Limits...
Hypoxic Preconditioning Suppresses Glial Activation and Neuroinflammation in Neonatal Brain Insults.

Chen CY, Sun WZ, Kang KH, Chou HC, Tsao PN, Hsieh WS, Fu WM - Mediators Inflamm. (2015)

Bottom Line: Hypoxia-ischemia brain insult induced significant brain weight reduction, profound cell loss, and reactive gliosis in the damaged hemisphere.Hypoxic preconditioning significantly attenuated glial activation and resulted in robust neuroprotection.This might therefore be a promising therapeutic approach for rescuing neonatal brain injury.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan ; Departments of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.

ABSTRACT
Perinatal insults and subsequent neuroinflammation are the major mechanisms of neonatal brain injury, but there have been only scarce reports on the associations between hypoxic preconditioning and glial activation. Here we use neonatal hypoxia-ischemia brain injury model in 7-day-old rats and in vitro hypoxia model with primary mixed glial culture and the BV-2 microglial cell line to assess the effects of hypoxia and hypoxic preconditioning on glial activation. Hypoxia-ischemia brain insult induced significant brain weight reduction, profound cell loss, and reactive gliosis in the damaged hemisphere. Hypoxic preconditioning significantly attenuated glial activation and resulted in robust neuroprotection. As early as 2 h after the hypoxia-ischemia insult, proinflammatory gene upregulation was suppressed in the hypoxic preconditioning group. In vitro experiments showed that exposure to 0.5% oxygen for 4 h induced a glial inflammatory response. Exposure to brief hypoxia (0.5 h) 24 h before the hypoxic insult significantly ameliorated this response. In conclusion, hypoxic preconditioning confers strong neuroprotection, possibly through suppression of glial activation and subsequent inflammatory responses after hypoxia-ischemia insults in neonatal rats. This might therefore be a promising therapeutic approach for rescuing neonatal brain injury.

No MeSH data available.


Related in: MedlinePlus

Hypoxia preconditioning suppresses prolonged hypoxia-induced inflammation in the BV-2 microglial cell line. (a) Brief hypoxia exposure (0.5, 1, and 2 h) before prolonged hypoxia damage (4 h) significantly reduced the production of nitrite. ***P < 0.001 compared with hypoxia control. (b) mRNA expression of tumor necrosis factor-alpha (TNF-α) was suppressed by brief hypoxia preconditioning. **P < 0.01 compared with normoxia control and *P < 0.05 compared with hypoxia control. (c) mRNA expression of interleukin-1 beta (IL-1β) was also suppressed by brief hypoxia preconditioning. ***P < 0.001 compared with normoxia control and **P < 0.01 compared with hypoxia control. ((a), (b), (c)) The data represent the mean ± standard error of the mean (SEM), based on five independent experiments in each group.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4530271&req=5

fig6: Hypoxia preconditioning suppresses prolonged hypoxia-induced inflammation in the BV-2 microglial cell line. (a) Brief hypoxia exposure (0.5, 1, and 2 h) before prolonged hypoxia damage (4 h) significantly reduced the production of nitrite. ***P < 0.001 compared with hypoxia control. (b) mRNA expression of tumor necrosis factor-alpha (TNF-α) was suppressed by brief hypoxia preconditioning. **P < 0.01 compared with normoxia control and *P < 0.05 compared with hypoxia control. (c) mRNA expression of interleukin-1 beta (IL-1β) was also suppressed by brief hypoxia preconditioning. ***P < 0.001 compared with normoxia control and **P < 0.01 compared with hypoxia control. ((a), (b), (c)) The data represent the mean ± standard error of the mean (SEM), based on five independent experiments in each group.

Mentions: We then used mixed primary glial cultures to investigate the effect of hypoxia preconditioning. The cells were preexposed to hypoxia for 0.5, 1, or 2 h and then returned to the normoxia incubator. Twenty-four hours later, these cells were incubated in a hypoxia chamber again for 4 h, which mimics the in vivo model of hypoxia preconditioning. The production of nitrite after reoxygenation was decreased significantly by hypoxia preconditioning for 0.5 h, but not for 1 or 2 h (Figure 5(a)), and cell viability stayed the same. The expression of proinflammatory genes was also evaluated by RT-PCR (Figure 5(b)). Hypoxia preconditioning for 0.5 h significantly suppressed the expression of COX-2 genes. These results indicate that hypoxia preconditioning for 0.5 h exerts the most pronounced effect on suppression of inflammatory mediators in primary mixed glial cultures. To examine the response of isolated microglia, the same experimental protocol was also applied in the BV-2 microglial cell line. The levels of nitrite were decreased significantly by 0.5–2 h hypoxia preconditioning (Figure 6(a)). The expression levels of TNF-α (Figure 6(b)) and IL-1β (Figure 6(c)) were suppressed by 0.5 h hypoxia preconditioning in the BV-2 cell line.


Hypoxic Preconditioning Suppresses Glial Activation and Neuroinflammation in Neonatal Brain Insults.

Chen CY, Sun WZ, Kang KH, Chou HC, Tsao PN, Hsieh WS, Fu WM - Mediators Inflamm. (2015)

Hypoxia preconditioning suppresses prolonged hypoxia-induced inflammation in the BV-2 microglial cell line. (a) Brief hypoxia exposure (0.5, 1, and 2 h) before prolonged hypoxia damage (4 h) significantly reduced the production of nitrite. ***P < 0.001 compared with hypoxia control. (b) mRNA expression of tumor necrosis factor-alpha (TNF-α) was suppressed by brief hypoxia preconditioning. **P < 0.01 compared with normoxia control and *P < 0.05 compared with hypoxia control. (c) mRNA expression of interleukin-1 beta (IL-1β) was also suppressed by brief hypoxia preconditioning. ***P < 0.001 compared with normoxia control and **P < 0.01 compared with hypoxia control. ((a), (b), (c)) The data represent the mean ± standard error of the mean (SEM), based on five independent experiments in each group.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4530271&req=5

fig6: Hypoxia preconditioning suppresses prolonged hypoxia-induced inflammation in the BV-2 microglial cell line. (a) Brief hypoxia exposure (0.5, 1, and 2 h) before prolonged hypoxia damage (4 h) significantly reduced the production of nitrite. ***P < 0.001 compared with hypoxia control. (b) mRNA expression of tumor necrosis factor-alpha (TNF-α) was suppressed by brief hypoxia preconditioning. **P < 0.01 compared with normoxia control and *P < 0.05 compared with hypoxia control. (c) mRNA expression of interleukin-1 beta (IL-1β) was also suppressed by brief hypoxia preconditioning. ***P < 0.001 compared with normoxia control and **P < 0.01 compared with hypoxia control. ((a), (b), (c)) The data represent the mean ± standard error of the mean (SEM), based on five independent experiments in each group.
Mentions: We then used mixed primary glial cultures to investigate the effect of hypoxia preconditioning. The cells were preexposed to hypoxia for 0.5, 1, or 2 h and then returned to the normoxia incubator. Twenty-four hours later, these cells were incubated in a hypoxia chamber again for 4 h, which mimics the in vivo model of hypoxia preconditioning. The production of nitrite after reoxygenation was decreased significantly by hypoxia preconditioning for 0.5 h, but not for 1 or 2 h (Figure 5(a)), and cell viability stayed the same. The expression of proinflammatory genes was also evaluated by RT-PCR (Figure 5(b)). Hypoxia preconditioning for 0.5 h significantly suppressed the expression of COX-2 genes. These results indicate that hypoxia preconditioning for 0.5 h exerts the most pronounced effect on suppression of inflammatory mediators in primary mixed glial cultures. To examine the response of isolated microglia, the same experimental protocol was also applied in the BV-2 microglial cell line. The levels of nitrite were decreased significantly by 0.5–2 h hypoxia preconditioning (Figure 6(a)). The expression levels of TNF-α (Figure 6(b)) and IL-1β (Figure 6(c)) were suppressed by 0.5 h hypoxia preconditioning in the BV-2 cell line.

Bottom Line: Hypoxia-ischemia brain insult induced significant brain weight reduction, profound cell loss, and reactive gliosis in the damaged hemisphere.Hypoxic preconditioning significantly attenuated glial activation and resulted in robust neuroprotection.This might therefore be a promising therapeutic approach for rescuing neonatal brain injury.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan ; Departments of Pediatrics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.

ABSTRACT
Perinatal insults and subsequent neuroinflammation are the major mechanisms of neonatal brain injury, but there have been only scarce reports on the associations between hypoxic preconditioning and glial activation. Here we use neonatal hypoxia-ischemia brain injury model in 7-day-old rats and in vitro hypoxia model with primary mixed glial culture and the BV-2 microglial cell line to assess the effects of hypoxia and hypoxic preconditioning on glial activation. Hypoxia-ischemia brain insult induced significant brain weight reduction, profound cell loss, and reactive gliosis in the damaged hemisphere. Hypoxic preconditioning significantly attenuated glial activation and resulted in robust neuroprotection. As early as 2 h after the hypoxia-ischemia insult, proinflammatory gene upregulation was suppressed in the hypoxic preconditioning group. In vitro experiments showed that exposure to 0.5% oxygen for 4 h induced a glial inflammatory response. Exposure to brief hypoxia (0.5 h) 24 h before the hypoxic insult significantly ameliorated this response. In conclusion, hypoxic preconditioning confers strong neuroprotection, possibly through suppression of glial activation and subsequent inflammatory responses after hypoxia-ischemia insults in neonatal rats. This might therefore be a promising therapeutic approach for rescuing neonatal brain injury.

No MeSH data available.


Related in: MedlinePlus