Lesser known mast cell mediators (Part 6)

Granulocyte macrophage colony-stimulating factor (GM-CSF) is a growth factor for white blood cells. It induces stem cells to make granulocytes (neutrophils, eosinophils, basophils, mast cells) and monocytes. The molecule activates STAT5, a protein that initiates gene expression. It is found at high levels in the joints of rheumatoid arthritis patients.

Fibroblast growth factor 2 (FGF2, also known as basic fibroblast growth factor, bFGF) is involved in angiogenesis, proliferation and wound healing. FGF2 binds heparin. It is thought that during wound healing, heparin degrading enzymes activate FGF2, driving the development of new blood vessels.

Neutrophin 3 is a nerve growth factor that regulates the survival and growth of neurons and synapses.

Nerve growth factor (NGF) regulates neuron survival and axonal growth. In its absence, neurons undergo apoptosis. It has been found to induce ovulation in some mammals. NGF is often elevated in inflammatory conditions as it suppresses inflammation. Children with autism sometimes have high levels of NGF in their cerebral spinal fluid. Low levels of NGF are seen in metabolic syndromes, type 2 diabetes and obesity.

Platelet derived growth factor (PDGF) is a growth factor that participates in blood vessel growth. It is a required factor for the division of fibroblasts, connective tissue cells important in wound healing.

Nitric oxide (NO, also endothelium derived relaxing factor, EDRF) is a cell signaling molecule and potent vasodilator. It is a precursor to nitroglycerin. It is produced by several nitric oxide synthase enzymes. NO maintains blood vessels by preventing vascular muscle contraction and aggregation of cells on the endothelium. NO has a well described variety of activities.

Leukotriene B4 is a cell signaling molecule. It facilitates the transition of white blood cells from the endothelium into tissues. It also forms reactive oxygen species.

Leukotriene C4 is one of the components of the slow reacting substance of anaphylaxis (SRS-A). It is secreted during anaphylaxis and contributes to the inflammatory processes. It causes prolonged, slow contraction of smooth muscle and bronchoconstriction. It is 5000x more potent than histamine in this capacity but acts more slowly and lasts longer.

Platelet activating factor (PAF) mediates a variety of immune activities, including various inflammatory processes and anaphylaxis. It is also a vasodilator and bronchoconstrictor. At high concentrations, PAF can cause severe airway inflammation to such degree as to be life threatening.

 

All mediators listed here are produced by mast cells upon stimulation and are not stored in granules.