Interleukin-17-targeted treatment in patients with spondyloarthritis and associated cardiometabolic risk profile.

Spondyloarthritis is a group of immune-mediated rheumatic disorders that significantly impact patients' physical function and quality of life. Patients with spondyloarthritis experience a greater prevalence of cardiometabolic disorders, such as obesity, hypertension, dyslipidemia and diabetes mellitus, and these comorbidities are associated with increased spondyloarthritis disease activity and risk of cardiovascular events. This narrative review summarizes the evidence for a physiological link between inflammatory status and cardiometabolic comorbidities in spondyloarthritis, as well as the impact of interleukin (IL)-17 blockade versus other molecular mechanisms in patients with cardiometabolic conditions. The IL-23/IL-17 axis plays a pivotal role in the pathophysiology of spondyloarthritis by promoting inflammation and tissue remodeling at the affected joints and entheses. The importance of the IL-23/IL-17 signaling cascade in underlying sub-clinical inflammation in common cardiometabolic disorders suggests the existence of shared pathways between these processes and spondyloarthritis pathophysiology. Thus, a bidirectional relationship exists between the effects of biologic drugs and patients' cardiometabolic profile, which must be considered during treatment decision making. Biologic therapy may induce changes in patients' cardiometabolic status and cardiometabolic conditions may conversely impact the clinical response to biologic therapy. Available evidence regarding the impact of IL-17 blockade with secukinumab on cardiometabolic parameters suggests this drug does not interfere with traditional cardiovascular risk markers and could be associated with a decreased risk of cardiovascular events. Additionally, the efficacy and retention rates of secukinumab do not appear to be negatively affected by obesity, with some studies reporting a positive impact on clinical outcomes, contrary to that described with other approaches, such as tumor necrosis factor blockade. In this article, we also review evidence for this bidirectional association with other treatments for spondyloarthritis. Current evidence suggests that IL-17-targeted therapy with secukinumab is highly effective in spondyloarthritis patients with cardiometabolic comorbidities and may provide additional cardiometabolic benefits.

Enhanced Stress Response in 5-HT1AR Overexpressing Mice: Altered HPA Function and Hippocampal Long-Term Potentiation.

Postsynaptic 5-HT1A receptors (5-HT1AR) play an important role in anxiety and stress, although their contribution is still controversial. Previous studies report that mice overexpressing postsynaptic 5-HT1ARs show no changes in basal anxiety, though the influence of stress conditions has not been addressed yet. In this study, we used this animal model to evaluate the role of 5-HT1ARs in anxiety response after pre-exposure to an acute stressor. Under basal conditions, 5-HT1AR overexpressing animals presented high corticosterone levels and a lower mineralocorticoid/glucocorticoid receptor ratio. After pre-exposure to a single stressor, they showed a high anxiety-like response, associated with a blunted increase in corticosterone levels and higher c-Fos activation in the prefrontal cortex. Moreover, these mice also presented a lack of downregulation of hippocampal long-term potentiation after stress exposure. Therefore, higher postsynaptic 5-HT1AR activation might predispose to a high anxious phenotype and an impaired stress coping behavior.

Behavioral, neurochemical and molecular changes after acute deep brain stimulation of the infralimbic prefrontal cortex.

Deep brain stimulation (DBS) is a treatment that has shown some efficacy in treatment-resistant depression. In particular, DBS of the subcallosal cingulate gyrus (Brodmann's area 25, Cg25) has been successfully applied to treat refractory depression. In the rat, we have demonstrated that DBS applied to infralimbic (IL) cortex elevates the levels of glutamate and monoamines in the prefrontal cortex, and requires the stimulation of cortical α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptors for its antidepressant-like effects. However, the molecular targets of IL DBS are not fully known. To gain insight into these pathways, we have investigated whether IL DBS is able to reverse the behavioral, biochemical and molecular changes exhibited by the olfactory bulbectomized (OBX) rat. Our results revealed that 1 h IL DBS diminished hyperlocomotion, hyperemotionality and anhedonia, and increased social interaction shown by the OBX rats. Further, IL DBS increased prefrontal efflux of glutamate and serotonin in both sham-operated and OBX rats. With regard to molecular targets, IL DBS increases the synthesis of brain-derived neurotrophic factor (BDNF) and the GluA1 AMPA receptor subunit, and stimulates the Akt/mammalian target of rapamycin (mTOR) as well as the AMPA receptor/c-AMP response element binding (CREB) pathways. Temsirolimus, a known in vivo mTOR blocker, suppressed the antidepressant-like effect of IL DBS in naïve rats in the forced swim test, thus demonstrating for the first time that mTOR signaling is required for the antidepressant-like effects of IL DBS, which is in line with the antidepressant response of other rapid-acting antidepressant drugs.

Cannabidiol induces rapid-acting antidepressant-like effects and enhances cortical 5-HT/glutamate neurotransmission: role of 5-HT1A receptors.

Cannabidiol (CBD), the main non-psychotomimetic component of marihuana, exhibits anxiolytic-like properties in many behavioural tests, although its potential for treating major depression has been poorly explored. Moreover, the mechanism of action of CBD remains unclear. Herein, we have evaluated the effects of CBD following acute and chronic administration in the olfactory bulbectomy mouse model of depression (OBX), and investigated the underlying mechanism. For this purpose, we conducted behavioural (open field and sucrose preference tests) and neurochemical (microdialysis and autoradiography of 5-HT1A receptor functionality) studies following treatment with CBD. We also assayed the pharmacological antagonism of the effects of CBD to dissect out the mechanism of action. Our results demonstrate that CBD exerts fast and maintained antidepressant-like effects as evidenced by the reversal of the OBX-induced hyperactivity and anhedonia. In vivo microdialysis revealed that the administration of CBD significantly enhanced serotonin and glutamate levels in vmPFCx in a different manner depending on the emotional state and the duration of the treatment. The potentiating effect upon neurotransmitters levels occurring immediately after the first injection of CBD might underlie the fast antidepressant-like actions in OBX mice. Both antidepressant-like effect and enhanced cortical 5-HT/glutamate neurotransmission induced by CBD were prevented by 5-HT1A receptor blockade. Moreover, adaptive changes in pre- and post-synaptic 5-HT1A receptor functionality were also found after chronic CBD. In conclusion, our findings indicate that CBD could represent a novel fast antidepressant drug, via enhancing both serotonergic and glutamate cortical signalling through a 5-HT1A receptor-dependent mechanism.

Serotonin 5-HT4 receptors: A new strategy for developing fast acting antidepressants?

The regulation of the activity of brain monoaminergic systems has been the focus of attention of many studies since the first antidepressant drug emerged 50 years ago. The search for novel antidepressants is deeply linked to the search for fast-acting strategies, taking into account that 2-4 weeks of treatment with classical antidepressant are required before clinical remission of the symptoms becomes evident. In the recent years several hypotheses have been proposed on the basis of the existence of alterations in brain synaptic plasticity in major depression. Recent evidences support a role for 5-HT4 receptors in the pathogenesis of depression as well as in the mechanism of action of antidepressant drugs. In fact, chronic treatment with antidepressant drugs appears to modulate, at different levels, the signaling pathway associated to 5-HT4 receptors, as well as their levels of expression in the brain. Moreover, several experimental studies have identified this receptor subtype as a promising new target for fast-acting antidepressant strategy: the administration of partial agonists of this receptor induces a number of responses similar to those observed after chronic treatment with classical antidepressants, but with a rapid onset of action. They include efficacy in behavioral models of depression, rapid desensitization of 5-HT1A autoreceptors, and modifications in the expression of several molecular markers of brain neuroplasticity. Although much work remains to be done in order to clarify the real therapeutic potential of these drugs, the evidences reviewed below support the hypothesis that 5-HT4 receptor partial agonists could behave as rapid and effective antidepressants.

Neural plasticity and proliferation in the generation of antidepressant effects: hippocampal implication.

It is widely accepted that changes underlying depression and antidepressant-like effects involve not only alterations in the levels of neurotransmitters as monoamines and their receptors in the brain, but also structural and functional changes far beyond. During the last two decades, emerging theories are providing new explanations about the neurobiology of depression and the mechanism of action of antidepressant strategies based on cellular changes at the CNS level. The neurotrophic/plasticity hypothesis of depression, proposed more than a decade ago, is now supported by multiple basic and clinical studies focused on the role of intracellular-signalling cascades that govern neural proliferation and plasticity. Herein, we review the state-of-the-art of the changes in these signalling pathways which appear to underlie both depressive disorders and antidepressant actions. We will especially focus on the hippocampal cellularity and plasticity modulation by serotonin, trophic factors as brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) through intracellular signalling pathways-cAMP, Wnt/ ß -catenin, and mTOR. Connecting the classic monoaminergic hypothesis with proliferation/neuroplasticity-related evidence is an appealing and comprehensive attempt for improving our knowledge about the neurobiological events leading to depression and associated to antidepressant therapies.

Social isolation differentially affects anxiety and depressive-like responses of bulbectomized mice.

Social isolation in rodents may interfere in their behavioural responses on paradigms used to test anxiety- and depressive-like states. Herein we study the influence of social isolation upon the behavioural responses of olfactory bulbectomized mice (OBX). In the open-field test (OFT), social isolation enhanced OBX-induced hyperactivity and exploratory behaviour. However, OBX-induced anxiety in the OFT (central activity) was less apparent after isolation, due to the increased level of anxiety showed by the sham-isolated counterparts. In the novelty-suppressed feeding (NSF), isolation derived in an increased latency to feeding of both OBX and sham mice. The isolation did not affect the response of OBX mice and sham mice in the forced-swimming test (FST). Interestingly, OBX animals exhibited an increased immobility time during the FST, though a dramatic decrease in the climbing scores. Finally, OBX-induced anhedonia in the sucrose intake test was not affected by housing conditions. Our findings demonstrate that social isolation influences the performance of OBX mice in some behavioural paradigms, thus facilitating the characterization of depressive-like states, and by contrast, hindering anxiety-related behaviours. This fact should be taken into account in order to minimize economical and time-consuming efforts when assessing potential antidepressant and anxiolytic drugs.

New strategies in the development of antidepressants: towards the modulation of neuroplasticity pathways.

Over the past five decades, the pharmacological treatment of depression has been based on the pathophysiological hypothesis of a deficiency in monoamines, mainly serotonin and noradrenaline. Antidepressant prescribed today, all of them designed to enhance central monoaminergic tone, present several important limitations, including a 2-5 weeks response lag and also a limited clinical efficacy. As it is increasingly evident that the abnormalities associated to depression go beyond monoamines, the development of better antidepressants will depend on the identification and understanding of new cellular targets. In this regard, much evidence supports a role for cellular and molecular mechanisms of neuroplasticity, including neurotrophic inputs, in mood disorders, in parallel with the biological features associated to stress conditions. In order to illustrate the possible relevance of neuroplasticity-related pathways for the therapy of depressive states, we here review the biological evidence supporting some therapeutic strategies in a very initial phase of development (modulation of the Wnt/GSK-3ß/ß-catenin pathway, potentiation of endocannabinoid activity, agonism of 5-HT(4) receptors), which involve modulation of downstream mechanisms and neuroplasticity circuits. These strategies also show the existence of mixed mechanisms of action, constituting a nexus between the "classic" aminergic theory and the "new" neuroplasticity hypothesis.