Stimulation Of Nitric Oxide Production Research Articles

Immunoglobulins G modulate endothelial function and affect insulin sensitivity in humans

Background and aimsData from animals suggest that immunoglobulins G (IgG) play a mechanistic role in atherosclerosis and diabetes through endothelial dysfunction and insulin resistance. Patients with common variable immunodeficiency (CVID), who have low circulating levels of IgG and are treated with intravenous polyclonal IgG (IVIgG), may provide an ideal model to clarify whether circulating IgG modulate endothelial function and affect insulin sensitivity in humans. Methods and resultsWe studied 24 patients with CVID and 17 matched healthy controls (HC). Endothelial function was evaluated as flow mediated dilation (FMD) of the brachial artery at baseline and 1, 7, 14, and 21 days after IVIgG infusion in the CVID patients. We measured also plasma glucose, insulin, and calculated the HOMA-IR index. We also investigated the role of human IgG on the production of Nitric Oxide (NO) in vitro in Human Coronary Artery Endothelial Cells (HCAEC).Compared to HC, FMD of CVID patients was significantly impaired at baseline (9.4 ± 0.9 and 7.6 ± 0.6% respectively, p < 0.05) but rose above normal levels 1 and 7 days after IVIgG infusion to return at baseline at 14 and 21 days. Serum insulin concentration and HOMA-IR index dropped by 50% in CVID patients after IVIgG (p < 0.002 vs. baseline). In vitro IgG stimulated NO production in HCAEC. ConclusionsReduced IgG levels are associated with endothelial dysfunction and IVIgG stimulates endothelial function directly while improving insulin sensitivity. The current findings may suggest an anti-atherogenic role of human IgG.

Enterococcus faecalis and Staphylococcus aureus stimulate nitric oxide production in macrophages and fibroblasts in vitro

Aim: Nitric oxide (NO) is an important mediator related to damage of the pulp tissue and at the same time to regenerative pulp processes. However, it is not clear how common endodontic microorganisms can regulate this mediator. This study aimed to investigate NO production by macrophages and fibroblasts against Enterococcus faecalis- and Staphylococcus aureus-antigens. Methods: RAW 264.7 macrophages and L929 fibroblast cell lines were stimulated with different heat-killed (HK) antigen concentrations (105-108 colony forming units - CFU) from E. faecalis and S. aureus with or without interferon-gamma (IFN-γ). Cell viability by MTT colorimetric assay and NO production from the culture supernatants were evaluated after 72 h. Results: Data here reported demonstrated that none of the antigen concentrations decreased cell viability in macrophages and fibroblasts. The presence of HK-S. aureus and HK-E. faecalis antigen- stimulated NO production with or without IFN-γ on RAW 264.7. The HK-S. aureus antigen stimulated NO production in L929 fibroblasts with or without IFN-γ, and the highest concentration of HK-E. faecalis with IFN-γ also stimulated NO production by these cells. Conclusion: The amount of NO produced by macrophages and fibroblasts may be involved in the concentration and type of prevalent endodontic microorganisms, generating new answers for the understanding of pulpal revascularization/regeneration processes.

The contributions of hydroxylamine and nitrite to NO and N2O production in alkaline and acidic vegetable soils

The contribution of hydroxylamine (NH2OH) and nitrite (NO2−) to nitric oxide (NO) and nitrous oxide (N2O) production remains unclear in vegetable production soils. Soils collected from six typical greenhouse vegetable fields were incubated for 48 h following amendment with 1 mM NaNO2, 10 μM NH2OH, or 1 mM NaNO2 + 10 μM NH2OH. The importance of abiotic processes on the NO and N2O formation from the NH2OH and NO2− were studied by irradiating the soil samples with γ-irradiation. NO2− amendment significantly stimulated NO production, while the NH2OH-dependent NO production was minimal. NH2OH stimulated more abiotic N2O production in alkaline soils than in acidic soils (p < 0.05), while NO2− stimulated more biotic N2O production in acidic soils than in alkaline soils (p < 0.05). The NH2OH- and NO2−-dependent sources produced biotic or abiotic N2O with site preference (SP) values of 27.4–36.5‰, which is similar to those from ammonia-oxidizing archaea (AOA) or ammonia-oxidizing bacteria (AOB) sources (25.1–34.2‰), indicating that abiotic N2O production were closely linked with biotic NH3 oxidation. The variability of NO2−+NH2OH-induced N2O production can be explained by the soil organic carbon and iron concentrations, whereas NO2−-induced NO production can be explained by the soil pH. NO2− addition dominated NO production in all soils. Furthermore, NO2− addition increased biotic N2O production in acidic soils, while NH2OH addition increased abiotic N2O production in alkaline soils. The presence of NO2− could significantly stimulate the abiotic conversion of NH2OH to N2O in soils with low soil organic carbon and high iron concentrations. Thus, assessing the abundance of NH2OH and NO2− could provide crucial information for understanding NO and N2O production procedures in vegetable soils. • The chemical decomposition of NO2− dominated NO production in all soils. • The NH2OH stimulated abiotic N2O production in alkaline soils. • The NO2− stimulated biotic N2O production in acidic soils. • The SP for abiotic NO2−-/NH2OH-related N2O were in the same range as AOB/AOA sources.

Echinacoside‑induced nitric oxide production in endothelial�cells: Roles of androgen receptor and the PI3K‑Akt pathway

Echinacoside (ECH) is a natural compound with an endothelium‑dependent vasodilatory effect. Nitric oxide (NO) is an important vasorelaxant released from endothelial cells. In order to examine the molecular mechanism of ECH‑induced NO production in endothelial cells, the present study investigated the involvement of androgen receptor (AR) and the phosphatidylinositol 3‑kinase (PI3K)/protein kinaseB (Akt) pathway in the phosphorylation of endothelial nitric oxide synthase (eNOS) in human umbilical vein endothelial cells (HUVECs). Using the fluorescent probe DAF‑FM, the production of NO was found to be significantly increased, and eNOS was phosphorylated at Ser1177 in a concentration‑​dependent manner under 0.01‑10µM ECH treatment in HUVECs. In addition, NO production and eNOS phosphorylation induced by ECH were diminished when pretreated with the AR antagonist nilutamide, or when transfected with AR small interfering RNAs. Furthermore, the ECH‑induced phosphorylation of the Akt at Ser473 was abrogated by 5µM wortmannin (a PI3K inhibitor). These data indicated that ECH stimulated NO production via the AR‑dependent activation of eNOS in HUVECs, and that the PI3K/Akt pathway may be involved in eNOS phosphorylation induced by ECH.

Induction of nitric oxide synthesis: a strategy to defend against high environmental ammonia-induced oxidative stress in primary hepatocytes of air-breathing catfish, Clarias magur.

Air-breathing magur catfish (Clarias magur) regularly face the problem of exposure to high environmental ammonia (HEA) as one of the major pollutants in their natural habitats that causes considerable toxic effects at the cellular level, including that of oxidative stress. The major objective of the present study was to demonstrate the antioxidant activity of endogenously produced nitric oxide (NO) to defend against ammonia-induced oxidative stress in primary hepatocytes of magur catfish during exposure to HEA. Exposure to NH4Cl (5 mmol l-1) led to a significant increase in intracellular ammonia concentration with a sharp rise of hydrogen peroxide (H2O2) and malondialdehyde (MDA) concentrations within 3 h in primary hepatocytes, which decreased gradually at later stages of treatment. This phenomenon was accompanied by a significant increase in superoxide dismutase (SOD) and catalase (CAT) activity as a consequence of induction of corresponding genes. HEA exposure also led to the stimulation of NO production due to induction of inducible nitric oxide synthase (iNOS) activity, as a consequence of up-regulation of the nos2 gene. Most interestingly, when NO production by hepatocytes under ammonia stress was blocked by adding certain inhibitors [aminoguanidine and 3-(4-methylphenylsulfonyl)-2-propenenitrile] to the culture medium, there was a further rise of H2O2 and MDA concentrations in hepatocytes. These were accompanied by the lowering of SOD and CAT activity with less expression of corresponding genes. Thus, it can be contemplated that magur catfish use the strategy of stimulation of NO production, which ultimately induces the SOD-CAT enzyme system to defend against ammonia-induced oxidative stress.

How can nitric oxide help osteogenesis?

Nitric oxide (NO) is endogenously produced free radical that plays important biological roles, such as, the promotion of vasodilation, angiogenesis, tissue repair, wound healing process, antioxidant, antitumoral and antimicrobial actions. Although the regenerative effects of NO in soft tissues have been extensively reported, its role in bone tissue repair has not been completely addressed. Both constitutive and inducible forms of NO synthase (NOS) are expressed in bone-derived cells, and some important cytokines, such as IL-1 and TNF, are potent stimulators of NO production. The effects of NO on bone tissue are dependent on its concentration. NO has dichotomous biological effects, at low concentrations (pico-nano molar range), NO may promote proliferation, differentiation and survival of osteoblasts, whereas at high concentrations (micromolar range) NO may inhibit bone resorption and formation. Therefore, at a certain concentration range, NO can avoid osteoclast-mediated bone resorption and promote osteoblast growth. Due to the potential beneficial effects of NO in bone tissue regeneration, the exogenous administration of NO might find important biomedical applications. As NO is a free radical and a gas, the administration of NO donors/generators has been explored in tissue repair. The delivery of NO to the bone using macromolecular NO releasing scaffolds has been shown to increase osteogenesis with a relevant impact in dental and orthopedist areas. In this sense, this review presents and discusses the recent and important progresses in the effects of NO/NO donors in bone tissue, and highlights the promising approach in the design and use of NO donors allied to biomaterials in the sustained and localized NO release for bone tissue regeneration.

Expression and function of the stromal cell-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) in the swine ovarian follicle

The most characterized stromal cell-derived factor-1 (SDF-1) variants are the isoform α, which is the predominant one but undergoes rapid proteolysis, and the β isoform, which is more resistant. Through the interaction with a specific chemokine receptor called CXCR4, SDF-1 is able to regulate different physiological processes. The aim of this study was to verify the expression and potential functional role of SDF-1 and CXCR4 in the porcine ovary. Firstly, the expression of SDF-1 and its receptor in different ovarian districts was verified for the first time. Thereafter, the effect of SDF-1 β isoform (51–72) fragment on functional parameters, such as proliferation, metabolic activity, redox status, nitric oxide production, and steroidogenic activity, was assessed on granulosa cells collected from follicles. In addition, the potential effect of this protein in vascular events was verified through investigations on porcine aortic (AOC) endothelial cells, such as the production of nitric oxide and viability tests. The proliferation and metabolic activity were not affected by treatment with the cytokine. As regard to steroidogenesis, the peptide stimulated both estrogen (P = 0.049) and progesterone production (P = 0.039). Redox status was affected by the examined substance since superoxide anion was inhibited (P = 0.001), while antioxidant power (P = 0.034), as well as nitric oxide generation, were stimulated (P = 0.034). Tests performed on AOCs showed significant stimulation of nitric oxide production (P = 0.004) by the examined peptide, while cell viability was unaffected. Therefore, the potential role of cytokine in the mechanisms involved in the regulation of follicular function can be hypothesized.

Prepubertal overexposure to manganese induce precocious puberty through GABAA receptor/nitric oxide pathway in immature female rats

Gamma-aminobutyric acid (GABA) plays a critical role in regulation of gonadotropin-releasing hormone (GnRH) through GABAA receptor (GABAAR). Nitric oxide (NO) production has correlation with GABA and regulates GnRH secretion. This study was performed to examine the mechanisms by which manganese (Mn) accelerate puberty onset involves GABAAR/NO pathway in the preoptic area-anterior hypothalamus (POA-AH) in immature female rats. First, female rats received daily dose of MnCl2 0 (saline), 2.5, 5 and 10 mg/kg b.w by oral gavage during postnatal day (PND) 21–32. Animals administered with 10 mg/kg MnCl2 exhibited earlier puberty onset age and advanced ovary and uterus development than these in saline-treatment group. Furthermore, we found that decrease of GABAAR result in elevated production of nitric oxide synthase1 (NOS1), NO and GnRH in the POA-AH. Second, we recorded the neuronal spikes alternation after perfusion with GABAAR inhibitor bicuculline (BIC), GABAAR agonist isoguvacine (isog), and MnCl2 from the POA-AH in acute brain slices of PND21 rats. Spontaneous firing revealed a powerful GABAAR-mediated action on immature POA-AH and confirm that MnCl2 has a significant effect on GABAAR. Third, we revealed that decrease in NOS1 and NO production by treatment with isog-alone or isog+MnCl2 contribute to the decrease of GnRH in the POA-AH and a delayed puberty onset age compared to treatment with MnCl2-alone. Together, these results suggested that excessive exposure to MnCl2 stimulates NO production through decreased GABAAR in the POA-AH to advance puberty onset in immature female rats.

An osteogenic helioxanthin derivative suppresses the formation of bone-resorbing osteoclasts.

ObjectiveThe helioxanthin derivative 4-(4-methoxyphenyl)thieno[2,3-b:5,4-c′]dipyridine-2-carboxamide (TH) is a low-molecular-weight compound that was identified through screening for osteogenic compounds that enhance the activity of mouse preosteoblastic MC3T3-E1 cells. In the present study, we found that TH suppressed osteoclast differentiation.MethodsUsing the hematopoietic stem cells of ddY mice, TH was added to the culture in the experimental group, and the number of osteoclasts was measured with rhodamine phalloidin staining and TRAP staining. In osteo assay, bone resorption area was compared by the von Kossa staining.ResultsSpecifically, TH inhibited the cyclic guanosine monophosphate (cGMP)-degrading activity of phosphodiesterase (PDE), promoted nitric oxide (NO) production, and dose-dependently suppressed osteoclast differentiation in an osteoclast formation culture of mouse bone marrow cells. The NO-competitive guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) attenuated the suppressive activity of TH on osteoclast differentiation. Conclusion: Given the previously reported suppressive action of cGMP on osteoclastogenesis, our data suggest that TH negatively impacts osteoclast differentiation at least to some extent by stimulating NO production and inhibiting PDE activity, both of which lead to the upregulation of intracellular cGMP. This study supports the potential use of TH as a novel antiosteoporotic reagent that not only stimulates bone formation but also inhibits bone resorption.

Prevention of Osteoporosis in the Ovariectomized Rat by Oral Administration of a Nutraceutical Combination That Stimulates Nitric Oxide Production.

Osteoporosis represents an imbalance between bone formation and bone resorption. As a result of low estrogen levels, it is markedly prevalent during menopause, thus making such patients susceptible to fractures. Both bone formation and resorption are modulated by nitric oxide (NO). Currently, there are no risk-free pharmaceutical prevention therapies for osteoporosis. COMB-4, a nutraceutical combination of Paullinia cupana, Muira puama, ginger, and L-citrulline, known to activate the NO-cGMP pathway, was reported to accelerate fracture healing in the rat. To determine whether COMB-4 could be effective in preventing menopausal osteoporosis, it was compared to estradiol (E2) in an ovariectomized (OVX) rat osteoporosis model. Nine-month-old female Sprague Dawley rats were divided into SHAM, OVX, OVX+E2, and OVX+COMB-4. After 100 days of treatment, bone mineral density (BMD) and bone mineral content (BMC) were measured by DXA scan. TRAP staining was performed in the femur and lumbar vertebrae. TRACP 5b and osteocalcin levels were assayed in the serum. MC3T3-E1 cells were differentiated into osteoblasts and treated with COMB-4 for one week in order to evaluate calcium deposition by Alizarin staining, cGMP production by ELISA, and upregulation of the nitric oxide synthase (NOS) enzymes by RT-PCR. OVX resulted in a decrease in BMD, BMC, and serum osteocalcin and an increase in serum TRACP 5b. Except for an increase in BMC with COMB-4, both E2 and COMB-4 reverted all bone and serum markers, as well as the number of osteoclasts in the vertebrae, to SHAM levels. Incubation of MC3T3-E1 cells with COMB-4 demonstrated an increase in the three NOS isoforms, cGMP, and calcium deposition. COMB-4 increased BMD in OVX rats by inhibiting bone resorption and increasing calcium deposition presumably via activation of the NO-cGMP pathway. It remains to be determined whether COMB-4 could be a potential nutraceutical therapy for the prevention of premenopausal bone loss.

Effects of the Catechol and Methoxy Metabolites of 17β-Estradiol on Nitric Oxide Production by Ovine Uterine Artery Endothelial Cells.

Nitric oxide (NO) production is essential to facilitate rises in uterine blood flow (UBF) during pregnancy. It has been proposed that the metabolites of E2β, 2-hydroxyestradiol (2-OHE2), 4-hydroxyestradiol (4-OHE2), 2-methoxyestradiol (2-ME2), and 4-methoxyestradiol (4-ME2) play a role in mediating vasodilation and rises in UBF during pregnancy. We previously showed that the E2β metabolites stimulate prostacyclin production in pregnancy-derived ovine uterine artery endothelial cells (P-UAECs); however, it is unknown whether the E2β metabolites also induce NO production. Herein, UAECs derived from nonpregnant and pregnant ewes were used to test the hypothesis that E2β metabolites stimulate NO production in a pregnancy-specific manner. Specific estrogen receptor (ER) and adrenergic receptor (AR) antagonists were used to determine the roles of ERs or ARs in E2β metabolite-induced NO production. E2β and its metabolites increased total nitric oxide metabolites (NOx) levels (NO2 + NO3) in P-UAECs, but not in NP-UAECs. Pretreatment with combined 1 µmol/L 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1H-pyrazole dihydrochloride (MPP; ER-α antagonist) and 1 µmol/L 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP; ER-β antagonist) inhibited the rises in NOx levels stimulated by E2β and 2-ME2, but had no effect on 2-OHE2-, 4-OHE2-, or 4-ME2-stimulated rises in NOx levels. Pretreatment with yohimbine (α2-AR antagonist) and propranolol (β2,3-AR antagonist) inhibited the rises in NOx levels stimulated by 2-OHE2, but not by E2β, 4-OHE2, 2-ME2, or 4-ME2. These data demonstrate that E2β metabolites stimulate NO synthesis via ERs or ARs in UAECs in a pregnancy-specific manner, suggesting that these metabolites contribute to rises in vasodilation and UBF during pregnancy.

Role of Nox4 in Angiotensin II‐Mediated Changes in Volume Dynamics and Nitric Oxide Production in Podocytes

Nitric oxide (NO) is a powerful vasodilator that serves important functions in the kidney such as regulation of renal hemodynamics, pressure natriuresis, and diuresis. Significant reduction in NO production has been found to play a role in the pathogenesis of hypertension. Our recent studies revealed that Angiotensin II (Ang II), in addition to causing a release of calcium, stimulates NO production in the glomerular podocytes. This signaling pathway can be also triggered by extracellular application of hydrogen peroxide (H2O2) and is significantly reduced with the development of salt‐sensitive hypertension and kidney injury in Dahl salt‐sensitive (SS) rats (Palygin et al., Nitric Oxide, 2018). Recently, using a knock out of NADPH oxidase 4 (Nox4) in SS rats (SSNox4−/−), one of the primary source of renal reactive oxygen species (ROS) and specifically H2O2 we described the reduction in intracellular calcium activation in podocytes as well as H2O2 production in isolated glomeruli in response to Ang II (Ilatovskaya et al., J Am Soc Nephrol. 2018). Overall, SSNox4−/− rats displayed a protective phenotype with a significant reduction of albuminuria, glomeruli injury and reduction in the elevation of blood pressure under high salt challenge (Cowley et al., Hypertension, 2016). Here we used this model to characterize the effects of alterations in the balance in the relationship between ROS and NO production in podocytes and establish the relation between Nox4 and glomerular/podocyte volume dynamics. The in vivo concentration of H2O2, measured by biosensors amperometry as catalase sensitive current, was significantly reduced in both cortex and medullar parts of the SSNox4−/− rat kidney compared to wild type SS rats, indicating a direct association between Nox4 and the production of renal ROS. We found that acute application of Ang II promoted opposite changes in glomeruli and podocyte volumes, where glomeruli volume decreased, and podocyte volume increased approximately by 18% in SS rats. Overall, SSNox4−/− rats exhibited an increase in total NO production (by 16% to compare with SS), calculated using confocal microscopy as a total integral of NO fluorescent transient (DAF‐FM dye) in the population of podocytes within a freshly isolated glomerulus. In SSNox4−/− rats the elevation in NO together with declining in H2O2 levels directly correlated with an increase of podocyte volume in response to Ang II (13% vs. SS control). We anticipate a rapid podocyte volume change dependent on intracellular NO production and reflecting the ability of these cells to dynamically regulate the permeability of glomeruli filtration barrier. Thus far, we can conclude that in the absence of Nox4 the podocytes shift the ROS production in response to Ang II towards the increase of intracellular NO bioavailability and a decrease of renal H2O2 production. This mechanism may play a key role in the protection of glomeruli form oxidative stress and elevation of blood pressure during the development of salt‐sensitive hypertension.Support or Funding InformationNHLBI R35 HL135749; P01 HL116264; AHA 18PRE34030127; ADA 1‐15‐BS‐172; DK‐020595 Pilot &amp; Feasibility projectThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cerebral Vascular Function in a Murine Model of Experimental Cerebral Malaria

Cerebral Malaria (CM) is among the most severe complications of malarial infection, with a mortality rate of 15–20%. Many survivors of CM develop lasting neurological sequalae, cognitive and behavioral impairments, or epilepsy. However, the etiology of CM is poorly defined, and treatment strategies are limited.Studies in the murine model of experimental cerebral malaria (ECM) have demonstrated cerebral blood flow (CBF) impairments that are associated with decreased nitric oxide (NO) bioavailability, blood brain barrier disruption, endothelial activation, impaired pial vessel reactivity, and cerebral ischemia. While these complications have been observed in vivo, cerebral artery function has not specifically been evaluated in ECM. Therefore, the aim of this study was to interrogate vasoreactivity and NO bioavailability in cerebral arteries (CAs) isolated from ECM mice, with the hypothesis that arterial vasodilatory function would be impaired by ECM.ECM was induced by Plasmodium berghei ANKA (PbA) infection in 10–12 week old C57Bl/6J mice and confirmed by murine coma score. On day 6 post‐infection, CBF was measured by laser speckle imaging. Cerebral arteries (CAs) were dissected from the brain into a modified Krebs buffer. Cerebral vasoreactivity was assessed by ex vivo pressure myography in middle cerebral arteries (MCA) obtained from control (n=4) and ECM (n=7) mice. NO production from dissected vessels was measured in an ex vivo Daf‐2 fluorescence assay (n=6, n=6).As expected, ECM mice had a significant, 25% reduction in CBF. However, ex vivo MCAs from ECM mice maintained robust endothelium‐dependent vasodilation to methacholine (MCh), which was inhibited by L‐NAME. ECM MCAs also exhibited normal dose responses to serotonin‐induced vasoconstriction and nitroprusside‐induced vasodilation, suggesting normal vasoreactivity of ECM cerebral arteries. Similarly, the results of the ex vivo Daf‐2 assay showed that the MCh‐induced NO production from ECM arteries was comparable to controls. To test whether ECM plasma would induce vascular dysfunction in ex vivo CAs, we incubated CAs obtained from ECM (n=2) and control (n=6) mice in plasma collected from ECM or control animals. Surprisingly, we found that plasma from ECM mice increased NO production of both ECM and control CAs.These unexpected results indicate that NO bioavailability and vasoreactivity are preserved in cerebral vessels in ECM, and that circulating factors in the plasma during PbA infection actively stimulate NO production. Our next focus will be on reconciling decreased CBF with preserved vascular function, as well as identifying the NO‐stimulating mediator(s) present within ECM plasma.Support or Funding InformationResearch and funding support from NIAID Division of Intramural Research.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The phytosphingosine-CD300b interaction promotes zymosan-induced, nitric oxide-dependent neutrophil recruitment.

Zymosan is a glucan that is a component of the yeast cell wall. Here, we determined the mechanisms underlying the zymosan-induced accumulation of neutrophils in mice. Loss of the receptor CD300b reduced the number of neutrophils recruited to dorsal air pouches in response to zymosan, but not in response to lipopolysaccharide (LPS), a bacterial membrane component recognized by Toll-like receptor 4 (TLR4). An inhibitor of nitric oxide (NO) synthesis reduced the number of neutrophils in the zymosan-treated air pouches of wild-type mice to an amount comparable to that in CD300b-/- mice. Treatment with clodronate liposomes decreased the number of NO-producing, CD300b+ inflammatory dendritic cells (DCs) in wild-type mice, thus decreasing NO production and neutrophil recruitment. Similarly, CD300b deficiency decreased the NO-dependent recruitment of neutrophils to zymosan-treated joint cavities, thus ameliorating subsequent arthritis. We identified phytosphingosine, a lipid component of zymosan, as a potential ligand of CD300b. Phytosphingosine stimulated NO production in inflammatory DCs and promoted neutrophil recruitment in a CD300b-dependent manner. Together, these results suggest that the phytosphingosine-CD300b interaction promotes zymosan-dependent neutrophil accumulation by inducing NO production by inflammatory DCs and that CD300b may contribute to antifungal immunity.

Production of Nitric Oxide and Phosphatidic Acid is Involved in Activation of Plasma Membrane H+-ATPase in Maize Root Tips in Simulated Drought Stress

Nitric oxide (NO), phospholipase D (PLD) and plasma membrane (PM) H+-ATPase play crucial roles in plant response to drought stress, but the mechanisms of their function and their relationships in this process are still unclear. Here, we investigated how NO regulate PM H+-ATPase activity in maize (Zea mays L.) root tips in drought stress via inducing PLD-derived phosphatidic acid (PA) formation. Our results showed that drought stress stimulated NO production, up-regulated ZmPLD gene expression and stimulated PLD activity, coupled with PA production. With the elevation of PA content in a specific period (6 to 24 h after treatment), the PM H+-ATPase was stimulated. The NO scavenger impaired drought-induced PLD activation, PA formation and PM H+-ATPase activation at 12 h after treatment. The PLD inhibitor impaired drought-induced PA formation and PM H+-ATPase activation at 12 h after treatment. The NO scavenger, PLD inhibitor and PM H+-ATPase inhibitor aggravated the injury caused by drought stress. Exogenous NO alleviated the injury through a further elevation and a longer maintenance of ZmPLD gene expression, PLD activity, PA content and PM H+-ATPase activity in drought stress. The stimulation effect of exogenous NO on PA formation and PM H+-ATPase activation at 12 h after treatment were partly inhibited by the PLD inhibitor. The results suggested that as an early signal, NO triggers maize plant response to drought stress through increasing PM H+-ATPase activity in root tips. PLD-derived PA acts downstream of NO in this process.

In Vitro Immune-Enhancing Activity of Ovotransferrin from Egg White via MAPK Signaling Pathways in RAW 264.7 Macrophages.

Ovotransferrin (OTF) is a well-known protein of the transferrin family with strong iron chelating activity, resulting in its antimicrobial activity. Furthermore, OTF is known to have antioxidant, anticancer, and antihypertensive activities. However, there have been few studies about the immune-enhancing activity of OTF. In current study, we investigated the immune-enhancing activity of OTF using the murine macrophage cells in vitro. The effect of OTF on production of pro-inflammatory mediators and cytokines were determined using Griess assay and quantitative real-time PCR. Using Neutral Red uptake assay, we confirmed the effect of OTF on phagocytic activity of macrophages. Ovotransferrin significantly increased the production of nitric oxide (NO) and secretion of inducible nitric oxide synthase (iNOS) mRNA with no cytotoxic activity. Ovotransferrin (2 mg/mL) stimulated NO production up to 31.9±3.5 μM. Ovotransferrin significantly increased the mRNA expression levels of pro-inflammatory cytokines which are tumor necrosis factor-α (TNF-α), Interleukin-1β (IL-1β), and IL-6: OTF (2 mg/mL) treatment increased the secretion of mRNA for TNF-α, IL-1β, and IL-6 by 22.20-, 37.91-, and 6.17-fold of the negative control, respectively. The phagocytic activity of macrophages was also increased by OTF treatment significantly compared with negative control. Also, OTF treatment increased phosphorylation level of MAPK signaling pathways. These results indicated that OTF has immune-enhancing activity by activating RAW 264.7 macrophages via MAPK pathways.

Parenteral L-Arginine Improves Mitochondrial Function in Children with Sickle Cell Disease Admitted for Vaso-Occlusive Pain Episodes

Introduction: Vaso-occlusive pain episodes (VOE) are the leading cause of emergency department visits and hospitalization in patients with sickle cell disease (SCD). There is currently no standard therapy for treating the underlying causes of VOE; supportive care & symptomatic pain relief with parenteral opioids is the mainstay of therapy. Prior work by Morris & colleagues has demonstrated that patients in VOE show depleted concentrations of plasma L-arginine (Arg), and that supplementation with Arg significantly decreases total parenteral opioid use and improves pain scores during hospitalization in these patients (Morris et al 2013, Haematologica). The mechanisms by which Arg mediates these positive effects remain unclear, but are potentially due to its ability to modulate metabolism through increased Arg transport or affect vascular signaling through the stimulation of nitric oxide production. The Shiva lab has previously demonstrated that platelet mitochondrial function is altered in patients with SCD compared to healthy controls (Cardenas et al 2014, Blood). This alteration is manifested as a decrease in mitochondrial electron transport Complex V (ATP Synthase) activity, which leads to decreased respiration and increased detrimental oxidant production. Here we hypothesized that treatment of SCD patients in VOE with Arg increases mitochondrial function.Methods: In a pharmacokinetic study, 10 subjects with Hb-SS or Sb0-thalassemia hospitalized for VOE (age 14±3 years, 70% male, 80% Hb-SS) were randomized to treatment utilizing one of 3 dosing schemes of L-arginine: 1) 100mg/kg IV three times/day (n=3); 2) loading dose (200mg/kg) then 100mg/kg three times/day (n=4); or 3) loading dose (200mg/kg) followed by continuous infusion (300mg/kg/day) until discharge (n=3). Platelet rich plasma was isolated & stored at baseline & discharge for each subject & mitochondrial electron transport complex activities, protein expression, as well as protein carbonyls were measured.Results: Compared to a cohort of SCD patients in steady state, all subjects in VOE had a significantly decreased complex V activity (Fig 1A). Notably, complex V activity was increased at discharge in subjects with VOE treated with Arg in all three dosing schemes. However, the increase in complex V activity was greatest when utilizing a loading dose. (Fig 1B, p<0.001). While complex IV & citrate synthase activities were not changed in platelets from subjects with VOE compared to SCD patients in steady state (data not shown), the activities of these enzymes were also significantly increased in VOE subjects after Arg treatment when utilizing a loading dose( Fig 1C-D, p<0.01). These changes with Arg do not appear to be due to increased mitochondrial number as quantification of mitochondrial DNA before and after Arg was not different (Fig 1E). Complex V protein expression was also unchanged after Arg treatment (data not shown). However, Arg treatment did significantly decrease levels of protein carbonyls in the platelet rich plasma across all treatment dosing schemes (Fig 1F, p<0.01 in all dosing groups), suggesting a decrease in oxidative stress.Conclusion: These data demonstrate for the first time that Arg supplementation increases mitochondrial activity and decreases oxidative stress in children with SCD and VOE. Our prior study showed that complex V inhibition leads to increased mitochondrial oxidant production in platelets from SCD patients. The improvement in complex V function & decreased oxidative markers observed with Arg treatment are consistent with Arg-induced decrease in mitochondrial oxidant generation. However, Arg treatment potentially regulates other oxidant sources and could decrease overall oxidative stress in SCD patients. Arg therapy has been reported to improve symptoms associated with MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes) suggesting an impact of arginine on mitochondrial activity that may be beneficial for patients with SCD. With the recent FDA approval of L-glutamine, which is an Arg prodrug, this is also a potential consequence of glutamine that warrants further study. This increase in mitochondrial function may mechanistically contribute to decreased pain and ultimately less opioid requirement after IV Arg treatment in SCD, as well as have further implications for improved metabolism and oxidative signaling in these patients. DisclosuresDampier:Pfizer: Research Funding. Morris:Pfizer: Consultancy; MAST Therapeutics: Research Funding; UCSF-Benioff Children's Hospital Oakland: Patents & Royalties: For nutritional supplement licensed to Lifetrients; Calithera: Consultancy; FDA: Research Funding; NIH/NHLBI: Research Funding.

Abstract 17307: TGR5 Contributes to Improved Perivascular Adipose Tissue Function (PVAT) After Vertical Sleeve Gastrectomy in Mice

PVAT is a critical regulator of vascular contractility and its dysfunction contributes to obesity-induced hypertension (HTN). Bariatric surgery, such as vertical sleeve gastrectomy (VSG), causes high rates of HTN remission prior to weight loss, and rescues PVAT function by increasing nitric oxide (NO) production. We have previously validated a VSG mouse model that recapitulates the body weight-independent lowering of blood pressure. VSG increases bile acid (BA) signaling through the BA receptor, TGR5. TGR5 stimulates NO production from endothelial cells (ECs) but the role of TGR5 signaling in adipocyte NO production is unknown. We hypothesized that VSG increases NO bioavailability within PVAT in a TGR5-dependent manner. High fat diet (HFD)-fed male C57BLmice underwent VSG or sham surgery ( n =4-6) Sham (S) mice were food restricted to match body weight to VSG mice. Vascular contractility was reduced in VSG mice (Max contraction (%): S: 30±2, VSG: 23±3; P &lt;0.05). To assess the role of TGR5 on NO production within PVAT, we performed western blotting on mesenteric PVAT from VSG or sham-operated HFD-fed TGR5 WT and KO mice. eNOS phosphorylation was increased in PVAT in VSG WT, but not VSG KO (western blot quantification (AU): S WT: 1.0±0.1, VSG WT: 1.3±0.1, S KO: 1.1±0, VSG KO: 1.0±0.1; P &lt;0.05). To determine how TGR5 regulates PVAT NO production, we assessed the impact of TGR5 on microRNA-21 (miR-21) expression. MiR-21 stimulates NO production in ECs but its role in adipocytes in unknown. Thus, we hypothesized that TGR5 regulates NO production within PVAT by upregulating miR-21. MiR-21 expression was increased in PVAT from VSG-operated TGR5 WT mice but not KO compared to sham controls (western blot quantification (AU): S WT: 0.9±0.1, VSG WT: 2.1±0.5, S KO: 0.7±0.6, VSG KO: 0.6±0.1; P &lt;0.05). We further investigated whether TGR5 activation and miR-21 overexpression stimulate NO production in adipocytes. Mature 3T3-L1 adipocytes were treated with INT-777 or transfected with miR-21 mimic. TGR5 activation and miR-21 overexpression increased eNOS phosphorylation ( P &lt;0.05). In conclusion, our data suggest that VSG increases NO bioavailability in PVAT by activating adipocyte TGR5 signaling and upregulating miR-21 expression.

Abstract 16844: Relative Endothelial Toxicity of Tobacco Smoke and E-Cigarette Aerosol: A Functional and Mechanistic Assessment

Background: Smoking cigarettes decreases expression of eNOS in the endothelium, resulting in lower nitric oxide (NO) secretion and decreased flow-mediated dilation in the conducting arteries. In contrast, the effects of e-cigarettes (e-cigs) on endothelial function are just beginning to be studied and the mechanisms of action are unclear. Aim: To test the hypothesis that circulating factors from e-cigarette users decrease endothelial eNOS protein levels and NO secretion in primary endothelial cell cultures, relative to nonsmokers and cigarette smokers. Methods: 36 healthy individuals were recruited and grouped as nonsmokers (n=12), cigarette smokers (n=7), and e-cig users (n=17). Human umbilical vein endothelial cells (HUVECs) were cultured at 20,000 cells per well in 24-well culture plate. Serum samples from individual subjects and endothelial growth media were added at a 1:1 ratio to confluent cells and incubated for 12 hours (basal condition), followed by fresh medium containing VEGF at 50 ng/ml for 30 min (stimulated condition). The amount of NO liberated from cells was measured in culture supernatants by the chemilumin- escence method using a NO analyzer. Endothelial NO synthase (eNOS) protein levels in HUVECs was measured in cell lysates by ELISA. NO and eNOS results were normalized to cell number. Results: The cells treated with serum from e-cig users vs. nonsmokers produced less NO upon stimulation (P&lt;.03) and contained less eNOS protein (P&lt;.03). eNOS protein level was lower in the e-cig user serum group than in the cigarette smoker serum group (P&lt;.05), although stimulated NO production was decreased less by e-cig user serum than by smoker serum. Lower eNOS levels in the cigarette group vs. non-smoker group was not significant, but stimulated NO was significantly lower in the cigarette group vs. nonsmoker (P&lt;.006; see figure). Conclusion: Exposure of cultured endothelial cells to circulating factors from e-cig users, relative to non-users, leads to lower eNOS protein levels and decreased NO production.

Antihypertensive Effect of Piper sarmentosum in L-NAME-Induced Hypertensive Rats

Hypertension is one of the risk factors for cardiovascular diseases and has been associated with about 13% of global deaths worldwide. Oxidative stress and reduced nitric oxide (NO) bioavailability contribute to the development of endothelial dysfunction and subsequently hypertension. Nɷ-nitro-L-arginine methyl ester hydrochloride (L-NAME) inhibits NO synthesis; leading to hypertension. Piper sarmentosum (PS) is an herb with antioxidant, antiatherosclerosis and antiinflammation properties. PS also stimulated NO production by endothelial cells. The aim of this study was to determine the effects of aqueous extract of Piper sarmentosum (AEPS) on blood pressure, oxidative stress and the level of nitric oxide in L-NAME-induced hypertensive rats. Hypertension was induced by oral administration of L-NAME (100 mg/L) in drinking water for four weeks. The rats were concurrently treated with AEPS by oral gavage in serial doses (125, 250 and 500 mg/kg/day). Blood pressure was measured using non-invasive tail-cuff method at baseline and fortnightly thereafter. Serum level of NO and an oxidative stress marker, malondialdehyde (MDA) were measured at baseline and at the end of treatment. The results showed that treatment with three different doses of AEPS successfully reduced systolic blood pressure (p<0.001), diastolic blood pressure (p<0.05) and mean arterial pressure (p<0.05) in L-NAME-induced hypertensive rats. Treatment with AEPS also reduced MDA level (p<0.001) and increased serum NO (p<0.001) in L-NAME-induced hypertensive rats. The findings showed that AEPS decreased blood pressure by protecting against oxidative stress and increasing NO in L-NAME-induced hypertensive rats.