Neurodegenerative diseases

Discovery of Imidazoquinazolinone Derivatives as TSPO Ligands Modulating Neurosteroidogenesis and Cellular Bioenergetics in Neuroblastoma Cells Expressing Amyloid Precursor Protein

ChemistrySelect, 2017, 2, 22, 6452-6457

Starting from the central benzodiazepine receptor (CBR) ligand CGS‐13767, we designed a series of imidazoquinazolinone derivatives acting as 18 kDa translocator protein (TSPO) ligands, and deprived of affinity for CBR. These compounds, as well as ligands of reference (Ro5‐4864, XBD173, SSR180575), were assessed for their ability to restore neurosteroidogenesis and energy production in SH‐SY5Y neuroblastoma cell lines expressing amyloid protein precursor (APP). Our results show the potential neuroprotective effect of TSPO ligands, but highlight a strong discrepancy in the active concentrations, nanomolar for ATP production while pregnenolone production is restored in the micromolar range.

The translocator protein ligand XBD173 improves clinical symptoms and neuropathological markers in the SJL/J mouse model of multiple sclerosis

Biochimica et Biophysica Acta (BBA) Molecular Basis of Disease, 2017, 1863, 12, 3016-3027

Multiple sclerosis (MS) is a severe autoimmune disease characterized by inflammatory, demyelinating and neurodegenerative components causing motor, sensory, visual and/or cognitive symptoms. The relapsing-remitting MS affecting 85% of patients is reliably mimicked by the proteolipid-protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) SJL/J-mouse model. Significant progress was made for MS treatment but the development of effective therapies devoid of severe side-effects remains a great challenge. Here, we combine clinical, behavioral, histopathological, biochemical and molecular approaches to demonstrate that low and well tolerated doses (10–20 mg/kg) of TSPO ligand XBD173 (Emapunil) efficiently ameliorate clinical signs and neuropathology of PLP-EAE mice. In addition to the conventional clinical scoring of symptoms, we applied the robust behavioral Catwalk-method to confirm that XBD173 (10 mg/kg) increases the maximum contact area parameter at EAE-disease peak, indicating an improvement/recovery of motor functions. Consistently, histopathological studies coupled with microscope-cellSens quantification and RT-qPCR analyzes showed that XBD173 prevented demyelination by restoring normal protein and mRNA levels of myelin basic protein that was significantly repressed in PLP-EAE mice spinal cord and brain. Interestingly, ELISA-based measurement revealed that XBD173 increased allopregnanolone concentrations in PLP-EAE mice spinal and brain tissues. Furthermore, flow cytometry assessment demonstrated that XBD173 therapy decreased serum level of pro-inflammatory cytokines, including interleukin-17AInterleukin-6 and tumor-necrosis-factor alpha in PLP-EAE mice. As the optimal XBD173 dosing exerting the maximal beneficial action in EAE mice is the lower 10 mg/kg dose, the paper opens interesting perspectives for the development of efficient and safe therapies against MS with slight or no side-effects.

Structure-Activity Relationship Study around Guanabenz Identifies Two Derivatives Retaining Antiprion Activity but Having Lost alpha 2-Adrenergic Receptor Agonistic Activity

ACS Chemical Neuroscience, 2014, 5(10), 1075-1082

Guanabenz (GA) is an orally active α2-adrenergic agonist that has been used for many years for the treatment of hypertension. We recently described that GA is also active against both yeast and mammalian prions in an α2-adrenergic receptor-independent manner. These data suggest that this side-activity of GA could be explored for the treatment of prion-based diseases and other amyloid-based disorders. In this perspective, the potent antihypertensive activity of GA happens to be an annoying side-effect that could limit its use. In order to get rid of GA agonist activity at α2-adrenergic receptors, we performed a structure–activity relationship study around GA based on changes of the chlorine positions on the benzene moiety and then on the modifications of the guanidine group. Hence, we identified the two derivatives 6 and 7 that still possess a potent antiprion activity but were totally devoid of any agonist activity at α2-adrenergic receptors. Similarly to GA, 6 and 7 were also able to inhibit the protein folding activity of the ribosome (PFAR) which has been suggested to be involved in prion appearance/maintenance. Therefore, these two GA derivatives are worth being considered as drug candidates.

 Graphical abstract

The neuroprotector kynurenic acid increases neuronal cell survival through neprilysin induction

Neuropharmacology, 2013, 70, 254-260

Kynurenic acid (KYNA), one of the main product of the kynurenine pathway originating from tryptophan, is considered to be neuroprotective. Dysregulation of KYNA activity is thought to be involved in neurodegenerative diseases, the physiopathology of which evokes excitotoxicity, oxidative stress and/or protein aggregation. The neuroprotective effect of KYNA is generally attributed to its antagonistic action on NMDA receptors. However, this single target action appears insufficient to support KYNA beneficial effects against complex neurodegenerative processes including neuroinflammation, β-amyloid peptide (Aβ) toxicity and apoptosis. Novel insights are therefore required to elucidate KYNA neuroprotective mechanisms. Here, we combined cellular, biochemical, molecular and pharmacological approaches to demonstrate that low micromolar concentrations of KYNA strongly induce neprilysin (NEP) gene expression, protein level and enzymatic activity increase in human neuroblastoma SH-SY5Y cells. Furthermore, our studies revealed that KYNA exerts a protective effect on SH-SY5Y cells by increasing their viability through a mechanism independent from NMDA receptors. Interestingly, KYNA also induced NEP activity and neuroprotection in mouse cortical neuron cultures the viability of which was more promoted than SH-SY5Y cell survival under KYNA treatment. KYNA-evoked neuroprotection disappeared in the presence of thiorphan, an inhibitor of NEP activity. NEP is a well characterized metallopeptidase whose deregulation leads to cerebral Aβ accumulation and neuronal death in Alzheimer's disease. Therefore, our results suggest that a part of the neuroprotective role of KYNA may depend on its ability to induce the expression and/or activity of the amyloid-degrading enzyme NEP in nerve cells.