Abstract P108: Inflammatory Factors And Metalloproteinases Levels Are Elevated In Aorta Of Patients With Abdominal Aortic Aneurysm

Introduction: The pathophysiology of abdominal aortic aneurysm (AAA) remains poorly understood. The identification of the mechanisms involved in growth, progression, and the risk of aortic rupture could bring a novel treatment perspective and improve patient outcomes. Inflammatory mediators and metalloproteinases (MMPs) 2 and 9 have been shown to contribute to the pathophysiology of AAA in humans. It is widely recognized that these mediators produce both local (tissue) and systemic (circulation) responses. Therefore, in this study, we sought to characterize the inflammatory and MMP-2 and MMP-9 profiles in the aorta and plasma in patients with AAA.

Methodology: Plasma and aorta tissue from AAA patients(n=31)were obtained during conventional AAA correction surgeries at Ribeirão Preto Medical School Hospital-University of São Paulo. The control samples were obtained from organ donors without AAA (n=15). The levels of inflammatory markers (IL-6,IL-8,TGFbeta) and MMPs were measured by radio immunoassay and zymography, respectively, in plasma and aorta.

Results: Levels of IL-6 (p=0.001), IL-8 (p=0.01) and TGF beta (p=0.05) were significantly elevated in the aorta of AAA patients, but not in plasma, when compared to control group. Interestingly, levels of IL-6 (p=0.05) and IL-8 (p=0.02) were lower both in the aorta and plasma of controls. MMP-2 and MMP-9 levels were upregulated in plasma (p=0.02 and p=0.0007, respectively) and in aorta (p=0.017 and p=0.03, respectively) of AAA patients when compared to controls. The tissular levels of MMP-2 and MMP-9 were upregulated in the aorta in both AAA patients (p=0.001 and p=0.0001, respectively) and controls (p=0.008 and p=0.001, respectively) when compared to plasmatic levels of respective groups.

Conclusion: Our data show that a profile of AAA patients is characterized by locally elevated inflammation factors and MMPs, and systemically elevated MMPs levels. This might suggest that the local response in aortais an important pathway in the pathophysiology of AAA development.

Chronic Treatment With Acetylcholinesterase Inhibitors Attenuates Vascular Dysfunction in Spontaneously Hypertensive Rats

BACKGROUND

Acetylcholinesterase inhibition prevents autonomic imbalance, reduces inflammation, and attenuates the development of hypertension. Considering that vascular dysfunction is a crucial feature of arterial hypertension, we investigated the effects of chronic administration of acetylcholinesterase inhibitors-pyridostigmine or donepezil-on vascular reactivity of spontaneously hypertensive rats (SHR).

METHODS

Endothelium-dependent relaxant responses to acetylcholine (ACh) and contractile responses induced by electric field stimulation (EFS) and alpha-adrenergic agonist were studied in mesenteric resistance arteries from SHR and Wistar Kyoto rats. SHR were treated for 16 weeks with vehicle, pyridostigmine (1.5 mg/kg/day) or donepezil (1.4 mg/kg/day).

RESULTS

Pyridostigmine and donepezil decreased the vasoconstrictor responses to EFS, which were increased in vehicle-treated SHR. Acetylcholinesterase inhibition increased the modulatory effects of nitric oxide (NO) on SHR vascular reactivity, that is, N(ω)-nitro-(L)-arginine methyl ester (L-NAME) increased EFS-induced contractions and reduced ACh-induced relaxation, with more significant effects in pyridostigmine- and donepezil-treated SHR. The acetylcholinesterase inhibitors also decreased vascular reactive oxygen species levels.

CONCLUSIONS

This study demonstrates for the first time that long-term administration of acetylcholinesterase inhibitors, pyridostigmine or donepezil, attenuates vascular reactivity dysfunction in SHR by decreasing reactive oxygen species generation and increasing NO bioavailability; possibly via increased endothelial NO synthase activity, and inhibition of NADPH oxidase activity.

NLRP3 Inflammasome Mediates Aldosterone-Induced Vascular Damage

BACKGROUND

Inflammation is a key feature of aldosterone-induced vascular damage and dysfunction, but molecular mechanisms by which aldosterone triggers inflammation remain unclear. The NLRP3 inflammasome is a pivotal immune sensor that recognizes endogenous danger signals triggering sterile inflammation.

METHODS

We analyzed vascular function and inflammatory profile of wild-type (WT), NLRP3 knockout (NLRP3^-/-), caspase-1 knockout (Casp-1^-/-), and interleukin-1 receptor knockout (IL-1R^-/-) mice treated with vehicle or aldosterone (600 µg·kg^-1·d^-1 for 14 days through osmotic mini-pump) while receiving 1% saline to drink.

RESULTS

Here, we show that NLRP3 inflammasome plays a central role in aldosterone-induced vascular dysfunction. Long-term infusion of aldosterone in mice resulted in elevation of plasma interleukin-1β levels and vascular abnormalities. Mice lacking the IL-1R or the inflammasome components NLRP3 and caspase-1 were protected from aldosterone-induced vascular damage. In vitro, aldosterone stimulated NLRP3-dependent interleukin-1β secretion by bone marrow-derived macrophages by activating nuclear factor-κB signaling and reactive oxygen species generation. Moreover, chimeric mice reconstituted with NLRP3-deficient hematopoietic cells showed that NLRP3 in immune cells mediates aldosterone-induced vascular damage. In addition, aldosterone increased the expression of NLRP3, active caspase-1, and mature interleukin-1β in human peripheral blood mononuclear cells. Hypertensive patients with hyperaldosteronism or normal levels of aldosterone exhibited increased activity of NLRP3 inflammasome, suggesting that the effect of hyperaldosteronism on the inflammasome may be mediated through high blood pressure.

CONCLUSIONS

Together, these data demonstrate that NLRP3 inflammasome, through activation of IL-1R, is critically involved in the deleterious vascular effects of aldosterone, placing NLRP3 as a potential target for therapeutic interventions in conditions with high aldosterone levels.

Abstract P073: Chemerin Receptor Antagonism Improves Vascular Insulin Signaling in Diabetic Mice

Adipose tissue releases many adipokines, including chemerin, which produces its effects through activation of chemokine-like receptor 1 (ChemR23). Chemerin influences major aspects of the metabolic syndrome, including adipogenesis and insulin sensitivity in adipocytes and skeletal muscle cells. Considering that chemerin impairs vascular reactivity and that amongst its many actions, insulin also influences vascular function, we postulate that chemerin decreases insulin-induced vasodilatation, by reducing PI3K/Akt signaling, and impairs glucose uptake by vascular smooth muscle cells (VSMC). Mesenteric arteries, endothelial cells (EC) or VSMC from C57Bl6 mice were incubated with chemerin (0.5 ng/mL, 1 h) or vehicle (veh). Chemerin decreased insulin-induced relaxation (0.1 - 3000 ng/mL, pD2: chemerin: 94.5±0.1 vs. veh: 23.6±0,1), which was prevented by the ChemR23 antagonist CCX 832 (pD2: veh= 16.9±0.1; chem= 174.1±0.1, CCX+chem= 37.4±0.1) and a PI3K activator (YS-49) (pD2: veh= 23.0±0.1; chem= 108.5±0.1, YS-49+chem= 28.5±0.1). Chemerin also decreased PI3K (0.8±0.1 vs. veh 1.1±0.1), Akt (0.8±0.1 vs. veh 1.2±0.1) and AMPK [0.7±0.2 vs. veh 1.0 ±0.1] phosphorylation in VSMC. IRS1 and IRS2 gene expression was decreased in VSMC stimulated with chemerin. In addition, chemerin decreased insulin-stimulated NO production in EC through activation of ChemR23 and PI3K and inhibited insulin-stimulated glucose uptake by VSMC (counts per minute: 5668±729.0 vs. veh 9923±662.7), which was mediated by ChemR23, AMPK and PI3K. Importantly, ChemR23 antagonism in diabetic (db/db) mice partially reversed decreased insulin-induced vasodilatation (mesenteric resistance arteries; pD2: db/m: 6.1±1.0; db/db: 7.3±0.2; db/db+CCX832: 6.9±0.3). In conclusion, chemerin decreases vascular insulin responses by reducing PI3K/Akt and AMPK signaling. Moreover, chemerin/ChemR23 system plays a crucial role in impaired vascular insulin signaling in diabetes, suggesting its involvement in the pathogenesis of vascular insulin resistance. Our study may contribute to a better understanding of the role of chemerin in vascular insulin dysfunction in diabetes- and obesity-associated diseases. Financial Support: FAPESP, Brazil.

Abstract 276: Chemerin Decreases Vascular Insulin Signaling

Proinflammatory adipokines are key mediators of insulin resistance. The adipokine chemerin influences major aspects of the metabolic syndrome, including adipogenesis and glucose homeostasis in adipocytes and skeletal muscle cells. Amongst its many actions insulin also influences vascular function. Considering that chemerin impairs vascular reactivity, and that its effects in the vascular actions of insulin have not been investigated, we postulate that chemerin decreases vascular responses to insulin by reducing PI3K/Akt signaling. Isometric force was recorded in mesenteric arteries from C57Bl6 mice, incubated with chemerin (0.5 ng/mL, 1 h) or vehicle (veh). Chemerin decreased relaxation responses to insulin (0.1 - 3000 ng/mL, pD2: chemerin: 94.5±0.1 vs. veh: 23.6±0,1) and to ACh (pD2: 5.2±0.1 vs. veh 6.6±0.1). Chemerin effects on insulin-induced vasodilatation were reverted by the PI3K activator YS-49 (pD2: veh= 23.0±0.1; chem= 108.5±0.1, YS-49+chem= 28.5±0.1) and by inhibitors of p38 (pD2: veh= 23.0±0.1; chem= 108.5±0.1, SB203580+chem= 27.1±0.1) and ERK1/2 (pD2: veh= 24.6±0.1; chem= 112.0±0.1, PD98059+chem= 25.4±0.1). Chemerin also decreased PI3K [arbitrary units (a.u.): 0.8±0.1 vs. veh 1.1±0.1) and Akt (a.u.: 0.8±0.1 vs. veh 1.2±0.1) phosphorylation in cultured vascular smooth muscle cells (VSMCs). Furthermore, chemerin inhibited insulin-stimulated glucose uptake by VSMCs ([3H] 2-deoxy-glucose (2DG) uptake, counts per minute: 5668±729.0 vs. veh 9923±662.7). In conclusion, chemerin decreases insulin vascular responses by reducing PI3K/Akt signaling and by activating the MAPK pathway. These results suggest that chemerin may be involved in the pathogenesis of vascular insulin resistance. Our study may contribute to a better understanding of the role of factors released by the adipose tissue on insulin vascular responsiveness and, consequently, on the vascular dysfunction in obesity and obesity-associated diseases. Financial Support: FAPESP.

Peroxisome proliferator-activated receptor-gamma ligand, 15-deoxy-Delta12,14-prostaglandin J2, reduces neutrophil migration via a nitric oxide pathway

Ligands for peroxisome proliferator-activated receptor gamma (PPAR-gamma), such as 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) have been implicated as a new class of anti-inflammatory compounds with possible clinical applications. Based on this concept, this investigation was designed to determine the effect of 15d-PGJ2-mediated activation of PPAR-gamma ligand on neutrophil migration after an inflammatory stimulus and clarify the underlying molecular mechanisms using a mouse model of peritonitis. Our results demonstrated that 15d-PGJ2 administration decreases leukocyte rolling and adhesion to the inflamed mesenteric tissues by a mechanism dependent on NO. Specifically, pharmacological inhibitors of NO synthase remarkably abrogated the 15d-PGJ2-mediated suppression of neutrophil migration to the inflammatory site. Moreover, inducible NOS-/- mice were not susceptible to 15d-PGJ2-mediated suppression of neutrophil migration to the inflammatory sites when compared with their wild type. In addition, 15d-PGJ2-mediated suppression of neutrophil migration appeared to be independent of the production of cytokines and chemokines, since their production were not significantly affected in the carrageenan-injected peritoneal cavities. Finally, up-regulation of carrageenan-triggered ICAM-1 expression in the mesenteric microcirculation vessels was abrogated by pretreatment of wild-type mice with 15d-PGJ2, whereas 15d-PGJ2 inhibited F-actin rearrangement process in neutrophils. Taken together these findings demonstrated that 15d-PGJ2 suppresses inflammation-initiated neutrophil migration in a mechanism dependent on NO production in mesenteric tissues.

Trypanosoma cruzi-infected cardiomyocytes produce chemokines and cytokines that trigger potent nitric oxide-dependent trypanocidal activity

BACKGROUND

The pathogenesis of myocarditis that occurs in Trypanosoma cruzi-infected mice is still poorly understood. Therefore, it is important to know the mediators that trigger leukocyte migration to the heart as well as the cellular source of these possible mediators. In this study, we investigated (1) NO synthase (NOS) induction, (2) NO synthesis, (3) trypanocidal activity, and (4) chemokine and cytokine mRNA expression by isolated cardiomyocytes infected with T cruzi.

METHODS AND RESULTS

Mouse cardiomyocytes were isolated, infected with T cruzi, and evaluated for induction of inducible NOS (iNOS), nitrite production, trypanocidal activity, and cytokine and chemokine mRNA expression. We found that T cruzi-infected murine embryonic cardiomyocytes produced nitrite and expressed mRNAs for the chemokines chemokine growth-related oncogene, monokine induced by interferon-gamma, macrophage inflammatory protein-2, interferon-gamma-inducible protein, RANTES, and monocyte chemotactic protein, for iNOS, and for the cytokines tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta. Separate addition of IL-1beta, interferon-gamma, TNF-alpha or monocyte chemotactic protein, macrophage inflammatory protein-2, and interferon-gamma-inducible protein, to cultured cardiomyocytes resulted in NO production but low trypanocidal activity. However, simultaneous addition of IL-1beta, interferon-gamma, and TNF-alpha or the chemokines to cultures resulted in the induction of iNOS, high levels of nitrite, and a marked trypanocidal activity. The iNOS/L-arginine pathway mediated the latter activity, inasmuch as it was inhibited by treatment with N:(G)-monomethyl-L-arginine.

CONCLUSIONS

These results indicate that iNOS activation and the proinflammatory cytokines and chemokines produced by cardiomyocytes are likely to control parasite growth and cell influx, thus contributing to the pathogenesis of chagasic cardiomyopathy seen in T cruzi-infected mice.