Chemical Activated LUciferase gene eXpression (CALUX) is a
ligand-dependent nuclear receptor-based
bioassay used in the detection of specific chemicals or classes of chemicals in samples. It consists of a modified
cell line
An immortalised cell line is a population of cells from a multicellular organism which would normally not proliferate indefinitely but, due to mutation, have evaded normal cellular senescence and instead can keep undergoing division. The cell ...
that has been stably transfected with a
DNA construct with a
luciferase
Luciferase is a generic term for the class of oxidative enzymes that produce bioluminescence, and is usually distinguished from a photoprotein. The name was first used by Raphaël Dubois who invented the words ''luciferin'' and ''luciferase'', ...
reporter gene under control of receptor-specific DNA
response elements that can stimulate
transcription of the inserted luciferase
gene and produce the light-generating enzyme which can be easily measured. The DNA response elements can be varied in order to provide binding sites for other receptors that are regulated by a chemical or class of chemicals of interest that want to be detected. Thus, numerous CALUX bioassays have been developed for detection of diverse chemicals of interest. Most applications have been directed toward the detection of environmentally harmful chemicals, such as those affecting the endocrine system (
environmental hormones
Xenohormones or environmental hormones produced outside of the human body which exhibit endocrine hormone-like properties. They may be either of natural origin, such as phytoestrogens, which are derived from plants, or of synthetic origin. These co ...
).
CALUX is an effect based screening method as it measures the total effect
ligands
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...
(from a sample) have on a specific receptor. Unlike
chemical analysis, CALUX is thus able to measure total activity on the receptor of interest. This includes both identified and unidentified activators (
agonists) and inhibitors (
receptor antagonists).
Applications
The aryl hydrocarbon receptor (AhR)-responsive (AhR-CALUX) bioassay is commonly used in the detection of
dioxins and dioxin-like compounds in sample extracts. It is based on the molecular mechanism by which the
AhR activates gene expression.
AhR-CALUX is used by researchers and companies that want to screen for the presence of
dioxins and dioxin-like compounds in a wide variety of biological and environmental matrices, commercial and consumer products and in food and feed in order to evaluate their safety and/or level of contamination. While the measurement of dioxin and related dioxin-like chemicals in a sample extract using the AhR-CALUX bioassay is significantly cheaper than the chemical analysis requiring gas chromatography - high-resolution mass spectrometry (GC-HRMS), it only provides a measurement of the total level of AhR-active dioxins and related dioxin-like chemicals in a sample extract and determination of the specific congeners requires analysis any GC-HRMS. Additionally, given the recently established role of the AhR in human health and disease, the AhR-CALUX bioassay is also being used widely as a high-throughput screening method to identify and characterize AhR-active chemicals as potential human therapeutic drugs.
Environmental chemicals having sex hormone-like activity are detected by similar bioassays as well, including the Estrogen Receptor-Responsive CALUX (ER-CALUX) and Androgen Receptor-Responsive CALUX (AR-CALUX).
See also
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Bioanalytical equivalent
A bioanalytical equivalent (BEQ) is a unit of measure in the field of bioassays. It is used for example in the bioassay CALUX Chemical Activated LUciferase gene eXpression (CALUX) is a ligand-dependent nuclear receptor-based bioassay used in the de ...
References
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Biotechnology
Toxicology
Environmental technology