The renin-angiotensin system and its receptors

Angiotensin-(1-7) plays an important role in regulating spermatogenesis in Trachemys scripta elegans under salinity stress

Elevation in water salinity can threaten the spermatogenesis and fertility of freshwater animals. The role of the renin-angiotensin system (RAS) in regulating spermatogenesis has attracted considerable attention. Our previous study found that red-eared sliders (Trachemys scripta elegans), could survive in 10 PSU water for over 1 year. To understand the chronic impact of salinity on testicular spermatogenesis and underlying mechanisms, male T. s. elegans were subjected to treatment with water of 5 PSU and 10 PSU for a year, and spermatogenesis and regulation of the RAS signal pathway was assessed. Results showed induced inflammation in the testes of T. s. elegans in the 10 PSU group, as evidenced by a decrease in the number of testicular germ cells from 1586 to 943. Compared with the control group, the levels of proinflammatory genes, including TNF-α, IL-12A and IL-6 were elevated 3.1, 0.3, and 1.4 times, respectively, in animals exposed to 10 PSU water. Testicular antiapoptotic processes of T. s. elegans might involve the vasoactive peptide angiotensin-(1-7) in the RAS, as its level was significantly increased from 220.2 ng ml-1 in controls to 419.2 ng ml-1 in the 10 PSU group. As expected, specific inhibitor (A-779) for the Ang-(1-7) acceptor effectively prevented the salinity-induced upregulation of genes encoding anti-inflammatory and antiapoptotic factors (TGF-β1, Bcl-6) in the testis of the 10 PSU animals, whereas it promoted the upregulation of proinflammatory and proapoptotic factors (TNF-α, IL-12A, IL-6, Bax and caspase-3). Our data indicated that Ang-(1-7) attenuates the effect of salinity on inflammation and apoptosis of the testis in T. s. elegans. A new perspective to prevent salinity-induced testis dysfunction is provided.

Renin-angiotensin-aldosterone system inhibitors as a risk factor for chronic subdural hematoma recurrence: A matter of debate

OBJECTIVES

Chronic subdural hematoma (cSDH) is a common central nervous system condition. Recent reports indicate that cSDH affects long-term prognosis; however, its definitive risk factors remain unknown. An antihypertensive drug, renin-angiotensin-aldosterone system inhibitors (RAASi), can affect vascular permeability and cell proliferation processes, which may suppress the recurrence of cSDH. However, several studies have reported negative results to this effect. Therefore, we aimed to evaluate antihypertensive drugs, including RAASi, as risk factors for recurrent cSDH.

MATERIALS AND METHODS

A total of 203 consecutive cases of surgically treated cSDH were retrospectively reviewed. Clinical and radiological parameters were compared between the groups with and without cSDH recurrence to identify risk factors.

RESULTS

Of the included cases, 68 (33.5%) used RAASi and 37 (18.2%) developed recurrence within 60 days of surgery. In the multiple logistic regression analysis adjusted by composite risk score, the odds ratios (95% confidence interval) of RAASi, calcium channel blockers, diuretics, β and α blockers, for the recurrent risk of cSDH after surgery were 2.49 (1.16, 5.42), 1.79 (0.84, 3.82), 1.83 (0.62, 4.87), 0.90 (0.28, 2.44), and 0.96 (0.21, 3.20), respectively. The Cox proportional hazard model also demonstrated that RAASi-use was an independent risk factor for cSDH recurrence.

CONCLUSIONS

Present series suggests RAASi-use as a risk factor for cSDH recurrence, although the role of RAASi-use in cSDH remains debatable. Further studies for deeper understanding of the microenvironment of hematoma and the surroundings are preferable. (235 words).

Sodium Homeostasis, a Balance Necessary for Life

Body sodium (Na) levels must be maintained within a narrow range for the correct functioning of the organism (Na homeostasis). Na disorders include not only elevated levels of this solute (hypernatremia), as in diabetes insipidus, but also reduced levels (hyponatremia), as in cerebral salt wasting syndrome. The balance in body Na levels therefore requires a delicate equilibrium to be maintained between the ingestion and excretion of Na. Salt (NaCl) intake is processed by receptors in the tongue and digestive system, which transmit the information to the nucleus of the solitary tract via a neural pathway (chorda tympani/vagus nerves) and to circumventricular organs, including the subfornical organ and area postrema, via a humoral pathway (blood/cerebrospinal fluid). Circuits are formed that stimulate or inhibit homeostatic Na intake involving participation of the parabrachial nucleus, pre-locus coeruleus, medial tuberomammillary nuclei, median eminence, paraventricular and supraoptic nuclei, and other structures with reward properties such as the bed nucleus of the stria terminalis, central amygdala, and ventral tegmental area. Finally, the kidney uses neural signals (e.g., renal sympathetic nerves) and vascular (e.g., renal perfusion pressure) and humoral (e.g., renin-angiotensin-aldosterone system, cardiac natriuretic peptides, antidiuretic hormone, and oxytocin) factors to promote Na excretion or retention and thereby maintain extracellular fluid volume. All these intake and excretion processes are modulated by chemical messengers, many of which (e.g., aldosterone, angiotensin II, and oxytocin) have effects that are coordinated at peripheral and central level to ensure Na homeostasis.

Angiotensin AT2 Receptor Stimulation Alleviates Collagen-Induced Arthritis by Upregulation of Regulatory T Cell Numbers

The angiotensin AT₂ receptor (AT₂R) is a main receptor of the protective arm of the renin-angiotensin system and exerts for instance anti-inflammatory effects. The impact of AT₂R stimulation on autoimmune diseases such as rheumatoid arthritis (RA) is not yet known. We investigated the therapeutic potential of AT₂R-stimulation with the selective non-peptide AT₂R agonist Compound 21 (C21) in collagen-induced arthritis (CIA), an animal model for inflammatory arthritis. Arthritis was induced by immunization of DBA/1J mice with collagen type II (CII). Prophylactic and therapeutic C21 treatment alleviates arthritis severity and incidence in CIA. Joint histology revealed significantly less infiltrates of IL-1 beta and IL-17A expressing cells and a well-preserved articular cartilage in C21- treated mice. In CIA, the number of CD4⁺CD25⁺FoxP3⁺ regulatory T (Treg) cells significantly increased upon C21 treatment compared to vehicle. T cell differentiation experiments demonstrated increased expression of FoxP3 mRNA, whereas IL-17A, STAT3 and IFN-gamma mRNA expression were reduced upon C21 treatment. In accordance with the mRNA data, C21 upregulated the percentage of CD4⁺FoxP3⁺ cells in Treg polarizing cultures compared to medium-treated controls, whereas the percentage of CD4⁺IL-17A⁺ and CD4⁺IFN-gamma⁺ T cells was suppressed. To conclude, C21 exerts beneficial effects on T cell-mediated experimental arthritis. We found that C21-induced AT₂R-stimulation promotes the expansion of CD4⁺ regulatory T cells and suppresses IL-17A production. Thus, AT₂R-stimulation may represent an attractive treatment strategy for arthritis.

Antihypertensive Effect of Dietary β-Conglycinin in the Spontaneously Hypertensive Rat (SHR)

Dietary β-conglycinin has been shown to increase plasma adiponectin concentration and decrease visceral adipose tissue weight in rats. Since adiponectin is one of the factors regulating blood pressure, as well as modulating lipid metabolism, we examined whether dietary β-conglycinin affects blood pressure in spontaneously hypertensive rats. The experimental diets were prepared according to the AIN-93G formula containing 20% protein, either casein (Control) or casein replaced with soy protein isolate (SOY) or β-conglycinin (β-CON) at the proportion of 50%. Male rats (SHR/Izm, 6 wk-old) were fed the diets for 7 weeks. The SOY compared with the Control significantly suppressed the blood pressure both at week 4 (p = 0.011, Control vs. SOY) and thereafter, and β-CON had even higher suppression (p = 0.0002, Control vs. β-CON). SOY and β-CON increased plasma adiponectin concentration followed by an increase in plasma nitric oxide and possibly a decreasing trend of gene expressions of angiotensinogen in the liver and renin in the kidney. The results indicated suppression by β-conglycinin of increasing blood pressure through an enhancement of plasma adiponectin, probably in combination with a regulation of the renin–angiotensin system in spontaneously hypertensive rats.

A Novel Modulator of the Renin–Angiotensin System, Benzoylaconitine, Attenuates Hypertension by Targeting ACE/ACE2 in Enhancing Vasodilation and Alleviating Vascular Inflammation

The monoester alkaloids in Aconitum carmichaelii, including benzoylaconitine (BAC), benzoylmesaconine, and benzoylhypaconitine, were found to have anti-hypertensive effects in spontaneously hypertension rats (SHRs), of which BAC is the strongest. However, its antihypertensive target and underlying molecular mechanisms remain unclear. In this study, first, we screened the antihypertensive targets of BAC by using the CVDPlatform (www.cbligand.org/CVD) and found that ACE/ACE2 are the most possible targets. Then, we verified the effect of BAC on ACE/ACE2 by virtual docking, SPR, enzyme activity assay, and HUVECs cell experiment. We found that BAC could bind with ACE/ACE2, inhibit ACE activity and protein expression, and activate ACE2 enzyme activity. Using vascular function test in vitro, we found that BAC could target ACE/ACE2 to enhance endothelium-dependent vasorelaxation. In BAC-treated SHRs, the levels of ACE and AngII in serum were reduced while Ang (1–7) was increased significantly, and the expression of ACE was reduced, which suggested that BAC can inhibit ACE and activate ACE2 to inhibit AngI to AngII and promote AngII to Ang (1–7) to inhibit vasoconstriction and finally attenuate hypertension. Furthermore, the signaling pathways with regard to vasorelaxation and vascular inflammation were investigated. The results showed that BAC could significantly activate Akt/eNOS, increase NO production, and promote endothelial-related vasodilation; BAC could also reduce inflammatory factors TNF-α and IL6, inhibition of COX-2 expression, and IKB-α phosphorylation to reduce vascular inflammation in SHRs. In brief, BAC targets ACE/ACE2 to enhance endothelium-dependent vasorelaxation and reduce vascular inflammation to attenuate hypertension as a potential modulator of the renin–angiotensin system.

Update on Angiotensin II Subtype 2 Receptor: Focus on Peptide and Nonpeptide Agonists

Angiotensin II (Ang II) is the most dominant effector component of the renin-angiotensin system (RAS) that generally acts through binding to two main classes of G protein-coupled receptors, namely Ang II subtype 1 receptor (AT1R) and angiotensin II subtype 2 receptor (AT2R). Despite some controversial reports, the activation of AT2R generally antagonizes the effects of Ang II binding on AT1R. Studying AT2R signaling, function, and its specific ligands in cell culture or animal studies has confirmed its beneficial effects throughout the body. These characteristics classify AT2R as part of the protective arm of the RAS that, along with functions of Ang (1-7) through Mas receptor signaling, modulates the harmful effects of Ang II on AT1R in the activated classic arm of the RAS. Although Ang II is the primary ligand for AT2R, we have summarized other natural or synthetic peptide and nonpeptide agonists with critical evaluation of their structure, mechanism of action, and biologic activity. SIGNIFICANCE STATEMENT: AT2R is one of the main components of the RAS and has a significant prospective for mediating the beneficial action of the RAS through its protective arm on the body's homeostasis. Targeting AT2R offers substantial clinical application possibilities for modulating various pathological conditions. This review provided concise information regarding the AT2R peptide and nonpeptide agonists and their potential clinical applications for various diseases.

Evaluation of the Effect of Captopril and Losartan on Tacrolimus-induced Nephrotoxicity in Rats

BACKGROUND

Tacrolimus is an immunosuppressive drug. Activation of the renin-angiotensin system (RAS) and associated inflammations may exacerbate the toxic effects of tacrolimus. Given the significant role of the kidney in RAS this study aimed to evaluate the effect of captopril as an angiotensin-converting enzyme (ACE) blocker and losartan as an angiotensin II receptor blocker on tacrolimus-induced nephrotoxicity.

MATERIALS AND METHODS

In total, 36 adult male rats weighing 200-250 gr were completely randomized and divided into six groups (control, tacrolimus, tacrolimus and losartan, tacrolimus and captopril, losartan, and captopril) for 30 days. Afterwards, blood urea nitrogen (BUN), creatinine (Cr) and ACE2 enzyme were measured. Also, both kidneys were collected for histological examinations.

RESULTS

The level of BUN and Cr significantly increased in tacrolimus group. The level of BUN and Cr were lower in the groups treated with a combination of tacrolimus and losartan or captopril. While ACE2 level increased in the groups receiving a combination of tacrolimus and losartan or captopril, the level of increase was insignificant, compared to the group treated with tacrolimus alone. The glomerulus diameter and the thickness of the renal proximal tubular epithelium significantly decreased in the group treated with tacrolimus alone. the mentioned variables increased in the group treated with a combination of tacrolimus and losartan or captopril, compared to the tacrolimus group.

CONCLUSION

According to this study, tacrolimus increased the BUN and Cr levels while decreasing the ACE2 levels. However, tacrolimus in combination with losartan or captopril seemed to decrease the nephrotoxicity of the drug.

Fibrogenesis in LAMA2-Related Muscular Dystrophy Is a Central Tenet of Disease Etiology

LAMA2-related congenital muscular dystrophy, also known as MDC1A, is caused by loss-of-function mutations in the alpha2 chain of Laminin-211. Loss of this protein interrupts the connection between the muscle cell and its extracellular environment and results in an aggressive, congenital-onset muscular dystrophy characterized by severe hypotonia, lack of independent ambulation, and early mortality driven by respiratory complications and/or failure to thrive. Of the pathomechanisms of MDC1A, the earliest and most prominent is widespread and rampant fibrosis. Here, we will discuss some of the key drivers of fibrosis including TGF-beta and renin–angiotensin system signaling and consequences of these pathways including myofibroblast transdifferentiation and matrix remodeling. We will also highlight some of the differences in fibrogenesis in congenital muscular dystrophy (CMD) with that seen in Duchenne muscular dystrophy (DMD). Finally, we will connect the key signaling pathways in the pathogenesis of MDC1A to the current status of the therapeutic approaches that have been tested in the preclinical models of MDC1A to treat fibrosis.

The role of adiponectin in placentation and preeclampsia

Preeclampsia is not fully understood; and few biomarkers, therapeutic targets, and therapeutic agents for its management have been identified. Original investigative findings suggest that abnormal placentation triggers preeclampsia and leads to hypertension, proteinuria, endothelial dysfunction, and inflammation, which are characteristics of the disease. Because of the regulatory roles that it plays in several metabolic processes, adiponectin has become a cytokine of interest in metabolic medicine. In this review, we have discussed the role of adiponectin in trophoblast proliferation, trophoblast differentiation, trophoblast invasion of the decidua, and decidual angiogenesis, which are the major phases of placentation. Also, we have highlighted the physiological profile of adiponectin in the course of normal pregnancy. Moreover, we have discussed the involvement of adiponectin in hypertension, endothelial dysfunction, inflammation, and proteinuria. Furthermore, we have summarized the reported relationship between the maternal serum adiponectin level and preeclampsia. The available evidence indicates that adiponectin level physiologically falls as pregnancy advances, regulates placentation, and exhibits protective effects against the symptoms of preeclampsia and that while hyperadiponectinemia is evident in normal-weight preeclamptic women, hypoadiponectinemia is evident in overweight and obese preeclamptic women. Therefore, the clinical use of adiponectin as a biomarker, therapeutic target, or therapeutic agent against the disease looks promising and should be considered.

Delayed Captopril Administration Mitigates Hematopoietic Injury in a Murine Model of Total Body Irradiation

The increasing potential for accidental radiation exposure from either nuclear accidents or terrorist activities has escalated the need for radiation countermeasure development. We previously showed that a 30-day course of high-dose captopril, an ACE inhibitor, initiated 1–4 h after total body irradiation (TBI), improved Hematopoietic Acute Radiation Syndrome (H-ARS) and increased survival in mice. However, because of the time likely required for the deployment of a stockpiled radiation countermeasure to a radiation mass casualty site, there is a need for therapies that can be administered 24–48 hours after initial exposure. Using C57BL/6 mice exposed to an LD_50-80/30 of ⁶⁰Co TBI (7.75–7.9 Gy, 0.615 Gy/min), we show that low-dose captopril administration, initiated as late as 48 h post-TBI and continued for 14 days, significantly enhanced overall survival similarly to high-dose, rapid administration. Captopril treatment did not affect radiation-induced cell cycle arrest genes or the immediate loss of hematopoietic precursors. Reduced mortality was associated with the recovery of bone marrow cellularity and mature blood cell recovery at 21–30 days post-irradiation. Captopril reduced radiation-induced cytokines EPO, G-CSF, and SAA in the plasma. Finally, delayed captopril administration mitigated brain micro-hemorrhage at 21 days post-irradiation. These data indicate that low dose captopril administered as late as 48 h post-TBI for only two weeks improves survival that is associated with hematopoietic recovery and reduced inflammatory response. These data suggest that captopril may be an ideal countermeasure to mitigate H-ARS following accidental radiation exposure.

Predisposition of Angiotensin-converting Enzyme Deletion/Deletion Genotype to Coronary Artery Disease with Type 2 Diabetes Mellitus in South India

BACKGROUND

Worldwide, South Asians contribute to a high proportion of coronary artery disease (CAD) burden, mainly attributed to a high prevalence of diabetes. Early identification of such high-risk individuals would enable aggressive disease modification and prevention of complications. Definition of susceptible genotypes early in the course of disease may be one such avenue for reduction in morbidity and mortality from CAD.

AIM

Our study was aimed to investigate the insertion/deletion polymorphism of angiotensin-converting enzyme (ACE I/D) gene and susceptibility to CAD in patients with type 2 diabetes mellitus (T2DM) in a South Indian population.

SUBJECTS AND METHODS

ACE (I/D) genotyping was performed by polymerase chain reaction specific primer for 187 CAD patients and 185 age- and sex-matched controls.

RESULTS

We observed that the ACE"II" genotype was found to be significantly associated with CAD patients (odds ratio [OR] = 1.689; P = 0.028). However, multiple logistic regression analysis revealed that ACE "DD" genotype was found to be most predominant risk factor for CAD patients with T2DM (OR = 6.118; P = 0.001).

CONCLUSION

Our results showed that ACE (I/D) genotypes and alleles presented functional dimorphism in the development of CAD and CAD with T2DM patients in South India. This finding may be extremely useful in identifying subsets of patients where early aggressive treatment of risk factors is warranted.

Evidence of changes in alpha-1/AT1 receptor function generated by diet-induced obesity

To study whether hypercaloric diet-induced obesity deteriorates vascular contractility of rat aorta through functional changes in α₁ adrenergic and/or AT1 Angiotensin II receptors. Angiotensin II- or phenylephrine-induced contraction was tested on isolated aorta rings with and without endothelium from female Wistar rats fed for 7 weeks with hypercaloric diet or standard diet. Vascular expression of Angiotensin II Receptor type 1 (AT1R), Angiotensin II Receptor type 2 (AT2R), Cyclooxygenase-1 (COX-1), Cyclooxygenase-2 (COX-2), inducible Nitric Oxide Synthase (iNOS) and endothelial Nitric Oxide Synthase (eNOS), as well as blood pressure, glucose, insulin and angiotensin II blood levels were measured. Diet-induced obesity did not significantly change agonist-induced contractions (Emax and pD₂ hypercaloric diet vs standard diet n.s.d.) of both intact (e+) or endothelium free (e-) vessels but significantly decrease both phenylephrine and angiotensin II contraction (Emax p < 0.01 hypercaloric diet vs standard diet) in the presence of both prazosin and losartan but only in endothelium-intact vessels. Diet-induced obesity did not change angiotensin II AT1, AT2 receptor proteins expression but reduced COX-1 and NOS2 ( p < 0.05 vs standard diet). Seven-week hypercaloric diet-induced obesity produces alterations in vascular adrenergic and angiotensin II receptor dynamics that suggest an endothelium-dependent adrenergic/angiotensin II crosstalk. These changes reflect early-stage vascular responses to obesity.

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.

Role of Renin-Angiotensin-converting Enzyme Level and ACE Gene Polymorphism in Patients with Nonalcoholic Fatty Liver Disease

Introduction

In this study, we aimed to investigate the histological and clinical effect of angiotensin-converting enzyme (ACE) and ACE gene polymorphism in nonalcoholic fatty liver disease (NAFLD) and their roles in the progression of the disease.

Materials and methods

Liver function tests, body mass index, waist circumference, lipid parameters, fasting blood glucose (FBG), hemoglobin A1c (HbA1c), homeostasis model assessment-IR (HOMA-IR), ACE, and ACE gene polymorphism were evaluated in the NAFLD group and control group. The study group was evaluated by dividing the group into four subgroups by ACE gene polymorphism (D/D homozygous, I/I homozygous, D/I heterozygous, I/D heterozygous). Liver biopsies were evaluated according to Brunt Classification.

Results

A total of 31 patients who were diagnosed with NAFLD and 40 healthy individuals were included in the study. The ACE level was found to be 11.69 ± 1.99 in the NAFLD group and 11.52 ± 1.72 in the control group (p = 0.70). There was a negative correlation between ACE levels and HOMA-IR levels (p = 0.008, r= −0.512). Biochemical parameters were not different among ACE gene polimorphism subgroups, except FBG (between D/D, I/D and D/I, I/D; p = 0.02). When the ACE levels were compared in terms of grade and stage, no significant difference was found (for stage and grade p = 0.68). The ACE gene polymorphism subgroups did not differ by histopathologic findings; grade and stage (for grade p = 0.42, for stage p = 0.92).

Conclusion

In this study, we could not find a correlation of ACE and ACE gene polymorphism with metabolic risk factors and the disease severity in NAFLD.

How to cite this article

Tekatas DD, Bahcecioglu IH, Ispiroglu M, Sahin A, Ilhan N, Yalniz M, Demirel U. Role of Renin–Angiotensin-converting Enzyme Level and ACE Gene Polymorphism in Patients with Nonalcoholic Fatty Liver Disease. Euroasian J Hepato-Gastroenterol 2016;6(2):137-142.

Salt, Angiotensin II, Superoxide, and Endothelial Function

Proper function of the vascular endothelium is essential for cardiovascular health, in large part due to its antiproliferative, antihypertrophic, and anti-inflammatory properties. Crucial to the protective role of the endothelium is the production and liberation of nitric oxide (NO), which not only acts as a potent vasodilator, but also reduces levels of reactive oxygen species, including superoxide anion (O2•-). Superoxide anion is highly injurious to the vasculature because it not only scavenges NO molecules, but has other damaging effects, including direct oxidative disruption of normal signaling mechanisms in the endothelium and vascular smooth muscle cells. The renin-angiotensin system plays a crucial role in the maintenance of normal blood pressure. This function is mediated via the peptide hormone angiotensin II (ANG II), which maintains normal blood volume by regulating Na+ excretion. However, elevation of ANG II above normal levels increases O2•- production, promotes oxidative stress and endothelial dysfunction, and plays a major role in multiple disease conditions. Elevated dietary salt intake also leads to oxidant stress and endothelial dysfunction, but these occur in the face of salt-induced ANG II suppression and reduced levels of circulating ANG II. While the effects of abnormally high levels of ANG II have been extensively studied, far less is known regarding the mechanisms of oxidant stress and endothelial dysfunction occurring in response to chronic exposure to abnormally low levels of ANG II. The current article focuses on the mechanisms and consequences of this less well understood relationship among salt, superoxide, and endothelial function.

Experimental gestational diabetes mellitus induces blunted vasoconstriction and functional changes in the rat aorta

Diabetic conditions increase vascular reactivity to angiotensin II in several studies but there are scarce reports on cardiovascular effects of hypercaloric diet (HD) induced gestational diabetes mellitus (GDM), so the objective of this work was to determine the effects of HD induced GDM on vascular responses. Angiotensin II as well as phenylephrine induced vascular contraction was tested in isolated aorta rings with and without endothelium from rats fed for 7 weeks (4 before and 3 weeks during pregnancy) with standard (SD) or hypercaloric (HD) diet. Also, protein expression of AT₁R, AT₂R, COX-1, COX-2, NOS-1, and NOS-3 and plasma glucose, insulin, and angiotensin II levels were measured. GDM impaired vasoconstrictor response (P < 0.05 versus SD) in intact (e+) but not in endothelium-free (e−) vessels. Losartan reduced GDM but not SD e− vasoconstriction (P < 0.01 versus SD). AT₁R, AT₂R, and COX-1 and COX-2 protein expression were significantly increased in GDM vessels (P < 0.05 versus SD). Results suggest an increased participation of endothelium vasodilator mediators, probably prostaglandins, as well as of AT₂ vasodilator receptors as a compensatory mechanism for vasoconstrictor changes generated by experimental GDM. Considering the short term of rat pregnancy findings can reflect early stage GDM adaptations.

Molecular mechanisms of inherited thoracic aortic disease - from gene variant to surgical aneurysm

Aortic dissection is a catastrophic event that has a high mortality rate. Thoracic aortic aneurysms are the clinically silent precursor that confers an increased risk of acute aortic dissection. There are several gene mutations that have been identified in key structural and regulatory proteins within the aortic wall that predispose to thoracic aneurysm formation. The most common and well characterised of these is the FBN1 gene mutation that is known to cause Marfan syndrome. Others less well-known mutations include TGF-β1 and TGF-β2 receptor mutations that cause Loeys-Dietz syndrome, Col3A1 mutations causing Ehlers-Danlos Type 4 syndrome and Smad3 and-4, ACTA2 and MYHII mutations that cause familial thoracic aortic aneurysm and dissection. Despite the variation in the proteins affected by these genetic mutations, there is a unifying pathological end point of medial degeneration within the wall of the aorta characterised by vascular smooth muscle cell loss, fragmentation and loss of elastic fibers, and accumulation of proteoglycans and glycosaminoglycans within vascular smooth muscle cell-depleted areas of the aortic media. Our understanding of these mutations and their post-translational effects has led to a greater understanding of the pathophysiology that underlies thoracic aortic aneurysm formation. Despite this, there are still many unanswered questions regarding the molecular mechanisms. Further elucidation of the signalling pathways will help us identify targets that may be suitable modifiers to enhance treatment of this often fatal condition.

Association between the ACE insertion/deletion polymorphism and pterygium in Sardinian patients: a population based case-control study

OBJECTIVE

The purpose of the study was to examine whether the insertion (I) and/or deletion (D) polymorphism of ACE confers susceptibility to primary pterygium in Sardinian patients in a case-control study.

METHODS AND RESULTS

Polymorphism genotyping was performed by nested PCR using genomic DNA extracted from the whole peripheral blood of participants with (n=251) and without (n=260) pterygium. DD, ID and II genotype frequencies were: 48%, 39% and 13%, respectively, for patients with pterygium, and 15%, 40% and 44%, respectively, for the control group. A statistically significant difference was found between the pterygium and control groups for the ACE I/D polymorphism (p<0.001). Moreover, a statistically significant difference was found between the DD and II groups (p<0.01; OR=10.49; 95% CI 6.18 to 17.79), DD+ID versus II group (p<0.01; OR=5.23; 95% CI 3.37 to 8.13) and DD versus ID groups (p<0.01; OR=3.21; 95% CI 2.04 to 5.04).

CONCLUSIONS

Statistical analysis showed that the DD genotype is associated with an increased risk of developing pterygium, and with a good chance that the D allele may play an important role in the development of disease.

Association between angiotensin-converting enzyme gene insertion/deletion polymorphism and pancreatitis risk: A meta-analysis

OBJECTIVE

Many studies have focused on the relationship between the angiotensin-converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism and pancreatitis risk, but the results remain inconsistent. Thus, a meta-analysis was carried out to derive a more precise estimation of the association between ACE I/D polymorphism and pancreatitis risk.

METHODS

Relevant publications were searched in several widely used databases and seven studies from six eligible articles were included in the meta-analysis. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between ACE I/D polymorphism and pancreatitis risk.

RESULTS

Significant associations between ACE I/D polymorphism and pancreatitis risk were observed in both overall meta-analysis for DI versus II (OR=0.80, 95% CI=0.67-0.96) and DD + DI versus II (OR=0.83, 95% CI=0.70-0.98), and acute pancreatitis subgroup for DI versus II (OR=0.65, 95% CI=0.44-0.95). However, no significant pancreatitis risk variation was detected for all genetic models in the subgroup meta-analysis based on ethnicity.

CONCLUSIONS

According to the results of our meta-analysis, the ACE I/D polymorphism probably associates with pancreatitis risk, especially acute pancreatitis risk, with the I allele acting as a risk factor.

Association of angiotensin-converting enzyme gene insertion/deletion polymorphism with decreased risk for basal cell carcinoma

The incidence of basal cell carcinoma (BCC) is significantly reduced in individuals treated with inhibitors of angiotensin I-converting enzyme (ACE) that produces angiotensin II. The objective of this study was to investigate the possible association of a functional polymorphism in the ACE gene, which affects its transcription, with risk for BCC. In DNA samples of 92 patients with BCC and 103 healthy controls of Greek origin and comparable age and gender, we studied the ACE gene insertion/deletion (I/D) polymorphism. Fisher's exact test was used for comparison of allele and genotype frequencies between the control and patients' groups. The detected low expression I allele frequency in the group of BCC patients was significantly decreased compared to controls (15.8 vs. 31.1 %, respectively; P = 0.001). ID heterozygotes exhibited 3.06 times lower BCC risk, compared with DD homozygotes (P = 0.001; OR = 0.327, 95 % CI = 0.174-0.615). The protective role of I allele was particularly prominent in women (P = 0.007, OR = 0.299, 95 % CI = 0.125-0.716), while for men it exhibited a marginal level (P = 0.041). These findings indicate that the low expression ACE I allele carriers have a decreased risk for BCC. The protective effect of the ID genotype against BCC may be explained by a possible underlying mechanism involving the effect of produced angiotensin II levels on its receptors due to putatively different binding affinity.

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.

Renin mRNA is upregulated in testes and testicular cells in response to treatment with aflatoxin B1

Aflatoxin B(1) (AFB(1)) has been shown to affect fertility in many species; however, the exact molecular mechanisms associated with the disruption are not known. Our objectives were to determine changes in testicular gene expression due to exposure to AFB(1) and to investigate which cell types were affected by treatment with AFB(1). Male mice 4 wk of age were administered a daily placebo (control; N = 9) or 50 μg/kg AFB(1) (AFB(1) treated; N = 10) daily for 45 days. Males were then mated to four females each for 8 days. Male mice were characterized as being "Tolerant" (N = 3) or "Intolerant" (N = 3) to the effects of AFB(1) based on positive terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining in the testes and the number of pups sired. Tolerant males produced a similar average number of fetuses (mean ± SEM) (12.5 ± 1.2) per male as selected control males (13.4 ± 1.2), but more fetuses (P = 0.01) than Intolerant males (7.6 ± 1.2). The number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells in Intolerant males tended to be (P = 0.10) greater (136.5 ± 27.2) than in Tolerant (55.0 ± 22.2) and selected control (54.3 ± 22.2) males. Affymetrix microarray (Sunnyvale, CA, USA) analysis revealed differential expression (P < 0.05) of 193 extra cellular space and signaling genes, 49 signal transduction genes, 45 immune regulation genes, and 230 cell differentiation genes in the testis. Renin was commonly represented amongst many clusters and was chosen for further analyses. Upregulation (P < 0.001) of Renin in Tolerant mice (N = 3) compared with Intolerant mice (N = 3) was confirmed by real-time reverse transcription polymerase chain reaction (RT-PCR) (P = 0.05). This upregulation (P = 0.01) was also observed in representative AFB(1) treated males (N = 8) compared with control males (N = 8) selected for real-time reverse transcription polymerase chain reaction analysis. Spermatogonia cultured in vitro and treated with 0, 5, 10, or 20 μg/mL AFB(1) (N = 6 per treatment) resulted in a 10-fold upregulation (P = 0.01) of Renin message at the 20 μg/mL level, whereas Leydig tumor cells showed similar differences (P = 0.03) in message for Renin in treated (10 and 20 μg/mL) versus control cell cultures. Based on these results, we inferred a role for Renin at the molecular level in the response to the adverse effects of AFB(1) in male mice.

Increased ACE in extrahepatic cholangiocarcinoma as a clue for activated RAS in biliary neoplasms

AIM

Cholangiocarcinoma (CCA) is a primary neoplastic tumor of the epithelial lining of the biliary tree which carries a poor prognosis despite combined therapeutic strategies. Although the exact etiology remains obscure, it has been suggested that locally produced Angiotensin II (Ang II) in intrahepatic CCA tissues plays a key role in the proliferation and activation of CCA. In the present study, we aimed to analyze the relationship between the levels of circulating angiotensin converting enzyme (ACE), an important molecule of the renin-angiotensin system (RAS), and biliary disorders.

PATIENTS AND METHODS

The study group comprised 19 extrahepatic cholangiocarcinoma (EHCC) (16 patients with hilar, three patients with distal CCA), and 15 choledocolithiasis (CL) patients, with 15 controls. Median age of EHCC, CL and healthy controls were 67 (48-82), 65 (29-87) and 56 (23-74) respectively. ACE was measured by monitoring the alteration in absorbance at 340 nm of the hydrolysis of furylacrylolylphenylalanylglycylglycine (FAPGG) to FAP and GG on an analyzer. The ACE activity in the sample was determined by comparing the sample reaction rate to that obtained with the ACE calibrator.

RESULTS

Serum mean ACE levels were 56.6±27.4 U/L, 32.9±14.6 U/L and 28.6±10.6 U/L for patients with EHCC, CL and healthy controls, respectively. Serum ACE levels were significantly higher in patients with EHCC compared to CL and control groups. No significant differences with respect to ACE levels were observed between CL and control groups.

CONCLUSION

Circulating ACE in the context of RAS might be associated with EHCC development by creating a local environment enriched with cytokines and other growth factors that may promote cholangiocyte turnover.

Proteomic analysis of mare follicular fluid during late follicle development

Background

Follicular fluid accumulates into the antrum of follicle from the early stage of follicle development. Studies on its components may contribute to a better understanding of the mechanisms underlying follicular development and oocyte quality. With this objective, we performed a proteomic analysis of mare follicular fluid. First, we hypothesized that proteins in follicular fluid may differ from those in the serum, and also may change during follicle development. Second, we used four different approaches of Immunodepletion and one enrichment method, in order to overcome the masking effect of high-abundance proteins present in the follicular fluid, and to identify those present in lower abundance. Finally, we compared our results with previous studies performed in mono-ovulant (human) and poly-ovulant (porcine and canine) species in an attempt to identify common and/or species-specific proteins.

Methods

Follicular fluid samples were collected from ovaries at three different stages of follicle development (early dominant, late dominant and preovulatory). Blood samples were also collected at each time. The proteomic analysis was carried out on crude, depleted and enriched follicular fluid by 2D-PAGE, 1D-PAGE and mass spectrometry.

Results

Total of 459 protein spots were visualized by 2D-PAGE of crude mare follicular fluid, with no difference among the three physiological stages. Thirty proteins were observed as differentially expressed between serum and follicular fluid. Enrichment method was found to be the most powerful method for detection and identification of low-abundance proteins from follicular fluid. Actually, we were able to identify 18 proteins in the crude follicular fluid, and as many as 113 in the enriched follicular fluid. Inhibins and a few other proteins involved in reproduction could only be identified after enrichment of follicular fluid, demonstrating the power of the method used. The comparison of proteins found in mare follicular fluid with proteins previously identified in human, porcine and canine follicular fluids, led to the identification of 12 common proteins and of several species-specific proteins.

Conclusions

This study provides the first description of mare follicular fluid proteome during the late follicle development stages. We identified several proteins from crude, depleted and enriched follicular fluid. Our results demonstrate that the enrichment method, combined with 2D-PAGE and mass spectrometry, can be successfully used to visualize and further identify the low-abundance proteins in the follicular fluid.

The relationship of ACE and CETP gene polymorphisms with cardiovascular disease in a cohort of Asian Indian patients with and those without type 2 diabetes

INTRODUCTION

Hypertension and dyslipidemia have been associated with cardiovascular disease (CVD). We investigated the association of candidate gene polymorphisms in angiotensin-converting enzyme (ACE) and cholesterol ester transfer protein (CETP) genes in a cohort of Asian Indian patients with and those without type 2 diabetes.

METHODS

PCR-based genotyping of insertion/deletion (I/D) polymorphism of ACE (rs4646994) and -629C>A of CETP (rs1800775) was carried out in 520 individuals, of whom 160 had CVD+type 2 diabetes mellitus (T2DM), 90 were CVD patients without T2DM, 150 had T2DM with no cardiovascular complications, and 120 were age- and sex-matched healthy controls.

RESULTS

With respect to the ACE gene I/D polymorphism, there was a higher percentage of D/D genotype in CVD+T2DM patients, but it was not statistically significant, while the CETP -629A allele was significantly associated with CVD+T2DM patients (P=.000007; odds ratio=0.46; 95% confidence interval=0.32-0.65) as compared with the normal controls and not with CVD alone. Additive interactions between the AA+I/I genotypes, AC+I/D genotypes, and AC+D/D were identified between the patients and the controls with P values of .0052, .0009, and .0078, respectively.

CONCLUSIONS

Our study suggests that candidate gene polymorphism -629C>A of CETP may serve as a susceptibility biomarker for CVD in T2DM patients. Analyzing the combined effect of both ACE and CETP genotypes would enhance the sensitivity and specificity of CVD risk estimation in the T2DM patients in our population.

ACE2, a promising therapeutic target for pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a chronic lung disease with poor diagnosis and limited therapeutic options. The currently available therapies are ineffective in improving the quality of life and reducing mortality rates. There exists a clear unmet medical need to treat this disease, which necessitates the discovery of novel therapeutic targets/agents for safe and successful therapy. An altered renin–angiotensin system (RAS) has been implicated as a causative factor in the pathogenesis of PAH. Angiotensin II (Ang II), a key effector peptide of the RAS, can exert deleterious effects on the pulmonary vasculature resulting in vasoconstriction, proliferation, and inflammation, all of which contribute to PAH development. Recently, a new member of the RAS, angiotensin converting enzyme 2 (ACE2), was discovered. This enzyme functions as a negative regulator of the angiotensin system by metabolizing Ang II to a putative protective peptide, angiotensin-(1–7). ACE2 is abundantly expressed in the lung tissue and emerging evidence suggests a beneficial role for this enzyme against lung diseases. In this review, we focus on ACE2 in relation to pulmonary hypertension and provide proof of principle for its therapeutic role in PAH.

Lack of heterologous receptor desensitization induced by angiotensin II type 1 receptor activation in isolated normal rat thoracic aorta

We tested whether heterologous receptor desensitization induced by activation of AT1 receptors may explain the purported relaxation produced by angiotensin II in normal rat aorta. Also, the role for AT2 receptors in the promotion of vasodilation was studied. In endothelium-intact and endothelium-denuded aortic rings, angiotensin II elicited biphasic contractions, which were significantly depressed when repeated in each tissue. Angiotensin II produced biphasic responses on phenylephrine preconstricted endothelium-intact and endothelium-denuded tissues, without reducing precontractile tone. These responses were abolished in the presence of the AT1 receptor antagonist losartan, but no relaxing responses to angiotensin II were uncovered. PD123319 did not influence angiotensin II responses in endothelium-intact tissues precontracted with phenylephrine; thus, under AT2 receptors blockade the contractile effects of angiotensin II were not overexposed. In conclusion, angiotensin II-induced biphasic responses can be attributed to AT1 receptors activation and rapid desensitization with time. Desensitization proved to be homologous in nature, since precontractile tone induced by phenylephrine was not depressed by angiotensin II (i.e., angiotensin II did not induce heterologous α1-adrenergic receptors desensitization). We found no functional evidence of the participation of AT2 receptors in angiotensin II elicited biphasic contractions. Angiotensin II does not exert relaxant effects in normal rat aorta.

The renin-angiotensin system in retinal health and disease: Its influence on neurons, glia and the vasculature

Renin-Angiotensin System is classically recognized for its role in the control of systemic blood pressure. However, the retina is recognized to have all the components necessary for angiotensin II formation, suggestive of a role for Angiotensin II in the retina that is independent of the systemic circulation. The most well described effects of Angiotensin II are on the retinal vasculature, with roles in vasoconstriction and angiogenesis. However, it is now emerging that Angiotensin II has roles in modulation of retinal function, possibly in regulating GABAergic amacrine cells. In addition, Angiotensin II is likely to have effects on glia. Angiotensin II has also been implicated in retinal vascular diseases such as Retinopathy of Prematurity and diabetic retinopathty, and more recently actions in choroidal neovascularizaiton and glaucoma have also emerged. The mechanisms by which Angiotensin II promotes angiogensis in retinal vascular diseases is indicative of the complexity of the RAS and the variety of cell types that it effects. Indeed, these diseases are not purely characterized by direct effects of Angiotensin II on the vasculature. In retinopathy of prematurity, for example, blockade of AT1 receptors prevents pathological angiogenesis, but also promotes revascularization of avascular regions of the retina. The primary site of action of Angiotensin II in this disease may be on retinal glia, rather than the vasculature. Indeed, blockade of AT1 receptors prevents glial loss and promotes the re-establishment of normal vessel growth. Blockade of RAS as a treatment for preventing the incidence and progression of diabetic retinopathy has also emerged based on a series of studies in animal models showing that blockade of the RAS prevents the development of a variety of vascular and neuronal deficits in this disease. Importantly these effects may be independent of actions on systemic blood pressure. This has culminated recently with the completion of several large multi-centre clinical trials that showed that blockade of the RAS may be of benefit in some at risk patients with diabetes. With the emergence of novel compounds targeting different aspects of the RAS even more effective ways of blocking the RAS may be possible in the future.

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.

Association of angiotensin-converting enzyme gene insertion/deletion polymorphism with increased risk for oral cancer

INTRODUCTION

In light to recently found contribution of factors associated with thrombosis and inflammation to carcinogenesis, we investigated the possible association of angiotensin I- converting enzyme (ACE) with increased risk for oral cancer.

MATERIALS AND METHODS

In DNA samples of 160 patients with oral squamous cell carcinoma and 153 healthy controls of comparable ethnicity, age and sex, we studied the insertion/deletion (I/D) polymorphism in the ACE gene, which affects its transcription.

RESULTS

The I allele frequencies were significantly increased in patients compared to controls, 40.6% versus 27.5% (p < 0.001), respectively. The II homozygotes had a three-fold greater risk for developing oral cancer (odds ratio 3.17, 95% C.I. 1.32-7.61). A significant increase of I alleles was observed in patients regardless their smoking or alcohol consumption habits, early or advanced stage of cancer, presence or absence of a family history for cancer or thrombophilia (Fischer values p < 0.05).

DISCUSSION

These findings suggest that the I/D polymorphism, by affecting the ACE gene expression, is associated with the progress of oral oncogenesis.

Decreased muscle ACE activity enhances functional response to endurance training in rats, without change in muscle oxidative capacity or contractile phenotype

In the present study, we tested the hypothesis that chronic ANG I-converting enzyme (ACE) inhibition could improve the training-induced improvement in endurance exercise performance and that this could be related to enhanced skeletal muscle metabolic efficiency. Female Wistar rats were assigned to four groups comprising animals either maintained sedentary or endurance trained (Sed and Tr, respectively), and treated or not for 10 wk with an ACE inhibitor, perindopril (2 mg·kg−1·day−1) (Per and Ct, respectively) ( n = 8 each). Trained rats underwent an 8-wk treadmill training protocol that consisted of 2 h/day running at 30 m/min on a 8% decline. Before the start of and 1 wk before the end of experimental conditioning, the running time to exhaustion of rats was measured on a treadmill. The training program led to an increase in endurance time, higher in Tr-Per than in Tr-Ct group (125% in Tr-Ct vs. 183% in Tr-Per groups, P < 0.05). Oxidative capacity, measured in saponin-permeabilized fibers of slow soleus and fast plantaris muscles, increased with training, but less in Tr-Per than in Tr-Ct rats. The training-induced increase in citrate synthase activity also was less in soleus from Tr-Per than Tr-Ct rats. The training-induced increase in the percentage of the type IIa isoform of myosin heavy chain (MHC) (45%, P < 0.05) and type IIx MHC (25%, P < 0.05) associated with decreased type IIb MHC (34%, P < 0.05) was minimized by perindopril administration. These findings demonstrate that the enhancement in physical performance observed in perindopril-treated animals cannot be explained by changes in mitochondrial respiration and/or MHC distribution within muscles involved in running exercise.

Neuronal and glial cell expression of angiotensin II type 1 (AT1) and type 2 (AT2) receptors in the rat retina

The bio-active peptide, angiotensin II (Ang II), has been suggested to exert a neuromodulatory effect on inner retinal neurons. In this study, we examined the distribution of angiotensin receptors (ATRs) in the developing and mature rat retina and optic nerve using immunofluorescence immunocytochemistry. Double-labeling experiments were performed with established markers to identify different retinal cell populations. In adult retinae, ATRs were observed on neurons involved in "ON" pathways of neurotransmission. Angiotensin II type 1 receptors (AT(1)Rs) were expressed by a sub-population of "ON" cone bipolar cells that also labeled for G alpha(0) and islet-1. Extra-neuronal expression of AT(1)Rs was evident on retinal astrocytes, Müller cells and blood vessels. Immunoreactivity for the angiotensin II type 2 receptor (AT(2)R) was observed on conventional and displaced GABAergic amacrine cells. Co-localization studies showed that AT(2)R-expressing amacrine cells constituted at least two separate sub-populations. Cell counts revealed that all wide-field amacrine cells expressing protein kinase C-alpha were also AT(2)R-positive; a further subset of amacrine cells expressing AT(2)Rs and stratifying in sublamina "b" of the inner plexiform layer (IPL) was identified. Developmental expression of AT(1)Rs was dynamic, involving multiple inner neuronal classes. At postnatal day 8 (P8), AT(1)R immunoreactivity was observed on putative ganglion cells. The characteristic bipolar cell labeling observed in adults was not evident until P13. In contrast, AT(2)Rs were detected as early as P2 and localized specifically to amacrine cells from this age onward. These data provide further evidence for the potential role of angiotensin II in the modulation of retinal neurons and glia. The differential pattern of expression of these receptors across these cell types is similar to that observed in the brain and suggests that a similar functional role for Ang II may also exist within the retina.

Angiotensin-converting enzyme gene DD genotype neither increases susceptibility to acute pancreatitis nor influences disease severity

BACKGROUND

The renin-angiotensin system (RAS) has been implied in the pathogenesis of various diseases including acute and chronic pancreatitis. Angiotensin-converting enzyme (ACE) is the key enzyme in activating the RAS. Deletion (D)-type polymorphism in the 16th intron of the ACE gene has been associated with higher serum levels of the enzyme. Inhibition of ACE was found to ameliorate acute pancreatitis in animal models suggesting that ACE plays a role in pathogenesis and progression of acute pancreatitis. Objectives were to investigate the occurrence of the ACE insertion/deletion (I/D) polymorphism in acute pancreatitis patients and its association with the severity of the disease.

MATERIAL AND METHODS

Seventy-nine acute pancreatitis patients and 95 healthy controls were evaluated. Acute pancreatitis cases were grouped as mild or severe according to the Atlanta criteria.

MAIN OUTCOME MEASURE

The presence of the ACE I/D polymorphism.

RESULTS

ACE gene I and D allele frequency of patients (44% and 56%) were similar to controls (45% and 55%, respectively). There were no significant differences in severity of pancreatitis between patients with the ACE-insertion or ACE-insertion/deletion versus ACE-deletion genotypes.

CONCLUSIONS

The ACE gene deletion polymorphism is neither a risk factor for development of acute pancreatitis nor contributes to the severity of disease or development of complications.

Angiotensin-converting enzyme in skeletal muscle: sentinel of blood pressure control and glucose homeostasis

Recent evidence suggests a coordinated regulation by the local renin-angiotensin system (RAS) and tissue kallikrein-kinin system (TKKS) of blood flow and substrate supply in oxidative red myofibres of skeletal muscle tissue during endurance exercise. The performance of these myofibres is dependent on the increased oxidation of substrates facilitated by augmenting nutritive blood flow and glucose uptake. Humoral factors released by the contracting fibres, such as adenosine and kinins, are suggested to be responsible for this metabolic adjustment. The considerable drain of blood volume and the enormous consumption of glucose during endurance exercise require a control mechanism for the maintenance of blood pressure (BP) and glucose homeostasis. This is achieved by the sympathetic nervous system and its subordinate RAS, which is located in the nutritive vessels and parenchyma of the red myofibres. The angiotensin-converting enzyme (ACE) is the primary enzyme responsible for kinin degradation during exercise, underscoring the important interrelationship between the RAS and the TKKS in the critical role of kinins in the multifactorial regulation of muscle bioenergetics and glucose and BP homeostasis. Importantly, overactivity of the ACE, as occurs in individuals displaying risk factors such as overweight, causes exaggerated BP response and reduced glucose disposal. If they persist over years, compensatory responses to this ACE overactivity, such as hypersecretion of insulin and compliance of the vessel walls, will inevitably be exhausted, leading ultimately to the manifestation of type 2 diabetes and hypertension. This concept also provides a unifying explanation for the beneficial effects of ACE-inhibitors and Angiotensin II receptor antagonists in the treatment of hypertension and insulin resistance.

The Angiotensin-Converting Enzyme Gene Polymorphism is Associated with Pregnancy Miscarriage and Placental Insufficiency

Research of past decades has shown that pregnancy miscarriage (PM) and placental insufficiency (PI) underlie severe obstetric pathologies that result in complications of fetal development. The occurrence of PI developed during previous PMs varied from 47.6 to 77.3%. Pregnancy miscarriage can be considered to be the clinical manifestation of PI, which is a common complication in women with a previous history of PM. Endothelial dysfunction in the mother and in the fetoplacental complex are basic causes of PI. The angiotensin-converting enzyme (ACE) plays a key role in maintenance of proper balance between vasoconstriction and vasodilatation of blood vessels, and thus, in blood pressure regulation. DNA samples were genotyped for insertion/deletion (I/D) polymorphism of the ACE gene by polymerase chain reaction (PCR) assay. This study shows that the frequency of allele I of the ACE gene in DNA samples from placentae of the women with PM and PI (group 4) is twice as high than in the placentae of women with a PM history but without PI in the current pregnancy (group 3) (64.6 and 30.4%, respectively, p <0.001). Odds ratio (OR) analyses showed that the D/D genotype in placentae increases by 3-fold the risk of PI in women negative for PM history. The presence of the I/I genotype in patients positive for PM history increases the risk of PI 2.6-fold. It is concluded that the D/D genotype in placentae correlates with increased risk of PI in women negative for PM history, whereas the I/I genotype is a risk factor for PI in patients positive for PM history.

Comparison of ACE activity in amphibian tissues: Rana esculenta and Xenopus laevis

Angiotensin converting enzyme (ACE) is the dipeptidyl-carboxypeptidase of the renin-angiotensin system involved in the control of blood pressure and hydromineral metabolism. It converts angiotensin I to angiotensin II, the biologically active octapeptide. Angiotensin converting enzyme-like activity has been demonstrated in a wide range of vertebrates. The presence of ACE was investigated in tissues of two amphibian species, the frog Rana esculenta and the toad Xenopus laevis. ACE activities were determined by specific substrate hydrolysis in gut, gonads, lung, kidney, heart, liver, skin, erythrocytes, and muscle homogenates and plasma by means of high performance liquid chromatography. Significant ACE activity was found in gut, gonads, lung and kidney, while that in heart, liver, skin, erythrocytes, muscle, and plasma was very low. Testis of toad contained the highest ACE activity, while that in erythrocytes of male and female frogs was notable.

Lack of significant association of an insertion/deletion polymorphism in the angiotensin converting enzyme (ACE) gene with tropical calcific pancreatitis

Background

The genetic basis of tropical calcific pancreatitis (TCP) is different and is explained by mutations in the pancreatic secretory trypsin inhibitor (SPINK1) gene. However, mutated SPINK1 does not account for the disease in all the patients, neither does it explain the phenotypic heterogeneity between TCP and fibro-calculous pancreatic diabetes (FCPD). Recent studies suggest a crucial role for pancreatic renin-angiotensin system during chronic hypoxia in acute pancreatitis and for angiotensin converting enzyme (ACE) inhibitors in reducing pancreatic fibrosis in experimental models. We investigated the association of ACE gene insertion/deletion (I/D) polymorphism in TCP patients using a case-control approach. Since SPINK1 mutations are proposed a modifier role, we also investigated its interaction with the ACE gene variant.

Methods

We analyzed the I/D polymorphism in the ACE gene (g.11417_11704del287) in 171 subjects comprising 91 TCP and 80 FCPD patients and compared the allelic and genotypic frequency in them with 99 healthy ethnically matched control subjects.

Results

We found 46% and 21% of TCP patients, 56% and 19.6% of FCPD patients and 54.5% and 19.2% of the healthy controls carrying the I/D and D/D genotypes respectively (P>0.05). No significant difference in the clinical picture was observed between patients with and without the del allele at the ACE in/del polymorphism in both categories. No association was observed with the presence or absence of N34S SPINK1 mutation in these patients.

Conclusion

We conclude that the ACE insertion/deletion variant does not show any significant association with the pathogenesis, fibrosis and progression of tropical calcific pancreatitis and the fibro-calculous pancreatic diabetes.

Proteomic analysis of recurrent spontaneous abortion: Identification of an inadequately expressed set of proteins in human follicular fluid

Recurrent spontaneous abortion (RSA), defined as the loss of three or more consecutive pregnancies prior to the 20th week of gestation, affects up to 5% of the child-bearing population. To investigate the proteins associated with RSA, the protein expression in human follicular fluid was analyzed using 2-DE. Follicular fluid contains a variety of biologically important proteins for oocyte fertilization and follicle maturation in the mammalian reproductive process. Therefore, it can be used as a provisional source for identifying proteins involved in RSA. In this study, we identified five aberrantly expressed proteins (complement component C3c chain E, fibrinogen gamma, antithrombin, angiotensinogen, and hemopexin precursor) in follicular fluid from RSA patients with MALDI-TOF-MS and nano-LC MS/MS. Western blot analysis confirmed that the protein expression level of fibrinogen gamma and antithrombin was less in follicular fluid from RSA patients than those from normal controls. Semiquantitative RT-PCR and real-time PCR analyses revealed that mRNA level of these coagulation factors was also decreased significantly in chorionic villi of RSA patients compared with normal samples. Taken all together, it is likely that coagulation factors (fibrinogen gamma and antithrombin) play an important role in maintaining the normal pregnancy.

Biphasic actions of angiotensin IV on renal blood flow in the rat

Our aim was to investigate the changes in renal blood flow during brief exposure of the renal vasculature to angiotensin IV (Ang IV). Total renal blood flow was measured by electromagnetic flowmetry in pentobarbital-anesthetized male Sprague Dawley rats. Intrarenal injection of Ang I, Ang II and Ang III produced a dose-dependent vasoconstriction. In contrast, Ang IV and Ang-(3-10) produced a dose-dependent rapid vasoconstriction (lasting seconds) followed by a transient vasodilatation (lasting minutes). The biphasic response to Ang IV was unchanged in rats pre-treated with captopril, whereas the Ang-(3-10) response was abolished implying that its vasoactive activity was due to the generation of Ang IV. The vasodilatory component of Ang IV was unaffected by indomethacin. The biphasic vasoactive response of Ang IV was unaffected by divalinal-Ang IV (AT(4) receptor antagonist) or PD 123319 (AT(2) receptor antagonist), but greatly reduced by losartan or L-158,809 (AT(1) receptor antagonists). These results suggest that Ang IV is distinct from other angiotensins in that it possesses non-prostaglandin mediated renal vasodilatory activity that is apparently linked to the renal vascular AT(1) receptor.

Splice variant-specific silencing of angiotensin II type 1a receptor messenger RNA by RNA interference in vascular smooth muscle cells

In the rat, two distinct angiotensin II type 1a (rAT(1a)) receptor mRNAs are synthesized from a single rAT(1a) receptor gene by alternative splicing. These two transcripts are comprised of exons 1, 2, and 3 (E1,2,3) or exons 1 and 3 (E1,3). Since exon 3 contains the entire coding region, both transcripts encode identical rAT(1a) receptors. Real-time PCR revealed that in rat aortic smooth muscle cells (RASMC), E1,2,3 mRNA accounted for 69.5+/-0.9% of total rAT(1a) receptor mRNA. The aim of this study was to use RNA interference (RNAi) to selectively silence the rAT(1a) receptor splice variants. Forty-eight hour treatment of RASMC with E1,3-targeting siRNA (10nM; S1(E1,3)) resulted in a 91.2+/-0.5% (n=3, P<0.001) reduction in E1,3 mRNA and a 19.0+/-3.0% (n=4, P<0.05) reduction in AT(1) receptor specific binding compared with cells treated with a non-silencing control siRNA; under these conditions, no effect was observed on levels of E1,2,3 mRNA. Conversely, treatment with E1,2,3-targeting siRNA (S2(E2)) had no effect on E1,3 mRNA while reducing E1,2,3 mRNA by 73.9+/-4.2% (n=3, P<0.001), and AT(1) receptor binding by 39.4+/-5.4% (n=4, P<0.001) compared with control. These data show that the majority of functional AT(1) receptor expression in RASMC derives from the E1,2,3 splice variant. These data also demonstrate that rAT(1a) receptor mRNA can be silenced in a splice-variant specific manner using siRNA in RASMC, thus providing an excellent model system for investigating the role of alternative splicing in the regulation of rAT(1a) receptor expression.

Haemodynamic effects of AT1 inhibition and Ca2+-channel blockade in hypertensive patients during isometric stress

To assess the effects of valsartan and amlodipine on the haemodynamics of forearm circulation in hypertensive patients undergoing isometric stress. A total of 24 patients with essential hypertension were subjected to a double blind-cross-over study. The artery left arm flow (strain gauge plethysmography), distensibility of digital arteries (piezoelectric plethysmography) and blood pressure were measured. District resistance was calculated as the ratio between mean arterial pressure and blood flow. The tests were performed at basal conditions (T0) and after 8 days (T8) of therapy with valsartan (160 mg) or amlodipine (10 mg), at rest and during handgrip (HG); treatments were inverted after 15 days of washout. Valsartan and amlodipine reduced blood pressure after 8 days (P<0.05), handgrip increased systolic and diastolic values and heart rate at T0 and only a slight raising in diastolic values at T8. The recovery time of pressure values was longer in hypertensives treated with amlodipine (P<0.05). The forearm flow increased after HG (at T0 an T8) and increased even further after valsartan (P<0.005). Valsartan increased arteriolar distensibility, expressed by the ratio between time to peak and total time (PT/TT) calculated on the sphygmic wave. Amlodipine did not affect PT/TT ratio, whereas it reduced local resistance (T8 vs T0, P<0.05). The reduction effect of valsartan on resistance was detectable also during handgrip, on the contrary amlodipine did not control the increase. Inhibition of AT1 is able to reduce haemodynamic modifications elicited by isometric stress in hypertensive patients.

Interactions between atrial natriuretic peptide and the renin–angiotensin system during salt-sensitivity exhibited by the proANP gene-disrupted mouse

To understand the involvement of the systemic and cardiac components of the renin-angiotensin system (RAS) in the development of cardiac hypertrophy induced by salt intake, the present study analyzed the effect of high dietary salt (8.0% NaCl) in mice possessing a full complement (+/+) or ablation (-/-) of atrial natriuretic peptide (ANP). A 3 week treatment of 8.0% NaCl was able to induce cardiac hypertrophy in both genotypes, though exaggerated hypertrophy was noted in the ANP -/- mouse. Although a marked decrease in angiotensin II (Ang II) plasma levels in both genotypes fed a high salt diet was observed, systemic RAS mRNA components were altered only in the ANP-/- animals and remained unchanged in ANP+/+ mice. Decreased Ang II plasma levels were better correlated with decreases in angiotensinogen protein expression observed in both genotypes. High salt had no effect on cardiac RAS mRNA components in the ANP-/- animals, but did cause a significant decrease in some cardiac RAS mRNA components in ANP+/+ mice. As expected, high salt was able to increase plasma ANP levels and ventricular mRNA expression of ANP (ANP+/+ mice only) and B-type NP in both genotypes. The latter peptides are key cardiac markers of hypertrophy whose increased expression correlate well with the physical salt-induced cardiac alterations observed in this study. These findings suggest that although the RAS does not play a key role in salt-induced cardiac hypertrophy, ANP is an important determinant of the degree of salt-sensitivity observed in the proANP gene-disrupted animal.