Cilostazol as an adjunctive treatment in major depressive disorder: a pilot randomized, double-blind, and placebo-controlled clinical trial

Cilostazol pretreatment prevents PTSD-related anxiety behavior through reduction of hippocampal neuroinflammation

Current pharmacological treatments against post-traumatic stress disorder (PTSD) lack adequate efficacy. As a result, intense research has focused on identifying other molecular pathways mediating the pathogenesis of this condition. One such pathway is neuroinflammation, which has demonstrated a role in PTSD pathogenesis by causing synaptic dysfunction, neuronal death, and functional impairment in the hippocampus. Phosphodiesterase (PDE) inhibitors (PDEIs) have emerged as promising therapeutic agents against neuroinflammation in other neurological conditions. Furthermore, PDEIs have shown some promise in animal models of PTSD. However, the current model of PTSD pathogenesis, which is based on dysregulated fear learning, implies that PDE inhibition in neurons should enhance the acquisition of fear memory from the traumatic event. As a result, we hypothesized that PDEIs may improve PTSD symptoms through inhibiting neuroinflammation rather than long-term potentiation-related mechanisms. To this end, we tested the therapeutic efficacy of cilostazol, a selective inhibitor of PDE3, on PTSD-related anxiety symptoms in the underwater trauma model of PTSD. PDE3 is expressed much more richly in microglia and astrocytes compared to neurons in the murine brain. Furthermore, we used hippocampal indolamine 2,3-dioxygenase 1 (IDO) expression and interleukin 1 beta (IL-1β) concentration as indicators of neuroinflammation. We observed that cilostazol pretreatment prevented the development of anxiety symptoms and the increase in hippocampal IDO and IL-1β following PTSD induction. As a result, PDE3 inhibition ameliorated the neuroinflammatory processes involved in the development of PTSD symptoms. Therefore, cilostazol and other PDEIs may be promising candidates for further investigation as pharmacological therapies against PTSD.

Phosphodiesterase inhibitors in psychiatric disorders

RATIONALE

Challenges in drug development for psychiatric disorders have left much room for the introduction of novel treatments with better therapeutic efficacies and indices. As a result, intense research has focused on identifying new targets for developing such pharmacotherapies. One of these targets may be the phosphodiesterase (PDE) class of enzymes, which play important roles in intracellular signaling. Due to their critical roles in cellular pathways, these enzymes affect diverse neurobiological functions from learning and memory formation to neuroinflammation.

OBJECTIVES

In this paper, we reviewed studies on the use of PDE inhibitors (PDEIs) in preclinical models and clinical trials of psychiatric disorders including depression, anxiety, schizophrenia, post-traumatic stress disorder (PTSD), bipolar disorder (BP), sexual dysfunction, and feeding disorders.

RESULTS

PDEIs are able to improve symptoms of psychiatric disorders in preclinical models through activating the cAMP-PKA-CREB and cGMP-PKG pathways, attenuating neuroinflammation and oxidative stress, and stimulating neural plasticity. The most promising therapeutic candidates to emerge from these preclinical studies are PDE2 and PDE4 inhibitors for depression and anxiety and PDE1 and PDE10 inhibitors for schizophrenia. Furthermore, PDE3 and 4 inhibitors have shown promising results in clinical trials in patients with depression and schizophrenia.

CONCLUSIONS

Larger and better designed clinical studies of PDEIs in schizophrenia, depression, and anxiety are warranted to facilitate their translation into the clinic. Regarding the other conditions discussed in this review (most notably PTSD and BP), better characterization of the effects of PDEIs in preclinical models is required before clinical studies.

Phosphodiesterase inhibitor and selective serotonin reuptake inhibitor combination therapy versus monotherapy for the treatment of major depressive disorder: a systematic review and meta-analysis

OBJECTIVE

Selective serotonin reuptakeinhibitors (SSRIs) are the gold standard treatment for major depressive disorder (MDD). However, the use of phosphodiesterase (PDE) inhibitors in the treatment of MDD remains unclear. Our study aims to compare the effect of PDE inhibitor combination therapy to SSRI monotherapy for the treatment of MDD.

METHODS

We performed a comprehensive literature search using PubMed, EMBASE, and Web of Science databases, for studies that assess the impact of PDE inhibitor therapy on MDD patients. The primary outcome of our study was treatment response rate at the end of study time. Pooled odds ratio (OR) and corresponding 95% confidence intervals (CIs) were calculated using the random-effects model. A P-value <0.05 was considered statistically significant.

RESULTS

A total of four randomized control trials (RCTs), including 270 patients with MDD, were included in the analysis. Follow-up periods ranged from 6 to 12 weeks. The PDE inhibitor group was associated with a significantly higher treatment response rate (OR, 4.77; 95% CI, 2.05-11.12; P = 0.0003).

CONCLUSION

Our meta-analysis demonstrated that MDD patients receiving PDE inhibitor combination therapy had a higher treatment response rate than MDD patients receiving SSRI monotherapy. Further large-scale RCTs with long-term follow-ups are necessary to validate our findings.

White Matter Alterations in Depressive Disorder

Depressive disorder is the most prevalent affective disorder today. Depressive disorder has been linked to changes in the white matter. White matter changes in depressive disorder could be a result of impaired cerebral blood flow (CBF) and CBF self-regulation, impaired blood-brain barrier function, inflammatory factors, genes and environmental factors. Additionally, white matter changes in patients with depression are associated with clinical variables such as differential diagnosis, severity, treatment effect, and efficacy assessment. This review discusses the characteristics, possible mechanisms, clinical relevance, and potential treatment of white matter alterations caused by depressive disorders.