Innate immune stimulation by monophosphoryl lipid A prevents chronic social defeat stress-induced anxiety-like behaviors in mice

Exploring the molecular mechanisms of comorbidity of myocardial infarction and anxiety disorders by combining multiple data sets with in vivo experimental validation

BACKGROUND

The incidence of comorbidity between myocardial infarction (MI) and anxiety disorders is increasing. However, the biological association between them has not been fully understood.

OBJECTIVE

This study aims to investigate the molecular mechanisms of comorbidity between MI and anxiety disorders and to predict their key genes and potential therapeutic drugs.

METHODS

We searched Gene Expression Omnibus databases and performed differential analyses using the limma package to identify the functional enrichment of differential genes. Next, we constructed regulatory networks to investigate the relationship between hub genes and autophagy, ferroptosis, and immunity. Furthermore, we predicted transcription factors by R package, constructed a miRNA network, performed the single-cell analysis of key gene expression, and predicted drug targeting of differential genes using the Connectivity Map database.

RESULTS

The datasets for MI and anxiety disorders were analyzed for up and down-regulated differential genes, resulting in 35 intersecting differential genes. The top 10 feature genes from each dataset were intersected using Random Forest, resulting in the identification of three intersecting genes: STK17B, AKIRIN2, and WDR77. Validation of the above key genes was carried out by in vitro experiments. We examined the gene expression of STK17B, WDR77 and AKIRIN2 in the hippocampus and myocardial infarction border zone respectively by qPCR and WB, and the results confirmed that the above are the key genes for myocardial infarction and anxiety. There is a significant correlation between the comorbidity mechanism of myocardial infarction and anxiety disorders with ferroptosis and immunity. The construction of the miRNA network revealed that miR-205 and let-7 had higher average connectivity among the three hub genes. The single-cell analysis revealed significant expression of key genes in Endothelial cells, Cardiomyocytes, Macrophages, and Fibroblasts datasets. Cd274 showed a higher correlation with key genes in myocardial infarction and anxiety disorders.

CONCLUSION

Validation by multiple datasets and in vitro experiments showed that STK17B, AKIRIN2, and WDR77 are the key genes in the comorbidity of myocardial infarction and anxiety disorders, and ferroptosis and immunity are the key links in the comorbidity mechanism of myocardial infarction and anxiety disorders.

Higher atherogenic index of plasma is associated with increased major depressive disorder: insights from a nationally representative study

Background

Emerging studies reveal a shared pathophysiological underpinning for metabolic problems and mental illnesses. The present study aimed to determine the association between atherogenic index of plasma (AIP) and the incidence of major depressive disorder (MDD).

Methods

7,951 subjects of US adults were collected from the National Health and Nutrition Examination Survey (NHANES) 2005-2018. MDD was evaluated through the Patient Health Questionnaire (PHQ-9). Multivariate logistic regression, sensitivity analysis, and spline smoothing plot method were used to identify the relationship between AIP and MDD. The cut-off point was calculated using recursive partitioning analysis when segmenting effects emerged. The area under the receiver operating characteristic (ROC) curve (AUC) and Hosmer-Lemeshow test were conducted to evaluate the performance of AIP in identifying MDD. Subgroup analyses and interaction tests were used to explore whether the association was stable in different populations.

Results

A positive correlation between AIP and PHQ-9 score and MDD was both observed in 7,951 subjects included in the study, with a significant threshold of -0.42 determined using recursive partitioning analysis. In the fully adjusted model, a positive association between AIP and PHQ-9 score and MDD was observed (β=0.46, 95% CI 0.14~0.78; OR=1.42, 95% CI 1.04~1.93). Individuals in the highest AIP quartile had a 0.39-unit higher PHQ-9 score (β=0.39, 95% CI 0.12~0.66) and a significantly 33% greater risk of MDD than those in the lowest AIP quartile (OR=1.33, 95% CI 1.02~1.73). Spline smoothing plot analysis further confirmed the positive and non-linear association between AIP and PHQ-9 and MDD. ROC analysis (AUC=0.771) and the Hosmer-Lemeshow test (χ2 = 14.239, P=0.076) suggested an excellent performance and goodness-of-fit of the relatively optimal model. DCA and CIC analysis also revealed a favorable overall net benefit and clinical impact of the model. Subgroup analyses and interaction tests revealed that the association between AIP and PHQ-9 score and MDD remained consistent across different subgroups and was not modified by other covariates, and this positive correlation was more pronounced in those with diabetes or hypertension.

Conclusion

An elevated AIP is linked to a higher chance of MDD, especially in those with diabetes or hypertension. Resolving dyslipidemia and managing comorbidities may help reduce the likelihood of developing MDD.

Astrocyte Activation in the ACC Contributes to Comorbid Anxiety in Chronic Inflammatory Pain and Involves in The Excitation-Inhibition Imbalance

Neurons within the anterior cingulate cortex (ACC) orchestrate the co-occurrence of chronic pain and anxiety. The ACC hyperactivity plays a crucial role in the emotional impact of neuropathic pain. Astrocyte-mediated neuroinflammatory is responsible for regulating the balance between excitation-inhibition (E/I) in the brain. However, there is limited understanding of the possible contributions of astrocytes in the ACC to comorbidity of anxiety and chronic inflammatory pain. This paper aims to investigate the possible contribution of astrocytes in the ACC to the comorbidity between anxiety and chronic inflammatory pain, as well as their involvement in the E/I imbalance of pyramidal cells. Our results show that CFA rats displayed allodynia and anxiety-like behaviors. The E/I balance in the ACC shifts to excitement in comorbidity of chronic pain and anxiety by western blotting, and electrophysiological recording. Result of RNA-Seq also indicated that E/I imbalance and neuroinflammation of ACC were involved in pain-anxiety comorbidity. Then, positive cells of GFAP but not Iba1 in the contralateral ACC were increased; the mRNA expression of GFAP and its activation-related proinflammatory cytokines (TNF-α, IL-6, and IL-1β) in the contralateral ACC were also elevated. Furthermore, specific chemogenic inhibition of ACC astrocytes reversed comorbid pain and anxiety and suppressed high ACC excitability. Our data suggest that astrocytes participate in comorbid pain and anxiety and excitation-inhibition imbalance in ACC. Inhibition astrocyte activation can reduce anxiety related to pain and restore the imbalance in the ACC. These findings shed light on the involvement of astrocytes in comorbid conditions, offering valuable insights into a potential therapeutic approach for the co-occurrence of chronic pain and anxiety.

Systemic Tumors Can Cause Molecular Changes in the Hippocampus That May Have an Impact on Behavior after Chronic Social Stress

Evidence indicates that chronic social stress plays a significant role in the development of cancer and depression. Although their association is recognized, the precise physiological mechanism remains unknown. In our previous work, we observed that OF1 males subjected to chronic social defiance exhibited anhedonia, and those who developed tumors in the lung showed anxiety-associated behaviors. In this study, we observed that tumor-bearing OF1 mice presented higher levels of 3-HK, and this increase may be due to IDO. No differences in hippocampal catecholamine levels were observed. Our results suggest that a systemic tumor can induce molecular changes in the hippocampal kynurenine pathway that may impact behavior.

Comparative analysis of the nucleus accumbens transcriptional features in multiple depressive animal models

Chronic stress is deemed a significant clinical contributor to depression. The use of animal models of chronic stress can fully reveal the complex pathological mechanisms and their changing trends in the pathogenesis of depression, which is crucial for both disease prevention and therapy. It is also unknown how various forms of stress differ in their impact on animal physiology and behavior. The nucleus accumbens (NAc), an essential brain area for the pathophysiology of depression, and its underlying neural mechanisms remain unclear. Here, we systematically compared transcriptional signatures in the NAc of four chronic stress models in rats: chronic unpredictable mild stress (CUMS), chronic social defeat stress (CSDS), learned helplessness (LH), chronic restraint stress (CRS). The majority of differentially expressed genes (DEGs) were unique to a single depression model, while the rank-rank hypergeometric overlap analysis showed that the CSDS and CRS models had the greatest overlap, and the CRS and CUMS models had the least. Then, we performed pathway analysis of the differential genes and found that the neuroactive ligand-receptor interaction pathway was significantly enriched not only in the LH, CRS and CSDS stress models, but also significantly enriched in stress genes that were also altered in at least two stress models. Finally, we found three hub genes (Dcx, Tnc and Wdfy4) by constructing co-expression networks for stress genes. In summary, our research has the potential to offer fresh insights into the molecular mechanisms underlying depression induced by different types of stress, highlighting both their similarities and differences. It may provide valuable clues for understanding the pathogenesis of depression.

Intranasal Monophosphoryl Lipid a Administration Ameliorates depression-like Behavior in Chronically Stressed Mice Through Stimulation of Microglia

We and others have reported that systematic stimulation of the central innate immune system by a low dose of lipopolysaccharide (LPS) can improve depression-like behavior in chronically stressed animals. However, it is unclear whether similar stimulation by intranasal administration could improve depression-like behavior in animals. We investigated this question using monophosphoryl lipid A (MPL), a derivative of LPS that lacks the adverse effects of LPS but is still immuno-stimulatory. We found that a single intranasal administration of MPL at a dose of 10 or 20 µg/mouse, but not at a dose of 5 µg/mouse, ameliorated chronic unpredictable stress (CUS)-induced depression-like behavior in mice, as evidenced by the decrease in immobility time in tail suspension test and forced swimming test and the increase in sucrose intake in sucrose preference test. In the time-dependent analysis, the antidepressant-like effect of a single intranasal MPL administration (20 µg/mouse) was observed 5 and 8 h but not 3 h after drug administration and persisted for at least 7 days. Fourteen days after the first intranasal MPL administration, a second intranasal MPL administration (20 µg/mouse) still showed an antidepressant-like effect. The innate immune response mediated by microglia might mediate the antidepressant-like effect of intranasal MPL administration, because both inhibition of microglial activation by pretreatment with minocycline and depletion of microglia by pretreatment with PLX3397 prevented the antidepressant-like effect of intranasal MPL administration. These results suggest that intranasal administration of MPL can produce significant antidepressant-like effects in animals under chronic stress conditions via stimulation of microglia.

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.