Prenatal Isoflurane Exposure Induces Developmental Neurotoxicity in Rats: the Role of Gut Microbiota

Fetal exposure to inhaled anesthetics, such as isoflurane, may lead to neurodevelopmental impairment in offspring. Yet, the mechanisms of prenatal isoflurane-induced developmental neurotoxicity have not been fully elucidated. Gut microbiota is a pivotal modulator of brain development and functions. While the antibiotic effect of isoflurane has been previously investigated, the relationship between prenatal isoflurane exposure and postnatal gut microbiota, brain biology, and behavior remains unknown. In the present study, we treated pregnant rats with 2% isoflurane for 4 h on gestational day 14. Their offspring were tested with novel object recognition task on postnatal day 28 (P28) to assess cognition. Fecal microbiome was assessed using 16S RNA sequencing. We also analyzed hippocampal expression of brain-derived neurotrophic factor (BDNF) in P28 rat brains. To further explore the role of gut microbiota on prenatal isoflurane-induced developmental neurotoxicity, we treated rats with mixed probiotics on P14 for 14 days and evaluated novel object recognition and hippocampal expression of BDNF on P28. Results indicate that prenatal exposure to isoflurane significantly decreased novel object recognition (novel object preference ratio: mean difference (MD) - 0.157; 95% confidence interval (CI) - 0.234 to - 0.080, P < 0.001) paralleled by diminished expression of hippocampal BDNF in juvenile rats. Prenatal exposure to isoflurane also significantly altered the diversity and composition of gut microbiota. Treatment with probiotics mitigated these changes in cognition (novel object preference ratio: isoflurane group vs. control group: MD - 0.177; 95% CI - 0.307 to - 0.047, P = 0.006; probiotic group vs. isoflurane group: MD 0.140; 95% CI 0.004 to 0.275, P = 0.042) and BDNF expression. Taken together, our findings suggest that gut dysbiosis may be involved in the pathogenesis of maternal isoflurane exposure-induced postnatal cognitive impairment. To determine the causal relationship between gut microbiota and cognition in prenatal anesthetic-induced developmental neurotoxicity, further studies are needed.