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Regulation of autophagy via PERK-eIF2α effectively relieve the radiation myelitis induced by iodine-125.

Yang Z, Xu Y, Xu L, Maccauro G, Rossi B, Chen Y, Li H, Zhang J, Sun H, Yang Y, Xu D, Liu X - PLoS ONE (2013)

Bottom Line: The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells.The results were consistent with that by MTT and Annexin-FITC/PT staining.The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics, Kunming General Hospital of Chengdu Military Command, the Third Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, P. R. China ; Department of Orthopaedic Oncology, Agostino Gemelli Hospital, Catholic University of Rome, Largo Francesco Vito 1, Rome, Italy.

ABSTRACT
Radiation myelitis is the most serious complication in clinical radiotherapy for spinal metastases. We previously showed that (125)I brachytherapy induced apoptosis of spinal cord neurons accompanied by autophagy. In this study, we further investigated the mechanism by which (125)I radiation triggered autophagy in neural cells. We found that autophagy induced by (125)I radiation was involved in endoplasmic reticulum (ER) stress and mainly dependent on PERK-eIF2α pathway. The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells. Meanwhile, the expressions of phosphorylated-Akt s473 and caspase3/8 all significantly increased in neural cells transfected with a PERK siRNA and which enhanced apoptosis of neurons after (125)I radiation. The results were consistent with that by MTT and Annexin-FITC/PT staining. In animal model of banna pigs with radiation myelitis caused by (125)I brachytherapy, we have successfully decreased PERK expression by intrathecal administration of the lentivirus vector. The apoptosis rate was significantly higher than that in control group and which deteriorated radiation myelitis of banna pigs. Thus, autophagy caused by (125)I radiation was mainly as an attempt of cell survival at an early stage, but it would be a self-destructive process and promoted the process of apoptosis and necrosis radiated by (125)I for more than 72 hours. The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.

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Induction of autophagy by 125I was dependent on PERK-eIF2α signal pathway.(A) Neural cells were treated with 125I for 5 days and tunicamycin (TUN) for 24 h. The levels of protein from PERK-eIf2α pathway were measured by immunoblot analyses. Results shown in each panel were representative of at least three independent experiments. (B) Quantification of the levels of protein from PERK-eIf2α pathway in neural cells following 24 h of treatment with tunicamycin (TUN) or 125I. Neuron cells treated with TUN were as positive controls and the untreated neurons were as negative controls (NSC-0). Data were representative of mean ± SEM. *, statistically significance in one-way anova test; *, P<0.05; **, P<0.005; ***, P<0.0005.
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pone-0076819-g003: Induction of autophagy by 125I was dependent on PERK-eIF2α signal pathway.(A) Neural cells were treated with 125I for 5 days and tunicamycin (TUN) for 24 h. The levels of protein from PERK-eIf2α pathway were measured by immunoblot analyses. Results shown in each panel were representative of at least three independent experiments. (B) Quantification of the levels of protein from PERK-eIf2α pathway in neural cells following 24 h of treatment with tunicamycin (TUN) or 125I. Neuron cells treated with TUN were as positive controls and the untreated neurons were as negative controls (NSC-0). Data were representative of mean ± SEM. *, statistically significance in one-way anova test; *, P<0.05; **, P<0.005; ***, P<0.0005.

Mentions: Based on previous in vitro results, the rat neurons were continuously exposed at 24mCi for 5 days. As demonstrated in Figure 3A, western blot analysis demonstrated that the expression levels of PERK, eIF2α, ATF4 and LC3-II highly increased. We also detected the phosphorylation levels of PERK and eIF2 after 125I irradiation. The results showed that phosphorylation levels of PERK and eIF2 were highly elevated at 24mCi for 5 days. Here, neural cells stimulated by tunicamycin were as positive controls and untreated neurons were used as negative controls. This was consistent with that by real time RT-PCR (Figure 3B).


Regulation of autophagy via PERK-eIF2α effectively relieve the radiation myelitis induced by iodine-125.

Yang Z, Xu Y, Xu L, Maccauro G, Rossi B, Chen Y, Li H, Zhang J, Sun H, Yang Y, Xu D, Liu X - PLoS ONE (2013)

Induction of autophagy by 125I was dependent on PERK-eIF2α signal pathway.(A) Neural cells were treated with 125I for 5 days and tunicamycin (TUN) for 24 h. The levels of protein from PERK-eIf2α pathway were measured by immunoblot analyses. Results shown in each panel were representative of at least three independent experiments. (B) Quantification of the levels of protein from PERK-eIf2α pathway in neural cells following 24 h of treatment with tunicamycin (TUN) or 125I. Neuron cells treated with TUN were as positive controls and the untreated neurons were as negative controls (NSC-0). Data were representative of mean ± SEM. *, statistically significance in one-way anova test; *, P<0.05; **, P<0.005; ***, P<0.0005.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3818370&req=5

pone-0076819-g003: Induction of autophagy by 125I was dependent on PERK-eIF2α signal pathway.(A) Neural cells were treated with 125I for 5 days and tunicamycin (TUN) for 24 h. The levels of protein from PERK-eIf2α pathway were measured by immunoblot analyses. Results shown in each panel were representative of at least three independent experiments. (B) Quantification of the levels of protein from PERK-eIf2α pathway in neural cells following 24 h of treatment with tunicamycin (TUN) or 125I. Neuron cells treated with TUN were as positive controls and the untreated neurons were as negative controls (NSC-0). Data were representative of mean ± SEM. *, statistically significance in one-way anova test; *, P<0.05; **, P<0.005; ***, P<0.0005.
Mentions: Based on previous in vitro results, the rat neurons were continuously exposed at 24mCi for 5 days. As demonstrated in Figure 3A, western blot analysis demonstrated that the expression levels of PERK, eIF2α, ATF4 and LC3-II highly increased. We also detected the phosphorylation levels of PERK and eIF2 after 125I irradiation. The results showed that phosphorylation levels of PERK and eIF2 were highly elevated at 24mCi for 5 days. Here, neural cells stimulated by tunicamycin were as positive controls and untreated neurons were used as negative controls. This was consistent with that by real time RT-PCR (Figure 3B).

Bottom Line: The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells.The results were consistent with that by MTT and Annexin-FITC/PT staining.The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedics, Kunming General Hospital of Chengdu Military Command, the Third Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, P. R. China ; Department of Orthopaedic Oncology, Agostino Gemelli Hospital, Catholic University of Rome, Largo Francesco Vito 1, Rome, Italy.

ABSTRACT
Radiation myelitis is the most serious complication in clinical radiotherapy for spinal metastases. We previously showed that (125)I brachytherapy induced apoptosis of spinal cord neurons accompanied by autophagy. In this study, we further investigated the mechanism by which (125)I radiation triggered autophagy in neural cells. We found that autophagy induced by (125)I radiation was involved in endoplasmic reticulum (ER) stress and mainly dependent on PERK-eIF2α pathway. The expressions of LC3II, ATG12 and PI3K were significantly suppressed in PERK knockout neural cells. Meanwhile, the expressions of phosphorylated-Akt s473 and caspase3/8 all significantly increased in neural cells transfected with a PERK siRNA and which enhanced apoptosis of neurons after (125)I radiation. The results were consistent with that by MTT and Annexin-FITC/PT staining. In animal model of banna pigs with radiation myelitis caused by (125)I brachytherapy, we have successfully decreased PERK expression by intrathecal administration of the lentivirus vector. The apoptosis rate was significantly higher than that in control group and which deteriorated radiation myelitis of banna pigs. Thus, autophagy caused by (125)I radiation was mainly as an attempt of cell survival at an early stage, but it would be a self-destructive process and promoted the process of apoptosis and necrosis radiated by (125)I for more than 72 hours. The study would be useful and helpful to maximize efficiency of radiation therapy in clinical therapy.

Show MeSH
Related in: MedlinePlus