The pro-resolving lipid mediator Maresin 1 ameliorates pain responses and neuroinflammation in the spared nerve injury-induced neuropathic pain: A study in male and female mice.

Specialized pro-resolving mediators (SPMs) have recently emerged as promising therapeutic approaches for neuropathic pain (NP). We evaluated the effects of oral treatment with the SPM Maresin 1 (MaR1) on behavioral pain responses and spinal neuroinflammation in male and female C57BL/6J mice with spared nerve injury (SNI)-induced NP. MaR1, or vehicle, was administered once daily, on post-surgical days 3 to 5, by voluntary oral intake. Sensory-discriminative and affective-motivational components of pain were evaluated with von Frey and place escape/avoidance paradigm (PEAP) tests, respectively. Spinal microglial and astrocytic activation were assessed by immunofluorescence, and the spinal concentration of cytokines IL-1ß, IL-6, IL-10, and macrophage colony-stimulating factor (M-CSF) were evaluated by multiplex immunoassay. MaR1 treatment reduced SNI-induced mechanical hypersensitivity on days 7 and 11 in both male and female mice, and appeared to ameliorate the affective component of pain in males on day 11. No definitive conclusions could be drawn about the impact of MaR1 on the affective-motivational aspects of pain in female mice, since repeated suprathreshold mechanical stimulation of the affected paw in the dark compartment did not increase the preference of vehicle-treated SNI females for the light side, during the PEAP test session (a fundamental assumption for PAEP's validity). MaR1 treatment also reduced ipsilateral spinal microglial and astrocytic activation in both sexes and marginally increased M-CSF in males, while not affecting cytokines IL-1ß, IL-6 and IL-10 in either sex. In summary, our study has shown that oral treatment with MaR1 (i) produces antinociception even in an already installed peripheral NP mouse model, and (ii) this antinociception may extend for several days beyond the treatment time-frame. These therapeutic effects are associated with attenuated microglial and astrocytic activation in both sexes, and possibly involve modulation of M-CSF action in males.

Evaluation of urinary cysteinyl leukotrienes as biomarkers of severity and putative therapeutic targets in COVID-19 patients.

BACKGROUND: Cysteinyl leukotrienes (CysLT) are potent inflammation-promoting mediators, but remain scarcely explored in COVID-19. We evaluated urinary CysLT (U-CysLT) relationship with disease severity and their usefulness for prognostication in hospitalized COVID-19 patients. The impact on U-CysLT of veno-venous extracorporeal membrane oxygenation (VV-ECMO) and of comorbidities such as hypertension and obesity was also assessed. METHODS: Blood and spot urine were collected in "severe" (n = 26), "critically ill" (n = 17) and "critically ill on VV-ECMO" (n = 17) patients with COVID-19 at days 1-2 (admission), 3-4, 5-8 and weekly thereafter, and in controls (n = 23) at a single time point. U-CysLT were measured by ELISA. Routine markers, prognostic scores and outcomes were also evaluated. RESULTS: U-CysLT did not differ between groups at admission, but significantly increased along hospitalization only in critical groups, being markedly higher in VV-ECMO patients, especially in hypertensives. U-CysLT values during the first week were positively associated with ICU and total hospital length of stay in critical groups and showed acceptable area under curve (AUC) for prediction of 30-day mortality (AUC: 0.734, p = 0.001) among all patients. CONCLUSIONS: U-CysLT increase during hospitalization in critical COVID-19 patients, especially in hypertensives on VV-ECMO. U-CysLT association with severe outcomes suggests their usefulness for prognostication and as therapeutic targets.

Urinary Cysteinyl Leukotrienes as Biomarkers of Endothelial Activation, Inflammation and Oxidative Stress and Their Relationship with Organ Dysfunction in Human Septic Shock.

Cysteinyl leukotrienes (CysLT) are potent vascular leakage-promoting agents but have been scarcely explored in human septic shock (SS). We evaluated CysLT at admission and during hospitalization and their correlation with endothelial dysfunction, inflammation, oxidative stress, the renin-angiotensin-aldosterone system, and cardiac, renal, respiratory, and hepatic parameters in SS patients. Blood and spot-urine samples were collected at days 1-2 (admission), 3-4, and 5-8 in SS patients (n = 13) and at a single time point in controls (n = 22). Urinary CysLT (u-CysLT) and isoprostanes, plasma, and urinary angiotensinogen, serum myeloperoxidase, and IL-10 were quantified by ELISA. Serum intercellular-adhesion molecule-1, vascular cell-adhesion molecule-1, E-selectin, tumor necrosis factor-α, IL-1ß, and IL-6 were measured by multiplex immunoassays. Routine markers were evaluated using automated analyzers. At admission, SS patients had increased u-CysLT, endothelial activation, inflammation, oxidative stress, and plasma and urinary angiotensinogen, as well as cardiac, respiratory, hepatic, and renal injury/dysfunction. There were no changes in u-CysLT during hospitalization. Both correlation and multivariate analyses showed positive relationships of u-CysLT with endothelial activation, inflammation, oxidative stress, proteinuria, and hepatic injury/dysfunction markers. These results suggest that u-CysLT may be potential non-invasive biomarkers for monitoring the pathophysiological mechanisms underlying SS, as well as putative therapeutic targets.

Endothelitis profile in acute heart failure and cardiogenic shock patients: Endocan as a potential novel biomarker and putative therapeutic target.

Aims: Inflammation-driven endothelitis seems to be a hallmark of acute heart failure (AHF) and cardiogenic shock (CS). Endocan, a soluble proteoglycan secreted by the activated endothelium, contributes to inflammation and endothelial dysfunction, but has been scarcely explored in human AHF. We aimed to evaluate serum (S-Endocan) and urinary endocan (U-Endocan) profiles in AHF and CS patients and to correlate them with biomarkers/parameters of inflammation, endothelial activation, cardiovascular dysfunction and prognosis. Methods: Blood and spot urine were collected from patients with AHF (n = 23) or CS (n = 25) at days 1-2 (admission), 3-4 and 5-8 and from controls (blood donors, n = 22) at a single time point. S-Endocan, U-Endocan, serum IL-1ß, IL-6, tumour necrosis factor-α (S-TNF-α), intercellular adhesion molecule-1 (S-ICAM-1), vascular cell adhesion molecule-1 (S-VCAM-1) and E-selectin were determined by ELISA or multiplex immunoassays. Serum C-reactive protein (S-CRP), plasma B-type natriuretic peptide (P-BNP) and high-sensitivity troponin I (P-hs-trop I), lactate, urea, creatinine and urinary proteins, as well as prognostic scores (APACHE II, SAPS II) and echocardiographic left ventricular ejection fraction (LVEF) were also evaluated. Results: Admission S-Endocan was higher in both patient groups, with CS presenting greater values than AHF (AHF and CS vs. Controls, p < 0.001; CS vs. AHF, p < 0.01). Admission U-Endocan was only higher in CS patients (p < 0.01 vs. Controls). At admission, S-VCAM-1, S-IL-6 and S-TNF-α were also higher in both patient groups but there were no differences in S-E-selectin and S-IL-1ß among the groups, nor in P-BNP, S-CRP or renal function between AHF and CS. Neither endocan nor other endothelial and inflammatory markers were reduced during hospitalization (p > 0.05). S-Endocan positively correlated with S-VCAM-1, S-IL-6, S-CRP, APACHE II and SAPS II scores and was positively associated with P-BNP in multivariate analyses. Admission S-Endocan raised in line with LVEF impairment (p = 0.008 for linear trend). Conclusion: Admission endocan significantly increases across AHF spectrum. The lack of reduction in endothelial and inflammatory markers throughout hospitalization suggests a perpetuation of endothelial dysfunction and inflammation. S-Endocan appears to be a biomarker of endothelitis and a putative therapeutic target in AHF and CS, given its association with LVEF impairment and P-BNP and its positive correlation with prognostic scores.

DU Is Induced by Low Levels of Urinary ATP in a Rat Model of Partial Bladder Outlet Obstruction: The Incidence of Both Events Decreases after Deobstruction.

Objectives: To investigate, in initial phases of bladder outlet obstruction (BOO), the urinary ATP levels, the incidence of detrusor underactivity (DU), and if they change after deobstruction. Methods: Adult female Wistar rats submitted to partial BOO (pBOO) and sham-obstruction were used. Cystometry was performed 3 or 15 days after pBOO and fluid was collected from the urethra for ATP determination. Bladders were harvested for morphological evaluation of the urothelium. DU was defined as the average of voiding contractions (VC) of sham-operated animals, with 3 SD at 15 days after the sham surgery. In another group of animals in which pBOO was relieved at 15 days and bladders were let to recover for 15 days, the incidence of DU and ATP levels were also accessed. The Kruskal-Wallis test was followed by Dunn's multiple comparisons test, and Spearman's correlation test was used. Results: DU was present in 13% and 67% of the bladders at 3 and 15 days after pBOO, respectively, and in 20% of the bladders at 15 days after deobstruction. ATP levels were significantly lower in DU/pBOO versus sham and non-DU/pBOO rats. A strong positive correlation between ATP levels and VC/min was obtained (r = 0.63). DU bladders had extensive areas in which umbrella cells appeared stretched, the width exceeding that presented by sham animals. Conclusions: Low urothelial ATP parallels with a high incidence of DU early after pBOO.

Inflammation in Human Heart Failure: Major Mediators and Therapeutic Targets.

Inflammation has been recognized as a major pathophysiological contributor to the entire spectrum of human heart failure (HF), including HF with reduced ejection fraction, HF with preserved ejection fraction, acute HF and cardiogenic shock. Nevertheless, the results of several trials attempting anti-inflammatory strategies in HF patients have not been consistent or motivating and the clinical implementation of anti-inflammatory treatments for HF still requires larger and longer trials, as well as novel and/or more specific drugs. The present work reviews the different inflammatory mechanisms contributing to each type of HF, the major inflammatory mediators involved, namely tumor necrosis factor alpha, the interleukins 1, 6, 8, 10, 18, and 33, C-reactive protein and the enzymes myeloperoxidase and inducible nitric oxide synthase, and their effects on heart function. Furthermore, several trials targeting these mediators or involving other anti-inflammatory treatments in human HF are also described and analyzed. Future therapeutic advances will likely involve tailored anti-inflammatory treatments according to the patient's inflammatory profile, as well as the development of resolution pharmacology aimed at stimulating resolution of inflammation pathways in HF.

Adenosine A2A and A3 Receptors as Targets for the Treatment of Hypertensive-Diabetic Nephropathy.

Diabetic nephropathy (DN) and hypertension are prime causes for end-stage renal disease (ESRD) that often coexist in patients, but are seldom studied in combination. Kidney adenosine levels are markedly increased in diabetes, and the expression and function of renal adenosine receptors are altered in experimental diabetes. The aim of this work is to explore the impact of endogenous and exogenous adenosine on the expression/distribution profile of its receptors along the nephron of hypertensive rats with experimentally-induced diabetes. Using spontaneously hypertensive (SHR) rats rendered diabetic with streptozotocin (STZ), we show that treatment of SHR-STZ rats with an agonist of adenosine receptors increases A2A immunoreactivity in superficial glomeruli (SG), proximal tubule (PCT), and distal tubule (DCT). Differently, treatment of SHR-STZ rats with a xanthinic antagonist of adenosine receptors decreases adenosine A3 immunoreactivity in SG, PCT, DCT, and collecting duct. There is no difference in the immunoreactivity against the adenosine A1 and A2B receptors between the experimental groups. The agonist of adenosine receptors ameliorates renal fibrosis, probably via A2A receptors, while the antagonist exacerbates it, most likely due to tonic activation of A3 receptors. The reduction in adenosine A3 immunoreactivity might be due to receptor downregulation in response to prolonged activation. Altogether, these results suggest an opposite regulation exerted by endogenous and exogenous adenosine upon the expression of its A2A and A3 receptors along the nephron of hypertensive diabetic rats, which has a functional impact and should be taken into account when considering novel therapeutic targets for hypertensive-diabetic nephropathy.

Endocan: A novel biomarker for risk stratification, prognosis and therapeutic monitoring in human cardiovascular and renal diseases.

The vascular endothelium is localized at the interface between the blood and surrounding tissues, playing a pivotal role in the maintenance of tissue-fluid homeostasis and in the regulation of host defense, inflammation, vascular tone and remodeling, angiogenesis and haemostasis. The dysfunctional endothelium was shown to be implicated in the pathophysiology of several endothelial-dependent disorders, such as arterial hypertension, coronary artery disease, heart failure and chronic kidney disease, in which it is an early predictor of cardiovascular events. Endocan is a soluble dermatan sulphate proteoglycan mainly secreted by the activated endothelium. It is upregulated by several proinflammatory cytokines and proangiogenic factors and may itself contribute to the inflammatory status. In addition of being a surrogate marker of inflammation and endothelial dysfunction, it seems to be involved in the regulation of several proliferative and neovascularization processes. Therefore, its utility as a biomarker in a wide spectrum of diseases has been increasingly explored. Here, we review the current evidence concerning the role of endocan in several human cardiovascular and renal diseases, where it seems to be a promising biomarker for risk stratification, prognosis and therapeutic monitoring.

Diabetes downregulates renal adenosine A2A receptors in an experimental model of hypertension.

Studies on diabetic nephropathy rarely take into account that the co-existence of diabetes and hypertension is frequent and further aggravates the prognosis of renal dysfunction. Adenosine can activate four subtypes of adenosine receptors (A1, A2A, A2B and A3) and has been implicated in diabetic nephropathy. However, it is not known if, in hypertensive conditions, diabetes alters the presence/distribution profile of renal adenosine receptors. The aim of this work was to describe the presence/distribution profile of the four adenosine receptors in six renal structures (superficial/deep glomeruli, proximal/distal tubules, loop of Henle, collecting tubule) of the hypertensive kidney and to evaluate whether it is altered by diabetes. Immunoreactivities against the adenosine receptors were analyzed in six renal structures from spontaneously hypertensive rats (SHR, the control group) and from SHR rats with diabetes induced by streptozotocyin (SHR-STZ group). Data showed, for the first time, that all adenosine receptors were present in the kidney of SHR rats, although the distribution pattern was specific for each adenosine receptor subtype. Also, induction of diabetes in the SHR was associated with downregulation of adenosine A2A receptors, which might be relevant for the development of hypertensive diabetic nephropathy. This study highlights the adenosine A2A receptors as a potential target to explore to prevent and/or treat early diabetes-induced hyperfiltration, at least in hypertensive conditions.

Adenosine A2A Receptors Modulate α-Synuclein Aggregation and Toxicity.

Abnormal accumulation of aggregated α-synuclein (aSyn) is a hallmark of sporadic and familial Parkinson's disease (PD) and related synucleinopathies. Recent studies suggest a neuroprotective role of adenosine A2A receptor (A2AR) antagonists in PD. Nevertheless, the precise molecular mechanisms underlying this neuroprotection remain unclear. We assessed the impact of A2AR blockade or genetic deletion (A2AR KO) on synaptic plasticity and neuronal cell death induced by aSyn oligomers. We found that impairment of LTP associated with aSyn exposure was rescued in A2AR KO mice or upon A2AR blockade, through an NMDA receptor-dependent mechanism. The mechanisms underlying these effects were evaluated in SH-SY5Y cells overexpressing aSyn and rat primary neuronal cultures exposed to aSyn. Cell death in both conditions was prevented by selective A2AR antagonists. Interestingly, blockade of these receptors did not interfere with aSyn oligomerization but, instead, reduced the percentage of cells displaying aSyn inclusions. Altogether, our data raise the possibility that the well-documented effects of A2AR antagonists involve the control of the latter stages of aSyn aggregation, thereby preventing the associated neurotoxicity. These findings suggest that A2AR represent an important target for the development of effective drugs for the treatment of PD and related synucleinopathies.

Activation of adenosine receptors improves renal antioxidant status in diabetic Wistar but not SHR rats.

BACKGROUND: Diabetes and hypertension independently contribute to renal injury, and the major mechanisms involved are increased reactive oxygen species (ROS) bioavailability and renin-angiotensin system (RAS) activation. We investigated the role of adenosine in controlling ROS production and RAS activation associated with renal dysfunction in hypertension and diabetes. METHODS: Fourteen days after induction of diabetes with streptozotocin in 12-week-old male Wistar and spontaneously hypertensive (SHR) rats, animals were treated during 7 days with 2-chloroadenosine (CADO group, 5 mg/kg/d), a stable analogue of adenosine, or underwent a sham operation procedure. At the end of the study (day 21), intra-arterial systolic blood pressure (SBP) was measured, and 24-h urine and plasma samples and renal tissue were collected. RESULTS: CADO treatment decreased the plasma glucose concentration and glucose and protein excretion by more than 30% in both strains. CADO treatment decreased SBP in diabetic SHR rats (143 ± 8 versus 114 ± 4 mmHg, p < 0.05), but not in diabetic Wistar rats. The hypotensive effect of CADO was associated to a ∼70% increase in plasma angiotensinogen (AGT) concentration and a ∼50% decrease in urinary AGT excretion. CADO also caused a decrease in medullary and cortical hydrogen peroxide production of about 40%, which was associated with a proportional increase in glutathione peroxidase (GPx) activity in diabetic Wistar but not in diabetic SHR animals. CONCLUSIONS: These results suggest that activation of adenosine receptors improves renal antioxidant capacity in diabetic Wistar but not SHR rats, although it improves glucose metabolism in both strains. Furthermore, activation of adenosine receptors does not seem to be directly influencing AGT production.

Angiotensin II contributes to glomerular hyperfiltration in diabetic rats independently of adenosine type I receptors.

Increased angiotensin II (ANG II) or adenosine can potentiate each other in the regulation of renal hemodynamics and tubular function. Diabetes is characterized by hyperfiltration, yet the roles of ANG II and adenosine receptors for controlling baseline renal blood flow (RBF) or tubular Na(+) handling in diabetes is presently unknown. Accordingly, the changes in their functions were investigated in control and 2-wk streptozotocin-diabetic rats after intrarenal infusion of the ANG II AT1 receptor antagonist candesartan, the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), or their combination. Compared with controls, the baseline blood pressure, RBF, and renal vascular resistance (RVR) were similar in diabetics, whereas the glomerular filtration rate (GFR) and filtration fraction (FF) were increased. Candesartan, DPCPX, or the combination increased RBF and decreased RVR similarly in all groups. In controls, the GFR was increased by DPCPX, but in diabetics, it was decreased by candesartan. The FF was decreased by candesartan and DPCPX, independently. DPCPX caused the most pronounced increase in fractional Na(+) excretion in both controls and diabetics, whereas candesartan or the combination only affected fractional Li(+) excretion in diabetics. These results suggest that RBF, via a unifying mechanism, and tubular function are under strict tonic control of both ANG II and adenosine in both control and diabetic kidneys. Furthermore, increased vascular AT1 receptor activity is a contribution to diabetes-induced hyperfiltration independent of any effect of adenosine A1 receptors.

Vitamin A in prevention of bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) remains one of the most serious challenges in the care of the very preterm infants, affecting approximately one-quarter of infants born < 1500g birth weight and 30% < 1000g. Oxygen toxicity may contribute to its pathogenesis. Vitamin A concentrations are lower in BPD infants which may result in a reduction of the antioxidant protection. It has been found to up regulate genes necessary for fetal lung growth and increase surfactant production in animal models and is also involved in the modulation of immunological and inflammatory responses by regulation of cytokine production. Retinoic acid plays a key role in lung development improving alveolar septation. Evidence exists that vitamin A supplementation for very low birth weight (VLBW) infants, beyond that routinely given in multivitamin preparations, is associated with a reduction in death or BPD. So, parenteral administration of vitamin A to the newborn is one of the current recommended preventive therapies for BPD (number needed to treat 12; 95% CI: 6-94; The information on long-term neurodevelopmental status suggests no evidence of either benefit or harm. Estimates for cerebral palsy range from a number needed to treat of 11 to a number needed to harm of 33. Nowadays, it seems that administration of antenatal vitamin A to the mother in late pregnancy associated with neonatal supplementation can better prevent the development of BPD in areas of endemic vitamin A deficiency. The benefits, in terms of vitamin A status, safety and acceptability of delivering vitamin A in an intravenous emulsion compared with repeat intramuscular injections, the association of vitamin A prenatal and postnatal, as well as the effectiveness and safety of administered high dose vitamin A in ELBW infants await evaluation and should be assessed in further trials.

Vitamin A in Prevention of Bronchopulmonary Dysplasia.

Bronchopulmonary dysplasia (BPD) remains one of the most serious challenges in the care of the very preterm infants, affecting approximately one-quarter of infants born <1500g birth weight and 30% <1000g. Oxygen toxicity may contribute to its pathogenesis. Vitamin A concentrations are lower in BPD infants which may result in a reduction of the antioxidant protection. It has been found to up regulate genes necessary for fetal lung growth and increase surfactant production in animal models and is also involved in the modulation of immunological and inflammatory responses by regulation of cytokine production. Retinoic acid plays a key role in lung development improving alveolar septation. Evidence exists that vitamin A supplementation for very low birth weight (VLBW) infants, beyond that routinely given in multivitamin preparations, is associated with a reduction in death or BPD. So, parenteral administration of vitamin A to the newborn is one of the current recommended preventive therapies for BPD (number needed to treat 12; 95% CI:6-94; The information on long-term neurodevelopmental status suggests no evidence of either benefit or harm. Estimates for cerebral palsy range from a number needed to treat of 11 to a number needed to harm of 33. Nowadays, is seems that administration of antenatal vitamin A to the mother in late pregnancy associated with neonatal supplementation can better prevent the development of BPD in areas of endemic vitamin A deficiency. The benefits, in terms of vitamin A status, safety and acceptability of delivering vitamin A in an intravenous emulsion compared with repeat intramuscular injections, the association of vitamin A prenatal and postnatal, as well as the effectiveness and safety of administered high dose vitamin A in ELBW infants waits evaluation and should be assessed in further trials.

Does chronic pain alter the normal interaction between cardiovascular and pain regulatory systems? Pain modulation in the hypertensive-monoarthritic rat.

UNLABELLED: Hypertension-associated hypoalgesia is widely recognized in acute pain conditions. In chronic pain states, however, the relationship between blood pressure and pain sensitivity is still ill-defined, with different authors reporting negative, positive, or even no relationship at all. This work addresses this issue, using complete Freund's adjuvant (CFA)-induced monoarthritis in different models of hypertension: Spontaneous (spontaneously hypertensive rats, SHR), induced by infusion of angiotensin II (ANG) or 1,3-dipropyl-8-sulfophenylxanthine (DPSPX, an adenosine receptors' antagonist), and renal artery ligation (RAL). Nociceptive responses associated with monoarthritis were evaluated by different behavioral tests (von Frey, ankle-bend and CatWalk) and by quantification of Fos expression at the dorsal horn upon noxious stimulation. In all hypertension models, higher von Frey thresholds and lower Fos expression were detected in hypertensive rats with chronic inflammatory pain, as compared to normotensive monoarthritic rats. In SHR and DPSPX, but not ANG or RAL models, hypertensive animals displayed lower inflammation than normotensives. Ankle-bend and CatWalk results indicated lower pain sensitivity in hypertensive rats only in SHR and DPSPX models. The present study shows the importance of using multiple models of hypertension, and evaluating pain responses by various methods, to better understand the complexity of the interactions between pain and cardiovascular regulatory systems. PERSPECTIVE: This study used different models of hypertension to investigate whether chronic pain alters the normal integration of cardiovascular and pain regulatory systems. A complete understanding of the mechanisms underlying the complex interactions between these systems may disclose future therapeutic approaches to treat hypertension/chronic pain comorbidity states.

Role of superoxide and hydrogen peroxide in hypertension induced by an antagonist of adenosine receptors.

Treatment of Wistar rats for 7 days with 1,3-dipropyl-8-sulfophenylxanthine (DPSPX), an antagonist of adenosine receptors, induces long-lasting hypertension associated with marked changes in vascular structure and reactivity and renin-angiotensin system activation. This study aimed at evaluating the role of oxidative stress in the development of DPSPX-induced hypertension and also at identifying the relative contribution of superoxide radical (O2.-) vs hydrogen peroxide (H2O2). Vascular and systemic prooxidant/antioxidant status was evaluated in sham (saline, i.p., 7 days) and DPSPX (90 microg/kg/h, i.p., 7 days)-treated rats. Systolic blood pressure was determined by invasive and non-invasive methods. The activity of vascular NADPH oxidase, superoxide dismutase (SOD), catalase and glutathione peroxidase was assayed by fluorometric/spectrophotometric methods. H2O2 levels were measured using an Amplex Red Hydrogen Peroxide kit. Plasma thiobarbituric acid reactive substances and plasma antioxidant capacity were also measured. In addition we tested the effects of antioxidants or inhibitors of reactive oxygen species generation on blood pressure, vascular hyperplasia and oxidative stress parameters. DPSPX-hypertensive rats showed increased activity of vascular NADPH oxidase, SOD, catalase and glutathione peroxidase, as well as increased H2O2 generation. DPSPX-hypertensive rats also had increased plasma lipid peroxidation and decreased plasma antioxidant capacity. Treatment with apocynin (1.5 mmol/l, per os, 14 days), or with polyethylene glycol (PEG)-catalase (10,000 U/kg/day, i.p., 8 days), prevented the DPSPX-induced effects on blood pressure, vascular structure and H2O2 levels. Tempol (3 mmol/l, per os, 14 days) failed to inhibit these changes, unless PEG-catalase was co-administered. It is concluded that O2.- generation with subsequent formation of H2O2 plays a major role in the development of DPSPX-induced hypertension.

Purinergic receptors in the splanchnic circulation.

There is considerable evidence that purines are vasoactive molecules involved in the regulation of blood flow. Adenosine is a well known vasodilator that also acts as a modulator of the response to other vasoactive substances. Adenosine exerts its effects by interacting with adenosine receptors. These are metabotropic G-protein coupled receptors and include four subtypes, A(1), A(2A), A(2B) and A(3). Adenosine triphosphate (ATP) is a co-transmitter in vascular neuroeffector junctions and is known to activate two distinct types of P2 receptors, P2X (ionotropic) and P2Y (metabotropic). ATP can exert either vasoconstrictive or vasorelaxant effects, depending on the P2 receptor subtype involved. Splanchnic vascular beds are of particular interest, as they receive a large fraction of the cardiac output. This review focus on purinergic receptors role in the splanchnic vasomotor control. Here, we give an overview on the distribution and diversity of effects of purinergic receptors in splanchnic vessels. Pre- and post-junctional receptormediated responses are summarized. Attention is also given to the interactions between purinergic receptors and other receptors in the splanchnic circulation.

Inhibition of nociceptive responses of spinal cord neurones during hypertension involves the spinal GABAergic system and a pain modulatory center located at the caudal ventrolateral medulla.

The mechanisms of hypertension-induced hypoalgesia were studied in a model of hypertension induced by adenosine receptors blockade with the non-selective antagonist 1,3-dipropyl-8-sulfophenylxanthine (DPSPX) during 7 days. Based on the positive correlation between pain thresholds and noxious-evoked expression of the c-fos protooncogene in spinal cord neurones, we used this marker of nociceptive activation of spinal neurones to evaluate the involvement of the spinal GABAergic system and the caudal ventrolateral medulla (VLM), an important inhibitory component of the supraspinal endogenous pain modulatory system. In DPSPX-treated animals, a 20% increase in blood pressure was achieved along with a decrease in Fos expression in the superficial (laminae I-II) and deep (laminae III-VII) dorsal horn. In these animals, lower percentages of neurones labeled for GABAB receptors that expressed Fos were obtained in the superficial dorsal horn. Lesioning the VLMlat with quinolinic acid prevented the decrease in Fos expression at the spinal cord of DPSPX-hypertensive rats whereas in normotensive animals, no changes in Fos expression were detected. The present results support previous findings that hypertension is associated with a decrease of nociceptive activation of spinal cord neurones, through descending inhibition exerted by the VLMlat. This study further shows that during hypertension a decrease in the expression of GABAB receptors in nociceptive spinal neurones occurs, probably due to changes in the local GABAergic inhibitory system.

Lesion of the caudal ventrolateral medulla prevents the induction of hypertension by adenosine receptor blockade in rats.

The continuous infusion for 7 days of the adenosine receptor antagonist 1,3-dipropyl-8-sulfophenylxanthine (DPSPX) causes a sustained hypertension in rats, with an enhancement of sympathetic neurotransmission and activation of the renin-angiotensin system. We studied the involvement of the caudal ventrolateral medulla in the establishment of this hypertensive model by evaluating the effect of local lesioning in blood pressure (BP). Male adult Wistar rats received stereotaxic injections of 0.3 mul of saline or quinolinic acid (QA; 180 mM) in the caudal ventrolateral medulla followed by abdominal implant of minipump for infusion of saline or DPSPX (90 microg(-1) kg(-1) h(-1)). BP was measured in conscious animals every 2 days for 12 days. The sustained increase of BP (22.1 mm Hg; P < 0.001) detected in rats infused with DPSPX was reverted (6.7 mm Hg; P > 0.05) from day six onwards in animals with lesion of the lateralmost part of caudal ventrolateral medulla (VLMlat). The present results suggest that the development of hypertension induced by adenosine receptor antagonist involves the participation of the VLMlat. They further add new data as to the functional complexity of this medullary area involved in a variety of functions such as cardiovascular, respiratory, motor and pain control.

Pre- and postjunctional effects of angiotensin II in hypertension due to adenosine receptor blockade.

Prejunctional facilitation of [3H]noradrenaline release induced by sympathetic nerve stimulation and postjunctional contractile effects of angiotensin II were studied in the mesenteric artery and vein of 1,3-dipropyl-8-sulfophenylxanthine (DPSPX)-hypertensive rats. Male Wistar rats received infusions of saline or DPSPX (90 microg/kg/h) i.p.. Blood pressure was determined by tail-cuff. The prejunctional effect of angiotensin II was similar in artery and vein preparations of control rats and was increased in DPSPX-hypertensive rats. In contrast, the contractile effect of angiotensin II was much more pronounced in the mesenteric vein than in the mesenteric artery of control rats and was markedly reduced in DPSPX-hypertensive rats. We conclude that (1) the increased prejunctional effect of angiotensin II may contribute to, while (2) the decreased contractile effect of angiotensin II may attenuate DPSPX-induced hypertension. This study also supports the hypothesis that pre- and postjunctional angiotensin II receptors are different.