Clinical Staphylococcus aureus inhibits human T-cell activity through interaction with the PD-1 receptor

IMPORTANCE

Therapies that target and aid the host immune defense to repel cancer cells or invading pathogens are rapidly emerging. Antibiotic resistance is among the largest threats to human health globally. Staphylococcus aureus (S. aureus) is the most common bacterial infection, and it poses a challenge to the healthcare system due to its significant ability to develop resistance toward current available therapies. In long-term infections, S. aureus further adapt to avoid clearance by the host immune defense. In this study, we discover a new interaction that allows S. aureus to avoid elimination by the immune system, which likely supports its persistence in the host. Moreover, we find that blocking the specific receptor (PD-1) using antibodies significantly relieves the S. aureus-imposed inhibition. Our findings suggest that therapeutically targeting PD-1 is a possible future strategy for treating certain antibiotic-resistant staphylococcal infections.

RT-qPCR assay for detection of mink astrovirus in outbreaks of diarrhea on Danish mink farms

Diarrhea in mink kits is a major cause of disease and mortality in the mink production. The etiology remains unknown in most outbreaks due to a lack of diagnostic assays. In the current study we present an RT-qPCR method to detect mink astrovirus in fecal samples from mink kits with diarrhea. All sampled animals were classified based on age and patoanatomical evaluation as having pre-weaning diarrhea, diarrhea in the growth period or as having no macroscopic signs of diarrhea. Fecal samples were analyzed for MiAstV with RT-qPCR, next generation sequencing and electron microscopy in parallel. Mink astrovirus was detected with RT-qPCR in 92 out of 203 samples. This detection was confirmed by next generation sequencing in a high proportion of samples (22/27), and by visualization of astrovirus particles with EM in some of the samples. Mink astrovirus was highly prevalent (68%) among kits in the outbreaks of pre-weaning diarrhea, in particular outbreaks from May, while less prevalent in outbreaks in June. Mink astrovirus was detected in outbreaks of diarrhea in the growth period, though in a much lesser extent than in the pre-weaning period. The role of mink astrovirus in the diarrhea disease complex of mink remain to be investigated, and for that purpose this sensitive and robust RT-qPCR can be a valuable tool in the future.

Metabolism of short-chain fatty acid propionate induces surface expression of NKG2D ligands on cancer cells

SCFAs are primarily produced in the colon by bacterial fermentation of nondigestible carbohydrates. Besides providing energy, SCFAs can suppress development of colon cancer. The mechanism, however, remains elusive. Here, we demonstrate that the SCFA propionate upregulates surface expression of the immune stimulatory NKG2D ligands, MICA/B by imposing metabolic changes in dividing cells. Propionate-mediated MICA/B expression did not rely on GPR41/GPR43 receptors but depended on functional mitochondria. By siRNA-directed knockdown, we could further link phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme in gluconeogenesis to propionate regulation of MICA/B expression. Moreover, knockdown of Rictor and specific mTOR inhibitors implicated mTORC2 activity with metabolic changes that control MICA/B expression. SCFAs are precursors to short-chain acyl-CoAs that are used for histone acylation thereby linking the metabolic state to chromatin structure and gene expression. Propionate increased the overall acetylation and propionylation and inhibition of lysine acetyltransferases (KATs) that are responsible for adding acyl-CoAs to histones reduced propionate-mediated MICA/B expression, suggesting that propionate-induced acylation increases MICA/B expression. Notably, propionate upregulated MICA/B surface expression on colon cancer cells in an acylation-dependent manner; however, the impact of mitochondrial metabolism on MICA/B expression was different in colon cancer cells compared with Jurkat cells, suggesting that continuous exposure to propionate in the colon may provide an enhanced capacity to metabolize propionate. Together, our findings support that propionate causes metabolic changes resulting in NKG2D ligand surface expression, which holds potential as an immune activating anticancer therapy.

Staphylococcus aureus induces cell-surface expression of immune stimulatory NKG2D ligands on human monocytes

Staphylococcus aureus is among the leading causes of bacterial infections worldwide. The pathogenicity and establishment of S. aureus infections are tightly linked to its ability to modulate host immunity. Persistent infections are often associated with mutant staphylococcal strains that have decreased susceptibility to antibiotics; however, little is known about how these mutations influence bacterial interaction with the host immune system. Here, we discovered that clinical S. aureus isolates activate human monocytes, leading to cell-surface expression of immune stimulatory natural killer group 2D (NKG2D) ligands on the monocytes. We found that expression of the NKG2D ligand ULBP2 (UL16-binding protein 2) is associated with bacterial degradability and phagolysosomal activity. Moreover, S. aureus-induced ULBP2 expression was linked to altered host cell metabolism, including increased cytoplasmic (iso)citrate levels, reduced glycolytic flux, and functional mitochondrial activity. Interestingly, we found that the ability of S. aureus to induce ULBP2 and proinflammatory cytokines in human monocytes depends on a functional ClpP protease in S. aureus These findings indicate that S. aureus activates ULBP2 in human monocytes through immunometabolic mechanisms and reveal that clpP inactivation may function as a potential immune evasion mechanism. Our results provide critical insight into the interplay between the host immune system and S. aureus that has evolved under the dual selective pressure of host immune responses and antibiotic treatment. Our discovery of an immune stimulatory pathway consisting of human monocyte-based defense against S. aureus suggests that targeting the NKG2D pathway holds potential for managing persistent staphylococcal infections.

Cytoplasmic Citrate Flux Modulates the Immune Stimulatory NKG2D Ligand MICA in Cancer Cells

Immune surveillance of cancer cells is facilitated by the Natural Killer Group 2D (NKG2D) receptor expressed by different lymphocyte subsets. It recognizes NKG2D ligands that are rarely expressed on healthy cells, but upregulated by tumorigenesis, presenting a target for immunological clearance. The molecular mechanisms responsible for NKG2D ligand regulation remain complex. Here we report that cancer cell metabolism supports constitutive surface expression of the NKG2D ligand MHC class I chain-related proteins A (MICA). Knockout of the N-glycosylation gene N-acetylglucosaminyltransferase V (MGAT5) in HEK293 cells induced altered metabolism and continuous high MICA surface expression. MGAT5 knockout cells were used to examine the association of cell metabolism and MICA expression through genetic, pharmacological and metabolic assays. Findings were verified in cancer cell lines. Cells with constitutive high MICA expression showed enhanced spare respiratory capacity and elevated mitochondrial efflux of citrate, determined by extracellular flux analysis and metabolomics. MICA expression was reduced by inhibitors of mitochondrial function, FCCP and etomoxir e.g., and depended on conversion of citrate to acetyl-CoA and oxaloacetate by ATP citrate lyase, which was also observed in several cancer cell types. Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) analysis revealed that upregulated MICA transcription was associated with an open chromatin structure at the MICA transcription start site. We identify mitochondria and cytoplasmic citrate as key regulators of constitutive MICA expression and we propose that metabolic reprogramming of certain cancer cells facilitates MICA expression and NKG2D-mediated immune recognition.

Fumarate Upregulates Surface Expression of ULBP2/ULBP5 by Scavenging Glutathione Antioxidant Capacity

Fumarate is a tricarboxylic acid cycle metabolite whose intracellular accumulation is linked to inflammatory signaling and development of cancer. In this study, we demonstrate that endogenous fumarate accumulation upregulates surface expression of the immune stimulatory NK group 2, member D (NKG2D) ligands ULBP2 and ULBP5. In agreement with this, accumulation of fumarate by the therapeutic drug dimethyl fumarate (DMF) also promotes ULBP2/5 surface expression. Mechanistically, we found that the increased ULBP2/5 expression was dependent on oxidative stress and the antioxidants N-acetylcysteine and glutathione (GSH) abrogated ULBP2/5 upregulated by DMF. Fumarate can complex with GSH and thereby exhaust cells of functional GSH capacity. In line with this, inhibition of GSH reductase (GR), the enzyme responsible for GSH recycling, promoted ULBP2/5 surface expression. Loss of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) associates with a malignant form of renal cancer characterized by fumarate accumulation and increased production of reactive oxygen species, highlighting fumarate as an oncometabolite. Interestingly, FH-deficient renal cancer cells had low surface expression of ULBP2/5 and were unresponsive to DMF treatment, suggesting that the fumarate-stimulating ULBP2/5 pathway is abrogated in these cells as an immune-evasive strategy. Together, our data show that ULBP2/5 expression can be upregulated by accumulation of fumarate, likely by depleting cells of GSH antioxidant capacity. Given that DMF is an approved human therapeutic drug, our findings support a broader use of DMF in treatment of cancers and inflammatory conditions.

Short-term effect of oral amoxicillin treatment on the gut microbial community composition in farm mink (Neovison vison)

It is well documented that antibiotics have pronounced modulatory effects on the intestinal bacterial community of both humans and animals, with potential health consequences. The gut microbiota of mink has however attracted little attention due to low bacterial load and fast gastrointestinal transit time, questioning its relevance. In this study, we hypothesise that oral amoxicillin treatment affects the gut microbiota in mink. This was investigated in a controlled trial including 24 animals of which 12 were treated with amoxicillin for 7 days. By applying 16S rRNA gene sequencing, we found that the faecal microbiota was markedly altered already after 2 days of treatment, with a surprising increase in diversity to resemble the feed. The diversity within the mucosa at termination was however reduced, which indicates this compartment as an important colonisation site in mink. No impact on blood biochemistry, lipid metabolism, serum amyloid A, vitamins A and E and histomorphology of the gut and liver was found; however, a slight decrease in fat digestibility was observed. We suggest that early-life use of amoxicillin in mink production may be counteractive as dysbiosis of the microbiota during infancy is increasingly being recognised as a risk factor for future health.

Abortion and mortality in farm mink (Neovison vison) associated with feed-born Clostridium limosum

Disease in mink clinically characterized by abortion and increased mortality among pregnant female mink on 28 Danish farms was observed during April and May 2015. Most of these farms suffered extensive disease problems, including a significant increase in the number of mated females without litters. Pathological, microbiological and molecular biological methods were applied to investigate the cause of disease. Necropsies of animals found dead revealed fragile and partially dissolved (liquefying) uterine tissue, with the presence of Gram positive rod-shaped bacteria. These slow growing bacteria were isolated by anaerobic culturing and identified as Clostridium limosum by both MALDI-TOF mass spectrometry analysis and 16S rRNA gene sequencing. All the performed tests for relevant differential diagnoses were negative. Foodborne disease was indicated because all the affected farms were served by the same feed factory. A specific PCR-based analysis was developed for positive identification of C. limosum and used to screen archived feed samples from the implicated feed factory. Both C. limosum 16S rRNA genes and C. limosum collagenase genes were identified in both mixed feed and more specifically in raw chicken carcass used as one of the components in the mixed feed, which was therefore identified as the most likely source of contamination. Based on the results of this investigation it is concluded that C. limosum can be associated with abortion and increased mortality in pregnant mink females and it is consequently recommended that raw materials contaminated with C. limosum should be avoided in mink feed, in particular during the whelping season.

The gastrointestinal tract of farmed mink (Neovison vison) maintains a diverse mucosa-associated microbiota following a 3-day fasting period

Although it is well documented that the gut microbiota plays an important role in health and disease in mammalian species, this area has been poorly studied among carnivorous animals, especially within the mustelidae family. The gastrointestinal tract of carnivores is characterized by its short length and fast transit time, as compared to omnivores and herbivores, which is due to the low level of inherent fermentation. Mink represents an example of this, which have a GI tract only four times the length of the body and a transit time of approximately 4-5 hr. In this study, we used high-throughput 16S rRNA gene sequencing to explore the resident gut microbiota of the mink in terms of intra-and interindividual diversity. We report, for the first time, that the mucosa-associated bacterial community within the colon is diverse and dissimilar from the community found in the feed. We found large interindividual differences in bacterial composition between individual animals being dominated generally by the phylum Firmicutes, but in some cases also Proteobacteria or Fusobacteria. The bacterial load and community structure within the mucus was not severely impacted by 3 days of fasting, which implies that a resident and stable microbiota is hosted by these animals.

Associations between biosecurity and outbreaks of canine distemper on Danish mink farms in 2012-2013

Background

During 8 months from July 2012 to February 2013, a major outbreak of canine distemper involving 64 mink farms occurred on the Danish peninsula of Jutland. The canine distemper outbreak was associated with exposure of farmed mink to infected wild carnivores and could represent a deficit in biosecurity on the mink farms. The aim of this study was to investigate the extent and association of specific biosecurity measures with the outbreak. The study was carried out in an epidemiological case–control design. The case group consisted of the 61 farms, which had a confirmed outbreak of canine distemper from July 2012 to February 2013. The control group included 54 farms without an outbreak of canine distemper in 2012 or 2013, selected as the closest geographical neighbour to a case farm.

Results

The results showed that significantly more control than case farms had vaccinated their mink against canine distemper virus. Mortality was only assessed on the case farms, and there was a non-significantly lower mortality on vaccinated farms than on the non-vaccinated farms. Furthermore, the proportion of farms with observations of wild red foxes (Vulpes vulpes) inside the farm enclosures were larger for case farms, indicating that the control farms had a better biosecurity or were not equally exposed to canine distemper virus. Generally, all farms had very few specific precautions at the gate entrance in respect to human visitors as well as animals. The use of biosecurity measures was very variable in both case and control farms. Not using plastic boot covers, presence of dogs and cats, presence of demarcated area for changing clothes when entering and leaving the farm area and presence of hand washing facilities significantly lowered the odds of the farm having a canine distemper virus outbreak.

Conclusions

The results of the study indicate that consistent use of correct vaccination strategies, implementation of biosecurity measures and limiting human and animal access to the mink farm can be important factors in reducing the risk for canine distemper outbreaks.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-015-0159-2) contains supplementary material, which is available to authorized users.

Dynamic Changes in Cytosolic ATP Levels in Cultured Glutamatergic Neurons During NMDA-Induced Synaptic Activity Supported by Glucose or Lactate

We have previously shown that synaptic transmission fails in cultured neurons in the presence of lactate as the sole substrate. Thus, to test the hypothesis that the failure of synaptic transmission is a consequence of insufficient energy supply, ATP levels were monitored employing the ATP biosensor Ateam1.03YEMK. While inducing synaptic activity by subjecting cultured neurons to two 30 s pulses of NMDA (30 µM) with a 4 min interval, changes in relative ATP levels were measured in the presence of lactate (1 mM), glucose (2.5 mM) or the combination of the two. ATP levels reversibly declined following NMDA-induced neurotransmission activity, as indicated by a reversible 10-20 % decrease in the response of the biosensor. The responses were absent when the NMDA receptor antagonist memantine was present. In the presence of lactate alone, the ATP response dropped significantly more than in the presence of glucose following the 2nd pulse of NMDA (approx. 10 vs. 20 %). Further, cytosolic Ca(2+) homeostasis during NMDA-induced synaptic transmission is partially inhibited by verapamil indicating that voltage-gated Ca(2+) channels are activated. Lastly, we showed that cytosolic Ca(2+) homeostasis is supported equally well by both glucose and lactate, and that a pulse of NMDA causes accumulation of Ca(2+) in the mitochondrial matrix. In summary, we have shown that ATP homeostasis during neurotransmission activity in cultured neurons is supported by both glucose and lactate. However, ATP homeostasis seems to be negatively affected by the presence of lactate alone, suggesting that glucose is needed to support neuronal energy metabolism during activation.

A conserved WW domain-like motif regulates invariant chain-dependent cell-surface transport of the NKG2D ligand ULBP2

Malignant cells expressing NKG2D ligands on their cell surface can be directly sensed and killed by NKG2D-bearing lymphocytes. To ensure this immune recognition, accumulating evidence suggests that NKG2D ligands are trafficed via alternative pathways to the cell surface. We have previously shown that the NKG2D ligand ULBP2 traffics over an invariant chain (Ii)-dependent pathway to the cell surface. This study set out to elucidate how Ii regulates ULBP2 cell-surface transport: We discovered conserved tryptophan (Trp) residues in the primary protein sequence of ULBP1-6 but not in the related MICA/B. Substitution of Trp to alanine resulted in cell-surface inhibition of ULBP2 in different cancer cell lines. Moreover, the mutated ULBP2 constructs were retained and not degraded inside the cell, indicating a crucial role of this conserved Trp-motif in trafficking. Finally, overexpression of Ii increased surface expression of wt ULBP2 while Trp-mutants could not be expressed, proposing that this Trp-motif is required for an Ii-dependent cell-surface transport of ULBP2. Aberrant soluble ULBP2 is immunosuppressive. Thus, targeting a distinct protein module on the ULBP2 sequence could counteract this abnormal expression of ULBP2.

The selenium metabolite methylselenol regulates the expression of ligands that trigger immune activation through the lymphocyte receptor NKG2D

For decades, selenium research has been focused on the identification of active metabolites, which are crucial for selenium chemoprevention of cancer. In this context, the metabolite methylselenol (CH3SeH) is known for its action to selectively kill transformed cells through mechanisms that include increased formation of reactive oxygen species, induction of DNA damage, triggering of apoptosis, and inhibition of angiogenesis. Here we reveal that CH3SeH modulates the cell surface expression of NKG2D ligands. The expression of NKG2D ligands is induced by stress-associated pathways that occur early during malignant transformation and enable the recognition and elimination of tumors by activating the lymphocyte receptor NKG2D. CH3SeH regulated NKG2D ligands both on the transcriptional and the posttranscriptional levels. CH3SeH induced the transcription of MHC class I polypeptide-related sequence MICA/B and ULBP2 mRNA. However, the induction of cell surface expression was restricted to the ligands MICA/B. Remarkably, our studies showed that CH3SeH inhibited ULBP2 surface transport through inhibition of the autophagic transport pathway. Finally, we identified extracellular calcium as being essential for CH3SeH regulation of NKG2D ligands. A balanced cell surface expression of NKG2D ligands is considered to be an innate barrier against tumor development. Therefore, our work indicates that the application of selenium compounds that are metabolized to CH3SeH could improve NKG2D-based immune therapy.

The NKG2D ligand ULBP2 is specifically regulated through an invariant chain-dependent endosomal pathway

Soluble ULBP2 is a marker for poor prognosis in several types of cancer. In this study we demonstrate that both soluble and cell surface-bound ULBP2 is transported via a so far unrecognized endosomal pathway. ULBP2 surface expression, but not MICA/B, could specifically be targeted and retained by affecting endosomal/lysosomal integrity and protein kinase C activity. The invariant chain was further essential for endosomal transport of ULBP2. This novel pathway was identified through screening experiments by which methylselenic acid was found to possess notable NKG2D ligand regulatory properties. The protein kinase C inhibitor methylselenic acid induced MICA/B surface expression but dominantly blocked ULBP2 surface transport. Remarkably, by targeting this novel pathway we could specifically block the production of soluble ULBP2 from different, primary melanomas. Our findings strongly suggest that the endosomal transport pathway constitutes a novel therapeutic target for ULBP2-producing tumors.

N-glycosylation of asparagine 8 regulates surface expression of major histocompatibility complex class I chain-related protein A (MICA) alleles dependent on threonine 24

NKG2D is an activating receptor expressed on several types of human lymphocytes. NKG2D ligands can be induced upon cell stress and are frequently targeted post-translationally in infected or transformed cells to avoid immune recognition. Virus infection and inflammation alter protein N-glycosylation, and we have previously shown that changes in cellular N-glycosylation are involved in regulation of NKG2D ligand surface expression. The specific mode of regulation through N-glycosylation is, however, unknown. Here we investigated whether direct N-glycosylation of the NKG2D ligand MICA itself is critical for cell surface expression and sought to identify the essential residues. We found that a single N-glycosylation site (Asn(8)) was important for MICA018 surface expression. The frequently expressed MICA allele 008, with an altered transmembrane and intracellular domain, was not affected by mutation of this N-glycosylation site. Mutational analysis revealed that a single amino acid (Thr(24)) in the extracellular domain of MICA018 was essential for the N-glycosylation dependence, whereas the intracellular domain was not involved. The HHV7 immunoevasin, U21, was found to inhibit MICA018 surface expression by affecting N-glycosylation, and the retention was rescued by T24A substitution. Our study reveals N-glycosylation as an allele-specific regulatory mechanism important for regulation of surface expression of MICA018, and we pinpoint the residues essential for this N-glycosylation dependence. In addition, we show that this regulatory mechanism of MICA surface expression is likely targeted during different pathological conditions.

Impact of radical operative treatment on the quality of life in women with vulvar cancer--a retrospective study

OBJECTIVES

For patients undergoing vulva surgery the quality of life (QoL) is generally accepted as an important outcome parameter in addition to long-term survival, mortality and complication rates. Less radical operative treatment can reduce morbidity and thereby improve quality of life. This study focuses on outcome in terms of QoL in patients comparing wide local excision (WLE) with radical vulvectomy and waiver of lymphonodectomy (LNE) with inguinofemoral lymphonodectomy.

METHODS

In a retrospective single-center study from 2000 to 2010, 199 patients underwent surgery for vulvar cancer. To assess QoL, the EORTC QLQ-C30 and a tumor-specific module questionnaire were sent to all patients in the follow-up period.

RESULTS

Women who underwent WLE have a superior QoL with regard to global health status and physical, role, emotional and cognitive functioning than those who underwent radical vulvectomy. Less radical surgery also implies less fatigue, nausea/vomiting, pain, insomnia, appetite loss, diarrhea and financial difficulties. After radical vulvectomy 89% of patients have sexual complications.

CONCLUSION

Radical operative treatment, such as radical vulvectomy, causes deterioration in the QoL of these patients. An individualized, less radical surgery must be the aim in the treatment of vulvar cancer.

Gut microbiota regulates NKG2D ligand expression on intestinal epithelial cells

Intestinal epithelial cells (IECs) are one of a few cell types in the body with constitutive surface expression of natural killer group 2 member D (NKG2D) ligands, although the magnitude of ligand expression by IECs varies. Here, we investigated whether the gut microbiota regulates the NKG2D ligand expression on small IECs. Germ-free and ampicillin-treated mice were shown to have a significant increase in NKG2D ligand expression. Interestingly, vancomycin treatment, which propagated the bacterium Akkermansia muciniphila and reduced the level of IFN-γ and IL-15 in the intestine, decreased the NKG2D ligand expression on IECs. In addition, a similar increase in A. muciniphila and a decreased NKG2D ligand expression was seen after feeding with dietary xylooligosaccharides. A pronounced increase in NKG2D ligand expression was furthermore observed in IL-10-deficient mice. In summary, our results suggest that the constitutive levels of NKG2D ligand expression on IECs are regulated by microbial signaling in the gut and further disfavor the intuitive notion that IEC NKG2D ligand expression is caused by low-grade immune reaction against commensal bacteria. It is more likely that constitutively high IEC NKG2D ligand expression is kept in check by an intestinal regulatory immune milieu induced by members of the gut microbiota, for example A. muciniphila.

CAF01 potentiates immune responses and efficacy of an inactivated influenza vaccine in ferrets

Trivalent inactivated vaccines (TIV) against influenza are given to 350 million people every year. Most of these are non-adjuvanted vaccines whose immunogenicity and protective efficacy are considered suboptimal. Commercially available non-adjuvanted TIV are known to elicit mainly a humoral immune response, whereas the induction of cell-mediated immune responses is negligible. Recently, a cationic liposomal adjuvant (dimethyldioctadecylammonium/trehalose 6,6'-dibehenate, CAF01) was developed. CAF01 has proven to enhance both humoral and cell-mediated immune responses to a number of different experimental vaccine candidates. In this study, we compared the immune responses in ferrets to a commercially available TIV with the responses to the same vaccine mixed with the CAF01 adjuvant. Two recently circulating H1N1 viruses were used as challenge to test the vaccine efficacy. CAF01 improved the immunogenicity of the vaccine, with increased influenza-specific IgA and IgG levels. Additionally, CAF01 promoted cellular-mediated immunity as indicated by interferon-gamma expressing lymphocytes, measured by flow cytometry. CAF01 also enhanced the protection conferred by the vaccine by reducing the viral load measured in nasal washes by RT-PCR. Finally, CAF01 allowed for dose-reduction and led to higher levels of protection compared to TIV adjuvanted with a squalene emulsion. The data obtained in this human-relevant challenge model supports the potential of CAF01 in future influenza vaccines.

Long-term high-physiological-dose growth hormone reduces intra-abdominal fat in HIV-infected patients with a neutral effect on glucose metabolism

OBJECTIVES

The aim of the study was to investigate the effect of long-term high-physiological-dose recombinant human growth hormone (rhGH) therapy on fat distribution and glucose metabolism in HIV-infected patients.

METHODS

Forty-six HIV-infected Caucasian men on highly active antiretroviral therapy (HAART), with an age range of 21-60 years and no significant comorbidity, were included in this randomized, placebo-controlled, double-blind, single-centre trial. Twenty-eight subjects were randomized to 0.7 mg/day rhGH, and 18 subjects to placebo, administered as daily subcutaneous injections between 1 and 3 pm for 40 weeks. Endpoints included changes in visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), limb fat mass, percentage of limb fat, plasma lipids, insulin resistance and glucose tolerance.

RESULTS

VAT and trunk fat mass decreased significantly in the GH group compared with the placebo group [-19 cm(2) (-11%) vs. 12 cm(2) (6%), P=0.03, and -548 g (-9%) vs. 353 g (6%), P<0.01, respectively]. The beneficial fat redistribution in the GH group occurred without concomitant changes in subcutaneous fat at the abdomen or extremities. rhGH therapy was well tolerated. Insulin resistance, glucose tolerance, and total plasma cholesterol and triglycerides did not significantly change during intervention.

CONCLUSIONS

Daily 0.7 mg rhGH treatment for 40 weeks reduced abdominal visceral fat and trunk fat mass in HIV-infected patients. This treatment appeared to be safe with respect to glucose tolerance and insulin sensitivity.

Propionic acid secreted from propionibacteria induces NKG2D ligand expression on human-activated T lymphocytes and cancer cells

We found that propionic acid secreted from propionibacteria induces expression of the NKG2D ligands MICA/B on activated T lymphocytes and different cancer cells, without affecting MICA/B expression on resting peripheral blood cells. Growth supernatant from propionibacteria or propionate alone could directly stimulate functional MICA/B surface expression and MICA promoter activity by a mechanism dependent on intracellular calcium. Deletion and point mutations further demonstrated that a GC-box motif around -110 from the MICA transcription start site is essential for propionate-mediated MICA promoter activity. Other short-chain fatty acids such as lactate, acetate, and butyrate could also induce MICA/B expression. We observed a striking difference in the molecular signaling pathways that regulate MICA/B. A functional glycolytic pathway was essential for MICA/B expression after exposure to propionate and CMV. In contrast, compounds with histone deacetylase-inhibitory activity such as butyrate and FR901228 stimulated MICA/B expression through a pathway that was not affected by inhibition of glycolysis, clearly suggesting that MICA/B is regulated through different molecular mechanisms. We propose that propionate, produced either by bacteria or during cellular metabolism, has significant immunoregulatory function and may be cancer prophylactic.

Expression and function of toll-like receptor 8 and Tollip in colonic epithelial cells from patients with inflammatory bowel disease

OBJECTIVE

Growing evidence indicates that innate immunity, including toll-like receptor (TLR) signalling, plays a role in inflammatory bowel disease (IBD). This may also apply in the case of TLR-8, which has recently been shown to reverse the immunosuppressive function of regulatory T cells. However, the role of TLR-8 in IBD is currently unknown, and therefore we investigated the expression of TLR-8 and its natural antagonist, Tollip, in normal and inflamed human gut, and examined whether the receptor is functionally active.

METHODS

TLR-8 and Tollip mRNA expression were measured in colonic epithelial cells (CEC) and lamina propria mononuclear cells (LPMNC) by quantitative polymerase chain reaction. TLR-8 protein expression was visualized in whole biopsy specimens by indirect immunofluorescence microscopy. Cellular localization of TLR-8 protein was assessed by immuno-electron microscopy. IL-8 secretion was measured by ELISA after stimulation with TLR-8 ligand.

RESULTS

TLR-8 mRNA and protein expression were substantially up-regulated in CEC from inflamed mucosa from patients with ulcerative colitis (approximately 350-fold, p<0.01) and Crohn's disease (approximately 45-fold, p<0.05) compared to controls. TLR-8 proteins resided on the luminal surface membrane and in intracellular organelles. Tollip was not increased in CEC from IBD patients. CEC from normal mucosa responded to TLR-8 stimulation by secreting IL-8. TLR-8 was expressed only on the mRNA level in LPMNC with no differences between IBD patients and controls.

CONCLUSION

Expression of TLR-8, but not Tollip, is highly up-regulated in the colonic epithelium from patients with active IBD. Since the receptor is functionally active, our data suggest that TLR-8 signalling is important in the pathogenesis of IBD.

Molecular regulation of MHC class I chain-related protein A expression after HDAC-inhibitor treatment of Jurkat T cells

In this study, we characterize the molecular signal pathways that lead to MHC class I chain-related protein A (MICA) expression after histone deacetylase (HDAC)-inhibitor (HDAC-i) treatment of Jurkat T cells. Chelating calcium with BAPTA-AM or EGTA potently inhibited HDAC- and CMV-mediated MICA/B expression. It was further observed that endoplasmic reticulum calcium stores were depleted after HDAC treatment. NF-kappaB activity can be induced by HDAC treatment. However, nuclear translocation of NF-kappaB p65 was not observed after HDAC treatment of Jurkat T cells and even though we could effectively inhibit p65 expression by siRNA, it did not modify MICA/B expression. To identify important elements in MICA regulation, we made a promoter construct consisting of approximately 3 kb of the proximal MICA promoter in front of GFP. Deletion analysis showed that a germinal center-box containing a putative Sp1 site from position -113 to -93 relative to the mRNA start site was important for HDAC and CMV-induced promoter activity. Sp1 was subsequently shown to be important, as targeted mutation of the Sp1 binding sequence or siRNA mediated down modulation of Sp1-inhibited MICA promoter activity and surface-expression.

Effects of endotoxaemia on markers of permeability, metabolism and inflammation in the large bowel of healthy subjects

BACKGROUND

Increased permeability and increased luminal concentrations of L-lactate have previously been shown in the large bowel in septic patients. To advance these observations, a human model of colorectal barrier failure in sepsis is desirable. Therefore, we assessed the effects of endotoxaemia on markers of permeability, metabolism and inflammation in the large bowel in healthy subjects.

METHODS

Twelve healthy male subjects received intravenous endotoxin (2 ng/kg body weight) or saline in a paired cross-over design. Colorectal permeability was assessed after 3, 6, 9 and 12 h by the systemic recovery of luminally instilled (99m)Tc-diethylenetriaminepentaacetate. Luminal concentrations of L-lactate were assessed by equilibrium dialysis. Mucosal biopsies from the large bowel were sampled after 6 and 12 h, and the apoptotic ratio of the epithelium was assessed by terminal deoxynucleotidyl transferase-mediated desoxyuridinetriphosphate nick end-labelling (TUNEL) assay and the expression of inducible nitric oxide synthase (iNOS) mRNA by reverse transcriptase-polymerase chain reaction.

RESULTS

Systemic effects of endotoxaemia were observed, including fever, tachycardia and strongly increased plasma values of tumour necrosis factor-alpha. By contrast, the colorectal permeability, luminal lactate concentrations, mucosal infiltration of inflammatory cells, epithelial apoptotic ratio and expression of iNOS were all unaffected by endotoxin.

CONCLUSIONS

No effect of a single intravenous dose of endotoxin was observed on markers of large bowel permeability, metabolism and inflammation in healthy subjects. This suggests that this part of the gut is relatively resistant to the systemic inflammation induced by experimental endotoxaemia in humans.

Interleukin-4 and 13 Induce the Expression and Release of Monocyte Chemoattractant Protein 1, Interleukin-6 and Stem Cell Factor From Human Detrusor Smooth Muscle Cells: Synergy With Interleukin-1β and Tumor Necrosis Factor-α

PURPOSE

Interstitial cystitis is characterized by an increased number of activated MCs in the detrusor muscle. However, to our knowledge the factors that influence the anatomical relationship between MCs and HDSMCs are unknown. MCP-1, IL-6 and SCF have a critical role in the regulation of MC development, signaling and function. We investigated whether HDSMCs are capable of expressing and releasing MCP-1, IL-6 and SCF in response to IL-4, IL-13, IL-1beta and tumor necrosis factor-alpha.

MATERIALS AND METHODS

HDSMCs were isolated and cultured using an explant technique. Protein expression, and the secretion of MCP-1, IL-6 and SCF were assayed by semiquantitative reverse transcriptase-polymerase chain reaction and specific enzyme-linked immunosorbent assay.

RESULTS

Unstimulated cells released low amounts of MCP-1, IL-6 and SCF. In cells stimulated by IL-4 MCP-1 mRNA was up-regulated by a mean factor +/- SD of 3.5 +/- 1.3, IL-6 mRNA was up-regulated by 3.8 +/- 1.3, the soluble form of SCF was up-regulated by 3.2 +/- 0.6 and the membrane bound form of SCF was up-regulated by 7.9 +/- 5.6. For IL-13 stimulated cells the values were 2.6 +/- 1.5, 3.6 +/- 2.1, 2.9 +/- 1.6 and 5.7 +/- 3.7, respectively. Soluble SCF mRNA expression was 5 times higher than the expression of mSCF mRNA. IL-4 and IL-13 given separately stimulated MCP-1, IL-6 and SCF secretion in a concentration (0.01 to 100 ng/ml) and time (0 to 24 hours) dependent manner. Furthermore, IL-1beta and tumor necrosis factor-alpha alone induced significant release of MCP-1, IL-6 and SCF but in combination with IL-4 or IL-13 it induced greater secretion of MCP-1, IL-6 and SCF.

CONCLUSIONS

To our knowledge these findings demonstrate for the first time that HDSMCs express and release MCP-1 and IL-6, and show relatively high expression of soluble SCF. This supports our hypothesis that HDSMCs may have an active role by orchestrating the local inflammatory response in the bladder wall with possible implications for the pathophysiology of detrusor mastocytosis.

Cancer cells become susceptible to natural killer cell killing after exposure to histone deacetylase inhibitors due to glycogen synthase kinase-3-dependent expression of MHC class I-related chain A and B

We show that histone deacetylase (HDAC) inhibitors lead to functional expression of MHC class I-related chain A and B (MICA/B) on cancer cells, making them potent targets for natural killer (NK) cell-mediated killing through a NK group 2, member D (NKG2D) restricted mechanism. Blocking either apoptosis or oxidative stress caused by HDAC inhibitor treatment did not affect MICA/B expression, suggesting involvement of a separate signal pathway not directly coupled to induction of cell death. HDAC inhibitor treatment induced glycogen synthase kinase-3 (GSK-3) activity and down-regulation of GSK-3 by small interfering RNA or by different inhibitors showed that GSK-3 activity is essential for the induced MICA/B expression. We thus present evidence that cancer cells which survive the direct induction of cell death by HDAC inhibitors become targets for NKG2D-expressing cells like NK cells, gammadelta T cells, and CD8 T cells.

Expression of Toll-like receptor 9 and response to bacterial CpG oligodeoxynucleotides in human intestinal epithelium

Recognition of repeat CpG motifs, which are common in bacterial, but not in mammalian, DNA, through Toll-like receptor (TLR)9 is an integral part of the innate immune system. As the role of TLR9 in the human gut is unknown, we determined the spectrum of TLR9 expression in normal and inflamed colon and examined how epithelial cells respond to specific TLR9 ligand stimulation. TLR9 expression was measured in human colonic mucosal biopsies, freshly isolated human colonic epithelial cells and HT-29 cells by reverse transcriptase-polymerase chain reaction or Western blotting. Colonic epithelial cell cultures were stimulated with a synthetic CpG-oligodeoxynucleotide (ODN), exhibiting strong immunostimulatory effects in B cells. Interleukin (IL)-8 secretion was determined by enzyme-linked immunosorbent assay, nuclear factor-kappaB (NF-kB) activity by electrophoretic mobility shift assay and IkB phosphorylation by Western blotting. TLR9 mRNA was equally expressed in colonic mucosa from controls (n = 6) and patients with ulcerative colitis or Crohn's disease disease (n = 13). HT-29 cells expressed TLR9 mRNA and protein and responded to CpG-ODN (P < 0.01), but not to non-CpG-ODN stimulation, by secreting IL-8, apparently in the absence of NF-kB activation. Primary epithelial cells isolated from normal human colon expressed TLR9 mRNA, but were completely unresponsive to CpG-ODN stimulation in vitro. In conclusion, differentiated human colonic epithelial cells are unresponsive to TLR9 ligand stimulation in vitro despite spontaneous TLR9 gene expression. This suggests that the human epithelium is able to avoid inappropriate immune responses to luminal bacterial products through modulation of the TLR9 pathway.

Expression of inducible nitric oxide synthase and effects of L-arginine on colonic nitric oxide production and fluid transport in patients with "minimal colitis"

OBJECTIVE

Some patients with idiopathic, chronic diarrhoea have minimal, non-specific colonic inflammation. As nitric oxide (NO) acts as a secretagogue in the colon, we studied the expression of inducible NO synthase (iNOS) in mucosal biopsies and the effects of NOS stimulation on colonic transfer of fluid and output of NO in patients with "minimal colitis".

MATERIAL AND METHODS

Twelve patients with idiopathic, chronic diarrhoea and "minimal colitis" and 6 healthy volunteers were included in the study. Expression of iNOS in colonic mucosal biopsies was quantified by Western blot analysis and localized by immunohistochemistry. The effects of topical L-arginine or placebo on colonic net fluid transfer and nitrite/nitrate (NOx) output were assessed during "steady state" perfusion of the whole colon. Concentrations of NOx were measured by Griess' assay.

RESULTS

The expression of iNOS was increased 10-fold (p<0.01) in patients with "minimal colitis" compared with that in healthy volunteers and localized to the colonic epithelium. Colonic absorption of fluid was impaired (mean (SEM) 1.5 (0.2) versus 3.0 (0.2) ml/min, p<0.001) and the output of NOx was increased (47 (4) nmol/min versus <37 nmol/min, p<0.05) in patients with "minimal colitis" compared with that in healthy volunteers. Luminal L-arginine (20 mM) reduced colonic absorption of fluid in both groups (95% confidence intervals (CIs) 21-50% in patients with "minimal colitis" versus 4-18% in healthy volunteers), but an increase in NOx output was detectable only in the group of patients (8-106%). In time control experiments, colonic net transfer rates of fluid and outputs of NOx were unaffected by placebo.

CONCLUSIONS

In patients with idiopathic, chronic diarrhoea and histopathological evidence of "minimal colitis", colonic absorption of fluid is impaired, while epithelial expression of iNOS and mucosal production of NO is enhanced. It could be speculated that NO in excess contributes to the diarrhoea observed in "minimal colitis".

Activation of nuclear factor kappaB in colonic mucosa from patients with collagenous and ulcerative colitis

BACKGROUND AND AIMS

Expression of inducible nitric oxide synthase (iNOS) is greatly upregulated in the colonic mucosa of patients with collagenous and ulcerative colitis. As the transcription factor nuclear factor kappaB (NFkappaB) is a major inducer of iNOS gene expression, we compared activation and transcriptional activity of NFkappaB in colonic mucosal biopsies from these patients.

PATIENTS

Eight patients with collagenous colitis, six with relapsing ulcerative colitis, and eight with uninflamed bowel were studied.

METHODS

NFkappaB DNA binding activity was assessed by electrophoretic mobility shift assay and inhibitor of NFkappaB (IkappaB) kinase (IKK) activity by immunocomplex kinase assay. In vivo recruitment of NFkappaB to the iNOS promoter was determined by chromatin immunoprecipitation analysis and transcriptional activity by NFkappaB gene expression profiling arrays. Cells showing NFkappaB activation were identified by immunohistochemistry.

RESULTS

In collagenous and ulcerative colitis, as opposed to uninflamed bowel, IKKbeta activity and strong NFkappaB DNA binding gave rise to activation of identical NFkappaB subunits and recruitment of transcriptionally active p65 to the iNOS promoter. In collagenous colitis, activated NFkappaB was observed only in epithelial cells while up to 10% of lamina propria macrophages showed activation in ulcerative colitis.

CONCLUSIONS

In collagenous and ulcerative colitis, colonic mucosal NFkappaB is activated and recruited to the iNOS promoter in vivo via an IKKbeta mediated pathway. As collagenous colitis is not associated with tissue injury, these data challenge the prevailing view that activation of NFkappaB per se mediates tissue injury. Our results suggest that downstream inflammatory reactions leading to tissue damage originate in lamina propria immune cells, as increased NFkappaB activity in collagenous colitis was localised solely in epithelial cells, but present also in macrophages in ulcerative colitis.

Superoxide production and expression of NAD(P)H oxidases by transformed and primary human colonic epithelial cells

BACKGROUND

Superoxide (O(2)(-)) generation through the activity of reduced nicotinamide dinucleotide (NADH) or reduced nicotinamide dinucleotide phosphate (NADPH) oxidases has been demonstrated in a variety of cell types, but not in human colonic epithelial cells.

AIMS

To measure O(2)(-) production and effects of modulators of NAD(P)H oxidase activity and inhibitors of potential O(2)(-) generating enzymes in cultures of human colonic epithelial cells. Expression of the catalytic subunits of NAD(P)H oxidase, Nox1 and gp91(phox) (phox, phagocytic oxidase), and the membrane bound subunit p22(phox) was assessed.

METHODS

The transformed colonic epithelial cell lines (DLD-1, HT-29, and Caco-2) were studied at subconfluence, confluence, and after differentiation. Primary colonic epithelial cells were isolated from mucosal biopsies from the normal human colon. Extracellular O(2)(-) production was measured by the cytochrome c reduction assay or luminol enhanced luminescence. Nox1, gp91(phox), and p22(phox) mRNA expression was assessed in colonic epithelial cells and blood neutrophils by reverse transcriptase-polymerase chain reaction.

RESULTS

Production rates of O(2)(-) were higher in subconfluent transformed cells (mean (SEM) 35.8 (4.2) nmol/mg of protein/h) and primary cells (40.4 (5.9)) than in confluent transformed cells (6.0 (0.9); p<0.01). The oxidoreductase inhibitor diphenylene iodonium significantly inhibited O(2)(-) production whereas NADPH and NADH increased production rates. In contrast, O(2)(-) was unaffected by phorbol myristate ester, N(G)-nitro-L-arginine methyl ester, indomethacin, or allopurinol. Nox1 mRNA was expressed in all colonic epithelial cells whereas gp91(phox) was detected only in HT-29 cells and neutrophils. p22(phox) was expressed in all cell types.

CONCLUSIONS

Cultures of transformed and primary epithelial cells from human colon may produce extracellular O(2)(-) through an NAD(P)H oxidase expressing Nox1 and p22(phox).

Constitutive expression of inducible nitric oxide synthase in the normal human colonic epithelium

BACKGROUND

Inducible nitric oxide synthase (iNOS) in the human colon is considered expressed only in inflammatory states such as ulcerative or collagenous colitis. As subtle iNOS labelling was previously observed in some colonic mucosal biopsies from a heterogeneous group of controls with non-inflamed bowel, we studied whether bowel preparation with bisacodyl or polyethylene glycol prior to sigmoidoscopy might induce iNOS expression.

METHODS

Ten healthy, non-smoking male subjects were investigated. Mucosal biopsies were taken from the sigmoid colon prior to bowel preparation and again 12 h after rectal administration of bisacodyl or polyethylene glycol in randomized order. Expression of iNOS protein was quantified by Western blot analysis and localized by immunohistochemistry.

RESULTS

iNOS was expressed in the colonic mucosal biopsies from all subjects and localized in the epithelial cells, particularly at the luminal border of the epithelial cells and more pronounced in the crypt epithelium. The expression of iNOS was unaffected by bowel preparation with bisacodyl or polyethylene glycol.

CONCLUSIONS

iNOS is constitutively expressed in the normal colonic epithelium. The results suggest that synthesis of iNOS protein is unaffected by bowel preparation with the secretagogue laxative, bisacodyl, or polyethylene glycol.

Expression of nitric oxide synthases and effects of L-arginine and L-NMMA on nitric oxide production and fluid transport in collagenous colitis

BACKGROUND AND AIMS

Luminal nitric oxide (NO) is greatly increased in the colon of patients with collagenous and ulcerative colitis. To define the source and consequence of enhanced NO production we have studied expression of NO synthase (NOS) isoforms and nitrotyrosine in mucosal biopsies from these patients. In addition, effects on colonic fluid transfer caused by manipulating the substrate of NOS were studied in patients with collagenous colitis.

PATIENTS

Eight patients with collagenous colitis, nine with active ulcerative colitis, and 10 with uninflamed bowel were included.

METHODS

Expression of NOS isoforms was quantified by western blotting. Inducible NOS (iNOS) and nitrotyrosine were localised by immunohistochemistry. Modulation of NOS activity by topical N(G)-monomethyl-L-arginine (L-NMMA) or L-arginine was assessed during perfusion of whole colon. Plasma and perfusate nitrite/nitrate (NOx) was measured by Griess' reaction.

RESULTS

Both in collagenous and ulcerative colitis, expression of iNOS was 10(2)-10(3) higher (p<0.001) than in uninflamed bowel and localised primarily to the epithelium. Endothelial NOS was evenly expressed in all groups while neuronal NOS was undetectable. Nitrotyrosine was markedly expressed in active ulcerative colitis but rarely detected in collagenous colitis and never in uninflamed bowel. In collagenous colitis, the output of NOx was markedly increased compared with uninflamed bowel (283 (58) v <37 nmol/min; p<0.01) and fluid was net secreted. L-NMMA reduced the output of NOx by 13-66% (95% confidence intervals) and secretion of fluid by 25-109% whereas L-arginine increased the output of NOx by 3-39% and secretion of fluid by 15-93%.

CONCLUSIONS

In collagenous colitis, as opposed to ulcerative colitis, upregulation of iNOS occurs in the absence of nitrotyrosine formation and mucosal damage. Excess generation of NO may be the primary cause of diarrhoea in this condition.

Serotonin modulates immune function in T cells from HIV-seropositive subjects

We have shown earlier increased intracellular levels of cAMP in peripheral lymphocytes from HIV-seropositive subjects and that a chemically induced decrease in this level increases cell proliferation and cytotoxicity. Others have shown that serotonin indirectly decreases intracellular cAMP levels in normal peripheral lymphocytes. In this study, we show that addition of serotonin decreases intracellular levels of cAMP in lymphocytes from HIV-seropositive subjects and significantly increases the proliferative capacity in vitro. However, the effect of serotonin varies with the initial proliferative response; e.g., these with the highest initial responses have the highest increases. An increase in IL-2 production may be a part of this mechanism since addition of serotonin to in vitro cultures of PHA-stimulated cells increases the expression of mRNA for IL-2 and IFN-gamma. The effect on lymphocyte proliferation was most likely mediated through the serotonin 5HT1a receptor because similar results could be obtained by using DPAT, a specific activator of this receptor. Changes in the expression of 5HT1a receptors as judged by the expression of mRNA could not explain why serotonin in vitro had a stronger enhancing effect on cell proliferation in some HIV-seropositive individuals than in others.

Pharmacodynamic dose finding of dimetindene in a sustained release formulation

A sustained release form of dimetindene (dimethindene maleate, Fenistil, CAS 3614-69-5) was developed based on a micropellet technique. Aim of the study was to evaluate the efficacy and duration of two doses of dimetindene in a sustained release pellet formulation with a standardised grass pollen provacation model (Vienna Challenge Chamber; VCC). The study with 12 grass pollen allergic volunteers--verified by case history, skin prick test (SPT), and radio allergo sorbent test (RAST)--was carried out in a placebo controlled, double blind, cross-over design. 12 h before a 4-h-lasting continuous challenge with permanent 1000 dactylis grass pollen in the VCC, administration of dimetindene (Fenistil R Pellets) in doses of 4 mg, 8 mg or identically appearing placebo was scheduled in three sessions. Nasal flow and resistance, nasal secretion and subjective symptoms were recorded at 15-min intervals during this long-term challenge under reproducible conditions. In comparison to placebo, dimetindene leads to a statistically significant reduction (p < 0.05) of nasal response and clinical symptoms for at least 16 h after treatment. The efficacy of 8 mg dimetindene was pronounced over 4 mg, however, the differences between both active treatments were not statistically significant. Therefore 4 mg dimetindene once a day is the adequate treatment for usual pollinotic disease conditions.