Hematopoietic regulation mediated by interactions among the neurokinins and cytokines

Pocket ACEs: Discovering new function within an old player

Angiotensin-converting enzyme (ACE) is canonically known for its role in the renin-angiotensin system (RAS) where its conversion of angiotensin I (Ang I) to the bioactive peptide angiotensin II (Ang II) helps to regulate blood pressure, electrolyte, and volume homeostasis. Further studies on ACE have shown that its enzymatic activity is relatively non-specific and functions outside of the RAS axis. Of the multiple systems it has been implicated in, ACE has been found to play an important role in the development and modulation of hematopoiesis and the immune system, both through the RAS and independently of the RAS axis.

Neurological Regulation of the Bone Marrow Niche

The bone marrow (BM) hematopoietic niche is the microenvironment where in the adult hematopoietic stem and progenitor cells (HSPCs) are maintained and regulated. This regulation is tightly controlled through direct cell-cell interactions with mesenchymal stromal stem (MSCs) and reticular cells, adipocytes, osteoblasts and endothelial cells, through binding to extracellular matrix molecules and through signaling by cytokines and hematopoietic growth factors. These interactions provide a healthy environment and secure the maintenance of the HSPC pool, their proliferation, differentiation and migration. Recent studies have shown that innervation of the BM and interactions with the peripheral sympathetic neural system are important for maintenance of the hematopoietic niche, through direct interactions with HSCPs or via interactions with other cells of the HSPC microenvironment. Signaling through adrenergic receptors (ARs), opioid receptors (ORs), endocannabinoid receptors (CRs) on HSPCs and MSCs has been shown to play an important role in HSPC homeostasis and mobilization. In addition, a wide range of neuropeptides and neurotransmitters, such as Neuropeptide Y (NPY), Substance P (SP) and Tachykinins, as well as neurotrophins and neuropoietic growth factors have been shown to be involved in regulation of the hematopoietic niche. Here, a comprehensive overview is given of their role and interactions with important cells in the hematopoietic niche, including HSPCs and MSCs, and their effect on HSPC maintenance, regulation and mobilization.

Biological and Pharmacological Aspects of the NK1-Receptor

The neurokinin 1 receptor (NK-1R) is the main receptor for the tachykinin family of peptides. Substance P (SP) is the major mammalian ligand and the one with the highest affinity. SP is associated with multiple processes: hematopoiesis, wound healing, microvasculature permeability, neurogenic inflammation, leukocyte trafficking, and cell survival. It is also considered a mitogen, and it has been associated with tumorigenesis and metastasis. Tachykinins and their receptors are widely expressed in various human systems such as the nervous, cardiovascular, genitourinary, and immune system. Particularly, NK-1R is found in the nervous system and in peripheral tissues and are involved in cellular responses such as pain transmission, endocrine and paracrine secretion, vasodilation, and modulation of cell proliferation. It also acts as a neuromodulator contributing to brain homeostasis and to sensory neuronal transmission associated with depression, stress, anxiety, and emesis. NK-1R and SP are present in brain regions involved in the vomiting reflex (the nucleus tractus solitarius and the area postrema). This anatomical localization has led to the successful clinical development of antagonists against NK-1R in the treatment of chemotherapy-induced nausea and vomiting (CINV). The first of these antagonists, aprepitant (oral administration) and fosaprepitant (intravenous administration), are prescribed for high and moderate emesis.

Neurokinin-2 receptor polymorphism predicts lymph node metastasis in colorectal cancer patients

To analyze the single nucleotide polymorphisms (SNPs) of two subtypes of neurokinin (NK) receptors, NK1R and NK2R (also known as TAC1R and TAC2R), in colorectal cancer (CRC), peripheral blood samples were collected from 199 CRC patients. Direct-sequencing was performed to identify the NK1R rs10198644 and NK2R rs4644560 SNPs. Genotype results were correlated with clinical factors. The allele frequencies of NK1R rs10198644 GC, CC and GG were 52, 17 and 31%, respectively, while that of NK2R rs4644560 GC, CC, and GG were 36, 50 and 14%, respectively. Patients with NK2R rs4644560 GC exhibited more positive lymph nodes than those with CC (mean, 2.2 vs. 1.3; P=0.016). Further analysis highlighted that the number of positive lymph nodes was also increased in the NK2R rs4644560 GC/NK1R rs10198644 GG group compared with the NK2R rs4644560 GG/NK1R rs10198644 GG group (mean, 2.2 vs. 0.9; P=0.04). These data suggested that the NK2R rs4644560 GC polymorphism alone or combination with NK1R rs10198644 GG may be a promising prognostic marker of lymph node metastasis in CRC patients.

Long-term comparative study of Substance-P with methylprednisolone on the development of osteoporosis

Steroids are treated for most inflammatory diseases but cause serious side effects such as diabetes and osteoporosis after their long-term usage. Recently, we identified novel roles of Substance-P (SP) in the suppression of the injury-mediated inflammation and also in stem cell mobilization. In this study, for clinical application of SP as an anti-inflammatory agent, its safety in long-term usage was evaluated with regard to diabetes and osteoporosis. Dexamethasone (DEX) and methylprednisolone (MP) were used as comparative drugs. While DEX-injection for 24 weeks developed severe weight loss, unstable blood glucose, and bone loss, SP-injection did not affect blood glucose and bone mass. MP-injection for 24 weeks also influenced blood glucose and body weight much milder than DEX-injection. After 66 weeks, MP-injection caused unstable blood glucose, alleviation in the age-related increase of body weight, and bone weakness, which was featured by reduction in collagen deposition and trabecular bone volume based on histological and micro CT analysis. However, SP-injection for 66 weeks rather increased collagen deposition, bone volume, and bone density. Therefore, this comparative study suggests that SP, even after long-term usage of effective dose, may not cause side effects such as osteoporosis in comparison to that of DEX and MP and can be developed as an anti-inflammatory agent and/or stem cell mobilizer for long-term treatment.

Angiotensin-converting enzyme and the tumor microenvironment: mechanisms beyond angiogenesis

The renin angiotensin system (RAS) is a network of enzymes and peptides that coalesce primarily on the angiotensin II type 1 receptor (AT1R) to induce cell proliferation, angiogenesis, fibrosis, and blood pressure control. Angiotensin-converting enzyme (ACE), the key peptidase of the RAS, is promiscuous in that it cleaves other substrates such as substance P and bradykinin. Accumulating evidence implicates ACE in the pathophysiology of carcinogenesis. While the role of ACE and its peptide network in modulating angiogenesis via the AT1R is well documented, its involvement in shaping other aspects of the tumor microenvironment remains largely unknown. Here, we review the role of ACE in modulating the immune compartment of the tumor microenvironment, which encompasses the immunosuppressive, cancer-promoting myeloid-derived suppressor cells, alternatively activated tumor-associated macrophages, and T regulatory cells. We also discuss the potential roles of peptides that accumulate in the setting of chronic ACE inhibitor use, such as bradykinin, substance P, and N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), and how they may undercut the gains of anti-angiogenesis from ACE inhibition. These emerging mechanisms may harmonize the often-conflicting results on the role of ACE inhibitors and ACE polymorphisms in various cancers and call for further investigations into the potential benefit of ACE inhibitors in some neoplasms.

The peptide network regulated by angiotensin converting enzyme (ACE) in hematopoiesis

The concept of a local bone marrow renin-angiotensin system (RAS) has been introduced and accumulating evidence suggests that the local RAS is actively involved in hematopoiesis. Angiotensin converting enzyme (ACE) is a key player in the RAS and makes the final effector angiotensin II. Besides angiotensin II, ACE also regulates a panel of bioactive peptides, such as substance P, Ac-SDKP and angiotensin 1-7. These peptides have also been individually reported in the regulation of pathways of hematopoiesis. In this setting, an ACE-regulated peptide network orchestrating hematopoiesis has emerged. Here, we focus on this peptide network and discuss the roles of ACE and its peptides in aspects of hematopoiesis. Special attention is given to the recent revelation that ACE is a bona fide marker of hematopoietic stem cells.

Tachykinins and Neurokinin Receptors in Bone Marrow Functions: Neural-Hematopoietic Link

After many decades of neuropeptide research, advances in the field of tachykinins have considerably increased and shown their implications in several physiological processes. In this review we focus on the role of the tachykinins in the regulation of hematopoietic functions. Evidence has shown that neural control of this process is emerging as a significant category in hematopoietic modulation. In the context of this regulation, we discuss the existence of a complex network involving the neurokinin receptors, tachykinins and cytokines. This network is tightly regulated by each of its components.

The change of cytokines in tear and blood after different pterygium operation

Pterygium is an invasion of altered ocular tissue into the cornea. Bone marrow-derived stem cells have been reported to be involved in wound healing under chemotactic factors after pterygium removal and pain may act as a trigger signal. We evaluated the change of systemic and local chemotactic factors that could affect the mobilization and migration of BMSCs to the wound bed after conventional bare sclera pterygium excision. We also applied temporary amniotic membrane patch after pterygium removal, and compared the changes of cytokines with those of conventional bare sclera excision group. Substance-P (SP), vascular endothelial growth factor (VEGF), and stem cell factor (SCF) were measured in plasma and tear using ELISA and migrating CD34(+) cells by flow cytometry. The results showed that post-operative pain was much reduced (p<0.05), and SP, VEGF and SCF kept consistently lower levels in plasma after temporary amniotic membrane application. Circulating CD34(+) cells increased slightly in the temporary amniotic membrane patch group compared with marked increase in the bare sclera group. Thus, the application of a temporary amniotic membrane after pterygium removal might be an effective therapeutic means by controlling pain and excessive infiltration of bone marrow-derived stem cells.

Non-canonical effects of anthrax toxins on haematopoiesis: implications for vaccine development

Anthrax receptor (ATR) shares similarities with molecules relevant to haematopoiesis. This suggests that anthrax proteins might bind to these mimicking molecules and exert non-specific haematopoietic effects. The haematopoietic system is the site of immune cell development in the adult. As such, ATR ligand, protective antigen (PA) and the other anthrax proteins, lethal factor, edema factor, could be significant to haematopoietic responses against Bacillus anthracis infection. Because haematopoiesis is the process of immune cell development, effects by anthrax proteins could be relevant to vaccine development. Here, we report on effects of anthrax proteins and toxins on early and late haematopoiesis. Flow cytometry shows binding of PA to haematopoietic cells. This binding might be partly specific because flow cytometry and Western blots demonstrate the presence of ATR1 on haematopoietic cell subsets and the supporting stromal cells. Functional studies with long-term initiating cell and clonogenic assays determined haematopoietic suppression by anthrax toxins and stimulation by monomeric proteins. The suppressive effects were not attributed to cell death, but partly through the induction of haematopoietic suppressors, interleukin (IL)-10 and CCL3 (MIP-1alpha). In summary, anthrax proteins affect immune cell development by effects on haematopoiesis. The type of effect, stimulation or suppression, depend on whether the stimulator is a toxin or monomeric protein. The studies show effects of anthrax proteins beginning at the early stage of haematopoiesis, and also show secondary mediators such as IL-10 and CCL3. The roles of other cytokines and additional ATR are yet to be investigated.

In vitro substance P-dependent induction of bone marrow cells in common (CD10) acute lymphoblastic leukaemia

The aim of the present research was to investigate the possible in vitro stimulatory effect of substance P (SP) on blasts induction in childhood common acute lymphoblastic leukaemia (ALL). Bone marrow aspirates were incubated with SP receptor agonist or antagonist (spantide) and subsequently assayed for the presence of human interleukin (IL)-1b using ELISA kit. Blast cells incubated with SP receptor agonist were found to result in a significant increase of IL-1b concentration while incubated with spantide resulted in control levels of IL-1b. These findings suggest the novel possible role of SP in blasts proliferation in childhood ALL of common (CD10) origin.

An in vitro method to study the effects of hematopoietic regulators during immune and blood cell development

In adults, hematopoiesis occurs in bone marrow (BM) through a complex process with differentiation of hematopoietic stem cells (HSCs) to immune and blood cells. Human HSCs and their progenitors express CD34. Methods on hematopoietic regulation are presented to show the effects of the chemokine, stromal-derived growth factor (SDF)-1I and the neuropeptide, substance P (SP). SDF-1I production in BM stroma causes interactions with HSCs, thereby retaining the HSCs in regions close to the endosteum, at low oxygen. Small changes in SDF-1I levels stimulate HSC functions through direct and indirect mechanisms. The indirect method occurs by SP production, which stimulates CD34+ cells, supported by ligand-binding studies, long-term culture-initiating cell assays for HSC functions, and clonogenic assays for myeloid progenitors. These methods can be applied to study other hematopoietic regulators.

Endogenous morphine/nitric oxide-coupled regulation of cellular physiology and gene expression: implications for cancer biology

Cancer is a simplistic, yet complicated, process that promotes uncontrolled growth. In this regard, this unconstrained proliferation may represent primitive phenomena whereby cellular regulation is suspended or compromised. Given the new empirical evidence for a morphinergic presence and its profound modulatory actions on several cellular processes it is not an overstatement to hypothesize that morphine may represent a key chemical messenger in the process of modulating proliferation of diverse cells. This has been recently demonstrated by the finding of a novel opiate-alkaloid selective receptor subtype in human multilineage progenitor cells (MLPC). Adding to the significance of morphinergic signaling are the findings of its presence in plant, invertebrate and vertebrate cells, which also have been shown to synthesize this messenger as well. Interestingly, we and others have shown that some cancerous tissues contain morphine. Furthermore, in medullary histolytic reticulosis, which is exemplified by cells having hyperactivity, the mu3 (mu3) opiate select receptor was not present. Thus, it would appear that morphinergic signaling has inserted itself in many processes taking a long time to evolve, including those regulating the proliferation of cells across diverse phyla.

Tachykinins and Hematopoiesis

Originally discovered in the 1930s, tachykinins have been a subject of renewed interest. Antagonists to the tachykinin receptors have shown potential in the treatment of a variety of maladies including neurodegenerative disorders, heart disease, pain perception and malignancies. Tachykinins have been the subject of intense studies due to their impact on hematopoiesis that has significant effects on endothelial tissue and vascular conditions. Hematopoiesis relies on a relatively small subset of bone marrow-resident hematopoietic stem cells. This review discusses the network developed by cytokines and the tachykinins to regulate hematopoiesis. An understanding of tachykinin effect on normal hematopoietic functions and their involvement in hematological disorders could lead to new treatments for bone marrow disorders such as fibrosis, leukemia and anemia.

The significance of substance P in physiological and malignant haematopoiesis

The role of substance P (SP) in physiological haematopoiesis is well established. However, it also seems to be important in the neoplastic transformation of bone marrow, leading to the development of acute leukaemia in children, and also metastases to bone marrow of solid tumours (particularly neuroblastoma and breast cancer) in early stages of these diseases. This review summarises the available data on SP involvement in both processes. In the future, SP antagonists may be used as anti-neoplastic drugs, for example by direct or indirect blocking of tumour cell proliferation through inhibition of growth factor production and interleukin-1b synthesis.

Nuclear factor-kappaB is central to the expression of truncated neurokinin-1 receptor in breast cancer: implication for breast cancer cell quiescence within bone marrow stroma

Breast cancer is a leading cause of mortality among women in the United States. Tac1 and neurokinin-1 (NK1) are involved in autocrine stimulation of breast cancer cells (BCCs). The single NK1 gene produces full-length (NK1-FL) and truncated (NK1-Tr) forms. NK1-Tr mediates malignancy in breast cells. We now report a critical role for nuclear factor-kappaB (NF-kappaB) in the expression of NK1-Tr, but not NK1-FL, in human BCCs. By Western and Northern blot analyses, NK1-FL and NK1-Tr were coexpressed in BCCs but were undetectable in nontumorigenic cells. Loss of repressive activity within the 5' flanking region of the NK1 partly accounts for constitutive expression of NK1 in BCCs but could not account for the presence of NK1-Tr. Transient transfections with dominant-negative and wild-type IkappaB show that activation of NF-kappaB is required for the expression of NK1-Tr. Tac1 gene was linked to the generation of NK1-Tr because its overexpression in BCCs led to the production of multiple cytokines that can activate NF-kappaB to mediate NK1-Tr expression. Studies with Tac1 knockdown BCCs and Tac1-expressing nontumorigenic breast cells verified a role for NF-kappaB in the expression of NK1-Tr. The quiescent phenotype of BCCs on contact with bone marrow stroma was partly explained by decreased NF-kappaB activation and undetectable NK1-Tr. In summary, this study shows a role for NF-kappaB in the expression of NK1-Tr in BCCs, which seems to be reversed by bone marrow stromal cells.

Stromal Derived Growth Factor-1α: Another Mediator in Neural-Emerging Immune System throughTac1Expression in Bone Marrow Stromal Cells

Stromal cell-derived growth factor-1alpha (SDF-1alpha) is a member of the CXC chemokines and interacts with the G protein, seven-transmembrane CXCR4 receptor. SDF-1alpha acts as a chemoattractant for immune and hemopoietic cells. The Tac1 gene encodes peptides belonging to the tachykinin family with substance P being the predominant member. Both SDF-1alpha and Tac1 peptides are relevant hemopoietic regulators. This study investigated the effects of SDF-1alpha on Tac1 expression in the major hemopoietic supporting cells, the bone marrow stroma, and addresses the consequence to hemopoiesis. Reporter gene assays with the 5' flanking region of Tac1 showed a bell-shaped effect of SDF-1alpha on luciferase activity with 20 ng/ml SDF-1alpha acting as stimulator, whereas 50 and 100 ng/ml SDF-1alpha acted as inhibitors. Gel shift assays and transfection with wild-type and mutant IkappaB indicate NF-kappaB as a mediator in the repressive effects at 50 and 100 ng/ml SDF-1alpha. Northern analyses and ELISA showed correlations among reporter gene activities, mRNA (beta-preprotachykinin I), and protein levels for substance P. Of relevance is the novel finding by long-term culture-initiating cell assays that showed an indirect effect of SDF-1alpha on hemopoiesis through substance P production. The results also showed neurokinin 1 and not neurokinin 2 as the relevant receptor. Another crucial finding is that substance P does not regulate the production of SDF-1alpha in stroma. The studies indicate that SDF-1alpha levels above baseline production in bone marrow stroma induce the production of substance P to stimulate hemopoiesis. Substance P, however, does not act as autocrine stimulator to induce the production of SDF-1alpha. This study adds SDF-1alpha as a mediator within the neural-immune-hemopoietic axis.

Oncogenic and metastatic properties of preprotachykinin-I and neurokinin-1 genes

Breast cancer (BC) remains the cancer with highest mortality among women in the United States. Entry of BC cells (BCCs) in bone marrow (BM) leads to poor prognosis. This review discusses studies showing interactions between BCCs and BM stroma, consequently providing BCCs with advantages of survival within BM. Myc transcription factor is investigated as a link between the transforming properties of peptides derived from the preprotachykinin-I gene (PPT-I) and Neurokinin-1 (NK1) receptor. A co-culture method previously described to model early integration of BCC in BM is used to study timeline changes of PPT-I and TGF-beta using northern analyses and a bioassay, respectively. The results show changes of both genes in BCCs and BM stroma. Relevance of these changes to homeostasis in BM is discussed. Myc has been shown to link the expressions of TGF-beta1 and PPT-I in BCCs. We now show a role for Myc in the expression of NK1. PPT-I and the chemokine SDF-1alpha induce the expression of each other through an autocrine mechanism. Since a role for Myc in SDF-1alpha-PPT-I axis has not been studied, we speculate on this finding, based on the cell-homing property of SDF-1alpha. Since Myc could be oncogenic, it might be involved in the transforming properties of PPT-I and NK1 while SDF-1alpha could be involved in cell-homing of BCCs through the regulation of PPT-I. The findings are discussed in the context of other related reports.

Tacrolimus: in vitro effects on myelopoiesis, apoptosis, and CD11b expression

BACKGROUND

Tacrolimus is a common component of multi-drug immunosuppressive regimens that are used for the prevention of rejection in transplant recipients. Tacrolimus therapy has been associated with anemia after transplantation, and recent clinical evidence in children suggests its association with the development of neutropenia for which an alternative etiology is not apparent. Mechanisms of suspected tacrolimus-related neutropenia have not been previously elucidated. We hypothesized that this variety of neutropenia might be due to a negative effect of tacrolimus on neutrophil production and/or survival.

METHODS

We designed in vitro studies to determine the dose-dependent effect of tacrolimus on myeloid cell production and/or apoptosis. CD34+ cells and neutrophils isolated from umbilical cord blood of term gestations were cultured with tacrolimus (0-1,000 ng/ml). To evaluate apoptosis, cells cultured for 24 hours were stained with annexin V-fluorescein isothiocyanate (V-FITC) and 7-amino-actinomycin D (7-AAD) and analyzed by flow cytometry. For clonal analysis, CD34+ cells cultured in cytokine-enhanced semi-solid media were scored for their myeloid/erythroid mix colony forming units (CFU-Mix) and myeloid (CFU-GM) progenitor cell contents.

RESULTS

Tacrolimus induced a dose-dependent enhancement of clonogenesis and survival of CD34+ cells at clinically relevant doses. Conversely, tacrolimus had no effect on the survival of mature neutrophils or on the upregulation of CD11b in response to chemotactic stimulation.

CONCLUSION

In contrast to our initial hypothesis, we observed that tacrolimus at clinically relevant concentrations enhanced clonogenesis of neutrophil progenitors and promoted their survival. Our in vitro studies suggest that tacrolimus alone is unlikely to be a significant factor in the neutropenia observed during immunosuppressive therapy.

The expression of neurokinin-1 and preprotachykinin-1 in breast cancer cells depends on the relative degree of invasive and metastatic potential

Breast cancer has a predilection for metastasis to the bone marrow. The preprotachykinin-I (PPT-I) gene has a central role in the early migration of breast cancer cells into the bone marrow, making this organ a latent repository of the cancer cells. This study investigated whether the invasive and metastatic potential of breast cancer cells correlate with the expression of the PPT-I gene and the receptors for its peptides, neurokinin-1 (NK-1) and NK-2. The studies compared cells that are non-tumorigenic (MCF12A), low metastatic and invasive potential (MCF7), and sublines of MCF with increased invasive and metastatic potential (LCC1 and LCC2). LCC2, but not LCC1 is tamoxifen resistant. Quantitative RT-PCR showed increased expression of PPT-I, NK-1 and NK-2 mRNA LCC1 and LCC2. MCF7 required stimulation by phorbol ester for NK-1 induction. The levels of NK-2 mRNA were significantly increased in LCC2. Clonogenic assays with specific receptor antagonists showed a predominant role for NK-2 in the proliferation of both LCC1 and LCC2. While the growth rate of LCC1 and LCC2 were similar, the latter showed increased migration. Use of a nude mouse model confirmed higher metastatic potential of LCC2, including increased migration to regions of the endosteum. Overall, these studies show a correlation between three neuroendocrine-related genes: PPT-I, NK-1 and NK-2 and the metastatic potential of specific breast cancer cells. These cells provide a model for future studies on bone marrow metastasis.

Specificity of a Vibrio vulnificus aminopeptidase toward kinins and other peptidyl substrates

Recently, phosphoglucose isomerase with a lysyl aminopeptidase (PGI-LysAP) activity was identified in Vibrio vulnificus. In this paper, we demonstrate the proteolytic cleavage of human-derived peptides by PGI-LysAP of V. vulnificus using three approaches: (i) a quantitative fluorescent ninhydrin assay for free lysine, (ii) matrix-assisted laser desorption ionization-two-stage time of flight mass spectrometry (MALDI-TOF-TOF), and (iii) Tricine gel electrophoresis. PGI-LysAP hydrolyzed bradykinin, Lys-bradykinin, Lys-(des-Arg9)-bradykinin, neurokinin A, Met-Lys-bradykinin, histatin 8, and a myosin light chain fragment. We detected the proteolytic release of free L-lysine from peptide digests using a rapid, simple, sensitive, and quantitative fluorescent ninhydrin assay, and results were confirmed by MALDI-TOF-TOF. The use of the fluorescent ninhydrin assay to quantitatively detect free lysine hydrolyzed from peptides is the first application of its kind and serves as a paradigm for future studies. The visualization of peptide hydrolysis was accomplished by Tricine gel electrophoresis. Proteolytic processing of kinins alters their affinities toward specific cellular receptors and initiates signal transduction mechanisms responsible for inflammation, vasodilation, and enhanced vascular permeability. By applying novel approaches to determine the proteolytic potential of bacterial enzymes, we demonstrate that PGI-LysAP has broad exopeptidase activity which may enhance V. vulnificus invasiveness by altering peptides involved in signal transduction pathways.

Preprotachykinin-A Gene Products Are Key Mediators of Lung Injury in Polymicrobial Sepsis

Preprotachykinin-A (PPT-A) gene products substance P and neurokinin-A have been shown to play an important role in neurogenic inflammation. To investigate the role of PPT-A gene products in lung injury in sepsis, polymicrobial sepsis was induced by cecal ligation and puncture in PPT-A gene-deficient mice (PPT-A(-/-)) and the wild-type control mice (PPT-A(+/+)). PPT-A gene deletion significantly protected against mortality, delayed the onset of lethality, and improved the long-term survival following cecal ligation and puncture-induced sepsis. PPT-A(-/-) mice also had significantly attenuated inflammation and damage in the lungs. The data suggest that deletion of the PPT-A gene may have contributed to the disruption in recruitment of inflammatory cells resulting in protection against tissue damage, as in these mice the sepsis-associated increase in chemokine levels is significantly attenuated.

G protein-coupled receptors in haematopoietic disruption

Haematopoiesis is the process by which blood and immune cells are replenished from a finite number of resident bone marrow (BM) haematopoietic stem cells (HSCs). Regulatory molecules within the BM microenvironment contribute developmental signals to an interactive network capable of ensuring ordered biological processes. Many bioactive molecules contribute to the network through G protein-coupled receptors (GPCRs). GPCRs are seven-transmembrane receptors that, following ligand binding, signal by activating coupled heterotrimeric G proteins. This review focuses on those bioactive molecules that regulate haematopoietic development through GPCRs. Chemokines (SDF-1alpha, MIP-1), opioids and tachykinins (SP, NK-A) are important G protein-coupled haematopoietic regulators. Their biology in normal and diseased haematopoiesis is discussed below, as well as their potential as therapeutic targets.

Long-term kindled seizures induce alterations in hematopoietic functions: role of serum leptin

Recent studies conducted in our laboratory have demonstrated marked increases in both serum leptin levels and colony numbers in bone marrow progenitor cells following long-term kindled seizures in rats. The present study sought to determine whether such changes in hematopoietic functions following kindling are linked to increased serum leptin levels. Kindled stage V seizures were induced for 30 days in Sprague-Dawley rats by stimulation of the basal complex of amygdala. The results revealed colony numbers in colony forming units-granulocyte/macrophage (CFU-GM) cultures from kindled rats increased significantly, an effect that was blocked by the presence of an anti-leptin antibody. The results further demonstrated that the addition of serum obtained from kindled rats to CFU-GM cultures from control rats significantly increased the numbers of colonies relative to non-serum added cultures. Moreover, the proliferative effects of serum from kindled rats were also blocked by adding an anti-leptin antibody. These findings were confirmed from the observations that the long isoform of the leptin receptor, which is capable of signal transduction, was present only in kindled, but not in control rats. Thus, the results provide evidence that the hematopoietic changes observed following long-term kindling are directly associated with elevated serum leptin levels.

The anti-proliferative effect of neurokinin-A on hematopoietic progenitor cells is partly mediated by p53 activating the 5' flanking region of neurokinin-2 receptor

The bone marrow (BM) is home to at least two stem cells, hematopoietic (HSC) and mesenchymal. Hematopoiesis is partly regulated through neurokinin-1 (NK-1) and NK-2 belonging to the family of G-protein/7-transmembrane receptors. NK-1 and NK-2 show preference for the neurotransmitters, substance P (SP) and neurokinin-A (NK-A), respectively. Hematopoietic suppression mediated by NK-A could be partly explained through the production of TGF-beta1 and MIP-1alpha. This study further characterizes mechanisms by which NK-A inhibits progenitor cell proliferation. The study addresses the hypothesis that p53 is a mediator of NK-A activation and this occurs partly through p53-mediated expression of NK-2. The studies first analyzed two consensus sequences for p53 in supershift assays. Reporter gene assays with NK-2 gene constructs and p53 expressing wild-type and mutant vectors, combined with cell proliferation assays, show NK-A activating p53 to inhibit the proliferation of K562 progenitors. These effects were reversed by hematopoietic stimulators, GM-CSF and SP. Verification studies with human CD34+/CD38- and CD34+/CD38+ BM progenitors show similar mechanisms with the expression of p21. This study reports on p53 as central to NK-A-NK-2 interaction in cell cycle quiescence of hematopoietic progenitors. These effects are reversed by at least two hematopoietic stimulators, SP and GM-CSF, with concomitant downregulation of p53.

Signal transduction pathways involved in the lineage-differentiation of NSCs: can the knowledge gained from blood be used in the brain?

Neural stem cells (NSC) are capable of differentiating toward neuronal, astrocytic, oligodendrocytic and glial lineages, depending on their spatial location within the central nervous system (CNS). Although, a lot of knowledge has been gained in the understanding of differentiation-specific signaling in hematopoietic (HSC) and mesenchymal (MSC) counterparts, the molecular mechanisms underlying lineage commitment in NSCs are just beginning to be understood. Furthermore, it is not well comprehended as to how the specification of one cell lineage can result in the suppression of parallel pathways in the NSCs. Thus, a thorough understanding of various signal transduction cascades activated via cytokines and growth factors, and the confounding effects of different CNS microenvironments are critically required to determine the full potential of NSCs. Our knowledge on the clonogenic ability, differentiation potential, and the inherent plasticity in both HSCs and MSCs may facilitate the understanding of lineage commitment in the NSCs as well. The information available from the marrow-derived stem cells may be extrapolated toward the similar signaling pathways in the neural precursors. From a number of previous studies, it is apparent that four distinctly different subsets of ligand-receptor superfamilies are involved in determining the fate of NSCs. These include 1) the transforming growth factor type-beta-1 (TGF-beta1) and bone morphogenetic protein (BMP) superfamily; 2) the platelet-derived and epidermal (PDGF/EGF) growth factors; 3) the interleukin-6, leukemia inhibitory factor, and ciliary neurotrophic factor (IL-6/LIF/CNTF) superfamily; and 4) the EGF-like Notch/Delta group of extracellular ligands. Ligand binding to the cell surface receptor activates the receptor's cytosolic catalytic domain and/or the receptor-associated protein-kinases, which in turn activate intracellular second messengers and different sets of transcription factors. Transcription factor oligomerization, nuclear localization, followed by their recognition of DNA elements, leads to the expression of lineage-specific genes. Association between different groups of transcription factors can also regulate their ability to transcriptionally activate different genes. The limited availability of coactivators and cosuppressors, which can sequester the transcription factor complexes toward or away from a specific gene locus, further adds to the complexity in the cross talk between different signaling cascades. Both concerted actions of temporally regulated signals and convergent effects of different signaling cascades can thus ultimately precipitate the phenotypic changes. It is beginning to be realized that in addition to the cytokines and growth factors, cell-to-cell and cell-to-extracellular matrix (ECM) interactions, are also important within the molecular scenario linked to both proliferation and differentiation of the stem cells. The cell surface molecules, which include cell adhesion molecules (CAMs), integrins, selectins, and the immunoglobulins, are well known to regulate HSC and MSC commitment within different tissue microenvironments and may have direct implications in understanding the NSC cell fate determination within different regions of the brain.

Mechanisms of selection mediated by interleukin-7, the preBCR, and hemokinin-1 during B-cell development

Many of the stromal-derived signals and factors that regulate B lymphopoiesis have been identified. We review recent evidence from our laboratory that shows that there are at least three phases during B-cell development when cells direct their own maturation, independent of stromal cells. Following the expression of the preB-cell receptor (preBCR), cells acquire the ability to proliferate in low levels of interleukin-7 (IL-7), which acts as a self-selecting mechanism to expand cells that have successfully expressed a preBCR in environments that are non-permissive to preBCR- cells. Second, the preBCR is required for a contact-mediated event between B-cell progenitors. Disruption at this stage prevents the further maturation of progenitors to the lipopolysaccharide (LPS)-responsive stage. Finally, the transition from IL-7 receptor to mature antigen receptor-based signaling is enhanced by a novel member of the tachykinin family, hemokinin-1. This series of maturation, survival, and differentiation signals is generated by B-lineage cells as they progress through developmental checkpoints on the way to becoming functionally mature cells.

Bone Marrow Stroma Influences Transforming Growth Factor-β Production in Breast Cancer Cells to Regulate c-myc Activation of the Preprotachykinin-I Gene in Breast Cancer Cells

Breast cancer cells (BCCs) have preference for the bone marrow (BM). This study used an in vitro coculture of BCCs and BM stroma to represent a model of early breast cancer metastasis to the BM. The overarching hypothesis states that once BCCs are in the BM, microenvironmental factors induce changes in the expression of genes for cytokines and preprotachykinin-I (PPT-I) in both BCCs and stromal cells. Consequently, the expression of both PPT-I and cytokines are altered to facilitate BCC integration within BM stroma. Cytokine and transcription factor arrays strongly suggested that transforming growth factor-beta (TGF-beta) and c-myc regulate the expression of PPT-I so as to facilitate BCC integration among stroma. Northern analyses and TGF-beta bioassays showed that stromal cells and BCCs influence the level of PPT-I and TGF-beta in each other. In cocultures, PPT-I and TGF-beta expressions were significantly (P < 0.05) increased and decreased, respectively. TGF-beta and PPT-I were undetectable in separate stromal cultures but were expressed as cocultures. Two consensus sequences for c-myc in the 5' flanking region of the PPT-I gene were shown to be functional using gel shift and reporter gene assays. Mutagenesis of c-myc sites, neutralization studies with anti-TGF-beta, and transient tranfections all showed that c-myc is required for TGF-beta-mediated induction of PPT-I in BCCs. TGF-beta was less efficient as a mediator of BCC integration within stroma for c-myc-BCCs. Because the model used in this study represents BCC integration within BM stroma, these studies suggest that TGF-beta is important to the regulation of PPT-I in the early events of bone invasion by BCCs.

Myelopoietic Response in Mice Exposed to Acute Cold/Restraint Stress: Modulation by Chlorella vulgaris Prophylactic Treatment

In this study, hematopoietic cells from mice pretreated with CVE and exposed to acute cold/restraint stress were stimulated in the presence of growth factors to form colonies, thus providing accurate information about the modulation of the green algae of the stress-induced changes in the hematopoietic response. Our results demonstrated that exposure to acute stress affected hematopoiesis. Mice exposed for a 2.5-hour time period of cold and restraint presented diminished clonal capacity for CFU-GM content per femur, which was decreased by as much as 50% compared with that in control mice, in spite of the significant increase in serum colony-stimulating activity (CSA). Treatment with 50 mg/kg CVE for 5 days, previously to the stress regimen, attenuates the effects of the stress, since comparable levels of myeloid progenitors were found in the bone marrow of both CVE/stress and control mice. Moreover, the sera from stressed mice pretreated with CVE further increased the CFU-GM formation. On the contrary, the spleen seemed to be less sensitive to acute stress in our experimental conditions. These findings are in line with our previous reports showing that the stress-induced reduction in bone marrow CFU-GM of rats exposed to electric shocks is mediated by activation of the HPA axis and by secretion of opioid agonists. No changes were observed in bone marrow, spleen and thymus total cell counts, and in relative organ weights. However, a 50% reduction in the body weight loss produced by the stress was observed in mice given the extract.

Neurotrophin-3 regulates mast cell functions in neonatal mouse skin

Nerve growth factor (NGF) has long been recognized as an important mast cell (MC) growth factor. To explore whether other neurotrophins (NTs) of the NGF family, which are widely expressed in mouse skin, affect the numbers and/or functions of MCs we examined the effects of NT-3 on neonatal skin MCs. We demonstrate that TrkC, the high affinity NT-3 receptor, is expressed by virtually all neonatal skin MCs in C57BL/6 mice, which indicates that MCs can respond to NT-3. Skin of neonatal and early postnatal NT-3-overexpressing mice (promoter: K14) displayed significantly and up to twofold increased numbers of MCs during the first 20 days after birth, as compared to wild-type mice. To check whether this increase in MC numbers in NT-3 transgenic mice reflects a higher rate of proliferation, we performed immunohistochemistry, which revealed that only 1-2% of all skin MCs both in NT-3-overexpressing and in wild-type controls showed Ki-67-positive nuclei, suggesting that the observed differences in the number of MCs do not reflect a higher rate of MC proliferation. Additionally, we show that the effect of NT-3 on the number of MCs is most likely to be stem cell factor (SCF)-independent, because NT-3 significantly downregulates secretion of SCF-protein in cultured dermal fibroblasts, as assessed by enzyme-linked immunosorbent assay. Numbers of skin MCs in neonatal TrkC-deficient mice were found to be modestly reduced, as compared to wild-type mice, indicating that NT-3 can modulate the number of MCs directly via TrkC, although TrkC does not seem to be essential for the number of basal MCs. To further analyze the effects of NT-3 on MCs, we stimulated skin organ culture of early postnatal C57BL/6 mouse skin with 5-50 ng/ml NT-3, which induced a significant increase in MC degranulation, as visualized by Giemsa staining. However, stimulation of isolated neonatal dermal skin MCs with NT-3 in vitro failed to result in MC activation, as measured by serotonin release. Our data suggest a role for NT-3 in the maturation of MCs, such as a TrkC-mediated stimulation of the differentiation of pre-existing, less mature MCs and/or by enhancing the migration of circulating MC precursors into the skin.

Autonomic innervation of immune organs and neuroimmune modulation

1. Increasing evidence indicates the occurrence of functional interconnections between immune and nervous systems, although data available on the mechanisms of this bi-directional cross-talking are frequently incomplete and not always focussed on their relevance for neuroimmune modulation. 2. Primary (bone marrow and thymus) and secondary (spleen and lymph nodes) lymphoid organs are supplied with an autonomic (mainly sympathetic) efferent innervation and with an afferent sensory innervation. Anatomical studies have revealed origin, pattern of distribution and targets of nerve fibre populations supplying lymphoid organs. 3. Classic (catecholamines and acetylcholine) and peptide transmitters of neural and non-neural origin are released in the lymphoid microenvironment and contribute to neuroimmune modulation. Neuropeptide Y, substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide represent the neuropeptides most involved in neuroimmune modulation. 4. Immune cells and immune organs express specific receptors for (neuro)transmitters. These receptors have been shown to respond in vivo and/or in vitro to the neural substances and their manipulation can alter immune responses. Changes in immune function can also influence the distribution of nerves and the expression of neural receptors in lymphoid organs. 5. Data on different populations of nerve fibres supplying immune organs and their role in providing a link between nervous and immune systems are reviewed. Anatomical connections between nervous and immune systems represent the structural support of the complex network of immune responses. A detailed knowledge of interactions between nervous and immune systems may represent an important basis for the development of strategies for treating pathologies in which altered neuroimmune cross-talking may be involved.

Substance P--a potent risk factor in childhood lymphoblastic leukaemia

The study focused on determining the expression of substance P (SP) in neoplastic bone marrow cells in childhood acute lymphoblastic leukaemia (ALL) in terms of its mRNA and the level of protein production. An attempt has also been made to demonstrate a correlation of SP with leukaemia risk factors and treatment failure. The study group comprised 120 children treated for ALL. Expression of SP was examined by in situ hybridisation with a 5'-biotinylated probe and by immunocytochemistry with specific anti-human SP antibody. Out of 80 patients with common ALL, the expression of SP was demonstrated in 33 cases (41.2%). In the group of 24 children with pre-B ALL, the presence of SP was noted in six cases (25.0%). Of 16 patients with T-cell leukaemia, SP expression was demonstrated in 13 cases (81.2%). The percentage of immunopositive cells in the SP-positive cases ranged from 79.8 to 97.3. Treatment failure in the children with ALL was closely related to the expression of SP observed at the beginning of treatment. The results showed a connection between the presence of SP-positive blasts and leukaemia relapse. This may indicate that SP expression, involved in the proliferation of the tumour cells, may represent a novel risk factor in ALL.

Crosstalk between neurokinin receptors is relevant to hematopoietic regulation: cloning and characterization of neurokinin-2 promoter

Neurokinin (NK)-1 and NK-2 receptors regulate hematopoiesis by interacting with neurotransmitters that belong to the tachykinin. This report studies the relationship between NK-1 and NK-2 in primary human bone marrow (BM) stroma, which supports hematopoiesis. Use of NK receptor antagonists and deficient stromal cells indicate that the neurotransmitter, substance P (SP), could exert dual hematopoietic effects (inhibitory or stimulatory), depending on the interacting receptor and crosstalk between NK-1 and NK-2. Cloning and identification of the minimal promoter for NK-2 and comparison with NK-1 promoter showed that the hematopoietic functions of NK receptors involve receptor crosstalk and the particular cytokine (IL-3, GM-CSF, TGF-beta or IL-1alpha). Crosstalk between NK-1 and NK-2 adds to communication within neural-hematopoietic axis.

Effects of kindled seizures upon hematopoiesis in rats

OBJECTIVE

Studies conducted in epilepsy patients and experimental animals have suggested a linkage between seizure activity and alterations in immune functions. However, little is known about the underlying mechanisms. The present study sought to determine whether chronic seizures result in changes in hematopoietic functions that contribute to alterations in immune function.

MATERIALS AND METHODS

Sprague-Dawley rats were implanted with electrodes in the basal amygdala or frontal cortex for induction of focal seizures by kindling. After inducing stage 5 seizures for 30 days, rats were sacrificed and assays for colony-forming units granulocyte/macrophage (CFU-GM) were performed to study progenitor cell functions. Long-term culture-initiating culture (LTC-IC) assays were employed to determine the effects of kindling upon bone marrow stroma. A Western blot for caspase-3 and CFU-GM assays from peripheral blood were used to determine the cause of reduced cellularity of bone marrow.

RESULTS

Kindled seizures of the basal amygdala resulted in decreases in bone marrow cellularity and hyperproliferation of colony-forming cells in peripheral blood and bone marrow. Modified LTC-IC assays, where co-cultures of bone marrow cells and stroma from experimental animals were employed, revealed that hyperproliferation of progenitor cells was not associated with alterations in stromal functions. The changes observed in this study were associated with seizure foci in the basal amygdaloid complex but not the frontal cortex.

CONCLUSION

Kindled seizures of the basal amygdala induce hyperproliferation of bone marrow progenitor cells, suggesting that alterations in immunological functions observed following seizure activity may be due to changes in hematopoietic functions. Such changes appear to be site specific within the brain.

Hematopoietic growth factor inducible neurokinin-1 type: a transmembrane protein that is similar to neurokinin 1 interacts with substance P

Neurokinin 1 (NK-1) is a member of seven transmembrane G protein-coupled receptors. NK-1 interacts with peptides belonging to the tachykinin family and showed preference for substance P (SP). NK-1 is induced in bone marrow (BM) stroma. NK-1-SP interactions could lead to changes in the functions of lymphohematopoietic stem cell (LHSC). This report describes the cloning and characterization of a cDNA clone isolated after screening of three cDNA libraries with an NK-1-specific probe. Based on its expression, the cDNA clone was designated hematopoietic growth factor inducible neurokinin-1 type (HGFIN). Computational analyses predicted that HGFIN is transmembrane with the carboxyl terminal extracellular. Proteomic studies with purified HGFIN and SP showed noncovalent interactions. HGFIN-SP interactions were supported by transient expression of HGFIN in CHO cells. Transient expression of HGFIN in unstimulated BM fibroblasts led to the induction of endogenous NK-1. Since NK-1 expression in BM fibroblasts requires cell stimulation, these studies suggest that there might be intracellular crosstalk between NK-1 and HGFIN. Northern analyses with total RNA from different BM cell subsets showed that HGFIN was preferentially expressed in differentiated cells. This suggests that HGFIN might be involved in the maturation of LHSC. HGFIN was detected in several other tissues, but not in brain where NK-1 is constitutively expressed.

Human bone marrow angiogenesis: in vitro modulation by substance P and neurokinin A

We have previously described a culture system for human bone marrow endothelial cells that organize into capillary tubes associated to pericytes. In the present work, we used this model to assess the angiogenic properties of tachykinins, which have been demonstrated to be involved in neuro-immuno-haematopoietic interactions. The substance P (SP) and neurokinin A (NKA) were similarly potent at increasing in vitro angiogenesis, via NK1 and NK2 receptors respectively. These mediators were not produced by cells in culture, suggesting that in vivo they may be released by nerve fibres in the bone marrow. Therefore, we looked for in situ innervation of the human bone marrow, unknown to date, using immunohistochemistry techniques. As in rodents, arterioles were largely innervated, associated with between one and 10 nerve fibres. Capillary innervation was more restrictive as a unique thin nerve fibre was found in the vicinity of only 6% of these vessels. Finally, no nerve fibres were observed in the vicinity of sinus walls. In conclusion, both in vitro results and the anatomical display of nerve fibres suggest a role in human bone marrow for the vasoactive neuropeptides SP and NKA, which were secreted into a perivascular location. These neural mediators might modulate blood flow in the bone marrow both in the short term by adjusting vascular tone and in the long term by inducing angiogenesis.

Developmental pattern of tachykinins during aging in several organs: effect of exogenous melatonin

Mammalian neurokinin A (NKA) and substance P (SP) are neuropeptides widely distributed in the body; they are potential regulators of the basal blood flow and therefore of the function of many organs and tissues. In the present investigation, we studied the age-dependent changes in NKA and SP in ovary, liver, pancreas and spleen as well as the role of exogenous melatonin on these changes. Female rats of 5, 15 or 25 months of age were studied. In the ovary, NKA concentrations did not change during aging. SP concentrations in the control group were significantly higher (P<0.01) in old rats than in the other two age groups studied. Melatonin treatment resulted in reduced concentrations as compared with those of the control old rats. In the pancreas, NKA and SP concentrations increased during aging, the young rats showing significantly lower values (P<0.01) than middle-aged and old rats for NKA and significantly lower (P<0.01) than the old rats for SP. After melatonin treatment the differences in NKA concentrations disappeared and SP decreased in middle-aged as compared with those in old rats. In the liver, NKA and SP concentrations in the control and melatonin-treated groups did not differ significantly for the three age groups studied. Splenic NKA in control and melatonin-treated groups increased from young to middle-age up to old ages. SP concentrations showed similar values at all ages except in melatonin-treated old rats; in these animals there were significantly higher concentrations than in young melatonin-treated rats. The effect of melatonin was mainly observed on the ovary and pancreas in old rats, with a reduction in the concentrations as compared with those observed in the young groups.

Substance P receptor expression on lymphocytes is associated with the immune response to respiratory syncytial virus infection

The kinetics and magnitude of SP receptor expression was determined for bronchoalveolar leukocyte cell subsets from BALB/c mice in the primary immune response to respiratory syncytial virus (RSV) and human parainfluenza virus-3 (PIV3) infection, and in the secondary immune response to RSV and PIV3 challenge. In both the primary and secondary responses to infection, expression of substance P (SP) receptors was markedly increased by infection, especially for T lymphocytes, compared to B220+, CD11b+ and CD14+ cells. CD4+ T lymphocytes predominantly expressed SP receptors in the secondary response. These results suggest that SP receptor expression may be important in the development of primary and secondary immune responses to respiratory virus infections.

Structural similarity between the bone marrow extracellular matrix protein and neurokinin 1 could be the limiting factor in the hematopoietic effects of substance P

In the adult bone marrow (BM), immune cells are replenished through the process of definitive hematopoiesis, which is regulated by a complex process of cellular and humoral interactions. The latter include substance P (SP), a neurotransmitter that is produced by neural and nonneural cells. Neurokinin-1 (NK-1), the high-affinity SP receptor, shares structural similarity with fibronectin, a component of the BM extracellular matrix proteins. This study examines how such similarity could alter the effects of SP on the proliferation of the immature BM progenitors. In vitro studies show that 1 ng fibronectin/mL enhanced the stimulatory effect of SP on the proliferation of primitive BM progenitors. This finding was studied by computational studies: proteomics and three-dimensional molecular modeling. Use of surface-enhanced laser desorption/ionization ProteinChip technology showed that despite the induction of neutral endopeptidase, exogenous fibronectin hindered the degradation of SP to SP(1-4). These findings support a protective role for fibronectin in the digestion of SP. Since SP(1-4) is a negative regulator of hematopoiesis, this report indicates that the structural similarity between fibronectin and NK-1 could be important for maintaining hematopoietic stimulation. These studies could be extrapolated to hematological disorders that are associated with SP-fibronectin complexes.

Inhibition of hematopoietic progenitor cell growth by Tyr-MIF, an endogenous opiate modulator, and its degradation products

There is increasing evidence that neuronal factors can affect hematopoietic cell proliferation. Endogenous opioids with specificity for several opioid receptor classes were tested for their ability to inhibit murine and human hematopoietic progenitor cell proliferation. Tyr-MIF, an opioid tetrapeptide (H-Tyr-Pro-Leu-Gly-NH2), demonstrated a dose-dependent inhibition of colony formation at concentrations < 10 uM, inhibiting M-CSF and G-CSF-responsive progenitor cells equally. Tyr-MIF did not inhibit the number of colonies responsive to recombinant interleukin 3 (rmIL-3) or recombinant murine granulocyte-macrophage colony stimulating factor (rmGM-CSF), but significantly reduced colony size of GM-CSF responsive colonies. Colony formation by human low density and CD34+ marrow cells in response to G-CSF was also inhibited by Tyr-MIF and was more sensitive to inhibition than murine progenitor cells. Colony formation by single CD34+ cells was also inhibited by Tyr-MIF, indicating an effect directly on progenitor cells. Incubation of marrow cells in liquid culture and removal of Tyr-MIF prior to quantitating progenitor cell proliferation demonstrated that opioid-induced inhibition was reversible. The inhibitory effect of Tyr-MIF was not blocked by naloxone, a mu receptor specific antagonist, or diminished in mu opioid receptor deficient mice. HPLC analysis of cell-free culture medium containing Tyr-MIF showed no presence of the parent peptide after 24 h while progenitor cell inhibitory activity was retained. Analysis of potential degradation products of Tyr-MIF indicated that only H-Gly-NH9 or H-Gly-NH2 containing peptides inhibited colony forming unit (CFU) proliferation. These results indicate that Tyr-MIF is a reversible inhibitor of mature hematopoietic progenitor cell proliferation, and that this effect is most likely mediated by the degradation product H-Gly-NH2. Potential applications including protection of myeloid cells after cytosuppresive therapy are discussed.

Differences in the expression of neurokinin receptor in neural and bone marrow mesenchymal cells: implications for neuronal expansion from bone marrow cells

The neurokinin-1 (NK-1) receptor interacts with peptides that belong to the tachykinin family. NK-1 is inducible in bone marrow (BM) stroma. In neural cells, its expression is high to constitutive. Screening of three cDNA libraries indicated that this different in NK-1 expression in neural and BM cells could not be explained by differences in the cDNA sequence. Analyses the 5' flanking sequence in BM stroma and three neural cell lines indicated that sequence +1/+358 relative to the transcription start (TS) site could account for the differences in NK-1 expression. Particular cytokines could reverse the repressive effects of region +1/+358 in BM stroma. The effects of NF-kappa B and cAMP activators were studied in stromal cells using a dominant negative inhibitor of NF-kappa B (I kappa B) or a repressor of CRE activators (ICERII gamma). The results showed that their effects of these transcription factors depended on the stimulating cytokine. This study provides insight into the tissue-specific differences in the expression of the NK-1 gene.

The dynamics of bone marrow stromal cells in the proliferation of multipotent hematopoietic progenitors by substance P: an understanding of the effects of a neurotransmitter on the differentiating hematopoietic stem cell

Communication within the hematopoietic-neuroendocrine-immune axis is partly mediated by neurotransmitters (e.g. substance P, SP) and cytokines. SP mediates neuromodulation partly through the stimulation of bone marrow (BM) progenitors. This study shows that SP, through the neurokinin-1 receptor, stimulates the proliferation of primitive hematopoietic progenitors: cobblestone-forming cells (CAFC, CD34+). This effect is optimal when macrophage is included within the fibroblast support. Indirect induction of IL-1 could be important in the proliferation of CAFC colonies by SP. Phenotypic and functional studies suggest that SP might directly interact with the CD34+/CD45(dim) population. These studies indicate that SP can initiate a cascade of biological responses in the BM stroma and stem cells to stimulate hematopoiesis.

Negative feedback on the effects of stem cell factor on hematopoiesis is partly mediated through neutral endopeptidase activity on substance P: a combined functional and proteomic study

Hematopoietic regulation is a complex but dynamic process regulated by intercellular and intracellular interactions within the bone marrow (BM) microenvironment. Through neurokinin-1 (NK-1) and NK-2 receptors, peptides (eg, substance P [SP]) encoded by the preprotachykinin-I gene mediate distinct hematopoietic effects. Cytokines, associated with hematopoietic stimulation, and SP regulate the expression of each other in BM mesenchymal and immune cells. Neutral endopeptidase (NEP) uses SP as a substrate to produce SP(1-4), which inhibits the proliferation of matured myeloid progenitor. This study determines whether the degradation of SP to SP(1-4) by endogenous NEP in BM stroma could be a feedback on hematopoietic stimulation by stem cell factor (SCF). SP(1-4) induced the production of transforming growth factor (TGF)-beta and tumor necrosis factor-alpha in BM stroma. TGF-beta production accounted for part of the inhibitory effects by SP(1-4) on the proliferation of early (granulocyte-macrophage colony-forming units) and late (long-term culture-initiating cells) hematopoietic progenitors. Enzyme-linked immunosorbent assays and/or protein-chip arrays indicated a timeline change of SP to SP(1-4) in BM stroma stimulated with SCF, which correlated with increase in NEP messenger RNA. Since SP and its fragment, SP(1-4), interact with the same receptor to mediate opposing hematopoietic effects, 2 interactive studies were done to understand the dual responses of NK-1: (1) a 3-dimensional molecular model of NK-1 and SP and (2) screening of a random dodecapeptide library for SP(1-4) interacting sites. The effects of SP(1-4) on hematopoietic progenitors and the timeline change of SP to SP(1-4), together with the 3-dimensional model, provide a partial explanation for the feedback on the stimulatory effects of SCF and SP on hematopoiesis.

Induction of hypoxia-inducible factor-1alpha and activation of caspase-3 in hypoxia-reoxygenated bone marrow stroma is negatively regulated by the delayed production of substance P

The bone marrow (BM), which is the major site of immune cell development in the adult, responds to different stimuli such as inflammation and hemorrhagic shock. Substance P (SP) is the major peptide encoded by the immune/hemopoietic modulator gene, preprotachykinin-1 (PPT-I). Differential gene expression using a microarray showed that SP reduced hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA levels in BM stroma. Because long-term hypoxia induced the expression of PPT-I in BM mononuclear cells, we used timeline studies to determine whether PPT-I is central to the biologic responses of BM stroma subjected to 30-min hypoxia (pO(2) = 35 mm Hg) followed by reoxygenation. HIF-1alpha mRNA and protein levels were increased up to 12 h. At this time, beta-PPT-I mRNA was detected with the release of SP at 16 h. SP release correlated with down-regulation of HIF-1alpha to baseline. A direct role for SP in HIF-1alpha expression was demonstrated as follows: 1) transient knockout of beta-PPT-I showed an increase in HIF-1alpha expression up to 48 h of reoxygenation; and 2) HIF-1alpha expression remained baseline during reoxygenation when stroma was subjected to hypoxia in the presence of SP. Reoxygenation activated the PPT-I promoter with concomitant nuclear translocation of HIF-1alpha that can bind to the respective consensus sequences within the PPT-I promoter. SP reversed active caspase-3, an indicator of apoptosis and erythropoiesis, to homeostasis level after reoxygenation of hypoxic stroma. The results show that during reoxgenation the PPT-I gene acts as a negative regulator on the expression of HIF-1alpha and active caspase-3 in BM stroma subjected to reoxygenation.

Mimicry between neurokinin-1 and fibronectin may explain the transport and stability of increased substance P immunoreactivity in patients with bone marrow fibrosis

Bone marrow (BM) fibrosis may occur in myeloproliferative diseases, lymphoma, myelodysplastic syndrome, myeloma, and infectious diseases. In this study, the role of substance P (SP), a peptide with pleiotropic functions, was examined. Some of its functions-angiogenesis, fibroblast proliferation, and stimulation of BM progenitors-are amenable to inducing BM fibrosis. Indeed, a significant increase was found in SP-immunoreactivity (SP-IR) in the sera of patients with BM fibrosis (n = 44) compared with the sera of patients with hematologic disorders and no histologic evidence of fibrosis (n = 46) (140 +/-12 vs 18 +/-3; P <.01). Immunoprecipitation of sera SP indicated that this peptide exists in the form of a complex with other molecule(s). It was, therefore, hypothesized that SP might be complexed with NK-1, its natural receptor, or with a molecule homologous to NK-1. To address this, 3 cDNA libraries were screened that were constructed from pooled BM stroma or mononuclear cells with an NK-1 cDNA probe. A partial clone (clone 1) was retrieved that was 97% homologous to the ED-A region of fibronectin (FN). Furthermore, sequence analyses indicated that clone 1 shared significant homology with exon 5 of NK-1. Immunoprecipitation and Western blot analysis indicated co-migration of SP and FN in 27 of 31 patients with BM fibrosis. Computer-assisted molecular modeling suggested that similar secondary structural features between FN and NK-1 and the relative electrostatic charge might explain a complex formed between FN (negative) and SP (positive). This study suggests that SP may be implicated in the pathophysiology of myelofibrosis, though its role would have to be substantiated in future research. (Blood. 2001;97:3025-3031)

Effects of preprotachykinin-I peptides on hematopoietic homeostasis. A role for bone marrow endopeptidases

Hematopoiesis is maintained by "fine-tuned" regulation among cytokines, neuropeptides, neurotransmitters, and neurotrophic factors. Neurotransmitters, derived from PPT-I exert immune and hematopoietic regulation. PPT-I is also expressed locally in bone marrow (BM) stromal cells. PPT-I peptides induce the production of cytokines in BM cells, resulting in regulation of both committed progenitors (CFU-GM) and primitive hematopoietic progenitors (CAFC). Both types of progenitors are regulated differently by the two major PPT-I peptides, SP and NK-A. Endopeptidases, present in BM cells, can digest SP to produce SP(1-4) and SP(4-11). In this study, we investigated the hematopoietic effects of these fragments on CFU-GM and CAFC. Similar to the two major intact PPT-I peptides (SP and NK-A), we observed different hematopoietic effects by SP(1-4) and SP(4-11). Whereas SP(1-4) exerted inhibitory effects on CFU-GM and CAFC, SP(4-11) mediated stimulatory effects. Similar to NK-A, the inhibitory effects of SP(1-4) can be partly explained by the induction of suppressive cytokines (TGF-beta, TNF-alpha, and INF-gamma). Use of antagonists and screening of a dodecapeptide expression library determined that the effects of SP(1-4) were mediated by NK-1. These results show that PPT-I peptides and their endopeptidase-derived fragments may add to the fine-tuned regulation on hematopoiesis. Furthermore, PPT-I may be exerting autoregulation to protect hematopoietic stem cells. These studies have relevance to stem cell protection and BM transplant.

Cloning of human preprotachykinin-I promoter and the role of cyclic adenosine 5'-monophosphate response elements in its expression by IL-1 and stem cell factor

Preprotachykinin-I gene (PPT-I) encodes several peptides with organ-specific functions that link the neuroendocrine-immune-hemopoietic axis. We cloned upstream of the initiation site of human PPT-I promoter and identified consensus sequences for two cAMP response elements (CRE). PPT-I is induced by cytokines including those that signal through the cAMP pathway. Therefore, we studied the role of the two CRE in IL-1alpha and stem cell factor (SCF) stimulation of bone marrow stroma because both cytokines induce endogenous PPT-I in these cells and activate the cAMP pathway. Furthermore, bone marrow stroma expresses the transcription factors regulated by the cAMP pathways such as the repressor (ICERIIgamma) and activator (CREMtau). Mutagenesis of the two CRE and/or cotransfection with vectors that express ICERIIgamma or CREMtau indicated that the two CRE have major roles in PPT-I expression. The two CRE are also required for optimal promoter activity by SCF and IL-1alpha. A particular cytokine could concomitantly induce PPT-I and the high affinity G protein-coupled receptor for PPT-I peptides, NK-1R. We showed that SCF, a representative cytokine, induced PPT-I and NK-1R leading to autocrine and/or paracrine cell activation. Because NK-1R activates cAMP through the G protein, the results suggest that the presence of CRE sequences within PPT-I promoter could be important in the regulation of PPT-I expression by cytokines, irrespective of their ability to signal through cAMP. As PPT-I is implicated in hemopoietic regulation, immune responses, breast cancer, and other neural functions, these studies add to the basic biology of these processes and could provide targets for drug development.