Metformin prevents renal interstitial fibrosis in mice with unilateral ureteral obstruction

Unilateral ureteral obstruction causes important tubulo-interstitial fibrosis in the kidney. Metformin reduces fibrosis in mice with diabetic nephropathy. We examined the effects of metformin in a mouse model of unilateral ureteral obstruction (UUO). Expression of inflammation and fibrosis markers was studied by immunohistochemistry, immunoblot and quantitative real-time polymerase chain reaction. Seven days after UUO, kidneys presented dilated tubules, expansion of the tubulo-interstitial compartment, and significant infiltration of inflammatory cells. Macrophage infiltration and inflammation markers expression were increased in obstructed kidneys and reduced by metformin. Metformin reduced expression of extracellular matrix proteins and profibrotic factor TGFβ in obstructed kidneys, measured by immunohistochemistry. Interstitial fibroblast activation was evident in obstructed kidneys and ameliorated by metformin. UUO did not affect adenosine monophosphate-activated kinase (AMPK) activity, but metformin activated AMPK. Our results show that metformin prevents or slows down the onset of renal inflammation and fibrosis in mice with UUO, an effect that could be mediated by activation of AMPK.

Apelin retards the progression of diabetic nephropathy

Apelin and its receptor APJ have pleiotropic effects in mice and humans and play a protective role in cardiovascular diseases at least partially by inhibiting oxidative stress. Our objective was to study the effect of apelin on the progression of kidney disease in mice with established type 1 diabetes. Ove26 mice with type 1 diabetes received daily subcutaneous injections of apelin for 2 or 14 wk. APJ localizes in the glomeruli and blood vessels of kidneys. Renal APJ expression was reduced in diabetic mice but increased after treatment with apelin. Apelin treatment did not affect glycemia, body weight, or blood pressure in diabetic mice. Whole kidney and glomerular hypertrophy, as well as renal inflammation, including monocyte chemoattractant protein 1 and vascular cell adhesion molecule 1 expression, NF-κB activation, and monocyte infiltration, was inhibited after short and long treatment with apelin. Apelin administration significantly reduced albuminuria at 6 mo. Short treatment with apelin was sufficient to reverse the downregulation of the antioxidant enzyme catalase. Expression of angiotensin II and angiotensin type 1 receptor (AT1) in kidneys from diabetic mice treated was not affected by apelin. These findings show for the first time that apelin exerts a protective effect on the diabetic kidney. Short administration is sufficient to reduce kidney and glomerular hypertrophy as well as renal inflammation, but prolonged treatment is required to improve albuminuria. This effect was independent of the activation of the renin angiotensin system but correlated with upregulation of the antioxidant catalase. Apelin may represent a novel tool to treat diabetic nephropathy.

Molecular events in matrix protein metabolism in the aging kidney

We explored molecular events associated with aging-induced matrix changes in the kidney. C57BL6 mice were studied in youth, middle age, and old age. Albuminuria and serum cystatin C level (an index of glomerular filtration) increased with aging. Renal hypertrophy was evident in middle-aged and old mice and was associated with glomerulomegaly and increase in mesangial fraction occupied by extracellular matrix. Content of collagen types I and III and fibronectin was increased with aging; increment in their mRNA varied with the phase of aging. The content of ZEB1 and ZEB2, collagen type I transcription inhibitors, and their binding to the collagen type Iα2 promoter by ChIP assay also showed age-phase-specific changes. Lack of increase in mRNA and data from polysome assay suggested decreased degradation as a potential mechanism for kidney collagen type I accumulation in the middle-aged mice. These changes occurred with increment in TGFβ mRNA and protein and activation of its SMAD3 pathway; SMAD3 binding to the collagen type Iα2 promoter was also increased. TGFβ-regulated microRNAs (miRs) exhibited selective regulation. The renal cortical content of miR-21 and miR-200c, but not miR-192, miR-200a, or miR-200b, was increased with aging. Increased miR-21 and miR-200c contents were associated with reduced expression of their targets, Sprouty-1 and ZEB2, respectively. These data show that aging is associated with complex molecular events in the kidney that are already evident in the middle age and progress to old age. Age-phase-specific regulation of matrix protein synthesis occurs and involves matrix protein-specific transcriptional and post-transcriptional mechanisms.

Stabilization of HIF-2α through redox regulation of mTORC2 activation and initiation of mRNA translation

HIF-2alpha plays a critical role in renal tumorigenesis. HIF-2alpha is stabilized in Von Hippel-Lindau (VHL)-deficient renal cell carcinoma through mechanisms that require ongoing mRNA translation. Mammalian target of Rapamycin (mTOR) functions in two distinct complexes, Raptor-associated mTORC1 and Rictor-associated mTORC2. Rictor-associated mTORC2 complex has been linked to maintaining HIF-2alpha protein in the absence of VHL, however the mechanisms remain to be elucidated. Although Raptor-associated mTORC1 is a known key upstream regulator of mRNA translation, initiation and elongation, the role of mTORC2 in regulating mRNA translation, is not clear. Complex assembly of the mRNA cap protein, eIF4E, with activators (eIF4G) and inhibitors (4E-BP1) are rate-limiting determinants of mRNA translation. Our laboratory has previously demonstrated that reactive oxygen species, mediated by p22^phox-based Nox oxidases, are enhanced in VHL-deficient cells and play a role in the activation of Akt on S473, a site phosphorylated by the mTORC2 complex. In this study, we examined the role of Rictor-dependent regulation of HIF-2alpha through eIF4E-dependent mRNA translation and examined the effects of p22^phox-based Nox oxidases on TORC2 regulation. We demonstrate for the first time that mTORC2 complex stability and activation is redox sensitive and further defined a novel role for p22^phox-based Nox oxidases in eIF4E-dependent mRNA translation through mTORC2. Furthermore, we provide the first evidence that silencing of p22^phox reduces HIF-2alpha-dependent gene targeting in vitro and tumor formation in vivo. The clinical relevance of these studies is demonstrated.

Large-scale synthesis of 5'-O-pixyl protected 2'-deoxynucleosides useful for oligonucleotide synthesis

Synthesis of 5'-O-pixylated 2'-deoxynucleosides 4 has been accomplished and the products are commercially available.

Pupil cycle time in the long-term neurologic assessment of divers

Pupil cycle time (PCT) is an ophthalmologic technique that measures the speed of nerve conduction throughout the pupil reflex arc. An abnormally prolonged measurement may reveal subtle lesions to the autonomic nervous system. This procedure was applied to the detection of lesions in 10 experienced professional divers and three control groups: 20 non-divers, 20 sport divers, and 10 trainee professional divers. The professional group demonstrated a prolonged mean pupil cycle time compared to other groups (F = 9.732, P < 0.001). Professional divers were significantly older than other subjects, reporting longer diving histories and a higher incidence of decompression sickness. Only professional divers had saturation or trimix experience. Two divers reported long-term visual or cognitive disturbances, but all subjects demonstrated normal visual acuity. Multiple regression analysis indicated that one variable had a predominant (P < 0.01) effect on PCT: the maximum depth attained using mixed gas breathing mixtures. The utility of the technique as a component of long-term neurologic examination is discussed.