As yet, little is known about the function of the glia of the enteric nervous system (ENS), particularly in an immune-stimulated environment. This prompted us to study the potential of cultured enteroglial cells for cytokine synthesis and secretion. Jejunal myenteric plexus preparations from adult rats were enzymatically dissociated, and enteroglial cells were purified by complement-mediated cytolysis and grown in tissue culture. Cultured cells were stimulated with recombinant rat interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha, and IL-6 mRNA expression and secretion were assessed using RT-PCR and a bioassay, respectively. Stimulation with TNF-alpha did not affect IL-6 mRNA expression, whereas IL-1beta stimulated IL-6 mRNA and protein synthesis in a time- and concentration-dependent fashion. In contrast, IL-6 significantly and dose-dependently suppressed IL-6 mRNA expression. In summary, we have presented evidence that enteric glial cells are a potential source of IL-6 in the myenteric plexus and that cytokine production by enteric glial cells can be regulated by cytokines. These findings strongly support the contention that enteric glial cells act as immunomodulatory cells in the enteric nervous system.

Inflammatory bowel disease is typically accompanied by functional and structural changes of the enteric nervous system. In pathological studies, cellular loss and axonal degeneration have been described in the myenteric plexus. However, more recent studies suggest that the proliferation rate of myenteric glial cells is enhanced in animal models of intestinal inflammation. Therefore, we have investigated the effect of different cytokines on the proliferative response of enteric glial cells (EGCs), comparing transformed enteric glial cell lines, primary astrocyte cultures and transformed oligodendrocytes. Cells were incubated in serum-free chemically defined medium in the presence or absence of either interleukin (IL)-1beta or IL-10 at concentrations ranging between 0.1 and 100 ng mL(-1) for 48 h. Subsequently, [3H]thymidine was added to each culture dish for an additional 6 h, and the amount of incorporated [3H] was assessed. IL-1beta significantly and dose-dependently suppressed [3H]-uptake by EGCs. In contrast, IL-10 induced a biphasic response; IL-10 at low concentrations (0.1 ng mL(-1)) caused a significant suppression of [3H]-uptake, whereas high concentrations (5-100 ng mL(-1)) significantly enhanced [3H] uptake. These results indicate that EGC proliferation can be modulated by cytokines. The differential effects of IL-1beta and IL-10 suggest that during intestinal inflammation there may be a regulatory interplay between different classes of cytokines modulating EGC proliferation.

Four clones of the yeast Candida albicans, isolated on the basis of their tolerance to clotrimazole, were compared with their parental strain in terms of growth, morphology, virulence, and cell surface complement receptor activity. In a newly described synthetic medium, these clones, designated Cl, C2, N, and P, produced germ tubes or pseudohyphae, but no true hyphae, in a pattern which was specific for each strain. The growth of each clone at 37°C, under conditions which favor the filamentous growth form of the organism, was equal to that of the parental strain (H12). The pathogenicity of each clone was tested in an intravenous mouse model.None of the mice infected with the tolerant clones but all of the mice infected with H12 developed severe renal candidiasis after infection with 1.4 x 106 to 2.0 x 106 CFU/ml. The number of CFU of each clone from the mouse kidney was reduced about 3 or 4 orders of magnitude in comparison with the wild type. As a correlate, we measured the complement receptor activity (CR2 and CR3) of each clone. The C3 ligands, iC3b and C3d, were conjugated to sheep erythrocytes (E) sensitized with antibody (A) to the erythrocytes (EA). We found that all tolerant clones showed reduced recognition of C3d-bearing sheep erythrocytes (EAC3d) in rosetting assays. Clone P showed more than an 80% reduction in rosetting of EAC3d in comparison with H12 cells. In contrast, recognition of iC3b (EAiC3b) by each of the clones was similar to that by H12 cells. When dithiothreitol extracts of clone P and H12 were compared by immunoblot, both quantitative and qualitative differences in reactivities were observed with antibodies specific for the Candida C3d receptor and with antiserum from a patient with chronic mucocutaneous candidiasis.

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