Products In Pathogenesis Research Articles

The role of cholesterol and its oxidation products in tuberculosis pathogenesis.

Mycobacterium tuberculosis causes tuberculosis (TB), one of the world's most deadly infections. Lipids play an important role in M. tuberculosis pathogenesis. M. tuberculosis grows intracellularly within lipid-laden macrophages and extracellularly within the cholesterol-rich caseum of necrotic granulomas and pulmonary cavities. Evolved from soil saprophytes that are able to metabolize cholesterol from organic matter in the environment, M. tuberculosis inherited an extensive and highly conserved machinery to metabolize cholesterol. M. tuberculosis uses this machinery to degrade host cholesterol; the products of cholesterol degradation are incorporated into central carbon metabolism and used to generate cell envelope lipids, which play important roles in virulence. The host also modifies cholesterol by enzymatically oxidizing it to a variety of derivatives, collectively called oxysterols, which modulate cholesterol homeostasis and the immune response. Recently, we found that M. tuberculosis converts host cholesterol to an oxidized metabolite, cholestenone, that accumulates in the lungs of individuals with TB. M. tuberculosis encodes cholesterol-modifying enzymes, including a hydroxysteroid dehydrogenase, a putative cholesterol oxidase, and numerous cytochrome P450 monooxygenases. Here, we review what is known about cholesterol and its oxidation products in the pathogenesis of TB. We consider the possibility that the biological function of cholesterol metabolism by M. tuberculosis extends beyond a nutritional role.

Research progress on the application of CRISPR/Cas9 technology in breast cancer treatment

Cancer is viewed as a severe health issue because it is one of the leading causes of mortality on a global scale. The most frequent type of cancer in women and one of the leading causes of mortality worldwide is breast cancer. Current treatments include surgical excision, hormone treatment, chemotherapy, radiotherapy, and targeted biological therapy. Although numerous treatments can relieve the symptoms or even cure the disease. Several genes are still waiting for discovery that affects the growing processes of tumors through a different pathway. Continuous effort is needed to develop more efficient and fewer side effect treatments. The genetic intervention has arisen as one of the most auspicious therapeutic alternatives in contemporary times. "CRISPR Cas9 has emerged as a compelling gene editing technology in the contemporary era, which is constructed by two main parts-the CRISPR-associated (Cas) endonuclease section and the CRISPR RNA (crRNA) section. CRISPR technology has been successfully utilized to establish gene-specific cell lines and animal models for studying gene function and their products in pathogenesis, as well as interactions between different genes. This paper summarizes the recent years of experiments using CRISPR/Cas9 technology to explore the mechanism of breast carcinogenesis, find appropriate therapeutic targets, and discuss the latent capacity of CRISPR/Cas9 technology in breast cancer treatment.

Expression of HIV-1 matrix protein p17 and association with B-cell lymphoma in HIV-1 transgenic mice

HIV-1 infection is associated with increased risk for B-cell lymphomas. How HIV infection promotes the development of lymphoma is unclear, but it may involve chronic B-cell activation, inflammation, and/or impaired immunity, possibly leading to a loss of control of oncogenic viruses and reduced tumor immunosurveillance. We hypothesized that HIV structural proteins may contribute to lymphomagenesis directly, because they can persist long term in lymph nodes in the absence of viral replication. The HIV-1 transgenic mouse Tg26 carries a noninfectious HIV-1 provirus lacking part of the gag-pol region, thus constituting a model for studying the effects of viral products in pathogenesis. Approximately 15% of Tg26 mice spontaneously develop leukemia/lymphoma. We investigated which viral proteins are associated with the development of leukemia/lymphoma in the Tg26 mouse model, and performed microarray analysis on RNA from spleen and lymph nodes to identify potential mechanisms of lymphomagenesis. Of the viral proteins examined, only expression of HIV-1 matrix protein p17 was associated with leukemia/lymphoma development and was highly expressed in bone marrow before disease. The tumor cells resembled pro-B cells, and were CD19+IgM-IgD-CD93+CD43+CD21-CD23-VpreB+CXCR4+ Consistent with the pro-B-cell stage of B-cell development, microarray analysis revealed enrichment of transcripts, including Rag1, Rag2, CD93, Vpreb1, Vpreb3, and Igll1 We confirmed RAG1 expression in Tg26 tumors, and hypothesized that HIV-1 matrix protein p17 may directly induce RAG1 in B cells. Stimulation of human activated B cells with p17 enhanced RAG1 expression in three of seven donors, suggesting that intracellular signaling by p17 may lead to genomic instability and transformation.

Role of receptor for advanced glycation end-products in pathogenesis of psoriasis

This review summarizes the existing knowledge regarding the role of receptor for advanced glycation end products in pathogenesis of psoriasis. This receptor plays a crucial role in the inflammatory response. By interacting with multiple ligands and activating several signaling mechanisms, receptor for advanced glycation end products regulates gene expression via a group of well-characterized transcription factors, such as NFkB and AP1. The expression of receptor for advanced glycation end products in both immune cells and their targets, a high stability of this receptor in complexes with ligands as well as a positive feedback loop, upregulating the expression of its certain ligands, suggest receptor for advanced glycation end products as a possible principal factor that promotes the development of psoriasis. Considering receptor for advanced glycation end products as a potential master regulator of several processes that play a crucial role in development of psoriatic plaques, we believe that further experimental studies are needed to elucidate how exactly this receptor converts a transient inflammatory reaction to a sustainable inflammatory response. These studies are also needed for the development of novel medications that target receptor for advanced glycation end products and signaling mechanisms that this receptor activates.

Reviews The role of fibrinogen, fibrin and fibrin(ogen) degradation products (FDPs) in tumor progression

Participation of fibrin, fibrinogen, and their degradation products in pathogenesis and progression of cancer may lead to complications of thromboembolic events. The tumor may be a source of fibrinogen. Fibrinogen inside the tumor is one of the factors of its growth and metastasis. Fibrinogen, fibrin and their degradation products possess proinflammatory activity. They indirectly stimulate endothelium to secrete von Willebrand factor, leading to activation of platelets accompanying neoplastic disorders. Fragments E and D are the end products of fibrin(ogen) degradation and E and DD are the end products of stabilized fibrin. E stimulates proliferation, migration and differentiation of endothelial cells, contributing to tumor vasculature. Increased levels of DD are observed in malignant neoplasms, such as breast, lung, colon and ovary cancers. In breast cancers DD correlates with progression of disease and metastasis. The role of fibrinogen and the products of its degradation in the progression of various tumors is not sufficiently understood.

Investigating Eucalyptus– pathogen and pest interactions to dissect broad spectrum defense mechanisms

BackgroundEucalyptus species, hybrids and clones are attacked byvarious fungal and bacterial pathogens and pests duringtheir life-time. Global climate changes are predicted tocreate favourable environments for such pathogens andpests and increase incidence of host jumping from othercrops, resulting in increased losses to the forestry indus-try [1]. The use of tolerant or resistant plant varieties aspart of an integrated disease management strategy isrecognised as a desirable means to curb disease inci-dence. Vertical resistanc e mediated by resistance ( R )genes, may be easily overcome by a pathogen and isthus not adequate on plantation species such as Euca-lyptus , which would be exposed to various pathogensduring its life-time. Broad spectrum resistance on theother hand, would be desirable to provide resistanceagainst multiple challenges [2].The aim of this study is to investigate mechanismsinvolved in host resistance with an emphasis on broad-spectrum resistance. The availability of the completegenome sequence of Eucalyptus grandis (http://www.eucagen.org) and the transcriptome sequence of aE. grandis X E. urophylla (GU) hybrid [3] has providedresources to investigate defense responses in the naturalhost. When a pathogen attacks a plant, the plantlaunches a sophisticated defense response involving phy-tohormones such as salicylic acid (SA), methyl jasmo-nate (MeJA) and ethylene (ET). These responses arefinely tuned and tailored to the invader [4]. Down-stream of the signalling cascade is the production ofpathogenesis related ( PR ) genes and antimicrobial geneswhich serve to limit the pathogen and afford protection.PR genes, such as PR-1 and PR-5, are known markers ofthe salicylic acid defense pathway, while PR-3 , PR-4 andthe lipoxygenase ( LOX ) genes are known markers of theMeJA and ET signalling pathways. The discovery of PRgenes in Eucalyptus is desirable as these genes have pre-viously been shown to afford broad spectrum resistancein other crops. We present our progress in exploitingthe Eucalyptus genomic and transcriptomic data for thediscovery of tree defense genes and explore the applica-tion thereof in determining which pathways areactivated in response to various pathogens.Materials and methods

Attenuation of host NO production by MAMPs potentiates development of the host in the squid-vibrio symbiosis

Bacterial pathogens typically upregulate the host's production of nitric oxide synthase (NOS) and nitric oxide (NO) as antimicrobial agents, a response that is often mediated by microbe-associated molecular patterns (MAMPs) of the pathogen. In contrast, previous studies of the beneficial Euprymna scolopes/Vibrio fischeri symbiosis demonstrated that symbiont colonization results in attenuation of host NOS/NO, which occurs in high levels in hatchling light organs. Here, we sought to determine whether V. fischeri MAMPs, specifically lipopolysaccharide (LPS) and the peptidoglycan derivative tracheal cytotoxin (TCT), attenuate NOS/NO, and whether this activity mediates the MAMPs-induced light organ morphogenesis. Using confocal microscopy, we characterized levels of NOS with immunocytochemistry and NO with a NO-specific fluorochrome. When added exogenously to seawater containing hatchling animals, V. fischeri LPS and TCT together, but not individually, induced normal NOS/NO attenuation. Further, V. fischeri mutants defective in TCT release did not. Experiments with NOS inhibitors and NO donors provided evidence that NO mediates apoptosis and morphogenesis associated with symbiont colonization. Attenuation of NOS/NO by LPS and TCT in the squid-vibrio symbiosis provides another example of how the host's response to MAMPs depends on the context. These data also provide a mechanism by which symbiont MAMPs regulate host development.

Identification of Potential Virulence Determinants by Himar1 Transposition of Infectious Borrelia burgdorferi B31

Lyme disease Borrelia organisms are highly invasive spirochetes that alternate between vertebrate and arthropod hosts and that establish chronic infections and elicit inflammatory reactions in mammals. Although progress has been made in the targeted mutagenesis of individual genes in infectious Borrelia burgdorferi, the roles of the vast majority of gene products in pathogenesis remain unresolved. In this study, we examined the feasibility of using transposon mutagenesis to identify infectivity-related factors in B. burgdorferi. The transformable, infectious strain 5A18 NP1 was transformed with the spirochete-adapted Himar1 transposon delivery vector pMarGent to create a small library of 33 insertion mutants. Single mouse inoculations followed by culture of four tissue sites and serology were used to screen the mutants for infectivity phenotypes. Mutants that appeared attenuated (culture positive at some sites) or noninfectious (negative at all sites) and contained the virulence-associated plasmids lp25 and lp28-1 were examined in more extensive animal studies. Three of these mutants (including those with insertions in the putative fliG-1-encoded flagellar motor switch protein and the guaB-encoded IMP dehydrogenase) were noninfectious, whereas four clones appeared to exhibit reduced infectivity. Serological reactivity in VlsE enzyme-linked immunosorbent assays correlated with the assignment of mutants to the noninfectious or attenuated-infectivity groups. The results of this study indicate that random transposon mutagenesis of infectious B. burgdorferi is feasible and will be of value in studying the pathogenesis of Lyme disease Borrelia.

Of mice, men, and elephants: Mycobacterium tuberculosis cell envelope lipids and pathogenesis

Mycolic acids and structures attached to them constitute a major part of the protective envelope of Mycobacterium tuberculosis, and for this reason, their role in tuberculosis pathogenesis has been extensively studied. In this issue of the JCI, Rao et al. examine the effect of trans-cyclopropanation of oxygenated mycolic acids attached to trehalose dimycolate (TDM) on the murine immune response to infection (see the related article beginning on page 1660). Surprisingly, they found that an M. tuberculosis mutant lacking trans-cyclopropane rings was hypervirulent in mice. The recent recognition of a hypervirulence phenotype in mice associated with laboratory and clinical M. tuberculosis strains with altered cell wall components has provided new insights into how M. tuberculosis may establish persistent infection. However, to date, characterization of these bioactive products in pathogenesis has been largely reductionistic; the relationship of their effects observed in mice to the persistent infection and tuberculosis caused by M. tuberculosis observed in humans remains obscure.

Transcriptional analysis of p30 major outer membrane multigene family of Ehrlichia canis in dogs, ticks, and cell culture at different temperatures.

Ehrlichia canis, an obligatory intracellular bacterium of monocytes and macrophages, causes canine monocytic ehrlichiosis. E. canis immunodominant 30-kDa major outer membrane proteins are encoded by a polymorphic multigene family consisting of more than 20 paralogs. In the present study, we analyzed the mRNA expression of 14 paralogs in experimentally infected dogs and Rhipicephalus sanguineus ticks by reverse transcription-PCR using gene-specific primers followed by Southern blotting. Eleven out of 14 paralogs in E. canis were transcribed in increasing numbers and transcription levels, while the mRNA expression of the 3 remaining paralogs was not detected in blood monocytes of infected dogs during the 56-day postinoculation period. Three different groups of R. sanguineus ticks (adult males and females and nymphs) were separately infected with E. canis by feeding on the infected dogs. In these pools of acquisition-fed ticks as well as in the transmission-fed adult ticks, the transcript from only one paralog was detected, suggesting the predominant transcription of that paralog or the suppression of the remaining paralogs in ticks. Expression of the same paralog was higher whereas expression of the remaining paralogs was lower in E. canis cultivated in dog monocyte cell line DH82 at 25 degrees C than in E. canis cultivated at 37 degrees C. Analysis of differential expression of p30 multigenes in dogs, ticks, or monocyte cell cultures would help in understanding the role of these gene products in pathogenesis and E. canis transmission as well as in designing a rational vaccine candidate immunogenic against canine ehrlichiosis.

Antifungal drug development: the identification of new targets

With the increasing prevalence of life-threatening systemic fungal infections in the human population, there is a need to develop new, more-effective antifungal agents. This, in turn, will depend upon the identification and exploitation of new antifungal targets — aspects of fungal cytology, metabolism and gene expression which are important for fungal pathogenesis, but which have no mammalian host counterpart. Such new targets have been identified through a combination of classical genetic, cytological and biochemical studies and are reviewed here, as is the potential for applying recombinant DNA techniques as a means of confirming the role of the identified gene products in pathogenesis.