Abstract
The endangered cold-water fish Brachymystax tsinlingensis (B. tsinlingensis) serves as a critical sentinel species for aquatic ecosystem responses to climate change. This study investigates heat stress impacts on behavior, physiology, and molecular homeostasis in B. tsinlingensis, and evaluates neuroprotective effects of anti-stress additives (vitamin C, gamma-aminobutyric acid, trehalose). Behavioral analysis showed a significant increase in center-zone entries under heat stress. Physiological assays showed a reduction in superoxide dismutase (SOD) and catalase (CAT) activities, alongside an upregulation of heat shock protein 70 (Hsp70), glucose-regulated protein 78 (GRP78), and caspase expression under heat stress, with a return to baseline levels following a 12 h recovery. For assays in the brain, histopathological examination identified vacuolation in cerebral tissue after heat stress. Quantitative proteomics analysis identified 831 differentially expressed proteins (DEPs) out of 8,955 proteins during the temperature change process. Pathway analysis revealed that the 'DNA replication' and 'Citrate cycle' pathways were inhibited by heat stress but reactivated during recovery, whereas the 'ECM-receptor interaction' and 'Cell adhesion molecules' pathways exhibited opposite trends. Intervention with additives showed that trehalose enhanced SOD, glutathione peroxidase (GPX), and CAT activities, as well as gene expression related to cell adhesion and barrier function. Gamma-aminobutyric acid maximally suppressed stress-related genes (Hsp70, long-chain-fatty-acid-CoA ligase, and arachidonate lipoxygenase), while vitamin C exhibited general but less targeted effects. As the first proteomic study on B. tsinlingensis, this work reveals that blood-brain barrier reconstruction and energy reallocation are key neural survival strategies under temperature change stress. Furthermore, trehalose demonstrates high potential as an anti-heat stress additive by enhancing both antioxidant defenses and blood-brain barrier integrity. These findings advance our understanding of heat adaptation mechanisms in cold-water fish species and provide scientific foundations for conserving B. tsinlingensis.