Insulin-stimulated chemokinesis in normal human neutrophils is dependent on D-glucose concentration and sensitive to inhibitors of tyrosine kinase and phosphatidylinositol 3-kinase

Hyperglycemia in vitro attenuates insulin-stimulated chemokinesis in normal human neutrophils. Role of protein kinase C activation

“…Because tyrosine phosphorylation of IRS-1 is a key step in the further downstream transduction of the insulin signal to PI 3-kinase, phospholipase C␥ (PLC␥), and Ras, as expected the activity of PI 3-kinase was also impaired by in vitro hyperglycemia [16]. It is interesting to note that the chemokinetic effect of insulin found at 5 mM D-glucose in normal human neutrophils was abolished at 15 mM glucose [9]. The precise molecular mechanisms behind this effect of high glucose on insulin-stimulated locomotion are unknown.…”

“…Neutrophil granulocytes were isolated from heparinized venous blood drawn from apparently healthy adult volunteers with the use of a sodium metrizoatedextran gradient (Polymorphoprep), as previously described [9]. In short, after centrifugation of venous blood on the gradient, the neutrophil-rich band was collected and, after hypotonic lysis of the remaining erythrocytes, the neutrophils were washed twice in PBS and finally suspended in calcium and magnesium-free KRH.…”

“…Type 1 diabetes is generally characterized by an absolute insulin deficiency, whereas in type 2 diabetes the insulin levels can be elevated mainly due to insulin resistance [6]. Recent studies indicate that insulin, at physiological and moderately elevated levels, stimulates chemotaxis [7] and chemokinesis in normal human neutrophils [8,9]. This effect of insulin was not sensitive to inhibition of protein kinase C (PKC) by staurosporine treatment [8] but dependent on tyrosine phosphorylation and phosphatidylinositol 3-kinase (PI 3-kinase) activity [9].…”

“…Recent studies indicate that insulin, at physiological and moderately elevated levels, stimulates chemotaxis [7] and chemokinesis in normal human neutrophils [8,9]. This effect of insulin was not sensitive to inhibition of protein kinase C (PKC) by staurosporine treatment [8] but dependent on tyrosine phosphorylation and phosphatidylinositol 3-kinase (PI 3-kinase) activity [9]. The importance of tyrosine phosphorylation and PI 3-kinase activity indicates that the insulin effect probably is mediated by similar signal transduction mechanisms as seen in other tissues, i.e.…”

Successful Intensive Insulin Treatment of Type 1 Diabetic Dogs Leads to Restoration of Peripheral Leukocyte Insulin Signaling Gene Expression and Enzyme Activities

“…Moreover, the increase in IRS-2 and PI3-K mRNA expression matches the baseline response to insulin observed for leukocytes isolated from normal healthy dogs when incubated with insulin in vitro. It is known that insulin action on neutrophils is mediated through PI3-kinase activation [42]. Since IRS proteins and PI3-K show a critical link to insulin signaling [52,54], changes in IRS-1 and/ or IRS-2 expression should be mirrored by changes in PI3-K expression.…”