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Low-dose γ-radiation inhibits IL-1β-induced dedifferentiation and inflammation of articular chondrocytes via blockage of catenin signaling.

Hong EH, Song JY, Lee SJ, Park IC, Um HD, Park JK, Lee KH, Nam SY, Hwang SG - IUBMB Life (2014)

Bottom Line: Here, we found that LDR, at doses of 0.5-2 centiGray (cGy), inhibited interleukin (IL)-1β-induced chondrocyte destruction without causing side effects, such as cell death and senescence.LDR also inhibited chondrocyte destruction through the catenin pathway induced by epidermal growth factor, phorbol 12-myristate 13-acetate, and retinoic acid.Collectively, these results identify the molecular mechanisms by which LDR suppresses pathophysiological processes and establish LDR as a potentially valuable therapeutic tool for patients with cytokine- or soluble factors-mediated cartilage disorders.

View Article: PubMed Central - PubMed

Affiliation: Division of Radiation Cancer Biology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea; Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul, Korea.

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Involvement of PI3K/Akt signaling in LDR-induced inhibition of chondrocyte destruction. (A): Chondrocytes were treated with 0.5 or 1 cGy of LDR in the absence (−) or presence (+) of 10 ng/mL IL-1β for 20 min. Expression and phosphorylation status of ERK, p38, and JNK were determined by Western blotting. (B): Chondrocytes were treated with 10 ng/mL IL-1β for the indicated times (top), with or without pretreatment with 40 μM Triciribine for 1 h prior to IL-1β treatment (bottom). Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting. (C, D): Chondrocytes were left untreated or were pretreated with 10 or 20 μM LY294002 for 1 h prior to treatment with 10 ng/mL IL-1β. After 48 h, the levels of type II collagen, Sox-9, I-κB, and COX-2 proteins were assessed by Western blotting (C, top). NF-κB transcriptional activity was determined by reporter gene assay. Data are expressed as means ± SDs (**P < 0.005 and ***P < 0.0005 compared to cells treated with IL-1β alone (C, bottom). Levels of catenin proteins were detected by Western blotting (D). (E): Chondrocytes were treated with 0.5 or 1 cGy of LDR for 12 h in the absence (−) or presence (+) of 10 ng/mL IL-1β. Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting.
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fig03: Involvement of PI3K/Akt signaling in LDR-induced inhibition of chondrocyte destruction. (A): Chondrocytes were treated with 0.5 or 1 cGy of LDR in the absence (−) or presence (+) of 10 ng/mL IL-1β for 20 min. Expression and phosphorylation status of ERK, p38, and JNK were determined by Western blotting. (B): Chondrocytes were treated with 10 ng/mL IL-1β for the indicated times (top), with or without pretreatment with 40 μM Triciribine for 1 h prior to IL-1β treatment (bottom). Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting. (C, D): Chondrocytes were left untreated or were pretreated with 10 or 20 μM LY294002 for 1 h prior to treatment with 10 ng/mL IL-1β. After 48 h, the levels of type II collagen, Sox-9, I-κB, and COX-2 proteins were assessed by Western blotting (C, top). NF-κB transcriptional activity was determined by reporter gene assay. Data are expressed as means ± SDs (**P < 0.005 and ***P < 0.0005 compared to cells treated with IL-1β alone (C, bottom). Levels of catenin proteins were detected by Western blotting (D). (E): Chondrocytes were treated with 0.5 or 1 cGy of LDR for 12 h in the absence (−) or presence (+) of 10 ng/mL IL-1β. Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting.

Mentions: To identify the mechanisms by which LDR modulates chondrocyte phenotype, we examined mitogen-activated protein kinase (MAPK) activation and Akt activation in IL-1β-treated chondrocytes before and after LDR exposure. All MAPK proteins, namely ERK, p38, and JNK, were activated by IL-1β treatment. LDR exposure did not affect IL-1β-induced activation of MAPKs (Fig. 3A), indicating that LDR acts through a MAPK signaling-independent pathway to modulate chondrocyte phenotype. Treatment of chondrocytes with IL-1β induced Akt phosphorylation and subsequently deactivated glycogen synthase kinase 3β (GSK3β), a substrate of Akt (Fig. 3B, top), whereas Triciribine, a specific inhibitor of the Akt signaling pathway, markedly attenuated the IL-1β-induced increase in Akt phosphorylation and thus reactivated GSK3β in chondrocytes (Fig. 3B, bottom). Interestingly, treatment with LY294002, another chemical inhibitor of PI3K/Akt signaling, led to recovery of type II collagen and Sox-9 expression, reduction of COX-2 expression, and inhibition of I-κB degradation in IL-1β-treated chondrocytes (Fig. 3C, top). Consistent with this, LY294002 significantly suppressed NF-κB transcriptional activity, decreasing NF-κB activity by approximately 48% and 68% at 10 and 20 μM, respectively, compared to chondrocytes treated with IL-1β alone (Fig. 3C, bottom). Notably, LY294002 treatment in IL-1β-treated chondrocytes led to downregulation of α-, β-, and γ-catenin protein levels induced by IL-1β (Fig. 3D). These results suggest that Akt activation is critically involved in IL-1β-induced chondrocyte disorders via catenin signaling. Therefore, we examined whether LDR modulates IL-1β-induced Akt activity and found that LDR at both 0.5 and 1 cGy suppressed Akt activation induced by IL-1β in chondrocytes (Fig. 3E). Taken together, our data indicate that LDR acts through blockade of the Akt signaling pathway, but not the MAPK pathway, to mitigate the IL-1β-induced destructive cellular phenotype of chondrocytes.


Low-dose γ-radiation inhibits IL-1β-induced dedifferentiation and inflammation of articular chondrocytes via blockage of catenin signaling.

Hong EH, Song JY, Lee SJ, Park IC, Um HD, Park JK, Lee KH, Nam SY, Hwang SG - IUBMB Life (2014)

Involvement of PI3K/Akt signaling in LDR-induced inhibition of chondrocyte destruction. (A): Chondrocytes were treated with 0.5 or 1 cGy of LDR in the absence (−) or presence (+) of 10 ng/mL IL-1β for 20 min. Expression and phosphorylation status of ERK, p38, and JNK were determined by Western blotting. (B): Chondrocytes were treated with 10 ng/mL IL-1β for the indicated times (top), with or without pretreatment with 40 μM Triciribine for 1 h prior to IL-1β treatment (bottom). Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting. (C, D): Chondrocytes were left untreated or were pretreated with 10 or 20 μM LY294002 for 1 h prior to treatment with 10 ng/mL IL-1β. After 48 h, the levels of type II collagen, Sox-9, I-κB, and COX-2 proteins were assessed by Western blotting (C, top). NF-κB transcriptional activity was determined by reporter gene assay. Data are expressed as means ± SDs (**P < 0.005 and ***P < 0.0005 compared to cells treated with IL-1β alone (C, bottom). Levels of catenin proteins were detected by Western blotting (D). (E): Chondrocytes were treated with 0.5 or 1 cGy of LDR for 12 h in the absence (−) or presence (+) of 10 ng/mL IL-1β. Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting.
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fig03: Involvement of PI3K/Akt signaling in LDR-induced inhibition of chondrocyte destruction. (A): Chondrocytes were treated with 0.5 or 1 cGy of LDR in the absence (−) or presence (+) of 10 ng/mL IL-1β for 20 min. Expression and phosphorylation status of ERK, p38, and JNK were determined by Western blotting. (B): Chondrocytes were treated with 10 ng/mL IL-1β for the indicated times (top), with or without pretreatment with 40 μM Triciribine for 1 h prior to IL-1β treatment (bottom). Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting. (C, D): Chondrocytes were left untreated or were pretreated with 10 or 20 μM LY294002 for 1 h prior to treatment with 10 ng/mL IL-1β. After 48 h, the levels of type II collagen, Sox-9, I-κB, and COX-2 proteins were assessed by Western blotting (C, top). NF-κB transcriptional activity was determined by reporter gene assay. Data are expressed as means ± SDs (**P < 0.005 and ***P < 0.0005 compared to cells treated with IL-1β alone (C, bottom). Levels of catenin proteins were detected by Western blotting (D). (E): Chondrocytes were treated with 0.5 or 1 cGy of LDR for 12 h in the absence (−) or presence (+) of 10 ng/mL IL-1β. Expression and phosphorylation status of Akt and GSK3α/β were determined by Western blotting.
Mentions: To identify the mechanisms by which LDR modulates chondrocyte phenotype, we examined mitogen-activated protein kinase (MAPK) activation and Akt activation in IL-1β-treated chondrocytes before and after LDR exposure. All MAPK proteins, namely ERK, p38, and JNK, were activated by IL-1β treatment. LDR exposure did not affect IL-1β-induced activation of MAPKs (Fig. 3A), indicating that LDR acts through a MAPK signaling-independent pathway to modulate chondrocyte phenotype. Treatment of chondrocytes with IL-1β induced Akt phosphorylation and subsequently deactivated glycogen synthase kinase 3β (GSK3β), a substrate of Akt (Fig. 3B, top), whereas Triciribine, a specific inhibitor of the Akt signaling pathway, markedly attenuated the IL-1β-induced increase in Akt phosphorylation and thus reactivated GSK3β in chondrocytes (Fig. 3B, bottom). Interestingly, treatment with LY294002, another chemical inhibitor of PI3K/Akt signaling, led to recovery of type II collagen and Sox-9 expression, reduction of COX-2 expression, and inhibition of I-κB degradation in IL-1β-treated chondrocytes (Fig. 3C, top). Consistent with this, LY294002 significantly suppressed NF-κB transcriptional activity, decreasing NF-κB activity by approximately 48% and 68% at 10 and 20 μM, respectively, compared to chondrocytes treated with IL-1β alone (Fig. 3C, bottom). Notably, LY294002 treatment in IL-1β-treated chondrocytes led to downregulation of α-, β-, and γ-catenin protein levels induced by IL-1β (Fig. 3D). These results suggest that Akt activation is critically involved in IL-1β-induced chondrocyte disorders via catenin signaling. Therefore, we examined whether LDR modulates IL-1β-induced Akt activity and found that LDR at both 0.5 and 1 cGy suppressed Akt activation induced by IL-1β in chondrocytes (Fig. 3E). Taken together, our data indicate that LDR acts through blockade of the Akt signaling pathway, but not the MAPK pathway, to mitigate the IL-1β-induced destructive cellular phenotype of chondrocytes.

Bottom Line: Here, we found that LDR, at doses of 0.5-2 centiGray (cGy), inhibited interleukin (IL)-1β-induced chondrocyte destruction without causing side effects, such as cell death and senescence.LDR also inhibited chondrocyte destruction through the catenin pathway induced by epidermal growth factor, phorbol 12-myristate 13-acetate, and retinoic acid.Collectively, these results identify the molecular mechanisms by which LDR suppresses pathophysiological processes and establish LDR as a potentially valuable therapeutic tool for patients with cytokine- or soluble factors-mediated cartilage disorders.

View Article: PubMed Central - PubMed

Affiliation: Division of Radiation Cancer Biology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea; Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul, Korea.

Show MeSH
Related in: MedlinePlus