Preventing Cholesterol-Induced Perk (Protein Kinase RNA-Like Endoplasmic Reticulum Kinase) Signaling in Smooth Muscle Cells Blocks Atherosclerotic Plaque Formation.

BACKGROUND: Vascular smooth muscle cells (SMCs) undergo complex phenotypic modulation with atherosclerotic plaque formation in hyperlipidemic mice, which is characterized by de-differentiation and heterogeneous increases in the expression of macrophage, fibroblast, osteogenic, and stem cell markers. An increase of cellular cholesterol in SMCs triggers similar phenotypic changes in vitro with exposure to free cholesterol due to cholesterol entering the endoplasmic reticulum, triggering endoplasmic reticulum stress and activating Perk (protein kinase RNA-like endoplasmic reticulum kinase) signaling. METHODS: We generated an SMC-specific Perk knockout mouse model, induced hyperlipidemia in the mice by AAV-PCSK9DY injection, and subjected them to a high-fat diet. We then assessed atherosclerotic plaque formation and performed single-cell transcriptomic studies using aortic tissue from these mice. RESULTS: SMC-specific deletion of Perk reduces atherosclerotic plaque formation in male hyperlipidemic mice by 80%. Single-cell transcriptomic data identify 2 clusters of modulated SMCs in hyperlipidemic mice, one of which is absent when Perk is deleted in SMCs. The 2 modulated SMC clusters have significant overlap of transcriptional changes, but the Perk-dependent cluster uniquely shows a global decrease in the number of transcripts. SMC-specific Perk deletion also prevents migration of both contractile and modulated SMCs from the medial layer of the aorta. CONCLUSIONS: Our results indicate that hypercholesterolemia drives both Perk-dependent and Perk-independent SMC modulation and that deficiency of Perk significantly blocks atherosclerotic plaque formation.

A Comparison of the Clinical, Viral, Pathologic, and Immunologic Features of Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and Coronavirus 2019 (COVID-19) Diseases.

CONTEXT.­: The purpose of this review was to compare 3 coronavirus diseases, including severe acute respiratory syndrome, Middle East respiratory syndrome, and COVID-19 caused by SARS-CoV, MERS-CoV, and SARS-CoV-2 viruses, respectively. OBJECTIVE.­: To cover the following topics: clinical considerations, viral characteristics, pathology, immune response, pathogenesis, and the prognosis associated with each coronavirus disease in humans. DATA SOURCES.­: Clinically, flu-like symptoms are usual at the time of presentation for all 3 diseases, but these vary from asymptomatic to severe multisystem involvement. The pathology associated with symptomatic severe acute respiratory syndrome and COVID-19 has been well described, the most prominent of which is diffuse alveolar damage. The immune response to each of these viruses is highly complex and includes both humoral and cellular components that can have a significant impact on prognosis. In severe cases of COVID-19, a dysregulated innate host immune system can initiate a hyperinflammatory syndrome dominated by endothelial dysfunction that can lead to a hypercoagulable state with microthrombi, resulting in a systemic microvascular and macrovascular disease. CONCLUSIONS.­: The severe acute respiratory syndrome and Middle East respiratory syndrome epidemics have been limited, involving approximately 8000 and 2500 individuals, respectively. In contrast, COVID-19 has resulted in a worldwide pandemic with more than 177 million cases and 3.9 million deaths as of June 15, 2021, and fatality rates ranging from less than 0.1% to approximately 10% depending upon the country. Ending on a positive note, the development of a number of vaccines, at least 6 of which now are in clinical use, should mitigate and eventually control the devastating COVID-19 pandemic.

The illness and death of King George VI of England: the pathologists' reassessment.

The illness and death of King George VI has received renewed attention based on the events portrayed in the Netflix blockbuster series, The Crown. The King, a heavy smoker, underwent a left total pneumonectomy in September 1951 for what euphemistically was called "structural abnormalities" of his left lung, but what in reality was a carcinoma. His physicians withheld this diagnosis from him, the public, and the medical profession. The continuation of hemoptysis following surgery suggested that his cancer had spread to his right lung. Although he made a slow and uneventful recovery from his surgery, King George VI died suddenly and unexpectedly in his sleep on February 6, 1952, at the age of 56. Since the King had a history of peripheral vascular disease, it was assumed that the cause of death was a "coronary thrombosis." In this report, we explore the cardiovascular and oncologic findings relating to his illness and death and consider an alternative explanation for his demise, namely, that he may have died of complications from a carcinoma that had originated in his left lung and spread to his right lung, as evidenced by continued hemoptysis. We suggest that this possibly could have led to his sudden death due to either a pulmonary embolus or a massive intra-thoracic hemorrhage rather than a "coronary thrombosis."

Endomyocardial nodular calcification as a cause of heart failure.

Massive cardiac calcification is rare, occurring in association with chronic diseases or more commonly with previous myocardial infarction. We present an intriguing case of massive myocardial calcification of the left ventricle in a young patient with restrictive cardiomyopathy and progressive heart failure who required transplantation. The patient's history and clinical presentation did not reveal the etiology of the myocardial calcification.

Cardiomyocyte PDGFR-beta signaling is an essential component of the mouse cardiac response to load-induced stress.

PDGFR is an important target for novel anticancer therapeutics because it is overexpressed in a wide variety of malignancies. Recently, however, several anticancer drugs that inhibit PDGFR signaling have been associated with clinical heart failure. Understanding this effect of PDGFR inhibitors has been difficult because the role of PDGFR signaling in the heart remains largely unexplored. As described herein, we have found that PDGFR-beta expression and activation increase dramatically in the hearts of mice exposed to load-induced cardiac stress. In mice in which Pdgfrb was knocked out in the heart in development or in adulthood, exposure to load-induced stress resulted in cardiac dysfunction and heart failure. Mechanistically, we showed that cardiomyocyte PDGFR-beta signaling plays a vital role in stress-induced cardiac angiogenesis. Specifically, we demonstrated that cardiomyocyte PDGFR-beta was an essential upstream regulator of the stress-induced paracrine angiogenic capacity (the angiogenic potential) of cardiomyocytes. These results demonstrate that cardiomyocyte PDGFR-beta is a regulator of the compensatory cardiac response to pressure overload-induced stress. Furthermore, our findings may provide insights into the mechanism of cardiotoxicity due to anticancer PDGFR inhibitors.

Characterization of the inflammatory and apoptotic cells in the aortas of patients with ascending thoracic aortic aneurysms and dissections.

OBJECTIVE: The histopathologic abnormality underlying ascending aortic aneurysm and dissection is medial degeneration, a lesion that is described as the noninflammatory loss of smooth muscle cells and elastic fibers. This study sought to determine whether inflammatory cells are present in medial degeneration and assess any possible contribution of these cells to apoptosis of smooth muscle cells. METHODS: Aortic specimens were obtained from patients undergoing prophylactic surgical repair of an ascending aortic aneurysm (n = 9) and type A dissection (n = 7), along with control patients dying of causes unrelated to aortic disease (n = 5). Immunohistochemical staining was performed to evaluate the presence of lymphocytes and macrophages, and markers of apoptosis were assessed in the aortas of patients with ascending aortic aneurysm and dissection. RESULTS: Immunohistochemical study indicated significantly more CD3+ cells in the aortas of patients with aneurysms or dissections than in control aortas (P = .020 and P = .0022, respectively). In addition, aortas of patients with aneurysms or dissections had more CD68+ cells (P = .01 and P = .005, respectively). CD3+ cells were localized in the media and surrounding the vasa vasorum in the adventitia. Cells yielding a positive result on in situ terminal transferase-mediated deoxyuridine triphosphate nick end-labeling were found in increased numbers in the aortas of patients with aneurysms or dissections relative to control aortas (P = .005 and P = .002, respectively). Furthermore, Fas and FasL were increased in the aortic samples from patients with aneurysms and dissections relative to control aortas. CONCLUSION: The coexistence of inflammatory cells with markers of apoptotic vascular cell death in the media of ascending aortas with aneurysms and type A dissections raises the possibility that activated T cells and macrophages may contribute to the elimination of smooth muscle cells and degradation of the matrix associated with thoracic aortic aneurysms and dissections.