Prostaglandin actions on the adrenergic nervous system

Tumor-Induced T Cell Polarization by Schwann Cells

Nerve-cancer crosstalk resulting in either tumor neurogenesis or intratumoral neurodegeneration is critically controlled by Schwann cells, the principal glial cells of the peripheral nervous system. Though the direct stimulating effect of Schwann cells on malignant cell proliferation, motility, epithelial-mesenchymal transition, and the formation of metastases have been intensively investigated, the ability of Schwann cells to affect the effector and regulatory immune cells in the tumor environment is significantly less studied. Here, we demonstrated that tumor cells could stimulate Schwann cells to produce high levels of prostaglandin E, which could be blocked by COX-2 inhibitors. This effect was mediated by tumor-derived TGF-β as neutralization of this cytokine in the tumor-conditioned medium completely blocked the inducible prostaglandin E production by Schwann cells. Similar protective effects were also induced by the Schwann cell pretreatment with TGF-βR1/ALK4/5/7 and MAPK/ERK kinase inhibitors of the canonical and non-canonical TGF-β signaling pathways, respectively. Furthermore, prostaglandin E derived from tumor-activated Schwann cells blocked the proliferation of CD3/CD28-activated T cells and upregulated the expression of CD73 and PD-1 on both CD4+ and CD8+ T cells, suggesting T cell polarization to the exhausted phenotype. This new pathway of tumor-induced T cell inhibition via the activation of neuroglial cells represents new evidence of the importance of nerve-cancer crosstalk in controlling tumor development and progression. A better understanding of the tumor-neuro-immune axis supports the development of efficient targets for harnessing this axis and improving the efficacy of cancer therapy.

Role of mucosal prostaglandins in vagally-mediated adaptive cytoprotection in the rat

This study was designed to investigate whether vagal innervation and mucosal prostaglandins (PGs) participate in gastric adaptive cytoprotection. Rats were divided into three groups; sham operation (control), truncal vagotomy or splanchnicotomy. In the first experiment, 100% ethanol (EtOH) was orally administered 15 min after pretreatment with 20% EtOH to all 3 groups. One hour later, the gastric mucosa was examined macroscopically. In a second experiment, the mucosal PG contents 15 min after administration of either 20% EtOH or saline were measured by high performance liquid chromatography. In truncal vagotomized rats, the adaptive cytoprotection caused by exposure to 20% EtOH in control and splanchnicotomized rats was not observed and an increase in hemorrhagic lesion severity was seen. In the control and splanchnicotomized rats, PGE2 contents were elevated following 20% EtHO treatment, as compared to those in the saline-treated rats. However, PGE2 contents in vagotomized rats were not altered by EtOH exposure, and were significantly lower than in the control and splanchnicotomized groups, whereas PGF2 alpha and PGD2 contents were significantly higher after EtOH administration as compared to those in saline-treated rats. These results suggest that vagal innervation is essential for adaptive cytoprotection and that the vagotomy-induced decrease in PGE2 and increases in PGF2 alpha and PGD2 following 20% EtOH administration, may be caused by a disturbance in adaptive cytoprotection.

Arachidonic acid cascade and signal transduction

Since a review on this topic in this Journal appeared (Wolfe, 1982), the CNS has proved to be a major focus in eicosanoid research. Although our knowledge is limited at the moment, the research in this field is rapidly growing. In this short review, we summarize recent progress of research (1982-1989) in this field with special attention directed to eicosanoid metabolism, functions of eicosanoids in the neuroendocrine system and synaptic transmission, current information on eicosanoid receptors, and the link between eicosanoids and cerebral circulation. Knowledge of the eicosanoids has paved the way to a better understanding of intercellular signal transduction systems, including neuronal functions.

Application of a new technique--blood pressure clamping--for analysis of prostaglandin interference with sympathetic neurotransmission in man

To circumvent baroreceptor reflexes following drug-induced interference sympathetic neurotransmission, a new technique - blood pressure clamping--has developed. This implies that the sympathetic activity in an awake human is 'clamped' at a supranormal level by infusion of a vasodilator. In 11 healthy volunteers nitroprusside or saline was randomly infused in two consecutive 2-h periods. Plasma and urinary catecholamine levels were analysed by liquid chromatography. The experiments were repeated after random administration of the prostaglandin synthesis inhibitor, ibuprofen, or placebo. In the basal state (no ibuprofen, saline infusion) the mean arterial blood pressure was 81.4 +/- 2.3 mmHg, the heart rate was 60.9 +/- 0.3 beats min-1 and the plasma level of noradrenaline was 1.12 +/- 0.15 nM. Infusion of nitroprusside at a dose lowering the mean blood pressure by 11.6 +/- 1.6 mmHg and increasing the heart rate to 74.6 +/- 2.9 beats min-1 elevated plasma noradrenaline to 2.86 +/- 0.39 nM. After pretreatment with ibuprofen (saline infusion), the systemic blood pressure, the heart rate, and the plasma and urinary levels of noradrenaline were unaffected in comparison to before drug (80.1 +/- 2.3 mmHg, 58.4 +/- 0.3 beats min-1 and 1.13 +/- 0.12 nM respectively). Infusion of nitroprusside at a rate lowering the blood pressure by 11.2 +/- 2.4 mmHg and increasing the heart rate to 74.4 +/- 0.5 beats min-1, elevated the plasma level of noradrenaline to 2.46 +/- 0.38 ng ml-1, which is not different from before ibuprofen. The amount of nitroprusside required to lower the blood pressure was not different in the presence and absence of ibuprofen.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma renin activity and cAMP in termination of pregnancy induced by sulprostone

Plasma renin activity (PRA), plasma concentrations of cyclic adenosine-3',5'-monophosphate (cAMP) and the serum levels of oestradiol, progesterone, chorionic gonadotrophin, potassium, sodium and calcium were estimated in connection with termination of pregnancy induced in 23 women by sulprostone, a derivative of prostaglandin E2. A rapid decrease in PRA was observed during and after infusion of 1000 micrograms or 1500 micrograms sulprostone. PRA returned to the initial values at 24 h after drug administration. The lowest levels of PRA were 36% and 51% of the initial values (P less than 0.001) in the two drug concentration groups. No significant changes were observed in the control group. The value for plasma cAMP did not correspond completely to the changes in PRA. Serum concentrations of oestradiol, progesterone and chorionic gonadotrophin showed a gradual decrease during drug administration. The changes in serum potassium, sodium and calcium were minimal. The decrease in PRA associated with sulprostone is very surprising. Our finding elucidates in part the still rather poorly known mechanisms and function of renin-angiotensin system in pregnancy.

Indomethacin in the treatment of ureteral colic: is fluid restriction necessary?

The effect of fluid load on pain was estimated in 60 patients with acute ureteral colic treated with 50 mg. intravenous indomethacin. One group received 3 l. fluid intravenously, while in another group all fluids were withheld for 6 hours. Pain was assessed with a visual analogue scale. No intergroup difference in regard to pain was found after 1, 3 and 6 hours of observation.

[Nutrition physiology studies with formula diets: metabolism of multiple unsaturated fatty acids and prostaglandin biosynthesis in the human]

Linoleic and linolenic acids are precursors for the biosynthesis of prostaglandins (PG) and related compounds. In man augmented linoleic acid intake results in stimulation of PG-biosynthesis, for PG originating from the kidney a stimulation only is found for PGE2. Dietary linolenic acid inhibits PG biosynthesis to a tenfold lesser degree than eicosapentaenoic acid. Renal PGE2 is depressed by linolenic acid intake, while no effect is found for PGF2 alpha up to 8 energy% of linolenic acid supply. Linoleic and linolenic acids additionally display effects on fatty acid metabolism. In contrast to the results of in vitro studies the supply with the precursor linoleic acid results in a decrease of arachidonic acid in cholesterolesters of plasma and in HDL-lecithin, while the intake of linolenic acid is without effect. From these data it is concluded that in vivo the conversion of linoleic to arachidonic acid occurs preferentially to the analogous conversion of linolenic to eicosapentaenoic acid.