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Jovialis
14-03-18, 02:22
Of all the challenges that come with a diagnosis of autism spectrum disorder (ASD), the social difficulties are among the most devastating. Currently, there is no treatment for this primary symptom of ASD. New research at the University at Buffalo reveals the first evidence that it may be possible to use a single compound to alleviate the behavioral symptoms by targeting sets of genes involved in the disease.

The research, published today in Nature Neuroscience, demonstrated that brief treatment with a very low dose of romidepsin, a Food and Drug Administration-approved anti-cancer drug, restored social deficits in animal models of autism in a sustained fashion.

The three-day treatment reversed social deficits in mice deficient in a gene called Shank 3, an important risk factor for ASD. This effect lasted for three weeks, spanning the juvenile to late adolescent period, a critical developmental stage for social and communication skills. That is equivalent to several years in humans, suggesting the effects of a similar treatment could potentially be long-lasting, the researchers say.

Profound, prolonged effect

"We have discovered a small molecule compound that shows a profound and prolonged effect on autism-like social deficits without obvious side effects, while many currently used compounds for treating a variety of psychiatric diseases have failed to exhibit the therapeutic efficacy for this core symptom of autism," said Zhen Yan, PhD, professor in the Department of Physiology and Biophysics in the Jacobs School of Medicine and Biomedical Sciences at UB, and senior author on the paper.

The study builds on her previous research from 2015. That work revealed how the loss of Shank 3 disrupts neuronal communications by affecting the function of the NMDA (n-methyl-D-aspartate) receptor, a critical player in regulating cognition and emotion, leading to deficits in social preference that are common in ASD.

In the new research, the UB scientists found they could reverse those social deficits with a very low dose of romidepsin, which, they found, restores gene expression and function using an epigenetic mechanism, where gene changes are caused by influences other than DNA sequences. Yan noted that human genetics studies have suggested that epigenetic abnormalities likely play a major role in ASD.

To pursue these promising findings, Yan has founded a startup company called ASDDR, which was awarded a Small Business Technology Transfer grant from the National Institutes of Health last summer for more than $770,000.

Epigenetics in ASD

Many of the mutations in ASD, Yan explained, result from chromatin remodeling factors, which are involved in dynamically changing the structure of chromatin, the complex of genetic material in the cell nucleus that condenses into chromosomes.

"The extensive overlap in risk genes for autism and cancer, many of which are chromatin remodeling factors, supports the idea of repurposing epigenetic drugs used in cancer treatment as targeted treatments for autism," said Yan.

She and her colleagues knew that chromatin regulators—which control how genetic material gains access to a cell's transcriptional machinery—were key to treating the social deficits in ASD, but the challenge was to know how to affect key risk factors at once.

"Autism involves the loss of so many genes," Yan explained. "To rescue the social deficits, a compound has to affect a number of genes that are involved in neuronal communication."

To do so, the team turned to a type of chromatin remodeler called histone modifiers. They modify proteins called histones that help organize genetic material in the nucleus so gene expression can be regulated. Since many genes are altered in autism, the UB scientists knew a histone modifier might be effective.

Loosening up chromatin

In particular, they were interested in histone deacetylase (HDAC), a family of histone modifiers that are critically involved in the remodeling of chromatin structure and the transcriptional regulation of targeted genes.

"In the autism model, HDAC2 is abnormally high, which makes the chromatin in the nucleus very tight, preventing genetic material from accessing the transcriptional machinery it needs to be expressed," said Yan. "Once HDAC2 is upregulated, it diminishes genes that should not be suppressed, and leads to behavioral changes, such as the autism-like social deficits."

But the anti-cancer drug romidepsin, a highly potent HDAC inhibitor, turned down the effects of HDAC2, allowing genes involved in neuronal signaling to be expressed normally.

"The HDAC inhibitor loosens up the densely packed chromatin so that the transcriptional machinery gains access to the promoter area of the genes; thus they can be expressed," Yan said.

The rescue effect on gene expression was widespread. When Yan and her co-authors conducted genome-wide screening at the Genomics and Bioinformatics Core at UB's New York State Center of Excellence in Bioinformatics and Life Sciences, they found that romidepsin restored the majority of the more than 200 genes that were suppressed in the autism animal model they used.

"The advantage of being able to adjust a set of genes identified as key autism risk factors may explain the strong and long-lasting efficacy of this therapeutic agent for autism." Yan explained. She and her colleagues will continue their focus on discovering and developing better therapeutic agents for autism.

https://medicalxpress.com/news/2018-03-autism-social-deficits-reversed-anti-cancer.html?utm_source=tabs&utm_medium=link&utm_campaign=story-tabs
https://www.nature.com/articles/s41593-018-0110-8

Maciamo
14-03-18, 11:56
So what they are saying is that romidepsin, an anti-cancer drug, is an an HDAC inhibitor which acts like an epigenetic therapy by loosening the histone around the some genes, thereby downregulating that gene's activity.

If so, it is likely that other histone deacetylase (HDAC) inhibitors (https://en.wikipedia.org/wiki/Histone_deacetylase_inhibitor) will have a similar effect. This class of drugs is already used as anti-epileptic, mood stabilisers, anti-depressant, and as a mitigator for neurodegenerative diseases such as Alzheimer's disease and Huntington's disease. All of them target specifically the HDAC2 enzyme.

One commonality between autism, epilepsy and some forms of depression is that hyperactivation of some brain regions. In other words, they subject's brain activity is too intense, which could be caused by the upregulation of the HDAC2 gene. HDAC inhibitors may help by lower that gene's expression and "relaxing" the brain. At least that's what I understood from that article.

Maciamo
14-03-18, 12:04
After looking it up online I found that butyric acid (butyrate) had strong HDACinhibiting activity. That's interesting because butyric acid is produced by good gut bacteria (see my article on the microbiome (https://www.vitamodularis.org/articles/how_to_interpret_your_microbiome_data.shtml)) and it has a protective role against inflammation and leaky gut syndrome. Autistic people typically suffer from irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD), two conditions also linked to low butyric acid in the gut. Consequently they do not benefit from the HDAC inhibiting activity of butyric acid, which in turn exacerbates the symptoms of autism.

There are many other potential HDAC inhibitors. This article (https://www.sciencedirect.com/science/article/pii/S2211383512000895) says:

"HDAC inhibitors can be structurally grouped into hydroxamates, cyclic peptides, aliphatic acids, benzamides, boronic acid-based compounds, benzofuranone and sulfonamide containing molecules and α/β peptide structures."

Butyric acid falls under aliphatic acids, while Romidepsin is a cyclic peptide.

Hydroxamates are apparently the most potent HDAC inhibitors. They include the drug Trichostatin A (TSA) (https://en.wikipedia.org/wiki/Trichostatin_A), an antifungal antibiotic and selectively inhibits the class I and II mammalian histone deacetylase (HDAC). That's interesting because fungal infections have also been linked with some cases of autism.

Some weaker natural HDAC inhibitors include sulforaphane (SFN) found in cruciferous vegetables, and some polyphenols like curcumin (from turmeric) and quercetin, found in berries (cranberries, blueberries, lingonberries) and some vegetables (radish, and cruciferous vegetables like kale and broccoli). That would explain why turmeric, broccoli and berries have been known to play a role against both cancer and autism.

Maciamo
14-03-18, 12:10
HDAC is linked to cell survival and proliferation. That's why its upregulation may lead to cancer development. Autistic (and epileptic) people have too many neurons in their brain, due to a lack of natural pruning through apoptosis in the first years of life. That would probably be caused by an excessive HDAC activity too, as that gene tells the cell not to die, even when they should. Makes sense.

HDAC is divided in four classes. It's especially the class I (HDAC1, HDAC2, HDAC3 and HDAC8) that are linked to cell proliferation (and survival).


This article (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4210916/)says that:

- Overexpression of HDAC1 is associated with gastric, prostate, ovarian cancers and Hodgkin's lymphoma, while underexpression is linked to colorectal cancer.

- Overexpression of HDAC2 is associated with ovarian cancer and Hodgkin's lymphoma.

- HDAC3 is associated with long-term memory and Type-2 diabetes.

- Mutations in the HDAC8 gene are associated with Cornelia de Lange disease; a syndromic form of intellectual disability.