Ophiobolin A Covalently Targets Mitochondrial Complex IV Leading to Metabolic Collapse in Cancer Cells.

Ophiobolin A (OPA) is a sesterterpenoid fungal natural product with broad anticancer activity. While OPA possesses multiple electrophilic moieties that can covalently react with nucleophilic amino acids on proteins, the proteome-wide targets and mechanism of OPA remain poorly understood in many contexts. In this study, we used covalent chemoproteomic platforms to map the proteome-wide reactivity of the OPA in a highly sensitive lung cancer cell line. Among several proteins that OPA engaged, we focused on two targets: lysine-72 of cytochrome c oxidase subunit 5A (COX5A) and cysteine-53 of mitochondrial hypoxia induced gene 1 domain family member 2A (HIGD2A). These two subunit proteins are part of complex IV (cytochrome C oxidase) within the electron transport chain and contributed significantly to the antiproliferative activity of OPA. OPA activated mitochondrial respiration in a COX5A- and HIGD2A-dependent manner, leading to an initial spike in mitochondrial ATP and heightened mitochondrial oxidative stress. OPA compromised mitochondrial membrane potential, ultimately leading to ATP depletion. We have used chemoproteomic strategies to discover a unique anticancer mechanism of OPA through activation of complex IV leading to compromised mitochondrial energetics and rapid cell death.

Enantioselective Total Synthesis of (-)-Caulamidine A.

Marine bryozoans continue to provide architecturally fascinating halogenated alkaloids that pose unique challenges for chemical synthesis. The antimalarial alkaloids caulamidines A and B, recently isolated from Caulibugula intermis, contain an intricate bis-amidine core and a chlorine-bearing neopentylic stereocenter. Compared to topologically similar C20 bis(cyclotryptamine) alkaloids, caulamidines possess an additional carbon atom of unknown biosynthetic origins, which renders their entire skeleton nonsymmetric and nondimeric. Herein, we report the first total synthesis of caulamidine A and confirm its absolute configuration. Key chemical findings include the exploitation of glycol bistriflate to facilitate a rapid, diastereoselective ketone-amidine annulation reaction and a highly diastereoselective hydrogen atom transfer to correctly establish the key chlorine-bearing stereogenic center.

Ultrasensitive Molecular Detection by Imaging of Centimeter-Scale Metasurfaces with a Deterministic Gradient Geometry.

Highly sensitive detection of trace amounts of substances is crucial for broad applications in healthcare, environmental monitoring, antiterrorism, etc., where cost effectiveness and portability are often demanded. Here, an ultrasensitive sensor is reported that can detect an angstrom-thick layer of adsorbed molecules through image acquisition and processing. The sensor features a centimeter-scale plasmonic metasurface with spatially varying geometry, where the light scattering is dependent on both the adsorbed substances and spatial locations. When illuminated with narrowband light (such as from a light emitting diode), the intensity pattern recorded on the metasurface changes with the surface-adsorbed molecules, enabling label-free, sensitive, and spectrometer-free molecular detection. The centimeter-scale size of the sensing area interfaces well with consumer-level imaging sensors on mobile devices without the need for microscopic optics and offers a high signal-to-noise ratio by leveraging the multimillion pixels for noise reduction. It is experimentally demonstrated that a single layer of Al2 O3 molecules deposited on the sensor, with a thickness of approximately one angstrom, can be detected by analyzing the images taken of the sensing chip. Furthermore, by integrating the sensor into a microfluidic setup, quantitative detection of BSA/anti-BSA immune complex formation events is demonstrated, which agrees well with the Langmuir isotherm model.

Gradient wettability induced by deterministically patterned nanostructures.

We report a large-scale surface with continuously varying wettability induced by ordered gradient nanostructures. The gradient pattern is generated from nonuniform interference lithography by utilizing the Gaussian-shaped intensity distribution of two coherent laser beams. We also develop a facile fabrication method to directly transfer a photoresist pattern into an ultraviolet (UV)-cured high-strength replication molding material, which eliminates the need for high-cost reactive ion etching and e-beam evaporation during the mold fabrication process. This facile mold is then used for the reproducible production of surfaces with gradient wettability using thermal-nanoimprint lithography (NIL). In addition, the wetting behavior of water droplets on the surface with the gradient nanostructures and therefore gradient wettability is investigated. A hybrid wetting model is proposed and theoretically captures the contact angle measurement results, shedding light on the wetting behavior of a liquid on structures patterned at the nanoscale.

P2X7 receptor regulates EMMPRIN and MMP­9 expression through AMPK/MAPK signaling in PMA­induced macrophages.

The rupture of atherosclerotic plaques may result in the formation of thrombi, which may induce subsequent cardiac events such as acute myocardial infarction. Overproduction of matrix metalloproteinases (MMPs) and extracellular matrix metalloproteinase inducers (EMMPRINs) by monocytes and macrophages may lead to rupture of atherosclerotic plaques as a result of the degradation of the extracellular matrix. The purinergic 2X7 receptor (P2X7R) is expressed in macrophages that are assembled in atherosclerotic lesions of human carotid arteries. P2X7R may serve a crucial role in the development of atherosclerosis; therefore, the present study aimed to determine whether P2X7R regulated the expression of EMMPRIN and MMP­9 in phorbol 12­myristate 13­acetate (PMA)­induced macrophages. In addition, the potential molecular mechanisms involved in this process were investigated. THP­1 human monocytic cells were pretreated with A­438079 (a specific inhibitor of P2X7R) for 1 h and subsequently incubated with or without PMA for 48 h. Exposure to A­438079 significantly decreased the expression of MMP­9 and EMMPRIN in the PMA­induced macrophages and attenuated the activation (phosphorylation) of mitogen­activated protein kinase (MAPK) signaling, including c­Jun N­terminal kinase, p38 and extracellular signal­regulated kinase. The present study also demonstrated that 5'­AMP­activated protein kinase (AMPK) was activated by PMA exposure during differentiation from monocytes to macrophages. This activation was reversed by A­438079 treatment through the inhibition of P2X7R expression. These results suggested that the inhibition of P2X7R may be able to suppress the AMPK/MAPK signaling pathway and consequently downregulate both EMMPRIN and MMP­9 expression in PMA­induced macrophages.

Wafer-scale nanopatterning using fast-reconfigurable and actively-stabilized two-beam fiber-optic interference lithography.

A fast-reconfigurable and actively-stabilized fiber-optic interference lithography system is demonstrated in this paper. Employment of fiber-optic components greatly enhances the flexibility of the whole system, simplifies its optical alignment, and suppresses the interference of mechanical vibrations. Active stabilization is implemented in the system and evaluated through modeling and experiment. We demonstrate 3-inch-diameter wafer-scale patterning of 240-nm-period grating lines with a sub-50-nm linewidth and an aspect ratio over 3. Two-dimensional patterns of different geometries and dimensions are also demonstrated to show the versatility of our system. Step-and-repeat exposure is demonstrated with independently controlled patterning fields of 2×2cm2 large.

Photophysical Tuning of N-Oxide-Based Probes Enables Ratiometric Photoacoustic Imaging of Tumor Hypoxia.

Hypoxia results when the oxygen supply to rapidly growing tumors becomes inadequate to support various physiological processes. This plays a role in tumor metastasis and treatment resistance. Therefore, identifying tumor hypoxia can guide treatment planning and predict patient responses. However, hypoxic volumes are heterogeneously dispersed throughout a tumor, making it a challenge to pinpoint them with any degree of accuracy. Herein, we report the development of ratiometric hypoxia probe 1 (rHyP-1), which is a hypoxia-responsive small-molecule probe designed for reliable hypoxia detection using photoacoustic imaging. Photoacoustic imaging utilizes near-infrared (NIR) light to induce the production of ultrasound signals, enabling high-resolution image acquisition at centimeter depths. Together with the ratiometric capability of rHyP-1, reliable hypoxia detection with unprecedented spatial resolution is possible while minimizing error associated with concentration dependence and tissue heterogeneity.

Inhibition of autophagy by berberine enhances the survival of H9C2 myocytes following hypoxia.

Hypoxia may induce apoptosis and autophagy to promote cardiomyocyte injury. The present study investigated the effect of berberine, a natural extract of Rhizoma Coptidis, on hypoxia­induced autophagy and apoptosis in the H9c2 rat myocardial cell line. Expression levels of apoptosis and autophagy markers were upregulated in H9c2 myocytes during hypoxia and cell viability was reduced. However, berberine significantly reduced hypoxia­induced autophagy in H9c2 myocytes, as demonstrated by the ratio of microtubule­associated proteins 1A/1B light chain 3 I/II and the expression levels of B­cell lymphoma 2 (Bcl­2)/adenovirus E1B 19 kDa protein­interacting protein 3, and promoted cell viability. In addition, expression levels of the Bcl­2 anti­apoptotic protein were significantly downregulated, and expression levels of pro­apoptotic proteins Bcl­2­associated X protein and cleaved caspase­3 were upregulated during hypoxia injury in cardiac myocytes. This was reversed by treatment with berberine or the autophagy inhibitor 3­methyladenine, whereas the autophagy agonist rapamycin had the opposite effects, suggesting that berberine reduces myocyte cell death via inhibition of autophagy and apoptosis during hypoxia. In addition, Compound C, a 5' adenosine monophosphate­activated protein kinase (AMPK) inhibitor, reduced apoptosis and autophagy in hypoxic myocytes, suggesting that the activation of the AMPK signaling pathway may be involved in this process. These findings suggested that berberine protects cells from hypoxia­induced apoptosis via inhibition of autophagy and suppression of AMPK activation. Therefore, berberine may be a potential therapeutic agent for the treatment of patients with cardiac myocyte injury and ischemia.