Role of Ox-LDL/LOX-1/NF-κB signaling pathway in regulation of atherosclerotic plaque growth by testosterone in male rabbits

CircTTLL13 Promotes TMZ Resistance in Glioma via Modulating OLR1-Mediated Activation of the Wnt/β-Catenin Pathway

Glioma, originating from neuroglial progenitor cells, is a type of intrinsic brain tumor with poor prognosis. temozolomide (TMZ) is the first-line chemotherapeutic agent for glioma. Exploring the mechanisms of circTTLL13 underlying TMZ resistance in glioma is of great significance to improve glioma treatment. Bioinformatics was adopted to identify target genes. The circular structure of circTTLL13 and its high expression in glioma cells were disclosed by quantitative real time-PCR (qRT-PCR) and PCR-agarose gel electrophoresis. Functional experiments proved that oxidized LDL receptor 1 (OLR1) promotes TMZ resistance of glioma cells. CircTTLL13 enhances TMZ resistance of glioma cells via modulating OLR1. Luciferase reporter, RNA-binding protein immunoprecipitation (RIP), RNA pulldown, mRNA stability, N6-methyladenosine (m6A) dot blot and RNA total m6A quantification assays were implemented, indicating that circTTLL13 stabilizes OLR1 mRNA via recruiting YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) and promotes m6A methylation of OLR1 pre-mRNA through recruiting methyltransferase-like 3 (METTL3). TOP/FOP-flash reporter assay and western blot verified that circTTLL13 activates Wnt/β-catenin signaling pathway by regulating OLR1. CircTTLL13 promotes TMZ resistance in glioma through regulating OLR1-mediated Wnt/β-catenin pathway activation. This study offers an insight into the efficacy improvement of TMZ for glioma treatment.

Oxidized-LDL inhibits testosterone biosynthesis by affecting mitochondrial function and the p38 MAPK/COX-2 signaling pathway in Leydig cells

Abnormal lipid/lipoprotein metabolism induced by obesity may affect spermatogenesis by inhibiting testosterone synthesis in Leydig cells. It is crucial to determine which components of lipoproteins inhibit testosterone synthesis. Circulating oxidized low-density lipoprotein (oxLDL), the oxidized form of LDL, has been reported to be an independent risk factor for decreased serum testosterone levels. However, whether oxLDL has a damaging effect on Leydig cell function and the detailed mechanisms have been rarely studied. This study first showed the specific localization of oxLDL and mitochondrial structural damage in testicular Leydig cells of high-fat diet-fed mice in vivo. We also found that oxLDL reduced the mitochondrial membrane potential (MMP) by disrupting electron transport chain and inhibited testosterone synthesis-related proteins and enzymes (StAR, P450scc, and 3β‑HSD), which ultimately led to mitochondrial dysfunction and decreased testosterone synthesis in Leydig cells. Further experiments demonstrated that oxLDL promoted lipid uptake and mitochondrial dysfunction by inducing CD36 transcription. Meanwhile, oxLDL facilitated COX2 expression through the p38 MAPK signaling pathway in Leydig cells. Blockade of COX-2 attenuated the oxLDL-induced decrease in StAR and P450scc. Our clinical results clarified that the increased serum oxLDL level was associated with a decline in circulating testosterone levels. Our findings amplify the damaging effects of oxLDL and provide the first evidence that oxLDL is a novel metabolic biomarker of male-acquired hypogonadism caused by abnormal lipid metabolism.

LOX-1 and atherosclerotic-related diseases

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), a scavenger receptor of oxidized low-density lipoprotein (ox-LDL) found in various cells, plays a crucial role in the formation and progression of atherosclerotic plaques. Animal studies have suggested that LOX-1 mediates the balance between internalization and degeneration of endothelial cells, thereby contributing to various steps in the atherosclerotic process, from initiation to plaque rupture. Under pathological conditions, the extracellular domain of membrane bound LOX-1 can be largely proteolytically cleaved into a soluble form (sLOX-1), which is proportional and linked to the LOX-1 expression level. Circulating levels of sLOX-1 are regarded as a risk biomarker for plaque rupture and acute coronary syndrome (ACS). Recently, studies have shown that sLOX-1 is also elevated in patients with acute stroke and can be a predictive biomarker for acute stroke. With the discovery of the vital role of LOX-1 in atherosclerosis, there is growing focus on the influence of LOX-1 in atherosclerotic-related diseases, including coronary arterial disease(CAD), stroke, and other cardiovascular events. Genetic polymorphisms of LOX-1 have been investigated and have been found to modulate the risk of these diseases. Most polymorphisms have been found to be risk factors, except for the splicing isoform LOXIN. This review concludes with a discussion of the potential future applications of LOX-1 for atherosclerotic-related diseases.

OxLDL promotes lymphangiogenesis and lymphatic metastasis in gastric cancer by upregulating VEGF‑C expression and secretion

Gastric cancer is one of the most malignant tumor types, and its metastasis is a notable cause of mortality. Among the methods of tumor metastasis, lymphatic metastasis is the predominant one in gastric cancer. A previous study reported that the plasma oxidized low-density lipoprotein (oxLDL) is the risk factor associated with the development of tumors in patients with abnormal lipid metabolism, but the influence of plasma oxLDL in the lymphatic metastasis of gastric cancer remains unclear. In the present study, the concentration of plasma oxLDL from patients with gastric cancer was detected with an ELISA kit, and the lymphatic vessel density in gastric cancer tissues was determined by D2-40 staining. The correlation analysis of oxLDL concentration and lymphatic vessel density demonstrated that plasma oxLDL was positively correlated with lymphatic metastasis in patients with gastric cancer. Subsequently, the popliteal lymph node metastasis animal experiment with nude mice confirmed that oxLDL could promote the lymphatic metastasis of gastric cancer. Following this, the western blotting and ELISA data demonstrated that oxLDL promoted the expression and secretion of vascular endothelia growth factor (VEGF)-C in gastric cancer cell lines. Finally, blocking the lectin-like oxLDL-1 (LOX-1) receptor, a specific receptor for oxLDL, and the nuclear factor (NF)-κB signaling pathway following oxLDL (50 µg/ml) treatment in HGC-27 cells revealed that oxLDL could activate the NF-κB signaling pathway mediated by LOX-1, with subsequent upregulation of VEGF-C expression, and secretion in and from gastric cancer cells, and finally that it could promote the lymphatic metastasis of gastric cancer. These data indicate the association between the plasma oxLDL and the lymphatic metastasis of gastric cancer, and indicate that oxLDL elimination may be a potential therapeutic target for the prevention and intervention of early lymph node metastasis in gastric cancer.

Microglia Ontology and Signaling

Microglia constitute the powerhouse of the innate immune system in the brain. It is now widely accepted that they are monocytic-derived cells that infiltrate the developing brain at the early embryonic stages, and acquire a resting phenotype characterized by the presence of dense branching processes, called ramifications. Microglia use these dynamic ramifications as sentinels to sense and detect any occurring alteration in brain homeostasis. Once a danger signal is detected, such as molecular factors associated to brain damage or infection, they get activated by acquiring a less ramified phenotype, and mount adequate responses that range from phagocyting cell debris to secreting inflammatory and trophic factors. Here, we review the origin of microglia and we summarize the main molecular signals involved in controlling their function under physiological conditions. In addition, their implication in the pathogenesis of multiple sclerosis and stress is discussed.

Nuclear Factor-κB Activation as a Pathological Mechanism of Lipid Metabolism and Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall with lipid-laden lesions, involving a complex interaction between multiple different cell types and cytokine networks. Inflammatory responses mark all stages of atherogenesis: from lipid accumulation in the intima to plaque formation and eventual rupture. One of the most important regulators of inflammation is the transcription factor nuclear factor-κB (NF-κB), which is activated through the canonical and noncanonical pathways in response to various stimuli. NF-κB has long been regarded as a proatherogenic factor, because it is implicated in multiple pathological processes during atherogenesis, including foam cell formation, vascular inflammation, proliferation of vascular smooth muscle cells, arterial calcification, and plaque progression. In contrast, inhibition of NF-κB signaling has been shown to protect against atherosclerosis. This chapter aims to discuss recent progress on the roles of NF-κB in lipid metabolism and atherosclerosis and also to highlight its potential therapeutic benefits.

Pepsin-pancreatin protein hydrolysates from extruded amaranth inhibit markers of atherosclerosis in LPS-induced THP-1 macrophages-like human cells by reducing expression of proteins in LOX-1 signaling pathway

BACKGROUND

Atherosclerosis is considered a progressive disease that affects arteries that bring blood to the heart, to the brain and to the lower end. It derives from endothelial dysfunction and inflammation, which play an important role in the thrombotic complications of atherosclerosis. Cardiovascular disease is the leading cause of death around the world and one factor that can contribute to its progression and prevention is diet. Our previous study found that amaranth hydrolysates inhibited LPS-induced inflammation in human and mouse macrophages by preventing activation of NF-κB signaling. Furthermore, extrusion improved the anti-inflammatory effect of amaranth protein hydrolysates in both cell lines, probably attributed to the production of bioactive peptides during processing. Therefore, the objective of this study was to compare the anti-atherosclerotic potential of pepsin-pancreatin hydrolysates from unprocessed and extruded amaranth in THP-1 lipopolysaccharide-induced human macrophages and suggest the mechanism of action.

RESULTS

Unprocessed amaranth hydrolysate (UAH) and extruded amaranth hydrolysate (EAH) showed a significant reduction in the expression of interleukin-4 (IL-4) (69% and 100%, respectively), interleukin-6 (IL-6) (64% and 52%, respectively), interleukin-22 (IL-22) (55% and 70%, respectively). Likewise, UAH and EAH showed a reduction in the expression of monocyte-chemo attractant protein-1 (MCP-1) (35% and 42%, respectively), transferrin receptor-1 (TfR-1) (48% and 61%, respectively), granulocyte-macrophage colony-stimulating factor (GM-CSF) (59% and 63%, respectively), and tumor necrosis factor-α (TNF-α) (60% and 63%, respectively). Also, EAH reduced the expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) (27%), intracellular adhesion molecule-1 (ICAM-1) (28%) and matrix metalloproteinase-9 (MMP-9) (19%), important molecular markers in the atherosclerosis pathway. EAH, led to a reduction of 58, 52 and 79% for LOX-1, ICAM-1 and MMP-9, respectively, by confocal microscopy.

CONCLUSIONS

Extruded amaranth hydrolysate showed potential anti-atherosclerotic effect in LPS-induced THP-1 human macrophage-like cells by reducing the expression of proteins associated with LOX-1 signaling pathway.

Role of advanced glycation end products in cellular signaling

Improvements in health care and lifestyle have led to an elevated lifespan and increased focus on age-associated diseases, such as neurodegeneration, cardiovascular disease, frailty and arteriosclerosis. In all these chronic diseases protein, lipid or nucleic acid modifications are involved, including cross-linked and non-degradable aggregates, such as advanced glycation end products (AGEs). Formation of endogenous or uptake of dietary AGEs can lead to further protein modifications and activation of several inflammatory signaling pathways. This review will give an overview of the most prominent AGE-mediated signaling cascades, AGE receptor interactions, prevention of AGE formation and the impact of AGEs during pathophysiological processes.