Abstract 283: Protective Role of Endogenous 20-HETE in Renal Ischemia-Reperfusion Injury

Previous studies have indicated that inhibitors of the synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE) protect against ischemia reperfusion injury (IRI) in the brain and heart. However, the role of endogenous 20-HETE in renal IRI has not been well characterized. The present study compared the susceptibility to IRI in Dahl salt-sensitive (S) rats in which the renal formation of 20-HETE is impaired versus that seen in normal Sprague-Dawley (SD) rats and in SS.5LEW 4A+ (4A+) congenic and SS.BN5 (BN5) consomic strains in which the CYP4A region of chromosome 5 was transferred from the Lewis or Brown Norway rats into the S genetic background. S, 4A+ and BN5 rats were fed a low salt diet and SD rats were fed a standard diet. IRI was induced by bilateral renal ischemia for 30 minutes followed by reperfusion. The 20-HETE production was measured using liquid chromatography-mass spectrometry (LC/MS). The renal production level of 20-HETE was significantly greater in SD, 4A+ and BN5 rats as compared to S rats and renal 20-HETE levels rose to a greater extent in these strains than in S rats following renal ischemia reperfusion. Plasma creatinine concentration rose to 3.7 ± 0.1 (n=6), 2.0 ± 0.4 (n=6), 1.9 ± 0.3 (n=6) and 2.2 ± 0.3 (n=6) mg/dl 24 hours following renal ischemia in S, 4A+, BN5 and SD rats, respectively. The kidney of S rats following IRI exhibited renal tubular necrosis and protein casts. The % of necrotic tubules in the corticomedullary regions of S rats (42.5 ± 3.5 %) was significantly higher than that seen in 4A+ (10.8 ± 3.8 %) or BN5 (10.2 ± 1.5 %) rats. The number of apoptotic tubular cells in the corticomedullary regions of S rats (125.3 ± 8.2 cells/field) was significantly higher than that seen in BN5 rats (46.8 ± 5.1 cells/field). Administration of the 20-HETE antagonist (6, 15-20-hydroxyeicosadecanoic acid) or the 20-HETE synthesis inhibitor (HET0016) abolished the resistance of 4A+ and BN5 rats to renal IRI and plasma creatinine levels rose to 4.0 ± 0.4 (n=4) and 3.8 ± 0.1 (n=4) mg/dl, respectively. The % of necrotic tubules respectively increased to 33.6 ± 6.9 % and 38.5 ± 5.5 % in 4A+ and BN5 rats and the number of apoptotic tubular cells increased to 119.2 ± 10.7 cells/field in BN5 rats. These data indicate that endogenously released 20-HETE plays a protective role in renal IRI.

Direct renin inhibition: extricating facts from façades

The renin–angiotensin system (RAS) affects vascular tone, cardiac output and kidney function. By these means the RAS plays a key role in the pathogenesis of arterial hypertension. As a result, RAS inhibition is highly effective not only in lowering blood pressure but also in reducing kidney disease progression (particularly when associated with proteinuria) and cardiovascular events.

Among RAS blocking agents, direct renin inhibitors have shown not only excellent efficacy in hypertension control but also pharmacologic tolerance that is comparable with other renin–angiotensin suppressors. Indeed, aliskiren, the only direct renin inhibitor available is effective in controlling blood pressure as monotherapy or in combination with other antihypertensive drugs, irrespective of patient’s age, ethnicity or sex. It is also effective in patients with metabolic syndrome, obesity and diabetes. Long-term studies comparing ‘hard endpoints’ of aliskiren therapy versus treatment with other RAS inhibitors, including cardiac and kidney protection, are currently ongoing. Combined with other antihypertensive agents, aliskiren not only improves their hypotensive response but may also lessen the adverse effects of other drugs. In high-risk patients, however, precautions should be taken when combining two or more renin–angiotensin inhibiting agents, as tissue perfusion may be highly renin-dependent in these patients and serious adverse side effects could take place.

Identification of a region of rat chromosome 1 that impairs the myogenic response and autoregulation of cerebral blood flow in fawn-hooded hypertensive rats

This study examined the effects of transfer of a 2.4-Mbp region of rat chromosome 1 (RNO1) from Brown Norway (BN) into fawn-hooded hypertensive (FHH) rats on autoregulation (AR) of cerebral blood flow (CBF) and the myogenic response of middle cerebral arteries (MCAs). AR of CBF was poor in FHH and FHH.1(BN) AR(-) congenic strains that excluded the critical 2.4-Mbp region. In contrast, AR was restored in FHH.1(BN) AR(+) congenic strains that included this region. The diameter of MCAs of FHH rats increased from 140 ± 14 to 157 ± 18 μm when transmural pressure was increased from 40 to 140 mmHg, but it decreased from 137 ± 5 to 94 ± 7 μm in FHH.1(BN) AR(+) congenic strains. Transient occlusion of MCAs reduced CBF by 80% in all strains. However, the hyperemic response following ischemia was significantly greater in FHH and AR(-) rats than that seen in AR(+) congenic strains (AR(-), 173 ± 11% vs. AR(+), 124 ± 5%). Infarct size and edema formation were also significantly greater in an AR(-) strain (38.6 ± 2.6 and 12.1 ± 2%) than in AR(+) congenic strains (27.6 ± 1.8 and 6.5 ± 0.9%). These results indicate that there is a gene in the 2.4-Mbp region of RNO1 that alters the development of myogenic tone in cerebral arteries. Transfer of this region from BN to FHH rats restores AR of CBF and vascular reactivity and reduces cerebral injury after transient occlusion and reperfusion of the MCA.

Local and systemic cellular immunity in early renal artery atherosclerosis

BACKGROUND AND OBJECTIVES

Modern imaging techniques have increased the incidental detection of renal atherosclerotic disease (RAD). Because immune activation may hasten RAD progression, identifying cellular immune markers might provide clues to clinical activity. In this study, cellular immune markers were assessed in early RAD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Immune cell markers in peripheral blood of two groups of hypertensive patients with normal carotid and coronary arteries were evaluated: 28 patients had incidental RAD and 22 patients had normal renal arteries; 21 renal arteries obtained at necropsy from individuals with history of hypertension and tissue evidence of RAD were examined and matched with 21 individuals with normal renal arteries. Cell subpopulations were measured by flow cytometry in peripheral blood and direct cell count, respectively, using T and dendritic cells monoclonal antibodies.

RESULTS

Peripheral blood of RAD patients showed increased numbers of cells expressing CD3, CD4, CD83, and CD86. CD4 to CD8 ratio was 8.3 ± 1.4 (RAD) to 3.4 ± 0.9 (normal; P<0.001). No differences were found in CD25, CD8, and S100 among groups. Postmortem samples from RAD showed increased CD3+, CD4+, CD86+, and S100+ cells, whereas CD25+ and CD8+ were unmodified between groups. CD4+ to CD8+ ratio was higher in the RAD(PM) group.

CONCLUSIONS

These results are consistent with an increased expression of immune cell markers in early RAD. Additional studies will explore if they may potentially turn into treatment targets to prevent disease progression.

[Abpm and duration of the antihypertensive effect: a study with a new formulation of sustained release losartan (CRONOS)]

Antihypertensive drugs action should last at least 24 h in order to enhance adherence, with positive impact on CV morbimortality. ABPM allow us to evaluate duration of action of drugs, against placebo, using Trough:Peak Ratio, antihypertensive effect in the last 4 h interdosis, and calculating the rate of BP morning surge. Losartán is an Antagonist At1 with good antihypertensive efficacy and renal, cardiac and cerebrovascular protection. Some studies shows less than 24 hs of action, that suggest twice a day dosing. The merge of a new formulation, Losartan Cronos, a bilayer tablet containing 50 mg of Losartan immediate release (IR) and 50 mg extended release (ER) would allow 24 h coverage, maintaining the previous advantages.

OBJECTIVES

To assess antihypertensive duration of action of Losartán Cronos in patients with essential hypertension throughout a 24-h dosing interval, using ABPM and response rates, AASI and Smoothness Index.

METHODS

97 essential hypertensives, where included and received a single morning dose of Losartán Cronos (50 mg of regular release and 50 mg of controlled and retarded release) during 8 weeks. Performed valid ABPM post placebo and post active treatment. Results Mean age 58 (26-86), 60% women. 63% treatment naïve. The mean reduction in BP from baseline to week 8 (end of treatment) was statistically significant for all times analyzed (24 hours, daytime, night-time, and last 4 hours monitoring). There were no significant changes in 24h heart rate. BP morning surge (mmHg/hour) decreased from 4.53 to 3,68 (p=0.03).T:P Ratio was 0.91 for SBP and 1.14 for DBP. Smoothness Index: SBP 2.86 (95% CI 1.84-3.7) - DBP 3.17 (95% CI 2.03-3.9) 19 patients had adverse events, no-one cough, all mild, without discontinuations. Conclusion Losartán Cronos demonstrated efficacy and safety, decreases BP without significant effects in heart rate, it reduces the pulse pressure, and its effect lasts for 24 hs, assessed by T:P ratio, last 4 hours effects, decreasing morning surge, also presenting homogeneous effect, since its Smoothness Index is high. Our results suggests daily monodose administration.

Evaluation of "Loss" and "End stage renal disease" after acute kidney injury defined by the Risk, Injury, Failure, Loss and ESRD classification in critically ill patients

PURPOSE

The Risk, Injury, Failure, Loss and ESRD (RIFLE) classification has been widely accepted for the definition of acute kidney injury (AKI); however, no study has described in detail the last two stages of the classification: "Loss" and "ESRD". We aim to describe and evaluate the development of "Loss" and "ESRD" in a group of critically ill patients.

METHODS

We conducted a retrospective analysis of cases prospectively collected from the Acute Physiology and Chronic Health Assessment (APACHE III) database. Subjects were consecutive critically ill patients >18 years of age admitted to three ICUs of two tertiary care academic hospitals, from January 2003 through August 2006, excluding those who denied research authorization, chronic hemodialysis therapy, kidney transplant recipients, readmissions, and admissions for less than 12 h for low risk monitoring.

RESULTS

11,644 patients were included in the study. The median age was 66 (interquartile range, 52-76), 90% were Caucasians and 54% of the patients were male. Half of the patients developed AKI, and most of the patients were in the Risk and Injury stages. From the patients that developed AKI, a total of 1,065 (19%) patients required renal replacement therapy (RRT), 415 (39%) underwent continuous renal replacement therapy (CRRT) and 650 (61%) underwent intermittent hemodialysis. A total of 281 patients on RRT did not survive hospital discharge, 97 patients progressed to "Loss", and 282 patients progressed to "ESRD". After multivariable adjustment, the progression to "ESRD" was associated with higher baseline creatinine, odds ratio (OR) 1.19 per every increase in creatinine of 0.1 mg/dl (95% CI, 1.11-1.29) P < 0.001; and less frequent use of CRRT, OR 0.18 (95% CI, 0.11-0.29) P < 0.001.

CONCLUSION

In this large retrospective study we found that almost 50% developed some form of AKI as defined by the RIFLE classification. Of these, 19% required RRT, and 4.9% progressed to "ESRD". "ESRD" was more likely in patients with elevated baseline creatinine and those treated with intermittent hemodialysis.

Renal response to amino acid infusion in essential hypertension

In the present study, we evaluated the renal response to a 4-hour infusion of amino acids in essential hypertensive patients, as well as the effects that dietary sodium restriction and enalapril (a converting enzyme inhibitor) had on this renal response. During normal sodium intake, amino acid infusion significantly increased renal plasma flow from 383 +/- 58 to 478 +/- 51 mL/min and glomerular filtration rate from 82 +/- 8 to 100 +/- 13 mL/min. All these effects were abolished when the patients received a low sodium diet (40 mmol/d) for 3 days before the amino acid infusion. The administration of enalapril to the patients during sodium restriction restored the amino acid-induced increment in renal plasma flow (from 388 +/- 35 to 573 +/- 48 mL/min) and glomerular filtration rate (from 88 +/- 9 to 103 +/- 10 mL/min). Mean arterial pressure remained unaltered under all experimental conditions. The results show that in patients with essential hypertension dietary sodium restriction prevents amino acid-induced increments in glomerular filtration rate and renal plasma flow and that this effect is restored during the simultaneous administration of enalapril.

Mechanisms of hypertension in renal radiation

This study was undertaken to investigate the role played by renal functional and structural changes in the development of radiation-induced hypertension. Four groups of rats were studied: 1) left kidney radiated, 2) sham procedure, 3) uninephrectomy followed 3 weeks later by radiation of the contralateral kidney, and 4) uninephrectomy followed by sham procedure 3 weeks later. All radiated rats became hypertensive at 12 weeks (p less than 0.05) and had higher protein excretion (p less than 0.05). In the presence of an intact contralateral kidney, radiation causes mild-to-moderate histological abnormalities, and therefore, creatinine clearance and water and sodium handling do not change. Plasma renin activity increased in this group (p less than 0.05). Radiated uninephrectomized rats showed decreased creatinine clearance (p less than 0.05), but renin activity remained unchanged. These rats developed severe histological abnormalities in glomeruli, interstitia, tubuli, and vessels resulting in increased sodium and water output. The average of individual tubular and interstitial scores correlated significantly with both water intake and output but not with sodium excretion. These studies suggest that in the presence of an intact kidney, renin is an important determinant in the development or maintenance of radiation hypertension, whereas in the absence of the contralateral kidney, severe histological changes and renal failure are prominent despite increased water intake and output. The more severe glomerular sclerosis and proteinuria in the latter model could be related to diminished renal mass.

Advanced digoxin toxicity in renal failure: treatment with charcoal hemoperfusion

Glycoside toxicity, a common and potentially fatal complication among patients taking digoxin, is treated basically by managing cardiac arrythmias until the patient can excrete enough drug to decrease the intoxication. Patients with renal failure, however, are particularly difficult to manage. We describe a case of advanced digoxin toxicity in an elderly man with severe renal failure, treated with a charcoal hemoperfusion device.

Chronic renal vein thrombosis

Twenty-eight patients with demonstrated chronic renal vein thrombosis were studied. In seven, only small venous channels were involved; in 21, both small and large veins were thrombosed. A constellation of findings occurred with such frequency in these patients that we believe it virtually diagnostic of renal venous obstruction. These findings include the nephrotic syndrome, great variability in proteinuria and glomerular filtration rate, pulmonary embolization, sterile pyuria, hematuria, hyperchloremic acidosis, decreased renal tubular threshold for glucose and increased fibrin degradation products. These findings are an indication for definitive angiographic and biopsy procedures. Prolonged anticoagulant therapy was generally very effective.

Immunoglobulin A glomerulonephritis: a clinicopathologic study

Renal biopsies from 10 patients staining predominantly for immunoglobulin A are reviewed. Historically, nine of 10 patients were less than 32 years of age; they all presented with either microscopic or gross hematuria. The initial creatinine clearances demonstrated good function in all patients; only one patient experienced a progressive decline in the creatinine clearance. Similarly, proteinuria was mild. The light and electron microscopic findings presented a variable pattern, including a group with changes confined to the mesangium, another group also having glomerular basement membrane changes, and one patient with severe, progressive glomerular sclerosis. Immunogluorescence demonstrated large amounts of IgA predominantly within the mesangium but occasionally involving the peripheral capillary loops. Serum IgA levels were elevated in six of eight patients tested, and two of five patients had elevated nasal IgA concentrations. These data suggest that there is an immunologic entity, IgA glomerulonephritis, characterized by the above clincial findings in association with elevated serum and occasionally nasal IgA levels, but that the pathologic findings are highly variable. Neither the mechanism nor the particular pathogenetic significance of the raised IgA levels is presently known. The similarities of this entity to the reported findings in anaphylactoid purpura are mentioned.