Plasma vitronectin is reduced in patients with myasthenia gravis: Diagnostic and pathophysiological potential.

Myasthenia gravis (MG) is an autoimmune disease leading to varying degrees of skeletal muscle weakness. It is caused by specific antibodies directed against definite components in the postsynaptic membrane at the neuromuscular junction (NMJ), such as the acetylcholine receptor (AChR) and the muscle-specific kinase (MUSK) receptor. In clinical practice, MG patients may be classified into three main subgroups based on the occurrence of serum autoantibodies directed against AChR or MUSK receptor or antibody-negative. As the MG subgroups differ in terms of clinical characteristics, disease pathogenesis, prognosis, and response to therapies, they could benefit from targeted treatment as well as the detection of other possible disease biomarkers. We performed proteomics on plasma fractions enriched in low-abundance proteins to identify potential biomarkers according to different autoimmune responses. By this approach, we evidenced a significant reduction of vitronectin in MG patients compared to healthy controls, irrespective of the autoantibodies NMJ target. The obtained results were validated by mono- and two-dimensional Western blotting analysis. Vitronectin is a multifunctional glycoprotein involved in the regulation of several pathophysiological processes, including complement-dependent immune response, coagulation, fibrinolysis, pericellular proteolysis, cell attachment, and spreading. The pathophysiological significance of the reduction of plasma vitronectin in MG patients has yet to be fully elucidated. It could be related either to a possible deposition of vitronectin at NMJ to counteract the complement-mediated muscle damage at this level or to a parallel variation of this glycoprotein in the muscle extracellular matrix with secondary induced alteration in clustering of AChRs at NMJ, as it occurs with variation in concentrations of agrin, another extracellular matrix component. The clinical value of measuring plasma vitronectin has yet to be defined. According to present findings, significantly lower plasma values of this glycoprotein might be indicative of an impaired complement-dependent immune response.

Identification of differentially expressed plasma proteins in atherosclerotic patients with type 2 diabetes.

Besides hyperglycaemia and insulin resistance, several factors are associated with a higher cardiovascular risk in type 2 diabetes mellitus (T2DM), many of them being closely related to each other owing to common origins or pathways. The pathophysiological mechanisms underlying vascular dysfunctions in diabetes include reduced bioavailability of nitric oxide, increased ROS and prothrombotic factors production, as well as activation of receptors for advanced glycation end-products. These alterations contribute to create a pro-inflammatory/thrombotic state that ultimately leads to plaque formation and complication. This study aimed at identifying differentially expressed plasma proteins between T2DM and non-diabetic patients undergoing carotid endarterectomy, by means of two-dimensional electrophoresis coupled with LC-MS/MS. Before analysis, plasma samples were enriched in low-expression proteins through combinatorial hexapeptide ligand libraries. Both mono- and two-dimensional western blotting were performed for data validation. Differentially expressed proteins were mapped onto STRING v10 to build a protein-protein interaction network. Sixteen differentially expressed spots were identified with a high score. Among them, there were fibrinogen beta and gamma chains, complement C1r, C3 and C4-B subcomponents, alpha-1-antitrypsin (AAT), vitronectin and CD5 antigen-like. Protein-Protein interaction analysis evidenced a network among differentially expressed proteins in which vitronectin seems to represent a potentially pivotal node among fibrinolysis, complement dependent immune responses and inflammation in accordance with a number of in vitro and in vivo evidences for a contributory role of these proteins to the development of diabetic atherosclerosis.

Evaluation of Early Markers of Nephropathy in Patients with Type 2 Diabetes Mellitus.

Aims. T2DM often remains undiagnosed for many years because hyperglycemia develops gradually and may not produce any symptoms. As patients with T2DM are at increased risk of microvascular and macrovascular complications, the preclinical diagnosis of the state is the key point of the disease management. Methods. We evaluated parameters such as GAGs/PGs, NAG, and NGAL in urine samples from 43 normoalbuminuric T2DM patients and 31 apparently healthy control subjects. Results. The total urinary GAG excretion showed no significant differences between patients and controls. The electrophoretic analysis evidenced the presence of UTI and its degradation products (LSC and SM-LSC), CS, and HS. We observed modifications of HS and total UTI (including UTI and its degradation products) relative contents in T2DM patients compared with controls whereas no differences in CS percentage were found. NGAL levels were significantly increased in T2DM patients and were positively correlated with both NAG (r = 0.606, p < 0.0001) and the presence of hypertension (r = 0.352, p < 0.05). Conclusions. These data suggest that the assessed molecules could represent useful markers to detect early renal impairment in patients with T2DM.

A 2DE approach for high-throughput antigen separation applicable to mAb production.

A constantly increasing number of mABs are required for the validation of a large proportion of proteomic and protein-protein interaction data. The development of new robotic platforms has greatly enhanced the throughput of monoclonal antibody production; however, the availability of highly purified proteins to use as antigens currently represents the major bottleneck of the process. In this article, we describe a new 2DE approach to purify hundreds of proteins from cellular extracts in a very cost-effective and time-efficient way. The accuracy of the new purification method is shown to be comparable to high-resolution analytical 2DE. The effectiveness and the throughput of the method to purify proteins suitable for the development of mAbs are then assessed. Using this methodology, we were able to separate 447 proteins starting from 50 mg of proteins extracted from HT29 cells. Fractions containing more than 30 µg of protein constantly induced immunization in mice. Using a high-throughput process for monoclonal antibody production, we obtained an average of 3.5 mAbs for each protein. According to pilot experiments, we can predict that starting from an unfractionated cellular extract it is possible to obtain approximately 200 proteins usable for monoclonal antibody development. Our results indicate that the number of antigens available for monoclonal antibody production can be further increased by running parallel separations. The proposed methodology will then facilitate the high-throughput monoclonal antibody process providing a vast array of high quality antigens at very low cost.

New antimalarial indolone-N-oxides, generating radical species, destabilize the host cell membrane at early stages of Plasmodium falciparum growth: role of band 3 tyrosine phosphorylation.

Although indolone-N-oxide (INODs) genereting long-lived radicals possess antiplasmodial activity in the low-nanomolar range, little is known about their mechanism of action. To explore the molecular basis of INOD activity, we screened for changes in INOD-treated malaria-infected erythrocytes (Pf-RBCs) using a proteomics approach. At early parasite maturation stages, treatment with INODs at their IC(50) concentrations induced a marked tyrosine phosphorylation of the erythrocyte membrane protein band 3, whereas no effect was observed in control RBCs. After INOD treatment of Pf-RBCs we also observed: (i) accelerated formation of membrane aggregates containing hyperphosphorylated band 3, Syk kinase, and denatured hemoglobin; (ii) dose-dependent release of microvesicles containing the membrane aggregates; (iii) reduction in band 3 phosphorylation, Pf-RBC vesiculation, and antimalarial effect of INODs upon addition of Syk kinase inhibitors; and (iv) correlation between the IC(50) and the INOD concentrations required to induce band 3 phosphorylation and vesiculation. Together with previous data demonstrating that tyrosine phosphorylation of oxidized band 3 promotes its dissociation from the cytoskeleton, these results suggest that INODs cause a profound destabilization of the Pf-RBC membrane through a mechanism apparently triggered by the activation of a redox signaling pathway rather than direct oxidative damage.