Spotlight pubs.acs.org/crt
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ENTOMOPATHOGENIC FUNGUS ACTIVATES OPPORTUNISTIC GUT MICROBIOTA FOR RAPID MOSQUITO MORTALITY As mosquitoes are vectors for a wide range of pathogens, methods of mosquito control are important for public health. The entomopathogenic fungus Beauveria bassiana is effective at killing mosquitoes but works relatively slowly compared to chemical insecticides. As gut microbiota in the mosquito can impact pathogenic infection, a team led by Sibao Wang examined the interaction between B. bassiana and the gut microbiota of the Anopheles stephensi mosquito ((2017) PNAS, 114, 5994−5999). The scientists treated mosquitoes with oral antibiotics to eliminate gut microbiota, then sprayed treated (axenic) and nontreated (nonaxenic) mosquitoes with B. bassiana. They found that nonaxenic mosquitoes died significantly faster (∼15 h) than their axenic counterparts, suggesting that B. bassiana pathogenicity is accelerated by gut microbiota. The researchers discovered that B. bassianainfected mosquitoes had a significant increase (∼3.7-fold) in midgut bacteria at 90 h.p.i. compared to that in uninfected mosquitoes. Specifically, there was a 3.4-fold increase in the bacteria Serratia marcescens which can act as an opportunistic pathogen. Feeding S. marcescens to axenic mosquitoes restored their vulnerability to B. bassiana infection. The authors found that fungal infection caused the overgrown S. marcescens to translocate from the midgut to the hemocoel. Injection of S. marcescens isolated from fungus-infected mosquitoes into the hemocoels of other mosquitoes resulted in a 1 d mortality rate of 94.5%, compared to a 5 d mortality rate of 3.6% following hemocoelic injection of an avirulent symbiont. This suggests that S. marcescens translocation to the hemocoel caused the opportunistic bacteria to become pathogenic. Overproliferation and subsequent translocation of S. marcescens might be facilitated by B. bassiana oosporein production; this toxin downregulates the expression of dual oxidase in the midgut of mosquitoes, causing a decreased immune response and dysbiosis of the midgut microbiota in the guts of infected mosquitoes. Abigail Druck Shudofsky
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was similar to that of the azole drug fluconazole (FLC). Neither probe 1 nor FLC inhibited the growth of a mutant lacking copies of the gene encoding the target cytochrome P450. The scientists then monitored probe 1 localization in C. albicans for 2 h after exposure using fluorescence microscopy. Probe 1 strongly colocalized with a mitochondrion-specific dye, in accordance with research suggesting that mitochondrial dysfunction alters azole susceptibility. This innovative work provides visual data for azole antifungal subcellular localization and can be used as a molecular tool to study the biological properties of azole antifungals and to guide future drug design. Abigail Druck Shudofsky
FLUORESCENT AZOLE PROBE ALLOWS REAL-TIME VISUALIZATION OF ANTIFUNGAL DRUGS IN LIVE CELLS
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Reprinted from Benhamou, R. I., Bibi, M., et al. (2017) ACS Chem. Biol., DOI: 10.1021/acschembio.7b00339. Copyright 2017 American Chemical Society.
Azole drugs are a first-line treatment against invasive fungal infections. These compounds target a cytochrome P450 enzyme that is required for the biosynthesis of ergosterol, an essential component of the yeast cell membrane. As the uptake and intracellular localization mechanisms of azole antifungals are unclear, a team led by Judith Berman and Micha Fridman designed and synthesized an azole-based fluorescent probe to study drug uptake, localization, activity, and efflux ((2017) ACS Chem. Biol., DOI: 10.1021/acschembio.7b00339). The conserved azole core structure is composed of a triazole or imidazole ring and a meta-dihalogenated phenyl ring. The authors conjugated the fluorescent dye dansyl (ex, ∼340 nm; em, ∼520 nm) to the triazole-containing core structure (probe 1). In silico docking computations indicated that probe 1 could occupy the target cytochrome P450 active site. The researchers determined that the antifungal activity of probe 1 against Candida albicans and Candida glabrata isolates © 2017 American Chemical Society
HYBRID SELF-HEALING STRUCTURAL COLOR HYDROGEL
Reprinted with permission from Fu, F., Chen, Z., Zhao, Z., Wang, H., Shang, L., Gu, Z., and Zhao, Y. Bioinspired SelfHealing Structural Color Hydrogel. (2017) PNAS, 114 (23) 5900−5905. Published: July 17, 2017 1367
DOI: 10.1021/acs.chemrestox.7b00168 Chem. Res. Toxicol. 2017, 30, 1367−1368
Chemical Research in Toxicology
Spotlight
The authors discovered a second generation irreversible Pol β inhibitor, 13, whose structure is based upon a previously identified molecule which inactivated the lyase activity of Pol β. 13 was obtained by screening a chemical library of 130 Pol β inhibitor candidates for inhibition of Pol β-mediated strand displacement synthesis. When 3 μM 13 was preincubated with Pol β for 30 min, the polymerase lost 99% of its lyase ability. A proinhibitor (pro-13) sensitized HeLa cells to the alkylating DNA damaging agent MMS, increasing its cytotoxicity ∼13-fold. This synergistic potentiation occurs through inhibition of DNA lesion repair; there was a ∼ 3-fold increase in abasic sites in DNA isolated from HeLa cells treated with both MMS and pro-13 compared to that of cells treated with MMS alone. Furthermore, the scientists found that the presence of pro-13 continued to induce significant cytotoxicity (∼100-fold) in cells even after MMS is removed. These results suggest that Pol β inhibitors can be powerful adjuvants for use with DNA damaging agents. Abigail Druck Shudofsky
Structural colors result not from pigments but from periodic photonic surface nanostructures that interact with light of certain wavelengths. Structural color hydrogels have limited survivability due to deterioration and damage accumulation; the self-healing fusion process can destroy photonic scaffolds in the nanostructure and result in color loss. A group led by Yuanjin Zhao used a composite polymer and protein nanostructure to develop a self-healing structural color hydrogel which retains its color ((2017) PNAS, 114, 5900−5905). The authors constructed the scaffold utilizing silica colloidal crystal templates which form an ordered structure with interconnected nanopores. They filled the template voids using a methacrylated gelatin (GelMA) pregel solution that polymerizes into a hydrogel upon UV light exposure. They then etched the silica nanoparticles with hydrofluoric acid to obtain an inverse opal scaffold. The GelMA scaffold ensured the stability of the inverse opal structure and resultant structural colors. The scientists then prepared a pregel composed of bovine serum albumin (BSA), glutaraldehyde, catalase, and glucose oxidase. This BSA protein filler provides self-healing capability as glutaraldehyde covalently attaches to the lysine residues of the proteins. Reversible imine bonding is maintained as the additive enzymes adjust the system pH in the presence of glucose and allow the protein hydrogel to heal. After the researchers immersed the dehydrated structure color hydrogel into the protein pregel solution, the glutaraldehyde cross-linked BSA hydrogel filler polymerized and filled the inverse opal scaffold, resulting in a colored hybrid hydrogel with a unique photonic band gap. Different sizes of silica nanoparticles result in different structural colors, and the researchers found that glucose could bond together scaffolds with differing nanometer aperture sizes. Composite structural color hydrogel elements can be assembled together and healed, resulting in stable flexible structures that can be used to construct 1D, 2D, and 3D materials. Abigail Druck Shudofsky
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ROCAGLATE DERIVATIVE INHIBITS ONCOGENE TRANSLATION AND SUPPRESSES MULTIPLE MYELOMA
Courtesy of Dr. Salomon Manier.
A large proportion of patients with the blood malignancy multiple myeloma (MM) have increased expression of the transcription factor MYC. MYC overactivity correlates with upregulated ribosomal production and protein translation. A team led by Irene M. Ghobrial and Salomon Manier identified a potent small-molecule inhibitor which interferes with MYC activation and MM oncogene translation ((2017) Sci. Transl. Med. 9, eaal2668). The authors screened a chemically diverse small-molecule library against two lymphoid cell lines with high MYC expression and then validated hits by testing them against five MM cell lines. Out of 2812 compounds, the three that most potently inhibited MM cell proliferation were all synthetic analogues of the rocaglate natural product class which inhibits protein synthesis. A structure−activity relationship study with 40 structurally related compounds identified CMLD010509, which had an IC50 of
