Receptor Stimulation Research Articles

Stimulation of Dopamine D4 Receptors in the Nucleus Accumbens Shell Increases Palatable Food Intake in Satiated Male Rats: Modulation by NMDA and AMPA Receptors

Background/Objectives: Palatability significantly influences food consumption, often leading to overeating and obesity by activating the brain’s reward systems. The nucleus accumbens (NAc) plays a central role in this process, modulating reward mechanisms primarily via dopamine through D2-like receptors (D2R, D3R, D4R). While the involvement of D2 receptors in feeding is well-documented, the role of D4 receptors (D4Rs) is less clear. Methods: Male Wistar rats received intra-NAc shell microinjections of the D4R agonist PD-168077 and the antagonist L-745870. This study also examined the modulation between D4R and glutamatergic transmission by administration of NMDA, NMDA receptor antagonist AP-5, AMPA, and AMPA receptor antagonist CNQX. Results: PD-168077 increased sweet solution intake by 46%, an effect that was reversed by L-745870. Pre-treatment with NMDA prevented the stimulatory effect of PD-168077, whereas the NMDA receptor antagonist AP-5 had no such effect. Additionally, AMPA administration reduced sweet solution intake by 63%, counteracting the effect of PD-168077, while the AMPA receptor antagonist CNQX, on its own, increased intake by 40%. Conclusions: These findings suggest that D4Rs promote hedonic feeding by modulating glutamatergic transmission in the NAc shell, highlighting the complexity of D4R involvement in food intake regulation. This study underscores the potential of targeting D4Rs for therapeutic interventions in eating disorders and obesity, though further research is essential to clarify the precise mechanisms through which D4R modulates AMPA and NMDA receptor activity in feeding behavior.

Beta-Adrenergic Activation of the Inward Rectifier K+ Current Is Mediated by the CaMKII Pathway in Canine Ventricular Cardiomyocytes

Several ion currents in the mammalian ventricular myocardium are substantially regulated by the sympathetic nervous system via β-adrenergic receptor activation, including the slow delayed rectifier K+ current and the L-type calcium current. This study investigated the downstream mechanisms of β-adrenergic receptor stimulation by isoproterenol (ISO) on the inward rectifier (IK1) and the rapid delayed rectifier (IKr) K+ currents using action potential voltage clamp (APVC) and conventional voltage clamp techniques in isolated canine left ventricular cardiomyocytes. IK1 and IKr were dissected by 50 µM BaCl2 and 1 µM E-4031, respectively. Acute application of 10 nM ISO significantly increased IK1 under the plateau phase of the action potential (0–+20 mV) using APVC, and similar results were obtained with conventional voltage clamp. However, β-adrenergic receptor stimulation did not affect the peak current density flowing during terminal repolarization or the overall IK1 integral. The ISO-induced enhancement of IK1 was blocked by the calcium/calmodulin kinase II (CaMKII) inhibitor KN-93 (1 µM) but not by the protein kinase A inhibitor H-89 (3 µM). Neither KN-93 nor H-89 affected the IK1 density under baseline conditions (in the absence of ISO). In contrast, parameters of the IKr current were not affected by β-adrenergic receptor stimulation with ISO. These findings suggest that sympathetic activation enhances IK1 in canine left ventricular cells through the CaMKII pathway, while IKr remains unaffected under the experimental conditions used.

Effects of the restrictive cardiomyopathy-associated cardiac troponin I K178E mutation on cAMP signalling at the myofilament

Abstract Background Catecholaminergic stimulation of cardiac β-adrenergic receptors (β-ARs) and subsequent cAMP signalling control cardiac inotropy and lusitropy. cAMP signalling is known to be compartmentalised to optimise sympathetic control by producing heterogeneous cAMP signals and protein kinase A (PKA) activation at distinct subcellular sites. This signalling may be disrupted in diseases such as restrictive cardiomyopathy (RCM) characterised by diastolic dysfunction, which is associated with certain mutations including the K178E missense mutation in cardiac troponin I (TPNI). The impaired ventricular relaxation associated with this mutation is thought to arise from myofilament calcium hypersensitivity, which can be modulated by PKA-dependent TPNI phosphorylation. However, a detailed understanding of the pathological effects mediated by the K178E-TPNI mutation is lacking. Purpose This study aims to determine whether the K178E-TPNI mutation alters local cAMP/PKA signalling at TPNI, potentially affecting myofilament calcium sensitivity and cardiac myocyte relaxation. Methods Real-time imaging of cAMP was carried out using the Fluorescence Resonance Energy Transfer (FRET)-based sensor CUTie (cAMP Universal Tag for imaging experiments) [1] fused to wild type (WT)- or K178E-TPNI. The sensors were expressed by transfection in neonatal rat ventricular myocytes (NRVMs) and FRET-changes were recorded at the myofilament on application of the β-AR stimulant isoproterenol (ISO). We further assessed the involvement of cAMP hydrolysing phosphodiesterases (PDEs) in the regulation of cAMP levels selectively at TPNI. Results The peak FRET-change and FRET-change after 5mins on ISO application were significantly higher in NRVMs expressing the mutant compared to the WT sensor, as was the rate of cAMP accumulation. A strong trend showed that the rise in FRET following PDE4 inhibition was larger in NRVMs expressing the WT compared to the mutant sensor, suggesting the involvement of this isoform in degrading cAMP locally at TPNI and reduced PDE4 activity in the presence of the K178E mutation. Co-immunoprecipitation analysis in HEK293 cells demonstrated interaction between WT-TPNI and a PDE4D isoform, and a weaker interaction of this isoform with the K178E-TPNI mutant. Conclusions This study shows that the K178E-TPNI mutation attenuates the TPNI/PDE4D interaction and alters the magnitude and kinetics of the local cAMP response at the myofilament. This mechanistic insight may aid the development of therapeutics targeting the TPNI/PDE4D interaction to treat RCM-associated diastolic dysfunction.The TPNI-CUTie SensorFRET Response Trace

Elderly patients are hyperresponsive to potent P2Y12 inhibitors

Abstract Background Aging has recently been associated with increased basal platelet activation and adenosine diphosphate (ADP) hyperreactivity on the one hand, but decreased platelet response to thrombin receptor stimulation on the other hand in individuals without antiplatelet therapy. In the current study, we investigated platelet response to agonist stimulation in elderly patients (70 years or older) on dual antiplatelet therapy with potent P2Y12 inhibitors. Methods Platelet aggregation in response to arachidonic acid (AA), ADP, collagen, the protease-activated receptor (PAR)-1 agonist SFLLRN and the PAR-4 agonist AYPGKF was assessed by multiple electrode aggregometry in 79 prasugrel- and 77 ticagrelor-treated patients 3 days after acute percutaneous coronary intervention. Results In the overall study population (n=156), patients aged ≥70 years (n=33) had lower platelet aggregation in response to AA, ADP and SFLLRN than younger patients (all p<0.05). In prasugrel-treated patients (n=79), those aged ≥70 years (n=13) showed significantly lower platelet aggregation in response to all agonists compared to younger patients (all p<0.05). In contrast, in ticagrelor-treated patients (n=77), those aged ≥70 years (n=20) only had significantly lower ADP-inducible platelet aggregation than younger patients (p=0.03), whereas platelet aggregation in response to AA, collagen, SFLLRN and AYPGKF was similar between elderly and younger patients on ticagrelor (all p>0.05). Among patients aged ≥70 years, prasugrel-treated patients showed significantly lower platelet aggregation in response to AA, collagen and AYPGKF than those receiving ticagrelor (all p<0.05). Conclusion Patients aged ≥70 years on potent P2Y12 inhibitors exhibit increased inhibition of ADP-inducible platelet aggregation. In addition, elderly patients on prasugrel show a significantly lower response to AA, collagen, SFLLRN and AYPGKF than younger patients.Platelet aggregation prasugrel patientsPlatelet aggregation ticagrelor patients

Histamine stimulates human microglia to alter cellular prion protein expression via the HRH2 histamine receptor

Although the cellular prion protein (PrPC) has been evolutionarily conserved, the role of this protein remains elusive. Recent evidence indicates that PrPC may be involved in neuroinflammation and the immune response in the brain, and its expression may be modified via various mechanisms. Histamine is a proinflammatory mediator and neurotransmitter that stimulates numerous cells via interactions with histamine receptors 1-4 (HRH1-4). Since microglia are the innate immune cells of the central nervous system, we hypothesized that histamine-induced stimulation regulates the expression of PrPC in human-derived microglia. The human microglial clone 3 (HMC3) cell line was treated with histamine, and intracellular calcium levels were measured via a calcium flux assay. Cytokine production was monitored by enzyme-linked immunosorbent assay (ELISA). Western blotting and quantitative reverse transcription-polymerase chain reaction were used to determine protein and gene expression of HRH1-4. Flow cytometry and western blotting were used to measure PrPC expression levels. Fluorescence microscopy was used to examine Iba-1 and PrPC localization. HMC3 cells stimulated by histamine exhibited increased intracellular calcium levels and increased release of IL-6 and IL-8, while also modifying PrPC localization. HMC3 stimulated with histamine for 6 and 24 hours exhibited increased surface PrPC expression. Specifically, we found that stimulation of the HRH2 receptor was responsible for changes in surface PrPC. Histamine-induced increases in surface PrPC were attenuated following inhibition of the HRH2 receptor via the HRH2 antagonist ranitidine. These changes were unique to HRH2 activation, as stimulation of HRH1, HRH3, or HRH4 did not alter surface PrPC. Prolonged stimulation of HMC3 decreased PrPC expression following 48 and 72 hours of histamine stimulation. HMC3 cells can be stimulated by histamine to undergo intracellular calcium influx. Surface expression levels of PrPC on HMC3 cells are altered by histamine exposure, primarily mediated by HRH2. While histamine exposure also increases release of IL-6 and IL-8 in these cells, this cytokine release is not fully dependent on PrPC levels, as IL-6 release is only partially reduced and IL-8 release is unchanged under the conditions of HRH2 blockade that prevent PrPC changes. Overall, this suggests that PrPC may play a role in modulating microglial responses.

Proangiogenic effect of thyrotropin receptor stimulating antibody in human umbilical vein endothelial cells.

This study aims to investigate the role of TRAb in the angiogenesis associated with Graves' disease (GD) and to elucidate its underlying mechanisms. Human thyroid follicular epithelial cells (Nthy-ori 3-1) and human umbilical vein endothelial cells (HUVECs) were treated with the monoclonal thyroid-stimulating antibody M22 and thyroid-stimulating hormone (TSH) at various concentrations. Cell viability, migration, and tube formation were evaluated using CCK-8, wound healing, and tube formation assays, respectively. Protein expressions of TSHR receptor (TSHR) and phosphorylated AKT (p-AKT) in M22-induced HUVECs were quantified via Western blotting. Proteomic analysis was employed to identify changes in protein expression profiles and relevant signaling pathways in GD specimens. Immunofluorescence assays were conducted to detect and localize the expressions of CD34 and PROX1 in GD specimens and normal thyroid tissues. M22 stimulated the proliferation of Nthy-ori 3-1 cells and HUVECs in a dose-dependent manner, while TSH exhibited an inverted U-shaped dose-response effect. M22 also dose-dependently promoted angiogenesis, and more effectively induced tube formation in HUVECs compared to TSH, although the difference was not statistically significant. A total of 16 proteins were significantly upregulated and 24 were downregulated in M22-induced HUVECs. Notably, PROX1, the most significantly upregulated protein, is closely associated with angiogenesis. Immunofluorescence confirmed that PROX1 was significantly more expressed in thyroid tissues from GD patients compared to normal tissues adjacent to papillary thyroid cancer (PTC), and it co-localized with CD34. TRAb enhances angiogenesis and upregulates PROX1 expression in HUVECs, suggesting a novel possible mechanism for goiter formation in GD.

α4 Nicotinic Acetylcholine Receptors in Lipopolysaccharide-Related Lung Inflammation

Sepsis remains an important healthcare challenge. The lungs are often affected in sepsis, resulting in acute lung injury characterized by inflammation. Mechanisms involving lipopolysaccharide (LPS) stimulation of toll-like receptor (TLR) signaling with induction of proinflammatory pathways have been implicated in this process. To date, however, studies targeting these pathways have failed to improve outcomes. We have found that LPS may also promote lung injury through the activation of α4 nicotinic acetylcholine receptors (α4 nAChRs) in immune cells. We observed increased expression of α4 nAChRs in human THP-1 monocytic cells exposed to LPS (100 ng/mL, 24 h). We also observed that LPS stimulated the expression of other relevant genes, including tumor necrosis factor-α, interleukin-1β, plasminogen activator inhibitor-1, the solute carrier family 7 member 11, extracellular superoxide dismutase, and transforming growth factor-β1. Of interest, dihydro-β-erythroidine hydrobromide (DHβE), a specific chemical inhibitor of α4 nAChRs, inhibited the LPS-induced expression of these genes. We generated mice with a global knockout mutation of the α4 nAChR subunit in the C57BL/6 background using CRISPR/Cas9 technology. The lungs of these LPS-treated animals demonstrated a reduction in the expression of the above-mentioned genes when compared with the lungs of wild-type animals. In support of the role of oxidative stress, we observed that LPS induced expression of the cystine transporter Slc7a11 in both THP-1 cells and in wild-type mouse lungs. The effects of LPS on THP-1 cells were blocked by the thiol antioxidant N-acetylcysteine and mimicked by redox stress. Importantly, the induction of IL-1β by redox stress was inhibited by the α4 nAChR inhibitor DHβE. Finally, we showed that LPS stimulated calcium influx in THP-1 cells, which was blocked by the α4 nAChR inhibitor. Our observations suggest that LPS promotes lung injury by stimulating redox stress, which activates α4 nAChR signaling and drives proinflammatory cytokine expression.

Abstract A051: Bitter agonists increase macrophage phagocytosis of head and neck squamous cell carcinoma cells

Abstract Head and neck squamous cell carcinoma (HNSCC) is the 7th most commonly diagnosed cancer worldwide and is expected to increase in incidence by 30% by 2030. The HNSCC microenvironment is characterized by substantial macrophage infiltration. However, tumor-associated macrophages often cultivate an immunosuppressive environment that aids tumor progression. Previous work has shown that macrophages express bitter taste receptors (T2Rs), a class of GPCRs that can be activated with bitter compounds. Previous work has also demonstrated that stimulation of T2Rs in macrophages with bitter agonists, such as denatonium benzoate, increases phagocytosis of bacteria, but the impact of bitterants on macrophage phagocytosis of tumor cells is unknown. The goal of this study was to assess the impact of bitter compounds on macrophage phagocytosis of HNSCC cells in vitro. Human peripheral blood mononuclear cells obtained from healthy donors were used to generate monocyte-derived macrophages (MDMs). To investigate the effects of bitter agonist stimulation on macrophage phagocytosis, CFSE-labeled MDMs and DAPI-labeled HNSCC cell line SCC47, were co-stimulated with denatonium benzoate, and macrophage phagocytosis was quantified. This revealed that treatment with denatonium benzoate led to a 70% increase in macrophage phagocytosis compared to controls. Additional analysis revealed a 1.8-fold increase in F-actin in MDMs in response to denatonium benzoate measured via CellMask™ Actin staining, and that macrophages had generated F-actin positive tunneling nanotubes (TNTs). Further characterization with live cell imaging showed that these TNTs were being utilized as a means of mitochondrial transfer as observed by MitoTracker™ and CellMask™ Actin staining. Furthermore, there was a 2.5-fold decrease in mitochondrial ATP production in MDMs stimulated with denatonium benzoate, possibly indicating metabolic reprogramming. Timelapse imaging of MDMs demonstrated a reduction in mitochondrial ATP production, with a concomitant increase in F-actin production. These observations were confirmed in Phorbol 12-myristate 13-acetate differentiated THP-1 cells. Taken together, these results indicate that bitter taste receptor stimulation may contribute to a more activated macrophage phenotype denoted by a decrease in mitochondrial ATP production, increased F-actin staining, and increased phagocytosis of tumor cells. Citation Format: Brianna L Hill, Sarah M Sywanycz, Zoey A Miller, Robert J Lee, Ryan M Carey. Bitter agonists increase macrophage phagocytosis of head and neck squamous cell carcinoma cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A051.

Short Link N Modulates Inflammasome Activity in Intervertebral Discs Through Interaction with CD14.

Intervertebral disc degeneration and pain are associated with the nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3) inflammasome activation and the processing of interleukin-1 beta (IL-1β). Activation of thehm inflammasome is triggered by Toll-like receptor stimulation and requires the cofactor receptor cluster of differentiation 14 (CD14). Short Link N (sLN), a peptide derived from link protein, has been shown to modulate inflammation and pain in discs in vitro and in vivo; however, the underlying mechanisms remain elusive. This study aims to assess whether sLN modulates IL-1β and inflammasome activity through interaction with CD14. Disc cells treated with lipopolysaccharides (LPS) with or without sLN were used to assess changes in Caspase-1, IL-1β, and phosphorylated nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). Peptide docking of sLN to CD14 and immunoprecipitation were performed to determine their interaction. The results indicated that sLN inhibited LPS-induced NFκB and Caspase-1 activation, reducing IL-1β maturation and secretion in disc cells. A significant decrease in inflammasome markers was observed with sLN treatment. Immunoprecipitation studies revealed a direct interaction between sLN and the LPS-binding pocket of CD14. Our results suggest that sLN could be a potential therapeutic agent for discogenic pain by mitigating IL-1β and inflammasome activity within discs.

Force versus Response: Methods for Activating and Characterizing Mechanosensitive Ion Channels and GPCRs.

Mechanotransduction is the process whereby cells convert mechanical signals into electrochemical responses, where mechanosensitive proteins mediate this interaction. To characterize these critical proteins, numerous techniques have been developed that apply forces and measure the subsequent cellular responses. While these approaches have given insight into specific aspects of many such proteins, subsequent validation and cross-comparison between techniques remain difficult given significant variations in reported activation thresholds and responses for the same protein across different studies. Accurately determining mechanosensitivity responses for various proteins, however, is essential for understanding mechanotransduction and potential physiological implications, including therapeutics. This critical review provides an assessment of current and emerging approaches used for mechanosensitive ion channel and G-Coupled Receptors (GPCRs) stimulation and measurement, with a specific focus on the ability to quantitatively measure mechanosensitive responses.

Sensitive fluorescent biosensor reveals differential subcellular regulation of PKC.

The protein kinase C (PKC) family of serine and threonine kinases, consisting of three distinctly regulated subfamilies, has been established as critical for various cellular functions. However, how PKC enzymes are regulated at different subcellular locations, particularly at emerging signaling hubs, is unclear. Here we present a sensitive excitation ratiometric C kinase activity reporter (ExRai-CKAR2) that enables the detection of minute changes (equivalent to 0.2% of maximum stimulation) in subcellular PKC activity. Using ExRai-CKAR2 with an enhanced diacylglycerol (DAG) biosensor, we uncover that G-protein-coupled receptor stimulation triggers sustained PKC activity at the endoplasmic reticulum and lysosomes, differentially mediated by Ca2+-sensitive conventional PKC and DAG-sensitive novel PKC, respectively. The high sensitivity of ExRai-CKAR2, targeted to either the cytosol or partitioning defective complexes, further enabled us to detect previously inaccessible endogenous atypical PKC activity in three-dimensional organoids. Taken together, ExRai-CKAR2 is a powerful tool for interrogating PKC regulation in response to physiological stimuli.

Activation of ventral pallidum-projecting neurons in the nucleus accumbens via 5-HT2C receptor stimulation regulates motivation for wheel running in male mice

Rodents have a strong motivation for wheel running; however, the neural mechanisms that regulate their motivation remain unknown. We investigated the possible involvement of serotonin (5-HT) systems in regulating motivation for wheel running in male mice. Systemic administration of a 5-HT1A receptor antagonist (WAY100635) increased the number of wheel rotations, whereas administration of a 5-HT2A or 5-HT2C receptor antagonist (volinanserin or SB242084, respectively) decreased it. In the open field test, neither WAY100635 nor volinanserin affected locomotor activity, whereas SB242084 increased locomotor activity. To identify the brain regions on which these antagonists act, we locally injected these into the motivational circuitry, including the nucleus accumbens (NAc), dorsomedial striatum (DM-Str), and medial prefrontal cortex (mPFC). Injection of SB242084 into the NAc, but not the DM-Str or mPFC, reduced the number of wheel rotations without altering locomotor activity. The local administration of WAY100635 or volinanserin to these brain regions did not affect the number of wheel rotations. Immunohistochemical analyses revealed that wheel running increased the number of c-Fos-positive cells in the NAc medial shell (NAc-MS), which was reduced by systemic SB242084 administration. In vitro slice whole-cell recordings showed that bath application of the 5-HT2C receptor agonist lorcaserin increased the frequency of spontaneous excitatory and inhibitory postsynaptic currents in the ventral tegmental area (VTA)-projecting neurons, whereas it only increased the frequency of spontaneous excitatory postsynaptic currents in ventral pallidum (VP)-projecting neurons in the NAc-MS. These findings suggest that the activation of VP-projecting NAc-MS neurons via 5-HT2C receptor stimulation regulates motivation for wheel running.

TRPC5 controls the adrenaline-mediated counter regulation of hypoglycemia.

Hypoglycemia triggers autonomic and endocrine counter-regulatory responses to restore glucose homeostasis, a response that is impaired in patients with diabetes and its long-term complication hypoglycemia-associated autonomic failure (HAAF). We show that insulin-evoked hypoglycemia is severely aggravated in mice lacking the cation channel proteins TRPC1, TRPC4, TRPC5, and TRPC6, which cannot be explained by alterations in glucagon or glucocorticoid action. By using various TRPC compound knockout mouse lines, we pinpointed the failure in sympathetic counter-regulation to the lack of the TRPC5 channel subtype in adrenal chromaffin cells, which prevents proper adrenaline rise in blood plasma. Using electrophysiological analyses, we delineate a previously unknown signaling pathway in which stimulation of PAC1 or muscarinic receptors activates TRPC5 channels in a phospholipase-C-dependent manner to induce sustained adrenaline secretion as a crucial step in the sympathetic counter response to insulin-induced hypoglycemia. By comparing metabolites in the plasma, we identified reduced taurine levels after hypoglycemia induction as a commonality in TRPC5-deficient mice and HAAF patients.

Safety and efficacy of up to 60h of iv istaroxime in pre-cardiogenic shock patients: Design of the SEISMiC trial.

Cardiogenic shock (CS) is linked to high morbidity and mortality rates, posing a challenge for clinicians. Interventions to improve tissue perfusion and blood pressure are crucial to prevent further deterioration. Unfortunately, current inotropes, which act through adrenergic receptor stimulation, are associated with malignant arrhythmias and poorer outcomes. Due to its unique mechanism of action, istaroxime should improve haemodynamics without adrenergic overactivation. The SEISMiC study is designed to examine the safety and efficacy (haemodynamic effect) of istaroxime administrated in pre-CS patients. The SEISMiC study is a multinational, multicentre, randomized, double-blind, placebo-controlled safety and efficacy study with two parts (A and B). The study enrols patients hospitalized for decompensated heart failure (pre-CS, not related to myocardial ischaemia) with persistent hypotension [systolic blood pressure (SBP) 70-100mmHg for at least 2h] and clinically confirmed congestion, NT-proBNP ≥1400pg/mL, and LVEF≤40%. Subjects must not have taken intravenous (iv) vasopressors, inotropes or digoxin in the past 6h. Eligible patients are randomized to receive IV infusion of istaroxime (different doses and regimens in Parts A and B) or placebo for up to 60h. Central haemodynamics, ECG Holter monitoring, cardiac ultrasound and biomarkers are recorded at predefined time points during the trial. The study's primary efficacy endpoint is the SBP area under the curve from baseline curve from baseline to 6 and 24h in the combined SEISMiC Parts A and B population. Key secondary efficacy endpoints include haemodynamic, laboratory and clinical measures in SEISMiC B alone in the combined SEISMiC A and B studies. The study results will contribute to our understanding of the role of istaroxime in pre-CS patients and potentially provide insight into the drug's haemodynamic effects and safety in this population.

5125 Severe Gestational Thyrotoxicosis Leading to Unwarranted Treatment

Abstract Disclosure: C. Bell: None. L.A. Barbour: None. Introduction: Gestational transient thyrotoxicosis (GTT) is the most common cause of thyrotoxicosis in pregnancy yet is often confused with Graves’. Although usually mild, we present a severe case leading to the unsupported use of anti-thyroid drugs (ATDs), which could have resulted in fetal hypothyroidism if continued. Case: A 30-year-old female G1P0 at 10 wks with a single gestation presented with 4 wks of vomiting, palpitations, and weight loss. She had no history of thyroid disease. She was diaphoretic and ill-appearing and had a non-tender, smooth normal-sized thyroid, a stare without exophthalmos, and a fine tremor. TSH was < 0.01, FT4 5.57 ng/dL (0.89-1.76), and TT3 201 ng/dL (60-181). TPO Ab 51 (< 60). TRAb, TSI Ab, and TgAb were negative. β-hCG level was 334,106 mIU/mL. She was diagnosed with GTT and briefly hospitalized for dehydration but was re-hospitalized 2 wks later with worsening symptoms and 25 lb weight loss. Unexpectedly, her FT4 and TT3 rose to 6.24 ng/dL and 339, respectively. A thyroid ultrasound showed mildly increased vascularity. PTU was started for seronegative Graves’ at 50 mg tid with metoprolol. After 3 days, her FT4 improved to 3.59 ng/dL and TT3 was 176. Further consultation recommended stopping PTU. She was sent home with metoprolol. Her symptoms and FT4 levels improved. FT4 was normal and hCG levels dropped to 54,821 by 18 wks. Discussion: GTT is caused by a transient elevation in T4 due to direct hCG stimulation of the TSH receptor. It is more common with multiple or molar gestations and hyperemesis gravidarum, also mediated by hCG. It typically results in mild thyrotoxicosis, highlighting the uniqueness of this case. Only a couple of case reports exist where GTT presented as severe thyrotoxicosis or thyroid storm and persisted this long. It is critical to distinguish GTT from Graves’ given their different outcomes and treatment. GTT is commonly misdiagnosed as Graves’ as both result in thyrotoxic labs and symptoms and can present in 1st trimester. GTT typically presents at 8-10 wks and lasts until 14-16 wks when hCG levels fall, but Graves’ may also improve by 2nd trimester due to the immune suppression of pregnancy. It is also possible for both to co-exist. hCG levels >100,000 are associated with GTT but due to the variable sialylation of hCG, which changes its affinity to the TSH receptor and half-life, they are unreliable diagnostically. Key clues supporting GTT include no goiter, exophthalmos, or symptoms pre-pregnancy, negative TRAb and TSI, and, notably, a lower T3/T4 ratio compared to Graves’, as seen in this case. To conclude, GTT is often mistaken for Graves’ but inappropriate use of ATDs can result in fetal hypothyroidism and does not improve outcomes. Although the severity of our case is unusual, accurate distinction from Graves’ by endocrinologists is crucial to ensure optimal maternal-fetal outcomes. Presentation: 6/1/2024

7947 Semaglutide Induced Pancreatitis: A Case Report

Abstract Disclosure: T. Altaweel: None. A. Mathew: None. P. Chalasani: None. L. Lawrence: None. S. Hussain: None. N. Aldaoud: None. Introduction/Background: As semaglutide (GLP1 RA) has become a cornerstone in diabetes and weight management, there have been studies indicating pancreatic inflammation with GLP1 RA use. We report a case of acute necrotizing pancreatitis secondary to semaglutide use.Clinical Case: A 52 year old male with a history of hypertension, morbid obesity with BMI of 40 kg/m2, alcohol induced pancreatitis presented to the hospital complaining of epigastric pain. On presentation, he appeared in distress due to pain but was hemodynamically stable. Physical examination revealed a moderately distended abdomen, tender to palpation over the epigastric area without guarding, and negative Murphy’s sign. The patient reported no alcohol consumption, tobacco usage, or recent abdominal injuries. Laboratory workup revealed elevated WBC 14.6 thous/mcL (4.5-10.5) and lipase 1941 U/L (<60). Abdominal ultrasound showed common bile duct 2 mm without gallstones and CT abdomen revealed acute pancreatitis with suspected necrosis in the pancreatic head and the pancreatic tail. Patient was started on aggressive fluid hydration, pain management and admitted to intensive care. Patient reported that he was started on semaglutide three months ago for weight management by his primary care physician. Patient improved symptomatically with pain control and tolerated oral intake. He was discharged home with recommendations not to resume semaglutide. Conclusion: Semaglutide involves direct stimulation of GLP-1 receptors in pancreatic cells, potentially leading to cell overgrowth, increased pancreatic weight, duct occlusion and inflammation. Despite the SUSTAIN-6 trial indicating no increased risk of acute pancreatitis in diabetic patients using semaglutide, atypical presentations of pancreatitis are noted in patients using the medication for weight management. When all identifiable causes of pancreatitis are eliminated, semaglutide-induced pancreatitis should be a primary consideration in the differential diagnosis. Physicians should exercise caution and give careful consideration when prescribing semaglutide for weight management in patients with conditions that increase risk for pancreatitis. Presentation: 6/2/2024

7609 Androgen Receptor Positive DCIS in a Transmasculine Individual on Testosterone Therapy

Abstract Disclosure: J. Kelly: None. B. Cohen: None. Introduction: The rate of breast cancer in transgender men is lower than in cisgender women, perhaps due to lower estrogen levels in the setting of suppression from exogenous testosterone, lack of clear guidelines on screening after top surgery, and increase in mastectomies. However, the impact of testosterone therapy on existing breast cancer is not known. Concerns regarding use of testosterone in patients with breast cancer include the potential for conversion of testosterone to estradiol, as well as direct androgen receptor (AR) stimulation. However, for some patients, hormone therapy is lifesaving and stopping gender affirming hormone therapy (GAHT) will negatively impact patient well-being. This creates a challenging clinical scenario when transgender patients on testosterone are diagnosed with breast cancer.Case Presentation: We present a case of a 29-year-old self-identified transmasculine nonbinary individual (assigned female at birth) who underwent chest reconstruction surgery after several months on daily transdermal testosterone therapy. A 4 cm DCIS ER+/AR+ with possible micro invasion was incidentally noted on pathology. They had no family history of breast cancer. The patient underwent chest MRI which was negative for persistent disease. The treating oncologist did not recommend Tamoxifen. The patient chose to discontinue testosterone therapy due to uncertainty regarding future breast cancer risk. However, due to worsening depression and fatigue, the patient chose to resume GAHT after receiving counseling of possible risk, though likely low, of cancer recurrence. Given that they had undergone bilateral mastectomy which, unlike chest reconstruction surgery where some breast tissue is left for contouring, all breast tissue was removed and given that chest MRI was negative for disease, cancer recurrence was felt to be low. Furthermore, though AR positivity was noted, the clinical implications are unclear and it is not known whether testosterone would stimulate tumor growth or potentially have antagonistic effects on ER signaling. Additionally, any stimulatory effects of AR signaling may be balanced by androgen suppression of gonadotroph production and reduction in estrogen production; this is more clearly associated with stimulatory effects on cancer growth. And finally, the potential risks of therapy must be weighed against the benefits provided to the patient’s well-being and mental health. Ultimately, the patient resumed testosterone therapy and has been doing well.Teaching Point: This case illustrates the uncertainties regarding the management of gender affirming testosterone therapy in patients with DCIS or breast cancer. It also highlights the need for a patient centered approach to decisions regarding changes to GAHT, to appropriately weigh the risks and benefits of continuing therapy. Presentation: 6/2/2024

Dynamic Transition of Regulatory T Cells to Cytotoxic Phenotype Amid Systemic Inflammation in Graves' Ophthalmopathy.

Graves' disease (GD) is an autoimmune condition that can progress to Graves' Ophthalmopathy (GO), leading to irreversible damage to orbital tissues and potential blindness. The pathogenic mechanism is not fully understood. In this study, we conducted single-cell multi-omics analyses on healthy individuals, GD patients without GO, newly diagnosed GO patients, and treated GO patients. Our findings revealed gradual systemic inflammation during GO progression, marked by overactivation of cytotoxic effector T cell subsets, and expansion of specific T cell receptor clones. Importantly, we observed a decline in the immunosuppressive function of activated regulatory T cells (aTreg) accompanied by a cytotoxic phenotypic transition. In vitro experiments revealed that dysfunction and transition of GO-autoreactive Treg were regulated by the yinyang1 (YY1) upon secondary stimulation of thyroid stimulating hormone receptor (TSHR) under inflammatory conditions. Furthermore, adoptive transfer experiments of GO mouse model confirmed infiltration of these cytotoxic Treg into the orbital lesion tissues. Notably, these cells were found to upregulate inflammation and promote pathogenic fibrosis of orbital fibroblasts (OFs). Our results revealed the dynamic changes in immune landscape during GO progression and provided novel insights into the instability and phenotypic transition of Treg, offering potential targets for therapeutic intervention and prevention of autoimmune diseases.

Disruption of mitochondrial electron transport impairs urinary concentration via AMPK-dependent suppression of aquaporin-2.

Urinary concentration is an energy-dependent process that minimizes body water loss by increasing aquaporin-2 (AQP2) expression in collecting duct (CD) principal cells. To investigate the role of mitochondrial (mt) ATP production in renal water clearance, we disrupted mt electron transport in CD cells by targeting ubiquinone (Q) binding protein QPC (UQCRQ), a subunit of mt complex III essential for oxidative phosphorylation. QPC-deficient mice produced less concentrated urine than controls, both at baseline and after type 2 vasopressin receptor stimulation with desmopressin. Impaired urinary concentration in QPC-deficient mice was associated with reduced total AQP2 protein levels in CD tubules, while AQP2 phosphorylation and membrane trafficking remained unaffected. In cultured inner medullary CD cells treated with mt complex III inhibitor antimycin A, the reduction in AQP2 abundance was associated with activation of 5' adenosine monophosphate-activated protein kinase (AMPK) and was reversed by treatment with AMPK inhibitor SBI-0206965. In summary, our studies demonstrated that the physiological regulation of AQP2 abundance in principal CD cells was dependent on mt electron transport. Furthermore, our data suggested that oxidative phosphorylation in CD cells was dispensable for maintaining water homeostasis under baseline conditions, but necessary for maximal stimulation of AQP2 expression and urinary concentration.

Alterations of striatal phosphodiesterase 10 A and their association with recurrence rate in bipolar I disorder

Phosphodiesterase 10 A (PDE10A), a pivotal element of the second messenger signaling downstream of the dopamine receptor stimulation, is conceived to be crucially involved in the mood instability of bipolar I disorder (BD-I) as a primary causal factor or in response to dysregulated dopaminergic tone. We aimed to determine whether striatal PDE10A availability is altered in patients with BD-I and assessed its relationship with the clinical characteristics of BD-I. This case-control study used positron emission tomography (PET) with 2-(2-(3-(4-(2-[18F]fluoroethoxy)phenyl)-7-methyl-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]MNI-659), a radioligand that binds to PDE10A, to examine the alterations of the striatal PDE10A availability in the living brains of individuals with BD-I and their association with the clinical characteristics of BD-I. [18F]MNI-659 PET data were acquired from 25 patients with BD-I and 27 age- and sex-matched healthy controls. Patients with BD-I had significantly lower PDE10A availability than controls in the executive (F = 8.86; P = 0.005) and sensorimotor (F = 6.13; P = 0.017) subregions of the striatum. Lower PDE10A availability in the executive subregion was significantly associated with a higher frequency of mood episodes in patients with BD-I (r = –0.546; P = 0.007). This study provides the first evidence of altered PDE10A availability in patients with BD-I. Lower PDE10A availability in the executive subregion of the striatum is associated with an increased recurrence risk, suggesting that PDE10A may prevent BD-I relapse. Further studies are required to elucidate the role of PDE10A in BD-I pathophysiology and explore its potential as a treatment target.