Exogenous inter-α inhibitor proteins prevent cell death and improve ischemic stroke outcomes in mice
Louise D. McCullough, … , Yow-Pin Lim, Venugopal Reddy Venna
Louise D. McCullough, … , Yow-Pin Lim, Venugopal Reddy Venna
Published September 1, 2021
Citation Information: J Clin Invest. 2021;131(17):e144898. https://doi.org/10.1172/JCI144898.
View: Text | PDF
Research Article Inflammation Neuroscience

Exogenous inter-α inhibitor proteins prevent cell death and improve ischemic stroke outcomes in mice

Abstract

Inter-α inhibitor proteins (IAIPs) are a family of endogenous plasma and extracellular matrix molecules. IAIPs suppress proinflammatory cytokines, limit excess complement activation, and bind extracellular histones to form IAIP-histone complexes, leading to neutralization of histone-associated cytotoxicity in models of sepsis. Many of these detrimental processes also play critical roles in the pathophysiology of ischemic stroke. In this study, we first assessed the clinical relevance of IAIPs in stroke and then tested the therapeutic efficacy of exogenous IAIPs in several experimental stroke models. IAIP levels were reduced in both ischemic stroke patients and in mice subjected to experimental ischemic stroke when compared with controls. Post-stroke administration of IAIP significantly improved stroke outcomes across multiple stroke models, even when given 6 hours after stroke onset. Importantly, the beneficial effects of delayed IAIP treatment were observed in both young and aged mice. Using targeted gene expression analysis, we identified a receptor for complement activation, C5aR1, that was highly suppressed in both the blood and brain of IAIP-treated animals. Subsequent experiments using C5aR1-knockout mice demonstrated that the beneficial effects of IAIPs are mediated in part by C5aR1. These results indicate that IAIP is a potential therapeutic candidate for the treatment of ischemic stroke.

Authors

Louise D. McCullough, Meaghan Roy-O’Reilly, Yun-Ju Lai, Anthony Patrizz, Yan Xu, Juneyoung Lee, Aleah Holmes, Daniel C. Kraushaar, Anjali Chauhan, Lauren H. Sansing, Barbara S. Stonestreet, Liang Zhu, Julia Kofler, Yow-Pin Lim, Venugopal Reddy Venna

×

Figure 1

Endogenous IAIP levels are significantly reduced 24 hours after stroke; and IAIPs are expressed in both mouse and human brain.

Options: View larger image (or click on image) Download as PowerPoint
Endogenous IAIP levels are significantly reduced 24 hours after stroke; ...
(A) Circulating IAIPs were significantly reduced in mouse plasma 24 hours after ischemic stroke compared with sham controls (data presented as mean ± SEM; ***P = 0.0004, t test). (B) IAIP-histone complexes were significantly elevated in mice at 24 hours after ischemic stroke compared with controls (mean ± SEM; *P = 0.0466, t test). (C) Plasma IAIPs were significantly lower in ischemic stroke patients than in risk factor–matched controls 24 hours after stroke (**P = 0.0022, Wilcoxon’s rank sum test; effect size Cohen’s d = 0.63). An outlier test detected 1 outlier in the stroke group (ROUT method). After removal of the outlier, the P value and effect size were 0.0011 and 0.73, respectively. (D) IAIP-histone complexes were significantly higher in ischemic stroke patients than in control patients 24 hours after stroke (**P = 0.0061, Wilcoxon’s rank sum test; effect size Cohen’s d = 0.30). An outlier test detected 4 outliers in the control group and 1 in the stroke group. After removal of these outliers, P was 0.0002, and effect size d was 0.93. (E–G) Regression analysis revealed a significant negative correlation between inflammatory markers and plasma IAIP levels. Plasma from stroke patients with higher IAIP levels had lower TNF-α (P = 0.0397), IFN-γ (P = 0.0229), and CCL11 (P = 0.018). (H) Immunohistochemistry on postmortem brains from stroke patients indicates that IAIPs are expressed in brain. Scale bars: 25 μm. (I) Fluorescence intensity data reveal that IAIP expression was significantly reduced in stroke brain (mean ± SEM; ***P = 0.0003, t test).