Nurr1 Modulation Mediates Neuroprotective Effects of Statins.

The ligand-sensing transcription factor Nurr1 emerges as a promising therapeutic target for neurodegenerative pathologies but Nurr1 ligands for functional studies and therapeutic validation are lacking. Here pronounced Nurr1 modulation by statins for which clinically relevant neuroprotective effects are demonstrated, is reported. Several statins directly affect Nurr1 activity in cellular and cell-free settings with low micromolar to sub-micromolar potencies. Simvastatin as example exhibits anti-inflammatory effects in astrocytes, which are abrogated by Nurr1 knockdown. Differential gene expression analysis in native and Nurr1-silenced cells reveals strong proinflammatory effects of Nurr1 knockdown while simvastatin treatment induces several neuroprotective mechanisms via Nurr1 involving changes in inflammatory, metabolic and cell cycle gene expression. Further in vitro evaluation confirms reduced inflammatory response, improved glucose metabolism, and cell cycle inhibition of simvastatin-treated neuronal cells. These findings suggest Nurr1 involvement in the well-documented but mechanistically elusive neuroprotection by statins.

Design of a Potent TLX Agonist by Rational Fragment Fusion.

As a master regulator of neurogenesis, the orphan nuclear receptor tailless homologue (TLX, NR2E1) maintains neuronal stem cell homeostasis by acting as a transcriptional repressor of tumor suppressor genes. It is hence considered as an appealing target for the treatment of neurodegenerative diseases, but a lack of potent TLX modulators as tools to probe pharmacological TLX control hinders further validation of its promising potential. Here, we report the development of a potent TLX agonist based on fragment screening, pharmacophore modeling, and fragment fusion. Pharmacophore similarity of a fragment screening hit and the TLX ligand ccrp2 provided a rational basis for fragment linkage, which resulted in several TLX activator scaffolds. Among them, the fused compound 10 evolved as a valuable TLX agonist tool with submicromolar potency and high selectivity over related nuclear receptors, rendering it suitable for functional studies on TLX.

The Transcriptional Repressor Orphan Nuclear Receptor TLX Is Responsive to Xanthines.

The orphan nuclear receptor tailless homologue (TLX) is expressed almost exclusively in neural stem cells acting as an essential factor for their survival and is hence considered as a promising drug target in neurodegeneration. However, few studies have characterized the roles of TLX due to the lack of ligands and limited functional understanding. Here, we identify xanthines including caffeine and istradefylline as TLX modulators that counteract the receptor's intrinsic repressor activity. Mutagenesis of residues lining a cavity within the TLX ligand binding domain altered the activity of these ligands, suggesting direct interactions with helix 5. Using xanthines as tool compounds, we observed a ligand-sensitive recruitment of the co-repressor silencing mediator for retinoid or thyroid-hormone receptors, TLX homodimerization, and heterodimerization with the retinoid X receptor. These protein-protein interactions evolve as factors that modulate the TLX function and suggest an unprecedented role of TLX in directly repressing other nuclear receptors.

Propranolol Activates the Orphan Nuclear Receptor TLX to Counteract Proliferation and Migration of Glioblastoma Cells.

The ligand-sensing transcription factor tailless homologue (TLX, NR2E1) is an essential regulator of neuronal stem cell homeostasis with appealing therapeutic potential in neurodegenerative diseases and central nervous system tumors. However, knowledge on TLX ligands is scarce, providing an obstacle to target validation and medicinal chemistry. To discover TLX ligands, we have profiled a drug fragment collection for TLX modulation and identified several structurally diverse agonists and inverse agonists of the nuclear receptor. Propranolol evolved as the strongest TLX agonist and promoted TLX-regulated gene expression in human glioblastoma cells. Structure-activity relationship elucidation of propranolol as a TLX ligand yielded a structurally related negative control compound. In functional cellular experiments, we observed an ability of propranolol to counteract glioblastoma cell proliferation and migration, while the negative control had no effect. Our results provide a collection of TLX modulators as initial chemical tools and set of lead compounds and support therapeutic potential of TLX modulation in glioblastoma.

The Medicinal Chemistry of Caffeine.

The purine alkaloid caffeine is the most widely consumed psychostimulant drug in the world and has multiple beneficial pharmacological activities, for example, in neurodegenerative diseases. However, despite being an extensively studied bioactive natural product, the mechanistic understanding of caffeine's pharmacological effects is incomplete. While several molecular targets of caffeine such as adenosine receptors and phosphodiesterases have been known for decades and inspired numerous medicinal chemistry programs, new protein interactions of the xanthine are continuously discovered providing potentially improved pharmacological understanding and a molecular basis for future medicinal chemistry. In this Perspective, we gather knowledge on the confirmed protein interactions, structure activity relationship, and chemical biology of caffeine on well-known and upcoming targets. The diversity of caffeine's molecular activities on receptors and enzymes, many of which are abundant in the CNS, indicates a complex interplay of several mechanisms contributing to neuroprotective effects and highlights new targets as attractive subjects for drug discovery.

A Selective Modulator of Peroxisome Proliferator-Activated Receptor γ with an Unprecedented Binding Mode.

The nuclear peroxisome proliferator-activated receptor γ has well-validated therapeutic potential in metabolic, inflammatory, and neurodegenerative pathologies, but its activation is also associated with marked adverse effects and novel modes of PPARγ modulation are required. Here, we report the discovery and profiling of a new PPARγ modulator chemotype endowed with remarkable potency and a distinct binding mode in the orthosteric PPARγ ligand-binding site. Its R-enantiomer evolved as a eutomer regarding PPARγ activation with a high eudysmic ratio. The new PPARγ modulator revealed outstanding selectivity over the PPARα and PPARδ subtypes and did not promote adipogenesis in primary human fibroblasts, discriminating it from established agonists.

A triple farnesoid X receptor and peroxisome proliferator-activated receptor α/δ activator reverses hepatic fibrosis in diet-induced NASH in mice.

Non-alcoholic steatohepatitis (NASH) - a hepatic manifestation of the metabolic syndrome - is a multifactorial disease with alarming global prevalence. It involves steatosis, inflammation and fibrosis in the liver, thus demanding multiple modes of action for robust therapeutic efficacy. Aiming to fuse complementary validated anti-NASH strategies in a single molecule, we have designed and systematically optimized a scaffold for triple activation of farnesoid X receptor (FXR), peroxisome proliferator-activated receptor (PPAR) α and PPARδ. Pilot profiling of the resulting triple modulator demonstrated target engagement in native cellular settings and in mice, rendering it a suitable tool to probe the triple modulator concept in vivo. In DIO NASH in mice, the triple agonist counteracted hepatic inflammation and reversed hepatic fibrosis highlighting the potential of designed polypharmacology in NASH.