Immune System Effects of Insulin-Like Peptide 5 in a Mouse Model

INTRODUCTION

Insulin-like peptide 5 (INSL5) is a peptide hormone with proposed actions in glucose homeostasis and appetite regulation via its cognate receptor, relaxin family peptide receptor 4 (RXFP4). Here, we look for evidence for their involvement in the immune system using a mouse model.

METHODS

In silico analyses: we queried public databases for evidence of expression of INSL5-RXFP4 in immune system tissues/cells (NCBI's SRA and GeoProfiles) and disorders (EMBO-EBI) and performed phylogenetic footprinting to look for evidence that they are regulated by immune-associated transcription factors (TFs). Experimental analyses: We characterized the expression and correlation of INSL5/RXFP4 and other immune system markers in central and peripheral immune organs from C57/bl6 mice in seven cohorts. We tested whether fluctuations in circulating INSL5 induce an immune response, by injecting mice with 30 μg/kg of INSL5 peptide in the peritoneum, and examining levels of immune markers and metabolic peptides in plasma. Lastly, we quantified the expression of Rxfp4 in T-cells, dendritic cells and cell lines derived from human and mouse and tested the hypothesis that co-incubation of ANA-1 cells in INSL5 and LPS alters cytokine expression.

RESULTS

We find Insl5 expression only in thymus (in addition to colon) where its expression was highly correlated with Il-7, a marker of thymocyte development. This result is consistent with our in silico findings that Insl5 is highly expressed in thymic DP, DN thymocytes and cortical TEC's, and with evidence that it is regulated by thymocyte-associated TF's. We find Rxfp4 expression in all immune organs, and moderately high levels in DCs, particularly splenic DCs, and evidence that it is regulated by immune-associated TF's, such as STAT's and GATA. Systemic effects: We observed significantly elevated concentrations of blood GLP-1, GIP, GCG and PYY following intraperitoneal injection of INSL5, and significantly altered expression of cytokines IL-5, IL-7, M-CSF, IL-15, IL-27 and MIP-2. Immune cell effects: Incubation of ANA-1 cells with INSL5 impeded cell growth and led to a transient elevation of IL-15 and sustained reduction in IL-1β, IL-6 and TNFα.

CONCLUSION

We propose that INSL5-RXFP4 play a novel role in both central and peripheral immune cell signaling.

Identification, expression, and innate immune responses of two insulin-like peptide genes in the razor clam Sinonovacula constricta

Insulin-like peptide (ILP) has emerged as a cell regulatory factor with multiple functions in vertebrates and invertebrates. In the present study, we identified and characterized two ILP genes, ILP1 and ILP2, in the razor clam Sinonovacula constricta. Both ILPs have a signal peptide and a mature domain consisting of six strictly conserved cysteines. The tertiary structure is divided into three main α-helices with a C-domain loop that separates helix 1 from helix 2. Both of ILPs were found to be regulated according to tissue type and developmental stage. After challenge with Vibrio anguillarum, Vibrio parahaemolyticus and Micrococcus lysodeikticus, the expression of two ILP genes was significantly up-regulated in the liver, hemocytes and mantle tissues, suggesting that the ILPs may play roles in the innate immunity in the razor clam Sinonovacula constricta.

Peripheral Ghrelin participates in glucostatic feeding mechanisms and in the anorexigenic signalling mediated by CART and CRF neurons

Ghrelin is upregulated under negative energy balance conditions, including starvation and hypoglycemia, while it is downregulated under situations of positive energy balance, such as feeding, hyperglycemia and obesity. The aims of this study were to assess potential ghrelin interactions with glucose levels in appetite control and to identify potential mechanisms involving orexigenic and anorexigenic ghrelin mediated signals by using a specific anti-ghrelin antibody. Our results confirm that peripheral ghrelin is an important signal in meal initiation and food intake stimulation. C-fos positive neurons in the PVN increased after insulin or 2-deoxyglucose administration. Moreover, we also demonstrate that peripheral ghrelin blockade with a specific anti-ghrelin antibody reduces, in part, the orexigenic signal induced by insulin and 2-DG administration. Furthermore, when we blocked peripheral ghrelin, c-fos positive CRF neurons and CART expression increased in the PVN, both under hypoglycemia or cytoglycopenia conditions, suggesting a neuronal activation (anorexigenic signalling) in this hypothalamic region. In summary, our findings imply that peripheral ghrelin plays an important role in regulatory "glucostatic" feeding mechanisms due to its role as a "hunger" signal affecting the PVN area, which may contribute to energy homeostasis through both orexigenic/anorexigenic pathways.

[Preparation and identification of monoclonal antibody against human GCRG213]

AIM

To prepare and characterize the monoclonal antibody against human GCRG213.

METHODS

The HIS-GCRG213 fusion protein was expressed in E.coli. Mice were immunized with the purified HIS-GCRG213 protein. Hybridoma cell lines secreting monoclonal antibodies against GCRG213 were screened by regular cell fusion and subcloning approach. The titer and specificity of the antibody was characterized by ELISA and Western blot, respectively. The expression of GCRG213 was determined using immunohistochemistry technique on paraffin-embedded tissue sections from normal gastric mucosal tissues and advanced gastric cancer.

RESULTS

The HIS-GCRG213 fusion protein with relative molecular mass of 20 800 was over expressed in E.coli. Two hybridoma cell lines which secreted monoclonal antibody specifically against human GCRG213 fusion protein were successfully obtained. The ascite titers of this monoclonal antibody reached 1:10(6);. Western blot analysis showed that the monoclonal antibody could bind to the recombinant HIS-GCRG213 protein specifically.The immunohistochemistry showed that GCRG213 were expressed higher in gastric cancer tissues than in normal ones.

CONCLUSION

The monoclonal antibody against human GCRG213 with high titer and specificity has been successfully prepared, which could be utilized as a useful reagent for further studying the biological function of the GCRG213.

Identifying tumor antigens in endocrine malignancies

Tumor antigens are surface molecules that are mostly cancer specific, often overexpressed and recognized by the immune system. Therefore, identifying tumor antigens is of key importance for developing new immunotherapies for incurable cancers. For endocrine malignancies, several different tumor-associated antigens have been described, including polypeptide hormones and/or vesicle-associated antigens in Th1-mediated autoimmune diseases. Other antigens have been identified by screening tumor DNA libraries. Furthermore, vaccination studies in humans and animal models have revealed a tumor-antigen-specific immunity and clinical responses with reduced tumor size. Here, we provide an overview of the recent progress achieved in identifying tumor antigens and predict how this knowledge can be used in the future for developing anti-tumor vaccinations.

Active immunization against ghrelin decreases weight gain and alters plasma concentrations of growth hormone in growing pigs

Ghrelin has been implicated in the control of food intake and in the long-term regulation of body weight. We theorize that preventing the ability of ghrelin to interact with its receptors, would eventually lead to decreased appetite and thereby decrease body weight gain. To test our hypothesis, pigs were actively immunized against ghrelin. Ghrelin((1-10)) was conjugated to BSA and emulsified in Freund's incomplete adjuvant and diethylaminoethyl-dextran. Primary immunization was given at 19 weeks of age (WOA), with booster immunizations given 20 and 40 days after primary immunization. Body weight (BW) and plasma samples were collected weekly beginning at 19 WOA, and feed intake was measured daily. Fourteen days after primary immunization, the percentage of bound (125)I-ghrelin in plasma from immunized pigs was increased compared with control animals (P<0.001). Voluntary feed intake was decreased more than 15% in animals that were actively immunized against ghrelin compared with controls. By the end of the experiment, immunized pigs weighed 10% less than control animals (P<0.1). Concentrations of GH were increased (P<0.05) in immunized pigs. Apoptosis was not observed in post-mortem samples obtained from the fundic region of the stomach. Our observations suggest that immunization against ghrelin induces mild anorexia. This procedure could potentially be used as a treatment to control caloric intake and obesity.

An immunohistochemical study of the localization and developmental expression of ghrelin and its functional receptor in the ovine placenta

BACKGROUND

Ghrelin is an orexigenic hormone principally produced by the stomach, but also by numerous peripheral tissues including the placenta. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation, and has been suggested to play a role in the developmental growth of the fetoplacental unit. The placental expression of ghrelin and its role in ruminant species is not known. We tested the hypotheses that ghrelin and its functional receptor, GHSR-1a, are present in tissues of the ovine placenta, and that their expression is linked to the stage of development.

METHODS

Antibodies raised against ghrelin and GHSR-1a were used in standard immunohistochemical protocols on placental tissues collected from pregnant ewes (n = 6 per gestational time point) at days 50, 80, 100, 128 and 135 of gestation (term approximately day 145). Immunostaining for ghrelin and GHSR-1a was quantified using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.

RESULTS

Positive immunostaining for ghrelin was detected in ovine placentae at all gestational time points, with staining localized to the maternal epithelium, caruncle and trophectoderm. There was a significant effect of gestational age (p < 0.001) on the placental expression of ghrelin, with maximal levels at gestational day 80. GHSR-1a immunostaining was detected in the fetal trophectoderm at all time points. In contrast to the gestational pattern of ghrelin expression, there was no effect of gestational age on placental GHSR-1a immunoexpression.

CONCLUSION

Ghrelin and GHSR-1a are both present in the ovine placenta, and ghrelin displays a developmentally-related pattern of expression. Therefore, these data strongly suggest that the ghrelin system may have a role in feto-placental development in sheep.

Obesity influences the food consumption and cytokine pattern in ghrelin-treated endotoxemic rats

Obese patients have an increased incidence of systemic infections and higher morbidity and mortality rates than normal weight subjects. Ghrelin is a potent orexigenic signal from the stomach and seems to play a role in the generation and control of immune interactions. To examine a possible benefit of a single ghrelin application on acute endotoxemia, chronic intravenous (i.v.) cannulated lean and diet-induced obese male LEW rats were treated with a bolus injection of either ghrelin (10 nmol/kg) or vehicle, 10 min prior to a challenge with a sublethal bolus of endotoxin (100 microg/kg) or vehicle. Multiple blood samples were taken within a period from 24 h before the experiment up to 24 h after the endotoxin challenge to measure ghrelin and cytokine levels. Additionally, food consumption was recorded and ghrelin expression in fore- and glandular stomach was evaluated immunohistochemically. Despite higher serum ghrelin levels, the food consumption was significantly decreased in obese endotoxemic rats compared to lean littermates after ghrelin treatment. Furthermore we could show an increase of anti-inflammatory IL-10 serum levels after ghrelin treatment of normal weight endotoxemic and an opposite effect in obese animals. As the therapy of disease-associated cachexia and various immunological problems in endotoxemia is still insufficient, peptides such as ghrelin with their modulating abilities for the endocrine and the immune system are of special interest. However, the present study shows that the beneficial effects of ghrelin were attenuated in obese endotoxemic animals. These data further document the necessity to differentiate between normal weight and obese subjects in the attempt to establish ghrelin as a therapeutic target in endotoxemia.

Obesity, inflammation, and vascular disease: the role of the adipose tissue as an endocrine organ

Insulin resistance, both in nondiabetic and diabetic subjects, is frequently associated with obesity, particularly with an excess of central fat. With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they are increasingly shown to influence several aspects in the pathogenesis of obesity-related diseases Until relatively recently, the role of fat itself in the development of obesity and its consequences was considered to be a passive one; adipocytes were considered to be little more than storage cells for fat. It is now clear that, in addition to storing calories as triglycerides, they also secrete a large variety of proteins, including cytokines, chemokines and hormone-like factors, such as leptin, adiponectin and resistin. This production of pro-atherogenic chemokines by adipose tissue is of particular interest since their local secretion, e.g. by perivascular adipose depots, may provide a novel mechanistic link between obesity and the associated vascular complications. Recent research has revealed many functions of adipocytokines extending far beyond metabolism, such as immunity, cancer and bone formation. This remarkable understanding is allowing us to more clearly define the role that adipocytes play in health and in obesity and how inflammatory mediators act as signaling molecules in this process. Moreover, on a molecular level, we are beginning to comprehend how such variables as hormonal control, exercise, food intake, and genetic variation interact and result in a given phenotype, and how pharmacological intervention may modulate adipose tissue biology.

Identification of immunoreactive plasma and stomach ghrelin, and expression of stomach ghrelin mRNA in the bullfrog, Rana catesbeiana

In this study, we established a radioimmunoassay (RIA) specific for ghrelin from the bullfrog Rana catesbeiana using a novel antibody raised against the C-terminal amino acid sequence of bullfrog ghrelin [13-28]. We also examined the distribution of ghrelin-producing cells in the stomachs of bullfrogs using this antibody and a cRNA probe specific for the bullfrog ghrelin gene. Ghrelin levels in plasma and stomach extracts were approximately 150 fmol/ml and 83-135 fmol/mg wet tissue, respectively. Reverse-phase high performance liquid chromatographic analysis, combined with bullfrog ghrelin RIA, revealed that ghrelin immunoreactivity in the stomach was composed of non-acylated ghrelin (des-acyl ghrelin) and several acylated forms of ghrelin bearing different fatty acid modifications, which could induce increases in intracellular Ca2+ in cells expressing the rat GH secretagogue receptor. In the stomach, the major storage form was acylated ghrelin. In bullfrog plasma, however, the majority of ghrelin immunoreactivity was des-acyl ghrelin and C-terminal fragments of frog ghrelin. Acylated ghrelin forms comprised only minor peaks. Ghrelin-immunopositive and ghrelin mRNA-expressing cells were observed within the mucosal layer of the stomach. Following starvation, significant increases in plasma ghrelin levels and stomach ghrelin mRNA levels were observed as early as 10 days after starvation. These results indicate that ghrelin is present in the stomach and plasma of the bullfrog, which can be detected with our novel antibody. Interestingly, the primary storage form of ghrelin in the stomach differed from the circulating form dominating in the plasma. Furthermore, increases in ghrelin levels in plasma and mRNA levels in the stomach after starvation suggest the possible involvement of ghrelin in energy homeostasis in the bullfrog.

Vaccination against weight gain

Obesity endangers the lives of millions of people worldwide, through comorbidities such as heart disease, cancers, type 2 diabetes, stroke, arthritis, and major depression. New approaches to control body weight remain a high priority. Vaccines traditionally have been used to protect against infectious diseases and, more recently, for unconventional targets such as drug addiction. Methodologies that could specifically modulate the bioavailability of an endogenous molecule that regulates energy balance might provide a new foundation for treating obesity. Here we show that active vaccination of mature rats with ghrelin immunoconjugates decreases feed efficiency, relative adiposity, and body weight gain in relation to the immune response elicited against ghrelin in its active, acylated form. Three active vaccines based on the 28-aa residue sequence of ghrelin, a gastric endocrine hormone, were used to immunize adult male Wistar rats (n = 17). Synthetic ghrelin analogs were prepared that spanned residues 1-10 [ghrelin (1-10) Ser-3(butanoyl) hapten, Ghr1], 13-28 [ghrelin (13-28) hapten, Ghr2], and 1-28 [ghrelin(1-28) Ser-3(butanoyl) hapten, Ghr3], and included n-butanoyl esters at Ser-3. Groups immunized with Ghr1 or Ghr3 showed greater and more selective plasma binding capacity for the active, Ser-3-(n-octanoyl) form of ghrelin as compared with Ghr2 or keyhole limpet hemocyanin vaccinated controls. Accordingly, they gained less body weight, with sparing of lean mass and preferential reduction of body fat, consistent with reduced circulating leptin levels. The ratio of brain/serum ghrelin levels was lower in rats with strong anti-ghrelin immune responses. Effects were not attributable to nonspecific inflammatory responses. Vaccination against the endogenous hormone ghrelin can slow weight gain in rats by decreasing feed efficiency.

Immunohistochemical evidence for an endocrine/paracrine role for ghrelin in the reproductive tissues of sheep

BACKGROUND

The gut hormone, ghrelin, is involved in the neuroendocrine and metabolic responses to hunger. In monogastric species, circulating ghrelin levels show clear meal-related and body weight-related changes. The pattern of secretion and its role in ruminant species is less clear. Ghrelin acts via growth hormone secretagogue receptors (GHSR-1a) to alter food intake, fat utilization, and cellular proliferation. There is also evidence that ghrelin is involved in reproductive function. In the present study we used immunohistochemistry to investigate the presence of ghrelin and GHSR-1a in sheep reproductive tissues. In addition, we examined whether ghrelin and GHSR-1a protein expression is developmentally regulated in the adult and fetal ovine testis, and whether there is an association with markers of cellular proliferation, i.e. stem cell factor (SCF) and proliferating cell nuclear antigen (PCNA).

METHODS

Antibodies raised against ghrelin and its functional receptor, GHSR-type 1a, were used in standard immunohistochemical protocols on various reproductive tissues collected from adult and fetal sheep. GHSR-1a mRNA presence was also confirmed by in situ hybridisation. SCF and PCNA immunoexpression was investigated in fetal testicular samples. Adult and fetal testicular immunostaining for ghrelin, GHSR-1a, SCF and PCNA was analysed using computer-aided image analysis. Image analysis data were subjected to one-way ANOVA, with differences in immunostaining between time-points determined by Fisher's least significant difference.

RESULTS

In adult sheep tissue, ghrelin and GHSR-1a immunostaining was detected in the stomach (abomasum), anterior pituitary gland, testis, ovary, and hypothalamic and hindbrain regions of the brain. In the adult testis, there was a significant effect of season (photoperiod) on the level of immunostaining for ghrelin (p < 0.01) and GHSR-1a (p < 0.05). In the fetal sheep testis, there was a significant effect of gestational age on the level of immunostaining for ghrelin (p < 0.001), GHSR-1a (p < 0.05), SCF (p < 0.05) and PCNA (p < 0.01).

CONCLUSION

Evidence is presented for the presence of ghrelin and its receptor in various reproductive tissues of the adult and fetal sheep. In addition, the data indicate that testicular expression of ghrelin and its receptor is physiologically regulated in the adult and developmentally regulated in the fetus. Therefore, the ghrelin ligand/receptor system may have a role (endocrine and/or paracrine) in the development (cellular proliferation) and function of the reproductive axis of the sheep.

Impact of Helicobacter pylori infection on gastric and plasma ghrelin dynamics in humans

OBJECTIVES

There are contradictory reports on the relationship between Helicobacter pylori and circulating ghrelin. We sought to clarify the influence of H. pylori infection on gastric and plasma ghrelin dynamics in humans.

METHODS

Using endoscopic biopsies from the corpus of 56 H. pylori-infected patients and 25 uninfected subjects, ghrelin mRNA expression levels and gastric ghrelin peptide contents were measured by real-time polymerase chain reaction and radioimmunoassay, respectively. We also measured plasma ghrelin concentrations and analyzed the numbers of ghrelin immunoreactive cells in the fundic gland area. Fifty-one patients with H. pylori infection were treated with a 7-day triple therapy consisting of lansoprazole, clarithromycin, and amoxicillin.

RESULTS

The gastric ghrelin mRNA expression level of H. pylori-positive patients (1.64 +/- 1.27 in arbitrary units) was significantly lower than in H. pylori-negative subjects (4.87 +/- 4.1, p < 0.0001). A similar trend was noted for ghrelin peptide contents (31.2 +/- 27.5 vs 81.2 +/- 64.1 ng/mg protein, respectively, p < 0.0001). There was no significant difference in the number of ghrelin immunoreactive cells/mm(2) in terms of H. plyori status. Plasma ghrelin concentrations in H. pylori-infected patients (144.6 +/- 7.8.8 fmol/ml) were significantly lower than in uninfected subjects (196.1 +/- 97.2, p < 0.05) and increased following cure of the infection. Plasma ghrelin levels correlated positively with the expression levels of ghrelin mRNA (r = 0.583, p < 0.0001) and peptide products (r = 0.574, p < 0.0001). There was a significant stepwise decrease in gastric ghrelin mRNA expression (p < 0.05), peptide contents (p < 0.01) and density of ghrelin immunoreactive cells (p < 0.05) with progression of histological severity of glandular atrophy in the corpus. The histological severity of chronic inflammation also negatively influenced the ghrelin mRNA expression (p < 0.001) and peptide production (p < 0.005).

CONCLUSIONS

H. pylori infection has a negative impact on gastric and plasma ghrelin dynamics. Chronic inflammatory and atrophic changes associated with the infection may affect gastric ghrelin biosynthesis and contribute to the low circulating levels.

Distribution of ghrelin-immunoreactive cells in human gastric mucosa: comparison with that of parietal cells

BACKGROUND

Ghrelin is a novel 28-amino-acid peptide isolated from rat and human stomach. This peptide is an endogenous ligand for the growth hormone secretagogue receptor and stimulates the release of growth hormones. Although the principal site of ghrelin synthesis has been reported to be in the stomach, there have been no reports of detailed descriptions of the distribution of ghrelin-immunoreactive cells in the stomach. We examined the distribution of ghrelin-immunoreactive cells in human gastric mucosa.

METHODS

We studied the tumor-free mucosa along the lesser curvature in 30 patients with gastric cancer. Sections were stained with hematoxylin and eosin and then subjected to ghrelin immunohistochemistry. The distribution of ghrelin-immunoreactive and parietal cells was studied by continuous cell counting in restricted fields along the lamina muscularis mucosa.

RESULTS

Ghrelin-immunoreactive cells were found in all regions, but were distributed mainly in the fundic region. The distribution of ghrelin-immunoreactive cells was positively correlated with that of parietal cells.

CONCLUSIONS

The results of this study suggested that the distribution of ghrelin-immunoreactive cells follows that of parietal cells.

Biochemical characterization and immunohistochemical localization of urotensin II in the human brainstem and spinal cord

The human urotensin II (UII) precursor encompasses several potential cleavage sites and thus, processing of pro-UII may generate various forms of mature UII including the peptides of 11 (UII11), 16 (UII16) and 19 (UII19) residues. Until now, the native form of human UII had not been characterized. Here, we show that the major UII peptide occurring in the human spinal cord corresponds to UII11. In contrast, neither the UII16 nor the UII19 forms could be detected. In 50% of the brainstem and in all the spinal cord extracts analysed, a second minor UII-immunoreactive peptide was resolved. Immunohistochemical labelling of the cervical segment of the human spinal cord revealed that the UII-immunoreactive material was confined to a subset of ventral horn motoneurones. These data provide the first evidence that in the human, the UII precursor, expressed in motoneurones, is processed at the tribasic KKR93 cleavage site to generate a mature form of UII of 11 amino acids. The absence of N-terminally elongated forms of UII of 16 and 19 residues indicates that pro-UII is not cleaved at the R85 or K88 monobasic sites. Finally, the minor UII-immunoreactive peptide detected in several tissue extracts might correspond to an extended form of UII resulting from the processing of the UII precursor at the basic RK50 or RK66 doublets.

Ghrelin: integrative neuroendocrine peptide in health and disease

OBJECTIVE

Ghrelin is a novel gastric hormone recognized in 1999 as a mediator of growth hormone release. Since growth hormone is anabolic, an important function of ghrelin may be to coordinate energy needs with the growth process. Newly discovered biologic roles of ghrelin imply that it may have other important physiological functions as well. This is a review of recent clinically relevant, yet less well-known, physiologic actions of ghrelin.

SUMMARY BACKGROUND DATA

Ghrelin has profound orexigenic, adipogenic, and somatotrophic properties, increasing food intake and body weight. Secreted predominantly from the stomach, ghrelin is the natural ligand for the growth hormone secretagogue receptor in the pituitary gland, thus fulfilling criteria of a brain-gut peptide. The brain-gut axis is the effector of anabolism by regulating growth, feeding, and metabolism via vagal afferents mediating ghrelin signaling. However, the wide tissue distribution of ghrelin suggests that it may have other functions as well.

METHODS

Systematic literature review of all PubMed citations between 1999 and August 2003 focusing on clinically relevant biochemical and physiological characteristics of ghrelin.

RESULTS

Ghrelin is an important component of an integrated regulatory system of growth and metabolism acting via the vagus nerve, and is implicated in a variety of altered energy states such as obesity, eating disorders, neoplasia, and cachexia. It also enhances immune responses and potentially down-regulates anti-inflammatory molecules. Ghrelin's role as a brain-gut peptide emphasizes the significance of afferent vagal fibers as a major pathway to the brain, serving the purpose of maintaining physiologic homeostasis.

CONCLUSIONS

The discovery of ghrelin has increased our understanding of feeding regulation, nutritional homeostasis, and metabolic processes. Further characterization of ghrelin's functions will likely generate new pharmacological approaches to diagnose and treat different disease entities including those related to the over-nutrition of obesity and the catabolic response to surgical trauma.

Molecular targets for immunocontraception

Effective contraception is necessary in countries where limiting population growth has become a public policy imperative. The main antigenic targets for contraceptive vaccine development can be listed as following: 1) sperm antigens, 2) zona pellucida antigens, 3) gonadotrophin-releasing hormone, 4) chorionic gonadotrophin, 5) other protein/peptide hormones (follicle-stimulating hormone, luteinizing hormone, luteinizing hormone-releasing hormone), and 6) gonadal steroid hormones. New techniques, such as the application of monoclonal antibodies, hybridoma and DNA recombinant technologies, have become useful in search for contraceptive candidates. Current state of development of contraceptive vaccines based on specific antigenic targets and trials in animal/human models are presented in this article.

Immunolocalization of PTHrP in the sublingual glands of three mammals

The present study deals with immunohistochemical localization of PTHrP in sublingual glands of white mouse, bank vole, and common vole. PTHrP immunoreactivity was observed in epithelial cells of striated, interlobular and main excretory ducts of the salivary glands in all the three animal species tested. However, we found no positive reaction for PTHrP in epithelial cells of the intercalated ducts. In striated duct cells, the reaction intensity was species-dependent. In bank vole and common vole, the reaction was very strong, while in white mouse very weak. In the remaining segments of excretory ducts (interlobular and main excretory duct) we found no species-related differences in the reaction intensity or character. Myoepithelial cells surrounding ducts and mucous tubules with serous demilunes in sublingual glands were also PTHrP-negative in all the three animal species tested.

Immunolocalization of PTHrP in prepubertal and pubertal testis of European bison

The present study deals with immunohistochemical localization of PTHrP in prepubertal and pubertal testis of European bison. PTHrP immunoreactivity was observed in germinal cells in the testis of both prepubertal and pubertal animals. In calves, PTHrP was found in germinal cells, in seminiferous tubules lacking the lumen. The reaction was strong and regularly distributed within the cytoplasm. In adult animals, the reaction showed differentiation in spermatogenic cells. Some cells were strongly and diffusely stained, others exhibited weaker reaction of granular pattern. Sertoli cells and Leydig cells were PTHrP-negative in calves and adult animals.

Blockade of parathyroid hormone-related protein prevents joint destruction and granuloma formation in streptococcal cell wall-induced arthritis

OBJECTIVE

To determine whether parathyroid hormone-related protein (PTHrP), an interleukin-1beta-inducible, bone-resorbing peptide that is produced in increasing amounts by the synovium in rheumatoid arthritis (RA), may play a role in the pathophysiology of joint destruction in RA.

METHODS

PTHrP expression and the effect of PTHrP 1-34 neutralizing antibody on disease progression were tested in streptococcal cell wall (SCW)-induced arthritis, an animal model of RA.

RESULTS

As has been reported in RA, while serum levels of PTHrP did not change during SCW-induced arthritis, PTHrP expression dramatically increased in the arthritic synovium. Treatment with PTHrP neutralizing antibody (versus control antibody) did not affect joint swelling in SCW-treated animals. However, PTHrP antibody significantly inhibited SCW-induced joint destruction, as measured by its ability to block increases in serum pyridinoline (a marker of cartilage and bone destruction), erosion of articular cartilage, decreases in femoral bone mineral density, and increases in the numbers of osteoclasts in eroded bone. Unexpectedly, granuloma formation at sites of SCW deposition in the liver and spleen was also inhibited by PTHrP antibody, an effect associated with significant decreases in the tissue influx of PTH/PTHrP receptor-positive neutrophils and in SCW-induced neutrophilia. In vitro, neutrophil chemotaxis was stimulated by PTHrP 1-34.

CONCLUSION

These findings suggest that PTHrP, consistent with its previously described osteolytic effects in metastatic bone disease, can also be an important mediator of joint destruction in inflammatory bone disorders, such as RA. Moreover, this study reveals heretofore unknown effects of PTHrP peptides on neutrophil function that could have important implications in the pathogenesis of inflammatory granulomatous disorders.

Ghrelin plays a minor role in the physiological control of cardiac function in the rat

We have previously reported that a 7-d pretreatment with hexarelin, a synthetic ligand of the GH secretagogue receptor (GHS-R), largely prevented damages induced by ischemia and reperfusion in isolated rat hearts. Our aim was to ascertain whether ghrelin, an endogenous ligand of the GHS-R, is physiologically endowed with cardioprotective activity. Hypophysectomized rats were treated in vivo for 7 d with either ghrelin (320 microg/kg) or hexarelin (80 microg/kg), and their hearts were subjected in vitro to the ischemia and reperfusion procedure. Ghrelin was far less effective than hexarelin in preventing increases in left ventricular end-diastolic pressure (15% and 60% protection for ghrelin and hexarelin, respectively), coronary perfusion pressure (10% and 45% reduction), and release of creatine kinase in the heart perfusate (15% and 55% reduction). In the second experiment, normal rats were passively immunized against ghrelin for 21 d before the ischemia and reperfusion procedure. In these isolated hearts, the ischemia-reperfusion damage was not significantly increased compared with control rats. After hypophysectomy, CD36 mRNA levels significantly increased, whereas those of atrial natriuretic factor significantly decreased. We conclude that: 1) ghrelin plays a minor role in the control of heart function; and 2) hexarelin effects are mediated in part by the GHS-R and largely by interactions with the CD36.

Endogenous ghrelin is an orexigenic peptide acting in the arcuate nucleus in response to fasting

Ghrelin, a circulating growth-hormone releasing peptide derived from stomach, stimulates food intake through neuropeptide Y (NPY) neurons of the arcuate nucleus in the hypothalamus (ARC). We examined the effect of ghrelin microinjected into the ARC and the influence of intracerebroventricular (i.c.v.) pretreatment with a GHRH or NPY receptor antagonist on ghrelin-induced food intake in free-feeding male rats. Ghrelin (0.1-1 microg) stimulated food intake in a dose-dependent manner, and this effect was reduced by 55-60% by the Y(5) NPY receptor antagonist (10 microg i.c.v.), but not by the GHRH receptor antagonist MZ-4-71 (10 microg i.c.v.). We also evaluated the effects of passive ghrelin immunoneutralization by the microinjection of anti-ghrelin immunoglobulins (IgGs) intracerebroventricularly or directly into the ARC on food intake in free-feeding and fasted male rats. i.c.v. administration of anti-ghrelin IgGs decreased cumulative food intake over 24 h, whereas microinfusion of anti-ghrelin IgGs into the ARC induced only a short-lived (2 and 6 h) effect. Collectively, these data would indicate that centrally derived ghrelin has a major role in the control of food intake in rats and, in this context, blood-born ghrelin would be effective only in relation to its ability to reach the ARC, which is devoid of blood-brain barrier.

Existence of ghrelin-immunopositive and -expressing cells in the proventriculus of the hatching and adult chicken

Ghrelin was isolated from the rat stomach as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) and has been found in the gastrointestinal tract of many vertebrates. Although the sequence and structure of chicken ghrelin has recently been determined, morphological characteristics of ghrelin cells in the chicken gastrointestinal tract are still obscure. In this study, we investigated ghrelin expression and distribution of ghrelin-producing cells in the hatching and adult chicken gastrointestinal tract by RT-PCR, immunohistochemistry and in situ hybridization. Ghrelin mRNA expression was observed mainly in the proventriculus in the hatching chicken and in the proventriculus, pylorus and duodenum of the adult chicken by RT-PCR. Ghrelin-immunopositive (ghrelin-ip) cells in the proventriculus were located at the mucosal layer but not in the myenteric plexus or smooth muscle layer. The number of ghrelin-ip cells in the adult chicken was greater than that in the hatching chicken. Interestingly, in the adult chicken, the number of ghrelin-ip cells were almost the same as that of ghrelin mRNA-expressing (ghrelin-ex) cells; however, in the hatching chicken, the number of ghrelin-ex cells was greater than that of ghrelin-ip cells. These results clearly demonstrate that ghrelin-producing cells exist in the chicken gastrointestinal tract, especially in the proventriculus, from hatching to adult stages of development, as well as in mammals.

Immunolocalization of ghrelin and its functional receptor, the type 1a growth hormone secretagogue receptor, in the cyclic human ovary

Ghrelin is a novel 28-amino acid peptide identified as the endogenous ligand for the GH secretagogue receptor (GHS-R). Besides its hallmark central neuroendocrine effects in the control of GH secretion and food intake, an unexpected reproductive facet of ghrelin has recently emerged because expression of this molecule and its cognate receptor has been demonstrated in rat testis. However, whether this signaling system is present in human gonads remains to be evaluated. In this study, we have assessed the presence and cellular location of ghrelin and its functional receptor, namely the type 1a GHS-R, in the cyclic human ovary by means of immunohistochemistry using specific polyclonal antibodies. Strong ghrelin immunostaining was demonstrated in ovarian hilus interstitial cells. In contrast, ghrelin signal was not detected in ovarian follicles at any developmental stage, nor was it present in newly formed corpora lutea (CL) at very early development. However, specific ghrelin immunoreactivity was clearly observed in young and mature CL, whereas expression of the peptide disappeared in regressing luteal tissue. Concerning the cognate receptor, ovarian expression of GHS-R1a protein showed a wider pattern of tissue distribution, with detectable specific signal in oocytes as well as somatic follicular cells; luteal cells from young, mature, old, and regressing CL; and interstitial hilus cells. Of particular note, follicular GHS-R1a peptide expression paralleled follicle development with stronger immunostaining in granulosa and theca layers of healthy antral follicles. In conclusion, our results are the first to demonstrate that ghrelin and its functional type 1a receptor are expressed in the cyclic human ovary with distinct patterns of cellular location. The presence of both components (ligand and receptor) of the ghrelin signaling system within the human ovary opens up the possibility of a potential regulatory role of this novel molecule in ovarian function under physiological and pathophysiological conditions.

High-affinity HLA-A(*)02.01 peptides from parathyroid hormone-related protein generate in vitro and in vivo antitumor CTL response without autoimmune side effects

Parathyroid hormone-related protein (PTH-rP), a protein produced by prostate carcinoma and other epithelial cancers, is a key agent in the development of bone metastases. We investigated whether the protein follows the self-tolerance paradigm or can be used as a target Ag for anticancer immunotherapy by investigating the immunogenicity of two HLA-A(*)02.01-binding PTH-rP-derived peptides (PTR-2 and -4) with different affinity qualities. PTH-rP peptide-specific CTL lines were generated from the PBMC of two HLA-A(*)02.01(+) healthy individuals, stimulated in vitro with PTH-rP peptide-loaded autologous dendritic cells and IL-2. The peptide-specific CTLs were able to kill PTH-rP(+)HLA-A(*)02.01(+) breast and prostate carcinoma cell lines. The two peptides were also able to elicit a strong antitumor PTH-rP-specific CTL response in HLA-A(*)02.01 (HHD) transgenic mice. The vaccinated mice did not show any sign of side effects due to cell-mediated autoimmunity or toxicity. In this study we describe two immunogenic and toxic-free PTH-rP peptides as valid candidates for the design of peptide-based vaccination strategies against prostate cancer and bone metastases from the most common epithelial malignancies.

Parathyroid hormone-related Peptide expression in cartilaginous tumors

Parathyroid hormone-related peptide is one of the most important regulators of chondrocyte proliferation. Although cartilaginous neoplasms express different collagens, including Types II and X, the pathogenesis of these tumors has not been elucidated. The current study examined the hypothesis that parathyroid hormone-related peptide is expressed in cartilaginous neoplasms and its level of expression may correlate with the proliferative rate of cartilaginous neoplasms with higher levels in more malignant tumors and lower levels in benign lesions. Two hundred thirty-four biopsy and resection specimens of benign and malignant cartilage tumors from 179 patients were retrieved from surgical pathology archival material and analyzed immunohistochemically using an antibody to human parathyroid hormone-related peptide. Most cartilaginous neoplasms had some level of expression of parathyroid hormone-related peptide, and tumors with a more proliferative phenotype had higher levels of parathyroid hormone-related peptide. Although benign lesions such as enchondromas and osteochondromas had low levels of parathyroid hormone-related peptide, malignant neoplasms such as extraskeletal myxoid chondrosarcomas, dedifferentiated chondrosarcomas, and mesenchymal chondrosarcomas expressed high levels of parathyroid hormone-related peptide. Parathyroid hormone-related peptide expression correlated with grade of malignancy in chondrosarcoma. Although there were highly significant differences between Grade I chondrosarcoma versus Grade II and Grade III lesions, the difference between Grade II and Grade III chondrosarcomas approached significance. Parathyroid hormone-related peptide may represent a new tumor marker with potential diagnostic use in classifying cartilaginous neoplasms.

Ghrelin immunoreactivity in human plasma is suppressed by somatostatin

OBJECTIVE

Ghrelin was recently identified as a specific endogenous ligand for the growth hormone secretagogue receptor (GHS-R). This new hormone was isolated from rat and human stomach and was reported to circulate in human plasma, but the regulation and physiological significance of ghrelin in humans have not been clarified. The present study was undertaken to test the following hypotheses: (1) prolonged fasting, which is known to stimulate GH secretion, is associated with changes in ghrelin immunoreactivity; (2) somatostatin in the systemic circulation regulates ghrelin secretion; and (3) GH affects ghrelin levels.

DESIGN AND PATIENTS

The study population included normal subjects investigated on three occasions (fasting alone, fasting and somatostatin infusion +/- GH); GH-deficient adults investigated after 12 and 36 h of fasting +/- GH, as well as patients with active acromegaly before and after somatostatin analogue treatment.

RESULTS

Somatostatin infusion lowered ghrelin levels 70-80% (P < 0.0001), whereas continued fasting +/- GH did not significantly affect ghrelin levels. In active acromegaly, suppression of plasma ghrelin levels was recorded after a single subcutaneous octreotide injection as well as during prolonged administration of slow-release octreotide.

CONCLUSIONS

(1) Amplification of GH release during prolonged fasting is not caused by an increase in ghrelin immunoreactivity, (2) systemic somatostatin suppresses plasma ghrelin levels independently of GH status, and (3) the feasibility of measuring ghrelin in the circulation provides an opportunity for studying the interaction between hormones and nutrition.

Immunoreactive ghrelin in human cord blood: relation to anthropometry, leptin, and growth hormone

BACKGROUND

Ghrelin is secreted by the stomach, the hypothalamus, and the placenta in humans and has growth hormone-secreting and orexigenic properties. Leptin is secreted mainly by the adipocyte, plays a major role in energy balance, and reflects fat mass in infants as well as adults. Leptin and ghrelin central effects are mediated, at least partly, through the neuropeptide Y/Y1 receptor pathway in the hypothalamus.

METHODS

We determined whether ghrelin is also present in the fetus and investigated its relationship to leptin, growth hormone, birth weight, and calf and abdominal circumferences in 90 full-term neonates.

RESULTS

Immunoreactive ghrelin was detected in all cord samples (mean +/- SD, 187 +/- 88 pmol/L; range, 66-594 pmol/L). In contrast to leptin, ghrelin concentrations of boys and girls were not statistically different. In female neonates, ghrelin is inversely correlated with anthropometric measures. In male neonates, ghrelin is positively correlated with leptin and negatively with growth hormone.

CONCLUSION

The presence of significant ghrelin concentrations in all neonates before the first feeding is intriguing. Unlike the fairly constant concentrations and effects of leptin over the short term, the wide variability of ghrelin concentrations observed in newborns raises the possibility that ghrelin secretion causes short-term changes in feeding behavior. We suggest that ghrelin may play a physiologic role in the initiation of feeding.

[Generation of monoclonal antibody Fab fragments to parathyroid hormone related protein by phage display technology]

OBJECTIVE

To develop monoclonal antibody Fab fragments using display technique.

METHODS

The mouse IgG Fab genes of heavy and light chains were amplified from spleen cells of a parathyroid hormone-related protein (PTHrP) immunized mouse. The combinatorial phage antibody library was prepared by inserting both heavy and light chain Fab genes into phagemid vector pComb3 and followed by infection of helper phage. The library was selected by purified recombinant PTHrP.

RESULTS

The combinatorial phage antibody library was constructed successfully and the specific mouse Fabs to PThrP were selected and expressed in E. coli.

CONCLUSIONS

The selected specific mouse Fabs can recognize PTHrP with high specificity.