Reduction in superoxide anion secretion and bactericidal activity of neutrophils from aged rats: reversal by the combination of gamma interferon and growth hormone

Updates on Old and Weary Haematopoiesis

Blood formation, or haematopoiesis, originates from haematopoietic stem cells (HSCs), whose functions and maintenance are regulated in both cell- and cell non-autonomous ways. The surroundings of HSCs in the bone marrow create a specific niche or microenvironment where HSCs nest that allows them to retain their unique characteristics and respond rapidly to external stimuli. Ageing is accompanied by reduced regenerative capacity of the organism affecting all systems, due to the progressive decline of stem cell functions. This includes blood and HSCs, which contributes to age-related haematological disorders, anaemia, and immunosenescence, among others. Furthermore, chronological ageing is characterised by myeloid and platelet HSC skewing, inflammageing, and expanded clonal haematopoiesis, which may be the result of the accumulation of preleukaemic lesions in HSCs. Intriguingly, haematological malignancies such as acute myeloid leukaemia have a high incidence among elderly patients, yet not all individuals with clonal haematopoiesis develop leukaemias. Here, we discuss recent work on these aspects, their potential underlying molecular mechanisms, and the first cues linking age-related changes in the HSC niche to poor HSC maintenance. Future work is needed for a better understanding of haematopoiesis during ageing. This field may open new avenues for HSC rejuvenation and therapeutic strategies in the elderly.

Inflammaging and the Lung

With the coming of the "silver tsunami," expanding the knowledge about how various intrinsic and extrinsic factors affect the immune system in the elderly is timely and of immediate clinical need. The global population is increasing in age. By the year 2030, more than 20% of the population of the United States will be older than 65 years of age. This article focuses on how advanced age alters the immune systems and how this, in turn, modulates the ability of the aging lung to deal with infectious challenges from the outside world and from within the host.

Innate immune responses in the ageing lung

The world is undergoing an unprecedented shift in demographics, with the number of individuals over the age of 60 years projected to reach 2 billion or more by 2050, representing 22% of the global population. Elderly people are at a higher risk for chronic disease and more susceptible to infection, due in part to age-related dysfunction of the immune system resulting from low-grade chronic inflammation known as 'inflamm-ageing'. The innate immune system of older individuals exhibits a diminished ability to respond to microbial threats and clear infections, resulting in a greater occurrence of many infectious diseases in elderly people. In particular, the incidence of and mortality from lung infections increase sharply with age, with such infections often leading to worse outcomes, prolonged hospital stays and life-threatening complications, such as sepsis or acute respiratory distress syndrome. In this review, we highlight research on bacterial pneumonias and pulmonary viral infections and discuss age-related changes in innate immunity that contribute to the higher rate of these infections in older populations. By understanding more clearly the innate immune defects in elderly individuals, we can design age-specific therapies to address lung infections in such a vulnerable population.

Repeated dose 28-day oral toxicity study of moniliformin in rats

Moniliformin is a Fusarium mycotoxin mainly produced by several species infecting grains in different climatic conditions. According to our previous studies, it is acutely toxic to rats, with an LD50 cut-off value of 25mg/kg b.w. To further assess the possible health risks of low dose exposure to moniliformin, a subacute oral toxicity study was conducted in Sprague-Dawley rats, adapting OECD guideline 407. Five dose groups and two satellite groups, each consisting of five male rats, were daily exposed to moniliformin by gavage. Two rats in the highest dose group, showed decreased activity followed by acute heart failure and death. The rats of the lower doses (<9mg/kg b.w.) showed no signs of toxicity. The daily intake of moniliformin strongly reduced the phagocytic activity of neutrophils in all dose groups. The decrease continued in the satellite group during the follow-up period, indicating a severe impact on the immune system and a LOAEL value of 3mg/kg b.w. for moniliformin. Moniliformin was rapidly excreted into urine, ranging between 20.2 and 31.5% daily and showed no signs of accumulation. The concentration of moniliformin in faeces was less than 2%, which suggests efficient absorption from the gastrointestinal tract.

Immunosenescence and organ transplantation

Increasing numbers of elderly transplant recipients and a growing demand for organs from older donors impose pressing challenges on transplantation medicine. Continuous and complex modifications of the immune system in parallel to aging have a major impact on transplant outcome and organ quality. Both, altered alloimmune responses and increased immunogenicity of organs present risk factors for inferior patient and graft survival. Moreover, a growing body of knowledge on age-dependent modifications of allorecognition and alloimmune responses may require age-adapted immunosuppression and organ allocation. Here, we summarize relevant aspects of immunosenescence and their possible clinical impact on organ transplantation.

Innate immune dysfunctions in aged mice facilitate the systemic dissemination of methicillin-resistant S. aureus

Elderly humans show increased susceptibility to invasive staphylococcal disease after skin and soft tissue infection. However, it is not understood how host immunity changes with aging, and how that predisposes to invasive disease. In a model of severe skin infection, we showed that aged mice (16- to 20-month-old) exhibit dramatic bacterial dissemination compared with young adult mice (2-month-old). Bacterial dissemination was associated with significant reductions of CXCL1 (KC), polymorphonuclear cells (PMNs), and extracellular DNA traps (NETs) at the infection site. PMNs and primary skin fibroblasts isolated from aged mice showed decreased secretion of CXCL2 (MIP-2) and KC in response to MRSA, and in vitro analyses of mitochondrial functions revealed that the mitochondrial electron transport chain complex I plays a significant role in induction of chemokines in the cells isolated from young but not old mice. Additionally, PMNs isolated from aged mice have reduced ability to form NETs and to kill MRSA. Expression of nuclease by S. aureus led to increased bacterial systemic dissemination in young but not old mice, suggesting that defective NETs formation in elderly mice permitted nuclease and non-nuclease expressing S. aureus to disseminate equally well. Overall, these findings suggest that gross impairment of both skin barrier function and innate immunity contributes to the propensity for MRSA to disseminate in aged mice. Furthermore, the study indicates that contribution of bacterial factors to pathogenicity may vary with host age.

Role of allergen sensitization in older adults

There is a common perception among physicians and patients that allergic diseases are not relevant in older adults. There is also recognition that innate and adaptive immune functions decline with aging. It is the function of a variety of immune cells in the form of allergic inflammation that is a hallmark of allergic diseases. In fact, there is a fairly consistent observation that measures of allergic sensitization, such as skin prick testing, specific IgE, or total IgE, decline with age. Nonetheless, the association between allergic sensitization and allergic diseases, particularly asthma and allergic rhinitis, remains robust in the older adult population. Consequently, an appropriate evaluation of allergic sensitivities is warranted and indicated in older asthma and rhinitis patients to provide optimal care for the individual and minimize any resultant morbidity and mortality.

Allergy and asthma in the elderly

Allergies and asthma are diseases that affect individuals of all ages, and their prevalence is comparable in all age groups. As age demographics in the United States and other countries shift to greater proportions and numbers of patients in the "elderly" categories, it is becoming increasingly important for clinicians to become aware of the impact of aging on a variety of diseases. Allergy and asthma are recognized as inflammatory disorders, and there are data demonstrating that age-related changes in immune function can have a significant impact on these disorders.

CXCR2-dependent mucosal neutrophil influx protects against colitis-associated diarrhea caused by an attaching/effacing lesion-forming bacterial pathogen

Enteropathogenic Escherichia coli (EPEC) is a major cause of diarrheal disease in young children, yet symptoms and duration are highly variable for unknown reasons. Citrobacter rodentium, a murine model pathogen that shares important functional features with EPEC, colonizes mice in colon and cecum and causes inflammation, but typically little or no diarrhea. We conducted genome-wide microarray studies to define mechanisms of host defense and disease in C. rodentium infection. A significant fraction of the genes most highly induced in the colon by infection encoded CXC chemokines, particularly CXCL1/2/5 and CXCL9/10, which are ligands for the chemokine receptors CXCR2 and CXCR3, respectively. CD11b(+) dendritic cells were the major producers of CXCL1, CXCL5, and CXCL9, while CXCL2 was mainly induced in macrophages. Infection of gene-targeted mice revealed that CXCR3 had a significant but modest role in defense against C. rodentium, whereas CXCR2 had a major and indispensable function. CXCR2 was required for normal mucosal influx of neutrophils, which act as direct antibacterial effectors. Moreover, CXCR2 loss led to severe diarrhea and failure to express critical components of normal ion and fluid transport, including ATPase beta(2)-subunit, CFTR, and DRA. The antidiarrheal functions were unique to CXCR2, since other immune defects leading to increased bacterial load and inflammation did not cause diarrhea. Thus, CXCR2-dependent processes, particularly mucosal neutrophil influx, not only contribute to host defense against C. rodentium, but provide protection against infection-associated diarrhea.

Changes in immune function in asthma in the elderly

Asthma is an inflammatory disorder of the airway. The airway inflammation of asthma is typically an allergic inflammation characterized by cells and mediators described as a "Th2" inflammatory response. There is a growing body of evidence describing changes in the function of immune cells upon aging, a phenomenon referred to as "immunosenescence". Several studies utilizing animal models and human subjects with asthma have begun to explore age-related effects on the airway inflammation in asthma. This review explores the existing data on the presence and effects of immunosenescence or age-related changes in immune function in asthma.

Staphylococcus aureus Panton-Valentine leukocidin contributes to inflammation and muscle tissue injury

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) threatens public health worldwide, and epidemiologic data suggest that the Panton-Valentine Leukocidin (PVL) expressed by most CA-MRSA strains could contribute to severe human infections, particularly in young and immunocompetent hosts. PVL is proposed to induce cytolysis or apoptosis of phagocytes. However, recent comparisons of isogenic CA-MRSA strains with or without PVL have revealed no differences in human PMN cytolytic activity. Furthermore, many of the mouse studies performed to date have failed to demonstrate a virulence role for PVL, thereby provoking the question: does PVL have a mechanistic role in human infection? In this report, we evaluated the contribution of PVL to severe skin and soft tissue infection. We generated PVL mutants in CA-MRSA strains isolated from patients with necrotizing fasciitis and used these tools to evaluate the pathogenic role of PVL in vivo. In a model of necrotizing soft tissue infection, we found PVL caused significant damage of muscle but not the skin. Muscle injury was linked to induction of pro-inflammatory chemokines KC, MIP-2, and RANTES, and recruitment of neutrophils. Tissue damage was most prominent in young mice and in those strains of mice that more effectively cleared S. aureus, and was not significant in older mice and mouse strains that had a more limited immune response to the pathogen. PVL mediated injury could be blocked by pretreatment with anti-PVL antibodies. Our data provide new insights into CA-MRSA pathogenesis, epidemiology and therapeutics. PVL could contribute to the increased incidence of myositis in CA-MRSA infection, and the toxin could mediate tissue injury by mechanisms other than direct killing of phagocytes.

Reactive oxygen intermediate-induced pathomechanisms contribute to immunosenescence, chronic inflammation and autoimmunity

Deregulation of reactive oxygen intermediates (ROI) resulting in either too high or too low concentrations are commonly recognized to be at least in part responsible for many changes associated with aging. This article reviews ROI-dependent mechanisms critically contributing to the decline of immune function during physiologic - or premature - aging. While ROI serve important effector functions in cellular metabolism, signalling and host defence, their fine-tuned generation declines over time, and ROI-mediated damage to several cellular components and/or signalling deviations become increasingly prevalent. Although distinct ROI-associated pathomechanisms contribute to immunosenescence of the innate and adaptive immune system, mutual amplification of dysfunctions may often result in hyporesponsiveness and immunodeficiency, or in chronic inflammation with hyperresponsiveness/deregulation, or both. In this context, we point out how imbalanced ROI contribute ambiguously to driving immunosenescence, chronic inflammation and autoimmunity. Although ROI may offer a distinct potential for therapeutic targeting along with the charming opportunity to rescue from deleterious processes of aging and chronic inflammatory diseases, such modifications, owing to the complexity of metabolic interactions, may carry a marked risk of unforeseen side effects.

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.

Age-related defects in B lymphopoiesis underlie the myeloid dominance of adult leukemia

Reduced lymphopoiesis during aging contributes to declines in immunity, but little consideration has been given to its effect on the development of hematologic disease. This report demonstrates that age-related defects in lymphopoiesis underlie the myeloid dominance of adult leukemia. Using a murine model of chronic myeloid leukemia, an adult-onset malignancy that arises from transformation of hematopoietic stem cells by the BCR-ABL(P210) oncogene, we demonstrate that young bone marrow (BM) cells that were transformed with BCR-ABL(P210) initiated both a myeloproliferative disorder (MPD) and B-lymphoid leukemia, whereas BCR-ABL(P210)-transformed old BM cells recapitulated the human disease by inducing an MPD with rare lymphoid involvement. In addition, the lesser severity of MPDs initiated from old BCR-ABL(P210)-transduced BM cells revealed unappreciated defects in aged myeloid progenitors. These data demonstrate that aging affects patterns of leukemogenesis and indicate that the effects of senescence on hematopoiesis are more extensive than previously appreciated.

Production of nitric oxide by murine peritoneal macrophages in vitro on treatment with prolactin and growth hormone: Involvement of protein tyrosine kinases, Ca++, and MAP kinase signal transduction pathways

Prolactin (PRL) and growth hormone (GH) (somatotropin) have been known to possess immunomodulatory properties. In the present studies we have investigated the production of nitric oxide (NO) and TNF-alpha by murine peritoneal macrophages in vitro on treatment with PRL and GH and the signal transduction mechanism involved. It is observed that significantly enhanced production of NO is induced in macrophages on treatment with PRL and GH. It is further observed that protein tyrosine kinases, MAP kinases and Ca(++) channeling are involved in NO production by macrophages on in vitro treatment with PRL and GH. GH and PRL induced nitric oxide did not have any effect on the expression and production of TNF-alpha. PRL or GH induced TNF-alpha production by murine macrophages was insensitive in the presence of competitive inhibitor of NOS, L-NMMA. Similarly, there is no autocrine or paracrine effect of TNF-alpha on GH or PRL induced NO production and iNOS expression.

NKT Cell Activation Mediates Neutrophil IFN-γ Production and Renal Ischemia-Reperfusion Injury

Previous work has shown that ischemia-reperfusion (IR) injury (IRI) is dependent on CD4(+) T cells from naive mice acting within 24 h. We hypothesize that NKT cells are key participants in the early innate response in IRI. Kidneys from C57BL/6 mice were subjected to IRI (0.5, 1, 3, and 24 h of reperfusion). After 30 min of reperfusion, we observed a significant increase in CD4(+) cells (145% of control) from single-cell kidney suspensions as measured by flow cytometry. A significant fraction of CD4(+) T cells expressed the activation marker, CD69(+), and adhesion molecule, LFA-1(high). Three hours after reperfusion, kidney IFN-gamma-producing cells were comprised largely of GR-1(+)CD11b(+) neutrophils, but also contained CD1d-restricted NKT cells. Kidney IRI in mice administered Abs to block CD1d, or deplete NKT cells or in mice deficient of NKT cells (Jalpha18(-/-)), was markedly attenuated. These effects were associated with a significant decrease in renal infiltration and, in activation of NKT cells, and a decrease in IFN-gamma-producing neutrophils. The results support the essential role of NKT cells and neutrophils in the innate immune response of renal IRI by mediating neutrophil infiltration and production of IFN-gamma.

Perioperative treatment with human growth hormone down-regulates apoptosis and increases superoxide production in PMN from patients undergoing infrarenal abdominal aortic aneurysm repair

BACKGROUND

Recombinant human growth hormone (hGH) therapy has a beneficial effect on catabolism and wound healing after major surgery. Polymorphonuclear neutrophils (PMN) play an important role in this context. In a prospective, double-blind, randomized, placebo-controlled trial we studied the effect of perioperative hGH treatment on postoperative wound healing and on changes in superoxide generation and susceptibility to apoptosis of PMN in elderly patients undergoing elective abdominal aortic aneurysm repair.

METHODS

Seven patients were treated with high-dose hGH (16 U/d) for nine days, seven patients with a placebo. IGF-I, neutrophil count, O2-production induced by opsonized zymosan and apoptosis of PMN were measured and correlated with clinical outcome.

RESULTS

Perioperative hGH treatment more than doubled the O2- production in PMN before and 24 h after surgery (p < 0.01). The long-term capacity of PMN to generate O2 in vitro was prolonged (p < 0.001) in the hGH group. Spontaneous and Fas-inducible apoptosis was strongly down-regulated in PMN after surgery in all patients (p < 0.01). hGH-treatment distinctly reduced apoptosis in PMN before and after surgery (p < 0.01). Clinical outcome was similar in both groups.

CONCLUSION

Perioperative hGH treatment results in an enhanced O2- production in PMN and in a prolongation of the functional life span of these cells. This may improve immune function and help to overcome the postoperative anergic state of the immune system especially in elderly individuals.

Aging and innate immune cells

The innate immune system serves an important role in preventing microbial invasion. However, it experiences significant changes with advancing age. Among the age-associated changes are: Aged macrophages and neutrophils have impaired respiratory burst and reactive nitrogen intermediates as a result of altered intracellular signaling, rendering them less able to destroy bacteria. Aged neutrophils are also less able to respond to rescue from apoptosis. Aged dendritic cells (DC) are less able to stimulate T and B cells. The altered T cell stimulation is a result of changes in human leukocyte antigen expression and cytokine production, and lower B cell stimulation is a result of changes in DC immune complex binding. Natural killer (NK) cells from the elderly are less capable of destroying tumor cells. NK T cells increase in number and have greater interleukin-4 production with age. Levels of various complement components are also altered with advancing age.

From hormones to immunity: the physiology of immunology

Discoveries in the physiology of immunology have increased at an increasing rate during the past two decades. It is now recognized that the immune system is just another physiological system that regulates, and is regulated by, other physiological systems such as the brain. These advances make it clear that recent findings in genomic biology must be interpreted in the context of the environment in which animals and humans live. Lack of a strong genetic basis for significant human mental health disorders, such as major depression, points to the critical importance of interactions. Several examples of environmental x genetic x disease interactions are presented. Regulation of cells of the hematopoietic lineage by two genes that control over 80% of postnatal growth, growth hormone and IGF-I, are then highlighted. The reciprocal relationship of how proinflammatory cytokines from the immune system regulate the growth hormone/IGF-I axis is also summarized. Particular emphasis is placed upon TNFalpha-induced IGF-I resistance in neurons, muscle cells and epithelial cells. This cytokine regulation of hormone action may ultimately be more important for human and animal health than direct effects of growth hormone and IGF-I on hematopoietic cells. Wasting of AIDS patients is given as an important clinical example of how TNFalpha from an activated immune system reduces IGF-I sensitivity in multiple physiologic systems, including muscle, nervous and hematopoietic tissues.

NF kappa B activation in mouse pituitary: comparison of response to interleukin-1 beta and lipopolysaccharide

The mouse anterior pituitary contains both types of interleukin (IL)-1 receptors, IL-1 receptor type I (IL-1RI) and IL-1 receptor type II (IL-1RII). These receptors are expressed mainly on somatotroph cells. In the present study, the ability of the mouse pituitary to respond in vivo to IL-1 or to lipopolysaccharide (LPS) was demonstrated by measuring, with an electrophoretic mobility shift assay, the presence of an active NF kappa B complex in cell nuclei from pituitaries of mice injected intraperitoneally with recombinant rat-IL-1 beta or LPS. Using immunohistochemistry with an antibody directed against the p65 NF kappa B subunit, a rapid and transient NF kappa B response to LPS was observed. This response was present predominantly in the nuclei of glial fibrillary acidic protein (GFAP)-positive cells and F4/80-labelled cells of the posterior and the anterior pituitary 15 min after stimulation and became faint after 2 h. In comparison, the early and strong NF kappa B response to IL-1 beta treatment was localized into somatotroph cells, GFAP positive cells and F4/80-labelled cells of the posterior and anterior pituitary. Activation of NF kappa B in response to IL-1 beta was no longer apparent in IL-1RI knockout mice, confirming that this receptor is essential for the transduction of IL-1 signal in the pituitary, but remained after LPS treatment. In addition, we investigated the effect of IL-1 on target genes by measuring the mRNA and proteins synthesis of growth hormone (GH), IL-6 and IL-1ra in the pituitary and the plasma. IL-1 beta was shown to induce a rapid and strong synthesis of IL-6 and IL-1ra in the pituitary but failed to regulate GH contents or release. These data suggest that the pituitary is able to respond to a systemic infection via cytokine-mediated responses transduced by IL-1.

Effects of prolactin on cloned human T-lymphocytes

To evaluate the possible role of prolactin (PRL) in T-lymphocytes, we monitored gene induction in one cytotoxic T-lymphocyte (CTL) clone derived from a patient with hemochromatosis and in several T-helper clones generated from a normal donor and a patient with multiple sclerosis. The CTL clone expressed conventional PRL receptor (PRLR), and PRL induced the expression of suppressor of cytokine signaling-3 (SOCS-3) and increased the expression of SOCS-2 and cytokine-inducible src homology-2 containing protein (CIS, another member of the SOCS family). As is the case in granulocytes, expression of a conventional receptor for PRL could not be shown by polymerase chain reaction analysis on three helper clones. In addition, as in granulocytes, PRL modulated the expression of genes such as the interferon-regulatory factor-1, inducible nitric oxide synthase, CIS, and SOCS-2. These effects were also elicited with ovine PRL and could be prevented by anti-PRL antibodies. Thus, the use of clones allowed the detection of direct effects of PRL on T-cells, even when these have few or no detectable PRLR, confirming that human T-lymphocytes are targets for PRL.

Rejection and recipient age

In transplantation the risk of acute rejection decreases with recipient age. This is clearly illustrated in transplantation of a non-vascularised tissue, such as the cornea. In vascularised transplants, such as kidneys, acute rejection decreases with recipient age, but the phenomenon is obscured by the fact that chronic allograft nephropathy increases with age, and is further confounded by increased death from infectious disease and drug-related causes. The underlying cellular mechanisms responsible for this weakening of rejection are discussed, as is defective signal transduction leading to decreased activation of cells and decreased resistance to immunosuppressive drugs. This supports a view that less intensive immunosuppressive drug therapy is desirable in elderly recipients. Although pharmacokinetic studies are documented, there are no routine assays to measure efficacy of these drugs in individual patients. In summary, the decline in acute rejection with increasing recipient age may be due both to immunosenescence and decreased resistance to immunosuppressive drugs. Future assays to test these mechanisms could be used to tailor therapy to individual needs.

Effects of prolactin on signal transduction and gene expression: possible relevance for systemic lupus erythematosus

Receptors for prolactin (PRL-R) are expressed in normal leukocytes from rat and man. PRL signals through PRL-R associated Janus tyrosine kinase (Jak)-2 and signal transducers and activators of transcription (Stat). In addition, in human leukocytes PRL also activates the p38 MAP kinase pathway. PRL, at physiological concentrations, stimulates the expression of the interferon regulatory factor (IRF)-1 gene in rat spleen and bone marrow cells. In man, genes induced by PRL include several members of the 'suppressors of cytokine signaling' (SOCS) family and inducible nitric oxide synthase (iNOS; in mononuclear cells and in granulocytes) and IRF-1 (in granulocytes). Thus, in normal leukocytes, PRL induces the expression of several genes relevant to innate and acquired immune responses. Sex hormones, such as estrogen and PRL, have been implicated in the pathogenesis of murine and human SLE. Also defective signaling in leukocytes is a feature of the disease. What the origin is of aberrant signaling processes in SLE lymphocytes and how they relate to tolerance breakdown and immunopathology is still unknown. It is not unlikely that PRL is a player at some level. The exact contribution of PRL to immune responses in normal subjects and in SLE patients is not known. Further work should also indicate whether PRL might contribute to the onset or progression of the disease and assess the possible benefits of manipulating PRL concentrations in patients.

Age-associated loss of bone marrow hematopoietic cells is reversed by GH and accompanies thymic reconstitution

Deterioration of the thymus gland during aging is accompanied by a reduction in plasma GH. Here we report gross and microscopic results from 24-month-old Wistar-Furth rats treated with rat GH derived from syngeneic GH3 cells or with recombinant human GH. Histological evaluation of aged rats treated with either rat or human GH displayed clear morphologic evidence of thymic regeneration, reconstitution of hematopoietic cells in the bone marrow, and multiorgan extramedullary hematopoiesis. Quantitative evaluation of formalin-fixed, hematoxylin and eosin-stained sections of bone marrow from aged rats revealed at least a 50% reduction in the number hematopoietic bone marrow cells, compared with that of young 3-month-old rats. This age-associated decline in bone marrow leukocytes, as well as the increase in bone marrow adipocytes, was significantly reversed by in vivo treatment with GH. Restoration of bone marrow cellularity was caused primarily by erythrocytic and granulocytic cells, but all cell lineages were represented and their proportions were similar to those in aged control rats. On a per-cell basis, GH treatment in vivo significantly increased the number of in vitro myeloid colony forming units in both bone marrow and spleen. Morphological evidence of enhanced extramedullary hematopoiesis was observed in the spleen, liver, and adrenal glands from animals treated with GH. These results confirm that GH prevents thymic aging. Furthermore, these data significantly extend earlier findings by establishing that GH dramatically promotes reconstitution of another primary hematopoietic tissue by reversing the accumulation of bone marrow adipocytes and by restoring the number of bone marrow myeloid cells of both the erythrocytic and granulocytic lineages.

Cytokine-like effects of prolactin in human mononuclear and polymorphonuclear leukocytes

Some biochemical events following the binding of prolactin (PRL) to its receptor in normal human leukocytes were investigated. PRL enhanced JAK2 phosphorylation in peripheral blood mononuclear cells (PBMC) but not in granulocytes. PRL also induced phosphorylation of Stat-5 in PBMC and Stat-1 in granulocytes. Subsequent binding of Stat-5- and of Stat-1-like molecules to a GAS responsive element from the beta-casein promoter was detected by EMSA. p38 MAPK (but not p42/p44 MAPK) was activated by PRL in both leukocyte populations. PRL induced iNOS and CIS mRNA expression in granulocytes. Increased expression of IRF-1 and SOCS-2 was observed in granulocytes and of SOCS-3 and iNOS in PBMC. Similar effects were obtained with ovine and human PRL. Antiserum to PRL reduced iNOS and IRF-1 expression induced by PRL in granulocytes and reduced iNOS expression in PBMC. Also, pretreatment of granulocytes with a p38 MAPK inhibitor (SB 203580) prevented in part PRL-induced iNOS and IRF-1 expression. In PBMC, the p38 inhibitor decreased PRL-induced iNOS gene expression. These results indicate that PRL-induced gene regulation in leukocytes requires the activation of at least two different pathways: the Stat and the MAP kinase pathways. Moreover, although PRL activates Stat in both leukocyte types, signal transduction is different in granulocytes and in PBMC. Most importantly, PRL modulates the expression of genes crucial to leukocyte function. The present findings reinforce the concept that PRL has "cytokine-like" activity in human leukocytes.

Modulation of the inflammatory reaction and neutrophil defense of the bovine lactating mammary gland by growth hormone

This review is focused on the possible interactions of prolactin and somatotrope hormone in the modulation of inflammation of the mammary gland. Several different models are examined: Escherichia coli, Streptococcus uberis, and endotoxin mastitis. Subsequently, the release of growth hormone and insulin-like growth factor during fever and mastitis, the immunophysiological effects of GH on E. coli mastitis, S. uberis and endotoxin mastitis, the galactopoietic action of rBST on healthy and mastitis cows as well as the immunologic effects of GH on leukocytes in healthy and diseased cows are discussed. It can be concluded that the underlying regulation of the neuro-endocrine network is fundamental in the normal function of the immune system.

Prophylactic treatment with growth hormone and insulin-like growth factor I improve systemic bacterial clearance and survival in a murine model of burn-induced gut-derived sepsis

The purpose of this investigation was to evaluate the effects of GH and IGF-I administration in a murine model of burn-induced gut-derived sepsis. BALB/C mice were treated with 4.8 mg/kg/day of GH, 24 mg/kg/day of IGF-I or saline for 4 days. They were then administered 10(10) E. coli by gavage and subjected to 20% full thickness flame burn. All mice received allogeneic blood transfusion 5 days before burn injury to induce mild immunosuppression. Seventy-three mice were observed for survival and 51 mice were sacrificed at 4 and 20 h postburn. Blood, mesenteric lymph nodes (MLN), spleen and liver were harvested aseptically, and viable bacterial counts in the organs were determined. The small intestine was harvested for the evaluation of villus height and mitoses in the crypts. GH and IGF-I groups showed a significantly better survival than the control group. GH and IGF-I groups had significantly greater villus height and mitoses/crypt than the control group. Translocation of bacteria was not significantly different among groups, however, the relation between the numbers of viable bacteria in MLN and blood suggests that both GH and IGF-I reduced systemic spread of translocated bacteria. It is concluded that GH and IGF-I had positive effects on outcome in this model of burn-induced gut-derived sepsis. It appears that GH and IGF-I may have immune-enhancing effects and that administration of these agents may be useful for burn injury.

Effect of bovine somatotropin on neutrophil functions and clinical symptoms during Streptococcus uberis mastitis

The effect of recombinant bovine somatotropin (bST) on the chemiluminescence, diapedesis, and expression of adhesion receptors (CD11a, CD11b, CD18) of isolated polymorphonuclear leukocytes was studied. The plasma concentrations of insulin-like growth factor-I (IGF-I), bST, cortisol, and alpha-lactalbumin were also monitored. In addition, general and local clinical symptoms and the differentiation of circulating leukocytes were also studied during experimentally induced Streptococcus uberis mastitis in cows. Ten cows were infected with 500 cfu of S. uberis O140J in both left quarters. Five cows were subcutaneously treated with 500 mg of recombinant bST 7 d before and after infection, and 5 control cows received the excipient. General (fever, tachycardia, inappetance, and depression) and local symptoms (swelling, pain, firmness, and flecks in milk) were more acute, severe, and longer-lasting in control cows. Treatment with bST had no effect on chemiluminescence and diapedesis of circulating polymorphonuclear leukocytes and no effect on the expression of adhesion receptors. Recombinant bST induced significantly higher IGF-I and bST concentrations in plasma. The leukopenia observed after infection was less pronounced in the bST-treated cows, and the number of circulating band neutrophils and metamyelocytes was significantly lower in the treated group. The concentration of cortisol did not differ between both groups, but the blood concentration of alpha-lactalbumin significantly increased in both groups from 6 d after infection. These results showed that treatment with recombinant bST improves animal welfare by protecting the cows from severe local and general clinical symptoms during subsequent S. uberis mastitis, but that it has no effect on chemiluminescence, diapedesis, and the expression of adhesion receptors of circulating polymorphonuclear leukocytes.

Advanced glycation in D-galactose induced mouse aging model

It was first reported in China that injection of a low dose of D-galactose into mice could induce changes which resembled accelerated aging. The aging model shows neurological impairment, decreased activity of anti-oxidant enzymes, and poor immune responses. However, the underlining mechanism remains largely unknown. D-galactose is a reducing sugar that can form advanced glycation endproducts (AGE) in vivo. To investigate the role of AGE in this aging model, a group of 5-month-old C57 mice were injected daily with D-galactose, D-galactose modified AGE-lysine (AGE-lysine), L-glucose, L-lysine, or control buffer for 8 weeks. Two additional groups were treated with the AGE formation inhibitor, aminoguanidine. The results show that D-galactose, L-glucose, and AGE-lysine treated mice had a significant increase in serum AGE levels, memory latency time and error rate, and skin hydroxyproline content. Similar to aged controls, these mice also had a significant decrease in motor activity, lymphocyte mitogenesis, interleukin-2 (IL-2) production, and superoxide dismutase (SOD) enzyme activity. The aminoguanidine treated D-galactose-injected mice, however, showed no significant changes in these parameters in comparison with young controls. These data indicate that D-galactose and L-glucose form AGEs in vivo and that elevated AGEs may accelerate the aging process. The fact that both D-galactose and AGE treated mice resemble aged mice suggests that advanced glycation, at least partially, accounts for the mechanism of this aging model.

Involvement of nitric oxide in protecting mechanism during experimental cryptococcosis

In the present study we investigated the role of nitric oxide (NO) in the effector mechanisms of host defense against Cryptococcus neoformans in vivo. Our results showed an increase of NO produced by the peritoneal macrophages from 14-days infected rats compared with normal rats. These cells were capable of killing C. neoformans to a greater extent than macrophages from noninfected rats (80% vs 20%, respectively). The killing of C. neoformans by infected cells was efficiently inhibited (80% to 35%, P < 0.001) by adding aminoguanidine (AG) to the cultures. We observed that in vivo administration of AG to the infected animals efficiently inhibited the metabolism producing NO and failed to affect that of normal animals. When the NO synthase (NOS) was inhibited in vivo in the infected animals, a marked increase of the fungi charge in the organs was observed with respect to the normal animals treated with AG. We also observed that the course of the infection is drastically modified after the inhibition of NO production because all the animals infected and treated with AG died from cryptococcosis before 20 days postinfection (p.i.). These results indicate that NO is a crucial molecule in the effector mechanisms in this infection model.

Growth hormone inhibits apoptosis and up-regulates reactive oxygen intermediates production by human polymorphonuclear neutrophils

BACKGROUND

Growth hormone (GH) regulates the immune and metabolic systems; however, the effects of GH on the functions and cell death of polymorphonuclear neutrophils (PMNs) are not well understood. Therefore, this study was designed to investigate the effects of GH on PMN apoptosis, reactive oxygen intermediates (ROI) production, CD16, and Fas expression. We also investigated the effects of GH on the functions of other circulating leukocytes (ie, monocytes and lymphocytes).

METHODS

Venous blood was collected from healthy volunteers. Whole blood was washed and pretreated with GH (0 or 100 ng/mL) for 3 hours and then cultured for 0, 4, or 12 hours. PMNs in washed whole blood were analyzed by flow cytometry for cell death, phorbol myristate acetate-stimulated ROI production, CD16, and Fas expression at each time point. Morphologic features also were assessed. PMN apoptosis was confirmed by chromatin staining and DNA gel electrophoresis.

RESULTS

GH inhibited PMN apoptosis at 12 hours of culture. GH enhanced ROI production by PMNs and monocytes throughout the 12-hour culture but had no effects on CD16 expression on PMNs. Furthermore, GH decreased Fas expression on PMNs at 4 hours of culture. However, there were no effects of GH on apoptosis of monocytes or lymphocytes for the duration of this experiment.

CONCLUSIONS

GH pretreatment down-regulates Fas expression on PMNs, inhibits apoptosis, and up-regulates ROI production. GH pretreatment also increases monocyte ROI production. Although activated PMNs have potentially harmful aspects, our results suggest that GH may improve host defense, mainly through enhancement of the PMN functional life span.

Functional activity of blood polymorphonuclear leukocytes as an oxidative stress biomarker in human subjects

In the present work, we studied the role of polymorphonuclear leukocytes (PMN) in aged individuals and coronary heart disease (CHD)-bearing patients, two physiopathological processes associated with overproduction of reactive oxygen species (ROS). The effects of antioxidant supplementation on the functional activity of PMN from CHD patients were also determined. The function of PMNs was evaluated by measuring of phagocytosis, killing activity, and ROS production. Luminol amplified chemiluminescence (CL) was used to estimate ROS production by stimulated PMNs. Total cholesterol and the LDL-cholesterol fraction from CHD patients were found to be higher than those recommended, returning to normal levels after antioxidant therapy. PMN CL of CHD patients was found to be higher than the associated control groups. Antioxidant therapy administrated to CHD patients lead to an increase in the killing activity accompanied by a decrease in PMN CL of these subjects. The study also showed that killing activity of PMN from human subjects over 60 years was significantly lower than the activity measured in younger subjects. PMN CL produced after stimulation was found to be positively correlated with the increasing age of human subjects (r=.946, p < .01).

Lack of involvement of nitric oxide in the macrophage-mediated inhibition of spleen cell proliferation during experimental cryptococcosis

We investigated the proliferative response to mitogens of spleen mononuclear (Spm) cells from Cryptococcus neoformans-infected rats. We determined reactive oxygen intermediates (ROI) and nitric oxide (NO) production by peritoneal and Spm cells, and evaluated the correlation of the proliferative response with NO and ROI production. The proliferative response of Spm cells from infected rats dramatically decreased at 14 and 21 days postinfection (PI). The unresponsiveness of Spm cells from 14-day infected rats was not abrogated by the addition of L-NAME and AG, indicating that NO is not involved in the antiproliferative response of experimental cells. When SOD, catalase, and indomethacin were added to the cultures, the suppression was still observed, indicating that ROI and prostaglandins are not involved in the unresponsiveness of lymphocytes. The proliferative response of lymphocytes from 14-day infected rats was significantly improved when cultures were made in the presence of Con A and exogenous IL-2. Additionally, a purified T-rich fraction from infected rats cultured with control macrophages recovered the normal proliferative response. This result indicates that macrophages from infected rats mediate the unresponsiveness of lymphocytes, probably by reducing the ability of lymphocytes to secrete IL-2.

The influence of growth hormone on tumour necrosis factor and neutrophil leukocyte function in sepsis

The aim of this study was to assess the influence of growth hormone (GH) in sepsis on the immune system represented by the circulating TNF-levels and the neutrophil leukocytes phagocytic capacity and respiratory burst, 22 piglets were randomized to 3 groups; pretreatment with GH (16 i.u.) before sepsis (n = 8), non-treated septic controls (n = 8), and non-septic controls (n = 6). Sepsis was induced by a standardized infusion of live E. coli. TNF was measured by a cytotoxic bioassay, while neutrophil function tests were carried out by flowcytometric assays. In brief, phagocytosis was evaluated by the neutrophils' ability to ingest FITC-labelled (fluorescein isothiocyanate) E. coli and intracellular release of oxygen metabolites was detected by the oxidation of 2',7'-dichlorofluorescin (DCFH) to the fluorescent 2',7'-dichlorofluorescein (DCF). Our data show a suppression of phagocytosis in the GH-treated group before sepsis; however, when challenged with Gram-negative bacteria, the phagocytic capacity was similar to that of the non-treated animals. The serum levels of TNF in the non-treated septic control group were twice the levels of those in the GH-treated group, 65.7 pg/ml (septic controls) vs 32.8 pg/ml (GH). Pretreatment with a single dose of GH few hours prior to sepsis does not seem to entail any further imbalance of the neutrophil function in sepsis. Lowering of the circulating TNF-levels is a presumptive favourable effect of GH in sepsis.

Hormones, lymphohemopoietic cytokines and the neuroimmune axis

The classical distinction between hormones and cytokines has become increasingly obscure with the realization that homeostatic responses to infection involve coordinated changes in both the neuroendocrine and immune systems. The hypothesis that these systems communicate with one another is supported by the ever-accruing demonstrations of a shared molecular network of ligands and receptors. For instance, leukocytes express receptors for hormones and these receptors modulate diverse biological activities such as the growth, differentiation and effector functions. Leukocyte lineages also synthesize and secrete hormones, such as insulin-like growth factor-I (IGF-I), in response to both growth hormone (GH) and also to cytokines such as tumor necrosis factor-alpha (TNF-alpha). Since hormones share intracellular signaling substrates and biological activities with classical lymphohemopoietic cytokines, neuroendocrine and immune tissues share a common molecular language. The physiological significance of this shared molecular framework is that these homeostatic systems can intercommunicate. One important example of this interaction is the mechanism by which bacterial lipopolysaccharide, by eliciting a pro-inflammatory cytokine cascade from activated leukocytes, modulate pituitary GH secretion as well as other CNS-controlled behavioral and metabolic events. This article reviews the cellular and molecular basis for this communication system and proposes novel mechanisms by which neuroendocrine-immune interactions converge to modulate disease resistance, metabolism and growth.

The immune effects of neuropeptides

Current evidence indicates that the neuroendocrine system is the highest regulator of immune/inflammatory reactions. Prolactin and growth hormone stimulate the production of leukocytes, including lymphocytes, and maintain immunocompetence. The hypothalamus-pituitary-adrenal axis constitutes the most powerful circuit regulating the immune system. The neuropeptides constituting this axis, namely corticotrophin releasing factor, adrenocorticotrophic hormone, alpha-melanocyte stimulating hormone, and beta-endorphin are powerful immunoregulators, which have a direct regulatory effect on lymphoid cells, regulating immune reactions by the stimulation of immunoregulatory hormones (glucocorticoids) and also by acting on the central nervous system which in turn generates immunoregulatory nerve impulses. Peptidergic nerves are major regulators of the inflammatory response. Substance P and calcitonin gene-related peptide are pro-inflammatory mediators and somatostatin is anti-inflammatory. The neuroendocrine regulation of the inflammatory response is of major significance from the point of view of immune homeostasis. Malfunction of this circuit leads to disease and often is life-threatening. The immune system emits signals towards the neuroendocrine system by cytokine mediators which reach significant blood levels (cytokine-hormones) during systemic immune/inflammatory reactions. Interleukin-1, -6, and TNF-alpha are the major cytokine hormones mediating the acute phase response. These cytokines induce profound neuroendocrine and metabolic changes by interacting with the central nervous system and with many other organs and tissues in the body. Corticotrophin releasing factor functions under these conditions as a major co-ordinator of the response and is responsible for activating the ACTH-adrenal axis for regulating fever and for other CNS effects leading to a sympathetic outflow. Increased ACTH secretion leads to glucocorticoid production. alpha-melanocyte stimulating hormone functions under these conditions as a cytokine antagonist and an anti-pyretic hormone. The sympathetic outflow, in conjunction with increased adrenal activity. leads to the elevation of catecholamines in the bloodstream and in tissues. Current evidence suggests that neuroimmune mechanisms are essential in normal physiology, such as tissue turnover, involution, atrophy, intestinal function, and reproduction. Host defence against infection, trauma and shock relies heavily on the neuroimmunoregulatory network. Moreover, abnormalities of neuroimmunoregulation contribute to the aetiology of autoimmune disease, chronic inflammatory disease, immunodeficiency, allergy, and asthma. Finally, neuroimmune mechanisms play an important role in regeneration and healing.

Granulation in livers of mice infected with Salmonella typhimurium is caused by superoxide released from host phagocytes

The pathophysiological roles of superoxide (O2.-) at the site of infection of facultative intracellular bacteria were examined in this study. To evaluate the actual in vivo generation of the superoxide, an ex vivo chemiluminescence assay was newly developed. When ICR mice were infected with a sublethal dose (8 x 10(4) CFU) of Salmonella typhimurium, the number of bacteria in the liver reached its peak at 5 days after infection (10(5.05) CFU/g of liver) and decreased thereafter. At 21 days after infection, the bacteria became undetectable. On the other hand, phorbol myristate 13-acetate-stimulated O2.- generation reached a maximum at 7 days after infection (mean photon count, 1,249 cps versus 28.8 cps before infection; n = 4) and decreased thereafter to a level similar to that before infection at 21 days after infection (28.8 cps). Histological examinations revealed that the total area of the lesions reached a peak at 7 days after infection (7.2 x 10(4) microns 2/10 visual fields). In the early phase, a microabscess with infiltration of polymorphonuclear cells was noted, and then, in the late stage, the lesion was replaced by granulation with mononuclear cell infiltration. When microscopic lesions were measured histologically, a significant correlation between the area of the lesions and phorbol myristate 13-acetate-stimulated O2.- generation was observed, which suggested that superoxide was responsible for the generation of the lesions. Modified superoxide dismutase, i.e., alpha-4-([6-(N-maleimido)hexanoyloxymethyl] cumyl)half-butyl-esterified poly(stylrene-co-malelic acid)-conjugated superoxide dismutase (SM-SOD), was then applied. When SM-SOD was administered to suppress the O2.- generation in vivo, the number of bacteria increased (10(6.1) CFU). However, the lesion formation was inhibited (total lesion area, 0.3 x 10(4) microns 2). These results suggest that the establishment of the microabscess and granuloma formation after S. typhimurium infection is not due to the bacteria per se but rather to the O2.- from the host's phagocytes. Two aspects of the O2.-, i.e., the bactericidal role and the tissue-injurious effect, were clearly demonstrated in this study. Therefore, the information obtained from these results is useful in designing treatment strategy for similar kinds of infection.

Immunology discovers physiology

Not so long ago, it was believed that the brain is totally devoid of immunologic reactions, that cytokines derived from activated leukocytes serve only as communication molecules between leukocytes and that the immune system is regulated solely by intrinsic mechanisms. One by one, these old-time, traditional views have fallen by the wayside as neuroscientists, endocrinologists and pharmacologists have begun to explore immunology. The old view was that the immune system is autonomous because it neither affects nor is it affected by other physiologic systems. The new view is that cells of the immune system are inextricably linked with other physiological systems, including the neuroendocrine, cardiovascular, reproductive and central nervous systems (CNS). Changes in one system evoke changes in the other, and it is likely that communication loops have evolved between cells of the immune system and those of other tissues to coordinate and regulate functional activities aimed at preserving homeostasis during inflammation. The integrated view of immunophysiologists that cells of the immune system interact with the entire body, rather than existing as a separate physiologic system that operates autonomously, should help to unravel a number of mysteries in immunoregulation, such as the well-recognized redundant and pleiotropic properties of cytokines. Unfortunately, very few of these ideas have been incorporated into studying immunity of domestic animals. A complete understanding of immunobiology will be achieved only after this new field of immunophysiology is integrated into current immunological thinking.(ABSTRACT TRUNCATED AT 250 WORDS)