Pretreatment with a single bolus injection of polyoxyethylene-modified superoxide dismutase prevents reperfusion induced arrhythmias in the anesthetized rat

Delayed Exacerbation of Acute Myocardial Ischemia/Reperfusion-Induced Arrhythmia by Tracheal Instillation of Diesel Exhaust Particles

For understanding the relationship between the increased incidence of sudden cardiac death and air pollution, we examined the effects of intratracheal instillation of diesel exhaust particles (DEP) on acute myocardial ischemia/reperfusion-induced arrhythmia in rats. The animals received 1 mg DEP 24-48 h before the ischemia/reperfusion (DEP-pretreated group, DEP-PRE), and were subjected to 3 successive brief ischemia/reperfusion (3 min ischemia followed by 5 min reperfusion) procedures. These were to make the animals tolerant to ischemia/reperfusion-related myocardial deterioration. Thereafter the animals were subjected to a 10-min ischemia followed by a 30-min reperfusion. In the experiments, an increased mortality was observed in the DEP-PRE group compared to the vehicle (0.05% Tween 80-PBS)-treated group. Forty-six percent of the animals in DEP-PRE died during the first 3-min reperfusion period. The animals of other groups were intratracheally instilled with DEP at the beginning of ischemia/reperfusion experiment, or were pretreated with polyethylene glycol-conjugated superoxide dismutase (1000 IU kg(-1), iv). In these animals, incidences of both arrhythmia and mortality were similar to those in the animals treated with the vehicle. In experiments to investigate the effects of DEP on the biochemical and hematological parameters, neutrophil count was elevated by a higher dose (5 mg) of DEP at 24 h after the intratracheal instillation, and oxygen radical production, which was induced by 12-O-tetradecanoylphorbol 13-acetate, was enhanced at 72 h. These results indicate that intratracheal DEP instillation exacerbates short-period ischemia/reperfusion-induced arrhythmia. Delivery and activation of peripheral neutrophils and oxygen radicals produced in neutrophils might participate in this exacerbation. This is the first article that demonstrates the arrhythmogenicity of DEP using intratracheal instillation in rats.

Polyethylene glycol-superoxide dismutase, a conjugate in search of exploitation

Without a doubt PEG-SOD has been the enzyme most studied in PEGylation. One can say that it represents the preferred model to assess chemistries for PEG activation, analytical procedures suitable for conjugate characterization, the influence of PEG size in conjugate removal from circulation and elimination of immunogenicity and antigenicity, and the effect of route of administration. The effect of PEG conjugation was studied in vitro and in vivo models in comparison with the free enzyme and the following conclusions may be drawn: (1) At the blood vessel level, PEG-SOD has been shown to provide a greater resistance to oxidant stress, to improve endothelium relaxation and inhibit lipid oxidation. (2) In the heart, PEG-SOD proved to be at least as effective as native SOD in treatment of reperfusion-induced arrhythmias and myocardial ischemia. (3) In the lung, PEG-SOD appeared to be able to reduce oxygen toxicity and E. coli-induced lung injury, but not in the treatment of lung physiopathology associated with endotoxin-induced acute respiratory failure and in the reduction of asbestos-induced cell damage. (4) On cerebral ischemia/reperfusion injuries the effect of PEG-SOD was uncertain, also due to the difficulty of cerebral cell penetration. (5) In kidney and liver ischemia both enzyme forms were found to ameliorate reperfusion damage. In view of so much positive research on PEG-SOD, it is surprising that no approved application in human therapy has been established and approved.

Effect of polyoxyethylene-modified superoxide dismutase on recovery of myocardial dysfunction after coronary stenosis in dogs

The effects of superoxide dismutase modified with polyoxyethylene (SOD-POE) on impairment of myocardial segment shortening (SS) during coronary stenosis plus pacing-induced tachycardia (CSPT) and the recovery after reperfusion was examined in anesthetized dogs. SOD-POE or saline was administered i.v. 30 min before reperfusion. Changes in hemodynamic variables and SS by CSPT were similar in both groups. However, the SOD-POE group showed improved recovery of SS compared with the control group. Results indicate that oxygen-derived free radicals may partially be involved in the genesis of myocardial dysfunction after CSPT-induced regional ischemia.