Prenatal hypoxia, habituation memory and oxidative stress

Hypoxia-ischemia (HI) is characterized by a reduced supply of oxygen during pregnancy, which leads to both central nervous system and peripheral injuries in the foetus, resulting in impairment in its development. The purpose of this study was to investigate behavioural changes and systemic oxidative stress in adult animals that have been affected by HI during pregnancy. HI was induced by the occlusion of the maternal uterine artery with aneurysm clamps for a period of 45 min on the 18th gestational day. Animals from the sham group were submitted to same surgical procedure as the HI animals, without occlusion of the maternal uterine artery. The control group consisted of non-manipulated healthy animals. At postnatal day 90, the pups were submitted to behavioural tests followed by blood collection. HI adult animals presented an increase in anxiety behaviour and a lack of habituation compared to both sham and control groups. Oxidative damage, assessed by protein and lipid oxidation in serum, did not differ between HI and sham-operated animals. However, HI animals presented reduced activity of the glutathione peroxidase enzyme and increased formation of nitrite, indicating alterations in the systemic antioxidant repair system. Our results suggest an association among HI, systemic oxidative stress and behavioural alterations.

High fat diets modulate nitric oxide biosynthesis and antioxidant defence in red blood cells from C57BL/6 mice

The consumption of a high fat (HF) diet is considered a risk factor for the development of obesity. On the other hand, a monounsaturated HF diet has beneficial cardiometabolic effects. Since nitric oxide (NO) modulates vascular homeostasis, we investigate whether HF diets that vary in fatty acid composition have a different effect on theL-arginine-NO pathway and oxidative stress in C57BL/6 mice red blood cells (RBC). The olive oil diet induced an activation of L-arginine transport compared to other diets. NO synthase (NOS) activity was increased in all unsaturated HF diets (olive, sunflower and canola oils). Moreover, the expression of endothelial NOS (eNOS) and inducible NOS (iNOS) was increased in the olive oil group. In contrast, NOS activity from the lard group was decreased associated with diminished l-arginine transport. Olive oil also induced superoxide dismutase activation. Inhibition of the L-arginine-NO pathway in the lard group could contribute to cardiovascular diseases, while unsaturated HF diets may have a protector effect via enhanced NO bioavailability.

The role of exercise on L-arginine nitric oxide pathway in chronic heart failure

Chronic heart failure (CHF) is a pathological state with high morbidity and mortality and the full understanding of its genesis remain to be elucidated. In this syndrome, a cascade of neurohormonal and hemodynamic mechanisms, as well as inflammatory mediators, are activated to improve the impaired cardiac function. Clinical and experimental observations have shown that CHF is associated with a generalized disturbance in endothelium-dependent vasodilation, which may contribute to the progression of ventricular and vascular remodelling in this syndrome. There is also accumulating evidence that disturbances in nitric oxide (NO) availability is involved in the development of heart failure at the systemic and cardiac levels. NO is a ubiquitous signalling molecule which causes potent vasodilation, inhibits platelet activation and regulates the contractile properties of cardiac myocytes. It is generated from the amino acid L-arginine via constitutive and inducible isoforms of the enzyme NO synthase (NOS). There is evidence that exercise, a nonpharmacological tool, improves symptoms, fitness (VO_2peak), quality of life and NO bioavailability in CHF population. This review examines different aspects of the L-arginine-NO pathway and inflammation in the physiopathology of CHF and highlights the important beneficial effects of exercise in this disease.

Chronic exercise reduces platelet activation in hypertension: upregulation of the L-arginine-nitric oxide pathway

Nitric oxide (NO) inhibits platelet function and plays a key role in the regulation of cardiovascular homeostasis. Essential hypertension is characterized by an increased risk of thrombus formation, and by an inhibition of intraplatelet NO bioactivity. We have previously shown that membrane transport of L-arginine is a rate-limiting step for platelet-derived NO synthesis. This study examined the effects of exercise on the platelet L-arginine-NO pathway and aggregation and systemic inflammation markers in 13 sedentary hypertensive patients subjected to 60 min of training activity (exercise group), predominantly aerobic, three times a week for a period of 12 weeks. Six sedentary hypertensive patients participated in the control group. After 12 weeks, L-arginine transport was significantly increased and associated with increased platelet NO synthase activity and cGMP levels and reduced platelet aggregation. Moreover, exercise training reduced plasma concentrations of fibrinogen and C-reactive protein and blood pressure. The control group did not change their previous intraplatelet L-arginine-NO results and systemic inflammatory markers levels. Thus, exercise training reduces inflammatory responses, restores NO synthesis in platelets and thereby contributes to the beneficial effects of exercise in hypertension. The present study adds exercise as a new tool to reduce morbidity and mortality associated with platelet activation in hypertension.

The role of bradykinin, AT2 and angiotensin 1-7 receptors in the EDRF-dependent vasodilator effect of angiotensin II on the isolated mesenteric vascular bed of the rat

1. The mechanisms involved in the vasodilator actions of angiotensin II (Ang II) have not yet been completely elucidated. We investigated the potential mechanisms that seem to be involved in the Ang II vasodilator effect using rat isolated mesenteric vascular bed (MVB). 2. Under basal conditions, Ang II does not affect the perfusion pressure of MVB. However, in vessels precontracted with norepinephrine, Ang II induces vasodilation followed by vasoconstriction. Vasoconstrictor, but not the vasodilation of Ang II, is inhibited by AT(1) antagonist (losartan). The vasodilator effect of Ang II was not inhibited by AT(2), angiotensin IV and angiotensin 1-7 receptor antagonists alone (PD 123319, divalinal, A 779, respectively). 3. The vasodilator effect of Ang II is significantly reduced by endothelial removal (deoxycholic acid), but not by indomethacin. Inhibition of NO-synthase by N(G)-nitro-l-arginine methyl ester (l-NAME) and guanylyl cyclase by 1H-[1,2,3] oxadiazolo [4,4-a] quinoxalin-1-one (ODQ) reduces the vasodilator effect of Ang II. This effect is also reduced by tetraethylammonium (TEA) or l-NAME, and a combination of l-NAME plus TEA increases the inhibitory effect of the antagonists alone. However, indomethacin does not change the residual vasodilator effect observed in vessels pretreated with l-NAME plus TEA. 4. In vessels precontracted with norepinephrine and depolarized with KCl 25 mm or treated with Ca(2+)-dependent K(+) channel blockers (charybdotoxin plus apamin), the effect of Ang II was significantly reduced. However, this effect is not affected by ATP and voltage-dependent K(+) channel blockers (glybenclamide and 4-aminopyridine). 5. Inhibition of kininase II with captopril significantly potentiates the vasodilator effect of bradykinin (BK) and Ang II in the rat MVB. The inhibitory effect of the B(2) receptor antagonist HOE 140 on the vasodilator effect of Ang II is further enhanced by PD 123319 and/or A 779. 6. The present findings suggest that BK plays an important role in the endothelium-dependent vasodilator effect of Ang II. Probably, the link between Ang II and BK release is modulated by receptors that bind PD 123319 and A 779.

Activation of L-arginine transport in peripheral blood mononuclear cells in chronic renal failure

Transport of LL-arginine, the precursor for nitric oxide (NO) synthesis, has been investigated in human peripheral blood mononuclear cells (PBMCs) obtained from healthy volunteers and chronic renal failure patients. Chronic renal failure patients were either on treatment by haemodialysis or continuous ambulatory peritoneal dialysis (CAPD). Saturable influx of L-arginine in PBMCs was mediated by the cationic amino acid transport systems y(+) and y(+)L. Initial rates of L-arginine transport (2 microM) via system y(+) were significantly increased in chronic renal failure patients, whereas transport via system y(+)L was unaffected. The increase in L-arginine transport via system y(+) was: 1.7-fold in uraemic patients on CAPD, 4.3-fold in uraemic patients pre-haemodialysis and 2.6-fold post-haemodialysis. When the intracellular PBMCs amino acid profile was analysed in chronic renal failure patients and control subjects, L-lysine and L-arginine concentrations were significantly increased in pre-haemodialysis uraemic patients and restored to normal values by haemodialysis and CAPD. The present study provides the first evidence that system y(+) mediates the increased transport of L-arginine in PBMCs from patients with chronic renal failure. The increased activity of system y(+) may provide the necessary supply of L-arginine to sustain NO synthesis in PBMCs exposed to increased levels of circulating cytokines in chronic renal failure.