Stress mediators regulate brain prostaglandin synthesis and peroxisome proliferator-activated receptor-gamma activation after stress in rats

Associations between psychological distress in adolescence and menstrual symptoms across life: Longitudinal evidence from the 1970 British Cohort Study

PURPOSE

This study aimed to investigate the association between psychological distress (PD) at age 16 and menstrual symptoms experienced across women's life.

METHODS

Up to 2584 females from the 1970 British Cohort Study, a study of individuals born within one week in 1970, were included. PD at age 16 was measured with the 12-item General Health Questionnaire. Three categories were derived: low PD (<11), moderate PD (11-15), and severe PD (>15). Five menstrual health symptoms were self-reported at each age (16, 30 and 42 years). Binomial logistic regressions examined associations between PD at age 16 and each individual symptom, adjusted for age of menarche, sleep and appetite problems, physical activity levels and socioeconomic position.

RESULTS

The most prevalent symptoms were "pain" (61 %), "painful period" (10 %) and "heavy period" (33 %) at ages 16, 30 and 42, respectively. At age 16, those with severe PD were more likely to experience depression (OR: 2.92; 95% CI: 2.31, 3.70)), irritability (1.67; 1.33, 2.11), menstrual pain (1.34; 1.01, 1.80), and headaches (1.29; 1.02, 1.63). A weak association was found between severe PD at age 16 and pre-menstrual tension at age 30 (1.72; 1.01, 2.83). At age 42, those with severe PD at age 16 were more likely to experience pre-menstrual tension (1.89; 1.46, 2.44), painful periods (1.64; 1.27, 2.11), and heavy periods (1.28; 1.00, 1.62).

DISCUSSION

Menstruating females with higher levels of PD in adolescence have an increased risk of menstrual symptoms across adolescence, early and mid-adulthood. Our findings suggest the need to consider early-life psychological interventions to improve women's menstrual experiences across their reproductive years.

Finding biomarkers of experience in animals

At a time when there is a growing public interest in animal welfare, it is critical to have objective means to assess the way that an animal experiences a situation. Objectivity is critical to ensure appropriate animal welfare outcomes. Existing behavioural, physiological, and neurobiological indicators that are used to assess animal welfare can verify the absence of extremely negative outcomes. But welfare is more than an absence of negative outcomes and an appropriate indicator should reflect the full spectrum of experience of an animal, from negative to positive. In this review, we draw from the knowledge of human biomedical science to propose a list of candidate biological markers (biomarkers) that should reflect the experiential state of non-human animals. The proposed biomarkers can be classified on their main function as endocrine, oxidative stress, non-coding molecular, and thermobiological markers. We also discuss practical challenges that must be addressed before any of these biomarkers can become useful to assess the experience of an animal in real-life.

Prostaglandin E2 Induces Long-Lasting Inhibition of Noradrenergic Neurons in the Locus Coeruleus and Moderates the Behavioral Response to Stressors

Neuronal activity is modulated not only by inputs from other neurons but also by various factors, such as bioactive substances. Noradrenergic (NA) neurons in the locus coeruleus (LC-NA neurons) are involved in diverse physiological functions, including sleep/wakefulness and stress responses. Previous studies have identified various substances and receptors that modulate LC-NA neuronal activity through techniques including electrophysiology, calcium imaging, and single-cell RNA sequencing. However, many substances with unknown physiological significance have been overlooked. Here, we established an efficient screening method for identifying substances that modulate LC-NA neuronal activity through intracellular calcium ([Ca2+]i) imaging using brain slices. Using both sexes of mice, we screened 53 bioactive substances, and identified five novel substances: gastrin-releasing peptide, neuromedin U, and angiotensin II, which increase [Ca2+]i, and pancreatic polypeptide and prostaglandin D2, which decrease [Ca2+]i Among them, neuromedin U induced the greatest response in female mice. In terms of the duration of [Ca2+]i change, we focused on prostaglandin E2 (PGE2), since it induces a long-lasting decrease in [Ca2+]i via the EP3 receptor. Conditional knock-out of the receptor in LC-NA neurons resulted in increased depression-like behavior, prolonged wakefulness in the dark period, and increased [Ca2+]i after stress exposure. Our results demonstrate the effectiveness of our screening method for identifying substances that modulate a specific neuronal population in an unbiased manner and suggest that stress-induced prostaglandin E2 can suppress LC-NA neuronal activity to moderate the behavioral response to stressors. Our screening method will contribute to uncovering previously unknown physiological functions of uncharacterized bioactive substances in specific neuronal populations.SIGNIFICANCE STATEMENT Bioactive substances modulate the activity of specific neuronal populations. However, since only a limited number of substances with predicted effects have been investigated, many substances that may modulate neuronal activity have gone unrecognized. Here, we established an unbiased method for identifying modulatory substances by measuring the intracellular calcium signal, which reflects neuronal activity. We examined noradrenergic (NA) neurons in the locus coeruleus (LC-NA neurons), which are involved in diverse physiological functions. We identified five novel substances that modulate LC-NA neuronal activity. We also found that stress-induced prostaglandin E2 (PGE2) may suppress LC-NA neuronal activity and influence behavioral outcomes. Our screening method will help uncover previously overlooked functions of bioactive substances and provide insight into unrecognized roles of specific neuronal populations.

Transcriptional Profiles of Mitochondrial Dynamics Markers Are Disturbed in Adrenal Glands of Stressed Adult Male Rats

Mitochondrial dynamics plays a significant role in shaping the mitochondrial network and maintaining mitochondrial function. Imbalanced mitochondrial dynamics can cause mitochondrial dysfunction leading to a wide range of diseases/disorders. The aim of this study was to investigate the expression of mitochondrial dynamics markers and regulatory molecules in whole adrenal glands, cortices, and medullae obtained from adult male rats exposed to acute and repeated psychophysical stress, the most common stress in human society. The transcriptional profiles of most of the mitochondrial dynamics markers investigated here were altered: 81%-(17/21) in the whole adrenal gland, 76.2%-(16/21) in the adrenal cortex, and 85.7%-(18/21) in the adrenal medulla. Changes were evident in representatives of every process of mitochondrial dynamics. Markers of mitobiogenesis were changed up to 62.5%-(5/8) in the whole adrenal gland, 62.5%-(5/8) in the adrenal cortex, and 87.5%-(7/8) in the adrenal medulla. Markers of mitofusion were changed up to 100%-(3/3) in the whole adrenal gland, 66.7%-(5/8) in the adrenal cortex, and 87.5%-(7/8) in the adrenal medulla, while all markers of mitofission and mitophagy were changed in the adrenal glands. Moreover, almost all markers of mitochondrial functionality were changed: 83.3%-(5/6) in the whole adrenal, 83.3%-(5/6) in the cortex, 66.7%-(4/6) in the medulla. Accordingly, the study highlights the significant impact of acute and repeated stress on mitochondrial dynamics in the adrenal gland.

PPARγ activation inhibits endocytosis of claudin-4 and protects against deoxynivalenol-induced intestinal barrier dysfunction in IPEC-J2 cells and weaned piglets

The role of peroxisome proliferator activated receptor gamma (PPARγ) in the regulation of adipocyte differentiation has been well characterized. Besides adipose tissue, PPARγ is also highly expressed in the intestine. However, the functional role of PPARγ in the regulation of intestinal function still remains poorly understood. In the present study, we sought to understand the role of PPARγ activation on regulation of intestinal barrier function in intestinal porcine epithelial cells (IPEC-J2) and weaned piglets exposed to the mycotoxin, deoxynivalenol (DON). PPARγ activation by rosiglitazone and troglitazone, two pharmacological PPARγ ligands, increased the protein expression of tight junction proteins (TJP), claudin-3 and 4. PPARγ inhibition increased endocytosis of claudin-4 which was reversed by its activation with troglitazone. DON exposure decreased the protein expression of TJP, and also significantly suppressed PPARγ transcriptional activity. Interestingly, PPARγ activation reversed the reduction of claudin-3 and 4 caused by DON in vitro and in vivo. PPARγ activation also partially restored the transepithelial electrical resistance (TEER) and reduced the permeability of fluorescein isothiocyanate-dextran (FITC-dextran) that have been negatively impacted by DON. These effects were lost in the presence of a specific PPARγ antagonist or in PPARγ knockout cells, confirming the importance of PPARγ in the regulation of intestinal barrier function and integrity. Likewise, in weaned pigs exposed to DON, the PPARγ agonist pioglitazone mitigated the impaired villus-crypt morphology caused by DON. Therefore, pharmacological and natural bioactive compounds with PPARγ stimulatory activities could be effective in preventing DON-induced gut barrier dysfunction.

Central injection of abscisic acid attenuates mood disorders induced by subchronic stress in male mice

Stressful life increases the risk of mental and psychological disorders and cognitive deficits. Abscisic acid (ABA) is a plant hormone that has been recently discovered in mammalians. ABA is produced in response to stressful stimuli and it can reduce anxiety-like behaviors and depression and improve cognitive function. This study was designed to evaluate the effects of microinjection of ABA on depression, anxiety, passive avoidance learning and memory deficits induced by subchronic stress. ABA (10 and 15  μ $\umu $ g/mouse, i.c.v.) was administered one week after recovery period for 4 consecutive days. A three-session forced swimming test (FST) protocol for induction of subchronic stress was administered to the mice. Exploratory, anxiety-like behavior, depression and cognitive function were assessed 24 h after the last swim stress session. The results indicated that ABA (15  μ $\umu $ g/mouse) could ameliorate anxiety and depression induced by FST. In addition, ABA had no effect on the subchronic stress-induced cognitive impairments. Taken together, the results suggest that ABA could improve anxiety and depression induced by subchronic stress.

Spermatozoa Develop Molecular Machinery to Recover From Acute Stress

This study was designed to search for the possible mechanism(s) of male (in/sub)fertility by following the molecular response of spermatozoa on acute psychological stress (the most common stress in human society) and on a 20-h time-dependent recovery period. To mimic in vivo acute stress, the rats were exposed to immobilization once every 3 h. The recovery periods were as follows: 0 (immediately after stress and 3 h after the light is on-ZT3), 8 (ZT11), 14 (ZT17), and 20 (ZT23) h after stress. Results showed that acute stress provoked effects evident 20 h after the end of the stress period. Numbers of spermatozoa declined at ZT17 and ZT23, while functionality decreased at ZT3 and ZT11, but recovered at ZT17 and ZT23. Transcriptional profiles of 91% (20/22) of tracked mitochondrial dynamics and functionality markers and 91% (20/22) of signaling molecules regulating both mitochondrial dynamics and spermatozoa number/functionality were disturbed after acute stress and during the recovery period. Most of the changes presented as increased transcription or protein expression at ZT23. The results of the principal component analysis (PCA) showed the clear separation of acute stress recovery effects during active/dark and inactive/light phases. The physiological relevance of these results is the recovered positive-acrosome-reaction, suggesting that molecular events are an adaptive mechanism, regulated by acute stress response signaling. The results of the PCA confirmed the separation of the effects of acute stress recovery on gene expression related to mitochondrial dynamics, cAMP, and MAPK signaling. The transcriptional patterns were different during the active and inactive phases. Most of the transcripts were highly expressed during the active phase, which is expected given that stress occurred at the beginning of the inactive phase. To the best of our knowledge, our results provide a completely new view and the first presentation of the markers of mitochondrial dynamics network in spermatozoa and their correlation with signaling molecules regulating both mitochondrial dynamics and spermatozoa number and functionality during recovery from acute stress. Moreover, the interactions between the proteins important for spermatozoa homeostasis and functionality (MFN2 and PRKA catalytic subunit, MFN2 and p38MAPK) are shown for the first time. Since the existing literature suggests the importance of semen quality and male fertility not only as the fundamental marker of reproductive health but also as the fundamental biomarkers of overall health and harbingers for the development of comorbidity and mortality, we anticipate our result to be a starting point for more investigations considering the mitochondrial dynamics markers or their transcriptional profiles as possible predictors of (in/sub)fertility.

The PPARg System in Major Depression: Pathophysiologic and Therapeutic Implications

To an exceptional degree, and through multiple mechanisms, the PPARg system rapidly senses cellular stress, and functions in the CNS in glial cells, neurons, and cerebrovascular endothelial cell in multiple anti-inflammatory and neuroprotective ways. We now know that depression is associated with neurodegeneration in the subgenual prefrontal cortex and hippocampus, decreased neuroplasticity, and defective neurogenesis. Brain-derived neurotrophic factor (BDNF) is markedly depleted in these areas, and is thought to contribute to the neurodegeneration of the subgenual prefrontal cortex and the hippocampus. The PPARg system strongly increases BDNF levels and activity in these brain areas. The PPARg system promotes both neuroplasticity and neurogenesis, both via effects on BDNF, and through other mechanisms. Ample evidence exists that these brain areas transduce many of the cardinal features of depression, directly or through their projections to sites such as the amygdala and nucleus accumbens. Behaviorally, these include feelings of worthlessness, anxiety, dread of the future, and significant reductions in the capacity to anticipate and experience pleasure. Physiologically, these include activation of the CRH and noradrenergic system in brain and the sympathetic nervous system and hypothalamic-pituitary-adrenal axis in the periphery. Patients with depression are also insulin-resistant. The PPARg system influences each of these behavioral and physiological in ways that would ameliorate the manifestations of depressive illness. In addition to the cognitive and behavioral manifestations of depression, depressive illness is associated with the premature onsets of coronary artery disease, stroke, diabetes, and osteoporosis. As a consequence, patients with depressive illness lose approximately seven years of life. Inflammation and insulin resistance are two of the predominant processes that set into motion these somatic manifestations. PPARg agonists significantly ameliorate both pathological processes. In summary, PPARg augmentation can impact positively on multiple significant pathological processes in depression. These include loss of brain tissue, defective neuroplasticity and neurogenesis, widespread inflammation in the central nervous system and periphery, and insulin resistance. Thus, PPARg agonists could potentially have significant antidepressant effects.

Norepinephrine and Glucocorticoids Modulate Chronic Unpredictable Stress-Induced Increase in the Type 2 CRF and Glucocorticoid Receptors in Brain Structures Related to the HPA Axis Activation

The stress response is multifactorial and enrolls circuitries to build a coordinated reaction, leading to behavioral, endocrine, and autonomic changes. These changes are mainly related to the hypothalamus-pituitary-adrenal (HPA) axis activation and the organism's integrity. However, when self-regulation is ineffective, stress becomes harmful and predisposes the organism to pathologies. The chronic unpredictable stress (CUS) is a widely used experimental model since it induces physiological and behavioral changes and better mimics the stressors variability encountered in daily life. Corticotropin-releasing factor (CRF) and glucocorticoids (GCs) are deeply implicated in the CUS-induced physiological and behavioral changes. Nonetheless, the CUS modulation of CRF receptors and GR and the norepinephrine role in extra-hypothalamic brain areas were not well explored. Here, we show that 14 days of CUS induced a long-lasting HPA axis hyperactivity evidenced by plasmatic corticosterone increase and adrenal gland hypertrophy, which was dependent on both GCs and NE release induced by each stress session. CUS also increased CRF₂ mRNA expression and GR protein levels in fundamental brain structures related to HPA regulation and behavior, such as the lateral septal nucleus intermedia part (LSI), ventromedial hypothalamic nucleus (VMH), and central nucleus of the amygdala (CeA). We also showed that NE participates in the CUS-induced increase in CRF₂ and GR levels in the LSI, reinforcing the locus coeruleus (LC) involvement in the HPA axis modulation. Despite the CUS-induced molecular changes in essential areas related to anxiety-like behavior, this phenotype was not observed in CUS animals 24 h after the last stress session.

The Impact of Obesity on Microglial Function: Immune, Metabolic and Endocrine Perspectives

Increased life expectancy in combination with modern life style and high prevalence of obesity are important risk factors for development of neurodegenerative diseases. Neuroinflammation is a feature of neurodegenerative diseases, and microglia, the innate immune cells of the brain, are central players in it. The present review discusses the effects of obesity, chronic peripheral inflammation and obesity-associated metabolic and endocrine perturbations, including insulin resistance, dyslipidemia and increased glucocorticoid levels, on microglial function.

Mitochondrial Dynamics Markers and Related Signaling Molecules Are Important Regulators of Spermatozoa Number and Functionality

Here, we study possible mechanisms of (in/sub)fertility related to the acute or repeated psychological stresses (the most common stresses in human society) by following the transcriptional profile of 22 mitochondrial dynamics/function markers and 22 signaling molecules regulating both mitochondrial dynamics and spermatozoa number/functionality. An in vivo study mimicking acute (once for 3 h) and repeated (3 h for 10 consecutive days) psychophysical stress was performed on adult rats. The analysis of hormones, the number/functionality of spermatozoa, and 44 transcriptional markers were performed on individual samples from up to 12 animals per group. Results showed that both types of stress reduced spermatozoa functionality (acute by 4.4-fold, repeated by 3.3-fold) and ATP production (acute by 2.3-fold, repeated by 14.5-fold), while only repeated stress reduces the number of spermatozoa (1.9-fold). Stress significantly disturbed transcription of 34-out-of-44 markers (77%). Mitochondrial dynamics and functionality markers: 18-out-of-22 =>82% (mitochondrial-biogenesis-markers –>6-out-of-8 =>75%; mitochondrial-fusion-markers –>3-out-of-3 =>100%; mitochondrial-fission-markers –>1-out-of-2 =>50%; mitochondrial-autophagy-markers –>3-out-of-3 =>100%; mitochondrial-functionality-markers –>5-out-of-6 =>83%). Markers of signaling pathways regulating both mitochondrial dynamics/functionality and spermatozoa number/functionality important for male (in/sub)fertility –>16-out-of-22 =>73% (cAMP-signaling-markers –>8-out-of-12 =>67%; MAPK-signaling-markers –>8-out-of-10 =>80%). Accordingly, stress-triggered changes of transcriptional profile of mitochondrial dynamics/functionality markers as well as signaling molecules regulating both mitochondrial dynamics and spermatozoa number and functionality represent adaptive mechanisms.

Aqueous extract of pomegranate enriched in ellagitannins prevents anxiety-like behavior and metabolic changes induced by cafeteria diet in an animal model of menopause

Women around menopause are vulnerable to present psychiatric and metabolic disorders; thus, therapies that contribute to treat both pathologies are required. Previous reports showed that an aqueous extract of pomegranate (Punica granatum), enriched in ellagitannins, exerts an antidepressant-like effect in ovariectomized rats. We analyze whether this aqueous extract of P. granatum (AE-PG) prevents the anxiety-like behavior induced by a cafeteria diet (CAF) in middle-aged ovariectomized rats at the same time that it prevents an increase in body weight, glucose, lipids, and the changes on mRNA expression of the peroxisome proliferator-activated receptor-gamma (PPAR-γ) in the liver. Also, the effects of AE-PG on the protein levels of PPAR-γphospho-PPAR-γ, extracellular signal-regulated protein kinase (ERK1/2) and phospho-ERK1/2 were measured in the hippocampus and amygdala. CAF induced anxiety-like behavior, augmented lipids and glucose blood levels, body weight, visceral fat, insulin resistance, and decreased mRNA expression of PPAR-γ in the liver. In rats fed with the CAF, AE-PG prevented the anxiety-like behavior, reduced body weight, lowered lipid levels, reduced insulin resistance, and increased PPAR-γ mRNA expression in the liver. In the hippocampus, ERK1/2 but not PPAR-γ protein levels were decreased by CAF, while AE-PG prevented these effects. In the amygdala, CAF increased the phosphorylation of PPARγ, and AE-PG prevented it. In contrast, AE-PG rescued the decreased ERK1/2 protein level in the hippocampus caused by CAF. In conclusion, AE-PG treatment prevented anxiogenic and metabolic effects induced by CAF, and its effects appear to be mediated by ERK1/2 and PPARγ depending on the brain area studied.

Reduced spermatozoa functionality during stress is the consequence of adrenergic-mediated disturbance of mitochondrial dynamics markers

Here we investigate the stress-signaling responsible for the effects of acute/repeated psychological stresses (the most common stresses in human society) on spermatozoa number and functionality, as well as the transcriptional profile of mitochondrial dynamics markers by using the in vivo and ex vivo approaches. Acute and repeated stress inhibit spermatozoa functionality (acute -> 3.2-fold, repeated -> 2.5-fold), while only repeated stress reduces the spermatozoa number (1.7-fold). Stress hormones mimic these effects and decrease the spermatozoa functionality (adrenaline: 10 µM -> 2.4-fold, 100 µM - > 2.8-fold; hydrocortisone: 50 pM -> 2.7-fold, 500 pM -> 8.5-fold). They also significantly disturb the transcriptional profile of all main mitochondrial dynamics markers in spermatozoa. Ex vivo manipulation of stress signaling in spermatozoa reveals that most of these effects are mediated through ɑ1-and/or-β-adrenergic receptors. The transcription of these receptors and their kinases in the same samples is under the significant influence of adrenergic signaling. Our results are the first to show the importance of mitochondrial dynamics markers in spermatozoa since the transcriptional profiles of sixteen-out-of-ninteen are disturbed by manipulation of stress-hormones-signaling. This is a completely new molecular approach to assess spermatozoa functionality and it is important for a better understanding of the correlations between stress, environmental-life-style and other factors, and male (in)fertility.

Thromboxane A2 in the paraventricular hypothalamic nucleus mediates glucoprivation-induced adrenomedullary outflow

Glucoprivation stimulates a rapid sympathetic response to release and/or secrete catecholamines into the bloodstream. However, the central regulatory mechanisms involving adrenoceptors and prostanoids production in the paraventricular hypothalamic nucleus (PVN) that are responsible for the glucoprivation-induced elevation of plasma catecholamines are still unresolved. In this study, we aimed to clarify whether glucoprivation-induced activation of noradrenergic neurons projecting to the PVN can induce α- and/or β-adrenergic receptor activation and prostanoids production in the PVN to elevate plasma catecholamine levels. We examined the effects of α- and β-adrenergic receptor antagonists, a cyclooxygenase inhibitor, a thromboxane A synthase inhibitor, and a PGE₂ subtype EP₃ receptor antagonist on intravenously administered 2-deoxy-D-glucose (2-DG)-induced elevation of noradrenaline in the PVN and plasma levels of catecholamine in freely moving rats. In addition, we examined whether intravenously administered 2-DG can increase prostanoids levels in the PVN microdialysates. Intracerebroventricular (i.c.v.) pretreatment with phentolamine (a non-selective α-adrenergic receptor antagonist) suppressed the 2-DG-induced increase in the plasma level of adrenaline, whereas i.c.v. pretreatment with propranolol (a non-selective β-adrenergic receptor antagonist) suppressed the 2-DG-induced elevation of the plasma level of noradrenaline. I.c.v. pretreatment with indomethacin (a cyclooxygenase inhibitor) and furegrelate (a thromboxane synthase inhibitor) attenuated the 2-DG-induced elevations of both noradrenaline and adrenaline levels. Furthermore, 2-DG administration elevated the thromboxane B₂ level, a metabolite of thromboxane A₂ in PVN microdialysates. Our results suggest that glucoprivation-induced activation of α- and β-adrenergic receptor in the brain including the PVN and then thromboxane A₂ production in the PVN, which are essential for the 2-DG-induced elevations of both plasma adrenaline and noradrenaline levels.

Maternal high-fat diet induces sex-specific changes to glucocorticoid and inflammatory signaling in response to corticosterone and lipopolysaccharide challenge in adult rat offspring

BACKGROUND

Maternal obesity as a result of high levels of saturated fat (HFD) consumption leads to significant negative health outcomes in both mother and exposed offspring. Offspring exposed to maternal HFD show sex-specific alterations in metabolic, behavioral, and endocrine function, as well as increased levels of basal neuroinflammation that persists into adulthood. There is evidence that psychosocial stress or exogenous administration of corticosterone (CORT) potentiate inflammatory gene expression; however, the response to acute CORT or immune challenge in adult offspring exposed to maternal HFD during perinatal life is unknown. We hypothesize that adult rat offspring exposed to maternal HFD would show enhanced pro-inflammatory gene expression in response to acute administration of CORT and lipopolysaccharide (LPS) compared to control animals, as a result of elevated basal pro-inflammatory gene expression. To test this, we examined the effects of acute CORT and/or LPS exposure on pro and anti-inflammatory neural gene expression in adult offspring (male and female) with perinatal exposure to a HFD or a control house-chow diet (CHD).

METHODS

Rat dams consumed HFD or CHD for four weeks prior to mating, during gestation, and throughout lactation. All male and female offspring were weaned on to CHD. In adulthood, offspring were 'challenged' with administration of exogenous CORT and/or LPS, and quantitative PCR was used to measure transcript abundance of glucocorticoid receptors and downstream inflammatory markers in the amygdala, hippocampus, and prefrontal cortex.

RESULTS

In response to CORT alone, male HFD offspring showed increased levels of anti-inflammatory transcripts, whereas in response to LPS alone, female HFD offspring showed increased levels of pro-inflammatory transcripts. In addition, male HFD offspring showed greater pro-inflammatory gene expression and female HFD offspring exhibited increased anti-inflammatory gene expression in response to simultaneous CORT and LPS administration.

CONCLUSIONS

These findings suggest that exposure to maternal HFD leads to sex-specific changes that may alter inflammatory responses in the brain, possibly as an adaptive response to basal neuroinflammation.

Activation of PPARγ Attenuates the Expression of Physical and Affective Nicotine Withdrawal Symptoms through Mechanisms Involving Amygdala and Hippocampus Neurotransmission

An isoform of peroxisome proliferator-activated receptors (PPARs), PPARγ, is the receptor for the thiazolidinedione class of anti-diabetic medications including pioglitazone. Neuroanatomical data indicate PPARγ localization in brain areas involved in drug addiction. Preclinical and clinical data have shown that pioglitazone reduces alcohol and opioid self-administration, relapse to drug seeking, and plays a role in emotional responses. Here, we investigated the behavioral effect of PPARγ manipulation on nicotine withdrawal in male Wistar rats and in male mice with neuron-specific PPARγ deletion (PPARγ^(-/-)) and their littermate wild-type (PPARγ^(+/+)) controls. Real-time quantitative RT-PCR and RNAscope in situ hybridization assays were used for assessing the levels of expression and cell-type localization of PPARγ during nicotine withdrawal. Brain site-specific microinjections of the PPARγ agonist pioglitazone were performed to explore the role of this system on nicotine withdrawal at a neurocircuitry level. Results showed that activation of PPARγ by pioglitazone abolished the expression of somatic and affective nicotine withdrawal signs in rats and in (PPARγ^(+/+)) mice. This effect was blocked by the PPARγ antagonist GW9662. During early withdrawal and protracted abstinence, the expression of PPARγ increased in GABAergic and glutamatergic cells of the amygdala and hippocampus, respectively. Hippocampal microinjections of pioglitazone reduced the expression of the physical signs of withdrawal, whereas excessive anxiety associated with protracted abstinence was prevented by pioglitazone microinjection into the amygdala. Our results demonstrate the implication of the neuronal PPARγ in nicotine withdrawal and indicates that activation of PPARγ may offer an interesting strategy for smoking cessation.SIGNIFICANCE STATEMENT Smoking cessation leads the occurrence of physical and affective withdrawal symptoms representing a major burden to quit tobacco use. Here, we show that activation of PPARγ prevents the expression of both somatic and affective signs of nicotine withdrawal. At molecular levels results show that PPARγ expression increases in GABAergic cells in the hippocampus and in GABA- and glutamate-positive cells in the basolateral amygdala. Hippocampal microinjections of pioglitazone reduce the insurgence of the physical withdrawal signs, whereas anxiety linked to protracted abstinence is attenuated by pioglitazone injected into the amygdala. Our results demonstrate the implication of neuronal PPARγ in nicotine withdrawal and suggest that PPARγ agonism may represent a promising treatment to aid smoking cessation.

Association of chronic inflammation and perceived stress with abnormal functional connectivity in brain areas involved with interoception in hepatitis C patients

BACKGROUND

Sickness behavioral changes elicited by inflammation may become prolonged and dysfunctional in patients with chronic disease, such as chronic hepatitis C (CHC). Neuroimaging studies show that the basal ganglia and insula are sensitive to systemic inflammation.

AIM

To elucidate the clinical and neurobiological aspects of prolonged illnesses in patients with CHC.

METHODS

Thirty-five CHC patients not treated with interferon-α or other antiviral therapy, and 30 control subjects matched for age and sex, were evaluated for perceived stress (perceived stress scale; PSS), depression (PHQ-9), fatigue and irritability through a visual analog scale (VAS), as well as serum levels of interleukin-6 (IL-6), prostaglandin E₂ (PGE₂) and oxidative stress markers. Functional MRI was performed, measuring resting-state functional connectivity using a region-of-interest (seed)-based approach focusing on the bilateral insula, subgenual anterior cingulate cortex and bilateral putamen. Between-group differences in functional connectivity patterns were assessed with two-sample t-tests, while the associations between symptoms, inflammatory markers and functional connectivity patterns were analyzed with multiple regression analyses.

RESULTS

CHC patients had higher PSS, PHQ-9 and VAS scores for fatigue and irritability, as well as increased IL-6 levels, PGE₂ concentrations and antioxidant system activation compared to controls. PSS scores positively correlated with functional connectivity between the right anterior insula and right putamen, whereas PHQ-9 scores correlated with functional connectivity between most of the seeds and the right anterior insula. PGE₂ (positively) and IL-6 (negatively) correlated with functional connectivity between the right anterior insula and right caudate nucleus and between the right ventral putamen and right putamen/globus pallidus. PGE₂ and PSS scores accounted for 46% of the variance in functional connectivity between the anterior insula and putamen.

CONCLUSIONS

CHC patients exhibited increased perceived stress and depressive symptoms, which were associated with changes in inflammatory marker levels and in functional connectivity between the insula and putamen, areas involved in interoceptive integration, emotional awareness, and orientation of motivational state.

Neuroendocrine Regulation of Brain Cytokines After Psychological Stress

There is growing evidence that stress-induced brain cytokines are important in the etiology of depression and anxiety. Here, we review how the neuroendocrine responses to psychological stressors affect the immediate and long-term regulation of inflammatory cytokines within the brain and highlight how the regulation changes across time with repeated stress exposure. In doing so, we report on the percentage of studies in the literature that observed increases in either IL-1β, TNF-α, or IL-6 within the hypothalamus, hippocampus, or prefrontal cortex after either acute or chronic stress exposure. The key takeaway is that catecholamines and glucocorticoids play critical roles in the regulation of brain cytokines after psychological stress exposure. Central catecholamines stimulate the release of IL-1β from microglia, which is a key factor in the further activation of microglia and recruitment of monocytes into the brain. Meanwhile, the acute elevation of glucocorticoids inhibits the production of brain cytokines via two mechanisms: the suppression of noradrenergic locus coeruleus neurons and inhibition of the NFκB signaling pathway. However, glucocorticoids and peripheral catecholamines facilitate inflammatory responses to future stimuli by stimulating monocytes to leave the bone marrow, downregulating inhibitory receptors on microglia, and priming inflammatory responses mediated by peripheral monocytes or macrophages. The activation of microglia and the elevation of peripheral glucocorticoid and catecholamine levels are both necessary during times of stress exposure for the development of psychopathologies.

Sex differences in the regulation of brain IL-1β in response to chronic stress

Elevations in brain interleukin-1 beta (IL-1β) during chronic stress exposure have been implicated in behavioral and cognitive impairments associated with depression and anxiety. Two critical regulators of brain IL-1β production during times of stress are glucocorticoids and catecholamines. These hormones work in opposition to one another to inhibit (via glucocorticoid receptors) or stimulate (via beta-adrenergic receptors: β-AR) IL-1β production. While chronic stress often heightens both corticosterone and catecholamine levels, it remains unknown as to how chronic stress may affect the "yin-yang" balance between adrenergic stimulation and glucocorticoid suppression of brain IL-1β. To investigate this further, male and female rats underwent 4 days of stress exposure or served as non-stressed controls. On day 5, animals were administered propranolol (β-AR antagonist), metyrapone (a glucocorticoid synthesis inhibitor), vehicle, or both drugs and brain IL-1β mRNA was measured by rtPCR in limbic brain areas. In males, administration of propranolol had no effect on IL-1β expression in non-stressed controls but significantly reduced IL-1β in the hippocampus and amygdala of chronically stressed animals. In females, propranolol significantly reduced IL-1β in the amygdala and hypothalamus of both control and stressed rats. In male rats, metyrapone treatment significantly increased IL-1β mRNA regardless of stress treatment in all brain areas, while in female rats metyrapone only increased IL-1β in the hypothalamus. Interestingly, propranolol treatment blocked the metyrapone-induced increase in brain IL-1β indicating the increase in brain IL-1β following metyrapone treatment was due to increase β-AR activation. Additional studies revealed that metyrapone significantly increases norepinephrine turnover in the hypothalamus and medial prefrontal cortex in male rats and that microglia appear to be the cell type contributing to the production of IL-1β. Overall, data reveal that stress exposure in male rats affects the regulation of brain IL-1β by the norepinephrine-β-AR pathway, while stress had no effect in the regulation of brain IL-1β in female rats.

Stress, inflammation, and eicosanoids: an emerging perspective

Clinical and experimental studies support the notion that adrenergic stimulation and chronic stress affect inflammation, metabolism, and tumor growth. Eicosanoids are also known to heavily influence inflammation while regulating certain stress responses. However, additional work is needed to understand the full extent of interactions between the stress-related pathways and eicosanoids. Here, we review the potential influences that stress, inflammation, and metabolic pathways have on each other, in the context of eicosanoids. Understanding the intricacies of such interactions could provide insights on how systemic metabolic effects mediated by the stress pathways can be translated into therapies for cancer and other diseases.

Cerebrovascular Injury After Serial Exposure to Chronic Stress and Abstinence from Methamphetamine Self-Administration

Cerebrovascular damage caused by either exposure to stress or the widely abused drug, methamphetamine (Meth) is known but stress and drug abuse frequently occur in tandem that may impact their individual cerebrovascular effects. This study examined their co-morbid cerebrovascular effects during abstinence from self-administered Meth after the exposure to chronic unpredictable stress (CUS). Exposure to CUS prior to unrestricted Meth self-administration had no effect on Meth intake in rats; however, the pro-inflammatory mediator cyclooxygenase-2 (COX-2) and the breakdown of cell-matrix adhesion protein β-dystroglycan in isolated cerebral cortical capillaries were increased after 3 days of abstinence and persisted for 7 days. These changes preceded decreases in occludin, a key structural protein component of the blood-brain barrier. The decrease in occludin was blocked by the COX-2 specific inhibitor nimesulide treatment during abstinence from Meth. The changes in COX-2, β-dystroglycan, and occludin were only evident following the serial exposure to stress and Meth but not after either one alone. These results suggest that stress and voluntary Meth intake can synergize and disrupt cerebrovasculature in a time-dependent manner during abstinence from chronic stress and Meth. Furthermore, COX-2 inhibition may be a viable pharmacological intervention to block vascular changes after Meth exposure.

Inhibition of Fatty Acid Amide Hydrolase by PF-3845 Alleviates the Nitrergic and Proinflammatory Response in Rat Hippocampus Following Acute Stress

BACKGROUND

Long-term exposure to stress has been demonstrated to cause neuroinflammation through a sustained overproduction of free radicals, including nitric oxide, via an increased inducible nitric oxide synthase activity. We previously demonstrated that inducible nitric oxide synthase activity and mRNA are significantly upregulated in the rat hippocampus following just 4 hours of restraint stress. Similar to nitric oxide, endocannabinoids are synthesized on demand, with preclinical observations suggesting that cannabinoid receptor agonists and endocannabinoid enhancers inhibit nitrergic activity. Specifically, previous work has shown that enhancement of endocannabinoids via inhibition of fatty acid amide hydrolase with PF-3845 reduced inducible nitric oxide synthase-expressing microglia following traumatic brain injury. However, this describes cannabinoid modulation following physical injury, and therefore the present study aimed to examine the effects of PF-3845 in the modulation of nitrergic and inflammatory-related genes within the hippocampus after acute stress exposure.

METHODS

Following vehicle or PF-3845 injections (5 mg/kg; i.p.), male Wistar rats were exposed to 0 (control), 60, 240, or 360 minutes of restraint stress after which plasma and dorsal hippocampus were isolated for further biochemical and gene expression analysis.

RESULTS

The results demonstrate that pretreatment with PF-3845 rapidly ameliorates plasma corticosterone release at 60 minutes of stress. An increase in endocannabinoid signalling also induces an overall attenuation in inducible nitric oxide synthase, tumor necrosis factor-alpha convertase, interleukin-6, cyclooxygenase-2, peroxisome proliferator-activated receptor gamma mRNA, and the transactivation potential of nuclear factor kappa-light-chain-enhancer of activated B cells in the hippocampus.

CONCLUSIONS

These results suggest that enhanced endocannabinoid levels in the dorsal hippocampus have an overall antinitrosative and antiinflammatory effect following acute stress exposure.

Acute stress alters the rates of degradation of cardiac muscle proteins

Stressful experiences can have detrimental effects on many aspects of health and wellbeing. The zebrafish (Danio rerio) is a widely used model for stress research and a stress phenotype can be induced by manipulating the environmental conditions and social interactions. In this study we have combined a zebrafish stress model with the measurement of degradation rates of soluble cardiac muscle proteins. The results showed that the greater the stress response in the zebrafish the lower the level of overall protein degradation. On comparing the rates of degradation for individual proteins it was found that four main pathways were altered in response to stress conditions with decreased degradation for proteins involved in glucose metabolism, gluconeogenesis, the ubiquitin-proteasome system (UPS) and peroxisomal proliferator-activated receptor (PPAR) signalling pathways. Taken together, these data indicate that under stress conditions zebrafish preserve cardiac muscle proteins required for the 'fight or flight' response together with proteins that play a role in stress mitigation. SIGNIFICANCE: This study is the first to investigate the impact of stressful experiences on the dynamics of protein turnover in cardiac muscle. Using an established zebrafish model of human stress it has been possible to map key pathways at the protein level. The results show that the rates of degradation of cardiac proteins involved in glucose metabolism, UPS activity, hypoxia and PPAR signalling are decreased in stressed zebrafish. These findings indicate that proteins involved in the 'fight or flight' response to stress are conserved by the heart together with proteins that play a role in stress mitigation. This work provides the basis for more detailed investigations aimed at understanding the molecular effects of stress, which has implications for human health and disease.

Regulatory and Mechanistic Actions of Glucocorticoids on T and Inflammatory Cells

Glucocorticoids (GCs) play an important role in regulating the inflammatory and immune response and have been used since decades to treat various inflammatory and autoimmune disorders. Fine-tuning the glucocorticoid receptor (GR) activity is instrumental in the search for novel therapeutic strategies aimed to reduce pathological signaling and restoring homeostasis. Despite the primary anti-inflammatory actions of GCs, there are studies suggesting that under certain conditions GCs may also exert pro-inflammatory responses. For these reasons the understanding of the GR basic mechanisms of action on different immune cells in the periphery (e.g., macrophages, dendritic cells, neutrophils, and T cells) and in the brain (microglia) contexts, that we review in this chapter, is a continuous matter of interest and may reveal novel therapeutic targets for the treatment of immune and inflammatory response.

Fat-brain connections: Adipocyte glucocorticoid control of stress and metabolism

Glucocorticoids act via multiple mechanisms to mobilize energy for maintenance and restoration of homeostasis. In adipose tissue, glucocorticoids can promote lipolysis and facilitate adipocyte differentiation/growth, serving both energy-mobilizing and restorative processes during negative energy balance. Recent data suggest that adipose-dependent feedback may also be involved in regulation of stress responses. Adipocyte glucocorticoid receptor (GR) deletion causes increased HPA axis stress reactivity, due to a loss of negative feedback signals into the CNS. The fat-to-brain signal may be mediated by neuronal mechanisms, release of adipokines or increased lipolysis. The ability of adipose GRs to inhibit psychogenic as well as metabolic stress responses suggests that (1) feedback regulation of the HPA axis occurs across multiple bodily compartments, and (2) fat tissue integrates psychogenic stress signals. These studies support a link between stress biology and energy metabolism, a connection that has clear relevance for numerous disease states and their comorbidities.

A multispecies approach for understanding neuroimmune mechanisms of stress

The relationship between stress challenges and adverse health outcomes, particularly for the development of affective disorders, is now well established. The highly conserved neuroimmune mechanisms through which responses to stressors are transcribed into effects on males and females have recently garnered much attention from researchers and clinicians alike. The use of animal models, from mice to guinea pigs to primates, has greatly increased our understanding of these mechanisms on the molecular, cellular, and behavioral levels, and research in humans has identified particular brain regions and connections of interest, as well as associations between stress-induced inflammation and psychiatric disorders. This review brings together findings from multiple species in order to better understand how the mechanisms of the neuroimmune response to stress contribute to stress-related psychopathologies, such as major depressive disorder, schizophrenia, and bipolar disorder.

Candesartan, angiotensin II type 1 receptor blocker is able to relieve age-related cognitive impairment

BACKGROUND

Candesartan is one of the standard antihypertensive drug belonging to AT1R angiotensin receptor blockers (ARBs) group. Beneficial effects of this drug in the treatment of hypertension are well recognized. In this study we tested a hypothesis that candesartan could alleviate age-related memory decline.

METHODS

Aged and young rats have been treated with candesartan (0.1mg kg^-1) for 21days and then underwent a battery of behavioral tests: for assessment of long-term memory (Passive avoidance test - PA), recognition memory (Object recognition test - OR), locomotor functions (Open field - OF) and anxiety behavior (Elevated plus maze - EPM).

RESULTS

Aged rats (2-years-old) displayed clear declining tendency in the retrieval of passive avoidance behavior showing thus increased forgetting. Prolonged administration of candesartan significantly (p<0.01) reversed this phenomenon causing recall measured as the avoidance latency, and surprisingly also showed the tendency to recall deterioration observed in the young rats. More optimistic results were achieved in the OR, where candesartan significantly improved recognition memory (p<0.001) of aged rats who performed even better than the young ones (p<0.05).

CONCLUSIONS

It appears that candesartan potently abolishes some kinds of aging-induced memory impairments and cognitive declines in aged rats, but in some circumstances it may even could increase the damage of memory. It seems that the use of sartans in the treatment of hypertension for patients with associated cognitive impairment, or for people in risk groups for such disorders can be an interesting alternative.

Pro-inflammatory immune-to-brain signaling is involved in neuroendocrine responses to acute emotional stress

Activation of the hypothalamo-pituitary-adrenal (HPA) axis by inflammatory stressors (e.g., bacterial lipopolysaccharide) is thought to involve vascular transduction of circulating cytokines, with perivascular macrophages (PVMs) along with endothelia, effecting activation of HPA control circuitry via inducible (cyclooxygenase-2- or COX-2-dependent) prostaglandin synthesis. To test the stressor-specificity of this mechanism, we examined whether ablation of PVMs or pharmacologic blockade of COX activity affected HPA responses to a representative emotional stressor, restraint. Exposing rats to a single 30min acute restraint episode provoked increased plasma levels of at least one proinflammatory cytokine, IL-6, microglial activation and multiple indices of cerebrovascular activation, including COX-2 expression and increased brain prostaglandin E₂ levels at 0-2h after stress. Pretreatment with the nonselective COX inhibitor, indomethacin, either icv (10μg in 5μl) or iv (1mg/kg) significantly reduced restraint-induced Fos expression in the paraventricular hypothalamic nucleus (PVH) by 45%, relative to vehicle-injected controls. A 75% reduction of the PVH activational response was seen in rats exposed to acute restraint 5-7days after ablation of brain PVMs by icv injection of liposomes encapsulating the bisphosphonate drug, clodronate. Basal plasma levels of ACTH and corticosterone were not altered in clodronate liposome-injected rats, but the peak magnitude of restraint-induced HPA secretory responses was substantially reduced, relative to animals pretreated with saline-filled liposomes. These findings support an unexpectedly prominent role for inducible prostaglandin synthesis by PVMs in HPA responses to acute restraint, a prototypic emotional stressor.

Paliperidone reverts Toll-like receptor 3 signaling pathway activation and cognitive deficits in a maternal immune activation mouse model of schizophrenia

The pathophysiology of psychotic disorders is multifactorial, including alterations in the immune system caused by exogenous or endogenous factors. Epidemiological and experimental studies indicate that infections during the gestational period represent a risk factor to develop schizophrenia (SZ) along lifetime. Here, we tested the hypothesis that the antipsychotic paliperidone regulates immune-related brain effects in an experimental model of SZ. A well described prenatal immune activation model of SZ in mice by maternal injection of the viral mimetic poly(I:C) during pregnancy was used. Young-adult offspring animals (60PND) received paliperidone ip (0.05 mg/kg) for 21 consecutive days. One day after last injection, animals were submitted to a cognitive test and brain frontal cortex (FC) samples were obtained for biochemical determinations. The adults showed an activated innate immune receptor TLR-3 signaling pathway, oxidative/nitrosative stress and accumulation of pro-inflammatory mediators such as nuclear transcription factors (i.e., NFκB) and inducible enzymes (i.e., iNOS) in FC. Chronic paliperidone blocked this neuroinflammatory response possibly by the synergic activation and preservation of endogenous antioxidant/anti-inflammatory mechanisms such as NRF2 and PPARγ pathways, respectively. Paliperidone administration also stimulated the alternative polarization of microglia to the M2 anti-inflammatory profile. In addition, paliperidone treatment improved spatial working memory deficits of this SZ-like animal model. In conclusion, chronic administration of paliperidone to young-adult mice prenatally exposed to maternal immune (MIA) challenge elicits a general preventive anti-inflammatory/antioxidant effect at both intracellular and cellular polarization (M1/M2) level in FC, as well as ameliorates specific cognitive deficits.

Genetic Deletion of Neuronal PPARγ Enhances the Emotional Response to Acute Stress and Exacerbates Anxiety: An Effect Reversed by Rescue of Amygdala PPARγ Function

PPARγ is one of the three isoforms of the Peroxisome Proliferator-Activated Receptors (PPARs). PPARγ is activated by thiazolidinediones such as pioglitazone and is targeted to treat insulin resistance. PPARγ is densely expressed in brain areas involved in regulation of motivational and emotional processes. Here, we investigated the role of PPARγ in the brain and explored its role in anxiety and stress responses in mice. The results show that stimulation of PPARγ by pioglitazone did not affect basal anxiety, but fully prevented the anxiogenic effect of acute stress. Using mice with genetic ablation of neuronal PPARγ (PPARγ^NestinCre), we demonstrated that a lack of receptors, specifically in neurons, exacerbated basal anxiety and enhanced stress sensitivity. The administration of GW9662, a selective PPARγ antagonist, elicited a marked anxiogenic response in PPARγ wild-type (WT), but not in PPARγ^NestinCre knock-out (KO) mice. Using c-Fos immunohistochemistry, we observed that acute stress exposure resulted in a different pattern of neuronal activation in the amygdala (AMY) and the hippocampus (HIPP) of PPARγ^NestinCre KO mice compared with WT mice. No differences were found between WT and KO mice in hypothalamic regions responsible for hormonal response to stress or in blood corticosterone levels. Microinjection of pioglitazone into the AMY, but not into the HIPP, abolished the anxiogenic response elicited by acute stress. Results also showed that, in both regions, PPARγ colocalizes with GABAergic cells. These findings demonstrate that neuronal PPARγ is involved the regulation of the stress response and that the AMY is a key substrate for the anxiolytic effect of PPARγ.

SIGNIFICANCE STATEMENT

Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) is a classical target for antidiabetic therapies with thiazolidinedione compounds. PPARγ agonists such as rosiglitazone and pioglitazone are in clinical use for the treatment of insulin resistance. PPARγ has recently attracted attention for its involvement in the regulation of CNS immune response and functions. Here, we demonstrate that neuronal PPARγ activation prevented the negative emotional effects of stress and exerted anxiolytic actions without influencing hypothalamic-pituitary-adrenal axis function. Conversely, pharmacological blockade or genetic deletion of PPARγ enhanced anxiogenic responses and increased vulnerability to stress. These effects appear to be controlled by PPARγ neuronal-mediated mechanisms in the amygdala.

High glucocorticoid levels during gestation activate the inflammasome in hippocampal oligodendrocytes of the offspring

Exposure to high levels of glucocorticoids (GCs) during early life induces long-lasting neuroinflammation. GCs induce rapid degranulation of mast cells, which release proinflammatory molecules promoting activation of microglia and astrocytes. The possible involvement of oligodendrocytes, however, remains poorly understood. It was studied whether high GC levels during gestation activates the inflammasome in hippocampal oligodendrocytes of mouse offspring. Oligodendrocytes of control pups showed expression of inflammasome components (NLRP3, ACS, and caspase-1) and their levels were increased by prenatal administration of dexamethasone (DEX), a synthetic GC. These cells also showed high levels of IL-1β and TNF-α, revealing activation of the inflammasome. Moreover, they showed increased levels of the P2X₇ receptor and pannexin1, which are associated to inflammasome activation. However, levels of connexins either were not affected (Cx29) or reduced (Cx32 and Cx47). Nonetheless, the functional states of pannexin1 and connexin hemichannels were elevated and directly associated to functional P2X₇ receptors. As observed in DEX-treated brain slices, hemichannel activity first increased in hippocampal mast cells and later in microglia and macroglia. DEX-induced oligodendrocyte hemichannel activity was mimicked by urocortin-II, which is a corticotropin-releasing hormone receptor (CRHR) agonist. Response to DEX and urocortin-II was inhibited by antalarmin (a CRHR blocker) or by mast cells or microglia inhibitors. The increase in hemichannel activity persisted for several weeks after birth and cross-fostering with a control mother did not reverse this condition. It is proposed that activation of the oligodendrocyte inflammasome might be relevant in demyelinating diseases associated with early life exposure to high GC levels. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 625-642, 2017.

Neuroprotective Role of L-NG-Nitroarginine Methyl Ester (L-NAME) against Chronic Hypobaric Hypoxia with Crowding Stress (CHC) Induced Depression-Like Behaviour

Improper neuroimmune responses following chronic stress exposure have been reported to cause neuronal dysfunctions leading to memory impairment, anxiety and depression like behaviours. Though several factors affecting microglial activation and consequent alteration in neuro-inflammatory responses have been well studied, role of NO and its association with microglia in stress induced depression model is yet to be explored. In the present study, we validated combination of chronic hypobaric hypoxia and crowding (CHC) as a stress model for depression and investigated the role of chronic stress induced elevated nitric oxide (NO) level in microglia activation and its effect on neuro-inflammatory responses in brain. Further, we evaluated the ameliorative effect of L-NG-Nitroarginine Methyl Ester (L-NAME) to reverse the stress induced depressive mood state. Four groups of male Sprague Dawley rat were taken and divided into control and CHC stress exposed group with and without treatment of L-NAME. Depression like behaviour and anhedonia in rats were assessed by Forced Swim Test (FST) and Sucrose Preference Test (SPT). Microglial activation was evaluated using Iba-1 immunohistochemistry and proinflammatory cytokines were assessed in the hippocampal region. Our result showed that exposure to CHC stress increased the number of active microglia with corresponding increase in inflammatory cytokines and altered behavioural responses. The inhibition of NO synthesis by L-NAME during CHC exposure decreased the number of active microglia in hippocampus as evident from decreased Iba-1 positive cells. Further, L-NAME administration decreased pro-inflammatory cytokines in hippocampus and improved behaviour of rats. Our study demonstrate that stress induced elevation of NO plays pivotal role in altered microglial activation and consequent neurodegenerative processes leading to depression like behaviour in rat.

Modulation of the antioxidant nuclear factor (erythroid 2-derived)-like 2 pathway by antidepressants in rats

Patients with major depression who are otherwise medically healthy have activated inflammatory pathways in their organism. It has been described that depression is not only escorted by inflammation but also by induction of multiple oxidative/nitrosative stress pathways. Nevertheless, there are finely regulated mechanisms involved in preserving cells from damage, such as the antioxidant nuclear transcription factor Nrf2. We aim to explore in a depression-like model the Nrf2 pathway in the prefrontal cortex (PFC) and the hippocampus of rats and to analyze whether antidepressants affect the antioxidant activity of the Nrf2 pathway. Male Wistar rats were exposed to chronic mild stress (CMS) and some of them were treated with desipramine, escitalopram or duloxetine. We studied the expression of upstream and downstream elements of the Nrf2 pathway and the oxidative damage induced by the CMS. After CMS, there is an inhibition of upstream and downstream elements of the Nrf2 pathway in the PFC (e.g. PI3K/Akt, GPx…). Moreover, antidepressant treatments, particularly desipramine and duloxetine, are able to recover some of these elements and to reduce the oxidative damage induced by the CMS. However, in the hippocampus, Nrf2 pathways are not that affected and antidepressants do not have many actions. In conclusion, Nrf2 pathway is differentially regulated by antidepressants in the PFC and hippocampus. The Nrf2 pathway is involved in the oxidative/nitrosative damage detected in the PFC and antidepressants have a therapeutic action through this pathway. However, it seems that Nrf2 is not involved in the effects caused by CMS in the hippocampus.

Stress triggers mitochondrial biogenesis to preserve steroidogenesis in Leydig cells

Adaptability to stress is a fundamental prerequisite for survival. Mitochondria are a key component of the stress response in all cells. For steroid-hormones-producing cells, including also Leydig cells of testes, the mitochondria are a key control point for the steroid biosynthesis and regulation. However, the mitochondrial biogenesis in steroidogenic cells has never been explored. Here we show that increased mitochondrial biogenesis is the adaptive response of testosterone-producing Leydig cells from stressed rats. All markers of mitochondrial biogenesis together with transcription factors and related kinases are up-regulated in Leydig cells from rats exposed to repeated psychophysical stress. This is followed with increased mitochondrial mass. The expression of PGC1, master regulator of mitochondrial biogenesis and integrator of environmental signals, is stimulated by cAMP-PRKA, cGMP, and β-adrenergic receptors. Accordingly, stress-triggered mitochondrial biogenesis represents an adaptive mechanism and does not only correlate with but also is an essential for testosterone production, being both events depend on the same regulators. Here we propose that all events induced by acute stress, the most common stress in human society, provoke adaptive response of testosterone-producing Leydig cells and activate PGC1, a protein required to make new mitochondria but also protector against the oxidative damage. Given the importance of mitochondria for steroid hormones production and stress response, as well as the role of steroid hormones in stress response and metabolic syndrome, we anticipate our result to be a starting point for more investigations since stress is a constant factor in life and has become one of the most significant health problems in modern societies.

Toward Omics-Based, Systems Biomedicine, and Path and Drug Discovery Methodologies for Depression-Inflammation Research

Meta-analyses confirm that depression is accompanied by signs of inflammation including increased levels of acute phase proteins, e.g., C-reactive protein, and pro-inflammatory cytokines, e.g., interleukin-6. Supporting the translational significance of this, a meta-analysis showed that anti-inflammatory drugs may have antidepressant effects. Here, we argue that inflammation and depression research needs to get onto a new track. Firstly, the choice of inflammatory biomarkers in depression research was often too selective and did not consider the broader pathways. Secondly, although mild inflammatory responses are present in depression, other immune-related pathways cannot be disregarded as new drug targets, e.g., activation of cell-mediated immunity, oxidative and nitrosative stress (O&NS) pathways, autoimmune responses, bacterial translocation, and activation of the toll-like receptor and neuroprogressive pathways. Thirdly, anti-inflammatory treatments are sometimes used without full understanding of their effects on the broader pathways underpinning depression. Since many of the activated immune-inflammatory pathways in depression actually confer protection against an overzealous inflammatory response, targeting these pathways may result in unpredictable and unwanted results. Furthermore, this paper discusses the required improvements in research strategy, i.e., path and drug discovery processes, omics-based techniques, and systems biomedicine methodologies. Firstly, novel methods should be employed to examine the intracellular networks that control and modulate the immune, O&NS and neuroprogressive pathways using omics-based assays, including genomics, transcriptomics, proteomics, metabolomics, epigenomics, immunoproteomics and metagenomics. Secondly, systems biomedicine analyses are essential to unravel the complex interactions between these cellular networks, pathways, and the multifactorial trigger factors and to delineate new drug targets in the cellular networks or pathways. Drug discovery processes should delineate new drugs targeting the intracellular networks and immune-related pathways.

Methamphetamine effects on blood-brain barrier structure and function

Methamphetamine (Meth) is a widely abuse psychostimulant. Traditionally, studies have focused on the neurotoxic effects of Meth on monoaminergic neurotransmitter terminals. Recently, both in vitro and in vivo studies have investigated the effects of Meth on the BBB and found that Meth produces a decrease in BBB structural proteins and an increase in BBB permeability to various molecules. Moreover, preclinical studies are validated by clinical studies in which human Meth users have increased concentrations of toxins in the brain. Therefore, this review will focus on the structural and functional disruption of the BBB caused by Meth and the mechanisms that contribute to Meth-induced BBB disruption. The review will reveal that the mechanisms by which Meth damages dopamine and serotonin terminals are similar to the mechanisms by which the blood-brain barrier (BBB) is damaged. Furthermore, this review will cover the factors that are known to potentiate the effects of Meth (McCann et al., 1998) on the BBB, such as stress and HIV, both of which are co-morbid conditions associated with Meth abuse. Overall, the goal of this review is to demonstrate that the scope of damage produced by Meth goes beyond damage to monoaminergic neurotransmitter systems to include BBB disruption as well as provide a rationale for investigating therapeutics to treat Meth-induced BBB disruption. Since a breach of the BBB can have a multitude of consequences, therapies directed toward the treatment of BBB disruption may help to ameliorate the long-term neurodegeneration and cognitive deficits produced by Meth and possibly even Meth addiction.

Neuroimmune mechanisms of stress: sex differences, developmental plasticity, and implications for pharmacotherapy of stress-related disease

The last decade has witnessed profound growth in studies examining the role of fundamental neuroimmune processes as key mechanisms that might form a natural bridge between normal physiology and pathological outcomes. Rooted in core concepts from psychoneuroimmunology, this review utilizes a succinct, exemplar-driven approach of several model systems that contribute significantly to our knowledge of the mechanisms by which neuroimmune processes interact with stress physiology. Specifically, we review recent evidence showing that (i) stress challenges produce time-dependent and stressor-specific patterns of cytokine/chemokine expression in the CNS; (ii) inflammation-related genes exhibit unique expression profiles in males and females depending upon individual, cooperative or antagonistic interactions between steroid hormone receptors (estrogen and glucocorticoid receptors); (iii) adverse social experiences incurred through repeated social defeat engage a dynamic process of immune cell migration from the bone marrow to brain and prime neuroimmune function and (iv) early developmental exposure to an inflammatory stimulus (carageenin injection into the hindpaw) has a lasting influence on stress reactivity across the lifespan. As such, the present review provides a theoretical framework for understanding the role that neuroimmune mechanisms might play in stress plasticity and pathological outcomes, while at the same time pointing toward features of the individual (sex, developmental experience, stress history) that might ultimately be used for the development of personalized strategies for therapeutic intervention in stress-related pathologies.

Novel aspects of glucocorticoid actions

Normal hypothalamic-pituitary-adrenal (HPA) axis activity leading to the rhythmic and episodic release of adrenal glucocorticoids (GCs) is essential for body homeostasis and survival during stress. Acting through specific intracellular receptors in the brain and periphery, GCs regulate behaviour, as well as metabolic, cardiovascular, immune and neuroendocrine activities. By contrast to chronic elevated levels, circadian and acute stress-induced increases in GCs are necessary for hippocampal neuronal survival and memory acquisition and consolidation, as a result of the inhibition of apoptosis, the facilitation of glutamatergic neurotransmission and the formation of excitatory synapses, and the induction of immediate early genes and dendritic spine formation. In addition to metabolic actions leading to increased energy availability, GCs have profound effects on feeding behaviour, mainly via the modulation of orexigenic and anorixegenic neuropeptides. Evidence is also emerging that, in addition to the recognised immune suppressive actions of GCs by counteracting adrenergic pro-inflammatory actions, circadian elevations have priming effects in the immune system, potentiating acute defensive responses. In addition, negative-feedback by GCs involves multiple mechanisms leading to limited HPA axis activation and prevention of the deleterious effects of excessive GC production. Adequate GC secretion to meet body demands is tightly regulated by a complex neural circuitry controlling hypothalamic corticotrophin-releasing hormone (CRH) and vasopressin secretion, which are the main regulators of pituitary adrenocorticotrophic hormone (ACTH). Rapid feedback mechanisms, likely involving nongenomic actions of GCs, mediate the immediate inhibition of hypothalamic CRH and ACTH secretion, whereas intermediate and delayed mechanisms mediated by genomic actions involve the modulation of limbic circuitry and peripheral metabolic messengers. Consistent with their key adaptive roles, HPA axis components are evolutionarily conserved, being present in the earliest vertebrates. An understanding of these basic mechanisms may lead to novel approaches for the development of diagnostic and therapeutic tools for disorders related to stress and alterations of GC secretion.

The HPA - Immune Axis and the Immunomodulatory Actions of Glucocorticoids in the Brain

In response to physiological and psychogenic stressors, the hypothalamic–pituitary–adrenal (HPA) axis orchestrates the systemic release of glucocorticoids (GCs). By virtue of nearly ubiquitous expression of the GC receptor and the multifaceted metabolic, cardiovascular, cognitive, and immunologic functions of GCs, this system plays an essential role in the response to stress and restoration of an homeostatic state. GCs act on almost all types of immune cells and were long recognized to perform salient immunosuppressive and anti-inflammatory functions through various genomic and non-genomic mechanisms. These renowned effects of the steroid hormone have been exploited in the clinic for the past 70 years and synthetic GC derivatives are commonly used for the therapy of various allergic, autoimmune, inflammatory, and hematological disorders. The role of the HPA axis and GCs in restraining immune responses across the organism is however still debated in light of accumulating evidence suggesting that GCs can also have both permissive and stimulatory effects on the immune system under specific conditions. Such paradoxical actions of GCs are particularly evident in the brain, where substantial data support either a beneficial or detrimental role of the steroid hormone. In this review, we examine the roles of GCs on the innate immune system with a particular focus on the CNS compartment. We also dissect the numerous molecular mechanisms through which GCs exert their effects and discuss the various parameters influencing the paradoxical immunomodulatory functions of GCs in the brain.

The inflamed axis: the interaction between stress, hormones, and the expression of inflammatory-related genes within key structures comprising the hypothalamic-pituitary-adrenal axis

Acute stress increases the expression of cytokines and other inflammatory-related factors in the CNS, plasma, and endocrine glands, and activation of inflammatory signaling pathways within the hypothalamic-pituitary-adrenal (HPA) axis may play a key role in later stress sensitization. In addition to providing a summary of stress effects on neuroimmune changes within the CNS, we present a series of experiments that characterize stress effects on members of the interleukin-1β (IL-1) super-family and other inflammatory-related genes in key structures comprising the HPA axis (PVN, pituitary and adrenal glands), followed by a series of experiments examining the impact of exogenous hormone administration (CRH and ACTH) and dexamethasone on the expression of inflammatory-related genes in adult male Sprague-Dawley rats. The results demonstrated robust, time-dependent, and asynchronous expression patterns for IL-1 and IL-1R2 in the PVN, with substantial increases in IL-6 and COX-2 in the adrenal glands emerging as key findings. The effects of exogenous CRH and ACTH were predominantly isolated within the adrenals. Finally, pretreatment with dexamethasone severely blunted neuroimmune changes in the adrenal glands, but not in the PVN. These findings provide novel insight into the relationship between stress, the expression of inflammatory signaling factors within key structures comprising the HPA axis, and their interaction with HPA hormones, and provide a foundation for better understanding the role of cytokines as modulators of hypothalamic, pituitary and adrenal sensitivity.

Tropisetron attenuates amyloid-beta-induced inflammatory and apoptotic responses in rats

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder featured by deposition of beta-amyloid (Aβ) plaques in the hippocampus and associated cortices and progressive cognitive decline. Tropisetron, a selective 5-HT3 receptor antagonist, is conventionally used to counteract chemotherapy-induced emesis. Recent investigations describe antiphlogistic properties for tropisetron. It has been shown that tropisetron protects against rat embolic stroke. We investigated protective properties of tropisetron in a beta-amyloid (Aβ) rat model of AD and possible involvement of 5-HT3 receptors.

MATERIAL AND METHODS

Aβ (1-42) was injected into the hippocampus of male rats. Animals were treated intracerebroventricularly with tropisetron, mCPBG (selective 5-HT3 receptor agonist) or mCPBG plus tropisetron on days 1, 3, 5 and 7. Seven days following Aβ administration, inflammatory markers (TNF-α, COX-2, iNOS and NF-κB), apoptotic markers (caspase 3 cytochrome c release) and calcineurin phosphatase activity were assessed in hippocampus.

RESULTS

Seven days following Aβ inoculation, control animals displayed dramatic increase in TNF-α, COX-2, iNOS, NF-κB, active caspase 3, cytochrome c release and calcineurin phosphatase activity in the hippocampus. Tropisetron significantly diminished the elevated levels of these markers and reversed the cognitive deficit. Interestingly, tropisetron was also found to be a potent inhibitor of calcineurin phosphatase activity. The selective 5-HT3 receptor agonist mCPBG, when co-administered with tropisetron, completely reversed the procognitive and anti-apoptotic properties of tropisetron while it could only partially counteract the anti-inflammatory effects. mCPBG alone significantly aggravated Aβ-induced injury.

CONCLUSION

Our findings indicate that tropisetron protects against Aβ-induced neurotoxicity in vivo through both 5-HT3 receptor-dependent and independent pathways.

Assessing competence of broccoli consumption on inflammatory and antioxidant pathways in restraint-induced models: estimation in rat hippocampus and prefrontal cortex

A growing body of evidence advocated the protective and therapeutic potential of natural compounds and phytochemicals used in diets against pathological conditions. Herein, the outcome of dietary whole broccoli consumption prior to restraint stress has been investigated in the hippocampus and prefrontal cortex of male rats, two important regions involved in the processing of responses to stressful events. Interestingly, a region-specific effect was detected regarding some of antioxidant defense system factors: nuclear factor erythroid-derived 2-related factor 2 (Nrf-2) antioxidant pathway, mitochondrial prosurvival proteins involved in mitochondrial biogenesis, and apoptotic cell death proteins. Dietary broccoli supplementation modulated the restraint-induced changes towards a consistent overall protection in the hippocampus. In the prefrontal cortex, however, despite activation of most of the protective factors, presumably as an attempt to save the system against the stress insult, some detrimental outcomes such as induced malate dehydrogenase (MDA) level and cleaved form of caspase-3 were detectable. Such diversity may be attributed in one hand to the different basic levels and/or availability of defensive mechanisms within the two studied cerebral regions, and on the other hand to the probable dose-dependent and hormetic effects of whole broccoli. More experiments are essential to demonstrate these assumptions.

Cyclooxygenase activity contributes to the monoaminergic damage caused by serial exposure to stress and methamphetamine

Methamphetamine (Meth) is a widely abused psychostimulant that causes long-term dopamine (DA) and serotonin (5-HT) depletions. Stress and Meth abuse are comorbid events in society and stress exacerbates Meth-induced monoaminergic terminal damage. Stress is also known to produce neuroinflammation. This study examined the role of the neuroinflammatory mediator, cyclooxygenase (COX), in the depletions of monoamines caused by serial exposure to chronic unpredictable stress (CUS) and Meth. CUS produced an increase in COX-2 protein expression and enhanced Meth-induced monoaminergic depletions in the striatum and hippocampus. The enhanced DA and 5-HT depletions in the striatum, but not the hippocampus, were prevented by pretreatment with COX inhibitor, ketoprofen, during stress or during Meth; however, ketoprofen did not attenuate the monoaminergic damage caused by Meth alone. The COX-dependent enhancement by stress of Meth-induced monoaminergic depletions was independent of hyperthermia, as ketoprofen did not attenuate Meth-induced hyperthermia. In addition, the EP1 receptor antagonist, SC-51089, did not attenuate DA or 5-HT depletions caused by stress and Meth. These findings illustrate that COX activity, but not activation of the EP1 receptor, is responsible for the potentiation of Meth-induced damage to striatal monoamine terminals by stress and suggests the use of anti-inflammatory drugs for mitigating the neurotoxic effects associated with the combination of stress and Meth.

Gemfibrozil pretreatment affecting antioxidant defense system and inflammatory, but not Nrf-2 signaling pathways resulted in female neuroprotection and male neurotoxicity in the rat models of global cerebral ischemia-reperfusion

Two important pathophysiological mechanisms involved during cerebral ischemia are oxidative stress and inflammation. In pathological conditions such as brain ischemia the ability of free radicals production is greater than that of elimination by endogenous antioxidative systems, so brain is highly injured due to oxidation and neuroinflammation. Fibrates as peroxisome proliferator-activated receptor (PPAR)-α ligands, are reported to have antioxidant and anti-inflammatory actions. In this study, gemfibrozil, a fibrate is investigated for its therapeutic potential against global cerebral ischemia-reperfusion (I/R) injury of male and female rats. This study particularly has focused on inflammatory and antioxidant signaling pathways, such as nuclear factor erythroid-related factor (Nrf)-2, as well as the activity of some endogenous antioxidant agents. It was found that pretreatment of animals with gemfibrozil prior to I/R resulted in a sexually dimorphic outcome. Within females it proved to be protective, modulating inflammatory factors and inducing antioxidant defense system including superoxide dismutase (SOD), catalase, as well as glutathione level. However, Nrf-2 signaling pathway was not affected. It also decreased malondialdehyde level as an index of lipid peroxidation. In contrast, gemfibrozil pretreatment was toxic to males, enhancing the expression of inflammatory factors such as tumor necrosis factor-α, nuclear factor-κB, and cyclooxygenase-2, and decreasing Nrf-2 expression and SOD activity, leading to hippocampal neurodegeneration. Considering that gemfibrozil is a commonly used anti-hyperlipidemic agent in clinic, undoubtedly more investigations are crucial to exactly unravel its sex-dependent neuroprotective/neurodegenerative potential.

Role of the Toll Like receptor (TLR) radical cycle in chronic inflammation: possible treatments targeting the TLR4 pathway

Activation of the Toll-like receptor 4 (TLR4) complex, a receptor of the innate immune system, may underpin the pathophysiology of many human diseases, including asthma, cardiovascular disorder, diabetes, obesity, metabolic syndrome, autoimmune disorders, neuroinflammatory disorders, schizophrenia, bipolar disorder, autism, clinical depression, chronic fatigue syndrome, alcohol abuse, and toluene inhalation. TLRs are pattern recognition receptors that recognize damage-associated molecular patterns and pathogen-associated molecular patterns, including lipopolysaccharide (LPS) from gram-negative bacteria. Here we focus on the environmental factors, which are known to trigger TLR4, e.g., ozone, atmosphere particulate matter, long-lived reactive oxygen intermediate, pentachlorophenol, ionizing radiation, and toluene. Activation of the TLR4 pathways may cause chronic inflammation and increased production of reactive oxygen and nitrogen species (ROS/RNS) and oxidative and nitrosative stress and therefore TLR-related diseases. This implies that drugs or substances that modify these pathways may prevent or improve the abovementioned diseases. Here we review some of the most promising drugs and agents that have the potential to attenuate TLR-mediated inflammation, e.g., anti-LPS strategies that aim to neutralize LPS (synthetic anti-LPS peptides and recombinant factor C) and TLR4/MyD88 antagonists, including eritoran, CyP, EM-163, epigallocatechin-3-gallate, 6-shogaol, cinnamon extract, N-acetylcysteine, melatonin, and molecular hydrogen. The authors posit that activation of the TLR radical (ROS/RNS) cycle is a common pathway underpinning many "civilization" disorders and that targeting the TLR radical cycle may be an effective method to treat many inflammatory disorders.

Risperidone normalizes increased inflammatory parameters and restores anti-inflammatory pathways in a model of neuroinflammation

Inflammation, caused by both external and endogenous factors, has been implicated as a main pathophysiological feature of chronic mental illnesses, including schizophrenia. An increase in pro-inflammatory cytokines has been described both in experimental models and in schizophrenia patients. However, not much is known about the effects that antipsychotic drugs have on intra- and intercellular mechanisms controlling inflammation. The aim of the present study was to investigate the possible anti-inflammatory effect of a standard schizophrenia treatment not only at the level of soluble mediators, but also at intra- and intercellular inflammatory pathways. The present study was conducted in a model of mild neuroinflammation using a lipopolysaccharide (LPS) challenge that was not an endotoxaemic dose (0.5 mg/kg i.p.) in young adult rats.

MAIN RESULTS

single doses of risperidone (0.3-3.0 mg/kg i.p.) prevented increased inflammatory parameters induced by LPS in brain cortex [expression of inflammatory cytokines, interleukin (IL)-1β and tumour necrosis factor (TNF)-α, activity of the inducible inflammatory enzymes nitric oxide synthase and cyclooxygenase, p38 mitogen-activated protein kinase (MAPK) and inflammatory nuclear transcription factor κB] and restored anti-inflammatory pathways decreased by LPS challenge (deoxyprostaglandins and peroxisome proliferator activated receptor γ). This is the first study demonstrating that risperidone elicits a preventive effect on the anti-inflammatory arm of the homeostatic mechanism controlling inflammation in a model of mild encephalitis in rats. Our findings suggest a possible protective effect of risperidone on brain cells.