Indirect Effects of Radiation Induce Apoptosis and Neuroinflammation in Neuronal SH-SY5Y Cells

Abstract

Recent studies have evaluated the role of direct radiation exposure in neurodegenerative disorders; however, association among indirect effects of radiation and neurodegenerative diseases remains rarely discussed. The objective of this study was to estimate the relative risk of neurodegeneration due to direct and indirect effects of radiation. (60)Co gamma ray was used as source of direct radiation whereas irradiated cell conditioned medium (ICCM) was used to mimic the indirect effect of radiation. To determine the potency of ICCM to inhibit neuronal cells survival colony forming assay was performed. The role of ICCM to induce apoptosis in neuronal SH-SY5Y cells was estimated by TUNEL assay and Annexin V/PI assay. Level of oxidative stress and the concentration of inflammatory cytokines after exposing to direct radiation and ICCM were evaluated by ELISA method. Expression of key apoptotic protein following direct and indirect radiation exposure was investigated by western blot technique. Experimental data manifest that ICCM account loss of cell survival and increase apoptotic induction in neuronal SH-SY5Y cells that was dependent on time and dose. Moreover, ICCM stimulate significant release of inflammatory cytokines i.e., tumor necrosis factor TNF-alpha (P < 0.01), Interleukin-1 (IL-1, P < 0.001), and Interleukin-6 (IL-6, P < 0.001) in neuronal SH-SY5Y cells and elevate the level of oxidative stress (MDA, P < 0.01). Up-regulation of key apoptotic protein expression i.e., Bax, Bid, cytochrome C, caspase-8 and caspase-3 confirms the toxicity of ICCM to neuronal cells. This study provides the evidence that indirect effect of radiation can be as much damaging to neuronal cells as direct radiation exposure can be. Hence, more focused research on estimation risks of indirect effect of radiation to CNS at molecular level may help to reduce the uncertainty about cure and cause of several neurodegenerative disorders.

The differential role of human macrophage in triggering secondary bystander effects after either gamma-ray or carbon beam irradiation

“…Interestingly, the yield of MN in the BASE-2B cells was enhanced to a middle level by TNF-α independent of its concentration but the MN yield was increased along with the concentration of IL-1α and approached to a much high level (Figs. 6C and 6D), which is consistent with other reports [51, 52]. Considering the dose relationship of MN induction in the secondary bystander cells and the kinetics of cytokine generations in both irradiated H446 cells and intermediate U937 cells, it can be proposed that a small portion of MN in the secondary bystander cells is induced by TNF-α uniformly and the other major part of MN is induced by IL-1α released from the intermediate U937 cells in a dose dependent manner.…”

Glial U87 cells protect neuronal SH-SY5Y cells from indirect effect of radiation by reducing oxidative stress and apoptosis

“…Previous studies have shown that glial U87 (astrocyte-like) cells protect neuroblastoma SK-N-SH (neuron-like) cells against neurodegenerative assaults [16]. Furthermore, recent studies have revealed the role of indirect effect of radiation in neurodegeneration [2]. In view of these facts, this study was designed to investigate the indirect effect of radiation on neuronal SH-SY5Y cells in the presence of glial U87 cells.…”

“…However, the intensity of this interaction depends on cell type, cellular growth state, type of radiation, and the biological endpoint being measured [1]. Recent reports have demonstrated the role of indirect effects of radiation in neurodegeneration [2]. Several aspects still require further exploration for a comprehensive interpretation about role of indirect radiation in neurodegeneration.…”

“…These reports may bring us to conclude that radiation-induced late effects are driven in part by chronic oxidative stress, which determined the oxidative stress as a main player in prompting the indirect effect of radiation in neurodegeneration [6]. Hence, the possibility of neurological damage induced by indirect effect of radiation could not be ignored [2].…”

The impact of high and low dose ionising radiation on the central nervous system

“…Cell viability and apoptosis are important implications of high dose irradiation across the cell populations of the CNS, as gamma irradiation at 10 Gy in cell cultures reduces cell survival and increases apoptosis through the up-regulation of key apoptotic proteins, including cytochrome-c, caspase-3 and decreased expression of anti-apoptotic Bcl-2. Concomitantly, elevated pro-inflammatory cytokines TNF-α, IL-1β and IL-6 and lipid peroxidation markers relative to sham irradiated controls also highlights critical inflammatory responses after high dose ionising radiation that can propagate radiation-induced injury [89].…”