Curcumin modulates TLR4/NF-κB inflammatory signaling pathway following traumatic spinal cord injury in rats

Abstract

Background

Curcumin, a polyphenolic compound extracted from the plant turmeric, has protective effects on spinal cord injury (SCI) through attenuation of inflammatory response. This study was designed to detect whether curcumin modulates toll-like receptor 4 (TLR4) and the nuclear factor-kappa B (NF-κB) inflammatory signaling pathway in the injured rat spinal cord following SCI.

Methods

Adult male Sprague–Dawley rats were subjected to laminectomy at T8–T9 and compression with a vascular clip. There were three groups: (a) sham group; (b) SCI group; and (g) SCI + curcumin group. We measured TLR4 gene and protein expression by real-time polymerase chain reaction and western blot analysis; NF-κB activity by electrophoretic mobility shift assay, inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels by enzyme-linked immunosorbent assay, hindlimb locomotion function by Basso, Beattie, and Bresnahan rating, spinal cord edema by wet/dry weight method, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis.

Results

The results showed that SCI induced the up-regulation of TLR4, NF-κB, and inflammatory cytokines in the injured rat spinal cord. Treatment with curcumin following SCI markedly down-regulated the levels of these agents related to the TLR4/NF-κB inflammatory signaling pathway. Administration of curcumin also significantly ameliorated SCI induced hind limb locomotion deficits, spinal cord edema, and apoptosis.

Conclusions

Post-SCI curcumin administration attenuates the TLR4/NF-κB inflammatory signaling pathway in the injured spinal cord, and this may be a mechanism whereby curcumin improves the outcome following SCI.     

Curcumin modulates TLR4/NF-κB inflammatory signaling pathway following traumatic spinal cord injury in rats

Background

Curcumin, a polyphenolic compound extracted from the plant turmeric, has protective effects on spinal cord injury (SCI) through attenuation of inflammatory response. This study was designed to detect whether curcumin modulates toll-like receptor 4 (TLR4) and the nuclear factor-kappa B (NF-κB) inflammatory signaling pathway in the injured rat spinal cord following SCI.

Methods

Adult male Sprague–Dawley rats were subjected to laminectomy at T8–T9 and compression with a vascular clip. There were three groups: (a) sham group; (b) SCI group; and (g) SCI + curcumin group. We measured TLR4 gene and protein expression by real-time polymerase chain reaction and western blot analysis; NF-κB activity by electrophoretic mobility shift assay, inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 levels by enzyme-linked immunosorbent assay, hindlimb locomotion function by Basso, Beattie, and Bresnahan rating, spinal cord edema by wet/dry weight method, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis.

Results

The results showed that SCI induced the up-regulation of TLR4, NF-κB, and inflammatory cytokines in the injured rat spinal cord. Treatment with curcumin following SCI markedly down-regulated the levels of these agents related to the TLR4/NF-κB inflammatory signaling pathway. Administration of curcumin also significantly ameliorated SCI induced hind limb locomotion deficits, spinal cord edema, and apoptosis.

Conclusions

Post-SCI curcumin administration attenuates the TLR4/NF-κB inflammatory signaling pathway in the injured spinal cord, and this may be a mechanism whereby curcumin improves the outcome following SCI.     

Uric acid induces inflammatory injury in HK-2 cells via PI3K/AKT/NF-κB signaling pathway

Objective To investigate the effects and underlying mechanisms of phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/NF-κB signaling pathway in human kidney-2 (HK-2) cells of hyperuricemic nephropathy. Methods HK-2 cells were cultured in vitro and randomly divided into control group and experimental group. The experimental group was induced by high uric acid (720 μmol/L) immersion for 48 h to establish a cell model of hyperuricemic nephropathy in vitro and subsequently divided into hyperuricemic group, overexpressed protease activated receptor 2 (PAR2) and knockdown PAR2 group. The expressions of PAR2, PI3K, AKT, NF-κB mRNA were measured by real-time PCR. The expressions of PAR2, PI3K, AKT and NF-κB protein were measured by Western blotting. The expressions of tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), interleukin-6 (IL-6), pro-interleukin-1β (pro-IL-1β), interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) were detected by enzyme linked immunosorbent assay (ELISA). Results (1) Compared with the control group, the expressions of PAR2, PI3K, AKT and NF-κB mRNA and protein in hyperuricemic group were significantly increased (all P＜0.05), the expressions of TNF-α, MCP-1, IL-6, pro-IL-1β, IL-1β and TGF-β1 in the supernatant in hyperuricemic group were significantly increased (all P＜0.01). (2) Compared with the hyperuricemic group, the expressions of PAR2, PI3K, AKT and NF-κB mRNA and protein in overexpressed PAR2 group were significantly increased (all P＜0.05), the expressions of TNF-α, MCP-1, IL-6, IL-1β and TGF-β1 in the supernatant were significantly increased (all P＜0.05). (3) Compared with the hyperuricemic group, the expression of PAR2, PI3K, AKT and NF-κB mRNA and protein in knockdown PAR2 group were significantly decreased (all P＜0.05), the expressions of IL-6, pro-IL-1β, IL-1β and TGF-β1 in the supernatant were significantly decreased (all P＜0.05). Conclusions In the process of uric acid-induced HK-2 cell damage, uric acid significantly up-regulates the expression of PI3K/AKT/NF-κB signaling pathway by activating PAR2, leading to a marked increase in inflammatory damage. Knocking down PAR2 inhibits the expression of PI3K/AKT/NF-κB signaling pathway, which can effectively reduce the inflammatory damage of HK-2 cells.     

Exogenous administration of PACAP alleviates traumatic brain injury in rats through a mechanism involving the TLR4/MyD88/NF-κB pathway

Pituitary adenylate cyclase-activating polypeptide (PACAP) is effective in reducing axonal damage associated with traumatic brain injury (TBI), and has immunomodulatory properties. Toll-like receptor 4 (TLR4) is an important mediator of the innate immune response. It significantly contributes to neuroinflammation induced by brain injury. However, it remains unknown whether exogenous PACAP can modulate TBI through the TLR4/adapter protein myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway. In this study, we investigated the potential neuroprotective mechanisms of PACAP pretreatment in a weight-drop model of TBI. PACAP38 was microinjected intracerebroventricularly before TBI. Brain samples were extracted from the pericontusional area in the cortex and hippocampus. We found that TBI induced significant upregulation of TLR4, with peak expression occurring 24?h post-trauma, and that pretreatment with PACAP significantly improved motor and cognitive dysfunction, attenuated neuronal apoptosis, and decreased brain edema. Pretreatment with PACAP inhibited upregulation of TLR4 and its downstream signaling molecules MyD88, p-IκB, and NF-κB, and suppressed increases in the levels of the downstream inflammatory agents interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), in the brain tissue around the injured cortex and in the hippocampus. Administration of PACAP both in vitro and in vivo attenuated the ability of the TLR4 agonist lipopolysaccharide (LPS) to increase TLR4 protein levels. Therefore, PACAP exerts a neuroprotective effect in this rat model of TBI, by inhibiting a secondary inflammatory response mediated by the TLR4/MyD88/NF-κB signaling pathway in microglia and neurons, thereby reducing neuronal death and improving the outcome following TBI.     

Metformin regulates inflammation and fibrosis in diabetic kidney disease through TNC/TLR4/NF-κB/mi R-155-5p inflammatory loop

BACKGROUND Type 2 diabetes mellitus(T2 DM) is significantly increasing worldwide, and the incidence of its complications is also on the rise. One of the main complications of T2 DM is diabetic kidney disease(DKD). The glomerular filtration rate(GFR) and urinary albumin creatinine ratio(UACR) increase in the early stage. As the disease progresses, UACR continue to rise and GFR begins to decline until endstage renal disease appears. At the same time, DKD will also increase the incidence and mortality of cardiovascular and cerebrovascular diseases. At present, the pathogenesis of DKD is not very clear. Therefore, exploration of the pathogenesis of DKD to find a treatment approach, so as to delay the development of DKD, is essential to improve the prognosis of DKD.AIM To detect the expression of tenascin-C(TNC) in the serum of T2 DM patients, observe the content of TNC in the glomerulus of DKD rats, and detect the expression of TNC on inflammatory and fibrotic factors in rat mesangial cells(RMCs) cultured under high glucose condition, in order to explore the specific molecular mechanism of TNC in DKD and bring a new direction for the treatment of DKD.METHODS The expression level of TNC in the serum of diabetic patients was detected by enzyme-linked immunosorbent assay(ELISA), the protein expression level of TNC in the glomerular area of DKD rats was detected by immunohistochemistry, and the expression level of TNC in the rat serum was detected by ELISA. Rat glomerular mesangial cells were cultured. Following high glucose stimulation, the expression levels of related proteins and m RNA were detected by Western blot and polymerase chain reaction, respectively.RESULTS ELISA results revealed an increase in the serum TNC level in patients with T2 DM. Increasing UACR and hypertension significantly increased the expression of TNC(P 0.05). TNC expression was positively correlated with glycosylated haemoglobin(Hb A1 c) level, body mass index, systolic blood pressure, and UACR(P 0.05). Immunohistochemical staining showed that TNC expression in the glomeruli of rats with streptozotocin-induced diabetes was significantly increased compared with normal controls(P 0.05). Compared with normal rats, serum level of TNC in diabetic rats was significantly increased(P 0.05), which was positively correlated with urea nitrogen and urinary creatinine(P 0.05). The levels of TNC, Toll-like receptor-4(TLR4), phosphorylated nuclear factor-κB p65 protein(Ser536)(p-NF-κB p65), and mi R-155-5 p were increased in RMCs treated with high glucose(P 0.05). The level of TNC protein peaked 24 h after high glucose stimulation(P 0.05). After TNC knockdown, the levels of TLR4, p-NF-κB p65, mi R-155-5 p, connective tissue growth factor(CTGF), and fibronectin(FN) were decreased, revealing that TNC regulated mi R-155-5 p expression through the TLR4/NF-κB p65 pathway, thereby regulating inflammation(NF-κB p65) and fibrosis(CTGF and FN) in individuals with DKD. In addition, metformin treatment may relive the processes of inflammation and fibrosis in individuals with DKD by reducing the levels of the TNC, p-NF-κB p65, CTGF, and FN proteins.CONCLUSION TNC can promote the occurrence and development of DKD. Interfering with the TNC/TLR4/NF-κB p65/mi R-155-5 p pathway may become a new target for DKD treatment.     

TLR4/NF-κB通路与骨质疏松症关系的研究进展

骨质疏松症(osteoporosis, OP)是一种普遍存在的与年龄相关的骨骼疾病，雌激素缺乏和衰老是主要病因，近年来越来越多的研究表明炎症反应在OP的发生发展过程中发挥重要作用。Toll样受体4(toll like receptor 4,TLR4)是Toll样受体家族的主要成员，是内毒素最重要的模式识别受体。TLR4是经典的炎症信号转导通路，当TLR4信号通路激活，与核因子κB (nuclear factorκB,NF-κB)转移到细胞核并释放炎性细胞因子(TNF-α、IL-1β、IL-6等),并抑制骨髓间充质干细胞成骨分化及钙盐沉积，促进破骨细胞成熟，最终导致OP。对TLR4信号通路与OP关系的研究不仅可以从炎症角度深入揭示OP的发病机制，还可以为OP的防治提供新的思路。     

Targeting curcusomes to inflammatory dendritic cells inhibits NF-κB and improves insulin resistance in obese mice

OBJECTIVE

To determine whether and by what mechanism systemic delivery of curcumin-containing liposomes improves insulin resistance in the leptin deficient (ob/ob) mouse model of insulin resistance.

RESEARCH DESIGN AND METHODS

Insulin resistant ob/ob mice with steatosis were injected intraperitoneally with liposome nanoparticles, entrapping the nuclear factor-κB (NF-κB) inhibitor curcumin (curcusomes), and uptake in liver and adipose tissue was determined by flow cytometry. The effects of curcusomes on macrophage NF-κB activation and cytokine production were assessed. Transfer experiments determined the role of hepatic tumor necrosis factor (TNF)/inducible nitric oxide synthase-producing dendritic cells (Tip-DCs) and adipose tissue macrophages (ATMs) in inflammation-induced insulin resistance, determined by homeostatic assessment of insulin resistance.

RESULTS

Phagocytic myeloid cells infiltrating the liver in ob/ob mice had the phenotypic characteristics of Tip-DCs that arise from monocyte precursors in the liver and spleen after infection. Targeting Tip-DCs and ATMs with curcusomes in ob/ob mice reduced NF-κB/RelA DNA binding activity, reduced TNF, and enhanced interleukin-4 production. Curcusomes improved peripheral insulin resistance.

CONCLUSIONS

Both hepatic Tip-DCs and ATMs contribute to insulin resistance in ob/ob mice. Curcusome nanoparticles inhibit proinflammatory pathways in hepatic Tip-DCs and ATMs and reverse insulin resistance. Targeting inflammatory DCs is a novel approach for type 2 diabetes treatment.Patients with type 2 diabetes produce insulin, but insulin signaling of cells and, hence, glucose disposal is attenuated, leading to insulin resistance. In obesity, metabolic tissue promotes the infiltration and activation of macrophages that have a proinflammatory phenotype. In contrast, macrophages present in lean tissue are phagocytic and function in tissue remodeling (1). Nuclear factor-κB (NF-κB) is an important pathway in activation of this proinflammatory state, and ablation of this signaling pathway in myeloid cells in mice prevents diet- and genetic-induced insulin resistance (2). Studies on obese mice indicate that where calories are restricted after development of insulin resistance, macrophages switch to a less activated or alternate activated state (3). These findings confirm that the activation state of metabolic tissue-infiltrating macrophages is plastic and amenable to modulation.The most promising treatments for type 2 diabetes are drugs that not only improve insulin signaling but also promote alternate macrophage activation, for example, thiazolidinediones, which are agonists of fatty acid sensors (4). However, these and other drugs do not cure type 2 diabetes, have unwanted side effects, and over time, patients may require increasing doses of insulin to regulate increasing blood glucose levels (5). Developing new drugs or approaches to promote alternate activation of macrophages represents a promising approach to treating diabetes.Studies on genetically obese ob/ob mice and obese mice consuming a high-fat diet have shown that oral curcumin inhibits macrophage infiltration of adipose tissue and NF-κB activation in the liver; increases the production of the adipokine adiponectin in adipose tissue; and ameliorates inflammation, hyperglycemia, and insulin resistance (6). Although pharmacologically safe, curcumin has poor bioavailability after oral administration (7). Liposomal delivery systems have been used to enhance the bioavailability and improve the delivery of curcumin (8). As a result of the high hydrophobicity of curcumin, these curcumin-containing liposomes (curcusomes) are stable when diluted and incubated in vitro or injected in vivo (9,10). We have shown that curcusomes are taken up by splenic and lymph node antigen-presenting cells, including macrophages, dendritic cells (DCs), and B cells in vivo; block NF-κB activity in these cells; and inhibit inflammatory disease in mouse models of antigen-induced arthritis (10).Given the capacity of curcusomes to target and block inflammatory activity of phagocytic antigen-presenting cells, we tested their effects in the ob/ob mouse model of obesity and hepatic and peripheral insulin resistance. The data indicate that tumor necrosis factor/inducible nitric oxide synthase (TNF/iNOS)-producing DCs (Tip-DCs) in ob/ob livers are inhibited and modulated by curcusomes, resulting in improvements in peripheral insulin resistance.     

TLR4/NF-κB信号通路在脊髓损伤中的作用

[目的]探讨TLR4/NF-κB信号通路在急性脊髓损伤发病机制中的作用。[方法] SD大鼠随机分为假手术组、损伤组和单唾液酸神经节苷酯组(monosialoganglioside, GM1组)。其中,前一组仅行假手术,后两组采用改良Allen法建立大鼠脊髓损伤模型。术后,GM1组给予静脉GM1,假手术组、损伤组静脉给予等量生理盐水。术后15 d处死动物,行RT-qPCR和Western-blot检测TLR4/NF-κB和炎性因子的mRNA和蛋白的表达。[结果]与假手术组相比,损伤组的TLR4/NF-κB通路和相关炎性因子和mRNA和蛋白表达均显著增加(P0.05)。与损伤组相比,GM1组的的TLR4/NF-κB通路和相关炎性因子和mRNA和蛋白表达显著下降(P0.05)。[结论] TLR4/NF-κB信号通路可能成为治疗继发性脊髓损伤新的作用靶点,GM1主要通过抑制TLR4/NF-κB信号通路而起到治疗脊髓损伤的作用。     

Rhein protects 5/6 nephrectomized rat against renal injury by reducing inflammation via NF-κB signaling

International Urology and Nephrology - Inflammation is well known to play a pivotal role in renal injury. Rhein is a major component of the medicinal Rhubarb. The aim of this study was to...     

miRNA-146调控TLR4/NF-κB通路促进滋养层细胞增殖和迁移

目的 探讨miRNA-146是否通过调控Toll样受体4/核因子-κB(TLR4/NF-κB)信号通路促进滋养层细胞HTR-8/SVneo增殖和迁移，以期为不明原因复发性流产(uRSA)的发病机制研究和防治提供参考。方法 (1)细胞研究：将转染后的胎盘滋养层细胞HTR-8/SVneo分成miRNA-146抑制剂组、抑制剂对照组、miRNA-146模拟物组、模拟物对照组，检测各组HTR-8/SVneo细胞生长的活力、增殖、凋亡、迁移情况，通过实时荧光定量PCR(qRT-PCR)和Western blot检测各组TLR4、NF-κB、肿瘤坏死因子(TNF-α)和白介素-6(IL-6)的mRNA和蛋白相对表达水平。(2)动物研究：建立Dicer酶敲除的uRSA小鼠模型，将正常妊娠小鼠作为对照组，通过qRT-PCR检测胎盘组织的miRNA-146 mRNA表达情况，采用免疫组织化学法检测胎盘组织的TLR4、NF-κB、TNF-α、IL-6蛋白表达情况。结果 (1)细胞研究：与模拟物对照组比较，miRNA-146模拟物组HTR-8/SVneo细胞克隆形成率、增殖能力及迁移能力显著增加(P<...     

TLR4/NF-κB信号通路在激素性股骨头坏死的作用

激素性股骨头坏死（steroid-induced osteonecrosis of the femoral head, SONFH）是由于糖皮质激素的大量使用最终造成股骨头坏死的一种代谢性疾病,而SONFH的发病机制迄今仍未完全明确,存在各种假说。研究表明,巨噬细胞参与的炎症反应可能是激素性股骨头坏死发生发展的重要促发因素之一。Toll样受体4 (toll like receptor 4, TLR4)/核转录因子-κB ((nuclear factor kappa-B, NF-κB)炎症信号通路能被短期内过量或长期使用的糖皮质激素激活,致NF-κB活化,使其原有结构发生改变,继而转入细胞核启动基因表达释放出大量炎性介质,如肿瘤坏死因子-α (tumor necrosis factorα, TNF-α)、白细胞介素-1β(interleukin-1beta, IL-1β)、白细胞介素-6 (interleukin-6, IL-6)等,使破骨细胞分化增强,骨吸收增加,同时抑制成骨细胞分化和骨形成,诱发其凋亡,对骨的结构造成影响,破坏骨稳态,最终引发股骨头塌陷、坏死。本文对TLR4/NF-κ...     

High-frequency near-infrared diode laser irradiation suppresses IL-1β-induced inflammatory cytokine expression and NF-κB signaling pathways in human primary chondrocytes

Lasers in Medical Science - Osteoarthritis (OA) and rheumatoid arthritis (RA) are common inflammation-associated cartilage degenerative diseases. Recent studies have shown that low-level diode...     

What is new in liver surgery? Focus on thermoablation and the relevance of the inflammatory response

Partial liver resection is a well established treatment for patients with liver tumors. It is associated with significant morbidity and some mortality, even in high volume centers. Less invasive modalities are currently available and deserve a place in the armamentarium of liver surgeons. This review discusses the role of thermoablation as a treatment modality for liver tumors. The minimal invasive possibility of percutaneous ablation is a great advantage. The limitation of ablation is the high incidence of ablation site recurrences. The inflammatory response is associated with the initiation of cancer at sites of chronic inflammation. There is also accumulating evidence that progression of tumors is also enhanced by an ongoing inflammatory response. The common denominator probably is angiogenesis. The paper supplies data about the interrelationship between inflammation, angiogenesis and tumor growth. Ablation of liver tumors is associated with a low inflammatory response, especially if it is performed percutaneous and thus deserves to be considered in patients with liver tumors.