Aminoglycoside antibiotics alter the electrogenic transport properties of cultured human proximal tubule cells

Aminoglycoside antibiotics: structure, functions and effects on in vitro plant culture and genetic transformation protocols

Plant transformation protocols generally involve the use of selectable marker genes for the screening of transgenic material. The bacterial gene nptII, coding for a neomycin phosphotransferase, and the hpt gene, coding for a hygromycin phosphotransferase, are frequently used. These enzymes detoxify aminoglycoside antibiotics by phosphorylation, thereby permitting cell growth in the presence of antibiotics. Nevertheless, the screening for transgenic regenerated shoots is often partial and difficult due to regeneration of escapes and chimeras. These difficulties can be caused, in part, by an incorrect assumption about the mode of action of antibiotics in bacterial and eukaryotic cells and in in vitro tissue culture. The information contained in this review could be useful to establish better selection strategies by taking into account factors such as explant complexity, transformation and selection protocols that allow better accessibility to cells of Agrobacterium and antibiotics, and faster regeneration methods that avoid collateral effects of antibiotics on recovered, putative transgenic shoots.

New insights into the mechanism of aminoglycoside nephrotoxicity: an integrative point of view

Nephrotoxicity is one of the most important side effects and therapeutical limitations of aminoglycoside antibiotics, especially gentamicin. Despite rigorous patient monitoring, nephrotoxicity appears in 10-25% of therapeutic courses. Traditionally, aminoglycoside nephrotoxicity has been considered to result mainly from tubular damage. Both lethal and sub-lethal alterations in tubular cells handicap reabsorption and, in severe cases, may lead to a significant tubular obstruction. However, a reduced glomerular filtration is necessary to explain the symptoms of the disease. Reduced filtration is not solely the result of tubular obstruction and tubular malfunction, resulting in tubuloglomerular feedback activation; renal vasoconstriction and mesangial contraction are also crucial to fully explain aminoglycoside nephrotoxicity. This review critically presents an integrative view on the interactions of tubular, glomerular, and vascular effects of gentamicin, in the context of the most recent information available. Moreover, it discusses therapeutic perspectives for prevention of aminoglycoside nephrotoxicity derived from the pathophysiological knowledge.

Transfection of young guinea pig vestibular cells in vitro with an adenovirus vector

This study shows distributions of lacZ-positive cells in the vestibular labyrinthine explants of young guinea pigs with mature ears. When adenovirus lacZ vectors were administered to the vestibular labyrinth following removal of the otoconial membrane, lacZ-positive cells were observed in the mesothelial cells in the perilymphatic space, in the sensory and supporting cells in the utricle and ampulla, and in the transitional and dark cells in the ampulla. When the otoconial membrane was preserved, lacZ-positive cells were not distributed in the utricular sensory epithelium. These findings suggest that adenovirus vectors can transform a variety of vestibular epithelial cells, but that it is difficult for adenovirus vectors to pass through the otoconial membrane.

Poly-l-aspartic acid protects cultured human proximal tubule cells against aminoglycoside-induced electrophysiological alterations

Cultured human proximal tubule cell monolayers maintained on permeable supports were treated simultaneously with the aminoglycoside antibiotic, gentamicin, and poly-L-aspartic acid (PAA), an inhibitor of aminoglycoside nephrotoxicity. Following 4 days of exposure, cell monolayers were placed into Ussing chambers to allow monitoring of transepithelial electrical properties. For each of the three cell isolates examined, aminoglycoside-induced alterations in electrogenic transport, reflected by changes in short-circuit current (Isc), as well as alterations in paracellular properties, indicated by changes in transepithelial electrical resistance (RT), were diminished in the presence of PAA. Alterations resulting from selective basolateral exposure to gentamicin were unchanged in the case of apically applied PAA and attenuated only when PAA acid was added basolaterally. This is the first demonstration of PAA inhibition of aminoglycoside-induced cellular alterations involving human cells.

Selective exposure of human proximal tubule cells to gentamicin provides evidence for a basolateral component of toxicity

The goal of the present study was to determine if cultured human proximal tubule (HPT) cells could provide evidence for a basolateral component of gentamicin toxicity. Six isolates of HPT cells were grown on Millicell filters and exposed to gentamicin either apically, basolaterally, or both apically and basolaterally. Toxicity was determined by the release of lactate dehydrogenase into the growth media. The results clearly demonstrated that basolateral exposure and combined apical and basolateral exposure to gentamicin resulted in significant levels of cell toxicity. In contrast, apical exposure to gentamicin elicited only marginal toxicity. The transepithelial flux of gentamicin was shown to be the same in either the apical to basolateral or the basolateral to apical direction. A two-step mechanism of gentamicin toxicity is proposed in order to integrate basolateral toxicity with known features of aminoglycoside nephrotoxicity.

Aminoglycoside antibiotics alter the paracellular transport properties of cultured human proximal tubule cells

Cell cultures retaining properties of the human proximal tubule were utilized to determine whether or not the aminoglycoside antibiotics alter paracellular transport. The transepithelial resistance (RT) of the human proximal tubule (HPT) cell monolayers was determined by Ussing chamber analysis of cells grown on permeable supports. This analysis revealed that RT was reduced as a result of aminoglycoside exposure and that the reduction corresponded to the known clinical nephrotoxicities of the aminoglycosides. Variation in the aminoglycoside concentration necessary to elicit this response was documented using 14 individual cell isolates. Ultrastructural analysis provided evidence indicating that the alterations in RT were not associated with general damage to the HPT cells. An examination of the structure of the tight junctions by freeze-fracture analysis demonstrated only minimal alteration of the sealing strands as a result of aminoglycoside exposure. Consequently, the reductions in RT were not directly associated with discernible tight junction structural alterations. Alteration in the paracellular route of transport, as indicated by altered RT values, was clearly documented as a result of aminoglycoside exposure. In addition, this alteration was accompanied by an increased density of intramembrane particles within the apical cell membrane.