Comparison of bacterial lipopolysaccharide-induced sickness behavior in rodents and humans: Relevance for symptoms of anxiety and depression

The sex-dependent response to psychosocial stress and ischaemic heart disease

Stress is an important risk factor for modern chronic diseases, with distinct influences in males and females. The sex specificity of the mammalian stress response contributes to the sex-dependent development and impacts of coronary artery disease (CAD). Compared to men, women appear to have greater susceptibility to chronic forms of psychosocial stress, extending beyond an increased incidence of mood disorders to include a 2- to 4-fold higher risk of stress-dependent myocardial infarction in women, and up to 10-fold higher risk of Takotsubo syndrome-a stress-dependent coronary-myocardial disorder most prevalent in post-menopausal women. Sex differences arise at all levels of the stress response: from initial perception of stress to behavioural, cognitive, and affective responses and longer-term disease outcomes. These fundamental differences involve interactions between chromosomal and gonadal determinants, (mal)adaptive epigenetic modulation across the lifespan (particularly in early life), and the extrinsic influences of socio-cultural, economic, and environmental factors. Pre-clinical investigations of biological mechanisms support distinct early life programming and a heightened corticolimbic-noradrenaline-neuroinflammatory reactivity in females vs. males, among implicated determinants of the chronic stress response. Unravelling the intrinsic molecular, cellular and systems biological basis of these differences, and their interactions with external lifestyle/socio-cultural determinants, can guide preventative and therapeutic strategies to better target coronary heart disease in a tailored sex-specific manner.

The NLRP3 Inflammasome in Stress Response: Another Target for the Promiscuous Cannabidiol

Many psychiatric patients do not respond to conventional therapy. There is a vast effort to investigate possible mechanisms involved in treatment resistance, trying to provide better treatment options, and several data points toward a possible involvement of inflammatory mechanisms. Microglia, glial, and resident immune cells are involved in complex responses in the brain, orchestrating homeostatic functions, such as synaptic pruning and maintaining neuronal activity. In contrast, microglia play a major role in neuroinflammation, neurodegeneration, and cell death. Increasing evidence implicate microglia dysfunction in neuropsychiatric disorders. The mechanisms are still unclear, but one pathway in microglia has received increased attention in the last 8 years, i.e., the NLRP3 inflammasome pathway. Stress response and inflammation, including microglia activation, can be attenuated by Cannabidiol (CBD). CBD has antidepressant, anti-stress, antipsychotic, anti-inflammatory, and other properties. CBD effects are mediated by direct or indirect modulation of many receptors, enzymes, and other targets. This review will highlight some findings for neuroinflammation and microglia involvement in stress-related psychiatric disorders, particularly addressing the NLRP3 inflammasome pathway. Moreover, we will discuss evidence and mechanisms for CBD effects in psychiatric disorders and animal models and address its potential effects on stress response via neuroinflammation and NLRP3 inflammasome modulation.

Unique Features of the Immune Response in BTBR Mice

Inflammation plays a considerable role in the pathogenesis of many diseases, including neurodegenerative and psychiatric ones. Elucidation of the specific features of an immune response in various model organisms, and studying the relation of these features with the behavioral phenotype, can improve the understanding of the molecular mechanisms of many psychopathologies. In this work, we focused on BTBR mice, which have a pronounced autism-like behavioral phenotype, elevated levels of oxidative-stress markers, an abnormal immune response, several structural aberrations in the brain, and other unique traits. Although some studies have already shown an abnormal immune response in BTBR mice, the existing literature data are still fragmentary. Here, we used inflammation induced by low-dose lipopolysaccharide, polyinosinic:polycytidylic acid, or their combinations, in mice of strains BTBR T+Itpr3tf/J (BTBR) and C57BL6/J. Peripheral inflammation was assessed by means of a complete blood count, lymphocyte immunophenotyping, and expression levels of cytokines in the spleen. Neuroinflammation was evaluated in the hypothalamus and prefrontal cortex by analysis of mRNA levels of proinflammatory cytokines (tumor necrosis factor, Tnf), (interleukin-1 beta, Il-1β), and (interleukin-6, Il-6) and of markers of microglia activation (allograft inflammatory factor 1, Aif1) and astroglia activation (glial fibrillary acidic protein, Gfap). We found that in both strains of mice, the most severe inflammatory response was caused by the administration of polyinosinic:polycytidylic acid, whereas the combined administration of the two toll-like receptor (TLR) agonists did not enhance this response. Nonetheless, BTBR mice showed a more pronounced response to low-dose lipopolysaccharide, an altered lymphocytosis ratio due to an increase in the number of CD4+ lymphocytes, and high expression of markers of activated microglia (Aif1) and astroglia (Gfap) in various brain regions as compared to C57BL6/J mice. Thus, in addition to research into mechanisms of autism-like behavior, BTBR mice can be used as a model of TLR3/TLR4-induced neuroinflammation and a unique model for finding and evaluating the effectiveness of various TLR antagonists aimed at reducing neuroinflammation.

Phytochemistry, Pharmacology and Molecular Mechanisms of Herbal Bioactive Compounds for Sickness Behaviour

The host's response to acute infections or tissue injury is a sophisticated and coordinated adaptive modification called sickness behaviour. Many herbs have been studied for their ability to protect animals against experimentally induced sickness behaviour. However, there is a lack of knowledge and experimental evidence on the use of herbal bioactive compounds (HBACs) in the management of sick behaviour. The goal of this review is to provide a concise summary of the protective benefits and putative mechanisms of action of phytochemicals on the reduction of lipopolysaccharide (LPS)-induced sickness behaviour. Relevant studies were gathered from the search engines Scopus, ScienceDirect, PubMed, Google Scholar, and other scientific databases (between 2000 and to date). The keywords used for the search included "Lipopolysaccharide" OR "LPS" OR "Sickness behaviour" OR "Sickness" AND "Bioactive compounds" OR "Herbal medicine" OR "Herbal drug" OR "Natural products" OR "Isolated compounds". A total of 41 published articles that represented data on the effect of HBACs in LPS-induced sickness behaviour were reviewed and summarised systemically. There were 33 studies that were conducted in mice and 8 studies in rats. A total of 34 HBACs have had their effects against LPS-induced changes in behaviour and biochemistry investigated. In this review, we examined 34 herbal bioactive components that have been tested in animal models to see if they can fight LPS-induced sickness behaviour. Future research should concentrate on the efficacy, safety, and dosage needed to protect against illness behaviour in humans, because there is a critical shortage of data in this area.

Gut-Brain Axis, Neurodegeneration and Mental Health: A Personalized Medicine Perspective

Neurological conditions such as neurodegenerative diseases and mental health disorders are a result of multifactorial underpinnings, leading to individual-based complex phenotypes. Demystification of these multifactorial connections will promote disease diagnosis and treatment. Personalized treatment rather than a one-size-fits-all approach would enable us to cater to the unmet healthcare needs based on protein-protein and gene-environment interactions. Gut-brain axis, as the name suggests, is a two-way biochemical communication pathway between the central nervous system (CNS) and enteric nervous system (ENS), enabling a mutual influence between brain and peripheral intestinal functions. The gut microbiota is a major component of this bidirectional communication, the composition of which is varied depending on the age, and disease conditions, among other factors. Gut microbiota profile is typically unique and personalized therapeutic intervention can aid in treating or delaying neurodegeneration and mental health conditions. Besides, research on the gut microbial influence on these conditions is gaining attention, and a better understanding of this concept can lead to identification of novel targeted therapies.

Graphical Abstract

Enhanced drug delivery by a prodrug approach effectively relieves neuroinflammation in mice

AIMS

Neuroinflammation is a prominent hallmark in several neurodegenerative diseases (NDs). Halting neuroinflammation can slow down the progression of NDs. Improving the efficacy of clinically available non-steroidal anti-inflammatory drugs (NSAIDs) is a promising approach that may lead to fast-track and effective disease-modifying therapies for NDs. Here, we aimed to utilize the L-type amino acid transporter 1 (LAT1) to improve the efficacy of salicylic acid as an example of an NSAID prodrug, for which brain uptake and intracellular localization have been reported earlier.

MAIN METHODS

Firstly, we confirmed the improved LAT1 utilization of the salicylic acid prodrug (SA-AA) in freshly isolated primary mouse microglial cells. Secondly, we performed behavioural rotarod, open field, and four-limb hanging tests in mice, and a whole-brain proteome analysis.

KEY FINDINGS

The SA-AA prodrug alleviated the lipopolysaccharide (LPS)-induced inflammation in the rotarod and hanging tests. The proteome analysis indicated decreased neuroinflammation at the molecular level. We identified 399 proteins linked to neuroinflammation out of 7416 proteins detected in the mouse brain. Among them, Gps2, Vamp8, Slc6a3, Slc18a2, Slc5a7, Rgs9, Lrrc1, Ppp1r1b, Gnal, and Adcy5/6 were associated with the drug's effects. The SA-AA prodrug attenuated the LPS-induced neuroinflammation through the regulation of critical pathways of neuroinflammation such as the cellular response to stress and transmission across chemical synapses.

SIGNIFICANCE

The efficacy of NSAIDs can be improved via the utilization of LAT1 and repurposed for the treatment of neuroinflammation. This improved brain delivery and microglia localisation can be applied to other inflammatory modulators to achieve effective and targeted CNS therapies.

Effects of spleen nerve denervation on depression-like phenotype, systemic inflammation, and abnormal composition of gut microbiota in mice after administration of lipopolysaccharide: A role of brain-spleen axis

BACKGROUND

Accumulating evidence suggests the role of brain-spleen axis as well as brain-gut-microbiota axis in inflammation-related depression. The spleen mediates anti-inflammatory effects of the vagus nerve which plays a role in depression. However, the role of spleen nerve in inflammation-related depression remains unclear.

METHODS

The effects of the splenic nerve denervation (SND) in the depression-like phenotype, systemic inflammation, and abnormal composition of gut microbiota in adult mice after administration of lipopolysaccharide (LPS) were examined.

RESULTS

LPS (0.5 mg/kg) caused depression-like phenotype, systemic inflammation, splenomegaly, increased expression of Iba1 (ionized calcium-binding adapter molecule 1) and decreased expression of postsynaptic density protein-95 (PSD-95) in the hippocampus in the sham-operated mice. In contrast, LPS did not produce depression-like phenotype, and abnormal expressions of Iba1 and PSD-95 in the hippocampus in the SND-operated mice. Furthermore, SND significantly blocked LPS-induced increased plasma levels of pro-inflammatory cytokine interleukin-6 although SND did not affect LPS-induced splenomegaly and increased plasma levels of tumor necrosis factor-α in mice. There were significant changes in several microbiota among the four groups. Interestingly, there were correlations between the relative abundance of several microbiota and Iba1 (or PSD-95) expression in the hippocampus. In addition, expression of Iba1 in the hippocampus was correlated with the relative abundance of several microbiota.

LIMITATIONS

Detailed mechanisms are unclear.

CONCLUSIONS

These results suggest that the splenic nerve plays a role in inflammation-related depression, microglial activation in the hippocampus, and that gut microbiota may regulate microglial function in the brain via gut-microbiota-brain axis.

ERK1/2-dependent BDNF synthesis and signaling is required for the antidepressant effect of microglia stimulation

Depressed mice have lower numbers of microglia in the dentate gyrus (DG). Reversal of this decline by a single low dose of lipopolysaccharide (LPS) may have antidepressant effects, but there is little information on the molecular mechanisms underlying this effect. It is known that impairment of brain-derived neurotrophic factor (BDNF) signaling is involved in the development of depression. Here, we used a combination of neutralizing antibodies, mutant mice, and pharmacological approaches to test the role of BDNF-tyrosine kinase receptor B (TrkB) signaling in the DG in the effect of microglial stimulation. Our results suggest that inhibition of BDNF signaling by infusion of an anti-BDNF antibody, the BDNF receptor antagonist K252a, or knock-in of the mutant BDNF Val68Met allele abolished the antidepressant effect of LPS in chronically stressed mice. Increased BDNF synthesis in DG, mediated by extracellular signal-regulated kinase1/2 (ERK1/2) signaling but not protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling, was essential for the antidepressant effect of microglial stimulation. These results suggest that increased BDNF synthesis through activation of ERK1/2 caused by a single LPS injection and subsequent TrkB signaling are required for the antidepressant effect of hippocampal microglial stimulation.

Systemic Lipopolysaccharide Challenge Induces Inflammatory Changes in Rat Dorsal Root Ganglia: An Ex Vivo Study

Inflammatory processes within the peripheral nervous system (PNS) are associated with symptoms of hyperalgesia and allodynia. Pro-inflammatory mediators, such as cytokines or prostaglandins, modulate the excitability of nociceptive neurons, called peripheral sensitization. Here, we aimed to examine if previously reported effects of in vitro stimulation with lipopolysaccharide (LPS) on primary cell cultures of dorsal root ganglia (DRG) reflect changes in a model of LPS-induced systemic inflammation in vivo. Male rats were intraperitoneally injected with LPS (100 µg/kg) or saline. Effects of systemic inflammation on expression of inflammatory mediators, neuronal Ca2+ responses, and activation of inflammatory transcription factors in DRG were assessed. Systemic inflammation was accompanied by an enhanced expression of pro-inflammatory cytokines and cyclooxygenase-2 in lumbar DRG. In DRG primary cultures obtained from LPS-treated rats enhanced neuronal capsaicin-responses were detectable. Moreover, we found an increased activation of inflammatory transcription factors in cultured macrophages and neurons after an in vivo LPS challenge compared to saline controls. Overall, our study emphasizes the role of inflammatory processes in the PNS that may be involved in sickness-behavior-associated hyperalgesia induced by systemic LPS treatment. Moreover, we present DRG primary cultures as tools to study inflammatory processes on a cellular level, not only in vitro but also ex vivo.

Resolution of depression: antidepressant actions of resolvins

Major depressive disorder, one of the most widespread mental illnesses, brings about enormous individual and socioeconomic consequences. Conventional monoaminergic antidepressants require weeks to months to produce a therapeutic response, and approximately one-third of the patients fail to respond to these drugs and are considered treatment-resistant. Although recent studies have demonstrated that ketamine, an N-methyl-D-aspartate receptor antagonist, produces rapid antidepressant effects in treatment-resistant patients, it also has undesirable side effects. Hence, rapid-acting antidepressants that have fewer adverse effects than ketamine are urgently required. D-series (RvD1-RvD6) and E-series (RvE1-RvE4) resolvins are endogenous lipid mediators derived from docosahexaenoic and eicosapentaenoic acids, respectively. These mediators reportedly play a pivotal role in the resolution of acute inflammation. In this review, we reveal that intracranial infusions of RvD1, RvD2, RvE1, RvE2, and RvE3 produce antidepressant-like effects in various rodent models of depression. Moreover, the behavioral effects of RvD1, RvD2, and RvE1 are mediated by the activation of the mechanistic target of rapamycin complex 1, which is essential for the antidepressant-like actions of ketamine. Finally, we briefly provide our perspective on the possible role of endogenous resolvins in stress resilience.

Adiposity affects emotional information processing

Obesity is a worldwide epidemic associated with severe health and psychological wellbeing impairments expressed by an increased prevalence of affective disorders. Emotional dysfunction is important due to its effect on social performance. The aim of the present narrative review is to provide a general overview of human research exploring emotional information processing in overweight and obese people. Evidence suggests that obesity is associated with an attenuation of emotional experience, contradictory findings about emotion recognition, and scarce research about automatic emotional information processing. Finally, we made some concluding considerations for future research on emotional information processing in overweight and obese people.

Anxiolytic and antidepressive potentials of rosmarinic acid: A review with a focus on antioxidant and anti-inflammatory effects

Depression and anxiety are the most prevalent neuropsychiatric disorders that have emerged as global health concerns. Anxiolytic and antidepressant drugs, such as benzodiazepines, selective serotonin reuptake inhibitors, monoamine oxidase inhibitors, and tricyclics, are the first line used in treating anxiety and depression. Although these drugs lack efficacy and have a delayed response time and numerous side effects, their widespread abuse and market continue to grow. Over time, traditional practices using natural and phytochemicals as alternative therapies to chemical drugs have emerged to treat many pathological conditions, including anxiety and depression. Recent preclinical studies have demonstrated that the phenolic compound, rosmarinic acid, is effective against several neuropsychiatric disorders, including anxiety and depression. In addition, rosmarinic acid showed various pharmacological effects, such as cardioprotective, hepatoprotective, lung protective, antioxidant, anti-inflammatory, and neuroprotective effects. However, the potentialities of the use of rosmarinic acid in the treatment of nervous system-related disorders, such as anxiety and depression, are less or not yet reviewed. Therefore, the purpose of this review was to present several preclinical and clinical studies, when available, from different databases investigating the effects of rosmarinic acid on anxiety and depression. These studies showed that rosmarinic acid produces advantageous effects on anxiety and depression through its powerful antioxidant and anti-inflammatory properties. This review will examine and discuss the possibility that the anxiolytic and anti-depressive effects of rosmarinic acid could be associated with its potent antioxidant and anti-inflammatory activities.

Characterization of the Metabolome of Breast Tissues from Non-Hispanic Black and Non-Hispanic White Women Reveals Correlations between Microbial Dysbiosis and Enhanced Lipid Metabolism Pathways in Triple-Negative Breast Tumors

Simple Summary

We previously showed that breast tumor tissues from women display an imbalance in abundance and composition of microbiota compared to normal healthy breast tissues. It is unknown whether these differences in breast tumor microbiota may be driven by alterations in microbial metabolites, leading to potentially protective or pathogenic consequences. The aim of our study was to conduct global metabolic profiling on normal and breast tumor tissues to identify differences in metabolite profiles and to determine whether breast microbial dysbiosis may be associated with enrichment of microbial metabolites in triple-negative breast cancer (TNBC) which disproportionately affects women of African ancestry. We observed significant correlations between elevated lipid metabolism pathways and microbial dysbiosis in TNBC tissues from both non-Hispanic black and white women. This is the first study to report an association between breast microbial dysbiosis and alterations in host metabolic pathways in breast tumors, including TNBC, of non-Hispanic black and non-Hispanic white women.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer that is non-responsive to hormonal therapies and disproportionately impact women of African ancestry. We previously showed that TN breast tumors have a distinct microbial signature that differs from less aggressive breast tumor subtypes and normal breast tissues. However, it is unknown whether these differences in breast tumor microbiota may be driven by alterations in microbial metabolites, leading to potentially protective or pathogenic consequences. The goal of this global metabolomic profiling study was to investigate alterations in microbial metabolism pathways in normal and breast tumor tissues, including TNBC, of non-Hispanic black (NHB) and non-Hispanic white (NHW) women. In this study, we profiled the microbiome (16S rRNA) from breast tumor tissues and analyzed 984 metabolites from a total of 51 NHB and NHW women. Breast tumor tissues were collected from 15 patients with TNBC, 12 patients with less aggressive luminal A-type (Luminal) breast cancer, and 24 healthy controls for comparison using UHPLC-tandem mass spectrometry. Principal component analysis and hierarchical clustering of the global metabolomic profiling data revealed separation between metabolic signatures of normal and breast tumor tissues. Random forest analysis revealed a unique biochemical signature associated with elevated lipid metabolites and lower levels of microbial-derived metabolites important in controlling inflammation and immune responses in breast tumor tissues. Significant relationships between the breast microbiome and the metabolome, particularly lipid metabolism, were observed in TNBC tissues. Further investigations to determine whether alterations in sphingolipid, phospholipid, ceramide, amino acid, and energy metabolism pathways modulate Fusobacterium and Tenericutes abundance and composition to alter host metabolism in TNBC are necessary to help us understand the risk and underlying mechanisms and to identify potential microbial-based targets.

Curcumin Diethyl γ-Aminobutyrate, a Prodrug of Curcumin, for Enhanced Treatment of Inflammatory Pain

Curcumin is a naturally occurring polyphenol compound with potential analgesic effects. It has been shown to improve pain-like behaviors in numerous models of pain. Despite its potential, curcumin exhibits poor physicochemical and pharmacokinetic properties, which hinder its oral therapeutic efficacy. Curcumin diethyl γ-aminobutyrate (CUR-2GE), a carbamate prodrug of curcumin, was designed to overcome these limitations and demonstrated greater anti-neuroinflammatory effects compared to curcumin in vitro. Thus, this study evaluated the effect of CUR-2GE and its parent compound on pain-like behaviors in carrageenan- and LPS-induced mouse models. The possible side effects of CUR-2GE were also assessed by exploring its effects on motor coordination and spontaneous locomotor activity after acute and chronic treatments. The results showed that CUR-2GE improved mechanical and thermal hyperalgesia and locomotor activity to a greater extent than curcumin in carrageenan-induced mice. These results are in line with the ability of CUR-2GE to suppress peripheral inflammation in the paw tissue of carrageenan-induced mice, indicated by a significant decrease in TNF-α and IL-6 expression levels. Similarly, in LPS-induced mice, CUR-2GE improved sickness and pain-like behaviors (exploratory behaviors and long-term locomotor activity) to a greater extent than curcumin. Furthermore, CUR-2GE significantly reduced the level of proinflammatory cytokines in both the plasma and spinal cord tissue of LPS-induced mice, exhibiting significantly higher inhibition than curcumin. Moreover, the motor coordination, and locomotive behaviors of mice were not affected by both acute and chronic administration of CUR-2GE, indicating no potential CNS side effects. Thus, CUR-2GE demonstrated enhanced therapeutic efficacy in mouse models of inflammatory pain without any possible CNS side effects, suggesting its potential to be developed as an analgesic agent against inflammatory pain.

LPS-induced impairment of Na+/K+-ATPase activity: ameliorative effect of tannic acid in mice

Acetylcholine is an excitatory neurotransmitter that modulates synaptic plasticity and communication, and it is essential for learning and memory processes. This neurotransmitter is hydrolyzed by acetylcholinesterase (AChE), which plays other cellular roles in processes such as inflammation and oxidative stress. Ion pumps, such as Na⁺/K⁺-ATPase and Ca²⁺-ATPase, are highly expressed channels that derive energy for their functions from ATP hydrolysis. Impairment of the cholinergic system and ion pumps is associated with neuropsychiatric diseases. Major depressive disorder (MDD) is an example of a complex disease with high morbidity and a heterogenous etiology. Polyphenols have been investigated for their therapeutic effects, and tannic acid (TA) has been reported to show neuroprotective and antidepressant-like activities. Animal models of depression-like behavior, such as lipopolysaccharide (LPS)-induced models of depression, are useful for investigating the pathophysiology of MDD. In this context, effects of TA were evaluated in an LPS-induced mouse model of depression-like behavior. Animals received TA for 7 days, and on the last day of treatment, LPS (830 μg/kg) was administered intraperitoneally. In vitro exposure of healthy brain to TA decreased the AChE activity. Additionally, this enzyme activity was decreased in cerebral cortex of LPS-treated mice. LPS injection increased the activity of Ca²⁺-ATPase in the cerebral cortex but decreased the enzyme activity in the hippocampus. LPS administration decreased Na⁺/K⁺-ATPase activity in the cerebral cortex, hippocampus, and striatum; however, TA administration prevented these changes. In conclusion, tannins may affect Na⁺/K⁺-ATPase and Ca²⁺-ATPase activities, which is interesting in the context of MDD.

Granulocyte-macrophage colony-stimulating factor-triggered innate immune tolerance against chronic stress-induced behavioral abnormalities in mice

Pre-stimulation of the innate immune is considered a potential strategy to prevent chronic stress-induced behavioral abnormalities in animals. In this study, we investigated whether granulocyte-macrophage colony-stimulating factor (GM-CSF), an immunostimulant used in the clinic to treat diseases of the hematopoietic system, can prevent chronic stress-induced behavioral abnormalities in mice. Our results showed that a single intraperitoneal injection of GM-CSF (100 μg/kg) one day before stress exposure prevented the depression- and anxiety-like behaviors induced by chronic social defeat stress (CSDS) in mice, including preventing the CSDS-induced increase in the immobility time in the tail suspension test and forced swimming test and decrease in the time spent in the interaction zone in the social interaction test, as well as preventing the CSDS-induced decrease in the time spent (i) in open arms in the elevated plus maze test, (ii) on the illuminated side in the light-dark test, and (iii) in the central region of the open field test. The single GM-CSF preinjection (100 μg/kg) also prevented the CSDS-induced increase in the expression levels of interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α) mRNA in the hippocampus and medial prefrontal cortex of the mice. Further analysis showed that the preventive effect of GM-CSF on CSDS-induced depression- and anxiety-like behaviors and neuroinflammatory responses was abolished by pretreatment with minocycline (an innate immune inhibitor). These results indicate that a single low dose of GM-CSF before injection could be a potential way to prevent behavioral abnormalities induced by chronic stress in mice.

Neuroscience: Detection of systemic inflammation by the brain

When confronted with illness, humans and animals undergo critical changes in their behavior and physiology. New research shows how neuronal circuits detect sickness and coordinate illness-specific responses.

Are sick people really more impulsive?: Investigating inflammation-driven impulsivity

In both animals and humans, inflammatory stimuli - especially infections and endotoxin injections - cause "sickness behaviors," including lethargy, malaise, and low mood. An emerging line of research asserts that inflammation may provoke present-focused decision making and impulsivity. The current article assesses that claim in the context of the broader literature - including preclinical models and clinical interventions. This literature presents three challenges to purported inflammation-impulsivity link that have not been addressed to date: (1) the nebulous and imprecise definition of impulsivity; (2) reverse causality; and (3) a lack of causal evidence. These challenges point to ways in which future research designs can improve upon the extant literature to further explore the ostensible relationship between inflammation and impulsivity.

Bodyweight, locomotion, and behavioral responses of the naked mole rat (Heterocephalus glaber) to lipopolysaccharide administration

The naked mole rat has unique biologic characteristics that include atypical inflammatory responses. Lipopolysaccharide induces inflammation which triggers brain centers controlling feeding, and behavior to result in “sick animal behavior”. We characterized the bodyweight, locomotor, and other behavioral responses of this rodent to lipopolysaccharide administration. Lipopolysaccharide caused weight losses, which were not prevented by TAK 242. In the open field test, lipopolysaccharide did not depress locomotion, while urination, defecation, and activity freezing were rare. The animals exhibited walling but not rearing and fast backward movements that were unaffected by lipopolysaccharide. Failure to depress locomotion suggests either a unique immunity-brain crosstalk or motor responses/centers that tolerate depressive effects of inflammation. The absence of activity freezing and rarity of urination and defecation suggests that novel environments or lipopolysaccharide do not induce anxiety, or that anxiety is expressed differently in the animal. The absence of rearing could be due to the design of the animal’s locomotor apparatus while fast backward movement could be a mechanism for quick escape from threats in the tunnels of their habitat. Our results elucidate the unique biology of this rodent, which elicits interest in the animal as a model for inflammatory research, although the findings require mechanistic corroborations.

Escherichia coli Mimetic Gold Nanorod-Mediated Photo- and Immunotherapy for Treating Cancer and Its Metastasis

Most cancer-related deaths are due to metastasis or recurrence. Therefore, the ultimate goal of cancer therapy will be to treat metastatic and recurrent cancers. Combination therapy for cancer will be one of trial for effective treating metastasis and recurrence. In this study, Escherichia coli-mimetic nanomaterials are synthesized using Escherichia coli membrane proteins, adhesion proteins, and gold nanorods, which are named E. coli mimetic AuNRs (ECA), for combination therapy against cancer and its recurrence. ECA treatment with 808 nm laser irradiation eliminates CT-26 or 4T1 tumors via a photothermal effect. ECA with laser irradiation induces activation of immune cells in the tumor-draining lymph nodes. The mice cured from CT-26 or 4T1 tumor by ECA are rechallenged with those cancer in the lung metastatic form, and the results showed that ECA treatment for the first CT-26 or 4T1 tumor challenge prevents cancer infiltration to the lung in the second challenge. This preventive effect of ECA against tumor growth in the second challenge is aided by cancer antigen-specific T cell immunity. Overall, these findings show that ECA is a nanomaterial with dual functions as a photothermal therapy for treating primary cancers and as immunotherapy for preventing recurrence and metastasis.

Baseline Pro-Inflammatory Cytokine Levels Moderate Psychological Inflexibility in Behavioral Treatment for Chronic Pain

Background: The medical and scientific communities struggle to understand chronic pain and find effective treatments. Multimodal approaches are encouraging but show significant individual differences. Methods: Seventy-eight persons (56 women) with chronic pain received Acceptance and Commitment Therapy and provided blood samples before and after treatment. The participants completed surveys with the blood sampling. Blood plasma was analyzed for IL-6 and TNF-α levels with the Olink Inflammation Panel (Olink Bioscience Uppsala, Sweden). The treatment effects and moderating effects of low-grade inflammation on changes in outcomes were analyzed using linear mixed models. Results: Pain interference (p < 0.001) and psychological inflexibility (p < 0.001) improved significantly during treatment, but pain intensity did not (p = 0.078). Cytokine levels did not change over the course of the treatment (IL-6/TNF-α p = 0.086/0.672). Mean baseline levels of IL-6 and TNF-α moderated improvement in psychological inflexibility during the course of treatment (p = 0.044), but cytokine levels did not moderate changes in pain interference (p = 0.205) or pain intensity (p = 0.536). Conclusions: Higher baseline inflammation levels were related to less improvement in psychological inflexibility. Low-grade inflammation may be one factor underlying the variability in behavioral treatment in chronic pain.

C-reactive protein is related to a distinct set of alterations in resting-state functional connectivity contributing to a differential pathophysiology of major depressive disorder

BACKGROUND

Several studies in major depressive disorder (MDD) have found inflammation, especially C-reactive protein (CRP), to be consistently associated with MDD and network dysfunction. The aim was to investigate whether CRP is linked to a distinct set of resting-state functional connectivity (RSFC) alterations.

METHODS

For this reason, we investigated the effects of diagnosis and elevated blood plasma CRP levels on the RSFC in 63 participants (40 females, mean age 31.4 years) of which were 27 patients with a primary diagnosis of MDD and 36 healthy control-subjects (HC), utilizing a seed-based approach within five well-established RSFC networks obtained using fMRI.

RESULTS

Of the ten network pairs examined, five showed increased between-network RSFC-values unambiguously connected either to a diagnosis of MDD or elevated CRP levels. For elevated CRP levels, increased RSFC between DMN and AN was found. Patients showed increased RSFC within DMN areas and between the DMN and ECN and VAN, ECN and AN and AN and DAN.

CONCLUSIONS

The results of this study show dysregulated neural circuits specifically connected to elevated plasma CRP levels and independent of other alterations of RSFC in MDD. This dysfunction in neural circuits might in turn result in a certain immune-inflammatory subtype of MDD.

Hydro-ethanol extract of Holarrhena floribunda stem bark exhibits anti-anaphylactic and anti-oedematogenic effects in murine models of acute inflammation

BACKGROUND

Holarrhena floribunda (G.Don) T.Durand & Schinz stem bark has anecdotal use in Ghanaian folk medicine for the management of inflammatory conditions. This study was conducted to investigate the in vivo anti-inflammatory activity of the bark extract using models of acute inflammation in male Sprague Dawley rats, C57BL/6 mice and ICR mice.

METHODS

A 70% hydro-ethanol extract of the stem bark (HFE) was evaluated at doses of 5-500 mg/kg bw. Local anaphylaxis was modelled by the pinnal cutaneous anaphylactic test. Systemic anaphylaxis or sepsis were modeled by compound 48/80 or lipopolysaccharide, respectively. Clonidine-induced catalepsy was used to investigate the effect on histamine signaling. Anti-oedematogenic effect was assessed by induction with carrageenan. Effects on mediators of biphasic acute inflammation were studied using histamine and serotonin (early phase) or prostaglandin E2 (late phase).

RESULTS

HFE demonstrated anti-inflammatory and/or anti-oedematogenic activity comparable to standard doses of aspirin and diclofenac (inhibitors of cyclooxygenases-1 and -2), chlorpheniramine (histamine H1-receptor antagonist), dexamethasone (glucocorticoid receptor agonist), granisetron (serotonin receptor antagonist) and sodium cromoglycate (inhibitor of mast cell degranulation). All observed HFE bioactivities increased with dose.

CONCLUSIONS

The data provide evidence that the extract of H. floribunda stem bark has anti-anaphylactic and anti-oedematogenic effects; by interfering with signalling or metabolism of histamine, serotonin and prostaglandin E2 which mediate the progression of inflammation. The anti-inflammatory and antihistaminic activities of HFE may be relevant in the context of the management of COVID-19.

Amyloid Beta Pathology Exacerbates Weight Loss and Brain Cytokine Responses following Low-Dose Lipopolysaccharide in Aged Female Tg2576 Mice

Systemic inflammation has been implicated in the progression of Alzheimer’s disease (AD); however, less is understood about how existing AD pathology contributes to adverse outcomes following acute inflammatory insults. In the present study, our goal was to determine how AD-associated amyloid beta (Aβ) pathology influences the acute neuroinflammatory and behavioral responses to a moderate systemic inflammatory insult. We treated 16–18-month-old female Tg2576 (Tg) mice, which overproduce human Aβ and develop plaques, and age-matched wild-type (WT) littermate mice with an intraperitoneal injection of 0.33 mg/kg lipopolysaccharide (LPS) or saline. Mice were then evaluated over the next 28 h for sickness/depressive-like behaviors (food intake, weight loss, locomotion, and sucrose preference), systemic inflammation (serum amyloid A, SAA), blood-brain barrier (BBB) disruption, astrogliosis (glial fibrillary acidic protein/GFAP), Aβ, and cytokine levels in the brain. We found that LPS caused a larger reduction in body weight in Tg vs. WT mice, but that other behavioral responses to LPS did not differ by genotype. BBB disruption was not apparent in either genotype following LPS. Concentrations of the systemic inflammatory marker, SAA, in the blood and brain were significantly increased with LPS but did not significantly differ by genotype. GFAP was increased in Tg mice vs. WT but was not significantly affected by LPS in either genotype. Finally, LPS-induced increases of eight cytokines (IL-1β, IL-6, IL-12 (p40), IL-10, IL-17A, MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5) were found to be significantly higher in Tg mice vs. WT. In summary, our data show that Aβ pathology exacerbates the neuroinflammatory response to LPS and identifies cytokines that are selectively regulated by Aβ. The association of worse neuroinflammation with greater weight loss in Tg mice suggests that Aβ pathology could contribute to poor outcomes following a systemic inflammatory insult.

Ananas comosus (L) Merrill (pineapple) fruit peel extract demonstrates antimalarial, anti-nociceptive and anti-inflammatory activities in experimental models

ETHNOPHARMACOLOGY RELEVANCE

Pineapple (Ananas comosus) peel is a major waste in pineapple canning industry and it is reported to be used in ethnomedicine as a component of herbal remedies for malarial management. This study aimed to evaluate the antimalarial, antinociceptive and anti-inflammatory properties of Ananas comosus peel extract (PEAC).

METHODS

Ananas comosus peel was extracted with 80% methanol. PEAC (100, 200 and 400 mg/kg) was investigated for antimalarial effect using Peter's 4-day suppressive test (4-DST) model in mice. Antinociceptive activity of PEAC was investigated in hot plate, acetic acid-induced writhing and formalin tests in mice. The anti-inflammatory activity was evaluated using the lipopolysaccharides-induced sickness behavior in mice and carrageenan-induced air pouch in rats' models.

RESULTS

PEAC could not significantly (p > 0.05) suppressed parasitemia level at 7-day post-infection in 4-DST. PEAC (400 mg/kg) mildly prolongs survival of infected mice up till day 21. PEAC demonstrated significant (p < 0.05) antinociceptive activity by increasing latency to jump on the hot plate, reduced number of writhings in acetic acid test and reduced paw licking time in 2^nd phase of formalin test. PEAC significantly reduced anxiogenic and depressive-like symptoms of sickness behavior in LPS-injected mice. PEAC demonstrated significant anti-inflammatory activity in carrageenan-induced air pouch experiment by reducing exudates formation, inflammatory cell counts, and nitrite, tumor necrosis factor-alpha and interleukin-6 levels.

CONCLUSION

Ananas comosus peel extract demonstrated mild antimalarial activity but significant anti-nociceptive and anti-inflammatory properties probably mediated via inhibition of pro-inflammatory mediators.

Stress-induced depressive-like behavior in male rats is associated with microglial activation and inflammation dysregulation in the hippocampus in adulthood

Neuroinflammation is increasingly recognized as playing a critical role in depression. Early-life stress exposure and constitutive differences in glucocorticoid responsiveness to stressors are two key risk factors for depression, but their impacts on the inflammatory status of the brain is still uncertain. Moreover, there is a need to identify specific molecules involved in these processes with the potential to be used as alternative therapeutic targets in inflammation-related depression. Here, we studied how peripubertal stress (PPS) combined with differential corticosterone (CORT)-stress responsiveness (CSR) influences depressive-like behaviors and brain inflammatory markers in male rats in adulthood, and how these alterations relate to microglia activation and miR-342 expression. We found that high-CORT stress-responsive (H-CSR) male rats that underwent PPS exhibited increased anhedonia and passive coping responses in adulthood. Also, animals exposed to PPS showed increased hippocampal TNF-α expression, which positively correlated with passive coping responses. In addition, PPS caused long-term effects on hippocampal microglia, particularly in H-CSR rats, with increased hippocampal IBA-1 expression and morphological alterations compatible with a higher degree of activation. H-CSR animals also showed upregulation of hippocampal miR-342, a mediator of TNF-α-driven microglial activation, and its expression was positively correlated with TNF-α expression, microglial activation and passive coping responses. Our findings indicate that individuals with constitutive H-CSR are particularly sensitive to developing protracted depression-like behaviors following PPS exposure. In addition, they show neuro-immunological alterations in adulthood, such as increased hippocampal TNF-α expression, microglial activation and miR-342 expression. Our work highlights miR-342 as a potential therapeutic target in inflammation-related depression.

Beneficial effects of QTC-4-MeOBnE in an LPS-induced mouse model of depression and cognitive impairments: The role of blood-brain barrier permeability, NF-κB signaling, and microglial activation

Clinical and preclinical investigations have suggested a possible biological link betweenmajor depressive disorder (MDD) and Alzheimer's disease (AD). Therefore, a pharmacologic approach to treating MDD could be envisioned as a preventative therapy for some AD cases. In line with this, 1-(7-chloroquinolin-4-yl)-N-(4-methoxybenzyl)-5-methyl-1H-1,2,3-triazole-4 carboxamide (QTC-4-MeOBnE) is characterized as an inhibitor of β-secretase, glycogen synthase kinase 3β, and acetylcholinesterase and has also shown secondary effects underlying the modulation of neurogenesis and synaptic plasticity pathways. Therefore, we investigated the effects of QTC-4-MeOBnE treatment (0.1 or 1 mg/kg) on depressive-like behavior and cognitive impairments elicited by repeated injections of lipopolysaccharide (LPS; 250 μg/kg) in mice. Injections of LPS for seven days led to memory impairments and depressive-like behavior, as evidenced in the Y-maze/object recognition test and forced swimming/splash tests, respectively. However, these impairments were prevented in mice that, after the last LPS injection, were also treated with QTC-4-MeOBnE (1 mg/kg). This effect was associated with restoring blood-brain barrier permeability, reducing oxidative/nitrosative biomarkers, and decreasing neuroinflammation mediated NF-κB signaling in the hippocampus and cortex of the mice. To further investigate the involvement with NF-κB signaling, we evaluated the effects of QTC-4-MeOBnE on microglial cell activation through canonical and non-canonical pathways and the modulation of the involved components. Together, our findings highlight the pharmacological benefits of QTC-4-MeOBnE in a mouse model of sickness behavior and memory impairments, supporting the novel concept that since this molecule produces anti-depressant activity, it could also be beneficial for preventing AD onset and related dementias in subjects suffering from MDD through inflammatory pathway modulation.

Common Fundamentals of Psoriasis and Depression

Psoriasis is an inflammatory, immune-mediated disease that is frequently associated with psychological comorbidities such as depression. The stigma patients feel because of the appearance of their skin may contribute to the high psycho-social burden of psoriasis. However, there is emerging evidence that overlapping biological mechanisms are, to a substantial degree, responsible for the close interaction between psoriasis and depression. Increased proinflammatory mediators, such as C-reactive protein or interleukin-6, are present in both psoriasis and depression, indicating that inflammation may represent a pathophysiological link between the diseases. Anti-inflammatory biologic therapies treat the clinical manifestations of psoriasis, but might also play a significant role in reducing associated depressive symptoms in patients with psoriasis. Comparison between single studies focusing on the change in depressive symptoms in psoriasis is limited by inconsistency in the depression screening tools applied.

Back to the future of psychoneuroimmunology: Studying inflammation-induced sickness behavior

What do we know about sickness behavior? In this article, I guide you through some of the complexity of sickness behavior occurring after an immune challenge. I highlight the many features of behavioral and affective changes induced during experimental endotoxemia in humans, and describe how little we know about many of these features. I argue that we need to dismantle the components of inflammation-induced sickness behavior, and study each component in detail. I also point out the large inter-individual differences in inflammation-induced behavioral and affective changes, and the fact that psychosocial factors likely interact with inflammation to shape inflammation-induced sickness behavior. PNI clearly lacks investigations of the vulnerability and resilient factors underlying the inter-individual variability in sickness behavior. Throughout the article, I base my argument on my published articles, and provide concrete examples from my experience and the data that I have collected over the past 10 years. Given the relevance of inflammation-induced sickness behavior for inflammation-associated depression and for how people react to infections, I encourage current and future psychoneuroimmunologists to return towards basic science of sickness behavior.

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Inflammation-related sickness behavior is relevant for inflammation-associated depression

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The many features of sickness behavior should be investigated in detail

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There are large inter-individual variability in sickness behavior

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Vulnerability and resilient factors predicting sickness responses are little known

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I call for a return towards basic science of sickness behavior.

Brain Perivascular Macrophages Do Not Mediate Interleukin-1-Induced Sickness Behavior in Rats

Sickness behavior, characterized by on overall reduction in behavioral activity, is commonly observed after bacterial infection. Sickness behavior can also be induced by the peripheral administration of Gram-negative bacterial lipopolysaccharide (LPS) or interleukin-1beta (IL-1β), a pro-inflammatory cytokine released by LPS-activated macrophages. In addition to the microglia, the brain contains perivascular macrophages, which express the IL-1 type 1 receptor (IL-1R1). In the present study, we assessed the role of brain perivascular macrophages in mediating IL-1β-induced sickness behavior in rats. To do so, we used intracerebroventricular (icv) administration of an IL-1β-saporin conjugate, known to eliminate IL-R1-expressing brain cells, prior to systemic or central IL-1β injection. Icv IL-1β-saporin administration resulted in a reduction in brain perivascular macrophages, without altering subsequent icv or ip IL-1β-induced reductions in food intake, locomotor activity, and social interactions. In conclusion, the present work shows that icv IL-1β-saporin administration is an efficient way to target brain perivascular macrophages, and to determine whether these cells are involved in IL-1β-induced sickness behavior.

Why we don't move: The importance of somatic maintenance and resting

A compelling ecological theory of movement and vigor must explain why humans and other animals spend so much time not moving. When we rest, our somatic maintenance systems continue to work. When our somatic maintenance requirements increase, we place greater subjective value on resting. To explain variation in movement and vigor, we must account for the subjective value of resting.

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Fatigue is one of the most common debilitating symptoms reported by persons with multiple sclerosis (MS). It reflects feelings of tiredness, lack of energy, low motivation, and difficulty in concentrating. It can be measured at a specific instant in time as a perception that arises from interoceptive networks involved in the regulation of homeostasis. Such ratings indicate the state level of fatigue and likely reflect an inability to correct deviations from a balanced homeostatic state. In contrast, the trait level of fatigue is quantified in terms of work capacity (fatigability), which can be either estimated (perceived fatigability) or measured (objective fatigability). Clinically, fatigue is most often quantified with questionnaires that require respondents to estimate their past capacity to perform several cognitive, physical, and psychosocial tasks. These retrospective estimates provide a measure of perceived fatigability. In contrast, the change in an outcome variable during the actual performance of a task provides an objective measure of fatigability. Perceived and objective fatigability do not assess the same underlying construct. Persons with MS who report elevated trait levels of fatigue exhibit deficits in interoceptive networks (insula and dorsal anterior cingulate cortex), including increased functional connectivity during challenging tasks. The state and trait levels of fatigue reported by an individual can be modulated by reward and pain pathways. Understanding the distinction between fatigue and fatigability is critical for the development of effective strategies to reduce the burden of the symptom for individuals with MS.

Behavioral and Neurochemical Shifts at the Hippocampus and Frontal Cortex Are Associated to Peripheral Inflammation in Balb/c Mice Infected with Brucella abortus 2308

Brucellosis is a zoonosis affecting 50,000,000 people annually. Most patients progress to a chronic phase of the disease in which neuropsychiatric symptoms upsurge. The biological processes underlying the progression of these symptoms are yet unclear. Peripheral inflammation mounted against Brucella may condition neurochemical shifts and hence unchained neuropsychiatric disorders. Our work aimed at establishing whether neurological, behavioral, and neurochemical disarrays are circumstantially linked to peripheral inflammation uprise secondary to Brucella abortus 2308 infections. We then evaluated, in control and Brucella-infected mice, skeletal muscle strength, movement coordination, and balance and motivation, as well as dopamine, epinephrine, norepinephrine, and serotonin availability in the cerebellum, frontal cortex, and hippocampus. Serum levels of proinflammatory cytokines and corticosterone in vehicle-injected and -infected mice were also estimated. All estimates were gathered at the infection acute and chronic phases. Our results showed that infected mice displayed motor disabilities, muscular weakness, and reduced motivation correlated with neurochemical and peripheral immunological disturbances that tended to decrease after 21 days of infection. The present observations support that disturbed peripheral inflammation and the related neurochemical disruption might lead to mood disorders in infected mice. Future experiments must be aimed at establishing causal links and to explore whether similar concepts might explain neurological and mood disorders in humans affected by brucellosis.

Automated home-cage monitoring as a potential measure of sickness behaviors and pain-like behaviors in LPS-treated mice

The use of endotoxin, such as lipopolysaccharide (LPS) as a model of sickness behavior, has attracted recent attention. To objectively investigate sickness behavior along with its pain-like behaviors in LPS-treated mice, the behavioral measurement requires accurate methods, which reflects clinical relevance. While reflexive pain response tests have been used for decades for pain assessment, its accuracy and clinical relevance remain problematic. Hence, we used automated home-cage monitoring LABORAS to evaluate spontaneous locomotive behaviors in LPS-induced mice. LPS-treated mice displayed sickness behaviors including pain-like behaviors in automated home-cage monitoring characterized by decreased mobile behaviors (climbing, locomotion, rearing) and increased immobility compared to that of the control group in both short- and long-term locomotive assessments. Here, in short-term measurement, both in the open-field test and automated home-cage monitoring, mice demonstrated impaired locomotive behaviors. We also assessed 24 h long-term locomotor activity in the home-cage system, which profiled the diurnal behaviors of LPS-stimulated mice. The results demonstrated significant behavioral impairment in LPS-stimulated mice compared to the control mice in both light and dark phases. However, the difference is more evident in the dark phase compared to the light phase owing to the nocturnal activity of mice. In addition, the administration of indomethacin as a pharmacological intervention improved sickness behaviors in the open-field test as well as automated home-cage monitoring, confirming that automated home-cage monitoring could be potentially useful in pharmacological screening. Together, our results demonstrate that automated home-cage monitoring could be a feasible alternative to conventional methods, such as the open-field test and combining several behavioral assessments may provide a better understanding of sickness behavior and pain-like behaviors in LPS-treated mice.

Knockout of NPFFR2 Prevents LPS-Induced Depressive-Like Responses in Mice

The precise neural mechanisms underlying the pathogenesis of depression are largely unknown, though stress-induced brain inflammation and serotonergic plasticity are thought to be centrally involved. Moreover, we previously demonstrated that neuropeptide FF receptor 2 (NPFFR2) overexpression provokes depressive-like behaviors in mice. Here, we assess whether NPFFR2 is involved in priming of depressive-like behaviors and downregulation of serotonergic 1A receptor (5HT1AR) after lipopolysaccharide (LPS) treatment. The forced swimming test (FST) and sucrose preference test (SPT) were used to quantify depressive-like phenotypes in wild-type (WT) and NPFFR2-knockout (KO) mice. A single dose of LPS (i.p. 1 mg/kg) readily caused increases in toll-like receptor 4 and tumor necrosis factor-α along with decreases in 5-HT1AR mRNA in the ventral hippocampus of WT mice. Furthermore, LPS treatment of WT mice increased immobility time in FST and decreased sucrose preference in SPT. In contrast, none of these effects were observed in NPFFR2-KO mice. While WT mice injected with lentiviral 5-HT1AR shRNA in the ventral hippocampus displayed an unaltered response after LPS challenge, LPS-challenged NPFFR2-KO mice displayed a profound decrease in sucrose preference when pretreated with 5-HT1AR shRNA. Taken together, these results suggest that NPFFR2 modulates LPS-induced depressive-like behavioral phenotypes by downregulating 5HT1AR in the ventral hippocampus.

Changes in Gene Expression and Neuroinflammation in the Hippocampus after Focal Brain Ischemia: Involvement in the Long-Term Cognitive and Mental Disorders

Ischemic brain injuries are accompanied by the long-term changes in gene expression in the hippocampus, the limbic system structure, involved in the regulation of key aspects of the higher nervous activity, such as cognitive functions and emotions. The altered expression of genes and proteins encoded by them may be related to the development of post-ischemic psycho-emotional and cognitive disturbances. Activation of neuroinflammation following stroke in the hippocampus has been suggested to play an essential role in induction of long-lasting consequences. Identification of changes in the gene expression patterns after ischemia and investigation of the dynamics of these changes in the hippocampus are the necessary first steps toward understanding molecular pathways responsible for the development of post-stroke cognitive impairments and mental pathologies.

How Does the Social Grouping of Animals in Nature Protect Against Sickness? A Perspective

Sickness behavior is broadly represented in vertebrates, usually in association with the fever response in response to acute infections. The reactions to sickness behavior in a group member or potential group member in humans is quite variable, depending upon circumstances. In animals, the reactions to sickness behavior in a group member or potential group member evoke a specific response that reflects the species-specific lifestyle. Groups of animals can employ varied strategies to reduce or address exposure to sickness. Most of these have scarcely been studied in nature from a disease perspective: (1) adjusting exposure to sick conspecifics or contaminated areas; (2) caring for a sick group member; (3) peripheralization and agonistic behaviors to strange non-group conspecifics; and (4) using special strategies at parturition when newborn are healthy but vulnerable. Unexplored in this regard is infanticide, where newborn that are born with very little immunity until they receive antibody-rich colostrum, could be a target of maternal infanticide if they manifest signs of sickness and could be infectious to littermates. The strategies used by different species are highly specific and dependent upon the particular circumstances. What is needed is a more general awareness and consideration of the possibilities that avoiding or adapting to sickness behavior may be driving some social behaviors of animals in nature.

Cannabidiol prevents lipopolysaccharide-induced sickness behavior and alters cytokine and neurotrophic factor levels in the brain

Background

Major depressive disorder (MDD) affects millions of people worldwide. While the exact pathogenesis is yet to be elucidated, the role of neuro-immune signaling has recently emerged. Despite major advances in pharmacotherapy, antidepressant use is marred by limited efficacy and potential side effects. Cannabidiol (CBD), a phytocannabinoid, exerts antidepressant-like effects in experimental animals. This study investigated the impact of CBD on sickness behavior (SB), a measure of depressive-like response, and neuro-immune changes induced by lipopolysaccharides (LPS) in mice.

Methods

Socially isolated rodents were administered with LPS to trigger SB. and treated with CBD or its vehicle. Animals were submitted to forced swimming test, to evaluate depressive-like behavior, and to open field test, to evaluate locomotory activity. Immediately after behavioral analyses, animals were euthanized and had their hypothalamus, prefrontal cortex and hippocampus dissected, to proceed neurotrophins and cytokines analyses. ELISA was used to detect IL-1β, BDNF and NGF; and cytometric beads array to measure IL-2, IL-4, IL-6, IFN-γ, TNF-α and IL-10 levels.

Results

CBD effectively prevented SB-induced changes in the forced swim test without altering spontaneous locomotion. This phytocannabinoid also partially reversed LPS-evoked IL-6 increase in both the hypothalamus and hippocampus. In addition, CBD prevented endotoxin-induced increase in BDNF and NGF levels in the hippocampus of SB animals.

Conclusions

Apparently, CBD prevents both behavioral and neuro-immunological changes associated with LPS-induced SB, which reinforces its potential use as an antidepressant which modulates neuroinflammation. This opens up potentially new therapeutic avenues in MDD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-021-00301-8.

Dendritic Cells: Neglected Modulators of Peripheral Immune Responses and Neuroinflammation in Mood Disorders?

Affective disorders (AD) including major depressive disorder (MDD) and bipolar disorder (BD) are common mood disorders associated with increased disability and poor health outcomes. Altered immune responses characterized by increased serum levels of pro-inflammatory cytokines and neuroinflammation are common findings in patients with AD and in corresponding animal models. Dendritic cells (DCs) represent a heterogeneous population of myeloid cells that orchestrate innate and adaptive immune responses and self-tolerance. Upon sensing exogenous and endogenous danger signals, mature DCs secrete proinflammatory factors, acquire migratory and antigen presenting capacities and thus contribute to neuroinflammation in trauma, autoimmunity, and neurodegenerative diseases. However, little is known about the involvement of DCs in the pathogenesis of AD. In this review, we summarize the current knowledge on DCs in peripheral immune responses and neuroinflammation in MDD and BD. In addition, we consider the impact of DCs on neuroinflammation and behavior in animal models of AD. Finally, we will discuss therapeutic perspectives targeting DCs and their effector molecules in mood disorders.

Antidepressant-like effects of helicid on a chronic unpredictable mild stress-induced depression rat model: Inhibiting the IKK/IκBα/NF-κB pathway through NCALD to reduce inflammation

We previously reported that helicid, an active plant monomer of Helicid nilgirica Bedd, had good antidepressant pharmacological activities. However, the potential mechanism of action remains unknown. Current investigation showed the antidepressant-like effects of helicid and its effects on the neurocalcin delta (NCALD) gene, and its mechanism of action through a depression model in rats exposed to chronic unpredictable mild stress (CUMS). We evaluated depression symptoms using the sucrose preference test (SPT), open field test (OFT), and forced swimming test (FST). By silencing NCALD and using rescue experiments, the IL-6, iNOS, IL-1β, COX-2, and TNF-α levels in the hippocampus or peripheral blood were determined using western blotting and ELISAs. The expression of IKKβ, p-IкBα, p-IKKβ, NF-кB p65, and IкBα were tested using western blots of the cytoplasmic or nuclear samples. Helicid and silencing NCALD relieved the CUMS-irritated depressive-like actions of rats, which were shown by increased consumption of sucrose, numbers of rearings, total running distance, zone crossings, and reduced immobility times. Helicid or silencing NCALD reversed the CUMS-induced high levels of IL-1β, COX-2, IL-6, TNF-α, and iNOS in the hippocampus or peripheral blood. Helicid or silencing NCALD also reduced the expressions of p-IκBα and p-IKKβ in the cytoplasm and the expression of nuclear NF-κB p 65 in hippocampus, and simultaneously elevated cytoplasmic expressions of IκBα, IKKβ, and NF-κB p65 in the hippocampus. Notably, after NCALD overexpression, the biochemical indices of rat helicid administration were reversed. In conclusion, the antidepressant action of helicid was mediated through NCALD in rats of CUMS by repressing hippocampal neuro-inflammation and abating the activation of the IKK/IκBα/NF-κB pathway.

What Does CATS Have to Do With Cancer? The Cognitive Activation Theory of Stress (CATS) Forms the SURGE Model of Chronic Post-surgical Pain in Women With Breast Cancer

Chronic post-surgical pain (CPSP) represents a highly prevalent and significant clinical problem. Both major and minor surgeries entail risks of developing CPSP, and cancer-related surgery is no exception. As an example, more than 40% of women undergoing breast cancer surgery struggle with CPSP years after surgery. While we do not fully understand the pathophysiology of CPSP, we know it is multifaceted with biological, social, and psychological factors contributing. The aim of this review is to advocate for the role of response outcome expectancies in the development of CPSP following breast cancer surgery. We propose the Cognitive Activation Theory of Stress (CATS) as an applicable theoretical framework detailing the potential role of cortisol regulation, inflammation, and inflammatory-induced sickness behavior in CPSP. Drawing on learning theory and activation theory, CATS offers psychobiological explanations for the relationship between stress and health, where acquired expectancies are crucial in determining the stress response and health outcomes. Based on existing knowledge about risk factors for CPSP, and in line with the CATS position, we propose the SURGEry outcome expectancy (SURGE) model of CPSP. According to SURGE, expectancies impact stress physiology, inflammation, and fear-based learning influencing the development and persistence of CPSP. SURGE further proposes that generalized response outcome expectancies drive adaptive or maladaptive stress responses in the time around surgery, where coping dampens the stress response, while helplessness and hopelessness sustains it. A sustained stress response may contribute to central sensitization, alterations in functional brain networks and excessive fear-based learning. This sets the stage for a prolonged state of inflammatory-induced sickness behavior - potentially driving and maintaining CPSP. Finally, as psychological factors are modifiable, robust and potent predictors of CPSP, we suggest hypnosis as an effective intervention strategy targeting response outcome expectancies. We here argue that presurgical clinical hypnosis has the potential of preventing CPSP in women with breast cancer.

Obeticholic Acid Inhibits Anxiety via Alleviating Gut Microbiota-Mediated Microglia Accumulation in the Brain of High-Fat High-Sugar Diet Mice

Anxiety is one of the complications of metabolic disorders (MDs). Obeticholic acid (OCA), the bile acids (BAs) derivative, is a promising agent for improving MDs in association with gut dysbiosis. Yet, its protective effect on MDs-driven anxiety remains unknown. Here, we assessed the serum biochemical parameters and behavioral performance by open field and Morris water maze tests in HFHS diet-induced MDs mice after OCA intervention for nine and 18 weeks. Moreover, antibiotics intervention for microbial depletion was conducted simultaneously. We found that OCA treatment inhibited the initiation and progression of anxiety in HFHS diet-MDs mice via a microbiota–BAs–brain axis: OCA decreased the neuroinflammatory microglia and IL-1β expression in the hippocampus, reversed intestinal barrier dysfunction and serum proinflammatory LPS to a normal level, modified the microbial community, including the known anxiety-related Rikenellaceae and Alistipes, and improved the microbial metabolites especially the increased BAs in feces and circulation. Moreover, the OCA-reversed bile acid taurocholate linked disordered serum lipid metabolites and indole derivatives to anxiety as assessed by network analysis. Additionally, microbial depletion with antibiotics also improved the anxiety, microgliosis and BAs enrichment in the experimental MDs mice. Together, these findings provide microbiota–BAs–brain axis as a novel therapeutic target for MDs-associated neuropsychiatric disorders.

Tumor Necrosis Factor (TNF) Is Required for Spatial Learning and Memory in Male Mice under Physiological, but Not Immune-Challenged Conditions

Increasing evidence demonstrates that inflammatory cytokines-such as tumor necrosis factor (TNF)-are produced at low levels in the brain under physiological conditions and may be crucial for synaptic plasticity, neurogenesis, learning and memory. Here, we examined the effects of developmental TNF deletion on spatial learning and memory using 11-13-month-old TNF knockout (KO) and C57BL6/J wild-type (WT) mice. The animals were tested in the Barnes maze (BM) arena under baseline conditions and 48 h following an injection of the endotoxin lipopolysaccharide (LPS), which was administered at a dose of 0.5 mg/kg. Vehicle-treated KO mice were impaired compared to WT mice during the acquisition and memory-probing phases of the BM test. No behavioral differences were observed between WT and TNF-KO mice after LPS treatment. Moreover, there were no differences in the hippocampal content of glutamate and noradrenaline between groups. The effects of TNF deletion on spatial learning and memory were observed in male, but not female mice, which were not different compared to WT mice under baseline conditions. These results indicate that TNF is required for spatial learning and memory in male mice under physiological, non-inflammatory conditions, however not following the administration of LPS. Inflammatory signalling can thereby modulate spatial cognition in male subjects, highlighting the importance of sex- and probably age-stratified analysis when examining the role of TNF in the brain.

Co-Occurrence of Symptoms and Gut Microbiota Composition Before Neoadjuvant Chemotherapy and Radiation Therapy for Rectal Cancer: A Proof of Concept

PURPOSE

To examine a) whether there are significant differences in gut microbial diversity and in the abundance of gut microbial taxa; and b) differences in predicted functional pathways of the gut microbiome between those participants with high co-occurring symptoms and those with low co-occurring symptoms, prior to neoadjuvant chemotherapy and radiation therapy (CRT) for rectal cancer.

METHODS

Rectal cancer patients (n = 41) provided stool samples for 16 S rRNA gene sequencing and symptom ratings for fatigue, sleep disturbance, and depressive symptoms prior to CRT. Descriptive statistics were computed for symptoms. Gut microbiome data were analyzed using QIIME2, LEfSe, and the R statistical package.

RESULTS

Participants with high co-occurring symptoms (n = 19) had significantly higher bacterial abundances of Ezakiella, Clostridium sensu stricto, Porphyromonas, Barnesiella, Coriobacteriales Incertae Sedis, Synergistiaceae, Echerichia-Shigella, and Turicibacter compared to those with low co-occurring symptoms before CRT (n = 22). Biosynthesis pathways for lipopolysaccharide, L-tryptophan, and colanic acid building blocks were enriched in participants with high co-occurring symptoms. Participants with low co-occurring symptoms showed enriched abundances of Enterococcus and Lachnospiraceae, as well as pathways for β-D-glucoronosides, hexuronide/hexuronate, and nicotinate degradation, methanogenesis, and L-lysine biosynthesis.

CONCLUSION

A number of bacterial taxa and predicted functional pathways were differentially abundant in patients with high co-occurring symptoms compared to those with low co-occurring symptoms before CRT for rectal cancer. Detailed examination of bacterial taxa and pathways mediating co-occurring symptoms is warranted.

So Many Faces, Phases, and Facets, Sickness Behavior Beyond Disciplines

Animals, including human beings, modify their behavior when they fall sick. Interestingly, sociology, biology, and psychology have at different times in their history developed constructs of illness or sickness behavior. The aims of the present paper are to consider sickness behavior in animals and humans and to evaluate to what extent the notions of sickness behavior would allow for interdisciplinary research. After distinguishing disease, illness, and sickness, the case will be made that illness behavior and sickness behavior can be considered heuristically as synonyms given the existence of some fluidity between the notion of illness and sickness. Based on this, different faces, phases, and facets of sickness behavior will be presented before addressing the question of how integration of constructs of sickness behaviors would be possible across biology, medicine, psychology, and sociology. It is concluded that interdisciplinary research on sickness behavior between biology, psychology, and sociology is possible and called for with regard to constructs, methods, and explanations, while keeping in mind differences in perspectives, for example between acute and chronic sickness behavior.

Relationship Between Blood Cytokine Levels, Psychological Comorbidity, and Widespreadness of Pain in Chronic Pelvic Pain

Background: Low-grade inflammation has been implicated in the etiology of depression, long-term fatigue and chronic pain. TNFα and IL-6 are perhaps the most studied pro-inflammatory cytokines in the field of psychoneuroimmunology. The purpose of our study was to further investigate these relationships in patients with chronic pelvic pain specifically. Using plasma samples from a large, well-described cohort of patients with pelvic pain and healthy controls via the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network, we examined the relationship between TNFα and IL-6 and comorbid psychological symptoms. We also investigated the relationship between IL-8 and GM-CSF, and widespreadness of pain. Methods: We included baseline blood samples in the analyses, 261 patients (148 women) and 110 healthy controls (74 women). Fourteen pro- and anti-inflammatory or regulatory cytokines were analyzed in a Luminex^® xMAP^® high-sensitivity assay. We used regression models that accounted for known factors associated with the outcome variables to determine the relationship between cytokine levels and clinical measures. Results: There were no statistical differences in cytokine levels between patients and healthy controls when controlling for age. In patients, TNFα was significantly associated with levels of fatigue (p = 0.026), but not with pain intensity or depression. IL-6 was not significantly related to any of the outcome variables. Women with pelvic pain showed a negative relationship between IL-8 and widespreadness of pain, while men did not (p = 0.003). For both sexes, GM-CSF was positively related to widespreadness of pain (p = 0.039). Conclusion: Our results do not suggest low-grade systemic inflammation in chronic pelvic pain. Higher TNFα blood levels were related to higher fatigue ratings, while higher systemic GM-CSF levels predicted more widespread pain. Our study further suggests a potentially protective role of IL-8 with regard to with regard to the widepreadness of pain in the body, at least for women.

Sick for science: experimental endotoxemia as a translational tool to develop and test new therapies for inflammation-associated depression

Depression is one of the global leading causes of disability, but treatments remain limited and classical antidepressants were found to be ineffective in a substantial proportion of patients. Thus, novel effective therapies for the treatment of depression are urgently needed. Given the emerging role of inflammation in the etiology and pathophysiology of affective disorders, we herein illustrate how experimental endotoxemia, a translational model of systemic inflammation, could be used as a tool to develop and test new therapeutic options against depression. Our concept is based on the striking overlap of inflammatory, neural, and affective characteristics in patients with inflammation-associated depression and in endotoxin-challenged healthy subjects. Experimental administration of endotoxin in healthy volunteers is safe, well-tolerated, and without known long-term health risks. It offers a highly standardized translational approach to characterize potential targets of therapies against inflammation-associated depression, as well as to identify characteristics of patients that would benefit from these interventions, and, therefore, could contribute to improve personalization of treatment and to increase the overall rate of responders.

Acute inflammation and psychomotor slowing: Experimental assessment using lipopolysaccharide administration in healthy humans

Data from clinical and cross-sectional studies suggest that inflammation contributes to psychomotor slowing and attentional deficits found in depressive disorder. However, experimental evidence is still lacking. The aim of this study was to clarify the effect of inflammation on psychomotor slowing using an experimental and acute model of inflammation, in which twenty-two healthy volunteers received an intravenous injection of lipopolysaccharide (LPS, dose: 0.8 ​ng/kg body weight) and of placebo, in a randomized order following a double-blind within-subject crossover design. A reaction time test and a go/no-go test were conducted 3 ​h after the LPS/placebo injection and interleukin (IL)-6 and tumor necrosis factor (TNF)-α concentrations were assessed. No effect of experimental inflammation on reaction times or errors for either test was found. However, inflammation was related to worse self-rated performance and lower effort put in the tasks. Exploratory analyses indicated that reaction time fluctuated more over time during acute inflammation. These data indicate that acute inflammation has only modest effects on psychomotor speed and attention in healthy subjects objectively, but alters the subjective evaluation of test performance. Increased variability in reaction time might be the first objective sign of altered psychomotor ability and would merit further investigation.

Evaluation of Brain Cytokines and the Level of Brain-Derived Neurotrophic Factor in an Inflammatory Model of Depression

INTRODUCTION

Major depressive disorder is considered a global public health problem. Inflammatory processes are likely involved in its pathophysiology, but the underlying mechanisms have remained uncertain.Here, we used the model of systemic lipopolysaccharide (LPS) injection to test the hypothesis that depressive-like behaviors occur along with changes in the levels of cytokines and brain-derived neurotrophic factor (BDNF) in the hippocampus (HC), prefrontal cortex (PFC), and hypothalamus (HT), and can be prevented by dexamethasone administration.

METHODS

Adult C57Bl/6 male mice were first isolated for 10 days, and thereafter received an injection of dexamethasone (6 mg/kg, intraperitoneal [i.p.]), saline followed by LPS (0.83 mg/kg, i.p.), or saline. After 6 h, animals were subjected to the forced-swim test (FST) and open-field tests. Immediately after the behavioral tests, they were euthanized and their brains were collected for the biochemical analyses.

RESULTS

LPS increased the immobility time and reduced the distance travelled in the FST and open-field test, respectively. Dexamethasone increased the immobility time in saline-treated mice but reduced this behavior in the LPS group. LPS increased the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and interferon (IFN)-γ in most of the regions evaluated. Dexamethasone prevented LPS-induced IL-6 in the HC, PFC, and HT. Interestingly, dexamethasone increased IL-4 and IL-10 levels in both the LPS- and saline-treated groups. Although dexamethasone reduced BDNF in saline-treated mice, it prevented LPS-induced reduction in this neurotrophic factor.

CONCLUSION

In summary, dexamethasone decreased proinflammatory and increased anti-inflammatory levels of cytokines and prevented a reduction in BDNF levels induced by the inflammatory stimulus. Thus, the attenuation of depressive-like behavior induced by dexamethasone may be related to the effects on these parameters.