1131. Involvement Of The Complement System In The Subarachnoid Hemorrhage (SAH)-Induced Hippocampal Abnormalities

Authors: Gavin W. Britz, MD, FAANS; Eugene Golanov, MD, PhD; Martin Sharpe, PhD; Evgueniy Bovshik; Angelique Regnier-Golanov, PhD; David Baskin, MD (Houston, TX)

Introduction:

95% of SAH survivors experience permanent neurocognitive disorders, which are compatible with SAH-induced atrophy of temporomesial area. The mechanisms of SAH-induced hippocampal damage are unclear. Recently we established that following SAH, complement system genes expression increases in hippocampus and block of C3, a central complement component, reverses negative effects of SAH in hippocampus. We hypothesize that SAH-induced cytokine release activates astrocytic complement, which negatively affect hippocampal neurons. To test this hypothesis, we explored effects of cytokines on the complement expression by human astrocytic culture and changes of complement components expression in the post-SAH hippocampus in mice.

Methods:

Normal human astrocytes (NHA) were grown to confluency, and TNFα (100nM), C3 (85nM) and TNFα+C3 were applied to the cultured cells. 24 hours later NHAs were fixed in 4% PFA, washed/permeabilized, and immunohistochemical analysis of C1q, CfB and C3 expression was performed using quantitative fluorescent microscopy. Perforation of the circle of Willis was used to model SAH in mice. Four days later, mice were intracardially perfused, brains were extracted, sliced and processed for IHC.

Results:

In NHA, quantitative immunofluorescence analysis showed that treatment of TNFα and C3 increased the expression of C3 (p=0.005) and CfB (p=0.007) but failed to do so when applied simultaneously. In vivo, SAH induced an  increase of CfB (p=0.04), C1q (p=0.05) and C3 (p=0.008) compared to Sham in the hippocampus. At the cellular level, C3 and C1q immunoreactivity was associated with astrocytes.

Conclusion:

Our observations suggest that astrocytes are capable of expression/release of complement components in response to cytokine stimulation in vitro and in vivo. We conclude that complement may play an important role in hippocampal dysfunction following SAH. Further exploration of the role of astrocytes and complement in the hippocampal damage following SAH will allow developing new therapeutic approaches to the treatment of long-term consequences of SAH.