Pharmacological augmentation of endocannabinoid signaling reduces the neuroendocrine response to stress

Sex-Specific Differences and the Role of Environmental Enrichment in the Expression of Hippocampal CB1 Receptors following Chronic Unpredictable Stress

Stress-related mental disorders have become increasingly prevalent, thus endangering mental health worldwide. Exploring stress-associated brain alterations is vital for understanding the possible neurobiological mechanisms underlying these changes. Based on existing evidence, the brain endogenous cannabinoid system (ECS) plays a significant role in the stress response, and disruptions in its function are associated with the neurobiology of various stress-related disorders. This study primarily focuses on investigating the impact of chronic unpredictable stress (CUS) on the expression of hippocampal cannabinoid type 1 (CB1) receptors, part of the ECS, in adult male and female Wistar rats. Additionally, it explores whether environmental enrichment (EE) initiated during adolescence could mitigate the CUS-associated alterations in CB1 expression. Wistar rats, shortly after weaning, were placed in either standard housing (SH) or EE conditions for a duration of 10 weeks. On postnatal day 66, specific subgroups of SH or EE animals underwent a 4-week CUS protocol. Western blot (WB) analysis was conducted in the whole hippocampus of the left brain hemisphere to assess total CB1 protein expression, while immunohistochemistry (IHC) was performed on the right hemisphere to estimate the expression of CB1 receptors in certain hippocampal areas (i.e., CA1, CA3 and dentate gyrus-DG). The WB analysis revealed no statistically significant differences in total CB1 protein levels among the groups; however, reduced CB1 expression was found in specific hippocampal sub-regions using IHC. Specifically, CUS significantly decreased CB1 receptor expression in the CA1 and DG of both sexes, whereas in CA3 the CUS-associated decrease was limited to SH males. Interestingly, EE housing proved protective against these reductions. These findings suggest a region and sex-specific endocannabinoid response to chronic stress, emphasizing the role of positive early experiences in the protection of the adolescent brain against adverse conditions later in life.

Oxytocin alleviates periodontitis in adult rats

OBJECTIVE

The objective of the study was to evaluate the expression of oxytocin receptors in normal and inflamed gingiva, as well as the effects of systemic administration of oxytocin in bone loss and gum inflammatory mediators in a rat model of experimental periodontitis.

BACKGROUND DATA

Current evidence supports the hypothesis of a disbalance between the oral microbiota and the host's immune response in the pathogenesis of periodontitis. Increased complexity of the microbial biofilm present in the periodontal pocket leads to local production of nitrogen and oxygen-reactive species, cytokines, chemokines, and other proinflammatory mediators which contribute to periodontal tissue destruction and bone loss. Oxytocin has been suggested to participate in the modulation of immune and inflammatory processes. We have previously shown that oxytocin, nitric oxide, and endocannabinoid system interact providing a mechanism of regulation for systemic inflammation. Here, we aimed at investigating not only the presence and levels of expression of oxytocin receptors on healthy and inflamed gingiva, but also the effects of oxytocin treatment on alveolar bone loss, and systemic and gum expression of inflammatory mediators involved in periodontal tissue damage using ligature-induced periodontitis. Therefore, anti-inflammatory strategies oriented at modulating the host's immune response could be valuable adjuvants to the main treatment of periodontal disease.

METHODS

We used an animal model of ligature-induced periodontitis involving the placement of a linen thread (Barbour flax 100% linen suture, No. 50; size 2/0) ligature around the neck of first lower molars of adult male rats. The ligature was left in place during the entire experiment (7 days) until euthanasia. Animals with periodontitis received daily treatment with oxytocin (OXT, 1000 μg/kg, sc.) or vehicle and/or atosiban (3 mg/kg, sc.), an antagonist of oxytocin receptors. The distance between the cement-enamel junction and the alveolar bone crest was measured in stained hemimandibles in the long axis of both buccal and lingual surfaces of both inferior first molars using a caliper. TNF-α levels in plasma were determined using specific rat enzyme-linked immunosorbent assays (ELISA). OXT receptors, IL-6, IL-1β, and TNF-α expression were determined in gingival tissues by semiquantitative or real-time PCR.

RESULTS

We show that oxytocin receptors are expressed in normal and inflamed gingival tissues in male rats. We also show that the systemic administration of oxytocin prevents the experimental periodontitis-induced increased gum expression of oxytocin receptors, TNF-α, IL-6, and IL-1β (p < .05). Furthermore, we observed a reduction in bone loss in rats treated with oxytocin in our model.

CONCLUSIONS

Our results demonstrate that oxytocin is a novel and potent modulator of the gingival inflammatory process together with bone loss preventing effects in an experimental model of ligature-induced periodontitis.

Nicotine exposure during breastfeeding alters the expression of endocannabinoid system biomarkers in female but not in male offspring at adulthood

Early nicotine exposure compromises offspring's phenotype at long-term in both sexes. We hypothesize that offspring exposed to nicotine during breastfeeding show deregulated central and peripheral endocannabinoid system (ECS), compromising several aspects of their metabolism. Lactating rats received nicotine (NIC, 6 mg/Kg/day) or saline from postnatal day (PND) 2 to 16 through implanted osmotic minipumps. Offspring were analyzed at PND180. We evaluated protein expression of N-acylphosphatidylethanolamide-phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), diacylglycerol lipase (DAGL), monoacylglycerol lipase (MAGL) and cannabinoid receptors (CB1 and/or CB2) in lateral hypothalamus, paraventricular nucleus of the hypothalamus, liver, visceral adipose tissue (VAT), adrenal and thyroid. NIC offspring from both sexes did not show differences in hypothalamic ECS markers. Peripheral ECS markers showed no alterations in NIC males. In contrast, NIC females had lower liver DAGL and CB1, higher VAT DAGL, higher adrenal NAPE-PLD and higher thyroid FAAH. Endocannabinoids biosynthesis was affected by nicotine exposure during breastfeeding only in females; alterations in peripheral tissues suggest lower action in liver and higher action in VAT, adrenal and thyroid. Effects of nicotine exposure during lactation on ECS markers are sex- and tissue-dependent. This characterization helps understanding the phenotype of the adult offspring in this model and may contribute to the development of new pharmacological targets for the treatment of several metabolic diseases that originate during development.

Cannabidiol: Bridge between Antioxidant Effect, Cellular Protection, and Cognitive and Physical Performance

The literature provides scientific evidence for the beneficial effects of cannabidiol (CBD), and these effects extend beyond epilepsy treatment (e.g., Lennox-Gastaut and Dravet syndromes), notably the influence on oxidative status, neurodegeneration, cellular protection, cognitive function, and physical performance. However, products containing CBD are not allowed to be marketed everywhere in the world, which may ultimately have a negative effect on health as a result of the uncontrolled CBD market. After the isolation of CBD follows the discovery of CB1 and CB2 receptors and the main enzymatic components (diacylglycerol lipase (DAG lipase), monoacyl glycerol lipase (MAGL), fatty acid amino hydrolase (FAAH)). At the same time, the antioxidant potential of CBD is due not only to the molecular structure but also to the fact that this compound increases the expression of the main endogenous antioxidant systems, superoxide dismutase (SOD), and glutathione peroxidase (GPx), through the nuclear complex erythroid 2-related factor (Nrf2)/Keep1. Regarding the role in the control of inflammation, this function is exercised by inhibiting (nuclear factor kappa B) NF-κB, and also the genes that encode the expression of molecules with a pro-inflammatory role (cytokines and metalloproteinases). The other effects of CBD on cognitive function and physical performance should not be excluded. In conclusion, the CBD market needs to be regulated more thoroughly, given the previously listed properties, with the mention that the safety profile is a very good one.

The use of biochemical indexes in hair for clinical studies of psychiatric diseases: What can we learn about mental disease from hair?

Analysis of hair samples provides unique advantages, including non-invasive sampling, sample stability, and the possibility of additional optimization of high sensitivity detection methods. Hair sample analysis is often used in psychiatric disease research to evaluate previous periods of stress encountered by patients. Glucocorticoid analysis is the most frequently tested indicator of stress. Furthermore, the hypothalamus-pituitary-gonad axis and endocannabinoid system also are involved in the occurrence and development of mental disorders. The endocannabinoid and sex hormone levels in patients experiencing mental illness are considerably different from levels observed in healthy individuals. Nevertheless, due to the different methods used to assess the degree of disease and the range of analytical methods involved in clinical research, the trends in changes for these biomarkers are not uniform. The correlations between changes in biomarker concentrations and illness severity also are not clear. The observed alterations suggest these biochemical substances in hair have potential as biomarkers for diagnosis or predictive treatment. However, the variable results obtained thus far could hamper further development of hair samples for clinical assessment in psychiatric disorders. This article summarizes the published reports documenting the changes in the content of relevant substances in hair in individuals experiencing mental illness and the degree of correlation. In the discussion section, we proposed several issues that should be considered in future studies of hair samples obtained from patients with mental disorders to promote the use of hair sample assessment as an aid in diagnosis or predictive treatment.

Combinatorial approaches for treating neuropsychiatric social impairment

Social behaviour is an essential component of human life and deficits in social function are seen across multiple psychiatric conditions with high morbidity. However, there are currently no FDA-approved treatments for social dysfunction. Since social cognition and behaviour rely on multiple signalling processes acting in concert across various neural networks, treatments aimed at social function may inherently require a combinatorial approach. Here, we describe the social neurobiology of the oxytocin and endocannabinoid signalling systems as well as translational evidence for their use in treating symptoms in the social domain. We leverage this systems neurobiology to propose a network-based framework that involves pharmacology, psychotherapy, non-invasive brain stimulation and social skills training to combinatorially target trans-diagnostic social impairment. Lastly, we discuss the combined use of oxytocin and endocannabinoids within our proposed framework as an illustrative strategy to treat specific aspects of social function. Using this framework provides a roadmap for actionable treatment strategies for neuropsychiatric social impairment. This article is part of the theme issue 'Interplays between oxytocin and other neuromodulators in shaping complex social behaviours'.

Endocannabinoid system in the neuroendocrine response to LPS-induced immune challenge

The endocannabinoid system plays a key role in the intersection of the nervous, endocrine, and immune system, regulating not only their functions but also how they interplay with each other. Endogenous ligands, named endocannabinoids, are produced “on demand” to finely regulate the synthesis and secretion of hormones and neurotransmitters, as well as to regulate the production of cytokines and other proinflammatory mediators.

It is well known that immune challenges, such as exposure to lipopolysaccharide (LPS), the main component of the Gram-negative bacteria cell wall, disrupts not only the hypothalamic-pituitary-adrenal axis but also affects other endocrine systems such as the hypothalamic-pituitary-gonadal axis and the release of oxytocin from the neurohypophysis. Here we explore which actors and molecular mechanisms are involved in these processes.

Hydroalcoholic Leaf Extract of Isatis tinctoria L. via Antioxidative and Anti-Inflammatory Effects Reduces Stress-Induced Behavioral and Cellular Disorders in Mice

Stress that can occur at different levels of a person’s life can cause and exacerbate various diseases. Oxidative stress and inflammation underlie this process at the cellular level. There is an urgent need to identify new and more effective therapeutic targets for the treatment of stress-induced behavioral disorders and specific drugs that affect these targets. Isatis tinctoria L. is a herbaceous species in the Brassicaceae family. Due to its potential antioxidant, nitric oxide- (NO-) inhibiting, anti-inflammatory, and neuroprotective properties, I. tinctoria could be used to treat depression, anxiety, and stress resistance. Hence, the present study is aimed at delineating whether administration of I. tinctoria leaf extract may improve stress-induced disorders in mice. A set of four behavioral tests was selected that together are suitable for phenotyping acute restraint stress-associated behaviors in mice, namely locomotor activity, social integration, dark/light box, and splash tests. The plasma and brains were collected. A brain-derived neurotrophic factor, tumor necrosis factor-alpha, C-reactive protein, corticosterone, NO, reactive oxygen species levels, superoxide dismutase and catalase activity, and ferric-reducing antioxidant power were measured. In mice stressed by immobilization, decreased locomotor activity, anxiety-like behavior, and contact with other individuals were observed, as well as increased oxidative stress and increased levels of nitric oxide in the brain and plasma C-reactive protein. A single administration of I. tinctoria leaf extract was able to reverse the behavioral response to restraint by a mechanism partially dependent on the modulation of oxidative stress, neuroinflammation, and NO reduction. In conclusion, Isatis tinctoria hydroalcoholic leaf extract can reduce stress-induced behavioral disturbances by regulating neurooxidative, neuronitrosative, and neuroimmune pathways. Therefore, it could be recommended for further research on clinical efficacy in depression and anxiety disorder treatment.

TRP Channels as Molecular Targets to Relieve Endocrine-Related Diseases

Transient receptor potential (TRP) channels are polymodal channels capable of sensing environmental stimuli, which are widely expressed on the plasma membrane of cells and play an essential role in the physiological or pathological processes of cells as sensors. TRPs often form functional homo- or heterotetramers that act as cation channels to flow Na⁺ and Ca²⁺, change membrane potential and [Ca²⁺]_i (cytosolic [Ca²⁺]), and change protein expression levels, channel attributes, and regulatory factors. Under normal circumstances, various TRP channels respond to intracellular and extracellular stimuli such as temperature, pH, osmotic pressure, chemicals, cytokines, and cell damage and depletion of Ca²⁺ reserves. As cation transport channels and physical and chemical stimulation receptors, TRPs play an important role in regulating secretion, interfering with cell proliferation, and affecting neural activity in these glands and their adenocarcinoma cells. Many studies have proved that TRPs are widely distributed in the pancreas, adrenal gland, and other glands. This article reviews the specific regulatory mechanisms of various TRP channels in some common glands (pancreas, salivary gland, lacrimal gland, adrenal gland, mammary gland, gallbladder, and sweat gland).

Molecular Alterations of the Endocannabinoid System in Psychiatric Disorders

The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.

TRPV1 blockers as potential new treatments for psychiatric disorders

The transient receptor potential vanilloid-1 channel (TRPV1) is responsible for decoding physical and chemical stimuli. TRPV1 is activated by capsaicin (a compound from chili peppers), heat (above 43°C) and acid environment, playing a major role in pain, inflammation and body temperature. Molecular and histological studies have suggested TRPV1 expression in specific brain regions, where it can be activated primarily by the endocannabinoid anandamide, fostering studies on its potential role in psychiatric disorders. TRPV1 blockers are effective in various animal models predictive of anxiolytic and antipanic activities, in addition to reducing conditioned fear. In models of antidepressant activity, these compounds reduce behavioral despair and promote active stress-coping behavior. TRPV1 blockers also reduce the effects of certain drugs of abuse and revert behavioral changes in animal models of neurodevelopmental disorders. The main limiting factor in developing TRPV1 blockers as therapeutic agents concerns their effects on body temperature, particularly hyperthermia. New compounds, which block specific states of the channel, could represent an alternative. Moreover, compounds blocking both TRPV1 and the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), termed dual TRPV1/FAAH blockers, have been investigated with promising results. Overall, preclinical studies yield favorable results with TRPV1 blockers in animal models of psychiatric disorders.

Effects of endocannabinoids on feed intake, stress response and whole-body energy metabolism in dairy cows

Endocannabinoids, particularly anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are instrumental in regulating energy homeostasis and stress response. However, little is known about the endocannabinoid system (ECS) in ruminants, although EC could improve dairy health and productivity, at least by increasing feed intake. In this study, we report if intraperitoneal (i.p.) AEA and 2-AG administration affects feed intake, whole-body macronutrient metabolism, isolation and restraint stress, and whether diet composition modulates circulating endocannabinoid concentrations in cows. Twenty Simmental cows in late lactation were fed a grass silage and a corn silage based diet. On each diet, cows received daily i.p. injections with either AEA (5 µg/kg; n = 7), 2-AG (2.5 µg/kg; n = 6) or saline (n = 7) for 8 days. Endocannabinoid administration for 5 days under free-ranging (non-stressed) conditions had no effect on feed intake or energy balance, but attenuated the stress-induced suppression of feed intake when housing changed to individual tie-stalls without social or tactile interaction. Endocannabinoids increased whole-body carbohydrate oxidation, reduced fat oxidation, and affected plasma non-esterified fatty acid concentrations and fatty acid contents of total lipids. There was no effect of endocannabinoids on plasma triglyceride concentrations or hepatic lipogenesis. Plasma AEA concentrations were not affected by diet, however, plasma 2-AG concentrations tended to be lower on the corn silage based diet. In conclusion, endocannabinoids attenuate stress-induced hypophagia, increase short-term feed intake and whole-body carbohydrate oxidation and decrease whole-body fat oxidation in cows.

Early Consumption of Cannabinoids: From Adult Neurogenesis to Behavior

The endocannabinoid system (ECS) is a crucial modulatory system in which interest has been increasing, particularly regarding the regulation of behavior and neuroplasticity. The adolescent-young adulthood phase of development comprises a critical period in the maturation of the nervous system and the ECS. Neurogenesis occurs in discrete regions of the adult brain, and this process is linked to the modulation of some behaviors. Since marijuana (cannabis) is the most consumed illegal drug globally and the highest consumption rate is observed during adolescence, it is of particular importance to understand the effects of ECS modulation in these early stages of adulthood. Thus, in this article, we sought to summarize recent evidence demonstrating the role of the ECS and exogenous cannabinoid consumption in the adolescent-young adulthood period; elucidate the effects of exogenous cannabinoid consumption on adult neurogenesis; and describe some essential and adaptive behaviors, such as stress, anxiety, learning, and memory. The data summarized in this work highlight the relevance of maintaining balance in the endocannabinoid modulatory system in the early and adult stages of life. Any ECS disturbance may induce significant modifications in the genesis of new neurons and may consequently modify behavioral outcomes.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R_. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

Cannabinoids and myocardial ischemia: Novel insights, updated mechanisms, and implications for myocardial infarction

Cannabis is the most widely trafficked and abused illicit drug due to its calming psychoactive properties. It has been increasingly recognized as having potential health benefits and relatively less adverse health effects as compared to other illicit drugs; however, growing evidence clearly indicates that cannabis is associated with considerable adverse cardiovascular events. Recent studies have linked cannabis use to myocardial infarction (MI); yet, very little is known about the underlying mechanisms. A MI is a cardiovascular disease characterized by a mismatch in the oxygen supply and demand of the heart, resulting in ischemia and subsequent necrosis of the myocardium. Since cannabis is increasingly being considered a risk factor for MI, there is a growing need for better appreciating its potential health benefits and consequences. Here, we discuss the cellular mechanisms of cannabis that lead to an increased risk of MI. We provide a thorough and critical analysis of cannabinoids' actions, which include modulation of adipocyte biology, regional fat distribution, and atherosclerosis, as well as precipitation of hemodynamic stressors relevant in the setting of a MI. By critically dissecting the modulation of signaling pathways in multiple cell types, this paper highlights the mechanisms through which cannabis may trigger life-threatening cardiovascular events. This then provides a framework for future pharmacological studies which can identify targets or develop drugs that modulate cannabis' effects on the cardiovascular system as well as other organ systems. Cannabis' impact on the autonomic outflow, vascular smooth muscle cells, myocardium, cortisol levels and other hemodynamic changes are also mechanistically reviewed.

A Guide to Targeting the Endocannabinoid System in Drug Design

The endocannabinoid system (ECS) is one of the most crucial systems in the human organism, exhibiting multi-purpose regulatory character. It is engaged in a vast array of physiological processes, including nociception, mood regulation, cognitive functions, neurogenesis and neuroprotection, appetite, lipid metabolism, as well as cell growth and proliferation. Thus, ECS proteins, including cannabinoid receptors and their endogenous ligands’ synthesizing and degrading enzymes, are promising therapeutic targets. Their modulation has been employed in or extensively studied as a treatment of multiple diseases. However, due to a complex nature of ECS and its crosstalk with other biological systems, the development of novel drugs turned out to be a challenging task. In this review, we summarize potential therapeutic applications for ECS-targeting drugs, especially focusing on promising synthetic compounds and preclinical studies. We put emphasis on modulation of specific proteins of ECS in different pathophysiological areas. In addition, we stress possible difficulties and risks and highlight proposed solutions. By presenting this review, we point out information pivotal in the spotlight of ECS-targeting drug design, as well as provide an overview of the current state of knowledge on ECS-related pharmacodynamics and show possible directions for needed research.

Transgene-free remote magnetothermal regulation of adrenal hormones

The field of bioelectronic medicines seeks to modulate electrical signaling within peripheral organs, providing temporally precise control of physiological functions. This is usually accomplished with implantable devices, which are often unsuitable for interfacing with soft and highly vascularized organs. Here, we demonstrate an alternative strategy for modulating peripheral organ function, which relies on the endogenous expression of a heat-sensitive cation channel, transient receptor potential vanilloid family member 1 (TRPV1), and heat dissipation by magnetic nanoparticles (MNPs) in remotely applied alternating magnetic fields. We use this approach to wirelessly control adrenal hormone secretion in genetically intact rats. TRPV1-dependent calcium influx into the cells of adrenal cortex and medulla is sufficient to drive rapid release of corticosterone and (nor)epinephrine. As altered levels of these hormones have been correlated with mental conditions such as posttraumatic stress disorder and major depression, our approach may facilitate the investigation of physiological and psychological impacts of stress.

Remote CB1 receptor antagonist administration reveals multiple sites of tonic and phasic endocannabinoid neuroendocrine regulation

Endogenous cannabinoids (endocannabinoids, eCB) are expressed throughout the body and contribute to regulation of the hypothalamo-pituitary-adrenal (HPA) axis and general stress reactivity. This study assessed the contributions of CB1 receptors (CB1R) in the modulation of basal and stress-induced neural and HPA axis activities. Catheterized adult male rats were placed in chambers to acclimate overnight, with their catheters connected and exteriorized from the chambers for relatively stress-free remote injections. The next morning, the CB1R antagonist AM251 (1 or 2 mg/kg) or vehicle was administered, and 30 min later, rats were exposed to loud noise stress (30 min) or no noise (basal condition). Blood, brains, pituitary and adrenal glands were collected immediately after the procedures for analysis of c-fos and CB1R mRNAs, corticosterone (CORT) and adrenocorticotropin hormone (ACTH) plasma levels. Basally, CB1R antagonism induced c-fos mRNA in the basolateral amygdala (BLA) and auditory cortex (AUD) and elevated plasma CORT, indicating disruption of eCB-mediated constitutive inhibition of activity. CB1R blockade also potentiated stress-induced hormone levels and c-fos mRNA in several regions such as the bed nucleus of the stria terminalis (BST), lateral septum (LS), and basolateral amygdala (BLA) and the paraventricular nucleus of the hypothalamus (PVN). CB1R mRNA was detected in all central tissues investigated, and the adrenal cortex, but at very low levels in the anterior pituitary gland. Interestingly, CB1R mRNA was rapidly and bidirectionally regulated in response to stress and/or antagonist treatment in some regions. eCBs therefore modulate the HPA axis by regulating both constitutive and activity-dependent inhibition at multiple levels.

Investigating the role of nitric oxide in stress adaptive process in electric foot shock stress-subjected mice

AIM

The present study was designed to investigate the role of nitric oxide (NO) in the non-development of stress adaptation in high-intensity foot-shock stress (HIFS) subjected mice.

METHODS

Mice were subjected to low-intensity shocks (LIFS i.e. 0.5 mA) or HIFS (1.5 mA) for 5 days. Stress-induced behavioral changes were assessed by actophotometer, hole board, open field and social interaction tests. Biochemically, the serum corticosterone levels were measured as a marker of stress. L-arginine (100 mg/kg and 300 mg/kg), as NO donor, and L-NAME (10 mg/kg and 30 mg/kg), as nitric oxide synthase (NOS) inhibitor, were employed as pharmacological agents.

RESULTS

A single exposure of LIFS and HIFS produced behavioral and biochemical alterations. However, there was the restoration of behavioral and biochemical alterations on 5^th day in response to repeated LIFS exposure suggesting the development of stress adaptation. However, no stress adaptation was observed in HIFS subjected mice. Administration of L-arginine (300 mg/kg) abolished the stress adaptive response in LIFS-subjected mice, while L-NAME (30 mg/kg) induced the development of stress adaptation in HIFS subjected mice.

CONCLUSION

It is concluded that an increase in the NO release may possibly impede the process of stress adaptation in HIFS-subjected mice.

The cellular and molecular basis of major depressive disorder: towards a unified model for understanding clinical depression

Major depressive disorder (MDD) is considered a serious public health issue that adversely impacts an individual's quality of life and contributes significantly to the global burden of disease. The clinical heterogeneity that exists among patients limits the ability of MDD to be accurately diagnosed and currently, a symptom-based approach is utilized in many cases. Due to the complex nature of this disorder, and lack of precise knowledge regarding the pathophysiology, effective management is challenging. The aetiology and pathophysiology of MDD remain largely unknown given the complex genetic and environmental interactions that are involved. Nonetheless, the aetiology and pathophysiology of MDD have been the subject of extensive research, and there is a vast body of literature that exists. Here we overview the key hypotheses that have been proposed for the neurobiology of MDD and highlight the need for a unified model, as many of these pathways are integrated. Key pathways discussed include neurotransmission, neuroinflammation, clock gene machinery pathways, oxidative stress, role of neurotrophins, stress response pathways, the endocannabinoid and endovanilloid systems, and the endogenous opioid system. We also describe the current management of MDD, and emerging novel therapies, with particular focus on patients with treatment-resistant depression (TRD).

The selenium-containing compound 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole reverses depressive-like behavior induced by acute restraint stress in mice: modulation of oxido-nitrosative stress and inflammatory pathway

RATIONALE AND OBJECTIVES

Stress-induced alterations in oxidative and inflammatory parameters have been implicated in the pathophysiology of mood disorders. Based on the antioxidant and anti-inflammatory properties of the selenium-containing compound 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole (CMI), we assessed its ability to reverse depression-like behavioral alterations, neuroinflammation, and oxidative imbalance induced by acute restraint stress.

METHODS

Mice submitted to restraint for 240 min received CMI (1 or 10 mg/kg, orally) 10 min after the end of the stress induction. Behavioral and biochemical tests were carried out after further 30 min.

RESULTS

Restraint-induced depression-like behavior in the tail suspension test (TST), splash test, and new object exploration test was reversed by CMI. None of the treatments evoked locomotor alteration. In addition, CMI abrogated restraint-induced increases in plasma levels of corticosterone and in markers of oxidative stress and impaired superoxide dismutase and catalase activity in the prefrontal cortex (PFC) and hippocampus (HC). CMI also blocked stress-induced downregulation of mRNA levels of glucocorticoid receptor and brain-derived neurotrophic factor and upregulation of nuclear factor kappa B, inducible nitric oxide synthase, tumor necrosis alpha, indoelamine-2,3-dioxygenase, and glycogen synthase kinase 3 beta in PFC and HC.

CONCLUSIONS

These preclinical results indicate that administration of selenium-containing compounds might help to treat depression associated with inflammation and oxidative stress. Graphical abstract ᅟ.

Sex differences in stress and immune responses during confinement in Antarctica

Background

Antarctica challenges human explorers by its extreme environment. The effects of these unique conditions on the human physiology need to be understood to best mitigate health problems in Antarctic expedition crews. Moreover, Antarctica is an adequate Earth-bound analogue for long-term space missions. To date, its effects on human physiology have been studied mainly in male cohorts though more female expeditioners and applicants in astronaut training programs are selected. Therefore, the identification of sex differences in stress and immune reactions are becoming an even more essential aim to provide a more individualized risk management.

Methods

Ten female and 16 male subjects participated in three 1-year expeditions to the German Antarctic Research Station Neumayer III. Blood, saliva, and urine samples were taken 1–2 months prior to departure, subsequently every month during their expedition, and 3–4 months after return from Antarctica. Analyses included cortisol, catecholamine and endocannabinoid measurements; psychological evaluation; differential blood count; and recall antigen- and mitogen-stimulated cytokine profiles.

Results

Cortisol showed significantly higher concentrations in females than males during winter whereas no enhanced psychological stress was detected in both sexes. Catecholamine excretion was higher in males than females but never showed significant increases compared to baseline. Endocannabinoids and N-acylethanolamides increased significantly in both sexes and stayed consistently elevated during the confinement. Cytokine profiles after in vitro stimulation revealed no sex differences but resulted in significant time-dependent changes. Hemoglobin and hematocrit were significantly higher in males than females, and hemoglobin increased significantly in both sexes compared to baseline. Platelet counts were significantly higher in females than males. Leukocytes and granulocyte concentrations increased during confinement with a dip for both sexes in winter whereas lymphocytes were significantly elevated in both sexes during the confinement.

Conclusions

The extreme environment of Antarctica seems to trigger some distinct stress and immune responses but—with the exception of cortisol and blood cell counts—without any major relevant sex-specific differences. Stated sex differences were shown to be independent of enhanced psychological stress and seem to be related to the environmental conditions. However, sources and consequences of these sex differences have to be further elucidated.

Capsaicin inhibits lipopolysaccharide-induced adrenal steroidogenesis by raising intracellular calcium levels

INTRODUCTION

Glucocorticoid release by adrenals has been described as significant to survive sepsis. The activation of transient receptor potential vanilloid type 1 (TRPV1) inhibited ACTH-induced glucocorticoid release by adrenal glands in vitro.

OBJECTIVE

The aim of this study was to investigate if capsaicin, an activator of TRPV1, would prevent LPS-induced glucocorticoid production by adrenals.

METHODS

Male Swiss-Webster mice were treated with capsaicin intraperitoneally (0.2 or 2 mg/kg) 30 min before LPS injection. All analyses were performed 2 h after the LPS stimulation, including plasma corticosterone and peritoneal IL-1β and TNF-α levels. Furthermore, murine adrenocortical Y1 cells were used to assess the effects of capsaicin on LPS-induced corticosterone production in vitro.

RESULTS

Capsaicin (2 mg/kg, i.p.) significantly reduced plasma corticosterone levels and adrenal hypertrophy induced by LPS without alter the levels of pro-steroidogenic cytokines IL-1β and TNF-α in peritoneal cavity of mice, while the dose of 0.2 mg/kg of capsaicin did not interfere with adrenal steroidogenesis, attested by RIA and ELISA, respectively. Y1 cells express TRPV1, measured by immunofluorescence and western blot, and capsaicin decreased LPS-induced corticosterone production by these cells in vitro. Capsaicin also induces calcium mobilization in Y1 cells in vitro.

CONCLUSIONS

These findings suggest that capsaicin inhibits corticosterone production induced by LPS by acting directly on adrenal cells producing glucocorticoids, in a mechanism probably associated with induction of a cytoplasmic calcium increase in these cells.

The Process of Acclimation to Chronic Hypoxia Leads to Submandibular Gland and Periodontal Alterations: An Insight on the Role of Inflammatory Mediators

The exposition to hypoxia is a stressful stimulus, and the organism develops acclimation mechanisms to ensure homeostasis, but if this fails, it leads to the development of pathological processes. Considering the large number of people under hypoxic conditions, it is of utmost importance to study the mechanisms implicated in hypoxic acclimation in oral tissues and the possible alteration of some important inflammatory markers that regulate salivary and periodontal function. It is the aim of the present study to analyze submandibular (SMG) and periodontal status of animals chronically exposed to continuous (CCH) or intermittent (CIH) hypoxia in order to elucidate the underlying molecular mechanisms that may lead to hypoxic acclimation. Adult Wistar rats were exposed to CCH or CIH simulating 4200 meters of altitude during 90 days. Salivary secretion was decreased in animals exposed to hypoxia, being lower in CIH, together with increased prostaglandin E₂ (PGE₂) content, TBARS concentration, and the presence of apoptotic nuclei and irregular secretion granules in SMG. AQP-5 mRNA levels decreased in both hypoxic groups. Only the CCH group showed higher HIF-1α staining, while CIH alone exhibited interradicular bone loss and increased concentration of the bone resorption marker CTX-I. In summary, animals exposed to CIH show a worse salivary secretion rate, which related with higher levels of PGE₂, suggesting a negative role of this inflammatory mediator during hypoxia acclimation. We link the weak immunorreactivity of HIF-1α in CIH with improper hypoxia acclimation, which is necessary to sustaining SMG physiology under this environmental condition. The alveolar bone loss observed in CIH rats could be due mainly to a direct effect of PGE₂, as suggested by its higher content in gingival tissue, but also to the indirect effect of hyposalivation. This study may eventually contribute to finding therapeutics to treat the decreased salivary flow, improving in that way oral health.

Modulations of Neuroendocrine Stress Responses During Confinement in Antarctica and the Role of Hypobaric Hypoxia

The Antarctic continent is an environment of extreme conditions. Only few research stations exist that are occupied throughout the year. The German station Neumayer III and the French-Italian Concordia station are such research platforms and human outposts. The seasonal shifts of complete daylight (summer) to complete darkness (winter) as well as massive changes in outside temperatures (down to -80°C at Concordia) during winter result in complete confinement of the crews from the outside world. In addition, the crew at Concordia is subjected to hypobaric hypoxia of ∼650 hPa as the station is situated at high altitude (3,233 m). We studied three expedition crews at Neumayer III (sea level) (n = 16) and two at Concordia (high altitude) (n = 15) to determine the effects of hypobaric hypoxia on hormonal/metabolic stress parameters [endocannabinoids (ECs), catecholamines, and glucocorticoids] and evaluated the psychological stress over a period of 11 months including winter confinement. In the Neumayer III (sea level) crew, EC and n-acylethanolamide (NAE) concentrations increased significantly already at the beginning of the deployment (p < 0.001) whereas catecholamines and cortisol remained unaffected. Over the year, ECs and NAEs stayed elevated and fluctuated before slowly decreasing till the end of the deployment. The classical stress hormones showed small increases in the last third of deployment. By contrast, at Concordia (high altitude), norepinephrine concentrations increased significantly at the beginning (p < 0.001) which was paralleled by low EC levels. Prior to the second half of deployment, norepinephrine declined constantly to end on a low plateau level, whereas then the EC concentrations increased significantly in this second period during the overwintering (p < 0.001). Psychometric data showed no significant changes in the crews at either station. These findings demonstrate that exposition of healthy humans to the physically challenging extreme environment of Antarctica (i) has a distinct modulating effect on stress responses. Additionally, (ii) acute high altitude/hypobaric hypoxia at the beginning seem to trigger catecholamine release that downregulates the EC response. These results (iii) are not associated with psychological stress.

Endocannabinoid hydrolase and cannabinoid receptor 1 are involved in the regulation of hypothalamus-pituitary-adrenal axis in type 2 diabetes

Hypothalamus-pituitary-adrenal (HPA) axis, as the key moderator in energy metabolism, plays an important role in diabetes. The endogenous cannabinoid system (eCBs) involves in neuronal functions, and simultaneously cannabinoid receptors are almost expressed in all regions of the hypothalamus according to a spate of reports. However, few data investigate the changes of eCBs and HPA axis in type 2 diabetes. In this study, five diabetes mellitus rhesus monkeys, five prediabetes rhesus monkeys and five healthy rhesus monkeys were observed. In the present study, we detected cell swelling and necrosis extensively in the paraventricular nucleus (PVN) and neurohypophysis in prediabetes and overt diabetes monkeys. The adrenocorticotropic hormone in the pituitary gland, adrenocorticotropic hormone receptor, and 11β-hydroxysteroid dehydrogenase in the adrenal gland were all hyper-secreted and expressed from healthy to overt diabetes. Meanwhile, the cortisol concentration in the adrenal gland was increased along with the progress of diabetes. It could be concluded that hyperfunction of the HPA axis exists in the type 2 Diabetes pathogenesis. However, we also found a weakened expression and secretion of corticotrophin releasing hormone and glucocorticoids receptor in PVN. The expression of corticotropin releasing hormone receptor 1 in pituitary gland decreased in prediabetes monkeys, but increased in overt diabetes monkeys. The downregulation of cannabinoid receptor 1 and upregulation of monoglycerol lipase and fatty acid amide hydrolase in PVN was involved in the pathogenesis of type 2 diabetes. Collectively, we can conclude that changes in endocannabinoid hydrolase and cannabinoid receptor might indicate the effect of downregulation of eCBs. It can be assumed that hyper-function of the HPA axis from healthy to overt diabetes is due to the undermining inhibition of eCBs. However, the regulatory mechanism of eCBs targets on the HPA axis need to be further explored.

Stress, alcohol and infection during early development: A brief review of common outcomes and mechanisms

Although stress is an adaptive physiological response to deal with adverse conditions, its occurrence during the early stages of life, such as infancy or adolescence, can induce adaptations in multiple physiological systems, including the reproductive axis, the hypothalamic-pituitary-adrenal (HPA) axis, the limbic cortex and the immune system. These early changes have consequences in adult life, as seen in the physiological and behavioural responses to stress. This review highlights the impact of several stress challenges incurred at various stages of development (perinatal, juvenile, adolescent periods) and how the developmental timing of early-life stress confers unique physiological adaptations that may persist across the lifespan. In doing so, we emphasise how intrinsic sex differences in the stress response might contribute to sex-specific vulnerabilities, the molecular processes underlying stress in the adult, and potential therapeutic interventions to mitigate the effects of early stage stress, including the novel molecular mechanism of SUMOylation as a possible key target of HPA regulation during early-life stress.

Endocannabinoids in Body Weight Control

Maintenance of body weight is fundamental to maintain one's health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.