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A member of a new subfamily of G protein-coupled receptors, protease-activated receptor 2 (PAR2), is highly expressed on endothelial cells and plays an important role in inflammation. The purpose of this study was to determine the molecular mechanism used by PAR2 to induce IL-8 production and thereby mediate cell adhesion. We observed that PAR2-activating peptide (PAR2-AP) significantly increase peripheral blood mononuclear cells adhere to endothelial cells. Both PAR2-AP and the endogenous PAR2 activator trypsin caused concentration- and time-dependent increase in endothelial IL-8 production, and this effect was concentration dependently and selectively attenuated by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Western blotting analysis showed that PAR2-AP induced phosphorylation of p38 MAPK and its upstream protein kinase MAPK kinase 3/6 (MKK3/6) in a time-dependent manner. Using reverse-transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, PAR2-AP was found to cause an increase in IL-8 mRNA expression and its transcription factor activating transcription factor 2, respectively,. As expected, these signals were suppressed by SB203580 in a concentration-dependent manner. Furthermore, introduction of dominant-negative vectors targeting p38 MAPK, MKK3, and MKK6 abolished PAR2-AP-mediated IL-8 production and cell adhesion function. In conclusion, PAR2 via p38 MAPK signaling regulates IL-8 production and thereby mediates cell adhesion.

Parkinson's disease (PD) is the second most common neurodegenerative disease, and there is still no effective way to stop its progress. Therefore, early detection is crucial for the prevention and the treatment of Parkinson's disease. The current diagnosis of Parkinson's disease, however, mainly depends on the symptoms, so it is necessary to establish a reliable imaging modality for PD diagnosis and its progression monitoring. Other studies and our previous ones demonstrated that substantia nigra hyperechogenicity (SNH) was detected by transcranial sonography (TCS) in the ventral midbrain of PD patients, and SNH is regarded as a characteristic marker of PD. The present study aimed to explore whether SNH could serve as a reliable imaging modality to monitor the progression of dopaminergic neurodegeneration of PD. The results revealed that the size of SNH was positively related with the degree of dopaminergic neuron death in PD animal models. Furthermore, we revealed that microglia activation contributed to the SNH formation in substantia nigra (SN) in PD models. Taken together, this study suggests that SNH through TCS is a promising imaging modality to monitor the progression of dopaminergic neurodegeneration of PD.

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