Linking Lysosomal Biomarkers and Ecotoxicological Effects at Higher Biological Levels - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 119

Normal autophagic
turnover; antioxidant
defenses effective

Oxidative stress and protective effect
of autophagy

100%

Augmented autophagic turnover
effective for removal of oxidatively
damaged proteins and organelles;
standard antioxidant defenses
compromised

Tier 1
defense

Autophagic turnover
compromised; antioxidant
defences ineffective;
irreversible cell injury and cell
death

Tier 2
defense

Tier 3
defense

0%

Healthy

Stressed Diseased

Cellular health status

FIGURE 5.6
Relationship between lysosomal stability and cellular health status, showing how autophagic degradation acts
as a second tier of defense against oxidative stress, and possibly as a third tier when autophagic capabilities are
compromised and the autophagic system may trigger cell death (i.e., apoptotic—type I, autophagic—type II, or
necrotic—type III) for removal of irreversibly damaged cells. Lysosomal stability is used here as an integrated
indicator of cellular well-being, that can be used as a generic yard-stick for interpreting the responses of many
biomarkers. (From Allen, J.I., Moore M.N., Mar. Environ. Res. , 58, 227-232, 2004; Moore, M.N. et al. Mutat. Res .,
552, 247-268, 2004a; Moore, M.N. et al., ICES Techniques in Marine Environmental Sciences (ICES, Copenhagen), 36,
1-31, 2004b; Moore, M.N. et al., Mar. Environ. Res. , 61, 278-304, 2006a. With permission.)

5.5 Can Lysosomal Biomarkers Be Developed for New Applications?
5.5.1 Understanding the Broader Significance of Autophagy in Evolution
of Tolerance to Fluctuating Environments and Pollutant Stress

Given that autophagic turnover is strongly evolutionarily conserved in the eukaryotes, it
is conjectured that up-regulation of autophagy may play a significant role in adaptation to
environments where induced oxidative stress is a major physiological problem, and where
the facility to rapidly sequester and recycle oxidatively damaged proteins and organ-
elles will provide a selective advantage (Cuervo 2004; Moore et al. 2006c, 2007). Estuarine
and coastal environments, where fluctuating salinity, nutrient, temperature, and oxygen
regimes are all important selective drivers and also inducers of autophagy, are likely to
be areas where it would be an adaptive advantage to be able to minimize the effects of
oxidative stress (Moore et al. 2006c, 2007). Furthermore, because near-shore and estuarine
environments are those most likely to be subjected to adverse human impacts, we have
a scenario where effective antioxidant protection may provide an evolutionary advan-
tage (Moore et al. 2006c). Consequently, we would expect to observe functional ecologi-
cal groupings of organisms in coastal and estuarine environments that have generic and