Probiotics Potentials in Improving Healthcare for Lung Diseases

As we know, the physiology and pathology of the respiratory and digestive tracts are closely interrelated. The correlation between these two systems explains why functional disorders in one organ can cause diseases in another. For instance, smoking is a major risk factor for Chronic Obstructive Pulmonary Disease (COPD) and Inflammatory Bowel Disease (IBD). COPD is an inflammatory respiratory condition requiring frequent visits to clinics and hospitals due to acute exacerbations [1]. Due to its prevalence, disease incidence, and high mortality rates, it has become a significant global health issue [2].

The global burden of COPD is estimated to be 4-5% and is predicted to be the third leading cause of death worldwide [3]. Recent studies suggest that diet and nutrition affect the gut microbiota and their metabolism, influencing the mucosal immune system of the lungs. Probiotics have been described as “beneficial bacteria that, when consumed in appropriate amounts, provide significant benefits to the human body” [4].

Probiotics are described as “live bacteria that, when used in appropriate amounts, confer long-term benefits to humans.” Probiotics can have multifaceted effects, playing a crucial role in the microbiota, where they exert direct antibacterial effects by competing with pathogens and indirectly by enhancing gut barrier protection. Studies have explored how diet and nutrition impact the microbiota and interact with the immune system to improve gut health. For example, probiotic therapy involves using healthy microbiota from healthy individuals in those suffering from inflammatory diseases [5]. Additionally, they enhance both local and systemic immune responses. In fact, treatment with probiotics helps alleviate inflammatory reactions in the lungs, and there’s encouraging evidence that gut bacteria support the enhancement of T-regulatory responses in the respiratory system [6].

Most of these products contain bacteria that produce lactic acid (lactic acid bacteria, e.g., Lactobacillus, Streptococcus, Bifidobacterium, and Enterococcus sp.) or non-pathogenic bacterial strains like Saccharomyces boulardii. The hypothesis about the microbiota suggests that antibiotic use has led to disruptions in the gut microbiota and disrupted the natural immune regulation mechanism via gut microbial intermediaries, leading to increased susceptibility to allergic diseases like asthma. This hypothesis provides a theoretical basis for using probiotic preparations to enhance immune function and treat diseases.

Probiotics as an Alternative Approach for Preventing Lung Diseases

• For Asthma

The increasing prevalence of asthma is becoming a global health concern, especially in densely populated areas undergoing rapid urbanization. In a human model of asthma, using Lactobacillus reuteri, Lactobacillus rhamnosus GG, and Bifidobacterium breve reduced the overactivity of the respiratory system with inflammatory cells like bronchoalveolar lavage fluid and lung tissue inflammation [7,8]. Apart from preventing asthma, biologic preparations also prevent allergic skin inflammation in infants and reduce food allergies. In in vivo treatment using heat-treated Mycobacterium vaccae preparations, specific regulatory T cells (Tregs) were formed against allergens, thereby aiding in reducing respiratory inflammation after allergies [8].

Regulating the gut microbiota with probiotics enhances the protective function of the gut mucosa, reducing antigen absorption through the mucosa and consequently reducing the allergens that the lungs receive through circulation. Furthermore, direct modulation of the microbiota can occur through the production of anti-inflammatory cytokines or altering dendritic cell function, leading to reduced allergic reactions.

• Influenza and Chronic Obstructive Pulmonary Disease (COPD)

Respiratory infections, primarily viral, directly affect disease incidence and mortality rates, indirectly exacerbating conditions like asthma. It’s been speculated that using probiotics can reduce viral infections and prevent the development of asthma. Additionally, the use of probiotics is associated with lower rates of ventilator-associated pneumonia, reduced respiratory infections in healthy adults and children, and decreased incidence of chronic flu. Smoking remains the most common lifestyle risk factor for both the pathogenesis of COPD and lung cancer. COPD is characterized by gradually worsening symptoms such as increased breathlessness, increased sputum production, and increased inflammation, leading to decreased lung function [1,3].

Acute episodes of COPD affect psychological well-being, with patients experiencing lower quality of life and decreased concentration, often leading to increased depression. Smoking reduces the cytotoxic activity of natural killer (NK) cells in individuals by releasing cytokines. NK cell activity in smokers is lower compared to non-smokers, but daily intake of Lactobacillus casei Shirota has the potential to prevent increased natural cell death activity in smokers [9,10]. This indicates that certain biological preparations might benefit COPD patients, especially those frequently infected with viruses. Notably, a diet rich in Lactobacillus plantarum prevents diseases in smokers [9].

In the future, it’s crucial to understand the mechanisms behind the actions of probiotics in the respiratory tract of diseased individuals. This understanding will enable appropriate approaches to using probiotics in lung diseases. A better understanding of the common gut microbiota in allergic lung inflammation patients and in children will offer opportunities to select specific strains or combinations to regulate immune responses during illness. Probiotics modulate the composition and/or activities of the gut microbiota, so knowledge about culturing gut microbiota is vital, not only from processed stool samples but also from tissue samples.

References:

1. Sun, Zhe, et al. “Dynamic changes of gut and lung microorganisms during chronic obstructive pulmonary disease exacerbations.” The Kaohsiung Journal of Medical Sciences 36.2 (2020): 107-113.
2. Espírito Santo, Christophe, et al. “Gut microbiota, in the halfway between nutrition and lung function.” Nutrients 13.5 (2021): 1716.
3. Vaughan, Annalicia, et al. “COPD and the gut-lung axis: the therapeutic potential of fibre.” Journal of thoracic disease 11. Suppl 17 (2019): S2173.
4. Guarner, Francisco, et al. “World Gastroenterology Organisation Practice Guideline: Probiotics and Prebiotics-May 2008: guideline.” South African Gastroenterology Review 6.2 (2008): 14-25.
5. Parvez, Suhel, et al. “Probiotics and their fermented food products are beneficial for health.” Journal of applied microbiology 100.6 (2006): 1171-1185.
6. Anand, Swadha, and Sharmila S. Mande. “Diet, microbiota and gut-lung connection.” Frontiers in microbiology9 (2018): 2147.
7. Hougee, S., et al. “Oral treatment with probiotics reduces allergic symptoms in ovalbumin-sensitized mice: a bacterial strain comparative study.” International archives of allergy and immunology151.2 (2010): 107-117.
8. Feleszko, W., et al. “Probiotic‐induced suppression of allergic sensitization and airway inflammation is associated with an increase of T regulatory‐dependent mechanisms in a murine model of asthma.” Clinical & Experimental Allergy37.4 (2007): 498-505.
9. Morimoto, Kanehisa, et al. “Modulation of natural killer cell activity by supplementation of fermented milk containing Lactobacillus casei in habitual smokers.” Preventive Medicine40.5 (2005): 589-594.
10. Naruszewicz, Marek, et al. “Effect of Lactobacillus plantarum 299v on cardiovascular disease risk factors in smokers.” The American journal of clinical nutrition76.6 (2002): 1249-1255.