Neuropsychiatric Properties of the ACE2/Ang-(1-7)/Mas Pathway: A Brief Review

Diminazene aceturate attenuates systemic inflammation via microbiota gut-5-HT brain-spleen sympathetic axis in male mice

The sympathetic arm of the inflammatory reflex is the efferent pathway through which the central nervous system (CNS) can control peripheral immune responses. Diminazene aceturate (DIZE) is an antiparasitic drug that has been reported to exert protective effects on various experimental models of inflammation. However, the pathways by which DIZE promotes a protective immunomodulatory effects still need to be well established, and no studies demonstrate the capacity of DIZE to modulate a neural reflex to control inflammation. C57BL/6 male mice received intraperitoneal administration of DIZE (2 mg/Kg) followed by lipopolysaccharide (LPS, 5 mg/Kg, i.p.). Endotoxemic animals showed hyperresponsiveness to inflammatory signals, while those treated with DIZE promoted the activation of the inflammatory reflex to attenuate the inflammatory response during endotoxemia. The unilateral cervical vagotomy did not affect the anti-inflammatory effect of DIZE in the spleen and serum. At the same time, splenic denervation attenuated tumor necrosis factor (TNF) synthesis in the spleen and serum. Using broad-spectrum antibiotics for two weeks showed that LPS modulated the microbiota to induce a pro-inflammatory profile in the intestine and reduced the serum concentration of tryptophan and serotonin (5-HT), while DIZE restored serum tryptophan and increased the hypothalamic 5-HT levels. Furthermore, the treatment with 4-Chloro-DL-phenylalanine (pcpa, an inhibitor of 5-HT synthesis) abolished the anti-inflammatory effects of the DIZE in the spleen. Our results indicate that DIZE promotes microbiota modulation to increase central 5-HT levels and activates the efferent sympathetic arm of the inflammatory reflex to control splenic TNF production in endotoxemic mice.

Bradykinin actions in the central nervous system: historical overview and psychiatric implications

Bradykinin (BK), a well-studied mediator of physiological and pathological processes in the peripheral system, has garnered less attention regarding its function in the central nervous system, particularly in behavioural regulation. This review delves into the historical progression of research focused on the behavioural effects of BK and other drugs that act via similar mechanisms to provide new insights into the pathophysiology and pharmacotherapy of psychiatric disorders. Evidence from experiments with animal models indicates that BK modulates defensive reactions associated with panic symptoms and the response to acute stressors. The mechanisms are not entirely understood but point to complex interactions with other neurotransmitter systems, such as opioids, and intracellular signalling cascades. By addressing the existing research gaps in this field, we present new proposals for future research endeavours to foster a new era of investigation regarding BK's role in emotional regulation. Implications for psychiatry, chiefly for panic and depressive disorders are also discussed.

Therapeutic potential and possible mechanisms of ginseng for depression associated with COVID-19

Recently, a global outbreak of COVID-19 has rapidly spread to various national regions. As the number of COVID-19 patients has increased, some of those infected with SARS-CoV-2 have developed a variety of psychiatric symptoms, including depression, cognitive impairment, and fatigue. A distinct storm of inflammatory factors that contribute to the initial disease but also a persistent post-acute phase syndrome has been reported in patients with COVID-19. Neuropsychological symptoms including depression, cognitive impairment, and fatigue are closely related to circulating and local (brain) inflammatory factors. Natural products are currently being examined for their ability to treat numerous complications caused by COVID-19. Among them, ginseng has anti-inflammatory, immune system stimulating, neuroendocrine modulating, and other effects, which may help improve psychiatric symptoms. This review summarizes the basic mechanisms of COVID-19 pneumonia, psychiatric symptoms following coronavirus infections, effects of ginseng on depression, restlessness, and other psychiatric symptoms associated with post-COVID syn-dromes, as well as possible mechanisms underlying these effects.

Recent advances in anxiety disorders: Focus on animal models and pathological mechanisms

Anxiety disorders have become one of the most severe psychiatric disorders, and the incidence is increasing every year. They impose an extraordinary personal and socioeconomic burden. Anxiety disorders are influenced by multiple complex and interacting genetic, psychological, social, and environmental factors, which contribute to disruption or imbalance in homeostasis and eventually cause pathologic anxiety. The selection of a suitable animal model is important for the exploration of disease etiology and pathophysiology, and the development of new drugs. Therefore, a more comprehensive understanding of the advantages and limitations of existing animal models of anxiety disorders is helpful to further study the underlying pathological mechanisms of the disease. This review summarizes animal models and the pathogenesis of anxiety disorders, and discusses the current research status to provide insights for further study of anxiety disorders.

Nerve growth factor and angiotensin converting enzyme 2 levels in children with neurodevelopmental disorders

OBJECTIVE

Neurodevelopmental disorders (NDDs) are the most common psychiatric disorders in childhood, and there are many factors in their etiology. In recent years, many biomarkers have been studied to elucidate the etiology of these disorders. In this study, it was aimed to investigate the levels of nerve growth factor (NGF) and angiotensin converting enzyme 2 (ACE2) in attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID).

METHODS

The study included 74 children with NDDs (the number of patients in ADHD, ASD and ID groups were 24, 25 and 25 respectively) and 30 healthy controls (HCs). Serum NGF and ACE2 levels were studied with ELISA kits, also complete blood count (CBC), levels of fasting glucose and serum lipids were assessed.

RESULTS

ACE2 levels were found to be lower in NDD group than HCs in girls. In boys with ASD, triglyceride levels were significantly higher than other groups. Also a positive correlation was found between ACE2 and NGF levels when all sample assessed together.

CONCLUSIONS

This study is a premise for investigating ACE2 and NGF in NDDs. The role of these markers in ADHD, ASD, ID and other NDDs and their associations with gender should be assessed by studies in which both larger sample groups and more disorders.

Activation of Angiotensin-converting Enzyme 2 Protects Against Lipopolysaccharide-induced Glial Activation by Modulating Angiotensin-converting Enzyme 2/Angiotensin (1-7)/Mas Receptor Axis

Neuroinflammation is associated with activation of glial cells and pro-inflammatory arm of the central Renin Angiotensin System (RAS) namely, Angiotensin-Converting Enzyme/Angiotensin II/Angiotensin Type 1 Receptor (ACE/Ang II/AT1R) axis. Apart from this, another axis of RAS also exists, Angiotensin-Converting Enzyme 2/Angiotensin (1-7)/Mas Receptor (ACE2/Ang (1-7)/MasR), which counters ACE/Ang II/AT1R axis by showing anti-inflammatory properties. However, the role of ACE2/Ang (1-7)/MasR axis has not been explored in glial activation and neuroinflammation. Hence, the present study tries to unveil the role of ACE2/Ang (1-7)/MasR axis in lipopolysaccharide (LPS)-induced neuroinflammation using diminazene aceturate (DIZE), an ACE2 activator, in astroglial (C6) and microglial (BV2) cells as well as male SD rats. We found that ACE2 activation efficiently prevented LPS-induced changes by decreasing glial activation, inflammatory signaling, cell migration, ROS generation via upregulation of ACE2/Ang (1-7)/MasR signaling. In addition, activation of ACE2/Ang (1-7)/MasR axis by DIZE significantly suppressed the pro-inflammatory ACE/Ang II/AT1R axis by reducing Ang II level in neuroinflammatory conditions induced by LPS in both in vitro and in vivo. ACE2/Ang (1-7)/MasR axis activation further decreased mitochondrial depolarization and apoptosis, hence providing neuroprotection. Furthermore, to validate that the beneficial effect of the ACE2 activator was indeed through MasR, a selective MasR antagonist (A779) was used that significantly blocked the anti-inflammatory effect of ACE2 activation by DIZE. Hence, our study demonstrated that ACE2 activation imparted neuroprotection by enhancing ACE2/Ang (1-7)/MasR signaling which in turn decreased glial activation, neuroinflammation, and apoptosis and improved mitochondrial health.

Role of neuroinflammation mediated potential alterations in adult neurogenesis as a factor for neuropsychiatric symptoms in Post-Acute COVID-19 syndrome-A narrative review

Persistence of symptoms beyond the initial 3 to 4 weeks after infection is defined as post-acute COVID-19 syndrome (PACS). A wide range of neuropsychiatric symptoms like anxiety, depression, post-traumatic stress disorder, sleep disorders and cognitive disturbances have been observed in PACS. The review was conducted based on PRISMA-S guidelines for literature search strategy for systematic reviews. A cytokine storm in COVID-19 may cause a breach in the blood brain barrier leading to cytokine and SARS-CoV-2 entry into the brain. This triggers an immune response in the brain by activating microglia, astrocytes, and other immune cells leading to neuroinflammation. Various inflammatory biomarkers like inflammatory cytokines, chemokines, acute phase proteins and adhesion molecules have been implicated in psychiatric disorders and play a major role in the precipitation of neuropsychiatric symptoms. Impaired adult neurogenesis has been linked with a variety of disorders like depression, anxiety, cognitive decline, and dementia. Persistence of neuroinflammation was observed in COVID-19 survivors 3 months after recovery. Chronic neuroinflammation alters adult neurogenesis with pro-inflammatory cytokines supressing anti-inflammatory cytokines and chemokines favouring adult neurogenesis. Based on the prevalence of neuropsychiatric symptoms/disorders in PACS, there is more possibility for a potential impairment in adult neurogenesis in COVID-19 survivors. This narrative review aims to discuss the various neuroinflammatory processes during PACS and its effect on adult neurogenesis.

Brain-Derived Neurotrophic Factor and Extracellular Vesicle-Derived miRNAs in an Italian Cohort of Individuals With Obesity: A Key to Explain the Link Between Depression and Atherothrombosis

Background

Obesity and depression are intertwined diseases often associated with an increased risk of cardiovascular (CV) complications. Brain-Derived Neurotrophic Factor (BDNF), altered in the brain both of subjects with depression and obesity, provides a potential link between depression and thrombosis. Since the relationship among peripheral BDNF, depression and obesity is not well-defined, the aim of the present report has been to address this issue taking advantage of the contribution played by extracellular vesicle (EV)-derived miRNAs.

Research Process

Associations among circulating BDNF, depression and EV-derived miRNAs related to atherothrombosis have been evaluated in a large Italian cohort of obese individuals (n = 743), characterized by the Beck Depression Inventory (BDI-II) score.

Results

BDI-II was negatively associated with BDNF levels without a significant impact of the rs6265 BDNF polymorphism; this association was modified by raised levels of IFN-γ. BDNF levels were linked to an increase of 80 EV-derived miRNAs and a decrease of 59 miRNAs related to atherosclerosis and thrombosis. Network analysis identified at least 18 genes targeted by these miRNAs, 7 of which involved in depression and CV risk. The observation of a possible link among BDNF, depression, and miRNAs related to atherothrombosis and depression in obesity is novel and may lead to a wider use of BDNF as a CV risk biomarker in this specific subject group.

Impact of ACE2 genetic variant on antidepressant efficacy of SSRIs

Identification of a new axis of angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7)/Mas receptor, in the renin-angiotensin system (RAS), has opened a new insight regarding the role of RAS and angiotensin in higher brain functions. ACE2 catabolizes angiotensin II and produces angiotensin (1-7), an agonist of Mas receptor. Mice lacking the Mas receptor (angiotensin 1-7 receptor) exhibit anxiety-like behaviours. The present study was conducted to test the hypothesis of the involvement of ACE2 genetic variant (G8790A) on response to selective serotonin reuptake inhibitors (SSRIs). In a randomised control trial, 200 newly diagnosed Iranian patients with major depressive disorder completed 6 weeks of fluoxetine or sertraline treatment. Patients with a reduction of 50% or more in the Hamilton Rating Scale for Depression score were considered responsive to treatment. G8790A polymorphism was determined in extracted DNAs using restriction fragment length polymerase chain reaction method. Our results show that the A allele and AA and GA genotypes were significantly associated with better response to SSRIs (p = 0.008; OR = 3.4; 95% CI = 1.4-8.5 and p = 0.027; OR = 3.3, 95% CI = 1.2-9.2, respectively). Moreover, patients with GA and AA genotypes responded significantly better to sertraline (p = 0.0002; OR = 9.1; 95% CI = 2.4-33.7). The A allele was significantly associated with better response to sertraline (p = 0.0001; OR = 7.6; 95% CI = 2.5-23.3). In conclusion, our results confirm the role of G8790A in response to some SSRIs.

Angiotensinergic Neurotransmissions in the Medial Amygdala Nucleus Modulate Behavioral Changes in the Forced Swimming Test Evoked by Acute Restraint Stress in Rats

We investigated the role of angiotensin II type 1 (AT1 receptor) and type 2 (AT2 receptor) and MAS receptors present in the medial amygdaloid nucleus (MeA) in behavioral changes in the forced swimming test (FST) evoked by acute restraint stress in male rats. For this, rats received bilateral microinjection of either the selective AT1 receptor antagonist losartan, the selective AT2 receptor antagonist PD123319, the selective MAS receptor antagonist A-779, or vehicle 10 min before a 60 min restraint session. Then, behavior in the FST was evaluated immediately after the restraint (15 min session) and 24 h later (5 min session). The behavior in the FST of a non-stressed group was also evaluated. We observed that acute restraint stress decreased immobility during both sessions of the FST in animals treated with vehicle in the MeA. The decreased immobility during the first session was inhibited by intra-MeA administration of PD123319, whereas the effect during the second session was not identified in animals treated with A-779 into the MeA. Microinjection of PD123319 into the MeA also affected the pattern of active behaviors (i.e., swimming and climbing) during the second session of the FST. Taken together, these results indicate an involvement of angiotensinergic neurotransmissions within the MeA in behavioral changes in the FST evoked by stress.

Physical exercise effects on the brain during COVID-19 pandemic: links between mental and cardiovascular health

The current pandemic was caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The quarantine period during corona virus disease 19 (COVID-19) outbreak might affect the quality of life leading thousands of individuals to diminish the daily caloric expenditure and mobility, leading to a sedentary behavior and increase the number of health disorders. Exercising is used as a non-pharmacological treatment in many chronic diseases. Here, we review the molecular mechanisms of physical exercise in COVID-19 pandemic on mental health. We also point links between exercise, mental, and cardiovascular health. The infection caused by SARS-CoV-2 affects host cells binding to angiotensin-converting enzyme-2 (ACE2), which is the receptor for SARS-CoV-2. If there is not enough oxygen supply the lungs and other tissues, such as the heart or brain, are affected. SARS-CoV-2 enhances ACE2 leading to inflammation and neuronal death with possible development of mood disorders, such as depression and anxiety. Physical exercise also enhances the ACE2 expression. Conversely, the activation of ACE2/Ang 1-7/Mas axis by physical exercise induces an antiinflammatory and antifibrotic effect. Physical exercise has beneficial effects on mental health enhancing IGF-1, PI3K, BDNF, ERK, and reducing GSK3β levels. In addition, physical exercise enhances the activity of PGC-1α/ FNDC5/Irisin pathway leading to neuronal survival and the maintenance of a good mental health. Thus, SARS-CoV-2 infection leads to elevation of ACE2 levels through pathological mechanisms that lead to neurological and cardiovascular complications, while the physiological response of ACE2 to physical exercise improves cardiovascular and mental health.