Atrial Thrombus and Embolic Stroke in a Patient With Surgical Appendage Ligation and Maze Procedure

This case illustrates the incomplete protection of surgical ligation of left atrial appendage and maze procedure at the time of mitral valve replacement against thromboembolic complications and recurrence of atrial fibrillation. The utility of surgical left atrial appendage ligation as stroke prophylaxis and identification of selected high-risk subjects are reviewed. (Level of Difficulty: Intermediate.)

A Critical Role of PCSK9 in Mediating IL-17-Producing T Cell Responses in Hyperlipidemia

We previously demonstrated that atherogenic Ldlr ^-/- Apobec1 ^-/- (LDb) double knockout mice lacking both low-density lipoprotein receptor (LDLR) and apolipoprotein B mRNA-editing catalytic polypeptide-1 (Apobec1) had increased serum IL-17 levels, with T cell programming shifted towards Th17 cells. In this study, we assessed the role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in T cell programming and atherogenesis. We deleted the Pcsk9 gene from LDb mice to generate Ldlr ^-/- Apobec1 ^-/- Pcsk9 ^-/- (LTp) triple knockout mice. Atherosclerosis in the aortic sinus and aorta were quantitated. Lymphoid cells were analyzed by flow cytometry, ELISA and real-time PCR. Despite of dyslipidemia, LTp mice developed barely detectable atherosclerotic lesions. The IL-17, was very low in plasma and barely detectable in the aortic sinus in the LTp mice. In the spleen, the number of CD4⁺CD8^- cells and splenocytes were much lower in the LDb mice than LTp mice, whereas, the IL-17-producing cells of γδTCR⁺ T cells and effector memory CD4⁺ T cells (CD44^hiCD4⁺) in the spleen were significantly higher in the LDb mice than in the LTp mice. The Rorc mRNA expression levels were elevated in LDb mice compared to LTp mice. When re-stimulated with an anti-CD3 Ab, CD44^hiCD4⁺ T cells from LDb mice secreted more IL-17 than those from LTp mice. T cells from LDb mice (with PCSK9) produce more IL-17 at basal and stimulated conditions when compared with LTp mice (without PCSK9). Despite the dyslipidemic profile and the lack of LDLR, atherogenesis is markedly reduced in LTp mice. These results suggest that PCSK9 is associated with changes in T cell programming that contributes to the development of atherosclerosis.

Pushing the limits of immune-related response: a case of "extreme pseudoprogression"

The advent of immune checkpoint targeted immunotherapy has seen a spectrum of immune-related phenomena in both tumor responses and toxicities. We describe a case of pseudoprogression that pushes the limits of immune-related response criteria and challenges the boundaries and definitions set by trial protocols. A middle-aged man with conventional clear cell renal cell carcinoma (RCC) had received multiple prior systemic treatments including vascular endothelial growth factor receptor tyrosine kinase inhibitors, as well as multiple surgeries and radiotherapy treatments. He was eventually started on nivolumab—the anti-programmed death receptor-1 monoclonal antibody approved for the treatment of advanced RCC. Clinical deterioration was observed soon after a 100 mg dose of nivolumab, with onset of acute renal failure and declining performance status. Radiologic progression was documented in multiple sites including worsening tumor infiltration of his residual kidney. The patient was on palliative treatment and visited by the home hospice team in an end-of-life situation. The patient unexpectedly improved and went on to achieve a durable tumor response. The case is illustrative of an extreme manifestation of pseudoprogression, and impels us to probe the assumptions and controversies surrounding this phenomenon.

Loss of Smooth Muscle α-Actin Leads to NF-κB-Dependent Increased Sensitivity to Angiotensin II in Smooth Muscle Cells and Aortic Enlargement

RATIONALE

Mutations in ACTA2, encoding the smooth muscle isoform of α-actin, cause thoracic aortic aneurysms, acute aortic dissections, and occlusive vascular diseases.

OBJECTIVE

We sought to identify the mechanism by which loss of smooth muscle α-actin causes aortic disease.

METHODS AND RESULTS

Acta2^-/- mice have an increased number of elastic lamellae in the ascending aorta and progressive aortic root dilation as assessed by echocardiography that can be attenuated by treatment with losartan, an angiotensin II (AngII) type 1 receptor blocker. AngII levels are not increased in Acta2^-/- aortas or kidneys. Aortic tissue and explanted smooth muscle cells from Acta2^-/- aortas show increased production of reactive oxygen species and increased basal nuclear factor κB signaling, leading to an increase in the expression of the AngII receptor type I a and activation of signaling at 100-fold lower levels of AngII in the mutant compared with wild-type cells. Furthermore, disruption of smooth muscle α-actin filaments in wild-type smooth muscle cells by various mechanisms activates nuclear factor κB signaling and increases expression of AngII receptor type I a.

CONCLUSIONS

These findings reveal that disruption of smooth muscle α-actin filaments in smooth muscle cells increases reactive oxygen species levels, activates nuclear factor κB signaling, and increases AngII receptor type I a expression, thus potentiating AngII signaling in vascular smooth muscle cells without an increase in the exogenous levels of AngII.

CTHRSSVVC Peptide as a Possible Early Molecular Imaging Target for Atherosclerosis

The purpose of our work was to select phages displaying peptides capable of binding to vascular markers present in human atheroma, and validate their capacity to target the vascular markers in vitro and in low-density lipoprotein receptor knockout (LDLr(-/-)) mouse model of atherosclerosis. By peptide fingerprinting on human atherosclerotic tissues, we selected and isolated four different peptides sequences, which bind to atherosclerotic lesions and share significant similarity to known human proteins with prominent roles in atherosclerosis. The CTHRSSVVC-phage peptide displayed the strongest reactivity with human carotid atherosclerotic lesions (p < 0.05), when compared to tissues from normal carotid arteries. This peptide sequence shares similarity to a sequence present in the fifth scavenger receptor cysteine-rich (SRCR) domain of CD163, which appeared to bind to CD163, and subsequently, was internalized by macrophages. Moreover, the CTHRSSVVC-phage targets atherosclerotic lesions of a low-density lipoprotein receptor knockout (LDLr(-/-)) mouse model of atherosclerosis in vivo to High-Fat diet group versus Control group. Tetraazacyclododecane-1,4,7,10-tetraacetic acid-CTHRSSVVC peptide (DOTA-CTHRSSVVC) was synthesized and labeled with (111)InCl₃ in >95% yield as determined by high performance liquid chromatography (HPLC), to validate the binding of the peptide in atherosclerotic plaque specimens. The results supported our hypothesis that CTHRSSVVC peptide has a remarkable sequence for the development of theranostics approaches in the treatment of atherosclerosis and other diseases.

Asian Immigrant Settlement and Adjustment in Australia

Asians have been the fastest growing overseas-born population inAustralia, more than doubling from 1981 to 1991. Based on the 1991 Census, this article broadly examines economic and social characteristics of the Asian-born population in Australia. Economic factors such as labor force participation, unemployment, occupation, income and housing reveal a great diversity in the settlement experience of the Asian-born, attributable to the diversity of backgrounds. The speed and success of adjustment by refugees and migrants from business, skill and family migrant streams are assisted by such social factors as English language proficiency.

Noninvasive detection of macrophages in atheroma using a radiocontrast-loaded phosphatidylserine-containing liposomal contrast agent for computed tomography

PURPOSE

Macrophage plays an important role in plaque destabilization in atherosclerosis. By harnessing the affinity of macrophages to certain phospholipid species, a liposomal contrast agent containing phosphatidylserine (PS) and X-ray computed tomographic (CT) contrast agent was prepared and evaluated for CT imaging of plaque-associated macrophages in rabbit models of atherosclerosis.

PROCEDURES

Liposomes containing PS and iodixanol were evaluated for their physicochemical characteristics, in vitro macrophage uptake, in vivo blood pool clearance, and organ distribution. Plaque enhancement in the aorta was imaged with CT in two atherosclerotic rabbit models.

RESULTS

In vitro macrophage uptake of PS liposomes increased with increasing amount of PS in the liposomes. Overall clearance of PS liposomes was more rapid than control liposomes. Smaller PS liposomes (d = 112 ± 4 nm) were more effective than control liposomes of similar size or larger control and PS liposomes (d = 172 ± 17 nm) in enhancing aortic plaques in both rabbit models.

CONCLUSIONS

Proper liposomal surface modification and appropriate sizing are important determinant for CT-based molecular imaging of macrophages in atheroma.

Abstract 458: Loss of Smooth Muscle α-actin in Mice Results in Thoracic Aortic Aneurysms via Increased Reactive Oxygen Species, Increased Nox4,and Increased Angiotensin II type 1 Receptor-Mediated Signaling

Objective: ACTA2 mutations cause 10-14% of familial thoracic aortic aneurysms and dissections. Mice deficient in smooth muscle α-actin (Acta2-/-) develop root and ascending thoracic aortic enlargement associated with thickening of the aortic media and fragmentation and disarray of elastic fibers. We hypothesized that blocking AT1 activation would block the aortic pathology and prevent aortic enlargement in Acta2-/- mice.

Methods and Results: Beginning at 4 weeks of age, Acta2-/- mice were treated with losartan or placebo (n≥10) for 6 months and echocardiograms were performed at baseline and every other month. The aortic root in Acta2-/- mice was found to undergo progressive dilatation. After 6 months of treatment, there was no difference in the diameter of the aortic root between wild-type (WT) mice and the losartan treated mice (p=0.44). Histologic analysis of Acta2-/- aortas demonstrated medial thickening and fragmentation of elastic fibers which was normalized by treatment with losartan. Gene expression of matrix metalloproteinase-2 and -9 (Mmp2, Mmp9), along with lumican and decorin, interleukin-6 (Il6) and phosphorylation of RelA (a subunit of nuclear factor κB, NF-κB) was increased in Acta2-/- aortas, and was corrected by treatment with losartan. NADPH oxidase 4 and AT1a mRNA was increased in Acta2-/- aortic smooth muscle cells (SMCs) and aortas. Increase of AT1a was blocked by lowering reactive oxygen species (ROS) with N-actetyl cysteine (NAC). Angiotensin II (AngII) dose response studies suggested Acta2-/- aortic SMCs had increased sensitivity to Ang II. Additionally, Acta2-/- SMCs had increased ROS compared to WT by flow cytometry (P<0.05). Increased ROS was also observed in aortic samples derived from Acta2-/- mice. Blocking ROS using NAC attenuated aneurysm formation by reducing the expression of Mmps and IL6 and reducing signaling through AT1 in Acta2-/- mice. Genetic deletion of AT1a attenuated ROS and expression of Mmps and IL6 levels in the Acta2-/-aortas but not to WT levels.

Conclusions: Our results demonstrate that complete loss of α-SMA leads to aortic dilation and pathologic changes by increasing SMC ROS levels, thus increasing sensitivity to AngII, which results in NF-κB activation and increased expression of Mmps and IL6.

CT imaging of myocardial scars with collagen-targeting gold nanoparticles

In the setting of myocardial ischemia, recovery of myocardial function by revascularization procedures depends on the extent of coronary disease and myocardial scar burden. Currently, computed tomographic (CT) imaging offers superior evaluation of coronary lesions but lacks the capability to measure the transmural extent of myocardial scar. Our work focuses on determining if collagen-targeting gold nanoparticles (AuNPs) can effectively target myocardial scar and provide adequate contrast for CT imaging. AuNPs were coated with a collagen-homing peptide, collagen adhesin (CNA35). Myocardial scar was created in mice by occlusion/reperfusion of the left anterior descending coronary artery. Thirty days later, un-gated CT imaging was performed. Over 6h, CNA35-AuNPs provided uniform and prolonged opacification of the vascular structures (100-130 HU). In mice with larger scar burden, focal contrast enhancement was detected in the myocardium, which was not apparent within that of control mice. Histological staining confirmed myocardial scar formation and accumulation of AuNPs.

FROM THE CLINICAL EDITOR

This team of investigators presents a collagen-targeting gold nanoparticle-based approach that enables the imaging of myocardial scars via CT scans in a rodent model. This information would enable clinicians to judge the recovery potential of myocardium more accurately than the current CT-scan based approaches.

Ultrasound-enhanced thrombolytic effect of tissue plasminogen activator-loaded echogenic liposomes in an in vivo rabbit aorta thrombus model--brief report

OBJECTIVE

Ultrasound enhances thrombolysis when combined with a thrombolytic and a contrast agent. This study aimed to evaluate the thrombolytic effect of our tissue plasminogen activator (tPA)-loaded echogenic liposomes (ELIP) in an in vivo clot model, with and without ultrasound treatment.

METHODS AND RESULTS

The femoral arteries of New Zealand White rabbits (n=4 per group) were cannulated. The abdominal aortas were denuded, and thrombi were created using a solution of sodium ricinoleate plus thrombin. Rabbits were then randomly selected to receive tPA-loaded ELIP (200 μg of tPA/5 mg of lipid) or empty ELIP with or without pulsed (color) Doppler ultrasound (5.7 MHz) for 2 minutes. Thrombus was imaged and echogenicity analyzed before and after ELIP injection. Blood flow velocities were measured at baseline, after clot formation, and serially after treatment up to 15 minutes. tPA-loaded ELIP highlighted thrombus in the abdominal aorta more effectively than empty ELIP (P<0.05). Ultrasound enhanced the thrombolytic effect of tPA-loaded ELIP, resulting in earlier and more complete recanalization rates (P<0.001).

CONCLUSION

This study demonstrates effective highlighting of clots and thrombolytic effect of tPA-loaded ELIP in an in vivo rabbit aorta clot model. Doppler ultrasound treatment enhances this thrombolytic effect, resulting in earlier and more complete recanalization rates.

Experimental models investigating the inflammatory basis of atherosclerosis

Inflammation is considered an important aspect in the development of atherosclerosis. Genetic manipulations of animal models susceptible to atherosclerosis have unraveled the contribution of various inflammatory pathways implicated in the development of atherosclerosis. These inflammatory pathways not only lead to the recruitment and entry of inflammatory cells into the arterial wall, they also modify the morphology and composition of atherosclerotic plaques. Certain inflammatory pathways, such as P-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, appear to play an important role in lesion initiation, whereas others, such as interleukin-10 and CD40/CD40 ligand, seem to contribute to lesion progression and morphologic changes. An understanding of these pathways will allow the development of new strategies in the management of atherosclerosis. This review provides a roadmap for better utilization of these models in atherosclerosis research.

Effect of inhibiting cholesteryl ester transfer protein on the kinetics of high-density lipoprotein cholesteryl ester transport in plasma: in vivo studies in rabbits

OBJECTIVE

Inhibitors of cholesteryl ester transfer protein (CETP) have been developed as potential anti-atherogenic agents. Theoretically, however, they may be pro-atherogenic by blocking one of the pathways for removing high-density lipoprotein (HDL) cholesteryl esters (CE) from plasma in the final step of reverse cholesterol transport. Here we describe how CETP inhibition in rabbits impacts on the kinetics of HDL CE transport in plasma.

METHODS AND RESULTS

Administration of a CETP inhibitor reduced CETP activity by 80% to 90% and doubled the HDL cholesteryl ester concentration. Multi-compartmental analysis was used to determine HDL CE kinetics in CETP-inhibited and control rabbits after injection of tracer amounts of both native and reconstituted HDL labeled with 3H in the CE moiety. In control rabbits, HDL CE was removed from plasma by both a direct pathway and an indirect pathway after transfer of HDL CE to the very-low-density lipoprotein/low-density lipoprotein fraction. In CETP-inhibited rabbits there was an almost complete block in removal via the indirect pathway. This did not compromise the overall removal of HDL CE from plasma, which was not different in control and inhibited animals.

CONCLUSIONS

Inhibiting CETP in rabbits does not compromise the removal of HDL CE from plasma.

Impact of Short-Term Administration of High-Density Lipoproteins and Atorvastatin on Atherosclerosis in Rabbits

OBJECTIVE

This study investigates effects of short-term administration of high-density lipoproteins (HDL) and a statin on atherosclerosis in cholesterol-fed rabbits. Effects of HDL apolipoprotein and phospholipid composition have also been investigated.

METHODS AND RESULTS

Aortic atherosclerosis was established over 17 weeks in 46 rabbits by balloon denudation and cholesterol feeding. During the past 5 days of the cholesterol-feeding period, animals received: (1) no treatment; (2) oral atorvastatin 5 mg/kg on each of the 5 days; or (3) infusions of HDL (8 mg/kg apolipoprotein A-I) on days 1 and 3 of the treatment phase. After euthanization, lesion size and composition were assessed by histological and immunohistochemical analysis. HDL (but not atorvastatin) reduced lesion size by 36% (P<0.05). The ratio of smooth muscle cells to macrophages in the lesions increased 2.6-fold in animals infused with HDL (P<0.05) and 4-fold in those receiving atorvastatin (P<0.01). HDL and atorvastatin reduced matrix metalloproteinase (MMP)-9 expression by 42% (P<0.05) and 45% (P<0.03), respectively. HDL increased thrombomodulin expression 2-fold (P<0.03). The beneficial effects on lesion area and plaque cellular composition were influenced by HDL phospholipid and apolipoprotein composition.

CONCLUSIONS

Infusing small amounts of HDL rapidly reduces lesion size and is comparable to atorvastatin in promoting a stable plaque phenotype.

Metabolism of apoA-I as lipid-free protein or as component of discoidal and spherical reconstituted HDLs: studies in wild-type and hepatic lipase transgenic rabbits

OBJECTIVE

Apolipoprotein (apo)A-I exists in 3 forms in plasma: as lipid-free apoA-I, as a component of pre-beta-migrating discoidal high density lipoproteins (HDLs), and as a component of alpha-migrating spherical HDLs. This study investigates (1) the in vivo metabolism of apoA-I in each of these forms and (2) the effects of hepatic lipase (HL) on apoA-I metabolism.

METHODS AND RESULTS

Wild-type and HL transgenic rabbits were studied. When lipid-free (125)I-apoA-I and 125I-apoA-I in pre-beta-migrating discoidal reconstituted HDLs (rHDLs) were injected into wild-type rabbits, the label rapidly appeared in alpha-migrating particles and decayed with the same fractional catabolic rate (FCR) as when they were injected as a component of spherical rHDLs. Spherical rHDLs did not change in size when they were injected into wild-type rabbits but were reduced in size in HL transgenic rabbits. The FCR of apoA-I in HL transgenic rabbits was double that in wild-type rabbits.

CONCLUSIONS

In vivo, (1) lipid-free apoA-I rapidly incorporates into preexisting alpha-migrating particles, (2) pre-beta-migrating discoidal HDLs are rapidly converted into alpha-migrating HDLs, (3) the FCR of apoA-I is independent of the form in which it is introduced into plasma, and (4) HL reduces the size of alpha-migrating HDLs and increases the rate of catabolism of apoA-I.

Indirect sandwich enzyme-linked immunosorbent assay (ELISA) for plasma apolipoprotein E

We have developed an indirect sandwich ELISA for measuring plasma apolipoprotein E (apo-E), using commercially available antibodies. A monoclonal anti-apo-E was used as the capture antibody and the captured apo-E detected with polyclonal anti-apo-E antiserum (goat). The detecting antibody was quantitated using horseradish peroxidase-conjugated rabbit immunoglobulin to goat immunoglobulins. There was no detectable cross-reactivity between the three antisera. Interference with the assay by apolipoprotein A-1, bilirubin and haemoglobin was not significant up to 1.7 g/L, 1250 mumol/L and 13.0 g/dL, respectively. The ELISA method showed high correlation with an established immunonephelometric method (ELISA apo.E = 1.04 Immunonephelometric apo-E + 16; r2 = 0.954, P < 0.0001, n = 39). The assay has a measuring range between 5 and 560 mg/L. The coefficient of duplicates was 2.0%, within-run coefficients of variation (CV) ranged from 3.7 to 6.0% and between-run CV from 6.1 to 15.1%. The reference range determined for 168 normotriglyceridaemic subjects was 20 to 130 mg/L. In an analysis of the lipoprotein subfractions isolated by ultracentrifugation as the fraction of density less than 1.25 g/mL and separated by gel permeation chromatography, apo-E was found to be associated with very low-density lipoprotein and large high-density lipoprotein.

People movements between Australia and Asian-Pacific nations: trends, issues and prospects

"This article examines the growth and diversification of...permanent, long and short-term movements of people from Asia and the Pacific and the growth in immigrant and local-born Australians departing Australia to live and work in Asia. The occasional controversies surrounding the growth of Asian arrivals and Australia's current push to integrate with the booming Asian economies are examined. The article concludes with a general discussion of the economic, social, cultural, and international consequences of the two-way movements of people between Australia and its Asian and Pacific neighbors."