Beyond Hemostasis: The Role of Platelets in Inflammation, Malignancy and Infection

Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada.
Cardiovascular & Haematological Disorders - Drug Targets(Formerly Current Drug Targets - Cardiovascular & Hematological Disorders) 07/2008; 8(2):99-117. DOI: 10.2174/187152908784533739
Source: PubMed


Platelets play a complex role in hemostasis and thrombosis. The expression of multiple membrane receptors, both constitutive and activation-dependent, mediates platelet adhesion and aggregation at sites of vascular lesion. Platelet activation leads to exocytosis of granular constituents, release of newly synthesized mediators, and discharge of membrane-bound transcellular signaling molecules. Many of the same mechanisms that play a role in hemostasis and thrombosis facilitate platelet participation in other physiological or pathological processes including inflammation, malignancy and the immune response. Platelet receptors such as GPIb/IX/V, P-selectin, P-selectin glycoprotein ligand 1, CD40 and the alphaIIbbeta3 integrin, crucial to hemostasis, have been implicated in the progression of such inflammatory conditions as atherosclerosis, rheumatoid arthritis and inflammatory bowel disease, in the progression and metastatic spread of malignancies, and in the immune response to bacterial challenge. The release of platelet granular contents, including adhesive proteins, growth factors and chemokines/cytokines, that serve to facilitate hemostasis and wound repair, also function in acute and chronic inflammatory disease and in tumor cell activation and growth. Platelets contribute to host defence as they recognise bacteria, recruit traditional immune cells to the site of infection and secrete bactericidal mediators. The primary focus of this review is the "non-haemostatic" functions of platelets in physiological and pathological states.

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    • "Tak utworzony enzym degraduje białka zewnątrzkomórkowej macierzy, w tym fibrynę. Zatem SAK zwiększa aktywność proteolityczną szczepów S. aureus, co prawdopodobnie odgrywa ważną rolę w generowaniu i uwalnianiu zmian zakrzepowo-zatorowych w przebiegu IZW [7] [9] [18] [20] [29] [38]. czas np. "
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    ABSTRACT: Platelets are primarily associated with their main function, hemostasis, although it is known that these cells also exhibit biological activity in cancer progression, inflammation and infectious processes. During infection platelets, due to the expression of specific receptors - Toll-like receptors (TLRs) - which recognize molecular patterns associated with pathogens - pathogen-associated molecular patterns (PAMPs) - are activated by the presence of microorganism components and/or substances released from damaged cells/tissue. Further antimicrobial activity of platelets is based on their capacity for phagocytosis, generation of reactive oxygen species (ROS), and the synthesis, storage and release of proteins/peptides with antimicrobial activity. Another mechanism of platelet action is their immunomodulatory activity. It is based mainly on the ability to secrete chemotactic factors allowing the accumulation of professional immunocompetent cells at the site of infection, thus enhancing the effective eradication of an infectious agent. In chronic infections, platelets, due to release of numerous growth factors and various cytokines, support mechanisms of acquired immunity. They accelerate the maturation of dendritic cells, stimulate B cells to be immunoglobulin-producing plasma cells and potentiate the activity of T cells. Unfortunately, in certain situations (the existence of specific risk factors) the interaction of microorganisms with activated platelets may also be the cause of pathology within the cardiovascular system.
    Postępy Higieny i Medycyny Doświadczalnej (Advances in Hygiene and Experimental Medicine) 05/2015; 69:624-32. DOI:10.5604/17322693.1153073 · 0.57 Impact Factor
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    • "Platelets have exhibited greater therapeutic potential than ever imagined, releasing growth factors and other molecules that help to repair damaged tissues [55]. Over 1,500 proteins are stored within platelets, including growth factors in platelet α-granules that have been proven to promote normal healing responses [56,57]. PRP, as a source of concentrated platelets, may help to restore the integrity of the cellular matrix of degenerating discs through the synergistic effects of multiple growth factors. "
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    ABSTRACT: Intervertebral disc degeneration (IDD) is a common orthopedic disease associated with mechanical changes that may result in significant pain. Current treatments for IDD mainly depend on conservative therapies and spinal surgeries that are only able to relieve the symptoms but do not address the cause of the degeneration and even accelerate the degeneration of adjacent segments. This has prompted research to improve our understanding of the biology of intervertebral disc healing and into methods to enhance the regenerative process. Recently, biological therapies, including active substances, gene therapy and tissue engineering based on certain cells, have been attracting more attention in the field of intervertebral disc repair and regeneration. Early selection of suitable biological treatment is an ideal way to prevent or even reverse the progressive trend of IDD. Growth factors have been enjoying more popularity in the field of regeneration of IDD and many have been proved to be effective in reversing the degenerative trend of the intervertebral disc. Identification of these growth factors has led to strategies to deliver platelet-derived factors to the intervertebral disc for regeneration. Platelet-rich plasma (PRP) is the latest technique to be evaluated for promoting intervertebral disc healing. Activation of the PRP leads to the release of growth factors from the α-granules in the platelet cytoplasm. These growth factors have been associated with the initiation of a healing cascade that leads to cellular chemotaxis, angiogenesis, synthesis of collagen matrix, and cell proliferation. This review describes the current understanding of IDD and related biological therapeutic strategies, especially the promising prospects of PRP treatment. Future limitations and perspectives of PRP therapy for IDD are also discussed.
    Arthritis research & therapy 10/2013; 15(5):220. DOI:10.1186/ar4353 · 3.75 Impact Factor
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    • "RANTES, PF4, SDF-1, MCP-1, CXCL5, CXCL7) and newly synthesized active cytokine-like factors [e.g. IL-1β, CD40 ligand (CD40L), β-thromboglobulin] are implicated in the development of atherosclerosis [41], [42], [43]. Recently, animal and (pre)clinical human studies have suggested that the two major platelet chemokines PF4 and RANTES, as well as CD40L, may be considered potential new candidates in the treatment of atherogenesis and inflammation [44]. "
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    ABSTRACT: Aim The purpose of this project was to evaluate the influence of circulating endothelial progenitor cells (EPCs) and platelet microparticles (PMPs) on blood platelet function in experimental hypertension associated with hypercholesterolemia. Methods Golden Syrian hamsters were divided in six groups: (i) control, C; (ii) hypertensive-hypercholesterolemic, HH; (iii) ‘prevention’, HHin-EPCs, HH animals fed a HH diet and treated with EPCs; (iv) ‘regression’, HHfin-EPCs, HH treated with EPCs after HH feeding; (v) HH treated with PMPs, HH-PMPs, and (vi) HH treated with EPCs and PMPs, HH-EPCs-PMPs. Results Compared to HH group, the platelets from HHin-EPCs and HHfin-EPCs groups showed a reduction of: (i) activation, reflected by decreased integrin 3β, FAK, PI3K, src protein expression; (ii) secreted molecules as: SDF-1, MCP-1, RANTES, VEGF, PF4, PDGF and (iii) expression of pro-inflammatory molecules as: SDF-1, MCP-1, RANTES, IL-6, IL-1β; TFPI secretion was increased. Compared to HH group, platelets of HH-PMPs group showed increased activation, molecules release and proteins expression. Compared to HH-PMPs group the combination EPCs with PMPs treatment induced a decrease of all investigated platelet molecules, however not comparable with that recorded when EPC individual treatment was applied. Conclusion EPCs have the ability to reduce platelet activation and to modulate their pro-inflammatory and anti-thrombogenic properties in hypertension associated with hypercholesterolemia. Although, PMPs have several beneficial effects in combination with EPCs, these did not improve the EPC effects. These findings reveal a new biological role of circulating EPCs in platelet function regulation, and may contribute to understand their cross talk, and the mechanisms of atherosclerosis.
    PLoS ONE 01/2013; 8(1):e52058. DOI:10.1371/journal.pone.0052058 · 3.23 Impact Factor
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