TNF-α-induced up-regulation of pro-inflammatory cytokines is reduced by phosphatidylcholine in intestinal epithelial cells

Abstract

BackgroundPhosphatidylcholine (PC) is a major lipid of the gastrointestinal mucus layer. We recently showed that mucus from patients suffering from ulcerative colitis has low levels of PC. Clinical studies reveal that the therapeutic addition of PC to the colonic mucus using slow release preparations is beneficial. The positive role of PC in this disease is still unclear; however, we have recently shown that PC has an intrinsic anti-inflammatory property. It could be demonstrated that the exogenous application of PC inhibits membrane-dependent actin assembly and TNF-α-induced nuclear NF-κB activation. We investigate here in more detail the hypothesis that the exogenous application of PC has anti-inflammatory properties.MethodsPC species with different fatty acid side chains were applied to differentiated and non-differentiated Caco-2 cells treated with TNF-α to induce a pro-inflammatory response. We analysed TNF-α-induced NF-κB-activation via the transient expression of a NF-κB-luciferase reporter system. Pro-inflammatory gene transcription was detected with the help of a quantitative real time (RT)-PCR analysis. We assessed the binding of TNF-α to its receptor by FACS and analysed lipid rafts by isolating detergent resistant membranes (DRMs).ResultsThe exogenous addition of all PC species tested significantly inhibited TNF-α-induced pro-inflammatory signalling. The expression levels of IL-8, ICAM-1, IP-10, MCP-1, TNF-α and MMP-1 were significantly reduced after PC pre-treatment for at least two hours. The effect was comparable to the inhibition of NF-kB by the NF-kB inhibitor SN 50 and was not due to a reduced binding of TNF-α to its receptor or a decreased surface expression of TNF-α receptors. PC was also effective when applied to the apical side of polarised Caco-2 cultures if cells were stimulated from the basolateral side. PC treatment changed the compartmentation of the TNF-α-receptors 1 and 2 to DRMs.ConclusionPC induces a prolonged inhibition of TNF-α-induced pro-inflammatory signalling. This inhibition may be caused by a shift of the TNF-α receptors at the surface to lipid rafts. Our results may offer a potential molecular explanation for the positive role of PC seen in clinical studies for the treatment of ulcerative colitis.

The probiotic Lactobacillus plantarum counteracts TNF-α-induced downregulation of SMCT1 expression and function

“…With regard to the mechanisms of counteracting the TNF-␣ effects, it is unlikely that the soluble factors in the LP-CS prevented the cytokine from binding to their receptors. This is because the supernatant was added apically, whereas TNF-␣ was added to the basolateral medium, as the receptors for TNF-␣ are known to be localized to the basolateral membranes of polarized IECs (32,43). Therefore, the activity of the LP-CS to counteract the TNF-␣ effects on SMCT1 expression and function appears to involve mechanisms independent of TNF-␣ binding to its receptors.…”

Neuroprotective effects of phosphatidylcholine and L-alpha-glycerylphosphorylcholine in experimental inflammation

“…GPC acts as a PC precursor (Gallazzini and Burg 2009), and the increased uptake of membrane-forming phospholipids, including PC, proved to exert an anti-infl ammatory infl uence in other experimental studies (Chao et al 1995, El-Hariri et al 1992, Er ő s et al 2009). Previous investigation revealed that PC treatment prevented microglia accumulation in the hippocampus (T ő k é s et al 2011), and further evidence for the mechanism of action is provided by recent in vitro fi ndings of an anti-TNF -a eff ect and specifi c inhibition of the Toll-like receptor 4-dependent infl ammatory pathway (Ishikado et al 2009, Treede et al 2009.…”

Physiological Significance of Lysophospholipids that Act on the Lumen Side of Mammalian Lower Digestive Tracts

“…38) Luminal applications of PC and LPC were reported to exert an anti-inflammatory effect on rat intestinal mucosa by reducing the up-regulation of proinflammatory cytokines induced by tumor necrosis factor-α (TNF-α)/nuclear factor κB, possibly through its incorporation into the lipid raft of the plasma membranes. 39) The shift in the phospholipid composition of the gastric mucus toward an increased ratio of LPC to PC might be induced by PLA 2 activity in humans infected with Helicobacter pylori, and thus impair the ability of the barrier to protect against bacterial pathogens and high-molecular weight components in foods. 40) Pretreatment with PC with one or two polyunsaturated fatty acyl groups prevented cold restraint stress-induced 41) and ethanol-and indomethacin-induced gastric ulcers in rats.…”