Key Points Closed head trauma sequentially releases tPA followed by uPA from injured brain. Increased uPA is responsible for delayed intracerebral hemorrhage, which is prevented by a tPA variant that inhibits uPA activity.

Inflammation and thrombosis are integrated, mutually reinforcing processes, but the interregulatory mechanisms are incompletely defined. Here, we examined the contribution of α-defensins (α-defs), antimicrobial proteins released from activated human neutrophils, on clot formation in vitro and in vivo. Activation of the intrinsic pathway of coagulation stimulates release of α-defs from neutrophils. α-Defs accelerate fibrin polymerization, increase fiber density and branching, incorporate into nascent fibrin clots, and impede fibrinolysis in vitro. Transgenic mice (Def++) expressing human α-Def-1 developed larger, occlusive, neutrophil-rich clots after partial inferior vena cava (IVC) ligation than those that formed in wild-type (WT) mice. IVC thrombi extracted from Def++ mice were composed of a fibrin meshwork that was denser and contained a higher proportion of tightly packed compressed polyhedral erythrocytes than those that developed in WT mice. Def++ mice were resistant to thromboprophylaxis with heparin. Inhibiting activation of the intrinsic pathway of coagulation, bone marrow transplantation from WT mice or provision of colchicine to Def++ mice to inhibit neutrophil degranulation decreased plasma levels of α-defs, caused a phenotypic reversion characterized by smaller thrombi comparable to those formed in WT mice, and restored responsiveness to heparin. These data identify α-defs as a potentially important and tractable link between innate immunity and thrombosis.

Approximately one-half of the patients who develop clinical atherosclerosis have normal or only modest elevations in plasma lipids, indicating that additional mechanisms contribute to pathogenesis. In view of increasing evidence that inflammation contributes to atherogenesis, we studied the effect of human neutrophil ␣-defensins on low density lipoprotein (LDL) trafficking, metabolism, vascular deposition, and atherogenesis using transgenic mice expressing human ␣-defensins in their polymorphonuclear leukocytes (Def ؉/؉ ). Accelerated Def Atherosclerosis and its thrombotic sequel, "atherothrombosis," are likely to remain the predominant cause of death in "developed" countries for decades to come. The etiology of this syndrome is multifactorial, and current predictors provide an incomplete estimate of the risk and opportunity for intervention. In a pooled analysis of over 87,000 persons with diagnosed coronary heart disease, one in five lacked any of the conventional risk factors: hypertension, smoking, high cholesterol, or diabetes (1). Furthermore, half of all cardiovascular events occur in patients with normal lipid levels (2). These data reveal the need to identify and mitigate as yet undescribed, but clinically relevant, risk factors for cardiovascular disease beyond those targeted in current practice.This problem is compounded by the lack of animal models that closely simulate human disease. Animal models used to study atherosclerosis, including its hyperlipidemic (3, 4) and inflammatory (5) components, are often characterized by striking elevations in plasma cholesterol, reaching plasma concentrations of 1500 -2200 mg/dl in LDLR Ϫ/Ϫ and 400 -450 mg/dl in ApoE Ϫ/Ϫ mice fed a high fat diet (3, 4), and most of the cholesterol is found in the VLDL fraction (3, 4). Neither these levels of lipids nor this distribution of lipoproteins is representative of findings in the vast majority of patients with atherosclerosis. Thus, there continues to be a need for new models to identify novel risk factors and novel approaches to intervention.We have identified human ␣-defensins 1-4, also known as human neutrophil peptides (HNPs), 2 as potentially having a role in the development of atherosclerosis. ␣-Defensins are antimicrobial proteins that constitute ϳ5% of the total protein in polymorphonuclear leukocytes (PMNs). ␣-Defensins are released from a subset of azurophilic granules when the PMNs are activated by a variety of agonists (6, 7). ␣-Defensins are abundant in human atherosclerotic coronary and carotid arteries (8, 9), and there is a significant correlation between the deposition of ␣-defensins in skin tissue and the severity of coronary artery disease (10). ␣-Defensins inhibit the degradation of low density lipoprotein (LDL) and Lp(a) by vascular cells (11), increase their binding and retention in extracellular matrix (12), and inhibit tissue-type plasminogen activator (tPA)-mediated fibrinolysis (13, 14).These observations have been confirmed and extended by others. Increased plasma levels of ␣-defensins are assoc...

Summary The inflammatory response to SARS/CoV‐2 (COVID‐19) infection may contribute to the risk of thromboembolic complications. α‐Defensins, antimicrobial peptides released from activated neutrophils, are anti‐fibrinolytic and prothrombotic in vitro and in mouse models. In this prospective study of 176 patients with COVID‐19 infection, we found that plasma levels of α‐defensins were elevated, tracked with disease progression/mortality or resolution and with plasma levels of interleukin‐6 (IL‐6) and D‐dimers. Immunohistochemistry revealed intense deposition of α‐defensins in lung vasculature and thrombi. IL‐6 stimulated the release of α‐defensins from neutrophils, thereby accelerating coagulation and inhibiting fibrinolysis in human blood, imitating the coagulation pattern in COVID‐19 patients. The procoagulant effect of IL‐6 was inhibited by colchicine, which blocks neutrophil degranulation. These studies describe a link between inflammation and the risk of thromboembolism, and they identify a potential new approach to mitigate this risk in patients with COVID‐19 and potentially in other inflammatory prothrombotic conditions.

Objective: Vaccines against COVID-19 induce specific antibodies whose titer is perceived as a reliable correlate of protection. Vitamin D confers complex regulatory effects on the innate and adaptive immunity. In this study, we explored a plausible impact of baseline vitamin D content on achieved immunity following COVID-19 vaccination. Methods: A retrospective observational study comprising 73,254 naïve subjects insured by the Leumit Health Service HMO, who were vaccinated between 1 February 2020 and 30 January 2022, with one available vitamin D level prior to vaccination, was performed. The association between 25(OH) vitamin D levels, SARS-COV-2 antibody titer, and post-vaccination PCR results were evaluated. Results: Of the study population, 5026 (6.9%) tested positive for COVID-19. The proportion of low 25(OH)D levels (<30 ng/mL) was significantly higher in the PCR-positive group (81.5% vs. 79%, p < 0.001). Multivariate analysis showed a higher incidence of breakthrough infection among non-smokers [1.37 (95%CI 1.22–1.54, p< 0.001)] and lower incidences among subjects with sufficient 25(OH)D levels (>30 ng/mL) [0.87 (95%CI 0.79–0.95, p—0.004)], hyperlipidemia [0.84 (95%CI 0.76–0.93, p< 0.001], depression [OR-0.87 (95%CI: 0.79–0.96, p< 0.005], socio-economic status >10 [0.67 (95%CI 0.61–0.73, p< 0.001)], and age >44 years. SARS-COV-2 antibody titers were available in 3659 vaccinated individuals. The prevalence of antibody titers (<50 AU) among PCR-positive subjects was 42% compared to 28% among PCR-negative subjects (p < 0.001). Baseline 25(OH)D levels showed an inverse relation to total antibody titers. However, no association was found with an antibody titer <50 AU/mL fraction. Conclusion Baseline 25(OH)D levels correlated with the vaccination-associated protective COVID-19 immunity. Antibody titers < 50 AU/mL were significantly linked to breakthrough infection but did not correlate with 25(OH)D levels.

Atherosclerosis, the predominant cause of death in well-resourced countries, may develop in the presence of plasma lipid levels within the normal range. Inflammation may contribute to lesion development in these individuals, but the underlying mechanisms are not well understood. Transgenic mice expressing α-def-1 released from activated neutrophils develop larger lipid and macrophage-rich lesions in the proximal aortae notwithstanding hypocholesterolemia caused by accelerated clearance of α-def-1/low-density lipoprotein (LDL) complexes from the plasma. The phenotype does not develop when the release of αdef-1 is prevented with colchicine. However, ApoE-/mice crossed with α-def-1 mice or given exogenous α-def-1 develop smaller aortic lesions associated with reduced plasma cholesterol, suggesting a protective effect of accelerated LDL clearance. Experiments were performed to address this seeming paradox and to determine if α-def-1 might provide a means to lower cholesterol and thereby attenuate atherogenesis. We confirmed that exposing ApoE-/mice to α-def-1 lowers total plasma cholesterol and decreases lesion size. However, lesion size was larger than in mice with total plasma cholesterol lowered to the same extent by inhibiting its adsorption or by ingesting a low-fat diet. Furthermore, α-def-1 levels correlated independently with lesion size in ApoE-/mice. These studies show that α-def-1 has competing effects on atherogenesis. Although α-def-1 accelerates LDL clearance from plasma, it also stimulates deposition and retention of LDL in the vasculature, which may contribute to development of atherosclerosis in individuals with normal or even low plasma levels of cholesterol. Inhibiting α-def-1 may attenuate the impact of chronic inflammation on atherosclerotic vascular disease.

Background: Previous studies, published before the advent of primary reperfusion, described the electrocardiographic features of ST-segment elevation myocardial infarction (STEMI) caused by total diagonal artery occlusion, as demonstrated at pre-discharge coronary angiography. We aimed to assess the electrocardiographic and echocardiographic features in STEMI unequivocally attributed to a diagonal lesion in the era of primary coronary intervention. Methods: The electrocardiograms and echocardiograms of patients sustaining STEMI caused by diagonal artery involvement were compared with those of patients with STEMI attributed to proximal or mid left anterior descending artery (LAD) lesions. ST-segment deviations were measured at four different points in each lead and analyzed against TIMI flow and SNuH score. The electrocardiographic and echocardiographic features of each group were mapped. Results: In contrast to previous studies claiming an ever-present incidence of at least 1-mm ST-segment elevation in leads I and aVL with diagonal STEMI, we report 86% of any ST-elevation in leads I, aVL and V2 (64-71% for ST-elevation >1 mm). Both higher SNuH score and pre-intervention TIMI flow were associated with larger lateral ST-elevations (85.7% and 86.4-95.5%, respectively). Higher prevalence of ST-depression in the inferior leads reflecting reciprocal changes was observed in patients with diagonal-induced STEMI (57-76% vs. 24-51% in LAD obstructions, p <0.05). Conclusion: The most sensitive and predictive sign for acute ischemia was any degree of ST-deviation measured 1 mm beyond the J point. ST-elevations in I, aVL and V 2 , sparing V 3-V 5 , strongly favor isolated diagonal lesion. Proximal LAD lesion lacking ST-segment elevations in leads I and aVL is primarily due to wraparound LAD anatomy.

Summary Patients who are severely affected by coronavirus disease 2019 (COVID‐19) may develop a delayed onset ‘cytokine storm’, which includes an increase in interleukin‐6 (IL‐6). This may be followed by a pro‐thrombotic state and increased D‐dimers. It was anticipated that tocilizumab (TCZ), an anti‐IL‐6 receptor monoclonal antibody, would mitigate inflammation and coagulation in patients with COVID‐19. However, clinical trials with TCZ have recorded an increase in D‐dimer levels. In contrast to TCZ, colchicine reduced D‐dimer levels in patients with COVID‐19. To understand how the two anti‐inflammatory agents have diverse effects on D‐dimer levels, we present data from two clinical trials that we performed. In the first trial, TCZ was administered (8 mg/kg) to patients who had a positive polymerase chain reaction test for COVID‐19. In the second trial, colchicine was given (0·5 mg twice a day). We found that TCZ significantly increased IL‐6, α‐Defensin (α‐Def), a pro‐thrombotic peptide, and D‐dimers. In contrast, treatment with colchicine reduced α‐Def and Di‐dimer levels. In vitro studies show that IL‐6 stimulated the release of α‐Def from human neutrophils but in contrast to colchicine, TCZ did not inhibit the stimulatory effect of IL‐6; raising the possibility that the increase in IL‐6 in patients with COVID‐19 treated with TCZ triggers the release of α‐Def, which promotes pro‐thrombotic events reflected in an increase in D‐dimer levels.