Disruption of the F-actin cytoskeleton and monolayer barrier integrity induced by PAF and the protective effect of ITF on intestinal epithelium

Tff3 Deficiency Differentially Affects the Morphology of Male and Female Intestines in a Long-Term High-Fat-Diet-Fed Mouse Model

Trefoil factor family protein 3 (Tff3) protects the gastrointestinal mucosa and has a complex mode of action in different tissues. Here, we aimed to determine the effect of Tff3 deficiency on intestinal tissues in a long-term high-fat-diet (HFD)-fed model. A novel congenic strain without additional metabolically relevant mutations (Tff3-/-/C57Bl6NCrl strain, male and female) was used. Wild type (Wt) and Tff3-deficient mice of both sexes were fed a HFD for 36 weeks. Long-term feeding of a HFD induces different effects on the intestinal structure of Tff3-deficient male and female mice. For the first time, we found sex-specific differences in duodenal morphology. HFD feeding reduced microvilli height in Tff3-deficient females compared to that in Wt females, suggesting a possible effect on microvillar actin filament dynamics. These changes could not be attributed to genes involved in ER and oxidative stress, apoptosis, or inflammation. Tff3-deficient males exhibited a reduced cecal crypt depth compared to that of Wt males, but this was not the case in females. Microbiome-related short-chain fatty acid content was not affected by Tff3 deficiency in HFD-fed male or female mice. Sex-related differences due to Tff3 deficiency imply the need to consider both sexes in future studies on the role of Tff in intestinal function.

Investigation of gastrointestinal injury-related biomarkers in dairy cattle with displaced abomasum

BACKGROUND

Displaced abomasum (DA) is one of the most important metabolic disorders of dairy cattle. In DA, ischaemic damage may occur as a result of impaired perfusion due to abomasal displacement, which may result in gastrointestinal mucosal damage.

OBJECTIVE

Investigation of gastrointestinal tissue damage in cattle with right displacement of the abomasum (RDA) and left displacement of the abomasum (LDA) using intestinal-related biomarkers.

METHODS

Forty-eight DA (24 LDA, 24 RDA) and 15 healthy Holstein dairy cows were enrolled between March 2021 and July 2022. Serum biomarkers including gamma-enteric smooth muscle actin (ACTG-2), liver-fatty acid binding proteins (L-FABP), platelet activating factor (PAF), trefoil factor-3 (TFF-3), leptin, claudin-3 and interleukin-8 (IL-8) concentrations were measured from venous blood samples.

RESULTS

L-FABP concentrations in the LDA group and TFF-3 concentrations in the RDA group were lower than in the control group. The leptin concentration of the RDA group was higher than that of the other groups. There was a negative correlation between lactate, leptin and IL-8 concentrations. There was a negative correlation between lactate and TFF-3, whereas leptin and lactate were positively correlated. Leptin was the more reliable biomarker for discriminating between RDA and LDA cases.

CONCLUSION

Changes in serum L-FABP, TFF-3 and leptin concentrations in cattle with DA may reflect acute intestinal injury and the subsequent repair phase. However, these biomarkers had poor diagnostic performance in discriminating between healthy and cattle with DA, while leptin emerged as the most useful marker in differentiating LDA from RDA cases.

Enhanced ileum function in weaned piglets via Laminaria digitata and alginate lyase dietary inclusion: A combined proteomics and metabolomics analysis

Laminaria digitata, a brown seaweed with prebiotic properties, can potentially enhance the resilience of weaned piglets to nutritional distress. However, their cell wall polysaccharides elude digestion by monogastric animals' endogenous enzymes. In vitro studies suggest alginate lyase's ability to degrade such polysaccharides. This study aimed to assess the impact of a 10% dietary inclusion of L. digitata and alginate lyase supplementation on the ileum proteome and metabolome, adopting a hypothesis-generating approach. Findings indicated that control piglets escalated glucose usage as an enteric energy source, as evidenced by the increased abundance of PKLR and PCK2 proteins and decreased tissue glucose concentration. Additionally, the inclusion of seaweed fostered a rise in proteins linked to enhanced enterocyte structural integrity (ACTBL2, CRMP1, FLII, EML2 and MYLK), elevated peptidase activity (NAALADL1 and CAPNS1), and heightened anti-inflammatory activity (C3), underscoring improved intestinal function. In addition, seaweed-fed piglets showed a reduced abundance of proteins related to apoptosis (ERN2) and proteolysis (DPP4). Alginate lyase supplementation appeared to amplify the initial effects of seaweed-only feeding, by boosting the number of differential proteins within the same pathways. This amplification is potentially due to increased intracellular nutrient availability, making a compelling case for further exploration of this dietary approach. SIGNIFICANCE: Pig production used to rely heavily on antibiotics and zinc oxide to deal with post-weaning stress in a cost-effective way. Their negative repercussions on public health and the environment have motivated heavy restrictions, and a consequent search for alternative feed ingredients/supplements. One of such alternatives is Laminaria digitata, a brown seaweed whose prebiotic components that can help weaned piglets deal with nutritional stress, by improving their gut health and immune status. However, their recalcitrant cell walls have antinutritional properties, for which alginate lyase supplementation is a possible solution. By evaluating ileal metabolism as influenced by dietary seaweed and enzyme supplementation, we aim at discovering how the weaned piglet adapts to them and what are their effects on this important segment of the digestive system.

Protective Effect of Citrus Medica limonum Essential Oil against Escherichia coli K99-Induced Intestinal Barrier Injury in Mice

Citrus Medica limonum essential oil (LEO) has been reported to have antibacterial and anti-inflammatory activities, but its protective effect in the intestine remains unknown. In this study, we researched the protective effects of LEO in relation to intestinal inflammation induced by E. coli K99. The mice were pretreated with 300, 600, and 1200 mg/kg LEO and then stimulated with E. coli K99. The results showed that E. coli K99 caused immune organ responses, intestinal tissue injury, and inflammation. LEO pretreatment dose-dependently alleviated these changes by maintaining a low index in the thymus and spleen and producing a high content of immunoglobulin A, G, and M (IgA, IgG, and IgM) and low content of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Intestinal integrity as a consequence of the LEO pretreatment may be related to the high mRNA expression of intestinal trefoil factor (ITF) and the low mRNA expression of transforming growth factor-β1 (TGF-β1). Conclusively, an LEO pretreatment can alleviate E. coli K99-induced diarrhea, immune organ response, and body inflammation in mice by reducing the levels of inflammatory cytokines and improving the levels of immunoglobulin, and the intestinal integrity remained highest when maintaining the high mRNA expression of ITF and keeping the mRNA expression of TGF-β1 low in the intestinal tissue.

Protective Effects of Natural Polysaccharides on Intestinal Barrier Injury: A Review

Owing to their minimal side effects and effective protection from oxidative stress, inflammation, and malignant growth, natural polysaccharides (NPs) are a potential adjuvant therapy for several diseases caused by intestinal barrier injury (IBI). More studies are accumulating on the protective effects of NPs with respect to IBI, but the underlying mechanisms remain unclear. Thus, this review aims to represent current studies that investigate the protective effects of NPs on IBI by directly maintaining intestinal epithelial barrier integrity (inhibiting oxidative stress, regulating inflammatory cytokine expression, and increasing tight junction protein expression) and indirectly regulating intestinal immunity and microbiota. Furthermore, the mechanisms underlying IBI development are briefly introduced, and the structure-activity relationships of polysaccharides with intestinal barrier protection effects are discussed. Potential developments and challenges associated with NPs exhibiting protective effects against IBI have also been highlighted to guide the application of NPs in the treatment of intestinal diseases caused by IBI.

Effect of Platelet-Activating Factor on Barrier Function of ARPE-19 Cells

Aim

To examine the effects of platelet-activating factor (PAF) on the barrier functions of cultured retinal pigment epithelial (RPE) cells.

Methods

A human RPE cell line (ARPE-19) was cultured on microporous filter supports and treated with PAF and WEB 2086, a specific PAF-receptor (PAF-R) antagonist. The permeability of the RPE monolayer was measured using transepithelial electrical resistance (TER) and sodium fluorescein flux. The expression of the tight junction protein zonula occludens (ZO)-1 and the adherens junction protein N-cadherin was assessed using immunohistochemistry and Western blotting. We also measured the vascular endothelial growth factor (VEGF) concentrations in PAF-treated cultures and re-measured RPE monolayer permeability in the presence of VEGF-neutralizing antibodies.

Results

PAF significantly decreased the TER and enhanced the sodium fluorescein flux of the RPE monolayer and downregulated the expression of ZO-1 and N-cadherin. These effects were abolished by WEB 2086-mediated blockage of the PAF-R. PAF stimulation increased VEGF expression in RPE cells, and the antibody-mediated neutralization of VEGF caused a partial recovery of the barrier properties.

Conclusion

The barrier functions of ARPE-19 cells were altered by PAF, and these effects were partly mediated by an upregulation of VEGF expression in these cells. Our results contribute to the growing body of evidence supporting the role of PAF in choroidal neovascularization. Our findings suggest that PAF is a novel target in the development of therapies for increased permeability of the RPE monolayer.

Inhibiting microRNA-7 Expression Exhibited a Protective Effect on Intestinal Mucosal Injury in TNBS-Induced Inflammatory Bowel Disease Animal Model

This study aimed to explore the expression and correlation of microRNA-7 (miR-7) and trefoil factor 3 (TFF3) genes and proteins in inflammatory bowel disease (IBD) mouse models and to elucidate the effect of miR-7 inhibition in the intestinal mucosa in IBD models. A TNBS-induced IBD mouse model was established. Changes in intestinal inflammation were observed by HE staining, and the expression levels of miR-7 and TFF3 were detected by RT-PCR. After miRNA-antagomir injection, the degree of colonic tissue damage and the expression levels of miR-7 and TFF3 in intestinal tissues were compared. TNBS-induced IBD mice showed significant weight loss, significantly decreased disease activity index (DAI), and a significantly increased pathological damage score. miR-7 was highly expressed in the colon tissue of IBD mice, and TFF3 was downregulated. Inhibition of the expression of miR-7 improved the stool characteristics and fecal occult blood (OB) of IBD mice, significantly increased the expression of TFF3 protein, and decreased the pathological damage scores. In the IBD mouse model, miR-7 posttranscriptionally regulates TFF3. The inhibition of miR-7 expression improves some clinical manifestations of IBD mice, reduces the pathological damage of the intestinal mucosa, and shows a protective effect in IBD.

Cell injury triggers actin polymerization to initiate epithelial restitution

The role of the actin cytoskeleton in the sequence of physiological epithelial repair in the intact epithelium has yet to be elucidated. Here, we explore the role of actin in gastric repair in vivo and in vitro gastric organoids (gastroids). In response to two-photon-induced cellular damage of either an in vivo gastric or in vitro gastroid epithelium, actin redistribution specifically occurred in the lateral membranes of cells neighboring the damaged cell. This was followed by their migration inward to close the gap at the basal pole of the dead cell, in parallel with exfoliation of the dead cell into the lumen. The repair and focal increase of actin was significantly blocked by treatment with EDTA or the inhibition of actin polymerization. Treatment with inhibitors of myosin light chain kinase, myosin II, trefoil factor 2 signaling or phospholipase C slowed both the initial actin redistribution and the repair. While Rac1 inhibition facilitated repair, inhibition of RhoA/Rho-associated protein kinase inhibited it. Inhibitors of focal adhesion kinase and Cdc42 had negligible effects. Hence, initial actin polymerization occurs in the lateral membrane, and is primarily important to initiate dead cell exfoliation and cell migration to close the gap.

Signalling mechanisms in PAF-induced intestinal failure

Capillary leakage syndrome, vasomotor disturbances and gut atony are common clinical problems in intensive care medicine. Various inflammatory mediators and signalling pathways are involved in these pathophysiological alterations among them platelet-activating factor (PAF). The related signalling mechanisms of the PAF-induced dysfunctions are only poorly understood. Here we used the model of the isolated perfused rat small intestine to analyse the role of calcium (using calcium deprivation, IP-receptor blockade (2-APB)), cAMP (PDE-inhibition plus AC activator), myosin light chain kinase (inhibitor ML-7) and Rho-kinase (inhibitor Y27632) in the following PAF-induced malfunctions: vasoconstriction, capillary and mucosal leakage, oedema formation, malabsorption and atony. Among these, the PAF-induced vasoconstriction and hyperpermeability appear to be governed by similar mechanisms that involve IP3 receptors, extracellular calcium and the Rho-kinase. Our findings further suggest that cAMP-elevating treatments - while effective against hypertension and oedema - bear the risk of dysmotility and reduced nutrient uptake. Agents such as 2-APB or Y27632, on the other hand, showed no negative side effects and improved most of the PAF-induced malfunctions suggesting that their therapeutic usefulness should be explored.

MicroRNA‑7‑5p regulates the expression of TFF3 in inflammatory bowel disease

Trefoil factor 3 (TFF3) serves an important role in intestinal mucosal damage and healing, and contributes to the pathogenesis and treatment of inflammatory bowel disease (IBD). The aim of the present study was to determine the association between TFF3 and microRNA-7-5p (miR-7-5p) in IBD. Tissue immunohistochemistry was applied to evaluate the relative expression of TFF3, and reverse transcription-quantitative polymerase chain reaction was performed to determine the expression of miR-7-5p in lesional tissue obtained from patients with IBD and healthy control tissues. A dual-luciferase reporter assay was used to investigate whether TFF3 was a target of miR-7-5p, and western blotting was performed to determine the expression of TFF3 when miR-7-5p was overexpressed or suppressed. The protein expression levels of TFF3 were decreased and miR-7-5p was overexpressed in the lesional tissue of patients with IBD compared with in healthy control tissues. TFF3 was identified as a target of miR-7-5p, and TFF3 protein expression was negatively regulated by miR-7-5p in human colonic epithelial LS174T cells. The present study demonstrated a negative association between the expression of miR-7-5p and TFF3 in IBD lesional tissues and normal tissues. In conclusion, TFF3 was identified as a novel target of miR-7-5p and miR-7-5p may serve as a promising therapeutic target for IBD.

Trefoil Factor Peptides and Gastrointestinal Function

Trefoil factor (TFF) peptides, with a 40-amino acid motif and including six conserved cysteine residues that form intramolecular disulfide bonds, are a family of mucin-associated secretory molecules mediating many physiological roles that maintain and restore gastrointestinal (GI) mucosal homeostasis. TFF peptides play important roles in response to GI mucosal injury and inflammation. In response to acute GI mucosal injury, TFF peptides accelerate cell migration to seal the damaged area from luminal contents, whereas chronic inflammation leads to increased TFF expression to prevent further progression of disease. Although much evidence supports the physiological significance of TFF peptides in mucosal defenses, the molecular and cellular mechanisms of TFF peptides in the GI epithelium remain largely unknown. In this review, we summarize the functional roles of TFF1, 2, and 3 and illustrate their action mechanisms, focusing on defense mechanisms in the GI tract.

ZO-1 and -2 Are Required for TRPV1-Modulated Paracellular Permeability

The tight junction–based paracellular pathway plays an important role in saliva secretion. Zonula occludens (ZO) proteins are submembranous proteins of tight junction complex; however, their function in salivary epithelium is poorly understood. Here, we found that activation of transient receptor potential vanilloid subtype 1 (TRPV1) by capsaicin increased rat saliva secretion both in vivo and ex vivo. Meanwhile, TRPV1 activation enlarged the width of tight junctions between neighboring acinar cells, increased the paracellular flux of 4-kDa fluorescein isothiocyanate (FITC)-dextran in submandibular gland (SMG) tissues, and decreased transepithelial electric resistance (TER) in SMG-C6 cells. ZO-1, -2, and -3 were distributed principally to the apical lateral region of acinar cells in SMG tissues and continuously encircled the peripheries of SMG-C6 cells in the untreated condition. TRPV1 activation obviously diminished ZO-1 and -2 staining, but not ZO-3 or β-catenin, at the cell-cell contacts ex vivo and in vitro. Moreover, in untreated SMG-C6 cells, ZO-1 and -2 single or double knockdown by small interfering RNA (siRNA) increased the paracellular flux of 4-kDa FITC-dextran. In capsaicin-treated cells, ZO-1 and -2 single or double knockdown abolished, whereas their re-expression restored, the capsaicin-induced increase in paracellular permeability. Furthermore, TRPV1 activation increased RhoA activity, and inhibition of either RhoA or Rho kinase (ROCK) abolished the capsaicin-induced TER decrease as well as ZO-1 and -2 redistribution. These results indicate that ZO-1 and -2 play crucial roles in both basal salivary epithelial barrier function and TRPV1-modulated paracellular transport. RhoA-ROCK signaling pathway is responsible for TRPV1-modulated paracellular permeability as well as ZO-1 and -2 redistribution.

HGF Gene Modification in Mesenchymal Stem Cells Reduces Radiation-Induced Intestinal Injury by Modulating Immunity

Background

Effective therapeutic strategies to address intestinal complications after radiation exposure are currently lacking. Mesenchymal stem cells (MSCs), which display the ability to repair the injured intestine, have been considered as delivery vehicles for repair genes. In this study, we evaluated the therapeutic effect of hepatocyte growth factor (HGF)-gene-modified MSCs on radiation-induced intestinal injury (RIII).

Methods

Female 6- to 8-week-old mice were radiated locally at the abdomen with a single 13-Gy dose of radiation and then treated with saline control, Ad-HGF or Ad-Null-modified MSCs therapy. The transient engraftment of human MSCs was detected via real-time PCR and immunostaining. The therapeutic effects of non- and HGF-modified MSCs were evaluated via FACS to determine the lymphocyte immunophenotypes; via ELISA to measure cytokine expression; via immunostaining to determine tight junction protein expression; via PCNA staining to examine intestinal epithelial cell proliferation; and via TUNEL staining to detect intestinal epithelial cell apoptosis.

Results

The histopathological recovery of the radiation-injured intestine was significantly enhanced following non- or HGF-modified MSCs treatment. Importantly, the radiation-induced immunophenotypic disorders of the mesenteric lymph nodes and Peyer’s patches were attenuated in both MSCs-treated groups. Treatment with HGF-modified MSCs reduced the expression and secretion of inflammatory cytokines, including tumor necrosis factor alpha (TNF-α) and interferon-gamma (IFN-γ), increased the expression of the anti-inflammatory cytokine IL-10 and the tight junction protein ZO-1, and promoted the proliferation and reduced the apoptosis of intestinal epithelial cells.

Conclusions

Treatment of RIII with HGF-gene-modified MSCs reduces local inflammation and promotes the recovery of small intestinal histopathology in a mouse model. These findings might provide an effective therapeutic strategy for RIII.

Platelet Activating Factor Receptor Activation Improves siRNA Uptake and RNAi Responses in Well-differentiated Airway Epithelia

Well-differentiated human airway epithelia present formidable barriers to efficient siRNA delivery. We previously reported that treatment of airway epithelia with specific small molecules improves oligonucleotide uptake and facilitates RNAi responses. Here, we exploited the platelet activating factor receptor (PAFR) pathway, utilized by specific bacteria to transcytose into epithelia, as a trigger for internalization of Dicer-substrate siRNAs (DsiRNA). PAFR is a G-protein coupled receptor which can be engaged and activated by phosphorylcholine residues on the lipooligosaccharide (LOS) of nontypeable Haemophilus influenzae and the teichoic acid of Streptococcus pneumoniae as well as by its natural ligand, platelet activating factor (PAF). When well-differentiated airway epithelia were simultaneously treated with either nontypeable Haemophilus influenzae LOS or PAF and transduced with DsiRNA formulated with the peptide transductin, we observed silencing of both endogenous and exogenous targets. PAF receptor antagonists prevented LOS or PAF-assisted DsiRNA silencing, demonstrating that ligand engagement of PAFR is essential for this process. Additionally, PAF-assisted DsiRNA transfection decreased CFTR protein expression and function and reduced exogenous viral protein levels and titer in human airway epithelia. Treatment with spiperone, a small molecule identified using the Connectivity map database to correlate gene expression changes in response to drug treatment with those associated with PAFR stimulation, also induced silencing. These results suggest that the signaling pathway activated by PAFR binding can be manipulated to facilitate siRNA entry and function in difficult to transfect well-differentiated airway epithelial cells.

Enhancing the intestinal absorption of low molecular weight chondroitin sulfate by conjugation with α-linolenic acid and the transport mechanism of the conjugates

The purpose of this report was to demonstrate the effect of amphiphilic polysaccharides-based self-assembling micelles on enhancing the oral absorption of low molecular weight chondroitin sulfate (LMCS) in vitro and in vivo, and identify the transepithelial transport mechanism of LMCS micelles across the intestinal barrier. α-Linolenic acid-low molecular weight chondroitin sulfate polymers(α-LNA-LMCS) were successfully synthesized, and characterized by FTIR, (1)HNMR, TGA/DSC, TEM, laser light scattering and zeta potential. The significant oral absorption enhancement and elimination half-life (t₁/₂) extension of LNA-LMCS2 in rats were evidenced by intragastric administration in comparison with CS and LMCS. Caco-2 transport studies demonstrated that the apparent permeability coefficient (Papp) of LNA-LMCS2 was significantly higher than that of CS and LMCS (p<0.001), and no significant effects on the overall integrity of the monolayer were observed during the transport process. In addition, α-LNA-LMCS micelles accumulated around the cell membrane and intercellular space observed by confocal laser scanning microscope (CLSM). Furthermore, evident alterations in the F-actin cytoskeleton were detected by CLSM observation following the treatment of the cell monolayers with α-LNA-LMCS micelles, which further certified the capacity of α-LNA-LMCS micelles to open the intercellular tight junctions rather than disrupt the overall integrity of the monolayer. Therefore, LNA-LMCS2 with low cytotoxicity and high bioavailability might be a promising substitute for CS in clinical use, such as treating osteoarthritis, atherosclerosis, etc.

Mycophenolic acid mediated disruption of the intestinal epithelial tight junctions

Gastrointestinal toxicity is a common adverse effect of mycophenolic acid (MPA) treatment in organ transplant patients, through poorly understood mechanisms. Phosphorylation of myosin light chain 2 (MLC2) is associated with epithelial tight junction (TJ) modulation which leads to defective epithelial barrier function, and has been implicated in GI diseases. The aim of this study was to investigate whether MPA could induce epithelial barrier permeability via MLC2 regulation. Caco-2 monolayers were exposed to therapeutic concentrations of MPA, and MLC2 and myosin light chain kinase (MLCK) expression were analyzed using PCR and immunoblotting. Epithelial cell permeability was assessed by measuring transepithelial resistance (TER) and the flux of paracellular permeability marker FITC-dextran across the epithelial monolayers. MPA increased the expression of MLC2 and MLCK at both the transcriptional and translational levels. In addition, the amount of phosphorylated MLC2 was increased after MPA treatment. Confocal immunofluorescence analysis showed redistribution of TJ proteins (ZO-1 and occludin) after MPA treatment. This MPA mediated TJ disruption was not due to apoptosis or cell death. Additionally ML-7, a specific inhibitor of MLCK was able to reverse both the MPA mediated decrease in TER and the increase in FITC-dextran influx, suggesting a modulating role of MPA on epithelial barrier permeability via MLCK activity. These results suggest that MPA induced alterations in MLC2 phosphorylation and may have a role in the patho-physiology of intestinal epithelial barrier disruption and may be responsible for the adverse effects (GI toxicity) of MPA on the intestine.

Enterocyte loss of polarity and gut wound healing rely upon the F-actin-severing function of villin

Efficient wound healing is required to maintain the integrity of the intestinal epithelial barrier because of its constant exposure to a large variety of environmental stresses. This process implies a partial cell depolarization and the acquisition of a motile phenotype that involves rearrangements of the actin cytoskeleton. Here we address how polarized enterocytes harboring actin-rich apical microvilli undergo extensive cell remodeling to drive injury repair. Using live imaging technologies, we demonstrate that enterocytes in vitro and in vivo rapidly depolarize their microvilli at the wound edge. Through its F-actin-severing activity, the microvillar actin-binding protein villin drives both apical microvilli disassembly in vitro and in vivo and promotes lamellipodial extension. Photoactivation experiments indicate that microvillar actin is mobilized at the lamellipodium, allowing optimal migration. Finally, efficient repair of colonic mechanical injuries requires villin severing of F-actin, emphasizing the importance of villin function in intestinal homeostasis. Thus, villin severs F-actin to ensure microvillus depolarization and enterocyte remodeling upon injury. This work highlights the importance of specialized apical pole disassembly for the repolarization of epithelial cells initiating migration.

PEGylated silicon nanowire coated silica microparticles for drug delivery across intestinal epithelium

Composite particles made by growing nanoscopic silicon wires from the surface of monodispersed, microsized silica beads were tested in this study for their ability to affect the integrity and permeability of an epithelial cell layer. Polyethylene glycol (PEG) is known to sterically stabilize particles and prevent protein binding; as such, it is a routine way to impart in vivo longevity to drug carriers. The effect of the silica beads, both with and without silicon nanowires and PEG, on the disruption of the tight junctions in Caco-2 cells was evaluated by means of: (a) analysis of the localization of zonula occludens-1 (ZO-1), claudin-1 and f-actin; (b) measurements of trans-epithelial electrical resistance (TEER); (c) real-time quantitative RT-PCR analysis of the expression of PKC-α and PKC-z, which regulate the fluidity of cell membranes, and RhoA and Rac1, which are mainly involved in mechanotransduction processes; and (d) drug permeability experiments with fluorescein-sodium. The results have shown that Si-nanowire-coated silica microparticles added to Caco-2 cells in culture lead to alterations in tight junction permeability and the localization of ZO-1 and f-actin, as well as to decreased width of ZO-1 and claudin-1 at the tight junction and increased expression of PKC transcripts. Si-nanowire-coated silica microparticles increased the permeability of Caco-2 cell monolayers to fluorescein-sodium in proportion to their amount. Effects indicative of loosening the Caco-2 cell monolayers and increasing their permeability were less pronounced for PEGylated particles, owing to their greater supposed inertness in comparison with the non-functionalized beads and nanowires. The analyzed Si-nanowire-coated silica microparticles have thus been shown to affect membrane barrier integrity in vitro, suggesting the possibility of using nanostructured microparticles to enhance drug permeability through the intestinal epithelium in vivo.