Transforming growth factor ␤1 (TGF-␤1) is a potent fibrotic factor responsible for the synthesis of extracellular matrix. TGF-␤1 acts through the TGF-␤ type I and type II receptors to activate intracellular mediators, such as Smad proteins, the p38 mitogen-activated protein kinase (MAPK), and the extracellular signal-regulated kinase pathway. We expressed the kinase domain of the TGF-␤ type I receptor [activin receptor-like kinase (ALK)5] and the substrate, Smad3, and determined that SB-431542 is a selective inhibitor of Smad3 phosphorylation with an IC 50 of 94 nM. It inhibited TGF-␤1-induced nuclear Smad3 localization. The p38 mitogen-activated protein kinase inhibitors SB-203580 and SB-202190 also inhibit phosphorylation of Smad3 by ALK5 with IC 50 values of 6 and 3 M, respectively. This suggests that these p38 MAPK inhibitors must be used at concentrations of less than 10 M to selectively address p38 MAPK mechanisms. However, the p38 MAPK inhibitor SB-242235 did not inhibit ALK5. To evaluate the relative contribution of Smad signaling and p38 MAPK signaling in TGF-␤1-induced matrix production, the effect of SB-431542 was compared with that of SB-242235 in renal epithelial carcinoma A498 cells. All compounds inhibited TGF-␤1-induced fibronectin (FN) mRNA, indicating that FN synthesis is mediated in part via the p38 MAPK pathway. In contrast, SB-431542, but not the selective p38 MAPK inhibitor SB-242235, inhibited TGF-␤1-induced collagen I␣1 (col I␣1). These data indicate that some matrix markers that are stimulated by TGF-␤1 are mediated via the p38 MAPK pathway (i.e., FN), whereas others seem to be activated via ALK5 signaling independent of the p38 MAPK pathway (i.e., col I␣1).

The insular cortex is involved in cardiac regulation. The left insula is predominantly responsible for parasympathetic cardiovascular effects. Damage to this area could shift cardiovascular balance towards increased basal sympathetic tone (a pro-arrhythmic condition) and contribute to the excess cardiac mortality following stroke. Acute left insular stroke increased basal cardiac sympathetic tone and was associated with a decrease in randomness of heart rate variability. In addition, phase relationships between heart rate and blood pressure were disturbed, implying a disruption of oscillators involved in cardiovascular control. The insula appears to be involved in human heart rate regulation and damage to it may encourage a pro-arrhythmic state.

SB-525334 (6-[2-tert-butyl-5-(6-methyl-pyridin-2-yl)-1H-imidazol-4-yl]-quinoxaline) has been characterized as a potent and selective inhibitor of the transforming growth factor-␤1 (TGF-␤1) receptor, activin receptor-like kinase (ALK5). The compound inhibited ALK5 kinase activity with an IC 50 of 14.3 nM and was ϳ4-fold less potent as an inhibitor of ALK4 (IC 50 ϭ 58.5 nM). SB-525334 was inactive as an inhibitor of ALK2, ALK3, and ALK6 (IC 50 Ͼ 10,000 nM). In cell-based assays, SB-525334 (1 M) blocked TGF-␤1-induced phosphorylation and nuclear translocation of Smad2/3 in renal proximal tubule cells and inhibited TGF-␤1-induced increases in plasminogen activator inhibitor-1 (PAI-1) and procollagen ␣1(I) mRNA expression in A498 renal epithelial carcinoma cells. In view of this profile, SB-525334 was used to investigate the role of TGF-␤1 in the acute puromycin aminonucleoside (PAN) rat model of renal disease, a model of nephritis-induced renal fibrosis. Orally administered doses of 1, 3, or 10 mg/kg/day SB-525334 for 11 days produced statistically significant reductions in renal PAI-1 mRNA. Also, the compound produced dose-dependent decreases in renal procollagen ␣1(I) and procollagen ␣1(III) mRNA, which reached statistical significance at the 10-mg/kg/day dose when compared with vehicle-treated PAN controls. Furthermore, PAN-induced proteinuria was significantly inhibited at the 10-mg/kg/day dose level. These results provide further evidence for the involvement of TGF-␤1 in the profibrotic changes that occur in the PAN model and for the first time, demonstrate the ability of a small molecule inhibitor of ALK5 to block several of the markers that are predictive of fibrosis and renal injury in this model.

Total body potassium (TBK) data calculated from longitudinal measurements over 18 y of 40K by whole-body counting of 564 male and 61 female healthy humans in a 2-pi liquid scintillation counter show little change in females younger than 50 y compared with males of those ages. Males show less TBK from 41 y onward as they age, with most rapid rate of loss between 41 and 60 y. Females have a rapid loss of TBK when they are older than 60 y; the loss is at a greater rate than that of males. Percent total body fat calculated from total body weight and lean body mass (LBM) derived from TBK document greater adiposity in females at all ages except ages 51-60 y when females are similar to males in change in percent fat per year per centimeter.