Insulin Generates Free Radicals by an NAD(P)H, Phosphatidylinositol 3′-Kinase-Dependent Mechanism in Human Skin Fibroblasts Ex Vivo

Ceolotto, Giulio; Bevilacqua, Michela; Papparella, Italia; Baritono, Elisabetta; Franco, Lorenzo; Corvaja, Carlo; Mazzoni, Martina; Semplicini, Andrea; Avogaro, Angelo

doi:10.2337/diabetes.53.5.1344

Cited by 77 publications

(57 citation statements)

References 41 publications

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“…Similarly, in skin fibroblasts, Ceolotto et al (114) found that insulin-stimulated ROS production was also dependent on PI 3Ј-kinase activity. In contrast, we reported that insulin-stimulated ROS generation in 3T3-L1 adipocytes, presumably via a Nox4-mediated pathway, was not sensitive to PI 3Ј-kinase inhibition (26).…”

Section: Generation Of H 2 O 2 By Cellular Insulin Stimulationmentioning

confidence: 99%

Redox Paradox

2005

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Propelled by the identification of a small family of NADPH oxidase (Nox) enzyme homologs that produce superoxide in response to cellular stimulation with various growth factors, renewed interest has been generated in characterizing the signaling effects of reactive oxygen species (ROS) in relation to insulin action. Two key observations made >30 years ago-that oxidants can facilitate or mimic insulin action and that H 2 O 2 is generated in response to insulin stimulation of its target cells-have led to the hypothesis that ROS may serve as second messengers in the insulin action cascade. Specific molecular targets of insulin-induced ROS include enzymes whose signaling activity is modified via oxidative biochemical reactions, leading to enhanced insulin signal transduction. These positive responses to cellular ROS may seem "paradoxical" because chronic exposure to relatively high levels of ROS have also been associated with functional ␤-cell impairment and the chronic complications of diabetes. The best-characterized molecular targets of ROS are the protein-tyrosine phosphatases (PTPs) because these important signaling enzymes require a reduced form of a critical cysteine residue for catalytic activity. PTPs normally serve as negative regulators of insulin action via the dephosphorylation of the insulin receptor and its tyrosinephosphorylated cellular substrates. However, ROS can rapidly oxidize the catalytic cysteine of target PTPs, effectively blocking their enzyme activity and reversing their inhibitory effect on insulin signaling. Among the cloned Nox homologs, we have recently provided evidence that Nox4 may mediate the insulin-stimulated generation of cellular ROS and is coupled to insulin action via the oxidative inhibition of PTP1B, a PTP known to be a major regulator of the insulin signaling cascade. Further characterization of the molecular components of this novel signaling cascade, including the mechanism of ROS generated by insulin and the identification of various oxidation-sensitive signaling targets in insulin-sensitive cells, may provide a novel means of facilitating insulin action in states of insulin resistance.

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Section: Generation Of H 2 O 2 By Cellular Insulin Stimulationmentioning

confidence: 99%

Redox Paradox

2005

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“…In response to dietary challenges, adipocytes and endothelial cells activate classical inflammatory pathways, which impair the metabolic action of insulin, paving the way to diabetes [3]. In turn, hyperglycemia and hyperinsulinemia elicit multiple pro-inflammatory responses [4][5][6]. This is reflected by mild elevation of inflammatory markers in patients with diabetes or the metabolic syndrome [7].…”

Section: Introductionmentioning

confidence: 99%

An unbalanced monocyte polarisation in peripheral blood and bone marrow of patients with type 2 diabetes has an impact on microangiopathy

et al. 2013

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AIM/HYPOTHESIS: Monocytes/macrophages play important roles in adipose and vascular tissues and can be polarised as inflammatory M1 or anti-inflammatory M2. We sought to analyse monocyte polarisation status in type 2 diabetes, which is characterised by chronic inflammation. METH-ODS: We enrolled 60 individuals without diabetes and 53 patients with type 2 diabetes. We quantified standard monocyte subsets defined by cluster of differentiation (CD)14 and CD16. In addition, based on the phenotype of polarised macrophages in vitro, we characterised and quantified more definite M1 (CD68(+)CCR2(+)) and M2 (CX3CR1(+)CD206(+)/CD163(+)) monocytes. We also analysed bone marrow (BM) samples and the effects of granulocyte-colony stimulating factor (G-CSF) stimulation in diabetic and control individuals. RESULTS: We found no alterations in standard monocyte subsets (classical, intermediate and non-classical) when comparing groups. For validation of M1 and M2 phenotypes, we observed that M2 were enriched in non-classical monocytes and had lower TNF-content, higher LDL scavenging and lower transendothelial migratory capacity than M1. Diabetic patients displayed an imbalanced M1/M2 ratio compared with the control group, attributable to a reduction in M2. The M1/M2 ratio was directly correlated with waist circumference and HbA1c and, among diabetic patients, M2 reduction and M1/M2 increase were associated with microangiopathy. A decrease in M2 was also found in the BM from diabetic patients, with a relative M2 excess compared with the bloodstream. BM stimulation with G-CSF mobilised M2 macrophages in diabetic but not in healthy individuals. CON-CLUSIONS/INTERPRETATION: We show that type 2 diabetes markedly reduces anti-inflammatory M2 monocytes through a dysregulation in bone-marrow function. This defect may have a negative impact on microangiopathy. DOI: https://doi.org/10.1007/s00125-013-2918-9Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-83908 Accepted Version Originally published at: Fadini, G P; de Kreutzenberg, S Vigili; Boscaro, E; Albiero, M; Cappellari, R; Kränkel, N; Landmesser, U; Toniolo, A; Bolego, C; Cignarella, A; Seeger, F; Dimmeler, S; Zeiher, A; Agostini, C; Avogaro, A (2013). An unbalanced monocyte polarisation in peripheral blood and bone marrow of patients with type 2 diabetes has an impact on microangiopathy. Diabetologia, 56 (8) (CX3CR1+CD206+/CD163+) monocytes. We also analysed bone marrow (BM) samples and the effects of G-CSF stimulation in type 2 diabetic and control subjects.Results. We found no alterations in standard monocyte subsets (classical, intermediate, and nonclassical) between groups. For validation of M1 and M2 phenotypes, we show that M2 were enriched in nonclassical monocytes, had lower TNF-α content, higher LDL scavenging and lower transendothelial migratory capacity than M1. Diabetic patients displayed an imbalanced M1/M2 ratio compared to controls, which was attributable to a reduction in M2. The M1/M2 ratio was d...

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“…In skin treated with LPS, NADPH oxidase in infiltrating neutrophils is well known to produce a large amount of superoxide anion (9) as it does in other organs. Although NADPH oxidase in the nonphagocytic cells has been less well characterized, a physiologically relevant low level of generation of free radical and neutrophil-like expression of NADPH oxidase subunits is also present in skin keratinocytes (10,11) and fibroblasts (12). However, there was a significant increase in the lipid radicals from the skin of mice treated with LPS for 6 h, even in gp91 phox knockout animals.…”

Section: Discussionmentioning

confidence: 78%

“…It is also present in keratinocytes (10,11) and fibroblasts (12). XO is activated in 12-O-tetradecanoyl-13-phorbol acetate-treated murine skin (13) and in human skin keratinocyte cells irradiated with UV B (14).…”

Section: Ipopolysaccharide (Lps) An Outer-membrane Component Ofmentioning

confidence: 99%

Free radical production requires both inducible nitric oxide synthase and xanthine oxidase in LPS-treated skin

Nakai

Kadiiska

Jiang

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Free radical formation has been investigated in diverse experimental models of LPS-induced inflammation. Here, using electron spin resonance (ESR) and the spin trap ␣-(4-pyridyl-1-oxide)-N-tertbutylnitrone, we have detected an ESR spectrum of ␣-(4-pyridyl-1-oxide)-N-tert-butylnitrone radical adducts in the lipid extract of mouse skin treated with LPS for 6 h. The ESR spectrum was consistent with the trapping of lipid-derived radical adducts. In addition, a secondary radical-trapping technique using dimethyl sulfoxide (DMSO) demonstrated methyl radical formation, revealing the production of hydroxyl radical. Radical adduct formation was suppressed by aminoguanidine, N-(3-aminomethyl)benzylacetamidine (1400W), or allopurinol, suggesting a role for both inducible nitric oxide synthase (iNOS) and xanthine oxidase (XO) in free radical formation. The radical formation was also suppressed in iNOS knockout (iNOS ؊/؊ ) mice, demonstrating the involvement of iNOS. NADPH oxidase was not required in the formation of these radical adducts because the ESR signal intensity was increased by LPS treatment in NADPH oxidase knockout (gp91 phox؊/؊ ) mice as much as it was in the wild-type mouse. Nitric oxide ( • NO) end products were increased in LPS-treated skin. As expected, the • NO end products were not suppressed by allopurinol but were by aminoguanidine. Interestingly, nitrotyrosine formation in LPStreated skin was also suppressed by aminoguanidine and allopurinol independently. Pretreatment with the ferric iron chelator Desferal had no effect on free radical formation. Our results imply that both iNOS and XO, but neither NADPH oxidase nor ferric iron, work synergistically to form lipid radical and nitrotyrosine early in the skin inflammation caused by LPS.lipopolysaccharide ͉ mouse skin L ipopolysaccharide (LPS), an outer-membrane component of Gram-negative bacteria, interacts with CD14, which then presents LPS to the Toll-like receptor 4 (1, 2); filling of this receptor activates inflammatory gene expression through nuclear factor B and mitogen-activated protein kinase signaling (3, 4). Over the years, LPS has frequently been used in experimental models of inflammation. The inflammatory response includes activation of free radical-generating enzymes in various types of cells that initiate host lipid peroxidation. For the detection and identification of these generated free radicals, the use of spin-trapping compounds appears to be the best method in vivo (5, 6). By using the electron spin resonance (ESR) spin-trapping technique, we have detected in vivo free radical production in lungs treated with LPS (7) or low-dose LPS plus diesel exhaust particles (8). In these articles, we have discussed the involvement of free radical-generating enzymes such as NADPH oxidase, xanthine oxidase (XO), and inducible nitric oxide synthase (iNOS).NADPH oxidase is generally activated in neutrophils that infiltrate the skin (9). It is also present in keratinocytes (10, 11) and fibroblasts (12). XO is activated in 12-O-tetradecanoyl-13-phorbol...

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Insulin Generates Free Radicals by an NAD(P)H, Phosphatidylinositol 3′-Kinase-Dependent Mechanism in Human Skin Fibroblasts Ex Vivo

Cited by 77 publications

References 41 publications

Redox Paradox

Redox Paradox

An unbalanced monocyte polarisation in peripheral blood and bone marrow of patients with type 2 diabetes has an impact on microangiopathy

Free radical production requires both inducible nitric oxide synthase and xanthine oxidase in LPS-treated skin

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