We found that when a site-specific binding protein interacts with the "handle" region of the prorenin prosegment, the prorenin molecule undergoes a conformational change to its enzymatically active state. This nonproteolytic activation is completely blocked by a decoy peptide with the handle region structure, which competitively binds to such a binding protein. Given increased plasma prorenin in diabetes, we examined the hypothesis that the nonproteolytic activation of prorenin plays a significant role in diabetic organ damage. Streptozotocin-induced diabetic rats were treated with subcutaneous administration of handle region peptide. Metabolic and renal histological changes and the renin-Ang system components in the plasma and kidneys were determined at 8, 16, and 24 weeks following streptozotocin treatment. Kidneys of diabetic rats contained increased Ang I and II without any changes in renin, Ang-converting enzyme, or angiotensinogen synthesis. Treatment with the handle region peptide decreased the renal content of Ang I and II, however, and completely inhibited the development of diabetic nephropathy without affecting hyperglycemia. We propose that the nonproteolytic activation of prorenin may be a significant mechanism of diabetic nephropathy. The mechanism and substances causing nonproteolytic activation of prorenin may serve as important therapeutic targets for the prevention of diabetic organ damage.

We found that when a site-specific binding protein interacts with the "handle" region of the prorenin prosegment, the prorenin molecule undergoes a conformational change to its enzymatically active state. This nonproteolytic activation is completely blocked by a decoy peptide with the handle region structure, which competitively binds to such a binding protein. Given increased plasma prorenin in diabetes, we examined the hypothesis that the nonproteolytic activation of prorenin plays a significant role in diabetic organ damage. Streptozotocin-induced diabetic rats were treated with subcutaneous administration of handle region peptide. Metabolic and renal histological changes and the renin-Ang system components in the plasma and kidneys were determined at 8, 16, and 24 weeks following streptozotocin treatment. Kidneys of diabetic rats contained increased Ang I and II without any changes in renin, Ang-converting enzyme, or angiotensinogen synthesis. Treatment with the handle region peptide decreased the renal content of Ang I and II, however, and completely inhibited the development of diabetic nephropathy without affecting hyperglycemia. We propose that the nonproteolytic activation of prorenin may be a significant mechanism of diabetic nephropathy. The mechanism and substances causing nonproteolytic activation of prorenin may serve as important therapeutic targets for the prevention of diabetic organ damage. IntroductionThe most striking abnormalities of the renin-Ang system (RAS) in the blood of diabetic animals are the decreased renin level and the increased prorenin level (1). Indeed, increased blood prorenin levels in human diabetics have been reported to predict microvascular complications (2). Recent studies have demonstrated that transgenic rats expressing prorenin have severe renal histopathology mimicking diabetic nephrosclerosis without hypertension (3) and show evidence that circulating prorenin may enter organs (4). The mechanism whereby intracellular prorenin causes organ damage remained unclear, however.Prorenin has a prosegment of 43 amino acid residues attached to the N terminus of mature (active) renin, and the prosegment folds into an active site cleft of mature renin to prevent catalytically productive interaction with angiotensinogen. When a proreninbinding protein interacts with the "handle" region of the prorenin prosegment, the prorenin molecule undergoes a conformational change to an enzymatically active state (5). This phenomenon is called nonproteolytic activation, and such binding proteins include a specific Ab to the prosegment (5), the N-acyl-D-glucos-

For defining the pathogenic effects of the (pro)renin receptor-transgenic rat, strains that overexpressed the human receptor were generated. Although transgenic rats were normotensive and euglycemic and had a renal angiotensin II (AngII) level that was comparable to that of wild-type rats, transgenic rats developed proteinuria with aging and significant glomerulosclerosis at 28 wk of age. In kidneys of 28-wk-old transgenic rats, mitogen-activated protein kinases (MAPK) were activated without recognizable tyrosine phosphorylation of the EGF receptor, and expression of TGF-␤1 was enhanced. In vivo infusion of the (pro)renin receptor blocker peptide (formerly handle region decoy peptide) significantly inhibited the development of glomerulosclerosis, proteinuria, MAPK activation, and TGF-␤1 expression in the kidneys, but the angiotensin-converting enzyme inhibitor did not attenuate these changes despite a significant decrease in the renal AngII level. In addition, recombinant rat prorenin stimulated MAPK activation in the human receptor-expressed cultured cells, but human receptor was unable to evoke the enzyme activity of rat prorenin. Thus, human (pro)renin receptor elicits slowly progressive nephropathy by AngII-independent MAPK activation in rats. This study clearly provided in vivo evidence for the AngII-independent MAPK activation by human (pro)renin receptor and induction of glomerulosclerosis with increased TGF-␤1 expression. T he (pro)renin receptor is a 350 -amino acid residue protein that has a single transmembrane domain and is expressed in various organs. It binds specifically to renin and prorenin and evokes nonproteolytic activation of prorenin (1), but a recent study showed that the enzymatic activity of the renin in the soluble phase and the receptorbound renin was similar (2). When the receptor binds inactive prorenin of the same species, the receptor-bound prorenin gains its enzyme activity (ability to generate angiotensin I [AngI]) without proteolytic cleavage of the prosegment of prorenin (3) presumably by a conformational change. This nonproteolytic activation of prorenin was considered to play a pivotal role in nephropathy and cardiomyopathy in animals model of diabetes and hypertension (4 -6). More recent studies demonstrated that renin upregulates TGF-␤1 and matrix proteins through a (pro)renin receptor without involving angiotensin II (AngII) in mesangial cells (7) and that the prorenin binding to a (pro)renin receptor plays a key role in the development of diabetic nephropathy in AngII type 1 receptor-deficient mice (8). These observations suggest that the (pro)renin receptor may elicit intracellular signals independent of the renin-angiotensin system (RAS), although it can also evoke the enzyme activity of prorenin.Nguyen et al.(1) produced in vitro evidence to suggest that the AngII-independent mechanisms of (pro)renin receptor action may involve a stimulation of tyrosine phosphorylation that leads to activation of the mitogen-activated protein kinase (MAPK). However, it is difficult to ...

Normal pregnancy relies on a careful balance between immune tolerance and suppression. It is known that strict regulation of maternal immune function, in addition to components of inflammation, is paramount to successful pregnancy, and any imbalance between proinflammatory and anti-inflammatory cytokines and chemokines can lead to aberrant inflammation, often seen in complicated pregnancies. Inflammation in complicated pregnancies is directly associated with increased mortality and morbidity of the mother and offspring. Aberrant inflammatory reactions in complicated pregnancies often lead to adverse outcomes, such as spontaneous abortion, preterm labor, intrauterine growth restriction, and fetal demise. The role of inflammation in different stages of normal pregnancy is reviewed, compared, and contrasted with aberrant inflammation in complicated pregnancies. The complications addressed are preterm labor, pregnancy loss, infection, preeclampsia, maternal obesity, gestational diabetes mellitus, autoimmune diseases, and inflammatory bowel disease. This article examines the role of various inflammatory factors contributing to aberrant inflammation in complicated pregnancies. By understanding the aberrant inflammatory process in complicated pregnancies, novel diagnostic tools and therapeutic interventions for modulating it appropriately can be identified.

The rat recombinant renin/prorenin receptor (AB188298 in DDJB), which conjugated with FLAG epitope in its N-terminus, was expressed in a baculovirus expression system. The recombinant receptor, prepared from the cytoplasmic fraction of the insect cells, was identified by Western blotting using anti-FLAG antibody. Prorenin as well as renin bound to the receptor with different binding affinities. Their K d values were estimated at 8.0 and 20 nM, respectively. The amounts of prorenin and renin bound to the immobilized receptors were 1.0 and 0.2 pmole, respectively. The prorenin bound to the receptor had renin activity and the renin kept the activity at similar level to that before the binding. The K m of their complexes was the same at 3.3 μM when sheep angiotensinogen was used as the substrate. Their V max values were 5.5 and 10 nM•h-1 , respectively. The molecular activities of prorenin and renin bound to the receptor were 1.1 and 10 h-1 , respectively. From these findings, rat prorenin as well as renin was indicated to bind to the recombinant receptor and express the enzymatic activity in vitro.