The anxiolytic-like effect of the aqueous extract of Punica granatum depends on the stress level of fish and mice: Evidence of a homeostatic re-establishing effect

Abstract

Pomegranate (Punica granatum) has shown potential anxiolytic and antidepressant effects in preclinical research, but its mechanisms remain unclear. Importantly, some evidence suggests that the effects of P. granatum depend on previous stress, suggesting an adaptogenic effect. This study aimed to evaluate the anxiolytic-like effects of an aqueous extract of P. granatum (AE-PG) on lambaris and zebrafish exposed to acute restraint stress (ARS) and female BALB/c mice exposed to unpredictable chronic mild stress (CUMS). In addition, we evaluated antidepressant-like effects in female BALB/c mice. Acute administration of AE-PG (1 mg/kg, i.p.) was tested in the novel tank test (NTT) in lambaris and zebrafish and in the light/dark test (LDT) in zebrafish, while chronic (7 days) administration of AE-PG (1 mg/kg, i.p.) was tested in the elevated plus-maze (EPM), open-field test (OFT), splash test (ST), and forced swim test (FST) in mice. ARS increased geotaxis and erratic swimming in the NTT, as well as scototaxis, risk assessment, and erratic swimming in the LDT. Acute pre-treatment with AE-PG blocked the effects of ARS on these anxiety-like endpoints in both lambaris and zebrafish. CUMS increased open arm avoidance in the EPM, thigmotaxis and horizontal and vertical exploration in the OFT, and immobility in the FST, and decreased grooming in the ST. Chronic treatment with AE-PG blocked the effects of CUMS on anxiety-like endpoints, and depression-like endpoints, in mice. An in silico analysis of the main compounds in AE-PG suggested a possible mechanism of action on a wide network of targets that converge on PI3K/Akt and show differential expression in brain regions associated with fear- and anxiety-like behavior. Molecular docking suggests that a compound from AE-PG, ellagic acid, is likely to act through estrogen receptors, which could help reestablish homeostatic balance in response to stress.