Pseudomonas aeruginosa PcrV Enhances the Nitric Oxide-Mediated Tumoricidal Activity of Tumor-Associated Macrophages via a TLR4/PI3K/AKT/mTOR-Glycolysis-Nitric Oxide Circuit.

Tumor-associated macrophages (TAMs), which display a tumor-supportive M2 phenotype, are closely related to tumor growth and metastasis. The reprogramming of TAMs toward a tumoricidal M1 profile has emerged as an attractive strategy for cancer immunotherapy. In this study, we found that the intratumoral injection of PcrV protein, a component of the Pseudomonas aeruginosa type 3 secretion system, suppressed tumor growth and increased apoptosis, inducible nitric oxide synthase (iNOS) expression, and the percentage of M1-polarized TAMs in tumor tissues. Furthermore, the intratumoral injection of PcrV-primed macrophages exerted a similar tumoricidal effect. In vitro analyses revealed that PcrV reeducated TAMs toward an antitumoral M1 phenotype and augmented their nitric oxide (NO)-mediated cytotoxicity against cancer cells. Mechanistically, we found that these effects were dependent on the activation of Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)-mediated regulation of a PI3K/AKT/mTOR-glycolysis-NO feedback loop via direct interaction with TLR4. Collectively, these results revealed a potential role for PcrV in cancer immunotherapy through the targeting of TAM plasticity.

FGF19/SOCE/NFATc2 signaling circuit facilitates the self-renewal of liver cancer stem cells.

Background & Aims: Liver cancer stem cells (LCSCs) mediate therapeutic resistance and correlate with poor outcomes in patients with hepatocellular carcinoma (HCC). Fibroblast growth factor (FGF)-19 is a crucial oncogenic driver gene in HCC and correlates with poor prognosis. However, whether FGF19 signaling regulates the self-renewal of LCSCs is unknown. Methods: LCSCs were enriched by serum-free suspension. Self-renewal of LCSCs were characterized by sphere formation assay, clonogenicity assay, sorafenib resistance assay and tumorigenic potential assays. Ca2+ image was employed to determine the intracellular concentration of Ca2+. Gain- and loss-of function studies were applied to explore the role of FGF19 signaling in the self-renewal of LCSCs. Results: FGF19 was up-regulated in LCSCs, and positively correlated with certain self-renewal related genes in HCC. Silencing FGF19 suppressed self-renewal of LCSCs, whereas overexpressing FGF19 facilitated CSCs-like properties via activation of FGF receptor (FGFR)-4 in none-LCSCs. Mechanistically, FGF19/FGFR4 signaling stimulated store-operated Ca2+ entry (SOCE) through both the PLCγ and ERK1/2 pathways. Subsequently, SOCE-calcineurin signaling promoted the activation and translocation of nuclear factors of activated T cells (NFAT)-c2, which transcriptionally activated the expression of stemness-related genes (e.g., NANOG, OCT4 and SOX2), as well as FGF19. Furthermore, blockade of FGF19/FGFR4-NFATc2 signaling observably suppressed the self-renewal of LCSCs. Conclusions: FGF19/FGFR4 axis promotes the self-renewal of LCSCs via activating SOCE/NFATc2 pathway; in turn, NFATc2 transcriptionally activates FGF19 expression. Targeting this signaling circuit represents a potential strategy for improving the therapeutic efficacy of HCC.

Berberine impairs coxsackievirus B3-induced myocarditis through the inhibition of virus replication and host pro-inflammatory response.

Berberine (BBR), an isoquinoline alkaloid isolated from Rhizoma coptidis, is reported to possess antiviral activity. Our previous study has shown that BBR alleviates coxsackievirus B3 (CVB3) replication in HeLa cells. However, the anti-CVB3 activity of BBR is still unclear in vivo. In this study, we explored the effect of BBR on CVB3-induced viral myocarditis in mice. These results demonstrated the beneficial effect of BBR on alleviating CVB3-induced myocarditis in vivo, which sheds new light on the utility of BBR as a therapeutic strategy against CVB3-induced viral myocarditis.

Type III Secretion Protein, PcrV, Impairs Pseudomonas aeruginosa Biofilm Formation by Increasing M1 Macrophage-Mediated Anti-bacterial Activities.

Pseudomonas aeruginosa biofilms employ a variety of strategies to hijack the host immune defense system to achieve chronic infection. However, the bacterial components that are involved in this process are not yet fully understood. PcrV, a needle tip protein of the P. aeruginosa type III secretion system (T3SS), was downregulated during P. aeruginosa biofilm infection. The impaired expression of the P. aeruginosa pcrV gene is associated with attenuated immune activation and an increased percentage of M2 macrophages following P. aeruginosa biofilm infection. Treatment with exogenous PcrV produced from Escherichia coli elevated tissue inflammation and the percentage of M1 macrophages, resulting in reduction in the biofilm burden. Further analyses demonstrated that the potential of PcrV to induce classically activated M1 macrophages as evidenced by the increased production of proinflammatory cytokines and anti-bacterial mediators, including inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS), as well as increased phagocytosis of bacteria. Mechanistically, PcrV-mediated promotion of macrophage M1 polarization and phagocytosis occurs through the activation of mitogen-activated protein kinases (MAPKs) and NF-κB signaling pathways. Collectively, these findings reveal a potential role of PcrV in skewing host immune defense to promote P. aeruginosa biofilm infection and provide new insights into the therapeutic strategies for P. aeruginosa biofilm infection.

STIM1 is a metabolic checkpoint regulating the invasion and metastasis of hepatocellular carcinoma.

Background: Cancer cells undergoing invasion and metastasis possess a phenotype with attenuated glycolysis, but enhanced fatty acid oxidation (FAO). Calcium (Ca2+)-mediated signaling pathways are implicated in tumor metastasis and metabolism regulation. Stromal-interaction molecule 1 (STIM1) triggered store-operated Ca2+ entry (SOCE) is the major route of Ca2+ influx for non-excitable cells including hepatocellular carcinoma (HCC) cells. However, whether and how STIM1 regulates the invasion and metastasis of HCC via metabolic reprogramming is unclear. Methods: The expressions of STIM1 and Snail1 in the HCC tissues and cells were measured by immunohistochemistry, Western-blotting and quantitative PCR. STIM1 knockout-HCC cells were generated by CRISPR-Cas9, and gene-overexpression was mediated via lentivirus transfection. Besides, the invasive and metastatic activities of HCC cells were assessed by transwell assay, anoikis rate in vitro and lung metastasis in vivo. Seahorse energy analysis and micro-array were used to evaluate the glucose and lipid metabolism. Results: STIM1 was down-regulated in metastatic HCC cells rather than in proliferating HCC cells, and low STIM1 levels were associated with poor outcome of HCC patients. During tumor growth, STIM1 stabilized Snail1 protein by activating the CaMKII/AKT/GSK-3ß pathway. Subsequently, the upregulated Snail1 suppressed STIM1/SOCE during metastasis. STIM1 restoration significantly diminished anoikis-resistance and metastasis induced by Snail1. Mechanistically, the downregulated STIM1 shifted the anabolic/catabolic balance, i.e., from aerobic glycolysis towards AMPK-activated fatty acid oxidation (FAO), which contributed to Snail1-driven metastasis and anoikis-resistance. Conclusions: Our data provide the molecular basis that STIM1 orchestrates invasion and metastasis via reprogramming HCC metabolism.

Microbiota-derived SSL6 enhances the sensitivity of hepatocellular carcinoma to sorafenib by down-regulating glycolysis.

Enhancing the sensitivity of hepatocellular carcinoma (HCC) cells to sorafenib (SFN) is an essential clinical bottleneck to be solved. Here we report that the expression of CD47 negatively correlated with HCC sensitivity to SFN. The microbiota-derived Staphylococcal superantigen-like protein 6 (SSL6) inhibited CD47 and promoted SFN-induced apoptosis of HCC cells Huh-7 and MHCC97H. Mechanistically, the sensitivity of HCC cells to SFN was inhibited by elevated Warburg effect (glycolysis), and SSL6 down-regulated PI3K/Akt-mediated glycolysis by blocking CD47. Knockdown of CD47 also dampened glycolysis and sensitized HCC cells to SFN. Moreover, SFN-resistant HCC cells exhibited enhanced glycolysis and CD47 expression. SSL6 significantly re-sensitized the resistant HCC cells to SFN. More importantly, we identified the anti-tumor effect of SSL6 in combination with SFN in HCC-bearing mice. Our results clarify the mechanism by which SSL6 enhances SFN sensitivity in HCC cells, providing a molecular basis for combination targeted therapy with microbiota-derived SSL6 to treat HCC.

The long noncoding RNA KCNQ1DN suppresses the survival of renal cell carcinoma cells through downregulating c-Myc.

Background: Long noncoding RNAs (lncRNAs) have been demonstrated to play essential roles in renal cell carcinoma (RCC). However, the role of lncRNA KCNQ1DN in RCC remains unclear. Methods: The expression of KCNQ1DN in RCC and the corresponding adjacent tissues was measured by qPCR. RNA fluorescence in situ hybridization (FISH) assay, methylation analysis, reporter gene assays and functional tests were performed to reveal the effects of KCNQ1DN on RCC. Results: In the present study, we found that lncRNA KCNQ1DN was notably decreased in RCC tissues and cell lines. RNA FISH assay showed that KCNQ1DN mainly localized to the cytoplasm. Methylation analysis revealed that the proximal region of KCNQ1DN promoter was hypermethylated in RCC tissues relative to the adjacent normal ones. Functional studies clarified that KCNQ1DN repressed the RCC cell growth and cell cycle progression. Mechanistically, KCNQ1DN inhibited the expression of c-Myc, which might further upregulate cyclin D1 and suppress p27 at mRNA and protein levels in RCC cells. Reporter gene assays revealed that the transcriptional activity of c-Myc promoter was inhibited by KCNQ1DN. The in vivo experiments in nude mice showed that KCNQ1DN overexpression dramatically repressed the growth of xenograft tumors and the expression of corresponding c-Myc. Conclusion: These results indicated that KCNQ1DN inhibit the growth of RCC cells in vitro and in vivo through repressing the oncogene c-myc, suggesting that KCNQ1DN may serve as a novel target for the treatment of RCC.

Allicin inhibits Pseudomonas aeruginosa virulence by suppressing the rhl and pqs quorum-sensing systems.

Pseudomonas aeruginosa is a virulent bacterium that secretes a variety of virulence factors that aid in establishing infections in individuals. Allicin, derived from garlic, has been shown to inhibit virulence factor production and biofilm formation in P. aeruginosa. However, the mechanisms underlying the allicin-mediated regulation of P. aeruginosa virulence remain unclear. In this study, we investigated the possible mechanisms underlying allicin-mediated virulence regulation in P. aeruginosa. The results showed that allicin attenuates the production of P. aeruginosa virulence-associated factors, such as elastase, pyocyanin, pyoverdine, and rhamnolipids, by inhibiting the rhl and pqs quorum-sensing systems. Further analysis revealed that the rhl and pqs systems play different roles during the allicin-mediated regulation process. Taken together, these results support the potential use of allicin as a therapeutic agent in controlling P. aeruginosa infection and associated mechanisms.

CVB3 Nonstructural 2A Protein Modulates SREBP1a Signaling via the MEK/ERK Pathway.

Coxsackievirus B3 (CVB3) is the predominant pathogen of viral myocarditis. In our previous study, we found that CVB3 caused abnormal lipid accumulation in host cells. However, the underlying mechanisms by which CVB3 disrupts and exploits the host lipid metabolism are not well understood. Sterol regulatory element binding protein 1 (SREBP1) is the major transcriptional factor in lipogenic genes expression. In this study, we demonstrated that CVB3 infection and nonstructural 2A protein upregulated and activated SREBP1a at the transcriptional level. Deletion analysis of SREBP1a promoter revealed that two regions, -1821/-1490 and -312/+217, in this promoter were both required for its activation by 2A. These promoter regions possessed several binding motifs for transcription factor SP1. Next, we used SP1-specific small interfering RNAs (siRNAs) to confirm that SP1 might be the essential factor in SREBP1a upregulation by 2A. Furthermore, we showed that MEK/ERK pathway was involved in the activation of SREBP1a by 2A and that blocking this signaling pathway with the specific inhibitor U0126 attenuated SREBP1a activation and lipid accumulation by 2A. Finally, we showed that inhibition of SREBP1 with siRNAs attenuated lipid accumulation induced by CVB3 infection and reduced virus replication. Moreover, inhibition of the MEK/ERK pathway also led to reduction of SREBP1a activation, lipid accumulation, and virus replication during CVB3 infection. Taken together, these data demonstrate that CVB3 nonstructural 2A protein activates SREBP1a at the transcription level through a mechanism involving MEK/ERK signaling pathway and SP1 transcription factor, which promotes cellular lipid accumulation and benefits virus replication.IMPORTANCE Coxsackievirus B3 (CVB3) infection is the leading cause of viral myocarditis, but effective vaccines and antiviral therapies against CVB3 infection are still lacking. It is important to understand the precise interactions between host and virus for the rational design of effective therapies. During infection, CVB3 disrupts and exploits host lipid metabolism to promote excessive lipid accumulation, which benefits virus replication. SREBP1 is the master regulator of cellular lipid metabolism. Here, we report that one of the viral nonstructural proteins, 2A, upregulates and activates SREBP1a. Furthermore, we find that inhibition of SREBP1 decreases CVB3 virus replication. These results reveal the regulation of SREBP1a expression by 2A and the roles of SREBP1 in lipid accumulation and viral replication during CVB3 infection. Our findings provide a new insight into CVB3 host interactions and inform a potential novel therapeutic target for this important pathogen.

Berberine Restricts Coxsackievirus B Type 3 Replication via Inhibition of c-Jun N-Terminal Kinase (JNK) and p38 MAPK Activation In Vitro.

BACKGROUND At present, the treatment of coxsackievirus-induced myocarditis remains difficult. Berberine (BBR), an isoquinoline alkaloid isolated from traditional medicine herbs, exhibits significant anti-viral efficacy against various viruses. However, the underlying mechanism by which BBR controls CVB3 infection has not yet been reported. The purpose of this study was to investigate the anti-viral efficacy of BBR against CVB3 infection and its mechanism. MATERIAL AND METHODS In our experiments, the protein levels of VP1 and MAPKs signal pathway were measured by Western blot. The mRNA level of VP1 was measured by RT-PCR. The virus titers were determined by TCID50 assay. RESULTS We found that BBR treatment significantly decreased CVB3 replication in HeLa cells. In addition, the BBR treatment reduced the phosphorylation levels of JNK and p38 MAPK upon CVB3 infection in both HeLa cells and primary rat myocardial cells. CONCLUSIONS Taken together, these results suggest that BBR inhibits CVB3 replication through the suppression of JNK and p38 MAPK activation, shedding new light on the investigation of therapeutic strategies against CVB3-induced viral myocarditis.

Metformin Induces Growth Inhibition and Cell Cycle Arrest by Upregulating MicroRNA34a in Renal Cancer Cells.

BACKGROUND Metformin is a widely used biguanide drug for the treatment of type 2 diabetes. It has been revaluated as a potential anti-cancer drug with promising activity in various tumors. However, the precise mechanisms underlying the suppression of cancer cells by metformin remain not well understood. MATERIAL AND METHODS In this study, human renal cell carcinoma cell line ACHN was used to investigate the anti-proliferation effect of metformin. A cell counting kit-8 assay was used to detect the cell viability. The cell cycle distribution and apoptosis were analyzed by flow cytometry. The expression of cyclin D1 and p27KIP1 was detected by Western blot. The underlying mechanism involving miRNA34a was further investigated by quantitative RT-PCR and transfection with miRNA inhibitor specific for miRNA34a in ACHN, 769-P, and A498 cells. RESULTS Metformin could significantly inhibit the proliferation of ACHN cells in a dose- and time-dependent manner. In addition, the results showed that metformin induced G0/G1 phase arrest and delayed entry into S phase in ACHN cells. It was shown that metformin downregulates the expression of cyclin D1 and increases the p27KIP1 level. Furthermore, metformin increased ACHN cell death. Lastly, miRNA34a was found to be upregulated by metformin in ACHN, 769-P, and A498 cells. Subsequently, it was demonstrated that inhibition of miRNA34a could partially attenuate the suppressive effect of metformin on renal cancer cell proliferation. CONCLUSIONS The study data revealed that metformin induced cell growth inhibition and cell cycle arrest partially by upregulating miRNA34a in renal cancer cells.

Role of ppGpp in Pseudomonas aeruginosa acute pulmonary infection and virulence regulation.

During infection, bacteria might generate adaptive responses to facilitate their survival and colonization in the host environment. The alarmone guanosine 5'-triphosphate-3'-diphosphate (ppGpp), the levels of which are regulated by the RelA and SpoT enzymes, plays a critical role in mediating bacterial adaptive responses and virulence. However, the mechanism by which ppGpp regulates virulence-associated traits in Pseudomonas aeruginosa is poorly understood. To investigate the regulatory role of ppGpp, the ppGpp-deficient strain ΔRS (relA and spoT gene double mutant) and the complemented strain ΔRS(++) (complemented with relA and spoT genes) were constructed. Herein, we reported that the ΔRS strain showed decreased cytotoxicity towards A549 human alveolar adenocarcinoma cell lines and led to reduced mortality, lung edema and inflammatory cell infiltration in a mouse model of acute pneumonia compared to wild-type PAO1 and the complemented strain ΔRS(++). Subsequent analyses demonstrated that the ΔRS strain displayed reduced T3SS expression, decreased levels of elastase activity, pyocyanin, pyoverdin and alginate, and inhibited swarming and biofilm formation compared to PAO1 and the complemented strain ΔRS(++). In addition, the results demonstrate that ppGpp-mediated regulation of T3SS, virulence factor production, and swarming occurs in a quinolone quorum-sensing system-dependent manner. Taken together, these results suggest that ppGpp is required for virulence regulation in P. aeruginosa, providing new clues for the development of interference strategies against bacterial infection.

Ndk, a novel host-responsive regulator, negatively regulates bacterial virulence through quorum sensing in Pseudomonas aeruginosa.

Pathogenic bacteria could adjust gene expression to enable their survival in the distinct host environment. However, the mechanism by which bacteria adapt to the host environment is not well described. In this study, we demonstrated that nucleoside diphosphate kinase (Ndk) of Pseudomonas aeruginosa is critical for adjusting the bacterial virulence determinants during infection. Ndk expression was down-regulated in the pulmonary alveoli of a mouse model of acute pneumonia. Knockout of ndk up-regulated transcription factor ExsA-mediated T3S regulon expression and decreased exoproduct-related gene expression through the inhibition of the quorum sensing hierarchy. Moreover, in vitro and in vivo studies demonstrated that the ndk mutant exhibits enhanced cytotoxicity and host pathogenicity by increasing T3SS proteins. Taken together, our data reveal that ndk is a critical novel host-responsive gene required for coordinating P. aeruginosa virulence upon acute infection.

Activation of AMPK restricts coxsackievirus B3 replication by inhibiting lipid accumulation.

Coxsackievirus B3 (CVB3) is the major pathogen of human viral myocarditis. CVB3 has been found to manipulate and modify the cellular lipid metabolism for viral replication. The cellular AMP-activated protein kinase (AMPK) is a key regulator of multiple metabolic pathways, including lipid metabolism. Here we explore the potential roles AMPK plays in CVB3 infection. We found that AMPK is activated by the viral replication during CVB3 infection in Hela cells and primary myocardial cells. RNA interference mediated inhibition of AMPK could increase the CVB3 replication in cells, indicating that AMPK contributed to restricting the viral replication. Next, we showed that CVB3 replication could be inhibited by several different pharmacological AMPK activators including metformin, A769662 and AICAR. And the constitutively active AMPK mutant (CA-AMPK) could also inhibit the CVB3 replication. Furthermore, we found that CVB3 infection increased the cellular lipid levels and showed that the AMPK agonist AICAR both restricted CVB3 replication and reduced lipid accumulation through inhibiting the lipid synthesis associated gene expression. We further found that CVB3 infection would also induce AMPK activated in vivo. The AMPK agonist metformin, which has been widely used in diabetes therapy, could decrease the viral replication and further protect the mice from myocardial histological and functional changes in CVB3 induced myocarditis, and improve the survival rate of infected mice. Lastly, it was demonstrated that the AICAR-mediated restriction of viral replication could be rescued partially by exogenous palmitate, the first product of fatty acid biosynthesis, demonstrating that AMPK activation restricted CVB3 infection through its inhibition of lipid synthesis. Taken together, these data in the present study suggest a model in which AMPK is activated by CVB3 infection and restricts viral replication by inhibiting the cellular lipid accumulation, and inform a potential novel therapeutic strategy for CVB3-associated diseases.

Elastase LasB of Pseudomonas aeruginosa promotes biofilm formation partly through rhamnolipid-mediated regulation.

Elastase LasB, an important extracellular virulence factor, is shown to play an important role in the pathogenicity of Pseudomonas aeruginosa during host infection. However, the role of LasB in the life cycle of P. aeruginosa is not completely understood. This report focuses on the impact of LasB on biofilm formation of P. aeruginosa PAO1. Here, we reported that the lasB deletion mutant (ΔlasB) displayed significantly decreased bacterial attachment, microcolony formation, and extracellular matrix linkage in biofilm associated with decreased biosynthesis of rhamnolipids compared with PAO1 and lasB complementary strain (ΔlasB(+)). Nevertheless, the ΔlasB developed restored biofilm formation with supplementation of exogenous rhamnolipids. Further gene expression analysis revealed that the mutant of lasB could result in the downregulation of rhamnolipid synthesis at the transcriptional level. Taken together, these results indicated that LasB could promote biofilm formation partly through the rhamnolipid-mediated regulation.

Disturbance of intraepithelial lymphocytes in a murine model of acute intestinal ischemia/reperfusion.

Strategically located at the epithelial basolateral surface, intraepithelial lymphocytes (IELs) are intimately associated with epithelial cells and maintain the epithelial barrier integrity. Intestinal ischemia-reperfusion (I/R)-induced acute injury not only damages the epithelium but also affects the mucosal barrier function. Therefore, we hypothesized that I/R-induced mucosal damage would affect IEL phenotype and function. Adult C57BL/6J mice were treated with intestinal I/R or sham. Mice were euthanized at 6 h after I/R, and the small bowel was harvested for histological examination and to calculate the transmembrane resistance. Occludin expression and IEL location were detected through immunohistochemistry. The IEL phenotype, activation, and apoptosis were examined using flow cytometry. Cytokine and anti-apoptosis-associated gene expressions were measured through RT-PCR. Intestinal I/R induced the destruction of epithelial cells and intercellular molecules (occludin), resulting in IEL detachment from the epithelium. I/R also significantly increased the CD8αß, CD4, and TCRαß IEL subpopulations and significantly changed IEL-derived cytokine expression. Furthermore, I/R enhanced activation and promoted apoptosis in IELs. I/R-induced acute intestinal mucosal damage significantly affected IEL phenotype and function. These findings provide profound insight into potential IEL-mediated epithelial barrier dysfunction after intestinal I/R.

Expression of coxsackievirus and adenovirus receptor (CAR)-Fc fusion protein in Pichia pastoris and characterization of its anti-coxsackievirus activity.

Coxsackievirus and adenovirus receptors (CARs) are the common cellular receptors which mediate coxsackievirus or adenovirus infection. Receptor trap therapy, which uses soluble viral receptors to block the attachment and internalization of virus, has been developed for the inhibition of virus infection. In this study, we have constructed a pPIC3.5K/CAR-Fc expression plasmid for the economical and scale-up production of CAR-Fc fusion protein in Pichia pastoris. The coding sequence of the fusion protein was optimized according to the host codon usage bias. The amount of the CAR-Fc protein to total cell protein was up to 10% by 1% methanol induction for 96h and the purity was up to 96% after protein purification. Next, the virus pull-down assay demonstrated the binding activity of the CAR-Fc to coxsackievirus. The analyses of MTT assay, immunofluorescence staining and quantitative real-time PCR after virus neutralization assay revealed that CAR-Fc could significantly block coxsackievirus B3 infection in vitro. In coxsackievirus B3 infected mouse models, CAR-Fc treatment reduced mortality, myocardial edema, viral loads and inflammation, suggesting the significant virus blocking effect in vivo. Our results indicated that the P. pastoris expression system could be used to produce large quantities of bioactive CAR-Fc for further clinical purpose.