Office phone: (859)257-6574
Fax: (859)257-8940
Lab phone: (859)123-4567
Research statement: My primary research interest is to understand the fine-tuned mechanisms of intestinal homeostasis and the pathological consequences of their disruption. The human gut harbors approximately 100 trillion microorganisms that actively interact with the intestinal monolayered cellular epithelium, leading in healthy individuals to a peaceful and mutually beneficial coexistence between host and its gut microflora. The epithelium acts as the primary barrier between potentially hazardous microbes and the interior of the body. Host cells recognize microorganisms through families of pattern recognition receptors, including the Toll-like receptors (TLRs). TLRs recognize broad classes of pathogen-associated molecular patterns, such as bacterial cell wall components, and microbial RNA and DNA. TLR ligation leads to the activation of the NF- k B and MAP kinase signaling pathways, resulting in activation of multiple target genes involved in pro- and anti-inflammatory responses. Under homeostasis, a balance is maintained between the expression of pro- and anti-inflammatory factors by the epithelium. However, depending on microbial virulence factors and/or the genetic susceptibility of the host, intestinal homeostasis can be disrupted leading to inflammation and tissue injury. I use the human colon adenocarcinoma cell-line HT-29 as an in vitro model system to study changes in intestinal gene expression as a consequence of exposure to microbial components and other stimuli. I have shown that treatment of HT-29 cells with purified LPS from E. coli, heat-killed or live E. coli cells causes up-regulation of pro-inflammatory factors such as IL-8 and TNF while also leading to increased expression of anti-inflammatory factors such as the polymeric immunoglobulin receptor (pIgR), A20 and MKP-1. Many of these genes are known to be activated through NF- k B pathways. I have developed clones of HT-29 cells stably transfected with small hairpin RNA molecules (shRNA) for the NF- k B sub-units RelA and RelB that cause selective gene knockdown by means of RNA interference technology. Treatment of these clones with different stimuli that signal through the NF- k B pathway should allow us to differentiate between the classical and alternative NF- k B pathways. I have also demonstrated that long-term exposure of HT-29 cells to TNF, a key cytokine involved in inflammatory responses, leads to up-regulation of the polymeric immunoglobulin receptor through transcriptional and post-transcriptional mechanisms. Under conditions of chronic exposure to TNF, a significant increase in the half-life of pIgR mRNA was observed. TNF is a well-known activator of the classical NF- k B pathway and studies designed to determine its effect on the 3’UTR of the PIGR gene should clarify the molecular mechanisms leading to increased message stability. I am also developing a mouse model system to study alterations in intestinal gene expression between wild-type mice and mice deficient in critical components of the TLR signaling pathway such as the intracellular adapter protein MyD88. I have demonstrated that MyD88 KO mice exhibit an altered intestinal gene expression profile compared to wild-type counterparts.
Selected publications:
Bruno, M.E.C. and C.S.Kaetzel. 2005. Long-term exposure of HT-29 human intestinal epithelial cell line to TNF causes sustained up-regulation of the polymeric Ig receptor and proinflammatory genes through transcriptional and posttranscriptional mechanisms. Journal of Immunology. 174: 7278-7284.
Bruno, M.E.C., R.B. West, T.A. Schneeman, E.H. Bresnick and C.S. Kaetzel. 2004. Upstream stimulatory factor but not c-Myc enhances transcription of the human polymeric immunoglobulin receptor gene. Molecular Immunology. 40:695-708.
Schneeman,T.A., M.E.C.Bruno ,H. Schjerven, F. Johansen, L. Chady and C.S. Kaetzel. 2005. Regulation of the polymeric Ig receptor by signaling through toll-like receptors 3 and 4: linking innate and adaptive immune responses. Journal of Immunology 175: 376-384.
Pedigo, N.G., H. Zhang, M.E.C. Bruno , C.S. Kaetzel, A. Dugan, P. Shanehsaz, N.J. Koszewski and D.M. Kaetzel. 2005. A5’-distal enhanceosome in the PDGF-A gene is activated in choriocarcinoma cells via ligand-independent binding of vitamin D receptor and constitutive jun kinase signaling. Oncogene. 24:2654-2666.
