Association of adiponectin and leptin with serum lipids and erythrocyte omega-3 and omega-6 fatty acids in dialysis patients.

AIMS: Besides regulating energy metabolism, leptin promotes and adiponectin suppresses inflammation which is a common feature of end-stage renal disease (ESRD). Omega-3 fatty acids (n-3FA) exert anti-inflammatory actions by inhibiting pro-inflammatory signal transduction pathways whereas arachidonic acid (an n-6FA) facilitates inflammation by mediating inflammatory signals and serving as precursor of pro-inflammatory eicosanoids. Given the functional overlap between adipokines and n-3FA and n-6FA, we sought to explore their interrelationship in patients with ESRD. METHODS: 44 ESRD patients maintained on hemodialysis (HD), 29 patients receiving peritoneal dialysis (PD), and 10 healthy subjects were enrolled. Body mass index (BMI), plasma leptin, adiponectin, lipids and CRP and erythrocyte fatty acids were measured. RESULTS: Compared to controls adiponectin was elevated and leptin level was reduced in the ESRD group. Adiponectin levels were comparable among PD and HD patients, but leptin and BMI were higher in PD than in HD patients. Despite comparable BMIs, female patients had higher leptin than male patients. Leptin levels were positively associations with BMI, total and LDL cholesterol whereas adiponectin was inversely related with BMI, triglycerides and CRP and directly associated with HDL cholesterol in ESRD patients. Plasma adiponectin was directly associated with erythrocyte n-3 FA (r = 0.581, p = 0.023) and inversely associated with n-6FA (r = -0.640, p = 0.010) in the HD patients. CONCLUSION: A direct association was found between plasma levels of adiponectin and HDL and erythrocyte n-3FA in ESRD patients. Prospective trials are needed to explore the effect of n-3FA supplementation on plasma adipokines and markers of oxidative stress and inflammation in this population.

Increased monocyte adhesion-promoting capacity of plasma in end-stage renal disease - response to antioxidant therapy.

UNLABELLED: End-stage renal disease (ESRD) causes accelerated atherosclerosis which is mediated by oxidative stress and inflammation. Activation and infiltration of monocytes represent the critical steps in atherogenesis which is advanced by oxidized LDL and inhibited by HDL. Via its main apolipoprotein (apoA-I) and constituent enzymes (paraoxonase; glutathione peroxidase (GPX), LCAT) HDL exerts potent antioxidant/anti-inflammatory functions. We have found marked reduction of HDL antioxidant/anti-inflammatory and heightened LDL pro-oxidant/pro-inflammatory activities in ESRD patients. Given the inseparable link between oxidative stress and inflammation, we tested the hypothesis that antioxidant therapy may improve anti-inflammatory (monocyte adhesion-promoting capacity) properties of plasma in ESRD patients. METHODS: We studied 20 hemodialysis patients who after a 4-week wash-out period were treated with a potent antioxidant cocktail (vitamin (v) E, 800 IU; vC, 250 mg; vB6, 100 mg; vB12, 250 µg and folic acid 10 mg daily) for 8 weeks. Twelve healthy volunteers served as control. Pre-dialysis plasma samples were obtained at the onset and conclusion of the study. Markers of oxidative stress and inflammation, apoA-I, HDL-associated enzymes and monocyte adhesion assay were measured using cultured aortic endothelial cells. RESULTS: ESRD patients exhibited reduced plasma level of apoA-1 and antioxidant enzymes, elevated markers of oxidative stress and inflammation and heightened monocyte adhesion-promoting capacity. Antioxidant therapy failed to improve these abnormalities. CONCLUSIONS: High doses of antioxidant vitamins fail to improve oxidative stress, inflammation or plasma monocyte adhesion-promoting capacity in ESRD patients. Thus, high doses of vitamins beyond the routinely-prescribed supplements do not appear to be beneficial in this patient population.

Leukocyte toll-like receptor expression in end-stage kidney disease.

BACKGROUND: End-stage renal disease (ESRD) is simultaneously associated with inflammation, impaired immunity and increased susceptibility to microbial infections. Innate immune cells, monocytes and polymorphonuclear leukocytes (PMN) recognize pathogens via toll-like receptors (TLR) triggering phagocytosis, cellular activation and secretion of inflammatory cytokines. Data on expression and function of TLRs in ESRD are limited. METHODS: Blood samples from 21 stable ESRD patients and 21 normal controls were processed for TLR2, TLR4, TLR7 and TLR 9 expression on monocytes and PMN by flow cytometry. TLR activity was examined by determining the response to TLR4 and TLR2 ligands. RESULTS: The ESRD group exhibited significant upregulation of TLR2 and TLR4 (but not TLR7 or TLR 9) expressions on monocytes and of TLR4 on PMN. This was coupled with heightened cytokine production in response to TLR4 activation with lipopolysaccharide. However, the response to TLR2 stimulation with peptidoglycan was unchanged in the ESRD group. CONCLUSIONS: Monocyte TLR2 and TLR4 and neutrophil TLR4 expressions and TLR4 activity are increased hemodialysis patients, representing another dimension of ESRD-associated inflammation.

Comparison of fatty acid contents of erythrocyte membrane in hemodialysis and peritoneal dialysis patients.

OBJECTIVE: Membrane fatty acid composition plays an important role in the cellular function. Erythrocyte fatty acid composition mirrors that of myocardium and is influenced by diet. Earlier studies have shown significant alterations of membrane fatty acid composition in ethnically mixed patients with end-stage renal disease. Given the impact of ethnic and dietary factors, we sought to examine membrane fatty acid composition in an ethnically homogeneous end-stage renal disease population residing in a coastal region of Korea with high fish consumption. DESIGN: Cross-sectional study. SETTING: Outpatient facility at Dong-A University Hospital, Busan, Republic of Korea. PATIENTS: We recruited 15 stable hemodialysis patients, 14 peritoneal dialysis patients, and 10 age- and gender-matched normal controls. Patients with significant malnutrition, short duration of dialysis, recent infection, malignancy, or liver disease were excluded. Dietary intake and use of omega-3 fatty acid supplements were determined. MAIN OUTCOME MEASURE: Erythrocyte membrane fatty acid contents measured by gas chromatography. RESULTS: Palmitoleic acid and alpha-linolenic acid levels were lower, whereas oleic acid, linoleic acid, and arachidonic acid levels were higher in patients with end-stage renal disease compared with the control group. Total monounsaturated fatty acids (palmitoleic acid and oleic acid) were significantly higher in peritoneal dialysis than in hemodialysis patients. Eicosapentaenoic acid and omega-3 docosapentaenoic acid were significantly higher, but total omega-6 fatty acids, omega-6/omega-3, and arachidonic acid/eicosapentaenoic acid ratios were significantly lower in hemodialysis patients consuming omega-3 supplements compared with those who did not. CONCLUSION: Patients with end-stage renal disease exhibited significant alterations in erythrocyte membrane fatty acids, which were partially modified by the dialysis modality and omega-3 fatty acid supplementation.

Effect of exercise on cardiac tissue oxidative and inflammatory mediators in chronic kidney disease.

BACKGROUND: Chronic renal failure (CRF) results in diminished physical activity and increased risk of cardiovascular disease (CVD). CVD risk factors are raised by sedentary life style and ameliorated by physical fitness in the general population. Accordingly, exercise improves hypertension, endothelial dysfunction, insulin resistance, dyslipidemia, inflammation and oxidative stress in high-risk populations. This study was designed to explore the effect of exercise on oxidative and inflammatory mediators in the left ventricle (LV) of CRF rats. METHODS AND RESULTS: One week after 5/6 nephrectomy female rats were housed in either regular cages or cages equipped with running wheels for 4 weeks. Sham-operated rats housed in regular cages served as controls. Sedentary CRF rats exhibited azotemia, hypertension, anemia, oxidative stress, activation of NF-kappaB and upregulations of reactive oxygen species-generating enzyme, NAD(P)H oxidase, MCP-1, cyclooxygenase-2 (COX-2), and PAI-1 in LV. The CRF rats assigned to the exercise group ran 6.8 +/- 0.7 km/day and 72 +/- 8 min/day. Voluntary exercise reversed NF-kappaB activation and lowered NAD(P)H oxidase, PAI-1, MCP-1 and COX-2 abundance, increased LV mass by raising myofibrillar proteins and ameliorated anemia without affecting renal function or arterial pressure. CONCLUSIONS: CRF resulted in upregulation of prooxidant/proinflammatory pathways in LV. These changes were ameliorated by exercise, which indicates the potential cardiovascular benefit of exercise in renal insufficiency.

Cardiovascular effects of lead exposure.

Several epidemiological and clinical studies have found a link between chronic lead exposure and elevated blood pressure. In addition, a few population studies have shown possible connection between lead exposure and other cardiovascular disorders including ischaemic coronary heart disease, cerebrovascular accidents, and peripheral vascular disease. The causal link between chronic lead exposure and hypertension (HTN) has been confirmed by several studies in experimental animals. In addition, the effects of lead on the heart and vascular function have been explored in a limited number of in vivo and in vitro studies. The in vivo, ex vivo and in vitro studies conducted in laboratory animal, cultured cells and isolated tissues have helped to elucidate many of the mechanisms by which lead exposure can cause HTN and cardiovascular disease. This review is intended to provide an overview of the epidemiology and the underlying mechanisms of lead-associated HTN and cardiovascular disease.

Renal senescence in 2008: progress and challenges.

Kidneys are significantly affected by profound anatomic and functional changes with senescence. These changes lead to decline in glomerular filtration rate, decreased urinary concentrating and diluting ability, diminished urinary acidification, and impaired potassium clearance, to list a few. Such changes make the elderly prone to drug toxicity and serious fluid and electrolyte imbalance. While the entire mystery of aging is far from being clear, the role of oxidative stress, telomere length, Klotho gene expression, and the renin angiotensin system seem to be the key mechanisms involved in aging. Aging, being a complex process, involves an array of intertwined molecular pathways. Simultaneous study of multiple molecular pathways in parallel could provide invaluable information in understanding the clinical course of kidney aging and elucidating mechanisms that play key roles in the aging process. A better understanding of these mechanisms may help to preserve renal function, improve morbidity and mortality, and hopefully reduce healthcare costs for the aging population.

Effects of dietary salt on intrarenal angiotensin system, NAD(P)H oxidase, COX-2, MCP-1 and PAI-1 expressions and NF-kappaB activity in salt-sensitive and -resistant rat kidneys.

BACKGROUND: Chronic consumption of a high-salt diet causes hypertension (HTN) and renal injury in Dahl salt-sensitive (SSR) but not salt-resistant rats (SRR). These events are, in part, mediated by oxidative stress and inflammation in the kidney and vascular tissues. Activation of the angiotensin II type 1 (AT(1)) receptor plays an important role in the pathogenesis of oxidative stress and inflammation in many hypertensive disorders. However, the systemic renin-angiotensin system (RAS) is typically suppressed in salt-sensitive HTN. This study was designed to test the hypothesis that differential response to a high-salt diet in SSR versus SRR may be related to upregulation of tissue RAS and pathways involved in inflammation and reactive oxygen species (ROS) production. METHODS AND RESULTS: SSR and SRR were studied 3 weeks after consumption of high- (8%) or low-salt (0.07%) diets. The SSR consuming a low-salt diet exhibited significant increases in AT(1) receptor, cyclooxygenase (COX) 2, plasminogen activator inhibitor (PAI) and phospho-I kappaB in the kidney as compared to those found in SRR. The high-salt diet resulted in severe HTN and proteinuria (in SSR but not SRR) and marked elevations of renal tissue monocyte chemoattractant protein 1, p22(phox), NADPH oxidase subunit 4, angiotensin-II-positive cell count, infiltrating T cells and macrophages and further increases in AT(1) receptor, COX-2, PAI-1 and phospho-I kappaB in the SSR group. The high-salt diet significantly lowered plasma renin activity (PRA) in SRR but not in the SSR. COX-1 abundance was similar on the low-salt diet and rose equally with the high-salt diet in both groups. Among subgroups of animals fed the low-salt diet, kidney glutathione peroxidase (GPX) abundance was significantly lower in the SSR than SRR. The high-salt diet raised GPX and mitochondrial superoxide dismutase (SOD) abundance in the SRR kidneys but failed to do so in SSR. Cu/Zn-SOD abundance was similar in the subgroups of SSR and SRR fed the low-salt diet. The high-salt diet resulted in downregulation of Cu/Zn-SOD in SSR but not SRR. CONCLUSIONS: Salt sensitivity in the SSR is associated with upregulations of the intrarenal angiotensin system, ROS-generating and proinflammatory/profibrotic proteins and an inability to raise antioxidant enzymes and maximally suppress PRA in response to high salt intake. These events can contribute to renal injury with high salt intake in SSR.

Intra-renal angiotensin II/AT1 receptor, oxidative stress, inflammation, and progressive injury in renal mass reduction.

Significant reduction of renal mass triggers a chain of events that result in glomerular hypertension/hyperfiltration, proteinuria, glomerulosclerosis, tubulointerstitial injury, and end-stage renal disease. These events are mediated by a constellation of hemodynamic, oxidative, and inflammatory reactions that are, in part, driven by local AT1 receptor (AT1r) activation by angiotensin II (Ang II). Here we explored the effects of 5/6 nephrectomy with and without AT1r blockade (losartan for 8 weeks) on AT1r and AT2r and Ang II-positive cell count, pathways involved in oxidative stress and inflammation [NAD(P)H oxidase, nuclear factor kappaB (NFkappaB), 12-lipooxygenase, cyclooxygenase (COX)-1, COX-2, monocyte chemoattractant protein (MCP)-1, plasminogen activator inhibitor (PAI)-1, renal T cell, and macrophage infiltration] as well as renal function and structure. The untreated group exhibited hypertension, deterioration of renal function and structure, reduced or unchanged plasma renin activity, aldosterone concentration, marked up-regulations of AT1r (250%), Ang II-expressing cell count (>20-fold), NAD(P)H oxidase subunits (gp91(phox,) p22(phox), and P47(phox); 20-40%), COX-2 (250%), 12-lipooxygenase (100%), MCP-1 (400%), and PAI-1 (>20-fold), activation of NFkappaB, and interstitial infiltrations of T cells and macrophages in the remnant kidneys. AT1r blockade attenuated the biochemical and histological abnormalities, prevented hypertension, and decelerated deterioration of renal function and structure. Thus, the study demonstrated a link between up-regulation of Ang II/AT1r system and oxidative stress, inflammation, hypertension, and progression of renal disease in rats with renal mass reduction.

Interplay of reactive oxygen species and nitric oxide in the pathogenesis of experimental lead-induced hypertension.

1. Lead is a common environmental and industrial toxin that can cause a variety of acute and chronic illnesses. For example, chronic exposure to low levels of lead has been shown to raise arterial pressure and promote renal and cardiovascular complications. 2. Several mechanisms have been identified by which chronic lead exposure can cause hypertension and cardiovascular disease. In recent years, increasing evidence has emerged pointing to the role of oxidative stress as a major mediator of lead-induced hypertension. 3. The present article provides an overview of the published studies on this subject.

Spontaneous leukocyte activation and oxygen-free radical generation in end-stage renal disease.

Oxidative stress and inflammation are common features and major mediators of atherosclerosis in end-stage renal disease (ESRD). Available evidence for oxidative stress in ESRD is indirect and based on accumulation of byproducts of interactions of reactive oxygen species (ROS) with various molecules. Inflammation is a major cause of oxidative stress. To explore the direct link between oxidative stress and inflammation in ESRD, we studied leukocyte integrin expression and ROS production in 18 ESRD patients and 18 controls. ESRD patients showed elevated plasma malondialdehyde (MDA) and increased superoxide and hydrogen peroxide (H(2)O(2)) production by granulocytes and monocytes before dialysis. Hemodialysis resulted in a further rise in plasma MDA and H(2)O(2) production by granulocytes and monocytes. Surface expression of Mac-1 (CD11b and CD18) on granulocytes and monocytes was significantly increased (denoting cell activation) in ESRD patients. Granularity of granulocytes was significantly reduced before dialysis and declined further after dialysis. The magnitude of ROS production by granulocytes and monocytes was directly related with CD11b expression as well as plasma ferritin and parathyroid hormone levels and was inversely related to protein catabolic rate. Thus, this study provides direct evidence of spontaneous leukocyte activation and increased ROS generation (hence the link between oxidative stress and inflammation) in ESRD patients.

Effect of renal injury-induced neurogenic hypertension on NO synthase, caveolin-1, AKt, calmodulin and soluble guanylate cyclase expressions in the kidney.

Single injection of a small quantity of phenol into the cortex of one kidney in rats results in development of persistent hypertension (HTN) which is thought to be mediated by activation of renal afferent and efferent sympathetic pathways and sodium retention. Nitric oxide (NO) plays a major role in regulation of renal vascular resistance, tubular Na(+) reabsorption, pressure natriuresis, and thereby systemic arterial pressure. The present study was performed to test the hypothesis that chronic renal injury-induced HTN may be associated with dysregulation of NO system in the kidney. Accordingly, urinary NO metabolite (NO(x)) and cGMP excretions as well as renal cortical tissue (right kidney) expressions of NO synthase (NOS) isoforms [endothelial, neuronal, and inducible NOS, respectively (eNOS, nNOS, and iNOS)], NOS-regulatory factors (Caveolin-1, phospho-AKt, and calmodulin), and second-messenger system (soluble guanylate cyclase [sGC] and phosphodiesterase-5 [PDE-5]) were determined in male Sprague-Dawley rats 4 wk after injection of phenol (50 mul of 10% phenol) or saline into the lower pole of left kidney. The phenol-injected group exhibited a significant elevation of arterial pressure, marked reductions of urinary NO(x) and cGMP excretions, downregulations of renal tissue nNOS, eNOS, Phospho-eNOS, iNOS, and alpha chain of sGC. However, renal tissue AKt, phospho-AKT, Calmodulin, and PDE-5 proteins were unchanged in the phenol-injected animals. In conclusion, renal injury in this model results in significant downregulations of NOS isoforms and sGC and consequent reductions of NO production and cGMP generation by the kidney, events that may contribute to maintenance of HTN in this model.

Naïve and central memory T-cell lymphopenia in end-stage renal disease.

End-stage renal disease (ESRD) is associated with increased propensity to infections, diminished response to vaccination, impaired cell-mediated immunity, and reduced CD4+/CD8+ T-lymphocyte ratio. Four subsets of CD4+ and CD8+ T cells have been recently identified: naïve cells (as yet uncommitted), central memory (CM) cells (previously programmed), and CD45RA-positive and CD45RA-negative effector memory (EM) cells (programmed to perform specific effector functions). The effect of ESRD on subpopulations of T lymphocytes is unclear and was studied here. Twenty-one hemodialysis patients and 21 age-matched controls were studied. Pre- and post-dialysis blood samples were obtained and analyzed by three-color flow cytometry. CD4+/CD8+ ratio and the numbers of the naïve and CM CD4+ and CD8+ T cells were significantly reduced, whereas the numbers of EM CD4+ and CD8+ T cells were unchanged in the ESRD group. The reduction of the naïve and CM T-cell counts in the ESRD group was associated with increased apoptosis of these cells. Negative correlations were found between severity of azotemia, oxidative stress, and hyperphosphatemia with the number of naïve T cells. Comparison of diabetic with non-diabetic ESRD patients revealed higher numbers of total CD8+ cells and EM CD8+ T cells in the diabetic group. Dialysis did not significantly change the naïve and CM CD4+ or CD8+ cell counts, but significantly lowered CD8+ EM cell count. Thus, ESRD results in increased apoptosis and diminished populations of naïve and CM T lymphocytes. This phenomenon may, in part, contribute to the impaired immune response in this population.

Involvement of endothelium and endothelin-1 in lead-induced smooth muscle cell dysfunction in rats.

Lead exposure induces dysfunction of the cyclic guanosine monophosphate-dependent vasodilator system through downregulation of soluble guanylate cyclase (sGC) expression. The endothelium not only releases vasodilators but also vasoconstrictors such as endothelin-1 (ET-1). Our aim was to explore the role of the vascular endothelium and ET-1 as possible mediators of lead-induced downregulation of sGC. Isolated aortic segments from Wistar Kyoto rats were incubated in the presence or absence of lead (1 parts per million) for 24 h. Endothelium was mechanically removed in some of the aorta segments. As reported previously, lead exposure induced downregulation of sGC protein expression in the intact aortic segments. However, lead exposure failed to significantly modify sGC-beta1 subunit expression in the endothelium-denuded aortic segments. Incubation with a selective ETA-type receptor inhibitor, BQ-123 (10(-6) mol/l), restored sGC protein expression in lead-exposed intact aortic segments. As it has also been previously observed, incubation in lead-containing medium resulted in the upregulation of cyclooxygenase-2 (COX-2) in the intact aortic segments. Denudation of endothelium partially abrogated this effect of lead. Incubation with BQ-123 prevented the lead-induced upregulation COX-2 in the intact aortic segments. However, neither ET-1 content nor ETA-type receptor expression were modified by lead exposure of the aortic segments. As conclusion, the endothelium through the activation of ETA-type receptors mediates the downregulation of sGC expression by lead in the vascular wall.

Dyslipidemia of chronic renal failure: the nature, mechanisms, and potential consequences.

Chronic renal failure (CRF) results in profound lipid disorders, which stem largely from dysregulation of high-density lipoprotein (HDL) and triglyceride-rich lipoprotein metabolism. Specifically, maturation of HDL is impaired and its composition is altered in CRF. In addition, clearance of triglyceride-rich lipoproteins and their atherogenic remnants is impaired, their composition is altered, and their plasma concentrations are elevated in CRF. Impaired maturation of HDL in CRF is primarily due to downregulation of lecithin-cholesterol acyltransferase (LCAT) and, to a lesser extent, increased plasma cholesteryl ester transfer protein (CETP). Triglyceride enrichment of HDL in CRF is primarily due to hepatic lipase deficiency and elevated CETP activity. The CRF-induced hypertriglyceridemia, abnormal composition, and impaired clearance of triglyceride-rich lipoproteins and their remnants are primarily due to downregulation of lipoprotein lipase, hepatic lipase, and the very-low-density lipoprotein receptor, as well as, upregulation of hepatic acyl-CoA cholesterol acyltransferase (ACAT). In addition, impaired HDL metabolism contributes to the disturbances of triglyceride-rich lipoprotein metabolism. These abnormalities are compounded by downregulation of apolipoproteins apoA-I, apoA-II, and apoC-II in CRF. Together, these abnormalities may contribute to the risk of arteriosclerotic cardiovascular disease and may adversely affect progression of renal disease and energy metabolism in CRF.

Expression of NOX-I, gp91phox, p47phox and P67phox in the aorta segments above and below coarctation.

Aorta coarctation results in hypertension (HTN) in the arterial tree proximal to stenosis and, as such, provides an ideal model to discern the effects of different levels of blood pressure on the vascular tissue in the same animal. Compelling evidence has emerged supporting the role of oxidative stress as a cause of HTN. However, whether or not HTN (independent of the circulating humoral factors) can cause oxidative stress is less certain. NAD(P)H oxidase isoforms are the main source of reactive oxygen species (ROS) in the vascular tissues. We therefore compared the expressions of NOX-I, gp91phox and the regulatory subunits of the enzyme in the aorta segments residing above and below coarctation in rats with abdominal aorta banding. Rats were studied 4 weeks after aorta banding above the renal arteries or sham operation. Subunits of NAD(P)H oxidase and its NOX-I isoform as well as endothelial NO synthase (eNOS) and nitrotyrosine (footprint of NO oxidation by superoxide) were measured in the aorta segments above and below coarctation. The gp91phox, p47phox, and p67phox subunits of NAD(P)H oxidase, NOX-I isoform, eNOS and nitrotyrosine were markedly increased in the aorta segment above coarctation (hypertensive zone), but were virtually unchanged in the segment below coarctation. Since, excepting blood pressure, all other conditions were constant, the upregulation of NAD(P)H oxidase isoforms and the increased NO oxidation in the aorta segment above, but not below, coarctation prove that HTN, per se, independent of circulating mediators can cause oxidative/nitrosative stress in the arterial wall. These observations suggest that HTN control may represent a specific form of antioxidant therapy for hypertensive disorders.

Bradykinin down-regulates, whereas arginine analogs up-regulates, endothelial nitric-oxide synthase expression in coronary endothelial cells.

Bradykinin (BK) is an endogenous vasoactive peptide that promotes vasodilation by stimulating the release of nitric oxide (NO) from endothelial cells via activation of endothelial NO synthase (eNOS). Although the role of BK in modulation of eNOS activity is well understood, its possible effect on eNOS expression remains uncertain. Several studies have demonstrated negative feedback regulation of eNOS by NO. Therefore, we hypothesized that sustained stimulation with BK may down-regulate eNOS expression in endothelial cells. Human coronary endothelial cells were incubated for 24 h with either BK alone or BK plus BK receptor type 1 or type 2 blockers. NO production and eNOS abundance (Western analysis) were determined. In separate experiments, cells were incubated with either an NOS inhibitor alone or in combination with BK. Incubation with BK caused a concentration-dependent rise in NO production and a dose-dependent decline in eNOS protein expression. These effects were abrogated by BK-2 blockade but unaffected by BK-1 blockade. In contrast, NOS inhibitors lowered NO production and raised eNOS abundance in a dose-dependent fashion. The effects of BK on NO production and eNOS expression were abrogated by the NOS inhibitor. Thus, sustained activation of eNOS by BK results in a compensatory down-regulation of eNOS, whereas its sustained inhibition leads to a compensatory up-regulation of eNOS. The observed modulations of eNOS expression are mediated by NO and represent an adaptive physiologic response.

HMG-CoA reductase inhibition reverses LCAT and LDL receptor deficiencies and improves HDL in rats with chronic renal failure.

Dyslipidemia is a prominent feature of chronic renal failure (CRF) and a major risk factor for atherosclerosis and the progression of renal disease. CRF-induced dyslipidemia is marked by hypertriglyceridemia and a shift in plasma cholesterol from HDL to the ApoB-containing lipoproteins. Several studies have demonstrated a favorable response to administration of 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors (statins) in CRF. This study was intended to explore the effect of statin therapy on key enzymes and receptors involved in cholesterol metabolism. Accordingly, CRF (5/6 nephrectomized) and sham-operated rats were randomized to untreated and statin-treated (rosuvastatin 20 mg x kg(-1) x day(-1)) groups and observed for 6 wk. The untreated CRF rats exhibited increased total cholesterol-to-HDL cholesterol ratio, diminished plasma lecithin:cholesterol acyltransferase (LCAT) and the hepatic LDL receptor, elevated hepatic acyl-CoA:cholesterol acyltransferase (ACAT), and no change in hepatic HMG-CoA reductase, cholesterol 7alpha-hydroxylase, or HDL receptor (SRB-1). Statin administration lowered HMG-CoA reductase activity, normalized plasma LCAT, total cholesterol-to-HDL cholesterol ratio, and hepatic LDL receptor but did not significantly change either plasma total cholesterol, hepatic cholesterol 7alpha-hydroxylase, total ACAT activity, or SRB-1 in the CRF animals. Statin administration to the normal control rats led to significant increases in plasma LCAT and hepatic LDL receptor, significant reductions of total cholesterol-to-HDL cholesterol ratio, hepatic HMG-CoA reductase activity, and cholesterol 7alpha-hydroxylase abundance with virtually no change in plasma cholesterol concentration. Thus administration of rosuvastatin reversed LCAT and LDL receptor deficiencies and promoted a shift in plasma cholesterol from ApoB-containing lipoproteins to HDL in CRF rats.

ACAT inhibition reverses LCAT deficiency and improves plasma HDL in chronic renal failure.

Chronic renal failure (CRF) is associated with increased risk of arteriosclerotic cardiovascular disease and profound alteration of plasma lipid profile. Uremic dyslipidemia is marked by increased plasma concentration of ApoB-containing lipoproteins and impaired high-density lipoprotein (HDL)-mediated reverse cholesterol transport. These abnormalities are, in part, due to acquired LCAT deficiency and upregulation of hepatic acyl-CoA:cholesterol acyltransferase (ACAT). ACAT catalyzes intracellular esterification of cholesterol, thereby promoting hepatic production of ApoB-containing lipoproteins and constraining HDL-mediated cholesterol uptake in the peripheral tissues. In view of the above considerations, we tested the hypothesis that pharmacological inhibition of ACAT may ameliorate CRF-induced dyslipidemia. 5/6 Nephrectomized rats were treated with either ACAT inhibitor IC-976 (30 mg.kg(-1).day(-1)) or placebo for 6 wk. Sham-operated rats served as controls. Key cholesterol-regulating enzymes, plasma lipids, and creatinine clearance were measured. The untreated CRF rats exhibited increased plasma low-density lipoprotein (LDL) and very LDL (VLDL) cholesterol, unchanged plasma HDL cholesterol, elevated total cholesterol-to-HDL cholesterol ratio, reduced liver microsomal free cholesterol, and diminished creatinine clearance. This was accompanied by reduced plasma LCAT, increased hepatic ACAT-2 mRNA, ACAT-2 protein and ACAT activity, and unchanged hepatic HMG-CoA reductase and cholesterol 7alpha-hydroxylase. ACAT inhibitor raised plasma HDL cholesterol, lowered LDL and VLDL cholesterol, and normalized total cholesterol-to-HDL cholesterol ratio without changing total cholesterol concentration (hence, a shift from ApoB-containing lipoproteins to HDL). This was accompanied by normalizations of hepatic ACAT activity and plasma LCAT. In conclusion, inhibition of ACAT reversed LCAT deficiency and improved plasma HDL level in CRF rats. Future studies are needed to explore the efficacy of ACAT inhibition in humans with CRF.

Acyl-coenzyme A:cholesterol acyltransferase inhibition ameliorates proteinuria, hyperlipidemia, lecithin-cholesterol acyltransferase, SRB-1, and low-denisty lipoprotein receptor deficiencies in nephrotic syndrome.

BACKGROUND: Nephrotic syndrome (NS) is associated with hyperlipidemia, altered lipid regulatory enzymes and receptors, and increased risk of progressive renal and cardiovascular diseases. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) catalyzes intracellular esterification of cholesterol and plays an important role in production of apolipoprotein B-containing lipoproteins, regulation of cholesterol-responsive proteins, and formation of foam cells. Because hepatic ACAT-2 is markedly upregulated in NS, we tested the hypothesis that inhibition of ACAT may improve cholesterol metabolism in NS. METHODS AND RESULTS: Rats with puromycin-induced NS were treated with either the ACAT inhibitor CI-976 or placebo for 2 weeks. Normal rats served as controls. Plasma lipids, renal function, and key lipid regulatory factors were measured. Untreated NS rats showed heavy proteinuria; hypoalbuminemia; elevated plasma cholesterol, triglyceride, LDL, VLDL, and total cholesterol-to-HDL cholesterol ratio; increased hepatic ACAT activity, ACAT-2 mRNA, and ACAT-2 protein; and reduced LDL receptor, HDL receptor, otherwise known as scavenger receptor B-1 (SRB-1) and plasma lecithin-cholesterol acyltransferase (LCAT). ACAT inhibitor reduced plasma cholesterol and triglycerides, normalized total cholesterol-to-HDL cholesterol ratio, and lowered hepatic ACAT activity without changing ACAT-2 mRNA or protein. This was accompanied by near normalizations of plasma LCAT, hepatic SRB-1, and LDL receptor and a significant amelioration of proteinuria and hypoalbuminemia. CONCLUSIONS: Pharmacological inhibition of ACAT reverses NS-induced LDL receptor, HDL receptor, and LCAT deficiencies; improves plasma lipid profile; and ameliorates proteinuria in nephrotic animals. Further studies are needed to explore the effect of ACAT inhibition in nephrotic humans.