Figure 1.

Endogenous and exogenous translocator protein 18 kDa (TSPO) ligands alleviate chronic microglia activation. In response to pathological signals from dying photoreceptors, Müller cells upregulate the expression and secretion of the endogenous TSPO ligand Diazepine binding inhibitor (DBI) protein. Simultaneously, microglia cells upregulate mitochondrial TSPO expression and take up the secreted DBI. Binding of DBI, its cleavage product triakontatetraneuropeptide (TTN) or the synthetic ligand XBD173 limits the magnitude of inflammatory responses and influences transition of microglia towards a ramified neuroprotective phenotype.