Cystic Fibrosis Transmembrane Conductance Regulator Reduces Microtubule-Dependent Campylobacter jejuni Invasion.

Campylobacterjejuni is a foodborne pathogen that induces gastroenteritis. Invasion and adhesion are essential in the process of C. jejuni infection leading to gastroenteritis. The mucosal layer plays a key role in the system of defense against efficient invasion and adhesion by bacteria, which is modulated by several ion channels and transporters mediated by water flux in the intestine. The cystic fibrosis transmembrane conductance regulator (CFTR) plays the main role in water flux in the intestine, and it is closely associated with bacterial clearance. We previously reported that C. jejuni infection suppresses CFTR channel activity in intestinal epithelial cells; however, the mechanism and importance of this suppression are unclear. This study sought to elucidate the role of CFTR in C. jejuni infection. Using HEK293 cells that stably express wild-type and mutated CFTR, we found that CFTR attenuated C. jejuni invasion and that it was not involved in bacterial adhesion or intracellular survival but was associated with microtubule-dependent intracellular transport. Moreover, we revealed that CFTR attenuated the function of the microtubule motor protein, which caused inhibition of C. jejuni invasion, but did not affect microtubule stability. Meanwhile, the CFTR mutant G551D-CFTR, which had defects in channel activity, suppressed C. jejuni invasion, whereas the ΔF508-CFTR mutant, which had defects in maturation, did not suppress C. jejuni invasion, suggesting that CFTR suppression of C. jejuni invasion is related to CFTR maturation but not channel activity. When these findings are taken together, it may be seen that mature CFTR inhibits C. jejuni invasion by regulating microtubule-mediated pathways. We suggest that CFTR plays a critical role in cellular defenses against C. jejuni invasion and that suppression of CFTR may be an initial step in promoting cell invasion during C. jejuni infection.

Reduction of Campylobacter jejuni contamination by using UVA-LED and sodium hypochlorite on the surface of chicken meat.

Campylobacter jejuni causes gastroenteritis in humans and is a major concern in food safety. Commercially prepared chicken meats are frequently contaminated with C. jejuni, which is closely associated with the diffusion of intestinal contents in poultry processing plants. Sodium hypochlorite (NaClO) is commonly used during chicken processing to prevent food poisoning; however, its antimicrobial activity is not effective in the organic-rich solutions. In this study, we investigated the potential of a new photo-disinfection system, UVA-LED, for the disinfection of C. jejuni-contaminated chicken surfaces. The data indicated that UVA irradiation significantly killed C. jejuni and that its killing ability was significantly facilitated in NaClO-treated chickens. Effective inactivation of C. jejuni was achieved using a combination of UVA and NaClO, even in the organic-rich condition. The results of this study show that synergistic disinfection using a combination of UVA and NaClO has potential beneficial effects in chicken processing systems.

Proximal deposition of collagen IV by fibroblasts contributes to basement membrane formation by colon epithelial cells in vitro.

The basement membrane (BM) underlying epithelial tissue is a thin layer of extracellular matrix that governs tissue integrity and function. Epithelial BMs are generally assembled using BM components secreted from two origins: epithelium and stroma. Although de novo BM formation involves self-assembly processes of large proteins, it remains unclear how stroma-derived macromolecules are transported and assembled, specifically in the BM region. In this study, we established an in vitro co-culture model of BM formation in which DLD-1 human colon epithelial cells were cultured on top of collagen I gel containing human embryonic OUMS-36T-2 fibroblasts as stromal cells. A distinct feature of our system is represented by OUMS-36T-2 cells which are almost exclusively responsible for synthesis of collagen IV, a major BM component. Exploiting this advantage, we found that collagen IV incorporation was significantly impaired in culture conditions where OUMS-36T-2 cells were not allowed to directly contact DLD-1 cells. Soluble collagen IV, once diluted in the culture medium, did not accumulate in the BM region efficiently. Live imaging of fluorescently tagged collagen IV revealed that OUMS-36T-2 cells deposited collagen IV aggregates directly onto the basal surface of DLD-1 cells. Collectively, these results indicate a novel mode of collagen IV deposition in which fibroblasts proximal to epithelial cells exclusively contribute to collagen IV assembly during BM formation.

Type III Secretion Effector VopQ of Vibrio parahaemolyticus Modulates Central Carbon Metabolism in Epithelial Cells.

Vibrio parahaemolyticus is a Gram-negative halophilic pathogen that frequently causes acute gastroenteritis and occasional wound infection. V. parahaemolyticus contains several virulence factors, including type III secretion systems (T3SSs) and thermostable direct hemolysin (TDH). In particular, T3SS1 is a potent cytotoxic inducer, and T3SS2 is essential for causing acute gastroenteritis. Although much is known about manipulation of host signaling transductions by the V. parahaemolyticus effector, little is known about the host metabolomic changes modulated by V. parahaemolyticus To address this knowledge gap, we performed a metabolomic analysis of the epithelial cells during V. parahaemolyticus infection using capillary electrophoresis-time of flight mass spectrometry (CE-TOF/MS). Our results revealed significant metabolomic perturbations upon V. parahaemolyticus infection. Moreover, we identified that T3SS1's VopQ effector was responsible for inducing the significant metabolic changes in the infected cells. The VopQ effector dramatically altered the host cell's glycolytic, tricarboxylic acid cycle (TCA), and amino acid metabolisms. VopQ effector disrupted host cell redox homeostasis by depleting cellular glutathione and subsequently increasing the level of reactive oxygen species (ROS) production.IMPORTANCE The metabolic response of host cells upon infection is pathogen specific, and infection-induced host metabolic reprogramming may have beneficial effects on the proliferation of pathogens. V. parahaemolyticus contains a range of virulence factors to manipulate host signaling pathways and metabolic processes. In this study, we identified that the T3SS1 VopQ effector rewrites host metabolism in conjunction with the inflammation and cell death processes. Understanding how VopQ reprograms host cell metabolism during the infection could help us to identify novel therapeutic strategies to enhance the survival of host cells during V. parahaemolyticus infection.

Cellular Tight Junctions Prevent Effective Campylobacter jejuni Invasion and Inflammatory Barrier Disruption Promoting Bacterial Invasion from Lateral Membrane in Polarized Intestinal Epithelial Cells.

Campylobacter jejuni invasion is closely related to C. jejuni pathogenicity. The intestinal epithelium contains polarized epithelial cells that form tight junctions (TJs) to provide a physical barrier against bacterial invasion. Previous studies indicated that C. jejuni invasion of non-polarized cells involves several cellular features, including lipid rafts. However, the dynamics of C. jejuni invasion of polarized epithelial cells are not fully understood. Here we investigated the interaction between C. jejuni invasion and TJ formation to characterize the mechanism of C. jejuni invasion in polarized epithelial cells. In contrast to non-polarized epithelial cells, C. jejuni invasion was not affected by depletion of lipid rafts in polarized epithelial cells. However, depletion of lipid rafts significantly decreased C. jejuni invasion in TJ disrupted cells or basolateral infection and repair of cellular TJs suppressed lipid raft-mediated C. jejuni invasion in polarized epithelial cells. In addition, pro-inflammatory cytokine, TNF-α treatment that induce TJ disruption promote C. jejuni invasion and lipid rafts depletion significantly reduced C. jejuni invasion in TNF-α treated cells. These data demonstrated that TJs prevent C. jejuni invasion from the lateral side of epithelial cells, where they play a main part in bacterial invasion and suggest that C. jejuni invasion could be increased in inflammatory condition. Therefore, maintenance of TJs integrity should be considered important in the development of novel therapies for C. jejuni infection.

Host cellular unfolded protein response signaling regulates Campylobacter jejuni invasion.

Campylobacter jejuni is a major cause of bacterial foodborne illness in humans worldwide. Bacterial entry into a host eukaryotic cell involves the initial steps of adherence and invasion, which generally activate several cell-signaling pathways that induce the activation of innate defense systems, which leads to the release of proinflammatory cytokines and induction of apoptosis. Recent studies have reported that the unfolded protein response (UPR), a system to clear unfolded proteins from the endoplasmic reticulum (ER), also participates in the activation of cellular defense mechanisms in response to bacterial infection. However, no study has yet investigated the role of UPR in C. jejuni infection. Hence, the aim of this study was to deduce the role of UPR signaling via induction of ER stress in the process of C. jejuni infection. The results suggest that C. jejuni infection suppresses global protein translation. Also, 12 h of C. jejuni infection induced activation of the eIF2α pathway and expression of the transcription factor CHOP. Interestingly, bacterial invasion was facilitated by knockdown of UPR-associated signaling factors and treatment with the ER stress inducers, thapsigargin and tunicamycin, decreased the invasive ability of C. jejuni. An investigation into the mechanism of UPR-mediated inhibition of C. jejuni invasion showed that UPR signaling did not affect bacterial adhesion to or survival in the host cells. Further, Salmonella Enteritidis or FITC-dextran intake were not regulated by UPR signaling. These results indicated that the effect of UPR on intracellular intake was specifically found in C. jejuni infection. These findings are the first to describe the role of UPR in C. jejuni infection and revealed the participation of a new signaling pathway in C. jejuni invasion. UPR signaling is involved in defense against the early step of C. jejuni invasion and thus presents a potential therapeutic target for the treatment of C. jejuni infection.