levels of MIF mRNA.
• Thrombin and collagen stimulated MIF release, while ADP and oxidized LDL did not.
• Platelet supernatants significantly enhanced monocyte chemotaxis, an effect blocked by MIF-neutralizing antibodies.

Conclusions:

• Platelets are a previously unrecognized source of secreted MIF, particularly upon activation by thrombin and collagen.
• Platelet-derived MIF contributes significantly to the chemotactic capacity of activated platelets.
• MIF plays a role in atherogenic cell recruitment, highlighting a novel mechanism in inflammatory processes.