Renin-angiotensin system in intestinal inflammation-Angiotensin inhibitors to treat inflammatory bowel diseases?

Inflammatory bowel diseases (IBDs) are chronic disorders of the gastrointestinal tract, which manifest in recurring gastrointestinal inflammation. The current treatment options of IBD are not curative and are lacking in aspects like prevention of fibrosis. New treatment options are needed to fulfil the unmet needs and provide alternatives to drugs with resistances and side effects. Drugs targeting the renin-angiotensin system (RAS), besides being antihypertensive, also possess anti-inflammatory and antifibrotic properties and could offer an inexpensive alternative to control inflammation and fibrosis in the gut. RAS inhibitors have been effective in preventing and alleviating colitis in preclinical studies, but available human data are still sparse. This review outlines the pathophysiological functions of RAS in the gut and summarizes preclinical studies utilizing pharmacological RAS inhibitors in the treatment of experimental colitis. We discuss the alterations in intestinal RAS and the available evidence of the benefits of RAS inhibitors for IBD patients. Retrospective studies comparing IBD patients using ACE inhibitors or angiotensin II receptor blockers have provided optimistic results regarding a milder disease course and fewer hospitalizations and corticosteroid use in patients using RAS inhibitors. Prospective studies are needed to evaluate the effectiveness of these promising medications in the treatment of IBD.

Polyphenolic Composition and in Vitro Antihypertensive and Anti-Inflammatory Effects of Cuphea lindmaniana and Cuphea urbaniana.

The present study investigates the chemical composition, anti-inflammatory, and antihypertensive activities, in vitro, from extracts of Cuphea lindmaniana and Cuphea urbaniana leaves. The extraction was performed ultrasound-assisted, and UHPLC/MS analysis was in positive mode ionization. The anti-inflammatory activity of the extracts and miquelianin were assayed at concentrations 0.001-10 µg/mL by chemotaxis on rat polymorphonuclear neutrophils. The antihypertensive activity was performed by angiotensin-converting enzyme (ACE) inhibition. From the nineteen proposed compounds, six of them are described for the first time in this genus. The extracts displayed antichemotactic effect with a reduction of 100 % of the neutrophil migration, in vitro, in most concentrations. The ACE-inhibition presented results ranging from 19.58 to 22.82 %. In conclusion, C. lindmaniana and C. urbaniana extracts contain a rich diversity of flavonoids and display in vitro anti-inflammatory and antihypertensive potential. Thus, this study could serve as a scientific baseline for further investigation, on developmental novel products with therapeutic actions.

Melanin-like nanoparticles loaded with an angiotensin antagonist for an improved photothermal cancer therapy.

An abnormal tumor growth induces solid stress in tumors, thus reducing blood perfusion. As a result, the impaired blood perfusion, with dense interstitial matrix in tumors significantly reduces the penetration and efficacy of nanotherapeutics. In this study, we have developed a losartan-loaded polydopamine nanoparticle (PLST) for the enhanced delivery of nanoparticles to tumors and improved photothermal cancer therapy. Losartan, an angiotensin inhibitor, is also able to alleviate the solid stress in tumors. It was laden on polydopamine nanoparticles via π-π stacking and was released upon tumor extracellular acidity. PLST reduced collagen production in vitro along with the lowered expression of profibrotic factors of TGF-ß1, CCN2, and TIMP-1. The in vivo studies reveal that PLST reduced solid stress in tumors, and the amount of PLST accumulated in tumors was enhanced. The efficiency of the photothermal ablation of tumors was significantly enhanced by using PLST.

Protective effects of tribulus terrestris extract and angiotensin blockers on testis steroidogenesis in copper overloaded rats.

The rational of the current study was to assess whether Tribulus terrestris extract (TTE) could alleviate long-term copper (Cu) overload-induced testicular dysfunction compared to enalapril and losartan. Rats were administered either vehicle (control group, n = 10) or copper sulfate pentahydrate (CuSO4·5H2O, 200 mg/kg, p.o) for 90 days (n = 40). Cu-treated rats were randomized into four equal groups. One group was left untreated (Cu group) while the remaining three groups were daily co-treated with one of the following treatments along with CuSO4: TTE (10 mg/kg, p.o); enalapril (30 mg/kg, p.o); losartan (10 mg/kg, p.o). Excess Cu intake resulted in Cu overload coupled with a significant elevation in systolic blood pressure and serum angiotensin II levels along with a reduction in serum nitric oxide level. All concomitant treatments led to an alleviation of such deleterious effects. However, only losartan failed to ameliorate angiotensin II elevation. Additionally, all treatments protected the testes against Cu-overload-elicited zinc depletion and oxidative stress. Regarding reproductive function, the relative weights of testes, serum levels of testosterone and luteinizing hormone; the expression of steroidogenic genes; the protein levels of angiotensin II type 1 receptor and angiotensin converting enzyme 1, in addition to its activity, they were significantly reduced. Amongst all treatments, only TTE and E were able to revert these reproductive changes. In conclusion TTE and E were able to protect against Cu overload-induced impairment of testicular steroidogenesis. Thus, they might be considered as prophylactic drugs of choice against hypertension and testicular dysfunction to ameliorate Cu overload risk.

Could angiotensin-modulating drugs be relevant for the treatment of Trypanosoma cruzi infection? A systematic review of preclinical and clinical evidence.

Although leucocytes are targets of renin-angiotensin system (RAS) effector molecules and RAS-modulating drugs exert immunomodulatory effects, their impact on Trypanosoma cruzi infection remains poorly understood. By using the framework of a systematic review, we integrated the preclinical and clinical evidence to investigate the relevance of angiotensin-inhibiting drugs on T. cruzi infections. From a comprehensive and structured search in biomedical databases, only original studies were analysed. In preclinical and clinical studies, captopril, enalapril and losartan were RAS-modulating drugs used. The main in vitro findings indicated that these drugs increased parasite uptake per host cells, IL-12 expression by infected dendritic cells and IFN-γ by T lymphocytes, in addition to attenuating IL-10 and IL-17 production by CD8 + T cells. In animal models, reduced parasitaemia, tissue parasitism, leucocytes infiltration and mortality were often observed in T. cruzi-infected animals receiving RAS-modulating drugs. In patients with Chagas' disease, these drugs exerted a controversial impact on cytokine and hormone levels, and a limited effect on cardiovascular function. Considering a detailed evaluation of reporting and methodological quality, the current preclinical and clinical evidence is at high risk of bias, and we hope that our critical analysis will be useful in mitigating the risk of bias in further studies.

Effect of Tulbaghia violacea on the blood pressure and heart rate in male spontaneously hypertensive Wistar rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Tulbaghia violacea Harv. (Alliaceae) is a small bulbous herb which belongs to the family Alliaceae, most commonly associated with onions and garlic. In South Africa, this herb has been traditionally used in the treatment of various ailments, including fever, colds, asthma, paralysis, hypertension and stomach problems. The aim of this study was to evaluate the effect of methanol leaf extracts (MLE) of Tulbaghia violacea on the blood pressure (BP) and heart rate (HR) in anaesthetized male spontaneously hypertensive rats; and to find out the mechanism(s) by which it acts. MATERIALS AND METHODS: The MLE of Tulbaghia violacea (5-150mg/kg), angiotensin I human acetate salt hydrate (ang I, 3.1-100µg/kg), angiotensin II human (ang II, 3.1-50µg/kg), phenylephrine hydrochloride (phenylephrine, 0.01-0.16mg/kg) and dobutamine hydrochloride (dobutamine, 0.2-10.0µg/kg) were infused intravenously, while the BP and HR were measured via a pressure transducer connecting the femoral artery and the Powerlab. RESULTS: Tulbaghia violacea significantly (p<0.01) reduced the systolic, diastolic, and mean arterial BP; and HR dose-dependently. Ang I, ang II, phenylephrine and dobutamine all increased the BP dose-dependently. The hypertensive effect of ang I and the HR-increasing effect of dobutamine were significantly (p<0.01) decreased by their co-infusion with Tulbaghia violacea (60mg/kg). However, the co-infusion of ang II or phenylephrine with Tulbaghia violacea (60mg/kg) did not produce any significant change in BP or HR when compared to the infusion of either agent alone in the same animal. CONCLUSIONS: Tulbaghia violacea reduced BP and HR in the SHR. The reduction in BP may be due to actions of the MLE on the ang I converting enzyme (ACE) and ß(1) adrenoceptors.

Treatment of IgA nephropathy: an update.

OBJECTIVE: To review current literature regarding treatment options for immunoglobulin A nephropathy (IgAN). DATA SOURCES: A MEDLINE search was performed using the terms IgA nephropathy, Berger's disease, immunoglobulin A nephropathy, angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, fish oil, omega-3 fatty acids, statins, hydroxymethylglutaryl-CoA reductase inhibitors, immunosuppressive therapy, corticosteroids, mycophenolate mofetil, cyclophosphamide, cyclosporine, azathioprine, leflunomide, antiplatelets, anticoagulants, vitamin E, infliximab, calcitriol, and intravenous immunoglobulins. A date limit was not set; however, focus was on publications from 1999 to June 2011 to review recent literature and therapeutic recommendations. STUDY SELECTION AND DATA EXTRACTION: All articles in English, including studies conducted in humans, meta-analyses, review articles, guidelines, statements, and reference citations, were identified and evaluated. DATA SYNTHESIS: IgAN is the most common primary glomerulonephritis worldwide, leading to end-stage renal disease in 20-30% of patients. Evidence guiding management of IgAN has been sparse and clinical trials have not conclusively demonstrated effective treatments, largely due to suboptimal methodologies. Treatment strategies have included management of blood pressure and lipids, improvement or stabilization of kidney function, and reduction of proteinuria. This review of IgAN provides an update regarding standard and nonconventional treatment options based on recently published literature. CONCLUSIONS: Supportive therapies, including angiotensin blockade, should be considered as first-line therapy for patients with urine protein >0.5 g/day and/or blood pressure >140/90 mm Hg. Corticosteroids could be considered as add-on or monotherapy for patients with urine protein >1 g/day with preserved renal function. Conclusive data are lacking for general treatment recommendations for the use of other therapies for IgAN.

Angiotensin blockade as sole treatment for proteinuric kidney disease in children.

BACKGROUND: The traditional management of children with proteinuric kidney disease is treatment with high dose steroids regardless of comorbid conditions such as obesity. This study evaluated the effect of angiotensin blockade (AB) alone as the sole management of children with non-diabetic proteinuric kidney disease. METHODS: Retrospective chart analysis was performed in 146 children. Seventeen were identified to have received angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker exclusively for management of proteinuria. Total proteinuria (Upr/cr), albuminuria (Ualb/cr), estimated glomerular filtration rate (eGFR), serum potassium and blood pressure were assessed at baseline and at 3-month intervals for over 24 months. RESULTS: Mean age was 11.2+/-4.8 years with 12 females. Eleven of 17 patients (65%) were overweight or obese. There was a significant decline in total proteinuria and albuminuria after 3-6 months of AB therapy and a further decline with longer duration of treatment (P<0.001). Although single vs dual AB were similarly effective in lowering total proteinuria, dual therapy was more effective in lowering albuminuria (single 57+/-23% vs dual 71+/-15%; P<0.02). The eGFR decreased from 'hyperfiltration' levels prior to initiation of AB to normal at the end of the treatment period (145+/-41-111+/-17 ml/min/1.73 m2; P=0.01). Systemic blood pressures remained normal throughout the study period. CONCLUSIONS: Angiotensin blockade alone appears to effectively control proteinuria and stabilize kidney function in children. This may provide an alternative to more toxic therapies, especially corticosteroids, in children with glomerular disorders such as those associated with obesity.

Melanin-concentrating hormone enhances sucrose intake.

Melanin-concentrating hormone (MCH) is known to be an important regulator for feeding and energy balance. MCH was recently reported to stimulate water intake independent of food intake. The purpose of the present study is to examine the dipsogenic response of MCH with special emphasis on sweetened beverages, the preference for which is well documented in diabetic animals. Our results showed that intracerebroventricular injection of MCH acutely increased food as well as water intake. Human (h)MCH and salmon (s)MCH increased water intake independent of food intake, which was not suppressed by angiotensin antagonists. hMCH and sMCH significantly increased both sucrose solution and food intake; on the other hand, agouti-related protein (AgRP) stimulated food but not sucrose intake when provided simultaneously. MCH-treated rats significantly increased the ingestion of sucrose and glucose solution, but not of saccharin, indicating that MCH-induced dipsogenic response is more related to caloric content than sweet taste per se. Significant correlation was observed between the sucrose intake and the mRNA expression of MCH and MCHR1 in normal rats. These results indicate that MCH may be an important regulator of sugar intake in normal as well as in obese diabetic animals.

Comparative effects of enalapril, enalaprilic acid and captopril in blocking angiotensin I-induced pressor and dipsogenic responses in spontaneously hypertensive rats.

The role of central angiotensin converting enzyme (ACE), in the maintenance of high blood pressure, was examined in unanesthetized spontaneously hypertensive rats (SHR). Pressor and dipsogenic responses induced by intracerebroventricular (ICV) injections of angiotensin I (AI) were elicited before and 30 min after either captopril (120-800 nanomoles ICV), enalapril (66-460 nanomoles ICV) and enalaprilic acid (70-280 nanomoles ICV). Enalapril was 1.6 (0.7-3.9) and 1.7 (0.9-2.9) times more potent than captopril in inhibiting AI-induced pressor and dipsogenic responses, respectively. Enalaprilic acid was 2.7 (1.1-7.1) and 2.9 (1.9-4.8) times more potent than captopril in inhibiting AI- (ICV administration) induced pressor and dipsogenic responses, respectively. None of the ACE inhibitors, in contrast, reduced the central actions of AII. Basal mean arterial pressure was not reduced by these ACE inhibitors after ICV administration. Administered orally at doses which produced similar hypotensive responses, neither captopril (30 mg/kg) nor enalapril (3 mg/kg) blocked the responses induced by AI given ICV (10 ng). These findings indicate that ACE inhibitors given acutely do not penetrate into the central nervous system sufficiently to block the dipsogenic and pressor responses induced by AI given ICV, and suggest that inhibition of central ACE may not be important to the acute antihypertensive activity of the ACE inhibitors tested.