Cyclic GMP and cell movement

Stimulation of guanylyl cyclase-D by bicarbonate

Guanylyl cyclases (GCs) catalyze the conversion of GTP to the second messenger cGMP. While some transmembrane GCs are receptors for extracellular ligands, other transmembrane GCs such as retinal-specific GC-E and GC-F are stimulated by cellular proteins. GC-D is expressed in a special group of olfactory sensory neurons. However, the direct regulatory mechanism of GC-D activity is not completely understood. Here we have demonstrated that bicarbonate directly increases the activity of purified GC-D. Bicarbonate also increases the cGMP levels in cells expressing GC-D. These results identify bicarbonate as a small molecule that regulates GC-D.

The functional significance of leucocytes in human reproduction

There is now considerable evidence that leucocytes and their products have significant effects on the functional capacity of spermatozoa both in the male and female reproductive tract. Recent advances in the accurate detection of these leucocytes and their products using monoclonal antibodies and a parallel increase in the application of sophisticated sperm function tests has now made it possible to further determine the influence of the leucocytes on sperm function. It is therefore likely that this field of reproductive biology will be an area of considerable activity in the near future.

A Rac-cGMP signaling pathway

The small GTPase Rac and the second messenger cGMP (guanosine 3',5'-cyclic monophosphate) are critical regulators of diverse cell functions. When activated by extracellular signals via membrane signaling receptors, Rac executes its functions through engaging downstream effectors such as p21-activated kinase (PAK), a serine/threonine protein kinase. However, the molecular mechanism by which membrane signaling receptors regulate cGMP levels is not known. Here we have uncovered a signaling pathway linking Rac to the increase of cellular cGMP. We show that Rac uses PAK to directly activate transmembrane guanylyl cyclases (GCs), leading to increased cellular cGMP levels. This Rac/PAK/GC/cGMP pathway is involved in platelet-derived growth factor-induced fibroblast cell migration and lamellipodium formation. Our findings connect two important regulators of cellular physiological functions and provide a general mechanism for diverse receptors to modulate physiological responses through elevating cellular cGMP levels.

Directional sensing of a phorbol ester gradient requires CD44 and is regulated by CD44 phosphorylation

Cancer progression is associated with enhanced directional cell migration, both of the tumour cells invading into the stroma and stromal cells infiltrating the tumour site. In cell-based assays to study directional cell migration, phorbol esters are frequently used as a chemotactic agent. However, the molecular mechanism by which these activators of protein kinase C (PKC) result in the establishment of a polarized migratory phenotype is not known. Here we show that CD44 expression is essential for chemotaxis towards a phorbol ester gradient. In an investigation of CD44 phosphorylation kinetics in resting and stimulated cells, Ser316 was identified as a novel site of phosphorylation following activation of PKC. PKC does not phosphorylate Ser316 directly, but rather mediates the activation of downstream Ser316 kinase(s). In transfection studies, a phosphorylation-deficient Ser316 mutant was shown to act in a dominant-negative fashion to impair chemotaxis mediated by endogenous CD44 in response to a phorbol ester gradient. Importantly, this mutation had no effect on random cell motility or the ability of cells to migrate directionally towards a cocktail of chemoattractants. These studies demonstrate that CD44 functions to provide directional cues to migrating cells without affecting the motility apparatus.

An attempt to integrate Western and Chinese medicine: rationale for applying Chinese medicine as chronotherapy against cancer

Current Western medical treatment lays its main emphasis on evidence-based medicine (EBM) and cure is assessed by quantifying the effects of treatment statistically. In contrast, in Chinese medicine, cure is generally assessed by evaluating the patient's "pattern" (Zheng) [cf. Glossary] and medicines are prescribed according to this. We believe that traditional Chinese medicine (TCM) cannot be evaluated precisely according to Western principles, in which a constant amount of the same medicine is given to a group of patients to be evaluated. When assessing cure using TCM, Zheng is more important than the determination of medical effects. This means that quantitative evaluation of TCM treatment can be very difficult. In this paper, we focused on the Yin-Yang [cf. Glossary]balance to determine Zheng, and at the same time attempted to determine the treatment effects by applying the concept of regulation of Yin-Yang according to chronotherapeutic principles. According to Zheng, advanced cancer patients generally lack both Yin and Yang. Chinese medical treatment therefore seeks to supplement both Yin and Yang. However, we divided patients into two groups and compared them with respect to survival. One group was administered a predominantly Yang (Qi) [cf. Glossary] tonic herbal treatment during the daytime, while the other group was administered Yin (Blood) [cf. Glossary] tonics during night time. A comparison of the results of treatment showed that the patients in the group receiving Yang (Qi) replenishment during the daytime lived longer than patients receiving Yin (Blood) nourishment during the night. Moreover, the patients in the daytime Yang (Qi) replenishment group also fared significantly better than patients treated solely by Western methods.

Trilinolein potentiates the pro-aggregating effect of phorbol-12-myristate 13-acetate in human polymorphonuclear leukocytes

Trilinolein, a triacylglycerol with linoleic acid as the only type of fatty acid residue in all three of the glycerol esterified positions, was recently reported to have an antiplatelet effect, mediated through stimulating nitric oxide and cyclic guanosine monophosphate (GMP) formation. In our study, trilinolein induced aggregation of human polymorphonuclear neutrophils (PMNs) and, pretreatment with 0.1 nM trilinolein enhanced phorbol-12-myristate 13-acetate (PMA) induced aggregation. Further investigation showed that trilinolein at concentrations ranging from 0.1 nM to 10 microM increased cyclic GMP formation after 10 min of incubation with PMNs. Pretreatment of trilinolein with 10 microM d-sphingosine, before being incubated with PMNs, attenuated the stimulatory effect of trilinolein on cyclic GMP formation, and pretreatment of 10 microM d-sphingosine also attenuated the aggregation induced by PMA and trilinolein. We conclude that trilinolein can induce the aggregation of human PMNs, and enhance the aggregation induced by PMA.

Effect of long-term corticosteroid therapy on monocyte chemotaxis in man

The influence of prednisolone on monocyte chemotactic activity in vitro at prednisolone concentrations comparable with those achieved in man following oral dosage has been investigated. Chemotactic activity of monocytes from each of sixteen normal subjects was suppressed by concentrations of prednisolone as low as 25 ng/ml (suppression of chemotaxis, 20%). Maximal suppression occurred at 100 ng/ml (suppression of chemotaxis, 48%) and no significant increase in suppression was produced by increasing the concentration to 200 ng/ml (suppression of chemotaxis, 53%). In contrast, monocytes isolated from ten patients receiving corticosteroid therapy showed no significant suppression of chemotactic activity when exposed to these concentrations of prednisolone, even though they exhibited a normal ability to respond to a chemotactic stimulus. The lack of suppression of monocyte chemotaxis in patients receiving corticosteroid therapy is unexplained, but may represent a change in the circulating monocyte or lymphocyte populations.

Signal transduction: activation of the guanylate cyclase-cyclic guanosine-3'-5' monophosphate system by hormones and free radicals

Intracellular communication and transmission of messages for many hormones and free radicals occur after the hormones and free radicals bind to their receptors by enhancing the activity of guanylate cyclase, the enzyme that catalyzes the conversion of guanosine triphosphate to the intracellular messenger cyclic guanosine-3'-5' monophosphate (cyclic GMP). The guanylate cyclase-linked receptors exist intracellularly (ie, cytoplasmic) and in membrane-bound forms. Enhancement of guanylate cyclase by hormones or free radicals increases intracellular cyclic GMP, which closes cation channels in the kidney while activating cation channels in the retina and olfactory cilia, either directly or by cyclic GMP-dependent protein kinase. Cyclic GMP also has potent blood pressure lowering properties. Cyclic GMP promotes growth by increasing DNA, RNA, and protein synthesis. Overactivity of this system is observed in Traveler's diarrhea, whereas underactivity occurs in Chediak-Higashi syndrome in which lysosomal enzyme release and chemotaxis are defective and can be corrected in vitro by addition of cyclic GMP.

Inhibition of human neutrophil beta2-integrin-dependent adherence by hyperbaric O2

Animal and clinical investigations have reported that exposure to hyperbaric O(2) improved the outcome of some reperfusion injuries. Animal studies have suggested that this may be due to an inhibition of leukocyte adherence to injured endothelium. This investigation tested the hypothesis that exposure to hyperbaric O(2) would inhibit beta2-integrin-dependent adherence of human neutrophils. Subjects were exposed to O(2) at partial pressures of up to 3 atmospheres absolute (ATA; 1 ATA = 0.1 MPa) for 45 min, and neutrophil binding to nylon columns and to fibrinogen-coated surfaces was measured. Exposure to O(2) at 2.8 or 3.0 ATA inhibited beta2-integrin-dependent neutrophil adherence but had no effect on the cell-surface expression of beta2-integrins, respiratory burst in response to phorbol ester, or non-beta2-integrin-dependent adherence to plastic plates coated with a fibronectin-like protein. beta2-Integrin adherence was restored by incubating blood with 8-bromoguanosine 3',5'-cyclic monophosphate (cGMP) and hyperbaric O(2) inhibited synthesis of cGMP by neutrophils stimulated with N-formyl-Met-Leu-Phe (FMLP). In studies of cell fractions, the activity of membrane guanylate cyclase was found to be increased by incubation with FMLP as well as by atrial natriuretic peptide (ANP) plus ATP. Hyperbaric O(2) had no effect on the basal activity of soluble or membrane-bound guanylate cyclase. However, hyperbaric O(2) inhibited the function of both the extracellular binding domain of membrane guanylate cyclase as well as intracellular catalytic activity. There are approximately 7,300 membrane guanylate cyclase molecules per cell, based on binding studies with ANP, with a dissociation constant of approximately 450 pM. Hyperbaric O(2) inhibits the function of human neutrophil beta2-integrins by a process linked to impaired synthesis of cGMP.

High-dose catecholamine treatment decreases polymorphonuclear leukocyte phagocytic capacity and reactive oxygen production

Flow cytometry was used to study phagocytic function (uptake of fluorescein isothiocyanate-labeled bacteria) and release of reactive oxygen products (dihydrorhodamine 123 converted to rhodamine 123) following phagocytosis by neutrophil granulocytes of heparinized whole blood treated with adrenaline, noradrenaline, dopamine, dobutamine, or orciprenaline. Reduced neutrophil phagocytosis and reactive oxygen production were seen at 12 micrograms of adrenaline per liter (72% each compared with control values); at 120 micrograms of noradrenaline (72% each), dobutamine (83 and 80%, respectively), and orciprenaline (81 and 80%, respectively) per liter; and at 100 micrograms of dopamine per liter (66 and 70%) (P < 0.05 for all). At these dosages, neutrophil chemotaxis was reduced to < 50% of control values for all catecholamines. Treatment with catecholamines at lower dosages had no significant effect on phagocytosis or generation of reactive oxygen products or chemotaxis. The phagocytic capacity of granulocytes was related to the generation of reactive oxygen products (r = 0.789; P < 0.05). The results demonstrate that catecholamines have a suppressive effect on the response of phagocytic cells to bacterial pathogens at high therapeutic levels in blood.

The role of cyclic nucleotides in neutrophil migration

1. The literature concerning the effects of cAMP and especially cGMP on neutrophil migration is reviewed. 2. Experiments with agents that enhance cGMP level, and with electroporated neutrophils in which cGMP was introduced, show that the nucleotide has different effects. There is a maximal stimulation at a specific concentration while higher concentrations are less effective or even inhibitory. 3. Some physiologically active peptides such as granulocyte-macrophage colony-stimulating factor (GM-CSF), atrial natriuretic factor, and endothelin appear to modify neutrophil migration via a cGMP-dependent mechanism. 4. Dependent on concentration and conditions (random migration vs. fMLP-activated migration, using nitric oxide (NO), NO donors, and inhibitors of NO synthase), NO has stimulatory or inhibitory effects on neutrophil migration. 5. The differential effects of cGMP and cAMP on neutrophil migration are discussed with regard to intracellular actions, metabolism, interaction with calcium, and relation to structural changes required for cell movement.

Cyclic nucleotide changes induced in human leukocytes by a product of axenically grown Entamoeba histolytica that inhibits human monocyte locomotion

Pulse exposure of human mononuclear phagocytes to the monocyte locomotion-inhibitory factor produced by Entamoeba histolytica (i.e., the 369- to 765-Da chromatographic fraction obtained from the supernatant fluid of axenically grown E. histolytica) led to a swift increase in the intracellular concentration of adenosine 3':5' cyclic monophosphate (cAMP). A weaker response was observed in human polymorphonuclear leukocytes, the locomotion of which, however, is not inhibited by this amebic factor. The same chromatographic fraction obtained from the axenic medium control lacked this effect, at least upon mononuclear phagocytes. On the other hand, both the monocyte locomotion-inhibitory factor and the axenic medium control, possibly through shared cultured medium components, induced comparable increases in guanosine 3':5' cyclic monophosphate (cGMP) in human mononuclear phagocytes and in polymorphonuclear leukocytes, thus suggesting that the latter-nucleotide is not critical for the leukotactic inhibitory phenomenon. Our results suggest that like other leukotactic inhibitors, the monocyte locomotion-inhibitory factor produced by E. histolytica operates through modulations of intracellular cAMP.

Potentiation and inhibition of migration of human neutrophils by auranofin

OBJECTIVES

As auranofin resembles some neutrophil activating sulphur containing compounds, it was decided to investigate whether it had activating effects on neutrophil migration in addition to the published inhibitory effects.

METHODS

The Boyden chamber assay was used to determine the migration velocity of human neutrophils. The difference between chemotaxis and chemokinesis was established with a chequerboard assay.

RESULTS

Low concentrations of auranofin stimulated human neutrophil migration; concentrations of auranofin higher than 1 mumol/l were inhibitory. Inhibitors of leukotriene formation, or of protein kinase C, had the same effect on auranofin induced potentiation of migration as on fMLP activated migration. Auranofin, at a concentration of 100 nmol/l, caused a transient increase in the cGMP level of neutrophils. The auranofin induced increase in migration was strongly inhibited by methylene blue and by LY83583, two inhibitors of cGMP accumulation.

CONCLUSIONS

The auranofin induced enhancement of migration is partly due to a chemokinetic effect, but mainly due to a chemotactic effect. The potentiating effect of auranofin on migration is not specifically due to the ability of the drug to inhibit protein kinase C activity or to generate leukotrienes. These results suggest that the enhancement of neutrophil migration by low levels of auranofin is related to the enhancement of cGMP levels in neutrophils.

The effect of cyclic GMP and cyclic AMP on migration by electroporated human neutrophils

Human neutrophils retain the ability to migrate when they are electroporated; this enables the study of potential mediators by direct application to the cell interior. Cyclic GMP strongly enhances random migration by electroporated human neutrophils. The effect is maximal at a concentration of 10 microM. The potentiating effect of cGMP is chemokinetic. Chemotaxis of electroporated neutrophils activated by formylmethionylleucylphenylalanine (fMLP) is stimulated by cGMP at concentrations up to 10 microM; higher concentrations inhibit chemotaxis. Cyclic AMP resembles cGMP in that both activation and inhibition may occur. However, activation occurs over a very small concentration range, and inhibition is a predominant feature. Cyclic nucleotide-activated migration is dependent on Ca2+, in contrast with activation of migration by fMLP.

Differential stimulation of neutrophil functions by pyrithioxine

The drug pyrithioxine strongly stimulated in vitro migration by rabbit peritoneal neutrophils. The stimulating effect appeared to be chemotactic rather than chemokinetic. Though the drug did not induce exocytosis by itself, it stimulated fMet-Leu-Phe-induced exocytosis. The effect on exocytosis induced by other activators was not statistically significant. No stimulating effect of pyrithioxine on superoxide production was observed, either in the absence or in the presence of activators. For a maximal stimulating effect on migration and exocytosis the presence of extracellular Ca2+ was required. Pyrithioxine caused an increase of cGMP level in neutrophils. The hypothesis is presented that the differential activation of neutrophil functions by pyrithioxine is mediated by cGMP, and that cGMP has a differential importance for the neutrophil functions studied.

Modulation of neutrophil migration by captopril

Because neutrophils might be involved in some of the therapeutic effects of captopril we studied the effect of captopril on neutrophil migration. Captopril strongly enhances migration by rabbit peritoneal neutrophils. Stimulation by captopril was maximal at a concentration of about 400 microM; at higher concentrations stimulation decreased again. The stimulatory effect is partly chemokinetic, and partly chemotactic. Captopril disulfide also stimulates migration, though the stimulating effect is less than that of captopril. Captopril-induced stimulation of migration was strongly inhibited by pretreatment of neutrophils with pertussis toxin, indicating that the stimulation is mediated by a pertussis toxin-sensitive G protein. Intact sulfhydryl groups on the cell surface are required for stimulation because inactivation of these groups with the non-penetrating sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) completely abolishes the stimulating effect of captopril and of captopril disulfide. Both captopril and captopril disulfide cause an enhancement of cyclic GMP level in the neutrophil. The enhancement of both the cGMP level and that of migration is blocked by methylene blue and by LY-83583, suggesting that the stimulating effect of captopril is mediated by cGMP. Inhibitors of NO generation, such as NG-monomethyl-L-arginine, NG-nitro-L-arginine and canavanine have no effect on captopril-induced stimulation of migration, indicating that NO is not involved in the stimulating effect of captopril.

Preliminary communication: possible role of reactive nitrogen intermediates in leucocyte-mediated sperm dysfunction

This preliminary study was designed to examine whether nitric oxide, a reactive nitrogen intermediate produced by leukocyte metabolism of L-arginine, could reduce sperm motility. Increasing doses (10(-6)-10(-4) M) of the nitric oxide-generating drug, sodium nitroprusside (SNP) were added to motile sperm preparations and incubated over 20 hr. Quantitative sperm motility measurements were made using a computer-assisted motility analyzer in each treated sample and controls over this time period. The percentage of motile sperm, progressive motility, and concentration of motile cells were all significantly reduced with all doses of SNP. This effect was not observed in preparations treated with oxyhaemoglobin (HbO2). Mean path velocity was unaltered. Sperm viability in SNP treated sperm did not differ significantly from that of control sperm over the same time period. We conclude that further experiments are required to determine whether the production of nitric oxide/reactive nitrogen intermediates in vivo by activated leukocytes could be a contributory factor in the development of immunologic infertility.

Glutathione-induced enhancement of neutrophil locomotion

Both reduced glutathione (GSH) and and its oxidized form, glutathione disulfide (GSSG), enhance neutrophil locomotion. The enhancement is mainly due to a chemokinetic effect, and partly due to a chemotactic effect. A number of other SH-group containing compounds were not effective in enhancing neutrophil migration. While random locomotion is not inhibited by the slowly-penetrating sulfhydryl agent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), the enhancement of migration due to GSH is completely inhibited. Pretreatment of neutrophils with pertussis toxin completely inhibited the GSH-induced stimulation of locomotion, suggesting that stimulation of migration by glutathione was mediated by a pertussis toxin sensitive G-protein. Chemotaxis towards GSH is inhibited by the same agents that inhibit fMet-Leu-Phe induced chemotaxis, except that colchicine was a more effective inhibitor of GSH-induced chemotaxis than of fMet-Leu-Phe directed chemotaxis. GSH enhances the intracellular concentration of cGMP, which might indicate that the effect on neutrophil locomotion is mediated by an effect on cGMP.

Stimulation of rabbit polymorphonuclear leukocyte locomotion by D-penicillamine

Treatment of polymorphonuclear leukocytes (PMNs) with penicillamine has little effect on chemotaxis of the cells towards fMet-Leu-Phe. In the absence of fMet-Leu-Phe however, penicillamine has a strong effect on PMN locomotion. Penicillamine-induced enhancement of PMN migration is for an important part due to a chemokinetic effect, but there is also a chemotactic effect. Pretreatment of PMNs with membrane-impermeable sulfhydryl reagents has little effect on random locomotion, but completely abolishes the activating effect of penicillamine. This suggests that for the activating effect of penicillamine intact sulfhydryl groups on the outer surface of the PMN are required. Extracellular calcium is no absolute requirement for PMN migration, neither for random locomotion nor for the activating effect of penicillamine. Removal of intracellular Ca2+ with membrane-penetrating Ca2+-complexing agents strongly inhibit penicillamine-induced enhancement of PMN migration, underlining a role for intracellular calcium. Penicillamine causes an increase of cGMP level in PMNs. Though a simple relationship seems unlikely it is possible that the enhancement of PMN migration, and the increase of cGMP level by penicillamine are related processes.

Mechanisms of action involved in the chemoattractant activity of three beta-lactamic antibiotics upon human neutrophils

The effects produced by three beta-lactamic antibiotics (N-formimidoyl thienamycin or imipenem, cefmetazole and cefoxitin) in vitro on protein carboxylmethylation, cAMP and cGMP levels in human polymorphonuclear neutrophils were studied. These antibiotics (50 micrograms/mL) exhibited chemoattractant activity for phagocytic cells and produced a fast (0.5 min) and significant stimulation of protein carboxylmethylation. They also increased intraphagocytic cGMP levels although no changes in cAMP levels were observed. Since the involvement of the above-mentioned mechanisms in leukotaxis have been established, the stimulation of neutrophil chemotaxis by the three antibiotics studied could possibly be mediated by one or more of these mechanisms.

Nitric oxide and prostacyclin. Divergence of inhibitory effects on monocyte chemotaxis and adhesion to endothelium in vitro

Monocyte-endothelial interactions are of fundamental importance in determining the movement of monocytes from the blood stream into the vessel wall. This study reports that two endothelium-derived factors, nitric oxide and prostacyclin, alter in vitro monocyte behavior. Nitric oxide (greater than 10(-5) M) inhibited monocyte adhesion to porcine aortic endothelial cell monolayers, whereas prostacyclin (10(-9) to 10(-5) M) had no effect. Both nitric oxide and prostacyclin inhibited monocyte chemotaxis stimulated by N-formyl-methionyl-leucyl-phenylalanine and induced dose-dependent increases in intracellular cyclic guanosine monophosphate and cyclic adenosine monophosphate concentrations, respectively. The cell surface expression of the CD11b/CD18 adhesion receptor, a glycoprotein complex known to mediate monocyte intracellular adhesion, was not altered by either nitric oxide or by prostacyclin. Thus, endothelium-derived nitric oxide and prostacyclin may have a physiological role in modulating monocyte-vascular wall interactions. Alterations in this system may contribute to the increased monocyte emigration from the blood stream into the vessel wall observed in atherogenesis.

Decrease in the carbamylcholine-induced chemotaxis of monocytes in myasthenia gravis

The carbamylcholine-induced chemotaxis of monocytes was decreased in patients with myasthenia gravis, whereas no change was found in the C5a-induced locomotion of these cells compared with that of the normal controls. The decrease in the chemotaxis induced by carbamylcholine correlated with the severity of clinical symptoms. The beneficial effect of thymectomy was also reflected in the improvement of chemotaxis. The method is simple, not expensive and could be used in the diagnosis of myasthenia gravis.

Migration of dog polymorphonuclear neutrophilic leukocytes to formylated peptides

Formylated peptides are potent stimulants of polymorphonuclear neutrophilic leukocyte (PMN) migration from species such as humans and rabbits. Interestingly, PMNs from dogs, cats, pigs and cows have been reported as refractory to N-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP) and generally are believed not to express formylpeptide receptors. Formylpeptides are a major component of conditioned media from E. coli cultures and believed to be a significant element in inflammatory responses elicited by E. coli. Our studies have found that E. coli filtrate was a potent stimulant of dog PMN migration. Inhibition of migration to E. coli filtrates by the antagonist t-botyloxycarbonyl-l-methionyl-l-leucyl-l-phenylalanine (t-boc-MLP) demonstrated that the migration was mediated through the formylated peptide receptor. Migration in response to peptides with higher affinity for the formylpeptide receptor than FMLP was further evidence for these receptors on the dog PMN. PMNs from dogs migrated in response to FMLP at high concentrations (100 microM); however, pretreatment with phorbol myristate acetate resulted in increased migration of dog PMNs in response to concentrations of FMLP as low as 1 pM. These results demonstrate that dog PMNs are responsive to formylpeptides and that these responses can be up-regulated by PMA. Thus PMNs from a species previously thought incapable of responding to formylpeptides can respond to formylpeptide analogs with high affinity for the receptor as well as be primed for enhanced migration to FMLP by PMA.

Forskolin and prostaglandin E2 regulate the generation of human cytolytic T lymphocytes

In this paper we examine the characteristics of human cytolytic T lymphocytes (CTL) generated in the presence of forskolin and PGE2. Forskolin and PGE2 suppressed the generation of class-I-specific CTL. The CTL generated in the presence of forskolin and PGE2 had different characteristics which included their ability to proliferate in response to the alloantigen and their lectin-mediated cytolytic activity. The CTL generated in the presence of forskolin had normal proliferative response to the alloantigen, whereas the CTL generated in the presence of PGE2 showed a suppressed proliferative ability to the alloantigen. The two groups of CTL were then tested for their activity in the process of lectin-dependent cell-mediated cytotoxicity. After the addition of PHA into the chromium release assay the CTL generated in the presence of forskolin normally lysed the nonspecific targets, whereas the CTL generated in the presence of PGE2 did not show the normal response in lysing the nonspecific targets. The results suggest that the cytolytic machinery was intact when the CTL were generated in the presence of forskolin but CTL were not able to either recognize or lyse the target cell. However, the CTL generated in the presence of PGE2 did not share the same characteristics as the CTL generated in the presence of forskolin because the CTL generated in the presence of PGE2 were unable to kill even in the presence of lectin. It appears that the inhibitory effects of forskolin were mediated by cAMP and not by its effects on the potassium channels because the 1,9-dideoxy derivative of forskolin which did not activate adenylate cyclase also did not suppress the generation of CTL. However, it was not established whether the diverse effects of PGE2 on the generation of CTL were mediated by cAMP-dependent, -independent or by both mechanisms.

Beta-adrenoceptor antagonist-induced psoriasiform eruption. Clinical and pathogenetic aspects

A number of beta-adrenoceptor blocking drugs have been reported to induce a papulosquamous eruption which resembles psoriasis. We report distinctive clinical, histopathologic, immunocytochemical, and electron microscopic features in beta-blocker-induced psoriasiform eruptions that differentiate this syndrome from psoriasis. Preliminary data suggest that biopsy specimens from eruptions caused by beta 1-selective adrenoceptor blocking agents (metoprolol and atenolol) were characterized by excessive degranulation of the neutrophils in the dermis, while the nonselective beta blockers (propranolol, nadolol, and sotalol) were marked by excessive release of proteolytic enzymes from macrophages, which are thought to possess beta 2-adrenergic receptors. Surprisingly, excessive release of enzymes by lymphocytes were noted in both the beta 1-selective and in the nonselective induced syndromes. It is believed that excessive lysosomal enzyme release by neutrophils, lymphocytes, and macrophages is responsible for the presence of basal keratinocyte herniations, which have previously been shown to correlate with hyperproliferation and psoriasiform changes, as well as with the presence of excessive proteolytic enzymes in the skin. It is postulated that the beta-blocker-induced syndrome may result from enhanced proliferation, motility, and activity of lymphocytes, neutrophils, and cells of the macrophage-Langerhans cell series, stemming from depressed intracellular cyclic adenosine monophosphate levels caused by the beta blockade.

The development of contact hypersensitivity in mouse skin is suppressed by tumor promoters

The ability of tumor promoters to suppress the development of contact hypersensitivity (CHS) was assessed by the mouse ear swelling assay. Application of the complete or second stage tumor promoters phorbol-12-myristate-13-acetate (PMA, 2 micrograms), croton oil (1%), benzoyl peroxide (20 mg), mezerein (2 micrograms), or phorbol-12-retinoate-13-acetate (PRA, 2 micrograms) to the abdominal surface of CF-1 female mice for 1 week (three treatments) prior to the sensitization of the same location with 0.5% 1-chloro-2,4-dinitrobenzene (DNCB) resulted in a 50% suppression (p less than 0.05) of the CHS response to DNCB. The first stage tumor promoters 4-O-Me-PMA (80 micrograms), calcium ionophore A23187 (80 micrograms), hydrogen peroxide (15%) and the non-promoting analogs phorbol-12,13-diacetate (PDA, 20 micrograms), phorbol (80 micrograms) or acetone did not suppress the response. The suppression of the development of CHS caused by PMA was dependent on the promoter being applied at the site of induction and was inhibited by application of the phospholipase A2 inhibitor dibromoacetophenone (100 micrograms), the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 100 micrograms), or the antiinflammatory steroid fluocinolone acetonide (2 micrograms). Application of PMA or mezerein 24 h prior to challenge with DNCB, to the ears of mice previously sensitized with DNCB resulted in a significant enhancement of the ear swelling response by 60% and 110%, respectively, compared with controls. The results demonstrate that tumor promoters suppress the development of CHS, and suggest the possibility that second stage promotion may involve suppression of the development of a tumor specific immune response.

The effects of megadoses of ascorbic acid on PMN chemotaxis and experimental gingivitis

A double-blind study was undertaken to determine the effects of megadose ascorbic acid supplementation on plasma ascorbate levels, polymorphonuclear neutrophil (PMN) chemotaxis and clinical and biochemical determinations of inflammatory progression in individuals with a mean daily ascorbate intake level of approximately twice the recommended daily allowances. Results indicate that although the group receiving ascorbate supplementation demonstrated a significant increase in plasma levels of the vitamin as compared to a placebo group, no significant differences with respect to PMN chemotaxis or responses to experimental gingivitis were found between the groups.

Retention of a functional resact receptor in isolated sperm plasma membranes

Resact, a peptide obtained from eggs, causes a change in the Mr, and a loss of 32P from a plasma membrane protein identified as guanylate cyclase. Here, a resact analog (125I-[Tyr1, Ser8] resact) was synthesized and shown to bind to isolated sperm membranes. Resact, but not speract, competed with the radiolabeled ligand for binding. When membranes were prepared under appropriate conditions, guanylate cyclase remained at Mr 160,000; the incubation of membranes with gamma-32P-ATP resulted in the formation of 32P-labeled guanylate cyclase. The addition of resact to the membranes caused a shift in the Mr, a complete loss of 32P, and a 70% reduction in guanylate cyclase activity within 1 min; resact had an ED 50 at 100 nM concentration. Speract failed to cause any of these effects. This represents the first demonstration of receptor-mediated responses of isolated sperm membranes identical to those seen in the intact cell.

Phorbol myristate acetate (PMA) suppresses polarization and locomotion and alters F-actin content of Walker carcinosarcoma cells

This study demonstrates a novel feature of PMA, its ability to suppress chemokinetic polarization and locomotion of tumor cells. Walker carcinosarcoma cells exhibit two distinct types of polarization and locomotion, i.e. spontaneous polarization characterized by ruffles at the front and stimulated polarization and locomotion in response to the microtubule-disassembling agents colchicine, vinblastine and nocodazole, which are characterized by blebbing at the front. The tumor promotor phorbol myristate acetate (PMA), but not phorbol, was found to suppress both types of polarization and random locomotion at concentrations between 10(-8) and 10(-6)M. The effect of 10(-6)M PMA was virtually complete within 5 min. Inhibition of locomotion was due to both a reduction in the speed of migrating cells and the proportion of migrating cells. Changes in shape and chemokinesis of Walker carcinosarcoma cells were associated with alterations in the relative amount and the topographical distribution of F-actin as determined by NBD-phallacidin binding. Suppression by PMA was associated with loss of the polar topographical distribution of F-actin visualized by NBD-phallacidin binding. In the presence of PMA, the relative amount of F-actin was higher than in unstimulated controls and lower in cells exposed to microtubule-disassembling agents.

Effects of modification of intracellularcyclic AMP levels on the imediate hypersensitivity reaction in vivo

Experiments were performed to study the effects of agents that elevate endogenous cyclic AMP levels on the progression of a reverse passive Arthus reaction in the pleural cavity of rats. Three hours after the onset of the reaction a marked reduction in histamine release was observed which correlated well with increases in cellular cyclic AMP concentration. The results at 6 hr suggested a relationship between cyclic AMP and leucocyte PGE, the latter being reduced dramatically both in the cells and in the fluid exudate by agents that elevate cyclic AMP. It was concluded that cyclic AMP may play an important regulatory role in vivo in the release of inflammatory mediators from leucocytes.

Chemotactic and random movement of cord-blood granulocytes

Chemotactic responsiveness and random movement of cord-blood granulocytes were studied with a modified Boyden's method. Cord-blood granulocytes were less active chemotactically than granulocytes from healthy children and adults, whereas the random filter movement of the cells from all three sources was about the same. In cord sera, concentrations of cell directed chemotaxis inhibitors were equal to those in sera from other age groups. Compared with the situation in healthy children and adults, the generation of chemotactic factors in cord-blood sera was impaired. This impairment was not related to an increased activity of chemotactic factor inactivators. Measurement of the cyclic nucleotide levels in granulocytes from cord-blood and from children belonging to various age groups revealed that the cord granulocytes have significantly lower concentrations of cAMP and cGMP, which could have been responsible for the decreased chemotactic responsiveness.

Effects of leukocyte inhibitory factor (LIF) on human neutrophil function

The effects of the lymphokine, leukocyte inhibitory factor (LIF), on human neutrophil function were studied. This soluble mediator, which is defined by its specific inhibition of neutrophil locomotion, does not interfere with chemotactic factor binding and does not affect basal or stimulated superoxide generation by neutrophils. In contrast, phagocytosis of opsonized Staphylococcus aureus is markedly inhibited by LIF, and degranulation is stimulated by this lymphokine. The possible mechanisms of LIF action on neutrophils are discussed.

Leishmania: chemotaxic responses of promastigotes and macrophages in vitro

Promastigotes of Leishmania move progressively up a concentration gradient of: various sugars, specific sugars attracting individual species of Leishmania; serum albumin and another unidentified constituent of serum; hemoglobin; and a factor generated by promastigotes in NNN medium. The movement of promastigotes up a concentration gradient of serum is optimal at a pH of 6.4 to 6.8 and a temperature of 28 degrees C and above. Cholinergic and adrenergic agents did not affect the attraction of serum for promastigotes, and cyclic nucleotides, inflammatory mediators, and macrophage products were not chemotaxic. It is postulated that the sugar chemotaxins influence the movement of promastigotes from the sand fly midgut to the esophagus, and serum chemotaxins may play a part in the entry of promastigotes into the skin of a mammal from the proboscis. Macrophages, the host cell of the obligate intracellular Leishmania species, were not attracted to any product of promastigotes. When, however, promastigotes interact with serum, complement is activated to form C5a which is chemotaxic for macrophages. Activation of complement by promastigotes is, at least partially, by the alternate pathway. Other chemotaxins resulting from promastigote interaction with serum may also be present. Promastigotes may also produce inhibitors of C5a activity.

Cytotaxin-induced cAMP peak in granulocytes: its relationship to crawling movements, chemokinesis and chemotaxis

The relationship between the short transient intracellular increase in cAMP levels on the one hand and chemotaxis or crawling movements on the other hand was investigated using human and equine granulocytes. C5ades arg, f-met-leu-phe, human serum albumin and immunoglobulin were used as stimulating agents. There was no strict correlation between the induction of crawling movements or of chemokinesis in general and the generation of the cAMP peak. But there was so far a strict parallelism between the occurrence of the chemotactic response and the cAMP peak. However, the magnitude of the peak was not representative for the extent of directional locomotion. It seems possible that cAMP is an essential step in the transduction of the chemotactic response, but there is no proof for a causal relationship as yet.

Calcium movement and membrane potential changes in the early phase of neutrophil activation by phorbol myristate acetate: a study with ion-selective electrodes

To quantitate calcium movements and membrane potential changes in stimulated neutrophils, we have measured net fluxes of Ca2+ and of the lipophilic cation tetraphenyl phosphonium by a very sensitive ion-selective electrode system. Activation of neutrophils by 3 X 10(-8) M phorbol 12-myristate, 13-acetate induces a release of approximately 20% of total cell calcium, with an initial lag period of less than 10 s. The Ca2+ outflux is markedly reduced in ATP-depleted cells and in the presence of a calmodulin inhibitor, thereby suggesting that it occurs by activation of the ATP-driven Ca2+ pump of the neutrophil plasmalemma. Activation of neutrophils also induces a transiently increased exchange of medium 45Ca with cell calcium, which is measurable a few seconds after cell exposure to the stimulant and peaks at approximately 40 s. Stimulation of neutrophils after attainment of steady-state accumulation of tetraphenyl phosphonium (resting potential of -67 mV) results in a marked depolarization, with a lag period of approximately 60 s. The rate and extent of depolarization are reduced by 40 and 65%, respectively, in a low Na+ medium but are not modified by an inhibitor of anion exchange across membranes. A high-K+ medium depolarizes neutrophils without either modifying their resting oxidative metabolism or impairing stimulability by the phorbol ester. Phorbol 12-myristate, which also exhibits no effect on the oxidative metabolism of neutrophils, does not induce Ca2+ extrusion and membrane potential changes. The causal relationship between Ca2+ mobilization, membrane potential changes and activation of neutrophil functions is discussed.

A short transient increase in cyclic adenosine 3', 5'-monophosphate levels of neutrophil granulocytes following exposure to chemotactic factors

Stimuli which are chemotactic for the retrospective neutrophils always produce a transient increase in cAMP within the first minute whereas the chemokinetic or other non-chemotactic stimuli tested have no such effect. The question as to whether the transient increase of cAMP levels plays any direct role in the transduction of a chemotactic stimulus cannot be answered. Restimulation experiments indicate that the extent of the cAMP response is not a reliable indicator for the chemotactic responsiveness of neutrophils; there is no quantitative correlation between these two parameters. Further detailed kinetic and quantitative studies of the cAMP system would be needed to clarify this point.

IgA-associated inhibition of polymorphonuclear leukocyte chemotaxis in neutrophilic dermatoses

The chemotactic activity of normal human polymorphonuclear leukocytes (PMNs) confronted with heat inactivated sera from patients with psoriasis as well as various chronic proliferative diseases was determined using modified Boyden chambers. By the addition of phorbol myristate acetate (PMA) at a concentration of 1 ng/ml the chemoattractant activities of the sera were greatly potentiated. However, the chemotactic migration of normal PMNs was strongly inhibited by sera from patients with long standing and wide spread psoriasis, pyoderma gangrenosum, severe acne conglobata, Sweet syndrome, and some patients with chronic arthritis following rheumatoid fever. In acute guttate psoriasis and atopic dermatitis increased migratory activities were seen. The inhibition of chemotaxis correlated with increased serum IgA levels as determined by radial immuno diffusion. Column chromatography (Sephacryl S-300) revealed serum fractions of strong inhibitory potency at a molecular weight near 200,000 Dalton. These inhibitory fractions were seen in patients with long standing neutrophil related diseases and could not be detected in normal control sera. It appears that inhibition of PMN chemotaxis is a secondary phenomenon and may play an autoregulatory role in PMN related inflammation.