Epithelial presenilin-1 drives colorectal tumour growth by controlling EGFR-COX2 signalling.

OBJECTIVE: Psen1 was previously characterised as a crucial factor in the pathogenesis of neurodegeneration in patients with Alzheimer's disease. Little, if any, is known about its function in the gut. Here, we uncovered an unexpected functional role of Psen1 in gut epithelial cells during intestinal tumourigenesis. DESIGN: Human colorectal cancer (CRC) and control samples were investigated for PSEN1 and proteins of theγ-secretase complex. Tumour formation was analysed in the AOM-DSS and Apc min/+ mouse models using newly generated epithelial-specific Psen1 deficient mice. Psen1 deficient human CRC cells were studied in a xenograft tumour model. Tumour-derived organoids were analysed for growth and RNA-Seq was performed to identify Psen1-regulated pathways. Tumouroids were generated to study EGFR activation and evaluation of the influence of prostanoids. RESULTS: PSEN1 is expressed in the intestinal epithelium and its level is increased in human CRC. Psen1-deficient mice developed only small tumours and human cancer cell lines deficient in Psen1 had a reduced tumourigenicity. Tumouroids derived from Psen1-deficient Apc min/+ mice exhibited stunted growth and reduced cell proliferation. On a molecular level, PSEN1 potentiated tumour cell proliferation via enhanced EGFR signalling and COX-2 production. Exogenous administration of PGE2 reversed the slow growth of PSEN1 deficient tumour cells via PGE2 receptor 4 (EP4) receptor signalling. CONCLUSIONS: Psen1 drives tumour development by increasing EGFR signalling via NOTCH1 processing, and by activating the COX-2-PGE2 pathway. PSEN1 inhibition could be a useful strategy in treatment of CRC.

Loss of Survivin in Intestinal Epithelial Progenitor Cells Leads to Mitotic Catastrophe and Breakdown of Gut Immune Homeostasis.

A tightly regulated balance of proliferation and cell death of intestinal epithelial cells (IECs) is essential for maintenance of gut homeostasis. Survivin is highly expressed during embryogenesis and in several cancer types, but little is known about its role in adult gut tissue. Here, we show that Survivin is specifically expressed in transit-amplifying cells and Lgr5(+) stem cells. Genetic loss of Survivin in IECs resulted in destruction of intestinal integrity, mucosal inflammation, and death of the animals. Survivin deletion was associated with decreased epithelial proliferation due to defective chromosomal segregation. Moreover, Survivin-deficient animals showed induced phosphorylation of p53 and H2AX and increased levels of cell-intrinsic apoptosis in IECs. Consequently, induced deletion of Survivin in Lgr5(+) stem cells led to cell death. In summary, Survivin is a key regulator of gut tissue integrity by regulating epithelial homeostasis in the stem cell niche.

IL-9 and its receptor are predominantly involved in the pathogenesis of UC.

OBJECTIVE: Several pathogenic roles attributed over the past two decades to either T helper (Th)1 or Th2 cells are increasingly becoming associated with interleukin (IL)-17 and most recently IL-9 signalling. However, the implication of IL-9 in IBD has not been addressed so far. DESIGN: We investigated the expression of IL-9 and IL-9R by using peripheral blood, biopsies and surgical samples. We addressed the functional role of IL-9 signalling by analysis of downstream effector proteins. Using Caco-2 cell monolayers we followed the effect of IL-9 on wound healing. RESULTS: IL-9 mRNA expression was significantly increased in inflamed samples from patients with UC as compared with controls. CD3(+) T cells were major IL-9-expressing cells and some polymorphonuclear leucocytes (PMN) also expressed IL-9. IL-9 was co-localised with the key Th9 transcription factors interferon regulatory factor 4 and PU.1. Systemically, IL-9 was abundantly produced by activated peripheral blood lymphocytes, whereas its receptor was overexpressed on gut resident and circulating PMN. IL-9 stimulation of the latter induced IL-8 production in a dose-dependent manner and rendered PMN resistant to apoptosis suggesting a functional role for IL-9R signalling in the propagation of gut inflammation. Furthermore, IL-9R was overexpressed on gut epithelial cells and IL-9 induced STAT5 activation in these cells. Moreover, IL-9 inhibited the growth of Caco-2 epithelial cell monolayers in wound healing experiments. CONCLUSIONS: Our results provide evidence that IL-9 is predominantly involved in the pathogenesis of UC suggesting that targeting IL-9 might become a therapeutic option for patients with UC.

IgA autoantibodies in the pemphigoids and linear IgA bullous dermatosis.

BACKGROUND: Patients with bullous pemphigoid (BP), mucous membrane pemphigoid (MMP) and pemphigoid gestationis (PG) have IgG antibodies against BP180 and BP230, components of the hemidesmosomes. Patients with linear IgA bullous dermatosis (LABD) have IgA autoantibodies against a 97/120-kDa protein which is highly homologous to a shedded fragment of the BP180-ectodomain. OBJECTIVES: The aim of our study was to determine the incidence of IgA autoantibodies directed against BP180/BP230 in the pemphigoids and LABD and to determine the antigenic regions that are targeted by IgA autoantibodies. METHODS: Utilizing baculovirus-expressed recombinant BP180 and BP230 proteins, we performed immunoblot analyses for IgA reactivity of sera from patients with BP (n = 30), MMP (n = 10), PG (n = 6), LABD (n = 6) and from control patients with non-related pruritic dermatoses (n = 8). RESULTS: IgA reactivity against BP180 and/or BP230 was detected in 19/30 of the BP, in 7/10 of the MMP, in 6/6 of the LABD and in 3/6 of the PG sera, respectively, but not in the control group. In all subgroups, the major antigenic site recognized by IgA antibodies was located within the NH(2)-terminus of the BP180-ectodomain, but only a minority of the sera showed also IgA reactivity against the BP180-NC16a-domain. IgA reactivity against the central domain of BP180 was more frequently seen than against its COOH-terminus. IgA against the COOH- and NH(2)-terminus of BP230, respectively, was detected in 6/30 of the BP, 1/10 of the MMP, 1/6 of the LABD and 0/8 control sera. CONCLUSION: IgA reactivity against BP180 and/or BP230 is a common finding in the pemphigoids.

Clinical activity of pemphigus vulgaris relates to IgE autoantibodies against desmoglein 3.

Pemphigus vulgaris (PV) is a severe autoimmune bullous skin disease and is primarily associated with IgG against desmoglein 3 (dsg3), a desmosomal adhesion protein. In light of the recent association of autoreactive T helper (Th) 2 cells with active PV, the present study sought to relate the occurrence of Th2-regulated dsg3-specific autoantibody subtypes, i.e. IgE and IgG4, in 93 well-characterized PV patients. Patients with acute onset PV (n=37) showed the highest concentrations of serum IgE and IgG4 autoantibodies, which were significantly lower in PV patients in remission (n=14). Furthermore, there was a strong correlation between dsg3-reactive IgE and IgG4 in acute onset, but not in chronic active (n=42) or remittent patients. Additionally, intercellular IgE deposits were detected in the epidermis of acute onset PV. Thus, dsg3-specific IgE and IgG4 autoantibodies are related to acute onset disease which provides additional support to the concept that PV is a Th2-driven autoimmune disorder.

Rituximab mediates a strong elevation of B-cell-activating factor associated with increased pathogen-specific IgG but not autoantibodies in pemphigus vulgaris.

Pemphigus vulgaris (PV) is a severe autoimmune disease affecting the skin and mucous membranes, characterized by autoantibodies mainly against desmoglein 3 (dsg3). This study investigated the effects of different treatment options on two B-cell mediators, B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL), in 19 PV patients on immunosuppressive drugs alone or in combination with immunoadsorption and anti-CD20 antibody, respectively. Serum BAFF and APRIL levels, circulating desmoglein-reactive autoantibodies, and serum IgG specific for varicella-zoster virus (VZV) and Epstein-Barr virus (EBV) were determined by ELISA before and at different time points after initiation of the respective therapy. In contrast to immunosuppressive therapy alone and in combination with adjuvant immunoadsorption, respectively, rituximab treatment led to a strong and significant elevation of BAFF, but not of APRIL levels, which normalized upon recovery of peripheral CD19(+) B cells. Moreover, rituximab treatment led to a statistically significant increase of anti-VZV-IgG and anti-EBV-IgG titers, whereas anti-dsg1 and -3 specific autoantibody titers decreased significantly. Our results suggest that elevated BAFF levels might exert a differential effect on the induction of autoreactive versus pathogen-specific IgG antibody production in PV patients, possibly due to promotion of antibody release of pathogen-specific long-lived plasma cells.

Rituximab exerts a dual effect in pemphigus vulgaris.

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease affecting the skin and mucous membranes. Autoreactive CD4(+) T helper (Th) lymphocytes are crucial for the autoantibody response against the desmosomal adhesion molecules, desmoglein (dsg)-3 and dsg1. Eleven patients with extensive PV were treated with the anti-CD20 antibody, rituximab (375 mg per m(2) body surface area once weekly for 4 weeks). Frequencies of autoreactive CD4(+) Th cells in the peripheral blood of the PV patients were determined 0, 1, 3, 6, and 12 months after rituximab treatment. Additionally, the clinical response was evaluated and serum autoantibody titers were quantified by ELISA. Rituximab induced peripheral B-cell depletion for 6-12 months, leading to a dramatic decline of serum autoantibodies and significant clinical improvement in all PV patients. The frequencies of dsg3-specific CD4(+) Th1 and Th2 cells decreased significantly for 6 and 12 months, respectively, while the overall count of CD3(+)CD4(+) T lymphocytes and the frequency of tetanus toxoid-reactive CD4(+) Th cells remained unaffected. Our findings indicate that the response to rituximab in PV involves two mechanisms: (1) the depletion of autoreactive B cells and (2) the herein demonstrated, presumably specific downregulation of dsg3-specific CD4(+) Th cells.