The long-term consequences of maternal LPS exposure

LPS, lipopolysaccharide, or better lipopolysaccharides are a group of large molecules consisting of a lipid attached to a polysaccharide. They are found on the outer cell membrane of Gram-negative bacteria and act as an endotoxin. It binds to the CD14/TLR4/MD2 receptor complex that can be found on the membrane of several immune cells (monocytes, dendritic cells, macrophages and B cells). Like PolyI:C, prenatal LPS, while not crossing the blood placental barrier, activates the maternal immune system which ultimately affect the foetus.

We currently have two projects aimed at investigating the long-term consequences of prenatal LPS treatment. In the first project, we specifically investigate how the timing of the maternal immune activation affects behaviour. Specifically, we have exposed pregnant rats to two consecutive injections of LPS on gestational days 10 and 11, 15 and 16 or 18 and 19. We have found that exposure on gestational days 10 and 11 (but not 15/16 or 18/19) leads to cognitive deficits in, among others, working memory capacity and selective attention. Additionally, we found that exposure of gestational days 15 and 16 (but not 10/11 and 18/19) leads to emotional deficits in, among others, reward sensitivity anticipatory pleasure and social interaction.

In the second project, we investigate the epigenetic changes induced by LPS. Specifically, we aim to perform both a targeted and a genome wide methylation approach. DNA methylation involves the addition of a methyl group on specific DNA nucleotides, typically (though not exclusively) cytosines. In most situations, DNA methylation leads to transcriptional repression, and thus to a reduction in protein production. By investigating different brain regions after LPS administration on gestational days 10 and 11 or 15 and 16, we hope to gain more insight into the neurobiological basis of the cognitive and emotional deficits induced by prenatal LPS.

This research is in part sponsored by a grant from the Neurological Foundation.

Maternal Immune Activation (MIA)

While we know that most psychiatric disorders have a strong genetic component, we equally know that none are purely determined by genetic factors alone. Studies in monozygotic (identical twins) show that if one half of the twin has a mental disorder, the other has a chance of about 40 to 60% of also developing the disorder. While this is much higher than the risk in the general population it is also much less than 100% even though both twins share all of their genes. This clearly indicates that non-genetic, environmental factors must also contribute to the development of mental disorders, such as major depression, schizophrenia and autism spectrum disorders. Unfortunately, environmental factors are much more difficult to identify than genetic factors. This is in part due to the fact that environmental factors often affect individuals long before the actual disorder develops and therefore are often only identified in retrospect. Genetic factors, on the other hand are in general constant and can be identified at any point in time.

One of the environmental factors that has often been implicated in mental disorders is a viral or bacterial infection during pregnancy. Over the last two decades, multiple epidemiological studies have linked such infections to the development of autism spectrum disorder and schizophrenia. However, recent studies have also provided evidence that such infections can increase the risk of substance abuse disorders and affective disorders such as anxiety disorder, major depression and bipolar disorders).

To investigate the long-term consequences of such infections, we use two different animal models using prenatal injections of either polyI:C or LPS leading to maternal immune activation (MIA). The reasons for using these drugs rather than actual infections, is partly because it is difficult to limit an infection to a single mother. Additionally, by using drugs we have more control regarding the duration of the maternal immune response, allowing us to investigate whether MIA at different points during development leads to different long-term changes.

The long-term consequences of maternal polyI:C exposure

Polyinosinic:polycytidylic acid (PolyI:C) is an immunostimulant that simulates viral infections. Like viruses, it does not see to cross the blood placental barrier but activates the maternal immune system by stimulating the TLR3 receptor (which is found on several immune cells, such as B-cells, macrophages and dendritic cells). Components of the maternal immune system, such as interleukin-6 and others are known to cross the blood placental barrier to reach the foetal brain. Interleukins are known to activate microglia (the brain’s immune system) and during development can cause, what is known as a cytokine storm. This is then thought to subsequently alter the connectivity between different brain regions as well as neurotransmitter functioning, such as serotonin.

We currently have two different projects investigating the long-term consequences of polyI:C, one focussing on behaviour, one on the neurobiological changes in the brain.

In the behavioural project, we are investigating whether polyI:C exposure on gestational day 15 leads to changes in social behaviour throughout the lifetime of the rat. Specifically, we study changes in maternal separation induced ultrasonic vocalizations, social approach avoidance and empathy, using a helping behaviour paradigm in which rats can help a trapped rat escape. In addition, we will investigate whether environmental enrichment from very early on reverses some of these behavioural deficits.

After the behavioural experiments, the brains of the animals exposed to polyi:C and/or environmental enrichment will be investigated. In this project, we will be using a variety of standard immunohistochemical and molecular techniques and will focus predominantly on oligodendrocytes and synaptic connectivity. Oligodendrocytes are the glial cells that are principally involved in forming the myelin sheet around axons of nerve cells and there is some clinical evidence suggesting that the myelination is altered in for instance schizophrenia and autism spectrum disorder. Likewise, both disorders have been associated with altered synaptic connectivity, although interestingly in opposite directions. Thus, while research has found an increased spine density in autism spectrum disorder, a decrease has been reported in schizophrenia. Given that prenatal polyI:C has been used as a model for both disorders, it will be interesting to see how it affects spine density in rats.

Linda

Linda’s doctoral research investigates the effect of an enriched environment on neural structures and empathy-driven social behaviours in Autism Spectrum Disorders.

My identity as a problem solver

How would you ‘define’ yourself?

How much time do you have 🙂 ? Well, most of all, I see myself as a problem solver and I’m driven to find solutions.

While preparing for this interview, I had a look at your LinkedIn page, and I was really impressed with the comments there by your former colleagues and employers. One said: “It’s really incredible to see her work. She doesn’t stop until the goal is achieved and even then she just…keeps…going. And with such precision. And accuracy. Leaving no stone unturned. No option unexplored. Nothing left to chance.”

I spent many years in the corporate world; in the private as well as the public sector. The knowledge I gained there helps me tackle my current project. I am especially grateful for my experience as a project manager and the ability to look at a project and scope it, looking at what the requirements are, what has to be achieved, and how to get there.

Using previous work experience for my PhD project

Can you think of any concrete example where your experience as a project manager benefitted your academic work?

Absolutely. While planning my PhD project I realised that, if I wanted to do everything I originally planned, I’d spend three years just in the lab collecting data… I could see that the plan didn’t take into account the time necessary for brain analysis or writing, so my ability to look at the big picture and then de-scope some of the components helped a lot. Maybe that’s also one of the advantages of being a mature student.

I should mention that a number of students mentioned that they are learning a lot from you, especially in regard to time management. Bart also commented on your meticulous OneNote.

That’s nice to hear. Bart never told me that! One trick I use to focus on a conversation and be present is to voice-record the meeting (with the other person’s permission) rather than take notes. It allows me to focus on the conversation at the time, and play it back later for my notes.

The challenges

Are there any challenges you have because of the stark differences between the corporate world the academia?

In the corporate world, there are also long term projects, so that’s a similarity. What’s different is that I’m used to having a team of people working fulltime on my project with me, with each person responsible for aspects of the work. That frees me up to focus on the management/production side of things. In academia, that’s different i.e. it’s mostly on me. I have a few helpers, but I have to manage the project and do the delivery work myself. So that’s definitely a challenge, but also very rewarding.

In my research, I have several work streams going on simultaneously. I’ve planned it all out, but the plan can easily get disrupted and a small delay might have a big impact, because testing needs to happen on certain days. Having it so finely tuned means any disruption is a challenge. The way around that is to factor in a bit of extra time to allow for things to crop up.

There are also no predefined work and break schedules like there are for staff. When I’m in the lab for 12 hours with only the animals for company, it’s easy to miss cues like morning tea or lunch breaks that you get when working around others.

Changing my career

I got the impression that you were very successful in your former life. So what made you start studying again?

Earlier in my career, when I was working at big agencies in NZ, I realised that I’d lost the enthusiasm for the work; every job was “just another website/web banner/execution”. In 2013, I enrolled in Psychology because I had always been fascinated by behaviour. I was driven by questions like: Why are people so different? I knew early on that I wanted to do a PhD, so I mapped out the pathway. Because I hadn’t majored in psychology (I have a Bachelor in Communication from Germany), I had to do a graduate diploma first, followed by my Honours. I was working and studying at the same time, which allowed me to “live in both worlds” and get a sense for academia.

Do you have any advice for people who are considering a similar career change?

As a mature student, you will be a lot more conscious about your choices in terms of how much time you spend on things. You have to pay to do a PhD and, if you are doing it fulltime, you are not earning, which is quite a lifestyle adjustment. I think educating yourself is always a good idea, but don’t forget to have a life as well. Balance is important. It is understandable that you devote yourself to your project, after all, it’s your baby, but I can totally see how relationships can break in this environment. So for people who are in relationships, I would advise that whatever you do, don’t ever neglect that. Because in the end, once you have your PhD, you want to make sure you also still have your partner.

Finding the meaning

I might never make the same kind of money that I used to; it’s not all about money though. The thing is, if I can give something back, if I can make a difference to one person’s life with the work I’ve been doing, that would make it all worthwhile for me.

It’s also amazing to see the rats in the enriched cages and how their personalities come out i.e. how different they are when compared to those in standard housing. While that’s just a small part of my research, it’s the part that gives me the most joy at this stage of the journey. If I need some happy time after a rough day, I just go there and spend some time with the rats.

What kind of future do you envision after your PhD ?

I would like to keep doing research, but I guess I might have to go to overseas. Maybe to the States or Germany for a postdoc. But after that, I’m hoping to come back to Wellington and do research.

Tell us more about your research interests

I am fascinated by the brain. Any behaviour–human or animal–is an expression of the underlying neural structural, but behaviour is incredibly prone to external influences. Like, for example, with the rats. If the night-light settings play up, it might impact the animal’s performance during testing that day/the next day, but it won’t change, for example, the number of dendritic spines. The set-up of the individual brain structures doesn’t change just because the animal had a “bad day”. There’s no need for interpretations when comparing physiological differences and I like that. These differences explain the behaviour, so it’s a way of getting to the bottom of it and that’s what enables scientists to bring it all together to tell one big story.