IL-33 Treatment Attenuates the Systemic Inflammation Reaction in Acinetobacter baumannii Pneumonia by Suppressing TLR4/NF-κB Signaling

The role of TLR4/NF-kB signaling axis in pneumonia: from molecular mechanisms to regulation by phytochemicals

Pneumonia, a leading global health challenge, is characterized by inflammation driven by dysregulated immune responses. Central to its pathogenesis is the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) signaling axis, which orchestrates the recognition of pathogen-associated molecular patterns (PAMPs) and initiates cascades that mediate innate immunity. While this pathway is essential for bacterial clearance, its overactivation can lead to excessive inflammation, tissue damage, and severe complications, including acute respiratory distress syndrome (ARDS) and sepsis. This review examines the role of the TLR4/NF-κB axis in pneumonia caused by various pathogens, including Streptococcus pneumoniae, Staphylococcus aureus, and SARS-CoV- 2, and highlights its dual role in immune defense and pathological inflammation. Furthermore, we explore molecular regulators and phytochemicals that modulate this axis, including baicalin, resveratrol, and sodium houttuyfonate, which exhibit promising therapeutic potential. By elucidating these mechanisms, this study provides insights into targeted interventions to balance immune responses and mitigate inflammation, paving the way for innovative treatments in pneumonia management.

Echinacoside attenuates Klebsiella pneumoniae-induced pneumonia via inhibition of the TLR4/NF-κB signaling

The Gram-negative bacterium Klebsiella pneumoniae (K. pneumoniae) is one major causative agent of community- and hospital-acquired pneumonia. Echinacoside (ECH) is a phenylethanoid glycoside isolated from Cistanche deserticola that possesses anti-inflammatory activity. Our research aimed to confirm whether ECH alleviates K. pneumoniae-induced pneumonia and explore the underlying regulatory mechanisms. BEAS-2B cells and BALB/c mice were infected by K. pneumoniae to establish the cellular and animal models, respectively, followed by ECH treatment. Inflammatory cytokine levels were detected by RT-qPCR and ELISA. The lung wet/dry (W/D) weight ratio and the myeloperoxidase (MPO) activity in lung tissues were examined. The pulmonary histopathologic changes were observed through hematoxylin and eosin (H&E) staining. The levels of TLR4/NF-κB pathway-associated molecules were estimated through western blotting, immunohistochemical, and immunohistochemical staining. K. pneumoniae infection caused lung histopathologic damage, enhanced MPO activity, elevated lung W/D weight ratio, and upregulated inflammatory cytokine levels in mice and promoted inflammatory cytokine expression in BEAS-2B cells, which were reversed by ECH treatment. K. pneumoniae infection-induced upregulation in TLR4, phosphorylated (p)-p65, and p-IκBα levels, and downregulation in IκBα levels in BEAS-2B cells and pneumonia mice were overturned by ECH treatment. ECH ameliorates K. pneumoniae-induced pneumonia through suppressing the TLR4/NF-κB pathway.

IL-33 deficiency inhibits Toxoplasma gondii infection by promoting NLRP3 inflammasome

NLRP3 inflammasome-mediated inflammatory responses play pivotal functions in innate immunity. However, its homeostatic regulation still needs to be better understood. Here we explore the effect and potential mechanism of IL-33 on NLRP3 inflammasome upon Toxoplasma gondii infection through a series of molecular biology and immunological experiments, including western blot, qRT-PCR, and ELISA. We demonstrated that T. gondii infection induces the expression of IL-33, and IL-33-deficient (IL-33-/-) mice exhibit longer survival time than wild-type (WT) mice upon T. gondii infection. IL-33 deficiency promotes the expression of NLRP3 and ASC and the secretion of IL-1β, while exogenous IL-33 inhibits NLRP3 inflammasome. Furthermore, T. gondii infection results in the M2 polarization of macrophages, exacerbated by exogenous IL-33, which also promotes the proliferation of T. gondii. These findings showed that IL-33 deficiency attenuates T. gondii infection by promoting NLRP3 inflammasome, advancing the understanding of the role of IL-33 in inflammation.

Innate immune mechanisms promote human response to Acinetobacter baumannii infection

Acinetobacter baumannii is an opportunistic Gram-negative bacterium representing one of the leading causes of ventilator-associated pneumonia. The development of pneumonia results from a complex interplay between pathogens and pulmonary innate mucosal immunity. Therefore, the knowledge of the host immune responses is pivotal for the development of effective therapeutics to treat A. baumannii infections. Previous studies were conducted using cell lines and animal models, but a comprehensive understanding of the interaction between A. baumannii and primary human immune cells is still lacking. To bridge this gap, we investigated the response of primary monocytes, macrophages, and dendritic cells to the A. baumannii-type strain and an epidemic clinical isolate. We found that all immune cells trigger different responses when interacting with A. baumannii. In particular, macrophages and monocytes mediate bacterial clearance, whereas monocytes and dendritic cells activate a late response through the production of cytokines, chemokines, and the expression of co-stimulatory molecules. The epidemic strain induces lower expression of interleukin-10 and CD80 compared with the type strain, potentially constituting two immune evasion strategies.

Virulence Factors and Pathogenicity Mechanisms of Acinetobacter baumannii in Respiratory Infectious Diseases

Acinetobacter baumannii (A. baumannii) has become a notorious pathogen causing nosocomial and community-acquired infections, especially ventilator-associated pneumonia. This opportunistic pathogen is found to possess powerful genomic plasticity and numerous virulence factors that facilitate its success in the infectious process. Although the interactions between A. baumannii and the pulmonary epitheliums have been extensively studied, a complete and specific description of its overall pathogenic process is lacking. In this review, we summarize the current knowledge of the antibiotic resistance and virulence factors of A. baumannii, specifically focusing on the pathogenic mechanisms of this detrimental pathogen in respiratory infectious diseases. An expansion of the knowledge regarding A. baumannii pathogenesis will contribute to the development of effective therapies based on immunopathology or intracellular signaling pathways to eliminate this harmful pathogen during infections.

Jiedu Yizhi Formula Improves Cognitive Function by Regulating the Gut Dysbiosis and TLR4/NF-κB Signaling Pathway

OBJECTIVE

The objective of this study was to explore the neuroprotective mechanism of JDYZF in treating AD from the perspective of inflammation and intestinal microflora.

METHODS

A total of 24 APP/PS1 mice were randomly divided into four groups: model (n = 6), JDYZF low-dose (n = 6), JDYZF high-dose (n = 6), and positive drug (n = 6), six C57 mice were used as the control group. The body weights and diets of all mice were examined daily. After 8 weeks of administration, the learning and memory of mice were evaluated by the Morris water maze test. The histopathological changes of hippocampus, liver and kidney in mice were observed by HE staining after being euthanized. The expression of p-tau in hippocampus tissue was detected by immunohistochemistry. After that, 16S rDNA sequencing was used to investigate the relationship between JDYZF and intestinal microbiota. Finally, a comparison of TLR4, p65, p-p65, iκB, p-iκB, and IL-1β protein expression in the hippocampus tissue of mice in each group was measured by Western blot.

RESULTS

The results showed that APP/PS1 mice taking JDYZF orally were generally in good condition. Compared with the control group, JDYZF significantly improved learning and memory ability in ethology. Histology showed that JDYZF improved the hippocampal structure of mice and inhibited the deposition of p-tau. JDYZF treatment could regulate the gut microbiota of APP/PS1 mice by increasing the richness of Lachnospiraceae, Ruminococcaceae, and Actinobacteria and reducing that of Alistipes and Muribaculaceae. It also significantly inhibited the activation of the TLR4/NF-κB signaling pathway in the brain. In addition, no obvious toxic reactions were found in the liver and kidney of APP/PS1 mice after taking JDYZF for 8 weeks.

CONCLUSION

The findings revealed that JDYZF improved cognitive ability and alleviated the TLR4/NF-κB signaling pathway in APP/PS1 mice, and the modulating the gut microbiota presented here may help illuminate its activation mechanism.

Silencing of Long Non-coding RNA H19 Alleviates Lipopolysaccharide (LPS)-induced Apoptosis and Inflammation Injury by Regulating miR-140-5p/TLR4 Axis in Cell Models of Pneumonia

OBJECTIVE

Mounting studies have clarified the link between long non-coding RNAs (lncRNAs) and pneumonia. This research aims to probe the function and regulatory mechanism of lncRNA H19 in lipopolysaccharide (LPS)-induced cell models of pneumonia.

METHODS

WI-38 cells were exposed to LPS for 12 h to mimic cell models of pneumonia. The relative expression of H19, miR-140-5p, and toll-like receptor 4 (TLR4) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The cell viability was detected by MTT assay. The protein expression of apoptosis-associated proteins (Bax and Bcl-2) and TLR4 were determined by western blot. Moreover, the content of interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were measured by enzyme-linked immunosorbent assay (ELISA). The target relationship between miR- 140-5p and H19/ TLR4 was confirmed by Dual luciferase reporter (DLR) assay.

RESULTS

LncRNA H19 and TLR4 were up-regulated, while miR-140-5p was downregulated in peripheral blood of patients with pneumonia and LPS-treated WI-38 cells compared with their controls. Silencing of H19 or miR-140-5p mimics facilitated cell viability, whereas repressed apoptosis and reduced content of TNF-α, IL-6, and IL-1β in LPS-induced WI-38 cells. H19 targeted miR-140-5p and it inversely regulated miR-140- 5p expression. MiR-140-5p targeted TLR4 and it inversely regulated TLR4 expression. H19 positively regulated TLR4 expression. Moreover, inhibition of miR-140-5p or overexpression of TLR4 reversed the effects of H19 silencing on cell viability, inflammation, and apoptosis in LPS-induced WI-38 cells.

CONCLUSION

Silencing of H19 inhibited apoptosis and inflammation by miR-140- 5p/TLR4 pathway in LPS-induced WI-38 cells.

Quorum Sensing and NF-κB Inhibition of Synthetic Coumaperine Derivatives from Piper nigrum

Bacterial communication, termed Quorum Sensing (QS), is a promising target for virulence attenuation and the treatment of bacterial infections. Infections cause inflammation, a process regulated by a number of cellular factors, including the transcription Nuclear Factor kappa B (NF-κB); this factor is found to be upregulated in many inflammatory diseases, including those induced by bacterial infection. In this study, we tested 32 synthetic derivatives of coumaperine (CP), a known natural compound found in pepper (Piper nigrum), for Quorum Sensing Inhibition (QSI) and NF-κB inhibitory activities. Of the compounds tested, seven were found to have high QSI activity, three inhibited bacterial growth and five inhibited NF-κB. In addition, some of the CP compounds were active in more than one test. For example, compounds CP-286, CP-215 and CP-158 were not cytotoxic, inhibited NF-κB activation and QS but did not show antibacterial activity. CP-154 inhibited QS, decreased NF-κB activation and inhibited bacterial growth. Our results indicate that these synthetic molecules may provide a basis for further development of novel therapeutic agents against bacterial infections.

Host Innate Immune Responses to Acinetobacter baumannii Infection

Acinetobacter baumannii has emerged as a major threat to global public health and is one of the key human pathogens in healthcare (nosocomial and community-acquired)-associated infections. Moreover, A. baumannii rapidly develops resistance to multiple antibiotics and is now globally regarded as a serious multidrug resistant pathogen. There is an urgent need to develop novel vaccines and immunotherapeutics as alternatives to antibiotics for clinical management of A. baumannii infection. However, our knowledge of host immune responses to A. baumannii infection and the identification of novel therapeutic targets are significantly lacking. This review highlights the recent advances and critical gaps in our understanding how A. baumannii interacts with the host innate pattern-recognition receptors, induces a cascade of inflammatory cytokine and chemokine responses, and recruits innate immune effectors (such as neutrophils and macrophages) to the site of infection for effective control of the infection. Such knowledge will facilitate the identification of new targets for the design and development of effective therapeutics and vaccines to fight this emerging threat.

The Mechanisms of Disease Caused by Acinetobacter baumannii

Acinetobacter baumannii is a Gram negative opportunistic pathogen that has demonstrated a significant insurgence in the prevalence of infections over recent decades. With only a limited number of “traditional” virulence factors, the mechanisms underlying the success of this pathogen remain of great interest. Major advances have been made in the tools, reagents, and models to study A. baumannii pathogenesis, and this has resulted in a substantial increase in knowledge. This article provides a comprehensive review of the bacterial virulence factors, the host immune responses, and animal models applicable for the study of this important human pathogen. Collating the most recent evidence characterizing bacterial virulence factors, their cellular targets and genetic regulation, we have encompassed numerous aspects important to the success of this pathogen, including membrane proteins and cell surface adaptations promoting immune evasion, mechanisms for nutrient acquisition and community interactions. The role of innate and adaptive immune responses is reviewed and areas of paucity in our understanding are highlighted. Finally, with the vast expansion of available animal models over recent years, we have evaluated those suitable for use in the study of Acinetobacter disease, discussing their advantages and limitations.

miRNA-302e attenuates inflammation in infantile pneumonia though the RelA/BRD4/NF-κB signaling pathway

In the present study, the main focus was investigating the role of microRNA (miRNA)-302e in infantile pneumonia (IP) and exploring the potential protective mechanisms. Briefly, the expression of miRNA-302e was reduced in a mouse model of IP. In addition, the administration of anti-miRNA-302e increased inflammation and induced the protein expression of RelA, bromodomain-containing protein 4 (BRD4) and nuclear factor (NF)-κB in the in vitro model of IP. In contrast, over-expression of miRNA-302e reduced inflammation and suppressed the protein expression of RelA, BRD4 and NF-κB in an in vitro model of IP. Small interfering (si)-RelA attenuated the effects of miRNA-302e on inflammation in an in vitro model of IP. Consistently, si-BRD4 or si-NF-κB attenuated the effects of miRNA-302e on inflammation in an in vitro model of IP. Taken together, the results of the present study demonstrated that miRNA-302e attenuated inflammation in IP through the RelA/ BRD4/ NF-κB signaling pathway.

Recent advances in the biology of IL-1 family cytokines and their potential roles in development of sepsis

The IL-1 family comprises two anti-inflammatory cytokines (IL-37, IL-38), two receptor antagonists (IL-1ra, IL-36ra), and seven ligand agonists (IL-1α, IL-1β, IL-33, IL-36α, IL-36β, IL-36γ). The members of this family exert pleiotropic effects on intercellular signaling, leading to pro- or anti-inflammatory responses. They initiate potent inflammatory and immune responses by binding to specific receptors in the IL-1 receptor family, and their activities are repressed by naturally occurring inhibitors. Various immune cells produce and are regulated by these crucial molecules, which appear to be involved in the pathogenesis of diverse diseases including cancer as well as inflammatory and autoimmune disorders. Recent decades have seen substantial progress in understanding how the IL-1 family contributes to the development of sepsis. In this review, we will briefly introduce the IL-1 family and discuss its critical role in inflammatory and immune responses. The potential significance of IL-1 members in sepsis will also be explored, together with the clinical implications for treating this dangerous condition.