Cardiomyocyte Apoptosis and Cardiac Angiotensin-Converting Enzyme in Spontaneously Hypertensive Rats

Abstract Increased apoptosis has been reported in the heart of rats with spontaneous hypertension and cardiac hypertrophy. This study was designed to investigate the relationship between apoptosis and hypertrophy in cardiomyocytes from the left ventricle of spontaneously hypertensive rats (SHR). In addition, we evaluated whether the development of cardiomyocyte apoptosis is related to blood pressure or to the activity of the local angiotensin-converting enzyme (ACE) in SHR. The study was performed in 16-week-old SHR, 30-week-old untreated SHR, and 30-week-old SHR treated with quinapril (10 mg · kg −1 · d −1 ) during 14 weeks before they were killed. Cardiomyocyte apoptosis was assessed by direct immunoperoxidase detection of digoxigenin-labeled 3′-hydroxyl ends of DNA. Nuclear polyploidization measured by DNA flow cytometry was used to assess cardiomyocyte hypertrophy. Compared with 16-week-old normotensive Wistar-Kyoto rats, 16-week-old SHR exhibited increased blood pressure ( P <.001), increased rate of tetraploidy ( P <.05), and similar levels of ACE activity and apoptosis. Compared with 30-week-old Wistar-Kyoto rats, 30-week-old SHR showed increased blood pressure ( P <.001), increased ACE activity ( P <.05), increased rate of tetraploidy ( P <.01), and increased apoptosis ( P <.01). Untreated 30-week-old SHR exhibited similar values of blood pressure and tetraploidy and higher ACE activity ( P <.05) and apoptosis ( P <.001) than 16-week-old SHR. A direct correlation ( P <.01) was found between ACE activity and the apoptotic index in untreated 30-week-old SHR. The long-term administration of quinapril was associated with the normalization of ACE activity and apoptosis in treated SHR. These results suggest that the timing and mechanisms responsible for apoptosis and hypertrophy of cardiomyocytes are different in SHR. Whereas hypertrophy seems to be an earlier alteration that develops in parallel with hypertension, apoptosis develops later in association with overactivity of the local ACE. Our data suggest that cell death dysregulation may be a novel target for antihypertensive agents that interfere with the renin-angiotensin system in hypertension

Efficient Synthesis and Characterization of Lactulosucrose by <i>Leuconostoc mesenteroides</i> B‑512F Dextransucrase

This work describes an efficient enzymatic synthesis and NMR structural characterization of the trisaccharide β-d-galactopyranosyl-(1→4)-β-d-fructofuranosyl-(2→1)-α-d-glucopyranoside, also termed as lactulosucrose. This oligosaccharide was formed by the <i>Leuconostoc mesenteroides</i> B-512F dextransucrase-catalyzed transfer of the glucosyl residue from sucrose to the 2-hydroxyl group of the reducing unit of lactulose. The enzymatic reaction was carried out under optimal conditions, i.e., at 30 °C in 20 mM sodium acetate buffer with 0.34 mM CaCl₂ at pH 5.2, and the effect of factors such as reaction time (0–48 h), enzyme charge (0.8, 1.6, and 2.4 U mL^–1), and sucrose:lactulose concentration ratios (20:40, 30:30, and 40:20, expressed in g/100 mL) on the formation of transfer products were studied. The highest formation in lactulosucrose was attained at 8 and 24–32 h by using 20%:40% and 30%:30% sucrose:lactulose mixtures, respectively, with 1.6 or 2.4 U mL^–1 dextransucrase, leading to lactulosucrose yields of 27–35% in weight respect to the initial amount of lactulose. Furthermore, minor tetra- and pentasaccharide, both probably derived from lactulose, were also detected and quantified. Likewise, the capacity of lactulosucrose to act as d-glucosyl donor once the sucrose was consumed, could explain its decrease from 16 to 24 h when the highest charge of dextransucrase was used. Considering the chemical structure of the synthesized oligosaccharides, lactulosucrose and its derivatives could potentially be excellent candidates for an emerging prebiotic ingredient

Intramolecular C–C Coupling Reactions of Alkynyl, Vinylidene, and Alkenylphosphane Ligands in Rhodium(III) Complexes

Electrophilic attack with methyl trifluoro­methane­sulfonate or tetrafluoro­boric acid, to new alkynyl rhodium complexes containing alkenylphosphanes, leads to butenynyl coupling products or to the unprecedented rhodaphosphacycle complexes [Rh­(η⁵-C₅Me₅)­{κ⁴-(<i>P</i>,<i>C</i>,<i>C</i>,<i>C</i>)-<i>ⁱ</i>Pr₂PCH₂C­(CH₂)­C­(CH₂R)­CC­(R)}]­[BF₄] (R = Ph (<b>11a</b>), <i>p</i>-tol (<b>11b</b>)). These complexes <b>11a</b>,<b>b</b> can be explained as a result of the coupling of three organic fragments in the molecule, the alkynyl, the vinylidene, generated <i>in situ</i> by reaction with HBF₄ (<b>A</b>), and the C–C double bond from the alkenylphosphane. DFT computational studies on the formation of complex <b>11a</b> suggest the [2 + 2] intramolecular cycloaddition between the double bond of the allylphosphane and the Cα–Cβ of the vinylidene <b>A</b> as the most plausible pathway for this reaction