Mild hypothermia alleviates early brain injury after subarachnoid hemorrhage via suppressing pyroptosis through AMPK/NLRP3 inflammasome pathway in rats

The Inflammasome: A Promising Potential Therapeutic Target for Early Brain Injury Following Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH), a severe cerebrovascular disorder, is principally instigated by the rupture of an aneurysm. Early brain injury (EBI), which gives rise to neuronal demise, microcirculation impairments, disruption of the blood-brain barrier, cerebral edema, and the activation of oxidative cascades, has been established as the predominant cause of mortality among patients with SAH. These pathophysiological processes hinge on the activation of inflammasomes, specifically the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)and absent in melanoma 2 (AIM2) inflammasomes. These inflammasomes assume a crucial role in downstream intracellular signaling pathways and hold particular significance within the nervous system. The activation of inflammasomes can be modulated, either by independently regulating these two entities or by influencing their engagement at specific target loci within the pathway, thereby attenuating EBI subsequent to SAH. Although certain clinical instances lend credence to this perspective, more in-depth investigations are essential to ascertain the optimal treatment regimen, encompassing dosage, timing, administration route, and frequency. Consequently, targeting the ensuing early brain injury following SAH represents a potentially efficacious therapeutic approach.

Investigation into the influence of mild hypothermia on regulating ferroptosis through the P53-SLC7A11/GPX4 signaling pathway in sepsis-induced acute lung injury

BACKGROUND

Sepsis-induced acute lung injury (S-ALI) significantly contributes to unfavorable clinical outcomes. Emerging evidence suggests a novel role for ferroptosis in the pathophysiology of ALI, though the precise mechanisms remain unclear. Mild hypothermia (32-34 °C) has been shown to inhibit inflammatory responses, reduce oxidative stress, and regulate metabolic processes. P53 has been reported to downregulate the transcriptional activity of solute carrier family 7 member 11 (SLC7A11), thereby limiting cystine uptake. This reduction in cystine availability compromises the activity of Glutathione peroxidase 4 (GPX4), a cystine-dependent enzyme, ultimately increasing cellular susceptibility to ferroptosis. However, it remains unclear whether mild hypothermia exerts protective effects through the P53-SLC7A11/GPX4 signaling pathway. This study investigates the influence of mild hypothermia on ferroptosis mediated by the P53-SLC7A11/GPX4 pathway in S-ALI.

METHODS

This study utilized both in vivo and in vitro models. In the vivo model, 64 Sprague-Dawley rats were employed, with 40 analyzed for survival outcomes. Sepsis was induced using the cecum ligation and puncture (CLP) method, after which rats were subjected to either normothermic (36-38 °C) or mild hypothermic (32-34 °C) conditions for a duration of 10 h. Twelve hours post-surgery, blood samples, bronchoalveolar lavage fluid, and lung tissue samples were harvested for histological analysis, measurement of inflammatory markers, wet/dry ratios, blood gas analysis, assessment of oxidative stress and ferroptosis, Western blotting, and RT-qPCR analysis. In the in vitro model, RLE-6TN cells were exposed to lipopolysaccharide (LPS) for 24 h under normothermic and mild hypothermic conditions. These cells were then evaluated for cell viability, inflammatory markers, oxidative stress levels, ferroptosis markers, as well as Western blot and RT-qPCR analyses.

RESULTS

CLP-induced sepsis led to elevated levels of inflammatory markers, increased lung injury scores, and heightened oxidative stress markers. These detrimental effects were significantly ameliorated by mild hypothermia. Furthermore, mild hypothermia reversed the modified expression of P53, SLC7A11, and GPX4 signaling molecules. Notably, mild hypothermia also improved the 5-day survival rate of CLP rats.

CONCLUSION

Mild hypothermia attenuates S-ALI and modulates ferroptosis through the P53-SLC7A11/GPX4 signaling pathway.

Selective Activation of G Protein-Coupled Estrogen Receptor 1 (GPER1) Reduces ER Stress and Pyroptosis via AMPK Signaling Pathway in Experimental Subarachnoid Hemorrhage

Neuroinflammation is a critical pathogenic event following hemorrhagic stroke. Endoplasmic reticulum (ER) stress-induced apoptosis and nucleotide-binding domain, leucine-rich repeat, and pyrin domain-containing protein 3(NLRP3)-associated pyroptosis can contribute to the escalation of neuroinflammatory responses, leading to increased brain damage. G protein-coupled estrogen receptor 1(GPER1), as the most extensively characterized brain-derived estrogen, was reported to trigger neuroprotective effects. However, the anti-apoptotic and anti-pyroptotic effect of GPER1 activation and the underlying mechanism has not been fully elucidated. We established the experimental SAH model by intravascular perforation. The GPER1 selective agonist G1 was intravenously administered 1 h following SAH. For mechanistic exploration, the selective inhibitor of adenosine monophosphate-activated protein kinase (AMPK), dorsomorphin, was administered via intracerebroventricular injection 30 min prior to SAH induction. Post-SAH assessments included SAH grade, the short-term and long-term neurological outcomes, brain edema, cerebral blood flow, transmission electron microscopy (TEM), western blot (WB), ELISA, TUNEL staining, Fluoro-Jade C staining (FJC), and immunofluorescence staining. The expression of GPER1 was observed to elevate at 6 h and peaked at 24 h subsequent to SAH, predominantly co-localized with neurons. Post-treatment with G1 markedly ameliorated both the short-term and long-term neurological deficits of SAH mouse, as well as inhibiting the expression of neuronal ER stress-associated apoptotic proteins (i.e., CHOP, GRP78, Caspase-12, Cleaved Caspase-3, Bax, Bcl2) and pyroptosis-associated proteins (i.e., NLRP3, ASC, Cleaved Caspase-1). Additionally, our research revealed that inhibition of AMPK with dorsomorphin attenuated the neuroprotective effects of G1. This was accompanied by modifications in the molecular pathways associated with ER stress-induced apoptosis and pyroptosis. These data herein elucidated that GPER1 exerted neuroprotective effects by mitigating neuroinflammation in an AMPK-dependent manner, which modulates neuronal ER stress-associated apoptosis and pyroptosis. Boosting the anti-apoptotic and anti-pyroptotic effect by activating GPER1 may be an efficient treatment strategy for SAH patients.

Update on Strategies to Reduce Early Brain Injury after Subarachnoid Hemorrhage

PURPOSE OF REVIEW

Early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (SAH) is the most influential clinical determinant of outcomes. Despite significant advances in understanding of the pathophysiology of EBI, currently no treatments to target EBI have been developed. This review summarizes recent advances in EBI research over the past five years with a focus on potential therapeutic targets.

RECENT FINDINGS

Mechanism-specific translational studies are converging on several pathophysiologic pathways: improved antioxidant delivery and the Sirt1/Nrf2 pathway for reactive oxygen species; NLRP3 inflammasome and microglial polarization for inflammation; and the PI3K/Akt pathway for apoptosis. Recently identified mechanistic components, such as microcirculatory failure and ferroptosis, need particular attention. Clinical studies developing radiographic markers and mechanism-specific, biofluid markers are attempting to bridge the translational therapeutic gap. There has been an exponential growth in EBI research. Further clinical studies which address specific pathophysiology mechanisms need to be performed to identify novel therapeutic approaches.

The regulation of pyroptosis by post-translational modifications: molecular mechanisms and therapeutic targets

Pyroptosis, a type of programmed cell death mediated by gasdermin family proteins, releases a large amount of immune stimulatory substances, which further contribute to inflammation and elicit an adaptive immune response against tumours and pathogens. And it occurs through multiple pathways that involve the activation of specific caspases and the cleavage of gasdermins. Post-translational modifications (PTMs) could influence the chemical properties of the modified residues and neighbouring regions, ultimately affecting the activity, stability, and functions of proteins to regulate pyroptosis. Many studies have been conducted to explore the influence of PTMs on the regulation of pyroptosis. In this review, we provide a comprehensive summary of different types of PTMs that influence pyroptosis, along with their corresponding modifying enzymes. Moreover, it elaborates on the specific contributions of different PTMs to pyroptosis and delves into how the regulation of these modifications can be leveraged for therapeutic interventions in cancer and inflammatory diseases.

Inhibition of phosphodiesterase 4 attenuates aquaporin 4 expression and astrocyte swelling following cerebral ischemia/reperfusion injury

We have previously shown that phosphodiesterase 4 (PDE4) inhibition protects against neuronal injury in rats following middle cerebral artery occlusion/reperfusion (MCAO/R). However, the effects of PDE4 on brain edema and astrocyte swelling are unknown. In this study, we showed that inhibition of PDE4 by Roflumilast (Roflu) reduced brain edema and brain water content in rats subjected to MCAO/R. Roflu decreased the expression of aquaporin 4 (AQP4), while the levels of phosphorylated protein kinase B (Akt) and forkhead box O3a (FoxO3a) were increased. In addition, Roflu reduced cell volume and the expression of AQP4 in primary astrocytes undergoing oxygen and glucose deprivation/reoxygenation (OGD/R). Consistently, PDE4B knockdown showed similar effects as PDE4 inhibition; and PDE4B overexpression rescued the inhibitory role of PDE4B knockdown on AQP4 expression. We then found that the effects of Roflu on the expression of AQP4 and cell volume were blocked by the Akt inhibitor MK2206. Since neuroinflammation and astrocyte activation are the common events that are observed in stroke, we treated primary astrocytes with interleukin-1β (IL-1β). Astrocytes treated with IL-1β showed decreased AQP4 and phosphorylated Akt and FoxO3a. Roflu significantly reduced AQP4 expression, which was accompanied by increased phosphorylation of Akt and FoxO3a. Furthermore, overexpression of FoxO3a partly reversed the effect of Roflu on AQP4 expression. Our findings suggest that PDE4 inhibition limits ischemia-induced brain edema and astrocyte swelling via the Akt/FoxO3a/AQP4 pathway. PDE4 is a promising target for the intervention of brain edema after cerebral ischemia.

Targeted Temperature Management for Poor Grade Aneurysmal Subarachnoid Hemorrhage: A Pilot Study

OBJECTIVE

We assessed the effectiveness and safety of target temperature management (TTM) in treating patients with poor-grade aneurysmal subarachnoid hemorrhage (aSAH). The primary objective was to evaluate the neurological outcome at 3 months. Secondary objectives were to assess mortality, delayed cerebral ischemia, cerebral edema, hydrocephalus, midline shift, and laboratory indicators related to TTM.

METHODS

A single-blind, nonrandomized controlled trial was conducted. After admission, patients with poor-grade aSAH (Hunt-Hess scores IV ∼ V) were assigned to a TTM group or a control group in a 1:1 ratio. TTM with core temperatures ranging from 36°C to 37°C was performed immediately and maintained until microclipping or endovascular embolization. Subsequently, rapid induction to 33°C ∼ 35°C was carried out and maintained for 3 to 5 days. Then, the patients underwent slow rewarming to 36°C ∼ 37°C and maintained at that temperature for a minimum of 48 hours.

RESULTS

Sixty patients (30 treated with TTM and 30 with standard treatment) were included in the study. At 3 months, a favorable prognosis (modified Rankin scale score 0 to 3) was significantly higher in the TTM group than in the control group (n = 14, 46.7% vs. n = 6, 20.0%, P = 0.028). Adjusted multivariate logistics regression analysis indicated that TTM (odds ratio = 0.20, 95% confidence interval: 0.05-0.77, P = 0.019) reduced the number of unfavorable prognoses 3 months after admission.

CONCLUSIONS

This study demonstrated the effectiveness and safety of TTM in patients with poor-grade aSAH, and its implementation improved neurological outcomes. Multicenter randomized controlled studies with a large number of patients are needed to confirm these observations.

Perampanel attenuates oxidative stress and pyroptosis following subarachnoid hemorrhage via the SIRT3/FOXO3α pathway

Subarachnoid hemorrhage (SAH) occurs most commonly after rupture of an aneurysm, resulting in high disability and mortality due to the absence of effective therapy. Its subsequent stage, early brain injury (EBI), promotes the sustainable development of injury in the brain and ultimately leads to poor prognosis. As a new antiepileptic drug, the effect of perampanel on EBI after SAH is unknown. Pyroptosis, a process of inflammatory programmed cell death, has been confirmed in most studies to play a substantial role in aggravating SAH-post EBI. Similarly, oxidative stress is closely involved in neuronal pyroptosis and the pathophysiological mechanism of SAH-post EBI, leading to a devastating outcome for SAH patients. Nonetheless, no studies have been conducted to determine whether perampanel reduces pyroptosis and oxidative stress in the context of SAH-induced EBI. Rat SAH model via endovascular perforation was constructed in this study, to assess the neuroprotective effect of perampanel on SAH-post EBI, and to clarify the possible molecular mechanism. By means of the neurological score, brain edema detection, FJB staining, immunofluorescence, WB, ELISA, and ROS assay, we found that perampanel can improve neuroscores and reduce brain edema and neuronal degeneration at 24 h after SAH; we also found that perampanel reduced oxidative stress, neuronal pyroptosis, and inhibition of the SIRT3-FOXO3α pathway at 24 h after SAH. When 3-TYP, an inhibitor of SIRT3, was administered, the effects of perampanel on the SIRT3-FOXO3a pathway, antioxidant stress, and neuronal pyroptosis were reversed. Taken together, our data indicate that perampanel attenuates oxidative stress and pyroptosis following subarachnoid hemorrhage via the SIRT3/FOXO3α pathway. This study highlights the application value of perampanel in subarachnoid hemorrhage and lays a foundation for clinical research and later transformation of perampanel in SAH.

A Preliminary Study of Mild Heat Stress on Inflammasome Activation in Murine Macrophages

Inflammation and mitochondrial-dependent oxidative stress are interrelated processes implicated in multiple neuroinflammatory disorders, including Alzheimer's disease (AD) and depression. Exposure to elevated temperature (hyperthermia) is proposed as a non-pharmacological, anti-inflammatory treatment for these disorders; however, the underlying mechanisms are not fully understood. Here we asked if the inflammasome, a protein complex essential for orchestrating the inflammatory response and linked to mitochondrial stress, might be modulated by elevated temperatures. To test this, in preliminary studies, immortalized bone-marrow-derived murine macrophages (iBMM) were primed with inflammatory stimuli, exposed to a range of temperatures (37-41.5 °C), and examined for markers of inflammasome and mitochondrial activity. We found that exposure to mild heat stress (39 °C for 15 min) rapidly inhibited iBMM inflammasome activity. Furthermore, heat exposure led to decreased ASC speck formation and increased numbers of polarized mitochondria. These results suggest that mild hyperthermia inhibits inflammasome activity in the iBMM, limiting potentially harmful inflammation and mitigating mitochondrial stress. Our findings suggest an additional potential mechanism by which hyperthermia may exert its beneficial effects on inflammatory diseases.