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BackgroundRenal ischemia–reperfusion injury (IRI) is a major factor causing acute kidney injury (AKI). No pharmacological treatments for prevention or amelioration of I/R-induced renal injury are available. Here we investigate the protective effects of treprostinil, a prostacyclin analog, against renal IRI in vivo.MethodsMale Sprague Dawley rats were subjected to bilateral renal ischemia (45 min) followed by reperfusion for 1–168 h. Treprostinil (100 ng/kg/min) or placebo was administered subcutaneously for 18–24 h before ischemia.ResultsTreatment with treprostinil both significantly reduced peak elevation and accelerated the return to baseline levels for serum creatinine and blood urea nitrogen versus I/R-placebo animals following IRI. I/R-treprostinil animals exhibited reduced histopathological features of tubular epithelial injury versus I/R-placebo animals. IRI resulted in a marked induction of messenger RNA coding for kidney injury biomarkers, kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin and for pro-inflammatory cytokines chemokine (C-C motif) ligand 2, interleukin 1β, interleukin 6 and intracellular adhesion molecular 1 in animals treated with placebo only relative to sham controls. Upregulation of expression of all these genes was significantly suppressed by treprostinil. Treprostinil significantly suppressed the elevation in renal lipid peroxidation found in the I/R-placebo group at 1-h post-reperfusion. In addition, renal protein expression of cleaved poly(ADP-ribose) polymerase 1 and caspase-3, -8 and -9 in I/R-placebo animals was significantly inhibited by treprostinil.ConclusionsThis study demonstrates the efficacy of treprostinil in ameliorating I/R-induced AKI in rats by significantly improving renal function early post-reperfusion and by inhibiting renal inflammation and tubular epithelial apoptosis. Importantly, these data suggest that treprostinil has the potential to serve as a therapeutic agent to protect the kidney against IRI in vivo.

The effect of myricetin (MY) and dihydromyricetin (DMY) on the activity of pepsin was evaluated. The interaction between MY and DMY with pepsin was investigated using multispectroscopic and molecular docking methods. Binding constant, number of binding sites, and thermodynamic parameters at different temperatures were measured. MY and DMY have no significant effect on the activity of pepsin. The results of fluorescence quenching revealed that MY and DMY could strongly quench the intrinsic fluorescence of pepsin through a static quenching procedure. The thermodynamic parameters showed that hydrophobic interactions played main roles in the interaction of MY with pepsin, while the Van der Waals' interactions and hydrogen bonds were mainly interactions between DMY and pepsin. The analysis of UV absorption spectra and molecular docking showed that MY and DMY induced conformational changes of pepsin. The synchronous fluorescence spectra indicated that microenvironment around tyrosine and tryptophan residues of pepsin were not changed obviously. The energy transfer from pepsin molecules to MY or DMY occurs with high probability. Displacement experiments indicated that DMY and MY could bind to the same site of pepsin.

The interaction of pepsin with daidzein (Dai) or genistein (Gen) was investigated using spectroscopic techniques under simulated physiological conditions. Dai and Gen can quench the fluorescence of pepsin and the quenching mechanism was a static process. The binding site number n and apparent binding constant K were measured at different temperatures. The thermodynamic parameters ΔΗ, ΔG and ΔS were calculated. The results indicated that van der Waals forces and hydrogen bond formation played major roles in the interaction of Dai or Gen with pepsin. The binding distance between pepsin and Dai or Gen was calculated according to energy transfer theory. The results of synchronous fluorescence spectra showed that the microenvironment and conformation of pepsin were changed. UV absorption and 3D fluorescence spectra showed that the binding interaction disturbed the microenvironment of amino acid residues and induced conformational changes in pepsin. Molecular docking results showed that Dai and Gen entered into the hydrophobic cavity of pepsin and two hydrogen bonds formed between Dai or Gen and pepsin. The results demonstrated that the interaction behavior between Dai and Gen with pepsin was slightly different, which denoted that the 5-hydroxyl group of Gen, to a certain extent, had an effect on ligand binding to proteins. Copyright © 2016 John Wiley & Sons, Ltd.