Prophylactic effects of arketamine, but not hallucinogenic psychedelic DOI nor non-hallucinogenic psychedelic analog lisuride, in lipopolysaccharide-treated mice and mice exposed to chronic restrain stress.

Anesthetic ketamine and classical psychedelics that act as 5-hydroxytryptamine-2A receptor (5-HT2AR) agonists demonstrated rapid and sustained antidepressant actions in patients with treatment-resistant depression. The new antidepressant arketamine is reported to cause long-lasting prophylactic effects in lipopolysaccharide (LPS)-treated mice and mice exposed to chronic restrain stress (CRS). However, no study has compared the prophylactic effects of DOI (2,5-dimethoxy-4-iodoamphetamine: a hallucinogenic psychedelic drug with potent 5-HT2AR agonism), lisuride (non-hallucinogenic psychedelic analog with 5-HT2AR and 5-HT1AR agonism), and arketamine on depression-like behaviors in mice. Saline (10 ml/kg), DOI (2.0 or 4.0 mg/kg), lisuride (1.0 or 2.0 mg/kg), or arketamine (10 mg/kg) was administered intraperitoneally (i.p.) to male mice 6 days before administration of LPS (1.0 mg/kg). Pretreatment with aketamine, but not DOI and lisuride, significantly ameliorated body weight loss, splenomegaly, the increased immobility time of forced swimming test (FST), and the decreased expression of PSD-95 in the prefrontal cortex (PFC) of LPS-treated mice. In another test, male mice received the same treatment one day before CRS (7 days). Pretreatment with aketamine, but not DOI and lisuride, significantly ameliorated the increased FST immobility time, the reduced sucrose preference in the sucrose preference test, and the decreased expression of PSD-95 in the PFC of CRS-exposed mice. These findings suggest that, unlike to arketamine, both DOI and lisuride did not exhibit long-lasting prophylactic effects in mouse models of depression.

Rapid antidepressant-like effect of non-hallucinogenic psychedelic analog lisuride, but not hallucinogenic psychedelic DOI, in lipopolysaccharide-treated mice.

Classical psychedelics with 5-hydroxytryptamine-2A receptor (5-HT2AR) agonism have rapid antidepressant actions in patients with depression. However, there is an ongoing debate over the role of 5-HT2AR in the antidepressant-like actions of psychedelics. In this study, we compared the effects of DOI (2,5-dimethoxy-4-iodoamphetamine: a hallucinogenic psychedelic drug with potent 5-HT2AR agonism), lisuride (non-hallucinogenic psychedelic analog with 5-HT2AR and 5-HT1AR agonisms), and the novel antidepressant (R)-ketamine on depression-like behavior and the decreased dendritic spine density in the brain of lipopolysaccharide (LPS)-treated mice. Saline (10 ml/kg), DOI (2.0 mg/kg), lisuride (1.0 mg/kg), or (R)-ketamine (10 mg/kg) was administered intraperitoneally to LPS (0.5 mg/kg, 23 h before)-treated mice. Both lisuride and (R)-ketamine significantly ameliorated the increased immobility time of forced swimming test, and the decreased dendritic spine density in the prelimbic region of medial prefrontal cortex, CA3 and dentate gyrus of hippocampus of LPS-treated mice. In contrast, DOI did not improve these changes produced after LPS administration. This study suggests that antidepressant-like effect of lisuride in LPS-treated mice is not associated with 5-HT2AR-related psychedelic effects. It is, therefore, unlikely that 5-HT2AR may play a major role in rapid-acting antidepressant actions of psychedelics although further detailed study is needed.

Repeated use of 3,4-methylenedioxymethamphetamine is associated with the resilience in mice after chronic social defeat stress: A role of gut-microbiota-brain axis.

3,4-Methylenedioxymethamphetamine (MDMA), the most widely used illicit compound worldwide, is the most attractive therapeutic drug for post-traumatic stress disorder (PTSD). Recent observational studies of US adults demonstrated that lifetime MDMA use was associated with lower risk of depression. Here, we examined whether repeated administration of MDMA can affect resilience versus susceptibility in mice exposed to chronic social defeat stress (CSDS). CSDS produced splenomegaly, anhedonia-like phenotype, and higher plasma levels of interleukin-6 (IL-6) in the saline-treated mice. In contrast, CSDS did not cause these changes in the MDMA-treated mice. Analysis of gut microbiome found several microbes altered between saline + CSDS group and MDMA + CSDS group. Untargeted metabolomics analysis showed that plasma levels of N-epsilon-methyl-L-lysine in the saline + CSDS group were significantly higher than those in the control and MDMA + CSDS groups. Interestingly, there were positive correlations between plasma IL-6 levels and the abundance of several microbes (or plasma N-epsilon-methyl-L-lysine) in the three groups. Furthermore, there were also positive correlations between the abundance of several microbes and N-epsilon-methyl-L-lysine in the three groups. In conclusion, these data suggest that repeated administration of MDMA might contribute to stress resilience in mice subjected to CSDS through gut-microbiota-brain axis.

Effects of spleen nerve denervation on depression-like phenotype, systemic inflammation, and abnormal composition of gut microbiota in mice after administration of lipopolysaccharide: A role of brain-spleen axis.

BACKGROUND: Accumulating evidence suggests the role of brain-spleen axis as well as brain-gut-microbiota axis in inflammation-related depression. The spleen mediates anti-inflammatory effects of the vagus nerve which plays a role in depression. However, the role of spleen nerve in inflammation-related depression remains unclear. METHODS: The effects of the splenic nerve denervation (SND) in the depression-like phenotype, systemic inflammation, and abnormal composition of gut microbiota in adult mice after administration of lipopolysaccharide (LPS) were examined. RESULTS: LPS (0.5 mg/kg) caused depression-like phenotype, systemic inflammation, splenomegaly, increased expression of Iba1 (ionized calcium-binding adapter molecule 1) and decreased expression of postsynaptic density protein-95 (PSD-95) in the hippocampus in the sham-operated mice. In contrast, LPS did not produce depression-like phenotype, and abnormal expressions of Iba1 and PSD-95 in the hippocampus in the SND-operated mice. Furthermore, SND significantly blocked LPS-induced increased plasma levels of pro-inflammatory cytokine interleukin-6 although SND did not affect LPS-induced splenomegaly and increased plasma levels of tumor necrosis factor-α in mice. There were significant changes in several microbiota among the four groups. Interestingly, there were correlations between the relative abundance of several microbiota and Iba1 (or PSD-95) expression in the hippocampus. In addition, expression of Iba1 in the hippocampus was correlated with the relative abundance of several microbiota. LIMITATIONS: Detailed mechanisms are unclear. CONCLUSIONS: These results suggest that the splenic nerve plays a role in inflammation-related depression, microglial activation in the hippocampus, and that gut microbiota may regulate microglial function in the brain via gut-microbiota-brain axis.

Metabolomics and molecular docking-directed antiarthritic study of the ethyl acetate extract from Celastrus orbiculatus Thunb.

ETHNOPHARMACOLOGICAL RELEVANCE: Celastrus orbiculatus Thunb., an important folk medicine, has long been used for the treatment of rheumatoid arthritis and its ethyl acetate extract (COE) has been reported to possess anticancer, antiinflammation and antiarthritic effects. However, the therapeutic effect and mechanism of COE treatment in rheumatoid arthritis has been rarely studied especially from the perspective of metabolomics. AIM OF STUDY: To reveal the therapeutic effects of COE on adjuvant-induced arthritis (AIA) rats through histopathological analysis, non-targeted metabolomics, and molecular docking study. MATERIALS AND METHODS: Forty-three Wistar rats were randomly divided into normal group, AIA model group, methotrexate group, and COE groups (80 mg/kg, 160 mg/kg and 320 mg/kg of ethyl acetate extract). Paw swelling and arthritis score were monitored through the experiment. Serum levels of tumor necrosis factor α (TNF-α) and nitric oxide were determined and histopathological evaluation was performed. Furthermore, Ultra-high performance liquid chromatography-linear trap quadrupole-Orbitrap-based metabolomics was employed to characterize metabolic changes of AIA rats after COE treatment and molecular docking was performed to predict the potential phytochemicals of COE against TNF-α. RESULTS: COE at three dosages could significantly relieve paw swelling and reduce arthritis scores of AIA rat. Histopathological analysis revealed remarkable decrease in synovial inflammation and bone erosion after COE treatment, especially at middle and high dosage. Additionally, COE down-regulated serum levels of TNF-α and nitric oxide. Serum metabolomics showed that 22 potential biomarkers for the COE treatment of AIA rats were identified, which were closely related to fatty acid metabolism, glycerophospholipid catabolism, and tryptophan metabolism. The molecular docking models predicted that olean-type triterpenes in COE may contribute most to therapeutic effects of rheumatoid arthritis through targeting TNF-α. CONCLUSIONS: COE could significantly relieve the arthritic symptoms in AIA rats and the ultra-high performance liquid chromatography-mass spectrometry based metabolomics proved to be an efficient method to characterize subtle metabolic changes of AIA rats after COE treatment.

Effects of (R)-ketamine on reduced bone mineral density in ovariectomized mice: A role of gut microbiota.

Depression is a high risk for osteoporosis, suggesting an association between depression and low bone mineral density (BMD). We reported that the novel antidepressant (R)-ketamine could ameliorate the reduced BMD in the ovariectomized (OVX) mice which is an animal model of postmenopausal osteoporosis. Given the role of gut microbiota in depression and bone homeostasis, we examined whether gut microbiota plays a role in the beneficial effects of (R)-ketamine in the reduced BMD of OVX mice. OVX or sham was operated for female mice. Subsequently, saline (10 ml/kg/day, twice weekly) or (R)-ketamine (10 mg/kg/day, twice weekly) was administered intraperitoneally into OVX or sham mice for the six weeks. The reduction of cortical BMD and total BMD in the OVX mice was significantly ameliorated after subsequent repeated intermittent administration of (R)-ketamine. Furthermore, there were significant changes in the α- and ß-diversity between OVX + saline group and OVX + (R)-ketamine group. There were correlations between several OTUs and cortical (or total) BMD. There were also positive correlations between the genera Turicibacter and cortical (or total) BMD. Moreover, there were correlations between several metabolites in blood and cortical (or total) BMD. These data suggest that (R)-ketamine may ameliorate the reduced cortical BMD and total BMD in OVX mice through anti-inflammatory actions via gut microbiota. Therefore, it is likely that (R)-ketamine would be a therapeutic drug for depressed patients with low BMD or patients with osteoporosis.

Nuclear factor of activated T cells 4 in the prefrontal cortex is required for prophylactic actions of (R)-ketamine.

(R, S)-ketamine has prophylactic antidepressant-like effects in rodents; however, the precise molecular mechanisms underlying its action remain unknown. Using RNA-sequencing analysis, we searched novel molecular target(s) that contribute to the prophylactic effects of (R)-ketamine, a more potent enantiomer of (R, S)-ketamine. Pretreatment with (R)-ketamine (10 mg/kg, 6 days before) significantly ameliorated body weight loss, splenomegaly, and increased immobility time of forced swimming test in lipopolysaccharide (LPS: 1.0 mg/kg)-treated mice. RNA-sequencing analysis of prefrontal cortex (PFC) and subsequent IPA (Ingenuity Pathway Analysis) revealed that the nuclear factor of activated T cells 4 (NFATc4) signaling might contribute to sustained prophylactic effects of (R)-ketamine. Quantitative RT-PCR confirmed that (R)-ketamine significantly attenuated the increased gene expression of NFATc4 signaling (Nfatc4, Cd4, Cd79b, H2-ab1, H2-aa) in the PFC of LPS-treated mice. Furthermore, pretreatment with NFAT inhibitors (i.e., NFAT inhibitor and cyclosporin A) showed prophylactic effects in the LPS-treated mice. Similar to (R)-ketamine, gene knockdown of Nfatc4 gene by bilateral injection of adeno-associated virus (AAV) into the mPFC could elicit prophylactic effects in the LPS-treated mice. In conclusion, our data implicate a novel NFATc4 signaling pathway in the PFC underlying the prophylactic effects of (R)-ketamine for inflammation-related depression.

Abnormalities of the composition of the gut microbiota and short-chain fatty acids in mice after splenectomy.

The brain-gut-microbiota axis is a complex multi-organ bidirectional signaling system between the brain and microbiota that participates in the host immune system. The spleen, as the largest immune organ in the body, has a key role in the brain-gut-microbiota axis. Here, we investigated whether splenectomy could affect depression-like phenotypes and the composition of the gut microbiota in adult mice. In behavioral tests, splenectomy did not cause depression-like behaviors in mice. Conversely, splenectomy led to significant alterations in the diversity of gut microbes compared with the findings in control (no surgery) and sham-operated mice. In an unweighted UniFrac distance analysis, the boxplots representing the splenectomy group were distant from those representing the other two groups. We found differences in abundance for several bacteria in the splenectomy group at the taxonomic level compared with the other two groups. Finally, splenectomy induced significant changes in lactic acid and n-butyric acid levels compared with those in the other groups. Interestingly, there were significant correlations between the counts of certain bacteria and lactic acid (or n-butyric acid) levels in all groups. These data suggest that splenectomy leads to an abnormal composition of the gut microbiota. It is likely that the spleen-gut-microbiota axis plays a crucial role in the composition of the gut microbiota by regulating immune homeostasis.

(R)-Ketamine ameliorates lethal inflammatory responses and multi-organ injury in mice induced by cecum ligation and puncture.

AIMS: Sepsis is a life-threatening organ dysfunction syndrome arising from infection-induced uncontrolled systemic inflammatory responses. Patients surviving severe sepsis also exhibit increased mortality due to enhanced vulnerability to infections. In this study, we examined whether (R)-ketamine could prevent against lethal sepsis-induced systemic inflammation and inflammatory organ injury. MAIN METHODS: Septic model was induced by cecal ligation and puncture (CLP) surgery on adult mice. (R)-ketamine (10 or 15 mg/kg) was administrated intraperitoneally (i.p.) 24 h before and/or immediately after CLP. KEY FINDINGS: Combined prophylactic and therapeutic use of (R)-ketamine (10 mg/kg), as well as either prophylactic or therapeutic use of (R)-ketamine at a single dose of 15 mg/kg did not reduce 14-day mortality after CLP. However, combined prophylactic and therapeutic use of (R)-ketamine (15 mg/kg) significantly increased 14-day survival rate, attenuated sepsis-induced marked drop in the rectal temperature and increase in the plasma levels of inflammatory cytokines [i.e., interleukin (IL)-6, IL-17A, tumor necrosis factor (TNF)-α, IL-1ß, and IL-10] 12 h after CLP. Furthermore, (R)-ketamine alleviated sepsis-induced increase in the organ injury markers such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), myocardial kinase (CK-MB), and creatinine 24 h after CLP. Moreover, the increased lung wet/dry weight ratio, pulmonary morphological injury and the pulmonary levels of inflammatory cytokines were also attenuated by (R)-ketamine. SIGNIFICANCE: Combined prophylactic and therapeutic use of (R)-ketamine could attenuate systemic inflammation and inflammatory multi-organ injury in mice after CLP-induced lethal sepsis. Therefore, (R)-ketamine would be a potential prophylactic and therapeutic drug for patients prone to sepsis.