mRNA profiling reveals the potential mechanism of TIPE2 in attenuating cognitive deficits in APP/PS1 mice

Acetylome analyses provide novel insights into the effects of chronic intermittent hypoxia on hippocampus-dependent cognitive impairment

Introduction

Chronic intermittent hypoxia (CIH) can negatively affect hippocampal function through various molecular mechanisms. Protein acetylation, a frequently occurring modification, plays crucial roles in synaptic plasticity and cognitive processes. However, the global protein acetylation induced by CIH in the hippocampus and its specific effects on hippocampal function and behavior remain poorly understood.

Methods

To address this gap, we conducted a study using liquid chromatography-tandem mass spectrometry to analyze the lysine acetylome and proteome of the hippocampus in healthy adult mice exposed to intermittent hypoxia for 4 weeks (as a CIH model) compared to normoxic mice (as a control).

Results

We identified and quantified a total of 2,184 lysine acetylation sites in 1,007 proteins. Analysis of these acetylated proteins revealed disturbances primarily in oxidative phosphorylation, the tricarboxylic acid (TCA) cycle, and glycolysis, all of which are localized exclusively to mitochondria. Additionally, we observed significant changes in the abundance of 21 proteins, some of which are known to be associated with cognitive impairments.

Discussion

This study helps to elucidate the molecular mechanisms underlying CIH-induced changes in protein acetylation in the hippocampus. By providing valuable insights into the pathophysiological processes associated with CIH and their impacts on hippocampal function, our findings contribute to a better understanding of the consequences of CIH-induced changes in protein acetylation in the hippocampus and the potential role of CIH in cognitive impairment.

TIPE2 ameliorates neuroinflammation and cognitive impairment in sepsis-associated encephalopathy through regulating RhoA/ROCK2-NF-κB signaling pathway

Sepsis-associated encephalopathy (SAE) is an acute brain dysfunction induced by systemic inflammation caused by sepsis and is one of the most common types of encephalopathy in intensive care units. Deteriorative neuroinflammation is closely related to the development of brain injury, which often transforms into common pathological manifestations in patients with severe sepsis. Therefore, taking necessary preventive and protective measures for potential brain injury and promptly reducing neuroinflammatory injury is necessary to improve the long-term prognoses of patients. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) can play a significant protective role in septic lung injury, but studies on its expression and role in neurological diseases are rare. In the present study, we found that TIPE2 can expressed in microglia and ameliorate brain injury caused by SAE by suppressing neuroinflammation. The RhoA/ROCK2 pathway is the central coordinator of tissue injury response, and the activation of RhoA participates in the lipopolysaccharide-induced activation of the nuclear factor kappa B (NF-κB) signaling pathway. The activation of RhoA and phosphorylation of NF-κB was enhanced after TIPE2 deficiency. Importantly, TIPE2 negatively regulates inflammatory responses in vivo and in vitro and plays a protective role in SAE by inhibiting the activation of RhoA/ROCK2-NF-κB signaling pathways. The ultimate aim of our proposed project is to provide a theoretical basis for the development of a novel strategy for the early prevention and therapy of SAE.

Research progress of TIPE2 in immune-related diseases

The tumor necrosis factor α-induced protein 8 (TNFAIP8) family, which consists of TNFAIP8 (TIPE), TNFAIP8L1 (TIPE1), TNFAIP8L2 (TIPE2) and TNFAIP8L3 (TIPE3), has recently emerged as a regulatory factor involved in immune response and tumorigenesis. Among its members, TIPE2 acts as a negative regulator of both innate and adaptive immunity, playing a crucial role in maintaining immune homeostasis by negatively regulating T cell receptor (TCR) and toll-like receptor (TLR) signal transduction. Immune homeostasis is an indispensable characteristic of the immune system, which prevents harmful inflammatory reactions and ensures the proper functioning of the body. A large number of studies have shown that abnormal TIPE2 expression exists in a variety of inflammation-related diseases such as asthma, colitis, and systemic lupus erythematosus, highlighting the importance of comprehending its function for the prevention and treatment of immune-related conditions. This review aims to provide an overview of the in vivo distribution and expression of TIPE2, its regulatory role in central and peripheral immune-related diseases, and the underlying mechanisms that govern its function in the inflammatory response. By delving into these aspects, a deeper understanding of the role and functionality of TIPE2 in inflammatory responses can be achieved.

TIPE2 regulates the response of BV2 cells to lipopolysaccharide by the crosstalk between PI3K/AKT signaling and microglia M1/M2 polarization

Tumor necrosis factor (TNF)-α-induced protein 8-like 2 (TIPE2) is a crucial negative regulator of both adaptive and innate immunity, which helps maintain the dynamic balance of the immune system by negatively regulating the signaling of T-cell receptors (TCR) and Toll-like receptors (TLR). In this study, we aimed to investigate the role and molecular mechanism of TIPE2 using a lipopolysaccharide (LPS)-induced inflammatory injury model in BV2 cells. Specifically, we constructed a BV2 cell line of TIPE2-overexpression or TIPE2-knockdown via lentiviral transfection. Our results demonstrated that overexpression of TIPE2 downregulated the expression of pro-inflammatory cytokines IL-1β and IL-6, which was reversed by knockdown of TIPE2 in the inflammation model of BV2 cells. In addition, overexpression of TIPE2 resulted in the conversion of BV2 cells to the M2 phenotype, while the knockdown of TIPE2 promoted the transformation of BV2 cells to the M1 phenotype. Notably, our co-culture experiments with neuronal cells SH-SY5Y showed that the overexpression of TIPE2 in inflammation-injured BV2 cells exhibited a protective effect on the neuronal cells. Finally, western blot analysis demonstrated that TIPE2 significantly reduced the expression of p-PI3K, p-AKT, p-p65, and p-IκBα in LPS treated BV2 cells, and inhibited the activation of NF-κB through the dephosphorylation of PI3K/AKT. These results suggest that TIPE2 plays an important role in mediating neuroinflammatory responses and may be involved in neuroprotection by modulating the phenotypic changes of BV2 cells and regulating the pro-inflammatory responses through the PI3K/AKT and NF-κB signaling pathways. In conclusion, our study provides new insights into the crucial role of TIPE2 in regulating neuroinflammatory responses and highlights its potential as a therapeutic target for neuroprotection.

TLR2/TLR4-Enhanced TIPE2 Expression Is Involved in Post-Hemorrhagic Shock Mesenteric Lymph-Induced Activation of CD4+T Cells

Purpose

Post hemorrhagic shock mesenteric lymph (PHSML) return contributes to CD4+ T cell dysfunction, which leads to immune dysfunction and uncontrolled inflammatory response. Tumor necrosis factor α induced protein 8 like-2 (TIPE2) is one of the essential proteins to maintain the immune homeostasis. This study investigated the role of TIPE2 in regulation of CD4+ T lymphocyte function in interaction of PHSML and TLR2/TLR4.

Methods

The splenic CD4+ T cells were isolated from various mice (WT, TLR2-/-, TLR4-/-) by immunomagnetic beads, and stimulated with PHSML, normal lymphatic fluid (NML), respectively. Application of TIPE2-carrying interfering fragments of lentivirus were transfected to WT, TLR4-/-, and TLR2-/- CD4+ T cells, respectively. After interference of TIPE2, they were stimulated with PHSML and NML for the examinations of TIPE2, TLR2, and TLR4 mRNA expressions, proliferation, activation molecules on surface, and cytokine secretion function.

Results

PHSML stimulation significantly upregulated TIPE2, TLR2, and TLR4 mRNA expressions, decreased proliferation, CD25 expression, and IFN-γ secretion, and increased the secretion ability of IL-4 in WT CD4+ T cells. TIPE2 silencing enhanced proliferative capacity, upregulated CD25 expression, and increased IFNγ secretion in CD4+ T cells. PHSML stimulated TLR2-/-CD4+ T or TLR4-/-CD4+ T cells of which TIPE2 were silenced. TLR2 or TLR4 knockout attenuated PHSML-induced CD4+ T cells dysfunction; PHSML stimulation of silent TIPE2-expressing TLR2-/-CD4+ T or TLR4-/-CD4+ T revealed that the coexistence of low TIPE2 expression with lack of TLR2 or TLR4 eliminated this beneficial effect.

Conclusion

TIPE2 improves the PHSML-mediated CD4+T cells dysfunction by regulating TLR2/TLR4 pathway, providing a new intervention target following hemorrhagic shock-induced immune dysfunction.

JWX-A0108, a positive allosteric modulator of α7 nAChR, attenuates cognitive deficits in APP/PS1 mice by suppressing NF-κB-mediated inflammation

Neuroinflammation plays an early and prominent role in the pathology of Alzheimer's disease (AD). Studies have shown that cholinergic lesion is a contributor for the pathophysiology of AD. The α7 nicotinic acetylcholine receptors (nAChRs), a subtype of nAChRs, are abundantly expressed in the brain regions related to cognition and memory, such as hippocampus and frontal cortex. The α7 nAChR is rapidly activated and desensitized by agonists. JWX-A0108 is a type I positive allosteric modulator (PAM) of α7 nAChR, which mainly enhances agonist-evoked peak currents. Here, we used the Morris Water Maze to evaluate the effect of JWX-A0108 on cognition and memory functions in APP/PS1 mice, and the mechanism related to anti-inflammatory effect. The results showed that JWX-A0108 could improve the learning and memory function of APP/PS1 transgenic mice in Morris water maze, decrease the expression of IL-1β, TNF-α, IL-6 in the brain and lower the phosphorylation level of IκBα (Ser32/36) and NF-κB p65 (Ser536), decrease the expression of Iba1, the microglia activation marker. Nissl staining showed that the CA3 and DG regions of hippocampus were damaged in APP/PS1 mice, which was improved by JWX-A0108. All of these effects of JWX-A0108 were reversed by MLA (α7 nAChR specific blocker). Taken together, the results reveal that JWX-A0108 improved the learning and memory function of APP/PS1 mice by enhancing the anti-inflammatory effect of the endogenous choline system through α7 nAChR, inhibited the activation of the NF-κB signaling pathway by inhibiting IκB phosphorylation, and ultimately inhibited inflammatory responses.