FTY720 ameliorates experimental MPO-ANCA-associated vasculitis by regulating fatty acid oxidation via the neutrophil PPARα-CPT1a pathway.

OBJECTIVES: Increasing studies demonstrated the importance of C5a and anti-neutrophil cytoplasmic antibody (ANCA)-induced neutrophil activation in the pathogenesis of ANCA-associated vasculitis (AAV). Sphingosine-1-phosphate (S1P) acts as a downstream effector molecule of C5a and enhances neutrophil activation induced by C5a and ANCA. The current study investigated the role of a S1P receptor modulator, FTY720, in experimental autoimmune vasculitis (EAV) and explored the immunometabolism-related mechanisms of FTY720 in modulating ANCA-induced neutrophil activation. METHODS: The effects of FTY720 in EAV were evaluated by quantifying haematuria, proteinuria, crescent formation, tubulointerstitial injury and pulmonary haemorrhage. RNA sequencing of renal cortex and gene enrichment analysis were performed. The proteins of key identified pathways were analysed in neutrophils isolated from peripheral blood of patients with active AAV and normal controls. We assessed the effects of FTY720 on ANCA-induced neutrophil respiratory burst and neutrophil extracellular traps formation (NETosis). RESULTS: FTY720 treatment significantly attenuated renal injury and pulmonary haemorrhage in EAV. RNA sequencing analyses of renal cortex demonstrated enhanced fatty acid oxidation (FAO) and peroxisome proliferator-activated receptor (PPAR) signalling in FTY720-treated rats. Compared with normal controls, patients with active AAV showed decreased FAO in neutrophils. FTY720-treated differentiated HL-60 cells showed increased expression of carnitine palmitoyltransferase 1a (CPT1a) and PPARα. Blocking or knockdown of CPT1a or PPARα in isolated human neutrophils and HL-60 cells reversed the inhibitory effects of FTY720 on ANCA-induced neutrophil respiratory burst and NETosis. CONCLUSION: FTY720 attenuated renal injury in EAV through upregulating FAO via the PPARα-CPT1a pathway in neutrophils, offering potential immunometabolic targets in AAV treatment.

Molecular Pathogenic Mechanisms of IgA Nephropathy Secondary to COVID-19 mRNA Vaccination.

INTRODUCTION: Accumulating evidence has disclosed that IgA nephropathy (IgAN) could present shortly after the second dose of COVID-19 mRNA vaccine. However, the undying mechanism remains unclear and we aimed to investigate the potential molecular mechanisms. METHODS: We downloaded gene expression datasets of COVID-19 mRNA vaccination (GSE201535) and IgAN (GSE104948). Weighted Gene Co-Expression Network Analysis (WGCNA) was performed to identify co-expression modules related to the second dose of COVID-19 mRNA vaccination and IgAN. Differentially expressed genes (DEGs) were screened, and a transcription factor (TF)-miRNA regulatory network and protein-drug interaction were constructed for the shared genes. RESULTS: WGCNA identified one module associated with the second dose of COVID-19 mRNA vaccine and four modules associated with IgAN. Gene ontology (GO) analyses revealed enrichment of cell cycle-related processes for the COVID-19 mRNA vaccine hub genes and immune effector processes for the IgAN hub genes. We identified 74 DEGs for the second dose of COVID-19 mRNA vaccine and 574 DEGs for IgAN. Intersection analysis with COVID-19 vaccine-related genes led to the identification of two shared genes, TOP2A and CEP55. The TF-miRNA network analysis showed that hsa-miR-144 and ATF1 might regulate the shared hub genes. CONCLUSIONS: This study provides insights into the common pathogenesis of COVID-19 mRNA vaccination and IgAN. The identified pivotal genes may offer new directions for further mechanistic studies of IgAN secondary to COVID-19 mRNA vaccination.

An Integrated Module Performs Selective 'On-Line' Epoxidation in the Biosynthesis of the Antibiotic Mupirocin.

The delineation of the complex biosynthesis of the potent antibiotic mupirocin, which consists of a mixture of pseudomonic acids (PAs) isolated from Pseudomonas fluorescens NCIMB 10586, presents significant challenges and the timing and mechanisms of several key transformations remain elusive.   Particularly intriguing are the steps that process the linear backbone from the initial polyketide assembly phase to generate the first cyclic intermediate PA-B. These include epoxidation as well as incorporation of the tetrahydropyran (THP) ring and fatty acid sidechain required for biological activity. Here, we show that the mini-module MmpE performs a rare online (ACP-substrate) epoxidation and is integrated ('in-cis') into the polyketide synthase via a docking domain. A linear polyketide fragment with 6 asymmetric centres was synthesised using a convergent approach and used to demonstrate substrate flux via an atypical KS0 and a previously unannotated ACP (MmpE_ACP). MmpE_ACP-bound synthetic substrates were critical in demonstrating successful epoxidation in vitro by the purified MmpE oxidoreductase domain. Alongside feeding studies, these results confirm the timing as well as chain length dependence of this selective epoxidation. These mechanistic studies pinpoint the location and nature of the polyketide substrate prior to the key formation of the THP ring and esterification that generate PA-B.

Inhibitor of apoptosis proteins antagonist SM164 ameliorates experimental MPO-ANCA-associated vasculitis via enhancing fatty acid oxidation in neutrophils.

OBJECTIVES: Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of life-threatening autoimmune diseases. Inhibitors of apoptosis proteins (IAPs) are a class of molecules engaged in cell death and inflammation, interventions of which are proven effective in a number of inflammatory diseases. Here we tested whether targeting IAPs could ameliorate AAV and explored the potential mechanism. METHODS: We collected 19 kidney specimens from patients with myeloperoxidase (MPO)-AAV to investigate the expression of IAPs. The IAP pan-inhibitor SM164 was used to treat the experimental autoimmune vasculitis (EAV) rat model of AAV. RNA sequencing of renal cortex and enrichment analysis were developed to interpret gene expression. Functional experiments were performed to investigate the role of SM164 on neutrophils and endothelial cells. RESULTS: The expression of three IAPs (cIAP1, cIAP2 and XIAP) was upregulated in kidneys of AAV patients compared with normal controls. SM164 dramatically reduced renal injury in EAV rats. Transcriptomic analysis revealed prominent alterations in fatty acid oxidation and respiratory burst following SM164 treatment. Functional studies demonstrated that SM164 inhibited neutrophil activation induced by MPO-ANCA positive IgG or serum from MPO-AAV patients, and such inhibitory effect was abolished by gene silencing or pharmacological inhibition of fatty acid oxidation. SM164 also inhibited the adhesion of neutrophils to endothelial cells with little effect on the endothelial injury induced by serum from MPO-AAV patients. CONCLUSION: Inhibition of IAPs with SM164 played a protective role in AAV through enhancing intracellular fatty acid oxidation in neutrophils.

Correction: Back et al. A New Micromonospora Strain with Antibiotic Activity Isolated from the Microbiome of a Mid-Atlantic Deep-Sea Sponge. Mar. Drugs 2021, 19, 105.

After publication of this article [...].

Structure and Function of the α-Hydroxylation Bimodule of the Mupirocin Polyketide Synthase.

Mupirocin is a clinically important antibiotic produced by a trans-AT Type I polyketide synthase (PKS) in Pseudomonas fluorescens. The major bioactive metabolite, pseudomonic acid A (PA-A), is assembled on a tetrasubstituted tetrahydropyran (THP) core incorporating a 6-hydroxy group proposed to be introduced by α-hydroxylation of the thioester of the acyl carrier protein (ACP) bound polyketide chain. Herein, we describe an in vitro approach combining purified enzyme components, chemical synthesis, isotopic labelling, mass spectrometry and NMR in conjunction with in vivo studies leading to the first characterisation of the α-hydroxylation bimodule of the mupirocin biosynthetic pathway. These studies reveal the precise timing of hydroxylation by MupA, substrate specificity and the ACP dependency of the enzyme components that comprise this α-hydroxylation bimodule. Furthermore, using purified enzyme, it is shown that the MmpA KS0 shows relaxed substrate specificity, suggesting precise spatiotemporal control of in trans MupA recruitment in the context of the PKS. Finally, the detection of multiple intermodular MupA/ACP interactions suggests these bimodules may integrate MupA into their assembly.

Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans.

Tetrahydropyrans (THPs) are common structural motifs found in natural products and synthetic therapeutic molecules. In Nature these 6-membered oxygen heterocycles are often assembled via intramolecular reactions involving either oxy-Michael additions or ring opening of epoxy-alcohols. Indeed, the polyether natural products have been particularly widely studied due to their fascinating structures and important biological properties; these are commonly formed via endo-selective epoxide-opening cascades. In this review we outline synthetic approaches for endo-selective intramolecular epoxide ring opening (IERO) of 4,5-epoxy-alcohols and their applications in natural product synthesis. In addition, the biosynthesis of THP-containing natural products which utilise IERO reactions are reviewed.

Ambruticins: tetrahydropyran ring formation and total synthesis.

The ambruticins are a family of polyketide natural products which exhibit potent antifungal activity. Gene knockout experiments are in accord with the proposal that the tetrahydropyran ring of the ambruticins is formed via the AmbJ catalysed epoxidation of the unsaturated 3,5-dihydroxy acid, ambruticin J, followed by regioselective cyclisation to ambruticin F. Herein, a convergent approach to the total synthesis of ambruticin J is described as well as model studies involving epoxidation and cyclisations of unsaturated hydroxy esters to give tetrahydropyrans and tetrahydrofurans. The total synthesis involves preparation of three key fragments which were united via a Suzuki-Miyaura cross-coupling and Julia-Kocienski olefination to generate the required carbon framework. Global deprotection to a triol and selective oxidation of the primary alcohol gave, after hydrolysis of the lactone, ambruticin J.

A New Micromonospora Strain with Antibiotic Activity Isolated from the Microbiome of a Mid-Atlantic Deep-Sea Sponge.

To tackle the growing problem of antibiotic resistance, it is essential to identify new bioactive compounds that are effective against resistant microbes and safe to use. Natural products and their derivatives are, and will continue to be, an important source of these molecules. Sea sponges harbour a diverse microbiome that co-exists with the sponge, and these bacterial communities produce a rich array of bioactive metabolites for protection and resource competition. For these reasons, the sponge microbiota constitutes a potential source of clinically relevant natural products. To date, efforts in bioprospecting for these compounds have focused predominantly on sponge specimens isolated from shallow water, with much still to be learned about samples from the deep sea. Here we report the isolation of a new Micromonospora strain, designated 28ISP2-46T, recovered from the microbiome of a mid-Atlantic deep-sea sponge. Whole-genome sequencing reveals the capacity of this bacterium to produce a diverse array of natural products, including kosinostatin and isoquinocycline B, which exhibit both antibiotic and antitumour properties. Both compounds were isolated from 28ISP2-46T fermentation broths and were found to be effective against a plethora of multidrug-resistant clinical isolates. This study suggests that the marine production of isoquinocyclines may be more widespread than previously supposed and demonstrates the value of targeting the deep-sea sponge microbiome as a source of novel microbial life with exploitable biosynthetic potential.

Sphingosine-1-phosphate receptor modulator FTY720 attenuates experimental myeloperoxidase-ANCA vasculitis in a T cell-dependent manner.

Sphingosine-1-phosphate (S1P) is a pleiotropic lysosphingolipid derived from the metabolism of plasma membrane lipids. The interaction between S1P and its ubiquitously expressed G-protein-coupled receptors (S1PR1-5) is crucial in many pathophysiological processes. Emerging evidence suggested a potential role for S1P receptors in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In the present study, we investigated the effects of three different S1P receptors modulators (FTY720, SEW2871 and TY52156) in a recognized rat model of experimental autoimmune vasculitis (EAV). The effects of treatments were evaluated with clinico-pathological parameters including hematuria, proteinuria, crescent formation, pulmonary hemorrhage, etc. In vitro functional studies were performed in a Jurkat T-cell line following stimulations of serum from myeloperoxidase-AAV patients. We found that only the FTY720 treatment significantly alleviated hematuria and proteinuria, and diminished glomerular crescent formation, renal tubulointerstitial lesions and pulmonary hemorrhage in EAV. The attenuation was accompanied by less renal T-cell infiltration, up-regulated mRNA of S1PR1 and down-regulated IL-1ß in kidneys, but not altered circulating ANCA levels, suggesting that the therapeutic effects of FTY720 were B-cell independent. Further in vitro studies demonstrated that FTY720 incubation could significantly inhibit the proliferation, adhesion, and migration, and increase apoptosis of T cells. In conclusion, the S1P modulator FTY720 could attenuate EAV through the reduction and inhibition of T cells, which might become a novel treatment of ANCA-associated vasculitis.

The expression of NOD2, NLRP3 and NLRC5 and renal injury in anti-neutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND: Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are intracellular sensors of pathogens and molecules from damaged cells to regulate the inflammatory response in the innate immune system. Emerging evidences suggested a potential role of NLRs in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). This study aimed to investigate the expression of nucleotide-binding oligomerization domain containing protein 2 (NOD2), NOD-like receptor family pyrin domain containing 3 (NLRP3) and NOD-like receptor family CARD domain containing 5 (NLRC5) in kidneys of AAV patients, and further explored their associations with clinical and pathological parameters. METHODS: Thirty-four AAV patients in active stage were recruited. Their renal specimens were processed with immunohistochemistry to assess the expression of three NLRs, and with double immunofluorescence to detect NLRs on intrinsic and infiltrating cells. Analysis of gene expression was also adopted in cultured human podocytes. The associations between expression of NLRs and clinicopathological parameters were analyzed. RESULTS: The expression of NOD2, NLRP3 and NLRC5 was significantly higher in kidneys from AAV patients than those from normal controls, minimal change disease or class IV lupus nephritis. These NLRs co-localized with podocytes and infiltrating inflammatory cells. The mean optical density of NOD2 in glomeruli was significantly higher in crescentic class than non-crescentic class, and correlated with levels of proteinuria and serum creatinine at renal biopsy. The mean optical density of NLRC5 in glomeruli was significantly higher in crescentic class than non-crescentic class, and correlated with proteinuria level, Birmingham Vasculitis Activity Score and the proportion of crescents in the renal specimen. CONCLUSIONS: The expression of three NLRs was upregulated in kidneys of AAV patients. The expression of NOD2 and NLRC5 was associated with the severity of renal lesions in AAV.

Control of ß-Branching in Kalimantacin Biosynthesis: Application of 13 C†NMR to Polyketide Programming.

The presence of ß-branches in the structure of polyketides that possess potent biological activity underpins the widespread importance of this structural feature. Kalimantacin is a polyketide antibiotic with selective activity against staphylococci, and its biosynthesis involves the unprecedented incorporation of three different and sequential ß-branching modifications. We use purified single and multi-domain enzyme components of the kalimantacin biosynthetic machinery to address in vitro how the pattern of ß-branching in kalimantacin is controlled. Robust discrimination of enzyme products required the development of a generalisable assay that takes advantage of 13 C NMR of a single 13 C label incorporated into key biosynthetic mimics combined with favourable dynamic properties of an acyl carrier protein. We report a previously unassigned modular enoyl-CoA hydratase (mECH) domain and the assembly of enzyme constructs and cascades that are able to generate each specific ß-branch.

Absolute Configuration of Periplosides C and F and Isolation of Minor Spiro-orthoester Group-Containing Pregnane-type Steroidal Glycosides from Periploca sepium and Their T-Lymphocyte Proliferation Inhibitory Activities.

Further phytochemical investigation of the root bark of Periploca sepium afforded nine new spiro-orthoester group-containing pregnane-type glycosides termed periplosides O-V and 3-O-formyl-periploside A. The structures of these glycosides along with the absolute configuration of the unique seven-membered formyl acetal-bridged spiro-orthoester function and the 4,6-dideoxy-3-O-methyl-Δ3-2-hexosulosyl moiety were elucidated on the basis of spectroscopic data interpretation and chemical transformation. The absolute configurations of the major compounds periplosides C and F were established by single-crystal X-ray diffraction analysis. The isolated compounds were evaluated for their inhibitory activities against the proliferation of T-lymphocytes. As a result, periploside C, the most abundant glycoside containing a spiro-orthoester moiety found in the plant, exhibited the most favorite selective index value (SI = 82.5). The length and constitution of the saccharide chain in the periplosides were found to influence the inhibitory activity and the SI value.

Diversity-oriented combinatorial biosynthesis of benzenediol lactone scaffolds by subunit shuffling of fungal polyketide synthases.

Combinatorial biosynthesis aspires to exploit the promiscuity of microbial anabolic pathways to engineer the synthesis of new chemical entities. Fungal benzenediol lactone (BDL) polyketides are important pharmacophores with wide-ranging bioactivities, including heat shock response and immune system modulatory effects. Their biosynthesis on a pair of sequentially acting iterative polyketide synthases (iPKSs) offers a test case for the modularization of secondary metabolic pathways into "build-couple-pair" combinatorial synthetic schemes. Expression of random pairs of iPKS subunits from four BDL model systems in a yeast heterologous host created a diverse library of BDL congeners, including a polyketide with an unnatural skeleton and heat shock response-inducing activity. Pairwise heterocombinations of the iPKS subunits also helped to illuminate the innate, idiosyncratic programming of these enzymes. Even in combinatorial contexts, these biosynthetic programs remained largely unchanged, so that the iPKSs built their cognate biosynthons, coupled these building blocks into chimeric polyketide intermediates, and catalyzed intramolecular pairing to release macrocycles or α-pyrones. However, some heterocombinations also provoked stuttering, i.e., the relaxation of iPKSs chain length control to assemble larger homologous products. The success of such a plug and play approach to biosynthesize novel chemical diversity bodes well for bioprospecting unnatural polyketides for drug discovery.

Selected Mutations Reveal New Intermediates in the Biosynthesis of Mupirocin and the Thiomarinol Antibiotics.

Thiomarinol and mupirocin are assembled on similar polyketide/fatty acid backbones and exhibit potent antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA). They both contain a tetrasubstituted tetrahydropyran (THP) ring that is essential for biological activity. Mupirocin is a mixture of pseudomonic acids (PAs). Isolation of the novel compound mupirocin P, which contains a 7-hydroxy-6-keto-substituted THP, from a ΔmupP strain and chemical complementation experiments confirm that the first step in the conversion of PA-B into the major product PA-A is oxidation at the C6 position. In addition, nine novel thiomarinol (TM) derivatives with different oxidation patterns decorating the central THP core were isolated after gene deletion (tmlF). These metabolites are in accord with the THP ring formation and elaboration in thiomarinol following a similar order to that found in mupirocin biosynthesis, despite the lack of some of the equivalent genes. Novel mupirocin-thiomarinol hybrids were also synthesized by mutasynthesis.

Synthesis of two new hydroxylated derivatives of spironolactone by microbial transformation.

Spironolactone is a medicinally important molecule that is clinically used in the treatment and management of many diseases such as oedema and ascites in cirrhosis of the liver, malignant ascites, nephrotic syndrome, chronic lung disease, resistant hypertension, congestive heart failure, and primary hyperaldosteronism. Microbial transformations of spironolactone by Cunninghamella elegans ATCC 9245 was carried out. Two new hydroxylated derivatives, 12ß-hydroxy-spironolactone and 2α-hydroxy-spironolactone, were synthesized. Their structures were characterized on the basis of the spectroscopic data. The substrate can be efficiently converted into the products within 72 h after its addition to the fermentation broth of C. elegans ATCC 9245.

Ionized water-soluble organic nanosheets with light/ultrasound dual excitation channels for efficient killing of multidrug-resistant bacteria.

A novel ionized heavy-atom-free two-dimensional organic nanosheet was prepared and exhibited highly selective generation of singlet oxygen under both light and ultrasound excitation. These ionized nanosheets displayed excellent dispersibility in water and enhanced singlet oxygen production efficiency compared to their non-assembled monomers. Antimicrobial experiments have revealed their potent bactericidal effects on drug-resistant E. coli and S. aureus under both visible light and ultrasound irradiation.

Engineered Imine Reductase Catalyzed Enantiodivergent Synthesis of Alkylated Amphetamines.

Less steric ketones exhibited low stereoselectivity toward M5 due to their difficulty in restricting the free rotation of the imine intermediate. An engineered enantio-complementary imine reductase from M5 was obtained with catalytic activity. We identified four key residues that play essential roles in controlling stereoselectivity. Two mutants, I149Y-W234L (up to 99%S ee) and L200M-F260M (up to 99%R ee), were achieved, showing excellent stereoselectivity toward the tested substrates, offering valuable biocatalysts for synthesizing alkylated amphetamines.

Combining total synthesis and genetic engineering to probe dihydropyran formation in ambruticin biosynthesis.

The ambruticins are a family of potent antifungal polyketide derived natural products isolated from the myxobacterium Sorangium cellulosum. Their unusual structures include a trisubstituted cyclopropyl group and two oxygen heterocycles, a tetrahydropyran (THP) and dihydropyran (DHP). Herein we report a flexible modular approach for the total synthesis of ambruticins which is used to prepare ambruticins F and S as well as in the first total synthesis of 20,21-dihydroambruticin F. The flexible strategy unites 3 fragments via Julia-Kocienski olefinations and provides important standards for investigation of dihydropyran formation in ambruticin biosynthesis. Cultures of wild-type S. cellulosum So ce10 produce mainly ambruticin S and the VS series of metabolites. An efficient electroporation method enabled gene knockout experiments which revealed that the ΔambP-S mutant of S. cellulosum accumulated the bisTHP polyketide 20,21-dihydroambruticin F. In contrast, the ΔambN-S mutant gave ambruticin F with the 20,21-alkene as the major metabolite confirming that AmbP and AmbO (a Rieske enzyme and flavin-dependent monooxygenase respectively) are implicated in 20,21-alkene formation. The results of feeding studies to a Sorangium strain containing only ambP and ambO are in accord with formation of the 20,21-alkene occurring prior to generation of the C3 to C7 dihydroxylated tetrahydropyran in ambruticin biosynthesis.

(M)- and (P)-bicelaphanol A, dimeric trinorditerpenes with promising neuroprotective activity from Celastrus orbiculatus.

(M)-Bicelaphanol A (1) and (P)-bicelaphanol A (2), two unprecedented dimeric trinorditerpenes existing as atropisomers, together with their monomer celaphanol A (3), were isolated from the root bark of Celastrus orbiculatus. The structures and absolute configurations of 1 and 2 were determined by spectroscopic and single-crystal X-ray diffraction analyses. Compound 1 exhibited a significant in vitro neuroprotective effect against a hydrogen peroxide-induced cell viability decrease in PC12 cells at 1 µM, while compounds 2 and 3 showed such effects at 10 µM.