SC-514, a selective inhibitor of IKKβ attenuates RANKL-induced osteoclastogenesis and NF-κB activation

Trifolirhizin reduces osteoclast formation and prevents inflammatory osteolysis by inhibiting RANKL-induced activation of NF-κB and MAPK signaling pathways and ROS

Inflammatory osteolysis is often caused by the excessive activation of osteoclasts stimulated by bacterial products such as lipopolysaccharide. The natural flavonoid trifolirhizin (TRI) has anti-inflammatory properties; however, its function in inflammatory bone lysis remains unclear. This study aimed to elucidate the potential regulatory mechanisms of TRI in osteoclasts.Tartrate-resistant acid phosphatase (TRAP) staining, acid secretion assays, podosomal actin belt fluorescence staining, and bone resorption assays were used to investigate the effects of TRI on osteoclast differentiation and bone resorption. A reactive oxygen species (ROS) measurement kit was used to detect the effect of TRI on ROS levels in osteoclasts. The effects of TRI on genes and signaling pathways related to osteoclast differentiation were determined by quantitative polymerase chain reaction (qPCR) and western blotting. A mouse model of lipopolysaccharide-mediated inflammatory osteolysis was established, and the effects of TRI treatment on bone mass were observed using micro-CT and histological examination. Mechanistically, TRI reduced ROS production by inhibiting receptor activator of nuclear factor-κB ligand (RANKL)-induced activation of the nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways, and by upregulating the expression levels of the anti-ROS enzymes heme oxygenase-1 (HO-1) and catalase (CAT), which contributed to the degradation of ROS, ultimately leading to a decrease in osteoclastogenesis. TRI inhibited osteoclast formation and ameliorated lipopolysaccharide (LPS)-mediated inflammatory osteolysis. Thus, TRI may be a candidate agent for anti-inflammatory osteolysis.

A Cross-Sectional Study to Evaluate the Role of the Nuclear Factor Kappa B (Nf-κB) Pathway in Regulating the Cytokine Cascade and as a Potential Therapeutic Target in Leprosy

Pattern recognition receptors (PRRs), which are found in microorganisms but not in hosts, allow Leprae bacilli to be recognized as foreign. Several kinds of pattern recognition receptors, such as toll-like receptors (TLRs), NOD-like receptors (NLRs) and RIG-1-like receptors (RLRs), are present in the innate immune system. Sen and Baltimore (1986) discovered the transcription factor nuclear factor kappa-B (NF-B), employed by eukaryotic cells to regulate immunity, cell differentiation and proliferation. This study aimed to evaluate the role of the nuclear factor kappa B (NF-B) pathway in controlling the cytokine cascade in leprosy due to a lack of understanding of the link between cytokines and the severity of leprosy. Clinically suspected Hansen's patients were analysed for 4 years. Newly diagnosed leprosy patients were considered to have leprosy disease control (LDC). The cases with active or new lesions and an increase in BI by at least 2+, 12 months after completion of MDT were considered leprosy disease relapse (LDR) cases. Age- and sex-matched healthy individuals served as our control group (HC). An ELISA was performed to measure the concentration of five human cytokines. By qRT-PCR, the quantitative expression of receptor genes (NOD1 and NOD2), cytokine genes and the expression of the transcription factor NFκβ were evaluated. This was followed by a transcription factor NFκβ assay to see its expression in the monocytes of study subjects. Nuclear factor NF-κβ was found to have a pronounced response in monocytes of HC and LDC patients and LDR cases when treated with NOD1 and NOD2 ligands. Our study concludes that the NF-kB pathway is involved in the induction and regulation of the cytokine cascade that contributes to chronic inflammation in leprosy.

Periplogenin attenuates LPS-mediated inflammatory osteolysis through the suppression of osteoclastogenesis via reducing the NF-κB and MAPK signaling pathways

The key target for treating inflammatory osteolysis is osteoclasts. In an inflammatory environment, osteoclast differentiation increases, and bone resorption is enhanced. Periplogenin (Ppg) is a traditional Chinese medicine. It has anti-inflammatory and antitumor effects, but its impact on inflammatory osteolysis is unknown. This study found that Ppg prevented LPS-induced skull osteolysis by inhibiting the expression of inflammatory cytokines and osteoclast production. In vitro, Ppg blocked the RANKL-induced generation of osteoclasts, the development of pseudopodia bands, and bone resorption. Ppg also attenuated the expression of NFATc1, c-Fos, CTSK, and Atp6v0d2 proteins by inhibiting the NFATc1 signaling pathway. In addition, Ppg inhibited the expression of osteoclast-specific genes, including NFATc1, c-Fos, CTSK, Atp6v0d2, and Mmp9. Moreover, Ppg also inhibited NF-κB and MAPK pathways. In vivo, Ppg reduced the number of osteoclasts on the surface of the bone and suppressed LPS-induced osteolysis of the skull. These outcomes suggest that Ppg can serve as a new alternative therapy for treating inflammatory osteolysis by inhibiting inflammation and osteoclasts.

CGK733 alleviates ovariectomy-induced bone loss through blocking RANKL-mediated Ca2+ oscillations and NF-κB/MAPK signaling pathways

Osteoporosis is a prevalent systemic metabolic disease in modern society, in which patients often suffer from bone loss due to over-activation of osteoclasts. Currently, amelioration of bone loss through modulation of osteoclast activity is a major therapeutic strategy. Ataxia telangiectasia mutated (ATM) inhibitor CGK733 (CG) was reported to have a sensitizing impact in treating malignancies. However, its effect on osteoporosis remains unclear. In this study, we investigated the effects of CG on osteoclast differentiation and function, as well as the therapeutic effects of CG on osteoporosis. Our study found that CG inhibits osteoclast differentiation and function. We further found that CG inhibits the activation of NFATc1 and ultimately osteoclast formation by inhibiting RANKL-mediated Ca2+ oscillation and the NF-κB/MAPK signaling pathway. Next, we constructed an ovariectomized mouse model and demonstrated that CG improved bone loss in ovariectomized mice. Therefore, CG may be a potential drug for the prevention and treatment of osteoporosis.

Antidementia medication acetylcholinesterase inhibitors have therapeutic benefits on osteoporotic bone by attenuating osteoclastogenesis and bone resorption

This study was designed to determine whether the use of acetylcholinesterase inhibitors (AChEIs), a group of drugs that stimulate acetylcholine receptors and are used to treat Alzheimer's disease (AD), is associated with osteoporosis protection and inhibition of osteoclast differentiation and function. Firstly, we examined the effects of AChEIs on RANKL-induced osteoclast differentiation and function with osteoclastogenesis and bone resorption assays. Next, we investigated the impacts of AChEIs on RANKL-induced nuclear factor κB and NFATc1 activation and expression of osteoclast marker proteins CA-2, CTSK and NFATc1, and dissected the MAPK signaling in osteoclasts in vitro by using luciferase assay and Western blot. Finally, we assessed the in vivo efficacy of AChEIs using an ovariectomy-induced osteoporosis mouse model, which was analyzed using microcomputed tomography, in vivo osteoclast and osteoblast parameters were assessed using histomorphometry. We found that Donepezil and Rivastigmine inhibited RANKL-induced osteoclastogenesis and impaired osteoclastic bone resorption. Moreover, AChEIs reduced the RANKL-induced transcription of Nfatc1, and expression of osteoclast marker genes to varying degrees (mainly Donepezil and Rivastigmine but not Galantamine). Furthermore, AChEIs variably inhibited RANKL-induced MAPK signaling accompanied by downregulation of AChE transcription. Finally, AChEIs protected against OVX-induced bone loss mainly by inhibiting osteoclast activity. Taken together, AChEIs (mainly Donepezil and Rivastigmine) exerted a positive effect on bone protection by inhibiting osteoclast function through MAPK and NFATc1 signaling pathways through downregulating AChE. Our findings have important clinical implications that elderly patients with dementia who are at risk of developing osteoporosis may potentially benefit from therapy with the AChEI drugs. Our study may influence drug choice in those patients with both AD and osteoporosis.

MicroRNA-146a negatively regulates inflammation via the IRAK1/TRAF6/NF-κB signaling pathway in dry eye

Inflammation is a key factor in the pathogenesis of dry eye disease (DED). We aimed to investigate the role of microRNA-146a (miR-146a) in regulating corneal inflammation in a mouse model of benzalkonium chloride (BAC)-induced dry eye and the TNF-α-induced NF-κB signaling pathway in human corneal epithelial cells (HCECs). A mouse model of dry eye was established by administering with BAC to BALB/c mice, and the expression of TNF-α, IL-1β, IL-6, IL-8, cyclooxygenase 2 (COX2), interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor-associated factor 6 (TRAF6) in the corneas of dry eye model mice was significantly increased; this was accompanied by the upregulation of miR-146a and activation of the NF-κB pathway. In vitro, TNF-α induced miR-146a expression in HCECs, while the NF-κB inhibitor SC-514 reduced the expression of miR-146a. Overexpression of miR-146a decreased the expression of IRAK1 and TRAF6, which have been identified as targets of miR-146a. Furthermore, overexpression of miR-146a suppressed NF-κB p65 translocation from the cytoplasm to the nucleus. Moreover, overexpression of miR-146a attenuated the TNF-α-induced expression of IL-6, IL-8, COX2 and intercellular adhesion molecule 1 (ICAM1), while inhibition of miR-146a exerted the opposite effect. Our results suggest that miR-146a mediates the inflammatory response in DED. MiR-146a negatively regulates inflammation in HCECs through the IRAK1/TRAF6/NF-κB pathway, and this may serve as a potential therapeutic approach for the treatment of DED.

An ankylosing spondylitis risk variant alters osteoclast differentiation

OBJECTIVE

To explore whether the variants in non-MHC proteasome gene is associated with ankylosing spondylitis and explain the role of the variant in the disease.

METHODS

Case-control analysis to identify ankylosing spondylitis predisposition genes; dual-luciferase reporter assay, immunoblot analysis and osteoclastogenesis assays to detect the function of the positive variant. Affected individuals was diagnosed according to the modified New York Criteria by at least two experienced rheumatologists, and rechecked by another rheumatologist.

RESULTS

The study included 1037 AS patients and 1014 no rheumatic and arthritis disease controls. The main age of AS onset is between 16 and 35 years old. HLA-B27-positive subjects comprised 90.0% of patients. A nonsynonymous SNP rs12717 in proteasome gene PSMB1 significantly associated with ankylosing spondylitis. Individuals with CC genotype had a higher onset risk compared with those with GG/GC genotypes (OR = 1.89, p= 0.0047). We also discovered that PSMB1 regulates the receptor activator of nuclear factor-κB (RANK)/RANK ligand (RANKL) signalling pathway and the disease-associated variant PSMB1-Pro11 significantly inhibits RANKL-induced NF-κB pathway in osteoclast differentiation via the degradation of IKK-β compared with PSMB1-Ala11. RANKL induced osteoclast differentiation was significantly lower in primary monocyte osteoclast precursor from individuals with genotype PSMB131C/31C compared with individuals with genotype PSMB131G/31G.

CONCLUSIONS

These results reveal a novel understanding of the bone formation and reabsorbing imbalance in AS. The new bone formation phenotype can be attributed to the inhibition of osteoclast differentiation by a more functional PSMB1 gene.

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

Restraint upon Embryonic Metatarsal Ex Vivo Growth by Hydrogel Reveals Interaction between Quasi-Static Load and the mTOR Pathway

Mechanical cues play a vital role in limb skeletal development, yet their influence and underpinning mechanisms in the regulation of endochondral ossification (EO) processes are incompletely defined. Furthermore, interactions between endochondral growth and mechanics and the mTOR/NF-ĸB pathways are yet to be explored. An appreciation of how mechanical cues regulate EO would also clearly be beneficial in the context of fracture healing and bone diseases, where these processes are recapitulated. The study herein addresses the hypothesis that the mTOR/NF-ĸB pathways interact with mechanics to control endochondral growth. To test this, murine embryonic metatarsals were incubated ex vivo in a hydrogel, allowing for the effects of quasi-static loading on longitudinal growth to be assessed. The results showed significant restriction of metatarsal growth under quasi-static loading during a 14-day period and concentration-dependent sensitivity to hydrogel-related restriction. This study also showed that hydrogel-treated metatarsals retain their viability and do not present with increased apoptosis. Metatarsals exhibited reversal of the growth-restriction when co-incubated with mTOR compounds, whilst it was found that these compounds showed no effects under basal culture conditions. Transcriptional changes linked to endochondral growth were assessed and downregulation of Col2 and Acan was observed in hydrogel-treated metatarsi at day 7. Furthermore, cell cycle analyses confirmed the presence of chondrocytes exhibiting S-G2/M arrest. These data indicate that quasi-static load provokes chondrocyte cell cycle arrest, which is partly overcome by mTOR, with a less marked interaction for NF-ĸB regulators.

D(-)-salicin inhibits RANKL-induced osteoclast differentiation and function in vitro

Osteoporosis is a disease, which causes huge economic and social burden. Using natural compound to treat such disease is beneficial for the fewer side effects and effectiveness. D-(-)-salicin (DSA) is a component extracted from the bark of Populus and Salix species. In our research, we discovered that DSA suppressed RANKL-induced differentiation of osteoclast in vitro in a dose-dependent manner. It was also found that the mineral resorbing activity by osteoclasts was depressed via DSA. For the mechanism, we confirmed the inhibitory effect, by which DSA suppressed osteoclast formation and function, was through the inhibition of ROS signaling, MAPK and NF-κB cascades. DSA also suppressed the expression and activity of NFATc1. Therefore, by inhibiting the ROS production, MAPK and NF-κB signal cascade, DSA inhibited the osteoclast differentiation and function in vitro.

Small molecule binding to inhibitor of nuclear factor kappa-B kinase subunit beta in an ATP non-competitive manner

Inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ) is a key regulator of the cannonical NF-κB pathway. IKKβ has been validated as a drug target for pathological conditions, which include chronic inflammatory diseases and cancer. Pharmacological studies revealed that chronic administration of ATP-competitive IKKβ inhibitors resulted in unexpected toxicity. We previously reported the discovery of 13-197 as a non-toxic IKKβ inhibitor that reduced tumor growth. Here, we show that 13-197 inhibits IKKβ in a ATP non-competitive manner and an allosteric pocket at the interface of the kinase and ubiquitin like domains was identified as the potential binding site.

Single Crystal X-Ray Structure for the Disordered Two Independent Molecules of Novel Isoflavone: Synthesis, Hirshfeld Surface Analysis, Inhibition and Docking Studies on IKKβ of 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6,7-dimethoxy-4H-chromen-4-one

The structure of the isoflavone compound, 3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-6,7-dimethoxy-4H-chromen-4-one (5), was elucidated by 2D-NMR spectra, mass spectrum and single crystal X-ray crystallography. Compound 5, C19H16O6, was crystallized in the monoclinic space group P21/c with the cell parameters; a = 12.0654(5) Å, b =11.0666(5) Å, c = 23.9550(11) Å, β = 101.3757(16)°, V = 3135.7(2) Å3, and Z = 8. The asymmetric unit of compound 5 consists of two independent molecules 5I and 5II. Both molecules exhibit the disorder of each methylene group present in their 1,4-dioxane rings with relative occupancies of 0.599(10) (5I) and 0.812(9) (5II) for the major component A, and 0.401(10) (5I) and 0.188(9) (5II) for the minor component B, respectively. Each independent molecule revealed remarkable discrepancies in bond lengths, bond angles and dihedral angles in the disordered regions of 1,4-dioxane rings. The common feature of the molecules 5I and 5II are a chromone ring and a benzodioxin ring, which are more tilted towards each other in 5I than in 5II. An additional difference between the molecules is seen in the relative disposition of two methoxy substituents. In the crystal, the molecule 5II forms inversion dimers which are linked into chains along an a-axis direction by intermolecular C–H⋯O interactions. Additional C–H⋯O hydrogen bonds connected the molecules 5I and 5II each other to form a three-dimensional network. Hirshfeld surface analysis evaluated the relative intermolecular interactions which contribute to each crystal structure 5I and 5II. Western blot analysis demonstrated that compound 5 inhibited the TNFα-induced phosphorylation of IKKα/β, resulting in attenuating further downstream NF-κB signaling. A molecular docking study predicted the possible binding of compound 5 to the active site of IKKβ. Compound 5 showed an inhibitory effect on the clonogenicity of HCT116 human colon cancer cells. These results suggest that compound 5 can be used as a platform for the development of an anti-cancer agent targeting IKKα/β.

Mycobacterium tuberculosis YrbE3A Promotes Host Innate Immune Response by Targeting NF-κB/JNK Signaling

Mycobacterium tuberculosis is considered a successful pathogen with multiple strategies to undermine host immunity. The YrbE3A is encoded by Rv1964 within the RD15 region present in the genome of Mtb, but missing in M. bovis, M. bovis BCG (Pasteur) strain, and M. smegmatis (Ms). However, little is known about its function. In this study, the YrbE3A gene was cloned into pMV261 and expressed in Ms and BCG, while the strains with the vector served as the controls. The YrbE3A was expressed on the mycobacterial membrane, and the purified protein could stimulate RAW264.7 cells to produce IL-6. Furthermore, the effect of the recombinant strains on cytokine secretion by RAW264.7 was confirmed, which varied with the host strains. Ms_YrbE3A increased significantly higher levels of TNF-α and IL-6 than did Ms_vec, while BCG_YrbE3A enhanced higher TNF-α than BCG_vec. The pathways associated with NF-κB p65 and MAPK p38/JNK, other than Erk1/2, regulated this process. In addition, mice were infected with Ms_YrbE3A and Ms-vec and were kinetically examined. Compared to Ms-vec, Ms_YrbE3A induced more serious inflammatory damage, higher levels of TNF-α and IL-6, higher numbers of lymphocytes, neutrophils, and monocytes in a time-dependent way, but lower lung bacterial load in lung. These findings may contribute to a better understanding of Mtb pathogenesis.

Fumitremorgin C Attenuates Osteoclast Formation and Function via Suppressing RANKL-Induced Signaling Pathways

Excessive bone resorption conducted by osteoclasts is considered as the main cause of osteoclast-related bone diseases such as osteoporosis. Therefore, the suppression of excessive osteoclast formation and function is one of the strategies to treat osteoclast-related bone diseases. Fumitremorgin C (Fum) is a mycotoxin extracted from Aspergillus fumigatus. It has been shown to have extensive pharmacological properties, but its role in the treatment of osteoclast-related bone diseases remains unclear. In this study, we aim to find out whether Fum can inhibit the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation and function. The results showed that Fum could significantly attenuate osteoclast formation and function at concentrations from 2.5 to 10 µM. The protein expression of bone resorption factors such as NFATc1, cathepsin K, V-ATPase-d2, and c-Fos was suppressed with the treatment of Fum at a concentration of 10 µM. In addition, Fum was also shown to suppress the activity of NF-κB, intracellular reactive oxygen species level, and MAPK pathway. Taken together, the present study showed that Fum could attenuate the formation and function of osteoclast via suppressing RANKL-induced signaling pathways, suggesting that Fum might be a potential novel drug in the treatment of osteoclast-related bone diseases.

An ultrasensitive fiveplex activity assay for cellular kinases

Protein kinases are enzymes whose abundance, protein-protein interactions, and posttranslational modifications together determine net signaling activity in cells. Large-scale data on cellular kinase activity are limited, because existing assays are cumbersome, poorly sensitive, low throughput, and restricted to measuring one kinase at a time. Here, we surmount the conventional hurdles of activity measurement with a multiplexing approach that leverages the selectivity of individual kinase-substrate pairs. We demonstrate proof of concept by designing an assay that jointly measures activity of five pleiotropic signaling kinases: Akt, IκB kinase (IKK), c-jun N-terminal kinase (JNK), mitogen-activated protein kinase (MAPK)-extracellular regulated kinase kinase (MEK), and MAPK-activated protein kinase-2 (MK2). The assay operates in a 96-well format and specifically measures endogenous kinase activation with coefficients of variation less than 20%. Multiplex tracking of kinase-substrate pairs reduces input requirements by 25-fold, with ~75 µg of cellular extract sufficient for fiveplex activity profiling. We applied the assay to monitor kinase signaling during coxsackievirus B3 infection of two different host-cell types and identified multiple differences in pathway dynamics and coordination that warrant future study. Because the Akt–IKK–JNK–MEK–MK2 pathways regulate many important cellular functions, the fiveplex assay should find applications in inflammation, environmental-stress, and cancer research.

Physical & mental activities enhance the neuroprotective effect of vinpocetine & coenzyme Q10 combination against Alzheimer & bone remodeling in rats

BACKGROUND

Alzheimer's disease is a neurodegenerative disorder characterized by a progressive decline of cognitive abilities as well as bone loss. Physical and mental activities maintain cognitive functions as well as increase bone mass by inhibiting bone resorption. VIN and CoQ10 are neuroprotective drugs that possess anti-inflammatory and antioxidant properties.

AIMS

To study the effect of PH&M on enhancing the neuroprotective role of VIN and CoQ10 combination during induction of AD model in rats besides their role against bone mass loss associated with AD model.

MAIN METHODS

Six groups of rats were received saline, AlCl₃, and PH&M daily either alone or with a combination of VIN and CoQ10 for 4 weeks. Various biochemical analyses were performed to evaluate the extent of brain damage such as ACHE, β-secretase, chitinase, Aβ, tau protein, and monoamines besides the inflammatory and antioxidant parameters. Serum levels of minerals as well as 25-OHD, PTH, RANKL, and OPG levels were measured to detect the extent of bone impairment. Also, histopathological changes were evaluated in different brain regions and hind paw.

KEY FINDINGS

VIN and CoQ10 combination together with PH&M significantly attenuated the neurodegeneration induced by AlCl₃ administration through the improvement of AD markers in brain tissue as well as oxidant and inflammatory markers. Bone resorption markers, serum minerals, and PTH levels were also normalized too.

SIGNIFICANCE

Neuroprotective drugs together with PH&M have a more protective effect against AD and bone loss rather than PH&M alone.

Discovery of new inhibitors against both NF-κB and osteoclastogenesis from in-house library with α, β-unsaturated-enone fragment

The α,β-unsaturated-enone contained natural products have been reported showing NF-κB inhibition effect. It is well known that NF-κB inhibitors can also be used to inhibit osteoclastogenesis. In a continual discovery new agents for anti-osteoclastogenesis, 8 different type compounds with α,β-unsaturated-enone fragments from our in-house library were evaluated for NF-κB inhibition and anti-osteoclastogenesis. Experimental results indicated five compounds exhibited inhibition of NF-κB signal pathway. Among them, one compound ((E)-2-(4-fluorobenzylidene)-3,4-dihydronaphthalen-1(2H)-one, 6a) simultaneously inhibits both osteoclastogenesis and NF-κB signal pathway. Furthermore, 12 compounds with similar scaffold with 6a were tested for anti-osteoclastogenesis. As a result, 9 compounds inhibited both NF-κB and osteoclastogenesis. Among them, compound 6b is the most potent inhibitor against NF-κB (IC₅₀ = 2.09 μM) and osteoclast differentiation (IC₅₀ = 0.86 μM). Further studies show that compound 6b blocks the phosphorylation of both p65 and IκBα, and suppresses NF-κB targeted gene expression without interfering MAPKs and PI3K/Akt signal transduction pathways. This study demonstrates that we can identify promising synthesized compounds with new scaffolds as therapeutic solutions against osteoclastogenesis inspired by the privileged fragment derived from natural leads.

Hepatitis B Virus Induces Autophagy to Promote its Replication by the Axis of miR-192-3p-XIAP Through NF kappa B Signaling

Hepatitis B virus (HBV) is a major risk factor for the development and progression of hepatocellular carcinoma. It has been reported that viral infection can interfere with cellular microRNA (miRNA) expression and participate in the pathogenesis of oncogenicity. Here, we report that decreasing levels of the expression of the miRNA miR-192-3p is associated with rising levels of HBV DNA in the serum of HBV patients. We revealed that HBV infection repressed the expression of miR-192-3p through hepatitis B x protein interaction with c-myc. We further showed that miR-192-3p was repressed by HBV transfection in vitro and in a mouse model, leading to cellular autophagy. Using an miRNA target prediction database miRBase, we identified X-linked inhibitor of apoptosis protein (XIAP) as a target gene of miR-192-3p and demonstrated that miR-192-3p directly targeted the XIAP 3'-untranslated region of XIAP messenger RNA. Importantly, we discovered that HBV promoted autophagy through miR-192-3p-XIAP axis and that this process was important for HBV replication in vitro and in vivo. We demonstrated that miR-192-3p functioned through the nuclear factor kappa B signaling pathway to inhibit autophagy, thereby reducing HBV replication. Conclusions: Our findings indicate that miR-192-3p is a regulator of HBV infection and may play a potential role in hepatocellular carcinoma. It may also serve as a biomarker or therapeutic target for HBV patients.

A simple and robust reporter gene assay for measuring the bioactivity of anti-RANKL therapeutic antibodies

The mechanism sketch of the reporter gene assay for the bioactivity determination of anti-RANKL mAbs.

The effects of IKK-beta inhibition on early NF-kappa-B activation and transcription of downstream genes

Small molecule approaches targeting the nuclear factor kappa B (NF-kB) pathway, a regulator of inflammation, have thus far proven unsuccessful in the clinic in part due to the complex pleiotropic nature of this network. Downstream effects depend on multiple factors including stimulus-specific temporal patterns of NF-kB activity. Despite considerable advances, genome-level impact of changes in temporal NF-kB activity caused by inhibitors and their stimulus dependency remains unexplored. This study evaluates the effects of pathway inhibitors on early NF-κB activity and downstream gene transcription. 3T3 fibroblasts were treated with SC-514, an inhibitor targeted to the NF-kB pathway, prior to stimulation with interleukin 1 beta (IL-1β) or tumor necrosis factor alpha (TNF-α). Stimulus induced NF-κB activation was quantified using immunofluorescence imaging over 90-minutes and gene expression tracked over 6-hours using mRNA TagSeq. When stimulated with IL-1β or TNF-α, significant differences (P < 0.05, two-way ANOVA), were observed in the temporal profiles of NF-κB activation between treated and untreated cells. Increasing numbers of differentially expressed genes (P < 0.01) were observed at higher inhibitor concentrations. Individual gene expression profiles varied in an inhibitor concentration and stimulus-dependent manner. The results in this study demonstrate small molecule inhibitors acting on pleiotropic pathway components can alter signal dynamics in a stimulus-dependent manner and affect gene response in complex ways.

Cajaninstilbene acid inhibits osteoporosis through suppressing osteoclast formation and RANKL-induced signaling pathways

Osteoporosis is a form of osteolytic disease caused by an imbalance in bone homeostasis, with reductions in osteoblast bone formation, and augmented osteoclast formation and resorption resulting in reduced bone mass. Cajaninstilbene acid (CSA) is a natural compound derived from pigeon pea leaves. CSA possesses beneficial properties as an anti-inflammatory, antibacterial, antihepatitis, and anticancer agent; however, its potential to modulate bone homeostasis and osteoporosis has not been studied. We observed that CSA has the ability to suppress RANKL-mediated osteoclastogenesis, osteoclast marker gene expression, and bone resorption in a dose-dependent manner. Mechanistically, it was revealed that CSA attenuates RANKL-activated NF-κB and nuclear factor of activated T-cell pathways and inhibited phosphorylation of key signaling mediators c-Fos, V-ATPase-d2, and ERK. Moreover, in osteoclasts, CSA blocked RANKL-induced ROS activity as well as calcium oscillations. We further evaluated the therapeutic effect of CSA in a preclinical mouse model and showed that in vivo treatment of ovariectomized C57BL/6 mice with CSA protects the mice from osteoporotic bone loss. Thus, this study demonstrates that osteolytic bone diseases can potentially be treated by CSA.

Targeting IKKβ in Cancer: Challenges and Opportunities for the Therapeutic Utilisation of IKKβ Inhibitors

Deregulated NF-κB signalling is implicated in the pathogenesis of numerous human inflammatory disorders and malignancies. Consequently, the NF-κB pathway has attracted attention as an attractive therapeutic target for drug discovery. As the primary, druggable mediator of canonical NF-κB signalling the IKKβ protein kinase has been the historical focus of drug development pipelines. Thousands of compounds with activity against IKKβ have been characterised, with many demonstrating promising efficacy in pre-clinical models of cancer and inflammatory disease. However, severe on-target toxicities and other safety concerns associated with systemic IKKβ inhibition have thus far prevented the clinical approval of any IKKβ inhibitors. This review will discuss the potential reasons for the lack of clinical success of IKKβ inhibitors to date, the challenges associated with their therapeutic use, realistic opportunities for their future utilisation, and the alternative strategies to inhibit NF-κB signalling that may overcome some of the limitations associated with IKKβ inhibition.

Benzo(a)pyrene in Cigarette Smoke Enhances HIV-1 Replication through NF-κB Activation via CYP-Mediated Oxidative Stress Pathway

Smoking aggravates HIV-1 pathogenesis and leads to decreased responses to antiretroviral therapy. In this study, we aim to find a molecular mechanism that would explain smoking-induced HIV-1 replication. Benzo(a)pyrene (BaP), a major carcinogen in cigarette, requires metabolic activation through cytochrome P450s (CYPs) to exert its toxic effects. We hypothesized that CYP-mediated BaP metabolism generates reactive oxygen species (ROS), and the resultant oxidative stress aggravates HIV-1 replication. As expected, we observed ~3 to 4-fold increase in HIV-1 replication in U1 cells and human primary macrophages after chronic BaP exposure. We also observed ~30-fold increase in the expression of CYP1A1 at mRNA level, ~2.5-fold increase in its enzymatic activity as well as elevated ROS and cytotoxicity in U1 cells. The knock-down of the CYP1A1 gene using siRNA and treatment with selective CYP inhibitors and antioxidants significantly reduced HIV-1 replication. Further, we observed a nuclear translocation of NF-κB subunits (p50 and p65) after chronic BaP exposure, which was reduced by treatment with siRNA and antioxidants/CYP inhibitors. Suppression of NF-κB pathway using specific NF-κB inhibitors also significantly reduced HIV-1 replication. Altogether, our results suggest that BaP enhances HIV-1 replication in macrophages by a CYP-mediated oxidative stress pathway followed by the NF-κB pathway.

Poria cocos polysaccharide attenuates RANKL-induced osteoclastogenesis by suppressing NFATc1 activity and phosphorylation of ERK and STAT3

Pathological fractures caused by osteolytic lesions seriously threaten the health of patients. Osteoclasts play important roles in bone resorption whose hyperfunction are closely related to osteolytic lesions. Studies on osteoclast differentiation and function assist in the prevention of excessive bone loss associated diseases. We screened a variety of natural compounds with anti-inflammatory effect and found that poria cocos polysaccharide (PCP) inhibited RANKL-induced osteoclast formation and bone resorption via TRAcP staining, immunofluorescence, RT-PCR and western blot. PCP down-regulated phosphorylation of STAT3, P38, ERK and JNK, and thus repressed the expression of NFAcT1 and c-Fos during RANKL-induced osteoclastogenesis. Besides, the expression of bone resorption related genes such as TRAcP and CTSK was suppressed by PCP. The results suggest that PCP can be invoked as a candidate for the treatment of osteolytic diseases by inhibiting osteoclastogenesis.

Achyranthes bidentata polysaccharide suppresses osteoclastogenesis and bone resorption via inhibiting RANKL signaling

Osteoclasts are highly differentiated multinucleated giant cells that play fundamental roles in bone resorption and in the pathogenesis of osteolytic conditions, such as osteoporosis and cancer-induced bone loss. Achyranthes bidentata polysaccharide (ABP) is a hydrophilic compound with anti-oxidation and anti-aging characteristics. The impact of ABP on RANKL-induced osteoclast formation and bone resorption has not been assessed, hence, in this study we investigated the effect of ABP on osteoclast formation and resorption in murine bone marrow derived osteoclasts. We found that ABP was able to suppress RANKL-induced osteoclast differentiation and bone resorption activity at concentrations above 6.5 µM, while demonstrating no cytotoxicity at concentrations up to 10 µM. The actions of ABP were mediated through inhibition of RANKL-induced c-Fos and NFATc1 gene and protein expression. Furthermore, we found that ABP suppressed NFATc1 transcriptional activity, and the phosphorylation of MAPK pathways induced by RANKL. Collectively, ABP attenuates RANKL-mediated osteoclast activity and signaling, and might serve as a potential therapeutic candidate for preventing bone loss related diseases.

Cyanidin Chloride inhibits ovariectomy-induced osteoporosis by suppressing RANKL-mediated osteoclastogenesis and associated signaling pathways

Over-production and activation of osteoclasts is a common feature of osteolytic conditions such as osteoporosis, tumor-associated osteolysis, and inflammatory bone erosion. Cyanidin Chloride, a subclass of anthocyanin, displays antioxidant and anti-carcinogenesis properties, but its role in osteoclastic bone resorption and osteoporosis is not well understood. In this study, we showed that Cyanidin Chloride inhibits osteoclast formation, hydroxyapatite resorption, and receptor activator of NF-κB ligand (RANKL)-induced osteoclast marker gene expression; including ctr, ctsk, and trap. Further investigation revealed that Cyanidin Chloride inhibits RANKL-induced NF-κB activation, suppresses the degradation of IκB-α and attenuates the phosphorylation of extracellular signal-regulated kinases (ERK). In addition, Cyanidin Chloride abrogated RANKL-induced calcium oscillations, the activation of nuclear factor of activated T cells calcineurin-dependent 1 (NFATc1), and the expression of c-Fos. Further, we showed that Cyanidin Chloride protects against ovariectomy-induced bone loss in vivo. Together our findings suggest that Cyanidin Chloride is capable of inhibiting osteoclast formation, hydroxyapatite resorption and RANKL-induced signal pathways in vitro and OVX-induced bone loss in vivo, and thus might have therapeutic potential for osteolytic diseases.

IκB kinase b Mediating the Downregulation of p53 and p21 by Lipopolysaccharide in Human Papillomavirus 16+ Cervical Cancer Cells

Background:

Cervical cancer is the second most common cancer of woman in the world, and human papillomavirus (HPV) infection plays an important role in the development of most of the cases. IκB kinase β (IKKβ) is a kinase-mediating nuclear factor kappa B (NF-κB) activation by phosphorylating the inhibitor of NF-κB (IκB) and is related by some diseases caused by virus infection. However, there is little known about the correlation between IKKβ and HPV infection in cervical cancer. This study aimed to investigate the expression of IKKβ protein in cervical cancer tissues and effects of inflammation on HPV positive or negative cervical cancer cells through detecting the expression of IKKβ, IκBα, p53, and p21 proteins after treated with lipopolysaccharide (LPS) to mimic bacterial infection. We also examined the effects of LPS on cervical cancer cells after blocking IKKβ with pharmacological inhibitor.

Methods:

Thirty-six matched specimens of cervical cancer and adjacent normal tissues were collected and analyzed in the study. The expression of IKKβ in the tissue specimens was determined by immunohistochemical staining. In addition, Western blot was used to detect the expression level changes of IKKβ, IκBα, p53, and p21 after LPS stimulated in the HPV16⁺ (SiHa) and HPV16⁻ (C33A) cervical cancer cell lines. Furthermore, the effects of IKKβ inhibitor SC-514 on LPS-induced expression change of these proteins were investigated.

Results:

The expression of IKKβ was higher in cervical cancer than adjacent normal tissues, and there was no significant difference between tumor differentiation, size, and invasive depth with IKKβ expression. The LPS, which increased the expression level of IKKβ protein but decreased in the IκBα, p53 and p21 proteins, was illustrated in HPV16⁺ (SiHa) but not in HPV16⁻ (C33A) cells. Moreover, IKKβ inhibitor SC-514 totally reversed the upregulation of IKKβ and downregulation of p53 and p21 by LPS in SiHa cells.

Conclusions:

IKKβ may mediate the downregulation of p53 and p21 by LPS in HPV16⁺ cervical cancer cells.

Nur77 attenuates endothelin-1 expression via downregulation of NF-κB and p38 MAPK in A549 cells and in an ARDS rat model

Acute respiratory distress syndrome (ARDS) is characterized by inflammatory injury to the alveolar and capillary barriers that results in impaired gas exchange and severe acute respiratory failure. Nuclear orphan receptor Nur77 has emerged as a regulator of gene expression in inflammation, and its role in the pathogenesis of ARDS is not clear. The objective of this study is to investigate the potential role of Nur77 and its underlying mechanism in the regulation of endothelin-1 (ET-1) expression in lipopolysaccharide (LPS)-induced A549 cells and an ARDS rat model. We demonstrate that LPS induced Nur77 expression and nuclear export in A549 cells. Overexpression of Nur77 markedly decreased basal and LPS-induced ET-1 expression in A549 cells, whereas knockdown of Nur77 increased the ET-1 expression. LPS-induced phosphorylation and nuclear translocation of NF-κB and p38 MAPK were blocked by Nur77 overexpression and augmented by Nur77 knockdown in A549 cells. In vivo, LPS induced Nur77 expression in lung in ARDS rats. Pharmacological activation of Nur77 by cytosporone B (CsnB) inhibited ET-1 expression in ARDS rats, decreased LPS-induced phosphorylation of NF-κB and p38 MAPK, and relieved lung, liver, and kidney injury. Pharmacological deactivation of Nur77 by 1,1-bis-(3'-indolyl)-1-(p-hydroxyphenyl)methane (DIM-C-pPhOH, C-DIM8) had no effect on ET-1 expression and lung injury. These results indicated that Nur77 decreases ET-1 expression by suppressing NF-κB and p38 MAPK in LPS-stimulated A549 cells in vitro, and, in an LPS-induced ARDS rat model, CsnB reduced ET-1 expression and lung injury in ARDS rats.

Amyloid β Peptide Enhances RANKL-Induced Osteoclast Activation through NF-κB, ERK, and Calcium Oscillation Signaling

Osteoporosis and Alzheimer’s disease (AD) are common chronic degenerative disorders which are strongly associated with advanced age. We have previously demonstrated that amyloid beta peptide (Aβ), one of the pathological hallmarks of AD, accumulated abnormally in osteoporotic bone specimens in addition to having an activation effect on osteoclast (Bone 2014,61:164-75). However, the underlying molecular mechanisms remain unclear. Activation of NF-κB, extracellular signal-regulated kinase (ERK) phosphorylates, and calcium oscillation signaling pathways by receptor activator NF-κB ligand (RANKL) plays a pivotal role in osteoclast activation. Targeting this signaling to modulate osteoclast function has been a promising strategy for osteoclast-related diseases. In this study, we investigated the effects of Aβ on RANKL-induced osteoclast signaling pathways in vitro. In mouse bone marrow monocytes (BMMs), Aβ exerted no effect on RANKL-induced osteoclastogenesis but promoted osteoclastic bone resorption. In molecular levels, Aβ enhanced NF-κB activity and IκB-α degradation, activated ERK phosphorylation and stimulated calcium oscillation, thus leading to upregulation of NFAT-c1 expression during osteoclast activation. Taken together, our data demonstrate that Aβ enhances RANKL-induced osteoclast activation through IκB-α degradation, ERK phosphorylation, and calcium oscillation signaling pathways and that Aβ may be a promising agent in the treatment of osteoclast-related disease such as osteoporosis.

Dihydroartemisinin, an Anti-Malaria Drug, Suppresses Estrogen Deficiency-Induced Osteoporosis, Osteoclast Formation, and RANKL-Induced Signaling Pathways

Osteoporosis is an osteolytic disease that features enhanced osteoclast formation and bone resorption. Identification of agents that can inhibit osteoclast formation and function is important for the treatment of osteoporosis. Dihydroartemisinin is a natural compound used to treat malaria but its role in osteoporosis is not known. Here, we found that dihydroartemisinin can suppress RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner. Dihydroartemisinin inhibited the expression of osteoclast marker genes such as cathepsin K, calcitonin receptor, and tartrate-resistant acid phosphatase (TRAcP). Furthermore, dihydroartemisinin inhibited RANKL-induced NF-κB and NFAT activity. In addition, using an in vivo ovariectomized mouse model, we show that dihydroartemisinin is able to reverse the bone loss caused by ovariectomy. Together, this study shows that dihydroartemisinin attenuates bone loss in ovariectomized mice through inhibiting RANKL-induced osteoclast formation and function. This indicates that dihydroartemisinin, the first physiology or medicine nobel prize discovery of China, is a potential treatment option against osteolytic bone disease. © 2015 American Society for Bone and Mineral Research.

Acanthoic acid inhibits LPS-induced inflammatory response by activating LXRα in human umbilical vein endothelial cells

Acanthoic acid, a pimaradiene diterpene isolated from Acanthopanax koreanum, has been reported to have anti-inflammatory activities. However, the effect of acanthoic acid on vascular inflammation has not been investigated. The aim of this study was to investigate the anti-inflammatory effects of acanthoic acid on lipopolysaccharide (LPS)-induced inflammatory response in human umbilical vein endothelial cells (HUVECs). The production of cytokines TNF-α and IL-8 was detected by ELISA. The expression of VCAM-1, ICAM-1, E-selectin, NF-κB and LXRα were detected by Western blotting. Adhesion of monocytes to HUVECs was detected by monocytic cell adhesion assay. The results showed that acanthoic acid dose-dependently inhibited LPS-induced TNF-α and IL-8 production. Acanthoic acid also inhibited TNF-α-induced IL-8 and IL-6 production. LPS-induced endothelial cell adhesion molecules, VCAM-1 and ICAM-1 were also inhibited by acanthoic acid. Acanthoic acid inhibited LPS-induced NF-κB activation. Furthermore, acanthoic acid dose-dependently up-regulated the expression of LXRα. In addition, our results showed that the anti-inflammatory effect of acanthoic acid was attenuated by transfection with LXRα siRNA. In conclusion, the anti-inflammatory effect of acanthoic acid is due to its ability to activate LXRα. Acanthoic acid may be a therapeutic agent for inflammatory cardiovascular disease.

Soyasaponin Ab inhibits lipopolysaccharide-induced acute lung injury in mice

Soyasaponin Ab (SA) has been reported to have anti-inflammatory effect. However, the effects of SA on lipopolysaccharide (LPS)-induced acute lung injury (ALI) have not been reported. The aim of this study was to investigate the anti-inflammatory effects of SA on LPS-induced ALI and clarify the possible mechanism. The mice were stimulated with LPS to induce ALI. SA was given 1h after LPS treatment. 12h later, lung tissues were collected to assess pathological changes and edema. Bronchoalveolar lavage fluid (BALF) was collected to assess inflammatory cytokines and nitric oxide (NO) production. In vitro, mice alveolar macrophages were used to investigate the anti-inflammatory mechanism of SA. Our results showed that SA attenuated LPS-induced lung pathological changes, edema, the expression of cycloxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in lung tissues, as well as TNF-α, IL-6, IL-1β, and NO production in mice. Meanwhile, SA up-regulated the activities of superoxide dismutase (SOD) and catalase decreased by LPS in mice. SA also inhibited LPS-induced TNF-α, IL-6 and IL-1β production as well as NF-κB activation in alveolar macrophages. Furthermore, SA could activate Liver X Receptor Alpha (LXRα) and knockdown of LXRα by RNAi abrogated the anti-inflammatory effects of SA. In conclusion, the current study demonstrated that SA exhibited protective effects against LPS-induced acute lung injury and the possible mechanism was involved in activating LXRα, thereby inhibiting LPS-induced inflammatory response.

Berberine Sulfate Attenuates Osteoclast Differentiation through RANKL Induced NF-κB and NFAT Pathways

Osteoporosis, a metabolic bone disease, is characterized by an excessive formation and activation of osteoclasts. Anti-catabolic treatment using natural compounds has been proposed as a potential therapeutic strategy against the osteoclast related osteolytic diseases. In this study, the activity of berberine sulfate (an orally available form of berberine) on osteoclast differentiation and its underlying molecular mechanisms of action were investigated. Using bone marrow macrophages (BMMs) derived osteoclast culture system, we showed that berberine sulfate at the dose of 0.25, 0.5 and 1 μM significantly inhibited the formation of osteoclasts. Notably, berberine sulfate at these doses did not affect the BMM viability. In addition, we observed that berberine sulfate inhibited the expression of osteoclast marker genes, including cathepsin K (Ctsk), nuclear factor of activated T cells cytoplasmic 1 (NFATc1), tartrate resistant acid phosphatase (TRAcP, Acp5) and Vacuolar-type H+-ATPase V0 subunit D2 (V-ATPase d2). Luciferase reporter gene assay and Western blot analysis further revealed that berberine sulfate inhibits receptor for activation of nuclear factor ligand (RANKL)-induced NF-κB and NFAT activity. Taken together, our results suggest that berberine sulfate is a natural compound potentially useful for the treatment of osteoporosis.

Protein kinase C inhibitor, GF109203X attenuates osteoclastogenesis, bone resorption and RANKL-induced NF-κB and NFAT activity

Osteolytic bone diseases are characterized by excessive osteoclast formation and activation. Protein kinase C (PKC)-dependent pathways regulate cell growth, differentiation and apoptosis in many cellular systems, and have been implicated in cancer development and osteoclast formation. A number of PKC inhibitors with anti-cancer properties have been developed, but whether they might also influence osteolysis (a common complication of bone invading cancers) is unclear. We studied the effects of the PKC inhibitor compound, GF109203X on osteoclast formation and activity, processes driven by receptor activator of NFκB ligand (RANKL). We found that GF109203X strongly and dose dependently suppresses osteoclastogenesis and osteoclast activity in RANKL-treated primary mouse bone marrow cells. Consistent with this GF109203X reduced expression of key osteoclastic genes, including cathepsin K, calcitonin receptor, tartrate resistant acid phosphatase (TRAP) and the proton pump subunit V-ATPase-d2 in RANKL-treated primary mouse bone marrow cells. Expression of these proteins is dependent upon RANKL-induced NF-κB and NFAT transcription factor actions; both were reduced in osteoclast progenitor populations by GF109203X treatment, notably NFATc1 levels. Furthermore, we showed that GF109203X inhibits RANKL-induced calcium oscillation. Together, this study shows GF109203X may block osteoclast functions, suggesting that pharmacological blockade of PKC-dependent pathways has therapeutic potential in osteolytic diseases.

Salvianolic acid B attenuates lung inflammation induced by cigarette smoke in mice

Salvianolic acid B (Sal B), a bioactive compound isolated from the Chinese herb Radix Salviae Miltiorrhizae, has been reported to exhibit anti-inflammatory and anti-oxidantive effects. The aim of this study was to investigate the protective effects of Sal B on cigarette smoke (CS)-induced acute lung inflammation. Sal B was given intraperitoneally (i.p.) to mice 1h before CS exposure daily for four consecutive days. Bronchoalveolar lavage fluid (BALF) was collected to assess the levels of inflammatory cytokines and cell counts. Lung tissues were used to analysis pathological changes, total glutathione (GSH), nuclear factor erythroid-2 related factor 2 (Nrf-2), and nuclear factor-kappa B (NF-κB) expression. The results showed that Sal B inhibited CS-induced lung pathological changes, the infiltration of inflammatory cells, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and monocyte chemoattractant protein 1 (MCP-1) productions. Sal B also up-regulated CS-induced total glutathione (GSH) production. Furthermore, Sal B was found to up-regulate Nrf-2, hemeoxygenase1 (HO1) expression and suppress CS-induced NF-κB activation. In conclusion, the current study demonstrated that Sal B exhibited a protective effect on CS-induced lung injury and the possible mechanism was involved in activating Nrf-2 and inhibiting NF-κB activation.

Switching off key signaling survival molecules to switch on the resolution of inflammation

Inflammation is a physiological response of the immune system to injury or infection but may become chronic. In general, inflammation is self-limiting and resolves by activating a termination program named resolution of inflammation. It has been argued that unresolved inflammation may be the basis of a variety of chronic inflammatory diseases. Resolution of inflammation is an active process that is fine-tuned by the production of proresolving mediators and the shutdown of intracellular signaling molecules associated with cytokine production and leukocyte survival. Apoptosis of leukocytes (especially granulocytes) is a key element in the resolution of inflammation and several signaling molecules are thought to be involved in this process. Here, we explore key signaling molecules and some mediators that are crucial regulators of leukocyte survival in vivo and that may be targeted for therapeutic purposes in the context of chronic inflammatory diseases.