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Modulation of post-stroke degenerative and regenerative processes and subacute protection by site-targeted inhibition of the alternative pathway of complement.

Alawieh A, Elvington A, Zhu H, Yu J, Kindy MS, Atkinson C, Tomlinson S - J Neuroinflammation (2015)

Bottom Line: Whereas both inhibitors significantly reduced microglia/macrophage activation and astrogliosis in the subacute phase, only CR2-fH improved neurological deficit and locomotor function, maintained neurogenesis markers, enhanced neuronal migration, and increased VEGF expression.The complement anaphylatoxins have been implicated in repair and regenerative mechanisms after CNS injury, and in this context CR2-fH significantly reduced, but did not eliminate the generation of C5a within the brain, unlike CR2-Crry that completely blocked C5a generation.Gene expression profiling revealed that CR2-fH treatment downregulated genes associated with apoptosis, TGFβ signaling, and neutrophil activation, and decreased neutrophil infiltration was confirmed by immunohistochemistry.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Children's Research Institute, Medical University of South Carolina, 173 Ashley Avenue BSB 201, Charleston, SC, 29425, USA. alawieh@musc.edu.

ABSTRACT

Background: Complement promotes neuroinflammation and injury in models of stroke. However, complement is also being increasingly implicated in repair and regeneration after central nervous system (CNS) injury, and some complement deficiencies have been shown to provide acute, but not subacute, protection after murine stroke. Here, we investigate the dual role of complement in injury and repair after cerebral ischemia and reperfusion.

Methods: We used complement-deficient mice and different complement inhibitors in a model of transient middle cerebral artery occlusion to investigate complement-dependent cellular and molecular changes that occur through the subacute phase after stroke.

Results: C3 deficiency and site-targeted complement inhibition with either CR2-Crry (inhibits all pathways) or CR2-fH (inhibits alternative pathway) significantly reduced infarct size, reduced apoptotic cell death, and improved neurological deficit score in the acute phase after stroke. However, only in CR2-fH-treated mice was there sustained protection with no evolution of injury in the subacute phase. Whereas both inhibitors significantly reduced microglia/macrophage activation and astrogliosis in the subacute phase, only CR2-fH improved neurological deficit and locomotor function, maintained neurogenesis markers, enhanced neuronal migration, and increased VEGF expression. These findings in CR2-fH-treated mice correlated with improved performance in spatial learning and passive avoidance tasks. The complement anaphylatoxins have been implicated in repair and regenerative mechanisms after CNS injury, and in this context CR2-fH significantly reduced, but did not eliminate the generation of C5a within the brain, unlike CR2-Crry that completely blocked C5a generation. Gene expression profiling revealed that CR2-fH treatment downregulated genes associated with apoptosis, TGFβ signaling, and neutrophil activation, and decreased neutrophil infiltration was confirmed by immunohistochemistry. CR2-fH upregulated genes for neural growth factor and mediators of neurogenesis and neuronal migration. Live animal imaging demonstrated that following intravenous injection, CR2-fH targeted specifically to the post-ischemic brain, with a tissue half-life of 48.5 h. Finally, unlike C3 deficiency, targeted complement inhibition did not increase susceptibility to lethal post-stroke infection, an important consideration for stroke patients.

Conclusions: Ischemic brain tissue-targeted and selective inhibition of alternative complement pathway provide self-limiting inhibition of complement activation and reduces acute injury while maintaining complement-dependent recovery mechanisms into the subacute phase after stroke.

No MeSH data available.


Related in: MedlinePlus

Different levels of C5a generation in brains from CR2-fH- and CR2-Crry-treated mice through subacute phase after stroke. a Relative C5a expression as determined by density scan of Western blot of ipsilateral brain tissue extract. Shown are relative expression levels normalized to level in wt control mice at 24 h. Mean +/− SEM, n = 4 animals per group, *p < 0.05. b Representative Western blot for C5a in brain homogenate
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Fig6: Different levels of C5a generation in brains from CR2-fH- and CR2-Crry-treated mice through subacute phase after stroke. a Relative C5a expression as determined by density scan of Western blot of ipsilateral brain tissue extract. Shown are relative expression levels normalized to level in wt control mice at 24 h. Mean +/− SEM, n = 4 animals per group, *p < 0.05. b Representative Western blot for C5a in brain homogenate

Mentions: Complement activation products, specifically C3a and/or C5a, have been implicated in promoting neuroregeneration after CNS injury. Therefore, since CR2-Crry inhibits all complement pathways and CR2-fH inhibits only the alternative pathway, a quantitative difference in the level of complement activation is one potential mechanism that could account for the different subacute outcomes and difference in SVZ neurogenesis. To assess this, we measured C5a levels in the ipsilateral hemisphere of mice on days 1, 3, and 7 after MCAO (Fig. 6). Compared to controls, CR2-fH significantly inhibited C5a generation when measured at 1 and 3 days after MCAO, but to a lesser extent than CR2-Crry, which almost completely blocked C5a generation. No differences in C5a levels were detected across the groups on day 7. This result is consistent with CR2-fH providing sufficient complement inhibition to provide protection from injury in the acute phase, while allowing for lectin and/or classical pathway generation of complement activation products at a level sufficient for promoting recovery and neurogenesis in the subacute phase.Fig. 6


Modulation of post-stroke degenerative and regenerative processes and subacute protection by site-targeted inhibition of the alternative pathway of complement.

Alawieh A, Elvington A, Zhu H, Yu J, Kindy MS, Atkinson C, Tomlinson S - J Neuroinflammation (2015)

Different levels of C5a generation in brains from CR2-fH- and CR2-Crry-treated mice through subacute phase after stroke. a Relative C5a expression as determined by density scan of Western blot of ipsilateral brain tissue extract. Shown are relative expression levels normalized to level in wt control mice at 24 h. Mean +/− SEM, n = 4 animals per group, *p < 0.05. b Representative Western blot for C5a in brain homogenate
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4696299&req=5

Fig6: Different levels of C5a generation in brains from CR2-fH- and CR2-Crry-treated mice through subacute phase after stroke. a Relative C5a expression as determined by density scan of Western blot of ipsilateral brain tissue extract. Shown are relative expression levels normalized to level in wt control mice at 24 h. Mean +/− SEM, n = 4 animals per group, *p < 0.05. b Representative Western blot for C5a in brain homogenate
Mentions: Complement activation products, specifically C3a and/or C5a, have been implicated in promoting neuroregeneration after CNS injury. Therefore, since CR2-Crry inhibits all complement pathways and CR2-fH inhibits only the alternative pathway, a quantitative difference in the level of complement activation is one potential mechanism that could account for the different subacute outcomes and difference in SVZ neurogenesis. To assess this, we measured C5a levels in the ipsilateral hemisphere of mice on days 1, 3, and 7 after MCAO (Fig. 6). Compared to controls, CR2-fH significantly inhibited C5a generation when measured at 1 and 3 days after MCAO, but to a lesser extent than CR2-Crry, which almost completely blocked C5a generation. No differences in C5a levels were detected across the groups on day 7. This result is consistent with CR2-fH providing sufficient complement inhibition to provide protection from injury in the acute phase, while allowing for lectin and/or classical pathway generation of complement activation products at a level sufficient for promoting recovery and neurogenesis in the subacute phase.Fig. 6

Bottom Line: Whereas both inhibitors significantly reduced microglia/macrophage activation and astrogliosis in the subacute phase, only CR2-fH improved neurological deficit and locomotor function, maintained neurogenesis markers, enhanced neuronal migration, and increased VEGF expression.The complement anaphylatoxins have been implicated in repair and regenerative mechanisms after CNS injury, and in this context CR2-fH significantly reduced, but did not eliminate the generation of C5a within the brain, unlike CR2-Crry that completely blocked C5a generation.Gene expression profiling revealed that CR2-fH treatment downregulated genes associated with apoptosis, TGFβ signaling, and neutrophil activation, and decreased neutrophil infiltration was confirmed by immunohistochemistry.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Children's Research Institute, Medical University of South Carolina, 173 Ashley Avenue BSB 201, Charleston, SC, 29425, USA. alawieh@musc.edu.

ABSTRACT

Background: Complement promotes neuroinflammation and injury in models of stroke. However, complement is also being increasingly implicated in repair and regeneration after central nervous system (CNS) injury, and some complement deficiencies have been shown to provide acute, but not subacute, protection after murine stroke. Here, we investigate the dual role of complement in injury and repair after cerebral ischemia and reperfusion.

Methods: We used complement-deficient mice and different complement inhibitors in a model of transient middle cerebral artery occlusion to investigate complement-dependent cellular and molecular changes that occur through the subacute phase after stroke.

Results: C3 deficiency and site-targeted complement inhibition with either CR2-Crry (inhibits all pathways) or CR2-fH (inhibits alternative pathway) significantly reduced infarct size, reduced apoptotic cell death, and improved neurological deficit score in the acute phase after stroke. However, only in CR2-fH-treated mice was there sustained protection with no evolution of injury in the subacute phase. Whereas both inhibitors significantly reduced microglia/macrophage activation and astrogliosis in the subacute phase, only CR2-fH improved neurological deficit and locomotor function, maintained neurogenesis markers, enhanced neuronal migration, and increased VEGF expression. These findings in CR2-fH-treated mice correlated with improved performance in spatial learning and passive avoidance tasks. The complement anaphylatoxins have been implicated in repair and regenerative mechanisms after CNS injury, and in this context CR2-fH significantly reduced, but did not eliminate the generation of C5a within the brain, unlike CR2-Crry that completely blocked C5a generation. Gene expression profiling revealed that CR2-fH treatment downregulated genes associated with apoptosis, TGFβ signaling, and neutrophil activation, and decreased neutrophil infiltration was confirmed by immunohistochemistry. CR2-fH upregulated genes for neural growth factor and mediators of neurogenesis and neuronal migration. Live animal imaging demonstrated that following intravenous injection, CR2-fH targeted specifically to the post-ischemic brain, with a tissue half-life of 48.5 h. Finally, unlike C3 deficiency, targeted complement inhibition did not increase susceptibility to lethal post-stroke infection, an important consideration for stroke patients.

Conclusions: Ischemic brain tissue-targeted and selective inhibition of alternative complement pathway provide self-limiting inhibition of complement activation and reduces acute injury while maintaining complement-dependent recovery mechanisms into the subacute phase after stroke.

No MeSH data available.


Related in: MedlinePlus