Adaptive response: some underlying mechanisms and open questions

Abstract

Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e.g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses -DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.

Gentiana asclepiadea and Armoracia rusticana can modulate the adaptive response induced by zeocin in human lymphocytes

“…The adaptive response involves the transcription of many genes and the activation of numerous signalling pathways that trigger cell defenses: more efficient detoxification of free radicals, DNA repair systems, induction of new proteins in irradiated/treated cells with conditioning dose, and enhanced antioxidant production [5]. One of the molecular mechanisms of adaptive response induced by zeocin in lymphocytes was SSBs and predominantly DSBs rejoining [4], similarly as proved before by Chankova et al in C. reinhardtii [4].…”

“…A lot of data are available concerning the use of zeocin as a selective agent for isolation of transformants in various testsystems [5,28] but data concerning DNA-damaging potential and zeocin molecular mechanism of action are scarce. Zeocin belongs to the bleomycin/phleomycin family of antibiotics which have radiomimetic properties (InvivoGEN, http://www.…”

“…Zeocin is a member of bleomycin/ phleomycin family of antibiotics isolated from culture broth of a Streptomyces verticullus mutant. It can bind to DNA and induce oxidative stress in different organisms producing predominantly single-(SSBs) and double-strand breaks (DSBs), as well as a DNA base loss resulting in apurinic/apyrimidinic (AP) sites [1,[4][5].…”

The expression of melanin-based plumage is separately modulated by exogenous oxidative stress and a melanocortin

“…A potential explanation could be that developing birds mounted an adaptive response (e.g. Dimova et al 2008) during the weeks of treatment, overcoming the initial challenge and reaching in fact higher levels of lipid integrity than those found in controls. However, we must be cautious in our conclusions because the specificity of the TBARS method has been questioned in respect of changes in lipid metabolism potentially interfering with their values (Monaghan et al 2009).…”

Radiation protection and secondary cancer prevention using biological radioprotectors in radiotherapy

“…There is a wealth of data showing a low level of radiation can induce so called "radioadaptive response" that during which biological systems which received a low dose of radiation become more resistant against any challenge dose of harmful agents (such as radiation). The main mechanism of radioadaptive response is unknown, but different experimental invivo/invitro studies by various endpoints have showed transcription of many genes and activation of numerous signaling pathways that trigger cell defenses more efficient detoxification of free radicals, DNA repair systems, induction of new proteins, enhanced antioxidant production, alteration in expression of genes associated with cell cycle regulation, DNA repair, signal transduction, apoptosis induction/tumorigenesis and damage response/ maintenance of genetic stability (P53-related functions), activation of protein kinase C through p38 MAP kinase resulting in P53, ERK, JNK kinases and WIP phosphatase activation and Ribose Polymerase-1 (PARP) activation 96 .…”