Biphasic Modulation of Apoptotic Pathways in Cryptosporidium parvum -Infected Human Intestinal Epithelial Cells

Abstract

The impact of Cryptosporidium parvum infection on host cell gene expression was investigated by microarray analysis with an in vitro model using human ileocecal HCT-8 adenocarcinoma cells. We found changes in 333 (2.6%) transcripts at at least two of the five (6, 12, 24, 48, and 72 h) postinfection time points. Fifty-one of the regulated genes were associated with apoptosis and were grouped into five clusters based on their expression patterns. Early in infection (6 and 12 h), genes with antiapoptotic roles were upregulated and genes with apoptotic roles were downregulated. Later in infection (24, 48, and 72 h), proapoptotic genes were induced and antiapoptotic genes were downregulated, suggesting a biphasic regulation of apoptosis: antiapoptotic state early and moderately proapoptotic state late in infection. This transcriptional profile matched the actual occurrence of apoptosis in the infected cultures. Apoptosis was first detected at 12 h postinfection and increased to a plateau at 24 h, when 20% of infected cells showed nuclear condensation. In contrast, experimental silencing of Bcl-2 induced apoptosis in 50% of infected cells at 12 h postinfection. This resulted in a decrease in the infection rate and a reduction in the accumulation of meront-containing cells. To test the significance of the moderately proapoptotic state late in the infection, we inhibited apoptosis using pancaspase inhibitor Z-VAD-FMK. This treatment also affected the progression of C. parvum infection, as reinfection, normally seen late (24 h to 48 h), did not occur and accumulation of mature meronts was impaired. Control of host apoptosis is complex and crucial to the life of C. parvum. Apoptosis control has at least two components, early inhibition and late moderate promotion. For a successful infection, both aspects appear to be required.

Molecular profiling of the gilthead sea bream (Sparus aurata L.) response to chronic exposure to the myxosporean parasite Enteromyxum leei

“…Apoptosis can be either initiated or down-regulated by parasitic infections, contributing to dissemination within the host, inhibiting or modulating host immune responses or facilitating the intracellular survival of the pathogen (Lüder et al, 2001;James and Green, 2004). Differential apoptotic responses have been demonstrated in parasitic infections of mammals, sometimes with a biphasic modulation (early down-regulation and late up-regulation) (Lüder et al, 2001;Liu et al, 2009) Philasterides dicentrarchi induces apoptosis of turbot pronephric leucocytes (Paramá et al, 2007), and severely E. scophthalmi-infected turbot have increased apoptotic rates in the digestive epithelium, which could facilitate the spreading of the parasite (Bermúdez et al, 2010). The skin culture fluid from channel catfish resistant to the ciliate Ichthyophthirius multifiliis induces apoptosis of parasite theronts (Xu et al, 2005).…”

Prevalence of Cryptosporidium sp. In Patients with Colorectal Cancer

“…The International Agency for Research on Cancer (IARC) has also deemed Opisthorchis viverrini and Clonorchis sinensis infections to be carcinogenic factors in the development of biliary tract cancer (24). Those chronic parasitoses may affect apoptosis and DNA repair disturbances (25,26).…”

Gene expression, oxidative stress and apoptotic changes in rabbit ileum experimentally infected with Eimeria intestinalis

“…Liu et al (2009) also realised that the merogony of Cryptosporidium parvum Tyzzer, 1912 upregulated the genes with antiapoptotic roles and downregulated the genes with apoptotic roles while gamogony and sporogony downregulated the anti-apoptotic genes and induced proapoptotic gene. Therefore, they suggested a biphasic regulation of apoptosis: antiapoptotic state in the early infection and apoptotic state in the mid and late infection.…”