Research ArticleStroke

Targeted complement inhibition salvages stressed neurons and inhibits neuroinflammation after stroke in mice

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Science Translational Medicine  16 May 2018:
Vol. 10, Issue 441, eaao6459
DOI: 10.1126/scitranslmed.aao6459
  • Fig. 1 Systemically administered B4Crry locally and transiently inhibits complement activation in the post-ischemic brain and reduces acute injury.

    Experiments performed in adult wild-type (WT) male mice treated with vehicle, B4scFv, or B4Crry or in C3−/− mice (as indicated in figure) that underwent 1-hour MCAO followed by reperfusion. (A) Biodistribution of 125I-radiolabeled B4Crry administered at 2 or 24 hours after MCAO and measured at 6 hours after administration in MCAO or sham animals. Two-way analysis of variance (ANOVA) with Bonferroni, n = 4; *P < 0.05, **P < 0.01, ***P < 0.001. (B) C3a concentration measured by enzyme-linked immunosorbent assay (ELISA) on brain homogenates from sham animals or MCAO animals treated with B4Crry or vehicle 2 hours after stroke. ANOVA with Bonferroni, n = 3 animals, *P < 0.05 and ***P < 0.001. (C) Immunofluorescence (IF) staining of C3d deposition in the ischemic hemisphere 24 hours after stroke. B4Crry was administered 2 hours after MCAO. Scale bars, 20 μm. (D) Infarct volume measured by tetraphenyl tetrazolium chloride (TTC) staining of 2-mm-thick sections at 24 or 72 hours after stroke in WT animals treated with vehicle, B4scFv, or B4Crry and in Rag1−/− mice. Treatments were administered 2 hours after MCAO, n = 8 per group (5 for Rag1−/−). ANOVA with Bonferroni, *P < 0.05 and **P < 0.01. (E) Neurological deficit scores at 24 or 72 hours after stroke. Kruskal-Wallis test, *P < 0.05.

  • Fig. 2 B4Crry administered acutely after MCAO improves long-term histopathological, motor, and cognitive recovery.

    Experiments performed in WT animals subjected to 1-hour MCAO and treated with vehicle, B4scFv, or B4Crry at 2 hours after MCAO or with B4Crry at 6 hours after MCAO. (A) Daily neurological deficit score collected throughout 15 days of recovery. Repeated-measures two-way ANOVA with Bonferroni, n = 9 [B4scFv and B4Crry (6 hours)] and n = 13 [vehicle and B4Crry (2 hours)], ^^^P < 0.001 comparing vehicle to B4scFv and B4Crry (2 hours) and ***P < 0.001 comparing vehicle to B4Crry (2 hours) and B4Crry (6 hours). (B) Infarct volumes reconstructed from serial Nissl-stained sections (200 μm apart) harvested 15 days after MCAO. One-way ANOVA with Bonferroni, n = 9 per group, *P < 0.05 and ****P < 0.001. (C) Lesion was reconstructed as described in fig. S6, and three-dimensional (3D) models show the lesion in red mapped to the ipsilateral hemisphere, the cortex in yellow, basal ganglia in green, and hippocampus in blue. A coronal cut was performed at Bregma +0.38, and cross-sectional views are shown to the right of 3D models. (D to F) Motor recovery measured by open-field locomotion (D), forelimb laterality (corner task, E), and pasta handling (F) over 15 days of recovery. Two-way ANOVA with Bonferroni, n = 8 animals per group and n = 12 animals per group for corner task vehicle and B4Crry (2 hours); *P < 0.05, **P < 0.01, ***P < 0.001. (G and H) Passive avoidance (G) and Barnes maze (H) tasks. Two-way ANOVA, n = 8 (Barnes), n = 8 [avoidance controls and B4Crry (6 hours)], and n = 11 [avoidance B4Crry (2 hours)]; *P < 0.05, **P < 0.01, ***P < 0.001 compared to controls (vehicle). (I) IF staining for Dcx+ neuroblasts migrating to the peri-infarct hippocampus and cortex 15 days after MCAO. Images represent 3D reconstruction of 20-μm z-stack. Scale bars, 20 μm. DAPI, 4′,6-diamidino-2-phenylindole. (J) Quantification of (I). Multiple t tests with Holm-Sidak correction, n = 5 animals (three fields per animal), *P < 0.05 and **P < 0.01. Data are reported as means ± SEM in all panels.

  • Fig. 3 B4Crry provides neuroprotection across different ischemia times, gender, and age and with delayed administration.

    Experiments performed in vehicle- or B4Crry-treated adult male mice that underwent 1-hour MCAO followed by 30 days of reperfusion. (A) Neurological deficit assessment performed over 30 days. Two-way ANOVA with Bonferroni, n = 9 (vehicle) and n = 6 (B4Crrry), **P < 0.01. (B and C) Infarct volume calculated from serial brain sections stained with Nissl (B) and forelimb laterality on corner task (C) 30 days after reperfusion. Student’s t test, two-tailed; n = 9 (vehicle) and 6 (B4Crrry), *P < 0.05 and ***P < 0.001. (D) Kaplan-Meier plot of survival over 30 days after stroke. Log-rank (Mantel-Cox) test, *P < 0.05. (E and F) Experiments performed in adult male mice with variable ischemia time, and outcomes assessed 24 hours after reperfusion. (E) Neurological deficit scores at 24 hours after MCAO. Multiple t tests with Holm-Sidak correction, n = 7 (30 and 90 min) and n = 13 (60 min), #P = 0.06 and *P < 0.05. (F) Infarct volume calculated from serial brain sections stained with Nissl 15 days after MCAO. Student’s t test, n = 6 per group, *P < 0.05 and $P = 0.06. (G and H) Experiments performed in adult female mice with 1-hour MCAO followed by 15 days of reperfusion. B4Crry/vehicle administered 2 hours after ischemia. (G) Neurological deficit assessed throughout recovery. Two-way ANOVA, n = 8 (vehicle) and n = 7 (B4Crry), *P < 0.05 and **P < 0.01. (H) Infarct volume assessed by Nissl staining 15 days after MCAO. Student’s t test, n = 7, *P < 0.05. (I) Neurological deficit and infarct volumes (measured by TTC) in aged male mice (10 months old) at 24 hours after 1-hour MCAO and B4Crry administration 2 hours after MCAO. Mann-Whitney test for neurological deficit and Student’s t test for infarct volume (I), n = 7 (vehicle) and n = 6 (B4Crry), *P < 0.05 and **P < 0.01. (J) Kaplan-Meier curve representing 7-day survival of aged animals after MCAO. Mantel-Cox test, n = 9, *P < 0.05. (K to N) Experiments performed in adult male mice with 1-hour MCAO followed by reperfusion, with B4Crry administration 24 hours after ischemia. (K) Neurological deficit assessment over 15 days after MCAO, n = 15 (vehicle) and 18 (B4Crry). Two-way ANOVA with Bonferroni, *P < 0.05 and **P < 0.01. (L) Normalized laterality index on corner task. Multiple t tests with Holm-Sidak correction, n = 9 (vehicle) and n = 9 (B4Crry), *P < 0.05 (M) Cognitive performance on Barnes maze learning and retention 9 to 15 days after MCAO. Two-way ANOVA with Bonferroni, n = 8 (vehicle) and n = 10 (B4Crry), ** P < 0.01. (N) Lesion volume reconstructed from Nissl-stained sections at 15 days after MCAO. Student’s t test, n = 10, ***P < 0.001. Three-dimensional models displayed with lesion in red. (O) Percentage of animals who died within 48 hours of MCAO because of intracerebral hemorrhage (ICH) after vehicle or B4Crry treatment. χ2 test, P > 0.05, n = 12 per group. Data are reported as means ± SEM in all panels.

  • Fig. 4 B4Crry inhibits microglial phagoptosis of c-fos–expressing neurons acutely after ischemia.

    Experiments performed in adult WT male mice treated with B4Crry, B4scFv, or vehicle or in C3−/− mice that underwent 1-hour MCAO followed by 24 hours of reperfusion. Treatments were administered 2 hours after ischemia (A) Top: Visualization of the location of selection of fields for IF staining for Figs. 4 and 5 using the mouse brain atlas. Bottom: IF for NeuN (red) showing neuronal density. (B) Quantification of neuronal cell density in three perilesional fields (240 μm × 240 μm) per animal (n = 5 animals per group). One-way ANOVA with Bonferroni, n = 5 per group, *P < 0.05. (C) IF staining and super-resolution microscopy of c-fos+ cells and microglia (Iba1+). (D) High-magnification volume  reconstruction of fields from (C) using Amira showing c-fos material within microglial cell bodies with black arrows. Scale bars, 100 μm. Fields are chosen using defined stereotactic location shown in (A). (E) Quantification of neuronal c-fos+ cell density in three perilesional fields. One-way ANOVA with Bonferroni. n = 5 per group, *P < 0.05. (F) Quantification of cleaved caspase-3 expression in c-fos+ cells (IF staining shown in fig. S11). (G) Quantification of neuronal Iba1+ cell density in three perilesional fields. One-way ANOVA with Bonferroni, n = 5 per group, *P < 0.05 and **P < 0.01. (H) Frequency of c-fos material within microglial cell bodies. ANOVA with Bonferroni, n = 4, ***P < 0.001. (I and J) High-resolution fields from the ipsilesional cortex showing c-fos and Iba1 localization (I) and Iba1 and NeuN localization (J). Left panels in (D) and (E): Three-dimensional reconstruction of a 20-μm stack using ZEN. Right panel in (D): Orthographic view showing colocalization of c-fos (green) and Iba1 (red). Right panel in (E): Orthographic view showing colocalization of Iba1 (green) and NeuN (red). Scale bars, 100 μm. Insets in (D) show DAPI counterstain (in blue). (K) Quantification of the number of Iba1 cells containing c-fos material over total number of Iba1 cells. ANOVA with Bonferroni, n = 4 animals per group, **P < 0.01. (L) Quantification of the density of Mac2+ cells in the ipsilateral hemisphere. ANOVA with Bonferroni, n = 4 per group, **P < 0.01 and ***P < 0.001. (M) Mac2 IF and localization of c-fos in perilesional brain areas. Scale bars, 100 μm. (N) IF using anti-FCRLS antibody. Scale bars, 100 μm. White boxes in (D) to (F) label regions of colocalization. (O) Quantification of IF shown in (N) and in fig. S11A showing percentage of c-fos+/Iba+ clusters located within FCRLS+ cells. Data are reported as means ± SEM in all panels.

  • Fig. 5 Microglia phagocytosis of stressed neurons is complement C3d–dependent.

    Experiments performed in adult male mice with 1-hour MCAO followed by 24 hours of reperfusion, with B4Crry or vehicle administered 2 hours after ischemia. (A) IF staining and super-resolution microscopy showing C3d, Iba1, c-fos, and DAPI in perilesional areas in vehicle-treated (A) or B4Crry-treated (B) mice. Left: Three-dimensional rendered view of 20-μm stack. Right: Orthographic view. Scale bars, 20 μm. For quantification of C3d deposition on c-fos+ neurons, refer to fig. S13. (C) Co-staining for NeuN, c-fos, Iba1, and C3d. Scale bars, 20 μm. Arrows point to site of C3d deposition at the microglia-neuron interface. (D) Top: Schematic illustration of the approach used to quantify neuronal-microglial interaction. NeuN-Iba1 contacts were first identified and then classified on the basis of the presence of C3d or c-fos expression. Non-neuronal cells were not identified or classified. Bottom: Distribution of Iba1-NeuN contacts based on C3d and c-fos immunoreactivity. Fisher exact test was used to compare the proportion of C3d+ contacts between vehicle- and B4Crry-treatment groups, showing a significant difference (P < 0.001). (E) IF staining for c-fos material within microglia and localized to phagolysosomal vesicles (LAMP1+). Arrows and rectangle show the site of colocalization. (F) Representative 3D view of NeuN material localizing within microglial phagolysosomal vesicles (LAMP1+). White rectangle indicates region of colocalization. Scale bars, 20 μm. (G and H) Quantification of LAMP1/c-fos/Iba1 overlay shown as intensity per pixel (G) and colocalized clusters (H). Black bars in (G) show the number of overlapping peaks. Student’s t test, n = 6 animals (three fields per animal), **P < 0.01. Data are reported as means ± SEM in all panels.

  • Fig. 6 Acute complement activation initiates inflammatory cascades that persist chronically after stroke.

    Experiments performed in adult male mice with 1-hour MCAO followed by reperfusion, with B4Crry or vehicle administered 2 hours after ischemia. (A to D) NanoString analysis of immunology-related gene expression 5 days after MCAO. (A) Clustergram of differentially expressed genes (P < 0.01, multiple t tests; see Supplementary Materials and Methods) between B4Crry- and vehicle-treated animals. Heat map represents fold expression relative to the average of the vehicle group for each gene. (B) Analysis of biological processes enriched in the set of genes down-regulated by B4Crry. (C) Gene expression changes in complement genes 5 days after MCAO and B4Crry or vehicle treatment. *P < 0.05. Multiple t tests with Bonferroni, n = 5 per group, P < 0.01. (D) Gene expression changes in genes involved in microglia/macrophage attraction and activation. Red borders around bars indicate significance. Multiple t tests with Bonferroni, n = 5 per group. P < 0.01. (E and F) Representative serial images of IF staining of full-brain sections for Mac2+ and Ym1+ microglia (E) and quantification of Iba1 colocalization with Mac2 or YM1 (F). Scale bars, 200 μm. Student’s t test. n = 4 animals (four fields per animal). *P < 0.05 and **P < 0.01. (G to I) Assessment of neurodegeneration by IF staining for neurons (NeuroTrace), dendrites (MAP2), and microglia (Iba1) 15 days after MCAO. (G) IF staining for neuronal (NeuroTrace), microglial (Iba1), and dendritic (MAP2) densities in the ipsilateral basal ganglia, cortex, and hippocampus in vehicle- and B4Crry-treated mice. Scale bar, 200 μm. Location of field selection and the approach used for quantification are shown in fig. S17. (H) Representative histograms from B4Crry- and vehicle-treated mice showing difference in dendritic density between the two groups. (I) Quantification of (G) and (H). Student’s t test, n = 5; *P < 0.05, **P < 0.01, ***P < 0.001. Data are reported as means ± SEM in all panels. FOV, field of view.

  • Fig. 7 Long-term complement deposition is associated with robust microgliosis and inflammatory cell infiltrate 15 days after MCAO.

    Experiments performed in adult male mice with 1-hour MCAO followed by 15 days of reperfusion with B4Crry or vehicle administered 2 hours after ischemia (A) IF staining of the evolving infarct core showing Mac2, C3d, CD31, and DAPI expression. Insets 1 and 2: High-resolution fields from (A). (B) High-resolution fields from B4Crry-treated animals corresponding to same location as inset 1 in (A). Scale bars, 200 μm. (C) IF for C3d, CD31, and DAPI. Fields are 3D-rendered stacks covering 20 μm. Scale bars, 200 μm. White arrows point to regions of overlap between C3d and CD31. (D and E) IF for CD3+ (D) and Gr1+ (E) cellular infiltrate in vehicle controls compared to B4Crry-treated animals. White bars, 200 μm. Black bars, 50 μm. (F) Quantification of (D) and (E). Student’s t test, n = 5, *P < 0.05 and **P < 0.01.

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/10/441/eaao6459/DC1

    Materials and Methods

    Fig. S1. B4Crry inhibits complement activation and IgM deposition on stressed neurons and endothelial cells in vitro.

    Fig. S2. B4Crry is retained specifically in target tissue with no effects on systemic complement activity.

    Fig. S3. B4Crry localizes to both the cerebral vasculature and parenchyma after murine stroke.

    Fig. S4. B4Crry inhibits acute and subacute IgM and C3d deposition in the penumbra.

    Fig. S5. B4Crry does not provide additional neuroprotection in C3−/− mice.

    Fig. S6. Three-dimensional reconstruction of lesions using Nissl-stained images.

    Fig. S7. B4Crry reduces lesion expansion 15 days after MCAO.

    Fig. S8. CR2Crry does not provide sustained neuroprotection beyond the acute phase of MCAO.

    Fig. S9. B4Crry does not increase mortality in a murine pneumonia model.

    Fig. S10. Live perilesional neurons express c-fos, and microglial cells are attracted to c-fos+ neurons.

    Fig. S11. Inhibition of complement by B4Crry inhibits microglial phagocytosis of stressed penumbra neurons.

    Fig. S12. B4Crry administered at 6 hours after MCAO also inhibits microglial phagocytosis of c-fos+ material.

    Fig. S13. B4Crry modulates complement-neuronal interaction.

    Fig. S14. B4Crry treatment preserves homeostatic microglial activity after stroke.

    Fig. S15. B4Crry affects immune system–related gene expression 5 days after MCAO.

    Fig. S16. Acute targeted inhibition of complement prevents chronic amplification of microglial activation weeks after MCAO.

    Fig. S17. Protocol for quantification of neuronal, dendritic, and microglial density.

    Fig. S18. Microgliosis is associated with loss of neurons after stroke.

    Fig. S19. B4Crry inhibits chronic IgM and C3d deposition in the brain 15 days after MCAO.

    Fig. S20. Modified annexin IV DAMP is expressed in postmortem human ischemic brain as assessed by B4scFv immunostaining.

    Fig. S21. B4 IgM and B4Crry bind to the ischemic penumbra of acute stroke patients.

    Fig. S22. Overview of the mechanism of action of B4Crry and the experimental paradigm.

    Fig. S23. Complement inhibition or deficiency did not affect regional cerebral blood flow after MCAO and reperfusion.

    Table S1. Characteristics of human stroke brain donors from which samples were used in immunostaining.

    Table S2. Detailed description of antibodies used in immunostaining studies.

    Movie S1. Representative field of c-fos material within microglia of vehicle-treated controls.

    Movie S2. Representative field of c-fos material within microglia of B4scFv-treated mice.

    Movie S3. Representative field of c-fos material within microglia of B4Crry-treated mice.

    Movie S4. Representative field of c-fos material within microglia of C3-deficient mice.

    Movie S5. Representative field showing attraction of Iba1+ microglia to c-fos+/NeuN+ neurons that are tagged by C3d opsonins.

    Movie S6. Representative field showing neuronal material (NeuN, red) within Lamp1+ vesicles inside Mac2+ inflammatory microglia.

    Movie S7. Representative field showing c-fos material (c-fos, red) within Lamp1+ vesicles inside Iba1+ microglia.

    References (3239)

  • Supplementary Material for:

    Targeted complement inhibition salvages stressed neurons and inhibits neuroinflammation after stroke in mice

    Ali Alawieh, E. Farris Langley, Stephen Tomlinson*

    *Corresponding author. Email: tomlinss{at}musc.edu

    Published 16 May 2018, Sci. Transl. Med. 10, eaao6459 (2018)
    DOI: 10.1126/scitranslmed.aao6459

    This PDF file includes:

    • Materials and Methods
    • Fig. S1. B4Crry inhibits complement activation and IgM deposition on stressed neurons and endothelial cells in vitro.
    • Fig. S2. B4Crry is retained specifically in target tissue with no effects on systemic complement activity.
    • Fig. S3. B4Crry localizes to both the cerebral vasculature and parenchyma after murine stroke.
    • Fig. S4. B4Crry inhibits acute and subacute IgM and C3d deposition in the penumbra.
    • Fig. S5. B4Crry does not provide additional neuroprotection in C3−/− mice.
    • Fig. S6. Three-dimensional reconstruction of lesions using Nissl-stained images.
    • Fig. S7. B4Crry reduces lesion expansion 15 days after MCAO.
    • Fig. S8. CR2Crry does not provide sustained neuroprotection beyond the acute phase of MCAO.
    • Fig. S9. B4Crry does not increase mortality in a murine pneumonia model.
    • Fig. S10. Live perilesional neurons express c-fos, and microglial cells are attracted to c-fos+ neurons.
    • Fig. S11. Inhibition of complement by B4Crry inhibits microglial phagocytosis of stressed penumbra neurons.
    • Fig. S12. B4Crry administered at 6 hours after MCAO also inhibits microglial phagocytosis of c-fos+ material.
    • Fig. S13. B4Crry modulates complement-neuronal interaction.
    • Fig. S14. B4Crry treatment preserves homeostatic microglial activity after stroke.
    • Fig. S15. B4Crry affects immune system–related gene expression 5 days after MCAO.
    • Fig. S16. Acute targeted inhibition of complement prevents chronic amplification of microglial activation weeks after MCAO.
    • Fig. S17. Protocol for quantification of neuronal, dendritic, and microglial density.
    • Fig. S18. Microgliosis is associated with loss of neurons after stroke.
    • Fig. S19. B4Crry inhibits chronic IgM and C3d deposition in the brain 15 days after MCAO.
    • Fig. S20. Modified annexin IV DAMP is expressed in postmortem human ischemic brain as assessed by B4scFv immunostaining.
    • Fig. S21. B4 IgM and B4Crry bind to the ischemic penumbra of acute stroke patients.
    • Fig. S22. Overview of the mechanism of action of B4Crry and the experimental paradigm.
    • Fig. S23. Complement inhibition or deficiency did not affect regional cerebral blood flow after MCAO and reperfusion.
    • Table S1. Characteristics of human stroke brain donors from which samples were used in immunostaining.
    • Table S2. Detailed description of antibodies used in immunostaining studies.
    • Legends for movies S1 to S7
    • References (3239)

    [Download PDF]

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Representative field of c-fos material within microglia of vehicle-treated controls.
    • Movie S2 (.mp4 format). Representative field of c-fos material within microglia of B4scFv-treated mice.
    • Movie S3 (.mp4 format). Representative field of c-fos material within microglia of B4Crry-treated mice.
    • Movie S4 (.mp4 format). Representative field of c-fos material within microglia of C3-deficient mice.
    • Movie S5 (.mp4 format). Representative field showing attraction of Iba1+ microglia to c-fos+/NeuN+ neurons that are tagged by C3d opsonins.
    • Movie S6 (.mp4 format). Representative field showing neuronal material (NeuN, red) within Lamp1+ vesicles inside Mac2+ inflammatory microglia.
    • Movie S7 (.mp4 format). Representative field showing c-fos material (c-fos, red) within Lamp1+ vesicles inside Iba1+ microglia.

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