Cryptosporidium parvum infection induces autophagy in intestinal epithelial cells

Abstract

Autophagy, a process of degradation and recycling of macromolecules and organelles to maintain cellular homeostasis, has also been shown to help eliminate invading pathogens. Conversely, various pathogens including parasites have been shown to modulate/exploit host autophagy facilitating their intracellular infectious cycle. In this regard, Cryptosporidium parvum (CP), a protozoan parasite of small intestine is emerging as a major global health challenge. However, the pathophysiology of cryptosporidiosis is mostly unknown. We have recently demonstrated CP‐induced epithelial barrier disruption via decreasing the expression of specific tight junction (TJ) and adherens junction (AJ) proteins such as occludin, claudin‐4 and E‐cadherin. Therefore, we utilised confluent Caco‐2 cell monolayers as in vitro model of intestinal epithelial cells (IECs) to investigate the potential role of autophagy in the pathophysiology of cryptosporidiosis. Autophagy was assessed by increase in the ratio of LC3II (microtubule associated protein 1 light chain 3) to LC3I protein and decrease in p62/SQSTM1 protein levels. CP treatment of Caco‐2 cells for 24 hr induced autophagy with a maximum effect observed with 0.5 × 106 oocyst/well. CP decreased mTOR (mammalian target of rapamycin, a suppressor of autophagy) phosphorylation, suggesting autophagy induction via mTOR inactivation. Measurement of autophagic flux utilizing the lysosomal inhibitor chloroquine (CQ) showed more pronounced increase in LC3II level in cells co‐treated with CP + CQ as compared to CP or CQ alone, suggesting that CP‐induced increase in LC3II was due to enhanced autophagosome formation rather than impaired lysosomal clearance. CP infection did not alter ATG7, a key autophagy protein. However, the decrease in occludin, claudin‐4 and E‐cadherin by CP was partially blocked following siRNA silencing of ATG7, suggesting the role of autophagy in CP‐induced decrease in these TJ/AJ proteins. Our results provide novel evidence of autophagy induction by CP in host IECs that could alter important host cell processes contributing to the pathophysiology of cryptosporidiosis.

ROS-AMPK/mTOR-dependent enterocyte autophagy is involved in the regulation of Giardia infection-related tight junction protein and nitric oxide levels

“…Helminth infections or helminth-secreted excretory/secretory (ES) products are known as the inducers of autophagy in different host cell types ( 21 – 23 ). In addition to helminths, infections by the protozoan parasites Toxoplasma gondii , Cryptosporidium parvum , Entamoeba histolytica , Plasmodium , and Leishmania also get involved in the induction of host cell autophagy ( 24 – 29 ; 30 ; 31 ). Some of the protozoans just mentioned can activate autophagy via an mTOR-dependent or -independent mechanism as noted ( 24 , 27 , 31 ).…”

Serum metabolomics in chickens infected with Cryptosporidium baileyi

“…Serum IgA was also demonstrated in hens infected with C. baileyi [ 62 ]. In one study, although Cryptosporidium -induced autophagy-associated molecules were not investigated in host sera, autophagy occurred in intestinal epithelial cells following C. parvum infection [ 63 ]. Cellular senescence has been reported in enteroids isolated from neonatal mice and immunocompetent adults following ex vivo C. parvum infection, and senescent cells can communicate with immune cells to invoke an immune response against C. parvum by upregulation of the inflammatory genes Mip-2 , Nos2 , Dkk1 , Icam-1 and IL-6 [ 64 ].…”

Oocyst Shedding Dynamics in Children with Cryptosporidiosis: a Prospective Clinical Case Series in Ethiopia

“…Significant progress has been made by several research groups in developing new pharmaceutical treatments ( 14 ), and an ongoing trial in Australian Aboriginal children may provide additional safety data for use of nitazoxanide in 3- to 5-month-olds ( 10 ). If prolonged duration of shedding is confirmed in the clinical setting, tangible secondary benefits of targeted cryptosporidiosis treatment may be to reduce transmission and to enable faster recovery of intestinal function ( 15 , 16 ). We therefore need reliable estimates for the duration of oocyst shedding in those settings where interventions against cryptosporidiosis are most needed, i.e., low-resource health care settings.…”