Human epidermal growth factor-on molecular forms present in urine and blood

The endosomal transcriptional regulator RNF11 integrates degradation and transport of EGFR

Maintenance of EGFR plasma membrane levels is critical for cell functioning. Scharaw et al. demonstrate that endosomal RNF11 is required for transcriptional up-regulation of COPII components, specifically facilitating EGFR transport in response to its lysosomal degradation after EGF stimulation.

Stimulation of cells with epidermal growth factor (EGF) induces internalization and partial degradation of the EGF receptor (EGFR) by the endo-lysosomal pathway. For continuous cell functioning, EGFR plasma membrane levels are maintained by transporting newly synthesized EGFRs to the cell surface. The regulation of this process is largely unknown. In this study, we find that EGF stimulation specifically increases the transport efficiency of newly synthesized EGFRs from the endoplasmic reticulum to the plasma membrane. This coincides with an up-regulation of the inner coat protein complex II (COPII) components SEC23B, SEC24B, and SEC24D, which we show to be specifically required for EGFR transport. Up-regulation of these COPII components requires the transcriptional regulator RNF11, which localizes to early endosomes and appears additionally in the cell nucleus upon continuous EGF stimulation. Collectively, our work identifies a new regulatory mechanism that integrates the degradation and transport of EGFR in order to maintain its physiological levels at the plasma membrane.

Characterization of human epidermal growth factor in human serum and urine under native conditions

The objective of this study was to investigate the molecular nature of the human epidermal growth factor (EGF) in serum and urine samples of normal subjects. Recombinant EGF emerged as a single peak and did not interact with human IgG1 and albumin up to the concentration of 12 microg/ml. Freshly separated human serum contained only trace amounts of EGF. However, EGF appeared and increased in serum separated from blood after spontaneous overnight clotting. The authentic 6 kDa form of EGF made up nearly 40% of the total EGF in serum and revealed relatively homogeneous feature. The remaining immunoreactive fractions corresponded to 160 kDa proEGF. Immunoreactive EGF in blood seemed to be associated with the EGF release from platelets. TSKgel G3000SW chromatography of freshly-voided morning and day urines revealed that urine samples mainly contained two major form of EGF; a high-molecular-weight (HMW) and low-molecular-weight (LMW) forms. In the sense of molecular nature of EGF contents, morning urine was more heterogeneous than day urine of the same individuals. The LMW form of EGF in morning urine, in which its proportion was more than 90% of the total EGF, revealed further heterogeneous feature generally containing three to four different components.

Ras mutation impairs epithelial barrier function to a wide range of nonelectrolytes

Although ras mutations have been shown to affect epithelial architecture and polarity, their role in altering tight junctions remains unclear. Transfection of a valine-12 mutated ras construct into LLC-PK1 renal epithelia produces leakiness of tight junctions to certain types of solutes. Transepithelial permeability of D-mannitol increases sixfold but transepithelial electrical resistance increases >40%. This indicates decreased paracellular permeability to NaCl but increased permeability to nonelectrolytes. Permeability increases to D-mannitol (Mr 182), polyethylene glycol (Mr 4000), and 10,000-Mr methylated dextran but not to 2,000,000-Mr methylated dextran. This implies a "ceiling" on the size of solutes that can cross a ras-mutated epithelial barrier and therefore that the increased permeability is not due to loss of cells or junctions. Although the abundance of claudin-2 declined to undetectable levels in the ras-overexpressing cells compared with vector controls, levels of occludin and claudins 1, 4, and 7 increased. The abundance of claudins-3 and -5 remained unchanged. An increase in extracellular signal-regulated kinase-2 phosphorylation suggests that the downstream effects on the tight junction may be due to changes in the mitogen-activated protein kinase signaling pathway. These selective changes in permeability may influence tumorigenesis by the types of solutes now able to cross the epithelial barrier.

Epidermal Growth Factor Induction of Phenotype-dependent Cell Cycle Arrest in Vascular Smooth Muscle Cells Is through the Mitogen-activated Protein Kinase Pathway

The heterogeneity of vascular smooth muscle cells is well established in tissue culture, but their differential responses to growth factors are not completely defined. We wished to identify effects of epidermal growth factor (EGF) on vascular smooth muscle cells in distinct phenotypes, such as spindle and epithelioid. We found that the EGF receptors were abundant in epithelioid cells but not spindle cells. EGF treatment inhibited serum-independent DNA synthesis, which was absent in spindle cells, of epithelioid cells. Additionally, using a pulse-chase assay, we found that bromodeoxyuridine-labeled cells failed to re-enter the S phase in the presence of EGF. These EGF effects were abolished by either inhibiting the EGF receptor tyrosine kinase with AG1478 or inhibiting the mitogen-activated protein kinase pathway with PD98059. In response to treatment with EGF, the EGF receptor was phosphorylated, which was correlated with phosphorylation and activation of p42/44 mitogen-activated protein kinases. Inhibition of EGF receptor phosphorylation and mitogen-activated protein kinase activation resulted in a reversal of the EGF-induced inhibition of bromodeoxyuridine incorporation and cell cycle arrest. Subsequent studies revealed that the activation of the EGF receptor and the mitogen-activated protein kinase pathway in epithelioid cells induced expression of the cell cycle inhibitory protein p27Kip1 but not p21Cip1. Taken together, our data demonstrate that the EGF receptor is abundantly expressed in epithelioid vascular smooth muscle cells and that the activation of this receptor results in cell cycle arrest through activation of the mitogen-activated protein kinase pathway.

Sialometrical and sialochemical analysis of patients with chronic graft-versus-host disease--a prolonged study

Patients with graft-versus-host disease (cGVHD) suffer from oral dryness and increased levels of oral infections and mucosal pathologies. The purpose of the current study was dual: 1) to investigate the salivary functional (sialometry) and compositional (sialochemistry) alterations induced by the disease during a 12-month period following the onset of the disease; and 2) to evaluate the effect of Salagen 30 mg/d on the salivary biochemical and immunological composition in cGVHD patients. Significant higher concentrations of salivary sodium (Na), magnesium (Mg), total protein (TP), albumin (Alb), epidermal growth factor (EGF), and total IgG accompanied by a concomitant increase in total IgA that did not reach significant value was observed in cGVHD patients in comparison with controls at both resting and stimulated conditions (p < 0.05) while salivary levels of potassium (K), calcium (Ca), and phosphate (P) were not altered. Two weeks of oral Salagen 30 mg/d resulted in normalization of the salivary biochemical and immunological compositional alterations in the cGVHD patients. Oral pilocarpine was able to reduce and normalize the elevated levels of Na, Mg, TP, Alb, EGF, IgG, and IgA salivary concentrations at both resting and stimulated conditions. The ability of oral pilocarpine to normalize and reverse salivary biochemical and immunological alterations induced by cGVHD is parallel to its stimulatory effect on salivary flow rates, as we previously showed. As the biochemical and immunological composition of the saliva results in its antimicrobial protective characteristics, the ability of oral pilocarpine (Salagen) to abrogate cGVHD salivary gland abnormalities may be of clinical importance.

Saliva analysis in the clinical setting: revisiting an underused diagnostic tool

BACKGROUND

One purpose of this study was to compare various biochemical and immunological parameters in blood and saliva that are routinely evaluated only in the blood for general medical requirements. Another purpose was to concomitantly compare these and other oral/salivary parameters differentially in whole, parotid, and submandibular and sublingual saliva to examine the source of those parameters and their specific concentrations.

METHODS

Twelve healthy individuals (6 women, 6 men) were examined in the blood-saliva comparison study, and 30 healthy individuals (15 women, 15 men) were studied in the intersalivary comparison study.

RESULTS

On the basis of the results we obtained, we suggest a classification scheme using a whole saliva compositional profile as a diagnostic tool in the evaluation of systemic and/or local pathologies. This system may be used to analyze various components of saliva beyond those analyzed in this study, thereby increasing the clinician's ability to locate and assess specific pathologies. We also suggest that consideration be given to the use of compositional saliva analysis in the diagnosis of general medical conditions in which there is a high correlation between the salivary and blood concentrations of relevant components.

CONCLUSION

We think that saliva analysis is a useful, worthwhile diagnostic tool because saliva collection is noninvasive, easy, and inexpensive and may be performed by the patient with no need for the involvement of medical personnel, if so desired.

Possible autocrine loop of the epidermal growth factor system in patients with benign prostatic hyperplasia treated with finasteride: a placebo-controlled randomized study

OBJECTIVE

To analyse the expression of the epidermal growth factor (EGF) system in prostate tissue and secretions obtained from patients with benign prostatic hyperplasia (BPH) treated with or without finasteride (which primarily targets the androgen-sensitive secretory epithelial cells in the prostate, with little effect on basal epithelial and stromal cells).

PATIENTS AND METHODS

The expression of the EGF system was evaluated by enzyme-linked immunosorbent assay and immunohistochemistry in samples of prostate tissue and secretions from patients with BPH randomized for treatment with finasteride or placebo for 3 months before surgery.

RESULTS

Prostate tissue expressed the EGF receptor (HER1) and HER2, and the ligands EGF, transforming growth factor alpha (TGFalpha), heparin-binding (HB) EGF, betacellulin and amphiregulin. Treatment with finasteride produced greater concentrations of amphiregulin (P < 0.05) than did placebo, did not change the level of TGFalpha, HER1 and HER2, and tended to decrease the concentration of EGF, betacellulin and HB-EGF in prostate tissue. Using immunohistochemistry, HER1 and TGFalpha were both localized to the basal epithelial cells, and there was a strong positive correlation among the tissue concentrations of HER1, HER2 and TGFalpha. Amphiregulin localized to the luminal secretory epithelium. Prostate secretions contained only EGF, which was at levels approximately 150 times higher than in prostate tissue; treatment with finasteride did not affect the concentration of EGF in prostate secretion.

CONCLUSIONS

There were only minor changes in the expression of TGFalpha, HER1 and HER2 after finasteride treatment. This may represent an important system for the continuous growth and homeostasis of the androgen-independent basal epithelial cells in the prostate.

Delivery of neurotrophic factors to the central nervous system: pharmacokinetic considerations

Neurotrophic factors are proteins with considerable potential in the treatment of central nervous system (CNS) diseases and traumatic injuries. However, a significant challenge to their clinical use is the difficulty associated with delivering these proteins to the CNS. Neurotrophic factors are hydrophilic, typically basic, monomeric or dimeric proteins, mostly in the size range of 5 to 30 kDa. Neurotrophic factors potently support the development, growth and survival of neurons, eliciting biological effects at concentrations in the nanomolar to femtomolar range. They are not orally bioavailable and the blood-brain and blood-cerebrospinal fluid barriers severely limit their ability to enter into and act on sites in the CNS following parenteral systemic routes of administration. Most neurotrophic factors have short in vivo half-lives and poor pharmacokinetic profiles. Their access to the CNS is restricted by rapid enzymatic inactivation, multiple clearance processes, potential immunogenicity and sequestration by binding proteins and other components of the blood and peripheral tissues. The development of targeted drug delivery strategies for neurotrophic factors will probably determine their clinical effectiveness for CNS conditions. Achieving significant CNS target site concentrations while limiting systemic exposure and distribution to peripheral sites of action will lessen unwanted pleiotropic effects and toxicity. Local introduction of neurotrophic factors into the CNS intraparenchymally by direct injection/infusion or by implantation of delivery vectors such as polymer matrices or genetically modified cells yields the highest degree of targeting, but is limited by diffusion restrictions and invasiveness. Delivery of neurotrophic factors into the cerebrospinal fluid (CSF) following intracerebroventricular or intrathecal administration is less invasive and allows access to a much wider area of the CNS through CSF circulation pathways. However, diffusional and cellular barriers to penetration into surrounding CNS tissue and significant clearance of CSF into the venous and lymphatic circulation are also limiting. Unconventional delivery strategies such as intranasal administration may offer some degree of CNS targeting with minimal invasiveness. This review presents a summary of the neurotrophic factors and their indications for CNS disorders, their physicochemical characteristics and the different approaches that have been attempted or suggested for their delivery to the CNS. Future directions for further research such as the potential for CNS disease treatment utilising combinations of neurotrophic factors, displacement strategies, small molecule mimetics, chimaeric molecules and gene therapy are also discussed.

The effect of pilocarpine on salivary constituents in patients with chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a complex clinical entity with various target organs, including the salivary glands. Oral pilocarpine (Salagen(R)), 30 mg/day, can ameliorate cGVHD-induced xerostomia and improve the flow rate from the major salivary glands. The purpose here was to evaluate the effect of this drug at 30 mg/day on salivary biochemical and immunological composition in cGVHD patients. Significantly higher concentrations of salivary sodium (Na), magnesium (Mg), total protein, albumin, epidermal growth factor (EGF) and total IgG, accompanied by a concomitant increase in total IgA which did not reach significance, were observed in cGVHD patients in comparison with controls, in both resting and stimulated conditions (p < 0.05), while salivary potassium, calcium and phosphate were not altered. Two weeks of oral pilocarpine, at 30 mg/day, resulted in normalization of the altered salivary biochemical and immunological composition in the cGVHD patients. Oral pilocarpine was able to reduce and normalise the elevated Na, Mg, total protein, albumin, EGF, IgG and IgA concentrations in both resting and stimulated conditions. The ability of oral pilocarpine to normalise and reverse the salivary biochemical and immunological alterations induced by cGVHD parallels its known stimulatory effect on salivary flow rates. As the biochemical and immunological composition of saliva provides its protective antimicrobial characteristics, the ability of pilocarpine to abrogate cGVHD salivary gland abnormalities may be of clinical significance.

Urinary excretion of Tamm-Horsfall protein and epidermal growth factor in chronic nephropathy

Tamm-Horsfall protein (THP) and epidermal growth factor (EGF) are both synthesized by tubular cells in the distal part of the nephron and excreted with the urine. The present study examines the urinary excretion rates of the two peptides in relation to functional tubular markers in patients with chronic nephropathy. Four groups of patients with moderate to severely reduced renal function were studied: glomerulonephritis (n = 10), diabetic nephropathy (n = 11), tubulointerstitial nephropathy (n = 13), and polycystic kidney disease (n = 8). The renal function was evaluated by glomerular filtration rate (GFR) as an indicator for the general renal function, lithium clearance (C(Li)) as an indicator for proximal tubular function, and absolute distal reabsorption of sodium (ADR(Na)) as an indicator for distal tubular function. The excretion rate of EGF was rather closely correlated with GFR, C(Li) and ADR(Na) (Spearman coefficients of variation 0.88, 0.69, and 0.74, respectively). The correlations between the excretion rate of THP and GFR, C(Li) and ADR(Na) were weaker (Spearman coefficients of variation 0.68, 0.42, and 0.44). When the effect of GFR had been accounted for by multiple variance analyses, the excretion rates of the two peptides were still associated with ADR(Na) but not with C(Li). In conclusion, the urinary excretion rates of especially EGF but also those of THP were correlated with renal function and distal tubular reabsorption of sodium in patients with chronic nephropathy.

Quantitation of the mRNA expression of the epidermal growth factor system: selective induction of heparin-binding epidermal growth factor-like growth factor and amphiregulin expression by growth factor stimulation of prostate stromal cells

The epidermal growth factor (EGF) system is a rapidly expanding system of growth factors involved in many aspects of normal and cancerous growth. We have developed a method for the quantitation of mRNA coding for all six growth factors activating the human EGF receptor (HER-1) and for the quantitation of mRNA for the receptors HER-1 and its preferred dimerization partner, HER-2. The method is based on the generation of specific RNA standards, which are amplified by reverse transcriptase-polymerase chain reaction (RT-PCR) with the sample RNA and a set of calibrators. The resulting calibration curve is used to quantitate the unknown samples, which require only a single RT-PCR reaction. Our method has the advantage that quantitation is based on coamplification of an internal RNA standard, thereby controlling both the PCR and RT reactions. In addition, the RNA standards for all growth factors and receptors are combined in a single RT reaction, which minimizes variation and allows the quantitation of all eight mRNA species with only 0.1 microg RNA. This makes the method suitable for studies in which the supply of material is limited. The developed method has enabled us to demonstrate that prostate stromal cells in primary culture express EGF, heparin-binding EGF (HB-EGF), amphiregulin, betacellulin, and epiregulin as well as the HER-1 and HER-2 receptors, whereas no transforming growth factor-alpha mRNA is found. Furthermore, activation of the EGF system in these cells by stimulation with HB-EGF or EGF in mitogenic doses causes a selective increase in the expression of amphiregulin and HB-EGF mRNA (more than 15-fold and 25-fold, respectively), whereas there is no increase in the expression of mRNA for the other growth factors or receptors. In accord with the increase in amphiregulin mRNA, the amount of amphiregulin peptide released from the cells is also increased. The selective induction of amphiregulin and HB-EGF by growth factor stimulation may represent a mechanism to amplify the initial growth factor signal in prostate stromal cells.

Synthesis and properties of an EGF-like domain (residues 361-406) in the extreme N-terminal region of the mouse EGF precursor

Various proteins contain EGF-like domains that are not ligands for the EGF receptor. In the present study a cognate polypeptide for residues 361-406 of the mouse EGF precursor was synthesized by the solid-phase method. The product was renatured under oxidative conditions since it probably has an EGF-like array of three cystine disulfide bonds in its native state. HPLC analysis of the renaturation reaction revealed formation of a peak material with no apparent free-SH groups. Accordingly, the HPLC retention time of this product was readily increased by treatment (reduction of disulfides) with dithiothreitol. The renatured 46-mer (PEGF-1) did not displace 125I-EGF bound to rat liver membranes and 125I-PEGF-1 did not exhibit specific binding to membrane preparations from the mouse liver, mammary gland, or kidney, with or without Ca2+ in the binding medium. Although PEGF-1 contains a putative Ca2+ binding motif, specific binding of this cation by the polypeptide could not be demonstrated by electromobility shiff or incubation with 45Ca2+. Immunoassay of PEGF-1 and EGF in fractions obtained following gel filtration of mouse urine revealed multiple peaks of PEGF-1 immunoreactivity with the major peaks eluting at an Mr > 30 kDa. In contrast, virtually all the EGF immunoreactivity eluted at a volume similar to that of 125I-EGF. These data suggest that selective cleavage of the PEGF-1 domain from the precursor does not occur with the proclivity known for that of EGF. Instead, the PEGF-1 probably functions coordinately with other EGF-like domains while tethered to the precursor backbone. Finally, localization of PEGF-1 immunoreactivity occurred only in cell populations of the mouse previously demonstrated as sites for EGF/EGF precursor, which suggests that PEGF-1 is exclusively a domain of the EGF precursor.

Time-dependent changes of levels of endogenous epidermal growth factor in submandibular glands, in kidneys, and in urine in rats during systemic treatment with EGF

BACKGROUND

Exogenous EGF influences the levels of endogenous EGF differently in the submandibular glands (SMG) and the kidneys. The aim of the present study was to examine the time-dependent changes in levels of endogenous EGF during 1-4 weeks of EGF treatment.

METHODS

Female rats were allocated into five groups receiving EGF subcutaneously (150 microg/kg/day) for 0 (controls), 1, 2, 3 and 4 weeks prior to sacrifice at an age of 12 weeks. At the end of the study period, 24-h urine samples were collected.

RESULTS

The weight of the SMG increased during EGF treatment (303+/-33 (controls), 359+/-37 (1 week EGF, P < 0.01), 390+/-30 (4 weeks EGF, P < 0.001) (mg mean+/-S.D.)). The EGF content of the SMG was unchanged after 1 week but threefold decreased after 4 weeks of treatment, respectively. The expression of EGF mRNA was decreased after 1 and 4 weeks as assessed with in situ hybridization. The weight of the kidneys was unchanged after 1 week and increased after 4 weeks of treatment (828+/-105 mg (controls) vs. 935+/-44 mg (4 weeks EGF, P < 0.005)). The renal content and the urinary excretion of EGF were significantly increased by 20-30% only in the group treated for 4 weeks.

CONCLUSION

EGF treatment induces a time-dependent decrease in the EGF content in the SMG most likely by reducing the biosynthesis of endogenous EGF. In contrast, the EGF content in kidneys and in urine was unchanged after 1 week and increased after prolonged treatment.

Systemic treatment with epidermal growth factor causes organ growth concomitant with reduced circulating levels of IGF-I and IGFBP-3: time-dependent changes in female rats

Systemic treatment with epidermal growth factor (EGF) in neonatal rats reduces circulating levels of insulin-like growth factor I (IGF-I) and causes somatic growth retardation. In this study, we investigated the effects of EGF treatment on the IGF system and on visceral organ growth and longitudinal growth in mature rats. We treated female Wistar rats for 0 (n = 16), 1 (n = 8), 2 (n = 8), 3 (n = 8), or 4 (n = 8) weeks with subcutaneous EGF (150 microg/kg/day). The animals were weighed once a week. At sacrifice, various viscera were removed and weighed. Blood and serum samples obtained at sacrifice were analysed for growth hormone (GH), IGF-I, IGF binding proteins (IGFBPs) and various routine parameters. EGF treatment increased the total body weight. All parts of the gastrointestinal tract, the liver, the pancreas, the spleen, the bladder, the suprarenal glands and the ovaries increased proportionately more in weight than the increase in total body weight; the heart and the kidneys increased proportionately in weight whereas the weight of the perirenal fat was reduced. There were no changes in tail length but the mean length of the tibia was slightly increased in the group treated for 4 weeks with EGF. Circulating GH was unchanged but IGF-I and IGFBP-3 were reduced approximately 25 and 45%, respectively, in all EGF treated groups. There were no changes in the hepatic content of IGF-I and IGFBPs. In conclusion, systemic EGF treatment causes visceral growth concomitant with reduced circulating levels of IGF-I and IGFBP-3 in mature female rats.

Urinary excretion of epidermal growth factor and Tamm-Horsfall protein in three rat models with increased renal excretion of urine

Epidermal growth factor (EGF) and Tamm-Horsfall protein (THP) are synthesized in the kidneys by the distal tubular cells and excreted into urine. The urinary excretion of these peptides has been suggested as a potential index for distal tubular function. The urinary excretion rates of EGF and THP were examined in three groups of rats with increased renal excretion of urine: uninephrectomy, non-osmotic polyuria and diabetic osmotic polyuria. Twenty-four hour urine samples were obtained after 7, 14 and 21 days. The urinary volume per kidney was doubled in uninephrectomy when compared to controls. There was a seven-fold increase in urinary volume in rats with non-osmotic polyuria and diabetic osmotic polyuria, as compared to controls. Uninephrectomy, non-osmotic polyuria and diabetes all affected the urinary excretion of EGF and THP differently. The EGF excretion in uninephrectomized rats was 60-80% of that of the controls, whereas THP excretion was unchanged, indicating that EGF excretion varied with renal tissue mass. Non-osmotic polyuria caused a five-fold increase in THP excretion but no change in EGF excretion. THP excretion in the diabetic rats was increased three-fold after 21 days when compared to controls, whereas EGF excretion was decreased when expressed per kidney weight. Immunohistochemistry demonstrated that EGF and THP were colocalized in the thick ascending limbs of Henle's loops and distal tubules in all five groups of rats. In conclusion, the EGF excretion appears to follow renal tissue mass and seems independent of urinary volume, whereas THP excretion is dependent mainly on urinary volume. This has implications for the use of EGF and/or THP excretion rates as an indicator for distal tubular function.

The effects of chronic administration of epidermal growth factor (EGF) to rats on the levels of endogenous EGF in the submandibular glands and kidneys

Epidermal growth factor (EGF) is mainly produced in the submandibular glands (SMG) and in the kidneys. It has recently been reported that EGF-related ligands may induce their own biosynthesis (autoinduction) in vitro. In the present paper, we investigated whether chronic systemic treatment with EGF influenced the amount of endogenous EGF in the SMG and kidneys. Eight-week-old female Wistar rats were treated with subcutaneous injections of placebo (n = 16) or human recombinant EGF (150 micrograms/kg per day, n = 8) for 4 weeks. Urine was sampled the last 24 h of the study period. At the time of killing, the SMG and the kidneys were removed. The SMG was larger in the EGF-treated animals, 229.8 +/- 35.5 (mean +/- SD) mg than in the control animals, 181.7 +/- 18.1 mg (P < 0.01). The total EGF content was smaller (0.51 +/- 0.15 vs. 1.12 +/- 0.40 nmol EGF/SMG, P < 0.001). The kidneys were larger in the EGF-treated animals (1.38 +/- 0.08 vs. 1.28 +/- 0.08 g, P < 0.05), but the EGF content and urinary excretions were not changed. In conclusion, chronic systemic treatment with EGF causes growth of the SMG with concomitantly reduced contents of EGF, and growth of the kidneys with unchanged content and excretion of EGF. These findings suggest that EGF may play a part in the regulation of the growth of the SMG and in EGF biosynthesis.

Development and validation of two solid-phase enzyme immunoassays (ELISA) for quantitation of human epidermal growth factors (hEGFs)

PURPOSE

The purpose of the present investigation was to develop and validate two separate enzyme-linked immunosorbent assays (ELISA) for quantitation of exogenous human epidermal growth factor (hEGF1-53) and its truncated fragment (hEGF1-48) in rat plasma.

METHODS

The present assay systems were based on the sandwiching of the antigen between a monoclonal mouse anti-hEGF1-53 antibody, pre-coated on a 96-well polystyrene plate, and a polyclonal rabbit anti-hEGF1-48 antibody, which is then detected with a peroxidase-labeled goat anti-rabbit antibody.

RESULTS

The calibration curves for hEGF1-48 and hEGF1-53 in plasma were validated over a concentration range of 7.8-250 and 62.5-1000 pg/ml, respectively. Determined from replicate assays of hEGF1-48 quality control samples, the intra-assay precision and accuracy were < or = 8.8% RSD and within +/- 9.8%; and the inter-assay precision and accuracy were < or = 14.8% RSD and within +/- 9.7% RE, respectively. Determined from replicate assays of hEGF1-53 quality control samples, the intra-assay precision and accuracy were < or = 10.0% RSD and within +/- 8.5%; and the inter-assay precision and accuracy were < or = 10.0% RSD and within +/- 5.7% RE, respectively. The limit of quantitation of the hEGF1-48 and hEGF1-53 assay using 200 microliters plasma per well is 7.8 and 62.5 pg/ml, respectively. These two ELISA methods are specific to hEGFs and do not cross-react with mouse EGF or other growth factors (TGF alpha, TGF beta, PDGF, and FGF) or lymphokines (IL1 beta and TNF alpha). These validated methods have been routinely applied to assay of plasma samples from various pharmacokinetic studies in rats receiving intravenous hEGFs. Both assay methods were also adapted to assay endogenous hEGFs in biological fluids of different animal species.

CONCLUSIONS

Two sensitive ELISA methods have been validated for quantitation of hEGF1-53 and hEGF1-48 in rat plasma. Their utility has been demonstrated in the application of assaying immunoreactive concentration of exogenous and endogenous epidermal growth factors.

Chronic treatment with epidermal growth factor stimulates growth of the urinary tract in the rat

Twenty-four male Wistar rats, 8 weeks old, were allocated into three groups and treated with human recombinant epidermal growth factor (EGF) administered subcutaneously in doses of 0, 30, and 150 micrograms/kg per day for 4 weeks. Blood sampling was done every 2nd week and urine sampling was done for 2 consecutive days every week. The most striking finding was that the ureters were dose dependently enlarged, due to growth of all layers of the ureteric wall. The urothelium of the bladder showed considerable hyperplasticity with a widening of the basal proliferative compartment and a normal differentiation pattern as observed by the expression of carbohydrate epitopes, characterized with lectinohistochemistry. Blood examination revealed a decrease in blood haemoglobin concentration and a slight increase in serum creatinine concentration in the high-dose group. There were no effects of EGF on the urinary excretion of electrolytes, proteins, and endogenous EGF.

An immunoassay designed to quantitate different molecular forms of rat urinary epidermal growth factor with equimolar potency: application on fresh rat urine

Different molecular weight forms of epidermal growth factor (EGF) are present in vivo and this makes quantitation of EGF difficult. Most immunoassays employ antibodies against 6-kDa EGF, and such assays are likely to underestimate the amount of high molecular weight forms of EGF. The purpose of the present study was to develop a processing-independent ELISA which is able to quantitate different molecular forms of rat EGF with equimolar potency. Our "old ELISA" used two polyclonal antibodies against rat submandibular gland EGF as catching and detecting antibodies, and 6-kDa EGF purified from rat urine as calibrator. This assay was modified to a processing-independent ELISA by converting the different forms of EGF in the samples as well as the calibrator to the same immunoreactive form of EGF prior to analysis. This could be achieved by trypsinization because trypsin cleaved the different molecular forms of rat urinary EGF to a single immunoreactive form. We applied both the "old ELISA" and the processing-independent ELISA on different molecular forms of EGF and demonstrated that the "old ELISA" underestimated high molecular weight forms by two thirds. The relative amounts of high and low molecular weight forms of EGF in urine have been debated, since different results have been obtained by different techniques. In order to address the problem it is important to quantitate the different molecular forms with equimolar potency. Employing the processing-independent ELISA we find that high molecular weight forms of EGF constitute 40% and 6-kDa EGF 60% of EGF in fresh rat urine.

Immunohistochemical and quantitative changes in salivary EGF, amylase and haptocorrin following radiotherapy for oral cancer

Epidermal growth factor (EGF), amylase and haptocorrin are molecules produced in the salivary glands. The aim of the present study was to determine immunohistochemical and quantitative alterations in EGF as compared with haptocorrin and amylase following radiotherapy for oral cancer. Changes in the salivary secretion of EGF are of interest because of the importance of EGF in mucosal regeneration. Immunohistochemical studies on normal tissue from parotid and submandibular glands have demonstrated EGF in the serous acini with a tendency to single cell expression in the parotid gland. Amylase has been found in the serous acini of both the submandibular and parotid glands. Haptocorrin was localized in the duct system of both glands. In the submandibular glands with radiotherapy induced sialoadenitis only very few acini with weak or no staining for EGF and amylase were demonstrated, while no changes were observed in the staining for haptocorrin. Analysis on stimulated whole saliva samples collected from 20 healthy individuals and from 20 patients prior to, and 1, 2 and 3 weeks following radiotherapy showed significant reduction in salivary contents of EGF and amylase after treatment as expressed per g protein (p < 0.0002). The salivary content of haptocorrin increased significantly after treatment (p < 0.002). These alterations may be explained by the different cellular sites of the molecules studied, the serous acini being more sensitive to ionising radiation than the duct system. The concentration of EGF in saliva before treatment was significantly higher in patients than in the control group (p < 0.02), which may indicate that the tumors induce increased secretion of salivary EGF, or alternatively that the oral tumors contribute with EGF to the saliva. In conclusion we have demonstrated a reduction in the mitogenic peptide EGF both immunohistochemically and quantitatively following irradiation for oral cancer, results which may contribute to the understanding of the clinical signs of mucositis.

Urinary excretion of epidermal growth factor in living human kidney donors and their recipients

Epidermal growth factor (EGF) is a growth-promoting peptide that is synthesized in the distal tubules of the kidney and excreted in urine. EGF has been suggested to play a role in the repair after renal tissue damage, as well as in compensatory growth of the remaining kidney after uninephrectomy. The present study examined the urinary EGF excretion after uninephrectomy and transplantation among relatives. The urinary EGF excretion rate and the glomerular filtration rate (GFR) were followed for 26-54 days in 16 healthy kidney donors and nine recipients. After uninephrectomy the median urinary EGF excretion rate in the donors was not 50% of the pre-operative value, but around 65% (95% confidence limits of the median on the fifth post-operative day: 59-72%). This suggests that there is a compensatory increase in the EGF excretion rate from the remaining kidney of around 30% after uninephrectomy. A similar compensatory increase was demonstrated for GFR, indicating that the compensatory changes in EGF excretion rate and GFR might be correlated. In the transplanted kidneys, GFR was consistently around 15% lower and EGF excretion rate around 40% lower than in the corresponding kidneys remaining in the donors. This might reflect ischaemic and drug-induced damage of the transplanted kidneys. The present study demonstrated a compensatory increase of around 30% in urinary EGF excretion from the remaining kidney after uninephrectomy in healthy humans. Whether EGF plays a role in the adaptive processes in the remaining kidney or whether changes in EGF excretion are merely of a secondary nature is still uncertain.

Systemic treatment with recombinant human epidermal growth factor accelerates healing of sclerotherapy-induced esophageal ulcers and prevents esophageal stricture formations in pigs

Human epidermal growth factor (EGF), a small polypeptide (6 kDa) with mitogenic properties, has been implicated in the protection of gastrointestinal mucosal integrity. The efficacy of EGF in the prevention and healing of sclerotherapy-induced esophageal lesions was investigated in 24 minipigs with surgically induced portal hypertension. In addition, the effect of EGF on intragastric acidity and pharmacokinetics was investigated as possible means to explain its protective mechanism of action. The animals underwent three weekly sessions of sclerotherapy with polidocanol 2% and were concomitantly and for an additional three weeks treated with either placebo or EGF administered paravenously in the esophagus and/or subcutaneously. The subcutaneous treatment with EGF significantly (P < 0.05) reduced esophageal stricture and scar formations associated with sclerotherapy. Gastric pH values were significantly (P < 0.01) elevated only in animals receiving subcutaneous injections of EGF. Furthermore, the subcutaneous administration of EGF was associated with unexpected prolonged plasma concentration of the peptide. These results suggest a possible clinical value of EGF as an adjunctive treatment with the sclerotherapy.

Stimulation of DNA synthesis in rabbit bladder wall after partial outlet obstruction and acute overdistension

Partial outlet obstruction of the rabbit urethrovesical junction (UVJ) has been used to induce pathology in the urinary bladder characteristic of obstructive damage observed in humans. The purpose of the experiments reported here was to compare the 3H-thymidine (3H-TdR) labelling of DNA in urinary bladders of male New Zealand White (NZW) rabbits subjected to partial outlet obstruction or overdistension. A total of 18 animals was used. Two normal controls, and 12 partially obstructed animals (at 1 day [D], 3D, 5D, 7D, 14D, and 21D) were injected (i.v.) with 3H-TdR at a dose of 0.5 microCi/g body weight. An additional 4 were overdistended to volumes 120% of maximum intravesical pressure, immediately emptied via the catheter, and injected with 3H-TdR 24 hr (1D) later. All animals were sacrificed up to 3.5 hr after injection of the label. DNA-associated radioactivity reached a peak at 3D after obstruction and was reduced substantially by 5D, although the level of incorporation remained well above control levels out to 21D. Levels of 3H-TdR incorporation 1D after overdistension bladders were about half of that found 1D following partial obstruction. The distribution of 3H-TdR labelled DNA in tissues was demonstrated by radioautography of histologic sections. One day following obstruction, 3H-Tdr incorporation was localized in the urothelium. Labelling of urothelium subsequent to 1D was reduced but remained above control levels until 21D. Labelled smooth muscle nuclei were observed only in control and 3D bladders, and they were measured at similar frequencies. Labelling of both intrinsic connective tissue (ICT) (mucosal, submucosal, and mural) and extrinsic connective tissue (ECT) (serosal) peaked at 3D after obstruction and declined thereafter but not to control levels. Labelling of ECT was, of course, limited to those bladders in which ECT was present (i.e., 3-21D). While the distribution of labelled cells in radioautograms was more variable 1D after obstruction than 1D after overdistension, the general cellular and biochemical responses to overdistension, as measured by DNA synthesis, are similar to those observed after partial outlet obstruction. Since the first sequela of obstruction is acute distension, these data support the assertion that the initial overdistension of the bladder initiates the cellular response to obstruction.