Procoagulant platelet activation promotes venous thrombosis.

Platelets are key players in cardiovascular disease and platelet aggregation represents a central pharmacological target, particularly in secondary prevention. However, inhibition of adenosine diphosphate and thromboxane signaling has low efficacy in preventing venous thromboembolism, necessitating the inhibition of the plasmatic coagulation cascade in this disease. Anticoagulation carries a significantly higher risk of bleeding complications, highlighting the need of alternative therapeutic approaches. We hypothesized that procoagulant activation (PA) of platelets promotes venous thrombus formation and that targeting PA could alleviate venous thrombosis. Here, we found elevated levels of procoagulant platelets in the circulation of patients with deep vein thrombosis (DVT) and pulmonary embolism, and in mice developing DVT following inferior vena cava stenosis. Further, we detected procoagulant activation of recruited platelets within murine and human venous thrombi. Mice with platelet-specific deficiency in central pathways of procoagulant activation - cyclophilin D and transmembrane protein 16F - were more resistant towards low flow-induced venous thrombosis. Finally, we found that a clinically approved carbonic anhydrase inhibitor, methazolamide, reduced platelet procoagulant activity and alleviated murine thrombus formation without affecting trauma-associated hemostasis. These findings identify an essential role of platelet procoagulant function in venous thrombosis and delineate novel pharmacological strategies targeting platelets in preventing venous thromboembolism.

Left and right ventricular dysfunction in patients with COVID-19-associated myocardial injury.

PURPOSE: SARS-COV-2 infection can develop into a multi-organ disease. Although pathophysiological mechanisms of COVID-19-associated myocardial injury have been studied throughout the pandemic course in 2019, its morphological characterisation is still unclear. With this study, we aimed to characterise echocardiographic patterns of ventricular function in patients with COVID-19-associated myocardial injury. METHODS: We prospectively assessed 32 patients hospitalised with COVID-19 and presence or absence of elevated high sensitive troponin T (hsTNT+ vs. hsTNT-) by comprehensive three-dimensional (3D) and strain echocardiography. RESULTS: A minority (34.3%) of patients had normal ventricular function, whereas 65.7% had left and/or right ventricular dysfunction defined by impaired left and/or right ventricular ejection fraction and strain measurements. Concomitant biventricular dysfunction was common in hsTNT+ patients. We observed impaired left ventricular (LV) global longitudinal strain (GLS) in patients with myocardial injury (-13.9% vs. -17.7% for hsTNT+ vs. hsTNT-, p = 0.005) but preserved LV ejection fraction (52% vs. 59%, p = 0.074). Further, in these patients, right ventricular (RV) systolic function was impaired with lower RV ejection fraction (40% vs. 49%, p = 0.001) and reduced RV free wall strain (-18.5% vs. -28.3%, p = 0.003). Myocardial dysfunction partially recovered in hsTNT + patients after 52 days of follow-up. In particular, LV-GLS and RV-FWS significantly improved from baseline to follow-up (LV-GLS: -13.9% to -16.5%, p = 0.013; RV-FWS: -18.5% to -22.3%, p = 0.037). CONCLUSION: In patients with COVID-19-associated myocardial injury, comprehensive 3D and strain echocardiography revealed LV dysfunction by GLS and RV dysfunction, which partially resolved at 2-month follow-up. TRIAL REGISTRATION: COVID-19 Registry of the LMU University Hospital Munich (CORKUM), WHO trial ID DRKS00021225.

Association of Complement and MAPK Activation With SARS-CoV-2-Associated Myocardial Inflammation.

IMPORTANCE: Myocardial injury is a common feature of patients with SARS-CoV-2 infection. However, the cardiac inflammatory processes associated with SARS-CoV-2 infection are not completely understood. OBJECTIVE: To investigate the inflammatory cardiac phenotype associated with SARS-CoV-2 infection compared with viral myocarditis, immune-mediated myocarditis, and noninflammatory cardiomyopathy by integrating histologic, transcriptomic, and proteomic profiling. DESIGN, SETTING, AND PARTICIPANTS: This case series was a cooperative study between the Ludwig Maximilian University Hospital Munich and the Cardiopathology Referral Center at the University of Tübingen in Germany. A cohort of 19 patients with suspected myocarditis was examined; of those, 5 patients were hospitalized with SARS-CoV-2 infection between March and May 2020. Cardiac tissue specimens from those 5 patients were compared with specimens from 5 patients with immune-mediated myocarditis, 4 patients with non-SARS-CoV-2 viral myocarditis, and 5 patients with noninflammatory cardiomyopathy, collected from January to August 2019. EXPOSURES: Endomyocardial biopsy. MAIN OUTCOMES AND MEASURES: The inflammatory cardiac phenotypes were measured by immunohistologic analysis, RNA exome capture sequencing, and mass spectrometry-based proteomic analysis of endomyocardial biopsy specimens. RESULTS: Among 19 participants, the median age was 58 years (range, 37-76 years), and 15 individuals (79%) were male. Data on race and ethnicity were not collected. The abundance of CD163+ macrophages was generally higher in the cardiac tissue of patients with myocarditis, whereas lymphocyte counts were lower in the tissue of patients with SARS-CoV-2 infection vs patients with non-SARS-CoV-2 virus-associated and immune-mediated myocarditis. Among those with SARS-CoV-2 infection, components of the complement cascade, including C1q subunits (transcriptomic analysis: 2.5-fold to 3.6-fold increase; proteomic analysis: 2.0-fold to 3.4-fold increase) and serine/cysteine proteinase inhibitor clade G member 1 (transcriptomic analysis: 1.7-fold increase; proteomic analysis: 2.6-fold increase), belonged to the most commonly upregulated transcripts and differentially abundant proteins. In cardiac macrophages, the abundance of C1q was highest in SARS-CoV-2 infection. Assessment of important signaling cascades identified an upregulation of the serine/threonine mitogen-activated protein kinase pathways. CONCLUSIONS AND RELEVANCE: This case series found that the cardiac immune signature varied in inflammatory conditions with different etiologic characteristics. Future studies are needed to examine the role of these immune pathways in myocardial inflammation.

Differences in Cardiac Magnetic Resonance Imaging Markers Between Patients With COVID-19-associated Myocardial Injury and Patients With Clinically Suspected Myocarditis.

PURPOSE: Coronavirus 2019 disease (COVID-19) has been shown to affect the myocardium, resulting in a worse clinical outcome. In this registry study, we aimed to identify differences in cardiac magnetic resonance imaging (CMRI) between COVID-19 and all-cause myocarditis. MATERIALS AND METHODS: We examined CMRI of patients with COVID-19 and elevated high-sensitivity serum troponin levels performed between March 31st and May 5th and compared them to CMRI of patients without SARS-CoV-2 infection with suspected myocarditis in the same time period. For this purpose, we evaluated Lake-Louise Criteria for myocarditis by determining nonischemic myocardial injury via T1-mapping, extracellular volume, late gadolinium enhancement, and myocardial edema (ME) by T2-mapping and fat-saturated T2w imaging (T2Q). RESULTS: A total of 15 of 18 (89%) patients with COVID-19 had abnormal findings. The control group consisted of 18 individuals. There were significantly fewer individuals with COVID-19 who had increased T2 (5 vs. 10; P=0.038) and all-cause ME (7 vs. 15; P=0.015); thus, significantly fewer patients with COVID-19 fulfilled Lake-Louise Criteria (6 vs. 17; P<0.001). In contrast, nonischemic myocardial injury was not significantly different. In the COVID-19 group, indexed end-diastolic volume of the left ventricle showed a significant correlation to the extent of abnormal T1 (R2=0.571; P=0.017) and extracellular volume (R2=0.605; P=0.013) and absolute T1, T2, and T2Q (R2=0.644; P=0.005, R2=0.513; P=0.035 and R2=0.629; P=0.038, respectively); in the control group, only extracellular volume showed a weak correlation (R2=0.490; P=0.046). CONCLUSIONS: Cardiac involvement in COVID-19 seems to show less ME than all-cause myocarditis. Abnormal CMRI markers correlated to left ventricle dilation only in the COVID-19 group. Larger comparative studies are needed to verify our findings.

Myocardial Inflammation and Dysfunction in COVID-19-Associated Myocardial Injury.

BACKGROUND: Myocardial injury, defined by elevated troponin levels, is associated with adverse outcome in patients with coronavirus disease 2019 (COVID-19). The frequency of cardiac injury remains highly uncertain and confounded in current publications; myocarditis is one of several mechanisms that have been proposed. METHODS: We prospectively assessed patients with myocardial injury hospitalized for COVID-19 using transthoracic echocardiography, cardiac magnetic resonance imaging, and endomyocardial biopsy. RESULTS: Eighteen patients with COVID-19 and myocardial injury were included in this study. Echocardiography revealed normal to mildly reduced left ventricular ejection fraction of 52.5% (46.5%-60.5%) but moderately to severely reduced left ventricular global longitudinal strain of -11.2% (-7.6% to -15.1%). Cardiac magnetic resonance showed any myocardial tissue injury defined by elevated T1, extracellular volume, or late gadolinium enhancement with a nonischemic pattern in 16 patients (83.3%). Seven patients (38.9%) demonstrated myocardial edema in addition to tissue injury fulfilling the Lake-Louise criteria for myocarditis. Combining cardiac magnetic resonance with speckle tracking echocardiography demonstrated functional or morphological cardiac changes in 100% of investigated patients. Endomyocardial biopsy was conducted in 5 patients and revealed enhanced macrophage numbers in all 5 patients in addition to lymphocytic myocarditis in 1 patient. SARS-CoV-2 RNA was not detected in any biopsy by quantitative real-time polymerase chain reaction. Finally, follow-up measurements of left ventricular global longitudinal strain revealed significant improvement after a median of 52.0 days (-11.2% [-9.2% to -14.7%] versus -15.6% [-12.5% to -19.6%] at follow-up; P=0.041). CONCLUSIONS: In this small cohort of COVID-19 patients with elevated troponin levels, myocardial injury was evidenced by reduced echocardiographic left ventricular strain, myocarditis patterns on cardiac magnetic resonance, and enhanced macrophage numbers but not predominantly lymphocytic myocarditis in endomyocardial biopsies.

Microphthalmia-Associated Transcription Factor (MITF) Regulates Immune Cell Migration into Melanoma.

Microphthalmia-associated transcription factor (MITF) is a key transcription factor in melanoma development and progression. MITF amplification and downregulation have been observed in a significant proportion of melanoma patients and correlate with clinical outcomes. Here, we have investigated the effect of MITF on melanoma chemokine expression and immune cell attraction. In B16F10 melanoma cells, MITF knockdown reduced expression of CXCL10, with concomitantly decreased attraction of immune cells and accelerated tumor outgrowth. Conversely, overexpression of MITF in YUMM1.1 melanoma cells also led to an increased immune cell attraction in vitro. Subcutaneous YUMM1.1 melanomas overexpressing MITF however showed a reduced immune infiltration of lymphocytes and an increased tumor growth. In human melanoma cell lines, silencing of MITF enhanced chemokine production and immune cell attraction, while overexpression of MITF led to lower immune cell attraction. In summary, our results show that MITF regulates chemokine expression in murine and in human melanoma cells, and affects in vivo immune cell attraction and tumor growth. These results reveal a functional relationship between MITF and immune cell infiltration, which may be exploited for cancer therapy.