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TNFR1-JNK signaling is the shared pathway of neuroinflammation and neurovascular damage after LPS-sensitized hypoxic-ischemic injury in the immature brain.

Wang LW, Chang YC, Chen SJ, Tseng CH, Tu YF, Liao NS, Huang CC, Ho CJ - J Neuroinflammation (2014)

Bottom Line: Etanercept (a TNF-α inhibitor) and AS601245 (a JNK inhibitor) protected against LPS-sensitized HI brain injury.The TNFR1-knockout but not TNFR2-knockout pups had significant reduction in JNK activation, attenuation of microglial activation, BBB breakdown and cleaved caspase-3 expression, and showed markedly less cortical and white matter injury than the wild-type pups after LPS-sensitized HI.TNFR1-JNK signaling is the shared pathway leading to neuroinflammation and neurovascular damage after LPS-sensitized HI in the immature brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Chi Mei Medical Center, Tainan, 710, Taiwan. lanwan@ms67.url.com.tw.

ABSTRACT

Background: Hypoxic-ischemia (HI) and inflammation are the two major pathogenic mechanisms of brain injury in very preterm infants. The neurovascular unit is the major target of HI injury in the immature brain. Systemic inflammation may worsen HI by up-regulating neuroinflammation and disrupting the blood-brain barrier (BBB). Since neurons and oligodendrocytes, microvascular endothelial cells, and microglia may closely interact with each other, there may be a common signaling pathway leading to neuroinflammation and neurovascular damage after injury in the immature brain. TNF-α is a key pro-inflammatory cytokine that acts through the TNF receptor (TNFR), and c-Jun N-terminal kinases (JNK) are important stress-responsive kinases.

Objective: To determine if TNFR1-JNK signaling is a shared pathway underlying neuroinflammation and neurovascular injury after lipopolysaccharide (LPS)-sensitized HI in the immature brain.

Methods: Postpartum (P) day-5 mice received LPS or normal saline (NS) injection before HI. Immunohistochemistry, immunoblotting and TNFR1- and TNFR2-knockout mouse pups were used to determine neuroinflammation, BBB damage, TNF-α expression, JNK activation, and cell apoptosis. The cellular distribution of p-JNK, TNFR1/TNFR2 and cleaved caspase-3 were examined using immunofluorescent staining.

Results: The LPS + HI group had significantly greater up-regulation of activated microglia, TNF-α and TNFR1 expression, and increases of BBB disruption and cleaved caspase-3 levels at 24 hours post-insult, and showed more cortical and white matter injury on P17 than the control and NS + HI groups. Cleaved caspase-3 was highly expressed in microvascular endothelial cells, neurons, and oligodendroglial precursor cells. LPS-sensitized HI also induced JNK activation and up-regulation of TNFR1 but not TNFR2 expression in the microglia, endothelial cells, neurons, and oligodendrocyte progenitors, and most of the TNFR1-positive cells co-expressed p-JNK. Etanercept (a TNF-α inhibitor) and AS601245 (a JNK inhibitor) protected against LPS-sensitized HI brain injury. The TNFR1-knockout but not TNFR2-knockout pups had significant reduction in JNK activation, attenuation of microglial activation, BBB breakdown and cleaved caspase-3 expression, and showed markedly less cortical and white matter injury than the wild-type pups after LPS-sensitized HI.

Conclusion: TNFR1-JNK signaling is the shared pathway leading to neuroinflammation and neurovascular damage after LPS-sensitized HI in the immature brain.

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Related in: MedlinePlus

TNF-α inhibition protected against lipopolysaccharide (LPS)-sensitized hypoxic-ischemic (HI) brain injury. (A) Etanercept at a dosage of 15 mg/kg (n = 16), but not 5 mg/kg (n = 12), significantly attenuated cortical injury (Nissl staining, upper panel), preserved myelination (MBP, middle panel), and reduced astrogliosis (GFAP, lower panel) compared to the vehicle-treated group (n = 14) after LPS-sensitized HI on P17. (B) The LPS + HI groups (n = 8) had significantly increased immunoreactivity of TNFR1 but not TNFR2 in the cortex (upper panel) and white matter (lower panel) 24 hours post-insult compared to the control groups (n = 6). The up-regulated TNFR1 was expressed in blood vessels (arrows) and non-vascular cells. Scale bar = 200 μm for MBP and 100 μm for others. Values are means ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05. GFAP, glial fibrillary acidic protein; MBP, myelin basic protein; TNFR, tumor necrosis factor receptor.
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Fig5: TNF-α inhibition protected against lipopolysaccharide (LPS)-sensitized hypoxic-ischemic (HI) brain injury. (A) Etanercept at a dosage of 15 mg/kg (n = 16), but not 5 mg/kg (n = 12), significantly attenuated cortical injury (Nissl staining, upper panel), preserved myelination (MBP, middle panel), and reduced astrogliosis (GFAP, lower panel) compared to the vehicle-treated group (n = 14) after LPS-sensitized HI on P17. (B) The LPS + HI groups (n = 8) had significantly increased immunoreactivity of TNFR1 but not TNFR2 in the cortex (upper panel) and white matter (lower panel) 24 hours post-insult compared to the control groups (n = 6). The up-regulated TNFR1 was expressed in blood vessels (arrows) and non-vascular cells. Scale bar = 200 μm for MBP and 100 μm for others. Values are means ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05. GFAP, glial fibrillary acidic protein; MBP, myelin basic protein; TNFR, tumor necrosis factor receptor.

Mentions: Compared to vehicle, etanercept significantly attenuated cortical injury at a dose of 15 mg/kg but not at 5 mg/kg treatment in the LPS + HI group, and preserved MBP expression and reduced astrogliosis in the white matter on P17 (Figure 5A).Figure 5


TNFR1-JNK signaling is the shared pathway of neuroinflammation and neurovascular damage after LPS-sensitized hypoxic-ischemic injury in the immature brain.

Wang LW, Chang YC, Chen SJ, Tseng CH, Tu YF, Liao NS, Huang CC, Ho CJ - J Neuroinflammation (2014)

TNF-α inhibition protected against lipopolysaccharide (LPS)-sensitized hypoxic-ischemic (HI) brain injury. (A) Etanercept at a dosage of 15 mg/kg (n = 16), but not 5 mg/kg (n = 12), significantly attenuated cortical injury (Nissl staining, upper panel), preserved myelination (MBP, middle panel), and reduced astrogliosis (GFAP, lower panel) compared to the vehicle-treated group (n = 14) after LPS-sensitized HI on P17. (B) The LPS + HI groups (n = 8) had significantly increased immunoreactivity of TNFR1 but not TNFR2 in the cortex (upper panel) and white matter (lower panel) 24 hours post-insult compared to the control groups (n = 6). The up-regulated TNFR1 was expressed in blood vessels (arrows) and non-vascular cells. Scale bar = 200 μm for MBP and 100 μm for others. Values are means ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05. GFAP, glial fibrillary acidic protein; MBP, myelin basic protein; TNFR, tumor necrosis factor receptor.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4300587&req=5

Fig5: TNF-α inhibition protected against lipopolysaccharide (LPS)-sensitized hypoxic-ischemic (HI) brain injury. (A) Etanercept at a dosage of 15 mg/kg (n = 16), but not 5 mg/kg (n = 12), significantly attenuated cortical injury (Nissl staining, upper panel), preserved myelination (MBP, middle panel), and reduced astrogliosis (GFAP, lower panel) compared to the vehicle-treated group (n = 14) after LPS-sensitized HI on P17. (B) The LPS + HI groups (n = 8) had significantly increased immunoreactivity of TNFR1 but not TNFR2 in the cortex (upper panel) and white matter (lower panel) 24 hours post-insult compared to the control groups (n = 6). The up-regulated TNFR1 was expressed in blood vessels (arrows) and non-vascular cells. Scale bar = 200 μm for MBP and 100 μm for others. Values are means ± SEM. ***P < 0.001, **P < 0.01, *P < 0.05. GFAP, glial fibrillary acidic protein; MBP, myelin basic protein; TNFR, tumor necrosis factor receptor.
Mentions: Compared to vehicle, etanercept significantly attenuated cortical injury at a dose of 15 mg/kg but not at 5 mg/kg treatment in the LPS + HI group, and preserved MBP expression and reduced astrogliosis in the white matter on P17 (Figure 5A).Figure 5

Bottom Line: Etanercept (a TNF-α inhibitor) and AS601245 (a JNK inhibitor) protected against LPS-sensitized HI brain injury.The TNFR1-knockout but not TNFR2-knockout pups had significant reduction in JNK activation, attenuation of microglial activation, BBB breakdown and cleaved caspase-3 expression, and showed markedly less cortical and white matter injury than the wild-type pups after LPS-sensitized HI.TNFR1-JNK signaling is the shared pathway leading to neuroinflammation and neurovascular damage after LPS-sensitized HI in the immature brain.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, Chi Mei Medical Center, Tainan, 710, Taiwan. lanwan@ms67.url.com.tw.

ABSTRACT

Background: Hypoxic-ischemia (HI) and inflammation are the two major pathogenic mechanisms of brain injury in very preterm infants. The neurovascular unit is the major target of HI injury in the immature brain. Systemic inflammation may worsen HI by up-regulating neuroinflammation and disrupting the blood-brain barrier (BBB). Since neurons and oligodendrocytes, microvascular endothelial cells, and microglia may closely interact with each other, there may be a common signaling pathway leading to neuroinflammation and neurovascular damage after injury in the immature brain. TNF-α is a key pro-inflammatory cytokine that acts through the TNF receptor (TNFR), and c-Jun N-terminal kinases (JNK) are important stress-responsive kinases.

Objective: To determine if TNFR1-JNK signaling is a shared pathway underlying neuroinflammation and neurovascular injury after lipopolysaccharide (LPS)-sensitized HI in the immature brain.

Methods: Postpartum (P) day-5 mice received LPS or normal saline (NS) injection before HI. Immunohistochemistry, immunoblotting and TNFR1- and TNFR2-knockout mouse pups were used to determine neuroinflammation, BBB damage, TNF-α expression, JNK activation, and cell apoptosis. The cellular distribution of p-JNK, TNFR1/TNFR2 and cleaved caspase-3 were examined using immunofluorescent staining.

Results: The LPS + HI group had significantly greater up-regulation of activated microglia, TNF-α and TNFR1 expression, and increases of BBB disruption and cleaved caspase-3 levels at 24 hours post-insult, and showed more cortical and white matter injury on P17 than the control and NS + HI groups. Cleaved caspase-3 was highly expressed in microvascular endothelial cells, neurons, and oligodendroglial precursor cells. LPS-sensitized HI also induced JNK activation and up-regulation of TNFR1 but not TNFR2 expression in the microglia, endothelial cells, neurons, and oligodendrocyte progenitors, and most of the TNFR1-positive cells co-expressed p-JNK. Etanercept (a TNF-α inhibitor) and AS601245 (a JNK inhibitor) protected against LPS-sensitized HI brain injury. The TNFR1-knockout but not TNFR2-knockout pups had significant reduction in JNK activation, attenuation of microglial activation, BBB breakdown and cleaved caspase-3 expression, and showed markedly less cortical and white matter injury than the wild-type pups after LPS-sensitized HI.

Conclusion: TNFR1-JNK signaling is the shared pathway leading to neuroinflammation and neurovascular damage after LPS-sensitized HI in the immature brain.

Show MeSH
Related in: MedlinePlus