Atherosclerosis 151 2000 433 – 441
Multiple cytokines regulate the expression of extracellular superoxide dismutase in human vascular smooth muscle cells
Pontus Stra˚lin, Stefan L. Marklund
Department of Medical Biosciences, Clinical Chemistry, Umea˚ Uni6ersity Hospital, S-
901 85
Umea˚, Sweden Received 12 February 1999; received in revised form 20 September 1999; accepted 4 October 1999
Abstract
Oxygen free radicals as well as immunological reactions have been suggested to play important roles in atherogenesis and other pathological processes of the blood vessel wall. We have previously shown that the vascular wall contains exceptionally large
amounts of extracellular superoxide dismutase EC-SOD and that the enzyme is produced and secreted to the extracellular space by the smooth muscle cells. In this work, we studied the influence of inflammatory cytokines on vascular smooth muscle cell
expression of EC-SOD, the mitochondrial manganese superoxide dismutase Mn-SOD and the cytosolic copper zinc superoxide dismutase CuZn-SOD. The expression of EC-SOD was up-regulated by interferon-g IFN-g and interleukin 4 IL-4, and was
down-regulated by tumor necrosis factor-a TNF-a. The ratio between the maximal stimulation and depression observed was around 20-fold. The responses were slow and developed over periods of several days. The Mn-SOD activity was strongly
up-regulated by TNF-a and IL-1a and moderately by IFN-g. The CuZn-SOD activity of the smooth muscle cells was not significantly influenced by any of the cytokines. The findings suggest that large changes in the SOD isoenzymes might occur in
vascular diseases, significantly altering the susceptibility of the vascular wall to adverse effects of the superoxide radical. © 2000 Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Superoxide dismutase; Superoxide radical; Atherosclerosis; Vascular smooth muscle cells; Free radicals www.elsevier.comlocateatherosclerosis
1. Introduction
The superoxide anion radical has increasingly been implicated in pathologies of the vascular wall. Many
potential sources in the wall have been established including membrane-bound NADH-oxidases [1], xan-
thine oxidase [2], the NADPH-oxidase of macrophages [3] and other phagocytes, and formation as by-products
by nitric oxide synthase [4] and by enzymes synthesizing prostanoids [5]. Increased formation of superoxide in
the vascular wall has been shown in a variety of patho- logical situations such as hypertension [6], diabetes [7]
and hyperlipidemia [8]. The superoxide radical reacts rapidly with nitric oxide NO to form peroxynitrite
[9,10]. This impairs potentially protective actions of NO such as vasodilatation [6], platelet deactivation [11],
leukocyte deactivation [12], and antioxidant effects [13]. The noxious peroxynitrite formed may in turn cause
adverse actions such as inducing peroxidation of lipo- proteins [14] and nitration of protein tyrosines in vital
proteins [15]. Extensive protein tyrosine nitration has been found in human atherosclerotic lesions [16]. The
superoxide radical has itself been implicated in the induction of oxidation of LDL by cultured cells [17 –
19], and in the marked enhancement of LDL oxidation caused by ceruloplasmin [20]. The superoxide radical
may thus play a significant role in atherogenesis [21,22].
It has recently been reported [23,24] that the human arterial wall contains exceptionally large amounts of
the secreted SOD isoenzyme EC-SOD [25], while the contents of the cytosolic CuZn-SOD [26] and the mito-
chondrial matrix Mn-SOD [27] are low compared to other tissues. The EC-SOD was found to be evenly
distributed in the wall, including large amounts in the
Corresponding author. Tel.: + 46-90-7851239; fax: + 46-90- 777296.
E-mail address
:
stefan.marklundklinkemi.umu.se S.L.
Marklund 0021-915000 - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved.
PII: S 0 0 2 1 - 9 1 5 0 9 9 0 0 4 2 7 - X
intima. The principal source of EC-SOD is the smooth muscle cells [23]. The strategic location sug-
gests that EC-SOD exerts an important protective role against pathologies induced by the superoxide radical
in the vascular wall.
Both inflammatory and immunological responses are integral parts of the atherosclerotic process, and
also occur in other diseases of the vascular wall. Infl- ammatory cytokines have previously been found to
influence the synthesis of EC-SOD by human dermal fibroblasts [28]. In the present study we examined the
effects of cytokines involved in inflammatory and im- munological responses on SOD isoenzyme expression
by human arterial smooth muscle cells. We found large effects on EC-SOD and Mn-SOD synthesis, sug-
gesting that cytokines formed in vascular diseases may significantly alter the response of the vascular wall to
superoxide radicals.
2. Methods
