Intracellular Calcium Ion Levels Research Articles

Role of calcium activated kinases and phosphatases in heat shock factor-1 activation.

HSF-1 is regulated at multiple molecular levels through intra- and intermolecular protein-protein interactions as well as by post-translational modification through phosphorylation. We have found that elevating intracellular calcium ion levels by exposure to the ionophore A23187 or thapsigargin inhibits the conversion of HSF-1 from a latent cytoplasmic form to its nuclear/DNA binding form. To examine a role for calcium/calmodulin regulated enzymes in this process, we examined the ability of specific inhibitors to abrogate the effects of calcium elevation. While the inhibitor of calmodulin dependent kinase II, KCN62 enhanced activation of HSF-1 during heat shock, it failed to block the inhibitory effects of calcium increase. By contrast, the immunosuppresant drugs cyclosporin A and FK506 abolished the effects of calcium elevation on HSF-1 activation. As the biological effects of the drugs are effected through inhibition of the calcium/calmodulin regulated phosphatase calcineurin, this suggests a role for calcineurin in antagonizing HSF-1 activity. The experiments suggest the existence of phosphorylated residue(s) in HSF-1 important in one or more of the processes that lead to activation (trimerization, nuclear localization, DNA binding) and which becomes dephosphorylated due to the activation of a calcium/calmodulin/calcineurin complex.

Chondroitin sulphate inhibits connective tissue mast cells.

1. Mast cells derive from the bone marrow and are responsible for the development of allergic and possibly inflammatory reactions. Mast cells are stimulated by immunoglobulin E (IgE) and specific antigen, but also by a number of neuropeptides such as neurotensin (NT), somatostatin or substance P (SP), to secrete numerous pro-inflammatory molecules that include histamine, cytokines and proteolytic enzymes. 2. Chondroitin sulphate, a major constituent of connective tissues and of mast cell secretory granules, had a dose-dependent inhibitory effect on rat peritoneal mast cell release of histamine induced by the mast cell secretagogue compound 48/80 (48/80). This inhibition was stronger than that of the clinically available mast cell 'stabilizer' disodium cromoglycate (cromolyn). Inhibition by chondroitin sulphate increased with the length of preincubation and persisted after the drug was washed off, while the effect of cromolyn was limited by rapid tachyphylaxis. 3. Immunologic stimulation of histamine secretion from rat connective tissue mast cells (CTMC) was also inhibited, but this effect was weaker in umbilical cord-derived human mast cells and was absent in rat basophilic leukemia (RBL) cells which are considered homologous to mucosal mast cells (MMC). Oligo- and monosaccharides were not as effective as the polysaccharides. 4. Inhibition, documented by light and electron microscopy, involved a decrease of intracellular calcium ion levels shown by confocal microscopy and image analysis. Autoradiography at the ultrastructural level showed that chondroitin sulphate was mostly associated with plasma and perigranular membranes. 5. Chondroitin sulphate appears to be a potent mast cell inhibitor of allergic and nonimmune stimulation with potential clinical implications.

Odontoblast differentiation: a response to environmental calcium?

The response of the dental pulp to calcium hydroxide has been well described but the process of pulpal repair leading to dentinal bridge formation appears complex and the mechanisms remain incompletely understood. Through the precise regulation of the free calcium ion in the cytosol, cells have been able to utilize anions such as phosphates for a wide range of activities such as energy production (oxidative phosphorylation). As anions are abundant in the cytosol, intracellular levels of calcium ions are kept low, several orders of magnitude less than that of the surrounding extracellular matrix. Consequently, cells are able to use calcium ions for the regulation of many cellular events. The binding of extracellular molecules such as cytokines, hormones or antibodies, with receptors on the plasma membrane may result in short- or long-term modifications to cellular metabolism, including the mechanisms of intracellular calcium homeostasis. Cell survival depends upon the ability to adapt to changes in the cell's micro-environment. Adaptation in turn results in altered cellular activity that may be interpreted as showing that the cell has become more or less specialised. In some instances this may include the resumption of mitotic activity. If the rate or magnitude of change exceeds a cell's adaptive capacity, the cell dies. Responses of cells to alterations in their environment are reviewed as they may provide an explanation for the success of calcium hydroxide in facilitating pulpal repair and the differentiation of odontoblasts.

Inhibition of leukotriene B4-INDUCED increase in intracellular calcium ion level of human peripheral blood polymorphonuclear leukocytes by Y-24180, an antagonist of platelet-activating factor receptor

Y - 24180 ( (±) - 4 - (2-chlorophenyl ) - 2 - [2 - (4-isobutylphenyl ) ethyl] - 6,9 - dimethyl - 6 H - thieno [3,2 - f ] [1,2,4] triazolo [4,3- a] [1,4] diazepine) , an antagonist of platelet-activating factor (PAF) receptor, has already been reported to inhibit leukotriene B 4 (LTB 4) -induced activation of polymorphonuclear leukocytes. In this article, to clarify the mechanism of inhibition of LTB 4-induced activation by Y-24180, we examined the effect of Y-24180 on LTB 4-induced increase in intracellular calcium ion ( [Ca 2] i) level of human polymorphonuclear leukocytes at a single cell level using a laser scanning confocal microscope. Preincubation with Y-24180 significantly inhibited the increase in [Ca 2] i level at 0.3–3 μM, while WEB 2086 (4- [3- [4- (2-chlorophenyl ) -9-methyl-6 H-thieno [3,2- f ] [1,2,4] triazolo [4,3- a] [1,4] diazepin-2-yl] propionyl] morpholine) , another PAF receptor antagonist, did not show the inhibitory effect at 3–30 μM, indicating that the difference in potency between these compounds was more than 100-fold. The LTB 4-induced increase in [Ca 2] i level was suppressed by microinjection of anti-PAF antibody, but not control antibody, into leukocytes. Microinjection of Y-24180 at 0.003–0.03 μM or WEB 2086 at 0.03–0.3 μM into leukocytes also inhibited the LTB 4-induced increase. The microinjection of WEB 2086 at the 10-fold greater concentrations than those of Y-24180 inhibited to the almost equal level to that obtained by Y-24180. In addition, microinjection of PAF into leukocytes induced the increase in [Ca 2] i level. Preincubation with Y-24180 at 1 or 3 μM significantly attenuated the PAF microinjection-induced increase, but WEB 2086 showed little effect at 3–30 μM. These results indicate that Y-24180 inhibits LTB 4-induced activation of leukocytes by suppressing the increase in [Ca 2] i level and the inhibitory effect is mediated by antagonistic action against intracellular PAF-induced up-regulation of [Ca 2] i level. The difference in inhibitory activity for the increase in [Ca 2] i level between Y-24180 and WEB 2086 when these are added in the culture medium may depend upon their aptitude for the transmembrane influx.

Effects of absorption enhancers on cytoskeletal actin filaments in Caco-2 cell monolayers

Histomorphological changes of actin filaments, intracellular levels of calcium ion, and amount of released lactate dehydrogenase (LDH) were examined, in order to elucidate the mechanism of action of three absorption Enhancers, i.e., sodium caprate (Cap-Na), sodium deoxycholate (Deo-Na), and dipotassium glycyrrhizinate (Grz-K), using Caco-2 cell monolayers. The structure of actin filaments in microvilli was slightly modified by 0.5 %(w/v) Grz-K and was significantly changed by 0.2 %(w/v) Cap-Na, 0.05 %(w/v) Deo-Na, and 0.0015 %(w/v) ionomycin. All of the enhancers, except Grz-K, induced significantly histomorphological changes in the actin filaments on the middle depth and basal side of the cells. Furthermore, the altered structure of the actin filaments in the monolayers was restored after removal of the Cap-Na, Grz-K and ionomycin, but not Deo-Na. Intracellular levels of calcium ion increased in the following order: ionomycin ≒ Cap-Na > Deo-Na. However, the intracellular calcium ion levels decreased by treatment with Grz-K. The changes in transepithelial electric resistance (TEER) at the initial stage of treatment with all enhancers correlated with intracellular calcium ion levels. These results suggest that one of the mechanisms by which these agents exert absorption-enhancing activity involves structural alterations in the cytoskeletal actin filaments which are provoked by changes in intracellular calcium ion levels. Only the monolayers which were treated with 0.05 %(w/v) Deo-Na released a significant amount of LDH and irreversibly altered the structure of actin filaments, thus indicating that Deo-Na might affect the actin filaments not only by increasing intracellular calcium ion level but also by other, presently unknown factors.

Melatonin in Cluster Headache

Cluster headache is an excruciatingly painful, essentially unilateral headache associated with homolateral autonomic signs. It has a highly distinctive temporal pattern. The attacks occur in cluster periods lasting weeks or months that are separated by remission periods of months or years. The pathogenesis of cluster headache is still unknown, although it is probable that the pain and autonomic manifestations result from the activation of the trigeminovascular system. The periodic nature of cluster headache [i.e. typically, cluster periods begin in spring or autumn (fall) when there is a rapid rate of change of the quantity of daylight, and, often, within a cluster period, the attacks recur on a daily basis with ‘clockwork’ regularity] suggests that activation of the trigeminovascular system could derive from the involvement of the hypothalamus, the site of the biological pacemaker. Since melatonin production is under the control of the hypothalamic pacemaker, the role of melatonin in cluster headache has been investigated. A number of studies have shown that melatonin levels are reduced during cluster periods, suggesting that the disorder is associated with a periodic dysfunction of hypothalamic structures. In this article, some of the biological functions of melatonin are reviewed in light of their possible relevance to the mechanisms that cause cluster headache. These include the role of melatonin in the regulation of circadian rhythms and the possible implications of its effects on γ-aminobutyric acid (GAB A) and serotonin (5-hydroxytryptamine; 5-HT) receptors, intracellular levels of calcium ions and prostaglandin production. Preliminary clinical data on the use of melatonin in the prophylaxis of cluster headache are discussed. In a double-blind, placebo-controlled clinical study, melatonin effectively prevented cluster headache in 50% of patients. This finding suggests the possible utility of melatonin as a second-line prophylactic agent, and provides additional evidence of a periodic central dysfunction in this disease.

Development of the tecto–thalamic projection neurons and the differential expressions ofcalcium-binding proteins in the rat

We studied expression of calbindin-D 28 K and parvalbumin in tecto–thalamic projection neurons and during the formation of their tecto–thalamic projections using a double-labeling with Fluoro–Gold. To discern the completion of these projections, Fluoro–Gold, an opalescent fluorescent dye, was injected into the dorsal lateral geniculate and/or the lateral posterior nucleus in rats of various ages from neonates to adults. After one day’s survival, the brains were removed and sections of the brain were immunohistochemically processed using Cy3, a red fluorescent dye, as a marker for calbindin-D 28 K or parvalbumin. The three types of tecto–thalamic neurons, which have been described previously in the adult rats, were identified in the present study. The results revealed that in developing rats: 1) A population of medium-sized neurons (the presumed pyriform cells) express calbindin-D 28 K as early as the day of birth prior to the formation of their tecto–thalamic projection that occured on postnatal day 4. Most (over 90%) of them project to the dorsal lateral geniculate nucleus; 2) A population of large neurons (the presumed wide-field vertical cells) express calbindin-D 28 K on postnatal day 7, and most of them (over 90%) project to the lateral posterior nucleus; 3) Another population of medium-sized neurons (the presumed narrow-field cells) express parvalbumin on post-natal day 17, but only a half (45%) of them project to the dorsal lateral geniculate nucleus. In the developing nervous system, calcium ions play important roles in the biological and molecular events underlying neural development. Changes in the free intracellular calcium ion level, indicating neuronal activity has been reported to be correlated with onset of calbindin-D 28 K or parvalbumin-immunoreactivity that participate in the regulation of intracellular calcium homeostasis in neurons. Therefore, the present findings may reflect distinct developmental events in the different classes of tectal relay neurons that form parallel visual pathways, but which have such different functions as the detection of luminance, discrimination of direction, and the detection of fast movements.

Immunotoxicity of environmentally relevant mixtures of polychlorinated aromatic hydrocarbons with methyl mercury on rat lymphocytes in vitro

AbstractThe immunosuppressive effects of methyl mercury (MH), polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐p‐dioxins (PCDDs), and dibenzofurans (PCDFs) are well established at high exposure levels but unclear at low exposure levels. We exposed Fischer 344 rat splenocytes, thymocytes, and peripheral blood lymphocytes in vitro for 72 h to MHg (0.1, 2 μg/ml), PCDD/PCDF mixtures (1, 15 pg/ml) of three PCDDs (2,3,7,8‐tetrachlorodibenzo‐p‐dioxin, 1,2,3,7,8‐pentachlorodibenzo‐p‐dioxin, and 1,2,3,4,7,8‐hexachlorodibenzo‐p‐dioxin) and two PCDFs (2,3,7,8‐tetrachlorodibenzofuran and 1,2,3,7,8‐pentachlorodibenzo‐furan), three Aroclor® (1242, 1254, 1260), PCB mixtures (0.01, 0.5 μg/ml), or combinations of MHg/PCB/PCDD/PCDF mixtures Mitogenic responses of lymphocytes to concanavalin A, phytohemagglutinin, or lipopolysaccharide/dextran sulfate were determined by 3H‐thymidine uptake; cytotoxicity and intracellular Ca2+ were determined by flow cytometry. Methylmercury (2 μg/ml and PCB/ PCDD/PCDF mixtures with 2 μg/ml MHg decreased the viability of splenocytes to 57 and 40% at 4 and 24 h, respectively. Basal intracellular calcium ion levels were unaffected by the treatments. Methylmercury suppressed the responses of lymphocytes to T and B cell mitogens. All combinations of MHg/PCB/PCDD/PCDF mixtures decreased mitogenic responses to levels similar to those to MHg alone. In contrast, PCB and PCDD/PCDF mixtures did not suppress but augmented responses of splenocytes and peripheral blood lymphocytes to T cell mitogens. Overall, no interactive toxicity was observed with MHg/PCB/PCDD/PCDF mixtures on cytotoxicity and lymphocyte mitogenic responses. Therefore, MHg may pose a greater threat than organochlorines to the mammalian immune system.

155 Inhibition of substance P-induced histamine release from rat peritoneal mast cells by 8-methoxypsoralen plus long-wave ultraviolet irradiation in parallel with the suppression of intracellular calcium ion level

155 Inhibition of substance P-induced histamine release from rat peritoneal mast cells by 8-methoxypsoralen plus long-wave ultraviolet irradiation in parallel with the suppression of intracellular calcium ion level

Impaired D-myo-inositol 1,4,5-triphosphate generation from cord blood polymorphonuclear leukocytes.

D-myo-Inositol 1,4,5-triphosphate (IP3) is a key second messenger in many cells, including macrophages, T and B cells, and neutrophils, in which it regulates free intracellular calcium ion levels. In human polymorphonuclear leukocytes the rise of intracellular [Ca2+] is the signal that activates a number of functions such as adherence, aggregation, chemotaxis, and degranulation, which are typically depressed in newborn infants. IP3 generation can be stimulated by N-formyl-methionyl-leucylphenylalanine (fMLP) tripeptide, which mimics the naturally occurring bacterial oligopeptides. In this study both neonatal and adult polymorphonuclear leukocytes were stimulated by fMLP (1 x 10(-6) M) and the levels of IP3 were assayed by a specific radiometric method. The time course of IP3 generation was studied for up to 60 s in a total of 10 samples. The response appeared reduced in cord blood samples. To confirm this observation, we extended our study to a larger number of samples, quantitating [IP3] at the time peak of 10 s. As expected IP3 generation was significantly (F test, p < 0.0001, n = 39) lower in newborns than in adults (means +/- SD = 0.64 +/- 0.25; 1.26 +/- 0.36, ng/10(6) cells, respectively). Besides soluble stimulus, neutrophils were treated with a particulate stimulus, namely serum-treated zymosan, which is also able to stimulate IP3 synthesis from polymorphonuclear leukocytes. Serum-treated zymosan produced a prolonged elevation in the level of IP3, reaching a plateau within 120 s in both cord blood and in control samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Osteopontin-induced modifications of cellular functions.

Osteopontin (OPN) serves both a cell attachment function and a cell signalling function via the alpha v beta 3 integrin. We have investigated the action on mammalian cells of recombinant OPN made both in E. coli and in human cells. In its cell signalling capacity it initiates a signal transduction cascade that includes changes in the intracellular calcium ion levels and the tyrosine phosphorylation status of several proteins including pp60src and components of focal adhesion complexes. Effects on gene expression include suppression of the induction of nitric oxide synthase by inflammatory mediators. OPN can also reduce cell peroxide levels, promote the survival of cells exposed to hypoxia, and inhibit the killing of tumor cells by activated macrophages.

072 Inhibition of substance P-induced histamine release from rat peritoneal mast cells by ultraviolet B irradiation: Suppressed intracellular calcium ion level as a possible mechanism

072 Inhibition of substance P-induced histamine release from rat peritoneal mast cells by ultraviolet B irradiation: Suppressed intracellular calcium ion level as a possible mechanism

A role for second messengers in the control of activation-associated modification of the surface of Trichinella spiralis infective larvae

The involvement of second messengers in the control of activation-induced changes to the surface of Trichinella spiralis infective larvae was investigated using membrane-permeant photo-activatable ‘caged’ compounds to alter intracellular levels of inositol trisphosphate (IP 3), calcium ions (Ca 2+) and cyclic AMP (cAMP). Activation of larvae by incubation in culture medium containing trypsin and bile was followed by the loss of the surface coat labelled with the fluorescent PKH26 lipid probe and this correlated with the reciprocal acquisition of surface lipophilicity detected using the fluorescent lipid probe octadecanoyl aminofluorescein (AF18). Optimal surface coat shedding and AF18 insertion was also achieved following photolysis of caged mediators liberating IP 3, Ca 2+ or cAMP within the parasite. Chelation of Ca 2+, however, abolished the effects of larval activation. Nevertheless, addition of cAMP (but not IP 3) to Ca 2+-depleted larvae overcame this inhibition and restored AF18 insertion to levels achieved by activated parasites. Therefore, the existence of a linear second messenger pathway involving the sequential release of IP 3, Ca 2+ and then cAMP is likely.

Calcium-binding proteins in the spiral ganglion of the monkey, Callithrix jacchus

Calcium-binding proteins can act as intermediaries between changing levels of free intracellular calcium ions and the physiological response of neurons. Some of these proteins, among them calbindin (CB), calretinin (CR) and parvalbumin (PV), can act as calcium buffers. A survey of previous studies in rodents and human fetuses leads to the impression that many spiral ganglion cells co-express CB, CR, and PV. The findings of the present study suggest that, in the adult marmoset, the expression of CB is restricted to a small number of cells, most likely type II ganglion cells, and that at least some of the numerous type I ganglion cells co-express CR and PV. In the neonate marmoset, large numbers of putative type I ganglion cells from the apical cochlear turn transiently expressed a light and granular labeling for CB-like immunoreactivity, in addition to the cells we believe to be type II ganglion cells exhibiting a strong and solid CB-like staining. The spiral ganglion cells in all developmental stages co-expressed the mitochondrial enzyme cytochrome oxidase. Furthermore, a small population of CB-LI axons of unknown origin was found to terminate near the CB-immunoreactive ganglion cells.

Involvement of intracellular calcium ions in the release of the fluorescent dye calcein by cholinergic and alpha-adrenergic agonists from rat parotid acinar cells.

Effects of cholinergic and adrenergic agonists on the secretion of the fluorescent dye calcein were examined to clarify the involvement of calcium ions in the secretion of calcein from acinar cells dispersed from the rat parotid gland. Addition of carbachol (CCh) and noradrenalin (NA), but not isoproterenol (IPR), enhanced the net release of calcein from acinar cells during the subsequent 10 min in a dose range from 10(-8) M to 10(-6) M. The net release of calcein reached a maximum 7 min after the addition of CCh. The release of calcein was suppressed by the simultaneous additions of atropine with CCh, or phenoxybenzamine with NA. Addition of CCh induced a sustained dose-dependent increase in the intracellular levels of calcium ions, ([Ca2+]i). Addition of NA at 10(-6) M increased [Ca2+]i. Phenoxybenzamine completely inhibited the NA-induced increase, but propranolol did not. The removal of extracellular calcium ions did not influence the release of calcein induced by 10(-6) M CCh, but it abolished the sustained increase in [Ca2+]i. The transient increase in [Ca2+]i induced by CCh was observed in the absence of extracellular calcium ions. A calcium ion chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) inhibited the CCh-induced release of calcein. The calcium ionophore, A23187 (2.5 x 10(-6) M), but not 10(-3) M dibutyryl cAMP, evoked the release of calcein. It also increased [Ca2+]i. Removal of extracellular calcium ions suppressed the A23187-induced release of calcein.(ABSTRACT TRUNCATED AT 250 WORDS)

Overcoming obstacles to metastasis ‐ defenses against host defenses: Osteopontin (OPN) as a shield against attack by cytotoxic host cells

Osteopontin (OPN) serves both a cell attachment function and a cell signalling function via the alpha v beta 3 integrin. In its cell attachment capacity it can promote attachment of both osteoclasts to bone hydroxyapatite and various other cell types to basement membrane/extracellular matrix. In its cell signalling capacity it initiates a signal transduction cascade that includes changes in the intracellular calcium ion levels and the tyrosine phosphorylation status of several proteins including paxillin. Effects on gene expression include suppression of the induction of nitric oxide synthase by inflammatory mediators. OPN can also reduce cell oxidant levels and inhibit the killing of tumor cells by activated macrophages and endothelial cells. We hypothesize that those cancer cells that produce OPN at elevated levels can suppress the oxidative burst, inhibit NO production, and thus protect themselves from killing by specific host cell types.

Na(+)-Ca2+ exchanger-like immunoreactivity and regulation of intracellular Ca2+ levels in fish retinal ganglion cells.

1. We have used two experimental approaches to examine regulation of intracellular calcium ion levels in fish retinal ganglion cells. In the first set of experiments, we ratio-imaged fura-2 emission intensity to estimate the concentration of free intracellular calcium ions ([Ca2+]i) in isolated goldfish retinal ganglion cells depolarized by increases in extracellular levels of potassium ions ([K+]o), in the presence and absence of extracellular sodium ions (Na+). Stepwise increases in [K+]o from 5 mM to as high as 60 mM produced stepwise increases in [Ca2+]i. These increases were sustained in the absence of external Na+, but transient and smaller in the presence of external Na+. The decline of [Ca2+]i in high-K, Na(+)-containing saline could be reversed by application of the ionophore monensin, or by replacement of external Na+ with either N-methyl-D-glucamine or lithium. In Na(+)-containing saline, [Ca2+]i fell to control levels after [K+]o was restored to control levels. 2. In the second set of experiments, we assessed Na(+)-Ca2+ exchanger-like immunoreactivity in goldfish retinal ganglion cells with the use of a polyclonal antiserum directed against Na(+)-Ca2+,K+ exchanger purified from bovine rod outer segments. This antiserum specifically stained the somata, neurites, and growth cones of isolated ganglion cells, the outer segments of rod photoreceptors, and (on Western blots prepared from mechanically isolated rods) protein displaying an apparent molecular mass of 210 kDa. 3. These results provide measurements of changes in [Ca2+]i of retinal ganglion cells depolarized in Na(+)-containing saline, and the distribution and apparent molecular weight of Na(+)-Ca2+ exchanger-like immunoreactivity in teleost retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyotrophic lateral sclerosis: Hypothetical pathogenesis

A hypothetical pathogenesis for a typical case of amyotrophic lateral sclerosis (ALS) follows from opinions of Rowland and results of neuroscientists at Baylor. ALS might typically result from an autoimmune disorder that causes IgG to enhance release of acetylcholine (ACh) from axon terminals. Motor neuron overactivity associated with fasciculation might result from enhanced release of ACh which is taken up by nicotinic ACh receptors. Increased levels of intracellular calcium ions might result from motor neuron overactivity associated with fasciculation. Neuronal cell degeneration and death might result from increased levels of intracellular calcium ions.

Temporal changes in intracellular free calcium levels in the developing neuroepithelium during neurulation in the chick

Intracellular free calcium ion (Ca 2+) levels of the developing chick neuroepithelium during neural tube closure (Hamburger and Hamilton stages 3–11 of embryonic development) were determined using the Hydrophobie acetoxymethyl ester of the fluorescent dye fura-2 (fura-2/AM). Temporal changes in the free Ca 2+ level in neuroepithelial cells are correlated with the degree of folding of the neuroepithelium. The concentration of intracellular Ca 2+ in the neuroepithelium reaches its highest level when apposing neural folds are actively making contact.

Calcium overload toxicity and functional impairment in peritoneal leukocytes elicited by glycogen or interleukin-1 beta.

Although calcium plays an important role in the activation of leukocytes for such processes as eicosanoid biosynthesis, secretion of granular constituents and superoxide generation, sustained high levels of intracellular calcium ions may be toxic. We have previously found that high concentrations of calcium ionophores induce a rapid-onset "calcium overload" toxicity in rat peritoneal leukocytes, in which functional responses such as beta-glucuronidase secretion, superoxide generation and leukotriene B4 synthesis are greatly attenuated, and some leakage of cytoplasmic LDH occurs. We have now compared this phenomenon in peritoneal leukocytes elicited from animals pretreated in three ways: glycogen, interleukin-1 beta (IL-1 beta) alone or glycogen plus IL-1 beta. Peritoneal administration of IL-1 beta caused elicitation of cells which were enriched in eosinophils; however, the functional responses of the cells in all three groups were broadly similar in terms of the ability of the agonists FMLP, PMA and A23187 to initiate superoxide generation, beta-glucuronidase secretion and leukotriene generation. Cells from all three treatment groups showed diminished responsiveness at 10(-5) M A23187, indicative of calcium overload toxicity. This was most evident for the superoxide and beta-glucuronidase responses. Some quantitative differences observed between treatment groups may reflect the different sensitivities of the various cells contained in the mixed leukocyte preparations. We conclude that IL-1 beta induces leukocyte emigration into the peritoneal cavity but that the cell population is different from that induced by glycogen. However, the cells retain susceptibility to calcium overload toxicity.