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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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3-NP induced increases in the mRNA and protein levels of HMGB1 and in the protein levels of p-JNK and caspase-3 in rat striatum in vivo.The time-course of 3-NP–induced changes in HMGB1 expression, JNK phosphorylation, and caspase-3 cleavage was determined by isolating striatal tissue from rats that were killed 12 or 24 h after intrastriatal infusion of 3-NP (300 nmol) or vehicle control (CONT; isotonic saline solution, 1 μL). Striatal tissues were dissected for preparation of striatal extracts for immunoblotting. (A-B) 3-NP induced upregulation of the mRNA and protein levels of HMGB1. (C-D) 3-NP induced alterations in the levels of JNK phosphorylation and cleaved caspase-3. 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 = 4 animals per group. Groups were compared by ANOVA followed by Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control.
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pone.0142901.g001: 3-NP induced increases in the mRNA and protein levels of HMGB1 and in the protein levels of p-JNK and caspase-3 in rat striatum in vivo.The time-course of 3-NP–induced changes in HMGB1 expression, JNK phosphorylation, and caspase-3 cleavage was determined by isolating striatal tissue from rats that were killed 12 or 24 h after intrastriatal infusion of 3-NP (300 nmol) or vehicle control (CONT; isotonic saline solution, 1 μL). Striatal tissues were dissected for preparation of striatal extracts for immunoblotting. (A-B) 3-NP induced upregulation of the mRNA and protein levels of HMGB1. (C-D) 3-NP induced alterations in the levels of JNK phosphorylation and cleaved caspase-3. 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 = 4 animals per group. Groups were compared by ANOVA followed by Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control.

Mentions: Our previous studies showed that 3-NP triggered p53-dependent activation of autophagy and cell death [7]. Due to an earlier report of interactions between HMGB1 and p53 as well as impact of p53 on HMGB1’s capacity to recognize DNA damage [10], we examined the effects of 3-NP on the expression of HMGB1 mRNA and protein in the striatum. Intrastriatal injection of 3-NP in rats significantly increased levels of HMGB1 mRNA and protein after 12 and 24 h (Fig 1A and 1B). It was shown that JNK modulation is an important molecular event in 3-NP–induced striatal degeneration [16] which led us to further investigate expression of p-JNK in striatal tissue after 3-NP exposure. Phosphorylation of JNK was increased after 12 and 24h post injection (Fig 1C) as well as enhanced activation of caspase-3, a key mediator of apoptosis signaling (Fig 1D). These results suggest that mitochondrial dysfunction induced by 3-NP triggered increased expression of HMGB1 and autophagy/apoptosis–relevant proteins.


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)

3-NP induced increases in the mRNA and protein levels of HMGB1 and in the protein levels of p-JNK and caspase-3 in rat striatum in vivo.The time-course of 3-NP–induced changes in HMGB1 expression, JNK phosphorylation, and caspase-3 cleavage was determined by isolating striatal tissue from rats that were killed 12 or 24 h after intrastriatal infusion of 3-NP (300 nmol) or vehicle control (CONT; isotonic saline solution, 1 μL). Striatal tissues were dissected for preparation of striatal extracts for immunoblotting. (A-B) 3-NP induced upregulation of the mRNA and protein levels of HMGB1. (C-D) 3-NP induced alterations in the levels of JNK phosphorylation and cleaved caspase-3. 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 = 4 animals per group. Groups were compared by ANOVA followed by Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4643922&req=5

pone.0142901.g001: 3-NP induced increases in the mRNA and protein levels of HMGB1 and in the protein levels of p-JNK and caspase-3 in rat striatum in vivo.The time-course of 3-NP–induced changes in HMGB1 expression, JNK phosphorylation, and caspase-3 cleavage was determined by isolating striatal tissue from rats that were killed 12 or 24 h after intrastriatal infusion of 3-NP (300 nmol) or vehicle control (CONT; isotonic saline solution, 1 μL). Striatal tissues were dissected for preparation of striatal extracts for immunoblotting. (A-B) 3-NP induced upregulation of the mRNA and protein levels of HMGB1. (C-D) 3-NP induced alterations in the levels of JNK phosphorylation and cleaved caspase-3. 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 = 4 animals per group. Groups were compared by ANOVA followed by Dunnet’s post hoc test before data conversion. All panels, **p <0.01 vs control.
Mentions: Our previous studies showed that 3-NP triggered p53-dependent activation of autophagy and cell death [7]. Due to an earlier report of interactions between HMGB1 and p53 as well as impact of p53 on HMGB1’s capacity to recognize DNA damage [10], we examined the effects of 3-NP on the expression of HMGB1 mRNA and protein in the striatum. Intrastriatal injection of 3-NP in rats significantly increased levels of HMGB1 mRNA and protein after 12 and 24 h (Fig 1A and 1B). It was shown that JNK modulation is an important molecular event in 3-NP–induced striatal degeneration [16] which led us to further investigate expression of p-JNK in striatal tissue after 3-NP exposure. Phosphorylation of JNK was increased after 12 and 24h post injection (Fig 1C) as well as enhanced activation of caspase-3, a key mediator of apoptosis signaling (Fig 1D). These results suggest that mitochondrial dysfunction induced by 3-NP triggered increased expression of HMGB1 and autophagy/apoptosis–relevant proteins.

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