Inhalation of concentrated particulate matter produces pulmonary inflammation and systemic biological effects in compromised rats.

Although significant progress has been made over the past few years, there is still debate on the causal fractions that are responsible for particulate matter (PM)-associated adverse health effects. A series of 1-d inhalation exposures to concentrated ambient particles (CAPs) were performed in compromised rats, focusing on pulmonary inflammation and changes in blood factors as biological outcomes. Studies were carried out in The Netherlands at an urban background location in Bilthoven, an industrialized location in the city of Utrecht, as well as at a location that is heavily dominated by freeway emissions. It was hypothesized that exposure to CAPs resulted in oxidative stress in the lung, producing a release of inflammatory mediators, which in turn can result in cardiovascular effects. Both spontaneously hypertensive rats and rats preexposed to ozone were studied. The effects were studied at 2d postexposure, focusing on pathology and cell proliferation, bronchoalveolar lavage fluid (BALF) analysis (including cytokines, biochemistry, cell differentials, cell viability and proliferation, and Clara-cell 16 protein), and blood analyses (fibrinogen, Clara-cell 16 protein, Von Willebrand factor, and cell differentials). Using CAPs exposures as a binary term, mild inflammation (increased numbers of neutrophils) and increased lung permeability (protein and albumin leakage in BALF) were evident. In addition, CAPs also produced increased fibrinogen concentrations in blood of spontaneously hypertensive rats. In conclusion, inhalation up to 3700 microg/m3 CAPs in the size range of 0.15-2.5 microm did induce statistically significant effects in the lung and blood, but the effects observed may not potentially be very biologically relevant. PM mass concentrations and lung permeability were weakly associated. This suggests that other PM metrics might be more appropriate.

Recombinant bovine uteroglobin at 1.6 A resolution: a preliminary X-ray crystallographic analysis.

Uteroglobin (UG) is a conserved protein which is induced by progesterone and secreted by the epithelia of various mammalian reproductive and respiratory organs. Recombinant bovine uteroglobin (recbUG), consisting of 80 amino acids with a C-terminal His6 tag, was overexpressed in Escherichia coli and purified. The protein was crystallized in two geometric forms, rhomboid and cuneate (wedge-shaped), by the hanging-drop vapour-diffusion method at 295 K. The rhomboid crystals diffracted to a maximum resolution of 1.6 A using synchrotron radiation. These crystals belong to space group P2(1)2(1)2, with unit-cell parameters a = 81.42, b = 82.82, c = 45.26 A, and contain four monomers per asymmetric unit. The cuneate crystals diffracted to 2.35 A resolution using a rotating-anode generator. These crystals belong to space group C222(1), with unit-cell parameters a = 43.39, b = 93.94, c = 77.30 A, and contain two molecules per asymmetric unit.

Lys 43 and Asp 46 in alpha-helix 3 of uteroglobin are essential for its phospholipase A2 inhibitory activity.

Uteroglobin (UG) is an anti-inflammatory, secreted protein with soluble phospholipase A2 (sPLA2)-inhibitory activity. However, the mechanism by which UG inhibits sPLA2 activity is unknown. UG is a homodimer in which each of the 70-amino acid subunits forms four alpha-helices. We previously reported that sPLA2-inhibitory activity of UG may reside in a segment of alpha-helix 3 that is exposed to the solvent. In addition, it has been suggested that UG may inhibit sPLA2 activity by binding and sequestering Ca++, essential for sPLA2 activation. By site-specific mutation, we demonstrate here that Lys 43 Glu, Asp 46 Lys or a combination of the two mutations in the full-length, recombinant human UG (rhUG) abrogates its sPLA2-inhibitory activity. We demonstrate further that recombinant UG does not bind Ca++ although when it is expressed with histidine-tag (H-tag) it is capable of binding Ca++. Taken together our results show that: (i) Lys 43 and Asp 46 in rhUG are critical residues for the sPLA2-inhibitory activity of UG and (ii) Ca++-sequestration by rhUG is not likely to be one of the mechanisms responsible for its sPLA2-inhibitory activity.

Purification and characterization of the mammaglobin/lipophilin B complex, a promising diagnostic marker for breast cancer.

Mammaglobin, a promising diagnostic marker for breast cancer, forms a covalent complex with lipophilin B. mRNA levels for each component of the complex were determined for a number of breast tumors and normal tissues, and correlation of message expression was highly significant between mammaglobin and lipophilin B (p < 0.0001). The complex was purified by both standard biochemical techniques and immunoaffinity chromatography. N-Terminal sequencing revealed that mammaglobin and lipophilin B are processed as predicted by cleavage of their signal sequence after amino acids 19 and 21, respectively. Three molecular masses-representing the fully glycosylated form, the complex without one of the carbohydrate chains, and the deglycosylated proteins-are detected by ProteinChip array SELDI-TOF mass spectrometry after partial enzymatic deglycosylation. This is consistent with the two predicted N-linked glycosylation sites in the primary sequence of mammaglobin and each site having an attached sugar of approximately 3500 Da. Reducing agents release lipophilin B from mammaglobin, and the free peptides are seen at their predicted molecular masses in the deglycosylated complex. Molecular modeling, secondary structure prediction, and circular dichroism indicate that the complex is a small alpha-helical globule that has three disulfide bridges and a carbohydrate chain at each pole. LC-ESI-MS shows that mammaglobin and lipophilin B are bonded in a head to tail orientation. This work describes the biochemistry of the mammaglobin/lipophilin B complex and lays the framework for use of this complex as a novel protein-based serological marker for breast cancer.

Mammaglobin is found in breast tissue as a complex with BU101.

The mammaglobin gene has been shown to be preferentially expressed in breast tissue. Few genes match its specificity. Mammaglobin has generated much interest, and studies are ongoing to develop diagnostic tests for breast cancer based on the detection of mammaglobin. While searching the Incyte Genomics Lifeseq database for tissue-specific markers, we observed a second secretoglobin, BU101, also known as lipophilin B. We report here that mammaglobin, in breast tissue, is found as a complex with BU101. The complex was isolated from breast cancer tissue and was characterized as the biologically relevant form of mammaglobin.

Discovery and perspectives from the blastokinin era.

The events and rationalizations that led to one discovery of the rabbit uterine protein, then called blastokinin, are narrated in historical perspective and related to the independent discovery of the same protein, named uteroglobin. The period when the name "blastokinin" remained in partial use, roughly from the original publication in 1967 until the early 1980s, is considered here as the blastokinin era. Subsequent perspectives, originating from the era, are presented on the hormonal regulation of blastokinin, as well as its distribution, biological function, and potential relationships with other entities that exist coincidentally.

Cloning and sequencing of the cDNA coding for pig pre-uteroglobin/Clara cell 10 kDa protein.

Using reverse transcription-polymerase chain reaction (RT-PCR) on pig lung mRNAs, we have cloned and sequenced an almost full-length complementary DNA (cDNA) coding for pig pre-uteroglobin/Clara cell 10 kDa protein (UG/CC10), a major secretory protein of lung Clara cells. The deduced amino acid sequence indicated a preprotein of 91 residues, 21 of which corresponded to the signal peptide. Comparison of the sequence with those of known pre-UG/CC10 from other species indicated that the pig protein resembles the structure shared by human and Lagomorpha pre-UG/CC10 but differ from the proteins from Rodentia that are composed of 96 aminoacids and contain signal peptides of 19 residues. Some amino acids, that form part of a hydrophobic pocket inside the mature protein, are well conserved in all UG/CC10 suggesting an important function of this cavity. Northern analysis indicated that pig UG/CC10 mRNA is abundant in lung but is not detectable in liver, uterus or epididymis. The results are discussed in relation to a possible physiological function of UG/CC10.

Surfactant-producing rabbit pulmonary alveolar type II cells synthesize and secrete an antiinflammatory protein, uteroglobin.

Neonatal respiratory distress syndrome (RDS) caused by surfactant deficiency is a common disorder in premature infants. Exogenous surfactant therapy improves survival in infants with RDS. However, the phospholipid component of the surfactant has been suggested to be inactivated by a phospholipid hydrolyzing enzyme, phospholipase A2 (PLA2). Although alveolar type II cells produce the surfactant, it is not known whether these cells have any mechanism to protect surfactant from PLA2 hydrolysis. Since alveolar Clara cells express uteroglobin (UG), a PLA2 inhibitory and antiinflammatory protein, and since it has been suggested that alveolar type II cells are derived from Clara cells, we sought to elucidate whether type II cells are also capable of expressing UG gene. By using radioimmunoassay, immunoprecipitation and Western blotting techniques we demonstrate for the first time that type II cells, isolated from mature rabbit lungs, synthesize and secrete UG. The transcription of the UG gene was detected by in situ hybridization using rabbit UG cDNA probe. These results imply that UG, synthesized by type II cells, may protect both endogenous and exogenous surfactant from PLA2 hydrolysis. Moreover, the antiinflammatory properties of UG may prevent the development of chronic inflammatory lung disease, a frequent complication of RDS.

Purified uteroglobin lacks anti-proteinase activity.

Rabbit uteroglobin was purified from both uterine fluids and lung lavages by a combination of gel filtration and ion-exchange column chromatography. Anti-trypsin and anti-papain activities were measured in the fractions of the eluates. Anti-proteinase activities were detected in minor contaminants eluting close to the uteroglobin peak but the protein itself was devoid of anti-proteinase activity. Ion-exchange-purified uteroglobin also lacked inhibitory activity of elastase, chymotrypsin or subtilisin. The presence of contaminants could explain the anti-proteinase activity reported occasionally for uteroglobin.

High level bacterial expression of uteroglobin, a dimeric eukaryotic protein with two interchain disulfide bridges, in its natural quaternary structure.

Bacterial expression of eukaryotic proteins is a tool of ever-increasing importance in biochemistry and molecular biology. However, the majority of the recombinant eukaryotic proteins that have been expressed in bacteria are produced as fusion proteins and not in their native conformation. In particular, correct formation of quaternary structures by recombinant proteins in bacterial hosts has been reported very rarely. To our knowledge, correct intracellular formation of multimeric structures containing more than one interchain disulfide bridge has not been reported so far. We have constructed three plasmids which are able to direct expression of recombinant rabbit uteroglobin, a homodimeric protein with two interchain disulfide bridges, in Escherichia coli. Among these, the plasmid pLE103-1, in which the expression of recombinant uteroglobin is controlled by a bacteriophage T7 late promoter, is by far the most efficient. With pLE103-1, recombinant uteroglobin production reached about 10% of total bacterial soluble proteins. This protein accumulated in bacterial cells in dimeric form, as it is naturally found in the rabbit uterus. Recombinant uteroglobin was purified to near-homogeneity and its NH2-terminal amino acid sequence was confirmed to be identical to that of its natural counterpart, except for 2 Ala residues the codons for which were added during the plasmid construction. This protein was found to be as active a phospholipase A2 inhibitor as natural uteroglobin on a molar basis. To our knowledge, this is the first report of high level bacterial expression of a full length eukaryotic homodimeric protein with two interchain disulfide bridges in its natural, biologically active form. The plasmid pLE103-1 may be useful to explore structure-function relationships of rabbit uteroglobin. In addition, this plasmid may be useful in obtaining high level bacterial expression of other eukaryotic proteins with quaternary structure, as well as for other general applications requiring efficient bacterial expression of cDNAs.

Recombinant rabbit uteroglobin expressed at high levels in E. coli forms stable dimers and binds progesterone.

In order to express uteroglobin in Escherichia coli we have constructed a DNA coding for complete mature rabbit uteroglobin by fusing genomic sequences from the second exon of the gene to an incomplete cDNA. This DNA was inserted into various positions of the polylinker cloning region of pDS expression vectors and the uteroglobin gene was expressed in E. coli by IPTG induction. Four different uteroglobin-derived proteins were produced containing 1, 3, 5 and 7 more N-terminal amino acids than the naturally occurring mature protein. The yield of soluble protein strongly increased with increasing length of the N-terminal additions. Protein and RNA analysis showed that this variation is most likely due to progressively higher translation efficiencies of the larger recombinants. UG7, the most efficiently synthesized recombinant protein, carrying seven additional N-terminal amino acids, was purified and further characterized. Like natural uteroglobin, UG7 forms a dimer and binds progesterone with an affinity indistinguishable to the natural protein. This bacterially produced protein can be used for detailed structure-function investigations of uteroglobin.

Purification of uteroglobin using monospecific antibodies coupled to divinylsulphone-activated agarose.

As a model for the isolation of a labile or trace protein, the purification of uteroglobin (UGL) by immunoaffinity chromatography is described. Antibody was isolated from sheep antiserum by immunoprecipitation, and coupled to divinylsulphone-activated agarose (Mini Leak). For the immunoabsorption stage rabbit uterine mucosal scrapings were defatted and incubated directly with the immunosorbent. After washing and desorption, the UGL preparation contained relatively few high molecular weight impurities and these were removed by gel chromatography. Purification was monitored at each step by two-dimensional SDS polyacrylamide gel electrophoresis and immunoelectrophoresis. Furthermore, affinity-purified UGL was tritiated with N-succinimidyl[2,3-3H]propionate and assayed by fluorography. In order to determine absolute UGL concentrations a competitive ELISA was developed.

Expression of a uteroglobin-like protein in human prostate.

Phospholipase A2 (PLA2) is a key enzyme that initiates the arachidonic acid cascade responsible for the synthesis of prostaglandins and leukotrienes, compounds well known for their inflammatory properties. Inhibition of this enzyme may modulate prostaglandin and leukotriene tissue levels. Uteroglobin is a potent PLA2 inhibitor found in rabbit uterus, prostate, seminal vesicle, and tracheobronchial tree. Tissue from ten human patients undergoing prostatectomy was examined for presence of a uteroglobin-like protein. Seven patients underwent transurethral resection and three had an open prostatectomy. Preoperative diagnosis in nine of the 10 patients was benign prostatic hypertrophy. One suspected, poorly differentiated, adenocarcinoma was confirmed and one unsuspected, well differentiated, adenocarcinoma was discovered. Specimens were submitted for Western blot, electron microscopy with immunogold staining, radioimmunoassay, and immunofluorescence. Six patients had evidence of uteroglobin-like protein, three with high levels (greater than or equal to 1000 pg./mg. protein), two with moderate levels (75 to 250 pg.), one with a low level (less than or equal to 75 pg.). Uteroglobin-like protein was present in all three patients who underwent open prostatectomy and in three of the seven patients with transurethral resections. The uteroglobin-like protein level was 2.5 to five times greater in both prostatic utricle specimens. All four assays corroborated these results. Because rabbit uteroglobin coats sperm and masks spermatic antigenicity in the rabbit female genital tract, this report of biochemical and immunological evidence for uteroglobin-like protein in the human prostate may have implications for human male fertility.

Isolation and characterization of uteroglobin from the lung of the hare (Lepus capensis).

Uteroglobin has been purified from hare lung by gel filtration and chromatography on carboxymethyl-cellulose. Hare uteroglobin appears homogeneous by electrophoresis under both denaturing and nondenaturing conditions. Its chemical and immunological properties as well as its ability to bind progesterone are compared to those of rabbit uteroglobin. The two proteins have the same N-terminal residue (glycine) and both lack tryptophan but differ in amino acid composition. Sodium dodecyl sulfate-gel electrophoresis shows that hare uteroglobin is composed of two subunits of identical Mr (about 7000) held together by disulfide bridges. The amino acid composition indicates a subunit composed of 65-67 residues, which is compatible with the apparent Mr observed. Thus, hare uteroglobin appears to be slightly smaller than the rabbit protein. Hare uteroglobin partially reacts with anti-rabbit uteroglobin in a radioimmunoassay and also binds progesterone, although this binding is relatively unaffected by dithiothreitol. The synthesis of hare uteroglobin in the uterus appears to be rather insensitive to ovarian steroid hormones.

Studies on proteins identical to male and female genital tract secretions.

Rabbit seminal plasma and rabbit uterine fluid six days post coitum were used for disc-electrophoretical and immunological studies. With an antiserum, that was partially neutralized with normal rabbit serum and the uterine fluid, in the seminal plasma four groups of antigens could be demonstrated: antigens of type E, occurring in the seminal plasma only, antigens of type EU, occurring in the seminal plasma and the uterine fluid, antigens of type ES, occurring in the seminal plasma and the serum, and antigens of type EUS, occurring in the seminal plasma, the uterine fluid and the serum. Special consideration of the EU-antigen group exhibited five proteins: with biochemical methods four of them could be identified as uteroglobin, seminal plasma acid glycoprotein, a proteinase, and an alkaline phosphatase.

Role of uteroglobin and transglutaminase in masking the antigenicity of implanting rabbit embryos.

Using rabbit as a model, the roles of uteroglobin (UG) and transglutaminase (TG) in masking the antigenicity of early developing mammalian embryo have been investigated. Maternal lymphocytes in vitro, when mixed with mitomycin-C inactivated blastomeres, incorporated H3-thymidine, suggesting recognition of embryonic antigens by these cells. However, pretreatment of blastomeres with pregnant uterine fluid (PUF) or with UG alone or in combination with TG (coagulation factor XIIIa), resulted in a significant and dose-dependent suppression of H3-thymidine incorporation into these lymphocytes. A complete suppression was achieved at a concentration of 250 micrograms of UG/ml, in the absence of TG. However, in the presence of TG, only 1.0 micrograms of UG/ml was required for total suppression. Neither nonpregnant uterine fluid (NPUF), nor myoglobin, a nonspecific protein similar in molecular weight to UG, had any suppressive effect. Incubation of uteroglobin with anti-UG or TG with its antiserum prior to the pretreatment of blastomeres eliminated the suppressive effect of these proteins. Inhibition of TG by neopentyl chloroethyl nitrosourea (NPCNU) also eliminated the suppressive effects of uteroglobin on H3-thymidine incorporation into maternal lymphocytes. These results suggest that in the pregnant uterus UG in conjunction with TG may play a specific role in masking the antigenicity of developing embryos during implantation.

Purification of human alpha uterine protein.

Human alpha uterine protein (AUP) has been prepared from extracts of decudua by antibody affinity chromatography, DEAE Sepharose chromatography and by filtration through Sephadex G-150. This procedure yielded a protein fraction containing AUP, which was labelled with 125I by chloramine T. When analysed by SDS gel electrophoresis this radioiodinated protein fraction was found to contain predominantly a single species of protein which was precipitated by antibodies against AUP in antibody-antigen crossed electrophoresis. Rabbit anti-AUP precipitated 55-65% of the tracer in a double-antibody system. Sephadex G150 gel filtration of AUP obtained before and after affinity chromatography provided a molecular weight estimate of 50000. Since SDS gel electrophoresis revealed a polypeptide molecular weight of 23000-25000, it is suggested that AUP is a dimer.

Characteristics of the purified uteroglobin-like protein from rabbit lung.

A uteroglobin-like protein was prepared from lung extracts of female rabbits by absorption to immobilized anti-uteroglobin immunoglobulin and purified to homogeneity by gel filtration on Sephacryl S-200. The final preparation is indistinguishable from uteroglobin according to its behaviour in Ouchterlony double-diffusion, polyacrylamide gel electrophoresis under denaturing and non-denaturing conditions, ultraviolet spectrum, tryptic peptide analysis, and progesterone-binding properties. Progesterone binding to the lung protein exhibits an affinity similar to that observed with authentic uteroglobin and is equally enhanced by reduction of the protein with dithiothreitol. Competition experiments with non-radioactive steroids demonstrate a similar steroid-specificity for both proteins. Progesterone binding causes a perturbation in the ultraviolet absorbance of tyrosine residues of the lung protein similar to that observed with uteroglobin. These data suggest that the proteins prepared from both sources are biochemically identical.