ARBs and ACE inhibitors for Autism, an old Peter idea finally explored in a research model

 

 A home run? Certainly worth further consideration. 

When I was doing my review of unexplored potential autism therapies several years ago, I did look at two closely related classes of drugs. ARBs and ACE inhibitors.

I wrote about it in blog posts and set out why I thought the ARB telmisartan was the best one to trial first.

 

           Targeting Angiotensin in Schizophrenia and Some Autism          

Just when you thought we had run out hormones to connect to autism and schizophrenia, today we have Angiotensin.

Angiotensin is a hormone that causes vasoconstriction and a subsequent increase in blood pressure. It is part of the renin-angiotensin system, which is a major target for drugs (ACE inhibitors) that lower blood pressure. Angiotensin also stimulates the release of aldosterone, a hormone that promotes sodium retention which also drives blood pressure up.

Angiotensin I has no biological activity and exists solely as a precursor to angiotensin II.

Angiotensin I is converted to angiotensin II  by the enzyme angiotensin-converting enzyme (ACE).  ACE is a target for inactivation by ACE inhibitor drugs, which decrease the rate of Angiotensin II production.  

It turns out that Angiotensin has some other properties very relevant to schizophrenia, some autism and quite likely many other inflammatory conditions. 

Blocking angiotensin-converting enzyme (ACE) induces those potent regulatory T cells that are lacking in autism and modulates Th1 and Th17 mediated autoimmunity.  See my last post on Th1,Th2 and Th17. 

In addition, Angiotensin II affects the function of the NKCC1/2 chloride cotransporters that are dysfunctional in much autism and at least some schizophrenia.

Then I wrote another post and made a trial of Telmisartan.

Angiotensin II in the Brain & Therapeutic Considerations

I was pleased to see that some researchers have recently published a paper on this subject. They chose an ACE inhibitor called Captopril.

 

Captopril restores microglial homeostasis and reverses ASD-like phenotype in a model of ASD induced by exposure in utero to anti-caspr2 IgG

Microglia play a crucial role in brain development, including synaptic pruning and neuronal circuit formation. Prenatal disruptions, such as exposure to maternal autoantibodies, can dysregulate microglial function and contribute to neurodevelopmental disorders like autism spectrum disorder (ASD). Maternal antibodies targeting the brain protein Caspr2, encoded by ASD risk gene Cntnap2, are found in a subset of mothers of children with ASD. In utero exposure to these antibodies in mice leads to an ASD-like phenotype in male but not in female mice, characterized by altered hippocampal microglial reactivity, reduced dendritic spine density, and impaired social behavior. Here, we studied the role of microglia in mediating the effect of in utero exposure to maternal anti-Caspr2 antibodies and whether we can ameliorate this phenotype. In this study we demonstrate that microglial reactivity emerges early in postnatal development and persists into adulthood following exposure in utero to maternal anti-Caspr2 IgG. Captopril, a blood-brain barrier permeable angiotensin-converting enzyme (ACE) inhibitor, but not enalapril (a non-BBB permeable ACE inhibitor) ameliorates these deficits. Captopril treatment reversed microglial activation, restored spine density and dendritic arborization in CA1 hippocampal pyramidal neurons, and improved social interaction. Single-cell RNA sequencing of hippocampal microglia identified a captopril-responsive subcluster exhibiting downregulated translation (eIF2 signaling) and metabolic pathways (mTOR and oxidative phosphorylation) in mice exposed in utero to anti-Caspr2 antibodies treated with saline compared to saline-treated controls. Captopril reversed these transcriptional alterations, restoring microglial homeostasis. Our findings suggest that exposure in utero to maternal anti-Caspr2 antibodies induces sustained neuronal alterations, microglial reactivity, and metabolic dysfunction, contributing to the social deficits in male offspring. BBB-permeable ACE inhibitors, such as captopril, warrant further investigation as a potential therapeutic strategy in a subset of ASD cases associated with microglial reactivity.

 

So here is an update that incorporates all these ideas and the new study.

 ___ 

Targeting the Brain Renin-Angiotensin System: From Schizophrenia to Autism (2025 Update)

By Peter Lloyd-Thomas, Epiphany ASD Blog

In 2017, I wrote about the idea that drugs targeting the renin–angiotensin system (RAS)—ACE inhibitors and ARBs—might have therapeutic effects beyond blood pressure, including in schizophrenia and autism. At that time, the discussion was mostly mechanistic. Today, new evidence strengthens the rationale and provides translational plausibility.

 

Why the Brain RAS Matters

While angiotensin II is best known for regulating blood pressure, the brain has its own RAS, which regulates:

·         AT₁ receptors → oxidative stress, neuroinflammation, microglial activation

·         AT₂ and Mas receptors → neuroprotection, mitochondrial function, anti-inflammatory signaling

·         ACE → converts Angiotensin I → II and degrades bradykinin, affecting cerebral blood flow

Shifting the balance from AT₁-dominated to AT₂/Mas signaling can normalize microglial function, improve neuronal energy metabolism, and support synaptic plasticity.

 

New Autism-Relevant Evidence (2025)

A recent study (Spielman et al., Molecular Psychiatry, 2025) used a mouse model of maternal anti-Caspr2 antibodies, a risk factor for some forms of autism. Male offspring showed:

·         Hyperactive microglia

·         Reduced hippocampal dendritic spines

·         Impaired social behavior

Captopril, a BBB-penetrant ACE inhibitor, reversed these deficits. In contrast, enalapril, which poorly crosses the BBB, was ineffective. Single-cell RNA sequencing revealed captopril restored microglial metabolic homeostasis (mTOR, oxidative phosphorylation, eIF2 signaling), linking microglial function directly to behavioral outcomes.

 

ACE Inhibitors vs ARBs: CNS and Immune Effects

Feature	ACE inhibitors (e.g., captopril)	ARBs (BBB-permeable, e.g., telmisartan)
↓ Ang II	Yes	No (blocks AT₁ receptor)
↑ Bradykinin / NO	Yes	No
BBB penetration	Variable — captopril high, enalapril low	Most low; telmisartan high
Microglial activation	↓ via less Ang II & more NO	↓ via AT₁ blockade
NKCC1/2 chloride cotransporters	Normalized via ↓ Ang II	Normalized via AT₁ blockade
Regulatory T cells (Tregs)	Strong ↑	Moderate ↑ (telmisartan strongest among ARBs)
Th1/Th17 autoimmunity	Modulated ↓	Modulated ↓
PPAR‑γ activation	No	Yes (telmisartan)
Evidence in ASD model	Captopril reversed phenotype (2025)	Mechanistically promising; anecdotal human benefit

Both classes modulate neuroinflammation, chloride signaling, and immune function, but ACE inhibitors and ARBs differ in mechanisms and potency.

 

Clinical Evidence in Schizophrenia

Telmisartan has been trialed in adults with schizophrenia (NCT00981526), primarily for metabolic side effects of antipsychotics (clozapine, olanzapine). Secondary observations included:

·         Improvement in negative symptoms

·         Modest cognitive benefits

·         Good tolerability over 12 weeks

This demonstrates CNS activity in humans, beyond metabolic effects, supporting translational plausibility for neuropsychiatric conditions.

 

Personal Observation in Autism

Years ago, I trialed telmisartan in my son. The effect was striking: he began singing spontaneously—something no other therapy had achieved. Singing engages emotion, motivation, and executive coordination, all dependent on healthy microglial and neuronal metabolism. While anecdotal, this observation aligns with mechanistic insights from both the mouse autism model and schizophrenia trials.

 

Safety and Accessibility

ACE inhibitors and ARBs are:

·         Widely prescribed globally for hypertension and heart protection

·         Generic, inexpensive, and safe in adults

·         Typically well-tolerated (ACE-i cough, hypotension, mild electrolyte changes)

This makes them practical candidates for drug repurposing in neurodevelopmental and neuropsychiatric disorders.

 

Mechanistic Summary

1.     Microglial hyperactivation contributes to synaptic and behavioral deficits in some autism subtypes.

2.     Brain RAS modulation (ACE-i or ARB) restores microglial homeostasis, improves energy metabolism, and supports synaptic plasticity.

3.     NKCC1/2 chloride cotransporter regulation: By reducing Ang II (ACE-i) or blocking AT₁ (ARB), these drugs normalize intracellular chloride, restoring proper GABAergic inhibition.

4.     Immune regulation: ACE inhibition induces regulatory T cells (Tregs) and modulates Th1/Th17 autoimmunity. BBB-penetrant ARBs like telmisartan also modulate these pathways, enhanced by PPAR‑γ activation.

5.     Behavioral outcomes: In mice, captopril reverses ASD-like phenotypes; anecdotal human reports suggest telmisartan may improve engagement, motivation, and communication.

 

Next Steps for Research

·         Carefully designed biomarker-driven pilot trials in humans, selecting individuals with evidence of neuroinflammation or maternal autoantibody exposure.

·         CNS-focused outcome measures (microglial imaging, inflammatory markers, synaptic function).

·         Behavioral endpoints relevant to autism (social interaction, expressive communication).

Or skip that and maybe make an n=1 trial?

 

Take-Home Message

Drugs long used for cardiovascular health may have untapped potential in neurodevelopmental and neuropsychiatric disorders. BBB-penetrant ACE inhibitors and ARBs, particularly telmisartan, can modulate:

·         Microglial activity

·         Neuronal chloride gradients

·         Immune regulation

Recent mouse data (Spielman et al., 2025) and human observations in schizophrenia support mechanistic plausibility and safety, making these drugs promising candidates for further study in selected autism subgroups.

 

References and Further Reading:

Spielman et al., Molecular Psychiatry, 2025: Captopril restores microglial homeostasis in anti-Caspr2 ASD model

NCT00981526, Telmisartan in schizophrenia (Fan X, 2018)

Lloyd-Thomas, 2017: Angiotensin II in the Brain

Lloyd-Thomas, 2017: Targeting Angiotensin in Schizophrenia and Some Autism

The CDC Suggests People with Severe Autism are at Elevated Risk from Covid-19 – Time to ACE it?

Elvin Jail in Iran, a hotbed for Covid-19 transmission. Iran has released 70,000 prisoners on furlough, including some foreign political prisoners

I was a little surprised to hear that people with neurodevelopmental disabilities are on the US Center for Disease Control (CDC) list of those at risk from the current Corona virus (Covid-19).  I can see no biological reason for this, but I can see the elevated risks for anyone living in an institution rather than at home, rather like cruise ships and prisons not being safe places to be living right now.

I did check that the CDC have such a list and indeed they do:

Appendix A: Underlying medical conditions that may increase the risk of serious COVID-19 for individuals of any age.

• Blood disorders (e.g., sickle cell disease or on blood thinners)

• Chronic kidney disease as defined by your doctor. Patient has been told to avoid or reduce the dose of medications because kidney disease, or is under treatment for kidney disease, including receiving dialysis

• Chronic liver disease as defined by your doctor. (e.g., cirrhosis, chronic hepatitis) Patient has been told to avoid or reduce the dose of medications because liver disease or is under treatment for liver disease.

• Compromised immune system (immunosuppression) (e.g., seeing a doctor for cancer and treatment such as chemotherapy or radiation, received an organ or bone marrow transplant, taking high doses of corticosteroids or other immunosuppressant medications, HIV or AIDS)

• Current or recent pregnancy in the last two weeks

• Endocrine disorders (e.g., diabetes mellitus)

• Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders)

• Heart disease (such as congenital heart disease, congestive heart failure and coronary artery disease)

• Lung disease including asthma or chronic obstructive pulmonary disease (chronic bronchitis or emphysema) or other chronic conditions associated with impaired lung function or that require home oxygen

• Neurological and neurologic and neurodevelopment conditions [including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy (seizure disorders), stroke, intellectual disability, moderate to severe developmental delay, muscular dystrophy, or spinal cord injury].

Treating Covid-19

There are well established strategies in place to treat flu pandemics, but Corona virus is different, although there are similarities.

There is already a great deal of research published, thanks to very fast working Chinese researchers.

In simple terms there are two strategies:-

1.     Inhibit the spread of the virus

2.     Halt the cytokine storm that triggers pneumonia and respiratory failure, should the disease progresses that far

If you fail in these two steps you are left with the same situation as occurred in the Spanish flu epidemic, where you treating what has become a bacterial infection in your lungs and hoping for the best. Nowadays we have antibiotics and a small number of ventilators.

Fortunately, initial studies have already been completed and show positive results in both (1) and (2) above.

Some of the drugs used to inhibit the spread of the virus are cheap generics, while one is a Japanese drug originally developed to treat the flu.

The last time the world was worried about a pandemic people stocked up with an antiviral drug called Tamiflu.  Tamiflu does not work for Coronavirus.

What does work are some old drugs originally used to treat malaria that include:-

1.     Hydroxychloroquine (HCQ), sold under the brand name Plaquenil
2.     Chloroquine, a 70 year-old drug sold under names including Resochin

In France Sanofi is offering to donate millions of doses of Plaquenil to the Government and in the US Bayer has offered to donate Resochin. 

It appears that Plaquenil works better and has less side effects.

In Japan they have a drug developed to treat flu called Favipiravir (also known as Avigan).  In trials it has the same effect as the old malaria drugs, it shortens the duration of the disease by about half and so reduces severity.

In all cases the drugs that target the replication of the virus need to be taken early on in the disease progression, to give any benefit.  This makes perfect sense.

What kills people in Covid-19 is the same thing as in the Spanish flu of 1918, it is a cytokine storm when the body’s immune system over-reacts and attacks your lungs.

If the disease progresses to this point you have to look at therapies to treat cytokine storms associated with severe influenza.

Here we have at least two interesting approaches:

1.     IL-6R antibodies (Roche’s Actemra)   
2.     S1P1 receptor agonist like Fingolimod (Gilenya)

Actemra is already in trials to treat Covid-19, but is injected.

Gilenya is an immunomodulating drug, mostly used for treating multiple sclerosis, taken by mouth.

One feature of Covid-19 is hypokalemia.  When sick these people excrete potassium in urine and become hypokalemic, they may need 3,000mg a day of potassium supplement.  As they get better, they stop losing potassium. This all relates to the angiotensin system, disturbed by the virus.

If you take bumetanide you excrete potassium, so if you get Covid-19 you would be wise to stop bumetanide, but keep taking potassium supplements. 

ACE2 Coronavirus and Italians

The reseach has already identified how the Covid-19 virus spreads in humans.  It uses Angiotensin converting enzyme 2 (ACE2) and ACE2 receptors.

To inhibit the spread of the virus you want less ACE2.

In normal times ACE2 is a very good thing to have and it is a marker for a healthy person. In some people they have variations of the gene that produces ACE2 or its receptor.  This variation is seen in Italians and also in sportsmen - not a good time to be an Italian sportsman.

Certain drugs increase ACE2 and certain drugs you might expect to lower ACE2 appear not to.

You might think Grandma’s ACE inhibitor, she takes to lower blood pressure would inhibit ACE2, but ACE inhibitors inhibit ACE1.  It appears they increase ACE2 receptor expression and ACE2 itself.

There are two issues, the number of receptors and the amount of the enzyme, both are relevant.

Chinese research on real patients found that those taking ACE inhibitors and ARBs had elevated levels of ACE2.

Ibuprofen has been reported to increase ACE2.  In children treated in France, there condition became much worse after treatment with Ibuprofen.

Glitazone drugs, that can help treat a cytokine storm, unfortunately seem to increase ACE2.  These drugs are used to treat type 2 diabetes.

ACE inhibitors and ARBs are also useful un treating a cytokine storm, but raise ACE2 and so must be avoided.

Practical Strategies

I should start by pointing out that researchers at Imperial College in London, who have analysed the data from a town in Northern Italy where 100% of the residents were tested for Covid-19, suggest that only one in eight people with the virus actually show symptoms.

German researchers think that over the next two years 60-70% of their population will catch the virus.

It is only the at-risk groups where mortality is going to be widespread.

I started writing this post when I heard some of Donald Trump’s “experts” standing beside him talking about the virus. I was not very impressed.  Then I read a newspaper interview with an “expert” in England saying how they would treat a new patient with Covid-19.  He would use Tamiflu and later antibiotics.

Where we live, they have very few ventilators and so it really makes sense to change the course of the disease so that you will never need one.

The generic drugs to stop the virus replicating are cheap, while the modern immunomodulatory drugs to halt the cytokine storm are extremely expensive.

My choice is Hydroxychloroquine (Plaquenil).  In France the published adult dose used is 600mg for 10 days. UPDATE I would also add Azithromycin, based on the chart at the end of this post.  In a small French trial the combination is remarkable, after 5 days the virus has gone in 100% of patients. This a cheap macrolide antibiotic, with long known immunomodulatory effects. 

If you look at the half-life of this drug, it is extremely long, over one month.  If I was treating myself for Covid-19 I would start with a higher dose and then taper it.  You need the greatest effect at the start, not the end of the therapy.

I do not actually believe that a healthy boy with autism, living at home, is at elevated risk of Covid-19, but if I am wrong, I will be giving Hydroxychloroquine (Plaquenil) immediately, should Covid-19 be confirmed.

These drugs have side effects and you would not want to use them when it is just a cold or flu.

Since Ibuprofen is reported to increase ACE2, I certainly will not be using it.

Paracetamol/acetaminophen has the big problem of depleting the body’s key antioxidant GSH.

GSH itself has a benefit on inhibiting virus replication.

Since I already give a large daily dose of NAC (N-acetylcysteine) to boost GSH levels, I would use paracetamol to treat a very high temperature in Covid-19.

I think Monty’s grandparents are the ones that might need the anti-cytokine storm therapy.

People with autism often have potent immune systems.  In the Spanish flu, it was young adults with good immune health that died.  They died because they generated potent cytokine storms in their lungs, which express ACE2 receptors and then they developed bacterial pneumonia. In medical jargon they developed acute respiratory distress syndrome (ARDS) and sepsis, causing death. 

In the first stage of Covid-19 a potent immune system should be an advantage, if it identifies the virus.  In the final stage of the disease, which most people avoid, an overactive immune system might not be a good thing.

I think that Hydroxychloroquine (Plaquenil) is a good insurance policy.

If I was a US Presidential candidate, or any other rich elderly person, I would put my order in for Actemra, just in case I needed it.

Actemra (Tocilizumab) is an expensive drug to treat arthritis in adults and children.  It is a humanized monoclonal antibody against the interleukin-6 receptor (IL-6R). Interleukin 6 (IL-6) is a cytokine that plays an important role in immune response and is implicated in the pathogenesis of many disease.  IL-6 is a key player in the cytokine storm in Covid-19.  It is taken by I/V infusion.

An advantage of the S1P1 agonists is that they are taken as tablets.

The following paper is very good and has links to the latest research papers from China, which are also very relevant:-

Are patients withhypertension and diabetes mellitus at increased risk for COVID-19 infection?

The most distinctive comorbidities of 32 non-survivors from a group of 52 intensive care unit patients with novel coronavirus disease 2019 (COVID-19) in the study by Xiaobo Yang and colleagues  were cerebrovascular diseases (22%) and diabetes (22%). Another study  included 1099 patients with confirmed COVID-19, of whom 173 had severe disease with comorbidities of hypertension (23·7%), diabetes mellitus (16·2%), coronary heart diseases (5·8%), and cerebrovascular disease (2·3%). In a third study, of 140 patients who were admitted to hospital with COVID-19, 30% had hypertension and 12% had diabetes. Notably, the most frequent comorbidities reported in these three studies of patients with COVID-19 are often treated with angiotensin-converting enzyme (ACE) inhibitors; however, treatment was not assessed in either study.

Human pathogenic coronaviruses (severe acute respiratory syndrome coronavirus [SARS-CoV] and SARS-CoV-2) bind to their target cells through angiotensin-converting enzyme 2 (ACE2), which is expressed by epithelial cells of the lung, intestine, kidney, and blood vessels.

The expression of ACE2 is substantially increased in patients with type 1 or type 2 diabetes, who are treated with ACE inhibitors and angiotensin II type-I receptor blockers (ARBs).

 Hypertension is also treated with ACE inhibitors and ARBs, which results in an upregulation of ACE2.

ACE2 can also be increased by thiazolidinediones and ibuprofen. These data suggest that ACE2 expression is increased in diabetes and treatment with ACE inhibitors and ARBs increases ACE2 expression. Consequently, the increased expression of ACE2 would facilitate infection with COVID-19. We therefore hypothesise that diabetes and hypertension treatment with ACE2-stimulating drugs increases the risk of developing severe and fatal COVID-19. 

The cytokine storm of severe influenza and development of immunomodulatory therapy

Severe influenza remains unusual in its virulence for humans. Complications or ultimately death arising from these infections are often associated with hyperinduction of proinflammatory cytokine production, which is also known as ‘cytokine storm'. For this disease, it has been proposed that immunomodulatory therapy may improve the outcome, with or without the combination of antiviral agents. Here, we review the current literature on how various effectors of the immune system initiate the cytokine storm and exacerbate pathological damage in hosts. We also review some of the current immunomodulatory strategies for the treatment of cytokine storms in severe influenza, including corticosteroids, peroxisome proliferator-activated receptor agonists, sphingosine-1-phosphate receptor 1 agonists, cyclooxygenase-2 inhibitors, antioxidants, anti-tumour-necrosis factor therapy, intravenous immunoglobulin therapy, statins, arbidol, herbs, and other potential therapeutic strategies.

  

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4711683/figure/fig1/?report=objectonly

Cytokine storm in the lung following severe influenza infection. (1) Viruses infect lung epithelial cells and alveolar macrophages to produce progeny viruses and release cytokines/chemokines (mainly contains interferons). (2) Cytokine/chemokine-activated macrophages and virally infected dendritic cells lead to a more extensive immune response and the initiation of cytokine storm. (3) Released chemokines attract more inflammatory cells to migrate from blood vessels into the site of inflammation, and these cells release additional chemokines/cytokines to amplify cytokine storm.

Summary of immunomodulatory therapy or strategies against severe influenza

Therapeutic agents or strategies	Summary
Corticosteroids	Alleviated the 2009 pandemic H1N1 influenza-infected patients with pneumonia.30 Ineffective as monotherapy in H5N1 influenza-infected mice.29 Increased long-term mortality in influenza-infected patients with pneumonia.27
PPARs agonists	Ciglitazone and troglitazone decreased the mortality of influenza-infected mice.34 Bezafibrate partially protected patients with influenza-associated encephalopathy.33 Gemfibrozil also decreased the production of IL-1, IL-6, and IFN-γ, but has no effects on the mortality of H5N1-infected mice when administered 48-h post-infection.31,32
S1P1 receptor 1 agonists	Reduced mortality of 2009 pandemic H1N1 influenza-infected mice over 80%, compared with 50% protection of oseltamivir.36
COX inhibitors	Ineffective as monotherapy in H5N1 influenza-infected mice, while effective when in combination with neuraminidase inhibitors.32
Antioxidants	N-acetylcysteine and glycyrrhizin inhibited H5N1 replication and pro-inflammatory gene expression in vitro39,40 but ineffective as monotherapy in vivo.45
Anti-TNF therapy	Effective in reducing the cytokine production and inflammatory cell infiltrates in influenza-infected murine lung but ineffective in improving survival of infected mice.47,48
IVIG therapy	Reduced 26% to 50% mortality of 2009 pandemic H1N1 and 1918 Spanish H1N1 influenza-infected patients.50,52
ACEIs or ARBs	Combined with caffeine or antivirals, alleviated lung injury and inhibited viral replication in H1N1, H3N2, and H5N1 influenza-infected mice.54 Ineffective in protecting 2009 pandemic H1N1-infected patients.55
CCR inhibitor	Increased survival of influenza-infected mice by 75%.58
AMPK activators	Increased survival for influenza-infected mice by 40%, while a combination with pioglitazone improved survival by 60%.59
OX40	Imparted a survival signal to the T cell via upregulating anti-apoptosis gene expression and eliminated weight loss in influenza-infected mice.60
SOCSs	Participated in a negative feedback loop in the JAK and epidermal growth factor receptor pathway to protect against severe cytokine storm during severe influenza.61
Macrolide	Decreased mortality, pro-inflammation, and inflammatory cell counts of influenza-infected mice.62
Arbidol	Reduced the mortality, lung lesion formation, and inflammation of severe influenza-infected mice.64
Herbs	Favorable in laboratorial data but limited clinical data for severe influenza.65,66,67,68,69,70,71

Polytherapy - Hydroxychloroquine plus Azithromycin (a macrolide, from the table above)

Click on figure below to enlarge it