Limits...
Ischemic Preconditioning Mediates Neuroprotection against Ischemia in Mouse Hippocampal CA1 Neurons by Inducing Autophagy.

Gao C, Cai Y, Zhang X, Huang H, Wang J, Wang Y, Tong X, Wang J, Wu J - PLoS ONE (2015)

Bottom Line: Using in vivo experiments, we found that LC3 expression was upregulated, accompanied by an increase in neuronal survival in hippocampal CA1 neurons in the preconditioning group.The neuroprotective effects of IPC on hippocampal CA1 neurons were completely inhibited by treatment with 3-MA.In contrast, hippocampal CA3 neurons did not show changes in autophagic activity or beneficial effects of IPC.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Tianjin Huanhu Hospital, Tianjin Key Laboratory of Cerebrovascular and Neurodegenerative Diseases, Tianjin, China.

ABSTRACT
The hippocampal CA1 region is sensitive to hypoxic and ischemic injury but can be protected by ischemic preconditioning (IPC). However, the mechanism through which IPC protects hippocampal CA1 neurons is still under investigation. Additionally, the role of autophagy in determining the fate of hippocampal neurons is unclear. Here, we examined whether IPC induced autophagy to alleviate hippocampal CA1 neuronal death in vitro and in vivo with oxygen glucose deprivation (OGD) and bilateral carotid artery occlusion (BCCAO) models. Survival of hippocampal neurons increased from 51.5% ± 6.3% in the non-IPC group (55 min of OGD) to 77.3% ± 7.9% in the IPC group (15 min of OGD, followed by 55 min of OGD 24 h later). The number of hippocampal CA1 layer neurons increased from 182 ± 26 cells/mm2 in the non-IPC group (20 min of BCCAO) to 278 ± 55 cells/mm2 in the IPC group (1 min × 3 BCCAO, followed by 20 min of BCCAO 24 h later). Akt phosphorylation and microtubule-associated protein light chain 3 (LC3)-II/LC3-I expression were increased in the preconditioning group. Moreover, the protective effects of IPC were abolished only by inhibiting the activity of autophagy, but not by blocking the activation of Akt in vitro. Using in vivo experiments, we found that LC3 expression was upregulated, accompanied by an increase in neuronal survival in hippocampal CA1 neurons in the preconditioning group. The neuroprotective effects of IPC on hippocampal CA1 neurons were completely inhibited by treatment with 3-MA. In contrast, hippocampal CA3 neurons did not show changes in autophagic activity or beneficial effects of IPC. These data suggested that IPC may attenuate ischemic injury in hippocampal CA1 neurons through induction of Akt-independent autophagy.

No MeSH data available.


Related in: MedlinePlus

Determination of the lethal OGD time and suitable IPC intervention in hippocampal neurons.(A) Time-dependent effects of hypoxia on neuronal death. Hippocampal neurons were exposed to OGD conditions for 0, 5, 10, 15, 30, or 55 min, followed by quantification of cell survival with MTT assays 24 h later. (B) Different OGD times conferred protection against the deleterious effects of 55 min of OGD. Hippocampal neurons were exposed to sublethal (0–30 min) OGD followed by 55 min of lethal OGD 24 h later. Values are given as percentages compared with cell survival in neurons maintained under normoxic conditions. Error bars denote SDs. *P < 0.01 compared with cells maintained under OGD for 0–30 min. $P < 0.01 compared with cells maintained under normoxic conditions. #P < 0.05 compared with cells maintained under 55 min of OGD.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4556686&req=5

pone.0137146.g001: Determination of the lethal OGD time and suitable IPC intervention in hippocampal neurons.(A) Time-dependent effects of hypoxia on neuronal death. Hippocampal neurons were exposed to OGD conditions for 0, 5, 10, 15, 30, or 55 min, followed by quantification of cell survival with MTT assays 24 h later. (B) Different OGD times conferred protection against the deleterious effects of 55 min of OGD. Hippocampal neurons were exposed to sublethal (0–30 min) OGD followed by 55 min of lethal OGD 24 h later. Values are given as percentages compared with cell survival in neurons maintained under normoxic conditions. Error bars denote SDs. *P < 0.01 compared with cells maintained under OGD for 0–30 min. $P < 0.01 compared with cells maintained under normoxic conditions. #P < 0.05 compared with cells maintained under 55 min of OGD.

Mentions: Hippocampal neurons were exposed to 0–55 min of OGD, followed by determination of cell survival by MTT assays 24 h later. Our results showed that exposure to 5, 10, 15, or 30 min of OGD stimulus and reperfusion for 24 h did not cause significant neuronal death. In contrast, exposure to 55 min of OGD decreased neuronal survival to 52% ± 12.9%, significantly lower relative to survival percentages after 0–30 min of OGD (p < 0.01; Fig 1A); therefore, the lethal OGD time was set as 55 min. To confirm whether different OGD times altered neuronal vulnerability to lethal OGD, we exposed hippocampal neurons to sublethal OGD for different times (5, 10, 15, or 30 min), followed by lethal OGD (55 min of OGD) 24 h later. We found that 15 min of OGD conferred protection against the deleterious effects of lethal OGD by increasing neuronal survival to 73% ± 18.2% (p < 0.05, Fig 1B). Therefore, we chose stimulation with 15 min OGD as the suitable IPC intervention in the subsequent experiments.


Ischemic Preconditioning Mediates Neuroprotection against Ischemia in Mouse Hippocampal CA1 Neurons by Inducing Autophagy.

Gao C, Cai Y, Zhang X, Huang H, Wang J, Wang Y, Tong X, Wang J, Wu J - PLoS ONE (2015)

Determination of the lethal OGD time and suitable IPC intervention in hippocampal neurons.(A) Time-dependent effects of hypoxia on neuronal death. Hippocampal neurons were exposed to OGD conditions for 0, 5, 10, 15, 30, or 55 min, followed by quantification of cell survival with MTT assays 24 h later. (B) Different OGD times conferred protection against the deleterious effects of 55 min of OGD. Hippocampal neurons were exposed to sublethal (0–30 min) OGD followed by 55 min of lethal OGD 24 h later. Values are given as percentages compared with cell survival in neurons maintained under normoxic conditions. Error bars denote SDs. *P < 0.01 compared with cells maintained under OGD for 0–30 min. $P < 0.01 compared with cells maintained under normoxic conditions. #P < 0.05 compared with cells maintained under 55 min of OGD.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556686&req=5

pone.0137146.g001: Determination of the lethal OGD time and suitable IPC intervention in hippocampal neurons.(A) Time-dependent effects of hypoxia on neuronal death. Hippocampal neurons were exposed to OGD conditions for 0, 5, 10, 15, 30, or 55 min, followed by quantification of cell survival with MTT assays 24 h later. (B) Different OGD times conferred protection against the deleterious effects of 55 min of OGD. Hippocampal neurons were exposed to sublethal (0–30 min) OGD followed by 55 min of lethal OGD 24 h later. Values are given as percentages compared with cell survival in neurons maintained under normoxic conditions. Error bars denote SDs. *P < 0.01 compared with cells maintained under OGD for 0–30 min. $P < 0.01 compared with cells maintained under normoxic conditions. #P < 0.05 compared with cells maintained under 55 min of OGD.
Mentions: Hippocampal neurons were exposed to 0–55 min of OGD, followed by determination of cell survival by MTT assays 24 h later. Our results showed that exposure to 5, 10, 15, or 30 min of OGD stimulus and reperfusion for 24 h did not cause significant neuronal death. In contrast, exposure to 55 min of OGD decreased neuronal survival to 52% ± 12.9%, significantly lower relative to survival percentages after 0–30 min of OGD (p < 0.01; Fig 1A); therefore, the lethal OGD time was set as 55 min. To confirm whether different OGD times altered neuronal vulnerability to lethal OGD, we exposed hippocampal neurons to sublethal OGD for different times (5, 10, 15, or 30 min), followed by lethal OGD (55 min of OGD) 24 h later. We found that 15 min of OGD conferred protection against the deleterious effects of lethal OGD by increasing neuronal survival to 73% ± 18.2% (p < 0.05, Fig 1B). Therefore, we chose stimulation with 15 min OGD as the suitable IPC intervention in the subsequent experiments.

Bottom Line: Using in vivo experiments, we found that LC3 expression was upregulated, accompanied by an increase in neuronal survival in hippocampal CA1 neurons in the preconditioning group.The neuroprotective effects of IPC on hippocampal CA1 neurons were completely inhibited by treatment with 3-MA.In contrast, hippocampal CA3 neurons did not show changes in autophagic activity or beneficial effects of IPC.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Tianjin Huanhu Hospital, Tianjin Key Laboratory of Cerebrovascular and Neurodegenerative Diseases, Tianjin, China.

ABSTRACT
The hippocampal CA1 region is sensitive to hypoxic and ischemic injury but can be protected by ischemic preconditioning (IPC). However, the mechanism through which IPC protects hippocampal CA1 neurons is still under investigation. Additionally, the role of autophagy in determining the fate of hippocampal neurons is unclear. Here, we examined whether IPC induced autophagy to alleviate hippocampal CA1 neuronal death in vitro and in vivo with oxygen glucose deprivation (OGD) and bilateral carotid artery occlusion (BCCAO) models. Survival of hippocampal neurons increased from 51.5% ± 6.3% in the non-IPC group (55 min of OGD) to 77.3% ± 7.9% in the IPC group (15 min of OGD, followed by 55 min of OGD 24 h later). The number of hippocampal CA1 layer neurons increased from 182 ± 26 cells/mm2 in the non-IPC group (20 min of BCCAO) to 278 ± 55 cells/mm2 in the IPC group (1 min × 3 BCCAO, followed by 20 min of BCCAO 24 h later). Akt phosphorylation and microtubule-associated protein light chain 3 (LC3)-II/LC3-I expression were increased in the preconditioning group. Moreover, the protective effects of IPC were abolished only by inhibiting the activity of autophagy, but not by blocking the activation of Akt in vitro. Using in vivo experiments, we found that LC3 expression was upregulated, accompanied by an increase in neuronal survival in hippocampal CA1 neurons in the preconditioning group. The neuroprotective effects of IPC on hippocampal CA1 neurons were completely inhibited by treatment with 3-MA. In contrast, hippocampal CA3 neurons did not show changes in autophagic activity or beneficial effects of IPC. These data suggested that IPC may attenuate ischemic injury in hippocampal CA1 neurons through induction of Akt-independent autophagy.

No MeSH data available.


Related in: MedlinePlus