Local umbilical cord blood renin?angiotensin system

Insights Into Vascular Anomalies, Cancer, and Fibroproliferative Conditions: The Role of Stem Cells and the Renin-Angiotensin System

Cells exhibiting embryonic stem cell (ESC) characteristics have been demonstrated in vascular anomalies (VAs), cancer, and fibroproliferative conditions, which are commonly managed by plastic surgeons and remain largely unsolved. The efficacy of the mTOR inhibitor sirolimus, and targeted therapies that block the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways in many types of cancer and VAs, further supports the critical role of ESC-like cells in the pathogenesis of these conditions. ESC-like cells in VAs, cancer, and fibroproliferative conditions express components of the renin-angiotensin system (RAS) – a homeostatic endocrine signaling cascade that regulates cells with ESC characteristics. ESC-like cells are influenced by the Ras/BRAF/MEK/ERK1/2 and PI3KCA/AKT/mTOR pathways, which directly regulate cellular proliferation and stemness, and interact with the RAS at multiple points. Gain-of-function mutations affecting these pathways have been identified in many types of cancer and VAs, that have been treated with targeted therapies with some success. In cancer, the RAS promotes tumor progression, treatment resistance, recurrence, and metastasis. The RAS modulates cellular invasion, migration, proliferation, and angiogenesis. It also indirectly regulates ESC-like cells via its direct influence on the tissue microenvironment and by its interaction with the immune system. In vitro studies show that RAS inhibition suppresses the hallmarks of cancer in different experimental models. Numerous epidemiological studies show a reduced incidence of cancer and improved survival outcomes in patients taking RAS inhibitors, although some studies have shown no such effect. The discovery of ESC-like cells that express RAS components in infantile hemangioma (IH) underscores the paradigm shift in the understanding of its programmed biologic behavior and accelerated involution induced by β-blockers and angiotensin-converting enzyme inhibitors. The findings of SOX18 inhibition by R-propranolol suggests the possibility of targeting ESC-like cells in IH without β-adrenergic blockade, and its associated side effects. This article provides an overview of the current knowledge of ESC-like cells and the RAS in VAs, cancer, and fibroproliferative conditions. It also highlights new lines of research and potential novel therapeutic approaches for these unsolved problems in plastic surgery, by targeting the ESC-like cells through manipulation of the RAS, its bypass loops and converging signaling pathways using existing low-cost, commonly available, and safe oral medications.

Pharmacological ACE-inhibition Mitigates Radiation-Induced Pneumonitis by Suppressing ACE-expressing Lung Myeloid Cells

PURPOSE

Radiation-induced lung injury is a major dose-limiting toxicity for thoracic radiotherapy patients. In experimental models, treatment with angiotensin converting enzyme (ACE) inhibitors mitigates radiation pneumonitis; however, the mechanism of action is not well understood. Here, we evaluate the direct role of ACE inhibition on lung immune cells.

METHODS AND MATERIALS

ACE expression and activity were determined in the lung immune cell compartment of irradiated adult rats following either high dose fractionated radiation therapy (RT) to the right lung (5 fractions x 9 Gy) or a single dose of 13.5 Gy partial body irradiation (PBI). Mitigation of radiation-induced pneumonitis with the ACE-inhibitor lisinopril was evaluated in the 13.5 Gy rat PBI model. During pneumonitis, we characterized inflammation and immune cell content in the lungs and bronchoalveolar lavage fluid (BALF). In vitro mechanistic studies were performed using primary human monocytes and the human monocytic THP-1 cell line.

RESULTS

In both the PBI and fractionated RT models, radiation increased ACE activity in lung immune cells. Treatment with lisinopril improved survival during radiation pneumonitis (p=0.0004). Lisinopril abrogated radiation-induced increases in BALF MCP-1 (CCL2) and MIP-1α cytokine levels (p < 0.0001). Treatment with lisinopril reduced both ACE expression (p=0.006) and frequency of CD45⁺CD11b⁺ lung myeloid cells (p=0.004). In vitro, radiation injury acutely increased ACE activity (p=0.045) and reactive oxygen species (ROS) generation (p=0.004) in human monocytes, whereas treatment with lisinopril blocked radiation-induced increases in both ACE and ROS. Interestingly, radiation-induced ROS generation was blocked by pharmacological inhibition of either NADPH oxidase 2 (NOX2) (p=0.012) or the type 1 angiotensin receptor (AGTR1) (p=0.013).

CONCLUSIONS

These data demonstrate radiation-induced ACE activation within the immune compartment promotes the pathogenesis of radiation pneumonitis, while ACE inhibition suppresses activation of pro-inflammatory immune cell subsets. Mechanistically, our in vitro data demonstrate radiation directly activates the ACE/AGTR1 pathway in immune cells and promotes generation of ROS via Nox2.

Enhanced Expression of the Local Haematopoietic Bone Marrow Renin-Angiotensin System in Polycythemia Rubra Vera

Local bone marrow (BM) renin-angiotensin system (RAS) affects physiological and pathological haematopoiesis, including erythropoiesis. In this study, quantitative expression of the messenger RNAs of the major RAS components – angiotensin-converting enzyme (CD143), renin and angiotensinogen – were measured in BM samples by quantitative real-time polymerase chain reaction, to evaluate the activity of local BM RAS in polycythemia rubra vera (PV) in comparison with normal erythropoiesis. The presence of CD143 was also investigated in the same BM samples by flow cytometry. Increased local synthesis of the major RAS components has been identified by demonstrating corresponding mRNAs in the BM of the patients with PV. Our findings indicate up-regulation of local BM RAS, together with down-regulation of the cell surface angiotensin-converting enzyme receptors, in the autonomous neoplastic clonal erythropoiesis of PV.

Local bone marrow renin-angiotensin system in primitive, definitive and neoplastic haematopoiesis

The locally active ligand peptides, mediators, receptors and signalling pathways of the haematopoietic BM (bone marrow) autocrine/paracrine RAS (renin-angiotensin system) affect the essential steps of definitive blood cell production. Haematopoiesis, erythropoiesis, myelopoiesis, formation of monocytic and lymphocytic lineages, thrombopoiesis and other stromal cellular elements are regulated by the local BM RAS. The local BM RAS is present and active even in primitive embryonic haematopoiesis. ACE (angiotensin-converting enzyme) is expressed on the surface of the first endothelial and haematopoietic cells, forming the marrow cavity in the embryo. ACE marks early haematopoietic precursor cells and long-term blood-forming CD34(+) BM cells. The local autocrine tissue BM RAS may also be active in neoplastic haematopoiesis. Critical RAS mediators such as renin, ACE, AngII (angiotensin II) and angiotensinogen have been identified in leukaemic blast cells. The local tissue RAS influences tumour growth and metastases in an autocrine and paracrine fashion via the modulation of numerous carcinogenic events, such as angiogenesis, apoptosis, cellular proliferation, immune responses, cell signalling and extracellular matrix formation. The aim of the present review is to outline the known functions of the local BM RAS within the context of primitive, definitive and neoplastic haematopoiesis. Targeting the actions of local RAS molecules could represent a valuable therapeutic option for the management of neoplastic disorders.

Elevated serum angiotensin converting enzyme levels as a reflection of bone marrow renin-angiotensin system activation in multiple myeloma

INTRODUCTION

Angiotensin converting enzyme (ACE) is a circulating enzyme that participates in the body's renin-angiotensin system (RAS) and is localized on the endothelial cell surface in the lung and other vascular beds. It catalyses the conversion of decapeptide angiotensin I to octapeptide angiotensin II. In the present study, we aimed to analyse the possible relationship between the levels of ACE in the context of RAS in multiple myeloma (MM) pathogenesis.

MATERIALS AND METHODS

The study was conducted on 25 MM patients (13 males, 12 females; median age 66 years, range 47-88) and 20 healthy controls. The clinical features of MM patients including demographics and laboratory findings were summarized. Serum ACE levels were measured by using commercially available kits.

RESULTS

The serum ACE levels of MM patients and controls were 32.60±20.26 and 15.35±6.47 respectively. Serum ACE levels were significantly higher in MM patients compared with control groups (p<0.001).

CONCLUSIONS

Being an important component of RAS, circulating ACE might be associated with clonal proliferation of malignant plasma cells in the bone marrow microenvironment. Identification of the pathobiological activity of the local RAS in MM would enlighten the biologic basis and clinical management of haematologic disorders.

Local bone marrow Renin-Angiotensin system and atherosclerosis

Local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) affects the growth, production, proliferation differentiation, and function of hematopoietic cells. Angiotensin II (Ang II), the dominant effector peptide of the RAS, regulates cellular growth in a wide variety of tissues in pathobiological states. RAS, especially Ang II and Ang II type 1 receptor (AT1R), has considerable proinflammatory and proatherogenic effects on the vessel wall, causing progression of atherosclerosis. Recent investigations, by analyzing several BM chimeric mice whose BM cells were positive or negative for AT1R, disclosed that AT1R in BM cells participates in the pathogenesis of atherosclerosis. Therefore, AT1R blocking not only in vascular cells but also in the BM could be an important therapeutic approach to prevent atherosclerosis. The aim of this paper is to review the function of local BM RAS in the pathogenesis of atherosclerosis.

Review: Pathobiological aspects of the local bone marrow renin-angiotensin system: a review

The local haematopoietic bone marrow (BM) renin—angiotensin system (RAS) mediates pathobiological alterations of haematopoiesis in an autocrine/paracrine/intracrine fashion. Recent data further indicated the existence of angiotensin-converting enzyme (ACE) in human primitive lympho-haematopoietic cells, embryonic, foetal and adult haematopoietic tissues. Human umbilical cord blood cells also express renin, angiotensinogen, and ACE mRNAs. As ACE and other angiotensin peptides function in human haematopoietic stem cells (HSCs) throughout haematopoietic ontogeny and adulthood, local RAS could also have a function in HSC plasticity, and the development of haematological neoplastic disorders. The presence of ACE on leukaemic blast cells within leukaemic BM, on erythroleukaemic cells, ACE-expressing macrophages in lymph nodes of Hodgkin disease, renin activity in leukaemic blasts, angiotensin II as an autocrine growth factor for AML, increased renin gene activity during NUP98-HOXA9 enhanced blast formation, higher levels of BB9/ACE (+) AML isoforms, and altered JAK-STAT pathway as a link between RAS and leukaemia indicated the wide pathobiological aspects of local BM RAS. The comparable biological actions of local RASs throughout the human body (including myocardium, pancreas, pituitary gland, ovary and kidney) represent the true basis for the search of their prominence in tissue functions. Recent data and perspectives of the local BM RAS in health and disease are reviewed in this paper.

Effects of Imatinib Mesylate on Renin–Angiotensin System (RAS) Activity during the Clinical Course of Chronic Myeloid Leukaemia

The renin–angiotensin system (RAS) is involved in cell growth, proliferation and differentiation in bone marrow in an autocrine–paracrine manner, and it modulates normal and neoplastic haematopoietic cell proliferation. This study aimed to assess expressions of the RAS components, renin, angiotensinogen and angiotensin-converting enzyme (ACE), during imatinib mesylate treatment of patients with chronic myeloid leukaemia (CML). Expressions of RAS components were studied in patients with CML at the time of diagnosis ( n = 83) and at 3, 6 and 12 months after diagnosis ( n = 35) by quantitative real-time polymerase chain reaction. De novo CML patients had increased ACE, angiotensinogen and renin mRNA levels and these expression levels decreased following administration of imatinib. The RAS activities were significantly different among Sokal risk groups of CML, highlighting the altered biological activity of RAS in neoplastic disorders. The results of this study confirm that haematopoietic RAS affects neoplastic cell production, which may be altered via administration of tyrosine kinase inhibitors such as imatinib mesylate.

Characterization of a local renin-angiotensin system in rat gingival tissue

BACKGROUND

The systemic renin-angiotensin system (RAS) promotes the plasmatic production of angiotensin (Ang) II, which acts through interaction with specific receptors. There is growing evidence that local systems in various tissues and organs are capable of generating angiotensins independently of circulating RAS. The aims of this study were to investigate the expression and localization of RAS components in rat gingival tissue and evaluate the in vitro production of Ang II and other peptides catalyzed by rat gingival tissue homogenates incubated with different Ang II precursors.

METHODS

Reverse transcription-polymerase chain reaction assessed mRNA expression. Immunohistochemical analysis aimed to detect and localize renin. A standardized fluorimetric method with tripeptide hippuryl-histidyl-leucine was used to measure tissue angiotensin-converting enzyme (ACE) activity, whereas high performance liquid chromatography showed products formed after the incubation of tissue homogenates with Ang I or tetradecapeptide renin substrate (TDP).

RESULTS

mRNA for renin, angiotensinogen, ACE, and Ang II receptors (AT(1a), AT(1b), and AT(2)) was detected in gingival tissue; cultured gingival fibroblasts expressed renin, angiotensinogen, and AT(1a) receptor. Renin was present in the vascular endothelium and was intensely expressed in the epithelial basal layer of periodontally affected gingival tissue. ACE activity was detected (4.95 +/- 0.89 nmol histidyl-leucine/g/minute). When Ang I was used as substrate, Ang 1-9 (0.576 +/- 0.128 nmol/mg/minute), Ang II (0.066 +/- 0.008 nmol/mg/minute), and Ang 1-7 (0.111 +/- 0.017 nmol/mg/minute) were formed, whereas these same peptides (0.139 +/- 0.031, 0.206 +/- 0.046, and 0.039 +/- 0.007 nmol/mg/minute, respectively) and Ang I (0.973 +/- 0.139 nmol/mg/minute) were formed when TDP was the substrate.

CONCLUSION

Local RAS exists in rat gingival tissue and is capable of generating Ang II and other vasoactive peptides in vitro.

Over-expression of angiotensin-converting enzyme (CD 143) on leukemic blasts as a clue for the activated local bone marrow RAS in AML

Local bone marrow renin-angiotensin system (RAS) is an autocrine-paracrine system affecting hematopoiesis. Angiotensin II type 1a (AT1a) receptors are present on the CD34+ hematopoietic stem cells. Angiotensin II stimulates the proliferation of bone marrow and umbilical cord blood hematopoietic progenitors. There are preliminary data that local RAS might also be involved in leukemogenesis. ACE hyper-function may lead to the acceleration of negative hematopoietic regulator peptide, AcSDKP, metabolism, which in turn lowers its level in the bone marrow micro-environment, finally removing the anti-proliferative effect of AcSDKP on the hematopoietic cells and blasts. Renin expression could have a role on the leukemia development and angiotensin may act as an autocrine growth factor for acute myeloid leukemia (AML) cells. The aim of this study is to search ACE (CD 143) surface antigen by flow-cytometric analyses on the leukemic blast cells taken from the bone marrow of the patients with AML. Bone marrow aspiration materials and peripheral blood samples were obtained from 11 patients with AML (eight males, three females; aged 46 (range 26-67) years) and six patients with non-malignant hematological disorders (four males, two females; aged 56 (range 22-71) years). ACE (CD 143) surface antigen was shown to be over-expressed in leukemic myeloid blast cells. ACE is positively correlated with bone marrow blast count. Elucidation of the pathological activity of the local RAS-mediated regulation of the leukemogenesis is both pathobiologically and clinically important, since the angiotensin peptides represent a molecular target in the disease management.