18F-DPA-714 PET Imaging for Detecting Neuroinflammation in Rats with Chronic Hepatic Encephalopathy

Neuroinflammation is considered to be the pathogenesis of hepatic encephalopathy (HE), and imaging neuroinflammation is implicated in HE management. (11)C-PK11195, a typical translocator protein (TSPO) radiotracer, is used for imaging neuroinflammation. However, it has inherent limitations, such as short half-life and limited availability. The purpose of this study was to demonstrate the efficiency of new generation TSPO radiotracer, (18)F-DPA-714, in detecting and monitoring neuroinflammation of chronic HE. This study was divided into two parts. The first part compared (18)F-DPA-714 and (11)C-PK11195 radiotracers in ten HE induced rats [bile duct ligation (BDL) and fed hyperammonemic diet (HD)] and 6 control rats. The animal subjects underwent dynamic positron emission tomography (PET) during 2-day intervals. The (11)C-PK11195 PET study showed no differences in whole brain average percent injected dose per gram (%ID/g) values at all time points (all P>0.05), while the (18)F-DPA-714 PET study showed higher whole brain average %ID/g values in HE rats compared to control group rats at 900 s to 3300 s after injecting radiotracer (all P<0.05). The second part of the study evaluated the effectiveness of ibuprofen (IBU) treatment to chronic HE. Forty rats were classified into six groups, including Sham+normal saline (NS), Sham+IBU, BDL+NS, BDL+HD+NS, BDL+IBU, and BDL+HD+IBU groups. (18)F-DPA-714 PET was used to image neuroinflammation. Whole and regional brain average %ID/g values, neurological features, inflammatory factors and activated microglia showed better in the IBU groups than in the NS groups (all P<0.05) and no difference was seen in the Sham groups compared to IBU groups (all P>0.05). In conclusion, this study demonstrated that (18)F-DPA-714 is an ideal TPSO radiotracer for imaging neuroinflammation and monitoring anti-neuroinflammation treatment efficacy of chronic HE.