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Inverse acinar regulation of Mrp2 and 3 represents an adaptive response to hepatocellular cholestatic injury. We studied whether obstructive cholestasis (bile duct ligation) and LPS treatment affect the zonal expression of Bsep (Abcb11), Mrp4 (Abcc4), Ntcp (Slc10a1), and Oatp isoforms (Slcolal, Slcola4, and slco1b2) in rat liver, as analyzed by semiquantitative immunofluorescence. Contribution of TNF-[alpha] and IL-1[beta] to transporter zonation in obstructive cholestasis was studied by cytokine inactivation. In normal liver Bsep, Mrp4, Ntcp, and Oatp1a1 were homogeneously distributed in the acinus, whereas Oatp1a4 and Oatp1b2 expression increased from zone 1 to 3. Glutamine synthetase-positive pericentral hepatocytes exhibited markedly lower Oatp1a4 expression than the remaining zone 3 hepatocytes. In cholestatic liver Bsep and Ntcp immunofluorescence in periportal hepatocytes significantly decreased to 66 [+ or -] 4% (P < 0.01) and 67 [+ or -] 7% (P < 0.05), whereas it was not altered in pericentral hepatocytes. Oatp1a4 was significantly induced in hepatocytes with a primarily low expression, i.e., in periportal hepatocytes and in glutamine synthetase-positive pericentral hepatocytes, Likewise, Oatp1b2 was upregulated in periportal hepatocytes. Mrp4 zonal induction was homogeneous. Inactivation of TNF-[alpha] and IL-1[beta] prevented periportal downregulation of Bsep. Recruitment of neutrophils and polymorphonuclear cells mainly occurred in the periportal zone. Likewise, IL- 1[beta] induction was largely found periportally. No significant transporter zonation was seen following LPS treatment. In conclusion, zonal downregulation of Bsep in obstructive cholestasis is associated with portal inflammation and is mediated by TNF-[alpha] and IL-1[beta]. Periportal downregulation of Ntcp and induction of Oatp1a4 and Oatp1b2 may represent adaptive mechanisms to reduce cholestatic injury in hepatocytes with profound downregulation of Bsep and Mrp2. hepatobiliary transport; bile salts; cytokines; acinar regulation; organic anion transporters

T-cell activation and the subsequent transformation of activated T cells into T-cell blasts require profound changes in cell volume. However, the impact of cell volume regulation for T-cell immunology has not been characterized. Here we studied the role of the cell-volume regulating osmolyte transporter Taut for T-cell activation in Taut-deficient mice. T-cell mediated recall responses were severely impaired in taut−/− mice as shown with B16 melanoma rejection and hapten-induced contact hypersensitivity. CD4+ and CD8+ T cells were unequivocally located within peripheral lymph nodes of unprimed taut−/− mice but significantly decreased in taut−/− compared with taut+/+ mice following in vivo activation. Further analysis revealed that Taut is critical for rescuing T cells from activation-induced cell death in vitro and in vivo as shown with TCR, superantigen, and antigen-specific activation. Consequently, reduction of CD4+ and CD8+ T cells in taut−/− mice upon antigen challenge resulted in impaired in vivo generation of T-cell memory. These findings disclose for the first time that volume regulation in T cells is an element in the regulation of adaptive immune responses and that the osmolyte transporter Taut is crucial for T-cell survival and T-cell mediated immune reactions. [ABSTRACT FROM AUTHOR]

Inverse acinar regulation of Mrp2 and 3 represents an adaptive response to hepatocellular cholestatic injury. We studied whether obstructive cholestasis (bile duct ligation) and LPS treatment affect the zonal expression of Bsep (Abcb11), Mrp4 (Abcc4), Ntcp (Slc10a1), and Oatp isoforms (Slc10a1, Slco1a4, and slco1b2) in rat liver, as analyzed by semiquantitative immunofluorescence. Contribution of TNF-α and IL-1β to transporter zonation in obstructive cholestasis was studied by cytokine inactivation. In normal liver Bsep, Mrp4, Ntcp, and Oatpla1 were homogeneously distributed in the acinus, whereas Oatpla4 and Oatplb2 expression increased from zone 1 to 3. Glutamine synthetase-positive pericentral hepatocytes exhibited markedly lower Oatpla4 expression than the remaining zone 3 hepatocytes. In cholestatic liver Bsep and Ntcp immunofluorescence in periportal hepatocytes significantly decreased to 66 ± 4% (P < 0.01) and 67 ± 7% (P < 0.05), whereas it was not altered in pericentral hepatocytes. Oatpla4 was significantly induced in hepatocytes with a primarily low expression, i.e., in periportal hepatocytes and in glutamine synthetase-positive pericentral hepatocytes. Likewise, Oatplb2 was upregulated in periportal hepatocytes. Mrp4 zonal induction was homogeneous. Inactivation of TNF-α and IL-1β prevented periportal downregulation of Bsep. Recruitment of neutrophils and polymorphonuclear cells mainly occurred in the periportal zone. Likewise, IL-1β induction was largely found periportally. No significant transporter zonation was seen following LPS treatment. In conclusion, zonal downregulation of Bsep in obstructive cholestasis is associated with portal inflammation and is mediated by TNF-α and IL-1β. Periportal downregulation of Ntcp and induction of Oatpla4 and Oatplb2 may represent adaptive mechanisms to reduce cholestatic injury in hepatocytes with profound downregulation of Bsep and Mrp2. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine whether the knockout of the taurine-transporter gene in the mouse affects the densities of GABAA, kainate, AMPA and NMDA receptors in the brain. The caudate-putamen, the hippocampus and its subregions, and the cerebellum of six homozygous taurine-transporter gene knockout mice and six wild-type (WT) animals were examined by means of quantitative receptor autoradiography. Saturation studies were carried out for all four receptor types in order to find possible intergroup differences in B max and K D values. Taurine-transporter gene knockout animals showed significantly higher GABAA receptor densities in the molecular layer of the hippocampal dentate gyrus and in the cerebellum than did WT animals. The densities of kainate receptors were significantly higher in the caudate-putamen, the CA1 and hilus regions of the hippocampus and in the cerebellum of knockout animals. The caudate-putamen and cerebellum of these mice also contained significantly higher AMPA receptor densities. However, there were no significant differences between knockout and WT animals concerning the densities of NMDA receptors. Reduced brain taurine levels are associated with increased GABAA, kainate and AMPA receptor densities in some of the regions we examined. [ABSTRACT FROM AUTHOR]

In nucleated cells cellular taurine is released prior to DNA fragmentation and the breakdown of phosphatidylserine asymmetry within the plasma membrane. Similar to what is seen in nucleated cells, phosphatidylserine asymmetry is also abolished in erythrocytes exposed to osmotic shock or oxidative stress. The present study has been performed to explore the sensitivity of erythrocytes from a taurine transporter knockout mouse (taut-/-) against osmotic shock and oxidative stress. Erythrocyte cell volume was estimated from forward scatter and breakdown of phosphatidylserine asymmetry was identified by determination of annexin binding using FACS analysis. Erythrocytes from taut-/- mice were compared to erythrocytes from wild type littermates (taut+/+). Plasma concentration and erythrocyte content of taurine was significantly lower in taut-/- than in taut+/+ mice, but the intraerythrocyte taurine concentration did not exceed the plasma concentration. Hyperosmotic shock (exposure to 700 mOsm) and oxidative stress (exposure to 0.1 mM tert-butyl-hydroperoxide) significantly decreased the cell volume and increased the number of annexin binding sites of erythrocytes from both, taut-/- and taut+/+ mice. However, decrease of cell volume and increase of annexin binding was significantly blunted in erythrocytes from taut-/- mice as compared to their taut+/+ littermates. Stimulation of erythropoiesis by prior hemorrhage did not abrogate the difference between taut+/+ and taut-/- erythrocytes. The present observations point to a decreased sensitivity of mature erythrocytes from taut-/- mice to osmotic shock and oxidative stress, rendering them more resistant to apoptosis. [ABSTRACT FROM AUTHOR]

NAD(P)H:quinone oxidoreductase (NQOR) and glutathione S-transferases (GST) are enzymes of interest in cell defence and drug resistance. Relative levels of NQOR mRNA in renal cell carcinomas were 28 ±24% (n=21) of those in non-neoplastic tissue and the enzyme activity decreased from 41±39 to 18±27 mU/mg protein (=23). In three of the cases, there was no measurable NQOR enzyme activity at all, indicating a polymorphism in the population for this gene. Relative GST-a mRNA levels in the tumours were on average 6±6% (=22) of the control value, whereas for GST-π mRNA smaller decreases as well as increases were found in the tumours as compared to control tissue, but, on average, the level remained unchanged. Overall GST activity measured with CDNB as a substrate was 152±157 mU/mg protein in tumour tissue and 342 ± 177 mU/mg protein in non-neoplastk tissue (=23). In all kidney tumour-derived cell lines NQOR mRNA was strongly expressed and on a per protein basis NQOR activity was about 10-fold higher than in the kidney tumour samples. GST-π but not GST-α mRNA was also present. Total GST enzyme activities in these cell lines were similar to those in kidney tumour samples. HepG2 cells exhibited expression of NQOR and GST-π GST-α was not detectable. NQOR activity in HepG2 was about four-fold higher than in kidney-derived cell lines. Thus, NQOR and GST-α are both down-regulated in renal carcinoma, but their expression diverges in carcinoma cell lines. [ABSTRACT FROM PUBLISHER]

Presents findings of a study on the role of taurine in liver physiology and in cell protection against various types of injury. Level of taurine in Kupffer and sinosoidal endothelial cells; Role of oval cell proliferation and neoplastic lesions in developing hepatitis and liver fibrosis in transgenic mice; Description of hepatocyte apoptosis and activation of the CD95 system; Cause of the mitochondrial dysfunction in transgenic mice.

Identifies taurine transport as a crucial factor for the maintenance of skeletal muscle function and total exercise capacity while cardiac muscle can compensate for the loss of taurine. Taurine transporter gene knockout; Analysis of taut-/- skeletal muscle; Upregulation of the cytosolic concentration of several organic solutes in heart but not in skeletal muscle.

An abstract of the article "Phenotype of the Taurine Transporter Knockout Mouse," by Ulrich Warskulat and colleagues is presented.

Deletion of the taurine transporter gene (taut) results in lowered levels of taurine, the most abundant amino acid in mammals. Here, we show that taut-/- mice have lost their ability to self-heal blood-stage infections with Plasmodium chabaudi malaria. All taut-/- mice succumb to infections during crisis, while about 90% of the control taut(+/+) mice survive. The latter retain unchanged taurine levels even at peak parasitemia. Deletion of taut, however, results in the lowering of circulating taurine levels from 540 to 264 micromol/liter, and infections cause additional lowering to 192 micromol/liter. Peak parasitemia levels in taut-/- mice are approximately 60% higher than those in taut(+/+) mice, an elevation that is associated with increased systemic tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) levels, as well as with liver injuries. The latter manifest as increased systemic ammonia levels, a perturbed capacity to entrap injected particles, and increased expression of genes encoding TNF-alpha, IL-1beta, IL-6, inducible nitric oxide synthase (iNOS), NF-kappaB, and vitamin D receptor (VDR). Autopsy reveals multiorgan failure as the cause of death for malaria-infected taut-/- mice. Our data indicate that taut-controlled taurine homeostasis is essential for resistance to P. chabaudi malaria. Taurine deficiency due to taut deletion, however, impairs the eryptosis of P. chabaudi-parasitized erythrocytes and expedites increases in systemic TNF-alpha, IL-1beta, and ammonia levels, presumably contributing to multiorgan failure in P. chabaudi-infected taut-/- mice.

Organic osmolytes, such as taurine, are involved in cell volume homeostasis and cell protection. Epidermal keratinocytes possess an osmolyte strategy, i.e., they take up taurine upon hyperosmotic stress and express the corresponding transporter TAUT. UVB irradiation also triggers taurine uptake and TAUT expression in this cell type. We therefore asked whether taurine plays a role in photoprotection. By using a TAUT-deficient mouse model, lack of taurine in the skin was found to cause a significantly higher sensitivity to UVB-induced immunosuppression. This was not due to an increased generation or decreased repair of UVB-induced DNA photoproducts in the skin of these animals. Instead, decreased skin taurine levels were associated with an increased formation of the soluble immunosuppressive molecule platelet-activating factor (PAF) from the membranes of UVB-irradiated epidermal cells. Blocking PAF activity in taut-deficient mice with a PAF receptor antagonist abrogated their increased sensitivity to UVB-induced immunosuppression. Moreover, taut -/- mice were more sensitive to PAF-mediated immunosuppression than taut +/+ mice. These data suggest that taurine uptake by epidermal cells prevents undue PAF formation, and thereby photoimmunosuppression. Thus, similar to nucleotide excision repair, taurine uptake is critically involved in photoprotection of the skin.

Taurine is the most abundant free amino acid in heart muscle and protects against heart failure. In the present study, the consequences of hereditary taurine deficiency on cardiac gene expression were examined in 2- and 15-16-month-old taurine transporter knockout (taut(-/-)) mice using a mouse-specific DNA microarray. This oligonucleotide-based microarray contains probes for 251 genes with relevance for heart function. Of these, 163 probes exhibited a reproducible hybridization signal and were analyzed. alpha-Actin type 1 mRNA levels were 70% lower in the heart of young and older taut(-/-) mice compared to wild-type controls. Interestingly, the hearts of taut(-/-) mice showed a switch from alpha-actin 1 to alpha-actin 2 expression, as confirmed by real-time PCR and Western blot analysis. In addition, mRNA levels of biomarkers for pressure overload and hypertension were upregulated in taut(-/-) hearts, i.e., atrial natriuretic factor (+848%), brain natriuretic peptide (+90%), cardiac ankyrin repeat protein (+118%), and procollagen 1a1, 1a2 and 3a1 (+40% at least). These results point to a stress situation in the heart of taut(-/-) mice under laboratory conditions, and it can be speculated that taut(-/-) hearts may be even more susceptible to failure in the wild when under exogenous stress.

Introduction: Proliferation and matrix synthesis of activated pancreatic stellate cells (PSCs) participate in the development of chronic pancreatitis. Besides other substances, endothelin-1 (ET-1) may influence the activation process of PSCs. Until now, ET-1 has not been studied in this particular cell type., Aims: To characterize PSCs in rat pancreas with respect to expression of ET(A)-receptors, production of ET-1, and physiological effects induced by ET-1 during PSC activation., Methodology: Immunocytochemical and ELISA techniques and cDNA microarray analysis were used. Physiologic effects were characterized by single cell measurements of free cytosolic Ca2+-concentration and of PSC contractility on collagen lattices., Results: Activation of PSCs in vitro, as assessed by alpha-smooth muscle actin expression, was accompanied by the de novo expression of ET(A)-receptors and synthesis of ET-1 mRNA and protein. Cytosolic Ca2+-concentration was increased upon ET-1 stimulation in activated but not in quiescent PSCs. Contractility of activated PSCs was significantly reduced by the selective ET(A)-receptor antagonist BQ123 but not by the ET(B)-receptor antagonist IRL-1038., Conclusions: The results suggest that ET-1 may act as a paracrine and autocrine factor for activated PSCs and may mediate contractions of activated, but not quiescent, PSCs.