Probing the molecular interactions between human Carbonic Anhydrases (hCAs) and a novel class of designed benzenesulfonamides

Carbonic Anhydrases (CAs, EC 4.2.1.1) are a family of monomeric Zinc metalloenzymes that catalyze the reversible hydration of CO2. The relevant role of this class of enzymes is the regulation of a broad range of physiological functions (gluconeogenesis, lipogenesis, and ureagenesis).[1] The family of human carbonic anhydrases (hCAs) comprises 15 different α-carbonic anhydrase isoforms: CA I-IV, CA VA and CA VB, CA VI-VII, CA IX, CA XII- XV and CARPs CA VIII, CA X, CA XI). In the last years, the attention toward this class of metalloproteins is in continuous growth because it was discovered their involvement in different diseases such as cancer,[2] glaucoma,[3] obesity,[4] and epilepsy.[5] Among the hCAs, the hCA VII is one of the least investigated cytosolic CA isoforms; it presents a limited distribution, being mainly expressed in the cortex, hippocampus, and thalamus regions within the mammalian brain where it is involved in generating neuronal excitation and seizures. Moreover hCA VII is expressed in other organs including the stomach, duodenum, colon, liver and skeletal muscle of mice. [2, 5-7] The hCA VII is currently considered to be involved in the mechanism of GABAergic generated seizures. [5, 8] Recently, its involvement in neuropathic pain control has been proposed by a mechanism which is not completely known. [6, 7, 9]Thereby, the investigation on hCA VII could also represent an interesting tool for the design of new pain killers useful for therapeutic applications. Several CA inhibitors such as acetazolamide (AAZ) and topiramate (TPM) have a long history as anticonvulsants, but their molecular targets and mechanisms of action at the neuronal network level are still poorly understood.[10] In the last years in the Department ChiBioFarAm – medicinal chemistry laboratories of the University of Messina, a collection of small molecules acting as carbonic anhydrase inhibitors had been discovered. The most active inhibitors displayed ki values in the nanomolar range. Unfortunately, some of them showed poor selectivity toward the more druggable isoforms. These inhibitors possess the sulfonamide portion as key chemical portion that binds the Zinc2+ ion that is located at the bottom of a deep cleft of catalytic site (Figure 1).[11] The other moieties of these compounds control the major or minor interactions with the hydrophilic and/or hydrophobic regions of catalytic pocket. The degree of this pattern of contacts might be considered responsible of the inhibitory potency as well as selectivity toward specific CA isoforms. During the three years doctoral course we chose to introduce new chemical moieties and modify these sulfonamides to obtain the new compounds. Specifically, we planned the synthesis of new compounds to improve inhibitory effects and isoforms selectivity. Therefore, we planned the synthesis of a series of new sulfonamides bearing the quinoline and isoquinoline skeleton that has been variously decorated through the introduction of chemical fragment as hydrophilic/hydrophobic anchoring groups. This series of novel hCAIs were in vitro tested against the hCA I, hCA II, hCA VII, hCA IX, hCA XII and hCA XIV. Structural and computational studies have been performed to explain the mechanism of inhibitory properties. Furthermore, in vivo studies were carried out to find new potential therapeutics for the treatment of brain pathologies.