Monitoring of Low-Intensity Exposures via Luminescent Bioassays of Different Complexity: Cells, Enzyme Reactions, and Fluorescent Proteins

Abstract

The current paper reviews the applications of luminescence bioassays for monitoring the results of low-intensity exposures which produce a stimulative effect. The impacts of radioactivity of different types (alpha, beta, and gamma) and bioactive compounds (humic substances and fullerenols) are under consideration. Bioassays based on luminous marine bacteria, their enzymes, and fluorescent coelenteramide-containing proteins were used to compare the results of the low-intensity exposures at the cellular, biochemical, and physicochemical levels, respectively. High rates of luminescence response can provide (1) a proper number of experimental results under comparable conditions and, therefore, proper statistical processing, with this being highly important for “noisy” low-intensity exposures; and (2) non-genetic, i.e., biochemical and physicochemical mechanisms of cellular response for short-term exposures. The results of cellular exposures were discussed in terms of the hormesis concept, which implies low-dose stimulation and high-dose inhibition of physiological functions. Dependencies of the luminescence response on the exposure time or intensity (radionuclide concentration/gamma radiation dose rate, concentration of the bioactive compounds) were analyzed and compared for bioassays of different organization levels.

Enzymatic Responses to Low-Intensity Radiation of Tritium

“…Therefore, luminous bacteria at initial stages of exposure ( Figure 1 B [ 16 ]) and the bacterial system of the coupled enzyme reactions ( Figure 3 ) demonstrated similar bioluminescence responses to tritium. The conclusion can be made that the coupled enzymatic reactions contribute to the adaptive response of the bacteria.…”

“…A prospect for evaluating the radiotoxic or radioprotective response can occur for luminous bacteria, systems of their coupled enzymatic reactions [16,25], as well as for individual enzymatic reactions.…”

“…By this, we compare the sensitivity of the biological systems of different levels of organization (cells, a coupled enzyme system, individual enzyme reactions of two types, and the photobiochemical process of proton transfer) to the chronic low-dose tritium irradiation. The study develops the approach [16] for comparing the responses of biological systems of different complexities to low-intensity factors. Previously, a low-dose exposure of the CLM-FP to tritium radiation did not reveal the intensification of the photobiochemical proton transfer; only inhibition was observed [49].…”

“…Hormesis is considered as a basis for the most general toxicological model, which involves opposite response types: the activation of physiological functions under low-dose exposures and their inhibition by higher doses. Two other toxicological models, linear and threshold, might be considered as particular cases of hormesis [ 8 , 15 , 16 , 17 ]. It is supposed that hormesis is a highly general phenomenon that is independent from the biological model and the level of organization of a biological system (e.g., cell, organ, or organism) [ 9 ].…”

Novel Segmented Concentration Addition Method to Predict Mixture Hormesis of Chlortetracycline Hydrochloride and Oxytetracycline Hydrochloride to Aliivibrio fischeri

“…Hormesis is a concentration-response phenomenon characterized by low-concentration stimulation and high-concentration inhibition [1], which typically has a nonmonotonic CRC [2]. For example, herbicide 2,4-D in low concentration (10-30 µg/L) had significant stimulatory effect on plant root growth [3].…”