Basal cytotoxicity

Another approach is to use other cell-based systems that may have a higher sensitivity but still are representative for fish toxicity (Castano et al. 2003 Segner 2004). Since basal cytotoxicity reflects adverse effects on cell structures and processes that are intrinsic to virtually all cells, most cell systems should show a similar response, and respond similarly when toxicity is measured by various viability criteria. Mammalian cells that are cultured at higher temperatures and that proliferate faster than fish cells, may therefore be more sensitive and could provide a better in vitro system to predict acute fish lethality particularly if cell growth is considered as the endpoint (Castano et al. 2003 Segner 2004). Castano and Gomez-Lechon (2005) compared the sensitivity of fish and mammalian cell lines to 51 chemicals during 24 or 48 h exposure (Fig. 7.1). 

Castano A. Gomez-Lechon M.J. (2005) Comparison of basal cytotoxicity data between mammalian and fish cell lines A literature survey. Toxicology In Vitro 19 695-705. 

Kramer NI, Krismartina M, Rico-Rico A, Blaauboer BJ, Hermens JLM (2012) Quantifying processes determining the free concentration of phenanthrene in basal cytotoxicity assays. Chem Res Toxicol 25(2) 436-445... 

Cell lines have been used extensively to study the cytotoxicity of substances to fish cells12,184. Most studies have employed tests of general or basal cytotoxicity rather than tests of injury to differentiated cells and their functions. Basal cytotoxicity refers to impairment to cellular activities shared by all or most cells. Evaluating basal cytotoxicity can be done in a variety of ways, which will be referred to as cell viability assays. Usually these tests are performed on cultures after exposure to putative toxicants for 72 h or less and can be described as short-term or acute assays. As a result of this short exposure, toxicants that act by inducing a particular cellular process, such as the xenobiotic metabolism, or by causing cumulative damage might be missed. 

Fish cell lines have been used to screen and rank ecotoxicants for their basal cytotoxicity. A variety of cytotoxic endpoints as outlined in section III. 1 have been used. The number of compounds that have been examined is large and individual compounds are listed in other reviews184. Here some of the ecotoxicant classes investigated and the cell lines used are described. Metals have been the most intensively studied and with the largest number of cell lines. These include BB, BF-2,... 

Large granular lymphocytes, not belonging to either the T- or B-cell lineage. Natural killer (NK) cells are considered part of the innate defense system since, in contrast to cytotoxic T-cells, they are able to kill certain tumor cells in vitro without prior sensitization. The basal activity of NIC cells increases dramatically following stimulation with type I IFNs. In addition, NK cells display Fc-receptors for IgG and are important mediators of Antibody-Dependent-Cell-mediated-Cytotoxicity (ADCC). 

ADM may evolve over several years, the extent of fiber atrophy provides an important indication of the chronicity of muscle degeneration. Acute muscle necrosis and phagocytosis give some indication as to how active the disease is at the time of biopsy. In most biopsies from ADM patients, the inflammatory cell foci are perivascular and perimysial rather than endomysial and are dominated by B-lymphocytes. The ratio of T4 lymphocytes (helper cells) to T8 lymphocytes (cytotoxic) generally indicates a predominance of the former. As in JDM, this is consistent with humoral mechanisms of cell damage, and vascular involvement is also apparent in the form of capillary endothelial cell abnormalities (tubular arrays) and duplication of basal lamina. Loss of myofibrillar ATPase from the central portions of fibers is a common prelude to muscle necrosis. 

Benzene metabolites have also been shown to damage murine hematopoietic cells in vitro (Seidel et al. 1991). In addition, benzene has been shown to decrease mitochondrial respiration and increase superoxide radical production in isolated rat heart mitochondria (Stolze and Nohl 1994). The effects of exposure of HL-60 cells (human promyelocytic leukemic cells) to hydroquinone, />benzoquinonc, or 1,2,4-benzene-triol were studied by Rao and Snyder (1995). The cytotoxic effect of the metabolites on HL-60 cells, measured as cell viability, could be ranked as />benzoquinone>hydroquinone> 1,2,4-benzenetriol, with viability from 50% to 70% after incubation with concentrations up to 100 pM for 4 hours. Basal levels of superoxide anion or nitric oxide production were not affected by incubation of the cells with the metabolites, but in the presence of TPA, each metabolite increased superoxide anion production however, nitric oxide production was increased with hydroquinone and />benzoquinonc, but not 1,2,4-benzenetriol. HL-60 cells showed increased production of hydrogen peroxide after exposure to the three benzene metabolites. This study suggests that benzene metabolites may predispose the cells to oxidative damage by inhibiting or reducing antioxidant mechanisms within the cell. 

---