Instrumental analysis applied to erythrocyte properties

Blood rheology as a mirror of endocrine and metabolic homeostasis in health and disease1

Rheological properties of plasma and blood cells are markedly influenced by the surrounding milieu: physicochemical factors, metabolism and hormones. Acid/base status, osmolality, lipid status, plasma protein pattern, oxidative stress induced by increased free radicals production, endothelium-derived factors such as nitric oxide (NO), achidonic acid derivatives modulate both red blood cell (RBC) and white cell mechanics. Therefore, regulatory axes involving liver, endothelium, kidney, pancreas, adrenal gland, endocrine heart, adipose tissue, pituitary gland, and surely other tissues play important roles in the regulation of blood fluidity. A comprehensive picture of all this complex network of regulatory loops is still unavailable but current progress of knowledge suggest that some attempts can currently be made.

Timolol effects on erythrocyte deformability and nitric oxide metabolism

Timolol maleate is a compound used in treatment for reducing increased intra-ocular pressure by limiting aqueous humor production. Decreased erythrocyte deformability (ED), increased activity of erythrocyte acetylcholinesterase (AChE), increased values of nitrosoglutathione (GSNO) and nitic oxide (NO) and decreased plasma levels of NO metabolites, were described in primary open angle glaucoma patients. In healthy human red blood cells (RBCs), timolol is an inhibitor of AChE and induces NO efflux and GSNO efflux from that blood component in lower concentration than those obtained in presence of the natural AChE substrate, acetylcholine (ACh). The signal transduction pathway in RBCs described for NO in dependence of AChE-ACh active complex involves Gi protein, protein tyrosine kinase (PTK like Syk and p53/56Lyn), protein tyrosine phosphatase (PTP) and adenylyl cyclase (AC).The aim of this in vitro study was to verify the effect of timolol maleate in ED, NO efflux and NO derivatives molecules (NOx) like nitrite (NO2-), nitrate (NO3-, peroxynitrite (-ONOO) and GSNO under the presence of PTK, PTP, AC and guanylyl cyclase (GC) enzyme proteins inhibitors.Blood samples from healthy donors were each one divided and were performed aliquots in absence (control aliquots) and presence of timolol or timolol plus each inhibitor and Gi protein uncoupling. No significant differences in erythrocyte NO efflux, GSNO, peroxynitrite, nitrite and nitrate concentrations in response to timolol when compared with the untreated blood samples aliquots were obtained.It was observed an increase in erythrocyte deformability at high shear stresses induced by the simultaneous presence of timolol and band 3 protein dephosphorylation by PTK syk inhibitor. No significant differences where verified in peroxynitrite levels in the blood aliquots in presence of timolol plus each enzyme inhibitor and Gi protein uncoupling in relation to the control aliquots. No variation of GSNO concentration occurs under the presence of timolol and AMGT (PTK lyn inhibitor) besides the significant higher values observed with each one of the other inhibitors. Nitrate concentration increases significantly in all aliquots with timolol plus each one of the inhibitors. The same was observe with nitrite levels with exception of the aliquots with timolol plus AMGT or timolol plus Gi protein uncoupling showing no significant values in relation to the control aliquots.Besides the changes in NO derivative molecules and NO efflux from RBCs obtained in this study with blood samples of healthy donors under the effect of timolol plus each inhibitor of the proteins participants in NO signal transduction mechanism, further analogue studies must be promoted with blood samples of patients with glaucoma or any other inflammatory vascular disease.

Human Erythrocyte Acetylcholinesterase in Health and Disease

The biochemical properties of erythrocyte or human red blood cell (RBC) membrane acetylcholinesterase (AChE) and its applications on laboratory class and on research are reviewed. Evidence of the biochemical and the pathophysiological properties like the association between the RBC AChE enzyme activity and the clinical and biophysical parameters implicated in several diseases are overviewed, and the achievement of RBC AChE as a biomarker and as a prognostic factor are presented. Beyond its function as an enzyme, a special focus is highlighted in this review for a new function of the RBC AChE, namely a component of the signal transduction pathway of nitric oxide.