Prostaglandin E2 regulation of human specific B-cell response: interaction with a monocyte product

Is There a Role for Bioactive Lipids in the Pathobiology of Diabetes Mellitus?

Inflammation, decreased levels of circulating endothelial nitric oxide (eNO) and brain-derived neurotrophic factor (BDNF), altered activity of hypothalamic neurotransmitters (including serotonin and vagal tone) and gut hormones, increased concentrations of free radicals, and imbalance in the levels of bioactive lipids and their pro- and anti-inflammatory metabolites have been suggested to play a role in diabetes mellitus (DM). Type 1 diabetes mellitus (type 1 DM) is due to autoimmune destruction of pancreatic β cells because of enhanced production of IL-6 and tumor necrosis factor-α (TNF-α) and other pro-inflammatory cytokines released by immunocytes infiltrating the pancreas in response to unknown exogenous and endogenous toxin(s). On the other hand, type 2 DM is due to increased peripheral insulin resistance secondary to enhanced production of IL-6 and TNF-α in response to high-fat and/or calorie-rich diet (rich in saturated and trans fats). Type 2 DM is also associated with significant alterations in the production and action of hypothalamic neurotransmitters, eNO, BDNF, free radicals, gut hormones, and vagus nerve activity. Thus, type 1 DM is because of excess production of pro-inflammatory cytokines close to β cells, whereas type 2 DM is due to excess of pro-inflammatory cytokines in the systemic circulation. Hence, methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 DM. Roux-en-Y gastric bypass and similar surgeries ameliorate type 2 DM, partly by restoring to normal: gut hormones, hypothalamic neurotransmitters, eNO, vagal activity, gut microbiota, bioactive lipids, BDNF production in the gut and hypothalamus, concentrations of cytokines and free radicals that results in resetting glucose-stimulated insulin production by pancreatic β cells. Our recent studies suggested that bioactive lipids, such as arachidonic acid, eicosapentaneoic acid, and docosahexaenoic acid (which are unsaturated fatty acids) and their anti-inflammatory metabolites: lipoxin A4, resolvins, protectins, and maresins, may have antidiabetic actions. These bioactive lipids have anti-inflammatory actions, enhance eNO, BDNF production, restore hypothalamic dysfunction, enhance vagal tone, modulate production and action of ghrelin, leptin and adiponectin, and influence gut microbiota that may explain their antidiabetic action. These pieces of evidence suggest that methods designed to selectively deliver bioactive lipids to pancreatic β cells, gut, liver, and muscle may prevent type 1 and type 2 DM.

Interleukin-1 inhibits PGE2 binding to macrophage-like P388D1 cells by a cyclic AMP-independent process

The interaction between interleukin IL-1 alpha and PGE2 on P388D1 cells has been investigated. Preincubation of murine macrophage-like cells, P388D1, with IL-1 alpha (0-73 pM) reduced the binding of PGE2 to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1 alpha decreased the PGE2 binding by lowering both the high and low affinity receptor binding capacities (from 0.31 +/- 0.02 to 0.12 +/- 0.01 fmol/10(6) cells for the high affinity receptor binding sites and from 2.41 +/- 0.12 to 1.51 +/- 0.21 fmol/10(6) cells for the low affinity receptor binding sites). However, the dissociation constants of the receptors of the IL-1 alpha-treated cells remained unchanged. Inhibition of PGE2 binding by IL-1 alpha did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1 alpha inhibits the binding of PGE2 to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE2.

Increased level of salivary prostaglandins in patients with major depression

We quantified the amounts of salivary prostaglandin (PG) D2, PGE2, and PGF2 alpha by radioimmunoassay in 32 patients with major depressive disorder, 16 patients with minor depressive disorder, 24 patients with neurotic disorders (panic, generalized anxiety, phobic, somatization, and obsessive compulsive), and 28 healthy controls. In the saliva of patients with major depressive disorder, the concentrations of immunoreactive PGs (PGD2, 385 +/- 71 pg/ml; PGE2, 498 +/- 105 pg/ml; PGF2 alpha, 444 +/- 100 pg/ml) were significantly higher than those of the healthy controls (PGD2, 129 +/- 18 pg/ml; PGE2, 207 +/- 25 pg/ml; PGF2 alpha, 164 +/- 17 pg/ml). On the other hand, the salivary concentrations of immunoreactive PGs from patients with minor depressive disorder or neurotic disorders were comparable to those of the controls. These results suggest that the level of salivary PGs may be an indicator of major depressive disorder.

Depression, immunocompetence, and prostaglandins of the E series

Plasma prostaglandin E1 and E2, and quantitative and qualitative measures of immune function, were determined in depressed patients and healthy controls. Prostaglandin E2 was significantly elevated in the depressed group, and prostaglandin E1 showed a trend in the same direction. Lymphocyte stimulation responses, as measured by phytohemagglutinin, concanavalin A, and pokeweed mitogen, were significantly lower in the depressed group. Helper and suppressor T cell percentages did not significantly differ in the two populations. In the depressed group, prostaglandin E1 showed a significant inverse correlation with concanavalin A, and prostaglandin E2 showed a similar trend. These preliminary data suggest prostaglandins of the E series may be related to abnormalities of cellular immunity previously documented in depression.

Effect of hydrocortisone on the in vitro human antibody response: interaction with monocytes and prostaglandins

The specific plaque-forming cell response induced by trinitrophenyl polyacrylamide beads in cultures of nonadherent human peripheral blood mononuclear cells (PBM) is resistant to the inhibitory effect of hydrocortisone (HC). Previous results showed that low concentrations (up to 10(-7 M) of HC inhibit the same response in cultures of unfractionated human PBM. It is shown that the addition of 5-10% monocytes to nonadherent PBM renders their response HC-sensitive. One mechanism of the interaction between HC and monocytes is the potentiation of prostaglandin E2-mediated suppression by HC, which can be demonstrated in vitro and after in vivo administration of HC. However, interaction with a non-prostaglandin-mediated suppression by monocytes should be involved, particularly with high (10(-6) M) concentrations of HC.