Blood platelets and inflammation: their relationship with liver and digestive diseases.

An expansion of knowledge from basic and clinical research has highlighted the critical role of platelets in inflammation and tissue repair in addition to their established contribution to hemostasis. Activated platelets are a rich source of mediators participating to inflammation and tissue regeneration. Platelet-derived microparticles recapitulate essential platelet functions and their contribution to the pathogenesis of inflammatory diseases has been emphasized. Recent findings suggest that platelets are both friends and foes for the liver. Platelets are essential to liver regeneration, platelet-derived serotonin being critical. However platelets can also exacerbate liver damage, as in immune-mediated injury. The dual role of platelets has recently been exemplified in animal models of liver fibrosis. Platelets release profibrogenic mediators, such as CXC Chemokine Ligand 4, that is instrumental in the progression of liver fibrosis. On the other hand, thrombocytopenia aggravates liver fibrosis, an outcome linked to the downregulation of hepatic stellate cell collagen production by platelet derived hepatocyte growth factor. CD154, a key molecule in inflammation, is expressed by platelets and is a pathogenic mediator in inflammatory bowel disease. Here, we summarize some of the mechanisms linking platelets with inflammation and comment few recent articles indicating why platelets may prove to be important pathogenic mediators in liver and gastrointestinal diseases.