Caspase-1-dependent mechanism mediating the harmful impacts of the quorum-sensing molecule N-(3-oxo-dodecanoyl)-l-homoserine lactone on the intestinal cells

Comparison between Lactobacillus rhamnosus GG and LuxS-deficient strain in regulating gut barrier function and inflammation in early-weaned piglets

Background

Early weaning-induced stress impairs the intestinal barrier function and adversely affects the health of piglet. Probiotics can be used to prevent and treat various intestinal diseases. Lactobacillus rhamnosus GG (LGG) has an LuxS/AI-2 quorum sensing (QS) system that senses environmental changes through chemical signaling molecules. The aim of the study was to explore whether luxS mutant affects the protective role of LGG in the gut barrier of weaned piglets by comparing the luxS mutant (ΔluxS) with its wild-type (WT).

Methods

Newborn piglets were orally administered with WT and ΔluxS at dosage of 10⁹ CFU, respectively. Accordingly, newborn piglets in the Con group were orally administered with PBS. Piglets were weaned on day 21 and euthanized on day 24, three days following weaning.

Results

Supplementation of ΔluxS in advance significantly boosted the relative abundances of healthy microbes (including Catenibacterium, Eubacterium, Lachnospiraceae and Bifidobacterium). WT and ΔluxS maintain intestinal barrier function mainly by promoting intestinal villus to crypt ratio (VCR), occludin protein expression and mucus secretion (P<0.05). Furthermore, LGG reduces pro-inflammatory mediators by inhibiting TLR4 and MAPK signal transduction (P<0.05).

Conclusion

Both WT and ΔluxS were shown to resist weaning stress by enhancing the intestinal barrier function of piglets. It has to be said that the ability of ΔluxS to maintain intestinal tissue morphology and promote mucus secretion significantly decreased compared with that of WT.

Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl) homoserine lactone induces calcium signaling-dependent crosstalk between autophagy and apoptosis in human macrophages

N-(3-oxododecanoyl) homoserine lactone (3oc) is a Pseudomonas aeruginosa secreted quorum-sensing signal molecule playing a crucial role in regulating quorum-sensing (QS) dependent biofilm formation and secretion of virulence factors. In addition to regulating quorum sensing, 3oc also plays an immunomodulatory role in the host by triggering regulated cell death in immune cells. The molecular mechanisms of 3oc in modulating macrophage pathologies are still unclear. In this study, we hypothesized the novel 3oc mediated crosstalk between autophagy and apoptosis at the interphase of calcium signaling in human macrophages. The study showed that 3oc induces mitochondrial dysfunction and apoptosis in macrophages through elevating cytosolic Ca⁺² ([Ca⁺²]_cyt) levels. Pre-treatment with the calcium-specific chelator BAPTA-AM effectively abrogated 3oc-induced apoptotic events, like mitochondrial ROS generation (mROS), mitochondrial membrane potential (MMP) drop, and phosphatidylserine (PS) exposure. The study also showed that 3oc induces autophagy, as assessed by the accumulation of autophagic vacuoles, induction of lysosomal biogenesis, upregulation of autophagy genes (LC3, BECLIN 1, STX17, PINK1, and TFEB), autophagosomes formation, and LC3 lipidation. Mechanistically, our study proved that 3oc-induced autophagy was [Ca⁺²]_cyt dependent as BAPTA-AM pre-treatment reduced autophagosome formation. Furthermore, inhibiting autophagy with chloroquine attenuated 3oc-induced apoptosis, while autophagy induction with rapamycin aggravated cell death, suggesting autophagy plays a role in cell death in 3oc-treated macrophages. In conclusion, our findings indicate that 3oc activates a multifaceted death signaling by activating autophagy and apoptosis through Ca⁺² signaling, and we propose pharmacological modulation of Ca⁺² signaling may act as a combinatorial therapeutic intervention in patients with Pseudomonas aeruginosa-associated infections.

Impact of quorum sensing signaling molecules in gram-negative bacteria on host cells: current understanding and future perspectives

Quorum sensing is a molecular signaling-based communication mechanism in prokaryotes. In the basic mode, signaling molecules released by certain bacteria are sensed by intracellular receptors or membrane-bound receptors of other members in the community, leading to the collective isogenic signaling molecule synthesis and synchronized activities. This regulation is important for the symbiosis of the bacterium with the host, as well as virulence and biofilm formation. Notably, quorum sensing signaling molecules are not only able to control microbial community behavior but can likewise regulate the physiological status of host cells. Here, we provide a comprehensive review of the importance of quorum sensing signaling molecules in gram-negative bacteria in regulating host cell function and gut health, and suggest possible opportunities for application in combating human and animal diseases by blocking the pathways through which quorum sensing signaling molecules exert their functions.

Gossip in the gut: Quorum sensing, a new player in the host-microbiota interactions

Bacteria are known to communicate with each other and regulate their activities in social networks by secreting and sensing signaling molecules called autoinducers, a process known as quorum sensing (QS). This is a growing area of research in which we are expanding our understanding of how bacteria collectively modify their behavior but are also involved in the crosstalk between the host and gut microbiome. This is particularly relevant in the case of pathologies associated with dysbiosis or disorders of the intestinal ecosystem. This review will examine the different QS systems and the evidence for their presence in the intestinal ecosystem. We will also provide clues on the role of QS molecules that may exert, directly or indirectly through their bacterial gossip, an influence on intestinal epithelial barrier function, intestinal inflammation, and intestinal carcinogenesis. This review aims to provide evidence on the role of QS molecules in gut physiology and the potential shared by this new player. Better understanding the impact of intestinal bacterial social networks and ultimately developing new therapeutic strategies to control intestinal disorders remains a challenge that needs to be addressed in the future.

Sulforaphane protects intestinal epithelial cells against lipopolysaccharide-induced injury by activating the AMPK/SIRT1/PGC-1ɑ pathway

The naturally occurring isothiocyanate sulforaphane, found in vegetables, shows promising anti-inflammatory, anti-apoptosis, and anti-oxidative effects. Whether sulforaphane protects against lipopolysaccharide (LPS)-induced injury in intestinal epithelial cells is unclear. The present study examines the ability of sulforaphane to protect Caco-2 cultures from LPS-induced injury, as well as the mechanism involved. Caco-2 cells were incubated for 24 h with 1 μg/mL LPS and different concentrations of sulforaphane (0.1–10 μM). Then, various indicators of oxidative stress, inflammation, apoptosis, and intestinal permeability were assayed. Sulforaphane increased cell viability and reduced lactate dehydrogenase activity in LPS-treated Caco-2 cells in a concentration-dependent manner. Sulforaphane weakened LPS-induced increases in intestinal epithelial cell permeability and oxidative stress (based on assays of reactive oxygen species, DMA, and H₂O₂), and it increased levels of antioxidants (SOD, GPx, CAT and T-AOC). At the same time, sulforaphane weakened the ability of LPS to induce production of inflammatory cytokines (IL-1β, IL-6, IL-8 and TNF-α) and the pro-apoptotic caspases-3 and −9. Sulforaphane also upregulated p-AMPK, SIRT1, and PGC-1ɑ, whose inhibitors antagonized the compound’s protective effects. Sulforaphane can protect intestinal epithelial cells against LPS-induced changes in intestinal permeability, oxidative stress, inflammation, and apoptosis. It appears to act by activating the AMPK/SIRT1/PGC-1ɑ pathway. The drug therefore shows potential for preventing LPS-induced intestinal injury.

N-(3-oxododecanoyl)-homoserine lactone disrupts intestinal barrier and induces systemic inflammation through perturbing gut microbiome in mice

As a quorum sensing signal molecule, N-(3-oxododecanoyl)-homoserine lactone (3OC12) regulate the population behavior of microorganisms. Many studies have proved that 3OC12 harm the physiological function of host intestinal epithelial cells. However, the detrimental effects of 3OC12 on intestinal health need verification in animals. Besides, the role of gut microbiome in 3OC12-induced intestinal damage also needs further understanding. In our study, 3OC12 was first administered to specific pathogen-free (SPF) mice, then the fecal microbiome of SPF mice was transplanted into germ-free (GF) mice to reveal the effects of 3OC12 on intestinal health and regulatory mechanisms of the intestinal microbiome. 3OC12 treatment significantly decreased body weight, shortened colonic length, disrupted the morphology of the colonic epithelium and increased the histopathological score of the colon in SPF mice. The levels of diamine peroxidase, d-lactate, TNF-α, IL-1β, and IL-8 were found to be significantly elevated in the serum of 3OC12 mice, while the levels of IL-10 were significantly reduced. Besides, the fecal microbial community of mice was also altered in the 3OC12-treated SPF mice. The results of fecal microbial transplantation (FMT) experiment showed that the phenotypes in SPF mice were almost reproduced in GF mice, manifested by body weight loss, colon damage and changed in serum chemical markers. More importantly, a joint analysis of fecal microbes in SPF and GF mice revealed Feature14_Elizabethkingia spp. was common differential bacteria in the feces of two kinds of mice treated with and without FMT. Our results demonstrated that 3OC12 challenge led to systemic inflammation and body weight loss in mice by disrupting intestinal barrier function, in which gut microbiome played a key role. These findings increased our understanding of the mechanism of intestinal injury caused by 3CO12, providing new ideas for the prevention and therapy of diseases caused by bacterial infection from the perspective of intestinal microbiome.

N-Acyl-Homoserine Lactones May Affect the Gut Health of Low-Birth-Weight Piglets by Altering Intestinal Epithelial Cell Barrier Function and Amino Acid Metabolism

BACKGROUND

In piglets, low birth weight (LBW) is associated with intestinal dysfunction, which affects their growth performance and causes economic losses.

OBJECTIVES

This study was designed to test whether microbial quorum sensing (QS) affects LBW-induced intestinal developmental defects in piglets.

METHODS

Seven normal-birth-weight (NBW; 1.36 ± 0.01 kg) and 7 LBW (0.89 ± 0.01 kg) piglets were selected. Feces were collected from piglets on 2, 21, and 50 days of age for detection of the QS signaling molecules, N-acyl-homoserine lactones (AHLs), and microbiota analysis. The associations between 2 long-chain AHLs [N-3-oxo-dodecanoyl-l-homoserine lactone (3OC12-HSL) and N-3-oxo-tetradecanoyl-l-homoserine lactone (3OC14-HSL)] and the microbes were tested using Spearman correlation coefficients. The effect of 3OC12-HSL and 3OC14-HSL on intestinal porcine epithelial cell-jejunum 2 (IPEC-J2) cell viability was investigated by cholecystokinin octapeptide assay. Transcriptomic analysis was performed by RNA sequencing on cells treated with 3OC12-HSL.

RESULTS

The concentrations of 3OC12-HSL and 3OC14-HSL in the feces of LBW piglets were higher than those in NBW piglets at age 50 d by 2.5- and 2.24-fold, respectively (P < 0.05). The microbial α diversity (observed species, abundance-based coverage estimator, and Shannon index) of LBW piglets was 81-91% lower than that of NBW piglets (P < 0.05). The relative abundance of Ruminococcaceae UCG-002/UCG-013 was 43.0% and 30.0% lower, respectively, in feces from LBW compared with NBW piglets (P < 0.05). 3OC12-HSL and Ruminococcaceae UCG-002/UCG-005/UCG-010 abundance were negatively correlated (ρ  ≤  -0.58). Treatment with 400 μM 3OC12-HSL markedly reduced IPEC-J2 cell viability by 47.5%. Transcriptomic data showed that 3OC12-HSL mainly changed the "import across plasma membrane" and "arginine and proline metabolism" of IPEC-J2 cells.

CONCLUSIONS

3OC12-HSL is a QS signaling molecule with an ability to impair gut health of LBW piglets. This finding adds to our understanding of the mechanisms responsible for gut injury in LBW piglets.

Environmental contaminant BPA causes intestinal damage by disrupting cellular repair and injury homeostasis in vivo and in vitro

Our previous studies have shown that the environmental contaminant bisphenol A (BPA) exhibits strong intestinal toxicity and can readily cause intestinal barrier dysfunction. However, the causal relationship between adverse biological processes of BPA-induced intestinal tissue and the role of key signaling molecules in it requires further investigation. In this study, we established a mouse and intestinal epithelial cell model of BPA treatment to determine the underlying molecular mechanisms of BPA-induced intestinal injury. The results showed that the BPA treatment increased the intestinal permeability and disrupted the barrier function by increasing the chemical marker content and tight junction expression in intestinal tissues and blood circulation. BPA also altered the oxidative and antioxidant status of intestinal epithelial cells by increasing ROS and RNS contents and decreasing the activity levels of SOD, GPx, CAT, and T-AOC. BPA further induced inflammatory responses by upregulating the gene abundance of key factors of the innate immune system (TLR2, TLR4, MyD88, and NF-κB), the transcriptional activity of NF-kB, and the secretion of pro-inflammatory cytokines (IL-1β, IL-6, IL-8, and TNF-α). Moreover, apoptosis was activated by BPA, whereas cell proliferation was inhibited by BPA. Mechanistically, co-treatment of intestinal epithelial cells with BPA using the oxidative stress scavenger NAC, the NF-κB-specific inhibitor JSH-23, and the apoptosis inhibitor Z-VAD-FMK, respectively, showed that BPA activates the innate immune response by inducing oxidative stress. Consequently, apoptosis is promoted, and cell proliferation is inhibited, ultimately disrupting the intestinal barrier function. Our findings provide insight into the pathogenesis of BPA-induced gut injury.

N-(3-oxododecanoyl)-l-homoserine lactone disrupts intestinal epithelial barrier through triggering apoptosis and collapsing extracellular matrix and tight junction

Microbes employ autoinducers of quorum sensing (QS) for population communication. Although the autoinducer of Pseudomonas aeruginosa LasI-LasR system, N-(3-oxododecanoyl)- l-homoserine lactone (3OC12), has been reported with deleterious effects on host cells, its biological effects on integrity of the intestinal epithelium and epithelial barrier are still unclear and need further investigation. In the present study, flow cytometry, transcriptome analysis and western blot technology have been adopted to investigate the potential molecular mechanisms of 3OC12 and its structurally similar analogs damage to intestinal epithelial cells. Our results indicated that 3OC12 and 3OC14 trigger apoptosis rather than necrosis and ferroptosis in intestinal epithelial cells. RNA-sequencing combined with bioinformatics analysis showed that 3OC12 and 3OC14 reduced the expression of genes from extracellular matrix (ECM)-receptor interaction pathway. Consistently, protein expressions from ECM and tight junction-associated pathway were significantly reduced after 3OC12 and 3OC14 challenge. In addition, 3OC12 and 3OC14 led to blocked cell cycle, decreased mitochondrial membrane potential, increased reactive oxygen species level and elevated Ca²⁺ concentration. Reversely, the antioxidant NAC could effectively mitigate the reduced expression of ECM and tight junction proteins caused by 3OC12 and 3OC14 challenge. Collectively, this study demonstrated that QS autoinducer exposure to intestinal epithelial cells ablates the ECM and tight junctions by triggering oxidative stress and apoptosis, and finally disrupts the intestinal epithelial barrier. These findings provide a rationale for defensing QS-dependent bacterial infections and potential role of NAC for alleviating the syndrome.

Anti-Inflammatory Effects of Analogues of N-Acyl Homoserine Lactones on Eukaryotic Cells

BACKGROUND

Since acyl-homoserine lactone (AHL) profiling has been described in the gut of healthy subjects and patients with inflammatory bowel disease (IBD), the potential effects of these molecules on host cells have raised interest in the medical community. In particular, natural AHLs such as the 3-oxo-C12-HSL exhibit anti-inflammatory properties. Our study aimed at finding stable 3-oxo-C12-HSL-derived analogues with improved anti-inflammatory effects on epithelial and immune cells.

METHODS

We first studied the stability and biological properties of the natural 3-oxo-C12-HSL on eukaryotic cells and a bacterial reporter strain. We then constructed and screened a library of 22 AHL-derived molecules. Anti-inflammatory effects were assessed by cytokine release in an epithelial cell model, Caco-2, and a murine macrophage cell line, RAW264.7, (respectively, IL-8 and IL-6) upon exposure to the molecule and after appropriate stimulation (respectively, TNF-α 50 ng/mL and IFN-γ 50 ng/mL, and LPS 10 ng/mL and IFN-γ 20 U/mL).

RESULTS

We found two molecules of interest with amplified anti-inflammatory effects on mammalian cells without bacterial-activating properties in the reporter strain. The molecules furthermore showed improved stability in biological medium compared to the native 3-oxo-C12-HSL.

CONCLUSIONS

We provide new bio-inspired AHL analogues with strong anti-inflammatory properties that will need further study from a therapeutic perspective.

Astragalus mongholicus Bunge and Panax Notoginseng Formula (A&P) Combined With Bifidobacterium Contribute a Renoprotective Effect in Chronic Kidney Disease Through Inhibiting Macrophage Inflammatory Response in Kidney and Intestine

There is increasing evidence that Chronic Kidney Disease (CKD) can cause intestinal dysfunction, which in turn aggravates the progression of kidney disease. Studies have shown that the immune response of macrophage plays an important role in promoting inflammation in kidney and intestine of CKD. Astragalus mongholicus Bunge and Panax notoginseng formula (A&P) is a widely used traditional medicine for the treatment of CKD in China, however, the underlying mechanism is largely unclear. In this study, we aimed to explore the role of A&P and Bifidobacterium combination treatment in regulation of inflammatory response of macrophage in kidney and intestine of CKD mouse, as well as the potential molecular mechanism. We established a CKD mouse model with 5/6 nephrectomy and a macrophage inflammatory cellular model with LPS and urotoxin in vivo and in vitro. The results showed that A&P combined with Bifidobacterium significantly reduced the expression and secretion of IL-1β, IL-6, TNFα, and MCP-1 in kidney and blood, as well as in inflammatory macrophage. Interestingly, A&P combined with Bifidobacterium strongly improved the intestinal flora and protected the intestinal barrier. Notably, the maintainer of macrophage polarization, Mincle, was activated in kidney and intestine of CKD mouse as well as in urotoxin stimulated macrophage, that was effectively inhibited by the treatment of A&P and Bifidobacterium combination. Overexpression of Mincle by genetic modification can abolish the inhibitory effects of A&P combined with Bifidobacterium on inflammation in urotoxin stimulated RAW264.7 cells. In summary, these findings demonstrated that A&P combined with Bifidobacterium can protect kidney against CKD by down-regulating macrophage inflammatory response in kidney and intestine via suppressing Mincle signaling, which provides a new insight in the treatment of CKD with traditional medicine.

Icariin Alleviates Bisphenol A Induced Disruption of Intestinal Epithelial Barrier by Maintaining Redox Homeostasis In Vivo and In Vitro

Bisphenol A (BPA), a globally prevalent environmental contaminant, has been shown to have the potential to disrupt intestinal barrier function. This study explored the mechanisms of BPA-induced intestinal barrier dysfunction. In addition, the protective effect of the natural product icariin (ICA) on BPA-induced intestinal barrier dysfunction was evaluated. BPA relieved oxidative stress (reactive oxygen species (ROS), reactive nitrogen species (RNS), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂)), suppressed antioxidant enzyme (superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant capacity (T-AOC)) activity, and increased gene expression and protein content of p38 mitogen-activated protein kinase (MAPK), giving rise to the dysfunctional gut in mice. ICA therapy effectively eased intestinal barrier dysfunction caused by BPA in vivo and in vitro. Treatment with p38 MAPK inhibitor (SB203580) significantly rescued the MODE-K cell barrier function disrupted by BPA challenge. However, treatment with p38 MAPK activator (anisomycin) did not attenuate the MODE-K cell barrier function impaired by BPA challenge. Overall, our data suggested that BPA disrupted intestinal barrier function in a p38 MAPK-dependent manner. Furthermore, we demonstrated that ICA regulated the redox equilibrium of intestinal epithelial cells by inhibiting the expression of p38 MAPK, thereby alleviating BPA-induced disruption of intestinal barrier function. These findings contributed to a better understanding of the mechanisms of BPA-induced intestinal barrier dysfunction and provided new insights into the prevention and treatment of BPA-induced intestinal diseases.

Decreased homoserine levels in metabolic syndrome

BACKGROUND AND AIMS

The pathogenesis Metabolic Syndrome (MetS), a common global problem, remains to be elucidated. As part of our exploratory metabolomics research we determined if homoserine levels are an early biomarker of nascent MetS.

METHODS

An exploratory study involving 28 patients with nascent MetS and 20 matched controls. Metabolites were studied from early morning urine samples and assayed by the NIH Western Metabolomics Center using gas chromatography time-of-flight mass spectrometry and were standardized to urine creatinine. All of the patients enrolled in the study had normal renal and hepatic function.

RESULTS

Patients with MetS had statistically significant increases in overall waist circumference, blood pressure, glucose, HOMA-IR, HbA1C in comparison to the control group. Additionally, increases in IL-1b, IL-6, TLR-4, endotoxin, and leptin were also seen in the MetS group subjects compared to the control group. The concentrations of homoserine were significantly decreased 3-fold in patients with MetS in comparison to the matched controls, p = 0.0027. Furthermore, levels of homoserine were inversely correlated to multiple biomarkers of inflammation and cardio-metabolic risk factors such as HbA1C, blood pressure, TLR-4, leptin, endotoxin, and SAT secreted fetuin A. In addition, homoserine was positively correlated with lysine and NAT.

CONCLUSIONS

In conclusion, low levels of homoserine could potentially contribute to the proinflammatory state in MetS.

Bisphenol A increases intestinal permeability through disrupting intestinal barrier function in mice

That an alteration of the intestinal permeability is associated with gut barrier function has been increasingly evident, which plays an important role in human and animal health. Bisphenol A (BPA), an industrial compound used worldwide, has recently been classified as an environmental pollutant. One of our earlier studies has demonstrated that BPA disrupts the intestinal barrier function by inducing apoptosis and inhibiting cell proliferation in the human colonic epithelial cells line. In this study, we investigated the effects of dietary BPA uptake on the colonic barrier function in mice, as well as the intestinal permeability. Dietary BPA uptake was observed to destroy the morphology of the colonic epithelium and increase the pathology score. The levels of endotoxin, diamine peroxidase, D-lactate, and zonulin were found to have been significantly elevated in both plasma and colonic mucosa. A decline in the number of intestinal goblet cells and in mucin 2 gene expression was observed in the mice belonging to the BPA group. The results of immunohistochemistry revealed that the expression of tight junction proteins (ZO-1, occludin, and claudin-1) in colonic epithelium of BPA mice decreased significantly, and their gene abundance was also inhibited. Moreover, dietary BPA uptake was also found to have significantly reduced colonic microbial diversity and altered microbial structural composition. The functional profiles of colonic bacterial community exhibited adverse effects of dietary BPA intake on the endocrine and digestive systems, as well as the transport and catabolism functions. Collectively, our study highlighted that dietary BPA increased the colonic permeability, and this effect was closely related to the disruption of intestinal chemistry and physical and biological barrier functions.

Original low birth weight deteriorates the hindgut epithelial barrier function in pigs at the growing stage

The deteriorative effect of low birth weight (LBW) on the mucosal permeability of the small intestine in piglets has been widely confirmed. However, whether the hindgut epithelial barrier function in LBW pigs is deteriorated during the growing stage is still unclear. Our study investigated differences in the hindgut epithelial barrier function between LBW and normal birth weight pigs during the growing stage (d 90). Our data demonstrated that the hindgut epithelium of LBW pigs has a high histopathological score, accompanied by decreased antioxidant capacity and increased apoptosis rate, as well as elevated expression and activity of caspase-3. In addition, the number of intestinal goblet cells and gene expression of mucin 2 were significantly down-regulated in LBW pigs. The expression of tight junction proteins (ZO-1 and occludin) was markedly inhibited by the LBW. The mRNA abundance of inflammatory cytokines such as TNF-α, IL-1β, and IL-8 was significantly increased in the hindgut mucosa of LBW pigs. Furthermore, our data revealed that LBW altered the intestinal microbial community in the hindgut mucosa of pigs. Collectively, these finding add to our understanding of the mechanisms responsible for hindgut epithelial barrier dysfunction in LBW pigs during the growing stage and facilitate the development of nutritional intervention strategies.-Tao, S., Bai, Y., Li, T., Li, N., Wang, J. Original low birth weight deteriorates the hindgut epithelial barrier function in pigs at the growing stage.

The protective effect of icariin and phosphorylated icariin against LPS-induced intestinal goblet cell dysfunction

In this study, we used LS174T cells as a model to investigate the protective effects of icariin and phosphorylated icariin on LPS-induced goblet cell dysfunction. Our results indicated that icariin and phosphorylated icariin increased the cell viability and decreased lactate dehydrogenase activity in LPS-treated LS174T cells. Icariin and phosphorylated icariin attenuated LPS-induced changes in mucin 2 synthesis and secretion. Besides, Icariin and phosphorylated icariin reduced the levels of ROS, MDA, and H₂O₂ and increased the activity of SOD, GPx, CAT, and T-AOC in LPS-treated LS174T cells. Moreover, the levels of IL-1β, IL-6, IL-8, and TNF-α were reduced in the Icariin and phosphorylated icariin group. Furthermore, Icariin and phosphorylated icariin decreased gene abundance or enzyme activity of Bip, XBP1, GRP78, CHOP, caspase-3, and caspase-4 in LPS-treated LS174T cells. Our data suggest that Icariin and phosphorylated icariin effectively attenuate LPS-induced intestinal goblet cell function damage through regulating oxidative stress, inflammation, apoptosis, and mucin expression.

The protective effect of icariin and phosphorylated icariin against LPS-induced intestinal epithelial cells injury

Icariin (ICA) and phosphorylated icariin (pICA) have excellent antiviral and antioxidant effects. However, whether ICA and pICA cause anti-LPS-induced intestinal damage remains unclear. In this study, we used Caco-2 cells as a model to investigate the protective effects of ICA and pICA on human colonic epithelial cells and explore their potential mechanisms. Our results indicated that ICA and pICA increased cell viability and decreased lactate dehydrogenase activity in Caco-2 cells. ICA and pICA also attenuated LPS-induced changes in intestinal epithelial cell permeability and reduced the levels of oxidative stress indicators, such as reactive oxygen species, malondialdehyde, and hydrogen peroxide, in Caco-2 cells. Antioxidant indicators, such as superoxide dismutase, glutathione peroxidase, catalase and total antioxidant capacity, were increased, while the levels of IL-1β, IL-6, IL-8 and TNF-α were reduced in the ICA and pICA groups. Furthermore, ICA and pICA decreased the gene abundance and enzyme activities of caspase-3, -8, -9 and -10 in Caco-2 cells. Our data suggest that ICA and pICA effectively attenuated LPS-induced changes in the oxidative stress, inflammation, apoptosis and intestinal permeability of intestinal epithelial cells. These findings provide new insight for treating LPS-induced intestinal injury.