AT1 Receptor Modulator Attenuates the Hypercholesterolemia-Induced Impairment of the Myocardial Ischemic Post-Conditioning Benefits

BACKGROUND AND OBJECTIVES: Ischemic post-conditioning (PostC) has been demonstrated as a novel strategy to harness nature's protection against myocardial ischemia-reperfusion (I/R). Hypercholesterolemia (HC) has been reported to block the effect of PostC on the heart. Angiotensin II type-1 (AT1) modulators have shown benefits in myocardial ischemia. The present study investigates the effect of a novel inhibitor of AT1, azilsartan in PostC of the heart of normocholesterolemic (NC) and HC rats. MATERIALS AND METHODS: HC was induced by the administration of high-fat diet to the animals for eight weeks. Isolated Langendorff's perfused NC and HC rat hearts were exposed to global ischemia for 30 min and reperfusion for 120 min. I/R-injury had been assessed by cardiac hemodynamic parameters, myocardial infarct size, release of tumor necrosis factor-alpha troponin I, lactate dehydrogenase, creatine kinase, nitrite in coronary effluent, thiobarbituric acid reactive species, a reduced form of glutathione, superoxide anion, and left ventricle collagen content in normal and HC rat hearts. RESULTS: Azilsartan post-treatment and six episodes of PostC (10 sec each) afforded cardioprotection against I/R-injury in normal rat hearts. PostC protection against I/R-injury was abolished in HC rat hearts. Azilsartan prevented the HC-mediated impairment of the beneficial effects of PostC in I/R-induced myocardial injury, which was inhibited by L-N⁵-(1-Iminoethyl)ornithinehydrochloride, a potent inhibitor of endothelial nitric oxide synthase (eNOS). CONCLUSION: Azilsartan treatment has attenuated the HC-induced impairment of beneficial effects of PostC in I/R-injury of rat hearts, by specifically modulating eNOS. Azilsartan may be explored further in I/R-myocardial injury, both in NC and HC conditions, with or without PostC.

Angiotensin II stimulates MCP-1 production in rat glomerular endothelial cells via NAD(P)H oxidase-dependent nuclear factor-kappa B signaling

Angiotensin II (Ang II) plays a crucial role in the pathogenesis of renal diseases. The objective of the present study was to investigate the possible inflammatory effect of Ang II on glomerular endothelial cells and the underlying mechanism. We isolated and characterized primary cultures of rat glomerular endothelial cells (GECs) and observed that Ang II induced the synthesis of monocyte chemoattractant protein-1 (MCP-1) in GECs as demonstrated by Western blot. Ang II stimulation, at concentrations ranging from 0.1 to 10 µm, of rat GECs induced a rapid increase in the generation of reactive oxygen species as indicated by laser fluoroscopy. The level of p47phox protein, an NAD(P)H oxidase subunit, was also increased by Ang II treatment. These effects of Ang II on GECs were all reduced by diphenyleneiodonium (1.0 µm), an NAD(P)H oxidase inhibitor. Ang II stimulation also promoted the activation of nuclear factor-kappa B (NF-κB). Telmisartan (1.0 µm), an AT1 receptor blocker, blocked all the effects of Ang II on rat GECs. These data suggest that the inhibition of NAD(P)H oxidase-dependent NF-κB signaling reduces the increase in MCP-1 production by GECs induced by Ang II. This may provide a mechanistic basis for the benefits of selective AT1 blockade in dealing with chronic renal disease.

Persistent hypertension and progressive renal injury induced by salt overload after short term nitric oxide inhibition

INTRODUCTION: Administration of the NO inhibitor Nwð-nitro-L-arginine methyl ester (NAME) and a high-salt diet (HS) promotes severe albuminuria and renal injury, which regresses upon discontinuation of treatments. OBJECTIVE: We investigated whether these changes reappear after reinstitution of HS, and whether they are prevented by treatment with the antilymphocyte agent mycophenolate mofetil (MMF) or the AT-1 receptor blocker losartan (L). Adult male Munich-Wistar rats received NAME and HS. A control Group (C) received only HS. After 20 days, rats receiving HS and NAME exhibited severe hypertension and albuminuria. After a 30-day recovery period, hypertension was attenuated and albuminuria had virtually disappeared. MATERIAL AND METHODS: Rats were then distributed among the following groups: HS, receiving HS; NS, receiving a normal salt (NS) diet; HS-MMF, receiving HS and MMF; HS-LOS, receiving HS and L; HS-HDZ, receiving HS and hydralazine (HDZ). Sixty days later, NS rats showed only slight albuminuria and renal damage or inflammation. In contrast, HS rats developed severe hypertension, marked glomerulosclerosis with interstitial expansion and renal infiltration by macrophages and angiotensin II-positive cells. The group treated with losartan had lowered blood pressure and a lack of albuminuria or renal injury. MMF provided similar protection without altering blood pressure, suggesting a nonhemodynamic effect, a hypothesis reinforced by the finding that HDZ lowered blood pressure without preventing renal injury. RESULTS: These results indicate that treatment with HS and NAME predisposes to the development of hypertension and renal injury upon salt overload, characterizing a new model of chronic nephropathy. CONCLUSION: The response to MMF or L, but not HDZ, suggests a key role for inflammatory rather than hemodynamic factors.

INTRODUÇÃO: A administração de Nômega-nitro-L-arginina metiléster (NAME), um inibidor da produção de NO, com dieta rica em sal (HS) promove albuminúria e dano renal graves, reversíveis ao interromperem-se os tratamentos. OBJETIVO: Investigamos se tais alterações recrudescem ao reinstituir-se a HS e se são prevenidas pelo micofenolato mofetil (MMF), um agente antilinfócito, ou losartan, um bloqueador do receptor AT-1. MATERIAL E MÉTODOS: Ratos Münich-Wistar machos adultos receberam NAME e HS. Um grupo controle (C) recebeu apenas HS. Após 20 dias, os ratos que receberam HS e NAME exibiam hipertensão e albuminúria graves. Após recuperação de 30 dias, a hipertensão atenuou-se e a albuminúria praticamente desapareceu. Formaram-se então os grupos: HS, recebendo HS; NS, recebendo dieta normal em sal (NS); HS-MMF, recebendo HS e MMF; HS-LOS, recebendo HS e losartan; HS-HDZ, recebendo HS e hidralazina. Após sessenta dias os ratos NS tinham albuminúria e dano/inflamação renal apenas discretos. Já os ratos HS desenvolveram hipertensão e glomerulosclerose acentuadas, expansão intersticial e infiltração renal por macrófagos e células positivas para angiotensina II. Losartan baixou a pressão arterial e preveniu albuminúria e lesão renal. MMF proporcionou proteção semelhante sem alteração pressórica, sugerindo a ação de mecanismos não hemodinâmicos, hipótese reforçada pelo achado de que a HDZ baixou a pressão arterial sem prevenir a nefropatia. RESULTADOS: Esses resultados indicam que o tratamento com HS e NAME predispõe ao desenvolvimento de hipertensão e lesão renal induzidos por excesso de sal, caracterizando um novo modelo de nefropatia crônica. CONCLUSÃO: A resposta ao MMF ou losartan, mas não à hidralazina, sugere o predomínio de fatores inflamatórios.

The effects of high glucose concentration, angiotensin II and its blockers on the production of IL-6 and fibronectin in cultured human mesangial cells / 대한내과학회지

BACKGROUND: Diabetic nephropathy is a leading cause of end-stage renal disease and is charaterized by activation of some growth factors (e.g., angiotensin II, endotelin-1, IL-8, and TGF-beta) and deposition of extracellular matrix proteins. Both ACE inhibitors and AT1 receptor blockers partially prevent renal hypertrophy in diabetes. Recently, IL-6 is thought to act as an autocrine growth factor for the mesangial cells. Angiotensin II (Ang II) is one of the noninflammatory stimulators of IL-6 release from mesangial cells. IL-6 have been implicated in glomerulonephritis, including mesangioproliferative glomerulonephritis. IL-6 may be associated with renal damage, especially mesangioproliferative diabetic nephropathy. However, little is known about the pathogenetic relations between IL-6 and diabetic nephropathy. METHODS: To evaluate the effects of high glucose concentration, Ang II and its blockers on IL-6 and fibronectin production, human mesangial cells were cultured in various conditions. Normal concentration (100 mg/dL) and high concentration of D-glucose (450 mg/dL), Ang II (10(-7)M), high glucose with Ang II, captopril (10(-6)M), and losartan (10(-6)M) were added. After 48 hours, IL-6 and fibronectin concentration in the supernatant were measured by ELISA method. RESULTS: The effects of various conditions on the production of IL-6 and fibronectin in cultured human mesangial cells were as follows: 1. The concentration of IL-6 in the supernatant was significantly low in high glucose group (9.9+/-0.2 pg/mL) compared to that in control group (18.0+/-6.2 pg/mL) (p<0.05), and there was no difference in the supernatant concentration of fibronectin between the groups of high glucose and control. 2. The concentration of IL-6 in the supernatant of Ang II group (28.0+/-5.0 pg/mL) was significantly higher than that in control group (18.0+/-6.2 pg/mL) (p<0.05), and there was no difference in the supernatant concentration of fibronectin between the groups of Ang II and control. 3. In the supernatant of high glucose with Ang II group, the concentration of IL-6 (20.0+/-4.0 pg/mL) was significantly higher than that of high glucose group (9.9+/-0.2 pg/mL) (p<0.05), and the concentration of fibronectin (3,100+/-50 pg/mL) was significantly higher than that of control group (2,840+/-290 pg/mL) (p<0.05). 4. The concentration of IL-6 in the supernatant was significantly lowered after the addition of captopril (10.7+/-1.8 pg/mL) and losartan (9.3+/-2.4 pg/mL) in high glucose with Ang II group (20.0+/-4.0 pg/mL) (p<0.05). 5. The concentration of fibronectin was significantly lowered after the addition of captopril (2,640+/-30 pg/mL) and losartan (2,440+/-230 pg/mL) in high glucose with Ang II group (3,100+/-50 pg/mL) (p<0.05). 6. There was no difference in the concentration of supernatant IL-6 and fibronectin between the groups of captopril and losartan. CONCLUSION: High glucose concentration decreases and Ang II increases the production of IL-6 by cultured human mesangial cells. Captopril and losartan decrease the production of IL-6 and fibronectin which have been stimulated by high glucose concentration and Ang II. These drugs may be useful in the treatment of renal disease, especially diabetic nephropathy, in which Ang II and high blood glucose are cooperative in the progression of nephropathy.