Rac1 Guides Porf-2 to Wnt Pathway to Mediate Neural Stem Cell Proliferation

Knockdown of Porf-2 restores visual function after optic nerve crush injury

Retinal ganglion cells (RGCs), the sole output neurons in the eyes, are vulnerable to diverse insults in many pathological conditions, which can lead to permanent vision dysfunction. However, the molecular and cellular mechanisms that contribute to protecting RGCs and their axons from injuries are not completely known. Here, we identify that Porf-2, a member of the Rho GTPase activating protein gene group, is upregulated in RGCs after optic nerve crush. Knockdown of Porf-2 protects RGCs from apoptosis and promotes long-distance optic nerve regeneration after crush injury in both young and aged mice in vivo. In vitro, we find that inhibition of Porf-2 induces axon growth and growth cone formation in retinal explants. Inhibition of Porf-2 provides long-term and post-injury protection to RGCs and eventually promotes the recovery of visual function after crush injury in mice. These findings reveal a neuroprotective impact of the inhibition of Porf-2 on RGC survival and axon regeneration after optic nerve injury, providing a potential therapeutic strategy for vision restoration in patients with traumatic optic neuropathy.

Wnt5A Signaling Regulates Gut Bacterial Survival and T Cell Homeostasis

In light of the demonstrated antagonism of Wnt5A signaling toward the growth of several bacterial pathogens, it was important to study the influence of Wnt5A on gut-resident bacteria and its outcome. Here, we demonstrate that in contrast to inhibiting the survival of the established gut pathogen Salmonella enterica, Wnt5A clearly promotes the survival of the common gut commensals Enterococcus faecalis and Lactobacillus rhamnosus within macrophages through a self-perpetuating Wnt5A-actin axis. A Wnt5A-actin axis furthermore regulates the subsistence of the natural bacterial population of the Peyer's patches, as is evident from the diminution in the countable bacterial CFU therein through the application of Wnt5A signaling and actin assembly inhibitors. Wnt5A dependency of the gut-resident bacterial population is also manifested in the notable difference between the bacterial diversities associated with the feces and Peyer's patches of Wnt5A heterozygous mice, which lack a functional copy of the Wnt5A gene, and their wild-type counterparts. Alterations in the gut commensal bacterial population resulting from either the lack of a copy of the Wnt5A gene or inhibitor-mediated attenuation of Wnt5A signaling are linked with significant differences in cell surface major histocompatibility complex (MHC) II levels and regulatory versus activated CD4 T cells associated with the Peyer's patches. Taken together, our findings reveal the significance of steady state Wnt5A signaling in shaping the gut commensal bacterial population and the T cell repertoire linked to it, thus unveiling a crucial control device for the maintenance of gut bacterial diversity and T cell homeostasis. IMPORTANCE Gut commensal bacterial diversity and T cell homeostasis are crucial entities of the host innate immune network, yet the molecular details of host-directed signaling pathways that sustain the steady state of gut bacterial colonization and T cell activation remain unclear. Here, we describe the protective role of a Wnt5A-actin axis in the survival of several gut bacterial commensals and its necessity in shaping gut bacterial colonization and the associated T cell repertoire. This study opens up new avenues of investigation into the role of the Wnt5A-actin axis in protection of the gut from dysbiosis-related inflammatory disorders.

Carvedilol Promotes Retinal Ganglion Cell Survival Following Optic Nerve Injury via ASK1-p38 MAPK Pathway

BACKGROUND

Carvedilol, which is considered as a nonselective β-adrenoreceptor blocker, has many pleiotropic activities. It also causes great impact on neuroprotection because of its antioxidant ability, which suggested that carvedilol may be effective in protecting RGCs from increased oxidative stress.

OBJECTIVE

To examine the effects of carvedilol on preventing Retinal Ganglion Cell (RGC) death in a mouse model of Optic Nerve Injury (ONI).

METHODS

C57BL/6J mice were subjected to Optic Nerve Injury (ONI) model and treated with carvedilol or placebo. Histological and morphometric studies were performed; the RGC number, the amount of neurons in the ganglion cell layer and the thickness of the Inner Retinal Layer (IRL) was quantified. The average thickness of Ganglion Cell Complex (GCC) was determined by the Spectral- Domain OCT (SD-OCT) assay. Immunohistochemistry, western blot and quantitative real-time PCR analysis were also applied.

RESULTS

Daily treatment of carvedilol reduced RGC death following ONI, and in vivo retinal imaging revealed that carvedilol can effectively prevent retinal degeneration. The expression of chemokines important for micorglia recruitment was deceased with carvedilol ingestion and the accumulation of retinal microglia is reduced consequently. In addition, the ONI-induced expression of inducible nitric oxide synthase in the retina was inhibited with carvedilol treatment in the retina. We also discovered that carvedilol suppressed ONI-induced activation of Apoptosis Signal-regulating Kinase-1 (ASK1) and p38 Mitogen-Activated Protein Kinase (MAPK) pathway.

CONCLUSION

The results of this study indicate that carvedilol can stimulate neuroprotection and neuroregeneration, and may be useful for treatment of various neurodegenerative diseases.

Porf-2 Inhibits Tumor Cell Migration Through the MMP-2/9 Signaling Pathway in Neuroblastoma and Glioma

Tumor migration and invasion are key pathological processes that contribute to cell metastasis as well as treatment failure in patients with malignant tumors. However, the mechanisms governing tumor cell migration remain poorly understood. By analyzing the tumor-related database and tumor cell lines, we found that preoptic regulatory factor-2 (Porf-2) is downexpressed in both neuroblastoma and glioma. Using in vitro assays, our data demonstrated that the expression of Porf-2 inhibits tumor cell migration both in neuroblastoma and glioma cell lines. Domain-mutated Porf-2 plasmids were then constructed, and it was found that the GAP domain, which plays a role in the inactivation of Rac1, is the functional domain for inhibiting tumor cell migration. Furthermore, by screening potential downstream effectors, we found that Porf-2 can reduce MMP-2 and MMP-9 expression. Overexpression of MMP-2 blocked the inhibitory effect of Porf-2 in tumor cell migration both in vitro and in vivo. Taken together, we show for the first time that Porf-2 is capable of suppressing tumor cell migration via its GAP domain and the downregulation of MMP-2/9, suggesting that targeting Porf-2 could be a promising therapeutic strategy for nervous system tumors.

Phosphatidylserine recognition and Rac1 activation are required for Müller glia proliferation, gliosis and phagocytosis after retinal injury

Müller glia, the principal glial cell type in the retina, have the potential to reenter the cell cycle after retinal injury. In mammals, proliferation of Müller glia is followed by gliosis, but not regeneration of neurons. Retinal injury is also accompanied by phagocytic removal of degenerated cells. We here investigated the possibility that proliferation and gliosis of Müller glia and phagocytosis of degenerated cells may be regulated by the same molecular pathways. After N-methyl-N–nitrosourea-induced retinal injury, degenerated photoreceptors were eliminated prior to the infiltration of microglia/macrophages into the outer nuclear layer, almost in parallel with cell cycle reentry of Müller glia. Inhibition of microglia/macrophage activation with minocycline did not affect the photoreceptor clearance. Accumulation of lysosomes and rhodopsin-positive photoreceptor debris within the cytoplasm of Müller glia indicated that Müller glia phagocytosed most photoreceptor debris. Pharmacological inhibition of phosphatidylserine and Rac1, key regulators of the phagocytic pathway, prevented cell cycle reentry, migration, upregulation of glial fibrillary acidic protein, and phagocytic activity of Müller glia. These data provide evidence that phosphatidylserine and Rac1 may contribute to the crosstalk between different signaling pathways activated in Müller glia after injury.

α2-Chimaerin is essential for neural stem cell homeostasis in mouse adult neurogenesis

Adult hippocampal neurogenesis, the lifelong generation of neurons in the dentate gyrus, is important for brain functioning, including learning, memory, and mood regulation. Its dysregulation is associated with cognitive decline and mood disorders. We discovered that the Rho GTPase-activating protein, α2-chimaerin, is essential for adult hippocampal neurogenesis, as it precisely regulates the transition of neural stem cells (NSCs) into intermediate progenitor cells (IPCs). Conditional knockout of α2-chimaerin in adult NSCs in the mouse hippocampus resulted in a loss of the Klotho-expressing NSC population and the premature differentiation of NSCs into IPCs, which impaired neuron production. These mice also exhibited compromised hippocampal synaptic plasticity and anxiety/depression-like behaviors. Thus, our findings revealed that α2-chimaerin is important in adult hippocampal neurogenesis.

Adult hippocampal neurogenesis involves the lifelong generation of neurons. The process depends on the homeostasis of the production of neurons and maintenance of the adult neural stem cell (NSC) pool. Here, we report that α2-chimaerin, a Rho GTPase-activating protein, is essential for NSC homeostasis in adult hippocampal neurogenesis. Conditional deletion of α2-chimaerin in adult NSCs resulted in the premature differentiation of NSCs into intermediate progenitor cells (IPCs), which ultimately depleted the NSC pool and impaired neuron generation. Single-cell RNA sequencing and pseudotime analyses revealed that α2-chimaerin–conditional knockout (α2-CKO) mice lacked a unique NSC subpopulation, termed Klotho-expressing NSCs, during the transition of NSCs to IPCs. Furthermore, α2-CKO led to defects in hippocampal synaptic plasticity and anxiety/depression-like behaviors in mice. Our findings collectively demonstrate that α2-chimaerin plays an essential role in adult hippocampal NSC homeostasis to maintain proper brain function.

Fire Needle Acupuncture Regulates Wnt/ERK Multiple Pathways to Promote Neural Stem Cells to Differentiate into Neurons in Rats with Spinal Cord Injury

BACKGROUND & OBJECTIVE

NSCs therapy is considered one of the most potential methods for spinal cord injury (SCI).

METHODS

We build the SCI model rats to investigate the therapeutic effect of fire needle acupuncture in improving the locomotor function of SCI rats and its possible mechanism. BBB scale was used for the motor ability of rats. The expression of Nestin, NSE, Gal-C, and GFAP was detected by immunohistochemistry. Wnt, GSK3β, β-catenin, ERK1/2, CyclinD1, and ngn1 were detected by western blot and PCR. The BBB score of both model group (1.20±0.94, 3.12±0.67, 5.34±1.57, 7.12±1.49) and fire needle group (1.70±0.58, 4.50±1.63, 7.53±2.41, 9.24±0.63) gradually increased after SCI. Furthermore, at d10 and d14, the fire needle group showed a significantly high score compared with that in model group at the same time (P<0.05). Fire needle increased Nestin, NSE, and Gal-C expression inhibited GFAP expression after SCI. Also, fire needle could up-regulate Wnt3a, GSK3β, β-catenin, and ngn1, and down-regulate ERK1/2, cyclinD1 gene and protein expression.

CONCLUSION

In conclusion, fire needle could improve lower limb locomotor function of SCI rats. Also, fire needles could promote endogenous NSCs proliferation differentiating into neurons, and the mechanism might be mediated by promoting the activation of Wnt/β-catenin and inhibiting the overexpression of ERK.

Neuronal GAP-Porf-2 transduces EphB1 signaling to brake axon growth

Axonal outgrowth and guidance require numerous extracellular cues and intracellular mediators that transduce signals in the growth cone to regulate cytoskeletal dynamics. However, the way in which cytoskeletal effectors respond to these signals remains elusive. Here, we demonstrate that Porf-2, a neuron-expressed RhoGTPase-activating protein, plays an essential role in the inhibition of initial axon growth by restricting the expansion of the growth cone in a cell-autonomous manner. Furthermore, the EphB1 receptor is identified as an upstream controller that binds and regulates Porf-2 specifically upon extracellular ephrin-B stimulation. The activated EphB forward signal deactivates Rac1 through the GAP domain of Porf-2, which inhibits growth cone formation and brakes axon growth. Our results therefore provide a novel GAP that regulates axon growth and braking sequentially through Eph receptor-independent and Eph receptor-dependent pathways.