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PlasmaThe Non-cellular Components of Blood
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Various proteins belong to this group of globulins: α2-Macroglobulin. This is a protease inhibitor in plasma and is the major protein in the α2-globulin fraction (∼80%). It has inhibitory functions on plasma trypsin, chymotrypsin and plasmin. The primary function of α2-macroglobulin may be to inhibit proteases produced by infectious organisms.Prothrombin. Prothrombin is a clotting factor synthesized by the liver. About 60% of the extracellular pool of prothrombin is in the plasma and 40% in the extravascular space. It has a rapid turnover.Haptoglobin. This is a heterogeneous group of globulins that bind free Hb and transport it to the liver.Ceruloplasmin. Ceruloplasmin is a plasma protein that carries copper and is produced in the liver. It also functions as an oxidase enzyme and oxidizes ferrous to ferric ions before the binding of iron to transferrin. As an acute-phase protein, it may modulate inflammation by its free-radical scavenging properties.
RAT α 2 -Macroglobulin and Related α-Macroglobulins in the Acute Phase Response
Published in Andrzej Mackiewicz, Irving Kushner, Heinz Baumann, Acute Phase Proteins, 2020
α2-M have been found to specifically bind a number of growth factors and cytokines in recent years. The cytokines that thus far have been found to bind to α2-M include growth hormone,66 platelet-derived growth factor (PDGF),67 transforming growth factors (TGFs) βj and β2,68 fibroblast growth factor (FGF),69 interleuken-6 (IL-6),70 interleukin-1 β (IL-lβ),71 tumor necrosis factor-α,72 and nerve growth factor (NGF).73 The study of the nature of the binding sites, the form of α-macroglobulin involved, and the physiological consequences of this binding are actively being pursued in several laboratories. A thorough review of the status of current work on cytokine binding by α-macroglobulins has recently been prepared by Bonner and Brody.74 Most of the studies have used human or bovine α2-M. However, a rat α-macroglobulin produced by alveolar macrophages was found to bind PDGF.75 Immunochemical methods have tentatively identified this protein as α1-M.80 Thus far, the physiological consequences of the cytokine binding has not been clarified. However, these findings have further strengthened the suspicions that α-macroglobulins have multiple physiological functions. Comparative studies of cytokine binding by the three different rat α- macroglobulins may be useful in clarifying the physiological roles of these proteins.
Inflammation
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
The α1-antitrypsin acts against thrombin, activated Factor XI, and in a limited way, against the action of kallikrein.134,138,185 The action of α2-macroglobulin is predominantly connected with its binding to proteins. It forms complexes with plasmin, kallikrein, thrombin, and chymotrypsin, and the complex formation does not prevent the complex from being active against the usual substrates of these enzymes. Some proteolytic activity still remains present, and when α2-macroglobulin-enzyme complexes are formed they are rapidly cleared from the circulation.180 It seems that in the binding between α2-macroglobulin and the enzyme the active site is not fully blocked, and therefore the enzyme is able to degrade some substances.179 The role of α2-macroglobulin is complex. When it binds to a protease, (1) the substrate specificity of the proteolytic enzyme is modified; (2) the activity of the bound protease is preserved, but the effect of other plasma inhibitors are minimized; and (3) the complex is rapidly cleared from the circulation. The inhibitory action of α2-macroglobulin is related to the size of the substrate. The higher the molecular weight of the substrate, the greater is the extent of inhibition.
Chymotrypsin attenuates adjuvant-induced arthritis by downregulating TLR4, NF-κB, MMP-1, TNF-α, IL-1β, and IL-6 expression in Sprague–Dawley rats
Published in Immunopharmacology and Immunotoxicology, 2022
Jianqiang Li, Linlin Wang, Guangting Zeng, Huilan Li, Jia Luo, Qijun Tian, Zanling Zhang
Chymotrypsin is a proteolytic enzyme with anti-inflammatory effects. It was found to be more effective than aspirin [8]. Chymotrypsin degrades proteins and has anti-inflammatory functions, inhibiting edema and promoting tissue repair. Low-dose chymotrypsin treatment is effective in inhibiting neutrophil migration into sites of inflammation in vivo [9]. It can also affect the migration of innate immune cells, which has an important effect on T cell polarization [9]. In models of acute and subacute inflammation, chymotrypsin has shown anti-inflammatory activity [8]. In an animal model of multiple sclerosis, administration of chymotrypsin successfully decreased clinical signs and decreased interleukin-17 and interferon-γ (IFN-γ) levels along with increased interleukin-4 and forkhead box P3 (FoxP3) levels [10]. Compared to untreated patients, chymotrypsin-administered burn patients showed a significant decrease in IL-1β and IL-6 levels in the serum [11]. α2-Macroglobulin is an important inhibitor of MMP activation [12]. The increased α2-macroglobulin level inhibited the activity of MMP, thus reducing the degradation and damage to joint tissue cells by MMP [4]. Supplementation with exogenous chymotrypsin has been shown to increase α2-macroglobulin levels [13]. Therefore, we hypothesize that chymotrypsin has a therapeutic effect on RA.
Signatures for chronic obstructive pulmonary disease (COPD) and asthma: a comparative genetic analysis
Published in British Journal of Biomedical Science, 2021
A Sahu, S Swaroop, S Kant, M Banerjee
A disintegrin and metalloproteinase 33 (ADAM33), an important protease, is specifically expressed in basal epithelial cells and vascular endothelium of lung airway epithelia and in smooth muscle cells [5]. It plays a role in proteolytic release of cell surface membrane proteins such as cytokines, growth factors, receptors [6] and cleavage of α2-macroglobulin which has important role in pulmonary defence [7]. ADAM33 normally performs airway remodelling, but in a pathogenic state, altered ADAM33 protein may enhance inflammation, thus, increasing the severity of the disease [8]. Single-nucleotide polymorphisms (SNPs) in ADAM33 may alter the function of ADAM33 protein. Studies have reported that SNPs in ADAM33 were associated with an accelerated decline of lung function in COPD as well as asthma patients [9]. The obstruction in COPD is not reversible while in asthma it is, and ADAM33 is one of the common remodelling genes involved in both diseases.
Serum proteome assessment in nonalcoholic fatty liver disease in children: a preliminary study
Published in Expert Review of Proteomics, 2020
Paweł Małecki, Joanna Tracz, Magdalena Łuczak, Magdalena Figlerowicz, Katarzyna Mazur-Melewska, Wojciech Służewski, Anna Mania
The importance of alpha-2-macroglobulin (α2 MG) in liver disease has been evaluated concerning various liver diseases. Initial research concerned patients with hepatitis B and C. Currently, three indicators of hepatic fibrosis are used, which take into account the concentration of this protein – FibroTest, FibroSPECT, Hepascore. Significantly higher alpha-2-macroglobulin levels were described in patients with advanced fibrosis (METAVIR F3-F4) [35,36]. In our study group, the concentration of this protease inhibitor, as well as the other one – alpha-1-antitrypsin, was significantly lower in NAFLD patients than in the control group. The reason for the observed condition may be reduced production of α2 MG by the affected liver or a decrease in concentration associated with consumption – α2 MG binds cytokines such as interleukin-6 (Il-6) and TNF-α, which level in NAFLD is elevated [37].