By Gilang Cahya 
In preclinical models, the inhalation of a mixture of living Lactobacilli bacteria attenuated pulmonary inflammation and improved lung function and structure for the chronic lung diseases bronchopulmonary dysplasia and chronic obstructive pulmonary disease. This groundbreaking research, published in the esteemed journal Nature Communications, has unveiled a novel therapeutic avenue for debilitating respiratory conditions, identifying a specific mechanism by which these beneficial bacteria exert their protective effects.
Unveiling the Mechanism: Lactobacilli’s Anti-inflammatory Power
The study, co-led by Charitharth Vivek Lal, M.D., a neonatologist at the University of Alabama at Birmingham (UAB), and Amit Gaggar, M.D., Ph.D., a UAB pulmonologist, delved into the intricacies of how a powder mixture of living Lactobacilli bacteria, administered as a live biotherapeutic product (LBP), effectively reduces neutrophilic inflammation and a wide spectrum of inflammatory markers in both bronchopulmonary dysplasia (BPD) and chronic obstructive pulmonary disease (COPD).
"Our findings provide a paradigm for the progression of structural lung disease," stated Dr. Lal. He elaborated that the research pinpoints Lactobacilli as crucial regulators of lung protease activity. This activity is intrinsically linked to the destructive processes driven by matrikine generation, extracellular matrix turnover, and chronic neutrophilic inflammation, all of which contribute to the irreversible damage of lung air sacs.
A Decade in the Making: From Observational Discovery to Therapeutic Development
The foundational insights for this research emerged in 2016. At that time, Dr. Lal and his UAB colleagues observed a significant correlation between severe BPD in infants and a diminished presence of Lactobacilli in their airways. Concurrently, they noted an increased abundance of proteobacteria and elevated concentrations of proteobacterial endotoxin. This initial observation laid the groundwork for hypothesizing a protective role for Lactobacilli in the lung and their potential as a therapeutic agent for chronic lung diseases.
The current study represents a significant leap forward, providing a concrete mechanism of action for Lactobacilli-based treatment. It demonstrates how these bacteria can mitigate downstream disease development and has rigorously tested the safety and efficacy of this inhaled LBP in relevant preclinical models. The research included a mouse pup model specifically designed to mimic BPD and three distinct mouse models representing various facets of COPD.
Understanding the Diseases: BPD and COPD
Bronchopulmonary dysplasia (BPD) is a serious chronic lung disease that primarily affects premature infants. It often arises as a consequence of lung damage sustained during intensive care, typically due to prolonged exposure to high oxygen concentrations or the mechanical ventilation required to support their underdeveloped lungs. The cumulative stress on these fragile airways can lead to long-term respiratory challenges.
Chronic obstructive pulmonary disease (COPD), on the other hand, is a progressive and largely irreversible lung disease that primarily affects older adults, with smoking being the most significant risk factor. COPD encompasses conditions like emphysema and chronic bronchitis, characterized by airflow limitation and inflammation of the lungs. Globally, COPD is a leading cause of mortality, claiming approximately 3 million lives annually and affecting an estimated 130,000 Americans each year. The identification of common inflammatory pathways between these disparate diseases offers a tantalizing prospect for broad-spectrum lung therapy.
The Ac-PGP Connection: A Key Inflammatory Marker
A critical aspect of the UAB researchers’ investigation involved exploring the role of acetylated proline-glycine-proline (Ac-PGP), an extracellular matrix-derived peptide. They hypothesized that BPD mouse models would exhibit heightened levels of Ac-PGP, mirroring observations in premature infants with BPD. This hypothesis was indeed validated in the BPD mouse models.
Further "gain-of-function" and "loss-of-function" studies illuminated the direct impact of Ac-PGP on lung health. Intranasal instillation of Ac-PGP in the mouse models led to an increase in neutrophilic inflammation and subsequent lung degradation. Conversely, when an inhibitor of Ac-PGP was administered alongside Ac-PGP, markers of neutrophilic inflammation significantly decreased, and the structural integrity of the lungs improved. This established Ac-PGP as a key mediator in the inflammatory cascade.
Lactobacilli’s Targeted Intervention: Inhibiting MMP-9 and Releasing L(+) Lactic Acid
The researchers then focused on how their proprietary Lactobacilli blend, comprising L. plantarum, L. acidophilus, and L. rhamnosus, exerted its therapeutic effects. They discovered that this specific blend acted synergistically to reduce the activity of matrix metalloproteinase-9 (MMP-9). MMP-9 is an enzyme that plays a critical role in breaking down extracellular matrix components, thereby facilitating the release of inflammatory peptides like Ac-PGP.
Intriguingly, the study also revealed that the supernatant derived from Lactobacilli growth medium exhibited a similar magnitude of MMP-9 reduction as the live Lactobacilli bacteria themselves. This led to a pivotal finding: L(+) lactic acid, a metabolic byproduct of Lactobacilli fermentation, was identified as a key anti-inflammatory molecule. In vitro studies demonstrated that L(+) lactic acid effectively reduced MMP-9 activity.
The significance of this finding is amplified by the fact that live Lactobacilli, when present in the lungs, appear to provide a sustained and controlled release of L(+) lactic acid. This ongoing delivery of an anti-inflammatory agent in a well-tolerated manner represents a highly desirable therapeutic characteristic.
Technological Innovation: Engineering Inhaled Probiotics for Deep Lung Delivery
A significant technological advancement underpinning this research was the development of an inhaled Lactobacilli powder. This innovation involved sophisticated particle engineering to create particles small enough to reach the deeper regions of the lungs, where much of the inflammatory damage occurs, while crucially preserving the viability of the bacteria. This advanced formulation is what enabled the testing of the live biotherapeutic product in the BPD and COPD models.
In the COPD mouse models, the Lactobacilli blend demonstrated remarkable efficacy. It successfully reduced inflammation within the lung microenvironment, whether administered concurrently with the insult or post-injury, underscoring its potent anti-inflammatory effects. The treatment led to a decrease in several pro-inflammatory markers and a notable elevation of the anti-inflammatory marker immunoglobulin A (IgA).
A Promising Alternative to Corticosteroids
Perhaps one of the most compelling findings was the direct comparison of the live biotherapeutic product’s performance against a standard treatment. The inhaled Lactobacilli blend was found to reduce MMP-9 and other pro-inflammatory cytokines as effectively as, and in some cases even better than, fluticasone furoate. Fluticasone furoate is a United States Food and Drug Administration (FDA)-approved inhaled corticosteroid commonly used in combination therapies for COPD. This suggests that the Lactobacilli-based therapy could potentially offer a more targeted and perhaps safer alternative to existing treatments, especially considering the potential side effects associated with long-term corticosteroid use.
Safety Profile and Future Directions
Crucially, safety and biodistribution studies conducted in one of the COPD mouse models provided reassuring results. Inhalation of the bacterial powder did not trigger adverse reactions or exacerbate existing disease. Furthermore, the Lactobacilli did not translocate to distant tissues or accumulate in unintended areas of the lungs, indicating a favorable safety profile and localized action.
"Inhaled live biotherapeutic products show promise in addressing common pathways of disease progression that in the future can be targeted at a variety of lung diseases," Dr. Lal emphasized. He further stated, "Preclinical animal data is suggestive, and safety of the potential drug in humans will be tested in a forthcoming clinical trial. Human adult safety data in COPD will help de-risk the pathway to approval for use of the drug in bronchopulmonary disease infants."
Broader Implications and the Path Forward
The implications of this research are far-reaching. The identification of a common inflammatory pathway modulated by Lactobacilli in both BPD and COPD suggests that this therapeutic approach could have broad applicability to a range of chronic lung conditions. The development of a safe and effective inhaled probiotic therapy could revolutionize the management of these diseases, offering a new paradigm of treatment that leverages the body’s own beneficial microorganisms.
The successful commercialization of this proprietary product through the UAB startup Alveolus Bio, Inc., highlights the translational success of this research. The patent, titled "Inhaled respiratory probiotics for lung diseases of infancy, childhood and adulthood," further underscores the potential for this technology to impact a wide age range and diverse pulmonary conditions.
A Collaborative Effort with Significant Funding
The study, "A Lactobacilli-based inhaled live biotherapeutic product attenuates pulmonary neutrophilic inflammation," involved a significant collaborative effort from researchers at the University of Alabama at Birmingham. The co-first authors are Teodora Nicola and Nancy Wenger from the UAB Department of Pediatrics, Division of Neonatology. Other key contributors include Xin Xu, Camilla Margaroli, Kristopher Genschmer, J. Edwin Blalock from the UAB Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine; and Michael Evans, Luhua Qiao, Gabriel Rezonzew, Youfeng Yang, Tamas Jilling, Kent Willis, and Namasivayam Ambalavanan from the UAB Department of Pediatrics, Division of Neonatology.
This ambitious research was made possible through substantial support from the National Heart, Lung, and Blood Institute of the National Institutes of Health, with grants HL141652, HL135710, HL166433, HL156275, and HL164156.
Dr. Lal holds significant leadership roles within UAB, serving as the director of Clinical Innovation at the Marnix E. Heersink Institute for Biomedical Innovation and as an associate professor in the Division of Neonatology. He is also the founder of UAB startups Alveolus Bio, Inc., and Resbiotic Nutrition, Inc., demonstrating a strong commitment to translating scientific discoveries into tangible health solutions. Dr. Gaggar is a professor in the Division of Pulmonary, Allergy and Critical Care Medicine. The Marnix E. Heersink School of Medicine at UAB houses both the Departments of Pediatrics and Medicine, fostering interdisciplinary collaboration essential for groundbreaking research like this. The future holds promise as this innovative inhaled probiotic therapy moves closer to human clinical trials, offering a beacon of hope for millions suffering from chronic lung diseases.
