A high-fat diet promotes cancer progression by inducing gut microbiota-mediated leucine production and PMN-MDSC differentiation.

A high-fat diet (HFD) is a high-risk factor for the malignant progression of cancers through the disruption of the intestinal microbiota. However, the role of the HFD-related gut microbiota in cancer development remains unclear. This study found that obesity and obesity-related gut microbiota were associated with poor prognosis and advanced clinicopathological status in female patients with breast cancer. To investigate the impact of HFD-associated gut microbiota on cancer progression, we established various models, including HFD feeding, fecal microbiota transplantation, antibiotic feeding, and bacterial gavage, in tumor-bearing mice. HFD-related microbiota promotes cancer progression by generating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). Mechanistically, the HFD microbiota released abundant leucine, which activated the mTORC1 signaling pathway in myeloid progenitors for PMN-MDSC differentiation. Clinically, the elevated leucine level in the peripheral blood induced by the HFD microbiota was correlated with abundant tumoral PMN-MDSC infiltration and poor clinical outcomes in female patients with breast cancer. These findings revealed that the "gut-bone marrow-tumor" axis is involved in HFD-mediated cancer progression and opens a broad avenue for anticancer therapeutic strategies by targeting the aberrant metabolism of the gut microbiota.

New Global Insights on the Regulation of the Biphasic Life Cycle and Virulence Via ClpP-Dependent Proteolysis in Legionella pneumophila.

Legionella pneumophila, an environmental bacterium that parasitizes protozoa, causes Legionnaires' disease in humans that is characterized by severe pneumonia. This bacterium adopts a distinct biphasic life cycle consisting of a nonvirulent replicative phase and a virulent transmissive phase in response to different environmental conditions. Hence, the timely and fine-tuned expression of growth and virulence factors in a life cycle-dependent manner is crucial for survival and replication. Here, we report that the completion of the biphasic life cycle and bacterial pathogenesis is greatly dependent on the protein homeostasis regulated by caseinolytic protease P (ClpP)-dependent proteolysis. We characterized the ClpP-dependent dynamic profiles of the regulatory and substrate proteins during the biphasic life cycle of L. pneumophila using proteomic approaches and discovered that ClpP-dependent proteolysis specifically and conditionally degraded the substrate proteins, thereby directly playing a regulatory role or indirectly controlling cellular events via the regulatory proteins. We further observed that ClpP-dependent proteolysis is required to monitor the abundance of fatty acid biosynthesis-related protein Lpg0102/Lpg0361/Lpg0362 and SpoT for the normal regulation of L. pneumophila differentiation. We also found that the control of the biphasic life cycle and bacterial virulence is independent. Furthermore, the ClpP-dependent proteolysis of Dot/Icm (defect in organelle trafficking/intracellular multiplication) type IVB secretion system and effector proteins at a specific phase of the life cycle is essential for bacterial pathogenesis. Therefore, our findings provide novel insights on ClpP-dependent proteolysis, which spans a broad physiological spectrum involving key metabolic pathways that regulate the transition of the biphasic life cycle and bacterial virulence of L. pneumophila, facilitating adaptation to aquatic and intracellular niches.

MicroRNA-31 mediated by interferon regulatory factor 7 signaling facilitates control of Mycobacterium tuberculosis infection.

Tuberculosis (TB) induced by Mycobacterium tuberculosis (M. tuberculosis) infection remains a global most deadly infectious disease. While development of more effective TB vaccines and therapeutics relies on identifications of true biomarkers designating an immune protection against M. tuberculosis infection, exact protective immune components against M. tuberculosis infection remain largely unidentified. We previously found that severe TB induced remarkable up-regulation of interferon regulatory factor 7 (IRF7) and IRF7-related gene signatures, implicating that some unknown downstream molecules in IRF7 signaling cascades may determine the M. tuberculosis infection outcomes and serve as a protective immune component against M. tuberculosis infection. Indeed, here, we observe that genetic ablation of IRF7 leads to more severe lung pathology, increased M. tuberculosis burdens, impaired differentiation of effector/memory T subsets, and extensively elevated expression of pro-inflammatory cytokines in lungs. Importantly, IRF7 is vital for sustaining expression of PD-1/PD-L1 and PD-1/PD-L1-modulated miRNA-31. Moreover, interventions of miRNA-31 expressions via administration of miRNA-31 agomir reduces lung pathology and bacilli burdens via inducing up-regulation of gene sets involved in biological processes of defense response or cellular and chemical homeostasis in lungs. Thus, this study uncovers previously unrecognized importance and mechanisms of IRF7-mediated miRNA-31 as a protective immune component against M. tuberculosis infection.

The Legionella pneumophila effector WipA disrupts host F-actin polymerisation by hijacking phosphotyrosine signalling.

The major virulence determinant of Legionella pneumophila is the type IVB secretion system (T4BSS), which delivers approximately 330 effector proteins into the host cell to modulate various cellular processes. However, the functions of most effector proteins remain unclear. WipA, an effector, was the first phosphotyrosine phosphatase of Legionella with unknown function. In this study, we found that WipA induced relatively strong growth defects in yeast in a phosphatase activity-dependent manner. Phosphoproteomics data showed that WipA was likely involved into endocytosis, FcγR-mediated phagocytosis, tight junction, and regulation of actin cytoskeleton pathways. Western blotting further confirmed WipA dephosphorylates several proteins associated with actin polymerisation, such as p-N-WASP, p-ARP3, p-ACK1, and p-NCK1. Thus, we hypothesised that WipA targets N-WASP/ARP2/3 complex signalling pathway, leading to disturbance of actin polymerisation. Indeed, we demonstrated that WipA inhibits host F-actin polymerisation by reducing the G-actin to F-actin transition during L. penumophila infection. Furthermore, the intracellular proliferation of wipA/legK2 double mutant was significantly impaired at the late stage of infection, although the absence of WipA does not confer any further effect on actin polymerisation to the legK2 mutant. Collectively, this study provides unique insights into the WipA-mediated regulation of host actin polymerisation and assists us to elucidate the pathogenic mechanisms of L. pnuemophila infection.

Gut Microbiota-Derived 3-Hydroxybutyrate Blocks GPR43-Mediated IL6 Signaling to Ameliorate Radiation Proctopathy.

Radiation proctopathy (RP) is a common complication of radiotherapy for pelvic malignancies with high incidence. RP accompanies by microbial dysbiosis. However, how the gut microbiota affects the disease remains unclear. Here, metabolomics reveals that the fecal and serous concentrations of microbiota-derived 3-hydroxybutyrate (3HB) are significantly reduced in RP mice and radiotherapeutic patients. Moreover, the concentration of 3HB is negatively associated with the expression of proinflammatory IL6 that is increased along with the severity of radiation damage. 3HB treatment significantly downregulates IL6 expression and alleviates IL6-mediated radiation damage. Irradiated cell-fecal microbiota co-culture experiments and in vivo assays show that such a radioprotection of 3HB is mediated by GPR43. Microbiome analysis reveals that radiation leads to a distinct bacterial community compared to untreated controls, in which Akkermansia muciniphila is significantly reduced in RP mice and radiotherapeutic patients and is associated with lower 3HB concentration. Gavage of A. muciniphila significantly increases 3HB concentration, downregulates GPR43 and IL6 expression, and ameliorates radiation damage. Collectively, these results demonstrate that the gut microbiota, including A. muciniphila, induce higher concentrations of 3HB to block GPR43-mediated IL6 signaling, thereby conferring radioprotection. The findings reveal a novel implication of the gut-immune axis in radiation pathophysiology, with potential therapeutic applications.

Comparative genomics analysis of Bacillus velezensis LOH112 isolated from a nonagenarian provides insights into its biocontrol and probiotic traits.

Bacillus velezensis has recently received increasing attention as a biological fungicide and a potential probiotic agent because of its broad spectrum of antibacterial and antifungal activities. Here, we evaluated the beneficial traits of a newly isolated B. velezensis strain LOH112 using comprehensive bioinformatics and comparative genomic analyses and in vitro experimental approaches. Whole genome sequencing and assembly results showed that the genome of LOH112 consists of a circular chromosome and a circular plasmid, which encodes proteins involved in important biological processes such as sporulation, quorum sensing, and antibiotic synthesis. LOH112 contains 13 secondary metabolism gene clusters responsible for the production of antimicrobial compounds. In vitro experiments showed that LOH112 effectively inhibits several fungi and Gram-positive pathogenic bacteria, hydrolyzes protein and cellulose, and is capable of forming strong adhesive biofilms. Furthermore, comparative genomics revealed that LOH112 contains 34 strain-specific orthologous gene clusters, including two caseinolytic protease P (clpP) genes responsible for proteomic homeostasis. Selective pressure analysis indicated that the transmembrane transporter and ATP-dependent alanine/valine adenylase genes were strongly positively selected, which may endow LOH112 with better biocontrol ability and potential probiotic properties. Collectively, these results not only provide insights into a deeper understanding of the genomic characterization of LOH112 but also imply the potential application of LOH112 as biocontrol and probiotic agents.

Ifnar gene variants influence gut microbial production of palmitoleic acid and host immune responses to tuberculosis.

Both host genetics and the gut microbiome have important effects on human health, yet how host genetics regulates gut bacteria and further determines disease susceptibility remains unclear. Here, we find that the gut microbiome pattern of participants with active tuberculosis is characterized by a reduction of core species found across healthy individuals, particularly Akkermansia muciniphila. Oral treatment of A. muciniphila or A. muciniphila-mediated palmitoleic acid strongly inhibits tuberculosis infection through epigenetic inhibition of tumour necrosis factor in mice infected with Mycobacterium tuberculosis. We use three independent cohorts comprising 6,512 individuals and identify that the single-nucleotide polymorphism rs2257167 'G' allele of type I interferon receptor 1 (encoded by IFNAR1 in humans) contributes to stronger type I interferon signalling, impaired colonization and abundance of A. muciniphila, reduced palmitoleic acid production, higher levels of tumour necrosis factor, and more severe tuberculosis disease in humans and transgenic mice. Thus, host genetics are critical in modulating the structure and functions of gut microbiome and gut microbial metabolites, which further determine disease susceptibility.

Gut Akkermansia muciniphila ameliorates metabolic dysfunction-associated fatty liver disease by regulating the metabolism of L-aspartate via gut-liver axis.

The gut bacterium Akkermansia muciniphila has been increasingly recognized for its therapeutic potential in treating metabolic disorders, including obesity, diabetes, and metabolicdysfunction-associated fatty liver disease (MAFLD). However, its underlying mechanism involved in its well-known metabolic actions needs further evaluation. The present study explored the therapeutic effect and mechanism of A. muciniphila in intervening MAFLD by using a high-fat and high-cholesterol (HFC) diet induced obese mice model. Mice treated with A. muciniphila efficiently reversed MAFLD in the liver, such as hepatic steatosis, inflammatory, and liver injury. These therapeutic effects persisted after long-term drug withdrawal and were slightly weakened in the antibiotics-treated obese mice. A. muciniphila treatment efficiently increased mitochondrial oxidation and bile acid metabolism in the gut-liver axis, ameliorated oxidative stress-induced cell apoptosis in gut, leading to the reshaping of the gut microbiota composition. These metabolic improvements occurred with increased L-aspartate levels in the liver that transported from the gut. The administration of L-aspartate in vitro or in mice displayed the similar beneficial metabolic effects mentioned above and efficiently ameliorated MAFLD. Together, these data indicate that the anti-MAFLD activity of A. muciniphila correlated with lipid oxidation and improved gut-liver interactions through regulating the metabolism of L-aspartate. A. muciniphila could be a potential agent for clinical intervention in MAFLD.

Proteomic characterization of Mycobacterium tuberculosis reveals potential targets of bostrycin.

Tuberculosis (TB) is caused by bacterial pathogen Mycobacterium tuberculosis (Mtb) and remains a major health problem worldwide. The increasing prevalence of drug-resistant Mtb strains and the extended duration of anti-TB regimens have created an urgent need for new anti-tuberculosis antibiotics with novel targets or inhibitory strategies. Anthracenedione compound bostrycin has been shown to inhibit the growth of Mtb in vitro and inhibit the activity of the effector protein tyrosine phosphatase (MptpB) secreted by Mtb. In this study, we characterized the proteomic profile of the Mtb strain H37Ra exposed to 1 mg/L and 25 mg/L of bostrycin for 24 h. Bioinformatic analysis of the differential abundant proteins indicated that bostrycin treatment may induce oxidative stress and interfere with essential processes such as synthesis of NAD(+) and the tricarboxylic acid cycle in mycobacteria. Then, the molecular docking of bostrycin and 15 candidates of targeted proteins showed that Rv3684 and Rv1908c got higher scores compared to MptpB, suggesting the direct interaction of bostrycin and these two proteins. Further docking of potential targeted proteins with the functional group-removal derivatives of bostrycin revealed possible key functional groups of bostrycin and provides direction for the modification of bostrycin in future. BIOLOGICAL SIGNIFICANCE: It is a challenging work to determine the potential target(s) of an antibiotic accurately and quickly. In this study, we conducted a proteomic analysis of Mtb responding to the treatment of bostrycin, and provided insight into the inhibiting mechanism of this anti-Mtb compound. The proper interaction of bostrycin and targeted proteins, as well as the interacting residues of targets, and functional groups of bostrycin were also identified within the docking surface, providing a direction for further modification of bostrycin. Our study also suggests a reference for the interaction analysis between mycobacteria and antibiotics, and provides potential targets information for other active anthraquinones.

The Temporal Expression of Global Regulator Protein CsrA Is Dually Regulated by ClpP During the Biphasic Life Cycle of Legionella pneumophila.

Legionella pneumophila, an environmental bacterium that parasitizes protozoa, is the causative pathogen of Legionnaires' disease. L. pneumophila adopts a distinct biphasic life cycle that allows it to adapt to environmental conditions for survival, replication, and transmission. This cycle consists of a non-virulent replicative phase (RP) and a virulent transmissive phase (TP). Timely and fine-tuned expression of growth and virulence factors in a life cycle-dependent manner is crucial. Herein, we report evidence that CsrA, a key regulator of the switch between the RP and the TP, is dually regulated in a ClpP-dependent manner during the biphasic life cycle of L. pneumophila. First, we show that the protein level of CsrA is temporal during the life cycle and is degraded by ClpP during the TP. The ectopic expression of CsrA in a ΔclpP mutant, but not in the wild type, inhibits both the initiation of the RP in vitro and the invasiveness to Acanthamoeba castellanii, indicating that the ClpP-mediated proteolytic pathway regulates the CsrA protein level. We further show that the temporally expressed IHFB is the transcriptional inhibitor of csrA and is degraded via a ClpP-dependent manner during the RP. During the RP, the level of CsrA is increased by promoting the degradation of IHFB and reducing the degradation of the accumulated CsrA via a ClpP-dependent manner. During the TP, the level of CsrA is decreased by inhibiting the degradation of IHFB and promoting the degradation of the accumulated CsrA via a ClpP-dependent manner as well. In conclusion, our results show that the growth-stage-specific expression level of CsrA is dually regulated by ClpP-dependent proteolysis at both the transcription and protein levels during the biphasic life cycle of L. pneumophila.

Recombinant Human Cytoglobin Prevents Atherosclerosis by Regulating Lipid Metabolism and Oxidative Stress.

Atherosclerosis is a chronic inflammatory vascular disease characterized by lipid accumulation and endothelial dysfunction. Cytoglobin has been shown to exert protective effects under oxidative stress conditions. The aim of this study was to determine whether recombinant human cytoglobin (rhCYGB) has protective effects against atherosclerosis. We intraperitoneally injected rhCYGB (0, 4, or 7 mg/kg BW) into the atherosclerotic rats daily for 60 days. The rhCYGB injections reduced low-density lipoprotein cholesterol (LDL-C) levels and increased high-density lipoprotein cholesterol levels in a dose-dependent manner, rhCYGB (7 mg/kg) significantly attenuated atherosclerosis. Blood proteins were separated by 2-dimensional electrophoresis and analyzed by mass spectrometry, and the majority of the proteins in question were participated in oxidative stress pathways and cardiovascular diseases. Human hepatocellular liver carcinoma cell line (HepG2) cells were treated with oleic acid (0.3 mmol/L), and Human acute monocytic leukemia cell line (THP-1) cells were incubated with oxidized LDL (ox-LDL; 50 µg/mL) to induce foam cell (FC) formation in vitro. Treatment with different concentrations of rhCYGB (0, 5, 10, and 15 µg/mL) significantly decreased the lipid droplet levels in HepG2 cells and cholesterol ester levels in FCs. Moreover, rhCYGB significantly increased superoxide dismutase and glutathione peroxidase activity and decreased malondialdehyde and nicotinamide adenine dinucleotide phosphate oxidase activity in cells. In addition, rhCYGB decreased NO and Reactive oxygen species (ROS) levels in FCs by functioning as an NO dioxygenase enzyme and ROS scavenger. Taken together, our findings indicate that rhCYGB prevented atherosclerosis by regulating lipid metabolism and oxidative stress. Our study provides insights into the possible usefulness of rhCYGB as an antiatherosclerosis agent.