Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Abstract

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

Keywords: COPD; COVID-19; SARS-CoV-2 infection; asthma; lung health; nutrients; pulmonary chronic diseases.

Figure 1

Pulmonary immunity overview. Lungs are in constant contact with many suspended substances, which are relatively harmless, such as pollutants, microbiota, and allergens. (A) Ciliated pseudostratified columnar epithelium covers all respiratory tract, providing a pathway for movement and conditioning of the air entering the lungs, as well as, controls the actions of the mucociliary escalator directing the particles to outside the lung. In association, Goblet cells produce mucins to create a protective layer of mucus, forming a first barrier of defense. Airway fluids also contain antimicrobial peptides (AMP), defensins, cytokines, and antibodies, mainly secretory IgA. To ensure the homeostasis, in the lamina propria, immune cells act both to identify and respond to sterile threats and to control the inflammatory process, preventing that inflammation from compromising lung function. In addition, follicular regions rich in T and B lymphocytes (BALT–bronchus-associated lymphoid tissue) play a crucial role in fighting against infections. (B) Alveolus are in broadly interaction with the external environment, where lung cells secrete surfactants proteins and alveolar macrophages are highly phagocytic.

Figure 2

Immunomodulatory properties of nutrients in lungs. Nutrients are able to ameliorate the development and severity of pulmonary diseases, since they can act on several immune cells and modulate immune response in inflammatory processes. In this context, minerals, flavonoids, vitamins, and fatty acids reduce the expression of inflammatory mediators (such as cytokines and chemokines), as well as, have antioxidant effect, decreasing the deleterious effects of asthma and chronic obstructive pulmonary disease (COPD) in the lungs. In addition, fibers and fatty acids also can modulate intestinal microbiota, which contribute to lung homeostasis through gut-lung axis. Regarding pulmonary viral infections, vitamins, and flavonoids are the main dietary components with antiviral action.

Figure 3

Possible role of nutrients in COVID-19 pulmonary pathophysiology. Some nutrients have been proposed during COVID-19. (A) Naringenin has been described as being able to inhibit infection SARS-CoV-2 infection. (B) Vitamins, minerals, and flavonoids can inhibit viral replication in many pulmonary infections, and naringenin already demonstrated ability to decrease viral replication of SARS-CoV-2. (C) These nutrients also have antioxidant role (inhibition of reactive oxygen species—ROS) and (D) anti-inflammatory activity (inhibition of transcription proinflammatory factors transcription) and may inhibit the deleterious effects of the cytokine storm and tissue damage present in COVID-19. In addition, vitamin D demonstrated a relevant role on glucose-treated monocytes, lowering the risk of oxidative stress and the release of IL-8 and CCL-2 by monocytes. This can be relevant since diabetes is considered a risk factor in COVID-19 patients, in addition to the fact that monocytes glycolysis is a mechanism used by SARS-CoV-2 to promote inhibition of T cells and tissue damage in the lungs.