PET imaging of TREM1 identifies CNS-infiltrating myeloid cells in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS) that causes substantial morbidity and diminished quality of life. Evidence highlights the central role of myeloid lineage cells in the initiation and progression of MS. However, existing imaging strategies for detecting myeloid cells in the CNS cannot distinguish between beneficial and harmful immune responses. Thus, imaging strategies that specifically identify myeloid cells and their activation states are critical for MS disease staging and monitoring of therapeutic responses. We hypothesized that positron emission tomography (PET) imaging of triggering receptor expressed on myeloid cells 1 (TREM1) could be used to monitor deleterious innate immune responses and disease progression in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We first validated TREM1 as a specific marker of proinflammatory, CNS-infiltrating, peripheral myeloid cells in mice with EAE. We show that the ⁶⁴Cu-radiolabeled TREM1 antibody-based PET tracer monitored active disease with 14- to 17-fold higher sensitivity than translocator protein 18 kDa (TSPO)-PET imaging, the established approach for detecting neuroinflammation in vivo. We illustrate the therapeutic potential of attenuating TREM1 signaling both genetically and pharmacologically in the EAE mice and show that TREM1-PET imaging detected responses to an FDA-approved MS therapy with siponimod (BAF312) in these animals. Last, we observed TREM1⁺ cells in clinical brain biopsy samples from two treatment-naïve patients with MS but not in healthy control brain tissue. Thus, TREM1-PET imaging has potential for aiding in the diagnosis of MS and monitoring of therapeutic responses to drug treatment.

Acyl Amidines by Pd-Catalyzed Aminocarbonylation: One-Pot Cyclizations and 11C Labeling

A protocol for the carbonylative synthesis of acyl amidines from aryl halides, amidines, and carbon monoxide catalyzed by Pd(0) is reported herein. Notably, carbon monoxide is generated ex situ from a solid CO source, and several productive palladium ligands were identified with complementary benefits and substrate scope. Furthermore, sequential one-pot, two-step protocols for the synthesis of 1,2,4-triazoles and 1,2,4-oxadiazoles via acyl amidine intermediates are reported. In addition, this approach was extended to isotopic labeling using [¹¹C]carbon monoxide to allow, for the first time, synthesis of ¹¹C-labeled acyl amidines as well as a ¹¹C-labeled 1,2,4-oxadiazole.

The Effects of Combining Cancer Drugs with Compounds Isolated from Combretum zeyheri Sond. and Combretum platypetalum Welw. ex M.A. Lawson (Combretaceae) on the Viability of Jurkat T Cells and HL-60 Cells

Combretum zeyheri and Combretum platypetalum have been shown to have anticancer, antibacterial, antituberculosis, and antifungal effects in both in vivo and in vitro studies. This study sought to evaluate the antiproliferative effects of compounds isolated from C. zeyheri and C. platypetalum on Jurkat T and HL-60 cancer cell lines in combination with doxorubicin and/or chlorambucil. At their GI50 concentrations, the isolated compounds were combined with the corresponding GI50 of chlorambucil and doxorubicin. The cytotoxic effects of the combined compounds were determined on BALB/c mouse peritoneal cells. All the 4 isolated compounds had significant cytotoxic effects on Jurkat T cells. Compounds CP 404 (1), CP 409 (2), CZ 453 (3), and CZ 455 (4) had GI50s on Jurkat T cells of 3.98, 19.33, 6.82, and 20.28 μg/ml, respectively. CP 404 (1), CP 409 (2), CZ 453 (3), and CZ 455 (4) showed GI50s of 14.18, 28.69, 29.87, and 16.46 μg/ml on HL-60 cancer cell lines, respectively. The most potent combination against Jurkat T cells was found to be CP 404 (1) and chlorambucil. This combination showed no cytotoxic effects when tested on BALB/c mouse peritoneal cells. It was concluded that the compounds extracted from C. zeyheri and C. platypetalum inhibit the growth of Jurkat T cells in vitro. The combination of the compounds with anticancer drugs enhanced their anticancer effects. The combination of CP 404 (1) and chlorambucil was found not to be toxic to normal mammalian cells. Therefore, CP 404 (1), 3-O-β-L-rrhamnopyranosyl-5,7,3'4',5'-pentahydroxyflavone, has the potential to be a source of lead compounds that can be developed for anticancer therapy. Further structure-activity relationship studies on this compound are warranted.

Synthesis of substituted 3,4-dihydroquinazolinones via a metal free Leuckart-Wallach type reaction

The 3,4-dihydroquinazolinone (DHQ) moiety is a highly valued scaffold in medicinal chemistry due to the vast number of biologically-active compounds based on this core structure. Current synthetic methods to access these compounds are limited in terms of diversity and flexibility and often require the use of toxic reagents or expensive transition-metal catalysts. Herein, we describe the discovery and development of a novel cascade cyclization/Leuckart-Wallach type strategy to prepare substituted DHQs in a modular and efficient process using readily-available starting materials. Notably, the reaction requires only the addition of formic acid or acetic acid/formic acid and produces H₂O, CO₂ and methanol as the sole reaction byproducts. Overall, the reaction provides an attractive entry point into this important class of compounds and could even be extended to isotopic labelling via the site-selective incorporation of a deuterium atom.

Development of a CD19 PET tracer for detecting B cells in a mouse model of multiple sclerosis

Background

B cells play a central role in multiple sclerosis (MS) through production of injurious antibodies, secretion of pro-inflammatory cytokines, and antigen presentation. The therapeutic success of monoclonal antibodies (mAbs) targeting B cells in some but not all individuals suffering from MS highlights the need for a method to stratify patients and monitor response to treatments in real-time. Herein, we describe the development of the first CD19 positron emission tomography (PET) tracer, and its evaluation in a rodent model of MS, experimental autoimmune encephalomyelitis (EAE).

Methods

Female C57BL/6 J mice were induced with EAE through immunization with myelin oligodendrocyte glycoprotein (MOG_1–125). PET imaging of naïve and EAE mice was performed 19 h after administration of [⁶⁴Cu]CD19-mAb. Thereafter, radioactivity in organs of interest was determined by gamma counting, followed by ex vivo autoradiography of central nervous system (CNS) tissues. Anti-CD45R (B220) immunostaining of brain tissue from EAE and naïve mice was also conducted.

Results

Radiolabelling of DOTA-conjugated CD19-mAb with ⁶⁴Cu was achieved with a radiochemical purity of 99% and molar activity of 2 GBq/μmol. Quantitation of CD19 PET images revealed significantly higher tracer binding in whole brain of EAE compared to naïve mice (2.02 ± 0.092 vs. 1.68 ± 0.06 percentage of injected dose per gram, % ID/g, p = 0.0173). PET findings were confirmed by ex vivo gamma counting of perfused brain tissue (0.22 ± 0.020 vs. 0.12 ± 0.003 % ID/g, p = 0.0010). Moreover, ex vivo autoradiography of brain sections corresponded with PET imaging results and the spatial distribution of B cells observed in B220 immunohistochemistry—providing further evidence that [⁶⁴Cu]CD19-mAb enables visualization of B cell infiltration into the CNS of EAE mice.

Conclusion

CD19-PET imaging can be used to detect elevated levels of B cells in the CNS of EAE mice, and has the potential to impact the way we study, monitor, and treat clinical MS.

Physiological blood-brain transport is impaired with age by a shift in transcytosis

The vascular interface of the brain, known as the blood-brain barrier (BBB), is understood to maintain brain function in part via its low transcellular permeability^1-3. Yet, recent studies have demonstrated that brain ageing is sensitive to circulatory proteins^4,5. Thus, it is unclear whether permeability to individually injected exogenous tracers-as is standard in BBB studies-fully represents blood-to-brain transport. Here we label hundreds of proteins constituting the mouse blood plasma proteome, and upon their systemic administration, study the BBB with its physiological ligand. We find that plasma proteins readily permeate the healthy brain parenchyma, with transport maintained by BBB-specific transcriptional programmes. Unlike IgG antibody, plasma protein uptake diminishes in the aged brain, driven by an age-related shift in transport from ligand-specific receptor-mediated to non-specific caveolar transcytosis. This age-related shift occurs alongside a specific loss of pericyte coverage. Pharmacological inhibition of the age-upregulated phosphatase ALPL, a predicted negative regulator of transport, enhances brain uptake of therapeutically relevant transferrin, transferrin receptor antibody and plasma. These findings reveal the extent of physiological protein transcytosis to the healthy brain, a mechanism of widespread BBB dysfunction with age and a strategy for enhanced drug delivery.

Microwave-Assisted aza-Friedel-Crafts Arylation of N-Acyliminium Ions: Expedient Access to 4-Aryl 3,4-Dihydroquinazolinones

A one-pot microwave-assisted aza-Friedel-Crafts arylation of N-acyliminium ions, generated in situ from o-formyl carbamates and different amines, is reported. This metal-free protocol provides rapid access to diverse 4-aryl 3,4-dihydroquinazolinones in excellent yield without any aqueous workup. A solvent-directed process for the selective aza-Friedel-Crafts arylation of electron-rich aryl/heteroaryl/butenyl-tethered N-acyliminium ions is also described.

11C-DPA-713 Versus 18F-GE-180: A Preclinical Comparison of Translocator Protein 18 kDa PET Tracers to Visualize Acute and Chronic Neuroinflammation in a Mouse Model of Ischemic Stroke

Neuroinflammation plays a key role in neuronal injury after ischemic stroke. PET imaging of translocator protein 18 kDa (TSPO) permits longitudinal, noninvasive visualization of neuroinflammation in both preclinical and clinical settings. Many TSPO tracers have been developed, however, it is unclear which tracer is the most sensitive and accurate for monitoring the in vivo spatiotemporal dynamics of neuroinflammation across applications. Hence, there is a need for head-to-head comparisons of promising TSPO PET tracers across different disease states. Accordingly, the aim of this study was to directly compare 2 promising second-generation TSPO tracers, ¹¹C-DPA-713 and ¹⁸F-GE-180, for the first time at acute and chronic time points after ischemic stroke. Methods: After distal middle cerebral artery occlusion or sham surgery, mice underwent consecutive PET/CT imaging with ¹¹C-DPA-713 and ¹⁸F-GE-180 at 2, 6, and 28 d after stroke. T2-weighted MR images were acquired to enable delineation of ipsilateral (infarct) and contralateral brain regions of interest (ROIs). PET/CT images were analyzed by calculating percentage injected dose per gram in MR-guided ROIs. SUV ratios were determined using the contralateral thalamus (SUV_Th) as a pseudoreference region. Ex vivo autoradiography and immunohistochemistry were performed to verify in vivo findings. Results: Significantly increased tracer uptake was observed in the ipsilateral compared with contralateral ROI (SUV_Th, 50-60 min summed data) at acute and chronic time points using ¹¹C-DPA-713 and ¹⁸F-GE-180. Ex vivo autoradiography confirmed in vivo findings demonstrating increased TSPO tracer uptake in infarcted versus contralateral brain tissue. Importantly, a significant correlation was identified between microglial/macrophage activation (cluster of differentiation 68 immunostaining) and ¹¹C-DPA-713- PET signal, which was not evident with ¹⁸F-GE-180. No significant correlations were observed between TSPO PET and activated astrocytes (glial fibrillary acidic protein immunostaining). Conclusion: ¹¹C-DPA-713 and ¹⁸F-GE-180 PET enable detection of neuroinflammation at acute and chronic time points after cerebral ischemia in mice. ¹¹C-DPA-713 PET reflects the extent of microglial activation in infarcted distal middle cerebral artery occlusion mouse brain tissue more accurately than ¹⁸F-GE-180 and appears to be slightly more sensitive. These results highlight the potential of ¹¹C-DPA-713 for tracking microglial activation in vivo after stroke and warrant further investigation in both preclinical and clinical settings.

Acetic acid-promoted cascade N-acyliminium ion/aza-Prins cyclization: stereoselective synthesis of functionalized fused tricyclic piperidines

A novel acetic acid-promoted metal-free cascade N-acyliminium ion/aza-Prins cyclization of o-formyl carbamates and homoallylamines is reported. This one-pot protocol provides efficient and rapid access to masked cis-hydroxyhexahydropyrido[1,2-c]quinazolin-6-ones with concomitant generation of two stereogenic centers, four C-C/C-O/C-N bonds and two new rings in good yield and excellent diastereoselectivity.

Synthesis of 11C-labeled Sulfonyl Carbamates through a Multicomponent Reaction Employing Sulfonyl Azides, Alcohols, and [11C]CO

We describe the development of a new methodology focusing on 11C-labeling of sulfonyl carbamates in a multicomponent reaction comprised of a sulfonyl azide, an alkyl alcohol, and [11C]CO. A number of 11C-labeled sulfonyl carbamates were synthesized and isolated, and the developed methodology was then applied in the preparation of a biologically active molecule. The target compound was obtained in 24±10 % isolated radiochemical yield and was evaluated for binding properties in a tumor cell assay; in vivo biodistribution and imaging studies were also performed. This represents the first successful radiolabeling of a non-peptide angiotensin II receptor subtype 2 agonist, C21, currently in clinical trials for the treatment of idiopathic pulmonary fibrosis.

A microwave-assisted multicomponent synthesis of substituted 3,4-dihydroquinazolinones

A series of structurally diverse 3,4-dihydroquinazolinones was synthesized via a novel cascade imine/cyclization/aza-Henry reaction in moderate to excellent yields.

Corticotropin-releasing hormone receptor subtype 1 is significantly up-regulated at the time of labor in the human myometrium

Circulating concentrations of CRH rise late in human pregnancy, reaching a peak at labor. The presence of functional CRH receptors, CRH-R1 and CRH-R2, in the human myometrium suggests that CRH may modulate uterine activity. We hypothesized that the number of CRH receptors would be higher in myometrium than fetal membranes (FM) and would change during labor. Myometrial samples were collected from the lower segment (LS) in nonpregnant, preterm (32 +/- 2 weeks), and term (39 +/- 1.6 weeks) pregnant patients before and at labor. Fundus and LS samples were also collected from nonpregnant, pregnant, laboring, and postpartum women. FM were collected at term and at labor. We identified CRH receptors in myometrium and FM by semiquantitative RT-PCR and immunohistochemistry. CRH-R1 messenger ribonucleic acid (mRNA) in the LS was decreased in pregnancy and increased significantly in both preterm and term labor (P < 0.05), but remained unchanged in the fundus. CRH-R2 mRNA was present in 28% of LS myometrium with no change at labor. CRH-R1 and CRH-R2 protein was localized to myometrial smooth muscle in nonpregnant and laboring patients, with lower levels at term. CRH-R1 mRNA was present in chorion and decidua, but CRH-R2 was undetectable in these tissues. We conclude that CRH-R1 is expressed preferentially in myometrium and FM. Changes in CRH receptors during labor are consistent with CRH mediating effects on myometrial activity.

The effects of estradiol-17 beta infusion into fetal sheep in late gestation

Activation of the hypothalamic-pituitary-adrenal (HPA) axis of fetal sheep during late gestation is associated with increases in plasma concentrations of adrenocorticotropic hormone (ACTH) and cortisol, and ultimately results in parturition. However, the mechanisms contributing to the concurrent increases in ACTH and cortisol are unclear. Plasma estradiol-17 beta (E2) concentrations increase progressively in the prepartum ovine fetus, and we hypothesized that E2 may influence HPA activity by affecting either basal and/or hypoxemia-stimulated ACTH release. We examined potential mechanisms, including altered expression of pro-opiomelanocortin (POMC) in fetal pituitary corticotrophs, and changes in corticosteroid binding globulin (CBG) and/or the enzymes 11 beta hydroxy steroid dehydrogenase (11 beta HSD)-1 or 11 beta HSD-2 in liver and placenta, that could alter negative feedback control. We infused fetal sheep at 127 d of gestation with either E2 (100 micrograms/24 h) or saline for 100 h. Fetal arterial blood samples were collected at 8 h intervals during the infusion of E2 or saline (n = 4), for measurement of basal plasma ACTH and cortisol concentrations, as well as plasma corticosteroid binding capacity (CBC). Placenta and fetal liver samples were collected at 100 h for measurement of placental 11 beta HSD-1 and 11 beta HSD-2 mRNA and hepatic CBG and 11 beta HSD-1 mRNA, by Northern blotting. Fetal pituitary samples were collected for measurement of POMC mRNA by in situ hybridization. In a separate experiment, fetuses were exposed to 2 h of hypoxemia at 75 h of E2 or saline infusion (n = 4), and fetal arterial blood samples were collected during the period of hypoxemia for measurement of plasma ACTH and cortisol concentrations. E2 infusion had no effect on basal plasma concentrations of ACTH or total cortisol, or on the stimulated levels of ACTH or total cortisol achieved in response to hypoxemia. Basal fetal pituitary POMC mRNA also did not change significantly with E2 infusion. No significant increases were observed in plasma CBC during E2 administration. However, hepatic CBG and 11 beta HSD-1 mRNA were significantly elevated in the livers of E2-treated fetuses. Placental 11 beta HSD-1 mRNA; but not 11 beta HSD-2 mRNA was increased by E2 treatment. These data do not support a direct effect of exogenous E2 at the level of basal or hypoxemia-stimulated ACTH output, but suggest that elevated E2 concentrations may alter the expression of genes encoding proteins implicated in tonic regulation of fetal HPA function.