|
Center for Epithelial Function in Health and Disease Investigator, Mentor(s) and Project
Intestinal Epithelial Wound Healing: NSAIDs and Calpain Inhibition Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used medications worldwide despite their well-documented gastrointestinal (GI) toxicity. The GI epithelium has several functions, the most important of which are nutrient absorption and barrier function, separating the internal milieu from the external environment. Mucosal restitution represents a primary repair modality in the GI tract, and allows resealing of the epithelial barrier in minutes to hours via reformation of tight junctions between cells. Restitution requires cell migration, but not cell proliferation nor differentiation and it is a well coordinated event relying on numerous cellular pathways. Recent evidence suggests that calpains (cysteine proteases) are vital to several key pathways of cell migration. Recently we have shown that: a) irrespective of COX selectivity, ulcerogenic NSAIDs inhibit cell migration after wounding; b) individual NSAIDs differ significantly in their effects on the cellular signals that modulate cell migration; and c) ulcerogenic NSAIDs either down-regulate calpain gene expression or up-regulate the constituent inhibitor, calpastatin. The experiments proposed by this project are designed specifically to link NSAID inhibition of cell migration with NSAID effects on events vital to calpain function within differentiated intestinal epithelial cells (IECs). The specific aims of this project are to:
The results of this project will provide valuable data immediately useful not only to the health care providers who need to make rational decisions about prescribing NSAIDs, but also to the industrial scientists who strive to develop less toxic alternatives to the drugs currently available. In addition, the knowledge gained from these studies may suggest novel strategies for the prevention and treatment of NSAID-induced GI ulcers, identify novel targets for new drug design, and initiate novel safety testing of new NSAIDs. Characterization of Canine Urogenital Beta-Defensins, A Novel Family of Epithelium-derived Antimicrobial Peptides
Our project goals are to elucidate the mechanisms
that regulate the synthesis and production of beta-defensins in
urogenital epithelial cells. Better understanding of these
epithelium–derived antibacterial peptides will demonstrate their
potential biological role in fighting urinary tract infections (UTI) in
dogs. Given the remarkable clinical and pathological similarities
between affected humans and dogs with UTI, we expect that knowledge
gained from this project will be used as a direct approach for utilizing
the dog as a suitable animal model to study beta-defensins as a major
component of the innate immunity in the host defense against urogenital
pathogens. Regulation of Epithelial Na+ Transport Function by CFTR. The regulation of sodium absorption by epithelial cells is key to understanding the pathological disruptions in many human diseases, yet it remains poorly understood. Sodium absorption via the epithelial sodium channel, ENaC, is believed to be regulated by the Cystic Fibrosis Transmembrane Conductance Regulator, CFTR. CFTR is a multifunctional protein that not only functions as a cAMP-gated chloride channel, but that also exists in a macromolecular signaling complex, interacting directly with scaffolding proteins, upstream modulators and downstream effectors (egs. the beta-adrenergic receptor and SLC26 transporter family members). On the other hand, direct molecular interactions between CFTR and ENaC have not been demonstrated. In general, the regulation of ENaC's net contribution to epithelial transport may be accomplished by changing its gating, its single channel conductance and/or the number of functional channels in the plasma membrane. The thyroid gland is an organ in which CFTR-transporter interactions at the level of the macromolecular signaling complex may influence ENaC activity critically. The disruption of those interactions may dysregulate ENaC and cause disease. The present proposal asks whether CFTR regulates epithelial sodium absorption by influencing a constitutive property of all cells, endocytosis, and hence changing the numbers of ENaC in the membrane. With regard to mechanism,
To address this hypothesis, the proposed study will use primary porcine thyroid epithelial cultures, a robust, bidirectionally transporting epithelial preparation. The approach incorporates measurements of short-circuit current and employs specific pharmacologic tools in these measurements, as well as in fluorescence microscopic assays of endocytic uptake, cell surface biotinylation, and immunolocalization studies. The combination of several methodologies will enable clear answers to the posed questions to be drawn, leading to novel insights that in turn will clear a path toward future questions. It is envisaged that these studies will fill a gap in knowledge that presently impedes overall progress in understanding diseases as diverse as Pendred syndrome, cystic fibrosis and polycystic kidney disease.
Regulation of Gap Junction Activators
Breast cancer patients initially respond to estrogen ablation therapy, but estrogen-independent cells almost always aggressively emerge, and the disease eventually progresses to what is defined as estrogen-independent breast cancer; at which point the tumor is no longer responsive to estrogen ablation therapy, and unrestrained progression of the disease is inevitable. It is believed that restoring gap junction activity is linked to drug sensitivity and reduction of tumorigenicity. Thus, increasing gap junction activity in breast tumor cells provides the targets to enhance anti-neoplastic therapies. Our lab is interested in small molecules that specifically activate gap junction activity and inhibit cancer cell growth. In Vivo Assessment of CASR Signaling Mechanisms
The calcium sensing receptor (CASR) plays a
central role in controlling systemic calcium homeostasis via
regulation of parathyroid hormone (PTH) production and controls
a wide variety of processes in other tissues, including epithelia.
We are using genetic engineering in mice to alter the expression
of signaling molecules thought to be involved in cellular responses
to CASR activation. Changes in several parameters, including PTH
secretion and parathyroid cell growth, as a result of altering
specific genes will be used to test hypotheses of the CASR
signaling process. Transepithelial Ion Transport in Mosquito Hindgut Controlled by Peptide Hormone
We are studying the mechanisms of transepithelial
ion transport in the hindgut epithelial cells of the African malaria
mosquito Anopheles Gambiae and its control by the peptide hormone
“ion transport peptide.” Molecular biology of this endocrine peptide
and hindgut epithelial physiology will be studied. Our research will
provide rational approaches to develop environmentally benign insecticidal
compounds that help to control diseases carried by these mosquitos. TLR Expression Alters Ischemia-induced Intestinal Epithelial Damage
This project focuses on the mechanism of intestinal damage
in response to ischemia/reperfusion (I/R) events including heart attacks and
strokes. Intestinal damage due to I/R events is mediated by components of the
immune system. One group of molecules called toll-like receptors are candidates
for involvement. The goal of this project is to understand the extent that
toll-like receptors contribute to intestinal damage. The hypothesis is that
specific toll-like receptors cause the intestinal inflammation associated with
damage induced by I/R. These studies will provide critical data to improve
our understanding of I/R injury.
|
