Modulation of chronic obstructive pulmonary disease progression by antioxidant metabolites from Pediococcus pentosaceus: enhancing gut probiotics abundance and the tryptophan-melatonin pathway

Abstract

Chronic obstructive pulmonary disease (COPD), a condition primarily linked to oxidative stress, poses significant health burdens worldwide. Recent evidence has shed light on the association between the dysbiosis of gut microbiota and COPD, and their metabolites have emerged as potential modulators of disease progression through the intricate gut-lung axis. Here, we demonstrate the efficacy of oral administration of the probiotic Pediococcus pentosaceus SMM914 (SMM914) in delaying the progression of COPD by attenuating pulmonary oxidative stress. Specially, SMM914 induces a notable shift in the gut microbiota toward a community structure characterized by an augmented abundance of probiotics producing short-chain fatty acids and antioxidant metabolisms. Concurrently, SMM914 synthesizes L-tryptophanamide, 5-hydroxy-L-tryptophan, and 3-sulfino-L-alanine, thereby enhancing the tryptophan-melatonin pathway and elevating 6-hydroxymelatonin and hypotaurine in the lung environment. This modulation amplifies the secretion of endogenous anti-inflammatory factors, diminishes macrophage polarization toward the M1 phenotype, and ultimately mitigates the oxidative stress in mice with COPD. The demonstrated efficacy of the probiotic intervention, specifically with SMM914, not only highlights the modulation of intestine microbiota but also emphasizes the consequential impact on the intricate interplay between the gastrointestinal system and respiratory health.

Keywords: COPD; Microbial metabolites; gut-lung axis; oxidative stress.

Graphical abstract

Figure 1.

Oral SMM914 attenuates CS-induced COPD. (a) Schematic diagram of the experimental system: mice received the oral gavage of normal saline (PBS and CS group) or SMM914 or SMM914 CS for 14 weeks (1×10⁹ CFU/twice a week) before and after being subjected to cigarette smoking. Time-related comparison from CS exposure (day 40,70, and 100) following smoking exposure. (b) Body weight change percentage. (c) The representative images of lung histopathology. The black arrows indicate damaged areas, characterized with denatured and collapsed epithelial cells, thickened alveolar septa, alveolar damage, and activated inflammatory cell infiltration. N = 3. (d) Histological scoring of lung tissues was evaluated in a blinded manner according to INHAND. (e) Lung functions analyses including Penh and EF₅₀ were measured after CS exposure for 14 weeks. (f) Serum TNF-α, IFN-γ and IL-6 concentrations after 14 weeks of CS treatment in the four groups described in (a). (g) Serum IL-10 concentrations after 14 weeks of CS exposure in the four groups described in (a).

Figure 2.

SMM914 provides protection to lung through balancing intestinal microbiota and regulating lung metabolism. (a) 16S rRNA sequencing analysis of stool samples at day 100 after CS exposure described in Figure 1(a). Graph depicts Shannon a-diversity index of grouped data. N = 5–6 mice per group. (b) Relative abundance of gut bacterial family in each group after CS exposure as described in Figure 1(a). N = 5–6 mice per group. (c) Bacterial genus altered by SMM914 in comparison with the CS group were shown in the random forest plot. (d) Score scatter plot from OPLS-DA model of PBS (n = 6), CS (n = 6), SMM914 (n = 5), SMM914CS (n = 6) of mice described in Figure 1(a). (e) Fold change plot of metabolic analysis for lung tissues from CS and PBS groups, respectively. (f) Bubble plot of metabolic pathway analysis for the lung tissues from SMM914CS and CS groups. (g) The hierarchical clustering heatmap of differentially metabolite expression of lungs between SMM914CS and CS groups.

Figure 3.

Pretreatment with the probiotic SMM914 attenuated OI-COPD. (a) Schematic diagram of the experimental system: mice received an oral gavage of normal saline (PBS and OI group), BIOI, or SMM914OI or L.pOI for 14 weeks (1 × 10⁹ CFU/twice a week) prior to being subjected to ozone treatment. N = 8–10 mice per group. (b) Body weight change percentage. N = 8–10 mice per group. (c) Lung function analyses including Penh and EF₅₀ were measured after 40 days. (d) The representative images of lung histopathology. The black arrows indicate damaged areas, characterized with denatured and collapsed epithelial cells, thickened alveolar septa, alveolar damage, and activated inflammatory cell infiltration. N = 3. (e) Histological scoring of lung tissues was performed in a blinded manner according to INHAND. (f) Serum TNF-α, IFN-γ and IL-6 concentrations after 40 days of ozone treatment in the four groups described in (a). N = 3. (g) Serum IL-10 concentrations after 40 days of ozone treatment in the four groups described in (a). N = 3. (h) Concentrations of the antioxidant index (SOD and CAT) in the lung from each group at day 40 after OI exposure of mice. N = 3. (i) Concentrations of the MDA in the lung from each group at day 40 after OI exposure of mice. N = 3.

Figure 4.

SMM914 alters the intestinal microbiota of the mice with ABX treatment. (a) 16S rRNA sequencing analysis of stool samples at day 40 after OI exposure described in Figure 3(a) graph depicts Shannon a-diversity index of grouped data. N = 3–5 mice per group. (b) Relative abundance of gut bacterial family in each group after OI exposure as described in Figure 3(a). N = 3–5 mice per group. (c) Bacterial genus altered by ABX treatment in comparison with the PBS group were shown in the random forest plot. (d) Bacterial genus altered by OI exposure and BI, SMM914, and L.P treatment in comparison with PBS were shown in the random forest plot. (e) Bacterial genus changed in four-time points shown in the random forest plot. (f) Live imaging of mice after orally administrating SMM914 at 15min, 45min, 2.5h and 4 h. (the schematic diagram on the right side illustrates the temporal details of SMM914 in the mouse intestine at various time points).

Figure 5.

SMM914 decelerates the progression of COPD through modulation of metabolites and gene expression. (a) Score scatter plot from OPLS-DA model of PBS (n = 3), OI (n = 3), BIOI (n = 3), L.POI (n = 3), SMM914OI (n = 3), of mice described in Figure 3(a). (b) Bubble plot of metabolic pathway analysis for each group in Figure 3(a). The color depth and bubble size indicate ln (p) values and the impact of the pathway. (c) Bubble plot of transcriptomic pathway analysis for each group in Figure 3(a). The color depth and bubble size indicate ln (p) values and the impact of the pathway. (d) Gene set enrichment analysis of OI, SMM914OI, and BIOI.

Figure 6.

SMM914 attenuates M1 macrophage polarization in the lung. (a) Immunofluorescence staining analysis of M1 (DAPI/F4/80/CD86) and M2 (DAPI/F4/80/CD163) macrophage polarization in each group from Figure 3(a). N = 3. (b) Quantification of immunofluorescence staining of macrophages polarized in different directions (F4/80+ cells, F4/80 CD86+ cells, F4/80 CD163+ cells). N = 3 (c) Representative IHC staining of Hspa1a and TLR4 in lung sections from five Ozone-induced mice groups (n = 3 per group) with corresponding quantification (d). AOD, average optical density.

Figure 7.

Oxidative stress is clinically relevant in COPD. (a) Values of CAT and SOD in the serum from the database. N = 3–6 individuals per group. (b) Concentrations of the antioxidant index (CAT and SOD) in the serum from the normal and AECOPD group. N = 21.