Serum factor from diabetic patients with or without retinopathy stimulates superoxide anion production by normal polymorphonuclear leukocytes

Oxygen free radicals (OFRs) have been implicated in the pathogenesis of diabetic microangiopathy. The effects of serum from insulin-dependent diabetes mellitus patients with or without retinopathy on the production of superoxide anion by normal polymorphonuclear leukocytes (PMNs) were measured spectrophotometrically and compared with that of age matched controls. Superoxide anion production by PMNs incubated with serum from retinopathy-free patients or patients with retinopathy was significantly higher than that of controls (P=0.0002 and 0.0001, respectively). Furthermore, superoxide anion production by PMNs incubated with serum from patients with retinopathy was significantly higher than retinopathy-free patients (P=0.02). These observations suggest that a diabetic serum factor provoked a significant generation of superoxide anion in normal PMNs, a phenomenon found parallel to the presence of retinopathy, indicating that OFRs may play a role in the progression of diabetic retinopathy. The nature of this serum factor remains to be clarified.