Jacob Green

Nephrotic syndrome and renal insufficiency associated with lithium therapy

Although the therapeutic administration of lithium in the psychiatric setting has been associated with various renal side effects, only a few reported cases have suggested a possible link to glomerular disease. We report two patients who, while taking lithium, developed heavy proteinuria caused by minimal change disease and acute renal insufficiency attributable to acute tubular necrosis. These clinical findings resolved on discontinuation of the drug, suggesting a role for lithium in their development. We also postulate that lithium, with its unique properties as a modulator of the phosphoinositol pathway, may play a key role in the pathogenesis of minimal change disease.

Interleukin-6 attenuates agonist-mediated calcium mobilization in murine osteoblastic cells.

Interleukin-6 (IL-6) is a multifunctional cytokine which is made by osteoblasts and has diverse effects on bone metabolism. We studied the interaction of IL-6 with the Ca2+ and cAMP signaling systems in the osteoblastic cell line UMR-106 and in primary osteoblastic cultures derived from neonatal rat calvariae. IL-6 did not alter basal intracellular calcium concentration ([Ca2+]i) but inhibited Ca2+ transients induced by parathyroid hormone (PTH), prostaglandin E2 (PGE2), and endothelin-1 in both dose- (100-400 U/ml) and time- (4-48 h) dependent manners. The effect of the cytokine was abolished by the tyrosine kinase inhibitor, herbimycin A (50 ng/ml). The IL-6 effect on the Ca2+ message system was related to suppressed production of hormonally induced inositol 1,4,5-triphosphate and inhibition of Ca2+ release from intracellular stores. Hormonally induced calcium entry pathways (estimated by using Mn2+ as a surrogate for Ca2+) were not, however, altered by the cytokine. IL-6 did not modulate cAMP generation in osteoblasts. With respect to osteoblast function, IL-6, although having no effect on cell proliferation by itself, greatly enhanced the antiproliferative effect of PGE2 and PTH. Because the production of IL-6 in osteoblasts is stimulated by calciotropic hormones (e.g., PTH and PGE2), the suppressive effect of the cytokine on hormonally induced Ca2+ transients may serve as an autocrine/paracrine mechanism for modulating the effect of hormones on bone metabolism.

A common mechanism for activation of the Na+/H+ exchanger by different types of stimuli.

The mechanism of activation of Na+/H+ exchanger by various stimuli was studied in the human epidermoid carcinoma cell line A431 and in peripheral blood mononuclear cells (PBM). Intracellular pH (pHi) was measured by using the fluorescent dye 2‘,7‘‐bis(carboxyethyl)‐5(6)‐carboxyfluorescein. Stimulation of A431 cells by epidermal growth factor (EGF), bradykinin (BK), phorbol‐12‐myristate 13‐acetate (PMA), and osmotic shrinkage resulted in exchanger activation. In PBM, activation of Na+/H+ exchanger was induced by concanavalin A (Con A) and phytohemagglutinin (PHA), as well as PMA and osmotic shrinkage. Inhibition of protein kinase C inhibited only PMA‐stimulated exchanger activation in both cell types. When osmotic shrinkage was applied after exposure of the cells to any agonist, augmentation of exchanger activation by osmotic stress was observed. These findings suggest that various stimuli activate Na+/H+ exchanger through different mechanisms. Kinetic analysis demonstrated that activation of the exchanger by any type of stimulus resulted in modification of the apparent affinities for intracellular H+ (H+i) and intracellular Na+ (Na+i) in opposite directions. While there is an increased apparent affinity for H+i, the apparent affinity for Na+i decreases. This finding suggests that in A431 cells this phenomenon serves as a common mechanism for activation of Na+/H+ exchanger by different stimuli.— Green, J.; Muallem, S. A common mechanism for activation of the Na+/H+ exchanger by different types of stimuli. FASEB J. 3: 2408‐2414; 1989.

Prostaglandins enhance parathyroid hormone-evoked increase in free cytosolic calcium concentration in osteoblast-like cells.

Prostaglandins (PGs) are autocrine or paracrine hormones that may interact with circulating hormones such as parathyroid hormone (PTH) in bone. We examined the interaction of the PGs, PGF2 alpha, PGE2, and 6-keto-PGF1 alpha with PTH to enhance the rapid, initial transient rise in free cytosolic calcium ([Ca2+]i) and cAMP levels stimulated by PTH. Pretreatment of UMR-106, MC3T3-E1, and neonatal rat calvarial osteoblast-like cells by PGs resulted in an enhancement of the early transient rise in [Ca2+]i stimulated by PTH. PGF2 alpha was approximately 100 times more potent than PGE2. PGE2 itself was more potent than 6-keto-PGF1 alpha in enhancing PTH-stimulated rise in [Ca2+]i. Near-maximal augmentation was achieved at PGF2 alpha doses of 10 nM and PGE2 of 1 microM. The degree of augmentation in [Ca2+]i by PGF2 alpha was independent of preincubation time. PGF2 alpha pretreatment did not alter the EC50 for the PTH-induced [Ca2+]i increase but only the extent of rise in [Ca2+]i at each dose of PTH. The augmented increase in [Ca2+]i was mostly due to enhanced PTH-mediated release of Ca2+ from intracellular stores. PGF2 alpha did not stimulate an increase in PTH receptor number as assessed by [125I]-PTH-related peptide binding. PG pretreatment partially reversed PTH inhibition of cell proliferation, suggesting that an increase in [Ca2+]i may play a role in tempering the anti-proliferative effect of PTH mediated by cAMP. These studies suggest a new mode by which PGs can affect cellular activity.

Chronic acidosis-induced growth retardation is mediated by proton-induced expression of Gs protein.

The etiology of skeletal growth retardation accompanying metabolic acidosis is not clear. Using ex vivo models for endochondral ossification, we showed that the cAMP/PKA pathway, probably triggered by proton sensitive G‐protein–coupled receptors, is responsible for impaired skeletal growth in acidosis.

Acute oliguric renal failure associated with unilateral renal embolism : A successful treatment with iloprost

A 66-year-old woman presented with acute-onset rapid atrial fibrillation and right upper quadrant pain which had appeared 24 h prior to admission. The patient also manifested acute oliguric renal failure (serum creatinine 6.9 mg/dl). Selective renal angiography revealed total occlusion of the right renal artery with normal visualization of the left kidney vasculature. The patient was treated with intra-arterial urokinase and intravenous heparin, with no response. Intravenous administration of the prostacyclin analogue, iloprost, resulted in rapid resolution (within hours) of the oliguric acute renal failure, in spite of the continuing presence of a nonfunctioning right kidney. We conclude that the etiology of the acute renal insult in this patient is probably related to unilateral renal arterial embolization accompanied by arterial spasm of the unaffected kidney. The contralateral vasospasm can be reversed by iloprost, which then leads to a rapid recovery from acute renal failure. We are unaware of prior reports documenting the beneficial effect of iloprost in a clinical setting as described here.

Inflammatory cytokines (IL-1α, TNF-α) and LPS modulate the Ca2+ signaling pathway in osteoblasts

Locally derived growth factors and cytokines in bone play a crucial role in the regulation of bone remodeling, i.e., bone formation and bone resorption processes. We studied the effect of interleukin (IL)-1α, tumor necrosis factor (TNF)-α, and Escherichia coli lipopolysaccharide (LPS) on the hormone-activated Ca2+ message system in the osteoblastic cell line UMR-106 and in osteoblastic cultures derived from neonatal rat calvariae. In both cell preparations, IL-1α, TNF-α, and LPS did not alter basal intracellular Ca2+ concentration ([Ca2+]i) but attenuated Ca2+ transients evoked by parathyroid hormone (PTH) and PGE2 in a dose (1-100 ng/ml)- and time (8-24 h)-dependent fashion. The cytokines modulated hormonally induced Ca2+ influx (estimated by using Mn2+ as a surrogate for Ca2+) as well as Ca2+ mobilization from intracellular stores. The latter was linked to suppressed production of hormonally induced inositol 1,4,5-trisphosphate. The effect of cytokines on [Ca2+]iwas abolished by the tyrosine kinase inhibitor herbimycin A (50 ng/ml). The cytokines effect was, however, independent of nitric oxide (NO) production, since NO donors (sodium nitroprusside) as well as permeable cGMP analogs augment, rather than attenuate, hormonally induced Ca2+ transients in osteoblasts. Given the stimulatory role of cytokines on NO production in osteoblasts, the disparate effects of cytokines and NO on the Ca2+ signaling pathway may serve an autocrine/paracrine mechanism for modulating the effect of calciotropic hormones on bone metabolism.

Minimal-Change Nephropathy and Malignant Thymoma

A 69-year-old woman presented with persistent dyspnea and continuous coughing and mediastinal mass. The mass was found to be a malignant thymoma and was resected incompletely. A full-blown nephrotic syndrome appeared 1 year after removal of the thymoma. Renal biopsy revealed minimal-change glomerulonephritis. There was no evidence of other autoimmune diseases or causes of the minimal-change glomerulonephritis.

Urinary acidification capacity in the elderly

Renal acidification in 18 healthy elderly subjects was studied using furosemide 80 mg orally, as a substance to stimulate H+ and K+ secretion by enhancing Na+ delivery and transport in the cortical collecting duct. In five subjects, group 2 (n=5), the furosemide failed to lower urinary pH below 5.5, but resulted in an increase in potassium excretion and decrease in net acid excretion. These effects were obliterated by amiloride, a drug which decreases transtubular epithelial voltage (lumen-negative) in the cortical collecting tubule (CCT) by blocking Na+ reabsorption. The serum bicarbonate in this group was normal, and they were considered as suffering from incomplete distal renal tubular acidosis (IC-DRTA). In group 1 (n=13), the furosemide resulted in a fall in urinary pH below 5.5, and in an increase in net acid excretion. Our results show that in a subgroup of elderly subjects there is a proton pump defect located in the cortical collecting duct, and that the elderly are susceptible to metabolic acidosis during stress conditions or high protein diet.

The Effects of Jaundice and Cholemia on Kidney Function and The Cardiovascular System

It has been known for four decades that patients with obstructive jaundice are at a high risk for postoperative acute renal failure (1–4). These patients also have greater falls in blood pressure following modest blood loss than patients without jaundice. The search for the cause of these complications of obstructive jaundice and attempts at prophylactic treatment in jaundiced patients undergoing surgery have prompted extensive experiments on animals with chronic bile duct ligation (CBDL) or animals in which the entire bile flow is diverted from the common bile duct to the systemic circulation-choledochocaval anastomosis (CDCA). While extrapolation to humans of conclusions obtained in animal studies should be made with caution, a growing body of evidence now suggests that bile constituents (e.g., bile acids, bilirubin, cholesterol) do not exert a direct nephrotoxic effect. Rather, retention of bile during cholestatic jaundice has deleterious effects on cardiovascular function and on blood volume. This, in turn, sensitizes the kidney to prerenal failure and acute tubular necrosis in postsurgical patients with obstructive jaundice.