Astrocyte‐specific expression of a soluble form of the murine complement control protein Crry confers demyelination protection in the cuprizone model

Abstract

Complement has been implicated as a potential effector mechanism in neurodegeneration; yet the precise role of complement in this process remains elusive. In this report, we have utilized the cuprizone model of demyelination-remyelination to examine the contribution of complement to disease. C1q deposition was observed in the corpus callosum of C57BL/6 mice during demyelination, suggesting complement activation by apoptotic oligodendrocyte debris. Simultaneously, these mice lost expression of the rodent complement regulatory protein, Crry. A soluble CNS-specific form of the Crry protein (sCrry) expressed in a transgenic mouse under the control of an astrocyte-specific promoter was induced in the corpus callosum during cuprizone treatment. Expression of this protein completely protected the mice from demyelination. Interestingly, sCrry mice had low levels of demyelination at later times when control mice were remyelinating. Although the sCrry transgenic mice had lower levels of demyelination, there was no decrease in overall cellularity, however there were decreased numbers of microglia in the sCrry mice relative to controls. Strikingly, sCrry mice had early recovery of mature oligodendrocytes, although they later disappeared. TUNEL staining suggested that production of the sCrry protein in the transgenic mice protected from a late apoptosis event at 3 weeks of cuprizone treatment. Our data suggest complement provides some protection of mature oligodendrocytes during cuprizone treatment but may be critical for subsequent remyelination events. These data suggest that temporal restriction of complement inhibition may be required in some disease settings.

CNS-specific expression of C3a and C5a exacerbate demyelination severity in the cuprizone model

“…3C). These findings were similar to what our lab has shown in previous cuprizone studies (Briggs et al, 2007). Conversely, the peak of microglial infiltration occurred at five weeks in both C3a and C5a transgenic groups (Fig.…”

“…Mice were returned to a normal diet after six weeks of cuprizone treatment to allow for remyelination (Briggs et al, 2007; Matsushima and Morell, 2001; Morell et al, 1998). …”

“…Tissue processing and microscopy were carried out as previously described (Arnett et al, 2001; Briggs et al, 2007). Briefly, mice were anesthetized and transcardially perfused with PBS, followed by 4% paraformaldehyde.…”

“…Results from our lab have determined that complement plays a role in the murine cuprizone-mediated demyelination and remyelination model. When a soluble CNS-specific form of the rodent complement regulatory protein, Crry (sCrry) was expressed, mice were protected from demyelination during cuprizone treatment, implicating a role for C3 and downstream complement proteins in this model (Briggs et al, 2007). In our current studies, we utilized the murine cuprizone model to assess the role of local C3a and C5a production in the brain during demyelination and remyelination.…”

Comparative Functional Evolution of Human and Mouse CR1 and CR2

“…The ability of the CR1 proteins to bind to both C3b and C4b allows for the control of classical, alternative and lectin pathway C3/C5 convertases. Soluble murine Crry proteins have also been used in analogous models to control complement activation (54, 55). …”