Platelets play an essential role in maintaining homeostasis in the circulatory system after an injury by forming a platelet thrombus, but they also occupy a central node in the intravascular innate immune system. This concept is supported by their extensive interactions with immune cells and the cascade systems of the blood. In this review we discuss the close relationship between platelets and the complement system and the role of these interactions during thromboinflammation. Platelets are protected from complement-mediated damage by soluble and membrane-expressed complement regulators, but they bind several complement components on their surfaces and trigger complement activation in the fluid phase. Furthermore, localized complement activation may enhance the procoagulant responses of platelets through the generation of procoagulant microparticles by insertion of sublytic amounts of C5b9 into the platelet membrane. We also highlight the role of post-translational protein modifications in regulating the complement system and the critical role of platelets in driving these reactions. In particular, modification of disulfide bonds by thiol isomerases and protein phosphorylation by extracellular kinases have emerged as important mechanisms to fine-tune complement activity in the platelet microenvironment. Lastly, we describe disorders with perturbed complement activation where part of the clinical presentation includes uncontrolled platelet activation that results in thrombocytopenia, and illustrate how complement-targeting drugs are alleviating the prothrombotic phenotype in these patients. Based on these clinical observations, we discuss the role of limited complement activation in enhancing platelet activation and consider how these drugs may provide opportunities for further dissecting the complex interactions between complement and platelets.

An important manifestation of severe COVID-19 is the ARDS-like lung injury that is associated with vascular endothelialitis, thrombosis, and angiogenesis. The intravascular innate immune system (IIIS), including the complement, contact, coagulation, and fibrinolysis systems, which is crucial for recognizing and eliminating microorganisms and debris in the body, is likely to be involved in the pathogenesis of COVID-19 ARDS. Biomarkers for IIIS activation were studied in the first 66 patients with COVID-19 admitted to the ICU in Uppsala University Hospital, both cross-sectionally on day 1 and in 19 patients longitudinally for up to a month, in a prospective study. IIIS analyses were compared with biochemical parameters and clinical outcome and survival. Blood cascade systems activation leading to an overreactive conjunct thromboinflammation was demonstrated, reflected in consumption of individual cascade system components, e.g., FXII, prekallikrein, and high molecular weight kininogen and in increased levels of activation products, e.g., C4d, C3a, C3d,g, sC5b-9, TAT, and D-dimer. Strong associations were found between the blood cascade systems and organ damage, illness severity scores, and survival. We show that critically ill COVID-19 patients display a conjunct activation of the IIIS that is linked to organ damage of the lung, heart, kidneys, and death. We present evidence that the complement and in particular the kallikrein/kinin system is strongly activated and that both systems are prognostic markers of the outcome of the patients suggesting their role in driving the inflammation. Already licensed kallikrein/kinin inhibitors are potential drugs for treatment of critically ill patients with COVID-19.

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The ongoing COVID-19 pandemic has caused significant morbidity and mortality worldwide, as well as profound effects on society. COVID-19 patients have an increased risk of thromboembolic (TE) complications, which develop despite pharmacological thromboprophylaxis. The mechanism behind COVID-19-associated coagulopathy remains unclear. Mannose-binding lectin (MBL), a pattern recognition molecule that initiates the lectin pathway of complement activation, has been suggested as a potential amplifier of blood coagulation during thromboinflammation. Here we describe data from a cohort of critically ill COVID-19 patients (n = 65) treated at a tertiary hospital center intensive care unit (ICU). A subset of patients had strongly elevated MBL plasma levels, and activity upon ICU admission, and patients who developed symptomatic TE (14%) had significantly higher MBL levels than patients without TE. MBL was strongly correlated to plasma D-dimer levels, a marker of COVID-19 coagulopathy, but showed no relationship to degree of inflammation or other organ dysfunction. In conclusion, we have identified complement activation through the MBL pathway as a novel amplification mechanism that contributes to pathological thrombosis in critically ill COVID-19 patients. Pharmacological targeting of the MBL pathway could be a novel treatment option for thrombosis in COVID-19. Laboratory testing of MBL levels could be of value for identifying COVID-19 patients at risk for TE events.

We have revisited the valence band electronic structure of NiO by means of hard x-ray photoemission spectroscopy (HAXPES) together with theoretical calculations using both the GW method and the local density approximation + dynamical mean-field theory (LDA+DMFT) approaches. The effective impurity problem in DMFT is solved through the exact diagonalization (ED) method. We show that the LDA+DMFT method in conjunction with the standard fully localized limit (FLL) and around mean field (AMF) double-counting alone cannot explain all the observed structures in the HAXPES spectra. GW corrections are required for the O bands and Ni-s and p derived states to properly position their binding energies. Our results establish that a combination of the GW and DMFT methods is necessary for correctly describing the electronic structure of NiO in a proper ab initio framework. We also demonstrate that the inclusion of photoionization cross section is crucial to interpret the HAXPES spectra of NiO. We argue that our conclusions are general and that the here suggested approach is appropriate for any complex transition metal oxide. DOI: 10.1103/PhysRevB.93.235138The electronic structure of the late 3d transition metal monoxides (TMO) has been studied intensely [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Despite their apparent simplicity, they exhibit a rich variety of physical properties. It is by now clear that most of these properties arise due to the strong Coulomb interaction among the 3d electrons of the transition metal ion.NiO is the archetype of TMO with strong correlation effects, and has often served as the system of choice when new experimental and theoretical methods are benchmarked. The electronic structure of NiO has remained enigmatic and controversial over the decades and have also become a major topic of textbooks on condensed matter physics [3][4][5]18,19]. Over the years, a number of x-ray photoemission spectroscopy (XPS) and bremsstrahlung isochromat spectroscopy (BIS) studies [13,[20][21][22][23] were carried out to address its electronic structure. There also have been several theoretical attempts, ranging from model approaches [3,[24][25][26][27]] to first-principles calculations [14,[28][29][30][31][32][33][34][35][36][37], to explain different spectroscopic manifestations of NiO.Initially, the electronic structure of NiO was interpreted using ligand field theory where the insulating gap is primarily determined by the large Coulomb interaction U between Ni-d states, an ideal case of a Mott insulator [3,18]. This interpretation, however, could not be reconciled with res-* These authors contributed equally to this work. † olle.eriksson@physics.uu.se ‡ sarma@sscu.iisc.ernet.in onance photoemission experiments [38,39], since it failed to capture the right character of the multielectron satellite observed at high binding energy (around 9 eV). Later, Fujimori et al. [24] explained using a cluster model that the high-energy satellite arises due to the d 7 final state configuration, which was consiste...

The insulin-like growth factor 1 receptor (IGF-1R) is known to promote survival and has also been implicated in the pathogenesis of several disease states, including cardiovascular disorders and cancer. Recently, we showed that binding of coagulation factor VIIa (FVIIa) to its receptor tissue factor (TF) protects cancer cells from TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis. Here we present evidence that this biological function of TF/FVIIa is dependent on the IGF-1R. IGF-1R inhibitors AG1024 and PPP as well as siRNA-mediated downregulation of IGF-1R, abolished the TF/FVIIa-mediated protection against TRAIL-induced apoptosis. Moreover, FVIIa rapidly induced a time- and concentration-dependent tyrosine phosphorylation of the IGF-1R in MDA-MB-231 breast cancer cells and in primary human monocytes, an event that was accompanied by IGF-1R chromatin binding and gene transcription. We hereby present novel evidence of a cross-talk between the coagulation and IGF-1R signalling systems, and propose that the IGF-1R is a key player in mediating TF/FVIIa-induced cell survival.

Background:The tissue factor/coagulation factor VIIa (TF/FVIIa) complex cleaves protease-activated receptor 2 (PAR2), but other non-coagulant substrates are not known. Results: Truncated isoforms of the tyrosine kinase receptors EphB2 and EphA2 were formed after FVIIa stimulation. Conclusion: EphB2 and EphA2 are identified as novel proteolytic substrates of TF/FVIIa. Significance: The results provide new insights into PAR2-independent functions of TF/FVIIa.

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