The synthesis of prostaglandins in platelets from patients with multiple sclerosis

A Systematic Review on the Role of Arachidonic Acid Pathway in Multiple Sclerosis

BACKGROUND & OBJECTIVE

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease characterized by destruction of oligodendrocytes, immune cell infiltration and demyelination. Inflammation plays a significant role in MS, and the inflammatory mediators such as eicosanoids, leukotrienes, superoxide radicals are involved in pro-inflammatory responses in MS. In this systematic review we tried to define and discuss all the findings of in vivo animal studies and human clinical trials on the potential association between arachidonic acid (AA) pathway and multiple sclerosis.

METHODS

A systematic literature search across Pubmed, Scopus, Embase and Cochrane database was conducted. This systematic review was performed according to PRISMA guidelines.

RESULTS

A total of 146 studies were included, of which 34 were conducted in animals, 58 in humans, and 60 studies reported the role of different compounds that target AA mediators or their corresponding enzymes/ receptors, and can have a therapeutic effect in MS. These results suggest that eicosanoids have significant roles in experimental autoimmune encephalomyelitis (EAE) and MS. The data from animal and human studies elucidated that PGI2, PGF2α, PGD2, isoprostanes, PGE2, PLA2, LTs are increased in MS. PLA2 inhibition modulates the progression of the disease. PGE1 analogues can be a useful option in the treatment of MS.

CONCLUSIONS

All studies reported the beneficial effects of COX and LOX inhibitors in MS. The hybrid compounds, such as COX-2 inhibitors/TP antagonists and 5-LOX inhibitors can be an innovative approach for multiple sclerosis treatment. Future work in MS should shed light in synthesizing new compounds targeting arachidonic acid pathway.

Prostaglandins in pathogenesis and treatment of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) characterized by inflammation, demyelination, axonal loss, and gliosis. The inflammatory lesions are manifested by a large infiltration and a heterogeneous population of cellular and soluble mediators of the immune system, such as T cells, B cells, macrophages, and microglia, as well as a broad range of cytokines, chemokines, antibodies, complement, and other toxic substances. Prostaglandins (PGs) are arachidonic acid-derived autacoids that have a role in the modulation of many physiological systems including the CNS, respiratory, cardiovascular, gastrointestinal, genitourinary, endocrine, and immune systems. PG production is associated with inflammation, a major feature in MS that is characterized by the loss of myelinating oligodendrocytes in the CNS. With respect to the role of PGs in the induction of inflammation, they can be effective mediators in the pathophysiology of MS. Thus use of agonists or antagonists of PG receptors may be considered as a new therapeutic protocol in MS. In this review, we try to clarify the role of PGs in immunopathology and treatment of MS.

Relevance of platelet factor four (PF4) plasma levels in multiple sclerosis

In order to study the role of platelets in Multiple Sclerosis (MS) we assessed, in a group of patients during a quiescent phase of the disease, the plasma levels of beta-thromboglobulin (beta-TG) and platelet factor four (PF4) both in absence of treatment and during administration of aspirin (ASA) at the dose of 50 mg/daily. In the MS patients studied, the basal plasma levels of beta-TG and PF4 were significantly higher than in control subjects. The increase in the beta-TG plasma levels occurred independently of the age, sex and severity of the disease, whereas the modification in the PF4 plasma levels was significantly correlated with the severity of the disease. Administration to the patients of ASA, at the dose that does not affect prostacyclin production, determined a decrease of beta-TG in 77% of the patients. Mean PF4 plasma levels remained unchanged. These results suggest that PF4 in the plasma of MS patients may originate not only from the platelets but also from the mast cells following platelet aggregating factor (PAF) stimulation and immunocomplex formation.

Encephalitogenic peptide and platelet aggregation in multiple sclerosis

Platelet aggregation (PA) stimulated by encephalitogenic peptide (EP) and PA induced by ADP were measured in 83 multiple sclerosis (MS) patients and 70 control subjects with other neurological diseases (OND). EP-stimulated PA was significantly increased in MS patients as compared with the controls. There was no significant difference in ADP-induced PA between patients with MS and OND. The results are discussed in terms of EP-stimulated platelets playing a role in the pathogenesis of MS by affecting the venular permeability of the brain.

Response to platelet-activating factor of platelets from patients with multiple sclerosis

The response of Multiple Sclerosis (MS) and control platelets to different concentrations of platelet-activating factor was studied. At concentrations in the range 10(-7) to 10(-5)M, it was found that the MS platelets tended to aggregate fully at lower concentrations than was the case with control platelets. At a concentration of 10(-6)M, it was found that in 19 cases the MS platelets gave a full aggregation response whilst 4 cases showed biphasic but full aggregation, whereas at this concentration the control platelets showed full aggregation in only 2 cases, biphasic but less complete aggregation in 5 cases and reversible aggregation in 16 cases. In crossover studies, it could be shown that MS platelets resuspended in control platelet-poor plasma still showed enhanced aggregability and that the response of control platelets was unaffected by resuspension in MS platelet-poor plasma. Differences were also seen in susceptibility of platelets of MS and control subjects to inhibition by indomethacin, bromophenacyl bromide (a phospholipase inhibitor) and verapamil (a Ca2+ antagonist). It is suggested that the hyperaggregability of the MS platelets could reside in the platelets themselves, and may be associated with enhanced phospholipase activity.

Glutathione peroxidase and reductase, glucose-6-phosphate dehydrogenase and catalase activities in multiple sclerosis

Our previous studies have demonstrated a decreased glutathione feroxidase (GSH-Px) activity of erythrocytes and leucocytes from multiple sclerosis (MS) patients. In the present communication these activities were compared with the activities of associated enzymes (glutathione reductase (GSSG-RD), glucose-6-phosphate dehydrogenase (G-6-PD) and catalase). All enzymic activities were compared between MS patients, other neurologic patients (ON patients) and normal control individuals. Compared to data of ON patients and normal controls, in MS the ratio of GSHPx/GSSGRD in lympho- and granulocytes was significantly decreased (2 alpha less than or equal to 0.05) by 35% and 51%, respectively. The significant correlation between GSSG-RD and the GSH-Px activity (2 alpha less than or equal to 0.05, r = 0.501) found in control lymphocytes was not present in MS lymphocytes. However, the lymphocyte GSH-Px activities of controls as well as of MS correlated with the corresponding serum selenium levels (2 alpha less than or equal to 0.05, r = 0.594 and 2 alpha less than or equal to 0.01, r = 0.967, respectively). The G-6-PD activity was insignificantly increased by 41% in MS lymphocytes compared to normal control. Catalase activity was unchanged in lymphocytes but decreased 50% in MS granulocytes compared to normal control. No significant differences were found between MS and the ON group. The catalase activity of MS erythrocytes was increased by 63% (2 alpha less than or equal to 0.05) in comparison with both the normal control and ON data.

Platelet aggregation and multiple sclerosis

Measurements of blood platelet aggregation were carried out in 30 patients suffering from multiple sclerosis (MS) and in 15 healthy individuals. Compared with the control group, the MS patients showed an increase in both spontaneous and induced (ADP and serotonin) platelet aggregation. The possible pathogenetic significance of these results is discussed.