Docosahexaenoic acid alleviates cell injury and improves barrier function by suppressing necroptosis signalling in TNF-α-challenged porcine intestinal epithelial cells

Bioactive lipids in the skin barrier mediate its functionality in health and disease

Our skin protects us from external threats including ultraviolet radiation, pathogens and chemicals, and prevents excessive trans-epidermal water loss. These varied activities are reliant on a vast array of lipids, many of which are unique to skin, and that support physical, microbiological and immunological barriers. The cutaneous physical barrier is dependent on a specific lipid matrix that surrounds terminally-differentiated keratinocytes in the stratum corneum. Sebum- and keratinocyte-derived lipids cover the skin's surface and support and regulate the skin microbiota. Meanwhile, lipids signal between resident and infiltrating cutaneous immune cells, driving inflammation and its resolution in response to pathogens and other threats. Lipids of particular importance include ceramides, which are crucial for stratum corneum lipid matrix formation and therefore physical barrier functionality, fatty acids, which contribute to the acidic pH of the skin surface and regulate the microbiota, as well as the stratum corneum lipid matrix, and bioactive metabolites of these fatty acids, involved in cell signalling, inflammation, and numerous other cutaneous processes. These diverse and complex lipids maintain homeostasis in healthy skin, and are implicated in many cutaneous diseases, as well as unrelated systemic conditions with skin manifestations, and processes such as ageing. Lipids also contribute to the gut-skin axis, signalling between the two barrier sites. Therefore, skin lipids provide a valuable resource for exploration of healthy cutaneous processes, local and systemic disease development and progression, and accessible biomarker discovery for systemic disease, as well as an opportunity to fully understand the relationship between the host and the skin microbiota. Investigation of skin lipids could provide diagnostic and prognostic biomarkers, and help identify new targets for interventions. Development and improvement of existing in vitro and in silico approaches to explore the cutaneous lipidome, as well as advances in skin lipidomics technologies, will facilitate ongoing progress in skin lipid research.

(-)-Epigallocatechin-3-gallate promotes intestinal epithelial proliferation and barrier function after ischemia/reperfusion injury via activation of Nurr1

CONTEXT

(-)-Epigallocatechin-3-gallate (EGCG) is involved in cell proliferation and ischemia/reperfusion (I/R) injury of several organs.

OBJECTIVE

To identify the role of EGCG in intestinal epithelial proliferation and barrier exposed to I/R injury.

MATERIAL AND METHODS

Fifty Sprague-Dawley rats were divided into sham, I/R, I/R + EGCG (12.5 mg/kg), I/R + EGCG (25 mg/kg) and I/R + EGCG (50 mg/kg). I/R group rats were subjected to intestinal ischemia for 1 h and 6 h reperfusion. The rats were supplemented with EGCG 12.5, 25 and 50 mg/kg daily for 3 days via intraperitoneal injection before surgery. We used IEC-6 to expose to hypoxia/reoxygenation (H/R) injury to mimic I/R in vivo. IEC-6 cells were divided into control, H/R and H/R + EGCG (40 μmol/L). The effects of EGCG and its mechanism was explored.

RESULTS

Pharmacological treatment with EGCG notably improves intestinal epithelial proliferation (12.5 mg/kg, 1.74-fold; 25 mg/kg, 2.93-fold, and 50 mg/kg, 4.33-fold) and barrier function after I/R injury. EGCG promoted cell proliferation (2.99-fold) and increased the expression of occludin (2.36-fold) and ZO-1 (1.64-fold) in IEC-6 cells after H/R injury. EGCG promoted proliferation of IEC-6 cells with ED50 values of 18.16 μmol/L. Further investigations indicated that EGCG activated Nurr1 expression in intestine after I/R injury. EGCG promote cell proliferation and increased the expression of occludin and ZO-1 in IEC-6 cells after H/R injury were abrogated in the knockdown of Nurr1 by siRNA.

DISCUSSION AND CONCLUSION

Our findings indicate that EGCG promotes intestinal epithelial cell proliferation and barrier function after I/R injury in vitro and in vivo via activation of Nurr1.

Macrocystis pyrifera Lipids Reduce Cytokine-Induced Pro-Inflammatory Signalling and Barrier Dysfunction in Human Keratinocyte Models

Atopic dermatitis is a chronic condition where epidermal barrier dysfunction and cytokine production by infiltrating immune cells exacerbate skin inflammation and damage. A total lipid extract from Macrocystis pyrifera, a brown seaweed, was previously reported to suppress inflammatory responses in monocytes. Here, treatment of human HaCaT keratinocytes with M. pyrifera lipids inhibited tumour necrosis factor (TNF)-α induced TNF receptor-associated factor 2 and monocyte chemoattractant protein (MCP)-1 protein production. HaCaT cells stimulated with TNF-α, interleukin (IL)-4, and IL-13 showed loss of claudin-1 tight junctions, but little improvement was observed following lipid pre-treatment. Three-dimensional cultures of HaCaT cells differentiated at the air-liquid interface showed increased MCP-1 production, loss of claudin-1 tight junctions, and trans-epidermal leakage with TNF-α, IL-4, and IL-13 stimulation, with all parameters reduced by lipid pre-treatment. These findings suggest that M. pyrifera lipids have anti-inflammatory and barrier-protective effects on keratinocytes, which may be beneficial for the treatment of atopic dermatitis or other skin conditions.

Selenium-enriched Cardamine violifolia protects against sepsis-induced intestinal injury by regulating mitochondrial fusion in weaned pigs

Sepsis is a life-threatening organ dysfunction caused by the dysregulated response of the host to an infection, and treatments are limited. Recently, a novel selenium source, selenium-enriched Cardamine violifolia (SEC) has attracted much attention due to its anti-inflammatory and antioxidant properties, but little is known about its role in the treatment of sepsis. Here, we found that SEC alleviated LPS-induced intestinal damage, as indicated by improved intestinal morphology, and increased disaccharidase activity and tight junction protein expression. Moreover, SEC ameliorated the LPS-induced release of pro-inflammatory cytokines, as indicated by decreased IL-6 level in the plasma and jejunum. Moreover, SEC improved intestinal antioxidant functions by regulating oxidative stress indicators and selenoproteins. In vitro, TNF-α-challenged IPEC-1 cells were examined and showed that selenium-enriched peptides, which are the main functional components extracted from Cardamine violifolia (CSP), increased cell viability, decreased lactate dehydrogenase activity and improved cell barrier function. Mechanistically, SEC ameliorated LPS/TNF-α-induced perturbations in mitochondrial dynamics in the jejunum and IPEC-1 cells. Moreover, CSP-mediated cell barrier function is primarily dependent on the mitochondrial fusion protein MFN2 but not MFN1. Taken together, these results indicate that SEC mitigates sepsis-induced intestinal injury, which is associated with modulating mitochondrial fusion.

Omega-3 polyunsaturated fatty acids alleviate early brain injury after traumatic brain injury by inhibiting neuroinflammation and necroptosis

Presently, traumatic brain injury (TBI) is a leading contributor to disability and mortality that places a considerable financial burden on countries all over the world. Docosahexaenoic acid and eicosapentaenoic acid are two kinds of omega-3 polyunsaturated fatty acids (ω-3 PUFA), both of which have been shown to have beneficial biologically active anti-inflammatory and antioxidant effects. However, the neuroprotective effect of ω-3 PUFA in TBI has not been proven, and its probable mechanism remains obscure. We suppose that ω-3 PUFA can alleviate early brain injury (EBI) via regulating necroptosis and neuroinflammation after TBI. This research intended to examine the neuroprotective effect of ω-3 and its possible molecular pathways in a C57BL/6 mice model of EBI caused by TBI. Cognitive function was assessed by measuring the neuronal necroptosis, neuroinflammatory cytokine levels, brain water content, and neurological score. The findings demonstrate that administration of ω-3 remarkably elevated neurological scores, alleviated cerebral edema, and reduced inflammatory cytokine levels of NF-κB, interleukin-1β (IL-1β), IL-6, and TNF-α, illustrating that ω-3 PUFA attenuated neuroinflammation, necroptosis, and neuronal cell death following TBI. The PPARγ/NF-κB signaling pathway is partially responsible for the neuroprotective activity of ω-3. Collectively, our findings illustrate that ω-3 can alleviate EBI after TBI against neuroinflammation and necroptosis.

Effects of TolC on the pathogenicity of porcine extraintestinal pathogenic Escherichia coli

Extraintestinal pathogenic Escherichia coli (ExPEC) is a well-known critical pathogenic zoonosis that causes extraintestinal infections in humans and animals by affecting their immune organs. Recently, research on the outer membrane protein of E. coli, tolerant colicin (TolC), a virulent protein in the formation of the ExPEC efflux pump, has been an attractive subject. However, the pathogenic mechanisms remain unclear. This study aimed to explore the role of TolC in the pathogenesis of the ExPEC strain PPECC42; a complementation strain (Cm-TolC) and an isogenic mutant (ΔTolC) were constructed. Loss of TolC drastically impaired the virulence of ExPEC in an experimental mouse model. ΔTolC showed a substantial decrease in the porcine aortic vascular endothelial cell (PAVEC) adherence, invasion, and pro-inflammatory response, in contrast to that of the wild type, with a reduced survival ratio in both the bacterial load and whole blood in mice. ΔTolC also showed decreased expression of necroptosis signals such as receptor-interacting protein kinase 1, phosphorylated mixed-lineage kinase domain-like protein, and mitochondrial proteins such as phosphoglycerate mutase family member 5. Our data suggest that TolC is closely associated with ExPEC pathogenesis. These results provide scientific grounds for exploring the potential of TolC as an effective drug target for controlling ExPEC infection, screening new inhibitors, and developing new drugs. This will allow for further prevention and control of ExPEC infection.

Kaempferol attenuates diquat-induced oxidative damage and apoptosis in intestinal porcine epithelial cells

Kaempferol, a flavonol component of plants, is well-known to exhibit multiple bioactivities, such as anti-oxidative and anti-apoptotic effects. However, the underlying mechanisms responsible for the beneficial effects remain elusive. This study was conducted to test the hypothesis that kaempferol attenuated diquat-induced oxidative damage and intestinal barrier dysfunction by ameliorating oxidative damage and apoptosis in intestinal porcine epithelial cells. Compared with the control group, diquat treatment led to enhanced intracellular ROS production, increased mitochondrial depolarization, and apoptosis, which were accompanied by cell cycle arrest at the G1 phase, reduced cell migration, and disrupted intestinal epithelial barrier function. These effects triggered by diquat were reversed by kaempferol. Further study showed that the protective effect of kaempferol was associated with an enhanced mRNA level of genes related to cell cycle progression (cyclin D1, CDK4, and E2F1) and genes implicated in the anti-oxidant system (GSR, GSTA4, and HO-1), up-regulated abundance of tight junctions (ZO-1, ZO-2, occludin, and claudin-4), as well as enhanced Nrf2, an anti-oxidant transcription factor. In conclusion, we revealed a functional role of kaempferol in the intestinal barrier. Ingestion of kaempferol-rich foods might be a potential strategy to improve the integrity and function of enterocytes.