Inflammation in the brain and periphery found in animal models of depression and its behavioral relevance

Bioinformatics Screening and Experimental Validation for Deciphering the Immune Signature of Late-Onset Depression

Background

Late-onset depression (LOD) is often associated with more severe cognitive impairment and a higher risk of disability and suicide. Emerging evidence suggests that immune system problems may be involved. This study aims to systematically characterize the genetic signature of LOD based on the immune landscape.

Methods

The expression profile of GSE76826 was obtained from the Gene Expression Omnibus (GEO) database to gather gene expression data for 10 LOD patients and 12 healthy controls (HC). Various analyses, such as Single-Sample Gene Set Enrichment Analysis (ssGSEA) and Weighted Gene Co-expression Network Analysis (WGCNA), were used to mine key genes closely related to LOD. ImmuCellAI helped us understand differences in the immune environment between LOD patients and controls, and we used an LOD animal model to validate the relevant immune characteristics.

Results

We found enriched immune pathways linked to LOD and adaptive immune responses. Using advanced bioinformatics techniques, we identified two key genes: apelin (APLN) and leptin (LEP), which have good diagnostic efficacy (AUC=0.925, 95% CI=1.00-0.83) for LOD. Neutrophil infiltration increased significantly in LOD, while CD8+ T lymphocytes (CD8_T) decreased. We finally constructed an animal model of LOD, validated two key genes and microglia marker genes in blood and hippocampus, and detected elevated pro-inflammatory factors such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α).

Conclusion

We identified and validated the presence of aberrant expression of APLN and LEP in LOD and described a possible immune mechanism involving increased release of IL-6 and TNF-α, leading to decreased CD8_T infiltration and increased neutrophil infiltration. Meanwhile, peripheral inflammation across the blood-brain barrier further promotes microglia activation, leading to neuronal damage.

Pathophysiological dynamics of acute myocardial infarction rats under chronic psychological stress at different time points

There is a lack of in-depth research on the impacts and changes in chronic psychological stress (CPS) on the cardiovascular system after acute myocardial infarction (AMI). This study aims to explore the comorbid mechanism and dynamic evolution of AMI exposed to CPS. 120 Wistar rats were randomly divided into Sham Operation group, Sham Operation + Chronic Unpredictable Mild Stress (CUMS) group, AMI group and AMI + CUMS group, with each group further divided into subgroups at days 7, 14, and 28. The AMI model was created by ligating the left anterior descending coronary artery, and CUMS model was used to induce CPS in rats. Behavioral changes were assessed through open field tests and sucrose preference tests. Cardiac function and structure were evaluated via echocardiography. The serum levels of TNFα, IL-6, NO, ET, CK-MB, cTNT, and ANP were measured using assay kits. Pathological changes in cardiac and brain tissues were observed under an optical microscope. Comparative analysis across different models revealed that CUMS significantly reduced behavioral activities in rats, with an interaction between CUMS and AMI affecting total distance (P < 0.05). Both CUMS and AMI significantly reduced cardiac function indicators, with their interaction effects on LVEF, LVFS, and CO (P < 0.05). AMI significantly altered cardiac structural parameters, particularly on day 28 (P < 0.05); while the impact of CUMS on cardiac structure was not significant, except for a notable reduction in LVAW/s on day 7 in AMI + CUMS group (P < 0.05). AMI caused significant changes in the serum biomarkers, while CUMS only significantly increased cTnT on day 7, ANP, TNFα, and IL-6 on day 14, and CK-MB on day 28, with their interaction effects on the three myocardial injury markers and TNFα (P < 0.05). Comparative analysis across different time points demonstrated that behavioral activity, cardiac function, CK-MB, cTnT, ANP, TNFα, and ET levels decreased significantly over time in the AMI model rats, while the left ventricular mass increased significantly (P < 0.05). Pathologically, compared with stress or AMI alone, the AMI + CUMS group exhibited more severe myocardia cellular degeneration and inflammatory infiltration, causing larger infract areas in myocardial tissue, as well as cell number decreases and morphological changes in hippocampal tissue. AMI with CPS exacerbates myocardial injury through sustained inflammation and endothelial dysfunction, leading to heart-brain pathology manifestations characterized by decreased cardiac function and hippocampal tissue damage.

Amyloban, extracted from Hericium erinaceus, ameliorates social deficits and suppresses the enhanced dopaminergic system in social defeat stress mice

Social dysfunctions are common in various psychiatric disorders, including depression, schizophrenia, and autism, and are long-lasting and difficult to treat. The development of treatments for social impairment is critical for the treatment of several psychiatric disorders. "Amyloban 3399," a product extracted from the mushroom Hericium erinaceus, markedly improves social dysfunctions in patients with treatment-resistant schizophrenia and depression. However, the molecular mechanism(s) through which amyloban ameliorates social impairment remains unclear. To clarify this mechanism, in this study, we aimed to establish a mouse model of social defeat stress (SDS) and investigate the effects of amyloban on social deficits. Amyloban administration ameliorated social deficits and the dopamine system activity in SDS mice. These findings suggest that there is a possibility that amyloban may improve social deficits by suppressing the hyperactivation of the dopaminergic system. Amyloban may be an effective treatment for social dysfunctions associated with various psychiatric disorders.

Ameliorated Effects of Fucoidan on Dextran Sulfate Sodium-Induced Ulcerative Colitis and Accompanying Anxiety and Depressive Behaviors in Aged C57BL/6 Mice

Fucoidan has shown better effects on the improvement of acute ulcerative colitis (UC). However, the specific mechanisms by which fucoidan improves UC-related behavioral disorders in aged mice, especially its effect on the gut-brain axis, remain to be further explored. C57BL/6 male mice aged 8 months were gavaged with 400 or 100 mg/kg bw day fucoidan for five consecutive weeks, with UC being induced by ad libitum to dextran sulfate sodium (DSS) solution in the fifth week. The results showed that fucoidan ameliorated UC and accompanying anxiety- and depressive-like behaviors with downregulated expressions of (NOD)-like receptor family and pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein (ASC), cysteine aspartate-specific protease-1 (Caspase-1) and interlekin-1β (IL-1β), and elevated mRNA levels of brain-derived neurotrophic factor (Bdnf) and postsynaptic-density protein 95 (Psd-95) in cortex and hippocampus. Furthermore, fucoidan improved the permeability of intestinal barrier and blood-brain barrier and restored the abnormal structure of the gut microbiota with a significantly decreased ratio of Firmicutes to Bacteroidota (F/B) and obviously increased abundance of Akkermansia. As a diet-derived bioactive ingredient, fucoidan might be a better alternative for the prevention of UC and accompanying anxiety- and depressive-like behaviors.

Bidirectional relationship between C-reactive protein and depressive symptoms considering cumulative effect among Chinese middle-aged and older adults

Introduction

Research examining the bidirectional relationship between C-reactive protein (CRP) and depressive symptoms, while accounting for cumulative effect of repeated episodes of CRP or depressive symptoms, is currently deficient in non-Western populations.

Methods

A nationally representative population-based cohort data from the Chinese Health and Retirement Longitudinal Study (CHARLS) was utilized. In bi-directional analysis, we considered both single determinations and two successive determinations of CRP or depressive symptoms. Multivariate logistic regression assessed the association between elevated CRP levels at baseline or repeated episodes of CRP elevations over two successive determinations and subsequent elevated depressive symptoms, and vice versa.

Results

Although single determinations of CRP or depressive symptoms yielded non-significant results in both directions, full multivariate models, adjusting for baseline depressive symptoms, socio-demographic characteristics, health-related behaviors, metabolic measures, and health status, revealed a significantly positive association based on two successive determinations of CRP or depressive symptoms. This significant association was observed between cumulative effects of sustained CRP elevations over two successive determinations (2 vs. 0) and subsequent elevated depressive symptoms (OR=1.58; 95% CI: 1.15 to 2.17) and between cumulative effect of repeated episodes of depression (2 vs. 0) and later elevated CRP (OR=1.26; 95% CI: 1.02 to 1.56). Furthermore, sex-stratified analyses confirmed the robustness of these relationships.

Conclusion

There are bidirectional associations between depressive symptoms and CRP, driven by the cumulative effect of repeated episodes of CRP or depressive symptoms among middle-aged and older Chinese adults. These findings hold significant clinical implications, highlighting the potential of both anti-inflammatory and anti-depression approaches.

NADPH-oxidases as potential pharmacological targets for thrombosis and depression comorbidity

There is a complex interrelationship between the nervous system and the cardiovascular system. Comorbidities of cardiovascular diseases (CVD) with mental disorders, and vice versa, are prevalent. Adults with mental disorders such as anxiety and depression have a higher risk of developing CVD, and people with CVD have an increased risk of being diagnosed with mental disorders. Oxidative stress is one of the many pathways associated with the pathophysiology of brain and cardiovascular disease. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is one of the major generators of reactive oxygen species (ROS) in mammalian cells, as it is the enzyme that specifically produces superoxide. This review summarizes recent findings on the consequences of NOX activation in thrombosis and depression. It also discusses the therapeutic effects and pharmacological strategies of NOX inhibitors in CVD and brain disorders. A better comprehension of these processes could facilitate the development of new therapeutic approaches for the prevention and treatment of the comorbidity of thrombosis and depression.

Vicarious defeat stress induces increased alcohol consumption in female mice: Role of neurokinin-1 receptor and interleukin-6

There is a high frequency of comorbidity of alcohol use disorder (AUD) and depression in human populations. We have studied this relationship in our lab using the social defeat stress (SDS) model, which results in both depression-like behaviours and increased alcohol consumption in male mice. However, standard SDS procedures are difficult to use in female mice due to a lack of territorial aggression. In the experiments presented here, we used vicarious defeat stress (VDS) to assess social withdrawal and alcohol consumption in female C57BL6/J mice. We also assessed the expression of interleukin-6 (IL6), which is a proinflammatory cytokine that is associated with depression in humans and sensitivity to SDS in mice. In these experiments, C57BL/6 female mice underwent 10 days of VDS where they witnessed the physical defeat of a male conspecific by an aggressive CD1 mouse. After the end of VDS, mice were either given access to alcohol or sacrificed for the measurement of IL6 expression. We found that VDS increased alcohol consumption and IL6 expression in the frontal cortex and hippocampus. Given that the neurokinin-1 receptor (NK1R) can mediate both stress-induced alcohol consumption and IL6 expression, we tested the ability of NK1R antagonism to reduce VDS-induced alcohol consumption and found that this treatment reduced alcohol intake in both VDS-exposed mice and in unstressed controls. The observed increase in alcohol consumption suggests that VDS is a model that can be utilized to study stress-induced alcohol consumption in female mice, and that this is sensitive to NK1R antagonism.

Investigating the Potential Mechanisms and Therapeutic Targets of Inflammatory Cytokines in Post-stroke Depression

Post-stroke depression (PSD) affects approximately one-third of stroke survivors, severely impacting general recovery and quality of life. Despite extensive studies, the exact mechanisms underlying PSD remain elusive. However, emerging evidence implicates proinflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-alpha, and interleukin-18, play critical roles in PSD development. These cytokines contribute to PSD through various mechanisms, including hypothalamic-pituitary-adrenal (HPA) axis dysfunction, neurotransmitter alterations, neurotrophic factor changes, gut microbiota imbalances, and genetic predispositions. This review is aimed at exploring the role of cytokines in stroke and PSD while identifying their potential as specific therapeutic targets for managing PSD. A more profound understanding of the mechanisms regulating inflammatory cytokine expression and anti-inflammatory cytokines like interleukin-10 in PSD may facilitate the development of innovative interventions to improve outcomes for stroke survivors experiencing depression.

Ketogenic diet changes microglial morphology and the hippocampal lipidomic profile differently in stress susceptible versus resistant male mice upon repeated social defeat

Psychological stress confers an increased risk for several diseases including psychiatric conditions. The susceptibility to psychological stress is modulated by various factors, many of them being modifiable lifestyle choices. The ketogenic diet (KD) has emerged as a dietary regime that offers positive outcomes on mood and health status. Psychological stress and elevated inflammation are common features of neuropsychiatric disorders such as certain types of major depressive disorder. KD has been attributed anti-inflammatory properties that could underlie its beneficial consequences on the brain and behavior. Microglia are the main drivers of inflammation in the central nervous system. They are known to respond to both dietary changes and psychological stress, notably by modifying their production of cytokines and relationships among the brain parenchyma. To assess the interactions between KD and the stress response, including effects on microglia, we examined adult male mice on control diet (CD) versus KD that underwent 10 days of repeated social defeat (RSD) or remained non-stressed (controls; CTRLs). Through a social interaction test, stressed mice were classified as susceptible (SUS) or resistant (RES) to RSD. The mouse population fed a KD tended to have a higher proportion of individuals classified as RES following RSD. Microglial morphology and ultrastructure were then analyzed in the ventral hippocampus CA1, a brain region known to present structural alterations as a response to psychological stress. Distinct changes in microglial soma and arborization linked to the KD, SUS and RES phenotypes were revealed. Ultrastructural analysis by electron microscopy showed a clear reduction of cellular stress markers in microglia from KD fed animals. Furthermore, ultrastructural analysis showed that microglial contacts with synaptic elements were reduced in the SUS compared to the RES and CTRL groups. Hippocampal lipidomic analyses lastly identified a distinct lipid profile in SUS animals compared to CTRLs. These key differences, combined with the distinct microglial responses to diet and stress, indicate that unique metabolic changes may underlie the stress susceptibility phenotypes. Altogether, our results reveal novel mechanisms by which a KD might improve the resistance to psychological stress.

Transcranial Direct Current Stimulation (tDCS) Promotes state-dependent Effects on Neuroinflammatory and Behavioral Parameters in rats Chronically Exposed to Stress and a Hyper-Palatable Diet

Chronic stress is a common condition affecting health, often associated with unhealthy eating habits. Transcranial direct current stimulation (tDCS) has been proposed to address these issues. Thus, this research investigated the effects of tDCS on biometric, behavioral, and neurochemical parameters in chronically stressed rats fed a hyper-palatable cafeteria diet (CAFD). The study lasted 8 weeks, with CAFD exposure and/or chronic restraint stress model (CRS - 1 h/day, 5 days/week, for 7 weeks) started concurrently. tDCS or sham sessions were applied between days 42 and 49 (0.5 mA, 20 min/day). CAFD increased body weight, caloric consumption, adiposity, and liver weight. It also altered central parameters, reducing anxiety and cortical levels of IL-10 and BDNF. In turn, the CRS resulted in increased adrenals in rats with standard diet (SD), and anxiety-like and anhedonic behaviors in rats with CAFD. tDCS provided neurochemical shifts in CAFD-fed stressed rats increasing central levels of TNF-α and IL-10, while in stressed rats SD-fed induced a decrease in the adrenals weight, relative visceral adiposity, and serum NPY levels. These data demonstrated the anxiolytic effect of CAFD and anxiogenic effect of stress in CAFD-fed animals. In addition, tDCS promoted state-dependent effects on neuroinflammatory and behavioral parameters in rats chronically exposed to stress and a hyper-palatable diet. These findings provide primary evidence for additional mechanistic and preclinical studies of the tDCS technique for stress-related eating disorders, envisioning clinical applicability.

Relationship between perceived stress, stress coping strategies, and clinical status in patients with rheumatoid arthritis

Coping with a chronic disease such as rheumatoid arthritis (RA) involves significant changes in life and promotes stressful situations. The inability to cope with stress can contribute to the lack of effectiveness of therapy. The aim of this study was to evaluate the relationship between perceived stress, coping strategies, and the clinical status of RA patients determined by C-reactive protein (CRP) and Disease Activity Score (DAS28). 165 subjects were studied, 84 of them had RA and the rest were controls. Standardised questionnaires were used: the Inventory for the Measurement of Coping Strategies (Mini-COPE) and the Perceived Stress Scale (PSS-10). A self-administered questionnaire was used to collect sociodemographic data. The blood levels of protein CRP and cortisol were determined. DAS28 was obtained from medical records. The study was cross-sectional. The mean severity of perceived stress PSS-10 was not significantly different between the control and study groups. RA patients most often used coping strategies such as active coping, planning, and acceptance. Compared to the control group, they used the strategy of turning to religion significantly more often (1.8 vs 1.4; p = 0.012). Women with RA who had higher cortisol levels were more likely to use positive reevaluation, seeking emotional support and instrumental support, as well as the denial strategy. In men with RA, high stress was associated with twice as high CRP levels compared to patients with low stress (p = 0.038). As the levels of CRP protein levels (p = 0.009) and the DAS28 index (p = 0.005) increased, patients were more likely to use a denial strategy.

Ketogenic diet alters microglial morphology and changes the hippocampal lipidomic profile distinctively in stress susceptible versus resistant male mice upon repeated social defeat

Psychological stress confers an increased risk for several diseases including psychiatric conditions. The susceptibility to psychological stress is modulated by various factors, many of them being modifiable lifestyle choices. The ketogenic diet (KD) has emerged as a dietary regime that offers positive outcomes on mood and health status. Psychological stress and elevated inflammation are common features of neuropsychiatric disorders such as certain types of major depressive disorder. KD has been attributed anti-inflammatory properties that could underlie its beneficial consequences on the brain and behavior. Microglia are the main drivers of inflammation in the central nervous system. They are known to respond to both dietary changes and psychological stress, notably by modifying their production of cytokines and relationships among the brain parenchyma. To assess the interactions between KD and the stress response, including effects on microglia, we examined adult male mice on control diet (CD) versus KD that underwent 10 days of repeated social defeat (RSD) or remained non-stressed (controls; CTRLs). Through a social interaction test, stressed mice were classified as susceptible (SUS) or resistant (RES) to RSD. The mouse population fed a KD tended to have a higher proportion of individuals classified as RES following RSD. Microglial morphology and ultrastructure were then analyzed in the ventral hippocampus CA1, a brain region known to present structural alterations as a response to psychological stress. Distinct changes in microglial soma and arborization linked to the KD, SUS and RES phenotypes were revealed. Ultrastructural analysis by electron microscopy showed a clear reduction of cellular stress markers in microglia from KD fed animals. Furthermore, ultrastructural analysis showed that microglial contacts with synaptic elements were reduced in the SUS compared to the RES and CTRL groups. Hippocampal lipidomic analyses lastly identified a distinct lipid profile in SUS animals compared to CTRLs. These key differences, combined with the distinct microglial responses to diet and stress, indicate that unique metabolic changes may underlie the stress susceptibility phenotypes. Altogether, our results reveal novel mechanisms by which a KD might improve the resistance to psychological stress.

Inflammation and Mental Health Disorders: Immunomodulation as a Potential Therapy for Psychiatric Conditions

Mood disorders are the leading cause of disability worldwide and their incidence has significantly increased after the COVID-19 pandemic. Despite the continuous surge in the number of people diagnosed with psychiatric disorders, the treatment methods for these conditions remain limited. A significant number of people either do not respond to therapy or discontinue the drugs due to their severe side effects. Therefore, alternative therapeutic interventions are needed. Previous studies have shown a correlation between immunological alterations and the occurrence of mental health disorders, yet immunomodulatory therapies have been barely investigated for combating psychiatric conditions. In this article, we have reviewed the immunological alterations that occur during the onset of mental health disorders, including microglial activation, an increased number of circulating innate immune cells, reduced activity of natural killer cells, altered T cell morphology and functionality, and an increased secretion of pro-inflammatory cytokines. This article also examines key studies that demonstrate the therapeutic efficacy of anti-inflammatory medications in mental health disorders. These studies suggest that immunomodulation can potentially be used as a complementary therapy for controlling psychiatric conditions after careful screening of candidate drugs and consideration of their efficacy and side effects in clinical trials.

Repurposing antimalarial artesunate for the prophylactic treatment of depression: Evidence from preclinical research

INTRODUCTION

Several studies have linked inflammation and oxidative stress with the pathogenesis of depression. Artesunate is a commonly used medication to treat malaria and has been shown to produce antioxidant, anti-inflammatory, and immunomodulatory effects. However, its prophylactic effects on depression and depression-related brain pathology are unknown.

METHODS

In Experiment 1, using a PC12 cell line, we investigated whether artesunate can prevent hydrogen peroxide (H₂ O₂ )-induced oxidative injury that mimics oxidative stress commonly observed in the depressed brain. Next, using lipopolysaccharide (LPS)-induced mouse model of depression, we investigated whether artesunate can prevent behavioral deficits observed in the open field test, novelty-suppressed feeding test, sucrose preference test, forced swimming test, and tail suspension procedure.

RESULTS

We found that artesunate significantly prevented a H₂ O₂ -induced reduction in PC12 cell activity, suggesting its antioxidant potential. We also found that mice pretreated with artesunate (5, 15 mg/kg) intraperitoneally (i.p.) prior to the LPS (.8 mg/kg, i.p.) treatment showed fewer and less severe depression- and anxiety-like behaviors than the LPS-treated control mice.

CONCLUSION

Our findings indicate that artesunate produces antioxidant effect, as well as antidepressant and anxiolytic effects. Importantly, our findings first demonstrate that artesunate can prevent LPS-induced depression- and anxiety-like symptoms, strongly suggesting its prophylactic potential in the treatment of depression and, perhaps, other psychiatric disorders associated with inflammation and oxidative stress.

Microglia Involves in the Immune Inflammatory Response of Poststroke Depression: A Review of Evidence

Poststroke depression (PSD) does not exist before and occurs after the stroke. PSD can appear shortly after the onset of stroke or be observed in the weeks and months after the acute or subacute phase of stroke. The pathogenesis of PSD is unclear, resulting in poor treatment effects. With research advancement, immunoactive cells in the central nervous system, particularly microglia, play a role in the occurrence and development of PSD. Microglia affects the homeostasis of the central nervous system through various factors, leading to the occurrence of depression. The research progress of microglia in PSD has been summarized to review the evidence regarding the pathogenesis and treatment target of PSD in the future.

Involvement of inflammatory responses in the brain to the onset of major depressive disorder due to stress exposure

Major depressive disorder (MDD) is a multifactorial disease affected by several environmental factors. Although several potential onset hypotheses have been identified, the molecular mechanisms underlying the pathogenesis of this disorder remain unclear. Several recent studies have suggested that among many environmental factors, inflammation and immune abnormalities in the brain or the peripheral tissues are associated with the onset of MDDs. Furthermore, several stress-related hypotheses have been proposed to explain the onset of MDDs. Thus, inflammation or immune abnormalities can be considered stress responses that occur within the brain or other tissues and are regarded as one of the mechanisms underlying the stress hypothesis of MDDs. Therefore, we introduce several current advances in inflammation studies in the brain that might be related to the pathophysiology of MDD due to stress exposure in this review.

S-Ketamine Pretreatment Alleviates Anxiety-Like Behaviors and Mechanical Allodynia and Blocks the Pro-inflammatory Response in Striatum and Periaqueductal Gray From a Post-traumatic Stress Disorder Model

This study aims to explore the regulatory effect of S-ketamine on the mechanical allodynia, anxiety-like behaviors and microglia activation in adult male rats exposed to an animal model of post-traumatic stress disorder (PTSD). The rat PTSD model was established by the exposure to single-prolonged stress (SPS), and 1 day later, rats were intraperitoneally injected with 5 mg/kg S-ketamine or normal saline, respectively. Paw withdrawal mechanical threshold was measured 2 days before, and 1, 3, 5, 7, 10, 14, 21 and 28 days after injection to assess mechanical allodynia in the SPS-exposed rats. For anxiety-like behaviors, the open field test and elevated plus maze test were performed at 7 and 14 days after S-ketamine treatment in the SPS-exposed rats, respectively. SPS-induced rats presented pronounced mechanical allodynia and anxiety-like behaviors, which were alleviated by S-ketamine treatment. After behavioral tests, rats were sacrificed for collecting the anterior cingulate cortex (ACC), prefrontal cortex (PFC), dorsal striatum, and periaqueductal gray (PAG). Protein levels of TNF-α, IL-1β, p-NF-κB, and NF-κB in brain regions were examined by Western blot. In addition, microglia activation in each brain region was determined by immunofluorescence staining of the microglia-specific biomarker Iba-1. Interestingly, pro-inflammatory cytokines were significantly upregulated in the dorsal striatum and PAG, rather than ACC and PFC. Activated microglia was observed in the dorsal striatum and PAG as well, and upregulated p-NF-κB was detected in the dorsal striatum. Inflammatory response, phosphorylation of NF-κB and microglia activation in certain brain regions were significantly alleviated by S-ketamine treatment. Collectively, S-ketamine is a promising drug in alleviating mechanical allodynia, anxiety-like behaviors, and pro-inflammatory responses in discrete brain regions in a model of PTSD.