Thus, HIF-1 in B220+bone marrow cells plays a key role in the glycolytic pathway during B cell development. Interestingly, many respiratory chain related-genes, including electron transfer-system-related, and oxidative phosphorylation-related genes, such asCyc(cytochrome c),Cyba(cytochrome b-245),Atp5k(ATP-synthase, H+transporting, mitochondorial F1F0 complex subunit e), andCox7c(cytochrome c oxidase, subunit VIIc) in HIF-1 deficient cells expressed much higher than those in control cells from 129 mice (Fig. agreement with these findings, HIF-1 deficient cells utilized pyruvate more efficiently than wild-type cells. The key role of HIF-1-enabled glycolysis in bone marrow B cells was also demonstrated by glucose deprivation duringin vitrobone marrow cell culture and by using a glycolysis inhibitor in the bone marrow cell culture. Taken together, these findings indicate that glucose dependency differs at different B cell developmental stages and that HIF-1 plays important role in the B Isoliquiritigenin cell development. Keywords:Rodent, B Cells, Cell Differentiation == Introduction == Effector cells of the immune system are exposed to low oxygen tensions during their development and functioning (13). Hypoxia-inducible factor (HIF)3-1, a transcription factor, may be essential for lymphocytes adaptation to hypoxia as it was shown with many other cell types and since it enables the synthesis of glycolytic enzymes for anaerobic metabolism, vascular endothelial growth factor (VEGF) for angiogenesis and erythropoietin for erythropoiesis among other activities (46). HIF-1 is a heterodimeric complex between HIF-1 and HIF-1 subunits. The HIF-1, which is LIFR also known as aryl hydrocarbon receptor nuclear translocator (ARNT), is expressed constitutively and is a partner for other transcription factors. HIF-1 mRNA is translated constitutively in an oxygen tension independent manner. However, its protein is degraded in proteasomes after ubiquitinylation under normoxic conditions. Under hypoxic conditions Isoliquiritigenin HIF-1 is stabilized and functions as a master regulator of adaptation to hypoxia (712). It has been also established that some humoral factors, such as growth factors, can stabilize HIF-1 protein expression in an oxygen Isoliquiritigenin tension independent fashion (13,14). To understand the mechanism as to how lymphocytes adapt to Isoliquiritigenin hypoxia, we have studied effects of deletion of the HIF-1 gene on T and B cell response using different mouse gene knockout and knock-down strategies (1517). Since HIF-1 deficiency causes embryonic death (4,18,19), we took advantage of RAG-2-deficient blastocyst complementation system to generate HIF-1/RAG-2 deficient chimeric mice, in which both T and B cells could develope Isoliquiritigenin only from HIF-1 deficient ES cells (20). The analysis of these HIF-1/RAG-2 chimeric mice revealed that deficiency of HIF-1 resulted in abnormal B-1-like cells in the peritoneal cavity. These cells expressed high levels of B220. We also observed the development of autoimmunity as reflected by accumulation of autoantibodies (anti-double strand DNA antibody and rheumatoid factor) in serum, deposits of IgG and IgM in kidney, and proteinuria as well as distortions of B cell development in bone marrow (15). While these earlier experiments established HIF-1 as an indispensable factor for normal B cell development and self-tolerance, the molecular mechanisms by which HIF-1 regulates B cell development and autoimmunity are not known. To elucidate the HIF-1-mediated regulatory mechanisms in B lymphocytes, we attempted to reveal the role of HIF-1 in B cell development in bone marrow. HIF-1 was shown to regulate the glycolytic pathway in many cell types (46) and the possible importance of glycolysis as a part of energy metabolism in T cell functions has been recently discussed (21). However, it was not established whether HIF-1-enabled energy supply from the glycolytic pathway is important during different stages of B cell development and whether all B cell precursors are equally dependent on HIF-1. By addressing these issues we demonstrate here that glucose dependency differs at different B cell developmental stages and that HIF-1 plays an important role in B cell development. == Materials and Methods == == Mice == The ES chimeric mice were generated by the injection ofHif1a/ES cells into blastocysts from C57BL/6 mice with or without RAG-2 deficiency as previously reported (15). Control wild type C57BL/6 mice and 129 mice were purchased from CLEA (Tokyo, Japan). All animals used in this study were housed under specific-pathogen free conditions in our Laboratory Animal Research Center and were handled according to Guidelines for the Care and Use of Laboratory Animals Center, Dokkyo Medical University (protocol #0341). == Cell preparation == Bone marrow B220+cells were fractionated into.
