Zinc Desferrioxamine Research Articles

Zinc–desferrioxamine attenuates retinal degeneration in the rd10 mouse model of retinitis pigmentosa

Iron-associated oxidative injury plays a role in retinal degeneration such as age-related macular degeneration and retinitis pigmentosa. The metallo-complex zinc–desferrioxamine (Zn/DFO) may ameliorate such injury by chelation of labile iron in combination with release of zinc. We explored whether Zn/DFO can affect the course of retinal degeneration in the rd10 mouse model of retinitis pigmentosa. Zn/DFO-treated animals showed significantly higher electroretinographic responses at 3 and 4.5weeks of age compared with saline-injected controls. Corresponding retinal (photoreceptor) structural rescue was observed by quantitative histological and immunohistochemical techniques. When administered alone, the components of the complex, Zn and DFO, showed a lesser, partial effect. TBARS, a marker of lipid peroxidation, and levels of oxidative DNA damage as quantified by 8-OHdG immunostaining were significantly lower in Zn/DFO-treated retinas compared with saline-injected controls. Reduced levels of retinal ferritin as well as reduced iron content within ferritin molecules were measured in Zn/DFO-treated retinas. The data, taken together, suggest that the protective effects of the Zn/DFO complex are mediated through modulation of iron bioavailability, leading to attenuation of oxidative injury. Reducing iron-associated oxidative stress using complexes such as Zn/DFO may serve as a “common pathway” therapeutic approach to attenuate injury in retinal degeneration.

Ischemic preconditioning of the rat retina: Protective role of ferritin

Ischemic preconditioning (IPC) of the retina, accomplished by ischemia of short duration, is highly effective in preventing subsequent severe injury caused by iron-dependent free radical burst after prolonged ischemia. To investigate the mechanistic basis for IPC rescue, we examined changes in the levels of the retinal redox-active and labile iron pool, ferritin, and ferritin-bound iron. Prolonged ischemia severely impaired retinal function, with total loss of the full-field electroretinographic response. IPC provided marked protection against such injury. Histological examination revealed that ischemia-associated structural damage and loss of cells in the outer and inner nuclear layers were largely prevented by IPC. Ferritin levels decreased after prolonged ischemia but remained close to normal when the ischemic episode was preceded by IPC. The protective effect of IPC on retinal function and ferritin was blocked by a zinc–desferrioxamine complex known to interfere with iron signaling. The results suggest a mechanism whereby IPC activates an iron signaling pathway leading to a marked increase in ferritin levels, which mediates resistance to prolonged ischemia.

Desferrioxamine and zinc–desferrioxamine reduce lens oxidative damage

Our purpose was to investigate the quality and morphology of cultured bovine lenses after exposure to hyperbaric oxygen (HBO) in the presence or absence of desferrioxamine (DFO) or zinc–desferrioxamine (Zn–DFO). Intact bovine lenses were cultured and exposed to HBO of 100% oxygen at 2.5 ATA for 120 min. One hundred and fifty lenses were included in the present study. Lenses were divided into study groups of 25 lenses each: (1a) HBO-exposed lenses; (1b) control lenses extracted from the contralateral eyes of group 1a and exposed to normal room air. (2a) HBO-exposed lenses treated with DFO; (2b) control lenses extracted from the contralateral eyes of group 2a exposed to normal room air in the presence of DFO (3a) HBO-exposed lenses treated with Zn–DFO; (3b) control lenses extracted from the contralateral eyes of group 3a, exposed to normal room air in the presence of Zn–DFO. Lens optical quality and structural changes were assessed. Oxygen toxicity to lenses was demonstrated by decreased light transmission, increase in focal length variability and a decrease in morphological integrity. Light intensity measurements showed a distinct pattern in control lenses. A different pattern was noticed for hyperbaric oxygen-exposed lenses. Focal length variability values were stable in control lenses and increased significantly in oxygen-exposed lenses. Structural damage to lenses was demonstrated by the appearance of bubbles between lens' fibers possibly demonstrating failure of lens tissue to cope with oxygen load. All measured parameters showed that both Zn–DFO and DFO attenuated the oxidative damage. The effect of DFO was small whereas Zn–DFO demonstrated a significantly stronger effect. Treatment of hyperbaric oxygen-exposed lenses with DFO only marginally reduced the oxidative damage. Treatment with Zn–DFO was superior in reducing the oxidative damage to lenses. These results indicate a possible role for Zn–DFO in the prevention of cataracts.

Zinc–desferrioxamine reduces damage to lenses exposed to hyperbaric oxygen and has an ameliorative effect on catalase and Na, K-ATPase activities

Our purpose was to investigate the effects of exposure to high partial pressure of oxygen on lens optical quality and on the activities of lenticular catalase and Na, K-ATPase in culture and to examine the effect of zinc–desferrioxamine (Zn–DFO) addition to cultured lenses exposed to high oxygen partial pressure on these parameters. Bovine lenses, kept in organ culture, were exposed to different combinations of partial pressure of oxygen with and without addition of Zn–DFO complex (20 μM) and examined during a 14-day period. Lens optical quality, catalase, and Na, K-ATPase activity were compared between study and control groups. Two hundred lenses were included in the present study. Decreased lenticular optical quality and decreased catalase and Na, K-ATPase activities were observed in lenses exposed to hyperbaric oxygen. Lenses exposed to normobaric oxygen showed a reduction in these parameters to a lesser degree. The damaging optical and enzymatic effects of oxygen on lenses in culture increased in magnitude along the culture period. Addition of Zn–DFO to the culture just before the exposure to hyperbaric oxygen eliminated most of the optical and enzymatic oxygen-induced damage. Addition of Zn–DFO after the first exposure demonstrated reduction in the oxidative damage induced reduction of optical quality in a time-dependent manner – the later the addition of Zn–DFO took place the smaller the protective effect observed. High oxygen load has toxic effects on bovine lenses in organ culture conditions as determined by optical parameters as well as reduction of catalase and Na, K-ATPase activities. These toxic effects can be attenuated by introducing Zn–DFO just before lenses are exposed to oxygen. The beneficial effect of Zn–DFO, applied after lenses have been exposed to hyperbaric oxygen, on the oxidative damage was time-dependent – the earlier the application the more significant the observed protective effect. The present results may indicate a possible future role for Zn–DFO as a protective agent against oxygen-induced human cataract formation.

Treatment of Ocular Tissues Exposed to Nitrogen Mustard: Beneficial Effect of Zinc Desferrioxamine Combined with Steroids

Exposure of the ocular surface to mustard gas chemical warfare leads to a destructive inflammatory reaction. Both steroids and a novel metalocomplex free radical scavenger, zinc desferrioxamine (Zn/DFO), have been shown to be effective separately in reducing ocular damage. The purpose of the present study was to investigate whether the effectiveness of both medications applied simultaneously is superior to the effectiveness of either one applied alone. One eye in each of 52 rabbits was exposed to 2% nitrogen mustard (NM). Topical treatment with eye drops of a metal complex-zinc desferrioxamine (Zn/DFO)-combined with dexamethasone phosphate (0.1%), was compared with the administration of saline or treatment with Zn/DFO or dexamethasone alone. Eight eyes (four animals) that were not exposed to NM served as the control. Examiners masked to the treatment groups assessed the extent of ocular injury and the response to treatment using clinical, histologic, and biochemical criteria. Treatment with the combination of Zn/DFO and dexamethasone was significantly more effective than was dexamethasone or Zn/DFO alone in reducing NM injury to ocular anterior segment structures. In combination-treated eyes, corneal re-epithelization was faster, corneal neovascularization was less severe, and intraocular pressure was not as severely elevated as in the saline or the Zn/DFO- or dexamethasone-alone groups. In addition, systemic antioxidant status was better conserved in the combination-treated animals. The findings suggest that the combination of topically applied Zn/DFO and dexamethasone, by virtue of their additive inhibitory effects on free radical formation and inflammation, should be considered as a basis for the treatment of ocular mustard gas injuries.

Ischaemic preconditioning but not isoflurane prevents post-ischaemic production of hydroxyl radicals in a canine model of ischaemia-reperfusion

Isoflurane has been shown to mimic ischaemic preconditioning (IPC). The protective effect of IPC, or applying isoflurane or perfusion with the 'push-pull' complex zinc-desferrioxamine (Zn-DFO) in the canine heart, was investigated. Thirty minutes after salicylate administration (100 mg kg(-1)) the heart was exposed. All dogs were subjected to a 10 min left anterior descending artery occlusion followed by 2 h of reperfusion. In Group I (n = 9) isoflurane (2.5%) was administered 10 min prior to and during ischaemia. In Group II (n = 8), IPC was elicited by 5 min coronary artery occlusion, followed by 5 min of reperfusion, prior to the 10 min ischaemia. In Group III (n = 9) Zn-DFO (2.5 mg kg(-1)) was given 10 min prior to ischaemia. The effects of these interventions were compared to control (n = 10). Coronary sinus blood concentrations of salicylate, 2,3-dihydroxybenzoic acid (DHBA), lactate, pH and oxygen content were monitored. In the control group, 2,3-DHBA increased by 32% above the pre-ischaemic value (P < 0.05). In contrast, in the IPC hearts, a significant decrease in the production of 2,3-DHBA was observed (40% lower than baseline, P < 0.01). In the isoflurane group only a 13% (and non-significant) decrease was noticed. In the Zn-DFO group a 33% decrease was found (P < 0.01). The increase in lactate concentrations in the IPC and Zn-DFO groups was significantly smaller than that of control and isoflurane groups. IPC protected the heart against the deleterious effects of reperfusion, possibly by amelioration of the level of oxygen-derived reactive species, and the complete inhibition of reactive hydroxyl radical production. Isoflurane did not prove to be as effective in reducing the free radical damage.

Redox metal chelation ameliorates radiation-induced bone marrow toxicity in a mouse model.

Since zinc desferrioxamine (Zn-DFO) has been shown to be a very potent protector against injuries induced by redox-active metal ions, we examined its protective effect against radiation-induced toxicity. We found that treatment with Zn-DFO given before TBI increased the survival of mice irradiated with 7.5 and 8.5 Gy. Zn-DFO also protected against radiation-induced myelosuppression and body weight loss, while soluble Il6 levels in serum were normalized in mice pretreated with Zn-DFO. We concluded that administration of Zn-DFO prior to TBI protected BALB/c mice from radiation-induced toxicity, increasing survival rates by up to 75%. The biological effect of Zn-DFO is known to result from its effect on the production of intracellular hydroxyl free radicals mediated by redox-active metal ions, and both metal chelation and zinc delivery appear to be equally likely mechanisms for this outcome. We suggest that radiation-induced toxicity is caused by the deleterious effect of redox-active metal ions, and that compounds which modulate this redox activity may act as radioprotectors.

Novel Protection Strategy against X-Ray-Induced Damage to Salivary Glands

Exposure of the major salivary glands to ionizing radiation often results in severe alterations in structure and function. The mechanism of these effects is still unknown, and no adequate prevention or treatment is yet available. The purpose of this study was to examine a mechanism based on the assumption that redox-active metal ions, which propagate the production of highly reactive free radicals, are responsible for the unique radiosensitivity of salivary glands. Zinc-desferrioxamine (Zn-DFO) was recently reported to be a very potent protector against the injuries induced by such metal ions in the vicinity of sensitive cellular targets. We chose to examine its protective potential against the damage to salivary glands induced by X rays. Head and neck irradiation (15 Gy) was delivered to rats 90 min after the intraperitoneal administration of 20 mg/kg Zn-DFO. This group was compared to two control groups, irradiated and nonirradiated. At 2 months after irradiation, both systemic and salivary parameters were analyzed. The results demonstrated that X irradiation induced a profound attenuation of body weight (30%) and a reduction of parotid gland saliva flow rate (74%), parotid gland weight (36%), submandibular gland/sublingual gland saliva flow rate (46%), and submandibular/sublingual gland weight (24%) (P < 0.01 for all parameters). The content of potassium in parotid gland saliva was increased by 46% (P < 0.01), while the protein content was unaltered. The increase in the potassium concentration of the saliva is considered to be another indication of salivary gland hypofunction. Administration of Zn-DFO prior to irradiation resulted in partial protection against radiation-induced injury to the parotid gland but not the submandibular gland. In the Zn-DFO-treated and irradiated group, the parotid gland saliva flow rate was reduced by 42%, the weight of the parotid gland was reduced by 13%, and the potassium concentration in the parotid gland saliva was increased by 21% (P < 0.05 for all parameters). These results give credence to the validity of the hypothesis which correlates radiation-induced damage of the salivary glands with the injurious role of intracellular redox-active metal ions. Furthermore, the results offer prospects in the clinical setting, as Zn-DFO is a modification of DFO, which is a clinically approved and widely used medication. Further examination of the clinical use of Zn-DFO is currently under way, focusing on its beneficial protective effect on healthy non-neoplastic tissue.

Topical use of zinc desferrioxamine for corneal alkali injury in a rabbit model.

To evaluate the efficacy of topical zinc desferrioxamine in acute corneal alkali injury in rabbits. Twenty rabbits were anesthetized and a standardized alkali burn (1N NaOH) was performed in the center of the cornea (7.5-mm diameter). The animals were randomly divided into two groups and treated (double-masked) with topical zinc desferrioxamine, 220 microM, (group 1) or its vehicle (group 2). Drops were applied 7 times/day for 28 days. Topical gentamicin, 0.3%, was instilled twice a day. Animals were evaluated twice a week. At each examination (using the slit-lamp), the depth of corneal ulcer was graded as follows: 0, no ulcer; 1, tissue loss less than one third of corneal thickness; 2, one third to two thirds tissue loss; 3, more than two thirds tissue loss; 4, descemetocele; or 5, perforation. Ulceration area, vascularization, and epithelial defects also were measured. During the study period, the grading of mean corneal ulcerations in group 1 ranged from 0.2 to 1.00, whereas in group 2, it ranged from 1.4 to 2.7. The mean grade and area of ulceration in group 2 were greater than those in group 1 (p < 0.05). Topical zinc desferrioxamine may be an adjunctive treatment in protecting the cornea against induced alkali injury.