Neuritin improves the neurological functional recovery after experimental intracerebral hemorrhage in mice

In vitro effects of recombinant human Neuritin on hair cell recovery post-gentamicin injury in SC lineage-tracing models: Involvement of notch and FGFR signaling

Hair cell (HC) loss, frequently induced by ototoxic agents such as gentamicin, leads to irreversible hearing loss. Because of the restricted regenerative capabilities of the mammalian inner ear, the exploration of therapeutic strategies to restore damaged HCs is critically needed. Recombinant human Neuritin (rhNeuritin), a neurotrophic factor with established roles in promoting cell survival and regeneration across various systems, presents itself as a promising therapeutic candidate for HC repair. In this study, we elucidate the protective effects of rhNeuritin on injured HCs and its capacity to facilitate HC regeneration post-damage. Through the use of cochlear Supporting Cell (SC) lineage-tracing models in neonatal mice, we demonstrate that SC trans-differentiation serves as the origin of HC regeneration following damage. Simultaneously, we uncover that rhNeuritin potentiates the proliferation of SC precursor cells. Mechanistic insights reveal that rhNeuritin-induced cochleae exhibit downregulation of the critical Notch pathway mediator, Hes1, and upregulation of the essential FGFR pathway component Erm, which together may underpin HC regeneration and the proliferation of SC precursors. Notably, rhNeuritin demonstrates significant preservation of HC structural integrity. These findings collectively highlight the therapeutic potential of rhNeuritin in addressing hearing loss resulting from HC damage, thereby opening a new avenue for the restoration of auditory function.

Serum neuritin as a predictive biomarker of early neurological deterioration and poor prognosis after spontaneous intracerebral hemorrhage: a prospective cohort study

Objective

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease characterized by high mortality and disability rates. Neuritin, significantly expressed in injured brain tissues, is implicated in the molecular mechanisms underlying acute brain injury. We aimed to explore the prognostic and predictive value of serum neuritin in ICH.

Methods

In this prospective cohort study, serum neuritin levels were measured at admission in 202 patients, on post-ICH days 1, 3, 5, 7, and 10 in 54 of these patients, and at the time of enrollment in 100 healthy controls. The Glasgow Coma Scale (GCS) and hematoma volume were used as severity indicators. A poor prognosis was defined as a modified Rankin Scale (mRS) score of 3-6 at 90 days after ICH. END was defined as a decrease of ≥2 points in the GCS score within 24 h of admission. A multivariate logistic regression model was used to assess the independent relationships between serum neuritin levels, END, and poor prognosis.

Results

Serum neuritin levels were significantly increased at the time of patient admission, continued to rise on day 1, peaked on day 3, and then gradually diminished from day 5 until day 10. The levels remained substantially higher in patients compared to healthy controls throughout the 10-day period. The levels were independently related to GCS scores and hematoma volume. In subgroup analyses, the levels showed a linear relationship with the likelihood of experiencing END and poor prognosis at the 90-day mark after ICH. Additionally, the levels were independently associated with END, ordinal mRS scores, and poor prognosis. Under receiver operating characteristic (ROC) curve analysis, serum neuritin levels effectively predicted both END and poor prognosis. Two models incorporating GCS, hematoma volume, and serum neuritin levels were developed and represented using two nomograms separately to estimate END risks and poor prognosis. These models demonstrated clinical efficiency, stability, and validity in ROC, calibration, and decision curve analyses. Internal validation of the models was conducted using a randomly extracted subset of 101 patients. Furthermore, two specific weighted scoring systems were developed to optimize clinical prediction of poor prognosis and END after ICH.

Conclusion

Elevated serum neuritin levels are strongly associated with disease severity, END, and 90-day poor neurological outcomes following ICH, establishing serum neuritin as a potential prognostic biomarker for ICH.

Preparation of recombinant neuritin protein

Neuritin plays an important role in promoting nerve injury repair and maintaining synaptic plasticity, making it a potential therapeutic target for the treatment of nerve injury and neurodegenerative diseases. The present study aimed to obtain an active, unlabeled neuritin protein. Initially, a neuritin protein expression system with an enterokinase site was constructed in Escherichia coli. After optimizing induction conditions and screening for high expression, a neuritin recombinant protein with purity exceeding 85 % was obtained through Ni-affinity chromatography. Subsequently, unlabeled neuritin with a molecular weight of 11 kDa was obtained through the enzymatic cleavage of the His label using an enterokinase. Furthermore, a neuritin recombinant protein with purity exceeding 95 % was obtained using gel chromatography. Functional investigations revealed that neurite outgrowth of PC12 cells was stimulated by the isolated neuritin. This study establishes a method to obtain active and unlabeled neuritin protein, providing a foundation for subsequent research on its biological functions.

Neuritin 1 Drives Therapeutic Preservation of Retinal Ganglion Cells in an Ex Vivo Human Glaucoma Model

Purpose: Glaucoma is a leading cause of irreversible blindness. Glaucomatous intraocular pressure (IOP) triggers deleterious effects, including gliosis, optic nerve (ON) axonal retraction, neurotrophic factor deprivation, inflammation, and other pathological events, leading to retinal ganglion cell (RGC) loss. Trophic factor impairment enhances RGC apoptosis susceptibility. Neuritin 1 (NRN1), a neurotrophic protein downstream of various neurotrophins, exhibited RGC protection and regeneration in axotomy models. We evaluated human recombinant NRN1's impact on human RGCs cultured in pressurized conditions within the ex vivo translaminar autonomous system to simulate glaucoma pathogenesis. Methods: Human glaucomatous and non-glaucomatous donor eyes were obtained from eye banks according to the Declaration of Helsinki. Initially, we evaluated NRN1and RGC marker expression in glaucoma and non-glaucomatous retina to determine the NRN1 level and its association with RGC loss. Further, we evaluated NRN1's therapeutic potential by treating pressurized human eyes at normal and high IOP for seven days. Retina, ON, and conditioned medium were analyzed for RGC survival (THY1, RBPMS), gliosis (GFAP), apoptosis (CASP3, CASP7), and extracellular matrix deposition (COLIV, FN) by qRT-PCR and western blotting. Paraphenylenediamine staining assessed ON axonal degeneration, whereas ex vivo electroretinogram assessed retinal activity. Results: Glaucomatous retinas exhibited significant reductions in both NRN1 (*p = 0.007, n = 5) and RGC marker expression (*p = 0.04, n = 5). NRN1 treatment reduced gliosis, extracellular matrix deposition, ON degeneration, and increased retinal activity in pressure-perfused eyes. Conclusions: Our study confirms that NRN1 enhances human RGC survival and improves retinal function in degenerative conditions, substantiating it as a promising candidate for rescuing human RGCs from degeneration.

Unraveling the protein post-translational modification landscape: Neuroinflammation and neuronal death after stroke

The impact of stroke on global health is profound, with both high mortality and morbidity rates. This condition can result from cerebral ischemia, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH). The pathophysiology of stroke involves secondary damage and irreversible loss of neuronal function. Post-translational modifications (PTMs) have been recognized as crucial regulatory mechanisms in ischemic and hemorrhagic stroke-induced brain injury. These PTMs include phosphorylation, glycosylation, ubiquitination, SUMOylation, acetylation, and succinylation. This comprehensive review delves into recent research on the PTMs landscape associated with neuroinflammation and neuronal death specific to cerebral ischemia, ICH, and SAH. This review aims to explain the role of PTMs in regulating pathologic mechanisms and present critical techniques and proteomic strategies for identifying PTMs. This knowledge helps us comprehend the underlying mechanisms of stroke injury and repair processes, leading to the development of innovative treatment strategies. Importantly, this review underscores the significance of exploring PTMs to understand the pathophysiology of stroke.

Neuritin promotes autophagic flux by inhibiting the cGAS-STING pathway to alleviate brain injury after subarachnoid haemorrhage

BACKGROUND

Early brain injury (EBI) is closely associated with poor prognosis in patients with subarachnoid haemorrhage (SAH), with autophagy playing a pivotal role in EBI. However, research has shown that the stimulator of interferon genes (STING) pathway impacts autophagic flux. While the regulatory impact of neuritin on EBI and autophagic flux has been established previously, the underlying mechanism remains unclear. This study aimed to determine the role of the cGAS-STING pathway in neuritin-mediated regulation of autophagic flux following SAH.

METHODS

A SAH model was established in male Sprague-Dawley rats via intravascular perforation. Neuritin overexpressions using adeno-associated virus, the STING antagonist "C-176," and the activator, "CMA," were determined to investigate the cGAS-STING pathway's influence on autophagic flux and brain injury post-SAH, along with the neuritin's regulatory effect on STING. In this study, SAH grade, neurological score, haematoxylin and eosin (H&E) staining, brain water content (BWC), sandwich enzyme-linked immunosorbent assay, Evans blue staining, immunofluorescence staining, western blot analysis, and transmission electron microscopy (TEM) were examined.

RESULTS

Neuritin overexpression significantly ameliorated neurobehavioural scores, blood-brain barrier injury, brain oedema, and impaired autophagic flux in SAH-induced rats. STING expression remarkably increased post-SAH. C-176 and CMA mitigated and aggravated autophagic flux injury and brain injury, respectively, while inhibiting and enhancing STING, respectively. Particularly, CMA treatment nullified the protective effects of neuritin against autophagic flux and mitigated brain injury.

CONCLUSION

Neuritin alleviated EBI by restoring impaired autophagic flux after SAH through the regulation of the cGAS-STING pathway.

Attenuation of neuronal ferroptosis in intracerebral hemorrhage by inhibiting HDAC1/2: Microglial heterogenization via the Nrf2/HO1 pathway

AIM

The class I histone deacetylases (HDACs) implicate in microglial heterogenization and neuroinflammation following Intracerebral hemorrhage (ICH). Ferroptosis has also been reported in the ICH model. However, the relationship between HDAC1/2's role in microglial heterogenization and neuronal ferroptosis remains unclear.

METHODS

In both in vivo and in vitro models of ICH, we used Romidepsin (FK228), a selective HDAC1/2 inhibitor, to investigate its effects on microglial heterogenization and neuronal ferroptosis. In the in vitro ICH model using Hemin, a transwell system was utilized to examine how microglia-driven inflammation and ICH-triggered neuronal ferroptosis interact. Immunostaining, Western blotting and RT-qPCR were used to evaluate the microglial heterogenization and neuronal ferroptosis. Microglial heterogenization, neuronal ferroptosis, and neurological dysfunctions were assessed in vivo ICH mice model performed by autologous blood injection.

RESULTS

HDAC1/2 inhibition altered microglial heterogenization after ICH, as showing the reducing neuroinflammation and shifting microglia towards an anti-inflammatory phenotype by immunostaining and qPCR results. HDAC1/2 inhibition reduced ferroptosis, characterized by high ROS and low GPx4 expression in HT22 cells, and reduced iron and lipid deposition post-ICH in vivo. Additionally, the Nrf2/HO1 signaling pathway, especially acetyl-Nrf2, activated in the in vivo ICH model due to HDAC1/2 inhibition, plays a role in regulating microglial heterogenization. Furthermore, HDAC1/2 inhibition improved sensorimotor and histological outcomes post-ICH, offering a potential mechanism against ICH.

CONCLUSION

Inhibition of HDAC1/2 reduces neuro-ferroptosis by modifying the heterogeneity of microglia via the Nrf2/HO1 pathway, with a particular focus on acetyl-Nrf2. Additionally, this inhibition aids in the faster removal of hematomas and lessens prolonged neurological impairments, indicating novel approach for treating ICH.

Stromal Interaction Molecule 1-Mediated Store-Operated Calcium Entry Promotes Autophagy Through AKT/Mammalian Target of Rapamycin Pathway in Hippocampal Neurons After Ischemic Stroke

The pathophysiological process of neuronal injury due to cerebral ischemia is complex among which disturbance of calcium homeostasis and autophagy are two major pathogenesis. However, it remains ambiguous whether the two factors are independent. Stromal interaction molecule 1 (STIM1) is the most important Ca²⁺ sensor mediating the store-operated Ca²⁺ entry (SOCE) through interacting with Orai1 and has recently been proven to participate in autophagy in multiple cells. In this study, we aimed to investigate the potential role of STIM1-induced SOCE on autophagy and whether its regulator function contributes to neuronal injury under hypoxic conditions using in vivo transient middle cerebral artery occlusion (tMCAO) model and in vitro oxygen and glucose deprivation (OGD) primary cultured neuron model respectively. The present data indicated that STIM1 induces autophagic flux impairment in neurons through promoting SOCE and inhibiting AKT/mTOR signaling pathway. Pharmacological inhibition of SOCE or downregulation of STIM1 with siRNA suppressed the autophagic activity in neurons. Moreover, stim1 knockdown attenuated neurological deficits and brain damage after tMCAO, which could be reversed by AKT/mTOR pathway inhibitor AZD5363. Together, the modulation of STIM1 on autophagic activation indicated the potential link between Ca²⁺ homeostasis and autophagy which provided evidence that STIM1 could be a promising therapeutic target for ischemic stroke.