Characterization of the TNF and IL-1 systems in human brain and blood after ischemic stroke

Bettina H Clausen,Bente Finsen,Helle H Nielsen,Bjarne W Kristensen,Lars H Frich,Kamilla Østergaard,Martin Wirenfeldt,Kate L Lambertsen,Sofie S Høgedal,Henrik D Schrøder

doi:10.1186/s40478-020-00957-y

Abstract

Preclinical and clinical proof-of-concept studies have suggested the effectiveness of pharmacological modulation of inflammatory cytokines in ischemic stroke. Experimental evidence shows that targeting tumor necrosis factor (TNF) and interleukin (IL)-1 holds promise, and these cytokines are considered prime targets in the development of new stroke therapies. So far, however, information on the cellular expression of TNF and IL-1 in the human ischemic brain is sparse.We studied 14 cases of human post-mortem ischemic stroke, representing 21 specimens of infarcts aged 1 to > 8 days. We characterized glial and leukocyte reactions in the infarct/peri-infarct (I/PI) and normal-appearing tissue (NAT) and the cellular location of TNF, TNF receptor (TNFR)1 and TNFR2, IL-1α, IL-1β, and IL-1 receptor antagonist (IL-1Ra). The immunohistochemically stained tissue sections received a score reflecting the number of immunoreactive cells and the intensity of the immunoreactivity (IR) in individual cells where 0 = no immunoreactive cells, 1 = many intermediately to strongly immunoreactive cells, and 2 = numerous and intensively immunoreactive cells. Additionally, we measured blood TNF, TNFR, and IL-1 levels in surviving ischemic stroke patients within the first 8 h and again at 72 h after symptom onset and compared levels to healthy controls.We observed IL-1α and IL-1β IR in neurons, glia, and macrophages in all specimens. IL-1Ra IR was found in glia, in addition to macrophages. TNF IR was initially found in neurons located in I/PI and NAT but increased in glia in older infarcts. TNF IR increased in macrophages in all specimens. TNFR1 IR was found in neurons and glia and macrophages, while TNFR2 was expressed only by glia in I/PI and NAT, and by macrophages in I/PI. Our results suggest that TNF and IL-1 are expressed by subsets of cells and that TNFR2 is expressed in areas with increased astrocytic reactivity. In ischemic stroke patients, we demonstrate that plasma TNFR1 and TNFR2 levels increased in the acute phase after symptom onset compared to healthy controls, whereas TNF, IL-1α, IL-1β, and IL-1Ra did not change.Our findings of increased brain cytokines and plasma TNFR1 and TNFR2 support the hypothesis that targeting post-stroke inflammation could be a promising add-on therapy in ischemic stroke patients.

Highlights

Inflammation is integral to the pathophysiology of ischemic stroke and a prime target for the development of new stroke therapies
Ionized calcium-binding adaptor molecule 1 (Iba1) score for macrophages was very low in normal-appearing tissue (NAT)
IL-1α, IL-1β, IL-1 receptor antagonist (IL-1Ra), and tumor necrosis factor (TNF) IR is located to subsets of cells We showed previously that TNF and IL-1β [11] and IL1α, IL-1β, IL-1Ra [12] are produced by subsets of microglia in experimental stroke

Summary

Introduction

Inflammation is integral to the pathophysiology of ischemic stroke and a prime target for the development of new stroke therapies. The inflammatory cytokines interleukin (IL)-1 and tumor necrosis factor (TNF) are pivotal in regulating immune responses following ischemic stroke (reviewed in [31]) and are potential targets in stroke therapy. IL-1β is rapidly upregulated in the blood [41, 55, 69] and brain [45] and exacerbates injury in experimental animal models (reviewed in [31]). The IL-1 receptor antagonist (IL-1Ra) is a natural competitive inhibitor of IL-1 signaling [23] and modulates the size of ischemic infarcts in experimental animal models [12, 37, 44, 49]. An IL-1β haplotype in postmenopausal women and hypertensive persons [3], and an IL-1α haplotype in Koreans [64] are associated with increased stroke risk

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