Platelets and inflammation: role of platelet-derived growth factor, adhesion molecules and histamine.

Despite the fact that the relationship between platelets and the inflammatory and immune responses has been reviewed previously, the allocation of platelets among the inflammatory cells is still at issue. Recent developments in our understanding of platelet-associated signalling events have offered new potential insights into platelet functions in inflammatory and immune-related diseases. In recent years, it has been established that a range of molecules, mainly associated with the platelet surface and/or the platelet granules, regulate the capacity of platelets to cross-talk with other inflammatory cells during the process of inflammation, and of vascular inflammation in particular. This is the case with platelet-derived growth factor (PDGF), secreted from platelet alpha-granules, with P-selectin, expressed on the platelet surface, and with platelet histamine, which is secreted from platelets in response to aggregatory and inflammatory stimuli. The nature and mechanism of action of these regulatory molecules, physiologically present in platelets and mobilised upon platelet activation and aggregation, is the subject of this review. The participation of platelets, through PDGF, P-selectin and histamine, is also discussed in overtly inflammatory disorders, such as acute respiratory distress syndrome, mesangial glomerulonephritis, chronic inflammatory bowel disease, disseminated intravascular inflammation, and allergic vasculitis, focusing on possible pharmacological interventions specifically active against growth factors, adhesion molecules and platelet histamine.