Hepatocyte growth factor protects PC12 cells against OGD/R-induced injury by reducing iron

Exploring the Causal Relationship Between Inflammatory Cytokines and MRI-Derived Brain Iron: A Mendelian Randomization Study

BACKGROUND

The association between inflammation and brain iron deposition is widely acknowledged. However, the precise causal impact of peripheral inflammatory cytokines on changes in brain iron content remains uncertain.

METHODS

The study utilized an available genome-wide association study (GWAS) summary associated with inflammatory cytokines from The Cardiovascular Risk in Young Finns Study and the FINRISK surveys. The GWAS data for brain iron markers were obtained from the UK Biobank. We assessed the iron content of each brain region using susceptibility-weighted magnetic resonance imaging, utilizing both quantitative susceptibility mapping and T2* measurements. The primary outcomes were susceptibility (χ) and T2*, which serve as indices of iron deposition. To investigate the causal relationship between exposure and outcome, we primarily employed inverse variance weighting, MR Egger, weighted median, simple mode, and weighted mode methods, collectively enhancing the robustness of our results.

RESULTS

The results of MR analyses demonstrate that our study unveiled that nerve growth factor-β, hepatocyte growth factor, interleukin-1 (IL-1), IL-8, macrophage inflammatory protein 1α, and tumor necrosis factor-α were associated with elevated brain iron content in the regions of left hippocampus, putamen, left thalamus, right pallidum, right hippocampus, left amygdala, respectively. Furthermore, our investigation provides evidence for a negative relationship between IL-1, IL-17, monocyte chemotactic protein-3, tumor necrosis factor-β, and brain iron content in distinct regions.

CONCLUSIONS

Our findings suggest a causal association between circulating inflammatory cytokines and brain iron deposition across various brain regions. This provides new insights into the immunopathogenesis of neurodegenerative diseases and potential preventive strategies targeting iron metabolism.

RXRγ attenuates cerebral ischemia-reperfusion induced ferroptosis in neurons in mice through transcriptionally promoting the expression of GPX4

Cerebral ischemia is a common cerebrovascular disease with high mortality and disability rate. Exploring its mechanism is essential for developing effective treatment for cerebral ischemia. Therefore, this study aims to explore the regulatory effect and mechanism of retinoid X receptor γ (RXRγ) on cerebral ischemia-reperfusion (I/R) injury. A mouse intraluminal middle cerebral artery occlusion model was established, and PC12 cells were exposed to anaerobic/reoxygenation (A/R) as an in vitro model in this study. Cerebral I/R surgery or A/R treatment induced ferroptosis, downregulated RXRγ and GPX4 (glutathione peroxidase 4) levels, upregulated cyclooxygenase-2 (COX-2) level and increased ROS (reactive oxygen species) level in A/R induced cells or I/R brain tissues in vivo or PC12 cells in vitro. Knockdown of RXRγ downregulated GPX4 and increased COX-2 and ROS levels in A/R induced cells. RXRγ overexpression has the opposite effect. GPX4 knockdown reversed the improvement of RXRγ overexpression on COX-2 downregulation, GPX4 upregulation and ferroptosis in PC12 cells. Furthermore, chromatin immunoprecipitation (ChIP) and luciferase reporter gene assays revealed that RXRγ bound to GPX4 promoter region and activated its transcription. Overexpression of RXRγ or GPX4 alleviated brain damage and inhibited ferroptosis in I/R mice. In conclusion, RXRγ-mediated transcriptional activation of GPX4 might inhibit ferroptosis during I/R-induced brain injury.