Captopril inhibits in vitro and in vivo the proliferation of primitive haematopoietic cells induced into cell cycle by cytotoxic drug administration or irradiation but has no effect on myeloid leukaemia cell proliferation

Angiotensin converting enzyme and angiotensin converting enzyme inhibitors in dermatology: a narrative review

INTRODUCTION

Angiotensin converting enzyme inhibitors (ACEI) are commonly used for cardiovascular diseases. The evidence supporting the use of ACEI in dermatology is limited.

AREAS COVERED

This review article was divided into three parts. The first part discusses ACEI in clinical use in dermatology. The second part reveals the relationship between angiotensin converting enzyme (ACE) and immune diseases, and further discusses the possible relationship between ACEI in clinical use in these diseases and ACE. The third part focuses on cutaneous adverse reactions of ACEI.

EXPERT OPINION

The use of ACEI in dermatology is mainly based on its properties as regulation of renin angiotensin system (RAS), but currently, with limited clinical use. The association of ACE and several diseases are well discussed, including COVID-19, psoriasis, sarcoidosis, systemic lupus erythematosus and vitiligo. The main cutaneous adverse effects of ACEI include angioedema, psoriasis and pemphigus. Plausible factors for these adverse reactions include accumulation of vasoactive mediators, preventing angiotension from binding to AT₁ receptor and AT₂ receptor and presence of circulating antibodies.

Repurposing Pharmaceuticals Previously Approved by Regulatory Agencies to Medically Counter Injuries Arising Either Early or Late Following Radiation Exposure

The increasing risks of radiological or nuclear attacks or associated accidents have served to renew interest in developing radiation medical countermeasures. The development of prospective countermeasures and the subsequent gain of Food and Drug Administration (FDA) approval are invariably time consuming and expensive processes, especially in terms of generating essential human data. Due to the limited resources for drug development and the need for expedited drug approval, drug developers have turned, in part, to the strategy of repurposing agents for which safety and clinical data are already available. Approval of drugs that are already in clinical use for one indication and are being repurposed for another indication is inherently faster and more cost effective than for new agents that lack regulatory approval of any sort. There are four known growth factors which have been repurposed in the recent past as radiomitigators following the FDA Animal Rule: Neupogen, Neulasta, Leukine, and Nplate. These four drugs were in clinic for several decades for other indications and were repurposed. A large number of additional agents approved by various regulatory authorities for given indications are currently under investigation for dual use for acute radiation syndrome or for delayed pathological effects of acute radiation exposure. The process of drug repurposing, however, is not without its own set of challenges and limitations.

A review of radiation countermeasures focusing on injury-specific medicinals and regulatory approval status: part III. Countermeasures under early stages of development along with 'standard of care' medicinal and procedures not requiring regulatory approval for use

PURPOSE

Terrorist attacks, with their intent to maximize psychological and economic damage as well as inflicting sickness and death on given targeted populations, are an ever-growing worldwide concern in government and public sectors as they become more frequent, violent, and sensational. If given the chance, it is likely that terrorists will use radiological or nuclear weapons. To thwart these sinister efforts, both physical and medical countermeasures against these weapons are currently being researched and developed so that they can be utilized by the first responders, military, and medical providers alike. This is the third article of a three-part series in which we have reviewed additional radiation countermeasures that are currently under early preclinical phases of development using largely animal models and have listed and discussed clinical support measures, including agents used for radiation-induced emesis, as well as countermeasures not requiring Food and Drug Administration approval.

CONCLUSIONS

Despite the significant progress that has been made in this area during the last several years, additional effort is needed in order to push promising new agents, currently under development, through the regulatory pipeline. This pipeline for new promising drugs appears to be unreasonably slow and cumbersome; possible reasons for this inefficiency are briefly discussed. Significant and continued effort needs to be afforded to this research and development area, as to date, there is no approved radioprotector that can be administered prior to high dose radiation exposure. This represents a very significant, unmet medical need and a significant security issue. A large number of agents with potential to interact with different biological targets are under development. In the next few years, several additional radiation countermeasures will likely receive Food and Drug Administration approval, increasing treatment options for victims exposed to unwanted ionizing irradiation.

Erythropoietin Regulation by Angiotensin II

The renin-angiotensin system (RAS) is a key regulator of blood pressure and blood volume homeostasis. The RAS is primarily comprised of the precursor protein angiotensinogen and the two proteases, renin and angiotensin-converting enzyme (ACE). Angiotensin I (Ang I) is derived from angiotensinogen by renin, but appears to have no biological activity. In contrast, angiotensin II (Ang II) that has a variety of biological functions in the cells is converted from Ang I through removal of two-C-terminal residues by ACE. The physiological effects of Ang II are due to Ang II signaling through specific receptor binding, resulting in muscle contraction leading to increased blood pressure and volume. To modulate RAS, three classes of drugs have been developed: (1) renin inhibitors to prevent angiotensinogen conversion to Ang I, (2) ACE inhibitors, to prevent Ang I processing to Ang II and (3) angiotensin receptor blockers, to inhibit Ang II signaling through its receptor. Studies using the RAS inhibitors and Ang II demonstrated that RAS signaling mediates actions of Ang II in the regulation of proliferation and differentiation of specific hematopoietic cell types, especially in the red blood cell lineage. Accumulating evidence indicates that RAS regulates EPO, an essential mediator of red cell production, for human anemia and erythropoiesis in vivo and in vitro. The regulation of EPO expression by Ang II may be responsible for maintaining red blood cell homeostasis. This review highlights the biological roles of RAS for blood cell and EPO homeostasis through Ang II signaling. The molecular mechanism for Ang II-induced EPO production of the cell or tissue type-specific expression is discussed.

Angiotensin II Regulation of Proliferation, Differentiation, and Engraftment of Hematopoietic Stem Cells

Emerging evidence indicates that differentiation and mobilization of hematopoietic cell are critical in the development and establishment of hypertension and hypertension-linked vascular pathophysiology. This, coupled with the intimate involvement of the hyperactive renin-angiotensin system in hypertension, led us to investigate the hypothesis that chronic angiotensin II (Ang II) infusion affects hematopoietic stem cell (HSC) regulation at the level of the bone marrow. Ang II infusion resulted in increases in hematopoietic stem/progenitor cells (83%) and long-term HSC (207%) in the bone marrow. Interestingly, increases of HSCs and long-term HSCs were more pronounced in the spleen (228% and 1117%, respectively). Furthermore, we observed higher expression of C-C chemokine receptor type 2 in these HSCs, indicating there was increased myeloid differentiation in Ang II-infused mice. This was associated with accumulation of C-C chemokine receptor type 2(+) proinflammatory monocytes in the spleen. In contrast, decreased engraftment efficiency of GFP(+) HSC was observed after Ang II infusion. Time-lapse in vivo imaging and in vitro Ang II pretreatment demonstrated that Ang II induces untimely proliferation and differentiation of the donor HSC resulting in diminished HSC engraftment and bone marrow reconstitution. We conclude that (1) chronic Ang II infusion regulates HSC proliferation, mediated by angiotensin receptor type 1a, (2) Ang II accelerates HSC to myeloid differentiation resulting in accumulation of C-C chemokine receptor type 2(+) HSCs and inflammatory monocytes in the spleen, and (3) Ang II impairs homing and reconstitution potentials of the donor HSCs. These observations highlight the important regulatory roles of Ang II on HSC proliferation, differentiation, and engraftment.

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs--aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted.

Renin-angiotensin system blockade: Its contribution and controversy

Angiotensin II is a key biological peptide in the renin-angiotensin system that regulates blood pressure and renal hemodynamics, and extensive experimental studies have shown that angiotensin II promotes diverse fibrotic changes and induces neovascularization in several inflammatory diseases. It is known that angiotensin II can be controlled using renin-angiotensin system blockade when angiotensin II is the main factor inducing a particular disease, and renin-angiotensin system blockade has assumed a central role in the treatment of inflammatory nephritis, cardiovascular disorders and retinopathy. In contrast, renin-angiotensin system blockade was found to have not only these effects but also other functions, such as inhibition of cancer growth, angiogenesis and metastasis. Numerous studies have sought to elucidate the mechanisms and support these antitumor effects. However, a recent meta-analysis showed that renin-angiotensin system blockade use might in fact increase the incidence of cancer, so renin-angiotensin system blockade use has become somewhat controversial. Although the renin-angiotensin system has most certainly made great contributions to experimental models and clinical practice, some issues still need to be resolved. The present review discusses the contribution and controversy surrounding the renin-angiotensin system up to the present time.

New approaches to radiation protection

Radioprotectors are compounds that protect against radiation injury when given prior to radiation exposure. Mitigators can protect against radiation injury when given after exposure but before symptoms appear. Radioprotectors and mitigators can potentially improve the outcomes of radiotherapy for cancer treatment by allowing higher doses of radiation and/or reduced damage to normal tissues. Such compounds can also potentially counteract the effects of accidental exposure to radiation or deliberate exposure (e.g., nuclear reactor meltdown, dirty bomb, or nuclear bomb explosion); hence they are called radiation countermeasures. Here, we will review the general principles of radiation injury and protection and describe selected examples of radioprotectors/mitigators ranging from small-molecules to proteins to cell-based treatments. We will emphasize agents that are in more advanced stages of development.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

Accelerated hematopoietic recovery with angiotensin-(1-7) after total body radiation

PURPOSE

Angiotensin (1-7) [A(1-7)] is a component of the renin angiotensin system (RAS) that stimulates hematopoietic recovery after myelosuppression. In a Phase I/IIa clinical trial, thrombocytopenia after chemotherapy was reduced by A(1-7). In this study, the ability of A(1-7) to improve recovery after total body irradiation (TBI) is shown with specific attention to radiation-induced hematopoietic injury.

MATERIALS AND METHODS

Mice were exposed to TBI (doses of 2-7 Gray [Gy]) of cesium 137 gamma rays, followed by treatment with A(1-7), typical doses were 100-1000 μg/kg given once or once daily for a specified number of days depending on the study. Animals are injected subcutaneously via the nape of the neck with 0.1 ml drug in saline. The recovery of blood and bone marrow cells was determined. Effects of TBI and A(1-7) on survival and bleeding time was also evaluated.

RESULTS

Daily administration of A(1-7) after radiation exposure improved survival (from 60% to 92-97%) and reduced bleeding time at day 30 after TBI. Further, A(1-7) increased early mixed progenitors (3- to 5-fold), megakaryocyte (2- to 3-fold), myeloid (3- to 6-fold) and erythroid (2- to 5-fold) progenitors in the bone marrow and reduced radiation-induced thrombocytopenia (RIT) (up to 2-fold). Reduction in the number of treatments to 3 per week also improved bone marrow recovery and reduced RIT. As emergency responder and healthcare systems in case of nuclear accident or/and terrorist attack may be overwhelmed, the consequence of delayed initiation of treatment was ascertained. Treatment with A(1-7) can be delayed up to 5 days and still be effective in the reduction of RIT or acceleration of bone marrow recovery.

CONCLUSIONS

The data presented in this paper indicate that A(1-7) reduces the consequences of critical radiation exposure and can be initiated well after initial exposure with maximal effects on early responding hematopoietic progenitors when treatment is initiated 2 days after exposure and 5 days after exposure for the later responding progenitors and reduced thrombocytopenia. There was some effect of A(1-7) even when given days after radiation exposure.

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.

The renin-angiotensin system and cancer: old dog, new tricks

For cancers to develop, sustain and spread, the appropriation of key homeostatic physiological systems that influence cell growth, migration and death, as well as inflammation and the expansion of vascular networks are required. There is accumulating molecular and in vivo evidence to indicate that the expression and actions of the renin-angiotensin system (RAS) influence malignancy and also predict that RAS inhibitors, which are currently used to treat hypertension and cardiovascular disease, might augment cancer therapies. To appreciate this potential hegemony of the RAS in cancer, an expanded comprehension of the cellular actions of this system is needed, as well as a greater focus on translational and in vivo research.

Timing of captopril administration determines radiation protection or radiation sensitization in a murine model of total body irradiation

OBJECTIVE

Angiotensin II (Ang II), a potent vasoconstrictor, affects the growth and development of hematopoietic cells. Mixed findings have been reported for the effects of angiotensin-converting enzyme (ACE) inhibitors on radiation-induced injury to the hematopoietic system. We investigated the consequences of different regimens of the ACE inhibitor captopril on radiation-induced hematopoietic injury.

MATERIALS AND METHODS

C57BL/6 mice were either sham-irradiated or exposed to (60)Co total body irradiation (0.6 Gy/min). Captopril was provided in the water for different time periods relative to irradiation.

RESULTS

In untreated mice, the survival rate from 7.5 Gy was 50% at 30 days postirradiation. Captopril treatment for 7 days prior to irradiation resulted in radiosensitization with 100% lethality and a rapid decline in mature blood cells. In contrast, captopril treatment beginning 1 hour postirradiation and continuing for 30 days resulted in 100% survival, with improved recovery of mature blood cells and multilineage hematopoietic progenitors. In nonirradiated control mice, captopril biphasically modulated Lin(-) marrow progenitor cell cycling. After 2 days, captopril suppressed G(0)-G(1) transition and a greater number of cells entered a quiescent state. However, after 7 days of captopril treatment Lin(-) progenitor cell cycling increased compared to untreated control mice.

CONCLUSION

These findings suggest that ACE inhibition affects hematopoietic recovery following radiation by modulating the hematopoietic progenitor cell cycle. The timing of captopril treatment relative to radiation exposure differentially affects the viability and repopulation capacity of spared hematopoietic stem cells and, therefore, can result in either radiation protection or radiation sensitization.

Characterization of angiotensin-converting enzyme expression during epidermis morphogenesis in humans: a potential marker for epidermal stem cells

BACKGROUND

Recent evidence has revealed that angiotensin-converting enzyme (ACE) participates in cutaneous wound healing and contributes to the pathophysiological process of some skin diseases. However, little is known about the role of ACE in epidermis morphogenesis during development.

OBJECTIVE

To clarify the expression pattern of ACE during embryonic development of human skin.

METHODS

Skin samples were obtained from aborted fetuses at different gestational ages and from healthy individuals. Localization of ACE, together with beta(1)-integrin, keratin 19 (K19) and p63 was examined by immunofluorescence and immunohistochemical staining.

RESULTS

In human fetal skin, at 11-13 weeks of gestation, ACE-positive cells were observed in the primitive epidermis. As the fetuses developed, ACE-positive cells appeared in all the epidermal layers. From 21 weeks of gestation, ACE expression was largely restricted to the basal layer of the fetal epidermis. In contrast, ACE-positive cells were found only in the adult skin basal layer which harbours epidermal stem cells. To explore the possible link between ACE and epidermal stem cells, we further examined the expression of beta(1)-integrin, K19 and p63, the putative markers for epidermal stem cells. Consistent with the results of ACE expression, from 21 weeks of gestation, the expression of beta(1)-integrin, K19 and p63 was mainly confined to the basal layer. Immunofluorescent double labelling revealed that ACE-positive cells substantially overlapped with beta(1)-integrin-, K19- and p63-positive cells.

CONCLUSIONS

Our results suggest that ACE may play a role in human epidermis morphogenesis during fetal life and serve as an unrecognized marker for keratinocyte progenitor cells.

Captopril as a potential inhibitor of lung tumor growth and metastasis

Lung cancer is the most common form of cancer in the world, and 90% of patients die from their disease. The angiotensin converting enzyme (ACE) inhibitors are used widely as antihypertensive agents, and it has been suggested that they decrease the risk of some cancers, although available data are conflicting. Accordingly, we investigated the anticancer activity of the ACE inhibitor, captopril, in athymic mice injected with highly tumorigenic LNM35 human lung cells as xenografts. Using this model, we demonstrated that daily IP administration of captopril (2.8 mg/mouse) for 3 weeks resulted in a remarkable reduction of tumor growth (58%, P < 0.01) and lymph node metastasis (50%, P= 0.088). There were no undesirable effects of captopril treatment on animal behavior and body weight. In order to determine the mechanism by which captopril inhibited tumor growth, we investigated the impact of this drug on cell proliferation, apoptosis, and angiogenesis. Immunohistochemical analysis demonstrated that captopril treatment significantly reduced the number of proliferating cells (Ki-67) in the tumor samples but was not associated with inhibition of tumor angiogenesis (CD31). Using cell viability and fluorescent activated cell sorting analysis tests, we demonstrated that captopril inhibited the viability of LNM35 cells by inducing apoptosis, providing insight about the mechanisms underlying its antitumorigenic activities. In view of these experimental findings, we conclude that captopril could be a promising option for the treatment of lung cancer.

Angiotensin-converting enzyme (CD143) marks hematopoietic stem cells in human embryonic, fetal, and adult hematopoietic tissues

Previous studies revealed that mAb BB9 reacts with a subset of CD34+ human BM cells with hematopoietic stem cell (HSC) characteristics. Here we map BB9 expression throughout hematopoietic development and show that the earliest definitive HSCs that arise at the ventral wall of the aorta and surrounding endothelial cells are BB9+. Thereafter, BB9 is expressed by primitive hematopoietic cells in fetal liver and in umbilical cord blood (UCB). BB9+CD34+ UCB cells transplanted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice contribute 10-fold higher numbers of multilineage blood cells than their CD34+BB9− counterparts and contain a significantly higher incidence of SCID-repopulating cells than the unfractionated CD34+ population. Protein microsequencing of the 160-kDa band corresponding to the BB9 protein established its identity as that of somatic angiotensin-converting enzyme (ACE). Although the role of ACE on human HSCs remains to be determined, these studies designate ACE as a hitherto unrecognized marker of human HSCs throughout hematopoietic ontogeny and adulthood.

Non-hormonal cell types in the pituitary candidating for stem cell

Hormone balances in the body are primarily governed by the hypothalamus-pituitary system. For its pivotal role, the pituitary gland relies on an assortment of different hormone-producing cell types, the proportions of which dynamically change in response to fluctuating endocrine demands. Mechanisms of pituitary cellular plasticity are at present far from understood, and may include proliferation and transdifferentiation of hormonal cells. Whether new cells also originate by recruitment from stem cells is unsettled, although this idea has frequently been proposed. Here, I will review these data by focusing on the non-hormonal cell types that have been advanced as candidates for the pituitary stem cell position.

Stem cells in the postnatal pituitary?

Tissue-specific stem cells are uncovered in a growing number of organs by their molecular expression profile and their potential for self-renewal, multipotent differentiation and tissue regeneration. Whether the pituitary gland also contains a pool of versatile 'master' cells that drive homeostatic, plastic and regenerative cell ontogenesis is at present unknown. Here, I will give an overview of data that may lend support to the existence of stem cells in the postnatal pituitary. During the many decades of pituitary research, various approaches have been used to hunt for the pituitary stem cells. Transplantation and regeneration studies advanced chromophobes as possible source of new hormonal cells. Clonogenicity approaches identified pituitary cells that clonally expand to floating spheres, or to colonies in adherent cell cultures. Behavioural characteristics and changes of marginal, follicular and folliculostellate cells during defined developmental and (patho-)physiological conditions have been interpreted as indicative of a stem cell role. Expression of potential stem cell markers like nestin, as well as topographical localization in the marginal zone around the cleft has also been considered to designate pituitary stem cells. Finally, a 'side population' was recently identified in the postnatal pituitary which in many other tissues represents a stem cell-enriched fraction. Taken together, in the course of the long-standing study of the pituitary, several arguments have been presented to support the existence of stem cells, and multiple cell types have been placed in the spotlight as possible candidates. However, none of these cells has until now unequivocally been shown to meet all quintessential characteristics of stem cells.

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.

A role for angiotensin-converting enzyme in the characterization, enrichment, and proliferation potential of adult murine pituitary colony-forming cells

Recently, we described a rare cell type within the adult murine pituitary gland with progenitor cell hallmarks (PCFCs). PCFCs are contained exclusively within a subpopulation of cells that import fluorescent beta-Ala-Lys-Nepsilon-AMCA (7-amino-4-methylcoumarin-3-acetic acid). Herein, we investigate the utility of cell surface molecules angiotensin-converting enzyme (ACE) and stem cell antigen-1 (Sca-1) to further enrich for PCFCs. ACE and Sca-1 were expressed on 61% and 55% of AMCA(+)CD45(-)CD31(-) cells, respectively, and coexpressed on 38%. ACE(+)Sca-1(+)AMCA(+) cells enriched for PCFCs by 195-fold over unselected cells. ACE(+)AMCA(+) cells enriched for PCFCs by 170-fold, and colonies were twofold larger than for AMCA(+) selection alone. Conversely, ACE(-)-selected cells reduced both colony-forming activity and size. Notably, colonies generated from AMCA(+) cells obtained from ACE(null) mice were 2.7-fold smaller than for wild-type mice. These data identify ACE as a previously unrecognized marker of PCFCs and suggest that ACE is functionally important for PCFC proliferation. Anatomically, the cells that imported AMCA and expressed ACE were situated in the marginal epithelial cell layer of the pituitary cleft and in the adjacent subluminal zone, thus supporting previous proposals that the luminal zone is a source of precursor cells in the adult pituitary.

Tetrapeptide AcSDKP Induces Postischemic Neovascularization Through Monocyte Chemoattractant Protein-1 Signaling

BACKGROUND

We investigated the putative proangiogenic activity and molecular pathway(s) of the tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) in a model of surgically induced hindlimb ischemia.

METHODS AND RESULTS

Hindlimb ischemia was induced by femoral artery ligature and an osmotic minipump was implanted subcutaneously to deliver low (0.12 mg/kg per day) or high (1.2 mg/kg per day) doses of AcSDKP, for 7 or 21 days. Angiography scores, arteriole density, capillary number, and foot perfusion were increased at day 21 in the high-dose AcSDKP-treated mice (by 1.9-, 1.8-, 1.3-, and 1.6-fold, respectively) compared with control animals (P<0.05, P<0.01, P<0.01, respectively). AcSDKP treatment for 24 hours upregulated the monocyte chemoattractant protein-1 (MCP-1) mRNA and protein levels by 1.5-fold in cultured endothelial cells (P<0.01). In the ischemic hindlimb model, administration of AcSDKP also enhanced MCP-1 mRNA levels by 90-fold in ischemic leg (P<0.001) and MCP-1 plasma levels by 3-fold (P<0.001 versus untreated ischemic control mice). MCP-1 levels upregulation were associated with a 2.3-fold increase in the number of Mac3-positive cells in ischemic area of AcSDKP-treated mice (P<0.001 versus untreated animals). Interestingly, AcSDKP-induced monocyte/macrophage infiltration and postischemic neovascularization was fully blunted in MCP-1-deficient animals.

CONCLUSIONS

AcSDKP stimulates postischemic neovascularization through activation of a proinflammatory MCP-1-related pathway.

Inhibition of angiotensin I–converting enzyme induces radioprotection by preserving murine hematopoietic short-term reconstituting cells

Angiotensin I–converting enzyme (ACE) inhibitors can affect hematopoiesis by several mechanisms including inhibition of angiotensin II formation and increasing plasma concentrations of AcSDKP (acetyl-N-Ser-Asp-Lys-Pro), an ACE substrate and a negative regulator of hematopoiesis. We tested whether ACE inhibition could decrease the hematopoietic toxicity of lethal or sublethal irradiation protocols. In all cases, short treatment with the ACE inhibitor perindopril protected against irradiation-induced death. ACE inhibition accelerated hematopoietic recovery and led to a significant increase in platelet and red cell counts. Pretreatment with perindopril increased bone marrow cellularity and the number of hematopoietic progenitors (granulocyte macrophage colony-forming unit [CFU-GM], erythroid burst-forming unit [BFU-E], and megakaryocyte colony-forming unit [CFU-MK]) from day 7 to 28 after irradiation. Perindopril also increased the number of hematopoietic stem cells with at least a short-term reconstitutive activity in animals that recovered from irradiation. To determine the mechanism of action involved, we evaluated the effects of increasing AcSDKP plasma concentrations and of an angiotensin II type 1 (AT1) receptor antagonist (telmisartan) on radioprotection. We found that the AT1-receptor antagonism mediated similar radioprotection as the ACE inhibitor. These results suggest that ACE inhibitors and AT1-receptor antagonists could be used to decrease the hematopoietic toxicity of irradiation.

Effects of Palladacycle Complex on Hematopoietic Progenitor Cells Proliferation In Vivo and In Vitro and Its Relation with the Inhibitory Properties of This Compound on the Angiotensin‐I Converting Enzyme Activity

In the present study, we introduce a new class of organometallic compound, the Biphosphinic Palladacycle Complex [Pd (C2, N-S(-)(dmpa)(dppf)] Cl (BPC), as an angiotensin-I converting-enzyme inhibitor (ACEI) with hematological regulation properties. When BPC was assayed as a competitive inhibitor over the hydrolysis of Abz-YRK (Dnp)-P-OH (Km = 7.0 microM), it showed a Kiapp = 0.2259 ng and a Ki value of 94.12 pg. Using murine long-term bone marrow cultures (LTBMCs) and clonal culture techniques, we also evaluated the capacity of this drug (1.18 microM) to module haematopoietic progenitor cells proliferation in vitro and in vivo. Our results demonstrated that BPC produces no toxicity to bone marrow cells, as determined by the unchanged cell number in the non-adherent layer at weeks 1, 2, and 8 and the increased number of adherent cells present in the BPC-treated LTBMCs. However, the proportion of CFU-Cs in the non-adherent cell layer was reduced at weeks 5, 6, 8, and 9. In vivo studies using the dose of 1 mg/kg of BPC, administered by subcutaneous route, presented similar result as those found in vitro, in the number of CFU-Cs. This latter finding may be explained by the inhibitory effects of this drug on the ACE activity, which probably result in increased levels of its substrate AcSDKP, a negative regulator of hematopoiesis.

I/D ACE gene polymorphism in survival of leukemia patients -- hypothesis and pilot study

Angiotensin-I converting enzyme (ACE) is involved not only in intracellular volume regulation but also in proliferation control. Since both ACE gene polymorphism (I/D ACE) and ABO blood group determine ACE level in peripheral blood and probably also in bone marrow, the hypothesis to the interindividual differences in survival of leukemic patients was suggested. The data of 25 patients of both sexes with acute myelogenous (AML), acute lymphatic (ALL), chronic myelogenous (CML) and chronic lymphatic (CLL) leukemia treated by conventional were used for the study. The overall survival (SUR) was estimated as the time from the date of diagnosis to the date of death. The difference between patient's individual SUR (iSUR) and median SUR according to the type of leukemia (mSUR) was calculated. This difference (iSUR-mSUR) varied with I/D ACE genotype (p<0.02) but neither with diagnosis nor with ABO blood group. The regression model for iSUR calculation, from mSUR and I/D ACE genotype, has been suggested.

Towards the understanding of the local hematopoietic bone marrow renin-angiotensin system

The classical view of the renin-angiotensin system (RAS) as a circulating endocrine system has evolved to organ- and tissue-based systems that perform paracrine/autocrine functions. Angiotensin II (Ang II), the dominant effector peptide of the RAS, regulates cellular growth in a wide variety of tissues in (patho)biological states. In 1996, we hypothesized that there exists a locally active RAS in the bone marrow affecting the growth, production, proliferation and differentiation of hematopoietic cells. Evidences supporting this hypothesis are growing. Ang II, through interacting with Ang II type 1 (AT1) receptor stimulates erythroid differentiation. This stimulatory effect of Ang II on erythropoiesis was completely abolished by a specific AT1 receptor antagonist, losartan. AT1a receptors are present on human CD34(+) hematopoietic stem cells. Ang II increases hematopoietic progenitor cell proliferation and this effect was also blocked by losartan. Angiotensin-converting enzyme (ACE) is involved in enhancing the recruitment of primitive stem cells into S-phase in hematopoietic bone marrow by degrading tetrapeptide AcSDKP. ACE inhibitors modified the circulating hematopoietic progenitors in healthy subjects. RAS may also affect pathological/neoplastic hematopoiesis. Renin has been isolated from leukemic blast cells. Higher bone marrow ACE levels in acute leukemic patients suggested that ACE is produced at higher quantities in the leukemic bone marrow. In this review, the 'State of the Art' of the local bone marrow RAS is summarized. A local RAS in the bone marrow can mediate, in an autocrine/paracrine fashion, some of the principal steps of hematopoietic cell production. To show a causal link between the components of RAS and the other regulatory hematopoietic growth factors is not only an academic curiosity. Elucidation of such a local bone marrow system may offer novel therapeutic approaches in pathologic/neoplastic conditions.

The tetrapeptide AcSDKP, an inhibitor of primitive hematopoietic cell proliferation, induces angiogenesis in vitro and in vivo

The tetrapeptide acetyl-Ser-Asp-Lys-Pro (AcSDKP), purified from bone marrow and constitutively synthesized in vivo, belongs to the family of negative regulators of hematopoiesis. It protects the stem cell compartment from the toxicity of anticancer drugs and irradiation and consequently contributes to a reduction in marrow failure. This current work provides experimental evidence for another novel biologic function of AcSDKP. We report that AcSDKP is a mediator of angiogenesis, as measured by its ability to modulate endothelial cell function in vitro and angiogenesis in vivo. AcSDKP at nanomolar concentrations stimulates in vitro endothelial cell migration and differentiation into capillary-like structures on Matrigel as well as enhances the secretion of an active form of matrix metalloproteinase-1 (MMP-1). In vivo, AcSDKP promotes a significant angiogenic response in the chicken embryo chorioallantoic membrane (CAM) and in the abdominal muscle of the rat. Moreover, it induces the formation of blood vessels in Matrigel plugs implanted subcutaneously in the rat. This is the first report demonstrating the ability of AcSDKP to interact directly with endothelial cells and to elicit an angiogenic response in vitro and in vivo.

[Telomerase activity in peripheral blood leukocytes from patients with essential hypertension]

BACKGROUND AND OBJECTIVE

Primary or secondary activation of the immune mechanisms that lead to proliferation and dysfunction of specific cellular groups appears to be involved in the pathogenesis and complications of essential hypertension. In view of the evidence that, on one hand, telomeric length determines the replicative capacity and life span of cells and, on the other hand, idiopathic hypertensive patients have peripheral white cell replicative disorders, we decided to investigate the relationship between the influence of telomerase activity in peripheral leukocytes as an indirect marker of telomeric length and the presence of arterial hypertension.

PATIENTS AND METHOD

Telomerase activity in peripheral white blood cells was measured in healthy individuals, in effectively treated hypertensive patients and in a non-well controlled hypertensive group. White blood cells were separated through a density gradient, then lysed and their DNA amplified by a polimerase chain reaction (PCR). Telomerase activity was determined with an ELISA specific kit.

RESULTS

The white blood cell count was higher in the hypertensive than the control group (p < 0.05). Telomerase activity was positive in all three groups but higher in patients under 45 year-old with bad controlled hypertension as compared with healthy individuals and patients under 45 year-old with well controlled hypertension (p < 0.05); in the latter group, telomerase activity was significantly lower than in the other groups (p < 0.05).

CONCLUSIONS

Our results indicate that there exists a relationship between telomerase activity in peripheral leukocytes, the proliferation of these white blood cells and the presence of essential arterial hypertension.