Identification of a Hippocampus-to-Zona Incerta Projection involved in Motor Learning.

Motor learning (ML), which plays a fundamental role in growth and physical rehabilitation, involves different stages of learning and memory processes through different brain regions. However, the neural mechanisms that underlie ML are not sufficiently understood. Here, a previously unreported neuronal projection from the dorsal hippocampus (dHPC) to the zona incerta (ZI) involved in the regulation of ML behaviors is identified. Using recombinant adeno-associated virus, the projections to the ZI are surprisingly identified as originating from the dorsal dentate gyrus (DG) and CA1 subregions of the dHPC. Furthermore, projection-specific chemogenetic and optogenetic manipulation reveals that the projections from the dorsal CA1 to the ZI play key roles in the acquisition and consolidation of ML behaviors, whereas the projections from the dorsal DG to the ZI mediate the retrieval/retention of ML behaviors. The results reveal new projections from the dorsal DG and dorsal CA1 to the ZI involved in the regulation of ML and provide insight into the stages over which this regulation occurs.

Ski promotes proliferation and inhibits apoptosis in fibroblasts under high-glucose conditions via the FoxO1 pathway.

OBJECTIVES: The present study clarified the role and signalling pathway of Ski in regulating proliferation and apoptosis in fibroblasts under high-glucose (HG) conditions. MATERIALS AND METHODS: The proliferation and apoptosis of rat primary fibroblasts were assessed using EdU incorporation and TUNEL assays. The protein and phosphorylation levels of the corresponding factors were measured using immunofluorescence staining and Western blotting. Immunoprecipitation was used to determine the interactions between Ski and FoxO1 or Ski and HDAC1. The Ski protein was overexpressed via recombinant adenovirus transfection, and FoxO1 and HDAC1 were knocked down using targeted small-interfering RNA. RESULTS: The present study found that HG inhibited fibroblast proliferation, increased apoptosis and reduced Ski levels in rat primary fibroblasts. Conversely, increasing Ski protein levels alleviated HG-induced proliferation inhibition and apoptosis promotion. Increasing Ski protein levels also increased Ski binding to FoxO1 to decrease FoxO1 acetylation, and interfering with FoxO1 caused loss of the regulatory effect of Ski in fibroblasts under HG. Increasing Ski protein levels decreased FoxO1 acetylation via HDAC1-mediated deacetylation. CONCLUSIONS: Therefore, these findings confirmed for the first time that Ski regulated fibroblast proliferation and apoptosis under HG conditions via the FoxO1 pathway.

Expression of a short antibody heavy chain peptide effectively antagonizes adenosine 2A receptor in vitro and in vivo.

BACKGROUND: Adenosine 2A receptor (A2AR) is involved in many physiological and pathological functions and serves as an important drug target. Inhibition of A2AR may alleviate symptoms associated with a variety of neuropsychiatric disorders. However, the currently used A2AR antagonists have specificity limitations. RESEARCH DESIGN AND METHODS: A Fab fragment (Fab2838) of an A2AR mouse monoclonal antibody can specifically bind to A2AR to form a complex and inhibit the activity of its receptor. We constructed the vector AntiA2AR, a small-molecule peptide that binds to and inhibits A2AR based on Fab2838. RESULTS: Experiments in HEK293T cells showed that peptide AntiA2AR of 29 peptides was the most effective among the synthesized peptides in inhibiting the A2AR downstream signal cAMP/PKA/CREB. In neurons, the AntiA2AR reversed the calcium flow change induced by the A2AR agonist CGS21680 (1 µM). Furthermore, AntiA2AR expression in the mice striatum weakened the p-PKA/p-CREB signal, enhanced locomotor abilities and increased time spent in the center area in the home-cage observation experiment and increased anxiolytic behavior in the elevated-plus maze test. CONCLUSIONS: Antagonistic peptide AntiA2AR can effectively block the A2AR signaling pathway. This provides a new strategy for the specific inhibition of A2AR and provides information needed for drug development.

PKC Mediates LPS-Induced IL-1ß Expression and Participates in the Pro-inflammatory Effect of A2AR Under High Glutamate Concentrations in Mouse Microglia.

Pathogens such as bacterial lipopolysaccharide (LPS) play an important role in promoting the production of the inflammatory cytokines interleukin-1 beta (IL-1ß) and tumour necrosis factor-α (TNF-α) in response to infection or damage in microglia. However, whether different signalling pathways regulate these two inflammatory factors remains unclear. The protein kinase C (PKC) family is involved in the regulation of inflammation, and our previous research showed that the activation of the PKC pathway played a key role in the LPS-induced transformation of the adenosine A2A receptor (A2AR) from anti-inflammatory activity to pro-inflammatory activity under high glutamate concentrations. Therefore, in the current study, we investigated the role of PKC in the LPS-induced production of these inflammatory cytokines in mouse primary microglia. GF109203X, a specific PKC inhibitor, inhibited the LPS-induced expression of IL-1ß messenger ribonucleic acid and intracellular protein in a dose-dependent manner. Moreover, 5 µM GF109203X prevented LPS-induced IL-1ß expression but did not significantly affect LPS-induced TNF-α expression. PKC promoted IL-1ß expression by regulating the activity of NF-κB but did not significantly impact the activity of ERK1/2. A2AR activation by CGS21680, an A2AR agonist, facilitated LPS-induced IL-1ß expression through the PKC pathway at high glutamate concentrations but did not significantly affect LPS-induced TNF-α expression. Taken together, these results suggest a new direction for specific intervention with LPS-induced inflammatory factors in response to specific signalling pathways and provide a mechanism for A2AR targeting, especially after brain injury, to influence inflammation by interfering with A2AR.

The ERK/CREB pathway is involved in the c-Ski expression induced by low TGF-ß1 concentrations during primary fibroblast proliferation.

Increasing evidence has suggested that bidirectional regulation of cell proliferation is one important effect of TGF-ß1 in wound healing. Increased c-Ski expression plays a role in promoting fibroblast proliferation at low TGF-ß1 concentrations, but the mechanism by which low TGF-ß1 concentrations regulate c-Ski levels remains unclear. In this study, the proliferation of rat primary fibroblasts was assessed with an ELISA BrdU kit. The mRNA and protein expression and phosphorylation levels of corresponding factors were measured by RT-qPCR, immunohistochemistry or Western blotting. We first found that low TGF-ß1 concentrations not only promoted c-ski mRNA and protein expression in rat primary fibroblasts but also increased the phosphorylation levels of Extracellular Signal-Regulated Kinases (ERK) and cAMP response element binding (CREB) protein. An ERK kinase (mitogen-activated protein kinase kinase, MEK) inhibitor significantly inhibited ERK1/2 phosphorylation levels, markedly reducing c-Ski expression and CREB phosphorylation levels and abrogating the growth-promoting effect of low TGF-ß1 concentrations. At the same time, Smad2/3 phosphorylation levels were not significantly changed. Taken together, these results suggest that the increased cell proliferation induced by low TGF-ß1 concentrations mediates c-Ski expression potentially through the ERK/CREB pathway rather than through the classic TGF-ß1/Smad pathway.

Perivascular AQP4 dysregulation in the hippocampal CA1 area after traumatic brain injury is alleviated by adenosine A2A receptor inactivation.

Traumatic brain injury (TBI) can induce cognitive dysfunction due to the regional accumulation of hyperphosphorylated tau protein (p-tau). However, the factors that cause p-tau to concentrate in specific brain regions remain unclear. Here, we show that AQP4 polarization in the perivascular astrocytic end feet was impaired after TBI, which was most prominent in the ipsilateral brain tissue surrounding the directly impacted region and the contralateral hippocampal CA1 area and was accompanied by increased local p-tau, changes in dendritic spine density and morphology, and upregulation of the adenosine A2A receptor (A2AR). The critical role of the A2AR signaling in these pathological changes was confirmed by alleviation of the impairment of AQP4 polarity and accumulation of p-tau in the contralateral CA1 area in A2AR knockout mice. Given that p-tau can be released to the extracellular space and that the astroglial water transport via AQP4 is involved in tau clearance from the brain interstitium, our results suggest that regional disruption of AQP4 polarity following TBI may reduce the clearance of the toxic interstitial solutes such as p-tau and lead to changes in dendritic spine density and morphology. This may explain why TBI patients are more vulnerable to cognitive dysfunction.