Sequence of rat liver alpha 2-macroglobulin and acute phase control of its messenger RNA

Alpha 2-macroglobulin acts as a clearance factor in the lysosomal degradation of extracellular misfolded proteins

Proteostasis regulates protein folding and degradation; its maintenance is essential for resistance to stress and aging. The loss of proteostasis is associated with many age-related diseases. Within the cell, molecular chaperones facilitate the refolding of misfolded proteins into their bioactive forms, thus preventing undesirable interactions and aggregation. Although the mechanisms of intracellular protein degradation pathways for intracellular misfolded proteins have been extensively studied, the protein degradation pathway for extracellular proteins remain poorly understood. In this study, we identified several misfolded proteins that are substrates for alpha 2-macroglobulin (α₂M), an extracellular chaperone. We also established a lysosomal internalization assay for α₂M, which revealed that α₂M mediates the lysosomal degradation of extracellular misfolded proteins. Comparative analyses of α₂M and clusterin, another extracellular chaperone, indicated that α₂M preferentially targets aggregation-prone proteins. Thus, we present the degradation pathway of α2M, which interacts with aggregation-prone proteins for lysosomal degradation via selective internalization.

Domain-Dependent Evolution Explains Functional Homology of Protostome and Deuterostome Complement C3-Like Proteins

Complement proteins emerged early in evolution but outside the vertebrate clade they are poorly characterized. An evolutionary model of C3 family members revealed that in contrast to vertebrates the evolutionary trajectory of C3-like genes in cnidarian, protostomes and invertebrate deuterostomes was highly divergent due to independent lineage and species-specific duplications. The deduced C3-like and vertebrate C3, C4 and C5 proteins had low sequence conservation, but extraordinarily high structural conservation and 2-chain and 3-chain protein isoforms repeatedly emerged. Functional characterization of three C3-like isoforms in a bivalve representative revealed that in common with vertebrates complement proteins they were cleaved into two subunits, b and a, and the latter regulated inflammation-related genes, chemotaxis and phagocytosis. Changes within the thioester bond cleavage sites and the a-subunit protein (ANATO domain) explained the functional differentiation of bivalve C3-like. The emergence of domain-related functions early during evolution explains the overlapping functions of bivalve C3-like and vertebrate C3, C4 and C5, despite low sequence conservation and indicates that evolutionary pressure acted to conserve protein domain organization rather than the primary sequence.

The evolutionary analysis of complement component C5 and the gene co-expression network and putative interaction between C5a and C5a anaphylatoxin receptor (C5AR/CD88) in human and two Cyprinid fish

The complement system is a complex network of soluble and membrane-associated serum proteins that regulate immune response. Activation of the complement C5 generates C5a and C5b which generate chemoattractive effect on myeloid cells and initiate the membrane attack complex (MAC) assembly. However, the study of evolutionary process and systematic function of C5 are still limited. In this study, we performed an evolutionary analysis of C5. Phylogeny analysis indicated that C5 sequences underwent complete divergence in fish and non-fish vertebrate. It was found that codon usage bias improved and provided evolution evidence of C5 in species. Notably, the codon usage bias of grass carp was evolutionarily closer to the zebrafish genome compared with humans and stickleback. This suggested that the zebrafish cell line may provide an alternative environment for heterologous protein expression of grass carp. Sequence comparison showed a higher similarity between human and mouse, grass carp, and zebrafish. Moreover, selective pressure analysis revealed that the C5 genes in fish and non-fish vertebrates exhibited different evolutionary patterns. To study the function of C5, gene co-expression networks of human and zebrafish were built which revealed the complexity of C5 function networks in different species. The protein structure simulation of C5 indicated that grass carp and zebrafish are more similar than to human, however, differences between species in C5a proteins are extremely smaller. Spatial conformations of C5a-C5AR (CD88) protein complex were constructed, which showed that possible interaction may exist between C5a and CD88 proteins. Furthermore, the protein docking sites/residues were measured and calculated according to the minimum distance for all atoms from C5a and CD88 proteins. In summary, this study provides insights into the evolutionary history, function and potential regulatory mechanism of C5 in fish immune responses.

Substrain-specific differences in bone parameters, alpha-2-macroglobulin circulating levels, and osteonecrosis incidence in a rat model

Osteonecrosis of the femoral head (ONFH) is a potentially devastating complication that occurs in up to 40% of young adults receiving chronic glucocorticoid (GC) therapy. Through a validated GC therapy rat model, we have previously shown that Wistar Kyoto (WK) rats exhibit a genetic susceptibility to GC-induced ONFH compared to Sasco Fischer (F344) rats. We have undertaken this study in order to investigate differences between these two strains for their bone parameters, alpha-2-macroglobulin (A2M) circulating levels and incidence of GC-induced osteonecrosis of the femoral head. WK and F344 rats were treated either with 1.5 mg/kg/day of prednisone or placebo for 6 months. Blood was taken every month. The femoral heads were harvested for histological examination to detect ONFH and analyzed with micro-computed tomography. After 3 months of GC-therapy, plasma A2M was elevated in treated rats only. GC-treated WK rats exhibited histological evidence of early ONFH through higher rates of cellular apoptosis and empty osteocyte lacunae in the subchondral bone compared to placebos and to F344 rats. Furthermore, micro-CT analysis exhibited femoral head collapse only in GC-treated WK rats. Interestingly, GC-treated F344 rats exhibited significant micro-CT changes, but such changes were less concentrated in the articular region and were accompanied histologically with increased marrow fat. These µCT and histological findings suggest that elevated A2M serum level is not predictive and suitable as an indicative biomarker for early GC-induced ONFH in rodents. Elevated A2M levels observed during GC treatment suggests that it plays role in the host reparative response to GC-associated effects. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1183-1194, 2017.

Identification of consensus biomarkers for predicting non-genotoxic hepatocarcinogens

The assessment of non-genotoxic hepatocarcinogens (NGHCs) is currently relying on two-year rodent bioassays. Toxicogenomics biomarkers provide a potential alternative method for the prioritization of NGHCs that could be useful for risk assessment. However, previous studies using inconsistently classified chemicals as the training set and a single microarray dataset concluded no consensus biomarkers. In this study, 4 consensus biomarkers of A2m, Ca3, Cxcl1, and Cyp8b1 were identified from four large-scale microarray datasets of the one-day single maximum tolerated dose and a large set of chemicals without inconsistent classifications. Machine learning techniques were subsequently applied to develop prediction models for NGHCs. The final bagging decision tree models were constructed with an average AUC performance of 0.803 for an independent test. A set of 16 chemicals with controversial classifications were reclassified according to the consensus biomarkers. The developed prediction models and identified consensus biomarkers are expected to be potential alternative methods for prioritization of NGHCs for further experimental validation.

Acute phase proteins are major clients for the chaperone action of α₂-macroglobulin in human plasma

Extracellular protein misfolding is implicated in many age-related diseases including Alzheimer's disease, macular degeneration and arthritis. In this study, putative endogenous clients for the chaperone activity of α₂-macroglobulin (α₂M) were identified after human plasma was subjected to physiologically relevant sheer stress at 37 °C for 10 days. Western blot analysis showed that four major acute phase proteins: ceruloplasmin, fibrinogen, α₁-acid glycoprotein and complement component 3, preferentially co-purified with α₂M after plasma was stressed. Furthermore, the formation of complexes between α₂M and these putative chaperone clients, detected by sandwich ELISA, was shown to be enhanced in response to stress. These results support the hypothesis that α₂M plays an important role in extracellular proteostasis by sequestering misfolded proteins and targeting them for disposal, particularly during acute phase reactions.

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.

Multiple forms of alpha-2 macroglobulin in shrimp Fenneropenaeus chinesis and their transcriptional response to WSSV or Vibrio pathogen infection

Alpha-2 macroglobulin (A2M) is a non-specific protease inhibitor involved in host defense. By full length cloning and sequencing we identified three distinct cDNAs for A2M in Chinese shrimp Fenneropenaeus chinesis, designated FcA2M-1, FcA2M-2 and FcA2M-3, respectively. Expression profiles in normal tissues as well as tissues after challenge by white spot syndrome virus (WSSV) and Vibrio pathogen were conducted for FcA2M-1 and FcA2M-2. The FcA2M-1 and FcA2M-2 cDNAs encode proteins with 1501 or 1502 amino acids, respectively, containing the typical conserved domain architecture of A2M. Similar to complement component C3, FcA2M-2 has a catalytic histidine, which may confer opsonic properties on this shrimp A2M. Six variants in the bait region were found in FcA2M-2 responding differently to Vibrio challenge, thereby widening the spectrum of inhibition and the diversity of immune recognition. FcA2M-1 and FcA2M-3, as well as most other protostomia invertebrate A2Ms identified so far, have a serine residue in the catalytic histidine position instead of the conserved asparagine residue found in vertebrate A2Ms. This, as inferred from a carp C3 molecule in which the catalytic histidine is substituted by a serine, suggests A2Ms in lower invertebrates possibly bear C3-like opsonic activity. These FcA2Ms showed much lower similarity to each other than to the A2Ms in other shrimp species, further supported by pylogenetic analysis. FcA2M-1 was found to be expressed most highly in hemocytes and lymphoid organ, while FcA2M-2 was expressed most highly in the heart and lymphoid organ, with the lowest expression in hemocytes. Challenge by WSSV or Vibrio pathogen increased the FcA2M-1 mRNA level in both hemocytes and lymphoid organ. After challenge, FcA2M-2 showed up-regulation in lymphoid organ but not in hemocytes. These expression features indicate that the different types of A2M in F. chinesis carry out different functions and that they are not simply functionally redundant.

Effects of metoclopramide-induced hyperprolactinemia on the prolactin receptor of murine endometrium

OBJECTIVE

To evaluate the effects of metoclopramide-induced hyperprolactinemia on the prolactin receptor of murine endometrium.

DESIGN

Experimental study using the RNA extraction to detect tissue prolactin receptor isoforms by reverse-transcriptase polymerase chain reaction (RT-PCR).

SETTING

University-based laboratory.

ANIMAL(S)

Seventy-two female swiss albino mice (Mus musculus), approximately 100 days old, were divided into six 12-animal groups: (GI) nonoophorectomized mice given vehicle; (GII) nonoophorectomized mice treated with metoclopramide; (GIII) oophorectomized mice treated with metoclopramide; (GIV) oophorectomized mice treated with metoclopramide and 17beta-estradiol; (GV) oophorectomized mice treated with metoclopramide and micronized progesterone; (GVI) oophorectomized mice treated with metoclopramide and a solution of 17beta-estradiol and micronized progesterone.

INTERVENTION(S)

Drugs were administered for 50 days. Following euthanasia, the middle portions of the uterine horns were removed, sectioned, and immediately frozen for RT-PCR procedures. Blood was collected for the dosage of prolactin and serum estrogen and progesterone using radioimmune assay.

MAIN OUTCOME MEASURE(S)

Identification of uterine prolactin receptor isoforms.

RESULT(S)

The PRL receptor and its isoform L were identified only in GI (control group) and GII (metoclopramide), the two groups with nonoophorectomized animals. The amount of PRL receptor mRNA and that of its isoform L from GII were the largest. No other isoforms of the prolactin receptor were identified in any of the groups.

CONCLUSION(S)

Our results suggest that replacement of estrogen and progestin may not increase the mRNA of endometrial PRL receptor in metoclopromide-induced hyperprolactinemia in rats after castration.

Temporal and spatial expression of IGF-I and IGFBP-1 during acute-phase response induced by localized inflammation in rats

OBJECTIVE

The acute-phase response (APR), a cytokine-induced defense reaction of the body that enhances the innate immunity mechanisms directed to eliminate the noxious agent and restrict the area of damage, is accompanied by numerous alterations of the IGF axis. The liver is a central organ of both the IGF system and the APR because it releases most of IGF-I and IGFBP-1 in the circulation and is the main target organ for acute-phase-cytokines such as IL-6.

METHODS

In the current work the expression of IGF-I and IGFBP-1 was studied in the liver and extrahepatic tissues in a rat model of localized inflammation induced by intramuscular injection of turpentine oil (TO). The mRNA expression of IGF-I and IGFBP-1 was determined by Northern blot analysis and quantitative RT-PCR. Circulating levels of IGF-I and IGFBP-1 were evaluated by radioimmunoassay and [(125)I]-IGF-I ligand blotting, respectively.

RESULTS

Administration of TO to the rats led to a significant reduction of IGF-I gene expression in the liver and spleen. These changes were accompanied by a reduction of serum IGF-I concentrations to approximately 50% of levels observed in control rats. In contrast to IGF-I, IGFBP-1 mRNA expression was rapidly elevated in the livers of TO-treated rats. IGFBP-1 transcripts were already detectable at 30 min after TO injection and reached their maximal levels by 6h. IGFBP-1 gene expression was also increased in the kidneys. This elevation, however, was delayed and less prominent than in the liver.

CONCLUSIONS

Our data demonstrate that localized inflammation induced by intramuscular TO injection is accompanied not only by decreased IGF-I but also by increased IGFBP-1 gene expression explaining at least in part the catabolic changes of metabolism observed during the acute-phase response.

The acute phase response in the rodent

In the rodent, the general response to acute inflammation and tissue damage is characterized by a complex rearrangement in the pattern of concentrations of proteins in the plasma leading to an increase in the sedimentation rate of erythrocytes, an increase in leukocyte concentration in the bloodstream, and a decrease in the hematocrit. Body temperature changes only slightly or not at all. The reasons for the change in plasma concentrations of proteins are changes in their rates of synthesis in the liver. Degradation of plasma proteins is not affected. The details of the acute phase response evolved in the interaction of species with their environment. Therefore, it is not surprising to find differences in the details of the acute phase response among species. For example, alpha 2-macroglobulin is a strongly positive acute phase reactant in the rat, but not in the mouse; C-reactive protein is a strongly positive acute phase protein in the mouse, but is not found in the rat. An inducible acute phase cysteine proteinase inhibitor system, which has evolved from a primordial kininogen gene, has been observed so far only in the rat. The changes in the synthesis rates of acute phase proteins during inflammation are closely reflected by corresponding changes in intracellular mRNA levels. In the liver, the capacity to induce the acute phase pattern of synthesis and secretion of plasma proteins probably develops around birth. Changes in mRNA levels are brought about by changes in transcription rates or by changes in mRNA stability. Kinetics of mRNA changes during the acute phase response differ for individual proteins. The main signal compound for eliciting the acute phase response in liver seems to be interleukin-6/interferon-beta 2/hepatocyte stimulating factor, whereas interleukin-1 leads to typical acute phase changes in mRNA levels only for alpha 1-acid glycoprotein, albumin, and transthyretin. Plasma protein genes are expressed in various extrahepatic tissues, such as the choroid plexus, the yolk sac, the placenta, the seminal vesicles, and other sites. All these tissues are involved in maintaining protein homeostasis in associated extracellular compartments by synthesis and secretion of proteins. Synthesis and secretion of plasma proteins in paracompartmental organs other than the liver is not influenced by the acute phase stimuli.

Synthesis of acute phase proteins in rats with cirrhosis exposed to lipopolysaccharide

BACKGROUND

In patients with cirrhosis, infection is frequent and a leading cause of death. This is secondary to various immunologic abnormalities in both the innate and the adaptive immune system. However, it remains unclear whether cirrhosis affects the inflammatory systemic component of the innate immunity, 'the acute phase response', mostly effectuated by the liver itself. We hypothesized that rats with cirrhosis raise a reduced acute phase response induced by lipopolysaccharide (LPS).

RESULTS

We examined the acute phase response induced by intraperitoneal injection of a low dose of LPS, in sham operated control animals and in rats with liver cirrhosis induced by bile duct ligation (BDL). We measured the serum concentrations of the most important acute phase proteins and their liver tissue gene expressions, assessed by mRNA levels. The BDL-model itself increased the serum concentration of alpha1-acid glycoprotein (alpha1AGP) and haptoglobin. LPS was lethal to 25% of the cirrhotic animals and to none of the controls. Twenty-four hours after LPS, the serum concentration of alpha1AGP and haptoglobin, the mRNA level of these acute phase proteins and of alpha2-macroglobulin and thiostatin rose to the same level in the animals with cirrhosis and in controls.

CONCLUSION

In rats with experimental cirrhosis LPS caused high mortality. In the survivors, the cirrhotic liver still synthesized acute phase proteins as the normal liver, indicating a normal hepatic contribution to this part of the acute phase response.

Proteases and protease inhibitors: a balance of activities in host-pathogen interaction

The immune system is the collection of effector molecules and cells of the host that act against invading parasites and their products. Secreted proteases serve important roles in parasitic metabolism and virulence and the several families of protein protease inhibitors of the plasma and blood cells play an important role in immunity by inactivating and clearing the protease virulence factors of parasites. The protease inhibitors are of two classes, the active-site inhibitors and the alpha2-macroglobulins. Inhibitors for the first class bind and inactivate the active site of the target protease. Proteins of the second class bind proteases by a unique molecular trap mechanism and deliver the bound protease to a receptor-mediated endocytic system for degradation in secondary lysosomes. Proteins of the alpha2-macroglobulin family are present in a variety of animal phyla, including the nematodes, arthropods, mollusks, echinoderms, urochordates, and vertebrates. A shared suite of unique functional characteristics have been documented for the alpha2-macroglobulins of vertebrates, arthropods, and mollusks. The alpha2-macroglobulins of nematodes, arthropods, mollusks, and vertebrates show significant sequence identity in key functional domains. Thus, the alpha2-macroglobulins comprise an evolutionarily conserved arm of the innate immune system with similar structure and function in animal phyla separated by 0.6 billion years of evolution.

Upregulation of heme oxygenase-1 gene by turpentine oil-induced localized inflammation: involvement of interleukin-6

Heme oxygenase-1 (HO-1) is the inducible isoform of an enzyme family responsible for heme degradation and was suggested to be involved in the acute phase response in the liver. However, the mechanisms of the HO-1 regulation under inflammatory conditions are poorly understood. Therefore, the purpose of the current work was to study the expression of HO-1 in the liver and other organs of rats with a localized inflammation after intramuscular injection of turpentine oil (TO). Since interleukin-6 (IL-6) is known to be a principal mediator of inflammation, the levels of this cytokine were also estimated in the animal model used. HO-1 and IL-6 expression was evaluated by Northern blot, in situ hybridization, Western blot, immunohistochemistry and enzyme-linked immunosorbent assay. In the liver and injured muscle, the HO-1 mRNA levels were dramatically increased 4-6 h after TO administration. HO-1 protein levels in the liver were elevated starting from 6-12 h after the treatment. In other internal organs such as the heart, kidney and large intestine, only a slight induction of HO-1 mRNA was observed. IL-6-specific transcripts appeared only in the injured muscle and were in accordance with serum levels of IL-6. In turn, temporal expression of IL-6 in the muscle and circulatory IL-6 levels correlated well with HO-1 expression in the liver and injured muscle. In the liver of control rats HO-1 protein was detected in Kupffer cells, while in TO-injected rats also hepatocytes became strongly HO-1 positive. Conversely, in the injured muscle, HO-1 immunoreactivity was attributed only to macrophages. Our data demonstrate that during localized inflammation HO-1 expression was rapidly and strongly induced in macrophages of injured muscle and in hepatocytes, and IL-6 derived from injured muscle seems to be responsible for the HO-1 induction in the liver.

Effect of lipopolysaccharide on in vivo and genetic regulation of rat urea synthesis

BACKGROUND

The acute phase response causes a negative nitrogen balance. It is unknown whether this involves regulation of hepatic urea synthesis.

METHODS

We examined the in vivo capacity of urea nitrogen synthesis (CUNS), mRNA levels of urea cycle enzyme genes and galactose elimination capacity (GEC) during moderate and severe acute phase response induced by low- and high-dose lipopolysaccharide (LPS) in rats.

RESULTS

Low-dose LPS doubled CUNS (P<0.05), decreased the mRNA level of the rate-limiting urea cycle enzyme (arginino succinate synthetase (ASS) by 26% (P<0.05) and did not change GEC. High-dose LPS did not change CUNS, decreased the mRNA level of the flux-generating enzyme carbamoyl phosphate synthetase (CPS) by 11% (P<0.05) and the rate-limiting urea cycle enzyme (ASS) by 27% (P<0.05) and almost halved GEC (P<0.05).

CONCLUSION

The moderate acute phase response up-regulated in vivo urea synthesis but had the opposite effect on gene level. The severe acute phase response decreased the functional liver mass that attenuated the increase in urea synthesis.

Elevated levels of serum alpha2 macroglobulin in wild black bears during hibernation

Bear serum alpha(2) macroglobulin (alpha(2)M) was purified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and partially characterized by tryptic digestion of alpha(2)M and analysis of the peptides by peptide mass fingerprinting. The molecular weight of bear serum alpha(2)M was 181 kDa, same as for human serum alpha(2)M, on SDS-PAGE. However, the MALDI mass spectrum of the tryptic digested bear serum alpha(2)M showed that it is different from human alpha(2)M or other data bank proteins. Liquid chromatography (LC)/mass spectrometry (MS)/MS of the proteolytic products of bear serum alpha(2)M showed eight peptides that had similarities to human alpha(2)M suggesting that the protein of interest was indeed alpha(2)M of bear. The polyclonal antibody against bear serum alpha(2)M recognized only one protein from the western blot of bear serum proteins. It also recognized human alpha(2)M. The levels of serum alpha(2)M were significantly increased during hibernating state as compared to active state of bears indicating its protective role from the consequences of the metabolic depression during hibernation.

Molecular cloning, structure and bait region splice variants of alpha2-macroglobulin from the soft tick Ornithodoros moubata

The sequence of a alpha(2)-macroglobulin (alpha(2)M) from the soft tick Ornithodoros moubata (TAM) was determined by cloning and sequencing of overlapping polymerase chain reaction (PCR) and rapid amplification of cDNA ends PCR products. The TAM cDNA sequence is 4,944 bp long and contains one open reading frame coding for a protein precursor composed of 1,494 amino-acid residues, including a 24-residue signal sequence. The mature protein is cleaved into two subunits similarly to the C3 and C4 components of complement and fish alpha(2)Ms. Phylogeny analysis revealed that TAM is closely related to Limulus alpha(2)M and displays the highest similarity to the partial sequence of alpha(2)M from hard tick Ixodes scapularis. The comparison of conserved cysteine residues between TAM and human and Limulus alpha(2)Ms made it possible to predict the pattern of disulfide bridges and explain the atypical molecular arrangement of TAM. Four variants of the TAM bait region differing only in a short central segment were found; our data indicate that TAM exists as a single-copy gene in the tick genome and its bait region variants likely arise by alternative splicing. TAM is produced by tick hemocytes and it is also significantly expressed in salivary glands. TAM mRNA levels were shown to be up-regulated upon blood meal.

Disruption of structural and functional integrity of alpha 2-macroglobulin by cathepsin E

alpha 2-Macroglobulin (alpha 2M) is an abundant glycoprotein with the intrinsic capacity for capturing diverse proteins for rapid delivery into cells. After internalization by the receptor- mediated endocytosis, alpha 2M-protein complexes were rapidly degraded in the endolysosome system. Although this is an important pathway for clearance of both alpha 2M and biological targets, little is known about the nature of alpha 2M degradation in the endolysosome system. To investigate the possible involvement of intracellular aspartic proteinases in the disruption of structural and functional integrity of alpha 2M in the endolysosome system, we examined the capacity of alpha 2M for interacting with cathepsin E and cathepsin D under acidic conditions and the nature of its degradation. alpha 2M was efficiently associated with cathepsin E under acidic conditions to form noncovalent complexes and rapidly degraded through the generation of three major proteins with apparent molecular masses of 90, 85 and 30 kDa. Parallel with this reaction, alpha 2M resulted in the rapid loss of its antiproteolytic activity. Analysis of the N-terminal amino-acid sequences of these proteins revealed that alpha 2M was selectively cleaved at the Phe811-Leu812 bond in about 100mer downstream of the bait region. In contrast, little change was observed for alpha 2M treated by cathepsin D under the same conditions. Together, the synthetic SPAFLA peptide corresponding to the Ser808-Ala813 sequence of human alpha 2M, which contains the cathepsin E-cleavage site, was selectively cleaved by cathepsin E, but not cathepsin D. These results suggest the possible involvement of cathepsin E in disruption of the structural and functional integrity of alpha 2M in the endolysosome system.

Regulation of insulin-like growth factor-I and of insulin-like growth factor binding protein-1, -3 and -4 in cocultures of rat hepatocytes and Kupffer cells by interleukin-6

BACKGROUND/AIMS

Catabolism is associated with decreased serum concentrations of insulin-like growth factor (IGF)-I and insulin-like growth factor binding protein (IGFBP)-3 associated with elevated IGFBP-3 protease activity and increased concentrations of IGFBP-1 and -4. The effects of the acute phase mediators interleukin (IL)-6, IL-1beta and tumor necrosis factor alpha (TNFalpha) on the biosynthesis of IGF-I and IGFBPs were studied in primary rat liver cells.

METHODS

mRNA levels of IGF-I and of IGFBPs were analyzed by Northern blotting, secretion of IGFBPs by [(125)I]IGF-I ligand blotting. Proteolytic activity was measured using iodinated recombinant IGFBP-3 as the substrate.

RESULTS

In hepatocytes, Kupffer cells (KC) and cocultures of hepatocytes with KC, IL-6 reduced IGF-I biosynthesis dose-dependently. IL-6 stimulated mRNA expression and protein secretion of IGFBP-1 and -4 in hepatocytes and that of IGFBP-3 in KC, respectively. In cocultures, biosynthesis of IGFBP-1, -3 and -4 was increased dose-dependently by IL-6, while the effects of IL-1beta or TNFalpha were less prominent. At neutral pH, proteolytic activity against IGFBP-3 was not detected in media of cocultures treated with IL-6.

CONCLUSIONS

The alterations of IGF-I, IGFBP-1 and -4 observed in catabolism correlate with the effects of IL-6 on the biosynthesis of these components in primary rat liver cells, while a neutral IGFBP-3 protease was not detectable.

Anaphylatoxin C5a actions in rat liver: synergistic enhancement by C5a of lipopolysaccharide-dependent alpha(2)-macroglobulin gene expression in hepatocytes via IL-6 release from Kupffer cells

The effects of the anaphylatoxins C5a and C3a on the liver are only poorly characterized in contrast to their well known systemic actions. Recently, it has been demonstrated that the anaphylatoxin C5a enhanced glucose output from hepatocytes (HC) indirectly via prostanoid release from Kupffer cells (KC). In the present study, it is shown that recombinant rat C5a (rrC5a), together with LPS, activated the gene of the acute phase protein alpha(2)-macroglobulin (alpha(2)MG) in HC also indirectly via IL-6 release from KC. RrC5a alone increased neither IL-6 mRNA in nor IL-6 release from KC, whereas LPS alone did so. However, rrC5a synergistically enhanced the LPS-dependent increase in IL-6 mRNA and IL-6 release. Only rIL-6, but not TNF-alpha or IL-1beta, enhanced alpha(2)MG mRNA in HC. In line with the actions of rrC5a and LPS on KC, conditioned medium of KC stimulated only with rrC5a did not increase alpha(2)MG mRNA in HC. However, medium of KC stimulated with rrC5a plus LPS induced alpha(2)MG mRNA expression in HC more strongly than medium from cells stimulated only with LPS; thus, C5a acted synergistically with LPS. The stimulatory effects of KC-conditioned medium could partially be inhibited by a neutralizing anti-IL-6 Ab, indicating that KC-derived IL-6 was a major mediator in C5a- plus LPS-elicited alpha(2)MG gene expression. These results suggest that C5a, besides enhancing glucose output via prostanoids, is involved in the initiation of the acute phase response in HC via proinflammatory cytokines from KC. This provides evidence for another important function of C5a in the regulation of hepatocellular defense reactions.

Liver gene regulation in rats following both 70 or 90% hepatectomy and endotoxin treatment

BACKGROUND

The metabolic state effect of liver failure on liver gene regulation was evaluated in a rat model.

METHODS

Following 70 or 90% hepatectomy and lipopolysaccharide or vehicle treatment at intervals up to 24 h, the liver remnants were analyzed for mRNA levels for acute-phase, liver-specific and growth-related proteins.

RESULTS

After 70% hepatectomy mRNA for alpha 1-acid glycoprotein, alpha 2-macroglobulin, thiostatin and fibrinogen, haptoglobin increased three- to sevenfold (P < 0.05), and mRNA for cyclin D and histone 3 increased seven- and 15-fold (P < 0.05), respectively. After lipopolysaccharide injection and 70% hepatectomy were done, mRNA for acute-phase proteins raised significantly (P < 0.05), more to five to 20-fold, while mRNA for growth-related proteins raised significantly (P < 0.05) less to three- to fourfold. After 90% hepatectomy, acute-phase protein mRNA increased five- to ninefold (P < 0.05) more than after 70% hepatectomy, while mRNA for histone 3 and cyclin D did not increase within 24 h, which indicates a delayed growth after 90% hepatectomy. In 90% of hepatectomized rats treated with lipopolysaccharide, acute-phase protein mRNA raised three- to sixfold (P < 0.05) less than after vehicle treatment.

CONCLUSION

In endotoxemia from liver failure, the synthesis of acute-phase proteins is upregulated by gene regulation at the expense of that for regeneration, which may be an appropriate response for immediate survival. In severe liver failure, endotoxin may interfere with the appropriate gene regulation.

Alpha2 macroglobulin elevation without an acute phase response in depressed adults with Down's syndrome: implications

Studies of immune function during depression in persons without intellectual disability (ID) have revealed elevated levels of alpha2 macroglobulin (alpha2M) and an acute phase protein (APP) response. Clinical observation suggests that people with Down's syndrome (DS) may have associated genetic abnormalities in their immune systems. The APP response and alpha2M changes in depressed versus non-depressed adults with DS was the subject of the present study. The serum pan-proteinase inhibitor alpha2M, and the AP proteins c-reactive protein (CRP), alpha1 antitrypsin (alpha1AT), ceruloplasmin (Cp), beta2 Macroglobulin (beta2M), transthyretin (Trans), serum amyloid protein (SAP), and albumin (Alb) were measured in 38 adults with DS, 19 of whom were diagnosed with and 19 without depression using a sandwich enzyme-linked immunosorbent assay (ELISA). The DSM-IV criteria were used for diagnoses. Medical and neurological examinations excluded medical disorders associated with APP response. Only alpha2M and CRP were significantly different in the depressed versus non-depressed groups. The alpha2M was higher, a response similar to one observed in depressed people without ID, but the CRP was lower in the depressed group, especially in those subjects not on psychotropic medications, contrary to the expected APP response to depression. The results suggest that alpha2M elevation in depressed adults with DS is independent of the APP response. An alternative explanation for its elevation is proposed linking the core symptom of depression with the mammalian dormancy/hibernation process. Further studies are needed to confirm that alpha2M elevation is specific to depression and that it might provide a helpful marker for the diagnosis of depression in people with ID.

Involvement of SOCS-1, the suppressor of cytokine signaling, in the prevention of prolactin-responsive gene expression in decidual cells

The cells forming the rat decidua produce PRL and PRL-related proteins and express both the long and short forms of the PRL receptor. Yet, only a defined subpopulation, the mesometrial cells, express the PRL-dependent alpha2-macroglobulin gene. This gene is silenced in vivo in the antimesometrial cells and in the GG-AD cell line, derived from antimesometrial cells. To examine whether the lack of alpha2-macroglobulin expression is due to defective components in the PRL signaling pathway, we compared the relative expression of Janus kinase 2 (Jak2), signal transducer and activator of transcription 5 a and b (Stat5 a and b), suppressor of cytokine signaling-1 (SOCS-1), and the tyrosine phosphatase SHP-2 mRNA in mesometrial and antimesometrial decidua on days 12 and 13 of pseudopregnancy, the time of maximal alpha2-macroglobulin expression. We found no significant differences in the relative expression of either Jak2, Stat5 (a and b), or SHP-2 in the two cell populations. However, we discovered a profound difference in the expression of SOCS-1, an inhibitor of the Jak/Stat pathway. This gene was highly expressed in the antimesometrial cells and in the GG-AD cells, which do not produce alpha2-macroglobulin. Immunoprecipitation experiments with GG-AD cells revealed that although Jak2 and Stat5 coprecipitate in response to PRL stimulation, no phosphorylation of Jak2 and Stat5 could be observed. To examine whether SOCS-1 plays a role in silencing the alpha2-macroglobulin gene, we cultured GG-AD cells in the presence of either a SOCS-1 antisense oligonucleotide or an irrelevant oligonucleotide for 4, 12, and 28 h. Cells were also treated with PRL. Within 4 h of SOCS-1 antisense treatment, alpha2-macroglobulin mRNA expression was initiated. After 28 h, only cells treated with PRL and SOCS-1 antisense oligonucleotide retained the ability to express the alpha2-macroglobulin gene. In summary, results of this study reveal that constitutive expression of SOCS-1 can prevent PRL signaling and that the lack of PRL-induced expression of alpha2-macroglobulin in a defined decidual cell population is largely due to SOCS-1 expression in these cells.

Differential suppression of liver-specific genes in regenerating rat liver induced by extended hepatectomy

BACKGROUND/AIMS

The function of the remnant liver is critical to survival of patients following an extended hepatectomy. The aim of this study was to determine whether proliferating hepatocytes in the remnant liver preserve the expression of liver-specific genes.

METHODS

Using regenerating rat livers after 30, 70, and 90% partial hepatectomy (PHx), Northern blot analyses were performed with probes for seven liver-specific genes, six growth-related genes, two housekeeping genes and two acute phase reactant protein genes.

RESULTS

During the regeneration after 90% PHx, the transcription of liver-specific genes showed three chronological patterns: transcription of serum albumin and cytochrome P450 2B decreased rapidly and reached a nadir at 6 to 24 h after PHx; those of apolipoprotein A-1, phosphoenolpyruvate carboxykinase and ornithine transcarbamylase decreased gradually until 24 to 48 h; those of UDP-glucuronosyltransferase and hepatocyte nuclear factor 4 did not show any changes until 48 h after PHx. In contrast, expression levels of all the growth-related genes and of housekeeping genes increased rapidly after PHx. After 30 and 70% PHx, expression of these genes changed in a similar manner to the 90% PHx case but to a lower extent.

CONCLUSIONS

Based upon the fractions of Ki-67 positive hepatocytes in remnant livers, we could estimate the degree of expression of each liver-specific gene in the proliferating hepatocytes. The serum albumin gene was completely suppressed, while that encoding UDP-glucuronosyltransferase was not affected. These results correlated well with the patterns of albumin and bilirubin in rat serum after PHx. Other liver-specific genes were moderately suppressed in proliferating hepatocytes. Thus, expression of liver-specific gene is differentially suppressed when hepatocytes enter a proliferation cycle. Those that are unaffected may be indispensable for maintaining the homeostasis of the living organism.

Loss of matrix metalloproteinase 9 activity in Theileria annulata-attenuated cells is at the transcriptional level and is associated with differentially expressed AP-1 species

The schizont stage of the protozoan parasite Theileria annulata reversibly transforms bovine monocytes into an immortalised and metastatic state. We have been studying T. annulata induction of host matrix metalloproteinases (MMP) which are involved in parasite dissemination and pathogenesis. We have observed that prolonged in vitro culture of T. annulata-infected cell lines results in their attenuation and this process is associated with alterations in both host and parasite gene expression. In particular, a loss in bovine MMP expression in later passage cultures suggests that these parasite-induced MMPs are virulence factors. As a means to further our understanding of the attenuation process we examine in detail the parasite-induced differential expression of one particular bovine proteinase, MMP9, in non-attenuated (p58) and attenuated (p158) passage levels of the Ode vaccine line. We show here that MMP9 expression is regulated at the transcriptional level and we suggest that a particular parasite-induced AP-1 recognition transcription factor present in the Ode non-attenuated line may have a role to play in the expression of this host gene.

Cell swelling activates STAT1 and STAT3 proteins in cultured rat hepatocytes

In this paper, we demonstrated that in cultured rat hepatocytes cell swelling induced the activation of STAT1 and STAT3 proteins without any effect on STAT4, STAT5 and STAT6 proteins. Cell swelling induced an activation of STAT proteins through an increase in the phosphorylation of the tyrosine residue also phosphorylated by interleukin-6, but without any activation of JAK kinases. The signaling pathway by which cell swelling activated STAT1 and STAT3 is discussed.

Rat liver myofibroblasts and hepatic stellate cells: different cell populations of the fibroblast lineage with fibrogenic potential

BACKGROUND & AIMS

Hepatic stellate cells (HSCs) are considered the principal matrix-producing cells of the damaged liver. However, other cell types of the fibroblast lineage that have not yet been characterized are also involved in liver tissue repair and fibrogenesis.

METHODS

We established cultures of cells of the fibroblast lineage, termed rat liver myofibroblasts, and analyzed their phenotypical and functional properties in comparison with HSCs.

RESULTS

HSCs and rat liver myofibroblasts were discernible by morphological criteria and growth behavior. Prolonged subcultivation of rat liver myofibroblasts was achieved, but HSCs were maintained in culture at maximum until second passage. HSCs were characterized by expression of glial fibrillary acidic protein, desmin, and vascular cell adhesion molecule 1, which were almost completely absent in rat liver myofibroblasts. For synthetic properties, HSCs and rat liver myofibroblasts displayed mostly overlapping properties with 4 striking differences. The complement-activating protease P100 and the protease inhibitor alpha(2)-macroglobulin were preferentially expressed by HSCs, whereas interleukin 6-coding messenger RNAs and the extracellular matrix protein fibulin 2 were almost exclusively detectable in rat liver myofibroblasts.

CONCLUSIONS

The data show that morphologically and functionally different fibroblastic populations, HSCs and rat liver myofibroblasts, can be derived from liver tissue. HSCs may not represent the single matrix-producing cell type of the fibroblast lineage in the liver.

Growth factors and gene expression in cultured rat hepatocytes

BACKGROUND/AIM

The aim of this study was to evaluate the effect of replication on function variables in cultured hepatocytes.

METHODS

Isolated rat hepatocytes were cultured in HCM medium and plated on collagen-coated dishes at cell densities from 0.2 x 10(5) (subconfluent) to 1.0 x 10(5) x cm(-2) (confluent) with and without addition of hepatocyte growth factor, epidermal growth factor and insulin-like growth factor-I. The synthesis rate was measured for DNA, albumin, urea, and glucose together with mRNA levels (Northern blots) for albumin, urea cycle enzymes, and acute phase and "house-keeping" proteins.

RESULTS

In subconfluent culture the synthesis of DNA and urea was higher (118% and 112%, respectively), and of albumin and glucose lower (40% and 67%, respectively) than in confluent culture. The mRNA levels of carbamoylphosphate synthase, argininosuccinate synthetase, argininosuccinate lyase, arginase, a2-macroglobulin, beta-fibrinogen, and albumin were lower (23%, 58%, 77%, 33%, 12%, 50%, and 51%, respectively) in subconfluent culture compared with confluent culture. Relatively increased levels were found for beta-actin (109%) and alpha-tubulin (136%). In subconfluent culture hepatocyte growth factor increased the DNA synthesis rate 6-fold, epidermal growth factor 3-fold, and insulin-like growth factor-I 2-fold; that of albumin, urea and glucose was not increased significantly. In confluent culture the effect of growth factors on synthesis rates was not significant, and the growth factors had little influence on mRNA levels.

CONCLUSIONS

Hepatocytes produce urea at the same rate in subconfluent as in confluent culture in spite of a lower mRNA level of urea cycle enzymes. Hepatocyte growth factor and epidermal growth factor increase DNA synthesis markedly in subconfluent culture only, without significantly changing the ratio between subconfluent and confluent culture of other variables. This suggests that active replication is not an important cause of the relatively low liver-specific function of hepatocytes in subconfluent culture.

Hepatocyte differentiation of WIF-B cells includes a high capacity of interleukin-6-mediated induction of alpha 1-acid glycoprotein and alpha 2-macroglobulin

Responsiveness to cytokine-mediated acute inflammatory stimuli of the highly differentiated and polarized WIF-B hybrid cell line was studied by measuring the induction of alpha 1-acid glycoprotein and alpha 2-macroglobulin mRNAs after interleukin-1, interleukin-6 and tumor necrosis factor-alpha treatments in the presence of dexamethasone. Compared with their Fao parent, WIF-B cells were 10 times more responsive to 24-h interleukin-6 induction regarding alpha 2-macroglobulin induction. At variance from the response measured in Fao cells, the late effects of interleukin-6 treatment confirmed the higher sensitivity of WIF-B cells to this cytokine as a 72-h treatment as 10 times more effective than a 24-h treatment at inducting alpha 1-acid glycoprotein mRNA. These findings highlight the hepatocyte differentiation of WIF-B cells compared with other hepatoma cell lines, with respect to the regulation of acute-phase protein gene expression. They also make WIF-B cells a convenient model to study the molecular effects of interleukin-6 in terms of transduction and/or transcription, and the many cross-talks that occur during the regulation of acute-phase protein gene expression.

Cytokine modulation by PX differently affects specific acute phase proteins during sepsis in rats

To explore the regulation of the acute phase response in vivo, the effects of pentoxifylline (PX) treatment (100 mg/kg ip 1 h before infection) were investigated in infected and pair-fed rats 2 and 6 days after an intravenous injection of live bacteria (Escherichia coli). PX treatment prevented the increase in plasma tumor necrosis factor (TNF)-alpha (peak 1.5 h after the infection) and resulted in an 84 and 61% inhibition of plasma interleukin (IL)-1beta and IL-6, respectively (peaks at 3 h). Plasma corticosterone kinetics were not modified by the treatment. Infection increased alpha1-acid glycoprotein (AGP), alpha2-macroglobulin (A2M), and fibrinogen plasma concentrations and decreased albumin levels. PX significantly reduced AGP plasma concentration as early as day 2 in infected animals but reduced A2M and fibrinogen plasma levels only at day 6. The treatment had no effect on the albumin plasma concentration. Hepatic AGP and fibrinogen mRNA levels increased in infected rats, whereas those of A2M were unchanged and those of albumin were decreased. Two days after infection, AGP and fibrinogen mRNA levels were reduced in treated infected animals. PX was ineffective in modifying those of A2M and albumin. These data demonstrate, in vivo, that different acute phase proteins are individually regulated in sepsis. The in vivo effects of PX treatment support the hypothesis that TNF-alpha plays an important role in the regulation of AGP production, whereas other factors seem to be involved in the regulation of A2M, fibrinogen, and albumin expression.

Regulation of alpha2-macroglobulin expression in rat Sertoli cells and hepatocytes by germ cells in vitro

Germ cells isolated from rat testes by trypsinization have been shown to yield unwanted artifacts in biological assays, since conditioned media derived from these germ cells (germ cell-conditioned media [GCCM]) can modulate Sertoli cell secretory function because of the presence of residual trypsin. To determine whether germ cells themselves can modulate Sertoli cell function, we isolated germ cells from tubules by a mechanical procedure and assessed the effect of these cells on Sertoli cell alpha2-macroglobulin (alpha2-MG) steady-state mRNA level. It was found that germ cells indeed could stimulate Sertoli cell alpha2-MG expression. This effect is probably mediated by a soluble factor(s) released from germ cells, since GCCM fractionated by HPLC contained multiple fractions that can stimulate Sertoli cell alpha2-MG expression dose-dependently. These results illustrate that germ cells play a role in regulating testicular alpha2-MG expression. Since Sertoli cells synthesize and secrete many of the serum proteins behind the blood-testis barrier that are also produced by hepatocytes, we sought to ascertain whether germ cells can affect hepatic alpha2-MG expression. When germ cells were cocultured with hepatocytes isolated from adult rats, the hepatocyte alpha2-MG steady-state mRNA level was shown to be stimulated by germ cells dose-dependently. Using different pools of fractions derived from GCCM after their fractionation by a preparative anion-exchange HPLC column, GCCM was found to contain a factor(s) that stimulated hepatocyte alpha2-MG expression dose-dependently. More importantly, the fractions that stimulated hepatocyte alpha2-MG expression had a retention time different from that of the factor(s) that affected Sertoli cell alpha2-MG expression. These data illustrate that germ cells secrete multiple biological factors capable of regulating alpha2-MG expression in the testis and the liver. In summary, this study reveals a possible physiological link between the testis and the liver in that germ cells may release a factor(s) capable of modulating alpha2-MG expression in both organs.

Markedly reduced bile acid synthesis but maintained levels of cholesterol and vitamin D metabolites in mice with disrupted sterol 27-hydroxylase gene

Sterol 27-hydroxylase is important for the degradation of the steroid side chain in conversion of cholesterol into bile acids and has been ascribed a regulatory role in cholesterol homeostasis. Its deficiency causes the autosomal recessive disease cerebrotendinous xanthomatosis (CTX), characterized by progressive dementia, xanthomatosis, and accelerated atherosclerosis. Mice with a disrupted cyp27 (cyp27(-/-)) had normal plasma levels of cholesterol, retinol, tocopherol, and 1,25-dihydroxyvitamin D. Excretion of fecal bile acids was decreased (<20% of normal), and formation of bile acids from tritium-labeled 7alpha-hydroxycholesterol was less than 15% of normal. Compensatory up-regulation of hepatic cholesterol 7alpha-hydroxylase and hydroxymethylglutaryl-CoA reductase (9- and 2-3-fold increases in mRNA levels, respectively) was found. No CTX-related pathological abnormalities were observed. In CTX, there is an increased formation of 25-hydroxylated bile alcohols and cholestanol. In bile and feces of the cyp27(-/-) mice only traces of bile alcohols were found, and there was no cholestanol accumulation. It is evident that sterol 27-hydroxylase is more important for bile acid synthesis in mice than in humans. The results do not support the contention that 27-hydroxylated steroids are critical for maintenance of cholesterol homeostasis or levels of vitamin D metabolites in the circulation.

Proteins of rat serum: II. Influence of some biological parameters of the two-dimensional electrophoresis pattern

This report complements the database already detailed for serum proteins of healthy adult male rats (P. Haynes et al., Electrophoresis 1998, 19, 1484-1492). The influence on the two-dimensional electrophoresis (2-DE) pattern of certain physiological conditions (sex, age) was studied as well as of changes in thyroid metabolism. We have extended the information about the major components of rat serum by identifying the proteins typical for the response to acute inflammation. Analyzing 27 spots, six proteins not found in control sera could be recognized; migration at overlapping or close positions with five already characterized proteins was observed for some. A compilation of all our rat data can be accessed through: http://weber.u.washington.edu/ruedilab/ aebersold.html.

Crystal structure of the receptor-binding domain of alpha 2-macroglobulin

BACKGROUND

The large plasma proteinase inhibitors of the alpha 2-macroglobulin superfamily inhibit proteinases by capturing them within a central cavity of the inhibitor molecule. After reaction with the proteinase, the alpha-macroglobulin-proteinase complex binds to the alpha-macroglobulin receptor, present in the liver and other tissues, and becomes endocytosed and rapidly removed from the circulation. The complex binds to the receptor via recognition sites located on a separate domain of approximately 138 residues positioned at the C terminus of the alpha-macroglobulin subunit.

RESULTS

The crystal structure of the receptor-binding domain of bovine alpha 2-macroglobulin (bRBD) has been determined at a resolution of 1.9 A. The domain primarily comprises a nine-strand beta structure with a jelly-roll topology, but also contains two small alpha helices.

CONCLUSIONS

The surface patch responsible for receptor recognition is thought to involve residues located on one of the two alpha helices of the bRBD as well as residues in two of the beta strands. Located on this alpha helix are two lysine residues that are important for receptor binding. The structure of bRBD is very similar to the approximately 100-residue C-terminal domain of factor XIII, a transglutaminase from the blood coagulation system.

Identification, origins and the diurnal role of the principal serine protease inhibitors in human tear fluid

PURPOSE

Previous work identified polymorphonuclear leukocyte (PMN) elastase as the major caseinolytic entity in tears collected after overnight eye closure. This study was designed to identify the principal serine protease inhibitors (serpins) in tears and to determine their function in the regulation of PMN cell proteases on eye closure.

METHODS

Reflex and closed eye tear samples were collected by microcapillary tube and centrifuged. After reflex and closed eye supernatants (R and C) were fractionated by HPLC, samples were subjected to casein zymography and reverse zymography. Western blots were utilized to screen tears and HPLC fractions for elastase, cathepsin G and proteinase-3 and to obtain semi-quantitative data on alpha 1-protease inhibitor (alp1), alpha 1-antichymotrypsin (alpha 1-Achy), secretory leukocyte protease inhibitor (SLPI), elafin and alpha 2-macroglobulin (alpha 2-M) as well as associated complexes and products. To confirm specificity of reactivity, samples were immunoprecipitated for a given protease or serpin and screened for the coprecipitation of interacting species.

RESULTS

Although R fluid contains no caseinolytic activity, it contains low levels of serpin-like activity principally in the form of SLPI (5-10 ng/microliter). Lesser amounts of alpha 2-M, alpha 1-Achy and alp1 (approximately < 1-3 ng/microliter) are also evident. C fluid is associated with very high levels of PMN cell proteases along with a approximately 5-20-fold increase in the concentrations of all of the above inhibitors. Trace levels of elafin were also detected. The concentrations of rapid reacting inhibitors exceeded that of proteases, with SLPI, alpha 1-Achy and alp1 being the principal functional entities. In atypical samples, complexes of elastase and alpha 2-M were also encountered.

CONCLUSIONS

SLPI, a known antimicrobial agent and an elastase and cathepsin G inhibitor, is the principal serpin in R fluid. C fluid is associated with a marked increase in the concentrations of an array of rapid reacting serpins capable of inhibiting all known PMN cell serine proteases. In the normal closed eye, the concentration of rapid reacting inhibitors always exceeds that of proteases with C fluid also containing a functional reserve of the slow reacting inhibitor alpha 2-M.

Cell swelling increased the alpha2-macroglobulin gene expression in cultured rat hepatocytes

The effect of cell swelling on the expression of the alpha2-macroglobulin (alpha2M) gene was studied in hepatocytes in culture. Hypoosmolarity induced an increase (3-fold increase) in the level of alpha2M mRNA through a corresponding stimulation of the rate of transcription of the alpha2M gene. The addition of raffinose (100 mM) corrected the effect of hypoosmolarity at both mRNA and transcriptional level, demonstrating that cell swelling per se was responsible for the observed effect on the expression of the alpha2M gene. Moreover, the effect of cell swelling was additive to that of interleukin 6, a major mediator of the acute-phase response.

Critical role of asparagine 1065 of human alpha2-macroglobulin in formation and reactivity of the thiol ester

It has been shown that the relative reaction preference of the C4 thiol ester toward oxygen and nitrogen nucleophiles upon activation by proteinase depends on whether residue 1106 is aspartate or histidine (Dodds, A. W., Ren, X.-D., Willis, A. C., and Law, S. K. A. (1996) Nature 379, 177-179). To determine if the equivalent residue in the related thiol ester-containing protein human alpha2-macroglobulin (alpha2M), asparagine 1065, plays a similar role, we have expressed and characterized four alpha2M variants in which this asparagine has been replaced by aspartate, alanine, histidine, or lysine. The change from asparagine resulted in an altered ability to form the thiol ester. This ranged from failure to form the thiol ester (Asn --> Asp) to a maximum extent of formation of about 50% (Asn --> Ala). For the three variants that were able to form the thiol ester, the rates of thiol ester cleavage by a given amine were found to be different from one another and slower in nearly all cases than plasma alpha2M, but with the same relative reactivity of methylamine > ethylamine > ammonia. The rate of conformational change that follows cleavage of thiol esters in a functional half-molecule was also found to differ between the variants and to be slower than plasma alpha2M. TNS emission spectra indicated that the conformations of the transformed variants differed measurably from transformed plasma alpha2M. These findings suggest that residue 1065 plays a critical role in human alpha2M, for formation of the thiol ester, for its subsequent reaction with nucleophiles, and for the conformational change induced by this reaction. By analogy with C4, where this residue influences the nucleophile preference through direct interaction with the thiol ester, residue 1065 in alpha2M is expected to be located in or very close to the thiol ester region in alpha2M.

Transforming growth factor-alpha's effects on astroglial-cholinergic cell interactions in the medial septal area in vitro are mediated by alpha 2-macroglobulin

We reported previously that two epidermal growth factor receptor ligands, epidermal growth factor and transforming growth factor-alpha, inhibit medial septal cholinergic cell phenotypic expression (choline acetyltransferase and acetylcholinesterase activities) in vitro indirectly via (a) soluble molecule(s) released from astrocytes [Kenigsberg R. L. et al. (1992) Neuroscience 50, 85-97; Kenigsberg R. L. and Mazzoni I. E. (1995) J. Neurosci. Res. 41, 734-744; Mazzoni I. E. and Kenigsberg R. L. (1996) Brain Res. 707, 88-99]. In the present study, we found that this response to transforming growth factor-alpha is mediated, for the most part, by alpha 2-macroglobulin, a potent protease inhibitor with a wide spectrum of biological activities. In this regard, the effects of transforming growth factor-alpha on cholinergic cells can be blocked with immunoneutralizing antibodies raised against alpha 2-macroglobulin. Furthermore, western blot analysis reveals that although alpha 2-macroglobulin is present in conditioned media from control septal cultures, it is more abundant in those treated with transforming growth factor-alpha. In addition, exogenous alpha 2-macroglobulin, both in its native and trypsin-activated forms, can mimic transforming growth factor-alpha's effects on septal cholinergic cell expression. However, while the native antiprotease can slightly but significantly decrease choline acetyltransferase activity, trypsin-activated alpha 2-macroglobulin, in the nanomolar range, induces as marked a decrease in this enzyme activity as that noted with transforming growth factor-alpha. Furthermore, trypsin-activated alpha 2-macroglobulin, like epidermal growth factor/transforming growth factor-alpha, decreases choline acetyltransferase activity by arresting its spontaneous increase that occurs with time in culture, does so in a reversible manner and is not neurotoxic. In addition, trypsin-activated alpha 2-macroglobulin, in the nanomolar range, can affect choline acetyltransferase in a dual manner, up-regulating it at low concentrations while down-regulating it at higher ones. These responses are identical in mixed neuronal-glial and pure neuronal septal cultures. Furthermore, when concentrations of trypsin-activated alpha 2-macroglobulin, which alone decrease choline acetyltransferase, are added simultaneously with nerve growth factor, they serve to potentiate the nerve growth factor-induced increase in enzymatic activity. As GABAergic cell expression is not affected by alpha 2-macroglobulin, it appears that the effects of this protease inhibitor on medial septal neuronal expression are neurotransmitter-specific. Finally, trypsin-activated but not native alpha 2-macroglobulin promotes a dose-dependent aggregation of the septal neurons. This change in morphology, however, is not related to those noted in choline acetyltransferase activity. In summary, these data suggest that the expression of alpha 2-macroglobulin in astroglia from the medial septal nucleus can be controlled by epidermal growth factor receptor ligands to impact the functioning of basal forebrain cholinergic neurons.

Effect of tumour necrosis factor-alpha on proliferation, activation and protein synthesis of rat hepatic stellate cells

BACKGROUND/AIMS

Hepatic stellate cells represent the principal matrix-synthesising cells of damaged liver and are targets of a number of cytokines currently under investigation. The study analyses the effects of tumour necrosis factor-alpha and interferon-gamma on proliferation, "activation" and protein synthesis of hepatic stellate cells.

METHODS

Primary cultures of hepatic stellate cells were exposed to tumour necrosis factor-alpha and interferon-gamma. Cell proliferation was studied by 3H-thymidine and bromo-deoxy-uridine incorporation. Protein synthesis was analysed using immunoprecipitation, Western- and Northern blotting techniques.

RESULTS

Proliferation of hepatic stellate cells was reduced by tumor necrosis factor-alpha and interferon-gamma, while "activation" of hepatic stellate cells as assessed by expression of smooth muscle alpha-actin and of TGF-beta/activin type I receptor was induced by tumour necrosis factor-alpha but downregulated by interferon-gamma. Tumour necrosis factor-alpha increased the synthesis of distinct extracellular matrix proteins, particularly of fibronectin and tenascin, but decreased collagen type III expression. In contrast, interferon-gamma reduced the synthesis of all connective tissue proteins tested. Among the protease inhibitors, interferon-gamma induced C1-esterase inhibitor synthesis, while tumour necrosis factor-alpha stimulated plasminogen activator inhibitor type 1 production.

CONCLUSIONS

Tumour necrosis factor-alpha and interferon-gamma decrease proliferation of hepatic stellate cells, while "activation" of hepatic stellate cells and synthesis of proteins involved in matrix metabolism are regulated in a differential, cytokine-specific manner, suggesting that both cytokines play an important role in liver repair.

Molecular evolution of the vertebrate immune system

Adaptive immunity is unique to the vertebrates, and the molecules involved (including immunoglobulins, T cell receptors and the major histocompatibility complex molecules) seem to have diversified very rapidly early in vertebrate history. Reconstruction of gene phylogenies has yielded insights into the evolutionary origin of a number of molecular systems, including the complement system and the major histocompatibility complex (MHC). These analyses have indicated that the C5 component of complement arose by gene duplication prior to the divergence of C3 and C4, which suggests that the alternative complement pathway was the first to evolve. In the case of the MHC, phylogenetic analysis supports the hypothesis that MHC class II molecules evolved before class I molecules. The fact that the MHC-linked proteasome components that specifically produce peptides for presentation by class I MHC appear to have originated before the separation of jawed and jawless vertebrates suggests that the MHC itself may have been present at this time. Immune system gene families have evolved by gene duplication, interlocus recombination and (in some cases) positive Darwinian selection favoring diversity at the amino acid level.

Expression of liver functions following sub-lethal and non-lethal doses of allyl alcohol and acetaminophen in the rat

BACKGROUND/AIMS

To relate severity of intoxication with allyl alcohol and acetaminophen to modulated hepatic gene expression of liver functions and regeneration.

METHODS

Rats fasted for 12 h received acetaminophen 3.5 or 5.6 g per kg body weight, or allyl alcohol 100 or 125 microl by gastric tube, doses producing no and about 30% mortality, respectively, within 2 days. In the morning 2, 6, 12, 24, and 36 h after intoxication, RNA was extracted from liver tissue. By slot blot hybridization mRNA levels were determined for acute phase proteins, enzymes involved in ammonia elimination and urea synthesis, and for proteins related to liver regeneration.

RESULTS

After allyl alcohol, mRNA of "positive" acute phase proteins was higher than after acetaminophen and increased with the dose, whereas after acetaminophen it decreased with the dose. The mRNA of the urea cycle enzymes and glutamine synthetase was uniformly reduced by allyl alcohol, whereas that of most urea cycle enzymes was above the controls after the non-lethal, but not after the sub-lethal, dose of acetaminophen. The mRNA of glutamine synthetase was significantly more reduced by acetaminophen than by allyl alcohol. The mRNA of cell-cycle dependent proteins was greatly reduced after both toxins, more after the higher dose.

CONCLUSIONS

The study shows that acetaminophen intoxication inhibits or fails to induce the expression of acute phase proteins in contrast to allyl alcohol intoxication. Allyl alcohol suppressed the expression of urea cycle enzymes, whereas that of the rate limiting enzymes carbamoylphosphate synthase and argininosuccinate synthetase was increased by the non-lethal but not by the sub-lethal dose of acetaminophen. The expression of the cell-cycle dependent proteins was more suppressed after the sub-lethal than after the non-lethal dose of both toxins. The data support the view that a fatal outcome of the intoxications depends more on the ability to regenerate than on the maintenance of liver-specific functions.

Molecular cloning of Limulus alpha 2-macroglobulin

The American horseshoe crab Limulus polyphemus contains alpha 2-macroglobulin (alpha 2M) in the hemolymph plasma and hemocytes. alpha 2M from Limulus shows many of the typical characteristics of mammalian alpha 2M, including the presence of an internal thiol-ester, reactivity with a diversity of endopeptidases, a unique proteinase-trapping mechanism, and reactivity with the mammalian alpha 2M receptor. Additionally, Limulus alpha 2M has the unique property that it regulates the limulin-based hemolytic system of the plasma. A cDNA encoding Limulus alpha 2M has been obtained from a hemocyte cDNA library. The open reading frame encodes an N-terminal signal sequence of 25 amino acid residues and a mature protein of 1482 residues. The entire amino acid sequence is similar to those of the mammalian alpha 2Ms (28-29% identity) and contains common features found in mammalian alpha 2Ms. a bait region, an internal thiol-ester site, and a receptor-binding domain. However, the N-terminal portion (positions 24-105) has no sequence similarity with those of mammalian alpha 2Ms, and it is structurally related to that of the human complement factor C8 chain, consistent with a role for Limulus alpha 2M in host defense. The component sugar analysis of Limulus alpha 2M showed the existence of a complex type of oligosaccharide chain similar to those of mammalian alpha 2M. However, unlike mammalian alpha 2M, no sialic acid was detected in Limulus alpha 2M and it contained approximately 3 mol/mol N-acetylgalactosamine, suggesting the presence of O-linked sugar chains, which have not been found in mammalian alpha 2M. Expression of alpha 2M was detected in hemocytes, but not in hepatopancreas, heart, stomach, intestine, coxal gland, brain and skeletal muscle. Furthermore, immunoblotting of large and small granules of the hemocytes with antiserum against alpha 2M indicated the presence of the alpha 2M in large granules. Trypsin-treated Limulus alpha 2M, but not the native alpha 2M, displaced methylamine-treated human 125I-alpha 2M from the human alpha 2M receptor with a Kd of 30 nM, suggesting conservation of the proteinase-clearance mechanisms between mammalian and arthropod evolutionary lineages.

Antiviral treatment with WIN 54 954 reduces mortality in murine coxsackievirus B3 myocarditis

BACKGROUND

Coxsackieviruses B (CBVs) are dominant causative agents in myocarditis and are associated with pathogenesis is some cases of dilated cardiomyopathy, a clinical entity with a poor survival without heart transplantation.

METHODS AND RESULTS

In vitro, the antiviral agent WIN 54 954 was shown to inhibit replication of CBV3 at a minimal inhibitory concentration value of 0.02 mg/L. Administration of WIN 54 954, 100 mg/kg BID PO, beginning on the day of infection resulted in complete protection from enteroviral mortality (P < .01). WIN 54 954 treatment did not abrogate the inflammatory reaction in the myocardium. No difference was found in the expression of surface lymphocyte subset markers. At 3 weeks, macrophages seemed to dominate the inflammatory reaction, regardless of treatment. There was no difference in CBV3 antibody titers, indicating that WIN 54 954 does not interfere with the development of protective immunity. Complement factors C3 and B were synthesized at a higher level during infection and correlated well with the degree of inflammatory reaction.

CONCLUSIONS

The results show that WIN 54 954 is a potent antiviral agent with a highly significant effect on survival in CBV-induced myocarditis in the A/J mouse if treatment is started early. It is suggested that the reduction in mortality seen with WIN 54 954 administration is due to an inhibitory effect on virus replication in affected organs that does not interfere with cellular or humoral immunity.

Expression of liver-specific functions in rat hepatocytes following sublethal and lethal acetaminophen poisoning

AIM

In order to study the short-term effect of moderate and severe reduction of liver function by acetaminophen poisoning of different severity on gene expression for liver-specific functions, rats were given 3.75 and 7.5 g per kg body weight acetaminophen intragastrically. The lower dose is associated with low mortality; after the higher dose, most rats die at between 12 and 24 h.

METHODS

In the morning, 1 1/2, 3, 6, 9, and 12 h after the injection, the rats were killed and RNA was extracted from liver tissue. By slot-blot hybridization mRNA steady-state levels were determined for enzymes involved in metabolic liver functions, i.e. ureagenesis, gluconeogenesis, and drug metabolism, for acute phase proteins, "house-keeping" proteins, and for proteins related to liver regeneration. Results were expressed as per cent of the level in similarly fasted, untreated rats of the same stock

RESULTS

After the smaller dose of acetaminophen, most of the examined mRNA levels were increasing during the experimental period, being two- to four-fold elevated in relation to control after 6 to 12 h. Rats receiving the lethal dose either showed no or a later and smaller increase, and in several cases a fall towards the end of the experiment. The greatest differences were seen for mRNA of arginase, beta-fibrinogen, alpha 1-acid glycoprotein, alpha-tubulin, histone 3, TGF beta, and cyclin d, i.e. proteins associated with acute phase response and liver cell replication and maintenance.

CONCLUSIONS

It is concluded that reversible intoxication with acetaminophen induces an adaptive modulation of mRNA expression of liver functions and regeneration which is lacking after severe intoxication. This adaptation, with emphasis on acute phase response and regeneration, may be crucial for recovery after acetaminophen intoxication. If this also applies to the intoxication in man, estimates of the corresponding variables may be clues to the prognosis of acetaminophen-induced fulminant hepatic failure.

Expression of messenger RNA for liver functions following 70% and 90% hepatectomy

AIMS/METHODS

The effect of moderate and severe reduction of the functional liver mass on gene expression for liver functions was studied in rats following 70% and 90% hepatectomy. At intervals up to 24 h after operation rats were killed and RNA was extracted from the remaining liver tissue. By slot-blot hybridization mRNA steady-state levels were determined for enzymes involved in metabolic 'liver-specific' functions, acute phase proteins, 'house-keeping', and growth-related proteins. Results were expressed as per cent of levels in a pool from fed control rats of the same gender and age.

RESULTS

Among 'liver-specific' metabolic functions only expression of gluconeogenesis, represented by phosphoenol carboxykinase mRNA, was augmented initially, followed by a fall to very low values after 90% hepatectomy. The drug metabolizing system represented by CYP2B1/2 mRNA was reduced to half of the control values. Expression of urea synthesis, as reflected by carbamoylphosphate synthetase mRNA, showed a gradual decline after 90% hepatectomy, in contrast to rising levels of argininosuccinate lyase and arginase mRNA, possibly serving polyamine rather than urea synthesis. The mRNA level of the acute phase protein alpha 1-acid glycoprotein showed a smaller and later rise in 90% than in 70% hepatectomized rats, whereas that of alpha 2-macroglobulin only increased after 90% hepatectomy like the 'house-keeping' beta-actin mRNA. A rise in histone 3, which coincides with mitosis, was only seen after 70% hepatectomy, indicating that after 90% hepatectomy the response to growth-stimulating factors is weak or delayed, supported by a delayed rise in cyclin d and low levels of growth hormone receptor mRNA.

CONCLUSIONS

It is concluded that attempts by gene regulation to adapt liver functions to a reduction of the liver mass depend on the amount of liver tissue lost. When the loss is nearly fatal, compensation for normal metabolic functions may be abandoned for efforts to regenerate, which, however, may be delayed or after all be too weak.

Identification of residues in alpha-macroglobulins important for binding to the alpha2-macroglobulin receptor/Low density lipoprotein receptor-related protein

Variants of the receptor binding domain of both human alpha2-macroglobulin and the corresponding domain of hen egg white ovomacroglobulin have been expressed in Escherichia coli and refolded in vitro. Competition experiments with methylamine-treated alpha2-macroglobulin for binding to the multifunctional alpha2-macroglobulin receptor identify two Lys residues (residues 1370 and 1374 in human alpha2-macroglobulin) spaced by three amino acid residues as crucial for receptor binding. From this result and mutational evidence from other ligands for the alpha2-macroglobulin receptor, a tentative sequence motif for receptor binding is proposed.