Introgression of Brown Norway \u3cem\u3eCYP4A\u3c/em\u3e Genes onto the Dahl Salt-Sensitive Background Restores Vascular Function in SS-5\u3csup\u3eBN\u3c/sup\u3e Consomic Rats

The present study tested the hypothesis that the Dahl SS (salt-sensitive) rat has vascular dysfunction due, in part, to the up-regulation of the CYP4A/20-HETE (cytochrome P450 ω-hydroxylase 4A)/20-hydroxyeicosatetraenoic acid) system. To assess the role of vascular 20-HETE, SS rats were compared with SS-5BN consomic rats, carrying CYP4A alleles on chromosome 5 from the normotensive BN (Brown Norway) introgressed on to the SS genetic background. Cerebral arteries from SS-5BN rats had less CYP4A protein than arteries from SS rats fed either NS (normal-salt, 0.4% NaCl) or HS (high-salt, 4.0% NaCl) diet. ACh (acetylcholine)-induced dilation of MCAs (middle cerebral arteries) from SS and SS-5BN rats was present in SS-5BN rats fed on either an NS or HS diet, but absent in SS rats. In SS rats fed on either diet, ACh-induced dilation was restored by acute treatment with the CYP4A inhibitor DDMS (N-methyl-sulfonyl-12,12-dibromododec-11-enamide) or the 20-HETE antagonist 20-HEDE [20-hydroxyeicosa-6(Z),15(Z)-dienoic acid]. The restored response to ACh in DDMS-treated SS rats was inhibited by L-NAME (NGnitro-L-arginine methyl ester) and unaffected by indomethacin or MS-PPOH [N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide]. Vascular relaxation responses to the NO donor C5FeN6Na2O were intact in both SS and SS-5BN rats and unaffected by the acute addition of DDMS, indicating that the vascular dysfunction of the SS rat is due to a reduced bioavailability of NO instead of failure of the VSMCs (vascular smooth muscle cells) to respond to the vasodilator. Superoxide levels in cerebral arteries of SS-5BN rats [evaluated semi-quantitatively by DHE (dihydroethidium) fluorescence] were lower than those in the arteries of SS rats. These findings indicate that SS rats have an up-regulation of the CYP4A/20-HETE pathway resulting in elevated ROS (reactive oxygen species) and reduced NO bioavailability causing vascular dysfunction

Interactions of Nitric Oxide and Superoxide Pathways in Hyperglycemic Endothelial Cells

Cardiovascular complications arising from diabetic hyperglycemia represents one of the leading causes of death and greatest public health challenges of modern societies. Despite state-of-the-art glucose control, diabetic patients remain at a markedly increased risk of cardiovascular disease. The loss of endothelial function (the development of diabetic endothelial dysfunction) has been implicated in the development of numerous diabetic cardiovascular diseases. The endothelial cell produces many vasoactive substances, hormones and cytoprotective biological factors. Endothelial cells are also involved in and affected by the initiation of inflammatory responses through the release and interaction of cytokines and other immune system molecules. Therefore, regulation of these signaling molecules is extremely important to the health of the vascular endothelium and, consequently, damage to the cells ability to control vessel tone and inflammation is a known hallmark to numerous cardiovascular diseases. Much of recent research attention is directed towards the loss of the ability of the diabetic vasculature to produce nitric oxide (vasodilator and anti-inflammatory hormone, a key component of vascular homeostasis). The observation that endothelial cells in diabetes fail to produce sufficient amount of nitric oxide and fail to relax in response to the endothelium-dependent vasorelaxants (e.g. acetylcholine, bradykinin, shear stress, etc.) has been documented by multiple studies, both in animal models of the disease and in human studies. In this dissertation, we investigated the molecular and enzymatic mechanisms associated with the loss of nitric oxide bioavailability and increase in oxidant formation using a hyperglycemic human umbilical vein endothelial cell model. Our results indicate that while hyperglycemia decreases overall nitric oxide levels, generation of nitric oxide is paradoxically increased, validating previous modeling data published by our lab. Furthermore, we were able to indirectly confirm this concomitant increase in superoxide and nitric oxide by showing a significant increase in the formation of nitrotyrosine in high glucose exposed endothelial cells. This illustrates that the parallel increase in superoxide and nitric oxide lead to increased reaction with one another, resulting in higher levels of the cytotoxic peroxynitrite molecule. To better understand the effects of angiotensin II and high glucose on gene regulation of oxidant generating enzymes involved in oxidative and nitrosative stress pathways, we performed real-time quantitative PCR for NADPH oxidase subunits and nitric oxide synthase isoforms in HUVEC\u27s. Results from our studies show that stimulating effects of angiotensin II on the activity of endothelial cell NADPH oxidases is enhanced in high-glucose exposed HUVEC\u27s. We also show that hyperglycemic endothelial cells are more sensitive to Ang II interaction, resulting in lower levels of nitric oxide bioavailability and increased nitrotyrosine formation. Our results also provide insight into the gene regulation of NADPH oxidase, eNOS and iNOS. Data shows that angiotensin II increases NADPH oxidase and iNOS mRNA levels in high-glucose exposed HUVECs, while eNOS expression is relatively unchanged. This further validates the hypothesis that high glucose initiates a protective response in endothelial cells by upregulating nitric oxide producing enzymes, iNOS, in an attempt to counteract/scavenge the increased production of superoxide by NADPH oxidase. This protective measure only exacerbates the oxidative and nitrosative stress environment of the cell, leading to increased cell damage and/or apoptosis. Studies in this dissertation will help clarify the molecular mechanisms and interactions involved in hyperglycemia induced oxidative and nitrosative stress, providing improved focus for treatment design towards improving/reversing high glucose induced endothelial cell dysfunction

Bothrops jararaca Peptide with Anti-Hypertensive Action Normalizes Endothelium Dysfunction Involved in Physiopathology of Preeclampsia

Preeclampsia, a pregnancy-specific syndrome characterized by hypertension, proteinuria and edema, is a major cause of fetal and maternal morbidity and mortality especially in developing countries. Bj-PRO-10c, a proline-rich peptide isolated from Bothrops jararaca venom, has been attributed with potent anti-hypertensive effects. Recently, we have shown that Bj-PRO-10c-induced anti-hypertensive actions involved NO production in spontaneous hypertensive rats. Using in vitro studies we now show that Bj-PRO-10c was able to increase NO production in human umbilical vein endothelial cells from hypertensive pregnant women (HUVEC-PE) to levels observed in HUVEC of normotensive women. Moreover, in the presence of the peptide, eNOS expression as well as argininosuccinate synthase activity, the key rate-limiting enzyme of the citrulline-NO cycle, were enhanced. In addition, excessive superoxide production due to NO deficiency, one of the major deleterious effects of the disease, was inhibited by Bj-PRO-10c. Bj-PRO-10c induced intracellular calcium fluxes in both, HUVEC-PE and HUVEC, which, however, led to activation of eNOS expression only in HUVEC-PE. Since Bj-PRO-10c promoted biological effects in HUVEC from patients suffering from the disorder and not in normotensive pregnant women, we hypothesize that Bj-PRO-10c induces its anti-hypertensive effect in mothers with preeclampsia. Such properties may initiate the development of novel therapeutics for treating preeclampsia

Bothrops jararaca Peptide with Anti-Hypertensive Action Normalizes Endothelium Dysfunction Involved in Physiopathology of Preeclampsia

Preeclampsia, a pregnancy-specific syndrome characterized by hypertension, proteinuria and edema, is a major cause of fetal and maternal morbidity and mortality especially in developing countries. Bj-PRO-10c, a proline-rich peptide isolated from Bothrops jararaca venom, has been attributed with potent anti-hypertensive effects. Recently, we have shown that Bj-PRO-10c-induced anti-hypertensive actions involved NO production in spontaneous hypertensive rats. Using in vitro studies we now show that Bj-PRO-10c was able to increase NO production in human umbilical vein endothelial cells from hypertensive pregnant women (HUVEC-PE) to levels observed in HUVEC of normotensive women. Moreover, in the presence of the peptide, eNOS expression as well as argininosuccinate synthase activity, the key rate-limiting enzyme of the citrulline-NO cycle, were enhanced. In addition, excessive superoxide production due to NO deficiency, one of the major deleterious effects of the disease, was inhibited by Bj-PRO-10c. Bj-PRO-10c induced intracellular calcium fluxes in both, HUVEC-PE and HUVEC, which, however, led to activation of eNOS expression only in HUVEC-PE. Since Bj-PRO-10c promoted biological effects in HUVEC from patients suffering from the disorder and not in normotensive pregnant women, we hypothesize that Bj-PRO-10c induces its anti-hypertensive effect in mothers with preeclampsia. Such properties may initiate the development of novel therapeutics for treating preeclampsia

eNOS Protects from Atherosclerosis Despite Relevant Superoxide Production by the Enzyme in apoE−/− Mice

All three nitric oxide synthase (NOS) isoforms are expressed in atherosclerotic plaques. NOS enzymes in general catalyse NO production. However, under conditions of substrate and cofactor deficiency, the enzyme directly catalyse superoxide formation. Considering this alternative chemistry, the effects of NOS on key events in spontaneous hyperlipidemia driven atherosclerosis have not been investigated yet. Here, we evaluate how endothelial nitric oxide synthase (eNOS) modulates leukocyte/endothelial- (L/E) and platelet/endothelial- (P/E) interactions in atherosclerosis and the production of nitric oxide (NO) and superoxide by the enzyme. Intravital microscopy (IVM) of carotid arteries revealed significantly increased L/E-interactions in apolipoproteinE/eNOS double knockout mice (apoE(-/-)/eNOS(-/-)), while P/E-interactions did not differ, compared to apoE(-/-). eNOS deficiency increased macrophage infiltration in carotid arteries and vascular cell adhesion molecule-1 (VCAM-1) expression, both in endothelial and smooth muscle cells. Despite the expression of other NOS isoforms (inducible NOS, iNOS and neuronal NOS, nNOS) in plaques, Electron Spin Resonance (ESR) measurements of NO showed significant contribution of eNOS to total circulating and vascular wall NO production. Pharmacological inhibition and genetic deletion of eNOS reduced vascular superoxide production, indicating uncoupling of the enzyme in apoE(-/-) vessels. Overt plaque formation, increased vascular inflammation and L/E- interactions are associated with significant reduction of superoxide production in apoE(-/-)/eNOS(-/-) vessels. Therefore, lack of eNOS does not cause an automatic increase in oxidative stress. Uncoupling of eNOS occurs in apoE(-/-) atherosclerosis but does not negate the enzyme's strong protective effects

Cardio-protective effects of pentraxin 3 produced from bone marrow-derived cells against ischemia/reperfusion injury

AbstractBackgroundInflammation is one of major mechanisms contributing to the pathogenesis of myocardial ischemia/reperfusion (I/R) injury. Pentraxin 3 (PTX3), produced in response to inflammatory signals, acts as a humoral arm of the innate immunity. Here we investigated the role of PTX3 produced from bone marrow-derived cells in myocardial I/R injury using PTX3-deficient (PTX3KO) mice.Methods and resultsPTX3KO mice and wild-type littermate (WT) mice were lethally irradiated and injected with bone marrow (BM) cells, generating four types of mice (WTWT-BM, WTPTX3KO-BM, PTX3KOWT-BM and PTX3KOPTX3KO-BM). Six weeks after BM transplantation, the myocardial I/R procedure (45min of left descending coronary artery ligation followed by 48h of reperfusion) was performed. Infarct size was greater in WT and PTX3KO mice with BM from PTX3KO donor (WTPTX3KO-BM and PTX3KOPTX3KO-BM) compared with WT and PTX3KO mice with BM from WT donor (WTWT-BM and PTX3KOWT-BM). Localization of PTX3 was observed in neutrophils and macrophages in WT and PTX3KO mice with BM from WT donor (WTWT-BM and PTX3KOWT-BM), while only in endothelial cells in WT mice with BM from PTX3KO donor (WTPTX3KO-BM). Infiltration of neutrophils and generation of reactive oxygen species (ROS) at ischemic border zones were greater in PTX3KO mice with BM from PTX3KO donor (PTX3KOPTX3KO-BM) than PTX3KO mice with BM from WT donor (PTX3KOWT-BM). Plasma levels and cardiac expressions of interleukin-6 were higher in PTX3KO mice with BM from PTX3KO donor (PTX3KOPTX3KO-BM) than PTX3KO mice with BM from WT donor (PTX3KOWT-BM). However, no significant differences in infarct size, infiltration of neutrophils, generation of ROS and plasma and cardiac levels of interleukin-6 were observed between WT and PTX3KO mice with BM from WT donor and between WT and PTX3KO mice with BM from PTX3KO donor. These results indicated that the lack of PTX3 produced from BM-derived cells, and not from cardiac resident cells, exacerbated myocardial injury after I/R.ConclusionPTX3 produced from bone marrow-derived cells plays a crucial role in cardiac protection against myocardial I/R injury by attenuating infiltration of neutrophils, generation of ROS and inflammatory cytokine

Effect of antioxidants on the oxidation of low density lipoprotein at lysosomal pH

Oxidised forms of low-densitylipoprotein (LDL) are widely belived to beinvolved in the pathogenesis of atherogenesis,but large clinical trials have not shown protectionof cardiovascular diseaseby antioxidants. Recently, it has been shownthat LDL can be oxidised by iron in the lysosomes of macrophages. We hypothesised that antioxidants would protect LDL against oxidation less well at lysosomal pH than at pH 7.4.LDL was enriched with α-tocopherol by incubating plasma with α-tocopherol and isolating the LDL. This enrichment inhibited LDL oxidation by copper ions (Cu2+) at pH 7.4,but not at pH4.5, as shown by spectrophotometry at 234 nm to measure conjugated dienes and by HPLC to measure individual oxidised lipids. α-Tocopherol enrichment did not inhibit LDL oxidation by Fe3+ (2, 5 or 20 μM) at pH4.5 ,but inhibiteitby 5 or 20 μM Fe2+,but not 2 μM Fe2+. This might help to explain whyα-tocopherol did not inhibit cardiovascular diseases inthe large clinical trials. The antioxidant tempol and probucol inhibited the late phase of LDL oxidation by Fe2+and Cu2+at pH 4.5 more than the early phase, possibly because they were located mainly in the phospholipid monolayer of LDL, rather than in the cholesteryl ester of the LDL particle. There is a suggestion that lysosomal dysfunction plays an important role in atherosclerosis. Thelysosomal oxidation of LDL aggregated by sphingomelinaseresulted in the production of the advanced lipid peroxidation product (ceroid).α-Tocopherol enrichment of macrophagesdid notprotectthem against apoptosis induced by H2O2.The work presented here also demonstrated LDL oxidisedFe2+at pH 4.5, decreasedendothelium-dependent vasodilatationof rat aortic rings. This suggests that VIlysosomallyoxidised LDL released from dead cells in atherosclerotic lesionsmight damage the endothelium.Takentogather,these results suggest that inhibiting the oxidation of LDLin lysosomes might be a therapy of atherosclerosis

Role of the T cell in the genesis of angiotensin II–induced hypertension and vascular dysfunction

Hypertension promotes atherosclerosis and is a major source of morbidity and mortality. We show that mice lacking T and B cells (RAG-1−/− mice) have blunted hypertension and do not develop abnormalities of vascular function during angiotensin II infusion or desoxycorticosterone acetate (DOCA)–salt. Adoptive transfer of T, but not B, cells restored these abnormalities. Angiotensin II is known to stimulate reactive oxygen species production via the nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase in several cells, including some immune cells. Accordingly, adoptive transfer of T cells lacking the angiotensin type I receptor or a functional NADPH oxidase resulted in blunted angiotensin II–dependent hypertension and decreased aortic superoxide production. Angiotensin II increased T cell markers of activation and tissue homing in wild-type, but not NADPH oxidase–deficient, mice. Angiotensin II markedly increased T cells in the perivascular adipose tissue (periadventitial fat) and, to a lesser extent the adventitia. These cells expressed high levels of CC chemokine receptor 5 and were commonly double negative (CD3+CD4−CD8−). This infiltration was associated with an increase in intercellular adhesion molecule-1 and RANTES in the aorta. Hypertension also increased T lymphocyte production of tumor necrosis factor (TNF) α, and treatment with the TNFα antagonist etanercept prevented the hypertension and increase in vascular superoxide caused by angiotensin II. These studies identify a previously undefined role for T cells in the genesis of hypertension and support a role of inflammation in the basis of this prevalent disease. T cells might represent a novel therapeutic target for the treatment of high blood pressure

Interleukin-6 counteracts therapy-induced cellular oxidative stress in multiple myeloma by up-regulating manganese superoxide dismutase

IL (interleukin)-6, an established growth factor for multiple myeloma cells, induces myeloma therapy resistance, but the resistance mechanisms remain unclear. The present study determines the role of IL-6 in re-establishing intracellular redox homoeostasis in the context of myeloma therapy. IL-6 treatment increased myeloma cell resistance to agents that induce oxidative stress, including IR (ionizing radiation) and Dex (dexamethasone). Relative to IR alone, myeloma cells treated with IL-6 plus IR demonstrated reduced annexin/propidium iodide staining, caspase 3 activation, PARP [poly(ADP-ribose) polymerase] cleavage and mitochondrial membrane depolarization with increased clonogenic survival. IL-6 combined with IR or Dex increased early intracellular pro-oxidant levels that were causally related to activation of NF-κB (nuclear factor κB) as determined by the ability of N-acetylcysteine to suppress both pro-oxidant levels and NF-κB activation. In myeloma cells, upon combination with hydrogen peroxide treatment, relative to TNF (tumour necrosis factor)-α, IL-6 induced an early perturbation in reduced glutathione level and increased NF-κB-dependent MnSOD (manganese superoxide dismutase) expression. Furthermore, knockdown of MnSOD suppressed the IL-6-induced myeloma cell resistance to radiation. MitoSOX Red staining showed that IL-6 treatment attenuated late mitochondrial oxidant production in irradiated myeloma cells. The present study provides evidence that increases in MnSOD expression mediate IL-6-induced resistance to Dex and radiation in myeloma cells. The results of the present study indicate that inhibition of antioxidant pathways could enhance myeloma cell responses to radiotherapy and/or chemotherapy