Role of soluble factors and three-dimensional culture in in vitro differentiation of intestinal macrophages.

AIM: To examine the factor(s) involved in differentiation of intestinal macrophages (IMACs) using a recently established in vitro model. METHODS: To test whether soluble or membrane bound factors induce IMAC-differentiation, freshly elutriated monocytes (MO) were incubated with conditioned media or cell membranes of intestinal epithelial cells (IEC) or cultured with IEC in transwell systems. To determine the importance of an active migration of MO, three-dimensional aggregates from a 1:1-mixture of MO and IEC were examined by immunohistochemistry and flow cytometry. Apoptosis was examined by caspase-3 Western blots. Extracellular matrix production in differentiation models was compared by immunohistochemistry. RESULTS: IMAC differentiation was observed in a complex three-dimensional co-culture model (multicellular spheroid, MCS) with IEC after migration of MO into the spheroids. By co-culture of MO with conditioned media or membrane preparations of IEC no IMAC differentiation was induced. Co-culture of MO with IEC in transwell-cultures, with the two cell populations separated by a membrane also did not result in intestinal-like differentiation of MO. In contrast to IEC-spheroids with immigrating MO in mixed MCS of IEC and MO only a small subpopulation of MO was able to survive the seven day culture period. CONCLUSION: Intestinal-like differentiation of MO in vitro is only induced in the complex three-dimensional MCS model after immigration of MO indicating a role of cell-matrix and/or cell-cell interactions during the differentiation of IMACs.

Serum soluble TNF receptor I and II levels correlate with disease activity in IBD patients.

BACKGROUND: Tumor necrosis factor alpha (TNFalpha) is a proinflammatory cytokine and an important mediator in the pathophysiology of inflammatory bowel disease (IBD). The effects of TNFalpha are mediated by 2 specific receptors, a 55-kDa protein (TNF-RI) and a 75-kDa receptor (TNF-RII), which are usually bound to the cell surface. Soluble TNF receptors I and II (sTNF-RI + II) are released by proteolytic cleavage of the extracellular domains of these receptors. Soluble TNF-Rs act as TNF antagonists and can inhibit TNFalpha-mediated proinflammatory effects. METHODS: Levels of sTNF-RI + II were measured using commercially available enzyme-linked immunosorbent assays (ELISAs). Serum levels of sTNF-RI + II of 76 healthy volunteers were compared to serum levels of 373 clinically well-characterized patients with Crohn's disease (CD) and 118 patients with ulcerative colitis (UC) with different disease activity from the German IBD competence network serum bank. CD patient subgroups were defined according to the Vienna Classification. RESULTS: The serum levels of sTNF-RI were significantly increased in all groups (active, chronic active, and remission) of CD and UC patients compared to healthy controls. sTNF-RII levels were significantly higher in active CD patients compared to UC patients with no overlap of the 95% confidence interval. Significantly higher values of sTNF-RII compared to controls were also observed in CD patients and UC patients in remission. There was no statistically significant difference in sTNF-RI or sTNF-RII levels when patient subgroups were analyzed according to disease behavior or disease localization. CONCLUSION: sTNF-RI is upregulated in the serum of IBD patients compared to healthy controls and could be used as a marker for disease activity. sTNF-RII levels are significantly more elevated in serum of active CD patients as compared to UC and could be used as an additional parameter to discriminate both diseases.

(E)-metanicotine hemigalactarate (TC-2403-12) inhibits IL-8 production in cells of the inflamed mucosa.

BACKGROUND: Nicotine is of therapeutic value in ulcerative colitis, but its administration is connected with adverse events. Nicotine derivatives are currently being tested to maintain the therapeutic effects and minimize adverse events. TC-2403-12 is a (E)-metanicotine hemigalactarate. The aim of this study was to determine the effectiveness of TC-2403-12 in the inhibition of TNF- and lipopolysaccharide (LPS)-induced cell activation. METHODS: Colonic epithelial cells (CEC), monocytes (MM6), granulocytes, and the intestinal epithelial cell line HT-29 were stimulated with TNF and LPS and treated with TC-2403-12. IL-8 secretion in the cell supernatants and NF-kappaB activation were determined by ELISA. Apoptosis was quantified by flow cytometry. RESULTS: In MM6 cells, IL-8 secretion was significantly decreased to 30% of control after TC-2403-12 treatment, with best results after pretreatment for 24 h. This decrease in cell activation was not due to apoptosis and was not mediated by inhibition of NF-kappaB activation. IL-8 production in neutrophils and primary CEC also tended to be decreased after TC-2403-12 treatment. TC-2403-12 had no influence on IL-8 secretion of HT-29 cells. CONCLUSION: TC-2403-12 effectively inhibited TNF- and LPS-induced IL-8 production in different cell types. No toxic effects occurred at the concentrations used. Preincubation of cells with TC-2403-12 showed the best effects.

Physiological role of macrophage inflammatory protein-3 alpha induction during maturation of intestinal macrophages.

Intestinal macrophages (IMAC) are a central component in the defense of the intestinal mucosa against luminal microbes. In normal mucosa, monocytes differentiate to immunologically tolerant IMAC with a typical phenotype lacking activation markers such as CD14 and TLRs 2 and 4. CD33+ IMAC were isolated from normal intestinal mucosa by immunomagnetic beads. A subtractive hybridization subtracting mRNA from normal IMAC from those of in vitro differentiated macrophages was performed. IMAC differentiation was studied in multicellular spheroids (MCS). Functional assays on migration of CD45R0+ T cells were performed in MCS coculture models. Of 76 clones, 3 obtained by subtractive mRNA hybridization showed >99% homology to mRNA of MIP-3alpha, indicating that this chemokine is induced in IMAC compared with in vitro differentiated macrophages. MIP-3alpha protein expression was confirmed in cryostat sections of normal intestinal mucosa by immunohistochemistry. IMAC in the lamina propria stained positive for MIP-3alpha. FACS of purified IMAC clearly indicated expression of MIP-3alpha in these cells. In the MCS-in vitro differentiation model for IMAC, MIP-3alpha protein expression was absent on day 1 but detectable on day 7 of coculture, demonstrating the induction of MIP-3alpha during differentiation of IMAC. IMAC attracted CD45R0+ T cells to migrate into an MCS coculture model. In human mucosa, a close contact between IMAC and CD45R0+ T cells could be demonstrated. MIP-3alpha is induced during the differentiation of monocytes into IMAC. Our data suggest that MIP-3alpha expression could be involved in the recruitment of CD45R0+ cells into the lamina propria.