Physiological, pharmacological and toxicological considerations of drug-induced structural cardiac injury.

The incidence of drug-induced structural cardiotoxicity, which may lead to heart failure, has been recognized in association with the use of anthracycline anti-cancer drugs for many years, but has also been shown to occur following treatment with the new generation of targeted anti-cancer agents that inhibit one or more receptor or non-receptor tyrosine kinases, serine/threonine kinases as well as several classes of non-oncology agents. A workshop organized by the Medical Research Council Centre for Drug Safety Science (University of Liverpool) on 5 September 2013 and attended by industry, academia and regulatory representatives, was designed to gain a better understanding of the gaps in the field of structural cardiotoxicity that can be addressed through collaborative efforts. Specific recommendations from the workshop for future collaborative activities included: greater efforts to identify predictive (i) preclinical; and (ii) clinical biomarkers of early cardiovascular injury; (iii) improved understanding of comparative physiology/pathophysiology and the clinical predictivity of current preclinical in vivo models; (iv) the identification and use of a set of cardiotoxic reference compounds for comparative profiling in improved animal and human cellular models; (v) more sharing of data (through publication/consortia arrangements) on target-related toxicities; (vi) strategies to develop cardio-protective agents; and (vii) closer interactions between preclinical scientists and clinicians to help ensure best translational efforts.

Chloride transport and the actions of nedocromil sodium and cromolyn sodium in asthma.

Nedocromil sodium has been shown to be capable of inhibiting chloride ion flux in mast cells, epithelial cells, and neurons. This feature may explain how it can prevent responses such as mast-cell degranulation, the effects of osmolarity changes in the airways, and neuronal activation. This mechanism may also provide a unifying hypothesis to explain the effects of nedocromil sodium on a range of cell types involved in asthma, such as sensory and efferent neurons and cells involved in inflammation.

[The effect of nedocromil sodium on the luminal-dependent chemiluminescence of whole-blood leukocytes]. / Vliianie nedokromila natriia na liuminolzavisimuiu khemiliuminestsentsiiu leikotsitov tsel'noi krovi.

Nedocromil sodium in concentrations of 10(-3) to 10(-9) M dose-dependently inhibits a zymosan (2 mg/ml)-induced chemiluminescence response (CLR) of whole blood leukocytes and, to a lesser extent, phorbol myrystate acetate (PMA)-induced CLR. The count of diformazan-positive granulocytes in the zymosan-induced nitroblue tetrazolium test slightly reduced in the presence of 10(5) nedocromil sodium. PMA in a dose of 10(-9) M did not induce CLR, but brought about leukocyte priming, thus sensitizing them to secondary triggering by suboptimal zymosan concentrations (0.5 mg/ml). A subsequent stimulation of leukocytes with PMA + zymosan demonstrated that nedocromil sodium (10(-7) M) inhibited mainly priming PMA rather than the zymosan-triggering step of leukocyte activation.

Protective effects of cyclophosphamide, cyclosporin A and FK506 against antigen-induced lung eosinophilia in guinea-pigs.

A close association has been recognized between activated T cells and eosinophils in asthma, albeit circumstantial. The present study attempted to investigate this relationship in an animal model of lung eosinophilia using the new generation of T cell-selective immunosuppressants, cyclosporin A and FK506, compared with the myelotoxic immunosuppressive agent cyclophosphamide. Antigen challenge of ovalbumin-sensitized guinea-pigs resulted in a lung eosinophilia which was assessed by bronchoalveolar lavage. All three agents caused a marked suppression of lung eosinophilia at 24 h post-challenge when the compounds were administered at the time of sensitization but not when administered for 3 days before lavage. However, the lung eosinophilia at 72 h post-challenge was reduced significantly by FK506 and by cyclophosphamide, but not by cyclosporin A, when the drugs were administered for 3 days, before lavage. These results strongly suggest the involvement of T cells in antigen-induced late phase (72 h) eosinophilia in guinea-pigs but not at 24 h. The effects of cyclophosphamide were always associated with a reduction in circulating white cell counts, whereas cyclosporin A and FK506 showed no myelotoxic properties. These results suggest the potential therapeutic use of selective, non-cytotoxic immunosuppressive agents in asthma.

FPL 62064, a topically active 5-lipoxygenase/cyclooxygenase inhibitor.

FLP 62064 [N-(4-methoxyphenyl)-1-phenyl-1H-pyrazole-3-amine] is a dual inhibitor of prostaglandin synthetase and 5-lipoxygenase. The compound had anti-inflammatory activity in vivo in a number of models. It inhibited peritoneal inflammation induced by immune-complex when given locally. When applied to the skin, FPL 62064 inhibited UV irradiation-induced erythema and PGE2 formation in the guinea pig and also oedema formation and eicosanoid production in the mouse ear produced by arachidonic acid. Co-injected with arachidonic acid in rabbit skin, FPL 62064 inhibited oedema and eicosanoid formation.

Modulation of neurogenic inflammation in rat trachea.

Antidromic stimulation of the cervical vagus nerve in anaesthetised rats resulted in plasma protein extravasation in the trachea. This response was potentiated significantly by pretreatment of the animals with an enkephalinase inhibitor, thiorphan (100 micrograms/kg). Exposure of animals to ozone (5-6 ppm) for 30 min caused a significant increase in the numbers of lung lavage epithelial cells but failed to potentiate neuronally-evoked tracheal oedema. Several compounds were investigated for anti-permeability effects on thiorphan-pretreated, nerve stimulated animals. Morphine (3 mg/kg) and salbutamol (100 micrograms/kg) were the most efficacious agents used and resulted in 66 +/- 14% and 61 +/- 9% inhibition of tracheal oedema, respectively. Sodium cromoglycate at 30 mg/kg produced a small but significant reduction in oedema (34 +/- 10%). Dexamethasone (3 mg/kg), methysergide (2 mg/kg) and theophylline (10 mg/kg) did not affect neurogenic oedema.

Sulphur dioxide-induced airway hyperreactivity and pulmonary inflammation in dogs.

Anaesthetised Beagle dogs were exposed to sulphur-dioxide (SO2) for 2 h and the pulmonary effects studied up to 24 h using bronchoalveolar lavage (BAL) and lung mechanics measurements. SO2-induced hyperreactivity to histamine was associated with epithelial cell shedding, an increase in airway permeability to plasma proteins and an increase in BAL PGE2 content. Leukotrienes were not recovered in BAL. Ibuprofen reduced hyperreactivity at 24 h post SO2 but not immediately after SO2 and had no effect on BAL cells at anytime. These results suggest that 2 phases of hyperreactivity exist--an immediate effect which may involve epithelial cell loss and a later phase which may be inflammatory.

Nedocromil sodium and sensory nerves in the dog lung.

The effect of nedocromil sodium on the main sensory nerve types in the dog lung has been studied. Nedocromil sodium (0.1, 1.0 and 10 mg/kg i.v.) did not stimulate or inhibit the discharge pattern of pulmonary stretch receptors, rapidly adapting irritant receptors or pulmonary C-fibre endings. Nedocromil sodium 5 micrograms/kg given into the aortic arch did, however, stimulate bronchial C-fibre endings. These endings were also stimulated when the drug was given by aerosol. The possibility that nedocromil sodium suppresses cough in the dog by stimulation of bronchial C-fibre endings is discussed.

The effect of ozone on reactivity of upper and lower airways in guinea-pigs.

1. The effect of ozone inhalation on the responsiveness of upper and lower airways to histamine was examined in guinea-pigs. 2. The exposure of conscious guinea-pigs to 3.5 p.p.m. ozone for 30 min rendered their lower airways 2-3 fold more sensitive to the bronchoconstrictor action of i.v. histamine, as assessed subsequently under anaesthesia. 3. The development of lower airway hyperreactivity was not modified by bilateral cervical vagotomy or pretreatment with BW 755C, FPL 55712 or SC-39070. 4. Under the conditions used, ozone exposure produced a mild inflammatory response as monitored by bronchoalveolar lavage, characterized by epithelial damage and prostaglandin E2 generation, but no cellular infiltration or oedema. 5. In contrast to the lower airways, upper airway resistance was reduced by i.v. histamine. This response was not affected by ozone exposure. 6. Isolated tracheal preparations taken from ozone-exposed guinea-pigs were not significantly more sensitive to histamine than control tissues. 7. The mechanism of hyperreactivity in this model is unknown but does not depend on leukotriene generation or a vagal reflex.

Models for evaluating the anti-inflammatory effects of inhibitors of arachidonic acid metabolism.

Inhibitors of arachidonic acid metabolism were characterized by their ability to modulate slow reacting substance (SRS) and prostaglandin E2 (PGE2) release from stimulated mouse peritoneal macrophages in-vitro. Differential effects of cyclo-oxygenase (CO) and lipoxygenase (LO) enzyme inhibitors and compounds which inhibit both enzymes were demonstrated using several animal models of inflammation. Carrageenan-impregnated sponges implanted subcutaneously in rats and immune-complexes injected intraperitoneally in mice produced inflammatory responses characterized respectively by polymorphonuclear (PMN) cell infiltration and by increased vascular permeability. Dual CO/LO inhibitors (eg. BW 755c and timegadine) were capable of suppressing both parameters and reduced SRS and PGE2 formation in-vivo. In contrast, selective CO inhibitors (e.g. indomethacin, naproxen and R-830) were less active against permeability, and potentiated SRS release. Although selective CO inhibitors reduced PMN migration, this occurred at doses which exceeded those required for inhibition of PGE2. Compounds possessing LO inhibitory activity suppressed the cellular component of an Arthus type reaction in the rat pleural cavity, but were less active than selective CO inhibitors against carrageenan-induced paw oedema in rats.

Changes in colonic tissue levels of inflammatory mediators in a guinea-pig model of immune colitis.

An immune colitis based on a delayed-type hypersensitivity reaction was induced in dinitrochlorobenzene (DNCB)-sensitized guinea-pigs by intrarectal challenge with DNCB. A low challenge dose (0.25% DNCB) induced mild inflammatory changes in the distal colon and rectum characterized by goblet cell depletion. A higher challenge concentration (5% DNCB) resulted in severe colonic ulceration with crypt abscess formation. The inflammatory mediators, histamine, 5-hydroxytryptamine (5HT), glandular kallikrein and PGE2 were measured in freeze-dried colonic mucosae. Histamine content was three times control (p less than 0.01) in 0.25% DNCB induced colitis, although no significant change was observed in 5% DNCB challenged animals. Mucosal 5HT content was significantly reduced (p less than 0.01) after both challenges. Glandular kallikrein content did not differ from control, while PGE2 was significantly (p less than 0.05) increased at both challenge doses. The possible significance of these changes with respect to severity of inflammation and aetiology of colitis is discussed.

Actions of anticolitic drugs on a guinea-pig model of immune colitis.

A cell-mediated immune colitis in guinea-pigs was examined for its response to several drugs used in the management of colitis as an attempt to obtain an appropriate model for evaluating potentially new anticolitic drugs. The experimentally-induced colitis was readily reproducible and possessed several features in common with the clinical disease: diarrhoea, rectal bleeding and body weight loss, together with ulceration and haemorrhage of the distal colon. Sulphasalazine, prednisolone and disodium chromoglycate appeared not to influence the manifestations of the colitis nor the macroscopic features of the inflamed colon. Azathioprine (AZA) at 100 mg/kg but not at 30 mg/kg modified the colitis in some but not all animals. This model appears to be of little value for the screening of anti-colitic agents.