My current focus in the Division of Mucosal Immunology at MGH is gene regulation and signal transduction downstream of the pro inflammatory cytokine, interleukin 1beta (IL-1). I am using tissue culture cell line models, both transformed and non transformed intestinal epithelial cells, together with human intestinal xenografts transplanted into nude mice, to define novel IL-1b signaling pathways specific to its function either as an intestinal growth factor involved in protection against pathogens and wound healing or as a pro-inflammatory mediator associated with disease. The phosphatidylinositol 3-kinase (PI3-K) pathway activated by IL-1 is a signaling pathway shown to mediate cell growth and survival in part via the acitivation of 2 important DNA binding proteins, activator protein 1 (AP-1) and nuclear factor kappa B, (NFkB), both associated with inflammation, I have identified a novel PI3-K dependent signaling pathway in the Caco-2 cell line, activated by IL-1, involved in AP-1 activation and interleukin-6 gene transcription (J. Biol. Chem 2008). I am now investigating the role of this novel pathway in both the normal and inflamed intestine as well as defining downstream components including specific AP-1 family members. The role of both IKK, a kinase of the IKK complex and TGF activated kinase (TAK1) both in normal and inflamed epithelium and in intestinal development and differentiation is also being explored. My long term goal is to develop novel therapeutic drug targets for the treatment of intestinal diseases including colon cancer, and inflammatory bowel disease.
Research in my lab is directed at understanding how immune responses to bacterial infection are influenced by host and environmental factors. Over the last 5 to 6 years, we have been characterizing the interactions between iron homeostasis and the response to infection. We have made significant contributions to this area, particularly with respect to the effects of the mammalian iron transporter ferroportin on microbial growth and host innate immunity. Recently, we have also started to analyze the effects of inflammation on iron metabolism. Our observations have provided mechanistic insights into the immunological consequences of disordered iron homeostasis and, conversely, into the effects of inflammatory diseases on iron handling.
Kriston Ganguli, MD
Instructor of Pediatrics
My research activities focus on understanding the developmentally regulated innate immune responses of the immature intestine and how this immaturity contributes to the exaggerated inflammatory response seen in necrotizing enterocolitis of preterm infants. Although probiotic bacteria has been shown to significantly reduce the incidence of necrotizing enterocolitis, an understandable hesitation in administering intact bacteria to neonates still exists. I have therefore focused on isolating and characterizing secreted factors of probiotic bacteria which attenuate the inflammatory response in immature intestinal epithelium. A soluble, heat-stable anti-inflammatory factor may ultimately provide a safe, novel approach to necrotizing enterocolitis prevention.
My laboratory studies epithelial morphogenesis and growth regulation in Caenorhabditis elegans. One of our objectives is to contribute to the understaning of the molecular basis of intestinal morphogenesis. C. elegans is a transparent roundworm whose internal organs are formed by different types of tubes constructed from distinct, yet simple, polarized epithelia. The simplicity of this organism when combined with its sophisticated genetic resources make it a powerful tool to examine tubulogenesis. We have recently identified a number of cytoskeletal genes that are required to build the apical/luminal and basolateral membranes of the intestine and other tubular organs. Understanding organ development will advance our understanding of the pathogenesis of human diseases related to these organs, which in turn should lead to novel approaches for their diagnosis and treatment. Specifically, we hope that this work will translate into a better understanding of: (1) the still enigmatic link between the development of cancer and the disruption of polarity, cell shape and developmental genes, and (2) developmental diseases of internal organs and the vasculature.
A major focus of our work is to understand processes that lead to mucosal barrier breach in the context of inflammation and disease within the lung and the digestive tract. Insults with the potential to compromise the mucosal barrier include microbial toxins that target or exploit the polarized mucosal epithelium or pathogens and their products that instigate inflammation resulting in recruitment of neutrophils that breach epithelial barriers and cause tissue damage. Neutrophils serve an important role in innate immunity charged with eradicating dangerous pathogens. Owing to the non-specific nature of the neutrophil arsenal, neutrophil infiltration of the mucosa can be detrimental to host tissue if sufficient resolution is not achieved following neutrophil mobilization. Destructive neutrophilic breach of the mucosa can occur in the airway and the gut in response to pathogenic infection or as a result of autoimmune or auto-inflammatory disease. Examples of such illness include cystic fibrosis, pneumonia, ARDS, & COPD in the lung and IBD & certain enteric infections in the gut. We have identified a neutrophil chemo-attractant that is critical to directing neutrophil breach of mucosal barriers. This molecule is an eicosanoid called hepoxilin A3 and it is produced by mucosal epithelial cells of both the lung and gut. Efforts are underway to better understand the genes involves in the synthesis of hepoxilin A3 by epithelial cells and to develop strategies to interfere with hepoxilin A3 function. Such approaches may prove efficacious in combating overzealous inflammation marked by neutrophil breach of mucosal barriers progressing to severe tissue damage, which characterizes numerous ailments of the lung and digestive tract. Ultimately a more thorough understanding of the mucosal barrier and its vulnerabilities will serve to drive development of therapeutics aimed at mucosal barrier fortification in the face of a diverse array of threats.
My research interest is in understanding the molecular mechanism of bacterial-epithelial crosstalk as it relates to the pathogenesis of intestinal inflammation in colitis and necrotizing enterocolitis (NEC), a life-threatening inflammatory bowel disorder of unknown cause that afflicts premature infants. I have discovered that the components of the Toll-like receptor (TLR) pathway are partly responsible for bacteria-mediated changes in fucosylation of the gut epithelium which plays a key role in epithelial barrier function in both immature and mature mice colon. TLR4 - mediated cell signaling in the pathogenesis of NEC has attracted increasing attention in the NEC research field. The location of the receptor in small intestine influences its function. However the distribution of TLR4 in the developing human colon is totally unknown. My current research is focusing on the distribution and trafficking of TLR4 on developing human colon, and how TLR4 regulates the glycosylation of human fetal colon as it relates to NEC. The hypothesis is that the mechanisms by which LPS triggers TLR4 signaling in the immature colon may have a different phenotype compared to mature colon. This study may bring a new understanding to the genesis of NEC and may lead to the discovery of novel, TLR4 –specific therapies for prevention of NEC.
Hai Ning Shi, DVM, PhD
Associate Professor of Pediatrics
My research interests are focused regulation of mucosal immunity in the gastrointestinal tract. We use both in vivo and in vitro approaches to elucidate the mechanisms by which an intestinal helminth infection modulates intestinal inflammation induced by pathogenic and non-pathogenic enteric bacteria. Using our recently established helminth-bacterial co-infection mouse model, we demonstrated that infection with the intestinal helminth parasite, Heligmosomoides polygyrus, results in the development of exacerbated intestinal inflammation in mice infected with the Gram-negative bacterial enteropathogen Citrobacter rodentium, a mouse pathogen similar to human EPEC. We are currently addressing the idea that the exacerbating effect on intestinal inflammation is the consequence of helminth induced (1) modulation of T cell function to a phenotype that promotes proinflammatory responses, in part by impairing intestinal epithelial barrier function, and (2) alterations in macrophage phenotype and function that compromise the ability to eliminate translocated bacteria. Another area of our research focuses on how intestinal colonization of probiotics and/or treatment with prebiotics early in life influences the development and regulation of host innate and adaptive immune responses. This research will provide greater insight into how intestinal microorganisms may alter the regulatory mechanisms of mucosal immunity, which may be instrumental in the establishment of more effective and safer preventive and therapeutic approaches for the treatment of immune mediated disorders and for the design of effective mucosal vaccines. The third area of my research is directed at clarifying the role of maternal factors during gestation in the development of immunity and the induction of allergic diseases in the early life of the offsprings. We ultimately seek to elicit information that may help protect children from developing food allergy and enhance their immune capacity to react to antigenic challenges.
My research interests are focused regulation of mucosal immunity in the gastrointestinal tract. Our recent work demonstrated that infection with the intestinal helminth parasite, Heligmosomoides polygyrus, results in the development of exacerbated intestinal inflammation in mice infected with the Gram-negative bacterial enteropathogen Citrobacter rodentium, a mouse pathogen similar to human EPEC. Our subsequent works suggest that one of the mechanisms by which helminth parasite may exert the effect on host immunity involve induction of alternatively activated macrophages. I am currently addressing the idea that the exacerbating effect on intestinal inflammation is the consequence of helminth induced alterations in macrophage phenotype and function that compromise the ability to eliminate translocated bacteria.
My primary responsibilities at Massachusetts General Hospital involve overseeing the Mucosal Immunology and Developmental Gastroenterology Laboratories at Building 114 MGH-East as part of the Gastroenterology and Nutrition Division at MGHfC at Harvard Medical School. These laboratories have five principal investigators, six postdoctoral fellows and two graduate students who study oral tolerance, gut inflammation and microbial-epithelial "crosstalk." My research efforts include defining the passive and active protective properties of human breast milk with regard to the protection from disease during the newborn period. I also study the development of human intestinal host defenses using human fetal organ cultures, cell lines, and xenograft transplant models. Specifically, my laboratory has reported that the human fetal epithelium responds inappropriately to both endotoxin and exotoxins, which helps to explain an increased incidence and severity of certain inflammatory and secretory diarrheas in this age group. More recently, we have studied the effect of initial colonizing microbiota on the development of mucosal protective function and the mechanism of probiotics in this process.
I have worked as a physician, an academic researcher for many years. My previous research involves 1) the relationship between breast feeding or other intestinal related nutrients and the development of the immature intestine; and 2) the relationship between mucosal immunity and inflammation diseases including inflammation bowel disease, asthma, and chronic inflammation-induced pulmonary hypertension. My research interest here is to define if and how commensal bacteria and environmental factors affect developmental immunologic programming in intestinal host defense. In particular, I will investigate the mechanisms of intestinal epithelia tolerance and epithelia integrity using cell lines, human xenograft transplants, murine models of necrotizing enterocolitis and allergic induced enteric inflammation. These studies will help design effective strategies for prevention and/or treatment of necrotizing enterocolitis and allergic related enteric inflammation.
Research • Curriculum Vita
Beth McCormick, PhD