Differential induction of PPAR-gamma by luminal glutamine and iNOS by luminal arginine in the rodent postischemic small bowel.

Using a rodent model of gut ischemia-reperfusion (I/R), we have previously shown that the induction of inducible nitric oxide synthase (iNOS) is harmful, whereas the induction of heme oxygenase 1 (HO-1) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is protective. In the present study, we hypothesized that the luminal nutrients arginine and glutamine differentially modulate these molecular events in the postischemic gut. Jejunal sacs were created in rats at laparotomy, filled with either 60 mM glutamine, arginine, or magnesium sulfate (osmotic control) followed by 60 min of superior mesenteric artery occlusion and 6 h of reperfusion, and compared with shams. The jejunum was harvested for histology or myeloperoxidase (MPO) activity (inflammation). Heat shock proteins and iNOS were quantitated by Western blot analysis and PPAR-gamma by DNA binding activity. In some experiments, rats were pretreated with the PPAR-gamma inhibitor G9662 or with the iNOS inhibitor N-[3(aminomethyl)benzyl]acetamidine (1400W). iNOS was significantly increased by arginine but not by glutamine following gut I/R and was associated with increased MPO activity and mucosal injury. On the other hand, PPAR-gamma was significantly increased by glutamine but decreased by arginine, whereas heat shock proteins were similarly increased in all experimental groups. The PPAR-gamma inhibitor G9662 abrogated the protective effects of glutamine, whereas the iNOS inhibitor 1400W attenuated the injurious effects of arginine. We concluded that luminal arginine and glutamine differentially modulate the molecular events that regulate injurious I/R-mediated gut inflammation and injury. The induction of PPAR-gamma by luminal glutamine is a novel protective mechanism, whereas luminal arginine appears harmful to the postischemic gut due to enhanced expression of iNOS.

Surface morphology of poly(caprolactone)-b-poly(dimethylsiloxane)-b-poly(caprolactone) copolymers: effects on protein adsorption.

Certain triblock copolymer surfaces have beneficial blood contacting properties that remain unexplained from a mechanistic perspective. In this study, poly(caprolactone-block-dimethylsiloxane-block-caprolactone) (PCL-b-PDMS-b-PCL) surfaces are characterized by dynamic contact angle analysis, angle-resolved X-ray photoelectron spectroscopy (XPS), and phase detection imaging atomic force microscopy (AFM). Surface morphology of films cast from 10 wt % MEK solutions are found to be semicrystalline possessing spherulites on the micron scale and alternating semicrystalline PCL-rich and amorphous PDMS-rich lamellae on the nanometer scale. Surface enrichment of the lower surface free energy block, PDMS, is observed using angle-resolved XPS but the surface composition still consists of both copolymer blocks. Films cast from 1 wt % solutions showed similar morphologies but incomplete surface coverage. Different textural features of adsorbed fibrinogen layers on coated and uncoated polypropylene are observed. The hypothesis that patterned block copolymer surfaces can affect protein adsorption and thus influence compatibility is partially supported by the findings of this study.