Modulating cerebello-thalamocortical pathways by neuronavigated cerebellar repetitive transcranial stimulation (rTMS).

OBJECTIVES: Increasing evidence suggests that dysfunctions of the cortico-cerebello-thalamocortical circuit are involved in the pathophysiology of neuropsychiatric disorders. This study explores the effects of cerebellar repetitive transcranial magnetic stimulation (rTMS) on cerebello-thalamocortical pathways. METHODS: Ten healthy volunteers received MRI-guided rTMS in four separate sessions (120% motor threshold, 1000 stimuli) over either the medial or the right lateral cerebellum using frequencies of 1 and 10 Hz. Motor cortex excitability was assessed before and after the intervention by paired-pulse transcranial magnetic stimulation. RESULTS: Depending on stimulation frequency, cerebellar rTMS differentially modified intracortical inhibition. Low frequency rTMS increased short intracortical inhibition (SICI), whereas high frequency rTMS had no significant effect on SICI. CONCLUSIONS: These results suggest that rTMS over the cerebellum can modulate cerebello-thalamocortical pathways in a frequency-specific manner.

The diminished postoperative capacity of blood leukocytes to produce IL-6 is associated with high concentrations of IL-6 in the circulation.

Surgical trauma is followed both by a transient increase of interleukin 6 (IL-6) concentrations in the serum and impaired function of circulating leukocytes. Perioperatively, we investigated the relationship of IL-6 concentrations in the serum with lipopolysaccharide (LPS)-stimulated cytokine production in the whole blood of patients undergoing elective major abdominal operations. In 50 patients, we found a transient increase of IL-6 concentrations in the serum. Six hours after skin incision, in vitro stimulated production of IL-6 and TNFalpha was diminished by 72% (P<0.05). A significant increase in cytokine production was observed three days postoperatively, however this was 63% below the preoperative values. Patients with high concentrations of circulating IL-6 showed a significantly lower stimulated IL-6 production than patients with low serum concentrations of IL-6. We conclude, that two opposing effects are associated with surgery: an activation leading to IL-6-release into the circulation, and a prolonged hyporesponsiveness of circulating leukocytes. These reactions are positively related.

Secretion of IL-6, monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, and TNFalpha by cultured intact human peritoneum.

The peritoneum is an important site of host defence. The mesothelial cells, lining the peritoneum, and the fibroblasts found in the layers below are potent sources of a variety of mediators. Furthermore, granulocytes, mast cells, and macrophages, either resident or attracted by inflammatory processes, are interspersed within the tissue. We investigated the production of mediators by samples of fresh human peritoneum. The method described here has the advantage that the cellular composition of the human peritoneum remains intact. Samples of peritoneum were excised at the beginning of elective abdominal operations in infection-free patients. The tissue was placed across the wells of a microtitre plate, fixed in place by the plate cover and incubated with culture medium with or without lipopolysaccharide (LPS) for up to 5 h. The accumulation of IL-6, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha) and TNFalpha in culture supernatants was measured by ELISA. Production of MCP-1 and IL-6 occurred spontaneously during incubation and was enhanced by as much as 4-fold in the presence of different concentrations of LPS (0. 5-500 ng/ml) in a dose-dependent manner. MIP-1alpha and TNFalpha were detected in culture supernatants of LPS-stimulated samples with concentrations about 8 times as high as those of samples cultured with no such stimulus. The addition of IL-1beta resulted in an increase in the release of IL-6 and MCP-1, similar to that observed with LPS stimulation, but failed to increase the production of TNFalpha. MIP-1alpha production was only marginally enhanced by IL-1beta. In conclusion, our experimental system is suitable for the investigation of chemokine and cytokine production by the human peritoneum, with the aim of assessing aspects of local immunocompetence.

[Production of chemokines by the human peritoneum]. / Das humane Peritoneum als Produzent von Chemokinen.

AIM OF THE STUDY: Peritonitis is characterised by a continued infiltration of the peritoneal cavity with leukocytes, attracted by chemotactic mediators. The aim of this study was to demonstrate the capacity of the human peritoneum to secrete chemokines and to show a therapeutic option by impairing the proinflammatory function of the peritoneum. METHODS: Peritoneum was obtained from 12 consenting patients undergoing abdominal surgery for noninflammatory diseases. After opening the peritoneal cavity a piece of the parietal peritoneum was excised and subsequently incubated with lipopolysaccharide (LPS, 50 ng/ml) +/- interleukin-10 (IL-10, 100 U/ml) for five hours in vitro. The culture supernatants were assayed for concentrations of interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and monocyte inflammatory protein-1 alpha (MIP-1 alpha) by using the ELISA. RESULTS: The cultured peritoneum secreted MCP-1 (mean (SEM): 3416 (659) pg/ml) and IL-8 (2946 (894) pg/ml). The presence of LPS resulted in a fourfold enhancement of this secretion (MCP-1: 13563 (1613), IL-8: 9854 (1305) pg/ml) and led to the production of MIP-1 alpha (1476 (240) pg/ml). The LPS-stimulated production of all of these chemokines was significantly diminished by the presence of IL-10. CONCLUSION: The reaction of the peritoneum to LPS indicates its proinflammatory function in the context of peritonitis caused by gram-negative bacteria. This inflammatory reaction might be diminished by application of IL-10.

Monocyte function before and after surgical trauma.

The monocyte/macrophage plays a key role in the network of immune reactions. Dependent on activation, it is able to produce various cytokines which act on other cells of the immune system in the sense of upregulation or downregulation. In addition, it presents antigens by the HLA-DR molecule as an initial trigger of an antigen-specific T-cell response. Monocyte function is affected by surgical disease and further affected by surgical trauma. We found the monocyte to be activated in a subgroup of patients before the operation, related to an increased rate of postoperative septic complications. After the operation, plasma concentrations of IL-6 and IL-10 were increased indicating the activation of an immune response. After surgery HLA-DR expression decreased as well as LPS-stimulated TNFalpha and IL-6 production, the latter indicating a hyporesponsiveness of peripheral blood cells (presumably monocytes) to further stimulation. On the other hand, continuously high plasma concentrations of activation markers like neopterin and IL-6 in the postoperative course were associated with complications and poor outcome. In postoperative septic shock monocytes may be almost areactive towards natural stimuli like bacteria and endotoxin, since IL-6 and TNFalpha production decreased to very low amounts. Adequate pre- and postoperative monocyte function is related to an uneventful postoperative course after major surgical operations. Surgical trauma affects monocyte function rendering it less reactive, which is a potential risk factor for postoperative septic complications.

Culture of human peritoneum--a new method to measure the local cytokine response and the effect of immunomodulators.

The production of cytokines and chemokines, which are involved in cell activation and cell migration in native pieces of peritoneum, was measured to investigate immune regulatory reactions in the human peritoneum. The samples were obtained during abdominal surgery and cultured immediately afterwards. In order to test therapeutic options in vitro, the effect of IL-10 and IFN-gamma on the cytokine and chemokine production was also studied. The chemokine monocyte chemotactic protein-1 (MCP-1) was produced and released spontaneously. When lipopolysaccharide (LPS) was added, MCP-1 production increased. In addition, TNF-alpha production was induced by LPS. When IL-10 was added, LPS-stimulated TNF-alpha production was reduced towards baseline levels, LPS-induced MCP-1 production was reduced by 37%. IFN-gamma did not affect LPS-induced TNF-alpha and MCP-1 production, but increased baseline MCP-1 production. It can be concluded that short-time culture of native human peritoneum is a method to investigate peritoneal chemokine and cytokine production in patients undergoing abdominal surgery. Further studies are intended to detect cytokine patterns which identify patients at risk of developing peritonitis. In addition, the effects of medications may be tested in vitro in order to investigate options for preventive modulation of the peritoneal immune response in such patients.