Glucocorticoid receptor blockade reverses postinjury macrophage suppression

Rapid nongenomic inhibitory effects of glucocorticoids on phagocytosis and superoxide anion production by macrophages

Traditionally, steroid hormone effects have been described as a result of the modulation of nuclear transcription, thus triggering genomic events that are responsible for physiological effects. Despite early observations of rapid steroid effects that were incompatible with this theory, nongenomic steroid effects have been widely recognized only recently. However, the nongenomic effect of glucocorticoid (GC) on anti-inflammation and immunosuppression has not been reported. Macrophages play important roles in inflammation and the immune response. The present experiment selected macrophages as experimental cells to explore the nongenomic effects and possible mechanisms of GCs on phagocytosis and superoxide anion production. Phagocytosis by macrophages was detected by the neutral red uptake assay. The superoxide anions were measured by cytochrome C reduction assay. It was found that both 10(-4) and 10(-5) mol/L corticosterone (CORT) rapidly inhibited uptake of neutral red by macrophages in less than 30 min, and the inhibition by the former was stronger than that of the latter. CORT (10(-4) to 10(-10) mol/L) rapidly inhibited superoxide anion production by macrophages in less than 30 min. The above-mentioned effects were insensitive to the GC-receptor antagonist mifepristone (RU486) and the translation inhibitor actidione. CORT coupled to bovine serum albumin (BSA-CORT) was able to mimic the rapid inhibitory effects of CORT. The results indicated that CORT could rapidly inhibit phagocytosis and superoxide anion production by mouse peritoneal macrophages in vitro in less than 30 min by a rapid, nongenomic mechanism, which contributes to the anti-inflammatory and immunosuppressive actions of GCs. These data shed a new light on the clinical application of GCs.

Glucocorticoid involvement in suppression of NK activity following surgery in rats

We studied plasma factors mediating suppression of NK activity (NKA) following surgery. Plasma from operated rats suppressed NKA of splenocytes, leukocytes, and purified natural killer (NK) cells, and charcoal stripping nullified suppression. The glucocorticoid antagonist mifepristone prevented suppression, whereas blockers of reactive oxygen metabolites, opioids, catecholamines, prostaglandin-E2, and histamine did not. NKA dropped as corticosterone levels peaked postoperatively, and administration of relevant doses of corticosterone suppressed NKA. Inhibition of glucocorticoid synthesis prevented plasma from suppressing NKA but merely attenuated NKA suppression in operated rats. Thus, postoperative concentrations of corticosterone can directly suppress NKA but additional factors probably act in vivo.

The promotion of tumor metastasis by surgery and stress: immunological basis and implications for psychoneuroimmunology

This mini-review emphasizes a psychoneuroimmunology (PNI) perspective of the hypothesis that stress and surgical excision of the primary tumor can promote tumor metastasis. It first establishes the empirical and theoretical basis for control of metastasis by cell-mediated immunity (CMI), as well as the interactive role of non-immunological risk factors. It then describes the various aspects of surgery that suppress CMI, and the neuroendocrine mechanisms mediating suppression by stress and surgery. Last, it briefly reviews the empirical evidence, from animal and human studies, for the promotion of metastasis by stress and surgery, with specific reference to the mediating role of CMI. It is concluded that: (a) Immunological mechanisms most likely play a role in limiting metastasis in patients with solid tumors. (b) Immunosuppression can be deleterious, especially when surgery is conducted early, before the tumor develops insurmountable mechanisms to escape immune destruction. (c) The most sensitive period for the establishment of metastases is the immediate aftermath of surgery. Interventions aiming at reducing stress and immunosuppression should thus strive to start beforehand. (d) 'Psychological and physiological insults activate similar neuroendocrine mechanisms of immunosuppression. Therefore, a multimodal therapeutic approach should be used to prevent tumor metastasis during the perioperative period. (e) Studies employing interventions aimed at reducing the surgical stress response should preferably assess immunological indices with an established clinical relevance, and follow up long-term recurrence provided sample size assure statistical power. (f) The progress toward earlier detection of cancer, and our growing understanding of immunosuppression, continuously improves the chances for successful PNI interventions.

Intra-abdominal sepsis: an immunocytochemical study of the small intestine mucosa

AIM

To investigate immunocytochemical changes in intestinal tissues from patients with intra-abdominal sepsis, and to relate the changes to the possibility of enhanced bacterial adhesion and translocation.

METHODS

Tissues from 17 patients suffering from intra-abdominal sepsis and from controls were sectioned and stained immunocytochemically for IgA, IgM, secretory component, J chain, and HLA-DR. Differences in the distribution and characteristics of positively staining cells between the patient groups were assessed.

RESULTS

Patients with intra-abdominal sepsis had noticeable reductions in numbers of IgA and IgM plasma cells, reduced J chain staining, and had little immunoglobulin on the surfaces of enterocytes. In contrast, HLA-DR positive cells were increased in the sepsis compared with the control group. The plasma cells present showed cytological changes suggestive of apoptosis.

CONCLUSIONS

Stress associated with sepsis and its immediate causes might result in increased plasma glucocorticoid levels that bring about apoptosis of mucosal plasma cells (or their precursors). The consequent reduction in expression of IgA and IgM may favour bacterial adhesion to the enterocytes and facilitate bacterial translocation into the tissues.