Gut bacteria B. adolescentis may be new preventive treatment for PF
In aging mouse model, beneficial bacteria shown to ease lung scarring
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Individuals with lingering signs of pulmonary fibrosis (PF) months after recovering from COVID-19 were found to be older and to have significantly lower levels than normal of beneficial gut bacteria, particularly Bifidobacterium and Blautia, a new study reports.
In follow-up experiments, a mouse model of PF given supplements of Bifidobacterium adolescentis — a Bifidobacterium species that naturally declines with age — showed reduced inflammation, less lung fibrosis, or scarring, and overall improved lung health, according to the researchers.
Importantly, the team noted, greater benefits were seen in older mice, which had initially shown more severe lung scarring than their younger counterparts.
“This study is the first to demonstrate the therapeutic effect of B. adolescentis against pulmonary fibrosis, revealing its potential as a prophylactic [preventive] and therapeutic intervention for pulmonary fibrosis complications through the gut-lung axis,” the researchers wrote.
The study, “B. adolescentis alleviates inflammation and suppresses PGE2 through remodling gut microbiota to attenuate pulmonary fibrosis in aging mice,” was published in the journal npj Science of Food.
PF is marked by the progressive scarring of lung tissue, which makes breathing increasingly difficult for patients. Older adults are typically more affected than younger people.
PF burden is rising, with increases after the COVID-19 pandemic
Its burden has risen steadily in recent years, especially after the COVID-19 pandemic, which left nearly one-third of people who recovered with long-term lung abnormalities, including fibrotic changes. Despite this increased prevalence, effective treatment options remain limited.
Growing evidence has shown that people with PF often exhibit gut dysbiosis, or disruptions in the balance of bacteria residing in the intestine. One frequently seen problem is a marked reduction in beneficial microbes such as the anti-inflammatory Bifidobacterium.
These shifts may impair gut barrier function and alter immune signaling along the gut-lung axis, potentially contributing to lung inflammation and fibrosis, the researchers noted.
Lower Bifidobacterium levels have also been linked to more severe COVID-19. Individuals who develop post-COVID pulmonary fibrosis often show prolonged gut dysbiosis and slower recovery of lung function.
According to the researchers, such findings “underscore … gut microbiota’s potential as a therapeutic target for pulmonary fibrosis.”
To explore this possibility, a team of researchers in China set out to investigate the link between Bifidobacterium and PF and to test whether supplementing Bifidobacterium adolescentis could offer therapeutic benefit.
The researchers first examined 33 people who had recovered from COVID-19 and returned for evaluation six months after hospital discharge between February and March 2020. All of the patients underwent lung CT imaging, lung function tests, and stool microbiota profiling. Based on CT evidence of fibrotic abnormalities, 15 were classified as nonfibrosis and 18 as fibrosis.
Those with fibrotic lesions were significantly older, showed worse lung function, and had a much lower Bifidobacterium/Blautia-to-Streptococcus (B/S) index, the researchers noted. That index compares the abundance of two beneficial gut bacteria — Bifidobacterium and Blautia — to that of Streptococcus, which has been linked to inflammation in the group’s prior work.
A lower B/S index correlated with higher CT fibrosis scores, indicating that individuals with more pronounced lung abnormalities also showed greater gut dysbiosis. In participants younger than 60, higher levels of Bifidobacterium and Blautia were significantly associated with better lung function; similar trends were seen in older adults but did not reach statistical significance.
B. adolescentis reduced scaring in young and aging mice
To further probe this link, the team then turned to a bleomycin-induced mouse model of PF, studying both young and aging mice. Bleomycin is widely used in research to induce PF-like lung scarring, allowing scientists to study how fibrosis develops and how it might be reversed.
As expected, aging mice developed more severe disease than younger ones, showing reduced physical activity and greater respiratory distress. The older mice also had higher levels of inflammatory markers, more extensive structural lung damage, and greater deposition of collagen, the primary protein that accumulates during scarring.
When orally given B. adolescentis, both young and aging animals showed significant reductions in inflammation, collagen buildup, and markers of lung injury. In older mice, fibrosis was reduced to levels similar to those seen in treated young mice, the researchers noted.
These benefits were accompanied by restored gut barrier integrity, which helped reduce the leakage of gut-derived inflammatory molecules into the bloodstream. B. adolescentis also reshaped the gut microbiota by increasing levels of beneficial bacteria, including Bifidobacterium, and Turicibacter, while reducing groups such as Ligilactobacillus, which were enriched in the PF model and correlated with activation of profibrotic genes.
Our study reveals the potential of B. adolescentis for the treatment of pulmonary fibrosis.
Further analyses revealed that B. adolescentis supplementation significantly lowered lung PGE₂ levels, a molecule implicated in inflammation, and activated the PPAR signaling pathway while suppressing Th17-related inflammation. These pathways are known regulators of fibroblast activity — fibroblasts being the cells that produce collagen— as well as immune and inflammatory responses.
These findings highlight the need for further study of this beneficial bacteria, the team noted.
“Our study reveals the potential of B. adolescentis for the treatment of pulmonary fibrosis and demonstrates the clinical value of age specific microbiota intervention strategies, which need to be further verified in population-based studies,” the researchers wrote.
