Franz Theuring

Endothelin-1 transgenic mice develop glomerulosclerosis, interstitial fibrosis, and renal cysts but not hypertension.

The human endothelin-1 (ET-1) gene under the control of its natural promoter was transferred into the germline of mice. The transgene was expressed predominantly in the brain, lung, and kidney. Transgene expression was associated with a pathological phenotype manifested by signs such as age-dependent development of renal cysts, interstitial fibrosis of the kidneys, and glomerulosclerosis leading to a progressive decrease in glomerular filtration rate. This pathology developed in spite of only slightly elevated plasma and tissue ET-1 concentrations. Blood pressure was not affected even after the development of an impaired glomerular filtration rate. Therefore, these transgenic lines provide a new blood pressure-independent animal model of ET-1-induced renal pathology leading to renal fibrosis and fatal kidney disease.

Targeted Deletion of the Epididymal Receptor HE6 Results in Fluid Dysregulation and Male Infertility

ABSTRACT Human epididymal protein 6 (HE6; also known as GPR64) is an orphan member of the LNB-7TM (B2) subfamily of G-protein-coupled receptors. Family members are characterized by the dual presence of a secretin-like (type II) seven-transmembrane (7TM) domain and a long cell adhesion-like extracellular domain. HE6 is specifically expressed within the efferent ductules and the initial segment of the epididymis, ductal systems involved in spermatozoon maturation. Here, we report that targeted deletion of the 7TM domain of the murine HE6 gene results in male infertility. Mutant mice reveal a dysregulation of fluid reabsorbtion within the efferent ductules, leading to a backup of fluid accumulation in the testis and a subsequent stasis of spermatozoa within the efferent ducts. The fertility phenotype of HE6 knockout mice identifies this receptor as a potential nonsteroidal, nontesticular target for future male contraceptives and identifies an in vivo function for a member of this unusual gene family.

Erythropoietin-induced excessive erythrocytosis activates the tissue endothelin system in mice.

The endothelium controls blood flow and pressure by releasing several vasoactive factors, among them the vasodilator nitric oxide (NO) and the potent vasoconstrictor endothelin‐1 (ET‐1). Although increased NO levels have been found in excessive erythrocytosis, little is known concerning ET‐1 expression in this condition. Thus, we examined the endothelin system in transgenic mice that due to constitutive overexpression of erythropoietin (Epo) reached hematocrit levels of ~80%. Surprisingly, despite generalized vasodilatation, polycythemic mice exhibited a two‐ to fivefold elevation in ET‐1 mRNA levels in aorta, liver, heart, and kidney. In line with this, increased expression of ET‐1 protein was detected in the pulmonary artery by immunohistochemical analysis. Compared with their wild‐type littermates, aortic rings of Epo transgenic animals exhibited a marked reduction in vascular reactivity to ET‐1 and big ET‐1, but this effect was abrogated upon preincubation with the NO synthase inhibitor N‐nitro‐l‐arginine methyl ester (L‐NAME). Pretreatment of polycythemic mice with the ETA receptor antagonist darusentan for 3 wk significantly prolonged their survival upon acute exposure to L‐NAME. Taken together, these results demonstrate for the first time that excessive erythrocytosis induces a marked activation of the tissue endothelin system that results in increased mortality upon blockade of NO‐mediated vasodilatation. Because ETA antagonism prolonged survival after acute blockade of NO synthesis, endothelin may be regarded as a contributor to the adverse cardiovascular effects of erythrocytosis and may thus represent a new target in the treatment of cardiovascular disease associated with erythrocytosis.

Lack of endothelial nitric oxide synthase promotes endothelin-induced hypertension: lessons from endothelin-1 transgenic/endothelial nitric oxide synthase knockout mice.

Endothelin-1 (ET-1) is one of the most potent biologic vasoconstrictors. Nevertheless, transgenic mice that overexpress ET-1 exhibit normal BP. It was hypothesized that vascular effects of ET-1 may be antagonized by an increase of the endothelial counterpart of ET-1, nitric oxide (NO), which is produced by the endothelial NO synthase (eNOS). Therefore, cross-bred animals of ET transgenic mice (ET+/+) and eNOS knockout (eNOS-/-) mice and were generated, and BP and endothelial function were evaluated in these animals. Endothelium-dependent and -independent vascular function was assessed as relaxation/contraction of isolated preconstricted aortic rings. The tissue ET and NO system was determined in aortic rings by quantitative real-time PCR and Western blotting. Systolic BP was similar in ET+/+ and wild-type (WT) mice but was significantly elevated in eNOS-/- mice (117 +/- 4 mmHg versus 94 +/- 6 mmHg in WT mice; P < 0.001) and even more elevated in ET+/+ eNOS-/- cross-bred mice (130 +/- 4 mmHg; P < 0.05 versus eNOS-/-). Maximum endothelium-dependent relaxation was enhanced in ET+/+ mice (103 +/- 6 versus 87 +/- 4% of preconstriction in WT littermates; P < 0.05) and was completely blunted in eNOS-/- (-3 +/- 4%) and ET+/+ eNOS-/- mice (-4 +/- 4%), respectively. Endothelium-independent relaxation was comparable among all groups. Quantitative real-time PCR as well as Western blotting revealed an upregulation of the aortic ET(A) and ET(B) receptors in ET+/+ eNOS-/-, whereas eNOS was absent in aortic rings of eNOS-/- and ET+/+ eNOS-/- mice. ET-1 aortic tissue concentrations were similar in WT mice and ET+/+ eNOS-/- mice most probably as a result of an enhanced clearance of ET-1 by the upregulated ET(B) receptor. These data show for the first time that in transgenic mice that overexpress human ET-1, additional knockout of eNOS results in a further enhancement of BP as compared with eNOS-/- mice. The human ET+/+ eNOS-/- mice therefore represent a novel model of hypertension as a result of an imbalance between the vascular ET-1 and NO systems.

Mice over-expressing the 5-HT1A receptor in cortex and dentate gyrus display exaggerated locomotor and hypothermic response to 8-OH-DPAT

The serotonin 1A (5-HT(1A)) receptor is one of the best described receptor subtypes of the serotonergic system. Due to the complex distribution pattern, the pre- and postsynaptic localisation, the impact on various monoamines, as well as the influence on a wide range of physiological functions, the contribution of 5-HT(1A) receptors to behavioural outcomes is difficult to define. In this study, we present a new transgenic mouse model with a prominent over-expression of the 5-HT(1A) receptor in the outer cortical layers (I-III) and the dentate gyrus. Behavioural studies revealed a slight decrease in baseline motor activity of homozygous mice during the open field test. Moreover, core body temperature of male transgenic mice was significantly lower than that of wild-type mice. Pharmacological studies with the 5-HT(1A) receptor agonist 8-OH-DPAT (0.1-2.5 mg/kg, i.p.) revealed an exaggerated drug response in mutant mice. 8-OH-DPAT led to a drastic decrease in motor activity in the open field and elevated plus maze test. This significant effect on motor activity became more apparent by investigating the serotonergic syndrome induced by 8-OH-DPAT. Concentration as low as 0.5 mg/kg 8-OH-DPAT caused immobility in transgenic mice for 30 min, head weaving behaviour, and backward walking, whereas in wild-type animals, typical behaviours of the serotonin syndrome were first observed at concentrations of 1.5 mg/kg and more. In addition, the 8-OH-DPAT induced hypothermia was more pronounced in mutant mice than in wild-type animals. Therefore, these genetically modified mice represent a promising model for further investigations of the role of 5-HT(1A) receptors.

Effects of oxidized and reduced forms of methylthioninium in two transgenic mouse tauopathy models

Given the repeated failure of amyloid-based approaches in Alzheimer’s disease, there is increasing interest in tau-based therapeutics. Although methylthioninium (MT) treatment was found to be beneficial in tau transgenic models, the brain concentrations required to inhibit tau aggregation in vivo are unknown. The comparative efficacy of methylthioninium chloride (MTC) and leucomethylthioninium salts (LMTX; 5–75 mg/kg; oral administration for 3–8 weeks) was assessed in two novel transgenic tau mouse lines. Behavioural (spatial water maze, RotaRod motor performance) and histopathological (tau load per brain region) proxies were applied. Both MTC and LMTX dose-dependently rescued the learning impairment and restored behavioural flexibility in a spatial problem-solving water maze task in Line 1 (minimum effective dose: 35 mg MT/kg for MTC, 9 mg MT/kg for LMTX) and corrected motor learning in Line 66 (effective doses: 4 mg MT/kg). Simultaneously, both drugs reduced the number of tau-reactive neurons, particularly in the hippocampus and entorhinal cortex in Line 1 and in a more widespread manner in Line 66. MT levels in the brain followed a sigmoidal concentration–response relationship over a 10-fold range (0.13–1.38 μmol/l). These data establish that diaminophenothiazine compounds, like MT, can reverse both spatial and motor learning deficits and reduce the underlying tau pathology, and therefore offer the potential for treatment of tauopathies.

An iterative calibration method with prediction of post-translational modifications for the construction of a two-dimensional electrophoresis database of mouse mammary gland proteins.

Protein databases serve as general reference recources providing an orientation on two‐dimensional electrophoresis (2‐DE) patterns of interest. The intention behind constructing a 2‐DE database of the water soluble proteins from wild‐type mouse mammary gland tissue was to create a reference before going on to investigate cancer‐associated protein variations. This database shall be deemed to be a model system for mouse tissue, which is open for transgenic or knockout experiments. Proteins were separated and characterized in terms of their molecular weight (Mr) and isoelectric point (pI) by high resolution 2‐DE. The proteins were identified using prevalent proteomics methods. One method was peptide mass fingerprinting by matrix‐assisted laser desorption/ionization‐mass spectrometry. Another method was N‐terminal sequencing by Edman degradation. By N‐terminal sequencing Mr and pI values were specified more accurately and so the calibration of the master gel was obtained more systematically and exactly. This permits the prediction of possible post‐translational modifications of some proteins. The mouse mammary gland 2‐DE protein database created presently contains 66 identified protein spots, which are clickable on the gel pattern. This relational database is accessible on the WWW under the URL: http://www.mpiib‐berlin.mpg.de/2D‐PAGE.

Impaired tight junction sealing and precocious involution in mammary glands of PKN1 transgenic mice.

The mammary gland undergoes a complex set of changes to establish copious milk secretion at parturition. To test the hypothesis that signaling through the Rho pathway plays a role in secretory activation, transgenic mice expressing a constitutively activated form of the Rho effector protein PKN1 in the mammary epithelium were generated. PKN1 activation had no effect in late pregnancy but inhibited milk secretion after parturition, diminishing the ability of transgenic dams to support a litter. Mammary gland morphology as well as increased apoptosis and expression of IFGBP5 and TGFβ3 suggest precocious involution in these animals. Furthermore, tight junction sealing at parturition was impaired in transgenic mammary glands as demonstrated by intraductal injection of [14C]sucrose. Consistent with this finding, tight junction sealing in response to glucocorticoid stimulation was highly impaired in EpH4 mammary epithelial cells expressing constitutively activated PKN1, whereas expression of a dominant-negative PKN1 mutant resulted in accelerated tight junction sealing in vitro. Tight junction formation was not impaired as demonstrated by the correct localization of occludin and ZO1 at the apical cell borders. Our results provide evidence that PKN1 participates in the regulation of tight junction sealing in the mammary gland by interfering with glucocorticoid signaling.

Transient overexpression of the 5-HT1A receptor impairs water-maze but not hole-board performance.

Previously, we showed that mice that overexpress the 5-HT(1A) receptor transiently from embryonic to perinatal stages show reduced anxiety and changes in brain serotonin turnover as adults. Here, we investigated the long-term effects of the temporary overexpression of the 5-HT(1A) receptor during early embryonic and perinatal development on the performance in two memory tasks. In the hole-board test mice that were homozygous for the transgene showed similar behavioral habituation but increased locomotion compared to heterozygous mice. In contrast water-maze performance of homozygous mice was impaired compared to heterozygous mice. These results suggest that a transient overexpression of 5-HT(1A) receptor during embryonic and perinatal development has detrimental effects on water-maze performance at adult stages.

Glucocorticoids regulate barrier function and claudin expression in intestinal epithelial cells via MKP-1

Barrier dysfunction is pivotal to the pathogenesis of inflammatory bowel diseases (IBD) and collagenous colitis. Glucocorticoids restore barrier function in Crohns disease, but whether this reflects attenuated inflammation or an epithelial-specific action has not yet been addressed. Using filter-grown Caco-2 monolayers as an in vitro model of the intestinal epithelial barrier, we observed that glucocorticoids induced a time- and dose-dependent increase in transepithelial electrical resistance (TEER) in a glucocorticoid receptor-dependent manner without altering flux of larger solutes or changing principal tight junction architecture. This was accompanied by reduced paracellular cation flux, reduced expression of the pore-forming tight junction component claudin-2, and upregulation of the sealing tight junction protein claudin-4. In contrast, expression of occludin, claudin-1, -7, or -8 was not altered. Dexamethasone increased expression and activity of MAPK phosphatase-1 and inhibition of this phosphatase prevented the glucocorticoid-induced changes in TEER and claudin expression, whereas inhibiting p38 or MEK1/2 was not sufficient to replicate the glucocorticoid effects. Upon exposure to IFN-γ, TNF-α, or IL-1β, TEERs declined in dexamethasone-treated cells but remained consistently higher than in cells not receiving glucocorticoids. Treatment with IFN/TNF resulted in an upregulation of claudin-2 that was significantly attenuated by dexamethasone, whereas increased claudin-2 expression upon IL-1β stimulation was not affected by glucocorticoids. Taken together, barrier augmentation might represent a previously unrecognized mechanism of action, potentially contributing to the therapeutic efficacy of glucocorticoids in IBD and collagenous colitis.