Induction of Monocyte Chemotactic Protein 1 in Colonic Epithelial Cells by Entamoeba histolytica Is Mediated via the Phosphatidylinositol 3-Kinase/p65 Pathway

Abstract

The role intestinal epithelial cells play in the pathogenesis of amebic colitis is poorly understood. Herein, we demonstrate that secreted and soluble ameba (Entamoeba histolytica) proteins (SAP) induce expression of the chemoattractant monocyte chemotactic protein (MCP) in the colonic epithelial cell lines Caco-2, T84, and LS174T. MCP-1 mRNA induction was both dose and time dependent, with peak induction occurring at 8 h and with 100 g/ml of SAP. Significant increase in MCP-1 protein expression was observed after 12 h. SAP failed to activate any of the mitogen-activated protein kinase pathways or IB kinase activity. Moreover, inhibiting the classical pathway of NF-B activation did not affect SAP-induced MCP-1 expression. Instead, we find that SAP-induced MCP-1 expression is dependent on posttranslational modification of the NFB p65 subunit. SAP induced phosphorylation of p65 and enhanced NF-B transcriptional activity, which are phosphatidylinositol 3-kinase (PI3 kinase) dependent. Treatment with PI3 kinase inhibitor LY290004 significantly abrogated the activation of Akt, p65, and MCP-1 mRNA induction. We conclude that colonic epithelial cells play a role in the initiation of inflammation by secreting chemokines in response to soluble ameba components.Entamoeba histolytica is an enteric protozoan parasite that is responsible for the disease amebiasis in humans. The disease affects 50 million people globally and is the fourth leading parasitic cause of death (14). Host inflammatory responses are thought to play an important role in the pathogenesis of intestinal amebiasis. However, the roles of intestinal epithelial cells (IEC) and mediators of colonic inflammation have not been fully elucidated.Invasive amebiasis is characterized by infiltration of immune cells such as leukocytes and lymphocytes (5). It has not been well established if this cellular infiltration is a cause or consequence of inflammation. The parasite has previously been shown to elicit interleukin-8 (IL-8) production from colonic epithelial cells (4, 15). IL-8 is a potent chemoattractant primarily for neutrophils, and its secretion alone does not explain the homing of other immune cells such as monocytes and lymphocytes seen in the amebic lesions (5). Monocyte chemotactic protein 1 (MCP-1) belongs to a group of C-C or ␤-chemokines, is produced by a variety of cells, including IEC, and is potently chemotactic for monocytes, lymphocytes, and basophils (10). Recently, amebic infection in a human intestinal xenograft model has been shown to increase a number of genes in the epithelial cells, including the MCP-1 gene (16). However, the mechanism of induction is not known and also it is not clear if ameba components themselves can directly induce this chemokine.The transcription factor NF-B regulates a number of genes involved in immune response and inflammation. It is composed of two subunits, most commonly of p65 and P50. Only p65 has the transactivating domains and hence is critical for NF-B activity. NF-B is activated by different pathways, includ...

Prostaglandin E2Produced byEntamoeba histolyticaBinds to EP4 Receptors and Stimulates Interleukin-8 Production in Human Colonic Cells

“…It has been found that both the C-X-C and C-C members of the chemokine family of proteins, as well as the proinflammatory cytokines IL-1␤, IL-6, and tumor necrosis factor alpha and the cell growth factor GM-CSF, are released by epithelial cells after bacterium-enterocyte interactions (27). Recently, we showed that in colonic epithelial cells, monocyte chemoattractant protein 1 is secreted in response to soluble ameba components via the phosphatidylinositol 3-kinase/P65 pathway (16). The release of this cytokine in vivo by the epithelium would be an effective means of initiating a mucosal inflammatory response.…”

Helicobacter pylori-Induced Interleukin-12 p40 Expression

“…There was no significant change in total p38 protein levels in VacAtreated Jurkat cells. Recent evidence suggests that the PI3K/ Akt pathway also modulates the NF-B signaling pathway (27). Therefore, Akt activation was checked with antibodies that specifically recognize phosphorylated Akt.…”

Fulminant Amoebic Colitis: Role of the Innate and Adaptive Immune Responses

“…The trophozoites of E. histolytica are capable of inhibiting the action of complement proteins Que et al, 2003;Que & Reed, 2000). c. Inflammation is induced by cytokines of colonic epithelial cells (Eckmann et al, 1995;Kammanadiminti et al, 2007;Seydel et al, 1997;Yu & Chadee, 1997). d. A type 2 (Th2) immune response predominates during amebic colitis.…”

“…Various researchers have queried about the role played by the immune response in this pathology (Ventura-Juárez et al, 2002. For instance, perhaps the inflammatory response has the objective of eliminating the amebas, only to end up participating in the pathogenesis (Kammanadiminti et al, 2007;Seydel et al, 1998).…”