Cyanobacteria–Probiotics Symbionts for Modulation of Intestinal Inflammation and Microbiome Dysregulation in Colitis

Academic Background

Inflammatory Bowel Disease (IBD) is a group of chronic inflammatory conditions of the gut, primarily including Crohn’s Disease (CD) and Ulcerative Colitis (UC). The pathogenesis of IBD is complex, involving dysfunction of the intestinal mucosal barrier, dysbiosis of the gut microbiota, and excessive immune responses and inflammatory factor release. Current treatments for IBD mainly rely on anti-inflammatory drugs and immunosuppressants, such as 5-aminosalicylic acid (5-ASA), corticosteroids, and tumor necrosis factor (TNF) antagonists. However, these treatments often fail to address the root causes of IBD and may lead to severe side effects with long-term use, such as opportunistic infections, malignancies, and liver toxicity.

In recent years, the role of the gut microbiota in the pathogenesis of IBD has been increasingly recognized, and probiotic therapy has shown potential as an adjunctive treatment. However, the bioavailability of orally administered probiotics is low in IBD patients, and they are susceptible to damage from reactive oxygen species (ROS) in the gut, limiting their therapeutic efficacy. Therefore, developing a novel treatment that can effectively suppress inflammation, restore intestinal barrier function, and modulate the gut microbiota has become a focus of current research.

Source of the Paper

This paper was co-authored by Jiali Yang, Shaochong Tan, and others, with the research team from the Department of Pharmaceutical Analysis, School of Pharmaceutical Sciences, Zhengzhou University, and the Department of Neuroscience, Institute of Brain Science and Disease, Qingdao University, among other institutions. The paper was published on December 16, 2024, in PNAS (Proceedings of the National Academy of Sciences), titled “Cyanobacteria–Probiotics Symbionts for Modulation of Intestinal Inflammation and Microbiome Dysregulation in Colitis.”

Research Process and Results

1. Research Design and Construction of the Symbiont

The research team used biomimetic mineralization technology to combine cyanobacteria (Synechocystis sp. PCC6803, SP) with probiotics (Bacillus subtilis, BS) to construct a cyanobacteria-probiotics symbiont (ASP@BS). The design of this symbiont is based on the ability of cyanobacteria to produce hydrogen gas (H2) under anaerobic conditions through the [NiFe]-hydrogenase enzyme, while the probiotic BS consumes oxygen to create a local anaerobic environment for the cyanobacteria, thereby activating the hydrogenase and promoting H2 production. H2, as a potent antioxidant, can scavenge ROS in the gut and alleviate inflammation.

2. In Vitro Validation of the Symbiont

The study first validated the symbiotic relationship between SP and BS in vitro. Through co-culture experiments, the researchers found that after co-culturing SP and BS, the oxygen concentration in the system gradually decreased, reaching almost zero after 8 hours. Meanwhile, the co-culture system produced 8.6 μmol of H2, while neither SP nor BS alone produced H2. Further experiments showed that the co-culture of SP and BS significantly increased hydrogenase activity and effectively scavenged hydroxyl radicals (•OH), with a clearance efficiency of 58.1%. Additionally, the symbiont significantly improved the survival rate of BS under high oxidative stress, indicating that SP has a protective effect on BS.

3. Preparation and Characterization of the Symbiont

To ensure the functionality of the symbiont in vivo, the research team synthesized ASP@BS using biomimetic mineralization. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) observations revealed that the particle size of ASP@BS was approximately 100 µm, with cyanobacteria and probiotics closely connected within the symbiont. Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) analyses further confirmed the successful synthesis of the symbiont. Additionally, stability experiments in simulated gastric fluid, bile salts, and simulated colonic fluid showed that the symbiont had high tolerance in the gastrointestinal environment.

4. In Vivo Anti-inflammatory and Gut Microbiota Modulation Effects of the Symbiont

In a DSS-induced acute colitis mouse model, ASP@BS demonstrated significant anti-inflammatory effects. Compared to the control group, the ASP@BS-treated mice showed less weight loss, milder colon shortening, and a significantly lower disease activity index (DAI). Histological analysis revealed that the colon structure of the ASP@BS-treated mice was nearly intact, with minimal inflammatory cell infiltration. Furthermore, ASP@BS significantly reduced ROS levels in colon tissues, decreased neutrophil infiltration, and restored the expression of tight junction proteins (ZO-1 and Occludin), indicating its ability to effectively restore intestinal barrier function.

5. Modulation of Gut Microbiota by the Symbiont

Through 16S rRNA gene sequencing, the researchers found that ASP@BS treatment significantly modulated the gut microbiota composition in colitis mice. Compared to the control group, the ASP@BS-treated mice showed increased gut microbiota diversity, with significantly higher relative abundances of beneficial bacteria such as Akkermansia muciniphila, Muribaculaceae, Lactobacillus murinus, and Bifidobacterium, while the relative abundances of potentially harmful bacteria such as Enterobacteriaceae and Romboutsia ilealis were significantly reduced. These results indicate that ASP@BS can restore gut microbiota balance by modulating the microbial community.

Conclusion and Significance

This study demonstrates that the cyanobacteria-probiotics symbiont (ASP@BS), through the synergistic interaction between cyanobacteria and probiotics, can effectively suppress inflammation, scavenge ROS, restore intestinal barrier function, and modulate the gut microbiota, providing a comprehensive solution for the treatment of IBD. Compared to traditional anti-inflammatory drugs, ASP@BS offers higher biosafety and therapeutic efficacy while avoiding the side effects associated with long-term drug use. Additionally, the biomimetic mineralization synthesis method ensures the stability and efficient delivery of ASP@BS in the gastrointestinal tract.

Research Highlights

1. Innovative Symbiont Design: The use of biomimetic mineralization technology to combine cyanobacteria with probiotics created a symbiont with synergistic effects, significantly enhancing H2 production and ROS scavenging capabilities.
2. Multifaceted Therapeutic Effects: ASP@BS not only suppresses inflammation but also restores intestinal barrier function and modulates the gut microbiota, offering a comprehensive solution for IBD treatment.
3. High Biosafety: Compared to traditional anti-inflammatory drugs, ASP@BS exhibits higher biosafety, with no observed significant toxicity.
4. Potential Applications: The successful development of ASP@BS provides new insights for the treatment of other inflammatory diseases, with broad application prospects.

Other Valuable Information

The success of this study is attributed to interdisciplinary collaboration, involving fields such as pharmacy, microbiology, and materials science. The research team successfully synthesized ASP@BS using biomimetic mineralization technology and validated its anti-inflammatory and gut microbiota-modulating effects through various experimental approaches. Additionally, the study provides detailed experimental data and methods, offering important references for future research.

This study not only provides new insights into the treatment of IBD but also opens new directions for the application of microbial symbionts in disease therapy.