Butyric acid and valeric acid attenuate stress-induced ferroptosis and depressive-like behaviors by suppressing hippocampal neuroinflammation.

Background: Depression is closely associated with stress-induced hippocampal damage and dysfunction. Emerging evidence demonstrates that the gut microbiota and its metabolites, acting as probiotics or prebiotics, can modulate brain structure and function via the gut-brain axis, thereby offering therapeutic potential for ameliorating related neurological and psychiatric disorders. This study delves into the contribution of the gut microbiota and its metabolites to stress-induced ferroptosis of hippocampal neurons and the associated molecular pathways.

Methods: This study used time-course stress paradigms combined with ferroptosis inhibitors to identify hippocampal neuronal ferroptosis. Fecal microbiota transplantation were conducted to analyze the role of gut microbiota in this process. Subsequently, 16 S rDNA sequencing and metabolomics techniques were applied to identify key gut microbiota and metabolites. Metabolites intervention were performed to examine their causal relationship with neuronal ferroptosis. Finally, we used histochemical and molecular assays to assess both intestinal and blood-brain barrier integrity as well as inflammation in peripheral blood and hippocampal tissue, along with GPR41/RhoA/Rock1 pathway changes, to preliminarily investigate the molecular mechanisms underlying stress-induced hippocampal neuronal ferroptosis.

Results: We demonstrated that stress triggered hippocampal neuronal ferroptosis and subsequent depressive-like behaviors in mice. Fecal microbiota transplantation successfully replicated the ferroptosis phenotype. Butyric acid and valeric acid were identified as key metabolites significantly reduced in the serum of acutely and chronically stressed mice, respectively. Intervention with these metabolites markedly alleviated ferroptosis. Furthermore, valerate intervention increased hippocampal GPR41 expression and significantly suppressed the pro-inflammatory RhoA/Rock1 pathway in chronically stressed mice, thereby reducing neuroinflammation and ameliorating neuronal ferroptosis. However, butyrate intervention showed no significant effect on the GPR41/RhoA/Rock1 pathway.

Conclusion: Stress induces ferroptosis in hippocampal neurons, where reduced abundance of short-chain fatty acid-producing bacteria plays a key role. Key metabolites butyric acid and valeric acid alleviate neuroinflammation to improve ferroptosis via the gut-brain axis in acute and chronic stress, respectively. Specifically, valeric acid exerts neuroprotective effect through the GPR41/RhoA/Rock1 pathway, whereas butyric acid-mediated protection likely operates through alternative mechanisms.