Human intestinal epithelial cells express interleukin-10 through Toll-like receptor 4-mediated epithelial-macrophage crosstalk

In the intestine, interaction between epithelial cells and macrophages (MΦs) create a unique immunoregulatory microenvironment necessary to maintain local immune and tissue homeostasis. Human intestinal epithelial cells (IECs) have been shown to express interleukin (IL)-10, which keeps epithelial integrity. We have demonstrated that bacterial signaling through Toll-like receptor (TLR) 4 induces 15-deoxy-Δ-12,14-prostaglandin J2 (15d-PGJ2) synthesis in intestinal MΦs by cyclooxygenase (Cox)-2 expression. Here, we show that TLR4 signaling generates crosstalk between IECs and MΦs that enhances IL-10 expression in IECs. Direct stimulation of TLR4 leads to the expression of IL-10 in IECs, while the presence of MΦs in a Transwell system induces another peak in IL-10 expression in IECs at a later time point. The second peak of the IL-10 expression is two times greater than the first peak. This late induction of IL-10 depends on the nuclear receptor peroxisome proliferator-activated receptor (PPAR) γ that is accumulated in IECs by TLR4-mediated inhibition of the ubiquitin-proteasomal pathway. TLR4 signaling in MΦs in turn synthesizes 15d-PGJ2 through p38 and ERK activation and Cox-2 induction, which activates PPARγ in IECs. These results suggest that TLR4 signaling maintains IL-10 production in IECs by generating epithelial-MΦs crosstalk, which is an important mechanism in the maintenance of intestinal homeostasis mediated through host-bacterial interactions.

TLR4 activates the β-catenin pathway to cause intestinal neoplasia

Colonic bacteria have been implicated in the development of colon cancer. We have previously demonstrated that toll-like receptor 4 (TLR4), the receptor for bacterial lipopolysaccharide (LPS), is over-expressed in humans with colitis-associated cancer. Genetic epidemiologic data support a role for TLR4 in sporadic colorectal cancer (CRC) as well, with over-expression favoring more aggressive disease. The goal of our study was to determine whether TLR4 played a role as a tumor promoter in sporadic colon cancer. Using immunofluorescence directed to TLR4, we found that a third of sporadic human colorectal cancers over-express this marker. To mechanistically investigate this observation, we used a mouse model that over-expresses TLR4 in the intestinal epithelium (villin-TLR4 mice). We found that these transgenic mice had increased epithelial proliferation as measured by BrdU labeling, longer colonic crypts and an expansion of Lgr5+ crypt cells at baseline. In addition, villin-TLR4 mice developed spontaneous duodenal dysplasia with age, a feature that is not seen in any wild-type (WT) mice. To model human sporadic CRC, we administered the genotoxic agent azoxymethane (AOM) to villin-TLR4 and WT mice. We found that villin-TLR4 mice showed an increased number of colonic tumors compared to WT mice as well as increased β-catenin activation in non-dysplastic areas. Biochemical studies in colonic epithelial cell lines revealed that TLR4 activates β-catenin in a PI3K-dependent manner, increasing phosphorylation of β-catenin(Ser552), a phenomenon associated with activation of the canonical Wnt pathway. Our results suggest that TLR4 can trigger a neoplastic program through activation of the Wnt/β-catenin pathway. Our studies highlight a previously unexplored link between innate immune signaling and activation of oncogenic pathways, which may be targeted to prevent or treat CRC.

The role of innate immunity in the host defense against intestinal bacterial pathogens

Eradication of infectious disease is our global health challenge. After encountering intestinal infection with a bacterial pathogen, the host defense program is initiated by local antigen-presenting cells (APCs) that eliminate invading pathogens by phagocytosis and establish localized inflammation by secreting cytokines and chemokines. These pathogen-experienced APCs migrate to the mesenteric lymph nodes, where host immune responses are precisely orchestrated. Initiation and regulation of this defense program appear to be largely dependent on innate immunity which is antigen non-specific and provides a rapid defense against broader targets. On the other hand, many bacterial enteropathogens have evoked abilities to modify the host defense program to their advantage. Therefore, better understanding of the host-pathogen interactions is essential to establish effective eradication strategies for enteric infectious diseases. In this review, we will discuss the current understanding of innate immune regulation of the host defense mechanisms against intestinal infection by bacterial pathogens.

TRIF mobilizes unique primary defense against Gram-negative bacteria in intestinal interface

The gastrointestinal tract is the largest mucosal surface in our body. It houses diverse microorganisms that collectively form the commensal microbial community. The security of this community is kept by host-microbial interactions and is violated by foreign pathogens that induce local as well as systemic pathology. In most cases, gastrointestinal infections are caused by Gram-negative enteropathogens, which trigger host immune responses through the TLR4 signaling pathways. Although TRIF is one of the major pathways downstream of TLR4, very little is known about how the TRIF pathway contributes to intestinal defense against pathogenic infection. Recently, we reported a unique role of TRIF signaling in host response to an enterophathogen Yersinia enterocolitica, which consisted of IFN-β induction from regional macrophages followed by activation of NK cells in the mesenteric lymph nodes. In this addendum, we show distinct roles for TRIF-dependent host response in intestinal vs. systemic infection with Gram-negative enterophathogens.

Host innate recognition of an intestinal bacterial pathogen induces TRIF-dependent protective immunity

TRIF signaling triggers the amplification of macrophage bactericidal activity sufficient to eliminate invading intestinal pathogens through the sequential induction of IFN-β and IFN-γ from macrophages and NK cells, respectively.

Toll-like receptor 4 (TLR4), which signals through the adapter molecules myeloid differentiation factor 88 (MyD88) and toll/interleukin 1 receptor domain-containing adapter inducing IFN-β (TRIF), is required for protection against Gram-negative bacteria. TRIF is known to be important in TLR3-mediated antiviral signaling, but the role of TRIF signaling against Gram-negative enteropathogens is currently unknown. We show that TRIF signaling is indispensable for establishing innate protective immunity against Gram-negative Yersinia enterocolitica. Infection of wild-type mice rapidly induced both IFN-β and IFN-γ in the mesenteric lymph nodes. In contrast, TRIF-deficient mice were defective in these IFN responses and showed impaired phagocytosis in regional macrophages, resulting in greater bacterial dissemination and mortality. TRIF signaling may be universally important for protection against Gram-negative pathogens, as TRIF-deficient macrophages were also impaired in killing both Salmonella and Escherichia coli in vitro. The mechanism of TRIF-mediated protective immunity appears to be orchestrated by macrophage-induced IFN-β and NK cell production of IFN-γ. Sequential induction of IFN-β and IFN-γ leads to amplification of macrophage bactericidal activity sufficient to eliminate the invading pathogens at the intestinal interface. Our results demonstrate a previously unknown role of TRIF in host resistance to Gram-negative enteropathogens, which may lead to effective strategies for combating enteric infections.

Constitutive activation of epithelial TLR4 augments inflammatory responses to mucosal injury and drives colitis-associated tumorigenesis

BACKGROUND

Chronic intestinal inflammation culminates in cancer and a link to Toll-like receptor-4 (TLR4) has been suggested by our observation that TLR4 deficiency prevents colitis-associated neoplasia. In the current study we address the effect of the aberrant activation of epithelial TLR4 on induction of colitis and colitis-associated tumor development. We take a translational approach to address the consequences of increased TLR signaling in the intestinal mucosa.

METHODS

Mice transgenic for a constitutively active TLR4 under the intestine-specific villin promoter (villin-TLR4 mice) were treated with dextran sodium sulfate (DSS) for acute colitis and azoxymethane (AOM)-DSS TLR4 expression was analyzed by immunohistochemistry in colonic tissue from patients with ulcerative colitis (UC) and UC-associated cancer. The effect of an antagonist TLR4 antibody (Ab) was tested in prevention of colitis-associated neoplasia in the AOM-DSS model.

RESULTS

Villin-TLR4 mice were highly susceptible to both acute colitis and colitis-associated neoplasia. Villin-TLR4 mice had increased epithelial expression of COX-2 and mucosal PGE₂ production at baseline. Increased severity of colitis in villin-TLR4 mice was characterized by enhanced expression of inflammatory mediators and increased neutrophilic infiltration. In human UC samples, TLR4 expression was upregulated in almost all colitis-associated cancer and progressively increased with grade of dysplasia. As a proof of principle, a TLR4/MD-2 antagonist antibody inhibited colitis-associated neoplasia in the mouse model.

CONCLUSIONS

Our results show that regulation of TLRs can affect the outcome of both acute colitis and its consequences, cancer. Targeting TLR4 and other TLRs may ultimately play a role in prevention or treatment of colitis-associated cancer.

The role of prostaglandin E2 (PGE 2) in toll-like receptor 4 (TLR4)-mediated colitis-associated neoplasia

Background

We have previously found that TLR4-deficient (TLR4-/-) mice demonstrate decreased expression of mucosal PGE ₂ and are protected against colitis-associated neoplasia. However, it is still unclear whether PGE ₂ is the central factor downstream of TLR4 signaling that promotes intestinal tumorigenesis. To further elucidate critical downstream pathways involving TLR4-mediated intestinal tumorigenesis, we examined the effects of exogenously administered PGE ₂ in TLR4-/- mice to see if PGE ₂ bypasses the protection from colitis-associated tumorigenesis.

Method

Mouse colitis-associated neoplasia was induced by azoxymethane (AOM) injection followed by two cycles of dextran sodium sulfate (DSS) treatment. Two different doses of PGE ₂ (high dose group, 200 μg, n = 8; and low dose group, 100 μg, n = 6) were administered daily during recovery period of colitis by gavage feeding. Another group was given PGE ₂ during DSS treatment (200 μg, n = 5). Inflammation and dysplasia were assessed histologically. Mucosal Cox-2 and amphiregulin (AR) expression, prostanoid synthesis, and EGFR activation were analyzed.

Results

In control mice treated with PBS, the average number of tumors was greater in WT mice (n = 13) than in TLR4-/- mice (n = 7). High dose but not low dose PGE ₂ treatment caused an increase in epithelial proliferation. 28.6% of PBS-treated TLR4-/- mice developed dysplasia (tumors/animal: 0.4 ± 0.2). By contrast, 75.0% (tumors/animal: 1.5 ± 1.2, P < 0.05) of the high dose group and 33.3% (tumors/animal: 0.3 ± 0.5) of the low dose group developed dysplasia in TLR4-/- mice. Tumor size was also increased by high dose PGE ₂ treatment. Endogenous prostanoid synthesis was differentially affected by PGE ₂ treatment during acute and recovery phases of colitis. Exogenous administration of PGE ₂ increased colitis-associated tumorigenesis but this only occurred during the recovery phase. Lastly, PGE ₂ treatment increased mucosal expression of AR and Cox-2, thus inducing EGFR activation and forming a positive feedback mechanism to amplify mucosal Cox-2.

Conclusions

These results highlight the importance of PGE ₂ as a central downstream molecule involving TLR4-mediated intestinal tumorigenesis.

A novel Toll-like receptor 4 antagonist antibody ameliorates inflammation but impairs mucosal healing in murine colitis

Dysregulated innate immune responses to commensal bacteria contribute to the development of inflammatory bowel disease (IBD). TLR4 is overexpressed in the intestinal mucosa of IBD patients and may contribute to uncontrolled inflammation. However, TLR4 is also an important mediator of intestinal repair. The aim of this study is to examine the effect of a TLR4 antagonist on inflammation and intestinal repair in two murine models of IBD. Colitis was induced in C57BL/6J mice with dextran sodium sulfate (DSS) or by transferring CD45Rb(hi) T cells into RAG1-/- mice. An antibody (Ab) against the TLR4/MD-2 complex or isotype control Ab was administered intraperitoneally during DSS treatment, recovery from DSS colitis, or induction of colitis in RAG1-/- mice. Colitis severity was assessed by disease activity index (DAI) and histology. The effect of the Ab on the inflammatory infiltrate was determined by cell isolation and immunohistochemistry. Mucosal expression of inflammatory mediators was analyzed by real-time PCR and ELISA. Blocking TLR4 at the beginning of DSS administration delayed the development of colitis with significantly lower DAI scores. Anti-TLR4 Ab treatment decreased macrophage and dendritic cell infiltrate and reduced mucosal expression of CCL2, CCL20, TNF-alpha, and IL-6. Anti-TLR4 Ab treatment during recovery from DSS colitis resulted in defective mucosal healing with lower expression of COX-2, PGE(2), and amphiregulin. In contrast, TLR4 blockade had minimal efficacy in ameliorating inflammation in the adoptive transfer model of chronic colitis. Our findings suggest that anti-TLR4 therapy may decrease inflammation in IBD but may also interfere with colonic mucosal healing.

Stabilization of a freeze-dried recombinant streptokinase formulation without serum albumin

AIM

To evaluate the stability and content homogeneity of a new freeze-dried and albumin-free formulation of recombinant streptokinase (SKr) that has recently been approved by the Cuban National Center for the Quality Control of Medicaments.

MATERIALS AND METHODS

The new formulation was stored at the intended recommended storage temperature of 4 degrees C, and under accelerated storage conditions (37 degrees C). The stability of the product was also examined after reconstitution and storage at room temperature (28 degrees C) for 24 h. Samples were periodically subjected to biological activity assays (S-2251 chromogenic-substrate method or in vitro clot-lysis assay), sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS/PAGE), pyrogen and sterility testing, abnormal toxicity screening, organoleptic evaluation, and measurement of residual moisture and pH.

RESULTS AND DISCUSSION

Accelerated storage (37 degrees C) data showed biochemical stability of SKr throughout the 6-month study with activity, remaining between 90 and 110% of its nominal value (0.75 x 10(6) IU/mL). SDS/PAGE-determined purity showed that SKr remained above 97 %. Furthermore, the formulation was non-pyrogenic, non-toxic, sterile and organoleptically acceptable. Real-time storage data confirmed the excellent biochemical long-term (30 months) stability of the new formulation of SKr. Comparison with other freeze-dried preparations showed that the new formulation was organoleptically better. The formulation was stable after reconstitution and storage at 28 degrees C for 24 h. The content homogeneity of this new formulation was also satisfactory.

CONCLUSIONS

This study demonstrated the stability and the content homogeneity of this formulation, despite the absence of albumin as stabilizer.

Laparoscopy-assisted vaginal hysterectomy compared with abdominal hysterectomy

The first 150 consecutive laparoscopic vaginal hysterectomy (LVH) cases done by Creighton University faculty members at Mercy Hospital, Council Bluffs, Iowa and at St Joseph Hospital, Omaha, Nebraska were compared with 194 abdominal hysterectomies (AHs) for benign or noninvasive disease. The results indicate that LVH can be accomplished with low morbidity, low length of stay, and with less patient discomfort than experienced by patients who undergo AH.

A critical analysis of laparoscopic assisted vaginal hysterectomies compared with vaginal hysterectomies unassisted by laparoscopy and transabdominal hysterectomies

The first 115 laparoscopically assisted vaginal hysterectomies (LAVH) done by our faculty surgeons were compared with 220 vaginal hysterectomies (VH) and 194 abdominal hysterectomies (AH) done in our affiliated hospitals over the same period of time. Logistic regression analysis indicates that LAVHs were done for cases that would significantly be more likely selected for AH than for VH (p less than 0.0001). Matched case control studies with 28 LAVH/VH and 34 LAVH/AH pairs and bivariate analyses demonstrated that LAVH can be accomplished with low morbidity, short lengths of stay, and little, if any, increase in operating times compared with VH and AH. The LAVH procedure can be expected to replace many AHs in the future.

Laparoscopy-assisted vaginal hysterectomy: report of seventy-five consecutive cases

Patients who underwent laparoscopy-assisted vaginal hysterectomy with or without adnexectomy experienced less fever, required less postoperative analgesia, were able to tolerate a full diet within 24 hours of surgery, and had a faster recovery and shorter hospital stay than patients who had abdominal or traditional vaginal hysterectomy.

Extracorporeal shock wave lithotripsy treatment of spinal cord injury patients

A total of 32 male patients with spinal cord injury underwent extracorporeal shock wave lithotripsy. The mean stone burden was 2.9 cm. (range 0.2 to 8.0 cm.) per renal unit. Of 41 renal units 27 (66 per cent) required ancillary endourological procedures preoperatively and 32 (78 per cent) required a single treatment with extracorporeal shock wave lithotripsy. Urine cultures were positive in 30 of 32 patients (94 per cent) before treatment. All patients with positive preextracorporeal shock wave lithotripsy urine cultures also had positive cultures after treatment. Followup (3-month) was available for 26 of 41 renal units (63 per cent) and showed 19 (73 per cent) to be free of stones or without any radiographic evidence of calcification overlying the collecting system. Seven staghorn calculi were treated with extracorporeal shock wave lithotripsy without prior debulking procedures. Two partial staghorn calculi were treated and rendered free of stones. None of the 5 kidneys with full staghorn calculi was rendered free of stones. We conclude that extracorporeal shock wave lithotripsy is effective for the treatment of unbranched and partial staghorn calculi in the spinal cord injury patient. However, extracorporeal shock wave lithotripsy alone is less effective for the treatment of full staghorn calculi.