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Lipolytic products of triglyceride-rich lipoproteins, i.e., free fatty acids, may cause activation and dysfunction of the vascular endothelium. Mechanisms of these effects may include lipid peroxidation. One of the major and biologically active products of peroxidation of n-6 fatty acids, such as linoleic acid or arachidonic acid, is the aldehyde 4-hydroxynonenal (HNE). To study the hypothesis that HNE may be a critical factor in endothelial cell dysfunction caused by free fatty acids, human umbilical endothelial cells (HUVEC) were treated with up to160 microM of linoleic or arachidonic acid. HNE formation was detected by immunocytochemistry in cells treated for 24 h with either fatty acid, but more markedly with arachidonic acid. To study the cellulareffects of HNE, HUVEC were treated with different concentrations of this aldehyde, and several markers of endothelial cell dysfunction were determined. Exposure to HNE for 6 and 9 h resulted in increased cellular oxidative stress. However, short time treatment with HNE did not cause activation of nuclear factor-kappaB (NF-kappaB). In addition, HUVEC exposure to HNE caused a dose-dependent decrease in production of both interleukin-8 (IL-8) and intercellular adhesion molecule-1 (ICAM-1). On the other hand, HNE exerted prominent cytotoxic effects in cultured HUVEC, manifested by morphological changes, diminished cellular viability, and impaired endothelial barrier function. Furthermore, HNE treatment induced apoptosis of HUVEC. These data provide evidence that HNE does not contribute to NF-kappaB-related mechanisms of the inflammatory response in HUVEC, but rather to endothelial dysfunction, cytotoxicity, and apoptotic cell death.

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Lipolytic products of triglyceride-rich lipoproteins, i.e., free fatty acids, may cause activation and dysfunction of the vascular endothelium. Mechanisms of these effects may include lipid peroxidation. One of the major and biologically active products of peroxidation of n-6 fatty acids, such as linoleic acid or arachidonic acid, is the aldehyde 4-hydroxynonenal (HNE). To study the hypothesis that HNE may be a critical factor in endothelial cell dysfunction caused by free fatty acids, human umbilical endothelial cells (HUVEC) were treated with up to160 microM of linoleic or arachidonic acid. HNE formation was detected by immunocytochemistry in cells treated for 24 h with either fatty acid, but more markedly with arachidonic acid. To study the cellulareffects of HNE, HUVEC were treated with different concentrations of this aldehyde, and several markers of endothelial cell dysfunction were determined. Exposure to HNE for 6 and 9 h resulted in increased cellular oxidative stress. However, short time treatment with HNE did not cause activation of nuclear factor-kappaB (NF-kappaB). In addition, HUVEC exposure to HNE caused a dose-dependent decrease in production of both interleukin-8 (IL-8) and intercellular adhesion molecule-1 (ICAM-1). On the other hand, HNE exerted prominent cytotoxic effects in cultured HUVEC, manifested by morphological changes, diminished cellular viability, and impaired endothelial barrier function. Furthermore, HNE treatment induced apoptosis of HUVEC. These data provide evidence that HNE does not contribute to NF-kappaB-related mechanisms of the inflammatory response in HUVEC, but rather to endothelial dysfunction, cytotoxicity, and apoptotic cell death.