BackgroundSystemic hypertension may be associated with an increased pulmonary vascular resistance, which we hypothesized could be, at least in part, mediated by increased leptin.MethodsVascular reactivity to phenylephrine (1 μmol/L), endothelin-1 (10 nmol/L) and leptin (0.001–100 nmol/L) was evaluated in endothelium-intact and -denuded isolated thoracic aorta and pulmonary arteries from spontaneously hypertensive versus control Wistar rats. Arteries were sampled for pathobiological evaluation and lung tissue for morphometric evaluation.ResultsIn control rats, endothelin-1 induced a higher level of contraction in the pulmonary artery than in the aorta. After phenylephrine or endothelin-1 precontraction, leptin relaxed intact pulmonary artery and aortic rings, while no response was observed in denuded arteries. Spontaneously hypertensive rats presented with increased reactivity to phenylephrine and endothelin-1 in endothelium-intact pulmonary arteries. After endothelin-1 precontraction, endothelium-dependent relaxation to leptin was impaired in pulmonary arteries from hypertensive rats. In both strains of rats, aortic segments were more responsive to leptin than pulmonary artery. In hypertensive rats, pulmonary arteries exhibited increased pulmonary artery medial thickness, associated with increased expressions of preproendothelin-1, endothelin-1 receptors type A and B, inducible nitric oxide synthase and decreased endothelial nitric oxide synthase, together with decreased leptin receptor and increased suppressor of cytokine signaling 3 expressions.ConclusionsAltered pulmonary vascular reactivity in hypertension may be related to a loss of endothelial buffering of vasoconstriction and decreased leptin-induced vasodilation in conditions of increased endothelin-1.

Although in vitro exposure to DEP produces a vascular oxidative stress, repeated in vivo exposures to DEP only impair vascular function in SHR, via an upregulation of p22phox. This suggests a synergistic effect on endothelial dysfunction between particulate air pollution and hypertension.

Decreased leptin-induced endothelium-dependent vasodilation has been reported in spontaneously hypertensive rats (SHR). Here, we report leptin-induced vasoconstriction in endothelium-denuded pulmonary artery and thoracic aorta from SHR and sought to characterize calcium handling underlying these mechanisms. Vasoreactivity to leptin was evaluated on pulmonary artery and thoracic aorta rings from 18 weeks old male SHR with or without calcium free medium, caffeine + thapsigargin + carbonyl cyanide-4-trifluoromethoxyphenylhydrazone emptying intracellular calcium stores, nifedipine a voltage-gated calcium channel inhibitor, SKF-96365 a transient receptor potential cation channels (TRPC) inhibitor, wortmaninn, a phosphatidylinositide 3-kinases (PI3K) inhibitor, or PD98059 a mitogen-activated protein kinase kinase (MAPKK) inhibitor. Calcium imaging was performed on cultured vascular smooth muscle cells incubated with leptin in presence or not of wortmaninn or PD98059. Leptin induced vasoconstriction in denuded pulmonary artery and thoracic aorta from SHR. Response was abolished when intra- or extracellular calcium stores were emptied, after blocking TRPC or voltage-dependent calcium channels or when using MAPKK or PI3K inhibitors. In vascular smooth muscle cells, leptin increased intracellular calcium. This rise was higher in SHR and abolished by MAPKK or PI3K inhibitors. TRPC6 gene expression was upregulated in arteries from SHR. Leptin-induced vasoconstriction in denuded arteries of SHR requires intracellular stores and is TRPC- and voltage-gated calcium channels dependent. Intracellular calcium increase is more pronounced in spontaneously hypertensive rats.

Background: Exposure to diesel exhaust particles (DEP) has long been associated with increased cardiovascular morbidity and mortality. The development of DEP toxicity seems to be linked to inflammation in which macrophages play a critical role. Macrophages can be polarized into proinflammatory M1 or anti-inflammatory M2 macrophages. The aim of this study was to identify the role of inflammation in DEP-induced toxicity by assessing the effects of DEP on macrophage polarization. Methods: Monocyte-derived macrophages (Mϕ) were stimulated with interferon γ and lipopolysaccharide or interleukin (IL)-4 to obtain M1 and M2 subtypes, respectively. To test the polarization capacity of DEP, Mϕ cells were exposed to DEP and compared to Mϕ, M1, and M2. We also studied the effects of DEP on already-polarized M1 or M2. The M1 markers assessed were tumor necrosis factor α (TNF-α) and IL-1β, while the M2 markers were the mannose receptor C type 1 (MRC-1) and transglutaminase 2 (TGM2). Results: Western blots revealed a 31 kDa band corresponding to pro-IL-1β, but only in M1-polarized macrophages. In M1, we also observed an upregulation of TNF-α messenger RNA (mRNA) expression. MRC-1 and TGM2 mRNA expression were only significantly enhanced in M2. DEP had no effect on any of the M1/M2 markers assessed. Moreover, DEP were not able to modify the phenotype of already-polarized M1 or M2. Conclusion: Mϕ incubation with DEP did not have any effect on macrophage polarization, at least on the markers assessed in this study, namely, TNF-α/IL-1β for M1, and MRC-1/TGM2 for M2. Hence, these data argue against an important role of inflammation in DEP-induced vascular toxicity.

Introduction and Aims: Aristolochic acid nephropathy is characterized not only by marked tubular atrophy and interstitial fibrosis but also by severe peritubular capillaries rarefaction. Human umbilical vein endothelial cells (HUVECs) and rat aortic rings were then used to assess the possible vascular toxicity of aristolochic acid (AA). Methods: HUVECs were incubated during 48h with or without AA (50 or 100 µM). Cell viability was measured by MTT assay. The number of nuclei was counted by DAPI. Pecam adhesion molecule (CD31) cell expression was analyzed by immunofluorescence. We studied the endothelium-dependent relaxations to acetylcholine (ACh) in rat aortas incubated for 1h with 200 µM AA, in the presence or in the absence of superoxide dismutase (SOD). Endothelium independent relaxations to sodium nitroprusside (SNP) were also tested on preparations after endothelium denudation. Results: AA exposure resulted in a significant decrease in the total count of cells which exhibited a typical spindle shape (CD31+ cells/ total count [%] vs controls [100%]: 60.27 ± 13.50 with AA 50 µM and 53.70 ± 8.82 with AA 100 µM, respectively). The MTT assay showed a dose-dependent toxicity of AA (cell viability [%] vs controls [100%]: 70.26 ± 4.80 with AA 50 µM and 12.50 ± 3.26 with AA 100 µM, respectively). ACh-induced relaxations were significantly impaired in rat aortic rings pre-incubated with AA 200 µM: the AUC was 170.9 ± 8.9 in control conditions vs 236.0 ± 8.7 in rings incubated with AA ( p < 0.0001). This effect was reversed after washing of the aortic rings or in the presence of SOD (200 UI). The toxicity was also observed in smooth muscle cells (VSC) as the concentration-response curves to sodium nitroprusside were also modified. Conclusions: Our data show 1) a dose-dependent toxicity of AA on HUVECs 2) an impaired ACh-induced relaxation of aortic rings reversed by SOD, suggesting that superoxide anion is responsible for the AA-mediated endothelial dysfunction 3) some alterations in VSC but to a lesser extent than the endothelial function.