Impaired phagocytosis by alveolar macrophages from diabetic rats is related to the deficient coupling of LTs to the Fe gamma R signaling cascade

Diabetic individuals are more susceptible to infections and this seems to be related to impaired phagocyte function. Alveolar macrophages (AMs) are the first barrier to prevent respiratory infections Leukotrienes (LTs) increase AM phagocytic activity via Fc gamma R. In this study, we compared AMs from diabetic and nondiabetic rats for phagocytosis via Fc gamma R and the roles of LTs and insulin Diabetes was induced in male Wistar rats by alloxan (42 mg/kg, i.v); macrophages were obtained by bronchoalveolar lavage and IgG-opsonised sheep red blood cells (IgG-SRBC) were used as targets. LTs were added to the AMs 5 min before the addition of IgG-SRBC. AMs were treated with a LT synthesis inhibitor (zileuton, 10 mu M), or antagonists of the LTB(4) receptor (CP105 696, 10 mu M) cys-LT receptor (MK571, 10 mu M), 30 or 20 min before the addition of IgG-SRBC, respectively. We found that the phagocytosis of IgG-SRBC by AMs from diabetic rats is impaired compared with non-diabetic rats. Treatment with the LT inhibitor/antagonists significantly reduced AM phagocytosis in non-diabetic but not diabetic rats. During the phagocytosis of IgG-SRBC LTB(4) and LTC(4) were produced by AMs from both groups. The addition of exogenous LTB(4) or LTD(4) potentiated phagocytosis similarly in both groups Phagocytosis was followed by the phosphorylation of PKC-delta. ERK and Akt This was reduced by zileuton treatment in AMs from non-diabetic but not diabetic rats The addition of insulin to AMs further increased the phagocytosis by increasing PKC-delta phosphorylation These results suggest that the impaired phagocytosis found in AMs from diabetic rats is related to a deficient coupling of LTs to the Fc gamma R signaling cascade and that insulin has a key role in this coupling An essential role for insulin in Innate immunity is suggested (C) 2010 Elsevier Ltd. All rights reserved.

SIGNALING PATHWAYS AND MEDIATORS IN LPS-INDUCED LUNG INFLAMMATION IN DIABETIC RATS: ROLE OF INSULIN

Diabetic patients are more susceptible to infections, and their inflammatory response is impaired. This is restored by insulin treatment. In the present study, we investigated the effect of insulin on LPS-induced signaling pathways and mediators in the lung of diabetic rats. Diabetic male Wistar rats (alloxan, 42 mg/kg i.v., 10 days) and control rats received intratracheal instillation of LPS (750 mu g/0.4 mL) or saline. Some diabetic rats were given neutral protamine Hagedorn insulin (4 IU s.c.) 2 h before LPS. After 6 h, bronchoalveolar lavage was performed for the release of mediators, and lung tissue was homogenized for analysis of LPS-induced signaling pathways. Relative to control rats, diabetic rats exhibited a significant reduction in the LPS-induced phosphorylation of extracellular signal-regulated kinase (64%), p38 (70%), protein kinase B (67%), and protein kinase C alpha (57%) and delta (65%) and in the expression of iNOS (32%) and cyclooxygenase 2 (67%) in the lung homogenates. The bronchoalveolar lavage fluid concentrations of NO (47%) and IL-6 (49%) were also reduced in diabetic rats, whereas the cytokine-induced neutrophil chemoattractant 2 (CINC-2) levels were increased 23%, and CINC-1 was not different from control animals. Treatment of diabetic rats with insulin completely or partially restored all these parameters. In conclusion, data presented show that insulin regulates mitogen-activated protein kinase, phosphatidylinositol 3`-kinase, protein kinase C pathways, expression of the inducible enzymes, cyclooxygenase 2 and iNOS, and levels of IL-6 and CINC-2 in LPS-induced lung inflammation in diabetic rats. These results suggest that the protective effect of insulin in sepsis could be due to modulation of cellular signal transduction factors.

SLC2A2 gene expression in kidney of diabetic rats is regulated by HNF-1 alpha and HNF-3 beta

We hypothesize that, in kidney of diabetic rats, hepatocyte nuclear factors (HNF-1 alpha. and HNF-3 beta) play a critical role in the overexpression of solute carrier 2A2 (SLC2A2) gene. Diabetic rats submitted or not to rapid (up to 12 h) and short-term (1, 4 and 6 days) insulin treatment were investigated. Twofold increase in GLUT2 mRNA was observed in diabetic, accompanied by significant increases in HNF-1 alpha and HNF-3 beta expression and binding activity. Additional 2-fold increase in GLUT2 mRNA and HNF-3 beta expression/activity was observed in 12-h insulin-treated rats. Six-day insulin treatment decreased GLUT2 mRNA and HNF-1 alpha expression and activity to levels of non-diabetic rats, whereas HNF-3 beta decreased to levels of non-insulin-treated diabetic rats. Our results provide evidence for a link between the overexpression of SLC2A2 gene and the transcriptional activity of HNF-1 alpha and HNF-3 beta in kidney of diabetic rats. Furthermore, recovery of SLC2A2 gene after 6-day insulin treatment also involves HNF-1 alpha and HNF-3 beta activity. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Sodium Tungstate on Some Biochemical Parameters of the Parotid Salivary Gland of Streptozotocin-Induced Diabetic Rats: A Short-Term Study

Several studies have shown the antidiabetic properties of sodium tungstate. In this study, we evaluated some biochemical parameters of the parotid salivary gland of streptozotocin-induced diabetic rats treated with sodium tungstate solution (2 mg/ml). The studied groups were: untreated control (UC), treated control (TC), untreated diabetic (UD), and treated diabetic (TD). After 2 and 6 weeks of treatment, parotid gland was removed and total protein and sialic acid (free and total) concentration and amylase and peroxidase activities were determined. Data were compared by variance analysis and Tukey test (p < 0.05). The sodium tungstate treatment modestly decreased the glycemia of streptozotocin-induced diabetic rats. At week 2 of the study, parotid gland of diabetic rats presented a reduction of total protein concentration (55%) and an increase of amylase (120%) and peroxidase (160%) activities, free (150%) and total (170%) sialic acid concentration. No alteration in the evaluated parameters at week 6 of the study was observed. Sodium tungstate presented no significant effect in parotid gland. Our results suggest that diabetes causes initial modification in biochemical composition of parotid. However, this gland showed a recovery capacity after 6 week of the experimental time. Sodium tungstate has no effect in peripheral tissues, such as salivary glands.