Heterogeneity of T cells in periapical lesions and in vitro validation of the proangiogenic effect of GZMA on HUVECs.

AIM: T cells are key immunomodulatory cells in periapical lesions. This study aimed to explore the roles of T cells in chronic apical periodontitis (CAP) using single-cell RNA sequencing and to further investigate Granzyme A (GZMA) in angiogenesis regulation. METHODOLOGY: A total of five CAP samples were collected for single-cell RNA sequencing. We performed subcluster and lineage-tracing analyses for T cells. According to differential gene expression, distinct biological functions enriched in T cells of CAP were presented by gene set enrichment analysis (GSEA) and compared with healthy gingiva (data obtained from the GEO database). CellChat was used to explore potential ligand-receptor interactions between T cells and endothelial cells in CAP. The coculture of primary human umbilical vein endothelial cells (HUVECs) and Jurkat T cells, as well as the addition of GZMA recombinant protein, was used to validate the predicted pair of GZMA and coagulation factor II thrombin receptor (F2R) by RT-PCR, angiogenesis and migration assays. RESULTS: A transcriptomic atlas of 44 746 individual cells was constructed from the periapical lesions of five patients with CAP by single-cell RNA-seq, and eight cell types were identified. We identified nine subsets of T cells and deciphered the cellular heterogeneity of T cells in CAP at the functional level by subclustering and GSEA. Lineage tracing revealed a distinct lineage of T cells in CAP and predicted the transition of the T cellular state upon CAP. GSEA revealed multiple biological processes and relevant angiogenesis genes upregulated in CAP T cells. GZMA-F2R pairs were predicted by cell-cell interactions in CAP. High expression of GZMA and F2R was observed in the coculture of HUVECs and Jurkat T cells, and the proangiogenic capacity of the GZMA recombinant protein was emphasized by in vitro experiments. CONCLUSIONS: Our study provides novel insights into the heterogeneity of T cells in periapical lesions and reveals the potential role of GZMA in T cells in regulating angiogenesis in HUVECs.

Effect of different endodontic access preparations on the biomechanical behavior of lithium disilicate and resin nanoceramic onlay restorations: An in vitro and 3D finite element analysis study.

STATEMENT OF PROBLEM: The effect of different sizes of endodontic access preparations on the performance of lithium disilicate glass-ceramic and resin nanoceramic onlay restorations is unclear. PURPOSE: The purpose of this in vitro and 3D finite element analysis study was to assess the effect of a conservative endodontic access cavity and a traditional endodontic access cavity on the fracture resistance and stress distribution of lithium disilicate glass-ceramic and resin nanoceramic onlays. MATERIAL AND METHODS: Sixty caries-free human mandibular molars were anatomically prepared for onlays and divided into 6 groups. After restoration with a lithium disilicate glass-ceramic (N=30) or resin nanoceramic (N=30), each material was further divided into traditional or conservative endodontic access cavity or intact tooth groups. After endodontic therapy and thermocycling, all specimens were submitted to a cycle fatigue test and then loaded until fracture. Failure type and location after debonding or fracture were classified and recorded. Furthermore, stress distribution in the 6 models was analyzed by using a finite element analysis software program. The data were compared by using a 2-way ANOVA test and the Tukey post hoc test (α=.05). The Weibull modulus and Weibull failure probabilities were also estimated for each group. RESULTS: The lithium disilicate glass-ceramic onlays had lower fracture resistance values than the resin nanoceramic onlays in both the traditional and conservative endodontic access cavity groups (P<.05). The fracture resistance of the 2 materials for onlays with endodontic access was significantly lower than that for the intact restorations (P<.05). No significant difference was found between the fracture resistance of Lava Ultimate restorations with traditional endodontic access and conservative endodontic access, while the fracture resistance of EMAX restorations with traditional endodontic access was significantly lower than that of restorations with conservative endodontic access (P<.05). A higher percentage of irreparable fractures was found in the 3 resin nanoceramic restoration groups. The von Mises stresses were higher in the lithium disilicate glass-ceramic restorations than in the resin nanoceramic restorations with the same access cavities. The von Mises stresses in the tooth structure were higher with the resin nanoceramic restorations than with the lithium disilicate glass-ceramic restorations with the same access cavities. CONCLUSIONS: An endodontic access cavity had more influence on the lithium disilicate glass-ceramic onlays than on the resin nanoceramic onlays, and a traditional endodontic access cavity significantly decreased the fracture resistance of lithium disilicate glass-ceramic onlays.

An in vitro study on the effects of serum proteins on Enterococcus faecalis adhesion to three types of root sealers and gutta-percha.

BACKGROUND: The extrusion of overfilled materials that extend beyond the apical foramina into the periradicular tissue may serve as a reservoir for bacterial adhesion and further affect recovery from periapical diseases. The aim of this study was to evaluate the effects of serum proteins on Enterococcus faecalis adhesion and survival on the surface of a calcium hydroxide-based root canal sealer (Apexit Plus), an epoxy resin sealer (AH-Plus) and a bioceramic sealer (iRoot SP). METHODS: Apexit Plus, AH-Plus and iRoot SP were evenly coated on gutta-percha, using gutta-percha alone as the control. After root canal sealer setting, the number of E. faecalis adhering to the root canal sealers and gutta-percha was counted in fetal bovine serum (FBS) or tryptic soy broth supplemented with 1% glucose (TSBG) by viable cell plate counts. The morphology of 7-day-old E. faecalis biofilms in FSB and TSBG was observed by scanning electron microscopy (SEM). Furthermore, E. faecalis biofilms on the three root canal sealers were labeled with a LIVE/DEAD BacLight™ Bacterial Viability Kit, and the ratios of viable to dead cells were analyzed using laser scanning microscopy operative software (Zen software). RESULTS: In the assays, after 1 and 7 days, the number of E. faecalis adhering to the root canal sealers or gutta-percha in FBS were significantly lower than those in TSBG (P < 0.05). In FBS, E. faecalis adhesion to iRoot SP and gutta-percha was reduced to a greater extent than that adhered to Apexit Plus and AH-Plus. Few E. faecalis accumulated on iRoot SP in FBS, whereas many bacteria assembled on iRoot SP and formed biofilms in TSBG. The ratio of viable cells in the E. faecalis biofilm on iRoot SP was the lowest. CONCLUSIONS: Calcium hydroxide-based root canal sealers, epoxy resin sealers and bioceramic sealers may provide a substrate for E. faecalis adhesion, and the bioceramic sealer in this study showed the least E. faecalis adhesion in the presence of serum proteins compared to the other two sealers.

Sodium fluoride induces apoptosis through reactive oxygen species-mediated endoplasmic reticulum stress pathway in Sertoli cells.

Excessive fluoride exposure is known to contribute to reproductive system dysfunction, ultimately leading to pathological damage and apoptosis in cells. Although both oxidative and endoplasmic reticulum (ER) stresses have been implicated in fluorosis, the signaling pathways and their roles in sodium fluoride (NaF)-induced apoptosis of Sertoli cells have been sparsely described. In this study, oxidative damage, ER stress, and apoptosis were analyzed after Sertoli cells were treated with varying doses of NaF for 24hr. Moreover, the antioxidant N-acetylcysteine (NAC) and pro-apoptotic transcription factor CHOP knockdown were used to clarify the precise interplay between reactive oxygen species (ROS), ER stress and their roles in NaF-induced apoptosis in Sertoli cells. The present study indicated that NaF significantly decreased cell viability and induced apoptosis in Sertoli cells. In addition, NaF exposure facilitated the accumulation of ROS and increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) in Sertoli cells. Treatment with NAC caused remarkable recovery from these NaF-induced responses. Meanwhile, excessive NaF triggered ER stress as evidenced by up-regulated glucose-regulated protein 78 kDa (GRP78), PKR-like ER kinase (PERK), phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α) and CCAAT/enhancer-binding protein-homologous protein (CHOP), without affecting total eukaryotic translation initiation factor 2α (eIF2α). NAC effectively blocked the activation of ER stress, suggesting that NaF-induced ROS is an early event that triggers ER stress. Taken together, the results demonstrate that the ROS-mediated ER stress pathway is the crucial mechanistic event involved in NaF-induced apoptosis of Sertoli cells.

Caspase-1 Inhibition Reduces Occurrence of PANoptosis in Macrophages Infected by E. faecalis OG1RF.

To investigate the effect of caspase-1 inhibition on PANoptosis in macrophages infected with Enterococcus faecalis OG1RF. RAW264.7 cells with and without pretreatment by caspase-1 inhibitor were infected with E. faecalis OG1RF at multiplicities of infection (MOIs). A live cell imaging analysis system and Western blot were applied to evaluate the dynamic curve of cell death and the expression of executor proteins of PANoptosis. The mRNA expression of IL-1ß and IL-18 was quantified by RT-qPCR. Morphological changes were observed under scanning electron microscopy. We found that PI-positive cells emerged earlier and peaked at a faster rate in E. faecalis-infected macrophages (Ef-MPs) at higher MOIs. The expression of the N-terminal domain of the effector protein gasdermin D (GSDMD-N), cleaved caspase-3 and pMLKL were significantly upregulated at MOIs of 10:1 at 6 h and at MOI of 1:1 at 12 h postinfection. In Ef-MPs pretreated with caspase-1 inhibitor, the number of PI-positive cells was significantly reduced, and the expression of IL-1ß and IL-18 genes and cleaved caspase-1/-3 and GSDMD-N proteins was significantly downregulated (p < 0.05), while pMLKL was still markedly increased (p < 0.05). Ef-MPs remained relatively intact with caspase-1 inhibitor. In conclusion, E. faecalis induced cell death in macrophages in an MOI-dependent manner. Caspase-1 inhibitor simultaneously inhibited pyroptosis and apoptosis in Ef-MPs, but necroptosis still occurred.

Hypoxia Alters the Proteome Profile and Enhances the Angiogenic Potential of Dental Pulp Stem Cell-Derived Exosomes.

Dental pulp stem cells (DPSCs) and their exosomes (Exos) are effective treatments for regenerative medicine. Hypoxia was confirmed to improve the angiogenic potential of stem cells. However, the angiogenic effect and mechanism of hypoxia-preconditioned DPSC-Exos are poorly understood. We isolated exosomes from DPSCs under normoxia (Nor-Exos) and hypoxia (Hypo-Exos) and added them to human umbilical vein endothelial cells (HUVECs). HUVEC proliferation, migration and angiogenic capacity were assessed by CCK-8, transwell, tube formation assays, qRT-PCR and Western blot. iTRAQ-based proteomics and bioinformatic analysis were performed to investigate proteome profile differences between Nor-Exos and Hypo-Exos. Western blot, immunofluorescence and immunohistochemistry were used to detect the expression of lysyl oxidase-like 2 (LOXL2) in vitro and in vivo. Finally, we silenced LOXL2 in HUVECs and rescued tube formation with Hypo-Exos. Hypo-Exos enhanced HUVEC proliferation, migration and tube formation in vitro superior to Nor-Exos. The proteomics analysis identified 79 proteins with significantly different expression in Hypo-Exos, among which LOXL2 was verified as being upregulated in hypoxia-preconditioned DPSCs, Hypo-Exos, and inflamed dental pulp. Hypo-Exos partially rescued the inhibitory influence of LOXL2 silence on HUVEC tube formation. In conclusion, hypoxia enhanced the angiogenic potential of DPSCs-Exos and partially altered their proteome profile. LOXL2 is likely involved in Hypo-Exos mediated angiogenesis.

Cyclic fatigue resistance for six types of nickel titanium instruments at artificial canals with different angles and radii of curvature.

This study evaluated the cyclic fatigue resistance for six types of 25# NiTi instruments. A traditional manufacturing instrument, an M wire instrument, a gold treatment instrument, a controlled memory (CM) wire instrument, a CM wire instrument with electrical discharge machining (EDM), and an R-phase heat treatment instrument, were operated in the different curved artificial canals. The fracture time (FT) and number of cycles to fracture (NCF) of the NiTi instruments were higher at 45° angles and double-curvature canals than at 60° angles. Except for the instruments with gold technology and EDM technology, others showed the longest FT and the highest NCF at an 8 mm radius of curvature. Morphological characteristics of cyclic fatigue were exhibited on the cross-section and lateral view of fracture fragments. The use of M-wire, R-phase wire, CM-wire, gold technology, EDM technology, and reciprocating movement were beneficial to enhance the cyclic fatigue resistance of NiTi files.

Single-Cell Sequencing Unveils the Heterogeneity of Nonimmune Cells in Chronic Apical Periodontitis.

Chronic apical periodontitis (CAP) is a unique dynamic interaction between microbial invasions and host defense mechanisms, resulting in infiltration of immune cells, bone absorption, and periapical granuloma formation. To help to understand periapical tissue pathophysiology, we constituted a single-cell atlas for 26,737 high-quality cells from inflammatory periapical tissue and uncovered the complex cellular landscape. The eight types of cells, including nonimmune cells and immune cells, were identified in the periapical tissue of CAP. Considering the key roles of nonimmune cells in CAP, we emphasized osteo-like cells, basal/stromal cells, endothelial cells, and epithelial cells, and discovered their diversity and heterogeneity. The temporal profiling of genomic alterations from common CAP to typical periapical granuloma provided predictions for transcription factors and biological processes. Our study presented potential clues that the shift of inflammatory cytokines, chemokines, proteases, and growth factors initiated polymorphic cell differentiation, lymphangiogenesis, and angiogenesis during CAP.

Real-Time Induction of Macrophage Apoptosis, Pyroptosis, and Necroptosis by Enterococcus faecalis OG1RF and Two Root Canal Isolated Strains.

To investigate the effects of two Enterococcus faecalis root canal isolated strains (CA1 and CA2) and of the OG1RF strain on apoptosis, pyroptosis, and necroptosis in macrophages. The virulence factors of E. faecalis CA1 and CA2 pathogenic strains were annotated in the Virulence Factors Database (VFDB). E. faecalis CA1, CA2, and OG1RF strains were used to infect RAW264.7 macrophages (MOI, 100:1). We assessed the viability of intracellular and extracellular bacteria and of macrophages at 2, 6, and 12 h post-infection. We used a live cell imaging analysis system to obtain a dynamic curve of cell death after infection by each of the three E. faecalis strains. At 6 and 12 h post-infection, we quantified the mRNA expression levels of PANoptosis-related genes and proteins by RT-qPCR and western blot, respectively. We identified ultrastructural changes in RAW264.7 cells infected with E. faecalis OG1RF using transmission electron microscopy. We found 145 and 160 virulence factors in the CA1 and CA2 strains, respectively. The extracellular CA1 strains grew faster than the CA2 and OG1RF strains, and the amount of intracellular viable bacteria in the OG1RF group was highest at 6 and 12 h post-infection. The macrophages in the CA1 infection group were the first to reach the maximum PI-positivity in the cell death time point curve. We found the expressions of mRNA expression of caspase-1, GSDMD, caspase-3, MLKL, RIPK3, NLRP3, IL-1ß and IL-18 and of proteins cleaved caspase-1, GSDMD, cleaved caspase-3 and pMIKL in the macrophages of the three infection groups to be upregulated (P<0.05). We detected ultrastructural changes of apoptosis, pyroptosis, and necroptosis in macrophages infected with E. faecalis. The three E. faecalis strains induced varying degrees of apoptosis, pyroptosis, and necroptosis that were probably associated with PANoptosis in macrophages. The E. faecalis CA1 strain exhibited faster growth and a higher real-time MOI, and it induced higher expression levels of some PANoptosis-related genes and proteins in the infected macrophages than the other strains tested.

X indening oral liquid improves cardiac function of rats with chronic cardiac failure via TGF-ß1/Smad3 and p38 MAPK pathway.

OBJECTIVE: Xindening oral liquid (Xin) is a widely used traditional Chinese medicine for the treatment of chronic heart failure (CHF). However, the exact mechanisms related to its therapeutic effects against CHF remain unclear. In the present study, we investigate the effects of Xin on cardiac function in CHF rats and the possible mechanisms involved. METHODS: Transverse aortic constriction (TAC) was conducted to induce a CHF rat model in this study. Sixty male Wistar rats were randomly assigned to six groups 28 days after TAC: sham; CHF model; Xin at concentrations of 5 ml/kg, 10 mL/kg, and 20 mL/kg; and QiLi 0.6 g/kg. After four weeks, the rats were treated with Xin (5, 10, or 20 mL/kg/d) for six weeks consecutively. At the end of the study, the cardiac function, heart weight index (HWI) and left ventricular mass index (LVMI), serum level of LDH, B-type natriuretic peptide (BNP), cTnI and CK-MB, and collagen volume fraction were studied. The expression of transforming growth factor-ß1 (TGF-ß1), drosophila mothers against decapentaplegic protein 3 (Smad3), and p38 mitogen activated protein kinase (p38 MAPK) were detected. RESULTS: The results showed that Xin treatment significantly improved cardiac function but decreased the serum level of LDH, BNP, cTnI, and CKMB of CHF rats. In addition, it reduced the HWI, LVMI, and collagen volume fraction compared with the model group. Xin treatment significantly improved cardiac function and attenuated cardiac fibrosis by suppressing the p38 MAPK and TGF-ß1/Smad3 signaling pathway in CHF rats. CONCLUSION: These results suggested that Xin might be a promising complementary treatment for CHF. More detailed experimental studies will be carried out in our subsequent research.

Inhibition of adriamycin-induced nephropathy in rats by herbs based kangshenoral solution.

The Chronic kidney disease (CKD) is characterized by the progressive loss in renal function over a period. The progression of CKD will finally result the End Stage Renal Disease (ESRD) Symptoms which needs permanent renal replacement therapies. Therefore, control the progression of CKD is necessary. In this study, based on the theory of Traditional Chinese Medicine and the Traditional Chinese Herbology, we developed the Kangshen Oral Solution based ona combination of different herbs for extraction. By utilizing adriamycin (ARD)-induced chronic renal failure in rats as the CKD model, our results demonstrated thatadministration of the Kangshen Oral Solution reduced the kidney disease induced weight loss in rats. The Kangshen Oral Solution could also relieve the proteinuria and kidney index induced by ARD which indicated the partially restoration of the kidney function. The improved kidney function was further supported by biochemical tests for blood total protein level, albumin level as well as cholesterol, triglycerides and Creatinine. Moreover, the histology examination also confirmed the ARD induced pathological changes in kidney was relieved by Kangshen Oral Solution. Taken together, these findings suggested Kangshen Oral solution could reduce ARD-induced nephropathy in rats model and may be employed as an alternative treatment for CKD patients.

Goldfish ghrelin: molecular characterization of the complementary deoxyribonucleic acid, partial gene structure and evidence for its stimulatory role in food intake.

Complementary deoxyribonucleic acid (cDNA) encoding goldfish preproghrelin was identified using rapid amplification of the cDNA ends (RACE) and reverse transcription (RT)-polymerase chain reaction (PCR). The 490 bp cDNA encodes a 103 amino acid preproghrelin which has a 26 amino acid signal region, 19 amino acid mature peptide and a 55 amino acid C-terminal peptide region. The mature peptide region of goldfish ghrelin has two putative cleavage sites and amidation signals (GRR); one after 12 amino acids and the other after 19 amino acids. The serine (S) in the second amino acid position in the "active core" of ghrelin is substituted with threonine (T). The goldfish ghrelin gene has four exons and three short introns and resembles the human ghrelin gene. Ghrelin messenger RNA (mRNA) expression was detected in the brain, pituitary, intestine, liver, spleen and gill by RT-PCR followed by Southern blot analysis, and in the intestine by Northern blot. Intracerebroventricular (ICV) injection of n-octanoylated goldfish ghrelin (1-19) stimulates food intake in goldfish.

Characterization of complementary deoxyribonucleic acids encoding preprogalanin and its alternative splice variants in the goldfish.

This paper reports the identification of five preprogalanin complementary deoxyribonucleic acids encoding preprogalanin peptides in the goldfish. Preprogalanin 1A, 1B and 1C are encoded in galanin gene 1 and 2A and 2B are encoded in gene 2. Preprogalanin 1B and 2B have a 24 amino acids insert in the mature peptide region and form 1C has a deletion of 23 amino acids in the middle of the galanin message associated peptide region. The mature peptides from the preprogalanin 1A and 1C are 29 amino acids. However, the mature peptide is 31 amino acids from preprogalanin 2A, 53 amino acids from 1B and 55 amino acids from 2B. The physiological significance of multiple forms of galanin peptide is unknown. Organization of galanin gene 1, which is similar to the mammalian galanin gene has been identified. Expression of preprogalanin messenger ribonucleic acids was widely detected in goldfish brain and several peripheral tissues.

Identification and characterization of a type five-like somatostatin receptor in goldfish pituitary.

In this study, a somatostatin receptor (Sst) cDNA was cloned and sequenced from goldfish pituitary. The cDNA encodes a 390-amino acid type five-like Sst (designated as gfSst(5)). The amino acid sequence of the receptor has slightly higher homology to mammalian Sst(5'), compared with other mammalian Sst subtypes and recently identified fish Sst(1), Sst(2) and Sst(3). In CCL39-SRE-Luci cells stably expressing the cloned receptor, agonist radioligand [125I]LTT-SRIF(28'), a mammalian SRIF(28) analog, bound to a homogenous population of receptors with high affinity (nM K(d)). Competition binding studies showed that all three natural goldfish SRIF ligands, SRIF(14), [Pro(2)]SRIF(14), and goldfish SRIF(28) (gfSRIF(28)), and LTT-SRIF(28) bind the cloned gfSst(5) with high affinity and significantly stimulate [35S]GTPgammaS binding, with SRIF(28) peptides showing higher affinity in receptor binding and potency in [35S]GTPgammaS binding compared with SRIF(14) peptides. The receptor gene is highly and predominately expressed in pituitary; lower levels of the receptor mRNA were also detected in different brain regions by reverse transcriptor-polymerase chain reaction (RT-PCR) followed by Southern blot analysis.

Somatostatin-like receptors in goldfish: cloning of four new receptors.

In this study, four somatostatin-like receptor (Sst) cDNAs were identified from goldfish pituitary, using RT-PCR screening and rapid amplification of cDNA ends (RACE) strategies. These include two type-five like Sst (Sst(5B) and Sst(5C)) and two type-three like Sst receptors (Sst(3A) and Sst(3B)), designated based on their amino acid sequence similarities to the known mammalian and fish Sst(5) and Sst(3). Both Sst(5C) and Sst(3A) mRNAs are widely expressed in all brain regions and pituitary; however, Sst(3B) expression is restricted to forebrain and Sst(5B) expression is mainly detected in pituitary and spinal cord.

Pharmacological characterisation of the goldfish somatostatin sst5 receptor.

Somatostatin (somatotropin release inhibiting factor, SRIF), exerts its effects via specific G protein coupled receptors of which five subtypes have been cloned (sst1-5). Recently, SRIF receptors have also been cloned from fish tissues. In this study, goldfish sst5 receptors (gfsst5) were expressed and characterised in the Chinese hamster lung fibroblast cell line, that harbours the luciferase reporter gene driven by the serum responsive element (CCL39-SRE-Luci). The agonist radioligands [125I]-LTT-SRIF-28 ([Leu8, DTrp22, 125I-Tyr25]SRIF-28) and [125I][Tyr10]cortistatin-14 labelled similar receptor densities with high affinity and in a saturable manner (pKd: 9.99-9.71; Bmax: 300-350 fmol mg-1). 5'-Guanylyl-imidodiphosphate inhibited radioligand binding to some degree (38.5-57.9%). In competition binding studies, the pharmacological profile of SRIF binding sites defined with [125I]LTT-SRIF-28 and [125I][Tyr10]cortistatin-14 correlated significantly (r2=0.97, n=20). Pharmacological profiles of human and mouse sst5 receptors expressed in CCL39 cells correlated markedly less with those of the gfsst5 profile (r2=0.52-0.78, n > or = b16). Functional expression of the gfsst5 receptor was examined by measurement of agonist-induced luciferase expression and stimulation of [35S]GTPgammaS ([35S]guanosine 5'-O-(3-thiotriphosphate) binding. Profiles were similar to those achieved in radioligand binding studies (r2=0.81-0.93, n=20), although relative potency (pEC50) was reduced compared to pKd values. Relative efficacy profiles of luciferase expression and [35S]GTPgammaS binding, were rather divergent (r2=0.48, n=20) with peptides showing full agonism at one pathway and absence of agonism at the other. BIM 23056 (D-Phe-Phe-Tyr-D-Trp-Lys-Val-Phe-D-Nal-NH2) acted as an antagonist on the effects of SRIF-14 (pKB=6.74 +/- 0.23) on stimulation of [35S]GTPgammaS binding. Pertussis toxin abolished the effect of SRIF-14 on luciferase expression and [35S]GTPgammaS binding suggesting coupling of the receptor to G(i)/G(o) proteins. In summary, the present studies demonstrate that the gfsst5 receptor has a similar pharmacological profile and transductional properties to mammalian sst5 receptors. The difference in efficacy profiles defined using different functional assays suggests numerous, agonist specific, conformational receptor states, and/or ligand-dependent receptor trafficking.

Effects of sex steroid hormones on the expression of somatostatin receptors sst1 and sst5 in goldfish pituitary and forebrain.

In the present paper the effects of estradiol and testosterone on the expression of the types 1 and 5 somatostatin receptors (sst1 and sst5) in the goldfish forebrain and pituitary were investigated. Estradiol increased the sst1 expression in both the forebrain and pituitary in a dose- and time-dependent manner. In addition, estradiol also increased the pituitary expression of sst5. On the other hand, testosterone had no effects on the expression of these receptor subtypes. Mature female goldfish were found to have higher sst1 and sst5 expression in the pituitary, as well as a higher expression of sst1 in the forebrain compared to sexually regressed animals. As estradiol treatment increases serum growth hormone levels in goldfish, these data suggest that sst1 and sst5 receptors are likely not directly involved in this aspect of growth hormone release.

Regulation of expression of somatostatin genes by sex steroid hormones in goldfish forebrain.

Recently, our laboratory has identified three distinct pre-pro-somatostatin (PSS) genes in goldfish brain: PSS-I encodes for somatostatin (SRIH)-14, PSS-II encodes SRIH-28, which contains [Glu(1), Tyr(7), Gly(10)] SRIH-14 at its C-terminus, and PSS-III encodes [Pro(2)] SRIH-14. In goldfish, increasing levels of the sex steroid estradiol increase the plasma levels of growth hormone (GH). However, whether sex steroids act at the level of the brain to regulate GH release is unclear. In the present study, the effects of sex steroids on the expression of the three PSS genes in goldfish forebrain were examined. The results demonstrate that treatment with estradiol significantly increases the expression of PSS-I and PSS-III genes in both male and female fish. The effects of estradiol were evident after only 2.5 days of treatment. Testosterone treatment increased the expression of PSS-I and PSS-III genes in female but not male fish, and only at the highest dose used. In addition, the effects of testosterone were evident only after treatment for 5 or 10 days and were blocked by an aromatase inhibitor, suggesting that testosterone must be converted to estradiol to exhibit the effect. Neither estradiol nor testosterone treatment had effects on the expression of the PSS-II gene. These results suggest that sex steroids can act either directly or indirectly on the brain to regulate PSS-I and PSS-III gene expression, influencing in turn the regulation of GH secretion.

Estradiol reduces pituitary responsiveness to somatostatin (SRIF-14) and down-regulates the expression of somatostatin sst2 receptors in female goldfish pituitary.

Sex steroid hormones have been shown to regulate somatostatin (SRIF) gene expression in goldfish brain, which in turn influences the regulation of GH secretion. In this study, the influences of sex steroids on pituitary responsiveness to SRIF-14 and the pituitary expression of a type two SRIF receptor (sst(2)) were examined. Results from in vitro perifusion of pituitary fragments show that pituitaries from estradiol-primed sexually regressed female fish have significantly lower GH release responsiveness to pulse exposure to SRIF-14 than pituitaries from control or testosterone-treated sexually regressed females. Results from in vitro static culture show that pituitaries from sexually mature female fish have lower GH release responsiveness to SRIF-14 than those from sexually regressed females. In addition, the sst(2) receptor mRNA levels in pituitaries from mature and recrudescent female fish are significantly lower than in sexually regressed female fish. Our results indicate that estradiol acts at the level of the pituitary to regulate GH secretion by influencing the responsiveness to SRIF-14. The underlying mechanism includes, in part, reduction of the expression of sst(2) receptors, presumably leading to the lower number of the receptors available for SRIF binding.