Expression of lymphocyte-derived growth hormone (GH) and GH-releasing hormone receptors in aging rats

Growth hormone releasing hormone signaling promotes Th17 cell differentiation and autoimmune inflammation

Dysregulation of Th17 cell differentiation and pathogenicity contributes to multiple autoimmune and inflammatory diseases. Previously growth hormone releasing hormone receptor (GHRH-R) deficient mice have been reported to be less susceptible to the induction of experimental autoimmune encephalomyelitis. Here, we show GHRH-R is an important regulator of Th17 cell differentiation in Th17 cell-mediated ocular and neural inflammation. We find that GHRH-R is not expressed in naïve CD4⁺ T cells, while its expression is induced throughout Th17 cell differentiation in vitro. Mechanistically, GHRH-R activates the JAK-STAT3 pathway, increases the phosphorylation of STAT3, enhances both non-pathogenic and pathogenic Th17 cell differentiation and promotes the gene expression signatures of pathogenic Th17 cells. Enhancing this signaling by GHRH agonist promotes, while inhibiting this signaling by GHRH antagonist or GHRH-R deficiency reduces, Th17 cell differentiation in vitro and Th17 cell-mediated ocular and neural inflammation in vivo. Thus, GHRH-R signaling functions as a critical factor that regulates Th17 cell differentiation and Th17 cell-mediated autoimmune ocular and neural inflammation.

Immunosuppression by opioids: Mechanisms of action on innate and adaptive immunity

Opioids are excellent analgesics for the clinical treatment of various types of acute and chronic pain, particularly cancer-related pain. Nevertheless, it is well known that opioids have some nasty side effects, including immunosuppression, which is commonly overlooked. As a result, the incidence of opportunistic bacterial and viral infections increases in patients with long-term opioid use. Nowadays, there are no effective medications to alleviate opioid-induced immunosuppression. Understanding the underlying molecular mechanism of opioids in immunosuppression can enable researchers to devise effective therapeutic interventions. This review comprehensively summarized the exogenous opioids-induced immunosuppressive effects and their underlying mechanisms, the regulatory roles of endogenous opioids on the immune system, the potential link between opioid immunosuppressive effect and the function of the central nervous system (CNS), and the future perspectives in this field.

Serum Metabonomics Reveals Key Metabolites in Different Types of Childhood Short Stature

Nowadays, short stature (SS) in childhood is a common condition encountered by pediatricians, with an increase in not just a few families. Various studies related to the variations in key metabolites and their biological mechanisms that lead to SS have increased our understanding of the pathophysiology of the disease. However, little is known about the role of metabolite variation in different types of childhood SS that influence these biological processes and whether the understanding of the key metabolites from different types of childhood SS would predict the disease progression better. We performed a systematic investigation using the metabonomics method and studied the correlation between the three groups, namely, the control, idiopathic short stature (ISS), and short stature due to growth hormone deficiency (GHD). We observed that three pathways (viz., purine metabolism, sphingolipid signaling pathway, and sphingolipid metabolism) were significantly enriched in childhood SS. Moreover, we reported that two short peptides (Thr Val Leu Thr Ser and Trp Ile Lys) might play a significant role in childhood SS. Various metabolites in different pathways including 9,10-DiHOME, 12-HETE, 12(13)-EpOME, arachidonic acid methyl ester, glycerophospho-N-arachidonoyl ethanolamine, curvulinic acid (2-acetyl-3,5-dihydroxyphenyl acetic acid), nonanoic acid, and N'-(2,4-dimethylphenyl)-N-methylformamidine in human serum were compared between 60 children diagnosed with SS and 30 normal-height children. More investigations in this area may provide insights and enhance the personalized treatment approaches in clinical practice for SS by elucidating pathophysiology mechanisms of experimental verification.

Improvement of cardiac and systemic function in old mice by agonist of growth hormone-releasing hormone

Age-related diseases such as cardiovascular diseases portend disability, increase health expenditures, and cause late-life mortality. Synthetic agonists of growth hormone-releasing hormone (GHRH) exhibit several favorable effects on heart function and remodeling. Here we assessed whether GHRH agonist MR409 can modulate heart function and systemic parameters in old mice. Starting at the age of 15 months, mice were injected subcutaneously with MR409 (10 µg/day, n = 8) or vehicle (n = 7) daily for 6 months. Mice treated with MR409 showed improvements in exercise activity, cardiac function, survival rate, immune function, and hair growth in comparison with the controls. More stem cell colonies were grown out of the bone marrow recovered from the MR409-treated mice. Mitochondrial functions of cardiomyocytes (CMs) from the MR409-treated mice were also significantly improved with more mitochondrial fusion. Fewer β-gal positive cells were observed in endothelial cells after 10 passages with MR409. In Doxorubicin-treated H9C2 cardiomyocytes, cell senescence marker p21 and reactive oxygen species were significantly reduced after cultured with MR409. MR409 also improved cellular ATP production and oxygen consumption rate in Doxorubicin-treated H9C2 cells. Mitochondrial protein OPA1 long isoform was significantly increased after treatment with MR409. The effects of MR409 were mediated by GHRH receptor and protein kinase A (PKA). In short, GHRH agonist MR409 reversed the aging-associated changes with respect of heart function, mobility, hair growth, cellular energy production, and senescence biomarkers. The improvement of heart function may be related to a better mitochondrial functions through GHRH receptor/cAMP/PKA/OPA1 signaling pathway and relieved cardiac inflammation.

Thyrotropin-Releasing Hormone (TRH) and Somatostatin (SST), but not Growth Hormone-Releasing Hormone (GHRH) nor Ghrelin (GHRL), Regulate Expression and Release of Immune Growth Hormone (GH) from Chicken Bursal B-Lymphocyte Cultures

It is known that growth hormone (GH) is expressed in immune cells, where it exerts immunomodulatory effects. However, the mechanisms of expression and release of GH in the immune system remain unclear. We analyzed the effect of growth hormone-releasing hormone (GHRH), thyrotropin-releasing hormone (TRH), ghrelin (GHRL), and somatostatin (SST) upon GH mRNA expression, intracellular and released GH, Ser133-phosphorylation of CREB (pCREB^S133), intracellular Ca²⁺ levels, as well as B-cell activating factor (BAFF) mRNA expression in bursal B-lymphocytes (BBLs) cell cultures since several GH secretagogues, as well as their corresponding receptors (-R), are expressed in B-lymphocytes of several species. The expression of TRH/TRH-R, ghrelin/GHS-R1a, and SST/SST-Rs (Subtypes 1 to 5) was observed in BBLs by RT-PCR and immunocytochemistry (ICC), whereas GHRH/GHRH-R were absent in these cells. We found that TRH treatment significantly increased local GH mRNA expression and CREB phosphorylation. Conversely, SST decreased GH mRNA expression. Additionally, when added together, SST prevented TRH-induced GH mRNA expression, but no changes were observed in pCREB^S133 levels. Furthermore, TRH stimulated GH release to the culture media, while SST increased the intracellular content of this hormone. Interestingly, SST inhibited TRH-induced GH release in a dose-dependent manner. The coaddition of TRH and SST decreased the intracellular content of GH. After 10 min. of incubation with either TRH or SST, the intracellular calcium levels significantly decreased, but they were increased at 60 min. However, the combined treatment with both peptides maintained the Ca²⁺ levels reduced up to 60-min. of incubation. On the other hand, BAFF cytokine mRNA expression was significantly increased by TRH administration. Altogether, our results suggest that TRH and SST are implicated in the regulation of GH expression and release in BBL cultures, which also involve changes in pCREB^S133 and intracellular Ca²⁺ concentration. It is likely that TRH, SST, and GH exert autocrine/paracrine immunomodulatory actions and participate in the maturation of chicken BBLs.

MECHANISMS IN ENDOCRINOLOGY: Lessons from growth hormone receptor gene-disrupted mice: are there benefits of endocrine defects?

Growth hormone (GH) is produced primarily by anterior pituitary somatotroph cells. Numerous acute human (h) GH treatment and long-term follow-up studies and extensive use of animal models of GH action have shaped the body of GH research over the past 70 years. Work on the GH receptor (R)-knockout (GHRKO) mice and results of studies on GH-resistant Laron Syndrome (LS) patients have helped define many physiological actions of GH including those dealing with metabolism, obesity, cancer, diabetes, cognition and aging/longevity. In this review, we have discussed several issues dealing with these biological effects of GH and attempt to answer the question of whether decreased GH action may be beneficial.

Regulation of Vascular Calcification by Growth Hormone-Releasing Hormone and Its Agonists

RATIONALE

Vascular calcification (VC) is a marker of the severity of atherosclerotic disease. Hormones play important roles in regulating calcification; estrogen and parathyroid hormones exert opposing effects, the former alleviating VC and the latter exacerbating it. To date no treatment strategies have been developed to regulate clinical VC.

OBJECTIVE

The objective of this study was to investigate the effect of growth hormone-releasing hormone (GHRH) and its agonist (GHRH-A) on the blocking of VC in a mouse model.

METHODS AND RESULTS

Young adult osteoprotegerin-deficient mice were given daily subcutaneous injections of GHRH-A (MR409) for 4 weeks. Significant reductions in calcification of the aortas of MR409-treated mice were paralleled by markedly lower alkaline phosphatase activity and a dramatic reduction in the expression of transcription factors, including the osteogenic marker gene Runx2 and its downstream factors, osteonectin and osteocalcin. The mechanism of action of GHRH-A was dissected in smooth muscle cells isolated from human and mouse aortas. Calcification of smooth muscle cells induced by osteogenic medium was inhibited in the presence of GHRH or MR409, as evidenced by reduced alkaline phosphatase activity and Runx2 expression. Inhibition of calcification by MR409 was partially reversed by MIA602, a GHRH antagonist, or a GHRH receptor-selective small interfering RNA. Treatment with MR409 induced elevated cytosolic cAMP and its target, protein kinase A which in turn blocked nicotinamide adenine dinucleotide phosphate oxidase activity and reduced production of reactive oxygen species, thus blocking the phosphorylation of nuclear factor κB (p65), a key intermediate in the ligand of receptor activator for nuclear factor-κ B-Runx2/alkaline phosphatase osteogenesis program. A protein kinase A-selective small interfering RNA or the chemical inhibitor H89 abolished these beneficial effects of MR409.

CONCLUSIONS

GHRH-A controls osteogenesis in smooth muscle cells by targeting cross talk between protein kinase A and nuclear factor κB (p65) and through the suppression of reactive oxygen species production that induces the Runx2 gene and alkaline phosphatase. Inflammation-mediated osteogenesis is thereby blocked. GHRH-A may represent a new pharmacological strategy to regulate VC.

Hormones in the immune system and their possible role. A critical review

Immune cells synthesize, store and secrete hormones, which are identical with the hormones of the endocrine glands. These are: the POMC hormones (ACTH, endorphin), the thyroid system hormones (TRH, TSH, T3), growth hormone (GH), prolactin, melatonin, histamine, serotonin, catecholamines, GnRH, LHRH, hCG, renin, VIP, ANG II. This means that the immune cells contain all of the hormones, which were searched at all and they also have receptors for these hormones. From this point of view the immune cells are similar to the unicells (Tetrahymena), so it can be supposed that these cells retained the properties characteristic at a low level of phylogeny while other cells during the evolution accumulated to form endocrine glands. In contrast to the glandular endocrine cells, immune cells are polyproducers and polyreceivers. As they are mobile cells, they are able to transport the stored hormone to different places (packed transport) or attracted by local factors, accumulate in the neighborhood of the target, synthesizing and secreting hormones locally. This is taking place, e.g. in the case of endorphin, where the accumulating immune cells calms pain caused by the inflammation. The targeted packed transport is more economical than the hormone-pouring to the blood circulation of glandular endocrines and the targeting also cares the other receptor-bearing cells timely not needed the effect. Mostly the immune-effects of immune-cell derived hormones were studied (except endorphin), however, it is not exactly cleared, while the system could have scarcely studied important roles in other cases. The evolutionary aspects and the known as well, as possible roles of immune-endocrine system and their hormones are listed and discussed.

Lymphocyte GH-axis hormones in immunity

The production and utilization of common ligands and their receptors by cells of the immune and neuroendocrine systems constitutes a biochemical information circuit between and within the immune and neuroendocrine systems. The sharing of ligands and receptors allows the immune system to serve as the sixth sense notifying the nervous system of the presence of foreign entities. Within this framework, it is also clear that immune cell functions can be altered by neuroendocrine hormones and that cells of the immune system have the ability to produce neuroendocrine hormones. This review summarizes a part of this knowledge with particular emphasis on growth hormone (GH). The past two decades have uncovered a lot of detail about the actions of GH, acting through its receptor, at the molecular and cellular level and its influence on the immune system. The production and action of immune cell-derived GH is less well developed although its important role in immunity is also slowly emerging. Here we discuss the production of GH, GH-releasing hormone (GHRH) and insulin-like growth factor-1 (IGF-1) and their cognate receptors on cells of the immune system and their influence via endocrine/autocrine/paracrine and intracrine pathways on immune function. The intracellular mechanisms of action of immune cell-derived GH are still largely unexplored, and it is anticipated that further work in this particular area will establish an important role for this source of GH in normal physiology and in pathologic situations.