P. Conti

Reduced mitogenic stimulation of human lymphocytes by extremely low frequency electromagnetic fields

Blastogenesis of human peripheral blood lymphocytes stimulated in vitro by non‐specific mitogens (PHA, ConA, PWM) upon exposure to extremely low frequency EMF has been studied. Different frequencies of square waveforms have been used. PHA‐stimulation resulted in strong inhibitions as measured by [3H]thymidine incorporation. A frequency window (3–50 Hz) within which ConA‐induced blastogenesis was significantly inhibited has been individuated. The mitogenic effect of PWM was significantly affected only at 3 Hz.

A role for Ca2+ in the effect of very low frequency electromagnetic field on the blastogenesis of human lymphocytes

The DNA synthesis of lymphocytes triggered by phytohemagglutinin or phorbol‐myristate‐acetate is strongly reduced by the externally applied electromagnetic field (ELF). Ca2+ uptake by stimulated lymphocytes is also reduced by ELF. The effect appears to be synergistic with that of the well‐known calcium blocker agent, verapamil.

Mitogen dose-dependent effect of weak pulsed electromagnetic field on lymphocyte blastogenesis

The effects of pulsed extremely low frequency electromagnetic fields on human peripheral blood lymphocyte mitogenesis induced by phytohaemoagglutinin, concanavalin A or calcium ionophore A23187 were studied. The dependence of the field effect on mitogen concentrations was investigated. Field exposure produced strong inhibition of DNA synthesis when optimal doses of mitogens were used, confirming our previous findings. Opposite effects were observed at suboptimal concentration of mitogens. Experiments performed by exposing cell cultures to the field for short periods indicated that a field application of at least 6 h is needed to influence irreversibly lymphocyte blastogenesis.

Augmentation of thromboxane production in vitro by polymorphonuclears and macrophages exposed to IL1/LP.

Human peripheral blood polymorphonuclear leukocytes (PMNs) and murine peritoneal macrophages (Mø) were stimulated to generate thromboxane upon treatment with highly purified human interleukin 1/leukocytic pyrogen (IL1/LP) at various concentrations. Thromboxane B2 was measured by radioimmunoassay in the cell-free supernatants of cell suspensions after 1 hour incubation at 37°C. Thromboxane B2 amounts increased in a way which depended on the dose of IL1 added to the cell cultures.

Inhibition of leukotriene B4 in neutrophils by lipoxins A4 and B4.

Lipoxins are derived from the oxygenation products of arachidonic acid in human leukocytes. They have exhibited selective biological effects different from those of other eicosanoids. We have examined the effect of lipoxin A4 and B4 (LXA4, LXB4) on the production of leukotriene B4 (LTB4) in human neutrophils. Cultured human polymorphonuclear leukocytes were preincubated with LXA and B and their ability to inhibit LTB4 generation was assessed after incubation with calcium ionophore A23187. We found that the pretreatment of neutrophils with lipoxins inhibit the release of LTB4 by A23187 stimulated PMNs. Our data suggests that LXA4 and B4 can contribute to immunosuppression in an inflammatory state via the inhibition of LTB4 synthesis.

Enhancing Effect of Electromagnetic Exposure on Calciumionophore (A23187), but Not IL-1, Induced Txa2 Release by Human Neutrophils

The exposure of human polymorphonuclears to an extremely low frequency (3 Hz) electromagnetic field for 1 hour had an enhancing effect on thromboxane A2 release stimulated by A23187 calcium ionophore. On the contrary, IL-1 stimulation of TxA2 production was not affected by an electromagnetic field, suggesting that interleukin-1 influence on thromboxane synthesis is not due to a calcium ionophore-like action.

A comparative study of the effects of some non-steroidal anti-inflammatory drugs on prostacyclin productionex vivo and on thromboxane B2 release by polymorphonuclearsin vitro

We have measured the formation of prostacyclin (PGI2) in the rat gastric mucosaex vivo following oral administration of indomethacin, protacine and sodium salicylate (SS). It has been found that protacine, like indomethacin but in contrast to SS, markedly reduces PGI2 synthesis as measured by inhibition of ADP-induced platelet aggregation. Parallel gastro-ulcerogenic studies demonstrate that protacine has very weak gastric irritancy when compared with indomethacin. In addition, the effect of these drugs has been evaluated on thromboxane B2 (TXB2) release by human polymorphonuclears (PMNs) stimulated with A23187 ionophorein vitro. It has been shown that protacine, like indomethacin, strongly inhibits cyclooxygenase activity as measured by radioimmunoassay of TXB2. SS partially prevents the inhibitory effect of either

Effects Induced “in vitro” by Extremely Low Frequency Electromagnetic Fields (E.L.F.) on Blastogenesis of Human Lymphocytes and on Thromboxane B-2-Release by Ionophore-Stimulated Neutrophils

Exposure to extremely low frequency electromagnetic fields (E.L.F.) can produce functional changes in biological systems. Dixey and Rein (1) have reported that 3H-noradrenaline release from PC12 cells is increased by a 500 Hz E.L.F. Pilla et al. (2) have observed that cell differentiation of frog blood cell is modified by exposure to a E.L.F., in a waveform and frequency-dependent way. The response of cultured bone and bone cells to hormones in the presence of E.L.F. have been studied by Luben et al. (3). E.L.F. exposure blocks the inhibition of collagen synthesis by parathyroid hormone, but it does not influence the effects of 1,25-di-hydroxy vitamin D3, a hormone that acts via a cytoplasmatic rather than a membrane receptor. Lyle et al. (4) describe an inhibitory effect of 450-MHz fields, sinusoidally modulated at frequencies from 0 to 100 Hz, on the T-lymphocyte cytotoxicity. In this report we describe the effects of E.L.F. on two different human cell systems “in vitro”: lymphocytes stimulated with non specific mitogens and polymorphonuclears leukocytes (P.M.N.) activated by calcium ionophore A23187 (5,6).

Effect of supernatants from PHA-stimulated and non-stimulated lymphocyte cultures on thromboxane B2 release by polymorphonuclear leukocytesin vitro

The present study involves the determination of the effect of supernatants obtained from mitogen-induced lymphocytes of human tonsils and containing lymphotoxins on human peripheral blood polymorphonuclear leukocytes (PMNs). PMNs treated with supernatants from phytohemagglutinin-stimulated lymphocytes were found to increase the release of thromboxane B2, compared to normal control levels. This increase was blocked by the preincubation of PMNs with indomethacin. The production or increase in production of thromboxanes may be induced by lymphotoxins since these substances have been reported to activate phospholipase A2 in target cell membranes, which may result in release of the thromboxane precursor, arachidonic acid.

Effect of indomethacin or aspirin in association with diflunisal or sodium salicylate on prostacyclin release by rat gastric mucosa

Non-steroidal anti-inflammatory drugs (NSAIDs) have a damaging effect on gastric and intestinal mucosa due to their inhibitory action of prostaglandin (PG) synthesis by blocking cyclooxygenase activity.Prostacyclin (PGI2) is the main metabolite of arachidonic acid in gastric mucosa and its production is inhibited by NSAIDs. Indomethacin or aspirin administration produce erosions and ulcers by inhibiting PGI2 generation in the stomach. Other NSAIDs such as diflunisal, and even more sodium salicylate in rats, produce a lower degree of gastric ulcerogenity than that observed when indomethacin or aspirin were given alone.In the present work tests were carried out to confirm if combinations of indomethacin or aspirin with diflunisal or sodium salicylate block PGI2 release from gastric mucosa less than the administration of the compounds alone. PGI2 generation by gastric mucosa was determined on aliquots of incubated mucosal strips tested for ADP-induced aggregation of human platelet rich plasma (PRP).The results were compared with those obtained with known amounts of authentic PGI2 on ADP-induced aggregation of PRP. The obtained data indicate that the PGI2 production found in rats treated with indomethacin or aspirin combined with diflunisal or sodium salicylate was higher than that found in rats treated with indomethacin or aspirin alone. This effect may be explained by competition between salicylates and other NSAIDs for binding sites on PG-synthetase and plasma proteins.