Optimisation of an enzymatic method for beta-galactosidase

A conserved long-distance telomeric silencing mechanism suppresses mTOR signaling in aging human fibroblasts

Telomeres are repetitive nucleotide sequences at the ends of each chromosome. It has been hypothesized that telomere attrition evolved as a tumor suppressor mechanism in large long-lived species. Long telomeres can silence genes millions of bases away through a looping mechanism called telomere position effect over long distances (TPE-OLD). The function of this silencing mechanism is unknown. We determined a set of 2322 genes with high positional conservation across replicatively aging species that includes known and candidate TPE-OLD genes that may mitigate potentially harmful effects of replicative aging. Notably, we identified PPP2R2C as a tumor suppressor gene, whose up-regulation by TPE-OLD in aged human fibroblasts leads to dephosphorylation of p70S6 kinase and mammalian target of rapamycin suppression. A mechanistic link between telomeres and a tumor suppressor mechanism supports the hypothesis that replicative aging fulfills a tumor suppressor function and motivates previously unknown antitumor and antiaging strategies.

Subnormothermic ex vivo liver perfusion reduces endothelial cell and bile duct injury after donation after cardiac death pig liver transplantation

An ischemic-type biliary stricture (ITBS) is a common feature after liver transplantation using donation after cardiac death (DCD) grafts. We compared sequential subnormothermic ex vivo liver perfusion (SNEVLP; 33°C) with cold storage (CS) for the prevention of ITBS in DCD liver grafts in pig liver transplantation (n = 5 for each group). Liver grafts were stored for 10 hours at 4°C (CS) or preserved with combined 7-hour CS and 3-hour SNEVLP. Parameters of hepatocyte [aspartate aminotransferase (AST), international normalized ratio (INR), factor V, and caspase 3 immunohistochemistry], endothelial cell (EC; CD31 immunohistochemistry and hyaluronic acid), and biliary injury and function [alkaline phosphatase (ALP), total bilirubin, and bile lactate dehydrogenase (LDH)] were determined. Long-term survival (7 days) after transplantation was similar between the SNEVLP and CS groups (60% versus 40%, P = 0.13). No difference was observed between SNEVLP- and CS-treated animals with respect to the peak of serum INR, factor V, or AST levels within 24 hours. CD31 staining 8 hours after transplantation demonstrated intact EC lining in SNEVLP-treated livers (7.3 × 10(-4) ± 2.6 × 10(-4) cells/μm(2)) but not in CS-treated livers (3.7 × 10(-4) ± 1.3 × 10(-4) cells/μm(2) , P = 0.03). Posttransplant SNEVLP animals had decreased serum ALP and serum bilirubin levels in comparison with CS animals. In addition, LDH in bile fluid was lower in SNEVLP pigs versus CS pigs (14 ± 10 versus 60 ± 18 μmol/L, P = 0.02). Bile duct histology revealed severe bile duct necrosis in 3 of 5 animals in the CS group but none in the SNEVLP group (P = 0.03). Sequential SNEVLP preservation of DCD grafts reduces bile duct and EC injury after liver transplantation.

α-Fucosidase as a novel convenient biomarker for cellular senescence

Due to its role in aging and antitumor defense, cellular senescence has recently attracted increasing interest. However, there is currently no single specific marker that can unequivocally detect senescent cells. Here, we identified α-L-fucosidase (α-Fuc) as a novel sensitive biomarker for cellular senescence. Regardless of the stress stimulus and cell type, α-Fuc activity was induced in all canonical types of cellular senescence, including replicative, DNA damage- and oncogene-induced senescence. Strikingly, in most models the degree of α-Fuc upregulation was higher than the induction of senescence-associated β-galactosidase (SA-β-Gal), the current gold standard for senescence detection. As α-Fuc is convenient and easy to measure, we suggest its utility as a valuable marker, in particular in cells with low SA-β-Gal activity.

Monogalactopyranosides of fluorescein and fluorescein methyl ester: synthesis, enzymatic hydrolysis by biotnylated β-galactosidase, and determination of translational diffusion coefficient

Fluorescein monoglycosides (D-galactopyranoside (FMG) and D-glucopyranoside) and their methyl ester (MFMG) have been prepared from acetobromoglucose/galactose and fluorescein methyl ester in good yields. Enzymatic hydrolysis experiments (using biotinylated β-galactosidase) of the galacto derivatives have been performed and kinetic parameters were calculated. A 15-20 times increase of the fluorescence intensity has been observed during the hydrolysis. A linear increase of fluorescence has been noted at short time and low concentration of substrate, making these compounds useful and sensitive probes for galactosidases. The magnitude of the Michaelis-Menten constant (K(m)) value for MFMG is higher than that of FMG suggesting a possible conformational change of the fluorogenic substrate. K(m) value for biotinylated β-Gal with FMG is lower than that for the native enzyme. This observation indicates higher substrate affinity of the biotinylated enzyme in comparison to the native enzyme. Translational diffusion coefficients have been measured, for both fluorogenic substrates and both the products, employing fluorescence correlation spectroscopy. Translational diffusion coefficients for fluorogenic substrates and the enzymatic hydrolysis products have been measured to be similar, in the range of 3.5-4.5×10(-10) m(2) s(-1). Thus an enhancement or retardation of the enzymatic kinetics due to difference in translational mobility of substrate and product is not that apparent.

Murine β-galactosidase stability is not dependent on temperature or protective protein/cathepsin A

GM1 gangliosidosis, a neurodegenerative disorder, and Morquio B disease, a skeletal disorder, are lysosomal storage disorders caused by inherited defects in the enzyme β-galactosidase (GLB1; EC 3.1.2.23; MIM #611458). Enzyme replacement therapy (ERT), a standard of care for a number of non-neuronopathic lysosomal storage disorders, is not yet available for GLB1 deficiency. Although functionally active recombinant human and feline GLB1 precursors have been purified, ERT has not yet been demonstrated in GM1 gangliosidosis or Morquio B disease models. A major obstacle to developing effective therapy may be the stability of human GLB1. We show here that mouse GLB1 has greater stability when compared to human GLB1, and that human GLB1 activity is temperature and protective-dependent on protein cathepsin A, while that of mouse GLB1 is not. These findings may impact on the eventual development of ERT for GLB1 deficiency. Despite our attempts to improve the extracellular stability of human GLB1 through sequence modification and the use of chemical chaperone N-butyldeoxygalactonojirimycin, the specific enzyme activity remained well below that of mGLB1.

A biosensor for the determination of β-galactosidase activity: a different viewpoint on biosensors

β-galactosidase splits lactose into glucose and galactose. Because of its biotechnological interest, we presented a biosensor system in order to monitor β-galactosidase activity. Immobilization steps of the biosensor were identified by cyclic voltammograms and electrochemical impedance spectroscopy. β-galactosidase was voltammetrically detected at about +150 mV (vs. Ag/AgCl) in citrate buffer solution (0.05 M, pH 4.8). The linear response for β-galactosidase detection was in the range of 0.0118 U mL(-1)to 0.47 U mL(-1)and a shorter response time of ∼50 s. Our results demonstrated the biosensor's electrochemical properties and analytical characteristics were very useful and effective for monitoring of β-galactosidase activity.

β-galactosidase determination by an electrochemical biosensor mediated with ferrocene

Abstract: In this paper, a new viewpoint on the activity determination of β-galactosidase is reported. Glucose oxidase was directly immobilized on a glassy carbon electrode and mediated by ferrocene. The biosensor's performance was based on mediated electron transfer by ferrocene, which reduced via glucose oxidase reaction. In this reaction, substrate of glucose oxidase, glucose was provided by the activity of β-galactosidase in the sample. The parameters of the fabrication process for the electrode were optimized. Experimental conditions influencing the biosensor performance, such as pH, ferrocene and lactose concentrations, and temperature, were investigated and assessed. Finally, the biosensor was successfully applied to determination of β-galactosidase activity of artificial intestinal juice.

Absence of direct effect of low-power millimeter-wave radiation at 60.4 GHz on endoplasmic reticulum stress

Millimeter waves (MMW) at frequencies around 60 GHz will be used in the very near future in the emerging local wireless communication systems and the potential health hazards of artificially induced environmental exposures represent a major public concern. The main aim of this study was to investigate the potential effects of low-power MMW radiations on cellular physiology. To this end, the human glial cell line, U-251 MG, was exposed to 60.4 GHz radiation at a power density of 0.14 mW/cm(2) and potential effect of MMW radiations on endoplasmic reticulum (ER) stress was investigated. ER is very sensitive to environmental insults and its homeostasis is altered in various pathologies. Through several assay systems, we found that exposure to 60.4 GHz does not modify ER protein folding and secretion, nor induces XBP1 or ATF6 transcription factors maturation. Moreover, expression of ER-stress sensor, BiP/GRP78 was examined by real-time PCR, in exposed or non-exposed cells to MMW radiations. Our data demonstrated the absence of significant changes in mRNA levels for BiP/GRP78. Our results showed that ER homeostasis does not undergo any modification at molecular level after exposure to low-power MMW radiation at 60.4 GHz. This report is the first study of ER-stress induction by MMW radiations.

Primary graft nonfunction and Kupffer cell activation after liver transplantation from non-heart-beating donors in pigs

More extensive use of non-heart-beating donors (NHBD) could reduce mortality on liver transplantation waiting lists, but this is associated with more primary nonfunction (PNF). We assessed which parameters are involved in the development of PNF in livers from NHBD in a previously validated pig liver transplantation model, in which livers were transplanted after exposure to incremental periods of warm ischemia. The risk of PNF was unacceptably high (>50%) when livers were exposed to >30 minutes' warm ischemia before a short cold ischemic period. This study examined how PNF is affected by Kupffer cell activation (beta-galactosidase), the generation of cytokines tumor necrosis factor alpha and interleukin 6, antioxidant mechanisms (ascorbic acid, alpha-tocopherol, reduced glutathione), circulating redox-active iron, and sinusoidal endothelial cell function (hyaluronic acid clearance). Kupffer cells were more activated in PNF recipients, as suggested by higher beta-galactosidase levels (15 minutes after reperfusion), and secondarily, by higher production of tumor necrosis factor alpha and interleukin 6 (180 minutes after reperfusion). In addition, alpha-tocopherol and reduced glutathione were lower, and ascorbic acid and redox-active iron higher in PNF recipients. Finally, PNF grafts displayed progressively decreasing hyaluronic acid clearance (suggesting sinusoidal endothelial cell dysfunction) and parenchymal edema. Consequently, a reduced-flow phenomenon was documented. In grafts from NHBD that are destined to fail, beta-galactosidase activity (a surrogate of Kupffer cell activation) is higher, proinflammatory cytokines are overproduced, some antioxidant mechanisms fail, and circulating redox-active iron is more rapidly released. A no-flow phenomenon is eventually observed in these failing grafts.

Non-heart-beating donor porcine livers: the adverse effect of cooling

Normothermic preservation has been shown to be advantageous in an experimental model of preservation of non-heart-beating donor (NHBD) livers, which have undergone significant warm ischemic injury. The logistics of clinical organ retrieval might dictate a period of cold preservation prior to warm perfusion. We have investigated the effects of a brief period of cold preservation on NHBD livers prior to normothermic preservation. Porcine livers were subjected to 60 minutes of warm ischaemia and then assigned to following groups: Group W (n = 5), normothermic preservation for 24 hours; and Group C (n = 6), cold preservation in University of Wisconsin solution for 1 hour followed by normothermic preservation for 23 hours (total preservation time, 24 hours). Synthetic function (bile production and factor V production) and cellular damage were compared on the ex vivo circuit during preservation. There was no significant difference in the synthetic function of the livers (bile production and factor V production). Markers of hepatocellular damage (alanine aminotransferase and aspartate aminotransferase release), sinusoidal endothelial cell dysfunction (hyaluronic acid), and Kupffer cell injury (beta-galactosidase) were significantly higher in Group C. The histology of the livers at the end of perfusion was similar. In conclusion, a brief-period cold preservation prior to normothermic perfusion maintains the synthetic function and metabolic activity but results in significant hepatocellular damage, sinusoidal endothelial cell dysfunction, and Kupffer cell injury. Transplant studies are required to establish whether livers treated in this way are viable for transplantation.