Dihydroorotase (DHOase), a dimetalloenzyme containing a carbamylated lysine within the active site, is a member of the cyclic amidohydrolase family, which also includes allantoinase (ALLase), ...dihydropyrimidinase (DHPase), hydantoinase, and imidase. Unlike most known cyclic amidohydrolases, which are tetrameric, DHOase exists as a monomer or dimer. Here, we report and analyze two crystal structures of the eukaryotic
DHOase (ScDHOase) complexed with malate. The structures of different DHOases were also compared. An asymmetric unit of these crystals contained four crystallographically independent ScDHOase monomers. ScDHOase shares structural similarity with
DHOase (EcDHOase). Unlike EcDHOase, ScDHOase can form tetramers, both in the crystalline state and in solution. In addition, the subunit-interacting residues of ScDHOase for dimerization and tetramerization are significantly different from those of other DHOases. The tetramerization pattern of ScDHOase is also different from those of DHPase and ALLase. Based on sequence analysis and structural evidence, we identify two unique helices (α6 and α10) and a loop (loop 7) for tetramerization, and discuss why the residues for tetramerization in ScDHOase are not necessarily conserved among DHOases.
Current clinical trials of combined EGFR-tyrosine kinase inhibitors (TKI) and immune checkpoint blockade (ICB) therapies show no additional effect. This raises questions regarding whether EGFR-TKIs ...attenuate ICB-enhanced CD8
T lymphocyte function. Here we show that the EGFR-TKI afatinib suppresses CD8
T lymphocyte proliferation, and we identify CAD, a key enzyme of
pyrimidine biosynthesis, to be a novel afatinib target. Afatinib reduced tumor-infiltrating lymphocyte numbers in Lewis lung carcinoma (LLC)-bearing mice. Early afatinib treatment inhibited CD8
T lymphocyte proliferation in patients with non-small cell lung cancer, but their proliferation unexpectedly rebounded following long-term treatment. This suggests a transient immunomodulatory effect of afatinib on CD8
T lymphocytes. Sequential treatment of afatinib with anti-PD1 immunotherapy substantially enhanced therapeutic efficacy in MC38 and LLC-bearing mice, while simultaneous combination therapy showed only marginal improvement over each single treatment. These results suggest that afatinib can suppress CD8
T lymphocyte proliferation by targeting CAD, proposing a timing window for combined therapy that may prevent the dampening of ICB efficacy by EGFR-TKIs. SIGNIFICANCE: This study elucidates a mechanism of afatinib-mediated immunosuppression and provides new insights into treatment timing for combined targeted therapy and immunotherapy. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/12/3270/F1.large.jpg.
Abstract
BACKGROUND: Axon degeneration leads to cytoskeletal disassembly, metabolism imbalance, and mitochondrial dysfunction during neurodegeneration or nerve injury.
OBJECTIVE: In this study, we ...assess the possibility of mitigating axon degeneration by local injection of mitochondria in a crushed sciatic nerve.
METHODS: Sciatic nerve explants cocultured with mitochondria were assessed for the optimal dosage in local injection and nerve regeneration potential. The left sciatic nerve was crushed in Sprague-Dawley rats and then local injection of mitochondria into the distal end of the injured nerve was conducted for further assessment.
RESULTS: Mitochondrial coculture attenuated cytoskeletal loss and oxidative stress in isolated nerve explants. In Vivo analyses also showed that mitochondrial transplantation improved animal neurobehaviors, electrophysiology of nerve conduction, and muscle activities. Mitochondria injection significantly attenuated the oxidative stress and increased the expression of neurotrophic factors both in injured nerves and denervated muscles, as well as restored muscular integrity, and increased the pool of muscular progenitor cells and total muscle weight.
CONCLUSION: Mitochondria injection can protect injured nerves from axonal degeneration both in Vitro and in Vivo. This improvement was accompanied with the expression of neurotrophic factors as well as the reduction of oxidative stress, which may account for the functional recovery of both injured nerves and denervated muscles.
Bacterial genotoxins damage host cells by targeting their chromosomal DNA. In the present study, we demonstrate that a genotoxin of Salmonella Typhi, typhoid toxin, triggers the senescence-associated ...secretory phenotype (SASP) by damaging mitochondrial DNA. The actions of typhoid toxin disrupt mitochondrial DNA integrity, leading to mitochondrial dysfunction and disturbance of redox homeostasis. Consequently, it facilitates the release of damaged mitochondrial DNA into the cytosol, activating type I interferon via the cGAS-STING pathway. We also reveal that the GCN2-mediated integrated stress response plays a role in the upregulation of inflammatory components depending on the STING signaling axis. These SASP factors can propagate the senescence effect on T cells, leading to senescence in these cells. These findings provide insights into how a bacterial genotoxin targets mitochondria to trigger a proinflammatory SASP, highlighting a potential therapeutic target for an anti-toxin intervention.
The anticonvulsant valproic acid (VPA) despite complex pharmacokinetics has been in clinical use for nearly 6 decades. Previous reports indicated neonates, infants, and toddlers/preschoolers had ...higher risk of valproate hepatotoxicity than adults. However, dosing recommendations for those less than 10 years of age are lacking. To decipher clinical puzzles, physiologically‐based pharmacokinetic (PBPK) models of VPA and its hepatotoxic metabolite 4‐ene‐VPA were constructed and simulated with particularly integrated information of drug‐metabolizing enzyme ontogeny. Adult and pediatric PK data of VPA (n = 143 subjects) and 4‐ene‐VPA (n = 8 subjects) collected from previous reports were used for model development and validation. Sensitivity analyses were performed to characterize ontogeny impacts of CYP2C9 and UGT2B7 on dispositions of VPA and 4‐ene‐VPA across age groups. Optimal VPA dosing for each pediatric age group was also predicted and objectively judged by ensuring VPA efficacy and avoiding 4‐ene‐VPA hepatotoxicity. The study revealed UGT2B7 ontogeny was quite influential on VPA clearance even in neonates and small children. Intrinsic clearance of CYP2C9 was the most prominent determinant for areas under the concentration‐time curve of VPA and 4‐ene‐VPA in infants, and toddlers/preschoolers, reflecting higher hepatotoxicity risk due to noxious 4‐ene‐VPA accumulation in these groups. The ontogeny‐based PBPK approach complements conventional allometric methods in dosing estimation for the young by providing more mechanistic insight of the processes changing with age. The established ontogeny‐based PBPK approach for VPA therapy deserves further corroboration by real‐world therapeutic data to affirm its clinical applicability.
High-frequency transcutaneous neuromuscular electrical nerve stimulation (TENS) is currently used for the administration of electrical current in denervated muscle to alleviate muscle atrophy and ...enhance motor function; however, the time window (i.e. either immediate or delayed) for achieving benefit is still undetermined. In this study, we conducted an intervention of sciatic nerve crush injury using high-frequency TENS at different time points to assess the effect of motor and sensory functional recovery.
Animals with left sciatic nerve crush injury received TENS treatment starting immediately after injury or 1 week later at a high frequency(100 Hz) or at a low frequency (2 Hz) as a control. In SFI gait analysis, either immediate or late admission of high-frequency electrical stimulation exerted significant improvement compared to either immediate or late administration of low-frequency electrical stimulation. In an assessment of allodynia, immediate high frequency electrical stimulation caused a significantly decreased pain threshold compared to late high-frequency or low-frequency stimulation at immediate or late time points. Immunohistochemistry staining and western blot analysis of S-100 and NF-200 demonstrated that both immediate and late high frequency electrical stimulation showed a similar effect; however the effect was superior to that achieved with low frequency stimulation. Immediate high frequency electrical stimulation resulted in significant expression of TNF-α and synaptophysin in the dorsal root ganglion, somatosensory cortex, and hippocampus compared to late electrical stimulation, and this trend paralleled the observed effect on somatosensory evoked potential. The CatWalk gait analysis also showed that immediate electrical stimulation led to a significantly high regularity index. In primary dorsal root ganglion cells culture, high-frequency electrical stimulation also exerted a significant increase in expression of TNF-α, synaptophysin, and NGF in accordance with the in vivo results.
Immediate or late transcutaneous high-frequency electrical stimulation exhibited the potential to stimulate the motor nerve regeneration. However, immediate electrical stimulation had a predilection to develop neuropathic pain. A delay in TENS initiation appears to be a reasonable approach for nerve repair and provides the appropriate time profile for its clinical application.
Delayed post-polypectomy bleeding (PPB) is a major complication of polypectomy. The effect of prophylactic hemoclipping on delayed PPB is uncertain. The aim of this study was to evaluate the ...effectiveness of prophylactic hemoclipping and identify the risk factors of delayed PPB.
Patients with polyps sized 6 to 20 mm underwent snare polypectomy from 2015 to 2017 were retrospectively reviewed. The patients with prophylactic hemoclipping for delayed PPB prevention were included in the clipping group, and those without prophylactic hemoclipping were included in the non-clipping group. The incidence of delayed PPB and time to bleeding were compared between the groups. Multivariate analysis was used to identify the risk factors of delayed PPB. Propensity score matching was used to minimize potential bias.
After propensity score matching, 612 patients with 806 polyps were in the clipping group, and 576 patients with 806 polyps were in the non-clipping group. There were no significant differences in the incidence of delayed PPB and days to bleeding between two groups (0.8% vs 1.3%, p = 0.4; 3.4 ± 1.94 days vs 4.13 ± 3.39 days, p = 0.94). In the multivariate analysis, the polyp size Odds ratio (OR):1.16, 95% confidence interval (CI):1.01-1.16, p = 0.03), multiple polypectomies (OR: 4.64, 95% CI:1.24-17.44, p = 0.02) and a history of anticoagulant use (OR:37.52, 95% CI:6.49-216.8, p < 0.001) were associated with delayed PPB.
In polyps sized 6 to 20 mm, prophylactic hemoclip placement did not decrease the risk of delayed PPB. Patients without risk factors including multiple polypectomies and anticoagulant use are no need to performing prophylactic hemoclipping.
Understanding the structural diversity of honeybee-infecting viruses is critical to maintain pollinator health and manage the spread of diseases in ecology and agriculture. We determine cryo-EM ...structures of T = 4 and T = 3 capsids of virus-like particles (VLPs) of Lake Sinai virus (LSV) 2 and delta-N48 LSV1, belonging to tetraviruses, at resolutions of 2.3-2.6 Å in various pH environments. Structural analysis shows that the LSV2 capsid protein (CP) structural features, particularly the protruding domain and C-arm, differ from those of other tetraviruses. The anchor loop on the central β-barrel domain interacts with the neighboring subunit to stabilize homo-trimeric capsomeres during assembly. Delta-N48 LSV1 CP interacts with ssRNA via the rigid helix α1', α1'-α1 loop, β-barrel domain, and C-arm. Cryo-EM reconstructions, combined with X-ray crystallographic and small-angle scattering analyses, indicate that pH affects capsid conformations by regulating reversible dynamic particle motions and sizes of LSV2 VLPs. C-arms exist in all LSV2 and delta-N48 LSV1 VLPs across varied pH conditions, indicating that autoproteolysis cleavage is not required for LSV maturation. The observed linear domino-scaffold structures of various lengths, made up of trapezoid-shape capsomeres, provide a basis for icosahedral T = 4 and T = 3 architecture assemblies. These findings advance understanding of honeybee-infecting viruses that can cause Colony Collapse Disorder.
Accurate and rapid identification of microbiotic communities using 16S ribosomal (r)RNA sequencing is a critical task for expanding medical and clinical applications. Next-generation sequencing (NGS) ...is widely considered a practical approach for direct application to communities without the need for in vitro culturing. In this report, a comparative evaluation of short-read (Illumina) and long-read (Oxford Nanopore Technologies (ONT)) platforms toward 16S rRNA sequencing with the same batch of total genomic DNA extracted from fecal samples is presented. Different 16S gene regions were amplified, bar-coded, and sequenced using the Illumina MiSeq and ONT MinION sequencers and corresponding kits. Mapping of the sequenced amplicon using MinION to the entire 16S rRNA gene was analyzed with the cloud-based EPI2ME algorithm. V3-V4 reads generated using MiSeq were aligned by applying the CLC genomics workbench. More than 90% of sequenced reads generated using distinct sequencers were accurately classified at the genus or species level. The misclassification of sequenced reads at the species level between the two approaches was less substantial as expected. Taken together, the comparative results demonstrate that MinION sequencing platform coupled with the corresponding algorithm could function as a practicable strategy in classifying bacterial community to the species level.
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