Surfactin Containing Bacillus licheniformis-Fermented Products Alleviate Dextran Sulfate Sodium-Induced Colitis by Inhibiting Colonic Inflammation and the NLRP3 Inflammasome in Mice

Surfactin's impact on gut microbiota and intestinal tumor cells

Surfactin exhibits multifunctional properties, including antimicrobial, anti-inflammatory, and antitumor activities, positioning it as a promising novel food additive. However, its specific effects on the gut environment remain largely unexplored. To investigate this, we conducted in vitro fermentation simulations to assess the impact of surfactin on gut microbiota. Additionally, we evaluated surfactin's inhibitory effects on HCT-116 cells. The results of the fermentation simulation indicated that surfactin significantly increased butyrate production and enhanced the relative abundance of Megamonas, Alistipes, the Oscillospiraceae NK4A214 group, and Methanobrevibacter smithii, while markedly inhibiting Desulfobacterota, potentially facilitating amino acid and lipid metabolism. Furthermore, surfactin significantly inhibited the proliferation of HCT-116 cells and promoted their apoptosis, without exhibiting cytotoxicity towards normal human intestinal epithelial crypt (HIEC) cells. In summary, surfactin demonstrates a favorable safety profile in the intestinal environment. This study contributes to our understanding of the interaction between surfactin and the gut environment.

Pig-Derived Probiotic Bacillus tequilensis YB-2 Alleviates Intestinal Inflammation and Intestinal Barrier Damage in Colitis Mice by Suppressing the TLR4/NF-κB Signaling Pathway

The search for new probiotics has been regarded as an important approach to improving intestinal health in animals. Bacillus has many advantages, such as strong resistance to harmful external factors, wide distribution, and easy colonization of the intestine. Hence, this study aims to screen for a probiotic Bacillus strain that improves animal intestinal health and to elucidate its probiotic mechanism so as to provide probiotic resources for the development of feed-using probiotic formulations. In this research, a strain of Bacillus was isolated from adult pig feces and named B. tequilensis YB-2. In vitro probiotic experiments showed that B. tequilensis YB-2 had strong acid and bile salt resistance, indicating that this strain can customize in the intestine. To further explore the effect of B. tequilensis YB-2 upon animal intestinal health, DSS-induced murine colitis models were established, and the body weight, colonic morphology, inflammatory cytokines level, and intestinal-barrier- and TLR4/NF-κB-pathway-related protein were determined. The results showed that mice receiving drinking water with 3% DSS were found to develop colitis symptoms, including body weight loss and increased disease activity index (DAI); colon length and microvilli shedding were shortened; tight junctions were disrupted; goblet cells decreased; anti-inflammatory cytokines were inhibited; and pro-inflammatory cytokines and the TLR4/NF-κB signaling pathway were activated. Notably, orally received B. tequilensis YB-2 alleviated symptoms of DSS-induced colitis in mice. The above results indicated that B. tequilensis YB-2 was capable of improving colitis in mice by weakening inflammation and intestinal barrier damage, and its mechanism may involve the TLR4/NF-κB pathway. Overall, this research suggests that B. tequilensis YB-2 has the potential to serve as an animal feed additive to prevent intestinal inflammation.

A Traditional Chinese Medicine, Zhenqi Granule, Potentially Alleviates Dextran Sulfate Sodium-Induced Mouse Colitis Symptoms

Ulcerative colitis (UC) is an inflammatory bowel disease that causes chronic inflammation in the large intestine. The etiology of UC is complex and incompletely understood, with potential contributing factors including genetic susceptibility, environmental influences, immune dysregulation, and gut barrier dysfunction. Despite available therapeutic drugs, the suboptimal cure rate for UC emphasizes the necessity of developing novel therapeutics. Traditional Chinese Medicine (TCM) has attracted great interest in the treatment of such chronic inflammatory diseases due to its advantages, such as multi-targets and low side effects. In this study, a mouse model of Dextran Sulfate Sodium (DSS)-induced acute colitis was established and the efficacy of Zhenqi Granule, a TCM preparation composed of the extractives from Astragali Radix and Fructus Ligustri Lucidi, was evaluated. The results showed that treatment with Zhenqi Granule prior to or post-DSS induction could alleviate the symptoms of colitis, including weight loss, diarrhea, hematochezia, colon length shortening, and pathological damage of colon tissues of the DSS-treated mice. Further, network pharmacology analysis showed that there were 98 common targets between the active components of Zhenqi Granule and the targets of UC, and the common targets were involved in the regulation of inflammatory signaling pathways. Our results showed that Zhenqi Granule had preventive and therapeutic effects on acute colitis in mice, and the mechanism may be that the active components of Zhenqi Granule participated in the regulation of inflammatory response. This study provided data reference for further exploring the mechanism of Zhenqi Granule and also provided potential treatment strategies for UC.

Involvement of the Bacillus SecYEG Pathway in Biosurfactant Production and Biofilm Formation

With Bacillus species, about 30% of extracellular proteins are translocated through the cytoplasmic membrane, coordinated by the Sec translocase. This system mainly consists of the cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel. The purpose of this work was to investigate the effects of the SecYEG export system on the production of industrial biomolecules, such as biosurfactants, proteases, amylases, and cellulases. Fifty-two isolates of Bacillus species were obtained from traditional fermented foods and then characterized using molecular microbiology methods. The isolates secreted exoenzymes that included cellulases, amylases, and proteases. We present evidence that a biosurfactant-like molecule requires the SecA ATPase and the SecYEG membrane channel for its secretion. In addition, we showed that biomolecules involved in biofilm formation required the SecYEG pathway. This work presents a novel seven-target fragment multiplex PCR assay capable of identification at the species level of Bacillus through a unique SecDF chromosomal gene. The bacterial membrane protein SecDF allowed the discrimination of Bacillus subtilis, B. licheniformis, B. amyloliquefaciens, and B. sonorensis. SecA was able to interact with AprE, AmyE, and TasA. The Rose Bengal inhibitor of SecA crucially affected the interaction of AprE, AmyE, TapA, and TasA with recombinant Gst-SecA. The Rose Bengal prevented Bacillus species from secreting and producing proteases, cellulases, amylases, and biosurfactant-like molecules. It also inhibited the formation of biofilm cell communities. The data support, for the first time, that the SecYEG translocon mediates the secretion of a biosurfactant-like molecule.

The Angiotensin II Receptor Neprilysin Inhibitor LCZ696 Inhibits the NLRP3 Inflammasome By Reducing Mitochondrial Dysfunction in Macrophages and Alleviates Dextran Sulfate Sodium-induced Colitis in a Mouse Model

The intracellular sensor protein complex known as the NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome plays a crucial role in regulating inflammatory diseases by overseeing the production of interleukin (IL)-1β and IL-18. Targeting its abnormal activation with drugs holds significant promise for inflammation treatment. This study highlights LCZ696, an angiotensin receptor-neprilysin inhibitor, as an effective suppressor of NLRP3 inflammasome activation in macrophages stimulated by ATP, nigericin, and monosodium urate. LCZ696 also reduces caspase-11 and GSDMD activation, lactate dehydrogenase release, propidium iodide uptake, and the extracellular release of NLRP3 and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) in ATP-activated macrophages, suggesting a potential mitigation of pyroptosis. Mechanistically, LCZ696 lowers mitochondrial reactive oxygen species and preserves mitochondrial integrity. Importantly, it does not significantly impact NLRP3, proIL-1β, inducible nitric oxide synthase, cyclooxygenase-2 expression, or NF-κB activation in lipopolysaccharide-activated macrophages. LCZ696 partially inhibits the NLRP3 inflammasome through the induction of autophagy. In an in vivo context, LCZ696 alleviates NLRP3-associated colitis in a mouse model by reducing colonic expression of IL-1β and tumor necrosis factor-α. Collectively, these findings suggest that LCZ696 holds significant promise as a therapeutic agent for ameliorating NLRP3 inflammasome activation in various inflammatory diseases, extending beyond its established use in hypertension and heart failure treatment.

Heat-Killed Saccharomyces boulardii Alleviates Dextran Sulfate Sodium-Induced Ulcerative Colitis by Restoring the Intestinal Barrier, Reducing Inflammation, and Modulating the Gut Microbiota

Ulcerative colitis (UC) is a global intestinal disease, and conventional therapeutic drugs often fail to meet the needs of patients. There is an urgent need to find efficient and affordable novel biological therapies. Saccharomyces boulardii has been widely used in food and pharmaceutical research due to its anti-inflammatory properties and gut health benefits. However, there is still a relatively limited comparison and evaluation of different forms of S. boulardii treatment for UC. This study aimed to compare the therapeutic effects of S. boulardii, heat-killed S. boulardii, and S. boulardii β-glucan on UC, to explore the potential of heat-killed S. boulardii as a new biological therapy. The results demonstrate that all three treatments were able to restore body weight, reduce the disease activity index (DAI), inhibit splenomegaly, shorten colon length, and alleviate histopathological damage to colonic epithelial tissues in DSS-induced colitis mice. The oral administration of S. boulardii, heat-killed S. boulardii, and S. boulardii β-glucan also increased the levels of tight junction proteins (Occludin and ZO-1), decreased the levels of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the serum, and suppressed the expressions of TNF-α, IL-1β, and IL-6 mRNA in the colon. In particular, in terms of gut microbiota, S. boulardii, heat-killed S. boulardii, and S. boulardii β-glucan exhibited varying degrees of modulation on DSS-induced dysbiosis. Among them, heat-killed S. boulardii maximally restored the composition, structure, and functionality of the intestinal microbiota to normal levels. In conclusion, heat-killed S. boulardii showed greater advantages over S. boulardii and S. boulardii β-glucan in the treatment of intestinal diseases, and it holds promise as an effective novel biological therapy for UC. This study is of great importance in improving the quality of life for UC patients and reducing the burden of the disease.

Lipopeptides from an isolate of Bacillus subtilis complex have inhibitory and antibiofilm effects on Fusarium solani

Bacillus subtilis species complex is known as lipopeptide-producer with biotechnological potential for pharmaceutical developments. This study aimed to identify lipopeptides from a bacterial isolate and evaluate their antifungal effects. Here, we isolated and identified a lipopeptide-producing bacterium as a species of Bacillus subtilis complex (strain UL-1). Twenty lipopeptides (six iturins, six fengycins, and eight surfactins) were identified in the crude extract (CE) and fractions (F1, F2, F3, and F4), and the highest content of total lipopeptides was observed in CE and F2. The chemical quantification data corroborate with the hemolytic and antifungal activities that CE and F2 were the most hemolytic and inhibited the fungal growth at lower concentrations against Fusarium spp. In addition, they caused morphological changes such as shortening and/or atypical branching of hyphae and induction of chlamydospore-like structure formation, especially in Fusarium solani. CE was the most effective in inhibiting the biofilm formation and in disrupting the mature biofilm of F. solani reducing the total biomass and the metabolic activity at concentrations ≥ 2 µg/mL. Moreover, CE significantly inhibited the adherence of F. solani conidia on contact lenses and nails as well as disrupted the pre-formed biofilms on nails. CE at 100 mg/kg was nontoxic on Galleria mellonella larvae, and it reduced the fungal burden in larvae previously infected by F. solani. Taken together, the lipopeptides obtained from strain UL-1 demonstrated a potent anti-Fusarium effect inducing morphological alterations and antibiofilm activities. Our data open further studies for the biotechnological application of these lipopeptides as potential antifungal agents. KEY POINTS: • Lipopeptides inhibit Fusarium growth and induce chlamydospore-like structures. • Lipopeptides hamper the adherence of conidia and biofilms of Fusarium solani. • Iturins, fengycins, and surfactins were associated with antifungal effects.