Molecular mechanisms of membrane polarity in renal epithelial cells

Exciting discoveries in the last decade have cast light onto the fundamental mechanisms that underlie polarized trafficking in epithelial cells. It is now clear that epithelial cell membrane asymmetry is achieved by a combination of intracellular sorting operations, vectorial delivery mechanisms and plasmalemma-specific fusion and retention processes. Several well-defined signals that specify polarized segregation, sorting, or retention processes have, now, been described in a number of proteins. The intracellular machineries that decode and act on these signals are beginning to be described. In addition, the nature of the molecules that associate with intracellular trafficking vesicles to coordinate polarized delivery, tethering, docking, and fusion are also becoming understood. Combined with direct visualization of polarized sorting processes with new technologies in live-cell fluorescent microscopy, new and surprising insights into these once-elusive trafficking processes are emerging. Here we provide a review of these recent advances within an historically relevant context.

Chronic kidney disease and global cardiovascular risk in essential hypertension

Recently published guidelines recognize the relevance of the finding of chronic kidney disease (CKD) in the stratification of risk of the hypertensive patient. Determination of the presence of microalbuminuria and estimation of glomerular filtration rate are mandatory in order to ensure an adequate evaluation of global cardiovascular (CV) risk in the hypertensive patient. Indices of altered renal function (e.g. microalbuminuria, increased serum creatinine concentrations, decrease in estimated creatinine clearance or overt proteinuria) are independent predictors of CV morbidity and mortality. Clustering of associated risk factors seems to justify the elevated CV morbidity and mortality observed in patients with essential hypertension and mild alterations of renal function. The increased prevalence of CKD in the general and in the hypertensive populations forces the recognition of its relevance and the need for an integrative therapeutic approach to fully protect simultaneously renal and CV systems.

Comparison of the antihypertensive effects of the fixed dose combination enalapril 10 mg/nitrendipine 20 mg vs losartan 50 mg/hydrochlorothiazide 12.5 mg, assessed by 24-h ambulatory blood pressure monitoring, in essential hypertensive patients

Fixed combinations of calcium channel blockers and angiotensin converting enzyme inhibitors represent an alternative to diuretic-based combination therapy. The aim of the present study was to compare the antihypertensive efficacy of the combination enalapril 10 mg/nitrendipine 20 mg (E/N) vs losartan 50 mg/hydrochlorothiazide 12.5 mg (L/H), assessed by 24-h ambulatory blood pressure monitoring. This multicentre, double-blind, parallel study included 97 hypertensive patients (office diastolic blood pressure (DBP) 90-109 mmHg and daytime DBP > 85 mmHg). After a 2- to 3-week period of single-blind placebo, they were randomized to receive double-blind treatment with E/N (n = 48) or L/H (n = 49) for a 4-week period. The primary outcome measure was the difference in 24-h DBP reduction between treatments from randomization to the end of the double-blind period. Secondary efficacy variables included differences in 24-h systolic (S) BP reduction, daytime, night-time and office SBP and DBP reduction, proportion of responders and controlled patients, trough-to-peak ratio and smoothness indexes. Safety was assessed by the proportion of patients with adverse events and the detection of laboratory abnormalities. No significant differences were observed in the primary outcome measure. The group receiving E/N tended to show greater reductions in most measures (24 h, daytime and office SBP and DBP) and higher BP control rates, but only the difference in the rate of office SBP control (< 140 mmHg) reached statistical significance (42.2 vs 22.4%; P = 0.048). The trough-to-peak ratios and smoothness indexes were similar in both groups. The incidence of adverse events related to the treatment was 27.1% (95% CI 14.5-39.6%) in E/N-treated patients and 14.3% (95% CI 4.5-45.8%) in the L/H group, but differences were not significant. The kind of event more frequently observed were flushing and headache in E/N, and dizziness and asthenia in L/H; all observed adverse events were mild. We conclude that E/N and L/H have a similar antihypertensive efficacy, assessed by office or ambulatory blood pressure monitoring. E/N achieved a significantly higher office SBP control rate, but this was accompanied by an apparently higher proportion of mild adverse events.

The calcium channel blocker controversy in patients with diabetic nephropathy: Is there an issue?

Chronic renal failure, proteinuria, and arterial hypertension run in parallel in the presence of diabetic nephropathy. New goal blood pressure levels have been established in diabetic patients: 130/85 mm Hg and 125/75 mm Hg depending on the level of proteinuria being below or above 1 g/d. New and lower threshold blood pressure (>130/85 mm Hg) to initiate pharmacologic therapy is required in the presence of diabetes mellitus in order to facilitate the strict blood pressure control that is required. It must be considered that both renal and cardiovascular protection are obtained with strict blood pressure control, which otherwise seems to require blockade of angiotensin II effects when proteinuria above 1 g/d is present. While awaiting the publication of long-term follow-up studies looking at renal and cardiovascular outcome in diabetic and other nephropathies in which calcium channel blockers are compared with other antihypertensive drugs, calcium channel blockers will remain the drugs needed to attain the expected goal blood pressure in diabetics, both alone (in the absence of microalbuminuria or macroalbuminuria) or in combination, particularly with angiotensin converting enzyme inhibitors.

ACE inhibitors and appearance of renal events in hypertensive nephrosclerosis

Nephrosclerosis constitutes a major cause of end-stage renal disease. Independently of blood pressure control, ACE inhibitors (ACEIs) are considered to be more nephroprotective than other antihypertensive agents. We have reviewed the long-term evolution of renal function in our series of essential hypertensive patients diagnosed as having nephrosclerosis when first seen in our unit. The analysis was performed depending on whether or not their antihypertensive therapy contained an ACEI alone or in combination for the whole follow-up. The end point was defined as the confirmation of a 50% reduction in creatinine clearance or entry in a dialysis program. A historical cohort of 295 patients was included in the analysis. Mean follow-up was 7.4+/-3.9 years. Diabetes prevalence was higher in ACEI-treated patients (25.7% versus 7.1%, P=0.000), but the diagnosis of diabetic nephropathy could not be confirmed on clinical grounds, including renal biopsy. Twenty-three out of 183 (12.6%) patients in the ACEI group and 23 out of 112 (20.5%) patients in the non-ACEI group experienced a renal event (P=0.0104 by log rank test). Similar results were observed when only nondiabetic patients were considered for the analysis. Cox regression analysis showed that baseline serum creatinine, absence of ACEI administration, mean proteinuria during follow-up, and age were independent predictors for the development of a renal event. In hypertensive nephrosclerosis, therapy containing an ACEI alone or in combination significantly reduces the incidence of renal events. This effect is independent of blood pressure control.

[Relationship between severity of essential arterial hypertension and the prevalence hyperuricemia]

BACKGROUND

Hyperuricemia has been associated with an increased risk of cardiovascular disease in hypertensive patients. However, the relation between serum urate and severity of hypertension has not been conclusively defined as yet. We aimed at finding out whether there exists an independent relationship between changes in the prevalence of hyperuricemia and severity of hypertension.

PATIENTS AND METHOD

We studied 3 cohorts of patients aged 35 to 60 years with essential hypertension diagnosed at a university hospital in Madrid, Spain. The first cohort (before 1981) included 325 patients, the second (from 1981 to 1989) comprised 271 patients and the third cohort (from 1990 to 1999) included 545 patients. Disease severity ranged from 1 to 6 according to blood pressure levels at diagnosis (WHO/ISH grades 1, 2 or 3 were assigned 1, 2 or 3 points, respectively) and target organ damage (left ventricular hypertrophy, hypertensive retinal vascular changes, and proteinuria above 300 mg/day; one point each).

RESULTS

Mean serum urate concentrations in the 3 cohorts were 6.6, 5.8 and 5.5 mg/dL, respectively (p < 0.05 for all comparisons). 39% of patients in the first cohort had a serum urate concentration > 7.0 mg/dL whereas only 18.1% patients in the third group showed hyperuricemia (difference: 20.9%; 95% CI, 10.1 to 32.3; p < 0.05). Severity of hypertension was higher in the first cohort (mean SD, 2.50 1.31 points) than in the third group (1.96 1.06 points; p < 0.05), with the second cohort showing an intermediate severity (2.23 1.01 points). Serum urate levels were directly related to the severity of hypertension in the 3 groups (r = 0.08, p < 0.05). In a multivariate analysis, after adjustment for confounding variables, serum urate had no significant association with severity of hypertension. However, target organ damage, systolic blood pressure and serum creatinine were all independent predictors of severity.

CONCLUSIONS

Favourable changes in the severity of hypertension for a time period significantly correlate with decreases in hyperuricemia prevalence in the same period. On the other hand, hyperuricemia appears to be an indirect marker of hypertensive renal damage.

Comparative study of home and office blood pressure in hypertensive patients treated with enalapril/HCTZ 20/6 mg: the ESPADA study

The introduction and generalization of 24-h ambulatory blood pressure (BP) monitoring has shown the clinical relevance of home BP. The aim of this study was to assess the validity of home-measured BP for monitoring and controlling patients with arterial hypertension while on a homogeneous treatment. An additional objective was to establish the degree of office BP control obtained. This was a prospective, longitudinal, observational and multicenter study in a cohort of 156 patients of both sexes, aged over 18 years and with essential hypertension. All of them received the fixed combination enalapril/HCTZ 20/6 mg as the only hypertensive agent for at least 4 weeks previously. Office BP was the average of three measurements. For home BP, a semi-automated device (OMRON HEM 705 CP) was used. The patients measured their BP twice a day for 2 consecutive days. The average differences between the two measuring methods were low, but significant: 3.99 mmHg for systolic BP (SBP; p < 0.05), 2.02 mmHg for diastolic BP (DBP; p < 0.05). Pearson's regression coefficient between the office and home values was highly significant (p < 0.0001) for SBP, DBP and heart rate. Home BP measurement was highly reproducible as shown by the high within-class correlation coefficient for individual measurements on the first day compared with the second: 0.88 (95% confidence interval, CI 0.82-0.92; p < 0.00001) for SBP and 0.89 for DBP (95% CI 0.83-0.93; p < 0.00001). The percentage of patients with strict office DBP and SBP control (< 140/90 mmHg) was 61.3% and with DBP control (<90 mmHg) 92%. In conclusion, in the ESPADA study, the application of home BP measurement is valid, reproducible and shows a high correlation with office BP.

[Aeromonas spp bacteremia: study of 12 cases and review of the literature]

Twelve cases of Aeromonas spp. bacteremia are here reviewed in adult patients occurred at our institution during a 6-year period. Three cases corresponded to patients with hematological disease and four had a solid neoplasm. The source of infection in seven patients was extra-nosocomial; infections in the five remaining patients were considered to be acquired in the hospital. In seven patients, potential portals of entry were found. The usual clinical presentation was febrile syndrome in all cases and only in two patients did the clinical picture evolve to fulminant septic shock. Speciation of microorganisms was determined in only four cases: 2 A. hydrophilia, 1 A. caviae, and 1 A. veronii. Most isolates were susceptible to aminoglycosides, cotrimozazol, phosphomycin, and quinolonos, and resistant to ampicillin. Three patients (25%) died as a result of the infection. Aeromonas spp. bacteremia represented 0.12% of blood cultures in our hospital and occurs in immunosuppressed patients although it may be reported in previously healthy individuals.

What is the optimal blood pressure target in renal patients?

Chronic renal failure and arterial hypertension run in parallel. New goal BP levels have been established as 130/85 mm Hg and 125/75 mm Hg, depending on whether the level of proteinuria is less than or greater than 1 g/d. New and lower threshold BP (> 130/85 mm Hg) to initiate pharmacologic therapy is required in the presence of renal failure, to facilitate the strict BP control that is required. Hence, it is necessary to consider that both renal and cardiovascular protection are obtained with strict BP control, which otherwise seems to require blockade of angiotensin II effects when proteinuria above 1 g/d is present.

[Fournier's gangrene. A study of 12 patients and a review]

We present the clinicoepidemiological and therapeutic characteristics of 12 patients with Fournier's gangrene. The mean age of the patients was 66 years and all had a known predisposing factor for the disease. In all cases there was a predominance of mixed flora (four Gram-positive cocci, nine Gram-negative bacilli and ten anaerobic pathogens), with only one case of bacteremia reported. Initial surgery was conducted and was complemented by antimicrobial administration (imipenem, cefotaxime, clindamycin, penicillin and gentamicin alone and in combination) and local treatment with sugar and povidone-iodine. Hyperbaric oxygen was not used in any cases. At the end of treatment a mesh graft could be applied in 11 patients, all of whom showed an excellent functional and aesthetic recovery. The mean time of hospital stay was lengthy (49 days). The good evolution of the lesions after starting the local treatments with the sugar povidone-iodine combination should be emphasized.

Inhibition of allergic late airway responses by inhaled heparin-derived oligosaccharides

Inhaled heparin has been shown to inhibit allergic bronchoconstriction in sheep that develop only acute responses to antigen (acute responders) but was ineffective in sheep that develop both acute and late airway responses (LAR) (dual responders). Because the antiallergic activity of heparin is molecular-weight dependent, we hypothesized that heparin-derived oligosaccharides (<2, 500) with potential anti-inflammatory activity may attenuate the LAR in the dual-responder sheep. Specific lung resistance was measured in 24 dual-responder sheep before and serially for 8 h after challenge with Ascaris suum antigen for demonstration of early airway response (EAR) and LAR, without and after treatment with inhaled medium-, low-, and ultralow-molecular-weight (ULMW) heparins and "non-anticoagulant" fractions (NAF) of heparin. Airway responsiveness was estimated before and 24 h postantigen as the cumulative provocating dose of carbachol that increased specific lung resistance by 400%. Only ULMW heparins caused a dose-dependent inhibition of antigen-induced EAR and LAR and postantigen airway hyperresponsiveness (AHR), whereas low- and medium-molecular-weight heparins were ineffective. The effects of ULMW heparin and ULMW NAF-heparin were comparable and inhibited the LAR and AHR even when administered "after" the antigen challenge. The ULMW NAF-heparin failed to inhibit the bronchoconstrictor response to histamine, carbachol, and leukotriene D(4), excluding a direct effect on airway smooth muscle. In six sheep, segmental antigen challenge caused a marked increase in bronchoalveolar lavage histamine, which was not prevented by inhaled ULMW NAF-heparin. The results of this study in the dual-responder sheep demonstrate that 1) the antiallergic activity of inhaled "fractionated" heparins is molecular-weight dependent, 2) only ULMW heparins inhibit the antigen-induced EAR and LAR and postantigen AHR, and 3) the antiallergic activity is mediated by nonanticoagulant fractions and resides in the ULMW chains of <2,500.

Effects of acid suppression and bismuth medications on the performance of diagnostic tests for Helicobacter pylori infection

OBJECTIVE

This study was designed to investigate whether acid suppression and bismuth medications interfere with the performance of diagnostic tests for Helicobacter pylori (H. pylori) infection.

METHODS

Sixty patients with previous diagnoses of atrophic gastritis and H. pylori infection made in gastric biopsies taken at Hospital Departmental, Pasto, Colombia, were enrolled in the study. 13C breath urea test (UBT) and stool antigen test (HpSA) were performed simultaneously. Two baseline tests were performed: one 7 days before and another the day before starting medications. A total of 20 patients received for 2 wk one of the following treatments: a) ranitidine; b) lansoprazole; or c) bismuth subsalicylate. The tests were repeated while the patients were on the prescribed medication on days 7 and 14 and then 2 wk after finishing the medication.

RESULTS AND CONCLUSIONS

Utilizing standard cut-off values for the tests, our results indicate that in the case of the 13C UBT test, ranitidine does not interfere with the results, whereas lansoprazole and bismuth may be expected to yield a significant proportion of false negative results (30-40% for lansoprazole and 45-55% for bismuth). In the case of the HpSA test, ranitidine does not interfere, whereas lansoprazole and bismuth may be expected to yield a nonsignificant proportion of false negative results (15-25% for lansoprazole and 10-15% for bismuth). Absolute values for both tests may be used to study the effects of the pharmacological agents on the characteristics of the infection.

Molecular-weight-dependent effects of nonanticoagulant heparins on allergic airway responses

We have hypothesized that antiallergic activity of inhaled heparin is molecular weight dependent and mediated by "nonanticoagulant fractions" (NAF-heparin). Therefore, we studied comparative effects of high-, medium-, and ultralow-molecular-weight (HMW, MMW, and ULMW, respectively) NAF-heparins on acute bronchoconstrictor response (ABR) and airway hyperresponsiveness (AHR) in allergic sheep. Specific lung resistance was measured in 23 allergic sheep, before and immediately after challenge with Ascaris suum antigen, without and after pretreatment with inhaled NAF-heparins. Airway responsiveness was estimated before and 2 h postantigen as the cumulative provocating dose of carbachol in breath units, which increased specific lung resistance by 400%. NAF-heparins attenuated ABR and AHR in a molecular-weight-dependent fashion. HMW NAF-heparin (n = 8) was the least effective agent: it attenuated ABR [inhibitory dose causing 50% protection (ID50) = 4 mg/kg] but had no effect on AHR. MMW NAF-heparin (n = 8) showed intermediate efficacy (ABR ID50 = 0.8 mg/kg, AHR ID50 = 1.4 mg/kg), whereas ULMW NAF-heparin (n = 7) was the most effective agent (ABR ID50 = 0.4 mg/kg, AHR ID50 = 0.2 mg/kg). ULMW NAF-heparin was 3.5 times more potent in attenuating antigen-induced AHR when administered "after" antigen challenge and failed to inhibit the bronchoconstrictor response to carbachol and histamine. In 15 additional sheep, segmental antigen challenge caused a marked increase in histamine in bronchoalveolar lavage fluid that was not prevented by any of the inhaled NAF-heparins. These data indicate that antiallergic activity of inhaled heparin is independent of its anticoagulant action and resides in the <2,500 ULMW chains. The antiallergic activity of NAF-heparins is mediated by an unknown biological action and may have therapeutic potential.

Microalbuminuria in essential hypertension

Microalbuminuria is frequently seen in patients with established essential hypertension, and is a predictor of a higher risk for cardiovascular and probably renal dysfunction. The presence of microalbuminuria has been shown to correlate with the other cardiovascular risk factors commonly seen in hypertensive patients. This fact indicates that the detection of an increased urinary albumin excretion could probably be the best index of an increased global cardiovascular risk in a given patient. Blood pressure control is accompanied by a fall in the content of albumin in urine. Agents with the capacity to block the renin-angiotensin system have shown a capacity to decrease urinary albumin excretion, which is independent of their ability to lower blood pressure. Whether or not a decrease in urinary albumin excretion is accompanied by an improved renal and cardiovascular prognosis in hypertensive patients remains to be elucidated.

Inhibition of antigen-induced airway hyperresponsiveness by ultralow molecular-weight heparin

Unfractionated heparin (UF-heparin) has been shown to prevent antigen-induced airway hyperresponsiveness (AHR), but it is ineffective when administered after the antigen challenge. We hypothesized that the failure of UF-heparin to modify postantigen AHR might depend on molecular weight. We therefore studied the effects of UF-heparin and three low-molecular-weight heparin fractions (medium-molecular-weight heparin [MMWH]; low-molecular-weight heparin [LMWH]; and ultralow-molecular-weight heparin [ULMWH]) on antigen-induced AHR and histamine release in bronchoalveolar lavage fluid (BALF). Specific lung resistance (SRL) was measured in 20 allergic sheep before, immediately after, and up to 2 h after challenge with Ascaris suum antigen. Airway responsiveness was expressed as the cumulative provocative dose of carbachol, in breath units, that increased SRL by 400% (PD400). PD400 was determined before and 2 h after antigen, both without and after treatment with aerosolized UF-heparin (1,000 U/kg) and various heparin fractions (0.04 mg/kg to 5 mg/kg) administered after the antigen challenge. Inhaled UF-heparin (n = 4), MMWH (n = 4), and LMWH (n = 6) failed to modify postantigen AHR when administered after the challenge. Only ULMWH (n = 6) inhibited postantigen AHR in a dose-dependent manner (percent protection ranged from 31% to 139%). In eight additional sheep, histamine in BALF was measured with a radioimmunoassay (RIA) before and after the segmental antigen challenge, without and after pretreatment with inhaled UF-heparin, LMWH, or ULMWH. Inhaled UF-heparin and LMWH inhibited antigen-induced histamine release as measured in BALF by 81% and 75%, respectively; whereas ULMWH was ineffective in this respect. We conclude that: (1) modification of antigen-induced AHR by fractionated heparins is molecular-weight dependent; and (2) only ULMWH attenuates AHR when administered after antigen challenge, via an unknown mast-cell-independent action.

Blood pressure control, proteinuria and renal outcome in chronic renal failure

The presence of proteinuria has been shown to be an excellent predictor for a worse outcome of renal function. Both proteinuria and arterial hypertension often coexist in the same patient, and therapy must be directed at decreasing protein excretion in the urine as well as lowering the blood pressure. Any antihypertensive agent has the capacity to lower proteinuria simply by lowering blood pressure. Furthermore, the antiproteinuric capacity of angiotensin-converting enzyme inhibitors can be equalized by other agents or their combination, provided that the fall in blood pressure is great enough. For this reason studies are needed in which the strict control of arterial hypertension combined with a decrease in proteinuria are considered.