The tissue renin-angiotensin system in the female reproductive tissues. A review

Meta-analysis of angiotensin-converting enzyme insersion/delection polymorphism and pre-eclampsia susceptibility

AIM

In recent years, there were many studies on angiotensin-converting enzyme insersion/delection (ACE I/D) polymorphism and pre-eclampsia susceptibility, but the conclusion was still inconclusive. Our study is to explore the relationship between the ACE I/D polymorphism and the risk of pre-eclampsia.

METHODS

The literature on the relationship between ACE I/D gene polymorphism and Pre-eclampsia susceptibility was obtained by searching the databases of Wanfang, VIP, Medline, CNKI, Embase, Pubmed and Springerlink, which was published from the establishment of the databases to October 2019. Taking the odds ratio (OR) value and its 95% confidence interval (CI) as the effect size, the Meta-analysis was carried out by using stata 15.0 software.

RESULTS

Thirty articles, consisting of 3184 patients and 3912 controls, were included. The results showed that allele D was compared with allele I, with the OR value of 1.29 (95% CI: 1.12 ~ 1.50, P < 0.05). Subgroup analysis showed that in Caucasians, allele D was associated with OR of 1.28 (95% CI: 1.08 ~ 1.53, P < 0.05). There was no significant difference in Asians. There was statistical significance in recessive gene model and homozygous gene model, as well as in that of Asian and Caucasian. In homozygous model, there was statistical significance, but subgroup analysis showed there was no statistical significance in Asian and Caucasian. There was no statistical significance in dominant model and heterozygous model.

CONCLUSION

The polymorphism of ACE I/D gene was associated with the risk of pre-eclampsia. Allele D and genotype DD may increase the risk of Pre-eclampsia in pregnant women.

Manipulating the angiotensin system--new approaches to the treatment of solid tumours

Angiotensin II (Ang II), a main effector peptide in the renin-angiotensin system (RAS), plays a fundamental role as a vasoconstrictor in controlling cardiovascular function and renal homeostasis. Ang II also acts as a growth promoter or angiogenic factor via type 1 angiotensin II receptors (AT1Rs) in certain tumour cell lines. Recent studies have shown the activation of the local RAS in various tumour tissues, including the abundant generation of Ang II by angiotensin-converting enzyme (ACE) and the upregulation of AT1R expression. Thus, considerable attention has been paid to the role of the RAS in cancer and its blockade as a new approach to the treatment of cancer. There is increasing evidence that the Ang II-AT1R system is involved in tumour growth, angiogenesis and metastasis in experimental models, suggesting the therapeutic potential of an ACE inhibitor and AT1R blocker, both of which have been used as antihypertensive drugs. In addition, specific Ang II-degrading enzymes are expressed in tumours and play a regulatory role in cell proliferation and invasion. This review focuses on the role of the Ang II-AT1R system in solid tumours, particularly in the progression of gynaecological cancer, and presents the clinical potential of manipulating the angiotensin system as a novel and promising strategy for cancer treatment.

Angiotensin II type 1 receptor expression in ovarian cancer and its correlation with tumour angiogenesis and patient survival

Angiotensin II, a main effector peptide in the renin–angiotensin system, acts as a growth-promoting and angiogenic factor via type 1 angiotensin II receptors (AT₁R). We have recently demonstrated that angiotensin II enhanced tumour cell invasion and vascular endothelial growth factor (VEGF) secretion via AT₁R in ovarian cancer cell lines in vitro. The aim of the present study was to determine whether AT₁R expression in ovarian cancer is correlated with clinicopathological parameters, angiogenic factors and patient survival. Immunohistochemical staining for AT₁R, VEGF, CD34 and proliferating cell nuclear antigen (PCNA) were analysed in ovarian cancer tissues (n=67). Intratumour microvessel density (MVD) was analysed by counting the CD34-positive endothelial cells. Type 1 angiotensin II receptors were expressed in 85% of the cases examined, of which 55% were strongly positive. Type 1 angiotensin II receptors expression was positively correlated with VEGF expression intensity and MVD, but not with histological subtype, grade, FIGO stage or PCNA labelling index. In patients who had positive staining for AT₁R, the overall survival and progression-free survival were significantly poor (P=0.041 and 0.017, respectively) as compared to those in patients who had negative staining for AT₁R, although VEGF, but not AT₁R, was an independent prognostic factor on multivariate analysis. These results demonstrated that AT₁R correlated with tumour angiogenesis and poor patient outcome in ovarian cancer, suggesting its clinical potential for a novel molecular target in strategies for ovarian cancer treatment.

Functional expression of the angiotensin II type 1 receptor in human ovarian carcinoma cells and its blockade therapy resulting in suppression of tumor invasion, angiogenesis, and peritoneal dissemination

PURPOSE

Angiotensin II is a bioactive peptide of the renin-angiotensin system, acting not only as a vasoconstrictor but also as a growth promoter via angiotensin II type 1 receptors (AT1R). The present study examined AT1R expression in human ovarian carcinoma and attempted to determine whether AT1R blocker could suppress the tumor progression.

EXPERIMENTAL DESIGN

Expression of AT1R, vascular endothelial growth factor (VEGF), and CD34 was immunohistochemically analyzed in ovarian tumor tissues (n=99). Effects of AT1R blocker on invasive potential and VEGF secretion in ovarian cancer cells were examined in vitro. Effects of AT1R blocker in vivo were evaluated in a mouse model of peritoneal carcinomatosis.

RESULTS

AT1R was expressed in 57 of 67 (85%) invasive ovarian adenocarcinomas and 12 of 18 (66%) borderline malignant tumors but in only 2 of 14 (14%) benign cystadenomas. In invasive carcinomas, VEGF expression intensity and intratumor microvessel density were significantly higher in cases that were strongly positive for AT1R (n = 37) compared with those in cases weakly positive (n = 20) or negative (n = 10) for AT1R. Angiotensin II significantly enhanced the invasive potential and VEGF secretion in AT1R-positive SKOV-3 ovarian cancer cells, both of which were completely inhibited by the AT1R blocker candesartan. Administration of candesartan into SKOV-3-transplanted athymic mice resulted in the reduction of peritoneal dissemination, decreased ascitic VEGF concentration, and suppression of tumor angiogenesis.

CONCLUSIONS

AT1R is functionally expressed in ovarian carcinoma and involved in tumor progression and angiogenesis. AT1R blockade therapy may become a novel and promising strategy for ovarian cancer treatment.

Current topic: the uteroplacental renin-angiotensin system

The components of the renin-angiotensin system (RAS) are expressed in the uteroplacental unit. The expression varies between species, probably due to the marked species differences in placental architecture. The conditions for angiotensin (Ang) II formation exist and Ang II receptors are present throughout the human uteroplacental unit, indicating the presence of a functional local RAS. The uteroplacental RAS interacts with other regulatory systems and in this way modulates various aspects of tissue function. It is suggested that the uteroplacental RAS is important for the regeneration of the endometrium after shedding, and for decidualization, implantation and placentation. The RAS participates in the regulation of the uteroplacental blood flow, prostaglandin synthesis and oestradiol secretion. Disturbances of the uteroplacental RAS may lead to dysfunctional bleeding and to reduced uteroplacental blood flow in pregnancies complicated by pre-eclampsia and intrauterine growth retardation.

Autoradiographic localization and characterization of angiotensin II receptors in the bovine placenta and fetal membranes

Autoradiography and angiotensin (Ang) II receptor binding studies showed that all parts of the bovine placenta and fetal membranes contained high densities of Ang II receptors throughout gestation. The receptors were predominantly subtype 2 (AT2) receptors in the fetal and subtype 1 (AT1) receptors in the maternal compartment. In the allantoamnionic membrane, Ang II receptors were evenly distributed in the mesenchymal tissue, with the highest expression around the few arteries. In the intercotyledonary and cotyledonary allantochorionic membrane, AT2 receptors as well as the less-expressed AT1 receptors were located on mesenchymal cells, especially adjacent to the allantoic endoderm, trophoblast cell layer, and arteries. In the mesenchymal tissue of the placentome, Ang II receptors were mostly expressed at the main branches of the fetal villi of the cotyledons. In the maternal part of the placentome, mainly AT1 receptors but also low densities of AT2 receptors and non-AT1/non-AT2 Ang II binding sites were found close to the stalk and at the main branches of the maternal crypts. Autoradiography revealed no changes in the pattern of distribution of the Ang II receptors throughout gestation. It is suggested that Ang II has an effect on regulatory as well as growth processes in these tissues.