IL-33/ST2 signaling pathway and Alzheimer's disease: A systematic review and meta-analysis

Role of the interleukin-33 (IL-33)/suppressor of tumorigenicity 2 (ST2) signaling in superoxide anion-triggered inflammation and pain behavior in mice

Reactive oxygen species such as superoxide anion have varied roles in inflammation and pain, which can be mimicked by potassium superoxide (KO2), the superoxide anion donor. Interleukin (IL)-33 has pleiotropic functions by activating its receptor suppression of tumorigenicity 2 (ST2). However, the role of IL-33/ST2 signaling in inflammatory pain initiated by reactive oxygen species (ROS) such as superoxide anion has not been investigated, which was the aim of the present study. IL-33 levels were assessed by enzyme-linked immunosorbent assay (ELISA). Mechanical and thermal hyperalgesia and overt pain were evaluated by electronic von Frey, hot plate, and abdominal writhing/paw flinching/licking, respectively. Edema and leukocyte recruitment (myeloperoxidase assay and total/differential cell count), antioxidant capacity, superoxide anion production and lipid peroxidation were assessed. Paw skin and spinal cord messenger ribonucleic acid (mRNA) expression of pro-inflammatory mediators and glial markers in the spinal cord were evaluated. Immunofluorescence was used to detect spinal glial and neuronal c-Fos activation. KO2 injection triggered IL-33 production in the paw skin and spinal cord of mice, induced hyperalgesia, edema, neutrophil recruitment to the paw tissue, overt pain-like behavior, and leukocyte recruitment to the peritoneum that were reduced in ST2 deficient mice. In the paw skin and spinal cord, KO2 triggered IL-33/ST2-dependent oxidative stress, and mRNA expression of inflammatory molecules, which were reduced by ST2 deficiency. KO2 induced spinal cord glial (at mRNA/protein levels) and neuronal activation in IL-33/ST2-dependent manner. IL-33/ST2 signaling mediates, at least in part, superoxide anion-induced inflammatory pain by modulating local and spinal inflammatory events.

Blood Angiogenesis Markers and Cognition in Older Adults at Risk for Dementia: Marqueurs sanguins de l'angiogenèse et cognition chez les personnes âgées à risque de démence

ObjectiveChanges in angiogenesis have been shown to contribute to cognitive decline and dementia. We aimed to identify angiogenesis blood markers associated with cognitive performance in older adults with mild cognitive impairment (MCI), remitted major depressive disorder (rMDD), or both (rMDD + MCI) who are at risk for dementia.MethodWe analyzed data from participants with MCI, rMDD, or rMDD + MCI in the Prevention of Alzheimer's Dementia with Cognitive Remediation plus Transcranial Direct Current Stimulation in Mild Cognitive Impairment and Depression study. Elastic net regression was used to select variables associated with cognitive performance among 19 angiogenesis markers and 6 covariates. Linear regressions were used to determine which of the selected angiogenesis markers were associated with cognitive performance, controlling for the selected covariates. Significant angiogenesis markers were independently analyzed without other angiogenesis markers, controlling for covariates, with subgroup analyses in those with and without rMDD.ResultsAngiogenin was the only selected marker associated with cognitive performance (β = 0.28, Padj = 0.03, f² = .02) when controlling for other selected markers (endothelial cell-specific molecule 1, e-selectin, interleukin-33 [IL-33], oncostatin M, platelet-derived growth factor-AB, IL-33 receptor, and tissue inhibitor of metalloproteinases-1) and selected covariates (age, education, apolipoprotein E ε4 status, diagnosis, and cardiovascular risk factors). When independently analyzed, angiogenin remained positively associated with cognitive performance (β = 0.21, P = 0.01, f² =.02), controlling for the covariates. In subgroup analyses, angiogenin was also associated with cognition in rMDD and rMDD + MCI participants (β =0.50, SE = 0.14, P < 0.001, f² = 0.08) and in MCI-only participants (β= 0.20, SE = 0.09, P = 0.02, f² = 0.02).ConclusionThe association of angiogenin with cognitive performance highlights a potentially novel biological pathway that could influence cognition in older adults at risk for dementia. Angiogenin may protect against cognitive decline, opening new avenues for innovative preventive, or therapeutic interventions.

RhoA/ROCK/GSK3β Signaling: A Keystone in Understanding Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive decline and loss of neuronal integrity. Emerging evidence suggests that RhoA, Rho-associated coiled-coil kinase (ROCK), and their downstream effector molecule glycogen synthase 3β (GSK3β) interact within a complex signaling pathway (RhoA/ROCK/GSK3β) that plays a crucial role in the pathogenesis of AD. RhoA, a small GTPase, along with its downstream effector, ROCK, regulates various cellular processes, including actin cytoskeleton dynamics, apoptosis, and synaptic plasticity. GSK3β, a serine/threonine kinase, plays a key role in neuronal function and AD pathology, including the regulation of tau phosphorylation and amyloid-beta cleavage. Overactive GSK3β has been closely linked to tau hyperphosphorylation, neurodegeneration, and the progression of AD. Thus, GSK3β has been considered as a promising therapeutic target for treating AD and mitigating cognitive impairment. However, clinical trials of GSK3β in AD have faced considerable challenges due to the complexity of the specific neuronal inhibition of GSK3β. In this review, we summarize the literature regarding the relationship of RhoA/ROCK and GSK3β signaling pathways in AD pathogenesis. We further discuss recent findings of the sTREM2-transgelin-2 (TG2) axis as a potential mediator of this complex pathway and provide our review on a novel targeting strategy for AD.

Disorder of neuroplasticity aggravates cognitive impairment via neuroinflammation associated with intestinal flora dysbiosis in chronic heart failure

BACKGROUND

Chronic heart failure (CHF) impairs cognitive function, yet its effects on brain structure and underlying mechanisms remain elusive. This study aims to explore the mechanisms behind cognitive impairment.

METHODS

CHF models in rats were induced by ligation of the left anterior descending coronary artery. Cardiac function was analyzed by cardiac ultrasound and hemodynamics. ELISA, immunofluorescence, Western blot, Golgi staining and transmission electron microscopy were performed on hippocampal tissues. The alterations of intestinal flora under the morbid state were investigated via 16S rRNA sequencing. The connection between neuroinflammation and synapses is confirmed by a co-culture system of BV2 microglia and HT22 cells in vitro. Results: CHF rats exhibited deteriorated cognitive behaviors. CHF induced neuronal structural disruption, loss of Nissl bodies, and synaptic damage, exhibiting alterations in multiple parameters. CHF rats showed increased hippocampal levels of inflammatory cytokines and activated microglia and astrocytes. Furthermore, the study highlights dysregulated PDE4-dependent cAMP signaling and intestinal flora dysbiosis, closely associated with neuroinflammation, and altered synaptic proteins. In vitro, microglial neuroinflammation impaired synaptic plasticity via PDE4-dependent cAMP signaling.

CONCLUSIONS

Neuroinflammation worsens CHF-related cognitive impairment through neuroplasticity disorder, tied to intestinal flora dysbiosis. PDE4 emerges as a potential therapeutic target. These findings provide insightful perspectives on the heart-gut-brain axis.

Interleukin-33/serum stimulation-2 pathway: Regulatory mechanisms and emerging implications in immune and inflammatory diseases

Interleukin (IL)- 33, a nuclear factor and pleiotropic cytokine of the IL-1 family, is gaining attention owing to its important role in chronic inflammatory and autoimmune diseases. This review extends our knowledge of the effects exerted by IL-33 on target cells by binding to its specific receptor serum stimulation-2 (ST2). Depending on the tissue context, IL-33 performs multiple functions encompassing host defence, immune response, initiation and amplification of inflammation, tissue repair, and homeostasis. The levels and activity of IL-33 in the body are controlled by complex IL-33-targeting regulatory pathways. The unique temporal and spatial expression patterns of IL-33 are associated with host homeostasis and the development of immune and inflammatory disorders. Therefore, understanding the origin, function, and processes of IL-33 under various conditions is crucial. This review summarises the regulatory mechanisms underlying the IL-33/ST2 signalling axis and its potential role and clinical significance in immune and inflammatory diseases, and discusses the current complex and conflicting findings related to IL-33 in host responses.

Circulating biomarkers of inflammaging and Alzheimer's disease to track age-related trajectories of dementia: Can we develop a clinically relevant composite combination?

Alzheimer's disease (AD) is a rapidly growing global concern due to a consistent rise of the prevalence of dementia which is mainly caused by the aging population worldwide. An early diagnosis of AD remains important as interventions are plausibly more effective when started at the earliest stages. Recent developments in clinical research have focused on the use of blood-based biomarkers for improve diagnosis/prognosis of neurodegenerative diseases, particularly AD. Unlike invasive cerebrospinal fluid tests, circulating biomarkers are less invasive and will become increasingly cheaper and simple to use in larger number of patients with mild symptoms or at risk of dementia. In addition to AD-specific markers, there is growing interest in biomarkers of inflammaging/neuro-inflammaging, an age-related chronic low-grade inflammatory condition increasingly recognized as one of the main risk factor for almost all age-related diseases, including AD. Several inflammatory markers have been associated with cognitive performance and AD development and progression. The presence of senescent cells, a key driver of inflammaging, has also been linked to AD pathogenesis, and senolytic therapy is emerging as a potential treatment strategy. Here, we describe blood-based biomarkers clinically relevant for AD diagnosis/prognosis and biomarkers of inflammaging associated with AD. Through a systematic review approach, we propose that a combination of circulating neurodegeneration and inflammatory biomarkers may contribute to improving early diagnosis and prognosis, as well as providing valuable insights into the trajectory of cognitive decline and dementia in the aging population.