Friday, 15 March 2013

Autism, maternal immune activated mice and suramin

Avid followers of the autism research circuit must have noticed the increasing tide of studies looking at a possible role for maternal immune activation (MIA) in relation to risk of offspring autism spectrum disorder (ASD). It's a topic I've covered more than once on this blog; predominantly in relation to the work of people like Paul Patterson and his colleagues (see here), observations on things like C-reactive protein (see here) and the various ways to experimentally mimic such MIA in the mouse model of autism / schizophrenia / other for example (see here).
Squeakers @ Wikipedia  

So it is in this post that I'm serving a double helping of the MIA model of autism as per the publication of studies from Jared Schwartzer and colleagues from the MIND Institute* (open-access) and Robert Naviaux and colleagues** (open-access).

Both studies looked at the effects of artificial induction of MIA in the mouse model following poly I:C use as an immunostimulant. Thereafter the two studies went their separate ways as Schwartzer looked at the variable of mouse strain on the after-effects of MIA on offspring and Naviaux looked at the role of purinergic signaling.

I'll say right now that I am neither qualified nor experienced enough to go into these papers with any great detail. So I won't; instead a brief overview of each - bearing in mind their open-access status - and some interesting factoids which have already been mentioned in the autism research peer-reviewed domain which might tie into results.

The work of Schwartzer and colleagues basically "indicate[s] the need to consider how genetic predisposition may exacerbate or protect against the effects of environmental insults in the etiology of ASD". In other words, based on a mouse model looking at different strains of mouse, the specific genetic make-up of that mouse model might impact on offspring presentation after an artificial MIA event.

In their case they looked at the C57BL/6J and BTBR T+tf/J inbred mouse strains and concluded that the dangermouse that is the BTBR strain combined with the poly I:C stressor seemed to "be synergistic resulting in greater behavioral impairment than from either factor alone" when compared with the C57BL/6J mouse strain. Some interesting variables are noted including elevations in cytokines like IL-6 (see here) and IL-17 (see here) in the BTBR offspring mice compared to C57BL/6J mice alongside some sex specific behavioural differences. All in all, some very interesting observations; and on that sex-specific notion, not completely at odds with other work in this area (see here).

The work of Naviaux and colleagues - summarised quite well here - has definitely taken the interest of the media as per headlines such as 'New drug that may help reverse autism' or should that be 'Century old drug could beat autism'. I'm confused. The long-and-short of it is that based on the analysis of the MIA mouse model - C57BL/6J mice - there was a suggestion that "hyperpurinergia is a fundamental and treatable feature of the multisystem abnormalities in the poly(IC) mouse model of autism spectrum disorders". Treatable via "antipurinergic therapy (APT)" which in this study was via the drug suramin. The observant reader should immediately be comparing Schwartzer and Naviaux and the MIA mouse models chosen and results obtained.

Anyhow, Naviaux et al continue in their observations on how MIA affected offspring mice and how the administration of suramin seemed to have some pretty wide-ranging effects on offspring mice. Alongside various behavioural effects on social and coordination issues, suramin administration was reported to show important effects such as "the preservation of cerebellar Purkinje cells", which as I discussed in a recent post, have more than a token link to cases of autism. "Suramin treatment strongly increased the expression of the nicotinic acetylcholine receptor subunit α7 (nAchRα7) in cerebral synaptosomes of MIA animals" was another potentially important finding in view of other work in this area. In all, "16 multisystem features of this model were either corrected or improved by suramin treatment".

Impressive stuff I hear you say. Indeed all the more impressive given that the authors on purpose did not start suramin treatment until 6 weeks because they "wished to test the hypothesis that many of the autism-like features of the MIA model were treatable after they appear". And apparently there is more to come according to the authors, with the promise of human trials of suramin...

But just before you pop down to your local doctor or pharmacist to ask for suramin (off-label), it might be worth pointing out a few things. Mice. Yep, this was a study of mice and as per the Schwartzer study, not necessarily the best and only mouse model of autism from an MIA point of view. Indeed if I needed to go back to the BTBR mouse and its overlap with autism, I might also recall some work looking at that most forgotten of autism research parameters, sulphate (sulfate) and findings related to the BTBR model (see here). Mice are not humans and suramin is to be added to a growing list of mouse findings with an autism slant (see here and here).

That the US National Cancer Institute holds an entry for suramin should also give you some idea as to what uses the drug has and why bearing in mind it was injected into the study mice. Alongside its anti-parasitic effects related to things like sleeping sickness, the activity of suramin has been linked to its blocking of various growth factor binding which might yet hold some clue to other effects of the drug outside of competitive inhibiting of purinergic signalling (see here and here). As with most medicines, there are other effects to keep in mind which might also tie into results. And then there are the reported side-effects...

I'm not by any means trying to belittle the Naviaux results of suramin in the MIA mouse model of autism so please do not take this post as such. I am very keen to see some replication studies done in other mouse and other animal models, just to see if the results stack up before progressing to human trials with the all-important focus on 'first do no harm' and whether other meds have similar actions. As such I'll keep my eye open for suramin and autism and perhaps post some updates.

In the meantime, the maternal immune activated hypothesis grinds forward...

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* Schwartzer JJ. et al. Maternal immune activation and strain specific interactions in the development of autism-like behaviors in mice. Translational Psychiatry. 2013; 3: e240.

** Naviaux RK. et al. Antipurinergic therapy corrects the autism-like features in the poly(IC) mouse model. PLoS ONE. 2013; 8: e57380.

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ResearchBlogging.org Schwartzer JJ, Careaga M, Onore CE, Rushakoff JA, Berman RF, & Ashwood P (2013). Maternal immune activation and strain specific interactions in the development of autism-like behaviors in mice. Translational psychiatry, 3 PMID: 23481627

Naviaux, R., Zolkipli, Z., Wang, L., Nakayama, T., Naviaux, J., Le, T., Schuchbauer, M., Rogac, M., Tang, Q., Dugan, L., & Powell, S. (2013). Antipurinergic Therapy Corrects the Autism-Like Features in the Poly(IC) Mouse Model PLoS ONE, 8 (3) DOI: 10.1371/journal.pone.0057380