The DDNC Research laboratory is located in the Biomedical Research Building (BRB) of the University at Buffalo - SUNY, South Campus, a relatively new, well equipped research facility, including 58 separate research modules. Our laboratory, located on the fourth floor (Rooms 422 and 426) of the BRB, occupies approximately 1,250 sq. feet of space. Our laboratory is well equipped for research endeavors involving molecular biology and cell biology (refrigerated high-speed and low-speed centrifuges, thermal cycler, -20C and -80C freezers, vertical and horizontal electrophoresis apparatus, Western blot transfer apparatus, cell culture hood and incubators, regular and fluorescence plate readers). There is also a large shared equipment work area equipped with multi-photon confocal microscope, upright and inverted fluorescence microscopes, FACS, real-time thermal cyclers, molecular imagers, nano-drop spectrometer, ultracentrifuges, gamma and beta counters, FPLC, HPLC and low temperature freezers. All research laboratories are located in close proximity on six floors (about 10 lab for each floor), which fosters continuing interaction, discussion and exchange of information between staff, postdoctoral fellows, graduate students and technologists.
Our research interests span the broad areas of gastroenterology. Ongoing research projects include:
Mechanism and regulation of gastric acid secretion.
Regulation of gastric acid secretion is the major treatment of many GI diseases including GERD, gastric, duodenal and esophageal ulcers. The spending in treating these conditions is substantial.
The gastric parietal cell, lining the lumen of the stomach, is responsible for the secretion of isotonic HCl (0.15M) into stomach. One ATP is consumed for every proton secreted into the stomach lumen and a lot of proton pump (H,K-ATPase, the alpha and beta subunits of this enzyme were discovered in 1967(1) and 1990(2)) is required for this job. To accommodate these many proton pumps, the apical plasma membrane, in the resting state, is expanded in the form of numerous invaginations which express relatively short microvilli, and a large compartment of cytoplasmic membranes, commonly called tubulovesicles, fully loaded with proton pumps. Upon stimulation by hismatine initiated PKA signaling, these tubulovesicles traffic to and fuse with apical membrane, forming densely packed microvilli comparable to those found on the brush border membrane of small intestine. This intracellular trafficking and fusion events bring proton pumps to their post for active acid secretion. In time, these proton pumps are brought back into the cytoplasm (by way of endocytosis) for a reliable mechanism to turn off acid secretion. Although the membrane recycling theory was raised a long time ago(3), there are still many major gaps in the understanding of the mechanism for the regulation of acid secretion, which are the research interests of our laboratory. Techniques employed include isolation and primary culture of gastric parietal cells, measurement of acid secretion, fractionation of different membranes by differential and gradient centrifugation.
Schematic representation of the parietal cell in resting and stimulated states. Drastic morphological change occurs with stimulation. In the resting state the apical canaliculi extend into the cell presenting short microvilli. Tubulovesicles containing cargo H,K pumps (red) abound in the cytoplasmic space. There are also many mitochondria.
Using gastric parietal cell model to study general cell biological questions: how membrane trafficking is regulated by small G-proteins, how filamentous actin supports the dynamic change of microvilli on apical membrane.
The parietal cell has a remarkably large volume of intracellular membrane trafficking adapted to the elegant mechanism for the regulation of acid secretion. This means that this cell is abundant in those protein machineries required for membrane trafficking and fusion, exocytosis and endocytosis. For instance, no other cell type expresses the amount of syntaxin3 found in parietal cell. Therefore, parietal cell is the top choice for elucidating many of the core questions in cell biology. Techniques used to attack these questions include immunoabsorption, differential ultra-centrifugation, IMAC, 2D-electrophoresis, LC-MSMS, and confocal microscopy.
Pathogenesis of Nonalcoholic Steatohepatitis (NASH)
NASH research is funded by the Peter and Tommy Fund. NASH is a disease of the liver that is associated with obesity and adult onset, or type II, diabetes. NASH is not a benign disease. Many people with NASH have a shorter life expectancy than those who no not have NASH. NASH is associated with cirrhosis and is the third most common reason for liver transplantation in adults. No one knows what causes NASH, but it is known that in obese people there is increased fat in the liver. In addition to fat, cells that cause inflammation are found in the liver in patients with NASH. It is thought that these inflammatory cells may cause liver damage that results in fibrosis, cirrhosis and ultimately liver failure. The purpose of this research is to understand the relationship between obesity and the molecular factors that control inflammation so the interaction of the two can be better understood and treatments developed.
NASH and alcoholic steatohepatitis share many histological features. Both NASH and alcoholic steatohepatitis patients exhibit macrovesicular and microvesicular fat in hepatocytes. The number and size of Mallory bodies, and the pattern of pericellular fibrosis are also indistinguishable between two disease groups. Previous studies suggested that intestinal bacteria produced more alcohol in obese mice than lean animals. Therefore, we hypothesized and provided the first molecular evidence that alcohol metabolism contributes to the pathogenesis of NASH (Baker et al, 2010).
Fatty liver is a prerequisite for the development of NASH. The homeostasis of hepatic lipid depends on the dynamic balance of multiple metabolic pathways. Previous studies focusing on individual pathway or enzyme drew conflicting conclusions on the molecular mechanism for the accumulation of lipid in hepatocytes. With a high through-put technique, we compared all the major pathways in parallel. We are expecting to publish the exciting results in the near future.
Oxidative stress is believed to be a major factor mediating the transition from simple steatosis to NASH. The prevention or mitigation of oxidative stress in patients with simple steatosis could prevent NASH. Our current research examines two facets of this problem: 1) what are the molecular mechanisms causing oxidative stress; 2) what are the molecular mechanisms that our body take to fight oxidative stress. Many novel findings have been observed in the lab and we are in the process of confirming these observations..
About Laboratory Members
Lixin Zhu, PhD – Assistant Professor. He is responsible for the overall administration and direction of all the research projects.
After graduation from Nankai University, a top research university in China, he was accepted into the graduate program in Shanghai Institute of Biochemistry, the Chinese Academy of Sciences. With his mentors, Professors Guang-Di Li and Yuan Wang, he studied the molecular virology of hepatitis C and developed attenuated live-viral vaccines against hepatitis C, using the modified vaccinia virus Ankara stain as the vector. In this collaborative work, he, Professor Wang’s group and Dr. Gerd Sutter’s group (then in the Institute for Molecular Virology, GSF, Munich, Germany) demonstrated that the invented vaccines are able to elicit protective humoral and cellular immune responses targeting hepatitis C antigens in a murine model.
His postdoc research was all about gastric parietal cell. His major work was focused on a phosphoprotein called ezrin. This protein is discovered in parietal cell(4) and other cells almost simultaneously. Using FRET (fluorescence resonance energy transfer) technique, he studied ezrin conformation in a relatively native state. With his mentor Dr. John G. Forte (University of California, Berkeley), he demonstrated how ezrin phosphorylation regulates the conformation and activity of this protein and the effects on parietal cell acid secretion. His discovery that ezrin phosphorylation is underwent fast turnover may shed light on similar phosphorylation events in different model systems. Besides this, he also participated in the studies of parietal cell membrane trafficking, in collaboration with Dr. Serhan Karvar (University of Southern California).
His current research interests are expanded from gastric parietal cell into the whole GI tract. Together with the dedicated M.D. researchers (Dr. R. Baker, Dr. S. Baker, Dr. Razan Alkhouri, Dr. Diana Moya and Dr Colleen Nugent) in the DDNC to better understand the pathophysiology of these diseases for better diagnosis and treatments.
Wensheng Liu, Ph.D. – Research Assistant Professor. Dr. Liu received his Ph.D. in Pharmacology from University of Buffalo. He completed his postdoctoral training in Roswell Park Cancer Institute. His research was focused on the molecular mechanisms of breast cancer. Dr. Liu joined our research laboratory in July, 2009. His research interests include the molecular pathogenesis and non-invasive biomarkers of Nonalcoholic Steatohepatitis.
Fun at the Lab!
PEDIATRIC GASTROENTEROLOGISTS & NUTRITIONISTS
Copyright © Digestive Diseases and Nutrition Center. All Rights Reserved.