Andrew S. Brem

Mutations in the chloride channel gene, CLCNKB, cause Bartter's syndrome type III

Analysis of patients with inherited hypokalaemic alkalosis resulting from salt–wasting has proved fertile ground for identification of essential elements of renal salt homeostasis and blood–pressure regulation. We now demonstrate linkage of this phenotype to a segment of chromosome 1 containing the gene encoding a renal chloride channel, CLCNKB. Examination of this gene reveals loss–of–function mutations that impair renal chloride reabsorption in the thick ascending limb of Henles loop. Mutations in seventeen kindreds have been identified, and they include large deletions and nonsense and missense mutations. Some of the deletions are shown to have arisen by unequal crossing over between CLCNKB and the nearby related gene, CLCNKA. Patients who harbour CLCNKB mutations are characterized by hypokalaemic alkalosis with salt–wasting, low blood pressure, normal magnesium and hyper– or normocalciuria; they define a distinct subset of patients with Bartters syndrome in whom nephrocalcinosis is absent. These findings demonstrate the critical role of CLCNKB in renal salt reabsorption and blood–pressure homeostasis, and demonstrate the potential role of specific CLCNKB antagonists as diuretic antihypertensive agents.

Rat proximal tubule cell line transformed with origin-defective SV40 DNA: autocrine ANG II feedback

The renal proximal tubule (PT) is a major site for a complete tissue renin-angiotensin system (RAS) and produces endogenous angiotensin II (ANG II). The present studies demonstrate autocrine RAS feedback in a line of origin-defective SV40 plasmid transformed immortalized rat PT cells (IRPTC) designated as line 93-p-2-1, which are highly differentiated and express all RAS components. Receptor competition assays and Southern blot following RT-PCR demonstrated that these IRPTC express AT1 and AT2 angiotensin receptor subtypes. Autocrine RAS feedback was examined following exposure to ANG II (10-8 M), and it was noted that angiotensinogen mRNA increases significantly by 1 h and remains elevated through 24 h. The AT1 blocker losartan prevents this increase. Moreover, ANG II upregulates expression of ANG II receptor mRNA (both AT1 and AT2). Thus the present studies demonstrate positive ANG II feedback with angiotensinogen and ANG II receptors in PTC, suggesting that the main site of such intrarenal feedback in vivo is within PT. ANG II secreted by line 93-p-2-1 is increased by isoproterenol, suggesting β-adrenergic regulation in IRPTC.

Localization of 2 11β-OH Steroid Dehydrogenase Isoforms in Aortic Endothelial Cells

11β-hydroxysteroid dehydrogenase (11β-HSD) is expressed in vascular smooth muscle cells (VSMC) but has not been reported to be present in vascular endothelial cells. This enzyme assists in regulati...

Primary Renal Lymphoma

Lymphomatous involvement of the kidneys is a common manifestation of systemic non-Hodgkins lymphoma but associated renal dysfunction is uncommon. In contrast, lymphoma originating within the kidneys is a rare event. We report a case of primary renal lymphoma presenting with renal insufficiency and hypertension in a 10-year-old boy.

Bidirectional activity of 11β-hydroxysteroid dehydrogenase in vascular smooth muscle cells

Endogenous glucocorticoids (GC) can be metabolized through the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD); in the rat, corticosterone (B) is converted to its inactive metabolite 11-dehydrocorticosterone (A). Since increased tissue concentrations of GCs may affect blood pressure by potentiating the vasoactive effects of alpha-adrenergic agonists and possibly other pressors, we studied the metabolism of corticosterone in freshly dissected aortae and cultured vascular smooth muscle cells (VSMC). Incubations were generally conducted for 60 min with 10(-8) M steroid; steroids were isolated and identified by HPLC. In aortic minces stripped of endothelium, the oxo-reductase reaction of A back to B was nearly 4 times greater than the dehydrogenase reaction of B to A (2.8 +/- 0.5 x 10(-11) versus 7.3 +/- 1.0 x 10(-12) mol/mg protein). This pattern was also seen in cultured VSMC during growth and quiescent states (growth A to B 3.2 +/- 0.4 x 10(-12) versus B to A 9.7 +/- 0.9 x 10(-13) mol/mg protein; quiescent A to B 8.8 +/- 0.1 x 10(-12) versus B to A 1.2 +/- 0.2 x 10(-12) mol/mg protein). Enzyme activity in either direction was less during growth, correlating with a decrease in mRNA for 11 beta-OHSD. In cell homogenates containing 200 microM NADP(H), the enzyme functioned equally in either direction at pH 7.4 with an apparent Km for corticosterone of approximately 2 x 10(-7) M. Carbenoxolone, an inhibitor of 11 beta-OHSD, suppressed the dehydrogenase reaction to a greater degree than the reverse oxo-reductase reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

11β-Hydroxysteroid dehydrogenase antisense affects vascular contractile response and glucocorticoid metabolism

Glucocorticoids (GCs) are metabolized in vascular tissue by two isoforms of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD). 11 beta-HSD2 is unidirectional and metabolizes GCs to their respective inactive 11-dehydro derivatives. 11 beta-HSD1 is bi-directional, also possessing reductase activity and thus the ability to regenerate active GC from the 11-dehydro derivatives. In vascular tissue, GCs amplify the pressor responses to catecholamines and angiotensin II and may down-regulate certain depressor systems such as nitric oxide and prostaglandins. We hypothesize that both 11 beta-HSD2 and 11 beta-HSD1 regulate GC levels in vascular tissue and are part of additional mechanisms that control vascular tone. We examined the effects of specific antisense oligomers to 11 beta-HSD2 and 11 beta-HSD1 on GC metabolism and contractile response to phenylephrine (PE) in rat aortic rings. In aortic rings incubated (24 h) with corticosterone (B) (10 nmol/l) and 11 beta-HSD2 antisense (3 micromol/l), the contractile response to graded concentrations of PE (PE: 10 nmol/l - 1 micromol/l) were significantly (P < 0.05) increased compared to rings incubated with B and 11 beta-HSD2 nonsense. 11 beta-HSD1 antisense oligomers also enhanced the ability of B to amplify the contractile response to PE. In addition, 11 beta-HSD2 and 11 beta-HSD1 antisense also decreased the metabolism of B to 11-dehydro-B. 11-Dehydro-B (100 nmol/l) also amplified the contractile response to PE in aortic rings (P < 0.01), most likely due to the generation of active corticosterone by 11 beta-HSD1-reductase; this effect was significantly attenuated by 11 beta-HSD1 antisense. 11 beta-HSD1 antisense also caused a marked decrease in the metabolism of 11-dehydro-B back to B by 11 beta-HSD1-reductase. These findings underscore the importance of 11 beta-HSD2 and 11 beta-HSD1 in regulating local concentrations of GCs in vascular tissue. They also indicate that decreased 11 beta-HSD2 activity may be a possible mechanism in hypertension and that 11 beta-HSD1-reductase may be a possible target for anti-hypertensive therapy.

EFFECTS OF LICORICE DERIVATIVES ON VASCULAR SMOOTH MUSCLE FUNCTION

Vascular smooth muscle contains a bidirectional form of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD) which can inactivate (dehydrogenase) endogenous circulating glucocorticoids (GCs) or activate (oxo-reductase) 11-dehydro-metabolites by their conversion back to the parent steroid. Enzyme direction in vascular smooth muscle (VSM) has potential physiological consequences since GCs may enhance the response to known vasoconstrictors. We determined that carbenoxolone is a competitive inhibitor of 11beta-HSD contained in VSM cells with a lower Ki for forward dehydrogenase reaction (0.02 microM) compared to the oxo-reductase reaction (0.41 microM). To test whether changes in enzyme directional activity can affect the contractile response, aortae from adrenally intact Sprague Dawley rats were removed and sectioned into 2.5 mm rings. Rings were incubated with corticosterone 10 nM plus carbenoxolone (CBX) 10 microM (a concentration well above the Ki for both the dehydrogenase and oxo-reductase reaction) for 24 hrs. These rings showed an enhanced dose dependent contractile response to phenylephrine (PE) 0.01 microM(-1) microM and to angiotensin II 1 microM compared to rings incubated with corticosterone alone, CBX alone, or controls: [e.g. response to PE 1 microM in mg of contractile force, mean +/- SE: corticosterone plus CBX 1495 +/- 162 (n=10) vs corticosterone 1039 +/- 64 (n=9), p<0.05]. Aortic rings preincubated with 11-dehydrocorticosterone 10(-7)M and CBX 10 microM displayed a decreased contractile response compared to 11-dehydrocorticosterone alone. Thus in situ glucocorticoid metabolism is important in mediating the constrictor responses of vascular tissue.

The functional roles of 11β-HSD1: vascular tissue, testis and brain

Abstract Glucocorticoid hormones bind both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) exerting a broad spectrum of actions in various tissues. The concentrations of glucocorticoid hormones in the target cells are regulated by 11β-hydroxysteroid dehydrogenases, type 1 (11β-HSD1) and type 2 (11β-HSD2). 11β-HSD2 is a unidirectional dehydrogenase, which inactivates biologically active glucocorticoid into inert metabolite, while 11β-HSD1 is a bi-directional oxidoreductase, which either inactivates biologically active glucocorticoid or activates inert metabolite into active forms. GRs and MRs are present in various tissues and mediate a broad spectrum of physiological actions. The co-existence of 11β-HSD1 with these two types of receptors plays an important role in regulation of glucocorticoid actions. This review examines the roles of 11β-HSD1 in vascular tissues, testis, brain and other tissues such as placental, retinal and adipose tissues.

Psychosocial characteristics and coping skills in children maintained on chronic dialysis

Psychosocial character traits and coping skills were examined in 12 children with end-stage renal failure. Six of the children were maintained on in-center hemodialysis and 6 were treated with home peritoneal dialysis. All of the patients felt a lack of ability to control their lives. The incidence of anxiety, depression, and hostility did not appear to vary from a population of healthy adolescents. Personal and social adjustment scores were, on average, on the 20th percentile. Coping skills appeared to be most influenced by the mode of dialysis treatment. Home peritoneal dialysis patients utilized self-reliance as a coping process more often than their counterparts on hemodialysis. We conclude that children maintained on chronic dialysis therapy demonstrate reasonable psychological adjustment with some differences in social and emotional functioning when compared with healthy children, and that the type of treatment chosen may influence the development of certain coping skills.

Protein-losing enteropathy in systemic lupus erythematosus

A 12-year-old girl, who was later found to have systemic lupus erythematosus (SLE), had a protein-losing enteropathy. Histologic documentation of intestinal lymphangiectasia in the absence of congestive heart failure, retroperitoneal masses, or constrictive pericarditis marks this case as demonstrating a unique association of SLE with intestinal lymphangiectasia.