Neuroimmunomodulation in the gastrointestinal tract

Decidual mast cells might be involved in the onset of human first-trimester abortion

PROBLEM

The aim of the present study was to identify the role of mast cells and substance P (SP)-containing nerve fibers in human decidua in normal and pathological pregnancies.

METHOD OF STUDY

We collected decidua from women undergoing termination of normal pregnancies and from abortions. The presence of mast cells and SP was detected by immunohistochemistry.

RESULTS

We observed a sparse distribution of mast cells in the normal pregnancies (36.7 tryptase+ mast cells/mm2 decidua). In the decidua from abortion, we found a dramatic increase in the number of mast cells (448.7 and 469.2 tryptase+ mast cells/mm2 decidua in primary and secondary abortions, respectively). In addition, we observed an increase of SP-positive nerve fibers in the decidua of abortions.

CONCLUSIONS

Our data suggest that decidual mast cells may play an important role in the onset of abortion, due to the production of cytokines, such as tumor necrosis factor-alpha.

Apposition of enteric nerve fibers to plasma cells and immunoblasts in the mouse small bowel

Light (LM) and electron microscopy (EM) were used to investigate the structural relationship between enteric nerves and the population of immune cells in the mouse small bowel. By LM, the osmium-zinc iodide procedure was used for visualizing nerve fibers; the incidence of nerve-plasma cell contacts in the mucosa and submucosa was calculated to be approximately 4 times and, respectively, 3 times greater than would be expected by chance alone (P < 0.0001). EM revealed close, synaptic-like contacts between axonal varicosities and plasma cells or B immunoblasts. The results presented here provide systematic quantitative evidence that a structural foundation for communication between nerve fibers and B cells exists in the mouse small bowel.

Somatostatin does not attenuate intestinal injury in dextran sodium sulphate-induced subacute colitis

FRom several in vitro and in vivo studies involvement of somatostatin (SMS) in intestinal inflammation emerge. Acute colitis induced in rats is attenuated by the long-acting SMS analogue octreotide. We studied the potential beneficial effect of SMS on non-acute experimental colitis. BALB/c mice received either saline, SMS-14 (36 or 120 microg daily) or octreotide (3 microg daily) subcutaneously delivered by implant osmotic pumps. A non-acute colitis was induced by administration of dextran sodium sulphate (DSS) 10% in drinking water during 7 days. DSS evoked a mild, superficial pancolitis, most characterized by mucosal ulceration and submucosal influx of neutrophils. Neither SMS-14 nor octreotide reduced mucosal inflammatory score or macroscopical disease activity, although reduction of intestinal levels of interleukin-1beta (IL-1beta), IL-6 and IL-10 during DSS was augmented both by SMS and octreotide. A slight increase of neutrophil influx was seen during SMS administration in animals not exposed to DSS. In conclusion, SMS or its long-acting analogue did not reduce intestinal inflammation in non-acute DSS-induced colitis. According to the cytokine profile observed, SMS-14 and octreotide further diminished the reduction of intestinal macrophage and Th2 lymphocyte activity.

Interdependence of the endocrine and immune systems

The cross-talk involving the endocrine and immune systems is now largely established. These systems actually use similar ligands and receptors to establish a physiological intra- and inter-system communication circuitry, which apparently plays a relevant role in homeostasis (reviewed in Blalock, 1992). Accordingly, classical hormones such as prolactin (PRL), growth hormone (GH) and even glucocorticoids (GC) can be produced by cells of the immune system, whereas a variety of cytokines, originally described as being produced by cells of the immune system, are synthesized and released by a variety of endocrine glands and nervous tissue. Moreover, specific receptors for such distinct molecular families can be detected in both the immune and endocrine systems.