Granulocyte-colony stimulating factor promotes brain repair following traumatic brain injury by recruitment of microglia and increasing neurotrophic factor expression

Neuroplastic and Pro-cognitive Effects of Granulocyte Colony Stimulating Factor in Healthy Adults: A Pilot Study

OBJECTIVE

Granulocyte colony-stimulating factor (G-CSF) is a growth factor used to regulate the mobilization of bone marrow progenitor cells and has been shown to promote brain repair and reduce inflammation. This study aimed to investigate the pro-cognitive and neuroplastic effects of G-CSF in healthy adults.

METHODS

Sixteen healthy adults or donors of hematopoietic stem cell transplantation received G-CSF injections for 5 consecutive days, and their blood samples were collected before, immediately after, and 3 weeks after the G-CSF injections. Twelve subjects underwent neuropsychological testing before and 12 weeks after the G-CSF injections.

RESULTS

The study found that G-CSF administration resulted in significant improvements in cognitive function, as measured by the Rey- Osterrieth Complex Figure test for immediate recall, delayed recall, and recognition score at 12 weeks after the injections. The blood levels of brain-derived neurotrophic factor, interleukin-4, and interleukin-8 were significantly increased immediately after the injections and returned to baseline levels after 3 weeks. There was no significant change in the plasma level of Multimer Detection System-oligomerized amyloid beta.

CONCLUSION

Our results might suggest that G-CSF has neuroplastic and pro-cognitive effects in healthy adults. However, further study containing a larger sample size is needed to confirm our findings.

Administration of Δ9-Tetrahydrocannabinol Following Controlled Cortical Impact Restores Hippocampal-Dependent Working Memory and Locomotor Function

Hypothesis: Administration of the phytocannabinoid Δ9-tetrahydrocannabinol (Δ9-THC) will enhance brain repair and improve short-term spatial working memory in mice following controlled cortical impact (CCI) by upregulating granulocyte colony-stimulating factor (G-CSF) and other neurotrophic factors (brain-derived neurotrophic factor [BDNF], glial-derived neurotrophic factor [GDNF]) in hippocampus (HP), cerebral cortex, and striatum. Materials and Methods: C57BL/6J mice underwent CCI and were treated for 3 days with Δ9-THC 3 mg/kg intraperitoneally (i.p.). Short-term working memory was determined using the spontaneous alternations test during exploratory behavior in a Y-maze. Locomotor function was measured as latency to fall from a rotating drum (rotometry). These behaviors were recorded at baseline and 3, 7, and 14 days after CCI. Groups of mice were euthanized at 7 and 14 days. Extent of microgliosis, astrocytosis, and G-CSF, BDNF, and GDNF expression were measured at 7 and 14 days in cerebral cortex, striatum, and HP on the side of the trauma. Levels of the most abundant endocannabinoid (2-arachidonoyl-glycerol [2-AG]) was also measured at these times. Results: Δ9-THC-treated mice exhibited marked improvement in performance on the Y-maze indicating that treatment with the phytocannabinoid could reverse the deficit in working memory caused by the CCI. Δ9-THC-treated mice ran on the rotarod longer than vehicle-treated mice and recovered to normal rotarod performance levels at 2 weeks. Δ9-THC-treated mice, compared with vehicle-treated animals, exhibited significant upregulation of G-CSF as well as BDNF and GDNF in the cerebral cortex, striatum, and HP. Levels of 2-AG were also increased in the Δ9-THC-treated mice. Conclusion: Administration of the phytocannabinoid Δ9-THC promotes significant functional recovery from traumatic brain injury (TBI) in the realms of working memory and locomotor function. This beneficial effect is associated with upregulation of brain 2-AG, G-CSF, BDNF, and GDNF. The latter three neurotrophic factors have been previously shown to mediate brain self-repair following TBI and stroke.

Recovery from Traumatic Brain Injury Following Treatment with Δ9-Tetrahydrocannabinol Is Associated with Increased Expression of Granulocyte-Colony Stimulating Factor and Other Neurotrophic Factors

Introduction: The hematopoietic cytokine granulocyte-colony stimulating factor (G-CSF) is well known to stimulate proliferation of blood stem/progenitor cells of the leukocyte lineage, but is also recognized as a neurotrophic factor involved in brain self-repair processes. G-CSF administration has been shown to promote recovery from experimental models of traumatic brain injury (TBI) and to modulate components of the endocannabinoid system (eCS). Conversely, Δ9-tetrahydrocannabinol (Δ9THC) treatment of normal mice has been shown to increase blood levels of G-CSF in the periphery. Hypothesis: Administration of the phytocannabinoid Δ9THC will enhance brain repair following controlled cortical impact (CCI) by upregulating G-CSF and other neurotrophic factors (brain-derived neurotrophic factor [BDNF] and glial-derived neurotrophic factor [GDNF]) in brain regions. Materials and Methods: C57BL/6J mice underwent CCI and were treated for 3 days with THC 3 mg/kg intraperitoneally. Motor function on a rotarod was recorded at baseline and 3, 7, and 14 days after CCI. Groups of mice were euthanized at 7 and 14 days. G-CSF, BDNF, and GDNF expression were measured at 7 and 14 days in cerebral cortex, striatum, and hippocampus on the side of the trauma. Results: Δ9THC-treated mice ran on the rotarod longer than vehicle-treated mice and recovered to normal rotarod performance levels at 2 weeks. These mice, compared to vehicle-treated animals, exhibited significant upregulation of G-CSF as well as BDNF and GDNF in cerebral cortex, striatum, and hippocampus. Conclusion: Administration of the phytocannabinoid Δ9THC promotes significant recovery from TBI and is associated with upregulation of brain G-CSF, BDNF, and GDNF, neurotrophic factors previously shown to mediate brain self-repair following TBI and stroke.

Combined Effect of Co-administration of Stromal Cell-Derived Factor-1 and Granulocyte-Colony Stimulating Factor on Rat Model of Alzheimer’s Disease

Introduction

Alzheimer’s disease (AD) is a neurodegenerative disease that is characterized by amyloid plaque deposits, neuronal cell loss, and memory impairment. Granulocyte-colony stimulating factor (G-CSF) is a growth factor associated with AD improvement. Stromal cell-derived factor-1 (SDF-1) mediates therapeutic effects of G-CSF. This study investigated the effect of combination treatment of G-CSF and SDF-1 on amyloid plaque deposits, apoptosis, and behavior of AD rats.

Methods

Intracerebroventricular amyloid-beta [Aβ(1-42)] peptide was used to induce AD in Aβ rats. There were six groups including naive control, sham-operated, Aβ, Aβ + G-CSF, Aβ + SDF-1, and Aβ + G-CSF + SDF-1. SDF-1 intra-cerebroventricular (ICV), G-CSF Subcutaneous (SC), or a combination of them were administered to Aβ rats weekly for 2 months. The cognition and memory were assessed using the novel object recognition, passive avoidance, and Morris water maze tests. Next, rat brains were removed and the amyloid plaque and apoptosis were detected in the brain and hippocampus using immunohistochemistry and TUNEL assay, respectively.

Results

The amyloid-beta and apoptotic cell levels dropped in groups receiving SDF-1 and G-CSF combination compared to the Aβ group. Also, number of microglial cells increased significantly in the combination group compared to other treatment groups. Moreover, learning and memory were significantly improved in the combination group compared to the Aβ groups (P < 0.05).

Conclusion

SDF-1 and G-CSF combination therapy can offer a promising strategy for AD.

Granulocyte Colony-Stimulating Factor for Treatment of Patients with Chronic Traumatic Brain Injury: A Preliminary Pre-Post Study

Chronic traumatic brain injury (TBI) can cause permanent disability and thereby negatively affect patients, families, and society. Currently, there is no effective treatment for patients with chronic TBI. One possible option is granulocyte colony-stimulating factor (G-CSF), which has potential neuroregenerative and neuroprotective effects through its ability to mobilize hematopoietic stem cells and increase neurogenic growth factor levels. Previous studies have shown that G-CSF administration is safe for patients with neurological diseases such as stroke and dementia. The present study aimed to explore the safety and efficacy of G-CSF use in patients with chronic TBI. Methods: 38 patients with chronic TBI were administered 3-day rounds of G-CSF (10 μg/kg per day) once a month for 6 months. These patients were clinically evaluated using the modified Rankin scale (mRS) and Karnofsky Performance Score (KPS). Laboratory measures of the leucocyte counts and differential count percentage were also assessed. Results: At the 6-month follow-up, further assessment showed that patients tolerated the treatment well with only mild and transient side effects being observed. Further clinical evaluation showed significant improvements in mRS and KPS after G-CSF treatment. Laboratory results also confirmed the action of the medication, with increased leukocytosis and band forms. Conclusions: The results suggest that 6-month chronic G-CSF treatment is safe for patients with chronic TBI and may provide clinical benefits and neurological improvements. The adverse effects of the treatment, however, are transient and usually tolerable. Thus, these preliminary findings suggest that future clinical trials of G-CSF use in patients with chronic TBI are warranted.

Granulocyte Colony-Stimulating Factor Enhances Brain Repair Following Traumatic Brain Injury Without Requiring Activation of Cannabinoid Receptors

Introduction: Treatment of traumatic brain injury (TBI) with granulocyte colony-stimulating factor (G-CSF) has been shown to enhance brain repair by direct neurotrophic actions on neural cells and by modulating the inflammatory response. Administration of cannabinoids after TBI has also been reported to enhance brain repair by similar mechanisms. Objectives: The primary objective of this study was to test the hypothesis that G-CSF mediates brain repair by interacting with the endocannabinoid system. Methods and Results: (i) Mice that underwent controlled cortical impact (CCI) were treated with G-CSF for 3 days either alone or in the presence of selective cannabinoid receptor 1 (CB1-R) or cannabinoid receptor 2 (CB2-R) agonists and antagonists. The trauma resulted in decreased expression of CB1-R and increased expression of CB2-R in the cortex, striatum, and hippocampus. Cortical and striatal levels of the major endocannabinoid ligand, 2-arachidonoyl-glycerol, were also increased by the CCI. Administration of the hematopoietic cytokine, G-CSF, following TBI, resulted in mitigation or reversal of trauma-induced CB1-R downregulation and CB2-R upregulation in the three brain regions. Treatment with CB1-R agonist (WIN55) or CB2-R agonist (HU308) mimicked the effects of G-CSF. (ii) Pharmacological blockade of CB1-R or CB2-R was not effective in preventing G-CSF's mitigation or reversal of trauma-induced alterations in these receptors. Conclusions: These results suggest that cellular and molecular mechanisms that mediate subacute effects of G-CSF do not depend on activation of CB1 or CB2 receptors. Failure of selective CB receptor antagonists to prevent the effects of G-CSF in this model has to be accepted with caution. CB receptor antagonists can interact with other CB and non-CB receptors. Investigation of the role of CB receptors in this TBI model will require studies with CB1-R and in CB2-R knockout mice to avoid nonspecific interaction of CB receptor agents with other receptors.

Optimization and validation of a modified radial-arm water maze protocol using a murine model of mild closed head traumatic brain injury

Cognitive impairments can be a significant problem after a traumatic brain injury (TBI), which affects millions worldwide each year. There is a need for establish reproducible cognitive assays in rodents to better understand disease mechanisms and to develop therapeutic interventions towards treating TBI-induced impairments. Our goal was to validate and standardize the radial arm water maze (RAWM) test as an assay to screen for cognitive impairments caused by TBI. RAWM is a visuo-spatial learning test, originally designed for use with rats, and later adapted for mice. The present study investigates whether test procedures, such us the presence of extra-maze cues influences learning and memory performance. C57BL/6 mice were tested in an 8-arm RAWM using a four-day protocol. We demonstrated that two days of training, exposing the mice to extra-maze cues and a visible platform, influenced learning and memory performance. Mice that did not receive training performed poorer compared to mice trained. To further validate our RAWM protocol, we used scopolamine. We, also, demonstrated that a single mild closed head injury (CHI) caused deficits in this task at two weeks post-CHI. Our data supported the use of 7 trials per day and a spaced training protocol as key factor to unmask memory impairment following CHI. Here, we provide a detailed standard operating procedure for RAWM test, which can be applied to a variety of mouse models including neurodegenerative diseases and pathology, as well as when pharmacological approaches are used.

Bidirectional Microglia-Neuron Communication in Health and Disease

Microglia are ramified cells that exhibit highly motile processes, which continuously survey the brain parenchyma and react to any insult to the CNS homeostasis. Although microglia have long been recognized as a crucial player in generating and maintaining inflammatory responses in the CNS, now it has become clear, that their function are much more diverse, particularly in the healthy brain. The innate immune response and phagocytosis represent only a little segment of microglia functional repertoire that also includes maintenance of biochemical homeostasis, neuronal circuit maturation during development and experience-dependent remodeling of neuronal circuits in the adult brain. Being equipped by numerous receptors and cell surface molecules microglia can perform bidirectional interactions with other cell types in the CNS. There is accumulating evidence showing that neurons inform microglia about their status and thus are capable of controlling microglial activation and motility while microglia also modulate neuronal activities. This review addresses the topic: how microglia communicate with other cell types in the brain, including fractalkine signaling, secreted soluble factors and extracellular vesicles. We summarize the current state of knowledge of physiological role and function of microglia during brain development and in the mature brain and further highlight microglial contribution to brain pathologies such as Alzheimer’s and Parkinson’s disease, brain ischemia, traumatic brain injury, brain tumor as well as neuropsychiatric diseases (depression, bipolar disorder, and schizophrenia).

Effects of an Inhibitor of Monocyte Recruitment on Recovery from Traumatic Brain Injury in Mice Treated with Granulocyte Colony-Stimulating Factor

Administration of the hematopoietic growth factor granulocyte-colony stimulating Factor (G-CSF) has been reported to enhance recovery from controlled cortical impact (CCI) in rodent models. G-CSF exerts actions in both the periphery (stimulation of hematopoiesis) and in the brain, where it serves as a neurotrophic factor, promoting neuronal survival and stimulating neural stem/progenitor cell proliferation in the hippocampus. In order to distinguish the direct CNS actions of G-CSF from its peripheral actions, experiments were designed to block the recruitment of peripheral monocytes to the site of the lesion produced by CCI. The selective C-C motif receptor 2 (CCR2) antagonist (RS504303) was co-administered with G-CSF for three days after CCI in a chimeric mouse previously transplanted with GFP-expressing (GFP+) blood stem-progenitor cells. Results: The drug significantly impaired infiltration of GFP+ bone marrow-derived cells to the frontal cortex and striatum without impeding recovery performance and hippocampal neurogenesis in the behavioral test, the Radial Arm Water Maze (RAWM). Administration of the CCR2 antagonist alone, without G-CSF, was effective in promoting recovery in RAWM. These results support the hypothesis that the direct action of G-CSF on neural cells, independent of its hematopoietic effects, is primarily responsible for enhanced recovery from CCI. In addition, this study confirms the importance of CCR2 and its ligand, monocyte chemotactic protein-1 (MCP-1), in mediating the inflammatory response following CCI.

Acupuncture Improved Neurological Recovery after Traumatic Brain Injury by Activating BDNF/TrkB Pathway

How to promote neural repair following traumatic brain injury (TBI) has long been an intractable problem. Although acupuncture has been demonstrated to facilitate the neurological recovery, the underlying mechanism is elusive. Brain-derived neurotrophic factor (BDNF) exerts substantial protective effects for neurological disorders. In this study, we found that the level of BDNF and tropomyosin receptor kinase B (TrkB) was elevated spontaneously after TBI and reached up to the peak at 12 h. Nevertheless, this enhancement is quickly declined to the normal at 48 h. After combined stimulation at the acupoints of Baihui, Renzhong, Hegu, and Zusanli, we found that BDNF and TrkB were still significantly elevated at 168 h. We also observed that the downstream molecular p-Akt and p-Erk1/2 were significantly increased, suggesting that acupuncture could persistently activate the BDNF/TrkB pathway. To further verify that acupuncture improved recovery through activating BDNF/TrkB pathway, K252a (specific inhibitor of TrkB) was treated by injection stereotaxically into lateral ventricle. We observed that K252a could significantly prevent the acupuncture-induced amelioration of motor, sensation, cognition, and synaptic plasticity. These data indicated that acupuncture promoted the recovery of neurological impairment after TBI by activating BDNF/TrkB signaling pathway, providing new molecular mechanism for understanding traditional therapy of acupuncture.

Pumping the Brakes: Neurotrophic Factors for the Prevention of Cognitive Impairment and Dementia after Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of disability and death worldwide, affecting as many as 54,000,000-60,000,000 people annually. TBI is associated with significant impairments in brain function, impacting cognitive, emotional, behavioral, and physical functioning. Although much previous research has focused on the impairment immediately following injury, TBI may have much longer-lasting consequences, including neuropsychiatric disorders and cognitive impairment. TBI, even mild brain injury, has also been recognized as a significant risk factor for the later development of dementia and Alzheimer's disease. Although the link between TBI and dementia is currently unknown, several proposed mechanisms have been put forward, including alterations in glucose metabolism, excitotoxicity, calcium influx, mitochondrial dysfunction, oxidative stress, and neuroinflammation. A treatment for the devastating long-term consequences of TBI is desperately needed. Unfortunately, however, no such treatment is currently available, making this a major area of unmet medical need. Increasing the level of neurotrophic factor expression in key brain areas may be one potential therapeutic strategy. Of the neurotrophic factors, granulocyte-colony stimulating factor (G-CSF) may be particularly effective for preventing the emergence of long-term complications of TBI, including dementia, because of its ability to reduce apoptosis, stimulate neurogenesis, and increase neuroplasticity.

Physical exercise induces structural alterations in the hippocampal astrocytes: exploring the role of BDNF-TrkB signaling

While it has been known that physical activity can improve cognitive function and protect against neurodegeneration, the underlying mechanisms for these protective effects are yet to be fully elucidated. There is a large body of evidence indicating that physical exercise improves neurogenesis and maintenance of neurons. Yet, its possible effects on glial cells remain poorly understood. Here, we tested whether physical exercise in mice alters the expression of trophic factor-related genes and the status of astrocytes in the dentate gyrus of the hippocampus. In addition to a significant increase in Bdnf mRNA and protein levels, we found that 4 weeks of treadmill and running wheel exercise in mice, led to (1) a significant increase in synaptic load in the dentate gyrus, (2) alterations in astrocytic morphology, and (3) orientation of astrocytic projections towards dentate granule cells. Importantly, these changes were possibly linked to increased TrkB receptor levels in astrocytes. Our study suggests that astrocytes actively respond and could indeed mediate the positive effects of physical exercise on the central nervous system and potentially counter degenerative processes during aging and neurodegenerative disorders.