Expression of FOXO transcription factors in the brain following traumatic brain injury

The role of Foxo3a in neuron-mediated cognitive impairment

Cognitive impairment (COI) is a prevalent complication across a spectrum of brain disorders, underpinned by intricate mechanisms yet to be fully elucidated. Neurons, the principal cell population of the nervous system, orchestrate cognitive processes and govern cognitive balance. Extensive inquiry has spotlighted the involvement of Foxo3a in COI. The regulatory cascade of Foxo3a transactivation implicates multiple downstream signaling pathways encompassing mitochondrial function, oxidative stress, autophagy, and apoptosis, collectively affecting neuronal activity. Notably, the expression and activity profile of neuronal Foxo3a are subject to modulation via various modalities, including methylation of promoter, phosphorylation and acetylation of protein. Furthermore, upstream pathways such as PI3K/AKT, the SIRT family, and diverse micro-RNAs intricately interface with Foxo3a, engendering alterations in neuronal function. Through several downstream routes, Foxo3a regulates neuronal dynamics, thereby modulating the onset or amelioration of COI in Alzheimer's disease, stroke, ischemic brain injury, Parkinson's disease, and traumatic brain injury. Foxo3a is a potential therapeutic cognitive target, and clinical drugs or multiple small molecules have been preliminarily shown to have cognitive-enhancing effects that indirectly affect Foxo3a. Particularly noteworthy are multiple randomized, controlled, placebo clinical trials illustrating the significant cognitive enhancement achievable through autophagy modulation. Here, we discussed the role of Foxo3a in neuron-mediated COI and common cognitively impaired diseases.

Pegylated polymeric micelles of boswellic acid-selenium mitigates repetitive mild traumatic brain injury: Regulation of miR-155 and miR-146a/BDNF/ Klotho/Foxo3a cue

This study aims to explore the protective machinery of pegylated polymeric micelles of boswellic acid-selenium (PMBS) against secondary neuronal damage triggered by mild repetitive traumatic brain injury (RTBI). After PMBS characterization in terms of particle size, size distribution, zeta potential, and transmission electronic microscopy, the selected formula was used to investigate its potency against experimental RTBI. Five groups of rats were used; group 1 (control) and the other four groups were subjected to RTBI. Groups 2 was RTBI positive control, while 3, 4, and 5 received boswellic acid (BSA), selenium (SEL), and PMBS, respectively. The open-field behavioral test was used for behavioral assessment. Subsequently, brain tissues were utilized for hematoxylin and eosin staining, Nissl staining, Western blotting, and ELISA in addition to evaluating microRNA expression (miR-155 and miR-146a). The behavioral changes, oxidative stress, and neuroinflammation triggered by RTBI were all improved by PMBS. Moreover, PMBS mitigated excessive glutamate-induced excitotoxicity and the dysregulation in miR-155 and miR-146a expression. Besides, connexin43 (Cx43) expression as well as klotho and brain-derived neurotrophic factor (BDNF) were upregulated with diminished neuronal cell death and apoptosis because of reduced Forkhead Box class O3a(Foxo3a) expression in the PMBS-treated group. The current study has provided evidence of the benefits produced by incorporating BSA and SEL in PEGylated polymeric micelles formula. PMBS is a promising therapy for RTBI. Its beneficial effects are attributed to the manipulation of many pathways, including the regulation of miR-155 and miR-146a expression, as well as the BDNF /Klotho/Foxo3a signaling pathway.

Knockdown of FOXO4 protects against OGD/R‑induced cerebral microvascular endothelial cell injury and regulates the AMPK/Nrf2/HO‑1 pathway through transcriptional activation of CTRP6

Cerebral ischemia is a type of cerebrovascular disease with high disability and mortality rates. The expression of forkhead box protein O4 (FOXO4) in the brain is increased following traumatic brain injury. To the best of our knowledge, however, the role of FOXO4 as well as its mechanism in cerebral ischemia has not been reported so far. For the establishment of an in vitro cellular injury model, human brain microvascular endothelial HCMEC/D3 cells were induced by oxygen-glucose deprivation/reoxygenation (OGD/R). mRNA and protein expressions of FOXO4 and C1q/tumor necrosis factor-related protein 6 (CTRP6) in OGD/R-induced HCMEC/D3 cells were detected by reverse transcription-quantitative (RT-q)PCR and western blotting. The transfection efficacy of small interfering (si)- and overexpression (Ov)-FOXO4 and si-CTRP6 was assessed using RT-qPCR and western blotting. Cell Counting Kit-8 and TUNEL assay were used to assess viability and apoptosis of HCMEC/D3 cells induced by OGD/R, respectively. A FITC-Dextran assay kit was applied to determine endothelial permeability and immunofluorescence assay was used for the measurement of the tight junction protein zonula occludens-1. The levels of oxidative stress markers and inflammatory cytokines were assessed with corresponding assay kits. The binding sites of transcription factor, FOXO4 and CTRP6 promoter were predicted using HDOCK SERVER. Luciferase reporter assay was used to detect the activity of the CTRP6 promoter while chromatin immunoprecipitation assay was used to evaluate the binding ability of the FOXO4 and CTRP6 promoter. Western blotting was used for the detection of apoptosis- and AMPK/Nrf2/heme oxygenase-1 (HO-1) pathway-associated proteins, along with tight junction proteins. The expression of FOXO4 was increased in OGD/R-induced HCMEC/D3 cells. After interfering with FOXO4 in cells, the viability of the OGD/R-induced HCMEC/D3 cells was increased while apoptosis was decreased. Furthermore, FOXO4 interference improved cellular barrier dysfunction but inhibited oxidative stress and the inflammatory response in HCMEC/D3 cells induced by OGD/R. FOXO4 knockdown regulated CTRP6 transcription in HCMEC/D3 cells. Knockdown of FOXO4 regulated expression of CTRP6 and protected OGD/R-induced HCMEC/D3 cell injury via the AMPK/Nrf2/HO-1 pathway. The present study indicated that FOXO4 knockdown activated CTRP6 to protect against cerebral microvascular endothelial cell injury induced by OGD/R via the AMPK/Nrf2/HO-1 pathway.

Cognitive Impairment in Multiple Sclerosis

Almost three million individuals suffer from multiple sclerosis (MS) throughout the world, a demyelinating disease in the nervous system with increased prevalence over the last five decades, and is now being recognized as one significant etiology of cognitive loss and dementia. Presently, disease modifying therapies can limit the rate of relapse and potentially reduce brain volume loss in patients with MS, but unfortunately cannot prevent disease progression or the onset of cognitive disability. Innovative strategies are therefore required to address areas of inflammation, immune cell activation, and cell survival that involve novel pathways of programmed cell death, mammalian forkhead transcription factors (FoxOs), the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), and associated pathways with the apolipoprotein E (APOE-ε4) gene and severe acute respiratory syndrome coronavirus (SARS-CoV-2). These pathways are intertwined at multiple levels and can involve metabolic oversight with cellular metabolism dependent upon nicotinamide adenine dinucleotide (NAD+). Insight into the mechanisms of these pathways can provide new avenues of discovery for the therapeutic treatment of dementia and loss in cognition that occurs during MS.

Smurf2-Mediated Ubiquitination of FOXO4 Regulates Oxygen-glucose Deprivation/Reperfusion-induced Pyroptosis of Cortical Neurons

BACKGROUND

Smad ubiquitination regulatory factor 2 (Smurf2) has been observed to alleviate ischemia-reperfusion injury. This study sought to explore the molecular mechanism of Smurf2-mediated forkhead box O4 (FOXO4) ubiquitination in oxygen-glucose deprivation/ reperfusion (OGD/R)-induced pyroptosis of cortical neurons.

METHODS

Human cortical neurons (HCN-2) were subjected to OGD/R to establish a cell model of cerebral stroke. Smurf2, FOXO4, and doublecortin domain containing 2 (DCDC2) expressions were determined by RT-qPCR and Western blot. LDH release, pyroptosis-related proteins NLRP3, GSDMD-N, and cleaved-caspase-3, as well as inflammatory factors IL-1β and IL-18, were assessed by LDH assay kit, Western blot, and ELISA. The ubiquitination level of FOXO4 was determined by ubiquitination assay. The bindings of Smurf2 to FOXO4 and FOXO4 to DCDC2 were testified by Co-IP, ChIP, and dual-luciferase assays. Rescue experiments were designed to validate the role of FOXO4/DCDC2 in the pyroptosis of HCN-2 cells.

RESULTS

Smurf2 was weakly expressed, while FOXO4 and DCDC2 were prominently expressed in OGD/R-treated HCN-2 cells. Smurf2 overexpression promoted LDH release, reduced NLRP3, GSDMD-N, and cleaved-caspase-3 proteins, and decreased IL-1β and IL-18 concentrations. Sumrf2 improved the ubiquitination level of FOXO4 to downregulate its protein level. FOXO4 is bound to the DCDC2 promoter to facilitate its transcription. Overexpression of FOXO4 or DCDC2 reversed the inhibition of Smurf2 overexpression on pyroptosis of OGD/Rtreated HCN-2 cells.

CONCLUSION

Smurf2 overexpression facilitated the ubiquitination of FOXO4 to reduce its protein level, thereby suppressing DCDC2 transcription and restricting OGD/R-induced pyroptosis of cortical neurons.

FOXO4 alleviates hippocampal neuronal damage in epileptic mice via the miR-138-5p/ROCK2 axis

Epilepsy (EP) is one of the most universal neurological disorders. This study investigated the mechanism of forkhead box protein O4 (FOXO4) on hippocampal neuronal damage in EP mice. Initially, the EP mouse model and the in vitro HT-22 cell model were established. EP seizures and neuronal damage in mice were assessed. FOXO4, microRNA (miR)-138-5p, and rho-associated coiled-coil containing protein kinase 2 (ROCK2) levels in hippocampal tissues or HT-22 cells were examined. The cell viability and apoptosis of HT-22 cells were determined. The concentrations of oxidative stress markers and the levels of inflammatory cytokines in hippocampal tissues or HT-22 cells were detected. We found that FOXO4 was poorly expressed in EP. FOXO4 overexpression alleviated hippocampal neuronal damage in EP mice and improved HT-22 cell viability and inhibited apoptosis, and decreased oxidative stress and inflammation in hippocampal tissue and HT-22 cells. The bindings of miR-138-5p to FOXO4 and ROCK2 were analyzed, which showed that FOXO4 promoted miR-138-5p via binding to the miR-138-5p promoter region, and miR-138-5p inhibited ROCK2 expression. Joint experiments showed that miR-138-5p suppression or ROCK2 overexpression reversed the alleviation of FOXO4 overexpression on hippocampal neuronal damage. FOXO4 inhibited ROCK2 expression via promoting miR-138-5p expression, thus alleviating hippocampal neuronal damage in EP mice.

Cognitive Impairment and Dementia: Gaining Insight through Circadian Clock Gene Pathways

Neurodegenerative disorders affect fifteen percent of the world's population and pose a significant financial burden to all nations. Cognitive impairment is the seventh leading cause of death throughout the globe. Given the enormous challenges to treat cognitive disorders, such as Alzheimer's disease, and the inability to markedly limit disease progression, circadian clock gene pathways offer an exciting strategy to address cognitive loss. Alterations in circadian clock genes can result in age-related motor deficits, affect treatment regimens with neurodegenerative disorders, and lead to the onset and progression of dementia. Interestingly, circadian pathways hold an intricate relationship with autophagy, the mechanistic target of rapamycin (mTOR), the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), mammalian forkhead transcription factors (FoxOs), and the trophic factor erythropoietin. Autophagy induction is necessary to maintain circadian rhythm homeostasis and limit cortical neurodegenerative disease, but requires a fine balance in biological activity to foster proper circadian clock gene regulation that is intimately dependent upon mTOR, SIRT1, FoxOs, and growth factor expression. Circadian rhythm mechanisms offer innovative prospects for the development of new avenues to comprehend the underlying mechanisms of cognitive loss and forge ahead with new therapeutics for dementia that can offer effective clinical treatments.