TNF-alpha enhances contraction and inhibits endothelial NO-cGMP relaxation in systemic vessels of pregnant rats

Perivascular Adipose Tissue and Vascular Smooth Muscle Tone: Friends or Foes?

Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H₂S, H₂O₂, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies.

Involvement of AGE and Its Receptors in the Pathogenesis of Hypertension in Elderly People and Its Treatment

Both systolic and diastolic blood pressures increase with age up to 50 to 60 years of age. After 60 years of age systolic pressure rises to 84 years of age but diastolic pressure remains stable or even decreases. In the oldest age group (85-99 years), the systolic blood pressure (SBP) is high and diastolic pressure (DBP) is the lowest. Seventy percent of people older than 65 years are hypertensive. This paper deals with the role of advanced glycation end products (AGE) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the development of hypertension in the elderly population. Plasma/serum levels of AGE are higher in older people as compared with younger people. Serum levels of AGE are positively correlated with age, arterial stiffness, and hypertension. Low serum levels of sRAGE are associated with arterial stiffness and hypertension. Levels of sRAGE are negatively correlated with age and blood pressure. Levels of sRAGE are lower in patients with arterial stiffness and hypertension than patients with high levels of sRAGE. AGE could induce hypertension through numerous mechanisms including, cross-linking with collagen, reduction of nitric oxide, increased expression of endothelin-1, and transforming growth factor-β (TGF-β). Interaction of AGE with RAGE could produce hypertension through the generation of reactive oxygen species, increased sympathetic activity, activation of nuclear factor-kB, and increased expression of cytokines, cell adhesion molecules, and TGF- β. In conclusion, the AGE-RAGE axis could be involved in hypertension in elderly people. Treatment for hypertension in elderly people should be targeted at reduction of AGE levels in the body, prevention of AGE formation, degradation of AGE in vivo, downregulation of RAGE expression, blockade of AGE-RAGE interaction, upregulation of sRAGE expression, and use of antioxidants.

Reliability of Rodent and Rabbit Models in Preeclampsia Research

In vivo studies on the pathology of gestation, including preeclampsia, often use small mammals such as rabbits or rodents, i.e., mice, rats, hamsters, and guinea pigs. The key advantage of these animals is their short reproductive cycle; in addition, similar to humans, they also develop a haemochorial placenta and present a similar transformation of maternal spiral arteries. Interestingly, pregnant dams also demonstrate a similar reaction to inflammatory factors and placentally derived antiangiogenic factors, i.e., soluble fms-like tyrosine kinase 1 (sFlt-1) or soluble endoglin-1 (sEng), as preeclamptic women: all animals present an increase in blood pressure and usually proteinuria. These constitute the classical duet that allows for the recognition of preeclampsia. However, the time of initiation of maternal vessel remodelling and the depth of trophoblast invasion differs between rabbits, rodents, and humans. Unfortunately, at present, no known animal replicates a human pregnancy exactly, and hence, the use of rabbit and rodent models is restricted to the investigation of individual aspects of human gestation only. This article compares the process of placentation in rodents, rabbits, and humans, which should be considered when planning experiments on preeclampsia; these aspects might determine the success, or failure, of the study. The report also reviews the rodent and rabbit models used to investigate certain aspects of the pathomechanism of human preeclampsia, especially those related to incorrect trophoblast invasion, placental hypoxia, inflammation, or maternal endothelial dysfunction.

Selective Phosphodiesterase 1 Inhibition Ameliorates Vascular Function, Reduces Inflammatory Response, and Lowers Blood Pressure in Aging Animals

Diminished nitric oxide-cGMP-mediated relaxation plays a crucial role in cardiovascular aging, leading to decreased vasodilation, vascular hypertrophy and stiffening, and ultimately, cardiovascular dysfunction. Aging is the time-related worsening of physiologic function due to complex cellular and molecular interactions, and it is at least partly driven by DNA damage. Genetic deletion of the DNA repair enzyme ERCC1 endonuclease in Ercc1Δ/- mice provides us an efficient tool to accelerate vascular aging, explore mechanisms, and test potential treatments. Previously, we identified the cGMP-degrading enzyme phosphodiesterase 1 as a potential treatment target in vascular aging. In the present study, we studied the effect of acute and chronic treatment with ITI-214, a selective phosphodiesterase 1 inhibitor on vascular aging features in Ercc1Δ/- mice. Compared with wild-type mice, Ercc1Δ/- mice at the age of 14 weeks showed decreased reactive hyperemia, diminished endothelium-dependent and -independent responses of arteries in organ baths, carotid wall hypertrophy, and elevated circulating levels of inflammatory cytokines. Acute ITI-214 treatment in organ baths restored the arterial endothelium-independent vasodilation in Ercc1Δ/- mice. An 8-week treatment with 100 mg/kg per day ITI-214 improved endothelium-independent relaxation in both aorta and coronary arteries, at least partly restored the diminished reactive hyperemia, lowered the systolic and diastolic blood pressure, normalized the carotid hypertrophy, and ameliorated inflammatory responses exclusively in Ercc1Δ/- mice. These findings suggest phosphodiesterase 1 inhibition would provide a powerful tool for nitric oxide-cGMP augmentation and have significant therapeutic potential to battle arteriopathy related to aging. SIGNIFICANCE STATEMENT: The findings implicate the key role of phosphodiesterase 1 in vascular function and might be of clinical importance for the prevention of mortalities and morbidities related to vascular complications during aging, as well as for patients with progeria that show a high risk of cardiovascular disease.

TNFα and Reactive Oxygen Signaling in Vascular Smooth Muscle Cells in Hypertension and Atherosclerosis

Hypertension and atherosclerosis, the predecessors of stroke and myocardial infarction, are chronic vascular inflammatory reactions. Tumor necrosis factor alpha (TNFα), the "master" proinflammatory cytokine, contributes to both the initiation and maintenance of vascular inflammation. TNFα induces reactive oxygen species (ROS) production which drives the redox reactions that constitute "ROS signaling." However, these ROS may also cause oxidative stress which contributes to vascular dysfunction. Mice lacking TNFα or its receptors are protected against both acute and chronic cardiovascular injury. Humans suffering from TNFα-driven inflammatory conditions such as rheumatoid arthritis and psoriasis are at increased cardiovascular risk. When treated with highly specific biologic agents that target TNFα signaling (Etanercept, etc.) they display marked reductions in that risk. The ability of TNFα to induce endothelial dysfunction, often the first step in a progression toward serious vasculopathy, is well recognized and has been reviewed elsewhere. However, TNFα also has profound effects on vascular smooth muscle cells (VSMCs) including a fundamental change from a contractile to a secretory phenotype. This "phenotypic switching" promotes proliferation and production of extracellular matrix proteins which are associated with medial hypertrophy. Additionally, it promotes lipid storage and enhanced motility, changes that support the contribution of VSMCs to neointima and atherosclerotic plaque formation. This review focuses on the role of TNFα in driving the inflammatory changes in VSMC biology that contribute to cardiovascular disease. Special attention is given to the mechanisms by which TNFα promotes ROS production at specific subcellular locations, and the contribution of these ROS to TNFα signaling.

Biopolymer-Delivered, Maternally Sequestered NF-κB (Nuclear Factor-κB) Inhibitory Peptide for Treatment of Preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy that causes significant acute and long-term risk to the mother and the baby. The multifaceted maternal syndrome is driven by overproduction of circulating anti-angiogenic factors, widespread inflammation, and endothelial dysfunction. Nuclear factor-κB (NF-κB) is a transcription factor that plays a central role in the inflammatory response. Its activity is increased in the preeclamptic placenta, and it promotes the systemic endothelial dysfunction present in preeclampsia. There is an acute need for new therapeutics targeted to the causative pathways of preeclampsia. Our group has developed a drug delivery system based on the bioengineered protein ELP (elastin-like polypeptide) that is capable of stabilizing therapeutics in the maternal circulation and preventing their placental transfer. Here we used the ELP carrier system to deliver a peptide known to inhibit the NF-κB pathway. This polypeptide, containing a cell-penetrating peptide and an NF-κB inhibitory peptide derived from the p50 nuclear localization sequence (abbreviated SynB1-ELP-p50i), blocked NF-κB activation and prevented TNF-α (tumor necrosis factor alpha)-induced endothelin production in vitro. Fusion of the p50i peptide to the SynB1-ELP carrier slowed its plasma clearance and prevented its placental transfer in pregnant rats, resulting in increased deposition in the maternal kidney, liver, and placenta relative to the free peptide. When administered in a rat model of placental ischemia, SynB1-ELP-p50i partially ameliorated placental ischemia-induced hypertension and reduced placental TNF-α levels with no signs of toxicity. These data support the continued development of ELP-delivered NF-κB inhibitors as maternally sequestered anti-inflammatory agents for preeclampsia therapy.

Skeletal muscle as a protagonist in the pregnancy metabolic syndrome

The pregnant woman normally shows clinical manifestations similar to a metabolic syndrome (MS), due to her metabolic and hemodynamic adaptations in order to share nutrients with the child. If those adjustments are surpassed, a kind of pregnancy MS (PregMS) could appear, characterized by excessive insulin resistance and vascular maladaptation. Skeletal muscle (SKM) must be a protagonist in the PregMS: SKM strength and mass have been associated inversely with MS incidence in non-pregnant patients, and in pregnant women muscular activity modulates metabolic and vascular adaptations that favor better outcomes. Of note, a sedentary lifestyle affects exactly in the other way. Those effects may be explained not only by the old paradigm of SKM being a great energy consumer and store, but because it is an endocrine organ whose chronic activity or deconditioning correspondingly releases myokines modulating insulin sensitivity and cardiovascular adaptation, by direct or indirect mechanisms not well understood. In this document, we present evidence to support the concept of a PregMS and hypothesize on the role of the SKM mass, fiber types composition and myokines in its pathophysiology. Also, we discuss some exercise interventions in pregnancy as a way to test our hypotheses.

Endotoxin-induced cerebral pathophysiology: differences between fetus and newborn

As the comparative pathophysiology of perinatal infection in the fetus and newborn is uncertain, this study contrasted the cerebral effects of endotoxemia in conscious fetal sheep and newborn lambs. Responses to intravenous bacterial endotoxin (lipopolysaccharide, LPS) or normal saline were studied on three consecutive days in fetal sheep (LPS 1 μg/kg, n = 5; normal saline n = 5) and newborn lambs (LPS 2 μg/kg, n = 10; normal saline n = 5). Cerebro-vascular function was assessed by monitoring cerebral blood flow (CBF) and cerebral vascular resistance (CVR) over 12 h each day, and inflammatory responses were assessed by plasma TNF alpha (TNF-α), nitrate and nitrite concentrations. Brain injury was quantified by counting both resting and active macrophages in the caudate nucleus and periventricular white matter (PVWM). An acute cerebral vasoconstriction (within 1 h of LPS injection) occurred in both the fetus (ΔCVR +53%) and newborn (ΔCVR +63%); subsequently prolonged cerebral vasodilatation occurred in the fetus (ΔCVR -33%) in association with double plasma nitrate/nitrite concentrations, but not in the newborn. Abundant infiltration of activated macrophages was observed in both CN and PVWM at each age, with the extent being 2-3 times greater in the fetus (P < 0.001). In conclusion, while the fetus and newborn experience a similar acute disruption of the cerebral circulation after LPS, the fetus suffers a more prolonged circulatory disruption, a greater infiltration of activated macrophages, and an exaggerated susceptibility to brain injury.

The Role of Interleukin-10 in the Pathophysiology of Preeclampsia

PURPOSE OF REVIEW

The pathophysiology of preeclampsia is complex and not entirely understood. A key feature in preeclampsia development is an immunological imbalance that shifts the maternal immune response from one of tolerance towards one promoting chronic inflammation and endothelial dysfunction. As a key regulator of immunity, IL-10 not only has immunomodulatory activity, but also directly benefits vasculature and promotes successful cellular interactions at the maternal-fetal interface. Here we focus on the mechanisms by which the dysregulation of IL-10 may contribute to the pathophysiology of preeclampsia.

RECENT FINDINGS

Dysregulation of IL-10 has been demonstrated in various animal models of preeclampsia. Decreased IL-10 production in both placenta and peripheral blood mononuclear cells has been reported in human studies, but with inconsistent results. The significance of IL-10 in preeclampsia has shifted from a key biomarker to one with therapeutic potential. As such, a better understanding of the role of this cytokine in the pathophysiology of preeclampsia is of paramount importance.

Human Vascular Microphysiological System for in vitro Drug Screening

In vitro human tissue engineered human blood vessels (TEBV) that exhibit vasoactivity can be used to test human toxicity of pharmaceutical drug candidates prior to pre-clinical animal studies. TEBVs with 400–800 μM diameters were made by embedding human neonatal dermal fibroblasts or human bone marrow-derived mesenchymal stem cells in dense collagen gel. TEBVs were mechanically strong enough to allow endothelialization and perfusion at physiological shear stresses within 3 hours after fabrication. After 1 week of perfusion, TEBVs exhibited endothelial release of nitric oxide, phenylephrine-induced vasoconstriction, and acetylcholine-induced vasodilation, all of which were maintained up to 5 weeks in culture. Vasodilation was blocked with the addition of the nitric oxide synthase inhibitor L-N^G-Nitroarginine methyl ester (L-NAME). TEBVs elicited reversible activation to acute inflammatory stimulation by TNF-α which had a transient effect upon acetylcholine-induced relaxation, and exhibited dose-dependent vasodilation in response to caffeine and theophylline. Treatment of TEBVs with 1 μM lovastatin for three days prior to addition of Tumor necrosis factor – α (TNF-α) blocked the injury response and maintained vasodilation. These results indicate the potential to develop a rapidly-producible, endothelialized TEBV for microphysiological systems capable of producing physiological responses to both pharmaceutical and immunological stimuli.

Increased risk for the development of preeclampsia in obese pregnancies: weighing in on the mechanisms

Preeclampsia (PE) is a pregnancy-specific disorder typically presenting as new-onset hypertension and proteinuria. While numerous epidemiological studies have demonstrated that obesity increases the risk of PE, the mechanisms have yet to be fully elucidated. Growing evidence from animal and human studies implicate placental ischemia in the etiology of this maternal syndrome. It is thought that placental ischemia is brought about by dysfunctional cytotrophoblast migration and invasion into the uterus and subsequent lack of spiral arteriole widening and placental perfusion. Placental ischemia/hypoxia stimulates the release of soluble placental factors into the maternal circulation where they cause endothelial dysfunction, particularly in the kidney, to elicit the clinical manifestations of PE. The most recognized of these factors are the anti-angiogenic sFlt-1 and pro-inflammatory TNF-α and AT1-AA, which promote endothelial dysfunction by reducing levels of the provasodilator nitric oxide and stimulating production of the potent vasoconstrictor endothelin-1 and reactive oxygen species. We hypothesize that obesity-related metabolic factors increase the risk for developing PE by impacting various stages in the pathogenesis of PE, namely, 1) cytotrophoblast migration and placental ischemia; 2) release of soluble placental factors into the maternal circulation; and 3) maternal endothelial and vascular dysfunction. This review will summarize the current experimental evidence supporting the concept that obesity and metabolic factors like lipids, insulin, glucose, and leptin affect placental function and increase the risk for developing hypertension in pregnancy by reducing placental perfusion; enhancing placental release of soluble factors; and by increasing the sensitivity of the maternal vasculature to placental ischemia-induced soluble factors.

Pregnant rats treated with a high-fat/prooxidant Western diet with ANG II and TNF-α are resistant to elevations in blood pressure and renal oxidative stress

Oxidative stress and inflammation are risk factors for hypertension in pregnancy. Here, we examined the 24-h mean arterial pressure (MAP) via telemetry and the nitric oxide (NO) and redox systems in the kidney cortex, medulla, and aorta of virgin and pregnant rats treated with a high-fat/prooxidant Western diet (HFD), ANG II, and TNF-α. Female Sprague-Dawley rats were given a normal diet (ND) or a HFD for 8 wk before mating. Day 6 of pregnancy and age-matched virgins were implanted with minipumps infusing saline or ANG II (150 ng·kg(-1)·min(-1)) + TNF-α (75 ng/day) for 14 days. Groups consisted of Virgin + ND + Saline (V+ND) (n = 7), Virgin + HFD +ANG II and TNF-α (V+HFD) (n = 7), Pregnant + ND + Saline (P+ND) (n = 6), and Pregnant + HFD + ANG II and TNF-α (P+HFD) (n = 8). After day 6 of minipump implantation, V+HFD rats displayed an increase in MAP on days 7, 8, and 10-15 vs. V+ND rats. P+HFD rats, after day 6 of minipump implantation, showed an increase in MAP only on day 7 vs. P+ND rats. P+HFD rats had a normal fall in 24-h MAP, hematocrit, plasma protein concentration, and osmolality at late pregnancy. No change in kidney cortex, medulla, or aortic oxidative stress in P+HFD rats. P+HFD rats displayed a decrease in nNOSβ abundance, but no change in kidney cortex NOx content vs. P+ND rats. Pregnant rats subjected to a chronic HFD and prooxidant and proinflammatory insults have a blunted increase in 24-h MAP and renal oxidative stress. Our data suggest renal NO bioavailability is not altered in pregnant rats treated with a HFD, ANG II, and TNF-α.

Perivascular adipose tissue, vascular reactivity and hypertension

Most blood vessels are surrounded by a variable amount of adventitial adipose tissue, perivascular adipose tissue (PVAT), which was originally thought to provide mechanical support for the vessel. It is now known that PVAT secretes a number of bioactive substances including vascular endothelial growth factor, tumor necrosis factor-alpha (TNF-α), leptin, adiponectin, insulin-like growth factor, interleukin-6, plasminogen activator substance, resistin and angiotensinogen. Several studies have shown that PVAT significantly modulated vascular smooth muscle contractions induced by a variety of agonists and electrical stimulation by releasing adipocyte-derived relaxing (ADRF) and contracting factors. The identity of ADRF is not yet known. However, several vasodilators have been suggested including adiponectin, angiotensin 1-7, hydrogen sulfide and methyl palmitate. The anticontractile effect of PVAT is mediated through the activation of potassium channels since it is abrogated by inhibiting potassium channels. Hypertension is characterized by a reduction in the size and amount of PVAT and this is associated with the attenuated anticontractile effect of PVAT in hypertension. However, since a reduction in size and amount of PVAT and the attenuated anticontractile effect of PVAT were already evident in prehypertensive rats with no evidence of impaired release of ADRF, there is the possibility that the anticontractile effect of PVAT was not directly related to an altered function of the adipocytes per se. Hypertension is characterized by low-grade inflammation and infiltration of macrophages. One of the adipokines secreted by macrophages is TNF-α. It has been shown that exogenously administered TNF-α enhanced agonist-induced contraction of a variety of vascular smooth muscle preparations and reduced endothelium-dependent relaxation. Other procontractile factors released by the PVAT include angiotensin II and superoxide. It is therefore possible that the loss could be due to an increased amount of these proinflammatory and procontractile factors. More studies are definitely required to confirm this.

Chemotactic activity of gestational tissues through late pregnancy, term labor, and RU486-induced preterm labor in Guinea pigs

PROBLEM

Is increased leukocyte chemotactic activity (CA) from gestational tissues necessary for term or preterm labor in guinea pigs?

METHOD OF STUDY

Tissue extracts were prepared from pregnant guinea pig decidua-myometrium, cervix, fetal membranes (amniochorion), and placenta during early third trimester (n = 8), term not in labor (TNL, n = 5), and term spontaneous labor (TL, n = 6), RU486-induced preterm labor (PTL, n = 6), or controls (cPTL, n = 5). Leukocyte CA was assessed using a modified Boyden chamber assay. Extract chemokine and maternal progesterone concentrations were quantified by enzyme immunoassay.

RESULTS

Only the extracts from amniochorion demonstrated increased CA through late gestation and labor. In contrast, CA was decreased in extracts from amniochorion and cervix from animals after RU486-induced PTL. Maternal progesterone concentrations remained high in all groups.

CONCLUSION

Leukocyte CA of intrauterine tissues is increased in term spontaneous labor. However, RU486-induced preterm labor occurs in the absence of increased CA.

Caffeic acid phenethyl ester, a 5-lipoxygenase enzyme inhibitor, alleviates diabetic atherosclerotic manifestations: effect on vascular reactivity and stiffness

Atherosclerosis is a major macrovascular complication of diabetes that increases the risks for myocardial infarction, stroke, and other vascular diseases. The effect of a selective 5-lipoxygenase enzyme inhibitor; caffeic acid phenethyl ester (CAPE) on diabetes-induced atherosclerotic manifestations was investigated. Insulin deficiency or resistance was induced by STZ or fructose respectively. Atherosclerosis developed when rats were left for 8 or 12 weeks subsequent STZ or fructose administration respectively. CAPE (30 mg kg(-1) day(-1)) was given in the last 6 weeks. Afterwards, blood pressure (BP) was recorded. Then, isolated aorta reactivity to KCl and phenylephrine (PE) was studied. Blood glucose level, serum levels of insulin, tumor necrosis factor α (TNF-α) as well as advanced glycation end products (AGEs) were determined. Moreover aortic haem oxygenase-1 (HO-1) protein expression and collagen deposition were also assessed. Insulin deficiency and resistance were accompanied with elevated BP, exaggerated response to KCl and PE, elevated serum TNF-α and AGEs levels. Both models showed marked increase in collagen deposition. However, CAPE alleviated systolic and diastolic BP elevations and the exaggerated vascular contractility to both PE and KCl in both models without affecting AGEs level. CAPE inhibited TNF-α serum level elevation, induced aortic HO-1 expression and reduced collagen deposition. CAPE prevented development of hyperinsulinemia in insulin resistance model without any impact on the developed hyperglycemia in insulin deficiency model. In conclusion, CAPE offsets the atherosclerotic changes associated with diabetes via amelioration of the significant functional and structural derangements in the vessels in addition to its antihyperinsulinemic effect in insulin resistant model.

Protein Kinase C Inhibitors as Modulators of Vascular Function and their Application in Vascular Disease

Blood pressure (BP) is regulated by multiple neuronal, hormonal, renal and vascular control mechanisms. Changes in signaling mechanisms in the endothelium, vascular smooth muscle (VSM) and extracellular matrix cause alterations in vascular tone and blood vessel remodeling and may lead to persistent increases in vascular resistance and hypertension (HTN). In VSM, activation of surface receptors by vasoconstrictor stimuli causes an increase in intracellular free Ca(2+) concentration ([Ca(2+)]i), which forms a complex with calmodulin, activates myosin light chain (MLC) kinase and leads to MLC phosphorylation, actin-myosin interaction and VSM contraction. Vasoconstrictor agonists could also increase the production of diacylglycerol which activates protein kinase C (PKC). PKC is a family of Ca(2+)-dependent and Ca(2+)-independent isozymes that have different distributions in various blood vessels, and undergo translocation from the cytosol to the plasma membrane, cytoskeleton or the nucleus during cell activation. In VSM, PKC translocation to the cell surface may trigger a cascade of biochemical events leading to activation of mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK), a pathway that ultimately increases the myofilament force sensitivity to [Ca(2+)]i, and enhances actin-myosin interaction and VSM contraction. PKC translocation to the nucleus may induce transactivation of various genes and promote VSM growth and proliferation. PKC could also affect endothelium-derived relaxing and contracting factors as well as matrix metalloproteinase (MMPs) in the extracellular matrix further affecting vascular reactivity and remodeling. In addition to vasoactive factors, reactive oxygen species, inflammatory cytokines and other metabolic factors could affect PKC activity. Increased PKC expression and activity have been observed in vascular disease and in certain forms of experimental and human HTN. Targeting of vascular PKC using PKC inhibitors may function in concert with antioxidants, MMP inhibitors and cytokine antagonists to reduce VSM hyperactivity in certain forms of HTN that do not respond to Ca(2+) channel blockers.

Etanercept Prevents Decrease of Cochlear Blood Flow Dose-Dependently Caused by Tumor Necrosis Factor Alpha

Objectives:

Tumor necrosis factor alpha (TNF-alpha) is a mediator of inflammation and microcirculation in the cochlea. This study aimed to quantify the effect of a local increase of TNF-alpha and study the effect of its interaction with etanercept on cochlear microcirculation.

Methods:

Cochlear lateral wall vessels were exposed surgically and assessed by intravital microscopy in guinea pigs in vivo. First, 24 animals were randomly distributed into 4 groups of 6 each. Exposed vessels were superfused repeatedly either with 1 of 3 different concentrations of TNF-alpha (5.0, 0.5, and 0.05 ng/mL) or with placebo (0.9% saline solution). Second, 12 animals were randomly distributed into 2 groups of 6 each. Vessels were pretreated with etanercept (1.0 μg/mL) or placebo (0.9% saline solution), and then treated by repeated superfusion with TNF-alpha (5.0 ng/mL).

Results:

TNF-alpha was shown to be effective in decreasing cochlear blood flow at a dose of 5.0 ng/mL (p < 0.01, analysis of variance on ranks). Lower concentrations or placebo treatment did not lead to significant changes. After pretreatment with etanercept, TNF-alpha at a dose of 5.0 ng/mL no longer led to a change in cochlear blood flow.

Conclusions:

The decreasing effect that TNF-alpha has on cochlear blood flow is dose-dependent. Etanercept abrogates this effect.

Changes in cardiac structure in hypertension produced by placental ischemia in pregnant rats: effect of tumor necrosis factor blockade

OBJECTIVES

Chronic reduction of uteroplacental perfusion pressure (RUPP) in pregnant rats leads to placental ischemia, maternal endothelial cell dysfunction, hypertension and elevated levels of tumor necrosis factor-alpha (TNF-α). In this study we investigated the hypothesis that placental ischemia in pregnant rat, a model of preeclampsia, stimulates cardiac hypertrophy and fibrosis via a TNF-α-dependent mechanism.

METHODS

Normal pregnant Sprague-Dawley rats and RUPP rats were evaluated on day 19 of gestation. To test the role of TNF-α in mediating change in the RUPP rat heart, a TNF-α inhibitor, etanercept, was administered on day 18 of gestation at a dose of 0.8 mg/kg, s.c.

RESULTS

In comparison to normal pregnant rats, RUPP animals display enlarged cardiomyocytes, microvascular rarefaction, fibrosis, apoptosis as well as increased expression of markers of heart hypertrophy and fibrosis. Etanercept (E) treatment prevented enlargement of cardiomyocytes, fibrosis and apoptosis and this was accompanied by significantly lowered blood pressure in RUPP rats. Etanercept treatment lowered expression of mRNA for brain natriuretic peptide, a marker of cardiac hypertrophy. It also heightened expression of endothelial nitric oxide synthase and its phosphorylation as well as oxytocin receptor identified in cardiac microvessels. TNF-α inhibition prevented microvascular rarefaction in the heart as indicated by augmented CD31, a marker of angiogenesis.

CONCLUSIONS

These results suggest that RUPP leads to microvascular rarefaction in the heart, exaggerated cardiomyocyte size, apoptosis, fibrosis, and the alteration of cardiac gene expression that are modulated by the inflammatory cytokine TNFα.

Pentoxifylline alleviates vascular impairment in insulin resistance via TNF-α inhibition

Deterioration of vascular reactivity plays a pivotal role in vascular complications. Pentoxifylline (PTX) is a well-tolerated drug used to treat vascular insufficiency. We investigated the protective effect of PTX against vascular impairment in insulin resistance. Insulin resistance was induced by fructose (10%) in drinking water while PTX was concurrently administered (50 mg/kg(-1)) for 8 weeks. Serum levels of glucose, insulin, tumor necrosis factor alpha (TNF-α) were determined. Isolated aorta reactivity to phenylephrine (PE), potassium chloride (KCl), and acetylcholine (ACh) was studied, as was nitric oxide (NO) generation and histopathology. Insulin resistance was accompanied with a significant elevation in serum TNF-α level, marked leukocytes infiltration, and endothelial pyknosis. PTX inhibited insulin resistance and prevented TNF-α elevation, leukocyte infiltration and endothelial pyknosis. Vascular dysfunction was evident in insulin resistance as increased vascular contractility to PE and decreased relaxation to ACh, whereas PTX protected against this dysfunction. Notably, in vitro incubation with TNF-α (1 ng/ml(-1)) increased contractility to PE and decreased relaxation to ACh while concomitant PTX (1 mM) incubation partially restored response to ACh but not to PE. Furthermore, TNF-α reduced ACh-induced NO generation, whereeas PTX restored it. In conclusion, PTX protects from the impairment in vascular reactivity in insulin resistance, by a mechanism involving TNF-α inhibition.

Protective effects of hydrogen-rich saline in preeclampsia rat model

Hydrogen has been reported as a novel antioxidant to selectively reduce levels of toxic reactive-oxygen species (ROS). We investigated the effects of hydrogen-rich saline on the prevention of oxidative injuries in N(omega)-nitro-L-arginine methyl ester (L-NAME) induced rat model of preeclampsia (PE). Sprague-Dawley rats (n = 50) were randomized into five groups: non-pregnant; normal pregnancy; pregnancy + hydrogen saline, 5 ml/kg, intraperitoneal (i.p.); pregnancy + L-NAME, 60 mg/kg (i.p.); pregnancy + L-NAME + hydrogen saline rats. Terminations of pregnancy were performed on day 22 of gestation, when the placentas and kidneys were microscopically inspected; tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and malonyldialdehyde (MDA) were assessed; and the mean systolic BP, level of proteinuria, resorptions, and pups birth weights were recorded. It was found that the pups of hypertensive gravid rats treated with hydrogen-rich saline presented fewer number of resorptions than those of the group of pregnancy + L-NAME, 60 mg/kg i.p. (P < 0.05). Additionally, hydrogen-rich saline treatment decreased the blood and placental MDA, proteinuria and the pro-inflammatory cytokine TNF-α, IL-1β in the placental tissues compared with those in L-NAME-treated rats (all P < 0.05). The mean systolic BP showed no significant difference except on day 22 of gestation (P < 0.05). The preventive administration of hydrogen significantly attenuated the severity of PE, which might be ascribed to a reduction in inflammation response and oxidative stress. It could be concluded that hydrogen can be an effective antioxidant in the management of PE.

Animal models of pre-eclampsia

The cardinal features of human pre-eclampsia, hypertension and proteinuria, are mimicked in animal models. Increasingly, the accuracy of inducing 'pure' systemic endothelial dysfunction is regarded as critical in differentiating mechanisms of pre-eclampsia from other conditions which induce hypertension (e.g. glomerulonephritis, renal denervation or manipulation of the renin-angiotensin system). A recent study in baboons has identified the timing of induction of maternal endothelial damage after acute uteroplacental ischaemia (UPI). The endothelial changes in the glomerulus are indicative of a direct endothelial toxin and mimic the lesions seen in human pre-eclampsia; the extent of hypertension and proteinuria are also similar. This animal model identifies systemic and placental sFLT-1 (soluble fms-like tyrosine kinase-1) as a potential mediator of endothelial damage. This research involving primates with haemomonochorial placentas makes translation of these results to humans very compelling for understanding the mechanisms of human disease. Similar endothelial dysfunction has been identified in baboons treated with anti-inflammatory inhibitors. Similar studies in rodents have identified a relationship between angiotensin II agonistic antibodies, UPI/reduced uteroplacental perfusion pressure, angiogenic markers, and cytokines. We can now identify vasoconstrictive mediators of the hypertensive and endothelial response such as endothelin 1, the renin-angiotensin system, or other hormones such as oestrogens in primate models.

Interleukin-10 inhibits the in vivo and in vitro adverse effects of TNF-alpha on the endothelium of murine aorta

TNF-α is a proinflammatory cytokine and is an important mediator of maternal endothelial dysfunction leading to preeclampsia. In this study, we tested whether IL-10 protects against TNF-α-induced endothelial dysfunction in murine aorta. In in vitro experiments, aortic rings of C57BL/6 female mice were incubated in Dulbecco's modified Eagle's medium in the presence of either vehicle (distilled H(2)O), TNF-α (4 nmol/l), or recombinant mouse IL-10 (300 ng/ml) or in the presence of both TNF-α and IL-10 for 22 h at 37°C. In in vivo experiments C57BL6/IL-10 knockout female mice were treated with saline or TNF-α (220 ng·kg(-1)·day(-1)) for 14 days. Aortic rings were isolated from in vitro and in vivo experiments and mounted in a wire myograph (Danish Myotech) and stretched to a tension of 5 mN. Endothelium-dependent relaxation was assessed by constructing cumulative concentration-response curves to acetylcholine (ACh, 0.001-10 μmol/l) during phenylephrine (10 μmol/l)-induced contraction. As a result, overnight exposure of aortic rings to TNF-α resulted in significant blunted maximal relaxing responses (E(max)) to ACh compared with untreated rings (22 ± 4 vs. 82 ± 3%, respectively). IL-10 knockout mice treated with TNF-α showed significant impairment in ACh responses (E(max)) compared with C57BL/6 mice treated with TNF-α (51 ± 3 vs. 72 ± 3%, respectively). Western blot analysis showed that endothelial nitric oxide synthase (eNOS) expression was reduced by TNF-α in in vitro and in vivo experiments, whereas IL-10 restored the eNOS expression. In conclusion, the anti-inflammatory cytokine IL-10 prevents impairment in endothelium-dependent vasorelaxation caused by TNF-α by protecting eNOS expression.

Estrogen receptor-mediated enhancement of venous relaxation in female rat: implications in sex-related differences in varicose veins

BACKGROUND

A greater incidence of varicose veins has been reported in premenopausal women than in men. We hypothesized that the sex differences in venous function reflect reduced constriction and enhanced venous dilation in women due to direct venous relaxation effects of estrogen on specific estrogen receptors (ER).

METHODS

Circular segments of inferior vena cava (IVC) from male and female Sprague-Dawley rats were suspended between two wires, and isometric contraction (in mg/mg tissue) to phenylephrine, angiotensin II (AngII), and 96 mM KCl was measured. To investigate sex differences in venous smooth muscle, Ca(2+) release from the intracellular stores, and Ca(2+) entry from the extracellular space, the transient phenylephrine contraction in 0 Ca(2+) Krebs was measured. Extracellular CaCl(2) (0.1, 0.3, 0.6, 1, 2.5 mM) was added, and the [Ca(2+)](e)-dependent contraction was measured. To investigate sex differences in venous endothelial function, acetylcholine-induced relaxation was measured. To test the role of specific ERs, the amount of venous tissue ERs was measured using Western blots, and the venous relaxation in response to 17beta-estradiol (E2, activator of most ERs), 4,4,'4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)-tris-phenol (PPT; ERalpha agonist), 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERbeta agonist), and ICI 182,780 (ERalpha/ERbeta antagonist, and G protein-coupled receptor 30 [GPR30] agonist) was measured in IVC segments nontreated or treated with the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME).

RESULTS

Phenylephrine caused concentration-dependent contraction that was less in female (max 104.2 +/- 16.2) than male IVC (172.4 +/- 20.4). AngII (10(-6))-induced contraction was also less in female (81.0 +/- 11.1) than male IVC (122.5 +/- 15.0). Phenylephrine contraction in 0 Ca(2+) Krebs was insignificantly less in female (4.8 +/- 1.8) than male IVC (7.2 +/- 1.7), suggesting little difference in the intracellular Ca(2+) release mechanism. In contrast, the [Ca(2+)](e)-dependent contraction was significantly reduced in female than male IVC. Also, contraction to membrane depolarization by 96 mM KCl, which stimulates Ca(2+) influx, was less in female (129.7 +/- 16.7) than male IVC (319.7 +/- 30.4), supporting sex differences in Ca(2+) entry. Acetylcholine relaxation was greater in female (max 80.6% +/- 4.1%) than male IVC (max 48.0% +/- 6.1%), suggesting sex differences in the endothelium-dependent relaxation pathway. Western blots revealed greater amounts of ERalpha, ERbeta, and GPR30 in female than male IVC. ER agonists caused concentration-dependent relaxation of phenylephrine contraction in female IVC. E2-induced relaxation (max 76.5% +/- 3.4%) was more than DPN (74.8% +/- 9.1%), PPT (71.4% +/- 12.5%), and ICI 182,780 (67.4% +/- 7.8%), and was similar in L-NAME-treated and nontreated IVC.

CONCLUSION

The reduced alpha-adrenergic, AngII, depolarization-induced, and [Ca(2+)](e)-dependent venous contraction in female rats is consistent with sex differences in the Ca(2+) entry mechanisms, possibly due to enhanced endothelium-dependent vasodilation and increased ER expression/activity in female rats. E2/ER-mediated venous relaxation in female rats is not prevented by NOS blockade, suggesting activation of an NO-independent relaxation pathway. The decreased venous contraction and enhanced E2/ER-mediated venous relaxation would lead to more distensible veins in female rats.

Autoantibody-mediated angiotensin receptor activation contributes to preeclampsia through tumor necrosis factor-alpha signaling

Preeclampsia is a prevalent life-threatening hypertensive disorder of pregnancy for which the pathophysiology remains largely undefined. Recently, a circulating maternal autoantibody, the angiotensin II type I (AT(1)) receptor agonistic autoantibody (AA), has emerged as a contributor to disease features. Increased circulating maternal tumor necrosis factor alpha (TNF-alpha) is also associated with the disease; however, it is unknown whether this factor directly contributes to preeclamptic symptoms. Here we report that this autoantibody increases the proinflammatory cytokine TNF-alpha in the circulation of AT(1)-AA-injected pregnant mice but not in nonpregnant mice. Coinjection of AT(1)-AA with a TNF-alpha neutralizing antibody reduced cytokine availability in AT(1)-AA-injected pregnant mice. Moreover, TNF-alpha blockade in AT(1)-AA-injected pregnant mice significantly attenuated the key features of preeclampsia. Autoantibody-induced hypertension was reduced from 131+/-4 to 110+/-4 mm Hg, and proteinuria was reduced from 212+/-25 to 155+/-23 microg of albumin per milligram of creatinine (both P<0.05). Injection of AT(1)-AA increased the serum levels of circulating soluble fms-like tyrosine kinase 1 and soluble endoglin (34.1+/-5.1, 2.4+/-0.3 ng/mL, respectively) and coinjection with the TNF-alpha blocker significantly reduced their levels (21.7+/-3.4 and 1.2+/-0.4 ng/mL, respectively). Renal damage and placental abnormalities were also decreased by TNF-alpha blockade. Lastly, the elevated circulating TNF-alpha in preeclamptic patients is significantly correlated with the AT(1)-AA bioactivity in our patient cohort. Similarly, the autoantibody, through AT(1) receptor-mediated TNF-alpha induction, contributed to increased soluble fms-like tyrosine kinase 1, soluble endoglin secretion, and increased apoptosis in cultured human villous explants. Overall, AT(1)-AA is a novel candidate that induces TNF-alpha, a cytokine that may play an important pathogenic role in preeclampsia.

Vascular and cellular calcium in normal and hypertensive pregnancy

Normal pregnancy is associated with significant hemodynamic changes in the cardiovascular system in order to meet the metabolic demands of mother and fetus. These changes include increased cardiac output, decreased vascular resistance, and vascular remodeling in the uterine and systemic circulation. Preeclampsia (PE) is a major complication of pregnancy characterized by proteinuria and hypertension. Several risk factors have been implicated in the pathogenesis of PE including genetic and dietary factors. Ca2+ is an essential dietary element and an important regulator of many cellular processes including vascular function. The importance of adequate dietary Ca2+ intake during pregnancy is supported by many studies. Pregnancy-associated changes in Ca2+ metabolism and plasma Ca2+ have been observed. During pregnancy, changes in intracellular free Ca2+ concentration ([Ca2+](i)) have been described in red blood cells, platelets and immune cells. Also, during pregnancy, an increase in [Ca2+](i) in endothelial cells (EC) stimulates the production of vasodilator substances such as nitric oxide and prostacyclin. Normal pregnancy is also associated with decreased vascular smooth muscle (VSM) [Ca2+](i) and possibly the Ca2+-sensitization pathways of VSM contraction including protein kinase C, Rho-kinase, and mitogen-activated protein kinase. Ca2+-dependent matrix metalloproteinases could also promote extracellular matrix degradation and vascular remodeling during pregnancy. Disruption in the balance between dietary, plasma and vascular cell Ca2+ may be responsible for some of the manifestation of PE including procoagulation, decreased vasodilation, and increased vasoconstriction and vascular resistance. The potential benefits of Ca2+ supplements during pregnancy, and the use of modulators of vascular Ca2+ to reduce the manifestations of PE in susceptible women remain an important area for experimental and clinical research.

TNF-alpha infusion impairs corpora cavernosa reactivity

INTRODUCTION

Erectile dysfunction (ED), as well as cardiovascular diseases (CVDs), is associated with endothelial dysfunction and increased levels of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha).

AIM

We hypothesized that increased TNF-alpha levels impair cavernosal function.

METHODS

In vitro organ bath studies were used to measure cavernosal reactivity in mice infused with vehicle or TNF-alpha (220 ng/kg/min) for 14 days. Gene expression of nitric oxide synthase isoforms was evaluated by real-time polymerase chain reaction.

MAIN OUTCOME MEASURES

Corpora cavernosa from TNF-alpha-infused mice exhibited decreased nitric oxide (NO)-dependent relaxation, which was associated with decreased endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) cavernosal expression.

RESULTS

Cavernosal strips from the TNF-alpha-infused mice displayed decreased nonadrenergic-noncholinergic (NANC)-induced relaxation (59.4 +/- 6.2 vs. control: 76.2 +/- 4.7; 16 Hz) compared with the control animals. These responses were associated with decreased gene expression of eNOS and nNOS (P < 0.05). Sympathetic-mediated, as well as phenylephrine (PE)-induced, contractile responses (PE-induced contraction; 1.32 +/- 0.06 vs. control: 0.9 +/- 0.09, mN) were increased in cavernosal strips from TNF-alpha-infused mice. Additionally, infusion of TNF-alpha increased cavernosal responses to endothelin-1 and endothelin receptor A subtype (ET(A)) receptor expression (P < 0.05) and slightly decreased tumor necrosis factor-alpha receptor 1 (TNFR1) expression (P = 0.063).

CONCLUSION

Corpora cavernosa from TNF-alpha-infused mice display increased contractile responses and decreased NANC nerve-mediated relaxation associated with decreased eNOS and nNOS gene expression. These changes may trigger ED and indicate that TNF-alpha plays a detrimental role in erectile function. Blockade of TNF-alpha actions may represent an alternative therapeutic approach for ED, especially in pathologic conditions associated with increased levels of this cytokine.

Plasma-Mediated Vascular Dysfunction in the Reduced Uterine Perfusion Pressure Model of Preeclampsia

Preeclampsia is associated with widespread maternal vascular dysfunction, which is thought to be mediated by circulating factor(s). The aim of the study was to characterize vascular function in the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia and to investigate the role of plasma factors in mediating any observed changes in vascular reactivity. Mean arterial blood pressure and vascular function were measured in RUPP and control rats. Mesenteric vessels from both virgin and pregnant rats were exposed for 1 hour or overnight to plasma from both RUPP and control rats and their vascular function assessed. RUPP rats were characterized by severe hypertension, restricted fetal growth, and reduced placental weight ( P <0.001). Vasorelaxation was impaired in resistance vessels from RUPP compared with control rats (acetylcholine: R max 70±3 versus 92±1 [NP] and 93±3% [sham], P <0.01; bradykinin: 40±2 versus 62±2 [NP] and 59±4% [sham], P <0.001). Incubation of vessels from pregnant (but not virgin) animals with RUPP plasma overnight resulted in an attenuation of vasorelaxant responses (acetylcholine: 63±7 versus 86±2%, P <0.05; bradykinin: 35±5 versus 55±6%, P <0.001). The residual relaxant response in RUPP plasma-treated vessels was not further attenuated after treatment with N ω -nitro- l -arginine methyl ester (acetylcholine: 57±7 versus 63±7%, ns; bradykinin: 37±5 versus 35±5%, ns). The RUPP rat model is characterized by an impaired response to vasodilators which may be attributable to one or more circulating factors. This plasma-mediated endothelial dysfunction appears to be a pregnancy-dependent effect. Furthermore, nitric oxide–mediated vasorelaxation appears to be absent in RUPP plasma-treated vessels.

Role of Reactive Oxygen Species in Tumor Necrosis Factor-alpha Induced Endothelial Dysfunction

Endothelial cell injury and dysfunction are the major triggers of pathophysiological processes leading to cardiovascular disease. Endothelial dysfunction (ED) has been implicated in atherosclerosis, hypertension, coronary artery disease, vascular complications of diabetes, chronic renal failure, insulin resistance and hypercholesterolemia. Although now recognized as a class of physiological second messengers, reactive oxygen species (ROS) are important mediators in cellular injury, specifically, as a factor in endothelial cell damage. Uncontrolled ROS production and/or decreased antioxidant activity results in a deleterious state referred to as 'oxidative stress'. A candidate factor in causing ROS production in endothelial cells is tumor necrosis factor alpha (TNF-α), a pleiotropic inflammatory cytokine. TNF-α has been shown to both be secreted by endothelial cells and to induce intracellular ROS formation. These observations provide a potential mechanism by which TNF-α may activate and injure endothelial cells resulting in ED. In this review, we focus on the relationship between intracellular ROS formation and ED in endothelial cells or blood vessels exposed to TNF-α to provide insight into the role of this important cytokine in cardiovascular disease.

TNF-alpha alters nitric oxide- and endothelium-derived hyperpolarizing factor-mediated vasodilatation in human omental arteries

OBJECTIVE

To investigate the effect of TNF-alpha on the endothelial function of human systemic arteries.

METHODS

Omental arteries were obtained from healthy pregnant women undergoing Cesarean section and examined using isometric wire myography.

RESULTS

Incubation with TNF-alpha (1nM) alone did not alter bradykinin-mediated endothelium-dependent relaxation of arteries. However, TNF-alpha did attenuate nitric oxide- (NO) and prostacyclin-independent endothelial-mediated relaxation. Similarly, in vessels constricted with a high potassium solution (60 mM), which inhibits vasodilatation via endothelial-derived hyperpolarising factor (EDHF), TNF-alpha incubation also attenuated bradykinin-induced vasodilatation.

CONCLUSIONS

The vasorelaxant capacity of human systemic arteries is compromised by TNF-alpha incubation in the presence of NO/prostacyclin or EDHF-blockade.

Inhibition of nitric oxide synthetase at mid-gestation in rats is associated with increases in arterial pressure, serum tumor necrosis factor-alpha, and placental apoptosis

BACKGROUND

Reduced uteroplacental perfusion and maternal cardiovascular dysfunction have been considered to be the main pathophysiological features of preeclampsia. In order to determine whether inhibition of nitric oxide synthetase (NOS) during the initial stage of placentation is associated with impaired placental development and maternal cardiovascular dysfunction, we studied the effect of N-nitro-arginine methyl ester (L-NAME), a NOS inhibitor, on morphological changes in the placenta, maternal blood pressure, and serum tumor necrosis factor-alpha (TNF-alpha) in pregnant rats during the initial stage of placentation.

METHODS

Pregnant Wister rats were treated during mid-gestation (days 8-14) with either L-NAME or saline. On day 20 of pregnancy the rats were killed, and maternal blood and placentas were extracted and examined.

RESULTS

In comparison with pregnant saline-treated control rats (blood pressure 119 +/- 9 mm Hg), pregnant rats treated with L-NAME displayed significant hypertension (blood pressure 178 +/- 7 mm Hg), which continued even after the withdrawal of L-NAME administration (P < 0.01). In L-NAME-treated pregnant rats, morphological examination showed decreased populations of placental trophoblast lineages, and a significant increase in placental trophoblast apoptosis. Serum TNF-alpha levels at day 20 of pregnancy were significantly higher in treated pregnant rats (21.2 +/- 9.6 pg/ml) than in control pregnant rats (3.3 +/- 2.8 pg/ml) (P < 0.01).

CONCLUSIONS

Inhibition of NOS at mid-gestation in pregnant rats is associated with increases in arterial pressure, placental apoptosis, and serum TNF-alpha, all of which have been implicated as being pathophysiological features of preeclampsia.

Role of sex steroids in modulating tumor necrosis factor alpha-induced changes in vascular function and blood pressure

BACKGROUND

We previously showed that the infusion of tumor necrosis factor alpha (TNF-alpha) induces hypertension and vascular dysfunction in late pregnant but not virgin rats. In the present study, we tested the hypothesis that levels of ovarian hormones to mimic pregnancy are required for TNF-alpha-induced changes in vascular function and blood pressure in rats.

METHODS

Twenty-one-day-release pellets containing 17beta-estradiol, progesterone, or both were implanted in ovariectomized (OVX) rats. Sham OVX rats were used as controls. Twelve days after implantation, TNF-alpha or vehicle was infused via osmotic minipumps (days 12 to 17). On day 18, mean arterial pressure was measured, and animals were sacrificed to assess vascular function.

RESULTS

Average estrogen and progesterone levels across all groups were 106 +/- 6 pg/mL and 88 +/- 5 ng/mL, respectively. The level of TNF-alpha was 41 +/- 7 pg/mL compared with OVX rats infused with vehicle (4 +/- 1 pg/mL). The results show that TNF-alpha did not cause elevated mean arterial pressure in OVX rats with increased estrogen, progesterone, or both. Vascular responses to the endothelium-dependent and independent agonists, acetylcholine and sodium nitroprusside, were also unchanged. Phenylephrine-induced contraction was moderately but significantly increased at the highest concentrations (10(-4) M) only in TNF-alpha-infused rats.

CONCLUSIONS

These data suggest that increased ovarian hormones to the levels observed during pregnancy are not sufficient to promote TNF-alpha-induced increases in blood pressure or vascular dysfunction.

Hypoxia and Reoxygenation: a Possible Mechanism for Placental Oxidative Stress in Preeclampsia

Preeclampsia is a human pregnancy-specific disorder that is diagnosed by the new appearance of hypertension and proteinuria after 20 weeks' gestation. It is a leading cause of perinatal morbidity and mortality, and the only intervention that effectively reverses the syndrome is delivery. Oxidative stress of the placenta is considered to be a key intermediary step in the pathogenesis of preeclampsia, but the cause for the stress remains unknown. Hypoxia-reoxygenation (H/R) injury, as a result of intermittent placental perfusion secondary to deficient trophoblast invasion of the endometrial arteries, is a possible mechanism. In this review, we present evidence to show that there is a plausible basis from which to assume that blood flow in the intervillous space will be intermittent in all normal pregnancies. The intermittency will be exacerbated by impaired conversion of the spiral arteries, or by the presence of atherotic changes that reduce their caliber as seen in preeclampsia. Placental oxidative stress can be the consequences of fluctuations in oxygen concentrations after H/R through the actions of reactive oxygen species. On this basis, there will be a complete spectrum of placental changes among the normal, the late onset and the early onset preeclamptic states. Viewing the syndrome as a continuum of H/R insults provides new insight into the pathophysiology of pregnancy that will hope fully lead to improved clinical interventions.

Hypertension produced by reductions in uterine perfusion in the pregnant rat: role of interleukin 6

The purpose of this study was to determine the role of interleukin (IL) 6 in mediating the increase in arterial pressure (AP) in response to chronic reductions in uterine perfusion pressure (RUPP) in pregnant rats. AP was higher in RUPP rats (138+/-1 mm Hg) than in normal pregnant (NP) rats (104+/-1 mm Hg). Serum IL-6 levels in the RUPP rats were 104.5+/-28.6 pg/mL as compared with 36.6+/-7.4 pg/mL in NP rats. To determine the long-term effects of a 2- to 3-fold elevation in plasma IL-6 on renal function and AP in pregnant rats, we infused IL-6 for 5 days (2.5 ng/day) in NP rats starting at day 14 of gestation. Five days later, serum IL-6 levels were 55.5+/-6.5 pg/mL in the control NP rats and 157.0+/-36.1 pg/mL in the IL-6-treated NP rats. AP was higher in the IL-6-treated NP rats (115+/-3 mm Hg) as compared with NP controls (101+/-1 mm Hg) at day 19 of gestation. Renal plasma flow and GFR were lower in the IL-6-treated NP rats than in the NP group. IL-6 increased plasma renin activity but did not affect endothelin in IL-6-treated NP rats. In contrast to the NP rats, IL-6 had no effect on AP or renal hemodynamics in virgin rats. In summary, these data indicate that plasma IL-6 is elevated in response to chronic reductions in uterine perfusion in pregnant rats and that a comparable elevation in plasma IL-6 increases AP and reduces renal function in pregnant rats.

Perioperative myocardial infarction in non-cardiac surgery. Pathophysiology and clinical implications

Advances in surgical and anaesthetic techniques and an aging patient population have resulted in more complex procedures being performed in greater numbers of aged subjects and in patients with a high likelihood of significant cardiovascular disease. Nearly one fourth of non-cardiac surgical procedures (major intra-abdominal, thoracic, vascular, and orthopaedic procedures) performed in persons older than 65 years have been found to be associated with significant perioperative cardiovascular morbidity and mortality. During previous years the main attempt was to define strategies to accurately estimate perioperative cardiovascular risk based either on the characteristics of surgery and on patient characteristics. More recently preventive medical strategies have been proposed. Therefore, the physician has to be aware of the key elements useful to calculate the perioperative cardiovascular risk, and of the medical preventive treatment or further interventions to adopt in patients candidate to surgery.

Paracrine role for periadventitial adipose tissue in the regulation of arterial tone

Recent studies propose a paracrine role for periadventitial adipose tissue in the regulation of vascular tone. This regulation depends on the anatomical integrity of the periadventitial adipose tissue and involves adipocyte-derived relaxing factor (ADRF). Although the nature of ADRF is largely unknown, it is released by periadventitial adipocytes and induces vasorelaxation by opening K+ channels in the plasma membrane of smooth muscle cells. Alterations in the paracrine role of periadventitial adipose tissue might have a role in vascular dysfunction in hypertension and metabolic disease. Therefore, understanding alterations in ADRF release and the K+ channels involved will help further our understanding of the increased cardiovascular risk and development of chronic vascular disease in obesity. Furthermore, ADRF and perhaps its putative targets might represent exciting new targets for the development of drugs to treat cardiovascular disorders.

Animal models of preeclampsia

There have been many attempts to produce animal models that mimic the hypertensive disorders of pregnancy, especially preeclampsia, but most are incomplete when compared to the full spectrum of the human disease. This review assesses a number of these models, organized according to the investigators attempt to focus on a specific pathogenic mechanism believed to play a role in the human disease. These mechanisms include uterine ischemia, impairments in the nitric oxide system, insulin resistance, overactivity of the autonomic nervous and/or renin-angiotensin systems, activation of a systemic inflammatory response, and most recently, activation of circulating proteins that interfere with angiogenesis. In addition a model of renal disease that mimics superimposed preeclampsia is discussed. Defining these animal models should help in our quest to understand the cause, as well as to test preventative and therapeutic strategies in the management of these hypertensive disorders of pregnancy.