Quantitative analysis of cytokine-induced vascular toxicity and vascular leak in the mouse brain.
A storm of inflammatory cytokines is released during treatment with pro-inflammatory cytokines, such as interleukin-2 (IL-2), closely approximating changes initially observed during sepsis. These signals induce profound changes in neurologic function and cognition. Little is known about the mechanisms involved. We evaluated a number of experimental methods to quantify changes in brain blood vessel integrity in a well-characterized IL-2 treatment mouse model. Measurement of wet versus dry weight and direct measurement of small molecule accumulation (e.g. [(3)H]-H(2)O, sodium fluorescein) were not sensitive or reliable enough to detect small changes in mouse brain vascular permeability. Estimation of brain water content using proton density magnetic resonance imaging (MRI) measurements using a 7T mouse MRI system was sensitive to 1-2% changes in brain water content, but was difficult to reproduce in replicate experiments. Successful techniques included use of immunohistochemistry using specific endothelial markers to identify vasodilation in carefully matched regions of brain parenchyma and dynamic contrast enhanced (DCE) MRI. Both techniques indicated that IL-2 treatment induced vasodilation of the brain blood vessels. DCE MRI further showed a 2-fold increase in the brain blood vessel permeability to gadolinium in IL-2 treated mice compared to controls. Both immunohistochemistry and DCE MRI data suggested that IL-2 induced toxicity in the brain results from vasodilation of the brain blood vessels and increased microvascular permeability, resulting in perivascular edema. These experimental techniques provide us with the tools to further characterize the mechanism responsible for cytokine-induced neuropsychiatric toxicity.
Irwan
Yetty Y
YY
Section of Melanoma, Renal Cancer and Immunotherapy, Nevada Cancer Institute, Las Vegas, NV 89135, United States of America.
Feng
Yi
Y
Gach
H Michael
HM
Symanowski
James T
JT
McGregor
John R
JR
Veni
Gopalkrishna
G
Schabel
Matthias
M
Samlowski
Wolfram E
WE
D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply* / Q000187:drug effects / Q000276:immunology; D002199:Capillary Permeability / Q000187:drug effects; D005260:Female; D007150:Immunohistochemistry; D007376:Interleukin-2 / Q000633:toxicity*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009929:Organ Size / Q000187:drug effects; D013047:Specific Pathogen-Free Organisms; D014652:Vascular Diseases / Q000139:chemically induced* / Q000276:immunology
D007376:Interleukin-2