Dopamine D2 receptor supersensitivity in the hypothalamus of olfactory bulbectomized mice

Anxiolytic effects of Enterococcus faecalis 2001 on a mouse model of colitis

Ulcerative colitis (UC) is a refractory inflammatory bowel disease, which is known to cause psychiatric disorders such as anxiety and depression at a high rate in addition to peripheral inflammatory symptoms. However, the pathogenesis of these psychiatric disorders remains mostly unknown. While prior research revealed that the Enterococcus faecalis 2001 (EF-2001) suppressed UC-like symptoms and accompanying depressive-like behaviors, observed in a UC model using dextran sulfate sodium (DSS), whether it has an anxiolytic effect remains unclear. Therefore, we examined whether EF-2001 attenuates DSS-induced anxiety-like behaviors. Treatment with 2% DSS for seven days induced UC-like symptoms and anxiety-like behavior through the hole-board test, increased serum lipopolysaccharide (LPS) and corticosterone concentration, and p-glucocorticoid receptor (GR) in the prefrontal cortex (PFC), and decreased N-methyl-D-aspartate receptor subunit (NR) 2A and NR2B expression levels in the PFC. Interestingly, these changes were reversed by EF-2001 administration. Further, EF-2001 administration enhanced CAMKII/CREB/BDNF-Drebrin pathways in the PFC of DSS-treated mice, and labeling of p-GR, p-CAMKII, and p-CREB showed colocalization with neurons. EF-2001 attenuated anxiety-like behavior by reducing serum LPS and corticosterone levels linked to the improvement of UC symptoms and by facilitating the CAMKII/CREB/BDNF-Drebrin pathways in the PFC. Our findings suggest a close relationship between UC and anxiety.

Polarization to M1-type microglia in the hippocampus is involved in depression-like behavior in a mouse model of olfactory dysfunction

Impaired olfactory function may be associated with the development of psychiatric disorders such as depression and anxiety; however, knowledge on the mechanisms underlying psychiatric disorders is incomplete. A reversible model of olfactory dysfunction, zinc sulfate (ZnSO4) nasal-treated mice, exhibit depression-like behavior accompanying olfactory dysfunction. Therefore, we investigated olfactory function and depression-like behaviors in ZnSO4-treated mice using the buried food finding test and tail suspension test, respectively; investigated the changes in the hippocampal microglial activity and neurogenesis in the dentate gyrus by immunohistochemistry; and evaluated the inflammation and microglial polarity related-proteins in the hippocampus using western blot study. On day 14 after treatment, ZnSO4-treated mice showed depression-like behavior in the tail suspension test and recovery of the olfactory function in the buried food finding test. In the hippocampus of ZnSO4-treated mice, expression levels of ionized calcium-binding adapter molecule 1 (Iba1), cluster of differentiation 40, inducible nitric oxide synthase, interleukin (IL)-1β, IL-6, tumor necrosis factor-α, cleaved caspase-3, as well as the number of Iba1-positive cells and cell body size increased, and arginase-1 expression and neurogenesis decreased. Except for the increased IL-6, these changes were prevented by a microglia activation inhibitor, minocycline. The findings suggest that neuroinflammation due to polarization of M1-type hippocampal microglia is involved in depression accompanied with olfactory dysfunction.

Hippocampal and gut AMPK activation attenuates enterocolitis-like symptoms and co-occurring depressive-like behavior in ulcerative colitis model mice: Involvement of brain-gut autophagy

Patients with inflammatory bowel disease, including ulcerative colitis (UC) and Crohn's disease, have a high incidence of psychiatric disorders, including depression and anxiety. However, the underlying pathogenic mechanism remains unknown. Dextran sulfate sodium (DSS)-treated mice, a model of UC, exhibit depressive-like behavior and reduced adenosine monophosphate-activated protein kinase (AMPK) activity, which regulates various physiological functions in the brain and gut. However, comprehensive studies on UC pathophysiology with co-occurring depression focused on brain-gut AMPK activity are lacking. Therefore, we aimed to investigate whether resveratrol (RES), an AMPK activator, prevented DSS-induced UC-like symptoms and depressive-like behavior. DSS treatment induced UC-like pathology and depressive-like behavior, as assessed via the tail suspension test. Moreover, western blotting and immunohistochemical studies revealed that DSS increased p-p70S6 kinase (Thr389), p62, tumor necrosis factor-α, interleukin (IL)-1β, IL-18, NLR family pyrin domain containing 3 (NLRP3), cleaved caspase-1, cleaved Gasdermin-D (GSDMD), and cleaved caspase-3 expression levels in the rectum and hippocampus, and increased CD40, iNOS, and Kelch-like ECH-associated protein 1 expression levels, and the number of Iba1-positive cells in the hippocampus, and decreased p-AMPK and LC3II/I expression levels, and the number of NF-E2-related factor 2 (Nrf2)-positive cells, and reduced neurogenesis in the hippocampus. These changes were reversed by the RES administration. RES also enhanced PGC1α and SOD1 expression in the hippocampus of DSS-treated male mice. Moreover, NLRP3 staining was observed in the neurons and microglia, and cleaved GSDMD staining in neurons in the hippocampus of DSS-treated mice. Notably, RES prevented UC-like pathology and depressive-like behavior and enhancement of autophagy, decreased rectal and hippocampal inflammatory cytokines and inflammasome, and induced the Nrf2-PGC1α-SOD1 pathway in the hippocampus, resulting in neurogenesis in the hippocampal dentate gyrus. Our findings suggest that brain-gut AMPK activation may be an important therapeutic strategy in patients with UC and depression.

Naringenin, a Functional Food Component, Improves Motor and Non-Motor Symptoms in Animal Model of Parkinsonism Induced by Rotenone

Parkinson's disease (PD) and other age-related neurodegenerative ailments have a strong link to oxidative stress. Bioflavonoid naringenin has antioxidant properties. The effects of pre- and post-naringenin supplementation on a rotenone-induced PD model were examined in this work. Naringenin (50 mg/kg, p.o.) was administered to rats for two weeks before the administration of rotenone in the pre-treatment phase. In contrast, rotenone (1.5 mg/kg, s.c.) was administered for eight days before naringenin (50 mg/kg, p.o.) was supplemented for two weeks in the post-treatment phase. During behavioral investigation, the motor and non-motor signs of PD were observed. Additionally, estimation of neurochemical and biochemical parameters was also carried out. Compared to controls, rotenone treatment substantially increased oxidative stress, altered neurotransmitters, and caused motor and non-motor impairments. Rotenone-induced motor and non-motor impairments were considerably reduced by naringenin supplementation. The supplementation also increased antioxidant enzyme activities and restored the changes in neurotransmitter levels. The findings of this work strongly imply that daily consumption of flavonoids such as naringenin may have a therapeutic potential to combat PD.

Activation of cholinergic system partially rescues olfactory dysfunction-induced learning and memory deficit in mice

Deficits in olfaction are associated with neurodegenerative disorders such as Alzheimer's disease. A recent study reported that intranasal zinc sulfate (ZnSO₄)-treated mice show olfaction and memory deficits. However, it remains unknown whether olfaction deficit-induced learning and memory impairment is associated with the cholinergic system in the brain. In this study, we evaluated olfactory function by the buried food find test, and learning and memory function by the Y-maze and passive avoidance tests in ZnSO₄-treated mice. The expression of choline acetyltransferase (ChAT) protein in the olfactory bulb (OB), prefrontal cortex, hippocampus, and amygdala was assessed by western blotting. Moreover, we observed the effect of the acetylcholinesterase inhibitor physostigmine on ZnSO₄-induced learning and memory deficits. We found that intranasal ZnSO₄-treated mice exhibited olfactory dysfunction, while this change was recovered on day 14 after treatment. Both short-term and long-term learning and memory were impaired on days 4 and 7 after treatment with ZnSO₄, whereas the former, but not the latter, was recovered on day 14 after treatment. A significant correlation was observed between olfactory function and short-term memory, but not long-term memory. Treatment with ZnSO₄ decreased the ChAT level in the OB on day 4, and increased and decreased the ChAT levels in the OB and hippocampus on day 7, respectively. Physostigmine improved the ZnSO₄-induced deficit in short-term, but not long-term, memory. Taken together, the present results suggest that short-term memory may be closely associated with olfactory function via the cholinergic system.