PERK-STING-RIPK3 pathway facilitates cognitive impairment by inducing neuronal necroptosis in sepsis-associated encephalopathy

Non-Canonical STING-PERK Pathway Modulation of Cellular Senescence and Therapeutic Response in Sepsis-Associated Acute Kidney Injury

Abstract-This study explored the role of the non-canonical STING-PERK signaling pathway in sepsis-associated acute kidney injury (SA-AKI). Gene expression data from the GEO database and serum STING protein levels in patients with SA-AKI were analyzed. An LPS-induced mouse model and an in vitro model using HK-2 cells were used to investigate the role of STING in SA-AKI. STING expression was suppressed using shRNA silencing technology and the STING inhibitor C176. Kidney function, inflammatory markers, apoptosis, and senescence were measured. The role of the STING-PERK pathway was investigated by silencing PERK in HK-2 cells and administering the PERK inhibitor GSK2606414. STING mRNA expression and serum STING protein levels were significantly higher in patients with SA-AKI. Suppressing STING expression improved kidney function, reduced inflammation, and inhibited apoptosis and senescence. Silencing PERK or administering GSK2606414 suppressed the inflammatory response, cell apoptosis, and senescence, suggesting that PERK is a downstream effector in the STING signaling pathway. The STING-PERK signaling pathway exacerbates cell senescence and apoptosis in SA-AKI. Inhibiting this pathway could provide potential therapeutic targets for SA-AKI treatment.

Hyperbaric oxygen preconditioning rescues prolonged underwater exercise-induced hippocampal dysfunction by regulating microglia activation and polarization

Underwater exercise is becoming increasingly prevalent, during which brain function is necessary but is also at risk. However, no study has explored how prolonged exercise affect the brain in underwater environment. Previous studies have indicated that excessive exercise in common environment causes brain dysfunction but have failed to provide appropriate interventions. Numerous evidence has indicated the neuroprotective effect of hyperbaric oxygen preconditioning (HBO-PC). The objective of this study was to investigate the cognitive effect of prolonged underwater exercise (PUE) and to explore the potential neuroprotective effect of HBO-PC in underwater environment. Rats swimming for 3 h in a simulated hyperbaric chamber (2.0 ATA) was used to establish the PUE animal model and HBO-PC (2.5 ATA for 1, 3,5 times respectively) was administrated before PUE. The results demonstrated that PUE triggers anxiety-like behaviors, cognitive impairment accompanied by hippocampal dysfunction, microglia activation and neuroinflammation. Conversely, 3 HBO-PC rescued anxiety-like behaviors and cognitive impairment. Mechanistically, 3 HBO-PC reduced microglia activation and switched the activated microglia from a pro-inflammatory to neuroprotective phenotype. These findings illustrated that PUE induces anxiety-like behaviors and cognitive impairment and HBO-PC of proper frequency may provide an appropriate and less invasive intervention for protecting the brain in underwater exercise.

Focus on the cGAS-STING Signaling Pathway in Sepsis and Its Inflammatory Regulatory Effects

Sepsis is a severe systemic inflammatory response commonly occurring in infectious diseases, caused by infection with virulent pathogens. In the pathogenesis of sepsis, the cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase-stimulator of interferon genes (cGAS-STING) signaling pathway serves a crucial role as a fundamental immunoregulatory mechanism. This signaling pathway activates STING upon recognizing intracellular DNA damage and pathogen-derived DNA, subsequently inducing the production of numerous inflammatory mediators, including interferon and inflammatory cytokines, which in turn trigger an inflammatory response. The aim of this paper is to explore the activation mechanism of the cGAS-STING signaling pathway in sepsis and its impact on inflammatory regulation. By delving into the mechanism of action of the cGAS-STING signaling pathway in sepsis, we aim to identify new therapeutic strategies for the treatment and prevention of sepsis.

STING signaling in the brain: Molecular threats, signaling activities, and therapeutic challenges

Stimulator of interferon genes (STING) is an innate immune signaling protein critical to infections, autoimmunity, and cancer. STING signaling is also emerging as an exciting and integral part of many neurological diseases. Here, we discuss recent advances in STING signaling in the brain. We summarize how molecular threats activate STING signaling in the diseased brain and how STING signaling activities in glial and neuronal cells cause neuropathology. We also review human studies of STING neurobiology and consider therapeutic challenges in targeting STING to treat neurological diseases.

The critical roles of STING in mitochondrial homeostasis

The stimulator of interferon genes (STING) is a crucial signaling hub in the immune system's antiviral and antimicrobial defense by detecting exogenous and endogenous DNA. The multifaceted functions of STING have been uncovered gradually during past decades, including homeostasis maintenance and overfull immunity or inflammation induction. However, the subcellular regulation of STING and mitochondria is poorly understood. The main functions of STING are outlined in this review. Moreover, we discuss how mitochondria and STING interact through multiple mechanisms, including the release of mitochondrial DNA (mtDNA), modulation of mitochondria-associated membrane (MAM) and mitochondrial dynamics, alterations in mitochondrial metabolism, regulation of reactive oxygen species (ROS) production, and mitochondria-related cell death. Finally, we discuss how STING is crucial to disease development, providing a novel perspective on its role in cellular physiology and pathology.

Endoplasmic reticulum stress-mediated cell death in cardiovascular disease

The endoplasmic reticulum (ER) plays a vital function in maintaining cellular homeostasis. Endoplasmic reticulum stress (ERS) can trigger various modes of cell death by activating the unfolded protein response (UPR) signaling pathway. Cell death plays a crucial role in the occurrence and development of diseases such as cancer, liver diseases, neurological diseases, and cardiovascular diseases. Several cardiovascular diseases including hypertension, atherosclerosis, and heart failure are associated with ER stress. ER stress-mediated cell death is of interest in cardiovascular disease. Moreover, an increasing body of evidence supports the potential of modulating ERS for treating cardiovascular disease. This paper provides a comprehensive review of the UPR signaling pathway, the mechanisms that induce cell death, and the modes of cell death in cardiovascular diseases. Additionally, we discuss the mechanisms of ERS and UPR in common cardiovascular diseases, along with potential therapeutic strategies.

Oxytocin alleviates cognitive and memory impairments by decreasing hippocampal microglial activation and synaptic defects via OXTR/ERK/STAT3 pathway in a mouse model of sepsis-associated encephalopathy

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction, characterized by cognitive and memory impairments closely linked to hippocampal dysfunction. Though it is well-known that SAE is a diffuse brain dysfunction with microglial activation, the pathological mechanisms of SAE are not well established and effective clinical interventions are lacking. Oxytocin (OXT) is reported to have anti-inflammatory and neuroprotective roles. However, the effects of OXT on SAE and the underlying mechanisms are not clear.

METHODS

SAE was induced in adult C57BL/6J male mice by cecal ligation and perforation (CLP) surgery. Exogenous OXT was intranasally applied after surgery. Clinical score, survivor rate, cognitive and memory behaviors, and hippocampal neuronal and non-neuronal functions were evaluated. Cultured microglia challenged with lipopolysaccharide (LPS) were used to investigate the effects of OXT on microglial functions, including inflammatory cytokines release and phagocytosis. The possible intracellular signal pathways involved in the OXT-induced neuroprotection were explored with RNA sequencing.

RESULTS

Hippocampal OXT level decreases, while the expression of OXT receptor (OXTR) increases around 24 h after CLP surgery. Intranasal OXT application at a proper dose increases mouse survival rate, alleviates cognitive and memory dysfunction, and restores hippocampal synaptic function and neuronal activity via OXTR in the SAE model. Intraperitoneal or local administration of the OXTR antagonist L-368,899 in hippocampal CA1 region inhibited the protective effects of OXT. Moreover, during the early stages of sepsis, hippocampal microglia are activated, while OXT application reduces microglial phagocytosis and the release of inflammatory cytokines, thereby exerting a neuroprotective effect. OXT may improve the SAE outcomes via the OXTR-ERK-STAT3 signaling pathway.

CONCLUSION

Our study uncovers the dysfunction of the OXT signal in SAE and shows that intranasal OXT application at a proper dose can alleviate SAE outcomes by reducing microglial overactivation, suggests that OXT may be a promising therapeutic approach in managing SAE patients.

Novel insight into cGAS-STING pathway in ischemic stroke: from pre- to post-disease

Ischemic stroke, a primary cause of disability and the second leading cause of mortality, has emerged as an urgent public health issue. Growing evidence suggests that the Cyclic GMP-AMP synthase (cGAS)- Stimulator of interferon genes (STING) pathway, a component of innate immunity, is closely associated with microglia activation, neuroinflammation, and regulated cell death in ischemic stroke. However, the mechanisms underlying this pathway remain inadequately understood. This article comprehensively reviews the existing literature on the cGAS-STING pathway and its multifaceted relationship with ischemic stroke. Initially, it examines how various risk factors and pre-disease mechanisms such as metabolic dysfunction and senescence (e.g., hypertension, hyperglycemia, hyperlipidemia) affect the cGAS-STING pathway in relation to ischemic stroke. Subsequently, we explore in depth the potential pathophysiological relationship between this pathway and oxidative stress, endoplasmic reticulum stress, neuroinflammation as well as regulated cell death including ferroptosis and PANoptosis following cerebral ischemia injury. Finally, it suggests that intervention targeting the cGAS-STING pathway may serve as promising therapeutic strategies for addressing neuroinflammation associated with ischemic stroke. Taken together, this review concludes that targeting the microglia cGAS-STING pathway may shed light on the exploration of new therapeutic strategies against ischemic stroke.

Targeting sting to reduce sepsis-induced acute intestinal injury

BACKGROUND

Sepsis is a dysregulated host response to infection syndrome leading to life-threatening organ dysfunction. Sepsis-induced intestinal dysfunction is a key element in the progression to multisystem organ failure. The stimulator of interferon genes is an intracellular protein implicated in intestinal injury in sepsis. H151, a small molecule inhibitor of stimulator of interferon genes, has not yet been studied as a potential therapeutic in sepsis. We hypothesize that H151 therapeutically reduces sepsis-induced acute intestinal injury.

METHODS

Male mice underwent cecal ligation and puncture and were treated with intraperitoneal H151 (10 mg/kg body weight) or vehicle. Intestines and serum were collected for analysis 20 hours after cecal ligation and puncture. Oral gavage of mice with FITC-dextran was performed 15 hours after cecal ligation and puncture. Five hours after gavage, serum was collected, and intestinal permeability was assessed. Mice were monitored for 10 days after cecal ligation and puncture to assess survival.

RESULTS

Zonula occludens 1 tight junctional protein expression was reduced after cecal ligation and puncture and recovered with H151 treatment. This was associated with a 62.3% reduction in intestinal permeability as assessed by fluorimetry. After cecal ligation and puncture, treatment with H151 was associated with a 58.7% reduction in intestinal histopathologic injury (P < .05) and a 56.6% reduction in intestinal apoptosis (P < .05). Intestinal myeloperoxidase activity was decreased by 70.8% after H151 treatment (P < .05). Finally, H151 improved 10-day survival from 33% to 80% after cecal ligation and puncture (P = .011).

CONCLUSION

H151, a novel stimulator of interferon genes inhibitor, reduces intestinal injury, inflammation, and permeability when administered as a treatment for cecal ligation and puncture-induced sepsis. Thus, targeting stimulator of interferon genes shows promise as a therapeutic strategy to ameliorate sepsis-induced acute intestinal injury.

Acute and long-term cognitive impairment following sepsis: mechanism and prevention

INTRODUCTION

Sepsis is a severe host response to infection, which induces both acute and long-term cognitive impairment. Despite its high incidence following sepsis, the underlying mechanisms remain elusive and effective treatments are not available clinically.

AREA COVERED

This review focuses on elucidating the pathological mechanisms underlying cognitive impairment following sepsis. Specifically, the authors discuss the role of systemic inflammation response, blood-brain barrier disruption, neuroinflammation, mitochondrial dysfunction, neuronal dysfunction, and Aβ accumulation and tau phosphorylation in cognitive impairment after sepsis. Additionally, they review current strategies to ameliorate cognitive impairment.

EXPERT OPINION

Potential interventions to reduce cognitive impairment after sepsis include earlier diagnosis and effective infection control, hemodynamic homeostasis, and adequate brain perfusion. Furthermore, interventions to reduce inflammatory response, reactive oxygen species, blood-brain barrier disruption, mitochondrial dysfunction, neuronal injury or death could be beneficial. Implementing strategies to minimize delirium, sleep disturbance, stress factors, and immobility are also recommended. Furthermore, avoiding neurotoxins and implementing early rehabilitation may also be important for preventing cognitive impairment after sepsis.