Today’s post is complicated, but may be of interest to those people interested in Nitric Oxide therapies (Agmatine, Cocoa Flavanols, Beetroot, Taurine, Citrulline etc) and those who think they are treating earlier hypoxia/ischemia.
As usual, I am making simplifications, but the science behind the general ideas already exists. When it comes to the details regarding VEGF and autism, there are big gaps in the science.
We have already seen that something as simple as improving blood flow appears to be therapeutic in some people with autism. Perhaps there should even be a post called “cold feet and autism”.
One reader of this blog, Seth, has commented before that he sees autism as essentially vascular in nature. Today’s research suggests it does indeed include microvascular abnormalities.
Rather than simply reduced blood flow, the problem, in at least some autism, appears to be unstable blood flow, which is much more complex.
I do take a leap in logic to suggest that this is likely linked to the known abnormalities in Vascular Endothelial Growth Factor (VEGF) and in VEGF receptor 1 (VEGFR-1). It also appears that the VEGF anomalies that lead to angiogenesis may be part of the reason for the increased prevalence of chronic inflammatory diseases including asthma, atopic dermatitis, psoriasis, and rheumatoid arthritis.
Ideally you might want to normalize VEGF, even later in life. The use of anti-angiogenic drugs has been suggested. Angiogenesis inhibitors were once seen as potential wonder drugs to treat cancer.
It does seem that just simply targeting vascular resistance is helpful for some people with autism.
VEGF is regulated by many things, some are highly complex and are usually studied with regard to cancer, like Wnt signaling and Ras. Recall that both Wnt and Ras are relevant to autism. One simple thing that influences VEGF is nitric oxide (NO), but it is not a simple relationship. As highlighted by our reader Tyler, intermittent fasting (IF) can also be used to increase VEGF. Research suggests that intermittent fasting (IF) is actually a simple but potent tool to both prevent and treat metabolic disorders, including but not limited to type 2 diabetes.
In the case of autism, where both VEGF and NO are likely to be low, it does seem quite likely that by increasing the production of NO you will increase the expression of VEGF. So the amino acid L-citrulline is likely to increase VEGF.
In the rat study below, L-citrulline increased eNOS and VEGF; we presume NO also increased.
Blood Flow in Autistic Brains
Now we get to the autism-specific research.
A team of scientists has found evidence that people with autism have unstable vessels in the brain which prevents the proper delivery of blood flow, according to research published in the Journal of Autism and Developmental Disorders.
“In a typical brain, blood vessels are stable, thereby ensuring a stable distribution of blood,” said Patricia Whitaker-Azmitia, PhD, professor in the Department of Psychology and director of the Graduate Program in Integrative Neurosciences at Stony Brook University, N.Y., in a statement. “Whereas in the autism brain, the cellular structure of blood vessels continually fluctuates, which results in circulation that is fluctuating and, ultimately, neurologically limiting.”
Sustained angiogenesis may contribute to prolonged neuroplasticity in the ASD brain. We propose the sustained splitting angiogenesis is a necessary component to maintain the heightened neuronal activity reported in ASD patients. Many biological and functional indicators are increased in ASD including cerebral metabolic rate, regional synchronous electrical activity sensitivity to sound; cortical activity in deactivation centers at rest, low-level visuospatial processing, visual-tactile interactions; attention to low-level perceptual information and over-connected, redundant cortical networks. It can be suggested that sustained rearrangement of microvasculature permits excessive shorter and local connections to be maintained and prevents the growth of longer and more complex brain connections required for language and social interactions. Use of anti-angiogenic drugs may provide a novel treatment strategy for reducing neuronal activity in ASD patients by inhibiting vascular plasticity.
Brain tissue from children (left) and adults (right) with autism (top) but not controls (bottom) shows dividing cells lining blood vessels.
Angiogenesis and Lymphangiogenesis
It looks like, at least in today’s subgroup of autism, we want less angiogenesis but more lymphangiogenesis. The ideal way to do this is via VEGF/VEGFRs.
Here it may be helpful to explain the meaning of some new terminology.
“Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels
Angiogenesis is a normal and vital process in growth and development, as well as in wound healing and in the formation of granulation tissue. However, it is also a fundamental step in the transition of tumors from a benign state to a malignant one, leading to the use of angiogenesis inhibitors in the treatment of cancer.”
“Lymphangiogenesis is the formation of lymphatic vessels from pre-existing lymphatic vessels in a method believed to be similar to angiogenesis (blood vessel development).
Lymphangiogenesis plays an important physiological role in homeostasis, metabolism and immunity. Impaired or excessive lymphatic vessel formation has been implicated in a number of pathological conditions including neoplasm metastasis, oedema, rheumatoid arthritis, psoriasis, lymphangiomatosis and impaired wound healing.”
Lymphatic system and the Brain
As highlighted recently by our reader Tanya, a pretty basic gap in science’s understanding of how the brain works has just been addressed. It is all about where do the waste products produced in the brain go to.
Scientists have found evidence that the brain is connected to body’s central lymphatic system.
This then begs the question of what happens when this system does not work well. Is this a feature of some neurological disease? If that were the case, it would likely be associated with reduced lymphangiogenesis.
Running through your body is a network of channels and junctions called the lymphatic system, which siphons off waste and fluids like a biological sewer.
It was long thought the brain was excluded from this web of anatomical plumbing. After being spotted in mice brains two years ago, researchers have now confirmed the presence of lymphatic vessels in human brains, fueling speculation over the kinds of diseases they might be responsible for.
VEGF and VEGF receptors
There are four types of VEGF and they act through three types of receptors. Confusingly, the receptors have been given multiple names.
In severe autism there is reduced VEGF, but we do not know which type(s) but there is increased expression of the receptor VEGFR-1 also known as Flt-1. VEGFR-2 expression is normal, this is the best understood receptor.
This receptor VEGFR-1 is activated by VEGF-A and VEGF-B.
Objective:
To study vascular endothelial growth factor (VEGF) and its soluble receptors sVEGFR-1 and -2 in autism.
Design and methods:
We measured serum levels of angiogenic molecules in 22 patients with severe autism and 28 controls.
Results:
Patients and controls had similar sVEGFR-2 levels, but VEGF levels were lower and sVEGFR-1 higher in patients with autism.
Conclusion:
The imbalance between VEGF and its receptor sVEGFR-1 may be involved in the pathophysiology of autism.
Hypoxia related autism
It is well known that hypoxia-ischemia insults early in life can cause cognitive dysfunction and likely autism. In the very recent paper below, it is suggested that altered VEGF signaling is the mechanism that causes the damage to the brain.
Neurovascular dysfunction and the role of vascular endothelial growth factor (VEGF) have been explored in neurodevelopmental disorders including schizophrenia, bipolar disorder, major depressive and mood disorders, and autism. These disorders are correlated with hypoxia-ischemia insults during early life and are strongly associated with cognitive dysfunction. This review focuses on the hypoxia-regulated protein, VEGF, to discuss its crucial roles in brain development and function. These data implicate that alterations to VEGF signaling during early life can impair neural development, underlying the severe cognitive deficits observed in neurodevelopmental disorders.
Recent Findings
VEGF has been linked to neurological processes that influence learning and memory. VEGF is advancing towards being a novel biomarker and possible therapeutic for neurological disorders. Prenatal environmental enrichment positively impacted neurotrophic factors, brain structure, and memory in rodent models.
Summary
Understanding the molecular mechanisms of VEGF in neurodevelopment will create intervention strategies for at-risk children born to adverse early-life events. By proactively working with those in a pliable neurodevelopmental state, we hope to ameliorate cognitive deficits to increase their chance to develop into high-functioning adults with disabilities.
Hypoxia-Induced Angiogenesis - Good and Evil
Hypoxia promotes vessel growth by upregulating multiple pro-angiogenic pathways that mediate key aspects of endothelial, stromal, and vascular support cell biology. Interestingly, recent studies show that hypoxia influences additional aspects of angiogenesis, including vessel patterning, maturation, and function.
VEGF, considered a master regulator of angiogenesis in its own right, causes endothelial cells to detach from the parent vessel and migrate into the neighboring stroma. Hypoxia is the principal regulator of VEGF expression, as it is a direct transcriptional target of both HIF-1α and HIF-2α.
Allergy and inflammation resulting from angiogenesis
Angiogenesis and lymphangiogenesis, the growth of new vessels from preexisting ones, have received increasing interest due to their role in tumor growth and metastatic spread. However, vascular remodeling, associated with vascular hyperpermeability, is also a key feature of many chronic inflammatory diseases including asthma, atopic dermatitis, psoriasis, and rheumatoid arthritis. The major drivers of angiogenesis and lymphangiogenesis are vascular endothelial growth factor- (VEGF-)A and VEGF-C, activating specific VEGF receptors on the lymphatic and blood vascular endothelium. Recent experimental studies found potent anti-inflammatory responses after targeted inhibition of activated blood vessels in models of chronic inflammatory diseases. Importantly, our recent results indicate that specific activation of lymphatic vessels reduces both acute and chronic skin inflammation. Thus, antiangiogenic and prolymphangiogenic therapies might represent a new approach to treat chronic inflammatory disorders, including those due to chronic allergic inflammation.
Figure 1: VEGF-binding properties and distinct VEGF receptor expression on lymphatic and blood vascular endothelium. VEGFs bind to the three VEGF receptor tyrosine kinases, leading to the formation of VEGFR dimers. Blood vascular endothelial cells express VEGFR-1 and VEGFR-2, whereas lymphatic endothelial cells express VEGFR-2 and VEGFR-3. VEGF-A—which binds both VEGFR-1 and VEGFR-2—can directly induce blood and lymphatic vascular remodeling. VEGF-C and -D bind VEGFR-3 and, after proteolytic processing, also VEGFR-2, thus inducing angiogenesis and lymphangiogenesis.
There is clear evidence that in humans, vascular remodeling occurs in many chronic inflammatory disorders. Even though different anti-inflammatory drugs are on the market, there is no specific therapy that interferes with the pathological vascular changes that occur during inflammation. Angiogenesis and lymphangiogenesis are tightly linked to chronic inflammation, and targeting the blood vessels and lymphatic vessels has been shown to be an effective strategy in different experimental mouse models of chronic inflammation. One has to keep in mind, however, that in most conditions the vascular activation likely represents a downstream event that maintains the inflammatory process, but not the pathogenetic cause of the respective disease, which often has remained unknown. Nonetheless, antiangiogenic and prolymphangiogenic therapies might represent new approaches to treat chronic inflammatory disorders, including those due to chronic allergic inflammation.
Conclusion
I did start this post by saying this subject is complicated.
From the previous post on nitric oxide, it looked like L-citrulline, L-norvaline, Agmatine and other NO increasing substances could be therapeutic. Cold hands and feet seem to be very common in autism.
It seems likely that the NO increasing therapies will likely also increase VEGF, which I think is a good thing.
From today’s post we see that rather than just a single VEGF we have five broad types (A,B,C, D and PIGF), but even just VEGF-A has various different forms. We do not have detailed research on autism and specific subtypes of VEGF.
We have the four different VEGF receptors and we know VEGFR-1 is over expressed. We do not have a clever way to counter this. More VEGFR-3 expression would be helpful and that is again a case of changing the balance between inflammatory cytokines, which as we know is usually disturbed in autism.
The inflammatory cytokine IL-6 induces VEGF-C production which leads to both angiogenesis and lymphangiogenesis; this is why people with cancer and high IL-6 may have a poor prognosis.
Regarding VEGF and autism we clearly lack 95% of the science. Strange things are afoot and we are just guessing.
For the time being, I see increasing vascular permeability via eNOS as therapeutic, even though today’s post suggests that antiangiogenic therapies could be helpful, which may seem contradictory.
The kind of drugs that would reduce the activity of VEGFR-1/Flt-1 would be very expensive cancer drugs. Hypoxia also downregulates VEGFR-1/Flt-1.
Inflammatory cytokines regulate VEGFR-3/Flt-4 and hence control of lymphangiogenesis. Interferon gamma (IFNγ) upregulates VEGFR-3/Flt-4, while Interleukin 1 beta (IL1β) down regulates it.
So more IFNγ and less IL1β might help.
Although expensive, interferon gamma (IFNγ) has been shown to be effective in treating severe atopic dermatitis. This would make sense since it induces lymphangiogenesis and the research suggests this should improve inflammatory disease.
CONCLUSIONS:
We conclude that rIFN-gamma appears to be a safe long-term therapy for patients with severe atopic dermatitis.
So perhaps interferon-gamma (IFNγ) for some autism? Quite possibly, just look for the ones with asthma, atopic dermatitis, psoriasis or juvenile arthritis.
