Sst Expression Research Articles

Comparative distribution of somatostatin and somatostatin receptors in PTU-induced hypothyroidism.

Propylthiouracil (PTU)-induced hypothyroidism is a well-established model for assessing hormonal and morphological changes in thyroid as well as other central and peripheral tissues. Somatostatin (SST) is known to regulate hormonal secretion and synthesis in endocrine tissues; however, nothing is currently known about the distribution of SST and its receptor in hypothyroidism. In the present study, the comparative immunohistochemical distribution of SST and somatostatin receptors (SSTRs) were analyzed in PTU-induced hypothyroid rats. Rats were treated with PTU for 15 days followed by a co-administration of levothyroxine (LVT) for 15 days. After PTU and LVT treatments (day 30), rats were further administered LVT alone for 15 more days (day 45). The subcellular distribution of SST and SSTR subtypes was determined by peroxidase immunohistochemistry in the thyroid gland collected from control and treated rats. SST and SSTR subtypes were found to be moderately expressed in control thyroid tissues. SST and SSTR subtypes like immunoreactivity increased significantly in follicular and parafollicular epithelial cells in the thyroid of PTU-treated rats. The PTU-induced changes in the expression of SST and SSTR subtypes were suppressed by the administration of the LVT. In addition to thyroid tissues, SST and SSTRs expression was also changed in non-follicular tissues including blood vessels, smooth muscle cells, and connective tissue following treatments. The present study revealed a distinct subcellular distribution of SST and SSTR subtypes in the thyroid and provides a new insight for the role of SST and SSTR subtypes in hypothyroidism in addition to its well-established role in negative regulation of hormonal secretion.

Somatostatin enhances visual processing and perception by suppressing excitatory inputs to parvalbumin-positive interneurons in V1.

Somatostatin (SST) is a neuropeptide expressed in a major subtype of GABAergic interneurons in the cortex. Despite abundant expression of SST and its receptors, their modulatory function in cortical processing remains unclear. Here, we found that SST application in the primary visual cortex (V1) improves visual discrimination in freely moving mice and enhances orientation selectivity of V1 neurons. We also found that SST reduced excitatory synaptic transmission to parvalbumin-positive (PV+) fast-spiking interneurons but not to regular-spiking neurons. Last, using serial block-face scanning electron microscopy (SBEM), we found that axons of SST+ neurons in V1 often contact other axons that exhibit excitatory synapses onto the soma and proximal dendrites of the PV+ neuron. Collectively, our results demonstrate that the neuropeptide SST improves visual perception by enhancing visual gain of V1 neurons via a reduction in excitatory synaptic transmission to PV+ inhibitory neurons.

Expression of the Novel Cardiac Biomarkers sST2, GDF-15, suPAR, and H-FABP in HFpEF Patients Compared to ICM, DCM, and Controls.

Background: Heart failure with preserved ejection fraction (HFpEF) remains an ongoing therapeutic and diagnostic challenge to date. In this study we aimed for an analysis of the diagnostic potential of four novel cardiovascular biomarkers, GDF-15, H-FABP, sST2, and suPAR in HFpEF patients compared to controls as well as ICM, and DCM. Methods: In total, we included 252 stable outpatients and controls (77 DCM, 62 ICM, 18 HFpEF, and 95 controls) in the present study. All patients were in a non-decompensated state and on a stable treatment regimen. Serum samples were obtained and analyzed for GDF-15 (inflammation, remodeling), H-FABP (ischemia and subclinical ischemia), sST2 (inflammation, remodeling) and suPAR (inflammation, remodeling) by means of ELISA. Results: A significant elevation of GDF-15 was found for all heart failure entities compared to controls (p < 0.005). Similarly, H-FABP evidenced a significant elevation in all heart failure entities compared to the control group (p < 0.0001). Levels of sST2 were significantly elevated in ICM and DCM patients compared to the control group and HFpEF patients (p < 0.0001). Regarding suPAR, a significant elevation in ICM and DCM patients compared to the control group (p < 0.0001) and HFpEF patients (p < 0.01) was observed. An AUC analysis identified H-FABP (0.792, 95% CI 0.713–0.870) and GDF-15 (0.787, 95% CI 0.696–0.878) as paramount diagnostic biomarkers for HFpEF patients. Conclusion: Based on their differences in secretion patterns, novel cardiovascular biomarkers might represent a promising diagnostic tool for HFpEF in the future.

Altered Expression of GABAergic Markers in the Forebrain of Young and Adult Engrailed-2 Knockout Mice.

Impaired function of GABAergic interneurons, and the subsequent alteration of excitation/inhibition balance, is thought to contribute to autism spectrum disorders (ASD). Altered numbers of GABAergic interneurons and reduced expression of GABA receptors has been detected in the brain of ASD subjects and mouse models of ASD. We previously showed a reduced expression of GABAergic interneuron markers parvalbumin (PV) and somatostatin (SST) in the forebrain of adult mice lacking the Engrailed2 gene (En2-/- mice). Here, we extended this analysis to postnatal day (P) 30 by using in situ hybridization, immunohistochemistry, and quantitative RT-PCR to study the expression of GABAergic interneuron markers in the hippocampus and somatosensory cortex of En2-/- and wild type (WT) mice. In addition, GABA receptor subunit mRNA expression was investigated by quantitative RT-PCR in the same brain regions of P30 and adult En2-/- and WT mice. As observed in adult animals, PV and SST expression was decreased in En2-/- forebrain of P30 mice. The expression of GABA receptor subunits (including the ASD-relevant Gabrb3) was also altered in young and adult En2-/- forebrain. Our results suggest that GABAergic neurotransmission deficits are already evident at P30, confirming that neurodevelopmental defects of GABAergic interneurons occur in the En2 mouse model of ASD.

SPARC: The Emergence Of Cardioprotection From The Vagus Nerve Mediated Brain‐Heart Network

Heart disease remains the number one cause of mortality in the world in spite of significant efforts aimed at treatment. The use of vagal stimulation in the treatment of heart failure has shown mixed successes, suggesting that the treatment has potential, but that the mechanism incompletely understood. Vagal activity confers a robust cardioprotective effect in both humans and animal models, preferentially originating specifically from the dorsal motor nucleus of the vagus (DMV) and deriving a significant benefit from intact gut projections, not just cardiac. In order to examine the DMV response to heart failure, myocardial infarction was induced in male Sprague Dawley rats. DMV neurons were isolated in small pools of single cells using laser capture microdissection 1 week and 3 weeks after infarction and their gene expression assayed. The results show a transcriptional shift towards a neurosecretory phenotype starting at 1 week and increasing in recruitment of neurons to 3 weeks. This was evidenced by the upregulation of ion channels associated with a pacemaker phenotype, an upregulation several neuropeptides. This response to chronic ischemic damage in the heart demonstrates that neurons of the DMV are capable of adaptive responses in the context of peripheral organ damage. The LAD ligation shift appears mediated in part by upregulation of Pax4a, a transcription factor most active during stem cell development of neurosecretory cells during embryonic development. This phenotype is characterized by upregulation of Cacna1d (Cav1.3) and Hcn2 along with increased expression of Cck and Sst. This work suggests that the neurons of the DMV adaptively respond to the dynamics present in the periphery, elucidating the means by which the nature of vagal activity responds to heart failure. The autonomic nervous system plays a significant role in the pathogenesis of cardiovascular disease. Through demonstration of shifting neuronal phenotypes in central neurons in response to peripheral stimuli, we suggest that neuron peptide or neurotransmitter phenotypes are not static in adult rodents. This suggests that even “reflexes” are modifiable dynamic systems. With such plasticity in the transcriptional programming existing in autonomic brain regions there can be new potential therapeutic interventions for cardiovascular disease aimed at leveraging the autonomic nervous system.Support or Funding InformationSupported by the NIH Common Fund SPARC Program award OT2 OD023848 and NIH NHLBI Multiscale Modeling award U01 HL133360.

SST5 expression and USP8 mutation in functioning and silent corticotroph pituitary tumors.

ObjectiveSomatostatin receptor type 5 (SST5) is inconsistently expressed by corticotroph tumors, with higher expression found in corticotropinomas having ubiquitin-specific protease 8 (USP8) mutations. Aims were to study the correlation between characteristics of corticotropinomas and SST5 expression/USP8 mutation status and to describe the response to pasireotide in five patients.DesignRetrospective cohort study.MethodsClinico-biochemical, radiological and pathological data of 62 patients, operated for a functioning or silent corticotropinoma between 2013 and 2017, were collected. SST5 expression was measured by immunohistochemistry (clone UMB-4, Abcam, IRS > 1 being considered positive), and Sanger sequencing was performed on 50 tumors to screen for USP8 mutations.ResultsSST5 expression was positive in 26/62 pituitary tumors. A moderate or strong IRS was found in 15/58 corticotropinomas and in 13/35 functioning corticotropinomas. Among functioning tumors, those expressing SST5 were more frequent in women (22/24 vs 9/15, P = 0.04) and had a lower grade (P = 0.04) compared to others. USP8 mutations were identified in 13/50 pituitary tumors and were more frequent in functioning compared to silent tumors (11/30 vs 2/20, P = 0.05). SST5 expression was more frequent in USP8mut vs USP8wt tumors (10/11 vs 7/19, P = 0.007). Among treated patients, normal urinary free cortisol levels were obtained in three patients (IRS 0, 2 and 6), while a four-fold decrease was observed in one patient (IRS 4).ConclusionSST5 expression appears to be associated with functioning, USP8mut and lower grade corticotropinomas. A correlation between SST5 expression or USP8mut and response to pasireotide remains to be confirmed.

Somatostatin, Olfaction, and Neurodegeneration.

Alzheimer’s and Parkinson’s diseases are the most prevalent neurodegenerative disorders in aging. Hyposmia has been described as an early symptom that can precede cognitive and motor deficits by decades. Certain regions within the olfactory system, such as the anterior olfactory nucleus, display the neuropathological markers tau and amyloid-β or α-synuclein from the earliest stages of disease progression in a preferential manner. Specific neuronal subpopulations, namely those expressing somatostatin (SST), are preferentially affected throughout the olfactory and limbic systems. SST is a neuropeptide present in a subpopulation of GABAergic interneurons throughout the brain and its main function is to inhibit principal neurons and/or other interneurons. It has been reported that SST expression is reduced by 50% in Alzheimer’s disease and that it is related to the formation of Aβ oligomers. The mechanisms underlying the preferential vulnerability of SST-expressing neurons in Alzheimer’s disease (and, to a minor extent, in Parkinson’s disease) are not known but analysis of the available data could shed light on their etiology. This short review aims to update the knowledge of functional features of somatostatin within the olfactory system and its role in olfactory deficits during neurodegeneration.

Knocking Out SST Gene of BGC823 Gastric Cancer Cell by CRISPR/Cas9 Enhances Migration, Invasion and Expression of SEMA5A and KLF2.

BackgroundThe impact and potential molecular mechanisms of SST in the occurrence and development of GC have not been determined.Materials and MethodsTwo pairs of sgRNA and reporter were designed according to targeting sequence of SST gene for double-nicking. Plasmids were transfected into 293T for selecting sgRNA with higher cutting efficiency. The subline which has knocked-out SST gene were selected by FACS and verified by sequencing and expression level. Moreover, the migration and invasion ability was evaluated by wound healing and transwell after knocking out SST. Besides, the protein expression of SEMA5A and KLF2 were observed by Western blotting and LSCM. Last, we detected the expression levels of SST, SEMA5A, and KLF2 in GC tissues by Western blotting.ResultsThe results revealed that the new subline 1E9, which had knocked out SST gene, was established by CRISPR/Cas9. In addition, the knockout of SST in GC cells markedly increased migration and invasion ability. The results also demonstrated that the knockout of SST increased the expression of SEMA5A and KLF2. The expression level of SST was decreased in GC tissues, and its decrease was associated with overexpression of SEMA5A and KLF2.ConclusionSST plays an inhibitory role in the migration and invasion of GC cell BGC823. The protein expression levels of SEMA5A and KLF2 were enhanced in GC cells and tissues lacking SST expression.

PRDX6 Promotes the Differentiation of Human Mesenchymal Stem (Stromal) Cells to Insulin-Producing Cells.

Mesenchymal stem cells (MSCs) can be differentiated in vitro to form insulin-producing cells (IPCs). However, the proportion of induced cells is modest. Extracts from injured pancreata of rodents promoted this differentiation, and three upregulated proteins were identified in these extracts. The aim of this study was to evaluate the potential benefits of adding these proteins to the differentiation medium alone or in combination. Our results indicate that the proportion of IPCs among the protein(s)-supplemented samples was significantly higher than that in the samples with no added proteins. The yield from samples supplemented with PRDX6 alone was 4-fold higher than that from samples without added protein. These findings were also supported by the results of fluorophotometry. Gene expression profiles revealed higher levels among protein-supplemented samples. Significantly higher levels of GGT, SST, Glut-2, and MafB expression were noted among PRDX6-treated samples. There was a stepwise increase in the release of insulin and c-peptide, as a function of increasing glucose concentrations, indicating that the differentiated cells were glucose sensitive and insulin responsive. PRDX6 exerts its beneficial effects as a result of its biological antioxidant properties. Considering its ease of use as a single protein, PRDX6 is now routinely used in our differentiation protocols.

Reduced cortical somatostatin gene expression in a rat model of maternal immune activation

Alterations in GABAergic interneurons and glutamic acid decarboxylase (GAD) are observed in the brains of people with schizophrenia. Studies also show increased density of interstitial white matter neurons (IWMN), including those containing GAD and somatostatin (SST) in the brain in schizophrenia. Maternal immune activation can be modelled in rodents to investigate the relationship between prenatal exposure to infections and increased risk of developing schizophrenia. We reported that maternal immune activation induced an increase in density of somatostatin-positive IWMN in the adult rat offspring. Here we hypothesised that maternal immune activation induced in pregnant rats by polyinosinic:polycytidylic acid would alter SST and GAD gene expression as well as increase the density of GAD-positive IWMNs in the adult offspring. SST gene expression was significantly reduced in the cingulate cortex of adult offspring exposed to late gestation maternal immune activation. There was no change in cortical GAD gene expression nor GAD-positive IWMN density in adults rats exposed to maternal immune activation at either early or late gestation. This suggests that our model of maternal immune activation induced by prenatal exposure of rats to polyinosinic:polycytidylic acid during late gestation is able to recapitulate changes in SST but not other GABAergic neuropathologies observed in schizophrenia.

Somatostatin and chemokine CXCR4 receptor expression in pancreatic adenocarcinoma relative to pancreatic neuroendocrine tumours.

Pancreatic adenocarcinoma (PAC) represents one of the most fatal types of cancer with an exceptionally poor prognosis, underscoring the need for improved diagnostic and treatment approaches. An over-expression of somatostatin receptors (SST) as well as of the chemokine receptor CXCR4 has been shown for many tumour entities. Respective expression data for PAC, however, are scarce and contradictory. Overall, 137 tumour samples from 70 patients, 26 of whom were diagnosed with PAC and 44 with pancreatic neuroendocrine tumour (PanNET), were compared in terms of SST and CXCR4 expression by immunohistochemical analysis using well-characterized rabbit monoclonal antibodies. Only SST1 and CXCR4 expression was detected in PAC tumours, with SST1 present in 42.3% and CXCR4 in 7.7% of cases. However, the overall staining intensity was very weak. In contrast to the tumour cells, in many PAC cases, tumour capillaries exhibited strong SST3, SST5, or CXCR4 expression. In PanNETs, SST2 was the most-prominently expressed receptor, observed in 75.0% of the tumours at medium-strong intensity. SST5, SST1, and CXCR4 expression was detected in 20.5%, 15.9%, and 11.4% of PanNET cases, respectively, but the staining intensity was only weak. SST2 positivity in PanNET, but not in PAC, was associated with favourable patient outcomes. SST or CXCR4 expression in PAC is clearly of no therapeutic relevance. However, indirect targeting of these tumours via SST3, SST5, or CXCR4 on tumour microvessels may represent a promising additional therapeutic strategy.

Targeted Derivation of Organotypic Glucose- and GLP-1-Responsive β Cells Prior to Transplantation into Diabetic Recipients.

SummaryGeneration of functional β cells from pluripotent sources would accelerate diagnostic and therapeutic applications for diabetes research and therapy. However, it has been challenging to generate competent β cells with dynamic insulin-secretory capacity to glucose and incretin stimulations. We introduced transcription factors, critical for β-cell development and function, in differentiating human induced pluripotent stem cells (PSCs) and assessed the impact on the functionality of derived β-cell (psBC) progeny. A perifusion system revealed stepwise transduction of the PDX1, NEUROG3, and MAFA triad (PNM) enabled in vitro generation of psBCs with glucose and GLP-1 responsiveness within 3 weeks. PNM transduction upregulated genes associated with glucose sensing, insulin secretion, and β-cell maturation. In recipient diabetic mice, PNM-transduced psBCs showed glucose-responsive insulin secretion as early as 1 week post transplantation. Thus, enhanced pre-emptive β-cell specification of PSCs by PNM drives generation of glucose- and incretin-responsive psBCs in vitro, offering a competent tissue-primed biotherapy.

Tissue Cytokine IL-33 Modulates the Cytotoxic CD8 T Lymphocyte Activity During Nutrient Deprivation by Regulation of Lineage-Specific Differentiation Programs.

IL-1 family member IL-33 exerts a variety of immune activating and regulating properties and has recently been proposed as a prognostic biomarker for cancer diseases, although its precise role in tumor immunity is unclear. Here we analyzed in vitro conditions influencing the function of IL-33 as an alarmin and a co-factor for the activity of cytotoxic CD8+ T cells in order to explain the widely discussed promiscuous behavior of IL-33 in vivo. Circulating IL-33 detected in the serum of healthy human volunteers was biologically inactive. Additionally, bioactivity of exogenous recombinant IL-33 was significantly reduced in plasma, suggesting local effects of IL-33, and inactivation in blood. Limited availability of nutrients in tissue causes necrosis and thus favors release of IL-33, which—as described before—leads to a locally high expression of the cytokine. The harsh conditions however influence T cell fitness and their responsiveness to stimuli. Nutrient deprivation and pharmacological inhibition of mTOR mediated a distinctive phenotype characterized by expression of IL-33 receptor ST2L on isolated CD8+ T cells, downregulation of CD8, a transitional CD45RAlowROlow phenotype and high expression of secondary lymphoid organ chemokine receptor CCR7. Under nutrient deprivation, IL-33 inhibited an IL-12 induced increase in granzyme B protein expression and increased expression of GATA3 and FOXP3 mRNA. IL-33 enhanced the TCR-dependent activation of CD8+ T cells and co-stimulated the IL-12/TCR-dependent expression of IFNγ. Respectively, GATA3 and FOXP3 mRNA were not regulated during TCR-dependent activation. TCR-dependent stimulation of PBMC, but not LPS, initiated mRNA expression of soluble IL-33 decoy receptor sST2, a control mechanism limiting IL-33 bioactivity to avoid uncontrolled inflammation. Our findings contribute to the understanding of the compartment-specific activity of IL-33. Furthermore, we newly describe conditions, which promote an IL-33-dependent induction of pro- or anti-inflammatory activity in CD8+ T cells during nutrient deprivation.

Elevated expression of serum soluble ST2 in clinical relapse after stopping long-term Nucleos(t)ide analogue therapy for chronic hepatitis B

BackgroundThe virological or clinical relapse is common in chronic hepatitis B (CHB) patients after stopping long-term nucleos(t)ide analogue (NA) therapy. Soluble growth stimulation expressed gene 2 (sST2), one of the Toll-like/interleukin-1 receptor members, is involved in a variety of inflammatory processes and immune responses. However, the expression and function of serum sST2 in CHB patients after stopping NA treatment remains unknown.MethodsA total of 91 non-cirrhotic Asian patients with CHB who discontinued NA therapy according to international guidelines were prospectively followed up to 240 weeks. All patients were divided into clinical relapse group and non-clinical relapse (including sustained virological response and only virological relapse) group according HBV DNA and ALT levels. The serum levels of sST2 of all participants were determined by ELISA and compared between each two groups.ResultsClinical relapse occurred in 26 patients and virological relapse occurred in 57 patients. We found that there was a positive correlation between sST2 expression and HBsAg, ALT, HBV DNA, and anti-HBc levels in CHB patients after discontinuation of NA treatment. Levels of serum sST2 in clinical relapse patients showed a rising trend and most patients showed peak sST2 levels at the point of clinical relapse. Moreover, the sST2 levels of clinical relapse group at week 12, week 24 and week 48 were relatively higher than non-clinical relapse group. However, the level of sST2 at the end of treatment was not an effective biological marker for the early prediction of clinical relapse after discontinuation of long-term NA therapy.ConclusionsIn conclusion, we found that an increase in sST2 in clinical relapse patients might be associated with an inflammation-related immune response after discontinuation of NA treatment.Trial registrationThe trial was retrospectively registered at Chinese Clinical Trial Registry: ChiCTR-OOC-17013970. Registration date: December 15, 2017.

Central somatostatin signaling and regulation of food intake.

The discovery of somatostatin (SST) in the hypothalamus implicated the peptide in the inhibition of growth hormone release. However, as observed for numerous neuropeptides, SST was neither restricted to this one brain site nor to this one function. Subsequent studies established a widespread but specific expression of SST in the central nervous system of rodents and humans along with the expression patterns of five receptors (sst1-5 ). Among biological actions, the activation of central SST signaling induced a robust stimulation of food and water intake, which is mediated by the sst2 as assessed using selective sst agonists. The past years have witnessed the identification of brain SST circuitries involved using chemogenetic and optogenetic approaches and further established a physiological orexigenic role of brain SST signaling. The present review will discuss these recent findings.

MON-459 ONO-5788, a Novel Oral Small Molecule Somatostatin Receptor Type-2 (SST2) Agonist, Attenuates GH Hypersecretion in Human GH-Secreting, Pituitary Adenoma-Derived Cells

Somatostatin receptor ligands (SRL) and GHR antagonists are used for persistent or recurrent acromegaly following noncurative surgery and as primary therapy for patients unsuitable for surgery. We tested in vitro action of a novel oral SRL compound ONO-5788 and its active metabolite (ONO-ST1-641) which signals via SST2. With IRB approval and informed consent, 12 human somatotroph adenomas, obtained at transsphenoidal resection were cultured. In the 1st cohort, 8 somatotroph adenomas were treated with ONO-ST1-641 (0, 100, 1000 nM) and octreotide (OCT, 100 nM) for 24 h, and media collected at 2, 6, and 24 h respectively to assess GH and PRL concentrations by ELISA. Cells harvested at 24 h were used to measure mRNA levels of SST2 and SST5, hormone genes and cell cycle genes CDKN1A, CDKN1B by qPCR. Three of 8 tumors (38%) responded to ONO-ST1-641 and OCT as early as 2 and 6 h. GH was significantly reduced by OCT (18% to 58% reduction, P<0.05) and similarly attenuated by ONO-ST1-641 (28 to 59% reduction, P<0.05). GH secretion in 6 of 8 tumors (75%) was decreased at 24 h, showing reduction by OCT and ONO-ST1-641 by up to 48% (P<0.01) and 50% (P<0.01), respectively. PRL levels were undetectable, very low or unchanged by treatments. Related compound ONO-5788 showed similar responses. SST2 and SST5 expression was unchanged during treatments in the 6/8 responders as assessed by TaqMan qPCR using HPRT1 and GAPDH as controls. Neither was GH, PRL, CGA, CDKN1A and CDKN1B mRNA expression altered by ONO-ST1-641 or OCT for 24 h, as assessed by SYBR qPCR using RPL13A, GAPDH and 18S as controls, suggesting that ONO-ST1-641 did not affect these hormone genes and cell cycle regulator mRNA levels. In the 2nd cohort, pretreatment baseline SST2 and SST5 expression were assessed in 4 cultured tumors treated with ONO-ST1-641 (0, 100, 1000 nM) or OCT (100 nM) for 6 h. Untreated tumor cell mRNA was extracted at baseline to assess SST2 and SST5 expression and GH and PRL measured at 6 h. Two of 4 tumors were unresponsive to both ONO-ST1-641 and OCT, 1 showed mild GH reduction by ONO-ST1-641 (15%) but not by OCT. Notably, 1 specimen expressing highly abundant baseline SST2 exhibited marked GH suppression by ONO-ST1-641 and OCT at 6 h (63 and 62%, respectively, P<0.01). High baseline SST2 expression further validated by Western blot and confocal immunofluorescence, imply that SST receptor expression associates with ONO-ST1-641 responsiveness. Available SRLs and GHR antagonists are parenteral, requiring lifelong injection, with variable and suboptimal efficacy, necessitating development of novel oral small molecule drugs for acromegaly. Our study provides preclinical evidence that ONO-5788 and its active metabolite attenuate GH hypersecretion in primary somatotroph adenoma cells cultures, suggesting the potential application of ONO-5788 for acromegaly patients.

Yin-Yang 1 transcription factor modulates ST2 expression during adverse cardiac remodeling post-myocardial infarction

BackgroundThe cardioprotective effects of metformin remain poorly defined. Interleukin (IL)-33/ST2L signaling is a novel cardioprotective pathway, which is antagonized by the soluble isoform sST2. No data exist about the regulation of ST2 expression. This study aimed to evaluate the pathophysiological implication of Yin-Yang 1 (Yy1) transcription factor in cardiac remodeling and the expression of the soluble ST2 isoform. Methods and resultsMyocardial infarction (MI) was induced in Wistar rats randomly receiving metformin or saline solution by permanent ligation of the left anterior coronary artery. In addition, a model of cardiomyocyte “biochemical strain” was used. Metformin administration improved post-MI cardiac remodeling, an effect that was associated with increased IL-33 and reduced sST2 levels in the myocardium. The anti-remodeling effects of metformin were also associated with a decrease in the transcription factor Yy1 intranuclear level and lower levels of phosphorylated HDAC4 within the cytoplasmic space. These effects were also observed in a cardiomyocyte biochemical strain model, where Yy1 silencing or HDAC4 inhibition blocked sST2 production in cardiomyocytes. Metformin blocked the HDAC4 phosphorylation induced by MI, preventing its export from the nucleus to the cytosol. The presence of dephosphorylated HDAC4 in the nucleus acted as a co-repressor of Yy1, repressing sST2 expression. ConclusionThe transcription factor Yy1 regulates sST2 expression, and repression of Yy1 by metformin results in lower levels of sST2 that are associated with favorable myocardial remodeling. The manipulation of YY1 or its co-repressor HDAC4 emerge as new targets to modulate ST2/IL33 signaling and prevent adverse cardiac remodeling.

Clinical significance of filamin A in patients with acromegaly and its association with somatostatin and dopamine receptor profiles

Filamin-A (FLNA) plays a crucial role in somatostatin receptor (sst) subtype-2 signaling in somatotropinomas. Our objective was to investigate the in vivo association between FLNA and sst2 expression, sst5 expression, dopamine receptor subtype-2 (D2) expression, somatostatin receptor ligand (SRL) responsiveness and tumor invasiveness in somatotropinomas. Quantitative real-time PCR was used to evaluate the absolute mRNA copy numbers of FLNA/sst2/sst5/D2 in 96 somatotropinomas. FLNA, sst2 and sst5 protein expression levels were also evaluated using immunohistochemistry. The Knosp-Steiner criteria were used to evaluate tumor invasiveness. Median FLNA, sst2, sst5 and D2 copy numbers were 4,244, 731, 156 and 3,989, respectively. Thirty-one of the 35 available tumors (89%) were immune positive for FLNA in the cytoplasm and membrane but not in the nucleus. FLNA and sst5 expression were positively correlated at the mRNA and protein levels (p < 0.001 and p = 0.033, respectively). FLNA was positively correlated with sst2 mRNA in patients who were responsive to SRL (p = 0.014, R = 0.659). No association was found between FLNA and tumor invasiveness. Our findings show that in somatotropinomas FLNA expression positively correlated with in vivo sst5 and D2 expression. Notably, FLNA was only correlated with sst2 in patients who were controlled with SRL. FLNA was not associated with tumor invasiveness.

Regional and temporal regulation and role of somatostatin receptor subtypes in the mouse brain following systemic kainate-induced acute seizures

Somatostatin reduces neuronal excitability via somatostatin receptors (Sst1-Sst5) and inhibits seizure activity. However, the expression status of the Sst subtypes in epileptic mice and their role in the antiepileptic effects of somatostatin remain unclear. Here, we show that the Sst subtypes are regulated differently by epileptic neuronal activity in mice. Systemic kainate injection rapidly and transiently elevated the Sst2 and Sst3 mRNA and reduced Sst1 and Sst4 mRNA in the hippocampus; however, among all the subtypes, only Sst2 mRNA was increased in the excitatory neurons of the basolateral amygdala, accompanied by a decrease in the level of Sst2 protein. Following kainate administration, recovery from seizure was delayed by reduced expression of Sst2 in the basolateral amygdala, but not in the dentate gyrus of the hippocampus; higher expression levels of Bdnf, a neuronal activity marker, were observed in both conditions. These results suggest that Sst2 contributes to seizure termination by feedback inhibition in the amygdala. This could be a potential therapeutic target for acute seizures.

Reduced expression of somatostatin in GABAergic interneurons derived from induced pluripotent stem cells of patients with parkin mutations

Parkinson’s disease (PD) is associated with both motor and non-motor symptoms, including constipation, sensory neuropathy, depression, dementia and sleep disorder. Somatostatin (SST) is considered to be a modulator of GABAergic inhibitory transmission, and its levels are reduced in cerebrospinal fluid of PD patients. In the present study, we evaluated the changes in the expression of SST in GABAergic neurons derived from induced pluripotent stem cells (iPSCs) of PD patients. Neural cells were co-treated with the Wnt antagonist IWP-2 and Shh during neurosphere formation to induce GABA-positive forebrain interneurons. Quantitative analyses showed no significant differences, but slight decreases, in the potency of differentiation into GABAergic neurons derived from iPSCs between healthy control and patients with PARK2 mutations, who have been classified as a type of early-onset familial PD due to mutations in the parkin gene. Under this condition, the mRNA level of SST in GABAergic interneurons derived from iPSCs of PARK2-specific PD patients significantly decreased as neural maturation progressed. We also found that SST-positive GABAergic neurons were clearly reduced in GABAergic neurons derived from iPSCs of patients with PARK2 mutations. These findings suggest that the reduction in the expression level of SST in GABAergic interneurons of PD may, at least partly, lead to complex PD-induced symptoms.