Brush Border Research Articles

Impact of porcine brush border membrane enzymes on INFOGEST in vitro digestion model: A step forward to mimic the small intestinal phase

Brush border membrane (BBM) enzymes greatly affect the bioaccessibility and bioavailability of food nutrients. Despite their physiological importance, a step simulating the final stage of intestinal digestion has not yet been included in the harmonized protocols for in vitro digestion, primarily due to the challenges of replicating the dynamics of intestinal degradation. Herein, we propose an advancement toward a more physiologically relevant method, complementing the harmonized static gastric-duodenal digestion INFOGEST model with the missing small intestinal phase. BBM hydrolase activity, incubation time, at pH 7.2 were established to reproduce the small intestinal conditions. Skim milk powder, as a model of protein food, was subjected to the in vitro static digestion. Immediately after the duodenal phase, digesta were supplemented with BBM vesicles purified from pig jejunum. To comply with the dynamic nature of intestinal digestion and balance the spontaneous inactivation of hydrolases, BBM supplements were added every two hours throughout 6 h incubation time. Peptide degradation was monitored at each stage of digestion by amino acid analysis, free α-amino group assay, HPLC, LC-MS/MS. Hydrolysis by BBM peptidases led to a significant increase of free amino acids, reflecting the known level of amino acid adsorption (> 90 %) in humans after eating milk proteins. LC-MS/MS analysis demonstrated that BBM hydrolases erode progressively the peptides released by gastro-duodenal processing up to stable sequence motifs. The approach described is particularly relevant when the endpoint is identifying the peptide sequences that cannot be further hydrolysed by digestive enzymes or to determine the amino acid bio-accessibility.

Engineering of phosphatidylserine-targeting ROS-responsive polymeric prodrug for the repair of ischemia-reperfusion-induced acute kidney injury

Ischemia-reperfusion-induced acute kidney injury (IR-AKI) commonly occurs in situations such as hemorrhagic shock, kidney transplantation, and cardiovascular surgery. As one of the significant causes of AKI, IR-AKI is characterized by its high incidence and mortality rates. Currently, effective inflammation control is the key for the treatment of IR-AKI. In this study, we developed an ROS-responsive polymeric prodrugs (Zn-D/DTH) which could target the externalized PS of apoptotic cells, and then responsively released HDM (anti-inflammatory peptides) in the presence of intracellular ROS. Zn-D/DTH effectively ameliorated renal function and mitigated pathological alterations such as the loss of the brush border, tubular dilation, and accumulation of cellular debris within the tubular lumens. Furthermore, Zn-D/DTH greatly reduced the generation of pro-inflammatory factors like IL-6, COX-2, and iNOS in renal tissues, suggesting its protective role largely stems from suppression of the inflammatory response. Additional mechanism exploration revealed that Zn-D/DTH markedly decreased the expression levels of TLR4 and MyD88, as well as the phosphorylation of NF-κB in the damaged kidneys. This, in turn, reduced the number of apoptotic tubular cells and the activity of Caspase 9 and Caspase 3 caused by ischemia-reperfusion. Additionally, Zn-D/DTH treatment showed improvement in the long-term renal damage and fibrosis induced by ischemia-reperfusion. The experimental outcomes indicated that Zn-D/DTH attenuated renal ischemia-reperfusion injury and delayed the transition from acute kidney injury to chronic kidney disease by downregulating the TLR4/MyD88/NF-κB signaling pathway and reducing the expression of apoptotic caspases, thereby inhibiting inflammation and reducing cell apoptosis.

Cry1Ac toxin binding in the velvetbean caterpillar Anticarsia gemmatalis: study of midgut aminopeptidases N.

The velvetbean caterpillar Anticarsia gemmatalis is one of the main soybean defoliators in Brazil. Currently, the main biopesticide used to control insect pests worldwide is the bacteria Bacillus thuringiensis (Bt), which produces entomopathogenic Crystal toxins (Cry) that act in the midgut of susceptible insects, leading them to death. The mode of action of Cry toxins in the midgut involves binding to specific receptors present on the brush border of epithelial cells such as aminopeptidase N (APN), alkaline phosphatase (ALP), cadherin, and others. Mutations in these receptors, among other factors, may be involved in the development of resistance; identification of functional Cry receptors in the midgut of A. gemmatalis is crucial to develop effective strategies to overcome this possible scenario. This study's goal is to characterize APNs of A. gemmatalis and identify a receptor for Cry1Ac in the midgut. The interaction of Bt spores with the midgut epithelium was observed in situ by immunohistochemistry and total aminopeptidase activity was estimated in brush border membrane vesicle (BBMV) samples, presenting higher activity in challenged individuals than in control ones. Ten APN sequences were found in a A. gemmatalis' transcriptome and subjected to different in silico analysis, such as phylogenetic tree, multiple sequence alignment and identification of signal peptide, activity domains and GPI-anchor signal. BBMV proteins from 5th instar larvae were submitted to a ligand blotting using activated Cry1Ac toxin and a commercial anti-Cry polyclonal antibody; corresponding bands of proteins that showed binding to Cry toxin were excised from the SDS-PAGE gel and subjected to mass spectrometry analysis, which resulted in the identification of seven of those APNs. Quantitative PCR was realized to compare expression levels between individuals subjected to sublethal infection with Bt spores and control ones, presenting up- and downregulations upon Bt infection. From these results, we can infer that aminopeptidases N in A. gemmatalis could be involved in the mode of action of Cry toxins in its larval stage.

Solid-state fermentation of green lentils by Lactiplantibacillus plantarum leads to formation of distinct peptides that are absorbable and enhances DPP-IV inhibitory activity in an intestinal Caco-2 cell model.

Food-derived bioactive compounds mimicking the effects of incretin therapies offer promising opportunities for combination therapies with functional foods, where food matrix interactions, gastrointestinal enzyme activity, and in situ bioactivity should be key considerations. In this study, green lentils were solid-state fermented with Lactiplantibacillus plantarum ATCC8014, in vitro digested and exposed to brush border enzymes of a Caco-2 cell monolayer. Intestinal absorption of peptides and DPP-IV inhibitory activity were then investigated. LC-MS/MS profiles showed that peptides mainly originated from parental proteins of the vicilin, convicilin and legumin families. Fermentation led to the formation of more hydrophobic peptides when compared to the unfermented flour and up to 33.6% of them were transported to the basolateral side of a Caco-2 cell monolayer. Peptides with more than 22 amino acids and with a mass greater than 2000 Da were minimally transported. 73 peptides were uniquely identified in the basolateral fraction suggesting that they resulted from the activity of the brush border enzymes. The DPP-IV activity of Caco-2 cells grown as a polarized monolayer was decreased by 37.3% when exposed to in vitro digested 72 h-fermented lentil flour and 10% when exposed to the unfermented one. Inhibition of DPP-IV in the basolateral fluids was improved in a dose-dependent manner and reached 7.9% when 500 mg mL-1 of in vitro digested 72 h fermented lentil flour was used. Glucose absorption and uptake were minimally affected, suggesting that the previously observed hypoglycemic properties of lentils are likely due to activity on DPP-IV rather than on the inhibition of glucose absorption.

Exploring the Cardiorenal Benefits of SGLT2i: A Comprehensive Review

The history of sodium-glucose cotransporter 2 inhibitors (SGLT2i) is so long and started in 1835 when Petersen extracted a compound called phlorizin from apple tree bark. About fifty years later, von Mering discovered its glucosuric properties. In the 1980s, it was discovered that the glucosuria resulted from inhibition by phlorizin of glucose reabsorption by the renal tubules, which lowered blood glucose levels in diabetic rats. Nowadays, beyond their glucose-lowering effects, growing evidence suggests significant cardiorenal benefits associated with SGLT2i therapy. Indeed, several clinical trials, including landmark studies such as EMPA-REG OUTCOME, CANVAS Program, and DECLARE-TIMI 58, have demonstrated robust reductions in cardiovascular events, particularly heart failure hospitalizations and cardiovascular mortality, among patients treated with SGLT2i. However, subsequent trials showed that SGLT2i benefits extend beyond the diabetic population, encompassing individuals with and without diabetes. Additionally, SGLT2i exhibit nephroprotective effects, manifesting as a slowing of the progression of chronic kidney disease and a reduction in the risk of end-stage kidney disease. The mechanisms underlying the cardiorenal benefits of SGLT2i are multifactorial and include improvements in glycemic control, reduction in arterial stiffness, modulation of inflammation and oxidative stress, reduction of intraglomerular pression and promotion of natriuresis and diuresis through inhibition of SGLT2 in the luminal brush border of the first segments of the proximal kidney tubule. This narrative review aims to explore the cardiorenal outcomes of SGLT2i, encompassing their mechanisms of action, clinical evidence, safety profile, and implications for clinical practice.

Hexokinase 2 expression in apical enterocytes correlates with inflammation severity in patients with inflammatory bowel disease

BackgroundInflammation is characterized by a metabolic switch promoting glycolysis and lactate production. Hexokinases (HK) catalyze the first reaction of glycolysis and inhibition of epithelial HK2 protected from colitis in mice. HK2 expression has been described as elevated in patients with intestinal inflammation; however, there is conflicting data from few cohorts especially with severely inflamed individuals; thus, systematic studies linking disease activity with HK2 levels are needed.MethodsWe examined the relationship between HK2 expression and inflammation severity using bulk transcriptome data derived from the mucosa of thoroughly phenotyped inflammatory bowel disease (IBD) patients of two independent cohorts including both subtypes Crohn’s disease (CD) and ulcerative colitis (UC). Publicly available single-cell RNA sequencing data were analyzed, and immunofluorescence staining on colonic biopsies of unrelated patients with intestinal inflammation was performed to confirm the RNA-based findings on cellular and protein level.ResultsHK2 expression gradually increased from mild to intermediate inflammation, yet strongly declined at high inflammation scores. Expression of epithelial marker genes also declined at high inflammation scores, whereas that of candidate immune marker genes increased, indicating a cellular remodeling of the mucosa during inflammation with an infiltration of HK2-negative immune cells and a loss of terminal differentiated epithelial cells in the apical epithelium—the main site of HK2 expression. Normalizing for the enterocyte loss clearly identified epithelial HK2 expression as gradually increasing with disease activity and remaining elevated at high inflammation scores. HK2 protein expression was mostly restricted to brush border enterocytes, and these cells along with HK2 levels vanished with increasing disease severity.ConclusionsOur findings clearly define dysregulated epithelial HK2 expression as an indicator of disease activity in intestinal inflammation and suggest targeted HK2-inhibition as a potential therapeutic avenue.

Effect of dietary glycerol monolaurate supplementation on gene expression, intestinal mucosa and microbiota of juvenile black sea bream (Acanthopagrus schlegelii).

Glycerol monolaurate (GML) is a chemical compound derived from the combination of lauric acid and glycerol, exhibiting potent antimicrobial properties. An eight-week feeding trial was conducted to evaluate the effects of dietary supplementation of Glycerol Monolaurate (GML) on juvenile black sea bream. The control diet included 24% fish meal, while five additional diets were formulated with increasing GML concentrations: 0.01% (GML1), 0.02% (GML2), 0.04% (GML3), 0.08% (GML4), and 0.16% (GML5). Each diet was assigned to triplicate tanks. At the end of the experiment, serum immune and antioxidant in liver were non-significantly different among the groups. The relative gene expression of IGF-1 and GH in liver was statistically higher in the GML3 treated. The relative gene expression of IL-1, TGF, TNF-1, CCK, CLDN1, CASS-3 and GPR41 in intestine were statistically higher in the GML3 group. The photomicrographs of transmission electron microscope of the intestine were also studied. The GML supplemented groups had longer brush borders. The cells seemed to be joined by an intact junctional complex without visible intercellular spaces. The observed variations in phyla, class, and genus did not demonstrate statistical significance. Proteobacteria, Cyanobacteria, Firmicutes and Actinobacteria in the phylum, and Oxyphotobacteria, Bacteroidia, Holophagae and Negativicutes in the class, Brevundimonas, and Achromobacter in the genera were all substantially increased with higher levels of GML supplementation. Based on these results, it is suggested that glycerol monolaurate (GML) may serve as a potential dietary supplement for promoting different gene expression and intestinal health in black sea bream.

Intestinal Epithelial Cell Brush Border Membrane Cl:HCO3 Exchanger Regulation by Mast Cells in Chronic Ileitis.

Malabsorption of NaCl is the primary cause of diarrhea in inflammatory bowel disease (IBD). Coupled NaCl absorption occurs via the dual operation of Na:H and Cl:HCO3 exchange in the brush border membrane (BBM) of villus cells. Cl:HCO3 exchange is mediated by BBM transporters DRA (downregulated in adenoma) and PAT1 (putative anion transporter 1) in the mammalian small intestine. DRA/PAT1-mediated Cl:HCO3 exchange was significantly downregulated in the BBM of villus cells in a rabbit model of chronic ileitis, while Na:H exchange was unaffected. The inhibition of Cl:HCO3 exchange was restored in the rabbits when treated with a broad-spectrum immunomodulator, i.e. a glucocorticoid, indicating that the downregulation of DRA/PAT1 is likely to be immune-mediated during chronic enteritis. Mucosal mast cells are one type of key immune cells that are known to proliferate and release immune inflammatory mediators, thus playing a significant role in the pathogenesis of IBD. However, how mast cells may regulate DRA- and PAT1-mediated Cl:HCO3 exchange in a rabbit model of chronic ileitis is unknown. In this study, treatment of rabbits with chronic intestinal inflammation with the mast cell stabilizer ketotifen did not affect the mucosal architecture of the inflamed intestine. However, ketotifen treatment reversed the inhibition of Cl:HCO3 activity in the BBM of villus cells. This restoration of Cl:HCO3 activity to normal levels by ketotifen was found to be secondary to restoring the affinity of the exchangers for its substrate chloride. This observation was consistent with molecular studies, where the mRNA and BBM protein expressions of DRA and PAT1 remained unaffected in the villus cells under all experimental conditions. Thus, this study indicates that mast cells mediated the inhibition of coupled NaCl absorption by inhibiting Cl:HCO3 exchange in a rabbit model of chronic enteritis.

Chronic kidney disease amplifies severe kidney injury and mortality in a mouse model of skin arsenical exposure.

In previously published work, we elucidated the role of cutaneous arsenical exposure in promoting acute kidney injury (AKI) in adult healthy mice. Here, we determine whether pre-existing chronic kidney disease (CKD) increases the severity of AKI. Following exposure to aristolochic acid (AA) (a nephrotoxic phytochemical in humans), mice manifested classical markers of CKD, including robust interstitial fibrosis and loss in kidney function. Skin challenge with phenylarsine oxide (PAO), a surrogate for warfare arsenicals, led to significantly worse kidney injury, as evidenced by tubulointerstitial fibrosis, glomerulosclerosis, a persistent loss of estimated glomerular filtration rate and mortality in AA-induced CKD mice compared to mice without CKD. These PAO-challenged CKD mice exhibited enhanced production of serum/urine NGAL, and a significant rise in serum creatinine along with histological markers of kidney injury, including brush border loss, tubular atrophy, cast formation, glomerular injury, and interstitial inflammatory cell infiltration. Serum cytokines IL-4, IL-6, IFN-γ, IL-12p70, TNF-α, and IL-18 significantly elevated in CKD mice following PAO exposure when compared to animals exposed to PAO alone. Furthermore, we found increased TUNEL-positive tubular cells in the kidneys of CKD mice following PAO exposure, suggesting enhanced PAO-mediated cell death in CKD mice. Mechanistically, we determined that DNA damage-regulated p53 signaling was a major mediator of cellular responses to PAO in CKD mice. In summary, our data demonstrate that CKD significantly increased severity of AKI following exposure to arsenicals and suggest that human populations with preexisting CKD could be highly susceptible to arsenical-mediated kidney injury and associated morbidity and mortality.

Effects of dietary succinic acid supplementation on growth performance, digestive ability, intestinal development and immunity of large yellow croaker (Larimichthys crocea) larvae

The application of artificial micro-diet is an effective way to improve and standardize the quality of aquatic animal larvae. However, the widespread adoption of micro-diet faces a bottleneck due to the limited utilization capacity of the larvae. A 30-day feeding experiment was carried out to investigate the effect of dietary succinic acid (SA) on the growth performance, digestive ability, intestinal development, and immunity of large yellow croaker larvae (initial body weight 11.33 ± 0.57 mg). Four isonitrogenous and isolipidic diets were formulated, incorporating 0.00%, 0.01%, 0.02% and 0.03% SA separately. The results showed that a diet with 0.02% SA significantly increased both the final body weight and the specific growth rate of the larvae. Regarding digestive ability, 0.01% SA supplementation significantly enhanced trypsin activity in both intestinal and pancreatic segments. In addition, 0.01% SA supplementation notably improved amylase activity in the intestinal segment, while diets with 0.01%-0.02% SA significantly improved lipase activity in the pancreatic segment. In terms of intestinal development, 0.01% SA supplementation remarkably boosted the activities of alkaline-phosphatase and leucine-aminopeptidase on brush border membrane in intestine. Furthermore, 0.03% SA supplementation significantly increased the expression of occludin. In terms of immunity, larvae fed diets with 0.01%-0.02% SA exhibited significantly higher lysozyme activity compared to the control group. Supplementation with 0.01% SA also significantly increased both iNOS activity and NO content. In summary, the findings of this study suggested that adding 0.02% SA can improve the growth performance of large yellow croaker larvae by improving digestive enzymes activities, promoting intestinal development, and enhancing nonspecific immunity.

Exopeptidase combination enhances the degradation of isotopically labelled gluten immunogenic peptides in humans.

Celiac disease is a common autoimmune-like enteropathy caused by an aberrant response to incompletely digested dietary gluten. Gluten immunogenic peptides including the immunodominant 33-mer are thought to be resistant to proteolytic digestion by human gastrointestinal peptidases. We developed a novel enzyme therapy approach to support gluten peptide digestion using a combination of two tandem-acting exopeptidases, AMYNOPEP, that complement the intrinsic enzymatic activity of intestinal brush border enterocytes. We evaluated the effects of AMYNOPEP supplementation on 33-mer degradation in vitro and in vivo. In a cross-over clinical study, healthy volunteers with no gastrointestinal disorders were given stable isotope (SI) labelled 33-mer peptides in the presence of varying peptide substrates and caloric loads, with and without AMYNOPEP. 33-mer degradation products (SI-labelled single amino acids) were measured in the blood plasma using LC-MS/MS. AMYNOPEP achieved rapid, complete amino-to-carboxyl terminal degradation of the 33-mer in vitro, generating single amino acids and dipeptides. In healthy volunteers, AMYNOPEP supplementation significantly increased 33-mer degradation and absorption of SI-labelled amino acids even in the presence of competing substrates. Specifically, we observed a 2.8-fold increase in the Cmax of stable isotope-labelled amino acids in the presence of wheat gluten. The absorption kinetics of labelled amino acids derived from 33-mer digestion with AMYNOPEP closely resembled that of SI-labelled X-Proline dipeptides administered without enzyme supplementation, highlighting the rapid hydrolytic activity of AMYNOPEP on polypeptides. AMYNOPEP achieved complete degradation of the 33-mer into single amino acids and dipeptides in vitro and significantly improved 33-mer degradation kinetics in healthy volunteers, as measured by labelled amino acid detection, warranting further investigation into the potential therapeutic benefits of exopeptidase combinations for patients with gluten-related health disorders including celiac disease.

8672 Disrupted Glucocorticoid Receptor Mediated Signalling Causes a Primary Cilia Defect in the Fetal Mouse Renal Tubule

Abstract Disclosure: J. Lao: None. K.L. Short: None. J. Ng: None. D.L. Cottle: None. T.J. Cole: None. Primary cilia are microtubule-based organelles that protrude from cell membranes to mediate diverse developmental signalling pathways and senses extracellular stimuli to maintain tissue homeostasis. We show that glucocorticoid (GC) signalling via the glucocorticoid receptor (GR) is a regulator of normal primary cilia formation in kidney renal tubules. RNA sequencing of whole E18.5 fetal kidney from mice with global deletion of the GR (GR-null) compared to littermate wild-type controls identified significantly reduced mRNA levels of key ciliogenesis-related genes. Further analysis of whole fetal kidney RNA by real-time-qPCR confirmed reduced mRNA levels for the cilia-associated proteins Ccp110 (fold -2.18), Cep97 (fold -1.78), Cep290 (fold -2.91), Kif3a (fold -1.82) and Rpgr (fold -1.90). Confocal microscopy revealed abnormal, stunted primary cilia in renal proximal tubules, collecting ducts and podocytes in GR-null or in renal tubule conditional GR-deleted mice, created using the HoxB7 Cre-driver allele. Primary cilia length was significantly decreased in kidney proximal tubule cells in GR-null mice (5.01 ± 0.11μm) compared with wildtype controls (6.20 ± 0.15μm). Furthermore, scanning electron microscopy of E18.5 GR-null kidney further confirmed aberrant primary cilia morphology in the proximal renal tubules and the absence of an apical brush border. Activation of GR signalling with the synthetic GC dexamethasone in cultured mouse IMCD3 kidney tubule cells significantly increased primary cilia length (2.89 ± 0.04μm) compared to vehicle controls (2.46 ± 0.28μm), an effect blocked by the GR antagonist RU486 (vehicle + RU486: 2.06 ± 0.02μm, dexamethasone + RU486: 2.00 ± 0.02μm). Aurora kinase A (AURKA) is a known regulator of primary cilia formation via the AKT cell signalling pathway and distinct proteins at different stages of the mitotic cell cycle. AURKA protein levels were downregulated in GR-null kidney and in IMCD3 cells which suggest GR regulates AURKA to control the assembly and disassembly of primary cilia. Together, these results demonstrate that GC signalling via the GR is required for normal primary ciliogenesis in the developing renal tubule and suggests that synthetic GR agonists may provide a novel therapeutic option for human ciliopathies such as those observed in forms of polycystic kidney disease. Presentation: 6/2/2024

Polyphenols from unconventional fruit by-products protect human epithelial intestinal cells from oxidative damage

Polyphenols from discards of unconventional fruits, namely guava (Psidium guajava L.), jerivá (Syagrus romanzoffiana), butiá (Butia catarinensis), and sea buckthorn (Hippophae rhamnoids L.) have shown in vitro capacity to ameliorate risk factors associated with chronic diseases. To verify their effects in models simulating human physiology, human colorectal adenocarcinoma (Caco-2) cells can be used to reproduce the small intestine's brush border. Therefore, differentiated Caco-2 cells were treated with phenolic extracts from guava processing discards and jerivá, butiá, and sea buckthorn seeds. Cells were assessed for cytotoxicity through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cellular antioxidant activity (CAA) by fluorescence decline of treated cells mixed with a free radical. Selected extract concentrations induced Caco-2 cytotoxicity mostly in the 100–150 μg/mL range. For CAA, extracts from guava, jerivá, and butiá by-products displayed a hormetic-like behavior, showing antioxidant effect at low concentrations while becoming prooxidants at higher concentrations. In some instances, restoration of the antioxidant effect followed, possibly due to cellular adaptative mechanisms. Sea buckthorn seeds extract showed the most consistent CAA response among all samples. Hence, polyphenols from fruit by-products showed antioxidant activity in Caco-2 cells, although future research should concentrate on assessing their absorption and evaluating their effects in other cell models.

Delivery of imiquimod to intestinal lymph nodes following oral administration

Intestinal lymph nodes are involved in the progression of colorectal cancer (CRC). Tumours suppress the activation of dendritic cells (DCs) in draining lymph nodes, diminishing anti-cancer immune response. Imiquimod (IMQ) facilitates DCs activation via toll-like receptor 7, suggesting that targeted delivery of IMQ to intestinal lymph nodes can improve the treatment of CRC. This study aims to enhance the delivery of IMQ to intestinal lymph nodes by a highly lipophilic prodrug approach. Amide prodrugs were synthesised by conjugating IMQ with saturated and unsaturated medium- to long-chain fatty acids. Their potential for intestinal lymphatic transport was assessed by their affinity to chylomicrons and solubility in long-chain triglycerides. Further selection of prodrug candidates was determined by resistance to enzymatic hydrolysis in intestinal lumen and release of IMQ in the lymphatics using fasting state simulated intestinal fluid supplemented with esterases, brush border enzyme vesicles and plasma. Key pharmacokinetic parameters and biodistribution in rats were assessed for the most promising compounds, prodrugs 5 and 8. The plasma concentration–time profile of IMQ following oral administration of the prodrugs was less erratic in comparison to the administration of unmodified IMQ. The lymph-to-plasma ratios of IMQ concentration increased 1.9- and 1.7-fold using prodrugs 5 and 8 in comparison to administration of unmodified IMQ, respectively. Importantly, the average concentration of IMQ in mesenteric lymph nodes (MLN) was 11.2- and 7.6-fold higher than in plasma following the administration of prodrugs 5 and 8, respectively. Additionally, the non-specific wide distribution of IMQ into various organs and tissues was reduced with prodrugs. This work suggests that the highly lipophilic prodrug approach can efficiently deliver IMQ to intestinal lymphatics. In addition, this study demonstrates the feasibility of an amide prodrug approach for intestinal lymphatic targeting.

BPP43_05035 is a Brachyspira pilosicoli cell surface adhesin that weakens the integrity of the epithelial barrier during infection

ABSTRACT The anaerobic spirochete Brachyspira causes intestinal spirochetosis, characterized by the intimate attachment of bacterial cells to the colonic mucosa, potentially leading to symptoms such as diarrhea, abdominal pain, and weight loss. Despite the clinical significance of Brachyspira infections, the mechanism of the interaction between Brachyspira and the colon epithelium is not known. We characterized the molecular mechanism of the B. pilosicoli-epithelium interaction and its impact on the epithelial barrier during infection. Through a proteomics approach, we identified BPP43_05035 as a candidate B. pilosicoli surface protein that mediates bacterial attachment to cultured human colonic epithelial cells. The crystal structure of BPP43_05035 revealed a globular lipoprotein with a six-bladed beta-propeller domain. Blocking the native BPP43_05035 on B. pilosicoli, either with a specific antibody or via competitive inhibition, abrogated its binding to epithelial cells, which required cell surface-exposed N-glycans. Proximity labeling and interaction assays revealed that BPP43_05035 bound to tight junctions, thereby increasing the permeability of the epithelial monolayer. Extending our investigation to humans, we discovered a downregulation of tight junction and brush border genes in B. pilosicoli-infected patients carrying detectable levels of epithelium-bound BPP43_05035. Collectively, our findings identify BPP43_05035 as a B. pilosicoli adhesin that weakens the colonic epithelial barrier during infection.

Regulation of Enterocyte Brush Border Membrane Primary Na-Absorptive Transporters in Human Intestinal Organoid-Derived Monolayers.

In the small intestine, sodium (Na) absorption occurs primarily via two apical transporters, Na-hydrogen exchanger 3 (NHE3) and Na-glucose cotransporter 1 (SGLT1). The two primary Na-absorptive pathways were previously shown to compensatorily regulate each other in rabbit and rat intestinal epithelial cells. However, whether NHE3 and SGLT1 regulate one another in normal human enterocytes is unknown, mainly due to a lack of appropriate experimental models. To investigate this, we generated 2D enterocyte monolayers from human jejunal 3D organoids and used small interfering RNAs (siRNAs) to knock down NHE3 or SGLT1. Molecular and uptake studies were performed to determine the effects on NHE3 and SGLT1 expression and activity. Knockdown of NHE3 by siRNA in enterocyte monolayers was verified by qPCR and Western blot analysis and resulted in reduced NHE3 activity. However, in NHE3 siRNA-transfected cells, SGLT1 activity was significantly increased. siRNA knockdown of SGLT1 was confirmed by qPCR and Western blot analysis and resulted in reduced SGLT1 activity. However, in SGLT1 siRNA-transfected cells, NHE3 activity was significantly increased. These results demonstrate for the first time the functionality of siRNA in patient-derived organoid monolayers. Furthermore, they show that the two primary Na absorptive pathways in human enterocytes reciprocally regulate one another.

Histochemical Analysis and Distribution of Digestive Enzymes in the Gastrointestinal System of the European Barracuda Sphyraena sphyraena (Linnaeus, 1758).

In this study, we examined the gastrointestinal tract of the European barracuda (Sphyraena sphyraena) living in the Adriatic Sea near Dubrovnik, Croatia. The study aimed to identify the presence and distribution of four digestive enzymes: alkaline phosphatase, aminopeptidase, acid phosphatase, and non-specific esterase. We found that alkaline phosphatase activity was present in the brush border of the enterocytes in all the investigated intestinal segments. The activity of the alkaline phosphatase was the strongest in the pyloric caeca but strong only in the basal part of the intestinal villi in the anterior and middle intestinal segments. In the posterior intestinal segment, alkaline phosphatase had strong activity along the entire villi. The activity of acid phosphatase was weak in all the investigated parts of the intestine, except in the posterior part, where it was moderate. Aminopeptidase was detected in the brush border of the intestinal epithelium, with stronger activity in the pyloric caeca and anterior part of the intestine and weaker activity posteriorly. The activity of the non-specific esterase was moderate in the pyloric caeca and anterior part of the intestine, while it was weak in the posterior segment and the lamina propria in all parts of the digestive tract. Weak acid phosphatase activity was observed only in the lamina propria of the posterior part of the intestine. This study is the first to evaluate the activity of digestive enzymes in the European barracuda.

MiR-27a-3p regulates intestinal cell proliferation and differentiation through Wnt/β-catenin signalling.

Intestinal stem cells differentiate into absorptive enterocytes, characterised by increased brush border enzymes such as intestinal alkaline phosphatase (IAP), making up the majority (95%) of the terminally differentiated cells in the villus. Loss of integrity of the intestinal epithelium plays a key role in inflammatory diseases and gastrointestinal infection. Here, we show that the intestinal microRNA (miR)-27a-3p is an important regulator of intestinal epithelial cell proliferation and enterocyte differentiation. Repression of endogenous miR-27a-3p leads to increased enterocyte differentiation and decreased intestinal epithelial cell proliferation in mouse and human small intestinal organoids. Mechanistically, miR-27a-3p regulates intestinal cell differentiation and proliferation at least in part through the regulation of retinoic acid receptor α (RXRα), a modulator of Wnt/β-catenin signalling. Repression of miR-27a-3p increases the expression of RXRα and concomitantly, decreases the expression of active β-catenin and cyclin D1. In contrast, overexpression of miR-27a-3p mimic decreases the expression of RXRα and increases the expression of active β-catenin and cyclin D1. Moreover, overexpression of the miR-27a-3p mimic results in impaired enterocyte differentiation and increases intestinal epithelial cell proliferation. These alterations were attenuated or blocked by Wnt inhibition. Our study demonstrates an miR-27a-3p/RXRα/Wnt/β-catenin pathway that is important for the maintenance of enterocyte homeostasis in the small intestine.

Downregulation of APN1 and ABCC2 mutation in Bt Cry1Ac-resistant Trichoplusia ni are genetically independent.

The resistance to the insecticidal protein Cry1Ac from the bacterium Bacillus thuringiensis (Bt) in the cabbage looper, Trichoplusia ni, has previously been identified to be associated with a frameshift mutation in the ABC transporter ABCC2 gene and with altered expression of the aminopeptidase N (APN) genes APN1 and APN6, shown as missing of the 110-kDa APN1 (phenotype APN1¯) in larval midgut brush border membrane vesicles (BBMV). In this study, genetic linkage analysis identified that the APN1¯ phenotype and the ABCC2 mutation in Cry1Ac-resistant T. ni segregated independently, although they were always associated under Cry1Ac selection. The ABCC2 mutation and APN1¯ phenotype were separated into two T. ni strains respectively. Bioassays of the T. ni strains with Cry1Ac determined that the T. ni with the APN1¯ phenotype showed a low level resistance to Cry1Ac (3.5-fold), and the associated resistance is incompletely dominant in the background of the ABCC2 mutation. Whereas the ABCC2 mutation-associated resistance to Cry1Ac is at a moderate level, and the resistance is incompletely recessive in the genetic background of downregulated APN1. Analysis of Cry1Ac binding to larval midgut BBMV indicated that the midgut in larvae with the APN1¯ phenotype had reduced binding affinity for Cry1Ac, but the number of binding sites remained unchanged, and the midgut in larvae with the ABCC2 mutation had both reduced binding affinity and reduced number of binding sites for Cry1Ac. The reduced Cry1Ac binding to BBMV from larvae with the ABCC2 mutation or APN1¯ phenotype correlated with the lower levels of resistance.IMPORTANCEThe soil bacterium Bacillus thuringiensis (Bt) is an important insect pathogen used as a bioinsecticide for pest control. Bt genes coding for insecticidal proteins are the primary transgenes engineered into transgenic crops (Bt crops) to confer insect resistance. However, the evolution of resistance to Bt proteins in insect populations in response to exposure to Bt threatens the sustainable application of Bt biotechnology. Cry1Ac is a major insecticidal toxin utilized for insect control. Genetic mechanisms of insect resistance to Cry1Ac are complex and require to be better understood. The resistance to Cry1Ac in Trichoplusia ni is associated with a mutation in the ABCC2 gene and also associated with the APN expression phenotype APN1¯. This study identified the genetic independence of the APN1¯ phenotype from the ABCC2 mutation and isolated and analyzed the ABCC2 mutation-associated and APN1¯ phenotype-associated resistance traits in T. ni to provide new insights into the genetic mechanisms of Cry1Ac resistance in insects.

Structured multicellular intestinal spheroids (SMIS) as a standardized model for infection biology

Background3D cell culture models have recently garnered increasing attention for replicating organ microarchitecture and eliciting in vivo-like responses, holding significant promise across various biological disciplines. Broadly, 3D cell culture encompasses organoids as well as single- and multicellular spheroids. While the latter have found successful applications in tumor research, there is a notable scarcity of standardized intestinal models for infection biology that mimic the microarchitecture of the intestine. Hence, this study aimed to develop structured multicellular intestinal spheroids (SMIS) specifically tailored for studying molecular basis of infection by intestinal pathogens.ResultsWe have successfully engineered human SMIS comprising four relevant cell types, featuring a fibroblast core enveloped by an outer monolayer of enterocytes and goblet cells along with monocytic cells. These SMIS effectively emulate the in vivo architecture of the intestinal mucosal surface and manifest differentiated morphological characteristics, including the presence of microvilli, within a mere two days of culture. Through analysis of various differentiation factors, we have illustrated that these spheroids attain heightened levels of differentiation compared to 2D monolayers. Moreover, SMIS serve as an optimized intestinal infection model, surpassing the capabilities of traditional 2D cultures, and exhibit a regulatory pattern of immunological markers similar to in vivo infections after Campylobacter jejuni infection. Notably, our protocol extends beyond human spheroids, demonstrating adaptability to other species such as mice and pigs.ConclusionBased on the rapid attainment of enhanced differentiation states, coupled with the emergence of functional brush border features, increased cellular complexity, and replication of the intestinal mucosal microarchitecture, which allows for exposure studies via the medium, we are confident that our innovative SMIS model surpasses conventional cell culture methods as a superior model. Moreover, it offers advantages over stem cell-derived organoids due to scalability and standardization capabilities of the protocol. By showcasing differentiated morphological attributes, our model provides an optimal platform for diverse applications. Furthermore, the investigated differences of several immunological factors compared to monotypic monolayers after Campylobacter jejuni infection underline the refinement of our spheroid model, which closely mimics important features of in vivo infections.