Activation and potential interactions between the arachidonic acid and L-arginine:nitric oxide pathways in glomerulonephritis

Regulation of renal 12(S)-hydroxyeicosatetraenoic acid in diabetes by angiotensin AT1 and AT2 receptors

Diabetes is associated with increased production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE]. The mechanisms involved in this process remain unclear. We hypothesized that hyperglycemia and angiotensin II (ANG II) regulate renal 12(S)-HETE production via a balance between angiotensin AT(1) and AT(2) receptors activities. Using a microdialysis technique, renal interstitial fluid (RIF) levels of ANG II and 12(S)-HETE were monitored in normal control and streptozotocin-induced diabetic rats at baseline and then weekly thereafter for 12 wk. In a second group of normal and diabetic rats, 3 wk after development of diabetes, we monitored RIF 12(S)-HETE levels in response to acute AT(1) receptor blockade with valsartan or AT(2) receptor blockade with PD123319 individually or combined. Two weeks after induction of diabetes there was a 404% increase in ANG II (P < 0.05), a 149% increase in 12S-HETE (P < 0.05), and a 649% increase in urinary albumin excretion (P < 0.05). These levels remained elevated throughout the study. PD123319 given alone had no effect on 12(S)-HETE. Valsartan decreased 12(S)-HETE by 61.6% (P < 0.0001), a response that was abrogated when PD123319 was given with valsartan. These data demonstrate that hyperglycemia increases renal ANG II and 12(S)-HETE levels. The increase in 12(S)-HETE is mediated via AT(1) receptor. The attenuation of the effects of AT(1) receptor blockade by PD123319 suggests that AT(2) receptor contributes to the downregulation of renal 12(S)-HETE production.

Cyclooxygenase-2 protein and prostaglandin E(2) production are up-regulated in a rat bladder inflammation model

Cyclooxygenase-1 and cyclooxygenase-2 mRNAs and proteins and prostaglandin E(2) production are evaluated in a rat model of inflammation in which Escherichia coli lipopolysaccharide is intraperitoneally injected or intravesically instilled into the bladder. While cyclooxygenase-1 mRNA and protein and cyclooxygenase-2 mRNA do not change in bladders treated with lipopolysaccharide, cyclooxygenase-2 protein is elevated in bladders from rats intravesically instilled with lipopolysaccharide or phosphate buffered saline (PBS) or intraperitoneally injected with lipopolysaccharide. Urinary prostaglandin E(2) levels and prostaglandin E(2) synthesis in bladder particulates are elevated by intravesical instillation and intraperitoneal injection of lipopolysaccharide. The nitric oxide donor, S-nitroso-N-acetyl-D,L-penicillamine, increases prostaglandin E(2) synthesis in bladders from lipopolysaccharide intravesically instilled and intraperitoneally injected rats. Lipopolysaccharide increases prostaglandin E(2) synthesis by increasing cyclooxygenase-2 protein levels in rat bladder and prostaglandin E(2) synthesis may be further elevated by increases in nitric oxide caused by an up-regulation of inducible nitric oxide synthase (iNOS).

Antioxidant susceptibility of pathogenic pathways in subjects with antiphospholipid antibodies: a pilot study

The pathogenesis of antiphospholipid antibody (aPL) related thrombosis is multifactorial and includes, amongst others, enhanced coagulation activation measured as prothrombin fragment 1 + 2 (F1 + 2), elevated plasma levels of von Willebrand factor (vWF), plasminogen activator inhibitor (PAI) and endothelin-1 (ET-1) as well as heightened thromboxane generation and lipid peroxidation. To evaluate the antioxidant susceptibility of some of the above pathways, probucol (500 mg/d orally, a cholesterol lowering agent bearing antioxidant properties) was administered for a three week period to 14 subjects with aPL and to seven healthy controls. At baseline aPL participants showed higher plasma levels of vWF (P = 0.006), ET-1 (P = 0.0002) and enhanced urinary excretion of 11-dehydro-thromboxane-B2 (TXB2) (P = 0.0004), F2-isoprostanes (marker of lipid peroxidation) (P = 0.02) and albumin (P = 0.04) than controls. In the aPL group baseline IgG anticardiolipin (aCL) titre positively related with urinary TXB2 (r2 = 0.43, P = 0.01) and inversely with urinary NOx (r2 = -0.6, P = 0.005) whereas urinary NOx and TXB2 were negatively correlated (r2 = -0.42, P = 0.01). After the treatment period significant decreases from baseline values were noted for PAI (P = 0.01), ET-1 (P = 0.006), TXB2 (P = 0.02), F2-isoprostanes (P = 0.01) and albuminuria (P = 0.01) in aPL participants but not in controls. These pilot data support oxidative sensitive mechanisms and a potential role for antioxidant treatment in the pathogenesis of aPL induced vasculopathy.