Inhibition of macrophage activation by calcium channel blockers and calmodulin antagonists

In vitro modulation of human neutrophil superoxide anion generation by various calcium channel antagonists used in ischemia-reperfusion resuscitation

Generation of toxic oxygen species by activated polymorphonuclear leukocytes (PMNs) may represent an important mechanism of ischemia-reperfusion injury. Concentration-response data concerning inhibition of superoxide anion (O2-) generation by NADPH oxidoreductase (NADPH OR) from isolated human PMN were generated for five calcium channel antagonists commonly utilized in ischemia-reperfusion investigational therapeutics. Regression analysis derived IC50 values for verapamil, nimodipine, nicardipine and lidoflazine were 45, 20, 12 and 7 microM respectively. Inhibition of the extent of reaction at 5 min paralleled inhibition of initial velocity. No inhibition by flunarizine was noted at concentrations less than or equal to 25 microM (where it did not alter reaction mixture composition). Only nicardipine demonstrated a significant concentration-response effect relative to prolonging lag time preceding O2- synthesis. Inhibition appeared at least partially reversible for all five agents. Neither PMN activation/desensitization, free-radical scavenging, nor PMN cytotoxicity appeared to be involved in the inhibition of PMN O2- synthesis by these agents. Ca2+ antagonist inhibition of PMN NADPH OR appears to involve more than simple inhibition of Ca2+ flux across the PMN plasma membrane. Direct inhibition of the intracellular events involved in the activation and/or activity of NADPH OR may be operative.

Atherosclerosis: current concepts on pathogenesis and interventional therapies

Atherosclerosis, the primary pathological condition accounting for most stroke syndromes, has been the intense focus of epidemiological, basic, and clinical investigations. Since these studies have direct bearing on the prevention of atherothrombotic brain infarction, this review emphasizes those advances in treatment resulting from their findings. The two most prominent theories on the pathogenesis of atherosclerosis relate to aberrations in lipoprotein metabolism and to enhanced proliferation of smooth muscle cells; likely, the theories are complementary. As a practical guideline for preventive therapy, the importance of using the total cholesterol level is stressed, although finer distinctions must rely on the low-density and high-density lipoprotein concentrations and their normalization. Since prevention of stroke may ultimately be its most effective therapy, consideration of cholesterol level, akin to strategies for preventing coronary heart disease, and efforts to avert platelet adhesion or aggregation and coagulation are warranted.

Involvement of Ca2+-dependent pathways in the inhibition of human natural killer (NK) cell activity by cortisol

The role of Ca2+ as a second messenger of the glucocorticoid inhibition of human natural killer (NK) cell activity was evaluated using Ca2+ entry blockers (verapamil and its desmethoxy derivatives LU46973 and LU47093), calmodulin antagonists (pimozide and two naphthalensulfonamide derivatives, W-7 and W-13), the Ca2+ channel agonist BAY K 8644 and the calcium ionophore A23187. Peripheral blood mononuclear (PBM) cell preparations were incubated for 20 h with 1 x 10(-6) M cortisol and these agents in various combinations (concentration range: 1 x 10(-9) -1 x 10(-5) M) and then assayed in a direct 4-h cytolytic assay using 51Cr-labeled K 562 target cells. Exposure to cortisol led to a significant reduction of NK cell activity (about 50% vs. spontaneous activity). Ca2+ entry blockers and calmodulin antagonists were per se minimally effective, but significantly enhanced cortisol-dependent inhibition of NK cell activity. Raising extracellular Ca2+ by CaCl2 or intracellular Ca2+ by the calcium channel agonist BAY K 8644 or the ionophore A23187 resulted in an appreciable reduction of these effects. Similar results were obtained when these substances were added to monocyte-depleted or NK cell-enriched suspensions exposed to cortisol. Our data are consistent with the view that extra- and intracellular Ca2+ plays a role in the control of human NK cell activity. It is also conceivable that both calcium flux into the cell and the calcium calmodulin system are involved in the cortisol-induced inhibition of natural cytotoxicity.

Inhibiting noradrenergic overactivity by inhibition of thromboxane and concomitant activation of opiate receptors via dietary means

A yin-yang hypothesis is presented linking noradrenergic activity, thromboxane, melatonin, left hemisphere functioning, and cyclic AMP on the one hand, and dopamine, beta-endorphin, calcium, right hemisphere functioning, and cyclic GMP on the other. It is further suggested that there is a yoking of NA, TXA2, serotonin and melatonin in the left hemisphere, and a similar yoking of DA, BE, calcium and cGMP in the right. Evidence is presented to support the hypothesis that each element (NA, TXA2, etc.) on one side can modulate or balance a corresponding element (DA, BE, etc.) on the other. It is suggested that thromboxane is the key element in noradrenergic overactivity and that not taking this into consideration has confounded much prior research. This theory takes into account information processing models as well as pharmacological data and neurochemical theory on coupling of adenylate cyclase to its hormone receptors. Inhibiting noradrenergic overactivity can be obtained by inhibiting thromboxane and concomitantly activating opiate receptors. This protocol may have clinical utility in treating a wide range of disorders such as: anxiety, depression, schizophrenia, sleeplessness, withdrawal states, enuresis, Gilles de la Tourette syndrome, Parkinsonism, Alzheimers, dementia, anorexia, infant ruminations, essential tremor, spasticity of spinal cord injury, diarrhoea, ulcerative colitis, extrapyramidal symptoms, akathisia, neuroleptic malignant syndrome, attention deficit disorder, hyperhidrosis, and possibly AIDS.

The role of free oxygen radicals in the expulsion of primary infections of Nippostrongylus brasiliensis

The many and varied pathological, immunological and physiological manifestations of infection with Nippostrongylus brasiliensis may be unified by considering the role of leukocyte-generated free oxygen radicals in worm expulsion. Aside from directly damaging the adult stage of N.brasiliensis and possibly leading to its elimination from the small intestine, free radicals may also damage intestinal cells, thereby contributing to the gut pathology characteristic of infection. gamma-Interferon (and possibly tumour necrosis factor) may be involved in the initiation of free radical generation in response to N. brasiliensis and may also contribute to various side effects of infection such as hypertriglyceridaemia and cachexia. gamma-Interferon may initiate free radical generation via the agency of protein kinase C, an enzyme that can induce various additional responses including lysosomal enzyme and amine secretion and arachidonic acid metabolism. The possible interactions between these mediators and free radicals are subtle and diverse and may profoundly affect the course of infection.

The effect of calcium channel blockers and calmodulin inhibitors on the macrophage factor-stimulated synthesis of collagenase by rabbit chondrocytes

Macrophages and monocytes secrete a factor(s) which can stimulate the synthesis of collagenase in synovial cells and in chondrocytes. Incubation of rabbit chondrocytes with macrophage conditioned medium (MCM) and with the calcium channel blockers, nifedipine, verapamil or diltiazem (up to 200 microM) had no effect on collagenase synthesis. However, TMB-8 (8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride), an inhibitor of internal calcium movement, did inhibit the process with an IC50 of approximately 130 microM. The calmodulin antagonists, trifluoperazine, chlorpromazine and calmidazolium (R-24571) were effective inhibitors of the process with IC50's of 40 microM, 18 microM and 3.5 microM, respectively. Collagenase activity itself was not affected by these agents. The data suggests that calmodulin and/or internal calcium movement may play a role in the macrophage factor-stimulated synthesis of collagenase in rabbit chondrocytes.

Increased capacity of lymphocytes to lyse tumor cells in vitro and production of lymphotoxins after cisplatin treatment

Spleen lymphocytes from C3H/He mice when treated with cisplatin show increased cytostasis and cytotoxicity against Dalton's lymphoma cells in vitro. Cisplatin treatment of splenocytes does not render them cytotoxic/or cytostatic against normal splenocytes. Splenocytes on treatment with cisplatin also produce tumor cell-specific cytotoxic/cytostatic factors (lymphotoxins) which have cytolytic and cytostatic effect on Dalton's lymphoma cells. The increased cytotoxicity of splenocytes on treatment with cisplatin is reversed by the calcium channel blocker nifedipine and the calmodulin antagonist chlorpromazine, suggesting a role of calcium in cisplatin-activated lymphocyte-mediated cytotoxicity.

Ca2+-channel blockers modulate the oxidative burst induced with arachidonic acid in macrophage-like P 388D1 cells. Interaction with peripheral benzodiazepines

Ca2+-channel blockers are shown to modulate, like peripheral benzodiazepines, the oxidative burst induced by arachidonic acid in the macrophage-like P 388D1 cell line. Nifedipine (1 and 10 nM) enhanced the cellular response to arachidonate; this stimulation by nifedipine was reversed by PK 1195, a specific antagonist for the peripheral benzodiazepine binding site. Verapamil (5 microM), on the other hand, antagonized the stimulation of the oxidative burst by benzodiazepines. The data suggest some possible interaction of Ca2+-channel blockers at the benzodiazepine binding site or at a secondary step in the activation mechanism. None of the molecules modulated the calcium influx triggered by arachidonate. Instead, the oxidative response of P 388D1 cells to arachidonate was inhibited by K+-channel blockers, quinidine and tetraethylammonium bromide.

Lack of a central role for calcium in the induction and release of human interleukin-1

This study examines the potential role of calcium in the activation of human monocytes by bacterial lipopolysaccharide (LPS) to produce interleukin-1 (IL-1). Monocytes cannot be triggered to produce IL-1 through addition of calcium ionophores. Triggering of IL-1 production by LPS cannot be blocked by depletion of extracellular calcium, blockade of calcium channels, or addition of agents which antagonize the effects of intracellular calcium. Finally, the addition of LPS does not induce the mobilization of intracellular free calcium as measured by quin-2 fluorescence.

Nifedipine-induced hyporeactivity in delayed hypersensitivity skin tests

Four patients and three healthy volunteers were submitted to delayed hypersensitivity skin tests to candidin, tuberculin, streptokinase/streptodornase (SK/SD) and mumps antigen before and after a 1 week treatment with nifedipine 10 mg q. 8h. A decrease in the scores of induration and erythema was observed, especially in response to SK/SD antigen challenge. We conclude that nifedipine may induce an anergy status in delayed hypersensitivity skin tests.

The effect of calmodulin antagonists on the activation of RAW-264 macrophage-like cells for tumor cell killing

The effects of several calmodulin antagonists on the activation of RAW-264 macrophage-like cells for tumor cell killing were investigated. At concentrations ranging from 5 X 10(-8) to 5 X 10(-7) M, calmidazolium, trifluoperazine, chlorprothixene, chlorpromazine and W-13 inhibited the development of cytolytic activity, evoked in RAW-264 by treatment with lymphokine and lipopolysaccharide, in a dose-dependent manner. Since the order of the potency of these drugs against the activation of RAW-264 cells was much the same as their ability to inhibit calmodulin-dependent phosphodiestherase activity: calmidazolium greater than trifluoperazine greater than chlorprothixene greater than chlorpromazine greater than W-13, and because W-12, a nonactive analog of W-13, failed to inhibit the process of activation, we believe that the development of cytolytic activity in RAW-264 cells may be dependent on calmodulin. At micromolar concentrations, calmodulin antagonists (except calmidazolium) enhanced the process of activation. The enhancement of cytolytic activity was neither the result of the toxicity of these drugs nor related to their effects on intracellular calcium. It was entirely dependent on the presence of stimulants but occurred independently from the stage of macrophage activation, and most likely was due to the nonspecific interference of these agents with calmodulin-independent processes.