Targeting TSPO Reduces Inflammation and Apoptosis in an In Vitro Photoreceptor-Like Model of Retinal Degeneration

Abstract

The 18 kDa translocator protein (TSPO) is predominantly located in the mitochondrial outer membrane, playing an important role in steroidogenesis, inflammation, survival, and cell proliferation. Its expression in the CNS, and mainly in glial cells, is upregulated in neuropathologies and brain injury. In this study, the potential of targeting TSPO for the therapeutic treatment of inflammatory-based retinal neurodegeneration was evaluated by means of an in vitro model of lipopolysaccharide (LPS)-induced degeneration in 661 W cells, a photoreceptor-like cell line. After the assessment of the expression of TSPO in 661W cells, which, to the best of our knowledge, was never investigated so far, the anti-inflammatory and cytoprotective effects of a number of known TSPO ligands, belonging to the class of N,N-dialkyl-2-arylindol-3-ylglyoxylamides (PIGAs), were evaluated, using the classic TSPO ligand PK11195 as the reference standard. All tested PIGAs showed the ability to modulate the inflammatory and apoptotic processes in 661 W photoreceptor-like cells and to reduce LPS-driven cellular cytotoxicity. The protective effect of PIGAs was, in all cases, reduced by cotreatment with the pregnenolone synthesis inhibitor SU-10603, suggesting the involvement of neurosteroids in the protective mechanism. As inflammatory processes play a crucial role in the retinal neurodegenerative disease progression toward photoreceptors' death and complete blindness, targeting TSPO might represent a successful strategy to slow down this degenerative process that may lead to the inexorable loss of vision.

A Window to the Brain: The Retina to Monitor the Progression and Efficacy of Saffron Repron® Pre-Treatment in an LPS Model of Neuroinflammation and Memory Impairment

“…Retinal tissues were lysed with modified RIPA buffer, described by [ 54 ], while the brain and hippocampus were lysed with RIPA buffer (150 mM NaCl, 50 mM Tris-HCl pH 8, 1% Igepal, 0.5% Na-deoxycholate, 0.1% SDS and protease inhibitors, 1 µM Orthovanadate, and 0.1 mg/mL PMSF), and proteins quantified with a Bradford assay. The procedure of electrophoretic run of protein samples, antibodies incubation, and analysis was described previously in [ 55 ]. Briefly, 25 μg of each cell protein extract was mixed with the Laemmli 2X solution and resolved by electrophoresis SDS-PAGE, supported by the use of precast stain-free gel, and after activation, the separated proteins were transferred to PVDF membranes.…”

Indol-3-ylglyoxylamide as Privileged Scaffold in Medicinal Chemistry

“…Compounds 8 and 12 ( Figure 8 ) were also evaluated for their effect on inflammatory-based retinal neurodegeneration in an in vitro model of lipopolysaccharide (LPS)-induced degeneration in 661W cells, a photoreceptor-like cell line [ 59 ]. Both compounds modulated the inflammatory and apoptotic processes in 661W cells and reduce LPS-driven cytotoxicity, effects that were shown to be mediated by neurosteroids [ 59 ].…”

Chronic administration of XBD173 ameliorates cognitive deficits and neuropathology via 18 kDa translocator protein (TSPO) in a mouse model of Alzheimer’s disease

“…As such, novel compounds that target both depression and dementia would constitute a novel therapeutic approach. The 18 kDa TSPO protein, located on the outer mitochondrial membrane, is known to orchestrate several important functions including cholesterol transfer into mitochondria, TSPO ligands-induced neurosteroidogenesis, mitochondrial homeostasis, gliosis, and apoptosis (13, 14). Contrary to benzodiazepines which are positive allosteric modulators of GABA A receptors, neurosteroids act through a different site than that targeted by benzodiazepines.…”