Receptor Ligands Research Articles

Effector Functions of Dendritic Cells in Cancer: Role of Cytotoxicity and Growth Inhibition.

The tumor microenvironment plays a critical role in modulating immune responses associated with tumorigenesis, tumor progression, and metastasis. Dendritic cells (DC) play a key role in preventing and progression of metastatic neoplasia by driving and restoring dysfunctional immune systems and obliterating immunosuppression, thus obstructing tumor evasion. In this review, we will discuss the functions of tumor-infiltrating DC in anti-tumor resistance, prevention of tumor recurrence, and immunosuppression. We will also describe DC metabolism, differentiation, and plasticity, which are essential for its function. Cancers like Lymphomas may be able to corrupt immune surveillance by reducing natural killer cell numbers. Thus, interactions between lymphoma and DC with reference to cytotoxicity may be an important event, likely to be mediated via activation with interferon-γ (IFN-γ) and Toll like receptors (TLR) ligands. Mechanisms of DC-mediated cytotoxicity and the role of apoptosis and death receptors, including the role played by nitric oxide, etc., are of immense significance. We will also look into the molecular mechanisms in the tumor microenvironment, reduced drug sensitivity, and tumor relapse, as well as methods for combating drug resistance and focusing on immunosuppressive tumor networks. We will address how DC mediated cytotoxicity in combination with drugs affects tumor growth and expansion in relation to checkpoint inhibitors and regulatory T cells. Innovative approaches for therapeutic modulation of this immunosuppressive adoptive DC immunotherapy will be highlighted, which is necessary for future personalized therapeutic applications.

RXR nuclear receptor signaling modulates lipid metabolism and triggers lysosomal clearance of alpha-synuclein in neuronal models of synucleinopathy

Disease-modifying strategies for Parkinson disease (PD), the most common synucleinopathy, represent a critical unmet medical need. Accumulation of the neuronal protein alpha-synuclein (αS) and abnormal lipid metabolism have each been implicated in PD pathogenesis. Here, we elucidate how retinoid-X-receptor (RXR) nuclear receptor signaling impacts these two aspects of PD pathogenesis. We find that activated RXR differentially regulates fatty acid desaturases, significantly reducing the transcript levels of the largely brain-specific desaturase SCD5 in human cultured neural cells and PD patient-derived neurons. This was associated with reduced perilipin-2 protein levels in patient neurons, reversal of αS-induced increases in lipid droplet (LD) size, and a reduction of triglyceride levels in human cultured cells. With regard to αS proteostasis, our study reveals that RXR agonism stimulates lysosomal clearance of αS. Our data support the involvement of Polo-like kinase 2 activity and αS S129 phosphorylation in mediating this benefit. The lowering of cellular αS levels was associated with reduced cytotoxicity. Compared to RXR activation, the RXR antagonist HX531 had the opposite effects on LD size, SCD, αS turnover, and cytotoxicity, all supporting pathway specificity. Together, our findings show that RXR-activating ligands can modulate fatty acid metabolism and αS turnover to confer benefit in cellular models of PD, including patient neurons. We offer a new paradigm to investigate nuclear receptor ligands as a promising strategy for PD and related synucleinopathies.

Research progress on interferon and cellular senescence.

Since the 12 major signs of aging were revealed in 2023, people's interpretation of aging will go further, which is of great significance for understanding the occurrence, development, and intervention in the aging process. As one of the 12 major signs of aging, cellular senescence refers to the process in which the proliferation and differentiation ability of cells decrease under stress stimulation or over time, often manifested as changes in cell morphology, cell cycle arrest, and decreased metabolic function. Interferon (IFN), as a secreted ligand for specific cell surface receptors, can trigger the transcription of interferon-stimulated genes (ISGs) and play an important role in cellular senescence. In addition, IFN serves as an important component of SASP, and the activation of the IFN signaling pathway has been shown to contribute to cell apoptosis and senescence. It is expected to delay cellular senescence by linking IFN with cellular senescence and studying the effects of IFN on cellular senescence and its mechanism. This article provides a review of the research on the relationship between IFN and cellular senescence by consulting relevant literature.

Pulmonary Adenocarcinoma with Enteric Differentiation without TTF-1 Expression Is a Very Rare Subtype with Limited Treatment Options and Poor Prognosis

Plain Language SummaryPulmonary adenocarcinoma with enteric differentiation (PAED) without expression of thyroid transcription factor-1 (TTF-1) is an extremely rare and hard-to-treat variant of lung cancer. We collected clinicopathological data of 121 Caucasian patients with pulmonary adenocarcinoma without TTF-1 expression, their systemic therapy options, and the efficacy of their systemic treatment including 79 cases without a PAED and 42 cases with a PAED, compared these subgroups, and investigated patients’ response to chemotherapy and immunotherapy as first-line treatment. A comparison of clinicopathological data of TTF-1-negative PAED and non-PAED patients revealed a significantly lower frequency of high programmed death receptor ligand 1 (PD-L1) expression in PAED resulting in the lack of single-agent immunotherapy (p = 0.032) in this subgroup. Frequencies of an activating Kirsten rat sarcoma viral oncogene homolog (KRAS) gene mutation were high in both groups (46.7% and 50.0%), but a G12C gene mutation was seldomly noted (in 6.7% and 18.5% of patients with evaluable data). Median overall survival (OS) was poor in both groups (10 and 12 months). The majority of PAED patients received platinum-based and taxane-containing chemotherapy or chemo-/immunotherapy with an objective response rate of 31.6% and a disease control rate of 57.9%. Median progression-free survival (PFS) and OS of PAED patients with systemic therapy were very poor (3.9 months and 5.9 months). Caucasian patients with a TTF-1-negative PAED have a poor prognosis with reduced response rates to standard first-line systemic therapy and short survival times (PFS and OS).

The immunological and pharmacokinetic evaluation of Lipid-PLGA hybrid nanoparticle-based oxycodone vaccines

The current opioid epidemic is one of the most profound public health crises facing the United States. Despite that it has been under the spotlight for years, available treatments for opioid use disorder (OUD) and overdose are limited to opioid receptor ligands such as the agonist methadone and the overdose reversing drugs such as naloxone. Vaccines are emerging as an alternative strategy to combat OUD and prevent relapse and overdose. Most vaccine candidates consist of a conjugate structure containing the target opioid attached to an immunogenic carrier protein. However, conjugate vaccines have demonstrated some intrinsic shortfalls, such as fast degradation and poor recognition by immune cells. To overcome these challenges, we proposed a lipid-PLGA hybrid nanoparticle (hNP)-based vaccine against oxycodone (OXY), which is one of the most frequently misused opioid analgesics. The hNP-based OXY vaccine exhibited superior immunogenicity and pharmacokinetic efficacy in comparison to its conjugate vaccine counterpart. Specifically, the hNP-based OXY vaccine formulated with subunit keyhole limpet hemocyanin (sKLH) as the carrier protein and aluminum hydroxide (Alum) as the adjuvant (OXY-sKLH-hNP(Alum)) elicited the most potent OXY-specific antibody response in mice. The induced antibodies efficiently bound with OXY molecules in blood and suppressed their entry into the brain. In a following dose-response study, OXY-sKLH-hNP(Alum) equivalent to 60 μg of sKLH was determined to be the most promising OXY vaccine candidate moving forward. This study provides evidence that hybrid nanoparticle-based vaccines may be superior vaccine candidates than conjugate vaccines and will be beneficial in treating those suffering from OUD.

5β-Dihydrosteroids: Formation and Properties.

5β-Dihydrosteroids are produced by the reduction of Δ4-3-ketosteroids catalyzed by steroid 5β-reductase (AKR1D1). By analogy with steroid 5α-reductase, genetic deficiency exists in AKR1D1 which leads to errors in newborn metabolism and in this case to bile acid deficiency. Also, like the 5α-dihydrosteroids (e.g., 5α-dihydrotestosterone), the 5β-dihydrosteroids produced by AKR1D1 are not inactive but regulate ligand access to nuclear receptors, can act as ligands for nuclear and membrane-bound receptors, and regulate ion-channel opening. For example, 5β-reduction of cortisol and cortisone yields the corresponding 5β-dihydroglucocorticoids which are inactive on the glucocorticoid receptor (GR) and provides an additional mechanism of pre-receptor regulation of ligands for the GR in liver cells. By contrast, 5β-pregnanes can act as neuroactive steroids at the GABAA and NMDA receptors and at low-voltage-activated calcium channels, act as tocolytic agents, have analgesic activity and act as ligands for PXR, while bile acids act as ligands for FXR and thereby control cholesterol homeostasis. The 5β-androstanes also have potent vasodilatory properties and work through blockade of Ca2+ channels. Thus, a preference for 5β-dihydrosteroids to work at the membrane level exists via a variety of mechanisms. This article reviews the field and identifies gaps in knowledge to be addressed in future research.

Putting a cap on the glycome: Dissecting human sialyltransferase functions

Human glycans are capped with sialic acids and these nine-carbon sugars mediate many of the biological functions and interactions of glycans. Structurally diverse sialic acid caps mark human cells as self and they form the ligands for the Siglec immune receptors and other glycan-binding proteins. Sialic acids enable host interactions with the human microbiome and many human pathogens utilize sialic acids to infect host cells. Alterations in sialic acid-carrying glycans, sialoglycans, can be found in every major human disease including inflammatory conditions and cancer. Twenty sialyltransferase family members in the Golgi apparatus of human cells transfer sialic acids to distinct glycans and glycoconjugates. Sialyltransferases catalyze specific reactions to form unique sialoglycans or they have shared functions where multiple family members generate the same sialoglycan product. Moreover, some sialyltransferases compete for the same glycan substrate, but create different sialic acid caps. The redundant and competing functions make it difficult to understand the individual roles of the human sialyltransferases in biology and to reveal the specific contributions to pathobiological processes. Recent insights hint towards the existence of biosynthetic rules formed by the individual functions of sialyltransferases, their interactions, and cues from the local Golgi environment that coordinate sialoglycan biosynthesis. In this review, we discuss the current structural and functional understanding of the human sialyltransferase family and we review recent technological advances that enable the dissection of individual sialyltransferase activities.

A Multi-Angle Approach to Predict Peptide-GPCR Complexes: The N/OFQ-NOP System as a Successful AlphaFold Application Case Study.

With nearly 700 structures solved and a growing number of customized structure prediction algorithms being developed at a fast pace, G protein-coupled receptors (GPCRs) are an optimal test case for validating new approaches for the prediction of receptor active state and ligand bioactive conformation complexes. In this study, we leveraged the availability of hundreds of peptide GPCRs in the active state and both classical homology and artificial intelligence (AI) based protein modeling combined with docking and AI-based peptide structure prediction approaches to predict the nociceptin/orphanin FQ-NOP receptor active state complex (N/OFQ-NOPa). The In Silico generated hypotheses were validated via the design, synthesis, and pharmacological characterization of novel linear N/OFQ(1-13)-NH2 analogues, leading to the discovery of a novel antagonist (3B; pKB = 6.63) bearing a single ring-constrained residue in place of the Gly2-Gly3 motif of the N/OFQ message sequence (FGGF). While the experimental validation was ongoing, the availability of the Cryo-EM structure of the predicted complex enabled us to unambiguously validate the generated hypotheses. To the best of our knowledge, this is the first example of a peptide-GPCR complex predicted with atomistic accuracy (full complex Cα RMSD < 1.0 Å) and of the N/OFQ message moiety being successfully modified with a rigid scaffold.

LPA3 agonist-producing Bacillus velezensis ADS024 is efficacious in multiple neuroinflammatory disease models

Neuroinflammation is a common component of neurological disorders. In the gut-brain-immune axis, bacteria and their metabolites are now thought to play a role in the modulation of the nervous and immune systems which may impact neuroinflammation. In this respect, commensal bacteria of humans have recently been shown to produce metabolites that mimic endogenous G-protein coupled receptor (GPCR) ligands. To date, it has not been established whether plant commensal bacteria, which may be ingested by animals including humans, can impact the gut-brain-immune axis via GPCR agonism. We screened an isopropanol (IPA) extract of the plant commensal Bacillus velezensis ADS024, a non-engrafting live biotherapeutic product (LBP) with anti-inflammatory properties isolated from human feces, against a panel of 168 GPCRs and identified strong agonism of the lysophosphatidic acid (LPA) receptor LPA3. The ADS024 IPA extracted material (ADS024-IPA) did not agonize LPA2, and only very weakly agonized LPA1. The agonism of LPA3 was inhibited by the reversible LPA1/3 antagonist Ki16425. ADS024-IPA signaled downstream of LPA3 through G-protein-induced calcium release, recruitment of β-arrestin, and recruitment of the neurodegeneration-associated proteins 14–3-3γ, ε and ζ but did not recruit the β isoform. Since LPA3 agonism was previously indirectly implicated in the reduction of pathology in models of Parkinson’s disease (PD) and multiple sclerosis (MS) by use of the nonselective antagonist Ki16425, and since we identified an LPA3-specific agonist within ADS024, we sought to examine whether LPA3 might indeed be part of a broad underlying mechanism to control neuroinflammation. We tested oral treatment of ADS024 in multiple models of neuroinflammatory diseases using three models of PD, two models of MS, and a model each of amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD), and chemo-induced peripheral neuropathy (CIPN). ADS024 treatment improved model-specific functional effects including improvements in motor movement, breathing and swallowing, and allodynia suggesting that ADS024 treatment impacted a universal underlying neuroinflammatory mechanism regardless of the initiating cause of disease. We used the MOG-EAE mouse model to examine early events after disease initiation and found that ADS024 attenuated the increase in circulating lymphocytes and changes in neutrophil subtypes, and ADS024 attenuated the early loss of cell-surface LPA3 receptor expression on circulating white blood cells. ADS024 efficacy was partially inhibited by Ki16425 in vivo suggesting LPA3 may be part of its mechanism. Altogether, these data suggest that ADS024 and its LPA3 agonism activity should be investigated further as a possible treatment for diseases with a neuroinflammatory component.

Screening and toxicity evaluation of natural compounds as adenosine 2a and 2b receptor ligands: insights from molecular docking, dynamics, and ADMET analysis

Recent studies suggest that immunological and inflammatory responses in cardiovascular disorders, such as hypertension, myocardial infarction, ischemia injury, heart failure, arrhythmias, and atherosclerosis, may be affected by changes in the adenosine system. Pharmacological modulation of adenosine occurs through its receptor subtypes. In numerous preclinical studies, the activation of adenosine receptor 2A (A2AR) or the blockade of adenosine receptor 2B (A2BR) has shown promising results against cardiovascular diseases. This in silico study aimed to identify potential natural compounds that can activate A2AR or block A2BR without causing toxicity. Natural compounds were screened using COlleCtion of Open Natural ProdUcTs (COCONUT) or Natural Product Activity and Species Source Database (NPASS) databases to find agonists for A2AR or an antagonists/inverse agonists for A2BR. These compounds were then pre-filtered based on their toxicity profiles. The remaining compounds were subjected to molecular docking against A2AR and A2BR followed by molecular dynamics simulations were conducted. Finally, selected compounds’ ADMET properties were determined using ADMETlab 2.0 web tool. Ultimately, one novel natural compound with potential agonistic activity (COCONUT IDs: CNP0450901) for A2AR and one antagonist/inverse agonist (rauwolscine) for A2BR were identified.

Inhibition of TLR4 and NLRP3 leads to the exacerbation of IgE specific antibodies in mouse allergic models based on subcutaneous or intranasal immunization respectively

A significant increase in the prevalence of diseases linked with IgE production can be seen in recent years, but the question about the role of TLR receptors in this process remains controversial. According to the hygiene hypothesis, the decrease of the contact of the individual with pathogens that contain PRR receptor ligands in the recent years leads to the development of allergic diseases. The aim of this work was to investigate whether TLR4 and NLRP3 receptor activation contributes to allergen-specific antibody formation. BALB/c mice were immunized according to two different protocols. In the first one, OVA antigen was administered in 0.1 µg dose 2-3 times a week for 6 weeks by subcutaneous route. In the second one, OVA was administered in 0.3 µg dose intranasally in combination with 4 ng of benzo(a)pyrene (BaP) 2 times a week for 8 weeks. In both cases, TLR4 and NLRP3 receptor inhibitors, namely TLR4-IN-C34 in 1 mg/kg dose and CY- 09 in 20 mg/kg dose respectively were also administered to the some of the mice. Specific antibody production was determined by ELISA. Immunization of mice with TLR4-IN-C34 significantly (p 0.01) amplify IgE production (about 2.5 times in comparison with control group), but has no effect on specific IgG1 production in subcutaneous model. Specific IgE titers in the control group immunized without small molecule inhibitor and in the TLR4-IN-C34 group were (3±0.6) × 103 and (8±2) × 103, respectively. In this model, CY-09 administration has no effect on humoral immune response. In the secondary (intranasal) model, BaP significantly increase specific IgE and IgG1 production. CY-09 but not TLR4-IN-C34 administered in combination with BaP significant (p 0.05) and approximately 2 times enhances specific IgE but not IgG1 production. Specific IgE titers in the control group without inhibitor and in the CY-09 group were (2.0±0.4) × 102 and (5.1±0.3) × 102, respectively. So, PRR-activation, in our case activation of TLR4 in the model based on subcutaneous immunization or NLRP3 in the model based on intranasal antigen administration with BaP suppressed the production of allergen-specific IgE, but not IgG1. These data are in consistent with the hygiene theory of allergy development.

Transient frequency preference responses in cell signaling systems

Ligand–receptor systems, covalent modification cycles, and transcriptional networks are the fundamental components of cell signaling and gene expression systems. While their behavior in reaching a steady-state regime under step-like stimulation is well understood, their response under repetitive stimulation, particularly at early time stages is poorly characterized. Yet, early-stage responses to external inputs are arguably as informative as late-stage ones. In simple systems, a periodic stimulation elicits an initial transient response, followed by periodic behavior. Transient responses are relevant when the stimulation has a limited time span, or when the stimulated component’s timescale is slow as compared to the timescales of the downstream processes, in which case the latter processes may be capturing only those transients. In this study, we analyze the frequency response of simple motifs at different time stages. We use dose-conserved pulsatile input signals and consider different metrics versus frequency curves. We show that in ligand–receptor systems, there is a frequency preference response in some specific metrics during the transient stages, which is not present in the periodic regime. We suggest this is a general system-level mechanism that cells may use to filter input signals that have consequences for higher order circuits. In addition, we evaluate how the described behavior in isolated motifs is reflected in similar types of responses in cascades and pathways of which they are a part. Our studies suggest that transient frequency preferences are important dynamic features of cell signaling and gene expression systems, which have been overlooked.

Dopaminergic cAMP signaling in mouse olfactory bulb astrocytes

Cyclic AMP (cAMP) is an important second messenger in virtually all animal cell types, including astrocytes. In the brain, it modulates energy metabolism, development and synaptic plasticity. Dopamine receptors are G protein-coupled receptors that affect cAMP production by adenylyl cyclases. They are divided into two subgroups, D1-like receptors linked to Gs proteins stimulating cAMP production and D2-like receptors linked to Gi/o proteins inhibiting cAMP production. In the present study, we investigated the effect of dopamine receptor activation on cAMP dynamics in astrocytes of the mouse olfactory bulb, the brain region with the largest population of dopaminergic neurons. Using the genetically encoded cAMP sensor Flamindo2 we visualized changes in the cytosolic cAMP concentration and showed that dopamine application results in a transient increase in cAMP. This cAMP increase could be mimicked by the D1-like receptor agonist A 68930 and was inhibited by the D1-like receptor antagonist SCH 23390, whereas D2-like receptor ligands had no effect on the astrocytic cAMP concentration. Thus, olfactory bulb astrocytes express D1-like receptors that are linked to cAMP production.

In vitro pharmacological characterization of growth hormone secretagogue receptor ligands using the dynamic mass redistribution and calcium mobilization assays

Ghrelin modulates several biological functions via selective activation of the growth hormone secretagogue receptor (GHSR). GHSR agonists may be useful for the treatment of anorexia and cachexia, while antagonists and inverse agonists may represent new drugs for the treatment of metabolic and substance use disorders. Thus, the identification and pharmacodynamic characterization of new GHSR ligands is of high interest. In the present work the label-free dynamic mass redistribution (DMR) assay has been used to evaluate the pharmacological activity of a panel of GHSR ligands. This includes the endogenous peptides ghrelin, desacyl-ghrelin and LEAP2(1–14). Among synthetic compounds, the agonists anamorelin and HM01, the antagonists HM04 and YIL-781, and the inverse agonist PF-05190457 have been tested, together with HM03, R011, and H1498 from patent literature. The DMR results have been compared to those obtained in parallel experiments with the calcium mobilization assay. Ghrelin, anamorelin, HM01, and HM03 behaved as potent full GHSR agonists. YIL-781 behaved as a partial GHSR agonist and R011 as antagonist in both the assays. LEAP2(1–14) resulted a GHSR inverse agonist in DMR but not in calcium mobilization assay. PF-05190457, HM04, and H1498 behaved as GHSR inverse agonists in DMR experiments, while they acted as antagonists in calcium mobilization studies. In conclusion, this study provided a systematic pharmacodynamic characterization of several GHSR ligands in two different pharmacological assays. It demonstrated that the DMR assay can be successfully used particularly to discriminate between antagonists and inverse agonists. This study may be useful for the selection of the most appropriate compounds to be used in future studies.

PET imaging of [52 Mn]Mn-DOTATATE and [52 Mn]Mn-DOTA-JR11.

Manganese-52 is gaining interest as an isotope for PET imaging due to its desirable decay and chemical properties for radiopharmaceutical development. Somatostatin receptor 2 (SSTR2) is significantly overexpressed by neuroendocrine tumors (NETs) and is an important target for nuclear imaging and therapy. As an agonist, [68Ga]Ga-DOTATATE has demonstrated significant internalization upon interaction with receptor ligands, whereas [68Ga]Ga-DOTA-JR11(as an antagonist) exhibits limited internalization but better pharmacokinetics and increased tumor uptake. The goal of this study was to label both DOTATATE and DOTA-JR11 peptides with 52Mn in high radiochemical yields (RCY) and sufficient specific activity. A comparison of these two compounds was performed in in vitro and in vivo studies in animals with somatostatin receptor-positive xenografts to characterize differences in cell, tumor, and tissue uptake. Radiolabeling of DOTATATE and DOTA-JR11 was carried out by combining varying concentrations of the peptides with [52Mn]MnCl2. In vitro stability of the radiotracers was determined in mouse serum. In vitro cell uptake and internalization assays were performed in SSTR2 + AR42J cells and negative controls. In vivo biodistribution and longitudinal PET imaging was evaluated in mice bearing AR42J tumors. Both [52Mn]Mn-DOTATATE and [52Mn]Mn-DOTA-JR11showed affinity for SSTR2 in AR42J cells. However, the uptake of [52Mn]Mn-DOTATATE was higher (11.95 ± 0.71%/ mg) compared to [52Mn]Mn-DOTA-JR11 (7.31 ± 0.38%/ mg) after 2 h incubation. After 4 h incubation, 53.13 ± 1.83% of the total activity of [52Mn]Mn-DOTATATE was internalized, whereas only 20.85 ± 0.59% of the total activity of [52Mn]Mn-DOTA-JR11 was internalized. The PET images revealed similar biodistribution results, with [52Mn]Mn-DOTATATE showing a significant tumor uptake of 11.16 ± 2.97% ID/g, while [52Mn]Mn-DOTA-JR11 exhibited a lower tumor uptake of 2.11 ± 0.30% ID/g 4 h post-injection. The synthesis of both radiotracers was accomplished with high RCY and purity. The cell uptake and internalization of [52Mn]Mn-DOTATATE showed higher levels compared to [52Mn]Mn-DOTA-JR11. PET images of the radiotracers in AR42J tumor bearing mice demonstrated similar biodistribution in all organs except the tumor, with [52Mn]Mn-DOTATATE showing higher tumor uptake compared to [52Mn]Mn-DOTA-JR11. The variations in properties of these tracers could be used to guide further imaging and treatment studies.

Predicting Response to Medical Treatment in Acromegaly via Granulation Pattern, Expression of Somatostatin Receptors Type 2 and 5 and E-Cadherin.

Resistance to first-generation somatostatin receptor ligand (fgSRL) treatment in acromegaly is common, making the identification of biomarkers that predict fgSRL response a desired goal. We conducted a retrospective analysis on 21 patients with acromegaly who underwent surgery and subsequent pharmacological treatment. Through immunohistochemistry (IHC), we assessed the expression of the somatostatin receptor subtypes SSTR2 and SSTR5, E-Cadherin, and cytokeratin granulation pattern (sparsely or densely). Patients were divided into responders and non-responders based on their biochemical response to fgSRL and/or the newer agent, Pasireotide, or the GH-blocker, Pegvisomant. Patients resistant to fgSRL (n = 12) exhibited lower SSTR2 and E-Cadherin expressions. Sparsely granulated tumors were more frequent in the non-responder group. SSTR2 (p = 0.024, r = 0.49) and E-Cadherin (p = 0.009, r = 0.64) positively correlated with the Insulin-like Growth Factor 1 (IGF-1) decrease after fgSRL, while SSTR5 (p = 0.107, r = -0.37) showed a trend towards negative correlation. SSTR5 positivity seemed to be associated with Pasireotide response, albeit the number of treated patients was too low (n = 4). No IHC markers correlated with Pegvisomant response. Our findings suggest that densely granulated tumors, with positive SSTR2 and E-Cadherin seem to be associated with favorable fgSRL responses. The strongest predictive value of the studied markers was found for E-Cadherin, which seems to surpass even SSTR2.

Structure and Function of Somatostatin and its Receptors in Endocrinology.

Somatostatin analogs, such as octreotide (OCT), lanreotide, and pasireotide, which function as somatostatin receptor ligands (SRLs), are the main drugs used for the treatment of acromegaly. These ligands are also used as important molecules for radiation therapy and imaging of neuroendocrine tumors (NETs). Somatostatin receptors (SSTRs) are canonical G protein-coupled proteins (GPCRs) that play a role in metabolism, growth, and pathological conditions such as hormone disorders, neurological diseases, and cancers. Cryogenic electron microscopy (cryo-EM) combined with the protein structure prediction platform AlphaFold has been used to determine the three-dimensional structures of many proteins. Recently, several groups published a series of papers illustrating the three-dimensional structure of SSTR2, including that of the inactive/activated SSTR2-G protein complex bound to different ligands. The results revealed the residues that contribute to the ligand binding pocket and demonstrated that Trp8-Lys9 (the W-K motif) in somatostatin analogs is the key motif in stabilizing the bottom part of the binding pocket. In this review, we discuss the recent findings related to the structural analysis of SSTRs and SRLs, the relationships between the structural data and clinical findings, and the future development of novel structure-based therapies.

A Pilot Electroencephalography Study of the Effect of CT1812 Treatment on Synaptic Activity in Patients with Mild to Moderate Alzheimer’s Disease

BackgroundCT1812 is a first-in-class, sigma-2 receptor ligand, that prevents and displaces binding of amyloid beta (Aβ) oligomers. Normalization of quantitative electroencephalography (qEEG) markers suggests that CT1812 protects synapses from Aβ oligomer toxicity.ObjectivesEvaluate CT1812 impact on synaptic function using qEEG measurements.DesignPhase 2, randomized, double-blind, placebo-controlled, 4-week crossover study.SettingVU University Medical Center and Brain Research Center Amsterdam, The Netherlands.ParticipantsAdults with mild or moderate Alzheimer’s disease (AD).InterventionA daily 300 mg dose of CT1812 or placebo for 4 weeks.MeasurementsA resting-state, eyes closed qEEG assessment occurred on Day 1 and on Day 29 of Treatment Periods 1 and 2, and at follow-up. The primary endpoint was global relative theta power (4–8 Hz), along with secondary EEG measures including global alpha corrected Amplitude Envelope Correlation (AEC-c). Cognitive and functional assessments, fluid biomarkers, and safety and tolerability were assessed.Results16 patients were randomized, and 15 completed. A non-significant (p=0.123) but consistent reduction occurred in global relative theta power and in relative theta power in frontal, temporal, parietal, occipital and central (p<0.006) brain regions with CT1812. A nominally significant (p=0.034) improvement was observed in global alpha AEC-c. Adverse events occurred in 11 patients with CT1812 and 6 with placebo -most commonly nausea, diarrhea, and procedural headache. No severe or serious AEs, deaths or discontinuations were reported.ConclusionCT1812 improved established EEG markers of spontaneous brain activity (spectral power, functional connectivity) in patients with mild-to-moderate AD, suggesting improved neuronal/synaptic function within a 4-week timespan.

Inflammatory disease status and response to TNF blockade are associated with mechanisms of endotoxin tolerance

The mechanisms of endotoxin tolerance (ET), which down-regulate inflammation, are well described in response to exogenous toll-like receptor ligands, but few studies have focused on ET-associated mechanisms in inflammatory disease. As blocking TNF can attenuate the development of ET, the effect of anti-TNF on the expression of key ET-associated molecules in inflammatory auto-immune disease was measured; changes in inflammatory gene expression were confirmed using an ET bioassay. The expression of immunomodulatory molecules was measured in a murine model of arthritis treated with anti-TNF and the expression of ET-associated molecules was measured in whole blood in rheumatoid arthritis (RA) and ankylosing spondylitis (AS) patients, before and after therapy. The expression of ET-associated genes was also measured in RA patient monocytes before and after therapy, in anti-TNF responders and non-responders. Tnfaip3, Ptpn6 and Irak3 were differentially expressed in affected paws, spleens, lymph nodes and circulating leucocytes in experimental murine arthritis treated with anti-TNF. Prior to therapy, the expression of TNFAIP3, INPP5D, PTPN6, CD38 and SIGIRR in whole blood differed between human healthy controls and RA or AS patients. In blood monocytes from RA patients, the expression of TNFAIP3 was significantly reduced by anti-TNF therapy in non-responders. Prior to therapy, anti-TNF non-responders had higher expression of TNFAIP3 and SLPI, compared to responders. Although the expression of TNFAIP3 was significantly higher in RA non-responders prior to treatment, the post-treatment reduction to a level similar to responders did not coincide with a clinical response to therapy.

Modulation of Ceramide-Induced Apoptosis in Enteric Neurons by Aryl Hydrocarbon Receptor Signaling: Unveiling a New Pathway beyond ER Stress.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a persistent organic pollutant and a potent aryl hydrocarbon receptor (AHR) ligand, causes delayed intestinal motility and affects the survival of enteric neurons. In this study, we investigated the specific signaling pathways and molecular targets involved in TCDD-induced enteric neurotoxicity. Immortalized fetal enteric neuronal (IM-FEN) cells treated with 10 nM TCDD exhibited cytotoxicity and caspase 3/7 activation, indicating apoptosis. Increased cleaved caspase-3 expression with TCDD treatment, as assessed by immunostaining in enteric neuronal cells isolated from WT mice but not in neural crest cell-specific Ahr deletion mutant mice (Wnt1Cre+/-/Ahrb(fl/fl)), emphasized the pivotal role of AHR in this process. Importantly, the apoptosis in IM-FEN cells treated with TCDD was mediated through a ceramide-dependent pathway, independent of endoplasmic reticulum stress, as evidenced by increased ceramide synthesis and the reversal of cytotoxic effects with myriocin, a potent inhibitor of ceramide biosynthesis. We identified Sptlc2 and Smpd2 as potential gene targets of AHR in ceramide regulation by a chromatin immunoprecipitation (ChIP) assay in IM-FEN cells. Additionally, TCDD downregulated phosphorylated Akt and phosphorylated Ser9-GSK-3β levels, implicating the PI3 kinase/AKT pathway in TCDD-induced neurotoxicity. Overall, this study provides important insights into the mechanisms underlying TCDD-induced enteric neurotoxicity and identifies potential targets for the development of therapeutic interventions.