Clinical significance of serum high-molecular-mass alkaline phosphatase, alkaline phosphatase-lipoprotein-X complex, and intestinal variant alkaline phosphatase

An Alkaline Phosphatase-Responsive Aggregation-Induced Emission Photosensitizer for Selective Imaging and Photodynamic Therapy of Cancer Cells

Fluorescence-guided photodynamic therapy (PDT) has been considered as an emerging strategy for precise cancer treatment by making use of photosensitizers (PSs) with reactive oxygen species (ROS) generation. Some efficient PSs have been reported in recent years, but multifunctional PSs that are responsive to cancer-specific biomarkers are rarely reported. In this study, we introduced a phosphate group as a cancer-specific biomarker of alkaline phosphatase (ALP) on a PS with the features of aggregation-induced emission (AIE) for cancer cell imaging and therapy. In cancer cells with high ALP expression, the phosphate group on the AIE probe is selectively hydrolyzed by ALP. Consequently, the hydrophobic probe residue is aggregated in aqueous media and gives a "turn on" fluorescent response. Moreover, fluorescence-guided PDT was realized by the aggregates of probe residue with strong ROS generation efficiency under white light irradiation. Overall, this work presents a strategy of applying ALP-responsive AIE PS for specific imaging cancer cells and succeeding with specific PDT upon the cancer biomarker stimulated responsive reactions.

Recent Advances in the Enzyme-Activatable Organic Fluorescent Probes for Tumor Imaging and Therapy

The exploration of advanced probes for cancer diagnosis and treatment is of high importance in fundamental research and clinical practice. In comparison with the traditional "always-on" probes, the emerging activatable probes enjoy advantages in promoted accuracy for tumor theranostics by specifically releasing or activating fluorophores at the targeting sites. The main designing principle for these probes is to incorporate responsive groups that can specifically react with the biomarkers (e. g., enzymes) involved in tumorigenesis and progression, realizing the controlled activation in tumors. In this review, we summarize the latest advances in the molecular design and biomedical application of enzyme-responsive organic fluorescent probes. Particularly, the fluorophores can be endowed with ability of generating reactive oxygen species (ROS) to afford the photosensitizers, highlighting the potential of these probes in simultaneous tumor imaging and therapy with rational design. We hope that this review could inspire more research interests in the development of tumor-targeting theranostic probes for advanced biological studies.

Novel ratiometric fluorescent probe for real-time detection of alkaline phosphatase and its application in living cells

A novel ratiometric fluorescent probe has been developed through a simple synthetic route for the detection of alkaline phosphatase(ALP) in aqueous media and for fluorescence imaging in living cells. The introduction of a spontaneous-degradation spacer in the design of the fluorescent probe is beneficial for the ratio detection method and allows the selection of a fluorophore with an amino group. Under catalysis by ALP, the phosphate monoester bond breaks; this is followed by 1,4-elimination, decomposition of the carbamate moiety, and subsequent formation of the 4-amine-1,8-naphthalimide fluorophore. The probe APN shows a significant fluorescence colour change from blue to green in response to ALP, and the fluorescence intensity ratio of the probe solution (F₅₅₀/F₄₈₀) has a good linear relationship with the ALP concentration in the range of 0 to 100 U L^-1. Our studies have demonstrated that APN exhibits high accuracy in recognising ALP, with a detection limit as low as 0.16 U L^-1. Furthermore, the probe shows very good biocompatibility, which is beneficial for its application in biological systems.

Multicolor and photothermal dual-mode assay of alkaline phosphatase based on the UV light-assisted etching of gold nanorods

A multicolor and photothermal dual-mode assay for sensitive alkaline phosphatase (ALP) determination was realized based on the 3,3',5,5'-tetramethylbenzidine (TMB)-induced etching of gold nanorods (AuNRs). TMB was oxidized under ultraviolet light irradiation to form TMB⁺. In the presence of ALP, ascorbic acid phosphate (AAP) is converted to ascorbic acid, which can then reduce the levels of TMB⁺, resulting in lower concentrations of TMB⁺. The remaining TMB⁺ was transformed into TMB²⁺ after the addition of HCl solution. AuNRs were etched by TMB²⁺ to produce a multicolor and photothermal change. Based on the degree of AuNRs etching, this highly sensitive dual-mode assay provided a linear range of 1.0-8.0 mU/mL, with detection limits of 0.34 mU/mL for the multicolor assay and 0.11 mU/mL for the photothermal assay. This method was successfully applied to the determination of ALP in serum samples.

A turn-on near-infrared fluorescent probe for visualization of endogenous alkaline phosphatase activity in living cells and zebrafish

Alkaline phosphatase (ALP) is an essential hydrolase and widely distributed in living organisms. It plays important roles in various physiological and pathological processes. Herein, a turn-on near-infrared (NIR) fluorescent probe (DXMP) was developed for sensitive detection of ALP activity both in vitro and in vivo based on the intramolecular charge transfer (ICT) mechanism. Upon incubation with ALP, DXMP exhibited a strong fluorescence increment at 640 nm, which was attributed to the fact that ALP-catalyzed cleavage of the phosphate group in DXMP induced the transformation of DXMP into DXM-OH. The probe exhibited prominent features including outstanding selectivity, high sensitivity, and excellent biocompatibility. More importantly, it has been successfully used to detect and image endogenous ALP in living cells and zebrafish.

Recent Progress in Small Spirocyclic, Xanthene-Based Fluorescent Probes

The use of fluorescent probes in a multitude of applications is still an expanding field. This review covers the recent progress made in small molecular, spirocyclic xanthene-based probes containing different heteroatoms (e.g., oxygen, silicon, carbon) in position 10'. After a short introduction, we will focus on applications like the interaction of probes with enzymes and targeted labeling of organelles and proteins, detection of small molecules, as well as their use in therapeutics or diagnostics and super-resolution microscopy. Furthermore, the last part will summarize recent advances in the synthesis and understanding of their structure-behavior relationship including novel computational approaches.

In situ localization of alkaline phosphatase activity in tumor cells by an aggregation-induced emission fluorophore-based probes

In situ detection of certain specific enzyme activities in cells is deeply attached to tumor diagnosis. Conventional enzyme-responsive fluorescent probes have difficulty detecting targeted enzymes in situ in cells due to the low detection accuracy caused by the spread of fluorescence probes. In order to solve this problem, we have designed and synthesized an enzyme-responsive, water-soluble fluorescent probe with AIE characteristics, which could aggregate and precipitate to produce in situ fluorescence when reacting with the targeted enzyme in cells. The AIE fluorophore (TPEQH) was utilized to design the enzyme-responsive, fluorescent probe (TPEQHA) by introducing a phosphate group on to it, which could be specifically decomposed by the targeted enzyme, namely alkaline phosphatase (ALP). In tumor cells, TPEQH was highly produced due to the interaction of phosphate on the TPEQHA and the overexpressed ALP. Water-insoluble TPEQH then precipitated and release fluorescence in situ, thereby successfully detecting the ALP. Furthermore, the expression level of ALP could be determined by the fluorescence intensity of TPEQH with higher accuracy due to the inhibition of TPEQH leak, which demonstrated a potential application of in suit ALP detection in both clinical diagnosis and scientific research of tumor.

A fluorescent turn-on probe based on isophorone for the rapid detection of alkaline phosphatase and its application in bioimaging

Biological species analyses on account of fluorescence detection technology are receiving increasing attention, because they combine the advantages both powerful detection capability and excellent imaging technology. By effectively integrating isophorone and phosphate group via p-hydroxybenzaldehyde, the alkaline phosphatase (ALP) detection probe was obtained. Based on the enzyme-catalyzed dephosphorization course, phosphate group was separated from the probe by ALP and released yellow fluorescence signal. Upon addition with ALP, the probe exhibited high selectivity, short response time (6 min) and longer emission peak shift (570 nm). Furthermore, bioimaging experiment results indicated that the probe could detect endogenous ALP effectively.

Lipoprotein-X fifty years after its original discovery

AIMS

To review the formation, catabolism, and the possible atherogenic properties of Lp-X.

DATA SYNTHESIS

The conversion of cholesterol to bile acids is regulated by several mechanisms including cholesterol 7 alpha hydroxylase, fibroblast growth factor 19, and farnesoid X receptors. During cholestasis these mechanisms are altered and there is an accumulation of bile acids and cholesterol in plasma. The hypercholesterolemia observed in cholestasis is due to the presence of an anomalous lipoprotein called lipoprotein-X (Lp-X). Lp-X is a lipoprotein rich in phospholipid and free cholesterol present in plasma of patients with cholestasis and, with some variations, in patients with lecithin-cholesterol-acyl-transferase deficiency (LCAT), and after lipid infusion. Lp-X is formed from a bile lipoprotein moving to the blood vessels where it incorporates small quantities of triglycerides, apo-C and esterified cholesterol and becomes a "mature" Lp-X. The activity of the phosphatidilcholine canalicular transporter Mdr2 P-glycoprotein (homologous to the human ABCB4) is essential for LpX appearance, since its suppression abolishes Lp-X formation. However, the concentration of Lp-X in plasma is determined also by the degree of the cholestasis, the residual liver function, and the LCAT deficiency. The Lp-X catabolism seems to be mediated by the reticuloendothelial system and possibly the kidney.

CONCLUSIONS

Lp-X might be considered a defense mechanism against the toxic effect of free cholesterol in cholestasis. The frequency of cardiovascular events in patients affected by primary biliary cholangitis, in whom the Lp-X is present in high concentration, are not increased. Further studies could now clarify the remaining open questions on the role of Lp-X in the dyslipidemia of cholestasis.

FRET Effect between Fluorescent Polydopamine Nanoparticles and MnO2 Nanosheets and Its Application for Sensitive Sensing of Alkaline Phosphatase

As an essential and universal hydrolase, alkaline phosphatase (ALP) has been identified as a crucial indicator of various diseases. Herein, we, for the first time, expanded the application of fluorescent polydopamine (F-PDA) nanoparticles to nanoquencher-based biosensing system, as well as discovered the reversible quenching effect of manganese dioxide (MnO₂) nanosheets on the fluorescence of F-PDA nanoparticles and intensively confirmed the quenching mechanism of Förster resonance energy transfer by using transmission electron microscopy, UV-vis, Fourier transform infrared spectroscopy, and fluorescence lifetime experiments. By means of the ALP-triggered generation of ascorbic acid (AA) from the substrate ascorbic acid 2-phosphate, the AA-triggered reduction of MnO₂ nanosheets to Mn²⁺, as well as the clear quenching mechanism of F-PDA nanoparticles by MnO₂ nanosheets, we have developed a label-free, low-cost, visual, and facile synthetic fluorescent biosensor for convenient assay of ALP activity. The fluorescent bioassay shows a good linear relationship from 1 to 80 mU/mL (R² = 0.999), with a low detection limit of 0.34 mU/mL, and the excellent applicability in human serum samples demonstrates potential applications in clinical diagnosis and biomedical research.

Determination of the activity of alkaline phosphatase by using nanoclusters composed of flower-like cobalt oxyhydroxide and copper nanoclusters as fluorescent probes

The authors describe a sensitive fluorometric method for the determination of the activity of alkaline phosphatase (ALP). It is based on the use of a composite prepared consisting of flower-like cobalt oxyhydroxide (CoOOH) and copper nanoclusters (CuNCs). On formation of the CuNC-CoOOH aggregates, the fluorescence of the CuNCs is quenched by the CoOOH sheets. If, however, the CoOOH sheets are reduced to Co(II) ions in the presence of ascorbic acid (AA), fluorescence recovers. AA is formed in-situ by hydrolysis of the substrate ascorbic acid 2-phosphate (AA2P) as catalyzed by ALP. Thus, the ALP activity can be detected indirectly by kinetic monitoring of the increase in fluorescence, best at excitation/emission wavelengths of 335/410 nm. The assay allows ALP to be determined in 0.5 to 150 mU·mL^-1 activity range and with a 0.1 mU·mL^-1 detection limit. The method was successfully applied to the determination of ALP activity in (spiked) human serum samples. The assay has attractive features in being of the off-on type and immune against false positive results. Graphical Abstract A fluorescent bioassay is reported for the determination of the activity of alkaline phosphatase (ALP). It is exploiting the ascorbic acid (AA)-induced decomposition of nanoclusters composed of flower-like cobalt oxyhydroxide and copper nanoclusters. ALP catalyzes hydrolysis of ascorbic acid 2-phosphate (AA2P) and dephosphorylation to form AA.

Recent progresses in small-molecule enzymatic fluorescent probes for cancer imaging

An overview of recent advances in small-molecule enzymatic fluorescent probes for cancer imaging, including design strategies and cancer imaging applications.

Naked-eye sensitive detection of alkaline phosphatase (ALP) and pyrophosphate (PPi) based on a horseradish peroxidase catalytic colorimetric system with Cu(ii)

In this paper, a novel colorimetric method for the detection of alkaline phosphatase (ALP) and pyrophosphate (PPi) was designed based on a Cu²⁺–horseradish peroxidase (HRP)–3,3′,5,5′-tetra-methylbenzidine (TMB)–H₂O₂ system.

A highly sensitive homogeneous electrochemical assay for alkaline phosphatase activity based on single molecular beacon-initiated T7 exonuclease-mediated signal amplification

A highly sensitive homogeneous electrochemical assay for alkaline phosphatase activity based on single molecular beacon-initiated T7 exonuclease-assisted signal amplification.

A ratiometric fluorescent probe based on ESIPT and AIE processes for alkaline phosphatase activity assay and visualization in living cells

Alkaline phosphatase (ALP) activity is regarded as an important biomarker in medical diagnosis. A ratiometric fluorescent probe is developed based on a phosphorylated chalcone derivative for ALP activity assay and visualization in living cells. The probe is soluble in water and emits greenish-yellow in aqueous buffers. In the presence of ALP, the emission of probe changes to deep red gradually with ratiometric fluorescent response due to formation and aggregation of enzymatic product, whose fluorescence involves both excited-state intramolecular proton transfer and aggregation-induced emission processes. The linear ratiometric fluorescent response enables in vitro quantification of ALP activity in a range of 0-150 mU/mL with a detection limit of 0.15 mU/mL. The probe also shows excellent biocompatibility, which enables it to apply in ALP mapping in living cells.

A new fluorometric turn-on assay for alkaline phosphatase and inhibitor screening based on aggregation and deaggregation of tetraphenylethylene molecules

Based on the consideration that compound 1 with a -PO3H2 group can be hydrolyzed into compound 3 which shows low solubility in aqueous solutions and thus aggregation can occur easily, a new fluorescence turn-on assay has been constructed for alkaline phosphatase (ALP) with compound 1. ALP at concentrations as low as 18 mU mL(-1) can be assayed with compound 1. Moreover, compound 1 has been successfully applied for ALP assay in living cells. Also, compound 1 is useful for screening inhibitors of ALP.

A dual-mode fluorescence “turn-on” biosensor based on an aggregation-induced emission luminogen

A dual-mode fluorescent biosensor based on TPE-TEG-PA is developed for protamine quantification and alkaline phosphatase activity assay.

Biochemical diagnosis of liver disease

It is important that clinicians and laboratorians, including clinical chemists and pathologists, recognize and understand the clinical significance of abnormal liver function tests. The liver regulates many important metabolic functions. Hepatic injury is associated with distortion of these metabolic functions. Hepatic disease can be evaluated and diagnosed by determining serum concentrations of a number of serum analytes. Many serum analytes exist to assist in the biochemical diagnosis of liver disease. The focus of this paper is on the analytes which are associated with hepatic necrosis, cholestasis, defects in excretion and end stage hepatic disease which results in decreased synthetic function. The abnormalities of these serum analytes will be correlated with the important types of liver disease.

A simple prognostic scoring system for patients with unresectable hepatocellular carcinoma treated by chemo-embolization

BACKGROUND

Hepatocellular carcinoma (HCC) comprises heterogeneous groups of patients with differing outcomes.

METHODS

In order to attempt to identify patient sub-sets, we retrospectively examined the records of 750 patients with biopsy-proven unresectable HCC, who were treated with hepatic artery chemo-embolization and were followed till death. We used the Cox proportional hazard model, as it was neutral with respect to prejudged cut-off between short and long survival.

RESULTS

On univariate analysis, we found a shorter survival to be associated with male gender, presence of cirrhosis, portal hypertension, portal vein thrombosis and elevations of bilirubin, GGTP, ALKP, AFP, DCP, PT and albumin. Five factors were found to be statistically significant (p<0.05) on multivariate analysis, namely presence of cirrhosis or ascites and elevations of AFP, ALKP or GGTP. We developed a simplified scoring system based upon the sum of the hazard ratios of each of these five factors. By combining the two factors with the heaviest hazard ratios from our multivariable analysis, namely AFP (+ = >100 ng/mL) and ALKP (+ = >100 IU/mL), we found a simple parsimonious prognostic tool, which segregated the patients into survival groups, namely AFP- ALKP-; either AFP+ or ALKP+; and AFP+ ALKP+; these three groups corresponded to a 24-month survival of 70%, 32% and 12%, respectively.

CONCLUSION

we found that only two lab functions, AFP and ALKP levels, in our large HCC patient cohort undergoing hepatic artery chemo-embolization, had prognostic significance.

Severe hypercholesterolemia mediated by lipoprotein X in patients with chronic graft-versus-host disease of the liver

We describe a series of cases of extreme hypercholesterolemia mediated by lipoprotein X in patients with chronic graft-versus-host disease of the liver after an allogeneic bone marrow transplant. All of the patients presented with a total cholesterol in excess of 1000 mg/dl (25.9 mmol/l). At the time they were also noted to have pseudohyponatremia. Cholesterol appeared to be predominantly carried by lipoprotein X. Intrahepatic cholestasis leading to reflux of bile lipoproteins into the bloodstream and subsequent formation of protein X appears to be the mechanism underlying this phenomenon. Complications, including retinal cholesterol thromboembolism and cholesteroloma of the lung have been seen in the patient with the highest cholesterol levels. Severe hypercholesterolemia is an important, and likely more common than previously reported, long-term complication of allogeneic hematopoietic stem cell transplantation. It is important for clinicians to familiarize themselves with the diagnostic and therapeutic challenges this condition presents.

Cytochrome c forms complexes and is partly reduced at interaction with GPI-anchored alkaline phosphatase

Cytochrome (cyt) c forms complexes, undergoes a conformational change and becomes partly reduced at interaction with membrane anchored alkaline phosphatase (AP), a glycoprotein which is released into the body fluid in forms differing in hydrophobicity. The proportion of products formed in the mixtures depends on pH, ionic strength, temperature and the buffer composition. The reaction terminates in an equilibrium between cyt c(FeII) and other cyt c conformers. Optimal conditions for the rate of the reaction are 100 mM glycine/NaOH, pH 9.7-9.9, at which 68-74% of cyt c is found in the reduced state. The interaction affects compactness of the haem cleft as shown by changes induced in CD spectra of the Soret region and changes in optical characteristics of phenylalanine, tyrosine and tryptophan residues. Differential scanning calorimetry of AP+cyt c mixtures revealed a creation of at least two types of complexes. A complex formed by non-coulombic binding prevails at substoichiometric AP/cyt c ratios, at higher ratios more electrostatic attraction is involved and at 1:1 molar ratio an apparent complexity of binding forces occurs. The rapid phase of the cyt c(FeII) formation depends on the presence of the hydrophobic alkylacylphosphoinositol (glycosylphosphatidylinositol) moiety, the protein part of the enzyme participates in an electrostatic and much slower phase of cyt c(FeII) creation. The results show that non-coulombic interaction may participate at interaction of cyt c with cellular proteins.

The function of alkaline phosphatase in the liver: regulation of intrahepatic biliary epithelium secretory activities in the rat

We studied the effects of alkaline phosphatase (AP) on the secretory processes of the rat intrahepatic biliary epithelium as well as the role of the intrahepatic biliary epithelium in the uptake and biliary secretion of exogenous AP. The effects of acute and chronic administration of AP on bile secretory parameters were investigated in vivo in normal and bile duct ligated (BDL) rats and in vitro in isolated rat bile duct units (IBDU). In vivo, acute AP administration decreased bile flow and biliary bicarbonate excretion and abolished secretin choleresis in BDL rats but not in normal rats. On the contrary, the AP inhibitor, levamisole, increased in BDL rat bile flow and biliary bicarbonate excretion. In vitro, basal and secretin-stimulated Cl(-)/HCO(3)(-) exchanger activity in IBDU was immediately inhibited by AP intraluminal microinjection (apical exposure) but only after a prolonged exposure to the basolateral pole. Levamisole increased the Cl(-)/HCO(3)(-) exchanger activity of IBDU. A significant basolateral uptake of AP occurs in IBDU with a progressive transport to the apical domain. AP chronic treatment increased AP and gamma-glutamyltranspeptidase (gamma-GT) activities in the intrahepatic bile ducts and hepatocyte canalicular pole, promoted enlargement of bile canaliculi, and decreased bile flow and biliary bicarbonate excretion. In conclusion, the intrahepatic biliary epithelium plays a role in the uptake and biliary secretion of serum AP. AP inhibits the secretory processes of the intrahepatic biliary epithelium and induces features of intrahepatic cholestasis after chronic administration. These findings indicate that AP plays an active role in down-regulating the secretory activities of the intrahepatic biliary epithelium.