Growth hormone protects human lymphocytes from irradiation-induced cell death

Endocrine disorders in Kearns-Sayre syndrome with different severity of symptoms: two case reports and a literature review

Kearns-Sayre Syndrome (KSS) is a variant of mitochondrial disorder caused by a Mitochondrial Deoxyribonucleic Acid (mtDNA) deletion. Clinical manifestations of KSS can include different organ and system involvement. Different organ malfunctions, more often cardiac dysfunction, can lead to death. No effective treatment of this condition exists to date. Here, we report two patients with KSS. Female patient with a large-scale deletion of 7,020 base pairs (bp) suffered from hypogonadism, diabetes mellitus with fluctuating glucose levels, and had poor general health. A male patient with a common 4,977 bp deletion did not have diabetes mellitus but had impaired glucose tolerance. He also had a higher level of general health than our female patient. Both patients had reduced Bone Mineral Density (BMD). In female patients, calcium and vitamin D supplementation combined with metabolic therapy and nutritional drink supplements helped increase BMD (up to 32% in L1-L4). Comparing these two patients suggests that the larger the mtDNA deletion is, the more severe the course of the disease is. Not only does the size of the mtDNA deletion probably determine the severity of the disease, but also such factors as mtDNA heteroplasmy level, presence of mtDNA duplications, and pleioplasmy. Moreover, continuous nonconsecutive metabolic therapy and nutritional supplements are helpful in the prevention of deterioration of symptoms and general health.

The protection role of human growth hormone on skin cells following ultraviolet B exposure

BACKGROUND

Ultraviolet-B (UVB) radiation is the leading environmental cause of skin damage and photoaging. The epidermis and dermis layers of the skin mainly absorb UVB. UVB stimulates apoptosis, cell cycle arrest, generation of reactive oxygen species, and degradation of collagen and elastin fibers.

OBJECTIVE

This study investigated the potential of human growth hormone (hGH) in protecting the skin fibroblasts and keratinocytes (HFFF-2 and HaCaT cell lines) from UVB-induced damage.

METHODS

The MTT assay was performed to evaluate UVB-induced mitochondrial damage via assessing the mitochondrial dehydrogenase activity, and flow cytometry was carried out to investigate the effects of UVB and hGH on the cell cycle and apoptosis of UVB-irradiated cells. In addition, the fold change mRNA expression levels of Type I collagen and elastin in HFFF-2 cells were evaluated using the qRT-PCR method following UVB exposure.

RESULTS

We observed that treatment of cells with hGH before UVB exposure inhibited UVB-induced loss of mitochondrial dehydrogenase activity, apoptosis, and sub-G1 population formation in both cell lines. We also found that hGH-treated HFFF-2 cells showed up-regulated mRNA expression of Type I collagen, elastin, and IGF-1 in response to UVB irradiation.

CONCLUSION

These findings suggest hGH as a potential anti-UVB compound that can protect skin cells from UVB-induced damage. Our findings merit further investigation and can be used to better understand the role of hGH in skin photoaging.

Growth hormone receptor agonists and antagonists: From protein expression and purification to long-acting formulations

Recombinant human growth hormone (rhGH) and GH receptor antagonists (GHAs) are used clinically to treat a range of disorders associated with GH deficiency or hypersecretion, respectively. However, these biotherapeutics can be difficult and expensive to manufacture with multiple challenges from recombinant protein generation through to the development of long-acting formulations required to improve the circulating half-life of the drug. In this review, we summarize methodologies and approaches used for making and purifying recombinant GH and GHA proteins, and strategies to improve pharmacokinetic and pharmacodynamic properties, including PEGylation and fusion proteins. Therapeutics that are in clinical use or are currently under development are also discussed.

Growth hormone enhances the CD34+ stem cells repopulation of the male albino rat thymus gland in cyclophosphamide induced injury: immunohistochemical and electron microscopic study

Cyclophosphamide (CP) is a chemotherapeutic drug that has a harmful effect on the immune system. Growth hormone (GH) is a peptide hormone that can enhance thymic functions in cases of immunosuppression. Therefore, the present study was performed to study the possible protective effect of growth hormone on cyclophosphamide-induced changes in the rat thymus gland. Sixty-four adult male albino rats were used and divided into three main groups. Group I (Control group). Group II (CP group) received 200 mg/kg body weight CP by a single intra-peritoneal injection. Group III (CP& GH group) received GH in a dose of 2 mg/kg body weight/day by subcutaneous injection starting 5 days before cyclophosphamide injection till the end of the experiment. Administration of CP (Group II) resulted in marked histopathological changes in thymus. Thymic cortex showed depletion of thymoblasts. There was a decrease in CD34 immune positively stained stem cells and an increase in CD68 immune positively stained macrophages. Ultrastructurally, thymoblasts were markedly degenerated and the most of epithelial reticular cells were vacuolated. Administration of GH (group III) showed preservation of the histological structure of the thymus. In conclusion, growth hormone could protect against cyclophosphamide induced thymic damage.

Dual Characters of GH-IGF1 Signaling Pathways in Radiotherapy and Post-radiotherapy Repair of Cancers

Radiotherapy remains one of the most important cancer treatment modalities. In the course of radiotherapy for tumor treatment, the incidental irradiation of adjacent tissues could not be completely avoided. DNA damage is one of the main factors of cell death caused by ionizing radiation, including single-strand (SSBs) and double-strand breaks (DSBs). The growth hormone-Insulin-like growth factor 1 (GH-IGF1) axis plays numerous roles in various systems by promoting cell proliferation and inhibiting apoptosis, supporting its effects in inducing the development of multiple cancers. Meanwhile, the GH-IGF1 signaling involved in DNA damage response (DDR) and DNA damage repair determines the radio-resistance of cancer cells subjected to radiotherapy and repair of adjacent tissues damaged by radiotherapy. In the present review, we firstly summarized the studies on GH-IGF1 signaling in the development of cancers. Then we discussed the adverse effect of GH-IGF1 signaling in radiotherapy to cancer cells and the favorable impact of GH-IGF1 signaling on radiation damage repair to adjacent tissues after irradiation. This review further summarized recent advances on research into the molecular mechanism of GH-IGF1 signaling pathway in these effects, expecting to specify the dual characters of GH-IGF1 signaling pathways in radiotherapy and post-radiotherapy repair of cancers, subsequently providing theoretical basis of their roles in increasing radiation sensitivity during cancer radiotherapy and repairing damage after radiotherapy.

The effects of growth hormone on therapy resistance in cancer

Pituitary derived and peripherally produced growth hormone (GH) is a crucial mediator of longitudinal growth, organ development, metabolic regulation with tissue specific, sex specific, and age-dependent effects. GH and its cognate receptor (GHR) are expressed in several forms of cancer and have been validated as an anti-cancer target through a large body of in vitro, in vivo and epidemiological analyses. However, the underlying molecular mechanisms of GH action in cancer prognosis and therapeutic response had been sparse until recently. This review assimilates the critical details of GH-GHR mediated therapy resistance across different cancer types, distilling the therapeutic implications based on our current understanding of these effects.

Growth Hormone (GH) Deficient Mice With GHRH Gene Ablation Are Severely Deficient in Vaccine and Immune Responses Against Streptococcus pneumoniae

The precise impact of the somatotrope axis upon the immune system is still highly debated. We have previously shown that mice with generalized ablation of growth hormone (GH) releasing hormone (GHRH) gene (Ghrh^−/−) have normal thymus and T-cell development, but present a marked spleen atrophy and B-cell lymphopenia. Therefore, in this paper we have investigated vaccinal and anti-infectious responses of Ghrh^−/− mice against S. pneumoniae, a pathogen carrying T-independent antigens. Ghrh^−/− mice were unable to trigger production of specific IgM after vaccination with either native pneumococcal polysaccharides (PPS, PPV23) or protein-PPS conjugate (PCV13). GH supplementation of Ghrh^−/− mice restored IgM response to PPV23 vaccine but not to PCV13 suggesting that GH could exert a specific impact on the spleen marginal zone that is strongly implicated in T-independent response against pneumococcal polysaccharides. As expected, after administration of low dose of S. pneumoniae, wild type (WT) completely cleared bacteria after 24 h. In marked contrast, Ghrh^−/− mice exhibited a dramatic susceptibility to S. pneumoniae infection with a time-dependent increase in lung bacterial load and a lethal bacteraemia already after 24 h. Lungs of infected Ghrh^−/− mice were massively infiltrated by inflammatory macrophages and neutrophils, while lung B cells were markedly decreased. The inflammatory transcripts signature was significantly elevated in Ghrh^−/− mice. In this animal model, the somatotrope GHRH/GH/IGF1 axis plays a vital and unsuspected role in vaccine and immunological defense against S. pneumoniae.

The Impact of Growth Hormone Therapy on the Apoptosis Assessment in CD34+ Hematopoietic Cells from Children with Growth Hormone Deficiency

Growth hormone (GH) modulates hematopoietic cell homeostasis and is associated with apoptosis control, but with limited mechanistic insights. Aim of the study was to determine whether GH therapeutic supplementation (GH-TS) could affect apoptosis of CD34+ cells enriched in hematopoietic progenitor cells of GH deficient (GHD) children. CD34+ cells from peripheral blood of 40 GHD children were collected before and in 3rd and 6th month of GH-TS and compared to 60 controls adjusted for bone age, sex, and pubertal development. Next, apoptosis assessment via different molecular techniques was performed. Finally, to comprehensively characterize apoptosis process, global gene expression profile was determined using genome-wide RNA microarray technology. Results showed that GH-TS significantly reduced spontaneous apoptosis in CD34+ cells (p < 0.01) and results obtained using different methods to detect early and late apoptosis in analyzed cells population were consistent. GH-TS was also associated with significant downregulation of several members of TNF-alpha superfamily and other genes associated with apoptosis and stress response. Moreover, the significant overexpression of cyto-protective and cell cycle-associated genes was detected. These findings suggest that recombinant human GH has a direct anti-apoptotic activity in hematopoietic CD34+ cells derived from GHD subjects in course of GH-TS.

Direct antiapoptotic effects of growth hormone are mediated by PI3K/Akt pathway in the chicken bursa of Fabricius

Growth hormone (GH) is expressed in several extra-pituitary tissues, including the primary and secondary lymphoid organs of the immune system. In birds, GH mRNA and protein expression show a specific developmental distribution pattern in the bursa of Fabricius (BF), particularly in epithelial and B cells. Changes in the bursal concentration and distribution of locally produced GH during ontogeny suggest it is involved in B cell differentiation and maturation, as well as in a functional survival role in this organ, which may be mediated by paracrine/autocrine mechanisms. Here, we analyzed the anti-apoptotic effect of GH in BF and the intracellular signaling pathways involved in this activity. Also, we studied if this effect was exerted directly by GH or mediated indirectly by IGF-I. Bursal cell cultures showed an important loss of their viability after 4h of incubation and a significant increase in apoptosis. However, treatment with 10nM GH or 40 nM IGF-I significantly increased B cell viability (16.7 ± 0.67% and 13.4 ± 1.12%, respectively) when compared with the untreated controls. In addition, the presence of apoptotic bodies (TUNEL) dramatically decreased (5.5-fold) after GH and IGF-I treatments, whereas co-incubation with anti-GH or anti-IGF-I, respectively, blocked their anti-apoptotic effect. Likewise, both GH and IGF-I significantly inhibited caspase-3 activity (by 40 ± 2.0%) in these cultures. However, the use of anti-IGF-I could not reverse the GH anti-apoptotic effects, thus indicating that these were exerted directly. The addition of 100 nM wortmannin (a PI3K/Akt inhibitor) blocked the GH protective effects. Also, GH stimulated (3-fold) the phosphorylation of Akt in bursal cells, and adding wortmannin or an anti-GH antibody inhibited this effect. Furthermore, GH was capable to stimulate (7-fold) the expression of Bcl-2. Taken together, these results indicate that the direct anti-apoptotic activity of GH observed in the chicken bursal B cell cultures might be mediated through the PI3K/Akt pathway.

The Effect of Growth Hormone Administration on the Regulation of Mitochondrial Apoptosis in-Vivo

The purpose of this study was to determine whether recombinant human growth hormone (rhGH) would show any significant effects on the expression of apoptosis regulating proteins in peripheral blood mononuclear cells (PBMCs). Additionally, the potential for post-transcriptional regulation of gene expression by miRNA was assessed in two cellular compartments, the cytosol and the mitochondria. Ten male subjects were subcutaneously injected with either rhGH (1 mg) or saline (0.9%) for seven consecutive days in a double-blinded fashion. Blood sampling was undertaken prior to treatment administration and over a period of three weeks following treatment cessation. Bcl-2 and Bak gene and protein expression levels were measured in PBMCs, while attention was also directed to the expression of miR-181a and miR-125b, known translational inhibitors of Bcl-2 and Bak respectively. Results showed that rhGH significantly decreased Bak protein concentrations compared to placebo samples for up to 8 days post treatment. While cytosolic miRNA expression was not found to be significantly affected by rhGH, measurement of the expression of miR-125b in mitochondrial fractions showed a significant down-regulation eight days post-rhGH administration. These findings suggest that rhGH induces short-term anti-apoptotic effects which may be partially mediated through a novel pathway that alters the concentration of mitochondrially-associated miRNAs.

Expression and function of chicken bursal growth hormone (GH)

Growth hormone (GH) has several effects on the immune system. Our group has shown that GH is produced in the chicken bursa of Fabricius (BF) where it may act as an autocrine/paracrine modulator that participates in B-cell differentiation and maturation. The time course of GH mRNA and protein expression in the BF suggests that GH may be involved in development and involution of the BF, since GH is known to be present mainly in B lymphocytes and epithelial cells. In addition, as GH is anti-apoptotic in other tissues, we assessed the possibility that GH promotes cell survival in the BF. This work focused on determining the mechanism by which GH can inhibit apoptosis of B cells and if the PI3K/Akt pathway is activated. Bursal cell cultures were treated with a range of GH concentrations (0.1-100nM). The addition of 10nM GH significantly increased viability (16.7±0.6%) compared with the control and decreased caspase-3 activity to 40.6±6.5% of the control. Together, these data indicate that GH is produced locally in the BF and that the presence of exogenous GH in B cell cultures has antiapoptotic effects and increases B cell survival, probably through the PI3k/Akt pathway.

Autocrine human GH promotes radioresistance in mammary and endometrial carcinoma cells

Although recent advances in breast cancer treatment regimes have improved patient prognosis, resistance to breast cancer therapies, such as radiotherapy, is still a major clinical challenge. In the current study, we have investigated the role of autocrine human GH (hGH) in resistance to ionising radiation (IR)-based therapy. Cell viability and total cell number assays demonstrated that autocrine hGH promoted cell regrowth in the mammary carcinoma cell lines, MDA-MB-435S and T47D, and the endometrial carcinoma cell line, RL95-2, following treatment with IR. In addition, autocrine hGH enhanced MDA-MB-435S and T47D cell clonogenic survival following radiation exposure. The enhanced clonogenic survival afforded by autocrine hGH was mediated by JAK2 and Src kinases. Investigation into the DNA repair capacity demonstrated that autocrine hGH reduced IR-induced DNA damage in MDA-MB-435S and T47D cells. Functional antagonism of hGH increased RL95-2 sensitivity to IR in cell viability and total cell number assays, reduced clonogenic survival and enhanced the induction of DNA damage. Thus, autocrine hGH reduced sensitivity to treatment with IR in mammary and endometrial carcinoma cell lines in vitro, while functional antagonism of hGH sensitised endometrial carcinoma cells to IR. Functional antagonism of hGH, used in conjunction with radiotherapy, may therefore enhance treatment efficacy and improve the prognosis of patients with breast and endometrial cancer.

Impact of different concentrations of human recombinant growth hormone on T lymphocytes

The aim of the present study is to evaluate the effects induced by increasing concentrations of human recombinant growth hormone on T lymphocytes. Ten healthy volunteers and twelve subjects with symptomatic allergies were enrolled in the study. Peripheral blood mononuclear cells and purified T lymphocytes were cultured in the presence of graded concentrations of growth hormone. Following appropriate in vitro stimulations, the proportion of apoptotic T cells, the percentage of activated T lymphocyte subpopulations, the phytohemagglutinin responsiveness and the Th2 response were assessed by flow cytometry analysis. Moreover, in order to evaluate the phosphoinositol-3-kinase signaling pathway involvement, cells were also analyzed after treatment with LY294002. The treatment with different concentrations of growth hormone did not influence the activation pattern of un-stimulated T lymphocytes. On the contrary, growth hormone was able to modify the CD38/HLA-DR co-expression of T cells activated with phytohemoagglutinin. A different response was observed when samples obtained from healthy donors and from subjects with symptomatic allergies were analysed. Moreover, growth hormone treatment was able to increase the Th2 response in the samples obtained from healthy donors only. The results of the present study strongly support the hypothesis that growth hormone administration may play an important role in conditions of impaired/activated immune systems. The observation that growth hormone administration at high doses may reverse its effects and that it may promote a Th2-oriented response have significant clinical implications when considering the use of this hormone for artificially enhancing the physical performances of healthy athletes.

Expression of the growth hormone/insulin-like growth factor axis during Balb/c thymus ontogeny and effects of growth hormone upon ex vivo T cell differentiation

AIMS

We address the question of the expression and the role of the growth hormone/insulin-like growth factor (GH/IGF) axis in the thymus.

METHODS

Using RT-qPCR, the expression profile of various components of the somatotrope GH/IGF axis was measured in different thymic cell types and during thymus embryogenesis in Balb/c mice. The effect of GH on T cell differentiation was explored via thymic organotypic culture.

RESULTS

Transcription of Gh, Igf1, Igf2 and their related receptors predominantly occurred in thymic epithelial cells (TEC), while a low level of Gh and Igf1r transcription was also evidenced in thymic T cells (thymocytes). Gh, Ghr, Ins2, Igf1, Igf2, and Igfr1 displayed distinct expression profiles depending on the developmental stage. The protein concentrations of IGF-1 and IGF-2 were in accordance with the profile of their gene expression. In fetal thymus organ cultures (FTOC) derived from Balb/c mice, treatment with exogenous GH resulted in a significant increase of double negative CD4-CD8- T cells and CD4+ T cells, together with a decrease in double positive CD4+CD8+ T cells. These changes were inhibited by concomitant treatment with GH and the GH receptor (GHR) antagonist pegvisomant. However, GH treatment also induced a significant decrease in FTOC Gh, Ghr and Igf1 expression.

CONCLUSION

These data show that the thymotropic properties of the somatotrope GH/IGF-1 axis involve an interaction between exogenous GH and GHR expressed by TEC. Since thymic IGF-1 is not increased by GH treatment, the effects of GH upon T cell differentiation could implicate a different local growth factor or cytokine.

Role of the growth hormone-IGF-1 axis in cancer

A substantial body of evidence supports a role for the growth hormone (GH)-IGF-1 axis in cancer incidence and progression. This includes epidemiological evidence relating elevated plasma IGF-1 to cancer incidence as well as a lack of cancers in GH/IGF-1 deficiency. Rodent models lacking GH or its receptor are strikingly resistant to the induction of a wide range of cancers, and treatment with the GH antagonist pegvisomant slows tumor progression. While GH receptor expression is elevated in many cancers, autocrine GH is present in several types, and overexpression of autocrine GH can induce cell transformation. While the mechanism of autocrine action is not clear, it does involve both STAT5 and STAT3 activation, and probably nuclear translocation of the GH receptor. Development of a more potent GH receptor antagonist or secretion inhibitor is warranted for cancer therapy.

Rejuvenation of the aging thymus: growth hormone-mediated and ghrelin-mediated signaling pathways

One of the major fundamental causes for the aging of the immune system is the structural and functional involution of the thymus, and the associated decline in de novo naïve T-lymphocyte output. This loss of naïve T-cell production weakens the ability of the adaptive immune system to respond to new antigenic stimuli and eventually leads to a peripheral T-cell bias to the memory phenotype. While the precise mechanisms responsible for age-associated thymic involution remain unknown, a variety of theories have been forwarded including the loss of expression of various growth factors and hormones that influence the lymphoid compartment and promote thymic function. Extensive studies examining two hormones, namely growth hormone (GH) and ghrelin (GRL), have demonstrated their contributions to thymus biology. In the current review, we discuss the literature supporting a role for these hormones in thymic physiology and age-associated thymic involution and their potential use in the restoration of thymic function in aged and immunocompromised individuals.

Growth hormone mitigates against lethal irradiation and enhances hematologic and immune recovery in mice and nonhuman primates

Medications that can mitigate against radiation injury are limited. In this study, we investigated the ability of recombinant human growth hormone (rhGH) to mitigate against radiation injury in mice and nonhuman primates. BALB/c mice were irradiated with 7.5 Gy and treated post-irradiation with rhGH intravenously at a once daily dose of 20 microg/dose for 35 days. rhGH protected 17 out of 28 mice (60.7%) from lethal irradiation while only 3 out of 28 mice (10.7%) survived in the saline control group. A shorter course of 5 days of rhGH post-irradiation produced similar results. Compared with the saline control group, treatment with rhGH on irradiated BALB/c mice significantly accelerated overall hematopoietic recovery. Specifically, the recovery of total white cells, CD4 and CD8 T cell subsets, B cells, NK cells and especially platelets post radiation exposure were significantly accelerated in the rhGH-treated mice. Moreover, treatment with rhGH increased the frequency of hematopoietic stem/progenitor cells as measured by flow cytometry and colony forming unit assays in bone marrow harvested at day 14 after irradiation, suggesting the effects of rhGH are at the hematopoietic stem/progenitor level. rhGH mediated the hematopoietic effects primarily through their niches. Similar data with rhGH were also observed following 2 Gy sublethal irradiation of nonhuman primates. Our data demonstrate that rhGH promotes hematopoietic engraftment and immune recovery post the exposure of ionizing radiation and mitigates against the mortality from lethal irradiation even when administered after exposure.

Growth hormone expression in stromal and non-stromal cells in the bursa of Fabricius during bursal development and involution: Causal relationships?

Growth hormone (GH) is expressed in the chicken bursa of Fabricius (BF), an organ that undergoes three distinct developmental stages: rapid growth (late embryogenesis until 6-8 weeks of age [w]), plateaued growth (between 10 and 15w), and involution (after 18-20w). The distribution and abundance of GH-immunoreactivity (GH-IR) and GH mRNA expression in stromal and non-stromal bursal cells during development, as well as the potential anti-apoptotic effect of GH in bursal cell survival were the focus of this study. GH mRNA expression was mainly in the epithelial layer and in epithelial buds at embryonic day (ED) 15; at 2w it was widely distributed within the follicle and in the interfollicular epithelium (IFE); at 10w it clearly diminished in the epithelium; whereas at 20w it occurred in only a few cortical cells and in the connective tissue. Parallel changes in the relative proportion of GH mRNA expression (12, 21, 13, 1%) and GH-IR (19, 18, 11, <3%) were observed at ED 15, 2w, 10w, and 20w, respectively. During embryogenesis, GH-IR co-localized considerably with IgM-IR, but scarcely with IgG-IR, whereas the opposite was observed after hatching. Significant differences in bursal cell death occurred during development, with 9.3% of cells being apoptotic at ED 15, 0.4% at 2w, 0.23% at 10w, and 21.1% at 20w. Addition of GH increased cultured cell survival by a mechanism that involved suppression (up to 41%) of caspase-3 activity. Results suggest that autocrine/paracrine actions of bursal GH are involved in the differentiation and proliferation of B lymphocytes and in BF growth and cell survival in embryonic and neonatal chicks, whereas diminished GH expression in adults may result in bursal involution.

Expression, regulation and biological actions of growth hormone (GH) and ghrelin in the immune system

Immune and neuroendocrine systems have bidirectional communications. Growth hormone (GH) and an orexigenic hormone ghrelin are expressed in various immune cells such as T lymphocytes, B lymphocytes, monocytes and neutrophils. These immune cells also bear receptors for hormones: growth hormone receptor (GHR) for GH and growth hormone secretagogue receptor (GHS-R) for ghrelin. The expression of GH in immune cells is stimulated by ghrelin as in anterior pituitary cells, whereas the regulation of GH secretion in the immune system by other peptides seems to be different from that in the anterior pituitary gland. Cytokines and mitogens enhance GH secretion from immune cells. GH has several biological actions in the immune system: enhancing thymopoiesis and T cell development, modulating cytokine production, enhancing B cell development and antibody production, priming neutrophils and monocytes for superoxide anion secretion, enhancing neutrophil adhesion and monocyte migration and anti-apoptotic action. Biological actions of ghrelin include attenuation of septic shock and anti-inflammatory actions, modulating phagocytosis, and enhancing thymopoiesis. The effect of ghrelin may be direct or through GH production, and that of GH may be direct or through insulin like growth factor-I (IGF-I) production. Elucidation of the roles of GH and ghrelin in the immune system may shed light on the treatment and prevention of immunological disorders such as AIDS and organ damages due to obesity/ageing-related chronic inflammation.

Neuroendocrine hormones such as growth hormone and prolactin are integral members of the immunological cytokine network

Neuroendocrine hormones such as growth hormone (GH) and prolactin (PRL) have been demonstrated to accelerate the recovery of the immune response after chemotherapy and bone marrow transplantation and to enhance the restoration of immunity in individuals infected with HIV and in normal individuals with compromised immune systems associated with aging. As the mechanism of action of these hormones has been elucidated, it has become clear that they are integral members of the immunological cytokine/chemokine network and share regulatory mechanisms with a wide variety of cytokines and chemokines. The members of this cytokine network induce and can be regulated by members of the suppressor of cytokine signaling (SOCS) family of intracellular proteins. In order to take advantage of the potential beneficial effects of hormones such as GH or PRL, it is essential to take into consideration the overall cytokine network and the regulatory effects of SOCS proteins.

Variable outcome of growth hormone administration in respiratory chain deficiency

Genetic defects of oxidative phosphorylation (OXPHOS) are known to account for a variety of neuromuscular and non-neuromuscular symptoms in childhood, including growth hormone (GH) deficiency. However GH administration for GH deficiency is controversial in OXPHOS deficiencies as GH is a mitosis-stimulator which may increase energy demand for cell proliferation. Here, we report the observation of four unrelated children with OXPHOS deficiency or bearing a mitochondrial DNA rearrangement and growth retardation, who required GH therapy. The first patient had no GH deficiency while the other three had low GH response to test stimulations. The condition of the first two patients quickly deteriorated under GH administration, GH was then stopped and subsequent clinical improvement was noted. In the other two patients, no adverse event was noted but various additional organs were involved following GH administration. In all patients, no benefit was observed concerning growth response as growth speed remained unchanged. These observations question the use of GH as a treatment of growth retardation for patients with OXPHOS deficiency.

Is growth hormone a radioprotective agent?

There is currently substantial clinical interest in growth hormone (GH) as a protective agent against radiation-related normal tissue injury. To further assess the potential radiation injury-preventive effects of GH, these effects were studied in rats by using a radiation-induced skin injury model. Group 1 received neither GH nor irradiation (control group). Group 2 received 30 Gy of gamma irradiation as a single dose to the right hind legs of the rats (radiation group). Group 3 and 4 received the same irradiation plus either 0.01 U/kg/day GH (RT + 0.01 GH group) or 0.02 U/kg/day GH (RT + 0.02 GH group) subcutaneously. Clinically and histopathologically, acute skin reactions were assessed by two independent experts in radiation oncology and pathology, respectively. Irradiation increased dermatitis in rats when compared with the control group. The severity of radiodermatitis in the rats in the RT + 0.01 GH and RT + 0.02 GH groups was significantly lower than that in the RT group; radiodermatitis developed earlier in the RT group than in the other groups. GH was efficacious in preventing epidermal atrophy, dermal degeneration such as oedema and collagen fibre loss, and hair follicle atrophy, but not better than in the control group. These results are preliminary to studies that will be performed with higher doses of GH in radiation-treated cancer patients, with the aim of reducing radiation-induced toxicity.