Abstract:Aim To investigate whether platelet factor 4 （PF4） modulates the matrix metalloproteinase-9（MMP-9） expression of macrophages. Methods THP-1 monocytes were differentiated into monocyte-derived macrophages by phorbol 12-myristate 13-acetate （PMA）. After incubation with PF4 （0～200 μg/L）, the MMP-9 expression of macrophages was determined by reverse-transcription polymerase chain reaction （RT-PCR） and Western blot. To determine the role of toll-like receptor 4 （TLR4） in the regulation of MMP-9 expression, macrophages were pretreated with TLR4 blocker for 30 min, then incubated with PF4. Results Macrophages that were untreated showed a relatively low MMP-9 and TLR4 mRNA or protein levels treatment of macrophages with PF4 increased MMP-9 and TLR4 expression. However, the high levels of MMP-9 and TLR4 expression induced by PF4 were significantly attenuated in the presence of TLR4 blocker.Conclusions PF4 may up-regulate MMP-9 expression in macrophages via TLR4.

Abstract:Aim To investigate the effects of platelet factor 4 (PF4) on the expression of Toll like receptors 2 (TLR2) in human umbilical vein endothelial cells-ECV304. Methods The effects of PF4 on the expression of TLR2 in ECV304 were determined by reverse-transcription polymerase chain reaction,Western Blotting and immunohistochemistry analysis. Results In comparison with blank group,the levels of TLR2 mRNA and protein upregulated (n=5,P><0.05) in time dependent manner in PF4 (100 μg/L) group,but it could not be inhibited by heparin. Using immunohistochemical staining and image analysis methods,the TLR2 expression in ECV304 in PF4 group was increased compared with blank group(0.060 399±0.020 998 vs 0.001 385±0.000 953,P><0.05). Conclusion PF4 promotes the expression of TLR2 mRNA and protein in human umbilical vein endothelial cells. The result of study is useful for platelet to play effect on innate immunity in chronic inflammatory such as atherosclerosis.

Abstract:Aim To investigate a potential role of Toll-like receptor 2(TLR2) and platelet factor 4(PF4) in atherosclerosis,We assessed their expression in murine atherosclerotic plaques.Methods Twenty apolipoprotein E-/-mice at the age of 12 weeks were fed by high-fat diet,ten C57BL/6 mice at the age of 8 weeks were fed by standard laboratory chow for 12 weeks,then all of the animal were euthanized.Blood was sampled from the eye,the serum lipids was enzymatically detected.The thoracic and abdominalis aorta was fixed by in situ liquid flow.Thoracic aorta was fix in 10% formalin,paraffin imbedding,serial sections,and HE staining.Aortic lesions of high-fat diet-fed apolipoprotein E-/-mice were examined for TLR2 and PF4 expression by immunohistochemistry.Results Aortic atherosclerotic lesions in all apolipoprotein E-/-mice expressed TLR2,whereas aortic tissue obtained from control C57BL/6J mice showed no TLR2 expression.Serial sections immunostaining showed TLR2 localizing with macrophages and endothelial cells in murine atherosclerotic lesions.Furthermore,PF4 expression in murine atherosclerotic plaques were also observed.Conclusions TLR2 is expressed by macrophages and endothelial cells in murine atherosclerotic lesions,and we find that PF4 is also expressed in the plaques.They may play a role to enhance and sustain the innate immue and inflammatory responses.