Targeted Central Nervous System Irradiation with Proton Microbeam Induces Mitochondrial Changes in Caenorhabditis elegans

Abstract

Fifty percent of all patients with cancer worldwide require radiotherapy. In the case of brain tumors, despite the improvement in the precision of radiation delivery with proton therapy, studies have shown structural and functional changes in the brains of treated patients with protons. The molecular pathways involved in generating these effects are not completely understood. In this context, we analyzed the impact of proton exposure in the central nervous system area of Caenorhabditis elegans with a focus on mitochondrial function, which is potentially implicated in the occurrence of radiation-induced damage. To achieve this objective, the nematode C. elegans were micro-irradiated with 220 Gy of protons (4 MeV) in the nerve ring (head region) using the proton microbeam, MIRCOM. Our results show that protons induce mitochondrial dysfunction, characterized by an immediate dose-dependent loss of the mitochondrial membrane potential (ΔΨm) associated with oxidative stress 24 h after irradiation, which is itself characterized by the induction of the antioxidant proteins in the targeted region, observed using SOD-1::GFP and SOD-3::GFP strains. Moreover, we demonstrated a two-fold increase in the mtDNA copy number in the targeted region 24 h after irradiation. In addition, using the GFP::LGG-1 strain, an induction of autophagy in the irradiated region was observed 6 h following the irradiation, which is associated with the up-regulation of the gene expression of pink-1 (PTEN-induced kinase) and pdr-1 (C. elegans parkin homolog). Furthermore, our data showed that micro-irradiation of the nerve ring region did not impact the whole-body oxygen consumption 24 h following the irradiation. These results indicate a global mitochondrial dysfunction in the irradiated region following proton exposure. This provides a better understanding of the molecular pathways involved in radiation-induced side effects and may help in finding new therapies.

Proton Microbeam Targeted Irradiation of the Gonad Primordium Region Induces Developmental Alterations Associated with Heat Shock Responses and Cuticle Defense in Caenorhabditis elegans

“…During the experiment, at least 300 nematodes were micro-irradiated with 300 Gy of protons (3 MeV) in the Z2-Z3 area. The selected dose is in agreement with previous experiments performed on C. elegans, with doses ranging from 100 to 400 Gy [17,[41][42][43].…”

“…Extending this approach to charged-particle microbeams could help to characterize the specific radiationinduced biological responses. Charged-particle microbeams provide the possibility of selectively irradiating living cells with a precise dose and dose delivery timing [13][14][15][16][17][18]. Initially developed to target adherent mammalian cells, the use of charged-particle microbeams have progressively broadened to encompass the irradiation of three-dimensional tissue models and small in vivo multicellular system [19][20][21][22].…”

“…Amongst the well-characterized biological models, the nematode C. elegans is particularly suited to the specific constraints of targeted irradiations [16,[23][24][25]. And several reports have detailed the use of C. elegans at charged-particle microbeam end stations [16,17,23,24,[26][27][28].…”

Preventive Action of Beta-Carotene against the Indoxyl Sulfate-Induced Renal Dysfunction in Male Adult Zebrafish via Regulations of Mitochondrial Inflammatory and β-Carotene Oxygenase-2 Actions

“…The isoform of SOD2 is specifically located in the inner mitochondrial matrix [73]. All three isoforms contribute to the regulation of mitochondrial membrane potential and mitochondrial electron transport chain functions [74]. Moreover, the antioxidative defense enzymes, i.e., SOD2 and GPX1, contribute to the progression of renal dysfunction [75].…”