Abstract
OBJECTIVES: To investigate the molecular mechanism of helicid for improving depressive-like behaviors in rats exposed to chronic unpredictable mild stress (CUMS). METHODS: SD rats were randomly divided into normal control group (n=20) and CUMS group (n=70) to receive no stimulation and mild unpredictable stress for 6 weeks, respectively. After successful modeling, CUMS rats were further divided into 7 subgroups for intracerebroventricular injection with saline, adeno-associated virus (AAV) vector, or AAV carrying si-NCALD (NCALD silencing experiment, n=10); or intracerebroventricular injection with saline, saline with daily helicid gavage, AAV vector with helicid gavage, or NCALD-overexpressing AAV with helicid gavage (NCALD overexpresison experiment, n=10). The depressive state of the rats was evaluated by assessing changes in body weight, sucrose preference, and open field test. The expressions of NCALD, sGCα1, sGCβ1, PKG1/2, and cleaved-caspase 3 in the hippocampus of the rats were detected by Western blotting, and hippocampal cGMP level was determined with ELISA. RESULTS: Compared with the normal control rats, CUMS rats showed significantly increased hippocampal expressions of NCALD and cleaved caspase-3 and abnormal activation of the sGC/cGMP/PKG pathway. Silencing NCALD by intracerebroventricular injection of AAV-si-NCALD significantly reduced cleaved caspase-3 and inhibited sGC/cGMP/PKG pathway activation in the hippocampus, and improved depressive-like behaviors of the rats. Helicid treatment produced similar effects, but its effect was abolished by intracerebroventricular injection of NCALD-overex-pressing AAV. CONCLUSIONS: Helicid relieves depressive-like behaviors in CUMS rats by downregulating NCALD, inhibiting abnormal sGC/cGMP/PKG activation, and reducing hippocampal apoptosis.