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Mitochondrial Translocation of High Mobility Group Box 1 Facilitates LIM Kinase 2-Mediated Programmed Necrotic Neuronal Death.

Hyun HW, Ko AR, Kang TC - Front Cell Neurosci (2016)

Bottom Line: LIMK2 knockdown effectively attenuated SE-induced neuronal death and HMGB1 import into mitochondria accompanied by inhibiting nuclear HMGB1 release and abnormal mitochondrial elongation.However, LMB did not prevent mitochondrial elongation induced by SE, but inhibited the HMGB1 import into mitochondria.The efficacy of LMB was less effective to attenuate SE-induced neuronal death than that of LIMK2 siRNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University Chuncheon, Kangwon-Do, South Korea.

ABSTRACT
High mobility group box 1 (HMGB1) acts a signaling molecule regulating a wide range of inflammatory responses in extracellular space. HMGB1 also stabilizes nucleosomal structure and facilitates gene transcription. Under pathophysiological conditions, nuclear HMGB1 is immediately transported to the cytoplasm through chromosome region maintenance 1 (CRM1). Recently, we have reported that up-regulation of LIM kinase 2 (LIMK2) expression induces HMGB1 export from neuronal nuclei during status epilepticus (SE)-induced programmed neuronal necrosis in the rat hippocampus. Thus, we investigated whether HMGB1 involves LIMK2-mediated programmed neuronal necrosis, but such role is not reported. In the present study, SE was induced by pilocarpine in rats that were intracerebroventricularly infused with saline, control siRNA, LIMK2 siRNA or leptomycin B (LMB, a CRM1 inhibitor) prior to SE induction. Thereafter, we performed Fluoro-Jade B staining, western blots and immunohistochemical studies. LIMK2 knockdown effectively attenuated SE-induced neuronal death and HMGB1 import into mitochondria accompanied by inhibiting nuclear HMGB1 release and abnormal mitochondrial elongation. LMB alleviated SE-induced neuronal death and nuclear HMGB1 release. However, LMB did not prevent mitochondrial elongation induced by SE, but inhibited the HMGB1 import into mitochondria. The efficacy of LMB was less effective to attenuate SE-induced neuronal death than that of LIMK2 siRNA. These findings indicate that nuclear HMGB1 release and the subsequent mitochondrial import may facilitate and deteriorate programmed necrotic neuronal deaths. The present data suggest that the nuclear HMGB1 release via CRM1 may be a potential therapeutic target for the programmed necrotic neuronal death induced by SE.

No MeSH data available.


Related in: MedlinePlus

Effect of LIMK2 knockdown and LMB on SE-induced nuclear high mobility group box 1 (HMGB1) release at 3 days after SE. (A) Representative photographs of HMGB1 and NeuN in CA1 neurons. Following SE, nuclear HMGB1 expression is reduced in CA1 neurons. Both LIMK2 siRNA and LMB attenuate SE-induced nuclear HMGB1 release and loss of NeuN expression in CA1 neurons, as compared to control siRNA and vehicle, respectively. The effect of LINK2 siRNA is higher than that of LMB. Scale bar = 25 μm. (B) Quantitative values (mean ± SEM) of the fraction of HMGB1 neurons in total CA1 neurons (n = 7, respectively). *p < 0.05 vs. non-SE; #p < 0.05 vs. control siRNA or vehicle, respectively.
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Figure 2: Effect of LIMK2 knockdown and LMB on SE-induced nuclear high mobility group box 1 (HMGB1) release at 3 days after SE. (A) Representative photographs of HMGB1 and NeuN in CA1 neurons. Following SE, nuclear HMGB1 expression is reduced in CA1 neurons. Both LIMK2 siRNA and LMB attenuate SE-induced nuclear HMGB1 release and loss of NeuN expression in CA1 neurons, as compared to control siRNA and vehicle, respectively. The effect of LINK2 siRNA is higher than that of LMB. Scale bar = 25 μm. (B) Quantitative values (mean ± SEM) of the fraction of HMGB1 neurons in total CA1 neurons (n = 7, respectively). *p < 0.05 vs. non-SE; #p < 0.05 vs. control siRNA or vehicle, respectively.

Mentions: Since translocation of HMGB1 from the nucleus to the cytoplasm indicates the necrotic degeneration of various cells (Scaffidi et al., 2002; Faraco et al., 2007; Kim et al., 2014), we investigated whether LIMK2 knockdown or LMB affects SE-induced nuclear HMGB1 export induced by SE. In non-SE animals, HMGB1 expression was restricted to nuclei in CA1 neurons, and the fraction of HMGB1 positive neurons in total CA1 neurons was 94% (Figures 2A,B). Three days after SE, the number of total CA1 neurons was decreased to 36% of non-SE animals, and the fraction of HMGB1 positive neurons in total CA1 neurons was also reduced to 12% (p < 0.05 vs. non-SE animals, Figures 2A,B). Both LIMK2 siRNA and LMB effectively attenuated nuclear HMGB1 release and neuronal death induced by SE (p < 0.05 vs. control siRNA and vehicle, respectively, Figures 2A,B), but LIMK2 siRNA was more effective than LMB (p < 0.05, Figures 2A,B). These findings indicate that nuclear HMGB1 export may be involved in SE-induced neuronal death.


Mitochondrial Translocation of High Mobility Group Box 1 Facilitates LIM Kinase 2-Mediated Programmed Necrotic Neuronal Death.

Hyun HW, Ko AR, Kang TC - Front Cell Neurosci (2016)

Effect of LIMK2 knockdown and LMB on SE-induced nuclear high mobility group box 1 (HMGB1) release at 3 days after SE. (A) Representative photographs of HMGB1 and NeuN in CA1 neurons. Following SE, nuclear HMGB1 expression is reduced in CA1 neurons. Both LIMK2 siRNA and LMB attenuate SE-induced nuclear HMGB1 release and loss of NeuN expression in CA1 neurons, as compared to control siRNA and vehicle, respectively. The effect of LINK2 siRNA is higher than that of LMB. Scale bar = 25 μm. (B) Quantitative values (mean ± SEM) of the fraction of HMGB1 neurons in total CA1 neurons (n = 7, respectively). *p < 0.05 vs. non-SE; #p < 0.05 vs. control siRNA or vehicle, respectively.
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Related In: Results  -  Collection

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Figure 2: Effect of LIMK2 knockdown and LMB on SE-induced nuclear high mobility group box 1 (HMGB1) release at 3 days after SE. (A) Representative photographs of HMGB1 and NeuN in CA1 neurons. Following SE, nuclear HMGB1 expression is reduced in CA1 neurons. Both LIMK2 siRNA and LMB attenuate SE-induced nuclear HMGB1 release and loss of NeuN expression in CA1 neurons, as compared to control siRNA and vehicle, respectively. The effect of LINK2 siRNA is higher than that of LMB. Scale bar = 25 μm. (B) Quantitative values (mean ± SEM) of the fraction of HMGB1 neurons in total CA1 neurons (n = 7, respectively). *p < 0.05 vs. non-SE; #p < 0.05 vs. control siRNA or vehicle, respectively.
Mentions: Since translocation of HMGB1 from the nucleus to the cytoplasm indicates the necrotic degeneration of various cells (Scaffidi et al., 2002; Faraco et al., 2007; Kim et al., 2014), we investigated whether LIMK2 knockdown or LMB affects SE-induced nuclear HMGB1 export induced by SE. In non-SE animals, HMGB1 expression was restricted to nuclei in CA1 neurons, and the fraction of HMGB1 positive neurons in total CA1 neurons was 94% (Figures 2A,B). Three days after SE, the number of total CA1 neurons was decreased to 36% of non-SE animals, and the fraction of HMGB1 positive neurons in total CA1 neurons was also reduced to 12% (p < 0.05 vs. non-SE animals, Figures 2A,B). Both LIMK2 siRNA and LMB effectively attenuated nuclear HMGB1 release and neuronal death induced by SE (p < 0.05 vs. control siRNA and vehicle, respectively, Figures 2A,B), but LIMK2 siRNA was more effective than LMB (p < 0.05, Figures 2A,B). These findings indicate that nuclear HMGB1 export may be involved in SE-induced neuronal death.

Bottom Line: LIMK2 knockdown effectively attenuated SE-induced neuronal death and HMGB1 import into mitochondria accompanied by inhibiting nuclear HMGB1 release and abnormal mitochondrial elongation.However, LMB did not prevent mitochondrial elongation induced by SE, but inhibited the HMGB1 import into mitochondria.The efficacy of LMB was less effective to attenuate SE-induced neuronal death than that of LIMK2 siRNA.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University Chuncheon, Kangwon-Do, South Korea.

ABSTRACT
High mobility group box 1 (HMGB1) acts a signaling molecule regulating a wide range of inflammatory responses in extracellular space. HMGB1 also stabilizes nucleosomal structure and facilitates gene transcription. Under pathophysiological conditions, nuclear HMGB1 is immediately transported to the cytoplasm through chromosome region maintenance 1 (CRM1). Recently, we have reported that up-regulation of LIM kinase 2 (LIMK2) expression induces HMGB1 export from neuronal nuclei during status epilepticus (SE)-induced programmed neuronal necrosis in the rat hippocampus. Thus, we investigated whether HMGB1 involves LIMK2-mediated programmed neuronal necrosis, but such role is not reported. In the present study, SE was induced by pilocarpine in rats that were intracerebroventricularly infused with saline, control siRNA, LIMK2 siRNA or leptomycin B (LMB, a CRM1 inhibitor) prior to SE induction. Thereafter, we performed Fluoro-Jade B staining, western blots and immunohistochemical studies. LIMK2 knockdown effectively attenuated SE-induced neuronal death and HMGB1 import into mitochondria accompanied by inhibiting nuclear HMGB1 release and abnormal mitochondrial elongation. LMB alleviated SE-induced neuronal death and nuclear HMGB1 release. However, LMB did not prevent mitochondrial elongation induced by SE, but inhibited the HMGB1 import into mitochondria. The efficacy of LMB was less effective to attenuate SE-induced neuronal death than that of LIMK2 siRNA. These findings indicate that nuclear HMGB1 release and the subsequent mitochondrial import may facilitate and deteriorate programmed necrotic neuronal deaths. The present data suggest that the nuclear HMGB1 release via CRM1 may be a potential therapeutic target for the programmed necrotic neuronal death induced by SE.

No MeSH data available.


Related in: MedlinePlus