Medium-Chain Lipid Conjugation Facilitates Cell-Permeability and Bioactivity

Fast unmasking toxicity of safe personal care products

Personal care products are used several times a day and come into contact with the skin for many hours. As hazard-related data on products are rare, an imaging safety screening was developed. For the first time, it detected known and unknown hazardous compounds in 140 personal care products from 20 different product segments, including beauty and lifestyle products. The evidence-based chromatographic-hazard-related profiling detected genotoxic, cytotoxic, and estrogenic compounds, which were assigned to structural groups, and revealed that personal care products are not as safe as stated. Wound-healing and nipple creams in contact with babies as well as lipsticks used by adolescents were shown to contain highly toxic compounds able to enter the bloodstream via wounds, micro-injuries or bleeding gums and contaminate nature when washed off. Dose-response curves pointed to half-maximal genotoxic effect doses (EC50) of around 60 µg of such products which can easily be exceeded by a factor of 100,000 for only 6 g product applied or for an aggregated use of various products increasing genotoxic exposure, as observed in consumer profiles. Simulated metabolization via S9 liver enzymes did not lead to detoxification. The new safety screening not only unmasked quickly the toxicity of personal care products but also provided an understanding of how to produce hazard-free products. It empowers industries to produce future products in compliance with their standards and claims in terms of consumer health, ethics, environmental compatibility, and sustainability, and authorities to control the safety of products on the market and tackle the current underregulation.

Iterative Optimization Yields Stapled Peptides with Superior Pharmacokinetics and Potency for Renal Fibrosis Treatment

Renal fibrosis, resulting from myofibroblast-mediated excessive extracellular matrix (ECM) deposition, lacks effective treatments. Novel peptide DR3penA developed by our group showed therapeutic potential for fibrotic diseases; however, its application was hindered by poor stability and bioavailability. To address this unmet need, we implemented stepwise optimization of DR3penA. The conformationally restricted analogs designed via structural predictions enhanced both activity and stability. Through structure-activity relationship analysis and cleavage site mapping, introducing unnatural amino acids improved stability. Fatty acid modifications conferred fibroblast-selective cytotoxicity and improved pharmacokinetics. After several rounds of progressive modification, peptide 27 exhibited remarkable stability, with a 5.68-fold extended half-life compared to DR3penA. Following profibrotic stimuli, peptide 27 effectively inhibited myofibroblast activation, epithelial-mesenchymal transition, and ECM synthesis. It also attenuated renal fibrosis in a unilateral ureteral obstruction model. Our study leverages multiple modifications that integrate cell and animal models to identify peptide 27 as a promising candidate for renal fibrosis therapy.

A sequential esterification-ring closing metathesis-Nozaki-Hiyama-Kishi strategy for constructing a natural product-like library of tetrahydrofuran-containing macrolides

Polyketide-like macrolides (pMLs) represent a privileged class of compounds with a high incidence of bioactivity, however their structural complexity challenges their synthesis and more general study. Here we report the synthesis of a library of tetrahydrofuran-containing pMLs underpinned by a robust and convergent build/couple/pair/couple synthetic approach. The library comprises 170 pMLs originating from 17 building blocks, 10 of which were synthesized using a proline-catalyzed α-chlorination aldol reaction. Northern and southern hemisphere building blocks were coupled using either an oxidation/Horner-Wadsworth-Emmons sequence or a saponification/Steglich esterification strategy. Coupled fragments were cyclized via ring closing metathesis to yield macrocycles 14-16 atoms in size, which we diversified using 3 eastern side chain vinyl iodides through a Nozaki-Hiyama-Kishi reaction.

Design, synthesis and structure-activity relationship of novel 1,2,4-triazolopyrimidin-5-one derivatives targeting GABAA1 and Nav1.2 with antiepileptic activity

A novel class of 7-phenyl-[1,2,4]triazol-5(4H)-one derivatives was designed and synthesized, and their in vivo anticonvulsant activities were evaluated using subcutaneous pentylenetetrazole (Sc-PTZ) and maximal electroshock (MES) tests. Compounds 3u, 4f and 4k exhibited significant anticonvulsant activities in the Sc-PTZ model with ED50 values of 23.7, 17.1 and 18.3 mg/kg, respectively. Neurotoxicity was accessed using the rotarod assay and none of the compounds demonstrated neurotoxicity at maximum solubility, with all TD50 values exceeding 267 mg/kg. This resulted in protective indexes (PI = TD50/ED50) values of greater than 11.3, 15.6 and 14.6, respectively. Compared to control drugs such as sodium phenytoin, sodium valproate, and carbamazepine, compounds 3u, 4f and 4k displayed superior anticonvulsant activities and reduced neurotoxicity. Mechanism results indicated that compounds 4k and 4f were sensitive to the subunit configuration of synaptic α1β2γ2 GABAA receptors, while compounds 3u and 4f dose-dependently reduced the peak amplitude of Nav1.2 currents. These structural compounds may provide a foundation for the further design of novel antiepileptic molecules with low neurotoxicity.

The Optimized Lipid-Modified Prodrug for CNV Treatment

Choroidal neovascularization (CNV) is a prevalent cause of vision impairment. The primary treatment for CNV involves intravitreal injections of anti-vascular endothelial growth factor antibodies. Nevertheless, this approach still faces numerous limitations like poor patient compliance, high therapy expenditure and lack of response in some individuals. Herein, a series of anti-neovascularization prodrugs, SU5402 (SU), modified with lipids of varying chain lengths (C12, C16, C20, C24, C28) is synthesized (SU-C12, SU-C16, SU-C20, SU-C24, SU-C28). 1% polyvinyl alcohol (PVA) is used as a stabilizer to create nanoformulations of five prodrugs named SU-C12 NPs, SU-C16 NPs, SU-C20 NPs, SU-C24 NPs, SU-C28 NPs. Among these, SU-C20 NPs significantly prolong the retention of bioactive drug in the eye for up to 70 d. Moreover, SU-C20 NPs demonstrate superior tissue permeability via enhanced cellular endocytosis and exocytosis. With its prolonged retention and improved penetration, SU-C20 NPs reduce the fluorescence intensity of fundus leakage by 42.5% and the fluorescence area by 51.5% in CNV mice after four weeks, effectively inhibiting the progression of CNV. Altogether, small molecule drug SU is innovatively modified to improve its effectiveness for treating fundus neovascular diseases, proposing an alternative therapy for wet age-related macular degeneration (wAMD).

Multifunctional Zwitterionic N-Oxide Polymers to Overcome Cascade Physiological Barriers for Efficient Anticancer Drug Delivery

For efficient anticancer drug delivery, cascade physiological barriers must be overcome, which requires the drug delivery vehicles to possess different or even opposite properties at different stages. Poly(tertiary amine-oxide) (PTAO) polymers with the zwitterionic feature have distinct antifouling properties in blood circulation, which can be reduced and protonated in hypoxic tumors to promote cellular internalization. Nevertheless, the effects of various PTAO structures have not been studied systemically and optimized. In this report, the side groups of PTAO are proposed to be optimized by modulating the structures. Poly(2-(N-oxide-hexamethyleneimino)ethyl methacrylate) (POC7A) with a cyclic seven-membered ring is screened as the optimized PTAO structure for in vivo applications. Moreover, the block copolymer POC7A-block-poly(ε-caprolactone) (POC7A-PCL) is prepared for the formation of micelles in aqueous solution for delivery of doxorubicin (DOX). The zwitterionic nature of POC7A shells with efficient bioreductive activity and protonation in the tumor microenvironment endows the micelles with excellent antifouling properties for long blood circulation, efficient tumor accumulation, deep penetration, and effective cellular internalization. Thus, the DOX-loaded micelles exhibit potent antitumor efficacy after intravenous administration. Zwitterionic POC7A can be used as antifouling shells of the anticancer drug delivery nanocarriers to overcome the cascade physiological barriers efficiently.

Mitochondria-targeting artesunate-rhein conjugates: Linker-modulated cell-permeability, heme-affinity and anticancer activity

Heme, abundant in the mitochondria of cancer cells, is a key target for the anticancer activity of artemisinin (ART). Current strategies to enhance the anticancer activity of ART focus solely on its delivery to heme-enriched subcellular localizations while overlooking the decisive effects of ART-heme interactions. Here, we propose an ingenious strategy that synergizes mitochondria-targeted drug delivery and linker-mediated drug conformation modulation, thereby significantly enhancing the anticancer activity of ART. By strategically conjugating artemisinin (ART) with the mitochondria-targeting rhein (R) using different linkers, we aimed to precisely adjust the conformation of the conjugates. Comprehensive computational analysis revealed that the conjugate with the optimal linker length (C4) displayed a favorable conformation that facilitated cell permeability and exhibited the highest binding affinity to heme and Fe ions. Moreover, it exhibited superior tumor suppression capabilities both in vitro and in vivo, overcoming the uncertainty of in vivo application caused by the rapid clearance of the conventional mitochondria-targeted cation TPP+, and even inducing immunogenic cell death associated with immunotherapy. This novel strategy opens up a new avenue for the development of drug conjugate systems.

Navigating a 1E+60 Chemical Space of Peptide/Peptoid Oligomers

Herein we report a virtual library of 1E+60 members, a common estimate for the total size of the drug-like chemical space. The library is obtained from 100 commercially available peptide and peptoid building blocks assembled into linear or cyclic oligomers of up to 30 units, forming molecules within the size range of peptide drugs and potentially accessible by solid-phase synthesis. We demonstrate ligand-based virtual screening (LBVS) using the peptide design genetic algorithm (PDGA), which evolves a population of 50 members to resemble a given target molecule using molecular fingerprint similarity as fitness function. Target molecules are reached in less than 10,000 generations. Like in many journeys, the value of the chemical space journey using PDGA lies not in reaching the target but in the journey itself, here by encountering non-obvious analogs. We also show that PDGA can be used to generate median molecules and analogs of non-peptide target molecules.

γ-Secretase Cleaves Bifunctional Fatty Acid-Conjugated Small Molecules with Amide Bonds in Mammalian Cells

Connecting two small molecules, such as ligands, fluorophores, or lipids, together via a linker with amide bonds is a widely used strategy to generate synthetic bifunctional molecules for various biological and biomedical applications. Such bifunctional molecules have been used in live-cell experiments under the assumption that they should be stable in cells. However, we recently found that a membrane-targeting bifunctional molecule, composed of a lipopeptide and the small-molecule ligand trimethoprim, referred to as mgcTMP, underwent amide-bond cleavage in mammalian cells. In this work, we first identified γ-secretase as the major protease degrading mgcTMP in cells. We next investigated the intracellular degradation of several different types of amide-linked bifunctional compounds and found that N-terminally fatty acid-conjugated small molecules are susceptible to γ-secretase-mediated amide-bond cleavage. In contrast, amide-linked bifunctional molecules composed of two small molecules, such as ligands and hydrophobic groups, which lack lipid modification, did not undergo intracellular degradation. These findings highlight a previously overlooked consideration for the development and application of lipid-based bifunctional molecules in chemical biology research.

Side-chain-engineered fluorescent dyes for 3D and long-term dynamic tracking of the plasma membrane in living cells

The plasma membrane involves in many important biological events such as cell fusion and programmed cell death, but most of current plasma membrane probes cannot meet the requirement of long-term specific anchoring to the plasma membrane. Herein, we propose a molecular side-chain engineering strategy to modulate the long-term imaging performance of fluorescent dyes to the plasma membrane by regulating the cell permeability and anchoring ability. A series of FMR dyes with different lengths of side chains were designed and synthesized, and their transmembrane behaviours and staining performance were evaluated in living HeLa cells. We found that short-chain and medium-chain FMR dyes have excellent cell permeability without the labeling ability to the plasma membrane while the long-chain FMR dyes specifically stain the plasma membrane and can be firmly anchored to the plasma membrane for a long period of time. These long-chain FMR dyes have high stain specificality to the plasma membrane, and C10-FMR can be anchored to the plasma membrane of living cells for 2 h, which enables it to continuously monitor dynamic changes of the plasma membrane. The three-dimensional precision imaging of various cells was achieved using C10-FMR, which provides an opportunity to obtain complete information on the three-dimensional spatial morphology of the plasma membrane. The PEG-induced cell fusion of chicken red blood cells and H2O2-induced apoptosis of HeLa cells were monitored by real-time tracking of dynamic changes of the plasma membrane during these processes, which provide solid examples to prove the usefulness of these fluorescent dyes as long-term imaging tools. This work validates the hypothesis that cell permeability of membrane dyes can be readily regulated by tuning the side chains, and provides the effective design strategy of fluorescent dyes for 3D and long-term dynamic tracking of the plasma membrane of diverse animal cells.

Minimizing higher-order aggregation maximizes iron mobilization by small molecules

The natural product hinokitiol mobilizes iron across lipid bilayers at low concentrations and restores hemoglobinization in iron transporter protein-deficient systems. But hinokitiol fails to similarly mobilize iron at higher concentrations, limiting its uses in chemical biology and medicine. Here we show that at higher concentrations, hinokitiol3:Fe(III) complexes form large, higher-order aggregates, leading to loss of transmembrane iron mobilization. Guided by this understanding and systematic structure-function studies enabled by modular synthesis, we identified FeM-1269, which minimally aggregates and dose-dependently mobilizes iron across lipid bilayers even at very high concentrations. In contrast to hinokitiol, FeM-1269 is also well-tolerated in animals at high doses for extended periods of time. In a mouse model of anemia of inflammation, FeM-1269 increases serum iron, transferrin saturation, hemoglobin and hematocrit. This rationally developed iron-mobilizing small molecule has enhanced potential as a molecular prosthetic for understanding and potentially treating iron transporter deficiencies.

Wash-Free Bacterial Gram-Typing and Photodynamic Inactivation with Long-Chain-Tailed BODIPY Derivatives

The rapid identification of bacterial Gram types and their viability, as well as efficient bacterial elimination are crucial for managing bacterial infections yet present important challenges. In this research, we utilized long-chain-tailed BODIPY derivatives to address these hurdles. Our data indicated that these derivatives can distinguish bacteria types and their viability in aqueous solutions through a concise turn-on fluorescent response. Among them, B-8 stained both live and dead bacteria, and B-14 offered a wash-free staining. B-18 demonstrated the highest affinity to selectively fluorescent label viable gram-positive bacteria with a 53.2-fold fluorescent enhancement. Confocal imaging confirmed that B-18 can serve as an effective membrane-specific probe for facilitating the typing between gram-negative and gram-positive bacteria in a wash-free manner. Additionally, B-18 displayed selective photodynamic inactivation at 1 μM toward gram-positive bacteria. In vivo studies variformed the ideal photodynamic therapeutic efficacy of B-18 against methicillin-resistant Staphylococcus aureus in mice wound infections.

Engineering Novel Amphiphilic Platinum(IV) Complexes to Co-Deliver Cisplatin and Doxorubicin

In this study, we report a novel platinum-doxorubicin conjugate that demonstrates superior therapeutic indices to cisplatin, doxorubicin, or their combination, which are commonly used in cancer treatment. This new molecular structure (1) was formed by conjugating an amphiphilic Pt(IV) prodrug of cisplatin with doxorubicin. Due to its amphiphilic nature, the Pt(IV)-doxorubicin conjugate effectively penetrates cell membranes, delivering both cisplatin and doxorubicin payloads intracellularly. The intracellular accumulation of these payloads was assessed using graphite furnace atomic absorption spectrometry and fluorescence imaging. Since the therapeutic effects of cisplatin and doxorubicin stem from their ability to target nuclear DNA, we hypothesized that the amphiphilic Pt(IV)-doxorubicin conjugate (1) would effectively induce nuclear DNA damage toward killing cancer cells. To test this hypothesis, we used flow the cytometric analysis of phosphorylated H2AX (γH2AX), a biomarker of nuclear DNA damage. The Pt(IV)-doxorubicin conjugate (1) markedly induced γH2AX in treated MDA-MB-231 breast cancer cells, showing higher levels than cells treated with either cisplatin or doxorubicin alone. Furthermore, MTT cell viability assays revealed that the enhanced DNA-damaging capability of complex 1 resulted in superior cytotoxicity and selectivity against human cancer cells compared to cisplatin, doxorubicin, or their combination. Overall, the development of this amphiphilic Pt(IV)-doxorubicin conjugate represents a new form of combination therapy with improved therapeutic efficacy.

Biguanide-Vancomycin Conjugates are Effective Broad-Spectrum Antibiotics against Actively Growing and Biofilm-Associated Gram-Positive and Gram-Negative ESKAPE Pathogens and Mycobacteria

Strategies to increase the efficacy and/or expand the spectrum of activity of existing antibiotics provide a potentially fast path to clinically address the growing crisis of antibiotic-resistant infections. Here, we report the synthesis, antibacterial efficacy, and mechanistic activity of an unprecedented class of biguanide-antibiotic conjugates. Our lead biguanide-vancomycin conjugate, V-C6-Bg-PhCl (5e), induces highly effective cell killing with up to a 2 orders-of-magnitude improvement over its parent compound, vancomycin (V), against vancomycin-resistant enterococcus. V-C6-Bg-PhCl (5e) also exhibits improved activity against mycobacteria and each of the ESKAPE pathogens, including the Gram-negative organisms. Furthermore, we uncover broad-spectrum killing activity against biofilm-associated Gram-positive and Gram-negative bacteria as well as mycobacteria not observed for clinically used antibiotics such as oritavancin. Mode-of-action studies reveal that vancomycin-like cell wall synthesis inhibition with improved efficacy attributed to enhanced engagement at vancomycin binding sites through biguanide association with relevant cell-surface anions for Gram-positive and Gram-negative bacteria. Due to its potency, remarkably broad activity, and lack of acute mammalian cell toxicity, V-C6-Bg-PhCl (5e) is a promising candidate for treating antibiotic-resistant infections and notoriously difficult-to-treat slowly growing and antibiotic-tolerant bacteria associated with chronic and often incurable infections. More generally, this study offers a new strategy (biguanidinylation) to enhance antibiotic activity and facilitate clinical entry.

Molecular engineering of fluorescent dyes for long-term specific visualization of the plasma membrane based on alkyl-chain-regulated cell permeability

Long-term visualization of changes in plasma membrane dynamics during important physiological processes can provide intuitive and reliable information in a 4D mode. However, molecular tools that can visualize plasma membranes over extended periods are lacking due to the absence of effective design rules that can specifically track plasma membrane fluorescent dye molecules over time. Using plant plasma membranes as a model, we systematically investigated the effects of different alkyl chain lengths of FMR dye molecules on their performance in imaging plasma membranes. Our findings indicate that alkyl chain length can effectively regulate the permeability of dye molecules across plasma membranes. The study confirms that introducing medium-length alkyl chains improves the ability of dye molecules to target and anchor to plasma membranes, allowing for long-term imaging of plasma membranes. This provides useful design rules for creating dye molecules that enable long-term visualization of plasma membranes. Using the amphiphilic amino-styryl-pyridine fluorescent skeleton, we discovered that the inclusion of short alkyl chains facilitated rapid crossing of the plasma membrane by the dye molecules, resulting in staining of the cell nucleus and indicating improved cell permeability. Conversely, the inclusion of long alkyl chains hindered the crossing of the cell wall by the dye molecules, preventing staining of the cell membrane and demonstrating membrane impermeability to plant cells. The FMR dyes with medium-length alkyl chains rapidly crossed the cell wall, uniformly stained the cell membrane, and anchored to it for a long period without being transmembrane. This allowed for visualization and tracking of the morphological dynamics of the cell plasma membrane during water loss in a 4D mode. This suggests that the introduction of medium-length alkyl chains into amphiphilic fluorescent dyes can transform them from membrane-permeable fluorescent dyes to membrane-staining fluorescent dyes suitable for long-term imaging of the plasma membrane. In addition, we have successfully converted a membrane-impermeable fluorescent dye molecule into a membrane-staining fluorescent dye by introducing medium-length alkyl chains into the molecule. This molecular engineering of dye molecules with alkyl chains to regulate cell permeability provides a simple and effective design rule for long-term visualization of the plasma membrane, and a convenient and feasible means of chemical modification for efficient transmembrane transport of small molecule drugs.

Isoprenoid CARTs: In Vitro and In Vivo mRNA Delivery by Charge-Altering Releasable Transporters Functionalized with Archaea-inspired Branched Lipids

The delivery of oligonucleotides across biological barriers is a challenge of unsurpassed significance at the interface of materials science and medicine, with emerging clinical utility in prophylactic and therapeutic vaccinations, immunotherapies, genome editing, and cell rejuvenation. Here, we address the role of readily available branched lipids in the design, synthesis, and evaluation of isoprenoid charge-altering releasable transporters (CARTs), a pH-responsive oligomeric nanoparticle delivery system for RNA. Systematic variation of the lipid block reveals an emergent relationship between the lipid block and the neutralization kinetics of the polycationic block. Unexpectedly, iA21A11, a CART with the smallest lipid side chain, isoamyl-, was identified as the lead isoprenoid CART for the in vitro transfection of immortalized lymphoblastic cell lines. When administered intramuscularly in a murine model, iA21A11-mRNA complexes induce higher protein expression levels than our previous lead CART, ONA. Isoprenoid CARTs represent a new delivery platform for RNA vaccines and other polyanion-based therapeutics.

Lanosterol regulates abnormal amyloid accumulation in LECs through the mediation of cholesterol pathway metabolism

Age-related cataract (ARC) is the predominant cause of global blindness, linked to the progressive aging of the lens, oxidative stress, perturbed calcium homeostasis, hydration irregularities, and modifications in crystallin proteins. Currently, surgical intervention remains the sole efficacious remedy, albeit carrying inherent risks of complications that may culminate in irreversible blindness. It is urgent to explore alternative, cost-effective, and uncomplicated treatment modalities for cataracts. Lanosterol has been widely reported to reverse cataracts, but the mechanism of action is not yet clear. In this study, we elucidated the mechanism through which lanosterol operates in the context of cataract reversal. Through the targeted suppression of sterol regulatory element-binding protein 2 (SREBP2) followed by lanosterol treatment, we observed the restoration of lipid metabolism disorders induced by SREBP2 knockdown in lens epithelial cells (LECs). Notably, lanosterol exhibited the ability to effectively counteract amyloid accumulation and cellular apoptosis triggered by lipid metabolism disorders. In summary, our findings suggest that lanosterol, a pivotal intermediate in lipid metabolism, may exert its therapeutic effects on cataracts by influencing lipid metabolism. This study shed light on the treatment and pharmaceutical development targeting Age-related Cataracts (ARC).

Rational Identification of Novel Antibody-Drug Conjugate with High Bystander Killing Effect against Heterogeneous Tumors

Bystander-killing payloads can significantly overcome the tumor heterogeneity issue and enhance the clinical potential of antibody-drug conjugates (ADC), but the rational design and identification of effective bystander warheads constrain the broader implementation of this strategy. Here, graph attention networks (GAT) are constructed for a rational bystander killing scoring model and ADC construction workflow for the first time. To generate efficient bystander-killing payloads, this model is utilized for score-directed exatecan derivatives design. Among them, Ed9, the most potent payload with satisfactory permeability and bioactivity, is further used to construct ADC. Through linker optimization and conjugation, novel ADCs are constructed that perform excellent anti-tumor efficacy and bystander-killing effect in vivo and in vitro. The optimal conjugate T-VEd9 exhibited therapeutic efficacy superior to DS-8201 against heterogeneous tumors. These results demonstrate that the effective scoring approach can pave the way for the discovery of novel ADC with promising bystander payloads to combat tumor heterogeneity.

Targeted sampling of natural product space to identify bioactive natural product-like polyketide macrolides

Polyketide or polyketide-like macrolides (pMLs) continue to serve as a source of inspiration for drug discovery. However, their inherent structural and stereochemical complexity challenges efforts to explore related regions of chemical space more broadly. Here, we report a strategy termed the Targeted Sampling of Natural Product space (TSNaP) that is designed to identify and assess regions of chemical space bounded by this important class of molecules. Using TSNaP, a family of tetrahydrofuran-containing pMLs are computationally assembled from pML inspired building blocks to provide a large collection of natural product-like virtual pMLs. By scoring functional group and volumetric overlap against their natural counterparts, a collection of compounds are prioritized for targeted synthesis. Using a modular and stereoselective synthetic approach, a library of polyketide-like macrolides are prepared to sample these unpopulated regions of pML chemical space. Validation of this TSNaP approach by screening this library against a panel of whole-cell biological assays, reveals hit rates exceeding those typically encountered in small molecule libraries. This study suggests that the TSNaP approach may be more broadly useful for the design of improved chemical libraries for drug discovery.

Synthesis of Triphenylphosphonium-Linked Derivative of 3,5-Ditert-butyl-4-hydroxybenzylidene-malononitrile (SF6847) via Knoevenagel Reaction Yields an Effective Mitochondria-Targeted Protonophoric Uncoupler

Mitochondrial uncouplers are actively sought as potential therapeutics. Here, we report the first successful synthesis of mitochondria-targeted derivatives of the highly potent uncoupler 3,5-ditert-butyl-4-hydroxybenzylidene-malononitrile (SF6847), bearing a cationic alkyl(triphenyl)phosphonium (TPP) group. As a key step of the synthesis, we used condensation of a ketophenol with malononitrile via the Knoevenagel reaction. SF-C5-TPP with a pentamethylene linker between SF6847 and TPP, stimulating respiration and collapsing membrane potential of rat liver mitochondria at submicromolar concentrations, proved to be the most effective uncoupler of the series. SF-C5-TPP showed pronounced protonophoric activity on a model planar bilayer lipid membrane. Importantly, SF-C5-TPP exhibited rather low toxicity in fibroblast cell culture, causing mitochondrial depolarization in cells at concentrations that only slightly affected cell viability. SF-C5-TPP was more effective in decreasing the mitochondrial membrane potential in the cell culture than SF6847, in contrast to the case of isolated mitochondria. Like other zwitterionic uncouplers, SF-C5-TPP inhibited the growth of Bacillus subtilis in the micromolar concentration range.

Hydrogel-encapsulated medium chain lipid-modified zeolite imidazole framework-90 as a promising platform for oral delivery of proteins

The administration of protein therapeutics through oral means is seen as a convenient and painless experience for patients, making it a significant consideration in the field of drug delivery. Nevertheless, the challenging conditions within the gastrointestinal tract, along with the obstacles to absorption, impede the efficient transportation of proteins. Here, we successfully implemented post-synthetic modifications to attach medium-chain lipids (C10) onto the surface of zeolitic imidazole framework-90 (ZIF-90), then encapsulated the nanoparticles with sodium alginate, resulting in a potential platform for the oral administration of proteins. By means of biomimetic mineralization, ZIF-90 achieves a simple and efficient encapsulation of proteins of varying sizes, while shielding them against degradation by digestive enzymes. Sodium alginate hydrogel protects proteins against gastric acid and helps the cargo to rapidly penetrate the mucus layer. Through a mixed mechanism dominated by micropinocytosis, the C10-conjugated ZIF-90 (ZIF-90-C10) can be uptake by Caco-2 cells with a 200-400% increase and transported through the Golgi apparatus after escaping from lysosomes, exhibiting enhanced uptake in the overall gastrointestinal tract. Furthermore, ZIF-90-C10 retains its adenosine triphosphate-responsive release, which drastically lowers the likelihood of accumulation in vivo and allows targeted delivery for disease cells. Our work highlights mid-chain lipid conjugation as a potent approach to enhancing nanoparticle delivery efficiency and a potential strategy for oral delivery of biomacromolecules when combined with pH-responsive gels.

Conjugating uncoupler compounds with hydrophobic hydrocarbon chains to achieve adipose tissue selective drug accumulation

One potential approach for treating obesity is to increase energy expenditure in brown and white adipose tissue. Here we aimed to achieve this outcome by targeting mitochondrial uncoupler compounds selectively to adipose tissue, thus avoiding side effects from uncoupling in other tissues. Selective drug accumulation in adipose tissue has been observed with many lipophilic compounds and dyes. Hence, we explored the feasibility of conjugating uncoupler compounds with a lipophilic C8-hydrocarbon chain via an ether bond. We found that substituting the trifluoromethoxy group in the uncoupler FCCP with a C8-hydrocarbon chain resulted in potent uncoupling activity. Nonetheless, the compound did not elicit therapeutic effects in mice, likely as a consequence of metabolic instability resulting from rapid ether bond cleavage. A lipophilic analog of the uncoupler compound 2,6-dinitrophenol, in which a C8-hydrocarbon chain was conjugated via an ether bond in the para-position (2,6-dinitro-4-(octyloxy)phenol), exhibited increased uncoupling activity compared to the parent compound. However, in vivo pharmacokinetics studies suggested that 2,6-dinitro-4-(octyloxy)phenol was also metabolically unstable. In conclusion, conjugation of a hydrophobic hydrocarbon chain to uncoupler compounds resulted in sustained or improved uncoupling activity. However, an ether bond linkage led to metabolic instability, indicating the need to conjugate lipophilic groups via other chemical bonds.

Optical Control of Proteasomal Protein Degradation with a Photoswitchable Lipopeptide

Photolipids have emerged as attractive tools for the optical control of lipid functions. They often contain an azobenzene photoswitch that imparts a cis double-bond upon irradiation. Herein, we present the application of photoswitching to a lipidated natural product, the potent proteasome inhibitor cepafungin I. Several azobenzene-containing lipids were attached to the cyclopeptide core, yielding photoswitchable derivatives. Most notably, PhotoCep4 exhibited a 10-fold higher cellular potency in its light-induced cis-form, matching the potency of natural cepafungin I. The length of the photolipid tail and distal positioning of the azobenzene photoswitch with respect to the macrocycle is critical for this activity. In a proteome-wide experiment, light-triggered PhotoCep4 modulation showed high overlap with constitutively active cepafungin I. The mode of action was studied using crystallography and revealed an identical binding of the cyclopeptide in comparison to cepafungin I, suggesting that differences in their cellular activity originate from switching the tail structure. The photopharmacological approach described herein could be applicable to many other natural products as lipid conjugation is common and often necessary for potent activity. Such lipids are often introduced late in synthetic routes, enabling facile chemical modifications.

Overcoming barriers to medium-chain fatty alcohol production

Medium-chain fatty alcohols (mcFaOHs) are aliphatic primary alcohols containing six to twelve carbons that are widely used in materials, pharmaceuticals, and cosmetics. Microbial biosynthesis has been touted as a route to less-abundant chain-length molecules and as a sustainable alternative to current petrochemical processes. Several metabolic engineering strategies for producing mcFaOHs have been demonstrated in the literature, yet processes continue to suffer from poor selectivity and mcFaOH toxicity, leading to reduced titers, rates, and yields of the desired compounds. This opinion examines the current state of microbial mcFaOH biosynthesis, summarizing engineering efforts to tailor selectivity and improve product tolerance by implementing engineering strategies that circumvent or overcome mcFaOH toxicity.

Elucidating the cell penetrating properties of self-assembling β-peptides

Self-assembling lipopeptide hydrogels have been widely developed for the delivery of therapeutics due to their rapid gelation, injectability, and highly controlled physicochemical properties. Lipopeptides are also known for their membrane-associating and cell penetrating properties, which may impact on their application in cell-encapsulation. Self-assembling lipidated-β3-peptide materials developed in our laboratory have previously been used in cell culture as 2D substrates, thus as a continuation of this work we aimed to encapsulate cells in 3D by forming a hydrogel. We therefore assessed the self-assembling lipidated-β3-peptides for cell-penetrating properties in mesenchymal stems cells (MSC) using fluorescence microscopy and membrane association with surface plasmon resonance spectroscopy (SPR). The results demonstrated that lipidated β3-peptides penetrate the MSC plasma membrane and localise to the mitochondrial network. While self-assembling lipopeptide hydrogels have shown tremendous potential for delivery of therapeutics, further optimisation may be required to minimise the membrane uptake of the lipidated-β3-peptides for cell encapsulation applications.

Direct Modulators of K-Ras-Membrane Interactions

Protein-membrane interactions (PMIs) are ubiquitous in cellular signaling. Initial steps of signal transduction cascades often rely on transient and dynamic interactions with the inner plasma membrane leaflet to populate and regulate signaling hotspots. Methods to target and modulate these interactions could yield attractive tool compounds and drug candidates. Here, we demonstrate that the conjugation of a medium-chain lipid tail to the covalent K-Ras(G12C) binder MRTX849 at a solvent-exposed site enables such direct modulation of PMIs. The conjugated lipid tail interacts with the tethered membrane and changes the relative membrane orientation and conformation of K-Ras(G12C), as shown by molecular dynamics (MD) simulation-supported NMR studies. In cells, this PMI modulation restricts the lateral mobility of K-Ras(G12C) and disrupts nanoclusters. The described strategy could be broadly applicable to selectively modulate transient PMIs.

Exploring the Impact of Head Group Modifications on the Anticancer Activities of Fatty-Acid-like Platinum(IV) Prodrugs: A Structure-Activity Relationship Study

We conducted the first comprehensive investigation on the impact of head group modifications on the anticancer activities of fatty-acid-like Pt(IV) prodrugs (FALPs), which are a class of platinum-based metallodrugs that target mitochondria. We created a small library of FALPs (1-9) with diverse head group modifications. The outcomes of our study demonstrate that hydrophilic modifications exclusively enhance the potency of these metallodrugs, whereas hydrophobic modifications significantly decrease their cytotoxicity. To further understand this interesting structure-activity relationship, we chose two representative FALPs (compounds 2 and 7) as model compounds: one (2) with a hydrophilic polyethylene glycol (PEG) head group, and the other (7) with a hydrophobic hydrocarbon modification of the same molecular weight. Using these FALPs, we conducted a targeted investigation on the mechanism of action. Our study revealed that compound 2, with hydrophilic modifications, exhibited remarkable penetration into cancer cells and mitochondria, leading to subsequent mitochondrial and DNA damage, and effectively eradicating cancer cells. In contrast, compound 7, with hydrophobic modifications, displayed a significantly lower uptake and weaker cellular responses. The collective results present a different perspective, indicating that increased hydrophobicity may not necessarily enhance cellular uptake as is conventionally believed. These findings provide valuable new insights into the fundamental principles of developing metallodrugs.

Rationally Designed Pyrimidine Compounds: Promising Novel Antibiotics for the Treatment of Staphylococcus aureus-Associated Bovine Mastitis

Staphylococcus aureus is one of the major pathogens causing bovine mastitis, and antibiotic treatment is most often inefficient due to its virulence and antibiotic-resistance attributes. The development of new antibiotics for veterinary use should account for the One Health concept, in which humans, animals, and environmental wellbeing are all interconnected. S. aureus can infect cattle and humans alike and antibiotic resistance can impact both if the same classes of antibiotics are used. New effective antibiotic classes against S. aureus are thus needed in dairy farms. We previously described PC1 as a novel antibiotic, which binds the S. aureus guanine riboswitch and interrupts transcription of essential GMP synthesis genes. However, chemical instability of PC1 hindered its development, evaluation, and commercialization. Novel PC1 analogs with improved stability have now been rationally designed and synthesized, and their in vitro and in vivo activities have been evaluated. One of these novel compounds, PC206, remains stable in solution and demonstrates specific narrow-spectrum activity against S. aureus. It is active against biofilm-embedded S. aureus, its cytotoxicity profile is adequate, and in vivo tests in mice and cows show that it is effective and well tolerated. PC206 and structural analogs represent a promising new antibiotic class to treat S. aureus-induced bovine mastitis.

Bacterial Pathogen Channels Medium-Sized Fatty Acids into Malleicyprol Biosynthesis

Bacterial pathogens of the Burkholderia pseudomallei (BP) group cause life-threatening infections in both humans and animals. Critical for the virulence of these often antibiotic-resistant pathogens is the polyketide hybrid metabolite malleicyprol, which features two chains, a short cyclopropanol-substituted chain and a long hydrophobic alkyl chain. The biosynthetic origin of the latter has remained unknown. Here, we report the discovery of novel overlooked malleicyprol congeners with varied chain lengths and identify medium-sized fatty acids as polyketide synthase (PKS) starter units that constitute the hydrophobic carbon tails. Mutational and biochemical analyses show that a designated coenzyme A-independent fatty acyl-adenylate ligase (FAAL, BurM) is essential for recruiting and activating fatty acids in malleicyprol biosynthesis. In vitro reconstitution of the BurM-catalyzed PKS priming reaction and analysis of ACP-bound building blocks reveal a key role of BurM in the toxin assembly. Insights into the function and role of BurM hold promise for the development of enzyme inhibitors as novel antivirulence therapeutics to combat infections with BP pathogens.

Ester-stabilized phosphorus ylides as protonophores on bilayer lipid membranes, mitochondria and chloroplasts

Triphenylphosphonium ylides are commonly used as key intermediates in the Wittig reaction. Based on the known acidities of stabilized ylide precursors, we proposed that a methylene group adjacent to phosphorus in these compounds can ensure proton shuttling across lipid membranes. Here, we synthesized (decyloxycarbonylmethyl)triphenylphosphonium bromide (CMTPP-C₁₀) by reaction of triphenylphosphine with decyl bromoacetate. This phosphonium salt precursor of the ester-stabilized phosphorus ylide along with its octyl (CMTPP-C₈) and dodecyl (CMTPP-C₁₂) analogues was found to be a carrier of protons in mitochondrial, chloroplast and artificial lipid membranes, suggesting that it can reversibly release hydrogen ions and diffuse through the membranes in both zwitterionic (ylide) and cationic forms. The CMTPP-C₁₀-mediated electrical current across planar bilayer lipid membranes exhibited pronounced proton selectivity. Similar to conventional protonophores, known to uncouple electron transport and ATP synthesis, CMTPP-C_n (n = 8, 10, 12) stimulated mitochondrial respiration, while decreasing membrane potential, at micromolar concentrations, thereby showing the classical uncoupling activity in mitochondria. CMTPP-C₁₂ also caused dissipation of transmembrane pH gradient on chloroplast membranes. Importantly, CMTPP-C₁₀ exhibited substantially lower toxicity in cell culture, than C₁₂TPP. Thus, we report the finding of a new class of ylide-type protonophores, which is of substantial interest due to promising therapeutic properties of uncouplers.

Novel Sulfonamide Derivatives Containing a Piperidine Moiety as New Bactericide Leads for Managing Plant Bacterial Diseases

Plant bacterial diseases are an intractable problem due to the fact that phytopathogens have acquired strong resistances for traditional pesticides, resulting in restricting the quality and yield of agricultural products around the world. To develop new agrochemical alternatives, we prepared a novel series of sulfanilamide derivatives containing piperidine fragments and assessed their antibacterial potency. The bioassay results revealed that most molecules displayed excellent in vitro antibacterial potency towards Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac). In particular, molecule C₄ exhibited outstanding inhibitory activity toward Xoo with EC₅₀ value of 2.02 µg mL^-1, which was significantly better than those of the commercial agents bismerthiazol (EC₅₀ = 42.38 µg mL^-1) and thiodiazole copper (EC₅₀ = 64.50 µg mL^-1). A series of biochemical assays confirmed that compound C₄ interacted with dihydropteroate synthase, and irreversibly damaged the cell membrane. In vivo assays showed that the molecule C₄ presented acceptable curative and protection activities of 34.78% and 39.83%, respectively, at 200 µg mL^-1, which were greater than those of thiodiazole and bismerthiazol. This study highlights the valuable insights for the excavation and development of new bactericides that can concurrently target dihydropteroate synthase and bacterial cell membranes.

Lessons for Oral Bioavailability: How Conformationally Flexible Cyclic Peptides Enter and Cross Lipid Membranes

Cyclic peptides extend the druggable target space due to their size, flexibility, and hydrogen-bonding capacity. However, these properties impact also their passive membrane permeability. As the "journey" through membranes cannot be monitored experimentally, little is known about the underlying process, which hinders rational design. Here, we use molecular simulations to uncover how cyclic peptides permeate a membrane. We show that side chains can act as "molecular anchors", establishing the first contact with the membrane and enabling insertion. Once inside, the peptides are positioned between headgroups and lipid tails─a unique polar/apolar interface. Only one of two distinct orientations at this interface allows for the formation of the permeable "closed" conformation. In the closed conformation, the peptide crosses to the lower leaflet via another "anchoring" and flipping mechanism. Our findings provide atomistic insights into the permeation process of flexible cyclic peptides and reveal design considerations for each step of the process.

Miniaturized Synthetic Palmitoylation Motifs for Small-Molecule Localization in Living Cells

Conjugating small-molecule ligands to synthetic motifs that can localize to specific organelles or membranes in living cells is a practical approach to develop compounds as chimeric tools or drugs that can manipulate biological processes in a subcellular site-specific manner. However, the number of available organelle-targeted synthetic motifs for small-molecule localization is limited. We have recently developed a synthetic myristoyl-^DCys motif for small-molecule localization that undergoes S-palmitoylation via the cellular palmitoylation machinery and localizes to the Golgi surface. Herein, we show that the lipid acyl chain of the myristoyl (C14)-^DCys motif can be as short as 10-carbons and still retain the palmitoylation-dependent Golgi localization property in cells. This discovery led to the identification of four new derivatives for small-molecule localization: tridecanoyl (C13)-, dodecanoyl (C12)-, undecanoyl (C11)-, and decanoyl (C10)-^DCys motifs. We demonstrated that even the short decanoyl-^DCys palmitoylation motif could be used to generate small-molecule ligand conjugates that functioned as chemical tools for controlling protein localization and cell signaling. The miniaturized synthetic palmitoylation motifs identified in this work may find applications in creating various Golgi-localizable chimeric molecules for use in chemical biology and drug development.