Ontogeny of inter-alpha inhibitor proteins in ovine brain and somatic tissues

Inter-alpha inhibitor proteins (IAIPs) found in relatively high concentrations in human plasma are important in inflammation. IAIPs attenuate brain damage in young and adult subjects, decrease during sepsis and necrotizing enterocolitis in premature infants, and attenuate sepsis-related inflammation in newborn rats. Although a few studies have reported adult organ-specific IAIP expression, information is not available on age-dependent IAIP expression. Given evidence suggesting IAIPs attenuate brain damage in young and adult subjects, and inflammation in newborns, we examined IAIP expression in plasma, cerebral cortex (CC), choroid plexus (CP), cerebral spinal fluid (CSF), and somatic organs in fetal, newborn, and adult sheep to determine the endogenous expression patterns of these proteins during development. IAIPs (enzyme-linked immunosorbent assay) were higher in newborn and adult than fetal plasma (P < 0.05). Western immunoblot detected 125 kDa PaI (Pre-alpha Inhibitor) and 250 kDa IaI (Inter-alpha Inhibitor) in plasma, CNS, and somatic organs. PaI expression in CC and CP was higher in fetuses than newborns and adults, but IaI expression was higher in adults than fetuses and newborns. Both PaI and IaI were higher in fetal than newborn CSF. IAIPs exhibited organ-specific ontogenic patterns in placenta, liver, heart, and kidney. These results provide evidence for the first time that plasma, brain, placenta, liver, heart, and kidney express IAIPs throughout ovine development and that expression patterns are unique to each organ. Although exact functions of IAIPs in CNS and somatic tissues are not known, their presence in relatively high amounts during development suggests their potential importance in brain and organ development.

Down-regulation of matriptase by overexpression of bikunin attenuates cell invasion in prostate carcinoma cells

The precise mechanisms of metastasis in prostatic cancer are still unknown. A subculture cell line (PC-J) was isolated from the metastasis human prostate cell line PC-3. In vitro cell proliferation, wound healing and invasion assays revealed that tumorigenesis and metastasis differed between PC-3 and PC-J cells. Eight weeks after nude mice were prostate-injected with PC-J and PC-3 cells, the PC-3 group had low tumor volume and exhibited metastasis whereas the PC-J group had high tumor volume and no metastasis. Subsequent RT-PCR and immunoblot assays indicated that matriptase was the putative metastatic gene. Overexpression of bikunin significantly reduced the gene expression of matriptase, which attenuated in vitro cell invasion in the PC-3 cells. In vitro and xenograft animal models indicated different metastatic characteristics between PC-3 and PC-J cells, suggesting that matriptase plays an important role in the metastasis of prostate cancer.

Role of serum-derived hyaluronan-associated protein-hyaluronan complex in ovarian cancer

The objective of this study was to determine if the level of serum hyaluronan (HA), serum-derived HA-associated protein (SHAP)-HA complex, and urinary trypsin inhibitor (UTI) correlate with the clinical outcome of ovarian cancer patients. The relationship of metalloproteinase and its inhibitor with HA and the SHAP-HA complex was also examined. Serum and urine samples were obtained from 45 patients with ovarian cancer, 22 patients with benign ovarian tumors and 50 healthy women. Concentrations of serum HA and UTI were measured by an inhibitory sandwich enzyme-linked immunosorbent assay, and concentrations of the serum SHAP-HA complex were measured by a sandwich enzyme-linked immunosorbent assay. Concentrations of MMP-2, MMP-9 and TIMP-1 were measured by a one-step enzyme immunoassay. The levels of HA, SHAP-HA complex, MMP-9 and TIMP-1 were higher in the ovarian cancer group than in the benign ovarian tumor group. In ovarian cancer patients, the levels of HA, SHAP-HA complex and MMP-9 were higher in the stage III/IV group than in the stage I/II group, and the levels of SHAP-HA complex, MMP-9 and TIMP-1 were higher in the non-responder group than in the responder group. The serum concentration of SHAP-HA complex had a significant correlation with HA, MMP-9 and TIMP-1 in ovarian cancer patients. The patients with elevated SHAP-HA complex had a shorter disease-free survival compared with those with normal levels of SHAP-HA complex. The multiple regression analysis revealed that SHAP-HA complex is the significant independent variable for progression-free survival. The elevated level of SHAP-HA complex may indicate the prognosis of recurrence and reflect the tumor metastasis associated with MMP-9 in ovarian cancer patients.

Up-regulation of alpha1-microglobulin by hemoglobin and reactive oxygen species in hepatoma and blood cell lines

alpha(1)-Microglobulin is a 26-kDa glycoprotein synthesized in the liver, secreted to the blood, and rapidly distributed to the extravascular compartment of all tissues. Recent results show that alpha(1)-microglobulin has heme-binding and heme-degrading properties and it has been suggested that the protein is involved in the defense against oxidation by heme and reactive oxygen species. In the present study the influence of hemoglobin and reactive oxygen species (ROS) on the cellular expression of alpha(1)-microglobulin was investigated. Oxy- and methemoglobin, free heme, and Fenton reaction-induced hydroxyl radicals induced a dose-dependent up-regulation of alpha(1)-microglobulin on both mRNA and protein levels in hepatoma cells and an increased secretion of alpha(1)-microglobulin. The up-regulation was reversed by the addition of catalase and ascorbate, and by reacting hemoglobin with cyanide which prevents redox reactions. Furthermore, the blood cell lines U937 and K562 expressed alpha(1)-microglobulin at low levels, and this expression increased up to 11-fold by the addition of hemoglobin. These results suggest that alpha(1)-microglobulin expression is induced by ROS, arising from redox reactions of hemoglobin or from other sources and are consistent with the hypothesis that alpha(1)-microglobulin participates in the defense against oxidation by hemoglobin, heme, and reactive oxygen species.

Production of recombinant human alpha1-microglobulin and mutant forms involved in chromophore formation

Alpha(1)-Microglobulin, a 26 kDa lipocalin present in plasma and tissues, carries a set of unknown chromophores, bound to C34, K92, K118 and K130, which cause its charge and size heterogeneity. In man, the protein is found in two forms, full length and lacking the C-terminal tetrapeptide LIPR (t-alpha(1)-microglobulin), both which are heme-binding and the latter with heme-degrading properties. We report cloning and overexpression of full length alpha(1)-microglobulin (wt protein), t-alpha(1)-microglobulin (wtdeltaLIPR) and the mutants C34S, K(92,118,130)T and C34S/K(92,118,130)T, the latter subsequently abbreviated as K(3)T and C34S/K(3)T, in Escherichia coli. After purification and refolding from inclusion bodies, all proteins were correctly folded as determined by far-UV circular dichroism and radioimmunoassay. As revealed by gel filtration, recombinant alpha(1)-microglobulins had lower tendencies to form dimers than human plasma or urine analogues. All alpha(1)-microglobulin forms displayed higher amounts of the chromophore than bovine serum albumin but significantly lower than the human urine or plasma counterparts. Differences in the absorbance and fluorescence profiles are consistent with a model where the chromophore is formed by a series of reactions with heme or other chromophore precursors and where C34 is essential for binding of the ligand, K92, K118 and K130 are involved in transformation into the chromophore and LIPR inhibits the latter reaction.

Classification of cancer types by measuring variants of host response proteins using SELDI serum assays

Protein expression profiling has been increasingly used to discover and characterize biomarkers that can be used for diagnostic, prognostic or therapeutic purposes. Most proteomic studies published to date have identified relatively abundant host response proteins as candidate biomarkers, which are often dismissed because of an apparent lack of specificity. We demonstrate that 2 host response proteins previously identified as candidate markers for early stage ovarian cancer, transthyretin and inter-alpha trypsin inhibitor heavy chain 4 (ITIH4), are posttranslationally modified. These modifications include proteolytic truncation, cysteinylation and glutathionylation. Assays using Surface Enhanced Laser Desorption/Ionization Time of Flight Mass Spectrometry (SELDI-TOF-MS) may provide a means to confer specificity to these proteins because of their ability to detect and quantitate multiple posttranslationally modified forms of these proteins in a single assay. Quantitative measurements of these modifications using chromatographic and antibody-based ProteinChip array assays reveal that these posttranslational modifications occur to different extents in different cancers and that multivariate analysis permits the derivation of algorithms to improve the classification of these cancers. We have termed this process host response protein amplification cascade (HRPAC), since the process of synthesis, posttranslational modification and metabolism of host response proteins amplifies the signal of potentially low-abundant biologically active disease markers such as enzymes.

Dialysis adequacy, residual renal function and serum concentrations of selected low molecular weight proteins in patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

Low molecular weight proteins (LMWP) are considered uremic toxins. There is controversy whether in peritoneal dialysis (PD) the elimination of these toxins is influenced mainly by dialysis or by residual renal function (RRF).

MATERIAL/METHODS

The aim of our study was to evaluate the relationship between serum levels of selected LMWPs, dialysis adequacy, and RRF in PD patients. 27 stable subjects were studied, mean age 50+/-11, dialyzed for a median period of 10 months. Serum activity of acid RNA-se and alkaline RNA-se was measured by spectrophotometry, and serum alpha1-microglobulin ((alpha) 1M) concentration by ELISA. Kt/V and weekly creatinine clearance (wClCr) were assessed as adequacy indices (both as the sum of renal and dialysis components) and RRF as the mean of residual urea and creatinine clearances.

RESULTS

Significant inverse correlations were found between RRF and (alpha) 1M level, as well as alkaline RNA-se activity (p<0.0001). A similar relationship was found for residual Kt/V (p<0.0001 for (alpha) 1M and alkaline RNA-se). There was no significant correlation between acid RNA-se activity and any tested parameter of adequacy. When the cutoff points of wClCr = 60 L/week/m2, total Kt/V = 2.0, or RRF=2.0 ml/min were used, we found (alpha)1M level and alkaline RNA-se activity to be significantly lower in patients with higher values of the

CONCLUSIONS

RRF plays an important role in elimination of LMWP in PD. The activity of alkaline RNA-se and acid RNA-se behaves differently in these patients.

Inhibition of tumor growth and metastatic spreading by overexpression of inter-alpha-trypsin inhibitor family chains

The inter-alpha trypsin inhibitor (ITI) family is a group of proteins built up from different combinations of I light chain (ITI-L) and 3 highly homologous heavy chains (ITI-HI, -H2 and -H3). To investigate a potential role of the ITI family chains in cancer and metastasis spreading, we engineered human H460M cell lines expressing both the green fluorescent protein (GFP) and one of these chains. These clones were subcutaneously injected in athymic nude mice, and lung metastasis number and primary tumor weight were determined after 28 days. Expression of the ITI-L chain considerably decreased tumor weight and fluorescent lung metastasis number. ITI-HI and ITI-H3 chain expression induced a significant decrease of metastasis number, whereas no decrease of tumor weight could be detected. In vitro, ITI-L expression significantly decreased chemotaxis and ITI-HI and ITI-H3 expression increased cell attachment. These results argue for the antitumoral or antimetastatic properties of ITI-L, -HI and -H3 chains.

Initial induction and subsequent reduction of alpha(2u)-globulin in urine and serum of mature male rats after repeated intraperitoneal injections of (anti)estrogen

The influence of sex (anti)hormones on expression of alpha(2u)-globulin (a2uG) is complex and has not been sufficiently detailed. In order to assess the specificity of sex (anti)hormone action on a2uG expression and the utility of this approach as a sensitive screening method, mature male rats were given daily intraperitoneal injections of 17beta-estradiol (E2), dihydrotestosterone (DHT), tamoxifen (TX) and flutamide (FL) for 5 consecutive days. They were employed as representatives of estrogen, androgen, antiestrogen and antiandrogen categories, respectively. Urinary a2uG was specifically altered with E2 (1 microg/kg/day) and TX (50 mg/kg/day), but not by DHT (1 mg/kg/day) or FL (50 mg/kg/day). E2 and TX temporarily increased urinary a2uG on days 1 or 2, and days 2-4, respectively, followed by a return to the control level, and then a decrease with E2. The reduction in urinary a2uG on day 6 was more pronounced than the drop in serum a2uG. Serum hormone levels, and liver and testis weights were not remarkably altered with any treatment. Another strong xenoestrogen, diethylstilbestrol, also significantly reduced urinary and serum a2uG at 1 mg/kg/day on day 6. However, the other xenoestrogens (100 mg/kg/day of bisphenol A, nonylphenol, and dichlorodiphenyltrichloroethane, and 10 mg/kg/day of dieldrin) and phytoestrogens (10 mg/kg/day of genistein and daidzein) were without any appreciable influence. The results indicate that urinary a2uG is a sensitive indicator of estrogen action in mature male rats, with two different responses, initial induction and subsequent reduction.

A physiological model for ligand-induced accumulation of alpha 2u globulin in male rat kidney: roles of protein synthesis and lysosomal degradation in the renal dosimetry of 2,4,4-trimethyl-2-pentanol

A physiologically based pharmacokinetic (PBPK) model was constructed for the disposition of 2,4,4-trimethyl-2-pentanol (TMP-2-OH) in male rats and its induction of accumulation of renal alpha2u-globulin (alpha2u). The model included diffusion-restricted delivery of TMP-2-OH to compartments representing liver, lung, fat, kidney, GI tract, aggregated rapidly perfused tissues, and aggregated slowly perfused tissues. Metabolism by oxidation and glucuronidation was included for liver and kidneys. Rates of hepatic alpha2u production and resorption by renal proximal tubules were taken from the literature. Degradation of liganded alpha2u by renal lysosomal cathepsins was modeled with a Km value corresponding to the measured 30% reduction in proteolytic efficiency and with free and bound forms of alpha2u competing for access to the enzymes. Increased pinocytotic uptake of alpha2u into the kidney induces cathepsin activity. A model that ascribed renal alpha2u accumulation solely to reduced lysosomal proteolysis failed to reproduce the observed accumulation. The model could reproduce experimental observations if a transient increase in hepatic synthesis of alpha2u, stimulated by the presence of liganded alpha2u in the blood, and accelerated secretion of the protein from the liver were assumed. This model reproduces time course data of blood and kidney TMP-2-OH and renal alpha2u concentrations, suggesting that renal accumulation of alpha2u is not simply a consequence of reduced proteolytic degradation but may also involve a transient increase in hepatic alpha2u production. The model predicts increased delivery of TMP-2-OH to the kidney and consequent increased renal production of potentially toxic TMP-2-OH metabolites than would be the case if no alpha2u were present. Induced lysosomal activity and increased production of toxic metabolites may both contribute to the nephrotoxicity observed in male rats exposed to an alpha2u ligand or its precursor.

Temporal changes in mRNA expression for bikunin in the kidneys of rats during calcium oxalate nephrolithiasis

Inter-alpha-inhibitor and other bikunin-containing proteins are synthesized in relatively large quantities by the liver. These proteins function as Kunitz-type serine protease inhibitors and appear capable of inhibiting calcium oxalate (CaOx) crystallization in vitro. Preliminary studies have shown that renal tubular epithelial cells synthesize bikunin in response to CaOx challenge. To examine this response in vivo, a sensitive reverse transcription-quantitative competitive template-PCR was developed to detect and quantify poly(A)+ -tailed bikunin mRNA expression in kidney tissue from normal rats and rats developing CaOx nephrolithiasis after challenge with ethylene glycol. Bikunin mRNA expression in rat liver tissue was assessed as a positive control. The expression of bikunin mRNA in liver did not differ significantly between normal control rats and experimental rats with induced hyperoxaluria and renal CaOx crystallization. In contrast, there were significant temporal increases in the levels of bikunin mRNA expression in rat kidneys during CaOx nephrolithiasis after challenge with ethylene glycol. Urinary excretion of bikunin-containing proteins seemed to increase concomitantly. These findings indicate an association between the induction of hyperoxaluria/CaOx nephrolithiasis and the expression of the bikunin gene in rat kidneys.

Down-regulation of cytochrome P450 2C family members and positive acute-phase response gene expression by peroxisome proliferator chemicals

In this study, we show that peroxisome proliferator chemical (PPC) exposure leads to alterations in the expression of genes in rat liver regulated by the sex-specific growth hormone secretory pattern and induced during inflammation. Expression of the male-specific cytochrome P450 (P450) 2C11 and alpha2 urinary globulin (alpha2u) genes and the female-specific P450 2C12 gene was down-regulated by some PPC. Expression of P450 2C13, also under control by the sex-specific growth hormone secretory pattern, was not altered by PPC treatment, indicating that regulation of CYP2C family members does not involve perturbation of the growth hormone secretory pattern. In contrast to the increases in expression observed when inflammation was induced in male rats, two positive acute-phase response genes, alpha1-acid glycoprotein and beta-fibrinogen, were decreased by PPC exposure. The down-regulation of the P450 2C11 by WY-14,643 could be reproduced in cultured rat hepatocytes, indicating the down-regulation is a direct effect. Experiments in wild-type mice and mice that lacked a functional peroxisome proliferator-activated receptor-alpha gene showed that down-regulation by WY of alpha1-acid glycoprotein, beta-fibrinogen, and a mouse homologue of alpha2u was dependent on peroxisome proliferator-activated receptor-alpha expression. Our results demonstrate that PPC exposure leads to down-regulation of diverse liver-specific genes, including CYP2C family members important in hormonal homeostasis and acute-phase response genes important in inflammatory responses.

The H4P heavy chain of inter-alpha-inhibitor family largely differs in the structure and synthesis of its prolin-rich region from rat to human

The family of plasma proteins collectively referred to as Inter-alpha-Inhibitor (I alpha I) family is comprised of a set of multi-polypeptide molecules and a single-chain molecule designated I alpha IH4P. Although the 4 heavy chain precursors H1P to H4P that lead to these molecules are evolutionarily related, only H4P harbours a Pro-rich region (PRR) in its C-terminal third. A comparison of hepatic H4P cDNAs in human and rat has now unraveled an extensive variability of this PRR. Within the rat PRR, 6 repeats of a Gly-X-Pro motif participate in a collagen-like pattern that is absent in human. Within the human PRR, a domain that is absent in rat can be transcribed or deleted by alternative splicing which results in two variant forms of human H4P. In rat liver, the single mRNA is up-regulated by an acute, systemic inflammation whereas neither mRNA is up-regulated in human liver. Finally the shortest human mRNA is also transcribed in peripheral blood mononuclear cells where it is down-regulated by bacterial lipopolysaccharides. Therefore, in contrast to what is seen for the ITIH1 to -3 genes, the rat and human ITIH4 gene transcriptions and products thereof present marked differences, which suggests species-specific functions for I alpha IH4P.

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.

Physicochemical and biochemical characterization of human alpha 1-microglobulin expressed in baculovirus-infected insect cells

DNA encoding the signal peptide and the alpha 1-microglobulin part of the human alpha 1-microglobulin-bikunin gene was expressed in baculovirus-infected insect cells. Recombinant alpha 1-microglobulin was secreted and could be purified from the medium with a yield of 20-30 mg/ L. Biochemical and physicochemical characterization showed that the recombinant protein was very similar to alpha 1-microglobulin isolated from human urine and plasma, except that the recombinant protein had smaller N-linked oligosaccharides, lacked the O-linked oligosaccharide, and was devoid of sialic acid. Recombinant alpha 1-microglobulin migrated upon SDS-PAGE as two bands, 27 and 29 kDa, representing alpha 1-microglobulin with one and two N-linked carbohydrates, respectively. An overall structural similarity was indicated as antibodies raised against human urinary alpha 1-microglobulin were found to recognize recombinant, plasma, and urinary alpha 1-microglobulin in a similar manner. CD studies suggested an almost identical secondary structure for recombinant and urinary alpha 1-microglobulin but a slightly different structure for plasma alpha 1-microglobulin. The absorbance spectrum as well as visual examination demonstrated that recombinant, urinary, and plasma alpha 1-microglobulin carried a yellow-brown chromophore, but that plasma alpha 1-microglobulin was slightly less intensely colored. Although it is still a puzzle why the immunosuppressive plasma protein alpha 1-microglobulin and the protease inhibitor bikunin, which have no known function in common, are cotranslated from the same mRNA, it can be concluded that bikunin is not necessary for an adequate translation, folding, and secretion of alpha 1-microglobulin. Furthermore, since recombinant alpha 1-microglobulin was produced in large amounts and found to be very similar to plasma and urinary alpha 1-microglobulin, it may prove to be useful in structural and functional studies of the protein.

PPAR alpha mediates peroxisome proliferator-induced transcriptional repression of nonperoxisomal gene expression in mouse

The strain difference, peroxisome proliferator specificity and role of PPAR alpha in peroxisome proliferator-induced transcriptional repression of nonperoxisomal transthyretin and alpha2u-globulin genes were examined. The genes were repressed by four peroxisome proliferators in all seven mouse strains tested. The extent of repression was strongly dependent on both the mouse strains and type of proliferator, although the mRNA levels of PPAR alpha and its partner in heterodimerization, RXR alpha were not different. The role of PPAR alpha in repression was confirmed by the finding that PPAR alpha-null mice were not responsive to transcriptional repression. These results indicate that PPAR alpha plays an obligatory role in transcription of various genes, some of which are not related to lipid metabolism.

Ciprofibrate represses alpha 2u-globulin expression in liver and inhibits d-limonene nephrotoxicity

Peroxisome proliferators are a class of compounds which induce hepatomegaly and peroxisome proliferation in liver parenchymal cells. One of the earliest known effects of peroxisome proliferators is the rapid transcriptional activation of the genes responsible for the peroxisomal beta-oxidation system in liver. Long term administration of these chemicals to rats and mice results in the development of hepatocellular carcinomas. Here we report that mRNA for alpha 2u-globulin, a rodent male specific protein, is markedly reduced or undetectable by Northern blot analysis of total RNA in the livers of rats treated with ciprofibrate. This was further confirmed by immunoblot analysis using antibodies against alpha 2u-globulin. Nevertheless, immunohistochemical staining and in situ hybridization showed respectively the presence of a few cells that contained alpha 2u-globulin protein and its mRNA. The alpha 2u-globulin mRNA reappeared in the liver 2 weeks following the cessation of ciprofibrate treatment. Feeding of ciprofibrate for two weeks followed by simultaneous feeding of ciprofibrate and a nephrotoxic chemical d-limonene for 5 weeks revealed that ciprofibrate prevented the renal accumulation of alpha 2u-globulin and the nephrotoxicity associated with the binding of d-limonene with alpha 2u-globulin.

Expression of rat alpha 1-microglobulin-bikunin in baculovirus-transformed insect cells

cDNA encoding rat alpha 1-microglobulin-bikunin was ligated into the transfer vector pVL 1392 and recombined with a wild-type baculovirus. The resulting alpha 1-microglobulin-bikunin-encoding baculovirus was used to infect Trichoplusia ni (Hi-5) insect cells. The infected cells secreted alpha 1-microglobulin with maximal concentrations of 15 mg/liter 5 days after infection. The secreted proteins migrated upon SDS-PAGE as two major protein bands, 40 and 26 kDa, corresponding to alpha 1-microglobulin-bikunin and free alpha 1-microglobulin. The results suggested that the cells secreted mostly alpha 1-microglobulin-bikunin, which subsequently was cleaved in the medium, yielding free alpha 1-microglobulin. Both forms were isolated by monoclonal anti-alpha 1-microglobulin affinity chromatography, and alpha 1-microglobulin-bikunin separated from free alpha 1-microglobulin by gel chromatography. The yields of purified alpha 1-microglobulin-bikunin and free alpha 1-microglobulin were approximately 1 and 5 mg, respectively, per liter medium. Insect cell alpha 1-microglobulin displayed a size, shape, and charge heterogeneity similar to alpha 1-microglobulin isolated from rat urine. A panel of monoclonal antibodies raised against urinary alpha 1-microglobulin from several different species bound to rat urinary alpha 1-microglobulin and insect cell secreted alpha 1-microglobulin-bikunin and free alpha 1-microglobulin with approximately the same strength, indicating that the three proteins are folded in similar ways. The results of glycosidase treatments and lectin blotting indicate the absence of neuraminic acid but the presence of one N-linked oligosaccharide and an unspecified number of O-linked oligosaccharides in alpha 1-microglobulin-bikunin and free alpha 1-microglobulin.

Gene expression and protein distribution of inter-alpha-trypsin inhibitor in three human hepatoma cell lines

In standard culture conditions, three human hepatoma cell lines, Hep3B, PLC/PRF/5 and HepG2, were characterised by a predominant transcription of only two (H2 and L) among the four genes involved in the synthesis of inter-alpha-trypsin inhibitor (ITI)-related proteins. Pulse-chase experiments followed by immuno-precipitation with specific anti-L and anti-H ITI antisera showed that the proteins synthesised displayed a restricted L and/or H2 antigenic reactivity. Furthermore, while Hep3B and PLC/PRF/5 lines only synthesised ITI precursors (mainly the L-form), HepG2 cells were able to secrete an ITI-like protein. Immunocytochemical analyses substantiated these results with uneven distribution of heavy and light-chain polypeptide reactivity among the cells. The use of hepatoma cell models for the study of protein synthesis and assembly must therefore be considered cautiously.

Expression of the human complex-forming glycoprotein HC (alpha 1-microglobulin) in Escherichia coli

The mature form of human protein HC, or alpha 1-microglobulin, has been expressed in Escherichia coli. Protein HC is a member of the lipocalin superfamily of hydrophobic ligand-binding proteins, and carries a heterogeneous chromophore linked covalently by a reduction-resistant bond. Protein HC was first overexpressed as a C-LytA/HC fusion protein containing the C-terminal moiety of the pneumococcal lytic amidase (LytA). Recombinant C-LytA/HC was found to be an insoluble aggregate that was solubilized with 6 M guanidinium chloride and renatured by the addition of thiol reagents in the presence of L-arginine. Recombinant protein HC (rHC) was released from C-LytA/HC by trypsin digestion and purified by size-exclusion chromatography. rHC protein possesses an N-terminal amino-acid sequence identical to that of human protein HC, and a slightly lower molecular mass as determined by SDS-PAGE. Both C-LytA/HC and rHC reacted with polyclonal antibodies raised against native protein HC. A photodiode array detection system on-line with a HPLC system has allowed the identification of a chromophore associated to rHC protein displaying significant absorption in the visible region of the spectrum in resemblance to that found in the natural form of human protein HC.

Gene expression in the aging brown Norway rat epididymis

The mammalian epididymis is the site where spermatozoa are matured and then stored. Though many studies have described epididymal functions and their regulation, little is known about how aging affects this tissue. The Brown Norway rat, which does not show the many age-related pathologies common to other rat strains, was used as a model to study aging of the epididymis. The present study was designed to determine the effect of aging on the mRNA levels for selected markers of epididymal function. Brown Norway rats ranging in age from 6 to 30 months were examined at 6-month intervals; epididymides were sectioned into caput-corpus and cauda regions. Relative mRNA concentrations were assessed using Northern blot analysis and specific cDNAs for the rat 5 alpha-reductase isozymes, types 1 and 2; proenkephalin; the androgen receptor; epididymal proteins B/C and D/E; and sulfated glycoprotein-2 (SGP-2, clusterin). Northern blots were quantitated by densitometric scanning. In the caput-corpus epididymidis, 5 alpha-reductase type 1 and type 2 mRNA levels decreased significantly by 43% and 33%, respectively, between 6 and 12 months and by 64% and 40%, respectively, between 6 and 30 months. No significant change, however, was found in the expression of the 5 alpha-reductase mRNAs in the cauda epididymidis. Interestingly, proenkephalin mRNA was only detected in the caput-corpus epididymidis of 6-month-old rats. In marked contrast to the 5 alpha-reductase isozymes and proenkephalin, no significant age-related changes were observed in the mRNA levels for the androgen receptor, protein B/C, or protein D/E. No age-related changes in mRNA expression for SGP-2 occurred in the caput-corpus epididymidis. However, in the cauda epididymidis, SGP-2 mRNA levels rose by twofold between 6 and 18 months and then decreased sharply by 75% between 18 and 30 months. We conclude that as the epididymis ages, the expression of genes for certain specific markers of epididymal function is affected in a region-specific manner. Further, the decrease in the concentrations of the mRNAs for the 5 alpha-reductase isozymes and proenkephalin in the epididymis between 6 and 12 months is thus far the earliest marker for aging in the male reproductive tract of the Brown Norway rat.

d-Limonene induced hyaline droplet nephropathy in alpha 2u-globulin transgenic mice

d-Limonene is a hyaline droplet inducing agent and produces nephrotoxicity in male rats when the 1,2-epoxide metabolite binds to alpha 2u-globulin. Mice, which do not synthesize alpha 2u-globulin, are resistant to hyaline droplet nephropathy. In this study, the ability of d-limonene to cause hyaline droplet nephropathy in a transgenic mouse engineered to express alpha 2u-globulin was evaluated. The C57BL/6-derived mice excreted 0.4 +/- 0.1 mg alpha 2u-globulin/day, or approximately 16 mg alpha 2u-globulin/kg body wt. This represents about 30% of the amount excreted by adult male rats (11.9 +/- 1.1 mg/day or approximately 48 mg/kg). Transgenic mice excreted less mouse urinary protein (9.3 +/- 1.2 mg/day) than normal mice (15.1 +/- 1.6 mg/day). Unlike normal male rats, untreated transgenic mice did not show significant spontaneous hyaline droplet formation. Liver microsomes from naive transgenic mice oxidized d-limonene to the cis- and transisomers of the 1,2-epoxide, and following oral treatment with [14C]d-limonene reversible binding of d-limonene equivalents to renal cytosolic proteins was observed. Furthermore, with d-limonene treatment, hyaline droplets were observed in the transgenic mouse kidneys. These droplets, however, were much smaller in size than those seen in d-limonene-treated male rats. The accumulation of alpha 2u-globulin in the kidneys of transgenic mice and normal male rats before and after d-limonene treatment was analyzed by Western blotting. These results indicated that alpha 2u-globulin was present in the kidneys of the control transgenic mice, despite the lack of spontaneous hyaline droplet formation. After d-limonene treatment, approximately a three-fold increase in alpha 2u-globulin in the transgenic mouse kidney was observed, a response similar in magnitude to that seen in d-limonene-treated male rats. These results indicate that expression of alpha 2u-globulin in a species that does not normally develop hyaline droplet nephropathy is necessary and sufficient to render that species sensitive to this renal toxicity.

Selective interferon-alpha/beta effects on platelet-derived growth factor-stimulated processes in quiescent BALB/c-3T3 fibroblasts

Interferon-alpha/beta (IFN-alpha/beta) suppresses cell cycle activation by platelet-derived growth factor (PDGF) as well as the induction of the 31-kD (pI) and the 35-kD (pII) proteins in density-arrested BALB/c-3T3 cells. We report that elevation of [Ca2+]i by ionomycin induces the synthesis of the 31-kD protein, but not that of the 35-kD protein. Since IFN blocks the PDGF-induced elevation of [Ca2+]i, these results suggest that IFN treatment may suppress pI induction by impairing this PDGF-activated signal transduction pathway. In contrast, because ionomycin did not induce the 35-kD protein, the suppression by IFN of PDGF-induced pII appears to be mediated via a pathway distinct from that operating in the suppression of pI. In BALB/c-3T3 cells, IFN-alpha/beta did not itself affect the turnover or de novo synthesis of inositol phospholipids and the cellular content of diacylglycerol, nor did IFN block the enhancement of these parameters by PDGF.

Post-translational processing of the inter-alpha-trypsin inhibitor in the human hepatoma HepG2 cell line

In human hepatoma HepG2 cells, the serum inter-alpha-trypsin inhibitor (ITI)-like protein is synthesized from two protein precursors, the heavy chain (H) H2 and the light chain (L). Both of them carry sulphate groups involved in the chondroitin sulphate glycosaminoglycan (GAG) linkage, as demonstrated by [35S]sulphate labelling, chondroitinase digestion and inhibition with beta-D-xyloside, an artificial GAG acceptor. While inhibition of N-glycosylation prevented neither the maturation nor the secretion of the ITI-related entities, brefeldin A induced the accumulation of H and L precursors in the cells, therefore blocking subsequent association and maturation of the precursors before their secretion. The enzyme system involved in the ester linkage between H and L chains is localized in the trans-Golgi network since no ITI-like protein could be obtained in the presence of monensin; instead free heavy-chain protein forms and bikunin were secreted in culture supernatants. The ITI-like protein synthesized by HepG2 cells is therefore composed of two heavy chains HC2 linked to two bikunin chains by chondroitin sulphate bridges, although the GAG linkage between HC2 chains is presumably different. Further, a different maturation route leading to restricted heavy-chain forms, Hm and Hd, could be shown.

Cell proliferation and renal carcinogenesis

Enhanced cell proliferation occurs at several stages of renal tumorigenesis. Initiation by genotoxic nephrocarcinogens such as dimethylnitrosamine (DMN) is likely a result of DNA damage coupled with an initial burst of DNA synthesis associated with the cytotoxic effects of the compound. The level of initiation by DMN can be further enhanced by unilateral nephrectomy or hydronephrosis, which induces a brief burst of cell proliferation followed by tumorigenesis in the contralateral kidney. The role of sustained cell proliferation in renal tumor development is less well understood. The most compelling evidence comes from studies with nongenotoxic renal carcinogens such as unleaded gasoline and d-limonene, which induce alpha 2u-globulin (alpha G) nephropathy and renal epithelial tumors exclusively in male rats. Sustained increases in cell proliferation in these studies depend on the presence of a chemical-alpha G complex in phagolysosomes of P2 proximal tubule cells, which results in cytotoxicity and compensatory hyperplasia only in male F344 rats, but not female F344 rats or alpha G deficient male NBR rats. Furthermore, initiation-promotion experiments demonstrated a strong correlation between the dose-response of cell proliferation and the incidence of preneoplastic and neoplastic lesions. Clearly, similar correlative studies with a number of other renal carcinogens and non-carcinogens are warranted before general conclusions can be made. Cell proliferation is excessively elevated in tubules affected by chronic progressive nephropathy, but the significance of the lesion to renal carcinogenesis is unclear. Elucidating mechanisms of renal cell proliferation are necessary for our understanding of cause and effect relationships. An exciting recent finding is altered expression of transforming growth factor-alpha in hereditary rat renal cell carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmentally regulated transcription of the four liver-specific genes for inter-alpha-inhibitor family in mouse

The inter-alpha-inhibitor family is composed of the plasma-protease inhibitors inter-alpha-inhibitor, pre-alpha-inhibitor and bikunin. Inter-alpha-inhibitor and pre-alpha-inhibitor are distinct assemblies of bikunin with distinct sets from three heavy (H) chains designated H1, H2 and H3. These H chains are encoded by a set of three evolutionarily related H genes, and bikunin by an alpha-1-microglobulin/bikunin precursor gene (AMBP). This precursor is cleaved to yield bikunin, a member of the Kunitz-type protease-inhibitor superfamily, and alpha-1-microglobulin, which belongs to the lipocalin superfamily. Northern-blot experiments with RNAs obtained from various tissues in fetal and in adult mice indicated that the transcription of the four AMBP and H genes is liver-restricted, although there is expression of H3 in brain. An analysis of the H1, H2, H3 and AMBP transcripts, as well as of transcripts for other control genes, in liver during development showed a progressive increase in the amounts of the H1, H2, H3 and AMBP RNAs, which all peak transiently at day 5 after birth. This was shown by a nuclear run-on experiment to originate from a change in transcription rate. The transient and postnatal increase in transcription could be explained neither by the liver-restricted expression nor by a common origin of these four genes, nor by a perinatal requirement for many lipocalins or protease inhibitors. This suggests that all four genes are perinatally triggered at the level of similar elements in their transcriptional regulatory regions, a conclusion strengthened by the weak expression of the four genes that is seen in a mutant mouse strain (albino) that is deficient in some liver-specific transcription factors.

Serum amyloid P (female protein) of the Syrian hamster. Gene structure and expression

The structure and expression of the gene encoding serum amyloid P (SAP) component of the Syrian hamster have been studied by isolation of cosmid clones, nucleotide sequence analyses, and quantitation of nuclear run-on transcripts, nuclear RNA, mRNA, and protein levels. Hamster SAP, originally identified as female protein (FP), is a unique pentraxin because pretranslational expression of this gene is modulated by mediators of inflammation and sex steroids. SAP(FP) levels are high in sera from female hamsters and low in males. The response to inflammation is divergent; SAP(FP) levels decrease in females and increase in males during an acute phase response. The SAP(FP) gene encodes a 211 amino acid residue mature polypeptide as well as a 22-residue signal peptide. The intron/exon organization is similar to that of other pentraxins, but additional transcripts are generated from alternate polyadenylation sites in the 3' region. Circulating levels of SAP(FP) and the corresponding hepatic transcript levels are augmented by estrogen, while testosterone, dexamethasone, and progesterone cause a decrease in these levels. In addition the cytokines interleukin-1, -6, and tumor necrosis factor mediate a decrease in hepatic SAP(FP) transcript levels in female hamsters but did not cause a significant elevation of SAP(FP) mRNA in livers of male hamsters. The differences in expression of the SAP(FP) gene between male and female hamsters and between unstimulated male hamsters and male hamsters stimulated with an injection of lipopolysaccharide are due, at least in part, to alterations in transcription.

Differences in alpha 2u-globulins increased in male rat kidneys following treatment with several alpha 2u-globulin accumulating agents: cystein protease(s) play(s) an important role in production of kidney-type-alpha 2u-globulin

Effects of alpha 2u-globulin accumulating agents on alpha 2u-globulins in rat kidneys were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analysis. Treatment of male animals with decalin (150 mg/kg), 2,2,4-trimethylpentane (50 mg/kg), isophorone (150 mg/kg), d-limonene (150 mg/kg) or 1,4-dichlorobenzene (150 mg/kg) by gavage for 14 consecutive days in each case resulted in a marked intensification of a protein band corresponding to kidney-type-alpha 2u-globulin, with a molecular mass calculated to be approximately 16 kDa. However, intraperitoneal treatment with leupeptin and E-64 (two times 0.07 mmol/kg, for each), well known cystein protease inhibitors, while only slightly increasing this kidney-type-alpha 2u-globulin band, caused the intensification of a approximately 19-kDa molecular mass protein band which was revealed to be a native-type-alpha 2u-globulin by SDS-PAGE and immunoblotting. These results indicated that at least two types of alpha 2u-globulin can be increased in male rat kidney by chemical treatment. Moreover, cystein protease(s) appear(s) to play an important role in the degradation of alpha 2u-globulin and particularly in the conversion of native-type-alpha 2u-globulin to kidney-type-alpha 2u-globulin in rat kidneys.

Spatio-temporal expression of estrogen sulfotransferase within the hepatic lobule of male rats: implication of in situ estrogen inactivation in androgen action

Estrogen sulfotransferase (EST) catalyzes transfer of the sulfate group from phosphoadenosine phosphosulfate to estrogenic steroids. Since estrogen sulfates do not bind to the estrogen receptor with high affinity, EST can control the intracellular level of the receptor-active estrogens. Androgen action in the rat liver, as indicated by the androgenic induction of alpha 2u-globulin, is inhibited by low levels of estrogens. Thus, in situ estrogen inactivation by EST is expected to increase hepatic androgen sensitivity. During the lifespan of the animal, rat liver undergoes three distinct phases of androgen sensitivity, i.e. prepubertal androgen insensitivity, androgen sensitivity after approximately 40 days of age, and androgen insensitivity during senescence (greater than 750 days). EST in the liver is expressed only after puberty, when the liver becomes androgen sensitive. Furthermore, localization of EST and its corresponding mRNA within the lobular unit of the liver demonstrates that only androgen-responsive hepatocytes located around the central vein contain immunoreactive EST and its corresponding mRNA. These temporal and spatial correlations of EST expression and hepatic androgen sensitivity support the concept that steroid-inactivating enzymes play important roles in sex hormone action.

Synthesis of alpha 1-microglobulin in cultured rat hepatocytes is stimulated by interleukin-6, leukemia inhibitory factor, dexamethasone and retinoic acid

The secretion of alpha 1-microglobulin by primary cultures of rat hepatocytes was found to increase upon the addition of interleukin-6 or leukemia inhibitory factor, two mediators of acute phase response. This stimulatory effect was further enhanced by dexamethasone. alpha 1-Microglobulin is synthesized as a precursor also containing bikunin, and the precursor protein is cleaved shortly before secretion. Our results therefore suggest that both alpha 1-microglobulin and bikunin are acute phase reactants in rat hepatocytes. Furthermore, we found that retinoic acid, previously shown to be involved in the regulation of cell differentiation and development, also stimulated alpha 1-microglobulin synthesis. Only free, uncomplexed alpha 1-microglobulin (28,000 Da) was detected in the hepatocyte media, suggesting that the complex between alpha 1-microglobulin and alpha 1-inhibitor 3, found in rat serum, is formed outside the hepatocyte.

Application of molecular encapsulation for toxicology studies: comparative toxicity of p-Chloro-alpha, alpha, alpha-trifluorotoluene in alpha-cyclodextrin vehicle versus corn oil vehicle in male and female Fischer 344 rats and B6C3F1 mice

The application of alpha-cyclodextrin (alpha-CD) as an alternative vehicle for water insoluble and volatile chemicals was investigated in toxicity studies of p-chloro-alpha, alpha, alpha-trifluorotoluene (CTFT). Groups of F344 rats and B6C3F1 mice of each sex were administered CTFT (97% pure) by gavage in either corn oil or alpha-CD aqueous formulations daily for 14 consecutive days. The dose levels used were 10 (mice only), 50, 400, and 1000 mg/kg for corn oil vehicle and 10, 50, and 400 mg/kg (maximum achievable dose at gavage volume of 5 ml/kg) for alpha-CD vehicle. With both vehicles CTFT and alpha 2u-globulin were found to accumulate in the male rat kidney after 14 days of exposure and a dose-related toxic nephropathy was observed at dose of 50 mg/kg or higher. The hepatocellular hypertrophy and cytoplasmic vacuolation of the adrenal cortex which appeared in dosed male and female rats were also found to be independent of vehicle. Clinical pathology findings suggested a mild anemia and cholestasis in rats. With both vehicles no tissue bioaccumulation of CTFT was found in male or female mice. Vehicle-independent hepatocellular hypertrophy and cholestasis were also observed in mice at doses of 400 and 1000 mg/kg. In conclusion, the alpha-CD vehicle does not affect the toxic responses of CTFT in both sexes of both species. The results of the studies suggest that alpha-CD may be an appropriate alternative vehicle for toxicity studies.

Sexual dimorphism and growth hormone regulation of a hybrid gene in transgenic mice

The sexually dimorphic expression of the urinary protein genes of mice (Mup genes) in the liver is mediated by the different male and female temporal patterns of circulating GH. Normal females were induced to male levels when GH was administered by injection to mimic the male GH pattern, showing that expression at the male level does not require a male sex steroid status in addition to intermittent GH. Two Mup-alpha 2u-globulin hybrid transgenes with different Mup gene promoters showed sexually dimorphic expression, and their expression in females increased to male levels upon testosterone treatment. GH-deficient (lit/lit) mice did not express these transgenes, and GH-deficient females did not respond to testosterone treatment, showing that GH was required for induction. Both normal and GH-deficient females were induced to male levels when GH was administered by injection. This is the first report of a transgene responsive to GH. A transgene consisting of a Mup promoter fused to a Herpes simplex virus thymidine kinase reporter sequence also showed sexual dimorphism, although to a lesser degree. It was expressed at the same level in normal females and GH-deficient mice of both sexes and was induced when GH-deficient mice were treated with GH. We propose that this transgene has a basal constitutive expression, possibly due to the absence of any rodent DNA downstream of the promoter. Since expression of the transgene was significantly induced by GH, the GH response is due at least in part to sequences in the promoter region.

Biosynthesis of inter-α-trypsin inhibitor and α1-microglobulin in a human hepatoma cell line

1. Biosynthesis of alpha 1-microglobulin and inter-alpha-trypsin inhibitor was investigated in a human hepatoma cell line HepG-2. 2. alpha 1-Microglobulin was translated as a precursor common with the light chain of inter-alpha-trypsin inhibitor. 3. alpha 1-Microglobulin was synthesized and secreted into the growth medium within 30 min. 4. Processing of inter-alpha-trypsin-inhibitor-related proteins appeared slow and incomplete. The light chain was connected via a chondroitinsulphate to a heavy chain to form a 125,000-Mr protein and secreted within 1-4 hr.

NCI-Black-Reiter (NBR) male rats fail to develop renal disease following exposure to agents that induce alpha-2u-globulin (alpha 2u) nephropathy

The NCI-Black-Reiter (NBR) rat is the only strain of male rat known not to synthesize the hepatic form of the low molecular weight protein, alpha 2u-globulin. In previous studies, NBR rats were shown not to develop renal disease when exposed to decalin, a compound known to induce alpha 2u-globulin nephropathy in other rat strains. The objective of this study was to show that the presence of alpha 2u-globulin (alpha 2u) is essential for the development of this syndrome in rats exposed to 2,2,4-trimethylpentane (TMP), 1,4-dichlorobenzene (DCB), isophorone (IP), PS-6 unleaded gasoline (UG), and d-limonene (d-L). The induction of alpha 2u-nephropathy in F344 male rats with lindane was used as a positive control and this response was contrasted to male NBR and female F344 rats treated with lindane. Five to seven 11-week-old male NBR rats were exposed to TMP (500 mg/kg/day), DCB (500 mg/kg/day), IP (1000 mg/kg/day), UG (500 mg/kg/day), d-L (1650 mg/kg/day), or lindane (10 mg/kg/day) and five 11-week-old male and female F344 rats were exposed to lindane (10 mg/kg/day) by oral gavage on 4 consecutive days. NBR male and F344 male and female rats gavaged with corn oil were incorporated in the study as vehicle controls. The presence of hyaline droplets was assessed in perfusion-fixed kidneys by staining paraffin sections with Mallory-Heidenhein stain and in GMA sections with Lee's methylene basic blue fuchsin stain. Paraffin sections were also analyzed immunohistochemically for the presence of alpha 2u. Under exposure conditions that clearly induce alpha 2u-nephropathy in male F344 rats, no lesions, hyaline droplets, or alpha 2u were detectable in treated or control male NBR and female F344 rats. It is thus concluded that the presence of alpha 2u is causal to the development of renal disease in rats exposed to TMP, DCB, IP, UG, d-L, and lindane.

Plasma protein synthesis and secretion in the visceral yolk sac of the fetal rat: gene expression, protein synthesis and secretion

This report compares the relative levels of messenger RNA species coding for plasma proteins in rat visceral yolk sac and fetal liver from 12.5 days to 21.5 days gestation. Transthyretin, retinol-binding protein, transferrin and alpha 1-fetoprotein mRNAs were detected in both tissues, although relative levels were much higher in the yolk sac compared to fetal liver, in early gestation. Messenger RNA coding for the positive acute phase proteins thiostatin, fibrinogen, alpha 2-macroglobulin and alpha 1-antitrypsin were detected at a low but significant level in yolk sac, while the levels in fetal liver steadily increased from 16.5 days gestation and, with the exception of alpha 1-antitrypsin, reached levels higher than those found in adult liver just prior to birth. Albumin, inter-alpha 1-trypsin inhibitor, alpha 1-acid glycoprotein, haptoglobin, vitamin D-binding protein and ceruloplasmin messenger RNA levels were either very low or undetectable in yolk sac and fetal liver. Secretion of proteins by yolk sac endoderm occurred largely across the basolateral surface, i.e. towards the fetal compartment. These data support the hypothesis that one function of the yolk sac in the rat is the synthesis and secretion of a select group of plasma proteins to maintain homeostasis in the fetal compartment in the period before the fetal liver has matured sufficiently to carry out this function.

Effect of dihydrotestosterone on serum concentrations of alpha 2u-globulin and on spermatogenesis in melatonin-treated rats

Adult male rats were given s.c. injections of melatonin (400 micrograms/100 g body weight per day) for 14 days. On day 15, the weights of the testis and accessory sex organs were less, testicular 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity was inhibited, spermatogenesis was suppressed and serum levels of gonadotrophins, testosterone and alpha 2u-globulin were decreased compared with control animals injected with vehicle. In a third group of rats given the same dose of melatonin for 14 days, administration of dihydrotestosterone (DHT) at a dose of 25 micrograms/100 g body weight per day on days 8-14 resulted in serum levels of alpha 2u-globulin, FSH, LH and testosterone and testicular 17 beta-HSD activity similar to those seen in vehicle-injected control animals. Weights of the testes and accessory sex organs and spermatogenesis were normal after administration of DHT in melatonin-treated rats. In another group of rats, the depressive effects of melatonin treatment on plasma gonadotrophins were reversed by the administration of alpha 2u-globulin on days 8-14. It was concluded that treatment with DHT prevents the depressive action of melatonin on testicular function by inducing the synthesis of alpha 2u-globulin.

Armenian hamster female protein: a pentraxin under complex regulation

The serum of Armenian hamster (Cricetulus migratorius) contains a protein homologous to female protein (FP) that has been characterized in the Syrian (golden) hamster. Of unknown function, FP belongs to a family of proteins (called pentraxins) that have a common ancestral gene and are widely expressed in nature. Whereas serum concentration of FP in Syrian hamsters (SFP) is many fold greater (200- to 300-fold) in females vs. males, Armenian hamster FP (AFP) is only moderately elevated (approximately 3-fold) in female vs. males and only for the fall-winter months of the year. In the Armenian hamster testosterone administration to females or castration of males has no effect on AFP serum levels, whereas in Syrian hamster these treatments change SFP serum concentration to that characteristic of the opposite sex. Some sex steroid control of hepatic AFP synthesis is evident, however, as serum levels decrease after exogenous estrogen treatment. In contrast to Syrian hamster FP, normal levels of AFP are dependent on an intact hypophysial-pituitary axis and also are influenced by the season of the year. As an acute-phase protein, AFP responds in a typical fashion, with increasing serum levels detected in both sexes in contrast to the divergent sex-limited response in Syrian hamsters. Although AFP and SFP are similar structurally, morphologically, and antigenetically and share common binding specificities, the regulation of FP synthesis in Armenian hamster is very different from that previously found in Syrian hamster.

Differential in vitro transcription from the promoter of a rat alpha 2u globulin gene in liver and spleen nuclear extracts

When used in an in vitro transcription assay, the promoter of a cloned alpha 2u globulin gene is much more active in liver than in spleen nuclear extracts. Promoter deletion experiments suggest that both positive and negative regulatory mechanisms may be involved in the differential in vitro transcription from the alpha 2u globulin promoter in these two nuclear extracts. Interestingly, removal of promoter elements upstream from position -74 results in a significant increase of in vitro transcription in spleen but not in liver nuclear extracts, and thus reduces the difference in transcription observed with longer alpha 2u promoters in these two extracts. Deletion of additional nucleotides to position -43 strongly reduces the in vitro transcription efficiency of the promoter in extracts from both tissues. None of the examined promoters containing between 3000 and 22 nucleotides of 5' flanking regions are differentially transcribed in liver nuclear extracts from either male or female rats. Thus, in contrast to cell-type specificity, sex-specificity could not be observed in our in vitro transcription experiments. DNase I protection experiments with crude nuclear extracts and partially or highly purified nuclear proteins suggests the presence of six recognition sites for DNA-binding factors between the TATA element and position -210. Some of these factors could be identified as proteins that also bind to elements within the albumin gene promoter.

Human inter-alpha-trypsin inhibitor. Synthesis and maturation in hepatoma HepG2 cells

In hepatoma HepG2 cells, human inter-alpha-trypsin inhibitor (ITI) was synthesized as three heavy chains, H-1 (100 kDa), H-2 (110 kDa) and H-3 (113 kDa), and light hybrid chain (49.5 kDa) composed of alpha 1-microglobulin and HI-30 (ITI derivative, human inhibitor of 30 kDa). The association of at least two heavy chains, H-1 and H-3, with the HI-30 part of the light chain gave rise to a molecule similar to serum ITI. A composite protein (approximately 250 kDa) including heavy and light chains was also secreted, while alpha 1-microglobulin and ITI H-2 protein were released as separate entities. Light chain synthesis could be the limiting factor for ITI maturation.

Rapid postexposure decay of alpha 2u-globulin and hyaline droplets in the kidneys of gasoline-treated male rats

Unleaded gasoline induces nephropathy, characterized by rapid accumulation of hyaline (protein resorption) droplets in epithelial cells of the renal proximal convoluted tubules, only in male rats. The hepatic synthesis of the male rat-specific protein alpha 2u-globulin, a constituent of renal hyaline droplets, is unaltered by gasoline treatment (Olson et al., 1987). Renal alpha 2u-globulin content increased to 210% of control within 18 h of a single oral dose of gasoline (2.0 ml/kg); maximal levels (320% of control) were attained following gasoline administration for 3 d. Increases in renal alpha 2u-globulin caused by gasoline were accompanied by concurrent proliferation of hyaline droplets. However, within 3 d of terminating gasoline administration renal alpha 2u-globulin content decreased to the same level as that in unexposed rats, although renal hyaline droplet number returned to pretreatment levels somewhat more slowly. The conjoint effect of postexposure recovery and estradiol (an inhibitor of hepatic alpha 2u-globulin synthesis) administration was also determined in male rats. On postexposure d 3, 6, and 9, estradiol treatment (1 mg/kg, sc, 4 d, starting on d 9 of gasoline treatment) decreased renal alpha 2u-globulin content to 75%, 59%, and 48%, respectively, of that in rats allowed to recover from gasoline with no hormone treatment. Hepatic alpha 2u-globulin content in estradiol-treated rats was decreased by 74%, 97%, and 96% at the same intervals. Estradiol treatment during recovery from gasoline also appeared to increase the removal of accumulated hyaline droplets from the renal cortex. Thus, accumulation of alpha 2u-globulin-containing hyaline droplets after subacute exposure of male rats to gasoline is rapidly reversible, dependent on continuous exposure to gasoline and maintenance of the normal rate of hepatic alpha 2u-globulin synthesis. These results emphasize the dynamic state of renal cortical hyaline droplets and suggest strongly that gasoline hydrocarbons cause hyaline droplet accumulation by prolonging the half-time of degradation of alpha 2u-globulin.

Changes in transcriptional activity and matrix association of alpha 2u-globulin gene family in the rat liver during maturation and aging

Hepatic synthesis of alpha 2u-globulin in the male rat begins at puberty (about 40 days), reaches a peak level at about 80 days, and ceases at about 750-800 days of age. The age-dependent changes in alpha 2u-globulin synthesis are correlated with both the steady-state level of the hepatic mRNA for this protein and the rate of transcription of the alpha 2u-globulin gene family. Transcriptional activation of the alpha 2u-globulin gene family at puberty and cessation of transcription at senescence correlate with the association and dissociation of this gene domain with the nuclear matrix. Unlike the alpha 2u-globulin gene, the albumin gene in the liver shows preferential association with the nuclear matrix throughout the life. From these results we conclude that the age-dependent changes in alpha 2u-globulin synthesis are due to the alteration in the rate of transcription of the alpha 2u-globulin gene, and that the association of this gene domain to the nuclear matrix is a prerequisite to its transcriptional activation.

Rapid androgenic stimulation of alpha 2u-globulin synthesis in the perfused rat liver

Hepatic synthesis of alpha 2u-globulin and its mRNA in the male rat is dependent on androgen, glucocorticoid, T4, insulin, and GH. Some of these hormones may act directly on the liver, while others may influence alpha 2u-globulin synthesis through indirect physiological changes. In the present study the specific role of androgen in the synthesis of alpha 2u-globulin was examined in an in vitro liver perfusion system. The addition of 5 alpha-dihydrotestosterone to the medium perfused through livers from castrated rats resulted in a rapid increase (approximately 10-fold over the vehicle control within 120 min) in the circulating level of alpha 2u globulin. Labeling with [35S]-methionine showed that the androgen-mediated increase in the circulating level of alpha 2u-globulin is due to release of the newly synthesized protein. Quantification of alpha 2u-globulin mRNA in the perfused livers with and without androgen supplementation indicated that the increased mRNA level can only partially account for the elevation of the circulating level of this protein. From these results it is concluded that androgen can act directly on the liver to stimulate alpha 2u-globulin synthesis, and the hormone may influence more than one regulatory step.

Independent regulatory influence of growth hormone on the hepatic synthesis of alpha 2u-globulin

Administration of GH through sc injections to hypophysectomized male rats induces the hepatic mRNA for alpha 2u-globulin (a male-specific urinary protein) from an undetectable level to 43.4% of the normal male level. The same treatment administered to hypophysectomized-gonadectomized rats and androgen-insensitive Tfm rats induces alpha 2u-globulin mRNA to a level of only 5-10% of that in the normal male. However, none of these types of animals shows an appreciable response when GH is administered continuously through osmotic minipumps. Perfusion of the livers derived from hypophysectomized male rats with the blood from hypothyroid rabbits (also deficient in GH) was used to examine in vitro effects of GH on alpha 2u-globulin synthesis. Supplementation of the perfusion medium with GH and T4 failed to induce alpha 2u-globulin within the perfusion period of 120 min. These results show that GH can influence alpha 2u-globulin synthesis independent of the androgen and that the mode of administration of GH plays an important role in its biological response.

Effect of age and dietary restriction on the expression of alpha 2u-globulin

The effect of aging on the expression of alpha 2u-globulin was studied in liver tissue from 6-30-month-old male Fischer F344 rats. The synthesis of alpha 2u-globulin by suspensions of isolated hepatocytes decreased 90% between 6 and 22 months of age. The levels of alpha 2u-globulin mRNA and the transcription of alpha 2u-globulin genes by isolated liver nuclei decreased 80-85% between 5 and 24 months of age. Because alpha 2u-globulin has been suggested to be a "senescence marker protein," the expression of alpha 2u-globulin was measured in rats fed a diet restricted in calories. This dietary restriction procedure has been shown to increase significantly the longevity of rodents. The expression of alpha 2u-globulin was compared in liver tissue from 18-month-old rats fed ad libitum and a restricted diet (40% restriction of total calories). The synthesis, mRNA levels, and transcription of alpha 2u-globulin were 1.8-3-fold higher for liver tissue from restricted rats compared to liver tissue from rats fed ad libitum. Therefore, dietary restriction alters the age-related change in the expression of alpha 2u-globulin. Our results demonstrate that the changes in alpha 2u-globulin expression that arise during aging or dietary restriction are regulated at the level of transcription.

Sex-independent synthesis of alpha 2u-globulin and its messenger ribonucleic acid in the rat preputial gland: biochemical and immunocytochemical analyses

alpha 2u-Globulin is the principal urinary protein of the mature male rat. The major urinary source of this protein is the liver where it is synthesized and secreted by hepatocytes under hormonal regulation. High levels of alpha 2u-globulin and its messenger RNA (mRNA) are also present in the preputial gland of both male and female rats, and neither castration nor ovariectomy significantly alters the preputial concentration of this protein and its mRNA. Per unit mass of RNA and protein, the preputial gland as compared to liver contains about 3-fold higher level of alpha 2u-globulin mRNA and about 300-fold higher level of alpha 2u-globulin. Despite a 3-fold (300%) difference in the content of alpha 2u-globulin mRNA, nuclear run-off experiments show only a 30% higher rate of alpha 2u-globulin gene transcription in the preputial gland than in the liver. Immunocytochemical analyses reveal that the liver possesses two alpha 2u-globulin cell populations, one showing higher immunoreactivity than the other. In contrast, the preputial gland contains only one type of alpha 2u-globulin containing acinar cells, and a large amount of alpha 2u-globulin accumulates in the ductal lumen. From these results we conclude that the 300% higher level of alpha 2u-globulin mRNA in the preputial gland is not due to a corresponding difference in the rate of transcription of alpha 2u-globulin gene. Such a difference may represent tissue-specific regulation at a posttranscriptional level of mRNA metabolism. Furthermore, the huge difference in the alpha 2u-globulin content of the preputial gland and the liver is primarily due to the cellular and ductal accumulation of this protein in the preputial gland vs. its rapid secretion by the liver.