Glossary

Plain-English definitions of terms used across our Senolytics & Longevity Research section.

Jump to: A · C · D · E · F · H · L · M · N · P · S · T

A

ALT (alternative lengthening of telomeres): a telomerase-independent mechanism some cells, mainly certain cancer cell lines, use to maintain telomere length.

AMPK: AMP-activated protein kinase, an enzyme that senses cellular energy status. It is a frequent subject of metabolic research.

Apoptosis: a regulated form of programmed cell death. Senolytic research looks for agents that trigger apoptosis selectively in senescent cells.

C

Cardiolipin: a phospholipid found almost exclusively in the inner mitochondrial membrane, studied in relation to the organisation of the electron transport chain. See SS-31.

CD38: an enzyme that breaks down NAD+, studied in relation to age-related changes in NAD+ levels.

Cell-cycle arrest: a halt in the cycle of cell growth and division. In senescence the arrest is considered stable (essentially permanent).

COA (Certificate of Analysis): a document issued for a tested sample, giving its identity, purity and other analytical results, the method used, the laboratory and the report number. See Lab partners & testing.

Connectivity Map: a public database of gene-expression profiles from cells exposed to many compounds, used to compare expression “signatures”.

D

D-retro-inverso (DRI) peptide: a peptide built from D-amino acids with the sequence order inverted. The design is used to make peptides more resistant to breakdown by proteases. See FOXO4-DRI.

E

Endotoxin: lipopolysaccharide from the outer membrane of Gram-negative bacteria, measured in testing with the LAL assay and reported in EU (endotoxin units).

Extracellular matrix (ECM): the network of proteins (such as collagen) and other molecules surrounding cells in tissue.

F

Fibroblast: a connective-tissue cell that produces extracellular matrix. Fibroblasts are among the most widely used cell types in senescence research.

FOXO4: a forkhead-box transcription factor. In senescent cells it has been reported to bind p53.

H

Hallmarks of ageing: a widely cited framework grouping the biological changes associated with ageing into categories such as genomic instability, telomere attrition, mitochondrial dysfunction and cellular senescence [1].

Hayflick limit: the finite number of times normal human cells divide in culture before entering replicative senescence, first described in 1961.

HPLC (high-performance liquid chromatography): an analytical technique that separates the components of a sample. It is used to measure peptide purity as the percentage of the main peak’s area.

L

LAL assay: Limulus amebocyte lysate test, the standard method for detecting bacterial endotoxin.

LC-MS (liquid chromatography–mass spectrometry): HPLC coupled to a mass spectrometer. It confirms a compound’s identity by its molecular mass.

Lyophilised: freeze-dried. Research peptides are commonly supplied as lyophilised powders.

M

Mitochondria: organelles that produce most of the cell’s ATP through oxidative phosphorylation. They have their own small genome.

Mitochondrial-derived peptide: a peptide encoded within the mitochondrial genome, such as MOTS-c.

N

NAD+ / NADH: nicotinamide adenine dinucleotide in its oxidised (NAD+) and reduced (NADH) forms. It is a coenzyme in redox reactions and a substrate for sirtuins, PARPs and CD38. See NAD+ in ageing research.

P

p16^INK4a and p21^CIP1: cyclin-dependent kinase inhibitors that enforce cell-cycle arrest. They are widely used as senescence markers.

p53: a tumour-suppressor protein that coordinates responses to DNA damage, including cell-cycle arrest, senescence and apoptosis.

PARP: poly(ADP-ribose) polymerase, a family of enzymes involved in DNA repair that consume NAD+.

S

SA-β-gal: senescence-associated β-galactosidase activity detected at pH 6. It is a classic histochemical marker of senescent cells.

SASP: senescence-associated secretory phenotype, the cytokines, chemokines, growth factors and proteases released by many senescent cells.

Senescence (cellular): a stable state of cell-cycle arrest in which the cell remains metabolically active [2]. See Cellular senescence explained.

Senolytic: an agent studied for its ability to selectively induce death of senescent cells. See What are senolytics?

Senomorphic (senostatic): an agent studied for its ability to suppress features of senescence, such as the SASP, without killing the cell.

Sirtuins: a family of NAD+-dependent enzymes (SIRT1–SIRT7 in mammals) that remove acyl groups from proteins.

T

Telomerase: the enzyme (catalytic subunit TERT, hTERT in humans) that adds repeat sequences to telomeres.

Telomere: the repetitive DNA–protein structure capping the end of each chromosome. Telomeres shorten with successive divisions in many human cell types.

References

1. López-Otín C, Blasco MA, Partridge L, Serrano M, Kroemer G. Hallmarks of aging: an expanding universe. Cell. 2023;186(2):243-278. PubMed: https://pubmed.ncbi.nlm.nih.gov/36599349/ · DOI: https://doi.org/10.1016/j.cell.2022.11.001
2. Gorgoulis V, Adams PD, Alimonti A, et al. Cellular senescence: defining a path forward. Cell. 2019;179(4):813-827. PubMed: https://pubmed.ncbi.nlm.nih.gov/31675495/ · DOI: https://doi.org/10.1016/j.cell.2019.10.005