Prolyl oligopeptidase inhibitor KYP‐2047 alleviates inflammation in retinal pigment epithelium cells

AbstractPurposeRetinal inflammation and dysfunctional protein clearance are characteristics of age‐related macular degeneration (AMD) – the most common cause of blindness in the developed countries. Prolyl oligopeptidase (PREP) is a serine protease that has several functions in the cells including regulation of inflammatory mediators. In this study, we investigated the effects of PREP inhibitor KYP‐2047 on inflammation in retinal pigment epithelium (RPE) cells with blocked proteasomal clearance.MethodsProteasomal degradation in ARPE‐19 cells was inhibited by MG‐132. The cells were exposed to the PREP inhibitor KYP‐2047 (1 µM) for 15 min before adding MG‐132 (5 µM) for 6 h or 24 h. Cytotoxicity was determined using the lactate dehydrogenase (LDH) assay. Cytokine levels (IL‐6 and IL‐8) were measured from cell culture medium samples using the enzyme‐linked immunosorbent assay (ELISA) method. Autophagy markers p62/SQSTM1 and LC3 were determined using Western blot technique.ResultsCells suffering from MG‐132‐induced proteasomal blockade showed higher LDH leakage and IL‐8 secretion as well as accumulation of the autophagy marker p62/SQSTM1 and increased conversion of LC3‐I to LC3‐II. The PREP inhibitor KYP‐2047 reduced the levels of LDH and pro‐inflammatory cytokines IL‐6 and IL‐8 in human RPE cells exposed to MG‐132. KYP‐2047 did not have a significant effect on the levels of autophagy markers at the 24 h time point.ConclusionsPREP inhibitor KYP‐2047 protects human RPE cells from MG‐132‐mediated cytotoxicity and alleviates inflammation. Further studies are needed to uncover the underlying mechanism, but PREP inhibition is a promising therapy target in AMD.