Elsevier

Neuroscience

Volume 102, Issue 4, 14 February 2001, Pages 805-818
Neuroscience

Interleukin-6 deficiency reduces the brain inflammatory response and increases oxidative stress and neurodegeneration after kainic acid-induced seizures

https://doi.org/10.1016/S0306-4522(00)00515-7Get rights and content

Abstract

The role of interleukin-6 in hippocampal tissue damage after injection with kainic acid, a rigid glutamate analogue inducing epileptic seizures, has been studied by means of interleukin-6 null mice. At 35 mg/kg, kainic acid induced convulsions in both control (75%) and interleukin-6 null (100%) mice, and caused a significant mortality (62%) only in the latter mice, indicating that interleukin-6 deficiency increased the susceptibility to kainic acid-induced brain damage. To compare the histopathological damage caused to the brain, control and interleukin-6 null mice were administered 8.75 mg/kg kainic acid and were killed six days later. Morphological damage to the hippocampal field CA1–CA3 was seen after kainic acid treatment. Reactive astrogliosis and microgliosis were prominent in kainic acid-injected normal mice hippocampus, and clear signs of increased oxidative stress were evident. Thus, the immunoreactivity for inducible nitric oxide synthase, peroxynitrite-induced nitration of proteins and byproducts of fatty acid peroxidation were dramatically increased, as was that for metallothionein I+II, Mn-superoxide dismutase and Cu/Zn-superoxide dismutase. In accordance, a significant neuronal apoptosis was caused by kainic acid, as revealed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling and interleukin-1β converting enzyme/Caspase-1 stainings. In kainic acid-injected interleukin-6 null mice, reactive astrogliosis and microgliosis were reduced, while morphological hippocampal damage, oxidative stress and apoptotic neuronal death were increased. Since metallothionein-I+II levels were lower, and those of inducible nitric oxide synthase higher, these concomitant changes are likely to contribute to the observed increased oxidative stress and neuronal death in the interleukin-6 null mice.

The present results demonstrate that interleukin-6 deficiency increases neuronal injury and impairs the inflammatory response after kainic acid-induced seizures.

Section snippets

Experiments

IL-6 null knock-out (KO) mice36 were kindly provided by Dr Horst Bluethmann (CNS Department, Pharma Research Gene Technologies, F. Hoffmann-La Roche AG, CH-4070, Basel, Switzerland).

In a first experiment, adult normal (1295 v, n=8) and IL-6 KO (n=8) mice were injected i.p. with 35 mg/kg KA, which is a glutamate receptor agonist with excitotoxic effects.40 The number of mice showing seizures as well as the mortality were recorded. Because of the high mortality of the IL-6 KO mice, no

Susceptibility to kainic acid

Saline-injected mice of normal and IL-6 KO genotypes showed similar behavioral patterns. No spontaneous convulsions were seen in these mice. The administration of 35 mg/kg KA produced convulsions in both normal and IL-6 KO mice (Table 1), but the percentage of mice seizing and the number of convulsions were higher in the latter (P<0.05). Moreover, five out of eight (62.5%) of the IL-6 KO mice died in the following few hours after the KA administration, while none of the control mice died (P

Discussion

The IL-6 null mice are a unique tool for analysing the role of this cytokine on KA-induced hippocampal damage. The results clearly show that the IL-6 mice are more susceptible to KA-induced seizures, with a higher percentage of animals seizing and a greater mortality compared to control mice. Associated with this increased susceptibility, the IL-6 mice showed an impaired glial response to KA-induced seizures, an unbalanced antioxidant profile that led to an increased oxidative stress, and an

Conclusions

The present report demonstrates that IL-6 deficiency impairs significantly the gliosis induced by KA-induced seizures, and increases the oxidative stress and the neuronal death, processes where the partially blunted MT-I+II expression may have a relevant role.

Acknowledgements

We are indebted to Dr Horst Bluethmann (CNS Department, Pharma Research Gene Technologies, F. Hoffmann-La Roche AG, CH-4070, Basel, Switzerland) for his continuous support and for the generous gift of the IL-6 KO mice. The superb excellent technical assistence of Hanne Hadberg, Pernille S. Thomsen, Mette Søberg, Grazyna Hahn, Birgit Risto and Keld Stub is gratefully acknowledged. These studies were supported by Hjerteforeningen (MP), Kong Christian X's Fond (MP), Boldings Fond (MP), Fonden til

References (76)

  • J. Hernández et al.

    Endotoxin and intracerebroventricular injection of IL-1 and IL-6 induce rat brain metallothionein-I and -II

    Neurochem. Int.

    (1998)
  • J. Hernández et al.

    Transgenic expression of interleukin 6 in the central nervous system regulates brain metallothionein-I and -III expression in mice

    Brain Res. Molec. Brain Res.

    (1997)
  • S. Hopkins et al.

    Cytokines and the nervous system. I: Expression and recognition

    Trends Neurosci.

    (1995)
  • M.B. Jørgensen et al.

    Microglial and astroglial reactions to ischemic and kainic acid-induced lesions of the adult rat hippocampus

    Expl Neurol.

    (1993)
  • T. Kossmann et al.

    Interleukin-6 released in human cerebrospinal fluid following traumatic brain injury may trigger nerve growth factor production in astrocytes

    Brain Res.

    (1996)
  • G.W. Kreutzberg

    Microglia: a sensor for pathological events in the CNS

    Trends Neurosci.

    (1996)
  • B.W. Kristensen et al.

    Excitotoxic effects of non-NMDA receptor agonists in organotypic corticostriatal slice cultures

    Brain Res.

    (1999)
  • Y. Kushima et al.

    Interleukin-6 as a neurotrophic factor for promoting the survival of cultured catecholaminergic neurons in a chemically defined medium from fetal and postnatal rat midbrains

    Neurosci. Res.

    (1992)
  • J.S. Lazo et al.

    Enhanced sensitivity to oxidative stress in cultured embryonic cells from transgenic mice deficient in metallothionein I and II genes

    J. biol. Chem.

    (1995)
  • J.S. Lazo et al.

    The protein thiol metallothionein as an antioxidant and protectant against antineoplastic drugs

    Chem. Biol. Interact.

    (1998)
  • Y. Li et al.

    Reduced mitochondrial manganese-superoxide dismutase activity exacerbates glutamate toxicity in cultured mouse cortical neurons

    Brain Res.

    (1998)
  • J. Liu et al.

    Metallothionein (MT)-null mice are sensitive to cisplatin-induced hepatotoxicity

    Toxicol. appl. Pharmac.

    (1998)
  • M. Minami et al.

    Effects of kainic acid on messenger RNA levels of IL-1 beta, IL-6, TNF alpha and LIF in the rat brain

    Biochem. biophys. Res. Commun.

    (1991)
  • M. Penkowa et al.

    Impaired inflammatory response to glial cell death in genetically metallothionein-I- and -II-deficient mice

    Expl Neurol.

    (1999)
  • M Penkowa et al.

    IL-6 deficiency leads to reduced metallothionein-I+II expression and increased oxidative stress in the brain stem after 6-aminonicotinamide treatment

    Exp. Neurol.

    (2000)
  • V. Perry et al.

    Inflammation in the nervous system

    Curr. Opin. Neurobiol.

    (1995)
  • G. Raivich et al.

    Neuroglial activation repertoire in the injured brain: graded response, molecular mechanisms and cues to physiological function

    Brain Res. Rev.

    (1999)
  • K.M. Savolainen et al.

    Interactions of excitatory neurotransmitters and xenobiotics in excitotoxicity and oxidative stress: glutamate and lead

    Toxicol. Lett.

    (1998)
  • G. Sperk

    Kainic acid seizures in the rat

    Prog. Neurobiol.

    (1994)
  • S. Toulmond et al.

    Local infusion of interleukin-6 attenuates the neurotoxic effects of NMDA on rat striatal cholinergic neurons

    Neurosci. Lett.

    (1992)
  • M. Yamada et al.

    Interleukin-6 protects cultured rat hippocampal neurons against glutamate-induced cell death

    Brain Res.

    (1994)
  • H. Zheng et al.

    Metallothionein-I and -II knock-out mice are sensitive to cadmium-induced liver mRNA expression of c-jun and p53

    Toxicol. appl. Pharmac.

    (1996)
  • A. Abdel-Mageed et al.

    Antisense down-regulation of metallothionein induces growth arrest and apoptosis in human breast carcinoma cells

    Cancer Gene Ther.

    (1997)
  • C. Ali et al.

    Ischemia-induced interleukin-6 as a potential endogenous neuroprotective cytokine against NMDA receptor-mediated excitotoxicity in the brain

    J. cereb Blood Flow Metab.

    (2000)
  • M. Aschner

    Metallothionein (MT) isoforms in the central nervous system (CNS): regional and cell-specific distribution and potential functions as an antioxidant

    Neurotoxicology

    (1998)
  • N.G. Carlson et al.

    Inflammatory cytokines IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha impart neuroprotection to an excitotoxin through distinct pathways

    J. Immun.

    (1999)
  • Cassarino D. S. and Bennett J. P. Jr (1999) An evaluation of the role of mitochondria in neurodegenerative diseases:...
  • P.H. Chan et al.

    Reduced neurotoxicity in transgenic mice overexpressing human copper-zinc-superoxide dismutase

    Stroke

    (1990)
  • Cited by (0)

    View full text