TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its ...downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.
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•Phosphorylation of RIPK1 by MK2 acts as survival checkpoint in TNF signaling•TNF-induced activation of MK2 results in global RIPK1 phosphorylation•MK2-mediated phosphorylation suppresses RIPK1 kinase activation and cell death•Complex-II originates from RIPK1 in complex-I as well as cytosolic RIPK1
Jaco et al. show that MK2 directly phosphorylates RIPK1 at residue S321, suppressing the cytotoxic potential of RIPK1 and acting as a checkpoint within the TNF signaling pathway.
Loss of inhibitor of apoptosis proteins (IAPs), particularly cIAP1, can promote production of tumor necrosis factor (TNF) and sensitize cancer cell lines to TNF-induced necroptosis by promoting ...formation of a death-inducing signaling complex containing receptor-interacting serine/threonine-protein kinase (RIPK) 1 and 3. To define the role of IAPs in myelopoiesis, we generated a mouse with cIAP1, cIAP2, and XIAP deleted in the myeloid lineage. Loss of cIAPs and XIAP in the myeloid lineage caused overproduction of many proinflammatory cytokines, resulting in granulocytosis and severe sterile inflammation. In vitro differentiation of macrophages from bone marrow in the absence of cIAPs and XIAP led to detectable levels of TNF and resulted in reduced numbers of mature macrophages. The cytokine production and consequent cell death caused by IAP depletion was attenuated by loss or inhibition of TNF or TNF receptor 1. The loss of RIPK1 or RIPK3, but not the RIPK3 substrate mixed lineage kinase domain-like protein, attenuated TNF secretion and thereby prevented apoptotic cell death and not necrosis. Our results demonstrate that cIAPs and XIAP together restrain RIPK1- and RIPK3-dependent cytokine production in myeloid cells to critically regulate myeloid homeostasis.
•cIAPs and XIAP negatively regulate cytokine production, including TNF to disrupt myeloid lineage differentiation.•IAPs prevent RIPK1 and RIPK3 activity to limit cytokine production prior to cell death.
Inhibitor of apoptosis (IAP) proteins cIAP1, cIAP2, and XIAP (X‐linked IAP) regulate apoptosis and cytokine receptor signalling, but their overlapping functions make it difficult to distinguish their ...individual roles. To do so, we deleted the genes for IAPs separately and in combination. While lack of any one of the IAPs produced no overt phenotype in mice, deletion of cIap1 with cIap2 or Xiap resulted in mid‐embryonic lethality. In contrast, Xiap−/−cIap2−/− mice were viable. The death of cIap2−/−cIap1−/− double mutants was rescued to birth by deletion of tumour necrosis factor (TNF) receptor 1, but not TNFR2 genes. Remarkably, hemizygosity for receptor‐interacting protein kinase 1 (Ripk1) allowed Xiap−/−cIap1−/− double mutants to survive past birth, and prolonged cIap2−/−cIap1−/− embryonic survival. Similarly, deletion of Ripk3 was able to rescue the mid‐gestation defect of cIap2−/−cIap1−/− embryos, as these embryos survived to E15.5. cIAPs are therefore required during development to limit activity of RIP kinases in the TNF receptor 1 signalling pathway.
The inhibitor of apoptosis proteins cIAP1, cIAP2, and XIAP exert overlapping functions in apoptosis and cytokine signalling. A series of single‐ and double‐knockout mice reveal an essential function of IAP proteins in preventing TNF receptor 1‐induced, RIP kinase 1‐ and 3‐dependent cell death during embryogenesis.
Smac mimetics target inhibitor of apoptosis (IAP) proteins, thereby suppressing their function to facilitate tumor cell death. Here we have evaluated the efficacy of the preclinical Smac-mimetic ...compound A and the clinical lead birinapant on breast cancer cells. Both exhibited potent in vitro activity in triple-negative breast cancer (TNBC) cells, including those from patient-derived xenograft (PDX) models. Birinapant was further studied using in vivo PDX models of TNBC and estrogen receptor-positive (ER
) breast cancer. Birinapant exhibited single agent activity in all TNBC PDX models and augmented response to docetaxel, the latter through induction of TNF. Transcriptomic analysis of TCGA datasets revealed that genes encoding mediators of Smac-mimetic-induced cell death were expressed at higher levels in TNBC compared with ER
breast cancer, resulting in a molecular signature associated with responsiveness to Smac mimetics. In addition, the cell death complex was preferentially formed in TNBCs versus ER
cells in response to Smac mimetics. Taken together, our findings provide a rationale for prospectively selecting patients whose breast tumors contain a competent death receptor signaling pathway for the further evaluation of birinapant in the clinic.
This study first investigates the preparation and characterization of titanium dioxide/reduced graphene oxide (TiO2/rGO) and then proposes the fabrication of photoanode in dye-sensitized solar cell ...(DSSC) from synthesized materials. Herein, the TiO2/rGO nanocomposites were prepared by the incorporation of hydrothermal approach and co-precipitation method from the precursors of titanium (IV) isopropoxide and graphene oxide. The fabrication of photoanode from the as-prepared TiO2/rGO nanocomposite paste was carried out using screen-printing technique. The performance of fabricated DSSCs was evaluated by current density-voltage curves and electrochemical impedance spectroscopy. The characterizations of TiO2 nanoparticles, TiO2/rGO nanocomposites, and their precursors were confirmed by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. Experimental data showed that the optimal rGO weight percentage of 0.6% in the TiO2/rGO nanocomposite material fabricated DSSC successfully with the highest values of short-circuit current density (17.65 mA/cm2) and energy conversion efficiency (7.46%), approximately increasing 24% and 25%, respectively, in comparison with the pristine TiO2 material. Characterization results indicated that the incorporated hydrothermal co-precipitation method was efficient in producing well-defined spherical TiO2 nanoparticles decorated on the rGO sheets with an average diameter of 20–25 nm. Therefore, the TiO2/rGO nanocomposites with the eco-friendly and efficient synthesis method are highly promising for manufacturing and commercializing DSSCs widely.
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•The TiO2/rGO nanocomposite material was efficiently synthesized via the incorporated hydrothermal co-precipitation method.•The TiO2/rGO nanocomposite material was used for fabricating photoanode in DSSC using the screen-printing technique.•The rGO weight percentage of 0.6% in the TiO2/rGO optimized the DSSC performance with the highest values of JSC , τn, and η.•The characterization results indicated that TiO2 nanoparticles with the diameter range of 20–25 nm were attached to the rGO.
This study performed phytochemical and bioactive assessments of the mangrove
Lumnitzera racemosa
Willd. leaves. Bioassay-guided fractionation of the methanolic extracts led to the identification of ...thirty-six compounds (
1
–
36
), their structures were elucidated using detailed NMR spectroscopic and MS analysis. The extracts, fractions, and the isolated compounds were screened for potential antioxidant and cytotoxic activities. Antioxidant assays were performed using peroxyl radical-scavenging and reducing assays, whereas cytotoxicity was measured using MTT assays in HL-60 and Hel-299 cell lines. The methanolic extract, CH
2
Cl
2
and
n
-BuOH fractions (10.0 μg/mL) exhibited potent antioxidant activity, with Trolox equivalent (TE) values of 24.94 ± 0.59, 28.34 ± 0.20, and 27.09 ± 0.37 (μM), respectively. In addition, the isolated compounds exerted cytotoxic effects in a dose-dependent manner; compounds
1
and
14
exhibited the most potent cytotoxicity in HL-60 cells, with IC
50
values of 0.15 ± 0.29 and 0.60 ± 0.16 μM, respectively. To clarify the mechanism(s) behind these cytotoxic effects, we measured the time-dependent changes in apoptotic markers including the condensation and fragmentation of nuclear chromatin, and the downregulation of p-ERK1/2, p-AKT, and c-Myc levels.
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•The polyoxygenated sterols of the Vietnamese Menella woodin were investigated.•Four new polyoxygenated steroids were isolated and structurally elucidated.•Three isolated steroids ...have shown a reduction of ROS levels in macrophages.
Four new polyoxygenated sterol derivatives (1–4) along with the compounds (5–7) previously known from other biological sources were isolated from the gorgonian Menella woodin, collected from the Vietnamese waters. Structures of 1–4 were elucidated by the detailed NMR spectroscopic and mass-spectrometric analyses as well as comparison with those reported in literature data. Compounds 1, 4, and 6 decrease the production of reactive oxygen species (ROS) by the murine macrophages of RAW 264.7 line at induction by endotoxic lipopolysaccharide (LPS) from Escherichia coli.
In this study, reduced graphene oxide with immobilized silver nanoparticles cotton fabric (Ag/rGO/cotton) was produced by the dip-coating cotton in silver immobilizing onto graphene oxide (Ag/GO) ...suspension to prepared Ag/GO/cotton material followed by the addition of vitamin C (VC) as an environmentally friendly reducing agent. The characteristics of Ag/GO and modified cotton were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscope, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy. Silver nanoparticles (AgNPs) were uniformly distributed on the surface of graphene oxide (GO) sheets with an average size of 10–15 nm, while the cotton surface was evenly covered by Ag/rGO. The zone of inhibition against
Staphylococcus aureus
(
S. aureus
),
Pseudomonas aeruginosa
(
P. aeruginosa
), and
Escherichia coli
(
E. coli
) bacteria indicated that Ag/rGO/cotton possessed the highest antibacterial activity when compared to other modified cotton. Moreover, the Ag/rGO/cotton also exhibited effective hydrophobicity with a wetting angle of 103.85° ± 0.75°, which supported the prevention of bacterial infection and adherent on the cotton surface. To confirm the low cytotoxic property of Ag/rGO/cotton for human use, the cell viability of HepG2, A549, and Hek293 cell lines were evaluated when contacted with the material, while the low amount of leached Ag
+
from Ag/rGO/cotton was under the accepted limit. All results of the study confirmed that Ag/rGO/cotton possesses significant potential for several antibacterial applications such as protective equipment.
Graphic abstract
MAPK-activated protein kinase 2 (MK2) has diverse roles in cancer. In response to chemotherapy, MK2 inhibition is synthetically lethal to p53-deficiency. While
deletion is rare in glioblastomas, ...these tumors often carry
mutations. Here, we show that MK2 inhibition strongly attenuated glioblastoma cell proliferation through p53
stabilization and senescence. The senescence-inducing efficacy of MK2 inhibition was particularly strong when cells were co-treated with the standard-of-care temozolomide. However, MK2 inhibition also increased the stability of p53 mutants and enhanced the proliferation of p53-mutant stem cells. These observations reveal that in response to DNA damaging chemotherapy, targeting MK2 in p53-mutated cells produces a phenotype that is distinct from the p53-deficient phenotype. Thus, MK2 represents a novel drug target in 70% glioblastomas harboring intact
gene. However, targeting MK2 in tumors with
mutations may accelerate disease progression. These findings are highly relevant since
mutations occur in over 50% of all cancers.
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