nNOS-CAPON blockers produce anxiolytic effects by promoting synaptogenesis in chronic stress-induced animal models of anxiety.

BACKGROUND AND PURPOSE: Anxiety disorder is a common mental health disorder. However, there are few safe and fast-acting anxiolytic drugs available that can treat anxiety disorder. We previously demonstrated that the interaction of neuronal nitric oxide synthase (nNOS) with its carboxy-terminal PDZ ligand (CAPON) is involved in regulating anxiety-related behaviours. Here, we further investigated the anxiolytic effects of nNOS-CAPON disruptors in chronic stress-induced anxiety in animals. EXPERIMENTAL APPROACH: Mice were intravenously treated with nNOS-CAPON disruptors, ZLc-002 or Tat-CAPON12C, at the last week of chronic mild stress (CMS) exposure. Moreover, we also infused corticosterone (CORT) into the hippocampus of mice to model anxiety behaviours, and delivered ZLc-002 or Tat-CAPON12C into the hippocampus on the last week of chronic CORT treatment via pre-implanted cannula. Anxiety-related behaviours were examined using elevated plus maze (EPM), open-field (OF), novelty-suppressed feeding (NSF) and light-dark (LD) tests. The level of nNOS-CAPON interaction was determined by coimmunoprecipitation (CO-IP) and proximity ligation assay (PLA). The neural mechanisms underlying the behavioural effects of nNOS-CAPON uncoupling in anxiety animal models were assessed by western blot, immunofluorescence and Golgi-Cox staining. KEY RESULTS: We found that ZLc-002 and Tat-CAPON12C reversed CMS- or CORT-induced anxiety-related behaviours. Moreover, ZLc-002 and Tat-CAPON12C increased synaptogenesis along with improved dendritic remodelling in CMS mice or CORT-treated cultured neurons. Meanwhile, blocking nNOS-CAPON interaction significantly activated the cAMP response element-binding protein (CREB)-brain derived neurotrophic factor (BDNF) pathway, which is associated with synaptic plasticity. CONCLUSION AND IMPLICATIONS: Collectively, these results provide evidence for the anxiolytic effects of nNOS-CAPON un-couplers and their underlying mechanisms in anxiety disorders.