Effects of thalidomide on the generation of oxygen intermediates by zymosan-stimulated normal polymorphonuclear leukocytes

Interplay among oxidants, antioxidants, and cytokines in skin disorders: Present status and future considerations

The pathogenicity of skin disorders involves a complexity of physiological, immunological, environmental, and genetic phenomena. This review focuses on cross-talks between two main agents, the oxidants and cytokines network, which have recently been found to play important roles in the pathophysiology of a large variety of skin disorders, including carcinogenesis, UVB irradiation damages, inflammatory processes, and a series of diseases such as, psoriasis, pyoderma gangrenosum, atopic dermatitis, irritant contact dermatitis, and bacterial skin infections. In particular the review discusses the question how an interplay between oxidants and cytokines might be beneficial in wound-healing and in therapeutic strategies in clinical settings. These involve topical applications and oral administration of antioxidant and inflammatory-cytokines-neutralizing antibodies. Monitoring cytokine expression in skin disorders (inflammatory versus anti-inflammatory, or Th1 versus Th2 types of cytokines) will definitely help to evaluate the severity of injury, its type, and its role in therapy. Furthermore, it is expected that future studies should explore the possible roles of the synergistic interactions between antioxidants and cytokines and their impact on the Th1/Th2 cytokine networks balances.

Thalidomide reduces lipopolysaccharide/zymosan-induced acute lung injury in rats

Pharmacological therapies targeting fulminant lung inflammation in acute lung injury (ALI) need to be improved. We evaluated the effect of thalidomide, a chemical modulating both acute and chronic inflammation, on ALI induced by intravenous administration of lipopolysaccharide (LPS) and zymosan in male Sprague-Dawley rats. Injection of LPS and zymosan induced significant lung inflammation, as evidenced by increased neutrophil sequestration in lung tissue as well as enhanced nitric oxide metabolite (NO(x)(-)) production in the serum and bronchoalveolar lavage (BAL) fluid. Lactate dehydrogenase (LDH) activity and protein concentration in BAL fluid were significantly increased after administration of LPS and zymosan. Pulmonary microvascular permeability was determined using the Evans blue retention method, which showed a significant increase in microvascular permeability after LPS and zymosan administration, indicating the development of ALI. Animals that received thalidomide (100 mg/kg) 2 h prior to LPS injection had significantly reduced pulmonary NO(x)(-) production, pulmonary microvascular permeability, and LDH activity and protein concentration in BAL fluid. We therefore conclude that thalidomide ameliorates lung inflammation and reduces ALI induced by combined LPS and zymosan administration in rats.

Thalidomide in gastrointestinal disorders

Thalidomide was originally marketed as a sedative, but was removed from the market in 1961 after it was associated with an epidemic of severe birth defects. Subsequently, it has been shown to have therapeutic efficacy in a number of the gastrointestinal tract conditions characterised by immune dysregulation. The exact mechanism of the immunosuppressive effects of thalidomide is unknown; proposed mechanisms include inhibition of tumour necrosis factor alpha release and inhibition of angiogenesis. In chronic graft versus host disease, use of high dose thalidomide (1200 mg/day) may bring about a response in 20% of patients with refractory disease. Thalidomide 200 mg/day helps eradicate ulcers in 50% of patients with HIV-associated oral aphthous ulceration. In Behçet's disease, thalidomide 100 to 300 mg/day can decrease the number of mucocutaneous ulcers, although full remission occurs in less than 20% of patients. In Crohn's disease, thalidomide 50 to 300 mg/day may decrease the severity of mucosal disease and prompt closure of fistulae. Patients to be placed on thalidomide therapy must practice either abstinence or strict birth control; women must undergo regular pregnancy testing and utilise 2 forms of contraception. Other adverse effects include sedation (present in nearly all patients), symptomatic neuropathy (present in approximately 20%), and skin rashes. Given the potential toxicity, thalidomide use should generally be limited to clinical protocols with institutional review board oversight.

Thalidomide selectively modulates the density of cell surface molecules involved in the adhesion cascade

The mode of action of thalidomide (THD) in clinical cases of vasculitis is still not clear. Expression of adhesion molecules on endothelial cell lines was therefore assessed in vitro. THD is capable of changing the density of tumor necrosis factor alpha (TNFalpha) induced ICAM-1 (CD54), VCAM-1 (CD106) and E-selectin antigens on HUVEC. Furthermore, modulation of L-selectin (CD62L) by THD can be demonstrated on human leukocytes in vitro. The molecules investigated are involved in the neutrophil-endothelial cell interaction and participate in the adhesion cascade. Blunting of cytokine induced up-regulation of these adhesion molecules may account at least in part for anti-vasculitic effects of thalidomide.

Thalidomide in the treatment of graft-versus-host disease

The success of allogeneic bone marrow transplantation has been restricted by the occurrence of graft-versus-host disease (GVHD). Attempts at prevention and treatment of GVHD have resulted in only a limited improvement and the morbidity and mortality rate remains high. Thalidomide has been known to have immunosuppressive properties for over 20 years, but it has only recently been used in GVHD. Evidence is now accumulating as to its value both in animal models, and in humans where most benefit has been seen in chronic GVHD. We report our experience using thalidomide in GVHD following allogeneic bone marrow transplantation and review the literature.

Effect of sulphasalazine and its metabolites on the generation of reactive oxygen species

The relative in vitro anti-oxidant efficacy of sulphasalazine (salicylazosulphapyridine, SASP) and its metabolites (5-aminosalicylic acid, 5-ASA; sulphapyridine, SP) was examined by studying their effects on the generation of reactive oxygen species (ROS) using zymosan-stimulated polymorphonuclear leucocytes (PMNs) and a cell free, xanthine-xanthine oxidase system. Salicylazosulphapyridine, 5-ASA, and SP showed anti-oxidant effects to the various degrees. In particular, production of OH, which is one of the most potent reactive oxygen species, was remarkably suppressed by 5-ASA dose relatedly. These findings suggest that SASP and its metabolites play an important role in the inhibition of respiratory bursts. As the potent products of the respiratory burst by polymorphonuclear leucocytes are thought to be important inflammatory mediators, suppression of toxic reactive oxygen species generation by these agents may partly explain the therapeutic efficacy of SASP in ulcerative colitis, which is characterised by an acute mucosal inflammation dominated by polymorphonuclear leucocytes accumulation.

The effect of thalidomide on arachidonic acid metabolism in human polymorphonuclear leukocytes and platelets

The effect of thalidomide on the metabolism of arachidonic acid by purified washed human platelets and polymorphonuclear leukocytes was examined. The drug was found to be without effect under the conditions used. The action of thalidomide cannot therefore be attributed to a direct inhibition of prostaglandin or leukotriene biosynthesis.

Effect of antibiotics on the generation of reactive oxygen species

The relative antioxidant efficacy, in vitro, of several antibiotics was examined by studying their effects on the generation of reactive oxygen species (ROS) using zymosan-stimulated polymorphonuclear leukocytes (PMNL) and the cell-free, xanthine-xanthine oxidase system. The species investigated are superoxide radical anion (O2-.), hydrogen peroxide (H2O2), and hydroxyl radical (OH.). Three tetracyclines (tetracycline HCl, oxytetracycline HCl, and minocycline HCl), erythromycin, cephalexin, penicillin G, chloramphenicol, and streptomycin were used as test drugs. At concentrations comparable to therapeutic blood levels, tetracycline HCl, oxytetracycline HCl, minocycline HCl, and erythromycin inhibited some of the ROS production by PMNL. In the xanthine-xanthine oxidase system, only minocycline HCl suppressed the H2O2 level. Cephalexin, penicillin G, chloramphenicol, and streptomycin did not affect any of the ROS examined at the concentrations tested. The capacity of some of these agents to inhibit ROS generation by PMNL may account, in part, for their efficacy in inflammatory skin diseases such as acne vulgaris. The antioxidant effect of these antibiotics does not stem from their capability to scavenge ROS, but originates rather from their effect on PMNL cell function directly with resultant anti-inflammatory effects on the inflammatory processes.

Antioxidant action of antimalarials

The effects of antimalarials, chloroquine and quinacrine, on the generation of reactive oxygen species were examined both in polymorphonuclear leucocytes and in the xanthine-xanthine oxidase system. Antimalarials showed inhibitory effects on the production of reactive oxygen species probably by affecting cell functions, such as membrane phospholipid methylation. It is suggested that antimalarial agents can work as antioxidants at the site of inflammation protecting against auto-oxidative tissue damage with resultant anti-inflammatory effects.

Anti-oxidant action of metronidazole: a possible mechanism of action in rosacea

To elucidate the mechanism of action of metronidazole in the treatment of rosacea, the effect of metronidazole on the generation of reactive oxygen species was examined both in neutrophil and xanthine-xanthine oxidase systems. Metronidazole had anti-oxidant action which was not exerted by the scavenging of reactive oxygen species, but by having an effect on neutrophil cell functions. Beneficial effects of metronidazole in the treatment of papulopustular rosacea can in part be attributable to this anti-inflammatory effect.