Multiple metabolic pathways fuel the truncated tricarboxylic acid cycle of the prostate to sustain constant citrate production and secretion.

OBJECTIVE: The prostate is metabolically unique: it produces high levels of citrate for secretion via a truncated tricarboxylic acid (TCA) cycle to maintain male fertility. In prostate cancer (PCa), this phenotype is reprogrammed, making it an interesting therapeutic target. However, how the truncated prostate TCA cycle works is still not completely understood. METHODS: We optimized targeted metabolomics in mouse and human organoid models in ex vivo primary culture. We then used stable isotope tracer analyses to identify the pathways that fuel citrate synthesis. RESULTS: First, mouse and human organoids were shown to recapitulate the unique citrate-secretory program of the prostate, thus representing a novel model that reproduces this unusual metabolic profile. Using stable isotope tracer analysis, several key nutrients were shown to allow the completion of the prostate TCA cycle, revealing a much more complex metabolic profile than originally anticipated. Indeed, along with the known pathway of aspartate replenishing oxaloacetate, glutamine was shown to fuel citrate synthesis through both glutaminolysis and reductive carboxylation in a GLS1-dependent manner. In human organoids, aspartate entered the TCA cycle at the malate entry point, upstream of oxaloacetate. Our results demonstrate that the citrate-secretory phenotype of prostate organoids is supported by the known aspartate-oxaloacetate-citrate pathway, but also by at least three additional pathways: glutaminolysis, reductive carboxylation, and aspartate-malate conversion. CONCLUSIONS: Our results add a significant new dimension to the prostate citrate-secretory phenotype, with at least four distinct pathways being involved in citrate synthesis. Better understanding this distinctive citrate metabolic program will have applications in both male fertility as well as in the development of novel targeted anti-metabolic therapies for PCa.

A FACS-Free Purification Method to Study Estrogen Signaling, Organoid Formation, and Metabolic Reprogramming in Mammary Epithelial Cells.

Few in vitro models are used to study mammary epithelial cells (MECs), and most of these do not express the estrogen receptor α (ERα). Primary MECs can be used to overcome this issue, but methods to purify these cells generally require flow cytometry and fluorescence-activated cell sorting (FACS), which require specialized instruments and expertise. Herein, we present in detail a FACS-free protocol for purification and primary culture of mouse MECs. These MECs remain differentiated for up to six days with >85% luminal epithelial cells in two-dimensional culture. When seeded in Matrigel, they form organoids that recapitulate the mammary gland's morphology in vivo by developing lumens, contractile cells, and lobular structures. MECs express a functional ERα signaling pathway in both two- and three-dimensional cell culture, as shown at the mRNA and protein levels and by the phenotypic characterization. Extracellular metabolic flux analysis showed that estrogens induce a metabolic switch favoring aerobic glycolysis over mitochondrial respiration in MECs grown in two-dimensions, a phenomenon known as the Warburg effect. We also performed mass spectrometry (MS)-based metabolomics in organoids. Estrogens altered the levels of metabolites from various pathways, including aerobic glycolysis, citric acid cycle, urea cycle, and amino acid metabolism, demonstrating that ERα reprograms cell metabolism in mammary organoids. Overall, we have optimized mouse MEC isolation and purification for two- and three-dimensional cultures. This model represents a valuable tool to study how estrogens modulate mammary gland biology, and particularly how these hormones reprogram metabolism during lactation and breast carcinogenesis.

Structure-Based Design of Dimeric Bisbenzimidazole Inhibitors to an Emergent Trimethoprim-Resistant Type II Dihydrofolate Reductase Guides the Design of Monomeric Analogues.

The worldwide use of the broad-spectrum antimicrobial trimethoprim (TMP) has induced the rise of TMP-resistant microorganisms. In addition to resistance-causing mutations of the microbial chromosomal dihydrofolate reductase (Dfr), the evolutionarily and structurally unrelated type II Dfrs (DfrBs) have been identified in TMP-resistant microorganisms. DfrBs are intrinsically TMP-resistant and allow bacterial proliferation when the microbial chromosomal Dfr is TMP-inhibited, making these enzymes important targets for inhibitor development. Furthermore, DfrBs occur in multiresistance plasmids, potentially accelerating their dissemination. We previously reported symmetrical bisbenzimidazoles that are the first selective inhibitors of the only well-characterized DfrB, DfrB1. Here, their diversification provides a new series of inhibitors (K i = 1.7-12.0 µM). Our results reveal two prominent features: terminal carboxylates and inhibitor length allow the establishment of essential interactions with DfrB1. Two crystal structures demonstrate the simultaneous binding of two inhibitor molecules in the symmetrical active site. Observations of those dimeric inhibitors inspired the design of monomeric analogues, binding in a single copy yet offering similar inhibition potency (K i = 1.1 and 7.4 µM). Inhibition of a second member of the DfrB family, DfrB4, suggests the generality of these inhibitors. These results provide key insights into inhibition of the highly TMP-resistant DfrBs, opening avenues to downstream development of antibiotics for combatting this emergent source of resistance.

Investigation of Classical Organic and Ionic Liquid Cosolvents for Early-Stage Screening in Fragment-Based Inhibitor Design with Unrelated Bacterial and Human Dihydrofolate Reductases.

Drug design by methods such as fragment screening requires effective solubilization of millimolar concentrations of small organic compounds while maintaining the properties of the biological target. We investigate four organic solvents and three 1-butyl-3-methylimidazolium (BMIm)-based ionic liquids (ILs) as cosolvents to establish conditions for screening two structurally unrelated dihydrofolate reductases (DHFRs) that are prime drug targets. Moderate concentrations (10%-15%) of cosolvents had little effect on inhibition of the microbial type II R67 DHFR and of human DHFR (hDHFR), while higher concentrations of organic cosolvents generally decreased activity of both DHFRs. In contrast, a specific IL conserved the activity of one DHFR, while severely reducing the activity of the other, and vice versa, illustrating the differing effect of ILs on distinct protein folds. Most of the cosolvents investigated preserved the fold of R67 DHFR and had little effect on binding of the cofactor NADPH, but reduced the productive affinity for its substrate. In contrast, cosolvents resulted in modest structural destabilization of hDHFR with little effect on productive affinity. We conclude that the organic cosolvents, methanol, dimethylformamide, and dimethylsulfoxide, offer the most balanced conditions for early-stage compound screening as they maintain sufficient biological activity of both DHFRs while allowing for compound dissolution in the millimolar range. However, IL cosolvents showed poor capacity to solubilize organic compounds at millimolar concentrations, mitigating their utility in early-stage screening. Nonetheless, ILs could provide an alternative to classical organic cosolvents when low concentrations of inhibitors are used, as when characterizing higher affinity inhibitors.

The use of isomeric testosterone dimers to explore allosteric effects in substrate binding to cytochrome P450 CYP3A4.

Cytochrome P450 CYP3A4 is the main drug-metabolizing enzyme in the human liver, being responsible for oxidation of 50% of all pharmaceuticals metabolized by human P450 enzymes. Possessing a large substrate binding pocket, it can simultaneously bind several substrate molecules and often exhibits a complex pattern of drug-drug interactions. In order to better understand structural and functional aspects of binding of multiple substrate molecules to CYP3A4 we used resonance Raman and UV-VIS spectroscopy to document the effects of binding of synthetic testosterone dimers of different configurations, cis-TST2 and trans-TST2. We directly demonstrate that the binding of two steroid molecules, which can assume multiple possible configurations inside the substrate binding pocket of monomeric CYP3A4, can lead to active site structural changes that affect functional properties. Using resonance Raman spectroscopy, we have documented perturbations in the ferric and Fe-CO states by these substrates, and compared these results with effects caused by binding of monomeric TST. While the binding of trans-TST2 yields results similar to those obtained with monomeric TST, the binding of cis-TST2 is much tighter and results in significantly more pronounced conformational changes of the porphyrin side chains and Fe-CO unit. In addition, binding of an additional monomeric TST molecule in the remote allosteric site significantly improves binding affinity and the overall spin shift for CYP3A4 with trans-TST2 dimer bound inside the substrate binding pocket. This result provides the first direct evidence for an allosteric effect of the peripheral binding site at the protein-membrane interface on the functional properties of CYP3A4.

IL-1α Gene Deletion Protects Oligodendrocytes after Spinal Cord Injury through Upregulation of the Survival Factor Tox3.

Spinal cord injury (SCI) causes the release of danger signals by stressed and dying cells, a process that leads to neuroinflammation. Evidence suggests that inflammation plays a role in both the damage and repair of injured neural tissue. We show that microglia at sites of SCI rapidly express the alarmin interleukin (IL)-1α, and that infiltrating neutrophils and macrophages subsequently produce IL-1ß. Infiltration of these cells is dramatically reduced in both IL-1α(-/-) and IL-1ß(-/-) mice, but only IL-1α(-/-) mice showed rapid (at day 1) and persistent improvements in locomotion associated with reduced lesion volume. Similarly, intrathecal administration of the IL-1 receptor antagonist anakinra restored locomotor function post-SCI. Transcriptome analysis of SCI tissue at day 1 identified the survival factor Tox3 as being differentially regulated exclusively in IL-1α(-/-) mice compared with IL-1ß(-/-) and wild-type mice. Accordingly, IL-1α(-/-) mice have markedly increased Tox3 levels in their oligodendrocytes, beginning at postnatal day 10 (P10) and persisting through adulthood. At P10, the spinal cord of IL-1α(-/-) mice showed a transient increase in mature oligodendrocyte numbers, coinciding with increased IL-1α expression in wild-type animals. In adult mice, IL-1α deletion is accompanied by increased oligodendrocyte survival after SCI. TOX3 overexpression in human oligodendrocytes reduced cellular death under conditions mimicking SCI. These results suggest that IL-1α-mediated Tox3 suppression during the early phase of CNS insult plays a crucial role in secondary degeneration. SIGNIFICANCE STATEMENT: The mechanisms underlying bystander degeneration of neurons and oligodendrocytes after CNS injury are ill defined. We show that microglia at sites of spinal cord injury (SCI) rapidly produce the danger signal interleukin (IL)-1α, which triggers neuroinflammation and locomotor defects. We uncovered that IL-1α(-/-) mice have markedly increased levels of the survival factor Tox3 in their oligodendrocytes, which correlates with the protection of this cell population, and reduced lesion volume, resulting in unprecedented speed, level, and persistence of functional recovery after SCI. Our data suggest that central inhibition of IL-1α or Tox3 overexpression during the acute phase of a CNS insult may be an effective means for preventing the loss of neurological function in SCI, or other acute injuries such as ischemia and traumatic brain injuries.

Cytokine pathways regulating glial and leukocyte function after spinal cord and peripheral nerve injury.

Injury to the nervous system causes the almost immediate release of cytokines by glial cells and neurons. These cytokines orchestrate a complex array of responses leading to microgliosis, immune cell recruitment, astrogliosis, scarring, and the clearance of cellular debris, all steps that affect neuronal survival and repair. This review will focus on cytokines released after spinal cord and peripheral nerve injury and the primary signalling pathways triggered by these inflammatory mediators. Notably, the following cytokine families will be covered: IL-1, TNF, IL-6-like, TGF-ß, and IL-10. Whether interfering with cytokine signalling could lead to novel therapies will also be discussed. Finally, the review will address whether manipulating the above-mentioned cytokine families and signalling pathways could exert distinct effects in the injured spinal cord versus peripheral nerve.

Synthesis and preliminary in vitro biological evaluation of 7α-testosterone-chlorambucil hybrid designed for the treatment of prostate cancer.

The synthesis of 7α-testosterone-chlorambucil hybrid is reported. This compound is made from testosterone in a 6 step reaction sequence and with 23% overall yield. An alternative convergent reaction sequence yielded the same hybrid through a Grubbs metathesis reaction between chlorambucil allyl ester and 7α-allyltestosterone with 35% overall yield. MTT assays showed that the hybrid is selective towards hormone-dependent prostate cancer cell line (LNCaP (AR+)) and shows similar activity than the parent drug, chlorambucil. Thus, the new hybrid shows promising potential for drug targeting of hormone-dependent prostate cancer through its capacity of delivering chlorambucil directly to the site of treatment. This could extend the use of chlorambucil to prostate cancer in the future.

Fragment-based design of symmetrical bis-benzimidazoles as selective inhibitors of the trimethoprim-resistant, type II R67 dihydrofolate reductase.

The continuously increasing use of trimethoprim as a common antibiotic for medical use and for prophylactic application in terrestrial and aquatic animal farming has increased its prevalence in the environment. This has been accompanied by increased drug resistance, generally in the form of alterations in the drug target, dihydrofolate reductase (DHFR). The most highly resistant variants of DHFR are known as type II DHFR, among which R67 DHFR is the most broadly studied variant. We report the first attempt at designing specific inhibitors to this emerging drug target by fragment-based design. The detection of inhibition in R67 DHFR was accompanied by parallel monitoring of the human DHFR, as an assessment of compound selectivity. By those means, small aromatic molecules of 150-250 g/mol (fragments) inhibiting R67 DHFR selectively in the low millimolar range were identified. More complex, symmetrical bis-benzimidazoles and a bis-carboxyphenyl were then assayed as fragment-based leads, which procured selective inhibition of the target in the low micromolar range (K(i) = 2-4 µM). The putative mode of inhibition is discussed according to molecular modeling supported by in vitro tests.

P2X4 receptors influence inflammasome activation after spinal cord injury.

P2X(4) and P2X(7) are the predominant purinergic P2X receptor subtypes expressed on immune and neural cells. These receptor subtypes traffic between intracellular compartments and the plasma membrane and form protein interactions with each other to regulate ATP-dependent signaling. Our recent studies have shown that P2X(7) receptors in neurons and astrocytes activate NLRP1 inflammasomes, but whether P2X(4) receptors regulate inflammasome signaling is essentially unknown. Here, we demonstrate that P2X(4) receptors are expressed in neurons of the spinal cord. We provide direct evidence that spinal cord injury (SCI) induces an innate inflammatory response that leads to increased caspase-l cleavage and production of IL-1ß but not IL-18. Consistent with these findings, P2X(4) knock-out mice showed impaired inflammasome signaling in the cord, resulting in decreased levels of IL-1ß and reduced infiltration of neutrophils and monocyte-derived M1 macrophages, resulting in significant tissue sparing and improvement in functional outcomes. These results indicate that P2X(4) receptors influence inflammasome signaling involving caspase-1 activation and IL-1ß processing in neurons after SCI. P2X(4) might thus represent a potential therapeutic target to limit inflammatory responses associated with SCI and neurodegenerative disorders.

First synthesis of separable isomeric testosterone dimers showing differential activities on prostate cancer cells.

The synthesis of two separable isomeric testosterone dimers is reported. The dimers are made from testosterone in a 5 step sequence and with 36% overall yield. The key dimerization step was performed using Hoveyda-Grubb's metathesis catalysts on 7alpha-allyltestosterone with 75% yield. The synthesis led to separable isomeric dimers (trans and cis, 2:1). X-ray diffraction crystallography, performed on monocrystal of the minor isomer, confirms the cis geometry of the double bound between the two testosterone units. MTT assays showed that the cis dimer has the highest activity against prostate cancer cell lines. The novel cis dimer is more active than the antiandrogen cyproterone acetate indicating the possible therapeutic value of this molecule.

Astrocytes initiate inflammation in the injured mouse spinal cord by promoting the entry of neutrophils and inflammatory monocytes in an IL-1 receptor/MyD88-dependent fashion.

CNS injury stimulates the expression of several proinflammatory cytokines and chemokines, some of which including MCP-1 (also known as CCL2), KC (CXCL1), and MIP-2 (CXCL2) act to recruit Gr-1(+) leukocytes at lesion sites. While earlier studies have reported that neutrophils and monocytes/macrophages contribute to secondary tissue loss after spinal cord injury (SCI), recent work has shown that depletion of Gr-1(+) leukocytes compromised tissue healing and worsened functional recovery. Here, we demonstrate that astrocytes distributed throughout the spinal cord initially contribute to early neuroinflammation by rapidly synthesizing MCP-1, KC, and MIP-2, from 3 up to 12h post-SCI. Chemokine expression by astrocytes was followed by the infiltration of blood-derived immune cells, such as type I "inflammatory" monocytes and neutrophils, into the lesion site and nearby damaged areas. Interestingly, astrocytes from mice deficient in MyD88 signaling produced significantly less MCP-1 and MIP-2 and were unable to synthesize KC. Analysis of the contribution of MyD88-dependent receptors revealed that the astrocytic expression of MCP-1, KC, and MIP-2 was mediated by the IL-1 receptor (IL-1R1), and not by TLR2 or TLR4. Flow cytometry analysis of cells recovered from the spinal cord of MyD88- and IL-1R1-knockout mice confirmed the presence of significantly fewer type I "inflammatory" monocytes and the almost complete absence of neutrophils at 12h and 4days post-SCI. Together, these results indicate that MyD88/IL-1R1 signals regulate the entry of neutrophils and, to a lesser extent, type I "inflammatory" monocytes at sites of SCI.