Traumatic Brain Injury Leads to Increased Expression of Peripheral-Type Benzodiazepine Receptors, Neuronal Death, and Activation of Astrocytes and Microglia in Rat Thalamus

doi:10.1006/exnr.1999.7269

Experimental Neurology

Volume 161, Issue 1, January 2000, Pages 102-114

https://doi.org/10.1006/exnr.1999.7269 Get rights and content

Abstract

In mammalian CNS, the peripheral-type benzodiazepine receptor (PTBR) is localized on the outer mitochondrial membrane within the astrocytes and microglia. PTBR transports cholesterol to the site of neurosteroid biosynthesis. Several neurodegenerative disorders were reported to be associated with increased densities of PTBR. In the present study, we evaluated the changes in the PTBR density and gene expression in the brains of rats as a function of time (6 h to 14 days) after traumatic brain injury (TBI). Sham-operated rats served as control. Between 3 and 14 days after TBI, there was a significant increased in the binding of PTBR antagonist [³H]PK11195 (by 106 to 185%, P < 0.01, as assessed by quantitative autoradiography and in vitro filtration binding) and PTBR mRNA expression (by 2- to 3.4-fold, P < 0.01, as assessed by RT-PCR) in the ipsilateral thalamus. At 14 days after the injury, the neuronal number decreased significantly (by 85 to 90%, P < 0.01) in the ipsilateral thalamus. At the same time point, the ipsilateral thalamus also showed increased numbers of the glial fibrillary acidic protein positive cells (astrocytes, by ∼3.5-fold) and the ED-1 positive cells (microglia/macrophages, by ∼36-fold), the two cell types known to be associated with PTBR. Increased PTBR expression following TBI seems to be associated with microglia/macrophages than astrocytes as PTBR density at different periods after TBI correlated better with the number of ED-1 positive cells (r² = 0.95) than the GFAP positive cells (r² = 0.56). TBI-induced increased PTBR expression is possibly an adaptive response to cellular injury and may play a role in the pathophysiology of TBI.

References (63)

M.K. Baskaya et al.
The biphasic opening of the blood–brain barrier in the cortex and hippocampus after traumatic brain injury in rats
Neurosci. Lett.
(1997)
F. Bourdiol et al.
Increase in omega 3 (peripheral type benzodiazepine) binding sites in the rat cortex and striatum after local injection of interleukin-1, tumor necrosis factor-alpha and lipopolysaccharide
Brain Res.
(1991)
M.A. Colicos et al.
Delayed, selective neuronal death following experimental cortical impact injury in rats—Possible role in memory deficits
Brain Res.
(1996)
P. Desjardins et al.
Increased expression of the peripheral-type benzodiazepine receptor-isoquinoline carboxamide binding protein mRNA in brain following portacaval anastomosis
Brain Res.
(1997)
I. Ducis et al.
The benzodiazepine receptor in cultured astrocytes from genetically epilepsy-prone rats
Brain Res.
(1990)
A.A. Dunn-Meynell et al.
Histological markers of neuronal, axonal and astrocytic changes after lateral rigid impact traumatic brain injury
Brain Res.
(1997)
C.A. Frye et al.
Androgenic neurosteroids: Anti-seizure effects in an animal model of epilepsy
Psychoneuroendocrinology
(1998)
D.R. Gehlert et al.
Increased expression of peripheral benzodiazepine receptors in the facial nucleus following motor neuron axotomy
Neurochem. Int.
(1997)
T. Hirsch et al.
PK11195, a ligand of the mitochondrial benzodiazepine receptor, facilitates the induction of apoptosis and reverses Bcl-2-mediated cytoprotection
Exp. Cell Res.
(1998)
N. Jiang et al.
Progesterone is neuroprotective after transient middle cerebral artery occlusion in male rats
Brain Res.
(1996)

E. Joseph-Liauzun et al.

The Mr 18,000 subunit of the peripheral-type benzodiazepine receptor exhibits both benzodiazepine and isoquinoline carboxamide binding sites in the absence of the voltage-dependent anion channel or of the adenine nucleotide carrier

J. Biol. Chem.

(1997)

S.S. Kaya et al.

Apoptosis and expression of p53 response proteins and cyclin D1 after cortical impact in rat brain

Brain Res.

(1999)

K.E. Krueger

Molecular and functional properties of mitochondrial benzodiazepine receptors

Biochim. Biophys. Acta

(1995)

P. Lacor et al.

Enhanced expression of the peripheral benzodiazepine receptor (PBR) and its endogenous ligand octadecaneuropeptide (ODN) in the regenerating adult rat sciatic nerve

Neurosci. Lett.

(1996)

O.H. Lowry et al.

Protein measurement with the Folin phenol reagent

J. Biol. Chem.

(1951)

M.A. Matthews et al.

Focal brain injury and its effects on cerebral mantle, neurons, and fiber tracks

Brain Res.

(1998)

J.E. Pierce et al.

Enduring cognitive, neurobehavioral and histopathological changes persist for up to one year following severe experimental brain injury in rats

Neuroscience

(1998)

S.C. Ramsay et al.

Monitoring by PET of macrophage accumulation in brain after ischaemic stroke

Lancet

(1992)

V.L.R. Rao et al.

Characterization of binding sites for the omega3 receptor ligands [³H]PK11195 and [3H]RO5-4864 in human brain

Eur. J. Pharmacol.

(1997)

V.L.R. Rao et al.

Increased neuronal nitric oxide synthase expression in brain following portacaval anastomosis

Brain Res.

(1997)

R. Sprengel et al.

Molecular cloning and expression of cDNA encoding a peripheral-type benzodiazepine receptor

J. Biol. Chem.

(1989)

A. Urani et al.

The modulation by neurosteroids of the scopolamine-induced learning impairment in mice involves an interaction with sigma1 (sigma1) receptors

Brain Res.

(1998)

D.M. Zisterer et al.

Peripheral-type benzodiazepine receptors

Gen. Pharmacol.

(1997)

N. Aihara et al.

Altered immunoexpression of microglia and macrophages after mild head injury

J. Neurotrauma

(1995)

K.L. Black et al.

Specific high-affinity binding of peripheral benzodiazepine receptor ligands to brain tumors in rat and man

Cancer

(1990)

R.S. Clark et al.

Apoptosis-suppressor gene bcl-2 expression after traumatic brain injury in rats

J. Neurosci.

(1997)

E.L. Conway et al.

Temporal changes in glial fibrillary acidic protein messenger RNA and [³H]PK11195 binding in relation to imidazoline-12-receptor and alpha 2-adrenoceptor binding in the hippocampus following transient global forebrain ischaemia in the rat

Neuroscience

(1998)

P. Cornu et al.

Increase in omega 3 (peripheral-type benzodiazepine) binding site densities in different types of human brain tumors. A quantitative autoradiography study

Acta Neurochirurg.

(1992)

C.E. Dixon et al.

Protective effects of moderate hypothermia on behavioral deficits but not necrotic cavitation following cortical impact injury in the rat

J. Neurotrauma

(1998)

F. Desarnaud et al.

Progesterone stimulates the activity of the promoters of peripheral myelin protein-22 and protein zero genes in Schwann cells

J. Neurochem.

(1998)

P. Desjardins et al.

Portacaval anastomosis causes selective alterations of peripheral-type benzodiazepine receptor expression in rat brain and peripheral tissues

Neurochem. Int.

(1999)

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Regular ArticleTraumatic Brain Injury Leads to Increased Expression of Peripheral-Type Benzodiazepine Receptors, Neuronal Death, and Activation of Astrocytes and Microglia in Rat Thalamus

Abstract

Neurosci. Lett.

Brain Res.

Brain Res.

Brain Res.

Brain Res.

Brain Res.

Psychoneuroendocrinology

Neurochem. Int.

Exp. Cell Res.

Brain Res.

J. Biol. Chem.

Brain Res.

Biochim. Biophys. Acta

Neurosci. Lett.

J. Biol. Chem.

Brain Res.

Neuroscience

Lancet

Eur. J. Pharmacol.

Brain Res.

J. Biol. Chem.

Brain Res.

Gen. Pharmacol.

Altered immunoexpression of microglia and macrophages after mild head injury

J. Neurotrauma

Specific high-affinity binding of peripheral benzodiazepine receptor ligands to brain tumors in rat and man

Cancer

Apoptosis-suppressor gene bcl-2 expression after traumatic brain injury in rats

J. Neurosci.

Temporal changes in glial fibrillary acidic protein messenger RNA and [3H]PK11195 binding in relation to imidazoline-12-receptor and alpha 2-adrenoceptor binding in the hippocampus following transient global forebrain ischaemia in the rat

Neuroscience

Increase in omega 3 (peripheral-type benzodiazepine) binding site densities in different types of human brain tumors. A quantitative autoradiography study

Acta Neurochirurg.

Protective effects of moderate hypothermia on behavioral deficits but not necrotic cavitation following cortical impact injury in the rat

J. Neurotrauma

Progesterone stimulates the activity of the promoters of peripheral myelin protein-22 and protein zero genes in Schwann cells

J. Neurochem.

Portacaval anastomosis causes selective alterations of peripheral-type benzodiazepine receptor expression in rat brain and peripheral tissues

Neurochem. Int.

Regular Article
Traumatic Brain Injury Leads to Increased Expression of Peripheral-Type Benzodiazepine Receptors, Neuronal Death, and Activation of Astrocytes and Microglia in Rat Thalamus

Temporal changes in glial fibrillary acidic protein messenger RNA and [³H]PK11195 binding in relation to imidazoline-12-receptor and alpha 2-adrenoceptor binding in the hippocampus following transient global forebrain ischaemia in the rat