Reversal of LPS-induced immobility in mice by green tea polyphenols: possible COX-2 mechanism

Catechin Protects against Lipopolysaccharide-induced Depressive-like Behaviour in Mice by Regulating Neuronal and Inflammatory Genes

BACKGROUND

Many studies have suggested that tea has antidepressant effects; however, the underlying mechanism is not fully studied. As the main anti-inflammatory polyphenol in tea, catechin may contribute to the protective role of tea against depression.

OBJECTIVE

The objective of this study is to prove that catechin can protect against lipopolysaccharide (LPS)-induced depressive-like behaviours in mice, and then explore the underlying molecular mechanisms.

METHODS

Thirty-one C57BL/6J mice were categorized into the normal saline (NS) group, LPS group, catechin group, and amitriptyline group according to their treatments. Elevated Plus Maze (EPM), Tail Suspension Test (TST), and Open Field Test (OFT) were employed to assess depressive- like behaviours in mice. RNA sequencing (RNA-seq) and subsequent Bioinformatics analyses, such as differential gene analysis and functional enrichment, were performed on the four mouse groups.

RESULTS

In TST, the mice in the LPS group exhibited significantly longer immobility time than those in the other three groups, while the immobility times for the other three groups were not significantly different. Similarly in EPM, LPS-treated mice exhibited a significantly lower percentage in the time/path of entering open arms than the mice in the other three groups, while the percentages of the mice in the other three groups were not significantly different. In OFT, LPS-treated mice exhibited significantly lower percentages in the time/path of entering the centre area than those in the other three groups. The results suggested that the LPS-induced depression models were established successfully and catechin can reverse (LPS)-induced depressive-like behaviours in mice. Finally, RNA-seq analyses revealed 57 differential expressed genes (DEGs) between LPS and NS with 19 up-regulated and 38 down-regulated. Among them, 13 genes were overlapped with the DEGs between LPS and cetechin (in opposite directions), with an overlapping p-value < 0.001. The 13 genes included Rnu7, Lcn2, C4b, Saa3, Pglyrp1, Gpx3, Lyz2, S100a8, S100a9, Tmem254b, Gm14288, Hbb-bt, and Tmem254c, which might play key roles in the protection of catechin against LPS-induced depressive-like behaviours in mice. The 13 genes were significantly enriched in defense response and inflammatory response, indicating that catechin might work through counteracting changes in the immune system induced by LPS.

CONCLUSION

Catechin can protect mice from LPS-induced depressive-like behaviours through affecting inflammatory pathways and neuron-associated gene ontologies.

Neuropharmacological potential of various morphological parts of Camellia sinensis L

Camellia sinensis L. has long been used as a therapeutic agent for the Central nervous system (CNS) due to the presence of flavonoids. The present study aimed to evaluate the dose-dependent Neuropharmacological behavioral potential of Camellia sinensis seed and leaf extracts on mice. To evaluate the differential potential of leaf and seed extract various doses were prepared and examined in open field, head dip, rearing, cage cross, swimming and traction tests. One-way ANOVA set at P* < 0.05 followed by POST HOC LSD (P* < 0.01) was applied to evaluate the significant difference among the treatments. Herein both seed and leaf extract showed significant results at high doses. Interestingly leaf extract at high dose showed significant effect on mice CNS in open field and head dip test, while seed at high dose revealed significant stimulus on mice CNS in rearing, cage cross, swimming and traction tests. Overall results showed that seed produced more stimulant effect and less calmness as compared to leaf extract was. Tea leaves had already known as potential CNS stimulant drugs; current investigation suggests that tea seed can be used as an alternative CNS stimulant agent with more effective stimulant action.

Screening and analysis of cyclooxygenase-2 inhibitors from the complex matrix: A case study to illustrate the important effect of immobilized enzyme activity in magnetic ligand fishing

Magnetic ligand fishing is one of the most widely used methods to screen and separate potentially bioactive compounds from complex mixtures. However, it is poorly understood the ambiguous relations between immobilized enzyme activity and fishing results (accuracy and sensitivity). Therefore, to investigate the underlying relationship of them, we fabricated the immobilized enzyme with different activities by introducing a novel support material, nickel ions (Ni²⁺) functionalized magnetic mesoporous silica microspheres (MMSM@PDA-Ni²⁺). It possesses a higher activity than the previous report because of site-directed immobilization. Then, the immobilized COX-2 with different activities were prepared using different immobilization methods, including Ni²⁺ affinity-oriented immobilization, polydopamine (PDA) covalent immobilization, and conventional glutaraldehyde (GA) covalent immobilization. A standard mixture (COX-2 inhibitors and noninhibitors) and green tea extract were used to compare and evaluate the fishing results systematically. It displayed the fished inhibitors were dramatically reduced with the decreased activity of immobilized COX-2, indicating that immobilized enzyme activity played a critical role in a reliable magnetic ligand fishing analysis. This development questions some of the previous studies aimed at rapid screening bioactive compounds in natural products and opens new possibilities for accurate and sensitive magnetic ligand fishing analysis. Also, the introduced novel materials with mild immobilization strategy preserve enzyme activity and spatial conformational, therefore, provides a valuable tool in future applications.

Effect of Coffee in Lipopolysaccharide-Induced Indoleamine 2,3-Dioxygenase Activation and Depressive-like Behavior in Mice

Research has identified a potential inverse correlation between coffee consumption and the risk of depression. The aim of this study was to investigate the effects of caffeinated coffee on lipopolysaccharide-induced depressive-like behaviors and inflammatory biomarkers in an in vivo model of depression in a C57BL/6J mouse model. The behavioral studies showed that caffeinated coffee decreased immobility time in both the tail suspension test (caffeinated coffee 56.60 ± 9.17; p < 0.0001) and the forced swimming test (caffeinated coffee 28.80 ± 5.93; p < 0.0001), suggesting antidepressant-like activity. The effects of caffeinated coffee on the inflammatory biomarkers associated with depression supported the results observed in the behavioral studies. Statistically significant decreases in indoleamine 2,3-dioxygenase activity (p < 0.001) and the neopterin/biopterin ratio (p < 0.001) were observed in animals pretreated with caffeinated coffee 24 h post-lipopolysaccharide exposure in comparison to the lipopolysaccharide control group. In conclusion, this study has provided evidence to suggest that caffeinated coffee has antidepressant-like activities; however, further studies are required to fully investigate these effects.

The effect of the antipsychotic drug quetiapine and its metabolite norquetiapine on acute inflammation, memory and anhedonia

The atypical antipsychotic drug, quetiapine, has recently been suggested to not only show efficacy in schizophrenia, bipolar, major depressive and general anxiety disorders, but to also have a possible anti-inflammatory effect, which could be important in the treatment of the inflammatory aspects of psychiatric diseases. Male C57BL/6 mice were given either quetiapine (i.p. 10mg/kg), its main active metabolite norquetiapine (i.p. 10mg/kg), or saline as a vehicle control, once a day for 14days. On the 14th day, this dose was followed by a single dose of either LPS (i.p. 1mg/kg) or saline. 24h post LPS short-term recognition memory and anhedonia behaviour were measured using the Y-maze and saccharin preference test respectively. Immediately following behavioural testing, mice were culled before serum, prefrontal cortex and hippocampal analysis of cytokine levels was conducted. It was found that LPS challenge led to increased serum and brain cytokine levels as well as anhedonia, with no significant effect on recognition memory. Quetiapine and norquetiapine both increased levels of the anti-inflammatory cytokine IL-10 and decreased levels of the pro-inflammatory cytokine IFN-γ in serum 4h post LPS. Within the brain, a similar pattern was seen in gene expression in the hippocampus at 4h for Il-10 and Ifn-γ, however norquetiapine led to an increase in Il-1β expression in the PFC at 4h, while both drugs attenuated the increased Il-10 in different regions of the brain at 24h. These effects in the serum and brain, however, had no effect on the observed LPS induced changes in behaviour. Both quetiapine and its metabolite norquetiapine appear to have a partial anti-inflammatory effect on IL-10 and IFN-γ following acute LPS challenge in serum and brain, however these effects did not translate into behavioural changes.

Nrf2 participates in depressive disorders through an anti-inflammatory mechanism

A causative relationship between inflammation and depression is gradually gaining consistency. Because Nrf2 participates in inflammation, we hypothesized that Nrf2 could play a role in depressive disorders. In this study, we have observed that Nrf2 deletion in mice results in: (i) a depressive-like behavior evaluated as an increase in the immobility time in the tail-suspension test and by a decrease in the grooming time in the splash test, (ii) reduced levels of dopamine and serotonin and increased levels of glutamate in the prefrontal cortex, (iii) altered levels of proteins associated to depression such as VEGF and synaptophysin and (iv) microgliosis. Furthermore, treatment of Nrf2 knockout mice with the anti-inflammatory drug rofecoxib reversed their depressive-like behavior, while induction of Nrf2 by sulforaphane, in an inflammatory model of depression elicited by LPS, afforded antidepressant-like effects. In conclusion, our results indicate that chronic inflammation due to a deletion of Nrf2 can lead to a depressive-like phenotype while induction of Nrf2 could become a new and interesting target to develop novel antidepressive drugs.

Effect of green tea on reward learning in healthy individuals: a randomized, double-blind, placebo-controlled pilot study

BACKGROUND

Both clinical and preclinical studies revealed that regular intake of green tea reduced the prevalence of depressive symptoms, as well as produced antidepressant-like effects in rodents. Evidence proposed that disturbed reward learning has been associated with the development of anhedonia, a core symptom of depression. However, the relationship between green tea and reward learning is poorly investigated. Our goal was to test whether chronic treatment with green tea in healthy subjects affects the process of reward learning and subsequently regulates the depressive symptoms.

METHODS

Seventy-four healthy subjects participated in a double-blind, randomized placebo-controlled study with oral administration of green tea or placebo for 5weeks. We used the monetary incentive delay task to evaluate the reward learning by measurement of the response to reward trial or no-reward trial. We compared the reaction time of reward responsiveness between green tea and placebo treatment. Furthermore, we selected Montgomery-Asberg depression rating scale (MADRS) and 17-item Hamilton Rating Scale for Depression (HRSD-17) to estimate the depressive symptoms in these two groups.

RESULTS

The results showed chronic treatment of green tea increased reward learning compared with placebo by decreasing the reaction time in monetary incentive delay task. Moreover, participants treated with green tea showed reduced scores measured in MADRS and HRSD-17 compared with participants treated with placebo.

CONCLUSIONS

Our findings reveal that chronic green tea increased the reward learning and prevented the depressive symptoms. These results also raised the possibility that supplementary administration of green tea might reverse the development of depression through normalization of the reward function.

The role of dietary polyphenols on adult hippocampal neurogenesis: molecular mechanisms and behavioural effects on depression and anxiety

Although it has been long believed that new neurons were only generated during development, there is now growing evidence indicating that at least two regions in the brain are capable of continuously generating functional neurons: the subventricular zone and the dentate gyrus of the hippocampus. Adult hippocampal neurogenesis (AHN) is a widely observed phenomenon verified in different adult mammalian species including humans. Factors such as environmental enrichment, voluntary exercise, and diet have been linked to increased levels of AHN. Conversely, aging, stress, anxiety and depression have been suggested to hinder it. However, the mechanisms underlying these effects are still unclear and yet to be determined. In this paper, we discuss some recent findings addressing the effects of different dietary polyphenols on hippocampal cell proliferation and differentiation, models of anxiety, and depression as well as some proposed molecular mechanisms underlying those effects with particular focus on those related to AHN. As a whole, dietary polyphenols seem to exert positive effects on anxiety and depression, possibly in part via regulation of AHN. Studies on the effects of dietary polyphenols on behaviour and AHN may play an important role in the approach to use diet as part of the therapeutic interventions for mental-health-related conditions.

Do stress hormones connect environmental effects with behavior in the forced swim test?

Forced swim test (FST) is a widely used test for antidepressant development. Depression is a stress related disease, as hormones of the stress-axis can modify mood. However it is not clear, how the appearance of depressive-like behavior (floating) in FST is connected with changes in the stress-hormone levels. We hypothesized, that different manipulations would alter the behavior through changes in stress-hormone levels. First the effect of environmental alterations was studied. Increasing water-temperature enhanced floating time together with a decrease in adrenocorticotropin levels. During the dark phase of the day rats spent more time with floating independently from the actual lighting. Neither the phase nor the actual lighting had significant effect on adrenocorticotropin concentrations with higher corticosterone levels during the dark phase. At greater water depth rats float less but the size of animals had no effect. Water depth did not influence adrenocorticotropin and corticosterone responses, but the size of the rats significantly affected both factors. Secondly, administration of imipramine reduced floating and adrenocorticotropin level without affecting corticosterone. Despite the known connection between depression and stress we did not find a correlation between floating behavior and hormone levels. As an alternative mechanism imipramine-induced heart rate and core body temperature decrease was found by telemetric approach. This study is the first summary in rats examining the effect of wide range of environmental alterations during FST. It seems likely that both brain monoamines and stress-axis take part in the development of depression, but these pathways are regulated independently.

Platycodin D and 2''-O-acetyl-polygalacin D2 isolated from Platycodon grandiflorum protect ischemia/reperfusion injury in the gerbil hippocampus

Platycodi radix is used as a folk remedy for several conditions. In this study, we investigated the neuroprotective effects of five major extracts; deapioplatycoside E (DPE), platycoside E (PE), platyconic acid A (PA), platycodin D (PD) and 2''-o-acetyl-polygalacin D2 (PD2) isolated from the P.radix in the hippocampal CA1 region (CA1) 4 or 10 days after ischemia/reperfusion (I/R). Each extract was administered into gerbils with intraperitoneal injection (5 mg/kg/day) 10 days before ischemic surgery and the gerbils were sacrificed 4 or 10 days after I/R. Fluoro-Jade B (F-J B, a marker for neurodegeneration) positive ((+)) neurons increased significantly in the stratum pyramidale of the CA1 region in the vehicle-treated group after I/R. A similar pattern was observed in the DPE-, PE- and PA-treated groups; however, in the PD- and PD2-treated groups, F-J B(+) neurons were small in number. We also observed that activations of astrocytes and microglia in the CA1 region after I/R were blocked by the PD- and PD2 treatments. In addition, we found that Cu,Zn-superoxide dismutase (SOD1) immunoreactivity in the pyramidal layer of the PD- and PD2-treated groups was similar to that of the sham group and COX-2(+) and NF-kappaB(+) cells were significantly lower in the PD- and PD2-treated group than those in the vehicle-treated group after I/R. These results suggest that PD and PD2 rescue neurons in the CA1 region from an ischemic damage.

Chronic treatment with celecoxib reverses chronic unpredictable stress-induced depressive-like behavior via reducing cyclooxygenase-2 expression in rat brain

Recent clinical trails reported that adjunctive cyclooxygenase (COX)-2 inhibition with celecoxib is beneficial in treating depression. However, another clinical study showed celecoxib did not have inhibitory effect of COX-2 in human brain when given at a therapeutic dose. Therefore, whether celecoxib is exerting its influence through COX inhibition or by some other mechanism remains unclear. The present study further investigated the effect of celecoxib on COX-2 expression, prostaglandin E(2) (PGE2, a major COX-2-mediated inflammatory mediator) concentration and the depressive-like behaviors in rats. Celecoxib was administrated by oral gavage to naive rats (16 mg/kg) or stressed rats (2, 8, 16 mg/kg, respectively) for 21 days, or to stressed rats for a single dose (16 mg/kg). The results showed that 21 days chronic unpredictable stress induced depressive-like behaviors and increased the COX-2 expression and PGE2 concentration in rat brain. Chronic treatments with celecoxib alleviated the depressive-like behavior and reversed the levels of COX-2 expression and PGE2 concentration in stressed rat in a dose-dependent manner. Celecoxib also improved the emotional state and decreased COX-2 expression and PGE2 concentration in naive rats. In addition, a single dose of celecoxib treatment reversed COX-2 expression and PGE2 concentration, but didn't alter the depressive-like behavior in stressed rat. These results suggest that COX-2 enzyme might play a key role in pathophysiology of depression. Furthermore, these data indicate that chronic celecoxib treatment reverse chronic unpredictable stress-induced depressive-like behavior might via reducing COX-2 enzyme in brain, and the selective COX-2 inhibitors could be developed as potential remedies for the management of depression.

Green Tea Extract and Catechin Ameliorate Chronic Fatigue-Induced Oxidative Stress in Mice

Chronic fatigue syndrome (CFS) is an illness characterized by persistent and relapsing fatigue, often accompanied by numerous symptoms involving various body systems. The etiology of CFS remains unclear, but a number of studies have shown that oxidative stress may be involved in its pathogenesis. The present study was designed to investigate the protective effect of green tea extract (GTE) and catechin in the mouse model of CFS. Animals were subjected to a forced swimming test session of 6 minutes every day for 7 days; a significant increase in immobility time on successive days represented the CFS in mice. Biochemical analysis revealed that the chronic swim test significantly increased lipid peroxidation levels and decreased glutathione levels in mouse whole-brain homogenate. Treatment with GTE (25 or 50 mg/kg, i.p.) and catechin (50 or 100 mg/kg, i.p.) for 7 days reversed the increase in immobility time. Protection was correlated with the lowered levels of lipid peroxidation and restoration of reduced glutathione levels in the brains of fatigued mice. These findings strongly suggest the pivotal role of oxidative stress in the pathophysiology of CFS and that GTE and catechin could be used as potential agents in the management of CFS and warrant the inclusion of GTE and catechin in the treatment regimen of CFS patients.