α-Amyrin

Infectious-disease experiments test how pathogens interact with host barriers, innate immune receptors, inflammatory signaling, pathogen replication, and tissue injury; pattern-recognition receptors such as TLRs, RIG-I-like receptors, NOD-like receptors, and inflammasomes detect microbial molecules and activate NF-κB, interferon, and cytokine responses. The central hypothesis is that infection severity reflects the balance between pathogen burden and host response: protective inflammation restricts pathogen growth, whereas excessive or mislocalized inflammation contributes to tissue damage and disease phenotype. Unresolved questions include which host pathways are protective versus pathogenic, why some infection models fail to translate to human disease, and which combined readouts best predict clinically relevant infection outcomes.

Annexin V-based apoptosis assays rely on the detection of phosphatidylserine (PS) externalization from the inner leaflet of the plasma membrane to the outer leaflet, an early biochemical hallmark of apoptosis. Fluorescently labeled Annexin V binds PS in a calcium-dependent manner, enabling identification of early apoptotic cells by flow cytometry or fluorescence microscopy. When combined with a membrane-impermeant DNA-binding dye (e. g. , propidium iodide), this approach allows discrimination between viable (Annexin V−/dye−), early apoptotic (Annexin V+/dye−), and late apoptotic or necrotic (Annexin V+/dye+) cell populations by assessing membrane integrity and PS exposure.

The NLRP3 inflammasome is a cytosolic innate immune signaling platform that integrates priming signals and danger-signal activation to promote caspase-1 activation, maturation of IL-1β and IL-18, and gasdermin D-mediated pyroptotic cell death. The core experimental logic is to determine whether inflammatory disease phenotypes are driven by increased NLRP3 expression, ASC-containing inflammasome assembly, caspase-1 cleavage, GSDMD cleavage, and extracellular release of IL-1β/IL-18 rather than by nonspecific cell injury alone. The pathway is strongly linked to inflammation-related disease phenotypes because monosodium urate crystals activate NALP3/NLRP3 inflammasome signaling in gout-like crystal inflammation, cholesterol crystals activate NLRP3 inflammasomes in atherogenesis models, and DSS-induced intestinal inflammation has been reported to involve NLRP3 inflammasome activity. However, experimental colitis studies also show context-dependent protective effects of NLRP3 inflammasome co

PINK1/Parkin-mediated mitophagy pathway is a mitochondrial quality-control signaling axis in which mitochondrial depolarization stabilizes PINK1 on damaged mitochondria, activates Parkin recruitment and E3 ubiquitin ligase activity, promotes ubiquitination of outer mitochondrial membrane proteins, recruits selective autophagy adaptors, and drives lysosomal degradation of damaged mitochondria. In neurological disease research, this pathway is experimentally important because neurons, especially dopaminergic neurons, are highly dependent on mitochondrial integrity, and defective mitochondrial turnover can lead to mitochondrial dysfunction, oxidative stress, impaired neuronal survival, α-synuclein accumulation, and neuroinflammatory damage-associated signals. The genetic disease link is strongest in Parkinson’s disease because mutations in PRKN/parkin cause autosomal recessive juvenile parkinsonism, mutations in PINK1 cause hereditary early-onset Parkinson’s disease, and Drosophila studie

AMP-activated protein kinase, AMPK, is a conserved cellular energy sensor that responds to reduced cellular energy status and coordinates metabolism by increasing ATP-generating catabolic pathways while suppressing ATP-consuming anabolic processes. In metabolic disease research, the AMPK pathway is experimentally relevant because it regulates hepatic lipid synthesis, fatty acid oxidation, glucose production, skeletal-muscle glucose disposal, mTORC1-linked biosynthesis, autophagy, mitochondrial homeostasis, and whole-body energy balance. The central pathway logic is that energy stress, metformin, exercise-like stimulation, or direct AMPK activators increase AMPKα Thr172 phosphorylation and downstream substrate phosphorylation, including ACC and RAPTOR. Phosphorylation of ACC suppresses lipogenesis and supports fatty acid oxidation, whereas phosphorylation of RAPTOR suppresses mTORC1 signaling and links cellular energy status to growth and protein synthesis control. The pathway is linked

Breast cancer is a heterogeneous cancer, and it has been distinguished into four subtypes: luminal A, luminal B, HER2-positive and basal-like. Molecular mutations, epigenetic alterations, hormone exposure and immune microenvironment are related to the progression of breast cancer.

The following protocol uses the MTT colorimetric assay as a classic literature-established method for assessing cell viability/metabolic activity in cultured mammalian cells. MTT[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] is reduced by metabolically active cells to a colored formazan product; the amount of formazan is quantified spectrophotometrically and provides an indirect measure of metabolically active viable cells. Importantly, MTT reduction reflects cellular oxidoreductase/metabolic activity rather than an absolute direct count of living cells, so changes in cellular metabolism can alter the signal independently of cell number.

Apoptosis, also called programmed cell death, is generally characterized by distinct morphological characteristics.

TUNEL staining detects DNA strand breaks by using terminal deoxynucleotidyl transferase to add labeled nucleotides to exposed 3′-OH DNA termini, generating either microscopic staining in fixed cells or tissue sections, or fluorescence/cytometric signal in cell suspensions. TUNEL positivity reflects DNA fragmentation but should not be interpreted alone as definitive apoptosis, because TUNEL can also label necrotic, autolytic, mechanically damaged, or DNA-repair-associated DNA breaks.

Imiquimod (IMQ)-induced psoriasiform dermatitis is a widely used murine model in which topical application of IMQ, a Toll-like receptor 7 (TLR7) agonist, triggers innate immune activation in the skin and induces a psoriasis-like inflammatory cascade characterized by epidermal hyperplasia, immune cell infiltration, and cytokine production dominated by the IL-23/IL-17 axis. This inflammatory response is mediated through activation of dendritic cells and downstream induction of IL-23, IL-17A, IL-22, and related pro-inflammatory mediators, recapitulating key features of human plaque psoriasis and enabling mechanistic and therapeutic studies. The model is commonly induced using Aldara (5% IMQ cream) applied topically to murine skin, resulting in rapid onset of erythema, scaling, and thickening that can be quantified as disease severity indices and validated histologically.

The TPA (12-O-tetradecanoylphorbol-13-acetate) and croton oil-induced mouse ear edema model is a well-established acute cutaneous inflammation system used to evaluate topical anti-inflammatory activity by measuring edema formation, neutrophil infiltration, vascular permeability, and cytokine-mediated skin responses in vivo. The inflammatory response is triggered by topical application of phorbol esters (TPA) or croton oil constituents, leading to rapid activation of protein kinase C signaling, leukocyte recruitment, and increased vascular permeability, which can be quantified by ear thickness, weight, dye extravasation, and biochemical markers such as myeloperoxidase (MPO) activity and pro-inflammatory mediators in ear tissue homogenates. This model is widely used for screening anti-inflammatory agents, where reductions in edema and inflammatory biomarkers reflect suppression of acute dermal inflammation and immune cell infiltration. Histological evaluation typically confirms epidermal

Apoptosis is a regulated, generally non-lytic cell-death pathway that removes unwanted, damaged, infected, or abnormal cells through coordinated morphological changes, caspase activation, DNA fragmentation, and membrane remodeling. The intrinsic apoptosis pathway is controlled mainly by mitochondrial outer membrane permeabilization, BCL-2 family proteins, cytochrome c release, apoptosome formation, caspase-9 activation, and downstream executioner caspase-3/7 activation. The extrinsic apoptosis pathway is initiated by death receptors such as Fas, TNFR, and TRAIL receptors, which recruit adaptor proteins and activate caspase-8 before engaging executioner caspases or mitochondrial amplification through BID cleavage. Apoptosis is linked to many phenotypes, including cancer cell killing, tissue homeostasis, immune regulation, neurodegeneration, infection response, and treatment-induced cytotoxicity; unresolved questions include how apoptosis interacts with necroptosis, pyroptosis, ferroptos

Contact hypersensitivity (CHS) dermatitis is a T cell-mediated delayed-type (Type IV) immune reaction in which low-molecular-weight haptens applied to the skin bind host proteins to form complete antigens, triggering sensitization followed by a secondary inflammatory response upon re-exposure (elicitation phase), which is commonly quantified by ear swelling as a readout of skin inflammation in murine models. This model is widely used to study allergic contact dermatitis because it is antigen-specific, reproducible, and reflects key immunological events including dendritic cell activation, T cell priming in draining lymph nodes, and effector T cell-driven tissue inflammation. DNFB- and oxazolone-induced CHS models are standard systems for evaluating both acute and chronic T cell-dependent skin inflammation and for testing immunomodulatory interventions.