Kapβ2 Reverses Sevoflurane-Induced Hydrogel Phase Transition of hnRNPA2/B1-SG in Hypoxic Primary Rat Hippocampal Neurons.

Aims: Sevoflurane can aggravate the progression of neurodegeneration, although the underlying mechanisms remain incompletely understood. Our previous study identified a link between heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2/B1) and sevoflurane-induced neurocognitive impairments. The abnormal hydrogel phase transition of stress granules (SGs) assembled via liquid-liquid phase separation (LLPS) by hnRNPA2/B1 is a crucial element in neurodegeneration. Karyopherin-β2 (Kapβ2) is known to specifically recognize hnRNPA2/B1 and reverses the hydrogel transition of SGs. This study aimed to elucidate the mechanistic role of hnRNPA2/B1-SG phase transition in sevoflurane-induced hippocampal neuronal dysfunction under hypoxic conditions, and to determine whether Kapβ2 can mitigate these effects.

Methods: Using a hypoxic primary rat hippocampal neuron model and Kapβ2 overexpression, we investigated the effects of sevoflurane on hnRNPA2/B1 expression and subcellular distribution, phase separation dynamics, and the liquid-to-solid transition of hnRNPA2/B1-associated SGs. We also assessed neuronal function and cognitive protein expression. Experimental approaches included Western blotting, RT-qPCR, immunofluorescence staining, and fluorescence recovery after photobleaching (FRAP).

Results: In hypoxic hippocampal neurons, sevoflurane altered the nuclear-to-cytoplasmic distribution of hnRNPA2/B1, promoted abnormal LLPS, and facilitated the formation of irreversible solid-phase hnRNPA2/B1-containing SGs. These changes were associated with neuronal dysfunction and reduced expression of cognition-related proteins. Kapβ2 overexpression disrupted these aggregates, restored the dynamic reversibility of hnRNPA2/B1 LLPS, reversed the sevoflurane-induced hydrogel phase transition of hnRNPA2/B1-SGs, and enhanced the expression of cognition-related proteins.

Conclusion: The hydrogel phase transition of hnRNPA2/B1-SG is a key pathological mechanism of sevoflurane-induced hippocampal neuronal injury. Kapβ2 may serve as a potential therapeutic target to counteract sevoflurane-related neurotoxicity.