Astrocytes preserve the inflammation/resolution balance in a cellular neurotoxicity paradigm

Abstract

The inflammation/resolution balance is key in preventing neuroinflammation associated with central nervous system degenerative disorders. After neuronal injury, glial cells act as key regulators of inflammatory/anti-inflammatory homeostasis. We have recently reported that environmental neurotoxicants, such as the pesticide maneb, trigger dopaminergic neuronal death by ferroptosis. However, how glial cells respond to the pesticide has not been deeply investigated. In this work, we aimed to study biochemical signals associated with inflammation/resolution balance in glial cells. To this end, astrocytic cell lines, glial primary cultures, and secretomes from neuronal cells exposed to the neurotoxicant were used to untangle biochemical events associated with glial resolution. Astrocytes and primary glial cultures exposed to the pesticide showed increased glial fibrillary acidic protein (GFAP) expression, Nuclear Factor Kappa B (NFkB) nuclear translocation, and cyclooxygenase-2 (COX-2) expression. In the case of mixed cultures, microglia with increased Ionized calcium-binding adapter molecule 1 (IBA-1) and decreased Arginase-1 (Arg-1) expression were also detected. In this pro-inflammatory scenario, glial viability was slightly affected by the pesticide, and astrocytes were able to rescue neurons from pesticide-induced death. Regarding resolution pathways, the production of specialized pro-resolving lipid mediators is catalyzed by the concatenated metabolization of polyunsaturated fatty acids by phospholipases A2 (PLA2), lipoxygenases (ALOX), and cytochrome oxidases (CYP). When key lipid-mediated resolution pathways’ components such as sPLA2, ALOX-15, and CYP450 were blocked, we found a detrimental effect on astrocyte survival. In addition, the secretome of maned-exposed neurons was able to upregulate ALOX-15 expression and promote a proliferative phenotype in astrocytes. The neuronal proliferative effect on astrocytes was also found to be dependent on ALOX-15 and CYP450 activity. Altogether, our results suggest that the inflammation/resolution balance operates under mild injury conditions, attenuating astrocyte injury and promoting a neuroprotective phenotype.