Amyloid-ß-Induced Transglutaminase 2 Expression and Activities are Modulated by 2-Pentadecyl-2-Oxazoline in Mouse and Human Microglial Cell Lines.

BACKGROUND: Transglutaminase 2 is an ubiquitously multifunctional enzyme and the most widely studied of the transglutaminase family. Consistent with its role in promoting post-translational modifications of proteins, Transglutaminase 2 is involved in many physiological processes such as apoptosis, signal transduction, and cellular adhesion. Several findings indicate that Transglutaminase 2 plays a role in the pathological processes of various inflammation-related diseases, including neurodegenerative diseases. OBJECTIVE: We tested the potential modulatory effects on amyloid-ß-induced Transglutaminase 2 expression and activities of 2-pentadecyl-2-oxazoline, a plant-derived agent, which has shown effectiveness against chronic pain and associated neuropsychiatric disorders, both in mouse and human microglial cell lines. METHODS: We used biochemistry, molecular and cell biology techniques to evaluate the potential modulatory effects on amyloid-ß-induced Transglutaminase 2 expression and activities of 2- pentadecyl-2-oxazoline in mouse and human microglial cell lines. RESULTS: 2-pentadecyl-2-oxazoline was able to modulate amyloid-ß-induced Transglutaminase 2 expression and activities in mouse and human microglial cell lines. CONCLUSION: Transglutaminase 2 confirms its role as a neuroinflammation marker, the inhibition of which could be a potential preventive and therapeutic approach, while 2-pentadecyl-2-oxazoline is a potent modulator of the amyloid-ß-induced Transglutaminase 2 expression and activities in mouse and human microglial cell lines.

Potential role of the hydroxyl carboxylic acid receptor type 2 (HCAR2) in microglia pathophysiology: A possible cross-talk with C-X-C chemokine receptor 1 (CXCR1).

Following insults or injury, microglia cells are activated contributing to the cytotoxic response or by promoting an immune-mediated damage resolution. Microglia cells express HCA2R, a hydroxy carboxylic acid (HCA) receptor, which has been shown to mediate neuroprotective and anti-inflammatory effects. In this study we found that HCAR2 expression levels were increased in cultured rat microglia cells after Lipopolysaccharide (LPS) exposure. In a similar fashion, the treatment with MK 1903, a potent full agonist of HCAR2, increased the receptor protein levels. Moreover, HCAR2 stimulation prevented i) cells viability ii) morphological activation iii) pro/anti-inflammatory mediators production in LPS-treated cells. Likewise, HCAR2 stimulation reduced the proinflammatory mediators mRNA expression induced by neuronal chemokine fractalkine (FKN), a neuronal derived chemokine activating its unique receptor, chemokine receptor 1 (CX3CR1) on microglia surface. Interestingly, electrophysiological recordings in vivo revealed that MK1903 was able to prevent the increase of the nociceptive neurons (NS) firing activity mediated by the spinal FKN application in healthy rats. Collectively, our data demonstrate that HCAR2 is functionally expressed in microglia, by showing its capability to shift microglia toward an anti-inflammatory phenotype. Moreover, we indicated the contribute of HCAR2 in the FKN signaling and suggested a possible HCAR2/CX3CR1 functional interaction. This study paves the way for further investigations aimed at understanding the role HCAR2 as potential target in neuroinflammation-based CNS disorders. This article is part of the Special Issue on "The receptor-receptor interaction as a new target for therapy".