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Antitumor Activity of cGAMP via Stimulation of cGAS-cGAMP-STING-IRF3 Mediated Innate Immune Response
Immunotherapy is one of the key strategies for cancer treatment. The cGAS-cGAMP-STING-IRF3 pathway of cytosolic DNA sensing plays a pivotal role in antiviral defense. We report that the STING activator cGAMP possesses significant antitumor activity in mice by triggering the STING-dependent pathway directly. cGAMP enhances innate immune responses by inducing production of cytokines such as interferon-β, interferon-γ and stimulating dendritic cells activation, which induces the cross-priming of CD8
+
T cells. The antitumor mechanism of cGAMP was verified by STING and IRF3, which were up-regulated upon cGAMP treatment. STING-deficiency dramatically reduced the antitumor effect of cGAMP. Furthermore, cGAMP improved the antitumor activity of 5-FU and clearly reduced the toxicity of 5-FU. These results demonstrated that cGAMP is a novel antitumor agent and has potential applications in cancer immunotherapy.
Journal Article
Transcriptional Activation of the mrkA Promoter of the Klebsiella pneumoniae Type 3 Fimbrial Operon by the c-di-GMP-Dependent MrkH Protein
The Gram-negative bacterial pathogen Klebsiella pneumoniae forms biofilms to facilitate colonization of biotic and abiotic surfaces. The formation of biofilms by K. pneumoniae requires the expression of type 3 fimbriae: elongate proteinaceous filaments extruded by a chaperone-usher system in the bacterial outer membrane. The expression of the mrkABCDF cluster that encodes this fimbrial system is strongly positively regulated by MrkH, a transcriptional activator that responds to the second messenger, c-di-GMP. In this study, we analyzed the mechanism by which the MrkH protein activates transcriptional initiation from the mrkA promoter. A mutational analysis supported by electrophoretic mobility shift assays demonstrated that a 12-bp palindromic sequence (the MrkH box) centered at -78.5 is the binding site of MrkH. Deletion of half a turn, but not a full turn, of DNA located between the MrkH box and the mrkA promoter destroyed the ability of MrkH to activate mrkA transcription. In addition, a 10-bp AT-rich sequence (the UP element) centered at -63.5 contributed significantly to MrkH-dependent mrkA transcription. In vivo analysis of rpoA mutants showed that the R265 and E273 determinants in the C-terminal domain of RNA polymerase α subunit are needed for MrkH-mediated activation of mrkA transcription. Furthermore, results from mutagenesis of the mrkH gene suggest that the N-terminal region of the protein is involved in transcriptional activation. Taken together, our results suggest that MrkH activates mrkA expression by interacting directly with RNA polymerase, to overcome the inefficient transcriptional initiation caused by the presence of defective core promoter elements.
Journal Article
Croydon neurology: the impact of neuropsychiatry MDT in reducing service usage frequency in FND patients
Functional Neurological Disorder (FND) is a complex neurological condition with limited patient management resources. Patients with FND are high frequency users of the NHS. A gap is the lack of accessibility to appropriate services. We implemented a weekly neuropsychiatry multi- disciplinary team (MDT) meeting to discuss complex FND patients with mental health needs. The aim was to determine the impact of this in reducing service usage by patients with FND. All patients discussed in the first 6 months of the service were analysed (May to Oct 2022). Patient infor- mation regarding demographics, psychiatric factors, and NHS usage was gathered.41 patients with FND were discussed. 26 (63%) were accepted into neuropsychiatry clinic and 15 (37%) rejected with appropriate advice and signposting. 20 (49%) were previously known to mental health services. Following MDT implementation, a reduction in service usage was observed. However, a key limitation was unequal data comparison from 5 years prior to MDT introduction to 6 months after.The MDT allows for a pooling of resources and discussion, resulting in appropriate allocation of mental health services in accordance with patient needs. However, despite service usage reduction, the con- sequence of insufficient mental health support is delayed patient care.
Journal Article
Long-term medical and psychosocial outcomes in congenital diaphragmatic hernia survivors
ObjectiveSurvival rates for congenital diaphragmatic hernia (CDH) are increasing. The long-term outcomes of CDH survivors were compared with a healthy control group to assess the morbidity for guidance of antenatal counselling and long-term follow-up programmes.Participants and designParticipants born with CDH in Western Australia 1993–2008 were eligible with matched controls from the general population. Participants had comprehensive lung function tests, echocardiogram, low-dose chest CT scan and completed a Strengths and Difficulties Questionnaire (SDQ) and quality of life (QOL) questionnaire.Results34 matched case–control pairs were recruited. Demographic data between groups were similar. Cases were smaller at follow-up (weight Z-score of −0.2vs0.3; p=0.03; height Z-score of −0.3vs0.6; p=0.01). Cases had lower mean Z-scores for forced expiratory volume in 1 s (FEV1) (−1.49 vs −0.01; p=0.004), FEV1/forced vital capacity (−1.92 vs −1.2; p=0.009) and forced expiratory flow at 25-75% (FEF25-75) (−1.18vs0.23; p=0.007). Cases had significantly worse respiratory mechanics using forced oscillation technique. Subpleural triangles architectural distortion, linear opacities and scoliosis on chest CT were significantly higher in cases. Prosthetic patch requirement was associated with worse lung mechanics and peak cough flow. Cases had significantly higher rates of gastro-oesophageal reflux disease (GORD) and GORD medication usage. Developmental delay was significantly higher in cases. More cases had a total difficulties score in the high to very high range (25% vs 0%, p=0.03) on the SDQ and reported lower objective QOL scores (70.2 vs 79.8, p=0.02).ConclusionSurvivors of CDH may have significant adverse long-term medical and psychosocial issues that would be better recognised and managed in a multidisciplinary clinic.
Journal Article
Chemical inhibition of MrkH-dependent activation of type 3 fimbriae synthesis and biofilm formation by Klebsiella pneumoniae
Biofilm formation by
Klebsiella pneumoniae
is mediated by the type 3 fimbriae Mrk, and regulated by MrkH and 3’,5’-cyclic diguanylic acid (c-di-GMP). We sought to identify specific chemical inhibitors of
K. pneumoniae
biofilm formation that reduced the activity of MrkH. A compound N-(3-cyano-5,6,7,8-tetrahydro-4H-cyclohepta[b]thien-2-yl)-2-methoxybenzamide, JT71, reduced
K. pneumoniae mrkA
promoter activity and biofilm formation by 50% without affecting cell viability. Western blot analysis, hemagglutination assays, electron microscopy and qPCR showed that JT71 reduced type 3 fimbriae production, and transcription of
mrkA
and
mrkH
. JT71 demonstrated activity against other clinical and multi-drug resistant
K. pneumoniae
isolates, and a type 3 fimbriate-positive
Citrobacter koseri
strain. In silico molecule docking was used to illustrate that JT71 could bind directly to the MrkH protein and block its activity. JT71 possesses promising drug-likeness properties and is non-toxic to mammalian cells. Chemical inhibition of transcriptional regulators that control fimbriae expression can inhibit bacterial biofilm formation.
Journal Article
Vitamin C deficiency as an unusual cause of pulmonary hypertension and refusal to walk
Vitamin C deficiency has been a historical disease rarely seen nowadays. We illustrate a case of a boy with autism presenting with severe pulmonary hypertension and refusal to walk secondary to vitamin C deficiency. Initiating treatment with high-dose vitamin C reversed his symptoms and he regained full power of his lower limbs with total normalisation of his pulmonary pressures.
Journal Article
Carboxymethylcytosine is a natural base modification and a handle for bacteriophage DNA hypermodification
Bacteriophages possess a wide array of DNA modifications, with many acting as molecular camouflage to evade host immune defenses. Sequence databases contain numerous bacteriophage enzymes of unknown function, with some potentially involved in yet to be identified DNA modifications. Here we report the discovery of a DNA cytosine C5-carboxymethyltransferase (CmoX) in
Synechococcus
phage S-B43, which catalyzes the formation of a 5-carboxymethylcytosine (5cxmC), previously reported as an unnatural DNA modification formed by an engineered cytosine methyltransferase. The carboxy-S-adenosyl-L-methionine (Cx-SAM) cofactor required by CmoX is provided by a phage-encoded Cx-SAM synthase (CmoA), a homolog of the bacterial CmoA involved in tRNA modification. A crystal structure of CmoX in complex with Cx-SAM revealed the basis for its substrate selectivity, involving a key Arg residue interacting with the substrate carboxy group. In addition, we characterize a phage-encoded ATP-dependent amide ligase, CmoY that catalyzes the formation of 5cxmC-glycine amide. CmoA is present in many bacteriophage genomes, typically alongside CmoX and homologs of CmoY, suggesting that 5cxmC modification is a widespread naturally occurring DNA modification serving as a handle for further hypermodifications in bacteriophages. Our study underscores the ability of bacteriophages to repurpose RNA modification enzymes to expand their repertoire of DNA modifications.
DNA in many bacteriophages contains unusual chemical modifications. Here, the authors discover that carboxymethylcytosine is a natural DNA base and reveal its role as an intermediate enabling further DNA hypermodification.
Journal Article
A rare case of appendiceal haemorrhage causing life-threatening haematochezia
Our case involved a 28-year-old man who presented with life-threatening haematochezia. Computed tomography angiogram revealed contrast extravasation from the appendix pooling in the caecum. Management via laparoscopic stapled partial caecectomy was successful. Histopathology revealed focal mild acute appendicitis with focal ulceration to submucosa.
Journal Article