Neuroinflammation aggravated by traumatic brain injury at high altitude is reversed by L-serine via NFAT1-mediated microglial polarization

PHGDH-mediated serine synthesis in astrocytes supports neuroinflammation by sustaining NADH level to promote histone acetylation

Neuroinflammation contributes to the loss of dopamine neurons and motor dysfunctions in Parkinson's disease (PD). How cell metabolism regulates neuroinflammation by modulating epigenetic modifications is largely unknown. In this study, we found that the expression of phosphoglycerate dehydrogenase (PHGDH) which catalyzes the first step of the de novo serine synthesis pathway was mainly expressed in astrocytes and l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP) injection triggered the upregulation of PHGDH in astrocytes in substantia nigra. PHGDH inhibition or knockdown reduced proinflammatory cytokine production in primary astrocytes after LPS (lipopolysaccharide) stimulation which was not due to suppressed inflammatory signaling transduction. Mechanistically, PHGDH promotes proinflammatory cytokine transcription by sustaining nicotinamide adenine dinucleotide (NADH) accumulation to facilitate histone acetylation of cytokine promoters. Moreover, PHGDH inhibition-induced inflammatory response decreased neurotoxicity in vitro and alleviated astrocytes-mediated neuroinflammation and neurotoxicity in an MPTP mice model. This study reveals the role and mechanism of PHGDH-mediated serine synthesis in promoting the inflammatory response of astrocytes which may provide a potential target for neurological diseases involving neuroinflammation.

Phenothiazine Confers Neuroprotection via Dpp2/7 in High Altitude Traumatic Brain Injury Mouse Model

Zhang, Wenxin, Yuting Yang, Jing Guo, Fei Hu, Yuan Ma, and Qing Ouyang. Phenothiazine confers neuroprotection via Dpp2/7 in high altitude traumatic brain injury mouse model. High Alt Med Biol. 00:00-00, 2025. Background: Traumatic brain injury (TBI) in high altitude areas can lead to more severe cerebral edema, higher disability, and mortality than in low altitude areas. This study was designed to evaluate the neuroprotective effects and underlying mechanisms of phenothiazine on TBI at high altitudes. Methods: Mice were kept in a hypobaric chamber for 7 days under simulated conditions of 5,000 m above sea level. A controlled cortical impact (CCI) model was established and followed by phenothiazine (chlorpromazine and promethazine) and Dpp2/7 inhibitor UAMC00039 treatment. Hematoxylin-eosin (HE) staining, immunohistochemistry (IHC), western blot, label-free quantitative proteomics, and real-time quantitative polymerase chain reaction (RT-qPCR) assays were performed to assess the effects of phenothiazine and UAMC00039 on TBI. Results: HE staining confirmed that phenothiazine treatment could ameliorate CCI-induced brain injury. IHC, western blot, and RT-qPCR showed that cell apoptosis was alleviated by phenothiazine after high altitude TBI, as proved by the reduction of cleaved-Caspase-3 and increased Bcl-2 expression. Label-free quantitative proteomics, IHC, and western blot showed that phenothiazine significantly upregulated Dpp2/7 after high altitude TBI. Western blot and IHC showed that UAMC00039 treatment significantly reversed phenothiazine-mediated Bcl-2 upregulation and cleaved-Caspase-3 downregulation after high altitude TBI. Conclusions: The results indicated that phenothiazine offers neuroprotective effects via antiapoptosis after high altitude TBI, and this protective mechanism is associated with Dpp2/7-mediated Bcl-2 expression and Caspase-3 cleaving.

Exogenous L-Serine Alleviates Pasteurella multocida-Induced Inflammation by Reprogramming the Transcription and Metabolism of Macrophages

P. multocida is notorious for inducing excessive inflammation with high lethality in multiple animals, such as cattle, pigs, and chickens. Our previous study revealed that L-serine was decreased in the lungs of mice infected with P. multocida capsular type A strain CQ2 (PmCQ2), and 2 mg/kg of L-serine could alleviate PmCQ2-induced lung inflammation in vivo, which may largely depend on macrophages. However, the underlying intrinsic alterations remain unknown. Here, we demonstrated that 10 mM of L-serine significantly inhibited the release of inflammatory cytokines (e.g., IL-1β and TNF-α) by blocking inflammasome activation (including NALP1, NLRP3, NLRC4, AIM2, and Caspase-1) in PmCQ2-infected macrophages. Furthermore, the results of RNA-seq and metabonomics revealed that exogenous L-serine supplementation substantially reprogrammed macrophage transcription and metabolism. Mechanically, L-serine reduced inflammatory responses via the inhibition of glycolysis in macrophages based on a seahorse assay. Together, these findings characterize the intrinsic molecular alterations in activated macrophages and provide new targets for modulating P. multocida infection-induced macrophage inflammation.

High-altitude hypoxia aggravated neurological deficits in mice induced by traumatic brain injury via BACH1 mediating astrocytic ferroptosis

Traumatic brain injury (TBI) is one of the leading causes of disability and mortality, which was classified as low-altitude TBI and high-altitude TBI. A large amount of literature shows that high-altitude TBI is associated with more severe neurological impairments and higher mortality rates compared to low-altitude TBI, due to the special environment of high-altitude hypoxia. However, the role of high-altitude hypoxia in the pathogenesis of TBI remains unclear. In order to deeply investigate this scientific issue, we constructed a high-altitude hypoxic TBI model at different altitudes and used animal behavioral assessments (Modified neurological severity score, rotarod test, elevated plus maze test) as well as histopathological analyses (brain gross specimens, brain water content, Evans blue content, hypoxia inducible factor-1α, Hematoxylin-Eosin staining and ROS detection) to reveal its underlying principles and characteristics. We found that with higher altitude, TBI-induced neurological deficits were more severe and the associated histopathological changes were more significant. Single-nuclear RNA sequencing was subsequently employed to further reveal differential gene expression profiles in high-altitude TBI. We found a significant increase in ferroptosis of astrocytes in cases of high-altitude TBI compared to those at low-altitude TBI. Analyzing transcription factors in depth, we found that Bach1 plays a crucial role in regulating key molecules that induce ferroptosis in astrocytes following high-altitude TBI. Down-regulation of Bach1 can effectively alleviate high-altitude TBI-induced neurological deficits and histopathological changes in mice. In conclusion, high-altitude hypoxia may significantly enhance the ferroptosis of astrocytes and aggravate TBI by up-regulating Bach1 expression. Our study provides a theoretical foundation for further understanding of the mechanism of high-altitude hypoxic TBI and targeted intervention therapy.

NFAT1 Signaling Contributes to Bone Cancer Pain by Regulating IL-18 Expression in Spinal Microglia

AIMS

This study aimed to test the hypothesis that nuclear factor of activated T cells 1 (NFAT1) signaling contributes to bone cancer pain by regulating interleukin (IL)-18 expression in spinal microglia.

METHODS

This study was performed on male mice using a Lewis lung carcinoma-induced bone cancer pain model. Nociceptive behaviors were evaluated by measuring mechanical allodynia, thermal hyperalgesia, and spontaneous pain. Expression levels were measured via real-time quantitative polymerase chain reaction, western blotting, and immunofluorescence analysis. The effect of pharmacologic intervention of spinal NFAT1/IL-18 signaling on bone cancer pain was the primary outcome.

RESULTS

NFAT1 expression was upregulated in the spinal microglia after tumor inoculation. Pharmacological inhibition of NFAT1 upregulation prevented and reversed bone cancer-related pain behaviors. In spinal microglia, NFAT1 inhibition decreased p38 MAPK phosphorylation and IL-18 production. Blocking NFAT1 signaling suppressed tumor-induced neuronal sensitization and microglial activation as well as activation of the N-methyl-D-aspartate receptor and the subsequent Ca2+-dependent signaling.

CONCLUSION

Microglia NFAT1-p38 signaling contributes to bone cancer pain through IL-18-mediated central sensitization in spinal microglia. NFAT1 could be a potential target for therapeutic intervention to prevent bone cancer pain.

Black phosphorus quantum dots induced neurotoxicity, intestinal microbiome and metabolome dysbiosis in zebrafish (Danio rerio)

The potential toxicity of BPQDs has received considerable attention due to their increasing use in biomedical applications. In this study, the toxicity of BPQDs at concentrations of 5 μg/mL, 50 μg/mL, and 500 μg/mL on the brain-gut axis was assessed in zebrafish. Following 35 days of exposure, the neurotransmitter, locomotor behavior, gut barrier (physical barrier, chemical barrier, and microbial barrier), and gut content metabolism in zebrafish were evaluated. The results indicated that BPQDs induced the locomotor behavior abnormalities, inhibited acetylcholinesterase activity, induced dopaminase activity, and promoted apoptosis in zebrafish brain tissue. Meanwhile, BPQDs caused damage to the physical and chemical barriers in zebrafish intestinal tissue, which increased the permeability of the intestinal mucosa, and induced oxidative stress and apoptosis. The gut microbiota was analyzed by 16S rRNA gene sequencing. The results showed that BPQDs caused dysbiosis of the gut microbiota, resulting in decreased diversity. Specifically, the relative abundance of Firmicutes, Bacteroidetes, and Actinobacteria decreased, while the relative abundance of Proteobacteria and Clostriobacteria increased. At the genus level, the high concentration BPQDs showed a significant increase in Cetobacterium, Pleisionomas, Aeromonas, and other bacteria. Bioinformatic analysis revealed a correlation between the relative abundance of the gut microbiota and antioxidant levels, immune response, and apoptosis. Statistical analysis of the metabolomic revealed significant perturbations in several metabolic pathways, including amino acid, lipid, nucleotide, and energy metabolism. In addition, correlation analysis between microbiota and metabolism confirmed that gut microbiota dysbiosis was closely associated with metabolic dysfunction. The histopathologic injury supported the changes in biomarkers and the expression of related marker genes in the gut-brain axis, indicating the communication between the gut peripheral nerves and the CNS. The results indicate that BPQDs induce gut microbiota dysbiosis, disrupt metabolic function, and induce neurotoxicity, probably by disrupting the homeostasis of the microbiota-gut-brain axis. In summary, this study demonstrates the effects of BPQDs on physiological changes within the zebrafish brain-gut axis and provides valuable data for assessing the toxicological risks of BPQDs in aquatic ecosystems.

Unraveling the complex pathophysiology of white matter hemorrhage in intracerebral stroke: A single-cell RNA sequencing approach

AIM

This study aims to elucidate the cellular dynamics and pathophysiology of white matter hemorrhage (WMH) in intracerebral hemorrhage (ICH).

METHODS

Using varying doses of collagenase IV, a consistent rat ICH model characterized by pronounced WMH was established. Verification was achieved through behavioral assays, hematoma volume, and histological evaluations. Single-cell suspensions from the hemorrhaged region of the ipsilateral striatum on day three post-ICH were profiled using single-cell RNA sequencing (scRNA-seq). Gene Ontology (GO) and gene set variation analysis (GSVA) further interpreted the differentially expressed genes (DEGs).

RESULTS

Following WMH induction, there was a notable increase in the percentage of myeloid cells and oligodendrocyte precursor cells (OPCs), alongside a reduction in the percentage of neurons, microglia, and oligodendrocytes (OLGs). Post-ICH WMH showed homeostatic microglia transitioning into pro-, anti-inflammatory, and proliferative states, influencing lipid metabolic pathways. Myeloid cells amplified chemokine expression, linked with ferroptosis pathways. Macrophages exhibited M1 and M2 phenotypes, and post-WMH, macrophages displayed a predominance of M2 phenotypes, characterized by their anti-inflammatory properties. A surge in OPC proliferation aligned with enhanced ribosomal signaling, suggesting potential reparative responses post-WMH.

CONCLUSION

The study offers valuable insights into WMH's complex pathophysiology following ICH, highlighting the significance and utility of scRNA-seq in understanding the cellular dynamics and contributing to future cerebrovascular research.

Erianin promotes endogenous neurogenesis in traumatic brain injury rats

The objective of this study was to explore the positive influence and potential mechanism of Erianin on the recovery of brain cells following a traumatic brain injury (TBI). TBI rat models were prepared and treated with Erianin injection via tail vein. The assessment included evaluating the rats' levels of oxidative stress, inflammation, neuronal damage, mitochondrial damage, neuronal regeneration, transformation of pro-inflammatory microglial cells, activation status of the ERK signal pathway, and the functionality of their learning and memory. After administering Erianin, there was a suppression of oxidative stress, inflammation, nerve cell damage, and mitochondrial damage in the TBI rats. Additionally, there was an increase in neuronal regeneration in the cortex and hippocampus, inhibition of pro-inflammatory microglial cell transformation in the cortex, improvement in learning and memory function in TBI rats, and simultaneous inhibition of the activation of the ERK1/c-Jun signal pathway. The findings suggest that Erianin has the potential to reduce oxidative stress and inflammatory reaction in rats with TBI, safeguard nerve cells against apoptosis, stimulate the growth of new neural cells, ultimately enhancing the cognitive abilities and memory function of the rats. The inhibition of the ERK signaling pathway could be closely associated with these effects.

L-serine: Neurological Implications and Therapeutic Potential

L-serine is a non-essential amino acid that plays a vital role in protein synthesis, cell proliferation, development, and sphingolipid formation in the central nervous system. It exerts its effects through the activation of glycine receptors and upregulation of PPAR-γ, resulting in neurotransmitter synthesis, neuroprotection, and anti-inflammatory effects. L-serine shows potential as a protective agent in various neurological diseases and neurodegenerative disorders. Deficiency of L-serine and its downstream products has been linked to severe neurological deficits. Despite its crucial role, there is limited understanding of its mechanistic production and impact on glial and neuronal cells. Most of the focus has been on D-serine, the downstream product of L-serine, which has been implicated in a wide range of neurological diseases. However, L-serine is approved by FDA for supplemental use, while D-serine is not. Hence, it is imperative that we investigate the wider effects of L-serine, particularly in relation to the pathogenesis of several neurological deficits that, in turn, lead to diseases. This review aims to explore current knowledge surrounding L-serine and its potential as a treatment for various neurological diseases and neurodegenerative disorders.