epidermal-growth-factor and Polycystic-Kidney-Diseases

Members of the epidermal growth factor (EGF) family bind to ErbB (EGFR) family receptors which play an important role in the regulation of various fundamental cell processes including cell proliferation and differentiation. The normal rodent kidney has been shown to express at least three members of the ErbB receptor family and is a major site of EGF ligand synthesis. Polycystic kidney disease (PKD) is a group of diseases caused by mutations in single genes and is characterized by enlarged kidneys due to the formation of multiple cysts in both kidneys. Tubule cells proliferate, causing segmental dilation, in association with the abnormal deposition of several proteins. One of the first abnormalities described in cell biological studies of PKD pathogenesis was the abnormal mislocalization of the EGFR in cyst lining epithelial cells. The kidney collecting duct (CD) is predominantly an absorptive epithelium where electrogenic Na(+) entry is mediated by the epithelial Na(+) channel (ENaC). ENaC-mediated sodium absorption represents an important ion transport pathway in the CD that might be involved in the development of PKD. A role for EGF in the regulation of ENaC-mediated sodium absorption has been proposed. However, several investigations have reported contradictory results indicating opposite effects of EGF and its related factors on ENaC activity and sodium transport. Recent advances in understanding how proteins in the EGF family regulate the proliferation and sodium transport in normal and PKD epithelial cells are discussed here. This article is part of a Special Issue entitled: Polycystic Kidney Disease.

Topics: Animals; Cell Proliferation; Epidermal Growth Factor; Epithelial Cells; Epithelial Sodium Channels; ErbB Receptors; Humans; Ion Transport; Kidney; Models, Biological; Polycystic Kidney Diseases; Polycystic Kidney, Autosomal Dominant; Polycystic Kidney, Autosomal Recessive; Sodium; TRPP Cation Channels

Obstructive nephropathy is one of the most important causes of renal failure in infants and children, while polycystic kidney disease (PKD) is a major cause of renal failure in the adult population. This review summarizes the evidence that there may be a number of mechanisms common to the pathophysiology of both conditions. In animal models of obstructive nephropathy and PKD, the renal tubular expression of epidermal growth factor is suppressed, and expression of clusterin is increased, both of which suggest arrested maturation or dedifferentiation of the tubular cell. There is a marked increase in apoptosis of epithelial cells in dilated tubules, associated with an increase in apoptotic stimuli. The renin-angiotensin system is activated in both obstructive nephropathy and PKD, which may contribute to tubular atrophy and interstitial fibrosis, which characterize the progression of both conditions. Focal cystic dilatation of the tubule is found in obstructive nephropathy, while tubular obstruction is present in cystic kidney disease. It is therefore likely that elucidation of the effects of mechanical stretch on renal tubular epithelial cells will contribute to our understanding of both conditions.

Topics: Adult; Animals; Apoptosis; Child, Preschool; Epidermal Growth Factor; Humans; Infant; Kidney Diseases; Kidney Tubules; Polycystic Kidney Diseases; Renin-Angiotensin System; Ureteral Obstruction

Epidermal growth factor (EGF) is linked to the pathogenesis of polycystic kidney disease (PKD). We explored signaling pathways activated by EGF in orpk cilia (-) collecting duct cell line derived from a mouse model of PKD (hypomorph of the Tg737/Ift88 gene) with severely stunted cilia, and in a control orpk cilia (+) cell line with normal cilia. RT-PCR demonstrated mRNAs for EGF receptor subunits ErbB1, ErbB2, ErbB3, ErbB4, and mRNAs for Na(+)/H(+) exchangers (NHE), NHE-1, NHE-2, NHE-3, NHE-4, and NHE-5 in both cell lines. EGF stimulated proton efflux in both cell lines. This effect was significantly attenuated by MIA, 5-(n-methyl-N-isobutyl) amiloride, a selective inhibitor of NHE-1 and NHE-2, and orpk cilia (-) cells were more sensitive to MIA than control cells (P < 0.01). EGF significantly induced extracellular signal-regulated kinase (ERK) phosphorylation in both cilia (+) and cilia (-) cells (63.3 and 123.6%, respectively), but the effect was more pronounced in orpk cilia (-) cells (P < 0.01). MIA significantly attenuated EGF-induced ERK phosphorylation only in orpk cilia (-) cells (P < 0.01). EGF increased proliferation of orpk cilia (+) cells and orpk cilia (-) cells, respectively, and MIA at 1-5 μM attenuated EGF-induced proliferation in orpk cilia (-) cells without affecting proliferation of orpk cilia (+) cells. EGF-induced proliferation of both cell lines was significantly decreased by the EGFR tyrosine kinase inhibitor AG1478 and MEK inhibitor PD98059. These results suggest that EGF exerts mitogenic effects in the orpk cilia (-) cells via activation of growth-associated amiloride-sensitive NHEs and ERK.

Topics: Animals; Cell Line; Cell Proliferation; Cilia; Disease Models, Animal; Enzyme Activation; Epidermal Growth Factor; ErbB Receptors; Extracellular Signal-Regulated MAP Kinases; Isoenzymes; Kidney Tubules, Collecting; Mice; Mice, Transgenic; Phosphorylation; Polycystic Kidney Diseases; Protein Kinase Inhibitors; RNA, Messenger; Signal Transduction; Sodium-Hydrogen Exchangers; Transfection; Tumor Suppressor Proteins

Mechanisms of progression of chronic kidney disease (CKD), a major health care burden, are poorly understood. EGFR stimulates CKD progression, but the molecular networks that mediate its biological effects remain unknown. We recently showed that the severity of renal lesions after nephron reduction varied substantially among mouse strains and required activation of EGFR. Here, we utilized two mouse strains that react differently to nephron reduction--FVB/N mice, which develop severe renal lesions, and B6D2F1 mice, which are resistant to early deterioration--coupled with genome-wide expression to elucidate the molecular nature of CKD progression. Our results showed that lipocalin 2 (Lcn2, also known as neutrophil gelatinase-associated lipocalin [NGAL]), the most highly upregulated gene in the FVB/N strain, was not simply a marker of renal lesions, but an active player in disease progression. In fact, the severity of renal lesions was dramatically reduced in Lcn2-/- mice. We discovered that Lcn2 expression increased upon EGFR activation and that Lcn2 mediated its mitogenic effect during renal deterioration. EGFR inhibition prevented Lcn2 upregulation and lesion development in mice expressing a dominant negative EGFR isoform, and hypoxia-inducible factor 1α (Hif-1α) was crucially required for EGFR-induced Lcn2 overexpression. Consistent with this, cell proliferation was dramatically reduced in Lcn2-/- mice. These data are relevant to human CKD, as we found that LCN2 was increased particularly in patients who rapidly progressed to end-stage renal failure. Together our results uncover what we believe to be a novel function for Lcn2 and a critical pathway leading to progressive renal failure and cystogenesis.

Topics: Acute-Phase Proteins; Adult; Aged; Animals; Cell Line; Disease Progression; Epidermal Growth Factor; ErbB Receptors; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Lipocalin-2; Lipocalins; Male; Mice; Mice, Inbred Strains; Mice, Knockout; Middle Aged; Oncogene Proteins; Polycystic Kidney Diseases; Proto-Oncogene Proteins; Renal Insufficiency, Chronic; Young Adult

Mouse models for autosomal-dominant polycystic kidney disease (ADPKD), derived from homozygous targeted disruption of Pkd1 gene, generally die in utero or perinatally because of systemic defects. We introduced a loxP site and a loxP-flanked mc1-neo cassette into introns 30 and 34, respectively, of the Pkd1 locus to generate a conditional, targeted mutation. Significantly, before excision of the floxed exons and mc1-neo from the targeted locus by Cre recombinase, mice homozygous for the targeted allele appeared normal at birth but developed polycystic kidney disease with a slower progression than that of Pkd-null mice. Further, the homozygotes continued to produce low levels of full-length Pkd1-encoded protein, suggesting that slight Pkd1 expression is sufficient for renal cyst formation in ADPKD. In this viable model, up-regulation of heparin-binding epidermal growth factor-like growth factor accompanied increased epidermal growth factor receptor signaling, which may be involved in abnormal proliferation of the cyst-lining epithelia. Increased apoptosis in cyst epithelia was only observed in the later period that correlated with the cyst regression. Abnormalities in Na(+)/K(+)-ATPase, aquaporin-2, and vasopressin V2 receptor expression were also identified. This mouse model may be suitable for further studies of progression and therapeutic interventions of ADPKD.

Topics: Animals; Apoptosis; Aquaporin 2; Blotting, Western; Disease Models, Animal; Epidermal Growth Factor; ErbB Receptors; Heparin-binding EGF-like Growth Factor; Immunohistochemistry; In Situ Nick-End Labeling; Intercellular Signaling Peptides and Proteins; Mice; Mice, Knockout; Mutation; Polycystic Kidney Diseases; Proteins; Receptors, Vasopressin; Reverse Transcriptase Polymerase Chain Reaction; Sodium-Potassium-Exchanging ATPase; TRPP Cation Channels

Renal cyst formation is the hallmark of autosomal dominant polycystic kidney disease (ADPKD). ADPKD cyst-lining cells have an increased proliferation rate and are surrounded by an abnormal extracellular matrix (ECM). We have previously shown that Laminin 5 (Ln-5, a alpha(3)beta(3)gamma(2) trimer) is aberrantly expressed in the pericystic ECM of ADPKD kidneys. We report that ADPKD cells in primary cultures produce and secrete Ln-5 that is incorporated to the pericystic ECM in an in vitro model of cystogenesis. In monolayers, purified Ln-5 induces ERK activation and proliferation of ADPKD cells, whereas upon epidermal growth factor stimulation blocking endogenously produced Ln-5 with anti-gamma(2) chain antibody reduces the sustained ERK activation and inhibits proliferation. In three-dimensional gel culture, addition of purified Ln-5 stimulates cell proliferation and cyst formation, whereas blocking endogenous Ln-5 strongly inhibits cyst formation. Ligation of alpha(6)beta(4) integrin, a major Ln-5 receptor aberrantly expressed by ADPKD cells, induces beta(4) integrin phosphorylation, ERK activation, cell proliferation, and cyst formation. These findings indicate that Ln-5 is an important regulator of ADPKD cell proliferation and cystogenesis and suggest that Ln-5 gamma(2) chain and Ln-5-alpha(6)beta(4) integrin interaction both contribute to these phenotypic changes.

Topics: Cell Line; Cell Proliferation; Dimerization; Epidermal Growth Factor; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation; Humans; Integrin alpha6beta4; Kidney Diseases, Cystic; Laminin; Microscopy, Phase-Contrast; Phosphorylation; Polycystic Kidney Diseases; Protein Binding

Polycystic kidney (PCK) rats exhibit a multiorgan cyst pathology similar to human autosomal recessive polycystic kidney disease, and are proposed as an animal model of Caroli's disease with congenital hepatic fibrosis (CHF). This study investigated the expression and function of selected components of the mitogen activated protein kinase (MAPK) pathway in cultured intrahepatic biliary epithelial cells (BECs) of PCK rats. Compared to the proliferative activity of cultured BECs of control rats, those of the PCK rats were hyperresponsive to epidermal growth factor (EGF). The increase in BEC proliferation was accompanied by overexpression of MAPK/extracellular signal-regulated protein kinase (ERK) kinase 5 (MEK5), and subsequent phosphorylation of ERK5 in vitro. The increased proliferative activity was significantly inhibited by the transfection of short interfering RNA against MEK5 mRNA. An EGF receptor tyrosine kinase inhibitor, gefitinib ("Iressa", ZD1839), also significantly inhibited the abnormal growth of cultured BECs of PCK rats. By contrast, treatment with PD98059 and U0126, inhibitors for MEK1/2, was less effective. These results suggest that the activation of the MEK5-ERK5 cascade plays a pivotal role in the biliary dysgenesis of PCK rats, and also provide insights into the pathogenesis of Caroli's disease with CHF. As the MEK5-ERK5 interaction is highly specific, it may represent a potential target of therapy.

Topics: Animals; Bile Ducts, Intrahepatic; Caroli Disease; Cell Division; Cells, Cultured; Disease Models, Animal; DNA Primers; Epidermal Growth Factor; ErbB Receptors; MAP Kinase Kinase 5; Mitogen-Activated Protein Kinase 7; Oligonucleotide Array Sequence Analysis; Polycystic Kidney Diseases; Polymerase Chain Reaction; Rats; Rats, Inbred Strains; RNA, Messenger

Transforming growth factor-alpha (TGF-alpha) is abnormally expressed in autosomal recessive polycystic kidney disease (ARPKD). Tumor necrosis factor-alpha converting enzyme (TACE), a metalloproteinase, mediates TGF-alpha processing. In this study, we sought to determine whether TGF-alpha was an absolute requirement for renal cystogenesis and whether its absence would modulate disease severity or related growth factors/receptors expression. Bpk heterozygotes were bred with TGF-alpha null mice to produce cystic and noncystic offspring with or without TGF-alpha. Assessments included kidney weight (KW), body weight (BW), blood urea nitrogen (BUN), and kidney and liver immunohistology. Western analysis assessed kidney expression of amphiregulin (AR), epidermal growth factor (EGF), heparin-binding EGF (HB-EGF), and their receptors, EGFR and ErbB4. A PCR-based methodology for genotyping bpk mice was also developed. No significant differences in KW, BW, KW/BW%, or BUN were seen in cystic mice with versus without TGF-alpha. Cystic kidney disease and liver disease histology were similar. AR, EGF, HB-EGF, EGFR, and ErbB4 were abnormally expressed to an equal degree in kidneys of mice with versus without TGF-alpha. Although previous data suggest a critical role of TGF-alpha in murine PKD, these data show that TGF-alpha is not required for renal cyst formation or kidney or liver disease progression. We speculate that the therapeutic effect of WTACE2 could have been due to effects on several TACE targets, including TGF-alpha, AR, and ErbB4, as well as metalloproteinases other than TACE.

Topics: ADAM Proteins; ADAM17 Protein; Alleles; Amphiregulin; Animals; Blood Urea Nitrogen; Body Weight; Disease Progression; EGF Family of Proteins; Epidermal Growth Factor; ErbB Receptors; Genes, Recessive; Genotype; Glycoproteins; Heparin-binding EGF-like Growth Factor; Intercellular Signaling Peptides and Proteins; Kidney; Kidney Diseases, Cystic; Liver; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Mutation; Organ Size; Phenotype; Polycystic Kidney Diseases; Polymerase Chain Reaction; Receptor, ErbB-4; Transforming Growth Factor alpha

The effects of the ERK pathway on electrogenic transepithelial Na(+) absorption by renal collecting duct cells were determined. Approximately 90% of the unstimulated short-circuit current (15 +/- 1 microA/cm(2), n = 10) across conditionally immortalized murine collecting duct epithelial cells (mCT1) is amiloride sensitive and is likely mediated by apical epithelial Na(+) channels. Chronic exposure (24 h) of the epithelial monolayers to either EGF (50 ng/ml) or transforming growth factor-alpha (TGF-alpha; 20 ng/ml) reduced amiloride-sensitive short-circuit current by >60%. The inhibitory effect of EGF on Na(+) absorption was not due to inhibition of basolateral Na(+)-K(+)-ATPase, because the pump current elicited by permeabilization of apical membrane with nystatin was not reduced by EGF. Chronic exposure of the mCT1 cells to EGF (20 ng/ml, 24 h) elicited a 70-85% decrease in epithelial Na(+) channel subunit mRNA levels. Exposure of mCT1 cells to either EGF (20 ng/ml) or PMA (150 nM) induced rapid phosphorylation of p42/p44 (ERK1/2) and pretreatment of the monolayers with PD-98059 (an ERK kinase inhibitor; 30 microM) prevented phosphorylation of p42/p44. Similarly, pretreatment of mCT1 monolayers with PD-98059 prevented the EGF- and PMA-induced inhibition of amiloride-sensitive Na(+) absorption. The results of these studies demonstrate that amiloride-sensitive Na(+) absorption by renal collecting duct cells is regulated by the ERK pathway. This pathway may play a role in alterations in ion transport that occur in polycystic kidney disease.

Topics: Amiloride; Animals; Antineoplastic Agents; Carcinogens; Cell Line, Transformed; Cell Membrane; Diuretics; Dose-Response Relationship, Drug; Epidermal Growth Factor; Epithelial Sodium Channels; Gene Expression; Kidney Tubules, Collecting; MAP Kinase Signaling System; Mice; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases; Phosphorylation; Polycystic Kidney Diseases; RNA, Messenger; Sodium; Sodium Channels; Sodium-Potassium-Exchanging ATPase; Tetradecanoylphorbol Acetate; Tumor Necrosis Factor-alpha

Recessively transmitted polycystic kidney disease (PKD) in many murine models is characterized by the initial formation of proximal tubular cysts (stage 1), followed by growth and enlargement of renal collecting tubule (CT) cysts (stage 2). Previous studies have reported that stage 1 cyst formation and growth could be manipulated in vitro by using embryonic kidney explants and newborn explant microslices in organ culture.. Microslices of postnatal kidneys cultured on Transwell tissue culture inserts allow experimental manipulation of stage 2 CT cyst development and growth. This system was used to test a potential therapeutic compound for treatment of PKD. This compound, EKI-785, modulates altered epidermal growth factor receptor (EGFR) expression in CT cysts by inhibition of EGFR autophosphorylation.. These studies demonstrate that: (a) minor modifications of the previously described organ culture system permit successful culture of more mature renal tissue, and (b) cystic explants treated with EGF and EKI-785 demonstrated a marked reduction in CT cystic lesions compared with cystic explants treated with EGF alone.. This study suggests that pharmacological strategies can be used to decrease EGFR tyrosine kinase activity and CT cyst formation and enlargement in murine PKD.

Topics: Animals; Cell Division; Cell Survival; Disease Models, Animal; Enzyme Inhibitors; Epidermal Growth Factor; ErbB Receptors; Gene Expression Regulation, Enzymologic; Kidney Tubules, Collecting; Mice; Mice, Mutant Strains; Nephrons; Organ Culture Techniques; Phosphorylation; Polycystic Kidney Diseases; Protein-Tyrosine Kinases; Quinazolines

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.

Topics: Adjuvants, Immunologic; Adult; Aged; Diabetic Nephropathies; Epidermal Growth Factor; Female; Glomerular Filtration Rate; Glomerulonephritis; Humans; Kidney Failure, Chronic; Kidney Tubules, Distal; Kidney Tubules, Proximal; Loop of Henle; Male; Middle Aged; Mucoproteins; Polycystic Kidney Diseases; Uromodulin

In chronic renal failure, epidermal growth factor (EGF) excretion is decreased. In this study, asymptomatic adult polycystic kidney disease (APKD) patients with a relatively preserved glomerular filtration rate were examined. Excretion of EGF was studied in 6 patients with APKD (median age 42 years; serum creatinine [median] 95 [range-80-133] mumol/l) and compared with that of 28 healthy controls. EGF was determined in a spot morning urine by using a specific radioimmunoassay, and expressed in relation to creatinine excretion. Excretion of EGF in APKD was (median) 157 (range-13-359) and in the controls (median) 546 (range-238-1199) pmol/mmol creatinine (p < 0.001). Low excretion of EGF in APKD patients with preserved kidney function suggests a distal abnormality at an early stage of the disease, prior to the development of renal failure.

Topics: Adult; Aged; Case-Control Studies; Creatinine; Epidermal Growth Factor; Female; Glomerular Filtration Rate; Humans; Kidney Failure, Chronic; Kidney Tubules, Distal; Male; Middle Aged; Polycystic Kidney Diseases; Radioimmunoassay

Cystic change in polycystic kidney disease (PKD) is associated with epithelial hyperplasia, altered fluid and electrolyte transport, and de-differentiation of renal tubular epithelium. The role of polypeptide growth factors as potential modulators of cystic change remains an area of controversy. In this study, the expression of epidermal growth factor (EGF) and transforming growth factor-alpha (TGF alpha) were assessed by immunohistochemistry and image analysis in glucocorticoid-induced PKD in the newborn mouse. Newborn C3H mice received either 200 mg/kg methylprednisolone acetate (MPA) or 0.9% saline as a control. EGF expression was not detected in significant quantities in either MPA-treated or control animals. TGF alpha, however, was expressed in immature control kidney in a largely basolateral distribution. Expression increased significantly in association with cystic change in MPA-treated animals and was localized to the apical cell surface, implying altered polarity of secretion. There is no evidence that EGF is a mitogen in this early developmental model of PKD. TGF alpha, however, may be an important mediator of cystic change in immature or de-differentiated renal tubular epithelium.

Topics: Animals; Animals, Newborn; Anti-Inflammatory Agents; Disease Models, Animal; Epidermal Growth Factor; Immunohistochemistry; Methylprednisolone; Methylprednisolone Acetate; Mice; Mice, Inbred C3H; Polycystic Kidney Diseases; Transforming Growth Factor alpha

Acquired cystic disease of the kidney (ACDK) reveals abnormal epithelial cell growth which suggests a cotinuum of cyst, adenoma and renal cell carcinoma (RCC). In the present study, we examined potential role of vimentin and growth factors for cyst growth and proliferation in 20 cases with ACDK by immunoperoxidase staining method. 1281 cysts with single-layered epithelia and 89 cysts with multi-layered epithelia (atypical cyst) were studied. Intermediated filament, vimentin was positive in staining in 41.6% of cysts with single-layered epithelia, in 73.1% of cyst with multi-layered epithelia and in 100% of adenomas and RCCs. Vimentin expression, therefore, may be considered as an indication of cellular differentiation among proliferating tubular or intracystic cells. In order to evaluate the growth and/or proliferative capabilities of cyst epithelia, epidermal growth factor (EGF), epidermal growth factor receptor (EGFR) and c-erb B2 gene product were determined in cyst epithelia, adenoma and adenocarcinoma. EGF showed positive staining in 49.1% of cyst with single-layered epithelia, in 68.4% of cyst with multi-layered epithelia, in 2 of 3 adenomas and in 5 of 8 RCCs. EGFR expression was observed in 61.7% of cyst with single-layered epithelia, in 94.7% of cyst with multi-layered epithelia, in 100% of adenomas and RCCs. Co-expression of EGF and EGFR was observed in 40.3% of cyst with single-layered epithelia and in 67.1% of cyst with multi-layered epithelia. C-erb B2 gene product was positive in 9.7% of cyst with single-layered epithelia, in 100% of cyst with multi-layered epithelia and in 3 of 7 RCCs. These findings indicate that the expression of vimentin and overexpression of these growth factors and receptors appear to be one of the mechanisms operating in potentiating the abnormal growth of cyst epithelia, including potential for oncogenesis of RCC.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Epidermal Growth Factor; ErbB Receptors; Female; Humans; Immunohistochemistry; Male; Middle Aged; Polycystic Kidney Diseases; Proto-Oncogene Proteins; Receptor, ErbB-2; Vimentin

The C57BL/6J CPK heterozygous breeders secrete in urine a variant EGF-prohormone with a molecular mass of 154 kDa in addition to the normal 165 kDa EGF-prohormone. The 154 kDa prohormone is secreted as a heterodimer with the normal 165 kDa prohormone. The phenotypically normal littermates, like their parents, secrete the 154 and 165 kDa EGF-prohormones in urine while their cystic siblings secrete neither protein. Examination of renal extracts of normal littermates revealed the presence of the 165 kDa but not the 154 kDa EGF-prohormone; renal extracts of cystic siblings contained neither protein. Cyst fluid, however, contained 56 and 49 kDa EGF-immunoreactive proteins in high concentrations. The data suggest that in the absence of normal 165 kDa prohormone, the 154 kDa EGF-prohormone undergoes proteolysis and that the resultant fragments function as cystogens. Since normal siblings do not acquire renal cystic disease despite expressing the variant 154 kDa EGF-prohormone while the affected littermates, which lack the normal 165 kDa EGF-prohormone, manifest renal cystic disease, we suggest that congenital polycystic kidney disease is due to an inborn defect in the synthesis and secretion of the normal 165 kDa renal EGF-prohormone.

Topics: Adult; Animals; Disease Models, Animal; Electrophoresis, Polyacrylamide Gel; Epidermal Growth Factor; Female; Genes, Recessive; Heterozygote; Humans; Macromolecular Substances; Male; Metabolism, Inborn Errors; Mice; Mice, Inbred C57BL; Middle Aged; Molecular Weight; Phenotype; Polycystic Kidney Diseases; Protein Precursors; Reference Values

Normal Sprague Dawley (SPRD) rats of both sexes secrete an 165 kDa EGF prohormone in urine. Sexually mature Hannover-Sprague Dawley rats (Han:SPRD) heterozygous males and females with autosomal dominant polycystic kidney disease (ADPKD) secrete a prohormone of similar molecular mass in urine. The male, but not the female, also secretes two variant prohormone isoforms with molecular masses close to 200 kDa. Both the 165 and 200 kDa EGF prohormone isoforms are totally absent, in urine, at 11 months of age in male but not in female heterozygous Han:SPRD rats. At this age, the male kidneys exhibit numerous cysts filled with colorless fluids and these fluids contain abundant quantities of a 66 kDa EGF prohormone metabolite. Homozygous Han:SPRD rats which are born with cystic disease secrete only trace amounts of 165 kDa EGF prohormone in their urine while their normal looking littermates secrete the 165 kDa EGF prohormone in abundant quantities. The cyst fluids of homozygous rats contain trace amounts of 165 and 154 kDa EGF prohormone isoforms while the 66 kDa EGF prohormone metabolites present in abundant quantities. The massive amounts of 66 kDa EGF prohormone metabolite in cyst fluids of PKD rats suggests that EGF prohormone and its isoforms undergo aberrant proteolysis in association with cyst pathogenesis both in heterozygous and homozygous kidneys. The specific retention of the 66 kDa EGF prohormone metabolite within the cyst suggests that this molecule may function as a cystogen.

Topics: Animals; Disease Models, Animal; Epidermal Growth Factor; Female; Genes, Dominant; Glycopeptides; Heterozygote; Homozygote; Humans; Immunoblotting; Kidney; Male; Mice; Oligosaccharides; Polycystic Kidney Diseases; Protein Precursors; Proteinuria; Rats; Rats, Mutant Strains; Rats, Sprague-Dawley; Sex Factors

Polycystic kidney disease (PKD) represents a form of renal epithelial hyperplasia. The C57BL/6J-cpk mouse, which has an infantile form of PKD, has a dramatically reduced expression of renal prepro-epidermal growth factor (EGF) mRNA and immunoreactive protein. Since EGF promoted maturation of epithelia in the neonate, the relative lack of renal EGF may contribute to the development of the collecting duct cysts by delaying epithelial maturation.

Topics: Aging; Animals; Blotting, Northern; Epidermal Growth Factor; Epithelium; Gene Expression Regulation; Kidney Tubules, Distal; Mice; Mice, Inbred C57BL; Nucleic Acid Hybridization; Polycystic Kidney Diseases; RNA

The mechanisms responsible for renal cyst formation in congenital polycystic kidney disease remain unknown, although abnormalities of cellular metabolism, basement membrane components, and growth factors have been suggested. In the present study, we examined a potential role for epidermal growth factor (EGF) in cyst formation in a mouse model. We measured growth factor activity and concentration in renal cyst fluid, urine, and serum obtained from mice with congenital polycystic kidney disease (cpk). In affected mice, both growth factor activity of urine and the urinary EGF concentration were much lower than unaffected littermate controls even when corrected for creatinine concentration. Although the growth factor activity was much lower in affected mice, there were significant differences in the regional distribution of EGF in animals with cysts. Both growth factor activity and EGF concentration were greater in cyst fluid when compared to urine. Growth factor activity in cysts was completely inhibited by anti-EGF antibody using BALB/MK epithelial keratinocytes as targets. The expression of EGF mRNA in kidneys from affected mice was markedly decreased when compared to littermate controls. These results suggest that decreased EGF production and local differences in EGF concentration may contribute to cyst formation.

Topics: Animals; Blotting, Northern; Chromatography, Gel; Epidermal Growth Factor; Kidney; Mice; Polycystic Kidney Diseases; Radioimmunoassay; RNA, Messenger

The C57BL/6J-cpk mouse has an inheritable form of polycystic kidney disease similar to the autosomal recessive disorder seen in humans. Between approximately 1 and 3 weeks of age, affected cpk mice develop numerous large cysts in the collecting tubule segment of kidney nephrons. The present study examined the ontogeny of renal and submandibular gland prepro-epidermal growth factor (preproEGF) gene expression in the cpk mouse using Northern blot hybridization and immunohistochemistry. There was a virtual absence of renal preproEGF gene expression in cystic kidneys over the 3-week postnatal period, during which time renal preproEGF mRNA and proEGF/EGF protein normally reach significant levels. PreproEGF mRNA was expressed in salivary glands of cystic mice; however, this mRNA could not be further elevated with testosterone suggesting that there are abnormalities in the regulation of the preproEGF gene in the submandibular gland, as well as in the kidney. Since renal preproEGF expression during the early postnatal period occurs when collecting duct cysts form, it is possible that a deficiency in renal proEGF or EGF contributes to the rapid development of collecting duct cysts and the concomitant renal failure in the C57BL/6J-cpk cystic mouse.

Topics: Animals; Blotting, Northern; Epidermal Growth Factor; gamma-Glutamyltransferase; Gene Expression Regulation; Immunoenzyme Techniques; Kidney; Mice; Mice, Mutant Strains; Polycystic Kidney Diseases; Protein Precursors; RNA, Messenger; Submandibular Gland; Testosterone