Seven Tesla Evidence for Columnar and Rostral-Caudal Organization of the Human Periaqueductal Gray Response in the Absence of Threat: A Working Memory Study

The periaqueductal gray (PAG) is a small midbrain structure that surrounds the cerebral aqueduct, regulates brain-body communication, and is often studied for its role in "fight-or-flight" and "freezing" responses to threat. We used ultra-high-field 7 T fMRI to resolve the PAG in humans and distinguish it from the cerebral aqueduct, examining its in vivo function during a working memory task (N = 87). Both mild and moderate cognitive demands elicited spatially similar patterns of whole-brain blood oxygenation level-dependent (BOLD) response, and moderate cognitive demand elicited widespread BOLD increases above baseline in the brainstem. Notably, these brainstem increases were not significantly greater than those in the mild demand condition, suggesting that a subthreshold brainstem BOLD increase occurred for mild cognitive demand as well. Subject-specific masks were group aligned to examine PAG response. In PAG, both mild and moderate demands elicited a well-defined response in ventrolateral PAG, a region thought to be functionally related to anticipated painful threat in humans and nonhuman animals-yet, the present task posed only the most minimal (if any) "threat," with the cognitive tasks used being approximately as challenging as remembering a phone number. These findings suggest that the PAG may play a more general role in visceromotor regulation, even in the absence of threat.

Imaging High-Risk Atherothrombosis Using a Novel Fibrin-Binding Positron Emission Tomography Probe

BACKGROUND AND PURPOSE

High-risk atherosclerosis is an underlying cause of cardiovascular events, yet identifying the specific patient population at immediate risk is still challenging. Here, we used a rabbit model of atherosclerotic plaque rupture and human carotid endarterectomy specimens to describe the potential of molecular fibrin imaging as a tool to identify thrombotic plaques.

METHODS

Atherosclerotic plaques in rabbits were induced using a high-cholesterol diet and aortic balloon injury (N=13). Pharmacological triggering was used in a group of rabbits (n=9) to induce plaque disruption. Animals were grouped into thrombotic and nonthrombotic plaque groups based on gross pathology (gold standard). All animals were injected with a novel fibrin-specific probe ⁶⁸Ga-CM246 followed by positron emission tomography (PET)/magnetic resonance imaging 90 minutes later. ⁶⁸Ga-CM246 was quantified on the PET images using tissue-to-background (back muscle) ratios and standardized uptake value.

RESULTS

Both tissue-to-background (back muscle) ratios and standardized uptake value were significantly higher in the thrombotic versus nonthrombotic group (P<0.05). Ex vivo PET and autoradiography of the abdominal aorta correlated positively with in vivo PET measurements. Plaque disruption identified by ⁶⁸Ga-CM246 PET agreed with gross pathology assessment (85%). In ex vivo surgical specimens obtained from patients undergoing elective carotid endarterectomy (N=12), ⁶⁸Ga-CM246 showed significantly higher binding to carotid plaques compared to a D-cysteine nonbinding control probe.

CONCLUSIONS

We demonstrated that molecular fibrin PET imaging using ⁶⁸Ga-CM246 could be a useful tool to diagnose experimental and clinical atherothrombosis. Based on our initial results using human carotid plaque specimens, in vivo molecular imaging studies are warranted to test ⁶⁸Ga-CM246 PET as a tool to stratify risk in atherosclerotic patients.

FoxO1 as a Regulator of Aquaporin 5 Expression in the Salivary Gland

Forkhead box O1 (FoxO1) is a multifunctional initiator, mediator, and repressor of autoimmune diseases in an organ- or disease-specific manner. However, the role of FoxO1 in the salivary gland has not yet been elucidated. In this study, we discovered that FoxO1 and aquaporin 5 (AQP5) are both significantly downregulated in the patients with primary Sjögren syndrome, an autoimmune disease accompanying salivary gland dysfunction. Pharmacologic or genetic perturbation of FoxO1 in the rat salivary gland acinar cell line, SMG-C6, induced a significant downregulation of AQP5 expression, as observed in clinical specimens. There was a strong correlation between FoxO1 and AQP5 expression because FoxO1 is a direct regulator of AQP5 expression in salivary gland acinar cells through its interaction with the promoter region of AQP5. Serial injection of a FoxO1 inhibitor into mice induced a reduction of AQP5 expression in submandibular glands and, consequently, hyposalivation, which is one of the major clinical symptoms of primary Sjögren syndrome. However, there was no sign of inflammation or cell damage in the submandibular glands harvested from mice treated with the FoxO1 inhibitor. In conclusion, our findings indicate that FoxO1 in salivary gland tissue acts as a direct regulator of AQP5 expression. Thus, downregulation of FoxO1 observed in primary Sjögren syndrome is a putative mechanism for hyposalivation without the involvement of previously reported soluble factors in primary Sjögren syndrome patient sera.

Synthesis and Characterization of Fluorine-18-Labeled N-(4-Chloro-3-((fluoromethyl-d2)thio)phenyl)picolinamide for Imaging of mGluR4 in Brain

We have synthesized and characterized [18F]-N-(4-chloro-3-((fluoromethyl-d2)thio)phenyl)-picolinamide ([18F]15) as a potential ligand for the positron emission tomography (PET) imaging of mGluR4 in the brain. Radioligand [18F]15 displays central nervous system drug-like properties, including mGluR4 affinity, potent mGluR4 PAM activity, and selectivity against other mGluRs, as well as sufficient metabolic stability. Radiosynthesis was carried out in two steps. The radiochemical yield of [18F]15 was 11.6 ± 2.9% (n = 7, decay corrected) with a purity of 99% and a molar activity of 84.1 ± 11.8 GBq/μmol. Ex vivo biodistribution studies showed reversible binding of [18F]15 in all investigated tissues including the brain, liver, heart, lungs, and kidneys. PET imaging studies in male Sprague Dawley rats showed that [18F]15 accumulates in the brain regions known to express mGluR4. Pretreatment with the unlabeled mGluR4 PAM compounds 13 (methylthio analogue) and 15 showed significant dose-dependent blocking effects. These results suggest that [18F]15 is a promising radioligand for PET imaging mGluR4 in the brain.

Dual dose-dependent effects of fingolimod in a mouse model of Alzheimer's disease

Lipid metabolism is abnormal in Alzheimer’s disease (AD) brain leading to ceramide and sphingosine accumulation and reduced levels of brain sphingosine-1-phosphate (S1P). We hypothesize that changes in S1P signaling are central to the inflammatory and immune-pathogenesis of AD and the therapeutic benefits of fingolimod, a structural analog of sphingosine that is FDA approved for the treatment of multiple sclerosis. We recently reported that the neuroprotective effects of fingolimod in 5xFAD transgenic AD mice treated from 1–3 months of age were greater at 1 mg/kg/day than at 5 mg/kg/day. Here we performed a dose-response study using fingolimod from 0.03 to 1 mg/kg/day in 5xFAD mice treated from 1–8 months of age. At 1 mg/kg/day, fingolimod decreased both peripheral blood lymphocyte counts and brain Aβ levels, but at the lowest dose tested (0.03 mg/kg/day), we detected improved memory, decreased activation of brain microglia and astrocytes, and restored hippocampal levels of GABA and glycerophosphocholine with no effect on circulating lymphocyte counts. These findings suggests that, unlike the case in multiple sclerosis, fingolimod may potentially have therapeutic benefits in AD at low doses that do not affect peripheral lymphocyte function.

Abstract WP526: Molecular Imaging of Carotid Plaques Using a Fibrin-Binding PET Probe

Objectives: We aim to develop molecular fibrin imaging as a tool to stratify high risk atherosclerotic carotid plaques. Here, we describe our results with a fibrin-specific probe [ 68 Ga]CM-246 in two different experimental settings: ex vivo imaging of carotid endarterectomy specimens and in vivo / ex vivo imaging of atherosclerotic plaque rupture in rabbits.

Methods: We incubated discarded endarterectomy specimens (n=11) from asymptomatic patients with [ 68 Ga] CM-246 or a scrambled peptide control probe and measured uptake by autoradiography and a tissue binding assay. In a rabbit plaque rupture model of high cholesterol diet followed by abdominal aorta balloon injury (n=13) and subsequent pharmacological plaque rupture, in vivo and ex vivo PET-MR with [ 68 Ga]CM-246 was performed. Tissues were processed for autoradiography and histology to verify presence of fibrin and plaque rupture.

Results: Autoradiography (A-B) and tissue binding assays (C) with [ 68 Ga]CM-246 with human carotid plaques show increased tissue binding compared with non-specific control probe. Carstair’s staining (D) verified the presence of fibrin in the specimens (red stained areas). Rabbits with plaque rupture had an increase in [ 68 Ga]CM-246 signal in the abdominal aorta compared with the control group. At 105-120 min post probe injection, there was a clear PET uptake on the aorta in plaque rupture rabbit (E) compared with control rabbit (F). MR images were used to differentiate abdominal aorta (green arrows) and the inferior vena cava (blue arrows). T2-dark blood images confirmed the plaques in rupture (G) and control rabbits (H). ToF images were used to visualize aortic lumen in plaque rupture (I) and control rabbits (J). Ex-vivo PET imaging, autoradiography, and histology confirmed in vivo results.

Conclusions: We demonstrated that [ 68 Ga]CM-246 detects high-risk plaque in human and rabbits and can be a useful tool for the stratification of atherosclerotic plaques in patients.

Molecular magnetic resonance imaging accurately measures the antifibrotic effect of EDP-305, a novel farnesoid X receptor agonist

We examined a novel farnesoid X receptor agonist, EDP-305, for its antifibrotic effect in bile duct ligation (BDL) and choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) models of hepatic injury. We used molecular magnetic resonance imaging with the type 1 collagen-binding probe EP-3533 and the oxidized collagen-specific probe gadolinium hydrazide to noninvasively measure treatment response. BDL rats (n = 8 for each group) were treated with either low or high doses of EDP-305 starting on day 4 after BDL and were imaged on day 18. CDAHFD mice (n = 8 for each group) were treated starting at 6 weeks after the diet and were imaged at 12 weeks. Liver tissue was subjected to pathologic and morphometric scoring of fibrosis, hydroxyproline quantitation, and determination of fibrogenic messenger RNA expression. High-dose EDP-305 (30 mg/kg) reduced liver fibrosis in both the BDL and CDAHFD models as measured by collagen proportional area, hydroxyproline analysis, and fibrogenic gene expression (all P < 0.05). Magnetic resonance signal intensity with both EP-3533 in the BDL model and gadolinium hydrazide in the CDAHFD model was reduced with EDP-305 30 mg/kg treatment (P < 0.01). Histologically, EDP-305 30 mg/kg halted fibrosis progression in the CDAHFD model. Conclusion: EDP-305 reduced fibrosis progression in rat BDL and mouse CDAHFD models. Molecular imaging of collagen and oxidized collagen is sensitive to changes in fibrosis and could be used to noninvasively measure treatment response in clinical trials. (Hepatology Communications 2018;2:821-835).

Abstract 324: Molecular Imaging of High Risk Atherosclerotic Plaque Using Fibrin-Binding PET Probe

Objectives: There is a need for better stratification of atherosclerotic patients to identify individuals at high risk for a cardiovascular event. Two key hallmarks of plaque at high risk for rupture are intraplaque hemorrhage and evidence of prior rupture. The protein fibrin is strongly associated with both hemorrhage and rupture but it is not present in earlier stages of plaque development, suggesting that fibrin imaging would be sensitive for high risk plaque versus stable/early disease. Here, we describe imaging properties of a fibrin-specific PET probe for atherosclerotic plaque rupture in rabbits.

Methods: Rabbits were fed with high cholesterol diet (HCD) for 8 weeks followed by 2 weeks of normal diet. Two weeks after the initiation of HCD, endothelial denudation of abdominal aorta was performed using balloon catheter. At 10 weeks, rabbits were randomly divided into plaque rupture (n=8; triggered by Russell’s viper venom and histamine) and control group (n=4), injected with fibrin-binding probe [ 68 Ga]CM-246, and scanned on a PET/MRI. Then, vessels of interest were removed for ex-vivo PET, autoradiography, and histology.

Results: Rabbits with plaque rupture had >2-fold increase in [ 68 Ga]CM-246 signal in the abdominal aorta compared with the control group (A). At 105-120 min post probe injection, there was a clear PET uptake on the aorta in plaque rupture rabbit (B) compared with control rabbit (C). MR images were used to differentiate abdominal aorta (green arrows) and the inferior vena cava (blue arrows). T2-dark blood images confirmed the atherosclerotic plaques in plaque rupture (D) and control rabbits (E). ToF images were used to visualize aortic lumen in plaque rupture (F) and control rabbits (G). Ex vivo PET imaging (H) and autoradiography confirmed in vivo results.

Conclusions: We demonstrated that [ 68 Ga]CM-246 detects atherosclerotic plaque rupture in a rabbit model and can be a useful tool for the diagnosis of high-risk atherosclerotic plaque in patients.

ATX-MS-1467 Induces Long-Term Tolerance to Myelin Basic Protein in (DR2 × Ob1)F1 Mice by Induction of IL-10-Secreting iTregs

Introduction

Antigen-specific immunotherapy could provide a targeted approach for the treatment of multiple sclerosis that removes the need for broad-acting immunomodulatory drugs. ATX-MS-1467 is a mixture of four peptides identified as the main immune-dominant disease-associated T-cell epitopes in myelin basic protein (MBP), an autoimmune target for activated autoreactive T cells in multiple sclerosis. Previous animal studies have shown that ATX-MS-1467 treatment prevented the worsening of signs of disease in experimental autoimmune encephalitis (EAE) in the humanized (DR2 × Ob1)F1 mouse in a dose-dependent fashion.

Methods and Results

Our study extends these observations to show that subcutaneous treatment with 100 µg of ATX-MS-1467 after induction of EAE in the same mouse model reversed established clinical disability (p < 0.0001) and histological markers of inflammation and demyelination (p < 0.001) compared with vehicle-treated animals; furthermore, in longitudinal magnetic resonance imaging analyses, disruption of blood–brain barrier integrity was reversed, compared with vehicle-treated animals (p < 0.05). Chronic treatment with ATX-MS-1467 was associated with an enduring shift from a pro-inflammatory to a tolerogenic state in the periphery, as shown by an increase in interleukin 10 secretion, relative to interleukin 2, interleukin 17 and interferon γ, a decrease in splenocyte proliferation and an increase in interleukin 10⁺ Foxp3⁻ T cells in the spleen.

Conclusion

Our results suggest that ATX-MS-1467 can induce splenic iTregs and long-term tolerance to MBP with the potential to partially reverse the pathology of multiple sclerosis, particularly during the early stages of the disease.

Funding

EMD Serono, Inc., a business of Merck KGaA.

Abstinence to chronic methamphetamine switches connectivity between striatal, hippocampal and sensorimotor regions and increases cerebral blood volume response

Methamphetamine (meth), and other psychostimulants such as cocaine, present a persistent problem for society with chronic users being highly prone to relapse. We show, in a chronic methamphetamine administration model, that discontinuation of drug for more than a week produces much larger changes in overall meth-induced brain connectivity and cerebral blood volume (CBV) response than changes that occur immediately following meth administration. Areas showing the largest changes were hippocampal, limbic striatum and sensorimotor cortical regions as well as brain stem areas including the pedunculopontine tegmentum (PPTg) and pontine nuclei - regions known to be important in mediating reinstatement of drug-taking after abstinence. These changes occur concomitantly with behavioral sensitization and appear to be mediated through increases in dopamine D1 and D3 and decreases in D2 receptor protein and mRNA expression. We further identify a novel region of dorsal caudate/putamen, with a low density of calbindin neurons, that has an opposite hemodynamic response to meth than the rest of the caudate/putamen and accumbens and shows very strong correlation with dorsal CA1 and CA3 hippocampus. This correlation switches following meth abstinence from CA1/CA3 to strong connections with ventral hippocampus (ventral subiculum) and nucleus accumbens. These data provide novel evidence for temporal alterations in brain connectivity where chronic meth can subvert hippocampal - striatal interactions from cognitive control regions to regions that mediate drug reinstatement. Our results also demonstrate that the signs and magnitudes of the induced CBV changes following challenge with meth or a D3-preferring agonist are a complementary read out of the relative changes that occur in D1, D2 and D3 receptors using protein or mRNA levels.

Protective effects of 7,8-dihydroxyflavone on neuropathological and neurochemical changes in a mouse model of Alzheimer's disease

Interest in brain-derived neurotrophic factor (BDNF) was greatly enhanced when it was recognized that its expression is reduced in neurodegenerative disorders, especially in Alzheimer's disease (AD). BDNF signaling through the TrkB receptor has a central role in promoting synaptic transmission, synaptogenesis, and facilitating synaptic plasticity making the BDNF-TrkB signaling pathway an attractive candidate for targeted therapies. Here we investigated the early effect of the small molecule TrkB agonist, 7,8 dihydroxyflavone (7,8-DHF), on AD-related pathology, dendritic arborization, synaptic density, and neurochemical changes in the 5xFAD mouse model of AD. We treated 5xFAD mice with 7,8-DHF for 2 months beginning at 1 month of age. We found that, in this model of AD, 7,8-DHF treatment decreased cortical Aβ plaque deposition and protected cortical neurons against reduced dendritic arbor complexity but had no significant impact on the density of dendritic spines. In addition 7,8-DHF treatment protected against hippocampal increase in the level of choline-containing compounds and glutamate loss, but had no significant impact on hippocampal neurogenesis.

The reliability of the Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) among dermatologists, rheumatologists and neurologists

BACKGROUND

Previous studies have shown that skin disease in dermatomyositis (DM) is best assessed using the Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI). Although the CDASI has been validated for use by dermatologists, it has not been validated for use by other physicians such as rheumatologists and neurologists, who also manage patients with DM and assess skin activity in clinical trials.

OBJECTIVES

To assess the reliability of the CDASI among dermatologists, rheumatologists and neurologists.

METHODS

Fifteen patients with cutaneous DM were assessed using the CDASI and the Physician Global Assessment (PGA) by five dermatologists, five rheumatologists and five neurologists.

RESULTS

The mean CDASI activity scores for dermatologists, rheumatologists and neurologists were 21·0, 21·8 and 20·8, respectively. These mean scores were not different among the specialists. The CDASI damage score means for dermatologists, rheumatologists and neurologists were 5·3, 7·0 and 4·8, respectively. The mean scores between dermatologists and rheumatologists were significantly different, but the means between dermatologists and neurologists were not. The intraclass correlation coefficients (ICCs) for interrater reliability for CDASI activity and damage were good to excellent for dermatologists and rheumatologists, and moderate to excellent for neurologists. The ICCs for intrarater reliability for CDASI activity and damage were excellent for dermatologists and rheumatologists and moderate to excellent for neurologists. The PGA displayed lower interrater and intrarater reliability relative to the CDASI.

CONCLUSIONS

Our results confirm the reliability of the CDASI when used by dermatologists and rheumatologists. The data for its use by neurologists were not as robust.

Functional modulation of G-protein coupled receptors during Parkinson disease-like neurodegeneration

G-protein coupled dopamine and metabotropic glutamate receptors (mGlu) can modulate neurotransmission during Parkinson's disease (PD)-like neurodegeneration. PET imaging studies in a unilateral dopamine denervation model (6-OHDA) showed a significant inverse correlation of presynaptic mGlu4 and postsynaptic mGlu5 expression in the striatum and rapidly declining mGlu4 and enhanced mGlu5 expression in the hippocampus during progressive degeneration over time. Immunohistochemical studies verified the decreased mGlu4 expression in the hippocampus on the lesion side but did not show difference in mGlu5 expression between lesion and control side. Pharmacological MRI studies showed enhanced hemodynamic response in several brain areas on the lesion side compared to the control side after challenge with mGlu4 positive allosteric modulator or mGlu5 negative allosteric modulator. However, mGlu4 response was biphasic having short enhancement followed by negative response on both sides of brain. Studies in mGlu4 expressing cells demonstrated that glutamate induces cooperative increase in binding of mGlu4 ligands - especially at high glutamate levels consistent with in vivo concentration. This suggests that mGlu allosteric modulators as drug candidates will be highly sensitive to changes in glutamate concentration and hence metabolic state. These experiments demonstrate the importance of the longitudinal imaging studies to investigate temporal changes in receptor functions to obtain individual response for experimental drugs.

Surveillance of the Middle East respiratory syndrome (MERS) coronavirus (CoV) infection in healthcare workers after contact with confirmed MERS patients: incidence and risk factors of MERS-CoV seropositivity

Given the mode of transmission of Middle East respiratory syndrome (MERS), healthcare workers (HCWs) in contact with MERS patients are expected to be at risk of MERS infections. We evaluated the prevalence of MERS coronavirus (CoV) immunoglobulin (Ig) G in HCWs exposed to MERS patients and calculated the incidence of MERS-affected cases in HCWs. We enrolled HCWs from hospitals where confirmed MERS patients had visited. Serum was collected 4 to 6 weeks after the last contact with a confirmed MERS patient. We performed an enzyme-linked immunosorbent assay (ELISA) to screen for the presence of MERS-CoV IgG and an indirect immunofluorescence test (IIFT) to confirm MERS-CoV IgG. We used a questionnaire to collect information regarding the exposure. We calculated the incidence of MERS-affected cases by dividing the sum of PCR-confirmed and serology-confirmed cases by the number of exposed HCWs in participating hospitals. In total, 1169 HCWs in 31 hospitals had contact with 114 MERS patients, and among the HCWs, 15 were PCR-confirmed MERS cases in study hospitals. Serologic analysis was performed for 737 participants. ELISA was positive in five participants and borderline for seven. IIFT was positive for two (0.3%) of these 12 participants. Among the participants who did not use appropriate personal protective equipment (PPE), seropositivity was 0.7% (2/294) compared to 0% (0/443) in cases with appropriate PPE use. The incidence of MERS infection in HCWs was 1.5% (17/1169). The seroprevalence of MERS-CoV IgG among HCWs was higher among participants who did not use appropriate PPE.

Loss of Metabotropic Glutamate Receptor 5 Function on Peripheral Benzodiazepine Receptor in Mice Prenatally Exposed to LPS

Parental microglial induced neuroinflammation, triggered by bacterial- or viral infections, can induce neuropsychiatric disorders like schizophrenia and autism to offspring in animal models. Recent investigations suggest that microglia, the resident immune cells of the brain, provides a link between neurotransmission, immune cell activation, brain inflammation and neuronal dysfunction seen with the offspring. Relatively little is known about how reduction of brain inflammation and restoration of glial function are associated with diminution of brain degeneration and behavioral deficits in offspring. Increased mGluR5 expression and the long-lasting excitotoxic effects of the neurotoxin during brain development are associated with the glial dysfunctions. We investigated the relationship of mGluR5 and PBR and how they regulate glial function and inflammatory processes in mice prenatally exposed to LPS (120μg/kg, between gestational days 15 and 17), an inflammatory model of a psychiatric disorder. Using PET imaging, we showed that pharmacological activation of mGluR5 during 5 weeks reduced expression of classic inflammation marker PBR in many brain areas and that this molecular association was not present in LPS-exposed offspring. The post-mortem analysis revealed that the down regulation of PBR was mediated through activation of mGluR5 in astrocytes. In addition, we demonstrated that this interaction is defective in a mouse model of the psychiatric deficit offering a novel insight of mGluR5 involvement to brain related disorders and PBR related imaging studies. In conclusion, mGluR5 driven glutamatergic activity regulates astrocytic functions associated with PBR (cholesterol transport, neurosteroidogenesis, glial phenotype) during maturation and could be associated with neuropsychiatric disorders in offspring.

Re-exploring the N-phenylpicolinamide derivatives to develop mGlu4 ligands with improved affinity and in vitro microsomal stability

In recent years, mGlu4 has received great attention and research effort because of the potential benefits of mGlu4 activation in treating numerous brain disorders, such as Parkinson's disease (PD). Many positive allosteric modulators of mGlu4 have been developed. To better understand the role of mGlu4 in healthy and disease conditions, we are interested in developing an mGlu4 selective radioligand for in vivo studies. Thus, we had synthesized and studied [(11)C]2 as a PET tracer for mGlu4, which demonstrated some promising features as a PET radioligand as well as the limitation need to be improved. In order to develop an mGlu4 ligand with enhanced affinity and improved metabolic stability, we have modified, synthesized and evaluated a series of new N-phenylpicolinamide derivatives. The SAR study has discovered a number of compounds with low nM affinity to mGlu4. The dideuteriumfluoromethoxy modified compound 24 is identified as a very promising mGlu4 ligand, which has demonstrated enhanced affinity, improved in vitro microsomal stability, good selectivity and good permeability.

Radiosynthesis and evaluation of an 18F-labeled positron emission tomography (PET) radioligand for metabotropic glutamate receptor subtype 4 (mGlu4)

Four 4-phthalimide derivatives of N-(3-chlorophenyl)-2-picolinamide were synthesized as potential ligands for the PET imaging of mGlu₄ in the brain. Of these compounds, N-(3-chloro-4-(4-fluoro-1,3-dioxoisoindolin-2-yl)phenyl)-2-picolinamide (3, KALB001) exhibited improved binding affinity (IC₅₀ = 5.1 nM) compared with ML128 (1) and was subsequently labeled with ¹⁸F. When finally formulated in 0.1 M citrate buffer (pH 4) with 10% ethanol, the specific activity of [¹⁸F]3 at the end of synthesis (EOS) was 233.5 ± 177.8 GBq/μmol (n = 4). The radiochemical yield of [¹⁸F]3 was 16.4 ± 4.8% (n = 4), and the purity was over 98%. In vivo imaging studies in a monkey showed that the radiotracer quickly penetrated the brain with the highest accumulation in the brain areas known to express mGlu₄. Despite some unfavorable radiotracer properties like fast washout in rodent studies, [¹⁸F]3 is the first ¹⁸F-labeled mGlu₄ radioligand, which can be further modified to improve pharmacokinetics and brain penetrability for future human studies.

The effects of aging, housing and ibuprofen treatment on brain neurochemistry in a triple transgene Alzheimer's disease mouse model using magnetic resonance spectroscopy and imaging

We investigated a triple transgene Alzheimer's disease (AD) mouse model that recapitulates many of the neurochemical, anatomic, pathologic and behavioral defects seen in human AD. We studied the mice as a function of age and brain region and investigated potential therapy with the non-steroidal anti-inflammatory drug ibuprofen. Magnetic resonance spectroscopy (MRS) showed alterations characteristic of AD (i.e. increased myo-inositol and decreased N-acetylaspartate (NAA)). Mice at 6 months of age showed an increase in myo-inositol in the hippocampus at a time when the Aβ is intracellular, but not in amygdala or cortex. Myo-inositol increased as a function of age in the amygdala, cortex and striatum while NAA decreased only in the hippocampus and cortex at 17-23 months of age. Ibuprofen protected the increase of myo-inositol at six months of age in the hippocampus, but had no effect at 17-23 months of age (a time when Aβ is extracellular). In vivo MRI and MRS showed that at 17-23 months of age there was a significant protective effect of ibuprofen on hippocampal volume and NAA loss. Together, these data show the following: the increase in myo-inositol occurs before the decrease in NAA in hippocampus but not cortex; the hippocampus shows earlier changes than does the amygdale or cortex consistent with earlier deposition of Aβ40-42 in the hippocampus and ibuprofen protects against multiple components of the AD pathology. These data also show a profound effect of housing on this particular mouse model.

In vitro-growth and Gene Expression of Porcine Preantral Follicles Retrieved by Different Protocols

This study was conducted to determine how the isolation method of the porcine preantral follicles influenced the following follicular growth in vitro. Mechanical and enzymatical isolations were used for retrieving the follicles from prepubertal porcine ovaries, and in vitro-growth of the follicles and the expression of folliculogenesis-related genes were subsequently monitored. The enzymatic retrieval with collagenase treatment returned more follicles than the mechanical retrieval, while the percentage of morphologically normal follicles was higher with mechanical retrieval than with enzymatic retrieval. After 4 days of culture, mechanically retrieved, preantral follicles yielded more follicles with normal morphology than enzymatically retrieved follicles, which resulted in improved follicular growth. The mRNA expression of FSHR, LHR Cx43, DNMT1 and FGFR2 genes was significantly higher after culture of the follicles retrieved mechanically. These results suggest that mechanical isolation is a better method of isolating porcine preantral follicles that will develop into competent oocytes in in vitro culture.

First Report of Powdery Mildew Caused by Golovinomyces artemisiae on Artemisia annua in Korea

Artemisia annua L., known as sweet wormwood or sweet annie, is native to temperate Asia, but is naturalized throughout the world. It produces artemisinin, a potent antimalarial drug that is also effective in treating other parasitic diseases (4). In August 2013, hundreds of plants showing typical symptoms of powdery mildew were found in Seoul (37°36'29.4″ N 127°02'38.3″ E), Korea. Powdery mildew colonies first appeared as thin white patches, which progressed to abundant hyphal growth on both sides of the leaves, stems, and inflorescence. As symptoms continued to develop, the leaves became distorted and turned purplish-gray. Severe infections caused leaf withering and premature senescence. The same symptoms were found on sweet wormwoods in Nonsan (36°09'55.3″ N 127°01'07.1″ E) and Chuncheon (37°52'27.4″ N 127°43'10.0″ E), Korea. Voucher specimens were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or occasionally lobed. Conidiophores were cylindrical, measured 120 to 230 × 10 to 12.5 μm, and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of conidiophores were straight, cylindrical, and 54 to 100 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 30 to 40 × 15 to 20 μm (length/width ratio of 1.5 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Germ tubes were produced on the perihilar position of conidia. Primary conidia were apically rounded, basally subtruncate, and generally smaller than the secondary conidia. No chasmothecia were observed. The structures described above were typical of the powdery mildew Euoidium anamorph of the genus Golovinomyces, and the fungus measurements were similar to those of G. artemisiae (Grev.) V.P. Heluta (3). The complete internal transcribed spacer (ITS) region of rDNA from KUS-F27763 was amplified with primers ITS1/ITS4 and sequenced. The resulting sequence of 624 bp was deposited in GenBank (Accession No. KJ136112). The obtained ITS sequence shared >99% similarity with G. artemisiae on A. princeps and A. montana from Japan (AB077659 and AB077649) and A. argyi from China (KF056818). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy potted plants. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 5 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildews of A. annua caused by G. artemisiae have been reported in Japan, China, the Russian Far East, and Romania (1,2). To our knowledge, this is the first report of powdery mildew caused by G. artemisiae on A. annua in Korea. Since sweet wormwood production was only recently started on a commercial scale in Korea, powdery mildew infections pose a serious threat to the production of this plant, especially in organic farming where chemical control options are limited. References: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Societies Press, Tokyo, 1986. (2) U. Braun. The Powdery Mildews (Erysiphales) of Europe. G. Fischer Verlag, Jena, 1995. (3) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (4) P. J. Weathers et al. Phytochem. Rev. 10:173, 2011.

First Report of Powdery Mildew Caused by Golovinomyces sonchicola on Ixeris chinensis in Korea

Ixeris chinensis (Thunb.) Nakai, known as Chinese ixeris, is distributed from Siberia to Japan, including Korea, Taiwan, and China. The whole plant has been used in folk medicine in Asia (4). In Korea, the plants of Chinese ixeris have been gathered and used as a wild root vegetable. During summer to autumn of 2011, Chinese ixeris leaves were found to be heavily infected with a powdery mildew in several locations of Korea. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on both sides of the leaves, leading to drying of the leaves. The same symptoms on Chinese ixeris leaves were continuously observed in 2012 and 2013. Voucher specimens (n = 10) were deposited at Korea University Herbarium (KUS). Hyphal appressoria were moderately lobed or nipple-shaped. Conidiophores arose from the lateral part of the hyphae, measured 100 to 270 × 10 to 12.5 μm, and produced 2 to 6 immature conidia in chains with a sinuate outline. Basal parts of foot-cells in conidiophores were curved. Conidia were barrel-shaped to ellipsoid, measured 26 to 36 × 13 to 19 μm (length/width ratio = 1.7 to 2.4), lacked fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were ovate with conical-obtuse apex and subtruncate base. Germ tubes were produced on the perihilar position of conidia. Chasmothecia were not observed. The morphological characteristics were typical of the Euoidium type anamorph of the genus Golovinomyces, and the fungus measurements and structures were consistent with those of G. sonchicola U. Braun & R.T.A. Cook (1). To confirm the identification, internal transcribed spacer (ITS) region of rDNA sequences from a representative material (KUS-F26212) was amplified using primers ITS5/P3 and sequenced (3). The resulting 416-bp sequence was deposited in GenBank (Accession No. KF819857). A GenBank BLAST search revealed that the isolate showed >99% sequence similarity with those of G. cichoracearum from Sonchus spp. (e.g., AB453762, AF011296, JQ010848, etc.). G. sonchicola is currently confined to G. cichoracearum s. lat. on Sonchus spp., based on molecular sequence analyses (1). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted Chinese ixeris. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 days, whereas the controls remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildew infections of I. chinensis associated with Golovinomyces have been known in China (2). To our knowledge, this is the first report of powdery mildew disease caused by G. sonchicola on I. chinensis in Korea. Farming of Chinese ixeris has recently started on a commercial scale in Korea. Though no statistical data are available, we postulate the cultivation area in Korea to be approximately 200 ha, mostly growing without chemical controls. Occurrence of powdery mildews poses a potential threat to safe production of this vegetable, especially in organic farming. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) F. L. Tai. Bull. Chinese Bot. Sci. 2:16, 1936. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) S. J. Zhang et al. J. Nat. Prod. 69:1425, 2006.

Development of [(123)I]IPEB and [(123)I]IMPEB as SPECT Radioligands for Metabotropic Glutamate Receptor Subtype 5

mGlu5 play an important role in physiology and pathology to various central nervous system (CNS) diseases. Several positron emission tomography (PET) radiotracers have been developed to explore the role of mGlu5 in brain disorders. However, there are no single photon emission computed tomography (SPECT) radioligands for mGlu5. Here we report development of [(123)I]IPEB ([(123)I]1) and [(123)I]IMPEB ([(123)I]2) as mGlu5 radioligands for SPECT. [(123)I]1 and [(123)I]2 were produced by copper(I) mediated aromatic halide displacement reactions. The SPECT imaging using mouse models demonstrated that [(123)I]1 readily entered the brain and accumulated specifically in mGlu5-rich regions of the brain such as striatum and hippocampus. However, in comparison to the corresponding PET tracer [(18)F]FPEB, [(123)I]1 showed faster washout from the brain. The binding ratios of the striatum and the hippocampus compared to the cerebellum for [(123)I]1 and [(18)F]FPEB were similar despite unfavorable pharmacokinetics of [(123)I]1. Further structural optimization of 1 may lead to more viable SPECT radiotracers for the imaging of mGlu5.

Hypo-anxious phenotype of adolescent offspring prenatally exposed to LPS is associated with reduced mGluR5 expression in hippocampus

Many studies have reported long-term modulation of metabotropic glutamate receptor 5 (mGluR5) by inflammatory processes and a pharmacological modulation of mGluR5 is known to regulate anxiety level. However, it is not known if non-pharmacological modulation of mGluR5 by inflammation impaired the unconditional level of anxiety. In this study, we investigated this relation in LPS prenatal immune challenge (120μg/kg, 3x i.p. injection in late gestation), a developmental model of neuroinflammation in which some studies have reported hypo-anxious phenotype. Using positron emission tomographic imaging (PET) approaches, we have demonstrated a decrease in the binding potential of [¹⁸F]fluoro-5-(2-pyridinylethynyl)benzonitrile ([¹⁸F]FPEB, a radioligand for mGluR5) in hippocampus of adolescent offspring prenatally exposed to LPS, without significant change in the binding of [¹¹C]peripheral benzodiazepine receptor 28 ([¹¹C]PBR28), an inflammatory marker. In addition, dark-light box emergence test revealed a lower level of anxiety in LPS-exposed offspring and this behavioural phenotype was associated with the binding potential of [¹⁸F]FPEB in hippocampus. These results confirm that neuroinflammation during developmental phase modulates the physiology of mGluR5 and this alteration can be associated with behavioural phenotype related to anxiety. In addition, this study supports a hypotheses that mGluR5 could be used as a diagnostic target in anxiety.

Radiosynthesis of N-(4-chloro-3-[(11)C]methoxyphenyl)-2-picolinamide ([(11)C]ML128) as a PET radiotracer for metabotropic glutamate receptor subtype 4 (mGlu4)

N-(Chloro-3-methoxyphenyl)-2-picolinamide (3, ML128, VU0361737) is an mGlu4 positive allosteric modulator (PAM), which is potent and centrally penetrating. 3 is also the first mGlu4 PAM to show efficacy in a preclinical Parkinson disease model upon systemic dosing. As a noninvasive medical imaging technique and a powerful tool in neurological research, positron emission tomography (PET) offers a possibility to investigate mGlu4 expression in vivo under physiologic and pathological conditions. We synthesized a carbon-11 labeled ML128 ([(11)C]3) as a PET radiotracer for mGlu4, and characterized its biological properties in Sprague Dawley rats. [(11)C]3 was synthesized from N-(4-chloro-3-hydroxyphenyl)-2-picolinamide (2) using [(11)C]CH3I. Total synthesis time was 38±2.2min (n=7) from the end of bombardment to the formulation. The radioligand [(11)C]3 was obtained in 27.7±5.3% (n=5) decay corrected radiochemical yield based on the radioactivity of [(11)C]CO2. The radiochemical purity of [(11)C]3 was >99%. Specific activity was 188.7±88.8GBq/mol (n=4) at the end of synthesis (EOS). PET images were conducted in 20 normal male Sprague Dawley rats including 11 control studies, 6 studies blocking with an mGlu4 modulator (4) to investigate specificity and 3 studies blocking with an mGlu5 modulator (MTEP) to investigate selectivity. These studies showed fast accumulation of [(11)C]3 (peak activity between 1-3min) in several brain areas including striatum, thalamus, hippocampus, cerebellum, and olfactory bulb following with fast washout. Blocking studies with the mGlu4 modulator 4 showed 22-28% decrease of [(11)C]3 accumulation while studies of selectivity showed only minor decrease supporting good selectivity over mGlu5. Biodistribution studies and blood analyses support fast metabolism. Altogether this is the first PET imaging ligand for mGlu4, in which the labeled ML128 was used for imaging its in vivo distribution and pharmacokinetics in brain.