Detectable levels of pepsin remain in laryngeal epithelia after a reflux event. Pepsin bound there would be enzymatically inactive because the mean pH of the laryngopharynx is pH 6.8. Significantly, pepsin could remain in a form that would be reactivated by a subsequent decrease in pH, such as would occur during an acidic reflux event or possibly after uptake into intracellular compartments of lower pH.

Based upon several previous reports, no consistent relationship between multidrug resistance protein 1 (MRP1, ABCC1) expression and cellular sensitivity to mitoxantrone (MX) toxicity can be ascertained; thus, the role of MRP1 in MX resistance remains controversial. The present study, using paired parental, MRP1-poor, and transduced MRP1-overexpressing MCF7 cells, unequivocally demonstrates that MRP1 confers resistance to MX cytotoxicity and that resistance is associated with reduced cellular accumulation of MX. This MRP1-associated reduced accumulation of MX was partially reversed by treatment of cells with 50propionic acid]-an MRP inhibitor that increased MX accumulation in MRP1-expressing MCF7 cells but had no effect on MRP-poor MCF7 cells. Moreover, in vitro experiments using inside-out membrane vesicles show that MRP1 supports ATPdependent, osmotically sensitive uptake of MX. Unlike ABCG2 (breast cancer resistance protein, mitoxantrone-resistant protein), MRP1-mediated MX transport is dependent upon the presence of glutathione or its S-methyl analog. In addition, MX stimulates transport of [ 3 H]glutathione. Together, these data are consistent with the interpretation that MX efflux by MRP1 involves cotransport of MX and glutathione. The results suggest that MRP1-like the alternative MX transporters ABCG2 and ABCB1 (MDR1, P-glycoprotein)-can significantly influence tumor cell sensitivity to and pharmacological disposition of MX.

Autosomal recessive limb-girdle muscular dystrophy type 2G (LGMD2G) is an adult-onset myopathy characterized by distal lower limb weakness, calf hypertrophy and progressive decline in ambulation. The disease is caused by mutations in Tcap, a z-disc protein of skeletal muscle, although the precise mechanisms resulting in clinical symptoms are unknown. To provide a model for preclinical trials and for mechanistic studies, we generated knockout (KO) mice carrying a null mutation in the Tcap gene. Here we present the first report of a Tcap KO mouse model for LGMD2G and the results of an investigation into the effects of Tcap deficiency on skeletal muscle function in 4- and 12-month-old mice. Muscle histology of Tcap-null mice revealed abnormal myofiber size variation with central nucleation, similar to findings in the muscles of LGMD2G patients. An analysis of a Tcap binding protein, myostatin, showed that deletion of Tcap was accompanied by increased protein levels of myostatin. Our Tcap-null mice exhibited a decline in the ability to maintain balance on a rotating rod, relative to wild-type controls. No differences were detected in force or fatigue assays of isolated extensor digitorum longus (EDL) and soleus (SOL) muscles. Finally, a mechanical investigation of EDL and SOL indicated an increase in muscle stiffness in KO animals. We are the first to establish a viable KO mouse model of Tcap deficiency and our model mice demonstrate a dystrophic phenotype comparable to humans with LGMD2G.

We report herein the design and synthesis of a series of orally active, liver-targeted hypoxia-inducible factor prolyl hydroxylase (HIF-PHD) inhibitors for the treatment of anemia. In order to mitigate the concerns for potential systemic side effects, we pursued liver-targeted HIF-PHD inhibitors relying on uptake via organic anion transporting polypeptides (OATPs). Starting from a systemic HIF-PHD inhibitor (1), medicinal chemistry efforts directed toward reducing permeability and, at the same time, maintaining oral absorption led to the synthesis of an array of structurally diverse hydroxypyridone analogues. Compound 28a was chosen for further profiling, because of its excellent in vitro profile and liver selectivity. This compound significantly increased hemoglobin levels in rats, following chronic QD oral administration, and displayed selectivity over systemic effects.