Hepatic synthesis of alpha 2 (acute phase)-globulin of rat plasma

Cloning, distribution and primary immune characteristics of amphioxus alpha-2 macroglobulin

Alpha-2 macroglobulin (α(2)M), a broad-spectrum protease inhibitor, exists widely in vertebrates and invertebrates, but little information is available to date regarding α(2)M in amphioxus, an animal bridging from invertebrates to vertebrates. Here we first show that the full α(2)M cDNA of Branchiostoma japonicum (Bjα(2)m) contained 5545 bp with an open reading frame of 4593 bp encoding signal sequence of 16 amino acid residues and a mature protein of 1514 residues. The calculated molecular mass and pI of mature Bjα(2)M were 164.2 kDa and 4.6 respectively. Bjα(2)m was mainly expressed in the hepatic caecum and hind-gut in a tissue-specific manner, contrasting to the primary expression of α(2)M in vertebrate liver. Following challenge with lipopolysaccharide (LPS), Bjα(2)m expression was significantly up-regulated (7-folds) at 8 h and then declined to the base line at 16 h. Taken together, it is suggested that Bjα(2)M is an immune-relevant molecule possibly involved in the acute phase response via the digestive organs.

Transplacental transport of alpha 2-macroglobulin (alpha 2M) and induction of alpha 2M in maternal and neonatal rats with acute inflammation

The aims of this study were to investigate transplacental transport of alpha 2-macroglobulin (alpha 2M) in rats in rats and to examine the degree of alpha 2M induction in maternal and neonatal rats with acute inflammation. Serum was collected from healthy pregnant CD (IGS) rats, neonates of the pregnant rats and their cord blood. Additional serum samples were obtained from pregnant rats inoculated with an inflammatory agent, turpentine oil, their neonates and cord blood, and neonates inoculated with turpentine oil. The serum levels of alpha 2M were measured by means of an enzyme-linked immunosorbent assay. The average serum levels of alpha 2M in healthy neonates and cord blood were about 380 micrograms/ml. Serum a2M level in neonates inoculated with turpentine oil averaged about 580 micrograms/ml. Serum alpha 2M levels in maternal rats inoculated with turpentine oil, neonates from those rats and their cord blood were elevated, the values being 2,000 micrograms/ml or higher. It was demonstrated that induction of alpha 2M in neonatal rats was lower than in maternal rats when inoculated with turpentine oil. These results suggest that alpha 2M is transplacentally transported from maternal rats to fetal ones.

The acute phase response and innate immunity of fish

Tissue trauma or invasion by pathogens or parasites induce changes in the quantities of several macromolecules in animal body fluids. These changes comprise one aspect of the acute phase response (APR), which in toto involves metabolic changes in several organ systems. One clear indication of the response is the increase in synthesis and secretion by the liver of several plasma proteins, with simultaneous decreases in others. These acute phase proteins (APP) function in a variety of defense-related activities such as limiting the dispersal of infectious agents, repair of tissue damage, inactivation of proteases, killing of microbes and other potential pathogens, and restoration of the healthy state. Some APP are directly harmful to microbes, while others modify targets thus marking them for cell responses. Some work alone while others contribute to cascades. Proteins that are APP in mammals, and that have been identified in both teleosts and elasmobranchs include C-reactive protein, serum amyloid P, and several components of the Complement system. Others reported in teleosts include transferrin and thrombin. Of these, only CRP has been reported to increase in acute phase plasma. In trout, a precerebellin-like protein is an APP with unknown functions. A cDNA library enriched in fragments of transcripts that were more abundant in livers from fish undergoing an APR recently yielded sequences resembling 12 additional known APP, and as many others either not known to be APP, or not similar to others yet in public databases. It appears that, as in mammals, hepatocytes are the prime source of APP in fish, and that pro-inflammatory cytokines induce transcription of their genes.

Rational design of novel immunosuppressive drugs: analogues of azathioprine lacking the 6-mercaptopurine substituent retain or have enhanced immunosuppressive effects

Clinical use of the immunosuppressive drug azathioprine is limited by potentially serious toxic effects related to depression of bone marrow function. The immunosuppressive and toxic properties of azathioprine are regarded as being properties of the cytotoxicity of its metabolite, 6-mercaptopurine (6-MP). However, azathioprine has an immunosuppressive effect additional to that attributable to 6-MP alone, and we propose that this is associated with an action of the methylnitroimidazolyl substituent. This suggests a route to the rational design of nontoxic immunosuppressants by replacing the 6-MP component of azathioprine with nontoxic thiols. We have synthesized and tested in vitro 24 such analogues, with two being further tested in vivo. In the human mixed lymphocyte reaction, virtually all compounds showed some degree of activity, 10 compounds being more active than azathioprine. In vivo, two compounds were more effective than azathioprine at prolonging graft survival in mice. In an oral toxicity study in male CD1 mice at doses equivalent to those at which azathioprine caused severe bone marrow depression both analogues had no toxic effects. Our results show that the immunosuppressive effects and bone marrow toxicity of azathioprine are not a consequence of release of 6-MP alone, and with appropriate modification can be separated, an approach which may lead to less toxic immunosuppressive drugs.

Acute-phase response factor, a nuclear factor binding to acute-phase response elements, is rapidly activated by interleukin-6 at the posttranslational level

Interleukin-6 (IL-6) is known to be a major mediator of the acute-phase response in liver. We show here that IL-6 triggers the rapid activation of a nuclear factor, termed acute-phase response factor (APRF), both in rat liver in vivo and in human hepatoma (HepG2) cells in vitro. APRF bound to IL-6 response elements in the 5'-flanking regions of various acute-phase protein genes (e.g., the alpha 2-macroglobulin, fibrinogen, and alpha 1-acid glycoprotein genes). These elements contain a characteristic hexanucleotide motif, CTGGGA, known to be required for the IL-6 responsiveness of these genes. Analysis of the binding specificity of APRF revealed that it is different from NF-IL6 and NF-kappa B, transcription factors known to be regulated by cytokines and involved in the transcriptional regulation of acute-phase protein genes. In HepG2 cells, activation of APRF was observed within minutes after stimulation with IL-6 or leukemia-inhibitory factor and did not require ongoing protein synthesis. Therefore, a preexisting inactive form of APRF is activated by a posttranslational mechanism. We present evidence that this activation occurs in the cytoplasm and that a phosphorylation is involved. These results lead to the conclusions that APRF is an immediate target of the IL-6 signalling cascade and is likely to play a central role in the transcriptional regulation of many IL-6-induced genes.

Acute-phase response factor, a nuclear factor binding to acute-phase response elements, is rapidly activated by interleukin-6 at the posttranslational level

Interleukin-6 (IL-6) is known to be a major mediator of the acute-phase response in liver. We show here that IL-6 triggers the rapid activation of a nuclear factor, termed acute-phase response factor (APRF), both in rat liver in vivo and in human hepatoma (HepG2) cells in vitro. APRF bound to IL-6 response elements in the 5'-flanking regions of various acute-phase protein genes (e.g., the alpha 2-macroglobulin, fibrinogen, and alpha 1-acid glycoprotein genes). These elements contain a characteristic hexanucleotide motif, CTGGGA, known to be required for the IL-6 responsiveness of these genes. Analysis of the binding specificity of APRF revealed that it is different from NF-IL6 and NF-kappa B, transcription factors known to be regulated by cytokines and involved in the transcriptional regulation of acute-phase protein genes. In HepG2 cells, activation of APRF was observed within minutes after stimulation with IL-6 or leukemia-inhibitory factor and did not require ongoing protein synthesis. Therefore, a preexisting inactive form of APRF is activated by a posttranslational mechanism. We present evidence that this activation occurs in the cytoplasm and that a phosphorylation is involved. These results lead to the conclusions that APRF is an immediate target of the IL-6 signalling cascade and is likely to play a central role in the transcriptional regulation of many IL-6-induced genes.

Quantitative and qualitative changes of serum proteolytic activity in rats with liver damage induced by galactosamine

Serum proteolytic activity was determined in galactosamine-treated rats and in controls. Injection of the hepatotoxin at a dose of 400 mg/kg resulted in a 3.4-fold elevation in the serum proteolytic activity, while AST (aspartate aminotransferase), ALT (alanine aminotransferase) and bilirubin were increased by factors of 3.9, 8.8 and 4.5, respectively. Studies with proteinase inhibitors revealed that the serum proteolytic activity was partially metal-dependent as well as puromycin and antipain sensitive. Differences in susceptibility to a combination of N-ethylmaleimide and antipain indicated presence of different proteolytic systems in the sera of liver damaged and control rats. Separation of serum proteinases by gel filtration showed that the galactosamine-intoxicated rat serum contained activity which did not appear in the control serum. This activity was partially metal dependent, antipain and N-ethylmaleimide sensitive, and was more susceptible to dithiothreitol than the control activity. These findings demonstrate that hepatocellular damage induced by galactosamine caused not only an increase in serum proteinases, but was also associated with the appearance of enzymes not normally released by the liver of untreated animals.

Changes in serum and exudate levels of functional macroglobulins and anti-inflammatory effect of alpha 2-acute-phase macroglobulin on carrageenin-induced inflammation in rats

Serum and exudate levels of functional macroglobulins that have the ability to inhibit proteinases were determined at various times after carrageenin injection into a preformed air-pouch on the back of rats. The trypsin-inhibiting activity of serum macroglobulins increased after a lag period of 3 hr, reached a maximum at 24 hr, and decreased steadily until day 16 after carrageenin injection. This change was in good agreement with the change in the serum level of alpha 2-acute-phase macroglobulin. In contrast with the serum level, the exudate level of functional macroglobulins was negligible on day 1, detectable on day 3, and remained at almost the same level from day 5 to day 16 after carregeenin injection. Macroglobulins were partially purified from rat serum obtained at 20 hr after carregeenin injection, and their anti-inflammatory activity was studied. The partially purified alpha 2-acute-phase macroglobulin and the alpha 1 macroglobulin were injected into the air-pouch immediately after carrageenin injection, with the result that a single injection of the functionally active alpha 2-acute-phase macroglobulin significantly inhibited the formation of granulation tissue on day 4 after the carrageenin injection, whereas functionally inactive alpha 1 macroglobulin was without effect. These results suggest that the inhibitory activity of macroglobulins on the development of granulation tissue is due to the proteinase-inhibiting capacity of macroglobulins.

Synthesis of acute-phase alpha 2-macroglobulin during inflammation and pregnancy

A recent investigation of acute-phase alpha 2-macroglobulin (AP alpha 2M) concentration in the rat during pregnancy demonstrated a bimodal distribution, for which we suggested a maternal source of AP alpha 2M in early gestation and a fetal source in late gestation. This interpretation was supported by the findings of the present study, which employed organ culture techniques, incorporation of [35S]methionine, immunoprecipitation of radioactivity, and fluorography to measure synthesis of AP alpha 2M in specific fetal, adult, and maternal tissues. Preliminary results indicated that in adult male rats treated with croton oil (compared with nontreated males), AP alpha 2M was synthesized in kidney, spleen, thymus, and lymphocytes by 48 hr post induction, but synthesis in the liver was not evident. In the pregnant rat from 12 to 16 days (compared with nonpregnant females), synthesis of AP alpha 2M was high in metrial gland, moderate in spleen, thymus and lymphocytes, and absent in liver; at 21 days, synthesis of AP alpha 2M in these four maternal tissues had declined. Fetal synthesis of AP alpha 2M in yolk sac (12 to 16 days) and in liver (15 to 16 days) was significantly elevated, and at 21 days fetal liver still displayed marked synthesis. These data are consistent with the interpretation that an early maternal source of AP alpha 2M synthesis is the metrial gland and that in the fetus both yolk sac and liver are major sources of AP alpha 2M, the latter tissue continuing synthesis into late gestation. Lymphopoietic and lymph-containing tissues appear to be major sites of AP alpha 2M synthesis during inflammation and pregnancy.

Distribution of acute-phase alpha 2-macroglobulin in rat fetomaternal compartments

Rat acute-phase alpha 2-macroglobulin (AP alpha 2M) concentration was measured by radioimmunoassay in maternal serum, fetal plasma, maternal liver, fetal liver, and amniotic fluid as a function of gestational and neonatal age. The concentration profiles of AP alpha 2M in maternal serum and fetal plasma displayed two peaks, one in early gestation and another during late gestation. Synthesis of AP alpha 2M was confirmed by the immunoprecipitation of [35S]methionine incorporated into cultures of selected tissues. The following observations were made. 1) Maternal serum concentrations of AP alpha 2M were higher than those observed in fetal plasma in early gestation. This was attributable to a high level of maternal AP alpha 2M synthesis in metrial gland which was absent in liver and moderate in yolk sac. 2) In late gestation fetal plasma concentrations of AP alpha 2M greatly exceeded those observed in maternal serum. This could be explained by the pronounced synthesis of AP alpha 2M in fetal liver that was not apparent in maternal liver or yolk sac. 3) During labor, a transient increase in AP alpha 2M concentration was observed in maternal serum and fetal plasma. 4) During lactation a moderately elevated maternal serum concentration of AP alpha 2M was maintained. 5) Amniotic fluid concentration of AP alpha 2M was very low throughout gestation, which indicated that the fetal glomerulus was relatively impermeable to this large protein. It is concluded that in early gestation a principal maternal source of AP alpha 2M appears to be the metrial gland, whereas in late gestation fetal liver is a major source of AP alpha 2M appearing in fetal plasma from where some of this macroglobulin is speculated to be transported to the maternal circulation.

Synthesis of alpha 2-macroglobulin in rat hepatocytes and in a cell-free system

The biosynthesis and secretion of alpha 2-macroglobulin was studied in rat hepatocyte primary cultures. After immunoprecipitation of alpha 2-macroglobulin from a cell homogenate and the hepatocyte medium, two forms of alpha 2-macroglobulin with app. Mr of 176000 and 182000, respectively, were identified. A precursor-product relationship for the two alpha 2-macroglobulin forms was demonstrated by a pulse-chase experiment. The cellular form of alpha 2-macroglobulin could be deglycosylated by endoglucosaminidase H, whereas the medium form of alpha 2-macroglobulin remained unaffected. On the other hand, only the medium form of alpha 2-macroglobulin was found to be susceptible to neuraminidase. In vitro translation of rat liver poly(A)+ RNA resulted in a translation product of an app. Mr of 162000.

Plasma protein induction by isolated hepatocytes

Hepatocytes can be maintained in culture for periods of a few hours to many days. This review summarizes the metabolic characteristics of these cultures and describes their use in studying the regulation of plasma protein synthesis. Hormones selectively stimulate the synthesis of certain proteins. Cortisol stimulates the synthesis of fibrinogen and other acute-phase proteins; whereas, insulin stimulates albumin synthesis. In the latter case insulin increases the rate of a nuclear process. Mediators elaborated by leukocytes stimulate acute-phase protein synthesis in hepatocytes. Plasmin-generated fibrin peptides stimulate fibrinogen synthesis via a leukocytic mediator. Lipoprotein synthesis is stimulated by fatty acids and is inhibited by albumin and other macromolecules. These and other processes are susceptible to detailed analysis using sub-cellular fractions (mRNA, nuclei, transcription factors, etc.) isolated from hepatocytes. Studies on fetal or embryonic hepatocytes and hepatomas are yielding information on the regulation of secretory protein synthesis during development and following neoplastic transformation.

Purification and immunological determination of alpha 2-macroglobulin in serum from injured rats

Rat alpha 2-macroglobulin was isolated and purified from the pooled sera of turpentine-injected rats by sequential use of dextran sulphate, DEAE-cellulose and gel filtration chromatography. The final protein product obtained by this procedure proved to be alpha 2-macroglobulin of a high degree of purity based on electrophoretic, immunologic and centrifugal analysis. The alpha 2-macroglobulin preparation also binds stoichiometrically to trypsin preventing subsequent inhibition by protein trypsin inhibitors. SDS-polyacrylamide gel electrophoresis of rat alpha 2-macroglobulin after incubation with trypsin suggested that there are at least two susceptible peptide bonds in the 170,000-dalton alpha 2-macroglobulin subunit. The concentration of alpha 2-macroglobulin in the sera of rats was measured by electroimmuno assay a monospecific antiserum against alpha 2-macroglobulin. Purified alpha 2-macroglobulin was used as a standard. Sera from normal male rats contained 32 +/- 4 micrograms of alpha 2-macroglobulin per ml. To determine the time course of response of alpha 2-macroglobulin to inflammation, rats were subjected to either laparotomy or subcutaneous injection of turpentine. After either type of injury, the concentration of alpha 2-macroglobulin increased rapidly, reaching a maximum value of 110-140 times that of the control value by 24 h. Little difference was noted in responsiveness between the two sexes.

Stimulation of protein and RNA synthesis by methylmercury chloride in the liver of intact and adrenalectomized rats

(1) A single injection of methylmercury chloride in the rat (10-50 mg/kg) increased both in vivo and in vitro rates of 14C-leucine incorporation into the protein of the post-mitochondrial supernatant fraction of the liver. In contrast, no stimulation of protein synthesis was observed in the brain of the methylmercury-treated rats. (2) Methylmercury administration also stimulated RNA polymerase activities in isolated hepatic nuclei, stimulation of Mg-dependent activity being higher than that of Mn-dependent activity. (3) In experiments with adrenalectomized rats, it was found that the stimulatory effect of methylmercury on protein and RNA synthesis in the liver was mediated partly through the adrenal gland. (4) Analysis of serum by starch-block electrophoresis revealed that synthesis of all serum proteins, including albumin and alpha-gamma globulin fractions, was stimulated by methylmercury treatment. (5) These results suggest that the observed effects of methylmercury on the liver depend on mechanisms other than enhancement of the synthesis of acute-phase proteins.

Serum concentrations of alpha-macrofeto-protein (acute-phase alpha2-macroglobulin), a proteinase inhibitor, in pregnant and neonatal rats and in rats with acute inflammation

Alpha macrofetoprotein (AMF) or acute-phase alpha2 macroglobulin serum concentrations are elevated in pregnant, fetal, and newborn rats and in rats with experimentally induced acute inflammation when quantitated using a double-antibody radioimmunoassay. Concentrations of AMF are 17 +/- 2 microgram/ml and 32 +/- 6 microgram/ml in normal adult rat sera. Both maternal (1.2 mg/ml) and neonatal (9.3 mg/ml) concentrations are maximal at term. AMF serum concentrations of rats injected with croton oil into the hind footpads are unchanged for the first 4 h after injection, then increase to a maximum of 10.5 mg/ml 36 h after injection. Serum AMF concentrations correlate directly with the dose of croton oil and the increase in size (swelling) of the injured foot, and remain elevated during the course of inflammation for at least two weeks. The possible function of AMF as an antiproteinase limiting the extent of inflammation after acute tissue injury is discussed.

Inflammation inhibiting properties of rat alphaM foetoprotein (rat-alpha2 macroglobulin), an acute phase reactant

alphaMFoetoprotein of the rat (rat alpha2macroglobulin) is present in serum during foetal development. After birth, alphaMFP declines rapidly, but the protein returns after injury. The injury we used consisted of skin and muscle incision, laparotomy, BaSO4 i.p. The protein occurs also during liverregeneration, livercardinogenesis en during infections. Therefore, alphaMFP can be considered as an acute phase reactant. We found that this protein strongly inhibits inflammatory exudation caused by carrageenin, histamin, prostaglandin E2, 5HT and bradykinin. Furthermore, we found that alphaMFP suppresses completely inflammatory reactions during Ga1.N-hepatitis. In this condition, the primary biochemical lesion, consisting of liver UDPG depletion, does occur in spite of the protective effect of alphaMFP. Thus, the inflammatory inhibiting effects of alphaMFP seem to be an important mechanism reducing inflammatory reaction patterns.

Partial purification of the anti-inflammatory factor(s) in inflammatory exudate

1. The carrageenin foot test was established as a sensitive and reliable assay procedure for determining the anti-inflammatory activity of inflammatory exudates.2. Incubation alone at a temperature above 70 degrees C or with pronase at 37 degrees C destroyed the anti-inflammatory activity of exudate.3. The anti-inflammatory component of exudate was partially precipitated by 50% ammonium sulphate.4. A partial purification process was devised using Sephadex G-150 gel filtration and DEAE and CM cellulose ion exchange chromatography to obtain at least a 24 fold purification.5. Measurements of 11-hydroxycorticosteroid levels indicated that steroids were not involved in the mechanism by which the exudate produced its anti-inflammatory effects.

The influence of tumor growth on the synthesis of alpha 2-AP (acute phase) globulin of rat serum

The effects of growth of the Walker 256 carcinosarcoma on the α2-AP (acute phase) globulin, fibrinogen, seromucoid, and haptoglobin fractions of plasma were investigated in adult, male Sprague–Dawley rats in a longitudinal study. Early increases in α2-AP globulin and seromucoid levels were found to be related to the tissue injury associated with the implantation procedure. Significant elevations in the α2-AP globulin, fibrinogen, and seromucoid fractions coincided with the onset of progressive tumor growth. Serum haptoglobin concentrations exhibited a delayed rise. This was attributed to the in vivo formation of haptoglobin–hemoglobin complexes. It was suggested that the increases in all fractions reflected the release of humoral mediators from injured or necrotic cells wrhich stimulated increased synthesis of the fractions by the liver.