Decreased bone mineral density in ovariectomized mice is ameliorated after subsequent repeated intermittent administration of (R)-ketamine, but not (S)-ketamine

Repurposing Ketamine in the Therapy of Depression and Depression-Related Disorders: Recent Advances and Future Potential

Depression represents a prevalent and enduring mental disorder of significant concern within the clinical domain. Extensive research indicates that depression is very complex, with many interconnected pathways involved. Most research related to depression focuses on monoamines, neurotrophic factors, the hypothalamic-pituitary-adrenal axis, tryptophan metabolism, energy metabolism, mitochondrial function, the gut-brain axis, glial cell-mediated inflammation, myelination, homeostasis, and brain neural networks. However, recently, Ketamine, an ionotropic N-methyl-D-aspartate (NMDA) receptor antagonist, has been discovered to have rapid antidepressant effects in patients, leading to novel and successful treatment approaches for mood disorders. This review aims to summarize the latest findings and insights into various signaling pathways and systems observed in depression patients and animal models, providing a more comprehensive view of the neurobiology of anxious-depressive-like behavior. Specifically, it highlights the key mechanisms of ketamine as a rapid-acting antidepressant, aiming to enhance the treatment of neuropsychiatric disorders. Moreover, we discuss the potential of ketamine as a prophylactic or therapeutic intervention for stress-related psychiatric disorders.

Sex differences in the effects of repeated ketamine infusions on bone markers in patients with unipolar and bipolar depression

BACKGROUND

Patients with depression, especially women, are associated with low bone mineral density (BMD). Traditional antidepressants are associated with negative effects on BMD. Few studies have examined the effect of ketamine on BMD, and it remains unclear whether there are sex differences in the effects of ketamine on BMD in patients with depression.

METHODS

A total of 102 patients with unipolar and bipolar depression were administered six infusions of intravenous ketamine over a 12-day period. Plasma levels of eight bone markers were examined at baseline, 24 h after the sixth infusion and again 2 weeks (Days 13 and 26).

RESULTS

Linear mixed models showed all bone markers had significant time main effect (all p < 0.05). Compared with baseline, the whole sample showed increased levels of leptin and osteoprotegerin at Days 13 and 26, as well as Dickkopf-related protein 1 at Day 13, and decreased levels of osteocalcin, sclerostin, osteopontin, parathyroid hormone and fibroblast growth factor 23 at Days 13 and 26 (all p < 0.05). Females had a higher level of leptin at Days 13 and 26, and lower levels of osteocalcin and sclerostin at Day 13 than males (all p < 0.05). Increases of leptin were associated with depressive symptom improvements at Day 13 and Day 26 in females (both p < 0.05). In males, higher baseline osteocalcin levels were associated with greater depressive symptom improvement at Day 26 (β = 0.414, p = 0.009).

CONCLUSIONS

Our results suggest that repeated ketamine infusions may be associated with modulation of bone markers in patients with depression and present sex differences. Baseline osteocalcin level may be served as a predictor for the antidepressant effects of ketamine in males. Trial registration Data were derived from an open label clinical trial, which was registered at Chinese Clinical Trial Registry (ChiCTR-OOC-17012239). Registered 26 May 2017. http://www.chictr.org.cn.

Unfavorable effects of memantine on the skeletal system in female rats

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease (AD). NMDA receptors are expressed on bone cells. The aim of the present study was to investigate the effects of memantine on the rat musculoskeletal system. Taking into account that most of female AD patients are postmenopausal, the study was carried out on intact and ovariectomized (estrogen-deficient) rats. Mature Wistar rats were divided into following groups: non-ovariectomized (NOVX) control rats, NOVX rats treated with memantine, ovariectomized (OVX) control rats, and OVX rats treated with memantine. Memantine (2 mg/kg p.o.) was administered once daily for four weeks, starting one week after ovariectomy. The serum bone turnover marker and cytokine levels, bone density, mass, mineralization, mechanical properties, histomorphometric parameters of compact and cancellous bone, skeletal muscle mass and grip strength were determined. In NOVX rats, memantine slightly decreased the strength of compact bone of the femoral diaphysis (parameters in the yield point) and unfavorably affected histomorphometric parameters of cancellous bone (the femoral epiphysis and metaphysis). In OVX rats, in which estrogen deficiency induced osteoporotic changes, memantine increased the phosphorus content in the femoral bone mineral. No other effects on bone were observed in the memantine-treated OVX rats. In conclusion, the results of the present study indicated slight damaging skeletal effects of memantine in rats with normal estrogen levels.

Beneficial effects of arketamine on the reduced bone mineral density in susceptible mice after chronic social defeat stress: Role of the gut-microbiota-bone-brain axis

Patients with depression exhibit reduced bone mineral density (BMD). We previously reported that the new antidepressant arketamine improved the reduced BMD seen in chronic social defeat stress (CSDS) susceptible mice and ovariectomized mice. Considering the role of the gut microbiota in maintaining bone health, the current study investigated whether the gut microbiota, along with metabolites derived from the microbiome, play a role in the beneficial actions of arketamine with respect to the anhedonia-like behavior and reduced BMD seen in CSDS susceptible mice. A single administration of arketamine (10 mg/kg) ameliorated anhedonia-like behavior and decreased femoral neck cortical (and total) BMD in CSDS susceptible mice. There was a negative correlation between anhedonia-like behavior and BMD. Furthermore, significant differences in the abundance of microbiota (and plasma metabolites) were found between the CSDS + saline and CSDS + arketamine groups. Correlations were observed between the abundance of certain microbiota (and plasma metabolites) and cortical (and total) BMD. These data suggest that, in addition to its anti-anhedonia effect, arketamine might ameliorate the reduced cortical (and total) BMD seen in CSDS susceptible mice through the gut-microbiota-bone-brain axis. Therefore, arketamine could serve as a drug therapy for depressed patients with low BMD. This article is part of the Special Issue on "Ketamine and its Metabolites".

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 β-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.

(R)-ketamine as prophylactic and therapeutic drug for neurological disorders: beyond depression

Neurological disorders are the leading cause of disability and the second leading cause of death worldwide. The increasing social and economic burdens of neurological disorders are driven by global population growth and aging. Depression is a common psychiatric symptom in numerous neurological disorders. It is also a risk factor for Alzheimer's disease (AD) and other dementias, Parkinson's disease (PD), and stroke. The rapid-acting and sustained antidepressant actions of (R,S)-ketamine for severe depression was accidentally discovered. Interestingly, (R)-ketamine has greater potency and longer-lasting antidepressant-like effects than (S)-ketamine in rodents. Importantly, its side effects in rodents and humans are lower than those of (R,S)-ketamine and (S)-ketamine. Furthermore, (R)-ketamine could elicit beneficial actions in various rodent models of neurological disorders, including PD, multiple sclerosis (MS), and stroke. In this article, we review the potential of (R)-ketamine as a prophylactic or therapeutic drug for neurological disorders including AD and other dementias, PD, MS, and stroke.

Molecular mechanisms underlying the antidepressant actions of arketamine: beyond the NMDA receptor

The discovery of robust antidepressant actions exerted by the N-methyl-D-aspartate receptor (NMDAR) antagonist (R,S)-ketamine has been a crucial breakthrough in mood disorder research. (R,S)-ketamine is a racemic mixture of equal amounts of (R)-ketamine (arketamine) and (S)-ketamine (esketamine). In 2019, an esketamine nasal spray from Johnson & Johnson was approved in the United States of America and Europe for treatment-resistant depression. However, an increasing number of preclinical studies show that arketamine has greater potency and longer-lasting antidepressant-like effects than esketamine in rodents, despite the lower binding affinity of arketamine for the NMDAR. In clinical trials, non-ketamine NMDAR-related compounds did not exhibit ketamine-like robust antidepressant actions in patients with depression, despite these compounds showing antidepressant-like effects in rodents. Thus, the rodent data do not necessarily translate to humans due to the complexity of human psychiatric disorders. Collectively, the available studies indicate that it is unlikely that NMDAR plays a major role in the antidepressant action of (R,S)-ketamine and its enantiomers, although the precise molecular mechanisms underlying antidepressant actions of (R,S)-ketamine and its enantiomers remain unclear. In this paper, we review recent findings on the molecular mechanisms underlying the antidepressant actions of (R,S)-ketamine and its potent enantiomer arketamine. Furthermore, we discuss the possible role of the brain-gut-microbiota axis and brain-spleen axis in stress-related psychiatric disorders and in the antidepressant-like action of arketamine. Finally, we discuss the potential of arketamine as a treatment for cognitive impairment in psychiatric disorders, Parkinson's disease, osteoporosis, inflammatory bowel diseases, and stroke.

(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-1β, 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.

(R)-ketamine ameliorates the progression of experimental autoimmune encephalomyelitis in mice

Multiple sclerosis (MS) is an immune-mediated neurological disease that attacks the central nervous system, including spinal cord and brain. Experimental autoimmune encephalomyelitis (EAE) is the most commonly used model for MS. Depression is the most prevalent comorbidity in MS patients. We previously demonstrated that (R)-ketamine would be a novel antidepressant without side effects of ketamine. This study was undertaken to investigate whether (R)-ketamine could attenuate disease progression in EAE mouse model. (R)-ketamine (10 mg/kg/day for 15 days) significantly attenuated the reduction of body weight in EAE model mice compared to saline-treated mice. Furthermore, (R)-ketamine ameliorated the clinical EAE scores compared to saline-treated mice. Moreover, (R)-ketamine significantly attenuated the marked increases in the pathological scores, microglial activation, and blood-brain barrier integrity in the spinal cord compared to saline-treated mice. In conclusion, the current study suggests that (R)-ketamine could ameliorate EAE clinical scores and pathological changes in the spinal cord of EAE mice. Therefore, it is likely that (R)-ketamine would be a new potential prophylactic drug for MS.

(R)-Ketamine attenuates LPS-induced endotoxin-derived delirium through inhibition of neuroinflammation

RATIONALE

(R)-Ketamine produced beneficial effects in a variety of models of inflammatory diseases, including low dose of bacterial lipopolysaccharide (LPS) (0.5-1.0 mg/kg)-induced endotoxemia. LPS-treated mice have been used as animal model of delirium.

OBJECTIVES

We investigated the effects of (R)-ketamine in neuroinflammation and cognitive impairment in rodents after administration of high dose of LPS.

METHODS

LPS (5 mg/kg) or saline was administered intraperitoneally (i.p.) to mice. (R)-Ketamine (10 mg/kg) was administrated i.p. 24 h before and/or 10 min after LPS injection.

RESULTS

LPS (5.0 mg/kg) caused a remarkable splenomegaly and increased plasma levels of pro-inflammatory cytokines [i.e., interleukin (IL-6), IL-17A, and interferon (IFN)-γ]. There were positive correlations between spleen weight and plasma cytokines levels. Furthermore, LPS led to increased levels of pro-inflammatory cytokines in the prefrontal cortex (PFC) and hippocampus. Moreover, LPS impaired the natural and learned behaviors, as demonstrated by a decrease in the number of mice's entries and duration in the novel arm in the Y maze test and an increase in the latency of mice to eat the food in the buried food test. Interestingly, the treatment with (R)-ketamine (twice 24 h before and 10 min after LPS injection) significantly attenuated LPS-induced splenomegaly, central and systemic inflammation, and cognitive impairment.

CONCLUSION

Our results highlighted the importance of combined prophylactic and therapeutic use of (R)-ketamine in the attenuation of LPS-induced systemic inflammation, neuroinflammation, and cognitive impairment in mice. It is likely that (R)-ketamine could be a prophylactic drug for delirium.

Repeated Dosing of Ketamine in the Forced Swim Test: Are Multiple Shots Better Than One?

The anesthetic drug ketamine has been successfully repurposed as an antidepressant in human subjects. This represents a breakthrough for clinical psychopharmacology, because unlike monoaminergic antidepressants, ketamine has rapid onset, including in Major Depressive Disorder (MDD) that is resistant to conventional pharmacotherapy. This rapid therapeutic onset suggests a unique mechanism of action, which continues to be investigated in reverse translational studies in rodents. A large fraction of rodent and human studies of ketamine have focused on the effects of only a single administration of ketamine, which presents a problem because MDD is typically a persistent illness that may require ongoing treatment with this drug to prevent relapse. Here we review behavioral studies in rodents that used repeated dosing of ketamine in the forced swim test (FST), with an eye toward eventual mechanistic studies. A subset of these studies carried out additional experiments with only a single injection of ketamine for comparison, and several studies used chronic psychosocial stress, where stress is a known causative factor in some cases of MDD. We find that repeated ketamine can in some cases paradoxically produce increases in immobility in the FST, especially at high doses such as 50 or 100 mg/kg. Several studies however provide evidence that repeated dosing is more effective than a single dose at decreasing immobility, including behavioral effects that last longer. Collectively, this growing literature suggests that repeated dosing of ketamine has prominent depression-related effects in rodents, and further investigation may help optimize the use of this drug in humans experiencing MDD.

Decreased bone mineral density in ovariectomized mice is ameliorated after subsequent repeated intermittent administration of (R)-ketamine, but not (S)-ketamine

Aim

Depression is a common symptom in people with osteoporosis. (R)‐ketamine produced greater potency and longer‐lasting antidepressant‐like actions than (S)‐ketamine in rodents. Here, we examined the effects of two ketamine enantiomers on the reduced bone mineral density (BMD) in the ovariectomized (OVX) mice which is an animal model of postmenopausal osteoporosis.

Methods

Female ddY mice were OVX or sham‐operated. Subsequently, saline (10 mL/kg/d, twice weekly), (R)‐ketamine (10 mg/kg/d, twice weekly), or (S)‐ketamine (10 mg/kg/d, twice weekly) was administered intraperitoneally into OVX or sham mice for the 6 weeks. The femur from all mice was collected 3 days after the final injection, and BMD in the femur was measured.

Results

The reduction of cortical BMD and total BMD in the OVX mice was significantly ameliorated after subsequent repeated intermittent administration of (R)‐ketamine, but not (S)‐ketamine.

Conclusion

The study shows that (R)‐ketamine can ameliorate the reduced cortical BMD and total BMD in OVX mice. Therefore, (R)‐ketamine would be a novel therapeutic drug for women with osteoporosis.

(R)‐ketamine, but not (S)‐ketamine, ameliorated decreased bone mineral density in ovariectomized mice. Therefore, (R)‐ketamine would be a novel therapeutic drug for women with osteoporosis.