lipid-a and Kidney-Diseases

In previous studies, we found that lipid A, the biologically active component of lipopolysaccharide, triggers a rapid release of intracellular calcium, the activation of nitric oxide synthase (NOS), and nitric oxide (NO) production in rat proximal tubules. This pathway leads ultimately to cell death [as measured by the release of lactate dehydrogenase (LDH)], initiated by early generation of NO. In the present studies we found that lipid A produces a time- and concentration-dependent increase in lipid peroxidation [malondialdehyde (MDA) formation] prior to cell death. Furthermore, preventing lipid peroxidation protected against cell death. Lipid A (50 micro;g/ml) produced significant MDA formation in 30 min. The addition of two antioxidants 5 min prior to lipid A completely inhibited MDA formation and LDH release at 90 min. Preincubation with 5 mm GSH also significantly reduced MDA formation. The involvement of NOS activation in lipid A-induced lipid peroxidation was established when an NOS inhibitor and an inhibitor of intracellular calcium release completely blocked MDA formation. In addition, superoxide generation was significantly increased in the presence of lipid A, and the involvement of superoxide was established when superoxide dismutase protected against oxidant injury. The iron chelators deferoxamine (also a scavenger of peroxynitrite) and diethylenetriaminepentaacetic acid prevented lipid A-induced lipid peroxidation and cell death, indicating a role for iron and peroxynitrite. The addition of an NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl, prior to lipid A also completely protected tubule cells from lipid peroxidation and subsequent cell death. These results indicate that lipid A-stimulated NO generation in the rat proximal tubule initiates oxidant injury.

Topics: Animals; Antioxidants; Calcium; Chelating Agents; Enzyme Induction; Iron; Kidney Diseases; Kidney Tubules, Proximal; Lipid A; Lipid Peroxides; Male; Nitric Oxide; Nitric Oxide Synthase; Oxygen Consumption; Rats; Rats, Sprague-Dawley; Signal Transduction; Superoxides

Studies were done to evaluate the effects of the human monoclonal anti-lipid A IgM antibody A6(H4C5) on several components of the hemodynamic and renal toxicity of the cell wall lipopolysaccharide of E. coli 0111:B4. Antibody (0.25 to four mg./kg. BW) was administered 0.5 hour before, or premixed for one hour with, lipopolysaccharide (0.05 mg./kg., a 14 to 18% lethal dose), and the following measurements made over 0.5 to 3.5 hours of study: systemic arterial blood pressure, renal plasma flow, and glomerular filtration. The proximal tubular cell cytotoxicity of 90 mg./kg. of the cephalosporin cephaloridine was also quantified in similarly treated animals sacrificed 48 hours later. While one mg./kg. of antibody prevented the reduction by the lipopolysaccharide of renal plasma flow, it did not prevent the nephrotoxic synergy with cephaloridine, and four times the antibody dose did not prevent lipopolysaccharide-induced hypotension or reduced glomerular filtration. These amounts of this antibody protect leukopenic rabbits against the lethality of the slow onset bacteremic model of Pseudomonas conjunctivitis. It is suggested that the incompleteness of protection in this study may be the result of the sensitivity of the assay methods used and/or the acute endotoxemia produced in these animals.

Topics: Animals; Antibodies, Monoclonal; Blood Pressure; Endotoxins; Escherichia coli; Escherichia coli Infections; Female; Glomerular Filtration Rate; Kidney Diseases; Lipid A; Lipopolysaccharides; Rabbits; Renal Circulation

The levels of IgG- and IgM-antibodies against lipid A were determined by an ultramicro-ELISA in 54 children between 2 months and 13 years of age with non-obstructive urinary tract infections at the onset of the infection and subsequently after 3, 6 and 12 months. Children older than 2 years who later developed renal scarring as shown by intravenous pyelograms had higher levels of IgG antibodies than those without scars. This correlation was not found in children younger than 2 years of age. IgM-antibody levels did not correlate with the risk of scar formation. We conclude that the IgG-antibody level against lipid A is a useful indicator for early recognition of children over the age of two years who will later develop renal scars. The ultramicro-ELISA technique makes screening for children at risk possible at a low cost.

Topics: Adolescent; Bacterial Infections; Child; Child, Preschool; Enzyme-Linked Immunosorbent Assay; Female; Humans; Immunoglobulin G; Immunoglobulin M; Infant; Kidney Diseases; Lipid A; Male; Pyelonephritis; Risk; Urinary Tract Infections