Evolution of vertebrate fibrin formation and the process of its dissolution

Role of the angiopoietin-like protein family in the progression of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most frequent cause of chronic liver disease, with a range of conditions including non-alcoholic fatty liver, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Currently recognized as the liver component of the metabolic syndrome, NAFLD is intimately linked to metabolic diseases. Angiopoietin-like proteins (ANGPTLs) comprise a class of proteins that resemble angiopoietins structurally. It is closely related to obesity, insulin resistance and lipid metabolism, and may be the critical factor of metabolic syndrome. In recent years, many studies have found that there is a certain correlation between ANGPTLs and the occurrence and progression of NAFLD disease spectrum. This article reviews the possible mechanisms and roles of ANGPTL protein in the pathogenesis and progression of NAFLD.

Fibrinogen Chains Intrinsic to the Brain

We observed fine fibrin deposition along the paravascular spaces in naive animals, which increased dramatically following subarachnoid hemorrhage (SAH). Following SAH, fibrin deposits in the areas remote from the hemorrhage. Traditionally it is thought that fibrinogen enters subarachnoid space through damaged blood brain barrier. However, deposition of fibrin remotely from hemorrhage suggests that fibrinogen chains Aα, Bβ, and γ can originate in the brain. Here we demonstrate in vivo and in vitro that astroglia and neurons are capable of expression of fibrinogen chains. SAH in mice was induced by the filament perforation of the circle of Willis. Four days after SAH animals were anesthetized, transcardially perfused and fixed. Whole brain was processed for immunofluorescent (IF) analysis of fibrin deposition on the brain surface or in brains slices processed for fibrinogen chains Aα, Bβ, γ immunohistochemical detection. Normal human astrocytes were grown media to confluency and stimulated with NOC-18 (100 μM), TNF-α (100 nM), ATP-γ-S (100 μM) for 24 h. Culture was fixed and washed/permeabilized with 0.1% Triton and processed for IF. Four days following SAH fibrinogen chains Aα IF associated with glia limitans and superficial brain layers increased 3.2 and 2.5 times (p < 0.05 and p < 0.01) on the ventral and dorsal brain surfaces respectively; fibrinogen chains Bβ increased by 3 times (p < 0.01) on the dorsal surface and fibrinogen chain γ increased by 3 times (p < 0.01) on the ventral surface compared to sham animals. Human cultured astrocytes and neurons constitutively expressed all three fibrinogen chains. Their expression changed differentially when exposed for 24 h to biologically significant stimuli: TNFα, NO or ATP. Western blot and RT-qPCR confirmed presence of the products of the appropriate molecular weight and respective mRNA. We demonstrate for the first time that mouse and human astrocytes and neurons express fibrinogen chains suggesting potential presence of endogenous to the brain fibrinogen chains differentially changing to biologically significant stimuli. SAH is followed by increased expression of fibrinogen chains associated with glia limitans remote from the hemorrhage. We conclude that brain astrocytes and neurons are capable of production of fibrinogen chains, which may be involved in various normal and pathological processes.

The role of fibrinogen, fibrin and fibrin(ogen) degradation products (FDPs) in tumor progression

Participation of fibrin, fibrinogen, and their degradation products in pathogenesis and progression of cancer may lead to complications of thromboembolic events. The tumor may be a source of fibrinogen. Fibrinogen inside the tumor is one of the factors of its growth and metastasis. Fibrinogen, fibrin and their degradation products possess proinflammatory activity. They indirectly stimulate endothelium to secrete von Willebrand factor, leading to activation of platelets accompanying neoplastic disorders. Fragments E and D are the end products of fibrin(ogen) degradation and E and DD are the end products of stabilized fibrin. E stimulates proliferation, migration and differentiation of endothelial cells, contributing to tumor vasculature. Increased levels of DD are observed in malignant neoplasms, such as breast, lung, colon and ovary cancers. In breast cancers DD correlates with progression of disease and metastasis. The role of fibrinogen and the products of its degradation in the progression of various tumors is not sufficiently understood.

The protochordate Ciona intestinalis has a protein like full-length vertebrate fibrinogen

In a recent review, a putative fibrinogen-like protein in the protochordate Ciona intestinalis was noted. Unfortunately, computer-directed splicing had omitted several exons, mistakenly generating a single long polypeptide chain. In fact, 3 consecutive genes exist, the translated versions of which are homologous to individual vertebrate fibrinogen chains. The circulating form is likely a 6-chain covalent dimer, just as occurs in vertebrates.

The 2.0-A crystal structure of tachylectin 5A provides evidence for the common origin of the innate immunity and the blood coagulation systems

Because invertebrates lack an adaptive immune system, they had to evolve effective intrinsic defense strategies against a variety of microbial pathogens. This ancient form of host defense, the innate immunity, is present in all multicellular organisms including humans. The innate immune system of the Japanese horseshoe crab Tachypleus tridentatus, serving as a model organism, includes a hemolymph coagulation system, which participates both in defense against microbes and in hemostasis. Early work on the evolution of vertebrate fibrinogen suggested a common origin of the arthropod hemolymph coagulation and the vertebrate blood coagulation systems. However, this conjecture could not be verified by comparing the structures of coagulogen, the clotting protein of the horseshoe crab, and of mammalian fibrinogen. Here we report the crystal structure of tachylectin 5A (TL5A), a nonself-recognizing lectin from the hemolymph plasma of T. tridentatus. TL5A shares not only a common fold but also related functional sites with the gamma fragment of mammalian fibrinogen. Our observations provide the first structural evidence of a common ancestor for the innate immunity and the blood coagulation systems.