guanosine-diphosphate and Infections

Long-term exposure to standard peritoneal dialysis fluid (PDF) results in alterations in peritoneal morphology and function. Studies investigating the long-term effects on the peritoneum of a low-glucose degradation product (GDP) bicarbonate/lactate-buffered PDF demonstrated its superior biocompatibility. We examined the potential of the low-GDP bicarbonate/lactate-buffered solution to reverse or reduce standard PDF-induced peritoneal alterations.. Female Wistar rats received twice daily intraperitoneal infusions with either a lactate-buffered solution with 3.86% glucose at pH 5.5 (Dianeal, referred to as standard PDF), or a low-GDP bicarbonate/lactate-buffered solution with 3.86% glucose at physiologic pH (Physioneal, referred to as bicarbonate/lactate PDF) for different periods of time: (1) 12 weeks Dianeal (N= 9); (2) 12 weeks Physioneal (N= 9); (3) 20 weeks Dianeal (N= 11); (4) 20 weeks Physioneal (N= 10); (5) 12 weeks Dianeal followed by 8 weeks Physioneal (N= 10).. Chronic standard PDF exposure resulted in loss of ultrafiltration capacity, increased VEGF expression and vascular density, higher advanced glycation end product (AGE) accumulation, up-regulation of TGF-beta expression, and development of fibrosis compared to low-GDP bicarbonate/lactate-buffered PDF. The PDF-induced alterations were time-dependent. Crossover from standard PDF to low-GDP bicarbonate/lactate PDF resulted in a less impaired ultrafiltration (UF), less pronounced VEGF expression and neoangiogenesis, and less severe AGE accumulation, TGF-beta expression, and fibrosis compared to continuous standard PDF exposure for 20 weeks.. Low-GDP bicarbonate/lactate-buffered PDF has the potential to slow down standard PDF-induced peritoneal membrane damage.

Topics: Animals; Bicarbonates; Dialysis Solutions; Female; Guanosine Diphosphate; Infections; Lactic Acid; Models, Animal; Peritoneal Cavity; Rats; Rats, Wistar; Ultrafiltration; Viscera

IIGP1 belongs to a well defined family of 47-kDa GTPases whose members are present at low resting levels in mouse cells but are strongly induced transcriptionally by interferons and are implicated in cell-autonomous resistance to intracellular pathogens. Recombinant IIGP1 was expressed in Escherichia coli and purified to homogeneity. Here we present a detailed biochemical characterization of IIGP1 using various biochemical and biophysical methods. IIGP1 binds to GTP and GDP with dissociation constants in the micromolar range with at least 10 times higher affinity for GDP than for GTP. IIGP1 hydrolyzes GTP to GDP, and the GTPase activity is concentration-dependent with a GTP turnover rate of 2 min-1 under saturating protein concentrations. Functional interaction between IIGP1 molecules is shown by nucleotide-dependent oligomerization in vitro. Both cooperative hydrolysis of GTP and GTP-dependent oligomerization are blocked in a mutant form of IIGP1 modified at the C terminus. IIGP1 shares micromolar nucleotide affinities and oligomerization-dependent hydrolytic activity with the 67-kDa GTPase hGBP1 (induced by type I and type II interferons), with the antiviral Mx proteins (interferon type I-induced) and with the paradigm of the self-activating large GTPases, the dynamins, with which Mx proteins show homology. The higher relative affinity for GDP and the relatively low GTPase activity distinguish IIGP1, but this study clearly adds IIGP1 and thus the p47 GTPases to the small group of cooperative GTPase families that appear to characterize the development of intracellular resistance during the interferon response to infection. The present analysis provides essential parameters to understand the molecular mechanism by which IIGP1 participates in this complex resistance program.

Topics: Animals; Escherichia coli; Gene Expression; Glutathione Transferase; GTP Phosphohydrolases; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Diphosphate; Guanosine Triphosphate; Hydrolysis; Immunity, Innate; Infections; Kinetics; Mice; Protein Structure, Quaternary; Recombinant Fusion Proteins