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The role of glia in neurodevelopmental disorders

Image Credit:Pixabay

The role of glia in neurodevelopmental disorders

Neurons get the majority of our attention when we talk about the brain and neuroscience. After all, neurons drive action in the brain: they produce electricity, and they send signals to each other. This signaling helps organize information, create emotion, and produce motion. Neurons are, indeed, the stars of theshow.

 

Image Credit: Pixabay

However, there are other cells involved in brain activity. Collectively called glia (or glial cells), these are helper cells that perform many secondary functions that keep neurons healthy. For example, some glia “clean up” chemicals from the area around neurons. Others help filter the blood that neurons receive and act as immune cells. Others still help neurons organize and form connections to one another.

Glial cells don’t get a lot of attention, but they’re very important. Recent studies have implicated dysfunctions in glial cells with serious neurologic illnesses.1In particular, autism spectrum disorder (ASD) and ADHD may be affected by dysfunctional glia.

 

Some glial cells act as the primary immune mechanism in the brain and help to manage inflammation.2 These cells manage inflammation and immunity in several ways. Importantly, some glial cells can change shape when their immune function is activated. When activated in this way, they can help eliminate infection and clear an area of cellular debris.

However, an overactive immune system can be a problem. Many chronic illnesses result from immune dysfunction, and ASD may be associated with immune dysregulation. Researchers have observed the activated shape of glial cells in people with ASD.3 Furthermore, there is evidence to suggest immune activation during pregnancy is associated with offspring developing ASD.4This type of immune activation may be more damaging during developmental stages, especially if it is chronic.

 

Likewise, overactive immune function may be involved in ADHD. Children with ADHD tend to have elevated levels of an inflammatory marker expressed by glial cells compared to children without ADHD.5

In addition to their role in inflammation, glial cells can influence neurodevelopmental disorders in other ways. As previously mentioned, glia can help to “clean up” the chemical environment in the brain. This includes at the synapse, where one neuron communicates to another with neurotransmitters. After signals have been sent, glial cells help to remove excess neurotransmitters to avoid overactive synapses.

 

Neurotransmitter balance has been specifically indicated in both ADHD and ASD. Certain levels of neurotransmitters are known to be overactivein these disorders. Researchers have shown that dysfunctions in glia can contribute to dysregulated neurotransmitter uptake.6 In other words, stray neurotransmitters keep activating a neuron, even when there is no active signal.

Neurodevelopmental disorders are complex diseases involving many different systems. The examples listed here are just part of a larger puzzle involving neurons, glia, and other cells. A single dysfunction in glial cells is unlikely to be a sole cause of any disease.

Researchers are still looking to understand diseases like ADHD and ASD better. Future research can continue to examine the role of glial cells as well as neurons. Understanding the complex relationship between different cell types in the brain will provide greater details and help in discovering new and better treatments for these diseases.

 

References

  1. Kim YS, Choi J, Yoon B. Neuron-glia interactions in neurodevelopmental disorders. 2020; 9 (10):2176. doi: 10.3390/cells9102176
  2. Aloisi, F. Immune function of microglia. Glia. 2001; 35:165-179. doi: 10.1002/glia.1106
  3. Lee AS, Azmitia EC, Whitaker-Azmitia PM. Developmental microglial priming in postmortem autism spectrum disorder temporal cortex. Brain Behav Immun. 2017; 62:193-202. doi: 10.1016/j.bbi.2017.01.019
  4. Choi GB, Yim YS, Wong H, et al. The maternal interleukin-17a pathway in mice promotes autism-like phenotypes in offspring. 2016; 351:933-939. doi: 10.1126/science.aad0314
  5. Wei H, Zou H, Sheikh AM, et al. IL-6 is increased in the cerebellum of autistic brain and alters neural cell adhesion, migration and synaptic formation. J Neuroinflamm. 2011; 8:1-10. doi: 10.1186/1742-2094-8-52
  6. Higashimori H, Schin CS, Chiang MSR, et al. Selective deletion of astroglialFMRP dysregulates glutamate transporter GLT1 and contributes to fragile X syndrome phenotypes in vivo. J Neurosci. 2016; 36:7079-7094. doi: 10.1523/JNEUROSCI.1069-16.2016