Purification and biochemical characterization of angiotensin I-converting enzyme (ACE) from ostrich lung: The effect of 2,2,2-trifluoroethanol on ACE conformation and activity

This work reports the purification and biochemical characterization of angiotensin I-converting enzyme (ACE) from ostrich (Struthio camelus) lung. The molecular weight of the purified enzyme was approximately evaluated to be 200 kDa and the maximum enzyme activity was observed at pH 7.5. The enzyme activity was increased by detergents of Triton X-100 (0.01%), cetyltrimethylammonium bromide (CTAB) (0.1 and 1 mM) and sodium dodecyl sulfate (SDS) (0.1 mM), while decreased by Triton X-100 (1% and 10%) and SDS (1 mM and 10 mM). The secondary and tertiary structure and activity of ACE in the absence and presence of trifluoroethanol (TFE) were investigated using circular dichroism, fluorescence quenching and UV–visible spectroscopy, respectively. Our results revealed that TFE stabilizes ACE at low concentrations, while acts as a denaturant at higher concentration (20%). The K_m, K_cat and K_cat/K_m values of ostrich ACE towards FAPGG were 0.8 × 10^?4 M, 59,240 min^?1 and 74 × 10⁷ min^?1 M^?1, respectively. The values of IC₅₀ and K_i for captopril were determined to be 36.5 nM and 16.6 nM, respectively. In conclusion, ostrich lung ACE is a new enzyme which could be employed as a candidate for studying ACE structure and its natural or synthetic inhibitors.     

Myelopoiesis modulation by ACE hyperfunction in kinin B1 receptor knockout mice: Relationship with AcSDKP levels

Angiotensin I-converting enzyme (ACE), a common element of renin–angiotensin system (RAS) and kallikrein–kinin system (KKS), is involved in myelopoiesis modulation, mainly by cleaving the tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). Based on this finding and in our results showing B1 and B2 kinin receptors expression in murine bone marrow (BM) cells, we evaluated the ACE influence on myelopoiesis of kinin B1 receptor knockout mice (B1KO) using long-term bone marrow cultures (LTBMCs). Captopril and AcSDKP were used as controls. Enhanced ACE activity, expressed by non-hematopoietic cells (Ter-199^? and CD45^?), was observed in B1KO LTBMCs when compared to wild-type (WT) cells. ACE hyperfunction in B1KO cells was maintained when LTBMCs from B1KO mice were treated with captopril (1.0 μM) or AcSDKP (1.0 nM). Although no alterations were observed in ACE mRNA and protein levels under these culture conditions, 3.0 nM of AcSDKP increased ACE mRNA levels in WT LTBMCs. No alteration in the number of GM-CFC was seen in B1KO mice compared to WT animals, even when the former were treated with AcSDKP (10 μg/kg) or captopril (100 mg/kg) for 4 consecutive days. Hematological data also revealed no differences between WT and B1KO mice under basal conditions. When the animals received 4 doses of lipopolysaccharide (LPS), a decreased number of blood cells was detected in B1KO mice in relation to WT. We also found a decreased percentage of Gr1⁺/Mac-1⁺, Ter119⁺, B220⁺, CD3⁺, and Lin^?Sca1⁺c-Kit⁺ (LSK) cells in the BM of B1KO mice compared to WT animals. Low AcSDKP levels were observed in BM cultures from B1KO in comparison to WT cultures. We conclude that ACE hyperfunction in B1KO mice resulted in faster hydrolysis of AcSDKP peptide, which in turn decreased in BM tissues allowing HSC to enter the S stage of the cell cycle.     

Docosahexaenoic acid reverses angiotensin II-induced RECK suppression and cardiac fibroblast migration

The omega-3 polyunsaturated fatty acids (ω − 3 fatty acids) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been reported to inhibit or delay the progression of cardiovascular diseases, including myocardial fibrosis. Recently we reported that angiotensin II (Ang II) promotes cardiac fibroblast (CF) migration by suppressing the MMP regulator reversion-inducing-cysteine-rich protein with Kazal motifs (RECK), through a mechanism dependent on AT1, ERK, and Sp1. Here we investigated the role of miR-21 in Ang II-mediated RECK suppression, and determined whether the ω − 3 fatty acids reverse these effects. Ang II induced miR-21 expression in primary mouse cardiac fibroblasts (CFs) via ERK-dependent AP-1 and STAT3 activation, and while a miR-21 inhibitor reversed Ang II-induced RECK suppression, a miR-21 mimic inhibited both RECK expression and Ang II-induced CF migration. Moreover, Ang II suppressed the pro-apoptotic PTEN, and the ERK negative regulator Sprouty homologue 1 (SPRY1), but induced the metalloendopeptidase MMP2, all in a manner that was miR-21-dependent. Further, forced expression of PTEN inhibited Akt phosphorylation, Sp1 activation, and MMP2 induction. Notably, while both EPA and DHA reversed Ang II-mediated RECK suppression, DHA appeared to be more effective, and reversed Ang II-induced miR-21 expression, RECK suppression, MMP2 induction, and CF migration. These results indicate that Ang II-induced CF migration is differentially regulated by miR-21-mediated MMP induction and RECK suppression, and that DHA has the potential to upregulate RECK, and therefore may exert potential beneficial effects in cardiac fibrosis.     

Telmisartan attenuates aortic hypertrophy in hypertensive rats by the modulation of ACE2 and profilin-1 expression

Profilin-1 has recently been linked to vascular hypertrophy and remodeling. Here, we assessed the hypothesis that angiotensin (Ang) II type I receptor antagonist telmisartan improves vascular hypertrophy by modulation of expression of profilin-1 and angiotensin-converting enzyme 2 (ACE2). Ten-week-old male spontaneously hypertensive rats (SHR) were received oral administration of telmisartan (5 or 10 mg/kg; daily) or saline for 10 weeks. Compared with Wistar–Kyoto (WKY) rats, there were marked increases in systolic blood pressure and profilin-1 expression and reduced ACE2 and peroxisome proliferator activated receptor-γ (PPARγ) levels in aorta of SHR, associated with elevated extracellular-signal regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) phosphorylation signaling and aortic hypertrophy characterized with increased media thickness, which were strikingly reversed by telmisartan. In cultured human umbilical artery smooth muscle cells (HUASMCs), Ang II induced a dose-dependent increase in profilin-1 expression, along with decreased ACE2 protein expression and elevated ERK1/2 and JNK phosphorylation. In addition, blockade of ERK1/2 or JNK by either specific inhibitor was able to abolish Ang II-induced ACE2 downregulation and profilin-1 upregulation in HUASMCs. Importantly, treatment with telmisartan (1 or 10 μM) or recombinant human ACE2 (2 mg/ml) largely ameliorated Ang II-induced profilin-1 expression and ERK1/2 and JNK phosphorylation and augmented PPARγ ?expression in the cultured HUASMCs. In conclusion, telmisartan treatment attenuates vascular hypertrophy in SHR by the modulation of ACE2 and profilin-1 expression with a marked reversal of ERK1/2 and JNK phosphorylation signaling pathways.     

Endothelial permeability in vitro and in vivo: Protective actions of ANP and omapatrilat in experimental atherosclerosis

Increased arterial endothelial cell permeability (ECP) is considered an initial step in atherosclerosis. Atrial natriuretic peptide (ANP) which is rapidly degraded by neprilysin (NEP) may reduce injury-induced endothelial cell leakiness. Omapatrilat represents a first in class of pharmacological agents which inhibits both NEP and angiotensin converting enzyme (ACE). We hypothesized that ANP prevents thrombin-induced increases of ECP in human aortic ECs (HAECs) and that omapatrilat would reduce aortic leakiness and atherogenesis and enhance ANP mediated vasorelaxation of isolated aortas. Thrombin induced ECP determined by I¹²⁵ albumin flux was assessed in HAECs with and without ANP pretreatment. Next we examined the effects of chronic oral administration of omapatrilat (12 mg/kg/day, n = 13) or placebo (n = 13) for 8 weeks on aortic leakiness, atherogenesis and ANP-mediated vasorelaxation in isolated aortas in a rabbit model of atherosclerosis produced by high cholesterol diet. In HAECs, thrombin-induced increases in ECP were prevented by ANP. Omapatrilat reduced the area of increased aortic leakiness determined by Evans-blue dye and area of atheroma formation assessed by Oil-Red staining compared to placebo. In isolated arterial rings, omapatrilat enhanced vasorelaxation to ANP compared to placebo with and without the endothelium. ANP prevents thrombin-induced increases in ECP in HAECs. Chronic oral administration of omapatrilat reduces aortic leakiness and atheroma formation with enhanced endothelial independent vasorelaxation to ANP. These studies support the therapeutic potential of dual inhibition of NEP and ACE in the prevention of increased arterial ECP and atherogenesis which may be linked to the ANP/cGMP system.     

Cardioprotective effects of lipoic acid,quercetin and resveratrol on oxidative stress related to thyroid hormone alterations in long-term obesity

This study investigated possible mechanisms for cardioprotective effects of lipoic acid (LA), quercetin (Q) and resveratrol (R) on oxidative stress related to thyroid hormone alterations in long-term obesity. Female C57BL/6 mice were fed on high-fat diet (HFD), HFD + LA, HFD + R, HFD + Q and normal diet for 26 weeks. Body weight, blood pressure, thyroid hormones, oxidative stress markers, angiotensin converting enzyme (ACE), nitric oxide synthase (NOS) and ion pump activities were measured, and expression of cardiac genes was analyzed by real-time polymerase chain reaction. HFD induced marked increase (P < .05) in body weight, blood pressure and oxidative stress, while plasma triidothyronine levels reduced. ACE activity increased (P < .05) in HFD mice (0.69 ± 0.225 U/mg protein) compared with controls (0.28 ± 0.114 U/mg protein), HFD + LA (0.231 ± 0.02 U/mg protein) and HFD + Q (0.182 ± 0.096 U/mg protein) at 26 weeks. Moreover, Na⁺/K⁺-ATPase and Ca^2 +-ATPase activities increased in HFD mice whereas NOS reduced. A 1.5-fold increase in TRα1 and reduction in expression of the deiodinase iodothyronine DIO1, threonine protein kinase and NOS3 as well as up-regulation of AT1α, ACE, ATP1B1, GSK3β and Cja1 genes also occurred in HFD mice. Conversely, LA, Q and R inhibited weight gain; reduced TRα1 expression as well as increased DIO1; reduced ACE activity and AT1α, ATP1B1 and Cja1 gene expression as well as inhibited GSK3β; increased total antioxidant capacity, GSH and catalase activity; and reduced blood pressure. In conclusion, LA, resveratrol and quercetin supplementation reduces obesity thereby restoring plasma thyroid hormone levels and attenuating oxidative stress in the heart and thus may have therapeutic potential in heart diseases.     

Role of serum concentration of VEGFR1 and TIMP2 on clinical outcome in primary cervical cancer: Results of a companion protocol of the randomized,NOGGO–AGO phase III adjuvant trial of simultaneous cisplatin-based radiochemotherapy vs. carboplatin and paclitaxel containing sequential radiotherapy

ObjectiveAim of the present study was to analyze the expression-profile of IGF1, IGFBP3, sICAM1, sVCAM1, MMP2, MMP9, TIMP2, VEGFA, VEGFD, VEGFC and VEGFR1 in patients with high-risk FIGO-stage Ib-IIb cervical cancer.MethodsSerum from 68 cervical cancer patients treated within a phase-III-trial with either simultaneous cisplatin radiochemotherapy or sequential systemic carboplatin and paclitaxel followed by percutaneous irradiation was analyzed by ELISA. Both target expression and correlation with important clinicopathological factors were analyzed following standard statistic procedures.ResultsAll 68 patients underwent a primary radical hysterectomy with pelvic and/or paraaortic lymphadenectomy. 85.3% of the extirpated tumors had clear surgical margins (R0). Increased levels of VEGFR1, TIMP2 and MMP2 were significantly associated with positive surgical margins (p = 0.004, p = 0.018 and p = 0.004, respectively). High concentration of MMP2 and TIMP2 correlated additionally with an advanced age at time of diagnosis (p = 0.001 and p = 0.007, respectively). For the cut-off value of 100 pg/ml, an increased VEGFR1 was significantly associated with poor overall (OS) and progression-free (PFS) survival (p = 0.017 and p = 0.015, respectively). A TIMP2 concentration of lower than 90 ng/ml was significantly associated with poorer OS and PFS (p = 0.009 and p = 0.043, respectively). In the multivariate analysis, TIMP2 expression in serum was the only independent prognostic factor for OS (p = 0.032, HR = 6.51, 95% CI = 1.17–36.01).ConclusionsExpression-profile of specific biomarkers associated with tumor invasion, cell migration and angiogenesis seems to be of prognostic value for both OS and PFS in patients undergoing surgery due to primary cervical cancer. Further analyses are warranted to allow an implementation of such markers into clinical practice.     

ACE inhibitory,hypotensive and antioxidant peptide fractions from Mucuna pruriens proteins

Hydrolysates and peptide fractions obtained from Mucuna pruriens protein concentrate were studied for their angiotensin converting enzyme (ACE) inhibitory, hypotensive and antioxidant activities. The hydrolysate obtained by pepsin–pancreatin (HPP) was the most active with an ACE IC₅₀ value of 19.5 μg/mL, a Trolox equivalent antioxidant capacity (TEAC) value of 102.8 mM/mg and a ferric reducing power (FRP) IC₅₀ of 67.2 μg/mL. At a dose of 5 mg/kg HPP decrease systolic (32.2%) and diastolic (37%) blood pressure in rats more pronounced than Captopril. The peptide fraction <1 kDa from HPP was the most active with an ACE inhibitory of 10.2 μg/mL (IC₅₀), a TEAC value of 709.8 mM/mg and a FRP IC₅₀ of 54.9 μg/mL. These results indicate that the hydrolysates and peptide fractions of M. pruriens would be used as nutraceuticals ingredients for preventing and providing therapy against hypertension and diseases related to oxidative damage.     

Angiotensin-converting enzyme 2 ameliorates renal fibrosis by blocking the activation of mTOR/ERK signaling in apolipoprotein E-deficient mice

Angiotensin-converting enzyme 2 (ACE2) has been shown to prevent atherosclerotic lesions and renal inflammation. However, little was elucidated upon the effects and mechanisms of ACE2 in atherosclerotic kidney fibrosis progression. Here, we examined regulatory roles of ACE2 in renal fibrosis in the apolipoprotein E (ApoE) knockout (KO) mice. The ApoEKO mice were randomized to daily deliver either angiotensin (Ang) II (1.5 mg/kg) and/or human recombinant ACE2 (rhACE2; 2 mg/kg) for 2 weeks. Downregulation of ACE2 and upregulation of phosphorylated Akt, mTOR and ERK1/2 levels were observed in ApoEKO kidneys. Ang II infusion led to increased tubulointerstitial fibrosis in the ApoEKO mice with greater activation of the mTOR/ERK1/2 signaling. The Ang II-mediated renal fibrosis and structural injury were strikingly rescued by rhACE2 supplementation, associated with reduced mRNA expression of TGF-β1 and collagen I and elevated renal Ang-(1–7) levels. In cultured mouse kidney fibroblasts, exposure with Ang II (100 nmol L⁻¹) resulted in obvious elevations in superoxide generation, phosphorylated levels of mTOR and ERK1/2 as well as mRNA levels of TGF-β1, collagen I and fibronectin 1, which were dramatically prevented by rhACE2 (1 mg mL⁻¹) or mTOR inhibitor rapamycin (10 μmol L⁻¹). These protective effects of rhACE2 were eradicated by the Ang-(1–7)/Mas receptor antagonist A779 (1 μmol L⁻¹). Our results demonstrate the importance of ACE2 in amelioration of kidney fibrosis and renal injury in the ApoE-mutant mice via modulation of the mTOR/ERK signaling and renal Ang-(1–7)/Ang II balance, thus indicating potential therapeutic strategies by enhancing ACE2 action for preventing atherosclerosis and fibrosis-associated kidney disorders.     

Cathepsin G activity lowers plasma LDL and reduces atherosclerosis

Cathepsin G (CatG), a serine protease present in mast cells and neutrophils, can produce angiotensin-II (Ang-II) and degrade elastin. Here we demonstrate increased CatG expression in smooth muscle cells (SMCs), endothelial cells (ECs), macrophages, and T cells from human atherosclerotic lesions. In low-density lipoprotein (LDL) receptor-deficient (Ldlr^–/–) mice, the absence of CatG reduces arterial wall elastin degradation and attenuates early atherosclerosis when mice consume a Western diet for 3 months. When mice consume this diet for 6 months, however, CatG deficiency exacerbates atherosclerosis in aortic arch without affecting lesion inflammatory cell content or extracellular matrix accumulation, but raises plasma total cholesterol and LDL levels without affecting high-density lipoprotein (HDL) or triglyceride levels. Patients with atherosclerosis also have significantly reduced plasma CatG levels that correlate inversely with total cholesterol (r = –0.535, P < 0.0001) and LDL cholesterol (r = –0.559, P < 0.0001), but not with HDL cholesterol (P = 0.901) or triglycerides (P = 0.186). Such inverse correlations with total cholesterol (r = –0.504, P < 0.0001) and LDL cholesterol (r = –0.502, P < 0.0001) remain significant after adjusting for lipid lowering treatments among this patient population. Human CatG degrades purified human LDL, but not HDL. This study suggests that CatG promotes early atherogenesis through its elastinolytic activity, but suppresses late progression of atherosclerosis by degrading LDL without affecting HDL or triglycerides.     

Correlation between VEGFR-2 receptor kinase domain-containing receptor (KDR) mRNA and angiotensin II receptor type 1 (AT1-R) mRNA in endometrial cancer

PurposeAngiogenesis, a multistep process that results in new blood vessel formation from preexisting vasculature is essential for both the growth of solid tumour and for metastasis. Stimulation of vascular endothelial growth factor receptor (VEGFR), a transmembrane glycoprotein, results in mitogenesis. Within this family of receptors, VEGFR 2/kinase-insert-domain containing receptor appears to be principally upregulated during tumorigenesis. The aim of this study was to determine the expression of VEGFR-2/kinase-insert-domain containing receptor (KDR) and its correlation with angiotensin receptor type 1 (AT1-R) and clinical factors in endometrial carcinoma.MethodsThe expression of KDR and AT1-R was studied in endometrial carcinoma and normal endometrium by Real-time RT-PCR and Western blot analysis in 136 samples. The expression profile was correlated with the clinicopathological characteristics of endometrial adenocarcinoma.ResultsWe noted a significant correlation between the expression of KDR and AT1-R in tumour grade G1, G2 and G3 (R_s = 0.50; p = 0.002, R_s = 0.69; p = 0.0001, R_s = 0.52; p = 0.005, respectively). In stage I and stage II carcinoma, a significant correlation was also found between the expression of KDR and AT1-R (R_s = 0.70, p = 0.0001, R_s = 0.67; p = 0.001, respectively). Moreover significant correlation was observed between both KDR and AT1-R in tissue with different myometrial invasion (R_s = 0.54, p = 0.0001, R_s = 0.68; p = 0.0001; respectively for tumours with invasion into the inner half and invasion into the outer half).ConclusionsBasing on received correlation between AT1-R and KDR expression and previous results we speculate that angiotensin through AT1-R modulates KDR expression and thus have influence on local VEGF level. However, further studies are required to clarify the biological interaction between KDR, AT1-R and other hormonal regulators in endometrial carcinoma.     

Synthesis and evaluation of novel triazoles and mannich bases functionalized 1,4-dihydropyridine as angiotensin converting enzyme (ACE) inhibitors

A series of novel diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate embedded triazole and mannich bases were synthesized, and evaluated for their angiotensin converting enzyme (ACE) inhibitory activity. Screening of above synthesized compounds for ACE inhibition showed that triazoles functionalized compounds have better ACE inhibitory activity compared to that of mannich bases analogues. Among all triazoles we found 6h, 6i and 6j to have good ACE inhibition activity with IC₅₀ values 0.713 μM, 0.409 μM and 0.653 μM, respectively. Among mannich bases series compounds, only 7c resulted as most active ACE inhibitor with IC₅₀ value of 0.928 μM.     

Lipoic acid effects on established atherosclerosis

AimsAlpha-lipoic acid (LA) is a commonly used dietary supplement that exerts anti-oxidant and anti-inflammatory effects in vivo and in vitro. We investigated the mechanisms by which LA may confer protection in models of established atherosclerosis.Main methodsWatanabe heritable hyperlipidemic (WHHL) rabbits were fed with high cholesterol chow for 6 weeks and then randomized to receive either high cholesterol diet alone or combined with LA (20 mg/kg/day) for 12 weeks. Vascular function was analyzed by myography. The effects of LA on T cell migration to chemokine gradients was assessed by Boyden chamber. NF-κB activation was determined by measuring translocation and electrophoresis migration shift assay (EMSA).Key findingsLA decreased body weight by 15 ± 5% without alterations in lipid parameters. Magnetic Resonance Imaging (MRI) analysis demonstrated that LA reduced atherosclerotic plaques in the abdominal aorta, with morphological analysis revealing reduced lipid and inflammatory cell content. Consistent with its effect on atherosclerosis, LA improved vascular reactivity (decreased constriction to angiotensin II and increased relaxation to acetylcholine and insulin), inhibited NF-κB activation, and decreased oxidative stress and expression of key adhesion molecules in the vasculature. LA reduced T cell content in atherosclerotic plaque in conjunction with decreasing ICAM and CD62L (l-selectin) expression. These effects were confirmed by demonstration of a direct effect of LA in reducing T cell migration in response to CCL5 and SDF-1 and decreasing T cell adhesion to the endothelium by intra-vital microscopy.SignificanceThe present findings offer a mechanistic insight into the therapeutic effects of LA on atherosclerosis.     

Association between polymorphisms of matrix metalloproteinase 11 (MMP-11) and Kawasaki disease in the Korean population

AimsThis study was conducted to investigate the associations between single nucleotide polymorphisms (SNPs) of matrix metalloproteinases (MMPs) and Kawasaki disease (KD) in the Korean population.Main methodsA total 0f 101 KD patients and 306 healthy controls were examined. MMP7 (rs10502001, G/A, Arg77His), MMP11 (rs738792, T/C, Ala38Val), MMP12 (rs652438, A/G, Ile357Val) and MMP26 (rs2499953, A/G, Lys43Glu) genes were genotyped from the genomic DNA using direct sequencing. The results were then analyzed using logistic regression models, adjusting for gender as covariates.Key findingsThe four SNPs were in Hardy–Weinberg equilibrium. Only the MMP11 polymorphism (rs738792) was associated with KD. The SNP (rs738792) showed a statistically significant association with KD in the codominant (OR = 1.61, 95% CI = 1.11–2.34, P = 0.011) and dominant (OR = 1.92, 95% CI = 1.21–3.06, P = 0.006) models. However, there was no association between polymorphisms of other MMP genes and KD.SignificanceOverall, the results of this study indicate that MMP11 polymorphism may be associated with KD in the Korean population.     

Casein-derived tripeptide Ile-Pro-Pro improves angiotensin-(1-7)- and bradykinin-induced rat mesenteric artery relaxation

AimsMilk casein-derived bioactive tripeptides isoleucine–proline–proline (Ile–Pro–Pro) and valine–proline–proline (Val–Pro–Pro) lower blood pressure in animal models of hypertension and humans. In some studies, their angiotensin-converting enzyme (ACE)-inhibitory effect has been demonstrated. Besides classical ACE-angiotensin II-AT₁-receptor pathway (ACE-Ang II- AT₁), the significance of ACE2-angiotensin-(1–7)-Mas-receptor (ACE2-Ang-(1–7)-Mas) axis in the blood pressure regulation has now been acknowledged. The present study was aimed to further evaluate the renin–angiotensin system (RAS)-related vascular effects of Ile–Pro–Pro in vitro using rat mesenteric arteries.Main methodsSuperior mesenteric arteries of spontaneously hypertensive rat (SHR) were isolated, cut into rings and mounted in standard organ bath chambers. Endothelium-intact arterial rings were incubated in Krebs solution either with Ile–Pro–Pro, proline–proline (Pro–Pro), isoleucine (Ile), proline (Pro) or captopril for 6 h at + 37 °C and vascular reactivity was measured.Key findingsIn the presence of AT₁-antagonist valsartan, Ang II induced vasodilatation, which was more pronounced in the arteries incubated with Ile–Pro–Pro (P < 0.05) compared to the other compounds. Ang-(1–7)-induced vasodilatation was augmented by Ile–Pro–Pro or Pro (P < 0.001 vs. control). Mas-receptor antagonist A-779 did not alter the responses. Ile–Pro–Pro and Pro augmented also bradykinin-induced relaxations (P < 0.001 vs. control). Control arteries and arteries incubated with captopril showed only slight relaxations at higher bradykinin concentrations.SignificanceCasein-derived tripeptide Ile–Pro–Pro and amino acid Pro enhance the vasodilatory effect of Ang-(1–7) and bradykinin. The role of ACE2-Ang–(1–7)-Mas axis in the modulation of vascular tone by these compounds seems probable.     

Interaction with angiotensin-converting enzyme-encoding gene in female infertility: Insertion and deletion polymorphism studies

Angiotensin-converting enzyme (ACE), a key enzyme in the renin– angiotensin–aldosterone system, converts angiotensin I to angiotensin II. Ethnic origin should be carefully considered in studies pertaining to ACE I/D genotype and disease etiology. This study was evaluated between the ACE gene I/D polymorphism and female infertility in the Saudi population. Out of a A total of 300 women who participated in this study genomic DNA samples from the 150 infertile and 150 fertile women’s were isolated who has participated in this study. Genomic DNA was isolated using an Invitrogen kit according to the manufacturer’s protocol, and D allele specific primers were used for amplification by polymerase chain reaction. Electrophoresis was carried out on a 2% agarose gel. The mean age and BMI of the cases and controls were similar (p > 0.05), and a significant association was noted between the family history and female infertility (p = 0.0001). The D allele (OR: 1.67 [95% CI: 1.18–2.35], p = 0.003), DD genotype (OR: 2.46 [95% CI: 1.20–5.02], p = 0.01) and dominant model (OR: 1.97 [95% CI: 1.00–3.88], p = 0.04) were significantly associated with female infertility or fertility. The results of this study show that the ACE polymorphism plays an important role in female infertility in the Saudi population.     

Renal GLUT1 reduction depends on angiotensin-converting enzyme inhibition in diabetic hypertensive rats

AimsAngiotensin-converting enzyme (ACE) inhibitors are used in diabetic kidney disease to reduce systemic/intra-glomerular pressure. The objective of this study was to investigate whether reducing blood pressure (BP) could modulate renal glucose transporter expression, and urinary markers of diabetic nephropathy in diabetic hypertensive rats treated with ramipril or amlodipine.Main methodsDiabetes was induced in spontaneously-hypertensive rats (~ 210 g) by streptozotocin (50 mg/kg). Thirty days later, animals received ramipril 15 μg/kg/day (R, n = 10), or amlodipine 10 mg/kg/day (A, n = 8,) or water (C, n = 10) by gavage. After 30-day treatment, body weight, glycaemia, urinary albumin and TGF-β1 (enzyme-linked immunosorbent assay) and BP (tail-cuff pressure method) were evaluated. Kidneys were removed for evaluation of renal cortex glucose transporters (Western blotting) and renal tissue ACE activity (fluorometric assay).Key findingsAfter treatments, body weight (p = 0.77) and glycaemia (p = 0.22) were similar among the groups. Systolic BP was similarly reduced (p < 0.001) in A and R vs. C (172.4 ± 3.2; 186.7 ± 3.7 and 202.2 ± 4.3 mm Hg; respectively). ACE activity (C: 0.903 ± 0.086; A: 0.654 ± 0.025, and R: 0.389 ± 0.057 mU/mg), albuminuria (C: 264.8 ± 15.4; A: 140.8 ± 13.5 and R: 102.8 ± 6.7 mg/24 h), and renal cortex GLUT1 content (C: 46.81 ± 4.54; A: 40.30 ± 5.39 and R: 26.89 ± 0.79 AU) decreased only in R (p < 0.001, p < 0.05 and p < 0.001; respectively).SignificanceWe concluded that the blockade of the renin–angiotensin system with ramipril reduced early markers of diabetic nephropathy, a phenomenon that cannot be specifically related to decreased BP levels.     

Antihypertensive effect of an angiotensin I-converting enzyme inhibitory peptide from bullfrog (Rana catesbeiana Shaw) muscle protein in spontaneously hypertensive rats

To investigate biomedical and nutraceutical benefits of bullfrog (Rana catesbeiana Shaw) muscle protein, we examined an angiotensin I-converting enzyme (ACE I) inhibitory activity of various enzymatic hydrolystes of R. catesbeiana muscle protein in the present study. Among the enzymatic hydrolysates prepared using various commercial enzymes such as Alcalase, neutrase, pepsin, papain, α-chymotrypsin, and trypsin, Alcalase-proteolytic hydrolysates showed the highest ACE I inhibitory activity. During consecutive purification using a Hiprep 16/10 DEAE FF anion exchange and an octadecylsilane (ODS) C18 reversed phase liquid chromatographic techniques, a potent ACE I inhibitory peptide composed of 12 amino acids, Gly-Ala-Ala-Glu-Leu-Pro-Cys-Ser-Ala-Asp-Trp-Trp (M_w: 1.3 kDa) was isolated from R. catesbeiana muscle hydrolysates degraded by Alcalase. The purified peptide from R. catesbeiana muscle (RCMP-alca) has IC₅₀ value of 0.95 μM, and Lineweaver–Burk plots suggest that RCMP-alca play act as a non-competitive inhibitor against ACE I. Antihypertensive effect in spontaneously hypertensive rats (SHR) also revealed that oral administration of RCMP-alca can decrease systolic blood pressure significantly (P < 0.05). In addition, MTT assay showed no cytotoxicity on human embryonic lung fibroblasts cell line (MRC-5). The result of this study suggests that the ACE inhibitory peptide derived from R. catesbeiana muscle (RCMP-alca) could be potential candidates to develop nutraceuticals and pharmaceuticals.     

Purification and molecular docking study of angiotensin I-converting enzyme (ACE) inhibitory peptides from hydrolysates of marine sponge Stylotella aurantium

Angioteinsin I-converting enzyme (ACE) inhibitory peptide was isolated from marine sponge (Stylotella aurantium) hydrolysate prepared by various hydrolysis enzymes. The peptic hydrolysate exhibited highest ACE inhibitory activity among them and was fractionated into three ranges of molecular weight. The below 5 kDa fraction showed the highest ACE inhibitory activity and was used for subsequent purification steps. The amino acid sequences of the purified peptides were identified to be Tyr-Arg (337.2 Da), and Ile-Arg (287.2 Da). The purified peptides from marine sponge had an IC₅₀ value of 237.2 μM and 306.4 μM, respectively. The molecular docking study revealed that ACE inhibitory activity of the purified peptides was mainly attributed to the hydrogen bond interactions and Pi interaction between the dipeptides and ACE. The results suggest that marine sponge, S. aurantium would be an attractive raw material for the manufacture of anti-hypertensive nutraceutical ingredients.     

Low-dose chronic lead exposure increases systolic arterial pressure and vascular reactivity of rat aortas

Chronic lead exposure induces hypertension affecting endothelial function. We investigated whether low-concentration lead exposure alters blood pressure and vascular reactivity, focusing on the roles of NO, oxidative stress, cyclooxygenase-derived vasoconstrictor prostanoids, and the local angiotensin–renin system. Aortic rings from 3-month-old Wistar rats were treated daily with lead acetate (first dose 4 mg/100 g, subsequent doses 0.05 mg/100 g, im) or vehicle for 30 days. Treatment increased lead blood levels (12 μg/dl), blood pressure, and aortic ring contractile response to phenylephrine (1 nM–100 mM). Contractile response after L-NAME administration increased in both groups but was higher after lead treatment. Lead effects on R_max decreased more after apocynin and superoxide dismutase administration compared to control. Indomethacin reduced phenylephrine response more after lead treatment than in controls. The selective COX-2 inhibitor NS398, thromboxane A₂/prostaglandin H2 receptor antagonist SQ 29,548, TXA₂ synthase inhibitor furegrelate, EP₁ receptor antagonist SC 19220, and ACE inhibitor and AT₁ receptor antagonist losartan reduced phenylephrine responses only in vessels from lead-treated rats. Basal and stimulated NO release was reduced and local O₂⁻ liberation increased in the lead-treated group compared to controls. eNOS, iNOS, and AT₁ receptor protein expression increased with lead exposure, but COX-2 protein expression decreased. This is the first demonstration that blood Pb²⁺ (12 µg/dl) concentrations below the WHO-established values increased systolic blood pressure and vascular phenylephrine reactivity. This effect was associated with reduced NO bioavailability, increased reactive oxygen species production, increased participation of COX-derived contractile prostanoids, and increased renin–angiotensin system activity.