Angiotensin-(1–7) Inhibits Vascular Remodelling in Rat Jugular Vein Grafts via Reduced ERK1/2 and p38 MAPK Activity

Effects of Angiotensin 1-7 and Mas Receptor Agonist on Renal System in a Rat Model of Heart Failure

Congestive heart failure (CHF) is often associated with impaired kidney function. Over- activation of the renin-angiotensin-aldosterone system (RAAS) contributes to avid salt/water retention and cardiac hypertrophy in CHF. While the deleterious effects of angiotensin II (Ang II) in CHF are well established, the biological actions of angiotensin 1-7 (Ang 1-7) are not fully characterized. In this study, we assessed the acute effects of Ang 1-7 (0.3, 3, 30 and 300 ng/kg/min, IV) on urinary flow (UF), urinary Na⁺ excretion (UNaV), glomerular filtration rate (GFR) and renal plasma flow )RPF) in rats with CHF induced by the placement of aortocaval fistula. Additionally, the chronic effects of Ang 1-7 (24 µg/kg/h, via intra-peritoneally implanted osmotic minipumps) on kidney function, cardiac hypertrophy and neurohormonal status were studied. Acute infusion of either Ang 1-7 or its agonist, AVE 0991, into sham controls, but not CHF rats, increased UF, UNaV, GFR, RPF and urinary cGMP. In the chronic protocols, untreated CHF rats displayed lower cumulative UF and UNaV than their sham controls. Chronic administration of Ang 1-7 and AVE 0991 exerted significant diuretic, natriuretic and kaliuretic effects in CHF rats, but not in sham controls. Serum creatinine and aldosterone levels were significantly higher in vehicle-treated CHF rats as compared with controls. Treatment with Ang 1-7 and AVE 0991 reduced these parameters to comparable levels observed in sham controls. Notably, chronic administration of Ang 1-7 to CHF rats reduced cardiac hypertrophy. In conclusion, Ang 1-7 exerts beneficial renal and cardiac effects in rats with CHF. Thus, we postulate that ACE2/Ang 1-7 axis represents a compensatory response to over-activity of ACE/AngII/AT1R system characterizing CHF and suggest that Ang 1-7 may be a potential therapeutic agent in this disease state.

Atorvastatin Reduces Accumulation of Vascular Smooth Muscle Cells to Inhibit Intimal Hyperplasia via p38 MAPK Pathway Inhibition in a Rat Model of Vein Graft

Fundamento:

A taxa de falha de enxerto de veia safena um ano após a cirurgia de revascularização do miocárdio varia de 10% a 25%. O objetivo deste estudo foi de investigar se a atorvastatina pode reduzir o acúmulo de células musculares lisas vasculares para inibir a hiperplasia intimal por meio da inibição da via p38 MAPK.

Métodos:

Quarenta e cinco ratos Sprague-Dawley foram randomizados em três grupos. Trinta ratos foram submetidos à cirurgia de enxerto de veia e randomizados para tratamento com veículo ou atorvastatina; quinze ratos foram submetidos à cirurgia sham. Detectamos a hiperplasia intimal por meio de coloração com hematoxilina-eosina e a expressão de proteínas relacionadas por meio de análise imuno-histoquímica e Western blot. Foram realizadas as comparações por análise de variância de fator único e pelo teste da diferença mínima significativa de Fisher, com p < 0,05 considerado significativo.

Resultados:

A íntima analisada pela coloração com hematoxilina-eosina era dramaticamente mais espessa no grupo controle que no grupo atorvastatina e no grupo sham (p < 0,01). Os resultados da coloração imuno-histoquímica de α-SMA demonstraram que a porcentagem de células positivas para α-SMA no grupo controle era mais alta que no grupo atorvastatina (p < 0,01). Nós também avaliamos α-SMA, PCNA, p38 MAPK e fosforilação de p38 MAPK após o tratamento com estatina por meio de análise de Western blot e os resultados indicaram que a atorvastatina não levou à redução de p38 MAPK (p < 0,05); no entanto, resultou na inibição da fosforilação de p38 MAPK (p < 0,01) e reduziu significativamente os níveis de α-SMA e PCNA, em comparação com o grupo controle (p < 0,01).

Conclusão:

Nós demonstramos que a atorvastatina pode inibir o acúmulo de células musculares lisas vasculares por meio da inibição da via p38 MAPK e é capaz de inibir a hiperplasia intimal em modelos de enxerto de veia em ratos.

The ACE2/Angiotensin-(1-7)/MAS Axis of the Renin-Angiotensin System: Focus on Angiotensin-(1-7)

The renin-angiotensin system (RAS) is a key player in the control of the cardiovascular system and hydroelectrolyte balance, with an influence on organs and functions throughout the body. The classical view of this system saw it as a sequence of many enzymatic steps that culminate in the production of a single biologically active metabolite, the octapeptide angiotensin (ANG) II, by the angiotensin converting enzyme (ACE). The past two decades have revealed new functions for some of the intermediate products, beyond their roles as substrates along the classical route. They may be processed in alternative ways by enzymes such as the ACE homolog ACE2. One effect is to establish a second axis through ACE2/ANG-(1-7)/MAS, whose end point is the metabolite ANG-(1-7). ACE2 and other enzymes can form ANG-(1-7) directly or indirectly from either the decapeptide ANG I or from ANG II. In many cases, this second axis appears to counteract or modulate the effects of the classical axis. ANG-(1-7) itself acts on the receptor MAS to influence a range of mechanisms in the heart, kidney, brain, and other tissues. This review highlights the current knowledge about the roles of ANG-(1-7) in physiology and disease, with particular emphasis on the brain.

Endotoxin-induced skeletal muscle wasting is prevented by angiotensin-(1-7) through a p38 MAPK-dependent mechanism

Skeletal muscle atrophy induced during sepsis syndrome produced by endotoxin in the form of LPS (lipopolysaccharide), is a pathological condition characterized by the loss of strength and muscle mass, an increase in MHC (myosin heavy chain) degradation, and an increase in the expression of atrogin-1 and MuRF-1 (muscle-specific RING-finger protein 1), two ubiquitin E3 ligases belonging to the ubiquitin-proteasome system. Ang-(1-7) [Angiotensin-(1-7)], through its Mas receptor, has beneficial effects in skeletal muscle. We evaluated in vivo the role of Ang-(1-7) and Mas receptor on the muscle wasting induced by LPS injection into C57BL/10J mice. In vitro studies were performed in murine C2C12 myotubes and isolated myofibres from EDL (extensor digitorum longus) muscle. In addition, the participation of p38 MAPK (mitogen-activated protein kinase) in the Ang-(1-7) effect on the LPS-induced muscle atrophy was evaluated. Our results show that Ang-(1-7) prevents the decrease in the diameter of myofibres and myotubes, the decrease in muscle strength, the diminution in MHC levels and the induction of atrogin-1 and MuRF-1 expression, all of which are induced by LPS. These effects were reversed by using A779, a Mas antagonist. Ang-(1-7) exerts these anti-atrophic effects at least in part by inhibiting the LPS-dependent activation of p38 MAPK both in vitro and in vivo. We have demonstrated for the first time that Ang-(1-7) counteracts the skeletal muscle atrophy induced by endotoxin through a mechanism dependent on the Mas receptor that involves a decrease in p38 MAPK phosphorylation. The present study indicates that Ang-(1-7) is a novel molecule with a potential therapeutic use to improve muscle wasting during endotoxin-induced sepsis syndrome.

Azilsartan is associated with increased circulating angiotensin-(1-7) levels and reduced renovascular 20-HETE levels

BACKGROUND

Activation of angiotensin (ANG) II type 1 receptors (AT1R) promotes vasoconstriction, inflammation, and renal dysfunction. In this study, we addressed the ability of azilsartan (AZL), a new AT1R antagonist, to modulate levels of plasma ANG-(1-7) and renal epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid (20-HETE).

METHODS

Sprague-Dawley rats were infused with ANG II (125 ng/min) or vehicle (VEH). AZL (3 mg/kg/day) or VEH was administered starting 1 day prior to ANG II or VEH infusion. On day 10, plasma was obtained for measurement of ANG-(1-7) and kidneys for isolation of microvessels for EET and 20-HETE determination and histological evaluation.

RESULTS

Mean 24-hour blood pressure (BP) was not different between VEH and AZL treatment groups, whereas the BP elevation with ANG II infusion (121 ± 5 mm Hg) was completely normalized with AZL cotreatment (86 ± 3 mm Hg). The ANG II-induced renal damage was attenuated and cardiac hypertrophy prevented with AZL cotreatment. Plasma ANG-(1-7) levels (pg/ml) were increased with AZL treatment (219 ± 22) and AZL + ANG II infusion (264 ± 93) compared to VEH controls (74.62 ± 8). AZL treatment increased the ratio of EETs to their dihydroxyeicosatrienoic acid (DHET) metabolites and reduced 20-HETE levels.

CONCLUSIONS

Treatment with AZL completely antagonized the elevation of BP induced by ANG II, prevented cardiac hypertrophy, attenuated renal damage, and increased ANG-(1-7) and EET/DHET ratio while diminishing 20-HETE levels. Increased ANG-(1-7) and EETs levels may emerge as novel therapeutic mechanisms contributing to the antihypertensive and antihypertrophic actions of AZL treatment and their relative role compared to AT1R blockade may depend on the etiology of the hypertension.

Antitumor activity of cobrotoxin in human lung adenocarcinoma A549 cells and following transplantation in nude mice

The aim of the present study was to investigate cobra neurotoxin (cobrotoxin) activity in A549 cell lines transplanted into nude mice, and to explore its molecular mechanism. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method was used to detect the growth inhibition rate of cobrotoxin in human lung A549 adenocarcinoma cells and HFL1 lung fibroblasts. Cell colony formation assays were performed to determine the effect of cobrotoxin on A549 cell colony formation, and transmission electron microscopy was used to detect cobrotoxin autophagy. In addition, western blot analysis was performed to determine the effect of 3-methyl adenine (3-MA) activity on the inhibition of autophagy, SB203580 inhibition of the p38-mitogen-activated protein kinase (MAPK) pathway, and Beclin 1, LC3, p62, p38 and phosphorylated (p)-p38 protein expression. Nude mice were injected with human lung A549 cells, and intervention and control groups were compared with regard to tumor suppression. The MTT assay revealed that various concentrations of cobrotoxin inhibited growth of A549 cells, but not HFL1 cells. A549 cell colony formation decreased and autophagosome activity was significantly increased compared with the controls. Following 3-MA administration, SB203580 autophagosome activity decreased, and following cobrotoxin administration, Beclin 1, p-p38, and LC3-II protein expression significantly increased, whereas p62 expression significantly decreased. Following 3-MA inhibition of autophagy, Beclin 1, LC3-II and p62 expression increased. Furthermore, following SB203580 inhibition of the p38-MAPK pathway, Beclin 1, p-p38, LC3-II and p62 protein expression increased. Cobrotoxin exhibited inhibitory activity on the human lung cancer A549 cells transplanted into the nude mice, suppressing the tumor growth rate by 43.4% (cobrotoxin 40 μg/kg group). However, following the addition of 3-MA (10 mmol/kg) and SB203580 (5 mg/kg), the suppression of the tumor growth rate decreased significantly. Cobrotoxin inhibits the growth of human lung cancer A549 cells in vitro and A549 cells transplanted into nude mice. Furthermore, the induction of autophagy may be associated with the activation of the p38-MAPK pathway.

[Role of autophagy on cobrotoxin induced cell death of A549]

背景与目的

已有的研究表明眼镜蛇神经毒素具有抗肿瘤作用，而其在肺癌中的作用罕有研究。本研究观察cobrotoxin对人肺A549腺癌细胞株的抗肿瘤作用，探讨自噬和P38-MAPK通路在这过程中的作用。

方法

应用MTT法观察cobrotoxin对A549细胞和HFL1人肺成纤维细胞的生长抑制作用以及用3-MA抑制自噬、SB203580抑制P38-MAPK通路后cobrotoxin对A549细胞的生长抑制作用; 应用细胞集落平板克隆实验检测cobrotoxin对A549细胞的集落形成的影响; 蛋白免疫印迹法（Western blot）测定单独cobrotoxin作用、cobrotoxin分别联合3-MA抑制自噬和SB203580抑制P38-MAPK通路活性后A549细胞内beclin-1、LC3、P62、P38及pP38等蛋白表达水平。

结果

不同浓度cobrotoxin对A549细胞的生长有明显抑制作用，对HFL1人肺成纤维细胞无明显抑制作用，3-MA、SB203580作用后cobrotoxin对A549细胞的抑制作用降低; 不同浓度cobrotoxin可明显抑制A549细胞的集落形成; cobrotoxin作用后beclin-1、pP38蛋白表达水平明显提高，P62表达明显降低，Ⅱ型/Ⅰ型LC3比值增大，并有浓度依赖性，3-MA抑制自噬后beclin-1蛋白表达水平降低，P62表达增高、Ⅱ型/Ⅰ型LC3比值减小，SB203580抑制P38-MAPK通路后beclin-1、pP38蛋白表达水平降低，Ⅱ型/Ⅰ型LC3比值减小。

结论

cobrotoxin对人肺A549腺癌细胞体外生长有抑制作用，可能通过活化P38-MAPK通路激活自噬参与抗肿瘤过程。