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Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin.

ABSTRACT: Cryptosporidium parvum is an obligate intracellular protozoan capable of causing severe diarrheal disease in a wide variety of mammals, including humans. C. parvum infection has been associated with induction of apoptosis in exposed epithelial cells, and we now demonstrate that apoptosis is restricted to a subset of cells actively infected with C. parvum. Approximately 20% of the infected cells underwent apoptosis within 48 h of infection, suggesting that the majority of the infected cells are rescued from apoptosis. C. parvum infection resulted in low-level activation of multiple members of the caspase family, including caspase-2, -3, -4, -6, -8, and -9. The kinetics of caspase activation correlated with apoptosis over a 48-h time course. Pan caspase inhibitors reduced apoptosis of epithelial cells infected by C. parvum. Furthermore, C. parvum infection inhibited staurosporine-induced apoptosis and caspase-3/7 activation at 24 h and 48 h. Infection with C. parvum led to upregulation of genes encoding inhibitors of apoptosis proteins (IAPs), including c-IAP1, c-IAP2, XIAP, and survivin. Knockdown of survivin gene expression, but not that of c-IAP1, c-IAP2, or XIAP expression, increased caspase-3/7 activity as well as apoptosis of infected cells and decreased C. parvum 18S rRNA levels. These data suggest that the apoptotic response of infected intestinal epithelial cells is actively suppressed by C. parvum via upregulation of survivin, favoring parasite infection.

SUBMITTER: Liu J

PROVIDER: S-EPMC2493198 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin.

Liu Jin J Enomoto Shinichiro S Lancto Cheryl A CA Abrahamsen Mitchell S MS Rutherford Mark S MS

Infection and immunity 20080602 8

Cryptosporidium parvum is an obligate intracellular protozoan capable of causing severe diarrheal disease in a wide variety of mammals, including humans. C. parvum infection has been associated with induction of apoptosis in exposed epithelial cells, and we now demonstrate that apoptosis is restricted to a subset of cells actively infected with C. parvum. Approximately 20% of the infected cells underwent apoptosis within 48 h of infection, suggesting that the majority of the infected cells are r ...[more]

PMID: 18519556

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Project description:The protozoan parasite Cryptosporidium sp. is a leading cause of diarrheal disease in those with compromised or underdeveloped immune systems, particularly infants and toddlers in resource-poor localities. As an enteric pathogen, Cryptosporidium sp. invades the apical surface of intestinal epithelial cells, where it resides in close proximity to metabolites in the intestinal lumen. However, the effect of gut metabolites on susceptibility to Cryptosporidium infection remains largely unstudied. Here, we first identified which gut metabolites are prevalent in neonatal mice when they are most susceptible to Cryptosporidium parvum infection and then tested the isolated effects of these metabolites on C. parvum invasion and growth in intestinal epithelial cells. Our findings demonstrate that medium or long-chain saturated fatty acids inhibit C. parvum growth, perhaps by negatively affecting the streamlined metabolism in C. parvum, which is unable to synthesize fatty acids. Conversely, long-chain unsaturated fatty acids enhanced C. parvum invasion, possibly by modulating membrane fluidity. Hence, gut metabolites, either from diet or produced by the microbiota, influence C. parvum growth in vitro and may also contribute to the early susceptibility to cryptosporidiosis seen in young animals.IMPORTANCE Cryptosporidium sp. occupies a unique intracellular niche that exposes the parasite to both host cell contents and the intestinal lumen, including metabolites from the diet and produced by the microbiota. Both dietary and microbial products change over the course of early development and could contribute to the changes seen in susceptibility to cryptosporidiosis in humans and mice. Consistent with this model, we show that the immature gut metabolome influenced the growth of Cryptosporidium parvum in vitro Interestingly, metabolites that significantly altered parasite growth were fatty acids, a class of molecules that Cryptosporidium sp. is unable to synthesize de novo The enhancing effects of polyunsaturated fatty acids and the inhibitory effects of saturated fatty acids presented in this study may provide a framework for future studies into this enteric parasite's interactions with exogenous fatty acids during the initial stages of infection.

Project description:Purpose: Transcriptome profiling of Crytosporidium parvum infected lung and small intestinal organoids was performed to access the response of epithelial cells upon parasitic infection and to do a temporal analysis of the transcriptome of the parasite inside the organoid lumen. We isolated RNA from infected human lung and small intestinal organoids at 24 and 72 hour post infection. Methods: Organoids were grown in expansion or differentiation media and microinjected with equal amounts of Cryptosporidium oocysts. Media-injected organoids were used as a control .Expanding SI organoids were microinjected at 5-6 days after seeding, differentiated SI organoids were injected at 5 days after inducing differentiation. Lung organoids were incubated for 2 weeks after seeding for microinjection. RNA was extracted from 1-2 matrigel drops containing organoids. RNA was converted to cDNA and libraries were prepared using the CelSeq2 method and sequenced. Samples were sequenced on Illumina NextSeq500 by using 75-bp paired-end sequencing. Methods: Paired-end reads from Illumina sequencing were aligned to the human transcriptome genome and C. parvum transcriptome genome (Iowa strain) by BWA. DeSeq (v1.18.0) was used for read normalization and differential expression analysis (p-value adjustment 0.05 by method Benjamini-Hochberg). Gene set enrichment analysis (GSEA) was performed using gene lists for type I interferon response and regulation against normalized RNA-seq reads of injected SI and lung organoids using GSEA software v3.0 beta2. Results: At 24 hr post-infection,GO (gene ontology)-term analysis revealed that a substantial number of genes related to ‘cytoskeleton’ and ‘cell mobility’ were up-regulated in lung organoids. This suggests that infection by the parasites and subsequent formation of the intracellular stages within 24 hrs might affects cytoskeleton structures of host cells. After 72 hrs, many genes associated with the type I interferon pathway increased dramatically in lung and intestinal organoids. Results: After 72 hrs, many genes associated with the type I interferon pathway increased dramatically in lung and intestinal organoids. Multiple C. parvum genes were differentially expressed with a large fold change between 24 and 72 hr post-injection.At 24 hr post-infection, most of the enriched genes represented ribosomal proteins and ribosomal RNA subunits in both intestinal organoids and lung organoids. By contrast, at 72 hr post-infection, multiple oocyst-wall protein genes were up-regulated, confirming that the parasites formed new oocysts within the organoids. Conclusions: RNA sequencing of injected organoids revealed host epithelial responses upon parasite infection in differentiated SI organoids as well as in lung organoids.Upregulation of genes associated with type I interferon immunity in both SI and lung organoids.

Project description:• The origin of biological samples (In vitro infection of HCT-8 cells with Cryptosporidium parvum) Monolayers of the HCT-8 cells (ATCC CCL-244, American Type Culture Collection) were cultured in RPMI 1640 medium containing 10% fetal bovine serum and additional nutritional supplements. Cells in log phase were plated at 2×106 cells per 150 mm tissue culture dish and infected with sterilised Cryptosporidium parvum oocysts (Iowa strain). Purified oocysts were suspended in phosphate buffered saline, sterilised in 33% bleach for 7 min on ice, washed in Hank's buffered saline solution, and added to HCT-8 cultures at a ratio of one oocyst per cell. Following a 2 h excystation period at 37 °C, cells were washed with warm Hank's buffered saline solution, and cells were incubated in fresh supplemented media. Mock-infected cultures were treated identically, with the exception that oocysts were not added to the cultures. Three independent mock- and C. parvum-infected cultures were prepared for analysis. • The origin of mRNA samples At 6, 12, 24, 48, and 72h post-inoculation, cell culture media were removed and cultures were immediately lysed by the addition of 3.5 ml of Trizol® reagent (GIBCO BRL Life Technologies) directly to the culture plate. Total RNA was prepared as described by the manufacturer, and poly(A) mRNA was isolated using oligo-dT cellulose columns (Amersham Pharmacia Biotech). The qualities of total RNA and poly(A) mRNA preparations were assessed by Northern blot. • Protocols for conducting microarray hybridization Poly(A) mRNA was converted into ‘target’ suitable for hybridisation to Affymetrix microarray chips according to protocols provided by Affymetrix Inc. (Santa Clara, CA). Briefly, 2.0 g of poly(A) mRNA was reverse-transcribed to prepare double-stranded cDNA using T7-(dT)24 primer (GENSET Corp., La Jolla, CA) and Superscript II reverse transcriptase (GIBCO). Approximately 1 g of cDNA was used for in vitro transcription in the presence of biotinylated UTP and CTP using the Enzo BioArray High Yield RNA Transcript Labelling Kit (Enzo Diagnostics, Inc). This labelled cRNA was fragmented in 40 mM Tris–acetate (pH 8.1), 100 mM potassium acetate, and 30 mM magnesium acetate at 94 °C for 35 min. The integrity of cRNA and the efficiency of fragmentation were monitored by Northern blot analysis (not shown). Fragmented biotinylated cRNA targets were hybridised to HG-U95Av2 chips (Affymetrix) that contain probe sets for 12,600 human gene/transcripts. Fifteen micrograms of fragmented cRNA and appropriate controls were hybridised to the chips at 45 °C for 16 h with constant rotation at 60 rev./min. The chips were subsequently washed and stained with streptavidin–phycoerythrin conjugate using the GeneChip Fluidics station protocol EukGE_WS2 (Affymetrix). Following washing and staining, microarray chips were scanned twice at 3 m resolution using a Hewlett-Packard confocal scanner and hybridisation intensities for each of the genes/transcripts were collected from scanned images. • Analysis of microarray data Gene expression data were initially analysed with the GeneChip® expression analysis software (Affymetrix Microarray Suite, version 5.0). The fluorescence intensity of the genes/transcripts was measured for each probe array and, to minimise discrepancies due to non-biological variations, normalised by global scaling to 1000. Further data analyses were performed using GeneSpring software (version 6.0; Silicon Genetics, Redwood City, CA). Per gene normalisation was applied in which the expression signal of each gene in C. parvum-infected cells (raw data) was normalised to the median of its measurements in the mock-infected samples (control); and the ratio of expression levels between mock and infected samples was calculated as the mean value of normalised signal vs. control signal among three replicates. To identify genes with significantly altered expression, a series of statistical analyses (filtering) were performed: cut-off values for ratio of expression levels 1.80 and 0.55 were used to filter genes with expression level fold changes greater than ±1.8 in all three independent samples. Genes with fold change variations >1.5 across the three samples were excluded. Furthermore, a ‘statistical group comparison’ using Student's t-test/ANOVA was conducted to compare mean expression levels between mock-infected and infected samples, and the genes with significant differential expression (P<0.05) were selected. Identified differentially expressed genes were then annotated using GeneSpring's ‘Build Simplified Ontology’ constructor which hierarchically groups genes into meaningful biological categories (gene lists) based on the Gene Ontology Consortium Classifications. Various lists of regulated genes were created by cross-referencing annotated gene lists and applying assorted statistical and visualisation methods. Keywords: time-course

Dataset Information

Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin.

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Inhibition of apoptosis in Cryptosporidium parvum-infected intestinal epithelial cells is dependent on survivin.

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