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ARMIN WOLF ANAL REAL ACAD. FARM.

of cellular membrane damage and, hence, necrosis. However, using
histopathological criteria, neither apoptosis nor necrosis has been found in
man after CsA treatment.

In vivo, CsA induced apoptosis in tubular and intestinal cells of
rats(Thomas et al. 1998), and in mouse thymocytes (Saiagh et al. 1994).
In vitro, depending on the cellular system, CsA-induced apoptosis and
inhibition of apoptosis has been observed. For example, CsA acts as an
inhibitor of apoptosis in T and B lymphocytes (Ito et al. 1998) and in
neuronal cells (Kruman et al. 1999). Induction of programmed cell death
has been observed in thymocytes (Huss et al. 1995), in glioma cells
(Mosieniak et al. 1997), and in renal proximal tubular cells (Healy et al.
1998).

In rat hepatocyte primary cultures, we recently showed that CsA
causes oxidative stress, and that CsA cytotoxicity can be inhibited by
antioxidants (Wolf and Broadhurst 1992, Wolf and Donatsch 1990, Wolf
et al. 1994). The enhanced uptake of Ca2+ into liposomal vesicles (Wolf et
al. 1997) and an increase in extracellular Ca2+ (Ellouk-Achard et al. 1997)
have been demonstrated after treatment of rat hepatocytes with CsA. In
the current literature, oxidative stress and increased intracellular Ca2+
concentrations have been described as inducers of apoptosis (Buttke and
Sandstrom 1994), which suggests the potential role of CsA as an inducer
of apoptosis. In contrast, in the current literature, CsA was often used as a
specific inhibitor of mitochondrial Ca2+ release and of mitochondrial
membrane potential, and as a blocker of the MPT in rat hepatocytes
(Lemasters et al. 1998, Qian et al. 1997), all three are processes involved
in the inhibition of apoptosis.

To our knowledge, neither inhibition nor induction of apoptosis by
CsA has been described in the liver after in vivo treatment. It was recently
shown that CsA induced apoptosis in rat hepatocyte cultures treated for
48 hours in the presence of epidermal growth factor (EGF), with the DNA
laddering method applied as an indicator of apoptosis (Roman et al.
1998).

In order to obtain a better understanding of the nature and
mechanisms underlying the hepatic side effects of CsA, the present

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