The role of S-layer proteins (SLP), which form the outermost layer of cell walls in lactic acid bacteria (LAB), plays a crucial role in regulating immune-stimulating activity, thereby closely influencing LAB's ability to boost host immunity. In this study, the heterologous expression, purification, and characterization of L. acidophilus CICC6074-derived slpX protein and the molecular mechanism of its anti-inflammatory effect on LPS-induced RAW264.7 cells were investigated. Initially, the PCR results were shown to successfully clone the slpX DNA sequence by homologous recombination to obtain the pet-32a-slpX recombinant plasmid. SDS-PAGE results revealed that slpX protein with a molecular weight of 54 kDa was successfully obtained under 0.7 mmol/L IPTG-induced conditions, which was further demonstrated by western blot(WB) and LC-MS/MS. ELISA, WB and molecular docking results indicated that slpX protein can inhibit LPS-induced cellular inflammatory responses by linking to TLR4 and MD2 via hydrogen bonding and increasing the levels of anti-inflammatory factor IL-10 and decreasing the levels of inflammatory factors (TNF-α, IL-6, NO) and ROS via MAPK and NF-κB signaling pathways. The study is essential for the preparation of pure slpX protein and revealing its anti-inflammatory molecular mechanism.

In this study, 10 novel anti-inflammatory peptides were identified from duck liver, and their molecular mechanism was demonstrated based on machine learning and molecular docking. Using Sephadex G-15 gel chromatography separation, reversed-phase high-performance liquid chromatography purification, liquid chromatography-tandem mass spectrometry identification, and Biopep database comparison, 10 novel anti-inflammatory peptides were initially found. Their splendid ACE inhibition and anti-inflammatory properties were confirmed by machine learning. With binding energies less than -5.0 kcal/mol, molecular docking revealed that they could efficiently bind to the active pockets of TNF-, IL-6, COX-2, and NF-B proteins with efficiency, indicating that the compounds can spontaneously form complexes through hydrogen bonding and hydrophobic interactions with the protein binding pockets. In the LPS-induced RAW 264.7 cell model, the release of NO, TNF-α, and IL-6 and the mRNA expression of inflammatory factors (TNF-α, IL-6, COX-2, and NF-κB) were significantly inhibited by these peptides. We concluded it might be due to their anti-inflammatory effects by inhibiting the protein phosphorylation of IκBα in the cytoplasm and preventing the translocation of NF-κB p65 in the cytoplasm to the nucleus, thereby regulating the NF-κB signaling pathway. This study is essential for the screening of anti-inflammatory peptides and the investigation of the mechanism of action.

Hyperuricemia is a metabolic disorder caused by abnormal purine metabolism, resulting in abnormally high serum uric acid. In this study, a novel Levilactobacillus brevis PDD-5 isolated from salty vegetables was verified with the function of alleviating hyperuricemia. The relevant effects of L. brevis PDD-5 in lowering uric acid were analyzed by in vitro and in vivo experiments. The results showed that the L. brevis PDD-5 has (68.86 ± 15.46)% of inosine uptake capacity and (95.75 ± 3.30)% of guanosine uptake capacity in vitro. Oral administration of L. brevis PDD-5 to hyperuricemia rats reduced uric acid, creatinine, and urea nitrogen in serum, as well as decreased inosine and guanosine levels in the intestinal contents of rats. Analysis of relevant markers in the kidney by ELISA kits revealed that L. brevis PDD-5 alleviated oxidative stress and inflammation. Moreover, the gene expression of uric acid transporter 1 (URAT1) and glucose transporter 9 (GLUT9) was down-regulated, and the gene expression of organic anion transporter 1 (OAT1) was up-regulated after treatment with L. brevis PDD-5. Western blot analysis showed that L. brevis PDD-5 alleviated hyperuricemia-induced kidney injury through the NLRP3 pathway. These findings suggest that L. brevis PDD-5 can lower uric acid, repair kidney damage, and also has the potential to prevent uric acid nephropathy.

Lactic acid bacteria (LAB) fermentation is the simplest and safest way of food preservation, and the use of probiotics in yoghurt could provide dairy products with unique flavors, textures and health benefits. In this study, Lactobacillus bulgaricus, Streptococcus thermophilus, L. reuteri DSMZ 8533 and the potential probiotic strain L. plantarum A3 were used for the milk fermentation. Results found the texture properties such as hardness, consistency, and viscosity of the yoghurt were enhanced in the mixed culture condition. Furthermore, components like amino acid (leucine), vanilla (vanillin), C_18:3n6 (unsaturated fatty acids) were also accumulated in L. plantarum A3 fermented yoghurt, which leads to the significant sensory profiling difference compared with the former plain yoghurt. All these results proved L. plantarum A3 is a potential probiotic strain which could enhance the sensory and nutrition profiling of the fermented milk. Future work still needs to be done on the synergistic interaction between the traditional strains and the probiotics during the fermentation process.