Mannan oligosaccharide requires functional ETC and TLR for biological radiation protection to normal cells

Sweta Sanguri,Damodar Gupta

doi:10.1186/s12860-018-0161-4

Abstract

BackgroundLow LET Ionizing radiation is known to alter intracellular redox balance by inducing free radical generation, which may cause oxidative modification of various cellular biomolecules. The extent of biomolecule-modifications/ damages and changes in vital processes (viz. cellular homeostasis, inter−/intra-cellular signaling, mitochondrial physiology/dynamics antioxidant defence systems) are crucial which in turn determine fate of cells.ResultsIn the present study, we expended TLR expressing (normal/ transformed) and TLR null cells; and we have shown that mannan pretreatment in TLR expressing normal cells offers survival advantage against lethal doses of ionizing radiation. On the contrary, mannan pretreatment does not offer any protection against radiation to TLR null cells, NKE ρ° cells and transformed cells. In normal cells, abrupt decrease in mitochondrial membrane potential and endogenous ROS levels occurs following treatment with mannan. We intend to irradiate mannan-pretreated cells at a specific stage of perturbed mitochondrial functioning and ROS levels to comprehend if mannan pretreatment offers any survival advantage against radiation exposure to cells. Interestingly, pre-irradiation treatment of cells with mannan activates NFκB, p38 and JNK, alters mitochondrial physiology, increases expression of Cu/ZnSOD and MnSOD, minimizes oxidation of mitochondrial phospholipids and offers survival advantage in comparison to irradiated group, in TLR expressing normal cells.ConclusionThe study demonstrates that TLR and mitochondrial ETC functions are inevitable in radio-protective efficacy exhibited by mannan.

Highlights

Low LET Ionizing radiation is known to alter intracellular redox balance by inducing free radical generation, which may cause oxidative modification of various cellular biomolecules
Mannan (5 μg/ ml – 40 μg/ml) showed significant increase in hydrolyzed ONPG conc. (NFκB activity) up to 30 μg/ml, further increase in concentration showed no significant changes. 293/toll like receptor (TLR)-ve-lacZ+ve cells were taken as negative control and no significant color development of hydrolyzed ONPG was observed in case of at any treatment concentrations of mannan (Fig. 1)
The concentration of mannan in mediating changes in NFκB activation corroborates with changes in intracellular Mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) generation

Summary

Introduction

Low LET Ionizing radiation is known to alter intracellular redox balance by inducing free radical generation, which may cause oxidative modification of various cellular biomolecules. Several agonists of TLRs have been shown to possess protective efficacy against lethal effects of ionizing radiation and are currently under different stages of development as radiation countermeasure agent for ARS [4, 6, 7, 9]. Most of these have been screened for their ability to activate NFκB pathway and reduce radiation-induced cell death in various tissues [4]. In the present study we have shown that, mannan mediated alterations in mitochondrial physiology in immortalized normal cells reduces biological effects of γ-radiation and enhances the cell survival

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Discussion

Conclusion