The role of carbonic anhydrase in the pathogenesis of vascular calcification in humans.

Carbonic anhydrases are a group of isoenzymes that catalyze the reversible conversion of carbon dioxide into bicarbonate. They participate in a constellation of physiological processes in humans, including respiration, bone metabolism, and the formation of body fluids, including urine, bile, pancreatic juice, gastric secretion, saliva, aqueous humor, cerebrospinal fluid, and sweat. In addition, carbonic anhydrase may provide carbon dioxide/bicarbonate to carboxylation reactions that incorporate carbon dioxide to substrates. Several isoforms of carbonic anhydrase have been identified in humans, but their precise physiological role and the consequences of their dysfunction are mostly unknown. Carbonic anhydrase isoenzymes are involved in calcification processes in a number of biological systems, including the formation of calcareous spicules from sponges, the formation of shell in some animals, and the precipitation of calcium salts induced by several microorganisms, particularly urease-producing bacteria. In human tissues, carbonic anhydrase is implicated in calcification processes either directly by facilitating calcium carbonate deposition which in turn serves to facilitate calcium phosphate mineralization, or indirectly via its action upon γ-glutamyl-carboxylase, a carboxylase that enables the biological activation of proteins involved in calcification, such as matrix Gla protein, bone Gla protein, and Gla-rich protein. Carbonic anhydrase is implicated in calcification of human tissues, including bone and soft-tissue calcification in rheumatological disorders such as ankylosing spondylitis and dermatomyositis. Carbonic anhydrase may be also involved in bile and kidney stone formation and carcinoma-associated microcalcifications. The aim of this review is to evaluate the possible association between carbonic anhydrase isoenzymes and vascular calcification in humans.