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1.  Targeted Disruption of Murine Organic Anion-Transporting Polypeptide 1b2 (oatp1b2/Slco1b2) Significantly Alters Disposition of Prototypical Drug Substrates Pravastatin and Rifampin 
Molecular pharmacology  2008;74(2):320-329.
Organic anion transporting polypeptide (OATP) 1B1 and 1B3 are widely acknowledged as important and rate-limiting to the hepatic uptake of many drugs in clinical use. Accordingly, to better understand the in vivo relevance of OATP1B transporters, targeted disruption of murine Slco1b2 gene was carried out. Interestingly, Slco1b2−/− mice were fertile, developed normally, and did not exhibit any overt phenotypic abnormalities. We confirmed the loss of Oatp1b2 expression in liver using real-time PCR, Western Blot analysis and immunohistochemistry. Oatp1a4 and Oatp2b1, but not Oatp1a1 expression was greater in female Slco1b2−/− mice, but expression of other non-oatp transporters did not significantly differ between wildtype and Slco1b2−/− males. Total bilirubin level was elevated by 2-fold in the Slco1b2−/− mice despite that liver enzymes ALT and AST were normal. Pharmacological characterization was carried out using two prototypical substrates of human OATP1B1 and 1B3, rifampin and pravastatin. After a single intravenous dose of rifampin (1mg/kg), a 1.7-fold increase in plasma AUC was observed while the liver-to-plasma ratio was reduced by 5-fold, and nearly 8-fold when assessed at steady -state conditions after 24 hours of continuous subcutaneous (SC) infusion in Slco1b2−/− mice. Similarly, continuous SC-infusion at low dose rate (8 μg/hr) or high dose rate (32 μg/hr) pravastatin resulted in a 4-fold lower liver-plasma ratio in the in Slco1b2−/− mice. This is the first report of altered drug disposition profile in the Slco1b2 knockout mice and suggests the utility of this model for understanding the in vivo role of hepatic OATP transporters in drug disposition.
PMCID: PMC2562886  PMID: 18413659
2.  Severe diabetes, age-dependent loss of adipose tissue, and mild growth deficiency in mice lacking Akt2/PKBβ 
Journal of Clinical Investigation  2003;112(2):197-208.
The serine/threonine kinase Akt/PKB plays key roles in the regulation of cell growth, survival, and metabolism. It remains unclear, however, whether the functions of individual Akt/PKB isoforms are distinct. To investigate the function of Akt2/PKBβ, mice lacking this isoform were generated. Both male and female Akt2/PKBβ-null mice exhibit mild growth deficiency and an age-dependent loss of adipose tissue or lipoatrophy, with all observed adipose depots dramatically reduced by 22 weeks of age. Akt2/PKBβ-deficient mice are insulin resistant with elevated plasma triglycerides. In addition, Akt2/PKBβ-deficient mice exhibit fed and fasting hyperglycemia, hyperinsulinemia, glucose intolerance, and impaired muscle glucose uptake. In males, insulin resistance progresses to a severe form of diabetes accompanied by pancreatic β cell failure. In contrast, female Akt2/PKBβ-deficient mice remain mildly hyperglycemic and hyperinsulinemic until at least one year of age. Thus, Akt2/PKBβ-deficient mice exhibit growth deficiency similar to that reported previously for mice lacking Akt1/PKBα, indicating that both Akt2/PKBβ and Akt1/PKBα participate in the regulation of growth. The marked hyperglycemia and loss of pancreatic β cells and adipose tissue in Akt2/PKBβ-deficient mice suggest that Akt2/PKBβ plays critical roles in glucose metabolism and the development or maintenance of proper adipose tissue and islet mass for which other Akt/PKB isoforms are unable to fully compensate.
PMCID: PMC164287  PMID: 12843127
3.  Kinase Suppressor of Ras (KSR) Is a Scaffold Which Facilitates Mitogen-Activated Protein Kinase Activation In Vivo 
Molecular and Cellular Biology  2002;22(9):3035-3045.
While scaffold proteins are thought to be key components of signaling pathways, their exact function is unknown. By preassembling multiple components of signaling cascades, scaffolds are predicted to influence the efficiency and/or specificity of signaling events. Here we analyze a potential scaffold of the Ras/mitogen-activated protein kinase (MAPK) pathway, kinase suppressor of Ras (KSR), by generating KSR-deficient mice. KSR-deficient mice were grossly normal even though ERK kinase activation was attenuated to a degree sufficient to block T-cell activation and inhibit tumor development. Consistent with its role as a scaffold, high-molecular-weight complexes containing KSR, MEK, and ERK were lost in the absence of KSR. This demonstrates that KSR is a bona fide scaffold that is not required for but enhances signaling via the Ras/MAPK signaling pathway.
PMCID: PMC133772  PMID: 11940661
4.  The prostaglandin E2 EP1 receptor mediates pain perception and regulates blood pressure 
Journal of Clinical Investigation  2001;107(3):325-331.
The lipid mediator prostaglandin E2 (PGE2) has diverse biological activity in a variety of tissues. Four different receptor subtypes (EP1–4) mediate these wide-ranging effects. The EP-receptor subtypes differ in tissue distribution, ligand-binding affinity, and coupling to intracellular signaling pathways. To identify the physiological roles for one of these receptors, the EP1 receptor, we generated EP1-deficient (EP1–/–) mice using homologous recombination in embryonic stem cells derived from the DBA/1lacJ strain of mice. The EP1–/– mice are healthy and fertile, without any overt physical defects. However, their pain-sensitivity responses, tested in two acute prostaglandin-dependent models, were reduced by approximately 50%. This reduction in the perception of pain was virtually identical to that achieved through pharmacological inhibition of prostaglandin synthesis in wild-type mice using a cyclooxygenase inhibitor. In addition, systolic blood pressure is significantly reduced in EP1 receptor–deficient mice and accompanied by increased renin-angiotensin activity, especially in males, suggesting a role for this receptor in cardiovascular homeostasis. Thus, the EP1 receptor for PGE2 plays a direct role in mediating algesia and in regulation of blood pressure.
PMCID: PMC199184  PMID: 11160156
5.  Collagen-induced Arthritis Is Reduced in 5-Lipoxygenase-activating Protein-deficient Mice 
The Journal of Experimental Medicine  1997;185(6):1123-1130.
Collagen-induced arthritis in the DBA/1 mouse is an experimental model of human rheumatoid arthritis. To examine the role of leukotrienes in the pathogenesis of this disease, we have developed embryonic stem (ES) cells from this mouse strain. Here, we report that DBA/1 mice made deficient in 5-lipoxygenase-activating protein (FLAP) by gene targeting in ES cells develop and grow normally. Zymosan-stimulated leukotriene production in the peritoneal cavity of these mice is undetectable, whereas they produce substantial amounts of prostaglandins. The inflammatory response to zymosan is reduced in FLAP-deficient mice. The severity of collagen-induced arthritis in the FLAP-deficient mice was substantially reduced when compared with wild-type or heterozygous animals. This was not due to an immunosuppressive effect, because anti-collagen antibody levels were similar in wild-type and FLAP-deficient mice. These data demonstrate that leukotrienes play an essential role in both the acute and chronic inflammatory response in mice.
PMCID: PMC2196231  PMID: 9091585

Results 1-5 (5)