Principal Investigator
Research Team
Martin Hewison, PhD, is Professor Level IV in the Department of Orthopaedic Surgery, Geffen School of Medicine at UCLA. A molecular endocrinologist by training, Dr. Hewison heads a team of six researchers whose work is focused on exploring the role of vitamin D in human health. Dr Hewison’s group were the first to report widespread expression of the vitamin D-activating enzyme CYP27B1 in normal human tissues, providing a mechanism for localized concentration of active hormonal vitamin D. Subsequent studies have shown that this mechanism is dependent on serum vitamin D status, so that local immunomodulatory or antiproliferative effects of vitamin D may be compromised in individuals who are vitamin D insufficient. The current objective of Hewison group research is to explore this in more detail with specific emphasis on: 1) mechanisms controlling the bioavailability of vitamin D; 2) vitamin D and the regulation of infection and inflammation during pregnancy; 3) mechanisms involved in antibacterial effects of vitamin D; 4) novel targets for vitamin D responses in bone; 5) the importance of vitamin D for immune function in chronic kidney disease.
Dr. Hewison received his PhD from Guy’s Hospital Medical School at the University of London, England. Following on from this he became a faculty member in the Department of Medicine at University College London. In 1994 he moved to the University of Birmingham, where he established the UK’s major vitamin D research group. In 2004 he was appointed Professor of Molecular Endocrinology and a year later he moved to Cedars-Sinai Medical Center, Los Angeles, where he joined the Department of Endocrinology, Diabetes and Metabolism. He has since been recruited to the newly formed Department of Orthopaedic Surgery at UCLA, where his current group is now based. Dr Hewison is funded by an NIH grant to study “FGF23 and the regulation of vitamin D-induced immunity in CKD”, a March of Dimes grant to study “Vitamin D, inflammation and pre-term birth”, and a Kellogg Foundation grant on “Preventing Health Disparities During Pregnancy through Vitamin D (VitD) Supplementation”, but he is also co-investigator on several other NIH grants to UCLA and external collaborators. He is an ad-hoc reviewer on NIH study sections and a member of an NIH Data and Safety Monitoring Committee.
Wareeratn (Joyce) Chengprapakorn, MD
Wareeratn Chengprapakorn obtained her dental degree from Faculty of Dentistry, Chulalongkorn University in Bangkok, Thailand in 2004. She then worked for Maxillofacial Prosthodontic unit in Faculty of Dentistry, Chulalongkorn University for 5 years as a resident dentist rehabilitating patients with maxillofacial defects. After that she become staff for Department of Prosthodontics in Faculty of Dentistry Chulalongkorn University. Wareeratn began her PhD studies at UCLA in 2011, as part of the School of Dentistry’s Postgraduate Program. She is jointly mentored by Dr. Martin Hewison and Dr. Ischiro Nishimura in a project to investigate the effects of immunoactive toll-like receptors (TLR) on bone cell function. Members of the TLR family play a crucial role in promoting innate immune function by macrophages and dendritic cells. Expression of TLRs has also been described for skeletal cells such as osteoblasts, but the function of TLRs in this setting is unclear. Preliminary data produced by Wareeratn have shown that TLR ligands such as endotoxin (lipolysaccharide) stimulate vitamin D metabolism in bone-forming osteoblasts. This may be part of an antimicrobial mechanism in the skeleton but Wareeratn’s PhD project will also investigate a possible role for the TLR-vitamin D pathway in modulating bone formation and resorption. Outside of her research Wareeratn...
Rene Chun is an Associate Researcher in the Hewison Vitamin D research group. Rene received his undergraduate degree in Biochemistry from UCLA. He then obtained his PhD at UC Irvine in the laboratory of Dr. Hung Fan studying the molecular biology of the Tat protein of HIV. His post-doctoral training has included appointments at NIAID/NIH, UC San Francisco-VA Medical Center and Cedars-Sinai Medical Center. Currently, at UCLA, Rene works on several projects aimed at understanding the role of vitamin D as a regulator of human innate immune responses. He has recently published several studies detailing the role of vitamin D binding protein (DBP) in controlling the bioavailability of vitamin D. This project includes a collaboration with the University of Maryland to develop a novel mathematical model to predict ‘free’ and ‘bioavailable’ vitamin D. In addition to scientific research, he enjoys exploring the natural wonders of California with his wife, experiencing culture and the arts in LA, discussing theology and politics and is a long suffering Dodger and UCLA sports fan. Rene is happy to be back at his alma mater and helping fulfill the research and teaching mission of the Orthopaedic Hospital Research Center.
Nancy Q. Liu received her M.D. from Norman Bethune University of Medical Science in 1987. Since 1994 she has been involved in several biomedical and molecular biology projects as a postgraduate researcher at UCLA. She joined the Department of Orthopaedic Surgery in 2002, where her work was focused on investigation of the effects of the BMP pathway and RANK/RANKL axis in the metastatic bone lesions of prostate and lung cancers. In particular, studies assessed the tool of gene-therapy to promote bone healing during non-union and large bone defects. Since 2007, Nancy has worked as an Assistant Researcher within the Vitamin D Group of Dr Hewison. She is now investigating the influences of vitamin D on immune function at ‘barrier sites’. Nancy has published key papers on the role of vitamin D as a regulator of inflammation in the gastrointestinal tract. However, her main project is to assess the immunoregulatory effects of low vitamin D status during pregnancy. Recent studies using novel mouse models have shown that dysregulation of vitamin signaling during pregnancy has profound effects on placental inflammation and tissue histology. Other work has shown that mice raised on vitamin D-deficient diets develop elevated blood pressure during pregnancy. These findings suggest that vitamin D is a key factor in protecting against infection, inflammation, aberrant placentation and hypertension during pregnancy. The overall aim of this work is to support new clinical studies of vitamin D supplementation for pregnant women.
I graduated from Grant Medical College and Sir. J.J Group of Hospitals, Mumbai, India with a degree in Medicine. I then went on to complete my residency in Pediatrics at Penn State Children’s Hospital, Hershey, PA.
Currently, I am enrolled in a Pediatric Nephrology fellowship Program at the University of California, Los Angeles. Here under the guidance of Dr. Martin Hewison and Dr. Isidro Salusky I am working on research to explore how the vitamin D system affects iron homeostasis. In particular my studies will investigate the impact of vitamin D on iron regulatory proteins such as hepcidin and ferrorportin. Hepcidin (encoded by the HAMP gene) regulates the absorption, tissue distribution and extracellular concentrations of iron by suppressing ferroportin-mediated export of cellular iron. In chronic kidney disease elevated hepcidin and vitamin D-deficiency are associated with anemia, suggesting a role for vitamin D in iron homeostasis. The aim of my project will be to better characterize the mechanisms by which vitamin D supplementation may improve iron homeostasis and prevent anemia. When I am not working in the lab or doing clinical work, I enjoy reading, listening to music and hiking/other outdoor activities.
Jessica Sea graduated from CSU Channel Islands in 2010. As an undergraduate, she worked in Dr. Nitika Parmar’s lab researching the effects of oxidative stress on cancer cell proliferation for a year and with Dr. Charles Sackerson studying early Drosophila embryogenesis for two years.
In 2012, Jessica joined the UCLA ACCESS program and after rotating among an eclectic array of labs, decided to join Dr.s John Adams and Martin Hewison to explore the intricacies of non-classical vitamin D functions.
Her current research is focused on understanding vitamin D metabolism in the vascular endothelium and the mechanisms underpinning endothelial dysfunction related to vitamin D metabolic obstruction. Outside of the lab, Jessica loves taking her dogs to the park, spending time with family and friends, and discovering all the quirky places LA has to offer.
Kathryn Zavala graduated from the University of California, Berkeley with a double major in Molecular and Cellular Biology and Rhetoric. During her undergraduate studies, she investigated heme synthesis and its role in metabolic processes with Hani Atamna at the Oakland Children’s Hospital Research Center in Oakland, California. Following graduation, Kathryn relocated across the bay and joined the collaboration of Mark Schumacher and Helge Eilers at the University of California, San Francisco in the Department of Anesthesia and Perioperative Care. Her research projects focused on understanding the transcriptional regulation of the capsaicin receptor, TRPVI, as well as characterizing the functional properties of TRP-related ion channels and discovering novel activators/inhibitors of TRPV1 and TRPA1 expression. Currently, Kathryn is working towards her PhD in Molecular and Cell Developmental Biology at the University of California, Los Angeles. Her pre-doctoral training with John Adams and Martin Hewison involves research on vitamin D metabolism and its impact on human immunity. In particular her studies will explore how antibacterial mechanisms triggered by vitamin D may help to combat infection with Mycobacterium leprae (M. leprae), a mycobacterium that causes leprosy. The beneficial effects of vitamin D as a treatment for leprosy were recognized more than half a century ago but it is only in recent years that we have began to understand the cellular and molecular basis for this. Kathryn’s studies will focus on the mechanisms by which pattern cellular recognition receptors signal to components of the vitamin D system following upon encountering M. leprae. Experiments will also investigate the ways in which M. leprae can subvert vitamin D responses in more aggressive forms of leprosy. Kathryn will use RNA and protein analyses, as well as HPLC to study vitamin D activation and catabolism in different innate immune cell types following infection with M. leprae. She will also use gene expression and chromatin association analyses to study immune cell signaling following activation of vitamin D. When not immersed in the world of science, Kathryn enjoys cheering on her favorite sports teams, challenging crossword puzzles, and indulging in reality television.
