The influence of GAP-43 on orientation of cell division through G proteins

Spontaneous Neuronal Plasticity in the Contralateral Motor Cortex and Corticospinal Tract after Focal Cortical Infarction in Hypertensive Rats

OBJECTIVES

In this study, we investigated the spontaneous neural plasticity on the contralateral side in hypertensive rats, including the expression of nerve growth factors (synaptophysin [SYN] and growth-associated protein 43 [GAP-43]), and the association between nerve fiber sprouting and redistribution, and the recovery of motor functions following sensorimotor cortical infarction.

METHODS

Initially, Sprague-Dawley rats were induced with renal hypertension by the bilateral renal arteries clips method. Further, they were induced with cerebral ischemia by the middle cerebral artery electrocoagulation method; 70 male rats completed the study. We compared the changes in the corticospinal tract (CST) and the expressions of SYN and GAP-43 on the contralateral side in rats with cerebral infarction using immunohistochemical staining, western blot, and biotinylated dextran amine (BDA) tracing analyses. The recovery of motor function in rats after cortical infarction was evaluated by the foot-fault and beam-walk tests.

RESULTS

The motor behavior tests revealed that the motor function of rats could recover to various degrees after focal cortical infarction. Compared with the sham-operated group, the SYN and GAP-43 levels increased in the motor cortex of the opposite hemisphere within 28 days after middle cerebral artery occlusion (MCAO). The increase in SYN and GAP-43 expressions presented differently in layers Ⅱ, Ⅲ, and Ⅴ. The amount of BDA-positive fibers also increased significantly in the denervated cervical spinal gray matter on day 56 post-MCAO.

CONCLUSIONS

The increases in SYN and GAP-43 on the contralateral side of the motor cortex could promote CST sprouting and rewiring in the spinal cord gray matter and also spontaneous motor function recovery after cortical infarction.

Immunization with neural-derived peptides increases neurogenesis in rats with chronic spinal cord injury

Aims

Immunization with neural‐derived peptides (INDP) has demonstrated to be a promising therapy to achieve a regenerative effect in the chronic phase of the spinal cord injury (SCI). Nevertheless, INDP‐induced neurogenic effects in the chronic stage of SCI have not been explored.

Methods and Results

In this study, we analyzed the effect of INDP on both motor and sensitive function recovery; afterward, we assessed neurogenesis and determined the production of cytokines (IL‐4, IL‐10, and TNF alpha) and neurotrophic factors (BDNF and GAP‐43). During the chronic stage of SCI, rats subjected to INDP showed a significant increase in both motor and sensitive recovery when compared to the control group. Moreover, we found a significant increase in neurogenesis, mainly at the central canal and at both the dorsal and ventral horns of INDP‐treated animals. Finally, INDP induced significant production of antiinflammatory and regeneration‐associated proteins in the chronic stages of SCI.

Conclusions

These findings suggest that INDP has a neurogenic effect that could improve motor and sensitive recovery in the chronic stage of SCI. Moreover, our results also envision the use of INDP as a possible therapeutic strategy for other trauma‐related disorders like traumatic brain injury.

GAP-43 is involved in the orientation of cell division by interacting with GΑI during neurogenesis

Purpose: Recent studies have shown that growth-associated protein-43 (GAP-43) may influence the mitotic-spindle orientation of Madin-Darby Canine Kidney (MDCK) cells through interacting with G proteins in vitro. However, whether GAP-43 interacts with the G proteins under the influence of mitotic spindle positioning related to the orientation of cell division during neurogenesis remains unclear. In order to explore the molecular mechanism in vivo, the GAP-43 transgenic mice were produced and the angles of cell division in the ventricular zone (VZ) during neurogenesis (embryonic period between 13.5 and 17.5 days) were measured in both transgenic mice and wild type mice by spindle angle analysis.Materials and methods: The interaction of GAP-43 and Gαi was detected by co-immunoprecipitation (co-IP), whereas the localization of GAP-43 was determined by immunofluorescence.Results: The results obtained using co-IP and immunofluorescence showed that GAP-43 is localized on the cell membrane and interacts with Gαi. This interaction dramatically induced a significant increase in the proportion of horizontally and intermediately dividing cells during the embryonic period of 13.5 days in the transgenic mouse brain, as observed by spindle angle analysis.Conclusions: It can be concluded that GAP-43 is involved in the orientation of cell division by interacting with Gαi, and that this may be an important mechanism for neurogenesis in the mammalian brain.

Restorative effect of modified dioscorea pills on the structure of hippocampal neurovascular unit in an animal model of chronic cerebral hypoperfusion

Introduction

A considerable part of old people suffer from Chronic Cerebral Hypoperfusion (CCH) in their long lives but have no way to change. The Modified Dioscorea Pills (MDP), a Chinese compound herbal prescription, has good clinical efficacy for CCH related diseases such as Vascular Dementia, whereas, what happened and how MDP works in CCH need to be clarified. Here, we investigate the neural inflammation and gliosis, neuronal apoptosis and regeneration in an animal model of CCH and interfered with MDP to explore some mechanisms of this Chinese herbal medication.

Methods

40 rats were randomly divided into Sham operated Group, Model Group and MDP Group according to a Random Number Table. CCH models were made by the modified 2-VO (two vessels occlusion) operation. The intelligence of rats were measured by Morris Water Maze (MWM) test; H & E staining and transmission electron microscope (TEM) were applied to observe the pathological and ultrastructural changes in hippocampus; The expression of key genes including growth associated protein 43 (GAP-43) and vascular endothelial growth factor (VEGF) and key protein including Bax, Bcl-2, nuclear factor-κB (NF-κB p65), microtubule associated protein-2 (MAP-2), Oligodendrocyte transcription factor 2(Olig-2), glial fibrillary acidic protein (GFAP) of hippocampus were detected.

Results

CCH lead to learning and memorial impairment and MDP can partly restore them; Neural inflammation, Neuronal apoptosis and astrocyte hyperplasia were common in Model Group but they were partly reversed by MDP; The expressions of GAP-43mRAN and VEGF mRNA in Model Group were much higher than those in Sham operated Group, but they reached the highest in MDP Group (P < 0.01 or P < 0.05).

Conclusions

Through regulating the expressions of key genes and proteins, MDP partly restore the intrinsic structure of Neurovascular Unit (NVU) in hippocampus, which revealed one of its therapeutic mechanisms on CCH.

The effects of neuregulin-1β on intrafusal muscle fiber formation in neuromuscular coculture of dorsal root ganglion explants and skeletal muscle cells

Background

The formation of intrafusal muscle (IM) fibers and their contact with afferent proprioceptive axons is critical for construction, function, and maintenance of the stretch reflex. Many factors affect the formation of IM fibers. Finding new factors and mechanisms of IM fiber formation is essential for the reconstruction of stretch reflex arc after injury.

Methods

We established a coculture system of organotypic dorsal root ganglion (DRG) explants and dissociated skeletal muscle (SKM) cells. The formation of IM fibers was observed in this coculture system after neuregulin-1β (NRG-1β) incubation.

Results

We found that NRG-1β promoted outgrowth of neurites and migration of neurons from the organotypic DRG explants and that this correlated with an induction of growth-associated protein 43 (GAP-43) expression. NRG-1β also increased the amount of nuclear bag fibers and nuclear chain fibers by elevating the proportion of tyrosine kinase receptor C (TrkC) phenotypic DRG neurons. In addition, we found that the effects of NRG-1β could be blocked by inhibiting ERK1/2, PI3K/Akt, and JAK2/STAT3 signaling pathways.

Conclusion

These data imply that NRG-1β promoted neurite outgrowth and neuronal migration from the organotypic DRG explants and that this correlated with an induction of GAP-43 expression. The modulating effects of NRG-1β on TrkC DRG neuronal phenotype may link to promote IM fiber formation. The effects produced by NRG-1β in this neuromuscular coculture system provide new data for the therapeutic potential on IM fiber formation after muscle injury.

Electronic supplementary material

The online version of this article (10.1186/s13395-018-0175-9) contains supplementary material, which is available to authorized users.