Ceramide kinase regulates TNFα-stimulated NADPH oxidase activity and eicosanoid biosynthesis in neuroblastoma cells

Abstract

A persistent inflammatory reaction is a hallmark of chronic and acute pathologies in the central nervous system (CNS) and greatly exacerbates neuronal degeneration. The proinflammatory cytokine tumor necrosis factor alpha (TNFα) plays a pivotal role in the initiation and progression of inflammatory processes provoking oxidative stress, eicosanoid biosynthesis, and the production of bioactive lipids. We established in neuronal cells that TNFα exposure dramatically increased Mg2+-dependent neutral sphingomyelinase (nSMase) activity thus generating the bioactive lipid mediator ceramide essential for subsequent NADPH oxidase (NOX) activation and oxidative stress. Since many of the pleiotropic effects of ceramide are attributable to its metabolites, we examined whether ceramide kinase (CerK), converting ceramide to ceramide-1-phosphate, is implicated both in NOX activation and enhanced eicosanoid production in neuronal cells. In the present study, we demonstrated that TNFα exposure of human SH-SY5Y neuroblastoma caused a profound increase in CerK activity. Depleting CerK activity using either siRNA or pharmacology completely negated NOX activation and eicosanoid biosynthesis yet, more importantly, rescued neuronal viability in the presence of TNFα. These findings provided evidence for a critical function of ceramide-1-phospate and thus CerK activity in directly linking sphingolipid metabolism to oxidative stress. This vital role of CerK in CNS inflammation could provide a novel therapeutic approach to intervene with the adverse consequences of a progressive CNS inflammation.

Ceramide 1-phosphate induces macrophage chemoattractant protein-1 release: involvement in ceramide 1-phosphate-stimulated cell migration

“…This finding is particularly relevant when considering that macrophages play critical roles in chronic and acute inflammation and that these cells facilitate cancer cell migration (21,46). In addition, Barth et al (4) recently showed that ceramide kinase, the enzyme responsible for the phosphorylation of ceramide to C1P, regulates NADPH oxidase activity and eicosanoid biosynthesis in neuroblastoma cells, an action that is consistent with our recent finding that C1P increases the production of reactive oxygen species through activation of NADPH oxidase in macrophages (2). Besides these proinflammatory actions, increasing evidence suggests that C1P can aslo function as an anti-inflammatory agent under different experimental settings.…”

Cellular prion protein: A co-receptor mediating neuronal cofilin-actin rod formation induced by β-amyloid and proinflammatory cytokines

“…32 Both Ab and TNFa activate neutral sphingomyelinase generating ceramide and significantly changing the lipid raft environment. 21,33 Such changes could contribute to the proposed signaling pathway by altering interactions between raft components.…”

Implication of Ceramide Kinase in Adipogenesis

“…Subsequent studies by the same group demonstrated that C1P, the product of CerK, was a direct activator of cytosolic phospholipase A 2 [ 21 ], a major enzyme responsible for the regulation of arachidonic acid release in mammalian cells, and that eicosanoid levels were lower in primary mouse embryonic fibroblasts isolated from CerK knockout mice [ 22 ]. Moreover, depleting CerK activity using either specific siRNA to silence the gene encoding this kinase or the pharmacological inhibitor NVP-231 completely blocked eicosanoid biosynthesis [ 23 ]. Additionally, we show here that CerK-deficient cells cause potent reduction in the protein levels of the crucial adipogenesis marker PPAR γ , which is both necessary and sufficient for adipocyte differentiation [ 24 ], thereby suggesting that the loss of CerK might be detrimental for optimal adipogenic differentiation.…”