Chlamydia pneumoniae disturbs cholesterol homeostasis in human THP-1 macrophages via JNK-PPARγ dependent signal transduction pathways

Chlamydia pneumoniae (C. pneumoniae) induces macrophage-derived foam cell formation, a hallmark of early atherosclerosis, in the presence of low density lipoprotein (LDL). However, its mechanisms have yet to be elucidated. In this study we examined the effects of live, heat-killed and UV-inactivated C. pneumoniae on cholesterol metabolism in THP-1-derived macrophages and the role of c-Jun NH₂ terminal kinase (JNK), which may participate in the C. pneumoniae-induced disruption of intracellular cholesterol homeostasis. We investigated whether SP600125, a special JNK inhibitor, affects the expression of peroxisome proliferator-activated receptor gamma (PPARγ), and also its downstream target genes Acyl-CoA cholesterol acyltransferase-1 (ACAT1), ATP-binding cassette transporter A1 and G1 (ABCA1/G1) in human THP-1 macrophages infected with C. pneumoniae. In this paper we found that both live and inactivated C. pneumoniae infection induce intracellular cholesterol accumulation and foam cell formation. C. pneumoniae infection increased the expression of ACAT1 and decreased the expression of ABCA1/G1, all of which facilitated cholesterol accumulation and promoted macrophage-derived foam cell formation. However, these responses were attenuated by SP600125 in a dose-dependent manner. These results demonstrate for the first time that both live and inactivated C. pneumoniae infections disturb cholesterol homeostasis in human THP-1 macrophages and C. pneumoniae infection disturbs cholesterol homeostasis via JNK-PPARγ dependent signal transduction pathways.     

Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway

Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α.     

PLK1 promotes cholesterol efflux and alleviates atherosclerosis by up-regulating ABCA1 and ABCG1 expression via the AMPK/PPARγ/LXRα pathway

Polo-like kinase 1 (PLK1) is a serine/threonine kinase involving lipid metabolism and cardiovascular disease. However, its role in atherogenesis has yet to be determined. The aim of this study was to observe the impact of PLK1 on macrophage lipid accumulation and atherosclerosis development and to explore the underlying mechanisms. We found a significant reduction of PLK1 expression in lipid-loaded macrophages and atherosclerosis model mice. Lentivirus-mediated overexpression of PLK1 promoted cholesterol efflux and inhibited lipid accumulation in THP-1 macrophage-derived foam cells. Mechanistic analysis revealed that PLK1 stimulated the phosphorylation of AMP-activated protein kinase (AMPK), leading to activation of the peroxisome proliferator-activated receptor γ (PPARγ)/liver X receptor α (LXRα) pathway and up-regulation of ATP binding cassette transporter A1 (ABCA1) and ABCG1 expression. Injection of lentiviral vector expressing PLK1 increased reverse cholesterol transport, improved plasma lipid profiles and decreased atherosclerotic lesion area in apoE-deficient mice fed a Western diet. PLK1 overexpression also facilitated AMPK and HSL phosphorylation and enhanced the expression of PPARγ, LXRα, ABCA1, ABCG1 and LPL in the aorta. In summary, these data suggest that PLK1 inhibits macrophage lipid accumulation and mitigates atherosclerosis by promoting ABCA1- and ABCG1-dependent cholesterol efflux via the AMPK/PPARγ/LXRα pathway.     

Inhibition of hepatocyte nuclear factor 1β contributes to cisplatin nephrotoxicity via regulation of nf-κb pathway

Cisplatin nephrotoxicity has been considered as serious side effect caused by cisplatin-based chemotherapy. Recent evidence indicates that renal tubular cell apoptosis and inflammation contribute to the progression of cisplatin-induced acute kidney injury (AKI). Hepatocyte nuclear factor 1β (HNF1β) has been reported to regulate the development of kidney cystogenesis, diabetic nephrotoxicity, etc However, the regulatory mechanism of HNF1β in cisplatin nephrotoxicity is largely unknown. In the present study, we examined the effects of HNF1β deficiency on the development of cisplatin-induced AKI in vitro and in vivo. HNF1β down-regulation exacerbated cisplatin-induced RPTC apoptosis by indirectly inducing NF-κB p65 phosphorylation and nuclear translocation. HNF1β knockdown C57BL/6 mice were constructed by injecting intravenously with HNF1β-interfering shRNA and PEI. The HNF1β scramble and knockdown mice were treated with 30 mg/kg cisplatin for 3 days to induce acute kidney injury. Cisplatin treatment caused increased caspase 3 cleavage and p65 phosphorylation, elevated serum urea nitrogen and creatinine, and obvious histological damage of kidney such as fractured tubules in control mice, which were enhanced in HNF1β knockdown mice. These results suggest that HNF1β may ameliorate cisplatin nephrotoxicity in vitro and in vivo, probably through regulating NF-κB signalling pathway.     

Identification of novel LncRNA targeting Smad2/PKCα signal pathway to negatively regulate malignant progression of glioblastoma

Glioblastoma multiforme (GBM) is a highly proliferative cancer with generally poor prognosis and accumulating evidence has highlighted the potential of long noncoding RNAs (lncRNAs) in the biological behaviors of glioma cells. This study focused on the identification of lncRNAs to identify targets for possible GBM prognosis. Microarray expression profiling found that 1,759 lncRNAs and 3,026 messenger RNAs (mRNAs) were upregulated, and 1932s lncRNA and 2,979 mRNAs were downregulated in GBM. Bioinformatics analysis and experimental verification identified TCONS_00020456 (TCON) for further analysis. In situ hybridization, along with immunohistochemical and receiver operating characteristic analysis determined TCON (truncation value = 3.5) as highly sensitive and specific in GBM. Grade IV patients with glioma life span with different lncRNA staining scores were analyzed. TCON staining scores below 3.5 indicated poor prognosis (life span ranging from 0.25 to 7 months), even if the glioma was surgically removed. TCON decreased significantly in GBM, and showed a coexpressional relationship with Smad2 and protein kinase C α (PKCα). Overexpression of TCON reduced the proliferation on one hand and migration, invasion on the other. TCON also inhibited epithelial–mesenchymal transformation and glioma progression in vivo, based on a nude mouse tumorigenicity assay. In addition, we predicted a potential binding site and intersection that microRNAs targeting Smad2, PKCα, and TCON through RACE pretest and bioinformatics analysis. Taken together, TCON, regarded as oncosuppressor, targeting the Smad2/PKCα axis plays a novel role in inhibiting the malignant progression of glioma. Moreover, it also demonstrates that the level of TCON can be used as a prognostic and diagnostic biomarker for GBM.     

Gene regulation and signal transduction in the ICE–CBF–COR signaling pathway during cold stress in plants

Low temperature is an abiotic stress that adversely affects the growth and production of plants. Resistance and adaptation of plants to cold stress is dependent upon the activation of molecular networks and pathways involved in signal transduction and the regulation of cold-stress related genes. Because it has numerous and complex genes, regulation factors, and pathways, research on the ICE–CBF–COR signaling pathway is the most studied and detailed, which is thought to be rather important for cold resistance of plants. In this review, we focus on the function of each member, interrelation among members, and the influence of manipulators and repressors in the ICE–CBF–COR pathway. In addition, regulation and signal transduction concerning plant hormones, circadian clock, and light are discussed. The studies presented provide a detailed picture of the ICE–CBF–COR pathway.     

TRPM2 contributes to LPS/IFNγ-induced production of nitric oxide via the p38/JNK pathway in microglia

Microglia are immune cells that maintain brain homeostasis at a resting state by surveying the environment and engulfing debris. However, in some pathological conditions, microglia can produce neurotoxic factors such as pro-inflammatory cytokines and nitric oxide (NO) that lead to neuronal degeneration. Inflammation-induced calcium (Ca²⁺) signaling is thought to underlie this abnormal activation of microglia, but the mechanisms are still obscure. We previously showed that combined application of lipopolysaccharide and interferon γ (LPS/IFNγ) induced-production of NO in microglia from wild-type (WT) mice is significantly reduced in microglia from transient receptor potential melastatin 2 (TRPM2)-knockout (KO) mice. Here, we found that LPS/IFNγ produced a late-onset Ca²⁺ signaling in WT microglia, which was abolished by application of the NADPH oxidase inhibitor diphenylene iodonium (DPI) and ML-171. In addition, pharmacological blockade or gene deletion of TRPM2 channel in microglia did not show this Ca²⁺ signaling. Furthermore, pharmacological manipulation and Western blotting revealed that Ca²⁺ mobilization, the proline-rich tyrosine kinase 2 (Pyk2), p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun NH2-terminal kinase (JNK) contributed to TRPM2-mediated LPS/IFNγ-induced activation, while the extracellular signal-regulated protein kinase (ERK) did not. These results suggest that LPS/IFNγ activates TRPM2-mediated Ca²⁺ signaling, which in turn increases downstream p38 MAPK and JNK signaling and results in increased NO production in microglia.     

Modulation of host HIF-1α activity and the tryptophan pathway contributes to the anti-Toxoplasma gondii potential of nanoparticles

BackgroundToxoplasmosis constitutes a large global burden that is further exacerbated by the shortcomings of available therapeutic options, thus underscoring the urgent need for better anti-Toxoplasma gondii therapy or strategies. Recently, we showed that the anti-parasitic action of inorganic nanoparticles (NPs) could, in part, be due to changes in redox status as well as in the parasite mitochondrial membrane potential.MethodsIn the present study, we explored the in vitro mode of action of the anti-T. gondii effect of NPs by evaluating the contributions of host cellular processes, including the tryptophan pathway and hypoxia-inducing factor activity. NPs, at concentrations ranging from 0.01 to 200 µg/ml were screened for anti-parasitic activity. Sulfadiazine and/or pyrimethamine served as positive controls.ResultsWe found that interplay among multiple host cellular processes, including HIF-1α activity, indoleamine 2,3-dioxygenase activity, and to a larger extent the tryptophan pathway, contribute to the anti-parasitic action of NPs.ConclusionTo our knowledge, this is the first study to demonstrate an effect of NPs on the tryptophan and/or kynurenine pathway.General significanceOur findings deepen our understanding of the mechanism of action of NPs and suggest that modulation of the host nutrient pool may represent a viable approach to the development of new and effective anti-parasitic agents.     

Regulatory T cells differentiation in visceral adipose tissues contributes to insulin resistance by regulating JAZF-1/PPAR-γ pathway

Regulatory T cell (Treg) activity and differentiation in visceral adipose tissue (VAT) play an important role in inhibiting chronic inflammation and insulin resistance. Whether JAZF-1 and PPAR-γ mediate VAT Treg differentiation to promote the inhibition of chronic inflammation and insulin resistance remains unclear. Here, we investigated the roles of JAZF-1 and PPAR-γ in VAT Treg differentiation, inflammation and insulin resistance using a transgenic mouse model. First, we determined that the levels of glucose and insulin biochemical markers in the JAZF-1 transgenic general feeding or high-fat groups were lower than those in the wild-type general feeding or high-fat groups. Second, the levels of CD4⁺, CD25⁺, and FOXP3⁺ differentiation markers in the JAZF-1 transgenic general feeding or high-fat groups were significantly higher than those in the wild-type groups. PPAR-γ inhibition was associated with low levels of CD4⁺, CD25⁺ and FOXP3⁺ differentiation markers. Third, the levels of TNF-α, IL-1β and IL-6 in the JAZF-1 transgenic groups were lower than those in the wild-type groups, whereas IL-10 and TGF-β levels were higher in the JAZF-1 transgenic groups than in the wild-type groups. After using the PPAR-γ inhibitor, we observed that TNF-α, IL-1β and IL-6 increased, while IL-10 and TGF-β decreased. We found that JAZF-1 and PPAR-γ could promote Tregs differentiation and regulate insulin resistance by synergistically decreasing the expression levels of TNF-α, IL-1β and IL-6 and increasing those of IL-10 and TGF-β.     

The signal transduction pathway of PKC/NF-κB/c-fos may be involved in the influence of high glucose on the cardiomyocytes of neonatal rats

Background

Our aim was to compare the effects of a Paleolithic ('Old Stone Age') diet and a diabetes diet as generally recommended on risk factors for cardiovascular disease in patients with type 2 diabetes not treated with insulin.

Methods

In a randomized cross-over study, 13 patients with type 2 diabetes, 3 women and 10 men, were instructed to eat a Paleolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; and a Diabetes diet designed in accordance with dietary guidelines during two consecutive 3-month periods. Outcome variables included changes in weight, waist circumference, serum lipids, C-reactive protein, blood pressure, glycated haemoglobin (HbA1c), and areas under the curve for plasma glucose and plasma insulin in the 75 g oral glucose tolerance test. Dietary intake was evaluated by use of 4-day weighed food records.

Results

Study participants had on average a diabetes duration of 9 years, a mean HbA1c of 6,6% units by Mono-S standard and were usually treated with metformin alone (3 subjects) or metformin in combination with a sulfonylurea (3 subjects) or a thiazolidinedione (3 subjects). Mean average dose of metformin was 1031 mg per day. Compared to the diabetes diet, the Paleolithic diet resulted in lower mean values of HbA1c (-0.4% units, p = 0.01), triacylglycerol (-0.4 mmol/L, p = 0.003), diastolic blood pressure (-4 mmHg, p = 0.03), weight (-3 kg, p = 0.01), BMI (-1 kg/m², p = 0.04) and waist circumference (-4 cm, p = 0.02), and higher mean values of high density lipoprotein cholesterol (+0.08 mmol/L, p = 0.03). The Paleolithic diet was mainly lower in cereals and dairy products, and higher in fruits, vegetables, meat and eggs, as compared with the Diabetes diet. Further, the Paleolithic diet was lower in total energy, energy density, carbohydrate, dietary glycemic load, saturated fatty acids and calcium, and higher in unsaturated fatty acids, dietary cholesterol and several vitamins. Dietary GI was slightly lower in the Paleolithic diet (GI = 50) than in the Diabetic diet (GI = 55).

Conclusion

Over a 3-month study period, a Paleolithic diet improved glycemic control and several cardiovascular risk factors compared to a Diabetes diet in patients with type 2 diabetes.

Trial registration

ClinicalTrials.gov NCT00435240.     

Radiation-induced upregulation of γ-glutamyltransferase in colon carcinoma cells is mediated through the Ras signal transduction pathway

The activity of γ-glutamyltransferase (GGT) is frequently upregulated in tumor cells after oxidative stress and may thus increase the availability of amino acids needed for biosynthesis of the antioxidant glutathione. As γ-radiation of tumor cells can result in oxidative stress, we investigated whether such treatments modulate the enzyme level in colon carcinoma CC531 cells. Radiation of these cells blocked cell proliferation, increased cellular size, initiated apoptosis and upregulated GGT activity and protein levels in a dose- and time-related manner. A slight but significant increase in the cellular level of reactive oxygen species (ROS) was found directly after radiation but appeared not to cause the GGT elevation. Thus, other mechanisms than cellular oxidative stress appear to be responsible for the radiation-induced upregulation of GGT. Stable transfection of activated Ras in a human colon carcinoma cell line expressing wild-type Ras resulted in an increased GGT level, while a reduced enzyme level was demonstrated in another cell line with constitutively activated Ras after stably transfection with a dominant-negative Ras mutant. Moreover, addition of specific protein kinase inhibitors that blocked downstream targets PI-3K and MEK1/2 of Ras, prior to and after radiation, attenuated the radiation-induced activation of GGT. These results support a role for Ras, being frequently activated after radiation, in regulating the level of GGT and also indicate that GGT participates in radioresistance.     

ifn-γ-dependent secretion of IL-10 from Th1 cells and microglia/macrophages contributes to functional recovery after spinal cord injury

Transfer of type-1 helper T-conditioned (Th1-conditioned) cells promotes functional recovery with enhanced axonal remodeling after spinal cord injury (SCI). This study explored the molecular mechanisms underlying the beneficial effects of pro-inflammatory Th1-conditioned cells after SCI. The effect of Th1-conditioned cells from interferon-γ (ifn-γ) knockout mice (ifn-γ^−/− Th1 cells) on the recovery after SCI was reduced. Transfer of Th1-conditioned cells led to the activation of microglia (MG) and macrophages (MΦs), with interleukin 10 (IL-10) upregulation. This upregulation of IL-10 was reduced when ifn-γ^−/− Th1 cells were transferred. Intrathecal neutralization of IL-10 in the spinal cord attenuated the effects of Th1-conditioned cells. Further, IL-10 is robustly secreted from Th1-conditioned cells in an ifn-γ-dependent manner. Th1-conditioned cells from interleukin 10 knockout (il-10^−/−) mice had no effects on recovery from SCI. These findings demonstrate that ifn-γ-dependent secretion of IL-10 from Th1 cells, as well as native MG/MΦs, is required for the promotion of motor recovery after SCI.     

Biology and signal transduction pathways of the Lymphotoxin-αβ/LTβR system

This review focuses on the biological functions and signalling pathways activated by Lymphotoxin α (LTα)/Lymphotoxin β (LTβ) and their receptor LTβR. Genetic mouse models shed light on crucial roles for LT/LTβR to build and to maintain the architecture of lymphoid organs and to ensure an adapted immune response against invading pathogens. However, chronic inflammation, autoimmunity, cell death or cancer development are disorders that occur when the LT/LTβR system is twisted. Biological inhibitors, such as antagonist antibodies or decoy receptors, have been developed and used in clinical trials for diseases associated to the LT/LTβR system. Recent progress in the understanding of cellular trafficking and NF-κB signalling pathways downstream of LTα/LTβ may bring new opportunities to develop therapeutics that target the pathological functions of these cytokines.     

Remifentanil preconditioning alleviating brain damage of cerebral ischemia reperfusion rats by regulating the JNK signal pathway and TNF-α/TNFR1 signal pathway

Tumor necrosis factor (TNF) and the TNF receptor (TNFR) superfamily play very important roles for cell death as well as normal immune regulation. Previous studies have strongly suggested that c-Jun N-terminal kinase (JNK) signaling pathway plays a critical role in ischemic brain injury. The purpose of this investigation was to examine the protective effect of remifentanil preconditioning in cerebral ischemia/reperfusion injury (CIR) and its possible molecular mechanism. Results showed that Remifentanil pretreatment significantly decreased the CD4⁺ and increased the CD8⁺ in cerebral tissues. Additionally, CD4⁺/CD8⁺ in CIR + Remifentanil group was markedly lower than that in CIR group. TNF-α and TNFR1 in CIR + Remifentanil group rats was found to be significant lower than that in CIR group rats. The expression levels of Cyt-c, caspase-3, caspase-9 and pJNK proteins in brain of CIR + Remifentanil group rats were found to significantly decreased compared to CIR group rats. In addition, decreased ROS level indirectly inhibit JNK activation and cell death in CIR rat receiving Remifentanil preconditioning. From current experiment results, at least two signal pathways involve into the process of Remifentanil preconditioning inhibiting cerebral damage induced by ischemia reperfusion. The inhibitory effects of Remifentanil preconditioning on the brain damage are achieved probably through blocking the activation of TNF-α/TNFR1, JNK signal transduction pathways, which implies that Remifentanil preconditioning may be a potential and effective way for prevention of the ischemic/reperfusion injury through the suppression extrinsic apoptotic signal pathway induced by TNF-α/TNFR1, JNK signal pathways. Taken together, this study indicated that regulation of the TNF-α/TNFR1 and JNK signal pathways may provide a new therapy for cerebral damage induced by ischemia and reperfusion.     

SDF-1α (CXCL12) regulation of lateral mobility contributes to activation of LFA-1 adhesion

Regulation of integrin activity enables leukocytes to circulate freely, avoiding inappropriate adhesion while maintaining the ability to adhere quickly at sites of infection or inflammation. This regulation involves at least two components: affinity for ligand and affinity-independent avidity effects such as lateral mobility. Using lymphocyte function associated antigen-1 (LFA-1) as a model, we investigated the role of integrin release from cytoskeletal motion constraints in response to the chemokine stromal cell-derived factor-1 (SDF-1α) in this process. All experiments were done in primary T cells to avoid nonphysiological activation processes often seen with the use of cell lines. We found that SDF-1α releases LFA-1 from cytoskeletal constraints as effectively as does cytochalasin D. The resultant increased diffusion is correlated with a robust increase in LFA-1-mediated adhesion under physiological shear stress. We further investigated the role of the highly conserved GFFKR sequence in the LFA-1 cytoplasmic domain. We report that the GFFKR sequence is both necessary and sufficient for regulation of the SDF-1α-triggered proadhesive release from cytoskeleton interactions. While this does not address the role of transient SDF-1α-induced conformational changes in the activation process, these results strongly suggest that any model of chemokine-induced LFA-1 activation must take into account chemokine-induced integrin lateral mobility. In addition, these results have ramifications for models of differential binding of LFA-1 to surface-bound vs. soluble intercellular adhesion molecule-1.