Elsevier

Chemico-Biological Interactions

Volumes 143–144, 1 February 2003, Pages 587-596
Chemico-Biological Interactions

Aldose reductase mediates the mitogenic signals of cytokines

https://doi.org/10.1016/S0009-2797(02)00194-1Get rights and content

Abstract

Chronic hyperglycemia is associated with the activation of aldose reductase (AR), an increase in cytokines such as TNF-α and IL-8 and oxidative stress. Alterations in this interdependent cascade of signals may be responsible for the diabetes-induced increase in the incidence and severity of cardiovascular diseases such as atherosclerosis and hypertension. We have previously shown that inhibition of AR prevents cultured vascular smooth muscle cell (VSMC) growth and restenosis of balloon-injured carotid arteries. To identify the mechanisms by which inhibition of AR prevents cell growth, we examined the effects of AR inhibition on mitogenic signaling by cytokines. Stimulation with TNF-α led to the activation of the transcription factor NF-κB and enhanced VSMC growth. Treatment with the AR inhibitors sorbinil or tolrestat, attenuated mitogen-induced activation of NF-κB and VSMC proliferation. In cultured VSMC, AR inhibitors prevented signaling events upstream of NF-κB activation, i.e. IκB-α phosphorylation and IκB-α degradation. Inhibition of AR also prevented protein kinase C (PKC) activation by TNF-α, but did not affect PKC activation by phorbol esters, indicating that inhibition of AR interrupts mitogenic signaling upstream of PKC. Together, these results indicate a pivotal role of AR or its reaction product(s) in the mitogenic signals initiated by cytokines that are elevated in diabetes and its cardiovascular complications such as atherosclerosis. These observations suggest a possible therapeutic use of AR inhibitors in these pathological conditions.

Introduction

Although the precise mechanisms by which diabetes accelerates atherogenesis are not well understood, the formation of advanced glycosylation end-products (AGE), increased oxidative stress and lipid peroxidation have been implicated as causative factors in the higher cardiovascular risk of diabetics [1], [2], [3]. Increased oxidative stress during diabetes could lead to the generation of reactive carbonyl species that display a variety of proatherogenic effects [4]. Several of these carbonyls are substrates of aldose reductase (AR), an aldo–keto-reductase, which has been implicated in the development of diabetic complications [2], [5]. Aldose reductase inhibitors (ARI) attenuate some of the prolonged complications of diabetes such as peripheral neuropathy, cataractogenesis, nephropathy, and retinopathy [6]. However, the role of AR in mediating the vascular complications of diabetes remains unknown. In contrast to the injurious role of AR in diabetes, which has been linked to the accumulation of osmotically active sorbitol derived from the reduction of glucose by AR, our recent studies show that AR may be a key component of cellular metabolism for the detoxification of aldehydes derived from lipid peroxidation [7], [8]. In vitro the enzyme is an efficient catalyst for the reduction of a wide range of aliphatic and aromatic aldehydes, particularly short- or medium-chain alkenals and 4-hydroxyalkenals, which are the most abundant and cytotoxic end products of lipid peroxidation [7]. We have demonstrated that AR is an efficient catalyst for reducing glutathione-alkenal conjugates [8], indicating that the enzyme may be important in preventing the cellular accumulation of lipid peroxidation-derived aldehydes or their metabolites.

Previous studies have shown that oxidative stress caused during hyperglycemia or atherosclerosis leads to the formation and accumulation of lipid peroxidation product such as 4-hydroxy-trans-2-nonenal (HNE) [9]. High titers of antibodies against protein-HNE adducts have been demonstrated in atherosclerotic humans and in animal models of atherosclerosis. Moreover, the formation of HNE and/or related aldehyde-modified protein or lipoprotein adducts in atherosclerotic lesions has been documented [10]. Free HNE is a mitogen for VSMCs, and inhibition of its metabolism by AR inhibitors prevents VSMC growth in culture and in balloon-injured arteries [11], [12]. These observations indicate that the formation and reactivity of HNE may be an important component of mitogenic signaling, which in VSMC is mediated and triggered by reactive oxygen species (ROS) such as hydrogen peroxide and superoxide anions. The ROS trigger a variety of responses in VSMC and stimulate several redox-sensitive kinases such as the MAP kinases, protein kinase-C (PKC) and enhance the expression of several genes such as, TNFα and IL-8 by activating specific transcription factors [13], [14]. Since both cytokines and growth factors generate ROS and presumably lipid-derived aldehydes that could potentially mediate their proliferative/apoptotic responses, we investigated the role of AR in these processes. Particularly significant in the signaling cascade may be the activation of the redox-sensitive transcription factor NF-κB, which is stimulated by both TNF-α and growth factors [15], [16].

The activation of NF-κB by ROS has been demonstrated during hyperglycemia, as well as during cytokine and growth factor stimulation, and the activators of NF-κB such as TNFα and IL-1 are enhanced during atherogenesis [17], [18]. It has been shown previously that TNF-α is the main mitogen responsible for the proliferation of VSMC in balloon-injured arteries [18]. The generation of TNF-α is also increased during diabetes, and the hyperproliferative responses of diabetic vessels have been linked to increased TNF-α activity [19]. As we have shown that AR efficiently reduces lipid-derived aldehydes and their glutathione conjugates, we tested the hypothesis that AR could be an important regulator of VSMC growth, and that the pro-mitogenic effects of AR are in part due to its ability to facilitate NF-κB signaling. We demonstrate here that inhibition of AR by sorbinil or tolrestat prevents TNF-α- induced cell growth and the activation of NF-κB, indicating that AR may be an important regulator of NF-κB-mediated signaling during inflammation, atherosclerosis, and diabetes.

Section snippets

Materials

Dulbecco's modified eagle's medium (DMEM), PBS, penicillin/streptomycin solution, trypsin and fetal bovine serum were purchased from Invitrogen. Antibodies against IκB-α and p50 were obtained from Santa Cruz Biotechnology. Phospho-IκB-α (Ser32) antibody was purchased from New England Biolabs. Consensus oligonucleotides for NF-κB (5′-AGTTGAGGGGACTTTCCCAGGC-3′) and AP1 (5′-CGCTTGATGAGTCAGCCGGAA-3′) transcription factors were obtained from Promega Corp. Sorbinil and tolrestat were gifts from

AR inhibitors attenuate TNF-α-induced VSMC proliferation

We examined the effect of the two structurally different AR inhibitors, sorbinil and tolrestat, on TNF-α-induced mitogenic signaling. Stimulation of VSMC for 24 h with TNF-α resulted in increased cell proliferation compared to non-stimulated cells (Fig. 1) as measured by cell counts using Trypan blue, thymidine incorporation, and MTT assay. Incubation of VSMC for 24 h with 10–20 μM sorbinil or tolrestat prior to stimulation with TNF-α prevented VSMC proliferation. In the absence of TNF-α, ARI

Discussion

Abnormal VSMC proliferation underlies the high propensity of diabetics for restenosis and could be an important factor in the increased incidence and severity of atherosclerosis due to diabetes. It has been reported that inhibition of AR prevents hyperproliferation and the hypertrophy of VSMC in high glucose medium, suggesting that AR may be an important mediator of glucose-induced VSMC growth [22]. However, subsequent studies have shown that even under normal glucose concentrations, inhibition

Acknowledgements

This work was supported in part by NIH grants DK36118 (to S.K.S.) and HL55477 (to A. Bhatnagar). We are grateful to Dr B.B. Aggarwal, University of Texas, MD Anderson Cancer Institute, Houston, TX, for providing recombinant TNF-α.

References (25)

  • S. Srivastava et al.

    Involvement of aldose reductase in the metabolism of atherogenic aldehydes

    Chem. Biol. Interact.

    (2001)
  • M.M. Chaturvedi et al.

    Assay for redox-sensitive transcription factors

    Methods Enzymol.

    (2000)
  • W. Baynes et al.

    Glycoxidation and lipoxidation in atherogenesis

    Free Radic. Biol. Med.

    (2000)
  • A.M. Schmidt et al.

    Activation of receptor for advanced glycation end products: a mechanism for chronic vascular dysfunction in diabetic vasculopathy and atherosclerosis

    Circ. Res.

    (1999)
  • P. Reaven et al.

    Effect of streptozotocin-induced hyperglycemia on lipid profiles, formation of advanced glycation endproducts in lesions, and extent of atherosclerosis in LDL receptor-deficient mice

    Arterioscler. Thromb. Vasc. Biol.

    (1997)
  • R. Bucala

    Lipid and lipoprotein modification by advanced glycosylation end-products: role in atherosclerosis

    Exp. Phsyiol.

    (1997)
  • L. Costantino et al.

    Diabetes complications and their potential prevention: aldose reductase inhibition and other approaches

    Med. Res. Rev.

    (1999)
  • S. Srivastava et al.

    Structural and kinetic determinants of aldehyde reduction by aldose reductase

    Biochemistry

    (1999)
  • K.V. Ramana et al.

    Selective recognition of glutathiolated aldehydes by aldose reducase

    Biochemistry

    (2000)
  • R.G. Salomon et al.

    HNE-derived 2-pentylpyrroles are generated during oxidation of LDL, are more prevalent in blood plasma from patients with renal disease or atherosclerosis, and are present in atherosclerotic plaques

    Chem. Res. Toxicol.

    (2000)
  • K. Uchida

    Michael addition-type 4-hydroxy-2-nonenal adducts in modified low-density lipoproteins: markers for atherosclerosis

    Biochemistry

    (1994)
  • J. Ruef et al.

    Involvement of aldose reductase in vascular smooth muscle cell growth and lesion formation after arterial injury

    Arterioscler. Thromb. Vasc. Biol.

    (2000)
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