Haptoglobin and the inflammatory and oxidative status in experimental diabetic rats: antioxidant role of haptoglobin

Haptoglobin is a hemoglobin-binding acute-phase protein which possesses anti-inflammatory and antioxidative properties. In this study, we investigated changes in protein expression of rat haptoglobin under diabetes-related inflammatory and oxidative stress conditions induced by an i.p. injection of streptozotocin. The progress of diabetes during an 8-week follow-up period was associated with the increased presence of haptoglobin in the serum and in the liver. This increase was most prominent during the first 2 weeks after which it started to decline. Temporary changes in haptoglobin expression strongly correlated with the serum levels of TNF-α and IL-6. Lower haptoglobin expression at the fourth week and thereafter correlated with a decrease in TNF-α concentration and changes in the TNF-α/IL-6 ratio. Based on the decrease of GSH/GSSG ratio and antioxidant enzyme activities in the liver until the end of fourth week, it was concluded that the liver was exposed to oxidative stress and injury which in the presence of the abovementioned inflammatory mediators lead to different haptoglobin expression profiles at different stages of diabetes. An inverse correlation was observed between the haptoglobin and free iron serum levels in diabetic rats. The higher levels of haptoglobin during the first 2 weeks were accompanied by a lower level of free iron. In view of the established function of haptoglobin, we discuss its possible role in decreasing oxidative stress during the early stage of diabetes (AU)

Haptoglobin and the inflammatory and oxidative status in experimental diabetic rats: antioxidant role of haptoglobin.

Haptoglobin is a hemoglobin-binding acute-phase protein which possesses anti-inflammatory and antioxidative properties. In this study, we investigated changes in protein expression of rat haptoglobin under diabetes-related inflammatory and oxidative stress conditions induced by an i.p. injection of streptozotocin. The progress of diabetes during an 8-week follow-up period was associated with the increased presence of haptoglobin in the serum and in the liver. This increase was most prominent during the first 2 weeks after which it started to decline. Temporary changes in haptoglobin expression strongly correlated with the serum levels of TNF-α and IL-6. Lower haptoglobin expression at the fourth week and thereafter correlated with a decrease in TNF-α concentration and changes in the TNF-α/IL-6 ratio. Based on the decrease of GSH/GSSG ratio and antioxidant enzyme activities in the liver until the end of fourth week, it was concluded that the liver was exposed to oxidative stress and injury which in the presence of the above-mentioned inflammatory mediators lead to different haptoglobin expression profiles at different stages of diabetes. An inverse correlation was observed between the haptoglobin and free iron serum levels in diabetic rats. The higher levels of haptoglobin during the first 2 weeks were accompanied by a lower level of free iron. In view of the established function of haptoglobin, we discuss its possible role in decreasing oxidative stress during the early stage of diabetes.

The rat acute-phase protein α2-macroglobulin plays a central role in amifostine-mediated radioprotection.

Previously we reported that elevated circulating concentrations of the acute-phase (AP) protein α(2)-macroglobulin (α(2)M), either as typically occurring in pregnant female rats or after administration to male rats, provides radioprotection, displayed as 100% survival of experimental animals exposed to total-body irradiation with 6.7 Gy (LD(50/30)) x-rays, that is as effective as that afforded by the synthetic radioprotector amifostine. The finding that amifostine administration induces a 45-fold increase in α(2)M in the circulation led us to hypothesise that α(2)M assumes an essential role in both natural and amifostine-mediated radioprotection in the rat. In the present work we examined the activation of cytoprotective mechanisms in rat hepatocytes after the exogenous administration of α(2)M and amifostine. Our results showed that the IL6/JAK/STAT3 hepatoprotective signal pathway, described in a variety of liver-injury models, upregulated the α(2)M gene in amifostine-pretreated animals. In both α(2)M- and amifostine-pretreated rats we observed the activation of the Akt signalling pathways that mediate cellular survival. At the cellular level this was reflected as a significant reduction of irradiation-induced DNA damage that allowed for the rapid and complete restoration of liver mass and ultimately at the level of the whole organism the complete restoration of body weight. We conclude that the selective upregulation of α(2)M plays a central role in amifostine-provided radioprotection.