Senescence-associated phenotypes in Akita diabetic mice are enhanced by absence of bradykinin B2 receptors

We have previously reported that genetically increased angiotensin-converting enzyme levels, or absence of the bradykinin B2 receptor, increase kidney damage in diabetic mice. We demonstrate here that this is part of a more general phenomenon — diabetes and, to a lesser degree, absence of the B2 receptor, independently but also largely additively when combined, enhance senescence-associated phenotypes in multiple tissues. Thus, at 12 months of age, indicators of senescence (alopecia, skin atrophy, kyphosis, osteoporosis, testicular atrophy, lipofuscin accumulation in renal proximal tubule and testicular Leydig cells, and apoptosis in the testis and intestine) are virtually absent in WT mice, detectable in B2 receptor–null mice, clearly apparent in mice diabetic because of a dominant mutation (Akita) in the Ins2 gene, and most obvious in Akita diabetic plus B2 receptor–null mice. Renal expression of several genes that encode proteins associated with senescence and/or apoptosis (TGF-β1, connective tissue growth factor, p53, α-synuclein, and forkhead box O1) increases in the same progression. Concomitant increases occur in 8-hydroxy-2′-deoxyguanosine, point mutations and deletions in kidney mitochondrial DNA, and thiobarbituric acid–reactive substances in plasma, together with decreases in the reduced form of glutathione in erythrocytes. Thus, absence of the bradykinin B2 receptor increases the oxidative stress, mitochondrial DNA damage, and many senescence-associated phenotypes already present in untreated Akita diabetic mice

Transforming growth factor-β1 and diabetic nephropathy

Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy

The kallikrein–kinin system in health and in diseases of the kidney

Since kallikrein was discovered as a vasodilatory substance in human urine, the kallikrein–kinin system (KKS) has been considered to play a physiological role in controlling blood pressure. Gene targeting experiments in mice in which the KKS has been inactivated to varying degrees have, however, questioned this role, because basal blood pressures are not altered. Rather, these experiments have shown that the KKS has a different and important role in preventing changes associated with normal senescence in mice, and in reducing the nephropathy and accelerated senescence-associated phenotypes induced in mice by diabetes. Other experiments have shown that the KKS suppresses mitochondrial respiration, partly by nitric oxide and prostaglandins, and that this suppression may be a key to understanding how the KKS influences senescence-related diseases. Here we review the logical progression and experimental data leading to these conclusions, and discuss their relevance to human conditions

The kallikrein–kinin system and oxidative stress

The Kallikrein-kinin system (KKS) constitutes a complex multi-enzyme cascade that produces several bioactive kinin peptides and their derivatives including bradykinin. In addition to the classical notion of the KKS as a potent vasodilator and a mediator of inflammatory responses, recent studies suggest a link between the KKS and oxidative stress. A number of established mouse model with altered levels of KKS components opened the way to evaluate precise functions of the KKS. Here we review recent findings on the role of the KKS in cardiovascular diseases and chronic kidney diseases, and discuss potential benefits of KKS activation in these diseases

Prolactin alters blood pressure by modulating the activity of endothelial nitric oxide synthase

Prolactin is a hormone secreted by the pituitary gland that controls changes in the breast to enable milk production after the baby is born. In some mothers with pregnancy-related high blood pressure (BP), the concentration of prolactin in the blood is higher than normal, but whether this causes the high BP or is a consequence of it is uncertain. To answer this question, we have generated experimental mice that produce prolactin in the liver when we feed them a substance, indole-3-carbinol (IC3), that is found in broccoli. When fed normal chow, the mice are well, but, when fed IC3, they develop high BP and heart problems. This suggests that pregnant women with abnormally high prolactin levels may need special attention

Rab3a, a small GTP-binding protein, is required for the stabilization of the murine leukaemia virus Gag protein

We recently identified a CD63-interacting protein to understand the role of CD63 in virion production of the human immunodeficiency virus type 1, and we have found that Rab3a forms a complex with CD63. In this study, we analysed the effect of Rab3a on virion production of the murine leukaemia virus (MLV), which is another member of the retrovirus family. We found that Rab3a silencing induced lysosomal degradation of the MLV Gag protein, and recovery of the Rab3a expression restored the level of the Gag protein through a complex formation of MLV Gag and Rab3a, indicating that Rab3a is required for MLV Gag protein expression. In contrast, CD63 silencing decreased the infectivity of released virions but had no effect on virion production, indicating that CD63 facilitates the infectivity of released MLV particles. Although Rab3a induced CD63 degradation in uninfected cells, the complex of MLV Gag and Rab3a suppressed the Rab3a-mediated CD63 degradation in MLV-infected cells. Finally, we found that the MLV Gag protein interacts with Rab3a to stabilize its own protein and CD63 that facilitates the infectivity of released MLV particles. Considering the involvement of Rab3a in lysosome trafficking to the plasma membrane, it may also induce cell surface transport of the MLV Gag protein

Altering the Expression in Mice of Genes by Modifying Their 3′ Regions

Polymorphic differences altering expression of genes without changing their products probably underlie human quantitative traits affecting risks of serious diseases, but methods for investigating such quantitative differences in animals are limited. Accordingly, we have developed a procedure for changing the expression in mice of chosen genes over a 100-fold range while retaining their chromosomal location and transcriptional controls. To develop the procedure, we first dissected the effects in embryonic stem (ES) cells of elements within and downstream of the 3' untranslated region (UTR) of a single copy transgene at the Hprt locus. As expected, protein expression varied with the steady-state level and half-life of the mRNA. The rank order of expression with various tested 3' regions is the same in ES cells, and in cardiomyocytes and trophoblastocytes derived from them. In mice having two functionally different native genes with modified 3'UTRs, the desired expression was obtained