Inhibition of platelet function by GSTM1-null human peripheral lymphocytes exposed to benzo(a)pyrene-induced challenge

Recent epidemiological studies proposed that the glutathione S-transferase (GST) M1-null genotype may contribute to diseases associated with oxidative stress. The genetic polymorphism exhibited by the GSTM1 may be an important factor in risk toward oxidant chemicals. In this study, we investigated the effect of GSTM1-null genotype in lymphocyte and oxidative stress-dependent inhibition of platelet aggregation. To determine whether GSTM1 deficiency is a genetic determinant of cell toxicity toward oxidant chemicals, lymphocytes were incubated in vitro with low levels of benzo(a)pyrene (BaP), cumene hydroperoxide (CumOOH), or trans-stilbene oxide that do not decrease cell viability, and were assessed for oxidative damage and for the lymphocyte-dependent inhibition of platelet response. Malondialdehyde and carbonyl levels, and the oxidation of cis-parinaric acid, were used as biomarkers of oxidative stress in lymphocytes. Following stimulation by BaP or CumOOH, when peroxidation-dependent changes in these parameters were compared between the GSTM1-null genotype and the positive genotype, no significant differences were found between the two genotypes. On the other hand, preincubation of the lymphocytes with BaP or CumOOH attenuated their inhibitory action on ADP-induced platelet aggregation. However, our results indicate that lymphocytes of individuals with the GSTM1-null genotype have greater inhibitory activity on platelet function after exposure to BaP, but not CumOOH, although they are not more susceptible to in vitro oxidative stress

Effect of glucagon-like peptide-1(7-36) and exendin-4 on the vascular reactivity in streptozotocin/nicotinamide-induced diabetic rats

We investigated the vascular effects of glucagon-like peptide-1 (GLP-1) and Exendin-4 in type 2 diabetic rat aortae. Studies were performed in a normal control group (NC) (0.2 ml i. p. saline, n = 10), streptozotocin (STZ)/ nicotinamide diabetic control group ( DC) ( a single dose of 80 mg/kg STZ i. p. injection 15 min after administration of 230 mg/kg nicotinamide i. p.), GLP-1 (GLPC) control group ( 1 mu g/kg twice daily i. p. for 1 month, n = 10), Exendin-4 control group (EXC) ( 0.1 mu g/kg twice daily i. p. for 1 month, n = 10), GLP-1-treated diabetic group (GLPT) ( 1 mu g/kg twice daily i. p. for 1 month, n = 10), and Exendin-4-treated diabetic group (EXT) ( 0.1 mu g/kg twice daily i. p. for 1 month, n = 10). One month of GLP-1 and Exendin-4 treatment significantly decreased the blood glucose levels of diabetic rats ( 113 +/- 2 mg/dl, p < 0.001, and 117 +/- 1 mg/ dl, p < 0.001, respectively versus 181 +/- 9 mg/ dl in the DC group). Sensitivity (pD(2)) and maximum response (% Max. Relax) of acetylcholine-stimulated relaxations in the DC group (pD(2) : 6.73 +/- 0.12 and 55 +/- 6, respectively) were decreased compared with the nondiabetic NC group (pD(2) : 7.41 +/- 0.25, p < 0.05, and 87 +/- 4, p < 0.01). Treating diabetic rats with GLP-1, pD(2) values and with Exendin-4, Max. Relax % values of aortic strips to acetylcholine returned to near non-diabetic NC values (pD(2) : 7.47 +/- 0.15, p < 0.05, and 87 +/- 3, p < 0.01, respectively). Maximal contractile responses (E-max) to noradrenaline in aortic strips from the diabetic DC group (341 +/- 27 mg tension/mg wet weight) were significantly decreased compared with the non-diabetic NC ( 540 +/- 66 mg tension/mg wet weight, p < 0.001) and the GLPT group ( 490 +/- 25 mg tension/ mg wet weight, p < 0.05). There were no significant differences in pD(2) values of aortic strips to noradrenaline from all groups. E-max to KCl in aortic strips from the DC group ( 247 +/- 10 mg tension/ mg wet weight, p < 0.01) was significantly decreased compared with non-diabetic NC group ( 327 +/- 26 mg tension/ mg wet weight). Treating diabetic rats with GLP-1 (GLPT), E-max values of aortic strips to KCl returned to near non-diabetic NC values ( 271 +/- 12 mg tension/ mg wet weight). GLP-1 and ( partially) Exendin-4 treatment could improve the increased blood glucose level and normalize the altered vascular tone in type 2 diabetic rats. Copyright (C) 2005 S. Karger AG, Basel

Platelet function and fibrinolytic activity in patients with bronchial asthma

Platelets have the capacity to release mediators with potent inflammatory or anaphylactic properties. Platelet factor-4 (PF4) and beta-thromboglobulin (BTG) are two of these mediators. On the otter hand, plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) are two important mediators of fibrinolysis. Borh mediators are secreted mainly by vascular endothelium. Plasma levels of PF4, BTG, PAI-1, and tPA may show changes in chronic inflammatory diseases such as asthma. This study examined the role of thrombocytes and the function of the endothelium in asthmatic patients during an attack and during a stable phase. Eighteen patients with known allergic asthma who came to our emergency department with an asthma attack and 14 control subjects were included in the study. Blood samples were taken after starting therapy with salbutamol inhalation. Lung function tests were performed after receiving the first emergency therapy for asthma. Plasma levels of PF4, BTG, PA-1, tPA were determined before starting steroid therapy and after receiving 1 week of steroid therapy. Plasma levels of PF4 among patients with an asthma attack were significantly higher than those of controls (150.5 +/- 8.92 IU/mL vs. 92.5 +/- 7.63 IU/mL, p<0.001). A further increase in plasma PF4 levels was detected after steroid therapy (163.5 +/- 9.16 IU/mL). Plasma BTG levels of patients on admission were not statistically different from those in the control group (140.4 +/- 6.34 IU/ml, vs. 152.2 +/- 8.71 IU/mL). An increase was detected after therapy (171.6 +/- 7.27 IU/mL) and post-treatment plasma levels were statistically meaningful versus the controls. Plasma levels of tPA and PAI were statistically higher than those in controls in asthmatic patients on admission (6.01 +/- 2.72 vs. 5.4 +/- 2.3 ng/mL for tPA and 75.2 +/- 27.2 ng/mL vs. 32.7 +/- 14.3 ng/mL for PAI-1). Further increases were detected in two parameters after 1 week of therapy with steroids (tPA levels were 6.85 +/- 2.96 ng/mL and PAI-1 levels were 83.5 +/- 29.6 ng/mL). There seems to be an increased activity of platelets during an asthma attack. Elevated PAI-1 and tPA levels may also indicate the activated endothelium in asthma. Increases of plasma levels of PAI-1 and tPA after steroid therapy need further investigation because elevated PAI-1 levels enhance airway remodeling