Keap1-Nrf2-IN-13

Fibrosis and collagen morphometry is based on the quantitative visualization of fibrillar collagen deposition in tissue sections using histochemical stains such as Sirius Red (Picrosirius Red) or Masson's trichrome, followed by image-based or polarization-enhanced analysis to estimate collagen proportional area as a surrogate of extracellular matrix accumulation during fibrotic remodeling. Sirius Red combined with polarized light microscopy enhances detection of collagen fibers due to birefringence properties, enabling more specific visualization of collagen type I and III fibrils compared to conventional bright-field histology, while whole-section or region-restricted digital morphometry reduces field-selection bias in fibrosis assessment. Alternative quantitative approaches include second harmonic generation (SHG) and two-photon excited fluorescence microscopy, which enable label-free detection of fibrillar collagen and have been validated against histological staining and biochemica

Sirius Red or picrosirius red staining is a histochemical method for visualizing collagen-rich extracellular matrix in tissue sections, and collagen fibers are detected as red-stained structures under bright-field microscopy with enhanced birefringence under polarized light. Picrosirius red is useful for assessing total collagen organization, distribution, and fibrosis burden, but polarized color should not be interpreted as a definitive collagen type I versus type III readout because color is affected by fiber orientation, thickness, and packing.

Cytotoxicity assays are usually based on the assessment of cell membrane damage, which can also be indirectly detected by measuring cell viability. Detection methods include MTT assay, CKK-8 assay, LDH assay and ATP assay, etc.

The pull-down assay is an in vitro technique used to detect physical interactions between two or more proteins and an invaluable tool for confirming a predicted protein-protein interaction or identifying novel interacting partners. This method typically involves the use of affinity purification with various wash and elution steps.

Immunoprecipitation (IP) is an experimental method that uses the principle of antibody specific binding to purify and enrich target proteins.

ROS/oxidative-stress fluorescent staining uses cell-permeant fluorogenic probes that become fluorescent after oxidation inside cells or tissues; commonly used examples include DCFH-DA/DCFDA for broad cellular oxidant detection, DHE for superoxide-related signal detection, MitoSOX for mitochondrial superoxide-related signal detection, and CellROX probes for oxidative-stress-associated fluorescence readouts. The assay detects probe oxidation rather than a single ROS species unless the probe and analysis method have been chemically validated for that species. DCFH-DA enters cells, is deacetylated by intracellular esterases to DCFH, and produces fluorescent DCF after oxidation, so the readout is used as an operational measure of total cellular oxidative stress rather than a species-specific ROS measurement. DHE and MitoSOX can report superoxide-related oxidation, but red fluorescence alone can include non-specific ethidium-like oxidation products; HPLC or optimized spectral approaches are

Masson’s Trichrome (collagen/trichrome staining) is a histological technique that differentially stains tissue compartments using sequential acidic dyes to distinguish collagen from muscle and cytoplasmic components based on dye affinity and tissue permeability differences, enabling visualization of fibrosis and connective tissue architecture in histological sections. The classical formulation typically uses Weigert's iron hematoxylin for nuclear staining, Biebrich scarlet-acid fuchsin for cytoplasm and muscle, and aniline blue (or light green variants) for collagen, producing a characteristic blue/green collagen signal contrasted against red cytoplasm and dark nuclei. The staining principle relies on selective displacement of smaller dye molecules by larger anionic dyes in collagen-rich regions under controlled acidified conditions, which enhances collagen-specific dye retention. This property makes the method widely used for fibrosis assessment in organs such as heart, liver, lung, a

Bimolecular fluorescence complementation detects protein-protein proximity in living or fixed cells by fusing two candidate interaction partners to nonfluorescent N- and C-terminal fragments of a fluorescent protein; when the partners interact or remain close enough, the fluorescent fragments complement, mature, and generate a fluorescent signal at the site of the protein complex. The BiFC readout is fluorescence intensity and subcellular localization of the reconstituted fluorophore, which reflects formation or stabilization of a protein complex rather than direct biochemical binding kinetics; BiFC is therefore useful for mapping where interactions occur in cancer cells, neurons, macrophages, organoid-derived cells, or drug-screening systems, but results should be validated by independent assays such as co-IP or Western blot. BiFC signal formation is delayed by fluorophore maturation and can stabilize otherwise transient complexes, so it is not a real-time reversible interaction assay

Co-immunoprecipitation technology can verify protein interaction based on the specific immune reaction between antibodies and antigens.

The yeast two-hybrid assay detects binary protein-protein interactions by separating a transcription factor into a DNA-binding domain fused to a "bait" protein and a transcriptional activation domain fused to a "prey" protein; if bait and prey interact in yeast, the transcription factor is reconstituted and activates reporter genes such as HIS3, ADE2, lacZ, MEL1, or other selectable/readable reporters. The readout is yeast growth on selective medium and/or reporter activity, which reflects proximity-dependent transcriptional activation in the yeast nucleus rather than direct biochemical binding in the original mammalian, tumor, neuronal, macrophage, or organoid context. Because yeast two-hybrid can generate false positives and false negatives, interaction claims should be validated using independent assays such as co-immunoprecipitation, Western blot, immunofluorescence colocalization, BiFC, pull-down, or mammalian two-hybrid assays.