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Transiently lowering tumor necrosis factor-α synthesis ameliorates neuronal cell loss and cognitive impairments induced by minimal traumatic brain injury in mice.

Baratz R, Tweedie D, Wang JY, Rubovitch V, Luo W, Hoffer BJ, Greig NH, Pick CG - J Neuroinflammation (2015)

Bottom Line: TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h.These results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Anthropology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel. renanaba@post.tau.ac.il.

ABSTRACT

Background: The treatment of traumatic brain injury (TBI) represents an unmet medical need, as no effective pharmacological treatment currently exists. The development of such a treatment requires a fundamental understanding of the pathophysiological mechanisms that underpin the sequelae resulting from TBI, particularly the ensuing neuronal cell death and cognitive impairments. Tumor necrosis factor-alpha (TNF-α) is a cytokine that is a master regulator of systemic and neuroinflammatory processes. TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.

Methods: To elucidate the role of TNF-α in TBI, particularly as a drug target, the present study evaluated (i) time-dependent TNF-α levels and (ii) markers of apoptosis and gliosis within the brain and related these to behavioral measures of 'well being' and cognition in a mouse closed head 50 g weight drop mild TBI (mTBI) model in the presence and absence of post-treatment with an experimental TNF-α synthesis inhibitor, 3,6'-dithiothalidomide.

Results: mTBI elevated brain TNF-α levels, which peaked at 12 h post injury and returned to baseline by 18 h. This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h. Selective impairments in measures of cognition, evaluated by novel object recognition and passive avoidance paradigms - without changes in well being, were evident at 7 days after injury. A single systemic treatment with the TNF-α synthesis inhibitor 3,6'-dithiothalidomide 1 h post injury prevented the mTBI-induced TNF-α elevation and fully ameliorated the neuronal loss (NeuN), elevations in astrocyte number (GFAP) and BID, and cognitive impairments. Cognitive impairments evident at 7 days after injury were prevented by treatment as late as 12 h post mTBI but were not reversed when treatment was delayed until 18 h.

Conclusions: These results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

No MeSH data available.


Related in: MedlinePlus

Neuronal loss and apoptosis is induced by mTBI in cerebral cortex ipsilateral to injury and mitigated by 3,6′-dithiothalidomide. At 72 h post injury, cerebral cortex ipsilateral to mTBI was assessed for cellular changes. (A) and (B) A decline in neuronal number indicative of neuronal loss (NeuN - green) was evident post mTBI (p < 0.01). Treatment with 3,6′-dithiothalidomide at 1 h post-injury prevented such a change. (A) and (C) An elevation in BID (a marker for apoptosis - red) was evident within mTBI brains (p < 0.001). No changes in apoptotic cell death were found in animals that were treated with 3,6′-dithiothalidomide (as compared to sham animals). Within (A) (representative sections within the cerebral cortex), the bar is equal to 20 μm in length.
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Fig3: Neuronal loss and apoptosis is induced by mTBI in cerebral cortex ipsilateral to injury and mitigated by 3,6′-dithiothalidomide. At 72 h post injury, cerebral cortex ipsilateral to mTBI was assessed for cellular changes. (A) and (B) A decline in neuronal number indicative of neuronal loss (NeuN - green) was evident post mTBI (p < 0.01). Treatment with 3,6′-dithiothalidomide at 1 h post-injury prevented such a change. (A) and (C) An elevation in BID (a marker for apoptosis - red) was evident within mTBI brains (p < 0.001). No changes in apoptotic cell death were found in animals that were treated with 3,6′-dithiothalidomide (as compared to sham animals). Within (A) (representative sections within the cerebral cortex), the bar is equal to 20 μm in length.

Mentions: Illustrated in Figures 3A and 4A are brain regions (cerebral cortex and dentate gyrus, respectively) displaying immunofluorescence associated with (i) NeuN, a neuronal nuclear protein that is widely used as a marker of adult neurons, and with (ii) BID, a proapoptotic Bcl-2 protein. Quantification of NeuN staining revealed a neuronal loss in both the cortex [F(3,13) = 7.198, p < 0.005, Figure 3B] and dentate gyrus [F(3,15) = 5.641, p < 0.05, Figure 4B]. Post hoc analyses revealed that the mTBI alone group was different from all other groups (p < 0.05) in both brain regions and was reduced by 42.5% and 22.3% versus sham values in cortex and dentate gyrus, respectively. Correlated with this was an elevation in apoptotic cell number, as revealed from BID staining in the cortex [F(3,13) = 23.067, p < 0.0001, Figure 3C] and in dentate gyrus [F(3,13) = 6.301, p < 0.05, Figure 4C]. Likewise, post hoc analyses demonstrated that the mTBI group was different from all other groups (p < 0.0001, p < 0.05, respectively; and 2.76- and 1.91-fold compared to their respective sham values). In addition and illustrated in Figures 5A and 6A, mTBI-challenged mice had an elevation in astrocyte number (3.37- and 1.39-fold, respectively), as revealed by GFAP staining, within the cortex [F(3,13) = 37.641, p < 0.0001, Figure 5B] and dentate gyrus [F(3,13) = 13.284, p < 0.001, Figure 6B]. The administration of 3,6′-dithiothalidomide 1 h post injury ameliorated all mTBI-induced changes in neuron, BID, and astrocyte number as, notably, no differences were found between the mTBI + 3,6′-dithiothalidomide and the sham groups. Finally, no changes were evident between any groups (sham, mTBI, and mTBI + drug) in the total cell numbers, as revealed from DAPI staining, within the cortex and dentate gyrus [F(3,15) = 1.009, NS, Figure 5C; F(3,15) = 2.251, NS, Figure 6C].Figure 3


Transiently lowering tumor necrosis factor-α synthesis ameliorates neuronal cell loss and cognitive impairments induced by minimal traumatic brain injury in mice.

Baratz R, Tweedie D, Wang JY, Rubovitch V, Luo W, Hoffer BJ, Greig NH, Pick CG - J Neuroinflammation (2015)

Neuronal loss and apoptosis is induced by mTBI in cerebral cortex ipsilateral to injury and mitigated by 3,6′-dithiothalidomide. At 72 h post injury, cerebral cortex ipsilateral to mTBI was assessed for cellular changes. (A) and (B) A decline in neuronal number indicative of neuronal loss (NeuN - green) was evident post mTBI (p < 0.01). Treatment with 3,6′-dithiothalidomide at 1 h post-injury prevented such a change. (A) and (C) An elevation in BID (a marker for apoptosis - red) was evident within mTBI brains (p < 0.001). No changes in apoptotic cell death were found in animals that were treated with 3,6′-dithiothalidomide (as compared to sham animals). Within (A) (representative sections within the cerebral cortex), the bar is equal to 20 μm in length.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Fig3: Neuronal loss and apoptosis is induced by mTBI in cerebral cortex ipsilateral to injury and mitigated by 3,6′-dithiothalidomide. At 72 h post injury, cerebral cortex ipsilateral to mTBI was assessed for cellular changes. (A) and (B) A decline in neuronal number indicative of neuronal loss (NeuN - green) was evident post mTBI (p < 0.01). Treatment with 3,6′-dithiothalidomide at 1 h post-injury prevented such a change. (A) and (C) An elevation in BID (a marker for apoptosis - red) was evident within mTBI brains (p < 0.001). No changes in apoptotic cell death were found in animals that were treated with 3,6′-dithiothalidomide (as compared to sham animals). Within (A) (representative sections within the cerebral cortex), the bar is equal to 20 μm in length.
Mentions: Illustrated in Figures 3A and 4A are brain regions (cerebral cortex and dentate gyrus, respectively) displaying immunofluorescence associated with (i) NeuN, a neuronal nuclear protein that is widely used as a marker of adult neurons, and with (ii) BID, a proapoptotic Bcl-2 protein. Quantification of NeuN staining revealed a neuronal loss in both the cortex [F(3,13) = 7.198, p < 0.005, Figure 3B] and dentate gyrus [F(3,15) = 5.641, p < 0.05, Figure 4B]. Post hoc analyses revealed that the mTBI alone group was different from all other groups (p < 0.05) in both brain regions and was reduced by 42.5% and 22.3% versus sham values in cortex and dentate gyrus, respectively. Correlated with this was an elevation in apoptotic cell number, as revealed from BID staining in the cortex [F(3,13) = 23.067, p < 0.0001, Figure 3C] and in dentate gyrus [F(3,13) = 6.301, p < 0.05, Figure 4C]. Likewise, post hoc analyses demonstrated that the mTBI group was different from all other groups (p < 0.0001, p < 0.05, respectively; and 2.76- and 1.91-fold compared to their respective sham values). In addition and illustrated in Figures 5A and 6A, mTBI-challenged mice had an elevation in astrocyte number (3.37- and 1.39-fold, respectively), as revealed by GFAP staining, within the cortex [F(3,13) = 37.641, p < 0.0001, Figure 5B] and dentate gyrus [F(3,13) = 13.284, p < 0.001, Figure 6B]. The administration of 3,6′-dithiothalidomide 1 h post injury ameliorated all mTBI-induced changes in neuron, BID, and astrocyte number as, notably, no differences were found between the mTBI + 3,6′-dithiothalidomide and the sham groups. Finally, no changes were evident between any groups (sham, mTBI, and mTBI + drug) in the total cell numbers, as revealed from DAPI staining, within the cortex and dentate gyrus [F(3,15) = 1.009, NS, Figure 5C; F(3,15) = 2.251, NS, Figure 6C].Figure 3

Bottom Line: TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h.These results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Anthropology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel. renanaba@post.tau.ac.il.

ABSTRACT

Background: The treatment of traumatic brain injury (TBI) represents an unmet medical need, as no effective pharmacological treatment currently exists. The development of such a treatment requires a fundamental understanding of the pathophysiological mechanisms that underpin the sequelae resulting from TBI, particularly the ensuing neuronal cell death and cognitive impairments. Tumor necrosis factor-alpha (TNF-α) is a cytokine that is a master regulator of systemic and neuroinflammatory processes. TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.

Methods: To elucidate the role of TNF-α in TBI, particularly as a drug target, the present study evaluated (i) time-dependent TNF-α levels and (ii) markers of apoptosis and gliosis within the brain and related these to behavioral measures of 'well being' and cognition in a mouse closed head 50 g weight drop mild TBI (mTBI) model in the presence and absence of post-treatment with an experimental TNF-α synthesis inhibitor, 3,6'-dithiothalidomide.

Results: mTBI elevated brain TNF-α levels, which peaked at 12 h post injury and returned to baseline by 18 h. This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h. Selective impairments in measures of cognition, evaluated by novel object recognition and passive avoidance paradigms - without changes in well being, were evident at 7 days after injury. A single systemic treatment with the TNF-α synthesis inhibitor 3,6'-dithiothalidomide 1 h post injury prevented the mTBI-induced TNF-α elevation and fully ameliorated the neuronal loss (NeuN), elevations in astrocyte number (GFAP) and BID, and cognitive impairments. Cognitive impairments evident at 7 days after injury were prevented by treatment as late as 12 h post mTBI but were not reversed when treatment was delayed until 18 h.

Conclusions: These results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

No MeSH data available.


Related in: MedlinePlus