Diarrheal diseases caused by infectious agents continue to pose a serious health problem, especially in infants. It is, therefore, necessary to develop novel efficacious drugs to treat diarrhea. Intestinal serotonin transporter (SERT), involved in regulation of luminal 5-HT availability, is an important candidate to target because of its implications in several diarrheal disorders. The proposed studies are focused at examining the role of serotonin transporter (SERT) in the pathophysiology of diarrhea associated with infection by an important food-borne pathogen, Enteropathogenic E. coli (EPEC). Because of the lack of a known toxin, pathophysiology of EPEC-induced early diarrhea remained elusive for many years. Emerging studies have revealed that mechanism(s) underlying EPEC associated diarrhea are multi-factorial. Our recent studies showed that EPEC inhibits SERT in the intestinal epithelial cells via activation of protein tyrosine phosphatases. However, the detailed mechanisms underlying EPEC induced inhibition of SERT are not known. We hypothesize that EPEC induced signaling events alter SERT phosphorylation levels to cause its inhibition that may contribute to associated diarrhea. The present studies will systematically examine the effects of EPEC infection on SERT utilizing both in vitro and in vivo models. Studies proposed in Specific Aim 1 will identify the specific serine/threonine/tyrosine phosphatases involved in SERT modulation post-infection and will identify the structural domains that harbor SERT phosphorylation site(s).
Specific Aim 2 will critically elucidate the mechanisms of acute inhibitio of SERT in response to EPEC infection by assessing the role of cellular phosphatases in the native mouse ileum. In addition, the effect of phosphatases on serotonergic machinery (5-HT synthesis and release) will be examined to model the net impact of EPEC infection in complex native intestine. Overall, the proposed studies will help provide valuable insights into the host-microbial epithelial interaction underlying pathophysiology of EPEC- associated diarrhea as well as will increase our understanding of phosphorylation/dephosphorylation mechanisms governing SERT activity under physiological and pathophysiological conditions.
Diarrheal disease is the second leading cause of death in children under five years old, and is responsible for killing 1.5 million children every year. Therefore, it is important to discover new drugs that can effectively treat diarrhea. Our studies are aiming to investigate how a food-borne bacterium, EPEC modulates intestinal serotonin transporter (SERT) to cause diarrhea. Because of implication of SERT in diarrheal disorders, the outcome of these studies may provide new insights into therapeutic modalities for intestinal infectious or diarrheal disorders.
|Priyamvada, Shubha; Anbazhagan, Arivarasu N; Gujral, Tarunmeet et al. (2015) All-trans-retinoic Acid Increases SLC26A3 DRA (Down-regulated in Adenoma) Expression in Intestinal Epithelial Cells via HNF-1Î². J Biol Chem 290:15066-77|
|Nazir, Saad; Kumar, Anoop; Chatterjee, Ishita et al. (2015) Mechanisms of Intestinal Serotonin Transporter (SERT) Upregulation by TGF-Î²1 Induced Non-Smad Pathways. PLoS One 10:e0120447|
|Malhotra, Pooja; Soni, Vinay; Kumar, Anoop et al. (2014) Epigenetic modulation of intestinal cholesterol transporter Niemann-Pick C1-like 1 (NPC1L1) gene expression by DNA methylation. J Biol Chem 289:23132-40|
|Singh, Varsha; Kumar, Anoop; Raheja, Geetu et al. (2014) Lactobacillus acidophilus attenuates downregulation of DRA function and expression in inflammatory models. Am J Physiol Gastrointest Liver Physiol 307:G623-31|
|Kumar, Anoop; Hecht, Cameron; Priyamvada, Shubha et al. (2014) Probiotic Bifidobacterium species stimulate human SLC26A3 gene function and expression in intestinal epithelial cells. Am J Physiol Cell Physiol 307:C1084-92|
|Petiwala, Sakina M; Li, Gongbo; Ramaiya, Atulkumar et al. (2014) Pharmacokinetic characterization of mangosteen (Garcinia mangostana) fruit extract standardized to Î±-mangostin in C57BL/6 mice. Nutr Res 34:336-45|
|Ma, Ke; Malhotra, Pooja; Soni, Vinay et al. (2014) Overactivation of intestinal SREBP2 in mice increases serum cholesterol. PLoS One 9:e84221|
|Gill, Ravinder K; Kumar, Anoop; Malhotra, Pooja et al. (2013) Regulation of intestinal serotonin transporter expression via epigenetic mechanisms: role of HDAC2. Am J Physiol Cell Physiol 304:C334-41|