Pinocembrin mitigates depressive-like behaviors induced by chronic unpredictable mild stress through ameliorating neuroinflammation and apoptosis

Abstract

Background: The majority of patients with chronic fatigue have a risk of comorbidity with depression. Pinocembrin (PB) is a kind of flavonoid molecule isolated from honey and propolis and has antimicrobial, anti-inflammatory, antioxidant, and anticancer function. The purpose of the current study was to determine the possible function of PB on treatment of depression.

Methods: A chronic unpredictable mild stress (CUMS) mouse model was established to mimic the depressive-like behaviors in vivo. The depressive-like behaviors of CUMS mice were measured by sucrose preference test (SPT), open field test (OFT), forced swim test (FST) and tail suspension test (TST). The concentration of reactive oxygen species (ROS), malondialdehyde (MDA) and the activity or superoxide dismutase (SOD) were detected by commercial kit. The inflammatory factor including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-10 and transforming growth factor (TGF)-β were examined.

Results: We found that PB alleviated the decreasing of sucrose preference and body weight. CUMS mice significantly increased the immobility time but decreased latency to abandon in FST, increased the immobility time in TST, and reduced crossing score and rearing score in OFT, whereas these changes were reversed by PB treatment. More importantly, PB decreased the concentration of ROS and MDA, but increased the SOD activity, suggesting that it could protected against oxidative stress in CUMS mice. Interestingly, PB inhibited cell apoptosis and regulated inflammatory factors expression in hippocampus of CUMS mice. Moreover, PB activated Nrf2/HO-1 signal pathway but inhibited the phosphorylation of NF-kB.

Conclusions: In conclusion, PB mitigated CUMS-induced depressive-like behaviors through ameliorating neuroinflammation and apoptosis.

Trial registration: Not Applicable.

Keywords: Apoptosis; Chronic unpredictable mild stress; Neuroinflammation; Oxidative stress; Pinocembrin.

Fig. 1

PB alleviated sucrose preference and body weight in CUMS mice (A) Experimental schedule. A total of 40 C57BL/6 J mice randomly divided into 5 groups: (a) Control; (b) Control+PB; (c) CUMS; (d) CUMS+PB; (e) CUMS+IMI. Meanwhile, the IMI treatment was served as a positive control, and IMI was administrated every day during the UCSM experiments by oral gavage. The unpredictable chronic mild stress (UCMS) protocols and PB treatment lasted 6 weeks and 3 weeks, respectively. Before the UCMS procedure, the sucrose preference and body weight were measured and lasted for once a week. Sucrose preference was measured in UCMS weekly. The depressive-like behavioral assessment was assessed at the end of the experiments. The sucrose preference (B) and body weight (C) were detected once a week. Eight mice per group. **p < 0.01 vs. Control. #p < 0.05, ##p < 0.01 vs. CUMS

Fig. 2

PB alleviated depressive-like behaviors of CUMS mice a PB decreased the immobility time but increased latency to abandon of CUMS mice in the forced swimming test (FST). b PB reduced the immobility time of CUMS mice in the tail suspension test (TST). c PB promoted crossing score and rearing score of CUMS mice in the open field test (OFT), with no change in grooming score. Eight mice per group. **p < 0.01 vs. Control. #p < 0.05, ##p < 0.01 vs. CUMS

Fig. 3

PB protected against oxidative stress in hippocampus of CUMS mice a PB inhibited ROS production, which was measured using the DCFH-DA fluorescent probe under a fluorescence microscope at a magnification of × 400. b The fluorescence intensity was calculated and was correlated with the ROS level. c The concentration of MDA was measured, suggesting that PB decreased MDA concentration in CUMS mice. d The activity of SOD was measured, indicating that PB promoted SOD activity in CUMS mice. **p < 0.01 vs. Control. ##p < 0.01 vs. CUMS

Fig. 4

PB inhibited the cell apoptosis in hippocampus from CUMS mice The cell apoptosis in hippocampus of CUMS mice was determined by TUNEL assay and IHC assay of cleaved caspase-3 (200×), bar = 50 μm

Fig. 5

PB regulated inflammatory factors expression in CUMS mice B The expression of IL-1β, TNF-α, IL-10 and TGF-β in mice were determined by qRT-PCR. b The concentrations of IL-1β, TNF-α, IL-10 and TGF-β in hippocampus of mice were detected by ELISA assay. **p < 0.01 vs. Control. ##p < 0.01 vs. CUMS

Fig. 6

PB activated Nrf2/HO-1 signal pathway but inhibited the phosphorylation of NF-kB The changes of expression of Nrf2, HO-1, Bcl-2, Bax, p-NF-kB, NF-kB were assessed by western blot. **p < 0.01 vs. Control. #p < 0.05, ##p < 0.01 vs. CUMS

Fig. 7

This cartoon depicted PB activated Nrf2/HO-1 signal pathway but inhibited the phosphorylation of NF-kB, and then ameliorated neuroinflammation and oxidative stress, further inhibited cell apoptosis and mitigated CUMS-induced depressive-like behaviors