Secretory Phospholipase A2 activity in serum and cerebrospinal fluid of patients with relapsing-remitting multiple sclerosis

Potential neurotoxic activity of diverse molecules released by astrocytes

Astrocytes are the main support cells of the central nervous system. They also participate in neuroimmune reactions. In response to pathological and immune stimuli, astrocytes transform to reactive states characterized by increased release of inflammatory mediators. Some of these molecules are neuroprotective and inflammation resolving while others, including reactive oxygen species (ROS), nitric oxide (NO), matrix metalloproteinase (MMP)- 9, L-glutamate, and tumor necrosis factor α (TNF), are well-established toxins known to cause damage to surrounding cells and tissues. We hypothesized that similar to microglia, the brain immune cells, reactive astrocytes can release a broader set of diverse molecules that are potentially neurotoxic. A literature search was conducted to identify such molecules using the following two criteria: 1) evidence of their expression and secretion by astrocytes and 2) direct neurotoxic action. This review describes 14 structurally diverse molecules as less-established astrocyte neurotoxins, including C-X-C motif chemokine ligand (CXCL)10, CXCL12/CXCL12(5-67), FS-7-associated surface antigen ligand (FasL), macrophage inflammatory protein (MIP)- 2α, TNF-related apoptosis inducing ligand (TRAIL), pro-nerve growth factor (proNGF), pro-brain-derived neurotrophic factor (proBDNF), chondroitin sulfate proteoglycans (CSPGs), cathepsin (Cat)B, group IIA secretory phospholipase A₂ (sPLA₂-IIA), amyloid beta peptides (Aβ), high mobility group box (HMGB)1, ceramides, and lipocalin (LCN)2. For some of these molecules, further studies are required to establish either their direct neurotoxic effects or the full spectrum of stimuli that induce their release by astrocytes. Only limited studies with human-derived astrocytes and neurons are available for most of these potential neurotoxins, which is a knowledge gap that should be addressed in the future. We also summarize available evidence of the role these molecules play in select neuropathologies where reactive astrocytes are a key feature. A comprehensive understanding of the full spectrum of neurotoxins released by reactive astrocytes is key to understanding neuroinflammatory diseases characterized by the adverse activation of these cells and may guide the development of novel treatment strategies.

Identification, expression and enzyme activity of the group III sPLA2 s in Cyprinus carpio L

Five group III secreted phospholipase (pla2g3s) homologous genes located on different linkage groups were identified from common carp (Cyprinus carpio), which we named Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3b, Ccpla2g3c1 and Ccpla2g3c2. The five genes encode 530, 525, 461, 752 and 753 amino acids, respectively. Sequence analysis showed that the Ccpla2g3as contain seven exons and the others contain four exons. Synteny analysis of fish pla2g3s indicated that pla2g3a and pla2g3b were from the same ancestor gene, and Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3c1 and Ccpla2g3c2 were from the specific genome duplication of common carp. Due to the significant variation of the pla2g3bs from common carp and zebrafish (Danio rerio), they formed a separate group in the phylogenetic tree. The tissue distributions of Ccpla2g3s coincided with their expression profiles during the embryo stages. The expression levels of Ccpla2g3as and Ccpla2g3cs were low at the embryo stages, and they were abundant in the liver and brain, respectively, whereas the expression of Ccpla2g3b was high at 0.5 h after fertilization and in the ovary. We obtained three soluble recombinant proteins of the bee venom-like PLA2 (BVLP) from Ccpla2g3 and evaluated their PLA₂ enzyme properties. The optimum pHs of MBP-a1-BVLP, MBP-b-BVLP and MBP-c1-BVLP were 7.5, 7.0 and 8.0, respectively, and specific activities were 7.68 ± 0.66, 4.155 ± 0.158 and 1.93 ± 0.05 U μmol^-1 , respectively. The K_d for Ca²⁺ of MBP-b-BVLP was the lowest (2.6 μM), whereas the values for both MBP-a1-BVLP and MBP-c1-BVLP were about 15 μM. The K_m values of three proteins ranged from 31.9 to 41.91 μM.

The role of phospholipase A2 in multiple Sclerosis: A systematic review and meta-analysis

Phospholipases A2 (PLA₂) are a diverse group of enzymes that cleave the fatty acids of membrane phospholipids. They play critical roles in pathogenesis of neurodegenerative diseases such as multiple sclerosis by enhancing oxidative stress and initiating inflammation. The levels of PLA₂ activity in MS patients compared to controls and role of inhibiting PLA₂ activity on severity scores in different experimental models are not comprehensively assessed in the light of varying evidence from published studies. The objective of this systematic review is to determine the association between PLA₂ activity and multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). We performed a systematic review of six studies that assessed PLA₂ activity in MS patients compared to controls and nine studies that assessed PLA₂ activity in EAE. sPLA₂ nor Lp-PLA₂ activity were not increased in MS compared to controls in five of those six studies. A difference in sPLA₂ activity was only found in a study that measured the enzyme activity in urine. However, inhibiting cPLA₂ or sPLA₂ led to lower clinical severity or no signs of EAE in mice, and a lower incidence of EAE lesions compared to animals without cPLA₂ inhibition. These findings indicate that PLA₂ appears to play a role in the pathogenesis of EAE.