Bradykinin and Kininogens in Bovine Milk

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Assessment of the potential allergenicity of a Milk Basic Protein fraction

BACKGROUND

A specific basic fraction of bovine milk, termed Milk Basic Protein (MBP), has the potential to provide nutritionally important benefits if used as a food ingredient. Although derived from milk, MBP is intended for use as an ingredient in other foods. Cows' milk is a well studied, commonly allergenic food. Although the proteins in MBP are not identified as milk allergens, food products containing MBP will be labelled as containing milk as a caution to milk allergic consumers under food labelling guidelines in the US and the European Union as MBP has not been demonstrated to be free of milk allergens. However, as part of an overall safety evaluation of MBP, the developers sought to evaluate the potential allergenicity of the primary protein components for characteristics of allergenic food proteins and to assess whether intake of these proteins at intended use levels could present a significant new allergenic risk for consumers.

OBJECTIVE

To evaluate the potential allergenicity of the five identified proteins in MBP. While extensive studies have not demonstrated allergenicity of lactoferrin, the four other proteins are less studied. The four were tested here by sequence identity comparison to known allergens, and for stability of these proteins in acidic pepsin as a characteristic common to many food allergens.

METHODS

Sequences of the proteins were compared to those listed in AllergenOnline.com, by methods recommended for the evaluation of proteins introduced in crops through genetic engineering. Pepsin stability was assessed by incubating the various proteins in simulated gastric fluid at pH 1.2 with porcine pepsin for up to 60 min at 37 degrees C, with samples withdrawn and analyzed at specific times.

RESULTS

No significant sequence similarities were identified for the MBP proteins compared to known allergens. All but one of the protein components of MBP were digested relatively quickly by pepsin. The more stable protein will be of low abundance as consumed in contrast to most pepsin-stable food allergens.

CONCLUSIONS

Based on molecular characteristics and expected exposure, the protein components in MBP are unlikely to present any increased risk of allergy for milk allergic subjects or of cross-reactivity for other allergic subjects. However, since the proteins are derived from milk, products containing MBP will need to be labelled as containing milk proteins to warn milk allergic subjects of the potential risk of allergic reactions.

The Fragments of Bovine High Molecular Weight Kininogen Promote Osteoblast Proliferation In Vitro

High molecular weight (HMW) kininogen is known to be a large plasma protein and cleaved by plasma proteinase kallikrein, then it generates four fragments in the blood coagulation cascade: heavy chain, bradykinin, fragment 1.2, and light chain. The fragment 1.2 has also been found in the basic protein fraction of bovine milk as a bioactive protein which promotes osteoblast proliferation. The milk basic protein has been shown to be a multi functional edible protein which promotes bone formation and inhibits bone resorption. In the present study, we purified the fragment 1.2 from bovine plasma and assessed it could promote osteoblast proliferation and posses the activity after pepsin digestion. Purified plasma HMW kininogen did not promote the proliferation, however, the kallikrein-cleaved HMW kininogen promoted the proliferation. The fragment 1.2, purified from the proteolysate, also promoted the proliferation. The pepsin digestion was performed according to the method of the assessment of allergenesity of genetically modified crops. After pepsin digestion, the fragment 1.2 generated resistant fragments and showed the promoting activity of osteoblast proliferation. These results suggest that the enzymatically-digested fragments of bovine HMW kininogen are able to be a naturally occurred active protein that promotes the bone formation by oral administration.

The release and vascular action of bradykinin in the isolated perfused bovine udder

It has been postulated that the mammary kinin system may play a role in modulating mammary blood flow. Until the present study, the local release of bradykinin (BK) or other kinin system constituents into the mammary vasculature had not been reported and there were also conflicting findings on the action of BK on udder vasculature. Udders were removed from healthy lactating cows at slaughter. Pairs of ipsilateral quarters were perfused with Tyrode solution through the external pudendalis artery and drained via the cranial superficial epigastric vein. Mammary secretion was collected through teat cannulae. The perfusion pressure was linearly related to perfusate flux between 60 and 210 ml min(-1) and the flow rate was adjusted (110-150 ml min(-1)) to give a basal pressure of 85 mmHg. PO2, PCO2 and pH in the venous effluent perfusate stabilised at 157 +/- 10 mmHg, 50.1 +/- 2.4 mmHg and 7.1 +/- 0.03, respectively. The venous effluent contained immunoreactive BK and BK precursor, tissue kallikrein activity, and bradykinin-destroying enzyme. The concentration of BK stabilised at 378 +/- 48 pg (ml perfusate)(-1), that of trypsin-activated BK precursor was 679 +/- 59 pg BK equivalents ml(-1) and that of tissue kallikrein, measured as cleavage of D-Val.Leu.Arg-p-nitroanilide (D-Val.Leu.Arg-pNA), was 5.5 +/- 1.7 nmol p-NA h(-1) ml(-1). Arterial infusion of phenylephrine (0.49-490 microM) produced increases in perfusion pressure (vasoconstriction). Acetylcholine (ACh) (0.55-55 microM) and BK (0.1-10 microM) produced only vasodilatation. BK (EC50 = 1.00+/-0.04 microM) was a more potent vasodilator than ACh (EC50 = 9.57+/-0.49 microM). The basal BK concentration was 250 times below the threshold for vasoactivity. The udder produced a milk-like secretion, which was dependent on perfusate flow and contained a concentration of BK which remained unchanged from 60 to 180 min of perfusion (231 +/- 31 pg ml(-1)) unlike that in the venous effluent which doubled between 60 and 120 min. Thus, in addition to its secretion into milk, BK, together with its precursor and tissue kallikrein, is continuously released into the vasculature of the isolated, perfused, lactating bovine udder.

Serine protease inhibitor TPCK prevents Taxol-induced cell death and blocks c-Raf-1 and Bcl-2 phosphorylation in human breast carcinoma cells

The mechanism of Taxol-induced apoptosis was investigated in MCF-7 human breast carcinoma cells. Taxol-induced apoptosis was associated with phosphorylation of both c-Raf-1 and Bcl-2 and activation of ERK and JNK MAP kinases. The serine protease inhibitor N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) effectively blocked apoptosis, but N-p-tosyl-L-lysine chloromethyl ketone (TLCK), another serine protease inhibitor, was without effect. TPCK treatment also prevented phosphorylation of c-Raf-1 and Bcl-2 in response to Taxol treatment. The serine protease inhibitor did not alter JNK activity, but it enhanced Taxol-induced activation of ERK1/2. Treatment of cells with the inhibitor of MEK activation, PD98059, prevented Taxol-induced ERK activation both in the presence and absence of TPCK, but did not influence survival of either Taxol- or Taxol plus TPCK-treated cells. In addition, PD98059 had no effect on c-Raf-1 or Bcl-2 phosphorylation. Thus, while the Taxol-induced phosphorylations of c-Raf-1 and Bcl-2 proteins appear to be coupled, these events can be disassociated from ERK1/2 activation. In summary, these findings suggest that phosphorylation of c-Raf-1 and Bcl-2, but not ERK1/2, are important signaling events in Taxol-induced apoptosis of MCF-7 breast cancer cells and that a TPCK inhibitable protease(s) is required for these processes.

The release of bradykinin in bovine mastitis

The kinin peptides are released during inflammation and are amongst the most potent known mediators of vasodilatation, pain and oedema. Despite early reports of the presence of kinins in milk, no previous study has investigated the role of the kinin system in bovine mastitis. The present study indicated that mastitis was accompanied by raised levels of bradykinin (BK) in milk and the increased levels of BK correlated with the severity of mastitis. Raised BK levels in mastitic milk were not dependent on the presence of inflammatory cells, nor were they secondary to changes in blood levels of BK. In milk from sub-clinically inflamed quarters, BK was raised in those milks where Staphylococcus aureus (S. aureus) was isolated but not in those milks where no pathogen was isolated. Increasing S. aureus artificially, also caused an increase in the milk BK. Increases in milk BK were not restricted only to the mastitic quarters of the udder. In udders in which mastitis was detected in one or more quarters, BK increases were also detected in the apparently uninvolved quarters.

Activation of the complement system by synthetic DNA complexes: a potential barrier for intravenous gene delivery

We have examined the complement-activating properties of synthetic cationic molecules and their complexes with DNA. Commonly used gene delivery vehicles include complexes of DNA with polylysine of various chain lengths, transferrin-polylysine, a fifth-generation poly(amidoamine) (PAMAM) dendrimer, poly(ethyleneimine), and several cationic lipids (DOTAP, DC-Chol/DOPE, DOGS/DOPE, and DOTMA/DOPE). These agents activate the complement system to varying extents. Strong complement activation is seen with long-chain polylysines, the dendrimer, poly(ethyleneimine), and DOGS (half-maximal at about 3 microM amine content in the assay used). Compared to these compounds, the other cationic lipids (in liposome formulations) are weak activators of the complement system (half-maximal approximately 50-100 microM positive charge in assay). Complement activation by polylysine is strongly dependent on the chain length. Short-chain oligolysines are comparable to cationic lipids in their activation of complement. Incubation of these compounds with DNA to form complexes reduces complement activation in virtually all cases. The degree of complement activation by DNA complexes is strongly dependent on the ratio of polycation and DNA (expressed as the charge ratio) for polylysine, dendrimer, poly(ethyleneimine), and DOGS. To a lesser degree, charge ratio also influences complement activation by monovalent cationic lipid-DNA complexes. For polylysine-DNA complexes, complement activation can be considerably reduced by modifying the surface of preformed DNA complexes with polyethyleneglycol (half-maximal approximately 20 microM amine content). The data suggests that, by appropriate formulation of DNA complexes, complement activation can be minimized or even avoided. These findings should facilitate the search for DNA complex formulations appropriate for reproducible intravenous gene delivery.

Nonviral gene therapy: the promise of genes as pharmaceutical products

Although most research on gene therapy has focused on the use of recombinant viruses to deliver genes to cells in vivo, progress also has been made toward developing nonviral, pharmaceutical formulations of genes for in vivo human therapy. Various methods for nonviral gene therapy have been proposed. Some approaches are aimed at developing "artificial viruses" that attempt to mimic the process of viral infection using synthetic materials. Others apply the theory and methods of advanced, particulate drug delivery to deliver DNA to select somatic targets. These approaches employ DNA complexes containing lipid, protein, peptide, or polymeric carriers as well as ligands capable of targeting the DNA complex to cell-surface receptors on the target cell and ligands for directing the intracellular trafficking of DNA to the nucleus. Nonviral systems have been used to deliver genes to the lung, liver, endothelium, epithelium, and tumor cells and have been shown to be generally safe. More than a dozen clinical trials are currently underway using nonviral systems for disease indications including cystic fibrosis and cancer. Future advances in nonviral systems will be based on an emerging appreciation of the biological constraints on the fate and function of DNA within the body and within the cell.

Gene expression following direct injection of DNA into liver

The liver is an attractive target tissue for gene therapy. Current approaches for hepatic gene delivery include retroviral and adenoviral vectors, liposome/DNA, and peptide/DNA complexes. This study describes a technique for direct injection of DNA into liver that led to significant gene expression. Gene expression was characterized in both rats and cats following injection of plasmid DNA encoding several different proteins. Luciferase activity was measured after injection of plasmid DNA encoding the luciferase gene (pCMVL), beta-galactosidase (beta-Gal) activity was evaluated in situ using plasmid DNA encoding Lac Z (pCMV beta), and serum concentration of secreted human alpha-1-antitrypsin was measured following injection of plasmid DNA encoding this protein (pRC/CMV-sHAT). Several variables, including injection technique, DNA dose, and DNA diluent, were investigated. Direct injection of pCMVL resulted in maximal luciferase expression at 24-48 hr. beta-Gal staining demonstrated that the majority of transfected hepatocytes were located near the injection site. Significant concentrations of human alpha-1-antitrypsin were detected in the serum of animals injected with pRC/CMV-sHAT. These findings demonstrate the general principle that direct injection of plasmid DNA into liver can lead to significant gene expression.

Overexpression of human methylmalonyl CoA mutase in mice after in vivo gene transfer with asialoglycoprotein/polylysine/DNA complexes

Methylmalonic acidemia resulting from genetic deficiency of methylmalonyl CoA mutase (MCM) is an often fatal metabolic disease. Somatic gene therapy for this disorder may require gene replacement in the liver. We describe overexpression of MCM in the liver of mice after in vivo gene delivery using asialoglycoprotein/polylysine/DNA (ASO/PL/DNA) targeted delivery to the liver of plasmids expressing recombinant MCM. After intravenous administration of the ASO/PL/DNA complex, the vector sequences are cleared from the blood with t1/2 = 2.5 min and > 95% of the vector is taken up by the liver. Vector sequences are cleared from the liver with t1/2 = 1.0-1.3 hr. MCM enzyme activity in the liver increases to levels 30-40% over baseline 6-24 hr after injection. No acute or chronic toxicity was observed. This net level of expression is likely to be therapeutic for MCM if the complex could be administered repetitively to treat acute episodes of life-threatening acidosis or establish a steady-state level of MCM activity. Repetitive administration of the ASO/PL/DNA complexes in mice was associated with formation of antibodies against asialo-orosomucoid and the asialo-orosomucoid complex but not against DNA.

Multicompartment, numerical model of cellular events in the pharmacokinetics of gene therapies

DNA expression vectors may be administered to patients like conventional medicines to have a finite and controlled duration of action. The clinical application of these medicines will require a precise understanding of the kinetics of the administered gene, the mRNA transcript, and the gene product. The apparent kinetic properties of the therapeutic gene product, including the level and duration of action, will be determined by various intrinsic kinetic processes including: (i) distribution and biological fate of the DNA expression vector; (ii) rates of DNA uptake into cells and dynamics of intracellular trafficking; (iii) half-life of the DNA vector in the cell; (iv) transcription rate; (v) half-life of mRNA; (vi) translation rate; and (vii) post-translational processing, distribution, and fate of the gene product. To consider in a theoretical manner how the intrinsic kinetics of cellular processes may affect the apparent level of a therapeutic gene product over time, we have constructed a multicompartment, numerical model. The model has six compartments, designated MILIEU, ENDOSOME, CELL, RNA, PROTEIN, and PRODUCT. The apparent level and kinetics of the gene product over time are calculated with different values for the intrinsic t1/2 of DNA in the MILIEU, ENDOSOME, and CELL; the intrinsic t1/2 of mRNA; the intrinsic t1/2 of the gene product; endosomal stability; and transcription rate. The model demonstrates how first-order kinetics can result from the summation of complex kinetic processes and provides a theoretical basis for future pharmacokinetic studies. This theoretical model illustrates how the half-lives of DNA, RNA, and gene product each affect the level of the product and highlights strategies for enhancing the therapeutic profile of gene therapies.

The plasminogen activation system in bovine milk: differential localization of tissue-type plasminogen activator and urokinase in milk fractions is caused by binding to casein and urokinase receptor

We have analyzed the occurrence of components of the plasminogen activation system in bovine milk. Zymographic analyses showed that tissue-type plasminogen activator (t-PA) occurred in association with casein micelles, partially as a complex with type-1 plasminogen activator inhibitor (PAI-1), whereas urokinase-type plasminogen activator (u-PA) was confined to milk leukocytes. Whey contained a component with a plasminogen dependent proteolytic activity which was shown to be plasma prekallikrein (PPK). The u-PA in the milk leukocytes was shown to be bound to urokinase receptor (u-PAR). A purification to near-homogeneity of the bovine u-PAR was undertaken. Investigating the novel t-PA binding to casein micelles by ligand blotting and Sepharose immobilized casein, multimeric forms of kappa-casein and dimeric alpha s2-casein were identified as t-PA binding components. The kappa-casein gene and the fibrinogen gene are believed to have evolved from a common ancestor. Thus, the recent finding that casein enhances t-PA catalyzed plasminogen activation (Marcus, G., Hitt, S., Harvey, S.R. and Tritsch, G.L. (1993) Fibrinolysis 7, 229-236), and the observed t-PA/casein binding suggests that the casein micelle, which also contains plasminogen, may serve as a matrix for t-PA-catalyzed plasminogen activation in milk.

Galactosylated histone-mediated gene transfer and expression

We have developed a novel, highly efficient DNA delivery system to accomplish gene transfer through the asialoglycoprotein receptor-mediated endocytosis pathway. Natural nuclear DNA-binding proteins, the histones (H1, H2a, H2b, H3, and H4), were modified and used as receptor-targeted DNA carriers. Galactosylated with a coupling agent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, the histones and albumin were conjugated to DNA and then used to transfect HepG2 cells, which display the asialoglycoprotein receptor. The extent of galactosylation was determined for all histone subgroups and albumin with 14C-labeled galactose. A reporter gene for the bacterial chloramphenicol acetyltransferase (CAT), under the control of the 5' long terminal repeat (LTR) of Rous sarcoma virus, was used for comparisons of transfection efficiency of various carrier proteins. The CAT activity resulting from histone H1-mediated transfection was 1.66 unit per 10(6) cells, the highest among histone subgroups. The galactyosylated histone H1 was also eleven times more effective than the asialo-orosomucoid-polylysine. Ten galactosyl units are attached to histone H1 by the galactosylation reaction. Differences in the extent of galactosylation could not explain different transfection efficiencies among various proteins studied in this report. Treatment with galactose oxidase abolished the transfection ability of both the galactosylated histone H1 and asialo-orosomucoid. The intrinsic DNA-binding domains and nuclear location signal sequences are unique to histones as receptor-targeted DNA carriers, and are advantageous for effective gene delivery.

Gene transfer in regenerating muscle

We have compared the efficiency of direct gene transfer in normal and regenerating rat skeletal muscle. Muscle necrosis and regeneration was induced by intramuscular injection of bupivacaine in the soleus muscle of adult rats. Plasmids containing beta-galactosidase (beta-gal) or chloramphenicol acetyltransferase (CAT) genes driven by viral promoters were injected 3 days after bupivacaine treatment into the regenerating and the contralateral uninjured muscles. Expression of CAT activity was > 80-fold higher in regenerating compared to control muscles at 7 days post-transfection, but decreased at 30 and 60 days. Southern blot analysis showed that the predominant form of CAT DNA was episomal in transfected muscles; however, CAT activity measurements performed on the same transfected muscles showed no precise correlation between enzymatic activity and amount of plasmid DNA. Expression of beta-gal was detected in numerous regenerating fibers of the injured soleus muscles at 7 days post-transfection; in contrast, only rare positive fibers were found in control muscles. Focal infiltrates of mononuclear cells, which surround and invade selectively beta-gal-positive fiber segments, were observed at 30 days post-transfection, suggesting that immune mechanisms are implicated in the progressive loss of transgenes with time. The finding that regenerating muscle fibers display a higher efficiency of transfection may be relevant to gene therapy of Duchenne muscular dystrophy, because regenerating fibers are numerous in the early stages of the disease.

Factors in ruminant colostrum that influence cell growth and murine IgE antibody responses

Bovine colostrum was investigated as a source of biologically active molecules capable of stimulating the growth of mammalian cells in culture and modifying the immune response in a murine model. An extract prepared from bovine colostral whey by cation exchange and reversed-phase chromatography stimulated the growth of L6 rat myoblasts, Balb/c-3T3 mouse fibroblasts and BHK-21 baby hamster kidney cells with equal or greater potency than fetal bovine serum. Fractionation of the bovine colostral extract by gel-permeation chromatography in M-acetic acid identified a number of cell-growth factors for each cell type. Bovine colostral extract was compared with an ovine colostral whey preparation for its ability to modulate IgE antibody responses in mice. Doses of 8 and 4 mg/d of ovine colostral whey or bovine colostral extract specifically suppressed IgE antibody responses, whereas at lower doses suppression did not occur. We conclude that bovine colostrum contains cell-growth factors as well as immunomodulatory factors that are able to regulate the IgE response in a heterologous species.

Evaluation of relative promoter strength in primary hepatocytes using optimized lipofection

For most genetic deficiencies manifested in the liver, maximization of gene expression in hepatocytes will be an important factor in achieving successful gene therapy. A rapid, highly efficient, and nontoxic method for transfecting DNA into hepatocytes was used to compare directly promoter strengths of various cellular and viral promoters. Conditions are described here for transfecting 5-10% of primary hepatocytes using the positively charged liposomes, Lipofectin. Cells are not damaged by this method as they continue to transcribe genes controlled by liver specific promoters and can survive for over 2 weeks in culture. We find that the cytomegalovirus, SR alpha, and beta-actin promoters are more active than the SV40, RSV, RNA polymerase II, albumin, alpha 1-antitrypsin, or phosphoenolpyruvate carboxykinase promoters. A simple TK promoter and a TK promoter with the polyoma enhancer (MCI) were almost completely inactive. This information will be useful in the construction of vectors designed to express genes efficiently in primary hepatocytes for purposes of gene therapy, although the stability of expression from these promoters will need to be demonstrated in hepatocytes in vivo.

Neuroendocrine peptides in milk

Milk, which is a mammal-specific biologic fluid, contains several neuroendocrine peptides at concentrations higher than those found in plasma. These neuroendocrine peptides can be synthesized or processed in the mammary gland or excreted into milk through various pathways. In addition, certain milk proteins, notably casein, can be enzymatically processed to release "exorphins," peptides with opioid activities. In suckling mammals, hormones and neuropeptides are absorbed through the gastrointestinal tract and appear intact in the plasma. This absorption is age dependent and could have physiologic significance in neonatal development.