Unimolecular Chemiexcited Oxygenation of Pathogenic Amyloids

Pathogenic protein aggregates, called amyloids, are etiologically relevant to various diseases, including neurodegenerative Alzheimer disease. Catalytic photooxygenation of amyloids, such as amyloid-β (Aβ), reduces their toxicity; however, the requirement for light irradiation may limit its utility in large animals, including humans, due to the low tissue permeability of light. Here, we report that Cypridina luciferin analogs, dmCLA-Cl and dmCLA-Br, promoted selective oxygenation of amyloids through chemiexcitation without external light irradiation. Further structural optimization of dmCLA-Cl led to the identification of a derivative with a polar carboxylate functional group and low cellular toxicity: dmCLA-Cl-acid. dmCLA-Cl-acid promoted oxygenation of Aβ amyloid and reduced its cellular toxicity without photoirradiation. The chemiexcited oxygenation developed in this study may be an effective approach to neutralizing the toxicity of amyloids, which can accumulate deep inside the body, and treating amyloidosis.

Synthesis and anti-tumor activities in human leukemia-derived cells of polyenylpyrroles with a methyl group at the conjugated polyene terminus

To develop novel drugs for treating T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML) which are highly malignant hematological tumors, a series of analogs having a polyenylpyrrole structure of natural compounds (rumbrin and auxarconjugatin B) were synthesized and investigated their structure-activity relationships (SAR) of in vitro anti-T-ALL and anti-AML activities. We obtained three findings: (1) introduction of a methyl group at the conjugated polyene terminus enhanced anti-T-ALL activity, (2) analogs with a 3-chloropyrrole moiety had even higher selectivity for T-ALL cells, and (3) some analogs were effective against AML-derived cells. Among the studied compounds, 3-chloro-2-(8-ethoxycarbonylnona-1,3,5,7-tetraenyl) pyrrole 4e was the most promising candidate of T-ALL- and AML-treating drug. This study provides useful structural information for designing novel drugs treating T-ALL and AML.

Identification of compounds that preferentially suppress the growth of T-cell acute lymphoblastic leukemia-derived cells

T-cell acute lymphoblastic leukemia (T-ALL) is one of the most frequently occurring cancers in children and is associated with a poor prognosis. Here, we performed large-scale screening of natural compound libraries to identify potential drugs against T-ALL. We identified three low-molecular-weight compounds (auxarconjugatin-B, rumbrin, and lavendamycin) that inhibited the proliferation of the T-ALL cell line CCRF-CEM, but not that of the B lymphoma cell line Raji in a low concentration range. Among them, auxarconjugatin-B and rumbrin commonly contained a polyenyl 3-chloropyrrol in their chemical structure, therefore we chose auxarconjugatin-B for further analyses. Auxarconjugatin-B suppressed the in vitro growth of five human T-ALL cell lines and two T-ALL patient-derived cells, but not that of adult T-cell leukemia patient-derived cells. Cultured normal T cells were several-fold resistant to auxarconjugatin-B. Auxarconjugatin-B and its synthetic analogue Ra#37 depolarized the mitochondrial membrane potential of CCRF-CEM cells within 3 h of treatment. These compounds are promising seeds for developing novel anti-T-ALL drugs.

In vivo optical imaging of tumor stromal cells with hypoxia-inducible factor activity

Tumors contain various stromal cells, such as immune cells, endothelial cells, and fibroblasts, which contribute to the development of a tumor-specific microenvironment characterized by hypoxia and inflammation, and are associated with malignant progression. In this study, we investigated the activity of intratumoral hypoxia-inducible factor (HIF), which functions as a master regulator of the cellular response to hypoxia and inflammation. We constructed the HIF activity-monitoring reporter gene hypoxia-response element-Venus-Akaluc (HVA) that expresses the green fluorescent protein Venus and modified firefly luciferase Akaluc in a HIF activity-dependent manner, and created transgenic mice harboring HVA transgene (HVA-Tg). In HVA-Tg, HIF-active cells can be visualized using AkaBLI, an ultra-sensitive in vivo bioluminescence imaging technology that produces an intense near-infrared light upon reaction of Akaluc with the D-luciferin analog AkaLumine-HCl. By orthotopic transplantation of E0771, a mouse triple negative breast cancer cell line without a reporter gene, into HVA-Tg, we succeeded in noninvasively monitoring bioluminescence signals from HIF-active stromal cells as early as 8 days after transplantation. The HIF-active stromal cells initially clustered locally and then spread throughout the tumors with growth. Immunohistochemistry and flow cytometry analyses revealed that CD11b+ F4/80+ macrophages were the predominant HIF-active stromal cells in E0771 tumors. These results indicate that HVA-Tg is a useful tool for spatiotemporal analysis of HIF-active tumor stromal cells, facilitating investigation of the roles of HIF-active tumor stromal cells in tumor growth and malignant progression.

Creation of Artificial Luciferase 60s from Sequential Insights and Their Applications to Bioassays

In this study, a series of new artificial luciferases (ALucs) was created using sequential insights on missing peptide blocks, which were revealed using the alignment of existing ALuc sequences. Through compensating for the missing peptide blocks in the alignment, 10 sibling sequences were artificially fabricated and named from ALuc55 to ALuc68. The phylogenetic analysis showed that the new ALucs formed an independent branch that was genetically isolated from other natural marine luciferases. The new ALucs successfully survived and luminesced with native coelenterazine (nCTZ) and its analogs in living mammalian cells. The results showed that the bioluminescence (BL) intensities of the ALucs were interestingly proportional to the length of the appended peptide blocks. The computational modeling revealed that the appended peptide blocks created a flexible region near the active site, potentially modulating the enzymatic activities. The new ALucs generated various colors with maximally approximately 90 nm redshifted BL spectra in orange upon reaction with the authors' previously reported 1- and 2-series coelenterazine analogs. The utilities of the new ALucs in bioassays were demonstrated through the construction of single-chain molecular strain probes and protein fragment complementation assay (PCA) probes. The success of this study can guide new insights into how we can engineer and functionalize marine luciferases to expand the toolbox of optical readouts for bioassays and molecular imaging.

Coelenterazine Indicators for the Specific Imaging of Human and Bovine Serum Albumins

Albumin assays in serum are important for the prognostic assessment of many life-threatening diseases, such as heart failure, liver disease, malnutrition, inflammatory bowel disease, infections, and kidney disease. In this study, synthetic coelenterazine (CTZ) indicators are developed to quantitatively illuminate human and bovine serum albumins (HSA and BSA) with high specificity. Their functional groups were chemically modified to specifically emit luminescence with HSA and BSA. The CTZ indicators were characterized by assaying the most abundant serum proteins and found that the CTZ indicators S6 and S6h were highly specific to HSA and BSA, respectively. Their colors were dramatically converted from blue, peaked at 480 nm, to yellowish green, peaked at 535 nm, according to the HSA-BSA mixing ratios, wherein the origins and mixing levels of the albumins can be easily determined by their colors and peak positions. The kinetic properties of HSA and BSA were investigated in detail, confirming that the serum albumins catalyze the CTZ indicators, which act as pseudo-luciferases. The catalytic reactions were efficiently inhibited by specific inhibitors, blocking the drug-binding sites I and II of HSA and BSA. Finally, the utility of the CTZ indicators was demonstrated through a quantitative imaging of the real fetal bovine serum (FBS). This study is the first example to show that the CTZ indicators specify HSA and BSA with different colors. This study contributes to the expansion of the toolbox of optical indicators, which efficiently assays serum proteins in physiological samples. Considering that these CTZ indicators immediately report quantitative optical signals with high specificity, they provide solutions to conventional technical hurdles on point-of-care assays of serum albumins.

Bright Molecular Strain Probe Templates for Reporting Protein-Protein Interactions

Imaging protein-protein interactions (PPIs) is a hot topic in molecular medicine in the postgenomic sequencing era. In the present study, we report bright and highly sensitive single-chain molecular strain probe templates which embed full-length Renilla luciferase 8.6-535SG (RLuc86SG) or Artificial luciferase 49 (ALuc49) as reporters. These reporters were deployed between FKBP-rapamycin binding domain (FRB) and FK506-binding protein (FKBP) as a PPI model. This unique molecular design was conceptualized to exploit molecular strains of the sandwiched reporters appended by rapamycin-triggered intramolecular PPIs. The ligand-sensing properties of the templates were maximized by interface truncations and substrate modulation. The highest fold intensities, 9.4 and 16.6, of the templates were accomplished with RLuc86SG and ALuc49, respectively. The spectra of the templates, according to substrates, revealed that the colors are tunable to blue, green, and yellow. The putative substrate-binding chemistry and the working mechanisms of the probes were computationally modeled in the presence or absence of rapamycin. Considering that the molecular strain probe templates are applicable to other PPI models, the present approach would broaden the scope of the bioassay toolbox, which harnesses the privilege of luciferase reporters and the unique concept of the molecular strain probes into bioassays and molecular imaging.

Bioluminescence imaging using d-luciferin and its analogs for visualizing Bdnf expression in living mice; different patterns of bioluminescence signals using distinct luciferase substrates

Brain-derived neurotrophic factor (BDNF) plays a crucial role in numerous brain functions, including memory consolidation. Previously, we generated a Bdnf-Luciferase transgenic (Bdnf-Luc) mouse strain to visualize changes in Bdnf expression using in vivo bioluminescence imaging (BLI). We successfully visualized activity-dependent Bdnf induction in living mouse brains using a d-luciferin analog, TokeOni, which distributes to the brain and produces near-infrared bioluminescence. In this study, we compared the patterns of bioluminescence signals within the whole body of the Bdnf-Luc mice produced by d-luciferin, TokeOni, and seMpai, another d-luciferin analog that produces a near-infrared light. As recently reported, hepatic background signals were observed in wild-type mice when using TokeOni. Bioluminescence signals were strongly observed from the region containing the liver when using d-luciferin and TokeOni. Additionally, we detected signals from the brain when using TokeOni. Compared with d-luciferin and TokeOni, signals were widely detected in the whole body of Bdnf-Luc mice by seMpai. The signals produced by seMpai were strong in the regions containing skeletal muscles in particular. Taken together, the patterns of bioluminescence signals in Bdnf-Luc mice vary when using different luciferase substrates. Therefore, the expression of Bdnf in tissues and organs of interest could be visualized by selecting an appropriate substrate.

Crystalline-state chemiluminescence reactions of two-fluorophore-linked adamantylideneadamantane 1,2-dioxetane isomers accompanied by solid-to-solid phase transitions

Structural isomers (cis-syn, cis-anti and trans isomers) of an adamantylideneadamantane 1,2-dioxetane having two fluorophore side chains were prepared and investigated their chemiluminescence (CL) properties in the crystalline state. Real-time monitoring...

Absorption Spectra for Firefly Bioluminescence Substrate Analog: TokeOni in Various pH Solutions

AkaLumine hydrochloride, named TokeOni, is one of the firefly luciferin analogs, and its reaction with firefly luciferase produces near-infrared (NIR) bioluminescence. Prior to studying the bioluminescence mechanism, basic knowledge about the chemical structures, electronic states, and absorption properties of TokeOni at various pH values of solution has to be acquired. In this paper, the absorption spectra for TokeOni and AkaLumine at pH 2-10 were measured. Density functional theory (DFT) calculations, time-dependent DFT calculations, and the vibrational analyses were carried out. The absorption spectra indicate that the chemical forms of TokeOni in solutions are same as those of AkaLumine. The peaks at pH 7-10 in the absorption spectra correspond to the excitation from the ground state of a carboxylate anion of AkaLumine, the peak at pH 2 corresponds to the excitation from the ground state of a carboxylate anion with an N-protonated thiazoline ring and N-protonated dimethylamino group of AkaLumine, and the peak at pH 4 corresponds to the excitation from the ground state of a carboxylate anion with an N-protonated thiazoline ring of AkaLumine.

How to Select Firefly Luciferin Analogues for In Vivo Imaging

Bioluminescence reactions are widely applied in optical in vivo imaging in the life science and medical fields. Such reactions produce light upon the oxidation of a luciferin (substrate) catalyzed by a luciferase (enzyme), and this bioluminescence enables the quantification of tumor cells and gene expression in animal models. Many researchers have developed single-color or multicolor bioluminescence systems based on artificial luciferin analogues and/or luciferase mutants, for application in vivo bioluminescence imaging (BLI). In the current review, we focus on the characteristics of firefly BLI technology and discuss the development of luciferin analogues for high-resolution in vivo BLI. In addition, we discuss the novel luciferin analogues TokeOni and seMpai, which show potential as high-sensitivity in vivo BLI reagents.

High Sensitivity In Vivo Imaging of Cancer Metastasis Using a Near-Infrared Luciferin Analogue seMpai

Bioluminescence imaging (BLI) is useful to monitor cell movement and gene expression in live animals. However, D-luciferin has a short wavelength (560 nm) which is absorbed by tissues and the use of near-infrared (NIR) luciferin analogues enable high sensitivity in vivo BLI. The AkaLumine-AkaLuc BLI system (Aka-BLI) can detect resolution at the single-cell level; however, it has a clear hepatic background signal. Here, to enable the highly sensitive detection of bioluminescence from the surrounding liver tissues, we focused on seMpai (C₁₅H₁₆N₃O₂S) which has been synthesized as a luciferin analogue and has high luminescent abilities as same as AkaLumine. We demonstrated that seMpai BLI could detect micro-signals near the liver without any background signal. The solution of seMpai was neutral; therefore, seMpai imaging did not cause any adverse effect in mice. seMpai enabled a highly sensitive in vivo BLI as compared to previous techniques. Our findings suggest that the development of a novel mutated luciferase against seMpai may enable a highly sensitive BLI at the single-cell level without any background signal. Novel seMpai BLI system can be used for in vivo imaging in the fields of life sciences and medicine.

Development of near-infrared firefly luciferin analogue reacted with wild-type and mutant luciferases

Interestingly, only the D-form of firefly luciferin produces light by luciferin-luciferase (L-L) reaction. Certain firefly luciferin analogues with modified structures maintain bioluminescence (BL) activity; however, all L-form luciferin analogues show no BL activity. To this date, our group has developed luciferin analogues with moderate BL activity that produce light of various wavelengths. For in vivo bioluminescence imaging, one of the important factors for detection sensitivity is tissue permeability of the number of photons emitted by L-L reaction, and the wavelengths of light in the near-infrared (NIR) range (700-900 nm) are most appropriate for the purpose. Some NIR luciferin analogues by us had performance for in vivo experiments to make it possible to detect photons from deep target tissues in mice with high sensitivity, whereas only a few of them can produce NIR light by the L-L reactions with wild-type luciferase and/or mutant luciferase. Based on the structure-activity relationships, we designed and synthesized here a luciferin analogue with the 5-allyl-6-dimethylamino-2-naphthylethenyl moiety. This analogue exhibited NIR BL emissions with wild-type luciferase (λ_max = 705 nm) and mutant luciferase AlaLuc (λ_max = 655 nm).

An allylated firefly luciferin analogue with luciferase specific response in living cells

An allylated firefly luciferin was successfully synthesized and its bioluminescence properties were evaluated. When applied to cellular imaging in combination with Eluc, which is one of the commercially available luciferases, this analogue displayed a luciferase-specific bioluminescence signal with prolonged emission (>100 min).

Multicolor Bioluminescence Obtained Using Firefly Luciferin

Firefly bioluminescence is widely used in life science research as a useful analysis tool. For example, the adenosine-5`-triphosphate (ATP)-dependent enzymatic firefly bioluminescence reaction has long been utilized as a microbial monitoring tool. Rapid and sensitive firefly luciferin-luciferase combinations are used not only to measure cell viability but also for reporter-gene assays. Recently, bioluminescence was utilized as a noninvasive, real-time imaging tool for living subjects to monitor cells and biological events. However, the number of commercialized luciferase genes is limited and tissue-permeable near-infrared (NIR) region emitting light is required for in vivo imaging. In this review, recent studies describing synthetic luciferin analogues predicted to have red-shifted bioluminescence are summarized. Luciferase substrates emitting red, green, and blue light that were designed and developed in our laboratory are presented. The longest emission wavelength of the synthesized luciferin analogues was recorded at 675 nm, which is within the NIR region. This compound is now commercially available as "Aka Lumine®".

Synthesis of Firefly Luciferin Analogues and Evaluation of the Luminescent Properties

Five new firefly luciferin (1) analogues were synthesized and their light emission properties were examined. Modifications of the thiazoline moiety in 1 were employed to produce analogues containing acyclic amino acid side chains (2-4) and heterocyclic rings derived from amino acids (5 and 6) linked to the benzothiazole moiety. Although methyl esters of all of the synthetic derivatives exhibited chemiluminescence activity, only carboluciferin (6), possessing a pyrroline-substituted benzothiazole structure, had bioluminescence (BL) activity (λmax =547 nm). Results of bioluminescence studies with AMP-carboluciferin (AMP=adenosine monophosphate) and AMP-firefly luciferin showed that the nature of the thiazoline mimicking moiety affected the adenylation step of the luciferin-luciferase reaction required for production of potent BL. In addition, BL of 6 in living mice differed from that of 1 in that its luminescence decay rate was slower.

Self-reported medication adherence and health status in late adulthood: the role of beliefs

In this study, we explore the role of subjective beliefs in determining self-reports of medication adherence and health status in 90 older adults (M age = 71.7 years, SD = 7.44). Self-reported adherence was predicted by personal health locus of control beliefs, but not by medical factors nor beliefs regarding one's own health care professionals. Self-reported health was predicted by medical factors, perceptions of one's health care professional, and health locus of control. These results suggest that self-reported adherence is primarily a belief-laden construct whereas self-reported health consists of both an objective assessment of health and a subjective belief-laden component. Exploratory analyses conducted on younger-old and older-old age groups indicated that medical factors may be less important to older-old adults' perceived health status than the younger-old adults.