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Biomedical subjects

H J Gröne

Publications and source records attributed to H J Gröne.

At least 19 recordsLinked to original sources

Beneficial effects of CCR1 blockade on the progression of chronic renal allograft damage.

The biology of chemokines and their receptors have been linked to the development of chronic allograft damage. Effects of CCR1 antagonist BX 471 were studied in a Fischer to Lewis renal transplantation model at days 10, 21 and 42 after transplantation. BX 471 treatment did not effectively reduce signs of acute rejection at day 10 but significantly improved allograft function and morphology at day 21 posttransplantation. When therapy was initiated on day 21 after transplantation, glomerulosclerosis and tubulointerstitial fibrosis were significantly inhibited by day 42 posttransplantation. Parallel decrease in infiltrating and proliferating mononuclear cells (ED1, CD8 and Ki67) was observed in treated allografts. Expression of acute phase reactive and proinflammatory genes (HO-1, osteopontin) and molecules associated with fibrosis (PAI-1, TGF-beta1, biglycan) was downregulated at day 21; reduced collagen deposition was observed, parallel to a significant lower number of alpha-SMA+ interstitial myofibroblasts. In situ hybridization demonstrated that biglycan expression was reduced following CCR1 blockade in interstitium of treated allografts. CCR1 antagonism was found to inhibit CCL5-induced secretion of biglycan by macrophages in vitro. CCR1 blockade significantly inhibited development and progression of chronic allograft damage. CCR1 antagonists may represent a therapeutic option for chronic inflammation and fibrosis in renal grafts.

Animals↗

Exanthema and acute anuric renal failure.

A 15-year-old girl with a history of Kawasaki disease was admitted to our nephrological department due to acute renal failure. Despite antibiotic therapy because of fever and the symptoms of a pharyngitis in the last few days, the girl showed persisting fever and developed arthralgias, an exanthema and a rising serum creatinine as well as anuria. A wide variety of differential diagnoses has to be thought of because of the history of the Kawasaki disease (symptoms like fever, pharyngitis, exanthema and arthralgia), i.e. hemolytic-uremic syndrome, vasculitis, ascending infection, postinfection glomerulonephritis. In consideration of etiologically unclear "rapidly progressive renal failure" with anuria and thrombocytopenia an immediate renal biopsy was done and revealed a severe drug induced acute interstitial nephritis. Due to this diagnosis we treated the patient with corticosteroids. Within 4 weeks serum creatinine declined to 1.8 mg/dl but did not normalize.

Acute Kidney Injury↗

Differential expression of beta-chemokines MCP-1 and RANTES and their receptors CCR1, CCR2, CCR5 in acute rejection and chronic allograft nephropathy of human renal allografts.

BACKGROUND: The beta-chemokines MCP-1 (CCL2) and RANTES (CCL5) have been shown to play important roles in acute renal transplant rejection (AR) and chronic allograft nephropathy (CAN). The potential relationship of expression of these chemokines, their chemokine receptors CCR1, CCR2, CCR5, and the cell populations of inflammatory infiltrate, histological and clinical diagnoses were investigated in biopsies at the time of AR and compared with biopsies of CAN. METHODS: In 24 renal transplant biopsies with AR (n = 15) and CAN (n = 9), the expression of MCP-1 and RANTES, their receptors CCR1, CCR2, and CCR5 and the infiltration with monocytes/macrophages and T cells were studied. RESULTS: As previously described, chemokine and chemokine receptor expression was found mainly in mononuclear cells infiltrating the interstitium and glomeruli. In the tubulointerstitial area and glomeruli the expression of MCP-1, RANTES, and their receptors correlated with an infiltration by monocytes/macrophages. Biopsies with CAN revealed a lower expression of MCP-1, RANTES, CCR1, CCR2 and CCR5 in tubulointerstitial cells, and a significantly lower infiltration with MRP14-positive monocytes/macrophages than biopsies with AR. In AR, MCP-1 and CCR1 showed a lower expression compared to RANTES, CCR2, and CCR5. CONCLUSIONS: The positive correlation between chemokines and chemokine receptors and infiltrating leukocytes during acute rejection, the lower but detectable expression of MCP-1, RANTES, CCR1, CCR2 and CCR5 in CAN, and the differences in the quantity of expression between the different chemokines and chemokine receptors point to a complex regulation of chemokine expression in renal allografts. Since chemokines are not only involved in inflammation but also in tissue regeneration, this could have impact on the development of CAN.

Adult↗

Up-regulation of the human serum and glucocorticoid-dependent kinase 1 in glomerulonephritis.

Glomerulonephritis is paralleled by excessive formation of transforming growth factor-beta (TGF-beta), which participates in the pathophysiology of the disease. Recently, a novel downstream target of TGF-beta has been identified, i.e. the human serum and glucocorticoid-dependent kinase 1 (hSGK1), a serine/threonine kinase participating in the regulation of Na(+) transport. The present study was performed to elucidate transcriptional regulation of hSGK1 in glomerulonephritis. To this end, in situ hybridization was performed in biopsies from patients with clinical diagnosis of glomerulonephritis. hSGK1 transcript levels were moderately enhanced in 5 out of 9 patients and strongly enhanced in 4 out of 9 patients. Distal nephron epithelial cell hSGK1 transcript levels were low or absent in 7 of the 9 patients but markedly enhanced in 2 of the 9 patients. In conclusion, glomerulonephritis leads to glomerular and in some cases to epithelial up-regulation of hSGK1 transcription.

Adult↗

[Gene expression profiling in prostatic cancer].

Basic aspects of the biology and molecular alterations in prostate carcinoma remain poorly understood. New diagnostic and prognostic markers for prostate carcinoma may add additional information to current histopathological diagnosis. In order to achieve these goals, a comprehensive gene expression analysis was performed on non-metastasizing, untreated prostate cancer tissues. RNA expression profiles of approximately 12,600 sequences from 26 human prostate tissues (17 adenocarcinomas and 9 normal adjacent to cancer tissues) were investigated using high-density oligonucleotide microarray technology (Affymetrix). We identified 63 genes which were significantly increased (at least 2.5-fold) and 153 genes which were decreased (at least 2.5-fold). Upregulated genes included several which had not yet been described, such as the genes encoding the specific granule protein (SGP28), several members of the histone family, and the alpha-methylacyl-CoA racemase, but also previously reported ones such as hepsin, LIM domain kinase 2, and carcinoma-associated antigen GA733-2. Laser capture-microdissection of epithelial and stromal compartments from cancer and histologically normal specimens followed by an amplification protocol for low amounts of RNA (< 0.1 microgram) allowed us to distinguish between gene expression profiles characteristic of epithelial cells and those typical of stroma. Most of the genes identified in bulk tumor material as upregulated were indeed overexpressed in cancerous epithelium rather than in the stromal compartment. DNA microarray data for up- and downregulated genes were confirmed by quantitative RT-PCR. We demonstrated that development of prostate cancer is associated with downregulation as well as upregulation of genes that show complex differential regulation in epithelia and stroma. Some of the alterations in gene expression identified in this study may prove useful in development of novel diagnostic and therapeutic strategies. Gene expression profiling of microdissected tumor cells in prostate biopsies may supplement histopathologic diagnosis.

Adenocarcinoma↗

Deleted in Malignant Brain Tumors 1 is a versatile mucin-like molecule likely to play a differential role in digestive tract cancer.

Deleted in Malignant Brain Tumors 1 (DMBT1) has been proposed as a candidate tumor suppressor gene for brain, lung, and digestive tract cancer. In particular, alterations of the gene and/or a loss of expression have been observed in gastric, colorectal, and esophageal carcinomas. Initial evidence has accumulated that DMBT1 may represent a multifunctional protein. Because the consequences of a loss of DMBT1 function may be different depending on its original function in a particular tissue, we wondered if it is appropriate to assume a uniform role for DMBT1 in digestive tract carcinomas. We hypothesized that a systematic characterization of DMBT1 in the human alimentary tract would be useful to improve the understanding of this molecule and its role in digestive tract carcinomas. Our data indicate that the expression pattern and subcellular distribution of DMBT1 in the human alimentary tract is reminiscent of epithelial mucins. Bovine gallbladder mucin is identified as the DMBT1 homologue in cattle. An elaborate alternative splicing may generate a great variety of DMBT1 isoforms. Monolayered epithelia display transcripts of 6 kb and larger, and generally show a lumenal secretion of DMBT1 indicating a role in mucosal protection. The esophagus is the only tissue displaying an additional smaller transcript of approximately 5 kb. The stratified squamous epithelium of the esophagus is the only epithelium showing a constitutive targeting of DMBT1 to the extracellular matrix (ECM) suggestive of a role in epithelial differentiation. Squamous cell carcinomas of the esophagus show an early loss of DMBT1 expression. In contrast, adenocarcinomas of the esophagus commonly maintain higher DMBT1 expression levels. However, presumably subsequent to a transition from the lumenal secretion to a targeting to the ECM, a loss of DMBT1 expression also takes place in adenocarcinomas. Regarding DMBT1 as a mucin-like molecule is a new perspective that is instructive for its functions and its role in cancer. We conclude that DMBT1 is likely to play a differential role in the genesis of digestive tract carcinomas. However, although DMBT1 originally has divergent functions in monolayered and multilayered epithelia, carcinogenesis possibly converges in a common pathway that requires an inactivation of its functions in the ECM.

Adenocarcinoma↗

Hypochlorite-modified (lipo)proteins are present in rabbit lesions in response to dietary cholesterol.

Myeloperoxidase (MPO), a heme enzyme secreted by activated phagocytes, generates an array of oxidants proposed to play critical roles in host defense, tissues damage, and foam cell formation. Although neutrophils are the major source for MPO, the enzyme could be identified abundantly in circulating monocytes and monocytes/macrophages in rabbit lesions. MPO is the only enzyme known to generate hypochlorous acid (HOCl) and HOCl-modified lipoproteins have pronounced atherogenic and/or proinflammatory features in vivo and in vitro. Using specific monoclonal antibodies, HOCl-modified (lipo)proteins were detected in atherosclerotic plaques of heterozygous Watanabe heritable hyperlipidemic rabbits and to a lesser extent in a specific strain of New Zealand White rabbits with a high atherosclerotic response to hypercholesterolemia. Colocalization of immunoreactive MPO and HOCl-modified-epitopes in serial sections of rabbit lesions provides convincing evidence for MPO-H2O2-chloride system-mediated oxidation of (lipo)proteins under in vivo conditions. We propose that monocyte-derived MPO could connect chronic inflammatory conditions with arterial lipid/lipoprotein deposition during diet-induced atherogenesis in rabbits.

Animals↗

Sympathetic reinnervation of rat kidney grafts.

BACKGROUND: Reinnervation occurs in many transplanted tissues and organs. Sympathetic reinnervation in rat kidney grafts was investigated. METHODS: Rats were syngeneically transplanted with a kidney and bilaterally nephrectomized. Reinnervation was assessed by immunohistochemical staining for neuron-specific protein gene product 9.5 (PGP 9.5) and by tissue norepinephrine measurements in grafts removed 1.5 (n=6), 3 (n=7), 6 (n=8), and 9 (n=7) months after transplantation. RESULTS: PGP 9.5-positive neural structures were significantly reduced in grafts removed 1.5 and 3 months after transplantation compared with native kidneys with slightly increased numbers at 6 and 9 months after transplantation. Median transplant norepinephrine concentrations remained at approximately 3% compared with native kidneys until 9 months after transplantation. CONCLUSIONS: In transplanted rat kidneys, some reinnervation occurs in the hilum within 9 months after transplantation. This is not accompanied by a significant recovery of norepinephrine concentration in renal tissue indicating persistent sympathetic denervation.

Animals↗

Impairment of mossy fiber long-term potentiation and associative learning in pituitary adenylate cyclase activating polypeptide type I receptor-deficient mice.

The pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor (PAC1) is a G-protein-coupled receptor binding the strongly conserved neuropeptide PACAP with 1000-fold higher affinity than the related peptide vasoactive intestinal peptide. PAC1-mediated signaling has been implicated in neuronal differentiation and synaptic plasticity. To gain further insight into the biological significance of PAC1-mediated signaling in vivo, we generated two different mutant mouse strains, harboring either a complete or a forebrain-specific inactivation of PAC1. Mutants from both strains show a deficit in contextual fear conditioning, a hippocampus-dependent associative learning paradigm. In sharp contrast, amygdala-dependent cued fear conditioning remains intact. Interestingly, no deficits in other hippocampus-dependent tasks modeling declarative learning such as the Morris water maze or the social transmission of food preference are observed. At the cellular level, the deficit in hippocampus-dependent associative learning is accompanied by an impairment of mossy fiber long-term potentiation (LTP). Because the hippocampal expression of PAC1 is restricted to mossy fiber terminals, we conclude that presynaptic PAC1-mediated signaling at the mossy fiber synapse is involved in both LTP and hippocampus-dependent associative learning.

Animals↗

Constitutive activation of hypoxia-inducible genes related to overexpression of hypoxia-inducible factor-1alpha in clear cell renal carcinomas.

The transcription factor hypoxia-inducible factor (HIF)-1 is an important mediator of hypoxic adaptation of tumor cells and controls several genes that have been implicated in tumor growth. Oxygen-dependent degradation of HIF-1alpha, the regulatory subunit, requires binding to the von Hippel Lindau (VHL) protein. Because functional inactivation of the VHL tumor suppressor gene occurs in up to 70% of clear cell renal carcinomas, we investigated whether this results in overexpression of HIF-1alpha and its target genes. Immunoblotting revealed increased expression of HIF-1alpha in 24 of 32 (75%) clear cell renal carcinomas but only 3 of 8 non-clear cell renal tumors. Somatic mutations of the VHL gene were detected only in clear cell renal carcinomas that overexpressed HIF-1alpha. None of the HIF-1alpha-negative tumors displayed a VHL mutation. The level of HIF-1alpha mRNA was not different between tumors and adjacent kidney tissue. Immunohistochemistry revealed distinct patterns of nuclear staining for HIF-1alpha, depending on histological type and overall abundance of HIF-1alpha. In those clear cell renal carcinomas that showed increased expression on immunoblots, HIF-1alpha was expressed in almost all cells. In the remaining clear cell and in non-clear cell tumors, staining was focal; these different patterns thus were compatible with genetic stabilization in contrast to microenvironmental stimulation of HIF-1alpha as the primary mechanism. The mRNA expression of two known target genes of HIF-1alpha, vascular endothelial growth factor and glucose transporter 1, increased progressively with increasing amounts of HIF-1alpha in tumor extracts. In addition, glucose transporter 1 protein levels correlated with HIF-1alpha abundance. In conclusion, the data provide in vivo evidence for a constitutive up-regulation of HIF-1alpha in the majority of clear cell renal carcinomas, which leads to more widespread accumulation of this transcription factor than hypoxic stimulation. These observations are most likely linked to functional inactivation of the VHL gene product. Increased expression of HIF-1alpha is associated with alterations in gene expression patterns that are likely to contribute to tumor phenotype and progression.

Adenocarcinoma, Clear Cell↗

Selective recruitment of Th2-type cells and evasion from a cytotoxic immune response mediated by viral macrophage inhibitory protein-II.

The viral CC chemokine macrophage inhibitory protein-II (vMIP-II) encoded by human herpes virus 8 (HHV-8) binds to multiple chemokine receptors, however, its ability to control the initial recruitment of specific leukocyte subtypes from the peripheral circulation has not been fully clarified. Here we show that vMIP-II blocks the firm arrest and transmigration of monocytes or Th1-like T lymphocytes triggered by RANTES immobilized on activated human microvascular endothelium (HMVEC) under flow conditions. The internalization of the receptors CCR1 and CCR5 that mediate arrest and transmigration of these cells in response to RANTES was prevented by vMIP-II, supporting its role as an antagonist of CCR1 and CCR5. In contrast, vMIP-II triggered the firm arrest of eosinophils and Th2-like T cells by engaging CCR3, as confirmed by its down-regulation. Immunohistochemical analysis of HHV-8-associated Kaposi's sarcoma lesions marked by vMIP-II expression and mononuclear cell infiltration revealed a predominance of Th2-type CCR3(+) lymphocytes over Th1-type CXCR3(+)/CCR5(+) leukocytes, indicating that as a CCR3 agonist vMIP-II can drive a Th2-type immune response in vivo. Thus, our data provide evidence for a immunomodulatory role of vMIP-II in directing inflammatory cell recruitment away from a Th1-type towards a Th2-type response and thereby facilitating evasion from cytotoxic reactions.

CCR5 Receptor Antagonists↗

Characterization of a novel EGFP reporter mouse to monitor Cre recombination as demonstrated by a Tie2 Cre mouse line.

The use of the Cre/loxP system has greatly empowered the field of gene targeting. Here we describe the successful establishment of a novel knock-in EGFP reporter mouse line to monitor Cre-induced recombination in the vast majority of cell types. The value of this reporter mouse line is demonstrated by the use of a novel Tie2Cre transgenic mouse line that facilitates gene targeting in endothelial and hematopoietic cells. High efficiency of recombination was found in all endothelial cells and in the majority of hematopoietic cells but was absent in other tissues. Furthermore, in the second generation, the Tie2Cre mouse can be used to get 100% recombination of one allele, whilst allowing tissue specific in the second, therefore offering excellent efficiency.

Alleles↗

Glucuronide and glucoside conjugation of mycophenolic acid by human liver, kidney and intestinal microsomes.

Mycophenolic acid (MPA) is primarily metabolized to a phenolic glucuronide (MPAG) as well as to two further minor metabolites: an acyl glucuronide (AcMPAG) and a phenolic glucoside (MPAG1s). This study presents investigations of the formation of these metabolites by human liver (HLM), kidney (HKM), and intestinal (HIM) microsomes, as well as by recombinant UDP-glucuronosyltransferases. HLM (n=5), HKM (n=6), HIM (n=5) and recombinant UGTs were incubated in the presence of either UDP-glucuronic acid or UDP-glucose and various concentrations of MPA. Metabolite formation was followed by h.p.l.c. All microsomes investigated formed both MPAG and AcMPAG. Whereas the efficiency of MPAG formation was greater with HKM compared to HLM, AcMPAG formation was greater with HLM than HKM. HIM showed the lowest glucuronidation efficiency and the greatest interindividual variation. The capacity for MPAGls formation was highest in HKM, while no glucoside was detected with HIM. HKM produced a second metabolite when incubated with MPA and UDP-glucose, which was labile to alkaline treatment. Mass spectrometry of this metabolite in the negative ion mode revealed a molecular ion of m/z 481 compatible with an acyl glucoside conjugate of MPA. All recombinant UGTs investigated were able to glucuronidate MPA with K:(M:) values ranging from 115.3 to 275.7 microM l(-1) and V(max) values between 29 and 106 pM min(-1) mg protein(-1). Even though the liver is the most important site of MPA glucuronidation, extrahepatic tissues particularly the kidney may play a significant role in the overall biotransformation of MPA in man. Only kidney microsomes formed a putative acyl glucoside of MPA.

Glucuronates↗

Glycoinositolphosphosphingolipids (basidiolipids) of higher mushrooms.

The basidiolipids of six mushroom species, i.e. the basidiomycetes Amanita virosa (engl., death cup), Calvatia exipuliformis (engl., puffball), Cantharellus cibarius (engl., chanterelle), Leccinum scabrum (engl., red birch boletus), Lentinus edodes (jap., Shiitake), and Pleurotus ostreatus (engl., oystermushroom), were isolated, and their chemical structures investigated. All glycolipids are structurally related to those of the Agaricales (engl., field mushroom). They are glycoinositolphosphosphingolipids, their ceramide moiety consisting of t18:0-trihydroxysphinganine and an alpha-hydroxy long-chain fatty acid. In contrast to a previous study [Jennemann, R., Bauer, B.L., Bertalanffy, H., Geyer, R., Gschwind, R.M., Selmer, T. & Wiegandt, H. (1999) Eur. J. Biochem. 259, 331--338], the glycoside anomery of the hexose (mannose) connected to the inositol of all investigated basidiomycete glycolipids, including the basidiolipids of Agaricus bisporus, was determined unequivocally to be alpha. Therefore, the root structure of all basidiolipids consists of alpha-DManp-2Ins1-[PO(4)]-Cer. In addition, for some mushroom species, the occurrence of an inositol substitution position variant, alpha-Manp-4Ins1-[PO(40]-Cer, is shown. The carbohydrate of chanterelle basidiolipids consists solely of mannose, i.e. Cc1, Man alpha-3 or -6Man alpha; Cc2, Man alpha-3(Man alpha-6)Man alpha-. All other species investigated show extension of the alpha-mannoside in the 6-position by beta-galactoside, which, in some instances, is alpha-fucosylated in 2-position (Fuc alpha-2)Gal beta-6Man alpha-. Further sugar chain elongation at the beta-galactoside may be in 3- and/or 6-position by alpha-galactoside, e.g. Ce4, Po2, Gal alpha-3-(Gal alpha-6)(Fuc alpha-2)Gal beta-6Man alpha-, whereas A. virosa, Av-3, has a more complex, highly alpha-fucosylated terminus, Gal alpha-3 (Fuc alpha-2)(Fuc alpha-6)Gal alpha-2(Gal alpha-3)Gal beta-6Man alpha-. L. edodes basidiolipids show further elongation by alpha-mannoside, e.g. Le3, Man alpha-2Man alpha-6Gal alpha-3(Fuc alpha-2)Gal beta-6Man alpha-, C. exipuliformis glycolipid by alpha-glucoside, i.e. Ce3, Glc alpha-6Gal beta-6Man alpha-. Basidiolipid Ls1 from L. scabrum, notably, has a 3-alpha-mannosylated alpha-fucose, i.e. Gal alpha-6(Man alpha-3Fuc alpha-2)Gal alpha-6Gal beta-6Man alpha-. In conclusion, basidiolipids, though identical in their ceramide constitution, display wide and systematic mushroom species dependent variabilities of their chemical structures.

Agaricales↗

Evaluation of long-term treatment with indomethacin in hereditary hypokalemic salt-losing tubulopathies.

OBJECTIVE: Evaluation of the benefit/risk ratio of long-term treatment with indomethacin in salt-losing tubulopathies with special attention to renal function. STUDY DESIGN: Twelve patients (median age, 14.9 years) had received indomethacin for a median of 13 years (median cumulative dose, 10.7 g/kg). Creatinine clearance, serum electrolyte levels, endocrine status, and excretion of prostaglandins and electrolytes were examined during indomethacin therapy and after its withdrawal. All patients underwent ultrasound-guided renal biopsy. For statistical evaluation, the Wilcoxon test and Pearson correlation coefficient were used. RESULTS: After indomethacin withdrawal, the biochemical features of the tubulopathy reappeared. The median creatinine clearance rose from 67.4 to 96.5 mL/min/1.73 m(2) (P <.05) but remained subnormal in 4 patients. Ultrasonography elucidated medullary nephrocalcinosis in 8 patients. Renal tissue showed slight/moderate focal tubular atrophy and interstitial fibrosis in 8 patients. Comparison with biopsy specimens, obtained 11 to 14 years before study participation from 5 patients, revealed no progression. A correlation between fractional sodium and magnesium excretion and percentage of altered tubulointerstitial compartment was found (P <.001). The 4 patients with mutations in the gene of the inwardly rectifying adenosine triphosphate-regulated potassium channel (ROMK) had almost normal renal histologic findings and normal renal function. CONCLUSION: Renal function and histology are unaffected by long-term indomethacin treatment.

Adolescent↗

Human heterophile antibodies recognizing distinct carbohydrate epitopes on basidiolipids from different mushrooms.

Investigating the immune properties of basidiolipids, i.e., glycoinositolphosphoceramides (GIPC) of basidiomytes, higher mushrooms, it was detected that sera of normal adult human subjects contained IgG2 and IgM heterophile antibodies (hetAbs) that immunoreacted with these lipids. However, this immune recognition was not shared by the glycolipids of all mushroom species. The basidiolipids of Amanita virosa (eng., death cup) and Cantharellus cibarius (engl., chantarelle), of all mushroom species studied, did not bind antibodies of normal human sera. In addition, only certain basidiolipids of the other mushroom species that have been investigated, i.e., Agaricus bisporus (engl., field mushroom), Calvatia exipuliformis engl., puffball), Lentinus edodes (jap., Shiitake), Leccinum scabrum (engl., red birch boletus), and Pleurotus ostreatus (engl., oyster mushroom), immunoreacted with the human hetAbs. The basidiolipids that were recognized by the human hetAbs had either terminal Galalpha1-6Gal < or Galbeta1-6Man< epitopes. Enzymatic destruction of the respective carbohydrate epitopes abolished the previous immune reactivity. It is assumed that contact with non human antigens causes generation of the anti-basidiolipid antibodies.

Adult↗

Mammary gland development and lactation are controlled by different glucocorticoid receptor activities.

OBJECTIVE: Regulation of physiological processes by glucocorticoids is achieved by binding to the glucocorticoid receptor (GR) and subsequent modulation of gene expression, either by DNA binding-dependent mechanisms or via protein-protein interaction with other transcription factors. The purpose of this study was to define the molecular mechanism of GR underlying the control of mammary gland development and lactation. DESIGN: To dissect the mechanism of GR action in the mammary gland, we used genetically modified mice carrying a DNA binding-defective GR. These mice retain the ability to regulate transcription by protein-protein interaction but fail to control gene expression by DNA binding-dependent mechanisms. Thus, they allow the study of the mode of GR action in vivo. METHODS: The development of the mammary gland and milk protein synthesis during lactation were studied using histological and biochemical methods. RESULTS: Our findings demonstrated that the lack of the DNA binding function of GR impairs the ductal development of the mammary gland in virgin females and that this can presumably be accounted for by reduced proliferation of epithelial cells. In contrast, lactating females have normally differentiated mammary glands and are fully capable of milk protein production. This is in good agreement with the demonstration that the DNA binding-defective GR is still able to interact with phosphorylated Stat5 proteins, suggesting that transcriptional regulation by protein-protein interaction forms the basis of glucocorticoid action in this process. CONCLUSIONS: The present study has demonstrated that GR plays an important role in the mammary gland and that it uses different molecular modes of action to control development and milk protein synthesis.

Animals↗