Honghua Zheng

Background: Epoxyeicosatrienoic acids (EETs) are bioactive lipid mediators derived from arachidonic acid (ARA) via cytochrome P450 (CYP450) enzymes. They exert pleiotropic effects including anti‐inflammation, anti‐apoptosis, antioxidant activity, and vasodilation. Soluble epoxide hydrolase (sEH) rapidly hydrolyzes EETs to inactive diols, and its inhibition has emerged as a promising strategy to potentiate EET‐mediated benefits. This review synthesizes current evidence on the roles and mechanisms of EETs and sEH in major neurological disorders and discusses translational challenges and future directions. Methods: A narrative review was conducted to synthesize evidence on the biosynthesis and metabolism of EETs, the expression and regulation of brain cytochrome P450 epoxygenases and sEH, the neuroprotective effects of EETs, and the therapeutic potential of sEH inhibitors, and to identify current limitations and future strategies for sEH‐targeted therapies. Results: EETs ameliorate multiple neurological disorders through anti‐inflammatory and anti‐apoptotic effects, increased cerebral blood flow, reduced excitotoxicity, decreased dendritic spine loss, reduced oxidative stress, and enhanced neurosteroid secretion. In animal models, sEH inhibition elevates endogenous EET bioavailability, slows progression of various central nervous system diseases, and attenuates brain injury. However, sEH inhibitor development faces several challenges, including species differences in CYP expression, insufficient blood–brain barrier penetration, bleeding risks, failure of some candidates in late‐stage trials, and the limitations of single‐target inhibition. Conclusions: EETs are endogenous multifaceted neuroprotective mediators that act through convergent anti‐inflammatory, anti‐apoptotic, and vascular mechanisms. sEH inhibition represents a highly attractive yet challenging therapeutic strategy for a wide spectrum of central nervous system disorders. Future progress requires: development of brain‐penetrant or dual‐target sEH inhibitors; identification of EET‐specific G protein‐coupled receptors (GPCRs) and biomarkers for patient stratification; improved preclinical models that better translate to humans; and rigorous clinical evaluation to define safety and efficacy.

Background: Shared pathophysiological mechanisms exist between epilepsy and its associated comorbidities, with neuroinflammation playing a key role. 1-Trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) is a soluble epoxide hydrolase (sEH) inhibitor that exhibits potent, broad-spectrum anti-inflammatory effects by preventing the hydrolysis of epoxyeicosatrienoic acids (EETs). However, the potential anti-epileptic and comorbidity-alleviating effects of TPPU, along with the underlying molecular mechanisms, remain to be elucidated. Methods: Electroencephalogram (EEG) recordings and Racine score were used to monitor seizures. Behavioral tests were employed to assess seizure-associated cognitive and anxiety-like comorbidities in mice. Whole-cell patch-clamp recordings were used to evaluate synaptic function. RNA-sequencing was conducted to elucidate the molecular mechanisms underlying the neuroprotective effects of TPPU in the KA-induced chronic epileptic model. Results: Behavioral assessments, EEG monitoring, and whole-cell patch-clamp recordings revealed that TPPU significantly mitigated seizure severity and anxiety/depressive-like behaviors, and enhanced cognitive function in kainic acid (KA)-induced chronic epileptic mice. TPPU exhibited neuroprotective properties by reducing neuronal apoptosis and neuroinflammation. Bulk RNA-sequencing analysis indicated that TPPU protected against neuroinflammation during epileptogenesis. Mechanistic investigations revealed that TPPU suppresses Akt/mTOR pathway activation. Conclusions: Our findings establish the Akt/mTOR axis as a critical pathway mediating the protective actions of TPPU against epilepsy and its comorbidities in murine models. This work not only advances our understanding of epilepsy pathophysiology but also identifies novel targets for the development of comprehensive therapeutic strategies.

Colony-stimulating factor 1 receptor (CSF1R), primarily expressed on microglia in the central nervous system (CNS), is essential for microglial homeostasis and survival. CSF1R dysfunction, due to a monoallelic mutation, causes CSF1R-related leukoencephalopathy (CRL), a primary microgliopathy. CSF1R undergoes proteolytic cleavage to release soluble CSF1R (sCSF1R), which is decreased in the serum of CRL patients. However, the biological function of sCSF1R remains unknown. Here, we found that sCSF1R alleviated cognitive impairment and anxiety-like behavior in Csf1r ^+/− mice. Importantly, we identified CSF1R as a target binding protein of sCSF1R on microglia. Notably, sCSF1R inhibited the activation and inflammatory factor expression of Csf1r ^+/− microglia by reducing the phosphorylation of CSF1R (Y723) and NF-κB (S468 and S536). These results demonstrate that sCSF1R exerts neuroprotective effects by binding membrane-bound CSF1R and inhibiting pathological microglial activation by inhibiting the nuclear translocation of NF-κB. These findings identify sCSF1R as a potential therapeutic agent for CRL.

Growing genetic and pathological evidence has identified microglial dysfunction as a key contributor to the pathogenesis and progression of various neurological disorders, positioning microglia replacement as a promising therapeutic strategy. Traditional bone marrow transplantation (BMT) methods for replenishing brain microglia have limitations, including low efficiency and the potential for brain injury because of preconditioning regimens, such as irradiation or chemotherapy. Moreover, BM-derived cells that migrate to the brain do not recapitulate the phenotypic and functional properties of resident microglia. Here, we present a microglia transplantation strategy devoid of any conditioning, termed “tricyclic microglial depletion for transplantation” (TCMDT). This approach leverages three cycles of microglial depletion using the colony stimulating factor 1 receptor (CSF1R) inhibitor PLX3397, creating an optimal window for efficient engraftment of exogenous microglia. Transplantation of primary cultured microglia by TCMDT successfully restored the identity and functions of endogenous microglia. To evaluate the therapeutic potential of TCMDT, we applied this strategy to two distinct mouse models of neurologic disorder. In a Sandhoff disease model, a neurodegenerative lysosomal storage disorder caused by hexosaminidase subunit beta ( Hexb ) deficiency, TCMDT effectively replaced deficient microglia, attenuating neurodegeneration and improving motor performance. Similarly, in an Alzheimer’s disease (AD)–related amyloid mouse model carrying the triggering receptor expressed on myeloid cells 2 (Trem2) R47H mutation, our transplantation strategy rescued microglial dysfunction and mitigated AD-related pathology. Overall, our study introduces TCMDT as a practical, efficient, and safe approach for microglia replacement, suggesting therapeutic potential for treating neurological disorders associated with microglial dysfunction.

Accumulation of astrocytes around β-amyloid (Aβ) plaques is one of the earliest neuropathological changes in Alzheimer's disease (AD), but the underlying mechanisms and significance remain unclear. Cell adhesion molecule protocadherin-γC5 (Pcdh-γC5) has been reported to implicate in AD. Here, we find elevated expression levels of Pcdh-γC5 in the brain of 5×FAD mice and Aβ-treated astrocytes and further reveal that Pcdh-γC5 deficiency leads to exacerbated Aβ deposition in 5×FAD mice. Deletion of Pcdh-γC5 impairs astrocyte migration, astrocytic response to Aβ signaling, and Aβ phagocytosis in both cultured astrocytes in vitro and 5×FAD mice in vivo. Both male and female mice were used in this study. Our findings support a model in which increased expression level of Pcdh-γC5 promotes astrocyte migration in response to Aβ signaling and engulfment and phagocytosis of neurotoxic Aβ plaques, therefore exerting a critical neuroprotective function in AD.

Mutations in colony stimulating factor 1 receptor (CSF1R) result in CSF1R‐related disorder (CSF1R‐RD). Our previous study demonstrated a proteolytic generation of a soluble CSF1R (sCSF1R) that could potentially serve as a diagnostic biomarker of CSF1R‐RD. Herein, we observed that sCSF1R is released into peripheral serum as a highly glycosylated monomer in Csf1r^+/− mice that mimic the clinical symptoms of CSF1R‐RD patients. Notably, we found that serum sCSF1R could distinguish CSF1R‐RD cohorts from controls with high accuracy as evaluated by receiver operating characteristic (ROC) curves. This study demonstrates that reduced sCSF1R in serum may serve as a diagnostic biomarker for CSF1R‐RD. ANN NEUROL 2025;97:397–403

Neuronal hyperactivity induced by β‐amyloid (Aβ) is an early pathological feature in Alzheimer's disease (AD) and contributes to cognitive decline in AD progression. However, the underlying mechanisms are still unclear. Here, we revealed that Aβ increased the expression level of synaptic adhesion molecule protocadherin‐γC5 (Pcdh‐γC5) in a Ca²⁺‐dependent manner, associated with aberrant elevation of synapses in both Aβ‐treated neurons in vitro and the cortex of APP/PS1 mice in vivo. By using Pcdhgc5 gene knockout mice, we demonstrated the critical function of Pcdh‐γC5 in regulating neuronal synapse formation, synaptic transmission, and cognition. To further investigate the role of Pcdh‐γC5 in AD pathogenesis, the aberrantly enhanced expression of Pcdh‐γC5 in the brain of APP/PS1 mice was knocked down by shRNA. Downregulation of Pcdh‐γC5 efficiently rescued neuronal hyperactivity and impaired cognition in APP/PS1 mice. Our findings revealed the pathophysiological role of Pcdh‐γC5 in mediating Aβ‐induced neuronal hyperactivity and cognitive deficits in AD and identified a novel mechanism underlying AD pathogenesis. image

Sporopollenin exine capsules can regulate the viability, migration, and phagocytosis of microglia without pro-inflammation and protect microglia against LPS-induced inflammation through the TLR4 signaling pathway.

Background: Mutations in colony-stimulating factor 1 receptor (CSF1R) are known to cause adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), which has been recently demonstrated as a primary microgliopathy characterized by cognitive impairment. Although the molecular mechanism underlying CSF1R-mediated microgliopathy remains unclear, therapeutic strategies have generally targeted modulation of microglial function. In particular, the microglial inhibitor, minocycline, has been shown to attenuate learning and memory deficits in several neurodegenerative diseases. The objectives of this study were to investigate the pathogenic mechanisms underlying ALSP and to explore the therapeutic effects of minocycline in an in vivo model of ALSP. We hypothesized that inhibiting microglial activation via minocycline could reverse the behavior and pathological defects in ALSP model mice. Methods: We generated a Csf1r haploinsufficiency mouse model of ALSP using CRISPR/Cas9 genome editing and conducted electrophysiological recordings of long-term potentiation (LTP) and behavioral tests to validate the recapitulation of clinical ALSP characteristics in 8- to 11-month-old mice. RNA-sequencing was used to explore enriched gene expression in the molecular pathogenesis of ALSP. Microglial activation was assessed by immunofluorescent detection of Iba1 and CD68 in brain sections of male ALSP mice and pro-inflammatory activation and phagocytosis were assessed in Csf1r^+/− microglia. Therapeutic effects were assessed by behavioral tests, histological analysis, and morphological examination after four weeks of intraperitoneal injection with minocycline or vehicle control in Csf1r^+/− mice and wild-type control littermates. Results: We found that synaptic function was reduced in LTP recordings of neurons in the hippocampal CA1 region, while behavioral tests showed impaired spatial and cognitive memory specifically in male Csf1r^+/− mice. Increased activation, pro-inflammatory cytokine production, and enhanced phagocytic capacity were also observed in Csf1r^+/− microglia. Treatment with minocycline could suppress the activation of Csf1r^+/− microglia both in vitro and in vivo. Notably, the behavioral and pathological deficits in Csf1r^+/− mice were partially rescued by minocycline administration, potentially due to inhibition of microglial inflammation and phagocytosis in Csf1r^+/− mice. Conclusions: Our study shows that CSF1R deficiency results in aberrant microglial activation, characterized by a pro-inflammatory phenotype and enhanced phagocytosis of myelin. Our results also indicate that microglial inhibition by minocycline can ameliorate behavioral impairment and ALSP pathogenesis in CSF1R-deficient male mice, suggesting a potential therapeutic target for CSF1R-related leukoencephalopathy. Collectively, these data support that minocycline confers protective effects against CSF1R-related microgliopathy in male ALSP model mice.