Inhibition of NLRP1-Dependent Pyroptosis Prevents Glycogen Synthase Kinase-3β Overactivation-Induced Hyperphosphorylated Tau in Rats

NLRP1 inflammasome in neurodegenerative disorders: From pathology to therapies

Neuroinflammation is a critical component in neurodegenerative disorders. The inflammasome, facilitates the cleavage of caspase-1, leading to the maturation and subsequent secretion of inflammatory factors interleukin (IL)-1β and IL-18. Consequently, pyroptosis mediated by gasdermin D, exacerbates neuroinflammation. Among the inflammasomes, NLRP1/3 are predominant in the central nervous system (CNS), Although NLRP1 was the earliest discovered inflammasome, the specific involvement of NLRP1 in neurodegenerative diseases remains to be fully elucidated. Recently, the discovery of an endogenous inhibitor of NLRP1, dipeptidyl peptidase 9, suggests the feasibility of producing of small-molecule drugs targeting NLRP1. This review describes the latest findings on the role of the NLRP1 inflammasome in the pathology of neurodegenerative disorders, including Alzheimer's disease, and summarises the regulatory mechanisms of NLRP1 inflammasome activation in the CNS. Furthermore, we highlight the recent progress in developing small-molecule and biological inhibitors that modulate the NLRP1 infammasome for the treatment of neurodegenerative disorders, some of which are advancing to preclinical testing. SIGNIFICANCE STATEMENT: The objective of this review is to synthesise the research on the structure, activation, and regulatory mechanisms of the NLRP1 inflammasome, along with its potential impact on both acute and chronic neurodegenerative conditions. The discovery of endogenous inhibitors, such as dipeptidyl peptidase 9 and thioredoxin, and their interaction with NLRP1 suggest the possibility of developing NLRP1-targeted small-molecule drugs for the treatment of neurodegenerative disorders. This review also discusses the use of both direct and indirect NLRP1 inhibitors as prospective therapeutic strategies for these conditions.

Proximal tubular FHL2, a novel downstream target of hypoxia inducible factor 1, is a protector against ischemic acute kidney injury

Four-and-a-half LIM domains protein 2 (FHL2) is an adaptor protein that may interact with hypoxia inducible factor 1α (HIF-1α) or β-catenin, two pivotal protective signaling in acute kidney injury (AKI). However, little is known about the regulation and function of FHL2 during AKI. We found that FHL2 was induced in renal tubular cells in patients with acute tubular necrosis and mice model of ischemia-reperfusion injury (IRI). In cultured renal proximal tubular cells (PTCs), hypoxia induced FHL2 expression and promoted the binding of HIF-1 to FHL2 promoter. Compared with control littermates, mice with PTC-specific deletion of FHL2 gene displayed worse renal function, more severe morphologic lesion, more tubular cell death and less cell proliferation, accompanying by downregulation of AQP1 and Na, K-ATPase after IRI. Consistently, loss of FHL2 in PTCs restricted activation of HIF-1 and β-catenin signaling simultaneously, leading to attenuation of glycolysis, upregulation of apoptosis-related proteins and downregulation of proliferation-related proteins during IRI. In vitro, knockdown of FHL2 suppressed hypoxia-induced activation of HIF-1α and β-catenin signaling pathways. Overexpression of FHL2 induced physical interactions between FHL2 and HIF-1α, β-catenin, GSK-3β or p300, and the combination of these interactions favored the stabilization and nuclear translocation of HIF-1α and β-catenin, enhancing their mediated gene transcription. Collectively, these findings identify FHL2 as a direct downstream target gene of HIF-1 signaling and demonstrate that FHL2 could play a critical role in protecting against ischemic AKI by promoting the activation of HIF-1 and β-catenin signaling through the interactions with its multiple protein partners.

Dendrobium nobile Lindl. alkaloid decreases Tau hyperphosphorylation via regulating PI3K/Akt/GSK-3β pathway in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANT

Dendrobium is a traditional and precious Chinese medicinal herb. The Compendium of Materia Medica describes its effects as "benefiting intelligence and dispelling shock, lightning the body and extending life". Dendrobium nobile Lindl. is a precious variety of Dendrobium. Our previous data showed Dendrobium nobile Lindl. alkaloid (DNLA) has significant neuroprotective effects and can improve cognitive dysfunction. However, the specific effects and mechanisms of action of its main active component, DNLA, on cognitive dysfunction caused by Tau hyperphosphorylation, are still unclear.

AIM OF THE RESEARCH

This study aimed to determine the effects of DNLA on phosphatidylinositol-3 kinase (PI3K)/protein kinase B (Akt)/glycogen synthase kinase 3β (GSK-3β) pathway, thus to explore the mechanisms of DNLA to inhibit Tau hyperphosphorylation.

MATERIALS AND METHODS

We used wortmannin (WM) and GF-109203X (GFX)-induced hyperphosphorylation of Tau in N2a cells and rats to detect the protective mechanism of DNLA in vivo and in vitro. In vitro, the effect of modeling method on Tau hyperphosphorylation was screened and verified by Western Blotting (WB), and the regulation of Tau hyperphosphorylation and PI3K/Akt/GSK-3β pathway by different concentrations of DNLA was detected by WB. In vivo, MWM was used to detect the effect of DNLA on model rats, and then Nissl staining was used to detect the loss of neurons. Finally, WB was used to detect the regulation of Tau hyperphosphorylation and PI3K/Akt/GSK-3β pathway by different concentrations of DNLA.

RESULTS

DNLA could rescue the abnormal PI3K/Akt/GSK-3β pathway and reverse the hyperphosphorylation of Tau induced by WM and GFX in N2a cells. Furthermore, DNLA improved the learning and memory of WM and GFX-induced model rats. Moreover, DNLA regulated PI3K/Akt/GSK-3β pathway and reduced the p-Tau and neuronal damage in the hippocampus of model rats.

CONCLUSION

DNLA may be a promising candidate for reducing hyperphosphorylation of Tau.

New insights into glycogen synthase kinase-3: A common target for neurodegenerative diseases

Glycogen synthase kinase 3 (GSK-3) is a highly conserved protein serine/threonine kinase that plays a central role in a wide variety of cellular processes to coordinate catabolic and anabolic pathways and regulate cell growth and fate. There is increasing evidence showing that abnormal glycogen synthase kinase 3 (GSK-3) is associated with the pathogenesis and progression of many disorders, such as cancer, diabetes, psychiatric diseases, and neurodegenerative diseases. In this review, we summarize recent findings about the regulatory role of GSK-3 in the occurrence and development of multiple neurodegenerative diseases, mainly focusing on Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The aim of this study is to provide new insight into the shared working mechanism of GSK-3 as a therapeutic target of multiple neurodegenerative diseases.

Dimethyl Fumarate Alleviates Adult Neurogenesis Disruption in Hippocampus and Olfactory Bulb and Spatial Cognitive Deficits Induced by Intracerebroventricular Streptozotocin Injection in Young and Aged Rats

The disorder of adult neurogenesis is considered an important mechanism underlying the learning and memory impairment observed in Alzheimer's disease (AD). The sporadic nonhereditary form of AD (sAD) affects over 95% of AD patients and is related to interactions between genetic and environmental factors. An intracerebroventricular injection of streptozotocin (STZ-ICV) is a representative and well-established method to induce sAD-like pathology. Dimethyl fumarate (DMF) has antioxidant and anti-inflammatory properties and is used for multiple sclerosis treatment. The present study determines whether a 26-day DMF therapy ameliorates the disruption of adult neurogenesis and BDNF-related neuroprotection in the hippocampus and olfactory bulb (OB) in an STZ-ICV rat model of sAD. Considering age as an important risk factor for developing AD, this study was performed using 3-month-old (the young group) and 22-month-old (the aged group) male Wistar rats. Spatial cognitive functions were evaluated with the Morris water maze task. Immunofluorescent labelling was used to assess the parameters of adult neurogenesis and BDNF-related neuroprotection in the hippocampus and OB. Our results showed that the STZ-ICV evoked spatial learning and memory impairment and disturbances in adult neurogenesis and BDNF expression in both examined brain structures. In the aged animals, the deficits were more severe. We found that the DMF treatment significantly alleviated STZ-ICV-induced behavioural and neuronal disorders in both age groups of the rats. Our findings suggest that DMF, due to its beneficial effect on the formation of new neurons and BDNF-related neuroprotection, may be considered as a promising new therapeutic agent in human sAD.