This study characterizes the receptor binding and functional effects of 2R)-2-hydroxycyclopentyl)-amino]purin-9-yl}(4S,5S,2R,3R)-5-[(2-fluorophenylthio)methyl]-oxolane-3,4-diol], a novel N 6 -5Ј-substituted adenosine analog and A 1 -adenosine receptor (A 1 AdoR) agonist, on rat epididymal and inguinal adipocytes and on the isolated heart and compares these effects with those caused by the full agonist N 6 -cyclopentyladenosine (CPA). In addition, the hypothesis that adipocyte A 1 AdoR are a heterogeneous population with regard to their affinities for ligands was tested. CVT-3619 was 10 -100-fold selective for A 1 AdoR versus other AdoR and bound to adipocyte membranes with high (K H ϭ 14 nM) and low (K L ϭ 5.4 M) affinities. CVT-3619 reduced cyclic AMP content and release of nonesterified fatty acids from epididymal adipocytes with IC 50 values of 6 and 44 nM, respectively. CVT-3619 was a partial agonist relative to CPA to reduce lipolysis in epididymal and inguinal adipocytes. CVT-3619 did not change atrial rate in rat heart and caused a small (6-ms) prolongation of the stimulus-to-His bundle interval without causing atrioventricular block in guinea pig heart (effects mediated by A 1 AdoR), whereas CPA caused atrioventricular block and near cessation of atrial electrical activity. CVT-3619 increased coronary conductance (effect mediated by A 2A AdoR) only at concentrations Ն10 M. Rat epididymal adipocyte A 1 AdoR had similar affinities for the antagonist 8-cyclopentyl-1,3-dipropylxanthine in the presence of three dissimilar A 1 AdoR agonists (2-chloro-N 6 -cyclopentyladenosine, N 6 -sulfophenyladenosine, and N-5Ј-ethylcarboxamidoadenosine) as determined by Schild analysis. It was concluded that rat epididymal adipocyte A 1 AdoR are a homogeneous receptor population with regard to affinities for ligands and that CVT-3619 is a partial agonist with selectivity for A 1 AdoR and inhibition of lipolysis.

Hepatic ischaemia/reperfusion (I/R), a major cause of liver damage associated with multiple trauma, haemorrhagic and septic shock, and liver transplantation, contributes significantly to multiple organ failure. Development of novel sensitive biomarkers that detect early stages of liver damage is vital for effective management and treatment of ischaemic liver injury. By using high-throughput immunoblotting and cation-anion exchange chromatography/reversed-phase liquid chromatography-tandem mass-spectrometry, we identified several hepatic proteins, including argininosuccinate synthase (ASS) and estrogen sulfotransferase (EST-1), which were degraded in the liver and rapidly released into circulation during I/R injury. ASS accumulated in serum within 10 min, reached a steady state at 30 min, and persisted up until 3 h after reperfusion following 30 min of total hepatic ischaemia. EST-1 appeared rapidly in blood and attained maximum within 1 hour followed by a decline at 3 h of reperfusion. No ASS or EST-1 protein was detected in serum of control or sham operated rats. ASS and EST-1 exhibited greater sensitivity and specificity toward I/R liver injury as compared with alanine aminotransferase (ALT), an established marker of hepatocellular necrosis. In contrast, serum ASS and EST-1 were undetectable in rats with chronic alcoholic liver disease, while the levels of ALT protein were significantly increased. In addition, ASS, but not EST-1 or ALT accumulated in blood only 6 h after treatment with hepatotoxic combination of lipopolysaccharide and D-galactosamine. These data demonstrate the utility of ASS and EST-1 as novel sensitive and specific biomarkers of acute liver ischaemic injury for prospective clinical studies.

BackgroundLactic acid, a natural by-product of glycolysis, is produced at excess levels in response to impaired mitochondrial function, high-energy demand, and low oxygen availability. The enzyme involved in the production of β-amyloid peptide (Aβ) of Alzheimer's disease, BACE1, functions optimally at lower pH, which led us to investigate a potential role of lactic acid in the processing of amyloid precursor protein (APP).Methodology/Principal FindingsLactic acid increased levels of Aβ40 and 42, as measured by ELISA, in culture medium of human neuroblastoma cells (SH-SY5Y), whereas it decreased APP metabolites, such as sAPPα. In cell lysates, APP levels were increased and APP was found to interact with ER-chaperones in a perinuclear region, as determined by co-immunoprecipitation and fluorescence microscopy studies. Lactic acid had only a very modest effect on cellular pH, did increase the levels of ER chaperones Grp78 and Grp94 and led to APP aggregate formation reminiscent of aggresomes.Conclusions/SignificanceThese findings suggest that sustained elevations in lactic acid levels could be a risk factor in amyloidogenesis related to Alzheimer's disease through enhanced APP interaction with ER chaperone proteins and aberrant APP processing leading to increased generation of amyloid peptides and APP aggregates.

DNA fragmentation factors (DFF) form protein complexes consisting of nuclease DFF40/CAD and inhibitory chaperon DFF45/ICAD. Although activated caspase-3 has been shown to cleave DFF complexes with the release of active DFF40 and DNA fragmentation, the organ-specific mechanisms of DFF turnover during liver injury accompanied by massive apoptosis are unclear. In this study, we investigated hepatic profile of DFF40-immunopositive proteins in two models of liver injury in rats: acute ischemia/reperfusion (I/R) and chronic alcohol administration. We show that DFF40-like proteins occur in intact rat liver mainly as a 52kDa protein. Hepatic I/R-induced caspase-3 activation and a time-dependent accumulation of DFF40-positive protein fragments (40 and 20kDa), most likely via specific caspase-3 cleavage as evidenced by in vitro digestion of intact liver tissue with recombinant caspase-3. In addition, immunoprecipitation with DFF40 followed by Western blot with active caspase-3 antibody revealed the presence of active caspase-3 in DFF40-immunopositive 20kDa proteins. Chronic alcohol administration in rats also resulted in a dose-dependent fragmentation of DFF40 proteins similar to I/R injury. Collectively, these data demonstrate that DFF40 immunopositive proteins exist in the liver as distinct, tissue-specific molecular forms that may be processed by caspase-3 during both acute and chronic liver injury.