Blocking the REDD1/TXNIP axis ameliorates LPS-induced vascular endothelial cell injury through repressing oxidative stress and apoptosis

Geniposide Combined With Notoginsenoside R1 Attenuates Inflammation and Apoptosis in Atherosclerosis via the AMPK/mTOR/Nrf2 Signaling Pathway

Inflammation and apoptosis of vascular endothelial cells play a key role in the occurrence and development of atherosclerosis (AS), and the AMPK/mTOR/Nrf2 signaling pathway plays an important role in alleviating the symptoms of AS. Geniposide combined with notoginsenoside R1 (GN combination) is a patented supplement for the prevention and treatment of AS. It has been proven to improve blood lipid levels and inhibit the formation of AS plaques; however, it is still unclear whether GN combination can inhibit inflammation and apoptosis in AS by regulating the AMPK/mTOR/Nrf2 signaling pathway and its downstream signals. Our results confirmed that the GN combination could improve blood lipid levels and plaque formation in ApoE^−/− mice fed with a high-fat diet (HFD), inhibit the secretion of serum inflammatory factors and oxidative stress factors. It also decreased the expression of pyrin domain containing protein 3 (NLRP3) inflammasome-related protein and Bax/Bcl2/caspase-3 pathway-related proteins. At the same time, the GN combination could also inhibit the H₂O₂-induced inflammatory response and apoptosis of human umbilical vein endothelial cells (HUVECs), which is mainly related to the activation of the AMPK/mTOR pathway by GN combination, which in turn induces the activation of Nrf2/HO-1 signal. In addition, the above phenomenon could be significantly reversed by dorsomorphin. Therefore, our experiments proved for the first time that the GN combination can effectively inhibit AS inflammation and apoptosis by activating the AMPK/mTOR/Nrf2 signaling pathway to inhibit the NLRP3 inflammasome and Bax/Bcl2/caspase-3 pathway.

Bakkenolide‑IIIa ameliorates lipopolysaccharide‑induced inflammatory injury in human umbilical vein endothelial cells by upregulating LINC00294

Inflammation, which causes injury to vascular endothelial cells, is one of the major factors associated with atherosclerosis (AS); therefore, inhibition of endothelial inflammation is a key step toward preventing AS. The present study aimed to investigate the effects of bakkenolide-IIIa (Bak-IIIa), an important active component of bakkenolides, on endothelial inflammation, as well as the mechanisms underlying such effects. Lipopolysaccharide (LPS)-damaged human umbilical vein endothelial cells (HUVECs) were treated with Bak-IIIa. The results of the MTT assay and enzyme-linked immunosorbent assay indicated that Bak-IIIa significantly alleviated survival inhibition, and decreased the levels of LPS-induced TNF-α, interleukin (IL)-1β, IL-8, and IL-6. Furthermore, long noncoding RNA (lncRNA) microarray analyses revealed 70 differentially expressed lncRNAs (DELs) in LPS-damaged HUVECs treated with Bak-IIIa. lncRNA target prediction results revealed that 44 DELs had 52 cis-targets, whereas 12 DELs covered 386 trans-targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes analyses of the trans-targets indicated that three GO terms were associated with inflammation. Therefore, 17 targets involved in these GO terms and six relevant DELs were screened out. Validation via reverse transcription-quantitative PCR indicated that the fold change of NR_015451 (LINC00294) was the highest among the six candidates and that overexpression of LINC00294 significantly alleviated LPS-induced survival inhibition and inflammatory damage in HUVECs. In conclusion, Bak-IIIa ameliorated LPS-induced inflammatory damage in HUVECs by upregulating LINC00294. Thus, Bak-IIIa exhibited potential for preventing vascular inflammation.

The stress response protein REDD1 as a causal factor for oxidative stress in diabetic retinopathy

Diabetic Retinopathy (DR) is a major cause of visual dysfunction, yet much remains unknown regarding the specific molecular events that contribute to diabetes-induced retinal pathophysiology. Herein, we review the impact of oxidative stress on DR, and explore evidence that supports a key role for the stress response protein regulated in development and DNA damage (REDD1) in the development of diabetes-induced oxidative stress and functional defects in vision. It is well established that REDD1 mediates the cellular response to a number of diverse stressors through repression of the central metabolic regulator known as mechanistic target of rapamycin complex 1 (mTORC1). A growing body of evidence also supports that REDD1 acts independent of mTORC1 to promote oxidative stress by both enhancing the production of reactive oxygen species and suppressing the antioxidant response. Collectively, there is strong preclinical data to support a key role for REDD1 in the development and progression of retinal complications caused by diabetes. Furthermore, early proof-of-concept clinical trials have found a degree of success in combating ischemic retinal disease through intravitreal delivery of an siRNA targeting the REDD1 mRNA. Overall, REDD1-associated signaling represents an intriguing target for novel clinical therapies that go beyond addressing the symptoms of diabetes by targeting the underlying molecular mechanisms that contribute to DR.

The Emerging Role of TXNIP in Ischemic and Cardiovascular Diseases; A Novel Marker and Therapeutic Target

Thioredoxin interacting protein (TXNIP) is a metabolism- oxidative- and inflammation-related marker induced in cardiovascular diseases and is believed to represent a possible link between metabolism and cellular redox status. TXNIP is a potential biomarker in cardiovascular and ischemic diseases but also a novel identified target for preventive and curative medicine. The goal of this review is to focus on the novelties concerning TXNIP. After an overview in TXNIP involvement in oxidative stress, inflammation and metabolism, the remainder of this review presents the clues used to define TXNIP as a new marker at the genetic, blood, or ischemic site level in the context of cardiovascular and ischemic diseases.

Inhibition of EZH2 attenuates coronary heart disease by interacting with microRNA-22 to regulate the TXNIP/nuclear factor-κB pathway

NEW FINDINGS

What is the central question of this study? The relevance of microRNA-22 (miR-22) has been indicated in coronary heart disease (CHD). How does it exert a protective role in CHD? What is the main finding and its importance? EZH2 inhibited transcription of the miR-22 promoter, thus modulating cell proliferation in human umbilical vein endothelial cells and vascular smooth muscle cells to induce CHD.

ABSTRACT

MicroRNA-22 (miR-22) was indicated to modulate cell proliferation in human umbilical vein endothelial cells (HUVECs) under exposure to environmental toxicants. In the present study, we investigated the involvement of miR-22 in the mediation of HUVEC and vascular smooth muscle cell (VSMC) function, hence in the development of coronary heart disease (CHD). miR-22 expression was reduced in serum of CHD patients. Restoration of miR-22 decreased the proliferation, migration and invasion of VSMCs and increased apoptotic cells and inflammatory factors. In contrast, upregulation of miR-22 led to opposite trends in HUVECs. Chromatin immunoprecipitation and dual-luciferase assays validated that enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2) inhibited transcription of miR-22 promoter. EZH2, overexpressed in serum from CHD patients, diminished VSMC apoptosis, but facilitated HUVEC apoptosis. Luciferase reporter assays confirmed that thioredoxin-interacting protein (TXNIP) was a new direct target of miR-22. Overexpression of TXNIP blocked the function of miR-22 in HUVECs and VSMCs. Taken together, these findings will shed light on the role and mechanism of EZH2 in viability, migration, invasion and apoptosis via the miR-22/TXNIP axis in VSMCs and HUVECs, which might provide new insights into the treatment of CHD.

Is REDD1 a metabolic double agent? Lessons from physiology and pathology

The Akt/mechanistic target of rapamycin (mTOR) signaling pathway governs macromolecule synthesis, cell growth, and metabolism in response to nutrients and growth factors. Regulated in development and DNA damage response (REDD)1 is a conserved and ubiquitous protein, which is transiently induced in response to multiple stimuli. Acting like an endogenous inhibitor of the Akt/mTOR signaling pathway, REDD1 protein has been shown to regulate cell growth, mitochondrial function, oxidative stress, and apoptosis. Recent studies also indicate that timely REDD1 expression limits Akt/mTOR-dependent synthesis processes to spare energy during metabolic stresses, avoiding energy collapse and detrimental consequences. In contrast to this beneficial role for metabolic adaptation, REDD1 chronic expression appears involved in the pathogenesis of several diseases. Indeed, REDD1 expression is found as an early biomarker in many pathologies including inflammatory diseases, cancer, neurodegenerative disorders, depression, diabetes, and obesity. Moreover, prolonged REDD1 expression is associated with cell apoptosis, excessive reactive oxygen species (ROS) production, and inflammation activation leading to tissue damage. In this review, we decipher several mechanisms that make REDD1 a likely metabolic double agent depending on its duration of expression in different physiological and pathological contexts. We also discuss the role played by REDD1 in the cross talk between the Akt/mTOR signaling pathway and the energetic metabolism.

P53 in the impaired lungs

Our laboratory is focused on investigating the supportive role of P53 towards the maintenance of lung homeostasis. Acute lung injury, acute respiratory distress syndrome, chronic obstructive pulmonary disease, pulmonary fibrosis, bronchial asthma, pulmonary arterial hypertension, pneumonia and tuberculosis are respiratory pathologies, associated with dysfunctions of this endothelium defender (P53). Herein we review the evolving role of P53 towards the aforementioned inflammatory disorders, to potentially reveal new therapeutic possibilities in pulmonary disease.

Sevoflurane preconditioning inhibits cardiomyocyte injury induced by oxygen‑glucose deprivation by modulating TXNIP

The thioredoxin interaction protein (TXNIP) has been reported to be closely related to cell oxidative stress, apoptosis and inflammation. TXNIP is involved in the regulation of oxidative stress in lung and renal injury. However, it is unclear as to whether it participates in the protective effects of sevoflurane preconditioning in cardiomyocyte injury caused by oxidative stress in ischemia. In the present study, H9c2 cardiomyocytes were cultured with 0, 1.5, 2, 3.5, 5 or 6% sevoflurane for 3 h, followed by exposure to oxygen and glucose deprivation. The results demonstrated that oxygen and glucose deprivation induced an increase in TXNIP expression, lactate dehydrogenase (LDH) release, caspase‑3 activity, reactive oxygen species and malondialdehyde production. Preconditioning of the H9c2 cells with 3.5% sevoflurane suppressed TXNIP expression, LDH leakage, caspase‑3 activity, reactive oxygen species and malondialdehyde production, and it promoted cell viability. TXNIP overexpression reversed the effects of 3.5% sevoflurane preconditioning on caspase‑3 activity, reactive oxygen production and cell viability. Furthermore, TXNIP modulated p27 expression via PKB (protein kinase B/AKT) phosphorylation following preconditioning with 3.5% sevoflurane, and oxygen and glucose deprivation. On the whole these findings indicated that sevoflurane preconditioning protected the H9c2 cells against injury induced by oxygen and glucose deprivation by modulating TXNIP, AKT activation and p27 signaling.

Anti-Inflammatory Activity of Adenosine 5'-Trisphosphate in Lipopolysaccharide-Stimulated Human Umbilical Vein Endothelial Cells Through Negative Regulation of Toll-Like Receptor MyD88 Signaling

Activation of TLR4-MyD88-NF-κB signaling by lipopolysaccharide (LPS) evokes a proinflammatory immune response, and plays a pivotal role in initiation and progression of atherosclerosis (AS). ATP (adenosine 5'-trisphosphate), a powerful extracellular signal transduction molecule, functions to regulate immune inflammatory responses depending on the type of P2 receptors and cell lines. In this study, we first performed RT-PCR to detect the mRNA expression of monocyte chemoattractant protein-1 (MCP-1), IL-8, and IL-1β induced by different concentrations of LPS in human umbilical vein endothelial cells (HUVECs). Protein level of TLR4 signaling including TLR4, myeloid differentiation factor (MyD88), and CD14 induced by LPS (1 μg/mL) at different times (0, 10, 30, 60, 120 min) was analyzed by Western blot. Then, RT-PCR was performed to detect the effect of different concentrations of ATP on mRNA expression of IL-1β and MCP-1 induced by LPS (1 μg/mL) and the TLR4 signaling pathway. Western blot was performed to detect the effect of low concentrations of ATP on phosphorylation of p65 induced by 1 μg/mL LPS. Finally, we used P2Y receptor blocker Suramin to verify whether the role of ATP on LPS-induced inflammatory cytokine expression was through P2Y receptors. The results showed that LPS upregulated the expression of MCP-1, IL-8, and IL-1β in a dose-dependent manner accompanied by the activation of TLR4-MyD88 signaling in HUVECs. Only low concentration ATP (1, 10 μM) inhibited LPS-induced mRNA expression of IL-1β and MCP-1. ATP at low concentrations also downregulated the mRNA expression of TLR4, CD14, and MyD88 and inhibited LPS-induced phosphorylation of p65. Furthermore, Suramin, a nonspecific P2Y receptor antagonist, did not attenuate the inhibition of ATP on LPS-induced IL-1β and MCP-1 expression. Taking this together, low concentration ATP inhibited LPS-induced inflammation in HUVECs by negatively regulating TLR4-MyD88 signaling, and P2Y receptors were not involved in this process, which might provide new ideas for prevention and treatment of inflammatory diseases such as AS.

Down-Regulation of Essential Synaptic Components by GI-Tract Microbiome-Derived Lipopolysaccharide (LPS) in LPS-Treated Human Neuronal-Glial (HNG) Cells in Primary Culture: Relevance to Alzheimer's Disease (AD)

Trans-synaptic neurotransmission of both electrical and neurochemical information in the central nervous system (CNS) is achieved through a highly interactive network of neuron-specific synaptic proteins that include pre-synaptic and post-synaptic elements. These elements include a family of several well-characterized integral- and trans-membrane synaptic core proteins necessary for the efficient operation of this complex signaling network, and include the pre-synaptic proteins: (i) neurexin-1 (NRXN-1); (ii) the synaptosomal-associated phosphoprotein-25 (SNAP-25); (iii) the phosphoprotein synapsin-2 (SYN-2); and the post-synaptic elements: (iv) neuroligin (NLGN), a critical cell adhesion protein; and (v) the SH3-ankyrin repeat domain, proline-rich cytoskeletal scaffolding protein SHANK3. All five of these pre- and post-synaptic proteins have been found to be significantly down-regulated in primary human neuronal-glial (HNG) cell co-cultures after exposure to Bacteroides fragilis lipopolysaccharide (BF-LPS). Interestingly, LPS has also been reported to be abundant in Alzheimer's disease (AD) affected brain cells where there are significant deficits in this same family of synaptic components. This "Perspectives" paper will review current research progress and discuss the latest findings in this research area. Overall these experimental results provide evidence (i) that gastrointestinal (GI) tract-derived Gram-negative bacterial exudates such as BF-LPS express their neurotoxicity in the CNS in part through the directed down-regulation of neuron-specific neurofilaments and synaptic signaling proteins; and (ii) that this may explain the significant alterations in immune-responses and cognitive deficits observed after bacterial-derived LPS exposure to the human CNS.

The Post-amyloid Era in Alzheimer's Disease: Trust Your Gut Feeling

The amyloid hypothesis, the assumption that beta-amyloid toxicity is the primary cause of neuronal and synaptic loss, has been the mainstream research concept in Alzheimer's disease for the past two decades. Currently, this model is quietly being replaced by a more holistic, “systemic disease” paradigm which, like the aging process, affects multiple body tissues and organs, including the gut microbiota. It is well-established that inflammation is a hallmark of cellular senescence; however, the infection-senescence link has been less explored. Microbiota-induced senescence is a gradually emerging concept promoted by the discovery of pathogens and their products in Alzheimer's disease brains associated with senescent neurons, glia, and endothelial cells. Infectious agents have previously been associated with Alzheimer's disease, but the cause vs. effect issue could not be resolved. A recent study may have settled this debate as it shows that gingipain, a Porphyromonas gingivalis toxin, can be detected not only in Alzheimer's disease but also in the brains of older individuals deceased prior to developing the illness. In this review, we take the position that gut and other microbes from the body periphery reach the brain by triggering intestinal and blood-brain barrier senescence and disruption. We also surmise that novel Alzheimer's disease findings, including neuronal somatic mosaicism, iron dyshomeostasis, aggressive glial phenotypes, and loss of aerobic glycolysis, can be explained by the infection-senescence model. In addition, we discuss potential cellular senescence targets and therapeutic strategies, including iron chelators, inflammasome inhibitors, senolytic antibiotics, mitophagy inducers, and epigenetic metabolic reprograming.