Deoxyribonuclease I is essential for DNA fragmentation induced by gamma radiation in mice

Excipient-Free Ionizable Polyester Nanoparticles for Lung-Selective and Innate Immune Cell Plasmid DNA and mRNA Transfection

Extrahepatic nucleic acid delivery using polymers typically requires the synthesis and purification of custom monomers, post-synthetic modifications, and incorporation of additional excipients to augment their stability, endosomal escape, and in vivo effectiveness. Here, we report the development of a single-component and excipient-free, polyester-based nucleic acid delivery nanoparticle platform comprising ionizable N-methyldiethanolamine (MDET) and various hydrophobic alkyl diols (Cp) that achieves lung-selective nucleic acid transfection in vivo. PolyMDET and polyMDET-Cp polyplexes displayed high serum and enzymatic stability, while delivering pDNA or mRNA to "hard-to-transfect" innate immune cells. PolyMDET-C4 and polyMDET-C6 mediated high protein expression in lung alveolar macrophages and dendritic cells without inducing tissue damage or systemic inflammatory responses. Improved strategies using readily available starting materials to produce a simple, excipient-free, non-viral nucleic acid delivery platform with lung-selective and innate immune cell tropism has the potential to expedite clinical deployment of polymer-based genetic medicines.

1,2,3,4-Tetrahydroisoquinoline Derivatives as a Novel Deoxyribonuclease I Inhibitors

Herein we report an assessment of 24 1,2,3,4-tetrahydroisoquinoline derivatives for potential DNase I (deoxyribonuclease I) inhibitory properties in vitro. Four of them inhibited DNase I with IC₅₀ values below 200 μM. The most potent was 1-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)propan-2-one (2) (IC₅₀ =134.35±11.38 μM) exhibiting slightly better IC₅₀ value compared to three other active compounds, 2-[2-(4-fluorophenyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]-1-phenylethan-1-one (15) (IC₅₀ =147.51±14.87 μM), 2-[2-(4-fluorophenyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]cyclohexan-1-one (18) (IC₅₀ =149.07±2.98 μM) and 2-[6,7-dimethoxy-2-(p-tolyl)-1,2,3,4-tetrahydroisoquinolin-1-yl]cyclohexan-1-one (22) (IC₅₀ =148.31±2.96 μM). Cytotoxicity assessment of the active DNase I inhibitors revealed a lack of toxic effects on the healthy cell lines MRC-5. Molecular docking and molecular dynamics simulations suggest that interactions with Glu 39, His 134, Asn 170, Tyr 211, Asp 251 and His 252 are an important factor for inhibitors affinity toward the DNase I. Observed interactions would be beneficial for the discovery of new active 1,2,3,4-tetrahydroisoquinoline-based inhibitors of DNase I, but might also encourage researchers to further explore and utilize potential therapeutic application of DNase I inhibitors, based on a versatile role of DNase I during apoptotic cell death.

Apoptotic DNase network: Mutual induction and cooperation among apoptotic endonucleases

DNA fragmentation produced by apoptotic DNases (endonucleases) leads to irreversible cell death. Although apoptotic DNases are simultaneously induced following toxic/oxidative cell injury and/or failed DNA repair, the study of DNases in apoptosis has generally been reductionist in approach, focusing on individual DNases rather than their possible cooperativity. Coordinated induction of DNases would require a mechanism of communication; however, mutual DNase induction or activation of DNases by enzymatic or non‐enzymatic mechanisms is not currently recognized. The evidence presented in this review suggests apoptotic DNases operate in a network in which members induce each other through the DNA breaks they produce. With DNA breaks being a common communicator among DNases, it would be logical to propose that DNA breaks from other sources such as oxidative DNA damage or actions of DNA repair endonucleases and DNA topoisomerases may also serve as triggers for a cooperative DNase feedback loop leading to elevated DNA fragmentation and subsequent cell death. Therefore, mutual induction of apoptotic DNases has serious implications for studies focused on activation or inhibition of specific DNases as a strategy for therapeutic intervention aimed at modulation of cell death.

4-4-(Anilinomethyl)-3-[4-(trifluoromethyl)phenyl]-1H-pyrazol-1-ylbenzoic acid derivatives as potent anti-gram-positive bacterial agents

A collection of potent antimicrobials consisting of novel 1,3-bis-benzoic acid and trifluoromethyl phenyl derived pyrazoles has been synthesized and tested for antibacterial activity. The majority of trifluoromethyl phenyl derivatives are highly potent growth inhibitors of Gram-positive bacteria and showed low toxicity to human cultured cells. In particular, two compounds (59 and 74) were selected for additional studies. These compounds are highly effective against Staphylococcus aureus as shown by a low minimum inhibitory concentration (MIC), a bactericidal effect in time-kill assays, moderate inhibition of biofilm formation as well as biofilm destruction, and a bactericidal effect against stationary phase cells representing non-growing persister cells. Multistep resistance assays showed a very low tendency for S. aureus and Enterococcus faecalis to develop resistance through mutation. Additionally, in vivo mouse model studies showed no harmful effects at doses up to 50 mg/kg using 14 blood plasma organ toxicity markers or TUNEL assay in liver and kidney. Investigations into the mode of action by performing macromolecular synthesis inhibition studies showed a broad range of inhibitory effects, suggesting targets that have a global effect on bacterial cell function.

4-chloro eugenol interacts synergistically with artesunate against drug resistant P. falciparum inducing oxidative stress

4-chloro eugenol (4CE), a semisynthetic analog of phytomolecule eugenol exhibited potent antiplasmodial activity with IC₅₀ in the range of 1.5-5 μM against sensitive as well as drug resistant strain of P. falciparum. This analog also showed synergy with a clinically used antimalarial drug artesunate and was able to curtail the IC₅₀ of artesunate up to 4-5 folds. Although, 4CE did not show any effect on heme polymerization, the most common drug target in the malaria parasite, it could increase the level of reactive oxygen species (ROS) and reactive nitrogen species (RNS) alone as well as in combination with artesunate. Further, 4CE induced oxidative stress was observed to affect the macromolecules in terms of DNA damage, protein carbonylation and lipid peroxidation. At the physiological level, cellular organelles like mitochondria and endoplasmic reticulum were observed to be get affected by 4CE in terms of membrane depolarization and calcium ion leakage respectively. These observations could be validated by expression analysis of oxidative stress responsive genes and proteins. Further, in in vivo assay, 4CE showed significant chemo-suppression of parasitemia as well as an increase in mean survival time in the murine malaria model. Interestingly, in combination with artesunate, 4CE showed higher chemo-suppression as well as enhanced mean survival time at a much lower concentrations of both the partners as compared to an individual dose of artesunate and 4CE. A combination of 4CE and artesunate was also observed to attenuate cerebral malaria pathogenesis.

DNase I Induces Other Endonucleases in Kidney Tubular Epithelial Cells by Its DNA-Degrading Activity

Endonuclease-mediated DNA fragmentation is both an immediate cause and a result of apoptosis and of all other types of irreversible cell death after injury. It is produced by nine enzymes including DNase I, DNase 2, their homologs, caspase-activated DNase (CAD) and endonuclease G (EndoG). The endonucleases act simultaneously during cell death; however, regulatory links between these enzymes have not been established. We hypothesized that DNase I, the most abundant of endonucleases, may regulate other endonucleases. To test this hypothesis, rat kidney tubular epithelial NRK-52E cells were transfected with the DNase I gene or its inactive mutant in a pECFP expression vector, while control cells were transfected with the empty vector. mRNA expression of all nine endonucleases was studied using real-time RT-PCR; DNA strand breaks in endonuclease genes were determined by PCR and protein expression of the enzymes was measured by Western blotting and quantitative immunocytochemistry. Our data showed that DNase I, but not its inactive mutant, induces all other endonucleases at varying time periods after transfection, causes DNA breaks in endonuclease genes, and elevates protein expression of several endonucleases. This is the first evidence that endonucleases seem to be induced by the DNA-degrading activity of DNase I.

Dysregulation of TLR9 in neonates leads to fatal inflammatory disease driven by IFN-γ

Recognition of self-nucleic acids by innate immune receptors can lead to the development of autoimmune and/or autoinflammatory diseases. Elucidating mechanisms associated with dysregulated activation of specific receptors may identify new disease correlates and enable more effective therapies. Here we describe an aggressive in vivo model of Toll-like receptor (TLR) 9 dysregulation, based on bypassing the compartmentalized activation of TLR9 in endosomes, and use it to uncover unique aspects of TLR9-driven disease. By inducing TLR9 dysregulation at different stages of life, we show that while dysregulation in adult mice causes a mild systemic autoinflammatory disease, dysregulation of TLR9 early in life drives a severe inflammatory disease resulting in neonatal fatality. The neonatal disease includes some hallmarks of macrophage activation syndrome but is much more severe than previously described models. Unlike TLR7-mediated disease, which requires type I interferon (IFN) receptor signaling, TLR9-driven fatality is dependent on IFN-γ receptor signaling. NK cells are likely key sources of IFN-γ in this model. We identify populations of macrophages and Ly6C^hi monocytes in neonates that express high levels of TLR9 and low levels of TLR7, which may explain why TLR9 dysregulation is particularly consequential early in life, while symptoms of TLR7 dysregulation take longer to manifest. Overall, this study demonstrates that inappropriate TLR9 responses can drive a severe autoinflammatory disease under homeostatic conditions and highlights differences in the diseases resulting from inappropriate activation of TLR9 and TLR7.

Expanding the Toolbox for Label-Free Enzyme Assays: A Dinuclear Platinum(II) Complex/DNA Ensemble with Switchable Near-IR Emission

Switchable luminescent bioprobes whose emission can be turned on as a function of specific enzymatic activity are emerging as important tools in chemical biology. We report a promising platform for the development of label-free and continuous enzymatic assays in high-throughput mode based on the reversible solvent-induced self-assembly of a neutral dinuclear Pt(II) complex. To demonstrate the utility of this strategy, the switchable luminescence of a dinuclear Pt(II) complex was utilized in developing an experimentally simple, fast (10 min), low cost, and label-free turn-on luminescence assay for the endonuclease enzyme DNAse I. The complex displays a near-IR (NIR) aggregation-induced emission at 785 nm in aqueous solution that is completely quenched upon binding to G-quadruplex DNA from the human c-myc oncogene. Luminescence is restored upon DNA degradation elicited by exposure to DNAse I. Correlation between near-IR luminescence intensity and DNAse I concentration in human serum samples allows for fast and label-free detection of DNAse I down to 0.002 U/mL. The Pt(II) complex/DNA assembly is also effective for identification of DNAse I inhibitors, and assays can be performed in multiwell plates compatible with high-throughput screening. The combination of sensitivity, speed, convenience, and cost render this method superior to all other reported luminescence-based DNAse I assays. The versatile response of the Pt(II) complex to DNA structures promises broad potential applications in developing real-time and label-free assays for other nucleases as well as enzymes that regulate DNA topology.

Synthesis and DNase I inhibitory properties of new benzocyclobutane-2,5-diones

Aim: Eight new benzocyclobutane-2,5-diones (1a–1h) were synthesized, and their inhibitory properties against bovine pancreatic DNase I were examined in vitro. Methods & results: Compounds 1a–1h were synthesized using photocycloaddition of duroquinone with various phenyl-substituted ethylenes in the presence of 18W compact fluorescent lamp (visible light). Two compounds, 1,3,4,6-tetramethyl-7-phenylbicyclo[4.2.0]oct-3-ene-2,5-dione (1a) and 1,3,4,6-tetramethyl-7-p-tolylbicyclo[4.2.0]oct-3-ene-2,5-dione (1b) inhibited DNase I in a noncompetitive manner with IC50 values below 150 μM and showed to be more potent DNase I inhibitors than crystal violet, used as a positive control. In order to analyze potential binding sites for the studied compounds with DNase I, molecular docking study was performed. Conclusion: The studied benzocyclobutane-2,5-diones offer a good starting point for a design of new DNase I inhibitors.

Gamma-Tocotrienol Protects the Intestine from Radiation Potentially by Accelerating Mesenchymal Immune Cell Recovery

Natural antioxidant gamma-tocotrienol (GT3), a vitamin E family member, provides intestinal radiation protection. We seek to understand whether this protection is mediated via mucosal epithelial stem cells or sub-mucosal mesenchymal immune cells. Vehicle- or GT3-treated male CD2F1 mice were exposed to total body irradiation (TBI). Cell death was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Villus height and crypt depth were measured with computer-assisted software in tissue sections. Functional activity was determined with an intestinal permeability assay. Immune cell recovery was measured with immunohistochemistry and Western blot, and the regeneration of intestinal crypts was assessed with ex vivo organoid culture. A single dose of GT3 (200 mg/kg body weight (bwt)) administered 24 h before TBI suppressed cell death, prevented a decrease in villus height, increased crypt depth, attenuated intestinal permeability, and upregulated occludin level in the intestine compared to the vehicle treated group. GT3 accelerated mesenchymal immune cell recovery after irradiation, but it did not promote ex vivo organoid formation and failed to enhance the expression of stem cell markers. Finally, GT3 significantly upregulated protein kinase B or AKT phosphorylation after TBI. Pretreatment with GT3 attenuates TBI-induced structural and functional damage to the intestine, potentially by facilitating intestinal immune cell recovery. Thus, GT3 could be used as an intestinal radioprotector.

Serotonin transporter protects the placental cells against apoptosis in caspase 3-independent pathway

Serotonin (5-HT) and its specific transporter, SERT play important roles in pregnancy. Using placentas dissected from 18d gestational SERT-knock out (KO), peripheral 5-HT (TPH1)-KO, and wild-type (WT) mice, we explored the role of 5-HT and SERT in placental functions in detail. An abnormal thick band of fibrosis and necrosis under the giant cell layer in SERT-KO placentas appeared only moderately in TPH1-KO and minimally present in WT placentas. The majority of the changes were located at the junctional zone of the placentas in SERT. The etiology of these findings was tested with TUNEL assays. The placentas from SERT-KO and TPH1-KO showed 49- and 8-fold increase in TUNEL-positive cells without a concurrent change in the DNA repair or cell proliferation compared to WT placentas. While the proliferation rate in the embryos of TPH1-KO mice was 16-fold lower than the rate in gestational age matched embryos of WT or SERT-KO mice. These findings highlight an important role of continuous 5-HT signaling on trophoblast cell viability. SERT may contribute to protecting trophoblast cells against cell death via terminating the 5-HT signaling which changes cell death ratio in trophoblast as well as proliferation rate in embryos. However, the cell death in SERT-KO placentas is in caspase 3-independent pathway.

Regulation of Apoptotic Endonucleases by EndoG

Cells contain several apoptotic endonucleases, which appear to act simultaneously before and after cell death by destroying the host cell DNA. It is largely unknown how the endonucleases are being induced and whether they can regulate each other. This study was performed to determine whether apoptotic mitochondrial endonuclease G (EndoG) can regulate expression of other apoptotic endonucleases. The study showed that overexpression of mature EndoG in kidney tubular epithelial NRK-52E cells can increase expression of caspase-activated DNase (CAD) and four endonucleases that belong to DNase I group including DNase I, DNase X, DNase IL2, and DNase γ, but not endonucleases of the DNase 2 group. The induction of DNase I-type endonucleases was associated with DNA degradation in promoter/exon 1 regions of the endonuclease genes. These results together with findings on colocalization of immunostained endonucleases and TUNEL suggest that DNA fragmentation after EndoG overexpression was caused by DNase I endonucleases and CAD in addition to EndoG itself. Overall, these data provide first evidence for the existence of the integral network of apoptotic endonucleases regulated by EndoG.

Novel cytoprotective inhibitors for apoptotic endonuclease G

Apoptotic endonuclease G (EndoG) is responsible for DNA fragmentation both during and after cell death. Previous studies demonstrated that genetic inactivation of EndoG is cytoprotective against various pro-apoptotic stimuli; however, specific inhibitors for EndoG are not available. In this study, we have developed a high-throughput screening assay for EndoG and have used it to screen a chemical library. The screening resulted in the identification of two potent EndoG inhibitors, PNR-3-80 and PNR-3-82, which are thiobarbiturate analogs. As determined by their IC₅₀s, the inhibitors are more potent than ZnCl₂ or EDTA. They inhibit EndoG at one or two orders of magnitude greater than another apoptotic endonuclease, DNase I, and do not inhibit the other five tested cell death-related enzymes: DNase II, RNase A, proteinase, lactate dehydrogenase, and superoxide dismutase 1. Exposure of natural EndoG-expressing 22Rv1 or EndoG-overexpressing PC3 cells rendered them significantly resistant to Cisplatin and Docetaxel, respectively. These novel EndoG inhibitors have the potential to be utilized for amelioration of cell injuries in which participation of EndoG is essential.

Novel high-throughput deoxyribonuclease 1 assay

Deoxyribonuclease I (DNase I), the most active and abundant apoptotic endonuclease in mammals, is known to mediate toxic, hypoxic, and radiation injuries to the cell. Neither inhibitors of DNase I nor high-throughput methods for screening of high-volume chemical libraries in search of DNase I inhibitors are, however, available. To overcome this problem, we developed a high-throughput DNase I assay. The assay is optimized for a 96-well plate format and based on the increase of fluorescence intensity when fluorophore-labeled oligonucleotide is degraded by the DNase. The assay is highly sensitive to DNase I compared to other endonucleases, reliable (Z' ≥ 0.5), and operationally simple, and it has low operator, intraassay, and interassay variability. The assay was used to screen a chemical library, and several potential DNase I inhibitors were identified. After comparison, 2 hit compounds were selected and shown to protect against cisplatin-induced kidney cell death in vitro. This assay will be suitable for identifying inhibitors of DNase I and, potentially, other endonucleases.

C/EBPδ deficiency sensitizes mice to ionizing radiation-induced hematopoietic and intestinal injury

Knowledge of the mechanisms involved in the radiation response is critical for developing interventions to mitigate radiation-induced injury to normal tissues. Exposure to radiation leads to increased oxidative stress, DNA-damage, genomic instability and inflammation. The transcription factor CCAAT/enhancer binding protein delta (Cebpd; C/EBPδ is implicated in regulation of these same processes, but its role in radiation response is not known. We investigated the role of C/EBPδ in radiation-induced hematopoietic and intestinal injury using a Cebpd knockout mouse model. Cebpd−/− mice showed increased lethality at 7.4 and 8.5 Gy total-body irradiation (TBI), compared to Cebpd+/+ mice. Two weeks after a 6 Gy dose of TBI, Cebpd−/− mice showed decreased recovery of white blood cells, neutrophils, platelets, myeloid cells and bone marrow mononuclear cells, decreased colony-forming ability of bone marrow progenitor cells, and increased apoptosis of hematopoietic progenitor and stem cells compared to Cebpd+/+ controls. Cebpd−/− mice exhibited a significant dose-dependent decrease in intestinal crypt survival and in plasma citrulline levels compared to Cebpd+/+ mice after exposure to radiation. This was accompanied by significantly decreased expression of γ-H2AX in Cebpd−/− intestinal crypts and villi at 1 h post-TBI, increased mitotic index at 24 h post-TBI, and increase in apoptosis in intestinal crypts and stromal cells of Cebpd−/− compared to Cebpd+/+ mice at 4 h post-irradiation. This study uncovers a novel biological function for C/EBPδ in promoting the response to radiation-induced DNA-damage and in protecting hematopoietic and intestinal tissues from radiation-induced injury.

Protective effect of zinc-N-acetylcysteine on the rat kidney during cold storage

Cold storage of kidneys before transplantation is problematic because of the limited survival time of the allografts. In this study, zinc-N-acetylcysteine (ZnNAC) was shown to be a potent endonuclease inhibitor and antioxidant, and it was tested as a potential additive to a cold storage solution for kidney preservation. Exposure of normal rat kidney NRK-52E cells to ZnNAC resulted in zinc delivery to the cells as determined by TFL-Zn fluorophore and partial protection of the cells against injury by cold storage in University of Wisconsin solution (UWS) as measured by propidium iodide assay. Ex vivo, rat kidneys demonstrated time- and temperature-dependent DNA fragmentation as assessed by TUNEL assay, indicating irreversible cell death. DNA fragmentation was faster in the medulla than in the cortex, and tubules were affected more than glomeruli. Perfusion of rat kidneys with cold ZnNAC solution in UWS significantly inhibited cell death both in the cortex and medulla at concentrations of 0.3-30 mM compared with UWS alone, with a maximum effect at 1-10 mM ZnNAC. Cold storage of the kidney significantly increased quantities of cleaved caspase-3 and endonuclease G (EndoG) in the tissue, which were abolished by 10 mM ZnNAC, indicating its ability to suppress both caspase-dependent and -independent cell death. Therefore, supplementation of UWS with ZnNAC can decrease DNA fragmentation and protect kidney allografts from cell death due to cold storage.

Gene expression analysis of Xenopsylla cheopis (Siphonaptera: Pulicidae) suggests a role for reactive oxygen species in response to Yersinia pestis infection

Fleas are vectors for a number of pathogens including Yersinia pestis, yet factors that govern interactions between fleas and Y. pestis are not well understood. Examining gene expression changes in infected fleas could reveal pathways that affect Y. pestis survival in fleas and subsequent transmission. We used suppression subtractive hybridization to identify genes that are induced in Xenopsylla cheopis (Rothschild) (Siphonaptera: Pulicidae) in response to oral or hemocoel infection with Y. pestis. Overall, the transcriptional changes we detected were very limited. We identified several genes that are likely involved in the production or removal of reactive oxygen species (ROS). Midgut ROS levels were higher in infected fleas and antioxidant treatment before infection reduced ROS levels and resulted in higher bacterial loads. An ROS-sensitive mutant strain of Y. pestis lacking the OxyR transcriptional regulator showed reduced growth early after infection. Our results indicate that ROS may limit Y. pestis early colonization of fleas and that bacterial strategies to overcome ROS may enhance transmission.

Interferon regulatory transcription factor 3 protects mice from uterine horn pathology during Chlamydia muridarum genital infection

Mice with the type I interferon (IFN) receptor gene knocked out (IFNAR KO mice) or deficient for alpha/beta IFN (IFN-α/β) signaling clear chlamydial infection earlier than control mice and develop less oviduct pathology. Initiation of host IFN-β transcription during an in vitro chlamydial infection requires interferon regulatory transcription factor 3 (IRF3). The goal of the present study was to characterize the influence of IRF3 on chlamydial genital infection and its relationship to IFN-β expression in the mouse model. IRF3 KO mice were able to resolve infection as well as control mice, overcoming increased chlamydial colonization and tissue burden early during infection. As previously observed for IFNAR KO mice, IRF3 KO mice generated a potent antigen-specific T cell response. However, in contrast to IFNAR KO mice, IRF3 KO mice exhibited unusually severe dilatation and pathology in the uterine horns but normal oviduct pathology after infection. Although IFN-β expression in vivo was dependent on the presence of IRF3 early in infection (before day 4), the IFN-independent function of IRF3 was likely driving this phenotype. Specifically, early during infection, the number of apoptotic cells and the number of inflammatory cells were significantly less in uterine horns from IRF3 KO mice than in those from control mice, despite an increased chlamydial burden. To delineate the effects of IFN-β versus IRF3, neutralizing IFN-β antibody was administered to wild-type (WT) mice during chlamydial infection. IFN-β depletion in WT mice mimicked that in IFNΑR KO mice but not that in IRF3 KO mice with respect to both chlamydial clearance and reduced oviduct pathology. These data suggest that IRF3 has a role in protection from uterine horn pathology that is independent of its function in IFN-β expression.