Inhalation of particulate matter containing environmentally persistent free radicals induces endothelial dysfunction mediated via AhR activation at the air-blood interface

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators.

Can a simple echocardiographic Doppler VTI based flow comparison between the RVOT and LVOT assist in identifying patients with a significant atrial septal defect?

Background

Detection of haemodynamically significant shunting from atrial septal defect (ASD) can be identified by using the pulmonary-systemic flow ratio (Qp/Qs). However, calculation of Qp/Qs by echocardiography relies on geometric assumptions that outflow tracts are circular, suffers from squared linear measures, and accurate measurement of right ventricular outflow tract (RVOT) diameter is challenging. Whilst adults with ASD should have overt right ventricular dilatation, RV sizing on echocardiography is often subjective and underappreciated. We evaluated whether a dimensionless index of flow (VTI) differences between the RVOT and left ventricular outflow tract (LVOT) could assist in identifying patients with ASD, and compared it with relative atrial index (RAI), a parameter previously assessed in identifying atrial shunting.

Methods

Data from 64 consecutive patients who underwent ASD closure and had no concomitant lesions, were compared with 63 normal controls. RVOT VTI, LVOT VTI, LVOT diameter, and atrial areas were measured.

Results

Between controls and ASD patients, there was no difference in LVOT VTI or forward stroke volume, but ASD patients had significantly higher RVOT VTI. The RVOT-LVOT VTI ratio was 1:1 in controls and 1.5:1 in ASD patients. Area under the ROC curve analysis of RVOT-LVOT VTI ratio was 0.83, and a ratio of 1.1:1 predicted patients with ASD with 86% sensitivity and 73% specificity. In comparison, the area under the ROC curve analysis of RAI was 0.70, and an RAI of 1.05:1 predicted patients with ASD with 77% sensitivity and 44% specificity.

Conclusion

Calculation of the dimensionless RVOT-LVOT VTI ratio is simple, and may be a useful additional semi-quantitative tool to assist cardiologists and sonographers in detecting atrial shunting, particularly in patients with borderline or overt right heart dilatation, and identify who patients should undergo further evaluation.

Funding Acknowledgement

Type of funding sources: None.

Hepatocyte ploidy in cats with and without hepatocellular carcinoma

BACKGROUND

Domestic cats rarely develop hepatocellular carcinoma. The reason for the low prevalence is unknown. Reductions in hepatocellular ploidy have been associated with hepatic carcinogenesis. Recent work in mice has shown that livers with more polyploid hepatocytes are protected against the development of hepatocellular carcinoma. Hepatocyte ploidy in the domestic cat has not been evaluated. We hypothesized that ploidy would be reduced in peri-tumoral and neoplastic hepatocytes compared to normal feline hepatocytes. Using integrated fluorescence microscopy, we quantified the spectra of ploidy in hepatocellular carcinoma and healthy control tissue from paraffin embedded tissue sections.

RESULTS

Feline hepatocytes are predominantly mononuclear and the number of nuclei per hepatocyte did not differ significantly between groups. Normal cats have a greater number of tetraploid hepatocytes than cats with hepatocellular carcinoma.

CONCLUSIONS

Total hepatocellular polyploidy in normal cat liver is consistent with values reported in humans, yet cellular ploidy (nuclei per cell) is greater in humans than in cats. Tetraploid cat hepatocytes are predominantly mononuclear.

P889 3D guided CT assessment to define the right pulmonary vein on standard apical 4-chamber view

Introduction

Pulmonary vein(PV) assessment is an integral component of the transthoracic echocardiogram(TTE) examination; typically assessed in the apical four-chamber view(A4Ch). There is disagreement in current textbooks and literature regarding which specific right pulmonary vein is visualised on A4Ch; as either the right superior(RSPV) or right inferior PV(RIPV).

Given the high reliability of cardiac CT for PV assessment, we aimed to characterize right PV anatomy on A4Ch by utilizing multi-modality comparison of echocardiography and a 3D-guided A4Ch on CT.

Methods

Retrospective analysis was performed on consecutive patients with TTE demonstrating PV flow(by colour or pulse-wave Doppler) and cardiac CT within 30days; studies not meeting image quality criteria excluded. To simulate the A4Ch on CT, multi-planar reconstruction was used to create an image plane including right PV ostia and LV apex. This image was rotated along the long-axis to achieve an A4Ch with both ventricles and atria, tricuspid and mitral valves in view without LVOT or aorta. This was attempted for right superior, inferior and middle(RMPV, if present) PV’s.

Results

50 patients were analysed: mean age 66yrs, 48% female, mean LA volume(indexed) 43.5ml/m². A4Ch was feasible in 100%(n = 50) of CT simulations using the RIPV, only 24%(n = 12) were feasible using RSPV with all excluded cases due to LVOT/aorta persistently in view. RMPV was present in 6 cases with feasible A4ch in 67%.

Conclusion

This study demonstrates that the right PV on A4Ch is highly likely to be the RIPV due to the RSPV being anatomically impossible in the significant majority of cases.

Abstract P889 Figure. CT multiplanar reconstruction of A4Ch

Biodistribution and toxicity of orally administered poly (lactic-co-glycolic) acid nanoparticles to F344 rats for 21 days

Aim: Quantify the biodistribution and assess the toxicity of PLGA (poly-lactic-co-glycolic acid) and surface-modified PLGA chitosan (PLGA/Chi) nanoparticles (NPs) orally administered for 7, 14 and 21 days to F344 rats. Materials & methods: Fluorescent NPs were tracked in F344 rat tissues, and toxicity was evaluated by alkaline phosphatase and alanine transaminase levels, and by histologic examination of tissue samples. Results: Biodistribution of PLGA and PLGA/Chi were similar, with highest amounts found in the intestine and liver. Alkaline phosphatase increased significantly in treated rats. Mild histological differences were detected in the intestine and liver. Conclusion: PLGA and PLGA/Chi NPs behaved similarly presenting minimal toxicity in the liver and intestine, but not in kidney, lung and brain.

Role for the left atrial appendage occlusion device in managing thromboembolic risk in atrial fibrillation

Only 50% of patients who would benefit from warfarin therapy for atrial fibrillation (AF) receive treatment because of clinical concerns regarding chronic anti-coagulation. Percutaneous strategies to treat AF, including pulmonary vein isolation with a curative intent or atrioventricular nodal ablation and implantation of a permanent pacemaker for palliative rate control, have not eliminated the need to manage thromboembolic risk. With the development of a percutaneous left atrial appendage (LAA) occlusion device (the WATCHMAN percutaneous left atrial appendage occluder - Atritech Inc., Plymouth, MN, USA) for thromboembolic protection in non-valvular AF a significant therapeutic option for select patients may be available. We present the first case performed in Australia (24 November 2009) and explore this new methodology.

Possible role of glial cells in the onset and progression of Lyme neuroborreliosis

BACKGROUND

Lyme neuroborreliosis (LNB) may present as meningitis, cranial neuropathy, acute radiculoneuropathy or, rarely, as encephalomyelitis. We hypothesized that glia, upon exposure to Borrelia burgdorferi, the Lyme disease agent, produce inflammatory mediators that promote the acute cellular infiltration of early LNB. This inflammatory context could potentiate glial and neuronal apoptosis.

METHODS

We inoculated live B. burgdorferi into the cisterna magna of rhesus macaques and examined the inflammatory changes induced in the central nervous system (CNS), and dorsal root nerves and ganglia (DRG).

RESULTS

ELISA of the cerebrospinal fluid (CSF) showed elevated IL-6, IL-8, CCL2, and CXCL13 as early as one week post-inoculation, accompanied by primarily lymphocytic and monocytic pleocytosis. In contrast, onset of the acquired immune response, evidenced by anti-B. burgdorferi C6 serum antibodies, was first detectable after 3 weeks post-inoculation. CSF cell pellets and CNS tissues were culture-positive for B. burgdorferi. Histopathology revealed signs of acute LNB: severe multifocal leptomeningitis, radiculitis, and DRG inflammatory lesions. Immunofluorescence staining and confocal microscopy detected B. burgdorferi antigen in the CNS and DRG. IL-6 was observed in astrocytes and neurons in the spinal cord, and in neurons in the DRG of infected animals. CCL2 and CXCL13 were found in microglia as well as in endothelial cells, macrophages and T cells. Importantly, the DRG of infected animals showed significant satellite cell and neuronal apoptosis.

CONCLUSION

Our results support the notion that innate responses of glia to B. burgdorferi initiate/mediate the inflammation seen in acute LNB, and show that neuronal apoptosis occurs in this context.

Relationship between B7-H4, regulatory T cells, and patient outcome in human ovarian carcinoma

B7-H4 is a recently identified B7 family member. We previously showed that ovarian tumor and associated macrophages expressed B7-H4; tumor B7-H4+ macrophages and CD4+CD25+FOXP3+ regulatory T cells (Treg cells) suppressed tumor-associated antigen-specific T-cell immunity. To determine the pathologic relationship between B7-H4, macrophages, and Treg cells in the tumor environment, in addition to Treg cell numbers, we quantified B7-H4 expression in the tumor and tumor-associated macrophages in 103 patients with ovarian carcinoma. We observed that the intensity of B7-H4 expression in macrophages was significantly correlated with Treg cell numbers in the tumor. Further, both Treg cells and macrophage B7-H4, but not tumor B7-H4, were negatively associated with patient outcome. Tumor Treg cells enabled macrophages to spontaneously produce interleukin (IL)-10 and IL-6. Tumor macrophages stimulated B7-H4 expression in an autocrine manner through IL-10 and IL-6. Our previous work showed that tumor-associated macrophages spontaneously produced chemokine CCL22 to mediate Treg cell trafficking into tumor, and Treg cells induced B7-H4 on antigen-presenting cells (APC) including macrophages. Altogether, our data support the concept that there is a mechanistic interaction between Treg cells and macrophage, and that Treg cells may convey the suppressive activity to APCs through B7-H4 induction in human ovarian cancer.