Dysregulation of the complement cascade in the hSOD1G93Atransgenic mouse model of amyotrophic lateral sclerosis

Abstract

BackgroundComponents of the innate immune complement system have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS); however, a comprehensive examination of complement expression in this disease has not been performed. This study therefore aimed to determine the expression of complement components (C1qB, C4, factor B, C3/C3b, C5 and CD88) and regulators (CD55 and CD59a) in the lumbar spinal cord of hSOD1G93A mice during defined disease stages.MethodshSOD1G93A and wild-type mice were examined at four different ages of disease progression. mRNA and protein expression of complement components and regulators were examined using quantitative PCR, western blotting and ELISA. Localisation of complement components within lumbar spinal cord was investigated using immunohistochemistry. Statistical differences between hSOD1G93A and wild-type mice were analysed using a two-tailed t-test at each stage of disease progression.ResultsWe found several early complement factors increased as disease progressed, whilst complement regulators decreased; suggesting overall increased complement activation through the classical or alternative pathways in hSOD1G93A mice. CD88 was also increased during disease progression, with immunolocalisation demonstrating expression on motor neurons and increasing expression on microglia surrounding the regions of motor neuron death.ConclusionsThese results indicate that local complement activation and increased expression of CD88 may contribute to motor neuron death and ALS pathology in the hSOD1G93A mouse. Hence, reducing complement-induced inflammation could be an important therapeutic strategy to treat ALS.

The role of complement system in amyotrophic lateral sclerosis

“…Our results showed that there was no significant difference in survival time extension between the two dosing groups, suggesting that the pathogenic involvement of C5a occurs subsequent to day 91. This is in agreement with our previous experiments showing upregulation of CD88 at 130 and 175 days in hSOD1 G93A mice, indicating that C5a exacerbates disease pathology but does not initiate the onset of disease (Lee et al, 2013). Although there was no difference in survival time extension between the two dosing groups, hSOD1 G93A mice treated post onset of motor deficit did not show improved hind-limb grip strength but delayed age reaching 75%…”

“…In contrast to these studies, our laboratories have previously shown that chronic administration of a specific C5a receptor CD88 antagonist PMX205 in hSOD1 G93A transgenic rats markedly delayed the onset of motor symptoms and increased survival, compared to untreated animals (Woodruff et al, 2008a). Further, data presented in Chapter 3 demonstrated up-regulation of CD88 in the lumbar spinal cord of hSOD1 G93A transgenic mice as disease progressed, suggesting that C5a-CD88 signalling may have a pathogenic role in the disease progression of ALS (Lee et al, 2013).…”

“…In support of this finding, we have shown that chronic administration of a specific CD88 antagonist PMX205 in hSOD1 G93A transgenic rats have markedly delayed the onset of motor symptoms and increased survival, compared to untreated animals (Woodruff et al, 2008a). In addition, up-regulation of CD88 has also been observed in numerous neurodegenerative diseases in rodents (Yasojima et al, 1999, Singhrao et al, 1999, Woodruff et al, 2006, including ALS (Woodruff et al, 2008a, Humayun et al, 2009), so it is plausible to propose that downstream complement C5a-CD88 signalling may have a pathogenic role in the disease progression of ALS (Lee et al, 2013). …”

“…PMX205 treatment at this lower dose did not affect survival time when compared with vehicle treated hSOD1 G93A mice (mean end stage of disease, vehicle = 170.6 ± 2.2 days and PMX205 = 174.5 ± 3.4 days, n = 5 -6, P = 0.8897; Figure 4.1A). Decline in neuromotor performance was also assessed in these animals using body weight and hind-limb grip strength as it is a more sensitive measure of detecting motor deficit symptoms in hSOD1 G93A mice compared to rota-rod performance (Lee et al, 2013). There was no significant difference in body weight alterations between vehicle and PMX205 treated hSOD1 G93A mice (n = 5 -6, P > 0.05; Figure 4.1B).…”

“…Previous studies have shown increase in CD88 expression in multiple rodent models of ALS (Woodruff et al, 2008a, Humayun et al, 2009, Lee et al, 2013; hence this study aimed to elucidate whether the up-regulation of CD88 in the lumbar spinal cord of hSOD1 G93A mice were contributing to disease progression. hSOD1 G93A mice were orally dosed with the selective CD88 antagonist PMX205 beginning from 35 days of age with two different concentrations (3mg/kg/day and 9mg/kg/day).…”