Lipopolysaccharide prevents valproic acid-induced apoptosis via activation of nuclear factor-κB and inhibition of p53 activation

H3K27 tri-demethylase JMJD3 inhibits macrophage apoptosis by promoting ADORA2A in lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI) is a common critical disease, which is characterized by an uncontrolled, acute inflammatory response, diffuse lung damage and ultimately directly deteriorates into acute respiratory distress syndrome. The number of pro-inflammatory macrophages is related to the severity of ALI. Up-regulation of lipopolysaccharide (LPS)-activated macrophage apoptosis can reduce the pro-inflammatory reactions. Jumonji domain-containing protein D3 (JMJD3)-mediated histone 3 lysine 27 trimethylation (H3K27me3) demethylation may promote the pro-inflammatory response of macrophages under LPS stimulation. However, the mechanism of JMJD3 affecting macrophage apoptosis is still not clear. To explore this gap in knowledge, the ALI mice model with intratracheal administration of LPS and RAW264.7 cells with LPS stimulation were used as in vivo and in vitro experiments. The expression of JMJD3 and H3K27me3 and their cellular localization were analysed in lung tissue. Apoptosis was evaluated using TUNEL staining and flow cytometry. Expression of H3K27me3, ADORA2A and C/EBPβ were compared among different treatments and chromatin immunoprecipitation was performed to investigate the regulatory relationship. Our study showed that JMJD3 expression was upregulated in LPS-induced ALI mice and RAW264.7 cells. JMJD3-indued H3K27me3 demethylation inhibited caspase-3 cleavage by upregulating ADORA2A to decrease LPS-stimulated macrophage apoptosis and promoted the inflammatory reaction. This H3K27me3 demethylation also increased C/EBPβ expression, which may enhance ADORA2A expression further. Besides, inhibiting ADORA2A can also promote LPS-limited macrophage apoptosis. Moreover, the inhibition of JMJD3 in vivo and in vitro relieved the inhibition of macrophage apoptosis thus leading to the resolution of the inflammation. JMJD3 might inhibit macrophage apoptosis by promoting ADORA2A expression in LPS-induced ALI.

Lipopolysaccharide-induced DNA damage response activates nuclear factor κB signalling pathway via GATA4 in dental pulp cells

AIM

To investigate the role of GATA-binding protein 4 (GATA4) in the inflammatory response induced by DNA double-strand breaks (DSBs) in human dental pulp cells (hDPCs).

METHODOLOGY

Lipopolysaccharide (LPS) was used for stimulating inflammation in dental pulp tissue in vivo and hDPCs in vitro. Expression levels of GATA4 and γ-H2A.X (a marker for DSBs) were detected at different stages of pulpitis in a rat model and human pulp tissues by immunohistochemistry. Real-time quantitative polymerase chain reaction and Western blot were performed to assess expression of GATA4 and γ-H2A.X and the activation of nuclear factor κB (NF-κB) in hDPCs stimulated by LPS. The comet assay was used for detecting the extent of DSBs in hDPCs. Immunocytochemistry and Western blot were utilized to evaluate expression of γ-H2A.X and GATA4 and activation of NF-κB in hDPCs pre-treated with inhibitors of DNA damage response or transfected with GATA4 small interfering RNA before the treatment of LPS. Data were analysed statistically using one-way anova or Kruskal-Wallis tests.

RESULTS

The expression of GATA4 and activation of DNA damage response and NF-κB in inflamed pulp tissue and LPS-treated hDPCs were identified. Significantly decreased expression of GATA4 and significantly decreased inflammatory processes in hDPCs were demonstrated via suppression of DNA damage response (P < 0.05). In GATA4-knockdown cells, the expression of γ-H2A.X did not change, but nuclear translocation of p65 was significantly suppressed (P < 0.05) upon induction by LPS.

CONCLUSIONS

Lipopolysaccharide-induced DSBs activated the NF-κB signalling pathway in hDPCs, and GATA4 acts as a positive moderator of the progress. The involvement of GATA4 in this pathology may serve as a therapeutic target in pulpitis.

Differential induction of nuclear factor-like 2 signature genes with toll-like receptor stimulation

Inflammation is associated with production of reactive oxygen species (ROS) and results in the induction of thioredoxin (TXN) and peroxiredoxins (PRDXs) and activation of nuclear factor-like 2 (Nrf2). In this study we have used the mouse RAW 264.7 macrophage and the human THP-1 monocyte cell line to investigate the pattern of expression of three Nrf2 target genes, PRDX1, TXN reductase (TXNRD1) and heme oxygenase (HMOX1), by activation of different Toll-like receptors (TLRs). We found that, while the TLR4 agonist lipopolysaccharide (LPS) induces all three genes, the pattern of induction with agonists for TLR1/2, TLR3, TLR2/6 and TLR7/8 differs depending on the gene and the cell line. In all cases, the extent of induction was HMOX1>TXNRD1>PRDX1. Since LPS was a good inducer of all genes in both cell lines, we studied the mechanisms mediating LPS induction of the three genes using mouse RAW 264.7 cells. To assess the role of ROS we used the antioxidant N-acetylcysteine (NAC). Only LPS induction of HMOX1 was inhibited by NAC while that of TXNRD1 and PRDX1 was unaffected. These three genes were also induced by phorbol myristate acetate (PMA), a ROS-inducer acting by activation of protein kinase C (PKC). The protein kinase inhibitor staurosporine inhibited the induction of all three genes by PMA but only that of HMOX1 by LPS. This indicates that activation of these genes by inflammatory agents is regulated by different mechanisms involving either ROS or protein kinases, or both.

Exploring the Drug Repurposing Versatility of Valproic Acid as a Multifunctional Regulator of Innate and Adaptive Immune Cells

Valproic acid (VPA) is widely recognized for its use in the control of epilepsy and other neurological disorders in the past 50 years. Recent evidence has shown the potential of VPA in the control of certain cancers, owed in part to its role in modulating epigenetic changes through the inhibition of histone deacetylases, affecting the expression of genes involved in the cell cycle, differentiation, and apoptosis. The direct impact of VPA in cells of the immune system has only been explored recently. In this review, we discuss the effects of VPA in the suppression of some activation mechanisms in several immune cells that lead to an anti-inflammatory response. As expected, immune cells are not exempt from the effect of VPA, as it also affects the expression of genes of the cell cycle and apoptosis through epigenetic modifications. In addition to inhibiting histone deacetylases, VPA promotes RNA interference, activates histone methyltransferases, or represses the activation of transcription factors. However, during the infectious process, the effectiveness of VPA is subject to the biological nature of the pathogen and the associated immune response; this is because VPA can promote the control or the progression of the infection. Due to its various effects, VPA is a promising alternative for the control of autoimmune diseases and hypersensitivity and needs to be further explored.

Valproic acid increases NF-κB transcriptional activation despite decreasing DNA binding ability in P19 cells, which may play a role in VPA-initiated teratogenesis

The nuclear factor-kappa B (NF-κB) family of transcription factors regulate gene expression in response to diverse stimuli. We previously demonstrated that valproic acid (VPA) exposure in utero decreases total cellular protein expression of the NF-κB subunit p65 in CD-1 mouse embryos with a neural tube defect but not in phenotypically normal littermates. This study evaluated p65 mRNA and protein expression in P19 cells and determined the impact on DNA binding ability and activity. Exposure to 5mM VPA decreased p65 mRNA and total cellular protein expression however, nuclear p65 protein expression was unchanged. VPA reduced NF-κB DNA binding and nuclear protein of the p65 DNA-binding partner, p50. NF-κB transcriptional activity was increased with VPA alone, despite decreased phosphorylation of p65 at Ser276, and when combined with tissue necrosis factor α. These results demonstrate that VPA increases NF-κB transcriptional activity despite decreasing DNA binding, which may play a role in VPA-initiated teratogenesis.

Lipopolysaccharide induces ICAM-1 expression via a c-Src/NADPH oxidase/ROS-dependent NF-κB pathway in human pulmonary alveolar epithelial cells

Upregulation of intercellular adhesion molecule-1 (ICAM-1) is frequently implicated in lung inflammation. Lipopolysaccharide (LPS) has been shown to play a key role in inflammation via adhesion molecule induction and then causes lung injury. However, the mechanisms underlying LPS-induced ICAM-1 expression in human pulmonary alveolar epithelial cells (HPAEpiCs) remain unclear. We showed that LPS induced ICAM-1 expression in HPAEpiCs, revealed by Western blotting, RT-PCR, real-time PCR, and promoter assay. Pretreatment with the inhibitor of c-Src (protein phosphatase-1, PP1), reactive oxygen species (ROS) (Edaravone), NADPH oxidase (apocynin and diphenyleneiodonium chloride), EGFR (AG1478), PDGFR (AG1296), phosphatidylinositol-3-kinase (PI3K) (LY294002), MEK1/2 (U0126), or NF-κB (Bay11-7082) and transfection with siRNAs of c-Src, EGFR, PDGFR, Akt, p47 phox, Nox2, Nox4, p42, and p65 markedly reduced LPS-induced ICAM-1 expression and monocyte adherence to HPAEpiCs challenged with LPS. In addition, we established that LPS stimulated phosphorylation of c-Src, EGFR, PDGFR, Akt, or p65, which was inhibited by pretreatment with their respective inhibitors. LPS induced Toll-like receptor 4 (TLR4), MyD88, TNF receptor-associated factor 6 (TRAF6), c-Src, p47 phox, and Rac1 complex formation 2, which was attenuated by transfection with c-Src or TRAF6 siRNA. Furthermore, LPS markedly enhanced NADPH oxidase activation and intracellular ROS generation, which were inhibited by PP1. We established that LPS induced p42/p44 MAPK activation via a c-Src/NADPH oxidase/ROS/EGFR, PDGFR/PI3K/Akt-dependent pathway in these cells. Finally, we observed that LPS significantly enhanced NF-κB and IκBα phosphorylation, NF-κB translocation, and NF-κB promoter activity, which were inhibited by PP1, Edaravone, apocynin, diphenyleneiodonium chloride, AG1478, AG1296, LY294002 , or U0126. These results demonstrated that LPS induces p42/p44 MAPK activation mediated through the TLR4/MyD88/TRAF6/c-Src/NADPH oxidase/ROS/EGFR, PDGFR/PI3K/Akt pathway, which in turn initiates the activation of NF-κB and ultimately induces ICAM-1 expression in HPAEpiCs.

Therapeutic Approaches to Histone Reprogramming in Retinal Degeneration

Recent data have revealed epigenetic derangements and subsequent chromatin remodeling as a potent biologic switch for chronic inflammation and cell survival which are important therapeutic targets in the pathogenesis of several retinal degenerations. Histone deacetylases (HDACs) are a major component of this system and serve as a unique control of the chromatin remodeling process. With a multitude of targeted HDAC inhibitors now available, their use in both basic science and clinical studies has widened substantially. In the field of ocular biology, there are data to suggest that HDAC inhibition may suppress neovascularization and may be a possible treatment for retinitis pigmentosa and dry age-related macular degeneration (AMD). However, the effects of these inhibitors on cell survival and chemokine expression in the chorioretinal tissues remain very unclear. Here, we review the multifaceted biology of HDAC activity and pharmacologic inhibition while offering further insight into the importance of this epigenetic pathway in retinal degenerations. Our laboratory investigations aim to open translational avenues to advance dry AMD therapeutics while exploring the role of acetylation on inflammatory gene expression in the aging and degenerating retina.

NOD1, a new player in cardiac function and calcium handling

AIMS

Inflammation is a significant contributor to cardiovascular disease and its complications; however, whether the myocardial inflammatory response is harmonized after cardiac injury remains to be determined. Some receptors of the innate immune system, including the nucleotide-binding oligomerization domain-like receptors (NLRs), play key roles in the host response after cardiac damage. Nucleotide-binding oligomerization domain containing 1 (NOD1), a member of the NLR family, is expressed in the heart, but its functional role has not been elucidated. We determine whether selective NOD1 activation modulates cardiac function and Ca(2+) signalling.

METHODS AND RESULTS

Mice were treated for 3 days with the selective NOD1 agonist C12-iE-DAP (iE-DAP), and cardiac function and Ca(2+) cycling were assessed. We found that iE-DAP treatment resulted in cardiac dysfunction, measured as a decrease in ejection fraction and fractional shortening. Cardiomyocytes isolated from iE-DAP-treated mice displayed a decrease in the L-type Ca(2+) current, [Ca(2+)]i transients and Ca(2+) load, and decreased expression of phospho-phospholamban, sarcoplasmic reticulum-ATPase, and Na(+)-Ca(2+) exchanger. Furthermore, iE-DAP prompted 'diastolic Ca(2+) leak' in cardiomyocytes, resulting from increased Ca(2+) spark frequency and RyR2 over-phosphorylation. Importantly, these iE-DAP-induced changes in Ca(2+) cycling were lost in NOD1(-/-) mice, indicating that iE-DAP exerts its actions through NOD1. Co-treatment of mice with iE-DAP and a selective inhibitor of NF-κB (BAY11-7082) prevented cardiac dysfunction and Ca(2+) handling impairment induced by iE-DAP.

CONCLUSION

Our data provide the first evidence that NOD1 activation induces cardiac dysfunction associated with excitation-contraction coupling impairment through NF-κB activation and uncover a new pro-inflammatory player in the regulation of cardiovascular function.

New insights into the molecular and epigenetic effects of antitumor Pt(IV)-valproic acid conjugates in human ovarian cancer cells

Substitutionally inert Pt(IV) prodrugs, combining bioactive axial ligands with Pt(IV) derivatives of antitumor Pt(II) compounds, represent a new generation of anticancer drugs. The rationale behind these prodrugs is to release, by reductive elimination inside the cancer cell, an active Pt(II) drug which binds nuclear DNA as well as bioactive ligands that may potentiate toxic effects of the Pt(II) drugs by an independent pathway. Platinum prodrugs, such as Pt(IV) derivatives of cisplatin containing axial valproic acid (VPA) ligands, destroy cancer cells with greater efficacy than conventional cisplatin. These axial ligands were chosen because VPA inhibits histone deacetylase (HDAC) activity, thereby decondensing chromatin and subsequently increasing the accessibility of DNA within chromatin to DNA-binding agents. We examined the mechanism of cytotoxic activity of Pt(IV) derivatives of cisplatin with VPA axial ligands. Particular attention was paid to the role of the VPA ligand in these Pt(IV) prodrugs in the mechanism underlying their toxic effects in human ovarian tumor cells. We demonstrate that (i) treatment of the cells with these prodrugs resulted in enhanced histone H3 acetylation and decondensation of heterochromatin markedly more effectively than free VPA; (ii) of the total Pt inside the cells, a considerably higher fraction of Pt from the Pt(IV)-VPA conjugates is bound to DNA than from the conjugates with biologically inactive ligands. The results indicate that the enhanced cytotoxicity of the Pt(IV)-VPA conjugates is a consequence of several processes involving enhanced cellular accumulation, downregulation of HDACs and yet other biochemical processes (not involving HDACs) which may potentiate antitumor effects.

Liver immune responses to inflammatory stimuli in a diet-induced obesity model of zebrafish

Obesity- and metabolic syndrome-related diseases are becoming important medical challenges for the western world. Non-alcoholic fatty liver disease (NAFLD) is a manifestation of these altered conditions in the liver, and inflammation appears to be a factor that is tightly connected to its evolution. In this study, we used a diet-induced obesity approach in zebrafish (Danio rerio) based on overfeeding to analyze liver transcriptomic modulation in the disease and to determine how obesity affects the immune response against an acute inflammatory stimulus such as lipopolysaccharide (LPS). Overfed zebrafish developed an obese phenotype, showed signs of liver steatosis, and its modulation profile resembled that observed in humans, with overexpression of tac4, col4a3, col4a5, lysyl oxidases, and genes involved in retinoid metabolism. In response to LPS, healthy fish exhibited a typical host defense reaction comparable to that which occurs in mammals, whereas there was no significant gene modulation when comparing expression in the liver of LPS-stimulated and non-stimulated obese zebrafish at the same statistical level. The stimulation of obese fish represents a double-hit to the already damaged liver and can help understand the evolution of the disease. Finally, a comparison of the differential gene activation between stimulated healthy and obese zebrafish revealed the expected difference in the metabolic state between healthy and diseased liver. The differentially modulated genes are currently being studied as putative new pathological markers in NAFLD-stimulated liver in humans.

Antitumor platinum(IV) derivatives of oxaliplatin with axial valproato ligands

We report new anticancer prodrugs, platinum(IV) derivatives of oxaliplatin conjugated with valproic acid (VPA), a well-known drug having histone deacetylase inhibitory activity. Like most platinum(IV) derivatives, the cytotoxicity of the conjugates was lower in cell culture than that of oxaliplatin, but greater than those of its Pt(IV) derivative containing biologically inactive axial ligands in several cancer cell lines. Notably, these conjugates display activity in both cisplatin sensitive- and resistant tumor cells capable of both markedly enhanced accumulation in tumor cells and acting in a dual threat manner, concurrently targeting histone deacetylase and genomic DNA. These results demonstrate the dual targeting strategy to be a valuable route to pursue in the design of platinum agents which may be more effective in cancer types that are typically resistant to therapy by conventional cisplatin. Moreover, platinum(IV) derivatives containing VPA axial ligands seem to be promising dual-targeting candidates for additional preclinical studies.

A novel mechanism for inhibition of lipopolysaccharide-induced proinflammatory cytokine production by valproic acid

The inhibitory effect of valproic acid (VPA) on lipopolysaccharide (LPS)-induced inflammatory response was studied by using mouse RAW 264.7 macrophage-like cells. VPA pretreatment attenuated LPS-induced phosphorylation of phosphatidylinositol 3-kinase (PI3K) and Akt, but not nuclear factor (NF)-κB and mitogen-activated protein kinases. VPA reduced phosphorylation of MDM2, an ubiquitin ligase and then prevented LPS-induced p53 degradation, followed by enhanced p53 expression. Moreover, p53 small interfering RNA (siRNA) abolished the inhibitory action of VPA on LPS-induced NF-κB p65 transcriptional activation and further LPS-induced tumor necrosis factor (TNF)-α and interleukin (IL)-6 production. VPA prevented LPS-induced degradation of phosphatase and tensin homologue deleted on chromosome ten (PTEN) and up-regulated the PTEN expression. Taken together, VPA was suggested to down-regulate LPS-induced NF-κB-dependent transcriptional activity via impaired PI3K/Akt/MDM2 activation and enhanced p53 expression. A detailed mechanism for inhibition of LPS-induced inflammatory response by VPA is discussed.