Nitric Oxide- the Nobel prize winning molecule, can play a critical role in the Covid-19 cure
The world is still grappling with the Covid19 pandemic and researchers are trying hard to find a cure via repurposed drugs. One such molecule, which has shown great promise is Nitric oxide. Dr. Mihir Shah (MDS, pediatric dentistry) describes in detail the data available on the use of Nitric oxide.
Nitric oxide was discovered by Robert F., Louis J. Ignarro, and Ferid Murad for which they were awarded Nobel prize in 1998.
Covid19 was earlier postulated to be respiratory tract infection, but now we know that severe Covid19 is associated with endothelial dysfunction & cytokine storm. Nitric oxide has the potential to act not only at the stage of initial infection in the respiratory tract but also in the prevention & management of endothelial dysfunction & complications associated with the same.
Here we discuss Nitric Oxide under the following topics:
- Nitric Oxide & Types of Nitric Oxide Synthase enzymes
- Covid19 infection & Complications
- Role of Nitric Oxide as Initial Line of Defence
- Role of Nitric Oxide in Advanced Stage of Inflammation
- Role of Nitric Oxide in Blood vessels
- Vitamin D & Nitric Oxide: Is there any connection
- Studies on Nitric Oxide & Covid19
- Optimization of Nitric Oxide in our Body
A. What is Nitric Oxide?
Nitric Oxide (NO) is a molecule that is naturally produced in the nose as well as throughout the body. It has antiviral, antibacterial & anti-inflammatory effects. It also is a potent vasodilator that causes blood vessels to widen and stimulates the release of certain hormones, such as insulin and human growth hormone. It is used as a pharmacological inhalational agent as well for various ailments.
In our body, there are three main types of Nitric Oxide Synthase enzyme
- eNOS- In mammals, the endothelial isoform is the primary signal generator in the control of vascular tone (vasodilator), insulin secretion, and airway tone, which is involved in the regulation of cardiac function and angiogenesis.
- iNOS- The inducible isoform iNOS produces large amounts of NO as a defense mechanism. It is synthesized by many cell types in response to cytokines and is an important factor in the response of the body to attack by viruses, parasites, bacterial infection, and tumor growth
- nNOS- The neuronal isoform is involved in the development of the nervous system.
- Covid19 Infection & Complications
Covid-19 infection is caused by the Sars-Cov-2 virus first reported in Wuhan China. The spectrum of Covid19 Infection is associated with a broad spectrum of clinical respiratory syndromes, ranging from mild upper airway symptoms to progressive life-threatening viral pneumonia with severe respiratory failure & multiorgan damage.
The lung injury of Sars-Cov-2 infected patients appears to happen due to the following
- Directly through viral disruption of alveolar and bronchial epithelial cells and macrophages, and indirectly via triggering inflammatory mediators.
- The severe form is due to heightened host response- Hyperinflammation & cytokine storm
- Role of Nitric Oxide as Initial Line of Defence
Covid19 begins primarily as a Respiratory tract infection via Breathing. Breathing is the most important function of The Nose. The nasal cavity, turbinates, and paranasal sinuses play important physiological functions by filtering, warming, and humidifying inhaled air. They are lined by epithelium which is the first line of defense against infection. The epithelium of paranasal air sinuses & nasopharynx produces a unique molecular gas called Nitric Oxide- NO via NO synthase (NOS) enzymes
Role of Nitric Oxide in Airway
- NO is produced up to 10ppm & it produces antimicrobial effects against bacteria, fungi, viruses, etc which may help prevent pulmonary infections
- NO brings about bronchodilatory effects & vasodilatory effects in the lungs.
- It has surfactant action & it activates ciliary movement and mucus secretion to remove dust and pathogens.
- NO has been shown to have an antiviral effect on several DNA and RNA virus families (Colasanti, Persichini, Venturini, & Ascenzi, 1999).
- The NO-mediated S-nitrosation of viral molecules might be an intriguing general mechanism for the control of the virus's life cycle. In this regard, it is conceivable that NO could nitrosylate cysteine-containing enzymes and proteins, including nucleocapsid proteins and glycoproteins, present in the coronavirus.
- NO has been shown to have an antiviral effect on several DNA and RNA virus families through NO-mediated S-nitrosation & inactivates them by modifying proteins and nucleic acids that are essential for viral replication including herpesvirus, rhinovirus, hantavirus, and the SarsCov-1
- Invitro studies have now shown that Nitric oxide is an effective antiviral agent against SarsCov-2 as well.
(Nitric oxide has a high potential to be an effective antiviral agent at this stage. Continue Reading below about the section on Optimization of Nitric Oxide in Airway with Breathing Techniques.)
- Role of Nitric Oxide in Advanced Stage of Inflammation (Killing Stage & Healing Stage)
During the advanced stage of inflammation, there is Diffuse Alveolar Damage with perivascular T-cell infiltration, Pulmonary Vasoconstriction, and tissue inflammation.
The understanding of activation and differentiation of macrophages in inflammation is essential for understanding the immunology of inflammation. These cells are categorized into two principal subtypes,
- M1 macrophages, which secrete great quantities of Proinflammatory cytokines (such as IFN-γ, TNF-α, IL-6, and IL-12, etc), nitric oxide and reactive oxygen species (ROS),
Patients with severe disease have increased pro-inflammatory cytokines (Cytokine Storm)
- M2 macrophages release large concentrations of Anti-inflammatory cytokines such as IL-10, TGF-β, and IL-1 receptor antagonists.
The most important dichotomy in Macrophage function as we see here is that
M1 macrophages Kill (infectious organisms, virus-infected cells, or tumor cells) & M2 macrophages Heal (sterile wounds and, with less success, cancer).
However, Killing comes at a price: M1-mediated killing is associated with collateral tissue damage that M2 macrophages must clean up and heal after the dangerous invader has been eliminated.
Recent evidence suggests that the polarization of Macrophages from M1 (Proinflammatory) to M2 (Anti-inflammatory) occurs using (Nitric Oxide) NO- VASP (Vasodilator-stimulated phosphoprotein) pathway. This constitutes an important pathway in the prevention of the cytokine storm.
Thus, Nitric Oxide plays an important role in Macrophage polarization & the prevention of Cytokine storm.
- Nitric Oxide & Its Role in Blood Vessels:
Due to these pro-inflammatory cytokines & pulmonary vasoconstriction, there is associated Pulmonary Vascular Endothelialitis, Microthrombosis, and intussusceptive Angiogenesis. These may further lead to Respiratory failure & multiorgan damage
Nitric Oxide is a potent vasodilator and may help to reverse pulmonary vasoconstriction. This may thus help in oxygenation of the blood in the pulmonary arterioles & prevent Hypoxia as well which is the main issue of the complication of Covid19. Vasodilation of blood vessels may also help in the prevention of the formation of microthrombi & the complication associated with the same.
(Continue Reading below about section on Dietary ways to Optimize Nitric Oxide in our Body)
- Nitric Oxide & Vitamin D: Is there any connection
Vitamin D is the most talked-about Vitamin since the start of the pandemic as the evidence is getting clear that the complications of Covid 19 are more common in patients with Vitamin D deficiency
Growing literature & evidence now suggest the endothelial function of Vitamin D is carried out by stimulation of release of Nitric Oxide from blood vessels. This also confirms the Role of Vitamin D in the prevention of Cytokine Storm
Similarly, sun exposure, sauna exposure also helps in the release of Nitric Oxide
- Studies on Inhaled Nitric Oxide:
Inhaled Nitric oxide (iNo) if started early have shown good success rate in the treatment of Covid19 as shown in multiple research papers. This was also seen during the 2003 pandemic of Sarscov1
One such study reports that in spontaneously breathing patients with Covid-19 who underwent therapy with iNO, more than half did not require mechanical ventilation after treatment. These findings suggest that iNO therapy may have a role in preventing the progression of hypoxic respiratory failure in Covid-19 patients. Inhaled Nitric Oxide has also shown success in a patient with Idiopathic Pulmonary hypertension.
Inhaled Nitric oxide at 160-200 ppm is shown to be well-tolerated and may benefit pregnant patients with COVID-19 with hypoxic respiratory failure.
Also, multiple papers suggest that impairment of Nitric Oxide production is seen in Diabetes mellitus & Hypertension which are also main comorbidities associated with Covid19 complications & mortality. This also suggests that Nitric Oxide may have a potential role in the prevention & management of Covid19.
8. Optimization of Nitric Oxide in body
Breathing Techniques to Boost Nitric Oxide Levels
According to Louis Ignarro, (Nobel Prize for the discovery of NO) in April’20 published “Inhaled Nitric Oxide and COVID-19” - “One practice to consider during this coronavirus pandemic is to breathe or inhale through the NOSE and exhale through the Mouth”
Jan Martel in May’20 has published “Could nasal nitric oxide help to mitigate the severity of COVID-19?
- Exclusive Nose Breathing throughout the day & night is a must for optimum availability of Nitric Oxide from the Nose. Mouth breathers tend to have lower levels of Nitric oxide as nitric oxide is produced in the nose & not in the mouth.
- A slow rate of breathing from 6-10 breaths per minute can not only help to increase Nitric Oxide but also improves Heart Rate variability.
- Humming (similar to chanting Om with Nose) can increase Nitric oxide up to 3000ppm.
This is similar to Brahmari Pranayama which is also recommended by the Ministry of Health and Family welfare as part of Yoga guidelines for Covid19 patients.
- Breath-holding after exhalation for 5-10seconds (& more time under professional guidance) helps to increase Nitric oxide. (Contraindicated in CVD patients, pregnancy, or any other major ailments)
Dietary Methods to optimize Nitric oxide in our body.
- Diet rich in Nitrates helps to increase Nitric oxide. Nitrates are reduced to Nitrites by oral bacteria in the Oral Cavity. Hence it is important to use antimicrobial Mouthwashes judiciously as mouthwashes may reduce the availability of these bacteria and reduce Nitric oxide as well.
The foods highest in nitrate include beetroots, watermelon, pomegranate, garlic, leafy greens such as kale, arugula, chard, and spinach. Others include parsley, Chinese cabbage, leeks, celery, radishes, and turnips.
- Diet Rich in L Arginine, Citrulline, Vitamin C also helps to optimize Nitric oxide levels
Nitric Oxide is a promising agent that has not only shown antiviral action against Sars-cov-2 but also optimizes body functions & prevents any major complications associated with Covid19.
Randomised Controlled trials are underway in the use of inhaled Nitric Oxide (iNO) which will definitely lead us the way. Randomised Controlled trials must also be carried out in the Role of various Breathing techniques & Dietary measures to optimize Nitric Oxide for the prevention & management of Covid19.
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Dr. Mihir Shah is a Pediatric Dentist & Certified Orofacial Myology Specialist
practicing in Mumbai. He works in the field of Preventive Pediatric Dentistry for
the prevention of Dental Malocclusion & Dental Caries. His forte includes Airway
dentistry for Dental management of Mouth Breathing, Sleep Disordered Breathing &
Obstructive Sleep Apnea in children.