Hippocampal neurogenesis is changed by brain injury. When neuroinflammation accompanies injury, activation of resident microglial cells promotes the release of inflammatory cytokines and reactive oxygen/nitrogen species like nitric oxide (NO). In these conditions, NO promotes proliferation of neural stem cells (NSC) in the hippocampus. However, little is known about the role of NO in the survival and differentiation of newborn cells in the injured dentate gyrus. Here we investigated the role of NO following seizures in the regulation of proliferation, migration, differentiation, and survival of NSC in the hippocampus using the kainic acid (KA) induced seizure mouse model. We show that NO increased the proliferation of NSC and the number of neuroblasts following seizures but was detrimental to the survival of newborn neurons. NO was also required for the maintenance of long-term neuroinflammation. Taken together, our data show that NO positively contributes to the initial stages of neurogenesis following seizures but compromises survival of newborn neurons.

Aims: Nitric oxide (NO) is involved in the upregulation of endogenous neurogenesis in the subventricular zone and in the hippocampus after injury. One of the main neurogenic pathways activated by NO is the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway, downstream of the epidermal growth factor receptor. However, the mechanism by which NO stimulates cell proliferation through activation of the ERK/MAPK pathway remains unknown, although p21Ras seems to be one of the earliest targets of NO. Here, we aimed at studying the possible neurogenic action of NO by post-translational modification of p21Ras as a relevant target for early neurogenic events promoted by NO in neural stem cells (NSCs). Results: We show that NO caused S-nitrosylation (SNO) of p21Ras in Cys118, which triggered downstream activation of the ERK/MAPK pathway and proliferation of NSC. Moreover, in cells overexpressing a mutant Ras in which Cys118 was replaced by a serine–C118S–, cells were insensitive to NO, and no increase in SNO, in ERK phosphorylation, or in cell proliferation was observed. We also show that, after seizures, in the presence of NO derived from inducible nitric oxide synthase, there was an increase in p21Ras cysteine modification that was concomitant with the previously described stimulation of proliferation in the dentate gyrus. Innovation: Our work identifies p21Ras and its SNO as an early target of NO during signaling events that lead to NSC proliferation and neurogenesis. Conclusion: Our data highlight Ras SNO as an early event leading to NSC proliferation, and they may provide a target for NO-induced stimulation of neurogenesis with implications for brain repair. Antioxid. Redox Signal. 28, 15–30.

Nitric oxide (NO) is well established as a regulator of neurogenesis. NO increases the proliferation of neural stem cells (NSC), and is essential for hippocampal injury-induced neurogenesis following an excitotoxic lesion. One of the mechanisms underlying non-classical NO cell signaling is protein S-nitrosylation. This post-translational modification consists in the formation of a nitrosothiol group (R-SNO) in cysteine residues, which can promote formation of other oxidative modifications in those cysteine residues. S-nitrosylation can regulate many physiological processes, including neuronal plasticity and neurogenesis. In this work, we aimed to identify S-nitrosylation targets of NO that could participate in neurogenesis. In NSC, we identified a group of proteins oxidatively modified using complementary techniques of thiol redox proteomics. S-nitrosylation of some of these proteins was confirmed and validated in a seizure mouse model of hippocampal injury and in cultured hippocampal stem cells. The identified S-nitrosylated proteins are involved in the ERK/MAPK pathway and may be important targets of NO to enhance the proliferation of NSC.