Losartan protects liver against ischaemia/reperfusion injury through PPAR-γ activation and receptor for advanced glycation end-products down-regulation.

BACKGROUND AND PURPOSE: PPAR-γ has been reported to be a protective regulator in ischaemia/reperfusion (I/R) injury. The receptor for advanced glycation end-products (RAGE) plays a major role in the innate immune response, and its expression is associated with PPAR-γ activation. Several angiotensin receptor blockers possess partial agonist activities towards PPAR-γ. Therefore, this study investigated the action of losartan, particularly with regard to PPAR-γ activation and RAGE signalling pathways during hepatic I/R. EXPERIMENTAL APPROACH: Mice were subjected to 60 min of ischaemia followed by 6 h of reperfusion. Losartan (0.1, 1, 3 and 10 mg · kg⁻¹) was administered 1 h prior to ischaemia and immediately before reperfusion. GW9662, a PPAR-γ antagonist, was administered 30 min prior to first pretreatment with losartan. KEY RESULTS: Losartan enhanced the DNA-binding activity of PPAR-γ in I/R. Losartan attenuated the increased serum alanine aminotransferase activity, TNF-α and IL-6 levels, and nuclear concentrations of NF-κB in I/R. GW9662 reversed these beneficial effects. Losartan caused a decrease in apoptosis as assessed by TUNEL assay, in release of cytochrome c and in cleavage of caspase-3, and these effects were abolished by GW9662 administration. Losartan attenuated not only I/R-induced RAGE overexpression, but also its downstream early growth response protein-1-dependent macrophage inflammatory protein 2 level; phosphorylation of p38, ERK and JNK; and subsequent c-Jun phosphorylation. GW9662 reversed these effects of losartan administration. CONCLUSIONS AND IMPLICATIONS: Our findings suggest that losartan ameliorates I/R-induced liver damage through PPAR-γ activation and down-regulation of the RAGE signalling pathway.

Combination therapy with an angiotensin II receptor blocker and an HMG-CoA reductase inhibitor in experimental subtotal nephrectomy.

BACKGROUND: Angiotensin receptor 1 blockers (ARB) are standard nephroprotective drugs in chronic kidney disease. There is less evidence for a nephroprotective effect of HMG-CoA reductase inhibitors (statins) and much less is known about potential benefits of combination therapy. We evaluated the therapeutic potential of a statin alone or in combination with an ARB in experimental chronic kidney disease. METHODS: Subtotally nephrectomized (5/6 Nx) rats were treated early with vehicle, losartan, cerivastatin or losartan/cerivastatin. Expression of messenger RNA (mRNA) was assessed by real-time reverse transcription-polymerase chain reaction. Tissue proteins were localized by immunohistochemistry. Nuclear factor-κB (NF-κB) activation was measured in whole kidneys. RESULTS: In contrast to the sham group, at 6 weeks, vehicle-treated 5/6 Nx rats displayed renal lesions, albuminuria and increased blood pressure, serum creatinine and total kidney NF-κB p65 DNA-binding activity and preproendothelin-1, fibronectin and type I and III collagen mRNA. NF-κB activation correlated with albuminuria and histological renal injury. Losartan or combination therapy preserved renal function, abrogated albuminuria and improved glomerular and interstitial histology. Cerivastatin alone preserved renal function and improved interstitial injury but did not influence albuminuria, glomerular histology or NF-κB activation. Losartan/cerivastatin normalized kidney NF-κB activation and extracellular matrix mRNA expression pattern. The effect of losartan alone on these parameters was less intense. All treatments decreased preproendothelin-1 mRNA and preserved interstitial capillaries. CONCLUSIONS: In a chronic kidney disease model, early treatment with either an ARB or a statin preserved renal function although the mechanisms differed. Combination therapy with an ARB and a statin did not confer clear-cut advantages on biochemical and histological parameters over ARB alone, although it further improved the kidney NF-κB and gene expression profile.

Effect of left ventricular reverse remodeling on long-term prognosis after therapy with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers and ß blockers in patients with idiopathic dilated cardiomyopathy.

It remains unknown whether left ventricular (LV) reverse remodeling (LVRR) after therapy with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers and ß blockers is correlated with prognosis in patients with idiopathic dilated cardiomyopathy. Forty-two patients with idiopathic dilated cardiomyopathy treated with the therapy were studied. Complete left ventricular reverse remodeling was defined as LV end-diastolic dimension ≤ 55 mm and fractional shortening ≥ 25% at the last echocardiographic assessment. The incidence of complete LVRR was significantly higher in patients who survived than in those who died or underwent heart transplantation. Patients were divided into 3 groups: death or transplantation, alive with complete LVRR, and alive without complete LVRR. Although patients who died or underwent transplantation did not show any LV improvements, those with complete LVRR showed significant improvements at 1 to 6 months after starting the therapy. Patients without complete LVRR also showed small but significant improvements at 1 to 6 months. The decrease in LV end-systolic dimension from the initial value to that at 1 to 6 months was an independent determinant of future cardiac death or transplantation. In conclusion, complete LVRR is related to favorable prognosis in patients with idiopathic dilated cardiomyopathy. The extent of left ventricular reverse remodeling at 1 to 6 months after starting the therapy is predictive of long-term prognosis.

Targeting the degradation of angiotensin II with recombinant angiotensin-converting enzyme 2: prevention of angiotensin II-dependent hypertension.

Angiotensin (Ang)-converting enzyme 2 (ACE2) cleaves Ang II to form Ang-(1-7). Here we examined whether soluble human recombinant ACE2 (rACE2) can efficiently lower Ang II and increase Ang-(1-7) and whether rACE2 can prevent hypertension caused by Ang II infusion as a result of systemic versus local mechanisms of ACE2 activity amplification. rACE2 was infused via osmotic minipumps for 3 days in conscious mice or acutely in anesthetized mice. rACE2 caused a dose-dependent increase in serum ACE2 activity but had no effect on kidney or cardiac ACE2 activity. After Ang II infusion (40 pmol/min), rACE2 (1 mg/kg per day) resulted in normalization of systolic blood pressure and plasma Ang II. In acute studies, rACE2 (1 mg/kg) prevented the rapid hypertensive effect of Ang II (0.2 mg/kg), and this was associated with both a decrease in Ang II and an increase in Ang-(1-7) in plasma. Moreover, during infusion of Ang II, the effect of rACE2 on blood pressure was unaffected by a specific Ang-(1-7) receptor blocker, A779 (0.2 mg/kg), and infusing supraphysiologic levels of Ang-(1-7) (0.2 mg/kg) had no effect on blood pressure. We conclude that, during Ang II infusion, rACE2 effectively degrades Ang II and, in the process, normalizes blood pressure. The mechanism of rACE2 action results from an increase in systemic, not tissue, ACE2 activity and the lowering of plasma Ang II rather than the attendant increase in Ang-(1-7). Increasing ACE2 activity may provide a new therapeutic target in states of Ang II overactivity by enhancing its degradation, an approach that differs from the current focus on blocking Ang II formation and action.

Antagonist of the type-1 ANG II receptor prevents against LPS-induced septic shock in rats.

PURPOSE: Type 1 angiotensin II (AT1) receptor antagonists have anti-inflammatory effects in vitro and in patients. The purpose of this study was to investigate whether losartan (LOS), an AT1 receptor antagonist, reduces lung damage by inhibiting the induction of high mobility group box 1 (HMGB1) protein and cytokines by lipopolysaccharide (LPS; serotype: O127:B8) in a rat model. METHODS: We used male Wistar rats. Control group rats received a 0.9% NaCl solution. The LOS + LPS group rats received LOS (50 mg kg(-1)) before LPS (7.5 mg kg(-1)) administration. LPS group rats received injection of LPS (7.5 mg kg(-1)). MEASUREMENTS AND RESULTS: We performed immunohistochemistry, ELISA, and western blot analysis to examine the suppressive effects of LOS on LPS-induced cytokine induction. Plasma concentrations of cytokines (IL-6 and TNF-alpha) and HMGB1 (p < 0.05) were markedly reduced in the LOS + LPS group compared to the LPS group. LOS also inhibited the LPS-mediated decrease in angiotensin-converting enzyme 2 (ACE2) activity (p < 0.05). Immunohistochemical analysis revealed positive staining for ACE2 in lungs from both control and LOS + LPS groups. The intensity and degree of ACE2 labeling in lung tissue sections from the LPS group were markedly reduced compared to the control and LOS + LPS groups (p < 0.05). Additionally, RAW264.7 murine macrophages were stimulated with LPS, with or without simultaneous LOS treatment, resulting in inhibition of IkappaB phosphorylation. CONCLUSIONS: Treatment with LOS improved lung injury in an endotoxin shock model system by an anti-inflammatory action that inhibits reduction of ACE2.

Targeting TGF-beta and the extracellular matrix in Marfan's syndrome.

Marfan's syndrome is a genetic disorder affecting connective tissues, and it can lead to death due to aortic defects if left untreated. beta-blocker therapy has been used to slow the progression of this disease. Brooke et al. (2008) now report that combining angiotensin II receptor blockade by losartan with beta-blocker treatment is an effective treatment combination therapy for this disorder.

The role of renin-angiotensin-aldosterone system-based therapy in diabetes prevention and cardiovascular and renal protection.

Hypertension increases the risk of type 2 diabetes mellitus (T2DM) and cardiovascular disease. In addition to lowering blood pressure, blockade of the renin-angiotensin-aldosterone system (RAAS) reduces the risk of new-onset T2DM and offers renal protection. Using a MEDLINE search, we identified multiple trials that reported the incidence of T2DM in patients taking inhibitors of RAAS. In this review, we will discuss the RAAS as a potential target in diabetes prevention and the mechanisms through which inhibitors of this system achieve such an important effect. We will also shed light on the beneficial cardiovascular and renal effects of RAAS blockade. Although multiple studies have demonstrated that inhibitors of RAAS, especially angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, can reduce the incidence of T2DM, randomized controlled studies are still needed to further elucidate their exact role in diabetes prevention.

Regulation of prostate cancer cell growth and PSA expression by angiotensin II receptor blocker with peroxisome proliferator-activated receptor gamma ligand like action.

BACKGROUND: We previously reported that angiotensin II (AII) activated the proliferation of prostate cancer cells, and its antagonist, an AII receptor type 1 (AT1R) blocker (ARB), inhibited the proliferation of prostate cancer in vitro and in vivo. In the present study, we investigated whether telmisartan, an ARB, has a unique feature as a peroxisome proliferator-activated receptor gamma (PPARgamma) ligand, and its suppressive potential on prostate cancer cells. METHODS: Cell count or MTT assay were carried out for growth suppression of prostate cancer cells. Phosphorylation of mitogen-activated protein kinase (MAPK), specific expression of prostate specific antigen (PSA) and AT1R were investigated by western blot. To confirm the PPARgamma activity of ARBs, luciferase assay using PSA promoter and PPARgamma response elements (PPRE) plasmids was performed. RESULTS: The results showed that cell proliferation and signal transduction were inhibited by telmisartan treatment. Also, inhibition of PSA expression by telmisartan was confirmed by western blot and luciferase assay, indicating that an ARB acted in a similar way such as an anti-androgenic agent in prostate cancer cells. CONCLUSION: The present study showed ARBs, especially those possessing a PPARgamma ligand-like structure, have a potential antagonistic effect on androgen-dependent and -independent prostate cancer.

Angiotensin II induces monocyte chemoattractant protein-1 expression via a nuclear factor-kappaB-dependent pathway in rat preadipocytes.

Both monocyte chemoattractant protein-1 (MCP-1), a member of chemokine family, and angiotensinogen, a precursor of angiotensin (ANG) II, are produced by adipose tissue and increased in obese state. MCP-1 has been shown to decrease insulin-stimulated glucose uptake and several adipogenic genes expression in adipocytes in vitro, suggesting its pathophysiological significance in obesity. However, the pathophysiological interaction between MCP-1 and ANG II in adipose tissue remains unknown. The present study was undertaken to investigate the potential mechanisms by which ANG II affects MCP-1 gene expression in rat primary cultured preadipocytes and adipose tissue in vivo. ANG II significantly increased steady-state MCP-1 mRNA levels in a time- and dose-dependent manner. The ANG II-induced MCP-1 mRNA and protein expression was completely abolished by ANG II type 1 (AT1)-receptor antagonist (valsartan). An antioxidant/NF-kappaB inhibitor (pyrrolidine dithiocarbamate) and an inhibitor of 1kappaB-alpha phosphorylation (Bay 11-7085) also blocked ANG II-induced MCP-1 mRNA expression. ANG II induced translocation of NF-kappaB p65 subunit from cytoplasm to nucleus by immunocytochemical study. Luciferase assay using reporter constructs containing MCP-1 promoter region revealed that two NF-kappaB binding sites in its enhancer region were essential for the ANG II-induced promoter activities. Furthermore, basal mRNA and protein of MCP-1 during preadipocyte differentiation were significantly greater in preadipocytes than in differentiated adipocytes, whose effect was more pronounced in the presence of ANG II. Exogenous administration of ANG II to rats led to increased MCP-1 expression in epididymal, subcutaneous, and mesenteric adipose tissue. In conclusion, our present study demonstrates that ANG II increases MCP-1 gene expression via ANG II type 1 receptor-mediated and NF-kappaB-dependent pathway in rat preadipocytes as well as adipose MCP-1 expression in vivo. Thus the augmented MCP-1 expression by ANG II in preadipocytes may provide a new link between obesity and cardiovascular disease.

AT1 receptor antagonism ameliorates acute pancreatitis-associated pulmonary injury.

Acute pancreatitis (AP) is an inflammatory disease characterized by tissue edema, necrosis and hemorrhage. The mortality rate associated with this disease is particularly high when the inflammation has become systemic. Recently, activation of the pancreatic renin-angiotensin system (RAS) was shown to play a role in AP. The present study investigated whether administering an AT1 receptor antagonist decreases the severity of AP and pancreatitis-induced systemic inflammation, particularly pulmonary injury. Rats with AP-associated lung injury were induced by multiple doses of caerulein, which was demonstrated in the previous studies. Three injections of losartan (200 microg/ kg/h) were given 30 min prior to the first injection of caerulein. The results demonstrated that caerulein injections resulted in significant increases in pancreatic and pulmonary myeloperoxidase (MPO) activities, and losartan treatment attenuates these effects. Lung microvascular permeability was also significantly improved by losartan treatment. Losartan prevented caerulein-induced pancreatic and pulmonary morphological alterations, but not elevations in serum alpha-amylase or pancreas/body weight ratio. These data indicate that losartan treatment can attenuate pancreatic and lung injury. Thus, the implication is that a blockade of AT1 receptors may have a clinical application for the treatment of AP and, perhaps more importantly, subsequent pulmonary complications.

Transepithelial transport of telmisartan in caco-2 monolayers.

Telmisartan is the most recently marketed angiotensin II type 1 receptor antagonist. Drug-drug interactions involving transporters can directly affect the therapeutic safety and efficacy of many important drugs. In clinical practice, telmisartan is coadministered with many kinds of drugs. However, little is known about the contribution of transporters to the intestinal transport of telmisartan. The aim of this study was to determine the transport mechanism of telmisartan across intestinal epithelial cells. In the presence of an inwardly directed proton gradient, the apical-to-basal transport of telmisartan was greater than basal-to-apical transport. Thus, we focused on the uptake mechanism of telmisartan across brush-border membranes. The uptake of telmisartan by Caco-2 cells was shown to be energy- and proton-dependent. Although some monocarboxylates inhibited the uptake of telmisartan, L-lactic acid, which is a typical substrate of the monocarboxylate transporter (MCT) 1-MCT4, did not affect the uptake of telmisartan. Preloading of acetic acid enhanced the uptake of telmisartan, showing a trans-stimulation effect. These results suggest that the carrier-mediated transport system is involved in the uptake of telmisartan by Caco-2 cells and that the apical-localized transport system is similar to MCTs, but not MCT1-MCT4. It is possible that telmisartan reduce the absorption of coadministered drugs by sharing the MCTs. Since MCTs have an important role in the intestinal absorption of pharmacologically active compounds, it is important to be aware of the potential of telmisartan-drug interactions involving MCTs and to act in order to prevent undesirable and harmful consequences.

Reaching for aggressive blood pressure goals: role of angiotensin receptor blockade in combination therapy.

Elevated blood pressure, particularly systolic blood pressure, increases the risk of cardiovascular and renal complications in patients with diabetes. Current national guidelines set the blood pressure goal for those with diabetes at < 130/80 mm Hg, which is lower than the goal for the general population (<140/90 mm Hg). Achieving this goal, however, remains difficult, with blood pressure control rates being lower for patients with diabetes than for those without diabetes. Large clinical trials have demonstrated that in most cases, patients will require 2 or more antihypertensive agents to achieve goal blood pressure. The renin-angiotensin-aldosterone system plays a key role in regulation of blood pressure. The angiotensin AT1 receptor blockers (ARBs), which block the effects of angiotensin II, not only lower blood pressure but also provide target-organ protection. These agents are generally well-tolerated, with a side effect profile similar to placebo. Clinical comparisons of different drugs within the class have shown that olmesartan, the newest ARB, produced greater reductions in blood pressure than other agents and that a greater percentage of patients treated with olmesartan reached target blood pressure. Combining an ARB with a diuretic may allow more patients to reach goal blood pressure.

Mortality and morbidity reduction with Candesartan in patients with chronic heart failure and left ventricular systolic dysfunction: results of the CHARM low-left ventricular ejection fraction trials.

BACKGROUND: Patients with symptomatic chronic heart failure (CHF) and reduced left ventricular ejection fraction (LVEF) have a high risk of death and hospitalization for CHF deterioration despite therapies with angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and even an aldosterone antagonist. To determine whether the angiotensin-receptor blocker (ARB) candesartan decreases cardiovascular mortality, morbidity, and all-cause mortality in patients with CHF and depressed LVEF, a prespecified analysis of the combined Candesartan in Heart Failure Assessment of Reduction in Mortality and morbidity (CHARM) low LVEF trials was performed. CHARM is a randomized, double-blind, placebo-controlled, multicenter, international trial program. METHODS AND RESULTS: New York Heart Association (NYHA) class II through IV CHF patients with an LVEF of < or =40% were randomized to candesartan or placebo in 2 complementary parallel trials (CHARM-Alternative, for patients who cannot tolerate ACE inhibitors, and CHARM-Added, for patients who were receiving ACE inhibitors). Mortality and morbidity were determined in 4576 low LVEF patients (2289 candesartan and 2287 placebo), titrated as tolerated to a target dose of 32 mg once daily, and observed for 2 to 4 years (median, 40 months). The primary outcome (time to first event by intention to treat) was cardiovascular death or CHF hospitalization for each trial, with all-cause mortality a secondary end point in the pooled analysis of the low LVEF trials. Of the patients in the candesartan group, 817 (35.7%) experienced cardiovascular death or a CHF hospitalization as compared with 944 (41.3%) in the placebo group (HR 0.82; 95% CI 0.74 to 0.90; P<0.001) with reduced risk for both cardiovascular deaths (521 [22.8%] versus 599 [26.2%]; HR 0.84 [95% CI 0.75 to 0.95]; P=0.005) and CHF hospitalizations (516 [22.5%] versus 642 [28.1%]; HR 0.76 [95% CI 0.68 to 0.85]; P<0.001). It is important to note that all-cause mortality also was significantly reduced by candesartan (642 [28.0%] versus 708 [31.0%]; HR 0.88 [95% CI 0.79 to 0.98]; P=0.018). No significant heterogeneity for the beneficial effects of candesartan was found across prespecified and subsequently identified subgroups including treatment with ACE inhibitors, beta-blockers, an aldosterone antagonist, or their combinations. The study drug was discontinued because of adverse effects by 23.1% of patients in the candesartan group and 18.8% in the placebo group; the reasons included increased creatinine (7.1% versus 3.5%), hypotension (4.2% versus 2.1%), and hyperkalemia (2.8% versus 0.5%), respectively (all P<0.001). CONCLUSIONS: Candesartan significantly reduces all-cause mortality, cardiovascular death, and heart failure hospitalizations in patients with CHF and LVEF < or =40% when added to standard therapies including ACE inhibitors, beta-blockers, and an aldosterone antagonist. Routine monitoring of blood pressure, serum creatinine, and serum potassium is warranted.

Comparative effects of candesartan and amlodipine in a monkey atherosclerotic model.

Angiotensin II receptor blockers could prevent the development of atherosclerosis beyond reducing blood pressure in monkeys fed a high-cholesterol diet. However, it has been unclear whether hypotensive effects improve atherosclerosis in primates. We investigated whether antihypertensive agents, an angiotensin II receptor antagonist, candesartan, and a calcium channel blocker, amlodipine, prevent areas of atherosclerotic lesions in the aorta of monkeys fed a high-cholesterol diet. Seventeen male monkeys fed a high-cholesterol diet for 6 months were grouped as follows: a high-cholesterol diet group (n=5), a candesartan-treated group (1 mg/kg per day, n=6) and an amlodipine-treated group (5 mg/kg per day, n=6). Candesartan and amlodipine showed a similar hypotensive effect by decreasing the systolic blood pressure approximately 20 mmHg, while these agents did not affect serum cholesterol levels. The ratio of atherosclerotic area to total area in thoracic aorta was significantly decreased by treatment with candesartan, but the ratio tended to be decreased by treatment with amlodipine. Although the angiotensin-converting enzyme activity in plasma was not changed by treatment with candesartan or amlodipine, the angiotensin-converting enzyme activity in the thoracic aorta was obviously reduced by treatment with candesartan, but not with amlodipine. Therefore, a blockade of angiotensin II action rather than a hypotensive effect may play an important role in preventing the development of atherosclerosis in primates.