Complement system activation contributes to the ependymal damage induced by microbial neuraminidase
Authors: Paul P Tamburini
Krista Johnson
María Dolores López-Ávalos
Jesús M Grondona
B Paul Morgan
Timothy R Hughes
Pedro Fernández-Llebrez
Pablo Granados-Durán
Journal: Journal of Neuroinflammation (2016)
Discipline: NEUROSCIENCE & BEHAVIOR
Keywords: Anti-C5; Brain ventricles; C6-deficient rats; Complement system; Ependymal cells
Affiliations: Departamento de Biología Celular, Genética y Fisiología, IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, 29071, Spain., Institute of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, UK., Alexion Pharmaceuticals Inc., 352 Knotter Drive, Cheshire, CT, 06410, USA., Departamento de Biología Celular, Genética y Fisiología, IBIMA, Facultad de Ciencias, Universidad de Málaga, Málaga, 29071, Spain. .

Abstract:  Background: In the rat brain, a single intracerebroventricular injection of neuraminidase from Clostridium perfringens induces ependymal detachment and death. This injury occurs before the infiltration of inflammatory blood cells; some reports implicate the complement system as a cause of these injuries. Here, we set out to test the role of complement. Methods: The assembly of the complement membrane attack complex on the ependymal epithelium of rats injected with neuraminidase was analyzed by immunohistochemistry. Complement activation, triggered by neuraminidase, and the participation of different activation pathways were analyzed by Western blot. In vitro studies used primary cultures of ependymal cells and explants of the septal ventricular wall. In these models, ependymal cells were exposed to neuraminidase in the presence or absence of complement, and their viability was assessed by observing beating of cilia or by trypan blue staining. The role of complement in ependymal damage induced by neuraminidase was analyzed in vivo in two rat models of complement blockade: systemic inhibition of C5 by using a function blocking antibody and testing in C6-deficient rats. Results: The complement membrane attack complex immunolocalized on the ependymal surface in rats injected intracerebroventricularly with neuraminidase. C3 activation fragments were found in serum and cerebrospinal fluid of rats treated with neuraminidase, suggesting that neuraminidase itself activates complement. In ventricular wall explants and isolated ependymal cells, treatment with neuraminidase alone induced ependymal cell death; however, the addition of complement caused increased cell death and disorganization of the ependymal epithelium. In rats treated with anti-C5 and in C6-deficient rats, intracerebroventricular injection of neuraminidase provoked reduced ependymal alterations compared to non-treated or control rats. Immunohistochemistry confirmed the absence of membrane attack complex on the ependymal surfaces of neuraminidase-exposed rats treated with anti-C5 or deficient in C6. Conclusions: These results demonstrate that the complement system contributes to ependymal damage and death caused by neuraminidase. However, neuraminidase alone can induce moderate ependymal damage without the aid of complement. 

Retracted: No

PubPeer comments:
 Figures 6 and 7 appear to include a duplicated image (cropped differently), although they represent 2 sets of animals. *** Figure 6, C5 rats ![file] *** Figure 7, C6 rats ![file] , 
 You are right and we had not realized the error. It probably happened when choosing the control image for the plate. But rest assured, animals NOT injected with neuraminidase (both those with C5 inhibited and C6 mutants) do not have any labeling on the apical surface of the ependyma. , 
 #2 Thank you for your response. Will you be contacting the journal to publish a correction? ,