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Since Giambérini and Cajaraville (2005) showed that the digestive gland lysosomal
response in freshwater zebra mussels
Dreissena polymorpha
was related to exposure time
and to cadmium concentration, the potential of this biomarker in freshwater biomonitor-
ing has been widely explored. After
in vitro
exposure to the antimicrobial agent triclosan
and the antibiotic trimethoprim, the lysosomal stability assay applied to zebra mussel
hemocytes did not show any significant differences as compared to baseline levels (Binelli
et al. 2009a), whereas
in vivo
exposure to triclosan induced a clear destabilization of lyso-
somal membranes (Binelli et al. 2009b), with the
in vivo
effect of trimethoprim remaining
moderate (Binelli et al. 2009c). The same team also revealed destabilization of the lyso-
somal membrane in zebra mussels after exposure to the pharmaceuticals paracetamol
(Parolini et al. 2010) and ibuprofen (Parolini et al. 2011) and the illicit drug cocaine (Binelli
et al. 2012). A multibiomarker approach carried out to investigate the state of contamina-
tion of the River Lambro/River Po confluence in Italy revealed a destabilization of zebra
mussel lysosomal membranes most likely induced by polychlorobiphenyls and dichloro-
diphenyl-trichloroethanes (Binelli et al. 2010). In another freshwater bivalve (
Unio pictorum
)
transplanted into a metal polluted river basin, the loss of lysosomal membrane stability
clearly discriminated among sites (Guidi et al. 2010). The sensitivity of the lysosomal mem-
brane to the modulation of cell redox equilibrium was well illustrated since a multiple
regression analysis showed that more than 80% of the neutral red retention test variance
was explained by the sum of antioxidant responses (Guidi et al. 2010).
The fact that lysosome stability represents a key component of cell responses to chemi-
cal stress was also shown in freshwater snails
Lymnaea stagnalis
exposed to the herbicides
fomesafen or atrazine (Russo et al. 2007, 2009) and land snails
Helix aspersa
(exposed to the
fungicide copper oxychloride in the laboratory or in the field; Snyman et al. 2000, 2002) and
Eobania vermiculata
collected from polluted areas in the field or treated with trace metals in
the laboratory (Itziou and Dimitriadis 2011).
In vivo
and
in vitro
exposures of the neotropical freshwater fish
Prochilodus lineatus
to lead
have also indicated that this metal induces a destabilization of the lysosomal membrane
(Monteiro et al. 2011).
The social amoeba
Dictyostelium discoideum
has been utilized recently as an experimental
model to study the biological effects of adverse environmental conditions. In particular,
the cellular changes induced by inorganic as well as organic pollutants on the activity of
the lysosomal vacuolar system have been studied (Dondero et al. 2006). The results showed
that nanomicromolar concentrations of mercury or benzo[
a
]pyrene are able to destabilize
the lysosomal membranes in the amoebae, thus confirming the high sensitivity of the neu-
tral red retention assay (Lowe et al. 1992; Lowe and Pipe 1994; Dondero et al. 2006; Moore
et al. 2006a; Sanzi Cortez et al. 2012) used in these experiments.
The relationship between the destabilization of lysosomal membranes and the autopha-
gic rate has been established using d2EGFP recombinant amoebae (Dondero et al. 2006).
A d2EGFP strain characterized by a sufficiently rapid turnover has been utilized to ver-
ify the possible effects induced by pollutant concentrations able to destabilize lysosomal
membranes. In the amoebae, the results confirmed that destabilization of lysosomal mem-
branes is associated with a parallel increase in the catabolic rate of d2EGFP. This clearly
indicates that the activation of the lysosomal vacuolar system in amoebae maintained in a
standard medium suitable to support cell growth and division, represents the initial event
of an increased autophagic activity itself representing an important aspect of the physi-
ological response of the protozoan to environmental stressors (Dondero et al. 2006).
In the field of terrestrial ecotoxicology, earthworms (e.g.,
Eisenia
sp.,
Lumbricus
sp.) are
widely used as model organisms to assess soil quality (Spurgeon et al. 2003; Römbke et
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