Use of Hoechst 33342 staining to detect apoptotic changes in bovine mononuclear phagocytes infected with Mycobacterium avium subsp. paratuberculosis

Innate immune markers that distinguish red deer (Cervus elaphus) selected for resistant or susceptible genotypes for Johne's disease

While many factors contribute to resistance and susceptibility to infectious disease, a major component is the genotype of the host and the way in which it is expressed. Johne’s disease is a chronic inflammatory bowel disease affecting ruminants and is caused by infection with Mycobacterium avium subspecies paratuberculosis (MAP). We have previously identified red deer breeds (Cervus elaphus) that are resistant; have a low rate of MAP infection and do not progress to develop Johne’s disease. In contrast, susceptible breeds have a high rate of MAP infection as seen by seroconversion and progress to develop clinical Johne’s disease. The aim of this study was to determine if immunological differences exist between animals of resistant or susceptible breeds. Macrophage cultures were derived from the monocytes of deer genotypically defined as resistant or susceptible to the development of Johne’s disease. Following in vitro infection of the cells with MAP, the expression of candidate genes was assessed by quantitative PCR as well as infection rate and cell death rate. The results indicate that macrophages from susceptible animals show a significantly higher upregulation of inflammatory genes (iNOS, IL-1α, TNF-α and IL-23p19) than the macrophages from resistant animals. Cells from resistant animals had a higher rate of apoptosis at 24 hours post infection (hpi) compared to macrophages from susceptible animals. The excessive expression of inflammatory mRNA transcripts in susceptible animals could cause inefficient clearing of the mycobacterial organism and the establishment of disease. Controlled upregulation of inflammatory pathways coupled with programmed cell death in the macrophages of resistant animals may predispose the host to a protective immune response against this mycobacterial pathogen.

Influenza virus A/Beijing/501/2009(H1N1) NS1 interacts with β-tubulin and induces disruption of the microtubule network and apoptosis on A549 cells

NS1 of influenza A virus is a key multifunctional protein that plays various roles in regulating viral replication mechanisms, host innate/adaptive immune responses, and cellular signalling pathways. These functions rely on its ability to participate in a multitude of protein-protein and protein-RNA interactions. To gain further insight into the role of NS1, a tandem affinity purification (TAP) method was utilized to find unknown interaction partner of NS1. The protein complexes of NS1 and its interacting partner were purified from A549 cell using TAP-tagged NS1 as bait, and co-purified cellular factors were identified by mass spectrometry (MS). We identified cellular β-tubulin as a novel interaction partner of NS1. The RNA-binding domain of NS1 interacts with β-tubulin through its RNA-binding domain, as judged by a glutathione S-transferase (GST) pull-down assay with the GST-fused functional domains of NS1. Immunofluorescence analysis further revealed that NS1 with β-tubulin co-localized in the nucleus. In addition, the disruption of the microtubule network and apoptosis were also observed on NS1-transfected A549 cells. Our findings suggest that influenza A virus may utilize its NS1 protein to interact with cellular β-tubulin to further disrupt normal cell division and induce apoptosis. Future work will illustrate whether this interaction is uniquely specific to the 2009 pandemic H1N1 virus.

Arsenic-induced alteration in intracellular calcium homeostasis induces head kidney macrophage apoptosis involving the activation of calpain-2 and ERK in Clarias batrachus

We had earlier shown that exposure to arsenic (0.50 μM) caused caspase-3 mediated head kidney macrophage (HKM) apoptosis involving the p38-JNK pathway in Clarias batrachus. Here we examined the roles of calcium (Ca(2+)) and extra-cellular signal-regulated protein kinase (ERK), the other member of MAPK-pathway on arsenic-induced HKM apoptosis. Arsenic-induced HKM apoptosis involved increased expression of ERK and calpain-2. Nifedipine, verapamil and EGTA pre-treatment inhibited the activation of calpain-2, ERK and reduced arsenic-induced HKM apoptosis as evidenced from reduced caspase-3 activity, Annexin V-FITC-propidium iodide and Hoechst 33342 staining. Pre-incubation with ERK inhibitor U 0126 inhibited the activation of calpain-2 and interfered with arsenic-induced HKM apoptosis. Additionally, pre-incubation with calpain-2 inhibitor also interfered with the activation of ERK and inhibited arsenic-induced HKM apoptosis. The NADPH oxidase inhibitor apocynin and diphenyleneiodonium chloride also inhibited ERK activation indicating activation of ERK in arsenic-exposed HKM also depends on signals from NADPH oxidase pathway. Our study demonstrates the critical role of Ca(2+) homeostasis on arsenic-induced HKM apoptosis. We suggest that arsenic-induced alteration in intracellular Ca(2+) levels initiates pro-apoptotic ERK and calpain-2; the two pathways influence each other positively and induce caspase-3 mediated HKM apoptosis. Besides, our study also indicates the role of ROS in the activation of ERK pathway in arsenic-induced HKM apoptosis in C. batrachus.

Comparative immunological and microbiological aspects of paratuberculosis as a model mycobacterial infection

Paratuberculosis or Johne's disease of livestock, which is caused by Mycobacterium avium subsp. paratuberculosis (MAP), has increased in prevalence and expanded in geographic and host ranges over about 100 years. The slow and progressive spread of MAP reflects its substantial adaptation to its hosts, the technical limitations of diagnosis, the lack of practical therapeutic approaches, the lack of a vaccine that prevents transmission and the complexity and difficulty of the on-farm control strategies needed to prevent infection. More recently evidence has accumulated for an association of MAP with Crohn's disease in humans, adding to the pressure on animal health authorities to take precautions by controlling paratuberculosis. Mycobacterial infections invoke complex immune responses but the essential determinants of virulence and pathogenesis are far from clear. In this review we compare the features of major diseases in humans and animals that are caused by the pathogenic mycobacteria M. ulcerans, M. avium subsp. avium, M. leprae, M. tuberculosis and MAP. We seek to answer key questions: are the common mycobacterial infections of humans and animals useful "models" for each other, or are the differences between them too great to enable meaningful extrapolation? To simplify this, the immunopathogenesis of mycobacterial infections will be defined at cellular, tissue, animal and population levels and the key events at each level will be discussed. Many pathogenic processes are similar between divergent mycobacterial diseases, and at variance between virulent and avirulent isolates of mycobacteria, suggesting that the research on the pathogenesis of one mycobacterial disease will be informative for the others.

Anti-proliferative and pro-apoptotic actions of a novel human and mouse ovarian tumor-associated gene OTAG-12: downregulation, alternative splicing and drug sensitization

In studying the age dependence and chronology of ovarian tumors in follicle stimulating hormone receptor knockout mice, we identified a novel ovarian tumor associated gene-12 (OTAG-12), which is progressively downregulated and maps to Chr. 8B3.3. OTAG-12 protein overexpression in mouse ovarian and mammary tumor cells suggested powerful anti-proliferative effects. In human epithelial ovarian cancers (OCs) and OC cell lines, OTAG-12 mRNA expression is downregulated in comparison with normal ovaries. Cloning and identification revealed that human OTAG-12 mapping to gene-rich Chr. 19p13.12 is expressed in three spliced forms: hOTAG-12a, hOTAG-12b and hOTAG-12c, of which b is predominant in the normal ovary. Functionally active hOTAG-12b is a simple protein with no disulfide bonds and a nuclear localization signal is present in all variants. Transfection of OTAG-12 variants in OC and tumorigenic HEK293 cells confirmed nuclear localization. hOTAG-12b overexpression in OC and HEK293 cells effectively suppressed cell growth, anchorage-dependent and independent colony formation followed by apoptosis, whereas hOTAG-12a and hOTAG-12c had no such effects. Deletion mutants identified the critical importance of carboxyl terminus for hOTAG-12b function. Doxycycline-inducible growth inhibition of HEK293 cells by hOTAG-12a was associated with effects on G2 cell cycle arrest and apoptosis induction. hOTAG-12b expression rendered tumorigenic cells more sensitive to four apoptotic stimuli including etoposide-a topoisomerase-II inhibitor. Doxycycline-induced hOTAG-12b expression blocked xenograft tumor growth in nude mice, whereas hOTAG-12a was ineffective. Although p53-pathway-dependent apoptotic agents could upregulate endogenous hOTAG-12b and p53 in UCI-101/107 OC cells, hOTAG-12b could also induce apoptosis in p53-null and platinum-resistant SKOV3 OC cells and Doxycycline-induced hOTAG-12b did not alter p53. Further study showed that hOTAG-12b increases mRNAs of pro-apoptotic genes such as BAD, GADD45α and CIEDB, while inhibiting anti-apoptotic NAIP and Akt1 expression, suggesting that hOTAG-12b-induced apoptosis might be p53-independent. These results indicate that hOTAG-12b is a putative ovarian tumor suppressor gene warranting further studies.

Neuroprotection of interleukin-6 against NMDA-induced apoptosis and its signal-transduction mechanisms

We have previously shown that interleukin-6 (IL-6)-protected neurons against the suppression of neuronal vitality and overload of intracellular Ca(2+) induced by glutamate or N-methyl-D: -aspartate (NMDA). Herein we provide further evidence for IL-6 neuroprotection against NMDA-induced apoptosis and explore the signal-transduction mechanisms underlying the anti-apoptotic action of IL-6. Cerebellar granule neurons (CGNs) from postnatal 8-day infant rats were chronically exposed to IL-6 (40 or 120 ng/ml) for 8 days, and stimulated with NMDA (100 μM) for 30 min. To observe the signaling pathways, we employed AG490 (5 or 10 μM), an inhibitor of Janus kinases (JAKs), or LY294002 (5 or 10 μM), an inhibitor of phosphatidylinositol 3-kinase (PI3K), to pretreat the CGNS together with IL-6. The levels of phosphorylation for the downstream effectors of JAKs and PI3K, i.e., phosphorylated STAT3 and Akt, were quantified by Western blot assay. In the cultured CGNs with various drug exposures, the expressions of Bcl-2, Bax, and caspase-3 were measured by real-time PCR and Western blot, and the percentage of apoptotic nuclei was tested by Hoechst 33342 staining. After the CGNs were chronically exposed to IL-6, NMDA stimulation led to an increase in the expression of Bcl-2 mRNA and a decrease in the expression of Bax and caspase-3 mRNAs and proteins when compared with those neurons lacking IL-6 exposure. IL-6 pretreatment of the neurons without NMDA stimulation concentration-dependently enhanced the expressions of Bcl-2 mRNA and protein while attenuating the expressions of Bax and caspase-3 mRNAs and proteins in comparison with control lacking any treatment. Furthermore, IL-6 prevented the increase in the percentage of apoptotic neurons induced by NMDA. The combined pretreatment of the CGNs with AG490 and IL-6 or with LY294002 and IL-6 reduced these anti-apoptotic effects of IL-6. Neither AG490 nor LY294002 exposure alone altered the expressions of Bcl-2, Bax, and cleaved caspase-3 proteins. IL-6 up-regulated the levels of phosphorylated STAT3 and Akt, and this was blocked by AG490 and LY294002, respectively. These results suggest that IL-6 protects neurons against NMDA-induced apoptosis, and that the IL-6 neuroprotection is jointly mediated by JAK-STAT3 and PI3K-Akt signaling pathways.

Rapid neutrophil destruction following phagocytosis of Staphylococcus aureus

Mechanisms underlying the enhanced virulence phenotype of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) are incompletely defined, but presumably include evasion of killing by human polymorphonuclear leukocytes (PMNs or neutrophils). To better understand this phenomenon, we investigated the basis of rapid PMN lysis after phagocytosis of USA300, a prominent CA-MRSA strain. Survival of USA300 clinical isolates after phagocytosis ultimately resulted in neutrophil lysis. PMNs containing ingested USA300 underwent morphological changes consistent with apoptosis, but lysed rapidly thereafter (within 6 h), whereas cells undergoing FAS-mediated apoptosis or phagocytosis-induced cell death remained intact. Phagosome membranes remained intact until the point of PMN destruction, suggesting lysis was not caused by escape of S. aureus from phagosomes or the cytolytic action of pore-forming toxins. Microarray analysis of the PMN transcriptome after phagocytosis of representative community-associated S. aureus and healthcare-associated MRSA strains revealed changes unique to community-associated S. aureus strains, such as upregulation of transcripts involved in regulation of calcium homeostasis. Collectively, the data suggest that neutrophil destruction after phagocytosis of USA300 is in part a form of programmed necrosis rather than direct lysis by S. aureus pore-forming toxins. We propose that the ability of CA-MRSA strains to induce programmed necrosis of neutrophils is a component of enhanced virulence.

Assessment of live candidate vaccines for paratuberculosis in animal models and macrophages

Mycobacterium avium subsp. paratuberculosis (basonym M. paratuberculosis) is the causative agent of paratuberculosis, a chronic enteritis of ruminants. To control the considerable economic effect that paratuberculosis has on the livestock industry, a vaccine that induces protection with minimal side effects is required. We employed transposon mutagenesis and allelic exchange to develop three potential vaccine candidates, which were then tested for virulence with macrophages, mice, and goats. All three models identified the WAg906 mutant as being the most attenuated, but some differences in the levels of attenuation were evident among the models when testing the other strains. In a preliminary mouse vaccine experiment, limited protection was induced by WAg915, as evidenced by a reduced bacterial load in spleens and livers 12 weeks following intraperitoneal challenge with M. paratuberculosis K10. While we found macrophages and murine models to be rapid and cost-effective alternatives for the initial screening of M. paratuberculosis mutants for attenuation, it appears necessary to do the definitive assessment of attenuation with a ruminant model.

γ-Irradiation Enhances Apoptosis Induced by Cannabidiol, a Non-psychotropic Cannabinoid, in Cultured HL-60 Myeloblastic Leukemia Cells

Two non-psychotropic cannabinoids, cannabidiol (CBD) and cannabidiol-dimethylheptyl (CBD-DMH), induced apoptosis in a human acute myeloid leukemia (AML) HL-60 cell line. Apoptosis was determined by staining with bisBenzimide and propidium iodide. A dose dependent increase of apoptosis was noted, reaching 61 and 43% with 8 microg/ml CBD and 15 microg/ml CBD-DMH, respectively, after a 24 h treatment. Prior exposure of the cells to gamma-irradiation (800 cGy) markedly enhanced apoptosis, reaching values of 93 and 95%, respectively. Human monocytes from normal individuals were resistant to either cannabinoids or gamma-irradiation. Caspase-3 activation was observed after the cannabinoid treatment, and may represent a mechanism for the apoptosis. Our data suggest a possible new approach to treatment of AML.

Simian virus 40 small T antigen activates AMPK and triggers autophagy to protect cancer cells from nutrient deprivation

As tumors grow larger, they often experience an insufficient supply of oxygen and nutrients. Hence, cancer cells must develop mechanisms to overcome these stresses. Using an in vitro transformation model where the presence of the simian virus 40 (SV40) small T (ST) antigen has been shown to be critical for tumorigenic transformation, we investigated whether the ST antigen has a role to play in regulating the energy homeostasis of cancer cells. We find that cells expressing the SV40 ST antigen (+ST cells) are more resistant to glucose deprivation-induced cell death than cells lacking the SV40 ST antigen (-ST cells). Mechanistically, we find that the ST antigen mediates this effect by activating a nutrient-sensing kinase, AMP-activated protein kinase (AMPK). The basal level of active, phosphorylated AMPK was higher in +ST cells than in -ST cells, and these levels increased further in response to glucose deprivation. Additionally, inhibition of AMPK in +ST cells increased the rate of cell death, while activation of AMPK in -ST cells decreased the rate of cell death, under conditions of glucose deprivation. We further show that AMPK mediates its effects, at least in part, by inhibiting mTOR (mammalian target of rapamycin), thereby shutting down protein translation. Finally, we show that +ST cells exhibit a higher percentage of autophagy than -ST cells upon glucose deprivation. Thus, we demonstrate a novel role for the SV40 ST antigen in cancers, where it functions to maintain energy homeostasis during glucose deprivation by activating AMPK, inhibiting mTOR, and inducing autophagy as an alternate energy source.

Tactics of Mycobacterium avium subsp. paratuberculosis for intracellular survival in mononuclear phagocytes

Johne's disease is a condition that refers to chronic granulomatous enteritis in ruminants. It is believed that survival and replication of Mycobacterium (M.) paratuberculosis in mononuclear phagocytes plays an important role in the pathogenesis of Johne's disease. However, it is not clear how M. paratuberculosis survives for long time periods in mononuclear phagocytes, nor is it clear which factors trigger multiplication of these bacilli and result in the development of Johne's disease. Investigating the intracellular fate of M. paratuberculosis is challenging because of its very slow growth (more than two months to form visible colonies on media). Existing animal models also have limitations. Despite those obstacles, there has been progress in understanding the intracellular survival tactics of M. paratuberculosis and the host response against them. In this review, we compare known aspects of the intracellular survival tactics of M. paratuberculosis with those of other mycobacterial species, and consider possible mycobactericidal mechanisms of mononuclear phagocytes.

Photodynamic activity of platinum(IV) chloride surface-modified TiO2 irradiated with visible light

The visible light-induced phototoxicity of titanium dioxide modified with platinum(IV) chloride complexes, [TiO2/PtCl4], was tested. In vitro experiments with the mouse melanoma cells (S-91) have demonstrated phototoxicity of the [TiO2/PtCl4] material. Detection of efficiently generated various reactive oxygen species (.OH, O2. -, H2O2, 1O2) and also reactive chlorine species has proven the photodynamic activity of the tested material, induced by visible light (lambda>455 nm). The cellular death (recognized as a necrosis) is a result of the cell membrane peroxidation.

A New Approach for Measuring Single-Cell Oxygen Consumption Rates

A novel system that has enabled the measurement of single-cell oxygen consumption rates is presented. The experimental apparatus includes a temperature controlled environmental chamber, an array of microwells etched in glass, and a lid actuator used to seal cells in the microwells. Each microwell contains an oxygen sensitive platinum phosphor sensor used to monitor the cellular metabolic rates. Custom automation software controls the digital image data collection for oxygen sensor measurements, which are analyzed using an image-processing program to yield the oxygen concentration within each microwell versus time. Two proof-of-concept experiments produced oxygen consumption rate measurements for A549 human epithelial lung cancer cells of 5.39 and 5.27 fmol/min/cell, closely matching published oxygen consumption rates for bulk A549 populations.

Effects of an anti-oxidative ACAT inhibitor on apoptosis/necrosis and cholesterol accumulation under oxidative stress in THP-1 cell-derived foam cells

THP-1 cell-derived foam cells were exposed to oxidative stress through combined treatment with acetylated LDL (acLDL) and copper ions (Cu2+). The foam cells showed caspase-dependent apoptotic changes on exposure to oxidative stress for 6 h, and necrotic changes with the leakage of LDH after 24 h. KY-455, an anti-oxidative ACAT inhibitor, and ascorbic acid (VC) but not YM-750, an ACAT inhibitor, prevented apoptotic and necrotic changes. These preventive effects of KY-455 and VC were accompanied by the inhibition of lipid peroxidation in culture medium containing acLDL and Cu2+, suggesting the involvement of oxidized acLDL in apoptosis and necrosis. Foam cells accumulated esterified cholesterol (EC) for 24 h in the presence of acLDL without Cu2+, which was suppressed by KY-455 and YM-750. Foam cells showed necrotic changes and died in the presence of acLDL and Cu2+. KY-455 but not YM-750 prevented cell death and reduced the amount of EC accumulated. The foam cells treated with VC further accumulated EC without necrotic changes for 24 h even in the presence of acLDL and Cu2+. YM-750 as well as KY-455 inhibited lipid accumulation when co-incubated with VC in foam cells exposed to oxidative stress. It is concluded that an anti-oxidative ACAT inhibitor or the combination of an antioxidant and an ACAT inhibitor protects foam cells from oxidative stress and effectively reduces cholesterol levels, which would be a promising approach in anti-atherosclerotic therapy.

Assessment of cell viability in a three-dimensional enzymatically cross-linked collagen scaffold

Microbial transglutaminase (mTGase) is an enzyme that introduces a covalent bond between peptide bound glutamine and lysine residues. Proteins cross-linked in this manner are often more resistant to proteolytic degradation and show increased tensile strength. This study evaluates the effects of mTGase mediated cross-linking of collagen on the cellular morphology, behaviour and viability of murine 3T3 fibroblasts following their seeding into collagen scaffolds. Additionally, cell mediated scaffold contraction, porosity and level of cross-linking of the scaffold has been analysed using image analysis software, scanning electron microscopy (SEM), colorimetric assays, and Fourier transform infrared spectroscopy (FTIR). We demonstrate that the biocompatibility and cellular morphology, when comparing cultures of fibroblasts integrated in mTGase cross-linked collagen scaffolds with the native collagen counterparts, remained unaffected. It has been also elicited that the structural characteristics of collagen have been preserved while introducing enzymatically resistant covalent bonds.

Role of the MAPKERKpathway in regulation of cytokine expression byMycobacterium aviumsubspparatuberculosis–exposed bovine monocytes

OBJECTIVE

To evaluate the role of the mitogen-activated protein kinase extracellular signal-regulated kinase (MAPK(ERK)) pathway in the interaction between Mycobacterium avium subsp paratuberculosis (MAP) organisms and bovine monocytes.

SAMPLE POPULATION

Monocytes obtained from healthy adult Holstein dairy cows that were not infected with MAP organisms.

PROCEDURES

Monocytes and MAP organisms were incubated together with or without a specific inhibitor of the MAPK(ERK) pathway (PD98059), and the capacity of monocytes to express tumor necrosis factor alpha (TNF)-alpha and interleukin (IL)-10 and -12, produce nitric oxide, acidify phagosomes, kill MAP organisms, and undergo apoptosis was evaluated.

RESULTS

The MAPK(ERK) pathway was activated within 10 minutes after addition of MAP organisms to monocytes. Addition of PD98059 to monocyte-MAP mixtures decreased monocyte TNF-alpha and IL-12 mRNA expression but had no effect on IL-10 mRNA expression. Treatment with PD98059 failed to induce significant alterations in phagosome acidification, organism killing, nitric oxide production, or apoptosis of MAP-exposed monocytes.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that the MAPK(ERK) pathway was activated during the interaction of MAP organisms with monocytes, which initiated TNF-alpha and IL-12 mRNA expression but failed to initiate antimicrobial activity. The MAPK(ERK) pathway may be involved in initiating proinflammatory and proimmune responses in MAP infection in cattle.

Life and death in bovine monocytes: the fate of Mycobacterium avium subsp. paratuberculosis

We previously reported that the number of acid-fast bacilli within Mycobacterium paratuberculosis-infected bovine monocytes increased steadily during an 8-day incubation period in vitro, despite a decrease in the number of viable bacilli as estimated by a radiometric method. In this study, we used differential live/dead staining of bacilli from infected monocytes to show that the percentage of viable bacilli decreased during an 8-day incubation period. We observed poor phagosome-lysosome fusion in monocytes that had ingested viable M. paratuberculosis (30% phagosome-lysosome fusion), while monocytes that ingested heat killed M. paratuberculosis exhibited 94% phagosome-lysosome fusion at 24h after infection. Treatment with the selective Ca(2+)/CaM and PI3 kinase inhibitors (i.e. KN62 and Wortmannin) in combination increased the survival of M. paratuberculosis in bovine monocytes without significantly altering phagosome-lysosome fusion. Scanning electron microscopy suggested that M. paratuberculosis-infected monocytes were less differentiated (smaller and less spreading) than uninfected monocytes at 4 and 8 days of infection. Overall, these data suggest that both multiplication and killing of intracellular M. paratuberculosis occur concomitantly in bovine monocytes. Monocytes in turn may be adversely affected by the bacilli, their products, or factors released from infected monocytes.

Modulation of eukaryotic cell apoptosis by members of the bacterial order Actinomycetales

Apoptosis, or programmed cell death, is normally responsible for the orderly elimination of aged or damaged cells, and is a necessary part of the homeostasis and development of multicellular organisms. Some pathogenic bacteria can disrupt this process by triggering excess apoptosis or by preventing it when appropriate. Either event can lead to disease. There has been extensive research into the modulation of host cell death by microorganisms, and several reviews have been published on the phenomenon. Rather than covering the entire field, this review focuses on the dysregulation of host cell apoptosis by members of the order Actinomycetales, containing the genera Corynebacterium, Mycobacterium, Rhodococcus, and Nocardia.

Differential expression of genes encoding CD30L and P-selectin in cattle with Johne's disease: Progress toward a diagnostic gene expression signature

Mycobacterium avium subspecies paratuberculosis (Mycobacterium paratuberculosis), the causative agent of paratuberculosis (paraTB) or Johne's disease in ruminants, is a health problem for the global cattle industry with significant economic losses related to decreased milk production and reduced fertility. Commonly paraTB in cattle is diagnosed by antibody detection by serum enzyme-linked immunosorbent assay (ELISA), by detection of the pathogen by cultivation of individual faecal samples, or by in vitro measurement of cell mediated immune responses using the IFN-gamma test. There is an ongoing need for developing new diagnostic approaches as all currently available diagnostic tests for paraTB may fail to detect sub-clinical infection. We used cDNA microarrays to simultaneously measure expression of over 1300 host genes to help identify a subset of gene expression changes that might provide a unique gene expression signature for paraTB infection. In the present study, non-stimulated leukocytes isolated from 10 sub-clinical paraTB infected cows were examined for genes being expressed at significantly different levels than in similar cells from control cows with the same herd background. We included cattle (Holstein) from two locations (Denmark and USA) for the microarray experiment. Our results indicate that expression profiles of at least 52 genes are different in leukocytes from M. paratuberculosis infected cattle compared to control cattle. Gene expression differences were verified by quantitative real-time reverse transcriptase polymerase chain reactions (qRT-PCR) on the same group of cattle (Holstein) used for the microarray experiment. In order to assess the generality of the observed gene expression, a second and different group of cattle (Jersey) was also examined using qRT-PCR. Out of the seven genes selected for qRT-PCR, CD30 ligand (CD30L) and P-selectin were consistently differentially expressed in freshly isolated leukocytes from paraTB infected and control animals of both breeds of cattle. Although further work is clearly needed to develop a more complete gene expression signature specific for paraTB, our results demonstrate that a subset of genes in leukocytes are consistently expressed at different levels, depending upon M. paratuberculosis infection status.

Evaluation of silicon nanoporous membranes and ECM-based microenvironments on neurosecretory cells

Understanding the interactions between microfabricated synthetic interfaces and cultured cells expressing a neuronal phenotype are critical for advancing research in the field of neural engineering such as neural recording and stimulation and neural microdevice interactions with the human brain. Here we explore the integration of these two components for therapeutic applications of neural prostheses. Microfabricated silicon nanoporous membranes were investigated for their effects on survival, proliferation, and differentiation of the well-known PC12 clonal line. Specifically, cell morphology, examined through fluorescence staining, were comparable in many respects on both silicon membrane and widely-used polystyrene culture surfaces. The attachment and differentiation of PC12 cells cultured on collagen and laminin-modified membranes and standard tissue culture surfaces were similar. Lastly, the differentiation response and tyrosine hydroxylase activity of PC12 cells embedded in a type I collagen matrix on experimental membrane substrates while exposed to NGF were significant and indistinguishable from tissue-culture polystyrene (TC-PS) surfaces. Results from this research suggest that microfabricated silicon nanoporous membranes may be useful, biocompatible permselective structures for neuroprosthetic applications and that collagen may be a useful immobilizing matrix for PC12 cells loaded in implantable macroencapsulation devices designed for the treatment of neurodegenerative disorders.

A comparison of ovine monocyte-derived macrophage function following infection with Mycobacterium avium ssp. avium and Mycobacterium avium ssp. paratuberculosis

Mycobacterium avium ssp. paratuberculosis causes Johne's disease in ruminants, whereas the antigenically and genetically similar subspecies Mycobacterium avium ssp. avium is less virulent. In this study, we compared one strain of each subspecies for its ability to survive, induce cytokines, suppress MHC class I and II expression and induce apoptosis or necrosis in ovine monocyte-derived macrophages. Both subspecies survived intracellularly and induced the secretion of IL-10. Low levels of TNF-alpha were detected after infection with both subspecies at 4 h. IL-12 was not upregulated after infection. Downregulation of MHC class I and II was evident in response to infection with both M. avium ssp. avium and M. avium ssp. paratuberculosis. No significant cytotoxicity was detectable in ovine macrophages after the addition of bacteria. M. avium ssp. paratuberculosis induced slightly more apoptosis than M. avium ssp. avium. Still the overall rate of apoptosis was very low and both subspecies suppressed LPS-induced macrophage apoptosis.

Epidermal growth factor-dependent enhancement of axonal regeneration in the pond snail Lymnaea stagnalis: role of phagocyte survival

Peripheral nerve injury triggers complex responses from neuronal as well as from multiple nonneuronal cell types. These responses are coordinated by a wide spectrum of secreted and nonsecreted factors, including growth factors, cytokines, and cell adhesion molecules. These molecules originate from different sources and act both locally at the site of injury as well as centrally at the location of the neuronal cell bodies. One of the signal systems frequently implicated in this process is the epidermal growth factor (EGF) family and its receptors. Expression of members of this family as well as that of EGF-receptors is upregulated in different cell types after peripheral nerve injury. However, the functional significance of this response is unclear. Using a simple invertebrate model system (Lymnaea stagnalis), the present study implicates the EGF/EGF-receptor system in the survival of ionized calcium-binding adaptor molecule 1 (Iba1)-positive phagocytes that reside in the nervous system. We show that inhibiting the EGF-signaling pathway enhances cell death in this type of cell, an effect paralleled by a substantial reduction in axonal regeneration. Therefore, complementing our previous observation that Lymnaea EGF provides trophic support to axotomized neurons, the present results emphasize the significance of nonneuronal actions of EGF receptor ligands in axonal regeneration. Thus, we add a novel perspective to the ongoing discussion on the functional significance of the EGF signaling system in the injury responses of the nervous system.

Expression of interleukin-10 and suppressor of cytokine signaling-3 associated with susceptibility of cattle to infection with Mycobacterium avium subsp paratuberculosis

OBJECTIVE

To determine functional characteristics of monocytes obtained from cows with subclinical infection with Mycobacterium avium subsp paratuberculosis (MAP) that may have predisposed those cows to becoming infected with MAP SAMPLE POPULATION: Monocytes obtained from 5 uninfected cows and 5 cows subclinically infected with MAP in a herd with a high prevalence of paratuberculosis (ie, Johne's disease).

PROCEDURES

Monocytes from uninfected and subclinically infected cows were incubated with MAP for 2, 6, 24, 72, or 96 hours. Variables measured included expression of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-10, IL-12, transforming growth factor-beta, and suppressor of cytokine signaling-3 (SOCS-3); apoptosis of monocytes; acidification of phagosomes; and killing of MAP.

RESULTS

Monocytes from infected cows had greater expression of IL-10 and SOCS-3 at 2 hours of coincubation with MAP and lower expression of TNF-alpha and IL-12 when results for all incubation times were combined. Monocytes from infected cows had a greater capacity to acidify phagosomes. No differences were observed in the rate of apoptosis or capacity of monocytes to kill MAP organisms.

CONCLUSIONS AND CLINICAL RELEVANCE

Monocytes obtained from cows with subclinical infection with MAP had upregulated expression of IL-10 and SOCS-3 within the first 2 hours after exposure to MAP organisms. Although this did not inhibit acidification of phagosomes, apoptosis of monocytes, or attenuation of the capacity to kill MAP organisms, it may have attenuated the capacity of mononuclear phagocytes to initiate inflammatory and adaptive immune responses.

A critical role of interleukin-10 in the response of bovine macrophages to infection by Mycobacterium avium subsp paratuberculosis

OBJECTIVES

To evaluate the role of interleukin (IL)-10 in the inability of monocyte-derived bovine macrophages to kill Mycobacterium avium subsp paratuberculosis organisms in vitro.

SAMPLE POPULATION

Monocytes were obtained from healthy adult Holstein dairy cows that had negative results when tested for infection with M avium subsp paratuberculosis.

PROCEDURE

Monocyte-derived macrophages were incubated with M avium subsp paratuberculosis for 2, 6, 24, 72, or 96 hours with or without addition of saturating concentrations of a goat anti-human IL-10 that has been documented to neutralize bovine IL-10 activity. Variables assessed included ingestion and killing of M avium subsp paratuberculosis; expression of tumor necrosis factor (TNF)-alpha, IL-12, IL-8, major histocompatability (MHC) class II, vacuolar H+ ATPase, and B cell CLL/lymphoma 2 (BCL-2); production of nitric oxide; acidification of phagosomes; and apoptosis of macrophages.

RESULTS

Neutralization of IL-10 enabled macrophages to kill 57% of M avium subsp paratuberculosis organisms within 96 hours. It also resulted in an increase in expression of TNF-alpha, IL-12, IL-8, MHC class II, and vacuolar H+ ATPase; decrease in expression of BCL-2; increase in acidification of phagosomes; apoptosis of macrophages; and production of nitric oxide.

CONCLUSIONS AND CLINICAL RELEVANCE

The capacity of M avium subsp paratuberculosis to induce IL-10 expression may be a major determinant of virulence for this organism.

Johne's disease, inflammatory bowel disease, and Mycobacterium paratuberculosis

Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed.

Sequential patterns of gene expression by bovine monocyte-derived macrophages associated with ingestion of mycobacterial organisms

We investigated mechanisms involved in killing of mycobacterial organisms by comparing the response of bovine monocyte-derived macrophages to ingestion of Mycobacterium avium subsp. paratuberculosis or M. avium subsp. avium organisms. Previous studies have shown that bovine macrophages have the capacity to kill M. avium subsp. avium organisms in vitro but cannot kill M. avium subsp. paratuberculosis organisms. We used bovine cDNA microarray technology to investigate sequential gene expression by bovine monocyte-derived macrophages and function assays to correlate gene expression with biological activity. Results of the gene expression studies indicated substantial differences between macrophages phagocytizing the two organisms. At 2, 6, and 24h after infection, 12, 53, and 19 genes, respectively, were differentially expressed. Over all time periods, approximately twice as many genes had lower expression in M. avium subsp. paratuberculosis-infected macrophages than had greater expression. Differentially regulated genes of most interest to antimicrobial responses included inflammatory molecules (transforming growth factor-beta, thrombospondin 1, monocyte chemokine, and cathepsin K), phagosome-lysosome-related genes (H(+) ATPases, lysosomal-associated membrane protein 2, vesicle trafficking protein, and solute carrier protein), and apoptosis-related genes (tumor necrosis factor receptor-associated factor 2, and tumor protein p(53) binding protein). Function assays indicated that M. avium subsp. avium-infected macrophages had a greater capacity to acidify phagosomes and a greater percentage of apoptotic cells. In conclusion, these results suggest that a complex interaction between macrophages and mycobacterial organisms is involved in determining the fate of the organism. Although multiple genes and metabolic pathways are involved, the capacity of cells to acidify phagosomes and induce apoptosis appears to play a prominent role.