Increased levels of circulating platelet-derived microparticles in psoriasis: Possible implications for the associated cardiovascular risk

AIM: To evaluate platelet activation markers in psoriasis patients, compared to controls, and investigate their association with the inflammatory burden of psoriasis. METHODS: Forty psoriatic patients without cardiovascular disease, and 12 healthy controls were subjected to measurement of baseline platelet CD62P, CD63 and CD42b expression, platelet-leukocyte complexes, i.e., platelet-monocyte complexes (PMC), platelet-neutrophil complexes (PNC) and platelet-lymphocyte complexes, and concentrations of platelet-derived microparticles (PMPs) using flow cytometry. Both larger-size (0.5-0.9 μm) and smaller-size (< 0.5 μm) PMPs were determined. Serum interleukin (IL)-12 and IL-17 levels were also measured by enzyme-linked immunosorbent assay. The severity of psoriasis was evaluated by the Psoriasis Area Severity Index (PASI). RESULTS: PMP concentrations were significantly higher in psoriasis patients than controls [mean ± standard error of mean (SEM): 22 ± 5/μL vs 11 ± 6/μL; P = 0.018), for both smaller-size (10 ± 2/μL vs 4 ± 2/μL; P = 0.033) and larger-size (12 ± 3/μL vs 6 ± 4/μL; P = 0.014) PMPs. Platelet CD62P, CD63 and CD42b expression and circulating PMC and PNC were similar between the two groups. Lower circulating PLC were observed in psoriasis patients compared to controls (mean ± SEM: 16% ± 3% vs 23% ± 6%; P = 0.047). Larger-size PMPs were related with IL-12 levels (P < 0.001) and smaller-size PMPs with both IL-12 and IL-17 levels (P < 0.001). Total PMPs also correlated with IL-12 (P < 0.001). CD63 expression was positively correlated with both IL-12 and IL-17 (P < 0.05). Increased PASI score was associated with increased levels of larger-size PMPs (r = 0.45; P = 0.011) and increased CD63 expression (r = 0.47; P < 0.01). CONCLUSION: PMPs, known to be predictive of cardiovascular outcomes, are increased in psoriasis patients, and associated with high inflammatory disease burden. Enhanced platelet activation may be the missing link leading to cardiovascular events in psoriatic patients.