Masaomi Nangaku

Hypoxia and Dysregulated Angiogenesis in Kidney Disease.

Background: Accumulating evidence has demonstrated that renal hypoxia has a crucial role in the pathogenesis of acute kidney injury (AKI), chronic kidney disease (CKD), and AKI-to-CKD transition, ultimately culminating in end-stage kidney disease. Renal hypoxia in progressive CKD is intricately linked to persisting capillary loss, which is mainly due to dysregulated angiogenesis. Summary: In CKD, hypoxia-inducible factor (HIF) accumulates in the ischemic tubulointerstitium but fails to sufficiently stimulate angiogenic responses, partly because of blunted activation of HIF, which is best exemplified in diabetic kidney disease. In addition, vascular endothelial growth factor (VEGF) expression is downregulated, possibly because injured tubules are not able to express sufficient VEGF and inflammatory circumstances inhibit VEGF expression. The upregulation of antiangiogenic factors and the incompetence of endothelial progenitor cells (EPCs) may also play some roles in the inadequacy of capillary restoration. Administration of VEGF or angiopoietin-1 maintains peritubular capillaries in several kidney diseases; however, administration of a single angiogenic factor may lead to the formation of abnormal vessels and induce inflammation, resulting in worsening of hypoxia and tubulointerstitial fibrosis. HIF stabilization, which aims to achieve the formation of mature and stable vessels by inducing coordinated angiogenesis, is a promising strategy. Given that the effect of systemic HIF activation is highly context-dependent, further studies are needed to elucidate the precise roles of HIF in various kidney diseases. The adoptive transfer of EPCs or mesenchymal stem cells (MSCs) is a fascinating alternative strategy to restore the peritubular capillaries. Key Messages: Suppressed HIF activation and VEGF expression may be responsible for the dysregulated angiogenesis in progressive CKD. Administration of a single angiogenic factor can cause abnormal vessel formation and inflammation, leading to a detrimental result. Although further studies are warranted, HIF stabilization and adoptive transfer of EPCs or MSCs appear to be promising strategies to restore normal capillaries.

Cloning of a new human gene with short consensus repeats using the EST database

Abstractu2003The complement system, which provides many of the effector functions of humoral immunity and inflammation, is tightly regulated by various complement regulatory proteins. The most common structural feature of these proteins is a motif called short consensus repeat (SCR). In order to identify a new human complement regulatory protein, we performed a similarity search using SCR on the expressed sequence tag (EST) database and found a partial sequence of a new human gene. Using a probe containing this partial sequence, we obtained a full-length cDNA of this gene from a human umbilical vein endothelial cell (HUVEC) library. The sequencing reaction demonstrated an open reading frame of 1383 nucleotides coding for a 461 amino acid polypeptide with a deduced relative molecular mass of 51 000. Structural analysis showed that the protein has three SCRs with one transmembrane domain. A characteristic feature of these SCR was that they have six conserved cysteines per repeat instead of the usual four. Therefore, we named this cDNA THECY (three hexa-cysteine motifs). A six cysteine motif is a characteristic feature of selectins. We used northern blot analysis to show that a 2.0 kilobase (kb) transcript was ubiquitously present in most organs studied, and the mRNA was most abundant in the heart. In conclusion, we discovered a member of a new class of membrane-bound SCR-containing molecules using the EST database. Utilization of the EST database may be useful in the search for other new immunological proteins. The function of this gene remains to be elucidated.

Molecular mechanisms of experimental glomerulonephritis: an overview

Summary: Most glomerular diseases are autoimmune in nature with injury occurring as a consequence of antibody reacting with antigens on glomerular cell membranes or in glomerular matrix, or immune complex formation occurring on or near glomerular cell membrnes. Many of the structural and functional consequences of these events result from the response of resident glomerular cells to the injury, or may be induced by inflammatory effector cells derived from the circulation. In terms of glomerular cells, injury to the glomerular epithelial cell (GEC) may be induced by: (i) non‐complement fixing antibodies which mimic the glomerular lesions of minimal change nephrotic syndrome/focal glomerular sclerosis; or (ii) by antibodies which fix complement leading to GEC attack by C5b‐9 resulting in a lesion analogous to membranous nephropathy. C5b‐9 also mediates antibody induced injury to the mesangial cell resulting in a mesangioproliferative glomerulonephritis (IgA nephropathy, systemic lupus erythematosus; SLE) as well as to the glomerular endothelial cell (thrombotic microangiopathy, haemolytic uraemic syndrome). the effects of C5b‐9 may be lytic (mesangial cell, glomerular endothelial cell; GEN) or sublytic (GEC) resulting in stimulation of local oxident and protease production. Both lytic and sublytic effects are substantially modulated by cell‐bound complement regulatory proteins such as CD59 and Crry. When fixed or planted antigens are present in larger quantities and accessible to the circulation, complement activation generates chemotactic factors leading to neutrophil infiltration and producing injury through the myeloperoxidase (MPO)‐H2‐O2‐halide system, a mechanism substantially augmented by platelet‐neutrophil interaction (post‐infectious glomerulonephritis [GN], SLE). Macrophages may also be localized in glomeruli by either immune adherence mechanisms or as a consequence of cell mediated immune reactions in the glomerulus. Macrophages differ from neutrophils in producing large amounts of transforming growth factor‐β (TGF‐β) and procoagulants which contribute to crescent formation rapidly progressive glomerulonephritis (RPGN).

The Role of Humoral and Cell-Mediated Adaptive Immune Response

Glomerulonephritis is a major cause of chronic kidney disease worldwide and presents with various histological and clinical manifestations in terms of severity and duration, resulting in diverse clinical outcomes. Immune-mediated injury of the resident glomerular cells plays a critical role in many forms of glomerular injury and mounting evidence indicates that both humoral and cell-mediated mechanisms are involved.