Search Results (13)

IgG4 is an unusual immunoglobulin (Ig) and is the least component of IgG in humans. It is often asymmetrical and heterobivalent with weak Fc (fragment crystallizable region)-dependent effector function and ineffective complement activation, thus playing an unclear role in immune functions. IgE is an uncommon Ig, being important mostly in allergy and type 2 immunity. There are two rare chronic Ig-related fibroinflammatory diseases, namely IgG4-related disease (IgG4RD) and Kimura disease (KD), characterized by prominent IgG4- or IgE-positive plasma cells in the affected tissues, with or without blood elevations of the same Ig. The etiology of these two Ig-related diseases is unclear, though it appears that the pathogenesis in both is related to polarized Ig heavy chain isotype switching, concomitant with other cellular, cytokine and chemotaxin interactions that culminates in the characteristic pathologic manifestations of inflammation and fibrosis. IgG4RD and KD, despite having overlapping and differing features, may be connected by the similar pathogenetic polarized Ig isotype switching. Full article

Background/Objectives: Heterodimer peptides targeting more than one receptor can be advantageous, as tumors can simultaneously express more than one receptor type. For human breast cancer, a promising biological target is tumor angiogenesis through α_vβ₃ integrin expression. Another promising target is Neuropeptide Y receptors, considering Y₁R is overexpressed in 90% of human breast tumors. This article details the development and preclinical evaluation, both in vitro and in vivo, of a novel heterodimer peptide dual-receptor-targeting probe, [^99mTc]HYNIC-cRGDfk-NPY, designed for imaging breast tumors. Methods: Female BALB/c healthy mice were used to perform biodistrubution studies and female SCID mice were subcutaneously injected with MCF-7 and MDA-MB-231 tumor cells. [^99mTc]HYNIC-cRGDfk-NPY was intravenously administered to the mice, followed by ex vivo biodistribution studies and small-animal SPECT/CT imaging. Nonspecific tracer uptake in both models was determined by coinjecting an excess of unlabeled HYNIC-cRGDfk-NPY (100 µg) along with the radiolabeled tracer. Results: Imaging and biodistribution data demonstrate good uptake to estrogen receptor-positive (MCF-7) and triple-negative (MDA-MB-231) tumor models. The in vivo tumor uptakes of radiolabeled conjugate were 9.30 ± 3.25% and 4.93 ± 1.01% for MCF-7 and MDA-MB231, respectively. The tumor/muscle ratios were 5.65 ± 0.94 for the MCF-7 model and 7.78 ± 3.20 for MDA-MB231. Conclusions: [^99mTc]HYNIC-cRGDfk-NPY demonstrated rapid blood clearance, renal excretion, and in vivo tumor uptake, highlighting its potential as a tumor imaging agent. Full article

Since angiogenesis/neoangiogenesis has a major role in tumor development, progression and metastatic spread, the establishment of angiogenesis-targeting imaging and therapeutic vectors is of utmost significance. Aminopeptidase N (APN/CD13) is a pivotal biomarker of angiogenic processes abundantly expressed on the cell surface of active vascular endothelial and various neoplastic cells, constituting a valuable target for cancer diagnostics and therapy. Since the asparagine–glycine–arginine (NGR) sequence has been shown to colocalize with APN/CD13, the research interest in NGR-peptide-mediated vascular targeting is steadily growing. Earlier preclinical experiments have already demonstrated the imaging and therapeutic feasibility of NGR-based probes labeled with different positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radionuclides, including Gallium-68 (⁶⁸Ga), Copper-64 (⁶⁴Cu), Technetium-99m (^99mTc), Lutetium-177 (¹⁷⁷Lu), Rhenium-188 (¹⁸⁸Re) or Bismuth-213 (²¹³Bi). To improve the tumor binding affinity and the retention time of single-receptor targeting peptides, NGR motifs containing heterodimers have been introduced to identify multi-receptor overexpressing malignancies. Preclinical studies with various tumor-bearing experimental animals provide useful tools for the investigation of the in vivo imaging behavior of NGR-based heterobivalent ligands. Herein, we review the reported preclinical achievements on NGR heterodimers that could be highly relevant for the development of further target-specific multivalent compounds in diagnostic and therapeutic settings. Full article

Dysregulation of hippocampal neurogenesis is linked to several neurodegenereative diseases, where boosting hippocampal neurogenesis in these patients emerges as a potential therapeutic approach. Accumulating evidence for a neuropeptide Y (NPY) and galanin (GAL) interaction was shown in various limbic system regions at molecular-, cellular-, and behavioral-specific levels. The purpose of the current work was to evaluate the role of the NPY and GAL interaction in the neurogenic actions on the dorsal hippocampus. We studied the Y1R agonist and GAL effects on: hippocampal cell proliferation through the proliferating cell nuclear antigen (PCNA), the expression of neuroprotective and anti-apoptotic factors, and the survival of neurons and neurite outgrowth on hippocampal neuronal cells. The functional outcome was evaluated in the object-in-place task. We demonstrated that the Y1R agonist and GAL promote cell proliferation and the induction of neuroprotective factors. These effects were mediated by the interaction of NPYY1 (Y1R) and GAL2 (GALR2) receptors, which mediate the increased survival and neurites’ outgrowth observed on neuronal hippocampal cells. These cellular effects are linked to the improved spatial-memory effects after the Y1R agonist and GAL co-injection at 24 h in the object-in-place task. Our results suggest the development of heterobivalent agonist pharmacophores, targeting Y1R–GALR2 heterocomplexes, therefore acting on the neuronal precursor cells of the DG in the dorsal hippocampus for the novel therapy of neurodegenerative cognitive-affecting diseases. Full article

A recently developed artemisinin-quinoline hybrid, named 163A, has been shown to display potent activity against the asexual blood stage of Plasmodium, the malaria parasite. In this study, we determined its in vitro cytotoxicity to mammalian cells, its potency to suppress P. berghei hepatic infection and to decrease the viability of P. falciparum gametocytes, in addition to determining whether the drug exhibits efficacy of a P. berghei infection in mice. This hybrid compound has a low level of cytotoxicity to mammalian cells and, conversely, a high level of selectivity. It is potent in the prevention of hepatic stage development as well as in killing gametocytes, denoting a potential blockage of malaria transmission. The hybrid presents a potent inhibitory activity for beta-hematin crystal formation, in which subsequent assays revealed that its endoperoxide component undergoes bioactivation by reductive reaction with ferrous heme towards the formation of heme-drug adducts; in parallel, the 7-chloroquinoline component has binding affinity for ferric hemin. Both structural components of the hybrid co-operate to enhance the inhibition of beta-hematin, and this bitopic ligand property is essential for arresting the growth of asexual blood parasites. We demonstrated the in vivo efficacy of the hybrid as an erythrocytic schizonticide agent in comparison to a chloroquine/artemisinin combination therapy. Collectively, the findings suggest that the bitopic property of the hybrid is highly operative on heme detoxification suppression, and this provides compelling evidence for explaining the action of the hybrid on the asexual blood stage. For sporozoite and gametocyte stages, the hybrid conserves the potency typically observed for endoperoxide drugs, and this is possibly achieved due to the redox chemistry of endoperoxide components with ferrous heme. Full article

The large size of nanoparticles prevents rapid extravasation from blood vessels and diffusion into tumors. Multimodal imaging uses the physical properties of one modality to validate the results of another. We aim to demonstrate the use of a targeted thin layer-protected ultra-small gold nanoparticles (Au-NPs) to detect cancer in vivo using multimodal imaging with photoacoustic and computed tomography (CT). The thin layer was produced using a mixed thiol-containing short ligands, including MUA, CVVVT-ol, and HS-(CH2)₁₁-PEG₄-OH. The gold nanoparticle was labeled with a heterobivalent (HB) peptide ligand that targets overexpression of epidermal growth factor receptors (EGFR) and ErbB2, hereafter HB-Au-NPs. A human xenograft model of esophageal cancer was used for imaging. HB-Au-NPs show spherical morphology, a core diameter of 4.47 ± 0.8 nm on transmission electron microscopy, and a hydrodynamic diameter of 6.41 ± 0.73 nm on dynamic light scattering. Uptake of HB-Au-NPs was observed only in cancer cells that overexpressed EGFR and ErbB2 using photoacoustic microscopy. Photoacoustic images of tumors in vivo showed peak HB-Au-NPs uptake at 8 h post-injection with systemic clearance by ~48 h. Whole-body images using CT validated specific tumor uptake of HB-Au-NPs in vivo. HB-Au-NPs showed good stability and biocompatibility with fast clearance and contrast-enhancing capability for both photoacoustic and CT imaging. A targeted thin layer-protected gold nanoprobe represents a new platform for molecular imaging and shows promise for early detection and staging of cancer. Full article

Combining two peptides addressing two different receptors to a heterobivalent peptidic ligand (HBPL) is thought to enable an improved tumor-targeting sensitivity and thus tumor visualization, compared to monovalent peptide ligands. In the case of melanoma, the Melanocortin-1 receptor (MC1R), which is stably overexpressed in the majority of primary malignant melanomas, and integrin α_vβ₃, which is involved in lymph node metastasis and therefore has an important role in the transition from local to metastatic disease, are important target receptors. Thus, if a radiolabeled HBPL could be developed that was able to bind to both receptor types, the early diagnosis and correct staging of the disease would be significantly increased. Here, we report on the design, synthesis, radiolabeling and in vitro and in vivo testing of different SiFAlin-modified HBPLs (SiFA = silicon fluoride acceptor), consisting of an MC1R-targeting (GG-Nle-c(DHfRWK)) and an integrin α_vβ₃-affine peptide (c(RGDfK)), being connected by a symmetrically branching framework including linkers of differing length and composition. Kit-like ¹⁸F-radiolabeling of the HBPLs 1–6 provided the labeled products [¹⁸F]1–[¹⁸F]6 in radiochemical yields of 27–50%, radiochemical purities of ≥95% and non-optimized molar activities of 17–51 GBq/μmol within short preparation times of 25 min. Besides the evaluation of radiotracers regarding log_D(7.4) and stability in human serum, the receptor affinities of the HBPLs were investigated in vitro on cell lines overexpressing integrin α_vβ₃ (U87MG cells) or the MC1R (B16F10). Based on these results, the most promising compounds [¹⁸F]2, showing the highest affinity to both target receptors (IC_{50 (B16F10)} = 0.99 ± 0.11 nM, IC_{50 (U87MG)} = 1300 ± 288 nM), and [¹⁸F]4, exhibiting the highest hydrophilicity (log_D(7.4) = −1.39 ± 0.03), were further investigated in vivo and ex vivo in a xenograft mouse model bearing both tumors. For both HBPLs, clear visualization of B16F10, as well as U87MG tumors, was feasible. Blocking studies using the respective monospecific peptides demonstrated both peptide binders of the HBPLs contributing to tumor uptake. Despite the somewhat lower target receptor affinities (IC_{50 (B16F10)} = 6.00 ± 0.47 nM and IC_{50 (U87MG)} = 2034 ± 323 nM) of [¹⁸F]4, the tracer showed higher absolute tumor uptakes ([¹⁸F]4: 2.58 ± 0.86% ID/g in B16F10 tumors and 3.92 ± 1.31% ID/g in U87MG tumors; [¹⁸F]2: 2.32 ± 0.49% ID/g in B16F10 tumors and 2.33 ± 0.46% ID/g in U87MG tumors) as well as higher tumor-to-background ratios than [¹⁸F]2. Thus, [¹⁸F]4 demonstrates to be a highly potent radiotracer for the sensitive and bispecific imaging of malignant melanoma by PET/CT imaging and impressively illustrates the suitability of the underlying concept to develop heterobivalent integrin α_vβ₃- and MC1R-bispecific radioligands for the sensitive and specific imaging of malignant melanoma by PET/CT. Full article

Adenosine and dopamine interact antagonistically in living mammals. These interactions are mediated via adenosine A_2A and dopamine D₂ receptors (R). Stimulation of A_2AR inhibits and blockade of A_2AR enhances D₂R-mediated locomotor activation and goal-directed behavior in rodents. In striatal membrane preparations, adenosine decreases both the affinity and the signal transduction of D₂R via its interaction with A_2AR. Reciprocal A_2AR/D₂R interactions occur mainly in striatopallidal GABAergic medium spiny neurons (MSNs) of the indirect pathway that are involved in motor control, and in striatal astrocytes. In the nucleus accumbens, they also take place in MSNs involved in reward-related behavior. A_2AR and D₂R co-aggregate, co-internalize, and co-desensitize. They are at very close distance in biomembranes and form heteromers. Antagonistic interactions between adenosine and dopamine are (at least partially) caused by allosteric receptor–receptor interactions within A_2AR/D₂R heteromeric complexes. Such interactions may be exploited in novel strategies for the treatment of Parkinson’s disease, schizophrenia, substance abuse, and perhaps also attention deficit-hyperactivity disorder. Little is known about shifting A_2AR/D₂R heteromer/homodimer equilibria in the brain. Positron emission tomography with suitable ligands may provide in vivo information about receptor crosstalk in the living organism. Some experimental approaches, and strategies for the design of novel imaging agents (e.g., heterobivalent ligands) are proposed in this review. Full article

Over the past few years, an approach emerged that combines different receptor-specific peptide radioligands able to bind different target structures on tumor cells concomitantly or separately. The reason for the growing interest in this special field of radiopharmaceutical development is rooted in the fact that bispecific peptide heterodimers can exhibit a strongly increased target cell avidity and specificity compared to their corresponding monospecific counterparts by being able to bind to two different target structures that are overexpressed on the cell surface of several malignancies. This increase of avidity is most pronounced in the case of concomitant binding of both peptides to their respective targets but is also observed in cases of heterogeneously expressed receptors within a tumor entity. Furthermore, the application of a radiolabeled heterobivalent agent can solve the ubiquitous problem of limited tumor visualization sensitivity caused by differential receptor expression on different tumor lesions. In this article, the concept of heterobivalent targeting and the general advantages of using radiolabeled bispecific peptidic ligands for tumor imaging or therapy as well as the influence of molecular design and the receptors on the tumor cell surface are explained, and an overview is given of the radiolabeled heterobivalent peptides described thus far. Full article

In the 1980s and 1990s, the concept was introduced that molecular integration in the Central Nervous System could develop through allosteric receptor–receptor interactions in heteroreceptor complexes presents in neurons. A number of adenosine–dopamine heteroreceptor complexes were identified that lead to the A_2A-D₂ heteromer hypothesis of schizophrenia. The hypothesis is based on strong antagonistic A_2A-D₂ receptor–receptor interactions and their presence in the ventral striato-pallidal GABA anti-reward neurons leading to reduction of positive symptoms. Other types of adenosine A_2A heteroreceptor complexes are also discussed in relation to this disease, such as A_2A-D₃ and A_2A-D₄ heteroreceptor complexes as well as higher order A_2A-D₂-mGluR5 and A_2A-D₂-Sigma1R heteroreceptor complexes. The A_2A receptor protomer can likely modulate the function of the D₄ receptors of relevance for understanding cognitive dysfunction in schizophrenia. A_2A-D₂-mGluR5 complex is of interest since upon A_2A/mGluR5 coactivation they appear to synergize in producing strong inhibition of the D2 receptor protomer. For understanding the future of the schizophrenia treatment, the vulnerability of the current A_2A-D₂like receptor complexes will be tested in animal models of schizophrenia. A_2A-D₂-Simag1R complexes hold the highest promise through Sigma1R enhancement of inhibition of D2R function. In line with this work, Lara proposed a highly relevant role of adenosine for neurobiology of schizophrenia. Full article

Utilizing a pharmacophore hybridization approach, we have designed and synthesized a novel series of 28 new heterobivalent β-carbolines. The in vitro cytotoxic potential of each compound was evaluated against the five cancer cell lines (LLC, BGC-823, CT-26, Bel-7402, and MCF-7) of different origin—murine and human, with the aim of determining the potency and selectivity of the compounds. Compound 8z showed antitumor activities with half-maximal inhibitory concentration (IC₅₀) values of 9.9 ± 0.9, 8.6 ± 1.4, 6.2 ± 2.5, 9.9 ± 0.5, and 5.7 ± 1.2 µM against the tested five cancer cell lines. Moreover, the effect of compound 8z on the angiogenesis process was investigated using a chicken chorioallantoic membrane (CAM) in vivo model. At a concentration of 5 μM, compound 8z showed a positive effect on angiogenesis. The results of this study contribute to the further elucidation of the biological regulatory role of heterobivalent β-carbolines and provide helpful information on the development of vascular targeting antitumor drugs. Full article

Ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE) is a synthetic bile acid-phospholipid conjugate with profound hepatoprotective and anti-fibrogenic functions in vitro and in vivo. Herein, we aimed to demonstrate the inhibitory effects of UDCA-LPE on pro-fibrogenic integrin signalling. UDCA-LPE treatment of human embryonic liver cell line CL48 and primary human hepatic stellate cells induced a non-classical internalization of integrin β1 resulting in dephosphorylation and inhibition of SRC and focal adhesion kinase (FAK). Signalling analyses suggested that UDCA-LPE may act as a heterobivalent ligand for integrins and lysophospholipid receptor1 (LPAR1) and co-immunoprecipitation demonstrated the bridging effect of UDCA-LPE on integrin β1 and LPAR1. The disruption of either the UDCA-moiety binding to integrins by RGD-containing peptide GRGDSP or the LPE-moiety binding to LPAR1 by LPAR1 antagonist Ki16425 reversed inhibitory functions of UDCA-LPE. The lack of inhibitory functions of UDCA-PE and UDCA-LPE derivatives (14:0 and 12:0, LPE-moiety containing shorter fatty acid chain) as well as the consistency of the translocation of UDCA-LPE and integrins, which co-fractionated with LPE but not UDCA, suggested that the observed UDCA-LPE-induced translocation of integrins was mediated by LPE endocytic transport pathway. Full article

Heterobivalent peptidic ligands (HBPLs), designed to address two different receptors independently, are highly promising tumor imaging agents. For example, breast cancer has been shown to concomitantly and complementarily overexpress the neuropeptide Y receptor subtype 1 (NPY(Y₁)R) as well as the gastrin-releasing peptide receptor (GRPR). Thus, radiolabeled HBPLs being able to bind these two receptors should exhibit an improved tumor targeting efficiency compared to monospecific ligands. We developed here such bispecific HBPLs and radiolabeled them with ⁶⁸Ga, achieving high radiochemical yields, purities, and molar activities. We evaluated the HBPLs and their monospecific reference peptides in vitro regarding stability and uptake into different breast cancer cell lines and found that the ⁶⁸Ga-HBPLs were efficiently taken up via the GRPR. We also performed in vivo PET/CT imaging and ex vivo biodistribution studies in T-47D tumor-bearing mice for the most promising ⁶⁸Ga-HBPL and compared the results to those obtained for its scrambled analogs. The tumors could easily be visualized by the newly developed ⁶⁸Ga-HBPL and considerably higher tumor uptakes and tumor-to-background ratios were obtained compared to the scrambled analogs in and ex vivo. These results demonstrate the general feasibility of the approach to use bispecific radioligands for in vivo imaging of breast cancer. Full article