The Role of Behavioral Ecotoxicology in Environmental Protection.

For decades, we have known that chemicals affect human and wildlife behavior. Moreover, due to recent technological and computational advances, scientists are now increasingly aware that a wide variety of contaminants and other environmental stressors adversely affect organismal behavior and subsequent ecological outcomes in terrestrial and aquatic ecosystems. There is also a groundswell of concern that regulatory ecotoxicology does not adequately consider behavior, primarily due to a lack of standardized toxicity methods. This has, in turn, led to the exclusion of many behavioral ecotoxicology studies from chemical risk assessments. To improve understanding of the challenges and opportunities for behavioral ecotoxicology within regulatory toxicology/risk assessment, a unique workshop with international representatives from the fields of behavioral ecology, ecotoxicology, regulatory (eco)toxicology, neurotoxicology, test standardization, and risk assessment resulted in the formation of consensus perspectives and recommendations, which promise to serve as a roadmap to advance interfaces among the basic and translational sciences, and regulatory practices.

[GRADE guidelines: 18. How ROBINS-I and other tools to assess risk of bias in nonrandomized studies should be used to rate the certainty of a body of evidence]. / GRADE-Leitlinien: 18. Wie ROBINS-I und andere Instrumente zur Einschätzung des Risikos für Bias von nicht-randomisierten Studien verwendet werden sollten, um die Vertrauenswürdigkeit eines Evidenzkörpers zu bewerten.

OBJECTIVE: To provide guidance on how systematic review authors, guideline developers, and health technology assessment practitioners should approach the use of the risk of bias in nonrandomized studies of interventions (ROBINS-I) tool as a part of GRADE's certainty rating process. STUDY DESIGN AND SETTING: The study design and setting comprised iterative discussions, testing in systematic reviews, and presentation at GRADE working group meetings with feedback from the GRADE working group. RESULTS: We describe where to start the initial assessment of a body of evidence with the use of ROBINS-I and where one would anticipate the final rating would end up. The GRADE accounted for issues that mitigate concerns about confounding and selection bias by introducing the upgrading domains: large effects, dose-effect relations, and when plausible residual confounders or other biases increase certainty. They will need to be considered in an assessment of a body of evidence when using ROBINS-I. CONCLUSION: The use of ROBINS-I in GRADE assessments may allow for a better comparison of evidence from randomized controlled trials (RCTs) and nonrandomized studies (NRSs) because they are placed on a common metric for risk of bias. Challenges remain, including appropriate presentation of evidence from RCTs and NRSs for decision-making and how to optimally integrate RCTs and NRSs in an evidence assessment.

Modest and nonessential roles of the endocannabinoid system in immature hematopoiesis of mice.

Endocannabinoids are lipid mediators that signal via several seven-transmembrane domain G protein-coupled receptors. The endocannabinoid receptor CB2 is expressed on blood cells, including stem cells, and mediates the effects of cannabinoids on the immune system. The role of the endocannabinoid system in immature hematopoiesis is largely elusive. Both direct effects of endocannabinoids on stem cells and indirect effects through endocannabinoid-responsive niche cells like macrophages have been reported. Using two different CB2-deficient mouse models, we studied the role of the endocannabinoid system in immature hematopoiesis. Moreover, we utilized both models to assess the specificity of putative CB2 agonists. As heterodimerization of CB2 and CXCR4, which is highly expressed on hematopoietic stem cells, has already been described, we also assessed potential consequences of CB2 loss for CXCR4/CXCL12 signaling. Overall, no differential effects were observed with any of the compounds tested; the compounds barely induced signaling by themselves, whereas they attenuated CXCL12-induced signals in both CB2-competent and CB2-deficient cells. In vivo experiments were therefore by necessity restricted to loss-of-function studies in knockout (CB2-/-) mice: Except for mild lymphocytosis and slightly elevated circulating progenitor cells, homeostatic hematopoiesis in CB2-/- mice appears to be entirely normal. Mobilization in response to pharmacological stimuli, Plerixafor or G-CSF, was equally potent in wild-type and CB2-/- mice. CB2-/- bone marrow cells reconstituted hematopoiesis in lethally irradiated recipients with engraftment kinetics indistinguishable from those of wild-type grafts. In summary, we found the endocannabinoid system to be largely dispensable for normal murine hematopoiesis.

[GRADE: Using evidence to decision frameworks for adoption, adaptation and de novo generation of trustworthy guideline recommendations - GRADE-ADOLOPMENT]. / GRADE Evidence-to-Decision-Tabellen für die Übernahme, Anpassung und De-novo-Entwicklung von vertrauenswürdigen Empfehlungen: GRADE-ADOLOPMENT.

BACKGROUND: Guideline developers can: (1) adopt existing recommendations from others; (2) adapt existing recommendations to their own context; or (3) create recommendations de novo. Monetary and nonmonetary resources, credibility, maximization of uptake, as well as logical arguments should guide the choice of the approach and processes. OBJECTIVES: To describe a potentially efficient model for guideline production based on adoption, adaptation, and/or de novo development of recommendations utilizing the Grading of Recommendations Assessment, Development and Evaluation (GRADE) Evidence to Decision (EtD) frameworks. STUDY DESIGN AND SETTING: We applied the model in a new national guideline program producing 22 practice guidelines. We searched for relevant evidence that informs the direction and strength of a recommendation. We then produced GRADE EtDs for guideline panels to develop recommendations. RESULTS: In two waves, a total of 80 EtD frameworks was produced approximately 4 months and 146 EtDs in about 6 months. Use of the EtD frameworks allowed panel members to understand judgments of other guideline groups about the criteria that bear on guideline recommendations and then make their own judgments about those criteria in a systematic approach. CONCLUSION: The "GRADE-ADOLOPMENT" approach to guideline production combines adoption, adaptation, and, as needed, de novo development of recommendations. If guideline developers apply EtD criteria more widely and make their work publically available, this approach should prove even more useful.

Multigenerational effects of bisphenol A or ethinyl estradiol exposure on F2 California mice (Peromyscus californicus) pup vocalizations.

Rodent pups use vocalizations to communicate with one or both parents in biparental species, such as California mice (Peromyscus californicus). Previous studies have shown California mice developmentally exposed to endocrine disrupting chemicals, bisphenol A (BPA) or ethinyl estradiol (EE), demonstrate later compromised parental behaviors. Reductions in F1 parental behaviors might also be due to decreased emissions of F2 pup vocalizations. Thus, vocalizations of F2 male and female California mice pups born to F1 parents developmentally exposed to BPA, EE, or controls were examined. Postnatal days (PND) 2-4 were considered early postnatal period, PND 7 and 14 were defined as mid-postnatal period, and PND 21 and 28 were classified as late postnatal period. EE pups showed increased latency to emit the first syllable compared to controls. BPA female pups had decreased syllable duration compared to control and EE female pups during the early postnatal period but enhanced responses compared to controls at late postnatal period; whereas, male BPA and EE pups showed greater syllable duration compared to controls during early postnatal period. In mid-postnatal period, F2 BPA and EE pups emitted greater number of phrases than F2 control pups. Results indicate aspects of vocalizations were disrupted in F2 pups born to F1 parents developmentally exposed to BPA or EE, but their responses were not always identical, suggesting BPA might not activate estrogen receptors to the same extent as EE. Changes in vocalization patterns by F2 pups may be due to multigenerational exposure to BPA or EE and/or reduced parental care received.

[177Lu]pentixather: Comprehensive Preclinical Characterization of a First CXCR4-directed Endoradiotherapeutic Agent.

Purpose: Based on the clinical relevance of the chemokine receptor 4 (CXCR4) as a molecular target in cancer and on the success of [68Ga]pentixafor as an imaging probe for high-contrast visualization of CXCR4-expression, the spectrum of clinical CXCR4-targeting was expanded towards peptide receptor radionuclide therapy (PRRT) by the development of [177Lu]pentixather. Experimental design: CXCR4 affinity, binding specificity, hCXCR4 selectivity and internalization efficiency of [177Lu]pentixather were evaluated using different human and murine cancer cell lines. Biodistribution studies (1, 6, 48, 96h and 7d p.i.) and in vivo metabolite analyses were performed using Daudi-lymphoma bearing SCID mice. Extrapolated organ doses were cross-validated with human dosimetry (pre-therapeutic and during [177Lu]pentixather PRRT) in a patient with multiple myeloma (MM). Results: [177Lu]pentixather binds with high affinity, specificity and selectivity to hCXCR4 and shows excellent in vivo stability. Consequently, and supported by >96% plasma protein binding and a logP=-1.76, delaying whole-body clearance of [177Lu]pentixather, tumor accumulation was high and persistent, both in the Daudi model and the MM patient. Tumor/background ratios (7d p.i.) in mice were 499±202, 33±7, 4.0±0.8 and 116±22 for blood, intestine, kidney and muscle, respectively. In the patient, high tumor/kidney and tumor/liver dose ratios of 3.1 and 6.4 were observed during [177Lu]pentixather PRRT (7.8 GBq), with the kidneys being the dose-limiting organs. Conclusions: [177Lu]pentixather shows excellent in vivo CXCR4-targeting characteristics and a suitable pharmacokinetic profile, leading to high tumor uptake and retention and thus high radiation doses to tumor tissue during PRRT, suggesting high clinical potential of this [68Ga]pentixafor/[177Lu]pentixather based CXCR4-targeted theranostic concept.

Endocrine disruption by environmental gestagens in amphibians - A short review supported by new in vitro data using gonads of Xenopus laevis.

Endocrine disruption caused by various anthropogenic compounds is of persisting concern, especially for aquatic wildlife, because surface waters are the main sink of these so-called endocrine disruptors (ED). In the past, research focused on (anti)estrogenic, (anti)androgenic, and (anti)thyroidal substances, affecting primarily reproduction and development in vertebrates; however, other endocrine systems might be also targeted by ED. Environmental gestagens, including natural progestogens (e.g. progesterone (P4)) and synthetic progestins used for contraception, are supposed to affect vertebrate reproduction via progesterone receptors. In the present paper, we review the current knowledge about gestagenic effects in amphibians, focussing on reproduction and the thyroid system. In addition, we support the literature data with results of recent in vitro experiments, demonstrating direct impacts of the gestagens levonorgestrel (LNG) and P4 on sexually differentiated gonads of larval Xenopus laevis. The results showed a higher susceptibility of female over male gonads to gestagenic ED. Only in female gonads LNG, but not P4, had direct inhibitory effects on gene expression of steroidogenic acute regulatory protein and P450 side chain cleavage enzyme, whereas aromatase expression decreased in reaction to both gestagens. Surprisingly, beyond the expected ED effects of gestagens on reproductive physiology in amphibians, LNG drastically disrupted the thyroid system, which resembles direct effects on thyroid glands and pituitary along the pituitary-thyroid axis disturbing metamorphic development. In amphibians, environmental gestagens not only affect the reproductive system but at least LNG can impact also development by disruption of the thyroid system.

Characterization of vocalizations emitted in isolation by California mouse (Peromyscus californicus) pups throughout the postnatal period.

Rodent species, such as monogamous and biparental California mice, produce vocalizations as a means of communication. A temporal examination of vocalizations produced by California mice pups in isolation was performed. Pup recordings were performed for 3 min at ∼10.00 and 14.00 hrs on early postnatal days (PND) 2-4, 7, 21, and 28. Once initial recordings were finished, pups were returned to the home cage with parents and any siblings for 5 minutes to determine if active biparental responses resulted in an enhanced vocalization response when pups were isolated and retested. We also sought to determine whether potential reduction in vocalizations by older pups might be due to procedure-habituation procedure associated with less anxiety and/or possibly decreased need for parental care. Vocalizations were measured in weanling (30 days of age) "naïve" pups not previously isolated. Results show older pups took significantly longer to vocalize, indicated by increased latency before producing their initial syllable compared to earlier ages. With increasing age, pups demonstrated decreased syllable duration, reduced number and duration of phrases, and decreased number of syllables per phrase. No differences in pup vocalizations were observed before and after being placed back with parents, suggestive biparental potentiation may not exist in California mice pups. Comparison of the naïve to habituated weanling pups indicated the former group had more total calls but no other differences in vocalization parameters were detected between these 2 groups. Collectively, the findings suggest that as California mice pups mature and approach weaning they generally vocalize less in isolation. (PsycINFO Database Record

Diclofenac can exhibit estrogenic modes of action in male Xenopus laevis, and affects the hypothalamus-pituitary-gonad axis and mating vocalizations.

Diclofenac (DCF) is a non-steroidal analgesic and antiphlogistic. Due to its tremendous use, DCF can be found in the environment, especially in sewage, but also surface waters, ground and drinking water. Previous studies indicated that DCF can modulate the reproductive physiology of fish by altering the expression of important key enzymes of the hypothalamus-pituitary-gonad-axis (HPG-axis) and might act as an estrogenic endocrine disrupting chemical (EDC). Other studies, however, demonstrated that DCF does not exhibit any estrogenicity. Thus, in the present study we investigated whether an exposure to DCF can affect reproductive behavior and physiology of adult male X. laevis by analyzing DCF effects on the mate calling behavior of the frogs and on gene expression patterns of key biomarkers of the HPG-axis. In addition, plasma sex steroid levels were determined to gain detailed insights into the mechanisms of DCF action. We could demonstrate that DCF can act as EDC by exhibiting slight estrogenic modes of action. In addition, pharmacological impacts on gonadal steroidogenesis could be revealed leading to imbalances in sex steroid levels and ratios. DCF furthermore altered the calling behavior of exposed males, potentially reducing the mating and reproductive success of the frogs, possibly leading to severe population effects.

In Vivo PET Imaging of the Cancer Integrin αvß6 Using 68Ga-Labeled Cyclic RGD Nonapeptides.

Expression of the cellular transmembrane receptor αvß6 integrin is essentially restricted to malignant epithelial cells in carcinomas of a broad variety of lineages, whereas it is virtually absent in normal adult tissues. Thus, it is a highly attractive target for tumor imaging and therapy. Furthermore, αvß6 integrin plays an important role for the epithelial-mesenchymal interaction and the development of fibrosis. Methods: On the basis of the 68Ga chelators TRAP (triazacyclononane-triphosphinate) and NODAGA, we synthesized mono-, di-, and trimeric conjugates of the αvß6 integrin-selective peptide cyclo(FRGDLAFp(NMe)K) via click chemistry. These were labeled with 68Ga and screened regarding their suitability for in vivo imaging of αvß6 integrin expression by PET and ex vivo biodistribution in severe combined immunodeficiency mice bearing H2009 tumor (human lung adenocarcinoma) xenografts. For these, αvß6 integrin expression in tumor and other tissues was determined by ß6 immunohistochemistry. Results: Despite the multimers showing higher αvß6 integrin affinities (23-120 pM) than the monomers (260 pM), the best results-that is, low background uptake and excellent tumor delineation-were obtained with the TRAP-based monomer 68Ga-avebehexin. This compound showed the most favorable pharmacokinetics because of its high polarity (log D = -3.7) and presence of additional negative charges (carboxylates) on the chelator, promoting renal clearance. Although tumor uptake was low (0.65% ± 0.04% injected dose per gram tissue [%ID/g]), it was still higher than in all other organs except the kidneys, ranging from a maximum for the stomach (0.52 ± 0.04 %ID/g) to almost negligible for the pancreas (0.07 ± 0.01 %ID/g). A low but significant target expression in tumor, lung, and stomach was confirmed by immunohistochemistry. Conclusion: Because of highly sensitive PET imaging even of tissues with low αvß6 integrin expression density, we anticipate clinical applicability of 68Ga-avebehexin for imaging of αvß6 tumors and fibrosis by PET.

p,p'-Dichlordiphenyldichloroethylene (p,p'-DDE) can elicit antiandrogenic and estrogenic modes of action in the amphibian Xenopus laevis.

p,p'-Dichlordiphenyldichloroethylene (DDE) is a metabolite of the insecticide dichlorodiphenyltrichloroethane (DDT), an organochloride which was massively used from its discovery in 1939 until the early 1970's. Due to the tremendous half-life of DDT and DDE, both substances are to date environmentally relevant. Furthermore, DDT is still employed in many African countries in the context of the WHO's antimalaria campaign. In amphibians, DDE was found to act as antiandrogenic endocrine disrupting chemical (EDC), whereas in other species DDE was found to act as an estrogen. To determine the mode of action (MOA) of DDE in adult male Xenopus laevis, we exposed adult male frogs to different concentrations of DDE, as well as to the estrogenic EDC ethinylestradiol (EE2) and the antiandrogenic fungicide vinclozolin (VIN) for four consecutive nights. We then analyzed the mate calling behavior, which was previously shown to be affected by (anti)androgenic and (anti)estrogenic EDC in a MOA-specific manner, in order to assess whether DDE exposure results in estrogen-specific or antiandrogen-specific alterations of the mate calling behavior. Our results demonstrate that DDE alters the reproductive behavior of male X. laevis. Lowered sexual arousal of exposed males was indicated by a decreased production of advertisement calls and higher amounts of calls that suggest a sexually unaroused state of the males. Our results further indicate that DDE can display both, estrogenic and antiandrogenic MOA, either of which can have adverse effects on reproductive physiology and behavior in X. laevis. The disruption of the affected mating behavior, which is crucial for a successful reproduction, might result in a reduced reproductive success of DDE exposed animals.

Impaired gonadal and somatic development corroborate vulnerability differences to the synthetic estrogen ethinylestradiol among deeply diverged anuran lineages.

Amphibians are undergoing a global decline. One poorly investigated reason could be the pollution of aquatic habitats by endocrine disrupting compounds (EDCs). We tested the susceptibility to the synthetically stabilized estrogen 17α-ethinylestradiol (EE2) in three deeply diverged anuran species, differing in sex determination systems, types of gonadogenesis and larval ecologies. To understand whether data from the amphibian model Xenopus laevis (Pipidae) are analogous and applicable to only distantly related non-model amphibians, tadpoles of X. laevis, Hyla arborea (Hylidae) and Bufo viridis (Bufonidae) were simultaneously exposed to 50, 500 and 5000ng/L EE2 from hatching until completion of metamorphosis, using a flow-through-system under identical experimental conditions. Comparing molecularly established genetic with histologically assessed phenotypic sex in all species, we have recently shown that EE2 provoked numerous genetic-male-to-phenotypic-female sex reversals and mixed sex individuals, confirming overall its expected feminizing effect. In the present study, we focus on the influence of EE2 on gonadal and somatic development. Anatomy and histology revealed several species-specific effects. In both non-model species, H. arborea and B. viridis, high numbers of anatomically impaired gonads were observed. In H. arborea, exposed to 5000ng/L EE2, numerous underdeveloped gonads were detected. Whereas EE2 did not alter snout-to-vent length and body weight of X. laevis metamorphs, H. arborea showed a treatment-dependent decrease, while B. viridis exhibited an increase in body weight and snout-to-vent length. Apart from a concentration-dependent occurrence of yellowish skin color in several H. arborea, no organ-specific effects were detected. Since EE2 ubiquitously occurs in many aquatic ecosystems and affects sexual and somatic development, among EDCs, it may indeed contribute to amphibian decline. The inter-species variation in developmental EE2-effects corroborates species-specific vulnerability differences towards EDCs between deeply diverged amphibian groups.

Variation of Specific Activities of 68Ga-Aquibeprin and 68Ga-Avebetrin Enables Selective PET Imaging of Different Expression Levels of Integrins α5ß1 and αvß3.

68Ga-aquibeprin and 68Ga-avebetrin are tracers for selective in vivo mapping of integrins α5ß1 and αvß3, respectively, by PET. Because both tracers exhibit high affinity to their respective targets, the aim of this study was to investigate the influence of the specific activity of preparations of both tracers on in vivo imaging results. METHODS: Fully automated 68Ga labeling of 0.3 nmol of aquibeprin or avebetrin was done using buffered eluate fractions (600-800 MBq, pH 2) of an SnO2-based generator, affording the radiopharmaceuticals with specific activities greater than 1,000 MBq/nmol. Lower values ranging from 150 to 0.4 MBq/nmol were adjusted by addition of inactive compound (∼0.15-50 nmol) to the injected activity (∼20 MBq for PET, 5-7 MBq for biodistribution). For in vivo experiments, 6- to 12-wk-old female severe combined immunodeficiency mice bearing M21 xenografts (human melanoma, expressing both integrins α5ß1 and αvß3) were used. The expression density of integrin ß3 was determined by immunohistochemistry on paraffin slices. RESULTS: For mass doses (specific activities) of less than 20 pmol (>1,000 MBq/nmol) and 1 nmol (20 MBq/nmol) per mouse, respectively, uptake of 68Ga-aquibeprin and 68Ga-avebetrin in M21 tumors dropped from 5.3 and 3.5 to 3.0 and 2.4 percentage injected dose per gram (%ID/g), respectively. When less than 20 pmol was applied, high uptake of 68Ga-aquibeprin in the eyes (4.5 %ID/g) or 68Ga-avebetrin in adrenals (25.9 %ID/g), respectively, were found, which was reduced by 90% and 65% (0.44 and 6.2 %ID/g, respectively), for doses of 1 nmol. The highest tumor-to-tissue ratios were observed both in ex vivo biodistribution and PET for comparably large doses, for example, 6 nmol (0.65 mg/kg) 68Ga-aquibeprin per mouse (3.5 MBq/nmol). CONCLUSION: Presumably because of their high affinities, 68Ga-aquibeprin and 68Ga-avebetrin allow for selective addressing of target sites with different integrin expression levels by virtue of adjusting specific activity, which can be exploited for visualization of low-level target expression or optimization of tumor-to-background contrast.

Sex reversal assessments reveal different vulnerability to endocrine disruption between deeply diverged anuran lineages.

Multiple anthropogenic stressors cause worldwide amphibian declines. Among several poorly investigated causes is global pollution of aquatic ecosystems with endocrine disrupting compounds (EDCs). These substances interfere with the endocrine system and can affect the sexual development of vertebrates including amphibians. We test the susceptibility to an environmentally relevant contraceptive, the artificial estrogen 17α-ethinylestradiol (EE2), simultaneously in three deeply divergent systematic anuran families, a model-species, Xenopus laevis (Pipidae), and two non-models, Hyla arborea (Hylidae) and Bufo viridis (Bufonidae). Our new approach combines synchronized tadpole exposure to three EE2-concentrations (50, 500, 5,000 ng/L) in a flow-through-system and pioneers genetic and histological sexing of metamorphs in non-model anurans for EDC-studies. This novel methodology reveals striking quantitative differences in genetic-male-to-phenotypic-female sex reversal in non-model vs. model species. Our findings qualify molecular sexing in EDC-analyses as requirement to identify sex reversals and state-of-the-art approaches as mandatory to detect species-specific vulnerabilities to EDCs in amphibians.

Complementary, Selective PET Imaging of Integrin Subtypes α5ß1 and αvß3 Using 68Ga-Aquibeprin and 68Ga-Avebetrin.

UNLABELLED: Despite in vivo mapping of integrin αvß3 expression being thoroughly investigated in recent years, its clinical value is still not well defined. For imaging of angiogenesis, the integrin subtype α5ß1 appears to be a promising target, for which purpose we designed the PET radiopharmaceutical (68)Ga-aquibeprin. METHODS: (68)Ga-aquibeprin was obtained by click-chemistry (CuAAC) trimerization of a α5ß1 integrin-binding pseudopeptide on the triazacyclononane-triphosphinate (TRAP) chelator, followed by automated (68)Ga labeling. Integrin α5ß1 and αvß3 affinities were determined in enzyme linked immune sorbent assay on immobilized integrins, using fibronectin and vitronectin, respectively, as competitors. M21 (human melanoma)-bearing severe combined immunodeficient mice were used for biodistribution, PET imaging, and determination of in vivo metabolization. The expression of α5 and ß3 subunits was determined by immunohistochemistry on paraffin sections of M21 tumors. RESULTS: (68)Ga-aquibeprin shows high selectivity for integrin α5ß1 (50% inhibition concentration [IC50] = 0.088 nM) over αvß3 (IC50 = 620 nM) and a pronounced hydrophilicity (log D = -4.2). Severe combined immunodeficient mice xenografted with M21 human melanoma were found suitable for in vivo evaluation, as M21 immunohistochemistry showed not only an endothelial and strong cytoplasmatic expression of the ß3 integrin subunit but also an intense expression of the α5 integrin subunit particularly in the endothelial cells of intratumoral small vessels. Ex vivo biodistribution (90 min after injection) showed high uptake in M21 tumor (2.42 ± 0.21 percentage injected dose per gram), fast renal excretion, and low background; tumor-to-blood and tumor-to-muscle ratios were 10.6 ± 2.5 and 20.9 ± 2.4, respectively. (68)Ga-aquibeprin is stable in vivo; no metabolites were detected in mouse urine, blood serum, kidney, and liver homogenates 30 min after injection. PET imaging was performed for (68)Ga-aquibeprin and the previously described, structurally related c(RGDfK) trimer (68)Ga-avebetrin, which shows an inverse selectivity for integrin αvß3 (IC50 = 0.22 nM) over α5ß1 (IC50 = 39 nM). In vivo target specificity was proven by cross-competition studies; tumor uptake of either tracer was not affected by the coadministration of 40 nmol (∼5 mg/kg) of the respective other compound. CONCLUSION: (68)Ga-aquibeprin and (68)Ga-avebetrin are recommendable for complementary mapping of integrins α5ß1 and αvß3 by PET, allowing for future studies on the role of these integrins in angiogenesis, tumor progression, metastasis, and myocardial infarct healing.

First 18F-Labeled Pentixafor-Based Imaging Agent for PET Imaging of CXCR4 Expression In Vivo.

In vivo quantification of CXCR4 expression using [68Ga]pentixafor for positron emission tomography (PET) imaging has gained significant clinical interest as CXCR4 plays a fundamental role in oncology and possesses potential prognostic value when overexpressed. To combine the excellent CXCR4-targeting properties of pentixafor-based tracers with the favorable radionuclide properties of 18F for high-resolution PET imaging, we developed an Al18F-labeled 1,4,7-triazacyclononane-triacetic acid (NOTA) analog of pentixather. Al18F-labeling of NOTA-pentixather was performed in aqueous dimethyl sulfoxide (DMSO) at pH = 4 (105°C, 15 minutes). CXCR4 affinities were determined in competitive binding assays, and both biodistribution and small-animal PET studies were performed in Daudi lymphoma-bearing mice. Under non-optimized conditions, [18F]AlF-NOTA-pentixather was obtained in radiochemical yields of 45.5% ± 13.3% and specific activities of up to 24.8 GBq/µmol. Compared with [natGa]pentixafor, [natF]AlF-NOTA-pentixather showed 1.4-fold higher CXCR4 affinity. [18F]AlF-NOTA-pentixather displayed high and CXCR4-specific in vivo uptake in Daudi xenografts (13.9% ± 0.8% injected dose per gram [ID/g] at 1 hour post injection [p.i.]). Because of its enhanced lipophilicity (logP = -1.4), [18F]AlF-NOTA-pentixather showed increased accumulation in the gall bladder and intestines. However, tumor/background ratios of 7.0 ± 1.2, 2.0 ± 0.3, 2.2 ± 0.4, 16.5 ± 6.5, and 29.2 ± 4 for blood, liver, small intestine, gut, and muscle, respectively, allowed for high-contrast visualization of Daudi tumors using PET (1 hour p.i.). The relatively straightforward radiosynthesis and efficient CXCR4 targeting of [18F]AlF-NOTA-pentixather demonstrate the successful implementation of 18F-complexation chemistry and pentixather-based CXCR4 targeting. Upon pharmacokinetic optimization, this class of tracers holds great promise for future application in humans.

Twins in spirit - episode I: comparative preclinical evaluation of [(68)Ga]DOTATATE and [(68)Ga]HA-DOTATATE.

BACKGROUND: Recently, an intra-patient comparison demonstrated that the somatostatin (sst) ligand [(68)Ga]HA-DOTATATE ([(68)Ga]DOTA-3-iodo-Tyr(3)-octreotate) provides PET images comparable to or superior to those obtained with [(68)Ga]DOTATATE. To provide a comprehensive basis for nevertheless observed slight differences in tracer biodistribution and dosimetry, the characteristics of [(68)Ga]HA-DOTATATE were investigated in a detailed preclinical study. METHODS: Affinities of (nat)Ga-HA-DOTATATE and (nat)Ga-DOTATATE to sst1-5 were determined using membrane preparations and [(125)I]SST-28 as radioligand. Internalization into AR42J cells was studied in dual-tracer studies with [(125)I]TOC as internal reference. Biodistribution was investigated using AR42J tumor-bearing CD1 mice, and specificity of tracer uptake was confirmed in competition studies by coinjection of 0.8 mg TOC/kg. RESULTS: Sst2 affinities (IC50) of [(nat)Ga]HA-DOTATATE (1.4 ± 0.8 nM, logP: -3.16) and [(nat)Ga]DOTATATE (1.2 ± 0.6 nM, logP: -3.69) were nearly identical. Both compounds displayed IC50 > 1 µM for sst1,3,4, while sst5 affinity was markedly increased for (nat)Ga-HA-DOTATATE (102 ± 65 nM vs >1 µM for (nat)Ga-DOTATATE). [(nat)Lu]HA-DOTATATE and [(nat)Lu]DOTATATE showed slightly lower, identical sst2 affinities (2.0 ± 1.6 and 2.0 ± 0.8 nM, respectively) and sst3 affinities of 93 ± 1 and 162 ± 16 nM. Internalization of [(68)Ga]HA-DOTATATE was tenfold higher than that of [(125)I]TOC but only sixfold higher for [(68)Ga]DOTATATE and [(177)Lu]HA-DOTATATE. While [(68)Ga]HA-DOTATATE and [(68)Ga]DOTATATE had shown similar target- and non-target uptake in patients, biodistribution studies in mice at 1 h post injection (n = 5) revealed slightly increased non-specific uptake of [(68)Ga]HA-DOTATATE in the blood, liver, and intestines (0.7 ± 0.3, 1.0 ± 0.2, and 4.0 ± 0.7 %iD/g vs 0.3 ± 0.1, 0.5 ± 0.1, and 2.7 ± 0.8 %iD/g for [(68)Ga]DOTATATE). However, sst-mediated accumulation of [(68)Ga]HA-DOTATATE in the pancreas, adrenals, and tumor was significantly enhanced (36.6 ± 4.3, 10.8 ± 3.2, and 33.6 ± 10.9 %iD/g vs 26.1 ± 5.0, 5.1 ± 1.4, and 24.1 ± 4.9 %iD/g, respectively). Consequently, tumor/background ratios for [(68)Ga]HA-DOTATATE in the AR42J model are comparable or slightly increased compared to [(68)Ga]DOTATATE. CONCLUSIONS: The present preclinical data fully confirm the general biodistribution pattern and excellent in vivo sst-targeting characteristics previously observed for [(68)Ga]HA-DOTATATE in patients. The effect of slightly enhanced lipophilicity on background accumulation and normal organ dose is compensated by the high uptake of [(68)Ga]HA-DOTATATE in tumor. Thus, [(68)Ga]HA-DOTATATE represents a fully adequate, freely available substitute for [(68)Ga]DOTATATE and, given the superb sst-targeting characteristics of [(177)Lu]HA-DOTATATE in vitro, potential applicability for sst-targeted PRRT.

Disclosing the CXCR4 expression in lymphoproliferative diseases by targeted molecular imaging.

Chemokine ligand-receptor interactions play a pivotal role in cell attraction and cellular trafficking, both in normal tissue homeostasis and in disease. In cancer, chemokine receptor-4 (CXCR4) expression is an adverse prognostic factor. Early clinical studies suggest that targeting CXCR4 with suitable high-affinity antagonists might be a novel means for therapy. In addition to the preclinical evaluation of [(68)Ga]Pentixafor in mice bearing human lymphoma xenografts as an exemplary CXCR4-expressing tumor entity, we report on the first clinical applications of [(68)Ga]Pentixafor-Positron Emission Tomography as a powerful method for CXCR4 imaging in cancer patients. [(68)Ga]Pentixafor binds with high affinity and selectivity to human CXCR4 and exhibits a favorable dosimetry. [(68)Ga]Pentixafor-PET provides images with excellent specificity and contrast. This non-invasive imaging technology for quantitative assessment of CXCR4 expression allows to further elucidate the role of CXCR4/CXCL12 ligand interaction in the pathogenesis and treatment of cancer, cardiovascular diseases and autoimmune and inflammatory disorders.

17α-Ethinylestradiol can disrupt hemoglobin catabolism in amphibians.

Different chemical substances, which enter the environment due to anthropogenic influences, can affect the endocrine system and influence development and physiology of aquatic animals. One of these endocrine disrupting chemicals is the synthetic estrogen, 17α-ethinylestradiol (EE2), which is a main component of various oral contraceptives and demonstrably affects many different aquatic vertebrates at extremely low concentrations by feminization phenomena. The aim of the present study was to investigate whether a four week exposure to three different concentrations of EE2 (0.3 ng/L, 29.6 ng/L and 2960 ng/L) affects the catabolism of hemoglobin of the amphibian Xenopus laevis. The results of this study demonstrate for the first time that beside an increase of the hepatic vitellogenin gene expression, exposure to EE2 also decreases the gene expression of the hepatic heme oxygenase 1 and 2 (HO1, HO2), degrading heme of different heme proteins to biliverdin, as well as of the biliverdin reductase A (BLVRA), which converts biliverdin to bilirubin. The results further suggest that EE2 already at the environmentally relevant concentration of (29.6 ng/L) can disrupt hemoglobin catabolism, indicated by decreased gene expression of HO2, which becomes evident at the highest EE2 concentration that led to a severe increase of biliverdin in plasma.

CXCR4 prevents dispersion of granule neuron precursors in the adult dentate gyrus.

Neurogenesis in the adult dentate gyrus (DG) generates new granule neurons that differentiate in the inner one-third of the granule cell layer (GCL). The migrating precursors of these neurons arise from neural stem cells (NSCs) in the subgranular zone (SGZ). Although it is established that pathological conditions, including epilepsy and stroke, cause dispersion of granule neuron precursors, little is known about the factors that regulate their normal placement. Based on the high expression of the chemokine CXCL12 in the adult GCL and its role in guiding neuronal migration in development, we addressed the function of the CXCL12 receptor CXCR4 in adult neurogenesis. Using transgenic reporter mice, we detected Cxcr4-GFP expression in NSCs, neuronal-committed progenitors, and immature neurons of adult and aged mice. Analyses of hippocampal NSC cultures and hippocampal tissue by immunoblot and immunohistochemistry provided evidence for CXCL12-promoted phosphorylation/activation of CXCR4 receptors in NSCs in vivo and in vitro. Cxcr4 deletion in NSCs of the postnatal or mature DG using Cre technology reduced neurogenesis. Fifty days after Cxcr4 ablation in the mature DG, the SGZ showed a severe reduction of Sox2-positive neural stem/early progenitor cells, NeuroD-positive neuronal-committed progenitors, and DCX-positive immature neurons. Many immature neurons were ectopically placed in the hilus and inner molecular layer, and some developed an aberrant dendritic morphology. Only few misplaced cells survived permanently as ectopic neurons. Thus, CXCR4 signaling maintains the NSC pool in the DG and specifies the inner one-third of the GCL as differentiation area for immature granule neurons.