Herbal tools to help you beat asthma and lung infections
As we’ve learned all too well recently, we can’t take lung health for granted. Severe respiratory infections are on the rise, in addition to the chronic burdens of asthma, allergies, and air pollution.[1],[2] On top of that, many of us are experiencing smoke and particulate matter from the late summer wildfires burning, triggering asthmatic symptoms and compromising the respiratory health of everyone.
Unfortunately, the particulate matter from wildfire smoke and asthma can be factors that lower our resistance to respiratory tract infections as well. Fortunately, there are natural tools that not only intersect with the oxidative stress caused by smoke inhalation and the inflammation that contributes to asthma, but also help protect us from respiratory infections.
Lung inflammation is a common problem
Asthma, a long-term condition that affects people of all ages, causes wheezing, breathlessness, chest tightness, and coughing. Along with chronic obstructive pulmonary disease (COPD), asthma is a condition associated with inflammation in the lung airways.[3],[4],[5],[6]
The inflammation that occurs with asthma is known as a “Th2 shift.” This means that the immune system shifts away from an infection-fighting (Th1) state and towards an inflammatory (Th2) state.[7],[8]
One of the culprits in triggering a Th2 shift and thus increasing inflammation is a protein known as HMGB1.[9] HMGB1 levels were found to be five times higher in the lungs of patients with asthma than in healthy subjects, and levels were also correlated with asthma severity.[10],[11],[12] HMGB1 is a hot target for novel therapies for asthma, and also for severe respiratory infections, as we’ll discuss shortly.
The lung inflammation associated with asthma not only makes it difficult to breathe, but makes it harder for the immune system to fight off invaders.
The lung inflammation associated with asthma not only makes it difficult to breathe, but makes it harder for the immune system to fight off invaders.[13],[14] As a result, asthma increases the risk of respiratory infections.[2],[15],[16],[17] Respiratory infections in turn exacerbate the symptoms of asthma,[14],[15],[18],[19] creating a vicious circle. When one has these heightened risks, it is important to take extra protective steps.
Well-modulated inflammatory processes actually help clear lung infections.[20] In severe infections, however, the inflammatory response can spin out of control when the body releases too many inflammatory cytokines (peptides) into the blood too quickly.[21],[22],[23] The rapid and intense nature of the excessive release of cytokines can give rise to serious, possibly fatal lung damage.[24] One of the molecules responsible for this flood of cytokines is our previously-mentioned villain, HMGB1.[25]
While the scientific community actively works to identify anti-inflammatory and antiviral drugs to treat lung diseases, it’s worth examining the botanicals that have been used for centuries in traditional medicine to alleviate some of these problems.
In a previous article we discussed Andrographis paniculata and several other natural products with infection-fighting properties. Today we’ll focus on traditional herbal medicines for asthma, and see how they may also help fight viral infections.
How herbs help asthma and viral infections
Scientists at the Icahn School of Medicine at Mount Sinai in New York have extensively studied the use of herbs for asthma.[26] They developed a blend of three Chinese herbal medicines known as ASHMI, which stands for Anti-Asthma Simplified Herbal Medicine Intervention. The ASHMI formula is comprised of the three most effective herbs identified in a traditional 14-herb formula (MSSM-02) with a long history of use in China.[27] These include a water extract of Gan-Cao (Glycyrrhiza uralensis), commonly known as Chinese licorice; Ling-Zhi (Ganoderma lucidum), a medicinal mushroom commonly known as reishi; and Ku-Shen (Sophora flavescens), also known as shrubby sophora.
ASHMI has been studied extensively in the laboratory and in mice,[28],[29],[30],[31],[32],[33] and also has been evaluated in human clinical trials.[26],[34] Remarkably, in a placebo-controlled trial conducted over a four-week period, ASHMI was as effective as the standard corticosteroid treatment in controlling moderate to severe asthma symptoms, yet lacked the adverse effect of adrenal suppression.[26]
There was synergy among the three herbs, such that the ASHMI blend was more effective than any single constituent.
In studies of mice with established asthmatic responses, ASHMI was shown to provide persistent protection against lung inflammation without suppressing the immune system as a whole.[29] Immunosuppression, of course, is an adverse effect associated with corticosteroid use. In the mice and the human study,[26] the Th2-mediated allergic response was reduced, and there was a significant increase in the level of interferon, a cytokine that is essential for antiviral defenses. Notably, there was synergy among the three herbs, such that the ASHMI blend was more effective than any single constituent.[33]
Numerous studies suggest that the herbs that comprise ASHMI may help ameliorate not only asthma, but also viral respiratory infections.
Licorice
Glycyrrhizin, the predominant bioactive substance in , has been shown to decrease the production of inflammatory cytokines,[35],[36] improve the Th1/Th2 balance,[37] and ameliorate lung injury in animal models of inflammation.[38] Licorice also contains phytonutrients known as flavonoids that have been shown to help control lung inflammation.[33],[39] In the context of viral respiratory infections, glycyrrhizin has been shown to tamp down inflammatory cytokines, enhance interferon production, and inhibit viral replication.[40],[41],[42]
Glycyrrhizin significantly increased survival in mice exposed to a lethal quantity of influenza virus.
Potential remedies for viral infections can act either on the viral machinery itself or on host cells, and glycyrrhizin may well do both. It has been shown to bind to a cellular receptor known as ACE2 by which certain viruses enter the cell, thereby blocking the virus from accessing the cell’s machinery for further replication.[43],[44] This same cellular receptor also plays an important role in lung injury induced by influenza viruses.[45],[46],[47] In mice exposed to a lethal quantity of influenza virus, glycyrrhizin was shown to increase survival when administered before and during the infection.[48]
Glycyrrhizin also has the potential to block lung damage by binding and inhibiting HMGB1,[49],[50] which, as mentioned, has been implicated in the flood of cytokines that is associated with severe viral infections.[25],[51],[52],[53] Scientists at the Karolinska Institute in Sweden note an urgent need for human trials for glycyrrhizin and other potential HMGB1 blockers:[25] “The collated science shows that HMGB1 probably plays a pivotal part in the development of acute lung damage, regardless of cause…In publishing our review paper, we hope to give guidance on existing drugs with the potential to mitigate HMGB1-mediated damage,” says Professor Andersson, the head of the laboratory, who has been researching this protein for approximately 20 years.[54]
Note: It’s always a good idea to consult a qualified health professional if you are considering an herbal supplement regimen including Glycyrrhiza, as it can interact with prescribed medications and affect blood pressure in some individuals.[55]
Reishi
The second component of ASHMI, the medicinal mushroom known as reishi, has been shown to reduce cellular secretion of inflammatory cytokines,[56],[57] and to restore a healthy Th1/Th2 balance in patients with allergies.[58] In cells collected from asthma patients, a reishi extract suppressed the inflammation mediated by a cytokine known as tumor necrosis factor (TNF-α).[59] TNF-α is an important player not only in asthma, but also mediates the inflammatory response that can exacerbate symptoms of infections,[60] making reishi potentially useful in both contexts. Reishi has been shown in animal studies to reduce inflammation in both the gut and the lungs.[61],[62],[63]
Reishi was shown to inhibit an influenza virus enzyme known as neuraminidase, which is essential for viral replication.
The medicinal mushroom reishi also contains water-soluble substances (triterpenoids) with direct anti-viral effects.[64] Reishi was shown to inhibit an influenza virus enzyme known as neuraminidase (NA), which is essential for viral replication.[65] NA inhibitors are the main drugs used to treat influenza.
Reishi additionally contains β-glucans, which are polysaccharides (small carbohydrates) with prebiotic properties. When β-glucans are ingested, they help support the growth of healthy bacteria in the gut, reduce inflammation, and boost immunity.[66],[67],[68] A healthy microbiota helps reduce the risk of infections,[69] while a microbiota that is out of balance can make it easier for viruses, bacteria, and fungal infections to take hold.[70]
Shrubby Sophora
The third component of ASHMI, shrubby sophora (Sophora flavescens), also has been shown to modulate the production of inflammatory cytokines,[71] and reduce smooth muscle contraction in samples taken from asthmatic mice.[72] The contraction of smooth muscles contributes to the narrowing of the airways that is the hallmark of asthma attacks. A bioactive substance found in S. flavescens, known as matrine, has been shown to reduce cigarette smoke-induced lung inflammation in mice, suggesting that matrine may also help ameliorate COPD.[73]
S. flavescens contains antiviral substances as well.[74],[75],[76] An extract of S. flavescens was shown to inhibit influenza virus NA activity by 90%, an effect that was attributed to a bioactive ingredient known as a pterocarpan.[77] “We believe that this lead structure may be highly beneficial for the development of new drugs to combat this serious disease,” conclude the study authors.
S. flavescens also contains flavonoids that may curtail the lung damage associated with respiratory infections.
S. flavescens also contains flavonoids that may curtail the lung damage associated with respiratory infections, based on evidence from studies of tuberculosis in mice.[78] One particular flavonoid is capable of blocking a viral-induced cellular pathway known by its acronym, RANTES.[79] The RANTES pathway is implicated not only in asthma attacks,[80] but also in lung inflammation after viral infection.[81] This suggests that the components of sophora may be beneficial for both indications.
Summary
The herbs presented here have the potential to support lung health and, in particular, to ameliorate the effects of asthma and respiratory infections. While they have been tested in the clinic for asthma, the case for their use for respiratory infections is based on preclinical studies and traditional use. The evidence from these studies is compelling, however, and justifies clinical trials of these natural products as tools for respiratory health and protection.
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