Renin angiotensin system modulates mTOR pathway through AT2R in HIVAN

Mammalian target of rapamycin (mTOR) has been reported to contribute to the development of HIV-associated nephropathy (HIVAN). We hypothesized that HIV may be activating renal tissue mTOR pathway through renin angiotensin system (RAS) via Angiotensin Receptor Type II receptor (AT2R). Renal tissues of Vpr transgenic and Tg26 (HIVAN) mice displayed enhanced phosphorylation of mTOR and p70S6K. Aliskiren, a renin inhibitor attenuated phosphorylation of both mTOR and p70S6K in renal tissues of HIVAN mice. Interestingly, Angiotensin Receptor Type I (AT1R) blockade did not modulate renal tissue phosphorylation of mTOR in HIVAN mice; on the other hand, AT2R blockade attenuated renal tissue phosphorylation of mTOR in HIVAN mice. In vitro studies, both renin and Ang II displayed enhanced mouse tubular cell (MTC) phosphorylation of p70S6K in a dose dependent manner. HIV/MTC also displayed enhanced phosphorylation of both mTOR and p70S6K; interestingly this effect of HIV was further enhanced by losartan (an AT1R blocker). On the other hand, AT2R blockade attenuated HIV-induced tubular cell phosphorylation of mTOR and p70S6K, whereas, AT2R agonist enhanced phosphorylation of mTOR and p70S6K. These findings indicate that HIV stimulates mTOR pathway in HIVAN through the activation of renin angiotensin system via AT2R.     

Mechanisms of angiotensin II signaling on cytoskeleton of podocytes

Podocytes are significant in establishing the glomerular filtration barrier. Sustained rennin–angiotensin system (RAS) activation is crucial in the pathogenesis of podocyte injury and causes proteinuria. This study demonstrates that angiotensin II (Ang II) caused a reactive oxygen species (ROS)-dependent rearrangement of cortical F-actin and a migratory phenotype switch in cultured mouse podocytes with stable Ang II type 1 receptor (AT1R) expression. Activated small GTPase Rac-1 and phosphorylated ezrin/radixin/moesin (ERM) proteins provoked Ang II-induced F-actin cytoskeletal remodeling. This work also shows increased expression of Rac-1 and phosphorylated ERM proteins in cultured podocytes, and in glomeruli of podocyte-specific AT1R transgenic rats (Neph-hAT1 TGRs). The free radical scavenger DMTU eliminated Ang II-induced cell migration, ERM protein phosphorylation and cortical F-actin remodeling, indicating that ROS mediates the influence of Rac-1 on podocyte AT1R signaling. Heparin, a potent G-coupled protein kinase 2 inhibitor, was found to abolish ERM protein phosphorylation and cortical F-actin ring formation in Ang II-treated podocytes, indicating that phosphorylated ERM proteins are the cytoskeletal effector in AT1R signaling. Moreover, Ang II stimulation triggered down-regulation of α actinin-4 and reduced focal adhesion expression in podocytes. Signaling inhibitor assay of Ang II-treated podocytes reveals that Rac-1, RhoA, and F-actin reorganization were involved in expressional regulation of α actinin-4 in AT1R signaling. With persistent RAS activation, the Ang II-induced phenotype shifts from being dynamically stable to adaptively migratory, which may eventually exhaust podocytes with a high actin cytoskeletal turnover, causing podocyte depletion and focal segmental glomerulosclerosis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adverse host factors exacerbate occult HIV-associated nephropathy

In the present study, we hypothesized that HIV-1-induced occult HIV-associated nephropathy (HIVAN) would become apparent in the presence of adverse host factors. To test our hypothesis, Vpr mice (which display doxycycline-dependent Vpr expression in podocytes) with two, three, and four copies of the angiotensinogen (Agt) gene (Vpr-Agt-2, Vpr-Agt-3, and Vpr-Agt-4) were administered doxycycline for 3 weeks (to develop clinically occult HIVAN) followed by doxycycline-free water during the next 3 weeks. Subsequently, renal biomarkers were measured, and kidneys were harvested for renal histology. Vpr-Agt-2 developed neither proteinuria nor elevated blood pressure, and displayed minimal glomerular and tubular lesions only, without any microcyst formation. Vpr-Agt-3 showed mild glomerular and tubular lesions and microcyst formation, whereas Vpr-Agt-4 showed moderate proteinuria, hypertension, glomerular sclerosis, tubular dilation, microcysts, and expression of epithelial mesenchymal transition markers. Vpr-Agt-4 not only displayed enhanced renal tissue expression of Agt, renin, and angiotensin-converting enzyme, but also had higher renal tissue concentrations of angiotensin II. Moreover, renal cells in Vpr-Agt-4 showed enhanced expression of transforming growth factor-β, connective tissue growth factor, and vascular endothelial growth factor. These findings indicate that adverse host factors, such as the activation of the renin-angiotensin system, promote the progression of occult HIVAN to apparent HIVAN.     

Interstitial fibroblast-like cells express renin-angiotensin system components in a fibrosing murine kidney

Recently, the renin-angiotensin system (RAS) was implicated in organ fibrosis. However, few studies have examined the localization of RAS components, such as angiotensin II receptors, renin (REN), angiotensinogen (AGTN), and angiotensin-converting enzyme (ACE), in the fibrosing kidney. To localize these components in the fibrosing kidney, we used a murine model of renal fibrosis that shows an enhanced expression of angiotensin II type 1A receptor (AT(1A)R) and AGTN. Our results indicate that the overall expression of angiotensin II type 2 receptor (AT(2)R) and ACE was attenuated in this model, whereas REN expression was unchanged. In addition to tubular epithelial cells that were positive for AT(1A)R, AT(2)R, REN, and AGTN, interstitial fibroblast-like cells expressed AT(1A)R, REN, AGTN, and ACE in the fibrosing kidney. The interstitial fibroblast-like cells that were positive for AT(1A)R mRNA were further characterized as positive for the expression of vimentin and transforming growth factor-beta1. These data provide strong evidence for a tubulointerstitial RAS within the fibrosing kidney, and a linkage between the RAS and renal fibrogenesis.     

SIRT1 deficiency downregulates PTEN/JNK/FOXO1 pathway to block reactive oxygen species-induced apoptosis in mouse embryonic stem cells

Silent mating type information regulation 2 homolog 1 (SIRT1) plays a critical role in reactive oxygen species-triggered apoptosis in mouse embryonic stem (mES) cells. Here, we investigated a possible role for the PTEN/Akt/JNK pathway in the SIRT1-mediated apoptosis pathway in mES cells. Akt was activated by removal of anti-oxidant 2-mercaptoethanol in SIRT1(-/-) mES cells. Since PTEN is a negative regulator of Akt and its activity can be modulated by acetylation, we investigated if SIRT1 deacetylated PTEN to downregulate Akt to trigger apoptosis in anti-oxidant-free culture conditions. PTEN was hyperacetylated and excluded from the nucleus in SIRT1(-/-) mES cells, consistent with enhanced Akt activity. SIRT1 deficiency enhanced the acetylation/phosphorylation level of FOXO1 and subsequently inhibited the nuclear localization of FOXO1. Cellular acetylation levels were enhanced by DNA-damaging agent, not by removal of anti-oxidant. c-Jun NH2-terminal kinase (JNK) was activated by removal of anti-oxidant in SIRT1-dependent manner. Although p53 acetylation was stronger in SIRT1(-/-) mES cells, DNA-damaging stress activated phosphorylation and enhanced cellular levels of p53 irrespective of SIRT1, whereas removal of anti-oxidant slightly activated p53 only with SIRT1. Expression levels of Bim and Puma were increased in anti-oxidant-free culture conditions in an SIRT1-dependent manner and treatment with JNK inhibitor blocked induction of Bim expression. DNA-damaging agent activated caspase3 regardless of SIRT1. Our data support an important role for SIRT1 in preparing the PTEN/JNK/FOXO1 pathway to respond to cellular reactive oxygen species.     

AT2R deficiency mediated podocyte loss via activation of ectopic hedgehog interacting protein (Hhip) gene expression

Angiotensin II type 2 receptor (AT₂R) deficiency in AT₂R knockout (KO) mice has been linked to congenital abnormalities of the kidney and urinary tract; however, the mechanisms by which this occurs are poorly understood. In this study, we examined whether AT₂R deficiency impaired glomerulogenesis and mediated podocyte loss/dysfunction in vivo and in vitro. Nephrin‐cyan fluorescent protein (CFP)‐transgenic (Tg) and Nephrin/AT₂RKO mice were used to assess glomerulogenesis, while wild‐type and AT₂RKO mice were used to evaluate maturation of podocyte morphology/function. Immortalized mouse podocytes (mPODs) were employed for in vitro studies. AT₂R deficiency resulted in diminished glomerulogenesis in E15 embryos, but had no impact on actual nephron number in neonates. Pups lacking AT₂R displayed features of renal dysplasia with lower glomerular tuft volume and podocyte numbers. In vivo and in vitro studies demonstrated that loss of AT₂R was associated with elevated NADPH oxidase 4 levels, which in turn stimulated ectopic hedgehog interacting protein (Hhip) gene expression in podocytes. Consequently, ectopic Hhip expression activation either triggers caspase‐3 and p53‐related apoptotic processes resulting in podocyte loss, or activates TGFβ1–Smad2/3 cascades and α‐SMA expression to transform differentiated podocytes to undifferentiated podocyte‐derived fibrotic cells. We analyzed HHIP expression in the kidney disease database (Nephroseq) and then validated this using HHIP immunohistochemistry staining of human kidney biopsies (controls versus focal segmental glomerulosclerosis). In conclusion, loss of AT₂R is associated with podocyte loss/dysfunction and is mediated, at least in part, via augmented ectopic Hhip expression in podocytes. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Inhibition of p53 function prevents renin-angiotensin system activation and stretch-mediated myocyte apoptosis

To determine whether stretch-induced activation of p53 is necessary for the up-regulation of the local renin-angiotensin system and angiotensin II (Ang II)-induced apoptosis, ventricular myocytes were infected with an adenoviral vector carrying mutated p53, Adp53m, before 12 hours of stretch. Noninfected myocytes and myocytes infected with AdLacZ served as controls. Stretching of Adp53m-infected myocytes prevented stimulation of p53 function that conditioned the expression of p53-dependent genes; quantity of angiotensinogen (Aogen), AT(1), and Bax decreased, whereas Bcl-2 increased. Ang II generation was not enhanced by stretch. Conversely, stretch produced opposite changes in noninfected and AdLacZ-infected myocytes: Aogen increased twofold, AT(1) increased 2. 1-fold, Bax increased 2.5-fold, and Ang II increased 2.4-fold. These responses were coupled with 4.5-fold up-regulation of wild-type p53. Stretch elicited comparable adaptations in p53-independent genes, in the presence or absence of mutated p53; renin increased threefold, angiotensin-converting enzyme increased ninefold, and AT(2) increased 1.7-fold. Infection with Adp53m inhibited myocyte apoptosis after stretch. Conversely, stretch increased apoptosis by 6.2-fold in myocytes with elevated endogenous wild-type p53. Thus, a competitor of p53 function interfered with both stretch-induced Ang II formation and apoptosis, indicating that p53 is a major modulator of myocyte renin-angiotensin system and cell survival after mechanical deformation.     

SIRT1通过降低NF-κB p65乙酰化减轻高糖应激引起的大鼠肾小球系膜细胞损伤*

 目的： 研究沉默信息调节因子1（SIRT1）对高糖诱导的大鼠肾小球系膜细胞NF-κB p65蛋白乙酰化影响及其保护作用。方法: 培养大鼠肾小球系膜细胞,实验分为5组：正常对照组、甘露醇组、高糖组、白藜芦醇组和SIRT1 RNAi组。MTT比色法检测细胞活性;以实时荧光定量PCR检测SIRT1、单核细胞趋化蛋白1（MCP-1）、血管黏附分子1（VCAM-1）、肿瘤坏死因子α（TNF-α）和转化生长因子β1（TGF-β1）mRNA水平;Western blotting检测SIRT1和NF-κB p65乙酰化蛋白的表达水平,ELISA检测MCP-1、VCAM-1、TNF-α、TGF-β1和丙二醛（MDA）的含量。结果: 高糖刺激使肾小球系膜细胞的活力降低,超氧化物岐化酶（SOD）活性降低,MDA含量增加;SIRT1 mRNA及蛋白表达降低,NF-κB p65蛋白乙酰化水平增高,MCP-1、VCAM-1、TNF-α、TGF-β1 mRNA和蛋白水平增高。白藜芦醇可逆转高糖引起的变化,而沉默SIRT1基因使高糖诱导的系膜细胞NF-κB p56乙酰化水平、MCP-1、VCAM-1、TNF-α、TGF-β1 mRNA和蛋白水平升高。结论: 高糖可降低SIRT1水平,增加炎症因子的表达。SIRT1的激活可使NF-κB 的亚单位RelA/p65去乙酰化,从而抑制炎症因子的产生。SIRT1可作为治疗DN的潜在靶点。     

Podocytes are new cellular targets of haemoglobin‐mediated renal damage

Recurrent and massive intravascular haemolysis induces proteinuria, glomerulosclerosis, and progressive impairment of renal function, suggesting podocyte injury. However, the effects of haemoglobin (Hb) on podocytes remain unexplored. Our results show that cultured human podocytes or podocytes isolated from murine glomeruli bound and endocytosed Hb through the megalin–cubilin receptor system, thus resulting in increased intracellular Hb catabolism, oxidative stress, activation of the intrinsic apoptosis pathway, and altered podocyte morphology, with decreased expression of the slit diaphragm proteins nephrin and synaptopodin. Hb uptake activated nuclear factor erythroid‐2‐related factor 2 (Nrf2) and induced expression of the Nrf2‐related antioxidant proteins haem oxygenase‐1 (HO‐1) and ferritin. Nrf2 activation and Hb staining was observed in podocytes of mice with intravascular haemolysis. These mice developed proteinuria and showed podocyte injury, characterized by foot process effacement, decreased synaptopodin and nephrin expression, and podocyte apoptosis. These pathological effects were enhanced in Nrf2‐deficient mice, whereas Nrf2 activation with sulphoraphane protected podocytes against Hb toxicity both in vivo and in vitro. Supporting the translational significance of our findings, we observed podocyte damage and podocytes stained for Hb, HO‐1, ferritin and phosphorylated Nrf2 in renal sections and urinary sediments of patients with massive intravascular haemolysis, such as atypical haemolytic uraemic syndrome and paroxysmal nocturnal haemoglobinuria. In conclusion, podocytes take up Hb both in vitro and during intravascular haemolysis, promoting oxidative stress, podocyte dysfunction, and apoptosis. Nrf2 may be a potential therapeutic target to prevent loss of renal function in patients with intravascular haemolysis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Local bone interaction between renin-angiotensin system and kallikrein-kinin system in diabetic rat

Objective: This study was performed to investigate bone deteriorations and the involvement of skeletal renin-angiotensin system (RAS) and kallikrein-kinin system (KKS) of male rat in response to the hyperglycemia. Methods: The biomarkers in serum and urine were measured by ELISA kit, and tibias were taken for the measurement on gene, protein expression and histological analysis, feumrs were taken for the measurement on biomechanical parameters and micro-CT. Results: The DM1 showed the decreased level of osteocalcin, testosterone and FGF-23, and the increased level of serum CTX as compared to those of vehicle group. The H&E staining showed remarkable bone deteriorations, including increased disconnections and separation of trabecular bone among growth plate and joint cartilage in DM1 group. Biomechanically, the maximum load, maximum stress, and strain parameter of DM1 group was significantly lower than control group. Type 1 diabetic mice displayed bone loss shown the reduction of bone volume/total volume, trabecular number, trabecular thickness and bone mineral density. The STZ injection significantly up-regulated mRNA expression of AT1R, AGT, renin, renin-receptor, and ACE, and the expression of AT2R, B1R and B2R were down-regulated in tibia of rat in hyperglycemia group. The protein expression of renin, ACE and Ang II were significantly up-regulated, and AT2R, B1R and B2R were down-regulated in DM1 group. Conclusions: The treatment of hyperglycemia was detrimental to bone as compared to the vehicle group, and the underlying mechanism was mediated, at least partially, through down-regulation of KSS activity and up-regulation of RAS activity in local bone.     

Amelioration of crescentic glomerulonephritis by RhoA kinase inhibitor, Fasudil, through podocyte protection and prevention of leukocyte migration

The small GTPase RhoA is activated by the angiotensin II (AngII) type 1 receptor (AT1R), which is part of the local renin-angiotensin system that is involved in podocyte injury preceding glomerular crescent formation. We demonstrated previously that inhibition of AT1R protects against crescentic glomerular injury in Fc receptor-deficient mice (gamma -/-) with anti-glomerular basement membrane antibody-induced glomerulonephritis (anti-GBM GN). Here, we hypothesized that the RhoA kinase inhibitor, fasudil, attenuates AT1R-dependent crescentic GN. We examined anti-GBM GN in gamma -/- mice with or without fasudil treatment, and further investigated the underlying mechanisms in cultured differentiated podocytes and leukocytes. Fasudil markedly attenuated crescentic GN with a significant decrease in proteinuria and hematuria, infiltration of T cells and monocytes/macrophages as well as their local proliferation, and preservation of podocyte-specific proteins, including WT-1 and nephrin, in glomeruli. In vitro studies showed that AngII induced the down-regulation of both nephrin and WT-1 expression in podocytes, which was reversed by fasudil in a dose-dependent manner. Additionally, fasudil blocked the AngII-induced migration of both macrophages and T cells. Furthermore, we also examined lipopolysaccharide-induced nephrotic syndrome in severe combined immunodeficiency disease mice and found that fasudil failed to block the development of proteinuria because of a B7-1-dependent podocyte injury. In conclusion, fasudil treatment prevents crescent formation and disease progression in anti-GBM GN by preventing AngII-induced podocyte injury and leukocyte migration.     

Murine Denys-Drash syndrome: evidence of podocyte de-differentiation and systemic mediation of glomerulosclerosis

Denys-Drash syndrome (DDS) is caused by dominant mutations of the Wilms' tumour suppressor gene, WT1, and characterized by a nephropathy involving diffuse mesangial sclerosis, male pseudohermaphroditism and/or Wilms' tumourigenesis. Previously, we reported that heterozygosity for the Wt1tmT396 mutation induces DDS in heterozygous and chimeric (Wt1tmT396/+<-->+/+) mice. In the present study, the fate of Wt1 mutant cells in chimeric kidneys was assessed by in situ marker analysis, and immunocytochemistry was used to re-examine the claim that glomerulosclerosis (GS) is caused by loss of WT1 and persistent Pax-2 expression by podocytes. Wt1 mutant cells colonized glomeruli efficiently, including podocytes, but some sclerotic glomeruli contained no detectable Wt1 mutant cells. The development of GS was preceded by widespread loss of ZO-1 signal in podocytes (even in kidneys where <5% of glomeruli contained Wt1 mutant podocytes), increased intra-renal renin expression, and de novo podocyte TGF-beta1 expression, but not podocyte Pax-2 expression or loss of WT1, synaptopodin, alpha-actinin-4 or nephrin expression. However, podocytes in partially sclerotic glomeruli that still expressed WT1 at high levels showed reduced vimentin expression, cell cycle re-entry, and re-expressed desmin, cytokeratin and Pax-2. The results suggest that: (i) GS is not due to loss of WT1 expression by podocytes; (ii) podocyte Pax-2 expression reflects re-expression rather than persistent expression, and is the consequence of GS; (iii) GS is mediated systemically and the mechanism involves activation of the renin-angiotensin system; and (iv) podocytes undergo typical maturational changes but subsequently de-differentiate and revert to an immature phenotype during disease progression.     

Podocyte loss involves MDM2‐driven mitotic catastrophe

Podocyte apoptosis as a pathway of podocyte loss is often suspected but rarely detected. To study podocyte apoptosis versus inflammatory forms of podocyte death in vivo, we targeted murine double minute (MDM)‐2 for three reasons. First, MDM2 inhibits p53‐dependent apoptosis; second, MDM2 facilitates NF‐κB signalling; and third, podocytes show strong MDM2 expression. We hypothesized that blocking MDM2 during glomerular injury may trigger p53‐mediated podocyte apoptosis, proteinuria, and glomerulosclerosis. Unexpectedly, MDM2 blockade in early adriamycin nephropathy of Balb/c mice had the opposite effect and reduced intra‐renal cytokine and chemokine expression, glomerular macrophage and T‐cell counts, and plasma creatinine and blood urea nitrogen levels. In cultured podocytes exposed to adriamycin, MDM2 blockade did not trigger podocyte death but induced G2/M arrest to prevent aberrant nuclear divisions and detachment of dying aneuploid podocytes, a feature of mitotic catastrophe in vitro and in vivo. Consistent with these observations, 12 of 164 consecutive human renal biopsies revealed features of podocyte mitotic catastrophe but only in glomerular disorders with proteinuria. Furthermore, delayed MDM2 blockade reduced plasma creatinine levels, blood urea nitrogen, tubular atrophy, interstitial leukocyte numbers, and cytokine expression as well as interstitial fibrosis. Together, MDM2‐mediated mitotic catastrophe is a previously unrecognized variant of podocyte loss where MDM2 forces podocytes to complete the cell cycle, which in the absence of cytokinesis leads to podocyte aneuploidy, mitotic catastrophe, and loss by detachment. MDM2 blockade with nutlin‐3a could be a novel therapeutic strategy to prevent renal inflammation, podocyte loss, glomerulosclerosis, proteinuria, and progressive kidney disease. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

RAS及其基因多态性与原发性高血压

肾素-血管紧张素系统(RAS)在调节盐代谢和血压的调控以及高血压的发病中起着重要的作用,RAS是迄今为止研究最广泛的高血压相关基因。现对RAS中的3个重要成员血管紧张素转换酶(ACE)、血管紧张素原(AGT)和血管紧张素Ⅱ1型受体(AT1R)的特性、分布、基因定位、基因结构、基因多态性及其与高血压的关系进行了系统的综述。     

蛇床子素通过抑制SIRT1的表达增强阿霉素对p53野生型前列腺癌细胞的凋亡诱导活性

目的:探讨中药活性成分蛇床子素对阿霉素抗前列腺癌作用的影响及机制。方法:MTT法检测前列腺癌细胞系LNCaP在阿霉素和蛇床子素处理下的细胞活力。Western blot实验检测阿霉素和蛇床子素对LNCaP细胞中沉默信息调节因子1(SIRT1)、p53、乙酰化p53和Puma的表达水平、细胞色素C的释放水平及caspase-9和caspase-3活化水平的影响。流式细胞术检测阿霉素和蛇床子素对LNCaP细胞凋亡的影响。结果:蛇床子素联合治疗能明显提高阿霉素对p53野生型前列腺癌细胞系LNCaP的杀伤力。蛇床子素处理能显著抑制LNCaP细胞中SIRT1的表达,转染SIRT1过表达质粒后,蛇床子素、阿霉素联合治疗对LNCaP细胞的杀伤力受到显著抑制(P0.05)。蛇床子素联合阿霉素显著升高LNCaP细胞p53蛋白的表达水平和乙酰化水平,转染p53 si RNA后,蛇床子素对阿霉素的协同作用明显减弱。蛇床子素联合阿霉素显著诱导LNCaP细胞细胞色素C从线粒体释放到细胞质中,增强细胞中的caspase-9及下游caspase-3的活性并诱导细胞发生凋亡。结论:蛇床子素通过下调前列腺癌LNCaP细胞中SIRT1的表达促进阿霉素诱导的p53依赖的细胞凋亡。     

Nef interaction with actin compromises human podocyte actin cytoskeletal integrity

The HIV-1 accessory protein Nef is considered to play an important role in the development of a podocyte phenotype in HIV-1 associated nephropathy. We hypothesized that Nef may be altering the podocyte phenotype both structurally and functionally. To elucidate the involved mechanisms, podocyte proteins interacting with Nef were identified using GST pull down assay and yeast two hybrid assay. The GST pull down assay on protein extracts made from stable colonies of conditionally immortalized human podocytes expressing Nef (Nef/CIHP) displayed a band at 45 kD, which was identified as actin by mass spectrometry. Yeast two hybrid assay identified the following Nef-interacting proteins: syntrophin, filamin B, syntaxin, translational elongation factor 1, and zyxin. The Nef–actin and Nef–zyxin interactions were confirmed by co-localization studies on Nef/CIHP stable cell lines. The co-localization studies also showed that Nef/CIHP stable cell lines had a decreased number of actin filaments (stress fibers), displayed formation of lamellipodia, and increased number of podocyte projections (filopodia). Nef/CIHP displayed an enhanced cortical F-actin score index (P < 0.001) and thus indicated a reorganization of F-actin in the cortical regions. Microarray analysis showed that Nef enhanced the expression of Rac1, syndecan-4, Rif, and CDC42 and attenuated the expression of syndecan-3 and syntenin. In addition, Nef/CIHPs displayed a diminished sphingomyelinase (ASMase) activity. Functionally, Nef/CIHPs displayed diminished attachment and enhanced detachment to their substrate. These findings indicate that Nef interaction with actin compromises the podocyte cytoskeleton integrity.     

The renin-angiotensin system in kidney development

All components of the renin-angiotensin system (RAS) are highly expressed in the developing kidney in a pattern suggesting a role for angiotensin II in renal development. In support of this notion, pharmacological interruption of angiotensin II type-1 (AT(1)) receptor signalling in animals with an ongoing nephrogenesis produces specific renal abnormalities characterized by papillary atrophy, abnormal wall thickening of intrarenal arterioles, tubular atrophy associated with expansion of the interstitium, and a marked impairment in urinary concentrating ability. Similar changes in renal morphology and function develop also in mice with targeted inactivation of genes encoding renin, angiotensinogen, angiotensin-converting enzyme, or both AT(1) receptor isoforms simultaneously. Taken together, these results clearly indicate that an intact signalling through AT(1) receptors is a prerequisite for normal renal development. The present report mainly reviews the renal abnormalities induced by blocking the RAS pharmacologically in experimental animal models. In addition, pathogenetic mechanisms are discussed.     

Effects of placental insufficiency on the ovine fetal renin-angiotensin system

We postulated that chronic placental insufficiency would be associated with reduced expression of renal renin and angiotensinogen genes in the fetal sheep. Placental development was restricted in ewes by removing the majority of caruncles prior to mating (placentally restricted (PR) group). The weights of PR fetuses were significantly reduced (P < 0.05, 2.98 +/- 0.33 kg) compared to control fetuses (4.20 +/- 0.30 kg). Kidney weights were also significantly reduced in the PR fetuses (P < 0.05, 8.4 +/- 0.9 g) compared with control fetuses (12.2 +/- 1.3 g). The ratios of renal renin/-actin mRNA levels were significantly reduced in PR fetuses (P < 0.001, 0.35 +/- 0.02) when compared to control animals (0.98 +/- 0.13). The renal angiotensinogen mRNA/18S rRNA ratio was significantly lower (P < 0.05, 0.28 +/- 0.13) in PR fetuses compared with control fetuses (0.72 +/- 0.10), while hepatic angiotensinogen was unaffected. There was a positive correlation between renal renin mRNA and renal angiotensinogen mRNA levels (r = 0.65, P < 0.05, n = 12). It is unlikely that these changes in renal angiotensinogen and renin mRNA were due to the small increment in plasma cortisol levels (< 5 nmol l-1). There was, however, a positive correlation between arterial PO2 and renal renin mRNA (r2 = 0.77, P < 0.01). Plasma renin levels were not different between the two groups. Thus, restriction of nutrient and oxygen supply throughout fetal life was associated with suppression of renal renin and renal angiotensinogen gene expression, with no effect on hepatic angiotensinogen mRNA levels. This specific suppression of fetal renal renin and angiotensinogen expression could alter the activity of the intrarenal RAS and so affect growth and development of the kidney.     

SIRT1, a histone deacetylase, regulates prion protein-induced neuronal cell death

Prion diseases associated with the conversion of the cellular prion protein (PrP(C)) to the misfolded isoform (PrP(Sc)), affect the central nervous system (CNS) of humans and animals. Resveratrol, an activator of class III histone deacetylase SIRT1, is important in attenuating cellular injury and oxidative stress. The present study investigated the effects of SIRT1 activation on prion protein-mediated neuronal cell death and examined its possible signals in intracellular apoptotic pathways. Resveratrol treatment significantly increased both SIRT1 protein expression and SIRT1 activity and protected neuronal cells against PrP (106-126)-induced cell death. Resveratrol-mediated SIRT1 activation decreased the acetylation of p53 and p65 induced by prion protein and SIRT1 inhibitor. SIRT1 activation also inhibited PrP (106-126)-mediated p38 mitogen-activating protein kinase (MAPK) activation and caspase-3 cleavage, and increased the expression of anti-apoptotic Bcl-xL protein. Furthermore, SIRT1 overexpression by using adenoviral vector protected neuronal cells against PrP (106-126). These results indicate that resveratrol inhibits PrP (106-126)-induced neuronal cell death by regulating SIRT1 activity and SIRT-related signaling, and suggest that prion-related disease may be attenuated by SIRT1 activation or by intake of SIRT1-activating molecules.