Lumbrokinase modulates tissue plasminogen activator and alleviates behavioral and cognitive deficits in mice with chronic social defeat stress

Lumbrokinase belongs to a group of fibrinolytic enzymes, particularly tissue plasminogen activator (tPA), which can facilitate the proteolytic maturation of brain-derived neurotrophic factor (BDNF). Drugs administered via oral or intravenous routes are often metabolized in the liver or kidneys, and these delivery methods for brain-targeted therapies must overcome the natural barriers of the central nervous system (CNS). Intranasal drug delivery via the nose-to-brain route has emerged as a promising approach to bypass these barriers, enhance drug penetration into the brain, and minimize exposure to peripheral organs. In this study, we demonstrate that intranasally administered lumbrokinase successfully reached the brain. Behaviorally, lumbrokinase significantly improved chronic social defeat stress (CSDS)-induced social avoidance and cognitive impairments. At the molecular level, CSDS increased hippocampal precursor BDNF (proBDNF) expression and reduced mature BDNF (mBDNF) compared with control mice. Importantly, lumbrokinase treatment promoted the expression of tPA and plasmin, thereby restoring the proBDNF/mBDNF balance in the hippocampus and reversing stress-induced maladaptive behaviors. Additionally, lumbrokinase increased TrkB, PSD95, and enhanced phosphorylation of PI3K, AKT, and mTOR in the hippocampus, indicating improved synaptic signaling and plasticity. In conclusion, this study demonstrates that intranasal delivery enables lumbrokinase to reach the brain effectively, providing robust therapeutic benefits against CSDS-induced behavioral and cognitive deficits. Enhancing plasmin-mediated BDNF maturation through non-invasive intranasal enzyme delivery may represent a promising approach for treating stress-related mood disorders. • Intranasal lumbrokinase alleviates CSDS-induced social and cognitive deficits. • Lumbrokinase restores tPA/plasmin levels and promotes proBDNF-to-mBDNF conversion. • Lumbrokinase enhances TrkB and PSD95 levels in the hippocampus. • Lumbrokinase activates PI3K/AKT/mTOR signaling in CSDS mice. • Non-invasive delivery shows therapeutic potential for mood disorders.