[Mechanistic study of cGAS-STING signaling pathway-mediated blood-brain barrier injury in the prefrontal cortex of 15-month-old mice with postoperative cognitive dysfunction].

Objective: To investigate the role and mechanism of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in mediating blood-brain barrier (BBB) injury within the prefrontal cortex of 15-month-old mice with postoperative cognitive dysfunction (POCD). Methods: Fifteen-month-old male C57BL/6J mice were enrolled and randomly assigned to experimental groups using a random-number table. Experiment 1: twenty-four mice were randomly divided into four groups (n=6): control group (no intervention), sham group, POCD group, and POCD+RU.521 group. On postoperative day 3, cognitive function and spontaneous activity were evaluated by the Morris water maze test and open field test. Prefrontal cortex tissues were subsequently collected for transcriptome sequencing. Experiment 2: twenty-four mice were randomly allocated to eight groups (n=3): sham group, sham+RU.521 group, sham+diABZI group, sham+diABZI+RU.521 group, POCD group, POCD+RU.521 group, POCD+diABZI group, and POCD+diABZI+RU.521 group. On postoperative day 3, prefrontal cortex tissues were harvested for detection of pathway-related protein expression by Western blotting, and assessment of BBB permeability by Evans blue leakage assay. Experiment 3: transcriptome sequencing was performed using prefrontal cortex tissues obtained from experiment 1. Experiment 4: eighteen mice were randomly allocated to three groups (n=6): sham group, POCD group, and POCD+RU.521 group. On postoperative day 3, prefrontal cortex tissues were collected to verify the mRNA expression of target genes by quantitative real-time polymerase chain reaction (RT-qPCR). The POCD model was established by isoflurane anesthesia combined with laparotomy. The cGAS-STING pathway was inhibited or activated by intraperitoneal injection of the cGAS inhibitor RU.521 (5 mg/kg), the STING agonist diABZI (2.5 mg/kg), or diABZI combined with RU.521 at 2 h before surgery, respectively. Results: Compared with the sham group, the POCD group exhibited longer escape latency, lower percentage of time in the target quadrant, and fewer platform crossings in the Morris water maze test, as well as shorter total locomotor distance and less residence time in the central area in the open field test. Compared with the sham group, the relative expression levels of cGAS, STING, p-IRF3 and p-TBK1 in the prefrontal cortex were significantily higher, whereas the relative expression levels of tight junction proteins ZO-1 and Claudin5 were significantily lower, and the Evans blue content in brain tissue was significantily higher in the POCD group (all P<0.05). Intraperitoneal administration of diABZI further aggravated the aforementioned pathway activation, downregulation of tight junction proteins and BBB injury in POCD mice, while intraperitoneal administration of RU.521 reversed these pathological changes and ameliorated cognitive impairment; all these differences were statistically significant (all P<0.05). Compared with the sham group, the sham+diABZI group showed higher expression of cGAS-STING pathway-related proteins and more severe BBB injury, which could be reversed by combined administration with RU.521. Transcriptome sequencing combined with RT-qPCR identified Sdc4, Nnt, Gpt2, Rbp7 and Mertk as relevant target genes. Conclusion: Excessive activation of the cGAS-STING signaling pathway is involved in the pathogenesis of POCD in 15-month-old mice. Inhibition of this pathway can ameliorate postoperative cognitive impairment by alleviating prefrontal cortex blood-brain barrier injury and regulating the expression of relevant target genes.