The P2X7 receptor mediates the uptake of organic cations in canine erythrocytes and mononuclear leukocytes: comparison to equivalent human cell types

We previously demonstrated that canine erythrocytes express the P2X7 receptor, and that the function and expression of this receptor is greatly increased compared with human erythrocytes. Using 86Rb+ (K+) and organic cation flux measurements, we further compared P2X7 in erythrocytes and mononuclear leukocytes from these species. Concentration response curves of BzATP- and ATP-induced 86Rb+ efflux demonstrated that canine P2X7 was less sensitive to inhibition by extracellular Na+ ions compared to human P2X7. In contrast, canine and human P2X7 showed a similar sensitivity to the P2X7 antagonists KN-62 and Mg2+. KN-62 and Mg2+ also inhibited ATP-induced choline+ uptake into canine and human erythrocytes. BzATP and ATP but not ADP or NAD induced ethidium+ uptake into canine monocytes, T- and B-cells. ATP-induced ethidium+ uptake was twofold greater in canine T-cells compared to canine B-cells and monocytes. KN-62 inhibited the ATP-induced ethidium+ uptake in each cell type. P2X7-mediated uptake of organic cations was 40- and fivefold greater in canine erythrocytes and lymphocytes (T- and B-cells), respectively, compared to equivalent human cell types. In contrast, P2X7 function was threefold lower in canine monocytes compared to human monocytes. Thus, P2X7 activation can induce the uptake of organic cations into canine erythrocytes and mononuclear leukocytes, but the relative levels of P2X7 function differ to that of equivalent human cell types

Arene-fused 1,2-oxazole N-oxides and derivatives. The impact of the N-O dipole and substitution on their aromatic character and reactivity profile. Can it be a useful structure in synthesis? A theoretical insight

DFT calculations have shown that the N-O dipole of benzene- and naphthalene-fused 1,2-oxazole N-oxides causes a distortion of their σ and π frame, concentrated on the 1,2-oxazole ring, such that it increases its susceptibility to opening. The distortion forces the benzene ring into some diene geometry, thus, reducing π delocalization over the bi- or tricyclic structure and ultimately their aromatic character. C-3 substitution has a marked influence mainly on the naphthalene-fused N-oxides. C-5 and particularly C-6 substitution, as the position of most extended interaction with the N-O dipole through the π ring density, contribute to the distortion of the 1,2-oxazole geometry and thereby to the decrease of aromaticity of the structure. Bond uniformity (IA), average bond order (ABO) and Harmonic Oscillator Model of Aromaticity (HOMA) indices have been recruited to measure aromaticity changes. IA and ABO appear to be more credible to 1,2-benzoxazole N-oxides and 1,2-naphthoxazole N-oxides, respectively, while HOMA has been found equally reliable to both. Hardness and dipole moments follow similar trends. Energies, localization and separation of the four frontiers orbitals, i.e. HO, HO-1, and LU, LU+1, indicate a rather notable aromatic character of the N-oxides. Their reactivity profile, portrayed by descriptors such as Fukui and electro(nucleo)philicity Parr functions, shows good agreement with experimental outcomes towards electrophiles but succumbs to discrepancies towards nucleophiles due to the susceptibility of the hetero-ring to opening. The "push-pull" character of the N-O dipole and more importantly the extent of its double bonding direct site selectivity.Peer reviewe