Intracellular pH (pHi) (pHi)

Intracellular pH (pHi) refers to the measurement of the hydrogen ion concentration within the cytoplasm of a cell, typically maintained within a narrow range of 7.0 to 7.2 under physiological conditions (PMID: 21350449). It serves as a critical regulator of numerous cellular processes, including protein synthesis, enzyme kinetics, and the cell cycle, where even minor fluctuations can trigger or inhibit metabolic pathways (PMID: 29056289). While pHi is not a single molecular target like a protein or receptor, it is considered a therapeutic focal point, particularly in oncology, due to the 'inverted pH gradient' observed in cancer cells (PMID: 24721434). In malignant cells, the pHi is often more alkaline than in normal cells, which facilitates proliferation and helps evade apoptosis, while the extracellular environment becomes acidic to promote invasion (PMID: 32296062). Therapeutic strategies aimed at modulating intracellular pH focus on the inhibition of transport proteins and enzymes that regulate proton export, such as Sodium-hydrogen exchanger 1 (NHE1), Carbonic anhydrase IX (CA IX), and Monocarboxylate transporters (MCTs). By inducing intracellular acidification or preventing the maintenance of the alkaline state, drugs like Cariporide or CA IX inhibitors can selectively impair tumor cell survival and enhance the efficacy of chemotherapy (PMID: 28243160). Monitoring pHi remains a challenge in clinical settings, relying on advanced imaging techniques like MRS or specialized PET tracers to assess the metabolic and acid-base status of diseased tissues (PMID: 30127563).

Other names

Cytosolic pHCytoplasmic pHpHiInternal cellular pHIntracellular acid-base status

Modulation of intracellular pH is typically achieved by inhibiting or activating specific membrane transporters and enzymes, such as sodium-hydrogen exchangers (NHEs), carbonic anhydrases (CAs), monocarboxylate transporters (MCTs), and vacuolar-type H+-ATPases (V-ATPases), which regulate the extrusion or buffering of protons and bicarbonate ions.