Local Renin-Angiotensin system in normal hematopoietic and multiple myeloma-related progenitor cells

The Role of the Local Bone Marrow Renin-Angiotensin System in Multiple Myeloma

Objective:

Angiotensin II promotes growth and angiogenesis via type 1 receptors (AGTR1) in certain tumors. In this study, we examine the bone marrow AGTR1 expression in multiple myeloma (MM) and its relationship with the regulation of angiogenesis and prognostic factors.

Materials and Methods:

Bone marrow AGTR1 mRNA levels of 39 MM patients and 15 healthy controls were analyzed with quantitative RT-PCR. Immunohistochemical staining of the tissue vascular endothelial growth factor (VEGF), CD34, and factor VIIIrAg (fVIIIrAg) was used to assess bone marrow angiogenesis.

Results:

Bone marrow samples of the patients showed increased VEGF, fVIIIrAg, and CD34 staining and higher AGTR1 expression levels when compared to controls. Patients with severe-diffuse bone marrow infiltration showed higher bone marrow VEGF, fVIIIrAg, CD34, and AGTR1 mRNA levels when compared to other patients.

Conclusion:

AGTR1 expression was found positively correlated with plasma β2-microglobulin level and patients with increased AGTR1 expression showed increased bone marrow CD34 levels.

Loss of Angiotensin-Converting Enzyme 2 Exacerbates Diabetic Retinopathy by Promoting Bone Marrow Dysfunction

Angiotensin-converting enzyme 2 (ACE2) is the primary enzyme of the vasoprotective axis of the renin angiotensin system (RAS). We tested the hypothesis that loss of ACE2 would exacerbate diabetic retinopathy by promoting bone marrow dysfunction. ACE2^-/y were crossed with Akita mice, a model of type 1 diabetes. When comparing the bone marrow of the ACE2^-/y -Akita mice to that of Akita mice, we observed a reduction of both short-term and long-term repopulating hematopoietic stem cells, a shift of hematopoiesis toward myelopoiesis, and an impairment of lineage^- c-kit⁺ hematopoietic stem/progenitor cell (HS/PC) migration and proliferation. Migratory and proliferative dysfunction of these cells was corrected by exposure to angiotensin-1-7 (Ang-1-7), the protective peptide generated by ACE2. Over the duration of diabetes examined, ACE2 deficiency led to progressive reduction in electrical responses assessed by electroretinography and to increases in neural infarcts observed by fundus photography. Compared with Akita mice, ACE2^-/y -Akita at 9-months of diabetes showed an increased number of acellular capillaries indicative of more severe diabetic retinopathy. In diabetic and control human subjects, CD34⁺ cells, a key bone marrow HS/PC population, were assessed for changes in mRNA levels for MAS, the receptor for Ang-1-7. Levels were highest in CD34⁺ cells from diabetics without retinopathy. Higher serum Ang-1-7 levels predicted protection from development of retinopathy in diabetics. Treatment with Ang-1-7 or alamandine restored the impaired migration function of CD34⁺ cells from subjects with retinopathy. These data support that activation of the protective RAS within HS/PCs may represents a therapeutic strategy for prevention of diabetic retinopathy. Stem Cells 2018;36:1430-1440.

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.

Expression Profiles of the Individual Genes Corresponding to the Genes Generated by Cytotoxicity Experiments with Bortezomib in Multiple Myeloma

OBJECTIVE

Multiple myeloma (MM) is currently incurable due to refractory disease relapse even under novel anti-myeloma treatment. In silico studies are effective for key decision making during clinicopathological battles against the chronic course of MM. The aim of this present in silico study was to identify individual genes whose expression profiles match that of the one generated by cytotoxicity experiments for bortezomib.

MATERIALS AND METHODS

We used an in silico literature mining approach to identify potential biomarkers by creating a summarized set of metadata derived from relevant information. The E-MTAB-783 dataset containing expression data from 789 cancer cell lines including 8 myeloma cell lines with drug screening data from the Wellcome Trust Sanger Institute database obtained from ArrayExpress was "Robust Multi-array analysis" normalized using GeneSpring v.12.5. Drug toxicity data were obtained from the Genomics of Drug Sensitivity in Cancer project. In order to identify individual genes whose expression profiles matched that of the one generated by cytotoxicity experiments for bortezomib, we used a linear regression-based approach, where we searched for statistically significant correlations between gene expression values and IC50 data. The intersections of the genes were identified in 8 cell lines and used for further analysis.

RESULTS

Our linear regression model identified 73 genes and some genes expression levels were found to very closely correlated with bortezomib IC50 values. When all 73 genes were used in a hierarchical cluster analysis, two major clusters of cells representing relatively sensitive and resistant cells could be identified. Pathway and molecular function analysis of all the significant genes was also investigated, as well as the genes involved in pathways.

CONCLUSION

The findings of our present in silico study could be important not only for the understanding of the genomics of MM but also for the better arrangement of the targeted anti-myeloma therapies, such as bortezomib.

ACE2/Ang-(1-7)/Mas axis stimulates vascular repair-relevant functions of CD34+ cells

CD34(+) stem/progenitor cells have been identified as a promising cell population for the autologous cell-based therapies in patients with cardiovascular disease. The counter-regulatory axes of renin angiotensin system, angiotensin converting enzyme (ACE)/Ang II/angiotensin type 1 (AT1) receptor and ACE2/Ang-(1-7)/Mas receptor, play an important role in the cardiovascular repair. This study evaluated the expression and vascular repair-relevant functions of these two pathways in human CD34(+) cells. CD34(+) cells were isolated from peripheral blood mononuclear cells (MNCs), obtained from healthy volunteers. Expression of ACE, ACE2, AT1, and angiotensin type 2 and Mas receptors were determined. Effects of Ang II, Ang-(1-7), Norleu(3)-Ang-(1-7), and ACE2 activators, xanthenone (XNT) and diminazene aceturate (DIZE) on proliferation, migration, and adhesion of CD34(+) cells were evaluated. ACE2 and Mas were relatively highly expressed in CD34(+) cells compared with MNCs. Ang-(1-7) or its analog, Norleu(3)-Ang-(1-7), stimulated proliferation of CD34(+) cells that was associated with decrease in phosphatase and tensin homologue deleted on chromosome 10 levels and was inhibited by triciribin, an AKT inhibitor. Migration of CD34(+) cells was enhanced by Ang-(1-7) or Norleu(3)-Ang-(1-7) that was decreased by a Rho-kinase inhibitor, Y-27632. In the presence of Ang II, XNT or DIZE enhanced proliferation and migration that were blocked by DX-600, an ACE2 inhibitor. Treatment of MNCs with Ang II, before the isolation of CD34(+) cells, attenuated the proliferation and migration to stromal derived factor-1α. This attenuation was reversed by apocynin, an NADPH oxidase inhibitor. Adhesion of MNCs or CD34(+) cells to fibronectin was enhanced by Ang II and was unaffected by Ang-(1-7). This study suggests that ACE2/Ang-(1-7)/Mas pathway stimulates functions of CD34(+) cells that are cardiovascular protective, whereas Ang II attenuates these functions by acting on MNCs. These findings imply that activation of ACE2/Ang-(1-7)/Mas axis is a promising approach for enhancing reparative outcomes of cell-based therapies.