Allergen-induced bronchial eosinophilia in guinea-pigs is inhibited by both pre- and post-induction cyclosporin-A treatments.

Repeated treatment of sensitized guinea-pigs with cyclosporin-A (CS-A) before aerosol allergen challenge is known to inhibit the subsequent bronchial eosinophilia. It is not known, however, if the drug is also effective on established/on-going bronchial eosinophilia. We have, therefore, studied the effect of CS-A on allergen-induced eosinophil recruitment into the bronchoalveolar lavage (BAL) fluid of guinea-pigs when given before or after induction.Ovalbumin-immunized guinea-pigs were treated with CS-A (20 mg/kg subcutaneously) or vehicle daily for varying periods before a single aerosol allergen challenge. In animals in which bronchial eosinophilia was maintained with repeated aerosol allergen challenge, CS-A or vehicle was given daily for varying periods after the first allergen challenge. BAL and cell count were performed 24 h after the last challenge. In vehicle-treated animals, a single allergen challenge caused a 4-5 fold increase in the number of eosinophils in the BAL fluid after 24 h, declining to baseline by 7 days. In repeatedly-challenged animals, this response was sustained throughout. Eosinophil infiltration was significantly inhibited when CS-A was given daily for 7-14 days, but not for 1 or 3 days, before allergen challenge. When given during an established/on-going eosinophil infiltration, a significant inhibition was seen after administration for 5 or 7 days, but not for 1 or 3 days.These results show that repeated CS-A administration inhibits not only the induction of allergic bronchial eosinophilia but also the maintenance of an established one. This may be relevant in the treatment of allergic diseases, such as asthma, in which drug administration often begins when eosinophilia is already established.

The effect of salmeterol on human eosinophils is both stimulus- and response-dependent.

Salmeterol, a long-acting beta 2-adrenoceptor agonist, also possesses some anti-inflammatory properties, but whether eosinophils are the target of such action has been equivocal. To clarify the direct effect of salmeterol on eosinophil functions, we have studied the effect of the drug on the various responses of purified human eosinophils. Superoxide anions (O2-) release and adherence to fibronectin-coated plastic plates induced by platelet-activating factor (PAF), interleukin-5 (IL-5), leukotriene B4 (LTB4) and phorbol myristate acetate (PMA), as well as degranulation induced by C5a and formyl methionyl leucyl phenylalanine (FMLP), in the presence of cytochalasin B (CB) were studied. In the concentration range 10(-8)-10(-5) M, the drug inhibited PAF- and IL-5-induced O2- release, with an IC50 values of 3.2 +/- 1.2 x 10(-7) M and 2.2 +/- 0.4 x 10(-6) M, respectively, Superoxide anion release by LTB4 was only modestly inhibited while that due to PMA was completely unaffected. On the other hand, eosinophil adherence induced by all the 4 stimuli were significantly inhibited within the same concentration range. On eosinophil degranulation, the drug failed to significantly inhibit the release of eosinophil peroxidase (EPO) induced by either C5a or FMLP. In contrast, beta-hexoseaminidase (beta-HA) release by the same agents was significantly inhibited, the inhibition being more pronounced for FMLP-induced, than C5a-induced release. None of the effects of the drug was reversed by the selective beta 2-adrenoceptor antagonist ICI 118551 at a concentration of 10(-7) M. These results show that salmeterol may have some direct inhibitory effects on human eosinophil functions but that these effects are both stimulus- and response-dependent, and are unlikely to be mediated via beta 2 adrenoceptors.

Inhibition of alpha-tocopherol and calcium calmodulin-stimulated phosphodiesterase activity in vitro by anthracyclines.

1. The inhibition of alpha-tocopherol and calmodulin-stimulated phosphodiesterase activities was investigated in vitro. 2. Anthracyclines--doxorubicin, daunorubicin and aclacinomycin--inhibited calcium calmodulin-stimulated cyclic 3',5'-AMP (cAMP) nucleotide phosphodiesterase (EC. 3.1.4-17) activity (IC50 = 33.00 +/- 3.50-36.50 +/- 2.75 mumol/l). The stimulation of this enzyme by alpha-tocopherol was also inhibited by doxorubicin (IC50 = 18.50 +/- 4.00 mumol/l). 3. The anthracycline-induced inhibition of the calcium calmodulin and alpha-tocopherol-stimulated phosphodiesterase activity was competitive with calmodulin and alpha-tocopherol respectively. Increasing the concentration of the substrate, cAMP or calcium ions did not attenuate the drug-induced inhibition. The basal activity of the enzyme was not inhibited by concentration of doxorubicin up to 50 mumol/l. 4. In vivo, single dose drug distribution studies of the fluorescence of doxorubicin indicate that in the heart after a cardiotoxic dose (20 mg/kg), myocardial concentrations were achieved which could cause 70-80% inhibition of this phosphodiesterase enzyme. 5. Inhibition of calmodulin function by anthracyclines via direct interaction with calmodulin may contribute significantly to the effects of anthracyclines, such as disturbance in calcium homeostasis as well as acute and chronic deleterious effects on the myocardium. The action of alpha-tocopherol to bind or complex anthracycline may in part contribute to its protection against anthracycline-induced membrane damage and cardiotoxicity.

Calmodulin and alpha tocopherol as additional binding sites for doxorubicin.

The hydrophobic probes anthroylcholine (9AC), 8-anilino-1-napthalene sulfonate (ANSE), and 2-P-toluidinyl naphthalene 6-sulfonate (TNS) increased calcium-calmodulin (Ca2+-aM) fluorescence. This fluorescence was decreased by doxorubicin (DXR) in a dose-dependent fashion. The Ca2+ ion was an absolute requirement for the observed effects of DXR. DXR bound to the Ca2+-CaM complex (Kd = 4.2 X 10(-5) M, Bmax = 1.8) and to alpha tocopherol. The binding of untransformed (native) DXR to CaM was a reversible process. These data support a previous finding that DXR inhibits stimulation of calmodulin-deficient PDE (a CaM target enzyme) using either the Ca2+ CaM complex or alpha tocopherol by interacting with these agents, and suggest that other target enzymes for CaM may be similarly affected.

Dextran-induced gastric acid secretion in rats.

Dextran C (M.W. 60,000-70,000) employed as plasma expander in the treatment of hypovolemic shock, and which is known to induce histamine release from rat mast cells was studied for its effect on gastric acid secretion in rats. Dextran at doses even lower than the therapeutic dose in man (8-250 mg/kg) induced significant gastric acid secretion in intact anaesthetized rats. Pretreatment of the animals with 1 mg/kg cimetidine significantly reduced the increase in acid secretion while a higher dose of 10 mg/kg completely abolished the effect. The result thus suggests that dextran-induced gastric acid secretion in rats is mediated through histamine release.