Adamantaniline Derivatives Target ATP5B to Inhibit Translation of Hypoxia Inducible Factor-1α.

Hypoxia inducible factor-1α (HIF-1α) plays a critical role in cellular adaptation to hypoxia and it is a potential therapeutic target for anti-cancer drugs. Applying high-throughput screening, here it is found that HI-101, a small molecule containing an adamantaniline moiety, effectively reduces HIF-1α protein expression. With the compound as a hit, a probe (HI-102) is developed for target identification by affinity-based protein profiling. The catalytic ß subunit of mitochondrial FO F1 -ATP synthase, ATP5B, is identified as the binding protein of HI-derivatives. Mechanistically, HI-101 promotes the binding of HIF-1α mRNA to ATP5B, thus inhibiting HIF-1α translation and the following transcriptional activity. Further modifications of HI-101 lead to HI-104, a compound with good pharmacokinetic properties, exhibiting antitumor activity in MHCC97-L mice xenograft model, and HI-105, the most potent compound with an IC50 of 26 nm. The findings provide a new strategy for further developing HIF-1α inhibitors by translational inhibition through ATP5B.

Helicobacter pylori FabX contains a [4Fe-4S] cluster essential for unsaturated fatty acid synthesis.

Unsaturated fatty acids (UFAs) are essential for functional membrane phospholipids in most bacteria. The bifunctional dehydrogenase/isomerase FabX is an essential UFA biosynthesis enzyme in the widespread human pathogen Helicobacter pylori, a bacterium etiologically related to 95% of gastric cancers. Here, we present the crystal structures of FabX alone and in complexes with an octanoyl-acyl carrier protein (ACP) substrate or with holo-ACP. FabX belongs to the nitronate monooxygenase (NMO) flavoprotein family but contains an atypical [4Fe-4S] cluster absent in all other family members characterized to date. FabX binds ACP via its positively charged α7 helix that interacts with the negatively charged α2 and α3 helices of ACP. We demonstrate that the [4Fe-4S] cluster potentiates FMN oxidation during dehydrogenase catalysis, generating superoxide from an oxygen molecule that is locked in an oxyanion hole between the FMN and the active site residue His182. Both the [4Fe-4S] and FMN cofactors are essential for UFA synthesis, and the superoxide is subsequently excreted by H. pylori as a major resource of peroxide which may contribute to its pathogenic function in the corrosion of gastric mucosa.

UV254 irradiation of N-chloro-α-amino acids: Kinetics, mechanisms, and N-DBP formation potentials.

This study explores the degradation kinetics and mechanisms of N-chloro-α-amino acids and the changes in the formation potential of nitrogenous disinfection byproducts (N-DBPs) upon UV254 irradiation. UV254 irradiation significantly accelerated the degradation of all the tested N-chloro-α-amino acids compared to those in the dark. Both direct photolysis-induced cleavage of the N-Cl bonds and radical oxidation (e.g., Cl• and Cl2•-) involved reactions that contributed to their enhanced degradation. The fluence-based photolysis rate constants of the N-chloro-α-amino acids varied in the range of (1.06-5.47) × 10-3 cm2 mJ-1 at pH 6.0 and (0.74-2.79) × 10-3 cm2 mJ-1 at pH 8.0. The apparent quantum yields (Φapp) of the majority of the N-chloro-α-amino acids were in the range of 0.41-0.95 at pH 6.0 and 0.22-0.79 at pH 8.0, except N-chloroaspartic acid, N-chlorohistidine, and N-chloroalanine. UV254 irradiation significantly enhanced the formation of trichloronitromethane (TCNM) from the tested N-chloro-α-amino acids after post-chlorination, but exhibited various effects on the formation of dichloroacetonitrile (DCAN). A longer UV254 irradiation time generated more TCNM, and a lower pH produced more DCAN from the N-chloro-α-amino acids. The degradation pathways of N-chlorotyrosine, as a representative N-chloro-α-amino acid, are proposed, and the ß-scission and 1,2-H shift pathways led to the formation of different precursors of TCNM and DCAN. The results of this study improve our understanding of the fate of N-chloro-α-amino acids under UV254 irradiation and post-chlorination.

Molecular characterization of transformation and halogenation of natural organic matter during the UV/chlorine AOP using FT-ICR mass spectrometry.

UV/chlorine process, as an emerging advanced oxidation process (AOP), was effective for removing micro-pollutants via various reactive radicals, but it also led to the changes of natural organic matter (NOM) and formation of disinfection byproducts (DBPs). By using negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS), the transformation of Suwannee River NOM (SRNOM) and the formation of chlorinated DBPs (Cl-DBPs) in the UV/chlorine AOP and subsequent post-chlorination were tracked and compared with dark chlorination. In comparison to dark chlorination, the involvement of ClO•, Cl•, and HO• in the UV/chlorine AOP promoted the transformation of NOM by removing the compounds owning higher aromaticity (AImod) value and DBE (double-bond equivalence)/C ratio and causing the decrease in the proportion of aromatic compounds. Meanwhile, more compounds which contained only C, H, O, N atoms (CHON) were observed after the UV/chlorine AOP compared with dark chlorination via photolysis of organic chloramines or radical reactions. A total of 833 compounds contained C, H, O, Cl atoms (CHOCl) were observed after the UV/chlorine AOP, higher than 789 CHOCl compounds in dark chlorination, and one-chlorine-containing components were the dominant species. The different products from chlorine substitution reactions (SR) and addition reactions (AR) suggested that SR often occurred in the precursors owning higher H/C ratio and AR often occurred in the precursors owning higher aromaticity. Post-chlorination further caused the cleavages of NOM structures into small molecular weight compounds, removed CHON compounds and enhanced the formation of Cl-DBPs. The results provide information about NOM transformation and Cl-DBPs formation at molecular levels in the UV/chlorine AOP.

Copper Inhibition of Triplet-Sensitized Phototransformation of Phenolic and Amine Contaminants.

Excited triplet states of natural organic matter (3NOM*) are important reactive intermediates in phototransformation of organic contaminants in sunlit waters. The main goal of this study was to explore the influence of Cu on triplet-sensitized transformation rates of 20 selected phenolic and amine contaminants. Fourteen of the compounds examined exhibited a marked decrease in their 4-carboxybenzophenone (CBBP)-mediated phototransformation rate in the presence of trace amounts of Cu(II) (25-500 nM). Both mathematical modeling of these rate data and transient absorption spectroscopy measurements support the hypothesis that the decrease in the rate and extent of phototransformation of organic contaminants is due to the reduction of radical intermediates of the contaminants by photochemically formed Cu(I). The Cu-induced inhibition of oxidation of organic contaminants photosensitized by Suwannee River NOM (SRNOM) could also take place in the presence of nanomolar concentrations of Cu. The inhibitory effect of Cu on the oxidation rates of amine contaminants in SRNOM solutions was found to be significantly weaker compared to that in CBBP solutions, but little difference was observed on depletion of phenols. This behavior was attributed to the intrinsic inhibitory effect of the antioxidant moieties present in NOM on phototransformation of amine compounds, partially neutralizing the potential for further Cu inhibition.

Site-Selective Phosphoglycerate Mutase 1 Acetylation by a Small Molecule.

Post-translational modifications play vital roles in fine-tuning a myriad of physiological processes, and one of the most important modifications is acetylation. Here, we report a ligand-directed site-selective acetylation using KHAc, a derivative of a phosphoglycerate mutase 1 (PGAM1) inhibitor. KHAc binds to PGAM1 and transfers its acetyl group to the ε-NH2 of Lys100 to inactivate the enzyme. The acetyl transfer process was visualized by time-resolved crystallography, demonstrating that the transfer is driven by proximity effects. KHAc was capable of selectively and effectively acetylating Lys100 of PGAM1 in cultured human cells, accompanied by inhibited F-actin formation. Similar strategies could be used for exogenous control of other lysine post-translational modifications.

An allosteric PGAM1 inhibitor effectively suppresses pancreatic ductal adenocarcinoma.

Glycolytic enzyme phosphoglycerate mutase 1 (PGAM1) plays a critical role in cancer metabolism by coordinating glycolysis and biosynthesis. A well-validated PGAM1 inhibitor, however, has not been reported for treating pancreatic ductal adenocarcinoma (PDAC), which is one of the deadliest malignancies worldwide. By uncovering the elevated PGAM1 expressions were statistically related to worse prognosis of PDAC in a cohort of 50 patients, we developed a series of allosteric PGAM1 inhibitors by structure-guided optimization. The compound KH3 significantly suppressed proliferation of various PDAC cells by down-regulating the levels of glycolysis and mitochondrial respiration in correlation with PGAM1 expression. Similar to PGAM1 depletion, KH3 dramatically hampered the canonic pathways highly involved in cancer metabolism and development. Additionally, we observed the shared expression profiles of several signature pathways at 12 h after treatment in multiple PDAC primary cells of which the matched patient-derived xenograft (PDX) models responded similarly to KH3 in the 2 wk treatment. The better responses to KH3 in PDXs were associated with higher expression of PGAM1 and longer/stronger suppressions of cancer metabolic pathways. Taken together, our findings demonstrate a strategy of targeting cancer metabolism by PGAM1 inhibition in PDAC. Also, this work provided "proof of concept" for the potential application of metabolic treatment in clinical practice.

Synthesis and biological evaluation of anthraquinone derivatives as allosteric phosphoglycerate mutase 1 inhibitors for cancer treatment.

Phosphoglycerate mutase 1 (PGAM1) coordinates glycolysis, pentose phosphate pathway, and serine synthesis to promote tumor growth through the regulation of its substrate 3-phosphoglycerate (3 PG) and product 2-phosphoglycerate (2 PG). Herein, based on our previously reported PGAM1 inhibitor PGMI-004A, we have developed anthraquinone derivatives as novel allosteric PGAM1 inhibitors and the structure-activity relationship (SAR) was investigated. In addition, we determined the co-crystal structure of PGAM1 and the inhibitor 8g, demonstrating that the inhibitor was located at a novel allosteric site. Among the derivatives, compound 8t was selected for further study, with IC50 values of 0.25 and approximately 5 µM in enzymatic and cell-based assays, respectively. Mechanistically, compound 8t reduced the glycolysis and oxygen consumption rate in cancer cells, which led to decreased adenosine 5'-triphosphate (ATP) production and subsequent 5' adenosine monophosphate-activated protein kinase (AMPK) activation. The inhibitor 8t also exhibited good efficacy in delaying tumor growth in H1299 xenograft model without obvious toxicity. Taken together, this proof-of-principle work further validates PGAM1 as a potential target for cancer therapy and provides useful information on anti-tumor drug discovery targeting PGAM1.

Water Environment Assessment as an Ecological Red Line Management Tool for Marine Wetland Protection.

A 'red line' was established, identifying an area requiring for ecological protection in Tianjin, China. Within the protected area of the red line area, the Qilihai wetland is an important ecotope with complex ecological functions, although the ecosystem is seriously disturbed due to anthropogenic activities in the surrounding areas. This study assesses the water quality status of the Qilihai wetlands to identify the pollution sources and potential improvements based on the ecological red line policy, to improve and protect the waters of the Qilihai wetlands. An indicator system was established to assess water quality status using single factor evaluation and a comprehensive evaluation method, supported by data from 2010 to 2013. Assessment results show that not all indicators met the requirement of the Environmental Quality Standards for Surface Water (GB3838-2002) and that overall, waters in the Qilihai wetland were seriously polluted. Based on these findings we propose restrictions on all polluting anthropogenic activities in the red line area and implementation of restoration projects to improve water quality.