Lorena Amadio

Accelerated diabetic glomerulopathy in galectin-3/AGE receptor 3 knockout mice

Several molecules were shown to bind advanced glycation end products (AGEs) in vitro, but it is not known whether they all serve as AGE receptors and which functional role they play in vivo. We investigated the role of galectin‐3, a multifunctional lectin with (anti)adhesive and growth‐regulating properties, as an AGE receptor and its contribution to the development of diabetic glomerular disease, using a knockout mouse model. Galectin‐3 knockout mice obtained by gene ablation and the corresponding wild‐type mice were rendered diabetic with streptozotocin and killed 4 months later, together with age‐matched nondiabetic controls. Despite a comparable degree of metabolic derangement, galectin‐3‐deficient mice developed ac‐celerated glomerulopathy vs. the wild‐type animals, as evidenced by the more pronounced increase in protein‐uria, extracellular matrix gene expression, and mesan‐gial expansion. This was associated with a more marked renal/glomerular AGE accumulation, indicating it was attributable to the lack of galectin‐3 AGE receptor function. The galectin‐3‐deficient genotype was associated with reduced expression of receptors implicated in AGE removal (macrophage scavenger receptor A and AGE‐R1) and increased expression of those mediating cell activation (RAGE and AGE‐R2). These results show that the galectin‐3‐regulated AGE receptor pathway is operating in vivo and protects toward AGE‐induced tissue injury in contrast to that through RAGE.—Pugliese, G., Pricci, F., Iacobini, C., Leto, G., Amadio, L., Barsotti, P., Frigeri L., Hsu, D. K., Vlassara, H., Liu, F.‐T., Di Mario, U. Accelerated diabetic glomerulopathy in galectin‐3/AGE receptor 3 knockout mice. FASEB J. 15, 2471–2479 (2001)

Deletion of p66Shc Longevity Gene Protects Against Experimental Diabetic Glomerulopathy by Preventing Diabetes-Induced Oxidative Stress

p66Shc regulates both steady-state and environmental stress-dependent reactive oxygen species (ROS) generation. Its deletion was shown to confer resistance to oxidative stress and protect mice from aging-associated vascular disease. This study was aimed at verifying the hypothesis that p66Shc deletion also protects from diabetic glomerulopathy by reducing oxidative stress. Streptozotocin-induced diabetic p66Shc knockout (KO) mice showed less marked changes in renal function and structure, as indicated by the significantly lower levels of proteinuria, albuminuria, glomerular sclerosis index, and glomerular and mesangial areas. Glomerular content of fibronectin and collagen IV was also lower in diabetic KO versus wild-type mice, whereas apoptosis was detected only in diabetic wild-type mice. Serum and renal tissue advanced glycation end products and plasma isoprostane 8-epi-prostaglandin F2α levels and activation of nuclear factor κB (NF-κB) were also lower in diabetic KO than in wild-type mice. Mesangial cells from KO mice grown under high-glucose conditions showed lower cell death rate, matrix production, ROS levels, and activation of NF-κB than those from wild-type mice. These data support a role for oxidative stress in the pathogenesis of diabetic glomerulopathy and indicate that p66Shc is involved in the molecular mechanism(s) underlying diabetes-induced oxidative stress and oxidant-dependent renal injury.

Galectin-3/AGE-receptor 3 knockout mice show accelerated AGE-induced glomerular injury: evidence for a protective role of galectin-3 as an AGE receptor

We previously showed that mice lacking galectin‐3/AGE‐receptor 3 develop accelerated diabetic glomerulopathy. To further investigate the role of galectin‐3/AGE‐receptor function in the pathogenesis of diabetic renal disease, galectin‐3 knockout (KO) and coeval wild‐type (WT) mice were injected for 3 months with 30 μg/day of Nε‐carboxymethyllysine (CML)‐modified or unmodified mouse serum albumin (MSA). Despite receiving equal doses of CML, KO had higher circulating and renal AGE levels and showed more marked renal functional and structural changes than WT mice, with significantly higher proteinuria, albuminuria, glomerular, and mesangial area and glomerular sclerosis index. Renal 4‐hydroxy‐2‐nonenal content and NFκB activation were also more pronounced in KO‐CML vs. WT‐CML. Kidney mRNA levels of fibronectin, laminin, collagen IV, and TGF‐β were up‐regulated, whereas those of matrix metalloproteinase‐2 and ‐14 were down‐regulated, again more markedly in KO‐CML than WT‐CML mice. Basal and CML‐induced RAGE and 80K‐H mRNA levels were higher in KO vs. WT mice. MSA injection did not produce any significant effect in both genotypes. The association of galectin‐3 ablation with enhanced susceptibility to AGE‐induced renal disease, increased AGE levels and signaling, and altered AGE‐receptor pattern indicates that galectin‐3 is operating in vivo as an AGE receptor to afford protection toward AGE‐dependent tissue injury.

Role of Galectin-3 in Diabetic Nephropathy

The advanced glycosylation end products (AGE) participate in the pathogenesis of nephropathy and other diabetic complications through several mechanisms, including their binding to cell surface receptors. The AGE receptors include RAGE, the macrophage scavenger receptors, OST-48 (AGE-R1), 80K-H (AGE-R2), and galectin-3 (AGE-R3). Galectin-3 interacts with the beta-galactoside residues of cell surface and matrix glycoproteins via the carbohydrate recognition domain and with intracellular proteins via peptide-peptide associations mediated by its N-terminus domain. These structural properties enable galectin-3 to exert multiple functions, including the mRNA splicing activity, the control of cell cycle, the regulation of cell adhesion, the modulation of allergic reactions, and the binding of AGE. The lack of transmembrane anchor sequence or signal peptide suggests that it is associated with other AGE receptors, possibly AGE-R1 and AGE-R2, to form an AGE-receptor complex, rather than playing an independent role. In target tissues of diabetic vascular complications, such as the endothelium and mesangium, galectin-3 is weakly expressed under basal conditions and is markedly upregulated by the diabetic milieu (and to a lesser extent by aging). Galectin-3-deficient mice were found to develop accelerated diabetic glomerulopathy versus the wild-type animals, as evidenced by the more pronounced increase in proteinuria, mesangial expansion, and matrix gene expression. This was associated with a more marked renal/glomerular AGE accumulation, suggesting that it was attributable to the lack of galectin-3 AGE-receptor function. These data indicate that galectin-3 is upregulated under diabetic conditions and is operating in vivo to provide protection toward AGE-induced tissue injury, as opposed to RAGE.

Oxidative stress in diabetes-induced endothelial dysfunction involvement of nitric oxide and protein kinase C.

Reactive oxygen species (ROS) formation plays a major role in diabetes-induced endothelial dysfunction, though the molecular mechanism(s) involved and the contribution of nitric oxide (NO) are still unclear. This study using bovine retinal endothelial cells was aimed at assessing (i) the role of oxygen-dependent vs. NO-dependent oxidative stress in the endothelial cell permeability alterations induced by the diabetic milieu and (ii) whether protein kinase C (PKC) activation ultimately mediates these changes. Superoxide, lipid peroxide, and PKC activity were higher under high glucose (HG) vs. normal glucose throughout the 30 d period. Nitrite/nitrate and endothelial NO synthase levels increased at 1 d and decreased thereafter. Changes in monolayer permeability to 125I-BSA induced by 1 or 30 d incubation in HG or exposure to advanced glycosylation endproduct were reduced by treatment with antioxidants or PKC inhibitors, whereas NO blockade prevented only the effect of 1 d HG. HG-induced changes were mimicked by a PKC activator, a superoxide generating system, an NO and superoxide donor, or peroxynitrite (attenuated by PKC inhibition), but not a NO donor. The short-term effect of HG depends on a combined oxidative and nitrosative stress with peroxynitrite formation, whereas the long-term effect is related to ROS generation; in both cases, PKC ultimately mediates permeability changes.

Increased retinal endothelial cell monolayer permeability induced by the diabetic milieu: role of advanced non-enzymatic glycation and polyol pathway activation

Increased vascular permeability could be involved in the pathogenesis of diabetic retinopathy. The present study was aimed at assessing whether high glucose concentrations can impair retinal endothelial cell barrier function directly, irrespective of changes in other determinants of permeability, and the role of non‐enzymatic glycation and polyol pathway activation in these alterations.

Erratum. Deletion of p66Shc Longevity Gene Protects Against Experimental Diabetic Glomerulopathy by Preventing Diabetes-Induced Oxidative Stress. Diabetes 2006;55:1642–1650

In this article, there was a mistake in the assembly of Fig. 4. The image files shown in panels E – H of …