Javier Diez

Overexpression of Bax Protein and Enhanced Apoptosis in the Left Ventricle of Spontaneously Hypertensive Rats Effects of AT1 Blockade With Losartan

An association of increased apoptosis with overactivity of the local angiotensin-converting enzyme has been reported in cells from the left ventricle of adult rats with spontaneous hypertension (SHR). To gain insight into the regulation of cardiac apoptosis in arterial hypertension, we investigated the expression of the proteins Bcl-2 (an inhibitor of apoptosis) and Bax (an inducer of apoptosis) in the left ventricle of 30-week-old normotensive Wistar-Kyoto rats (WKY), SHR, and SHR treated with the angiotensin II type 1 receptor (AT1) antagonist losartan (20 mg x kg(-1) x d(-1)) during 14 weeks before death. The density of apoptotic cells was assessed by direct immunoperoxidase detection of biotin-labeled deoxyuridin nucleotides. The expression of Bcl-2 and Bax was assessed by Western blot analysis. Compared with WKY, untreated SHR exhibited increased (P<0.05) apoptosis, increased (P<0.01) Bax, and similar Bcl-2. The Bcl-2/Bax ratio (an inverse index of cell susceptibility to apoptosis) was lower (P<0.05) in untreated SHR than in WKY. The chronic administration of losartan was associated with the normalization of apoptosis, Bax expression, and the Bcl-2/Bax ratio in treated SHR. No changes in the expression of Bcl-2 were observed in these rats after treatment. No significant changes in the apoptotic density were observed between treated SHR with normal blood pressure and treated SHR with abnormally high blood pressure at the end of the treatment period. These results suggest that an association exists between increased apoptosis and overexpression of Bax oncoprotein in cells from the left ventricle of adult SHR. Chronic blockade of AT1 receptors prevents Bax overexpression and normalizes apoptosis in the left ventricle of SHR independently of its hemodynamic effect. On the basis of our findings, it can be proposed that the interaction of angiotensin II with its AT1 receptors may participate in the stimulation of Bax protein, which in turn renders cells from the left ventricle of SHR more susceptible to apoptosis.

p53-Mediated Upregulation of BAX Gene Transcription Is Not Involved in Bax-α Protein Overexpression in the Left Ventricle of Spontaneously Hypertensive Rats

An association of increased apoptosis with overexpression of the proapoptotic protein Bax-alpha has been reported in the left ventricle of adult spontaneously hypertensive rats (SHR). Both alterations were corrected in SHR that received long-term treatment with the AT1 antagonist losartan. To gain insight into the regulation of cardiac Bax-alpha protein in genetic hypertension, we investigated the expression of the protein p53 (a BAX gene transcription factor) and BAX mRNA in the left ventricle of 30-week-old Wistar-Kyoto rats (WKY), SHR, and SHR treated with losartan (20 mg. kg-1. d-1) during 14 weeks before death. The expression of p53 and Bax proteins was assessed by Western blot analysis. The expression of BAX mRNA was assessed by Northern blot analysis. The density of apoptotic cells was assessed by direct immunoperoxidase detection of biotin-labeled deoxyuridine nucleotides. Compared with WKY, untreated SHR exhibited increased apoptosis (P<0.05), increased Bax-alpha protein (P<0.05), and similar levels of p53 protein and BAX mRNA. Losartan given long term was associated with the normalization of apoptosis and Bax-alpha protein expression. The expression of BAX mRNA was decreased (P<0. 05) in treated SHR compared with untreated SHR. No changes in the expression of p53 protein were observed in losartan-treated SHR. These results suggest that overexpression of the Bax-alpha protein seen in the left ventricle of adult SHR with increased apoptosis is not related to a p53-mediated upregulation of BAX gene transcription. Our data also suggest that normalization of Bax-alpha protein observed in SHR after long-term blockade of angiotensin II type 1 receptors may be due to the inhibition of BAX gene transcription.

Loss of renal graft due to recurrent IgA nephropathy with rapidly progressive course: an unusual clinical evolution.

Recurrence of IgA nephropathy following renal transplantation has been described in 40-50% of patients, and it usually has a good outcome. We present the case of a 54-year-old man with IgA nephropathy who developed terminal renal failure in 1985, 3 years after the onset of the disease. In March 1986 he received a cadaveric renal allograft following treatment with ciclosporin and steroids. Eight months later he developed microhaematuria and proteinuria and 10 months later he developed acute nephritic syndrome and rapidly progressive renal failure. Renal biopsy disclosed an IgA nephropathy with epithelial crescents in 60% of glomeruli. Treatment with plasma exchange and cyclophosphamide was unsuccessful and the patient lost his graft and returned to regular haemodialysis 15 months after renal transplantation.

Quinapril inhibits c-Myc expression and normalizes smooth muscle cell proliferation in spontaneously hypertensive rats.

A number of data suggest that angiotensin II-dependent activation of the protooncogene c-myc participates in the proliferative response of smooth muscle cells (SMC) of rats with spontaneous hypertension (SHR). We therefore investigated the effects of chronic treatment with the angiotensin converting enzyme (ACE) inhibitor quinapril on the oncoprotein c-Myc and the proliferating cell nuclear antigen cyclin A in SMC of small intramyocardial arteries from the left ventricle of SHR. The expression of c-Myc and cyclin A was assessed by immunocytochemical analysis. The number of smooth muscle cells was assessed by morphometrical analysis. As compared to normotensive Wistar-Kyoto (WKY) rats, untreated SHR exhibited an increased percentages of cells expressing c-Myc (33% +/- 4% v 19% +/- 2%, mean +/- SEM, P < .005) and cyclin A (25 +/- 2 v 11% +/- 1%, P < .001). In quinapril-treated SHR compared with untreated SHR, we found decreased expression of c-Myc (22% +/- 2%, P < .005) and cyclin A (13% +/- 1%, P < .001). No significant differences were found between WKY rats and quinapril-treated SHR in the above parameters. Cyclin A was directly correlated with the number of SMCs in each group of rats. These results suggest that an enhanced expression of c-Myc may be involved in the increased proliferation seen in SMCs from small arteries of SHR. Quinapril administration normalizes proliferation in the SMCs of SHR, possibly by inhibiting the expression of the oncoprotein c-Myc and its effects on the cell cycle.

Red cell distribution width: a method that improves detection of iron deficiency in chronic hemodialysis patients.

Rafael Díaz-Tejeiro, MD, Department of Nephrology, University Clinic, School of Medicine, University of Navarra, E-31080 Pamplona (Spain) Dear Sir, The pathogenesis of anemia of maintenance hemodialysis patients is multifactorial. Superimposed iron deficiency because of the repetitive blood losses associated with dialyzer use and bleeding secondary to uremic gastroenteritis and platelet dysfunction is a common feature [1]· The sensitivity of various iron measurements varies with the severity of iron lack. On this basis iron deficiency is commonly divided into three stages: storage iron depletion, iron-deficient erythropoiesis and iron deficiency anemia [2]. Red cell indices, such as mean corpuscular volumen (MCV), mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration, are sensitive only in the second and the third stages [2]. Moreover, several reports have shown that the serum iron and trans-ferrin saturation are of little value in identifying iron deficiency in these patients [3]. Serial measurements of serum ferritin levels provide an acceptable alternative for monitoring iron balance in chronic hemodialysis patients [4]. The majority of studies have suggested that iron deficiency is associated with serum ferritin values of less than 55 ng/dl [5]. The use of a new red blood cell parameter, the red blood cell distribution width (RDW), which is offered as a routine parameter on automated blood count, in combination with MCV improves the classification of anemias and the early detection of iron deficiency [6, 7]. It has been demonstrated that RDW values greater than 14.6% are associated with decreased iron stores [6]. To evaluate the usefulness of the RDW in detecting iron deficiency we examinated blood samples from 27 patients in maintenance hemodialysis. Patients with morphologically identified red cell abnormalities and patients with MCV values greater than 100 fl were excluded because these abnormalities may also cause RDW elevation. All patients were treated with phosphate binders Table 1. Relation of MCV and MC V/ RDW with serum ferritin in 27 patients in chronic hemodialysis

Renin–Angiotensin–Aldosterone System and Cardiomyocyte Apoptosis in Hypertensive Heart Disease

In the past decade observations have been made showing that cardiomyocyte apoptosis is an integral feature of the structural remodeling of the hypertensive hypertrophied left ventricle. The loss and functional abnormalities of apoptotic cardiomyocytes may be a contributing cause to the transition from left ventricular hypertrophy to heart failure in hypertension. Although the available evidence suggests that apoptosis can be induced in cardiomyocytes by a variety of factors and pathways, a number of findings suggest that the effectors of the renin–angiotensin–aldosterone system can be critically involved in cardiomyocyte apoptosis in hypertension. This review will summarize recent evidence demonstrating the potential contribution of angiotensin II and other components of the system to cardiomyocyte apoptosis in hypertensive heart disease. In addition, some evidence regarding strategies aimed to detect and prevent apoptosis of cardiomyocytes in hypertensive patients will be considered.

Rat atrial natriuretic peptide stimulates K+ fluxes in human erythrocytes.

Ouabain- and bumetanide-resistant potassium fluxes were measured in human erythrocytes incubated in a medium containing calcium and a calcium ionophore. Pharmacological concentrations of rat atrial natriuretic peptide stimulated these fluxes. Although human erythrocytes lack atrial natriuretic peptide receptors, our results suggest that the hormone can modify transmembrane K+ movements.

Diuretics and transmembrane ionic exchanges : structure-activity relations and clinical applications

The study of membrane ion transport has facilitated the discovery of potent and quite specific inhibitory drugs. Some of these compounds are therapeutic agents acting on basic transport mechanisms as in the case of the cardiac glycosides on the myocardial sodium ion (Na+), potassium ion (K+) pump, and the loop diuretics on the renal Na+, K+, chloride (Cl-) co-transport system. The development of inhibitors for other transport systems such as Na+/hydrogen ion (H+), Na+/calcium ion (Ca2+) and bicarbonate (HCO3-)/Cl- exchangers requires the screening of a large number of molecules. For several reasons, the human red blood cell is one of the best models for screening the effect of drugs on ion transport mechanisms. The use of human red cells for pharmacologic studies of ion transport has increased the understanding of the structure-activity relations of diuretics. For instance, loop diuretics that are chemically neutral were considered for many years as drugs that act similarly to classic acid loop diuretics. They are now considered as potent inhibitors of HCO3-/Cl- anion exchange. A brief summary of the more recent results is given together with the perspectives of new fundamental and therapeutic applications of these compounds.

Effect of intrarenal adenosine on urinary excretion of prostaglandins and leukotrienes in the anesthesized dog.

Adenosine is a renal vasoconstrictor that plays an important role in mediating renal adaptive responses to decreases in renal perfusion pressure. It is known that adenosine acts on the metabolism of arachidonic acid, but the direct repercussions of adenosine in the production of renal prostaglandins and leukotrienes have not been studied. This study was undertaken to evaluate the effect of the intrarenal infusion of adenosine upon the urinary elimination of arachidonic acid derivatives. Samples of urine were collected with lysine acetylsalicylate and determination of prostaglandins (PGs) and leukotrienes (LTs) was performed by radioimmunoassay of samples previously separated by HPLC. The infusion of adenosine decreases the urinary excretion of 6-keto-PGF1 alpha and TxB2 significantly. There was no significant change in urinary excretion of PGE2 while LTB4 and LTC4 showed a tendency to increase. These results suggest that a fall in the synthesis of PGI2 along with an increase in LTC4, which is a constrictor of mesangial cells, could be responsible for the renal vasoconstriction phase of adenosine. Therefore, it was concluded that adenosine vasoconstriction is mediated through the inhibition of the cyclo-oxygenase pathway, diminishing the synthesis of PG vasodilators.