Proteolytic processing of galectin-3 by meprin metalloproteases is crucial for host-microbiome homeostasis

Neonatal microbiota colonization primes maturation of goblet cell-mediated protection in the pre-weaning colon

Regulated host-microbe interactions are a critical aspect of lifelong health. Colonic goblet cells protect from microorganisms via the generation of a mucus barrier structure. Bacteria-sensing sentinel goblet cells provide secondary protection by orchestrating mucus secretion when microbes breach the mucus barrier. Mucus deficiencies in germ-free mice implicate a role for the microbiota in programming barrier generation, but its natural ontogeny remains undefined. We now investigate the mucus barrier and sentinel goblet cell development in relation to postnatal colonization. Combined in vivo and ex vivo analyses demonstrate rapid and sequential microbiota-dependent development of these primary and secondary goblet cell protective functions, with dynamic changes in mucus processing dependent on innate immune signaling via MyD88 and development of functional sentinel goblet cells dependent on the NADPH/dual oxidase family member Duox2. Our findings identify new mechanisms of microbiota-goblet cell regulatory interaction and highlight the critical importance of the pre-weaning period for the normal development of protective systems that are key legislators of host-microbiota interaction.

Meprin β Modulates Brevican Proteolysis Impairing Neural Plasticity and Memory Formation

The metalloprotease meprin β is known for its multifunctional involvement in various physiological processes throughout the body including the brain. However, its broader functions within the brain besides amyloid β generation remain largely unexplored. To investigate this, we utilized a mouse model overexpressing meprin β in neurons within the cortex and hippocampus, regions crucial for learning and memory. Behavioral assessments, employing the Morris' Water Maze paradigm test, revealed impaired cognitive functions in animals overexpressing meprin β. Furthermore, electrophysiological recordings in hippocampal slices using multielectrode arrays showed an impaired long-term potentiation (LTP) in meprin β-overexpressing mice compared to wild-type counterparts. Intriguingly, concomitant with the LTP impairment, we observed an increased neuronal excitability. These findings underline the complicated interplay between meprin β abundance and behavioral manifestations, suggesting a broader impact on neural circuit dynamics. To elucidate the molecular mechanisms underlying these observed deficits, western blotting analyses were conducted to address the expression of glutamatergic receptors. Neither the expression of the N-methyl-D-aspartate (NMDA) nor the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor showed variation relative to each other. The application of N-terminomics identified brevican as a proteolytic substrate of meprin β and thus a potential key mediator linking meprin β overexpression to the observed effects. Previous studies have reported that brevican knockout in animal models influences learning and memory. Our data demonstrate that meprin β modulates brevican expression, likely contributing to the effects we have observed in our mouse model. These results shed light on the broader functional significance of meprin β in neurological processes.

Isobutyrate Confers Resistance to Inflammatory Bowel Disease through Host-Microbiota Interactions in Pigs

Supplementation with short-chain fatty acids (SCFAs) is a potential therapeutic approach for inflammatory bowel disease (IBD). However, the therapeutic effects and mechanisms of action of isobutyrate in IBD remain unclear. Clinical data indicate that the fecal levels of isobutyrate are markedly lower in patients with Crohn's disease than in healthy controls. Compared with healthy mice and healthy pigs, mice and pigs with colitis presented significantly lower isobutyrate levels. Furthermore, the level of isobutyrate in pigs was significantly negatively correlated with the disease activity index. We speculate that isobutyrate may play a crucial role in regulating host gut homeostasis. We established a model of dextran sulfate sodium-induced colitis in pigs, which have gastrointestinal structure and function similar to those of humans; we performed multiomic analysis to investigate the therapeutic effects and potential mechanisms of isobutyrate on IBD at both the animal and cellular levels and validated the results. Phenotypically, isobutyrate can significantly alleviate diarrhea, bloody stools, weight loss, and colon shortening caused by colitis in pigs. Mechanistically, isobutyrate can increase the relative abundance of Lactobacillus reuteri, thereby increasing the production of indole-3-lactic acid, regulating aryl hydrocarbon receptor expression and downstream signaling pathways, and regulating Foxp3+ CD4+ T cell recruitment to alleviate colitis. Isobutyrate can directly activate G protein-coupled receptor 109A, promote the expression of Claudin-1, and improve intestinal barrier function. In addition, isobutyrate can increase the production of intestinal SCFAs and 3-hydroxybutyric acid and inhibit the TLR4/MyD88/NF-κB signaling pathway to suppress intestinal inflammation. In conclusion, our findings demonstrate that isobutyrate confers resistance to IBD through host-microbiota interactions, providing a theoretical basis for the use of isobutyrate in alleviating colitis.

Targeted approach to determine the impact of cancer-associated protease variants

Several steps of cancer progression, from tumor onset to metastasis, critically involve proteolytic activity. To elucidate the role of proteases in cancer, it is particularly important to consider single-nucleotide variants (SNVs) that affect the active site of proteases, thereby influencing cleavage specificity, substrate processing, and thus cancer cell behavior. To facilitate systematic studies, we here present a targeted approach to determine the impact of cancer-associated protease variants (TACAP). Starting with the semiautomated identification of potential specificity-modulating SNVs, our workflow comprises mass spectrometry-based cleavage specificity profiling and substrate identification, localization, and inhibitor studies, followed by functional analyses investigating cancer cell properties. To demonstrate the feasibility of TACAP, we analyzed the meprin β R238Q variant. This amino acid exchange R238Q leads to a loss of meprin β's characteristic cleavage preference for acidic amino acids at P1' position, accompanied with changes in substrate pool and inhibitor affinity compared to meprin β wild type.

Intestinal mucus barrier: A potential therapeutic target for IBD

Intestinal mucus, a viscoelastic medium with mucin2 (MUC2) as its main component, covers the surface of intestinal epithelial cells and protects the intestine from invasion, forming the first barrier of the intestinal tract. Unlike the small intestine, where the mucus layer is a single layer, the colonic mucus layer can be divided into a sterile inner layer and an outer layer with bacterial colonization. Many of the substances in the mucus layer have beneficial effects on the intestinal epithelium, but the mucus layer is often affected by a variety of factors, mainly microbiological, dietary, and immunological. Inflammatory bowel disease (IBD) is a disease of increasing morbidity worldwide, with a complex etiology and a high relapse rate. In recent years, the mucus barrier in IBD has received increasing attention and is considered a key factor in the pathogenesis of IBD. Loss of goblet cells (GCs) and changes in the composition and properties of the mucus layer material are commonly found in the colon of IBD patients. Damage to the mucus layer may make it easier for microorganisms to access the intestinal epithelium and cause inflammation. There are currently a number of herbs and other therapies that can be used to treat IBD and repair the damaged mucus barrier. This review highlights the important role of the mucus layer in IBD and the therapies that target the mucus layer in IBD.

Ligands for Intestinal Intraepithelial T Lymphocytes in Health and Disease

The intestinal tract is constantly exposed to a diverse mixture of luminal antigens, such as those derived from commensals, dietary substances, and potential pathogens. It also serves as a primary route of entry for pathogens. At the forefront of this intestinal defense is a single layer of epithelial cells that forms a critical barrier between the gastrointestinal (GI) lumen and the underlying host tissue. The intestinal intraepithelial T lymphocytes (T-IELs), one of the most abundant lymphocyte populations in the body, play a crucial role in actively surveilling and maintaining the integrity of this barrier by tolerating non-harmful factors such as commensal microbiota and dietary components, promoting epithelial turnover and renewal while also defending against pathogens. This immune balance is maintained through interactions between ligands in the GI microenvironment and receptors on T-IELs. This review provides a detailed examination of the ligands present in the intestinal epithelia and the corresponding receptors expressed on T-IELs, including T cell receptors (TCRs) and non-TCRs, as well as how these ligand-receptor interactions influence T-IEL functions under both steady-state and pathological conditions. By understanding these engagements, we aim to shed light on the mechanisms that govern T-IEL activities within the GI microenvironment. This knowledge may help in developing strategies to target GI ligands and modulate T-IEL receptor expression, offering precise approaches for treating intestinal disorders.

Heterologous expression, purification, and biochemical characterization of protease 3075 from Cohnella sp. A01

Proteases as one of the most significant categories of commercial enzymes, serve nowadays as the key ingredients in detergent formulations. Therefore, identifying detergent-compatible proteases with better properties is a continuous exercise. Accordingly, we were interested in the recombinant production and characterization of protease 3075 as a novel enzyme from thermophilic indigenous Cohnella sp. A01. The biochemical and structural features of the protease were probed by employing bioinformatic methods and in vitro studies. The bioinformatics analysis discovered that protease 3075 belongs to the C56-PfpI superfamily. The protease 3075 gene was cloned and heterologous expressed in Escherichia coli (E. coli) BL21. It was found that the enzyme contains 175 amino acids and 525 bp with a molecular weight of 19 kDa. Protease 3075 revealed acceptable activity in the range of 40-80°C and pH 5.5-8. The optimum activity of the enzyme was observed at 70°C and pH 6. The activity of protease 3075 increased about 4-fold in the presence of Tween 80 and acetone, while its activity attenuated in the presence of iodoacetic acid and iodoacetamide. Docking analyses revealed the dominant interaction between Tween 80 and protease 3075, mediated by hydrogen bonds and Van der Waals forces. Furthermore, molecular dynamics simulations (MDS) showed that Tween 80 increased the stability of the protease 3075 structure. Altogether, our data provided a novel enzyme by genetic manipulation process that could have significant industrial applications.

Emerging role of galectin 3 in neuroinflammation and neurodegeneration

Neuroinflammation and neurodegeneration are key processes that mediate the development and progression of neurological diseases. However, the mechanisms modulating these processes in different diseases remain incompletely understood. Advances in single cell based multi-omic analyses have helped to identify distinct molecular signatures such as Lgals3 that is associated with neuroinflammation and neurodegeneration in the central nervous system (CNS). Lgals3 encodes galectin-3 (Gal3), a β-galactoside and glycan binding glycoprotein that is frequently upregulated by reactive microglia/macrophages in the CNS during various neurological diseases. While Gal3 has previously been associated with non-CNS inflammatory and fibrotic diseases, recent studies highlight Gal3 as a prominent regulator of inflammation and neuroaxonal damage in the CNS during diseases such as multiple sclerosis, Alzheimer's disease, and Parkinson's disease. In this review, we summarize the pleiotropic functions of Gal3 and discuss evidence that demonstrates its detrimental role in neuroinflammation and neurodegeneration during different neurological diseases. We also consider the challenges of translating preclinical observations into targeting Gal3 in the human CNS.

Fetal growth restriction induced by maternal gal-3 deficiency is associated with altered gut-placenta axis

Adverse intrauterine conditions may cause fetal growth restriction (FGR), a pregnancy complication frequently linked to perinatal morbidity and mortality. Although many studies have focused on FGR, the pathophysiological processes underlying this disorder are complex and incompletely understood. We have recently determined that galectin-3 (gal-3), a β-galactoside-binding protein, regulates pregnancy-associated processes, including uterine receptibility, maternal vascular adaptation and placentation. Because gal-3 is expressed at both sides of the maternal-fetal interface, we unraveled the contribution of maternal- and paternal-derived gal-3 on fetal-placental development in the prenatal window and its effects on the post-natal period. Deficiency of maternal gal-3 induced maternal gut microbiome dysbiosis, resulting in a sex-specific fetal growth restriction mainly observed in female fetuses and offspring. In addition, poor placental metabolic adaptions (characterized by decreased trophoblast glycogen content and insulin-like growth factor 2 (Igf2) gene hypomethylation) were only associated with a lack of maternal-derived gal-3. Paternal gal-3 deficiency caused compromised vascularization in the placental labyrinth without affecting fetal growth trajectory. Thus, maternal-derived gal-3 may play a key role in fetal-placental development through the gut-placenta axis.

Neonatal microbiota colonization drives maturation of primary and secondary goblet cell mediated protection in the pre-weaning colon

In the distal colon, mucus secreting goblet cells primarily confer protection from luminal microorganisms via generation of a sterile inner mucus layer barrier structure. Bacteria-sensing sentinel goblet cells provide a secondary defensive mechanism that orchestrates mucus secretion in response to microbes that breach the mucus barrier. Previous reports have identified mucus barrier deficiencies in adult germ-free mice, thus implicating a fundamental role for the microbiota in programming mucus barrier generation. In this study, we have investigated the natural neonatal development of the mucus barrier and sentinel goblet cell-dependent secretory responses upon postnatal colonization. Combined in vivo and ex vivo analyses of pre- and post-weaning colonic mucus barrier and sentinel goblet cell maturation demonstrated a sequential microbiota-dependent development of these primary and secondary goblet cell-intrinsic protective functions, with dynamic changes in mucus processing dependent on innate immune signalling via MyD88, and development of functional sentinel goblet cells dependent on the NADPH/Dual oxidase family member Duox2. Our findings therefore identify new mechanisms of microbiota-goblet cell regulatory interaction and highlight the critical importance of the pre-weaning period for the normal development of colonic barrier function.

Inhibition of LPS-Induced Inflammatory Response of Oral Mesenchymal Stem Cells in the Presence of Galectin-3

Galectin-3 (GAL-3) is a beta-galactoside binding lectin produced by mesenchymal stem cells (MSCs) and other cell sources under inflammatory conditions. Several studies have reported that GAL-3 exerts an anti-inflammatory action, regulated by its natural ligand GAL-3 BP. In the present study, we aimed to assess the GAL-3 mediated regulation of the MSC function in an LPS-induced inflammation setting. Human gingival mesenchymal stem cells (hGMSCs) were stimulated in vitro with LPSs; the expression of TLR4, NFκB p65, MyD88 and NALP3 were assessed in the hGMSCs via immunofluorescence imaging using confocal microscopy, Western blot assay, and RT-PCR before and after the addition of GAL-3, both alone and with the addition of its inhibitors. LPSs stimulated the expression of TLR4, NFκB p65, MyD88 and NALP3 in hGMSCs, which was inhibited by GAL-3. The addition of either GAL3-BP or the antibody to GAL-3 were able to revert the GAL-3-mediated effects, restoring the expression of TLR4, NFκB p65, MyD88 and NALP3. GAL-3 induces the downregulation of the LPS-induced inflammatory program in MSCs.