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HMGB1 Promotes Mitochondrial Dysfunction-Triggered Striatal Neurodegeneration via Autophagy and Apoptosis Activation.

Qi L, Sun X, Li FE, Zhu BS, Braun FK, Liu ZQ, Tang JL, Wu C, Xu F, Wang HH, Velasquez LA, Zhao K, Lei FR, Zhang JG, Shen YT, Zou JX, Meng HM, An GL, Yang L, Zhang XD - PLoS ONE (2015)

Bottom Line: Glycyrrhizin also significantly inhibited 3-NP-induced striatal damage.It was clear that HMGB1 was important for basal autophagy which was shown by rescue of cells through HMGB1 targeting shRNA approach.3-NP also induced the expression of HMGB1, p-JNK, and LC3-II in striatal neurons, and p-JNK expression was significantly reduced by shRNA knockdown of HMGB1, an effect that was reversed by exogenously increased expression of HMGB1.These results suggest that HMGB1 plays important roles in signaling for both autophagy and apoptosis in neurodegeneration induced by mitochondrial dysfunction.

View Article: PubMed Central - PubMed

Affiliation: Hematology Center, Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China.

ABSTRACT
Impairments in mitochondrial energy metabolism are thought to be involved in many neurodegenerative diseases. The mitochondrial inhibitor 3-nitropropionic acid (3-NP) induces striatal pathology mimicking neurodegeneration in vivo. Previous studies showed that 3-NP also triggered autophagy activation and apoptosis. In this study, we focused on the high-mobility group box 1 (HMGB1) protein, which is important in oxidative stress signaling as well as in autophagy and apoptosis, to explore whether the mechanisms of autophagy and apoptosis in neurodegenerative diseases are associated with metabolic impairment. To elucidate the role of HMGB1 in striatal degeneration, we investigated the impact of HMGB1 on autophagy activation and cell death induced by 3-NP. We intoxicated rat striata with 3-NP by stereotaxic injection and analyzed changes in expression HMGB1, proapoptotic proteins caspase-3 and phospho-c-Jun amino-terminal kinases (p-JNK). 3-NP-induced elevations in p-JNK, cleaved caspase-3, and autophagic marker LC3-II as well as reduction in SQSTM1 (p62), were significantly reduced by the HMGB1 inhibitor glycyrrhizin. Glycyrrhizin also significantly inhibited 3-NP-induced striatal damage. Neuronal death was replicated by exposing primary striatal neurons in culture to 3-NP. It was clear that HMGB1 was important for basal autophagy which was shown by rescue of cells through HMGB1 targeting shRNA approach.3-NP also induced the expression of HMGB1, p-JNK, and LC3-II in striatal neurons, and p-JNK expression was significantly reduced by shRNA knockdown of HMGB1, an effect that was reversed by exogenously increased expression of HMGB1. These results suggest that HMGB1 plays important roles in signaling for both autophagy and apoptosis in neurodegeneration induced by mitochondrial dysfunction.

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HMGB1 inhibitor glycyrrhizin inhibited 3-NP–induced upregulation of p-JNK and caspase-3 and death of striatal neurons in vivo.To study the effects of HMGB1 inhibition on phosphorylation of JNK, caspase-3 cleavage, and death of striatal neurons, striatal tissues were isolated from rats intrastriatally infused with glycyrrhizin (200 nmol) 1 h prior to 3-NP (300 nmol) infusion for an additional 24 h. (A-B) Glycyrrhizin inhibited 3-NP–induced increases in levels of p-JNK, LC3, SQSTM1, and cleaved caspase-3. (C) Cell death was identified by cresyl violet staining on brain sections from control and 3-NP–treated rats. Representative micrographs were taken in the center of the area injected with drugs (adjacent to needle tracks). (a and d) Vehicle treatment (CONT); (b and e) 3-NP treatment; (c and f) 3-NP + glycyrrhizin (Gly) treatment. Scale bars = 500 μm (a–c); 100 μm (d-f). (D) Quantitative analysis of the effects of glycyrrhizin on striatal lesions induced by 3-NP. Densities of protein bands were analyzed with an image analyzer (Sigma Scan Pro 5) and normalized to the loading control (β-actin). Bars represent mean ± SE; n = 3 samples per group. Groups were compared by ANOVA followed by the Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control. ##p <0.01 vs. 3-NP alone.
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pone.0142901.g002: HMGB1 inhibitor glycyrrhizin inhibited 3-NP–induced upregulation of p-JNK and caspase-3 and death of striatal neurons in vivo.To study the effects of HMGB1 inhibition on phosphorylation of JNK, caspase-3 cleavage, and death of striatal neurons, striatal tissues were isolated from rats intrastriatally infused with glycyrrhizin (200 nmol) 1 h prior to 3-NP (300 nmol) infusion for an additional 24 h. (A-B) Glycyrrhizin inhibited 3-NP–induced increases in levels of p-JNK, LC3, SQSTM1, and cleaved caspase-3. (C) Cell death was identified by cresyl violet staining on brain sections from control and 3-NP–treated rats. Representative micrographs were taken in the center of the area injected with drugs (adjacent to needle tracks). (a and d) Vehicle treatment (CONT); (b and e) 3-NP treatment; (c and f) 3-NP + glycyrrhizin (Gly) treatment. Scale bars = 500 μm (a–c); 100 μm (d-f). (D) Quantitative analysis of the effects of glycyrrhizin on striatal lesions induced by 3-NP. Densities of protein bands were analyzed with an image analyzer (Sigma Scan Pro 5) and normalized to the loading control (β-actin). Bars represent mean ± SE; n = 3 samples per group. Groups were compared by ANOVA followed by the Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control. ##p <0.01 vs. 3-NP alone.

Mentions: To determine if 3-NP–induced HMGB1 expression is involved in activation of autophagy and apoptosis, we examined the effects of the HMGB1-specific inhibitor glycyrrhizin on JNK phosphorylation, expression of LC3-II and cleavage of caspase-3 in 3-NP–treated rats. LC3 is a mammalian homologue of yeast Apg8p, and LC3-II is required for the formation of autophagosomes and has been defined as a marker of autophagy in mammalian cells [18]. Glycyrrhizin has been shown to inhibit HMGB1-mediated signaling, including apoptosis [19]. Our results show that pretreatment with glycyrrhizin significantly blocked 3-NP–mediated elevation of p-JNK and decline of autophagy substrate SQSTM1 (p62), and reduced activation of autophagy marker LC3-II and apoptosis marker caspase-3 (Fig 2A and 2B). These results prompted us to examine the effects of glycyrrhizin on 3-NP–induced death of striatal cells by cresyl violet staining 14 days after 3-NP treatment. Lesion sizes were measured in four coronal sections from each striatum. While 3-NP alone caused substantial loss of striatal neurons and gliosis, glycyrrhizin pretreatment (100 nmol) significantly reduced the size of 3-NP–induced striatal lesions (p <0.05, n = 6; Fig 2C and 2D). These results suggest that HMGB1 is involved in 3-NP–mediated activation of the autophagy and apoptosis pathways that lead to striatal neuronal death.


HMGB1 Promotes Mitochondrial Dysfunction-Triggered Striatal Neurodegeneration via Autophagy and Apoptosis Activation.

Qi L, Sun X, Li FE, Zhu BS, Braun FK, Liu ZQ, Tang JL, Wu C, Xu F, Wang HH, Velasquez LA, Zhao K, Lei FR, Zhang JG, Shen YT, Zou JX, Meng HM, An GL, Yang L, Zhang XD - PLoS ONE (2015)

HMGB1 inhibitor glycyrrhizin inhibited 3-NP–induced upregulation of p-JNK and caspase-3 and death of striatal neurons in vivo.To study the effects of HMGB1 inhibition on phosphorylation of JNK, caspase-3 cleavage, and death of striatal neurons, striatal tissues were isolated from rats intrastriatally infused with glycyrrhizin (200 nmol) 1 h prior to 3-NP (300 nmol) infusion for an additional 24 h. (A-B) Glycyrrhizin inhibited 3-NP–induced increases in levels of p-JNK, LC3, SQSTM1, and cleaved caspase-3. (C) Cell death was identified by cresyl violet staining on brain sections from control and 3-NP–treated rats. Representative micrographs were taken in the center of the area injected with drugs (adjacent to needle tracks). (a and d) Vehicle treatment (CONT); (b and e) 3-NP treatment; (c and f) 3-NP + glycyrrhizin (Gly) treatment. Scale bars = 500 μm (a–c); 100 μm (d-f). (D) Quantitative analysis of the effects of glycyrrhizin on striatal lesions induced by 3-NP. Densities of protein bands were analyzed with an image analyzer (Sigma Scan Pro 5) and normalized to the loading control (β-actin). Bars represent mean ± SE; n = 3 samples per group. Groups were compared by ANOVA followed by the Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control. ##p <0.01 vs. 3-NP alone.
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pone.0142901.g002: HMGB1 inhibitor glycyrrhizin inhibited 3-NP–induced upregulation of p-JNK and caspase-3 and death of striatal neurons in vivo.To study the effects of HMGB1 inhibition on phosphorylation of JNK, caspase-3 cleavage, and death of striatal neurons, striatal tissues were isolated from rats intrastriatally infused with glycyrrhizin (200 nmol) 1 h prior to 3-NP (300 nmol) infusion for an additional 24 h. (A-B) Glycyrrhizin inhibited 3-NP–induced increases in levels of p-JNK, LC3, SQSTM1, and cleaved caspase-3. (C) Cell death was identified by cresyl violet staining on brain sections from control and 3-NP–treated rats. Representative micrographs were taken in the center of the area injected with drugs (adjacent to needle tracks). (a and d) Vehicle treatment (CONT); (b and e) 3-NP treatment; (c and f) 3-NP + glycyrrhizin (Gly) treatment. Scale bars = 500 μm (a–c); 100 μm (d-f). (D) Quantitative analysis of the effects of glycyrrhizin on striatal lesions induced by 3-NP. Densities of protein bands were analyzed with an image analyzer (Sigma Scan Pro 5) and normalized to the loading control (β-actin). Bars represent mean ± SE; n = 3 samples per group. Groups were compared by ANOVA followed by the Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control. ##p <0.01 vs. 3-NP alone.
Mentions: To determine if 3-NP–induced HMGB1 expression is involved in activation of autophagy and apoptosis, we examined the effects of the HMGB1-specific inhibitor glycyrrhizin on JNK phosphorylation, expression of LC3-II and cleavage of caspase-3 in 3-NP–treated rats. LC3 is a mammalian homologue of yeast Apg8p, and LC3-II is required for the formation of autophagosomes and has been defined as a marker of autophagy in mammalian cells [18]. Glycyrrhizin has been shown to inhibit HMGB1-mediated signaling, including apoptosis [19]. Our results show that pretreatment with glycyrrhizin significantly blocked 3-NP–mediated elevation of p-JNK and decline of autophagy substrate SQSTM1 (p62), and reduced activation of autophagy marker LC3-II and apoptosis marker caspase-3 (Fig 2A and 2B). These results prompted us to examine the effects of glycyrrhizin on 3-NP–induced death of striatal cells by cresyl violet staining 14 days after 3-NP treatment. Lesion sizes were measured in four coronal sections from each striatum. While 3-NP alone caused substantial loss of striatal neurons and gliosis, glycyrrhizin pretreatment (100 nmol) significantly reduced the size of 3-NP–induced striatal lesions (p <0.05, n = 6; Fig 2C and 2D). These results suggest that HMGB1 is involved in 3-NP–mediated activation of the autophagy and apoptosis pathways that lead to striatal neuronal death.

Bottom Line: Glycyrrhizin also significantly inhibited 3-NP-induced striatal damage.It was clear that HMGB1 was important for basal autophagy which was shown by rescue of cells through HMGB1 targeting shRNA approach.3-NP also induced the expression of HMGB1, p-JNK, and LC3-II in striatal neurons, and p-JNK expression was significantly reduced by shRNA knockdown of HMGB1, an effect that was reversed by exogenously increased expression of HMGB1.These results suggest that HMGB1 plays important roles in signaling for both autophagy and apoptosis in neurodegeneration induced by mitochondrial dysfunction.

View Article: PubMed Central - PubMed

Affiliation: Hematology Center, Cyrus Tang Medical Institute, Soochow University, Suzhou, Jiangsu, China.

ABSTRACT
Impairments in mitochondrial energy metabolism are thought to be involved in many neurodegenerative diseases. The mitochondrial inhibitor 3-nitropropionic acid (3-NP) induces striatal pathology mimicking neurodegeneration in vivo. Previous studies showed that 3-NP also triggered autophagy activation and apoptosis. In this study, we focused on the high-mobility group box 1 (HMGB1) protein, which is important in oxidative stress signaling as well as in autophagy and apoptosis, to explore whether the mechanisms of autophagy and apoptosis in neurodegenerative diseases are associated with metabolic impairment. To elucidate the role of HMGB1 in striatal degeneration, we investigated the impact of HMGB1 on autophagy activation and cell death induced by 3-NP. We intoxicated rat striata with 3-NP by stereotaxic injection and analyzed changes in expression HMGB1, proapoptotic proteins caspase-3 and phospho-c-Jun amino-terminal kinases (p-JNK). 3-NP-induced elevations in p-JNK, cleaved caspase-3, and autophagic marker LC3-II as well as reduction in SQSTM1 (p62), were significantly reduced by the HMGB1 inhibitor glycyrrhizin. Glycyrrhizin also significantly inhibited 3-NP-induced striatal damage. Neuronal death was replicated by exposing primary striatal neurons in culture to 3-NP. It was clear that HMGB1 was important for basal autophagy which was shown by rescue of cells through HMGB1 targeting shRNA approach.3-NP also induced the expression of HMGB1, p-JNK, and LC3-II in striatal neurons, and p-JNK expression was significantly reduced by shRNA knockdown of HMGB1, an effect that was reversed by exogenously increased expression of HMGB1. These results suggest that HMGB1 plays important roles in signaling for both autophagy and apoptosis in neurodegeneration induced by mitochondrial dysfunction.

Show MeSH
Related in: MedlinePlus