The pharmacokinetic-pharmacodynamic model of azithromycin for lipopolysaccharide-induced depressive-like behavior in mice

Azithromycin preserves adult hippocampal neurogenesis and behavior in a mouse model of sepsis

The mammalian hippocampus can generate new neurons throughout life. Known as adult hippocampal neurogenesis (AHN), this process participates in learning, memory, mood regulation, and forgetting. The continuous incorporation of new neurons enhances the plasticity of the hippocampus and contributes to the cognitive reserve in aged individuals. However, the integrity of AHN is targeted by numerous pathological conditions, including neurodegenerative diseases and sustained inflammation. In this regard, the latter causes cognitive decline, mood alterations, and multiple AHN impairments. In fact, the systemic administration of Lipopolysaccharide (LPS) from E. coli to mice (a model of sepsis) triggers depression-like behavior, impairs pattern separation, and decreases the survival, maturation, and synaptic integration of adult-born hippocampal dentate granule cells. Here we tested the capacity of the macrolide antibiotic azithromycin to neutralize the deleterious consequences of LPS administration in female C57BL6J mice. This antibiotic exerted potent neuroprotective effects. It reversed the increased immobility time during the Porsolt test, hippocampal secretion of pro-inflammatory cytokines, and AHN impairments. Moreover, azithromycin promoted the synaptic integration of adult-born neurons and functionally remodeled the gut microbiome. Therefore, our data point to azithromycin as a clinically relevant drug with the putative capacity to ameliorate the negative consequences of chronic inflammation by modulating AHN and hippocampal-related behaviors.

Selective Inhibitors of Janus Kinase 3 Modify Responses to Lipopolysaccharides by Increasing the Interleukin-10-to-Tumor Necrosis Factor α Ratio

Janus kinase (JAK) inhibitors act at low doses (e.g., tofacitinib, 0.2-0.4 μmol/kg bid) in clinical use, suggesting an efficient underlying mode of action. We hypothesized that their effectiveness is due to their ability to raise the ratio of IL-10 to TNFα. Unlike other JAK isoforms, JAK3 is expressed mainly in hematopoietic cells and is essential for immune function. We used JAK3 selective inhibitors with preferential distribution to immune cells. Inhibition of JAK3 in human leukocytes reduced TNFα and IL-6 but maintained levels of IL-10, while pan-JAK inhibitors increased TNFα, IL-6, and IL-10. JAK1 is required for IL-10 receptor signaling, which suggests that, at exposure above the IC50 (55 nM for tofacitinib on JAK1), there is less feedback control of TNFα levels. This leads to self-limiting effects of JAK1 inhibitors and could place an upper limit on appropriate doses. In vivo, treating mice with JAK3 inhibitors before LPS administration decreased plasma TNFα and increased IL-10 above vehicle levels, suggesting that JAK3 inhibition may limit TNFα release by increasing IL-10 while leaving the IL-10 receptor functional. This mechanism should have general utility in controlling autoimmune diseases and can be conveniently observed by measuring the ratio of IL-10 to TNFα. In summary, our targeted, "leukotropic" inhibitors more effectively increased IL-10/TNFα ratios than unselective control compounds and could, therefore, be ideal for autoimmune therapy.

Gut Hormones as Potential Therapeutic Targets or Biomarkers of Response in Depression: The Case of Motilin

Recent research has identified the gut–brain axis as a key mechanistic pathway and potential therapeutic target in depression. In this paper, the potential role of gut hormones as potential treatments or predictors of response in depression is examined, with specific reference to the peptide hormone motilin. This possibility is explored through two methods: (1) a conceptual review of the possible links between motilin and depression, including evidence from animal and human research as well as clinical trials, based on a literature search of three scientific databases, and (2) an analysis of the relationship between a functional polymorphism (rs2281820) of the motilin (MLN) gene and cross-national variations in the prevalence of depression based on allele frequency data after correction for potential confounders. It was observed that (1) there are several plausible mechanisms, including interactions with diet, monoamine, and neuroendocrine pathways, to suggest that motilin may be relevant to the pathophysiology and treatment of depression, and (2) there was a significant correlation between rs2281820 allele frequencies and the prevalence of depression after correcting for multiple confounding factors. These results suggest that further evaluation of the utility of motilin and related gut peptides as markers of antidepressant response is required and that these molecular pathways represent potential future mechanisms for antidepressant drug development.

What Animal Models Can Tell Us About Long-Term Psychiatric Symptoms in Sepsis Survivors: a Systematic Review

Lower sepsis mortality rates imply that more patients are discharged from the hospital, but sepsis survivors often experience sequelae, such as functional disability, cognitive impairment, and psychiatric morbidity. Nevertheless, the mechanisms underlying these long-term disabilities are not fully understood. Considering the extensive use of animal models in the study of the pathogenesis of neuropsychiatric disorders, it seems adopting this approach to improve our knowledge of postseptic psychiatric symptoms is a logical approach. With the purpose of gathering and summarizing the main findings of studies using animal models of sepsis-induced psychiatric symptoms, we performed a systematic review of the literature on this topic. Thus, 140 references were reviewed, and most of the published studies suggested a time-dependent recovery from behavior alterations, despite the fact that some molecular alterations persist in the brain. This review reveals that animal models can be used to understand the mechanisms that underlie anxiety and depression in animals recovering from sepsis.

The Bidirectional Relationship of Depression and Inflammation: Double Trouble

Depression represents the number one cause of disability worldwide and is often fatal. Inflammatory processes have been implicated in the pathophysiology of depression. It is now well established that dysregulation of both the innate and adaptive immune systems occur in depressed patients and hinder favorable prognosis, including antidepressant responses. In this review, we describe how the immune system regulates mood and the potential causes of the dysregulated inflammatory responses in depressed patients. However, the proportion of never-treated major depressive disorder (MDD) patients who exhibit inflammation remains to be clarified, as the heterogeneity in inflammation findings may stem in part from examining MDD patients with varied interventions. Inflammation is likely a critical disease modifier, promoting susceptibility to depression. Controlling inflammation might provide an overall therapeutic benefit, regardless of whether it is secondary to early life trauma, a more acute stress response, microbiome alterations, a genetic diathesis, or a combination of these and other factors.

Three insights on psychoneuroimmunology of mood disorders to be taken from the COVID-19 pandemic

In the recent months, the world was taken by surprise by the outbreak of a coronavirus (SARS-CoV-2) pandemic (COVID-19). The COVID-19 pandemic is a unique opportunity to advance the understanding of the association of respiratory viruses with mood disorders and suicide. In this editorial, we explore three insights to the neuropsychoneuroimmunology of mood disorders that could be taken from the COVID-19 pandemic.

Depression's Unholy Trinity: Dysregulated Stress, Immunity, and the Microbiome

Depression remains one of the most prevalent psychiatric disorders, with many patients not responding adequately to available treatments. Chronic or early-life stress is one of the key risk factors for depression. In addition, a growing body of data implicates chronic inflammation as a major player in depression pathogenesis. More recently, the gut microbiota has emerged as an important regulator of brain and behavior and also has been linked to depression. However, how this holy trinity of risk factors interact to maintain physiological homeostasis in the brain and body is not fully understood. In this review, we integrate the available data from animal and human studies on these three factors in the etiology and progression of depression. We also focus on the processes by which this microbiota-immune-stress matrix may influence centrally mediated events and on possible therapeutic interventions to correct imbalances in this triune.

Pharmacokinetic-pharmacodynamic model of the antihypertensive interaction between telmisartan and hydrochlorothiazide in spontaneously hypertensive rats

OBJECTIVES

The goal of this study was to establish an integrated indirect response pharmacokinetic-pharmacodynamic model between telmisartan and hydrochlorothiazide to describe the antihypertensive interaction of these two drugs in spontaneously hypertensive rats.

METHODS

The blood pressure and plasma concentrations were measured by the tail-cuff test and high performance liquid chromatography-mass spectrometry, respectively, in spontaneously hypertensive rats. The current pharmacokinetic-pharmacodynamic model was based on the non-competitive pharmacodynamic interaction of two drugs acting on different physiological processes.

KEY FINDINGS

This model was able to acquire the temporal changes in drug concentration and blood pressure after administration of telmisartan or hydrochlorothiazide. The noncompetitive pharmacodynamic interaction assumed that the decreased blood pressure was attributed to the inhibitory function of telmisartan and stimulatory function of hydrochlorothiazide after administration of these two drugs. There was no significant pharmacokinetic change of telmisartan and hydrochlorothiazide in the different groups tested. The model predicted a synergistic pharmacodynamic interaction when telmisartan was administered in combination with hydrochlorothiazide, which was notably stronger than if the effects were additive.

CONCLUSION

The results showed that the presented pharmacokinetic-pharmacodynamic model was suitable for describing the antihypertensive interaction between telmisartan and hydrochlorothiazide.

Azithromycin: mechanisms of action and their relevance for clinical applications

Azithromycin is a macrolide antibiotic which inhibits bacterial protein synthesis, quorum-sensing and reduces the formation of biofilm. Accumulating effectively in cells, particularly phagocytes, it is delivered in high concentrations to sites of infection, as reflected in rapid plasma clearance and extensive tissue distribution. Azithromycin is indicated for respiratory, urogenital, dermal and other bacterial infections, and exerts immunomodulatory effects in chronic inflammatory disorders, including diffuse panbronchiolitis, post-transplant bronchiolitis and rosacea. Modulation of host responses facilitates its long-term therapeutic benefit in cystic fibrosis, non-cystic fibrosis bronchiectasis, exacerbations of chronic obstructive pulmonary disease (COPD) and non-eosinophilic asthma. Initial, stimulatory effects of azithromycin on immune and epithelial cells, involving interactions with phospholipids and Erk1/2, are followed by later modulation of transcription factors AP-1, NFκB, inflammatory cytokine and mucin release. Delayed inhibitory effects on cell function and high lysosomal accumulation accompany disruption of protein and intracellular lipid transport, regulation of surface receptor expression, of macrophage phenotype and autophagy. These later changes underlie many immunomodulatory effects of azithromycin, contributing to resolution of acute infections and reduction of exacerbations in chronic airway diseases. A sub-group of post-transplant bronchiolitis patients appears to be sensitive to azithromycin, as may be patients with severe sepsis. Other promising indications include chronic prostatitis and periodontitis, but weak activity in malaria is unlikely to prove crucial. Long-term administration of azithromycin must be balanced against the potential for increased bacterial resistance. Azithromycin has a very good record of safety, but recent reports indicate rare cases of cardiac torsades des pointes in patients at risk.