Nephrotoxicity Testing in Vitro: What We Know and What We Need to Know

Abstract

The kidney is affected by many chemicals. Some of the chemicals may even contribute to endstage renal disease and thus contribute considerably to health care costs. Because of the large functional reserve of the kidney, which masks signs of dysfunction, early diagnosis of renal disease is often difficult. Although numerous studies aimed at understanding the mechanisms underlying chemicals and drugs that target various renal cell types have delivered enough understanding for a reasonable risk assessment, there is still an urgent need to better understand the mechanisms leading to renal cell injury and organ dysfunction. The increasing use of in vitro techniques using isolated renal cells, nephron fragments, or cell cultures derived from specific renal cell types has improved our insight into the molecular mechanisms involved in nephrotoxicity. A short overview is given on the various in vitro systems currently used to clarify mechanistic aspects leading to sublethal or lethal injury of the functionally most important nephron epithelial cells derived from various species. Whereas freshly isolated cells and nephron fragments appear to represent a sufficient basis to study acute effects (hours) of nephrotoxins, e.g., on cell metabolism, primary cultures of these cells are more appropriate to study long-term effects. In contrast to isolated cells and fragments, however, primary cultures tend to first lose several of their in vivo metabolic properties during culture, and second to have only a limited life span (days to weeks). Moreover, establishing such primary cultures is a time-consuming and laborious procedure. For that reason many studies have been carried out on renal cell lines, which are easy to cultivate in large quantities and which have an unlimited life span. Unfortunately, none of the lines display a state of differentiation comparable to that of freshly isolated cells or their primary cultures. Most often they lack expression of key functions (e.g., gluconeogenesis or organic anion transport) of their in vivo correspondents. Therefore, the use of cell lines for assessment of nephrotoxic mechanisms will be limited to those functions the lines express. Upcoming molecular biology approaches such as the transduction of immortalizing genes into primary cultures and the utilization of cells from transgenic animals may in the near future result in the availability of highly differentiated renal cells with markedly extended life spans and near in vivo characteristics that may facilitate the use of renal cell culture for routine screening of nephrotoxins. -Environ Health Perspect 1 06(Suppl 2):559-569 (1998). http://ehpnetl.niehs.nih.gov/docs/1998/Suppl-2/ 559-569pfaller/abstract.html

Evaluation of Novel Acute Urinary Rat Kidney Toxicity Biomarker for Subacute Toxicity Studies in Preclinical Trials

“…The reason for this variation may be due to the difficulty of assessing renal toxicity using traditional markers, which are insensitive, as is the case with blood urea nitrogen (BUN) and serum creatinine. Although both are direct measurements of renal function, increases in serum concentrations of these biomarkers occur only after substantial renal injury, generally after loss of two thirds of the nephrons' functional capacity (Pfaller and Gstraunthaler 1998). In the case of acute kidney injury (AKI), the degeneration of renal tissue can appear between days and weeks (Bellomo et al 2004;Lameire, Van Biesen, and Vanholder 2005).…”

In vitro and in vivo toxicity evaluation of the freshwater cyanobacterium Heteroleiblenia kuetzingii

“…The structure and function of the renal system makes the kidney particularly vulnerable to the toxic action of xenobiotics [29]. It was found that renal epithelial cells of the proximal nephron are a target for nephrotoxic compounds due to a large number of transport systems and the presence of xenobiotic metabolizing enzymes such as cytochrome P-450, glucuronyl transferase, sulfotransferases, glutathione S-transferases and others [53].…”

“…It has been discussed that freshly isolated cells or their primary cultures more closely resemble the in vivo environment of the respective cell type compared to the cell lines, which lack expression of key functions (e.g. organic anion transport) of their in vivo correspondents as a result of prolonged cultivation [29]. Studies on the mechanism of action of the microcystins, indicated the need of such organic anion transporters in order for the toxic substance to be able to enter the cell [30,31].…”

Current standing and future prospects for the technologies proposed to transform toxicity testing in the 21st century

“…The kidneys receive large amounts of blood and maintain body homeostasis by regulating water, electrolyte concentrations, and blood pH-level. Because the kidneys are the major organs for the excretion of hydrophilic compounds and their metabolites, they are at high risk of exposure (Pfaller and Gstraunthaler, 1998). Renal epithelial cells of the proximal nephron are common target sites in the kidney, since they exhibit a large number of trans-in the cells or tissue instead of in the external culture medium.…”

“…1). Primary cell cultures can be prepared from liver, brain, kidney, or skin tissue and were shown to maintain morphological and biochemical in vivo characteristics (Tiffany-Castiglioni et al, 1999;Guillouzo, 1998;Pfaller and Gstraunthaler, 1998). Primary cells are normally grown under monolayer conditions, but since this represents a simplified and artificial model of the in vivo situation, growing cells within a three-dimensional (3D) structure has become increasingly popular (Griffith and Swartz, 2006).…”