TRPV1 is a Ca2+-permeable channel mostly studied as a pain receptor in sensory neurons. However, its role in other cell types is poorly understood. Here, we demonstrate that TRPV1 is functionally expressed in CD4+ T cells where it acts as a non-store-operated Ca2+ channel and contributes to T cell receptor (TCR)-induced Ca2+ influx, TCR signaling and T cell activation. In models of T cell-mediated colitis, TRPV1 promotes colitogenic T cell responses and intestinal inflammation. Furthermore, genetic and pharmacological inhibition of TRPV1 in human CD4+ T cells recapitulates the phenotype of murine Trpv1−/− CD4+ T cells. These findings suggest that TRPV1 inhibition could represent a new therapeutic strategy to restrain proinflammatory T cell responses.

TLR signaling is essential for intestinal tumorigenesis in Apcmin/+ mice, but the mechanisms by which this protein enhances tumor growth are unknown. Here we show that the Microflora-MyD88-ERK signaling in intestinal epithelial cells (IEC) promotes tumorigenesis by increasing the stability of the c-myc oncoprotein. Activation of ERK phosphorylates c-myc that prevents its ubiquitination and its subsequent proteasomal degradation. Accordingly, Apcmin/+/Myd88-/- mice display reduced levels of pERK and c-myc proteins in IEC, and a low incidence of IEC tumors. A MyD88-independent activation of ERK by EGF increases pERK and c-myc levels and restores the Min phenotype in Apcmin/+/Myd88-/- mice. Administration of an ERK inhibitor suppressed intestinal tumorigenesis in EGF-treated Apcmin/+/Myd88-/- and in Apcmin/+ mice and increased their survival. Our data reveal a new facet of oncogene-environment interaction, where the microflora-induced TLR activation regulates the expression of an oncogene that leads to IEC tumor growth in a susceptible host.

Objective Transient Receptor Potential Ankyrin-1 (TRPA1) and Vanilloid-1 (TRPV1) are calcium (Ca2+)-permeable ion channels mostly known as pain receptors in sensory neurons. However, growing evidence suggests their crucial involvement in the pathogenesis of IBD. We explored the possible contribution of TRPA1 and TRPV1 to T cell-mediated colitis. Design We evaluated the role of Trpa1 gene deletion in two models of experimental colitis (i.e., interleukin-10 knockout and T cell adoptive transfer models). We performed electrophysiological and Ca2+ imaging studies to analyze TRPA1 and TRPV1 functions in CD4+ T cells. We used genetic and pharmacological approaches to evaluate TRPV1 contribution to the phenotype of Trpa1−/− CD4+ T cells. We also analyzed TRPA1 and TRPV1 gene expression and TRPA1+TRPV1+ T cell infiltration in colonic biopsies from IBD patients. Results We identified a protective role for TRPA1 in T cell-mediated colitis. We demonstrated the functional expression of TRPA1 on the plasma membrane of CD4+ T cells and identified that Trpa1−/− CD4+ T cells have increased T-cell receptor (TCR)-induced Ca2+ influx, activation profile and differentiation into Th1-effector cells. This phenotype was abrogated upon genetic deletion or pharmacological inhibition of the TRPV1 channel in mouse and human CD4+ T cells. Finally, we found differential regulation of TRPA1 and TRPV1 gene expression as well as increased infiltration of TRPA1+TRPV1+ T cells in the colon of IBD patients. Conclusions Our study indicates that TRPA1 inhibits TRPV1 channel activity in CD4+ T cells, and consequently restrains CD4+ T cell activation and colitogenic responses. These findings may therefore have therapeutic implications for human IBD.

Cysteine proteinases are key virulence factors of the protozoan parasite Entamoeba histolytica. We have shown that cysteine proteinases play a central role in tissue invasion and disruption of host defenses by digesting components of the extracellular matrix, immunoglobulins, complement, and cytokines. Analysis of the E. histolytica genome project has revealed more than 40 genes encoding cysteine proteinases. We have focused on E. histolytica cysteine proteinase 1 (EhCP1) because it is one of two cysteine proteinases unique to invasive E. histolytica and is highly expressed and released. Recombinant EhCP1 was expressed in Escherichia coli and refolded to an active enzyme with a pH optimum of 6.0. We used positional-scanning synthetic tetrapeptide combinatorial libraries to map the specificity of the P1 to P4 subsites of the active site cleft. Arginine was strongly preferred at P2, an unusual specificity among clan CA proteinases. A new vinyl sulfone inhibitor, WRR483, was synthesized based on this specificity to target EhCP1. Recombinant EhCP1 cleaved key components of the host immune system, C3, immunoglobulin G, and pro-interleukin-18, in a time-and dose-dependent manner. EhCP1 localized to large cytoplasmic vesicles, distinct from the sites of other proteinases. To gain insight into the role of secreted cysteine proteinases in amebic invasion, we tested the effect of the vinyl sulfone cysteine proteinase inhibitors K11777 and WRR483 on invasion of human colonic xenografts. The resultant dramatic inhibition of invasion by both inhibitors in this human colonic model of amebiasis strongly suggests a significant role of secreted amebic proteinases, such as EhCP1, in the pathogenesis of amebiasis.The intestinal protozoan parasite Entamoeba histolytica is the etiologic agent of amebic colitis and liver abscess, which cause high rates of morbidity and mortality worldwide (49). The mechanism by which Entamoeba histolytica is able to invade and damage the host's target tissues has been the subject of intense research. Several virulence factors have been identified, including secreted cysteine proteinases (39, 42). These amebic enzymes have been implicated in the in vitro cytopathology of cell monolayers (20, 23), which correlates with the observed separation of colonic epithelial cells before invasion (51). Other correlates with invasion include the ability of cysteine proteinases to degrade extracellular matrix components (19) and colonic mucin (31, 32). Furthermore, cysteine proteinases enable E. histolytica to evade the host's immune defenses by activating and locally depleting complement (43), and by degrading anaphylotoxins C3a and C5a (41), human immunoglobulin G (IgG) (53), human IgA (21), and interleukin-18 (IL-18) (37).The recent completion of the Entamoeba histolytica genome project has revealed the presence of at least 40 genes encoding cysteine proteinases (25). Of all the cysteine proteinase genes, only ehcp1 and ehcp5 are unique to E. histolytica, as their orthologs are either absent (ehcp1) or nonfuncti...

Background: STAT3 suppresses carcinogenesis of intestinal tumors in Apc min mice. Results: STAT3 suppresses expression of SNAI in intestinal epithelium by regulating GSK3␤ activity. Conclusion: STAT3 induces degradation of SNAI by promoting GSK3␤ activity and thereby suppresses adenoma-to-adenocarcinoma transition in Apc min mice. Significance: Our data provide a new insight into the role of STAT3 in colorectal cancer biology.