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Double-Transgenic Mice



From the Abteilung Neuropathologie*
and
Abteilung Immunpathologie,
Pathologisches
Institut, Universität Bern, Bern, Switzerland; Institut für
Neuropathologie,
Universitätsklinikum
der Rheinisch-Westfälischen Technischen Hochschule Aachen,
Aachen, Germany; Abteilung
Pathophysiologie,§
1. Medizinische Klinik der
Universität Mainz, Mainz, Germany
Interleukin-6 (IL-6), a major cytokine with diverse effects
on cells mainly of the immune and hematopoietic systems, has
been linked to several neurological disorders such as acquired immune
deficiency syndrome dementia, multiple sclerosis, and
Alzheimers disease. Central nervous system (CNS)-specific expression
of IL-6 caused neurodegeneration, massive gliosis, and
vascular proliferation in transgenic mice. However, the effects
of systemically circulating IL-6 and its receptor IL-6R
on the CNS
are unknown. IL-6R
is the specific component of the IL-6 receptor
system and hence an important co-factor of IL-6. IL-6R
is bioactive
in a membrane-bound and in a soluble (s) form. We investigated the
effects of systemically elevated levels of either human IL-6 or human
sIL-6R
or both on the CNS of transgenic mice. Although IL-6 and
sIL-6R
single transgenic mice were free of neurological
disease, IL-6/sIL-6R
double-transgenic mice showed
neurological signs, such as tremor, gait
abnormalities, and paresis. However, these mice also
frequently showed prominent general weakness probably because of
the systemic effects of IL-6/IL-6R
such as liver damage and
plasmacytomas. IL-6/sIL-6R
transgenic mice exhibited massive
reactive gliosis. Lack of signs of neuronal breakdown
versus ample astrogliosis suggested that astrocytes were
selectively affected in these mice. There was neither vascular
proliferation nor inflammatory infiltration. Ultrastructural analysis
revealed blood-brain barrier (BBB) changes manifested by hydropic
astrocytic end-feet. However, albumin immunohistochemistry did
not reveal major BBB leakage. Our results indicate that increased and
constitutive systemic expression of IL-6 together with its soluble
receptor sIL-6R
is less harmful to the brain than to other organs.
The BBB remains primarily intact. IL-6/IL-6R
,
however, might be directly responsible for the selective
activation of astrocytes.
This article has been cited by other articles:
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O. P. Kristiansen and T. Mandrup-Poulsen Interleukin-6 and Diabetes: The Good, the Bad, or the Indifferent? Diabetes, December 1, 2005; 54(suppl_2): S114 - S124. [Abstract] [Full Text] [PDF] |
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