In vivo administration of calpeptin attenuates calpain activation and cardiomyocyte loss in pressure-overloaded feline myocardium

Calpain activation is linked to the cleavage of several cytoskeletal proteins and could be an important contributor to the loss of cardiomyocytes and contractile dysfunction during cardiac pressure overload (PO). Using a feline right ventricular (RV) PO model, we analyzed calpain activation during the early compensatory period of cardiac hypertrophy. Calpain enrichment and its increased activity with a reduced calpastatin level were observed in 24- to 48-h-PO myocardium, and these changes returned to basal level by 1 wk of PO. Histochemical studies in 24-h-PO myocardium revealed the presence of TdT-mediated dUTP nick-end label (TUNEL)-positive cardiomyocytes, which exhibited enrichment of calpain and gelsolin. Biochemical studies showed an increase in histone H2B phosphorylation and cytoskeletal binding and cleavage of gelsolin, which indicate programmed cardiomyocyte cell death. To test whether calpain inhibition could prevent these changes, we administered calpeptin (0.6 mg/kg iv) by bolus injections twice, 15 min before and 6 h after induction of 24-h PO. Calpeptin blocked the following PO-induced changes: calpain enrichment and activation, decreased calpastatin level, caspase-3 activation, enrichment and cleavage of gelsolin, TUNEL staining, and histone H2B phosphorylation. Although similar administration of a caspase inhibitor, N-benzoylcarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VD-fmk), blocked caspase-3 activation, it did not alleviate other aforementioned changes. These results indicate that biochemical markers of cardiomyocyte cell death, such as sarcomeric disarray, gelsolin cleavage, and TUNEL-positive nuclei, are mediated, at least in part, by calpain and that calpeptin may serve as a potential therapeutic agent to prevent cardiomyocyte loss and preserve myocardial structure and function during cardiac hypertrophy.     

Impedance analysis of renal vascular smooth muscle cells

Impedance of renal vascular smooth muscle cells (VSMCs) cultured on microelectrodes was measured by electric cell-substrate impedance sensing. Changes in measured impedance as a function of frequency were compared with the calculated values obtained from an extended cell-electrode model to estimate the junctional resistance, distance between the ventral cell surface and the substratum, and apical and basolateral membrane capacitances of renal VSMCs. This cell-electrode model was derived to accommodate the slender and rectangular shape of VSMCs. The calculated changes in impedance (Z_cal) based on the model agreed well with the experimental measurement (Z_exp), and the percentage error defined as |(Z_cal – Z_exp)/Z_exp| was 1.0%. To test the sensitivity of the new model for capturing changes in cell-cell and cell-substrate interactions induced by changes in cellular environment, we then applied this model to analyze timpedance changes induced by an integrin binding peptide in renal VSMCs. Our result demonstrates that integrin binding peptide decreases junctional resistance between cells, increases the distance between the basolateral cell surface and substratum, and increases the apical membrane capacitance, whereas the basolateral membrane capacitance stays relatively stable. This model provides a generic approach for impedance analysis of cell layers composed of slender, rectangular cells. electric cell-substrate impedance sensing; cell attachment; cell adhesion; extracellular matrix; integrin     

Fatty Acid Production from Amino Acids and α-Keto Acids by Brevibacterium linens BL2

Low concentrations of branched-chain fatty acids, such as isobutyric and isovaleric acids, develop during the ripening of hard cheeses and contribute to the beneficial flavor profile. Catabolism of amino acids, such as branched-chain amino acids, by bacteria via aminotransferase reactions and α-keto acids is one mechanism to generate these flavorful compounds; however, metabolism of α-keto acids to flavor-associated compounds is controversial. The objective of this study was to determine the ability of Brevibacterium linens BL2 to produce fatty acids from amino acids and α-keto acids and determine the occurrence of the likely genes in the draft genome sequence. BL2 catabolized amino acids to fatty acids only under carbohydrate starvation conditions. The primary fatty acid end products from leucine were isovaleric acid, acetic acid, and propionic acid. In contrast, logarithmic-phase cells of BL2 produced fatty acids from α-keto acids only. BL2 also converted α-keto acids to branched-chain fatty acids after carbohydrate starvation was achieved. At least 100 genes are potentially involved in five different metabolic pathways. The genome of B. linens ATCC 9174 contained these genes for production and degradation of fatty acids. These data indicate that brevibacteria have the ability to produce fatty acids from amino and α-keto acids and that carbon metabolism is important in regulating this event.     

Effect of nonylphenol on serum testosterone levels and testicular steroidogenic enzyme activity in neonatal, pubertal, and adult rats.

Previous dose range-finding studies with nonylphenol (NP) administered to rats in a soy- and alfalfa-free diet showed apparent feminization of several endpoints in male rats at doses of 25 ppm and above. One possible mechanism contributing to these effects is a reduction of testosterone at critical developmental periods. The present study was conducted as an adjunct to a multigeneration study and was designed to examine the effect of NP on testosterone production. Male rats in the F1 and F2 generations were exposed through their dams or directly to various dietary doses of NP (0, 25, 200 and 750 ppm) throughout gestation and until sacrifice at either postnatal day 2 (PND2), PND50, or PND140. Male pups in the F3 generation were examined only on PND2. At PND2, serum testosterone levels were significantly decreased in all groups exposed to NP in the F1 generation, but not in the F2 or F3 generations. The activity of 17alpha-hydroxylase/C17, 20 lyase (P450c17) in PND2 testicular homogenates was not affected by NP treatment. In F1 and F2 PND50 and PND140 rats, NP treatment did not affect serum testosterone levels. The absolute dorsolateral prostate weight was increased in the 200 and 750 ppm dose groups only in the F1 PND50 rats, however, no significant effects were observed in other male reproductive organs. NP treatment did not affect P450c17 activity in microsomes prepared from testes of F1 PND50 or PND140 rats. However, P450c17 activity was significantly decreased in testicular microsomes of F(2) PND50 (200 and 750 ppm dose groups) and PND140 (25, 200, and 750 ppm dose groups) rats. A decrease in testicular beta-nicotinamide adenine dinucleotide phosphate (NADPH) P450 reductase was also observed in all PND50 and PND140 NP-exposed rats of the F1 and F2 generations. The ability of NP to directly inhibit P450c17 activity in vitro at concentrations of 1-100 microM was also demonstrated. These results indicate that NP can inhibit the activity of enzymes involved in testosterone synthesis, but suggest minimal effects on testosterone or testosterone-dependent endpoints via this mechanism.     

Localization of the peptidase activity of human serum butyrylcholinesterase in a approximately 50-kDa fragment obtained by limited alpha-chymotrypsin digestion

Purified human serum butyrylcholinesterase (approximately 90-kDa subunit) is known to exhibit aryl acylamidase and peptidase activity. Limited alpha-chymotrypsin digestion of the purified butyrylcholinesterase gave three major protein fragments of approximately 50 kDa, approximately 21 kDa and approximately 20 kDa. In our earlier studies [Rao and Balasubramanian (1989) Eur. J. Biochem. 179, 639-644] we characterized the approximately 20-kDa fragment and showed that it exhibited both butyrylcholinesterase and aryl acylamidase activities. In the present studies the approximately 50-kDa fragment is characterized. This fragment, after isolation by Sephadex G-75 chromatography from a chymotryptic digest of purified butyrylcholinesterase, exhibited only peptidase activity and was devoid of cholinesterase and aryl acylamidase activities. It could bind to a column of Ricinus communis agglutinin bound to Sepharose, indicating its glycosylated nature and the presence of galactose. The peptidase activity in the approximately 50-kDa fragment could be immuno-precipitated by a polyclonal antibody raised against purified butyrylcholinesterase. SDS-gel electrophoresis of this fragment isolated by R. communis agglutinin-Sepharose and Sephadex G-75 chromatography showed a protein band of approximately 50 kDa by silver staining. Amino-terminal sequence analysis of the approximately 50-kDa fragment gave the sequence of Gly-Pro-Thr-Val-Asp which corresponded to amino acid residues 291-295 in the butyrylcholinesterase sequence [Lockridge et al. (1987) J. Biol. Chem. 262, 549-557]. The combined results suggested that alpha-chymotrypsin digestion of human serum butyrylcholinesterase resulted in the formation of a approximately 20-kDa fragment exhibiting both cholinesterase and aryl acylamidase activities and a approximately 50-kDa fragment exhibiting only peptidase activity.     

Purification and active site modification studies on glyoxalase I from monkey intestinal mucosa

Glyoxalase I ((R)-S-lactoylglutathione methylglyoxal-lyase (isomerizing), EC 4.4.1.5) from monkey intestinal mucosa was purified to homogeneity. The purified enzyme had a molecular weight of 48,000, composed of two apparently identical subunits. Active-site modification was carried out on the purified enzyme in presence and absence of S-hexylglutathione, a reversible competitive inhibitor of glyoxalase I. Modification by tetranitromethane and N-acetylimidazole caused inactivation of the enzyme. Inactivation by N-acetylimidazole was reversible with hydroxylamine treatment, suggesting the importance of tyrosine residues for the activity of the enzyme. The enzyme was inactivated by 2-hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide, 2,4,6-trinitrobenzenesulphonic acid, pyridoxal phosphate and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, indicating the importance of tryptophan, lysine and glutamic acid/aspartic acid residues for the activity of the enzyme. The enzyme was inactivated by diethyl pyrocarbonate and the activity was not restored by hydroxylamine treatment, suggesting that histidine residues may not be important for activity. Modification by N-ethylmaleimide and p-hydroxymercuribenzoate did not affect its activity, indicating that sulphydryl groups may not be important for activity. These studies indicated that the amino acids present in the active site of glyoxalase I from intestinal mucosa which may be important for activity are tyrosine, tryptophan, lysine and glutamic acid/aspartic acid residues.     

Poly (delta-L-ornithine)

Poly (delta-L-Orn) is an example of an iso-polypeptide (i.e. variant of the usual poly a-peptide chain), where the a-carboxyl and delta-amino groups of ornithine are used in polymerization while the a-amino groups form the side chain. A procedure for the synthesis of this iso-polypeptide is described. Circular dichroism studies of poly (delta-L-Orn) and its Na-Boc derivative suggest that these polymers might adopt a conformation in solution similar to the beta-pleated sheet.