1. Is this the right time for non-linear thinking
Is this the right time for non-linear thinking? Hormesis for dose responses
Evgenios AGATHOKLEOUS1,2,
contact:
1 JSPS international research fellow at Forestry & Forest Products
Research Institute (FFPRI), Hokkaido Research Center, Japan
2Hokkaido University, Japan
School of Agriculture
Lab. of Silviculture & Forest Ecology

2. 1. Dose response
History
"All things are poison and nothing is without poison; only the dose makes a thing not a poison” (Paracelsus)
The influence of Dr. Hermann Muller
(Nobel Prize in Physiology or Medicine 1946)
X-rays produced gene mutations in fruit flies (Muller 1927)
Proportionality Rule to characterize the effects of ionizing radiation on gene mutation (Muller, 1930)
2.5 decades of tension among radiation genetics and medical communities
Should the threshold dose-response model be replaced by a linear one for radiation (and later chemical) induced mutation?
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

3. 1. Dose response
History
National Academy of Sciences of the United States of America (Calabrese 2017a,b,c)
The carrying-over effect of the BEAR I Genetics
Panel (1956)
Major change in 1956: switch from the threshold to the linear no threshold (LNT) single hit model for reproductive cells (Calabrese 2017)
Radiation-induced genetic damage: cumulative and irreversible dose– response: linear
The recommendation by BEAR-1 Genetics Panel was generalized to somatic cells within several years and applied to cancer risk assessment (Calabrese 2014)
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

4. 1. Dose response
History
These changes led to a two tier system for risk assessment:
one for cancer risk assessment that would follow a linear dose-response and one for noncarcinogens that would follow a threshold dose-response.
The linear model assumed that induced mutations were not reparable and the damage was cumulative, leading to the belief that total dose, rather than dose rate, was the best predictor of damage.
By the end of the 1970s, all regulatory agencies in the U.S. had transitioned to the two tier approach with thresholds for non- carcinogens and LNT for carcinogens (Calabrese, 2009, 2015, 2016, 2017; Puskin, 2009; Calabrese & O’Connor 2014; Calabrese et al. 2015).
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

5. 1. Dose response
History
The general course of action for ecological risk assessment was initially framed by a threshold dose-response model assumption
This was the general state-of-the-art during later decades of the 20th century
However, over this time period new perspectives and challenges would emerge that could affect the process for risk assessment for carcinogens and non- carcinogens for humans and ecological receptors
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

6. 1. Dose response
History
The most significant developments involved the rediscovery and substantial documentation of the hormetic-biphasic dose-response.
The second was the concept that linear dose responses may be applied to some non-cancer endpoints, the effects of some endocrine disruptor agencies for humans, and the case of O3-induced injury on plants
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

7. Response as % of control
2. Dose response
LNT model
No threshold
Is one ppb of O3 toxic?
Response as % of control
School of Agriculture
Lab. of Silviculture & Forest Ecology
Exposure level
Agathokleous et al.

8. Response as % of control
2. Dose response
Threshold model
Toxicological threshold below which response is zero
threshold
Response as % of control
School of Agriculture
Lab. of Silviculture & Forest Ecology
Exposure level
Agathokleous et al.

9. Response as % of control
3. Dose response
Hormetic model
Biphasic dose response
The basis for hormesis dates approximately 130 years back, when Schulz experimented with yeast (Schulz, 1887, 1888) and Hueppe with bacteria (Hueppe, 1986)
Hormesis: (from the Greek word ὁρμέειν) was later termed by Southam and Ehrlich (1943)
NOAEL
Response as % of control
School of Agriculture
Lab. of Silviculture & Forest Ecology
Exposure level
Agathokleous et al.

10. Hormetic model 3. Dose response
Hundreds of agents and mixtures were found to induce hormesis across various experimental models including plants, algae, animals, bacteria, protozoa, microcosms, phytoplankton, viruses and mesocoms (Calabrese, 2001, 2015b, Calabrese & Baldwin, 2001, 2003b; Cedergreen et al., 2007; Cutler, 2013)
Hormesis was observed in many endpoints, such as behavior, growth, metabolism, survival and immunity, and is a matter of topics ranging from cell level to individual and community levels (Calabrese, 2001, 2015b; Calabrese & Baldwin, 2003b; Hayes, 2008)
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

11. Hormetic model 3. Dose response
Chemical and radiation hormesis commonly occurs in plants, as it has been observed thousands times and in more thousands endpoints, and has quantitative features similar to hormesis in animals, with MAX <200% of controls and a width < 10-fold (rarely >100-fold) in dose range (Calabrese and Blain, 2005, 2009, 2011; Hadacek et al., 2011; Cedergreen et al., 2005, 2007; Belz et al., 2008; Belz and Piepho, 2013; Calabrese, 2013b, 2015; Poschenrieder et al., 2013; Abbas et al., 2017; Agathokleous, 2017).
Hormesis is generalized as to stressor, plant species and biological endpoints (Calabrese and Baldwin, 2002, Cedergreen et al., 2007; Calabrese, 2005; Calabrese and Blain, 2005, 2009, 2011)
Satisfies the evaluation criteria and should serve as the default model in risk assessment of carcinogens and noncarcinogens for the purposes of regulatory agencies (Calabrese and Baldwin, 2003a,b; Calabrese, 2004, 2005, 2015; Cook and Calabrese, 2006).
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

12. Response as % of control
3. Dose response
Hormetic model
Things become more exciting….
MAX
MAX
MAX
NOAEL (or ZEP)
Response as % of control
DT=1-fold
1-fold
1-fold
DT=3-fold
1-fold
DT=5-fold
School of Agriculture
Lab. of Silviculture & Forest Ecology
Exposure level
Agathokleous et al.

13. Hormetic model 3. Dose response
Although not always mentioned in the scripts, indications for overcompensation stimulation in plants induced by low-level exposure to environmental factors have been previously found in the scientific literature for a variety of species and endpoints (e.g. Eamus et al., 1990; Yalpani et al., 1994; Pääkköönen et al., 1996; Ranieri et al., 2000; Gray et al., 2003; Hernández et al., 2004; Luo et al., 2009; Nikolova et al., 2010; Calatayud et al., 2011; Ye et al., 2011; Franzaring et al., 2013; Hoshika et al., 2013; Rozpadek et al., 2013, 2015; Vázquez-Ybarra et al., 2015; Carriero et al., 2016; Mashaheet, 2016; Sugai et al. 2018).
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

14. Hormetic model 3. Dose response
Environmental factors can also induce hormesis…..
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

15. 4. Message
The discipline of dose responses is greatly developed in the last two decades
Contemporary high-resolution experiments have widely indicated the fundamental need for a biphasic model in describing dynamic biological responses in numerous biological models
This would be the right time to consider biphasic dose-response relationships for ecosystem health
We need to provide contemporary scientific knowledge to decision makers of regulatory agencies for the benefit of the society
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

16. Thank you!
"Nothing under the sun is greater than education. By educating one person and sending him into the society of his generation, we make a contribution extending a hundred generations to come."
Acknowledgements: E. Agathokleous is a JSPS International Research Fellow. JSPS is a non-profit organization.
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.

17. If you are interested in my research please contact me!
Agathokleous, E., Paoletti, E., Manning, W.J., Kitao, M., Saitanis, C.J., Koike, T. (2018). High doses of ethylenediurea (EDU) as soil drenches did not increase leaf N content or cause phytotoxicity in willow grown in fertile soil. Ecotoxicology and Environmental Safety 147:
Agathokleous, E., Kitao, M., Kinose, Y. (2018). A review study on O3 phytotoxicity metrics for setting critical levels in Asia. Asian Journal of Atmospheric Environment 12(1). [In Press]
Agathokleous, E. (2017). Perspectives for elucidating the ethylenediurea (EDU) mode of action for protection against O3 phytotoxicity. Ecotoxicology and Environmental Safety 142:
Agathokleous, E., Sakikawa, T., Abu El-Ela, S.A., Mochizuki, T., Nakamura, M., Watanabe, M., Kawamura, K., Koike, T. (2017). Ozone alters the feeding behavior of the leaf beetle Agelastica coerulea (Coleoptera: Chrysomelidae) into leaves of Japanese white birch (Betula platyphylla var. japonica). Environmental Science and Pollution Research 24: 17577–17583.
Agathokleous, E., Vanderstock, A., Kita, K., Koike, T. (2017). Stem and crown growth of Japanese larch and its hybrid F1 grown in two soils and exposed to two free-air O3 regimes. Environmental Science and Pollution Research 24:
Agathokleous, E., Saitanis, C.J., Burkey, K.O., Ntatsi, G., Vougeleka, V., Mashaheet, A-S.M., Pallides, A. (2017). Application and further characterization of the snap bean S156/R123 ozone biomonitoring system in relation to ambient air temperature. Science of the Total Environment 580:
Agathokleous, E., Paoletti, E., Saitanis, C.J., Manning, W.J., Sugai, T., Koike, T. (2016). Impacts of ethylene diurea (EDU) soil drench and foliar spray in Salix sachalinensis protection against O3-induced injury. Science of the Total Environment 573:
Agathokleous, E., Saitanis, C.J., Stamatelopoulos, D., Mouzaki-Paxinou, A.-C., Paoletti, E., Manning, W.J. (2016). Olive oil for dressing plant leaves so as to avoid O3 injury. Water, Air & Soil Pollution 227:282.
Agathokleous, E., Paoletti, E., Saitanis, C.J., Manning, W.J., Koike, T. (2016). High doses of ethylene diurea (EDU) are not toxic to willow and act as nitrogen fertilizer. Science of the Total Environment :
Agathokleous, E., Watanabe, M., Eguchi, N., Nakaji, T., Satoh, F., Koike, T. (2016). Root production of Fagus crenata Blume saplings grown in two soils and exposed to elevated CO2 concentration: an 11-year free-air-CO2 enrichment (FACE) experiment in northern Japan. Water, Air, & Soil Pollution, 227: 187.
Agathokleous, E., Mouzaki-Paxinou, A.-C., Saitanis, C.J., Paoletti, E., Manning, W.J. (2016) The first toxicological study of the antiozonant and research tool ethylene diurea (EDU) using a Lemna minor L. bioassay: Hints to its mode of action. Environmental Pollution, 213:
Agathokleous, E., Watanabe, M., Nakaji, T., Wang, X., Satoh, F., Koike, T. (2016). Impact of elevated CO2 on root traits of a sapling community of three birches and an oak: a free-air-CO2 enrichment (FACE) in northern Japan. Trees: Structure and Function, 30:
Agathokleous, E., Saitanis, C.J., Wang, X., Watanabe, M., Koike, T. (2016). A review study on past 40 years of research on effects of tropospheric O3 on belowground structure, functioning and processes of trees: a linkage with potential ecological implications. Water, Air, & Soil Pollution, 227:33.
Agathokleous, E., Koike, T., Watanabe, M., Hoshika, Y., Saitanis, C.J. (2015). Ethylene-di-urea (EDU), an effective phytoprotectant against O3 deleterious effects and a valuable research tool. Journal of Agricultural Meteorology, 71(3):
Agathokleous, E., Saitanis, C.J., Koike, T. (2015). Tropospheric O3, the nightmare of wild plants: A review study. Journal of Agricultural Meteorology, 71(2):
School of Agriculture
Lab. of Silviculture & Forest Ecology
Agathokleous et al.