Heat-Killed Lacticaseibacillus paracasei Repairs Lipopolysaccharide-Induced Intestinal Epithelial Barrier Damage via MLCK/MLC Pathway Activation

Structure characterization and immunological activity of capsular polysaccharide from live and heat-killed Lacticaseibacillus paracasei 6235

Capsular polysaccharide (CPS) as a probiotic component has the ability to regulate the function of the host's immune system. However, how the structure and function of heat-killed CPS are altered remains unclear. In the present study, CPS were isolated and purified from live (LCPS) and heat-killed (HCPS) Lacticaseibacillus paracasei 6235. The differences in structure and immunomodulation between LCPS and HCPS were compared and analyzed. The results demonstrate that after heat killed, the molecular weight of CPS decreased from 23.4 kDa to 17.5 kDa, with the disappearance of galactosamine in the monosaccharide composition, and changes in the microstructure. Methylation analysis and nuclear magnetic resonance analysis revealed that the LCPS and HCPS are similar in structure, which main units of →3,4)-α-D-Glcp-(1→4)-α-D-Galp-(1→3)-β-L-Rhap-(1→6)-β-D-Galp-(1→, and repeating units of →3,4)-α-D-Glcp-(1→, →3)-β-L-Rhap-(1→, and →4)-α-D-Galp-(1→ residues. Furthermore, both LCPS and HCPS significantly downregulated the expression of pro-inflammatory cytokines in RAW264.7 cells induced by LPS. Specifically, HCPS reduced the levels of IL-6 and IL-1β by 79.38 % and 88.42 %, respectively, compared to LCPS. Concurrently, both LCPS and HCPS effectively mitigated inflammatory responses through the NF-κB and MAPK signaling pathways. Moreover, compared to LCPS, HCPS increased the protein expression levels of NF-κB/p-NF-κB and IκB/p-IκB by 26.14 % and 28.92 %, respectively. These results suggest that CPS has a role in modulating immune responses and that HCPS is more effective. This study can be further developed into new products related to postbiotics.

Mechanistic insights into the changes of biological activity and physicochemical characteristics in Lacticaseibacillus paracasei fortified milk powder during storage

To clarify the change mechanism of biological activity and physicochemical characteristics in Lacticaseibacillus paracasei JY025 fortified milk powder (LFMP) during storage, morphological observation, JY025 survival, storage stability, and metabolomics of LFMP were determined during the storage period in this study. The results showed that the LFMP had a higher survival rate of JY025 compared with the bacterial powder of JY025 (LBP) during storage, which suggested that milk powder matrix could reduce strain JY025 mortality under prolonged storage in the LFMP samples. The fortification of strain JY025 also affected the stability of milk powder during the storage period. There was lower water activity and higher glass transition temperature in LFMP samples compared with blank control milk powder (BCMP) during storage. Moreover, the metabolomics results of LFMP indicated that vitamin degradation, Maillard reaction, lipid oxidation, tricarboxylic acid cycle, and lactobacilli metabolism are interrelated and influence each other to create complicated metabolism networks.

Deciphering HIV-associated inflammation: microbiome's influence and experimental insights

PURPOSE OF REVIEW

To review novel experimental approaches for studying host:microbe interactions and their role in intestinal and systemic inflammation in people living with HIV (PLWH).

RECENT FINDINGS

Inflammation in PLWH is impacted by interactions between the microbiome, the intestinal epithelium, and immune cells. This complex interplay is not fully understood and requires a variety of analytical techniques to study. Using a multiomic systems biology approach provides hypothesis generating data on host:microbe interactions that can be used to guide further investigation. The direct interactions between host cells and microbes can be elucidated using peripheral blood mononuclear cells (PBMCs), lamina propria mononuclear cells (LPMC's) or human intestinal organoids (HIO). Additionally, the broader relationship between the host and the microbiome can be explored using animal models such as nonhuman primates and germ-free and double humanized mice.

SUMMARY

To explore complex host:microbe relationships, hypotheses are generated and investigations are guided by multiomic data, while causal components are identified using in-vitro and in-vivo assays.

Bifidobacterium animalis subsp. lactis HN019 live probiotics and postbiotics: production strategies and bioactivity evaluation for potential therapeutic properties

Introduction: B. animalis subsp. lactis HN019 is a commercially available well-characterized probiotic with documented effects on human health, such as the ability to enhance the immune function and to balance the intestinal microbiome. Therefore, optimizing the manufacturing process to improve sustainability, increasing biomass yields and viability, and avoiding animal -derived nutrients in the medium to meet vegan consumer's needs, is currently of interest. Besides the established use of live probiotic cells, alternative supplements indicated as postbiotics, like non-viable cells and/or probiotics derived bioactive molecules might be considered as potential next generation biotherapeutics. In fact, advantages of postbiotics include fewer technological limitations, such as easier production processes and scale-up, and even higher specificity. Methods: In this work, medium design together with different fermentation strategies such as batch, fed-batch and in situ product removal on lab-scale bioreactors were combined. Medium pretreatment by ultrafiltration and protease digestion was performed to reduce polysaccharidic contaminants and facilitate the purification of secreted exopolysaccharides (EPS). The latter were isolated from the fermentation broth and characterized through NMR, GC-MS and SEC-TDA analyses. The expression of TLR-4, NF-kb and IL-6 in LPS challenged differentiated CaCo-2 cells treated with EPS, live and heat-killed B. lactis cells/broth, was evaluated in vitro by western blotting and ELISA. Zonulin was also assessed by immunofluorescence assays. Results and Discussion: The titer of viable B. lactis HN019 was increased up to 2.9 ± 0.1 x 1010 on an animal-free semidefined medium by applying an ISPR fermentation strategy. Medium pre-treatment and a simple downstream procedure enriched the representativity of the EPS recovered (87%), the composition of which revealed the presence of mannuronic acid among other sugars typically present in polysaccharides produced by bifidobacteria. The isolated EPS, live cells and whole heat inactivated broth were compared for the first up to date for their immunomodulatory and anti-inflammatory properties and for their ability to promote intestinal barrier integrity. Interestingly, EPS and live cells samples demonstrated immune-stimulating properties by downregulating the expression of TLR-4 and NF-kb, and the ability to promote restoring the integrity of the intestinal barrier by up-regulating the expression of zonulin, one of the tight junctions forming proteins. Postbiotics in the form of heat killed broth only reduced NF-kb expression, whereas they did not seem effective in the other tested conditions.

Porcine Intestinal Mucosal Peptides Target Macrophage-Modulated Inflammation and Alleviate Intestinal Homeostasis in Dextrose Sodium Sulfate-Induced Colitis in Mice

Porcine intestinal mucosal proteins are novel animal proteins that contain large amounts of free amino acids and peptides. Although porcine intestinal mucosal proteins are widely used in animal nutrition, the peptide bioactivities of their enzymatic products are not yet fully understood. In the present study, we investigated the effect of porcine intestinal mucosal peptides (PIMP) on the RAW264.7 cell model of LPS-induced inflammation. The mRNA expression of inflammatory factors (interleukin 6, tumor necrosis factor-α, and interleukin-1β) and nitrous oxide levels were all measured by quantitative real-time PCR and cyclooxygenase-2 protein expression measured by Western blot. To investigate the modulating effect of PIMP and to establish a model of dextran sodium sulfate (DSS)-induced colitis in mice, we examined the effects of hematoxylin-eosin staining, myeloperoxidase levels, pro-inflammatory factor mRNA content, tight junction protein expression, and changes in intestinal flora. Nuclear factor κB pathway protein levels were also assessed by Western blot. PIMP has been shown in vitro to control inflammatory responses and prevent the activation of key associated signaling pathways. PIMP at doses of 100 and 400 mg/kg/day also alleviated intestinal inflammatory responses, reduced tissue damage caused by DSS, and improved intestinal barrier function. In addition, PIMP at 400 mg/kg/day successfully repaired the dysregulated gut microbiota and increased short-chain fatty acid levels. These findings suggest that PIMP may positively influence inflammatory responses and alleviate colitis. This study is the first to demonstrate the potential of PIMP as a functional food for the prevention and treatment of colitis.

Recombinant p40 Protein Promotes Expression of Occludin in HaCaT Keratinocytes: A Brief Communication

The ability of epithelial barriers to perform as the first defense line against external damage derives from tight junctions, protein complexes that block microorganisms through the paracellular space. Indeed, disturbances of barrier permeability caused by bacterial metabolites and other inflammatory stimuli are the consequence of changes in protein expression in these complexes. Postbiotics, molecules derived from bacteria with beneficial effects on the host, improve barrier function through the activation of survival pathways in epithelial cells. Lacticaseibacillus rhamnosus GG secretes the muramidase p40, which protects intestinal barriers through an EGFR-dependent pathway. In this work, we cloned, expressed, and purified the recombinant p40 protein from L. rhamnosus GR-1 to evaluate its effect on cell viability, cell cytotoxicity, TEER, and protein levels of tight junctions, as well as EGFR activation via Western blot on HaCaT keratinocytes subjected to LPS. We found a novel mutation at residue 368 that does not change the structure of p40. Our protein also reduces the LPS-induced increase in cell cytotoxicity when it is added prior to this stimulus. Furthermore, although LPS did not cause changes in barrier function, p40 increased TEER and occludin expression in HaCaT, but unlike previous work with p40 from LGG, we found that recombinant p40 did not activate EGFR. This suggests that recombinant p40 enhances epithelial barrier function through distinct signaling pathways.

Postbiotic Fractions of Probiotics Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG Show Immune-Modulating Effects

Probiotic bacteria belonging to Lactobacillus spp. are important producers of bioactive molecules, known as postbiotics, that play essential roles in the immunological support of the intestinal mucosa. In this study, the system of co-culture of intestinal epithelial cells with macrophage cells in vitro was used to study the potential effect of postbiotic fractions of L. rhamonosus and L. plantarum on the modulation of the immune response induced by pro-inflammatory stimuli. This study's results revealed that the presence of probiotic bacterial components on the mucosal surface in the early and late stage of inflammatory conditions is based on cellular interactions that control inflammation and consequent damage to the intestinal epithelium. In our studies, heat killed fractions of probiotic bacteria and their extracted proteins showed a beneficial effect on controlling inflammation, regardless of the strain tested, consequently protecting intestinal barrier damage. In conclusion, the presented results emphasize that the fractions of probiotic bacteria of L. plantarum and L. rhamnosus may play a significant role in the regulation of LPS-mediated cytotoxic activity in intestinal epithelial cells. The fractions of probiotic strains of L. rhamnosus and L. plantarum showed the potential to suppress inflammation, effectively activating the anti-inflammatory cytokine IL-10 and modulating the IL-18-related response.