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Generation of a unique fibroblast-activating factor by human monocytes
Abstract:
Purified human monocytes incubated with phytohemagglutinin (PHA), bacterial lipopolysaccharide (LPS), or serum-opsonized zymosan particles (OZ) generate human dermal fibroblast-activating activity, as assessed by increased fibroblast incorporation of [3H]-thymidine. A maximum concentration of fibroblast-activating activity was attained within 4 hr with OZ, whereas similar maximum levels required 12 hr with LPS and PHA. Sonicates of unstimulated monocytes had only minimal activity and the protein synthesis inhibitor cycloheximide suppressed significantly the appearance of fibroblast-activating activity, suggesting that the factors are generated prior to release. Filtration of supernates from OZ-stimulated monocytes on Sephadex G-75 yielded polydisperse fibroblast-activating activities, of which the major factors exhibited a mol. wt. of approximately 60,000 and 10,000. The supernates from PHA-stimulated monocytes had one predominant factor, termed fibroblast-activating factor of monocytes (FAF-M), with an apparent mol. wt. of 38,000 and a minor activity with a mol. wt. of 10,000. FAF-M was composed of two principles with isoelectric points of 5.1-5.2 and 4.0-4.2 and was free of interleukin-1, as determined by the absence of thymocyte-activating activity. FAF-M and other fibroblast-activating factors may contribute to wound healing and fibrosis in lesions characterized by mononuclear phagocyte infiltrates.
Insights
Human monocytes stimulated with PHA, LPS, or OZ produce fibroblast-activating factors. These factors, including fibroblast-activating factor of monocytes (FAF-M), may play a role in wound healing and fibrosis.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Monocytes are key immune cells involved in inflammation and tissue repair.
- Fibroblast activation is crucial for processes like wound healing and fibrosis.
Purpose of the Study:
- To investigate the generation and characteristics of fibroblast-activating factors produced by human monocytes.
- To identify the molecular properties of these monocyte-derived factors.
Main Methods:
- Human monocytes were stimulated with phytohemagglutinin (PHA), lipopolysaccharide (LPS), or opsonized zymosan (OZ).
- Fibroblast activation was assessed by [3H]-thymidine incorporation.
- Gel filtration (Sephadex G-75) and isoelectric focusing were used to characterize the factors.
- Interleukin-1 (IL-1) presence was evaluated by thymocyte activation assays.
Main Results:
- Monocyte stimulation generated significant fibroblast-activating activity.
- Peak activity was observed at 4 hours with OZ and 12 hours with LPS and PHA.
- Factors with molecular weights of approximately 60,000 and 10,000 were identified from OZ-stimulated monocytes.
- Fibroblast-activating factor of monocytes (FAF-M) with a molecular weight of 38,000 was identified from PHA-stimulated monocytes.
- FAF-M was free of interleukin-1 activity.
Conclusions:
- Human monocytes produce distinct fibroblast-activating factors upon stimulation.
- These factors, including FAF-M, may contribute to wound healing and fibrosis in inflammatory conditions involving monocytes.