The bioactive plant diterpene oridonin displays important pharmacological activities and is widely used in traditional Chinese medicine; however, its molecular mechanism of action is still incompletely described. In vitro and in vivo data have demonstrated anti-tumor activity of oridonin and its ability to interfere with several cell pathways; however, presently only the molecular chaperone HSP70 has been identified as a direct potential target of this compound. Here, using a combination of different proteomic approaches, innovative Cellular Thermal Shift Assay (CETSA) experiments, and classical biochemical methods, we demonstrate that oridonin interacts with Nucleolin, effectively modulating the activity of this multifunctional protein. The ability of oridonin to target Nucleolin and/or HSP70 could account for the bioactivity profile of this plant diterpene. Recently, Nucleolin has attracted attention as a druggable target, as its diverse functions are implicated in pathological processes such as cancer, inflammation, and viral infection. However, up to now, no small molecule as Nucleolin binders has been reported, thus our finding represents the first evidence of Nucleolin modulation by a small inhibitor.

Ten new (1–10) and six known (11–16) fusicoccane diterpenes were isolated from the roots of Hypoestes forsskaolii. The structural characterization of 1–10 was performed by spectroscopic analysis, including 1D and 2D NMR, ECD, and HRESIMS experiments. From a perspective of obtaining potential Hsp90α inhibitors, the isolates were screened by surface plasmon resonance measurements and their cytotoxic activity was assayed using Jurkat and HeLa cancer cells. Compound 6, 18-hydroxyhypoestenone, was shown to be the most active compound against Hsp90, and its interactions were studied also by biochemical and cellular assays and by molecular docking.

Proteomics based approaches are emerging as useful tools to identify the targets of bioactive compounds and elucidate their molecular mechanisms of action. Here, we applied a chemical proteomic strategy to identify the peroxisome proliferator-activated receptor γ (PPARγ) as a molecular target of the pro-apoptotic agent 15-ketoatractyligenin methyl ester (compound 1). We demonstrated that compound 1 interacts with PPARγ, forms a covalent bond with the thiol group of C285 and occupies the sub-pocket between helix H3 and the β-sheet of the ligand-binding domain (LBD) of the receptor by Surface Plasmon Resonance (SPR), mass spectrometry-based studies and docking experiments. 1 displayed partial agonism of PPARγ in cell-based transactivation assays and was found to inhibit the AKT pathway, as well as its downstream targets. Consistently, a selective PPARγ antagonist (GW9662) greatly reduced the anti-proliferative and pro-apoptotic effects of 1, providing the molecular basis of its action. Collectively, we identified 1 as a novel PPARγ partial agonist and elucidated its mode of action, paving the way for therapeutic strategies aimed at tailoring novel PPARγ ligands with reduced undesired harmful side effects.

Bioactive 2-benzazepines were accessed in an atom- and step-economical manner through a versatile palladium-catalyzed C-H activation strategy. The C-H arylation required low catalyst loading and a mild base, which was reflected by a broad scope and high functional-group tolerance. The benzotriazolodiazepinones were identified as new heat shock protein 90 (Hsp90) inhibiting lead compounds, with considerable potential for anti-cancer applications.

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Combination antiretroviral therapy (cART) improves life expectancy and lowers the incidence of central nervous system (CNS) opportunistic infections, lymphomas, and HIV-associated dementia in HIV+ people. However, mild-to-moderate HIV-associated neurocognitive disorders (HAND) persist in about 50% of HIV+ people, even when HIV replication is well controlled. In vitro, animal model, and clinical studies suggest that cART neurotoxicity could be a contributing factor to the progression of HAND. In this study, we developed two in vitro model systems using glutamatergic neurons derived from human induced pluripotent stem cells (hiPSC-Gluts) and fetal neural precursor cells (hNPCs) to assay for antiretroviral (ARV) effects on mature and developing neurons, respectively. We tested four ARVs: the nucleoside/nucleotide reverse transcriptase inhibitors tenofovir disproxil fumarate (TDF) and emtricitabine (FTC) and the integrase inhibitors dolutegravir (DTG) and elvitegravir (EVG). DTG, EVG, and TDF decreased hiPSC-Glut viability and neurite length; all four antiretrovirals decreased hiPSC-Glut synapse counts; and DTG and EVG decreased the frequency and magnitude of hiPSC-Glut calcium transients. The magnitude of these neurotoxic effects increased with longer ARV exposure times and with the exposure of hiPSC-Gluts to two or three ARVs simultaneously. These results suggest that certain ARVs could cause HAND by decreasing the survival and function of CNS neurons. In fetal hNPCs, TDF decreased viability and changed the distribution of epigenetic histone modifications, suggesting that this ARV may alter neurogenesis, which could impair cognition in adults and/or CNS development for those exposed to ARV in utero or early childhood. Our study establishes human preclinical neurotoxicity systems that can screen for potential ARV CNS toxicity and develop safer cART regimens.