Basic fibroblast growth factor induces miR-134 upregulation in astrocyte for cell maturation

The fibroblast growth factor system in cognitive disorders and dementia

Cognitive impairment is the core precursor to dementia and other cognitive disorders. Current hypotheses suggest that they share a common pathological basis, such as inflammation, restricted neurogenesis, neuroendocrine disorders, and the destruction of neurovascular units. Fibroblast growth factors (FGFs) are cell growth factors that play essential roles in various pathophysiological processes via paracrine or autocrine pathways. This system consists of FGFs and their receptors (FGFRs), which may hold tremendous potential to become a new biological marker in the diagnosis of dementia and other cognitive disorders, and serve as a potential target for drug development against dementia and cognitive function impairment. Here, we review the available evidence detailing the relevant pathways mediated by multiple FGFs and FGFRs, and recent studies examining their role in the pathogenesis and treatment of cognitive disorders and dementia.

bFGF promotes neurological recovery from neonatal hypoxic-ischemic encephalopathy by IL-1β signaling pathway-mediated axon regeneration

INTRODUCTION

Neonatal hypoxia-ischemic brain damage (HIBD) can lead to serious neuron damage and dysfunction, causing a significant worldwide health problem. bFGF as a protective reagent promotes neuron repair under hypoxia/ischemia (HI). However, how bFGF and downstream molecules were regulated in HI remains elusive.

METHODS

We established an in vitro HI model by culturing primary cortical neurons and treated with oxygen-glucose deprivation (OGD). We suppressed the expression of bFGF by using siRNA (small interfering RNA) interference to detect the neuronal morphological changes by immunofluorescence staining. To determine the potential mechanisms regulated by bFGF, the change of downstream molecular including IL-1β was examined in bFGF knockdown condition. IL-1β knockout (KO) rats were generated using CRISPR/Cas9-mediated technologies. We used an accepted rat model of HI, to assess the effect of IL-1β deletion on disease outcomes and carried out analysis on the behavior, histological, cellular, and molecular level.

RESULTS

We identified that OGD can induce endogenous expression of bFGF. Both OGD and knockdown of bFGF resulted in reduction of neuron numbers, enlarged cell body and shortened axon length. We found molecules closely related to bFGF, such as interleukin-1β (IL-1β). IL-1β was up-regulated after bFGF interference under OGD conditions, suggesting complex signaling between bFGF and OGD-mediated pathways. We found HI resulted in up-regulation of IL-1β mRNA in cortex and hippocampus. IL-1β KO rats markedly attenuated the impairment of long-term learning and memory induced by HI. Meanwhile, IL-1β^-/- (KO, homozygous) group showed better neurite growth and less apoptosis in OGD model. Furthermore, serine/threonine protein kinase (AKT1) mRNA and protein expression was significantly up-regulated in IL-1β KO rats.

CONCLUSIONS

We showed that IL-1β-mediated axon regeneration underlie the mechanism of bFGF for the treatment of HIBD in neonatal rats. Results from this study would provide insights and molecular basis for future therapeutics in treating HIBD.

MicroRNA134 of Ventral Hippocampus Is Involved in Cocaine Extinction-Induced Anxiety-like and Depression-like Behaviors in Mice

We previously found that cocaine abuse could increase microRNA134 (miR134) levels in the hippocampus; yet the roles of miR134 in cocaine-related abnormal psychiatric outcomes remain unknown. In this study, using the cocaine-induced conditioned place preference (CPP) mice model, we found that mice exhibit enhanced anxiety-like and depression-like behaviors during the cocaine extinction (CE) period of CPP, accompanied by obviously increased miR134 levels and decreased levels of 19 genes that are associated with synaptic plasticity, glia activity, and neurochemical microenvironments, in the ventral hippocampus (vHP). Knockdown of miR134 in vHP in vivo reversed the changes in 15 of 19 potential gene targets of miR134 and rescued the abnormal anxiety-like and depression-like behavioral outcomes in CE mice. In parallel, knockdown of miR134 reversed CE-induced changes in dendritic spines and synaptic proteins and increased the field excitatory postsynaptic potential (fEPSP) of CA1 pyramidal neurons in the vHP of CE mice. In addition, knockdown of miR134 suppressed the CE-enhanced microglia activity, inflammatory, apoptotic, and oxidative stress statuses in the vHP. With the data taken together, miR134 may be involved in cocaine-associated psychiatric problems, potentially via regulating the expressions of its gene targets that are related to synaptic plasticity and neurochemical microenvironments.

Presynaptic Dysfunction in Neurons Derived from Tay-Sachs iPSCs

Tay-Sachs disease (TSD) is a GM2 gangliosidosis lysosomal storage disease caused by a loss of lysosomal hexosaminidase-A (HEXA) activity and characterized by progressive neurodegeneration due to the massive accumulation of GM2 ganglioside in the brain. Here, we generated iPSCs derived from patients with TSD, and found similar potential for neural differentiation between TSD-iPSCs and normal iPSCs, although neural progenitor cells (NPCs) derived from the TSD-iPSCs exhibited enlarged lysosomes and upregulation of the lysosomal marker, LAMP1, caused by the accumulation of GM2 ganglioside. The NPCs derived from TSD-iPSCs also had an increased incidence of oxidative stress-induced cell death. TSD-iPSC-derived neurons showed a decrease in exocytotic activity with the accumulation of GM2 ganglioside, suggesting deficient neurotransmission in TSD. Our findings demonstrated that NPCs and mature neurons derived from TSD-iPSCs are potentially useful cellular models of TSD and are useful for investigating the efficacy of drug candidates in the future.

Dysregulated fibroblast growth factor (FGF) signaling in neurological and psychiatric disorders

The role of the fibroblast growth factor (FGF) system in brain-related disorders has received considerable attention in recent years. To understand the role of this system in neurological and psychiatric disorders, it is important to identify the specific members of the FGF family that are implicated, their location and the various mechanisms they can be modulated. Each disorder appears to impact specific molecular players in unique anatomical locations, and all of these could conceivably become targets for treatment. In the last several years, the issue of how to target this system directly has become an area of increasing interest. To date, the most promising therapeutics are small molecule inhibitors and antibodies that modulate FGF receptor (FGFR) function. Beyond attempting to modify the primary players affected by a given brain disorder, it may prove useful to target molecules, such as membrane-bound or extracellular proteins that interact with FGF ligands or FGFRs to modulate signaling.

The inactivation of extracellular signal-regulated kinase by glucagon-like peptide-1 contributes to neuroprotection against oxidative stress

Glucagon-like peptide-1 (GLP-1), an insulinotropic peptide secreted from enteroendocrine cells, has been known to have a neuroprotective effect. However, it is not fully understood the intracellular mediator of GLP-1 signaling in neuronal cells. In the present study, we examined the change in intracellular signaling of cortical neurons after GLP-1 application and luminal glucose stimulation in vitro and in vivo. GLP-1 receptor was highly expressed in cultured cortical neurons and brain tissues including the prefrontal cortex and hippocampus. The activation of GLP-1 receptor (5min) significantly decreased levels of phosphorylated extracellular signal-regulated kinase (pERK), which is involved in neuronal cell survival and death, in cultured cortical neurons. Oral glucose administration also rapidly reduced pERK levels in the prefrontal cortex, while intraperitoneal glucose injection did not show such an effect. Further, GLP-1 attenuated hydrogen peroxide-induced cell death and hyperactivity of ERK in cultured cortical neurons. It is possible that increased GLP-1 by luminal glucose stimulation affects cortical system including the maintenance of neuronal cell survival.