Hormesis provides a generalized quantitative estimate of biological plasticity

Abstract

Phenotypic plasticity represents an environmentally-based change in an organism's observable properties. Since biological plasticity is a fundamental adaptive feature, it has been extensively assessed with respect to its quantitative features and genetic foundations, especially within an ecological evolutionary framework. Toxicological investigations on the dose-response continuum (i.e., very broad dose range) that include documented evidence of the hormetic dose response zone (i.e., responses to doses below the toxicological threshold) can be employed to provide a quantitative estimate of phenotypic plasticity. The low dose hormetic stimulation is an adaptive response that reflects an environmentally-induced altered phenotype and provides a quantitative estimate of biological plasticity. Analysis of nearly 8,000 dose responses within the hormesis database indicates that quantitative features of phenotypic plasticity are highly generalizable, being independent of biological model, endpoint measured and chemical/physical stress inducing agent. The magnitude of phenotype changes indicative of plasticity is modest with maximum responses typically being approximately 30-60% greater than control values. The present findings provide the first quantitative estimates of biological plasticity and its capacity for generalization. Summary This article provides the first quantitative estimate of biological plasticity that may be generalized across plant, microbial, animal systems, and across all levels of biological organization. The quantitative features of plasticity are described by the hormesis dose response model. These findings have important biological, biomedical and evolutionary implications.

Fig. 1

Biological plasticity: A key to survival

Fig. 2

a Toxicologically based hormetic dose response. b Application of hormetic dose response to plasticity concept in toxicology

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 3

Selected examples of hormetic dose responses reflecting its occurrence across various biological models, endpoints, and chemical stressor agents

Fig. 4

Application of hormesis-based biphasic plasticity concept to animal behavior. • This example of hormesis-based plasticity indicates that a spectrum of behaviors (e.g. passivity, cautiousness, non-exploratory to aggressiveness, exploratory, boldness, “bravery”) can be adaptive and that these are modulated and expressed within the context of the hormetic dose response relationship. It would also be expected that some responses may be adaptive within a stimulatory and inhibitory mode. • In some cases one would expect an inverted U-shaped response with the high dose not having a response going below the control group (Calabrese ; Zoladz and Diamond 2009)

Fig. 5

Application of hormesis-based plasticity concept to pharmaceutical use of anxiolytic drugs