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Neuroprotection by selective neuronal deletion of Atg7 in neonatal brain injury.

Xie C, Ginet V, Sun Y, Koike M, Zhou K, Li T, Li H, Li Q, Wang X, Uchiyama Y, Truttmann AC, Kroemer G, Puyal J, Blomgren K, Zhu C - Autophagy (2016)

Bottom Line: There is an urgent need to elucidate the neuronal death mechanisms occurring after neonatal hypoxia-ischemia (HI).Neuronal deletion of Atg7 prevented HI-induced autophagy, resulted in 42% decrease of tissue loss compared to wild-type mice after the insult, and reduced cell death in multiple brain regions, including apoptosis, as shown by decreased caspase-dependent and -independent cell death.Moreover, we investigated the lentiform nucleus of human newborns who died after severe perinatal asphyxia and found increased neuronal autophagy after severe hypoxic-ischemic encephalopathy compared to control uninjured brains, as indicated by the numbers of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3)-, LAMP1 (lysosomal-associated membrane protein 1)-, and CTSD (cathepsin D)-positive cells.

View Article: PubMed Central - PubMed

Affiliation: a Center for Brain Repair and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg , Gothenburg , Sweden.

ABSTRACT
Perinatal asphyxia induces neuronal cell death and brain injury, and is often associated with irreversible neurological deficits in children. There is an urgent need to elucidate the neuronal death mechanisms occurring after neonatal hypoxia-ischemia (HI). We here investigated the selective neuronal deletion of the Atg7 (autophagy related 7) gene on neuronal cell death and brain injury in a mouse model of severe neonatal hypoxia-ischemia. Neuronal deletion of Atg7 prevented HI-induced autophagy, resulted in 42% decrease of tissue loss compared to wild-type mice after the insult, and reduced cell death in multiple brain regions, including apoptosis, as shown by decreased caspase-dependent and -independent cell death. Moreover, we investigated the lentiform nucleus of human newborns who died after severe perinatal asphyxia and found increased neuronal autophagy after severe hypoxic-ischemic encephalopathy compared to control uninjured brains, as indicated by the numbers of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3)-, LAMP1 (lysosomal-associated membrane protein 1)-, and CTSD (cathepsin D)-positive cells. These findings reveal that selective neuronal deletion of Atg7 is strongly protective against neuronal death and overall brain injury occurring after HI and suggest that inhibition of HI-enhanced autophagy should be considered as a potential therapeutic target for the treatment of human newborns developing severe hypoxic-ischemic encephalopathy.

No MeSH data available.


Related in: MedlinePlus

Hypoxia-ischemia induces neuronal autophagy in neonatal Atg7flox/+; Nes-Cre mice. (A) Representative immunoblotting of LC3B in Ctrl (Atg7flox/+; Nes-Cre) mice and (B) its corresponding quantification showed that LC3B-II (16 kDa) was increased in the ipsilateral hemisphere (IL) 24 h after HI compared to an uninjured control brain, (*, P < 0.05, n = 6). (C) Immunostaining of SQSTM1 in the cortex of Ctrl mice suggesting a decrease of its staining in neurons (RBFOX3) 24 h after HI. (D) Dying neurons in Ctrl mice exhibited increased electron density and nuclei with chromatin condensation. They possessed also typical autophagosomes with double membranes in the perikarya (black arrowheads) 24 h after HI. Squared areas are enlarged in the right panels.
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f0001: Hypoxia-ischemia induces neuronal autophagy in neonatal Atg7flox/+; Nes-Cre mice. (A) Representative immunoblotting of LC3B in Ctrl (Atg7flox/+; Nes-Cre) mice and (B) its corresponding quantification showed that LC3B-II (16 kDa) was increased in the ipsilateral hemisphere (IL) 24 h after HI compared to an uninjured control brain, (*, P < 0.05, n = 6). (C) Immunostaining of SQSTM1 in the cortex of Ctrl mice suggesting a decrease of its staining in neurons (RBFOX3) 24 h after HI. (D) Dying neurons in Ctrl mice exhibited increased electron density and nuclei with chromatin condensation. They possessed also typical autophagosomes with double membranes in the perikarya (black arrowheads) 24 h after HI. Squared areas are enlarged in the right panels.

Mentions: Twenty-four h after HI, immunoblot analysis revealed, as expected, an increase in LC3B-II levels in the ipsilateral hemisphere of Atg7flox/+; Nes-Cre (Ctrl) mice, indicating an increase in autophagosome formation (Fig. 1A, B). Moreover, immunohistochemistry for SQSTM1/p62 (a protein that is selectively degraded during autophagy) shows a reduction of neuronal SQSTM1 expression in the damaged hemisphere (Fig. 1C). Ultrastructural studies clearly revealed the formation of autophagosomes in dying neurons (Fig. 1D) of Ctrl mice after HI. Altogether, these data indicate that autophagy is increased in this mouse model of neonatal HI.Figure 1.


Neuroprotection by selective neuronal deletion of Atg7 in neonatal brain injury.

Xie C, Ginet V, Sun Y, Koike M, Zhou K, Li T, Li H, Li Q, Wang X, Uchiyama Y, Truttmann AC, Kroemer G, Puyal J, Blomgren K, Zhu C - Autophagy (2016)

Hypoxia-ischemia induces neuronal autophagy in neonatal Atg7flox/+; Nes-Cre mice. (A) Representative immunoblotting of LC3B in Ctrl (Atg7flox/+; Nes-Cre) mice and (B) its corresponding quantification showed that LC3B-II (16 kDa) was increased in the ipsilateral hemisphere (IL) 24 h after HI compared to an uninjured control brain, (*, P < 0.05, n = 6). (C) Immunostaining of SQSTM1 in the cortex of Ctrl mice suggesting a decrease of its staining in neurons (RBFOX3) 24 h after HI. (D) Dying neurons in Ctrl mice exhibited increased electron density and nuclei with chromatin condensation. They possessed also typical autophagosomes with double membranes in the perikarya (black arrowheads) 24 h after HI. Squared areas are enlarged in the right panels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835980&req=5

f0001: Hypoxia-ischemia induces neuronal autophagy in neonatal Atg7flox/+; Nes-Cre mice. (A) Representative immunoblotting of LC3B in Ctrl (Atg7flox/+; Nes-Cre) mice and (B) its corresponding quantification showed that LC3B-II (16 kDa) was increased in the ipsilateral hemisphere (IL) 24 h after HI compared to an uninjured control brain, (*, P < 0.05, n = 6). (C) Immunostaining of SQSTM1 in the cortex of Ctrl mice suggesting a decrease of its staining in neurons (RBFOX3) 24 h after HI. (D) Dying neurons in Ctrl mice exhibited increased electron density and nuclei with chromatin condensation. They possessed also typical autophagosomes with double membranes in the perikarya (black arrowheads) 24 h after HI. Squared areas are enlarged in the right panels.
Mentions: Twenty-four h after HI, immunoblot analysis revealed, as expected, an increase in LC3B-II levels in the ipsilateral hemisphere of Atg7flox/+; Nes-Cre (Ctrl) mice, indicating an increase in autophagosome formation (Fig. 1A, B). Moreover, immunohistochemistry for SQSTM1/p62 (a protein that is selectively degraded during autophagy) shows a reduction of neuronal SQSTM1 expression in the damaged hemisphere (Fig. 1C). Ultrastructural studies clearly revealed the formation of autophagosomes in dying neurons (Fig. 1D) of Ctrl mice after HI. Altogether, these data indicate that autophagy is increased in this mouse model of neonatal HI.Figure 1.

Bottom Line: There is an urgent need to elucidate the neuronal death mechanisms occurring after neonatal hypoxia-ischemia (HI).Neuronal deletion of Atg7 prevented HI-induced autophagy, resulted in 42% decrease of tissue loss compared to wild-type mice after the insult, and reduced cell death in multiple brain regions, including apoptosis, as shown by decreased caspase-dependent and -independent cell death.Moreover, we investigated the lentiform nucleus of human newborns who died after severe perinatal asphyxia and found increased neuronal autophagy after severe hypoxic-ischemic encephalopathy compared to control uninjured brains, as indicated by the numbers of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3)-, LAMP1 (lysosomal-associated membrane protein 1)-, and CTSD (cathepsin D)-positive cells.

View Article: PubMed Central - PubMed

Affiliation: a Center for Brain Repair and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg , Gothenburg , Sweden.

ABSTRACT
Perinatal asphyxia induces neuronal cell death and brain injury, and is often associated with irreversible neurological deficits in children. There is an urgent need to elucidate the neuronal death mechanisms occurring after neonatal hypoxia-ischemia (HI). We here investigated the selective neuronal deletion of the Atg7 (autophagy related 7) gene on neuronal cell death and brain injury in a mouse model of severe neonatal hypoxia-ischemia. Neuronal deletion of Atg7 prevented HI-induced autophagy, resulted in 42% decrease of tissue loss compared to wild-type mice after the insult, and reduced cell death in multiple brain regions, including apoptosis, as shown by decreased caspase-dependent and -independent cell death. Moreover, we investigated the lentiform nucleus of human newborns who died after severe perinatal asphyxia and found increased neuronal autophagy after severe hypoxic-ischemic encephalopathy compared to control uninjured brains, as indicated by the numbers of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3)-, LAMP1 (lysosomal-associated membrane protein 1)-, and CTSD (cathepsin D)-positive cells. These findings reveal that selective neuronal deletion of Atg7 is strongly protective against neuronal death and overall brain injury occurring after HI and suggest that inhibition of HI-enhanced autophagy should be considered as a potential therapeutic target for the treatment of human newborns developing severe hypoxic-ischemic encephalopathy.

No MeSH data available.


Related in: MedlinePlus