The effect of zinc on anaphylaxis in vivo in the guinea-pig

Zinc modulates airway epithelium susceptibility to death receptor-mediated apoptosis

The accelerated loss of lung epithelium through activation of extrinsic apoptosis is believed to play a causative role in lung pathogenesis. Previous investigations have shown that zinc is required to sustain lung epithelial cell viability under stress conditions and that depletion of intracellular zinc predisposes cells to apoptosis. In this investigation, we determined whether intracellular zinc deficiency enhanced the susceptibility of primary, differentiated cultures of human lung epithelium to death receptor-mediated apoptosis, leading to barrier dysfunction. Cultures obtained from multiple donors were exposed to stimuli that provoke death receptor-mediated apoptosis and depleted of intracellular zinc with a zinc-specific chelating agent. Transepithelial resistance, paracellular transport, caspase-8 and caspase-3 activity, and apoptosis were measured. Activation of extrinsic apoptosis or zinc chelation alone resulted in a nominal increase in caspase function and apoptosis without major evidence of barrier disruption. Activation of extrinsic apoptosis in addition to zinc depletion resulted in an abrupt decrease in transepithelial resistance, a substantial increase in apoptosis, and an increased paracellular leak. Cultures were rescued by supplementation with zinc sulfate. Further analysis revealed that exogenous zinc facilitates cell survival through activation of the phosphatidylinositol 3-kinase/Akt signaling pathway. We conclude that intracellular zinc is a vital factor in lung epithelium that protects cells from death receptor-mediated apoptosis and barrier dysfunction.

Zinc metabolism in airway epithelium and airway inflammation: basic mechanisms and clinical targets. A review

In addition to basic housekeeping roles in metalloenzymes and transcription factors, dietary zinc (Zn) is an important immunoregulatory agent, growth cofactor, and cytoprotectant with anti-oxidant, anti-apoptotic, and anti-inflammatory roles. These properties of Zn are of particular importance in maintaining homeostasis of epithelial tissues which are at the front line of defense. This review is about the role of Zn in airway epithelium (AE). The first part focuses on the cellular biology of Zn, and what is known about its distribution and function in AE. The second part of the review considers evidence for altered Zn metabolism in asthma and other chronic diseases of airway inflammation. Important issues arise from a potential therapeutic perspective as to the optimal ways to monitor circulating and epithelial Zn levels in patients and the most effective means of supplementing these levels.

Delineation of the protective action of zinc sulfate on ulcerative colitis in rats

The protective action of zinc compounds in Crohn's disease-like inflammatory bowel disease in animals has been shown. A similar action of zinc sulfate on ulcerative colitis has not been defined. The present study aimed to delineate the protective action of zinc sulfate and the pathogenic mechanisms of 2,4-dinitrobenzene sulfonic acid (DNBS)-induced ulcerative colitis in rats. Zinc sulfate at different concentrations was given either orally (p.o.) or rectally (p.r.) to rats at 42, 48, 66 and 72 h following the induction of colonic inflammation by DNBS. Rats were killed 96 h after instillation of DNBS rectally to assess the severity of colonic damage, myeloperoxidase and xanthine oxidase activities. The involvement of mast cell degranulation and histamine release in the pathogenesis of DNBS-induced colitis was determined by using a mast cell stabilizer (ketotifen) and histamine receptor blockers (terfenadine and ranitidine). DNBS given rectally produced inflammation and ulceration in rats with a pathology resembling ulcerative colitis. Myeloperoxidase activity but not xanthine oxidase activity was sharply increased by this agent. Intrarectal administration of zinc solution and parenteral injection of histamine blockers significantly reduced tissue damage and myeloperoxidase but not xanthine oxidase activity. Ketotifen, a mast cell stabilizer, also significantly decreased mucosal injury and myeloperoxidase activity in the colon. In conclusion, mast cell degranulation followed by histamine release plays an important role in the pathogenesis of DNBS-induced ulcerative colitis. Zinc given rectally has a therapeutic effect against this colitis model, perhaps through the reduction of inflammation and inhibition of the above pathogenic mechanisms.

New insights into the role of zinc in the respiratory epithelium

Over the past 30 years, many researchers have demonstrated the critical role of zinc (Zn), a group IIb metal, in diverse physiological processes, such as growth and development, maintenance and priming of the immune system, and tissue repair. This review will discuss aspects of Zn physiology and its possible beneficial role in the respiratory epithelium. Here we have detailed the mechanisms by which Zn diversely acts as: (i) an anti-oxidant; (ii) an organelle stabilizer; (iii) an anti-apopototic agent; (iv) an important cofactor for DNA synthesis; (v) a vital component for wound healing; and (vi) an anti-inflammatory agent. This paper will also review studies from the authors' laboratory concerning the first attempts to map Zn in the respiratory epithelium and to elucidate its role in regulating caspase-3 activated apoptosis. We propose that Zn, being a major dietary anti-oxidant has a protective role for the airway epithelium against oxyradicals and other noxious agents. Zn may therefore have important implications for asthma and other inflammatory diseases where the physical barrier is vulnerable and compromised.

Reactive oxygen species produced in metal-catalyzed oxidation of bis(trifluoromethyl)disulfide and protection by ZE

Bis(trifluoromethyl)disulfide (TFD), used as an industrial fumigant, was found to generate a thiyl free radical as seen by EPR/spin trapping. Oxygen appears to be an absolute requirement for radical production. The results obtained in this investigation implicate the production of thiyl and reactive oxygen species (ROS), superoxide radical anion and hydroxyl radicals, during TFD autoxidation. The rate of production of these free radical intermediates was found to increase in the presence of iron(III) and copper(II). In addition, the metal ion chelator DETAPAC and ROS scavengers ethanol, mannitol, and PEG-SOD/catalase were found to inhibit free radical production. Reactive oxygen species were not formed when a high-potency zinc plus antioxidant, ZE caps, was present. These results provide support for the pro-oxidation of TFD and a protective role for zinc.

Inhibitory effect of zinc oxide on contact allergy due to colophony

Contact allergy to a wound dressing with an adhesive mass consisting of colophony, zinc oxide and rubber (Mezinc) was studied in 179 patients with a history of eczema. 12 patients were found to be allergic to colophony, whereas only 4 of these patients also showed a positive patch test reaction to the wound dressing. 14 patients with verified moderate contact allergy to colophony were patch tested with adhesive mass (10%), Portuguese colophony (10%), zinc oxide (10%), purified resin acids (10%), and Portuguese colophony (10%), in combination with zinc oxide. Only 3 patients reacted to the adhesive mass, whereas all patients showed a positive patch test reaction to Portuguese colophony. A combination of zinc oxide (10%) with Portuguese colophony (10%) provoked a positive patch test reaction in only 5 of these 14 patients. An allergic reaction to abietic acid (90-95% purity) was found in 7 patients and to neoabietic acid (99 + %) in 3 patients, whereas no reactions to dehydroabietic (99 + %), isopimaric (99 + %) or levopimaric acids (98 + %) were found.