A mechanistic approach into a diabetic serum factor-mediated release of beta-glucuronidase in normal neutrophils.

The possible mechanism of diabetic serum factor (DSF)-mediated lysosomal degranulation has been investigated. It was observed that pertussis toxin, sodium fluoride and vanadate could significantly inhibit DSF-mediated beta-glucuronidase release, whereas atropine exhibited only a partial blockage against DSF. Since DSF can generate toxic free radicals, various free radical quenchers were tested in order to evaluate their contributions. Superoxide dismutase was found to be the most effective in inhibiting lysosomal release as compared to catalase and peroxidase. The mixtures of all the enzymes failed to exhibit any additive effect. Interaction of DSF with heparin, insulin and Con A revealed that heparin can completely block DSF-mediated lysosomal release. The implications of the observations are discussed.

Status of nitric oxide free radicals in diabetic neutrophils: effect of diabetic serum factor on the generation of these species in normal neutrophils and their relation to lysosomal degranulation.

Normal polymorphonuclear leukocytes (PMNL) in contrast to diabetic PMNL, generated significant amounts of .NO and NO2 when challenged with opsonised zymosan. Diabetic neutrophils, on the other hand, responded either weakly or insignificantly to the same stimulants. However, in resting state the levels of .NO and NO2 were higher in diabetic as compared to normal PMNL. Diabetic serum factor (DSF) provoked a significant generation of .NO and NO2 in normal PMNL, a phenomenon found parallel to the enhancement in cytosolic cathepsin D activity in normal cells on insult with DSF.

Plausible involvement of a diabetic serum factor in neutrophil membrane pathology.

With a view to determining the role of diabetic serum factor (DSF) in the progression of membrane pathology, time-dependent preincubation effects of DSF on certain membrane-bound enzymes of normal polymorphonuclear leucocytes (PMNL) have been studied. DSF is found to cause significant decrements in the activities of Na+/K+ ATPase, PLC and AcE of PMNL on in vitro incubation for 60 min, while the effect on Ca2+/Mg2+ ATPase appears only on prolonged incubation with an initial hike in activity at 5 min. The implications of these results have been discussed.