Interleukin-1beta reduces galactose transport in intestinal epithelial cells in a NF-kB and protein kinase C-dependent manner

Indigo alleviates psoriasis through the AhR/NF-κB signaling pathway: an in vitro and in vivo study

Background

Psoriasis is a chronic inflammatory skin disease. A strong association between the AhR/ NFκB axis and the inflammatory response in psoriasis. Indigo (IDG) has demonstrated significant anti-inflammatory properties. This study aimed to assess the anti-psoriatic efficacy of IDG while investigating the underlying mechanisms involved.

Methods

In the in vitro experiments, cell viability was assessed using the CCK-8. qRT-PCR was employed to measure the mRNA levels of NF-κB, TNF-α, IL-1β, AhR, and CYP1A1. Western blotting was conducted to examine alterations in cytoplasmic and nuclear AhR protein levels. Additionally, an IDG nanoemulsion (NE) cream was prepared for the in vivo experiments. A psoriasis-like skin lesion mice model was induced using IMQ (62.5 mg/day for 7 days). The severity of psoriasis was evaluated using PASI, and skin lesions were scored while epidermal thickness was assessed via HE staining. The expression of inflammatory markers, including IL-6, IL-13, IL-17A, MCP-1, and TNF-α, was detected in skin lesions using Luminex. The levels of CYP1A1, p65, and p-p65 proteins were determined by Western blotting.

Results

LPS stimulation significantly elevated TNF-α, IL-6, and NF-κB mRNA levels, which were notably reduced by IDG treatment. Additionally, IDG significantly enhanced the expression of AhR and CYP1A1 mRNA. Further investigation revealed that IDG facilitated AhR translocation from the cytoplasm to the nucleus. In the IMQ-induced psoriasis-like mouse model, IDG NE substantially ameliorated the severity of skin lesions. Moreover, IDG NE treatment reduced the upregulation of inflammatory cytokines such as IL-6, IL-17A, MCP-1, and TNF-α in IMQ-induced skin lesions. It was also observed that IDG NE treatment increased CYP1A1 protein expression while inhibiting p65 and p-p65 protein expression.

Conclusion

IDG emerges as a promising treatment for psoriasis, demonstrating effective therapeutic outcomes. Its mechanism of action is likely linked to the modulation of the AhR/NFκB signaling pathway.

LPS-squalene interaction on D-galactose intestinal absorption

The dynamic and complex interactions between enteric pathogens and the intestinal epithelium often lead to disturbances in the intestinal barrier, altered fluid, electrolyte, and nutrient transport and can produce an inflammatory response. Lipopolysaccharide (LPS) is a complex polymer forming part of the outer membrane of Gram-negative bacteria. On the other hand, squalene is a triterpene present in high levels in the extra-virgin olive oil that has beneficial effects against several diseases and it has also anti-oxidant and anti-inflammatory properties. The aim of this work was to study whether the squalene could eliminate the LPS effect on D-galactose intestinal absorption in rabbits and Caco-2 cells. The results have shown that squalene reduced the effects of LPS on sugar absorption. High LPS doses increased D-galactose uptake through via paracellular but also decreased the active sugar transport because the SGLT1 levels were diminished. However, the endotoxin effect on the paracellular way seemed to be more important than on the transcellular route. At the same time, an increased in RELM-β expression was observed. This event could be related to inflammation and cause a decrease in SGLT1 levels. In addition, MLCK protein is also increased by LPS which could lead to an increase in sugar transport through tight junctions. At low doses, the LPS could inhibit SGLT1 intrinsic activity. Bioinformatic studies by docking confirm the interaction between LPS-squalene as well as occur through MLCK and SGLT-1 proteins.

Cardiotrophin-1 decreases intestinal sugar uptake in mice and in Caco-2 cells

AIM

Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT-1 treatment on intestinal sugar absorption in different experimental models.

METHODS

rCT-1 effects on α-Methyl-D-glucoside uptake were assessed in everted intestinal rings from wild-type and CT-1(-/-) mice and in Caco-2 cells. rCT-1 actions on SGLT-1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot.

RESULTS

In vivo administration (0.2 mg kg(-1) ) of rCT-1 caused a significant decrease on α-Methyl-D-glucoside uptake in everted intestinal rings from wild-type and CT-1(-/-) mice after short-term and long-term treatments. Similarly, in vitro treatment (1-50 ng mL(-1) ) with rCT-1 reduced α-Methyl-D-glucoside uptake in everted intestinal rings. In Caco-2 cells, rCT-1 treatment (20 ng mL(-1) , 1 and 24 h) lowered apical uptake of α-Methyl-D-glucoside in parallel with a decrease on SGLT-1 protein expression. rCT-1 promoted the phosphorylation of STAT-3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre-treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT-1 on α-Methyl-D-glucoside uptake. AICAR also prevented the inhibition of SGLT-1 observed in rCT-1-treated cells.

CONCLUSIONS

CT-1 inhibits intestinal sugar absorption by the reduction of SGLT-1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti-obesity properties of CT-1.

Involvement of intracellular signaling in the IL-1β inhibitory effect on fructose intestinal absorption

A variety of bacteria and their excreted/secreted products having direct effects on epithelial ion transport and permeability and the release of cytokines during bacterial infection may impact directly on epithelial function. Interleukin-1β (IL-1β) is a pleiotropic cytokine that affects the intestinal absorption of nutrients. The aim of this work was to study the intracellular signaling pathways involved in the inhibitory effect of IL-1β on D-fructose intestinal transport in rabbit jejunum and Caco-2 cells. The results show that the cytokine inhibitory effect was completely reversed in presence of proteasome or PKC selective inhibitors in IL-1β treated rabbits. In addition, the activation of PI3K abolished the IL-1β effect. Likewise, these results were confirmed in Caco-2 cells. In addition, p-PI3K expression was increased by IL-1β-treatment whereas the expression of p-PKCα was not significantly affected. In summary, the results suggest that IL-1β could regulate the activation of pPKCα 73, pPI3K 55, and NF-kB proteins. These events could exert an inhibitory effect on fructose intestinal absorption by a modification of GLUT5 insertion to brush-border membrane and/or the functional transporter activity. This effect is independent of hormonal milieu and nervous stimuli.

Induction of heme oxygenase-1 attenuates lipopolysaccharide-induced inflammasome activation in human gingival epithelial cells

Interleukin-1β (IL-1β) is a pathogenic factor for the destruction of periodontal tissue in periodontitis. The processing of IL-1β is regulated by cytosolic machinery termed as the inflammasome, which recruits and activates caspase-1 and then cleaves pro-IL-1β to produce mature IL-1β. Porphyromonas gingivalis (P. gingivalis) infection and lipopolysaccharide (LPS) have been shown to activate the NLRP3 inflammasome and stimulate IL-1β production in human oral cells. Heme oxygenase-1 (HO-1) is an ubiquitous cytoprotective enzyme. The products of HO-1 exhibit protective biological activities, including antioxidant and anti-inflammatory effects. In the present study, we investigated the hypothesis that the induction of HO-1 inhibits the activation of the inflammasome and protects against LPS-induced inflammatory damage in cultured human gingival epithelial cells (GECs). Our results revealed that LPS induced the overexpression of the inflammasome components, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1, by western blot analysis. Co-immunoprecipitation analysis indicated that LPS increased the binding of NLRP3 and ASC, and confocal imaging revealed that LPS increased the immunostaining and co-localization of ASC and caspase-1, indicating that LPS enhanced the assembly/formation of the inflammasome components. Hemin, a potent HO-1 inducer, blocked the LPS-induced overexpression and the formation of the NLRP3 inflammasome. Furthermore, hemin also inhibited the LPS-induced increase in the production of IL-1β, as shown by enzyme-linked immunosorbent assay and blocked the nuclear translocation of pro-inflammatory nuclear factor-κB (NF-κB), as shown by confocal assays. As a result, hemin protected the cells from LPS-induced damage, which was demonstrated by the immunostaining pattern of the cell junction protein, E-cadherin. LPS produced a disturbed staining pattern of E-cadherin, suggesting the disruption of epithelial integrity, which was abolished in the hemin-treated cells. In conclusion, our data demonstrate that the induction of HO-1 by hemin attenuates LPS-induced inflammatory damage in human GECs through the inhibition of inflammasome activation.