Vibrio vulnificus VvhA induces NF-κB-dependent mitochondrial cell death via lipid raft-mediated ROS production in intestinal epithelial cells

Neuroprotective effects of ulinastatin on Escherichia coli meningitis rats through inhibiting PKCα phosphorylation and reducing zonula occludens-1 degradation

Ulinastatin, a broad-spectrum inflammatory inhibitor widely employed in the management of severe pancreatitis and sepsis, has not been extensively investigated for its therapeutic potential in bacterial meningitis. This study aims to assess the neuroprotective effects of ulinastatin on bacterial meningitis and elucidate its underlying mechanism. The rat model of bacterial meningitis was established by intracerebral injection of Escherichia coli. 3-week-old SD rats were randomly divided into 5 groups with 8 rats in each group, including control group, E.coli group, E.coli + UTI group (ulinastatin 50000IU/kg), E.coli + UTI + PMA group (ulinastatin 50000IU/kg + PMA 200 ug/kg), and E.coli + PMA group(PMA 200 ug/kg). Behavioral changes were assessed by Loeffler neurobehavioral score. Histomorphologic changes and apoptosis were assessed by hematoxylin and eosin staining, Nissl staining and TUNEL staining. Immunohistochemistry and immunofluorescence and western blotting were used to detect the expression levels of zonula occludens-1 (ZO-1) and phosphorylation protein kinase C (PKCα).It was found that ulinastatin treatment in Escherichia coli meningitis rats improved neurological function, alleviated meningeal inflammatory infiltration, reduced neuronal death, promoted the integrity of the blood-brain barrier structure. Moreover, phorbol myristate acetate (PMA, a protein kinase C activator), blocked the effective action of ulinastatin. These findings suggest that ulinastatin had neuroprotective effects on bacterial meningitis by inhibiting PKCα phosphorylation and reducing ZO-1 degradation, demonstrating that ulinastatin may be a promising strategy in the treatment of bacterial meningitis.

Study of the anti-cancer activity of a mesoporous silica nanoparticle surface coated with polydopamine loaded with umbelliprenin

A mesoporous silica nanoparticle (MSN) coated with polydopamine (PDA) and loaded with umbelliprenin (UMB) was prepared and evaluated for its anti-cancer properties in this study. Then UMB-MSN-PDA was characterized by dynamic light scattering (DLS), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM) and FTIR methods. UV-visible spectrometry was employed to study the percentage of encapsulation efficiency (EE%). UMB-MSN-PDA mediated cell cytotoxicity and their ability to induce programmed cell death were evaluated by MTT, real-time qPCR, flow cytometry, and AO/PI double staining methods. The size of UMB-MSN-PDA was 196.7 with a size distribution of 0.21 and a surface charge of -41.07 mV. The EE% was 91.92%. FESEM and TEM showed the spherical morphology of the UMB-MSN-PDA. FTIR also indicated the successful interaction of the UMB and MSN and PDA coating. The release study showed an initial 20% release during the first 24 h of the study and less than 40% during 168 h. The lower cytotoxicity of the UMB-MSN-PDA against HFF normal cells compared to MCF-7 carcinoma cells suggested the safety of formulation on normal cells and tissues. The induction of apoptosis in MCF-7 cells was indicated by the upregulation of P53, caspase 8, and caspase 9 genes, enhanced Sub-G1 phase cells, and the AO/PI fluorescent staining. As a result of these studies, it may be feasible to conduct preclinical studies shortly to evaluate the formulation for its potential use in cancer treatment.

The Yin and Yang of pathogens and probiotics: interplay between Salmonella enterica sv. Typhimurium and Bifidobacterium infantis during co-infection

Probiotic bacteria have been proposed as an alternative to antibiotics for the control of antimicrobial resistant enteric pathogens. The mechanistic details of this approach remain unclear, in part because pathogen reduction appears to be both strain and ecology dependent. Here we tested the ability of five probiotic strains, including some from common probiotic genera Lactobacillus and Bifidobacterium, to reduce binding of Salmonella enterica sv. Typhimurium to epithelial cells in vitro. Bifidobacterium longum subsp. infantis emerged as a promising strain; however, S. Typhimurium infection outcome in epithelial cells was dependent on inoculation order, with B. infantis unable to rescue host cells from preceding or concurrent infection. We further investigated the complex mechanisms underlying this interaction between B. infantis, S. Typhimurium, and epithelial cells using a multi-omics approach that included gene expression and altered metabolism via metabolomics. Incubation with B. infantis repressed apoptotic pathways and induced anti-inflammatory cascades in epithelial cells. In contrast, co-incubation with B. infantis increased in S. Typhimurium the expression of virulence factors, induced anaerobic metabolism, and repressed components of arginine metabolism as well as altering the metabolic profile. Concurrent application of the probiotic and pathogen notably generated metabolic profiles more similar to that of the probiotic alone than to the pathogen, indicating a central role for metabolism in modulating probiotic-pathogen-host interactions. Together these data imply crosstalk via small molecules between the epithelial cells, pathogen and probiotic that consistently demonstrated unique molecular mechanisms specific probiotic/pathogen the individual associations.

Novel formulation of parthenolide-loaded liposome coated with chitosan and evaluation of its potential anticancer effects in vitro

BACKGROUND

In this study the formulation of parthenolide (PN), an anticancer agent extracted from a natural product, into a liposome (PN-liposome), was examined. The surface of the PN-liposome was modified using chitosan (PN-chitosome). By using real-time quantitative PCR and flow cytometry, we examined the release of PN-chitosomes, cytotoxicity, and ability to induce apoptosis in vitro.

METHODS AND RESULTS

According to the present study, PN-chitosomes had a size of 251 nm which is acceptable for efficient enhanced permeation and retention (EPR) performance. PN-chitosomes were confirmed to be spherical in shape and size through FESEM analysis. In terms of encapsulation efficiency, 94.5% was achieved. PN-chitosome possessed a zeta potential of 34.72 mV, which was suitable for its stability. According to the FTIR spectra of PN and PN-chitosome, PN was chemically stable due to the intermolecular interaction between the liposome and the drug. After 48 h, only 10% of the PN was released from the PN-chitosome in PBS (pH 7.4), and less than 20% was released after 144 h.

CONCLUSION

In a dose-dependent manner, PN-chitosome exhibited anticancer properties that were more cytotoxic against cancer cells than normal cells. Moreover, the formulation activated both the apoptosis pathway and cytotoxic genes in real-time qPCR experiments. According to the cytotoxicity and activating apoptosis of the prepared modified particle, PN-chitosome may be helpful in the treatment of cancer.

Direct and indirect effects of pathogenic bacteria on the integrity of intestinal barrier

Bacterial translocation is a pathological process involving migration of pathogenic bacteria across the intestinal barrier to enter the systemic circulation and gain access to distant organs. This phenomenon has been linked to a diverse range of diseases including inflammatory bowel disease, pancreatitis, and cancer. The intestinal barrier is an innate structure that maintains intestinal homeostasis. Pathogenic infections and dysbiosis can disrupt the integrity of the intestinal barrier, increasing its permeability, and thereby facilitating pathogen translocation. As translocation represents an essential step in pathogenesis, a clear understanding of how barrier integrity is disrupted and how this disruption facilitates bacterial translocation could identify new routes to effective prophylaxis and therapy. In this comprehensive review, we provide an in-depth analysis of bacterial translocation and intestinal barrier function. We discuss currently understood mechanisms of bacterial-enterocyte interactions, with a focus on tight junctions and endocytosis. We also discuss the emerging concept of bidirectional communication between the intestinal microbiota and other body systems. The intestinal tract has established 'axes' with various organs. Among our regulatory systems, the nervous, immune, and endocrine systems have been shown to play pivotal roles in barrier regulation. A mechanistic understanding of intestinal barrier regulation is crucial for the development of personalized management strategies for patients with bacterial translocation-related disorders. Advancing our knowledge of barrier regulation will pave the way for future research in this field and novel clinical intervention strategies.

Pathogenic mechanism of Vibrio vulnificus infection

Vibrio vulnificus is a fatal, opportunistic human pathogen transmitted through the consumption of raw/undercooked seafood or direct contact. V. vulnificus infection progresses rapidly and has severe consequences; some cases may require amputation or result in death. Growing evidence suggests that V. vulnificus virulence factors and regulators play a large role in disease progression, involving host resistance, cellular damage, iron acquisition, virulence regulation and host immune responses. Its disease mechanism remains largely undefined. Further evaluation of pathogenic mechanisms is important for selecting appropriate measures to prevent and treat V. vulnificus infection. In this review, the possible pathogenesis of V. vulnificus infection is described to provide a reference for treatment and prevention.

Complex regulatory networks of virulence factors in Vibrio vulnificus

The fulminating zoonotic pathogen Vibrio vulnificus is the causative agent of fatal septicemia in humans and fish, raising tremendous economic burdens in healthcare and the aquaculture industry. V. vulnificus exploits various virulence factors, including biofilm-related factors and exotoxins, for its persistence in nature and pathogenesis during infection. Substantial studies have found that the expression of virulence factors is coordinately regulated by numerous transcription factors that recognize the changing environments. Here, we summarize and discuss the recent discoveries of the physiological roles of virulence factors in V. vulnificus and their regulation by transcription factors in response to various environmental signals. This expanded understanding of molecular pathogenesis would provide novel clues to develop an effective antivirulence therapy against V. vulnificus infection.

Fabrication of folic acid-conjugated chitosan-coated PLGA nanoparticles for targeted delivery ofPeganum harmalasmoke extract to breast cancer cells

In this study, PLGA-NPs coated with folic acid-chitosan (PCF-NPs) loaded withPeganum harmalasmoke extract (PSE) were synthesized (PSE-PCF-NPs), and their anti-cancer effects were evaluated. PSE-PCF-NPs were synthesized by the nanoprecipitation method and then characterized by DLS, SEM, and FTIR methods. HPLC and UV-vis spectroscopy were used to evaluate the PSE's folic acid (FA) binding and encapsulation. PSE-PCF-NPs-mediated cell viability and apoptosis were investigated by MTT, qPCR, flow cytometry, AO/PI, and DAPI staining. Anti-oxidant properties of PSE-PCF-NPs were evaluated by ABTS, DPPH, FRAP, and ROS. Angiogenic effects of PSE-PCF-NPs were assessed by CAM assay. The PSE-PCF-NPs (276.16 nm, PDI: 0.25, zeta-potential: +32.31 mV, FB: 67.6% and %EE: 89%) demonstrated selective toxicity on MCF-7 cells (IC₅₀: 75.65μg ml^-1). The occurrence of apoptosis in MCF-7 cells was confirmed by up-regulation of P53, Cas-3, and Cas-9 genes, increased SubG1 phase cells, and the results of fluorescent staining. Scavenging free radicals, reducing iron ions, increasing intracellular ROS, and decreasing SOD gene confirmed the anti- and pro-oxidant effects of PSE-PCF-NPs outside and inside MCF-7 cells. Reduction of angiogenic factors in CAM assay showed the anti-angiogenic effects of PSE-PCF-NPs. PSE-PCF-NPs, due to their anti-cancer properties, can be considered a therapeutic agent in cancer studies.

Identification and whole-genome sequencing analysis of Vibrio vulnificus strains causing pearl gentian grouper disease in China

Vibrio vulnificus is a pathogenic bacterium that causes disease in marine fish, affecting fish farming and human health worldwide. In May 2021, in the Bohai Bay region, a disease broke out in commercially farmed pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus), causing huge economic losses. The diseased fish had skin lesions, water accumulation in their abdomens, and showed tissue and organ damage. V. vulnificus biotype 2 has been reported in eels and other marine fish, but it is less reported in pearl gentian grouper. In this study, the pathogenic strain isolated from diseased fish was identified as V. vulnificus EPL 0201 biotype 2 on the basis of physiological and biochemical characteristics and the results of 16S rRNA gene and gyrB sequencing, virulence gene detection, and recursive infection experiments. To gain a comprehensive understanding of the pathogenicity and drug resistance of this strain, whole-genome sequencing was performed. Whole-genome analysis showed that the gene map of this strain was complete. The Virulence Factor Database annotation results showed that this strain had the key virulence factor genes vvhA and rtxA, which cause host disease. In addition, this strain had genes conferring resistance against cephalosporins, aminoglycosides, tetracyclines, and sulfonamides. Antimicrobial susceptibility testing confirmed the presence of these resistance genes identified in the genome. The results of this study show that V. vulnificus EPL 0201 biotype 2 is a multi-drug resistant strain with high pathogenicity.

Crosstalk between Lipid Rafts and Aging: New Frontiers for Delaying Aging

With the rapid aging in the global population, delay of aging has become a hot research topic. Lipid rafts (LRs) are microdomains in the plasma membrane that contain sphingolipids and cholesterol. Emerging evidence indicates an interesting interplay between LRs and aging. LRs and their components are altered with aging. Further, the aging process is strongly influenced by LRs. In recent years, LRs and their component signaling molecules have been recognized to affect aging by interfering with its hallmarks. Therefore, targeting LRs is a promising strategy to delay aging.

Biomimetic Nanosponges Enable the Detoxification of Vibrio vulnificus Hemolysin

Vibrio vulnificus (V. vulnificus) infection-associated multiple antibiotic resistance has raised serious public health concerns. Recently, nanosponges (NSs) have been expected to provide innovative platforms for addressing antibacterial and drug-resistant challenges by targeting various pore-forming toxins (PFTs). In the present study, we constructed NSs to explore the effects and possible mechanism of recombinant V. vulnificus hemolysin (rVvhA)-induced injuries. In vitro, NSs significantly reversed rVvhA-induced apoptosis and necrosis, and improved toxin-induced intracellular reactive oxygen species (ROS) production, adenosine triphosphate (ATP) depletion, and apoptosis signaling pathway disruption. To explore the clinical translation potential of NSs, we established VvhA-induced septicemia and wound infection mouse models, respectively, and further found NSs could notably attenuate rVvhA-induced acute toxicity and septicemia-associated inflammation, as well as local tissue damage. In a conclusion, NSs showed excellent protective effects against rVvhA-induced toxicity, thus providing useful insights into addressing the rising threats of severe V. vulnificus infections.

GSDMEa-mediated pyroptosis is bi-directionally regulated by caspase and required for effective bacterial clearance in teleost

Gasdermin (GSDM) is a family of pore-forming proteins that, after cleavage by caspase (CASP), induce a type of programmed necrotic cell death called pyroptosis. Gasdermin E (GSDME) is the only pyroptosis-inducing member of the GSDM family existing in teleost. To date, the regulation and function of teleost GSDME in response to bacterial infection remain elusive. In this study, we observed activation of GSDME, as well as multiple CASPs, in turbot Scophthalmus maximus during the infection of the bacterial pathogen Vibrio harveyi. Turbot has two GSDME orthologs named SmGSDMEa and SmGSDMEb. We found that SmGSDMEa was specifically cleaved by turbot CASP (SmCASP) 3/7 and SmCASP6, which produced two different N-terminal (NT) fragments. Only the NT fragment produced by SmCASP3/7 cleavage was able to induce pyroptosis. Ectopically expressed SmCASP3/7 activated SmGSDMEa, resulting in pyroptotic cell death. In contrast, SmCASP6 inactivated SmGSDMEa by destructive cleavage of the NT domain, thus nullifying the activation effect of SmCASP3/7. Unlike SmGSDMEa, SmGSDMEb was cleaved by SmCASP8 and unable to induce cell death. V. harveyi infection dramatically promoted the production and activation of SmGSDMEa, but not SmGSDMEb, and caused pyroptosis in turbot. Interference with SmCASP3/7 activity significantly enhanced the invasiveness and lethality of V. harveyi in a turbot infection model. Together, these results revealed a previously unrecognized bi-directional regulation mode of GSDME-mediated pyroptosis, and a functional difference between teleost GSDMEa and GSDMEb in the immune defense against bacterial infection.

Pre-injection of Zebrafish (Danio rerio) tnfb Polyclonal Antibody Decreases the Mortality of Vibrio vulnificus Infected Zebrafish

Tumor necrosis factor (TNF) plays an important role in an inflammatory cytokine storm. Over-secretion of TNF by the host in response to infection aggravates the disease. TNF expression level is positively correlated with the mortality caused by some bacterial infections. Therefore, using TNF antibody may alleviate the inflammation to resist bacterial infections. The function of fish TNF-b antibody in bacterial infection is still unclear. In this study, infection models of Vibrio vulnificus FJ03-X2 strain with high pathogenicity and strong virulence were established in zebrafish (Danio rerio) fibroblast cell line (ZF4 cells) and zebrafish. Zebrafish tnfb (Zetnf-b) gene was cloned and expressed by Escherichia coli BL21 (DE3), and Zetnf-b polyclonal antibody was prepared. Pre-injection of Zetnf-b polyclonal antibody and AG-126 before infecting with V. vulnificus could increase the survival rate of zebrafish by 36.6 and 46.7%, respectively. Pre-injection of Zetnf-b polyclonal antibody could effectively decrease the mortality of zebrafish infected by V. vulnificus. Thus, TNF polyclonal antibody therapy could be considered as an effective strategy to control V. vulnificus in fish.

Coral gasdermin triggers pyroptosis

Gasdermins are executioners of the inflammatory cell death pathway pyroptosis that has so far been studied exclusively in vertebrates. In this study, we identified gasdermin E (GSDME) homologs in several invertebrate species including corals. We report that coral GSDME was cleaved by caspase 3 at two sites, yielding two active isoforms of GSDME N-terminal domain that were capable of inducing pyroptosis. Ectopic coexpression of coral GSDME and caspase 3 in human cells promoted pyroptosis. Corals infected with Vibrio coralliilyticus, a bacterial pathogen causing rapid tissue necrosis of corals worldwide, exhibited necrotic death with elevated caspase 3 activity and GSDME cleavage, whereas inhibition of caspase 3 blocked GSDME cleavage and protected corals from necrotic death. These results indicate that functional gasdermin exists in invertebrates and that coral gasdermin is involved in pathogen-induced coral death. Furthermore, our studies also suggest that mediation of pyroptosis is an evolutionarily conserved function of gasdermins.

Vibrio vulnificus Hemolysin: Biological Activity, Regulation of vvhA Expression, and Role in Pathogenesis

The Vibrio vulnificus (V. vulnificus) hemolysin (VVH) is a pore-forming cholesterol-dependent cytolysin (CDC). Although there has been some debate surrounding the in vivo virulence effects of the VVH, it is becoming increasingly clear that it drives different cellular outcomes and is involved in the pathogenesis of V. vulnificus. This minireview outlines recent advances in our understanding of the regulation of vvhA gene expression, the biological activity of the VVH and its role in pathogenesis. An in-depth examination of the role of the VVH in V. vulnificus pathogenesis will help reveal the potential targets for therapeutic and preventive interventions to treat fatal V. vulnificus septicemia in humans. Future directions in VVH research will also be discussed.

Vibrio deploys type 2 secreted lipase to esterify cholesterol with host fatty acids and mediate cell egress

Pathogens find diverse niches for survival including inside a host cell where replication occurs in a relatively protective environment. Vibrio parahaemolyticus is a facultative intracellular pathogen that uses its type 3 secretion system 2 (T3SS2) to invade and replicate inside host cells. Analysis of the T3SS2 pathogenicity island encoding the T3SS2 appeared to lack a mechanism for egress of this bacterium from the invaded host cell. Using a combination of molecular tools, we found that VPA0226, a constitutively secreted lipase, is required for escape of V. parahaemolyticus from the host cells. This lipase must be delivered into the host cytoplasm where it preferentially uses fatty acids associated with innate immune response to esterify cholesterol, weakening the plasma membrane and allowing egress of the bacteria. This study reveals the resourcefulness of microbes and the interplay between virulence systems and host cell resources to evolve an ingenious scheme for survival and escape.

Nanosphere Loaded with Curcumin Inhibits the Gastrointestinal Cell Death Signaling Pathway Induced by the Foodborne Pathogen Vibrio vulnificus

Curcumin, a hydrophobic polyphenol of turmeric, has a variety of biological functions as a herbal supplement, but its poor gastric absorption rate is one of the major factors limiting its oral bioavailability. In the present study, we have investigated the functional role of a nanosphere loaded with curcumin (CN) during host cell death elicited by the Gram-negative bacterium V. vulnificus in human gastrointestinal epithelial HT-29 cells and an ileal-ligated mouse model. The recombinant protein (r) VvhA produced by V. vulnificus significantly reduced the viability of HT-29 cells. The cytotoxic effect of rVvhA was restored upon a treatment with CN (100 ng/mL), which had shown 1000-fold higher anti-apoptotic efficacy than curcumin. CN inhibited the phosphorylation of c-Src and PKC mediated by intracellular ROS responsible for the distinctive activation of the MAPKs in rVvhA-treated HT-29 cells. Interestingly, CN significantly restored the expression of Bax, Bcl-2, and cleaved caspase-3 as regulated by the phosphorylation of NF-κB. In mouse models of V. vulnificus infection, treatment with CN had a blocking effect that elevated the levels of TUNEL-positive DNA fragmentation and apoptosis-related proteins. These results indicate that CN is a functional agent that manipulates the V. vulnificus VvhA signaling pathway responsible for gastrointestinal cell death.

Vibrio vulnificus cytolysin induces inflammatory responses in RAW264.7 macrophages through calcium signaling and causes inflammation in vivo

Vibrio vulnificus is a food-borne marine pathogen that causes both life-threatening primary septicemia and necrotizing wound infections which accompany severe inflammation. Cytolysin is a very powerful virulence factor of V. vulnificus and is one of the likely candidates in the pathogenesis of V. vulnificus infections. However, the pathogenetic roles of cytolysin in V. vulnificus-induced inflammation are not well understood. In this study, we used the recombinant protein Vibrio vulnificus cytolysin (VVC) to demonstrate that VVC can induce inflammatory responses in RAW264.7 macrophages. Low dose (<5 μg/ml) VVC had no impact on cell viability and induced pro-inflammatory cytokines production in RAW264.7 macrophages such as IL-6 and TNF-α. Moreover, VVC induced p65, p38, ERK1/2, and AKT phosphorylation in RAW264.7 macrophages. We further demonstrated that BAPTA-AM, a specific intracellular calcium chelator, inhibited VVC-induced inflammatory responses including pro-inflammatory cytokines production and inflammatory signaling activation in RAW264.7 macrophages. In addition, VVC primed rather than actived NLRP3 inflammasome in RAW264.7 macrophages. To determine whether VVC have a direct inflammatory effect on the host, we examined the effects of VVC injected into the skin of mice. VVC stimulated a significant induction of mRNAs for the pro-inflammatory cytokine IL-6 and inflammatory chemokines such as MCP-1 and IP-10. Histology data also showed that VVC caused inflammatory responses in the skin of mice. Collectively, our findings indicated that VVC induced inflammatory responses in RAW264.7 macrophages and in vivo and suggested the possibility of targeting VVC as a strategy for the clinical management of V. vulnificus-induced inflammatory responses.

Epidemiology, pathogenetic mechanism, clinical characteristics, and treatment of Vibrio vulnificus infection: a case report and literature review

Vibrio vulnificus is a Gram-negative bacterium that belongs to the Vibrionaceae family. It represents a deadly opportunistic human pathogen which grows in water with the proper temperature and salinity, and is mostly acquired from seafood eating or direct contact. In susceptible individuals, a traumatic infection could be fatal, causing severe wound infection and even septic shock, and may require amputation. Global warming plays an important role in the geographical area expanding of Vibrio disease. The pathogenesis of Vibrio vulnificus-associated sepsis is very complex, including iron intake, cell injury, and adhesion-related protein and virulence regulation. Vibrio vulnificus infection mainly manifests clinical subtypes such as primary sepsis, traumatic infection, and gastroenteritis, with rapid symptom progression and signs of multiple organ dysfunction syndrome (MODS). It is important to assess these pathogenetic mechanisms in order to select more appropriate measures to prevent and treat Vibrio vulnificus infections, including antibiotic usage and surgical intervention. In this work, we report a typical case of successful treatment of necrotizing fasciitis caused by Vibrio vulnificus, and review the epidemiology, pathogenetic mechanism, clinical characteristics, and treatment of Vibrio vulnificus infection.

Inhibiting Ceramide Synthesis Attenuates Hepatic Steatosis and Fibrosis in Rats With Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common metabolic disorder diseases, which include a histological spectrum of conditions ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Dysregulated metabolism of sphingomyelin in the liver plays a critical role in the pathogenesis of NAFLD. Ceramides are central molecules of sphingolipid biosynthesis and catabolism and play an important role in insulin resistance, apoptosis, and inflammation. In addition, apoptosis is a main contributor to the development of NAFLD. This study detected whether the inhibition of ceramide synthesis ameliorated hepatic steatosis and fibrosis in rats with NAFLD. Sprague-Dawley rats were used to establish the NAFLD model. Here, we showed that hepatic ceramide, steatosis, and fibrosis increased in liver tissue from rats with NAFLD. Chronic treatment with myriocin inhibited ceramide and lipid accumulation and improved fibrosis in liver tissue samples of high fat diet (HFD)-fed rats. In addition, hepatic inflammation and apoptosis were markedly ameliorated in HFD-fed rats treated with myriocin. Furthermore, myriocin treatment regulated the expression of pro-apoptosis and anti-apoptosis proteins by inactivating the c-Jun N-terminal kinase (JNK) signaling pathway in the liver of HFD-fed rats. Collectively, ceramide plays an important role in the pathogenesis of NASH and may represent a potential therapeutic strategy to prevent NAFLD.

Transmembrane protein GRINA modulates aerobic glycolysis and promotes tumor progression in gastric cancer

BACKGROUND

Recent observations indicate a decreased cancer risk in patients with Alzheimer's disease (AD). AD is a severe neurodegenerative disorder characterized by progressive cognitive decline. The 8q24 region has been shown to be involved in AD aetiology. We aimed to identify and explore the potential oncogenes or antioncogenes on chromosome 8q24.

METHODS

We compared expression of genes on Chromosome 8q24 in 32 pairs of samples from The Cancer Genome Atlas (TCGA) database. We conducted bioinformatics analysis of the commonly used gastric cancer databases and performed clinical verification of gastric cancer samples, combined with assessment of biological function both in vitro and in vivo to determine the relationship between upregulated expression of GRINA and gastric cancer progression. We also explored the molecular mechanism of GRINA upregulation and its function in gastric cancer development and progression.

RESULTS

The expression of GRINA in cancer tissues was significantly higher than that in normal tissues. GRINA indicated poor prognosis in gastric cancer. GRINA promoted the proliferation, migration and invasion capacity of gastric cancer cells. GRINA was transcriptionally mediated by c-Myc and promotes cell cycle transition. GRINA knockdown decreased PI3K/Akt/mTOR signaling and glycolytic metabolism in gastric cancer cells. The apoptosis rate was significantly increased in gastric cancer cell lines after knockdown of GRINA. The expression of pro-apoptotic protein Bax was significantly upregulated, whereas the anti-apoptotic protein Bcl-2 was significantly downregulated in GRINA silenced cells.

CONCLUSIONS

Human gastric cancers have increased levels of GRINA, which promotes growth of gastric cancer and inhibits tumor cells apoptosis.

Haemolysin Sph2 of Leptospira interrogans induces cell apoptosis via intracellular reactive oxygen species elevation and mitochondrial membrane injury

Leptospira interrogans causes widespread leptospirosis in humans and animals, with major symptoms of jaundice and haemorrhage. Sph2, a member of the sphingomyelinase haemolysins, is an important virulence factor for leptospire. In this study, the function and mechanism of Sph2 in the pathogenesis of leptospirosis were investigated to further understand the pathogenesis of leptospire. Real-time PCR analysis of expression levels during cell invasion showed that sph2 gene expression was transiently induced in human umbilical vein endothelial cells (HUVECs), human embryo liver cells (L02), and human epithelial lung cells (L132), with expression levels reaching a peak after 45 min of infection. Further functional analysis of recombinant Sph2 (rSph2) by LDH assays and confocal microscopy showed that rSph2 can be internalised by cells both by causing cell membrane damage and by a damage-independent clathrin-mediated endocytosis pathway. Subsequently, rSph2 is able to translocate to mitochondria, which led to an increase in the levels of reactive oxygen species (ROS) and a decrease of the mitochondrial membrane potential (ΔΨ_m ). Further flowcytometry analyses after rSph2 exposure showed that 28.7%, 31%, and 27.3% of the HUVEC, L02, and L132 cells, respectively, became apoptotic. Because apoptosis could be decreased with the ROS inhibitor N-acetyl cysteine, these experiments suggested that rSph2 triggers apoptosis through mitochondrial membrane damage and ROS elevation. The ability of leptospiral haemolysin rSph2 to cause apoptosis likely contributes to the pathogenesis of leptospirosis.

Identification of 2',4'-Dihydroxychalcone as an Antivirulence Agent Targeting HlyU, a Master Virulence Regulator in Vibrio vulnificus

The emergence of antimicrobial resistance and rapid acclimation allows Vibrio vulnificus to rapidly propagate in the host. This problematic pathological scenario can be circumvented by employing an antivirulence strategy, treating Vibrio infections without hindering the bacterial growth. We developed a genome-integrated orthogonal inhibitor screening platform in E. coli to identify antivirulence agents targeting a master virulence regulator of V. vulnificus. We identified 2′,4′-dihydroxychalcone (DHC) from the natural compound library and verified that it decreases the expression of the major toxin network which is equivalent to the ∆hlyU deletion mutant. 2′,4′-DHC also reduced the hemolytic activity of V. vulnificus which was tested as an example of virulence phenotype. The electrophoretic mobility shift assay confirmed that 2′,4′-DHC specifically targeted HlyU and inhibited its binding to PrtxA1 promoter. Under in vivo conditions, a single dose of 2′,4′-DHC protected ~50% wax-worm larvae from V. vulnificus infection at a non-toxic concentration to both V. vulnificus and wax-worm larvae. In the current study, we demonstrated that an orthogonal reporter system is suitable for the identification of antivirulence compounds with accuracy, and identified 2′,4′-DHC as a potent antivirulence agent that specifically targets the HlyU virulence transcriptional regulator and significantly reduces the virulence and infection potential of V. vulnificus.

N-(3-oxododecanoyl)-l-homoserine lactone modulates mitochondrial function and suppresses proliferation in intestinal goblet cells

AIMS

The quorum-sensing molecule N‑(3‑oxododecanoyl)‑l‑homoserine lactone (C12-HSL), produced by the Gram negative human pathogenic bacterium Pseudomonas aeruginosa, modulates mammalian cell behavior. Our previous findings suggested that C12-HSL rapidly decreases viability and induces apoptosis in LS174T goblet cells.

MAIN METHODS

In this study, the effects of 100 μM C12-HSL on mitochondrial function and cell proliferation in LS174T cells treated for 4 h were evaluated by real-time PCR, enzyme-linked immunosorbent assay (ELISA) and flow cytometry.

KEY FINDINGS

The results showed that the activities of mitochondrial respiratory chain complexes IV and V were significantly increased (P < 0.05) in LS174T cells after C12-HSL treatment, with elevated intracellular ATP generation (P < 0.05). Flow cytometry analysis revealed significantly increased intracellular Ca²⁺ levels (P < 0.05), as well as disrupted mitochondrial activity and cell cycle arrest upon C12-HSL treatment. Apoptosis and cell proliferation related genes showed markedly altered expression levels (P < 0.05) in LS174T cells after C12-HSL treatment. Moreover, the paraoxonase 2 (PON2) inhibitor TQ416 (1 μM) remarkably reversed the above C12-HSL associated effects in LS174T cells.

SIGNIFICANCE

These findings indicated that C12-HSL alters mitochondrial energy production and function, and inhibits cell proliferation in LS174T cells, with PON2 involvement.

Uropathogenic Escherichia coli virulence factor hemolysin A causes programmed cell necrosis by altering mitochondrial dynamics

Uropathogenic Escherichia coli (UPEC) is the most common cause of urinary tract infections. In this study, UPEC strains harboring hemolysin A (HlyA) did not induce programmed cell death pathways by the activation of caspases. Instead, the UPEC pore-forming toxin HlyA triggered an increase in mitochondrial Ca²⁺ levels and manipulated mitochondrial dynamics by causing fragmentation of the mitochondrial network. Alterations in mitochondrial dynamics resulted in severe impairment of mitochondrial functions by loss of membrane potential, increase in reactive oxygen species production, and ATP depletion. Moreover, HlyA caused disruption of plasma membrane integrity that was accompanied by extracellular release of the danger-associated molecules high-mobility group box 1 (HMGB1) and histone 3 (H3). Our results indicate that UPEC induced programmed cell necrosis by irreversibly impairing mitochondrial function. This finding suggests a strategy devised by UPEC at the onset of infection to escape early innate immune response and silently propagate inside host cells.-Lu, Y., Rafiq, A., Zhang, Z., Aslani, F., Fijak, M., Lei, T., Wang, M., Kumar, S., Klug, J., Bergmann, M., Chakraborty, T., Meinhardt, A., Bhushan, S. Uropathogenic Escherichia coli virulence factor hemolysin A causes programmed cell necrosis by altering mitochondrial dynamics.

Melatonin inhibits apoptotic cell death induced by Vibrio vulnificus VvhA via melatonin receptor 2 coupling with NCF-1

Melatonin, an endogenous hormone molecule, has a variety of biological functions, but a functional role of melatonin in the infection of Gram-negative bacterium Vibrio vulnificus has yet to be described. In this study, we investigated the molecular mechanism of melatonin in the apoptosis of human intestinal epithelial (HCT116) cells induced by the hemolysin (VvhA) produced by V. vulnificus. Melatonin (1 μM) significantly inhibited apoptosis induced by the recombinant protein (r) VvhA, which had been inhibited by the knockdown of MT₂. The rVvhA recruited caveolin-1, NCF-1, and Rac1 into lipid rafts to facilitate the production of ROS responsible for the phosphorylation of PKC and JNK. Interestingly, melatonin recruited NCF-1 into non-lipid rafts to prevent ROS production via MT₂ coupling with Gαq. Melatonin inhibited the JNK-mediated phosphorylation of c-Jun responsible for Bax expression, the release of mitochondrial cytochrome c, and caspase-3/-9 activation during its promotion of rVvhA-induced apoptotic cell death. In addition, melatonin inhibited JNK-mediated phosphorylation of Bcl-2 responsible for the release of Beclin-1 and Atg5 expression during its promotion of rVvhA-induced autophagic cell death. These results demonstrate that melatonin signaling via MT₂ triggers recruitment of NCF-1 into non-lipid rafts to block ROS production and JNK-mediated apoptotic and autophagic cell deaths induced by rVvhA in intestinal epithelial cells.

Inhibition of cancer antioxidant defense by natural compounds

All classic, non-surgical anticancer approaches like chemotherapy, radiotherapy or photodynamic therapy kill cancer cells by inducing severe oxidative stress. Even tough chemo- and radiotherapy are still a gold standard in cancer treatment, the identification of non-toxic compounds that enhance their selectivity, would allow for lowering their doses, reduce side effects and risk of second cancers. Many natural products have the ability to sensitize cancer cells to oxidative stress induced by chemo- and radiotherapy by limiting antioxidant capacity of cancer cells. Blocking antioxidant defense in tumors decreases their ability to balance oxidative insult and results in cell death. Though one should bear in mind that the same natural compound often exerts both anti-oxidant and pro-oxidant properties, depending on concentration used, cell type, exposure time and environmental conditions. Here we present a comprehensive overview of natural products that inhibit major antioxidant defense mechanisms in cancer cells and discuss their potential in clinical application.

A Vibrio vulnificus VvpM Induces IL-1β Production Coupled with Necrotic Macrophage Death via Distinct Spatial Targeting by ANXA2

An inflammatory form of phagocyte death evoked by the Gram-negative bacterium Vibrio (V.) vulnificus (WT) is one of hallmarks to promote their colonization, but the virulence factor and infectious mechanism involved in this process remain largely unknown. Here, we identified extracellular metalloprotease VvpM as a new virulence factor and investigated the molecular mechanism of VvpM which acts during the regulation of the inflammatory form of macrophage death and bacterial colonization. Mutation of the vvpM gene appeared to play major role in the prevention of IL-1β production due to V. vulnificus infection in macrophage. However, the recombinant protein (r) VvpM caused IL-1β production coupled with necrotic cell death, which is highly susceptible to the knockdown of annexin A2 (ANXA2) located in both membrane lipid and non-lipid rafts. In lipid rafts, rVvpM recruited NOX enzymes coupled with ANXA2 to facilitate the production of ROS responsible for the epigenetic and transcriptional regulation of NF-κB in the IL-1β promoter. rVvpM acting on non-lipid rafts increased LC3 puncta formation and autophagic flux, which are required for the mRNA expression of Atg5 involved in the autophagosome formation process. The autophagy activation caused by rVvpM induced NLRP3 inflammasome-dependent caspase-1 activation in the promoting of IL-1β production. In mouse models of V. vulnificus infection, the VvpM mutant failed to elevate the level of pro-inflammatory responses closely related to IL-1β production and prevented bacterial colonization. These findings delineate VvpM efficiently regulates two pathogenic pathways that stimulate NF-κB-dependent IL-1β production and autophagy-mediated NLRP3 inflammasome via distinct spatial targeting by ANXA2.

Vibrio vulnificus induces mTOR activation and inflammatory responses in macrophages

Vibrio vulnificus (V. vulnificus), a Gram-negative marine bacterium, can cause life-threatening primary septicemia, especially in patients with liver diseases. How V. vulnificus affects the liver and how it acts on macrophages are not well understood. In this report, we demonstrated that V. vulnificus infection causes a strong inflammatory response, marked expansion of liver-resident macrophages, and liver damage in mice. We demonstrated further that V. vulnificus activates mTOR in macrophages and inhibition of mTOR differentially regulates V. vulnificus induced inflammatory responses, suggesting the possibility of targeting mTOR as a strategy to modulate V. vulnificus induced inflammatory responses.

Impact of Mediterranean diet on metabolic syndrome, cancer and longevity

Obesity symbolizes a major public health problem. Overweight and obesity are associated to the occurrence of the metabolic syndrome and to adipose tissue dysfunction. The adipose tissue is metabolically active and an endocrine organ, whose dysregulation causes a low-grade inflammatory state and ectopic fat depositions. The Mediterranean Diet represents a possible therapy for metabolic syndrome, preventing adiposopathy or "sick fat" formation.The Mediterranean Diet exerts protective effects in elderly subjects with and without baseline of chronic diseases. Recent studies have demonstrated a relationship between cancer and obesity. In the US, diet represents amount 30-35% of death causes related to cancer. Currently, the cancer is the second cause of death after cardiovascular diseases worldwide. Furthermore, populations living in the Mediterranean area have a decreased incidence of cancer compared with populations living in Northern Europe or the US, likely due to healthier dietary habits. The bioactive food components have a potential preventive action on cancer. The aims of this review are to evaluate the impact of Mediterranean Diet on onset, progression and regression of metabolic syndrome, cancer and on longevity.

Anti-lipoapoptotic effects of Alisma orientalis extract on non-esterified fatty acid-induced HepG2 cells

BACKGROUND

Liver steatosis was caused by lipid accumulation in the liver. Alisma orientale (AO) is recognized as a promising candidate with therapeutic efficacy for the treatment of nonalcoholic fatty liver disease (NAFLD). HepG2 hepatocyte cell line is commonly used for liver disease cell model.

METHOD

The HepG2 cells were cultured with the NEFAs mixture (oleic and palmitic acids, 2:1 ratio) for 24 h to induce hepatic steatosis. Then different doses of Alisma orientale extract (AOE) was treated to HepG2 for 24 h. Incubated cells were used for further experiments.

RESULTS

The AOE showed inhibitory effects on lipid accumulation in the Oil Red O staining and Nile red staining tests with no cytotoxicity at a concentration of 300 μg/mL. Fatty acid synthase (FASN) and acetyl-CoA carboxylase 1 (ACC1) mRNA and protein expression level were down-regulated after AOE treatment. Bcl-2 associated X protein (Bax) and c-Jun N-terminal kinase (JNK) mRNA expression level were decreased as well as p-JNK (activated form of JNK), Bax, cleaved caspase-9, caspase-3 protein expression level. Anti-apopototic B-cell lymphoma 2 (Bcl-2) protein level increased after AOE treatment. In addition, inflammatory protein expression including p-p65, p65, COX-2 and iNOS were inhibited by AOE treatment.

CONCLUSION

The results suggest that AOE has anti-steatosis effects that involve lipogenesis, anti-lipoapoptosis, and anti-inflammation in the NEFA-induced NAFLD pathological cell model.

In vitro and in vivo anti-Vibrio vulnificus activity of psammaplin A, a natural marine compound

Vibrio vulnificus is known to induce severely fulminant and fatal septicemia in susceptible hosts. In the present study, the antimicrobial activity of natural marine product-derived compounds against V. vulnificus, were investigated in vitro and in vivo. Twelve pure compounds were isolated from natural marine products and their inhibitory effects on V. vulnificus-induced cytotoxicity were determined in INT‑407 cells. Among the 12 pure compounds tested, treatment with psammaplin A significantly suppressed V. vulnificus‑induced cytotoxicity in INT‑407 cells. Notably, treatment with psammaplin A (5-50 µg) had improved survival rates compared with that in the untreated mice, when the mice were infected with V. vulnificus intraperitoneally. In addition, the bacterial load of V. vulnificus in several tissues (spleen, liver and small intestine) was significantly lower in psammaplin A‑treated mice than in untreated mice. Furthermore, psammaplin A treatment significantly suppressed the growth of V. vulnificus. Taken together, these results indicate that psammaplin A may be a potential agent for the prevention and treatment of V. vulnificus infections.

Vibrio cholerae GbpA elicits necrotic cell death in intestinal cells

Vibrio choleraeN-acetylglucosamine-binding protein GbpA is a secretory protein that facilitates the initial adherence of bacteria in the human intestine. Until now, considerable progress in the characterization of GbpA has been done, yet little is known about its role in host response. Our present studies demonstrated that GbpA at the amount secreted in the intestine resulted in decreased cell viability, altered cell morphology, disruption of cell membrane integrity and damage of cellular DNA indicating necrotic cell death. We observed that GbpA exposure leads to mitochondrial dysfunction, characterized by accumulation of reactive oxygen species (ROS), depolarization of mitochondrial membrane potential and depletion of ATP pool in host cells. Additionally, the intra-cellular ROS, accumulated in response to GbpA, were found to induce the migration of NF-κB from cytoplasm into nucleus in host cells. Taken together, these results prompted us to conclude that GbpA orchestrates a necrotic response in host cells which may have implications in immune response.

Vibrio vulnificus VvhA induces autophagy-related cell death through the lipid raft-dependent c-Src/NOX signaling pathway

VvhA, a virulent factor of Vibrio (V.) vulnificus, induces acute cell death in a destructive manner. Autophagy plays an important role in cell death, but the functional role of VvhA in autophagy-related cell death has not been elucidated yet. We found that rVvhA significantly increased LC3 puncta formation and autophagic flux in promoting the cell death of human intestinal epithelial Caco-2 cells. The cell death induced by rVvhA was independent of lysosomal permeabilizaton and caspase activation. rVvhA induced rapid phosphorylation of c-Src in the membrane lipid raft, which resulted in an increased interaction between lipid raft molecule caveolin-1 and NADPH oxidase (NOX) complex Rac1 for ROS production. NOX-mediated ROS signaling induced by rVvhA increased the phosphorylation of extracellular signal-regulated kinase (ERK) and eukaryotic translation initiation factor 2α (eIF2α) which are required for mRNA expression of Atg5 and Atg16L1 involved in autophagosome formation. In an in vivo model, VvhA increased autophagy activation and paracellular permeabilization in intestinal epithelium. Collectively, the results here show that VvhA plays a pivotal role in the pathogenesis and dissemination of V. vulnificus by autophagy upregulation, through the lipid raft-mediated c-Src/NOX signaling pathway and ERK/eIF2α activation.

Transgenic expression of omega-3 PUFA synthesis genes improves zebrafish survival during Vibrio vulnificus infection

Background

Highly desaturated n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are synthesized by desaturases and elongase. They exert hepatoprotective effects to prevent alcoholic fatty liver syndrome or cholestatic liver injury. However, it is unclear how n-3 PUFAs improve immune function in liver. Vibrio vulnificus, a gram-negative bacterial pathogen, causes high mortality of aquaculture fishes upon infection. Humans can become infected with V. vulnificus through open wounds or by eating raw seafood, and such infections may result in systemic septicemia. Moreover, patients with liver diseases are vulnerable to infection, and are more likely than healthy persons to present with liver inflammation following infection. This study quantified n-3 PUFAs and their anti-bacterial effects in Fadsd6 and Elvol5a transgenic zebrafish.

Results

Two transgenic zebrafish strains with strong liver specific expression of Fadsd6 and Elvol5a (driven by the zebrafish Fabp10 promoter) were established using the Tol2 system. Synthesis of n-3 PUFAs in these strains were increased by 2.5-fold as compared to wild type (Wt) fish. The survival rate in 24 h following challenge with V. vulnificus was 20 % in Wt, but 70 % in the transgenic strains. In addition, the bacteria counts in transgenic fish strains were significantly decreased. The expression levels of pro-inflammatory genes, such as TNF-α, IL-1β, and NF-κB, were suppressed between 9 and 12 h after challenge. This study confirms the anti-bacterial function of n-3 PUFAs in a transgenic zebrafish model.

Conclusions

Fadsd6 and Elvol5a transgenic zebrafish are more resistant to V. vulnificus infection, and enhance survival by diminishing the attendant inflammatory response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0208-1) contains supplementary material, which is available to authorized users.

Cyclo(phenylalanine-proline) induces DNA damage in mammalian cells via reactive oxygen species

Cyclo(phenylalanine‐proline) is produced by various organisms such as animals, plants, bacteria and fungi. It has diverse biological functions including anti‐fungal activity, anti‐bacterial activity and molecular signalling. However, a few studies have demonstrated the effect of cyclo(phenylalanine‐proline) on the mammalian cellular processes, such as cell growth and apoptosis. In this study, we investigated whether cyclo(phenylalanine‐proline) affects cellular responses associated with DNA damage in mammalian cells. We found that treatment of 1 mM cyclo(phenylalanine‐proline) induces phosphorylation of H2AX (S139) through ATM‐CHK2 activation as well as DNA double strand breaks. Gene expression analysis revealed that a subset of genes related to regulation of reactive oxygen species (ROS) scavenging and production is suppressed by the cyclo(phenylalanine‐proline) treatment. We also found that cyclo(phenylalanine‐proline) treatment induces perturbation of the mitochondrial membrane, resulting in increased ROS, especially superoxide, production. Collectively, our study suggests that cyclo(phenylalanine‐proline) treatment induces DNA damage via elevation of ROS in mammalian cells. Our findings may help explain the mechanism underlying the bacterial infection‐induced activation of DNA damage response in host mammalian cells.

The Makes Caterpillars Floppy (MCF)-Like Domain of Vibrio vulnificus Induces Mitochondrion-Mediated Apoptosis

The multifunctional-autoprocessing repeats-in-toxin (MARTXVv) toxin of Vibrio vulnificus plays a significant role in the pathogenesis of this bacterium through delivery of up to five effector domains to the host cells. Previous studies have established that the MARTXVv toxin is linked to V. vulnificus dependent induction of apoptosis, but the region of the large multifunction protein essential for this activity was not previously identified. Recently, we showed that the Makes Caterpillar Floppy-like MARTX effector domain (MCFVv) is an autoproteolytic cysteine protease that induces rounding of various cell types. In this study, we demonstrate that cell rounding induced by MCFVv is coupled to reduced metabolic rate and inhibition of cellular proliferation. Moreover, delivery of MCFVv into host cells either as a fusion to the N-terminal fragment of anthrax toxin lethal factor or when naturally delivered as a V. vulnificus MARTX toxin led to loss of mitochondrial membrane potential, release of cytochrome c, activation of Bax and Bak, and processing of caspases and poly-(ADP-ribose) polymerase (PARP-γ). These studies specifically link the MCFVv effector domain to induction of the intrinsic apoptosis pathway by V. vulnificus.

Rap1-mediated nuclear factor-kappaB (NF-κB) activity regulates the paracrine capacity of mesenchymal stem cells in heart repair following infarction

Paracrine effect is the major mechanism that underlies mesenchymal stem cells (MSC)-based therapy. This study aimed to examine how Rap1, telomeric repeat-binding factor 2-interacting protein 1 (Terf2IP), which is a novel modulator involved in the nuclear factor-kappaB (NF-κB) pathway, regulates the paracrine effects of MSC-mediated heart repair following infarction. NF-κB activity of stromal cells was increased by Rap1 as measured by pNF-κB-luciferase reporter activity, and this was abolished by IkB-dominant-negative protein. Knockdown of Rap1 with shRap1 resulted in diminished translocation of p65-NF-κB from the cytoplasm to nuclei in response to tumor necrosis factor-α (TNF-α) stimulation. Compared with BM-MSCs, Rap1^−/−-BM-MSCs displayed a significantly reduced ratio of phosphorylated NF-κB to NF-κB-p65 and of Bax to Bcl-2, and increased resistance to hypoxia-induced apoptosis by the terminal deoxynucleotidal transferase-mediated dUTP nick end labeling (TUNEL) assay. In contrast, re-expression of Rap1 in Rap1^−/−-BM-MSCs resulted in loss of resistance to apoptosis in the presence of hypoxia. Moreover, absence of Rap1 in BM-MSCs led to downregulation of NF-κB activity accompanied by reduced pro-inflammatory paracrine cytokines TNF-α, IL (interleukin)-6 and monocyte chemotactic protein-1 in Rap1^−/−-BM-MSCs compared with BM-MSCs. The apoptosis of neonatal cardiomyocytes (NCMCs) induced by hypoxia was significantly reduced when cocultured with Rap1^−/−-BM-MSC hypoxic-conditioned medium (CdM). The increased cardioprotective effects of Rap1^−/−-BM-MSCs were reduced when Rap1^−/−-BM-MSCs were reconstituted with Rap1 re-expression. Furthermore, in vivo study showed that transplantation of Rap1^−/−-BM-MSCs significantly improved heart function, decreased infarct size, prevented cardiomyocyte apoptosis and inhibited inflammation compared with controls and BM-MSCs (P<0.01). This study reveals that Rap1 has a critical role in the regulation of MSC paracrine actions. Compared with BM-MSCs, Rap1^−/−-BM-MSCs decreased NF-κB sensitivity to stress-induced pro-inflammatory cytokine production and reduced apoptosis. Selective inhibition of Rap1 in BM-MSCs may be a novel strategy to enhance MSC-based therapeutic efficacy in myocardial infarction.

Evaluation of recombinant leukocidin domain of VvhA exotoxin of Vibrio vulnificus as an effective toxoid in mouse model

Vibrio vulnificus hemolysin A (VvhA) is a pore forming toxin and plays an important role in the pathogenesis. The hemolytic and cytotytic property of VvhA toxin is associated with N-terminal leukocidin domain which triggers apoptotic signaling cascade in epithelial cells. The present study was undertaken to assess the protective efficacy of recombinant VvhA leukocidin domain (rL/VvhA) against VvhA toxin challenge using in vitro and in vivo assays. The rL/VvhA protein was found to be non-toxic with no significant hemolytic or cytotoxic effects. Intraperitoneal (I.P.) immunization of BALB/c mice with rL/VvhA protein elicited significantly higher specific serum antibody titer with mixed Th1/Th2 mediated immune responses. HeLa cell monolayer supplemented with anti-rL/VvhA antibodies were effectively protected (viability 86.69%) against lethal 5 LD50 toxin challenge. An effective in vitro proliferation of lymphocyte was observed upon re-stimulation of rL/VvhA primed splenocytes with formalin inactivated VvhA toxin (fVvhA). Co-expression of Th1/Th2 polarized cytokines (IFN-γ, IL-12 and IL-4), were seen in the cell culture supernatant. In contrast to sham immunized mice, rL/VvhA immunized mice demonstrated significant protection (90% survival) against native toxin challenge in vitro and in vivo infection models. These results suggested leukocidin domain of the VvhA toxin as protective immunogen for possible protection against V. vulnificus VvhA.