Ciprofloxacin and dexamethasone in combination attenuate S. aureus induced brain abscess via neuroendocrine-immune interaction of TLR-2 and glucocorticoid receptor leading to behavioral improvement

Core antibiotic resistance genes mediate gut microbiota to intervene in the treatment of major depressive disorder

INTRODUCTION

The relationship between depression and gut microbiota remains unclear, but an important role of gut microbiota has been verified. The relationship between gut microbiota and antibiotic resistance genes (ARGs) may be a potential new explanatory pathway.

METHODS

We collected samples from 63 depressed patients and 30 healthy controls for metagenomic sequencing. The two groups' microbiota characteristics, functional characteristics, and ARG differences were analyzed.

RESULTS

We obtained 30 differential KEGG orthologs (KOs) and their producers in 5 genera and 7 species by HUMAnN3. We found 6 KOs from Weissella_cibaria and Lactobacillus_plantaru are potentially coring functional mechanism of gut microbiota. Different metabolites including sphingolipids, pyrans, prenol lipids, and isoflavonoids also showed significance between MDD and HC. We detected 48 significantly different ARGs: 5 ARGs up-regulated and 43 ARGs down-regulated in MDD compared to HC. Based on Cox model results, Three ARGs significantly affected drug efficacy (ARG29, ARG105, and ARG111). Eggerthella, Weissella, and Lactobacillus were correlated with different core ARGs, which indicated different mechanisms in affecting MDD.

LIMITATIONS

The present study needs to be replicated in different ethnic groups. At the same time, a larger Chinese cohort study and detailed experimental verification are also the key to further discussion.

CONCLUSION

Our findings suggest that ARGs play a role in the interplay between major depressive disorder and gut microbiota. The role of ARGs should be taken into account when understanding the relationship between depression and gut microbiota.

Exploring the Therapeutic Potential of Terpenoids for Depression and Anxiety

This review focus on the terpenoids as potential therapeutic agents for depression and anxiety disorders, which naturally found in a variety of plants and exhibit a wide range of biological activities. Among the terpenoids discussed in this review are α-pinene, β-caryophyllene, α-phellandrene, limonene, β-linalool, 1, 8-cineole, β-pinene, caryophyllene oxide, p-cymene, and eugenol. All of these compounds have been studied extensively regarding their pharmacological properties, such as neuroprotective effect, anti-inflammation, antibacterial, regulation of neurotransmitters and antioxidant effect. Preclinical evidence are reviewed to highlight their diverse mechanisms of action and therapeutic potential to support antidepressant and anxiolytic properties. Additionally, challenges and future directions are also discussed to emphasize therapeutic utility of terpenoids for mental health disorders. Overall, this review provides a promising role of terpenoids as novel therapeutic agents for depression and anxiety, with potential implications for the development of more effective and well-tolerated treatments in the field of psychopharmacology.

Microglial Inflammatory Responses to SARS-CoV-2 Infection: A Comprehensive Review

Coronavirus disease 2019 (COVID-19) is primarily a respiratory disease causing a worldwide pandemic in the year of 2019. SARS-CoV-2 is an enveloped, positive-stranded RNA virus that could invade the host through spike protein and exhibits multi-organ effects. The Brain was considered to be a potential target for SARS-CoV-2 infection. Although neuropsychiatric symptoms and cognitive impairments were observed in COVID-19 patients even after recovery the mechanism of action is not well documented. In this review, the contribution of microglia in response to SARS-CoV-2 infection was discussed aiming to design a therapeutic regimen for the management of neuroinflammation and psycho-behavioral alterations. Priming of microglia facilitates the hyper-activation state when it interacts with SARS-CoV-2 known as the 'second hit'. Moreover, the microgliosis produces reactive free radicals and pro-inflammatory cytokines like IL-1β, IFN-γ, and IL-6 which ultimately contribute to a 'cytokine storm', thereby increasing the occurrence of cognitive and neurological dysfunction. It was reported that elevated CCL11 may be responsible for psychiatric disorders and ROS/RNS-induced oxidative stress could promote major depressive disorder (MDD) and phenotypic switching. Additionally, during SARS-CoV-2 infection microglia-CD8+ T cell interaction may have a significant role in neuronal cell death. This cytokine-mediated cellular cross-talking plays a crucial role in pro-inflammatory and anti-inflammatory balance within the COVID-19 patient's brain. Therefore, all these aspects will be taken into consideration for developing novel therapeutic strategies to combat SARS-CoV-2-induced neuroinflammation.

Experimental animal models for brain abscess: a systematic review

BACKGROUND

Brain abscess (BA) is a rare, but severe infection and experimental BA animal models may prove crucial for advances in treatment. This review describes the development of experimental BA models and the clinical advances obtained from these, in a historical perspective.

MATERIAL AND METHODS

Experimental BA studies from inception until June 15, 2022, were included by searching the PubMed and Embase databases. Inclusion required the use of an experimental BA animal model. Non-bacterial BA models, in vitro studies, veterinarian case-reports, and articles written in non-English language were excluded. Bias was not systematically assessed, and the review was not registered at the PROSPERO.

RESULTS

79 studies were included. The majority of animal BA models have been based on small rodents using Staphylococcus aureus. The models have delineated the natural development of BA and provided detailed descriptions of the histopathological characteristics consisting of a necrotic centre surrounded by layers of inflammatory cells and fibroblasts encapsulated by a dense collagenous layer. Radiological studies of animal BA have been shown to correlate with the corresponding stages of human BA in both computed tomography and magnetic resonance imaging and may guide diagnosis as well as the timing of neurosurgical intervention. Moreover, pharmacokinetic studies of the intracavitary penetration of various antimicrobials have helped inform medical treatment of BA. Other studies have examined the diverse effects of corticosteroids including decreased cerebral oedema, intracranial pressure, and intracavitary drug concentration, whereas concerns on decreased or weakened capsule formation could not be confirmed. Finally, studies on the immunological response to BA have highlighted potential future immunomodulatory targets.

CONCLUSIONS

Animal models have been vital for improvements in the management of BA. Experimental BA models resembling human disease including polymicrobial infection by oral cavity flora in large animals are needed.

Microglia activation in the mPFC mediates anxiety-like behaviors caused by Staphylococcus aureus strain USA300

INTRODUCTION

Staphylococcus aureus (S. aureus) is considered as one of the major causative agents of serious hospital- and community-acquired infections. Recent studies have reported that S. aureus infection induced neuroinflammation and was linked with some mental disorders. To evaluate the effects of S. aureus infection on abnormal behaviors, we conducted the present study.

METHODS

A S. aureus USA300-infected mouse model was established using bacterial suspension injection into tail vein. A series of behavioral tests were performed after USA300 infection. The expression of cytokines was detected in serum and mPFC. The number and some morphological parameters of microglia were also evaluated by immunofluorescence staining.

RESULTS

Anxiety-like behaviors, instead of locomotor activity impairment or depression-like behaviors, were observed in mice infected with S. aureus USA300 compared with control. S. aureus USA300 infection caused overexpression of IL-6, TNF-α, and IL-1β in serum, resulted in microglial over-activation and excessive release of proinflammatory cytokines in the mPFC. In addition, overexpression of TLR2 accompanied by increased GLS1 and p-STAT3 was observed in the mPFC of mice infected with S. aureus USA300.

CONCLUSION

This study provides evidence that S. aureus USA300 infection can lead to neuroinflammation in the mPFC of mice, which may contribute to the development of anxiety.

Ascorbic acid along with ciprofloxacin regulates S. aureus induced microglial inflammatory responses and oxidative stress through TLR-2 and glucocorticoid receptor modulation

Microglial inflammatory responses play a central role in the pathogenesis of S. aureus induced brain infections. Upon activation, microglia produces free radicals (ROS/RNS) and disrupts the cellular antioxidant defense to combat invading microorganisms. Despite conventional antibiotic or steroid therapy, microglial over-activation could not be controlled. So, an attempt had been taken by using a natural antioxidant ascorbic acid along with ciprofloxacin to regulate microglial over-activation by involving TLR-2 and glucocorticoid receptor (GR) in an in-vitro cell culture-based study. Combinatorial treatment during TLR-2 neutralization effectively reduced the bacterial burden at 60 min compared to the GR blocking condition (p < 0.05). Moreover, the infection-induced H₂O₂, O₂^.-, and NO release in microglial cell culture was diminished possibly by enhancing SOD and catalase activities in the same condition (p < 0.05). The arginase activity was markedly increased after TLR-2 blocking in the combinatorial group compared to single treatments (p < 0.05). Experimental results indicated that combinatorial treatment may act through up-regulating GR expression by augmenting endogenous corticosterone levels. However, better bacterial clearance could further suppress the TLR-2 mediated pro-inflammatory NF-κB signaling. From Western blot analysis, it was concluded that ciprofloxacin-ascorbic acid combination in presence of anti-TLR-2 antibody exhibited 81.25% inhibition of TLR-2 expression while the inhibition for GR was 3.57% with respect to the infected group. Therefore, during TLR-2 blockade ascorbic acid combination might be responsible for the restoration of redox balance in microglia via modulating TLR-2/GR interaction. The combination treatment could play a major role in the neuroendocrine-immune regulation of S. aureus induced microglial activation.