Acute neutrophilic vasculitis (leukocytoclasia) in 36 COVID-19 autopsy brains

BACKGROUND

Hypercytokinemia, the renin-angiotensin system, hypoxia, immune dysregulation, and vasculopathy with evidence of immune-related damage are implicated in brain morbidity in COVID-19 along with a wide variety of genomic and environmental influences. There is relatively little evidence of direct SARS-CoV-2 brain infection in COVID-19 patients.

METHODS

Brain histopathology of 36 consecutive autopsies of patients who were RT-PCR positive for SARS-CoV-2 was studied along with findings from contemporary and pre-pandemic historical control groups. Immunostaining for serum and blood cell proteins and for complement components was employed. Microcirculatory wall complement deposition in the COVID-19 cohort was compared to historical control cases. Comparisons also included other relevant clinicopathological and microcirculatory findings in the COVID-19 cohort and control groups.

RESULTS

The COVID-19 cohort and both the contemporary and historical control groups had the same rate of hypertension, diabetes mellitus, and obesity. The COVID-19 cohort had varying amounts of acute neutrophilic vasculitis with leukocytoclasia in the microcirculation of the brain in all cases. Prominent vascular neutrophilic transmural migration was found in several cases and 25 cases had acute perivasculitis. Paravascular microhemorrhages and petechial hemorrhages (small brain parenchymal hemorrhages) had a slight tendency to be more numerous in cohort cases that displayed less acute neutrophilic vasculitis. Tissue burden of acute neutrophilic vasculitis with leukocytoclasia was the same in control cases as a group, while it was significantly higher in COVID-19 cases. Both the tissue burden of acute neutrophilic vasculitis and the activation of complement components, including membrane attack complex, were significantly higher in microcirculatory channels in COVID-19 cohort brains than in historical controls.

CONCLUSIONS

Acute neutrophilic vasculitis with leukocytoclasia, acute perivasculitis, and associated paravascular blood extravasation into brain parenchyma constitute the first phase of an immune-related, acute small-vessel inflammatory condition often termed type 3 hypersensitivity vasculitis or leukocytoclastic vasculitis. There is a higher tissue burden of acute neutrophilic vasculitis and an increased level of activated complement components in microcirculatory walls in COVID-19 cases than in pre-pandemic control cases. These findings are consistent with a more extensive small-vessel immune-related vasculitis in COVID-19 cases than in control cases. The pathway(s) and mechanism for these findings are speculative.

A case-control autopsy series of liver pathology associated with novel coronavirus disease (COVID-19)

BACKGROUND

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for coronavirus disease 2019 (COVID-19) is most well-known for causing pulmonary injury, a significant proportion of patients experience hepatic dysfunction. The mechanism by which SARS-CoV2 causes liver injury is not fully understood. The goal of this study was to describe the hepatic pathology in a large cohort of deceased patients with COVID-19 as compared to a control group of deceased patients without COVID-19.

METHODS

Consented autopsy cases at two institutions were searched for documentation of COVID-19 as a contributing cause of death. A group of consecutive consented autopsy cases during the same period, negative for SARS-CoV-2 infection, was used as a control group. The autopsy report and electronic medical records were reviewed for relevant clinicopathologic information. H&E-stained liver sections from both groups were examined for pertinent histologic features. Select cases underwent immunohistochemical staining for CD 68 and ACE2 and droplet digital polymerase chain reaction (ddPCR) assay for evaluation of SARS-CoV2 RNA.

RESULTS

48 COVID-19 positive patients (median age 73, M:F 3:1) and 40 COVID-19 negative control patients (median age 67.5, M:F 1.4:1) were included in the study. The COVID-19 positive group was significantly older and had a lower rate of alcoholism and malignancy, but there was no difference in other comorbidities. The COVID-19 positive group was more likely to have received steroids (75.6 % vs. 36.1 %, p < 0.001). Hepatic vascular changes were seen in a minority (10.6 %) of COVID-19 positive cases. When all patients were included, there were no significant histopathologic differences between groups, but when patients with chronic alcoholism were excluded, the COVID-19 positive group was significantly more likely to have steatosis (80.9 % vs. 50.0 %, p = 0.004) and lobular inflammation (45.7 % vs. 20.7 %, p = 0.03). Testing for viral RNA by ddPCR identified 2 of the 18 (11.1 %) COVID-19 positive cases to have SARS-CoV-2 RNA detected within the liver FFPE tissue.

CONCLUSIONS

The most significant findings in the liver of COVID-19 positive patients were mild lobular inflammation and steatosis. The high rate of steroid therapy in this population may be a possible source of steatosis. Hepatic vascular alterations were only identified in a minority of patients and did not appear to play a predominant role in COVID-19 mediated hepatic injury. Low incidence of SARS-CoV-2 RNA positivity in liver tissue in our cohort suggests hepatic injury in the setting of COVID-19 may be secondary in nature.

SARS-CoV-2 infection of the pancreas promotes thrombofibrosis and is associated with new-onset diabetes

Evidence suggests an association between severe acute respiratory syndrome–cornavirus-2 (SARS-CoV-2) infection and the occurrence of new-onset diabetes. We examined pancreatic expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), the cell entry factors for SARS-CoV-2, using publicly available single-cell RNA sequencing data sets, and pancreatic tissue from control male and female nonhuman primates (NHPs) and humans. We also examined SARS-CoV-2 immunolocalization in pancreatic cells of SARS-CoV-2–infected NHPs and patients who had died from coronavirus disease 2019 (COVID-19). We report expression of ACE2 in pancreatic islet, ductal, and endothelial cells in NHPs and humans. In pancreata from SARS-CoV-2–infected NHPs and COVID-19 patients, SARS-CoV-2 infected ductal, endothelial, and islet cells. These pancreata also exhibited generalized fibrosis associated with multiple vascular thrombi. Two out of 8 NHPs developed new-onset diabetes following SARS-CoV-2 infection. Two out of 5 COVID-19 patients exhibited new-onset diabetes at admission. These results suggest that SARS-CoV-2 infection of the pancreas may promote acute and especially chronic pancreatic dysfunction that could potentially lead to new-onset diabetes.

ACE2 chromogenic immunostaining protocol optimized for formalin-fixed paraffin-embedded human tissue sections

Angiotensin-converting enzyme 2 (ACE2) is a key cellular entry factor for severe acute respiratory syndrome coronavirus 2. Hence, identifying cell types that express ACE2 is important for understanding the pathophysiology of coronavirus disease 2019. We performed extensive testing of multiple primary antibodies across various human tissue types. Here, we describe an optimized protocol for immunostaining of ACE2 in formalin-fixed paraffin-embedded human pancreas, small intestine, and kidney tissue sections obtained from organ donors and autopsies.

For complete details on the use and execution of this protocol, please refer to Kusmartseva et al. (2020).

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We present an immunostaining protocol for rabbit monoclonal IgG anti-ACE2, clone EPR4435(2)

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ACE2 staining has been optimized in human pancreas, small intestine, and kidney

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Protocol has been optimized using tissue sections from human organ donors and autopsies

Posttraumatic Stress Disorder and Cardiovascular Disease: State of the Science, Knowledge Gaps, and Research Opportunities

Posttraumatic stress disorder (PTSD) is characterized by a persistent maladaptive reaction after exposure to severe psychological trauma. Traumatic events that may precipitate PTSD include violent personal assaults, natural and human-made disasters, and exposure to military combat or warfare. There is a growing body of evidence for associations of PTSD with major risk factors for cardiovascular disease (CVD), such as hypertension and diabetes, as well as with major CVD outcomes, such as myocardial infarction and heart failure. However, it is unclear whether these associations are causal or confounded. Furthermore, the biological and behavioral mechanisms underlying these associations are poorly understood. Here, the available evidence on the association of PTSD with CVD from population, basic, and genomic research as well as from clinical and translational research are reviewed, seeking to identify major research gaps, barriers, and opportunities in knowledge acquisition and technology as well as research tools to support and accelerate critical research for near-term and longer-term translational research directions. Large-scale, well-designed prospective studies, capturing diverse and high-risk populations, are warranted that include uniform phenotyping of PTSD as well as broad assessment of biological and behavioral risk factors and CVD outcomes. Available evidence from functional brain imaging studies demonstrates that PTSD pathophysiology includes changes in specific anatomical brain regions and circuits, and studies of immune system function in individuals with PTSD suggest its association with enhanced immune inflammatory activity. However, establishment of animal models and human tissue biobanks is also warranted to elucidate the potential causal connection of PTSD-induced brain changes and/or inflammation with CVD pathophysiology. Emerging large-scale genome-wide association studies of PTSD will provide an opportunity to conduct mendelian randomization studies that test hypotheses regarding the presence, magnitude, and direction of causal associations between PTSD and CVD outcomes. By identifying research gaps in epidemiology and genomics, animal, and human translational research, opportunities to better justify and design future interventional trials are highlighted that may test whether treatment of PTSD or underlying neurobiological or immune dysregulation may improve or prevent CVD risk or outcomes.

Severe COVID-19 Is Characterized by an Impaired Type I Interferon Response and Elevated Levels of Arginase Producing Granulocytic Myeloid Derived Suppressor Cells

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19 that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1+ G-MDSC (Arg+G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg+G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

SARS-CoV-2 Infects Endothelial Cells In Vivo and In Vitro

SARS-CoV-2 infection can cause fatal inflammatory lung pathology, including thrombosis and increased pulmonary vascular permeability leading to edema and hemorrhage. In addition to the lung, cytokine storm-induced inflammatory cascade also affects other organs. SARS-CoV-2 infection-related vascular inflammation is characterized by endotheliopathy in the lung and other organs. Whether SARS-CoV-2 causes endotheliopathy by directly infecting endothelial cells is not known and is the focus of the present study. We observed 1) the co-localization of SARS-CoV-2 with the endothelial cell marker CD31 in the lungs of SARS-CoV-2-infected mice expressing hACE2 in the lung by intranasal delivery of adenovirus 5-hACE2 (Ad5-hACE2 mice) and non-human primates at both the protein and RNA levels, and 2) SARS-CoV-2 proteins in endothelial cells by immunogold labeling and electron microscopic analysis. We also detected the co-localization of SARS-CoV-2 with CD31 in autopsied lung tissue obtained from patients who died from severe COVID-19. Comparative analysis of RNA sequencing data of the lungs of infected Ad5-hACE2 and Ad5-empty (control) mice revealed upregulated KRAS signaling pathway, a well-known pathway for cellular activation and dysfunction. Further, we showed that SARS-CoV-2 directly infects mature mouse aortic endothelial cells (AoECs) that were activated by performing an aortic sprouting assay prior to exposure to SARS-CoV-2. This was demonstrated by co-localization of SARS-CoV-2 and CD34 by immunostaining and detection of viral particles in electron microscopic studies. Moreover, the activated AoECs became positive for ACE-2 but not quiescent AoECs. Together, our results indicate that in addition to pneumocytes, SARS-CoV-2 also directly infects mature vascular endothelial cells in vivo and ex vivo, which may contribute to cardiovascular complications in SARS-CoV-2 infection, including multipleorgan failure.

Endothelial cell infection and dysfunction, immune activation in severe COVID-19

Rationale: Pulmonary vascular endotheliitis, perivascular inflammation, and immune activation are observed in COVID-19 patients. While the initial SARS-CoV-2 infection mainly infects lung epithelial cells, whether it also infects endothelial cells (ECs) and to what extent SARS-CoV-2-mediated pulmonary vascular endotheliitis is associated with immune activation remain to be determined. Methods: To address these questions, we studied SARS-CoV-2-infected K18-hACE2 (K18) mice, a severe COVID-19 mouse model, as well as lung samples from SARS-CoV-2-infected nonhuman primates (NHP) and patient deceased from COVID-19. We used immunostaining, RNAscope, and electron microscopy to analyze the organs collected from animals and patient. We conducted bulk and single cell (sc) RNA-seq analyses, and cytokine profiling of lungs or serum of the severe COVID-19 mice. Results: We show that SARS-CoV-2-infected K18 mice develop severe COVID-19, including progressive body weight loss and fatality at 7 days, severe lung interstitial inflammation, edema, hemorrhage, perivascular inflammation, systemic lymphocytopenia, and eosinopenia. Body weight loss in K18 mice correlated with the severity of pneumonia, but not with brain infection. We also observed endothelial activation and dysfunction in pulmonary vessels evidenced by the up-regulation of VCAM1 and ICAM1 and the downregulation of VE-cadherin. We detected SARS-CoV-2 in capillary ECs, activation and adhesion of platelets and immune cells to the vascular wall of the alveolar septa, and increased complement deposition in the lungs, in both COVID-19-murine and NHP models. We also revealed that pathways of coagulation, complement, K-ras signaling, and genes of ICAM1 and VCAM1 related to EC dysfunction and injury were upregulated, and were associated with massive immune activation in the lung and circulation. Conclusion: Together, our results indicate that SARS-CoV-2 causes endotheliitis via both infection and infection-mediated immune activation, which may contribute to the pathogenesis of severe COVID-19 disease.

COVID-19 myocarditis: quantitative analysis of the inflammatory infiltrate and a proposed mechanism

COVID-19 has a significant effect upon the cardiovascular system. While a number of different cardiovascular histopathologies have been described at post-mortem examination, the incidence of typical viral myocarditis in COVID-19 positive patients appears very low [1-3]. In this study, we further characterize and quantify the inflammatory cell infiltrate in a COVID-19 study cohort and compare the findings to both an age and disease matched control cohort and a cohort of patients diagnosed with typical inflammatory myocarditis. All study and control cohorts had 1 or more of the comorbidities most commonly associated with severe disease (hypertension, type II diabetes, obesity, or known cardiovascular disease). The results demonstrate a skewed distribution of the number of CD68+ cells in COVID-19 hearts, with upper quantiles showing a significant increase as compared to both matched control hearts, and those with myocarditis. In contrast, hearts from typical inflammatory myocarditis contained increased numbers of CD4+, and CD8+ cells compared to both COVID-19 and control cohorts. In conclusion, the presence of an increased number of CD68+ cells suggests that COVID-19 may incite a form of myocarditis different from typical viral myocarditis, and associated with diffusely infiltrative cells of monocytes/macrophage lineage.

COVID-19: The Heart of the Matter-Pathological Changes and a Proposed Mechanism

The SARS-CoV-2 virus has resulted in over 88 million cases worldwide of COVID-19 as of January 2021. The heart is one of the most commonly affected organs in COVID-19, but the nature and extent of the cardiac pathology has remained controversial. It has been shown that patients infected with SARS-CoV-2 can sustain type 1 myocardial infarction in the absence of significant atherosclerotic coronary artery disease. However, many patients present with small elevations of troponin enzymes of unclear etiology which correlate with overall COVID-19 disease outcome. Early autopsy reports indicated variable levels of typical lymphocytic myocarditis, while radiology reports have indicated that myocarditis can be a persistent problem after recovery from acute illness, raising concern about participation in college athletics. In this communication, we review the literature to date regarding the gross and microscopic findings of COVID-19 cardiac involvement, present the findings from over 40 cases from our academic medical center, and propose mechanisms by which patients develop small elevations in troponin.  .

Expression of SARS-CoV-2 Entry Factors in the Pancreas of Normal Organ Donors and Individuals with COVID-19

Diabetes is associated with increased mortality from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Given literature suggesting a potential association between SARS-CoV-2 infection and diabetes induction, we examined pancreatic expression of angiotensin-converting enzyme 2 (ACE2), the key entry factor for SARS-CoV-2 infection. Specifically, we analyzed five public scRNA-seq pancreas datasets and performed fluorescence in situ hybridization, western blotting, and immunolocalization for ACE2 with extensive reagent validation on normal human pancreatic tissues across the lifespan, as well as those from coronavirus disease 2019 (COVID-19) cases. These in silico and ex vivo analyses demonstrated prominent expression of ACE2 in pancreatic ductal epithelium and microvasculature, but we found rare endocrine cell expression at the mRNA level. Pancreata from individuals with COVID-19 demonstrated multiple thrombotic lesions with SARS-CoV-2 nucleocapsid protein expression that was primarily limited to ducts. These results suggest SARS-CoV-2 infection of pancreatic endocrine cells, via ACE2, is an unlikely central pathogenic feature of COVID-19-related diabetes.

Myocarditis is rare in COVID-19 autopsies: cardiovascular findings across 277 postmortem examinations

The COVID-19 pandemic, the result of severe acute respiratory syndrome (SARS)-CoV-2, is a major cause of worldwide mortality with a significant cardiovascular component. While a number of different cardiovascular histopathologies have been reported at postmortem examination, their incidence is unknown, due to limited numbers of cases in any given study. A literature review was performed identifying 277 autopsied hearts across 22 separate publications of COVID-19 positive patients. The median age of the autopsy cohort was 75 and 97.6% had one or more comorbidities. Initial review of the data indicate that myocarditis was present in 20 hearts (7.2%); however, closer examination of additional reported information revealed that most cases were likely not functionally significant and the true prevalence of myocarditis is likely much lower (<2%). At least one acute, potentially COVID-19-related cardiovascular histopathologic finding, such as macro or microvascular thrombi, inflammation, or intraluminal megakaryocytes, was reported in 47.8% of cases. Significant differences in reporting of histopathologic findings occurred between studies indicating strong biases in observations and the need for more consistency in reporting. In conclusion, across 277 cases, COVID-19-related cardiac histopathological findings, are common, while myocarditis is rare.

Pulmonary and cardiac pathology in African American patients with COVID-19: an autopsy series from New Orleans

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread rapidly across the USA, causing extensive morbidity and mortality, particularly in the African American community. Autopsy can considerably contribute to our understanding of many disease processes and could provide crucial information to guide management of patients with coronavirus disease 2019 (COVID-19). We report on the relevant cardiopulmonary findings in, to our knowledge, the first autopsy series of ten African American decedents, with the cause of death attributed to COVID-19.

Methods

Autopsies were performed on ten African American decedents aged 44–78 years with cause of death attributed to COVID-19, reflective of the dominant demographic of deaths following COVID-19 diagnosis in New Orleans. Autopsies were done with consent of the decedents' next of kin. Pulmonary and cardiac features were examined, with relevant immunostains to characterise the inflammatory response, and RNA labelling and electron microscopy on representative sections.

Findings

Important findings include the presence of thrombosis and microangiopathy in the small vessels and capillaries of the lungs, with associated haemorrhage, that significantly contributed to death. Features of diffuse alveolar damage, including hyaline membranes, were present, even in patients who had not been ventilated. Cardiac findings included individual cell necrosis without lymphocytic myocarditis. There was no evidence of secondary pulmonary infection by microorganisms.

Interpretation

We identify key pathological states, including thrombotic and microangiopathic pathology in the lungs, that contributed to death in patients with severe COVID-19 and decompensation in this demographic. Management of these patients should include treatment to target these pathological mechanisms.

Funding

None.

Proteomic Architecture of Human Coronary and Aortic Atherosclerosis

BACKGOUND

The inability to detect premature atherosclerosis significantly hinders implementation of personalized therapy to prevent coronary heart disease. A comprehensive understanding of arterial protein networks and how they change in early atherosclerosis could identify new biomarkers for disease detection and improved therapeutic targets.

METHODS

Here we describe the human arterial proteome and proteomic features strongly associated with early atherosclerosis based on mass spectrometry analysis of coronary artery and aortic specimens from 100 autopsied young adults (200 arterial specimens). Convex analysis of mixtures, differential dependent network modeling, and bioinformatic analyses defined the composition, network rewiring, and likely regulatory features of the protein networks associated with early atherosclerosis and how they vary across 2 anatomic distributions.

RESULTS

The data document significant differences in mitochondrial protein abundance between coronary and aortic samples (coronary>>aortic), and between atherosclerotic and normal tissues (atherosclerotic<

CONCLUSIONS

The human arterial proteome can be viewed as a complex network whose architectural features vary considerably as a function of anatomic location and the presence or absence of atherosclerosis. The data suggest important reductions in mitochondrial protein abundance in early atherosclerosis and also identify a subset of plasma proteins that are highly predictive of angiographically defined coronary disease.

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Key Words

• atherosclerosis
• biomarkers
• mitochondria
• proteomics

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MESH Headings

• Adolescent
• Adult
• Aorta/chemistry
• Aorta/pathology
• Aortic Diseases/metabolism
• Aortic Diseases/pathology
• Atherosclerosis/metabolism
• Atherosclerosis/pathology
• Autopsy
• Biomarkers/analysis
• Coronary Artery Disease/metabolism
• Coronary Artery Disease/pathology
• Coronary Vessels/chemistry
• Coronary Vessels/pathology
• Female
• Humans
• Male
• Middle Aged
• Plaque, Atherosclerotic
• Protein Interaction Maps
• Proteins/analysis
• Proteomics/methods
• Tandem Mass Spectrometry
• Young Adult

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Grants

• R01 HL111362 NHLBI NIH HHS

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Affiliation(s)

David M Herrington Section on Cardiovascular Medicine, Department of Internal Medicine (D.M.H., C.F.Z., G.S.)
Chunhong Mao Biocomplexity Institute of Virginia Tech, Virginia Tech, Blacksburg (C.M.)
Sarah J Parker Advanced Clinical Biosystems Research Institute, Cedars-Sinai Heart Institute, and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (S.T.P., V.V., W.R.S., J.E.V.E.)
Zongming Fu Johns Hopkins Medical Institute, Baltimore, MD (Z.F.)
Guoqiang Yu Department of Electrical and Computer Engineering, Virginia Tech, Arlington (G.Y., L.C., Y.F., Yizhi Wang, Yue Wang)
Lulu Chen Department of Electrical and Computer Engineering, Virginia Tech, Arlington (G.Y., L.C., Y.F., Yizhi Wang, Yue Wang)
Vidya Venkatraman Advanced Clinical Biosystems Research Institute, Cedars-Sinai Heart Institute, and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (S.T.P., V.V., W.R.S., J.E.V.E.)
Yi Fu Department of Electrical and Computer Engineering, Virginia Tech, Arlington (G.Y., L.C., Y.F., Yizhi Wang, Yue Wang)
Yizhi Wang Department of Electrical and Computer Engineering, Virginia Tech, Arlington (G.Y., L.C., Y.F., Yizhi Wang, Yue Wang)
Timothy D Howard Department of Biochemistry (T.D.H.)
Goo Jun Department of Epidemiology, Human Genetics and Environmental Sciences, Human Genetics Center, School of Public Health, University of Texas Health Science Center at Houston (G.J., J.E.H.)
Caroline F Zhao Section on Cardiovascular Medicine, Department of Internal Medicine (D.M.H., C.F.Z., G.S.)
Yongmei Liu Department of Epidemiology, Division of Public Health Sciences (Y.L.), Wake Forest School of Medicine, Winston-Salem, NC
Georgia Saylor Section on Cardiovascular Medicine, Department of Internal Medicine (D.M.H., C.F.Z., G.S.)
Weston R Spivia Advanced Clinical Biosystems Research Institute, Cedars-Sinai Heart Institute, and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (S.T.P., V.V., W.R.S., J.E.V.E.)
Grace B Athas Department of Pathology, Louisiana State Health Science Center, New Orleans (G.B.A., D.T., R.C.V.H.)
Dana Troxclair Department of Pathology, Louisiana State Health Science Center, New Orleans (G.B.A., D.T., R.C.V.H.)
James E Hixson Department of Epidemiology, Human Genetics and Environmental Sciences, Human Genetics Center, School of Public Health, University of Texas Health Science Center at Houston (G.J., J.E.H.)
Richard S Vander Heide Department of Pathology, Louisiana State Health Science Center, New Orleans (G.B.A., D.T., R.C.V.H.)
Yue Wang Department of Electrical and Computer Engineering, Virginia Tech, Arlington (G.Y., L.C., Y.F., Yizhi Wang, Yue Wang)
Jennifer E Van Eyk Advanced Clinical Biosystems Research Institute, Cedars-Sinai Heart Institute, and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (S.T.P., V.V., W.R.S., J.E.V.E.)

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Whole Exome Sequencing to Identify Genetic Variants Associated with Raised Atherosclerotic Lesions in Young Persons

We investigated the influence of genetic variants on atherosclerosis using whole exome sequencing in cases and controls from the autopsy study “Pathobiological Determinants of Atherosclerosis in Youth (PDAY)”. We identified a PDAY case group with the highest total amounts of raised lesions (n = 359) for comparisons with a control group with no detectable raised lesions (n = 626). In addition to the standard exome capture, we included genome-wide proximal promoter regions that contain sequences that regulate gene expression. Our statistical analyses included single variant analysis for common variants (MAF > 0.01) and rare variant analysis for low frequency and rare variants (MAF < 0.05). In addition, we investigated known CAD genes previously identified by meta-analysis of GWAS studies. We did not identify individual common variants that reached exome-wide significance using single variant analysis. In analysis limited to 60 CAD genes, we detected strong associations with COL4A2/COL4A1 that also previously showed associations with myocardial infarction and arterial stiffness, as well as coronary artery calcification. Likewise, rare variant analysis did not identify genes that reached exome-wide significance. Among the 60 CAD genes, the strongest association was with NBEAL1 that was also identified in gene-based analysis of whole exome sequencing for early onset myocardial infarction.

Bioinformatic Analysis of Coronary Disease Associated SNPs and Genes to Identify Proteins Potentially Involved in the Pathogenesis of Atherosclerosis

Factors that contribute to the onset of atherosclerosis may be elucidated by bioinformatic techniques applied to multiple sources of genomic and proteomic data. The results of genome wide association studies, such as the CardioGramPlusC4D study, expression data, such as that available from expression quantitative trait loci (eQTL) databases, along with protein interaction and pathway data available in Ingenuity Pathway Analysis (IPA), constitute a substantial set of data amenable to bioinformatics analysis. This study used bioinformatic analyses of recent genome wide association data to identify a seed set of genes likely associated with atherosclerosis. The set was expanded to include protein interaction candidates to create a network of proteins possibly influencing the onset and progression of atherosclerosis. Local average connectivity (LAC), eigenvector centrality, and betweenness metrics were calculated for the interaction network to identify top gene and protein candidates for a better understanding of the atherosclerotic disease process. The top ranking genes included some known to be involved with cardiovascular disease (APOA1, APOA5, APOB, APOC1, APOC2, APOE, CDKN1A, CXCL12, SCARB1, SMARCA4 and TERT), and others that are less obvious and require further investigation (TP53, MYC, PPARG, YWHAQ, RB1, AR, ESR1, EGFR, UBC and YWHAZ). Collectively these data help define a more focused set of genes that likely play a pivotal role in the pathogenesis of atherosclerosis and are therefore natural targets for novel therapeutic interventions.

Novel therapeutic strategies for ischemic heart disease

Despite significant advances in the physician's ability to initiate myocardial reperfusion and salvage heart tissue, ischemic heart disease remains one of the leading causes of death in the United States. Consequently, alternative therapeutic strategies have been intensively investigated, especially methods of enhancing the heart's resistance to ischemic cell death - so called "cardioprotective" interventions. However, although a great deal has been learned regarding the methods and mechanisms of cardioprotective interventions, an efficacious therapy has yet to be successfully implemented in the clinical arena. This review discusses the current understanding of cardioprotection in the context of ischemic heart disease pathophysiology, highlighting those elements of ischemic heart disease pathophysiology that have received less attention as potential targets of cardioprotective intervention.

Cardioprotection and myocardial reperfusion: pitfalls to clinical application

With the advent of thrombolytic therapy and angioplasty, it has become possible to reduce myocardial infarct size through early reperfusion. Enormous effort has been expended to find therapies that can further reduce infarct size after early intervention. Animal studies have identified many cardioprotective pathways that have the potential to reduce infarct size if activated before the onset of ischemia. More recently, interventions effective at the onset of reperfusion have been described. Although basic research has identified many targets, most has been conducted in rodent models which may not be directly applicable to human disease and even promising agents have been disappointing in large-scale clinical trials. There are many potential explanations for this failure which is the subject of this review. Potential factors include (1) the variability inherent in the patient population, whereas animal studies usually use single sex homogeneous groups maintained on standard diets in carefully controlled environments; (2) the duration of ischemia is generally shorter in animal studies, resulting in potentially more salvageable myocardium than is often the case in patients; (3) that the animals are usually young without comorbidities, whereas the patient population is generally older and has significant comorbidities; (4) animals are not treated with medications a priori, whereas the patient population is often taking medications that may affect ischemic injury; and (5) animal studies may not involve thorough assessment of effects on organs other than the heart, whereas patients can experience adverse effects of treatment in other organs that can preclude clinical use.

Improved protein extraction and protein identification from archival formalin-fixed paraffin-embedded human aortas

PURPOSE

Evaluate combination of heat and elevated pressure to enhance protein extraction and quality of formalin-fixed (FF), and FF paraffin-embedded (FFPE) aorta for proteomics.

EXPERIMENT DESIGN

Proteins were extracted from fresh frozen aorta at room temperature (RT). FF and FFPE aortas (3 months and 15 years) were extracted at RT, heat alone, or a combination of heat and high pressure. Protein yields were compared, and digested peptides from the extracts were analyzed with MS.

RESULTS

Combined heat and elevated pressure increased protein yield from human FF or FFPE aorta compared to matched tissues with heat alone (1.5-fold) or at RT (8.3-fold), resulting in more proteins identified and with more sequence coverage. The length of storage did adversely affect the quality of proteins from FF tissue. For long-term storage, aorta was preserved better with FFPE than FF alone. Periostin and MGF-E8 were demonstrated suitable for MRM assays from FFPE aorta.

CONCLUSIONS AND CLINICAL RELEVANCE

Combination of heat and high pressure is an effective method to extract proteins from FFPE aorta for downstream proteomics. This method opens the possibility for use of archival and often rare FFPE aortas and possibly other tissues available to proteomics for biomarker discovery and quantification.

Conditional knockout of myocyte focal adhesion kinase abrogates ischemic preconditioning in adult murine hearts

Background

Our laboratory has previously demonstrated the importance of a cytoskeletal‐based survival signaling pathway using in vitro models of ischemia/reperfusion (IR). However, the importance of this pathway in mediating stress‐elicited survival signaling in vivo is unknown.

Methods and Results

The essential cytoskeletal signaling pathway member focal adhesion kinase (FAK) was selectively deleted in adult cardiac myocytes using a tamoxifen‐inducible Cre‐Lox system (α‐MHC‐MerCreMer). Polymerase chain reaction (PCR) and Western blot were performed to confirm FAK knockout (KO). All mice were subjected to a 40‐minute coronary occlusion followed by 24 hours of reperfusion. Ischemic preconditioning (IP) was performed using a standard protocol. Control groups included wild‐type (WT) and tamoxifen‐treated α‐MHC‐MerCreMer^+/−/FAK^WT/WT (experimental control) mice. Infarct size was expressed as a percentage of the risk region. In WT mice IP significantly enhanced the expression of activated/phosphorylated FAK by 36.3% compared to WT mice subjected to a sham experimental protocol (P≤0.05; n=6 hearts [sham], n=4 hearts [IP]). IP significantly reduced infarct size in both WT and experimental control mice (43.7% versus 19.8%; P≤0.001; 44.7% versus 17.5%; P≤0.001, respectively). No difference in infarct size was observed between preconditioned FAK KO and nonpreconditioned controls (37.1% versus 43.7% versus 44.7%; FAK KO versus WT versus experimental control; P=NS). IP elicited a 67.2%/88.8% increase in activated phosphatidylinositol‐3‐kinase (PI3K) p85/activated Akt expression in WT mice, but failed to enhance the expression of either in preconditioned FAK KO mice.

Conclusions

Our results indicate that FAK is an essential mediator of IP‐elicited cardioprotection and provide further support for the hypothesis that cytoskeletal‐based signaling is an important component of stress‐elicited survival signaling.

Regional expression of HOXA4 along the aorta and its potential role in human abdominal aortic aneurysms

BACKGROUND

The infrarenal abdominal aorta exhibits increased disease susceptibility relative to other aortic regions. Allograft studies exchanging thoracic and abdominal segments showed that regional susceptibility is maintained regardless of location, suggesting substantial roles for embryological origin, tissue composition and site-specific gene expression.

RESULTS

We analyzed gene expression with microarrays in baboon aortas, and found that members of the HOX gene family exhibited spatial expression differences. HOXA4 was chosen for further study, since it had decreased expression in the abdominal compared to the thoracic aorta. Western blot analysis from 24 human aortas demonstrated significantly higher HOXA4 protein levels in thoracic compared to abdominal tissues (P < 0.001). Immunohistochemical staining for HOXA4 showed nuclear and perinuclear staining in endothelial and smooth muscle cells in aorta. The HOXA4 transcript levels were significantly decreased in human abdominal aortic aneurysms (AAAs) compared to age-matched non-aneurysmal controls (P < 0.00004). Cultured human aortic endothelial and smooth muscle cells stimulated with INF-γ (an important inflammatory cytokine in AAA pathogenesis) showed decreased levels of HOXA4 protein (P < 0.0007).

CONCLUSIONS

Our results demonstrated spatial variation in expression of HOXA4 in human aortas that persisted into adulthood and that downregulation of HOXA4 expression was associated with AAAs, an important aortic disease of the ageing population.

Targeted intracellular catalase delivery protects neonatal rat myocytes from hypoxia-reoxygenation and ischemia-reperfusion injury

Hypoxia followed by reoxygenation and ischemia reperfusion cause cell death in neonatal rat ventricular myocytes primarily through the generation of oxidative stress. Extracellular catalase has not been effective in reducing or eliminating ischemia reperfusion- or hypoxia-reoxygenation-induced cell death due both to extracellular degradation and to poor cellular uptake.

AIMS

(1) To determine whether a cell-penetrating catalase derivative with enhanced peroxisome targeting efficiency (catalase-SKL) increases intracellular levels of the antioxidant enzyme in neonatal rat ventricular myocytes; and (2) to determine whether catalase-SKL protects against both hypoxia-reoxygenation and ischemia reperfusion injury.

METHODS

Neonatal rat ventricular myocytes were subjected to 3 or 6 h of hypoxia-reoxygenation or to 1 h of ischemia reperfusion. Extracellular catalase concentration, activity, and subcellular distribution were determined using standard techniques. Reactive oxygen species and related oxidative stress were visualized using 2',7'-dichlorofluorescin diacetate. Cell death was measured using trypan blue exclusion or lactate dehydrogenase release assays.

RESULTS

Extracellular catalase activity was higher in (catalase-SKL) transduced myocytes, was concentrated in a membranous cellular fraction, and potently inhibited oxidative stress. In contrast to nontransducible (unmodified) extracellular catalase, catalase-SKL-treated myocytes were protected against both hypoxia-reoxygenation and ischemia reperfusion.

CONCLUSIONS

(1) Catalase-SKL increased myocyte extracellular catalase content and activity and dramatically increased resistance to hydrogen peroxide-induced oxidation; (2) catalase-SKL protects against both hypoxia-reoxygenation and ischemia reperfusion; (3) catalase-SKL may represent a new therapeutic approach to protect hearts against myocardial hypoxia-reoxygenation or ischemia reperfusion.

Ischemic preconditioning and heat shock activate Akt via a focal adhesion kinase-mediated pathway in Langendorff-perfused adult rat hearts

Heat stress (HS)-induced cardioprotection is associated with the activation of focal adhesion kinase (FAK) and protein kinase B (Akt) in neonatal rat ventricular myocytes (NRVMs), suggesting that stress-induced activation of survival pathways may be important in protecting intact hearts from irreversible injury. The purposes of this study were 1) to examine the subcellular signaling pathways activated by HS and ischemic preconditioning (IP) in intact hearts, 2) to determine whether HS and IP activate an integrated survival pathway similar to that activated by HS in cultured NRVMs, and 3) to determine whether HS and IP reduce lethal cell injury in perfused intact hearts. Adult rat hearts perfused in the Langendorff mode were subjected to 25 min of global ischemia and 30 min of reperfusion (I/R) either 24 h after whole animal HS or following a standard IP protocol. Myocardial signaling was analyzed using Western blot analysis, whereas cell death was assayed by measuring lactate dehydrogenase release into the perfusate and confirmed by light microscopy. Similar to NRVMs, HS performed in the whole animal 24 h before I/R increased phosphorylation of FAK at tyrosine-397 and protein kinase B (Akt) and resulted in protection from cell death. Using IP as a myocardial stress also resulted in an increased phosphorylation/activation of both FAK and Akt and resulted in reduced cell death in adult perfused rat hearts subjected to I/R. In conclusion, 1) myocardial stress caused by whole animal HS activates cytoskeletal-based survival signaling pathways in whole heart tissue and reduces lethal I/R injury and 2) IP activates the same stress-induced survival pathway and the activation correlates with the well-known cardioprotective effect of IP on lethal I/R injury.

Heat stress activates AKT via focal adhesion kinase-mediated pathway in neonatal rat ventricular myocytes

Heat stress (HS)-induced cardioprotection is associated with increased paxillin localization to the membrane fraction of neonatal rat ventricular myocytes (NRVM). The purpose of this study was 1) to examine the subcellular signaling pathways activated by HS; 2) to determine whether myocardial stress organizes and activates an integrated survival pathway; and 3) to investigate potential downstream cytoprotective proteins activated by HS. After HS, NRVM were subjected to chemical inhibitors (CI) designed to simulate ischemia by inhibiting both glycolysis and mitochondrial respiration. Protein kinase B (AKT) expression (wild type) was increased selectively with an adenoviral vector. Cell signaling was analyzed with Western blot analysis, while oncosis/apoptosis was assayed by measuring Trypan blue exclusion and/or terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining, respectively. HS increased phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 but did not adversely affect the viability of NRVM before CI. HS increased association between FAK and phosphatidylinositol 3-kinase as well as causing a significant increase in AKT activity. Increased expression of wild-type AKT protected myocytes from both oncotic and apoptotic cell death. Increased expression of a FAK inhibitor, FRNK, reduced AKT phosphorylation in response to HS both at time 0 and after 10 min of CI compared with myocytes expressing empty virus. We conclude that myocardial stress activates cytoskeleton-based signaling pathways that are associated with protection from lethal cell injury.

Heat shock-induced cardioprotection activates cytoskeletal-based cell survival pathways

To define better the subcellular mechanism of heat shock (HS)-induced cardioprotection, we examined the effect of HS, as well as selective expression of individual HS proteins (HSPs), on cell injury in neonatal rat ventricular myocytes (NRVM). HS was induced in NRVM by a rapid elevation of temperature to 42 degrees C for 20 min followed by 20-24 h of recovery at 37 degrees C. Other NRVM were infected with a replication-deficient adenovirus encoding HSP27 or HSP70. On the same day, all groups were subjected to metabolic inhibition (MI). Cell injury was assayed by measurement of the percentage of total lactate dehydrogenase released, the percentage of cells staining with trypan blue, or TdT-mediated dUTP nick-end labeling, whereas cell signaling was assayed by immunoblot analysis and coimmunoprecipitation. Before MI, the viability of all treated groups did not differ significantly from control NRVM. HS resulted in a significant increase in HSP70 and HSP27 expression. Infection with either virus caused a significant increase in selective HSP content compared with control NRVM. HS protected NRVM from injury. Selective expression of HSP27 or HSP70 alone was not protective in NRVM, but dual infection with both viral vectors (HSP27 + HSP70) was protective. HS and HSP27 + HSP70 expression caused increased paxillin localization in the membrane fraction, which persisted in response to MI, compared with control NRVM. HS increased the integrin-paxillin-focal adhesion kinase interaction, whereas targeted inhibition of focal adhesion kinase activity abolished the integrin-paxillin association and resulted in an increase in cell death. HS and HSP27 + HSP70 expression increased the association of members of the focal adhesion complex and protected NRVM against irreversible injury. Cytoskeletal-based signaling pathways at focal adhesion junctions may represent a unique pathway of cardioprotection.

Effect of increased expression of cytoskeletal protein vinculin on ischemia-reperfusion injury in ventricular myocytes

The transition from reversible to irreversible ischemic injury (ischemia-reperfusion, I/R) occurs coincident with the loss of vinculin, a cytoskeletal protein involved in the attachment of the myofibrils to the sarcolemmal membrane. If the loss of vinculin were critical to the development of I/R, then increased levels of vinculin would be predicted to delay the onset of irreversible injury assuming that the protein is functional and localized to the proper subcellular site. The present study determined whether increased expression of vinculin, specifically in the cytoskeletal compartment, would provide protection from I/R injury. Neonatal rat myocytes were cultured and infected with a newly created replication-deficient adenovirus driving the expression of vinculin. I/R was induced with chemical inhibitors of glycolysis and mitochondrial respiration. Irreversible cell injury was assessed with lactate dehydrogenase (LDH) release. Virus-infected myocytes expressed significantly more vinculin in the cytoskeletal fraction and increased the expression of paxillin but sustained the same amount of injury in response to simulated I/R as control cells (n = 4; P = not significant, paired t-test). Hypothermic I/R (ischemia at 25 degrees C) resulted in a significant reduction in LDH release (P </= 0.02; n = 4). Virus-mediated overexpression of vinculin does not appear to represent a rational approach to overcoming I/R injury.

Increased expression of HSP27 protects canine myocytes from simulated ischemia-reperfusion injury

Previous studies have shown that adult rat myocytes can be protected from simulated ischemia-reperfusion (I/R) injury by small heat shock proteins (sHSPs). However, to date the cardioprotective effect of sHSPs has not been confirmed in adult myocytes from a large animal species. Left ventricular myocytes from adult dogs were cultured and infected with a replication-deficient adenovirus designed to increase expression of the human form of HSP27. The response to simulated I/R injury was compared using morphologic criteria. Virus-infected myocytes expressed two- to threefold more HSP27 and sustained less injury in response to simulated I/R than control cells (P < 0.001; paired t-test). Canine myocytes can be isolated, cultured, and induced to increase the expression of a foreign protein without significant effects on differentiation and/or viability. Increased expression of HSP27 provides significant protection from simulated I/R injury in adult canine myocytes. Determining the mechanism by which sHSPs protect from lethal cell injury will provide important new insights into the mechanism of irreversible cell injury in adult myocardium.