Mechanism of Action and Use of Radiomimetic Compounds (Part 2)

Abstract

Radiomimetic compounds, similarly to ionising radiation can directly or indirectly cause DNA damage. Two major groups of these compounds, alkylating agents and antimetabolites, have already been discussed in the first part of this article. The topic of this article is an overview of radiomimetic substances of biological origin; they are grouped and discussed upon their chemical structure. Some bacteria, belonging to the class of Actinobacteria can produce compounds with radiomimetic property as part of their defence mechanisms, such as bleomycins, enediynes, streptonigrins, etc. Radiomimetic compounds of bacterial origin can be divided into three main groups: radiomimetic glycopeptides, enediynes and quinone antibiotics. Each of them induces double-strand DNA breaks. Some of them work through their reactive radicals and the molecules are also transformed when they break DNA. Others, such as bleomycin and similar glycopeptides, have an enzyme-like catalytic effect as the molecule regenerates itself after interacting with DNA thus the same molecule can create new DNA breaks again. The damage caused by radiation and by bleomycin is very similar: double DNA strand breaks occur in close proximity to each other, below the lethal dose of the cell, so as the cell does not die, the DNA repair process is activated, which can lead to the formation of dicentric chromosomes and other detectable DNA alterations. This review briefly summarises the mechanism of action of bacterial radiomimetic compounds and their benefit.

Comet Assay: Multifaceted Options for Studies of Plant Stress Response

“…DNA damage in plants can be caused by environmental agents or can arise from endogenous sources. Environmental genotoxins include factors such as ionizing radiation, UV light, heavy metals, and an excess of aluminum or boron, as well as natural toxins, for instance antibiotics of the bleomycin family [24][25][26][27][28][29][30][31][32][33]; there are also a number of chemical mutagens (reviewed in [34][35][36]). Endogenous factors leading to DNA damage include reactive oxygen, nitrogen, and carbon species (ROS, RNS, and RCS); the spontaneous or enzymatic release of DNA bases, leading to the formation of apyrimidine/apurine (AP) sites; errors in DNA replication and recombination; and the activity of plant DNases (reviewed in [1,37]).…”

“…Common genotoxic stress factors include ionizing radiation such as gamma irradiation, X-rays, and short-waved UV-C, as well as exposure to radiomimetics, a large group of compounds acting directly on DNA-like alkylating agents and antibiotics of the bleomycin family, or drugs inhibiting DNA synthesis and repair like, e.g., antimetabolites [32,33].…”